WorldWideScience

Sample records for chain polymer arising

  1. Elastic Behavior of Polymer Chains

    Institute of Scientific and Technical Information of China (English)

    Teng Lu; Tao Chen; Hao-jun Liang

    2008-01-01

    The elastic behavior of the polymer chain was investigated in a three-dimensional off-lattice model. We sample more than 109 conformations of each kind of polymer chain by using a Monte Carlo algorithm, then analyze them with the non-Gaussian theory of rubberlike elasticity, and end with a statistical study. Through observing the effect of the chain flexibility and the stretching ratio on the mean-square end-to-end distance,the average energy, the average Helmholtz free energy, the elastic force, the contribution of energy to the elastic force, and the entropy contribution to elastic force of the polymer chain, we find that a rigid polymer chain is much easier to stretch than a flexible polymer chain. Also, a rigid polymer chain will become difficult to stretch only at a quite high stretching ratio because of the effect of the entropy contribution.These results of our simulation calculation may explain some of the macroscopic phenomena of polymer and biomacromolecular elasticity.

  2. Thermophoresis of linear polymer chains

    Science.gov (United States)

    Bringuier, Eric

    2011-05-01

    The thermophoresis of a linear polymer chain in a solvent is examined theoretically and is shown to be due to the action of two forces. The first one is Waldmann's thermophoretic force (stemming from the departure of the molecular-velocity distribution from Maxwell's equilibrium distribution), which here is extrapolated to a dense medium by using scaling considerations. The second force is due to the fact that the viscous friction varies with position owing to the temperature gradient, which brings a zeroth-order correction to the Stokes law of friction. The present scaling theory is compared with recent experiments and is found to account for: (i) the existence of both signs of the thermodiffusion coefficient; (ii) the absolute magnitude of the coefficient; (iii) the fact that it is independent of the chain length in the high-polymer limit; and (iv) the dependence on solvent viscosity. The variation of the coefficient for short chains is also examined.

  3. Structure of polymer chains under confinement

    Indian Academy of Sciences (India)

    Jyotsana Lal

    2008-11-01

    We observe by SANS the structure of neutral polystyrene and charged polystyrene sulphonate chains in semi-dilute solutions confined in a model nanoporous glass, Vycor. The size of the free chains in solution is always larger than the pore diameter, 70. The use of a suitable mixture of hydrogenated and deuterated solvents and polymers enables us to measure directly the form factor of one single chain among the others. Single chain form factor was observed both for bulk and confined chains using the condition of zero average contrast. Our measurements on neutral polymer chains are in agreement with the theoretical predictions established by Daoud and de Gennes for chains confined in a cylindrical pore when the chains are entangled and laterally squeezed but remain ideal at large scale along the cylinder axis because of the screening of the excluded volume interactions (so-called regime of ``semi-dilute cigars"). For confined charged polymers, a peak is observed whose intensity increases with molecular weight and the asymptotic 1/ scattering region is extended compared to the bulk. We infer that the chains are sufficiently extended, under the influence of confinement, to highlight the large scale disordered structure of Vycor even under contrast matched conditions. The asymptotic behaviour of the observed interchain structure factor is ≈ 1/2 and ≈ 1/ for free and confined chains respectively.

  4. Macromolecular recognition: Recognition of polymer side chains by cyclodextrin

    Science.gov (United States)

    Hashidzume, Akihito; Harada, Akira

    2015-12-01

    The interaction of cyclodextrins (CD) with water soluble polymers possessing guest residues has been investigated as model systems in biological molecular recognition. The selectivity of interaction of CD with polymer-carrying guest residues is controlled by polymer chains, i.e., the steric effect of polymer main chain, the conformational effect of polymer main chain, and multi-site interaction. Macroscopic assemblies have been also realized based on molecular recognition using polyacrylamide-based gels possessing CD and guest residues.

  5. Stretching of a polymer chain anchored to a surface: the massive field theory approach

    Science.gov (United States)

    Usatenko, Zoryana

    2014-09-01

    Taking into account the well-known correspondence between the field theoretical φ4 O(n)-vector model in the limit n → 0 and the behaviour of long-flexible polymer chains, the investigation of stretching of an ideal and a real polymer chain with excluded volume interactions in a good solvent anchored to repulsive and inert surfaces is performed. The calculations of the average stretching force which arises when the free end of a polymer chain moves away from a repulsive or inert surface are performed up to one-loop order of the massive field theory approach in fixed space dimensions d = 3. The analysis of the obtained results indicates that the average stretching force for a real polymer chain anchored to a repulsive surface demonstrates different behaviour for the cases \\tilde{z}\\ll1 and \\tilde{z}\\gg1 , where \\tilde{z}=z^\\prime/Rz . Besides, the results obtained in the framework of the massive field theory approach are in good agreement with previous theoretical results for an ideal polymer chain and results of a density functional theory approach for the region of small applied forces when deformation of a polymer chain in the direction of the applied force is not bigger than the linear extension of a polymer chain in this direction. The better agreement between these two methods is observed in the case where the number of monomers increases and the polymer chain becomes longer.

  6. The effect of chain flexibility and chain mobility on radiation crosslinking reactions of polymers

    International Nuclear Information System (INIS)

    Flexibility of polymer chains is an important factor to effects of radiation crosslinking of the polymer. Polymers with flexible chains are easier to be crosslinked, with lower dose of gelation, than polymers with more rigid chains. And it is known that most polymers with abnormal rigidity can be radiation-crosslinked only at high temperatures when the molecular chains get enough mobility. The flexibility of polymer chains also influences the relationship between degree of degradation and radiation dose. A chain flexibility factor β has been introduced to modify the Charlesby-Pinner equation of sol-fraction and radiation dose. The new relationship equation applies to a wider range of polymers in radiation crosslinking. Studies also show that for flexible polymers with lower Tg and molecular internal rotating factor, mechanism of radiation crosslinking is mainly in H type, whereas for rigid polymers with higher Tg and molecular internal rotating factor, mechanism of radiation crosslinking is mainly in T type

  7. Side Chain Engineering in Solution-Processable Conjugated Polymers

    KAUST Repository

    Mei, Jianguo

    2014-01-14

    Side chains in conjugated polymers have been primarily utilized as solubilizing groups. However, these side chains have roles that are far beyond. We advocate using side chain engineering to tune a polymer\\'s physical properties, including absorption, emission, energy level, molecular packing, and charge transport. To date, numerous flexible substituents suitable for constructing side chains have been reported. In this Perspective article, we advocate that the side chain engineering approach can advance better designs for next-generation conjugated polymers. © 2013 American Chemical Society.

  8. Segregation of chain ends to polymer melt surfaces and interfaces

    International Nuclear Information System (INIS)

    The conformation of polymer chains in the melt near an impenetrable boundary has recently been studied by molecular dynamics and off-lattice Monte Carlo simulations. Both types of calculations show an enhancement of the chain end density within a distance of approximately two polymer segment lengths of the interface relative to the bulk. In the absence of preferential interactions between monomers and the interface, the segregation arises from minimizing the loss of conformational entropy near an impenetrable boundary; i.e., by positioning an end near the surface, only one unit rather than two is reflected. In order to obtain an experimental measure of this effect, monodisperse polystyrene (PS) chains of molecular weight 63 000 with short blocks of deuterated polystyrene (dPS) at each end were prepared. The block length was kept as short as possible, while yet producing sufficient neutron scattering contrast in order to minimize any preferential surface segregation due to isotopic effects. The synthesis was carried out via living anionic polymerization of a purified styrene monomer in cyclohexane at 60 C, utilizing sec-butyllithium as the initiator. The process was terminated using degassed methanol

  9. Monotonicity of a Key Function Arised in Studies of Nematic Liquid Crystal Polymers

    Directory of Open Access Journals (Sweden)

    Hongyun Wang

    2007-01-01

    Full Text Available We revisit a key function arised in studies of nematic liquid crystal polymers. Previously, it was conjectured that the function is strictly decreasing and the conjecture was numerically confirmed. Here we prove the conjecture analytically. More specifically, we write the derivative of the function into two parts and prove that each part is strictly negative.

  10. Glassy dynamics in condensed isolated polymer chains.

    Science.gov (United States)

    Tress, Martin; Mapesa, Emmanuel U; Kossack, Wilhelm; Kipnusu, Wycliffe K; Reiche, Manfred; Kremer, Friedrich

    2013-09-20

    In the course of miniaturization down to the nanometer scale, much remains unknown concerning how and to what extent the properties of materials are changed. To learn more about the dynamics of condensed isolated polymer chains, we used broadband dielectric spectroscopy and a capacitor with nanostructured electrodes separated by 35 nanometers. We measured the dynamic glass transition of poly(2-vinylpyridine) and found it to be bulk-like; only segments closer than 0.5 nanometer to the substrate were weakly slowed. Our approach paves the way for numerous experiments on the dynamics of isolated molecules. PMID:24052303

  11. Dynamics in Blends of Long Polymers with Unentangled Short Chains

    OpenAIRE

    Colby, Ralph

    1997-01-01

    Scaling ideas for dynamics of polymer solutions are extended to the case of a solution of long chains (of N monomers) in unentangled short chains (of P monomers). The P chains can be sufficiently short to make the long chains partially swell (P < N1/2). While the configurational statistics of the partially swollen long chains are perfectly analogous to the case of a long chain in marginal solvent, the dynamics are qualitatively different because of differences in the screening of hydrodynamic...

  12. End-Grafted Polymer Chains onto Inorganic Nano-Objects

    Directory of Open Access Journals (Sweden)

    Demetra S. Achilleos

    2010-03-01

    Full Text Available Organic/inorganic nanohybrid materials have attracted particular scientific and technological interest because they combine the properties of the organic and the inorganic component. Inorganic nanoparticles exhibit interesting electrical, optical, magnetic and/or catalytic properties, which are related with their nano-scale dimensions. However, their high surface-to-volume ratio often induces agglomeration and leads to the loss of their attractive properties. Surface modification of the inorganic nano-objects with physically or chemically end-tethered polymer chains has been employed to overcome this problem. Covalent tethered polymer chains are realized by three different approaches: the “grafting to”, the “grafting from” and the “grafting through” method. This article reviews the synthesis of end-grafted polymer chains onto inorganic nanoparticles using “controlled/living” polymerization techniques, which allow control over the polymer characteristics and the grafting density of the end-tethered polymer chains.

  13. Nonaffine chain and primitive path deformation in crosslinked polymers

    Science.gov (United States)

    Davidson, J. D.; Goulbourne, N. C.

    2016-08-01

    Chains in a polymer network deform nonaffinely at small length scales due to the ability for extensive microscopic rearrangement. Classically, the conformations of an individual chain can be described solely by an end-to-end length. This picture neglects interchain interactions and therefore does not represent the behavior of a real polymer network. The primitive path concept provides the additional detail to represent interchain entanglements, and techniques have recently been developed to identify the network of primitive paths in a polymer simulation. We use coarse-grained molecular dynamics (MD) to track both chain end-to-end and primitive path deformation in crosslinked polymer networks. The range of simulated materials includes short chain unentangled networks to long, entangled chain networks. Both chain end-to-end and primitive path length are found to be linear functions of the applied deformation, and a simple relationship describes the behavior of a network in response to large stretch uniaxial, pure shear, and equi-biaxial deformations. As expected, end-to-end chain length deformation is nonaffine for short chain networks, and becomes closer to affine for networks of long, entangled chains. However, primitive path deformation is found to always be nonaffine, even for long, entangled chains. We demonstrate how the microscopic constraints of crosslinks and entanglements affect nonaffine chain deformation as well as the simulated elastic behavior of the different networks.

  14. Non-Markovian effects in the growth of a polymer chain

    OpenAIRE

    Sokolovski D.; Rusconi S.; Akhmatskaya E.; Asua J.M.

    2014-01-01

    Using simple exactly solvable models, we show that event-dependent time delays may lead to significant non-Poisson effects in the statistics of polymer chain growth. The results are confirmed by stochastic simulation of various growth scenarios. Our interest in mathematical aspects of non-Markovian growth arises from recent successful application of delayed probability density functions in stochastic modelling of controlled radical polymerization.

  15. Wear of conveyor chains with polymer rolls

    OpenAIRE

    Kerremans, Vincent; Rolly, Tom; DE BAETS, PATRICK; De Pauw, Jan; Sukumaran, Jacob; Perez Delgado, Yeczain

    2011-01-01

    Roller conveyor chains are common used to transport goods in production lines or assembly lines, such as pallets, cars or steel coils. They are sometimes used in severe environments, soiled with water, foreign particles, chemicals or other contaminants. Normal use will result in wear of the components of the chain which can lead to unexpected failure and costly production downtime. Today, few literature on the wear of conveyor chain is available and there are almost no reliable test-rigs to g...

  16. Polymer-like Behavior of Inorganic Nanoparticle Chain Aggregates

    International Nuclear Information System (INIS)

    Studies of the behavior of nanoparticle chain aggregates (NCA) have shown properties similar to those of molecular polymers. Like polymer chains, NCA tend to gather up and become more compact when heated. Under tensile stress, folded chain segments pull out and the NCA elongates. When the tension is relaxed, the chains contract. The stretching of NCA may contribute to the ductility of compacts made from nanoparticles, a subject of current research interest. In a well established technological application, carbon black and pyrogenic silica NCA produce remarkable increases in elastic modulus and tensile strength when added to commercial rubber. This may be due to the mechanical interaction between the polymer chains and NCA. However, basic mechanisms of NCA elasticity differ from those of molecular polymers. The alignment of chain segments when the NCA are subjected to tension probably results from rotation and translation at grain boundaries between neighboring nanocrystals. The elastic properties depend on the van der Waals forces between segments of the chain that fold to minimize surface free energy. Under tension, these segments pull out, but tend to reform when the tension is relaxed. The processes that lead to NCA formation and control the strength of interparticle bonds are briefly reviewed

  17. Relaxation Dynamics of Nanoparticle-Tethered Polymer Chains

    KAUST Repository

    Kim, Sung A

    2015-09-08

    © 2015 American Chemical Society. Relaxation dynamics of nanoparticle-tethered cis-1,4-polyisoprene (PI) are investigated using dielectric spectroscopy and rheometry. A model system composed of polymer chains densely grafted to spherical SiO2 nanoparticles to form self-suspended suspensions facilitates detailed studies of slow global chain and fast segmental mode dynamics under surface and geometrical confinement-from experiments performed in bulk materials. We report that unentangled polymer molecules tethered to nanoparticles relax far more slowly than their tethered entangled counterparts. Specifically, at fixed grafting density we find, counterintuitively, that increasing the tethered polymer molecular weight up to values close to the entanglement molecular weight speeds up chain relaxation dynamics. Decreasing the polymer grafting density for a fixed molecular weight has the opposite effect: it dramatically slows down chain relaxation, increases interchain coupling, and leads to a transition in rheological response from simple fluid behavior to viscoelastic fluid behavior for tethered PI chains that are unentangled by conventional measures. Increasing the measurement temperature produces an even stronger elastic response and speeds up molecular relaxation at a rate that decreases with grafting density and molecular weight. These observations are discussed in terms of chain confinement driven by crowding between particles and by the existence of an entropic attractive force produced by the space-filling constraint on individual chains in a self-suspended material. Our results indicate that the entropic force between densely grafted polymer molecules couples motions of individual chains in an analogous manner to reversible cross-links in associating polymers.

  18. Single chain stochastic polymer modeling at high strain rates.

    Energy Technology Data Exchange (ETDEWEB)

    Harstad, E. N. (Eric N.); Harlow, Francis Harvey,; Schreyer, H. L.

    2001-01-01

    Our goal is to develop constitutive relations for the behavior of a solid polymer during high-strain-rate deformations. In contrast to the classic thermodynamic techniques for deriving stress-strain response in static (equilibrium) circumstances, we employ a statistical-mechanics approach, in which we evolve a probability distribution function (PDF) for the velocity fluctuations of the repeating units of the chain. We use a Langevin description for the dynamics of a single repeating unit and a Lioville equation to describe the variations of the PDF. Moments of the PDF give the conservation equations for a single polymer chain embedded in other similar chains. To extract single-chain analytical constitutive relations these equations have been solved for representative loading paths. By this process we discover that a measure of nonuniform chain link displacement serves this purpose very well. We then derive an evolution equation for the descriptor function, with the result being a history-dependent constitutive relation.

  19. Grafted polymers layers: neutral chains to charged chains

    International Nuclear Information System (INIS)

    This work concerns an experimental study, by small angle neutrons scattering, of neutral or charged grafted polymers layers structures. The method consisted in exploiting the acknowledges got on neutral brushes, to reach the problem of grafted polyelectrolyte layers. The difficulty of charged layers making has been, until this day, an important obstacle to the experimental study of these systems. It has been partially resolved in the case of sodium sulfonate polystyrene layers, and allowed to study their structure. (N.C.). 72 refs., 74 figs., 24 tabs

  20. MOLECULAR DESIGN OF FUNCTIONAL POLYMERS BASED ON UNIQUE PROPERTIES OF POLYMER CHAINS

    Institute of Scientific and Technical Information of China (English)

    Mikiharu Kamachi

    2000-01-01

    The inclusion complex formation of α-CD, β-CD, and γ-CD with various water-soluble polymers has been investigated, and the relationship between the chain cross-sectional areas of the polymers and the diameters of the cavities of cyclodextrins (molecular recognition) was found. Polyrotaxanes and tubular polymers were prepared on the basis of molecular recognition. Several kinds of polymers having tetraphenylporphyrin (TPP) and paramagnetic metallotetraphenylporphyrin (AgTPP, CuTPP, VOTPP or ZnTPP) have been prepared by radical polymerization of the corresponding monomers. Visible spectra of these polymers show hypochromism in the Soret bands of TPP moieties as compared with those of monomers. Polymer effects were observed in the magnetic behavior and oxygen adsorption of paramagnetic metallotetraphenylporphyrin moieties. Moreover, polymer effects on photophysical and photochemical behavior were found in the amphiphilic polymers covalently tethered with small amounts of zinc(Ⅱ)-tetraphenylporphyrin (ZnTPP).

  1. MODELING THE CHAIN CONFORMATION OF POLYMER MELTS IN CONTRACTION FLOW

    Institute of Scientific and Technical Information of China (English)

    Qing Shen; Jian-feng Hu; Qing-feng Gu

    2003-01-01

    A constitutive model of quasi-Newtonian fluid based on the type of flow is used in abrupt planar contraction flow.The numerical results from finite element analysis are consistent with experimental data for stress patterns and velocity profiles in the flow field. The chain conformations of polymer melts are then investigated in such a planar contraction by using the phenomenological model with internal parameters proposed by the author. That is, the shape and orientation of polymer chain coils are predicted and discussed in different flow regions of the contraction flow field that possess simple shear flow, extensional flow, vortical flow, and mixed flow respectively.

  2. Scaling in rupture of polymer chains

    OpenAIRE

    Fugmann, S.; I. M. Sokolov

    2008-01-01

    We consider the rupture dynamics of a homopolymer chain pulled at one end at a constant loading rate r. Compared to single bond breaking, the existence of the chain introduces two new aspects into rupture dynamics: the non-Markovian aspect in the barrier crossing and the slow-down of the force propagation to the breakable bond. The relative impact of both these processes is investigated, and the second one was found to be the most important at moderate loading rates. The most probable rupture...

  3. Opacity and entanglement of polymer chains

    International Nuclear Information System (INIS)

    We argue that the mean crossing number of a random polymer configuration is simply a measure of opacity, without being closely related to entanglement as claimed by several authors. We present an easy way of estimating its asymptotic behaviour numerically. These estimates agree for random walks (theta polymers), for self-avoiding walks, and for compact globules with analytic estimates giving log N, a-b/N2ν-1, and N1/3, respectively, for the average number of crossings per monomer in the limit N→∞. While the result for compact globules agrees with a rigorous previous estimate, the result for self-avoiding random walks disagrees with previous numerical estimates. (author)

  4. Membrane consisting of polyquaternary amine ion exchange polymer network interpenetrating the chains of thermoplastic matrix polymer

    Science.gov (United States)

    Rembaum, A.; Wallace, C. J. (Inventor)

    1978-01-01

    An ion exchange membrane was formed from a solution containing dissolved matrix polymer and a set of monomers which are capable of reacting to form a polyquaternary ion exchange material; for example vinyl pyride and a dihalo hydrocarbon. After casting solution and evaporation of the volatile component's, a relatively strong ion exchange membrane was obtained which is capable of removing anions, such as nitrate or chromate from water. The ion exchange polymer forms an interpenetrating network with the chains of the matrix polymer.

  5. Supramolecular routes towards liquid crystalline side-chain polymers

    OpenAIRE

    Hammond, Matthew R.; Mezzenga, Raffaele

    2008-01-01

    Supramolecular attachment of mesogenic or non-mesogenic side chains to polymer backbones can result in the formation of liquid crystalline morphologies. The various parameters that can be tuned in order to achieve these morphologies, such as the type of non-covalent bonding chemistry (hydrogen bonding, ionic bonding, metal coordination, π–π interactions), the polymeric template architecture, and the side chain structure and properties, are reviewed in what follows, with emphasis placed on the...

  6. Single-chain folding of polymers for catalytic systems in water.

    Science.gov (United States)

    Terashima, Takaya; Mes, Tristan; De Greef, Tom F A; Gillissen, Martijn A J; Besenius, Pol; Palmans, Anja R A; Meijer, E W

    2011-04-01

    Enzymes are a source of inspiration for chemists attempting to create versatile synthetic catalysts. In order to arrive at a polymeric chain carrying catalytic units separated spatially, it is a prerequisite to fold these polymers in water into well-defined compartmentalized architectures thus creating a catalytic core. Herein, we report the synthesis, physical properties, and catalytic activity of a water-soluble segmented terpolymer in which a helical structure in the apolar core is created around a ruthenium-based catalyst. The supramolecular chirality of this catalytic system is the result of the self-assembly of benzene-1,3,5-tricarboxamide side chains, while the catalyst arises from the sequential ruthenium-catalyzed living radical polymerization of the different monomers followed by ligand exchange. The polymers exhibit a two-state folding process and show transfer hydrogenation in water. PMID:21405022

  7. Hyperbranched polymer stars with Gaussian chain statistics revisited.

    Science.gov (United States)

    Polińska, P; Gillig, C; Wittmer, J P; Baschnagel, J

    2014-02-01

    Conformational properties of regular dendrimers and more general hyperbranched polymer stars with Gaussian statistics for the spacer chains between branching points are revisited numerically. We investigate the scaling for asymptotically long chains especially for fractal dimensions df = 3 (marginally compact) and df = 2.5 (diffusion limited aggregation). Power-law stars obtained by imposing the number of additional arms per generation are compared to truly self-similar stars. We discuss effects of weak excluded-volume interactions and sketch the regime where the Gaussian approximation should hold in dense solutions and melts for sufficiently large spacer chains. PMID:24574057

  8. Dynamics of a polymer chain confined in a membrane.

    Science.gov (United States)

    Ramachandran, S; Komura, S; Seki, K; Gompper, G

    2011-05-01

    We present a Brownian dynamics theory with full hydrodynamics (Stokesian dynamics) for a Gaussian polymer chain embedded in a liquid membrane which is surrounded by bulk solvent and walls. The mobility tensors are derived in Fourier space for the two geometries, namely, a free membrane embedded in a bulk fluid, and a membrane sandwiched by the two walls. Within the preaveraging approximation, a new expression for the diffusion coefficient of the polymer is obtained for the free-membrane geometry. We also carry out a Rouse normal mode analysis to obtain the relaxation time and the dynamical structure factor. For large polymer size, both quantities show Zimm-like behavior in the free-membrane case, whereas they are Rouse-like for the sandwiched membrane geometry. We use the scaling argument to discuss the effect of excluded-volume interactions on the polymer relaxation time. PMID:21562968

  9. Anomalous chain diffusion in polymer nanocomposites for varying polymer-filler interaction strengths

    Science.gov (United States)

    Goswami, Monojoy; Sumpter, Bobby G.

    2010-04-01

    Anomalous diffusion of polymer chains in a polymer nanocomposite melt is investigated for different polymer-nanoparticle interaction strengths using stochastic molecular dynamics simulations. For spherical nanoparticles dispersed in a polymer matrix the results indicate that the chain motion exhibits three distinct regions of diffusion, the Rouse-like motion, an intermediate subdiffusive regime followed by a normal Fickian diffusion. The motion of the chain end monomers shows a scaling that can be attributed to the formation of strong “networklike” structures, which have been seen in a variety of polymer nanocomposite systems. Irrespective of the polymer-particle interaction strengths, these three regimes seem to be present with small deviations. Further investigation on dynamic structure factor shows that the deviations simply exist due to the presence of strong enthalpic interactions between the monomers with the nanoparticles, albeit preserving the anomaly in the chain diffusion. The time-temperature superposition principle is also tested for this system and shows a striking resemblance with systems near glass transition and biological systems with molecular crowding. The universality class of the problem can be enormously important in understanding materials with strong affinity to form either a glass, a gel or networklike structures.

  10. Self-Assembly of Emulsion Droplets into Polymer Chains

    Science.gov (United States)

    Bargteil, Dylan; McMullen, Angus; Brujic, Jasna

    We experimentally investigate `beads-on-a-string' models of polymers using the spontaneous assembly of emulsion droplets into linear chains. Droplets functionalized with surface-mobile DNA allow for programmable 'monomers' through which we can influence the three-dimensional structure of the assembled 'polymer'. Such model polymers can be used to study conformational changes of polypeptides and the principles governing protein folding. In our system, we find that droplets bind via complementary DNA strands that are recruited into adhesion patches. Recruitment is driven by the DNA hybridization energy, and is limited by the energy cost of surface deformation and the entropy loss of the mobile linkers, yielding adhesion patches of a characteristic size with a given number of linkers. By tuning the initial surface coverage of linkers, we control valency between the droplets to create linear or branched polymer chains. We additionally control the flexibility of the model polymers by varying the salt concentration and study their dynamics between extended and collapsed states. This system opens the possibility of programming stable three-dimensional structures, such as those found within folded proteins.

  11. Unconventional phase transitions in a constrained single polymer chain

    Energy Technology Data Exchange (ETDEWEB)

    Klushin, L I [Department of Physics, American University of Beirut, PO Box 11-0236, Beirut 1107 2020 (Lebanon); Skvortsov, A M, E-mail: leo@aub.edu.lb, E-mail: astarling@yandex.ru [Chemical-Pharmaceutical Academy, Prof. Popova 14, 197022 St Petersburg (Russian Federation)

    2011-11-25

    Phase transitions were recognized among the most fascinating phenomena in physics. Exactly solved models are especially important in the theory of phase transitions. A number of exactly solved models of phase transitions in a single polymer chain are discussed in this review. These are three models demonstrating the second order phase transitions with some unusual features: two-dimensional model of {beta}-structure formation, the model of coil-globule transition and adsorption of a polymer chain grafted on the solid surface. We also discuss models with first order phase transitions in a single macromolecule which admit not only exact analytical solutions for the partition function with explicit finite-size effects but also the non-equilibrium free energy as a function of the order parameter (Landau function) in closed analytical form. One of them is a model of mechanical desorption of a macromolecule, which demonstrates an unusual first order phase transition with phase coexistence within a single chain. Features of first and second order transitions become mixed here due to phase coexistence which is not accompanied by additional interfacial free energy. Apart from that, there exist several single-chain models belonging to the same class (adsorption of a polymer chain tethered near the solid surface or liquid-liquid interface, and escape transition upon compressing a polymer between small pistons) that represent examples of a highly unconventional first order phase transition with several inter-related unusual features: no simultaneous phase coexistence, and hence no phase boundary, non-concave thermodynamic potential and non-equivalence of conjugate ensembles. An analysis of complex zeros of partition functions upon approaching the thermodynamic limit is presented for models with and without phase coexistence. (topical review)

  12. Conformational switching of modified guest chains in polymer brushes

    Science.gov (United States)

    Romeis, D.; Sommer, J.-U.

    2013-07-01

    Using a numerical quasi off-lattice self-consistent field method which describes heterogeneous chains of spherical monomers we study the case of a densely grafted polymer brush with a fraction of free chain ends being replaced by a modified end-group differing in size and solvent selectivity. We can confirm the observation from molecular dynamics simulations that upon changing the solvent conditions, a switching in location of end-groups which are bigger than monomers from a state "exposed" to the solvent (on the top of the brush) to a "hidden" state (inside the brush) takes place. Our numerical method allows a detailed study of the switching effect as a function of the relevant parameters, such as grafting density, chain length, size of end-groups and their volume fraction. We find that the switching effect is enhanced for long chains, low fractions of modified chains, and big end-groups. We consider the case of low fraction of modified chains in more detail using a test chain method. Here, we explore the optimal grafting density as a function of the size of the end-groups, where the switching is most sensitive. These values can be in the experimental range for end-groups which are at least 3-4 times bigger than the monomers. The end-groups can be realized by attaching nano-particles to the last monomer of a brush-chain.

  13. Adsorption-driven translocation of polymer chain into nanopores

    Science.gov (United States)

    Yang, Shuang; Neimark, Alexander V.

    2012-06-01

    The polymer translocation into nanopores is generally facilitated by external driving forces, such as electric or hydrodynamic fields, to compensate for entropic restrictions imposed by the confinement. We investigate the dynamics of translocation driven by polymer adsorption to the confining walls that is relevant to chromatographic separation of macromolecules. By using the self-consistent field theory, we study the passage of a chain trough a small opening from cis to trans compartments of spherical shape with adsorption potential applied in the trans compartment. The chain transfer is modeled as the Fokker-Plank diffusion along the free energy landscape of the translocation pass represented as a sum of the free energies of cis and trans parts of the chain tethered to the pore opening. We investigate how the chain length, the size of trans compartment, the magnitude of adsorption potential, and the extent of excluded volume interactions affect the translocation time and its distribution. Interplay of these factors brings about a variety of different translocation regimes. We show that excluded volume interactions within a certain range of adsorption potentials can cause a local minimum on the free energy landscape, which is absent for ideal chains. The adsorption potential always leads to the decrease of the free energy barrier, increasing the probability of successful translocation. However, the translocation time depends non-monotonically of the magnitude of adsorption potential. Our calculations predict the existence of the critical magnitude of adsorption potential, which separates favorable and unfavorable regimes of translocation.

  14. Communication: Polarizable polymer chain under external electric field in a dilute polymer solution

    International Nuclear Information System (INIS)

    We study the conformational behavior of polarizable polymer chain under an external homogeneous electric field within the Flory type self-consistent field theory. We consider the influence of electric field on the polymer coil as well as on the polymer globule. We show that when the polymer chain conformation is a coil, application of external electric field leads to its additional swelling. However, when the polymer conformation is a globule, a sufficiently strong field can induce a globule-coil transition. We show that such “field-induced” globule-coil transition at the sufficiently small monomer polarizabilities goes quite smoothly. On the contrary, when the monomer polarizability exceeds a certain threshold value, the globule-coil transition occurs as a dramatic expansion in the regime of first-order phase transition. The developed theoretical model can be applied to predicting polymer globule density change under external electric field in order to provide more efficient processes of polymer functionalization, such as sorption, dyeing, and chemical modification

  15. Communication: Polarizable polymer chain under external electric field in a dilute polymer solution

    Science.gov (United States)

    Budkov, Yu. A.; Kolesnikov, A. L.; Kiselev, M. G.

    2015-11-01

    We study the conformational behavior of polarizable polymer chain under an external homogeneous electric field within the Flory type self-consistent field theory. We consider the influence of electric field on the polymer coil as well as on the polymer globule. We show that when the polymer chain conformation is a coil, application of external electric field leads to its additional swelling. However, when the polymer conformation is a globule, a sufficiently strong field can induce a globule-coil transition. We show that such "field-induced" globule-coil transition at the sufficiently small monomer polarizabilities goes quite smoothly. On the contrary, when the monomer polarizability exceeds a certain threshold value, the globule-coil transition occurs as a dramatic expansion in the regime of first-order phase transition. The developed theoretical model can be applied to predicting polymer globule density change under external electric field in order to provide more efficient processes of polymer functionalization, such as sorption, dyeing, and chemical modification

  16. Supramolecular polymer assembly in aqueous solution arising from cyclodextrin host–guest complexation

    Science.gov (United States)

    Wang, Jie; Qiu, Zhiqiang; Wang, Yiming; Li, Li; Pham, Duc-Truc; Prud’homme, Robert K

    2016-01-01

    Summary The employment of cyclodextrin host–guest complexation to construct supramolecular assemblies with an emphasis on polymer networks is reviewed. The main driving force for this supramolecular assembly is host–guest complexation between cyclodextrin hosts and guest groups either of which may be discrete molecular species or substituents on a polymer backbone. The effects of such complexation on properties at the molecular and macroscopic levels are discussed. It is shown that cyclodextrin complexation may be used to design functional polymer materials with tailorable properties, especially for photo-, pH-, thermo- and redox-responsiveness and self-healing. PMID:26877808

  17. Supramolecular polymer assembly in aqueous solution arising from cyclodextrin host-guest complexation.

    Science.gov (United States)

    Wang, Jie; Qiu, Zhiqiang; Wang, Yiming; Li, Li; Guo, Xuhong; Pham, Duc-Truc; Lincoln, Stephen F; Prud'homme, Robert K

    2016-01-01

    The employment of cyclodextrin host-guest complexation to construct supramolecular assemblies with an emphasis on polymer networks is reviewed. The main driving force for this supramolecular assembly is host-guest complexation between cyclodextrin hosts and guest groups either of which may be discrete molecular species or substituents on a polymer backbone. The effects of such complexation on properties at the molecular and macroscopic levels are discussed. It is shown that cyclodextrin complexation may be used to design functional polymer materials with tailorable properties, especially for photo-, pH-, thermo- and redox-responsiveness and self-healing. PMID:26877808

  18. Supramolecular polymer assembly in aqueous solution arising from cyclodextrin host–guest complexation

    Directory of Open Access Journals (Sweden)

    Jie Wang

    2016-01-01

    Full Text Available The employment of cyclodextrin host–guest complexation to construct supramolecular assemblies with an emphasis on polymer networks is reviewed. The main driving force for this supramolecular assembly is host–guest complexation between cyclodextrin hosts and guest groups either of which may be discrete molecular species or substituents on a polymer backbone. The effects of such complexation on properties at the molecular and macroscopic levels are discussed. It is shown that cyclodextrin complexation may be used to design functional polymer materials with tailorable properties, especially for photo-, pH-, thermo- and redox-responsiveness and self-healing.

  19. Charge photogeneration and transport in side-chain carbazole polymers and co-polymers

    KAUST Repository

    Li, Huawei

    2011-07-01

    The photoconductivity, hole mobility and charge photogeneration efficiency of a series of side-chain carbazole homopolymers and copolymers (with azo side-chains) have been investigated. Cyclic voltammetry measurement of frontier orbitals energies show that the HOMO energy is determined by the nature and the position of attachment of the linker between the main chain and the carbazole, the azo-moiety being not relevant in this respect. Hole mobility is not influenced by the HOMO energy but seems to depend on the degree of conformational mobility of the side-chains, reaching values of the order of 10-3cm2V-1s-1 in the best cases. The HOMO energy is instead extremely important when considering photogeneration efficiency, that can change by 10 orders of magnitude depending on the density of the carbazole side-chains in co-polymers and on the linker nature and attachment position. © 2011 Elsevier B.V. All rights reserved.

  20. SANS study of polymer chains in confined space

    International Nuclear Information System (INIS)

    The lateral and vertical components of the radius of gyration for a single block copolymer chain in the lamellar microdomain space formed by a mixture of diblock copolymers and homopolymers were investigated by means of small-angle neutron scattering (SANS), and the microdomain structures by small-angle X-ray scattering (SAXS). We used the homopolymers whose molecular weights are much smaller than that of the corresponding chains of the block copolymers so that the homopolymers are uniformly solubilized in the corresponding microdomains. The SANS result suggests that the block copolymer chains in the microdomain space are more compressed in the direction parallel to the interface and more stretched in the direction perpendicular to the interface than the corresponding unperturbed polymer chains with the same molecular weight. With increasing the volume fraction of the homopolymers the thickness of the lamellar microdomains increases. The block copolymer chains were found to undergo an isochoric affine deformation on addition of the homopolymers or with the change of the thickness of the lamellar microdomains. (author)

  1. Finite cohesion due to chain entanglement in polymer melts.

    Science.gov (United States)

    Cheng, Shiwang; Lu, Yuyuan; Liu, Gengxin; Wang, Shi-Qing

    2016-04-14

    Three different types of experiments, quiescent stress relaxation, delayed rate-switching during stress relaxation, and elastic recovery after step strain, are carried out in this work to elucidate the existence of a finite cohesion barrier against free chain retraction in entangled polymers. Our experiments show that there is little hastened stress relaxation from step-wise shear up to γ = 0.7 and step-wise extension up to the stretching ratio λ = 1.5 at any time before or after the Rouse time. In contrast, a noticeable stress drop stemming from the built-in barrier-free chain retraction is predicted using the GLaMM model. In other words, the experiment reveals a threshold magnitude of step-wise deformation below which the stress relaxation follows identical dynamics whereas the GLaMM or Doi-Edwards model indicates a monotonic acceleration of the stress relaxation dynamics as a function of the magnitude of the step-wise deformation. Furthermore, a sudden application of startup extension during different stages of stress relaxation after a step-wise extension, i.e. the delayed rate-switching experiment, shows that the geometric condensation of entanglement strands in the cross-sectional area survives beyond the reptation time τd that is over 100 times the Rouse time τR. Our results point to the existence of a cohesion barrier that can prevent free chain retraction upon moderate deformation in well-entangled polymer melts. PMID:26931322

  2. Star/linear polymer topology transformation facilitated by mechanical linking of polymer chains.

    Science.gov (United States)

    Aoki, Daisuke; Uchida, Satoshi; Takata, Toshikazu

    2015-06-01

    Topology transformation of a star polymer to a linear polymer is demonstrated for the first time. A three-armed star polymer possessing a mechanical linking of two polymer chains was synthesized by the living ring-opening polymerization of δ-valerolactone initiated by a pseudo[2]rotaxane having three hydroxy groups as the initiator sites on the wheel component and at both axle termini. The polymerization was followed by the propagation end-capping reaction with a bulky isocyanate not only to prevent the wheel component deslippage but also to introduce the urethane moiety at the axle terminal. The resulting rotaxane-linked star polymer with a fixed rotaxane linkage based on the ammonium/crown ether interaction was subjected to N-acetylation of the ammonium moiety, which liberated the components from the interaction to move the wheel component to the urethane terminal as the interaction site, eventually affording the linear polymer. The physical property change caused by the present topology transformation was confirmed by the hydrodynamic volume and viscosity. PMID:25892579

  3. MORPHOLOGICAL STUDIES OF A THERMOTROPIC SIDE-CHAIN LIQUID CRYSTALLINE POLYMER DURING MESOPHASE TRANSITIONS

    Institute of Scientific and Technical Information of China (English)

    Chi-bing Tan; Quan-ling Zhang; Shu-fan Zhang; Xia-yu Wang; Mao Xu

    1999-01-01

    The morphological features of a side-chain liquid crystalline polymer during the mesophase transitions were investigated by using the DSC technique. The polymer used was polyacrylate with mesogens of three benzene rings attached to the main chain through a flexible spacer. A special two-phase texture was observed in the transition temperature range. Similar to main-chain liquid crystalline polymers the transition process of the side-chain liquid crystalline polymer was composed of an initiation of the new phase at local places of the old phase matrix and a growth process of the new phase domains.

  4. COMPUTER SIMULATION OF A SINGLE POLYMER CHAIN IN DIFFERENT SOLVENTS

    Institute of Scientific and Technical Information of China (English)

    Yue-li Zheng; Rong Chen; De-lu Zhao; Da-cheng Wu

    2002-01-01

    In the present paper, the behavior of a single polymer chain under various solvent conditions was modeled by self-avoiding walks (SAW) with nearest neighbors attraction △ε on a simple cubic lattice. Determination of the θ-condition was based on the numerical results of the mean square radius of gyration and end-to-end distance. It was found that at the θtemperature △ε/kT equals -0.27. The exponents α in the Mark-Houwink equation with different interaction parameters are consistent with the results of experiments: under θ-condition, α= 0.5, and for a good solvent α = 0.74-0.84, respectively.

  5. High Performance All-Polymer Solar Cell via Polymer Side-Chain Engineering

    KAUST Repository

    Zhou, Yan

    2014-03-24

    An average PCE of 4.2% for all-polymer solar cells from 20 devices with an average J SC of 8.8 mA cm-2 are obtained with a donor-acceptor pair despite a low LUMO-LUMO energy offset of less than 0.1 eV. Incorporation of polystyrene side chains into the donor polymer is found to assist in reducing the phase separation domain length scale, and results in more than 20% enhancement of PCE. We observe a direct correlation between the short circuit current (J SC) and the length scale of BHJ phase separation, which is obtained by resonance soft X-ray scattering. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Improved power conversion efficiency of dye-sensitized solar cells using side chain liquid crystal polymer embedded in polymer electrolytes

    International Nuclear Information System (INIS)

    Side chain liquid crystal polymer (SCLCP) embedded in poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF-co-HFP)-based polymer electrolytes (PVdF-co-HFP:side chain liquid crystal polymer (SCLCP)) was prepared for dye-sensitized solar cell (DSSC) application. The polymer electrolytes contained tetrabutylammonium iodide (TBAI), iodine (I2), and 8 wt% PVdF-co-HFP in acetonitrile. DSSCs comprised of PVdF-co-HFP:SCLCP-based polymer electrolytes displayed enhanced redox couple reduction and reduced charge recombination in comparison to those of the conventional PVdF-co-HFP-based polymer electrolyte. The significantly increased short-circuit current density (Jsc, 10.75 mA cm−2) of the DSSCs with PVdF-co-HFP:SCLCP-based polymer electrolytes afforded a high power conversion efficiency (PCE) of 5.32% and a fill factor (FF) of 0.64 under standard light intensity of 100 mW cm−2 irradiation of AM 1.5 sunlight. - Highlights: • We developed the liquid crystal polymer embedded on polymer electrolyte for DSSCs. • We fabricated the highly efficient DSSCs using polymer electrolyte. • The best PCE achieved for P1 is 5.32% using polymer electrolyte

  7. Effects of nanostructure geometry on polymer chain alignment and device performance in nanoimprinted polymer solar cell

    Science.gov (United States)

    Yang, Yi; Mielczarek, Kamil; Zakhidov, Anvar; Hu, Walter

    2013-03-01

    Among the various organic photovoltaic devices, the conjugated polymer/fullerene approach has drawn the most research interest. The performance of these types of solar cells is greatly determined by the nanoscale morphology of the two components (donor/acceptor) and the molecular orientation/crystallinity in the photoactive layer. This article demonstrates our recent studies on the nanostructure geometry effects on the nanoimprint induced poly(3 hexylthiophene-2,5-diyl) (P3HT) chain alignment and photovoltaic performance. Out-of-plane and in-plane grazing incident X-ray diffractions are employed to characterize the chain orientations in P3HT nanogratings with different widths and heights. It is found that nanoimprint procedure changes the initial edge-on alignment in non-imprinted P3HT thin film to a vertical orientation which favors the hole transport, with an organization height H≥ 170 nm and width in the range of 60 nmcells show an increase in power conversion efficiency (PCE) with the decrease of nanostructure width, and with the increase of height and junction area. Devices with the highest PCE are made by the fully aligned and highest P3HT nanostructures (width w= 60 nm, height h= 170 nm), allowing for the most efficient charge separation, transport and light absorption. We believe this work will contribute to the optimal geometry design of nanoimprinted polymer solar cells.

  8. Stabilization of nanorods in polymer melts by end-adsorbed chains

    Science.gov (United States)

    Frischknecht, Amalie L.

    2007-03-01

    Adsorbed or grafted polymers are often used to provide steric stabilization of colloidal particles. When the particle size approaches the nanoscale, the curvature of the particles becomes relevant, and rules of thumb based on the behavior of polymers attached to flat surfaces may no longer apply. To investigate this effect for the case of cylindrical symmetry, I use a classical density functional theory applied to a coarse-grained model to study the polymer-mediated interactions between two nanorods. The rods are immersed in a polymer melt consisting of two kinds of chains: 1) a small fraction of chains of length N with ends that are attracted to the rods so that they form a polymer brush on the rods; and 2) a matrix of chains of length P which have no interactions with the rods. Calculations of the density profiles and potential of mean force reveal the effects of curvature compared to similar calculations for chains adsorbed to flat planar surfaces.

  9. Molecular dynamics simulations of the adsorption of polymer chains on graphyne and its family

    International Nuclear Information System (INIS)

    Molecular dynamics simulations are used to study the adsorption of polypropylene chains on the graphene, graphyne and its family. The effects of nanosheet side length, aspect ratio, temperature and number of repeat units are studied. It is shown that the nanosheets with more acetylene bonds have weaker bonding with polymer chains. Besides, the effects of side length and aspect ratio variation on the polymer/graphene interactions are lower than that of polymer/other studied nanosheet. Investigating the effect of temperature on the polypropylene/nanosheet interactions, it is shown that adsorption of polymer chain on the graphyne and its family is approximately independent of temperature. Moreover, it is seen that due to uniform structure of graphene, polymer chains with different repeat units are adsorbed on its surface by uniform shapes

  10. Shear Flow Induced Transition from Liquid-Crystalline to Polymer Behavior in Side-Chain Liquid Crystal Polymers

    Science.gov (United States)

    Noirez, L.; Lapp, A.

    1997-01-01

    We determine the structure and conformation of side-chain liquid-crystalline polymers subjected to shear flow in the vicinity of the smectic phase by neutron scattering on the velocity gradient plane. Below the nematic-smectic transition we observe a typical liquid-crystal behavior; the smectic layers slide, leading to a main-chain elongation parallel to the velocity direction. In contrast, a shear applied above the transition induces a tilted main-chain conformation which is typical for polymer behavior.

  11. Amphiphilic Polymer Micellar Disruption Based on Main-Chain Photodegradation.

    Science.gov (United States)

    Tian, Min; Cheng, Ruidong; Zhang, Jun; Liu, Zhaotie; Liu, Zhongwen; Jiang, Jinqiang

    2016-01-12

    The amphiphilic block copolymer poly(ethylene oxide)-b-poly(N,N'-dihydroxypyromellitimide-hexamethylene diisocyanate) (PEO-b-PNH) with photocleavable N-O urethanes has been prepared to investigate the photodegradation of the hydrophobic main chain and therefore the disruption of copolymer micelles. Measurements of absorption and emission spectra, optical transmittance, DLS analysis, and TEM observations were applied. It was shown that PEO-b-PNH could self-assemble into flower compound micelles in water. The photodegradation of the hydrophobic polyurethane within the micellar core upon irradiation with 365 nm light could be conveniently controlled by changing the irradiation intensity; furthermore, complete micellar disruption could be achieved when 42% of N-O urethanes were photocleaved. By using DOX as the hydrophobic guest, the drug release profile showed a linear leakage of DOX out of the swelling polymer micelles in the initial stage and thereafter a much more quick exponential decay of DOX precipitation because of the micellar disruption upon further irradiation. The diffusion experiment of the leaked DOX into buffer solution (pH 7.4) showed that the DOX leakage could be prominently accelerated by a very short time of 365 nm irradiation, indicating that the N-O photocleavage can serve as a "turn-on" switch for the release of DOX in aqueous media. PMID:26641733

  12. Grafted polymers layers: neutral chains to charged chains; Couches de polymeres greffes: des chaines neutres aux chaines chargees

    Energy Technology Data Exchange (ETDEWEB)

    Mir, Y.

    1995-09-29

    This work concerns an experimental study, by small angle neutrons scattering, of neutral or charged grafted polymers layers structures. The method consisted in exploiting the acknowledges got on neutral brushes, to reach the problem of grafted polyelectrolyte layers. The difficulty of charged layers making has been, until this day, an important obstacle to the experimental study of these systems. It has been partially resolved in the case of sodium sulfonate polystyrene layers, and allowed to study their structure. (N.C.). 72 refs., 74 figs., 24 tabs.

  13. A flexible polymer chain in a critical solvent: Coil or globule?

    Science.gov (United States)

    Budkov, Yu. A.; Kolesnikov, A. L.; Georgi, N.; Kiselev, M. G.

    2015-02-01

    We study the behavior of a flexible polymer chain in the presence of a low-molecular weight solvent in the vicinity of a liquid-gas critical point within the framework of a self-consistent field theory. The total free energy of the dilute polymer solution is expressed as a function of the radius of gyration of the polymer and the average solvent number density within the gyration volume at the level of the mean-field approximation. Varying the strength of attraction between polymer and solvent we show that two qualitatively different regimes occur at the liquid-gas critical point. In case of weak polymer-solvent interactions the polymer chain is in a globular state. On the contrary, in case of strong polymer-solvent interactions the polymer chain attains an expanded conformation. We discuss the influence of the critical solvent density fluctuations on the polymer conformation. The reported effect could be used to excert control on the polymer conformation by changing the thermodynamic state of the solvent. It could also be helpful to estimate the solvent density within the gyration volume of the polymer for drug delivery and molecular imprinting applications.

  14. Single-molecule study on polymer diffusion in a melt state: Effect of chain topology

    KAUST Repository

    Habuchi, Satoshi

    2013-08-06

    We report a new methodology for studying diffusion of individual polymer chains in a melt state, with special emphasis on the effect of chain topology. A perylene diimide fluorophore was incorporated into the linear and cyclic poly(THF)s, and real-time diffusion behavior of individual chains in a melt of linear poly(THF) was measured by means of a single-molecule fluorescence imaging technique. The combination of mean squared displacement (MSD) and cumulative distribution function (CDF) analysis demonstrated the broad distribution of diffusion coefficient of both the linear and cyclic polymer chains in the melt state. This indicates the presence of spatiotemporal heterogeneity of the polymer diffusion which occurs at much larger time and length scales than those expected from the current polymer physics theory. We further demonstrated that the cyclic chains showed marginally slower diffusion in comparison with the linear counterparts, to suggest the effective suppression of the translocation through the threading-entanglement with the linear matrix chains. This coincides with the higher activation energy for the diffusion of the cyclic chains than of the linear chains. These results suggest that the single-molecule imaging technique provides a powerful tool to analyze complicated polymer dynamics and contributes to the molecular level understanding of the chain interaction. © 2013 American Chemical Society.

  15. Conjugated polymers containing diketopyrrolopyrrole units in the main chain

    OpenAIRE

    Bernd Tieke; A. Raman Rabindranath; Kai Zhang; Yu Zhu

    2010-01-01

    Research activities in the field of diketopyrrolopyrrole (DPP)-based polymers are reviewed. Synthetic pathways to monomers and polymers, and the characteristic properties of the polymers are described. Potential applications in the field of organic electronic materials such as light emitting diodes, organic solar cells and organic field effect transistors are discussed.

  16. Fuel cell membrane materials by chemical grafting of aromatic main-chain polymers

    Energy Technology Data Exchange (ETDEWEB)

    Jannasch, P. [Department of Polymer Science and Engineering, Lund University, P.O. Box 124, SE-221 00 Lund (Sweden)

    2005-04-01

    An extensive world-wide pursuit for new efficient fuel cell membranes materials is currently motivating research on proton-conducting ionomers based on durable aromatic main-chain polymers. In this context, most ionomers have been prepared either by direct sulfonation of polymers, using for example fuming sulfuric acid, or by direct polymerizations using different sulfonated monomers. Far less exploited are chemical grafting reactions carried out to introduce sulfonic acid units, or alternative acidic units, directly on the polymer main-chain, or on side-chains to the polymer main-chain. This versatile method offers very interesting possibilities, not only to control the degree and the site of sulfonation, but also when it comes to manipulating the molecular mobility of the sulfonic acid units and their distance from the polymer main-chain. The length and nature of the grafted units have shown to have a large influence on for example the water-uptake characteristics and conductivity of ionomer membranes, especially at temperatures above 100 C. Grafting can also be used to introduce other useful functions to the polymers, or to crosslink membranes. This paper reviews various grafting reactions carried out on aromatic main-chain polymers, especially polybenzimidazoles and polysulfones, to prepare membrane materials, as well as the characteristics of these materials regarding their use in fuel cells. (Abstract Copyright [2005], Wiley Periodicals, Inc.)

  17. Record high hole mobility in polymer semiconductors via side-chain engineering.

    Science.gov (United States)

    Kang, Il; Yun, Hui-Jun; Chung, Dae Sung; Kwon, Soon-Ki; Kim, Yun-Hi

    2013-10-01

    Charge carrier mobility is still the most challenging issue that should be overcome to realize everyday organic electronics in the near future. In this Communication, we show that introducing smart side-chain engineering to polymer semiconductors can facilitate intermolecular electronic communication. Two new polymers, P-29-DPPDBTE and P-29-DPPDTSE, which consist of a highly conductive diketopyrrolopyrrole backbone and an extended branching-position-adjusted side chain, showed unprecedented record high hole mobility of 12 cm(2)/(V·s). From photophysical and structural studies, we found that moving the branching position of the side chain away from the backbone of these polymers resulted in increased intermolecular interactions with extremely short π-π stacking distances, without compromising solubility of the polymers. As a result, high hole mobility could be achieved even in devices fabricated using the polymers at room temperature. PMID:24053786

  18. DIGITAL ANALYSIS TECHNOLOGY FOR MORPHOLOGY OF POLYMER CHAIN COILS IN FLOW FIELDS

    Institute of Scientific and Technical Information of China (English)

    Chi-xing Zhou; Hong Zheng; Wei Yu; Ji-feng Yao; Yu-cheng Li

    2005-01-01

    Polymer chain coils with entanglement is a crucial scale of structures in polymer materials since their relaxation times are matching practical processing times. Based on the phenomenological model of polymer chain coils and a new finite element approach, we have designed a computer software including solver, pre- and post-processing modules, and developed a digital analysis technology for the morphology of polymer chain coils in flow fields (DAMPC). Using this technology we may simulate the morphology development of chain coils in various flow fields, such as simple shear flow, elongational flow,and any complex flow at transient or steady state. The applications made up to now show that the software predictions are comparable with experimental results.

  19. Molecularly imprinted polymers with assistant recognition polymer chains for bovine serum albumin

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    A new protein molecularly imprinted polymer (MIP) was prepared with grafting polyvinyl alcohol as assistant recognition polymer chains (ARPCs). The ARPCs and acrylamide monomers were interpenetrated and then polymerized on the surface of macroporous acrylate adsorbent spheres. The template BSA was removed by treatment with 2.00 mol L-1 potassium chloride (KCl) solution and the adsorbed proteins were detected with sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). 0.150, 0.500, and 2.00 mol L-1 KCl solutions were used as eluent to wash the adsorbed proteins. The SDS-PAGE results show that proteins washed out with 2.00 mol L-1KCl solution were from nonspecific adsorption of macroporous acrylate adsorbent spheres, and proteins washed out with 0.500 mol L-1KC1 solution were specific proteins imprinted by MIP resins. MIP resins with ARPCs had better recognition to the target proteins than that without ARPCs. The adsorption capacity of MIP resins immobilized ARPCs to the template BSA was about 80-100 μg g-1 when it was used for the adsorption of proteins mixture, and the specific adsorption of the target protein was obviously increased.

  20. Effect of chain architecture on the size, shape, and intrinsic viscosity of chains in polymer solutions: A molecular simulation study

    Science.gov (United States)

    Khabaz, Fardin; Khare, Rajesh

    2014-12-01

    Effect of chain architecture on the chain size, shape, and intrinsic viscosity was investigated by performing molecular dynamics simulations of polymer solutions in a good solvent. Four types of chains - linear, comb shaped, H-shaped, and star - were studied for this purpose using a model in which the solvent particles were considered explicitly. Results indicated that the chain length (N) dependence of the mean squared radius of gyration of the chains followed a power-law behavior intrinsic viscosity of the chains can be calculated by plotting the specific viscosity determined from simulations against the solution concentration. The intrinsic viscosity exhibited linear behavior with the reciprocal of the overlap concentration for all chain architectures studied. The molecular weight dependence of the intrinsic viscosity followed the Mark-Houwink relation, [η] = KMa, for all chain architectures. When comparing the calculated values of exponent a with the literature experimental values, agreement was found only for the H and star chains, and a disagreement for the linear and comb chains. The viscosity shrinking factor of the branched chains was compared with the available experimental data and the theoretical predictions and a general agreement was found.

  1. Synthesis of Main-Chain Chiral Quaternary Ammonium Polymers for Asymmetric Catalysis Using Quaternization Polymerization

    Directory of Open Access Journals (Sweden)

    Md. Masud Parvez

    2012-06-01

    Full Text Available Main-chain chiral quaternary ammonium polymers were successfully synthesized by the quaternization polymerization of cinchonidine dimer with dihalides. The polymerization occurred smoothly under optimized conditions to give novel type of main-chain chiral quaternary ammonium polymers. The catalytic activity of the polymeric chiral organocatalysts was investigated on the asymmetric benzylation of N-(diphenylmethylideneglycine tert-butyl ester.

  2. Local and chain dynamics in miscible polymer blends: A Monte Carlo simulation study

    OpenAIRE

    Luettmer-Strathmann, Jutta; Mantina, Manjeera

    2005-01-01

    Local chain structure and local environment play an important role in the dynamics of polymer chains in miscible blends. In general, the friction coefficients that describe the segmental dynamics of the two components in a blend differ from each other and from those of the pure melts. In this work, we investigate polymer blend dynamics with Monte Carlo simulations of a generalized bond-fluctuation model, where differences in the interaction energies between non-bonded nearest neighbors distin...

  3. Direct small angle neutron scattering observation of stretched chain conformation in nanocomposites: more insight of polymer contributions in mechanical reinforcement

    OpenAIRE

    Jouault, Nicolas; Dalmas, Florent; Said, Sylvère; Di Cola, Emanuela; Schweins, Ralf; Jestin, Jacques; Boué, François

    2010-01-01

    In this paper we present a direct measurement of stretched chain conformation in polymer nanocomposites in a large range of deformation using a specific contrast-matched SANS method. Whatever the filler structure and the chain length the results show a clear identity of chain deformation in pure and reinforced polymer and offer a new insight of the polymer chain contribution in the mechanical reinforcement. It suggests that glassy layer or glassy paths, recently proposed, should involve only ...

  4. Responsive behavior of 4-(N-maleimido)azobenzene in polymers with aromatic main chain and side chain linked units

    Energy Technology Data Exchange (ETDEWEB)

    Airinei, Anton; Rusu, Elena; Barboiu, Virgil, E-mail: airineia@icmpp.r [Romanian Academy, Iasi (Romania). Petru Poni Institute of Macromolecular Chemistry

    2010-07-01

    Polymer matrices with aromatic main chain and side chain linked units (polystyrene, polysulfone) were employed to construct thin films containing maleimidoazobenzene molecules in order to develop new materials with responsive properties. The photochromic behavior of the active compound was studied both in the solid and solution state for comparison. The thermal cis-trans isomerization of azobenzene chromophores in polymer films follows two different kinetic pathways. A double-exponential relaxation process (fast and slow) took place in polystyrene matrix under 70 deg C while the thermal isomerization at 70 deg C and higher follows a first-order kinetics. The cis isomer content corresponding to the photostationary state was found to be lower in polymer films than in solution. (author)

  5. Prediction of Solution Properties of Flexible-Chain Polymers: A Computer Simulation Undergraduate Experiment

    Science.gov (United States)

    de la Torre, Jose Garcia; Cifre, Jose G. Hernandez; Martinez, M. Carmen Lopez

    2008-01-01

    This paper describes a computational exercise at undergraduate level that demonstrates the employment of Monte Carlo simulation to study the conformational statistics of flexible polymer chains, and to predict solution properties. Three simple chain models, including excluded volume interactions, have been implemented in a public-domain computer…

  6. Experimental studies of the dynamic mechanical response of a single polymer chain

    DEFF Research Database (Denmark)

    Thormann, Esben; Evans, Drew R.; Craig, Vincent S. J.

    2006-01-01

    The high-frequency and low-amplitude dynamic mechanical response from a single poly(vinyl alcohol) chain was investigated. Modification of a commercial atomic force microscope enabled high-frequency and low-amplitude periodic deformations of polymer chains during extension to be performed. Such an...... mechanical response from poly(vinyl alcohol) does not differ from its static response. This result is not unexpected as poly(vinyl alcohol) is a highly flexible polymer with intramolecular relaxation processes taking place on a short time scale. The choice of a polymer with a fast relaxation allows its...

  7. A semiflexible polymer chain under geometrical restrictions: Only bulk behaviour and no surface adsorption

    Directory of Open Access Journals (Sweden)

    P.K. Mishra

    2014-06-01

    Full Text Available We analyse the conformational behaviour of a linear semiflexible homo-polymer chain confined by two geometrical constraints under a good solvent condition in two dimensions. The constraints are stair shaped impenetrable surfaces. The impenetrable surfaces are lines in a two dimensional space. The infinitely long polymer chain is confined in between such two (A and B surfaces. A lattice model of a fully directed self-avoiding walk is used to calculate the exact expression of the partition function, when the chain has attractive interaction with one or both the constraints. It has been found that under the proposed model, the chain shows only a bulk behaviour. In other words, there is no possibility of adsorption of the chain due to restrictions imposed on the walks of the chain.

  8. Lattice model of linear telechelic polymer melts. II. Influence of chain stiffness on basic thermodynamic properties

    International Nuclear Information System (INIS)

    The lattice cluster theory (LCT) for semiflexible linear telechelic melts, developed in Paper I, is applied to examine the influence of chain stiffness on the average degree of self-assembly and the basic thermodynamic properties of linear telechelic polymer melts. Our calculations imply that chain stiffness promotes self-assembly of linear telechelic polymer melts that assemble on cooling when either polymer volume fraction ϕ or temperature T is high, but opposes self-assembly when both ϕ and T are sufficiently low. This allows us to identify a boundary line in the ϕ-T plane that separates two regions of qualitatively different influence of chain stiffness on self-assembly. The enthalpy and entropy of self-assembly are usually treated as adjustable parameters in classical Flory-Huggins type theories for the equilibrium self-assembly of polymers, but they are demonstrated here to strongly depend on chain stiffness. Moreover, illustrative calculations for the dependence of the entropy density of linear telechelic polymer melts on chain stiffness demonstrate the importance of including semiflexibility within the LCT when exploring the nature of glass formation in models of linear telechelic polymer melts

  9. When does TMAO fold a polymer chain and urea unfold it?

    CERN Document Server

    Mondal, Jagannath; Berne, B J

    2013-01-01

    Longstanding mechanistic questions about the role of protecting osmolyte trimethylamine N- oxide (TMAO) which favors protein folding and the denaturing osmolyte urea are addressed by studying their effects on the folding of uncharged polymer chains. Using atomistic molecular dynamics simulations, we show that 1-M TMAO and 7-M urea solutions act dramatically differently on these model polymer chains. Their behaviors are sensitive to the strength of the attractive dispersion interactions of the chain with its environment: when these dispersion interactions are high enough, TMAO suppresses the formation of extended conformations of the hydrophobic polymer as compared to water, while urea promotes formation of extended conformations. Similar trends are observed experimentally on real protein systems. Quite surprisingly, we find that both protecting and denaturing osmolytes strongly interact with the polymer, seemingly in contrast with existing explanations of the osmolyte effect on proteins. We show that what rea...

  10. Single chain diffusion process and proton magnetic relaxation in polymer melts

    OpenAIRE

    Cohen-Addad, J.P.

    1982-01-01

    The present work aims at connecting properties of the quantum coherence of proton magnetic moments linked to strongly entangled polymer chains to low frequency dynamical properties of polymeric liquids. Theoretical and experimental results giving evidence for the presence of a residual tensorial spin coupling induced by chain confinement or crosslinks are commented by using a freely jointed chain model where every link is supposed to carry a proton pair. The submolecule concept is applied. Du...

