Self-Assembly of Narrowly Dispersed Brush Diblock Copolymers with Domain Spacing more than 100 nm

Science.gov (United States)

Gu, Weiyin; Sveinbjornsson, Benjamin; Hong, Sung Woo; Grubbs, Robert; Russell, Thomas

2012-02-01

Self-assembled structures of high molecular weight (MW), narrow molecular weight distribution brush block copolymers containing polylactic acid (PLA) and polystyrene (PS) side chains with similar MWs were studied in both the melt and thin films. The polynorbornene-backbone-based brush diblock copolymers containing approximately equal volume fractions of each block self-assembled into highly ordered lamellae with domain spacing over 100 nm, as revealed by SAXS, GISAXS and AFM. The domain size increased approximately linearly with backbone length, which indicated an extended conformation of the backbone in the ordered state. The length of side chains also played a significant role in terms of controlling the domain size. As the degree of polymerization (DP) increased, the symmetric brush diblock copolymers with longer side chains tended to form larger lamellar microdomains in comparison to those that have the same DP but shorter side chains.

Directing self-assembly of gold nanoparticles in diblock copolymer scaffold

Science.gov (United States)

Li, Qifang; He, Jinbo; Glogowski, Elizabeth; Emrick, Todd; Russell, Thomas

2007-03-01

A versatile hierarchical approach for directing self -assembly of gold nanostructures with size 2-3nm in diblock copolymer scaffolds is found. Diblock copolymer polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) is used to form a regular scaffold of highly anisotropic, stripe-like domains, and controlled differential wetting by dichloromethane and thermal annealing guides gold nanoparticles with half hydrophilic ligand to aggregate selectively along the scaffold, producing highly organized metal nanostructures. In as-cast block-copolymer and gold nanoparticles thin films, micelle structure and gold nanoparticles random distribution on scaffold are typically observed. However, samples annealed in dichloromethane exhibit well-defined short-range ordered nanostructure with gold nanoparticles located at the interface of PS and P2VP nanoscale domain. After annealing at 170 C, the gold nanoparticles at interface migrated into the middle of P2VP phase and exhibited long-range ordered hierarchical structures. Synergistic interactions between the gold nanoparticles and the PS-b-P2VP caused an orientation of the microdomains normal to the film surface.

Square and Rectangular Arrays from Directed Assembly of Sphere-forming Diblock Copolymers in Thin Films

Science.gov (United States)

Ji, Shengxiang; Nagpal, Umang; Liao, Wen; de Pablo, Juan; Nealey, Paul

2010-03-01

Patterns of square and rectangular arrays with nanoscale dimensions are scientifically and technologically important. Fabrication of square array patterns in thin films has been demonstrated by directed assembly of cylinder-forming diblock copolymers on chemically patterned substrates, supramolecular assembly of diblock copolymers, and self-assembly of triblock terpolymers. However, a macroscopic area of square array patterns with long-range order has not been achieved, and the fabrication of rectangular arrays has not been reported so far. Here we report a facile approach for fabricating patterns of square and rectangular arrays by directing the assembly of sphere-forming diblock copolymers on chemically patterned substrates. On stripe patterns, a square arrangement of half spheres, corresponding to the (100) plane of the body-centred cubic (BCC) lattice, formed on film surfaces. When the underlying pattern periods mismatched with the copolymer period, the square pattern could be stretched (up to ˜60%) or compressed (˜15%) to form rectangular arrays. Monte Carlo simulations have been further used to verify the experimental results and the 3-dimensional arrangements of spheres.

Synthesis, characterization and photoinduction of optical anisotropy in liquid crystalline diblock azo-copolymers

NARCIS (Netherlands)

Forcen, P.; Oriol, L.; Sanchez, S.; Alcala, R.; Hvilsted, S.; Jankova, K.; Loos, J.

2007-01-01

Diblock copolymers with polymethyl methacrylate and side chain liquid crystalline (LC) azopolymethacrylate blocks were synthesized by atom transfer radical polymerization (ATRP). The azobenzene content in these copolymers ranges from 52 to 7 wt %. For an azo content down to 20% they exhibit a LC

Adsorption kinetics of diblock copolymers from a micellar solution on silica and titania.

NARCIS (Netherlands)

Bijsterbosch, H.D.; Cohen Stuart, M.A.; Fleer, G.J.

1998-01-01

The solution and adsorption behavior of a series of diblock copolymers of hydrophobic poly(dimethyl siloxane) and hydrophilic poly(2-ethyl-2-oxazoline) was studied. These block copolymers formed large polydisperse micelles in an aqueous solution. The critical micelle concentration was lower than 2

Position transitions of polymer-grafted nanoparticles in diblock-copolymer nanocomposites

Directory of Open Access Journals (Sweden)

2011-04-01

Full Text Available Self-assembly of block copolymer/nanoparticle blends has promising applications in the design and fabrication of novel functional nanomaterials. Precise control of the spatial positions of nanoparticles within block copolymer-based nanomaterials is crucial to achieve some special physical properties and functions. Here, we employ the self-consistent field method to theoretically investigate the self-assembly of polymer grafted-nanoparticles in a diblock copolymer. It is found that by varying the size and selectivity of nanoparticles, one can not only produce various self-assembled nanostructures but also modulate the spatial positions of the nanoparticles, either at the copolymer interfaces or in the center of one copolymer phase, within the nanostructures. A denser grafted polymer brush plays a role of shielding effect on nanoparticles and can position them into the center of one copolymer phase. The nanostructural transition we observed is dictated by the competition between entropy and enthalpy. On the basis of a number of simulations, two phase diagrams of self-assembled nanostructures are constructed. This study may be helpful for optimal design of advanced materials with desired nanostructures and enhanced performance.

Diblock copolymers of polystyrene-b-poly(1,3-cyclohexadiene) exhibiting unique three-phase microdomain morphologies

KAUST Repository

Misichronis, Konstantinos

2016-03-31

The synthesis and molecular characterization of a series of conformationally asymmetric polystyrene-block-poly(1,3-cyclohexadiene) (PS-b-PCHD) diblock copolymers (PCHD: ∼90% 1,4 and ∼10% 1,2), by sequential anionic copolymerization high vacuum techniques, is reported. A wide range of volume fractions (0.27≤ϕPS≤0.91) was studied by transmission electron microscopy and small-angle X-ray scattering in order to explore in detail the microphase separation behavior of these flexible/semiflexible diblock copolymers. Unusual morphologies, consisting of PCHD core(PCHD-1,4)-shell(PCHD-1,2) cylinders in PS matrix and three-phase (PS, PCHD-1,4, PCHD-1,2) four-layer lamellae, were observed suggesting that the chain stiffness of the PCHD block and the strong dependence of the interaction parameter χ on the PCHD microstructures are important factors for the formation of this unusual microphase separation behavior in PS-b-PCHD diblock copolymers. © 2016 Wiley Periodicals, Inc.

Diblock copolymers of polystyrene-b-poly(1,3-cyclohexadiene) exhibiting unique three-phase microdomain morphologies

KAUST Repository

Misichronis, Konstantinos; Chen, Jihua; Kahk, Jong K.; Imel, Adam; Dadmun, Mark; Hong, Kunlun; Hadjichristidis, Nikolaos; Mays, Jimmy W.; Avgeropoulos, Apostolos

2016-01-01

The synthesis and molecular characterization of a series of conformationally asymmetric polystyrene-block-poly(1,3-cyclohexadiene) (PS-b-PCHD) diblock copolymers (PCHD: ∼90% 1,4 and ∼10% 1,2), by sequential anionic copolymerization high vacuum techniques, is reported. A wide range of volume fractions (0.27≤ϕPS≤0.91) was studied by transmission electron microscopy and small-angle X-ray scattering in order to explore in detail the microphase separation behavior of these flexible/semiflexible diblock copolymers. Unusual morphologies, consisting of PCHD core(PCHD-1,4)-shell(PCHD-1,2) cylinders in PS matrix and three-phase (PS, PCHD-1,4, PCHD-1,2) four-layer lamellae, were observed suggesting that the chain stiffness of the PCHD block and the strong dependence of the interaction parameter χ on the PCHD microstructures are important factors for the formation of this unusual microphase separation behavior in PS-b-PCHD diblock copolymers. © 2016 Wiley Periodicals, Inc.

Diblock Copolymer/Layered Silicate Nanocomposite Thin Film Stability

Science.gov (United States)

Limary, Ratchana; Green, Peter

2000-03-01

The stability of thin film symmetric diblock copolymers blended with layered silicate nanocomposites were examined using a combination of optical microscopy, atomic force microscopy (AFM), and X-ray diffraction (XRD). Two cases were examined PS-b-PMMA (polystyrene-b-polymethylacrylate) blended with montmorillonite stoichiometrically loaded with alkyl ammonium ions, OLS(S), and PS-b-PMMA blended with montmorillonite loaded with excess alkyl ammonium ions, OLS(E). XRD spectra show an increase in the gallery spacing of the OLSs, indicating that the copolymer chains have intercalated the layered silicates. AFM images reveal a distinct difference between the two nanocomposite thin films: regions in the vicinity of OLS(S) aggregates were depleted of material, while in the vicinity of OLS(E) aggregates, dewetting of the substrate occurred. We show that the stability of the copolymer/OLS nanocomposite films is determined by the enthalpic driving force associated with intercalation of the copolymer chains into the galleries of the modified OLS layers and by the substrate/organic modifier interactions.

Molecular Interaction Control in Diblock Copolymer Blends and Multiblock Copolymers with Opposite Phase Behaviors

Science.gov (United States)

Cho, Junhan

2014-03-01

Here we show how to control molecular interactions via mixing AB and AC diblock copolymers, where one copolymer exhibits upper order-disorder transition and the other does lower disorder-order transition. Linear ABC triblock copolymers possessing both barotropic and baroplastic pairs are also taken into account. A recently developed random-phase approximation (RPA) theory and the self-consistent field theory (SCFT) for general compressible mixtures are used to analyze stability criteria and morphologies for the given systems. It is demonstrated that the copolymer systems can yield a variety of phase behaviors in their temperature and pressure dependence upon proper mixing conditions and compositions, which is caused by the delicate force fields generated in the systems. We acknowledge the financial support from National Research Foundation of Korea and Center for Photofunctional Energy Materials.

Effect of sequence dispersity on morphology of tapered diblock copolymers from molecular dynamics simulations.

Science.gov (United States)

Levine, William G; Seo, Youngmi; Brown, Jonathan R; Hall, Lisa M

2016-12-21

Tapered diblock copolymers are similar to typical AB diblock copolymers but have an added transition region between the two blocks which changes gradually in composition from pure A to pure B. This tapered region can be varied from 0% (true diblock) to 100% (gradient copolymer) of the polymer length, and this allows some control over the microphase separated domain spacing and other material properties. We perform molecular dynamics simulations of linearly tapered block copolymers with tapers of various lengths, initialized from fluids density functional theory predictions. To investigate the effect of sequence dispersity, we compare systems composed of identical polymers, whose taper has a fixed sequence that most closely approximates a linear gradient, with sequentially disperse polymers, whose sequences are created statistically to yield the appropriate ensemble average linear gradient. Especially at high segregation strength, we find clear differences in polymer conformations and microstructures between these systems. Importantly, the statistical polymers are able to find more favorable conformations given their sequence, for instance, a statistical polymer with a larger fraction of A than the median will tend towards the A lamellae. The conformations of the statistically different polymers can thus be less stretched, and these systems have higher overall density. Consequently, the lamellae formed by statistical polymers have smaller domain spacing with sharper interfaces.

Stress relaxation experiments on a lamellar polystyrene-polyisoprene diblock copolymer melt

DEFF Research Database (Denmark)

Holmqvist, P.; Castelletto, V.; Hamley, I.W.

2001-01-01

The non-linear rheology of the lamellar phase of a polystyrene-polyisoprene diblock copolymer is studied by oscillatory shear experiments. The relaxation of the shear modulus, G(t, gamma) is studied as a function of strain amplitude, gamma, up to large amplitude strains, gamma = 100%. The decay...... of G(t, gamma) is analysed using the model-independent CONTIN inverse Laplace transform algorithm to obtain a series of relaxation times, which reveals multiple relaxation processes. The timescale for the fastest relaxation processes is compared to those previously observed for diblock copolymer melts...... via dynamic light scattering experiments. The slowest relaxation process may be related to the shear-induced orientation of the lamellae. It is shown that time-strain separability G(t, gamma)= G(t)h(gamma) can be applied, and the damping function h(gamma) is consistent with a strongly strain...

Microphase separation of a symmetric poly(styrene-B-paramethylstyrene) diblock copolymer

DEFF Research Database (Denmark)

Bartels, V.T.; Abetz, V.; Mortensen, K.

1994-01-01

The microphase separation in a symmetric diblock copolymer consisting of polystyrene and polyparamethylstyrene has been studied by small-angle neutron scattering. The observed peak changes with temperature in intensity, shape and position. The peak position shifts at the microphase separation tra...

Poly(4-vinylpyridine)-block-poly(N-acryloylpiperidine) diblock copolymers: synthesis, self-assembly and interaction

NARCIS (Netherlands)

Hofman, Anton H.; Alberda van Ekenstein, Gerhard; Woortman, Albert; ten Brinke, Gerrit; Loos, Katja

2015-01-01

Controlled radical polymerization of 4-vinylpyridine (4VP) and N-acryloylpiperidine (API) by the RAFT process allowed preparation of well-defined double hydrogen bond accepting P4VP-b-PAPI diblock copolymers. The miscibility of this new monomer pair was studied via a random copolymer blend approach

Crystallization in diblock copolymer thin films at different degrees of supercooling

DEFF Research Database (Denmark)

Darko, C.; Botiz, I.; Reiter, G.

2009-01-01

The crystalline structures in thin films of polystyrene-b-poly(ethylene oxide) (PS-b-PEO) diblock copolymers were studied in dependence on the degree of supercooling. Atomic force microscopy showed that the crystalline domains (lamellae) consist of grains, which are macroscopic at low and interme...

One-Pot Synthesis of Charged Amphiphilic Diblock and Triblock Copolymers Via High-Throughput Cu(0-Mediated Polymerization

Directory of Open Access Journals (Sweden)

Lenny Voorhaar

2017-07-01

Full Text Available Block copolymers containing functionalized monomers, for example those containing charged groups, can be used for many purposes, one of which is the design of polymeric supramolecular materials based on electrostatic interactions. In this paper the synthesis of diblock copolymers and ABA-triblock copolymers containing poly(n-butyl acrylate as a first or middle block and poly(2-(dimethylaminoethyl acrylate, poly(1-ethoxyethyl acrylate and poly(1-ethoxyethyl-2-carboxyethyl acrylate as second or outer blocks, resulting in block copolymers that can contain positive or negative charges, is reported. The polymerizations were performed and optimized via one-pot sequential monomer addition reactions via Cu(0-mediated polymerization using an automated parallel synthesizer. Different initiators, monomer concentrations and polymerization times were tested. While a bromide-containing initiator led to the best results for most monomers, when polymerizing 2-(dimethylaminoethyl acrylate the use of a chloride-containing initiator was necessary. Due to the slower polymerization using this initiator, a longer polymerization time was needed before addition of the second monomer. Using the optimized conditions, the diblock and triblock copolymers could be synthesized with good control over molecular weight and dispersities around 1.1 were obtained.

Adsorption and Aqueous Lubricating Properties of Charged and Neutral Amphiphilic Diblock Copolymers at a Compliant, Hydrophobic Interface

DEFF Research Database (Denmark)

Røn, Troels; Javakhishvili, Irakli; Jankova Atanasova, Katja

2013-01-01

We have investigated the adsorption and lubricating properties of neutral and charged amphiphilic diblock copolymers at a hydrophobic polydimethylsiloxane (PDMS) interface in an aqueous environment. The diblock copolymers consist of a hydrophilic block of either neutral poly(ethylene glycol) (PEG......) or negatively charged poly(acrylic acid) (PAA) and of a hydrophobic block of polystyrene (PS) or poly(2-methoxyethyl acrylate) (PMEA), thus generating PEG-b-X or PAA-b-X, where X block is either PS or PMEA. The molecular weight ratios were roughly 1:1 with each block ca. 5 kDa. Comparing the neutral PEG...... effective adsorption only when PMEA was employed as the anchoring block. For PAA-b-PS, the poor adsorption properties are chiefly attributed to micellization due to the high interfacial tension between the PS core and water. The poor lubricating properties of PAA-b-PS diblock copolymer for a PDMS...

Investigating self-assembly and metal nanoclusters in aqueous di-block copolymers solutions

CERN Document Server

Lo Celso, F; Triolo, R; Triolo, A; Strunz, P; Bronstein, L; Zwanziger, J; Lin, J S

2002-01-01

Self-assembling properties of di-block copolymers/ surfactant hybrids in aqueous solution can be exploited to obtain metal nanoparticles stable dispersion. Results will be presented here for polystyrene-block-poly(ethylene oxide) solutions. A SANS structural investigation has been performed over different molecular weights of both hydrophilic and hydrophobic block, by varying temperature and concentration of the copolymer. A SAXS characterization of micellar systems containing Pt nanoparticles is reported. (orig.)

Transformations to and from the gyroid phase in a diblock copolymer

DEFF Research Database (Denmark)

Vigild, Martin Etchells; Almdal, Kristoffer; Mortensen, K

1998-01-01

the ordered phases and the order-order transitions exhibited by a poly(ethylene-alt-propylene)-poly-(dimethylsiloxane) diblock copolymer. An intermediate structure-very similar to the hexagonal perforated layer (HPL) phase reported in other diblock systems-proves to be metastable, and we study the kinetics...... and epitaxy of its relaxation to the "gyroid" phase of Ia (3) over bar d symmetry. Likewise we study the relaxation of a supercooled hexagonal phase to the gyroid structure and also observe that the gyroid phase is bypassed in a slow cool from the hexagonal phase to the HPL-like structure. The origin...

Nanoscale protein arrays of rich morphologies via self-assembly on chemically treated diblock copolymer surfaces

International Nuclear Information System (INIS)

Song Sheng; Milchak, Marissa; Zhou Hebing; Lee, Thomas; Hanscom, Mark; Hahm, Jong-in

2013-01-01

Well-controlled assembly of proteins on supramolecular templates of block copolymers can be extremely useful for high-throughput biodetection. We report the adsorption and assembly characteristics of a model antibody protein to various polystyrene-block-poly(4-vinylpyridine) templates whose distinctive nanoscale structures are obtained through time-regulated exposure to chloroform vapor. The strong adsorption preference of the protein to the polystyrene segment in the diblock copolymer templates leads to an easily predictable, controllable, rich set of nanoscale protein morphologies through self-assembly. We also demonstrate that the chemical identities of various subareas within individual nanostructures can be readily elucidated by investigating the corresponding protein adsorption behavior on each chemically distinct area of the template. In our approach, a rich set of intricate nanoscale morphologies of protein arrays that cannot be easily attained through other means can be generated straightforwardly via self-assembly of proteins on chemically treated diblock copolymer surfaces, without the use of clean-room-based fabrication tools. Our approach provides much-needed flexibility and versatility for the use of block copolymer-based protein arrays in biodetection. The ease of fabrication in producing well-defined and self-assembled templates can contribute to a high degree of versatility and simplicity in acquiring an intricate nanoscale geometry and spatial distribution of proteins in arrays. These advantages can be extremely beneficial both for fundamental research and biomedical detection, especially in the areas of solid-state-based, high-throughput protein sensing. (paper)

A self-consistent field study of diblock copolymer/charged particle system morphologies for nanofiltration membranes

International Nuclear Information System (INIS)

Zhang, Bo; Ye, Xianggui; Edwards, Brian J.

2013-01-01

A combination of self-consistent field theory and density functional theory was used to examine the stable, 3-dimensional equilibrium morphologies formed by diblock copolymers with a tethered nanoparticle attached either between the two blocks or at the end of one of the blocks. Both neutral and interacting particles were examined, with and without favorable/unfavorable energetic potentials between the particles and the block segments. The phase diagrams of the various systems were constructed, allowing the identification of three types of ordered mesophases composed of lamellae, hexagonally packed cylinders, and spheroids. In particular, we examined the conditions under which the mesophases could be generated wherein the tethered particles were primarily located within the interface between the two blocks of the copolymer. Key factors influencing these properties were determined to be the particle position along the diblock chain, the interaction potentials of the blocks and particles, the block copolymer composition, and molecular weight of the copolymer

Interactions of poly(tert-butyl acrylate)-poly(styrene) diblock copolymers with lipids at the air-water interface.

Science.gov (United States)

Mudgil, Poonam; Dennis, Gary R; Millar, Thomas J

2006-08-29

Diblock copolymers with hydrophilic poly(tert-butyl acrylate) (PtBA) and hydrophobic poly(styrene) (PS) blocks were synthesized with a view to use them as a surfactant in tear film for increasing the ocular comfort in dry eye syndrome. Interactions of six PtBA-PS copolymers with four important lipids found in the tear film, namely cholesterol, cholesteryl palmitate, dipalmitoyl phosphatidylcholine, and phosphatidylinositol, were studied at the air-water interface using a Langmuir trough. Thermodynamics of mixing of the copolymers and the lipids in the mixed monolayers was determined by calculating excess free energy of mixing. The diblock copolymers showed repulsive interactions with cholesteol and cholesteryl palmitate, near neutral interactions with dipalmitoyl phosphatidylcholine, and attractive interactions with phosphatidylinositol. The lipids interacted with the PS component of the copolymer. The results indicate that a copolymer with a small hydrophilic group and a big hydrophobic group can be a likely candidate for forming stable interactions with the lipids present in the tear film and hence increase the ocular comfort.

Pearl-necklace complexes of flexible polyanions with neutral-cationic diblock copolymers

NARCIS (Netherlands)

Golinska, M.D.; Wolf, de F.A.; Cohen Stuart, M.A.; Hernandez Garcia, A.; Vries, de R.J.

2013-01-01

We study the complexation of very asymmetric diblock copolymers (consisting of a cationic block of 12 lysines connected to a 400 amino acid long hydrophilic polypeptide block with a net charge that is nearly zero) with oppositely charged sodium poly(acrylic acid) (NaPAA) with a range of molar masses

Monte Carlo simulation of diblock copolymer microphases by means of a 'fast' off-lattice model

DEFF Research Database (Denmark)

Besold, Gerhard; Hassager, O.; Mouritsen, Ole G.

1999-01-01

We present a mesoscopic off-lattice model for the simulation of diblock copolymer melts by Monte Carlo techniques. A single copolymer molecule is modeled as a discrete Edwards chain consisting of two blocks with vertices of type A and B, respectively. The volume interaction is formulated in terms...

SYNTHESIS OF pH-RESPONSIVE AMPHIPHILIC DIBLOCK COPOLYMERS CONTAINING POLYISOBUTYLENE via OXYANION-INITIATED POLYMERIZATION AND THEIR MULTIPLE SELF-ASSEMBLY MORPHOLOGIES

Institute of Scientific and Technical Information of China (English)

Huai-chao Wang; Ming-zu Zhang; Pei-hong Ni; Jin-lin He; Ying Hao; Yi-xian Wu

2013-01-01

Two pH-responsive amphiphilic diblock copolymers,namely polyisobutylene-block-poly[2-(N,N-dimethylamino)ethyl methacrylate] (PIB-b-PDMAEMA) and polyisobutylene-block-poly(metharylic acid) (PIB-b-PMAA),were synthesized via oxyanion-initiated polymerization,and their multiple self-assembly behaviors have been studied.An exo-o1efin-terminated highly reactive polyisobutylene (HRPIB) was first changed to hydroxyl-terminated PIB (PIB-OH) via hydroboration-oxidation of C=C double bond in the chain end,and then reacted with KH to yield a potassium alcoholate of PIB (PIB-O-K+).PIB-O-K+ was immediately used as a macroinitiator to polymerize DMAEMA monomer,resulting in a cationic diblock copolymer PIB-b-PDMAEMA.With the similar synthesis procedure,the anionic diblock copolymer PIB-b-PMAA could be prepared via a combination of oxyanion-initiated polymerization of tert-butyl methacrylate (tBMA) and subsequent hydrolysis of tert-butyl ester groups in PtBMA block.The functional PIB and block copolymers have been fully characterized by 1H-NMR,FT-IR spectroscopy,and gel permeation chromatography (GPC).These samples allowed us to systematically investigate the effects of block composition on the pH responsivity and various self-assembled morphologies of the copolymers in THF/water mixed solvent.Transmission electron microscopy (TEM) images revealed that these diblock copolymers containing small amount of original PIB without exo-olefin-terminated group are able to self-assemble into micelles,vesicles with different particle sizes and cylindrical aggregates,depending on various factors including block copolymer composition,solvent polarity and pH value.

Effect of shear on cubic phases in gels of a diblock copolymer

DEFF Research Database (Denmark)

Hamley, I.W.; Pople, J.A.; Fairclough, J.P.A.

1998-01-01

The effect of shear on the orientation of cubic micellar phases formed by a poly(oxyethylene)poly(oxybutylene) diblock copolymer in aqueous solution has been investigated using small-angle x-ray scattering (SAXS) and small-angle neutron scattering (SANS). SAXS was performed on samples oriented in...

Fabrication of poly(methyl methacrylate)-block-poly(methacrylic acid) diblock copolymer as a self-embrittling strippable coating for radioactive decontamination

International Nuclear Information System (INIS)

Liu Renlong; Zhang Huiyan; Li Yintao; Zhou Yuanlin; Zhang Quanping; Zheng Jian; Wang Shanqiang

2016-01-01

The poly(methyl methacrylate)-block-poly(methacrylic acid) diblock copolymer with different monomer compositions was synthesized via reversible addition-fragmentation chain transfer polymerization. Meanwhile, a novel self-embrittling strippable coating was prepared using the diblock copolymers, which is proposed to be used as radioactive decontamination agents without manual operation. Furthermore, the decontamination efficiencies of self-embrittling strippable coatings for radioactive contamination on glass, marble, and stainless steel surfaces were studied. (author)

Synthesis and characterization of a novel water-soluble cationic diblock copolymer with star conformation by ATRP

Energy Technology Data Exchange (ETDEWEB)

Li, Shuzhao [Department of Chemical Engineering, University of New Brunswick, Fredericton, NB E3B 5A3 (Canada); School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); Xiao, Miaomiao [Department of Chemical Engineering, University of New Brunswick, Fredericton, NB E3B 5A3 (Canada); Zheng, Anna [School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); Xiao, Huining, E-mail: hxiao@unb.ca [Department of Chemical Engineering, University of New Brunswick, Fredericton, NB E3B 5A3 (Canada)

2014-10-01

A water-soluble cationic diblock copolymer, CD-PAM-b-PMeDMA, was synthesized through atom transfer radical polymerization (ATRP) from a β-cyclodextrin (CD) macroinitiator with 10-active sites (10Br-β-CD). In order to reduce the cytotoxicity of the CD-PAM-b-PMeDMA, biocompatible polyacrylamide (PAM) was first introduced onto the surface of β-CD as a scaffold structure by ATRP using the 10Br-β-CD as a macroinitiator. The reaction conditions of AM were explored and optimized. The ATRP of [2-(methacryloyloxy)ethyl] trimethyl ammonium chloride (MeDMA) was also performed to synthesize the second cationic block using the resulting CD-PAM as a macroinitiator. The resulting diblock copolymer shows an increased hydrodynamic radius in aqueous solution with a pretty low concentration compared with β-CD. In addition, it appears a near-uniform coniform after being deposited on mica ascribed to the presence of an asymmetric 10-arm structure. - Highlights: • A 10-arm diblock polymer was prepared by ATRP for the potential use as a non-viral gene delivery. • PAM was first synthesized in a controlled manner considering its biocompatibility. • The hydrodynamic radius of the copolymer in aqueous solution increase to 130 nm from 7.5 nm of CD. • The copolymer appears coniform after deposited on mica surface due to the charge attraction.

Multiple patterns of diblock copolymer confined in irregular geometries with soft surface

Science.gov (United States)

Li, Ying; Sun, Min-Na; Zhang, Jin-Jun; Pan, Jun-Xing; Guo, Yu-Qi; Wang, Bao-Feng; Wu, Hai-Shun

2015-12-01

The different confinement shapes can induce the formation of various interesting and novel morphologies, which might inspire potential applications of materials. In this paper, we study the directed self-assembly of diblock copolymer confined in irregular geometries with a soft surface by using self-consistent field theory. Two types of confinement geometries are considered, namely, one is the concave pore with one groove and the other is the concave pore with two grooves. We obtain more novel and different structures which could not be produced in other two-dimensional (2D) confinements. Comparing these new structures with those obtained in regular square confinement, we find that the range of ordered lamellae is enlarged and the range of disordered structure is narrowed down under the concave pore confinement. We also compare the different structures obtained under the two types of confinement geometries, the results show that the effect of confinement would increase, which might induce the diblock copolymer to form novel structures. We construct the phase diagram as a function of the fraction of B block and the ratio of h/L of the groove. The simulation reveals that the wetting effect of brushes and the shape of confinement geometries play important roles in determining the morphologies of the system. Our results improve the applications in the directed self-assembly of diblock copolymer for fabricating the irregular structures. Project supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20121404110004), the Research Foundation for Excellent Talents of Shanxi Provincial Department of Human Resources and Social Security, China, and the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi Province, China.

Highly-Ordered Magnetic Nanostructures on Self-Assembled α-Al2O3 and Diblock Copolymer Templates

International Nuclear Information System (INIS)

Erb, Denise

2015-08-01

This thesis shows the preparation of nanostructured systems with a high degree of morphological uniformity and regularity employing exclusively selfassembly processes, and documents the investigation of these systems by means of atomic force microscopy (AFM), grazing incidence small angle X-ray scattering (GISAXS), and nuclear resonant scattering of synchrotron radiation (NRS). Whenever possible, the X-ray scattering methods are applied in-situ and simultaneously in order to monitor and correlate the evolution of structural and magnetic properties of the nanostructured systems. The following systems are discussed, where highly-ordered magnetic nanostructures are grown on α-Al 2 O 3 substrates with topographical surface patterning and on diblock copolymer templates with chemical surface patterning: - Nanofaceted surfaces of α-Al 2 O 3 - Magnetic nanostructures on nanofaceted α-Al 2 O 3 substrates - Thin films of microphase separated diblock copolymers - Magnetic nanostructures on diblock copolymer thin film templates The fact that the underlying self-assembly processes can be steered by external factors is utilized to optimize the degree of structural order in the nanostructured systems. The highly-ordered systems are well-suited for investigations with X-ray scattering methods, since due to their uniformity the inherently averaged scattered signal of a sample yields meaningful information on the properties of the contained nanostructures: By means of an in-situ GISAXS experiment at temperatures above 1000 C, details on the facet formation on α-Al 2 O 3 surfaces are determined. A novel method, merging in-situ GISAXS and NRS, shows the evolution of magnetic states in a system with correlated structural and magnetic inhomogeneity with lateral resolution. The temperature-dependence of the shape of Fe nanodots growing on diblock copolymer templates is revealed by in-situ GISAXS during sputter deposition of Fe. Combining in-situ GISAXS and NRS, the magnetization

Dilute solutions and phase behavior of polydisperse A-b-(A-co-B) diblock copolymers

Czech Academy of Sciences Publication Activity Database

Gromadzki, Daniel; Lokaj, Jan; Šlouf, Miroslav; Štěpánek, Petr

2009-01-01

Roč. 50, č. 11 (2009), s. 2451-2459 ISSN 0032-3861 Institutional research plan: CEZ:AV0Z40500505 Keywords : diblock copolymer * dilute solution properties * microphase separation Subject RIV: CD - Macromolecular Chemistry Impact factor: 3.573, year: 2009

Surface dynamics of micellar diblock copolymer films

Science.gov (United States)

Song, Sanghoon; Cha, Wonsuk; Kim, Hyunjung; Jiang, Zhang; Narayanan, Suresh

2011-03-01

We studied the structure and surface dynamics of poly(styrene)-b-poly(dimethylsiloxane) (PS-b-PDMS) diblock copolymer films with micellar PDMS surrounded by PS shells. By `in-situ' high resolution synchrotron x-ray reflectivity and diffuse scattering, we obtained exact thickness, electron density and surface tension. A segregation layer near the top surface was appeared with increasing temperature Surface dynamics were measured as a function of film thickness and temperature by x-ray photon correlation spectroscopy. The best fit to relaxation time constants as a function of in-plane wavevectors were analyzed with a theory based on capillary waves with hydrodynamics with bilayer model Finally the viscosities for the top segregated layer as well as for the bottom layer are obtained at given temperatures This work was supported by National Research Foundation of Korea (R15-2008-006-01001-0), Seoul Research and Business Development Program (10816), and Sogang University Research Grant (2010).

Dynamical self-arrest in symmetric and asymmetric diblock copolymer melts using a replica approach within a local theory.

Science.gov (United States)

Wu, Sangwook

2009-03-01

We investigate dynamical self-arrest in a diblock copolymer melt using a replica approach within a self-consistent local method based on dynamical mean-field theory (DMFT). The local replica approach effectively predicts (chiN)_{A} for dynamical self-arrest in a block copolymer melt for symmetric and asymmetric cases. We discuss the competition of the cubic and quartic interactions in the Landau free energy for a block copolymer melt in stabilizing a glassy state depending on the chain length. Our local replica theory provides a universal value for the dynamical self-arrest in block copolymer melts with (chiN)_{A} approximately 10.5+64N;{-3/10} for the symmetric case.

Preparation of polystyrene-poly(ethylene glycol) diblock copolymer by "living" free radical polymerization

DEFF Research Database (Denmark)

Chen, Xianyi; Gao, Bo; Kops, Jørgen

1998-01-01

terminated with a TEMPO unit (MPEG-TEMPO), which was further used to prepare the diblock copolymer PS-b-PEG by 'living' free radical polymerisation of styrene. The product was purified and identified by H-1 n.m.r. and GPC. However, large amounts of homopolystyrene was also formed by simultaneous thermal...

Synthesis and solution properties of PCL-b-PHPMA diblock copolymers containing stable nitroxyl radicals

Czech Academy of Sciences Publication Activity Database

Petrova, Svetlana; Klepac, Damir; Konefal, Rafal; Kereiche, S.; Kováčik, L.; Filippov, Sergey K.

2016-01-01

Roč. 49, č. 15 (2016), s. 5407-5417 ISSN 0024-9297 R&D Projects: GA MŠk(CZ) LH15213 Institutional support: RVO:61389013 Keywords : PCL-b-PHPMA diblock copolymers * TEMPO * EPR spectroscodpy Subject RIV: CD - Macromolecular Chemistry Impact factor: 5.835, year: 2016

Nanostructures and surface hydrophobicity of self-assembled thermosets involving epoxy resin and poly(2,2,2-trifluoroethyl acrylate)-block-poly(ethylene oxide) amphiphilic diblock copolymer.

Science.gov (United States)

Yi, Fangping; Zheng, Sixun; Liu, Tianxi

2009-02-19

Poly(2,2,2-trifluoroethyl acrylate)-block-poly(ethylene oxide) (PTFEA-b-PEO) amphiphilic diblock copolymer was synthesized via the reversible addition-fragmentation transfer polymerization of 2,2,2-triffluroethyl acrylate with dithiobenzoyl-terminated poly(ethylene oxide) as a chain-transfer agent. The amphiphilic diblock copolymer was incorporated into epoxy resin to prepare the nanostructured epoxy thermosets. The nanostructures were investigated by means of atomic force microscopy, small-angle X-ray scattering, and dynamic mechanical analysis. In terms of the miscibility of the subchains of the block copolymer with epoxy after and before curing reaction, it is judged that the formation of the nanostructures follows the mechanism of self-assembly. The static contact angle measurements indicate that the nanostructured thermosets containing PTFEA-b-PEO diblock copolymer displayed a significant enhancement in surface hydrophobicity as well as a reduction in surface free energy. The improvement in surface properties was ascribed to the enrichment of the fluorine-containing subchain (i.e., PTFEA block) of the amphiphilic diblock copolymer on the surface of the nanostructured thermosets, which was evidenced by surface atomic force microscopy and energy-dispersive X-ray spectroscopy.

Mesomorphic phase behaviour of low molar mass PEP-PDMS diblock copolymers synthesized by anionic polymerization

International Nuclear Information System (INIS)

Vigild, M.E.

1997-10-01

The phase behaviour of low molar mass poly(ethylene-alt-propylene) -poly(dimethylsiloxane) (PEP-PDMS) is investigated in this thesis by the combination of dynamical mechanical spectroscopy (rheology) to measure phase transition temperatures, and small-angle x-ray scattering to identify the morphology of encountered phases. Samples of PEP-PDMS in the range of 0.2-0.7 in volume fraction of PEP are studied. This diblock copolymer system exhibits the three classical phases of lamellar sandwich structure (LAM), hexagonally packed cylinders (HEX), and spheres arranged on a body centered cubic lattice (BCC). Furthermore the gyroid phase (Ia3d symmetry) of two interpenetrating networks was also identified as a stable phase of the PEP-PDMS system. Time resolved measurements of small-angle neutron scattering in tandem with simultaneous in-situ rheological measurements are performed on samples showing transitions between different ordered phases. The identification of especially the BCC and gyroid phases from scattering experiments is treated. By performing mesoscopic crystallographic measurements using a custom built goniometer it was unambiguously shown that the application of shear to an unoriented powder-like sample introduces uniaxial orientation of the gyroid phase. The orientation of the ordered phase is otherwise random, causing a two-dimensional powder. Finally this dissertation presents a discussion of relevant parameters for the description of diblock copolymer phase behaviour together with descriptions of anionic polymerization for the synthesis of copolymers, and various experimental techniques for the characterization of diblocks. (au)

Mesomorphic phase behaviour of low molar mass PEP-PDMS diblock copolymers synthesized by anionic polymerization

Energy Technology Data Exchange (ETDEWEB)

Vigild, M.E.

1997-10-01

The phase behaviour of low molar mass poly(ethylene-alt-propylene) -poly(dimethylsiloxane) (PEP-PDMS) is investigated in this thesis by the combination of dynamical mechanical spectroscopy (rheology) to measure phase transition temperatures, and small-angle x-ray scattering to identify the morphology of encountered phases. Samples of PEP-PDMS in the range of 0.2-0.7 in volume fraction of PEP are studied. This diblock copolymer system exhibits the three classical phases of lamellar sandwich structure (LAM), hexagonally packed cylinders (HEX), and spheres arranged on a body centered cubic lattice (BCC). Furthermore the gyroid phase (Ia3d symmetry) of two interpenetrating networks was also identified as a stable phase of the PEP-PDMS system. Time resolved measurements of small-angle neutron scattering in tandem with simultaneous in-situ rheological measurements are performed on samples showing transitions between different ordered phases. The identification of especially the BCC and gyroid phases from scattering experiments is treated. By performing mesoscopic crystallographic measurements using a custom built goniometer it was unambiguously shown that the application of shear to an unoriented powder-like sample introduces uniaxial orientation of the gyroid phase. The orientation of the ordered phase is otherwise random, causing a two-dimensional powder. Finally this dissertation presents a discussion of relevant parameters for the description of diblock copolymer phase behaviour together with descriptions of anionic polymerization for the synthesis of copolymers, and various experimental techniques for the characterization of diblocks. (au). 9 tabs., 40 ills., 81 refs.

Formation of integral asymmetric membranes of AB diblock and ABC triblock copolymers by phase inversion.