  11. Restrictions in Model Reduction for Polymer Chain Models in Dissipative Particle Dynamics

    KAUST Repository

    Moreno, Nicolas

    2014-06-06

    We model high molecular weight homopolymers in semidilute concentration via Dissipative Particle Dynamics (DPD). We show that in model reduction methodologies for polymers it is not enough to preserve system properties (i.e., density ρ, pressure p, temperature T, radial distribution function g(r)) but preserving also the characteristic shape and length scale of the polymer chain model is necessary. In this work we apply a DPD-model-reduction methodology for linear polymers recently proposed; and demonstrate why the applicability of this methodology is limited upto certain maximum polymer length, and not suitable for solvent coarse graining.

  12. State of mixing of deuterated and non-deuterated block polymer chains

    International Nuclear Information System (INIS)

    Prior to the small-angle neutron scattering study on the conformation of block polymer chains in the domain space, the state of mixing of two block polymers, an ordinary polystyrene-polyisoprene diblock polymer and a poly(deuterated styrene)-polyisoprene diblock polymer with a different molecular weight and composition, was investigated by a small-angle X-ray scattering (SAXS) technique. Only one kind of domain structure was observed for each blend, and the domain spacings obtained by SAXS were proportional to the two-thirds power of the number-average molecular weight of the blends (reduced to non-deuterated block polymer). The volume fractions of polystyrene domain in the blends evaluated by computer simulation of SAXS profiles well agreed with the values estimated from blend composition. All these facts suggest the molecular mixing of the two block polymers in the domain space. (author)

  13. Scattering function of semiflexible polymer chains under good solvent conditions.

    Science.gov (United States)

    Hsu, Hsiao-Ping; Paul, Wolfgang; Binder, Kurt

    2012-11-01

    Using the pruned-enriched Rosenbluth Monte Carlo algorithm, the scattering functions of semiflexible macromolecules in dilute solution under good solvent conditions are estimated both in d = 2 and d = 3 dimensions, considering also the effect of stretching forces. Using self-avoiding walks of up to N = 25,600 steps on the square and simple cubic lattices, variable chain stiffness is modeled by introducing an energy penalty ε(b) for chain bending; varying q(b) = exp (-ε(b)∕k(B)T) from q(b) = 1 (completely flexible chains) to q(b) = 0.005, the persistence length can be varied over two orders of magnitude. For unstretched semiflexible chains, we test the applicability of the Kratky-Porod worm-like chain model to describe the scattering function and discuss methods for extracting persistence length estimates from scattering. While in d = 2 the direct crossover from rod-like chains to self-avoiding walks invalidates the Kratky-Porod description, it holds in d = 3 for stiff chains if the number of Kuhn segments n(K) does not exceed a limiting value n(K)(*) (which depends on the persistence length). For stretched chains, the Pincus blob size enters as a further characteristic length scale. The anisotropy of the scattering is well described by the modified Debye function, if the actual observed chain extension (end-to-end distance in the direction of the force) as well as the corresponding longitudinal and transverse linear dimensions - (2), are used. PMID:23145745

  14. Mechanisms of chain adsorption on porous substrates and critical conditions of polymer chromatography.

    Science.gov (United States)

    Cimino, Richard T; Rasmussen, Christopher J; Brun, Yefim; Neimark, Alexander V

    2016-11-01

    Polymer adsorption is a ubiquitous phenomenon with numerous technological and healthcare applications. The mechanisms of polymer adsorption on surfaces and in pores are complex owing to a competition between various entropic and enthalpic factors. Due to adsorption of monomers to the surface, the chain gains in enthalpy yet loses in entropy because of confining effects. This competition leads to the existence of critical conditions of adsorption when enthalpy gain and entropy loss are in balance. The critical conditions are controlled by the confining geometry and effective adsorption energy, which depends on the solvent composition and temperature. This phenomenon has important implications in polymer chromatography, since the retention at the critical point of adsorption (CPA) is chain length independent. However, the mechanisms of polymer adsorption in pores are poorly understood and there is an ongoing discussion in the theoretical literature about the very existence of CPA for polymer adsorption on porous substrates. In this work, we examine the mechanisms of chain adsorption on a model porous substrate using Monte Carlo (MC) simulations. We distinguish three adsorption mechanisms depending on the chain location: on external surface, completely confined in pores, and also partially confined in pores in so-called "flower" conformations. The free energies of different conformations of adsorbed chains are calculated by the incremental gauge cell MC method that allows one to determine the partition coefficient as a function of the adsorption potential, pore size, and chain length. We confirm the existence of the CPA for chain length independent separation on porous substrates, which is explained by the dominant contributions of the chain adsorption at the external surface, in particular in flower conformations. Moreover, we show that the critical conditions for porous and nonporous substrates are identical and depend only on the surface chemistry. The theoretical

  15. Water Sorption and Hindered Diffusion with Different Chain Stiffness of Superabsorbent Polymer

    International Nuclear Information System (INIS)

    Water sorption and diffusion are essential physicochemical properties of a high-performance superabsorbent polymer (SAP). We combine the Park model with the obstruction-scaling model and the water clustering in confined spaces of the polymer hydrogel. Special attention is focused on elucidating the effect of chain stiffness by considering the conformation of the polymer chain. Theoretical model parameters are determined from the best fits by simultaneous nonlinear regressions for both sorption and corrected diffusion data based on previous experiments with poly(acrylamide-co-sodium acrylate) hydrogel. Predictions show that the hindered water diffusivity leads to a sigmoid curve with relative humidity aw, where it increases monotonically up to aw≅ 0.6 due to the swelling but decreases at higher aw caused by water clustering. Water diffusion decreases with increasing chain stiffness, and the larger persistence length provides a smaller opening radius in void spaces regarding the weak elastic deformation of hydrogel under the applied stress

  16. Primitive-path statistics of entangled polymers: mapping multi-chain simulations onto single-chain mean-field models

    Science.gov (United States)

    Steenbakkers, Rudi J. A.; Tzoumanekas, Christos; Li, Ying; Liu, Wing Kam; Kröger, Martin; Schieber, Jay D.

    2014-01-01

    We present a method to map the full equilibrium distribution of the primitive-path (PP) length, obtained from multi-chain simulations of polymer melts, onto a single-chain mean-field ‘target’ model. Most previous works used the Doi-Edwards tube model as a target. However, the average number of monomers per PP segment, obtained from multi-chain PP networks, has consistently shown a discrepancy of a factor of two with respect to tube-model estimates. Part of the problem is that the tube model neglects fluctuations in the lengths of PP segments, the number of entanglements per chain and the distribution of monomers among PP segments, while all these fluctuations are observed in multi-chain simulations. Here we use a recently proposed slip-link model, which includes fluctuations in all these variables as well as in the spatial positions of the entanglements. This turns out to be essential to obtain qualitative and quantitative agreement with the equilibrium PP-length distribution obtained from multi-chain simulations. By fitting this distribution, we are able to determine two of the three parameters of the model, which govern its equilibrium properties. This mapping is executed for four different linear polymers and for different molecular weights. The two parameters are found to depend on chemistry, but not on molecular weight. The model predicts a constant plateau modulus minus a correction inversely proportional to molecular weight. The value for well-entangled chains, with the parameters determined ab initio, lies in the range of experimental data for the materials investigated.

  17. Primitive-path statistics of entangled polymers: mapping multi-chain simulations onto single-chain mean-field models

    International Nuclear Information System (INIS)

    We present a method to map the full equilibrium distribution of the primitive-path (PP) length, obtained from multi-chain simulations of polymer melts, onto a single-chain mean-field ‘target’ model. Most previous works used the Doi–Edwards tube model as a target. However, the average number of monomers per PP segment, obtained from multi-chain PP networks, has consistently shown a discrepancy of a factor of two with respect to tube-model estimates. Part of the problem is that the tube model neglects fluctuations in the lengths of PP segments, the number of entanglements per chain and the distribution of monomers among PP segments, while all these fluctuations are observed in multi-chain simulations. Here we use a recently proposed slip-link model, which includes fluctuations in all these variables as well as in the spatial positions of the entanglements. This turns out to be essential to obtain qualitative and quantitative agreement with the equilibrium PP-length distribution obtained from multi-chain simulations. By fitting this distribution, we are able to determine two of the three parameters of the model, which govern its equilibrium properties. This mapping is executed for four different linear polymers and for different molecular weights. The two parameters are found to depend on chemistry, but not on molecular weight. The model predicts a constant plateau modulus minus a correction inversely proportional to molecular weight. The value for well-entangled chains, with the parameters determined ab initio, lies in the range of experimental data for the materials investigated. (paper)

  18. Chemically Realistic Tetrahedral Lattice Models for Polymer Chains: Application to Polyethylene Oxide.

    Science.gov (United States)

    Dietschreit, Johannes C B; Diestler, Dennis J; Knapp, Ernst W

    2016-05-10

    To speed up the generation of an ensemble of poly(ethylene oxide) (PEO) polymer chains in solution, a tetrahedral lattice model possessing the appropriate bond angles is used. The distance between noncovalently bonded atoms is maintained at realistic values by generating chains with an enhanced degree of self-avoidance by a very efficient Monte Carlo (MC) algorithm. Potential energy parameters characterizing this lattice model are adjusted so as to mimic realistic PEO polymer chains in water simulated by molecular dynamics (MD), which serves as a benchmark. The MD data show that PEO chains have a fractal dimension of about two, in contrast to self-avoiding walk lattice models, which exhibit the fractal dimension of 1.7. The potential energy accounts for a mild hydrophobic effect (HYEF) of PEO and for a proper setting of the distribution between trans and gauche conformers. The potential energy parameters are determined by matching the Flory radius, the radius of gyration, and the fraction of trans torsion angles in the chain. A gratifying result is the excellent agreement of the pair distribution function and the angular correlation for the lattice model with the benchmark distribution. The lattice model allows for the precise computation of the torsional entropy of the chain. The generation of polymer conformations of the adjusted lattice model is at least 2 orders of magnitude more efficient than MD simulations of the PEO chain in explicit water. This method of generating chain conformations on a tetrahedral lattice can also be applied to other types of polymers with appropriate adjustment of the potential energy function. The efficient MC algorithm for generating chain conformations on a tetrahedral lattice is available for download at https://github.com/Roulattice/Roulattice . PMID:27045228

  19. Dependence of polymer thin film adhesion energy on cohesive interactions between chains

    OpenAIRE

    Xia, Wenjie; Hsu, David; Keten, Sinan

    2014-01-01

    The adhesion of supported polymer thin films is predominantly influenced by the substrate-film interfacial properties. Utilizing steered molecular dynamics simulations, here we uncover that the cohesive noncovalent forces between polymer chains in the film also have a significant effect on the adhesive properties of supported film. We demonstrate that weaker interchain interactions, all else being the same, can induce higher adhesion energy within the interface. Three different adhesion regim...

  20. Drift of a polymer chain in a porous medium —A Monte Carlo study

    Science.gov (United States)

    Avramova, K.; Milchev, A.

    2002-01-01

    We investigate the drift of an end-labeled telehelic polymer chain in a frozen disordered medium under the action of a constant force applied to the one end of the macromolecule by means of an off-lattice bead spring Monte Carlo model. The length of the polymers N is varied in the range 8chains can be interpreted as described by a scaling theory based on Pincus blobs. The variation of drag velocity with C in this interval of field intensities is qualitatively described by the law of Mackie-Meares. The threshold field intensity B_ab{c} itself is found to decrease linearly with C.

  1. Naphthalene Tetracarboxydiimide-Based n-Type Polymers with Removable Solubility via Thermally Cleavable Side Chains.

    Science.gov (United States)

    Hillebrandt, Sabina; Adermann, Torben; Alt, Milan; Schinke, Janusz; Glaser, Tobias; Mankel, Eric; Hernandez-Sosa, Gerardo; Jaegermann, Wolfram; Lemmer, Uli; Pucci, Annemarie; Kowalsky, Wolfgang; Müllen, Klaus; Lovrincic, Robert; Hamburger, Manuel

    2016-02-01

    Multilayer solution-processed devices in organic electronics show the tendency of intermixing of subsequently deposited layers. Here, we synthesize naphthalene tetracarboxydiimide (NDI)-based n-type semiconducting polymers with thermally cleavable side chains which upon removal render the polymer insoluble. Infrared and photoelectron spectroscopy were performed to investigate the pyrolysis process. Characterization of organic field-effect transistors provides insight into charge transport. After the pyrolysis homogeneous films could be produced which are insoluble in the primary solvent. By varying curing temperature and time we show that these process parameters govern the amount of side chains in the film and influence the device performance. PMID:26829619

  2. Effects of alkyl chain positioning on conjugated polymer microstructure and field-effect mobilities

    KAUST Repository

    Schroeder, Bob C.

    2015-07-02

    Solubilizing alkyl chains play a crucial role in the design of semiconducting polymers because they define the materials solubility and processability as well as both the crystallinity and solid-state microstructure. In this paper, we present a scarcely explored design approach by attaching the alkyl side chains on one side (cis-) or on both sides (trans-) of the conjugated backbone. We further investigate the effects of this structural modification on the solid-state properties of the polymers and on the charge-carrier mobilities in organic thin-film transistors. Copyright © Materials Research Society 2015

  3. Equilibrium and shear-induced conformations of a side-chain liquid crystal polymer

    Science.gov (United States)

    Castelletto, V.; Noirez, L.; Vigoureux, P.

    2000-11-01

    These studies delineate the conformations adopted by a side-chain liquid-crystalline polymer subjected to a steady-state shear flow as well as the corresponding me so pha se director orientations. Two distinct director orientations are identified in the nematic phase, giving evidence of a shear-induced transition from a flow-aligning to a non flow-aligning behavior. This transition coincides, at rest, with a subtle change from prolate to oblate polymer main-chain conformation. In the smectic phase, the layers form multilayer cylinders oriented along the velocity axis.

  4. Dependence of crystallite formation and preferential backbone orientations on the side chain pattern in PBDTTPD polymers

    KAUST Repository

    El Labban, Abdulrahman

    2014-11-26

    (Figure Presented) Alkyl substituents appended to the π-conjugated main chain account for the solution-processability and film-forming properties of most π-conjugated polymers for organic electronic device applications, including field-effect transistors (FETs) and bulk-heterojunction (BHJ) solar cells. Beyond film-forming properties, recent work has emphasized the determining role that side-chain substituents play on polymer self-assembly and thin-film nanostructural order, and, in turn, on device performance. However, the factors that determine polymer crystallite orientation in thin-films, implying preferential backbone orientation relative to the device substrate, are a matter of some debate, and these structural changes remain difficult to anticipate. In this report, we show how systematic changes in the side-chain pattern of poly(benzo[1,2-b:4,5-b′]dithiophene-alt-thieno[3,4-c]pyrrole-4,6-dione) (PBDTTPD) polymers can (i) influence the propensity of the polymer to order in the π-stacking direction, and (ii) direct the preferential orientation of the polymer crystallites in thin films (e.g., "face-on" vs "edge-on"). Oriented crystallites, specifically crystallites that are well-ordered in the π-stacking direction, are believed to be a key contributor to improved thin-film device performance in both FETs and BHJ solar cells.

  5. Single-Molecule Imaging Reveals Topology Dependent Mutual Relaxation of Polymer Chains

    KAUST Repository

    Abadi, Maram

    2015-08-24

    The motion and relaxation of linear and cyclic polymers under entangled conditions are investigated by means of a newly developed single-molecule tracking technique, cumulative-area (CA) tracking. CA tracking enables simultaneous quantitative characterization of the diffusion mode, diffusion rate, and relaxation time that have been impossible with a widely used conventional single-molecule localization and tracking method, by analyzing cumulative areas occupied by the moving molecule. Using the novel approach, we investigate the motion and relaxation of entangled cyclic polymers, which have been an important but poorly understood question. Fluorescently labeled 42 kbp linear or cyclic tracer dsDNAs in concentrated solutions of unlabeled linear or cyclic DNAs are used as model systems. We show that CA tracking can explicitly distinguish topology-dependent diffusion mode, rate, and relaxation time, demonstrating that the method provides an invaluable tool for characterizing topological interaction between the entangled chains. We further demonstrate that the current models proposed for the entanglement between cyclic polymers which are based on cyclic chains moving through an array of fixed obstacles cannot correctly describe the motion of the cyclic chain under the entangled conditions. Our results rather suggest the mutual relaxation of the cyclic chains, which underscore the necessity of developing a new model to describe the motion of cyclic polymer under the entangled conditions based on the mutual interaction of the chains.

  6. Single polymer chains in poor solvent: using the bond fluctuation method with explicit solvent.

    Science.gov (United States)

    Jentzsch, Christoph; Werner, Marco; Sommer, Jens-Uwe

    2013-03-01

    We use the bond fluctuation model with explicit solvent to study single polymer chains under poor solvent conditions. Static and dynamic properties of the bond fluctuation model with explicit solvent are compared with the implicit solvent model, and the Θ-temperatures are determined for both solvent models. We show that even in the very poor solvent regime, dynamics is not frozen for the explicit solvent model. We investigate some aspects of the structure of a single collapsed globule and show that rather large chain lengths are necessary to reach the scaling regime of a dense sphere. The force-extension curve of a single polymer chain under poor solvent conditions in the fixed end-to-end distance ensemble is analyzed. We find that the transition of the tadpole conformation to the stretched chain conformation is rather smooth because of fluctuation effects, which is in agreement with recent experimental results. PMID:23485321

  7. Functional photochromic methylhydrosiloxane-based side chain liquid crystalline polymers

    Czech Academy of Sciences Publication Activity Database

    Tóth-Katona, T.; Cigl, Martin; Fodor-Csorba, K.; Hamplová, Věra; Jánossy, I.; Kašpar, Miroslav; Vojtylová, Terézia; Hampl, F.; Bubnov, Alexej

    2014-01-01

    Roč. 215, č. 8 (2014), s. 742-752. ISSN 1022-1352 R&D Projects: GA ČR GA13-14133S; GA MŠk 7AMB13PL038 Grant ostatní: AVČR(CZ) M100101204 Institutional support: RVO:68378271 Keywords : azo-polymers * nematics * polysiloxanes * self-assembly Subject RIV: JJ - Other Materials Impact factor: 2.616, year: 2014

  8. Recent advances in metathesis-derived polymers containing transition metals in the side chain

    Directory of Open Access Journals (Sweden)

    Ileana Dragutan

    2015-12-01

    Full Text Available This account critically surveys the field of side-chain transition metal-containing polymers as prepared by controlled living ring-opening metathesis polymerization (ROMP of the respective metal-incorporating monomers. Ferrocene- and other metallocene-modified polymers, macromolecules including metal-carbonyl complexes, polymers tethering early or late transition metal complexes, etc. are herein discussed. Recent advances in the design and syntheses reported mainly during the last three years are highlighted, with special emphasis on new trends for superior applications of these hybrid materials.

  9. Recent advances in metathesis-derived polymers containing transition metals in the side chain.

    Science.gov (United States)

    Dragutan, Ileana; Dragutan, Valerian; Simionescu, Bogdan C; Demonceau, Albert; Fischer, Helmut

    2015-01-01

    This account critically surveys the field of side-chain transition metal-containing polymers as prepared by controlled living ring-opening metathesis polymerization (ROMP) of the respective metal-incorporating monomers. Ferrocene- and other metallocene-modified polymers, macromolecules including metal-carbonyl complexes, polymers tethering early or late transition metal complexes, etc. are herein discussed. Recent advances in the design and syntheses reported mainly during the last three years are highlighted, with special emphasis on new trends for superior applications of these hybrid materials. PMID:26877797

  10. The Frozen State in the Liquid Phase of Side-Chain Liquid-Crystal Polymers

    International Nuclear Information System (INIS)

    Quenched isotropic melts of side-chain liquid-crystal polymers reveal surprisingly an anisotropic polymer conformation. This small-angle neutron-scattering (SANS) result is consistent with the identification of a macroscopic, solidlike response in the isotropic phase. Both experiments (rheology and SANS) indicate that the polymer system appears frozen on millimeter length scales and at the time scales of the observation. This result implies that the flow behavior is not the terminal behavior and that cross-links or entanglements are not a necessary condition to provide elasticity in melts

  11. Non-Stoichiometric Polymer-Cyclodextrin Inclusion Compounds: Constraints Placed on Un-Included Chain Portions Tethered at Both Ends and Their Relation to Polymer Brushes

    Directory of Open Access Journals (Sweden)

    Alan E. Tonelli

    2014-08-01

    Full Text Available When non-covalently bonded crystalline inclusion compounds (ICs are formed by threading the host cyclic starches, cyclodextrins (CDs, onto guest polymer chains, and excess polymer is employed, non-stoichiometric (n-s-polymer-CD-ICs, with partially uncovered and “dangling” chains result. The crystalline host CD lattice is stable to ~300 °C, and the uncovered, yet constrained, portions of the guest chains emanating from the CD-IC crystal surfaces behave very distinctly from their neat bulk samples. In CD-IC crystals formed with α- and γ-CD hosts, each containing, respectively, six and eight 1,4-α-linked glucose units, the channels constraining the threaded portions of the guest polymer chains are ~0.5 and 1.0 nm in diameter and are separated by ~1.4 and 1.7 nm. This results in dense brushes with ~0.6 and 0.4 chains/nm2 (or 0.8 if two guest chains are included in each γ-CD channel of the un-included portions of guest polymers emanating from the host CD-IC crystal surfaces. In addition, at least some of the guest chains leaving from a crystalline CD-IC surface re-enter another CD-IC crystal creating a network structure that leads to shape-memory behavior for (n-s-polymer-CD-ICs. To some extent, (n-s-polymer-CD-ICs can be considered as dense polymer brushes with chains that are tethered on both ends. Not surprisingly, the behavior of the un-included portions of the guest polymer chains in (n-s-polymer-CD-ICs are quite different from those of their neat bulk samples, with higher glass-transition and melt crystallization temperatures and crystallinities. Here we additionally compare their behaviors to samples coalesced from their stoichiometric ICs, and more importantly to dense polymer brushes formed by polymer chains chemically bonded to surfaces at only one end. Judging on the basis of their glass-transition, crystallization and melting temperatures, and crystallinities, we generally find the un-included portions of chains in (n-s-polymer

  12. Unlocking Chain Exchange in Highly Amphiphilic Block Polymer Micellar Systems: Influence of Agitation

    OpenAIRE

    Murphy, Ryan P.; Kelley, Elizabeth G.; Rogers, Simon A.; Sullivan, Millicent O.; Epps, Thomas H.

    2014-01-01

    Chain exchange between block polymer micelles in highly selective solvents, such as water, is well-known to be arrested under quiescent conditions, yet this work demonstrates that simple agitation methods can induce rapid chain exchange in these solvents. Aqueous solutions containing either pure poly(butadiene-b-ethylene oxide) or pure poly(butadiene-b-ethylene oxide-d 4) micelles were combined and then subjected to agitation by vortex mixing, concentric cylinder Couette flow, or nitrogen gas...

  13. Synthesis and property characterization of two novel side-chain isoindigo copolymers for polymer solar cells

    Directory of Open Access Journals (Sweden)

    X. Liu

    2015-11-01

    Full Text Available Two novel side-chain conjugated polymers, PTBT-TID and PTBT-TTID, based on the new synthetic thiophene-benzne-thiophene (TBT unit, side-chain isoindigo (ID unit, and the introduced thiophene π-bridge, have been designed and synthesized. The photophysical, electrochemical and photovoltaic properties of the two polymers have been systematically investigated. The two polymers possess relatively good solubility as well as excellent thermal stability up to 380°C, and all of the polymer solar cell (PSC devices based on the two polymers obtain high open circuit voltage (Voc of about 0.8 V. The polymer solar cells based on the polymer PTBT-TID show relatively higher efficiencies than the PTBT-TTID-based ones, due to the broader absorption spectrum, a relatively higher hole mobility, a lower HOMO (the highest occupied molecular orbital energy level, a stronger IPCE (the incident photon to current conversion efficiency response and a better microphase separation, Consequently, the device based on PTBT-TID:PC61BM (1:2, by weight gives the best power conversion efficiency (PCE of 2.04%, with a short-circuit current density (Jsc of 5.39 mA·cm–2, an open-circuit voltage (Voc of 0.83 V, and a fill factor (FF of 0.45.

  14. Single Chain Dynamic Structure Factor of Linear Polymers in an All-Polymer Nano-Composite

    OpenAIRE

    Arbe, Arantxa; Pomposo, José A.; Asenjo-Sanz, Isabel; Bhowmik, Debsindhu; Ivanova, Oxana; Kohlbrecher, Joachim; Colmenero, Juan

    2016-01-01

    We present neutron spin echo (NSE) experiments on the single chain dynamic structure factor of long poly(ethylene oxide) (PEO) linear chains in the presence of poly(methyl methacrylate)-based single-chain nanoparticles (SCNPs). A complementary structural characterization of the system discards a significant interpenetration of the components and reveals a close to globular conformation of the SCNPs when surrounded by PEO chains. Analogous NSE measurements on blends of PEO with the linear prec...

  15. Thermal reactions of polymer chains with coal structures

    Czech Academy of Sciences Publication Activity Database

    Straka, Pavel; Náhunková, Jana

    Cairns: Australian Institute of Energy, 2003 - (Jackson, R.), s. 15A2/1-15A2/9 [International Conference on Coal Science - Coal contributing to sustainable world development, 2nd - 6th November, Cairns/Queesland/Australia, 2003 /12./. Cairns (AU), 02.11.2003-06.11.2003] R&D Projects: GA AV ČR IBS3046004 Institutional research plan: CEZ:AV0Z3046908 Keywords : coal * polymer * TGA Subject RIV: DH - Mining, incl. Coal Mining www.aie.org.au

  16. Non-monotonic dependence of the rupture force in polymer chains on their lengths

    OpenAIRE

    Fugmann, S.; I. M. Sokolov

    2009-01-01

    We consider the rupture dynamics of a homopolymer chain pulled at one end at a constant loading rate. Our model of the breakable polymer is related to the Rouse chain, with the only difference that the interaction between the monomers is described by the Morse potential instead of the harmonic one, and thus allows for mechanical failure. We show that in the experimentally relevant domain of parameters the dependence of the most probable rupture force on the chain length may be non-monotonic, ...

  17. Novel Fluorinated Polymers Containing Short Perfluorobutyl Side Chains and Their Super Wetting Performance on Diverse Substrates.

    Science.gov (United States)

    Jiang, Jingxian; Zhang, Guangfa; Wang, Qiongyan; Zhang, Qinghua; Zhan, Xiaoli; Chen, Fengqiu

    2016-04-27

    Because the emission of perfluorooctanoic acid (PFOA) was completely prohibited in 2015, the widely used poly- and perfluoroalkyl substances with long perfluoroalkyl groups must be substituted by environmentally friendly alternatives. In this study, one kind of potential alternative (i.e., fluorinated polymers with short perfluorobutyl side chains) has been synthesized from the prepared monomers {i.e., (perfluorobutyl)ethyl acrylate (C4A), (perfluorobutyl)ethyl methacrylate (C4MA), 2-[[[[2-(perfluorobutyl)]sulfonyl]methyl]amino]ethyl acrylate (C4SA), and methacrylate (C4SMA)}, and the microstructure, super wetting performance, and applications of the synthesized fluorinated polymers were systematically investigated. The thermal and crystallization behaviors of the fluoropolymer films were characterized by differential scanning calorimetry and wide-angle X-ray diffraction analysis, respectively. Dynamic water-repellent models were constructed. The stable low surface energy and dynamic water- and oil-repellent properties of these synthesized fluorinated polymers with short perfluorobutyl side chains were attributed to the synergetic effect of amorphous fluorinated side chains in perfluoroalkyl acrylate and crystalline hydrocarbon pendant groups in stearyl acrylate. Outstanding water- and oil-repellent properties of fabrics and any other substrates could be achieved by a facile dip-coating treatment using a fluorinated copolymer dispersion. As a result, we believe that our prepared fluorinated copolymers are potential candidates to replace the fluoroalkylated polymers with long perfluorinated chains in nonstick and self-cleaning applications in our daily life. PMID:27052113

  18. Role of Chain Morphology and Stiffness in Thermal Conductivity of Amorphous Polymers.

    Science.gov (United States)

    Zhang, Teng; Luo, Tengfei

    2016-02-01

    Designing thermally conductive polymer is of scientific interest and practical importance for applications like thermal interface materials, electronics packing, and plastic heat exchangers. In this work, we study the fundamental relationship between the molecular morphology and thermal conductivity in bulk amorphous polymers. We use polyethylene as a model system and performed systematic parametric study in molecular dynamics simulations. We find that the thermal conductivity is a strong function of the radius of gyration of the molecular chains, which is further correlated to persistence length, an intrinsic property of the molecule that characterizes molecular stiffness. Larger persistence length can lead to more extended chain morphology and thus higher thermal conductivity. Further thermal conductivity decomposition analysis shows that thermal transport through covalent bonds dominates the effective thermal conductivity over other contributions from nonbonded interactions (van der Waals) and translation of molecules disregarding the morphology. As a result, the more extended chains due to larger persistence length provide longer spatial paths for heat to transfer efficiently and thus lead to higher thermal conductivity. In addition, rigid rod-like polymers with very large persistence length tend to spontaneously crystallize and form orientated chains, leading to a thermal conductivity increase by more than 1 order of magnitude. Our results will provide important insights into the design of thermally conductive amorphous polymers. PMID:26751002

  19. How does the scaling for the polymer chain in the dissipative particle dynamics hold?

    Directory of Open Access Journals (Sweden)

    J.M.Ilnytskyi

    2007-12-01

    Full Text Available We performed a series of simulations for a linear polymer chain in a solvent using dissipative particle dynamics to check the scaling relations for the end-to-end distance, radius of gyration and hydrodynamic radius in three dimensions. The polymer chains of up to 80 beads in explicit solvent of various quality are studied. To extract the scaling exponent ν, the data are analyzed using linear fits, correction-to-scaling forms and analytical fits to the histograms of radius of gyration distribution. For certain combinations of the polymer characteristics and solvent quality, the correction-to-scaling terms are found to be essential while for the others these are negligibly small. In each particular case the final value for the exponent ν was chosen according to the best least-squares fit. The values of ν obtained in this way are found within the interval ν=0.55/0.61 but are concentrated mostly around 0.59, which is very close to the best known theoretical result ν=0.588. The existence of this interval is attributed both to the peculiarities of the method and to the moderate chain lengths being simulated. Within this shortcoming, the polymer chain in this kind of modeling is found to satisfy the scaling relations for all three radii being considered.

  20. Causal Chains Arising from Climate Change in Mountain Regions: the Core Program of the Mountain Research Initiative

    Science.gov (United States)

    Greenwood, G. B.

    2014-12-01

    Mountains are a widespread terrestrial feature, covering from 12 to 24 percent of the world's terrestrial surface, depending of the definition. Topographic relief is central to the definition of mountains, to the benefits and costs accruing to society and to the cascade of changes expected from climate change. Mountains capture and store water, particularly important in arid regions and in all areas for energy production. In temperate and boreal regions, mountains have a great range in population densities, from empty to urban, while tropical mountains are often densely settled and farmed. Mountain regions contain a wide range of habitats, important for biodiversity, and for primary, secondary and tertiary sectors of the economy. Climate change interacts with this relief and consequent diversity. Elevation itself may accentuate warming (elevationi dependent warming) in some mountain regions. Even average warming starts complex chains of causality that reverberate through the diverse social ecological mountain systems affecting both the highlands and adjacent lowlands. A single feature of climate change such as higher snow lines affect the climate through albedo, the water cycle through changes in timing of release , water quality through the weathering of newly exposed material, geomorphology through enhanced erosion, plant communities through changes in climatic water balance, and animal and human communities through changes in habitat conditions and resource availabilities. Understanding these causal changes presents a particular interdisciplinary challenge to researchers, from assessing the existence and magnitude of elevation dependent warming and monitoring the full suite of changes within the social ecological system to climate change, to understanding how social ecological systems respond through individual and institutional behavior with repercussions on the long-term sustainability of these systems.

  1. Main chain acid-degradable polymers for the delivery of bioactive materials

    Science.gov (United States)

    Frechet, Jean M. J.; Standley, Stephany M.; Jain, Rachna; Lee, Cameron C.

    2012-03-20

    Novel main chain acid degradable polymer backbones and drug delivery systems comprised of materials capable of delivering bioactive materials to cells for use as vaccines or other therapeutic agents are described. The polymers are synthesized using monomers that contain acid-degradable linkages cleavable under mild acidic conditions. The main chain of the resulting polymers readily degrade into many small molecules at low pH, but remain relatively stable and intact at physiological pH. The new materials have the common characteristic of being able to degrade by acid hydrolysis under conditions commonly found within the endosomal or lysosomal compartments of cells thereby releasing their payload within the cell. The materials can also be used for the delivery of therapeutics to the acidic regions of tumors and other sites of inflammation.

  2. First steps toward the construction of a hyperphase diagram that covers different classes of short polymer chains

    Science.gov (United States)

    Sabeur, Sid

    2014-06-01

    We present the results of a multicanonical Monte Carlo study of flexible and wormlike polymer chains, where we investigate how the polymer structures observed during the simulations, mainly coil, liquid, and crystalline structures, can help to construct a hyperphase diagram that covers different polymer classes according to their thermodynamic behavior.

  3. Single-chain crosslinked star polymers via intramolecular crosslinking of self-folding amphiphilic copolymers in water

    OpenAIRE

    Terashima, Takaya; Sugita, Takanori; Sawamoto, Mitsuo

    2015-01-01

    Single-chain crosslinked star polymers with multiple hydrophilic short arms and a hydrophobic core were created as novel microgel star polymers of single polymer chains. The synthetic process involves the intramolecular crosslinking of self-folding amphiphilic random copolymers in water. For this process, amphiphilic random copolymers bearing hydrophilic poly(ethylene glycol) (PEG) and hydrophobic olefin pendants were synthesized by ruthenium-catalyzed living radical copolymerization of PEG m...

  4. Chain scission efficiency of some polymers in γ-radiation

    International Nuclear Information System (INIS)

    The G values of poly(methyl methacrylates) (PMMA), polycarbonates, and a polylactone for γ-radiation were determined by using a computer-assisted GPC as the primary tool for the measurement of the number-average molecular weights anti M/sub n/. The accuracy and precision of the automated GPC were found to have a normalized standard deviation (sigma/anti M/sub n/) of less than 7 percent. The G value of PMMA was determined to be essentially independent of molecular weight. For low molecular weight polymers, some nonlinearity in the 1/anti M/sub n/ versus dosage plot was observed at low dosage, i.e., about 1 Mrad

  5. Architecting functional group and spacer in polymer chain for enhancing selectivity towards uranium

    International Nuclear Information System (INIS)

    The imprinting of polymer chains containing ethylene glycol methacrylate phosphate (EGMP) for UO22+ ions was carried out. The EGMP monomer was preorganized by reacting with UO22+ ions in 2:1 mol ratio, and polymerizing the same along with the spacer monomer methylmethacrylate (MM) with or without crosslinker. After polymerization, UO22+ ions complexed in the gel samples were desorbed in 0.5 mol L-1 Na2CO3. The comparison of uptake of ions as a function of acidity in gels indicated that imprinting improved the selectivity of phosphate functional units in the poly EGMP chains towards UO22+ ions significantly with respect to the representative ions like Cd2+, Fe3+ and Eu3+ ions. However, Pu(IV) sorption was found to be same in as such preorganized gels containing 1:10 mole ratio of EGMP:MM in the polymer chains. (author)

  6. Thermochromism of a poly(phenylene vinylene): untangling the roles of polymer aggregate and chain conformation.

    Science.gov (United States)

    Wang, Chun-Chih; Gao, Yuan; Shreve, Andrew P; Zhong, Chang; Wang, Leeyih; Mudalige, Kumara; Wang, Hsing-Lin; Cotlet, Mircea

    2009-12-17

    We report reversible thermochromism of a conjugated polymer, poly{2,5-bis[3-(N,N-diethylamino)-1-oxapropyl]-1,4-phenylenevinylene} (DAO-PPV), in diluted solutions of toluene and 1,2-dichlorobenzene. By means of temperature- and solvent-dependent steady-state spectroscopy, picosecond time-resolved photoluminescence spectroscopy, and dynamic light scattering, we provide new insights into the role of polymer aggregates in defining the thermochromic behavior of PPVs. We find DAO-PPV to exhibit a low temperature state with vibronically structured red visible absorption and emission spectra. Structurally, this low temperature state is a densely packed and disordered polymer aggregate, which contains a fraction of well-ordered, packed polymer chains. These ordered regions serve as low energy trap sites for the more disordered regions in the aggregate, thus regulating the final emission of the aggregate and imposing a vibronically resolved emission spectrum, which is usually associated with emission from one or a few chromophores. The high temperature state of DAO-PPV is a loose aggregate, with structureless absorption and emission spectra in the green visible range. Structurally, the loose aggregate is a well-solvated aggregate retaining the physical dimension of the dense aggregate but for which interchain interactions are diminished with the increase of temperature. As a result, the spectroscopic behavior of the loose aggregate is very similar if not identical to that of the single polymer chain. Increased solubility untangles polymer aggregates into single, dispersed, polymer chains, as we demonstrate here for DAO-PPV in 1,2-dichlorobenzene and at high temperature. PMID:19928846

  7. Thermochromism of a Poly(phenylene vinylene): Untangling the Roles of Polymer Aggregate and Chain Conformation

    Energy Technology Data Exchange (ETDEWEB)

    Cotlet, M.; Wang, C.-C.; Gao, Y.; Shreve, A.P.; Zhong, C.; Wang, L.; Mudalige, K.; Wang, H.-L.

    2009-12-17

    We report reversible thermochromism of a conjugated polymer, poly{l_brace}2,5-bis[3-(N,N-diethylamino)-1-oxapropyl]-1,4-phenylenevinylene{r_brace} (DAO-PPV), in diluted solutions of toluene and 1,2-dichlorobenzene. By means of temperature- and solvent-dependent steady-state spectroscopy, picosecond time-resolved photoluminescence spectroscopy, and dynamic light scattering, we provide new insights into the role of polymer aggregates in defining the thermochromic behavior of PPVs. We find DAO-PPV to exhibit a low temperature state with vibronically structured red visible absorption and emission spectra. Structurally, this low temperature state is a densely packed and disordered polymer aggregate, which contains a fraction of well-ordered, packed polymer chains. These ordered regions serve as low energy trap sites for the more disordered regions in the aggregate, thus regulating the final emission of the aggregate and imposing a vibronically resolved emission spectrum, which is usually associated with emission from one or a few chromophores. The high temperature state of DAO-PPV is a loose aggregate, with structureless absorption and emission spectra in the green visible range. Structurally, the loose aggregate is a well-solvated aggregate retaining the physical dimension of the dense aggregate but for which interchain interactions are diminished with the increase of temperature. As a result, the spectroscopic behavior of the loose aggregate is very similar if not identical to that of the single polymer chain. Increased solubility untangles polymer aggregates into single, dispersed, polymer chains, as we demonstrate here for DAO-PPV in 1,2-dichlorobenzene and at high temperature.

  8. Monte Carlo simulations of a polymer chain conformation. The effectiveness of local moves algorithms and estimation of entropy

    OpenAIRE

    Mańka, Agnieszka; Nowicki, Waldemar; Nowicka, Grażyna

    2013-01-01

    A linear chain on a simple cubic lattice was simulated by the Metropolis Monte Carlo method using a combination of local and non-local chain modifications. Kink-jump, crankshaft, reptation and end-segment moves were used for local changes of the chain conformation, while for non-local chain rearrangements the "cut-and-paste" algorithm was employed. The statistics of local micromodifications was examined. An approximate method for estimating the conformational entropy of a polymer chain, based...

  9. Vitrification of thin polymer films: from linear chain to soft-colloid like behavior

    Science.gov (United States)

    Glynos, Emmanouil; Frieberg, Bradley; Sakellariou, Georgios; Chremos, Alexandros; Green, Peter

    2015-03-01

    The glass transition temperature Tg of sufficiently thin, supported, polymer films is dependent on the film thickness. Based on the nature of the polymer substrate interactions Tg may increase, ΔTg >0, or decrease, ΔTg polymer films supported by the same substrate. Specifically in the case of polystyrene (PS) macromolecules, with arms of molecular weight Marm= 32, where the polymer exhibits soft-colloid like behavior ΔTg ~ 0. For values of 40. The transition from the linear-chain to the soft-colloid behavior is gradual and occurs with increasing f and/or decreasing Marm. With the help of molecular dynamics simulations we rationalize this behavior in terms of competing entropic effects, associated with changes in f and Marm, which drives the ability of these molecules to efficiently pack at interfaces.

  10. Searching for low percolation thresholds within amphiphilic polymer membranes: The effect of side chain branching

    International Nuclear Information System (INIS)

    Percolation thresholds for solvent diffusion within hydrated model polymeric membranes are derived from dissipative particle dynamics in combination with Monte Carlo (MC) tracer diffusion calculations. The polymer backbones are composed of hydrophobic A beads to which at regular intervals Y-shaped side chains are attached. Each side chain is composed of eight A beads and contains two identical branches that are each terminated with a pendant hydrophilic C bead. Four types of side chains are considered for which the two branches (each represented as [C], [AC], [AAC], or [AAAC]) are splitting off from the 8th, 6th, 4th, or 2nd A bead, respectively. Water diffusion through the phase separated water containing pore networks is deduced from MC tracer diffusion calculations. The percolation threshold for the architectures containing the [C] and [AC] branches is at a water volume fraction of ∼0.07 and 0.08, respectively. These are much lower than those derived earlier for linear architectures of various side chain length and side chain distributions. Control of side chain architecture is thus a very interesting design parameter to decrease the percolation threshold for solvent and proton transports within flexible amphiphilic polymer membranes

  11. ZnO hybrid photovoltaics with variable side-chain lengths of thienothiophene polymer

    International Nuclear Information System (INIS)

    The effect of the side-chain length of poly(3,6-dialkylthieno[3,2-b]thiophene-co-bithiophene) (pATBT) on the performance of hybrid polymer-metal oxide photovoltaics (PVs) utilizing zinc oxide (ZnO) acceptor is investigated. The pATBT attached with a dodecyl side chain (pATBT-C12) in hybrid photovoltaics with ZnO was compared to pATBT with a hexadecyl side chain (pATBT-C16). Atomic force microscopic analysis reveals a smoother surface for the pATBT-C16 photoactive layer compared to the pATBT-C12. For hybrid PVs using pATBT-C16, the relative intensity of the external quantum efficiency (EQE) increased particularly in wavelength region associated with the ZnO. Furthermore, the EQE spectrum shows a red shift for pATBT-C16 indicating better structural ordering compared to hybrid PVs with pATBT-C12. As a result, the hybrid PV utilizing pATBT-C16:ZnO blend layer is observed to display a better performance with a power conversion efficiency of 1.02% compared to 0.672% of pATBT-C12:ZnO PV. - Highlights: • The effect of polymer side-chain length on hybrid photovoltaics is investigated. • Longer side chains positively influence structural and optical properties of hybrid films. • Longer side-chain length leads to better photovoltaic performance

  12. Searching for low percolation thresholds within amphiphilic polymer membranes: The effect of side chain branching

    Science.gov (United States)

    Dorenbos, G.

    2015-06-01

    Percolation thresholds for solvent diffusion within hydrated model polymeric membranes are derived from dissipative particle dynamics in combination with Monte Carlo (MC) tracer diffusion calculations. The polymer backbones are composed of hydrophobic A beads to which at regular intervals Y-shaped side chains are attached. Each side chain is composed of eight A beads and contains two identical branches that are each terminated with a pendant hydrophilic C bead. Four types of side chains are considered for which the two branches (each represented as [C], [AC], [AAC], or [AAAC]) are splitting off from the 8th, 6th, 4th, or 2nd A bead, respectively. Water diffusion through the phase separated water containing pore networks is deduced from MC tracer diffusion calculations. The percolation threshold for the architectures containing the [C] and [AC] branches is at a water volume fraction of ˜0.07 and 0.08, respectively. These are much lower than those derived earlier for linear architectures of various side chain length and side chain distributions. Control of side chain architecture is thus a very interesting design parameter to decrease the percolation threshold for solvent and proton transports within flexible amphiphilic polymer membranes.

  13. Searching for low percolation thresholds within amphiphilic polymer membranes: The effect of side chain branching

    Energy Technology Data Exchange (ETDEWEB)

    Dorenbos, G., E-mail: dorenbos@ny.thn.ne.jp [Sano 1107-2, Belle Crea 502, Susono 410-1118 (Japan)

    2015-06-14

    Percolation thresholds for solvent diffusion within hydrated model polymeric membranes are derived from dissipative particle dynamics in combination with Monte Carlo (MC) tracer diffusion calculations. The polymer backbones are composed of hydrophobic A beads to which at regular intervals Y-shaped side chains are attached. Each side chain is composed of eight A beads and contains two identical branches that are each terminated with a pendant hydrophilic C bead. Four types of side chains are considered for which the two branches (each represented as [C], [AC], [AAC], or [AAAC]) are splitting off from the 8th, 6th, 4th, or 2nd A bead, respectively. Water diffusion through the phase separated water containing pore networks is deduced from MC tracer diffusion calculations. The percolation threshold for the architectures containing the [C] and [AC] branches is at a water volume fraction of ∼0.07 and 0.08, respectively. These are much lower than those derived earlier for linear architectures of various side chain length and side chain distributions. Control of side chain architecture is thus a very interesting design parameter to decrease the percolation threshold for solvent and proton transports within flexible amphiphilic polymer membranes.

  14. Molecular imprinted polymer with positively charged, assistant recognition polymer chains for adsorption/enrichment of low content target protein

    Institute of Scientific and Technical Information of China (English)

    LONG Yi; SUN Yang; WANG Ying; XING XiaoCui; ZHAO Zhuo; WANG ChunHong; FAN YunGe; MI HuaiFeng

    2008-01-01

    Here, we introduce a new type of molecular imprinted polymer (MIP) with immobilized assistant recog-nition polymer chains (ARPCs) to create effective recognition sites and with bacterial cloned protein as template for adsorbing the low content target protein from cell extract. In this work, cloned pig cyclo-philin 18 (pCyP18), a peptidyl-prolyl cis/trans-isomerase, was used as template. The template protein was selectively assembled with ARPCs from their library, which consists of numerous limited length polymer chains with randomly distributed recognition sites of positively charged amino groups and immobilizing sites. These assemblies were adsorbed by porous microsphers and immobilized on them.After removing the template, binding sites complementary to the target protein in size, shape and the position of recognition groups were exposed, and their confirmation was preserved by the cross-linked structure. The synthesized MIP was used to adsorb the cellular pCyP18, and its proportional content was enriched more than hundred times. The extended experiment on imprinting bovine serum albumin (BSA) with ARPCs shows that this method is also suitable for large protein.

  15. Communication: Role of short chain branching in polymer structure and dynamics

    Science.gov (United States)

    Kim, Jun Mo; Baig, Chunggi

    2016-02-01

    A comprehensive understanding of chain-branching effects, essential for establishing general knowledge of the structure-property-phenomenon relationship in polymer science, has not yet been found, due to a critical lack of knowledge on the role of short-chain branches, the effects of which have mostly been neglected in favor of the standard entropic-based concepts of long polymers. Here, we show a significant effect of short-chain branching on the structural and dynamical properties of polymeric materials, and reveal the molecular origins behind the fundamental role of short branches, via atomistic nonequilibrium molecular dynamics and mesoscopic Brownian dynamics by systematically varying the strength of the mobility of short branches. We demonstrate that the fast random Brownian kinetics inherent to short branches plays a key role in governing the overall structure and dynamics of polymers, leading to a compact molecular structure and, under external fields, to a lesser degree of structural deformation of polymer, to a reduced shear-thinning behavior, and to a smaller elastic stress, compared with their linear analogues. Their fast dynamical nature being unaffected by practical flow fields owing to their very short characteristic time scale, short branches would substantially influence (i.e., facilitate) the overall relaxation behavior of polymeric materials under various flowing conditions.

  16. Cylindrical polymer brushes with dendritic side chains by iterative anionic reactions

    KAUST Repository

    Zhang, Hefeng

    2015-05-01

    We report in this paper an easy method for the synthesis of cylindrical polymer brushes with dendritic side chains through anionic reaction. The synthesis is accomplished by iteratively grafting a living block copolymer, polyisoprene-. b-polystyrenyllithium (PI-. b-PSLi), to the main chain and subsequently to the branches in a divergent way. PI segment is short and serves as a precursor for multifunctional branching unit. The grafting reaction involves two successive steps: i) epoxidation of internal double bonds of PI segments, either in main chain or side chains; ii) ring-opening addition to the resulting epoxy group by the living PI-. b-PSLi. Repeating the two steps affords a series of cylindrical polymer brushes with up to 3rd generation and extremely high molecular weight. The branching multiplicity depends on the average number of oxirane groups per PI segment, usually ca. 8 in the present work. The high branching multiplicity leads to tremendous increase in molecular weights of the cylindrical products with generation growth. Several series of cylindrical polymer brushes with tunable aspect ratios are prepared using backbones and branches with controlled lengths. Shape anisotropy is investigated in dilute solution using light scattering technique. Worm-like single molecular morphology with large persistence length is observed on different substrates by atomic force microscopy.

  17. Lattice model of linear telechelic polymer melts. I. Inclusion of chain semiflexibility in the lattice cluster theory

    International Nuclear Information System (INIS)

    The lattice cluster theory (LCT) for the thermodynamics of polymer systems has recently been reformulated to treat strongly interacting self-assembling polymers composed of fully flexible linear telechelic chains [J. Dudowicz and K. F. Freed, J. Chem. Phys. 136, 064902 (2012)]. Here, we further extend the LCT for linear telechelic polymer melts to include a description of chain semiflexibility, which is treated by introducing a bending energy penalty whenever a pair of consecutive bonds from a single chain lies along orthogonal directions. An analytical expression for the Helmholtz free energy is derived for the model of semiflexible linear telechelic polymer melts. The extension provides a theoretical tool for investigating the influence of chain stiffness on the thermodynamics of self-assembling telechelic polymers, and for further exploring the influence of self-assembly on glass formation in such systems

  18. Polymer chains and baryons in a strongly coupled quark-gluon plasma

    International Nuclear Information System (INIS)

    Recently there was a significant change of views on physical properties and underlying dynamics of quark-gluon plasma at T=170-350 MeV, produced in heavy ion collisions at RHIC. Instead of being a gas of q,g quasiparticles, a near-perfect liquid is observed. Also, precisely in this temperature interval, the interaction deduced from lattice studies is strong enough to support multiple binary bound states. This work is the first variational study of multibody bound states. We will consider: (i) 'polymer chains' of the type q-bar gg...gq; (ii) baryons (qqq); (iii) closed (3-)chains of gluons (ggg). We found that chains (i) form in exactly the same T range as binary states, with the same binding per bond. The binding and T-range for diquarks, baryons and closed 3-chains are also established

  19. Consistent model reduction of polymer chains in solution in dissipative particle dynamics: Model description

    KAUST Repository

    Moreno, Nicolas

    2015-06-30

    We introduce a framework for model reduction of polymer chain models for dissipative particle dynamics (DPD) simulations, where the properties governing the phase equilibria such as the characteristic size of the chain, compressibility, density, and temperature are preserved. The proposed methodology reduces the number of degrees of freedom required in traditional DPD representations to model equilibrium properties of systems with complex molecules (e.g., linear polymers). Based on geometrical considerations we explicitly account for the correlation between beads in fine-grained DPD models and consistently represent the effect of these correlations in a reduced model, in a practical and simple fashion via power laws and the consistent scaling of the simulation parameters. In order to satisfy the geometrical constraints in the reduced model we introduce bond-angle potentials that account for the changes in the chain free energy after the model reduction. Following this coarse-graining process we represent high molecular weight DPD chains (i.e., ≥200≥200 beads per chain) with a significant reduction in the number of particles required (i.e., ≥20≥20 times the original system). We show that our methodology has potential applications modeling systems of high molecular weight molecules at large scales, such as diblock copolymer and DNA.

  20. Consistent model reduction of polymer chains in solution in dissipative particle dynamics: Model description

    Science.gov (United States)

    Moreno, Nicolas; Nunes, Suzana P.; Calo, Victor M.

    2015-11-01

    We introduce a framework for model reduction of polymer chain models for dissipative particle dynamics (DPD) simulations, where the properties governing the phase equilibria such as the characteristic size of the chain, compressibility, density, and temperature are preserved. The proposed methodology reduces the number of degrees of freedom required in traditional DPD representations to model equilibrium properties of systems with complex molecules (e.g., linear polymers). Based on geometrical considerations we explicitly account for the correlation between beads in fine-grained DPD models and consistently represent the effect of these correlations in a reduced model, in a practical and simple fashion via power laws and the consistent scaling of the simulation parameters. In order to satisfy the geometrical constraints in the reduced model we introduce bond-angle potentials that account for the changes in the chain free energy after the model reduction. Following this coarse-graining process we represent high molecular weight DPD chains (i.e.,  ≥ 200 beads per chain) with a significant reduction in the number of particles required (i.e.,  ≥ 20 times the original system). We show that our methodology has potential applications modeling systems of high molecular weight molecules at large scales, such as diblock copolymer and DNA.

  1. Fluctuation-induced forces between rings threaded around a polymer chain under tension

    CERN Document Server

    Gilles, F M; Pastorino, C

    2016-01-01

    We characterize the fluctuation properties of a polymer chain under external tension and the fluctuation-induced forces between two ring molecules threaded around the chain. The problem is relevant in the context of fluctuation-induced forces in soft matter systems, features of liquid interfaces and to describe properties of polyrotaxanes and slide-ring materials. We perform molecular dynamics simulations of the Kremer-Grest bead-spring model for the polymer and a simple ring-molecule model, in the canonical ensemble. We study transverse fluctuations of the stretched chain, as a function of chain stretching and in the presence of ring-shaped threaded molecules. The fluctuation spectra of the chains are analyzed in equilibrium at constant temperature and the differences in presence of two ring molecules are compared. For the rings located at fixed distances, we find an attractive fluctuation-induced force between the rings, proportional to the temperature and decaying with the ring distance. We characterize th...

  2. Interaction of Nano-Sized Materials With Polymer Chains in Polymer-Nanocomposite Thin Films-An AFM Perspective

    International Nuclear Information System (INIS)

    Nanocomposite thin films were prepared with polyurethane as a matrix and organically modified clay as a filler. The interfacial interaction between the exfoliated clay nanoplatelets and the polymeric chains has been investigated by using Atomic Force Microscopy (AFM). The nanoclay platelets show a preferential association with the hard domains of polyurethane matrix on the surface of the thin films. The pendant hydroxyl group on the nanoplatelets attract the isocyanate of the polyisocyanate and a urethane group is formed. This leads to the 'clouding' and 'entwining' of the nanoplatelets by the hard segmental chains. This is the first visual evidence of nanomaterial filler and polymer matrix interaction and it could open up a spectrum of novel property achievements in nanocomposite thin films. Also the understanding of this interaction can lead to more controlled architecture of nanocomposites.

  3. Conformation and elasticity of a charged polymer chain bridging two nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Nowicki, W., E-mail: gwnow@amu.edu.pl; Nowicka, G. [Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89b, 61-614 Poznań (Poland)

    2013-12-07

    A complex composed of a charged flexible polymer chain irreversibly attached with its ends to surfaces of two nanoparticles was investigated using the Metropolis Monte Carlo method on a simple cubic lattice. The simulations were performed in the presence of explicit ions. The bridging chain and the nanoparticles bearing the same and the opposite sign charges were considered. Changes in the free energy of the complex upon its stretching or compression, together with the magnitude of the elastic force, were examined. The relative roles of energetic and entropic effects in determining the properties of the complex were identified. Also, the adsorption of charged monomers on the opposite-sign charged nanoparticles and its influence on the examined quantities was studied. Moreover, a simple semi-analytical approach to the thermodynamics of the polymer bridge was derived.

  4. Volume holographic recording in nanoparticle-polymer composites doped with multifunctional chain transfer agents

    Science.gov (United States)

    Guo, Jinxin; Fujii, Ryuta; Tomita, Yasuo

    2015-10-01

    We report on an experimental investigation of the properties of volume holographic recording in photopolymerizable nanoparticle-polymer composites (NPCs) doped with chain transferring multifunctional di- and tri-thiols as chain transfer agents. It is shown that the incorporation of the multifunctional thiols into NPCs more strongly influences on volume holographic recording than that doped with mono-thiol since more chemical reactions involve in the polymer network formation. It is found that, as similar to the case of mono-thiol doping, there exist optimum concentrations of di- and tri-thiols for maximizing the saturated refractive index modulation. It is also seen that recording sensitivity monotonically decreases with an increase in multifunctional thiol concentration due to the partial inhibition of the photopolymerization event by excessive thiols.

  5. Single-chain statistics and the upper wave-vector cutoff in polymer blends

    International Nuclear Information System (INIS)

    We derive the equation for the single-chain correlation function in polymer blends. The chains in the incompressible blend have a radius of gyration smaller than the radius of gyration for ideal chains. The chains shrink progressively as we approach the critical temperature Tc. The correction responsible for shrinking is proportional to 1/ √N , where N is the polymerization index. At T=Tc and for N=1000, the size of the chain has been estimated to be 10% smaller than the size of the ideal coil. The estimate relies on the appropriate cutoff. In the limit of N→∞ the chains approach the random walk limit. Additionally, we propose in this paper a self-consistent determination of the radius of gyration and the upper wave-vector cutoff. Our model is free from any divergences such as were encountered in the previous mean-field studies; we make an estimate of the chain size at the true critical temperature and not the mean-field one

  6. Endowing Single-Chain Polymer Nanoparticles with Enzyme-Mimetic Activity

    OpenAIRE

    Perez-Baena, Irma; Barroso-Bujans, Fabienne; Gasser, Urs; Arbe, Arantxa; Moreno Segurado, Ángel J.; Colmenero de León, Juan; Pomposo, José A.

    2013-01-01

    The development of simple, efficient, and robust strategies affording the facile construction of biomimetic organocatalytic nano-objects is currently a subject of great interest. Herein, a new pathway to artificial organocatalysts based on partially collapsed individual soft nano-objects displaying useful and diverse biomimetic catalytic functions is reported. Single-chain polymer nanoparticles endowed with enzyme-mimetic activity synthesized following this new route display (i) a relatively ...

  7. Anomalous Molecular Weight Dependence of Chain Dynamics in Unentangled Polymer Blends with Strong Dynamic Asymmetry

    OpenAIRE

    Arrese-Igor, Silvia; Alegría, Ángel; Moreno Segurado, Ángel J.; Colmenero de León, Juan

    2011-01-01

    We address the general question of how the molecular weight dependence of chain dynamics in unentangled polymers is modified by blending. By dielectric spectroscopy we measure the normal mode relaxation of polyisoprene in blends with a slower component of poly(ter-butylstyrene). Unentangled polyisoprene in the blend exhibits strong deviations from Rouse scaling, approaching 'entangled-like' behavior at low temperatures in concomitance with the increase of the dynamic asymmetry in the blend. T...

  8. Miscibility behavior and single chain properties in polymer blends: a bond fluctuation model study

    OpenAIRE

    Mueller, Marcus

    1999-01-01

    Computer simulation studies on the miscibility behavior and single chain properties in binary polymer blends are reviewed. We consider blends of various architectures in order to identify important architectural parameters on a coarse grained level and study their qualitative consequences for the miscibility behavior. The phase diagram, the relation between the exchange chemical potential and the composition, and the intermolecular paircorrelation functions for symmetric blends of linear chai...

  9. Flocculation of fine fluorite particles with Corynebacterium xerosis and commercial long chain polymers

    Directory of Open Access Journals (Sweden)

    Rigo Lisandra N.

    2002-01-01

    Full Text Available This work aimed to study, comparatively, the flocculation of fluorite particles with Corynebacterium xerosis cells and three commercial long chain polymers. Best flocculation results were obtained with cells of C. xerosis and with an anionic polyacrylamide. Both were effective in solids removal and water clarification, although flocculation with C. xerosis cells requires a higher dosage of reagent per mass unit of processed ore.

  10. Inducing Planar Orientation in Side‐Chain Liquid‐Crystalline Polymer Systems via Interfacial Control

    Science.gov (United States)

    2016-01-01

    Abstract For efficient photoresponses of liquid‐crystal (LC) azobenzene (Az) polymer systems, planar LC orientation of the Az mesogenic group is required because the light irradiation process usually occurs with normal incidence to the film surface. However, LC molecules with a rodlike shape tend to orient perpendicularly to the film surface according to the excluded volume effect theory. This review introduces new approaches for inducing planar orientation in side‐chain LC Az polymer films via interface and surface molecular designs. The planar orientation offers efficient in‐plane photoalignment and photoswitching to hierarchical LC architectures from molecular LC mesogens and LC phases to mesoscopic microphase‐separated structures. These approaches are expected to provide new concepts and possibilities in new LC polymer devices. PMID:26775770

  11. Water Sorption and Hindered Diffusion with Different Chain Stiffness of Superabsorbent Polymer

    Energy Technology Data Exchange (ETDEWEB)

    Chun, Myung-Suk; Lee, Dae-Young [Korea Institute of Science and Technology, Seoul (Korea, Republic of)

    2015-01-15

    Water sorption and diffusion are essential physicochemical properties of a high-performance superabsorbent polymer (SAP). We combine the Park model with the obstruction-scaling model and the water clustering in confined spaces of the polymer hydrogel. Special attention is focused on elucidating the effect of chain stiffness by considering the conformation of the polymer chain. Theoretical model parameters are determined from the best fits by simultaneous nonlinear regressions for both sorption and corrected diffusion data based on previous experiments with poly(acrylamide-co-sodium acrylate) hydrogel. Predictions show that the hindered water diffusivity leads to a sigmoid curve with relative humidity a{sub w}, where it increases monotonically up to aw{sub ≅} 0.6 due to the swelling but decreases at higher a{sub w} caused by water clustering. Water diffusion decreases with increasing chain stiffness, and the larger persistence length provides a smaller opening radius in void spaces regarding the weak elastic deformation of hydrogel under the applied stress.

  12. Path Integral Approach to a Single Polymer Chain with Random Media

    Science.gov (United States)

    Kunsombat, Ch.; Sa-Yakanit, V.

    In this paper we consider the problem of a polymer chain in random media with finite correlation. We show that the mean square end-to-end distance of a polymer chain can be obtained using the Feynman path integral developed by Feynman for treating the polaron problem and successfuly applied to the theory of heavily doped semiconductor. We show that for short-range correlation or the white Gaussian model we derive the results obtained by Edwards and Muthukumar using the replica method and for long-range correlation we obtain the result of Yohannes Shiferaw and Yadin Y. Goldschimidt. The main idea of this paper is to generalize the model proposed by Edwards and Muthukumar for short-range correlation to finite correlation. Instead of using a replica method, we employ the Feynman path integral by modeling the polymer Hamiltonian as a model of non-local quadratic trial Hamiltonian. This non-local trial Hamiltonian is essential as it will reflect the translation invariant of the original Hamiltonian. The calculation is proceeded by considering the differences between the polymer propagator and the trial propagator as the first cumulant approximation. The variational principle is used to find the optimal values of the variational parameters and the mean square end-to-end distance is obtained. Several asymptotic limits are considered and a comparison between this approaches and replica approach will be discussed.

  13. Synthesis and characterization of associating polymers which contain siloxanes chains; Synthese et caracterisation de polymeres associatifs porteurs de groupes siloxanes

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, V.

    1999-01-11

    Polymers that associate via physical interactions in solutions have received much attention as viscosifiers. Such associating polymers are now used in variety of applications due to their unique theological properties coating, food thickeners, paints, enhanced oil recovery, water treatment). They contain a hydrophilic main chain with hydrophobic side chain that is generally constituted of hydrocarbon or fluorocarbon groups. Novel copolymers with sites of association in aqueous solution were prepared by co-polymerizing acrylamide with an hydrophobic monomer containing siloxane parts. Rheological properties were studied as a function of polymer concentration, microstructure, shear rate and frequency in order to show intra intermolecular associations between the hydrophobic parts. The polymer solution viscosity increases as a function of the hydrophobic group content. Tests of adsorption show a high affinity of these copolymers with clay and the amount absorbed increase with the quantity of hydrophobic entities containing in the chain. These properties are enhanced compared to copolymers containing hydrocarbon chains. (authors) 456 refs.