Science.gov (United States)

Jung, Adina; Filiz, Volkan; Rangou, Sofia; Buhr, Kristian; Merten, Petra; Hahn, Janina; Clodt, Juliana; Abetz, Clarissa; Abetz, Volker

2013-04-12

The formation of integral asymmetric membranes from ABC triblock terpolymers by non-solvent-induced phase separation is shown. They are compared with the AB diblock copolymer precursors. Triblock terpolymers of polystyrene-block-poly(2-vinylpyridine)-block-poly(ethylene oxide) (PS-b-P2VP-b-PEO) with two compositions are investigated. The third block supports the formation of a membrane in a case, where the corresponding diblock copolymer does not form a good membrane. In addition, the hydrophilicity is increased by the third block and due to the hydroxyl group the possibility of post-functionalization is given. The morphologies are imaged by scanning electron microscopy. The influence of the PEO on the membrane properties is analyzed by water flux, retention, and dynamic contact angle measurements. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis, Characterization and Photoinduction of Optical Anisotropy in Liquid Crystalline Diblock Azo-Copolymers

DEFF Research Database (Denmark)

Forcén, P; Oriol, L; Sánchez, C

2007-01-01

Diblock copolymers with polymethyl methacrylate and side chain liquid crystalline WC) azopolymethacrylate blocks were synthesized by atom transfer radical polymerization (ATRP). The azobeazene content in these copolymers ranges from 52 to 7 wt %. For an azo conteat dowri to 20% they exhibit a LC...... anisotropy induced in these films by illumination with linearly polarized 488 nm light was studied and the resuits compared with those of the azo homopolymer and of a random copolymer with a similar composition. The formation of azo aggregates inside the azo blocks is strongly reduced in going from...... the homopolymer to the copolymers. Photoinduced azo orientation perpendicular to the 488 nm light polarization was found in aH the polymers. The orientational order parameter is very similar in the homopolymer and in the block copolymers with an azo content down to 20 wt %, while it is much lower in the random...

The effect of particle size on the morphology and thermodynamics of diblock copolymer/tethered-particle membranes

International Nuclear Information System (INIS)

Zhang, Bo; Edwards, Brian J.

2015-01-01

A combination of self-consistent field theory and density functional theory was used to examine the effect of particle size on the stable, 3-dimensional equilibrium morphologies formed by diblock copolymers with a tethered nanoparticle attached either between the two blocks or at the end of one of the blocks. Particle size was varied between one and four tenths of the radius of gyration of the diblock polymer chain for neutral particles as well as those either favoring or disfavoring segments of the copolymer blocks. Phase diagrams were constructed and analyzed in terms of thermodynamic diagrams to understand the physics associated with the molecular-level self-assembly processes. Typical morphologies were observed, such as lamellar, spheroidal, cylindrical, gyroidal, and perforated lamellar, with the primary concentration region of the tethered particles being influenced heavily by particle size and tethering location, strength of the particle-segment energetic interactions, chain length, and copolymer radius of gyration. The effect of the simulation box size on the observed morphology and system thermodynamics was also investigated, indicating possible effects of confinement upon the system self-assembly processes

The effect of particle size on the morphology and thermodynamics of diblock copolymer/tethered-particle membranes.

Science.gov (United States)

Zhang, Bo; Edwards, Brian J

2015-06-07

A combination of self-consistent field theory and density functional theory was used to examine the effect of particle size on the stable, 3-dimensional equilibrium morphologies formed by diblock copolymers with a tethered nanoparticle attached either between the two blocks or at the end of one of the blocks. Particle size was varied between one and four tenths of the radius of gyration of the diblock polymer chain for neutral particles as well as those either favoring or disfavoring segments of the copolymer blocks. Phase diagrams were constructed and analyzed in terms of thermodynamic diagrams to understand the physics associated with the molecular-level self-assembly processes. Typical morphologies were observed, such as lamellar, spheroidal, cylindrical, gyroidal, and perforated lamellar, with the primary concentration region of the tethered particles being influenced heavily by particle size and tethering location, strength of the particle-segment energetic interactions, chain length, and copolymer radius of gyration. The effect of the simulation box size on the observed morphology and system thermodynamics was also investigated, indicating possible effects of confinement upon the system self-assembly processes.

Fluctuations effects in diblock copolymer fluids: Comparison of theories and experiment

International Nuclear Information System (INIS)

Guenza, M.; Schweizer, K.S.

1997-01-01

The analytic Polymer Reference Interaction Site Model (PRISM) theory of structurally and interaction symmetric Gaussian diblock copolymer fluids is reformulated, extended, and applied to make predictions for experimentally observable equilibrium properties of the disordered state. These include the temperature, degree of polymerization, copolymer composition, and polymer density or concentration dependences of the peak scattering intensity, effective chi-parameter, and heat capacity. The location of the order-disorder transition is empirically estimated based on the disordered, strongly fluctuating state scattering function. Detailed numerical applications of PRISM theory demonstrates it provides an excellent description of the data. An in depth comparison of the mathematical structure and predictions of PRISM theory with the highly coarse-grained, incompressible Brazovski endash Leibler endash Fredrickson endash Helfand (BLFH) fluctuation corrected field theory is also carried out. Under some conditions (nearly symmetric composition, high melt densities, moderate temperatures) there are striking mathematical similarities between the predictions of the physically very different theories, although quantitative differences always persist. However, for strongly asymmetric copolymer compositions, short chains, compressible copolymer solutions, and low temperatures many qualitative differences emerge. The possibility of multiple, self-consistent fluctuation feedback mechanisms within the most general PRISM approach are identified, their qualitative features discussed, and contrasted with alternative versions of the fluctuation-corrected incompressible field theories due to BLFH and Stepanow. The predictions of PRISM and BLFH theory for the composition, copolymer density, temperature, and molecular weight dependence of the effective chi-parameter are presented and qualitatively compared with recent experiments. copyright 1997 American Institute of Physics

The Plumber’s Nightmare Phase in Diblock Copolymer/Homopolymer Blends. A Self-Consistent Field Theory Study.

KAUST Repository

Martinez-Veracoechea, Francisco J.; Escobedo, Fernando A.

2009-01-01

Using self-consistent field theory, the Plumber's Nightmare and the double diamond phases are predicted to be stable in a finite region of phase diagrams for blends of AB diblock copolymer (DBC) and A-component homopolymer. To the best of our

Small angle neutron scattering study on star di-block copolymers

International Nuclear Information System (INIS)

Ertugrul, O.

2006-01-01

Determining structural properties, phase transitions and stability of polymer mixtures is very important to produce new materials with desired and interesting properties. Small Angle Neutron Scattering Technique (SANS) has been one of the most powerful and intensely used methods for the characterization of polymers for last decades, m this study, we use a model based on Gaussian Random Phase Approximation (RPA) to describe Star Di-block Copolymers (SDC) mixtures with homo-polymers. We could able to predict the miscibility and phase transitions of the various mixtures along with their structure factors, producing a thermodynamic picture of the system. Also the results suggest that scattering intensity will be dictated by the structure factor of the core or shell parts of star polymer only, which depends on the homo-polymer type of the mixture

Morphology in binary blends of poly(vinyl methyl ether) and epsilon-caprolactone-trimethylene carbonate diblock copolymer

NARCIS (Netherlands)

Luyten, MC; Bogels, EJF; vanEkenstein, GORA; tenBrinke, G; Bras, W; Komanschek, BE; Ryan, AJ

The morphology of symmetric diblock copolymer of epsilon-caprolactone (PCL) and trimethylene carbonate (PTMC), in blends with poly(vinyl methyl ether) (PVME) is investigated with (modulated) differential scanning calorimetry (d.s.c.), time resolved small angle (SAXS) and wide angle (WAXS) X-ray

Morphology in binary blends of poly(vinyl methyl ether) and ε-caprolactone-trimethylene carbonate diblock copolymer

NARCIS (Netherlands)

Luyten, M.C.; Bögels, E.J.F.; Alberda van Ekenstein, G.O.R.; Brinke, G. ten; Bras, W.; Komanschek, B.E.; Ryan, A.J.

1997-01-01

The morphology of symmetric diblock copolymer of ε-caprolactone (PCL) and trimethylene carbonate (PTMC), in blends with poly(vinyl methyl ether) (PVME) is investigated with (modulated) differential scanning calorimetry (d.s.c.), time resolved small angle (SAXS) and wide angle (WAXS) X-ray

Effect of the Molecular Weight of AB Diblock Copolymers on the Lamellar Orientation in Thin Films

DEFF Research Database (Denmark)

Potemkin, Igor I.; Busch, Peter; Smilgies, Detlef-M

2007-01-01

We propose a theoretical explanation of the parallel and perpendicular lamellar orientations in free surface films of symmetric polystyrene-block-polybutadiene diblock copolymers on silicon substrates (with a native SiOx layer). Two approaches are developed: A correction to the strong segregation...

Micellar Structures of Hydrophilic/Lipophilic and Hydrophilic/Fluorophilic Poly(2-oxazoline) Diblock Copolymers in Water

DEFF Research Database (Denmark)

Ivanova, Ruzha; Komenda, Thomas; Bonné, Tune B.

2008-01-01

Amphiphilic poly(2-alkyl-2-oxazoline) diblock copolymers of 2-methyl-2-oxazoline (MOx) building the hydrophilic block and either 2-nonyl-2-oxazoline (NOx) for the hydrophobic or 2-(1H,1H',2H,2H'-perfluorohexyl)-2-oxazoline (FOx) for the fluorophilic block were synthesized by sequential living...

Supramolecular Assembly of Gold Nanoparticles in PS-b-P2VP Diblock Copolymers via Hydrogen Bonding

Science.gov (United States)

Jang, Se Gyu; Hawker, Craig J.; Kramer, Edward J.

2011-03-01

We report a simple route to control the spatial distribution of Au nanoparticles (Au-NPs) in PS- b -P2VP diblock copolymers using hydrogen bonding between P2VP and the hydroxyl-containing (PI-OH) units in PS- b -PIOH thiol-terminated ligands on Au-NP. End-functional thiol ligands of poly(styrene- b -1,2&3,4-isoprene-SH) are synthesized by anionic polymerization. After synthesis of Au-NPs, the inner PI block is hydroxylated by hydroboration and the resulting micelle-like Au-NPs consist of a hydrophobic PS outer brush and a hydrophilic inner PI-OH block. The influence of the hydroxyl groups is significant with strong segregation being observed to the PS/P2VP interface and then to the P2VP domain of lamellar-forming PS-b-P2VP diblock copolymers as the length of the PI-OH block is increased. The strong hydrogen bonding between nanoparticle block copolymer ligands and the P2VP block allows the Au-NPs to be incorporated within the P2VP domain to high Au--NP volume fractions ϕp without macrophase separation, driving transitions from lamellar to bicontinuous morphologies as ϕp increases.

Synthesis of Diblock copolymer poly-3-hydroxybutyrate -block-poly-3-hydroxyhexanoate [PHB-b-PHHx] by a β-oxidation weakened Pseudomonas putida KT2442

DEFF Research Database (Denmark)

Tripathi, Lakshmi; Wu, Lin-Ping; Chen, Jinchun

2012-01-01

), thermo- and mechanical analysis. NMR confirmed the existence of diblock copolymers consisting of 58 mol% PHB as the short chain length block with 42 mol% PHHx as the medium chain length block. The block copolymers had two glass transition temperatures (Tg) at 2.7°C and -16.4°C, one melting temperature...... (Tm) at 172.1°C and one cool crystallization temperature (Tc) at 69.1°C as revealed by differential scanning calorimetry (DSC), respectively. This is the first microbial short-chain-length (scl) and medium-chain-length (mcl) PHA block copolymer reported. CONCLUSIONS: It is possible to produce PHA......BACKGROUND: Block polyhydroxyalkanoates (PHA) were reported to be resistant against polymer aging that negatively affects polymer properties. Recently, more and more attempts have been directed to make PHA block copolymers. Diblock copolymers PHB-b-PHHx consisting of poly-3-hydroxybutyrate (PHB...

The lamellar period in symmetric diblock copolymer thin films studied by neutron reflectivity and AFM

DEFF Research Database (Denmark)

Gadegaard, N.; Almdal, K.; Larsen, N.B.

1999-01-01

The lamellar structure of a symmetric diblock copolymer was studied as a function of temperature. We used dPEP-PDMS with a molecular weight of 8.3 kg/mol as model system. The polymer was dissolved in chloroform and spin-casted on silicon wafers into thin uniform films. The degree and direction...

Thermal processing of diblock copolymer melts mimics metallurgy

Science.gov (United States)

Kim, Kyungtae; Schulze, Morgan W.; Arora, Akash; Lewis, Ronald M.; Hillmyer, Marc A.; Dorfman, Kevin D.; Bates, Frank S.

2017-05-01

Small-angle x-ray scattering experiments conducted with compositionally asymmetric low molar mass poly(isoprene)-b-poly(lactide) diblock copolymers reveal an extraordinary thermal history dependence. The development of distinct periodic crystalline or aperiodic quasicrystalline states depends on how specimens are cooled from the disordered state to temperatures below the order-disorder transition temperature. Whereas direct cooling leads to the formation of documented morphologies, rapidly quenched samples that are then heated from low temperature form the hexagonal C14 and cubic C15 Laves phases commonly found in metal alloys. Self-consistent mean-field theory calculations show that these, and other associated Frank-Kasper phases, have nearly degenerate free energies, suggesting that processing history drives the material into long-lived metastable states defined by self-assembled particles with discrete populations of volumes and polyhedral shapes.

Complex Macrophase-Separated Nanostructure Induced by Microphase Separation in Binary Blends of Lamellar Diblock Copolymer Thin Films

DEFF Research Database (Denmark)

Zhang, Jianqi; Posselt, Dorthe; Smilgies, Detlef-M.

2014-01-01

The nanostructures of thin films spin-coated from binary blends of compositionally symmetric polystyrene-b-polybutadiene (PS-b-PB) diblock copolymer having different molar masses are investigated by means of atomic force microscopy (AFM) and grazing-incidence small-angle X-ray scattering (GISAXS)...

Mechanical properties of a waterborne pressure-sensitive adhesive with a percolating poly(acrylic acid)-based diblock copolymer network: effect of pH.

Science.gov (United States)

Gurney, Robert S; Morse, Andrew; Siband, Elodie; Dupin, Damien; Armes, Steven P; Keddie, Joseph L

2015-06-15

Copolymerizing an acrylic acid comonomer is often beneficial for the adhesive properties of waterborne pressure-sensitive adhesives (PSAs). Here, we demonstrate a new strategy in which poly(acrylic acid) (PAA) is distributed as a percolating network within a PSA film formed from a polymer colloid. A diblock copolymer composed of PAA and poly(n-butyl acrylate) (PBA) blocks was synthesized using reversible addition-fragmentation chain transfer (RAFT) polymerization and adsorbed onto soft acrylic latex particles prior to their film formation. The thin adsorbed shells on the particles create a percolating network that raises the elastic modulus, creep resistance and tensile strength of the final film. When the film formation occurs at pH 10, ionomeric crosslinking occurs, and high tack adhesion is obtained in combination with high creep resistance. The results show that the addition of an amphiphilic PAA-b-PBA diblock copolymer (2.0 wt.%) to a soft latex provides a simple yet effective means of adjusting the mechanical and adhesive properties of the resulting composite film. Copyright © 2015 Elsevier Inc. All rights reserved.

Dynamics of Disordered PI-PtBS Diblock Copolymer

Science.gov (United States)

Watanabe, Hiroshi

2009-03-01

Viscoelastic (G^*) and dielectric (ɛ'') data were examined for a LCST-type diblock copolymer composed of polyisoprene (PI; M = 53K) and poly(p-tert- butyl styrene) (PtBS; M = 42K) blocks disordered at T PtBS block at low T and the dynamic heterogeneity due to PtBS was effectively quenched to give a frictional nonuniformity for the PI block relaxation. The ɛ'' data were thermo-rheologically complex at low T, partly due to this nonuniformity. However, the block connectivity could have also led to the complexity. For testing this effect, the ɛ'' data were reduced at the iso- frictional state defined with respect to bulk PI. In this state, the ɛ'' data of the copolymer at low and high T, respectively, were close to the data for the star-branched and linear bulk PI. Thus, the PI block appeared to be effectively tethered in space at low T thereby behaving similarly to the star arm while the PI block tended to move cooperatively with the PtBS block at high T to behave similarly to the linear PI, which led to the complexity of the ɛ'' data. The PtBS block also exhibited the complexity (noted from the G^* data), which was well correlated with the complexity of the PI block.

Incorporation of Amphipathic Diblock Copolymer in Lipid Bilayer for Improving pH Responsiveness

Directory of Open Access Journals (Sweden)

Tian Xia

2016-01-01

Full Text Available Diblock copolymers (mPEG-b-PDPA, which were designed to possess pH-sensitivity as well as amphipathy, were used as an intelligent lock in the liposomal membrane. The so-called pH-sensitive liposomes were prepared by simple mixing of the synthesized mPEG-b-PDPA with phospholipids and cholesterol. Fluorescence polarization at pH 7.4 showed that the membrane stability of the hybrid liposome was significantly increased compared with the pure liposome. Therefore, in the neutral environment, the leakage of doxorubicin (DOX was inhibited. However, when pH decreased to 6.0, DOX release rate increased by 60% due to the escape of copolymer. The effects of the membrane composition and the PDPA segment length on bilayer membrane functions were investigated. These results revealed that the synthesized copolymers increased the difference in DOX cumulative release between pH 7.4 and 6.0, that is, improved the pH-controllability of the drug release from hybrid liposomes.

Controlled supramolecular assembly of micelle-like gold nanoparticles in PS-b-P2VP diblock copolymers via hydrogen bonding.

Science.gov (United States)

Jang, Se Gyu; Kramer, Edward J; Hawker, Craig J

2011-10-26

We report a facile strategy to synthesize amphiphilic gold (Au) nanoparticles functionalized with a multilayer, micelle-like structure consisting of a Au core, an inner hydroxylated polyisoprene (PIOH) layer, and an outer polystyrene shell (PS). Careful control of enthalpic interactions via a systematic variation of structural parameters, such as number of hydroxyl groups per ligand (N(OH)) and styrene repeating units (N(PS)) as well as areal chain density of ligands on the Au-core surface (Σ), enables precise control of the spatial distribution of these nanoparticles. This control was demonstrated in a lamellae-forming poly(styrene-b-2-vinylpyridine) (PS-b-P2VP) diblock copolymer matrix, where the favorable hydrogen-bonding interaction between hydroxyl groups in the PIOH inner shell and P2VP chains in the PS-b-P2VP diblock copolymer matrix, driving the nanoparticles to be segregated in P2VP domains, could be counter balanced by the enthalphic penalty of mixing of the PS outer brush with the P2VP domains. By varying N(OH), N(PS), and Σ, the nanoparticles could be positioned in the PS or P2VP domains or at the PS/P2VP interface. In addition, the effect of additives interfering with the hydrogen-bond formation between hydroxyl groups on Au nanoparticles and P2VP chains in a diblock copolymer matrix was investigated, and an interesting pea-pod-like segregation of Au nanoparticles in PS domains was observed.

Nanoparticle Encapsulation in Diblock Copolymer/Homopolymer Blend Thin Film Mixtures

Science.gov (United States)

Zhao, Junnan; Chen, Xi; Green, Peter

2014-03-01

We investigated the organization of low concentrations of poly (2-vinylpyridine) (P2VP) grafted gold nanoparticles within a diblock copolymer polystyrene-b-poly (2-vinylpyridine) (PS-b-P2VP)/homopolymer polystyrene (PS) blend thin film. The PS-b-P2VP copolymers formed micelles, composed of inner cores of P2VP block and outer coronae of PS blocks, throughout the homopolymer PS. All nanoparticles were encapsulated within micelle cores and each micelle contained one or no nanoparticle, on average. When the host PS chains are much longer than corona chains, micelles tended to self-organize at the interfaces. Otherwise, they were dispersed throughout the PS host. In comparison to the neat PS-b-P2VP/PS blend, the nanoparticles/PS-b-P2VP/PS system had a higher density of smaller micelles, influenced largely by the number of nanoparticles in the system. The behavior of this system is understood in terms of the maximization of the nanoparticle/micelle core interactions and of the translational entropies of the micelles and the nanoparticles.