  14. Folding mechanism of a polymer chain with short-range attractions

    Science.gov (United States)

    Leitold, Christian; Dellago, Christoph

    2014-10-01

    We investigate the crystallization of a single, flexible homopolymer chain using transition path sampling. The chain consists of N identical spherical monomers evolved according to Langevin dynamics. While neighboring monomers are coupled via harmonic springs, the non-neighboring monomers interact via a hard core and a short-ranged attractive potential. For a sufficiently small interaction range λ, the system undergoes a first-order freezing transition from an expanded, disordered phase to a compact crystalline state. Using a new shooting move tailored to polymers combined with a committor analysis, we study the transition state ensemble of an N = 128 chain and search for possible reaction coordinates based on likelihood maximization. We find that typical transition states consist of a crystalline nucleus with one or more chain fragments attached to it. Furthermore, we show that the number of particles in the crystalline core is not well suited as a reaction coordinate. We then present an improved reaction coordinate, which includes information from the potential energy and the overall crystallinity of the polymer.

  15. A SLOW RELAXATION MODE OF POLYMER CHAINS IN A SEMIDILUTE SOLUTION

    Institute of Scientific and Technical Information of China (English)

    Jun-fang Li; Yi-jie Lu; Guang-zhao Zhang; Wei Li; Chi Wu

    2008-01-01

    Dust-free semidilute and concentrated polystyrene (PS) solutions in different solvents were prepared by slow evaporation and in situ anionic polymerization, which removes the effects of troublesome artifacts such as dust contamination and concentration gradient. The dynamics was reexamined by a combination of static and dynamic laser light scattering. In benzene and toluene (good solvents for PS), only one fast diffusive mode of polymer chains can be observed when the concentration (c) is up to 20%, which is attributed to thermally agitated fluctuation of "blobs" or chain segments.Static and dynamic correlation lengths (ξS and ξD) are scaled with c as ξSS(or ξD)~c-0.72±0.02. In cyclohexane, whose quality decreases with temperature in the range 32-50℃, an additional slow mode of polymer chains can be observed. Such a slow mode is viewed more obviously at a large scattering angle even in a concentrated solution with high chain entanglement. The present study indicates that the slow mode is due to the solvent quality.

  16. Acyclic Diene Metathesis (ADMET Polymerization for Precise Synthesis of Defect-Free Conjugated Polymers with Well-Defined Chain Ends

    Directory of Open Access Journals (Sweden)

    Tahmina Haque

    2015-03-01

    Full Text Available This accounts introduces unique characteristics by adopting the acyclic diene metathesis (ADMET polymerization for synthesis of conjugated polymers, poly(arylene vinylenes, known as promising molecular electronics. The method is more suitable than the other methods in terms of atom efficiency affording defect-free, stereo-regular (exclusive trans polymers with well-defined chain ends; the resultant polymers possess better property than those prepared by the conventional methods. The chain ends (vinyl group in the resultant polymer prepared by ruthenium-carbene catalyst(s can be modified by treating with molybdenum-alkylidene complex (olefin metathesis followed by addition of various aldehyde (Wittig type cleavage, affording the end-functionalized polymers exclusively. An introduction of initiating fragment, the other conjugated segment, and one-pot synthesis of end-functionalized block copolymers, star shape polymers can be achieved by adopting this methodology.

  17. ZnO hybrid photovoltaics with variable side-chain lengths of thienothiophene polymer

    Energy Technology Data Exchange (ETDEWEB)

    Han, SeungJin [Advanced Technology Institute, Department of Electronic Engineering, University of Surrey, Guildford GU2 7XH (United Kingdom); Fei, Zhuping [Department of Chemistry and Centre for Plastic Electronics, Imperial College London, South Kensington SW7 2AZ (United Kingdom); Jayawardena, K.D.G.I.; Beliatis, Michail J. [Advanced Technology Institute, Department of Electronic Engineering, University of Surrey, Guildford GU2 7XH (United Kingdom); Hahn, Yoon-Bong [School of Chemical Engineering, Chonbuk National University, Jeon-ju, Jeonbuk 561-756 (Korea, Republic of); Adikaari, A.A.D.T. [Advanced Technology Institute, Department of Electronic Engineering, University of Surrey, Guildford GU2 7XH (United Kingdom); Heeney, Martin J. [Department of Chemistry and Centre for Plastic Electronics, Imperial College London, South Kensington SW7 2AZ (United Kingdom); Silva, S. Ravi P., E-mail: s.silva@surrey.ac.uk [Advanced Technology Institute, Department of Electronic Engineering, University of Surrey, Guildford GU2 7XH (United Kingdom)

    2015-02-02

    The effect of the side-chain length of poly(3,6-dialkylthieno[3,2-b]thiophene-co-bithiophene) (pATBT) on the performance of hybrid polymer-metal oxide photovoltaics (PVs) utilizing zinc oxide (ZnO) acceptor is investigated. The pATBT attached with a dodecyl side chain (pATBT-C{sub 12}) in hybrid photovoltaics with ZnO was compared to pATBT with a hexadecyl side chain (pATBT-C{sub 16}). Atomic force microscopic analysis reveals a smoother surface for the pATBT-C{sub 16} photoactive layer compared to the pATBT-C{sub 12}. For hybrid PVs using pATBT-C{sub 16}, the relative intensity of the external quantum efficiency (EQE) increased particularly in wavelength region associated with the ZnO. Furthermore, the EQE spectrum shows a red shift for pATBT-C{sub 16} indicating better structural ordering compared to hybrid PVs with pATBT-C{sub 12}. As a result, the hybrid PV utilizing pATBT-C{sub 16}:ZnO blend layer is observed to display a better performance with a power conversion efficiency of 1.02% compared to 0.672% of pATBT-C{sub 12}:ZnO PV. - Highlights: • The effect of polymer side-chain length on hybrid photovoltaics is investigated. • Longer side chains positively influence structural and optical properties of hybrid films. • Longer side-chain length leads to better photovoltaic performance.

  18. Topological Constraints on Chain-Folding Structure of Semicrystalline Polymer as Studied by 13C-13C Double Quantum NMR

    Science.gov (United States)

    Hong, Youlee; Miyoshi, Toshikazu

    Chain-folding process is a prominent feature of long polymer chains during crystallization. Over the last half century, much effort has been paid to reveal the chain trajectory. Even though various chain-folding models as well as theories of crystallization at molecule levels have been proposed, they could be not reconciled due to the limited experimental evidences. Recent development of double quantum NMR with selective isotope labeling identified the chain-trajectory of 13C labeled isotactic poly(1-butene). The systematic experiments covered a wide range of parameters, i.e. kinetics, concentration, and molecular weight (Mw) . It was demonstrated that i) adjacent re-entry site was invariant as a function of crystallization temperature (Tc) , concentration, andMw, ii) long-range order of adjacent re-entry sequence is independence of kinetics at a given concentration while it decreased with increasing the polymer concentration at a given Tc due to the increased interruption between the chains, and iii) high Mw chains led to the multilayer folded structures in single crystals, but the melt state induced the identical short adjacent sequences of long and short polymer over a wide range of Tc due to the entanglements. The behaviors indicated that the topological restriction plays significant roles in the chain-folding process rather than the kinetics. The proposed framework to control the chain-folding structure presents a new perspective into the chain organization by either the intra- or inter-chain interaction. National Science Foundation Grants DMR-1105829 and 1408855.

  19. The chain sucker: translocation dynamics of a polymer chain into a long narrow channel driven by longitudinal flow.

    Science.gov (United States)

    Luo, Kaifu; Metzler, Ralf

    2011-04-01

    Using analytical techniques and Langevin dynamics simulations, we investigate the dynamics of polymer translocation into a narrow channel of width R embedded in two dimensions, driven by a force proportional to the number of monomers in the channel. Such a setup mimics typical experimental situations in nano/microfluidics. During the translocation process if the monomers in the channel can sufficiently quickly assume steady state motion, we observe the scaling τ ∼ N∕F of the translocation time τ with the driving force F per bead and the number N of monomers per chain. With smaller channel width R, steady state motion cannot be achieved, effecting a nonuniversal dependence of τ on N and F. From the simulations we also deduce the waiting time distributions under various conditions for the single segment passage through the channel entrance. For different chain lengths but the same driving force, the curves of the waiting time as a function of the translocation coordinate s feature a maximum located at identical s(max), while with increasing the driving force or the channel width the value of s(max) decreases. PMID:21476775

  20. Entanglement of conjugated polymer chains influences molecular self-assembly and carrier transport

    KAUST Repository

    Zhao, Kui

    2013-06-26

    The influence of polymer entanglement on the self-assembly, molecular packing structure, and microstructure of low-Mw (lightly entangled) and high-Mw (highly entangled) poly (3-hexylthiophene) (P3HT), and the carrier transport in thin-film transistors, are investigated. The polymer chains are gradually disentangled in a marginal solvent via ultrasonication of the polymer solution, and demonstrate improved diffusivity of precursor species (coils, aggregates, and microcrystallites), enhanced nucleation and crystallization of P3HT in solution, and self-assembly of well-ordered and highly textured fibrils at the solid-liquid interface. In low-Mw P3HT, reducing chain entanglement enhances interchain and intrachain ordering, but reduces the interconnectivity of ordered domains (tie molecules) due to the presence of short chains, thus deteriorating carrier transport even in the face of improving crystallinity. Reducing chain entanglement in high-Mw P3HT solutions increases carrier mobility up to ≈20-fold, by enhancing interchain and intrachain ordering while maintaining a sufficiently large number of tie molecules between ordered domains. These results indicate that charge carrier mobility is strongly governed by the balancing of intrachain and interchain ordering, on the one hand, and interconnectivity of ordered domains, on the other hand. In high-Mw P3HT, intrachain and interchain ordering appear to be the key bottlenecks to charge transport, whereas in low-Mw P3HT, the limited interconnectivity of the ordered domains acts as the primary bottleneck to charge transport. Conjugated polymer chains of poly(3-hexylthiophene) (P3HT) are gradually disentangled in solution and trends in carrier transport mechanisms in organic thin film transistors for low- and high-molecular weight P3HT are investigated. While intrachain and interchain ordering within ordered domains are the key bottlenecks to charge transport in high-Mw P3HT films, the limited interconnectivity of ordered

  1. Chain Dynamics in Solid Polymers and Polymerizing Systems as Revealed by Broadband Dielectric Spectroscopy

    Science.gov (United States)

    Williams, Graham

    2008-08-01

    A number of techniques are used to study the chain-dynamics of solid polymers, including those of dielectric relaxation [1-4], dynamic mechanical thermal analysis (DMTA) [1, 5], multinuclear NMR relaxations [6], quasi-elastic dynamic light scattering [7] and neutron scattering [8] (QELS & QENS) and transient fluorescence depolarization (TFD) [9]. Each technique has its own particular probe of the dynamics in a material. e.g. dielectric relaxation gives information on the angular motions of molecular chain-dipoles (for dipole relaxation) and the translational motions of ions (for f-dependent electrical conduction); NMR relaxations relate to the angular motions of chemical bonds; QELS relates to fluctuations in local refractive index; QENS to the time-dependent van Hove correlation function (suitably-defined) for proton-containing groups; TFD to the angular motions of fluorescent groups in a chain. Due to its relevance to practical applications of materials, DMTA is pre-eminent among the many physical techniques applied to solid polymers, but interpretations of behaviour in terms of molecular properties remain difficult since the direct link between an applied macroscopic stress and the molecular response of polymer chains in a bulk material remains an unsolved problem. Of the above techniques, Broadband Dielectric Spectroscopy (BDS) offers several advantages. (a) Materials may be studied in the frequency range 10-6 to 1010 Hz, over wide ranges of temperature and applied pressure, using commercially-available instrumentation. (b) Since the electrical capacitance of a film is inversely proportional its thickness, free-standing and supported films may be studied down to nm-thicknesses, giving e.g. information on the behaviour of the dynamic Tg as sample thickness approaches molecular dimensions. (c) Theoretical interpretations of dielectric relaxation and a.c. conduction are well-established in terms of Fourier transforms of molecular time correlation functions (TCFs

  2. Deformation and concentration fluctuations under stretching in a polymer network with free chains. The ''butterfly'' effect

    International Nuclear Information System (INIS)

    Small Angle Neutron Scattering gives access to concentration fluctuations of mobile labeled polymer chains embedded in a polymer network. At rest they appear progressively larger than for random mixing, with increasing ratio. Under uniaxial stretching, they decrease towards ideal mixing along the direction perpendicular to stretching, and can grow strongly along the parallel one, including the zero scattering vector q limit. This gives rise to intensity contours with double-winged patterns, in the shape of the figure '8', or of 'butterfly'. Random crosslinking and end-linking of monodisperse chains have both been studied. The strength of the 'butterfly' effect increases with the molecular weight of the free chains, the crosslinking ratio, the network heterogeneity, and the elongation ratio. Eventually, the signal collapses on an 'asymptotic' function I(q), of increasing correlation length with the elongation ratio. Deformation appears heterogeneous, maximal for soft areas, where the mobile chains localize preferentially. This could be due to spontaneous fluctuations, or linked to frozen fluctuations of the crosslink density. However, disagreement with the corresponding theoretical expressions makes it necessary to account for the spatial correlations of crosslink density, and their progressive unscreening as displayed by the asymptotic behavior. Networks containing pending labeled chains and free labeled stars lead to more precise understanding of the diffusion of free species and the heterogeneity of the deformation. It seems that the latter occurs even without diffusion for heterogeneous enough networks. In extreme cases (of the crosslinking parameters), the spatial correlations display on apparent fractal behavior, of dimensions 2 to 2.5, which is discussed here in terms of random clusters. 200 refs., 95 figs., 21 tabs., 10 appends

  3. Renormalization group for centrosymmetric gauge transformations of the dynamic motion for a Markov-ordered polymer chain

    International Nuclear Information System (INIS)

    A method is proposed for calculating the vibrational-state density averaged over all configurations for a polymer chain with Markov disorder. The method is based on using a group of centrally symmetric gauge transformations that reduce the dynamic matrix for along polymer chain to renormalized dynamic matrices for short fragments. The short-range order is incorporated exactly in the averaging procedure, while the long-range order is incorporated in the self-consistent field approximation. Results are given for a simple skeletal model for a polymer containing tacticity deviations of Markov type

  4. Side Chain Engineering of Naphthalenediimide-Based N-type Polymer for High-Performance All-Polymer Solar Cell near 6% Efficiency

    Science.gov (United States)

    Lee, Changyeon; Kang, Hyunbum; Lee, Wonho; Kim, Taesu; Kim, Ki-Hyun; Woo, Han Young; Wang, Cheng; Kim, Bumjoon; Pusan National University (PNU) Collaboration; Lawrence Berkeley National Laboratory Collaboration

    2015-03-01

    Despite the attractive features of all-polymer solar cells (all-PSCs), i.e., enhanced absorption coefficients, the tunability of their energetic and chemical properties and their thermal and mechanical stabilities, they still face the great challenge of having significantly low power conversion efficiency (PCE) values of only 3-5%. The prominent origins of the poor efficiency of all-PSCs are the undesirable features of the bulk-heterojunction (BHJ) blend morphology including the phase-separated large-scale domain size, reduced ordering of the polymer chains. Tuning side alkyl chains of conjugated polymers is an effective route for manipulating the blend morphology in BHJ type solar cells. However, the role of side chains in all-PSCs is poorly understood. Herein, we report high-performing all-PSCs with 5.96% efficiency by developing a series of naphthalenediimide (NDI)-based polymer acceptors with different alkyl side chains. We demonstrated that the use of the PNDIT with hexyldecyl side chains produced highly-ordered polymer stackings with strong face-on geometry and at the same time, forming the optimal BHJ morphology with finely separated phase domains, all of which contributed together to induce well-balanced μe/ μh ratio and generate efficient all-PSCs with PCEs near 6%.

  5. Universal properties of a single polymer chain in slit: Scaling versus MD simulations

    CERN Document Server

    Dimitrov, Dimitar I; Binder, Kurt; Klushin, Leonid I; Skvortsov, Alexander M

    2008-01-01

    We revisit the classical problem of a polymer confined in a slit in both of its static and dynamic aspects. We confirm a number of well known scaling predictions and analyse their range of validity by means of comprehensive Molecular Dynamics simulations using a coarse-grained bead-spring model of a flexible polymer chain. The normal and parallel components of the average end-to-end distance, mean radius of gyration and their distributions, the density profile, the force exerted on the slit walls, and the local bond orientation characteristics are obtained in slits of width $D$ = $4 \\div 10$ (in units of the bead radius) and for chain lengths $N=50 \\div 300$. We demonstrate that a wide range of static chain properties in normal direction can be described {\\em quantitatively} by analytic model - independent expressions in perfect agreement with computer experiment. In particular, the observed profile of confinement-induced bond orientation, is shown to closely match theory predictions. The anisotropy of confin...

  6. Stretching semiflexible polymer chains: evidence for the importance of excluded volume effects from Monte Carlo simulation.

    Science.gov (United States)

    Hsu, Hsiao-Ping; Binder, Kurt

    2012-01-14

    Semiflexible macromolecules in dilute solution under very good solvent conditions are modeled by self-avoiding walks on the simple cubic lattice (d = 3 dimensions) and square lattice (d = 2 dimensions), varying chain stiffness by an energy penalty ε(b) for chain bending. In the absence of excluded volume interactions, the persistence length l(p) of the polymers would then simply be l(p) = l(b)(2d - 2)(-1)q(b) (-1) with q(b) = exp(-ε(b)/k(B)T), the bond length l(b) being the lattice spacing, and k(B)T is the thermal energy. Using Monte Carlo simulations applying the pruned-enriched Rosenbluth method (PERM), both q(b) and the chain length N are varied over a wide range (0.005 ≤ q(b) ≤ 1, N ≤ 50,000), and also a stretching force f is applied to one chain end (fixing the other end at the origin). In the absence of this force, in d = 2 a single crossover from rod-like behavior (for contour lengths less than l(p)) to swollen coils occurs, invalidating the Kratky-Porod model, while in d = 3 a double crossover occurs, from rods to Gaussian coils (as implied by the Kratky-Porod model) and then to coils that are swollen due to the excluded volume interaction. If the stretching force is applied, excluded volume interactions matter for the force versus extension relation irrespective of chain stiffness in d = 2, while theories based on the Kratky-Porod model are found to work in d = 3 for stiff chains in an intermediate regime of chain extensions. While for q(b) ≪ 1 in this model a persistence length can be estimated from the initial decay of bond-orientational correlations, it is argued that this is not possible for more complex wormlike chains (e.g., bottle-brush polymers). Consequences for the proper interpretation of experiments are briefly discussed. PMID:22260610

  7. Ordering and dewetting in spin-coated films of a liquid crystalline main chain polymer

    International Nuclear Information System (INIS)

    The ordering of spin-coated films of a main-chain smectic liquid crystalline polymer with an azobenzene group connected by flexible spacers to a phenyl malonate unit has been studied as a function of film thickness using scanning force microscopy and UV/Vis spectroscopy. Already the as-prepared films are characterized by a significant out-of-plane orientation of the azobenzene groups. Annealing of films thicker than 7 nm results in aggregation and homeotropical alignment of azobenzene groups forming smectic layers parallel to the substrate. An optically isotropic mesophase was found upon annealing in the temperature range of smectic mesophase. Films thinner than the bilayer thickness of 7 nm exhibit a completely different behavior, whereby spin-coating results in a spontaneously homeotropic alignment of the azobenzene units. A subsequent annealing generates a structure of holes and rims. Within the holes a polymer monolayer remains, planarly aligned to substrate

  8. The Role of Chain Length in Nonergodicity Factor and Fragility of Polymers

    DEFF Research Database (Denmark)

    Dalle-Ferrie, Cecile; Niss, Kristine; Sokolov, Alexei;

    2010-01-01

    The mechanism that leads to different fragility values upon approaching the glass transition remains a topic of active discussion. Many researchers are trying to find an answer in the properties of the frozen glassy state. Following this approach, we focus here on a previously proposed relationship...... between the fragility of glass-formers and their nonergodicity factor, determined by inelastic X-ray scattering (IXS) in the glass. We extend this molecular liquid study to two model polymers— polystyrene (PS) and polyisobutylene (PIB)—for which we change the molecular weight. Polymers offer the...... opportunity to change the fragility without altering the chemical structure, just by changing the chain length. Thus, we specifically chose PS and PIB because they exhibit opposite dependences of fragility with molecular weight. Our analysis for these two polymers reveals no unique correlation between the...

  9. Understanding entangled polymers: What we can learn from athermal chain packings

    Science.gov (United States)

    Karayiannis, Nikos

    2012-02-01

    The study of random and ordered packings (from atoms and colloidal particles to sand grains) has been the focus of extensive research. This is not surprising since an understanding of the mechanisms that control morphology and packing is the key to the design and synthesis of novel ``smart'' materials and functionalities. In particular, the study of packings of chain molecules presents challenges but also insights which are absent in monatomic systems and further allows for a direction comparison with them. In this contribution we give an overview of our work on very dense and nearly jammed packings of athermal polymers. We show that chain molecules can be as efficiently and as densely packed as monatomic analogs up to the same maximally random jammed state. We also show that an exact correspondence can be established between the statistical-mechanical ensembles of packings of monatomic, and chain systems, which yields insights on the universality of jamming. By studying the effect of concentration on polymer size and on the underlying network of topological hindrances we precisely identify the distinct universal scaling regimes and the corresponding exponents. An unsuspected connection, valid from dilute up to very dense assemblies, is established between knots (of intermolecular origin) and entanglements (intermolecular constraints). We finally show that, against expectations, entropy-driven crystallization can occur in dense systems of athermal polymers once a critical volume fraction is reached. Such phase transition is driven by the increase in translational entropy: ordered sites exhibit enhanced mobility as their local free volume becomes more spherical and symmetric. Incipient nuclei develop well defined, stack-faulted layered crystal morphologies with a single stacking direction. The ordering transition and the resulting complex morphologies are analyzed, highlighting similarities and differences with respect to monatomic crystallization.

  10. Two unprecedented 1D coordination polymer chains based on tetranuclear copper(II) building blocks

    International Nuclear Information System (INIS)

    The reaction of copper(II) sulfate with pyridine in DMF or methanol yield two unprecedented Cu(II) coordination polymers {[Cu4(μ4-O)(py)4(SO4)4][μ-Cu(py)(DMF)2]}n(1) and {[Cu4(μ4-O)(py)4(SO4)4][μ-Cu(py)4]}n(2), respectively. Single-crystal X-ray diffraction indicated that compound 1 crystallizes in the monoclinic system, space group p2(1)/n, a=14.542(5) A, b=16.359(5) A, c=18.951(5) A, β=92.047(5)o, V=4505(2) A3, Z=4 while 2 is monoclinic C2/c, a=23.078(5) A, b=10.214(5) A, c=23.142(5) A, β=115.471(5)o, V=4925(3) A3, Z=4. Both of the two compounds consist of tetrahedral tetranuclear [Cu4(μ4-O)(py)4(SO4)4] clusters that are bridged by pentacoordinated Cu atom for 1 or hexacoordinated Cu atoms for 2 through the sulfate oxygen to form the infinite one-dimensional polymer chains. - Graphical abstract: Two unprecedented Cu(II) coordination polymers have been prepared by using solvothermal method; they consist of tetrahedral tetranuclear clusters that are bridged by unique Cu(II) atom through the sulfate oxygen to form the infinite one-dimensional polymer chains (a) for complex 1 and (b) for complex 2

  11. Controlled and selective placement of boron subphthalocyanines on either chain end of polymers synthesized by nitroxide mediated polymerization

    Directory of Open Access Journals (Sweden)

    Benoît H. Lessard

    2015-10-01

    Full Text Available In previous studies, we synthesized the first organic light emitting diode (OLED using boron subphthalocyanines (BsubPcs based polymers. When designing new polymer materials for organic electronic applications such as OLEDs or organic photovoltaic (OPV devices it is important to consider not only the contribution of each monomer but also the polymer chain ends. In this paper we establish a post-polymerization strategy to couple BsubPcs onto either the α- or the ω-chain end using chemically selective BsubPc derivatives. We outline how the chain ends of two representative polymers, poly(styrene (PS and poly(n-butylacrylate (BA, synthesized by nitroxide mediated polymerization (NMP, using BlocBuilder-MA as the initiating species, can be chemically modified by the incorporation of BsubPc chromophores. The addition of the BsubPc chromophore was confirmed through the use of a photodiode array detector (PDA connected in-line with a gel permeation chromatography (GPC setup. These findings represent the first reported method for the controlled and selective placement of a BsubPc chromophores on either end of a polymer produced by NMP. This strategy will therefore be utilized to make next generation BsubPc polymers for OLEDs and OPV devices. The extremely high molar extinction coefficient of BsubPc also make these polymers ideally suited for dye-labelling of polymers.

  12. Siloxane-Terminated Solubilizing Side Chains: Bringing Conjugated Polymer Backbones Closer and Boosting Hole Mobilities in Thin-Film Transistors

    KAUST Repository

    Mei, Jianguo

    2011-12-21

    We introduce a novel siloxane-terminated solubilizing group and demonstrate its effectiveness as a side chain in an isoindigo-based conjugated polymer. An average hole mobility of 2.00 cm 2 V -1 s -1 (with a maximum mobility of 2.48 cm 2 V -1 s -1), was obtained from solution-processed thin-film transistors, one of the highest mobilities reported to date. In contrast, the reference polymer with a branched alkyl side chain gave an average hole mobility of 0.30 cm 2 V -1 s -1 and a maximum mobility of 0.57 cm 2 V -1 s -1. This is largely explained by the polymer packing: our new polymer exhibited a π-π stacking distance of 3.58 Å, while the reference polymer showed a distance of 3.76 Å. © 2011 American Chemical Society.

  13. Theory and Monte Carlo simulations for the stretching of flexible and semi-flexible single polymer chains under external fields

    CERN Document Server

    Manca, Fabio; Palla, Pier Luca; Cleri, Fabrizio; Colombo, Luciano

    2012-01-01

    Recent developments of microscopic mechanical experiments allow the manipulation of individual polymer molecules in two main ways: \\textit{uniform} stretching by external forces and \\textit{non-uniform} stretching by external fields. Many results can be thereby obtained for specific kinds of polymers and specific geometries. In this work we describe the non-uniform stretching of a single, non-branched polymer molecule by an external field (e.g. fluid in uniform motion, or uniform electric field) by a universal physical framework which leads to general conclusions on different types of polymers. We derive analytical results both for the freely-jointed chain and the worm-like chain models based on classical statistical mechanics. Moreover, we provide a Monte Carlo numerical analysis of the mechanical properties of flexible and semi-flexible polymers anchored at one end. The simulations confirm the analytical achievements, and moreover allow to study the situations where the theory can not provide explicit and u...

  14. Effect of bidispersity in grafted chain length on grafted chain conformations and potential of mean force between polymer grafted nanoparticles in a homopolymer matrix.

    Science.gov (United States)

    Nair, Nitish; Wentzel, Nathaniel; Jayaraman, Arthi

    2011-05-21

    In efforts to produce polymeric materials with tailored physical properties, significant interest has grown around the ability to control the spatial organization of nanoparticles in polymer nanocomposites. One way to achieve controlled particle arrangement is by grafting the nanoparticle surface with polymers that are compatible with the matrix, thus manipulating the interfacial interactions between the nanoparticles and the polymer matrix. Previous work has shown that the molecular weight of the grafted polymer, both at high grafting density and low grafting density, plays a key role in dictating the effective inter-particle interactions in a polymer matrix. At high grafting density nanoparticles disperse (aggregate) if the graft molecular weight is higher (lower) than the matrix molecular weight. At low grafting density the longer grafts can better shield the nanoparticle surface from direct particle-particle contacts than the shorter grafts and lead to the dispersion of the grafted particles in the matrix. Despite the importance of graft molecular weight, and evidence of non-trivial effects of polydispersity of chains grafted on flat surfaces, most theoretical work on polymer grafted nanoparticles has only focused on monodisperse grafted chains. In this paper, we focus on how bidispersity in grafted chain lengths affects the grafted chain conformations and inter-particle interactions in an implicit solvent and in a dense homopolymer polymer matrix. We first present the effects of bidispersity on grafted chain conformations in a single polymer grafted particle using purely Monte Carlo (MC) simulations. This is followed by calculations of the potential of mean force (PMF) between two grafted particles in a polymer matrix using a self-consistent Polymer Reference Interaction Site Model theory-Monte Carlo simulation approach. Monte Carlo simulations of a single polymer grafted particle in an implicit solvent show that in the bidisperse polymer grafted particles

  15. In situ x-ray scattering study of a main-chain thermotropic liquid crystalline polymer under oscillatory shear flow

    Science.gov (United States)

    Vaish, Nitin; Burghardt, Wesley R.; Zhou, Weijun; Kornfield, Julia A.

    2000-03-01

    Liquid crystalline polymers (LCPs) have been the subject of extensive studies because of potential commercial applications and scientific challenges. The excellent mechanical properties of LCPs arise from highly anisotropic molecular structure, which develops as a complex interplay between molecular dynamics and the applied flow field. We study the behavior of model thermotropic main-chain LCP (DHMS-7,9) under oscillatory shear flow using in situ X-ray scattering techniques. Experiments were done in nematic (140^o C) and x-phase (110^o C) to study the effects of frequency (0.5 - 50 rps) and strain amplitude (50 200In nematic phase, strong alignment in the flow direction (‘parallel’) was observed. The steady state was reached quickly either at high strain amplitudes or high frequencies. In x-phase, molecules aligned in flow direction at high strain levels or oscillation frequency, while alignment in vorticity (‘perpendicular’) direction was observed at low strain amplitude or frequency. In addition, we present the flipping of orientation from parallel to perpendicular alignment as a result of step change in temperature from 140^o C to 110^o C and oscillatory motion from a pre-aligned parallel state in x-phase.

  16. 高分子单链的研究进展%Research Advances of Single Polymer Chain

    Institute of Scientific and Technical Information of China (English)

    洪晓东; 梁兵

    2012-01-01

    With the development of nano-technology in the field of polymer, researchers pay attention to the condensed state of single polymer chain. Single polymer chains were existed in micro- particles with nanometer scale, and geometric entanglements were not founded between polymer chains. This article reviews the progress of single polymer chain in recent years. The preparation methods of single polymer chain are introduced, such as atomizer spraying, freeze-drying, microemulsion polymerization, reverse precipitation and surface film spreading, meanwhile the characterization methods of single polymer chain and computer simulation technique for the conformation of polymer chains are reviewed; in the last section, the application of single polymer chain and unimolecular micelles in preparation of metal nano-particles are represented and the coming research fields of single polymer chain are prospected.%随着纳米科技在高分子领域的不断升温,高分子单链凝聚态的研究引起了人们的广泛重视。高分子单链以纳米尺度的微粒孤立存在,不存在分子链之间的几何缠结。本文综述了近年来国内外高分子单链的研究进展。首先介绍了高分子单链的主要制备方法如喷雾法、冷冻干燥法、微乳液聚合法、反向沉淀法以及表面扩展膜法,接着详细介绍了高分子单链的表征技术及高分子链构象的计算机模拟技术,最后介绍了高分子单链及单分子胶柬在制备金属纳米粒子领域的应用,并展望了高分子单链的研究领域和方向。

  17. NUMERICAL SIMULATION OF MORPHOLOGY OF POLYMER CHAIN COILS IN COMPLEX FLOWS

    Institute of Scientific and Technical Information of China (English)

    Hong Zheng; Wei Yu; Chi-xing Zhou

    2005-01-01

    A new coupled finite element formulation is proposed to calculate a conformation tensor model in two complex flows: a planar contraction flow and a planar flow around a symmetrically placed cylinder. The components of conformation tensor are first computed together with the velocity and pressure to describe the change of morphology of polymer chain coils in flow fields. Macroscopic quantities of viscoelastic flow are then calculated based on the conformation tensor. Comparisons between the numerical simulations and experiments for stress patterns and velocity profiles are carried out to prove the validity of the method.

  18. Charge Injection and Transport in Metal/Polymer Chains/Metal Sandwich Structure

    Institute of Scientific and Technical Information of China (English)

    LI Hai-Hong; LI Dong-Mei; LI Yuan; GAO Kun; LIU De-Sheng; XIE Shi-Jie

    2008-01-01

    @@ Using the tight-binding Su-Schrieffer-Heeger model and a nonadiabatic dynamic evolution method, we study the dynamic processes of the charge injection and transport in a metal/two coupled conjugated polymer chains/metal structure. It is found that the charge interchain transport is determined by the strength of the electric field and the magnitude of the voltage bias applied on the metal electrode. The stronger electric field and the larger voltage bias are both in favour of the charge interchain transport.

  19. Adsorption of a single polymer chain on a surface: effects of the potential range.

    Science.gov (United States)

    Klushin, Leonid I; Polotsky, Alexey A; Hsu, Hsiao-Ping; Markelov, Denis A; Binder, Kurt; Skvortsov, Alexander M

    2013-02-01

    We investigate the effects of the range of adsorption potential on the equilibrium behavior of a single polymer chain end-attached to a solid surface. The exact analytical theory for ideal lattice chains interacting with a planar surface via a box potential of depth U and width W is presented and compared to continuum model results and to Monte Carlo (MC) simulations using the pruned-enriched Rosenbluth method for self-avoiding chains on a simple cubic lattice. We show that the critical value U(c) corresponding to the adsorption transition scales as W(-1/ν), where the exponent ν=1/2 for ideal chains and ν≈3/5 for self-avoiding walks. Lattice corrections for finite W are incorporated in the analytical prediction of the ideal chain theory U(c)≈(π(2)/24)(W+1/2)(-2) and in the best-fit equation for the MC simulation data U(c)=0.585(W+1/2)(-5/3). Tail, loop, and train distributions at the critical point are evaluated by MC simulations for 1≤W≤10 and compared to analytical results for ideal chains and with scaling theory predictions. The behavior of a self-avoiding chain is remarkably close to that of an ideal chain in several aspects. We demonstrate that the bound fraction θ and the related properties of finite ideal and self-avoiding chains can be presented in a universal reduced form: θ(N,U,W)=θ(NU(c),U/U(c)). By utilizing precise estimations of the critical points we investigate the chain length dependence of the ratio of the normal and lateral components of the gyration radius. Contrary to common expectations this ratio attains a limiting universal value /=0.320±0.003 only at N~5000. Finite-N corrections for this ratio turn out to be of the opposite sign for W=1 and for W≥2. We also study the N dependence of the apparent crossover exponent φ(eff)(N). Strong corrections to scaling of order N(-0.5) are observed, and the extrapolated value φ=0.483±0.003 is found for all values of W. The strong correction to scaling effects found here explain why

  20. Slow knot formation by suppressed self-reptation in a collapsed polymer chain

    Science.gov (United States)

    Nakata, Mitsuo; Nakamura, Yoshiki; Sasaki, Naoki; Maki, Yasuyuki

    2012-02-01

    Chain-expansion processes from knotted globules have been measured for poly(methyl methacrylate) (PMMA) in the mixed solvent tert-butyl alcohol (TBA) + water (2.5 vol %) by static light scattering. The solution was quenched from the Θ temperature of 41.5 ∘C to 37.0 ∘C, aged there for a time period tp, and then returned rapidly to the Θ temperature. The chain-expansion process was determined as a time evolution of the expansion factor α2 after the temperature increase. The measurement was carried out by changing the aging time tp from 240 to 7200 min, and the molecular weight from Mw = 4.0 × 106 to 1.5 × 107, by taking advantage of the extremely slow chain aggregation in the solution. The chain-expansion process obtained for Mw = 1.22 × 107 became slow with increasing tp, which revealed the knot formation in single globules. The characteristic time of the chain expansion from globules aged for tp = 7200 min was found to depend on the molecular weight as Mw2.7. This exponent, which is close to 3, demonstrated a disentanglement process due to self-reptation. The present data were compared with the previous data of the chain expansion from compact globules aged at 25.0 ∘C. The comparison made at Mw = 1.22 × 107 and at the same values of tp revealed that the chain expansion from the globules aged at 25.0 ∘C was much faster than that from the globules at 37.0 ∘C, indicating a lower knot density in the more compact globules. It was conjectured that the knot formation due to self-reptation would be suppressed in a compact globule because an entire conformational change required by knot formation would become difficult to occur in the confined space of high segment concentration, particularly for a long polymer chain. The chain collapse of PMMA in the mixed solvent has been observed to occur extremely slowly at the later stage. This slow process was explained by the suppressed self-reptation.

  1. Theory of microphase separation on side-chain liquid-crystalline polymers with flexible spacers.

    Science.gov (United States)

    Hernández-Jiménez, M; Westfahl, H

    2007-05-01

    We model a melt of monodisperse side-chain liquid-crystalline polymers as a melt of comb copolymers in which the side groups are rod-coil diblock copolymers. We consider both excluded-volume and Maier-Saupe interactions. The first acts among any pair of segments while the latter acts only between rods. Using a free-energy functional calculated from this microscopic model, we study the spinodal stability of the isotropic phase against density and orientational fluctuations. The phase diagram obtained in this way predicts nematic and smectic instabilities as well as the existence of microphases or phases with modulated wave vector but without nematic ordering. Such microphases are the result of the competition between the incompatibility among the blocks and the connectivity constraints imposed by the spacer and the backbone. Also the effects of the polymerization degree and structural conformation of the monomeric units on the phase behavior of the side-chain liquid-crystalline polymers are studied. PMID:17541501

  2. Theoretical investigation of polymer chain stability in the metal coordinated azorubine and cyclam complex

    International Nuclear Information System (INIS)

    Highlights: • Ni(II)- and Zn(II)-coordinated cyclam–azorubine complexes are described using DFT. • Ni(II) coordinated system shows a reasonably small singlet–triplet energy gap. • Intersystem crossing gives high barrier between singlet and triplet geometries. • For the Zn(II) case only the singlet state is energetically favorable. • The stability of a longer polymer (oligomer) chain was described using DFTB. - Abstract: Theoretical investigations have been performed for unit systems with Ni(II) and Zn(II) coordination between azorubine and 1,4,8,11-tetraazacyclotetradecane (cyclam) complexes using the conventional DFT and the DFT-based tight binding (DFTB) methods. Two different geometries (short and long) and spin states (singlet and triplet) of the model system built by two mesylate groups and the cyclam ring together with Ni(II) and Zn(II) ions were energetically characterized. For the Ni(II) coordination complex the triplet geometry is preferred, but one could not exclude also the presence of the singlet spin configuration due to the huge energy barrier defined by the intersystem crossing. The intersystem crossing geometry of the singlet–triplet transition was studied in details and the corresponding spin–orbit couplings were discussed. For the Zn(II) coordination complex only the singlet state was found. Polymer chain build up from four unit systems presents irregular forms with strong coordination bonds between units

  3. Ionic polymer cluster energetics: Computational analysis of pendant chain stiffness and charge imbalance

    Science.gov (United States)

    Weiland, Lisa Mauck; Leo, Donald J.

    2005-06-01

    In recent years there has been considerable study of the potential mechanisms underlying the electromechanical response of ionic-polymer-metal composites. The most recent models have been based on the response of the ion-containing clusters that are formed when the material is synthesized. Most of these efforts have employed assumptions of uniform ion distribution within spherical cluster shapes. This work investigates the impact of dispensing with these assumptions in order to better understand the parameters that impact cluster shape, size, and ion transport potential. A computational micromechanics model applying Monte Carlo methodology is employed to predict the equilibrium state of a single cluster of a solvated ionomeric polymer. For a constant solvated state, the model tracks the position of individual ions within a given cluster in response to ion-ion interaction, mechanical stiffness of the pendant chain, cluster surface energy, and external electric-field loading. Results suggest that cluster surface effects play a significant role in the equilibrium cluster state, including ion distribution; pendant chain stiffness also plays a role in ion distribution but to a lesser extent. Moreover, ion pairing is rarely complete even in cation-rich clusters; this in turn supports the supposition of the formation of anode and cathode boundary layers.

  4. Synthesis and properties of aromatic polyethers containing poly(ethylene oxide) side chains as polymer electrolytes for lithium ion batteries

    International Nuclear Information System (INIS)

    Polymer electrolytes consisting of polar pyridine units in the backbone and poly(ethylene oxide) (PEO) side chains are designed for possible application in lithium ion batteries. In particular, aromatic polyethers bearing PEO side chains with varying length are synthesized either by copolymerization of the corresponding PEO based diols with different arylfluorides or by modification of dihydroxyl functionalized precursor polymers with poly(ethylene oxide) methyl ether tosylate. The formation of free standing films is dependent on the PEO content, polymers' composition as well as on the different monomers used. The mechanical properties study shows that the glass transition temperature can be controlled by varying the PEO content. Thermal stability is also influenced by the PEO length: the shorter the PEO side chain, the higher the stability. XRD analysis gives information about the desired amorphous character of these polymers, which is independent of the PEO content. Solid polymer electrolytes prepared by blending the PEO-based polymers with lithium salt and PEO 2000 (used as plasticizer) show ambient temperature conductivities in the range of 10−6 S/cm. To further improve conductivity doping of PEO-based polymers in liquid electrolyte (1 M LiPF6 in EC/DMC 1/1) in some cases results in high conductivities in the range of 10−3 S cm−1 at 80 °C. - Highlights: • Polymer electrolytes bearing PEO side chains of varying lengths were designed. • DMA and TGA show that Tg and Td can be controlled by varying the PEO content. • XRD confirms polymers amorphous character, independent of the PEO content. • Membranes doped in liquid electrolyte have high conductivities (10−3 S cm−1, 80 °C)

  5. Attachment of polymer chains on plasma-treated surfaces: experiments and modeling

    Energy Technology Data Exchange (ETDEWEB)

    Riccardi, C [Dipartimento di Fisica, Universita di Milano-Bicocca, Piazza della Scienza 3, 20126 Milano (Italy); Roman, H E [Max Planck Institute for the Physics of Complex Systems, Noethnitzer Str. 38, 01187 Dresden (Germany); Ziano, R, E-mail: roman@pks.mpg.d [Dipartimento di Medicina Sperimentale, Universita di Milano-Bicocca, Via Cadore 48, 20052 Monza (Italy)

    2010-07-15

    Deposition of linear polymers, such as polyethylene glycol (PEG), on a plasma-treated surface has been studied experimentally and theoretically by means of Monte Carlo (MC) simulations. Acrylic acid is deposited on a silicon wafer in the presence of argon at a pressure of 10 Pa by applying 30 W external power. Active carboxyl sites are obtained having a surface number density of {approx}2 sites nm{sup -2}. A homogeneous PEG solution is brought into contact with the treated surface (over 24 h) and a thin film of attached PEG chains is formed. Two different PEGs having molecular weights of 3000 and 5000 g mol{sup -1}, respectively, are considered. The corresponding thin film widths, W, are measured, yielding W(3000)=4.3{+-}3.1 nm and W(5000)=8.8{+-}1.8 nm. For the MC simulations, the linear polymers are modeled as an ensemble of self-avoiding walks of length N (number of monomers) on a simple cubic lattice, executing worm-like or reptation dynamics, which can become attached at an active carboxyl site on the surface. The numerical results for the film widths are in good agreement with the experimental findings. We find that less than 20% of active sites are effectively occupied by attached chains, corresponding to less than 5% of the total available surface sites. Scaling arguments predict universal power-law dependences of the film density, {rho}(N), as a function of polymer length, i.e. {rho}(N){approx}c/N{sup {nu}}, with c{approx_equal}5 g cm{sup -3} and {nu}{approx_equal}0.6. The model also predicts a dependence of the prefactor c on the density of carboxyl active sites.

  6. Free-radical-induced chain scission and cross-linking of polymers in aqueous solution - an overview

    International Nuclear Information System (INIS)

    In the radiolysis of N2O-saturated aqueous solutions the ·OH radicals in their reactions with polymers give rise to polymer-derived radicals. The kinetics of the formation and decay of these radicals are reviewed. Once a larger number of radicals are formed on one polymer molecule, e.g. upon pulse radiolysis, close-by radicals recombine more rapidly while the more distant ones survive for much longer times. Intermolecular cross-linking (between two polymer chains, increase in molecular weight) and intramolecular cross-linking (formation of small loops, no increase in polymer weight) are competing processes, and their relative yields thus depend on the dose rate and polymer concentration. Hydrogen-transfer reactions within the polymer, e.g. transformation of a secondary radical into a tertiary one, are common and facilitated by the high local density of reactive sites. Due to repulsive forces, the lifetime of radicals of charged polymers is substantially increased. This enables even relatively slow β-fragmentation reactions to become of importance. In the case of poly(methacrylic acid) this even leads to an unzipping, and the situation of equilibrium polymerisation is approached. Heterolytic β-fragmentation is possible when adequate leaving groups are available, e.g. in polynucleotides and DNA. In the presence of O2, chain scission occurs via oxyl radicals as intermediates

  7. Detachment of semiflexible polymer chains from a substrate: A molecular dynamics investigation

    Energy Technology Data Exchange (ETDEWEB)

    Paturej, J. [Leibniz-Institut of Poslymer Research Dresden, 01069 Dresden (Germany); Institute of Physics, University of Szczecin, Wielkopolska 15, 70451 Szczecin (Poland); Erbas, A. [Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208 (United States); Milchev, A. [Institute for Physical Chemistry, Bulgarian Academy of Sciences, 1113 Sofia (Bulgaria); Rostiashvili, V. G. [Max-Planck-Institute for Polymer Research, Ackermannweg 10, 55128 Mainz (Germany)

    2014-12-07

    Using Molecular Dynamics simulations, we study the force-induced detachment of a coarse-grained model polymer chain from an adhesive substrate. One of the chain ends is thereby pulled at constant speed off the attractive substrate and the resulting saw-tooth profile of the measured mean force 〈f〉 vs height D of the end-segment over the plane is analyzed for a broad variety of parameters. It is shown that the observed characteristic oscillations in the 〈f〉-D profile depend on the bending and not on the torsional stiffness of the detached chains. Allowing for the presence of hydrodynamic interactions (HI) in a setup with explicit solvent and dissipative particle dynamics-thermostat, rather than the case of Langevin thermostat, one finds that HI have little effect on the 〈f〉-D profile. Also the change of substrate affinity with respect to the solvent from solvophilic to solvophobic is found to play negligible role in the desorption process. In contrast, a changing ratio ε{sub s}{sup B}/ε{sub s}{sup A} of the binding energies of A- and B-segments in the detachment of an AB-copolymer from adhesive surface strongly changes the 〈f〉-D profile whereby the B-spikes vanish when ε{sub s}{sup B}/ε{sub s}{sup A}<0.15. Eventually, performing an atomistic simulation of (bio)-polymers, we demonstrate that the simulation results, derived from our coarse-grained model, comply favorably with those from the all-atom simulation.

  8. Michaelis-Menten dynamics of a polymer chain out of a dichotomous ATP-based motor

    International Nuclear Information System (INIS)

    We present a model of an ATP-fueled molecular machine which pushes a polymer through a pore channel. The machine acts between two levels (working-waiting), and the working one remains active for a fixed time giving a constant force. The activation rate of the machine can be put in relationship with the available ATP concentration in the solution, which gives the necessary energy supply. The translocation time shows a monotonic behaviour as a function of the activation frequency, and the velocity follows a Michaelis-Menten (MM) law that arises naturally in this description. The estimation of the stall force of the motor follows a corrected MM law which yet is to be checked in experimental investigations. The results presented here agree with recent biological experimental findings. (paper)

  9. Polymer gels with associating side chains and their interaction with surfactants.

    Science.gov (United States)

    Gordievskaya, Yulia D; Rumyantsev, Artem M; Kramarenko, Elena Yu

    2016-05-14

    Conformational behaviour of hydrophobically modified (HM) polymer gels in solutions of nonionic surfactants is studied theoretically. A HM gel contains hydrophobic side chains (stickers) grafted to its subchains. Hydrophobic stickers are capable to aggregate into joint micelles with surfactant molecules. Micelles containing more than one sticker serve as additional physical cross-links of the network, and their formation causes gel shrinking. In the proposed theoretical model, the interior of the gel/surfactant complex is treated as an array of densely packed spherical polymer brushes consisting of gel subchains tethered to the surface of the spherical sticker/surfactant micelles. Effect of stickers length and grafting density, surfactant concentration and hydrophobicity on gel swelling as well as on hydrophobic association inside it is analyzed. It is shown that increasing surfactant concentration can result in a gel collapse, which is caused by surfactant-induced hydrophobic aggregation of stickers, and a successive gel reswelling. The latter should be attributed to a growing fraction of surfactants in joint aggregates and, hence, increasing number of micelles containing only one sticker and not participating in gel physical cross-linking. In polyelectrolyte (PE) gels hydrophobic aggregation is opposed by osmotic pressure of mobile counterions, so that at some critical ionization degree hydrophobic association is completely suppressed. Hydrophobic modification of polymers is shown to open new ways for controlling gel responsiveness. In particular, it is discussed that incorporation of photosensitive groups into gel subchains and/or surfactant tail could give a possibility to vary the gel volume by light. Since hydrophobic aggregation regularities in gels and solutions are common, we hope our findings will be useful for design of polymer based self-healing materials as well. PMID:27179504

  10. Theory and Monte Carlo simulations for the stretching of flexible and semiflexible single polymer chains under external fields

    Science.gov (United States)

    Manca, Fabio; Giordano, Stefano; Palla, Pier Luca; Cleri, Fabrizio; Colombo, Luciano

    2012-12-01

    Recent developments of microscopic mechanical experiments allow the manipulation of individual polymer molecules in two main ways: uniform stretching by external forces and non-uniform stretching by external fields. Many results can be thereby obtained for specific kinds of polymers and specific geometries. In this work, we describe the non-uniform stretching of a single, non-branched polymer molecule by an external field (e.g., fluid in uniform motion, or uniform electric field) by a universal physical framework, which leads to general conclusions on different types of polymers. We derive analytical results both for the freely-jointed chain and the worm-like chain models based on classical statistical mechanics. Moreover, we provide a Monte Carlo numerical analysis of the mechanical properties of flexible and semiflexible polymers anchored at one end. The simulations confirm the analytical achievements, and moreover allow to study the situations where the theory cannot provide explicit and useful results. In all cases, we evaluate the average conformation of the polymer and its fluctuation statistics as a function of the chain length, bending rigidity, and field strength.

  11. Interplay Between Side Chain Pattern, Polymer Aggregation, and Charge Carrier Dynamics in PBDTTPD:PCBM Bulk-Heterojunction Solar Cells

    KAUST Repository

    Dyer-Smith, Clare

    2015-05-01

    Poly(benzo[1,2-b:4,5-b′]dithiophene–alt–thieno[3,4-c]pyrrole-4,6-dione) (PBDTTPD) polymer donors with linear side-chains yield bulk-heterojunction (BHJ) solar cell power conversion efficiencies (PCEs) of about 4% with phenyl-C71-butyric acid methyl ester (PC71BM) as the acceptor, while a PBDTTPD polymer with a combination of branched and linear substituents yields a doubling of the PCE to 8%. Using transient optical spectroscopy it is shown that while the exciton dissociation and ultrafast charge generation steps are not strongly affected by the side chain modifications, the polymer with branched side chains exhibits a decreased rate of nongeminate recombination and a lower fraction of sub-nanosecond geminate recombination. In turn the yield of long-lived charge carriers increases, resulting in a 33% increase in short circuit current (J sc). In parallel, the two polymers show distinct grazing incidence X-ray scattering spectra indicative of the presence of stacks with different orientation patterns in optimized thin-film BHJ devices. Independent of the packing pattern the spectroscopic data also reveals the existence of polymer aggregates in the pristine polymer films as well as in both blends which trap excitons and hinder their dissociation.

  12. Factors governing intercalation of fullerenes and other small molecules between the side chains of semiconducting polymers used in solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Miller, Nichole Cates; Gysel, Roman; Miller, Chad E.; Sweetnam, Sean; Sellinger, Alan; McGehee, Michael D. [Department of Materials Science and Engineering, Stanford University, Stanford, CA (United States); Cho, Eunkyung [School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA (United States); School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA (United States); Risko, Chad; Coropceanu, Veaceslav; Bredas, Jean-Luc [School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA (United States); Heeney, Martin; McCulloch, Iain [Department of Chemistry, Imperial College London (United Kingdom); Toney, Michael F. [Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA (United States)

    2012-10-15

    While recent reports have established significant miscibility in polymer:fullerene blends used in organic solar cells, little is actually known about why polymers and fullerenes mix and how their mixing can be controlled. Here, X-ray diffraction (XRD), differential scanning calorimetry (DSC), and molecular simulations are used to study mixing in a variety of polymer:molecule blends by systematically varying the polymer and small-molecule properties. It is found that a variety of polymer:fullerene blends mix by forming bimolecular crystals provided there is sufficient space between the polymer side chains to accommodate a fullerene. Polymer:tetrafluoro-tetracyanoquinodimethane (F4-TCNQ) bimolecular crystals were also observed, although bimolecular crystals did not form in the other studied polymer:non-fullerene blends, including those with both conjugated and non-conjugated small molecules. DSC and molecular simulations demonstrate that strong polymer-fullerene interactions can exist, and the calculations point to van der Waals interactions as a significant driving force for molecular mixing. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. Factors Governing Intercalation of Fullerenes and Other Small Molecules Between the Side Chains of Semiconducting Polymers Used in Solar Cells

    KAUST Repository

    Miller, Nichole Cates

    2012-08-22

    While recent reports have established signifi cant miscibility in polymer:fullerene blends used in organic solar cells, little is actually known about why polymers and fullerenes mix and how their mixing can be controlled. Here, X-ray diffraction (XRD), differential scanning calorimetry (DSC), and molecular simulations are used to study mixing in a variety of polymer:molecule blends by systematically varying the polymer and smallmolecule properties. It is found that a variety of polymer:fullerene blends mix by forming bimolecular crystals provided there is suffi cient space between the polymer side chains to accommodate a fullerene. Polymer:tetrafl uoro-tetracyanoquinodimethane (F4-TCNQ) bimolecular crystals were also observed, although bimolecular crystals did not form in the other studied polymer:nonfullerene blends, including those with both conjugated and non-conjugated small molecules. DSC and molecular simulations demonstrate that strong polymer-fullerene interactions can exist, and the calculations point to van der Waals interactions as a signifi cant driving force for molecular mixing. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Phase behaviour of a dispersion of charge-stabilised colloidal spheres with added non-adsorbing interacting polymer chains.

    Science.gov (United States)

    Gögelein, C; Tuinier, R

    2008-10-01

    We present a theory for the phase behaviour of mixtures of charge-stabilised colloidal spheres plus interacting polymer chains in good and theta -solvents within the framework of free-volume theory. We use simple but accurate combination rules for the depletion thickness around a colloidal particle and for the osmotic pressure up to the semi-dilute concentration regime. Hence, we obtain expressions for the free energy for mixtures of charged colloidal particles and non-adsorbing interacting polymers. From that, we calculate the phase behaviour, and discuss its topology in dependence on the competition between the charge-induced repulsion and the polymer-induced attraction. The homogeneous mixture of colloids and polymers becomes more stabilised against demixing when increasing the electrostatic repulsion. This charge-induced stabilisation is strongest for small polymer-to-colloid size ratios and is more pronounced for charged colloids mixed with polymers in a good solvent than for polymers in a theta -solvent. For the weakly charged regime we find that the phase diagram becomes salt-concentration-independent in the protein limit for charged colloids plus polymers in a theta -solvent. The liquid window, i.e., the concentration regimes where a colloidal liquid exists, is narrowed down upon increasing the charge-induced repulsion. Also this effect is more pronounced when charged colloids are mixed with polymer chains in a good solvent. In summary, we demonstrate that the solvent quality significantly influences the phase behaviour of mixtures of charged colloids plus non-adsorbing polymers if the range of the screened electrostatic repulsion becomes of the order of the range of the depletion-induced attraction. PMID:18791755

  15. Magnetic hydrophilic methacrylate-based polymer microspheres designed for polymerase chain reactions applications.

    Science.gov (United States)

    Spanová, Alena; Horák, Daniel; Soudková, Eva; Rittich, Bohuslav

    2004-02-01

    Magnetic hydrophilic non-porous P(HEMA-co-EDMA), P(HEMA-co-GMA) and PGMA microspheres were prepared by dispersion (co)polymerization of 2-hydroxyethyl methacrylate (HEMA) and ethylene dimethacrylate (EDMA) or glycidyl methacrylate (GMA) in the presence of several kinds of magnetite. It was found that some components used in the preparation of magnetic carriers interfered with polymerase chain reaction (PCR). Influence of non-magnetic and magnetic microspheres, including magnetite nanoparticles and various components used in their synthesis, on the PCR course was thus investigated. DNA isolated from bacterial cells of Bifidobacterium longum was used in PCR evaluation of non-interfering magnetic microspheres. The method enabled verification of the incorporation of magnetite nanoparticles in the particular methacrylate-based polymer microspheres and evaluation of suitability of their application in PCR. Preferably, electrostatically stabilized colloidal magnetite (ferrofluid) should be used in the design of new magnetic methacrylate-based microspheres by dispersion polymerization. PMID:14698232

  16. Tunable Crystal-to-Crystal Phase Transition in a Cadmium Halide Chain Polymer

    Directory of Open Access Journals (Sweden)

    Ulli Englert

    2011-07-01

    Full Text Available The chain polymer [{Cd(μ-X2py2}1∞] (X = Cl, Br; py = pyridine undergoes a fully reversible phase transition between a monoclinic low-temperature and an orthorhombic high-temperature phase. The transformation can be directly monitored in single crystals and can be confirmed for the bulk by powder diffraction. The transition temperature can be adjusted by tuning the composition of the mixed-halide phase: Transition temperatures between 175 K up to the decomposition of the material at ca. 350 K are accessible. Elemental analysis, ion chromatography and site occupancy refinements from single-crystal X-ray diffraction agree with respect to the stoichiometric composition of the samples.

  17. Nondriven Polymer Translocation Through a Nanopore:Scaling for Translocation Time with Chain Length

    Institute of Scientific and Technical Information of China (English)

    LI Hui; ZHANG Jing; LIU Hong; SUN Chia-chung

    2011-01-01

    We investigated the dynamics of the passage for a polymer chain through a nanopore in the absence of any external driving force with Weeks-Chandler-Andersen potential in two-dimensional simulations,in particular,focused our attention on the scaling law of the mean translocation time.We found that the effect of hydrodynamic interactions is the major factor in determining the scaling exponents with increasing pore size.The scaling close to N1+2v was observed when the hydrodynamic interactions were screened in the cases of small pore sizes,while the scaling close to N3v was obtained when the hydrodynamic interactions were present in the cases of large pore sizes.

  18. BIOMIMETIC SURFACE PREPARATION OF INERT POLYMER FILMS VIA GRAFTING LONG MONOALKYL CHAIN PHOSPHATIDYLCHOLINE

    Institute of Scientific and Technical Information of China (English)

    Peng-jun Wan; Dong-sheng Tan; Zheng-sheng Li; Xiao-qing Zhang; Jie-hua Li; Hong Tan

    2012-01-01

    To explore construction of novel mimicking biomembrane on biomaterials surfaces,a new polymerizable phosphatidylcholine containing a long monoalkyl chain ended with acryl group (AASOPC) was designed and synthesized,which was easily derived from the terminal amino group of 9-(2-amino-ethylcarbamoyl)-nonyl-l-phosphatidyl-choline (ASOPC) reacting with acryloyl chloride.The obtained AASOPC was grafted on poly(ethylene terephthalate) (PET) via surface-initiated atom-transfer radical polymerization (SI-ATRP) to form mimicking biomembrane.These modified surface structures of PET were investigated using water contact angle (WAC),X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM).The results indicated that the new mimicking phosphatidylcholine biomembrane could be prepared on inert polymer surfaces by using the acryloyl phosphatidylcholine (AASOPC) via surface-initiated atom transfer radical polymerization (SI-ATRP).

  19. Impact of charge carrier injection on single-chain photophysics of conjugated polymers

    CERN Document Server

    Hofmann, Felix J; Lupton, John M

    2016-01-01

    Charges in conjugated polymer materials have a strong impact on the photophysics and their interaction with the primary excited state species has to be taken into account in understanding device properties. Here, we employ single-molecule spectroscopy to unravel the influence of charges on several photoluminescence (PL) observables. The charges are injected either stochastically by a photochemical process, or deterministically in a hole-injection sandwich device configuration. We find that upon charge injection, besides a blue-shift of the PL emission and a shortening of the PL lifetime due to quenching and blocking of the lowest-energy chromophores, the non-classical photon arrival time distribution of the multichromophoric chain is modified towards a more classical distribution. Surprisingly, the fidelity of photon antibunching deteriorates upon charging, whereas one would actually expect the number of chromophores to be reduced. A qualitative model is presented to explain the observed PL changes. The resul...

  20. Biogenesis and the growth of DNA-like polymer chains: a computer simulation

    International Nuclear Information System (INIS)

    We study, through computer simulation, a crucial step of Biogenesis, namely the growth of self-replicating codified DNA-like polymers starting from a mixture of oligomers. We have adopted the growth scheme that has been recently proposed by Ferreira and Tsallis which incorporates usual ideas of autocatalysis through complementary pairs and within which a central role is played by the hydrogen-like links (characterized by the probabilities pAT and pCG of chemical bonding of the A-T and C-G pairs respectively) between the two chains of the growing polymer. We find that the average equilibrium polymeric length ξ diverges, for any fixed ratio (1-pAT)/(1-p sub (CG)), as ξ ∝ 1/r1-pAT. Selection of patterns may happen at all stages and in particular at chemical equilibrium. Selection occurs via two different mechanisms: (i) away from the critical point pAT = pCG = 1 if pAT ≠ pCG; (ii) both on and away from the critical point if the initial concentrations of nucleotides (A, T, C and G or their precursors) are different. (author)

  1. Theoretical modeling of the effect of polymer chain immobilization rates on holographic recording in photopolymers.

    Science.gov (United States)

    Mackey, Dana; O'Reilly, Paul; Naydenova, Izabela

    2016-05-01

    This paper introduces an improved mathematical model for holographic grating formation in an acrylamide-based photopolymer, which consists of partial differential equations derived from physical laws. The model is based on the two-way diffusion theory of [Appl. Opt.43, 2900 (2004)10.1364/AO.43.002900APOPAI1559-128X], which assumes short polymer chains are free to diffuse, and generalizes a similar model presented in [J. Opt. Soc. Am. B27, 197 (2010)10.1364/JOSAB.27.000197JOBPDE0740-3224] by introducing an immobilization rate governed by chain growth and cross-linking. Numerical simulations were carried out in order to investigate the behavior of the photopolymer system for short and long exposures, with particular emphasis on the effect of recording parameters (such as illumination frequency and intensity), as well as material permeability, on refractive index modulation, refractive index profile, and grating distortion. The model reproduces many well-known experimental observations, such as the decrease of refractive index modulation at high spatial frequencies and appearance of higher harmonics in the refractive index profile when the diffusion rate is much slower than the polymerization rate. These properties are supported by a theoretical investigation which uses perturbation techniques to approximate the solution over various time scales. PMID:27140889

  2. Free-radical-induced chain scission and cross-linking of polymers in aqueous solution. An overview

    International Nuclear Information System (INIS)

    Complete text of publication follows. In the radiolysis of N2O-saturated aqueous solutions OH are generated. In their reactions with polymers, they give rise to polymer-derived radicals. The kinetics of the formation and decay of these radicals are reviewed. The rate of reaction of a polymer with a reactive free radical is noticeably lower than that of an equivalent concentration of monomer due to the non-random distribution of the reaction sites. Once a larger number of radicals are formed on one polymer molecule, e.g. upon pulse radiolysis, close-by radicals recombine more rapidly while the more distant ones survive for much longer times than an equivalent concentration of freely diffusing radicals. Intermolecular cross-linking (between two polymer chains, increase in molecular weight) and intramolecular cross-linking (formation of small loops, no increase in polymer weight) are competing processes, and their relative yields thus depend on the dose rate and polymer concentration. Hydrogen-transfer reactions within the polymer, e.g. transformation of a secondary radical into a tertiary one, are common and facilitated by the high local density of reactive sites. Due to repulsive forces, the lifetime of radicals of charged polymers is substantially increased. This enables even relatively slow b-fragmentation reactions to become of importance. In the case of poly(methacrylic acid), where β-fragmentation is comparatively fast, this even leads to an unzipping, and as a consequence of the efficient release of methacrylic acid the situation of equilibrium polymerization is approached. Heterolytic β-fragmentation is possible when adequate leaving groups are available, e.g. in polynucleotides and DNA. In the presence of O2, chain scission occurs via oxyl radicals as intermediates. Some implications for technical applications are discussed

  3. Control of the anchoring behavior of polymer-dispersed liquid crystals: effect of branching in the side chains of polyacrylates.