Direct Observation of the BCC (100) Plane in Thin Films of Sphere-forming Diblock Copolymers

Science.gov (United States)

Ji, Shengxiang; Nagpal, Umang; Liao, Wen; de Pablo, Juan; Nealey, Paul

2010-03-01

In sphere-forming diblock copolymers, periodic arrays of spheres are arranged in a body-centred cubic (BCC) lattice structure in bulk. However, in thin films different surface morphologies were observed as a function of the film thickness, and the transition from the hexagonal array to the BCC (110) arrangement of spheres on film surfaces was located with respect to the increase of the film thickness. Here we report the first direct observation of the BCC (100) plane in thin films of poly (styrene-b-methyl methacrylate) diblock copolymers on homogeneous substrates. By balancing the surface energies of both blocks, the lower energy BCC (100) plane corresponding to a square arrangement of half spheres, formed on film surfaces when the film thickness was commensurate with the spacing, L100, between (100) planes or greater than 2 L100. A hexagonal arrangement of spheres was only observed when the thickness was less than 2 L100 and incommensurate with 1 L100. Monte Carlo (MC) simulation confirmed our experimental observation and was used to investigate the transition of the arrangement of spheres as a function of the film thickness.

Effect of diblock copolymer properties on the photophysical properties of dendrimer silicon phthalocyanine nanoconjugates

Science.gov (United States)

Chen, Kuizhi; Pan, Sujuan; Zhuang, Xuemei; Lv, Hafei; Que, Shoulin; Xie, Shusen; Yang, Hongqin; Peng, Yiru

2016-07-01

1-2 generation poly(benzyl aryl ether) dendrimer silicon phthalocyanines with axially disubstituted cyano terminal functionalities (G n -DSiPc(CN)4 n , (G n = n-generation dendrimer, n = 1-2)) were synthesized. Their structures were characterized by elemental analysis, IR, 1H NMR, and ESI-MS. Polymeric nanoparticles (G n -DSiPc(CN)4 n /m) were formed through encapsulating G n -DSiPc(CN)4 n into three monomethoxyl poly(ethylene glycol)-poly(ɛ-caprolactone) diblock copolymers (MPEG-PCL) with different hydrophilic/hydrophobic proportion, respectively. The effect of dendritic generation and the hydrophilic/hydrophobic proportion of diblock copolymers on the UV/Vis and fluorescence spectra of G n -DSiPc(CN)4 n and G n -DSiPc(CN)4 n /m were studied. The photophysical properties of polymeric nanoparticles exhibited dendritic generation and hydrophilic/hydrophobic proportion dependence. The fluorescence intensities and lifetimes of G n -DSiPc(CN)4 n /m were lower than the corresponding free dendrimer phthalocyanines. G n -DSiPc(CN)4 n encapsulated into MPEG-PCL with hydrophilic/hydrophobic molecular weight ratio 2000:4000 exhibited excellent photophysical property. The mean diameter of MPEG2000-PCL2000 micelles was about 70 nm, which decreased when loaded with G n -DSiPc(CN)4 n .

Self-diffusion investigations on a series of PEP-PDMS diblock copolymers with different morphologies by pulsed field gradient NMR

DEFF Research Database (Denmark)

Rittig, F.; Karger, J.; Papadakis, C.M.

1999-01-01

We report on temperature-dependent self-diffusion measurements of compositionally different and non-entangled poly(ethylene-co-propylene)-b-poly(dimethylsiloxane) PEP-PDMS diblock copolymers in the melt above and below the order-to-disorder transition temperature. Depending on the dimensionality...

Separation of parent homopolymers from diblock copolymers by liquid chromatography under limiting conditions of desorption 4. Role of eluent and temperature.

Science.gov (United States)

Berek, Dušan

2010-11-01

Liquid chromatography under limiting conditions of desorption (LC LCD) enables fast, base-line discrimination of both parent homopolymers from various diblock copolymers in one single step. The low molecular admixtures are fully separated, as well. General rules are discussed in detail for selection of mobile phases and temperature applied in LC LCD of block copolymers. Typical practical separation examples are presented. It is shown that both the composition of the well-selected LC LCD mobile phase and the temperature of experiment may vary in a broad range without affecting the basics of method. This implies that the method is robust and user friendly.

Mechanical Properties of Weakly Segregated Block Copolymers. 3. Influence of Strain Rate and Temperature on Tensile Properties of Poly(styrene-b-butyl methacrylate) Diblock Copolymers with Different Morphologies

NARCIS (Netherlands)

Weidisch, R.; Stamm, M.; Michler, G.H.; Fischer, H.R.; Jérôme, R.

1999-01-01

Poly(styrene-b-butyl methacrylate) diblock copolymers, PS-6-PBMA, with different morphologies are investigated with respect to the influence of strain rate and temperature on tensile properties. In the first part the mechanical properties of bicontinuous and perforated lamellar structure are

A pulsed field gradient NMR study of a ternary homopolymer/diblock copolymer blend in the bicontinuous microemulsion phase

Czech Academy of Sciences Publication Activity Database

Gröger, S.; Rittig, F.; Stallmach, F.; Almdal, K.; Štěpánek, Petr; Papadakis, C. M.

2002-01-01

Roč. 117, č. 1 (2002), s. 396-406 ISSN 0021-9606 R&D Projects: GA AV ČR IAA1050902 Institutional research plan: CEZ:AV0Z4050913 Keywords : polymer blends * diblock copolymer * dynamic light scattering Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.998, year: 2002

Numerical investigation of the contraction of neutral-charged diblock copolymer brushes in electric fields

International Nuclear Information System (INIS)

Chen, Yuwei; Li, Haiming; Zhu, Yuejin; Tong, Chaohui

2016-01-01

Using self-consistent field theory (SCFT), the contraction of neutral-charged A-B diblock copolymer brushes in electric fields generated by opposite surface charges on two parallel electrodes has been numerically investigated. The diblock copolymer chains were grafted with the free end of the neutral block to one electrode and immersed in a salt-free solution sandwiched between the two electrodes. The numerical results reveal that the charged monomers, A-B joint segment and the tail exhibit bimodal distributions under external electric fields, which are absent for homopolymer polyelectrolyte brushes. The dependences of the relative populations and peak positions of the two modes on various parameters such as block ratio, grafting density, chain length and strength of the applied electric field were systematically examined and the underlining mechanisms were elucidated. It was found in this study that, if the total amount of surface charges on the grafting electrode is no more than that of the counter-ions in the system, overall charge neutrality is generally maintained inside the brushes when including the contribution of surface charges on the grafting electrode. In such a case, the counter-ions expelled from the brushes are highly enriched in the immediate vicinity of the second electrode and an approximate charge balance between these expelled counter-ions and the opposite surface charges on the second electrode is achieved. (paper)

Structure and phase behaviour of diblock copolymer monolayers investigated by means of Monte Carlo simulation

International Nuclear Information System (INIS)

Słyk, Edyta; Rżysko, Wojciech; Bryk, Paweł

2015-01-01

We use grand canonical Monte Carlo simulation paired with multiple histogram reweighting, hyperparallel tempering and finite size scaling to investigate the structure and phase behaviour of monolayers of diblock copolymers. The chain molecules are arranged on the square lattice and we consider both fully flexible and rod-coil polymer models. In contrast to the majority of previous studies we assume that the interactions between the segments belonging to one of the two subunits are weaker than the remaining segment–segment interactions. We find that when the diblock copolymer is fully flexible, this choice of the interactions leads to a suppression of the ordered phase, and the phase behaviour is analogous to that of the fully flexible homopolymer model. However, when one of the subunits is rigid, we observe the formation of a novel hairpin chessboard ordered structure with fully stretched chains bent in the middle. The topology of the phase diagram depends on the chain length. For shorter chains the global phase diagram features a critical point and a triple point. For longer chains the gas—disordered liquid phase transition is suppressed and only the order–disorder transition remains stable. The resulting phase diagram is of the swan neck type. (paper)

Phase behavior of diblock copolymer/star-shaped polymer thin film mixtures.

Science.gov (United States)

Zhao, Junnan; Sakellariou, Georgios; Green, Peter F

2016-05-07

We investigated the phase behavior of thin film, thickness h≈ 100 nm, mixtures of a polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) diblock copolymer with star-shaped polystyrene (SPS) molecules of varying functionalities f, where 4 ≤f≤ 64, and molecular weights per arm Marm. The miscibility of the system and the surface composition varied appreciably with Marm and f. For large values of Marm, regardless of f, the miscibility of the system was qualitatively similar to that of linear chain PS/PS-b-P2VP mixtures - the copolymer chains aggregate to form micelles, each composed of an inner P2VP core and PS corona, which preferentially segregate to the free surface. On the other hand, for large f and small Marm, SPS molecules preferentially resided at the free surface. Moreover, blends containing SPS molecules with the highest values of f and lowest values of Marm were phase separated. These observations are rationalized in terms of competing entropic interactions and the dependence of the surface tension of the star-shaped molecules on Marm and f.

Broadband pH-Sensing Organic Transistors with Polymeric Sensing Layers Featuring Liquid Crystal Microdomains Encapsulated by Di-Block Copolymer Chains.

Science.gov (United States)

Seo, Jooyeok; Song, Myeonghun; Jeong, Jaehoon; Nam, Sungho; Heo, Inseok; Park, Soo-Young; Kang, Inn-Kyu; Lee, Joon-Hyung; Kim, Hwajeong; Kim, Youngkyoo

2016-09-14

We report broadband pH-sensing organic field-effect transistors (OFETs) with the polymer-dispersed liquid crystal (PDLC) sensing layers. The PDLC layers are prepared by spin-coating using ethanol solutions containing 4-cyano-4'-pentyl-biphenyl (5CB) and a diblock copolymer (PAA-b-PCBOA) that consists of LC-philic block [poly(4-cyano-biphenyl-4-oxyundecyl acrylate) (PCBOA)] and acrylic acid block [poly(acrylic acid) (PAA)]. The spin-coated sensing layers feature of 5CB microdomains (pH with only small amounts (10-40 μL) of analyte solutions in both static and dynamic perfusion modes. The positive drain current change is measured for acidic solutions (pH pH > 7) result in the negative change of drain current. The drain current trend in the present PDLC-i-OFET devices is explained by the shrinking-expanding mechanism of the PAA chains in the diblock copolymer layers.

A Molecular Simulation Approach to the Prediction of the Morphology of Self-Assembled Nanoparticles in Diblock Copolymers

Czech Academy of Sciences Publication Activity Database

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

2010-01-01

Roč. 20, č. 46 (2010), s. 10511-10520 ISSN 0959-9428 R&D Projects: GA ČR GA203/08/0094; GA AV ČR KAN400720701 Grant - others:EC(XE) TD0802/OC10053 Institutional research plan: CEZ:AV0Z40720504 Keywords : diblock copolymers * nanoparticles * computer simulation Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 5.101, year: 2010

Complex and hierarchical micelle architectures from diblock copolymers using living, crystallization-driven polymerizations.

Science.gov (United States)

Gädt, Torben; Ieong, Nga Sze; Cambridge, Graeme; Winnik, Mitchell A; Manners, Ian

2009-02-01

Block copolymers consist of two or more chemically distinct polymer segments, or blocks, connected by a covalent link. In a selective solvent for one of the blocks, core-corona micelle structures are formed. We demonstrate that living polymerizations driven by the epitaxial crystallization of a core-forming metalloblock represent a synthetic tool that can be used to generate complex and hierarchical micelle architectures from diblock copolymers. The use of platelet micelles as initiators enables the formation of scarf-like architectures in which cylindrical micelle tassels of controlled length are grown from specific crystal faces. A similar process enables the fabrication of brushes of cylindrical micelles on a crystalline homopolymer substrate. Living polymerizations driven by heteroepitaxial growth can also be accomplished and are illustrated by the formation of tri- and pentablock and scarf architectures with cylinder-cylinder and platelet-cylinder connections, respectively, that involve different core-forming metalloblocks.

Synthesis of Diblock copolymer poly-3-hydroxybutyrate -block-poly-3-hydroxyhexanoate [PHB-b-PHHx] by a β-oxidation weakened Pseudomonas putida KT2442.

Science.gov (United States)

Tripathi, Lakshmi; Wu, Lin-Ping; Chen, Jinchun; Chen, Guo-Qiang

2012-04-05

Block polyhydroxyalkanoates (PHA) were reported to be resistant against polymer aging that negatively affects polymer properties. Recently, more and more attempts have been directed to make PHA block copolymers. Diblock copolymers PHB-b-PHHx consisting of poly-3-hydroxybutyrate (PHB) block covalently bonded with poly-3-hydroxyhexanoate (PHHx) block were for the first time produced successfully by a recombinant Pseudomonas putida KT2442 with its β-oxidation cycle deleted to its maximum. The chloroform extracted polymers were characterized by nuclear magnetic resonance (NMR), thermo- and mechanical analysis. NMR confirmed the existence of diblock copolymers consisting of 58 mol% PHB as the short chain length block with 42 mol% PHHx as the medium chain length block. The block copolymers had two glass transition temperatures (Tg) at 2.7°C and -16.4°C, one melting temperature (Tm) at 172.1°C and one cool crystallization temperature (Tc) at 69.1°C as revealed by differential scanning calorimetry (DSC), respectively. This is the first microbial short-chain-length (scl) and medium-chain-length (mcl) PHA block copolymer reported. It is possible to produce PHA block copolymers of various kinds using the recombinant Pseudomonas putida KT2442 with its β-oxidation cycle deleted to its maximum. In comparison to a random copolymer poly-3-hydroxybutyrate-co-3-hydroxyhexanoate (P(HB-co-HHx)) and a blend sample of PHB and PHHx, the PHB-b-PHHx showed improved structural related mechanical properties.

Effect of diblock copolymer properties on the photophysical properties of dendrimer silicon phthalocyanine nanoconjugates

Energy Technology Data Exchange (ETDEWEB)

Chen, Kuizhi [Fujian Normal University, College of Materials Science & Engineering, Fujian Provincial Key Laboratory of Polymer Materials (China); Pan, Sujuan [Fujian Normal University, College of Chemistry & Engineering (China); Zhuang, Xuemei [Fuzhou No.2 Hospital (China); Lv, Hafei; Que, Shoulin [Fujian Normal University, College of Chemistry & Engineering (China); Xie, Shusen; Yang, Hongqin, E-mail: hqyang@fjnu.edu.cn [Fujian Normal University, Key Laboratory of Optoelectronic Science and Technology for Medicine of Ministry of Education (China); Peng, Yiru, E-mail: yirupeng@fjnu.edu.cn [Fujian Normal University, College of Chemistry & Engineering (China)

2016-07-15

1–2 generation poly(benzyl aryl ether) dendrimer silicon phthalocyanines with axially disubstituted cyano terminal functionalities (G{sub n}-DSiPc(CN){sub 4n}, (G{sub n} = n-generation dendrimer, n = 1–2)) were synthesized. Their structures were characterized by elemental analysis, IR, {sup 1}H NMR, and ESI-MS. Polymeric nanoparticles (G{sub n}-DSiPc(CN){sub 4n}/m) were formed through encapsulating G{sub n}-DSiPc(CN){sub 4n} into three monomethoxyl poly(ethylene glycol)-poly(ε-caprolactone) diblock copolymers (MPEG–PCL) with different hydrophilic/hydrophobic proportion, respectively. The effect of dendritic generation and the hydrophilic/hydrophobic proportion of diblock copolymers on the UV/Vis and fluorescence spectra of G{sub n}-DSiPc(CN){sub 4n} and G{sub n}-DSiPc(CN){sub 4n}/m were studied. The photophysical properties of polymeric nanoparticles exhibited dendritic generation and hydrophilic/hydrophobic proportion dependence. The fluorescence intensities and lifetimes of G{sub n}-DSiPc(CN){sub 4n}/m were lower than the corresponding free dendrimer phthalocyanines. G{sub n}-DSiPc(CN){sub 4n} encapsulated into MPEG–PCL with hydrophilic/hydrophobic molecular weight ratio 2000:4000 exhibited excellent photophysical property. The mean diameter of MPEG{sub 2000}–PCL{sub 2000} micelles was about 70 nm, which decreased when loaded with G{sub n}-DSiPc(CN){sub 4n}.Graphical abstract .

Antimicrobial activity of poly(acrylic acid) block copolymers

Energy Technology Data Exchange (ETDEWEB)

Gratzl, Günther, E-mail: guenther.gratzl@jku.at [Johannes Kepler University Linz, Institute for Chemical Technology of Organic Materials, Altenberger Str. 69, 4040 Linz (Austria); Paulik, Christian [Johannes Kepler University Linz, Institute for Chemical Technology of Organic Materials, Altenberger Str. 69, 4040 Linz (Austria); Hild, Sabine [Johannes Kepler University Linz, Institute of Polymer Science, Altenberger Str. 69, 4040 Linz (Austria); Guggenbichler, Josef P.; Lackner, Maximilian [AMiSTec GmbH and Co. KG, Leitweg 13, 6345 Kössen, Tirol (Austria)

2014-05-01

The increasing number of antibiotic-resistant bacterial strains has developed into a major health problem. In particular, biofilms are the main reason for hospital-acquired infections and diseases. Once formed, biofilms are difficult to remove as they have specific defense mechanisms against antimicrobial agents. Antimicrobial surfaces must therefore kill or repel bacteria before they can settle to form a biofilm. In this study, we describe that poly(acrylic acid) (PAA) containing diblock copolymers can kill bacteria and prevent from biofilm formation. The PAA diblock copolymers with poly(styrene) and poly(methyl methacrylate) were synthesized via anionic polymerization of tert-butyl acrylate with styrene or methyl methacrylate and subsequent acid-catalyzed hydrolysis of the tert-butyl ester. The copolymers were characterized via nuclear magnetic resonance spectroscopy (NMR), size-exclusion chromatography (SEC), Fourier transform infrared spectroscopy (FTIR), elemental analysis, and acid–base titrations. Copolymer films with a variety of acrylic acid contents were produced by solvent casting, characterized by atomic force microscopy (AFM) and tested for their antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. The antimicrobial activity of the acidic diblock copolymers increased with increasing acrylic acid content, independent of the copolymer-partner, the chain length and the nanostructure. - Highlights: • Acrylic acid diblock copolymers are antimicrobially active. • The antimicrobial activity depends on the acrylic acid content in the copolymer. • No salts, metals or other antimicrobial agents are needed.

Antimicrobial activity of poly(acrylic acid) block copolymers

International Nuclear Information System (INIS)

Gratzl, Günther; Paulik, Christian; Hild, Sabine; Guggenbichler, Josef P.; Lackner, Maximilian

2014-01-01

The increasing number of antibiotic-resistant bacterial strains has developed into a major health problem. In particular, biofilms are the main reason for hospital-acquired infections and diseases. Once formed, biofilms are difficult to remove as they have specific defense mechanisms against antimicrobial agents. Antimicrobial surfaces must therefore kill or repel bacteria before they can settle to form a biofilm. In this study, we describe that poly(acrylic acid) (PAA) containing diblock copolymers can kill bacteria and prevent from biofilm formation. The PAA diblock copolymers with poly(styrene) and poly(methyl methacrylate) were synthesized via anionic polymerization of tert-butyl acrylate with styrene or methyl methacrylate and subsequent acid-catalyzed hydrolysis of the tert-butyl ester. The copolymers were characterized via nuclear magnetic resonance spectroscopy (NMR), size-exclusion chromatography (SEC), Fourier transform infrared spectroscopy (FTIR), elemental analysis, and acid–base titrations. Copolymer films with a variety of acrylic acid contents were produced by solvent casting, characterized by atomic force microscopy (AFM) and tested for their antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. The antimicrobial activity of the acidic diblock copolymers increased with increasing acrylic acid content, independent of the copolymer-partner, the chain length and the nanostructure. - Highlights: • Acrylic acid diblock copolymers are antimicrobially active. • The antimicrobial activity depends on the acrylic acid content in the copolymer. • No salts, metals or other antimicrobial agents are needed

Patterned Diblock Co-Polymer Thin Films as Templates for Advanced Anisotropic Metal Nanostructures.

Science.gov (United States)

Roth, Stephan V; Santoro, Gonzalo; Risch, Johannes F H; Yu, Shun; Schwartzkopf, Matthias; Boese, Torsten; Döhrmann, Ralph; Zhang, Peng; Besner, Bastian; Bremer, Philipp; Rukser, Dieter; Rübhausen, Michael A; Terrill, Nick J; Staniec, Paul A; Yao, Yuan; Metwalli, Ezzeldin; Müller-Buschbaum, Peter

2015-06-17

We demonstrate glancing-angle deposition of gold on a nanostructured diblock copolymer, namely polystyrene-block-poly(methyl methacrylate) thin film. Exploiting the selective wetting of gold on the polystyrene block, we are able to fabricate directional hierarchical structures. We prove the asymmetric growth of the gold nanoparticles and are able to extract the different growth laws by in situ scattering methods. The optical anisotropy of these hierarchical hybrid materials is further probed by angular resolved spectroscopic methods. This approach enables us to tailor functional hierarchical layers in nanodevices, such as nanoantennae arrays, organic photovoltaics, and sensor electronics.

Temperature and pressure dependence of the order parameter fluctuations, conformational compressibility, and the phase diagram of the PEP-PDMS diblock copolymer

DEFF Research Database (Denmark)

Schwahn, D.; Frielinghaus, H.; Mortensen, K.

1996-01-01

The structure factor of a poly(ethylene-propylene)-poly(dimethylsiloxane) diblock copolymer has been measured by small-angle neutron scattering as a function of temperature and pressure. The conformational compressibility exhibits a pronounced maximum at the order-disorder phase transition. The p...

Study of structural morphologies of thermoresponsive diblock AB and triblock BAB copolymers (A = poly(N-isopropylacrylamide), B = polystyrene)

Science.gov (United States)

Rodríguez-Hidalgo, María del Rosario; Soto-Figueroa, César; Vicente, Luis

2018-03-01

Structural morphologies of diblock AB and triblock BAB copolymers (A = poly(N-isopropylacrylamide), B = polystyrene) in aqueous environment have been investigated by dissipative particle dynamics (DPD). In triblock copolymers insoluble PS blocks contract while soluble pNIPAM blocks stay at the periphery forming looped chains as corona. As the temperature is increased there is a continuous morphological transition and micelles form ellipsoidal structures with segregated polymer zones. The phase transition of looped pNIPAM chains occurs at lower temperature than for linear chains and within broader temperature range. It is discussed how the chain topology of pNIPAM affects the phase transition.

Self-assembly of block copolymer-based ionic supramolecules based upon multi-tail amphiphiles

DEFF Research Database (Denmark)

Asad Ayoubi, M.; Almdal, Kristoffer; Zhu, K.

2015-01-01

Utilising simple acid-base titration chemistry, a new family of Linear-b-Amphiphilic Comb (L-b-AC) ionic supramolecules [Soft Matter 2013, 9, 1540-1555] featuring multi-tail side-chains have been synthesized and examined by synchrotron SAXS. To three different parent diblock copolymers of poly...

Directed Self-Assembly of Diblock Copolymer Thin Films on Prepatterned Metal Nanoarrays.

Science.gov (United States)

Chang, Tongxin; Huang, Haiying; He, Tianbai

2016-01-01

The sequential layer by layer self-assembly of block copolymer (BCP) nanopatterns is an effective approach to construct 3D nanostructures. Here large-scale highly ordered metal nano-arrays prepared from solvent annealed thin films of polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) diblock copolymer are used to direct the assembly of the same BCP. The influence of initial loading concentration of metal precursor, the type of metal nanoparticle (gold, platinum, and silver), and the nanoparticle-substrate interaction on the directed assembly behavior of the upper BCP layer have been focused. It is found that the upper BCP film can be completely directed by the gold nanoarray with P2VP domain exclusively located between two adjacent gold nanowires or nanodots, which behaves the same way as on the platinum nanoarray. While the silver nanoarray can be destroyed during the upper BCP self-assembly with the silver nanoparticles assembled into the P2VP domain. Based on the discussions of the surface energy of nanoparticles and the interplay between nanoparticle-substrate interaction and nanoparticle-polymer interaction, it is concluded that the effect of immobilization of nanoparticles on the substrate, together with entropy effect to minimize the energetically unfavorable chain stretching contributes to the most effective alignment between each layer. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Trillions of quantum dots, fingerprints, nanolithography with diblock copolymers and annealing of striped phases

International Nuclear Information System (INIS)

Chaikin, Paul

2003-01-01

Full text: We have been using diblock copolymers as a new way to make ultradense patterns which cover wide areas on a variety of inorganic substrates. The feature sizes are determined by the length of the polymers and can range from ∼ 5 to 50 nm. The diblock copolymers form lamellar, cylindrical (hexagonal cross-section), and spherical (BCC) phases in bulk. We use monolayer films to make templates to transfer these patterns to metals, semiconductors etc. For example we cover a three inch wafer with ∼ 3 trillion posts, holes, etc. spaced by ∼ 25nm, to make quantum dots (for semiconductor lasers), metal particles and other structures. In trying to understand how the polymer patterns order we have used atomic force microscopy (AFM) to image the cylindrical phase which lies flat on a substrate. The patterns look like fingerprints and Benard rolls and the coarsening (annealing) law we observe is t (1/4) as in previous studies of these striped phases. This law remained unexplained for decades. However, we made time lapse AFM movies which show that the annealing dynamics is governed by the attraction of disclination PAIRS, quadrupoles, rather than simple +/- annihilation. This directly provides an explanation for the alignment of the striped patterns as a function of time. Thus these systems, while aimed at technological and fundamental electronic applications are also ideal materials for studying the dynamics of ordering. Recently we have also studied the thermodynamics and kinetics of the monolayer hexatic phase and used shear strain to macroscopically align the cylindrical and hexagonal patterns. (author)

The influence of chain stretching on the phase behavior of multiblock copolymer and comb copolymer melts

NARCIS (Netherlands)

Angerman, HJ; ten Brinke, G

The subject of this paper is inspired by microphase-separated copolymer melts in which a small-scale structure is present inside one of the phases of a large-scale structure. Such a situation can arise in a diblock copolymer melt, if one of the blocks of the diblock is in itself a multiblock

Imidazolium-based Block Copolymers as Solid-State Separators for Alkaline Fuel Cells and Lithium Ion Batteries

Science.gov (United States)

Nykaza, Jacob Richard

In this study, polymerized ionic liquid (PIL) diblock copolymers were explored as solid-state polymer separators as an anion exchange membrane (AEM) for alkaline fuel cells AFCs and as a solid polymer electrolyte (SPE) for lithium-ion batteries. Polymerized ionic liquid (PIL) block copolymers are a distinct set of block copolymers that combine the properties of both ionic liquids (e.g., high conductivity, high electrochemical stability) and block copolymers (e.g., self-assembly into various nanostructures), which provides the opportunity to design highly conductive robust solid-state electrolytes that can be tuned for various applications including AFCs and lithium-ion batteries via simple anion exchange. A series of bromide conducting PIL diblock copolymers with an undecyl alkyl side chain between the polymer backbone and the imidazolium moiety were first synthesized at various compositions comprising of a PIL component and a non-ionic component. Synthesis was achieved by post-functionalization from its non-ionic precursor PIL diblock copolymer, which was synthesized via the reverse addition fragmentation chain transfer (RAFT) technique. This PIL diblock copolymer with long alkyl side chains resulted in flexible, transparent films with high mechanical strength and high bromide ion conductivity. The conductivity of the PIL diblock copolymer was three times higher than its analogous PIL homopolymer and an order of magnitude higher than a similar PIL diblock copolymer with shorter alkyl side chain length, which was due to the microphase separated morphology, more specifically, water/ion clusters within the PIL microdomains in the hydrated state. Due to the high conductivity and mechanical robustness of this novel PIL block copolymer, its application as both the ionomer and AEM in an AFC was investigated via anion exchange to hydroxide (OH-), where a maximum power density of 29.3 mW cm-1 (60 °C with H2/O2 at 25 psig (172 kPa) backpressure) was achieved. Rotating disk

Diblock Polyelectrolytic Copolymers Containing Cationic Iron and Cobalt Sandwich Complexes: Living ROMP Synthesis and Redox Properties.

Science.gov (United States)

Gu, Haibin; Ciganda, Roberto; Hernandez, Ricardo; Castel, Patricia; Zhao, Pengxiang; Ruiz, Jaime; Astruc, Didier

2016-04-01

Diblock metallopolymer polyelectrolytes containing the two redox-robust cationic sandwich units [CoCp'Cp](+) and [FeCp'(η(6)-C6 Me6)](+) (Cp = η(5)-C5 H5; Cp' = η(5)-C5H4-) as hexafluorophosphate ([PF6](-)) salts are synthesized by ring-opening metathesis polymerization using Grubbs' third generation catalyst. Their electrochemical properties show full chemical and electrochemical reversibilities allowing fine determination of the copolymer molecular weight using Bard-Anson's electrochemical method by cyclic voltammetry. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Collective dynamics and self-diffusion in a diblock copolymer melt in the body-centered cubic phase

DEFF Research Database (Denmark)

Papadakis, C.M.; Rittig, F.; Almdal, K.

2004-01-01

The structure and dynamics of a strongly asymmetric poly(ethylene propylene)poly (dimethylsiloxane) (PEP-PDMS) diblock copolymer in the melt have been studied over a wide temperature range. Small-angle neutron scattering reveals that the sample exhibits two stable phases in this temperature range......: Above the order-to-disorder transition temperature, it is disordered, whereas the domain structure is body-centered cubic (bcc) below, being stable down to the lowest temperatures measured. In the disordered state, dynamic light scattering (DLS) in the polarized geometry reveals the heterogeneity mode...

Design of block-copolymer-based micelles for active and passive targeting

NARCIS (Netherlands)

Lebouille, Jérôme G J L; Leermakers, Frans A M; Cohen Stuart, Martien A.; Tuinier, Remco

2016-01-01

A self-consistent field study is presented on the design of active and passive targeting block-copolymeric micelles. These micelles form in water by self-assembly of triblock copolymers with a hydrophilic middle block and two hydrophobic outer blocks. A minority amount of diblock copolymers with the

Design of block-copolymer-based micelles for active and passive targeting

NARCIS (Netherlands)

Lebouille, Jérôme G.J.L.; Leermakers, Frans A.M.; Cohen Stuart, Martien A.; Tuinier, Remco

2016-01-01

A self-consistent field study is presented on the design of active and passive targeting block-copolymeric micelles. These micelles form in water by self-assembly of triblock copolymers with a hydrophilic middle block and two hydrophobic outer blocks. A minority amount of diblock copolymers with

Single-molecule tracking studies of flow-induced microdomain alignment in cylinder-forming polystyrene-poly(ethylene oxide) diblock copolymer films.

Science.gov (United States)

Tran-Ba, Khanh-Hoa; Higgins, Daniel A; Ito, Takashi

2014-09-25

Flow-based approaches are promising routes to preparation of aligned block copolymer microdomains within confined spaces. An in-depth characterization of such nanoscale morphologies within macroscopically nonuniform materials under ambient conditions is, however, often challenging. In this study, single-molecule tracking (SMT) methods were employed to probe the flow-induced alignment of cylindrical microdomains (ca. 22 nm in diameter) in polystyrene-poly(ethylene oxide) diblock copolymer (PS-b-PEO) films. Films of micrometer-scale thicknesses were prepared by overlaying a benzene solution droplet on a glass coverslip with a rectangular glass plate, followed by solvent evaporation under a nitrogen atmosphere. The microdomain alignment was quantitatively assessed from SMT data exhibiting the diffusional motions of individual sulforhodamine B fluorescent probes that preferentially partitioned into cylindrical PEO microdomains. Better overall microdomain orientation along the flow direction was observed near the substrate interface in films prepared at a higher flow rate, suggesting that the microdomain alignment was primarily induced by shear flow. The SMT data also revealed the presence of micrometer-scale grains consisting of highly ordered microdomains with coherent orientation. The results of this study provide insights into shear-based preparation of aligned cylindrical microdomains in block copolymer films from solutions within confined spaces.

Coupling of microphase separation and dewetting in weakly segregated diblock co-polymer ultrathin films.

Science.gov (United States)

Yan, Derong; Huang, Haiying; He, Tianbai; Zhang, Fajun

2011-10-04

We have studied the coupling behavior of microphase separation and autophobic dewetting in weakly segregated poly(ε-caprolactone)-block-poly(L-lactide) (PCL-b-PLLA) diblock co-polymer ultrathin films on carbon-coated mica substrates. At temperatures higher than the melting point of the PLLA block, the co-polymer forms a lamellar structure in bulk with a long period of L ∼ 20 nm, as determined using small-angle X-ray scattering. The relaxation procedure of ultrathin films with an initial film thickness of h = 10 nm during annealing has been followed by atomic force microscopy (AFM). In the experimental temperature range (100-140 °C), the co-polymer dewets to an ultrathin film of itself at about 5 nm because of the strong attraction of both blocks with the substrate. Moreover, the dewetting velocity increases with decreasing annealing temperatures. This novel dewetting kinetics can be explained by a competition effect of the composition fluctuation driven by the microphase separation with the dominated dewetting process during the early stage of the annealing process. While dewetting dominates the relaxation procedure and leads to the rupture of the ultrathin films, the composition fluctuation induced by the microphase separation attempts to stabilize them because of the matching of h to the long period (h ∼ 1/2L). The temperature dependence of these two processes leads to this novel relaxation kinetics of co-polymer thin films. © 2011 American Chemical Society

Water-stable diblock polystyrene-block-poly(2-vinyl pyridine) and diblock polystyrene-block-poly(methyl methacrylate) cylindrical patterned surfaces inhibit settlement of zoospores of the green alga Ulva.

Science.gov (United States)

Grozea, Claudia M; Gunari, Nikhil; Finlay, John A; Grozea, Daniel; Callow, Maureen E; Callow, James A; Lu, Zheng-Hong; Walker, Gilbert C

2009-04-13

Nanopatterned surfaces with hydrophobic and hydrophilic domains were produced using the diblock copolymer polystyrene-block-poly(2-vinyl pyridine) (PS-b-P2VP) and polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA). The PS-b-P2VP diblock copolymer, mixed with the cross-linker benzophenone and spin-coated onto silicon wafers, showed self-assembled cylindrical structures, which were retained after UV treatment for cross-linking. The thin films displayed cylindrical domains after immersion in water. This study shows that pattern retention in water is possible for a long period of time, at least for two weeks in pure water and three weeks in artificial seawater. The PS-b-PMMA diblock showed self-assembled cylindrical structures. PS-b-P2VP and PS-b-PMMA cylindrical patterned surfaces showed reduced settlement of zoospores of the green alga Ulva compared to unpatterned surfaces. The copolymers were investigated using atomic force microscopy and X-ray photoelectron spectroscopy.

Effects of PEO-PPO diblock impurities on the cubic structure of aqueous PEO-PPO-PEO pluronics micelles: fcc and bcc ordered structures in F127

DEFF Research Database (Denmark)

Mortensen, Kell; Pedersen, Walther Batsberg; Hvidt, S.

2008-01-01

We report on structural properties of PEO-PPO-PEO type of triblock block copolymers (Pluronics F127) with special emphasis on the effect of diblock PEO-PPO impurities on the ordered gel phase. Commercial F127 polymers contain as received roughly 20% PEO-PPO diblock and 80% PEO-PPO-PEO triblock...... copolymers. Aqueous solutions of F127 copolymers used as received form fee ordered micellar structure. Copolymers depleted with respect to the diblock impurity, resulting in a pure PEO-PPO-PEO triblock copolymer system, form bcc ordered micelles within the major parts of the gel phase. However, close...

A Quantitative Study of Tethered Chains in Various Solution Conditions Using Langmuir Diblock Copolymer Monolayers

Energy Technology Data Exchange (ETDEWEB)

Kent, Michael S.

1999-08-13

This article summarizes our investigations of tethered chain systems using Langmuir monolayer of polydimethysiloxane-poly styrene (PDMS-PS) diblock copolymers on organic liquids. In this system, the PDMS block adsorbs to the air surface while the PS block dangles into the subphase liquid. The air surface can be made either repulsive or attractive for the tethered PS chain segments by choosing a subphase liquid which has a surface tension lower or greater than that of PS, respectively. The segment profile of the PS block is determined by neutron reflection as a function of the surface density, the molecular weights of the PS and PDMS blocks, and the solution conditions. We cover the range of reduced surface density (SIGMA) characteristic of the large body of data in the literature for systems of chains tethered onto solid surfaces from dilute solution in good or theta solvent conditions (SIGMA < 12). We emphasize quantitative comparisons with analytical profile forms and scaling predictions. We find that the strong-stretching limit invoked in analytical SCF and scaling theories is not valid over this Z range. On the other hand, over a large portion of this range (SIGMA < 5) tethered layers are well described by a renormalization group theory addressing weakly interacting or noninteracting chains. Simultaneous with the study of the profile form, the free energy of the chains is examined through the surface tension. A strong increase in the surface pressure is observed with increasing surface density which determines the maximum surface density which can be achieved. This apparently nonequilibrium effect is attributed to steric interactions and limited lateral interpenetration. This effect may explain several outstanding discrepancies regarding the adsorption of end-functionalized chains and diblock copolymers onto solid surfaces.

One-step route to the fabrication of highly porous polyaniline nanofiber films by using PS-b-PVP diblock copolymers as templates.

Science.gov (United States)

Li, Xue; Tian, Shengjun; Ping, Yang; Kim, Dong Ha; Knoll, Wolfgang

2005-10-11

We report a new method to control both the nucleation and growth of highly porous polyaniline (PANI) nanofiber films using porous poly(styrene-block-2-vinylpyridine) diblock copolymer (PS-b-P2VP) films as templates. A micellar thin film composed of P2VP spheres within a PS matrix is prepared by spin coating a PS-b-P2VP micellar solution onto substrates. The P2VP domains are swollen in a selective solvent of acetic acid, which results in the formation of pores in the block copolymer film. PANI is then deposited onto the substrates modified with such a porous film using electrochemical methods. During the deposition, the nucleation and growth of PANI occur only at the pores of the block copolymer film. After the continued growth of PANI by the electrochemical deposition, a porous PANI nanofiber film is obtained.

Synthesis and self-assembly behavior of amphiphilic diblock copolymer dextran-block-poly(ε-caprolactone (DEX-b-PCL in aqueous media

Directory of Open Access Journals (Sweden)

2010-10-01

Full Text Available An amphiphilic diblock copolymer, dextran-block-poly(ε-caprolactone (DEX-b-PCL, with a series of welldefined chain lengths of each block was prepared by conjugating a dextran chain with a PCL block via aza-Michael addition reaction under mild conditions. For the dextran block, samples with relatively uniform molecular weight, 3.5 and 6.0 kDa, were used, and the PCL blocks were prepared via ring-opening polymerization at defined ratios of ε-caprolactone to initiator in order to give copolymers with mass fraction of dextran (fDEX ranging from 0.16 to 0.45. When these copolymers were allowed to self-assemble in aqueous solution, the morphology of assembled aggregates varied as a function of fDEX when characterized by transmission electron microscope (TEM, fluorescence microscope (FM and dynamic laser scattering (DLS. As fDEX decreases gradually from 0.45 to 0.16, the morphology of the copolymer assembly changes from spherical micelles to worm-like micelles and eventually to polymersomes, together with an increase in particle sizes.