    Science.gov (United States)

    Zhou, Jian; Collard, David M; Park, Jung O; Srinivasarao, Mohan

    2002-08-28

    A temperature-driven anchoring transition in a polymer/nematic fluid composite that is far from the bulk nematic-isotropic transition temperature is reported. A series of poly(methylheptyl acrylates) were studied to probe the subtle effects of the side chain structure of the polymer on control of the anchoring. A polymer-dispersed liquid crystal film made from TL205 and 1-methylheptyl acrylate shows only planar anchoring over the temperature range studied, while the films made from TL205 and each of the other methylheptyl acrylates or n-heptyl acrylate show the homeotropic-to-planar anchoring transition at temperatures between 70 and 78 degrees C. An interfacial model is proposed in which the different conformation of the side chains is suggested as the cause for the dramatic difference in the observed anchoring behavior. PMID:12188649

  4. Calculation of the Radius of Gyration for a Linear Flexible Polymer Chain with Excluded Volume Interaction.

    Science.gov (United States)

    Shanes, Fredrick Charles

    1990-01-01

    We have calculated the radius of gyration for a three dimensional linear flexible polymer chain with excluded volume interaction. The resulting is written as a perturbation series in the dimensionless excluded volume parameter z, and the series is written to O(z ^4) as = (Ll/6)(1 + 1.276190476z - 2.081948603z^2 + 6.564897382z^3 - 26.70629003z^4 + ...) where z = (3/2pil) ^{3/2}omegaL^ {1/2} with l the effective segment length, L the contour length, and omegal^2 the effective binary cluster integral for a pair of segments. The perturbation theory used to calculate has recently been applied to the mean square end-to-end distance for a linear flexible polymer chain by Muthukumar and Nickel. The theory essentially uses the continuum limit of the two -parameter model, Laplace transforms, and a diagrammatic expansion in conjunction with field theory methods. The perturbation theory was found to be much simpler to implement than the usual cluster expansion method, and thus we were able to extend the series from the previously known O(z^2) to O(z^4 ). The perturbation series for and are divergent, and are only valid for small z values. However, the most interesting information about these properties occurs for large z values. The large z limit of the and series were extracted by using the direct renormalization method, and estimates for the critical exponents and scaling amplitudes were obtained. A quantity that is of theoretical interest is the large z limit of the ratio 6/, since it is believed to be a universal constant (i.e., independent of the model). We calculated the ratio by applying four different renormalization schemes to the perturbation series for and , and we obtained a final estimate of 6 / = 0.9631 +/- 0.0003. We also analysed the Monte Carlo self-avoiding walk data for the ratio and found the large chain limit of 6 / = 0.9602 +/- 0.0002. The discrepancy between the two results could be due to the averaging procedure that we used to obtain the two

  5. Investigation of side chain liquid crystal polymers bearing cholesterol and bile acid derivatives

    Institute of Scientific and Technical Information of China (English)

    Zhang Junhua; Stephen Freiberg; Francois Brisse; C.Géraldine Bazuin; Zhu Xiaoxia

    2004-01-01

    Cholic acid (or 3a,7a,12a-trihydoxyl-5a-cholan-24-oic acid) and lithocholic acid (or 3a-hydroxyl-5a-cholanic-24-oic acid) are commonly occurring bile acids synthesized from cholesterol in the liver in mammals. They all possess a steroid skeleton containing four rings, three with six carbons and one with five carbons. The transformation of cholesterol to cholic acid results in two major structural changes that affect the steroid skeleton. The first is the hydrogenation of the double bond between C5 and C6 and the second is a conformational flip of ring A from the 5a-position to the 5a-position. In addition, one or more hydroxyl groups are added to the steroid skeleton. Outside of the ring system, C24 is converted from a saturated alkyl to a carboxylic acid group.Side chain polymers based on cholesterol moiety have been made as reported in the literature.Since bile acids and cholesterol are all in the family of steroid molecules, it is of interest to investigate whether bile acids may also act as mesogenic groups.Therefore, flexible spacer groups with 10 carbons are introduced between bile acid skeleton and the poymerizable double bonds. The monomers and polymers are compared with cholesterol and dihydrocholesterol monomers and polymers with the same spacers. Dihydrocholesterol is chosen to investigate the influence of the double bond in the formation of LC, given that both cholesterol and dihydrocholesterol have a planar structure but there is no double bond in the latter. These monomers and their corresponding polymers were characterized for their liquid crystalline (LC) properties by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and X-ray diffraction.It was found that only the compounds bearing the planar cholesterol moieties possess LC phases. It is concluded that the 5a-configuration between the first and second cycles on the steroid skeleton of bile acids does not favor proper alignment of the rigid part of the bile acid moieties

  6. LITHIUM ION CONDUCTING POLYMER ELECTROLYTES BASED ON ALTERNATING MALEIC ANHYDRIDE COPOLYMER WITH OLIGO-OXYETHYLENE SIDE CHAINS

    Institute of Scientific and Technical Information of China (English)

    DING Liming

    1996-01-01

    A comb polymer with oligo-oxyethylene side chains of the type -(CH2CH2O)12CH3 was prepared from methyl vinyl ether/maleic anhydride copolymer and poly (ethylene glycol) methyl ether. The polymer can dissolve LiClO4 salt to form homogeneous amorphous polymer electrolyte. The ac ion conduction was measured using the complex impedance method, and conductivities were investigated as functions of temperatures and salt concentration. The complexes were first found to have two classes of glass transition which increase with increasing salt content. The optimum conductivity attained at 25℃ is in the order of 5.50 × 10-6Scm-1. IR spectroscopy was used to study the cation-polymer interaction.

  7. Dissipative particle dynamics study of translational diffusion of rigid-chain rodlike polymer in nematic phase

    Science.gov (United States)

    Zhao, Tongyang; Wang, Xiaogong

    2013-09-01

    In this study, dissipative particle dynamics (DPD) method was employed to investigate the translational diffusion of rodlike polymer in its nematic phase. The polymer chain was modeled by a rigid rod composed of consecutive DPD particles and solvent was represented by independent DPD particles. To fully understand the translational motion of the rods in the anisotropic phase, four diffusion coefficients, D_{||}u, D_ bot u, D_{||}n, D_ bot n were obtained from the DPD simulation. By definition, D_{||}n and D_ bot n denote the diffusion coefficients parallel and perpendicular to the nematic director, while D_{||}u and D_ bot u denote the diffusion coefficients parallel and perpendicular to the long axis of a rigid rod u. In the simulation, the velocity auto-correlation functions were used to calculate the corresponding diffusion coefficients from the simulated velocity of the rods. Simulation results show that the variation of orientational order caused by concentration and temperature changes has substantial influences on D_{||}u and D_ bot u. In the nematic phase, the changes of concentration and temperature will result in a change of local environment of rods, which directly influence D_{||}u and D_ bot u. Both D_{||}n and D_ bot n can be represented as averages of D_{||}u and D_ bot u, and the weighted factors are functions of the orientational order parameter S2. The effect of concentration and temperature on D_{||}n and D_ bot n demonstrated by the DPD simulation can be rationally interpreted by considering their influences on D_{||}u, D_ bot u and the order parameter S2.

  8. Influence of chain topology and bond potential on the glass transition of polymer chains simulated with the bond fluctuation model

    Energy Technology Data Exchange (ETDEWEB)

    Freire, J J [Departamento de Ciencias y Tecnicas FisicoquImicas, Facultad de Ciencias, Universidad Nacional de Educacion a Distancia (UNED), Senda del Rey 9, 28040 Madrid (Spain)], E-mail: jfreire@invi.uned.es

    2008-07-16

    The bond fluctuation model with a bond potential has been applied to investigation of the glass transition of linear chains and chains with a regular disposition of small branches. Cooling and subsequent heating curves are obtained for the chain energies and also for the mean acceptance probability of a bead jump. In order to mimic different trends to vitrification, a factor B gauging the strength of the bond potential with respect to the long-range potential (i.e. the intramolecular or intermolecular potential between indirectly bonded beads) has been introduced. (A higher value of B leads to a preference for the highest bond lengths and a higher total energy, implying a greater tendency to vitrify.) Different cases have been considered for linear chains: no long-range potential, no bond potential and several choices for B. Furthermore, two distinct values of B have been considered for alternate bonds in linear chains. In the case of the branched chains, mixed models with different values of B for bonds in the main chain and in the branches have also been investigated. The possible presence of ordering or crystallization has been characterized by calculating the collective light scattering function of the different samples after annealing at a convenient temperature below the onset of the abrupt change in the curves associated with a thermodynamic transition. It is concluded that ordering is inherited more efficiently in the systems with branched chains and also for higher values of B. The branched molecules with the highest B values in the main chain bonds exhibit two distinct transitions in the heating curves, which may be associated with two glass transitions. This behavior has been detected experimentally for chains with relatively long flexible branches.

  9. Self-assembly of the hydrogel polymer chain consisting of chitosan and chondroitin sulphate in the presence of theophylline

    International Nuclear Information System (INIS)

    In this work, polyelectronic complex (PEC) consisting of two polysaccharides were developed. One is chitosan (QT), cationic polymer, produced by the chitin deacetylation and the other is chondroitin sulphate (CS), anionic polymer, extracted from bovine or porcine aorta. The PECs were prepared in the presence of theophylline (TEO) for evaluating the influence of this drug in the polymer chains reorganization, as well as, studying the mechanical properties and release of SC and TEO in aqueous solutions on different pH conditions. By the obtained results, it was observed that the 84QT/15SC/TEO (% in weight) hydrogel is pH responsive because the CS releasing is more effective at pH 8, while the release of the TEO is higher at pH 2. The hydrogel showed mechanical properties more resistant to pH 2, 8 and 10 and this was attributed to interactions between the polymer chains. Finally, the X-rays profile showed the presence of peaks associated to reorganization of the chains in the hydrogel is at times larger than the hydrogel in the absence of solute. (author)

  10. Structure and Electronic Properties of Polymer Chains and Graphene Nanoribbon Formed by Molecular Self-Assembly on Au(111)

    Science.gov (United States)

    Ma, Chuanxu; Fuentes-Cabrera, Miguel A.; Sumpter, Bobby G.; Hong, Kunlun; Li, An-Ping; Xiao, Zhongcan; Lu, Wenchang; Bernholc, J.

    Graphene nanoribbons (GNRs) with bandgaps are promising building blocks for ultra-fast electronics. Bottom-up synthesis of GNRs from aromatic hydrocarbon molecules has been proven to be an effective way to control GNR's width with atomically precise edge structures. Using scanning tunneling microscopy (STM), we study the formation of both linear polymer chains and narrow GNRs in the bottom-up self-assembly process with the DBBA molecules as the precursor on Au(111). The linear polymer chains are formed after the deposition of DBBA and 200 °C annealing for 30 min. The polymers can be converted to 7-AGNRs (seven-carbon wide armchair GNRs) after 400 °C annealing. Interestingly, second-layer polymer is seen to survive on the GNRs during the annealing process. This result indicates that the Au(111) substrate plays an important role in the dehydrogenation process and the formation of GNRs, which is confirmed by our DFT calculations. Electronically, the polymers show a bandgap of 3.4 eV, much larger than that of GNRs. After annealing at 500 °C for 30 min, wider GNRs can form: 14-AGNR, 21-AGNR. The 7-AGNR shows a typical edge state at -1.1 eV, while for 14-AGNR it is at -1.35 eV. Moreover, junctions of GNRs with different widths can be formed with pronounced boundary states.

  11. Impact of glucose polymer chain length on heat and physical stability of milk protein-carbohydrate nutritional beverages.

    Science.gov (United States)

    Chen, Biye; O'Mahony, James A

    2016-11-15

    This study investigated the impact of glucose polymer chain length on heat and physical stability of milk protein isolate (MPI)-carbohydrate nutritional beverages containing 8.5% w/w total protein and 5% w/w carbohydrate. The maltodextrin and corn syrup solids glucose polymers used had dextrose equivalent (DE) values of 17 or 38, respectively. Increasing DE value of the glucose polymers resulted in a greater increase in brown colour development, ionic calcium, protein particle size, apparent viscosity and pseudoplastic rheological behaviour, and greater reduction in pH, hydration and heat stability on sterilisation at 120°C. Incorporation of glucose polymers with MPI retarded sedimentation of protein during accelerated physical stability testing, with maltodextrin DE17 causing a greater reduction in sedimentation velocity and compressibility of sediment formed than corn syrup solids DE38. The results demonstrate that chain length of the glucose polymer used strongly impacts heat and physical stability of MPI-carbohydrate nutritional beverages. PMID:27283657

  12. Structure-property optimizations in donor polymers via electronics, substituents, and side chains toward high efficiency solar cells.

    Science.gov (United States)

    Uy, Rycel L; Price, Samuel C; You, Wei

    2012-07-26

    Many advances in organic photovoltaic efficiency are not yet fully understood and new insight into structure-property relationships is required to push this technology into broad commercial use. The aim of this article is not to comprehensively review recent work, but to provide commentary on recent successes and forecast where researchers should look to enhance the efficiency of photovoltaics. By lowering the LUMO level, utilizing electron-withdrawing substituents advantageously, and employing appropriate side chains on donor polymers, researchers can elucidate further aspects of polymer-PCBM interactions while ultimately developing materials that will push past 10% efficiency. PMID:22588903

  13. Side chain engineering of fused aromatic thienopyrazine based low band-gap polymers for enhanced charge carrier mobility

    KAUST Repository

    Mondal, Rajib

    2011-01-01

    A strategic side-chain engineering approach leads to the two orders of magnitude enhancement of charge carrier mobility in phenanthrene based fused aromatic thienopyrazine polymers. Hole carrier mobility up to 0.012 cm 2/Vs can be obtained in thin film transistor devices. Polymers were also utilized to fabricate bulk heterojunction photovoltaic devices and the maximum PCE obtained in these OPV\\'s was 1.15%. Most importantly, performances of the devices were correlated with thin morphological analysis performed by atomic force microscopy and grazing incidence X-ray scattering. © 2011 The Royal Society of Chemistry.

  14. Conjugated Polymer Chains Confined in Vertical Nanocylinders of a Block-Copolymer Film: Preparation, Characterization, and Optoelectronic Function

    KAUST Repository

    Dong, Ban Xuan

    2013-01-15

    Hybrid materials composed of phase-separated block copolymer films and conjugated polymers of the phenylenevinylene family (PPV) are prepared. The PPV chains are embedded in vertical cylinders of nanometer diameter in the block-copolymer films. The cylinders span continuously the whole film thickness of 70 nm. Incorporation of the PPV chains into the one-dimensional cylinders leads to modified photoluminescence spectra and to large absorption anisotropy. The hybrid films show electroluminescence from the PPV chains in a simple light-emitting device at minute doping concentrations, and also exhibit a factor of 19 increase in electron transport efficiency along the single PPV chains. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Impact of charge carrier injection on single-chain photophysics of conjugated polymers

    Science.gov (United States)

    Hofmann, Felix J.; Vogelsang, Jan; Lupton, John M.

    2016-06-01

    Charges in conjugated polymer materials have a strong impact on the photophysics and their interaction with the primary excited state species has to be taken into account in understanding device properties. Here, we employ single-molecule spectroscopy to unravel the influence of charges on several photoluminescence (PL) observables. The charges are injected either stochastically by a photochemical process or deterministically in a hole-injection sandwich device configuration. We find that upon charge injection, besides a blue-shift of the PL emission and a shortening of the PL lifetime due to quenching and blocking of the lowest-energy chromophores, the non-classical photon arrival time distribution of the multichromophoric chain is modified towards a more classical distribution. Surprisingly, the fidelity of photon antibunching deteriorates upon charging, whereas one would actually expect the opposite: the number of chromophores to be reduced. A qualitative model is presented to explain the observed PL changes. The results are of interest to developing a microscopic understanding of the intrinsic charge-exciton quenching interaction in devices.

  16. Ferrimagnetism and metal—insulator transition in an organic polymer chain

    International Nuclear Information System (INIS)

    The ferrimagnetism and quantum phase transition of a bipartite lozenge periodic Anderson-like organic polymer, in which the localized f electrons hybridize with the odd site conduction orbitals, are investigated by means of Green's function theory. The ground state turns out to be gapless ferrimagnetism. At a finite temperature, the ferrimagnetic-to-paramagnetic phase transition takes place. The Kondo screenings and Ruderman—Kittel—Kasuya—Yosida (RKKY) interaction can reduce and increase the transition temperature, respectively. Two Kondo screenings compete with each other, giving rise to the localized f electron spin screened antiferromagnetically. Accordingly, in a magnetic field, all spins are aligned along the chain easily, which is associated with metal—insulator transition. Furthermore, in a temperature-field plane, we reveal the gapless and spin polarized phases, which are characterized by susceptibility and specific heat, and whose behaviours are determined by the competition between the up-spin and down-spin hole excitations. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  17. Crystal structures and thermodynamics/kinetics of Zn(II) coordination polymers with helical chains

    Science.gov (United States)

    He, Tian; Yue, Ke-Fen; Zhao, Yi-xing; Chen, San-Ping; Zhou, Chun-sheng; Yan, Ni

    2016-07-01

    Solvothermal reactions of Zn(II) acetates and four V-shaped carboxylates ligands in the presence of 1,4-Bis(2-methyl-imidazol-1-yl)butane afforded four interesting Zn(II) coordination polymers with helical chains, namely, {[Zn(bib)(atibdc)]·2H2O}n (1), {[Zn(bib)(atbip)]·H2O}n (2), [Zn(bib)(2,2‧-tda)]}n (3) and {[Zn(bib)(5-tbipa)]·EtOH}n (4), (H2atibdc=5-amino-2,4,6-triiodoisophthalic acid, H2atbip=5-amino-2,4,6-tribromoisophthalic acid, 2,2‧-H2tad=2,2‧-thiodiacetic acid, 5-H2tbipa=5-tert-butyl-isophthalic acid). 1 reveals a 3D chiral framework with three kinds of helical chains along a, b and c axis. 2 shows a 2D step-type chiral framework with right-handed helical chains. 3 displays a wavelike 2D layer network possessing alternate left- and right-handed helical chains. 4 presents a four-connected 3D framework with zigzag and meso-helical chains. The different spacers and substituent group of carboxylic acid ligands may lead to the diverse network structures of 1-4. The fluorescent properties of complexes 1-4 were studied. In addition, the thermal decompositions properties of 1-4 were investigated by simultaneous TG/DTG-DSC technique. The apparent activation energy E and the pre-exponential factor (A) of skeleton collapse for the complexes 1-4 are calculated by the integral Kissinger's method and Ozawa-Doyle's method. The activation energy E (E1=209.658 kJ·mol-1, E2=250.037 kJ mol-1, E3=225.300 kJ mol-1, E4=186.529 kJ·mol-1) demonstrates that the reaction rate of the melting decomposition is slow. The thermodynamic parameters (ΔH‡, ΔG‡ and ΔS‡) at the peak temperatures of the DTG curves were also calculated. ΔG‡>0 indicates that the skeleton collapse is not spontaneous. ΔHd>0 suggests that the skeleton collapse is endothermic, corresponding to the intense endothermic peak of the DSC curve. The structural stability could be illustrated from the point of thermodynamics and kinetics. Their thermal decompositions properties of 1-4 were

  18. A new look at kinetic modeling of nonlinear free radical polymerizations with terminal branching and chain transfer to polymer

    OpenAIRE

    Dias, Rolando; Costa, Mário Rui

    2003-01-01

    The authors' previously developed method for the general kinetic analysis of nonlinear irreversible polymerizations based on moment generating functions is used for simulating free radical polymerization systems in which terminal branching and chain transfer to polymer are present, leading possibly to gel formation. The numerical solution of the equations needed for postgel predictions of sol fraction and average molecular weights (a major difficulty) is discussed with some detail. Finally, s...

  19. Dielectric properties of liquid-crystal azomethine polymer with a side alkyl-substituted chain, doped with fullerene C60

    Science.gov (United States)

    Kovalev, D. S.; Kostromin, S. V.; Musteaţa, V.; Cozan, V.; Bronnikov, S. V.

    2016-04-01

    We studied the actual and imaginary components of the dielectric constant of liquid-crystal azomethine polymer with a side chain, doped with 0.5 wt % of fullerene C60, over a wide range of temperatures and frequencies; measurements were made by means of dielectric spectroscopy. By analyzing the frequency dependence of the dielectric constant, we detected the relaxation processes (α, β1, and β2) in the nanocomposite, corresponding to certain modes of molecular motion and described them by the Arrhenius equations (β1- and β2-processes) and the Vogel-Fulcher-Tamman equation (α-process). An antiplasticization effect is discovered after doping the polymer with fullerene C60, which manifests itself in increasing the glass transition temperature of the nanocomposite compared to this parameter typical of pure polymer.

  20. The chain sucker: translocation dynamics of a polymer chain into a long narrow channel driven by longitudinal flow

    OpenAIRE

    Luo, Kaifu; Metzler, Ralf

    2011-01-01

    Using analytical techniques and Langevin dynamics simulations, we investigate the dynamics of polymer translocation into a narrow channel of width $R$ embedded in two dimensions, driven by a force proportional to the number of monomers in the channel. Such a setup mimics typical experimental situations in nano/micro-fluidics. During the the translocation process if the monomers in the channel can sufficiently quickly assume steady state motion, we observe the scaling $\\tau\\sim N/F$ of the tra...

  1. Biomedical applications of polymers derived by reversible addition - fragmentation chain-transfer (RAFT).

    Science.gov (United States)

    Fairbanks, Benjamin D; Gunatillake, Pathiraja A; Meagher, Laurence

    2015-08-30

    RAFT- mediated polymerization, providing control over polymer length and architecture as well as facilitating post polymerization modification of end groups, has been applied to virtually every facet of biomedical materials research. RAFT polymers have seen particularly extensive use in drug delivery research. Facile generation of functional and telechelic polymers permits straightforward conjugation to many therapeutic compounds while synthesis of amphiphilic block copolymers via RAFT allows for the generation of self-assembled structures capable of carrying therapeutic payloads. With the large and growing body of literature employing RAFT polymers as drug delivery aids and vehicles, concern over the potential toxicity of RAFT derived polymers has been raised. While literature exploring this complication is relatively limited, the emerging consensus may be summed up in three parts: toxicity of polymers generated with dithiobenzoate RAFT agents is observed at high concentrations but not with polymers generated with trithiocarbonate RAFT agents; even for polymers generated with dithiobenzoate RAFT agents, most reported applications call for concentrations well below the toxicity threshold; and RAFT end-groups may be easily removed via any of a variety of techniques that leave the polymer with no intrinsic toxicity attributable to the mechanism of polymerization. The low toxicity of RAFT-derived polymers and the ability to remove end groups via straightforward and scalable processes make RAFT technology a valuable tool for practically any application in which a polymer of defined molecular weight and architecture is desired. PMID:26050529

  2. Highly grafted polystyrene/polyvinylpyridine polymer gold nanoparticles in a good solvent: effects of chain length and composition.

    Science.gov (United States)

    Posel, Zbyšek; Posocco, Paola; Lísal, Martin; Fermeglia, Maurizio; Pricl, Sabrina

    2016-04-21

    In this work, the structural features of spherical gold nanoparticles (NPs) decorated with highly grafted poly(styrene) (PS), poly(vinylpyridine) (PVP) and PS-PVP diblock copolymer brushes immersed in a good solvent are investigated by means of Dissipative Particle Dynamics (DPD) simulations as a function of grafted chain length and of homopolymer and copolymer chain composition. For NPs grafted either by PS or PVP homopolymer brushes (selected as a proof of concept), good agreement between the Daoud-Cotton theory, experimental evidence, and our DPD simulations is observed in the scaling behavior of single chain properties, especially for longer grafted chains, and in brush thickness prediction. On the other hand, for grafted chain lengths comparable to NP dimensions parabolic-like profiles of the end-monomer distributions are obtained. Furthermore, a region of high concentration of polymer segments is observed in the monomer density distribution for long homopolymers. In the case of copolymer-decorated NPs, the repulsion between PS and PVP blocks is found to substantially influence the radius of gyration and the shape of the end-monomer distribution of the relevant polymer shell. Moreover, for diblock chains, the un-swollen region is observed to be thinner (and, correspondingly, the swollen layer thicker) than that of a NP modified with a homopolymer of the same length. Finally, the lateral segregation of PS and PVP blocks is evidenced by our calculations and a detailed analysis of the corona behavior is reported, thus revealing the key parameters in controlling the surface properties and the response of diblock copolymer modified nanoparticles. PMID:26980360

  3. Effect of cationic side-chains on intracellular delivery and cytotoxicity of pH sensitive polymer-doxorubicin nanocarriers

    Science.gov (United States)

    Fang, Chen; Kievit, Forrest M.; Cho, Yong-Chan; Mok, Hyejung; Press, Oliver W.; Zhang, Miqin

    2012-10-01

    Fine-tuning the design of polymer-doxorubicin conjugates permits optimization of an efficient nanocarrier to greatly increase intracellular uptake and cytotoxicity. Here, we report synthesis of a family of self-assembled polymer-doxorubicin nanoparticles and an evaluation of the effects of various types of side-chains on intracellular uptake and cytotoxicity of the nanocarriers for lymphoma cells. Monomers with three different cationic side-chains (CA) and pKa's, i.e., a guanidinium group (Ag), an imidazole group (Im), and a tertiary amine group (Dm), were comparatively investigated. The cationic monomer, poly(ethylene glycol) (PEG), and doxorubicin (Dox) were reacted with 1,4-(butanediol) diacrylate (BUDA) to prepare a poly(β-amino ester) (PBAE) polymer via Michael addition. All three polymer-Dox conjugates spontaneously formed nanoparticles (NP) through hydrophobic interactions between doxorubicin in aqueous solution, resulting in NP-Im/Dox, NP-Ag/Dox, and NP-Dm/Dox, with hydrodynamic sizes below 80 nm. Doxorubicin was linked to all 3 types of NPs with a hydrazone bond to assure selective release of doxorubicin only at acidic pH, as it occurs in the tumor microenvironment. Both NP-Im/Dox and NP-Ag/Dox exhibited much higher intracellular uptake by Ramos cells (Burkitt's lymphoma) than NP-Dm/Dox, suggesting that the type of side chain in the NPs determines the extent of intracellular uptake. As a result, NP-Im/Dox and NP-Ag/Dox showed cytotoxicity that was comparable to free Dox in vitro. Our findings suggest that the nature of surface cationic group on nanocarriers may profoundly influence their intracellular trafficking and resulting therapeutic efficacy. Thus, it is a crucial factor to be considered in the design of novel carriers for intracellular drug delivery.

  4. Dynamics of a self-avoiding polymer chain in slit, tube, and cube confinements.

    Science.gov (United States)

    Cui, Ting; Ding, Jiandong; Chen, Jeff Z Y

    2008-12-01

    Monte Carlo simulations are presented for the observation of the dynamics of a self-avoiding polymer in three types of confinement: slit, tube, and cube. We pay special attention to the parameter regime where the characteristic confinement dimension is smaller than the radius of gyration of the unconfined polymer. On the basis of the bond-fluctuation model, we measured the rotation time of the end-to-end vector of the polymer, the diffusion time for the center of the polymer to move a distance comparable to the root mean square end-to-end distance, and the looping time for the ends of the polymer to approach each other from an open position. As functions of the confinement width and polymer length, these three time scales are discussed in light of scaling theories. PMID:19256859

  5. Reversible Addition Fragmentation Chain Transfer (RAFT) Polymerization in Undergraduate Polymer Science Lab

    Science.gov (United States)

    Nguyen, T. L. U.; Bennet, Francesca; Stenzel, Martina H.; Barner-Kowollik, Christopher

    2008-01-01

    This 8-hour experiment (spread over two 4-hour sessions) is designed to equip students with essential skills in polymer synthesis, particularly in synthesizing polymers of well-defined molecular weight. The experiment involves the synthesis and characterization of poly(vinyl neodecanoate) via living free radical polymerization, specifically the…

  6. Extractant impregnation into polymer chain grafted onto porous membrane for high-speed separation of metal ion

    International Nuclear Information System (INIS)

    The analysis of radionuclides in radioactive wastes is essential to the safe and economical disposal of such wastes. Among radioactive species, actinides such as uranium and plutonium should be purified prior to radiometric measurements. Porous hollow-fiber membranes with a functionalized polymer chain can satisfy the requirements of speed and capacity for the separation of metal ions. In this study, Aliquat 336, tri-n-octylmethylammonium chloride, was impregnated to carboxy pentyl-amino (CPA) and octadecylamino (C18NH) group-containing polymer chains grafted onto a porous hollow-fiber membrane. The electrostatic interaction between the carboxyl moiety of the CPA group and the quarternary ammonium group of Aliquat 336 gave rise to a high-density impregnation of Aliquat 336. The C18NH group reinforced a hydrophobic interaction of the octadecyl part of the C18NH group of the graft chain with the alkyl moiety of Aliquat 336 which leads to stable impregnation of Aliquat 336 to the graft chain in aqueous solution. A mixture of water and ethanol was employed as a solvent for the impregnation of Aliquat 336. A higher water volume fraction induced a higher extension of the graft chain, resulting in an increase in the amount of Aliquat 336 impregnated. The amount of impregnated Aliquat 336 was 1.2 mol per kg of the GMA-grafted porous hollow-fiber membrane, which was 1.7 times higher than that using ethanol as a solvent of Aliquat 336. Palladium chloride (100 mg-Pd/L) dissolved in 1 M hydrochloric acid was forced to permeate through the pores of the Aliquat 336-impregnated membrane. The binding efficiency, defined as the ratio of number of moles of palladium adsorbed to half the number of moles of impregnated Aliquat 336, was found to be 69%. (author)

  7. The effect of sacrificial bonds on the mechanical behavior of a single polymer chain - A Monte Carlo study

    International Nuclear Information System (INIS)

    Full text: Understanding the basic building principles of biological materials from a fundamental point of view is a necessary prerequisite for possible transfer of these principles to technology. The byssal thread is an especially fascinating material showing high toughness, stiffness and extensibility. The byssal thread is secreted by marine mussels to adhere to rocky substrates. Being covered with a hard coating providing wear resistance, it shows an extensibility of more than 100 % with the ability of self-healing. Experimental studies on this system suggest that the high extensibility is due to so called 'sacrificial bonds' (SBs). Sacrificial Bonds are weaker than the covalent bonds holding the structure together and they can thermally induced open and close reversibly. The SBs break before the covalent bond rupture, providing hidden length and allowing for efficient energy dissipation. By this effect the toughness of the structure is significantly enhanced. These findings motivate the following simple model. The basic unit is a linear, covalently bonded polymer chain. Some of the monomers (so called sticky sites) can additionally form sacrificial bonds. Starting from a collapsed chain cyclic loading experiments were mimicked by determination of load-displacement curves by calculation of the mean force exerted by the chain for several end-to-end distances. The effect of the density and of the arrangement (ordered, random) of sticky sites on the mechanical behavior of the chain was investigated. For sufficiently high sticky site densities a pronounced hysteresis between stretching and relaxing of the chain could be observed. (author)

  8. Migration insertion polymerization (MIP) of cyclopentadienyldicarbonyldiphenylphosphinopropyliron (FpP): a new concept for main chain metal-containing polymers (MCPs).

    Science.gov (United States)

    Wang, Xiaosong; Cao, Kai; Liu, Yibo; Tsang, Brian; Liew, Sean

    2013-03-01

    We report a conceptually new polymerization technique termed migration insertion polymerization (MIP) for main chain metal-containing polymer (MCP) synthesis. Cyclopentadienyldicarbonyldiphenylphosphinopropyliron (FpP) is synthesized and polymerized via MIP, resulting in air stable poly(cyclopentadienylcarbonyldiphenylphosphinobutanoyliron) (PFpP) displaying narrow molecular weight distribution. The backbone of PFpP contains asymmetric iron units connected by both phosphine coordination and Fe-acyl bonds, which is representative of a new type of polymer. Furthermore, PFpP is tested to be soluble in a wide range of organic solvents and shown to possess reactive Fp end groups. PFpP amphiphiles have therefore been prepared via an end group migration insertion reaction in the presence of oligoethylene phosphine. PMID:23425192

  9. Thermodynamics of polymer nematics described with a worm-like chain model: particle-based simulations and SCF theory calculations

    Science.gov (United States)

    Greco, Cristina; Yiang, Ying; Kremer, Kurt; Chen, Jeff; Daoulas, Kostas

    Polymer liquid crystals, apart from traditional applications as high strength materials, are important for new technologies, e.g. Organic Electronics. Their studies often invoke mesoscale models, parameterized to reproduce thermodynamic properties of the real material. Such top-down strategies require advanced simulation techniques, predicting accurately the thermodynamics of mesoscale models as a function of characteristic features and parameters. Here a recently developed model describing nematic polymers as worm-like chains interacting with soft directional potentials is considered. We present a special thermodynamic integration scheme delivering free energies in particle-based Monte Carlo simulations of this model, avoiding thermodynamic singularities. Conformational and structural properties, as well as Helmholtz free energies are reported as a function of interaction strength. They are compared with state-of-art SCF calculations invoking a continuum analog of the same model, demonstrating the role of liquid-packing and fluctuations.

  10. New manufacturing routes for micro polymer manufacturing for the next decades – Process chains to strengthen EC economic power

    DEFF Research Database (Denmark)

    Bolt, Pieter; Azcarate, Sabino; Khan Malek, Chantal;

    functionalities such as interconnect and interfaces in components in order to reduce the number of parts and/or assembly costs. A consequence of this integration on the design level is a new value chain. Hence another trend is to look for integration of the functionalisation process (local surface finishing......, application of bio-reagents, local (nano-)surface structuring) into the component manufacturing process. This document deals with state-of-the-art and trend in manufacturing of polymer components and devices by means of replication processes. This report includes information on the tooling or manufacturing of...

  11. Influence of Side Chain Position on the Electrical Properties of Organic Solar Cells Based on Dithienylbenzothiadiazole-alt-phenylene Conjugated Polymers

    DEFF Research Database (Denmark)

    Livi, Francesco; Zawacka, Natalia Klaudia; Angmo, Dechan; Jørgensen, Mikkel; Krebs, Frederik C; Bundgaard, Eva

    2015-01-01

    the benzene ring where power conversion efficiencies of up to 3.6% were achieved. All studied materials were prepared with an objective of low-cost starting materials, simple synthesis, and simple processing conditions which was most successful for the polymer P5. The polymer P7 containing fluorine...... performance results were corroborated with full optical and morphological characterization of the conjugated polymers. We conclude that the determination of the best anchoring position for the side chains is the most rational starting point for the optimization of a polymer with a potential for large...

  12. New syndioregic main-chain, nonlinear optical polymers, and their ellipsometric characterization

    Science.gov (United States)

    Lindsay, Geoffrey A.; Nee, Soe-Mie F.; Hoover, James M.; Stenger-Smith, John D.; Henry, Ronald A.; Kubin, R. F.; Seltzer, Michael D.

    1991-12-01

    New nonlinear optical polymers (NLOP) having potential utility in waveguides for the modulation and switching of optical signals are reported. A new class of chromophoric polymers which assume a folded, polar conformation of the backbone have been prepared. The polymers have a syndioregic arrangement of chromophores within the backbone (i.e., a head-to-head, tail-to-tail configuration). Polymers were synthesized by the polymerization of difunctional, precoupled pairs of chromophores and difunctional, bridging groups. Glassy, noncentrosymmetric films were prepared by electric field poling and by Langmuir-Blodgett (LB) deposition. Characterization of multilayer LB films by null ellipsometry to determine the anisotropic refractive parameters was performed at different angles of incidence and at a wavelength of 1.0 (mu).

  13. Photoinduced changes of surface order in coumarin side-chain polymer films used for liquid crystal photoalignment

    International Nuclear Information System (INIS)

    Specular x-ray reflectivity probes morphological changes in a crosslinkable coumarin photoalignment polymer film resulting from ultraviolet irradiation. An ordered surface layer with density oscillations compatible with planar side-chain alignment is obtained before irradiation. The ordering is enhanced in the early stages of crosslinking. This is attributed to the photoinduced increase of mobility of the side-chains resulting from the creation of free volume by the crosslinking process. The expansion of the thin film confirms that free volume is created. The surface ordering decreases with prolonged ultraviolet irradiation because of increased material viscosity resulting from a high crosslinked density. The implications of surface ordering on liquid crystal photoalignment are discussed

  14. Segment density functions of polymer chains confined by absorbing or reflecting barriers

    Energy Technology Data Exchange (ETDEWEB)

    Paisner, M.J.

    1980-07-01

    A theoretical investigation into the segment density profile of confined chains has been undertaken herein, where the confinement is between a pair of infinite parallel walls which are reflecting or absorbing. Exact infinite series expressions are derived for the segment density functions of cilia, loops, bridges, and floating chains. These infinite series are easily evaluated numerically.

  15. Silicone chain extender

    DEFF Research Database (Denmark)

    2015-01-01

    The present invention relates to a silicone chain extender, more particularly a chain extender for silicone polymers and copolymers, to a chain extended silicone polymer or copolymer and to a functionalized chain extended silicone polymer or copolymer, to a method for the preparation thereof and...

  16. Statistics of polymer chains in cell membranes - an analogy to the statistics of electrons in Amorphous Semiconductors

    International Nuclear Information System (INIS)

    The end-to-end probability density of a polymer chain of length L is calculated in the spirit of Kuhn's theory with Edward's Hamiltonian involving a Gaussian random potential-energy function Φ(ρ),ρ = (x,y). The calculation is specified to the case when the polymer chain is sandwiched between two brush layers of a bilayer lipid membrane. An explicit formula is derived for the lateral dependence Rβ(|ρ-vector - ρ0-vector|,L), 1/β= kB.T, of the end-to-end probability density. This formula is exact for a model in which the autocorrelation function of is approximated as a quadratic function. The random field is defined with two parameters: η and λ - the r.m.s. deviation from the mean value and the correlation length, respectively. The distribution function is a Gaussian whose variance depends on the parameters η, β, λ, b and L. (b is the Kuhn step length.) (Authors)

  17. A statistical theory of coil-to-globule-to-coil transition of a polymer chain in a mixture of good solvents

    Science.gov (United States)

    Budkov, Yu. A.; Kolesnikov, A. L.; Kalikin, N. N.; Kiselev, M. G.

    2016-05-01

    We present an off-lattice statistical model of a single polymer chain in mixed-solvent media. Taking into account the polymer conformational entropy, renormalization of solvent composition near the polymer backbone, the universal intermolecular excluded-volume and van der Waals interactions within the self-consistent field theory, the reentrant coil-to-globule-to-coil transition (co-nonsolvency) has been described in this paper. For convenience we split the system volume in two parts: the volume occupied by the polymer chain and the volume of bulk solution. Considering the equilibrium between two sub-volumes, the polymer solvation free energy as a function of radius of gyration and co-solvent mole fraction within internal polymer volume has been obtained. Minimizing the free energy of solvation with respect to its arguments, we show two qulitatively different regimes of co-nonsolvency. Namely, at sufficiently high temperature the reentrant coil-to-globule-to-coil transition proceeds smoothly. On the contrary, when the temperature drops below a certain threshold value a coil-globule transition occurs in the regime of first-order phase transition, i.e., discontinuous changes of the radius of gyration and the local co-solvent mole fraction near the polymer backbone. We show that, when the collapse of the polymer chain takes place, the entropy and enthalpy contributions to the solvation free energy of the globule strongly grow. From the first principles of statistical thermodynamics we confirm earlier speculations based on the MD simulations results that the co-nonsolvency is the essentially enthalpic-entropic effect and is caused by enthalpy-entropy compensation. We show that the temperature dependences of the solution heat capacity change due to the solvation of the polymer chain are in qualitative agreement with the differential scanning calorimetry data for PNIPAM in aqueous methanol.

  18. Current Advances in the Carbon Nanotube/Thermotropic Main-Chain Liquid Crystalline Polymer Nanocomposites and Their Blends

    Directory of Open Access Journals (Sweden)

    Lin Li

    2012-03-01

    Full Text Available Because of their extraordinary properties, such as high thermal stability, flame retardant, high chemical resistance and high mechanical strength, thermotropic liquid crystalline polymers (TLCPs have recently gained more attention while being useful for many applications which require chemical inertness and high strength. Due to the recent advance in nanotechnology, TLCPs are usually compounded with nanoparticles to form particulate composites to enhance their properties, such as barrier properties, electrical properties, mechanical properties and thermal properties. Carbon-based nanofillers such as carbon nanotube (CNT, graphene and graphene oxide are the most common fillers used for the TLCP matrices. In this review, we focus on recent advances in thermotropic main-chain liquid crystalline polymer nanocomposites incorporated with CNTs. However, the biggest challenges in the preparation of CNT/TLCP nanocomposites have been shown to be inherent in the dispersion of CNTs into the TLCP matrix, the alignment and control of CNTs in the TLCP matrix and the load-transfer between the TLCP matrix and CNTs. As a result, this paper reviews recent advances in CNT/TLCP nanocomposites through enhanced dispersion of CNTs in TLCPs as well as their improved interfacial adhesion with the TLCP matrices. Case studies on the important role of chemically modified CNTs in the TLCP/thermoplastic polymer blends are also included.

  19. Existence of global weak solutions to compressible isentropic finitely extensible nonlinear bead-spring chain models for dilute polymers: The two-dimensional case

    Science.gov (United States)

    Barrett, John W.; Süli, Endre

    2016-07-01

    We prove the existence of global-in-time weak solutions to a general class of models that arise from the kinetic theory of dilute solutions of nonhomogeneous polymeric liquids, where the polymer molecules are idealized as bead-spring chains with finitely extensible nonlinear elastic (FENE) type spring potentials. The class of models under consideration involves the unsteady, compressible, isentropic, isothermal Navier-Stokes system in a bounded domain Ω in Rd, d = 2, for the density ρ, the velocity u ˜ and the pressure p of the fluid, with an equation of state of the form p (ρ) =cpργ, where cp is a positive constant and γ > 1. The right-hand side of the Navier-Stokes momentum equation includes an elastic extra-stress tensor, which is the classical Kramers expression. The elastic extra-stress tensor stems from the random movement of the polymer chains and is defined through the associated probability density function that satisfies a Fokker-Planck-type parabolic equation, a crucial feature of which is the presence of a centre-of-mass diffusion term. This extends the result in our paper J.W. Barrett and E. Süli (2016) [9], which established the existence of global-in-time weak solutions to the system for d ∈ { 2 , 3 } and γ >3/2, but the elastic extra-stress tensor required there the addition of a quadratic interaction term to the classical Kramers expression to complete the compactness argument on which the proof was based. We show here that in the case of d = 2 and γ > 1 the existence of global-in-time weak solutions can be proved in the absence of the quadratic interaction term. Our results require no structural assumptions on the drag term in the Fokker-Planck equation; in particular, the drag term need not be corotational. With a nonnegative initial density ρ0 ∈L∞ (Ω) for the continuity equation; a square-integrable initial velocity datum u˜0 for the Navier-Stokes momentum equation; and a nonnegative initial probability density function ψ0

  20. Novel polymer electrolytes based on cationic polyurethane with different alkyl chain length

    Science.gov (United States)

    Liu, Libin; Wu, Xiwen; Li, Tianduo

    2014-03-01

    A series of comb-like cationic polyurethanes (PUs) were synthesized by quaternizing different bromoalkane (C2H5Br, C8H17Br, and C14H29Br) with polyurethane. Solid polymer electrolytes were prepared by complexes cationic PUs with different content of LiClO4. All the solid polymer electrolytes had sufficient thermal stability as confirmed by TGA and exhibited a single-phase behavior evidenced by DSC results. For these electrolytes, FT-IR spectra indicated the formation of polymer-ion complexes. The ac impedance spectra show that the conductivity of the electrolytes follow the Arrhenius behavior, and ionic conductivity is associated with both the charge migration of ions between coordination sites and transmission between aggregates, as confirmed by FT-IR and SEM. Alkyl quaternary ammonium salts in the polymer backbone are recognized as inherent plasticizers, which make the electrolytes exhibit liquid-like behavior. The plasticizing effect of PU-C8 and PU-C14 electrolytes are more effective than that of PU-C2 electrolyte. Maximum ionic conductivity at room temperature for PU-C8 electrolytes containing 50 wt% LiClO4 reached 1.1 × 10-4 S cm-1. This work provides a new research clue that alkyl quaternary ammonium salts could be used as inherent plasticizers and hence make the system behave like a liquid with high ionic conductivity, while preserving the dimensional stability of the solids.

  1. Schiff base polymer based on triphenylamine moieties in the main chain. Characterization and studies in solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Sánchez, C.O. [Instituto de Ciencias Químicas, Facultad de Ciencias, Universidad Austral de Chile, Avda. Las Encinas 220, Campus Isla Teja, Valdivia (Chile); Bèrnede, J.C. [L' UNAM, Moltech Anjou, UMR 6200, 2 rue de la Houssinière, BP 92208, Nantes F-44000 (France); Cattin, L. [L' UNAM, Institut Jean Rouxel (IMN), UMR 6502, 2 rue de la Houssinière, BP 92208, Nantes F-44000 (France); Makha, M. [L' UNAM, Moltech Anjou, UMR 6200, 2 rue de la Houssinière, BP 92208, Nantes F-44000 (France); Gatica, N. [Departamento de Polímeros, Facultad de Ciencias, Universidad de Concepción, Avda. Edmundo Larenas 129, Concepción (Chile)

    2014-07-01

    Polytriphenylamine (PTPA), a Schiff base polymer containing triphenylamine (TPA) segments and whose monomer contains triphenylamine and thiophene end groups, was synthesized. The monomer structure enabled the polymerization to be performed under conditions similar to those of thiophene. Oxidative coupling using FeCl{sub 3} as oxidizing agent in anhydrous CHCl{sub 3} medium was employed for the polymer synthesis. Scanning electron microscopy, fluorescence spectroscopy, and cyclic voltammetry were used to characterize the polymer. PTPA exhibited high thermal stability with a mass loss of 13.3 % at 546.5 °C. The fluorescence spectrum showed emission at 300–550 nm and the optical band gap was found to be 2.6 eV. It was also established that PTPA forms complexes with Lewis acids, e.g. MoO{sub 3} and CuI. Its absorption band widened and extended up to the near-IR. It was seen that PTPA is rich in π-electrons and thus can act as electron donor. The value of the Highest Occupied Molecular Orbital (HOMO) was − 5.35 eV indicating its potential application in optoelectronic devices. An attempt was also made to investigate the photovoltaic potential of PTPA. Organic photovoltaic devices with various buffer layer structures, namely ITO/CuI/PTPA/C{sub 60}/BCP/Al, ITO/MoO{sub 3}/PTPA/C{sub 60}/BCP/Al, and ITO/MoO{sub 3}/CuI/PTPA/C{sub 60}/BCP/Al, where ITO stands for indium tin oxide and BCP for bathocuproine, were utilized for the studies. Power conversion efficiency of these devices ranged between 0.21 and 0.43% under simulated AM 1.5 illumination (100 mW cm{sup −2}). This result proved that polymers containing TPA in the main chain hold promising properties that would allow their use in photovoltaic devices. - Highlights: • A Schiff base polymer with triphenylamine and thiophene segments was synthesized. • In organic cells, the highest efficiency was obtained in a MoO{sub 3}/CuI double layer. • Polymer exhibited a power conversion efficiency between 0.21 and 0.43 %.

  2. Thermally triggered reversible transformation between parallel staggered stacking and plywood-like stacking of 1D coordination polymer chains.

    Science.gov (United States)

    Sun, Jian-Ke; Jin, Xu-Hui; Chen, Chao; Zhang, Jie

    2010-08-01

    An unusual example showing reversible interconversion of chain-like isomers under controlled experimental settings is reported, which illustrates the key role of assembly conditions for the target packing architecture with related properties. The reaction of Mn(II) ions with an organic ligand 2-hydroxypyrimidine-4,6-dicarboxylic acid (H(3)hpdc) at room temperature gives a coordination polymer {[Mn(3)(hpdc)(2)(H(2)O)(6)] x 2 H(2)O}(n) containing parallel staggered stacking, whereas the reaction under hydrothermal conditions at 150 degrees C affords a compound {[Mn(3)(hpdc)(2)(H(2)O)(6)] x H(2)O}(n) possessing plywood-like stacking. Interestingly, two compounds contain similar one-dimensional chain components with different orientations that can be controlled by thermodynamic factors. Thermally triggered reversible interconversion of the two compounds was verified by X-ray powder, IR, and element analysis. The spin-canted antiferromagnetic behaviors are observed in as-synthesized samples, and the influence of chain orientations on magnetic properties has been detected. PMID:20608747

  3. Self-consistent field theoretic simulations of amphiphilic triblock copolymer solutions: Polymer concentration and chain length effects

    Directory of Open Access Journals (Sweden)

    X.-G. Han

    2014-06-01

    Full Text Available Using the self-consistent field lattice model, polymer concentration φP and chain length N (keeping the length ratio of hydrophobic to hydrophilic blocks constant the effects on temperature-dependent behavior of micelles are studied, in amphiphilic symmetric ABA triblock copolymer solutions. When chain length is increased, at fixed φP, micelles occur at higher temperature. The variations of average volume fraction of stickers φcos and the lattice site numbers Ncols at the micellar cores with temperature are dependent on N and φP, which demonstrates that the aggregation of micelles depends on N and φP. Moreover, when φP is increased, firstly a peak appears on the curve of specific heat CV for unimer-micelle transition, and then in addition a primary peak, the secondary peak, which results from the remicellization, is observed on the curve of CV. For a long chain, in intermediate and high concentration regimes, the shape of specific heat peak markedly changes, and the peak tends to be a more broad peak. Finally, the aggregation behavior of micelles is explained by the aggregation way of amphiphilic triblock copolymer. The obtained results are helpful in understanding the micellar aggregation process.

  4. Synthesis and photovoltaic properties of the polymers base on thiophene derivatives with electron-deficient 3-nitro-1,2,4-triazole side chains

    International Nuclear Information System (INIS)

    Three soluble alternating conjugated copolymers PT-TZN, PF-TZN, and PBDT-TZN, composed of thiophene, fluorene, benzo[1,2-b:4,5-b′]dithiophene and thiophene derivatives with 3-nitro-1,2,4-triazole side chains, were synthesized via the palladium-catalyzed Suzuki coupling reaction and Stille coupling reaction. The effects of 3-nitro-1,2,4-triazole on the thermal, photophysical, electrochemical and photovoltaic properties were investigated. The introduction of the 3-nitro-1,2,4-triazole side chains is beneficial for lowering the bandgaps of the polymers. The bulk-heterojunction polymer solar cells were fabricated based on the blend of the as-synthesized polymers and the fullerene acceptor [6, 6]-phenyl-C61-butyric acid methyl ester. The maximum power conversion efficiency (1.13%) was obtained with PBDT-TZN as the electron donor under the illumination of Air Mass 1.5, 100 mW/cm2. - Highlights: • Three conjugated polymers with 3-nitro-1,2,4-triazole side chains were synthesized. • The introduction of the side chains favors lowering the bandgaps of the polymers. • The strong electron-withdrawing nitro group likely promotes excimer quenching

  5. Two Zn coordination polymers with meso-helical chains based on mononuclear or dinuclear cluster units

    Science.gov (United States)

    Qin, Ling; Qiao, Wen-Cheng; Zuo, Wei-Juan; Zeng, Si-Ying; Mei, Cao; Liu, Chang-Jiang

    2016-07-01

    Two zinc coordination polymers {[Zn2(TPPBDA)(oba)2]·DMF·1.5H2O}n (1), {[Zn(TPPBDA)1/2(tpdc)]·DMF}n (2) have been synthesized by zinc metal salt, nanosized tetradentate pyridine ligand with flexible or rigid V-shaped carboxylate co-ligands. These complexes were characterized by elemental analyses and X-ray single-crystal diffraction analyses. Compound 1 is a 2-fold interpenetrated 3D framework with [Zn2(CO2)4] clusters. Compound 2 can be defined as a five folded interpenetrating bbf topology with mononuclear Zn2+. These mononuclear or dinuclear cluster units are linked by mix-ligands, resulting in various degrees of interpenetration. In addition, the photoluminescent properties for TPPBDA ligand under different state and coordination polymers have been investigated in detail.

  6. Self-assembly of azobenzene based side-chain liquid crystalline polymer and -alkyloxybenzoic acids

    Indian Academy of Sciences (India)

    Kumarasamy Gayathri; Subramanian Balamurugan; Palaninathan Kannan

    2011-05-01

    Liquid crystalline pendant polymeric complexes have been obtained by supramolecular assembly of two mesogenic components namely, poly[4-(10-acryloyloxydecyloxy)-4'- phenylazobenzonitrile] (P10) and 4-alkyloxybenzoic acids (A7-A12). Hydrogen bond formed between carboxylic acid and cyano moiety served as molecular bridge. The polymeric complexes acquitted as undivided liquid crystalline properties exhibited stable and enantiotropic mesophases. The precursor, monomer and polymer were analysed by 1H-NMR and 13C-NMR spectroscopy. The hydrogen bonding interaction in polymer complexes (P10-A7 to P10-A12) was investigated by FT-IR spectroscopy. The thermal behaviours and textural analysis were studied by differential scanning calorimetry and polarized optical microscopy respectively.

  7. The effect of chain length and non-covalent interactions on blending of polymers

    Czech Academy of Sciences Publication Activity Database

    Šturcová, Adriana; Kratochvíl, Jaroslav; Dybal, Jiří; Sikora, Antonín

    Vienna: Technische Universität Wien, 2015 - (Lendl, B.; Koch, C.; Kraft, M.; Ofner, J.; Ramer, G.). MO503 ISBN 978-3-200-04205-6. [International Conference on Advanced Vibrational Spectroscopy /8./ - ICAVS8. 12.07.2015-17.07.2015, Vienna] R&D Projects: GA ČR(CZ) GAP108/12/0703 Institutional support: RVO:61389013 Keywords : inter-polymer complex * hydrogen bonding * FTIR Subject RIV: CD - Macromolecular Chemistry

  8. Photogeneration of free charge carriers in tenuously packed .pi. conjugated polymer chains

    Czech Academy of Sciences Publication Activity Database

    Menšík, Miroslav; Pfleger, Jiří; Rybak, A.; Jung, J.; Ulanski, J.; Halašová, Klára; Vohlídal, J.

    2011-01-01

    Roč. 22, č. 12 (2011), s. 2075-2083. ISSN 1042-7147 R&D Projects: GA ČR GA202/07/0643; GA AV ČR KAN100500652; GA AV ČR IAA401770601; GA MŠk 7E10040 Institutional research plan: CEZ:AV0Z40500505 Keywords : photogeneration of free charge carriers * charge transfer states * conjugated polymers Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.007, year: 2011

  9. Shear-Modulus Investigations of Monohydroxy Alcohols: Evidence for a Short-Chain-Polymer Rheological Response

    DEFF Research Database (Denmark)

    Hecksher, Tina; Jakobsen, Bo; Dyre, J. C.; Figuli, R.; Gainaru, Catalin; Wilhelm, Manfred; Böhmer, Roland

    2014-01-01

    Liquids composed of small-molecule monohydroxy alcohols are demonstrated to display rheological behavior typical for oligomeric chains. This observation was made possible by rheological experiments in which more than seven decades in frequency and more than five decades on the mechanical modulus ...... physical behavior of a wide range of hydrogen-bonded liquids....

  10. Development of a Universal Chain-Growth Polymerization Protocol of Conjugated Polymers: Toward a Variety of All-Conjugated Block-Copolymers

    OpenAIRE

    Verswyvel, Michiel; VERSTAPPEN, Pieter; De Cremer, Lieven; Verbiest, Thierry; Koeckelberghs, Guy

    2011-01-01

    This manuscript reports a universal chain-growth polymerization protocol for conjugated polymers. Herein, the Pd-based catalyst moiety dissociates from the growing active center into the solution and therefore, the controlled chain-growth character is not relying on any specific, system-related complexation, as is the case in polymerization methods reported before. This makes the protocol applicable on a broad range of monomers and, furthermore, also allows an easy one-pot synthesis of block-...

  11. Ultrafast Energy Transfer and Enhanced Two-Photon Absorption in a Novel Porphyrin Side-Chain Polymer

    Institute of Scientific and Technical Information of China (English)

    WANG Hui; HUANG Ya-Ping; DENG Li; ZHAO Fu-Li; LIN Wei-Zhu; WANG Jian; LIANG Zhao-Xi

    2004-01-01

    @@ Ultrafast relaxation processes and transient two-photon absorption are studied in a novel porphyrin side-chain polymer, 5-hydroxy-10, 15,20-triphenyl-porphyrin-poly(glycidyl methacrylate) (HTPP-PGMA), by using picosecond luminescence spectroscopy and femtosecond pump-probe techniques. HTPP-PGMA exhibits the ultrafast initial luminescence decay (~300ps), which is absent in the conventional porphyrin monomer such as TPP. Enhanced two-photon absorption was observed in HTPP-PGMA; the corresponding Im x(a) is about 2.8× 10-11 esu, which is almost one order of magnitude larger than that of the conventional porphyrin monomer (TPP) (~1.3 × 10-12 esu).The ultrafast energy transfer plays an important role in the excited-state relaxation dynamics observed in HTPPPGMA. The potential application of HTPP-PGMA in optical switching is discussed.

  12. Synthesis and Characterization of Carbazole-Benzothiadiazole-Based Conjugated Polymers for Organic Photovoltaic Cells with Triazole in the Main Chain

    Directory of Open Access Journals (Sweden)

    Eunhee Lim

    2013-01-01

    Full Text Available We have synthesized a series of carbazole-benzothiadiazole-triazole based copolymers, poly[(N-9′-heptadecanyl-2,7-carbazole-co-(5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole-co-((4-(4-butylphenyl-3,5-diphenyl-4H-1,2,4]triazole] (PCz3TBTz by Suzuki coupling polymerization. The optical and electrochemical properties of the copolymers could be tuned by changing the comonomer unit of triazole from 0% to 80%. Organic photovoltaic (OPV cells were fabricated by blending the synthesized polymers as a donor and PCBM as an acceptor. The material solubility and film morphology were improved by introducing the triazole unit in the main chain. Improved OPV device performance of 1.74% was achieved in the presence of an optimal amount of triazole moieties.

  13. Fabrication of chain-like Mn2O3 nanostructures via thermal decomposition of manganese phthalate coordination polymers

    International Nuclear Information System (INIS)

    A novel manganese coordination polymer [Mn(Pht)(H2O)]n as a precursor was obtained by chemical precipitation involving an aqueous solution of anhydrous manganese acetate and phthalate anion as a potential O-banded ligand. Fourier transform infrared (FT-IR) results proved that phthalate anions coordinate to metal cations as a chelating bidentate ligand, making polymeric structure. The Mn2O3 nanostructures have been prepared via thermal decomposition of as-prepared manganese phthalate polymers as precursor in the presence of oleic acid (OA) and triphenylphosphine (TPP) as a stabilizer and capping. Different approaches such as FT-IR, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were applied to characterize the products. TEM images and XRD analysis indicated that the as-synthesized chain-like Mn2O3 has a crystal phase of cubic syngony with a mean size of ∼40 nm.

  14. Polymer chain in a random array of topological obstacles: Classification and statistics of complex loops

    Science.gov (United States)

    Rostiashvili, V. G.; Nechaev, S. K.; Vilgis, T. A.

    1993-11-01

    An arbitrary complex polymer loop embedded in three-dimensional space and topologically entangled with a quenched array of randomly dstributed parallel rods is considered. It is shown that an ensemble of the complex loops, prepared in different possible ways, is equivalent to the ensemble of cactuslike graphs where the leaves of these cacti are simple loops. The free energy of the cactuslike graphs is calculated in the mean-field approximation. The critical condition for the collapse transition is obtained. The collapsed state of the complex loop with the density distributed over different leaves is shown to be preferable.

  15. Scaling of the rupture dynamics of polymer chains pulled at one end at a constant rate.

    Science.gov (United States)

    Fugmann, S; Sokolov, I M

    2009-02-01

    We consider the rupture dynamics of a homopolymer chain pulled at one end at a constant loading rate r . Compared to single bond breaking, the existence of the chain introduces two aspects into rupture dynamics: The non-Markovian aspect in the barrier crossing and the slow down of the force propagation to the breakable bond. The relative impact of both these processes is investigated, and the second one was found to be the most important at moderate loading rates. The most probable rupture force is found to decrease with the number of bonds as f{max} proportional, variant-[ln(const N/r)]2/3 and finally to approach a saturation value independent on N . All of our analytical findings are confirmed by extensive numerical simulations. PMID:19391768

  16. Silica-filled elastomers polymer chain and filler characterization by a SANS-SAXS approach

    CERN Document Server

    Botti, A; Richter, D; Urban, V; Ipns, A 6 4; Kohlbrecher, J; Straube, E

    2002-01-01

    A study of composites based upon commercially available silica fillers and networks of blends of protonated and deuterated anionically prepared polyisoprene is presented. The extraction of the single chain structure factor for SANS in the polymeric soft phase in isotropic and deformed state has been performed for the first time. The quasi three-component system could not be compositionally matched due to the internal structures of the activated fillers. For this, a parallel SAXS investigation provided the neccessary information on the filler structure which was lacking in the SANS analysis. Whereas mechanically clear reinforcement at low strains and filler-networking can be observed, the microscopic characterization of the chain deformation in the framework of the network tube model agrees with the estimates for hydrodynamic reinforcement of fractal fillers. (orig.)

  17. Preparation and Chemical Properties of π-Conjugated Polymers Containing Indigo Unit in the Main Chain

    Directory of Open Access Journals (Sweden)

    Hiroki Fukumoto

    2014-03-01

    Full Text Available π-Conjugated polymers based on indigo unit were prepared. Dehalogenative polycondensation of N-hexyl-6,6'-dibromoindigo with a zerovalent nickel complex gave a homopolymer, P(HexI, in 77% yield. Copolymer of N-hexyl-indigo and pyridine, P(HexI-Py, was also prepared in 50% yield. P(HexI showed good solubility in organic solvents, whereas P(HexI-Py was only soluble in acids such as HCOOH. The weight-average molecular weights (Mw of P(HexI and P(HexI-Py were determined to be 10,000 and 40,000, respectively, by a light scattering method. Pd-catalyzed polycondensation between 6,6'-dibromoindigo with N-BOC (BOC = t-butoxycarbonyl substituents and a diboronic compound of 9,9-dioctylfluorene afforded the corresponding alternating copolymer, P(BOCI-Flu, as a deep red solid in 98% yield. P(BOCI-Flu was soluble in N-methyl-2-pyrroridone and showed an Mw of 29,000 in GPC analysis. Treatment of P(BOCI-Flu with CF3COOH smoothly led to a BOC-deprotection reaction to give an insoluble deep green polymer, P(I-Flu, in a quantitative yield. Diffuse reflectance spectra of powdery P(BOCI-Flu and P(I-Flu showed peaks at about 580 nm and 630 nm, respectively, which are thought to originate from the indigo unit.

  18. Dynamical Process of Dissociation of Excitons in Polymer Chains with Impurities

    Institute of Scientific and Technical Information of China (English)

    ZHAO Hong-Xia; ZHAO Hui; CHEN Yu-Guang

    2011-01-01

    @@ Within an extended Su-Schrieffer-Heeger model including impurity interactions,the dynamical process of exciton dissociation in the presence of an external electric field is investigated by using a non-adiabatic evolution method Under the action of impurities,the stability as well as the effective mass of the exciton is reduced.Our results show that the field required to dissociate the excitons depends sensitively on the strength of the impurity potential.As the impurity potential strength increases,the dissociation field decreases effectively.The theoretical results are expected to provide useful predictions concerning which polymers with properly impurity-assisted interactions are likely to be more suitable for use in organic solar cells.%Within an extended Su-Schrieffer-Heeger model including impurity interactions, the dynamical process ofexciton dissociation in the presence of an external electric field is investigated by using a non-adiabatic evolution method. Under the action of impurities, the stability as well as the effective mass of the exciton is reduced. Our results show that the field required to dissociate the excitons depends sensitively on the strength of the impurity potential. As the impurity potential strength increases, the dissociation field decreases effectively. The theoretical results are expected to provide useful predictions concerning which polymers with properly impurity-assisted interactions are likely to be more suitable for use in organic solar cells.

  19. Computation of the Mean First-Encounter Time Between the Ends of a Polymer Chain

    Science.gov (United States)

    Amitai, A.; Kupka, I.; Holcman, D.

    2012-09-01

    Using a novel theoretical approach, we study the mean first-encounter time (MFET) between the two ends of a polymer. Previous approaches used various simplifications that reduced the complexity of the problem, leading, however, to incompatible results. We construct here for the first time a general theory that allows us to compute the MFET. The method is based on estimating the mean time for a Brownian particle to reach a narrow domain in the polymer configuration space. In dimension two and three, we find that the MFET depends mainly on the first eigenvalue of the associated Fokker-Planck operator and provide precise estimates that are confirmed by Brownian simulations. Interestingly, although many time scales are involved in the encounter process, its distribution can be well approximated by a single exponential, which has several consequences for modeling chromosome dynamics in the nucleus. Another application of our result is computing the mean time for a DNA molecule to form a closed loop (when its two ends meet for the first time).

  20. One-dimensional Zigzag Chain Coordination Polymer [Zn(μ-phth)(imi)2]∞ Bridged by o-Phthalato

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The reaction of zinc carbonate with o-phthalic acid and imidazole in an aqueous-alcohol solution led to the formation of colorless crystals of [Znμ-phthimi2]∞. Single-crystal X-ray analysis has revealed that the complex crystallizes in a monoclinic system, space group Pn with a = 8.394(2), b = 9.976(3), c = 9.959(3)A, β = 104.409(4)°, V = 807.6(4)A3, Z = 2, C14H12N4O4Zn, Mr = 365.6(5), Dc = 1.504 g/cm3, μ = 1.544 mm-1, F000 = 372, the final R = 0.0466 and wR = 0.1171 for 1834 reflections with I>2σ(I). The complex displays a zigzag infinite chain structure in which each zinc(Ⅱ)center is coordinated by two oxygen atoms and two nitrogen atoms to generate a ZnN2O2 distorted tetrahedral geometry. The neighboring zinc atoms are bridged by the o-phthalate ligand. Each chain is linked by hydrogen bonds with its neighbors to form a three-dimensional coordination polymer.

  1. A temperature control method for shortening thermal cycling time to achieve rapid polymerase chain reaction (PCR) in a disposable polymer microfluidic device

    DEFF Research Database (Denmark)

    Bu, Minqiang; Perch-Nielsen, Ivan R.; Sørensen, Karen Skotte;

    2013-01-01

    We present a temperature control method capable of effectively shortening the thermal cycling time of polymerase chain reaction (PCR) in a disposable polymer microfluidic device with an external heater and a temperature sensor. The method employs optimized temperature overshooting and undershooting...

  2. The effect of extended polymer chains on the properties of transparent multi-walled carbon nanotubes/poly(methyl methacrylate/acrylic acid) film

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Yuan-Li; Tien, Hsi-Wen; Ma, Chen-Chi M; Yu, Yi-Hsiuan; Yang, Shin-Yi; Wu, Sheng-Yen [Department of Chemical Engineering, National Tsing-Hua University, Hsin-Chu 30043, Taiwan (China); Wei, Ming-Hsiung, E-mail: ccma@che.nthu.edu.tw [Chemical Systems Research Division, Chung Shan Institute of Science and Technology, Tao Yuan 32546, Taiwan (China)

    2010-05-07

    Optically transparent and electrically conductive thin films composed of multi-walled carbon nanotube (MWCNT) reinforced polymethyl methacrylate/acrylic acid (PMMA/AA) were fabricated using a wire coating technique. Poly(acrylic acid) controls the level of MWCNT dispersion in aqueous mixtures and retains the well-dispersed state in the polymer matrix after solidification resulting from extended polymer chains by adjusting the pH value. The exfoliating the MWCNT bundles by extended polymer chains results in the excellent dispersion of MWCNT. It causes a lower surface electrical resistance at the same MWCNT content. The hydrophilic functional groups (-COO{sup -}NA{sup +}) also caused a decrease in the crystallization of PMMA and led to an increase in the transmittance.

  3. Extending framework based on the linear coordination polymers: Alternative chains containing lanthanum ion and acrylic acid ligand

    International Nuclear Information System (INIS)

    One-dimensional alternative chains of two lanthanum complexes: [La(L1)3(CH3OH)(H2O)2].5H2O (L1=anion of α-cyano-4-hydroxycinnamic acid ) 1 and [La(L2)3(H2O)2].3H2O (L2=anion of trans-3-(4-methyl-benzoyl)-acrylic acid) 2 were synthesized and structurally characterized by single-crystal X-ray diffraction, element analysis, IR and thermogravimetric analysis. The crystal structure data are as follows for 1: C31H36LaN3O17, triclinic, P-1, a=9.8279(4)A, b=11.8278(5)A, c=17.8730(7)A, α=72.7960(10)o, β=83.3820(10)o, γ=67.1650(10)-bar , Z=2, R1=0.0377, wR2=0.0746; for 2: C33H37LaO14, triclinic, P-1, a=8.7174(5)A, b=9.9377(5)A, c=21.153(2)A, α=81.145(2)o, β=87.591(2)o, γ=67.345(5)o, Z=2, R1=0.0869, wR2=0.220. 1 is a rare example of the alternative chain constructed by syn-syn and anti-syn coordination mode of carboxylato ligand arranged along the chain alternatively. La(III) ions in 2 are linked by two η3-O bridges and four bridges (two η2-O and two η3-O) alternatively. Both of the linear coordination polymers grow into two- and three-dimensional networks by packing through extending hydrogen-bond network directed by ligands

  4. Micro tooling technologies for polymer micro replication: direct, indirect and hybrid process chains

    DEFF Research Database (Denmark)

    Tosello, Guido; Hansen, Hans Nørgaard

    2009-01-01

    quality and performance of the corresponding micro mould. Traditional methods of micro tooling, such as various machining processes (e.g. micro milling, micro electrical discharge machining) have already reached their limitations with decreasing dimensions of mould inserts and cavities. To this respect......, tooling process chains based on combination of micro manufacturing processes (defined as hybrid tooling) have been established in order to obtain further features miniaturization and increased accuracy. In this paper, examples and performance of different hybrid tooling approaches as well as challenges......, opportunities and comparison between hybrid and direct tooling are presented....

  5. A string reaction coordinate for the folding of a polymer chain

    Science.gov (United States)

    Leitold, Christian; Lechner, Wolfgang; Dellago, Christoph

    2015-05-01

    We investigate the crystallization mechanism of a single, flexible homopolymer chain with short range attractions. For a sufficiently narrow attractive well, the system undergoes a first-order like freezing transition from an expanded disordered coil to a compact crystalline state. Based on a maximum likelihood analysis of committor values computed for configurations obtained by Wang-Landau sampling, we construct a non-linear string reaction coordinate for the coil-to-crystal transition. In contrast to a linear reaction coordinate, the string reaction coordinate captures the effect of different degrees of freedom controlling different stages of the transition. Our analysis indicates that a combination of the energy and the global crystallinity parameter Q6 provide the most accurate measure for the progress of the transition. While the crystallinity paramter Q6 is most relevant in the initial stages of the crystallization, the later stages are dominated by a decrease in the potential energy.

  6. Adsorption of a homopolymer chain onto a heterogeneous stripe-patterned surface studied using a directed walk model of the polymer

    International Nuclear Information System (INIS)

    Adsorption of a homopolymer chain onto a heterogeneous stripe-patterned surface is studied in the framework of the three-dimensional partially directed walk model of the polymer by using the generating function approach. Both annealed random and quenched regular (periodic) stripe-patterned surfaces are considered. For random surfaces the adsorption–desorption transition temperature is analyzed. Comparison of the transition points for random and the ‘equivalent’ regular surfaces (having the same average stripe width) shows that the transition temperature is higher for the random surface. For regular stripe-patterned surfaces, the phase diagram is derived and the temperature dependences of the main conformational and thermodynamic characteristics of the adsorbed chain are obtained. It is demonstrated that adsorption is accompanied by the orientation of the polymer along the stripes. At low temperature (in the strong adsorption regime), the polymer chain is localized onto a single adsorbing stripe. When the surface consists of narrow adsorbing stripes separated by wide nonadsorbing stripes, an additional second peak on the heat capacity temperature dependence emerges, which indicates that adsorption occurs as a two-stage process where chain localization on a single adsorbing stripe is completed prior to its full adsorption on this stripe. This effect is enhanced with increasing distance between adsorbing stripes. (paper)

  7. Effects of molecular structure on microscopic heat transport in chain polymer liquids

    International Nuclear Information System (INIS)

    In this paper, we discuss the molecular mechanism of the heat conduction in a liquid, based on nonequilibrium molecular dynamics simulations of a systematic series of linear- and branched alkane liquids, as a continuation of our previous study on linear alkane [T. Ohara et al., J. Chem. Phys. 135, 034507 (2011)]. The thermal conductivities for these alkanes in a saturated liquid state at the same reduced temperature (0.7Tc) obtained from the simulations are compared in relation to the structural difference of the liquids. In order to connect the thermal energy transport characteristics with molecular structures, we introduce the new concept of the interatomic path of heat transfer (atomistic heat path, AHP), which is defined for each type of inter- and intramolecular interaction. It is found that the efficiency of intermolecular AHP is sensitive to the structure of the first neighbor shell, whereas that of intramolecular AHP is similar for different alkane species. The dependence of thermal conductivity on different lengths of the main and side chain can be understood from the natures of these inter- and intramolecular AHPs

  8. Effects of molecular structure on microscopic heat transport in chain polymer liquids

    Energy Technology Data Exchange (ETDEWEB)

    Matsubara, Hiroki, E-mail: matsubara@microheat.ifs.tohoku.ac.jp; Kikugawa, Gota; Ohara, Taku [Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Bessho, Takeshi; Yamashita, Seiji [Higashifuji Technical Center, Toyota Motor Corporation, 1200 Mishuku, Susono, Shizuoka 410-1193 (Japan)

    2015-04-28

    In this paper, we discuss the molecular mechanism of the heat conduction in a liquid, based on nonequilibrium molecular dynamics simulations of a systematic series of linear- and branched alkane liquids, as a continuation of our previous study on linear alkane [T. Ohara et al., J. Chem. Phys. 135, 034507 (2011)]. The thermal conductivities for these alkanes in a saturated liquid state at the same reduced temperature (0.7T{sub c}) obtained from the simulations are compared in relation to the structural difference of the liquids. In order to connect the thermal energy transport characteristics with molecular structures, we introduce the new concept of the interatomic path of heat transfer (atomistic heat path, AHP), which is defined for each type of inter- and intramolecular interaction. It is found that the efficiency of intermolecular AHP is sensitive to the structure of the first neighbor shell, whereas that of intramolecular AHP is similar for different alkane species. The dependence of thermal conductivity on different lengths of the main and side chain can be understood from the natures of these inter- and intramolecular AHPs.

  9. Effects of molecular structure on microscopic heat transport in chain polymer liquids.

    Science.gov (United States)

    Matsubara, Hiroki; Kikugawa, Gota; Bessho, Takeshi; Yamashita, Seiji; Ohara, Taku

    2015-04-28

    In this paper, we discuss the molecular mechanism of the heat conduction in a liquid, based on nonequilibrium molecular dynamics simulations of a systematic series of linear- and branched alkane liquids, as a continuation of our previous study on linear alkane [T. Ohara et al., J. Chem. Phys. 135, 034507 (2011)]. The thermal conductivities for these alkanes in a saturated liquid state at the same reduced temperature (0.7Tc) obtained from the simulations are compared in relation to the structural difference of the liquids. In order to connect the thermal energy transport characteristics with molecular structures, we introduce the new concept of the interatomic path of heat transfer (atomistic heat path, AHP), which is defined for each type of inter- and intramolecular interaction. It is found that the efficiency of intermolecular AHP is sensitive to the structure of the first neighbor shell, whereas that of intramolecular AHP is similar for different alkane species. The dependence of thermal conductivity on different lengths of the main and side chain can be understood from the natures of these inter- and intramolecular AHPs. PMID:25933776

  10. The Rouse-Mooney model for coherent quasielastic neutron scatterings of single chains well entangled in polymer melts

    Science.gov (United States)

    Lin, Y.-H.; Huang, C.-F.

    2008-06-01

    The dynamic structure factor (DSF) for single (labeled) chains well entangled in polymer melts has been developed based on the Rouse-Mooney picture; the DSF functions derived from the Langevin equations of the model in both discrete and continuous forms are given. It is shown that for all practical purposes, it is sufficient to use the continuous form to analyze experimental results in the ``safe'' q region (q being the magnitude of the scattering wave vector q) where the Rouse-segment-based theories are applicable. The DSF form reduces to the same limiting form as that of the free Rouse chain as q2a2 or q2R2-->∞ (a and R being the entanglement distance and the root mean square end-to-end distance, respectively), confirming what has been expected physically. The natural reduction to the limiting form allows the full range of DSF curves to be displayed in terms of the reduced Rouse variable q2(Zdt)0.5 in a unified way. The displayed full range represents a framework or ``map,'' with respect to which effects occurring in different regions of the DSF may be located and studied in a consistent manner. One effect is the significant or noticeable deviations of the theoretical DSF curves from the limiting curve in the region ~4>q2(Zdt)0.5>~0.1 (a time region where tend boundary conditions in the Rouse-Mooney model are responsible for the correct prediction of the distribution of the q-split plateaus.

  11. The Arising of Results

    DEFF Research Database (Denmark)

    Sobisch, Jan-Ulrich

    2013-01-01

    Some Buddhist scholars have periodized the expected lifetime of the Buddha's teachings. According to them, these periods of 500 years each have different characteristics. The first is called 'the period of the results'. Therefore some scholars have claimed that only in the first 500 years after the...... Buddha results can arise. Kyobpa Jigten Sumgön has argued that results arise through practise as long as Dharma and Sangha exist....

  12. Rod like attapulgite/poly(ethylene terephthalate nanocomposites with chemical bonding between the polymer chain and the filler

    Directory of Open Access Journals (Sweden)

    Q. Fu

    2012-08-01

    Full Text Available Poly(ethylene terephthalate (PET nanocomposites containing rod-like silicate attapulgite (AT were prepared via in situ polymerization. It is presented that PET chains identical to the matrix have been successfully grafted onto simple organically pre-modified AT nanorods (MAT surface during the in situ polymerization process. The covalent bonding at the interface was confirmed by Fourier transform infrared spectroscopy (FTIR and thermogravimetric analysis (TGA. The content of grafted PET polymer on the surface of MAT was about 26 wt%. This high grafting density greatly improved the dispersion of fillers, interfacial adhesion as well as the significant confinement of the segmental motion of PET, as compared to the nanocomposites of PET/pristine AT (PET/AT. Owing to the unique interfacial structure in PET/MAT composites, their thermal and mechanical properties have been greatly improved. Compared with neat PET, the elastic modulus and the yield strength of PET/MAT were significantly improved by about 39.5 and 36.8%, respectively, by incorporating only 2 wt % MAT. Our work provides a novel route to fabricate advanced PET nanocomposites using rod-like attapulgite as fillers, which has great potential for industrial applications.

  13. Synthesis and Crystal Structure of a 1-D Chain Zinc(Ⅱ) Coordinated Polymer with N-p-Tolysulfonyl-glutamine

    Institute of Scientific and Technical Information of China (English)

    MA Lu-Fang; HUO Xian-Kuan; WANG Li-Ya; FAN Yao-Ting; ZHANG Su-Yun

    2007-01-01

    A novel coordination polymer {[Zn(ts-gln)(bipy)]·3H2O}n (ts-glnH2 = N-p-tolysulfonyl-glutamine, bipy = 2,2'-bipyridine) has been prepared and structuraily characterized by X-ray diffraction method. It crystallizes in orthorhombic, space group P212121 with a = 8.2622(5), b = 16.6244(10), c = 18.2807(10)(A), V = 2510.9(3)(A)3, C22H28N4O8SZn, Mr = 573.91, Z = 4, Dc =1.518 g/cm3, μ(MoKa) = 1.115 mm-1, F(000) = 1192, the final R = 0.0262 and wR = 0.0662 for 5691 independent reflections with Rint = 0.0240. The zinc(Ⅱ) atom is coordinated by N(3) and N(4)atoms of a bipy molecule, two carboxylate O(1) and O(2A) and amino N(1 ) atoms of ts-gln ligands,resulting in a square-pyramidal geometry. The title complex consists of an infinite zigzag chain of zinc(Ⅱ) ions linked by the carboxylate of N-p-tolysulfonyl-glutamine.

  14. Low half-wave voltage Y-branch electro-optic polymer modulator based on side-chain polyurethane-imide

    Science.gov (United States)

    Tang, Jie; Wang, Long-De; Li, Ruo-Zhou; Zhang, Qiang; Zhang, Tong

    2016-06-01

    A Y-branch electro-optic (EO) polymer modulator has been designed and fabricated. High performance side-chain polyurethane-imide (PUI) with a high EO coefficient of larger than 50 pm/V and a moderate glass-transition temperature (Tg) of 206∘C is used as EO polymer core layer of the modulator. The fabricated phase modulator exhibits a low half-wave voltage of 1.94 V at 1550 nm in single arm modulation with 1 cm EO interaction length and 2 cm total length. The results show that the modulator fabricated by side-chain PUI EO materials possesses potential applications in low driving voltage and low cost optical systems.

  15. Comparison of the Photovoltaic Characteristics and Nanostructure of Fullerenes Blended with Conjugated Polymers with Siloxane-Terminated and Branched Aliphatic Side Chains

    KAUST Repository

    Kim, Do Hwan

    2013-02-12

    All-organic bulk heterojunction solar cells based on blends of conjugated polymers with fullerenes have recently surpassed the 8% efficiency mark and are well on their way to the industrially relevant ∼15% threshold. Using a low band-gap conjugated polymer, we have recently shown that polymer side chain engineering can lead to dramatic improvement in the in-plane charge carrier mobility. In this article, we investigate the effectiveness of siloxy side chain derivatization in controlling the photovoltaic performance of polymer:[6,6]-phenyl-C[71]-butyric acid methyl ester (PC71BM) blends and hence its influence on charge transport in the out-of-plane direction relevant for organic solar cells. We find that, in neat blends, the photocurrent of the polymer with siloxy side chains (PII2T-Si) is 4 times greater than that in blends using the polymer with branched aliphatic side chains (PII2T-ref). This difference is due to a larger out-of-plane hole mobility for PII2T-Si brought about by a largely face-on crystallite orientation as well as more optimal nanoscale polymer:PC71BM mixing. However, upon incorporating a common processing additive, 1,8-diiodooctane (DIO), into the spin-casting blend solution and following optimization, the PII2T-ref:PC71BM OPV device performance undergoes a large improvement and becomes the better-performing device, almost independent of DIO concentration (>1%). We find that the precise amount of DIO plays a larger role in determining the efficiency of PII2T-Si:PC71BM, and even at its maximum, the device performance lags behind optimized PII2T-ref:PC71BM blends. Using a combination of atomic force microscopy and small- and wide-angle X-ray scattering, we are able to elucidate the morphological modifications associated with the DIO-induced changes in both the nanoscale morphology and the molecular packing in blend films. © 2012 American Chemical Society.

  16. Richness of Side-Chain Liquid-Crystal Polymers: From Isotropic Phase towards the Identification of Neglected Solid-Like Properties in Liquids

    OpenAIRE

    Wendorff, Joachim H; Patrick Baroni; Hakima Mendil-Jakani; Laurence Noirez

    2012-01-01

    Very few studies concern the isotropic phase of Side-Chain Liquid-Crystalline Polymers (SCLCPs). However, the interest for the isotropic phase appears particularly obvious in flow experiments. Unforeseen shear-induced nematic phases are revealed away from the N-I transition temperature. The non-equilibrium nematic phase in the isotropic phase of SCLCP melts challenges the conventional timescales described in theoretical approaches and reveal very long timescales, neglected until now. This spe...

  17. Fragmentation pathways of polymer ions.

    Science.gov (United States)

    Wesdemiotis, Chrys; Solak, Nilüfer; Polce, Michael J; Dabney, David E; Chaicharoen, Kittisak; Katzenmeyer, Bryan C

    2011-01-01

    Tandem mass spectrometry (MS/MS) is increasingly applied to synthetic polymers to characterize chain-end or in-chain substituents, distinguish isobaric and isomeric species, and determine macromolecular connectivities and architectures. For confident structural assignments, the fragmentation mechanisms of polymer ions must be understood, as they provide guidelines on how to deduce the desired information from the fragments observed in MS/MS spectra. This article reviews the fragmentation pathways of synthetic polymer ions that have been energized to decompose via collisionally activated dissociation (CAD), the most widely used activation method in polymer analysis. The compounds discussed encompass polystyrenes, poly(2-vinyl pyridine), polyacrylates, poly(vinyl acetate), aliphatic polyester copolymers, polyethers, and poly(dimethylsiloxane). For a number of these polymers, several substitution patterns and architectures are considered, and questions regarding the ionization agent and internal energy of the dissociating precursor ions are also addressed. Competing and consecutive dissociations are evaluated in terms of the structural insight they provide about the macromolecular structure. The fragmentation pathways of the diverse array of polymer ions examined fall into three categories, viz. (1) charge-directed fragmentations, (2) charge-remote rearrangements, and (3) charge-remote fragmentations via radical intermediates. Charge-remote processes predominate. Depending on the ionizing agent and the functional groups in the polymer, the incipient fragments arising by pathways (1)-(3) may form ion-molecule complexes that survive long enough to permit inter-fragment hydrogen atom, proton, or hydride transfers. PMID:20623599

  18. Unraveling the Nanostructure and Chain Conformation of Peptide-polymer Conjugates in Solution using Small-angle X-ray Scattering

    Science.gov (United States)

    Lund, Reidar; Xu, Ting; Dong, He

    For therapeutics, polymer functionalization, often by poly(ethylene glycol), PEG (``PEGylation''), is an effective method to improve the solubility, increase the life time and protect the proteins from the immune system[1]. However it is essential that the proteins maintain their structural integrity in solution- thus the role of the polymer and their interactions with proteins needs to be understood. In this work we show how small-angle X-ray scattering (SAXS) can be used as a powerful technique to characterize the structural components of peptide-polymer conjugates in solution [2, 3]. We specifically show that by applying detailed modelling very detailed structural features can be revealed, including the PEG chain conformation. In the presentation we will provide an overview of the methodology, specifically addressing peptides that form either alpha-helical bundles [2, 3] or beta-sheet structures [4, 5] and relate their structure in solution to their crystal structure.

  19. Side-chain tunability of furan-containing low-band-gap polymers provides control of structural order in efficient solar cells

    KAUST Repository

    Yiu, Alan T.

    2012-02-01

    The solution-processability of conjugated polymers in organic solvents has classically been achieved by modulating the size and branching of alkyl substituents appended to the backbone. However, these substituents impact structural order and charge transport properties in thin-film devices. As a result, a trade-off must be found between material solubility and insulating alkyl content. It was recently shown that the substitution of furan for thiophene in the backbone of the polymer PDPP2FT significantly improves polymer solubility, allowing for the use of shorter branched side chains while maintaining high device efficiency. In this report, we use PDPP2FT to demonstrate that linear alkyl side chains can be used to promote thin-film nanostructural order. In particular, linear side chains are shown to shorten π-π stacking distances between backbones and increase the correlation lengths of both π-π stacking and lamellar spacing, leading to a substantial increase in the efficiency of bulk heterojunction solar cells. © 2011 American Chemical Society.

  20. INVERSION SYMMETRY, ARCHITECTURE AND DISPERSITY, AND THEIR EFFECTS ON THERMODYNAMICS IN BULK AND CONFINED REGIONS: FROM RANDOMLY BRANCHED POLYMERS TO LINEAR CHAINS, STARS AND DENDRIMERS

    Directory of Open Access Journals (Sweden)

    P.D.Gujrati

    2002-01-01

    Full Text Available Theoretical evidence is presented in this review that architectural aspects can play an important role, not only in the bulk but also in confined geometries by using our recursive lattice theory, which is equally applicable to fixed architectures (regularly branched polymers, stars, dendrimers, brushes, linear chains, etc. and variable architectures, i.e. randomly branched structures. Linear chains possess an inversion symmetry (IS of a magnetic system (see text, whose presence or absence determines the bulk phase diagram. Fixed architectures possess the IS and yield a standard bulk phase diagram in which there exists a theta point at which two critical lines C and C' meet and the second virial coefficient A2 vanishes. The critical line C appears only for infinitely large polymers, and an order parameter is identified for this criticality. The critical line C' exists for polymers of all sizes and represents phase separation criticality. Variable architectures, which do not possess the IS, give rise to a topologically different phase diagram with no theta point in general. In confined regions next to surfaces, it is not the IS but branching and monodispersity, which becomes important in the surface regions. We show that branching plays no important role for polydisperse systems, but become important for monodisperse systems. Stars and linear chains behave differently near a surface.

  1. Exact solution of the thermodynamics and size parameters of a polymer confined to a lattice of finite size: Large chain limit

    Science.gov (United States)

    Snyder, Chad R.; Guttman, Charles M.; Di Marzio, Edmund A.

    2014-01-01

    We extend the exact solutions of the Di Marzio-Rubin matrix method for the thermodynamic properties, including chain density, of a linear polymer molecule confined to walk on a lattice of finite size. Our extensions enable (a) the use of higher dimensions (explicit 2D and 3D lattices), (b) lattice boundaries of arbitrary shape, and (c) the flexibility to allow each monomer to have its own energy of attraction for each lattice site. In the case of the large chain limit, we demonstrate how periodic boundary conditions can also be employed to reduce computation time. Advantages to this method include easy definition of chemical and physical structure (or surface roughness) of the lattice and site-specific monomer-specific energetics, and straightforward relatively fast computations. We show the usefulness and ease of implementation of this extension by examining the effect of energy variation along the lattice walls of an infinite rectangular cylinder with the idea of studying the changes in properties caused by chemical inhomogeneities on the surface of the box. Herein, we look particularly at the polymer density profile as a function of temperature in the confined region for very long polymers. One particularly striking result is the shift in the critical condition for adsorption due to surface energy inhomogeneities and the length scale of the inhomogeneities; an observation that could have important implications for polymer chromatography. Our method should have applications to both copolymers and biopolymers of arbitrary molar mass.

  2. Relationships between physical properties of polymers and cross-sectional area per polymer chain. Final report, August 1, 1980-July 31, 1982

    International Nuclear Information System (INIS)

    X-ray scattering patterns from amorphous polymers frequently contain halos corresponding to distances significantly greater than that of van der Waals packing of carbon atoms. Regularities in the positions of such halos as a function of pendant group size have been reported, primarily for the crystallizable comb polymers. This work concerns n-alkylacrylate, n-alkylmethacrylate, and cyclo-alkylmethacrylate polymers with small alkyl groups: regularities in halo position with alkyl group size are seen, but the behavior with size is quantitatively different than that of the comb polymers. A case is made for the existence of a moderate amount of intersegmental order as the normal condition in the condensed amorphous state. The behavior of poly(methylmethacrylate) is anomalous and studies on it may not be used to generalize about the structure of the amorphous state

  3. The Dependence of Strength in Plastics upon Polymer Chain Length and Chain Orientation: An Experiment Emphasizing the Statistical Handling and Evaluation of Data.

    Science.gov (United States)

    Spencer, R. Donald

    1984-01-01

    Describes an experiment (using plastic bags) designed to give students practical understanding on using statistics to evaluate data and how statistical treatment of experimental results can enhance their value in solving scientific problems. Students also gain insight into the orientation and structure of polymers by examining the plastic bags.…

  4. Hindered amine stabilizers as sources of markers of the heterogeneous photooxidation/photostabilization of carbon chain polymers

    Czech Academy of Sciences Publication Activity Database

    Pilař, Jan; Pospíšil, Jan

    Hauppauge: Nova Science Publishers, 2011 - (Segewicz, L.; Petrowsky, M.), s. 343-357 ISBN 978-1-60692-928-5 Institutional research plan: CEZ:AV0Z40500505 Keywords : polymer photodegradation * polymer photostabilization * hindered amine stabilizers Subject RIV: CD - Macromolecular Chemistry

  5. Escape transition of a polymer chain from a nanotube: how to avoid spurious results by use of the force-biased pruned-enriched Rosenbluth algorithm.

    Science.gov (United States)

    Hsu, Hsiao-Ping; Binder, Kurt; Klushin, Leonid I; Skvortsov, Alexander M

    2008-10-01

    A polymer chain containing N monomers confined in a finite cylindrical tube of diameter D grafted at a distance L from the open end of the tube may undergo a rather abrupt transition, where part of the chain escapes from the tube to form a "crownlike" coil outside of the tube. When this problem is studied by Monte Carlo simulation of self-avoiding walks on the simple cubic lattice applying a cylindrical confinement and using the standard pruned-enriched Rosenbluth method (PERM), one obtains spurious results, however, with increasing chain length the transition gets weaker and weaker, due to insufficient sampling of the "escaped" states, as a detailed analysis shows. In order to solve this problem, a new variant of a biased sequential sampling algorithm with resampling is proposed, force-biased PERM: the difficulty of sampling both phases in the region of the first order transition with the correct weights is treated by applying a force at the free end pulling it out of the tube. Different strengths of this force need to be used and reweighting techniques are applied. Using rather long chains (up to N=18000 ) and wide tubes (up to D=29 lattice spacings), the free energy of the chain, its end-to-end distance, the number of "imprisoned" monomers can be estimated, as well as the order parameter and its distribution. It is suggested that this algorithm should be useful for other problems involving state changes of polymers, where the different states belong to rather disjunct "valleys" in the phase space of the system. PMID:18999448

  6. Significant Improvement of Semiconducting Performance of the Diketopyrrolopyrrole-Quaterthiophene Conjugated Polymer through Side-Chain Engineering via Hydrogen-Bonding.

    Science.gov (United States)

    Yao, Jingjing; Yu, Chenmin; Liu, Zitong; Luo, Hewei; Yang, Yang; Zhang, Guanxin; Zhang, Deqing

    2016-01-13

    Three diketopyrrolopyrrole (DPP)-quaterthiophene conjugated polymers, pDPP4T-1, pDPP4T-2, and pDPP4T-3, in which the molar ratios of the urea-containing alkyl chains vs branching alkyl chains are 1:30, 1:20, and 1:10, respectively, were prepared and investigated. In comparison with pDPP4T without urea groups in the alkyl side chains and pDPP4T-A, pDPP4T-B, and pDPP4T-C containing both linear and branched alkyl chains, thin films of pDPP4T-1, pDPP4T-2, and pDPP4T-3 exhibit higher hole mobilities; thin-film mobility increases in the order pDPP4T-1 polymers after blending with PC71BM. Blended thin films of pDPP4T-1:PC71BM, pDPP4T-2:PC71BM, and pDPP4T-3:PC71BM exhibit higher power conversion efficiencies (PCEs) than pDPP4T:PC71BM, pDPP4T-A:PC71BM, pDPP4T-B:PC71BM, and pDPP4T-C:PC71BM. The PCE of pDPP4T-1:PC71BM reaches 6.8%. Thin films of pDPP4T-1, pDPP4T-2, and pDPP4T-3 and corresponding thin films with PC71BM were characterized with AFM, GIXRD, and STEM. The results reveal that the lamellar packing order of the alkyl chains is obviously enhanced for thin films of pDPP4T-1, pDPP4T-2, and pDPP4T-3; after thermal annealing, slight inter-chain π-π stacking emerges for pDPP4T-2 and pDPP4T-3. Blends of pDPP4T-1, pDPP4T-2, and pDPP4T-3 with PC71BM show a more pronounced micro-phase separation. These observations suggest that the presence of urea groups may further facilitate the assemblies of these conjugated polymers into nanofibers and ordered aggregation of PC71BM. PMID:26669732

  7. Influence of the ordered structure of short-chain polymer molecule all-trans-β-carotene on Raman scattering cross section in liquid

    Institute of Scientific and Technical Information of China (English)

    Qu Guan-Nan; OuYang Shun-Li; Wang Wei-Wei; Li Zuo-Wei; Sun Cheng-Lin; Men Zhi-Wei

    2011-01-01

    We measured the resonant Raman spectra of all-trans-β-carotene in solvents with different densities and concentrations at different temperatures. The results demonstrated that the Raman scattering cross section (RSCS) of short-chain polymer all-trans-β-carotene is extremely high in liquid. Resonance and strong coherent weakly damped CC bond vibrating properties play important roles under these conditions. Coherent weakly damped CC bond vibration strength is associated with molecular ordered structure. All-trans-β-carotene has highly ordered structure and strong coherent weakly damped CC bond vibrating properties, which lead to large RSCS in the solvent with large density and low concentration at low temperature.

  8. Organometallic Polymers.

    Science.gov (United States)

    Carraher, Charles E., Jr.

    1981-01-01

    Reactions utilized to incorporate a metal-containing moiety into a polymer chain (addition, condensation, and coordination) are considered, emphasizing that these reactions also apply to smaller molecules. (JN)

  9. Photoconductive properties of conjugated polymers

    CERN Document Server

    Halls, J J M

    1997-01-01

    The research described in my dissertation has involved the fabrication and characterisation of photovoltaic cells based on conjugated polymers, including the widely studied polymer poly(p-phenylenevinylene). These materials have semiconducting properties which arise from the delocalisation of electrons along the pi-electron systems of the polymer chains. Research into these materials is motivated both by their novel electronic properties, and also their potential for use in a wide range of applications including light-emitting diodes (LEDs), thin-film transistors, and photovoltaic cells (solar cells and light detectors). Light absorbed in a photovoltaic cell generates opposite charges which are collected at two different electrodes, giving rise to an electric current

  10. Liquid crystalline polymers IX Main chain thermotropic poly (azomethine – ethers containing thiazole moiety linked with polymethylene spacers

    Directory of Open Access Journals (Sweden)

    2007-04-01

    Full Text Available A new homologous series of thermally stable thermotropic liquid crystalline poly(azomethine-ethers based on thiazole moiety were synthesized by solution polycondensation of 4,4`-diformyl-α,ω-diphenoxyalkanes, I–IV or 4,4`-diformyl-2,2`-dimethoxy-α,ω-diphenoxyalkanes V–VIII with the new bis(2-aminothiazole monomer X. A model compound XI was synthesized from X with benzaldehyde and characterized by elemental and spectral analyses. The inherent viscosities of the resulting polymers were in the range 0.43–1.34 dI/g. All the poly(azomethine-ethers were insoluble in common organic solvents but dissolved completely in concentrated H2SO4 and formic acid. The mesomorphic properties of these polymers were studied as a function of the diphenoxyalkane space length. Their thermotropic liquid crystalline properties were examined by DSC and optical polarizing microscopy and demonstrated that the resulting polymers form nematic mesophases over wide temperature ranges. The thermogravimetric analyses of those polymers were evaluated by TGA and DSC measurements and correlated to their structural units. X-ray analysis showed that polymers having some degree of crystallinity in the region 2θ = 5–60°. In addition, the morphological properties of selected examples were tested by scanning electron microscopy.

  11. Charge carrier mobility, photovoltaic, and electroluminescent properties of anthracene-based conjugated polymers bearing randomly distributed side chains

    Czech Academy of Sciences Publication Activity Database

    Usluer, Ö.; Kästner, C.; Abbas, M.; Ulbricht, C.; Cimrová, Věra; Wild, A.; Birckner, E.; Tekin, N.; Sariciftci, N. S.; Hoppe, H.; Rathgeber, S.; Egbe, D. A. M.

    2012-01-01

    Roč. 50, č. 16 (2012), s. 3425-3436. ISSN 0887-624X R&D Projects: GA MŠk(CZ) 1M06031 Institutional research plan: CEZ:AV0Z40500505 Keywords : conjugated polymers * organic field-effect transistors * organic solar cells Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.543, year: 2012

  12. Decades-Scale Degradation of Commercial, Side-Chain, Fluorotelomer-Based Polymers in Soils and Water

    Science.gov (United States)

    Fluorotelomer-based polymers (FTPs) are a primary product of the jluorotelomer industry, yet the role of commercial FTPs in degrading to form perjluorocarboxylic acids (P FCAs), including perjluorooctanoic acid, and P FCA precursors, remains ill-defined. Here we report on a 376-d...

  13. Richness of Side-Chain Liquid-Crystal Polymers: From Isotropic Phase towards the Identification of Neglected Solid-Like Properties in Liquids

    Directory of Open Access Journals (Sweden)

    Joachim H. Wendorff

    2012-04-01

    Full Text Available Very few studies concern the isotropic phase of Side-Chain Liquid-Crystalline Polymers (SCLCPs. However, the interest for the isotropic phase appears particularly obvious in flow experiments. Unforeseen shear-induced nematic phases are revealed away from the N-I transition temperature. The non-equilibrium nematic phase in the isotropic phase of SCLCP melts challenges the conventional timescales described in theoretical approaches and reveal very long timescales, neglected until now. This spectacular behavior is the starter of the present survey that reveals long range solid-like interactions up to the sub-millimetre scale. We address the question of the origin of this solid-like property by probing more particularly the non-equilibrium behavior of a polyacrylate substituted by a nitrobiphenyl group (PANO2. The comparison with a polybutylacrylate chain of the same degree of polymerization evidences that the solid-like response is exacerbated in SCLCPs. We conclude that the liquid crystal moieties interplay as efficient elastic connectors. Finally, we show that the “solid” character can be evidenced away from the glass transition temperature in glass formers and for the first time, in purely alkane chains above their crystallization temperature. We thus have probed collective elastic effects contained not only in the isotropic phase of SCLCPs, but also more generically in the liquid state of ordinary melts and of ordinary liquids.

  14. Chain conformations of the component polymers and the microphase separation structures of homopolymer/block coplymer blends

    International Nuclear Information System (INIS)

    Microdomain spacings of lamellar structures formed by styrene homopolymer/styrene-2-vinylpyridine diblock copolymer/2-vinylpyridine homopolymer blends were measured by small-angle X-ray scattering (SAXS) and single chain conformations of block copolymers in the same blend system were measured by small-angle neutron scattering (SANS). The molecular weight of diblock copolymers is 78K-72K, and three kinds of styrene homopolymer (SH) and 2-vinylpyridine homopolymer (PH) pairs were blended, their molecular weight ratios to that of host block chains were 0.17, 0.38, and 0.78, respectively. Two blend ratios of homopolymer (H)/block copolymer (B), i.e. 1/2 and 1/1 were examined. It was found that the domain spacings of all blends are larger than that of pure block copolymer and that they are increasing with increasing the molecular weight of homopolymers and/or with increasing the volume fraction of homopolymers. Further, block chains in the blends were confirmed to have almost the same chain dimension as that of block chain in pure block copolymer system in the direction parallel to the domain interface irrespective of molecular weight and volume fraction of homopolymers. (author)

  15. Coil-bridge transition in a single polymer chain as an unconventional phase transition: Theory and simulation

    Science.gov (United States)

    Klushin, Leonid I.; Skvortsov, Alexander M.; Polotsky, Alexey A.; Hsu, Hsiao-Ping; Binder, Kurt

    2014-05-01

    The coil-bridge transition in a self-avoiding lattice chain with one end fixed at height H above the attractive planar surface is investigated by theory and Monte Carlo simulation. We focus on the details of the first-order phase transition between the coil state at large height H ⩾ Htr and a bridge state at H ⩽ Htr, where Htr corresponds to the coil-bridge transition point. The equilibrium properties of the chain were calculated using the Monte Carlo pruned-enriched Rosenbluth method in the moderate adsorption regime at (H/Na)tr ⩽ 0.27 where N is the number of monomer units of linear size a. An analytical theory of the coil-bridge transition for lattice chains with excluded volume interactions is presented in this regime. The theory provides an excellent quantitative description of numerical results at all heights, 10 ⩽ H/a ⩽ 320 and all chain lengths 40 free fitting parameters. A simple theory taking into account the effect of finite extensibility of the lattice chain in the strong adsorption regime at (H/Na)tr ⩾ 0.5 is presented. We discuss some unconventional properties of the coil-bridge transition: the absence of phase coexistence, two micro-phases involved in the bridge state, and abnormal behavior in the microcanonical ensemble.

  16. Modeling of Polymer Erosion

    OpenAIRE

    Göpferich, Achim; Langer, Robert S.

    1993-01-01

    The erosion of bioerodible polymers depends on many factors including the polymer chain length, bond cleavage velocity, swellability, crystallinity, and water diffusivity in the polymer matrix. This multitude of parameters makes modeling of erosion difficult. Only a few models exist that describe morphological changes of polymers during erosion qualitatively. In the present approach the polymer matrix was represented as the sum of small individual polymer matrix parts. The factors that determ...

  17. Linear side chains in benzo[1,2-b:4,5-b′]dithiophene-thieno[3,4-c] pyrrole-4,6-dione polymers direct self-assembly and solar cell performance

    KAUST Repository

    Cabanetos, Clement

    2013-03-27

    While varying the size and branching of solubilizing side chains in π-conjugated polymers impacts their self-assembling properties in thin-film devices, these structural changes remain difficult to anticipate. This report emphasizes the determining role that linear side-chain substituents play in poly(benzo[1,2-b:4,5-b′]dithiophene-thieno[3,4-c]pyrrole-4,6-dione) (PBDTTPD) polymers for bulk heterojunction (BHJ) solar cell applications. We show that replacing branched side chains by linear ones in the BDT motifs induces a critical change in polymer self-assembly and backbone orientation in thin films that correlates with a dramatic drop in solar cell efficiency. In contrast, we show that for polymers with branched alkyl-substituted BDT motifs, controlling the number of aliphatic carbons in the linear N-alkyl-substituted TPD motifs is a major contributor to improved material performance. With this approach, PBDTTPD polymers were found to reach power conversion efficiencies of 8.5% and open-circuit voltages of 0.97 V in BHJ devices with PC71BM, making PBDTTPD one of the best polymer donors for use in the high-band-gap cell of tandem solar cells. © 2013 American Chemical Society.

  18. SYNTHESIS AND PROPERTIES OF NEW SIDE-CHAIN LIQUID CRYSTALLINE POLYMER WITH LATERALLY ATTACHED MESOGENS BY ESTER GROUP

    Institute of Scientific and Technical Information of China (English)

    Qi-ding Mi; Qi-feng Zhou

    1999-01-01

    New liquid crystalline monomer, 2,5-bis[(4'-methoxyphenoxy)carbonyl]phenyl acrylate was successfully synthesized. Polyacrylate with laterally attached mesogens via ester linkage was also derived.This polymer forms an enantiotropic liquid crystal phase while its monomer exhibits a metastable nematic phase with respect to the crystalline state. However, its liquid crystallinity is very low as compared to that of poly { 2,5-bis[(4'-methoxyphenoxy)carbonyl] -styrene }.

  19. The effects of polymer side-chain structure on roughness formation of ArF photoresist in plasma etching processes

    International Nuclear Information System (INIS)

    Low etching resistance and roughness formation of ArF photoresist during plasma etching are serious problems. We have previously found that decisive factors affecting the plasma resistance and roughness formation in an ArF photoresist are determined by ultraviolet/vacuum ultraviolet radiation and roughness formation is dominated by chemical reactions. In this paper, on the basis of our previous findings on the interaction between radiation species from plasma and ArF photoresist polymers, we investigated the polymer structural dependence for the degradation mechanism of ArF photoresist in the plasma etching processes. The etching resistance of ArF photoresist was improved by controlling the elemental ratio of oxygen atoms and ring structures in photoresist polymer. Furthermore, lactone C=O bond is found to be a key factor for roughness formation during the etching process. We have revealed the importance of the molecular structure of ArF photoresist for improving the surface roughness and etching resistance during the plasma etching process. (paper)

  20. Hydrothermal synthesis, crystal structure and properties of a novel chain coordination polymer constructed by tetrafunctional phosphonate anions and cobalt ions

    International Nuclear Information System (INIS)

    A novel cobalt phosphonate, [Co(HL)(H2O)3]n (1) (L=N(CH2PO3H)33−) has been synthesized by hydrothermal reaction at 150 °C and structurally characterized by X-ray diffraction, infrared spectroscopy, elemental and thermogravimetric analysis. Complex 1 features a 1D chain structure with double-channel built from CoO6 octahedra bridged together by the phosphonate groups. Each cobalt ion is octahedrally coordinated by three phosphonate oxygen atoms and three water molecules. The coordinated water molecules can form the hydrogen bonds with the phosphonate oxygen atoms to link the 1D chains, building a 2D layered structure, further resulting in a 3D network. The luminescence spectrum indicates an emission maximum at 435 nm. The magnetic susceptibility curve exhibits a dominant antiferromagnetic behavior with a weakly ferromagnetic component at low temperatures. - Graphical abstract: The connectivity between cobalt ions and the ligands results in a chain structure with a 1D double-channel structure, which is constructed by A-type subrings and B-type subrings. - Highlights: • The tetrafunctional phosphonate ligand was used as the ligand. • A novel chain structure can be formed by A-type rings and B-type rings. • Two types of rings can form a 1D double-channel structure, along the c-axis

  1. Highly Grafted Polystyrene/polyvinylpyridine Polymer Gold Nanoparticles in a Good Solvent: Effects of Chain Length and Composition.

    Czech Academy of Sciences Publication Activity Database

    Posel, Zbyšek; Posocco, P.; Lísal, Martin; Fermeglia, M.; Pricl, S.

    2016-01-01

    Roč. 12, č. 15 (2016), s. 3600-3611. ISSN 1744-683X R&D Projects: GA ČR(CZ) GA13-02938S; GA MŠk LH12020 Institutional support: RVO:67985858 Keywords : block copolymers * chains * fiber optic sensors Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.029, year: 2014

  2. Hydrothermal synthesis, crystal structure and properties of a novel chain coordination polymer constructed by tetrafunctional phosphonate anions and cobalt ions

    Energy Technology Data Exchange (ETDEWEB)

    Guan, Lei, E-mail: gl_coord@163.com [School of Chemistry and Materials Science, Liaoning University of Petroleum and Chemical Engineering, Fushun 113001 (China); Wang, Ying [Center of Experiment, College of Chemistry, Chemical Engineering and Environmental Engineering, Liaoning University of Petroleum and Chemical Engineering, Fushun 113001 (China)

    2015-08-15

    A novel cobalt phosphonate, [Co(HL)(H{sub 2}O){sub 3}]{sub n} (1) (L=N(CH{sub 2}PO{sub 3}H){sub 3}{sup 3−}) has been synthesized by hydrothermal reaction at 150 °C and structurally characterized by X-ray diffraction, infrared spectroscopy, elemental and thermogravimetric analysis. Complex 1 features a 1D chain structure with double-channel built from CoO{sub 6} octahedra bridged together by the phosphonate groups. Each cobalt ion is octahedrally coordinated by three phosphonate oxygen atoms and three water molecules. The coordinated water molecules can form the hydrogen bonds with the phosphonate oxygen atoms to link the 1D chains, building a 2D layered structure, further resulting in a 3D network. The luminescence spectrum indicates an emission maximum at 435 nm. The magnetic susceptibility curve exhibits a dominant antiferromagnetic behavior with a weakly ferromagnetic component at low temperatures. - Graphical abstract: The connectivity between cobalt ions and the ligands results in a chain structure with a 1D double-channel structure, which is constructed by A-type subrings and B-type subrings. - Highlights: • The tetrafunctional phosphonate ligand was used as the ligand. • A novel chain structure can be formed by A-type rings and B-type rings. • Two types of rings can form a 1D double-channel structure, along the c-axis.

  3. Hydrothermal synthesis and crystal structure of copper (Ⅱ)coordination polymer composed of helix-like chains:[Cu(NIPH)(bpy)

    Institute of Scientific and Technical Information of China (English)

    YE Junwei; ZHANG Ping; YE Kaiqi; YE Ling; YANG Guangdi; WANG Yue

    2006-01-01

    Hydrothermal reactions of Cu (Ⅱ) acetate, 2,2'-bipyridyl (bpy) with 5-nitroisophthalic acid (H2NIPH) resulted in a new coordination polymer [Cu(NIPH)(bpy)] 1. Single crystal X-ray diffraction experiment indicates that 1 possesses a single helixlike chains, of which Cu atoms are coordinated by NIPH ligands and bpy ligands. Compound 1 crystallizes in the space group P2(1)/c, a = 0.955(19) nm, b = 1.259(3) nm, c= 1.3737(3) nm, β= 95.13(3)°, V=1.6455(6) nm3 and Z = 4. The TGA analysis shows that 1 has no remarkable weight loss up to 284℃, as a result of its high thermal stability. Magnetic measurements indicate an antiferromagnetic behavior of compound 1.

  4. Influence of the ordered structure of short-chain polymer molecule all-trans-β-carotene on Raman scattering cross section in liquid

    International Nuclear Information System (INIS)

    We measured the resonant Raman spectra of all-trans-β-carotene in solvents with different densities and concentrations at different temperatures. The results demonstrated that the Raman scattering cross section (RSCS) of short-chain polymer all-trans-β-carotene is extremely high in liquid. Resonance and strong coherent weakly damped CC bond vibrating properties play important roles under these conditions. Coherent weakly damped CC bond vibration strength is associated with molecular ordered structure. All-trans-β-carotene has highly ordered structure and strong coherent weakly damped CC bond vibrating properties, which lead to large RSCS in the solvent with large density and low concentration at low temperature. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  5. A temperature control method for shortening thermal cycling time to achieve rapid polymerase chain reaction (PCR) in a disposable polymer microfluidic device

    International Nuclear Information System (INIS)

    We present a temperature control method capable of effectively shortening the thermal cycling time of polymerase chain reaction (PCR) in a disposable polymer microfluidic device with an external heater and a temperature sensor. The method employs optimized temperature overshooting and undershooting steps to achieve a rapid ramping between the temperature steps for DNA denaturation, annealing and extension. The temperature dynamics within the microfluidic PCR chamber was characterized and the overshooting and undershooting parameters were optimized using the temperature-dependent fluorescence signal from Rhodamine B. The method was validated with the PCR amplification of mecA gene (162 bp) from methicillin-resistant Staphylococcus aureus bacterium (MRSA), where the time for 30 cycles was reduced from 50 min (without over- and undershooting) to 20 min. (paper)

  6. Influence of chain length and polymer concentration on the gelation of (amidated) low-methoxyl pectin induced by calcium.

    Science.gov (United States)

    Capel, François; Nicolai, Taco; Durand, Dominique; Boulenguer, Patrick; Langendorff, Virginie

    2005-01-01

    The gelation of low-methoxyl pectin (LMP) induced by addition of Ca2+ was studied by measuring the storage modulus as a function of temperature during cooling. Samples with different molar masses were prepared by mechanical degradation. The effect of the molar mass and the pectin concentration on the gelation properties was investigated. The effect of partial amidation was studied by comparing LMP and partially amidated LMP with the same molar mass and degree of methylation. The results are compared to those from a model developed for Ca2+-induced pectin gelation, and good agreement is found except at low concentrations and low molar masses where the gels are weaker than predicted. At low concentrations intrachain bonding weakens the gel, while the presence of small pectin chains weakens the gel because it neutralizes binding sites on larger chains. PMID:16283714

  7. A simple strategy to the side chain functionalization on the quinoxaline unit for efficient polymer solar cells.

    Science.gov (United States)

    Yuan, Jun; Qiu, Lixia; Zhang, Zhiguo; Li, Yongfang; He, Yuehui; Jiang, Lihui; Zou, Yingping

    2016-05-25

    A new tetrafluoridequinoxaline electron accepting block from a quinoxaline core, which is substituted with a fluorine atom onto its backbone and side chains, was designed. A new copolymer (PBDTT-ffQx) was synthesized from tetrafluoridequinoxaline and benzodithiophene. The copolymer was characterized in detail. The photovoltaic properties were well investigated. A high PCE of 8.6% based on the single junction device was obtained. PMID:27025274

  8. Recent developments in Inorganic polymers: A Review with focus on Si-Al based inorganic polymers

    OpenAIRE

    Shrray Srivastava; Ravindra Gadhave

    2015-01-01

    Inorganic polymers are a unique classification of polymers. They contain inorganic atoms in the main chain. Hybrids with organic polymers as well as those chains that contain metals as pendant groups are considered in a special sub-classification as organo-metallic polymers. The networks containing only inorganic elements in main chain are called inorganic polymers. The silicone rubber is the most commercial inorganic polymer. The organo-metallic and inorganic polymers have a different set of...

  9. From polymers to proteins: the effect of side chains and broken symmetry on the formation of secondary structures within a Wang-Landau approach.

    Science.gov (United States)

    Škrbić, Tatjana; Badasyan, Artem; Hoang, Trinh Xuan; Podgornik, Rudolf; Giacometti, Achille

    2016-05-25

    We use a micro-canonical Wang-Landau technique to study the equilibrium properties of a single flexible homopolymer where consecutive monomers are represented by impenetrable hard spherical beads tangential to each other, and non-consecutive monomers interact via a square-well potential. To mimic the characteristics of a protein-like system, the model is then refined in two different directions. Firstly, by allowing partial overlap between consecutive beads, we break the spherical symmetry and thus provide a severe constraint on the possible conformations of the chain. Alternatively, we introduce additional spherical beads at specific positions in the direction normal to the backbone, to represent the steric hindrance of the side chains in real proteins. Finally, we consider also a combination of these two ingredients. In all three systems, we obtain the full phase diagram in the temperature-interaction range plane and find the presence of helicoidal structures at low temperatures in the intermediate range of interactions. The effect of the range of the square-well attraction is highlighted, and shown to play a role similar to that found in simple liquids and polymers. Perspectives in terms of protein folding are finally discussed. PMID:27137225

  10. On the critical properties of the Edwards and the self-avoiding walk model of polymer chains

    International Nuclear Information System (INIS)

    We study the two- and three-dimensional, superrenormalizable Edwards model and the self-avoiding walk model of polymers. Using a Schwinger-Dyson equation and upper and lower bounds on correlations in terms of 'skeleton diagrams' we establish the existence of a non-trivial continuum limit in the two- and three-dimensional, superrenormalizable Edwards model. We also prove that perturbation theory is asymptotic for the continuum correlations of these models. A fairly detailed analysis of the approach to the critical point in the self-avoiding walk model is presented. In particular, we show that eta = 4, we discuss rigorous consequences of the conjecture that eta is non-negative; among other implications, we derive that the continuum limit is trivial and that γ = 1, in d >= 5 dimensions, and that corrections to mean-field scaling laws are at most logarithmic in four dimensions. (orig.)

  11. Photo-orientation of azobenzene side chain polymers parallel or perpendicular to the polarization of red HeNe light

    International Nuclear Information System (INIS)

    The mechanism of the light-induced orientation process of azobenzene-containing polymers caused by irradiation with linearly polarized red light is investigated. This process is surprising because there is almost no absorption at 633 nm. Depending on the photochemical pre-treatment and the exposure time, the azobenzene moieties can undergo two different orientation processes resulting in either a parallel or a perpendicular orientation with respect to the electric field vector of the incident light. The fast orientation of the photochromic groups with their long axis in the direction of the light polarization requires a photochemical pre-treatment in which non-polarized UV light generates Z-isomers. Due to this procedure the film becomes 'photochemically activated' for the subsequent polarized irradiation with red light. But on continued exposure a second, much slower reorientation process occurs which establishes an orientation of the azobenzene groups perpendicular to the electric field vector. The fast mechanism is probably caused by an angle-selective photo-isomerization of the Z-isomers to the E-isomers, while the subsequent slow reorientation process is caused by the well-known conventional photo-orientation taking place via the accumulation of a number of photoselection steps and the rotational diffusion minimizing the absorbance of the E-isomer. This process occurs in the steady state but at this wavelength with a very small concentration of Z-isomers. The competing mechanisms take place in the same polymer film under almost identical irradiation conditions, differing only in the actual concentration of the Z-isomers

  12. Polymer friction Molecular Dynamics

    OpenAIRE

    Sivebæk, Ion Marius; Samoilov, Vladimir N.; Persson, Bo N. J.

    2010-01-01

    We present molecular dynamics friction calculations for confined hydrocarbon solids with molecular lengths from 20 to 1400 carbon atoms. Two cases are considered: a) polymer sliding against a hard substrate, and b) polymer sliding on polymer. In the first setup the shear stresses are relatively independent of molecular length. For polymer sliding on polymer the friction is significantly larger, and dependent on the molecular chain length. In both cases, the shear stresses are proportional to ...

  13. In-situ ultrasonic compatibilization of binary blends of flexible chain polyesters and aromatic liquid crystalline polymers

    Science.gov (United States)

    Gunes, Kaan

    The objective of this research was to improve the properties of immiscible polymer blends by developing a new ultrasonic extrusion process. The ability of ultrasonic treatment to induce recombination reactions in polymer blends was anticipated to result in fast in-situ compatibilization of immiscible blends. In order to test this hypothesis, a new ultrasonic extruder operating at a frequency of 20 kHz at amplitudes of 5, 7.5, and 10 mum was developed. Polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and wholly aromatic liquid crystalline copolyesters (LCPs) were selected to illustrate the effect of ultrasonic treatment on copolymerization of components through transesterification reactions in blends. The LCPs studied were a copolymer of hydroxybenzoic and hydroxynaphthoic acid (LCP1) and a copolymer of dioxydiphenyl, terephthalic and isophthalic acid (LCP2). PET/PEN, PET/LCP1, PEN/LCP1, and LCP1/LCP2 blends and their components were subsequently injection molded and spun into fibers. PET underwent homopolymerization and degradation, respectively, at ultrasonic amplitudes of 7.5 mum and 10 mum, while PEN underwent degradation at all amplitudes. MALDI-TOF mass spectroscopy revealed greater amounts of hydroxyl and carboxyl terminated oligomers in ultrasonically treated PET and PEN. Transesterification (copolymer formation) was observed in PET/PEN blends, which was enhanced with ultrasonic treatment, as indicated by 1H NMR and MALDI-TOF. Oxygen permeability of compression molded films of untreated and ultrasonically treated PET/PEN blends followed theoretical predictions for miscible blends. Ultrasonic treatment of LCP1 at amplitudes of 7.5 and 10 mum led to improved mechanical properties of its injection moldings. On the other hand, LCP2 underwent degradation with treatment, leading to a reduction of mechanical properties of LCP2 and LCP1/LCP2 blends. However, due to enhanced fibrillation, these blends retained synergism such that moldings exhibited

  14. Dynamics of a Gaussian chain in the gas phase and in a confined geometry

    Science.gov (United States)

    Hasan, Md Sayed

    This dissertation involves a study of the dynamics of a Gaussian chain in different environments. In the first part, the dynamics of polymers in the gas phase are studied at the theta temperature. Since the mean free path in a gas is large, the collisions of the gas particles with the monomers are ballistic. This ballistic nature of collision can be combined with the probability distribution of a Gaussian chain to determine the correlation of random forces, and this correlation can be exploited to evaluate the friction constant zetap. The second part considers the internal friction of a Gaussian chain placed in a vacuum. The dynamics of a single chain can be described by the Langevin equation, where the random force terms arise from the random collisions of monomers with each other. To find the moment of these random forces, a Gaussian distribution of chain conformation is used. We show that this same mechanism of internal friction is also applicable in solutions. In the third part, the dynamics of polymer melts near a corrugated boundary are examined. Since the volume interaction is screened in melts, polymers can be treated as Gaussian chains. When a polymer melt flows near a smooth surface, there may exist a nonzero slip velocity. The velocity field for a perturbed boundary is derived using a slip boundary condition. As a chain moves near this boundary, it experiences an oscillatory shear and the frequency of the strain rate depends on the slip velocity. The dissipation rates for different slip velocities are evaluated.

  15. Self-assembly of the hydrogel polymer chain consisting of chitosan and chondroitin sulphate in the presence of theophylline;Propriedades de higrogeis constituidos de quitosana e sulfato decondroitina na presenca de teofilina intumescidos em diferentes pHs

    Energy Technology Data Exchange (ETDEWEB)

    Lopes, Lais C.; Piai, Juliana F.; Fajardo, Andre R.; Rubira, Adley F.; Muniz, Edvani C., E-mail: ecmuniz@uem.b [Universidade Estadual de Maringa (GMPC/UEM), PR (Brazil). Grupo de Materiais Polimericos e Compositos

    2009-07-01

    In this work, polyelectronic complex (PEC) consisting of two polysaccharides were developed. One is chitosan (QT), cationic polymer, produced by the chitin deacetylation and the other is chondroitin sulphate (CS), anionic polymer, extracted from bovine or porcine aorta. The PECs were prepared in the presence of theophylline (TEO) for evaluating the influence of this drug in the polymer chains reorganization, as well as, studying the mechanical properties and release of SC and TEO in aqueous solutions on different pH conditions. By the obtained results, it was observed that the 84QT/15SC/TEO (% in weight) hydrogel is pH responsive because the CS releasing is more effective at pH 8, while the release of the TEO is higher at pH 2. The hydrogel showed mechanical properties more resistant to pH 2, 8 and 10 and this was attributed to interactions between the polymer chains. Finally, the X-rays profile showed the presence of peaks associated to reorganization of the chains in the hydrogel is at times larger than the hydrogel in the absence of solute. (author)

  16. Star Polymers.

    Science.gov (United States)

    Ren, Jing M; McKenzie, Thomas G; Fu, Qiang; Wong, Edgar H H; Xu, Jiangtao; An, Zesheng; Shanmugam, Sivaprakash; Davis, Thomas P; Boyer, Cyrille; Qiao, Greg G

    2016-06-22

    Recent advances in controlled/living polymerization techniques and highly efficient coupling chemistries have enabled the facile synthesis of complex polymer architectures with controlled dimensions and functionality. As an example, star polymers consist of many linear polymers fused at a central point with a large number of chain end functionalities. Owing to this exclusive structure, star polymers exhibit some remarkable characteristics and properties unattainable by simple linear polymers. Hence, they constitute a unique class of technologically important nanomaterials that have been utilized or are currently under audition for many applications in life sciences and nanotechnologies. This article first provides a comprehensive summary of synthetic strategies towards star polymers, then reviews the latest developments in the synthesis and characterization methods of star macromolecules, and lastly outlines emerging applications and current commercial use of star-shaped polymers. The aim of this work is to promote star polymer research, generate new avenues of scientific investigation, and provide contemporary perspectives on chemical innovation that may expedite the commercialization of new star nanomaterials. We envision in the not-too-distant future star polymers will play an increasingly important role in materials science and nanotechnology in both academic and industrial settings. PMID:27299693

  17. One step grafting of iron phthalocyanine containing flexible chains on Fe3O4 nanoparticles towards high performance polymer magnetic composites

    International Nuclear Information System (INIS)

    To develop high-performance inorganic particles/polymer composites, the interfacial interaction and dispersion of inorganic particles are the two essential issues to be considered. Herein, we report an effective approach to graft iron phthalocyanine containing flexible chains (NP-ph) on Fe3O4 nanoparticles (NP-ph@Fe3O4). The hybrids were monodispersed solid nanoparticles with the average diameter of about 250 nm. About 16.8% of the phthalocyanine oligomer was incorporated into the resulting NP-ph@Fe3O4 nanoparticles. The NP-ph@Fe3O4 nanoparticles were subsequently used as the novel filler for preparation of high performance poly(arylene ether nitrile)s (PAEN) composites. The scanning electron microscopy (SEM) investigation showed that the NP-ph@Fe3O4 nanoparticles present better dispersion and interfacial compatibility with PAEN matrix than that of raw Fe3O4, which was further confirmed by rheological study. Consequently, the improved thermal stability and enhanced mechanical properties were obtained from composites using NP-ph@Fe3O4. Vibrating sample magnetometer (VSM) results showed that the prepared PAEN composites exhibited higher saturation magnetization and soft magnetic properties. Meanwhile, the saturation magnetization (Ms) of the PAEN/NP-ph@Fe3O4 composite films increased with the increase of the hybrid nanoparticles loading. Thus, the PAEN/NP-ph@Fe3O4 composite would find potential applications in organic magnetic films fields due to their high thermal stability, excellent flexibility and tunable magnetic properties. - Highlights: • An effective approach to graft CuPc containing flexible chains on Fe. • Effect on the mechanical, thermal and interfacial properties were investigated. • The dispersion state was characterized using parallel-plate rheometry. • The mechanism of interfacial compatibility was clarified

  18. One step grafting of iron phthalocyanine containing flexible chains on Fe{sub 3}O{sub 4} nanoparticles towards high performance polymer magnetic composites

    Energy Technology Data Exchange (ETDEWEB)

    Pu, Zejun; Zhou, Xuefei; Yang, Xulin; Jia, Kun, E-mail: Jiakun@uestc.edu.cn; Liu, Xiaobo, E-mail: liuxb@uestc.edu.cn

    2015-07-01

    To develop high-performance inorganic particles/polymer composites, the interfacial interaction and dispersion of inorganic particles are the two essential issues to be considered. Herein, we report an effective approach to graft iron phthalocyanine containing flexible chains (NP-ph) on Fe{sub 3}O{sub 4} nanoparticles (NP-ph@Fe{sub 3}O{sub 4}). The hybrids were monodispersed solid nanoparticles with the average diameter of about 250 nm. About 16.8% of the phthalocyanine oligomer was incorporated into the resulting NP-ph@Fe{sub 3}O{sub 4} nanoparticles. The NP-ph@Fe{sub 3}O{sub 4} nanoparticles were subsequently used as the novel filler for preparation of high performance poly(arylene ether nitrile)s (PAEN) composites. The scanning electron microscopy (SEM) investigation showed that the NP-ph@Fe{sub 3}O{sub 4} nanoparticles present better dispersion and interfacial compatibility with PAEN matrix than that of raw Fe{sub 3}O{sub 4}, which was further confirmed by rheological study. Consequently, the improved thermal stability and enhanced mechanical properties were obtained from composites using NP-ph@Fe{sub 3}O{sub 4}. Vibrating sample magnetometer (VSM) results showed that the prepared PAEN composites exhibited higher saturation magnetization and soft magnetic properties. Meanwhile, the saturation magnetization (Ms) of the PAEN/NP-ph@Fe{sub 3}O{sub 4} composite films increased with the increase of the hybrid nanoparticles loading. Thus, the PAEN/NP-ph@Fe{sub 3}O{sub 4} composite would find potential applications in organic magnetic films fields due to their high thermal stability, excellent flexibility and tunable magnetic properties. - Highlights: • An effective approach to graft CuPc containing flexible chains on Fe. • Effect on the mechanical, thermal and interfacial properties were investigated. • The dispersion state was characterized using parallel-plate rheometry. • The mechanism of interfacial compatibility was clarified.