Novel poly(ethylene oxide monomethyl ether)-b-poly(.epsilon.-caprolactone) diblock copolymers containing a pH-acid labile ketal group as a block linkage

Czech Academy of Sciences Publication Activity Database

Petrova, Svetlana; Jäger, Eliezer; Konefal, Rafal; Jäger, Alessandro; Venturini, Cristina Garcia; Spěváček, Jiří; Pavlova, Ewa; Štěpánek, Petr

2014-01-01

Roč. 5, č. 12 (2014), s. 3884-3893 ISSN 1759-9954 R&D Projects: GA ČR GAP208/10/1600; GA TA ČR TE01020118 Institutional support: RVO:61389013 Keywords : MPOE-b-PCL diblock copolymers * ring-opening polymerization * "click" chemistry Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 5.520, year: 2014

Inhomogeneity of block copolymers at the interface of an immiscible polymer blend

Science.gov (United States)

Ryu, Ji Ho; Kim, YongJoo; Lee, Won Bo

2018-04-01

We present the effects of structure and stiffness of block copolymers on the interfacial properties of an immiscible homopolymer blend. Diblock and two-arm grafted copolymers with variation in stiffness are modeled using coarse-grained molecular dynamics to compare the compatibilization efficiency, i.e., reduction of interfacial tension. Overall, grafted copolymers are located more compactly at the interface and show better compatibilization efficiency than diblock copolymers. In addition, an increase in the stiffness for one of the blocks of the diblock copolymers causes unusual inhomogeneous interfacial coverage due to bundle formation. However, an increase in the stiffness for one of blocks of the grafted copolymers prevents the bundle formation due to the branched chain. As a result, homogeneous interfacial coverage of homopolymer blends is realized with significant reduction of interfacial tension which makes grafted copolymer a better candidate for the compatibilizer of immiscible homopolymer blend.

Rapid Ordering in "Wet Brush" Block Copolymer/Homopolymer Ternary Blends.

Science.gov (United States)

Doerk, Gregory S; Yager, Kevin G

2017-12-26

The ubiquitous presence of thermodynamically unfavored but kinetically trapped topological defects in nanopatterns formed via self-assembly of block copolymer thin films may prevent their use for many envisioned applications. Here, we demonstrate that lamellae patterns formed by symmetric polystyrene-block-poly(methyl methacrylate) diblock copolymers self-assemble and order extremely rapidly when the diblock copolymers are blended with low molecular weight homopolymers of the constituent blocks. Being in the "wet brush" regime, the homopolymers uniformly distribute within their respective self-assembled microdomains, preventing increases in domain widths. An order-of-magnitude increase in topological grain size in blends over the neat (unblended) diblock copolymer is achieved within minutes of thermal annealing as a result of the significantly higher power law exponent for ordering kinetics in the blends. Moreover, the blends are demonstrated to be capable of rapid and robust domain alignment within micrometer-scale trenches, in contrast to the corresponding neat diblock copolymer. These results can be attributed to the lowering of energy barriers associated with domain boundaries by bringing the system closer to an order-disorder transition through low molecular weight homopolymer blending.

A new formulation of curcumin using poly (lactic-co-glycolic acid)—polyethylene glycol diblock copolymer as carrier material

International Nuclear Information System (INIS)

Tuyen Dao, Thi Phuong; Nguyen, To Hoai; To, Van Vinh; Ho, Thanh Ha; Nguyen, Tuan Anh; Dang, Mau Chien

2014-01-01

The aim of this study is to fabricate a nanoparticle formulation of curcumin using a relatively new vehicle as the matrix polymer: poly(lactic-co-glycolic acid) (PLGA)- polyethylene glycol (PEG) diblock copolymer, and to investigate the effects of the various processing parameters on the characteristics of nanoparticles (NPs). We successfully synthesized the matrix polymer of PLGA-PEG by conjugation of PLGA copolymer with a carboxylate end group to a heterobifunctional amine-PEG-methoxy using N-(3-dimethylaminopropyl)-N’-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide as conjugation crosslinkers. The composition of the formed product (PLGA-PEG) was characterized with 500 MHz 1 H nuclear magnetic resonance (NMR). The conjugation of PLGA-PEG was confirmed using Fourier transform infrared (FTIR) spectrum study. This diblock copolymer was then used to prepare the curcumin-loaded NPs through nanoprecipitation technique. With this method, we found that the size distribution depends on the type of solvent, the concentration of polymer and the concentration of surfactant. The particle size and size distribution were measured by dynamic light scattering (DLS). Transmission electron microscope (TEM) and scanning electron microscope (SEM) were used to confirm the size, structure and morphology of the successfully prepared NPs. All of our results showed that they are spherical and quite homologous with mean diameter around of 100–300 nm. Further, we evaluated encapsulation efficiency and some characteristics of NPs through high performance liquid chromatography (HPLC) analyses, zeta-potential measurements and x-ray diffraction studies. The HPLC analyses were performed to determine the amount of curcumin entrapped in NPs. The zeta-potential measurements confirmed the stability of NPs and the successful encapsulation of curcumin within NPs and the x-ray diffraction patterns showed the disordered-crystalline phase of curcumin inside the polymeric matrix. (paper)

Anomalous Behaviors of Block Copolymers at the Interface of an Immiscible Polymer Blend

Science.gov (United States)

Ryu, Ji Ho; Lee, Won Bo

We investigate the effects of structure and stiffness of block copolymers on the interface of an immiscible polymer blend using coarse-grained molecular dynamics (CGMD) simulation. The diblock and grafted copolymers, which are described by Kremer and Grest bead spring model, are used to compare the compatibilization efficiency, that is, reduction of the interfacial tension. It is found that, overall, the grafted copolymers are located more compactly at the interface and show better compatibilization efficiency than diblock copolymers. In addition, it is noted that an increase in the stiffness of one block of diblock copolymer causes inhomogeneous interfacial coverage due to bundle formation among the stiff blocks and orientational constraint on bundled structures near the interface, which makes copolymers poor compatibilizers. The dependence of anomalous orientational constraint on the chain length of homopolymers is also investigated. Theoretical and Computational Soft Matters Lab.

Vertical vs Lateral Macrophase Separation in Thin Films of Block Copolymer Mixtures

DEFF Research Database (Denmark)

Berezkin, Anatoly V.; Jung, Florian; Posselt, Dorthe

2017-01-01

Mixtures of two diblock copolymers of very different lengths may feature both macro- and microphase separation; however, not much is known about the mechanisms of separation in diblock copolymer thin films. In the present work, we study thin films of mixtures of two compositionally symmetric bloc...

Chemical modifications to vesicle forming diblock copolymers: Development of smart functional polymersome membranes

Science.gov (United States)

Katz, Joshua S.

2011-07-01

A major limitation to current treatment regimens for diseases is the inability to adequately deliver therapeutics. Many routes to encapsulation of these materials have been explored to improve biodistribution and better protect encapsulants from harsh biological conditions. One vehicle particularly attractive for encapsulation of such materials is the polymersome. While promising for translation to clinical use, there are still limitations in polymer chemistry and resulting polymersome behavior that will slow their adaptation. This thesis addresses several of these limitations. The first major limitation to polymersomes is lack of control over their release rate. Release is generally by simple diffusion, leading to a burst. To address this burst, Aim 1 proposes a route to stabilizing polymersome membranes through their polymerization. PCL-PEG copolymers were terminally acrylated and the acrylates polymerized in the membrane following vesicle assembly. Polymerization enhanced mechanical robustness of the membranes and reduced diffusion of encapsulated contents. To ultimately trigger release, Aim 2 presents a novel route to synthesizing diblock copolymers, enabling insertion of a functional group at the blocks' junction. To facilitate triggering of release, we inserted UV-cleavable 2-nitrophenylalanine. Polymersomes assembled from this polymer collapse upon exposure to light and molecules release. Demonstrating further utility of this synthetic route, fluorescent vesicles were prepared using fluorescent lysine as the joining molecule. These vesicles labeled dendritic cells, providing a novel route to cell labeling and tracking. The second limitation to vesicles promising for biomedical applications (made of PCL-PEG) is their solid membranes. Aim 3 demonstrates partial (or full) replacement of the PCL block with a caprolactone analogue, TOSUO, which is non-crystalline and assembles into soft, deformable vesicles. Increasing TOSUO content in the copolymer leads to

Morphological investigation of polydisperse asymmetric block copolymer systems of poly(styrene) and poly(methacrylic acid) in the strong segregation regime

DEFF Research Database (Denmark)

Asad Ayoubi, Mehran; Zhu, Kaizheng; Nyström, Bo

2013-01-01

Samples of compositionally (highly) asymmetric diblock copolymers and, also, mixtures of diblock and triblock copolymers (the latter obtained as end-coupling products of two diblock molecules of the mixture), composed of (a) monodisperse majority block(s) of poly(styrene) (PS) and a polydisperse...

Morphological transformations of diblock copolymers in binary solvents: A simulation study

Science.gov (United States)

Wang, Zheng; Yin, Yuhua; Jiang, Run; Li, Baohui

2017-12-01

Morphological transformations of amphiphilic AB diblock copolymers in mixtures of a common solvent (S1) and a selective solvent (S2) for the B block are studied using the simulated annealing method. We focus on the morphological transformation depending on the fraction of the selective solvent C S2, the concentration of the polymer C p , and the polymer-solvent interactions ɛ ij ( i = A, B; j = S1, S2). Morphology diagrams are constructed as functions of C p , C S2, and/or ɛ AS2. The copolymer morphological sequence from dissolved → sphere → rod → ring/cage → vesicle is obtained upon increasing C S2 at a fixed C p . This morphology sequence is consistent with previous experimental observations. It is found that the selectivity of the selective solvent affects the self-assembled microstructure significantly. In particular, when the interaction ɛ BS2 is negative, aggregates of stacked lamellae dominate the diagram. The mechanisms of aggregate transformation and the formation of stacked lamellar aggregates are discussed by analyzing variations of the average contact numbers of the A or B monomers with monomers and with molecules of the two types of solvent, as well as the mean square end-to-end distances of chains. It is found that the basic morphological sequence of spheres to rods to vesicles and the stacked lamellar aggregates result from competition between the interfacial energy and the chain conformational entropy. Analysis of the vesicle structure reveals that the vesicle size increases with increasing C p or with decreasing C S2, but remains almost unchanged with variations in ɛ AS2.

Photo-Induced Micellization of Block Copolymers

Directory of Open Access Journals (Sweden)

Satoshi Kuwayama

2010-11-01

Full Text Available We found novel photo-induced micellizations through photolysis, photoelectron transfer, and photo-Claisen rearrangement. The photolysis-induced micellization was attained using poly(4-tert-butoxystyrene-block-polystyrene diblock copolymer (PBSt-b-PSt. BSt-b-PSt showed no self-assembly in dichloromethane and existed as isolated copolymers. Dynamic light scattering demonstrated that the copolymer produced spherical micelles in this solvent due to irradiation with a high-pressure mercury lamp in the presence of photo-acid generators, such as bis(alkylphenyliodonium hexafluorophosphate, diphenyliodonium hexafluorophosphate, and triphenylsulfonium triflate. The 1H NMR analysis confirmed that PBSt-b-PSt was converted into poly(4-vinylphenol-block-PSt by the irradiation, resulting in self-assembly into micelles. The irradiation in the presence of the photo-acid generator also induced the micellization of poly(4-pyridinemethoxymethylstyrene-block-polystyrene diblock copolymer (PPySt-b-PSt. Micellization occurred by electron transfer from the pyridine to the photo-acid generator in their excited states and provided monodispersed spherical micelles with cores of PPySt blocks. Further, the photo-Claisen rearrangement caused the micellization of poly(4-allyloxystyrene-block-polystyrene diblock copolymer (PASt-b-PSt. Micellization was promoted in cyclohexane at room temperature without a catalyst. During micellization, the elimination of the allyl groups competitively occurred along with the photorearrangement of the 4-allyloxystyrene units into the 3-allyl-4-hydroxystyrene units.

Lateral Order and Self-Organized Morphology of Diblock Copolymer Micellar Films

Directory of Open Access Journals (Sweden)

Jiun-You Liou

2018-05-01

Full Text Available We report the lateral order and self-organized morphology of diblock copolymer polystyrene-block-poly(2-vinylpyridine, P(S-b-2VP, and micelles on silicon substrates (SiOx/Si. These micellar films were prepared by spin coating from polymer solutions of varied concentration of polymer in toluene onto SiOx/Si, and were investigated with grazing-incidence small-angle X-ray scattering (GISAXS and an atomic force microscope (AFM. With progressively increased surface coverage with increasing concentration, loosely packed spherical micelles, ribbon-like nanostructures, and a second layer of spherical micelles were obtained sequentially. Quantitative analysis and simulations of the micellar packing demonstrates that the spatial ordering of the loosely packed spherical micelles altered from short-range order to hexagonal order when the micellar coverage increased from small to moderate densities of the covered surface. At large densities, anisotropic fusion between spherical micelles caused the ribbon-like nanostructures to have a short-range spatial order; the ordering quality of the second layer was governed by the rugged surface of the underlying layer because the valleys between the ribbon-like nanostructures allowed for further deposition of spherical micelles.

Nanoporous Crosslinked Polyisoprene from Polyisoprene-Polydimethylsiloxane Block Copolymer

DEFF Research Database (Denmark)

Hansen, Michael Steffen; Vigild, Martin Etchells; Berg, Rolf Henrik

2004-01-01

The polyisoprene block of a polyisoprene-polydimethylsiloxane (PI-PDMS) diblock copolymer with 0.68 volume fraction of PI was tightly crosslinked with dicumylperoxide. The PDMS part of the obtained glassy material was subsequently quantitatively etched with anhydrous hydrogen fluoride or tetrabut......The polyisoprene block of a polyisoprene-polydimethylsiloxane (PI-PDMS) diblock copolymer with 0.68 volume fraction of PI was tightly crosslinked with dicumylperoxide. The PDMS part of the obtained glassy material was subsequently quantitatively etched with anhydrous hydrogen fluoride...

Copolymers at the solid - liquid interface

NARCIS (Netherlands)

Wijmans, C.M.

1994-01-01

Copolymers consisting of both adsorbing and nonadsorbing segments can show an adsorption behaviour which is very different from that of homopolymers. We have mainly investigated the adsorption of AB diblock copolymers, which have one adsorbing block (anchor) and one nonadsorbing block

Shear Alignment of Diblock Copolymers for Patterning Nanowire Meshes

Energy Technology Data Exchange (ETDEWEB)

Gustafson, Kyle T. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

2016-09-08

Metallic nanowire meshes are useful as cheap, flexible alternatives to indium tin oxide – an expensive, brittle material used in transparent conductive electrodes. We have fabricated nanowire meshes over areas up to 2.5 cm² by: 1) mechanically aligning parallel rows of diblock copolymer (diBCP) microdomains; 2) selectively infiltrating those domains with metallic ions; 3) etching away the diBCP template; 4) sintering to reduce ions to metal nanowires; and, 5) repeating steps 1 – 4 on the same sample at a 90° offset. We aligned parallel rows of polystyrene-b-poly(2-vinylpyridine) [PS(48.5 kDa)-b-P2VP(14.5 kDa)] microdomains by heating above its glass transition temperature (T_g ≈ 100°C), applying mechanical shear pressure (33 kPa) and normal force (13.7 N), and cooling below T_g. DiBCP samples were submerged in aqueous solutions of metallic ions (15 – 40 mM ions; 0.1 – 0.5 M HCl) for 30 – 90 minutes, which coordinate to nitrogen in P2VP. Subsequent ozone-etching and sintering steps yielded parallel nanowires. We aimed to optimize alignment parameters (e.g. shear and normal pressures, alignment duration, and PDMS thickness) to improve the quality, reproducibility, and scalability of meshes. We also investigated metals other than Pt and Au that may be patterned using this technique (Cu, Ag).

Magnetic field alignment of coil-coil diblock copolymers and blends via intrinsic chain anisotropy

Science.gov (United States)

Rokhlenko, Yekaterina; Majewski, Pawel; Larson, Steven; Yager, Kevin; Gopalan, Padma; Avgeropoulos, Apostolos; Chan, Edwin; Osuji, Chinedum

Magnetic fields can control alignment of self-assembled soft materials such as block copolymers provided there is a suitably large magnetic susceptibility anisotropy present in the system. Recent results have highlighted the existence of a non-trivial intrinsic anisotropy in coil-coil diblock copolymers, specifically in lamellar-forming PS-b-P4VP, which enables alignment at field strengths of a few tesla in systems lacking mesogenic components. Alignment is predicated on correlation in the orientation of end-end vectors implied by the localization of block junctions at the microdomain interface and is observed on cooling across the order-disorder transition in the presence of the field. For appropriate combinations of field strength and grain size, we can leverage intrinsic chain anisotropy to magnetically direct self-assembly of many non-mesogenic systems, including other coil-coil BCPs like PS-b-PDMS and PS-b-PMMA, blends of BCPs of disparate morphologies and MWs, and blends of BCPs with homopolymers. This is noteworthy as blends of PS-b-P4VP with PEO provide a route to form functional materials such as nanoporous films by dissolution of PEO, or aligned ion conduction materials. We survey these various systems using TEM and in-situ X-ray scattering to study the phase behavior and temperature-, time- and field- dependent dynamics of alignment.

Preparations, Properties, and Applications of Periodic Nano Arrays using Anodized Aluminum Oxide and Di-block Copolymer

Science.gov (United States)

Noh, Kunbae

2011-12-01

Self-ordered arrangements observed in various materials systems such as anodic aluminum oxide, polystyrene nanoparticles, and block copolymer are of great interest in terms of providing new opportunities in nanofabrication field where lithographic techniques are broadly used in general. Investigations on self-assembled nano arrays to understand how to obtain periodic nano arrays in an efficient yet inexpensive way, and how to realize advanced material and device systems thereof, can lead to significant impacts on science and technology for many forefront device applications. In this thesis, various aspects of periodic nano-arrays have been discussed including novel preparations, properties and applications of anodized aluminum oxide (AAO) and PS-b-P4VP (S4VP) di-block copolymer self-assembly. First, long-range ordered AAO arrays have been demonstrated. Nanoimprint lithography (NIL) process allowed a faithful pattern transfer of the imprint mold pattern onto Al thin film, and interesting self-healing and pattern tripling phenomena were observed, which could be applicable towards fabrication of the NIL master mold having highly dense pattern over large area, useful for fabrication of a large-area substrate for predictable positioning of arrayed devices. Second, S4VP diblock copolymer self-assembly and S4VP directed AAO self-assembly have been demonstrated in the Al thin film on Si substrate. Such a novel combination of two dissimilar self-assembly techniques demonstrated a potential as a versatile tool for nanopatterning formation on a Si substrate, capable of being integrated into Si process technology. As exemplary applications, vertically aligned Ni nanowires have been synthesized into an S4VP-guided AAO membrane on a Si substrate in addition to anti-dot structured [Co/Pd]n magnetic multilayer using S4VP self assembly. Third, a highly hexagonally ordered, vertically parallel aluminum oxide nanotube array was successfully fabricated via hard anodization technique

Self-assembling of poly(ε-caprolactone)-b-poly(ethylene oxide) diblock copolymers in aqueous solution and at the silica-water interface

International Nuclear Information System (INIS)

Leyh, B.; Vangeyte, P.; Heinrich, M.; Auvray, L.; De Clercq, C.; Jerome, R.

2004-01-01

Small-angle neutron scattering is used to investigate the self-assembling behaviour of poly(ε-caprolactone)-b-poly(ethylene oxide) diblock copolymers with various block lengths (i) in aqueous solution, (ii) in aqueous solution with the addition of sodium dodecyl sulphate (SDS) and (iii) at the silica-water interface. Micelles are observed under our experimental conditions due to the very small critical micellar concentration of these copolymers (0.01 g/l). The poly(ε-caprolactone) core is surrounded by a poly(ethylene oxide) corona. The micellar form factors have been measured at low copolymer concentrations (0.2 wt%) under selected contrast matching conditions. The data have been fitted to various analytical models to extract the micellar core and corona sizes. SDS is shown to induce partial micelle disruption together with an increase of the poly(ethylene oxide) corona extension from 25% (without SDS) to 70% (with SDS) of a completely extended PEO 114 chain. Our data at the silica-water interface are compatible with the adsorption of micelles

Phase Behavior of Diblock Copolymer–Homopolymer Ternary Blends: Congruent First-Order Lamellar–Disorder Transition

Energy Technology Data Exchange (ETDEWEB)

Hickey, Robert J.; Gillard, Timothy M.; Irwin, Matthew T.; Morse, David C.; Lodge, Timothy P.; Bates, Frank S. (UMM)

2016-10-13

We have established the existence of a line of congruent first-order lamellar-to-disorder (LAM–DIS) transitions when appropriate amounts of poly(cyclohexylethylene) (C) and poly(ethylene) (E) homopolymers are mixed with a corresponding compositionally symmetric CE diblock copolymer. The line of congruent transitions, or the congruent isopleth, terminates at the bicontinuous microemulsion (BμE) channel, and its trajectory appears to be influenced by the critical composition of the C/E binary homopolymer blend. Blends satisfying congruency undergo a direct LAM–DIS transition without passing through a two-phase region. We present complementary optical transmission, small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), and dynamic mechanical spectroscopy (DMS) results that establish the phase behavior at constant copolymer volume fraction and varying C/E homopolymer volume ratios. Adjacent to the congruent composition at constant copolymer volume fraction, the lamellar and disordered phases are separated by two-phase coexistence windows, which converge, along with the line of congruent transitions, at an overall composition in the phase prism coincident with the BμE channel. Hexagonal and cubic (double gyroid) phases occur at higher diblock copolymer concentrations for asymmetric amounts of C and E homopolymers. These results establish a quantitative method for identifying the detailed phase behavior of ternary diblock copolymer–homopolymer blends, especially in the vicinity of the BμE.

The Plumber’s Nightmare Phase in Diblock Copolymer/Homopolymer Blends. A Self-Consistent Field Theory Study.

KAUST Repository

Martinez-Veracoechea, Francisco J.

2009-11-24

Using self-consistent field theory, the Plumber\\'s Nightmare and the double diamond phases are predicted to be stable in a finite region of phase diagrams for blends of AB diblock copolymer (DBC) and A-component homopolymer. To the best of our knowledge, this is the first time that the P phase has been predicted to be stable using self-consistent field theory. The stabilization is achieved by tuning the composition or conformational asymmetry of the DBC chain, and the architecture or length of the homopolymer. The basic features of the phase diagrams are the same in all cases studied, suggesting a general type of behavior for these systems. Finally, it is noted that the homopolymer length should be a convenient variable to stabilize bicontinuous phases in experiments. © 2009 American Chemical Society.

Self-Assembly of Charged Amphiphilic Diblock Copolymers with Insoluble Blocks of Decreasing Hydrophobicity: From Kinetically Frozen Colloids to Macrosurfactants

Energy Technology Data Exchange (ETDEWEB)

M Jacquin; P Muller; H Cottet; O Theodoly

2011-12-31

We have investigated the self-assembly properties in aqueous solution of amphiphilic diblock copolymers with insoluble blocks of different hydrophobicity and demonstrated that the condition to obtain dynamic micelles is to design samples with insoluble blocks of low enough hydrophobicity. We focus here on results with new water-soluble amphiphilic diblock copolymers poly(diethyleneglycol ethylether acrylate)-b-poly(acrylic acid), or PDEGA-b-PAA. The physical characteristics of PDEGA-b-PAA micelles at high ionization have been determined by small angle neutron scattering (SANS). We show that PDEGA-b-PAA samples form micelles at thermodynamic equilibrium. The critical micelle concentrations (CMCs) decrease strongly with ionic strength and temperature due to a solvent quality decrease for, respectively, the corona and the core. This behavior of reversible aggregation is remarkable as compared to the behavior of kinetically frozen aggregation that has been widely observed with samples of similar architecture and different hydrophobic blocks, for example, poly(styrene)-b-poly(acrylic acid), PS-b-PAA, and poly(butyl acrylate)-b-poly(acrylic acid), PBA-b-PAA. We have measured the interfacial tension between water and the homopolymers PDEGA and PBA at, respectively, 3 and 20 mN/m at room temperature, which permits one to estimate the energy cost to extract a unimer from a micelle. The results are consistent with a micelle association that is fast for PDEGA-b-PAA and kinetically frozen PBA-b-PAA. Hence, PDEGA-b-PAA samples form a new system of synthetic charged macrosurfactant with unique properties of fast dynamic association, tunable charge, and water solubility even at temperatures and NaCl concentrations as high as 65 C and 1 M.

Toward an equilibrium structure in lamellar diblock copolymer thin films using solvent vapor annealing

DEFF Research Database (Denmark)

Sepe, Alessandro; Zhang, Jianqi; Perlich, Jan

2016-01-01

Solvent vapor annealing (SVA) is frequently used to improve the ordering in diblock copolymer thin films. An important question is which SVA protocol should be chosen to ensure thermodynamic equilibrium. Here, we investigate two thin films from a low molar-mass, lamellae-forming polystyrene....... SVA cycles were carried out with cyclohexane, and the structural changes were followed in-situ using time-resolved grazing-incidence small-angle X-ray scattering (GISAXS). Before and after SVA, Dlam,par is significantly lower than in the bulk, i.e. the equi-librium value of Dlam,par in thin film...... glassy again, affinely. During the second SVA cycle on the thin film, the scaling behavior of the lamellar thickness is identical to the one during the first drying and to the drying behavior of the thicker film. We conclude that one cycle of solvent vapor treatment with a degree of swelling of ca. 1...

Renormalization of the one-loop theory of fluctuations in polymer blends and diblock copolymer melts.

Science.gov (United States)

Grzywacz, Piotr; Qin, Jian; Morse, David C

2007-12-01

Attempts to use coarse-grained molecular theories to calculate corrections to the random-phase approximation (RPA) for correlations in polymer mixtures have been plagued by an unwanted sensitivity to the value of an arbitrary cutoff length, i.e., by an ultraviolet (UV) divergence. We analyze the UV divergence of the inverse structure factor S(-1)(k) predicted by a "one-loop" approximation similar to that used in several previous studies. We consider both miscible homopolymer blends and disordered diblock copolymer melts. We show, in both cases, that all UV divergent contributions can be absorbed into a renormalization of the values of the phenomenological parameters of a generalized self-consistent field theory (SCFT). This observation allows the construction of an UV convergent theory of corrections to SCFT phenomenology. The UV-divergent one-loop contribution to S(-1)(k) is shown to be the sum of (i) a k -independent contribution that arises from a renormalization of the effective chi parameter, (ii) a k-dependent contribution that arises from a renormalization of monomer statistical segment lengths, (iii) a contribution proportional to k(2) that arises from a square-gradient contribution to the one-loop fluctuation free energy, and (iv) a k-dependent contribution that is inversely proportional to the degree of polymerization, which arises from local perturbations in fluid structure near chain ends and near junctions between blocks in block copolymers.

Structural and rectifying junction properties of self-assembled ZnO nanoparticles in polystyrene diblock copolymers on (1 0 0)Si substrates

Science.gov (United States)

Ali, H. A.; Iliadis, A. A.; Martinez-Miranda, L. J.; Lee, U.

2006-06-01

The structural and electronic transport properties of self-assembled ZnO nanoparticles in polystyrene-acrylic acid, [PS] m/[PAA] n, diblock copolymer on p-type (1 0 0)Si substrates are reported for the first time. Four different block repeat unit ratios ( m/ n) of 159/63, 139/17,106/17, and 106/4, were examined in order to correlate the physical parameters (size, density) of the nanoparticles with the copolymer block lengths m and n. We established that the self-assembled ZnO nanoparticle average size increased linearly with minority block length n, while the average density decreased exponentially with majority block length m. Average size varied from 20 nm to 250 nm and average density from 3.5 × 10 7 cm -2 to 1 × 10 10 cm -2, depending on copolymer parameters. X-ray diffraction studies showed the particles to have a wurtzite crystal structure with the (1 0 0) being the dominant orientation. Room temperature current-voltage characteristics measured for an Al/ZnO-nanocomposite/Si structure exhibited rectifying junction properties and indicated the formation of Al/ZnO-nanocomposite Schottky type junction with a barrier height of 0.7 V.

A new process for fabricating nanodot arrays on selective regions with diblock copolymer thin film

Energy Technology Data Exchange (ETDEWEB)

Park, Dae-Ho [Department of Materials Science and Engineering, Polymer Research Institute, Pohang University of Science and Technology, San 31, Hyoja-Dong, Nam-Gu, Pohang 790-784 (Korea, Republic of)

2007-09-12

A procedure for micropatterning a single layer of nanodot arrays in selective regions is demonstrated by using thin films of polystyrene-b-poly(t-butyl acrylate) (PS-b-PtBA) diblock copolymer. The thin-film self-assembled into hexagonally arranged PtBA nanodomains in a PS matrix on a substrate by solvent annealing with 1,4-dioxane. The PtBA nanodomains were converted into poly(acrylic acid) (PAA) having carboxylic-acid-functionalized nanodomains by exposure to hydrochloric acid vapor, or were removed by ultraviolet (UV) irradiation to generate vacant sites without any functional groups due to the elimination of PtBA domains. By sequential treatment with aqueous sodium bicarbonate and aqueous zinc acetate solution, zinc cations were selectively loaded only on the carboxylic-acid-functionalized nanodomains prepared via hydrolysis. Macroscopic patterning through a photomask via UV irradiation, hydrolysis, sequential zinc cation loading and calcination left a nanodot array of zinc oxide on a selectively UV-shaded region.

Research Update: Triblock copolymers as templates to synthesize inorganic nanoporous materials

OpenAIRE

Yunqi Li; Bishnu Prasad Bastakoti; Yusuke Yamauchi

2016-01-01

This review focuses on the application of triblock copolymers as designed templates to synthesize nanoporous materials with various compositions. Asymmetric triblock copolymers have several advantages compared with symmetric triblock copolymers and diblock copolymers, because the presence of three distinct domains can provide more functional features to direct the resultant nanoporous materials. Here we clearly describe significant contributions of asymmetric triblock copolymers, especially p...

Monte Carlo simulation of AB-copolymers with saturating bonds

CERN Document Server

Chertovich, A V; Khokhlov, A R; Bohr, J

2003-01-01

Structural transitions in a single AB-copolymer chain where saturating bonds can be formed between A-and B-units are studied by means of Monte Carlo computer simulations using the bond fluctuation model. Three transitions are found, coil-globule, coil-hairpin and globule-hairpin, depending on the nature of a particular AB-sequence: statistical random sequence, diblock sequence and 'random-complementary' sequence (one-half of such an AB-sequence is random with Bernoulli statistics while the other half is complementary to the first one). The properties of random-complementary sequences are closer to those of diblock sequences than to the properties of random sequences. The model (although quite rough) is expected to represent some basic features of real RNA molecules, i.e. the formation of secondary structure of RNA due to hydrogen bonding of corresponding bases and stacking interactions of the base pairs in helixes. We introduce the notation of RNA-like copolymers and discuss in what sense the sequences studie...

Highly Flexible Self-Assembled V2O5 Cathodes Enabled by Conducting Diblock Copolymers

Science.gov (United States)

An, Hyosung; Mike, Jared; Smith, Kendall; Swank, Lisa; Lin, Yen-Hao; Pesek, Stacy; Verduzco, Rafael; Lutkenhaus, Jodie

Structural energy storage materials combining load-bearing mechanical properties and high energy storage performance are desired for applications in wearable devices or flexible displays. Vanadium pentoxide (V2O5) is a promising cathode material for possible use in flexible battery electrodes, but it remains limited by low Li+ diffusion coefficient and electronic conductivity, severe volumetric changes upon cycling, and limited mechanical flexibility. Here, we demonstrate a route to address these challenges by blending a diblock copolymer bearing electron- and ion-conducting blocks, poly(3-hexylthiophene)-block-poly(ethyleneoxide) (P3HT- b-PEO), with V2O5 to form a mechanically flexible, electro-mechanically stable hybrid electrode. V2O5 layers were arranged parallel in brick-and-mortar-like fashion held together by the P3HT- b-PEO binder. This unique structure significantly enhances mechanical flexibility, toughness and cyclability without sacrificing capacity. Electrodes comprised of 10 wt% polymer have unusually high toughness (293 kJ/m3) and specific energy (530 Wh/kg), both higher than reduced graphene oxide paper electrodes.

Effect of the hydrophilic block length on the surface-active and micellar thermodynamic properties of oxyethylene-oxybutylene diblock copolymers in aqueous solution

International Nuclear Information System (INIS)

Khan, A.; Usman, M.; Siddiq, M.; Fatima, G.; Harrison, W.

2009-01-01

The effect of hydrophilic block length on the surface and micellar thermodynamic properties of aqueous solution of E/sub 40/B/sub 8/, E/sub 80/B/sub 8/ and E/sub 120/B/sub 8/ diblock copolymers, were studied by surface tension measurements over a wide concentration and temperature range; where E stands for an oxyethylene unit and B for an oxybutylene unit. Like conventional surfactants, two breaks (change in the slope) were observed in the surface tension vs logarithm of concentration curve for all the three copolymers. Surface tension measurements were used to estimate surface excess concentrations (r m), area per molecule at air/water interface a and thermodynamic parameters for all adsorption of the pre-micellar region in the temperature range 20 to 50 degree C. Likewise the critical micelle concentration, CMC and thermodynamic parameters for micellization were also calculated for the post-micellar solutions at all temperatures. For comparison the thermodynamic parameters of adsorption and micellization are discussed in detail. The impact of varying E-block length and temperature on all calculated parameters are also discussed. This study shows the importance of hydrophobic-hydrophilic-balance (HHB) of copolymers on various surface and micellar properties. (author)

Tuning of thermally induced sol-to-gel transitions of moderately concentrated aqueous solutions of doubly thermosensitive hydrophilic diblock copolymers poly(methoxytri(ethylene glycol) acrylate)-b-poly(ethoxydi(ethylene glycol) acrylate-co-acrylic acid).

Science.gov (United States)

Jin, Naixiong; Zhang, Hao; Jin, Shi; Dadmun, Mark D; Zhao, Bin

2012-03-15

We report in this article a method to tune the sol-to-gel transitions of moderately concentrated aqueous solutions of doubly thermosensitive hydrophilic diblock copolymers that consist of two blocks exhibiting distinct lower critical solution temperatures (LCSTs) in water. A small amount of weak acid groups is statistically incorporated into the lower LCST block so that its LCST can be tuned by varying solution pH. Well-defined diblock copolymers, poly(methoxytri(ethylene glycol) acrylate)-b-poly(ethoxydi(ethylene glycol) acrylate-co-acrylic acid) (PTEGMA-b-P(DEGEA-co-AA)), were prepared by reversible addition-fragmentation chain transfer polymerization and postpolymerization modification. PTEGMA and PDEGEA are thermosensitive water-soluble polymers with LCSTs of 58 and 9 °C, respectively, in water. A 25 wt % aqueous solution of PTEGMA-b-P(DEGEA-co-AA) with a molar ratio of DEGEA to AA units of 100:5.2 at pH = 3.24 underwent multiple phase transitions upon heating, from a clear, free-flowing liquid (sol-to-gel transition temperature (T(sol-gel)) shifted to higher values, while the gel-to-sol transition (T(gel-sol)) and the clouding temperature (T(clouding)) of the sample remained essentially the same. These transitions and the tunability of T(sol-gel) originated from the thermosensitive properties of two blocks of the diblock copolymer and the pH dependence of the LCST of P(DEGEA-co-AA), which were confirmed by dynamic light scattering and differential scanning calorimetry studies. Using the vial inversion test method, we mapped out the C-shaped sol-gel phase diagrams of the diblock copolymer in aqueous buffers in the moderate concentration range at three different pH values (3.24, 5.58, and 5.82, all measured at ~0 °C). While the upper temperature boundaries overlapped, the lower temperature boundary shifted upward and the critical gelation concentration increased with the increase of pH. The AA content in PTEGMA-b-P(DEGEA-co-AA) was found to have a significant

Dynamic photoinduced realignment processes in photoresponsive block copolymer films: effects of the chain length and block copolymer architecture.

Science.gov (United States)

Sano, Masami; Shan, Feng; Hara, Mitsuo; Nagano, Shusaku; Shinohara, Yuya; Amemiya, Yoshiyuki; Seki, Takahiro

2015-08-07

A series of block copolymers composed of an amorphous poly(butyl methacrylate) (PBMA) block connected with an azobenzene (Az)-containing liquid crystalline (PAz) block were synthesized by changing the chain length and polymer architecture. With these block copolymer films, the dynamic realignment process of microphase separated (MPS) cylinder arrays of PBMA in the PAz matrix induced by irradiation with linearly polarized light was studied by UV-visible absorption spectroscopy, and time-resolved grazing incidence small angle X-ray scattering (GI-SAXS) measurements using a synchrotron beam. Unexpectedly, the change in the chain length hardly affected the realignment rate. In contrast, the architecture of the AB-type diblock or the ABA-type triblock essentially altered the realignment feature. The strongly cooperative motion with an induction period before realignment was characteristic only for the diblock copolymer series, and the LPL-induced alignment change immediately started for triblock copolymers and the PAz homopolymer. Additionally, a marked acceleration in the photoinduced dynamic motions was unveiled in comparison with a thermal randomization process.

Controlling sub-microdomain structure in microphase-ordered block copolymers and their nanocomposites

Science.gov (United States)

Bowman, Michelle Kathleen

Block copolymers exhibit a wealth of morphologies that continue to find ubiquitous use in a diverse variety of mature and emergent (nano)technologies, such as photonic crystals, integrated circuits, pharmaceutical encapsulents, fuel cells and separation membranes. While numerous studies have explored the effects of molecular confinement on such copolymers, relatively few have examined the sub-microdomain structure that develops upon modification of copolymer molecular architecture or physical incorporation of nanoscale objects. This work will address two relevant topics in this vein: (i) bidisperse brushes formed by single block copolymer molecules and (ii) copolymer nanocomposites formed by addition of molecular or nanoscale additives. In the first case, an isomorphic series of asymmetric poly(styrene-b -isoprene-b-styrene) (S1IS2) triblock copolymers of systematically varied chain length has been synthesized from a parent SI diblock copolymer. Small-angle x-ray scattering, coupled with dynamic rheology and self-consistent field theory (SCFT), reveals that the progressively grown S2 block initially resides in the I-rich matrix and effectively reduces the copolymer incompatibility until a critical length is reached. At this length, the S2 block co-locates with the S1 block so that the two blocks generate a bidisperse brush (insofar as the S1 and S2 lengths differ). This single-molecule analog to binary block copolymer blends affords unique opportunities for materials design at sub-microdomain length scales and provides insight into the transition from diblock to triblock copolymer (and thermoplastic elastomeric nature). In the second case, I explore the distribution of molecular and nanoscale additives in microphase-ordered block copolymers and demonstrate via SCFT that an interfacial excess, which depends strongly on additive concentration, selectivity and relative size, develops. These predictions are in agreement with experimental findings. Moreover, using a

Nanoformulation of D-α-tocopheryl polyethylene glycol 1000 succinate-b-poly(ε-caprolactone-ran-glycolide) diblock copolymer for breast cancer therapy.