  19. Electric current arising from unpolarized polyvinyl formal

    Indian Academy of Sciences (India)

    P K Khare; P L Jain; R K Pandey

    2000-10-01

    An appreciable electric current is observed in a system consisting of a polyvinyl formal (PVF) film in a sandwich configuration, in the temperature range 30–110°C. The maximum value of the current during first heating is found to be of the order of 10–10 A and its thermograms exhibit one transition (i.e. current peak) at around 60°C. The position of the current peak in thermal spectrum shifts with the heating rate. A temperature dependence of the open circuit voltage is also observed. The activation energy of the process responsible for the current is determined. The magnitude of the current is more in the case of dissimilar electrode systems. It is proposed that the electric current arising from unpolarized metal–polymer–metal system is a water activated phenomenon, which is influenced by the transitional changes of the polymer.

  20. Chain-length-dependent impact of band broadening on the molar-mass determination of synthetic polymers via size-exclusion chromatography.

    Science.gov (United States)

    Wolpers, Arne; Vana, Philipp

    2016-08-01

    The impact of band-broadening (BB) on the molar-mass determination of synthetic polymers via size-exclusion chromatography (SEC) is systematically studied. BB is simulated using the exponentially modified Gaussian (EMG) model, which combines the two inherent and distinct characteristics contributing to BB in SEC: symmetric Gaussian broadening and asymmetric skewing. It is demonstrated that BB both during the measurement of the analyte itself and during the calibration process has an individual impact on molar-mass determination. In this context, particularly skewing leads to a chain-length-dependent underestimation of molar masses, with deviations of the apparent from the true ones of only a few percent for low molar masses to up to 20% for high ones for reasonable extents of BB. The impact is shown to be independent of the shape of the analyte⬢s molar-mass distribution (MMD) and affects broad and multimodal MMDs similarly to narrow and unimodal ones. As a consequence, strategies are presented for a comprehensive quantitative correction of the observed effects, which may find their application in refined SEC software packages. The potential impact of the findings on general conceptions of repeatability and reproducibility within SEC experiments is discussed. PMID:27393628

  1. Self-assembly of silver(I) coordination polymers from aminopyrimidyl derivatives and malonate acid: From 1D chain to 2D layer

    Science.gov (United States)

    Sun, Di; Zhang, Na; Xu, Qin-Juan; Luo, Geng-Geng; Huang, Rong-Bin; Zheng, Lan-Sun

    2010-04-01

    Two new silver(I) coordination polymers (CPs) of the formula [Ag 2(dmapym) 4(mal)·H 2O] n ( 1) and [Ag 3(apym) 3(mal)NO 3] n ( 2) (dmapym = 2-amino-4,6-dimethylprimidine, apym = 2-aminopyrimidine, H 2mal = malonate) have been synthesized by reactions of AgNO 3 and 2-aminopyrimidyl ligands with malonate under the ammoniacal condition. Both complexes have been characterized by element analysis, IR and single-crystal X-ray diffraction. The monodentate dmapym and tridentate mal ligands link Ag(I) ions to give complex 1 a one-dimensional (1D) H-shaped chain structure. The complex 2 is a two-dimensional (2D) double sheet structure constructed by (4, 4) single sheet. Additionally, the hydrogen-bonding and C-H⋯π interactions also direct the self-assembly of supramolecular architectures. The photoluminescence properties of the 1 and 2 were investigated in the solid state at room temperature.

  2. Hydrothermal Synthesis and Crystal Structure of a Cadmium(Ⅱ) Polymer with One-dimensional Chain Structure: [Cd(bpy)(BDC)]n·nbpy

    Institute of Scientific and Technical Information of China (English)

    LI Xiu-Mei; NIU Yan-Ling; WANG Qing-Wei; CUI Yun-Cheng; LIU Bo

    2007-01-01

    A metal-organic coordination polymer [Cd(bpy)(BDC)]n·nbpy (bpy = 2,2'-bipyri- dine, H2BDC = terephthalic acid) has been hydrothermally synthesized and structurally characteri- zed by elemental analysis, IR spectrum, TG and single-crystal X-ray diffraction. The complex crystallizes in monoclinic, space group C2/c with a = 15.723(5), b = 21.695(5), c = 7.576(5)(A), β = 116.171(7)o, V = 2319.3(18)(A)3, C28H20CdN4O4, Mr = 588.88, Dc = 1.686 g/cm3, μ(MoKα) = 0.987 mm(1, F(000) = 1184, Z = 4, the final R = 0.0464 and wR = 0.0831 for 1882 observed reflections (Ⅰ > 2σI)). It exhibits a three-dimensional network with channels constructed from one-dimensional coordination chains via C-H…O hydrogen bonds and significant aromatic π-π stacking interactions.

  3. Entanglements of End Grafted Polymer Brushes in a Polymeric Matrix

    Science.gov (United States)

    Grest, Gary S.; Hoy, Robert S.

    2007-03-01

    The entanglement of a polymer brush immersed in a melt of mobile polymer chains is studied by molecular dynamics simulations. A primitive path analysis (PPA) is carried out to identify the brush/brush, brush/melt and melt/melt entanglements as a function of distance from the substrate. The PPA characterizes the microscopic state of conformations of the polymer chain and is ideally suited to identify chain/chain entanglements. We use a new thin-chain PPA technique to eliminate spurious non-entangled inter chain contacts arising from excluded volume. As the grafting density of the brush increases we find that the entanglements of the brush with the melt decrease as the system crosses over from the wet to dry brush regime. Results are compared to brush/brush entanglements in an implicit solvent of varying solvent quality. Sandia is a multiprogram laboratory operated by Sandia Corp., a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

  4. Adenosarcoma arising in hepatic endometriosis

    International Nuclear Information System (INIS)

    We report a case of adenosarcoma arising in hepatic endometriosis. Both CT and MR scans demontrated a huge heterogeneous mass containing septated, thick-walled cystic lesions. After enlarged right hepatectomy, the patient was asymptomatic with no abnormalities at liver and abdominal CT scan at 2-year follow-up. (orig.)

  5. Adenosarcoma arising in hepatic endometriosis

    Energy Technology Data Exchange (ETDEWEB)

    N' Senda, P.; Dahan, H.; Tubiana, J.M.; Arrive, L. [Service de Radiologie, Hopital Saint-Antoine, 75 - Paris (France); Wendum, D. [Service d' Anatomie Pathologie, Hopital Saint-Antoine, 75 - Paris (France); Balladur, P. [Service de Chirurgie Digestive et Generale, Hopital Saint-Antoine, 75 - Paris (France)

    2000-08-01

    We report a case of adenosarcoma arising in hepatic endometriosis. Both CT and MR scans demontrated a huge heterogeneous mass containing septated, thick-walled cystic lesions. After enlarged right hepatectomy, the patient was asymptomatic with no abnormalities at liver and abdominal CT scan at 2-year follow-up. (orig.)

  6. Antimocrobial Polymer

    Energy Technology Data Exchange (ETDEWEB)

    McDonald, William F. (Utica, OH); Huang, Zhi-Heng (Walnut Creek, CA); Wright, Stacy C. (Columbus, GA)

    2005-09-06

    A polymeric composition having antimicrobial properties and a process for rendering the surface of a substrate antimicrobial are disclosed. The composition comprises a crosslinked chemical combination of (i) a polymer having amino group-containing side chains along a backbone forming the polymer, (ii) an antimicrobial agent selected from quaternary ammonium compounds, gentian violet compounds, substituted or unsubstituted phenols, biguanide compounds, iodine compounds, and mixtures thereof, and (iii) a crosslinking agent containing functional groups capable of reacting with the amino groups. In one embodiment, the polymer is a polyamide formed from a maleic anhydride or maleic acid ester monomer and alkylamines thereby producing a polyamide having amino substituted alkyl chains on one side of the polyamide backbone; the crosslinking agent is a phosphine having the general formula (A)3P wherein A is hydroxyalkyl; and the antimicrobial agent is chlorhexidine, dimethylchlorophenol, cetyl pyridinium chloride, gentian violet, triclosan, thymol, iodine, and mixtures thereof.

  7. Side-chain functionalized poly(3-hexylthiophene)-based copolymers: synsthesis and characterization of derivatives for application in polymer solar cells

    OpenAIRE

    CAMPO, Bert

    2009-01-01

    Conjugated polymers combine semi-conductive electrical properties with desirable mechanical properties such as light weight and high mechanical strength and flexibility. This enables the development of new technologies and applications based on these materials. Poly(3-hexylthiophene) is a conjugated polymer that has been extensively investigated in polymer:fullerene bulk heterojunction solar cells. ...

  8. Shape memory polymers

    Science.gov (United States)

    Wilson, Thomas S.; Bearinger, Jane P.

    2015-06-09

    New shape memory polymer compositions, methods for synthesizing new shape memory polymers, and apparatus comprising an actuator and a shape memory polymer wherein the shape memory polymer comprises at least a portion of the actuator. A shape memory polymer comprising a polymer composition which physically forms a network structure wherein the polymer composition has shape-memory behavior and can be formed into a permanent primary shape, re-formed into a stable secondary shape, and controllably actuated to recover the permanent primary shape. Polymers have optimal aliphatic network structures due to minimization of dangling chains by using monomers that are symmetrical and that have matching amine and hydroxyl groups providing polymers and polymer foams with clarity, tight (narrow temperature range) single transitions, and high shape recovery and recovery force that are especially useful for implanting in the human body.

  9. Polymer nanocomposites: polymer and particle dynamics

    KAUST Repository

    Kim, Daniel

    2012-01-01

    Polymer nanocomposites containing nanoparticles smaller than the random coil size of their host polymer chains are known to exhibit unique properties, such as lower viscosity and glass transition temperature relative to the neat polymer melt. It has been hypothesized that these unusual properties result from fast diffusion of the nanostructures in the host polymer, which facilitates polymer chain relaxation by constraint release and other processes. In this study, the effects of addition of sterically stabilized inorganic nanoparticles to entangled cis-1,4-polyisoprene and polydimethylsiloxane on the overall rheology of nanocomposites are discussed. In addition, insights about the relaxation of the host polymer chains and transport properties of nanoparticles in entangled polymer nanocomposites are presented. The nanoparticles are found to act as effective plasticizers for their entangled linear hosts, and below a critical, chemistry and molecular-weight dependent particle volume fraction, lead to reduced viscosity, glass transition temperature, number of entanglements, and polymer relaxation time. We also find that the particle motions in the polymer host are hyperdiffusive and at the nanoparticle length scale, the polymer host acts like a simple, ideal fluid and the composites\\' viscosity rises with increasing particle concentration. © 2012 The Royal Society of Chemistry.

  10. Toxicology of Biomedical Polymers

    OpenAIRE

    P. V. Vedanarayanan; A. C. Fernandez

    1987-01-01

    This paper deals with the various types of polymers, used in the fabrication of medical devices, their diversity of applications and toxic hazards which may arise out of their application. The potential toxicity of monomers and the various additives used in the manufacture of biomedical polymers have been discussed along with hazards which may arise out of processing of devices such as sterilization. The importance of quality control and stringent toxicity evaluation methods have been emphasi...

  11. Construction of copper-based coordination polymers with 1D chain, 2D plane and wavy networks: Syntheses, structures, thermal behaviors and photoluminescence properties

    Indian Academy of Sciences (India)

    Jianghua Li; Chi Zhang

    2015-11-01

    Three Cu-based coordination polymers (CPs), including [CuII ( -1 -NCS)2 (O-1 -DMF)2 (2 -3,3’-bptz)] (1), [CuI (1,3-2-NCS)(2-3,3’-bptz)] (2) and [(CuI (1,3-μ2- NCS))(2-4,4’-bptz)] (3) (DMF = , -dimethyl formamide, 3,3’-bptz = 3,6-bis(3-pyridyl)tetrazine and 4,4’-bptz = 3,6-bis(4-pyridyl)tetrazine) have been successfully constructed by solution diffusion reactions by using Cu(NO3)2 ·3H2O or CuNCS and KNCS with 3,3’-bptz / 4,4’-bptz ligands, respectively. The resulting crystalline materials have been characterized by the single-crystal X-ray diffraction analyses, elemental analyses, FT-IR spectra, thermogravimetric analyses and powder X-ray diffraction (PXRD). Single crystal X-ray analyses revealed that CP 1 is organized in one-dimensional (1D) chain in which the Cu(II) ions are coordinated by 1 -NCS− anions and 1-DMF molecules, and linked by 2-3,3’-bptz bridging ligands. CPs ,2 and 3 are structural isomers. CP 2 exhibits two-dimensional (2D) (4,4)-plane-like network in which Cu(I) ions are linked by 2-NCS − and 2-3,3’-bptz ligands. In CP 3, Cu(I) ions are connected by 2 -NCS − and 2-4,4’-bptz ligands to form 2D saw-tooth wavy network. In addition, the photoluminescence properties of CPs 1-3 were also investigated in the solid state at room temperature.

  12. SUMO chains: polymeric signals.

    Science.gov (United States)

    Vertegaal, Alfred C O

    2010-02-01

    Ubiquitin and ubiquitin-like proteins are conjugated to a wide variety of target proteins that play roles in all biological processes. Target proteins are conjugated to ubiquitin monomers or to ubiquitin polymers that form via all seven internal lysine residues of ubiquitin. The fate of these target proteins is controlled in a chain architecture-dependent manner. SUMO (small ubiquitin-related modifier) shares the ability of ubiquitin to form chains via internal SUMOylation sites. Interestingly, a SUMO-binding site in Ubc9 is important for SUMO chain synthesis. Similar to ubiquitin-polymer cleavage by USPs (ubiquitin-specific proteases), SUMO chain formation is reversible. SUMO polymers are cleaved by the SUMO proteases SENP6 [SUMO/sentrin/SMT3 (suppressor of mif two 3)-specific peptidase 6], SENP7 and Ulp2 (ubiquitin-like protease 2). SUMO chain-binding proteins including ZIP1, SLX5/8 (synthetic lethal of unknown function 5/8), RNF4 (RING finger protein 4) and CENP-E (centromere-associated protein E) have been identified that interact non-covalently with SUMO chains, thereby regulating target proteins that are conjugated to SUMO multimers. SUMO chains play roles in replication, in the turnover of SUMO targets by the proteasome and during mitosis and meiosis. Thus signalling via polymers is an exciting feature of the SUMO family. PMID:20074033

  13. Loop polymer brushes from polymer single crystals

    Science.gov (United States)

    Zhou, Tian; Li, Christopher

    2014-03-01

    Loop polymer brushes represent a category of polymer brushes with both chain ends being tethered to a surface or interface with sufficiently high density. Due to this morphological difference, loop brushes exhibit distinct properties compared with traditional polymer brushes with single chain end being tethered. In our study, α, ω-functionalized polycaprolactone (PCL) single crystals were prepared as templates for polymer brush synthesis. By carefully controlling crystallization condition and immobilization, looped polymer brushes were successfully prepared. Comprehensive studies on the morphology and physical properties of these polymer brushes were carried out using Atomic Force Microscopy and FTIR. Advantages of using this method include exclusive loop morphology, high grafting density, controlled tethering sites and tunable loop size.

  14. Polymer chains with nonlinear interactions

    OpenAIRE

    Fugmann, Simon Martin

    2011-01-01

    Ziel dieser Arbeit ist es, den Einfluss der gekoppelten Dynamik in nichtlinearen Polymerketten auf Prozesse wie den thermischen Zerfall und den kraftinduzierten Abriss zu untersuchen. Dafür betrachten wir zunächst die Gleichgewichtsrelaxationseigenschaften von Ketten mit nichtlinearen Wechselwirkungspotentialen. Es kann gezeigt werden, dass die Relaxationseigenschaften des End-zu-End-Abstandes wie auch der Hauptkomponenten jene der harmonischen Kette sind. Die Korrelationszeiten weichen jedoc...

  15. Recent developments in Inorganic polymers: A Review with focus on Si-Al based inorganic polymers

    Directory of Open Access Journals (Sweden)

    Shrray Srivastava

    2015-12-01

    Full Text Available Inorganic polymers are a unique classification of polymers. They contain inorganic atoms in the main chain. Hybrids with organic polymers as well as those chains that contain metals as pendant groups are considered in a special sub-classification as organo-metallic polymers. The networks containing only inorganic elements in main chain are called inorganic polymers. The silicone rubber is the most commercial inorganic polymer. The organo-metallic and inorganic polymers have a different set of applications. The current paper is a review of current applications of polymers with inorganic back-bone networks, especially focusing on Si and Al based inorganic polymeric materials.

  16. Dust arising during steelmaking processes

    Directory of Open Access Journals (Sweden)

    P. Popielska-Ostrowska

    2012-12-01

    Full Text Available Purpose: This paper describes the dust arising during steelmaking processes.Design/methodology/approach: Steelmaking dusts may be a viable alternative for obtaining valuable and widely used metal which is zinc. On the other hand, heavy metals, it was as dangerous to the environment, and this in turn means that development of steelmaking dusts in the best possible way.Findings: The analysis of the formation of steelmaking dust.Research limitations/implications: Understanding the mechanism of steelmaking dusts will help to increase the participation of zinc recycling from wastes.Practical implications: Contained zinc in the dust can be recovered from the positive economic effect, and neutralization of hazardous waste to the desired environmental effect.Originality/value: Description of the mechanism of steelmaking dust, with particular emphasis on the distribution of zinc. The information is very important in the development of metal recovery technology from waste.

  17. Preparation of a bifunctional pyrazosulfuron-ethyl imprinted polymer with hydrophilic external layers by reversible addition-fragmentation chain transfer polymerization and its application in the sulfonylurea residue analysis.

    Science.gov (United States)

    Yang, Meixian; Zhang, Yingying; Lin, Shen; Yang, Xinlin; Fan, Zhijin; Yang, Lixia; Dong, Xiangchao

    2013-09-30

    A new bifunctional pyrazosulfuron-ethyl imprinted polymer was synthesized by the combination of molecular imprinting technology and living radical polymerization. In the synthesis, the pyrazosulfuron-ethyl imprinted polymer was obtained by the reversible addition-fragmentation chain transfer (RAFT) precipitation polymerization followed by grafting poly(glyceryl monomethacrylate) (pGMMA) by the post-RAFT polymerization. In this research, we used polyethylene glycol (PEG) as the polymeric porogen in order to increase the porosity of the material which is a new porogen application in the precipitation polymerization. The imprinted polymer has selectivity for the template and ability of humic acids exclusion which has shown the merits of molecularly imprinted polymers and restricted access materials. An online solid-phase extraction/HPLC method for the analysis of three sulfonylurea residues in soil samples has been developed and validated. The recovery of 81-99% in the spiked levels of 40-200 μg kg(-1) was obtained and the limit of detection (LOD) and limit of quantification (LOQ) were less than 4.8 and 15.9 μg kg(-1) respectively. The results demonstrated that this bifunctional material can be used for the efficient pyrazosulfuron-ethyl extraction in the sulfonylurea residue analysis from environmental samples. PMID:23953454

  18. Longitudinal relaxation of initially straight flexible and stiff polymers

    Science.gov (United States)

    Dimitrakopoulos, Panagiotis; Dissanayake, Inuka

    2004-11-01

    The present talk considers the relaxation of a single flexible or stiff polymer chain from an initial straight configuration in a viscous solvent. This problem commonly arises when strong flows are turned off in both industrial and biological applications. The problem is also motivated by recent experiments with single biopolymer molecules relaxing after being fully extended by applied forces as well as by the recent development of micro-devices involving stretched tethered biopolymers. Our results are applicable to a wide array of synthetic polymers such as polyacrylamides, Kevlar and polyesters as well as biopolymers such as DNA, actin filaments, microtubules and MTV. In this talk we discuss the mechanism of the polymer relaxation as was revealed through Brownian Dynamics simulations covering a broad range of time scales and chain stiffness. After the short-time free diffusion, the chain's longitudinal reduction at early intermediate times is shown to constitute a universal behavior for any chain stiffness caused by a quasi-steady relaxation of tensions associated with the deforming action of the Brownian forces. Stiff chains are shown to exhibit a late intermediate-time longitudinal reduction associated with a relaxation of tensions affected by the deforming Brownian and the restoring bending forces. The longitudinal and transverse relaxations are shown to obey different laws, i.e. the chain relaxation is anisotropic at all times. In the talk, we show how from the knowledge of the relaxation mechanism, we can predict and explain the polymer properties including the polymer stress and the solution birefringence. In addition, a generalized stress-optic law is derived valid for any time and chain stiffness. All polymer properties which depend on the polymer length are shown to exhibit two intermediate-time behaviors with the early one to constitute a universal behavior for any chain stiffness. This work was supported in part by the Minta Martin Research Fund. The

  19. Synthesis, crystal structure and properties of two 1D nano-chain coordination polymers constructed by lanthanide with pyridine-3,4-dicarboxylic acid and 1,10-phenanthroline

    International Nuclear Information System (INIS)

    The hydrothermal reactions of LnCl3.6H2O (Ln=Eu, Tb), pyridine-3,4-dicarboxylic acid (3,4-pydaH2), 1,10-phenthroline (phen) and NaOH in aqueous medium yield two metal-organic hybrid materials, [Eu2(3,4-pyda)3(phen)(H2O).H2O]n (1) and [Tb2(3,4-pyda)3(phen)(H2O).H2O]n (2), respectively. Both compounds have similar topology structure containing one-dimensional nano-chain, which is further assembled into a three-dimensional supramolecular network via π-π stacking interactions and hydrogen bonds. To the best of our knowledge, they represent the first example of nano-chain coordination polymers constructed by 3,4-pydaH2 and chelate heterocylic ligand. Interestingly, the 3,4-pyda anion exhibits three kinds of coordination modes in these complexes. The coordination modes of 3,4-pyda in complexes 1 and 2 have not been observed in other coordination polymers containing 3,4-pyda ligands. Compounds 1 and 2 exhibit strong fluorescent emission bands in the solid state at room temperature. Their magnetic analyses show that they exhibit different magnetic interactions. - Graphical abstract: Two novel lanthanide coordination polymers [M2(pydc)3(phen)(H2O).H2O]n (M=Eu(1) and Tb(2), pydc=pyridine-3,4-dicarboxylate, phen=1,10-phenthroline) have been synthesized and characterized. Both compounds reveal a one-dimensional nano-chain, which is further assembled into a three-dimensional supramolecular network via π-π stacking interactions and hydrogen bonds. Their luminescent and magnetic properties have been investigated

  20. Polymer friction Molecular Dynamics

    DEFF Research Database (Denmark)

    Sivebæk, Ion Marius; Samoilov, Vladimir N.; Persson, Bo N. J.

    We present molecular dynamics friction calculations for confined hydrocarbon solids with molecular lengths from 20 to 1400 carbon atoms. Two cases are considered: a) polymer sliding against a hard substrate, and b) polymer sliding on polymer. In the first setup the shear stresses are relatively...... independent of molecular length. For polymer sliding on polymer the friction is significantly larger, and dependent on the molecular chain length. In both cases, the shear stresses are proportional to the squeezing pressure and finite at zero load, indicating an adhesional contribution to the friction force....

  1. Stress relaxation via addition-fragmentation chain transfer in high Tg, high conversion methacrylate-based systems

    OpenAIRE

    Park, Hee Young; Kloxin, Christopher J.; Abuelyaman, Ahmed S.; Oxman, Joe D.; Bowman, Christopher N.

    2012-01-01

    To reduce shrinkage stress which arises during the polymerization of crosslinked polymers, allyl sulfide functional groups were incorporated into methacrylate polymerizations to determine their effect on stress relaxation via addition-fragmentation chain transfer (AFCT). Additionally, stoichiometrically balanced thiol and allyl sulfide-containing norbornene monomers were incorporated into the methacrylate resin to maximize the overall functional group conversion and promote AFCT while also en...

  2. Syntheses and Characterization of New Nickel Coordination Polymers with 4,4’-Dipyridylsulfide. Dynamic Rearrangements of One-Dimensional Chains Responding to External Stimuli: Temperature Variation and Guest Releases/Re-Inclusions

    Directory of Open Access Journals (Sweden)

    Hiroyuki Kawaguchi

    2010-08-01

    Full Text Available Crystal structures and dynamic rearrangements of one-dimensional coordination polymers with 4,4'-dipyridylsulfide (dps have been studied. Reaction of Ni(NO32·6H2O with dps in EtOH yielded [Ni(dps2(NO32]·EtOH (1, which had channels filled with guest EtOH molecules among the four Ni(dps2 chains. This coordination polymer reversibly transformed the channel structure responding to temperature variations. Immersion of 1 in m-xylene released guest EtOH molecules to yield a guest-free coordination polymer [Ni(dps2(NO32] (2a, which was also obtained by treatment of Ni(NO32·6H2O with dps in MeOH. On the other hand, removal of the guest molecules from 1 upon heating at 130 °C under reduced pressure produced a guest-free coordination polymer [Ni(dps2(NO32] (2b. Although the 2a and 2b guest-free coordination polymers have the same formula, they showed differences in the assembled structures of the one-dimensional chains. Exposure of 2b to EtOH vapor reproduced 1, while 2a did not convert to 1 in a similar reaction. Reaction of Ni(NO32·6H2O with dps in acetone provided [Ni(dps(NO32(H2O]·Me2CO (4 with no channel structure. When MeOH or acetone was used as a reaction solvent, the [Ni(dps2(NO32]·(guest molecule type coordination polymer ,which was observed in 1, was not formed. Nevertheless, the reaction of Ni(NO32·6H2O with dps in MeOH/acetone mixed solution produced [Ni(dps2(NO32]·0.5(MeOH·acetone (5, which has an isostructural Ni-dps framework to 1.

  3. Virus Adsorption Optimization Algorithm of Intrusion Tolerance System Based on Polymer Chain%基于高分子链的入侵容忍系统病毒吸附算法

    Institute of Scientific and Technical Information of China (English)

    刘进

    2014-01-01

    The maximum adsorption of virus can effectively guarantee the network security, and improve the safety perfor-mance of intrusion tolerance system. The traditional method takes random motion chain growth model, when an intrusion vi-rus shows in non uniform growth condition, and the adsorption capacity of the virus is not good. A optimization method of vi-rus adsorption of intrusion tolerance system is proposed based on polymer chain, the data fusion is obtained with linear pro-gramming technique, the intrusion tolerance system is described as five states of Markov chain, the security attributes analy-sis of intrusion tolerance system is obtained, the overlapping detection and vector operation are taken for simulating chain adsorption properties of polymer, the strong adsorption of virus is obtained. Simulation results show that, the algorithm can absorb 4 kinds of virus data on the polymer chain model surface effectively, clustering effect is nice, it has better real-time and robustness property.%对入侵病毒的最大化吸附可以有效保证网络安全,提高入侵容忍系统的安全防护性能。传统的入侵容忍系统检测和吸附病毒的方法采用链节点的随机运动生长模型,当入侵病毒为非均匀增长状态时,对病毒的吸附能力不好。提出一种基于高分子链的病毒优化吸附方法,采用线性规划技术进行入侵容忍系统状态数据融合,把入侵容忍系统描述为马尔科夫链的5个状态,进行入侵容忍系统安全属性分析,采用链重叠检测和向量化运算模拟高分子链吸附性能,实现对入侵病毒的强力吸附。仿真实验表明,采用该算法能把4类病毒入侵数据有效吸附在高分子链模型表面,聚类效果较好,具有较好的实时性和鲁棒性。

  4. Degradation effects in polymers

    International Nuclear Information System (INIS)

    The extremely long molecular chains of polymers can be broken easily by the absorption of a quantum of energy above the energy of the covalent bond of the main carbon chain, which typically is in the range of 5-10 eV. The energy of beta and gamma photons of 1 to 10 MeV surpasses by many orders of magnitude this minimum value, representing a high risk of degradation to all kind of polymers, naturals and synthetics alike. The protection of polymers against high doses (20 - 1000 kGy) requires efficient additives preventing and/or stopping chain reaction type oxidative degradation. Primary and secondary antioxidants work well here in synergy. Commercial raw materials are available for radiation-sterilizable medical devices made out of polyolefins and other thermoplastics. Similarly, polymer compounds of suitable formulae are offered commercially for high-dose applications of polymers in nuclear installations. The controlled degradation of polymers of large molecular mass - or even of cross-linked molecular structures - is a promising field of radiation application. One area here is related to recycling non-accessible polymers such as fluorinated plastics of cross-linked rubber products. Another large possible area is the controlled radiation degradation of natural polymer systems. Radiation may facilitate the access to cross-linked natural polymer systems, such as wood, plant cellulose and biomass in general, decreasing to use of aggressive chemicals. The result is energetically favorable, environmentally friendly new procedures and raw materials of natural origin. A limited dose applied to polymers - although may cause some degradation - however may initiate new bonds on the 'wounded' chain. The popular graft-copolymerization technique can be applied in new, up-coming polymer processing technologies such as alloying, composite processing and reconstitutive recycling. By this way, even those polymers described earlier as radiation-degrading types, can be cross

  5. Triclosan antimicrobial polymers

    OpenAIRE

    Petersen, Richard C.

    2016-01-01

    Triclosan antimicrobial molecular fluctuating energies of nonbonding electron pairs for the oxygen atom by ether bond rotations are reviewed with conformational computational chemistry analyses. Subsequent understanding of triclosan alternating ether bond rotations is able to help explain several material properties in Polymer Science. Unique bond rotation entanglements between triclosan and the polymer chains increase both the mechanical properties of polymer toughness and strength that are ...

  6. Polymer research by neutron scattering

    International Nuclear Information System (INIS)

    Polymer physics aims on an understanding of the macroscopic behavior of polymer systems on the basis of their molecular structure and dynamics. For this purpose neutrons serve as a unique probe, allowing a simultaneous investigation of polymer structure and dynamics on a molecular scale. Furthermore, hydrogen deuterium exchange facilitates molecular labeling and offers the possibility to observe selected chains or chain parts in dense systems. Neutron small angle scattering reveals information on the conformation and possible aggregation of polymer chains. Data on linear and star like molecules are shown as examples. High resolution neutron spin-echospectroscopy observes the molecular dynamics of long chain molecules. Results on the large scale motion of chins in polymer melts are presented. finally, experiments on chain relaxation close to the glass transition are displayed. Three distinctly different relaxation processes are revealed. (author)

  7. Quinacridone-Diketopyrrolopyrrole-Based Polymers for Organic Field-Effect Transistors

    Directory of Open Access Journals (Sweden)

    Kazuo Takimiya

    2013-03-01

    Full Text Available Incorporation of pigment or dye molecules as building units is of great interest in the development of semiconducting polymers, due to their strong intermolecular interactions arising from the strong local dipoles in the unit structure, which would facilitate the charge transport property. In this paper, semiconducting polymers based on well-known pigments, namely, quinacridone and diketopyrrolopyrrole, are synthesized and characterized. The π-stacking distances are found to be 3.5–3.8 Å, which is fairly narrow for semiconducting polymers, indicating that they possess strong intermolecular interactions. Interestingly, polymer orientation is influenced by the composition of alkyl side chains. While the edge-on orientation is observed when the linear alkyl groups are introduced for all the side chains, the face-on orientation is observed when the branched alkyl groups are introduced either in the quinacridone or diketopyrrolopyrrole unit. It is found that the electronic structure of the present polymers is mostly affected by that of the diketopyrrolopyrrole unit, as evidenced by the absorption spectra and computation. Although the field-effect mobility of the polymers is modest, i.e., in the order of 10−4–10−3 cm2/Vs, these findings could be important information for the development of semiconducting polymers.

  8. Synthesis, structures and magnetic properties of two 3D 3,4-pyridinedicarboxylate bridged manganese(II) coordination polymers incorporating 1D helical Mn(carboxylate)2 chain or Mn3(OH)2 chain

    International Nuclear Information System (INIS)

    The hydrothermal reactions of MnCl2.4H2O, 3,4-pyridinedicarboxylic acid (3,4-pydaH2) and triethylamine in aqueous medium yield two 3D metal-organic hybrid materials, [Mn(3,4-pyda)] (1) and [Mn3(OH)2(3,4-pyda)2(H2O)2] (2), respectively. In both complexes, each 3,4-pyda acts as a pentadentate ligand to connect five Mn(II) atoms via the pyridyl group and the two μ2-carboxylate groups (one in syn,anti-mode and one in syn-syn mode for 1 and both in syn,anti-mode for 2). Complex 1 possesses an interesting 3D coordination polymeric structure incorporating 1D helical Mn(μ2-carboxylate)2 chain units, in which each Mn(II) atom is coordinated in less common square pyramidal geometry to four carboxylato oxygen atoms and one pyridyl nitrogen atom. Each 3,4-pyda links three helical Mn(μ2-carboxylate)2 chains and each Mn(μ2-carboxylate)2 chain is linked by other eight helical Mn(μ2-carboxylate)2 chains via sharing 3,4-pyda bridges. Complex 2 is a 3D coordination network consisting of 1D Mn3(OH)2 chains and 3,4-pyda bridges. The repeating trimeric structural unit in the manganese(II) hydroxide chain consists of two edge-sharing symmetry-related manganese octahedra linked via μ3-OH to a vertex of Mn2 octahedron. Each 3,4-pyda links three Mn3(OH)2 chains and each Mn3(OH)2 chain is linked by other six Mn3(OH)2 chains via 3,4-pyda bridges, resulting in a 3D coordination solid. Magnetic measurements reveal that a weak antiferromagnetic interaction between the MnII ions occurs in complex 1 and a 3D magnetic ordering at about 7.0K in complex 2

  9. SANS studies of polymers

    International Nuclear Information System (INIS)

    Before small-angle neutron scattering (SANS), chain conformation studies were limited to light and small angle x-ray scattering techniques, usually in dilute solution. SANS from blends of normal and labeled molecules could give direct information on chain conformation in bulk polymers. Water-soluble polymers may be examined in H2O/D2O mixtures using contrast variation methods to provide further information on polymer structure. This paper reviews some of the information provided by this technique using examples of experiments performed at the National Center for Small-Angle Scattering Research (NCSASR)

  10. Thermally Activated Processes in Polymer Glasses

    OpenAIRE

    V. Parihar; Drosdoff, D.; Widom, A.; Srivastava, Y. N.

    2005-01-01

    A derivation is given for the Vogel-Fulcher-Tammann thermal activation law for the glassy state of a bulk polymer. Our microscopic considerations involve the entropy of closed polymer molecular chains (i.e. polymer closed strings). For thin film polymer glasses, one obtains open polymer strings in that the boundary surfaces serve as possible string endpoint locations. The Vogel-Fulcher-Tammann thermal activation law thereby holds true for a bulk polymer glass but is modified in the neighborho...

  11. Effect of traps on the transport of charge carriers in single chains of conjugated polymers and in their macroscopic ensembles. A kinetic approach

    Czech Academy of Sciences Publication Activity Database

    Sworakowski, J.; Nešpůrek, Stanislav

    Sao Paulo : University of Sao Paulo, 2005, s. 360-363. ISBN 0-7803-9116-0. [International Symposium on Electrets /12./. Salvador (BR), 11.09.2005-14.09.2005] Institutional research plan: CEZ:AV0Z40500505 Keywords : charge transport * traps * conjugated polymer Subject RIV: CD - Macromolecular Chemistry

  12. Mesomorphic structure of poly(styrene)-block-poly(4-vinylpyridine) with oligo(ethylene oxide)sulfonic acid side chains as a model for molecularly reinforced polymer electrolyte

    NARCIS (Netherlands)

    Kosonen, H; Valkama, S; Hartikainen, J; Eerikainen, H; Torkkeli, M; Jokela, K; Serimaa, R; Sundholm, F; ten Brinke, G; Ikkala, O; Eerikäinen, Hannele

    2002-01-01

    We report self-organized polymer electrolytes based on poly(styrene)-block-poly(4-vinylpyridine) (PS-block-P4VP). Liquidlike ethylene oxide (EO) oligomers with sulfonic acid end groups are bonded to the P4VP block, leading to comb-shaped supramolecules with the PS-block-P4VP backbone. Lithium perchl

  13. Synthetic Metal-Containing Polymers

    Science.gov (United States)

    Manners, Ian

    2004-04-01

    The development of the field of synthetic metal-containing polymers - where metal atoms form an integral part of the main chain or side group structure of a polymer - aims to create new materials which combine the processability of organic polymers with the physical or chemical characteristics associated with the metallic element or complex. This book covers the major developments in the synthesis, properties, and applications of synthetic metal-containing macromolecules, and includes chapters on the preparation and characterization of metal-containing polymers, metallocene-based polymers, rigid-rod organometallic polymers, coordination polymers, polymers containing main group metals, and also covers dendritic and supramolecular systems. The book describes both polymeric materials with metals in the main chain or side group structure and covers the literature up to the end of 2002.

  14. Time-dependent Diffusion Coefficient and Conventional Diffusion Constant of Nanoparticles in Polymer Melts by Mode-coupling Theory

    Institute of Scientific and Technical Information of China (English)

    Xin-yu Lai; Nan-rong Zhao

    2013-01-01

    Time-dependent diffusion coefficient and conventional diffusion constant are calculated and analyzed to study diffusion of nanoparticles in polymer melts.A generalized Langevin equation is adopted to describe the diffusion dynamics.Mode-coupling theory is employed to calculate the memory kernel of friction.For simplicity,only microscopic terms arising from binary collision and coupling to the solvent density fluctuation are included in the formalism.The equilibrium structural information functions of the polymer nanocomposites required by mode-coupling theory are calculated on the basis of polymer reference interaction site model with Percus-Yevick closure.The effect of nanoparticle size and that of the polymer size are clarified explicitly.The structural functions,the friction kernel,as well as the diffusion coefficient show a rich variety with varying nanoparticle radius and polymer chain length.We find that for small nanoparticles or short chain polymers,the characteristic short time non-Markov diffusion dynamics becomes more prominent,and the diffusion coefficient takes longer time to approach asymptotically the conventional diffusion constant.This constant due to the microscopic contributions will decrease with the increase of nanoparticle size,while increase with polymer size.Furthermore,our result of diffusion constant from modecoupling theory is compared with the value predicted from the Stokes-Einstein relation.It shows that the microscopic contributions to the diffusion constant are dominant for small nanoparticles or long chain polymers.Inversely,when nanonparticle is big,or polymer chain is short,the hydrodynamic contribution might play a significant role.

  15. Swelling molecular entanglement networks in polymer glasses.

    Science.gov (United States)

    McGraw, Joshua D; Dalnoki-Veress, Kari

    2010-08-01

    Entanglements in a polymer network are like knots between the polymer chains, and they are at the root of many phenomena observed in polymer systems. When a polymer glass is strained, cracklike deformations called crazes may be formed and the study of these regions can reveal much about the nature of entanglements. We have studied crazes in systems that are blends of long polymer chains diluted with chains of various small molecular weights. The range of diluting chain lengths is such that a fraction of them have conformations leading to entanglements. It has been found that a system with more short chains added acts like one in which the entanglement density is smaller than that in an undiluted system. We propose a model that quantitatively predicts the density of effective entanglements of a polydisperse system of polymer chains which is consistent with our experimental data. PMID:20866829

  16. Morphogenesis and Chain Behaviors Related to Crystallization in Ultrathin Polymer Films%聚合物超薄膜结晶相关的形貌形成及链行为

    Institute of Scientific and Technical Information of China (English)

    王命泰; Hans-Georg Braun; Evelyn Meyer; 朱俊

    2006-01-01

    聚合物超薄膜结晶是高分子物理领域的一个新研究课题,近来已引起人们的关注,其为人们在真实时空下研究聚合物结晶及相关链行为提供了可能.聚合物超薄膜结晶与膜厚(D)有很强的相关性,尤其是D<20nm的薄膜在结晶形貌和结晶动力学方面与本体结晶差别很大.已有的结果主要集中在结晶形貌、晶体尺寸、晶体生长速度和习性、晶体的熔融和结晶度等方面,涉及温度、膜厚、基片性质和膜的组成和结构对结晶的影响;然而,有些实验结果和解释彼此不完全一致,甚至有时相互矛盾.本文综述和讨论了近年来在超薄膜结晶方面的研究,重点在于结晶形貌的形成和相关的聚合物链行为.%As a new and intriguing topic in polymer physics, the crystallization in ultrathin films has received a considerable attention in recent years, and it has provided opportunities for studying polymer crystallization and related chain behaviors in real space and time. The crystallization in ultrathin polymer films depends strongly on film thickness (D), particularly those with D<20 nm exhibit a great deviation from bulk crystallization both in crystalline morphology and crystallization kinetics. The accumulated studies mainly focus on the morphology, crystal dimensions, crystal growth rate and habit,crystal melting and crystallinity etc., involving the influences of temperature, film thickness, chemical property of substrate, and film composition and structure on the crystallization; however, some experimental results and interpretations are not completely consistent with each other, and even contradictory sometimes. In the present paper, the recent activities related to the crystallization in ultrathin polymer films are reviewed and discussed, with emphasis upon the morphogenesis of crystallization and related chain behaviors.

  17. Generalized Langevin Theory Of The Brownian Motion And The Dynamics Of Polymers In Solution

    International Nuclear Information System (INIS)

    The review deals with a generalization of the Rouse and Zimm bead-spring models of the dynamics of flexible polymers in dilute solutions. As distinct from these popular theories, the memory in the polymer motion is taken into account. The memory naturally arises as a consequence of the fluid and bead inertia within the linearized Navier-Stokes hydrodynamics. We begin with a generalization of the classical theory of the Brownian motion, which forms the basis of any theory of the polymer dynamics. The random force driving the Brownian particles is not the white one as in the Langevin theory, but “colored”, i.e., statistically correlated in time, and the friction force on the particles depends on the history of their motion. An efficient method of solving the resulting generalized Langevin equations is presented and applied to the solution of the equations of motion of polymer beads. The memory effects lead to several peculiarities in the time correlation functions used to describe the dynamics of polymer chains. So, the mean square displacement of the polymer coils contains algebraic long-time tails and at short times it is ballistic. It is shown how these features reveal in the experimentally observable quantities, such as the dynamic structure factors of the scattering or the viscosity of polymer solutions. A phenomenological theory is also presented that describes the dependence of these quantities on the polymer concentration in solution. (author)

  18. Thiophene in Conducting Polymers: Synthesis of Poly(thiophene)s and Other Conjugated Polymers Containing Thiophenes, for Application in Polymer Solar Cells

    DEFF Research Database (Denmark)

    Livi, Francesco; Carlé, Jon Eggert; Bundgaard, Eva

    2015-01-01

    Conducting polymers based on thiophene are described. The polymers include poly(thiophene) with and without side-chains and other conjugated polymers in general, based on thiophene. The synthesis and characteristics of the polymers are described along with the application of these as light......-absorbing materials in polymer solar cells....

  19. Polymer-Layer Silicate Nanocomposites

    DEFF Research Database (Denmark)

    Potarniche, Catalina-Gabriela

    Nowadays, some of the material challenges arise from a performance point of view as well as from recycling and biodegradability. Concerning these aspects, the development of polymer layered silicate nanocomposites can provide possible solutions. This study investigates how to obtain polymer layered...

  20. Primary extradural meningioma arising from the calvarium

    Directory of Open Access Journals (Sweden)

    N Ravi

    2013-06-01

    Full Text Available Meningiomas are the most common intracranial tumours. Meningiomas arising at other locations are termed primary extradural meningiomas (EDM and are rare. Here we report a case of EDM arising from the calvarium – a primary calvarial meningioma (PCM.

  1. Small angle scattering and polymers

    International Nuclear Information System (INIS)

    The determination of polymer structure is a problem of interest for both statistical physics and industrial applications. The average polymer structure is defined. Then, it is shown why small angle scattering, associated with isotopic substitution, is very well suited to the measurement of the chain conformation. The corresponding example is the old, but pedagogic, measurement of the chain form factor in the polymer melt. The powerful contrast variation method is illustrated by a recent determination of the concentration profile of a polymer interface. (author) 12 figs., 48 refs

  2. Small angle scattering and polymers

    Energy Technology Data Exchange (ETDEWEB)

    Cotton, J.P. [Laboratoire Leon Brillouin (LLB) - Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France)

    1996-12-31

    The determination of polymer structure is a problem of interest for both statistical physics and industrial applications. The average polymer structure is defined. Then, it is shown why small angle scattering, associated with isotopic substitution, is very well suited to the measurement of the chain conformation. The corresponding example is the old, but pedagogic, measurement of the chain form factor in the polymer melt. The powerful contrast variation method is illustrated by a recent determination of the concentration profile of a polymer interface. (author) 12 figs., 48 refs.

  3. Molecular and supramolecular orientation in conducting polymers

    International Nuclear Information System (INIS)

    Intrinsic anisotropy in electrical and optical properties of conducting polymers constitutes a unique aspect that derives π-electron delocalization along the polymer backbone and from the weak inter-chain interaction. To acquire such an intrinsic property, conducting polymers have to be oriented macroscopically and microscopically (at the chain level). A review of the various techniques, including stretch-alignment of the polymer and of precursor polymers, polymerization in ordered media, i.e., in a liquid crystal solvent, and synthesis of liquid crystalline conducting polymers will be given. 29 refs

  4. SMS-5 Polymers and surfaces

    International Nuclear Information System (INIS)

    A layer of polymer chains tethered by one end to a surface is called polymer brush and known to show various unique properties such as prevention of protein adsorption and anti-fouling activity. However, the characterization of polymer brush is still not straightforward since the brush layer is embedded between solid and water interface. One of limited number of analytical methods to reveal solid/water interface structures is neutron reflectivity (NR). We have been applying NR to reveal the problems related to polymer brush at solid/water interfaces and here present two subjects related to polymer brush. The first subject will be dynamic polymer brush which utilizes the surface segregation phenomena of copolymers with surface-active blocks for preparing polymer brush in spontaneous process. We have reported hydrophilic polymer brushes formed at the interface between water and hydrophobic elastomer by the segregation of amphiphilic diblock copolymers blended in the elastomer. In this system, while the hydrophilic block with high surface energy avoids air surface, upon contact with water the hydrophilic block segregates to cover the interface between hydrophobic elastomer and water. Surprisingly high density dynamic polymer brush at D2O/polymer interfaces was observed by NR. The second subject will be evaluating inclusion kinetics of polyrotaxane formation using NR. A polyrotaxane is composed of a polymer chain and cyclic molecules such as polyethylene glycol (PEG) and cyclodextrin (CD). Inclusion complex formation of a polymer chain with cyclic molecules is an important step to synthesize polyrotaxanes. However, inclusion complex formation induces gelation or precipitation of the complex, and hence makes detailed observation of the reaction difficult. We fixed polymer chains on a substrate, which is polymer brush, and conducted in-situ time slice NR measurement. NR results showed that brush layer thickness gradually increases and reaches its plateau by inclusion

  5. Exact and Monte Carlo study of adsorption of a self-interacting polymer chain for a family of three-dimensional fractals

    International Nuclear Information System (INIS)

    We study the problem of adsorption of self-interacting linear polymers situated in fractal containers that belong to the three-dimensional (3D) Sierpinski gasket (SG) family of fractals. Each member of the 3D SG fractal family has a fractal impenetrable 2D adsorbing surface (which is, in fact, 2D SG fractal) and can be labelled by an integer b (2≤b≤∞). By applying the exact and Monte Carlo renormalization group (MCRG) method, we calculate the critical exponents ν (associated with the mean-squared end-to-end distance of polymers) and φ (associated with the number of adsorbed monomers), for a sequence of fractals with 2≤b≤4 (exactly) and 2≤b≤40 (Monte Carlo). We find that both ν and φ monotonically decrease with increasing b (that is, with increase of the container fractal dimension df), and the interesting fact that both functions, ν(b) and φ(b), cross the estimated Euclidean values. Besides, we establish the phase diagrams, for fractals with b=3 and b=4, which reveal the existence of six different phases that merge together at a multi-critical point, whose nature depends on the value of the monomer energy in the layer adjacent to the adsorbing surface

  6. Secondary structures in long compact polymers.

    Science.gov (United States)

    Oberdorf, Richard; Ferguson, Allison; Jacobsen, Jesper L; Kondev, Jané

    2006-11-01

    Compact polymers are self-avoiding random walks that visit every site on a lattice. This polymer model is used widely for studying statistical problems inspired by protein folding. One difficulty with using compact polymers to perform numerical calculations is generating a sufficiently large number of randomly sampled configurations. We present a Monte Carlo algorithm that uniformly samples compact polymer configurations in an efficient manner, allowing investigations of chains much longer than previously studied. Chain configurations generated by the algorithm are used to compute statistics of secondary structures in compact polymers. We determine the fraction of monomers participating in secondary structures, and show that it is self-averaging in the long-chain limit and strictly less than 1. Comparison with results for lattice models of open polymer chains shows that compact chains are significantly more likely to form secondary structure. PMID:17279930

  7. Two Isostructural Coordination Polymers Showing Diverse Magnetic Behaviors: Weak Coupling (Ni(II)) and an Ordered Array of Single-Chain Magnets (Co(II)).

    Science.gov (United States)

    Chen, Min; Zhao, Hui; Sañudo, E Carolina; Liu, Chun-Sen; Du, Miao

    2016-04-18

    Two isomorphic 3-D complexes with the formulas [M3(TPTA) (OH)2(H2O)4]n (M = Ni for 1 and Co for 2; H4TPTA = [1,1':4',1″-terphenyl]-2',3,3″,5'-tetracarboxylic acid) have been synthesized and magnetically characterized. Complexes 1 (Ni(II)) and 2 (Co(II)) have the same 1-D rod-shaped inorganic SBUs but exhibit significantly different magnetic properties. Complex 2(Co(II)) is a 3-D arrangement of a 1-D Co(II) single-chain magnet (SCM), while complex 1(Ni(II)) exhibits weak coupling. PMID:27022765

  8. Polymer semiconductor crystals

    OpenAIRE

    Jung Ah Lim; Feng Liu; Sunzida Ferdous; Murugappan Muthukumar; Briseno, Alejandro L.

    2010-01-01

    One of the long-standing challenges in the field of polymer semiconductors is to figure out how long interpenetrating and entangled polymer chains self-assemble into single crystals from the solution phase or melt. The ability to produce these crystalline solids has fascinated scientists from a broad range of backgrounds including physicists, chemists, and engineers. Scientists are still on the hunt for determining the mechanism of crystallization in these information-rich materials. Understa...

  9. Polymer Protected Gold Nanoparticles

    OpenAIRE

    Shan, Jun

    2006-01-01

    Polymer protected gold nanoparticles have successfully been synthesized by both "grafting-from" and "grafting-to" techniques. The synthesis methods of the gold particles were systematically studied. Two chemically different homopolymers were used to protect gold particles: thermo-responsive poly(N-isopropylacrylamide), PNIPAM, and polystyrene, PS. Both polymers were synthesized by using a controlled/living radical polymerization process, reversible addition-fragmentation chain transfer (RAFT)...

  10. Liquid crystalline polymers

    CERN Document Server

    Wang, Xin-Jiu

    2004-01-01

    This textbook consists of six chapters. The first chapter highlightsthe concept of liquid crystals, including chemical structure, phaseclassification, defect and texture, and continuum theory. It has beencarefully written to meet the needs of readers who do not specializein liquid crystals. The second chapter is related to the theoreticaldescription of liquid crystalline polymers, networks, and gels, whichdeals with subjects such as the formation of liquid crystallinity inthe polymer system, the phase transition and phase diagram, themolecular weight effect, chain conformation, physics proper

  11. Triclosan antimicrobial polymers

    Directory of Open Access Journals (Sweden)

    Richard C. Petersen

    2016-03-01

    Full Text Available Triclosan antimicrobial molecular fluctuating energies of nonbonding electron pairs for the oxygen atom by ether bond rotations are reviewed with conformational computational chemistry analyses. Subsequent understanding of triclosan alternating ether bond rotations is able to help explain several material properties in Polymer Science. Unique bond rotation entanglements between triclosan and the polymer chains increase both the mechanical properties of polymer toughness and strength that are enhanced even better through secondary bonding relationships. Further, polymer blend compatibilization is considered due to similar molecular relationships and polarities. With compatibilization of triclosan in polymers a more uniform stability for nonpolar triclosan in the polymer solid state is retained by the antimicrobial for extremely low release with minimum solubility into aqueous solution. As a result, triclosan is projected for long extended lifetimes as an antimicrobial polymer additive. Further, triclosan rapid alternating ether bond rotations disrupt secondary bonding between chain monomers in the resin state to reduce viscosity and enhance polymer blending. Thus, triclosan is considered for a polymer additive with multiple properties to be an antimicrobial with additional benefits as a nonpolar toughening agent and a hydrophobic wetting agent. The triclosan material relationships with alternating ether bond rotations are described through a complete different form of medium by comparisons with known antimicrobial properties that upset bacterial cell membranes through rapid fluctuating mechanomolecular energies. Also, triclosan bond entanglements with secondary bonding can produce structural defects in weak bacterial lipid membranes requiring pliability that can then interfere with cell division. Regarding applications with polymers, triclosan can be incorporated by mixing into a resin system before cure, melt mixed with thermoplastic polymers

  12. Toxicology of Biomedical Polymers

    Directory of Open Access Journals (Sweden)

    P. V. Vedanarayanan

    1987-04-01

    Full Text Available This paper deals with the various types of polymers, used in the fabrication of medical devices, their diversity of applications and toxic hazards which may arise out of their application. The potential toxicity of monomers and the various additives used in the manufacture of biomedical polymers have been discussed along with hazards which may arise out of processing of devices such as sterilization. The importance of quality control and stringent toxicity evaluation methods have been emphasised since in our country, at present, there are no regulations covering the manufacturing and marketing of medical devices. Finally the question of the general and subtle long term systemic toxicity of biomedical polymers have been brought to attention with the suggestion that this question needs to be resolved permanently by appropriate studies.

  13. Extended linear chain compounds

    CERN Document Server

    Linear chain substances span a large cross section of contemporary chemistry ranging from covalent polymers, to organic charge transfer com­ plexes to nonstoichiometric transition metal coordination complexes. Their commonality, which coalesced intense interest in the theoretical and exper­ imental solid state physics/chemistry communities, was based on the obser­ vation that these inorganic and organic polymeric substrates exhibit striking metal-like electrical and optical properties. Exploitation and extension of these systems has led to the systematic study of both the chemistry and physics of highly and poorly conducting linear chain substances. To gain a salient understanding of these complex materials rich in anomalous aniso­ tropic electrical, optical, magnetic, and mechanical properties, the conver­ gence of diverse skills and talents was required. The constructive blending of traditionally segregated disciplines such as synthetic and physical organic, inorganic, and polymer chemistry, crystallog...

  14. Increasing the Thermal Conductivity of Graphene-Polyamide-6,6 Nanocomposites by Surface-Grafted Polymer Chains: Calculation with Molecular Dynamics and Effective-Medium Approximation.

    Science.gov (United States)

    Gao, Yangyang; Müller-Plathe, Florian

    2016-02-25

    By employing reverse nonequilibrium molecular dynamics simulations in a full atomistic resolution, the effect of surface-grafted chains on the thermal conductivity of graphene-polyamide-6.6 (PA) nanocomposites has been investigated. The interfacial thermal conductivity perpendicular to the graphene plane is proportional to the grafting density, while it first increases and then saturates with the grafting length. Meanwhile, the intrinsic in-plane thermal conductivity of graphene drops sharply as the grafting density increases. The maximum overall thermal conductivity of nanocomposites appears at an intermediate grafting density because of these two competing effects. The thermal conductivity of the composite parallel to the graphene plane increases with the grafting density and grafting length which is attributed to better interfacial coupling between graphene and PA. There exists an optimal balance between grafting density and grafting length to obtain the highest interfacial and parallel thermal conductivity. Two empirical formulas are suggested, which quantitatively account for the effects of grafting length and density on the interfacial and parallel thermal conductivity. Combined with effective medium approximation, for ungrafted graphene in random orientation, the model overestimates the thermal conductivity at low graphene volume fraction (f 10%). For unoriented grafted graphene, the model matches the experimental results well. In short, this work provides some valuable guides to obtain the nanocomposites with high thermal conductivity by grafting chain on the surface of graphene. PMID:26800434

  15. Grafted polymer under shear flow

    Science.gov (United States)

    Kumar, Sanjiv; Foster, Damien P.; Giri, Debaprasad; Kumar, Sanjay

    2016-04-01

    A self-attracting-self-avoiding walk model of polymer chain on a square lattice has been used to gain an insight into the behaviour of a polymer chain under shear flow in a slit of width L. Using exact enumeration technique, we show that at high temperature, the polymer acquires the extended state continuously increasing with shear stress. However, at low temperature the polymer exhibits two transitions: a transition from the coiled to the globule state and a transition to a stem-flower like state. For a chain of finite length, we obtained the exact monomer density distributions across the layers at different temperatures. The change in density profile with shear stress suggests that the polymer under shear flow can be used as a molecular gate with potential application as a sensor.

  16. Manipulating Hydrophobic Interactions in Associative Polymer Solutions via Surfactant-Cyclodextrin Complexation

    Science.gov (United States)

    Talwar, Sachin; Harding, Jonathon; Khan, Saad A.

    2008-07-01

    Associative polymers in combination with cyclodextrin (CD) provide a potent tool to manipulate the solution rheology of aqueous solutions. In this study, we discuss the viability and scope of employing surfactants in such systems to facilitate a more versatile and effective tailoring of rheological properties. A model hydrophobically modified alkali-soluble emulsion (HASE) polymer is used which forms a transient physical network of intra- and inter-molecular hydrophobic junctions in solution arising from the interactions between hydrophobic groups grafted on the polymer backbone. The presence of these hydrophobic junctions significantly enhances the solution rheological properties with both the steady state viscosity and dynamic moduli exhibiting an increase by several orders of magnitude. The ability of nonionic surfactants to modulate and recover the hydrophobic interactions in these polymer solutions in the presence of cyclodextrin is examined. The presence of either a- or β-CD results in a dramatic decrease in viscosity and viscoelastic properties of the HASE polymer solution resulting from the encapsulation of polymer hydrophobes by CDs. Addition of nonionic surfactants to such systems promotes a competition between CDs and surfactant molecules to complex with polymer hydrophobes thereby altering the hydrophobic interactions. In this regard, nonylphenol ethoxylates (NPe) with different ethylene oxide (EO) chain lengths, which determine the surfactant hydrophilic-lipophilic balance (HLB), are used.

  17. Frictional properties of confined polymers

    DEFF Research Database (Denmark)

    Sivebæk, Ion Marius; Samoilov, Vladimir N; Persson, Bo N J

    2008-01-01

    We present molecular dynamics friction calculations for confined hydrocarbon solids with molecular lengths from 20 to 1400 carbon atoms. Two cases are considered: a) polymer sliding against a hard substrate, and b) polymer sliding on polymer. In the first setup the shear stresses are relatively...... independent of molecular length. For polymer sliding on polymer the friction is significantly larger, and dependent on the molecular chain length. In both cases, the shear stresses are proportional to the squeezing pressure and finite at zero load, indicating an adhesional contribution to the friction force...

  18. Polymer films

    Science.gov (United States)

    Granick, Steve; Sukhishvili, Svetlana A.

    2008-12-30

    A film contains a first polymer having a plurality of hydrogen bond donating moieties, and a second polymer having a plurality of hydrogen bond accepting moieties. The second polymer is hydrogen bonded to the first polymer.

  19. Development of water-repellent organic–inorganic hybrid sol–gel coatings on aluminum using short chain perfluoro polymer emulsion

    Energy Technology Data Exchange (ETDEWEB)

    Wankhede, Ruchi Grover, E-mail: 123.ruchi@gmail.com [IITB-Monash Research Academy, Mumbai 400076 (India); Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Mumbai 400076 (India); Morey, Shantaram [Dow Chemicals (India); Khanna, A.S. [Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Mumbai 400076 (India); Birbilis, N. [Department of Materials Engineering, Monash University, Victoria 3800 (Australia)

    2013-10-15

    The development of an organic–inorganic sol–gel coating system (thickness ∼ 2 μm) on aluminum is reported. The coating uses glycidoxytrimethoxysilane (GPTMS) and methyltrimethoxysilane (MTMS) as silane precursors, crosslinked with hexamethylmethoxymelamine (HMMM) and followed by hydrophobic modification using a water base short chain per-fluoro emulsion (FE). Such coating resulted in enhanced hydrophobicity with a contact angle of about 120° and sliding angle of 25° for a 20 μL water droplet. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements showed reduced corrosion upon coated substrates than the bare; correlated with both a higher degree of water repellency and formation of low permeable crosslinked sol–gel network. The structure of the coatings deposited was analyzed using Fourier transform infrared (FTIR) and X-ray photoelectron (XPS) spectroscopy, revealing replacement of hydrophillic surface hydroxyls groups with low energy per-fluoro groups.

  20. Development of water-repellent organic–inorganic hybrid sol–gel coatings on aluminum using short chain perfluoro polymer emulsion

    International Nuclear Information System (INIS)

    The development of an organic–inorganic sol–gel coating system (thickness ∼ 2 μm) on aluminum is reported. The coating uses glycidoxytrimethoxysilane (GPTMS) and methyltrimethoxysilane (MTMS) as silane precursors, crosslinked with hexamethylmethoxymelamine (HMMM) and followed by hydrophobic modification using a water base short chain per-fluoro emulsion (FE). Such coating resulted in enhanced hydrophobicity with a contact angle of about 120° and sliding angle of 25° for a 20 μL water droplet. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements showed reduced corrosion upon coated substrates than the bare; correlated with both a higher degree of water repellency and formation of low permeable crosslinked sol–gel network. The structure of the coatings deposited was analyzed using Fourier transform infrared (FTIR) and X-ray photoelectron (XPS) spectroscopy, revealing replacement of hydrophillic surface hydroxyls groups with low energy per-fluoro groups.

  1. Theory of polymer blends

    International Nuclear Information System (INIS)

    We have recently developed a new theoretical approach to the study of polymer liquids. The theory is based on the ''reference interaction site model'' (RISM theory) of Chandler and Andersen, which has been successful in describing the structure of small molecule liquids. We have recently extended our polymer RISM theory to the case of polymer blends. In the present investigation we have applied this theory to two special binary blends: (1) the athermal mixture where we isolate structural effects, and (2) the isotopic mixture in which structurally identical polymer chains interact with dissimilar attractive interactions. By studying these two special cases we are able to obtain insights into the molecular factors which control the miscibility in polymer mixtures. 18 refs., 2 figs

  2. Controlled Synthesis of Polymer Brushes via Polymer Single Crystal Templates

    Science.gov (United States)

    Zhou, Tian

    A novel synthetic method of polymer brushes using polymer single crystals (PSCs) as solid-state templates is introduced in this study. PSC has a quasi-2D lamellae structure with polymer chains fold back-and-forth perpendicular to the lamellae surfaces. During crystallization, the chain ends are excluded from the unit cell onto the lamellae surfaces, which makes the material extremely versatile in its functionality. Such structure holds the unique capability to harvest nanoparticles, or being immobilized onto macroscopic flat surfaces. After dissolving PSCs in good solvent, polymer brushes are chemically tethered on either nanoparticles or flat macroscopic surfaces. Because the chain-folding structure can be conveniently tailored by changing the molecular weight of polymer and the crystallization temperature, the thickness, grafting density and morphology of resulted polymer brushes can be precisely controlled. As a model system, poly(?-caprolactone) with thiol or alkoxysilane terminal groups was used, and polymer brushes were successfully prepared on both nanoparticles and glass/Au flat surfaces. The structure-property relationships of the as-prepared polymer brushes were studied in detail using multiple characterization techniques. First of all, when functionalizing nanoparticles, by engineering the chain-folding structure of the PSCs, interesting complex nanostructures can be formed by nanoparticles including Janus nanoparticles and nanoparticle dimers. These unique structures render hybrid nanoparticles very interesting responsive behavior which have been studied in detail in this dissertation. When grafted onto a flat surface on the other hand, not only the molecular weight and grafting density can be precisely controlled, the tethering points of a single polymer chain can also be conveniently tailored, resulting polymer brushes with either tail or loop structures. Such difference in brush structure can significantly alter the properties of functional surface

  3. Novel cathode interlayers based on neutral alcohol-soluble small molecules with a triphenylamine core featuring polar phosphonate side chains for high-performance polymer light-emitting and photovoltaic devices.

    Science.gov (United States)

    Chen, Dongcheng; Zhou, Hu; Liu, Ming; Zhao, Wei-Ming; Su, Shi-Jian; Cao, Yong

    2013-04-12

    A new family of neutral alcohol-soluble small molecular materials comprised of electron-rich triphenylamine (TPA) and fluorene featuring phosphonate side chains (FEP) is reported, namely 3TPA-FEP, 2TPA-2FEP and TPA-3FEP, which have different TPA and FEP contents. Due to their good solubility in polar solvents like alcohol, multilayer devices can be fabricated by a wet process from orthogonal solvents. Polymer light-emitting devices with these materials as a cathode interlayer and Al as the cathode show greatly enhanced efficiencies in contrast to control devices without such a cathode interlayer, and their efficiencies are comparable with or even higher than devices with the low work-function metal Ba/Al as the cathode. In addition, high-performance polymer solar cells based on the poly[N-9''-hepta-decanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT):[6,6]-phenyl C71 -butyric acid methyl ester (PC71 BM) system are also achieved with power conversion efficiencies of 7.21%, 6.90% and 6.89%, by utilizing 3TPA-FEP, 2TPA-2FEP and TPA-3FEP as the cathode interlayer, respectively. These efficiencies are also much higher than those for control devices without the cathode interlayer. Although TPA is well-known as a hole-transport unit, the current findings indicate that alcohol-soluble TPA-based small molecules are also a promising cathode interlayer for both electron injection and extraction. PMID:23386362

  4. Maple syrup urine disease: The E1{beta} gene of human branched-chain {alpha}-ketoacid dehydrogenase complex has 11 rather than 10 exons, and the 3{prime} UTR in one of the two E1{beta} mRNAs arises from intronic sequences

    Energy Technology Data Exchange (ETDEWEB)

    Chuang, J.L.; Chuang, D.T.; Cox, R.P. [Univ. of Texas Southwestern Medical Center, Dallas, TX (United States)

    1996-06-01

    Maple syrup urine disease (MSUD) or branched-chain ketoaciduria is caused by a deficiency in the mitochondrial branched-chain {alpha}-ketoacid dehydrogenase (BCKAD) complex. The clinical manifestations are characterized by accumulation of branched chain amino and {alpha}-ketoacids, which leads to severe cerebral edema with seizures, ketoacidosis, and mental retardation. The BCKAD complex comprises three catalytic components, i.e., a decarboxylase (E1) consisting of two E1{alpha} (M{sub r} = 46,000) and two E1{Beta} (M{sub r} = 37,500) subunits, a transacylase (E2) that contains 24 lipoic acid-bearing subunits, and a dehydrogenase (E3), which is a homodimeric flavoprotein. MSUD is genetically heterogeneous, since mutations in the E1{alpha} subunit (type IA MSUD), the E1{Beta} subunit (type IB), the E2 subunit (type II) and the E3 subunit (type III) have been described. The functional consequences of certain mutations in the BCKAD complex have been studied. 23 refs., 3 figs.

  5. Communication: When does a branched polymer become a particle?

    Science.gov (United States)

    Chremos, Alexandros; Douglas, Jack F

    2015-09-21

    Polymer melts with topologically distinct molecular structures, namely, linear chain, ring, and star polymers, are investigated by molecular dynamics simulation. In particular, we determine the mean polymer size and shape, and glass transition temperature for each molecular topology. Both in terms of structure and dynamics, unknotted ring polymers behave similarly to star polymers with f ≈ 5-6 star arms, close to a configurational transition point between anisotropic chains to spherically symmetric particle-like structures. These counter-intuitive findings raise fundamental questions regarding the importance of free chain-ends and chain topology in the packing and dynamics of polymeric materials. PMID:26395679

  6. ARISE: American renaissance in science education

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-09-14

    The national standards and state derivatives must be reinforced by models of curricular reform. In this paper, ARISE presents one model based on a set of principles--coherence, integration of the sciences, movement from concrete ideas to abstract ones, inquiry, connection and application, sequencing that is responsive to how people learn.

  7. Synthesis, Crystal Structure and Thermal Stability of a One-dimensional Chain Cobalt Coordination Polymer [ Co( 4,4 '-bipy)( 2,4,6- TMBA)2( CH3CH2OH)2]n

    Institute of Scientific and Technical Information of China (English)

    LI Wei; LI Chang-Hong; YANG Ying-Qun; CHEN Zhi-Min; KUANG Dai-Zhi; ZHANG Chun-Hua; KANG Yun-Fei

    2006-01-01

    A one-dimensional chain cobalt(Ⅱ) coordination polymer with 2,4,6-trimethylbenzoic acid, 4,4'-bipyridine and cobalt perchlorate anhydrous has been synthesized and characterized in the mixture solvent of water and alcohol. Crystal data for this complex: monoclinic, space group C2/c, a = 2.3805(8), b = 1.1464(4), c = 1.5807(5) nm, γ = 128.435(4)°, V= 3.3791(18) nm3,Dc = 1.246 g/cm3, Z = 4, F(000) = 1340, final GooF = 1.009, R = 0.0504 and wR = 0.1287.Structural analysis shows that the cobalt ion is coordinated with two nitrogen atoms of one 4,4'-bipyridine molecule and four oxygen atoms from two 2,4,6-trimethylbenzoic acid molecules and two alcohol molecules, giving a distorted octahedral coordination geometry. The result of TG analysis indicates that the title complex is stable till 200 ℃.

  8. Poly(arlyene ether sulfone) based semi-interpenetrating polymer network membranes containing cross-linked poly(vinyl phosphonic acid) chains for fuel cell applications at high temperature and low humidity conditions

    Science.gov (United States)

    Kim, Kihyun; Heo, Pilwon; Ko, Taeyun; Kim, Ki-hyun; Kim, Sung-Kon; Pak, Chanho; Lee, Jong-Chan

    2015-10-01

    Semi-interpenetrating polymer network (semi-IPN) membranes are prepared by in-situ casting and thermal-initiated radical polymerization of vinyl phosphonic acid (VPA) and bis(2-(methacryloyloxy)ethyl) phosphate (BMAEP) in N,N-dimethylacetamide solutions of sulfonated poly(arylene ether sulfone) (SPAES). The incorporation of VPA units into the SPAES membranes improves proton conductivity especially at high temperature and low humidity conditions. In addition the cross-linker, BMAEP, prevents the decrease of the mechanical and chemical stabilities by the aliphatic linear poly(vinyl phosphonic acid) chains in the semi-IPN membranes, and furthermore the phosphonic acid group in BMAEP can prevent the decrease of the proton conductivity by the formation of cross-linked structures. Therefore, the resulting semi-IPN membranes show high proton conductivities up to 15 mS cm-1 at 120 °C and 40% RH. The fuel cell performance (187 mW cm-2 at 120 °C and 40% RH) of membrane-electrode assembly (MEA) from the semi-IPN membrane is found to be superior to that (145 mW cm-2 at 120 °C and 40% RH) of MEA from the SPAES membrane. The durability test result at the operating conditions indicates that the semi-IPN membrane is electrochemically very stable maintaining the low hydrogen cross-over and high power densities.

  9. Role of Radical Species in Salicylaldiminato Ni(II) Mediated Polymer Chain Growth: A Case Study for the Migratory Insertion Polymerization of Ethylene in the Presence of Methyl Methacrylate.

    Science.gov (United States)

    Ölscher, Franz; Göttker-Schnetmann, Inigo; Monteil, Vincent; Mecking, Stefan

    2015-11-25

    To date, an inconclusive and partially contradictive picture exists on the behavior of neutral Ni(II) insertion polymerization catalysts toward methyl methacrylate (MMA). We shed light on this issue by a combination of comprehensive mechanistic NMR and EPR studies, isolation of a key Ni(I) intermediate, and pressure reactor studies with ethylene and MMA, followed by detailed polymer analysis. An interlocking mechanistic picture of an insertion and a free radical polymerization is revealed. Both polymerizations run simultaneously (25 bar ethylene, neat MMA, 70 °C); however, the chain growth cycles are independent of each other, and therefore exclusively a physical mixture of homo-PE and homo-PMMA is obtained. A Ni-C bond cleavage was excluded as a free radical source. Rather a homolytic P-C bond cleavage in the labile aryl phosphine ligand and the reaction of low-valent Ni(0/I) species with specific iodo substituted N^O (Ar-I) ligands were shown to initiate radical MMA polymerizations. Several reductive elimination decomposition pathways of catalyst precursor or active intermediates were shown to form low-valent Ni species. One of those pathways is a bimolecular reductive coupling via intermediate (N^O)Ni(I) formation. These intermediate Ni(I) species can be prevented from ultimate decomposition by capturing with organic radical sources, forming insertion polymerization active [(N^O)Ni(II)-R] species and prolonging the ethylene polymerization activity. PMID:26571229

  10. Ameloblastic Fibrosarcoma Arising in the Maxilla

    Science.gov (United States)

    Pillay, Rachael R.; Bilski, Arthur; Batstone, Martin

    2016-01-01

    Background: Ameloblastic fibrosarcoma (AFS) is a rare odontogenic neoplasm of the jaw that usually arises de novo or through a malignant change in the mesenchymal component of a preexisting or recurrent benign fibroma. The majority of AFS cases reported in the literature arise in the mandible. Case Report: A 35-year-old male presented with an asymptomatic left maxillary mass that on imaging was found to be effacing most of his maxillary sinus. He underwent a left maxillectomy with free-flap reconstruction and adjuvant radiotherapy to the tumor bed. Conclusion: Wide local excision remains the treatment of choice for AFS, given the poor survival rates of patients with recurrent disease. However, long-term studies and follow-up are needed to elucidate the role of adjuvant therapies in the primary treatment of AFS. PMID:27303223

  11. Parametrial and rectovaginal adenocarcinoma arising from endometriosis.

    Science.gov (United States)

    Ulrich, U; Rhiem, K; Kaminski, M; Wardelmann, E; Trog, D; Valter, M; Richter, O N

    2005-01-01

    Malignant extragonadal tumors arising from endometriosis are rare. We report on two cases. A 41-year-old gravida 1, para 1 (G1P1), with adenocarcinoma of the right parametrium arising from endometriosis and a 51-year-old G1P1 with endometriosis-associated rectovaginal adenocarcinoma were treated. Treatment included radical surgery plus radiation therapy. While the former patient was doing well 2 years after the primary diagnosis, the latter suffered a local pelvic recurrence 2 years later. Although there are no randomized controlled studies, radical surgery followed by radiation therapy seems generally to be the treatment of choice. The analysis of PTEN in various forms of endometriosis and its malignant transformation may help in understanding the early steps of tumorigenesis. PMID:16343215

  12. Phasic Triplet Markov Chains.

    Science.gov (United States)

    El Yazid Boudaren, Mohamed; Monfrini, Emmanuel; Pieczynski, Wojciech; Aïssani, Amar

    2014-11-01

    Hidden Markov chains have been shown to be inadequate for data modeling under some complex conditions. In this work, we address the problem of statistical modeling of phenomena involving two heterogeneous system states. Such phenomena may arise in biology or communications, among other fields. Namely, we consider that a sequence of meaningful words is to be searched within a whole observation that also contains arbitrary one-by-one symbols. Moreover, a word may be interrupted at some site to be carried on later. Applying plain hidden Markov chains to such data, while ignoring their specificity, yields unsatisfactory results. The Phasic triplet Markov chain, proposed in this paper, overcomes this difficulty by means of an auxiliary underlying process in accordance with the triplet Markov chains theory. Related Bayesian restoration techniques and parameters estimation procedures according to the new model are then described. Finally, to assess the performance of the proposed model against the conventional hidden Markov chain model, experiments are conducted on synthetic and real data. PMID:26353069

  13. Engineering thermal conductivity in polymer blends

    Science.gov (United States)

    Rashidi, Vahid; Coyle, Eleanor; Kieffer, John; Pipe, Kevin

    Weak inter-chain bonding in polymers is believed to be a bottleneck for both thermal conductivity and mechanical strength. Most polymers have low thermal conductivity (~0.1 W/mK), hindering their performance in applications for which thermal management is critical (e.g., electronics packaging). In this work, we use computational methods to study how hydrogen bonding between polymer chains as well as water content can be used to engineer thermal transport in bulk polymers. We examine how changes in the number of hydrogen bonds, chain elongation, density, and vibrational density of states correlate with changes in thermal conductivity for polymer blends composed of different relative constituent fractions. We also consider the effects of bond strength, tacticity, and polymer chain mass. For certain blend fractions, we observe large increases in thermal conductivity, and we analyze these increases in terms of modifications to chain chemistry (e.g., inter-chain bonding) and chain morphology (e.g., chain alignment and radius of gyration). We observe that increasing the number of hydrogen bonds in the system results in better packing as well as better chain alignment and elongation that contribute to enhanced thermal conductivity. The Air Force Office of Scientific Research, Grant No. FA9550-14-1-0010.

  14. An organism arises from every nucleus.

    OpenAIRE

    Nurullah Keklikoglu

    2009-01-01

    The fact that, cloning using somatic cell nuclear transfer (SCNT) method has been performed, opened new horizons for cloning, and changed the way of our understanding and approach to cell and nucleus. The progress in cloning technology, brought the anticipation of the ability to clone an organism from each somatic cell nucleus. Therefore, the 'Cell Theory' is about to take the additional statement as "An organism arises from every nucleus". The development of gene targeting procedures which c...

  15. Free radical transfer in polymers

    International Nuclear Information System (INIS)

    For the present study of free-radical transfer in polymers pulse radiolysis and product studies have been carried out in aqueous solutions using thus far only the water-soluble polymers polyacrylic acid, polymethacrylic acid and polyvinyl alcohol. When OH radicals, generated in the radiolysis of N2O-saturated aqueous solutions, react with polymers the lifetime of the polymer radical thus created very much depends on the number of radicals per polymer chain. When there are a large number of radicals per chain their bimolecular decay may be faster than the corresponding (diffusion controlled) decay of monomeric radicals, but when the macromolecule contains only few or even just one radical their lifetime is considerably prolonged. Highly charged polymers such as polyacrylic acid at high pH attain a rod-like conformation which again favors a long lifetime of the radicals. Under such conditions, radical transfer reactions can occur. For example, in polyacrylic acid OH radicals generate two kinds of radicals side by side. The radical in β-position to the carboxylate group converts into the thermodynamically more stable α-radicals by an H-transfer reaction as can be followed by spectrophotometry. Besides radical transfer reactions β-fragmentation reactions occur causing chain scission. Such reactions can be followed in a pulse radiolysis experiment by conductometry, because counter ions are released upon chain scission. Such a process is especially effective in the case of polymethacrylic acid, where it results in a chain depolymerization. An intramolecular H-abstraction is also observed in the γ-radiolysis of polyacrylic acid with the corresponding peroxyl radicals. This causes a chain reaction to occur. The resulting hydroperoxides are unstable and decarboxylate given rise to acetylacetone-like products. In polyvinyl alcohol the peroxyl radicals in α-position to the alcohol function undergo HO2-elimination. This prevents a scission of the polymer chain in the

  16. Interfacial Slip in Sheared Polymer Blends

    OpenAIRE

    Lo, Tak Shing; Mihajlovic, Maja; Shnidman, Yitzhak; Li, Wentao; Gersappe, Dilip

    2004-01-01

    We have developed a dynamic self-consistent field theory, without any adjustable parameters, for unentangled polymer blends under shear. Our model accounts for the interaction between polymers, and enables one to compute the evolution of the local rheology, microstructure and the conformations of the polymer chains under shear self-consistently. We use this model to study the interfacial dynamics in sheared polymer blends and make a quantitative comparison between this model and Molecular Dyn...

  17. Effects of anchored flexible polymers on mechanical properties of model biomembranes

    CERN Document Server

    Wu, Hao; 10.1063/1.4794653

    2013-01-01

    We have studied biomembranes with grafted polymer chains using a coarse-grained membrane simulation, where a meshless membrane model is combined with polymer chains. We focus on the polymer-induced entropic effects on mechanical properties of membranes. The spontaneous curvature and bending rigidity of the membranes increase with increasing polymer density. Our simulation results agree with the previous theoretical predictions.

  18. Biodegradable Polymers

    OpenAIRE

    Isabelle Vroman; Lan Tighzert

    2013-01-01

    Biodegradable materials are used in packaging, agriculture, medicine and other areas. In recent years there has been an increase in interest in biodegradable polymers. Two classes of biodegradable polymers can be distinguished: synthetic or natural polymers. There are polymers produced from feedstocks derived either from petroleum resources (non renewable resources) or from biological resources (renewable resources). In general natural polymers offer fewer advantages than synthetic polymers. ...

  19. Polymer semiconductor crystals

    Directory of Open Access Journals (Sweden)

    Jung Ah Lim

    2010-05-01

    Full Text Available One of the long-standing challenges in the field of polymer semiconductors is to figure out how long interpenetrating and entangled polymer chains self-assemble into single crystals from the solution phase or melt. The ability to produce these crystalline solids has fascinated scientists from a broad range of backgrounds including physicists, chemists, and engineers. Scientists are still on the hunt for determining the mechanism of crystallization in these information-rich materials. Understanding the theory and concept of crystallization of polymer semiconductors will undoubtedly transform this area from an art to an area that will host a bandwagon of scientists and engineers. In this article we describe the basic concept of crystallization and highlight some of the advances in polymer crystallization from crystals to nanocrystalline fibers.

  20. The role of intramolecular barriers on the glass transition of polymers: Computer simulations versus mode coupling theory.

    Science.gov (United States)

    Bernabei, Marco; Moreno, Angel J; Colmenero, Juan

    2009-11-28

    We present computer simulations of a simple bead-spring model for polymer melts with intramolecular barriers. By systematically tuning the strength of the barriers, we investigate their role on the glass transition. Dynamic observables are analyzed within the framework of the mode coupling theory (MCT). Critical nonergodicity parameters, critical temperatures, and dynamic exponents are obtained from consistent fits of simulation data to MCT asymptotic laws. The so-obtained MCT lambda-exponent increases from standard values for fully flexible chains to values close to the upper limit for stiff chains. In analogy with systems exhibiting higher-order MCT transitions, we suggest that the observed large lambda-values arise form the interplay between two distinct mechanisms for dynamic arrest: general packing effects and polymer-specific intramolecular barriers. We compare simulation results with numerical solutions of the MCT equations for polymer systems, within the polymer reference interaction site model (PRISM) for static correlations. We verify that the approximations introduced by the PRISM are fulfilled by simulations, with the same quality for all the range of investigated barrier strength. The numerical solutions reproduce the qualitative trends of simulations for the dependence of the nonergodicity parameters and critical temperatures on the barrier strength. In particular, the increase in the barrier strength at fixed density increases the localization length and the critical temperature. However the qualitative agreement between theory and simulation breaks in the limit of stiff chains. We discuss the possible origin of this feature. PMID:19947689

  1. Evidence for a jacketed nematic polymer

    OpenAIRE

    Hardouin, F.; Mery, S.; Achard, M.; Noirez, L.; Keller, P.

    1991-01-01

    The evidence for a “jacketed” structure at the scale of the chain dimensions in the nematic phase of a “side-on fixed” liquid crystal polysiloxane is reported by using small angle neutron scattering. We relate this anisotropy of chain conformation to the first measurements of the rotational viscosity coefficient in this new type of liquid crystal side-chain polymer.

  2. Chain reconfiguration in active noise

    Science.gov (United States)

    Samanta, Nairhita; Chakrabarti, Rajarshi

    2016-05-01

    In a typical single molecule experiment, the dynamics of an unfolded protein is studied by determining the reconfiguration time using long-range Förster resonance energy transfer, where the reconfiguration time is the characteristic decay time of the position correlation between two residues of the protein. In this paper we theoretically calculate the reconfiguration time for a single flexible polymer in the presence of active noise. The study suggests that though the mean square displacement grows faster, the chain reconfiguration is always slower in the presence of long-lived active noise with exponential temporal correlation. Similar behavior is observed for a worm-like semi-flexible chain and a Zimm chain. However it is primarily the characteristic correlation time of the active noise and not the strength that controls the increase in the reconfiguration time. In brief, such active noise makes the polymer move faster but the correlation loss between the monomers becomes slow.

  3. Chain reconfiguration in active noise

    International Nuclear Information System (INIS)

    In a typical single molecule experiment, the dynamics of an unfolded protein is studied by determining the reconfiguration time using long-range Förster resonance energy transfer, where the reconfiguration time is the characteristic decay time of the position correlation between two residues of the protein. In this paper we theoretically calculate the reconfiguration time for a single flexible polymer in the presence of active noise. The study suggests that though the mean square displacement grows faster, the chain reconfiguration is always slower in the presence of long-lived active noise with exponential temporal correlation. Similar behavior is observed for a worm-like semi-flexible chain and a Zimm chain. However it is primarily the characteristic correlation time of the active noise and not the strength that controls the increase in the reconfiguration time. In brief, such active noise makes the polymer move faster but the correlation loss between the monomers becomes slow. (paper)

  4. Conformational transitions of a semiflexible polymer in nematic solvents

    OpenAIRE

    Matsuyama, Akihiko

    2002-01-01

    Conformations of a single semiflexible polymer chain dissolved in a low molecular weight liquid crystalline solvents (nematogens) are examined by using a mean field theory. We takes into account a stiffness and partial orientational ordering of the polymer. As a result of an anisotropic coupling between the polymer and nematogen, we predict a discontinuous (or continuous) phase transition from a condensed-rodlike conformation to a swollen-one of the polymer chain, depending on the stiffness o...

  5. Angiomyolipoma arising in the gluteal region

    Institute of Scientific and Technical Information of China (English)

    Emmanouil Pikoulis; Constantine Bramis; Othon Mich; George Liapis; Evangelos Felekourasx; Vassiliki Kyriakou; John Griniatsos

    2007-01-01

    @@ Angiomyolipoma (AML) is a tumour of uncertain histogenesis originally believed to be a hamartomatous lesion, but recently recognized as a usually benign clonal mesenchymal neoplasm.1 Along with lymphagiomyomatosis (LAM), clear cell "sugar"tumour (CCST) and clear cell myelomelanocytic tumour (CCMMT), AML was classified in the so called perivascular epithelioid cell (PEComa) neoplasm family.1 Kidney constitutes the principal site of its development.Extrarenal AMLs are rare and to the best of our knowledge, only two cases of AML development in the soft tissues have been reported so far.2,3 We presented a 23 years old female patient with an AML arising in the left gluteal region.

  6. Malignant Insulinoma Arising from Intrasplenic Heterotopic Pancreas

    Directory of Open Access Journals (Sweden)

    Ismael Domínguez

    2009-05-01

    Full Text Available Context Heterotopic pancreas is defined as ectopic pancreatic tissue without vascular or anatomic continuity with the normal pancreas. The spleen is a rare site of origin. This case report describes a patient with a malignant insulinoma which originated from an intrasplenic heterotopic pancreas. Case report A 46-year-old man with three previous episodes of neuroglucopenic and adrenergic symptoms was referred to our hospital. A fasting test was performed and discontinued due to hypoglycemic symptoms. Preoperative studies failed to demonstrate any pancreatic lesions. However, a heterogeneous encapsulated tumor in the spleen was found on MRI. During surgery, only the splenic tumor was found, with neither vascular nor anatomical connections to the normal pancreas. Pathology reported a malignant insulinoma. Insulin and proinsulin were documented by immunohistochemistry. After one year of follow up, the patient is free of symptoms and no recurrent disease has been documented. Discussion Only seven cases of splenic heterotopic pancreas have been reported, six with cystic mucinous neoplasms. In addition, only one case of a malignant insulinoma arising from heterotopic pancreas has previously been described. This is the second case reported of an insulinoma arising from heterotopic pancreas and the first to originate from intrasplenic heterotopia.

  7. Ending Aging in Super Glassy Polymer Membranes

    Energy Technology Data Exchange (ETDEWEB)

    Lau, CH; Nguyen, PT; Hill, MR; Thornton, AW; Konstas, K; Doherty, CM; Mulder, RJ; Bourgeois, L; Liu, ACY; Sprouster, DJ; Sullivan, JP; Bastow, TJ; Hill, AJ; Gin, DL; Noble, RD

    2014-04-16

    Aging in super glassy polymers such as poly(trimethylsilylpropyne) (PTMSP), poly(4-methyl-2-pentyne) (PMP), and polymers with intrinsic microporosity (PIM-1) reduces gas permeabilities and limits their application as gas-separation membranes. While super glassy polymers are initially very porous, and ultra-permeable, they quickly pack into a denser phase becoming less porous and permeable. This age-old problem has been solved by adding an ultraporous additive that maintains the low density, porous, initial stage of super glassy polymers through absorbing a portion of the polymer chains within its pores thereby holding the chains in their open position. This result is the first time that aging in super glassy polymers is inhibited whilst maintaining enhanced CO2 permeability for one year and improving CO2/N-2 selectivity. This approach could allow super glassy polymers to be revisited for commercial application in gas separations.

  8. Ending aging in super glassy polymer membranes.

    Science.gov (United States)

    Lau, Cher Hon; Nguyen, Phuc Tien; Hill, Matthew R; Thornton, Aaron W; Konstas, Kristina; Doherty, Cara M; Mulder, Roger J; Bourgeois, Laure; Liu, Amelia C Y; Sprouster, David J; Sullivan, James P; Bastow, Timothy J; Hill, Anita J; Gin, Douglas L; Noble, Richard D

    2014-05-19

    Aging in super glassy polymers such as poly(trimethylsilylpropyne) (PTMSP), poly(4-methyl-2-pentyne) (PMP), and polymers with intrinsic microporosity (PIM-1) reduces gas permeabilities and limits their application as gas-separation membranes. While super glassy polymers are initially very porous, and ultra-permeable, they quickly pack into a denser phase becoming less porous and permeable. This age-old problem has been solved by adding an ultraporous additive that maintains the low density, porous, initial stage of super glassy polymers through absorbing a portion of the polymer chains within its pores thereby holding the chains in their open position. This result is the first time that aging in super glassy polymers is inhibited whilst maintaining enhanced CO2 permeability for one year and improving CO2/N2 selectivity. This approach could allow super glassy polymers to be revisited for commercial application in gas separations. PMID:24740816

  9. QCM-D studies on polymer behavior at interfaces

    CERN Document Server

    Liu, Guangming

    2013-01-01

    QCM-D Studies on Polymer Behavior at Interfaces reviews the applications of quartz crystal microbalance with dissipation (QCM-D) in polymer research, including the conformational change of grafted polymer chains, the grafting kinetics of polymer chains, the growth mechanism of polyelectrolyte multilayers, and the interactions between polymers and phospholipid membranes. It focuses on how QCM-D can be applied to the study of polymer behavior at various solid-liquid interfaces. Moreover, it clearly reveals the physical significance of the changes in frequency and dissipation associated with the

  10. Phase stability and dynamics of entangled polymer-nanoparticle composites.

    KAUST Repository

    Mangal, Rahul

    2015-06-05

    Nanoparticle-polymer composites, or polymer-nanoparticle composites (PNCs), exhibit unusual mechanical and dynamical features when the particle size approaches the random coil dimensions of the host polymer. Here, we harness favourable enthalpic interactions between particle-tethered and free, host polymer chains to create model PNCs, in which spherical nanoparticles are uniformly dispersed in high molecular weight entangled polymers. Investigation of the mechanical properties of these model PNCs reveals that the nanoparticles have profound effects on the host polymer motions on all timescales. On short timescales, nanoparticles slow-down local dynamics of the host polymer segments and lower the glass transition temperature. On intermediate timescales, where polymer chain motion is typically constrained by entanglements with surrounding molecules, nanoparticles provide additional constraints, which lead to an early onset of entangled polymer dynamics. Finally, on long timescales, nanoparticles produce an apparent speeding up of relaxation of their polymer host.

  11. Optimization problems arising in robust stability theory

    Energy Technology Data Exchange (ETDEWEB)

    Polyak, B.

    1994-12-31

    Robustness is one of the main topics in modern control theory. We consider one aspect of the theme - robust stability analysis under parametric uncertainty. It deals with stability problems for linear time-invariant differential or difference equations with uncertainties in their coefficients. Various optimization problems concerning {open_quotes}the largest{close_quotes} admissible uncertainty naturally arise. Examples: (1) Find the largest cube inscribed in stability domain; (2) Find the box with the largest volume preserving stability; (3) Describe a boundary of a two-dimensional image of a box under linear or nonlinear transformation; (4) Find a sum or a project of sets on a complex plane, e.g., find a product of n discs. These problems require new duality results and new necessary conditions of optimality.

  12. Radioisotopes: problems of responsibility arising from medicine

    International Nuclear Information System (INIS)

    Radioisotopes have brought about great progress in the battle against illnesses of mainly tumoral origin, whether in diagnosis (nuclear medicine) or in treatment (medical radiotherapy). They are important enough therefore to warrant investigation. Such a study is attempted here, with special emphasis, at a time when medical responsibility proceedings are being taken more and more often on the medicolegal problems arising from their medical use. It is hoped that this study on medical responsibility in the use of radioisotopes will have shown: that the use of radioisotopes for either diagnosis or therapy constitutes a major banch of medicine; that this importance implies an awareness by the practitioner of a vast responsibility, especially in law where legislation to ensure protection as strict as in the field of ionizing radiations is lacking. The civil responsibility of doctors who use radioisotopes remains to be defined, since for want of adequate jurisprudence we are reduced to hypotheses based on general principles

  13. Degenerate Diffusion Operators Arising in Population Biology

    CERN Document Server

    Epstein, Charles L

    2011-01-01

    We analyze a class of partial differential equations that arise as "backwards Kolmogorov operators" in infinite population limits of the Wright-Fisher models in population genetics and in mathematical finance. These are degenerate elliptic operators defined on manifolds with corners. The classical example is the Kimura diffusion operator, which acts on functions defined on the simplex in R^n. We introduce anisotropic Holder spaces, and prove existence, uniqueness and regularity results for the heat and resolvent equations defined by this class of operators. This suffices to prove that the C^0-graph closure generates a strongly continuous semigroup, and that the associated Martingale problem has a unique solution. We give a detailed description of the nullspace of the forward Kolmogorov operator.

  14. Juxtacortical chondromyxoid fibroma arising in an apophysis

    Energy Technology Data Exchange (ETDEWEB)

    Park, Seong Ho; Kong, Keun Young; Chung, Hye Won; Kang, Heung Sik [Dept. of Radiology, Seoul National University College of Medicine (Korea); Kim, Chong Jai [Dept. of Pathology, Seoul National University College of Medicine, Seoul (Korea); Lee, Sang Hoon [Dept. of Orthopaedic Surgery, Seoul National University College of Medicine, Seoul (Korea)

    2000-08-01

    We present a rare case of juxtacortical chondromyxoid fibroma arising in the lesser trochanter of the right femur which corresponds to an apophysis. Radiography showed a well-defined expansive lesion with a sclerotic margin measuring 5 x 3.5 cm in diameter in the lesser trochanter. On spin echo T1-weighted images, the lesion revealed low signal intensity similar to muscle. On spin echo T2-weighted images, the lesion revealed high heterogeneous signal intensity, which after gadolinium injection showed heterogeneous enhancement. The inner margin of the cortex was intact and adjacent bone marrow was of normal signal intensity. The outer margin of the lesion was also clearly defined and extension into adjacent soft tissue beyond the exophytic cortical outgrowth was not evident. (orig.)

  15. Periorbital nodular fasciitis arising during pregnancy

    Directory of Open Access Journals (Sweden)

    Brandon N Phillips

    2014-01-01

    Full Text Available Nodular fasciitis (NF is a benign proliferation of fibroblasts and myofibroblasts that rarely occurs in the periorbital region. We report what we believe to be the first case of periorbital NF associated with pregnancy. A case of intravascular fasciitis, a NF variant, has been reported during pregnancy, but it was not located in the periorbital region. A weak presence of estrogen receptors has been reported in NF. This may make it more susceptible to the hormone-related changes during pregnancy and contribute to the development of the lesion by stimulating fibroblasts and smooth muscle cell types. Although rare, NF should be considered in the differential diagnosis of periorbital soft-tissue masses arising during pregnancy.

  16. Nanoimprint lithography for functional polymer patterning

    Science.gov (United States)

    Cui, Dehu

    2011-07-01

    Organic semiconductors have generated huge interested in recent years for low-cost and flexible electronics. Current and future device applications for semiconducting polymers include light-emitting diodes, thin-film transistors, photovoltaic cells, photodetectors, lasers, and memories. The performance of conjugated polymer devices depends on two major factors: the chain conformation in polymer film and the device architecture. Highly ordered chain structure usually leads to much improved performance by enhancing interchain interaction to facilitate carrier transport. The goal of this research is to improve the performance of organic devices with the nanoimprint lithography. The work begins with the controlling of polymer chain orientation in patterned nanostructures through nanoimprint mold design and process parameter manipulation, and studying the effect of chain ordering on material properties. Then, step-and-repeat thermal nanoimprint technique for large-scale continuous manufacturing of conjugated polymer nanostructures is developed. After that, Systematic investigation of polymer chain configuration by Raman spectroscopy is carried out to understand how nanoimprint process parameters, such as mold pattern size, temperature, and polymer molecular weight, affects polymer chain configuration. The results indicate that chain orientation in nanoimprinted polymer micro- and nanostructures is highly related to the nanoimprint temperature and the dimensions of the mold structures. The ability to create nanoscale polymer micro- and nanostructures and manipulate their internal chain conformation establishes an original experimental platform that enables studying the properties of functional polymers at the micro- and nanoscale and understanding their fundamental structure-property relationships. In addition to the impact on basic research, the techniques developed in this work are important in applied research and development. Large-area conjugated polymer micro- and

  17. Conductive polymer-based material

    Science.gov (United States)

    McDonald, William F.; Koren, Amy B.; Dourado, Sunil K.; Dulebohn, Joel I.; Hanchar, Robert J.

    2007-04-17

    Disclosed are polymer-based coatings and materials comprising (i) a polymeric composition including a polymer having side chains along a backbone forming the polymer, at least two of the side chains being substituted with a heteroatom selected from oxygen, nitrogen, sulfur, and phosphorus and combinations thereof; and (ii) a plurality of metal species distributed within the polymer. At least a portion of the heteroatoms may form part of a chelation complex with some or all of the metal species. In many embodiments, the metal species are present in a sufficient concentration to provide a conductive material, e.g., as a conductive coating on a substrate. The conductive materials may be useful as the thin film conducting or semi-conducting layers in organic electronic devices such as organic electroluminescent devices and organic thin film transistors.

  18. High cation transport polymer electrolyte

    Science.gov (United States)

    Gerald, II, Rex E.; Rathke, Jerome W.; Klingler, Robert J.

    2007-06-05

    A solid state ion conducting electrolyte and a battery incorporating same. The electrolyte includes a polymer matrix with an alkali metal salt dissolved therein, the salt having an anion with a long or branched chain having not less than 5 carbon or silicon atoms therein. The polymer is preferably a polyether and the salt anion is preferably an alkyl or silyl moiety of from 5 to about 150 carbon/silicon atoms.

  19. Polymers in disordered environments

    Directory of Open Access Journals (Sweden)

    V. Blavatska

    2014-09-01

    Full Text Available A brief review of our recent studies aiming at a better understanding of the scaling behaviour of polymers in disordered environments is given. The main emphasis is on a simple generic model where the polymers are represented by (interacting self-avoiding walks and the disordered environment by critical percolation clusters. The scaling behaviour of the number of conformations and their average spatial extent as a function of the number of monomers and the associated critical exponents γ and ν are examined with two complementary approaches: numerical chain-growth computer simulations using the PERM algorithm and complete enumerations of all possible polymer conformations employing a recently developed very efficient exact counting method.

  20. Chemodectomas arising in temporal bone structures

    Energy Technology Data Exchange (ETDEWEB)

    Dickens, W.J.; Million, R.R.; Cassisi, N.J.; Singleton, G.T.

    1982-02-01

    Eighteen patients with chemodectomas arising in temporal bone structures were evaluated and treated at the University of Florida. Seventeen patients have each been followed a minimum of 3 years. Patients were retrospectively staged as having ''local'' or ''advanced'' disease, depending on the presence or absence of bone destruction and/or cranial nerve involvement. Fourteen of the patients received radiation therapy as all or part of their therapy; 6 patients were treated with radiation therapy alone, 3 patients were irradiated immediately postoperatively for residual disease, and 5 patients had radiation therapy for recurrence after operation. They were treated with cobalt-60 radiation with doses ranging from 3760 to 5640 rad. All irradiated patients demonstrated evidence of tumor regression, and none have had tumor recurrence with followup of 3-12 years. Of the 8 patients with cranial nerve paralysis prior to therapy, 5 had return of function of 1 or more cranial nerves. One of 6 patients treated initially with radiation therapy had a complication, while 6 of 8 patients irradiated postoperatively had complications. None of the complications were fatal. Three patients treated by operation for early disease limited to the hypotympanum had the disease controlled for 11-12 years. Guidelines for the selection of initial therapy are discussed.

  1. An organism arises from every nucleus.

    Directory of Open Access Journals (Sweden)

    Nurullah Keklikoglu

    2009-12-01

    Full Text Available The fact that, cloning using somatic cell nuclear transfer (SCNT method has been performed, opened new horizons for cloning, and changed the way of our understanding and approach to cell and nucleus. The progress in cloning technology, brought the anticipation of the ability to clone an organism from each somatic cell nucleus. Therefore, the 'Cell Theory' is about to take the additional statement as "An organism arises from every nucleus". The development of gene targeting procedures which can be applied with SCNT, showed us that it may be possible to obtain different versions of the original genetic constitution of a cell. Because of this opportunity which is provided by SCNT, in reproductive cloning, it would be possible to clone enhanced organisms which can adapt to different environmental conditions and survive. Furthermore, regaining the genetic characteristics of ancestors or reverse herediter variations would be possible. On the other hand, in therapeutic cloning, more precise and easily obtainable alternatives for cell replacement therapy could be presented. However, while producing healthier or different organisms from a nucleus, it is hard to foresee the side effects influencing natural processes in long term is rather difficult.

  2. Chemodectomas arising in temporal bone structures

    International Nuclear Information System (INIS)

    Eighteen patients with chemodectomas arising in temporal bone structures were evaluated and treated at the University of Florida. Seventeen patients have each been followed a minimum of 3 years. Patients were retrospectively staged as having ''local'' or ''advanced'' disease, depending on the presence or absence of bone destruction and/or cranial nerve involvement. Fourteen of the patients received radiation therapy as all or part of their therapy; 6 patients were treated with radiation therapy alone, 3 patients were irradiated immediately postoperatively for residual disease, and 5 patients had radiation therapy for recurrence after operation. They were treated with cobalt-60 radiation with doses ranging from 3760 to 5640 rad. All irradiated patients demonstrated evidence of tumor regression, and none have had tumor recurrence with followup of 3-12 years. Of the 8 patients with cranial nerve paralysis prior to therapy, 5 had return of function of 1 or more cranial nerves. One of 6 patients treated initially with radiation therapy had a complication, while 6 of 8 patients irradiated postoperatively had complications. None of the complications were fatal. Three patients treated by operation for early disease limited to the hypotympanum had the disease controlled for 11-12 years. Guidelines for the selection of initial therapy are discussed

  3. Radiological emergencies arising from accidents in Italy

    International Nuclear Information System (INIS)

    The Nuclear Safety and Health Protection Directorate (DISP) of ENEA has organized a structure of officers and technicians on call whenever an accident related to the activity of ENEA-DISP should occur. The most frequent events arise from natural misfortunes, crime, and deficiencies in public services. As regards technical operations such as measurements, removals, decontaminations and transport, DISP requests utilization of the different structures and equipment available to ENEA research centres and, in particular and most frequently, of the Safety and Radioprotection Division of the main ENEA centre: the Casaccia Research Centre. The technicians of this division are always available via telephone or radio, with the firm duty to be present within one hour from the call. The co-operation between these two structures enables timely and efficient intervention in many circumstances so that population and environmental risks can be avoided. Typical accidental situations are earthquakes, adverse atmospheric events, landslides, collapses, railway and road accidents, lost sources discovery, and seizure of illegally detained sources by judicial power. The paper briefly describes some of the situations which have occurred, and the actions carried out to recover sources and to re-establish safe environmental conditions. (author)

  4. Chemical hazards arising from shale gas extraction

    Directory of Open Access Journals (Sweden)

    Daria Pakulska

    2015-02-01

    Full Text Available The development of the shale industry is gaining momentum and hence the analysis of chemical hazards to the environment and health of the local population is extremely timely and important. Chemical hazards are created during the exploitation of all minerals, but in the case of shale gas production, there is much more uncertainty as regards to the effects of new technologies application. American experience suggests the increasing risk of environmental contamination, mainly groundwater. The greatest concern is the incomplete knowledge of the composition of fluids used for fracturing shale rock and unpredictability of long-term effects of hydraulic fracturing for the environment and health of residents. High population density in the old continent causes the problem of chemical hazards which is much larger than in the USA. Despite the growing public discontent data on this subject are limited. First of all, there is no epidemiological studies to assess the relationship between risk factors, such as air and water pollution, and health effects in populations living in close proximity to gas wells. The aim of this article is to identify and discuss existing concepts on the sources of environmental contamination, an indication of the environment elements under pressure and potential health risks arising from shale gas extraction. Med Pr 2015;66(1:99–117

  5. Physical properties of polymers handbook

    CERN Document Server

    2007-01-01

    This book offers concise information on the properties of polymeric materials, particularly those most relevant to physical chemistry and chemical physics. Extensive updates and revisions to each chapter include eleven new chapters on novel polymeric structures, reinforcing phases in polymers, and experiments on single polymer chains. The study of complex materials is highly interdisciplinary, and new findings are scattered among a large selection of scientific and engineering journals. This book brings together data from experts in the different disciplines contributing to the rapidly growing area of polymers and complex materials.

  6. Risk analysis for renewable energy projects due to constraints arising

    Science.gov (United States)

    Prostean, G.; Vasar, C.; Prostean, O.; Vartosu, A.

    2016-02-01

    Starting from the target of the European Union (EU) to use renewable energy in the area that aims a binding target of 20% renewable energy in final energy consumption by 2020, this article illustrates the identification of risks for implementation of wind energy projects in Romania, which could lead to complex technical implications, social and administrative. In specific projects analyzed in this paper were identified critical bottlenecks in the future wind power supply chain and reasonable time periods that may arise. Renewable energy technologies have to face a number of constraints that delayed scaling-up their production process, their transport process, the equipment reliability, etc. so implementing these types of projects requiring complex specialized team, the coordination of which also involve specific risks. The research team applied an analytical risk approach to identify major risks encountered within a wind farm project developed in Romania in isolated regions with different particularities, configured for different geographical areas (hill and mountain locations in Romania). Identification of major risks was based on the conceptual model set up for the entire project implementation process. Throughout this conceptual model there were identified specific constraints of such process. Integration risks were examined by an empirical study based on the method HAZOP (Hazard and Operability). The discussion describes the analysis of our results implementation context of renewable energy projects in Romania and creates a framework for assessing energy supply to any entity from renewable sources.

  7. Restructuring polymers via nanoconfinement and subsequent release

    Directory of Open Access Journals (Sweden)

    Alan E. Tonelli

    2012-08-01

    Full Text Available During the past several years my students and I have been utilizing certain small-molecule hosts to create nanostructured polymers. This is accomplished by first forming noncovalently bonded inclusion complexes (ICs between these small-molecule hosts and guest polymers, followed by the careful removal of the host crystalline lattice to obtain a coalesced bulk polymer. We have repeatedly observed that such coalesced polymer samples behave distinctly from those produced from their solutions or melts. Coalesced amorphous homopolymers exhibit higher glass-transition temperatures, while crystallizable homopolymers coalesced from their ICs display higher melting and crystallization temperatures, and sometimes different crystalline polymorphs. When ICs are formed with block copolymers or with two or more different homopolymers, the resulting coalesced samples can exhibit intimate mixing between the copolymer blocks, or between entire homopolymer chains. Each of the distinct behaviors observed for polymers coalesced from their ICs is a consequence of the structural organization of the polymer–host-ICs. Polymer chains in host-IC crystals are confined to occupy narrow channels (diameter ~0.5–1.0 nm formed by the small-molecule hosts around the included guest polymers during IC crystallization. This results in the separation and high extension of the included guest polymer chains, which leads, following the careful removal of the host molecule lattice, to unique behaviors for the bulk coalesced polymer samples. Apparently, substantial degrees of the extended and unentangled natures of the IC-included chains are retained upon coalescence. In this review we summarize the behaviors and uses of coalesced polymers, and attempt to draw conclusions on the relationship between their behavior and the organization/structures/conformations of the constituent polymer chains achieved upon coalescence from their ICs.

  8. Ratios of partition fucntions for the log-gamma polymer

    OpenAIRE

    Yılmaz, Atilla; Georgiou, Nicos; Rassoul-Agha, Firas; Seppaelaeinen, Timo

    2015-01-01

    We introduce a random walk in random environment associated to an underlying directed polymer model in 1 + 1 dimensions. This walk is the positive temperature counterpart of the competition interface of percolation and arises as the limit of quenched polymer measures. We prove this limit for the exactly solvable log-gamma polymer, as a consequence of almost sure limits of ratios of partition functions. These limits of ratios give the Busemann functions of the log-gamma polymer, and furnish ce...

  9. RIGHT SUPERIOR POLAR ARTERY ARISING FROM AORTA

    Directory of Open Access Journals (Sweden)

    Sreekanth

    2013-05-01

    Full Text Available ABSTRACT: The renal vasculature was always a subject of varia tions both in the number and pattern of portal of entry into kidney and Perihilar placement of the artery, vein and pelvis. Good anatomical insight is an essential prerequisite besides the surgical expertise. The cadaveric dissection at Shadan Institute of Medical Sciences, Teaching Hospital and Research Centre, revealed superior / upper polar artery arising from the lateral aspect of the aorta just proximal to the origin of Main Renal Artery (MRA. T he main renal artery and the accessory renal artery had almost a common point of origin. Th e peri-hilar segmentation of the main renal artery was a fork like pattern. One of the segmental arteries was long and had its portal of entry into the kidney by perforating the capsule of the ant erior substance of the kidney. The remaining segmental branches had their portal of ent ry through the hilum. The lower two segmental branches were placed anterior to the main renal vein causing altered hilar anatomy. A thorough knowledge of the frequently to the rarel y occurring wide range of variations of renal vasculature has significance in exploration and trea tment of renal trauma, renal transplantation, renal artery embolization, surgery for abdominal ao rtic aneurysm and conservative or radical renal surgery. Such a rare variation including the combination of extra renal peri-hilar segmentation of MRA with superior polar artery is wor thy of concern to the urologists harvesting kidneys from the live donors for performi ng transplantation procedures, partial nephrectomies for the hilar tumors and for Radiologi sts during interpretation of the angiograms

  10. Stochastic resonance during a polymer translocation process

    Science.gov (United States)

    Mondal, Debasish; Muthukumar, M.

    2016-04-01

    We have studied the occurrence of stochastic resonance when a flexible polymer chain undergoes a single-file translocation through a nano-pore separating two spherical cavities, under a time-periodic external driving force. The translocation of the chain is controlled by a free energy barrier determined by chain length, pore length, pore-polymer interaction, and confinement inside the donor and receiver cavities. The external driving force is characterized by a frequency and amplitude. By combining the Fokker-Planck formalism for polymer translocation and a two-state model for stochastic resonance, we have derived analytical formulas for criteria for emergence of stochastic resonance during polymer translocation. We show that no stochastic resonance is possible if the free energy barrier for polymer translocation is purely entropic in nature. The polymer chain exhibits stochastic resonance only in the presence of an energy threshold in terms of polymer-pore interactions. Once stochastic resonance is feasible, the chain entropy controls the optimal synchronization conditions significantly.

  11. Stochastic resonance during a polymer translocation process.

    Science.gov (United States)

    Mondal, Debasish; Muthukumar, M

    2016-04-14

    We have studied the occurrence of stochastic resonance when a flexible polymer chain undergoes a single-file translocation through a nano-pore separating two spherical cavities, under a time-periodic external driving force. The translocation of the chain is controlled by a free energy barrier determined by chain length, pore length, pore-polymer interaction, and confinement inside the donor and receiver cavities. The external driving force is characterized by a frequency and amplitude. By combining the Fokker-Planck formalism for polymer translocation and a two-state model for stochastic resonance, we have derived analytical formulas for criteria for emergence of stochastic resonance during polymer translocation. We show that no stochastic resonance is possible if the free energy barrier for polymer translocation is purely entropic in nature. The polymer chain exhibits stochastic resonance only in the presence of an energy threshold in terms of polymer-pore interactions. Once stochastic resonance is feasible, the chain entropy controls the optimal synchronization conditions significantly. PMID:27083746

  12. A multichain polymer slip-spring model with fluctuating number of entanglements for linear and nonlinear rheology

    Science.gov (United States)

    Ramírez-Hernández, Abelardo; Peters, Brandon L.; Andreev, Marat; Schieber, Jay D.; de Pablo, Juan J.

    2015-12-01

    A theoretically informed entangled polymer simulation approach is presented for description of the linear and non-linear rheology of entangled polymer melts. The approach relies on a many-chain representation and introduces the topological effects that arise from the non-crossability of molecules through effective fluctuating interactions, mediated by slip-springs, between neighboring pairs of macromolecules. The total number of slip-springs is not preserved but, instead, it is controlled through a chemical potential that determines the average molecular weight between entanglements. The behavior of the model is discussed in the context of a recent theory for description of homogeneous materials, and its relevance is established by comparing its predictions to experimental linear and non-linear rheology data for a series of well-characterized linear polyisoprene melts. The results are shown to be in quantitative agreement with experiment and suggest that the proposed formalism may also be used to describe the dynamics of inhomogeneous systems, such as composites and copolymers. Importantly, the fundamental connection made here between our many-chain model and the well-established, thermodynamically consistent single-chain mean-field models provides a path to systematic coarse-graining for prediction of polymer rheology in structurally homogeneous and heterogeneous materials.

  13. A multichain polymer slip-spring model with fluctuating number of entanglements for linear and nonlinear rheology

    International Nuclear Information System (INIS)

    A theoretically informed entangled polymer simulation approach is presented for description of the linear and non-linear rheology of entangled polymer melts. The approach relies on a many-chain representation and introduces the topological effects that arise from the non-crossability of molecules through effective fluctuating interactions, mediated by slip-springs, between neighboring pairs of macromolecules. The total number of slip-springs is not preserved but, instead, it is controlled through a chemical potential that determines the average molecular weight between entanglements. The behavior of the model is discussed in the context of a recent theory for description of homogeneous materials, and its relevance is established by comparing its predictions to experimental linear and non-linear rheology data for a series of well-characterized linear polyisoprene melts. The results are shown to be in quantitative agreement with experiment and suggest that the proposed formalism may also be used to describe the dynamics of inhomogeneous systems, such as composites and copolymers. Importantly, the fundamental connection made here between our many-chain model and the well-established, thermodynamically consistent single-chain mean-field models provides a path to systematic coarse-graining for prediction of polymer rheology in structurally homogeneous and heterogeneous materials

  14. A multichain polymer slip-spring model with fluctuating number of entanglements for linear and nonlinear rheology

    Energy Technology Data Exchange (ETDEWEB)

    Ramírez-Hernández, Abelardo, E-mail: abelardo@anl.gov; Pablo, Juan J. de, E-mail: depablo@uchicago.edu [Materials Science Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States); Institute for Molecular Engineering, The University of Chicago, Chicago, Illinois 60637 (United States); Peters, Brandon L.; Andreev, Marat; Schieber, Jay D., E-mail: schieber@iit.edu [Institute for Molecular Engineering, The University of Chicago, Chicago, Illinois 60637 (United States)

    2015-12-28

    A theoretically informed entangled polymer simulation approach is presented for description of the linear and non-linear rheology of entangled polymer melts. The approach relies on a many-chain representation and introduces the topological effects that arise from the non-crossability of molecules through effective fluctuating interactions, mediated by slip-springs, between neighboring pairs of macromolecules. The total number of slip-springs is not preserved but, instead, it is controlled through a chemical potential that determines the average molecular weight between entanglements. The behavior of the model is discussed in the context of a recent theory for description of homogeneous materials, and its relevance is established by comparing its predictions to experimental linear and non-linear rheology data for a series of well-characterized linear polyisoprene melts. The results are shown to be in quantitative agreement with experiment and suggest that the proposed formalism may also be used to describe the dynamics of inhomogeneous systems, such as composites and copolymers. Importantly, the fundamental connection made here between our many-chain model and the well-established, thermodynamically consistent single-chain mean-field models provides a path to systematic coarse-graining for prediction of polymer rheology in structurally homogeneous and heterogeneous materials.

  15. Chain Teleportation

    OpenAIRE

    Lee, Chien-er

    2004-01-01

    By means of the idea of measurements on the crossed space-time nonlocal observables, we extend the mechanism for the two-way quantum teleportation to the chain teleportation among N spatially separated spin-1/2 systems. Since in the process only the local interactions are used, the microcausality is automatically satisfied.

  16. ACTIVE INTERMEDIATES IN PHOTORADICAL AGING OF POLYMERS

    Institute of Scientific and Technical Information of China (English)

    M.Ya. Mel'nikov

    2001-01-01

    The data referring to the mechanism and efficiency of electronically excited macroradical and radical anion reactions, the important role of photochemical chain reactions in polymers are presented. It was found that by varying photon energy, temperature, photolysis time and competition between thermal and photochemical reactions, it is possible to change the functional composition and molecular weight distribution of polymers.

  17. Fluoroalkylation of aryl ether perfluorocyclobutyl polymers

    OpenAIRE

    Ligon, Clark; Ameduri, Bruno; Boutevin, Bernard; Smith, Dennis

    2008-01-01

    Post functionalization of aryl ether perfluorocyclobutyl (PFCB) polymers with fluoroalkyl side chains was accomplished with Umemoto's FITS reagents. The fluoroalkylated PFCB polymers (20 % functionalized) showed increases in both hydrophobicity and oleophobicity. Static contact angle for hexadecane was increased after fluoroalkylation from 0° to greater than 30° for the two PFCB polymers tested. Increased oil repellency makes these materials potential candidates for various coatings applicati...

  18. Thermally activated solvent bonding of polymers

    OpenAIRE

    Ng, S H; Tjeung, R. T.; Z. F. Wang; Lu, A. C. W.; Rodriguez, I.; de Rooij, Nicolaas F.

    2010-01-01

    We present a thermally activated solvent bonding technique for the formation of embedded microstructures in polymer. It is based on the temperature dependent solubility of polymer in a liquid that is not a solvent at room temperature. With thermal activation, the liquid is transformed into a solvent of the polymer, creating a bonding capability through segmental or chain interdiffusion at the bonding interface. The technique has advantages over the more commonly used thermal bonding due to it...

  19. ARISE - Advanced Radio Interferometry Between Space and Earth

    Science.gov (United States)

    Ulvestad, J. S.; Linfield, R. P.; Wannier, P. G.; Preston, R. A.; Hirabayashi, H.; Zensus, J. A.; Veal, G. R.

    1995-01-01

    A mission is described called ARISE, Advanced Radio Interferometry between Space and Earth. ARISE will will provide affordable very long baseline interferometry (VLBI) using second- generation VLBI and one or more inflatable space radio telescopes.

  20. Thermo-adjustable mechanical properties of polymer, lipid-based complex fluids

    Science.gov (United States)

    Firestone, Millicent; Lee, Sungwon

    2012-02-01

    Combined rheology (oscillatory and steady shear) and SAXS studies reveal details on the temperature-dependent, reversible mechanical properties of nonionic polymer, lipid-based complex fluids. Compositions prepared by introduction of the polymer as either a lipid conjugate or a triblock copolymer form an elastic gel as the temperature is increased to 18 C. The network is produced from PEO chain entanglement and physical crosslinks confined within the intervening aqueous layers of a multilamellar structured lyotropic mesophase. Although the complex fluids are weak gels, tuning of the gel strength can be achieved by temperature adjustment. The sol state formed at reduced temperature arises as a consequence of the well-solvated PEO chains adopting a non-interacting, conformational state. Complex fluids prepared with the triblock copolymers exhibit greater tunability in viscoelasticity than those containing the PEGylated-lipid conjugate because of the temperature-dependent water solubility of the central PPO block. The water solubility of PPO at reduced temperatures results in the polymer being expelled from the self-assembled amphiphilic bilayer, causing collapse of the swollen lamellar structure and loss of the PEO network. At elevated temperatures, the triblock reinserts into the bilayer producing an elastic gel. These studies identify macromolecular architectures for the facile preparation of dynamic soft materials possessing a range of mechanical properties that can be tuned by modest temperature control.

  1. Polymer Bose–Einstein condensates

    International Nuclear Information System (INIS)

    In this work we analyze a non-interacting one-dimensional polymer Bose–Einstein condensate in a harmonic trap within the semiclassical approximation. We use an effective Hamiltonian coming from the polymer quantization that arises in loop quantum gravity. We calculate the number of particles in order to obtain the critical temperature. The Bose–Einstein functions are replaced by series, whose high order terms are related to powers of the polymer length. It is shown that the condensation temperature presents a shift respect to the standard case, for small values of the polymer scale. In typical experimental conditions, it is possible to establish a bound for λ2 up to ≲10−16 m2. To improve this bound we should decrease the frequency of the trap and also decrease the number of particles

  2. Squamous cell carcinoma arising in an odontogenic cyst

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Jae Jung; Hwang, Eui Hwan; Lee, Sang Rae [Kyunghee University College of Medicine, Seoul (Korea, Republic of); Choi, Jeong Hee [Chonnam National University College of Medicine, Kwangju (Korea, Republic of)

    2003-12-15

    Squamous cell carcinoma arising in an odontogenic cyst is uncommon. The diagnosis of carcinoma arising in a cyst requires that there must be an area of microscopic transition from the benign epithelial cyst lining to the invasive squamous cell carcinoma. We report a histopathologically proven case of squamous cell carcinoma arising in a residual mandibular cyst in a 54-year-old woman.

  3. Thermo-cleavable polymers: Materials with enhanced photochemical stability

    DEFF Research Database (Denmark)

    Manceau, Matthieu; Petersen, Martin Helgesen; Krebs, Frederik C

    2010-01-01

    Photochemical stability of three thermo-cleavable polymers was investigated as thin films under atmospheric conditions. A significant increase in lifetime was observed once the side-chain was cleaved emphasizing the detrimental effect of solubilizing groups on the photochemical stability of...... conjugated polymers. In addition to their ease of processing, thermo-cleavable polymers thus also offer a greater intrinsic stability under illumination....

  4. A conducting polymer artificial muscle with 12% linear strain

    DEFF Research Database (Denmark)

    Bay, Lasse; West, Keld; Sommer-Larsen, P.;

    2003-01-01

    a freely suspended polymer foil in response to a potential change and it includes attention to the composition of the polymer, to the synthesis conditions, and involves microstructuring of the polymer. As such, an analysis of the influence of the alkyl chain length on the properties of PPy doped...

  5. On the embedding problem for discrete-time Markov chains

    OpenAIRE

    Guerry, Marie-Anne

    2013-01-01

    When a discrete-time homogenous Markov chain is observed at time intervals that correspond to its time unit, then the transition probabilities of the chain can be estimated using known maximum likelihood estimators. In this paper we consider a situation when a Markov chain is observed on time intervals with length equal to twice the time unit of the Markov chain. The issue then arises of characterizing probability matrices whose square root(s) are also probability matrices. ...

  6. Thermoresponsive Polymers for Nuclear Medicine: Which Polymer Is the Best?

    Science.gov (United States)

    Sedláček, Ondřej; Černoch, Peter; Kučka, Jan; Konefal, Rafał; Štěpánek, Petr; Vetrík, Miroslav; Lodge, Timothy P; Hrubý, Martin

    2016-06-21

    Thermoresponsive polymers showing cloud point temperatures (CPT) in aqueous solutions are very promising for the construction of various systems in biomedical field. In many of these applications these polymers get in contact with ionizing radiation, e.g., if they are used as carriers for radiopharmaceuticals or during radiation sterilization. Despite this fact, radiosensitivity of these polymers is largely overlooked to date. In this work, we describe the effect of electron beam ionizing radiation on the physicochemical and phase separation properties of selected thermoresponsive polymers with CPT between room and body temperature. Stability of the polymers to radiation (doses 0-20 kGy) in aqueous solutions increased in the order poly(N-vinylcaprolactam) (PVCL, the least stable) ≪ poly[N-(2,2-difluoroethyl)acrylamide] (DFP) polymer radiotherapeutics and sterilization of biomedical systems, cause significant increase in molecular weight due to cross-linking (except for POX, where this effect is weak). In the case of PVCL irradiated with low doses, the increase in molecular weight induced an increase in the CPT of the polymer. For PNIPAM and DFP, there is strong chain hydrophilization leading to an increase in CPT. From this perspective, POX is the most suitable polymer for the construction of delivery systems that experience exposure to radiation, while PVCL is the least suitable and PNIPAM and DFP are suitable only for low radiation demands. PMID:27238593

  7. Catch Chain

    OpenAIRE

    Talbert, Robert

    2010-01-01

    Catch Chain is a book of poems that traces the journey of a Corrections Officer who attempts to combat issues of isolation, inhumane treatment of inmates and societal rejection in jails by embarking upon a cross-country road trip. However, the same issues the officer initially wrestled with begin cropping up in different cities, on various highways and in a multitude of states. The excitement and adventure of the open road runs parallel to the recurring imprisonment of the guard's mind.

  8. Stress Relaxation in Entangled Polymer Melts

    DEFF Research Database (Denmark)

    Hou, Ji-Xuan; Svaneborg, Carsten; Everaers, Ralf;

    2010-01-01

    We present an extensive set of simulation results for the stress relaxation in equilibrium and step-strained bead-spring polymer melts. The data allow us to explore the chain dynamics and the shear relaxation modulus, G(t), into the plateau regime for chains with Z=40 entanglements and into the...

  9. COMPUTER SIMULATION OF POLYMER SOLUTION THERMODYNAMICS

    Institute of Scientific and Technical Information of China (English)

    1998-01-01

    The statistical counting method for the computer simulation of the thermodynamic quantities of polymer solution has been reviewed. The calculating results for a single athermal chain confirm the theory of the renormalization group. The results for the athermal solution are consistent with the scaling law of the osmotic pressure with the exponent 2.25. The results for a single chain with the segmental interaction are in a good agreement with the exact results obtained by the direct counting method. The results for the polymer solution show us that the Flory-Huggins parameter is strongly dependent on both the polymer concentration and the interaction energy between segments.

  10. Communication: Thermodynamic analysis of critical conditions of polymer adsorption

    International Nuclear Information System (INIS)

    Polymer adsorption to solid surfaces is a ubiquitous phenomenon, which has attracted long-lasting attention. Dependent on the competition between the polymer-solid adsorption and polymer-solvent solvation interactions, a chain may assume either 3d solvated conformation when adsorption is weak or 2d adsorbed conformation when adsorption is strong. The transition between these conformations occurring upon variation of adsorption strength is quite sharp, and in the limit of “infinite” chain length, can be treated as a critical phenomenon. We suggest a novel thermodynamic definition of the critical conditions of polymer adsorption from the equality of incremental chemical potentials of adsorbed and free chains. We show with the example of freely jointed Lennard-Jones chains tethered to an adsorbing surface that this new definition provides a link between thermodynamic and geometrical features of adsorbed chains and is in line with classical scaling relationships for the fraction of adsorbed monomers, chain radii of gyration, and free energy

  11. STUDIES ON ENHANCED CONDUCTIVITY OF STRETCHED CONDUCTING POLYMERS

    Institute of Scientific and Technical Information of China (English)

    WAN Meixiang

    1995-01-01

    A physical model of series of the conductivity on chain and the interchain conductivity between chains is proposed to explain enhanced conductivity of stretched conducting polymers.This model suggests that the enhanced conductivity for stretched conducting polymers might be due to increasing of the interchain conductivity between chains along the elongation direction after drawing processes if the conductivity on chain is assumed much larger than that of the interchain conductivity between chains. According to this model, it is expected that the temperature dependence of conductivity measured by four-probe method for stretched conducting polymers is controlled by a variation of the interchain conductivity between chains with temperature, which can be used to explain that a metallic temperature dependence of conductivity for stretched conducting polymers is not observed although the conductivity along the elongation direction is enhanced by two or three orders of magnitude.

  12. Origin of the red sites and energy transfer rates in single MEH-PPV chains at low temperature.

    Science.gov (United States)

    Feist, Florian A; Zickler, Martin F; Basché, Thomas

    2011-06-01

    Single poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) molecules dispersed in thin poly(methylmethacrylate) films have been investigated by fluorescence emission, excitation and time-resolved spectroscopy at 1.2 K. For the molecular weight studied (∼200 kDa) a bimodal distribution of emission maxima is observed. Based on a comparison of the spectroscopic properties of blue and red sites and on polarisation-resolved measurements, we argue in agreement with recent quantum-chemical calculations that the red subpopulation most probably does not arise from interchromophoric excitation delocalisation but is to be attributed to longer chromophoric units originating from ordered regions of a polymer chain, where due to constraints on the chain conformation larger conjugation lengths can be realised. In excitation spectra within the red spectral region we can identify multiple chromophoric units, among them chromophores without correspondence in the emission spectrum-donors of the intramolecular energy transfer. Zero-phonon lines of donor chromophores proved to be significantly broadened, indicating fast excited-state population decay due to energy transfer. Thus, a distribution of energy transfer times within MEH-PPV chains could be determined from donor zero-phonon line widths, with an average value of 3.9 ps. Our study represents the first direct measurement of energy transfer times in conjugated polymers, parameters that are crucial for the performance of many technical applications based on this class of material. PMID:21472962

  13. Phase transitions of a polymer threading a membrane coupled to coil-globule transitions

    OpenAIRE

    Matsuyama, Akihiko

    2004-01-01

    We theoretically study phase transitions of a polymer threading through a pore imbedded in a membrane. We focus on the coupling between a partition of the polymer segments through the membrane and a coil-globule transition of the single polymer chain. Based on the Flory model for collapse transitions of a polymer chain, we calculate the fraction of polymer segments and the expansion factor of a polymer coil on each side of the membrane. We predict a first-order phase transition of a polymer t...

  14. Entropic forces of single-chain confinement in spherical cavities.

    Science.gov (United States)

    Jin, Zhehui; Zhao, Shuangliang; Wu, Jianzhong

    2010-10-01

    Thermodynamic properties of a single chain in a confined space have been studied before with the polymer scaling theory and computer simulations. However, a comprehensive understanding of the entropic effects due to the molecular excluded volume and chain connectivity is emerging only recently, especially in the limit of large polymer packing densities as often encountered in biological systems. In this work, we propose a polymer density functional theory (DFT) to study the entropic forces for the confinement of single polymer chains in spherical cavities. At conditions accessible to Monte Carlo simulations, we show that the DFT predictions are in excellent agreement with the simulation results for the distributions of polymer segments as well as the free energy of confinement. The numerical efficiency of the DFT allows us to unify key conclusions from various theoretical analyses and experimental observations. PMID:21230306

  15. Classical Hodgkin Lymphoma Arising Adjacent to a Breast Implant.

    Science.gov (United States)

    Ryan, Ciara; Ged, Yasser; Quinn, Fiona; Walker, Jan; Kennedy, John; Gillham, Charles; Pittaluga, Stefania; McDermott, Ronan; Vandenberghe, Elisabeth; Grant, Cliona; Flavin, Richard

    2016-08-01

    Breast implant-associated lymphoma has recently gained wide recognition. Anaplastic large cell lymphoma (ALCL) is the most frequently diagnosed subtype in this setting but the spectrum is broadening. A 66-year-old woman developed swelling and itch around her saline implant 6 years after its insertion. Imaging revealed a fluid collection surrounding the implant with an adjacent mass. Microscopy showed sclerotic tissue punctuated by discrete cellular nodules comprising small lymphocytes, eosinophils and interspersed large atypical Hodgkin Reed-Sternberg (HRS)-like cells. The HRS-like cells stained positively for CD30 and CD15 by immunohistochemistry. Small T-lymphocytes formed rosettes around HRS-like cells. Appearances were consistent with classical Hodgkin lymphoma (HL). Multiplex polymerase chain reaction demonstrated no clonal rearrangements of immunoglobulin or T-cell receptor genes, however, a t(14;18)(q32;q21)BCL2-JH translocation involving the major breakpoint region of the bcl2 gene was present. Staging positron emission tomography-computed tomography scan revealed FDG-avid masses in the right axilla and pelvis. Subsequent pathological examination identified low-grade follicular lymphoma (FL) with a t(14;18) translocation at these sites. To our knowledge, this is the first case of HL arising adjacent to a breast implant. An awareness of this diagnosis is important as classical HL, with its prominent mixed inflammatory background, may be overlooked as a reactive process when histologically assessing capsulectomy specimens. It is also important in the differential diagnosis for implant-associated ALCL as both contain large atypical CD30-positive cells highlighting the need for full immunohistochemical and molecular workup in such cases. This case also adds to the large body of literature regarding the association between HL and FL. PMID:26888955

  16. Enhanced Photoresponse of Conductive Polymer Nanowires Embedded with Au Nanoparticles.

    Science.gov (United States)

    Zhang, Junchang; Zhong, Liubiao; Sun, Yinghui; Li, Anran; Huang, Jing; Meng, Fanben; Chandran, Bevita K; Li, Shuzhou; Jiang, Lin; Chen, Xiaodong

    2016-04-01

    A conductive polymer nanowire embedded with a 1D Au nanoparticle chain with defined size, shape, and interparticle distance is fabricated which demonstrates enhanced photoresponse behavior. The precise and controllable positioning of 1D Au nanoparticle chain in the conductive polymer nanowire plays a critical role in modulating the photoresponse behavior by excitation light wavelength or power due to the coupled-plasmon effect of 1D Au nanoparticle chain. PMID:26901850

  17. Polymer Chemistry

    Science.gov (United States)

    Williams, Martha; Roberson, Luke; Caraccio, Anne

    2010-01-01

    This viewgraph presentation describes new technologies in polymer and material chemistry that benefits NASA programs and missions. The topics include: 1) What are Polymers?; 2) History of Polymer Chemistry; 3) Composites/Materials Development at KSC; 4) Why Wiring; 5) Next Generation Wiring Materials; 6) Wire System Materials and Integration; 7) Self-Healing Wire Repair; 8) Smart Wiring Summary; 9) Fire and Polymers; 10) Aerogel Technology; 11) Aerogel Composites; 12) Aerogels for Oil Remediation; 13) KSC's Solution; 14) Chemochromic Hydrogen Sensors; 15) STS-130 and 131 Operations; 16) HyperPigment; 17) Antimicrobial Materials; 18) Conductive Inks Formulations for Multiple Applications; and 19) Testing and Processing Equipment.

  18. Bayesian analysis of variable-order, reversible Markov chains

    OpenAIRE

    Bacallado, Sergio

    2011-01-01

    We define a conjugate prior for the reversible Markov chain of order $r$. The prior arises from a partially exchangeable reinforced random walk, in the same way that the Beta distribution arises from the exchangeable Poly\\'{a} urn. An extension to variable-order Markov chains is also derived. We show the utility of this prior in testing the order and estimating the parameters of a reversible Markov model.

  19. Electroelasticity of polymer networks

    Science.gov (United States)

    Cohen, Noy; Dayal, Kaushik; deBotton, Gal

    2016-07-01

    A multiscale analysis of the electromechanical coupling in elastic dielectrics is conducted, starting from the discrete monomer level through the polymer chain and up to the macroscopic level. Three models for the local relations between the molecular dipoles and the electric field that can fit a variety of dipolar monomers are considered. The entropy of the network is accounted for within the framework of statistical mechanics with appropriate kinematic and energetic constraints. At the macroscopic level closed-form explicit expressions for the behaviors of amorphous dielectrics and isotropic polymer networks are determined, none of which admits the commonly assumed linear relation between the polarization and the electric field. The analysis reveals the dependence of the macroscopic coupled behavior on three primary microscopic parameters: the model assumed for the local behavior, the intensity of the local dipole, and the length of the chain. We show how these parameters influence the directional distributions of the monomers and the hence the resulting overall response of the network. In particular, the dependences of the polarization and the polarization induced stress on the deformation of the dielectric are illustrated. More surprisingly, we also reveal a dependence of the stress on the electric field which stems from the kinematic constraint imposed on the chains.

  20. Topology of contacts in interacting polymers

    Science.gov (United States)

    Dirschbacher, Nina

    Recent developments in the study of chromatin loop domains and gene regulation motivates us to investigate the topology of contacts in interacting polymers. To describe the chromatin loop formation we will use a bead on a string model with excluded volume and attractive polymer-polymer interaction simulated by self avoiding walks. The resulting chain configuration is a balance between these two interactions and can be a coiled state for good solvents or a collapsed one for poor solvent. We can classify the different chain configurations by their topological structures through the genus, a topological invariant of the resulting diagrams. The backtracking algorithm enables us to achieve exact numerical results for the genus distribution of the above mentioned model for small polymer lengths. Since pseudoknots decrease the entropy by restricting the possible configuration, we explore whether we see a suppression of pseudoknots for finite size polymers and intermediate strength of interaction.

  1. Plasmonic polymers unraveled through single particle spectroscopy

    Science.gov (United States)

    Slaughter, Liane S.; Wang, Lin-Yung; Willingham, Britain A.; Olson, Jana M.; Swanglap, Pattanawit; Dominguez-Medina, Sergio; Link, Stephan

    2014-09-01

    Plasmonic polymers are quasi one-dimensional assemblies of nanoparticles whose optical responses are governed by near-field coupling of localized surface plasmons. Through single particle extinction spectroscopy correlated with electron microscopy, we reveal the effect of the composition of the repeat unit, the chain length, and extent of disorder on the energies, intensities, and line shapes of the collective resonances of individual plasmonic polymers constructed from three different sizes of gold nanoparticles. Our combined experimental and theoretical analysis focuses on the superradiant plasmon mode, which results from the most attractive interactions along the nanoparticle chain and yields the lowest energy resonance in the spectrum. This superradiant mode redshifts with increasing chain length until an infinite chain limit, where additional increases in chain length cause negligible change in the energy of the superradiant mode. We find that, among plasmonic polymers of equal width comprising nanoparticles with different sizes, the onset of the infinite chain limit and its associated energy are dictated by the number of repeat units and not the overall length of the polymer. The intensities and linewidths of the superradiant mode relative to higher energy resonances, however, differ as the size and number of nanoparticles are varied in the plasmonic polymers studied here. These findings provide general guidelines for engineering the energies, intensities, and line shapes of the collective optical response of plasmonic polymers constructed from nanoparticles with sizes ranging from a few tens to one hundred nanometers.Plasmonic polymers are quasi one-dimensional assemblies of nanoparticles whose optical responses are governed by near-field coupling of localized surface plasmons. Through single particle extinction spectroscopy correlated with electron microscopy, we reveal the effect of the composition of the repeat unit, the chain length, and extent of

  2. Miscibility Phase Diagram of Ring Polymer Blends: A Topological Effect

    OpenAIRE

    Sakaue, Takahiro; Nakajima, Chihiro H.

    2016-01-01

    The miscibility of polymer blends, a classical problem in polymer science, may be altered, if one or both of the component do not have chain ends. Based on the idea of {\\it topological volume}, we propose a mean-field theory to clarify how the topological constraints in ring polymers affect the phase behavior of the blends. While the large enhancement of the miscibility is expected for ring-linear polymer blends, the opposite trend toward demixing, albeit comparatively weak, is predicted for ...

  3. Polyphosphazine-based polymer materials

    Science.gov (United States)

    Fox, Robert V.; Avci, Recep; Groenewold, Gary S.

    2010-05-25

    Methods of removing contaminant matter from porous materials include applying a polymer material to a contaminated surface, irradiating the contaminated surface to cause redistribution of contaminant matter, and removing at least a portion of the polymer material from the surface. Systems for decontaminating a contaminated structure comprising porous material include a radiation device configured to emit electromagnetic radiation toward a surface of a structure, and at least one spray device configured to apply a capture material onto the surface of the structure. Polymer materials that can be used in such methods and systems include polyphosphazine-based polymer materials having polyphosphazine backbone segments and side chain groups that include selected functional groups. The selected functional groups may include iminos, oximes, carboxylates, sulfonates, .beta.-diketones, phosphine sulfides, phosphates, phosphites, phosphonates, phosphinates, phosphine oxides, monothio phosphinic acids, and dithio phosphinic acids.

  4. SCATTERING FUNCTION OF POLYMER BLENDS

    Institute of Scientific and Technical Information of China (English)

    Lin-ping Ke; Mei-li Guo; De-lu Zhao

    2004-01-01

    For a system of flexible polymer molecules, the concepts of two concentrations, namely the segmental and the molecular concentrations, have been proposed in this paper. The former is equivalent to the volume fraction. The latter can be defined as the number of the gravity centers of macromolecules in a unit volume. The two concentrations should be correlated with each other by the conformational function of the polymer chain and should be discussed in different thermodynamic equations. On the basis of these concepts it has been proved that the Flory-Huggins entropy of mixing should be the result of the mixing "ideal gases of the gravity centers of macromolecules". The general correlation between the free energy of mixing and the scattering function (structural factor) of polymer blends has been studied based on the general fluctuation theory. When the Flory-Huggins free energy of mixing is adopted, the de Gennes scattering function of a polymer blend can be derived.

  5. Conjugated Polymers for Energy Production

    DEFF Research Database (Denmark)

    Livi, Francesco

    This dissertation is aimed at developing materials for flexible, large area, ITO-free polymer solar cells (PSCs) fully printed under ambient conditions. A large screening of conjugated polymers, both novel and well-known materials, has been carried out in order to find suitable candidates...... for scalable PSCs fully printed under ambient conditions [Adv. Energy Mater. 2015, 5, 1402186]. PPDTBT resulted to be the conjugated polymer with the best photovoltaic performance within the 104 synthesized macromolecules. Therefore, further studies have been done on such material. The impact of side chain...... arylation (DAr) and direct arylation polymerization (DArP) have been applied to the preparation of PPDTBT, making this polymer readily available in only 4 synthetic steps and thus easily transferable to a large scale-production setup. DArP avoids organometallic species and therefore is an appealing...

  6. Cyclic polymers from alkynes

    Science.gov (United States)

    Roland, Christopher D.; Li, Hong; Abboud, Khalil A.; Wagener, Kenneth B.; Veige, Adam S.

    2016-08-01

    Cyclic polymers have dramatically different physical properties compared with those of their equivalent linear counterparts. However, the exploration of cyclic polymers is limited because of the inherent challenges associated with their synthesis. Conjugated linear polyacetylenes are important materials for electrical conductivity, paramagnetic susceptibility, optical nonlinearity, photoconductivity, gas permeability, liquid crystallinity and chain helicity. However, their cyclic analogues are unknown, and therefore the ability to examine how a cyclic topology influences their properties is currently not possible. We have solved this challenge and now report a tungsten catalyst supported by a tetraanionic pincer ligand that can rapidly polymerize alkynes to form conjugated macrocycles in high yield. The catalyst works by tethering the ends of the polymer to the metal centre to overcome the inherent entropic penalty of cyclization. Gel-permeation chromatography, dynamic and static light scattering, viscometry and chemical tests are all consistent with theoretical predictions and provide unambiguous confirmation of a cyclic topology. Access to a wide variety of new cyclic polymers is now possible by simply choosing the appropriate alkyne monomer.

  7. Segmented conjugated polymers

    Indian Academy of Sciences (India)

    G Padmanaban; S Ramakrishnan

    2003-08-01

    Segmented conjugated polymers, wherein the conjugation is randomly truncated by varying lengths of non-conjugated segments, form an interesting class of polymers as they not only represent systems of varying stiffness, but also ones where the backbone can be construed as being made up of chromophores of varying excitation energies. The latter feature, especially when the chromophores are fluorescent, like in MEHPPV, makes these systems particularly interesting from the photophysics point of view. Segmented MEHPPV- samples, where x represents the mole fraction of conjugated segments, were prepared by a novel approach that utilizes a suitable precursor wherein selective elimination of one of the two eliminatable groups is affected; the uneliminated units serve as conjugation truncations. Control of the composition x of the precursor therefore permits one to prepare segmented MEHPPV- samples with varying levels of conjugation (elimination). Using fluorescence spectroscopy, we have seen that even in single isolated polymer chains, energy migration from the shorter (higher energy) chromophores to longer (lower energy) ones occurs – the extent of which depends on the level of conjugation. Further, by varying the solvent composition, it is seen that the extent of energy transfer and the formation of poorly emissive inter-chromophore excitons are greatly enhanced with increasing amounts of non-solvent. A typical S-shaped curve represents the variation of emission yields as a function of composition suggestive of a cooperative collapse of the polymer coil, reminiscent of conformational transitions seen in biological macromolecules.

  8. Polymer Informatics

    Science.gov (United States)

    Adams, Nico

    Polymers are arguably the most important set of materials in common use. The increasing adoption of both combinatorial as well as high-throughput approaches, coupled with an increasing amount of interdisciplinarity, has wrought tremendous change in the field of polymer science. Yet the informatics tools required to support and further enhance these changes are almost completely absent. In the first part of the chapter, a critical analysis of the challenges facing modern polymer informatics is provided. It is argued, that most of the problems facing the field today are rooted in the current scholarly communication process and the way in which chemists and polymer scientists handle and publish data. Furthermore, the chapter reviews existing modes of representing and communicating polymer information and discusses the impact, which the emergence of semantic technologies will have on the way in which scientific and polymer data is published and transmitted. In the second part, a review of the use of informatics tools for the prediction of polymer properties and in silico design of polymers is offered.

  9. Polymers & People

    Science.gov (United States)

    Lentz, Linda; Robinson, Thomas; Martin, Elizabeth; Miller, Mary; Ashburn, Norma

    2004-01-01

    Each Tuesday during the fall of 2002, teams of high school students from three South Carolina counties conducted a four-hour polymer institute for their peers. In less than two months, over 300 students visited the Charleston County Public Library in Charleston, South Carolina, to explore DNA, nylon, rubber, gluep, and other polymers. Teams of…

  10. All Polymer Micropump

    DEFF Research Database (Denmark)

    Hansen, Thomas Steen

    2008-01-01

    In this thesis an all polymer micropump, and the fabrication method required to fabricate this, are examined. Polymer microfluidic. devices are of major scientific interest because they can combine complicated chemical and biological analys~s in cheap and disposable devices. The electrode system...... room techniques. The conductive blend was coated with a layer of photoresist, exposed and developed. The resulting pattern was etched in a reactive ion etcher, yielding a well defined patterned with a resolution of approximately 2 J..lm. This technique was utilised to fabricate an ac electroosmotic...... a new short chained polyurethane. The resolution of the inkjet printer was in the order of 200 J-tm. The inkjet printed pattern is compared with the agarose stamping technique in a setup where the conductivity perpendicular to the stretching direction is measured on two electrodes fabricated by the two...

  11. Adenocarcinoma arising from the tailgut cyst: a case report

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Kyung Jae; Lee, Young Rae [Kangbuk Samsung Hospital, Samsung Medical Center, Seoul (Korea, Republic of)

    1995-09-15

    Tailgut cyst is a rare congenital anomaly arising in the retrorectal space. Malignancy arising from the tailgut cyst is very rare. We experienced a case of adenocarcinoma arising from the tailgut cyst. The findings of this rare tumor are bony destruction of the sacrum on plain radiograph, a cystic mass on ultrasound, a low attenuation mass with calcification and enhancement on CT, and a multiseptated cystic mass containing solid component on MRI.

  12. Wilms tumor arising in extracoelomic paravertebral soft tissues.

    LENUS (Irish Health Repository)

    Mulligan, Linda

    2012-02-01

    Extrarenal Wilms tumor (ERWT) is a well-established entity which most commonly arises within the genitourinary tract, including intracoelomic paranephric soft tissue. Rarely, ERWT arises within teratoma, and it tends to occur predominantly in distinct settings, such as females with spinal defects and males with testicular teratomas. We report a unique ERWT arising within an extracoelomic teratoma of the paraspinal musculature, thereby expanding the range of reported locations for this unusual tumor.

  13. Nanohelices from planar polymer self-assembled in carbon nanotubes

    Science.gov (United States)

    Fu, Hongjin; Xu, Shuqiong; Li, Yunfang

    2016-07-01

    The polymer possessing with planar structure can be activated and guided to encapsulate the inner space of SWNT and form a helix through van der Waals interaction and the π-π stacking effect between the polymer and the inner surface of SWNT. The SWNT size, the nanostructure and flexibility of polymer chain are all determine the final structures. The basic interaction between the polymer and the nanotubes is investigated, and the condition and mechanism of the helix-forming are explained particularly. Hybrid polymers improve the ability of the helix formation. This study provides scientific basis for fabricating helical polymers encapsulated in SWNTs and eventually on their applications in various areas.

  14. Bannai-Ito polynomials and dressing chains

    OpenAIRE

    Derevyagin, Maxim; Tsujimoto, Satoshi; Vinet, Luc; Zhedanov, Alexei

    2012-01-01

    Schur-Delsarte-Genin (SDG) maps and Bannai-Ito polynomials are studied. SDG maps are related to dressing chains determined by quadratic algebras. The Bannai-Ito polynomials and their kernel polynomials -- the complementary Bannai-Ito polynomials -- are shown to arise in the framework of the SDG maps.

  15. What's Wrong with the Wormlike Chain

    Science.gov (United States)

    Wiggins, Paul

    2005-03-01

    DNA bending on length scales shorter than a persistence length (50 nm) plays an essential role in the translation of genetic information from DNA to cellular function. Although the Wormlike Chain model successfully describes the bending of DNA on length scales longer than a persistence length, recent DNA cyclization experiments reveal that this model underestimates the probability of spontaneous sharp bending. Indeed, at the scales most relevant for biological processes, recent experiments give cyclization rates three orders of magnitude greater than that predicted by the Wormlike Chain model.In this talk, we reconcile the successes of the Wormlike Chain model in describing the long-length-scale mechanics of DNA, with its failure to describe bending on biologically relevant length scales. We present an exact statistical mechanics model for a polymer which can undergo a kinking transition and explicitly show that this high-curvature softening of the polymer constitutive relation can dramatically increase the probability of high curvature configurations while leaving the long-length-scale mechanics of the polymer virtually unchanged [P. Wiggins, R. Phillips, & P. Nelson: cond- mat/0409003, Phys Rev E in press]. Next, we present a new technique for describing stiff polymers which can be exploited to compute near-exact result for many polymer observables. We use these techniques and short-length-scale AFM measurements to construct a quantitative model for DNA bending mechanics applicable on the length scales relevant for many biological processes. This new model predicts the softening observed in short-contour-length cyclization measurements.

  16. Ideal-Chain Collapse in Biopolymers

    CERN Document Server

    Neumann, R M

    2000-01-01

    A conceptual difficulty in the Hooke's-law description of ideal Gaussian polymer-chain elasticity is sometimes apparent in analyses of experimental data or in physical models designed to simulate the behavior of biopolymers. The problem, the tendency of a chain to collapse in the absence of external forces, is examined in the following examples: DNA-stretching experiments, gel electrophoresis, and protein folding. We demonstrate that the application of a statistical-mechanically derived repulsive force, acting between the chain ends, whose magnitude is proportional to the absolute temperature and inversely proportional to the scalar end separation removes this difficulty.

  17. Dangling chain elastomers as repeatable fibrillar adhesives.

    Science.gov (United States)

    Sitti, Metin; Cusick, Brian; Aksak, Burak; Nese, Alper; Lee, Hyung-il; Dong, Hongchen; Kowalewski, Tomasz; Matyjaszewski, Krzysztof

    2009-10-01

    This work reports on repeatable adhesive materials prepared by controlled grafting of dangling hetero chains from polymer elastomers. The dangling chain elastomer system was prepared by grafting poly(n-butyl acrylate) (PBA) chains from prefunctionalized polydimethylsiloxane (PDMS) elastomer networks using atom transfer radical polymerization. To study the effects of chain growth and network strain as they relate to network adhesion mechanics, various lengths of PBA chains with degree of polymerizations (DP) of 65, 281, 508, and 1200 were incorporated into the PDMS matrix. PBA chains with a DP value of 281 grafted from a flat PDMS substrate showed the highest (approximately 3.5-fold) enhancement of nano- and macroscale adhesion relative to a flat raw (ungrafted and not prefunctionalized) PDMS substrate. Moreover, to study the effect of PBA dangling chains on adhesion in fibrillar elastomer structures inspired by gecko foot hairs, a dip-transfer fabrication method was used to graft PBA chains with a DP value of 296 from the tip endings of mushroom-shaped PDMS micropillars. A PBA chain covered micropillar array showed macroscale adhesion enhancement up to approximately 7 times relative to the flat ungrafted prefunctionalized PDMS control substrate, showing additional nonoptimized approximately 2-fold adhesion enhancement due to fibrillar structuring and mushroom-shaped tip ending. These dangling hetero chains on elastomer micro-/nanofibrillar structures may provide a novel fabrication platform for multilength scale, repeatable, and high-strength fibrillar adhesives inspired by gecko foot hairs. PMID:20355863

  18. Phase behaviour of polyethylene knotted ring chains

    Institute of Scientific and Technical Information of China (English)

    Wen Xiao-Hui; Zhang Lin-Xi; Xia A-Gen; Chen Hong-Ping

    2011-01-01

    The phase behaviour of polyethylene knotted ring chains is investigated by using molecular dynamics simulations.In this paper, we focus on the collapse of the polyethylene knotted ring chain, and also present the results of linear and ring chains for comparison. At high temperatures, a fully extensive knot structure is observed. The mean-square radius of gyration per bond〈S2〉/(Nb2)and the shape factor(δ*)depend on not only the chain length but also the knot type.With temperature decreasing, chain collapse is observed, and the collapse temperature decreases with the chain length increasing. The actual collapse transition can be determined by the specific heat capacity Cv, and the knotted ring chain undergoes gas-liquid-solid-like transition directly. The phase transition of a knotted ring chain is only one-stage collapse, which is different from the polyethylene linear and ring chains. This investigation can provide some insights into the statistical properties of knotted polymer chains.

  19. Alpha, Omega end group functionalization of RAFT polymers based on pentafluorophenyl esters and methane thiosulfonates

    OpenAIRE

    Roth, Peter J.

    2009-01-01

    While polymers with different functional groups along the backbone have intensively been investigated, there is still a challenge in orthogonal functionalization of the end groups. Such well-defined systems are interesting for the preparation of multiblock (co) polymers or polymer networks, for bio-conjugation or as model systems for examining the end group separation of isolated polymer chains. rnHere, Reversible Addition Fragmentation Chain Transfer (RAFT) polymerization was employed as m...

  20. Ring polymers in confined geometries

    CERN Document Server

    Usatenko, Z; Kuterba, P

    2016-01-01

    The investigation of a dilute solution of phantom ideal ring polymers and ring polymers with excluded volume interactions (EVI) in a good solvent confined in a slit geometry of two parallel repulsive walls and in a solution of colloidal particles of big size were performed. Taking into account the correspondence between the field theoretical $\\phi^4$ $O(n)$-vector model in the limit $n\\to 0$ and the behavior of long-flexible polymer chains in a good solvent the correspondent depletion interaction potentials, depletion forces and the forces which exert phantom ideal ring and ring polymer chains with EVI on the walls were obtained in the framework of the massive field theory approach at fixed space dimensions d=3 up to one-loop order. Additionally, the investigation of a dilute solution of phantom ideal ring polymers in a slit geometry of two inert walls and mixed walls with one repulsive and other one inert wall were performed and correspondent depletion interaction potentials and the depletion forces were cal...

  1. Twinning of Polymer Crystals Suppressed by Entropy

    Directory of Open Access Journals (Sweden)

    Nikos Ch. Karayiannis

    2014-09-01

    Full Text Available We propose an entropic argument as partial explanation of the observed scarcity of twinned structures in crystalline samples of synthetic organic polymeric materials. Polymeric molecules possess a much larger number of conformational degrees of freedom than low molecular weight substances. The preferred conformations of polymer chains in the bulk of a single crystal are often incompatible with the conformations imposed by the symmetry of a growth twin, both at the composition surfaces and in the twin axis. We calculate the differences in conformational entropy between chains in single crystals and chains in twinned crystals, and find that the reduction in chain conformational entropy in the twin is sufficient to make the single crystal the stable thermodynamic phase. The formation of cyclic twins in molecular dynamics simulations of chains of hard spheres must thus be attributed to kinetic factors. In more realistic polymers this entropic contribution to the free energy can be canceled or dominated by nonbonded and torsional energetics.

  2. Scaling theory of polymer thermodiffusion

    Science.gov (United States)

    Bringuier, E.

    2010-11-01

    The motion of a linear polymer chain in a good solvent under a temperature gradient is examined theoretically by breaking up the flexible chain into Brownian rigid rods, and writing down an equation of motion for each rod. The motion is driven by two forces. The first one is Waldmann’s thermophoretic force (stemming from the departure of the solvent’s molecular-velocity distribution from Maxwell’s equilibrium distribution) which here is extrapolated to a dense medium. The second force is due to the fact that the viscous friction varies with position owing to the temperature gradient, which brings an important correction to the Stokes law of friction. We use scaling considerations relying upon disparate length scales and omitting non-universal numerical prefactors. The present scaling theory is compared with recent experiments on the thermodiffusion of polymers and is shown to account for (i) the existence of both signs of the thermodiffusion coefficient of long chains, (ii) the order of magnitude of the coefficient, (iii) its independence of the chain length in the high-polymer limit and (iv) its dependence on the solvent viscosity.

  3. Processing polymers with cyclodextrins

    Science.gov (United States)

    Williamson, Brandon Robert

    Cyclodextrins (CDs) are cyclic starch molecules that have the unique ability to include a variety of small molecules and polymers inside their cavities, forming "Inclusion Complexes" (ICs). While much work has been done to understand the formation and behavior of these ICs, far less is known about the fundamental property changes that can occur when CD is used to alter polymer chain morphology. The goal of my graduate research has been to discover different ways to improve upon existing polymer properties through CD processing, as well as explore the possibility of creating a novel type of IC using non-traditional forms of cyclodextrin. Poly(ε-caprolactone) (PCL) was processed with alpha-CD to form an IC. The cyclodextrin was then stripped away to yield a PCL with elongated, unentangled, and constrained polymer chains, a process referred to as coalescence. The physical and rheological property changes resulting from this coalescence were then examined. It was found that reorganizing PCL in this manner resulted in an increase in the melt crystallization temperature of up to 25°C. Coalescence also decreased the tan delta of the material and increased the average hardness and Young's modulus by 33 and 53%, respectively. Non-stoichiometric ICs (NS-ICs), or ICs with at least parts of some polymer chains uncovered, were formed between poly (methyl methacrylate) (PMMA) and gamma-CD as well as a synthesized poly(ε-caprolactone)-poly(propylene glycol)-poly(ε-caprolactone) (PCL-PPG-PCL) triblock copolymer and beta-CD. The property changes of the non-complexed polymer chains were then studied. The PMMA/gamma-CD NS-IC samples were determined to be extremely heterogeneous, however glass transition temperature increases of up to 27°C above that of as-received PMMA were observed. Diffraction data for the PMMA NS-ICs suggests slight crystallinity at partial coverage, with a similar crystal structure to that of the fully covered IC. XRD, DSC and FTIR data revealed an almost

  4. Conformational Heat Capacity of Liquid Biodegradable Polymers in the Absence and Presence Water

    Science.gov (United States)

    Pyda, Marek; Nowak-Pyda, Elzbieta

    2007-03-01

    The conformational heat capacity of biodegradable polymers such as amorphous poly(lactic acid) PLA and starch with and without water have been evaluated from a fit of experimental data to a one-dimensional Ising-like model for two discrete states, characterized by parameters linked to stiffness, cooperativity, and degeneracy. For the starch-water system the additional changes in the conformational heat capacity arise from the interaction of the carbohydrate chains with water. The liquid heat capacities at constant pressure Cp, of amorphous PLA and partially liquid state of starch, starch-water have been computed as the sum of vibrational, external, and conformational contributions. The vibrational contribution was calculated as the heat capacity arising from group and skeletal vibrations. The external contribution was estimated from experimental data of the thermal expansivity and compressibility in the liquid state. The experimental liquid Cp agrees with these calculations to better than ±3%. The calculated liquid Cp with the solid Cp was employed in the quantitative thermal analysis of the experimental Cp of biodegradable polymer PLA, starch, and starch-water. Supported by European Union, grant (MIRG-CT-2006-036558), Cargill Dow LLC

  5. Reversible addition-fragmentation chain transfer polymerization in microemulsion.

    Science.gov (United States)

    O'Donnell, Jennifer M

    2012-04-21

    This tutorial review first details the uncontrolled microemulsion polymerization mechanism, and the RAFT polymerization mechanism to provide the necessary background for examining the RAFT microemulsion polymerization mechanism. The effect of the chain transfer agent per micelle ratio and the chain transfer agent aqueous solubility on the RAFT microemulsion polymerization kinetics, polymer molecular weight and polydispersity, and polymer nanoparticle size are discussed with a focus on oil-in-water microemulsions. Modeling of RAFT microemulsion polymerization kinetics and the resulting final polymer molecular weight are presented to assist with the analysis of observed experimental trends. Lastly, the current significance of RAFT microemulsion polymerization and the future directions are discussed. PMID:22246214

  6. Facilitation of polymer looping and giant polymer diffusivity in crowded solutions of active particles

    Science.gov (United States)

    Shin, Jaeoh; Cherstvy, Andrey G.; Kim, Won Kyu; Metzler, Ralf

    2015-11-01

    We study the dynamics of polymer chains in a bath of self-propelled particles (SPP) by extensive Langevin dynamics simulations in a two-dimensional model system. Specifically, we analyse the polymer looping properties versus the SPP activity and investigate how the presence of the active particles alters the chain conformational statistics. We find that SPPs tend to extend flexible polymer chains, while they rather compactify stiffer semiflexible polymers, in agreement with previous results. Here we show that higher activities of SPPs yield a higher effective temperature of the bath and thus facilitate the looping kinetics of a passive polymer chain. We explicitly compute the looping probability and looping time in a wide range of the model parameters. We also analyse the motion of a monomeric tracer particle and the polymer’s centre of mass in the presence of the active particles in terms of the time averaged mean squared displacement, revealing a giant diffusivity enhancement for the polymer chain via SPP pooling. Our results are applicable to rationalising the dimensions and looping kinetics of biopolymers at constantly fluctuating and often actively driven conditions inside biological cells or in suspensions of active colloidal particles or bacteria cells.

  7. Chain reaction

    International Nuclear Information System (INIS)

    Chain Reaction is a work of recent American political history. It seeks to explain how and why America came to depend so heavily on its experts after World War II, how those experts translated that authority into political clout, and why that authority and political discretion declined in the 1970s. The author's research into the internal memoranda of the Atomic Energy Commission substantiates his argument in historical detail. It was not the ravages of American anti-intellectualism, as so many scholars have argued, that brought the experts back down to earth. Rather, their decline can be traced to the very roots of their success after World War II. The need to over-state anticipated results in order to garner public support, incessant professional and bureaucratic specialization, and the sheer proliferation of expertise pushed arcane and insulated debates between experts into public forums at the same time that a broad cross section of political participants found it easier to gain access to their own expertise. These tendencies ultimately undermined the political influence of all experts. (author)

  8. Liquid crystalline order in polymers

    CERN Document Server

    Blumstein, Alexandre

    1978-01-01

    Liquid Crystalline Order in Polymers examines the topic of liquid crystalline order in systems containing rigid synthetic macromolecular chains. Each chapter of the book provides a review of one important area of the field. Chapter 1 discusses scattering in polymer systems with liquid crystalline order. It also introduces the field of liquid crystals. Chapter 2 treats the origin of liquid crystalline order in macromolecules by describing the in-depth study of conformation of such macromolecules in their unassociated state. The chapters that follow describe successively the liquid crystalli

  9. Synthesis of Fluorinated Polymers and Evaluation of Wettability

    Directory of Open Access Journals (Sweden)

    Tamami Kimura

    2016-03-01

    Full Text Available Two kinds of fluorinated polymers were synthesized: an acrylate polymer having a fluorinated triethylene glycol as a pendant group (2a and a fluoroalkyl acrylate polymer (2b. The contact angle of these fluorinated polymers against water, non-fluorinated alcohols and fluorinated alcohols were evaluated. As compared with the fluoroalkyl polymer (2b, fluoroethylene glycol polymer (2a showed smaller contact angle against water and non-fluorinated alcohols. This supports the proposition that changing the alkyl chain into the ethylene glycol-type chain gave some interaction between etheric oxygen and water or non-fluorinated alcohols. In addition, fluoroalkyl acrylate polymer (2b showed remarkably low values of critical surface tension.

  10. Self-Healing of Unentangled Polymer Networks with Reversible Bonds

    OpenAIRE

    Stukalin, Evgeny B.; Cai, Li-Heng; Kumar, N. Arun; Leibler, Ludwik; Rubinstein, Michael

    2013-01-01

    Self-healing polymeric materials are systems that after damage can revert to their original state with full or partial recovery of mechanical strength. Using scaling theory we study a simple model of autonomic self-healing of unentangled polymer networks. In this model one of the two end monomers of each polymer chain is fixed in space mimicking dangling chains attachment to a polymer network, while the sticky monomer at the other end of each chain can form pairwise reversible bond with the s...

  11. STATISTICAL MODELS FOR SEMI-RIGID NEMATIC POLYMERS

    Institute of Scientific and Technical Information of China (English)

    WANG Xinjiu

    1995-01-01

    Semi-rigid liquid crystal polymer is a class of liquid crystal polymers different from long rigid rod liquid crystal polymer to which the well-known Onsager and Flory theories are applied. In this paper, three statistical models for the semi-rigid nematic polymer were addressed. They are the elastically jointed rod model, worm-like chain model, and non-homogeneous chain model.The nematic-isotropic transition temperature was examined. The pseudo-second transition temperature is expressed analytically. Comparisons with the experiments were made and the agreements were found.

  12. Coloured Polymers

    OpenAIRE

    Pesando, I.

    1993-01-01

    We show that non-oriented coloured polymers (self--avoiding walks with different types of links) are in the same universality class of the ordinary self--avoiding walks, while the oriented coloured are not.

  13. Polymer electrolytes

    Czech Academy of Sciences Publication Activity Database

    Abbrent, Sabina; Greenbaum, S.; Peled, E.; Golodnitsky, D.

    Singapore: World Scientific Publishing, 2015 - (Dudney, N.; West, W.; Nanda, J.), s. 523-589 ISBN 978-981-4651-89-9 Institutional support: RVO:61389013 Keywords : polymer electrolytes * applications * mesuring techniques Subject RIV: CD - Macromolecular Chemistry

  14. The direct link model for polymer rings using topological field theory and the second topological moment in dense systems

    International Nuclear Information System (INIS)

    Polymer rings in solution are either permanently entangled or are not. Permanent topological restrictions give rise to additional entropic interactions apart from the ones arising due to mere chain flexibility or excluded volume. Conversely, entangled polymer rings systems may be formed by closing randomly entangled flexible linear chains. The dependence of linking numbers between randomly entangled rings on the chain length, more specifically the second topological moment 2>, i.e. the average squared linking number, may be determined. In this paper, an approach recently discussed in mathematical physics and called Abelian BF theory, is presented which allows one to express the linking constraint in its simplest form, the Gauss integral, in terms of two gauge fields. The model of Brereton and Shah for a single ring entangled with many other surrounding rings is rederived. The latter model is finally used to calculate the second topological moment, in agreement with a recent result by Ferrari, Kleinert, and Lazzizzera obtained using n-component φ4 theory for the limit n→0. (author)

  15. SYNTHESIS OF POLY(VINYLIDENE FLUORIDE) WITH LOW CONTENTS OF HEAD-TO-HEAD CHAIN

    Institute of Scientific and Technical Information of China (English)

    DUAN Youlu; YU Xiuying; XUE Ying; ZENG Miaoying; JI Shanrong

    1983-01-01

    The relations between polymerization conditions of vinylidene fluorideand contents of head-to-head chain in the polymer have been studied. It shows that the contents of head-to-head chain of the polymer are related to its polymerization temperature, but are not related with the kinds of initiators used. Therefore, poly(vinylidene fluoride) with low contents of head-to-head chain (ca. 3%)can be prepared under lower polymerization temperature. Plot of the contents of A chains against melting points of the polymer is linear, which can be expressed by an equation:A = 24.8 + 0.362 Tm(%).

  16. Density Functional Theory of Polymer Structure and Conformations

    Directory of Open Access Journals (Sweden)

    Zhaoyang Wei

    2016-04-01

    Full Text Available We present a density functional approach to quantitatively evaluate the microscopic conformations of polymer chains with consideration of the effects of chain stiffness, polymer concentration, and short chain molecules. For polystyrene (PS, poly(ethylene oxide (PEO, and poly(methyl methacrylate (PMMA melts with low-polymerization degree, as chain length increases, they display different stretching ratios and show non-universal scaling exponents due to their different chain stiffnesses. In good solvent, increase of PS concentration induces the decline of gyration radius. For PS blends containing short (m1 = 1 − 100 and long (m = 100 chains, the expansion of long chains becomes unobvious once m 1 is larger than 40, which is also different to the scaling properties of ideal chain blends.

  17. Rheology of cross-linked polymers and polymer foams: Theory and experimental results

    Science.gov (United States)

    Herman, John N.

    Typical polymers have a time-dependent response to loading which results in stress relaxation or creep. Models using springs/dashpots or Volterra integrals are capable of predicting the material response, but place little or no emphasis on the reasoning behind the response. This research proposes a microscopic reasoning behind polymer chain movement, while developing a model to predict the creep and stress relaxation of a polymer foam. Based on the theorized slip/stick of polymer chains as they slide past each other, this model successfully predicts the behavior of a PMI polymer foam under tensile loads. This model lends insights into polymer microscopic behavior, which may be used for the development of future polymer materials. When possible, industry standard test methods are used to obtain tensile creep and stress relaxation results from rectangular specimens of Rohacell 31 IG foam. A common set of material parameters is fitted to the data, validating the micromechanic reasoning to polymer chain movement. To gain insight into observed test result variability, an investigation of the elastic modulus and material density relationship is performed using nominal foam densities of 31 kg/m3, 51 kg/m3,, 71 kg/m3. Additional testing and modeling is performed to validate the model under load/partial-unload/ hold, load/unload/recovery, and load/instantaneous-unload test cycles. The model successfully captures the observed material nuances during these more complex loading cycles.

  18. Crater Chains

    Science.gov (United States)

    2003-01-01

    [figure removed for brevity, see original site] The large crater at the top of this THEMIS visible image has several other craters inside of it. Most noticeable are the craters that form a 'chain' on the southern wall of the large crater. These craters are a wonderful example of secondary impacts. They were formed when large blocks of ejecta from an impact crashed back down onto the surface of Mars. Secondaries often form radial patterns around the impact crater that generated them, allowing researchers to trace them back to their origin.Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.Image information: VIS instrument. Latitude 19.3, Longitude 347.5 East (12.5 West). 19 meter/pixel resolution.

  19. Internal friction and mode relaxation in a simple chain model

    OpenAIRE

    Fugmann, S.; I. M. Sokolov

    2009-01-01

    We consider equilibrium relaxation properties of the end-to-end distance and of principal components in a one-dimensional polymer chain model with nonlinear interaction between the beads. While for the single-well potentials these properties are similar to the ones of a Rouse chain, for the double-well interaction potentials, modeling internal friction, they differ vastly from the ones of the harmonic chain at intermediate times and intermediate temperatures. This minimal description within a...

  20. A constitutive law for degrading bioresorbable polymers.

    Science.gov (United States)

    Samami, Hassan; Pan, Jingzhe

    2016-06-01

    This paper presents a constitutive law that predicts the changes in elastic moduli, Poisson's ratio and ultimate tensile strength of bioresorbable polymers due to biodegradation. During biodegradation, long polymer chains are cleaved by hydrolysis reaction. For semi-crystalline polymers, the chain scissions also lead to crystallisation. Treating each scission as a cavity and each new crystal as a solid inclusion, a degrading semi-crystalline polymer can be modelled as a continuum solid containing randomly distributed cavities and crystal inclusions. The effective elastic properties of a degrading polymer are calculated using existing theories for such solid and the tensile strength of the degrading polymer is predicted using scaling relations that were developed for porous materials. The theoretical model for elastic properties and the scaling law for strength form a complete constitutive relation for the degrading polymers. It is shown that the constitutive law can capture the trend of the experimental data in the literature for a range of biodegradable polymers fairly well. PMID:26971070

  1. Critical adsorption of polymers in a medium with long-range correlated quenched disorder

    International Nuclear Information System (INIS)

    The process of adsorption on a planar wall of long flexible polymer chains in a medium with quenched long-range correlated disorder is investigated. We focus on the case of correlations between defects or impurities that decay according to the power law x-a for large distances x, where x=(r,z). A field theoretical approach in d=4-ε and directly in d=3 dimensions up to one-loop order for the semi-infinite |φ|4 m-vector model (in the limit m→0) with a planar boundary is used. The whole set of surface critical exponents at the adsorption threshold T=Ta, which separates the nonadsorbed region from the adsorbed one, is obtained. Moreover, we calculate the crossover critical exponent Φ and the set of exponents associated with it. We perform calculations in a double ε=4-d and δ=4-a expansion and also for a fixed dimension d=3, up to one-loop order for different values of the correlation parameter 2< a≤3. The obtained results indicate that for systems with long-range correlated quenched disorder a different set of surface critical exponents arises. All the surface critical exponents depend on a. Hence, the presence of long-range correlated disorder influences the process of adsorption of long flexible polymer chains on a wall in a significant way

  2. A thermodynamic study of shear banding in polymer solutions

    Science.gov (United States)

    Hooshyar, Soroush; Germann, Natalie

    2016-06-01

    Although shear banding is a ubiquitous phenomenon observed in soft materials, the mechanisms that give rise to shear-band formation are not always the same. In this work, we develop a new two-fluid model for semi-dilute entangled polymer solutions using the generalized bracket approach of nonequilibrium thermodynamics. The model is based on the hypothesis that the direct coupling between polymer stress and concentration is the driving mechanism of steady shear-band formation. To obtain smooth banded profiles in the two-fluid framework, a new stress-diffusive term is added to the time evolution equation for the conformation tensor. The advantage of the new model is that the differential velocity is treated as a state variable. This allows a straightforward implementation of the additional boundary conditions arising from the derivative diffusive terms with respect to this new state variable. To capture the overshoot of the shear stress during the start of a simple shear flow, we utilize a nonlinear Giesekus relaxation. Moreover, we include an additional relaxation term that resembles the term used in the Rouse linear entangled polymer model to account for convective constraint release and chain stretch to generate the upturn of the flow curve at large shear rates. Numerical calculations performed for cylindrical Couette flow confirm the independency of the solution from the deformation history and initial conditions. Furthermore, we find that stress-induced migration is the responsible diffusive term for steady-state shear banding. Because of its simplicity, the new model is an ideal candidate for the use in the simulation of more complex flows.

  3. Hyperbranched polymers from polymerization in solid state

    International Nuclear Information System (INIS)

    The macroscopic properties of polymers are directly related to the chemical characteristics of the monomeric units and also with the geometric arrangement of polymer chains. Thus, polymers were synthesized from two well-known chelators EDTA and EDA. We evaluated the conditions for the polymerization of the precursors in the solid state. The polymerization was carried out varying the proportions of reagents, aiming the polymers with different degrees of chain branching and the materials were characterized by FTIR. The materials obtained from the best condition for synthesis were purified by size-exclusion chromatography of and were subjected to characterization by FTIR and NMR of 1H and 13C. The content of end groups in these samples was determined by back titration. (author)

  4. Nanowear on polymer films of different architecture.

    Science.gov (United States)

    Berger, R; Cheng, Y; Förch, R; Gotsmann, B; Gutmann, J S; Pakula, T; Rietzler, U; Schärtl, W; Schmidt, M; Strack, A; Windeln, J; Butt, H-J

    2007-03-13

    In this paper, we describe atomic force microscope (AFM) friction experiments on different polymers. The aim was to analyze the influence of the physical architecture of the polymer on the degree and mode of wear and on the wear mode. Experiments were carried out with (1) linear polystyrene (PS) and cycloolefinic copolymers of ethylene and norbornene, which are stabilized by entanglements, (2) mechanically stretched PS, (3) polyisoprene-b-polystyrene diblock copolymers, with varying composition, (4) brush polymers consisting of a poly(methyl methacrylate) (PMMA) backbone and PS side chains, (5) PMMA and PS brushes grafted from a silicon wafer, (6) plasma-polymerized PS, and (7) chemically cross-linked polycarbonate. For linear polymers, wear depends critically on the orientation of the chains with respect to the scan direction. With increasing cross-link density, wear was reduced and ripple formation was suppressed. The cross-linking density was the dominating material parameter characterizing wear. PMID:17279781

  5. Graphs: Associated Markov Chains

    OpenAIRE

    Murthy, Garimella Rama

    2012-01-01

    In this research paper, weighted / unweighted, directed / undirected graphs are associated with interesting Discrete Time Markov Chains (DTMCs) as well as Continuous Time Markov Chains (CTMCs). The equilibrium / transient behaviour of such Markov chains is studied. Also entropy dynamics (Shannon entropy) of certain structured Markov chains is investigated. Finally certain structured graphs and the associated Markov chains are studied.

  6. Rheology and morphology of no-slip sheared polymer nanocomposite under creep condition

    Science.gov (United States)

    Mortezapour, Saba; Eslami, Hossein; Nedaaee Oskoee, Ehsan

    2015-07-01

    Dissipative particle dynamics simulations are performed on wet polymer nanocomposite blends under the discrete imposed velocity profile and no-slip boundary conditions. To be able to study the chain length dependency of the rheological properties, a number of blends of mono-disperse polymer chains of lengths varying from 10 to 100 repeat units and nanoparticles of diameters 2.5 and 5 have been simulated. The wall velocity was imposed on a thin polymer layer (the no-slip layer). Linear velocity profiles for polymer confined in the pore were observed at the steady state. We found that the flow has a shear thinning effect on the chains with a radius of gyration less than the filler radius. Long chains (with a radius of gyration longer than the filler's radius), however, obey the Newtonian behavior over a much wider shear rate than that which causes shear thinning in short chains. The effect of particle-monomer interactions, polymer entanglements, chain morphology, and link formation on the shear rate dependency of the viscosity coefficient has been studied. Our results show that the particle-polymer interactions have no effect on shear thinning behavior of the blend. In contrast, the long range polymer-polymer interactions and the chain length have considerable effects on the rheological behavior of the blend. Finally, the phase diagram of the rheological properties of polymer nanocomposite as a function of strain rate and the chain length is extracted.

  7. Modelling and Risk Management in the Offshore and Marine Industry Supply Chain

    OpenAIRE

    Carman Lee; K.C. Liew

    2012-01-01

    Supply chain risk management is primarily a process that involves the identification, assessment and mitigation of risks that arise in a particular supply chain system. Pertaining to that, the offshore and marine industry is one of the many industries that have seldom received much consideration when it comes to management of the supply chain system. The rig building facet of the offshore and marine industry was thus chosen as the main focus of the project to manage the risks that arise in a ...

  8. New method for preparing a liquid crystal polymer that exhibits linearly polarized white fluorescence

    Science.gov (United States)

    Zheng, Shi-jun; Kun, Wang; Kobayashi, Takaomi

    2011-03-01

    With the aim of developing a single-chain white-light-emitting polymer, liquid crystal (LC) polymers with a shish-kebab-type moiety on their cross-conjugated (p-phenylene)s-poly(p-phenylenevinylene)s main chain were synthesized by Gilch polymerization. They were characterized by nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and polarizing optical microscopy (POM). 1H-NMR indicated that the polymers had a shish-kebab structure, which strongly suppressed the formation of structural defects in the polymers. DSC revealed that the polymers had thermotropic LC properties, indicating that the LC polymers were enantiotropic. XRD showed that the polymers had a mesophase, which implies that they were in a smectic LC phase. A polymer with "kebabs" of 2,5-bis(4'-alkoxyphenyl)benzene was combined with an aligned polyimide film with orientated microgrooves. The polymer main chain was aligned due to the orientation of the "kebabs" of the uniform cross-conjugated structure. It lay between the kebabs and the "shish" of the polymer main chains. The aligned polymer main chain emitted yellow light while and the oriented LC side chains emitted blue light emission. These two emissions resulted in linearly polarized white fluorescence.

  9. Squamous cell carcinoma arising in mature cystic teratoma of ovary

    Directory of Open Access Journals (Sweden)

    Ranu Patni

    2014-01-01

    Full Text Available Squamous cell carcinoma of the ovary is a rare condition and usually arises in mature cystic teratoma (MCT or dermoid cyst of the ovary. The reported incidence of malignant transformation in MCT is approximately 2%. A case of squamous cell carcinoma arising in a dermoid cyst of the ovary presenting at an early stage is presented here. A 53-year-old postmenopausal lady, presented with the complaint of pain in right lower abdomen since one month and a large complex abdomino-pelvic mass on examination and investigations. Final histopathology was reported as squamous cell carcinoma of left ovary arising from dermoid cyst and a benign dermoid cyst in the right ovary. The patient was assigned to squamous cell carcinoma of the ovary arising in a mature cystic teratoma, surgical stage Ic2. In view of the poor prognosis, adjuvant chemotherapy was started.

  10. Localised fibrous mesothelioma arising in an intralobar pulmonary sequestration.

    OpenAIRE

    Paksoy, N.; Demircan, A.; Altiner, M; Artvinli, M

    1992-01-01

    A localised fibrous mesothelioma arising from an intralobar lung sequestration occurred in a 64 year old Turkish woman. This appears to be the first report of a mesothelioma occurring within a pulmonary sequestration.

  11. Malignant melanoma arising in mature cystic teratoma of the ovary

    OpenAIRE

    Heidi E Godoy; Kesterson, Joshua P.; Kasznica, John M.; Lele, Shashikant

    2011-01-01

    ► Teratomas are composed of elements of all three germ layers, all potentially capable of undergoing malignant transformation. ► A case of malignant melanoma arising in a mature teratoma is presented.

  12. Identities involving Bessel polynomials arising from linear differential equations

    OpenAIRE

    Kim, Taekyun; Kim, Dae San

    2016-01-01

    In this paper, we study linear di?erential equations arising from Bessel polynomials and their applications. From these linear differential equations, we give some new and explicit identities for Bessel polynomials.

  13. Secondary osteosarcoma arising after treatment for childhood hematologic malignancies

    OpenAIRE

    Okada, Atsushi; Hatori, Masahito; Hosaka, Masami; Watanuki, Munenori; Itoi, Eiji

    2009-01-01

    Secondary osteosarcoma arising after the treatment of hematologic malignancies other than Hodgkin's lymphoma is rare. We report two cases of secondary osteosarcoma arising after treatment for childhood hematologic malignancies (non-Hodgkin's lymphoma and lymphoblastic leukemia). A 10-year-old boy, at the age of 3, was diagnosed with non-Hodgkin's lymphoma. He received chemotherapy, radiation, and bone-marrow transplantation and then was in complete remission. At 6 years, he complained of incr...

  14. MYC Amplification in Angiosarcoma Arising from an Arteriovenous Graft Site

    Directory of Open Access Journals (Sweden)

    Kristen M. Paral

    2015-01-01

    Full Text Available Angiosarcoma arising in association with an arteriovenous graft (AVG or fistula is a unique clinicopathologic scenario that appears to be gaining recognition in the literature. Among reported cases, none has described high-level MYC gene amplification, a genetic aberration that is increasingly unifying the various clinicopathologic subdivisions of angiosarcoma. We therefore report the MYC gene status in a case of angiosarcoma arising at an AVG site.

  15. Number theory arising from finite fields analytic and probabilistic theory

    CERN Document Server

    Knopfmacher, John

    2001-01-01

    ""Number Theory Arising from Finite Fields: Analytic and Probabilistic Theory"" offers a discussion of the advances and developments in the field of number theory arising from finite fields. It emphasizes mean-value theorems of multiplicative functions, the theory of additive formulations, and the normal distribution of values from additive functions. The work explores calculations from classical stages to emerging discoveries in alternative abstract prime number theorems.

  16. Multiple Ectopic Hepatocellular Carcinomas Arising in the Abdominal Cavity

    OpenAIRE

    Miyake, Toru; Hoshino, Seiichiro; Yoshida, Yoichiro; AISU, NAOYA; Tanimura, Syu; Hisano, Satoshi; Kuno, Nobuaki; Sohda, Tetsuro; Sakisaka, Shotaro; Yamashita, Yuichi

    2012-01-01

    Ectopic hepatocellular carcinoma (HCC) is a very rare clinical entity that is defined as HCC arising from extrahepatic liver tissue. This report presents a case of ectopic multiple HCC arising in the abdominal cavity. A 42-year-old otherwise healthy male presented with liver dysfunction at a general health checkup. Both HCV antibody and hepatitis B surface antigen were negative. Laboratory examination showed elevations in serum alpha-fetoprotein and PIVKA-II. Ultrasonography and computed tomo...

  17. Cylindrical microemulsions: a polymer-like phase ?

    OpenAIRE

    Safran, S. A.; Turkevich, L.A.; Pincus, P

    1984-01-01

    The regions of stability of spherical, cylindrical, and lamellar phases of microemulsions are calculated within mean-field theory. In the cylindrical phase, thermal fluctuations determine a temperature dependent persistence length below which the cylinders are rigid (rod-like) and above which the cylinders are flexible (polymer-like). The length of the polymer-like chains depends on concentration and temperature. The radii of gyration of these flexible microemulsions are also calculated.

  18. Temperature-concentration diagram of polymer solutions

    International Nuclear Information System (INIS)

    A (T,C) diagram - were T is the temperature, C the monomer concentration - is described for polymer solutions, from a tricritical approach to the polymer theta point. Four different regions are defined in this diagram. For each of these regions the T, N, C, dependence of the mean square end to end distance of a chain, the screening length, the osmotic pressure, and the second virial coefficient are calculated. A scaling form is also given for the equation of state

  19. Brownian particles in supramolecular polymer solutions

    OpenAIRE

    Gucht, van der, J.; Besseling, N.A.M.; Knoben, W.; Bouteiller, L; Cohen Stuart, M. A.

    2003-01-01

    The Brownian motion of colloidal particles embedded in solutions of hydrogen-bonded supramolecular polymers has been studied using dynamic light scattering. At short times, the motion of the probe particles is diffusive with a diffusion coefficient equal to that in pure solvent. At intermediate time scales the particles are slowed down as a result of trapping in elastic cages formed by the polymer chains, while at longer times the motion is diffusive again, but with a much smaller diffusion c...

  20. Subdiffraction-Resolution Optical Measurements of Molecular Transport in Thin Polymer Films.

    Science.gov (United States)

    Pahal, Suman; Raichur, Ashok M; Varma, Manoj M

    2016-06-01

    The measurement of molecular transport within polymer films yields information about the internal structural organization of the films and is useful in applications such as the design of polymeric capsules for drug delivery. Layer-by-layer assembly of polyelectrolyte multilayer films has been widely used in such applications where the multilayer structure often exhibits anisotropic transport resulting in different diffusivities in the lateral (parallel to the film) and transverse (normal to the film) directions. Although lateral transport can be probed using techniques such as fluorescence recovery after photobleaching (FRAP), it cannot be applied to probing transverse diffusivity in polymer films smaller than the diffraction limit of light. Here we present a technique to probe the transport of molecules tagged with fluorphores in polymer films thinner than the optical diffraction limit using the modulation of fluorescence emission depending on the distance of the tagged molecules from a metal surface. We have used this technique to probe the diffusion of proteins biotin and bovine serum albumin (BSA) in polyelectrolyte multilayer films. We also studied the interdiffusion of chains in multilayer films using this technique. We observed a 3 order of magnitude increase in interdiffusion as a function of the ionic strength of the medium. This technique, along with FRAP, will be useful in studying anisotropic transport in polymer films, even those thinner than the diffraction limit, because the signal in this technique arises only from transverse and not lateral transport. Finally, this technique is also applicable to studying the diffusion of chromophore-labeled species within a polymer film. We demonstrate this aspect by measuring the transverse diffusion of methylene blue in the PAH-PAA multilayer system. PMID:27175850