Science.gov (United States)

Huang, Laiqiang; Chen, Hongbo; Zheng, Yi; Song, Xiaosong; Liu, Ranyi; Liu, Kexin; Zeng, Xiaowei; Mei, Lin

2011-10-01

The purpose of this research was to develop formulation of docetaxel-loaded biodegradable TPGS-b-(PCL-ran-PGA) nanoparticles for breast cancer chemotherapy. A novel diblock copolymer, d-α-tocopheryl polyethylene glycol 1000 succinate-b-poly(ε-caprolactone-ran-glycolide) [TPGS-b-(PCL-ran-PGA)], was synthesized from ε-caprolactone, glycolide and d-α-tocopheryl polyethylene glycol 1000 succinate by ring-opening polymerization using stannous octoate as catalyst. The obtained copolymers were characterized by (1)H NMR, GPC and TGA. The docetaxel-loaded TPGS-b-(PCL-ran-PGA) nanoparticles were prepared and characterized. The data showed that the fluorescence TPGS-b-(PCL-ran-PGA) nanoparticles could be internalized by MCF-7 cells. The TPGS-b-(PCL-ran-PGA) nanoparticles achieved significantly higher level of cytotoxicity than commercial Taxotere®. MCF-7 xenograft tumor model on SCID mice showed that docetaxel formulated in the TPGS-b-(PCL-ran-PGA) nanoparticles could effectively inhibit the growth of tumor over a longer period of time than Taxotere® at the same dose. In conclusion, the TPGS-b-(PCL-ran-PGA) copolymer could be acted as a novel and potential biologically active polymeric material for nanoformulation in breast cancer chemotherapy. This journal is © The Royal Society of Chemistry 2011

Structure–Conductivity Relationships in Ordered and Disordered Salt-Doped Diblock Copolymer/Homopolymer Blends

Energy Technology Data Exchange (ETDEWEB)

Irwin, Matthew T.; Hickey, Robert J.; Xie, Shuyi; So, Soonyong; Bates, Frank S.; Lodge, Timothy P. (UMM)

2016-11-21

We examine the relationship between structure and ionic conductivity in salt-containing ternary polymer blends that exhibit various microstructured morphologies, including lamellae, a hexagonal phase, and a bicontinuous microemulsion, as well as the disordered phase. These blends consist of polystyrene (PS, M_n ≈ 600 g/mol) and poly(ethylene oxide) (PEO, M_n ≈ 400 g/mol) homopolymers, a nearly symmetric PS–PEO block copolymer (M_n ≈ 4700 g/mol), and lithium bis(trifluoromethane)sulfonamide (LiTFSI). These pseudoternary blends exhibit phase behavior that parallels that of well-studied ternary polymer blends consisting of A and B homopolymers compatibilized by an AB diblock copolymer. The utility of this framework is that all blends have nominally the same number of ethylene oxide, styrene, Li⁺, and TFSI– units, yet can exhibit a variety of microstructures depending on the relative ratio of the homopolymers to the block copolymer. For the systems studied, the ratio r = [Li⁺]/[EO] is maintained at 0.06, and the volume fraction of PS homopolymer is kept equal to that of PEO homopolymer plus salt. The total volume fraction of homopolymer is varied from 0 to 0.70. When heated through the order–disorder transition, all blends exhibit an abrupt increase in conductivity. However, analysis of small-angle X-ray scattering data indicates significant structure even in the disordered state for several blend compositions. By comparing the nature and structure of the disordered states with their corresponding ordered states, we find that this increase in conductivity through the order–disorder transition is most likely due to the elimination of grain boundaries. In either disordered or ordered states, the conductivity decreases as the total amount of homopolymer is increased, an unanticipated observation. This trend with increasing homopolymer loading is hypothesized to result from an increased density of �

Immunotheranostic Polymersomes Modularly Assembled from Tetrablock and Diblock Copolymers with Oxidation-Responsive Fluorescence.

Science.gov (United States)

Du, Fanfan; Liu, Yu-Gang; Scott, Evan Alexander

2017-10-01

Intracellular delivery is a key step for many applications in medicine and for investigations into cellular function. This is particularly true for immunotherapy, which often requires controlled delivery of antigen and adjuvants to the cytoplasm of immune cells. Due to the complex responses generated by the stimulation of diverse immune cell populations, it is critical to monitor which cells are targeted during treatment. To address this issue, we have engineered an immunotheranostic polymersome delivery system that fluorescently marks immune cells following intracellular delivery. N -(3-bromopropyl)phthalimide end-capped poly(ethylene glycol)-bl-poly(propylene sulfide) (PEG-PPS-PI) was synthesized by anionic ring opening polymerization and linked with PEG-PPS-NH 2 via a perylene bisimide (PBI) bridge to form a tetrablock copolymer (PEG-PPS-PBI-PPS-PEG). Block copolymers were assembled into polymersomes by thin film hydration in phosphate buffered saline and characterized by dynamic light scattering, cryogenic electron microscopy and fluorescence spectroscopy. Polymersomes were injected subcutaneously into the backs of mice, and draining lymph nodes were extracted for flow cytometric analysis of cellular uptake and disassembly. Modular self-assembly of tetrablock / diblock copolymers in aqueous solutions induced π-π stacking of the PBI linker that both red-shifted and quenched the PBI fluorescence. Reactive oxygen species within the endosomes of phagocytic immune cell populations oxidized the PPS blocks, which disassembled the polymersomes for dequenching and shifting of the PBI fluorescence from 640 nm to 550 nm emission. Lymph node resident macrophages and dendritic cells were found to increase in 550 nm emission over the course of 3 days by flow cytometry. Immunotheranostic polymersomes present a versatile platform to probe the contributions of specific cell populations during the elicitation of controlled immune responses. Flanking PBI with two oxidation

Bicontinuous Phases in Diblock Copolymer/Homopolymer Blends: Simulation and Self-Consistent Field Theory

KAUST Repository

Martínez-Veracoechea, Francisco J.

2009-03-10

A combination of particle-based simulations and self-consistent field theory (SCFT) is used to study the stabilization of multiple ordered bicontinuous phases in blends of a diblock copolymer (DBC) and a homopolymer. The double-diamond phase (DD) and plumber\\'s nightmare phase (P) were spontaneously formed in the range of homopolymer volume fraction simulated via coarse-grained molecular dynamics. To the best of our knowledge, this is the first time that such phases have been obtained in continuum-space molecular simulations of DBC systems. Though tentative phase boundaries were delineated via free-energy calculations, macrophase separation could not be satisfactorily assessed within the framework of particle-based simulations. Therefore, SCFT was used to explore the DBC/homopolymer phase diagram in more detail, showing that although in many cases two-phase coexistence of a DBC-rich phase and a homopolymer-rich phase does precede the stability of complex bicontinuous phases the DD phase can be stable in a relatively wide region of the phase diagram. Whereas the P phase was always metastable with respect to macrophase separation under the thermodynamic conditions explored with SCFT, it was sometimes nearly stable, suggesting that full stability could be achieved in other unexplored regions of parameter space. Moreover, even the predicted DD- and P-phase metastability regions were located significantly far from the spinodal line, suggesting that these phases could be observed in experiments as "long-lived" metastable phases under those conditions. This conjecture is also consistent with large-system molecular dynamics simulations that showed that the time scale of mesophase formation is much faster than that of macrophase separation. © 2009 American Chemical Society.

Polymers and block copolymers of fluorostyrenes by ATRP

DEFF Research Database (Denmark)

Hvilsted, Søren; Borkar, Sachin; Abildgaard, Lillian

2002-01-01

Fully or partly fluorinated polymers have many desirable and intriguing properties. In the framework of a larger program on design and control of new functional block copolymers we recently employed the Atom Transfer Radical Polymerization (ATRP) protocol on 2,3,4,5,6-pentafluorostyrene (FS). We...... materials based on 2,3,5,6-tetrafiuoro-4-methoxy-styrene (TFMS). TFMS homopolymers as well as diblock copolymers with FS are produced by ATRP. Both types of novel polymers were subsequently demethylated and different side chains introduced on the resulting hydroxy sites....

High-density arrays of titania nanoparticles using monolayer micellar films of diblock copolymers as templates.

Science.gov (United States)

Li, Xue; Lau, King Hang Aaron; Kim, Dong Ha; Knoll, Wolfgang

2005-05-24

Highly dense arrays of titania nanoparticles were fabricated using surface micellar films of poly(styrene-block-2-vinylpyridine) diblock copolymers (PS-b-P2VP) as reaction scaffolds. Titania could be introduced selectively within P2VP nanodomains in PS-b-P2VP films through the binary reaction between water molecules trapped in the P2VP domains and the TiCl(4) vapor precursors. Subsequent UV exposure or oxygen plasma treatment removed the organic matrix, leading to titania nanoparticle arrays on the substrate surface. The diameter of the titania domains and the interparticle distance were defined by the lateral scale present in the microphase-separated morphology of the initial PS-b-P2VP films. The typical diameter of titania nanoparticles obtained by oxygen plasma treatment was of the order of approximately 23 nm. Photoluminescence (PL) properties were investigated for films before and after plasma treatment. Both samples showed PL properties with major physical origin due to self-trapped excitons, indicating that the local environment of the titanium atoms is similar.

Block copolymer morphologies confined by square-shaped particle: Hard and soft confinement

International Nuclear Information System (INIS)

Zhang Qiyi; Yang Wenyan; Hu Kaiyan

2016-01-01

The self-assembly of diblock copolymers confined around one square-shaped particle is studied systematically within two-dimensional self-consistent field theory (SCFT). In this model, we assume that the thin block copolymer film is confined in the vicinity of a square-shaped particle by a homopolymer melt, which is equivalent to the poor solvents. Multiple sequences of square-shaped particle-induced copolymer aggregates with different shapes and self-assembled internal morphologies are predicted as functions of the particle size, the structural portion of the copolymer, and the volume fraction of the copolymer. A rich variety of aggregates are found with complex internal self-assembled morphologies including complex structures of the vesicle, with one or several inverted micelle surrounded by the outer monolayer with the particle confined in the core. These results demonstrate that the assemblies of diblock copolymers formed around the square-shaped particle in poor solvents are of immediate interest to the assembly of copolymer and the morphology of biomembrane in the confined environment, as well as to the transitions of vesicles to micelles. (paper)

Self-Assembly of Rod-Coil Block Copolymers

National Research Council Canada - National Science Library

Jenekhe, S

1999-01-01

... the self-assembly of new rod-coil diblock, rod- coil-rod triblock, and coil-rod-coil triblock copolymers from solution and the resulting discrete and periodic mesostmctares with sizes in the 100...

Mesoscopic multiphase structures and the interfaces of block and graft copolymers in bulk

International Nuclear Information System (INIS)

Matsushita, Yushu

1996-01-01

Microphase-separated structures of copolymers with various architectures and their polymer/polymer interfaces were studied. They are SP diblock, PSP triblock, and SPP graft copolymers, where S and P denote polystyrene and poly(2-vinylpyridine), respectively. Morphological observations were carried out by means of transmission electron microscopy and small-angle X-ray scattering. Chain dimensions of component polymers were measured by small-angle neutron scattering and microphase-separated interfaces were observed by neutron reflectivity measurements using deuterium-labeled samples. It was clarified that morphological phase transitions among thermodynamically equilibrium structures for SP diblock and PSP triblock copolymers occur at almost the same compositions; however, those of SPP graft copolymers tend to occur at higher volume fraction of polystyrene, φ s , than those for block copolymers. As for alternating lamellar structures it turned out to be clear that lamellar domain spacings, D's, were scaled as the 2/3 power of the molecular weight of polymers irrespective of their architectures. S block chains of SP diblock and PSP triblock copolymers in lamellar structures were both confirmed to be deformed toward the direction perpendicular to the lamellar interfaces, but it revealed that their volumes were preserved. Further, S/P interfacial thicknesses of SP and PSP were essentially the same to each other and the values defined as the FWHM of the error functions which express the segment density distributions of the interfaces were determined to be about 4 nm. (author)

Hydrogen bonding strength of diblock copolymers affects the self-assembled structures with octa-functionalized phenol POSS nanoparticles.

Science.gov (United States)

Lu, Yi-Syuan; Yu, Chia-Yu; Lin, Yung-Chih; Kuo, Shiao-Wei

2016-02-28

In this study, the influence of the functional groups by the diblock copolymers of poly(styrene-b-4-vinylpyridine) (PS-b-P4VP), poly(styrene-b-2-vinylpyridine) (PS-b-P2VP), and poly(styrene-b-methyl methacrylate) (PS-b-PMMA) on their blends with octa-functionalized phenol polyhedral oligomeric silsesquioxane (OP-POSS) nanoparticles (NPs) was investigated. The relative hydrogen bonding strengths in these blends follow the order PS-b-P4VP/OP-POSS > PS-b-P2VP/OP-POSS > PS-b-PMMA/OP-POSS based on the Kwei equation from differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopic analyses. Small-angle X-ray scattering and transmission electron microscopic analyses show that the morphologies of the self-assembly structures are strongly dependent on the hydrogen bonding strength at relatively higher OP-POSS content. The PS-b-P4VP/OP-POSS hybrid complex system with the strongest hydrogen bonds shows the order-order transition from lamellae to cylinders and finally to body-centered cubic spheres upon increasing OP-POSS content. However, PS-b-P2VP/OP-POSS and PS-b-PMMA/OP-POSS hybrid complex systems, having relatively weaker hydrogen bonds, transformed from lamellae to cylinder structures at lower OP-POSS content (50 wt%).

Research Update: Triblock copolymers as templates to synthesize inorganic nanoporous materials

Directory of Open Access Journals (Sweden)

Yunqi Li

2016-04-01

Full Text Available This review focuses on the application of triblock copolymers as designed templates to synthesize nanoporous materials with various compositions. Asymmetric triblock copolymers have several advantages compared with symmetric triblock copolymers and diblock copolymers, because the presence of three distinct domains can provide more functional features to direct the resultant nanoporous materials. Here we clearly describe significant contributions of asymmetric triblock copolymers, especially polystyrene-block-poly(2-vinylpyridine-block-poly(ethylene oxide (abbreviated as PS-b-P2VP-b-PEO.

Aqueous dispersion polymerization: a new paradigm for in situ block copolymer self-assembly in concentrated solution.

Science.gov (United States)

Sugihara, Shinji; Blanazs, Adam; Armes, Steven P; Ryan, Anthony J; Lewis, Andrew L

2011-10-05

Reversible addition-fragmentation chain transfer polymerization has been utilized to polymerize 2-hydroxypropyl methacrylate (HPMA) using a water-soluble macromolecular chain transfer agent based on poly(2-(methacryloyloxy)ethylphosphorylcholine) (PMPC). A detailed phase diagram has been elucidated for this aqueous dispersion polymerization formulation that reliably predicts the precise block compositions associated with well-defined particle morphologies (i.e., pure phases). Unlike the ad hoc approaches described in the literature, this strategy enables the facile, efficient, and reproducible preparation of diblock copolymer spheres, worms, or vesicles directly in concentrated aqueous solution. Chain extension of the highly hydrated zwitterionic PMPC block with HPMA in water at 70 °C produces a hydrophobic poly(2-hydroxypropyl methacrylate) (PHPMA) block, which drives in situ self-assembly to form well-defined diblock copolymer spheres, worms, or vesicles. The final particle morphology obtained at full monomer conversion is dictated by (i) the target degree of polymerization of the PHPMA block and (ii) the total solids concentration at which the HPMA polymerization is conducted. Moreover, if the targeted diblock copolymer composition corresponds to vesicle phase space at full monomer conversion, the in situ particle morphology evolves from spheres to worms to vesicles during the in situ polymerization of HPMA. In the case of PMPC(25)-PHPMA(400) particles, this systematic approach allows the direct, reproducible, and highly efficient preparation of either block copolymer vesicles at up to 25% solids or well-defined worms at 16-25% solids in aqueous solution.

Dynamics of interacting edge defects in copolymer lamellae

Science.gov (United States)

Dalnoki-Veress, Kari; McGraw, Joshua D.; Rowe, Ian D. W.

2011-03-01

It is known that terraces at the interface of lamella forming diblock copolymers do not make discontinuous jumps in height. Rather, their profiles are smoothly varying. The width of the transition region between two lamellar heights is typically several hundreds of nanometres, resulting from a balance between surface tension, chain stretching penalties, and the enthalpy of mixing. What is less well known in these systems is what happens when two transition regions approach one another. In this study, we show that time dependent experimental data of interacting copolymer lamellar edges is consistent with a model that assumes a repulsion between adjacent edges. The range of the interaction between edge defects is consistent with the profile width of noninteracting diblock terraces. Financial support from NSERC of Canada is gratefully acknowledged.

Self-Assembly of Diblock Molecular Polymer Brushes in the Spherical Confinement of Nanoemulsion Droplets.

Science.gov (United States)

Steinhaus, Andrea; Pelras, Théophile; Chakroun, Ramzi; Gröschel, André H; Müllner, Markus

2018-05-02

Understanding the self-assembly behavior of polymers of various topologies is key to a reliable design of functional polymer materials. Self-assembly under confinement conditions emerges as a versatile avenue to design polymer particles with complex internal morphologies while simultaneously facilitating scale-up. However, only linear block copolymers have been studied to date, despite the increasing control over macromolecule composition and architecture available. This study extends the investigation of polymer self-assembly in confinement from regular diblock copolymers to diblock molecular polymer brushes (MPBs). Block-type MPBs with polystyrene (PS) and polylactide (PLA) compartments of different sizes are incorporated into surfactant-stabilized oil-in-water (chloroform/water) emulsions. The increasing confinement in the nanoemulsion droplets during solvent evaporation directs the MPBs to form solid nano/microparticles. Microscopy studies reveal an intricate internal particle structure, including interpenetrating networks and axially stacked lamellae of PS and PLA, depending on the PS/PLA ratio of the brushes. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of solvent quality and chain density on normal and frictional forces between electrostatically anchored thermoresponsive diblock copolymer layers

DEFF Research Database (Denmark)

An, Junxue; Liu, Xiaoyan; Dedinaite, Andra

2017-01-01

and a thermoresponsive block of poly(2-isopropyl-2-oxazoline), PIPOZ. We find that at a given temperature different polymer chain densities at the silica surface are achieved depending on the previous temperature history. We explore how this affects surface and friction forces between such layers using the atomic force......Equilibration in adsorbing polymer systems can be very slow, leading to different physical properties at a given condition depending on the pathway that was used to reach this state. Here we explore this phenomenon using a diblock copolymer consisting of a cationic anchor block....... The friction forces decrease in the cooling stage due to rehydration of the PIPOZ chain. A consequence of the adsorption hysteresis is that the friction forces measured at 25 °C are significantly lower after exposure to a temperature of 40 °C than prior to heating, which is due to higher polymer chain density...

Exploring Poly(ethylene glycol-Polyzwitterion Diblock Copolymers as Biocompatible Smart Macrosurfactants Featuring UCST-Phase Behavior in Normal Saline Solution

Directory of Open Access Journals (Sweden)

Noverra M. Nizardo

2018-03-01

Full Text Available Nonionic-zwitterionic diblock copolymers are designed to feature a coil-to-globule collapse transition with an upper critical solution temperature (UCST in aqueous media, including physiological saline solution. The block copolymers that combine presumably highly biocompatible blocks are synthesized by chain extension of a poly(ethylene glycol (PEG macroinitiator via atom transfer radical polymerization (ATRP of sulfobetaine and sulfabetaine methacrylates. Their thermoresponsive behavior is studied by variable temperature turbidimetry and 1H NMR spectroscopy. While the polymers with polysulfobetaine blocks exhibit phase transitions in the physiologically interesting window of 30–50 °C only in pure aqueous solution, the polymers bearing polysulfabetaine blocks enabled phase transitions only in physiological saline solution. By copolymerizing a pair of structurally closely related sulfo- and sulfabetaine monomers, thermoresponsive behavior can be implemented in aqueous solutions of both low and high salinity. Surprisingly, the presence of the PEG blocks can affect the UCST-transitions of the polyzwitterions notably. In specific cases, this results in “schizophrenic” thermoresponsive behavior displaying simultaneously an UCST and an LCST (lower critical solution temperature transition. Exploratory experiments on the UCST-transition triggered the encapsulation and release of various solvatochromic fluorescent dyes as model “cargos” failed, apparently due to the poor affinity even of charged organic compounds to the collapsed state of the polyzwitterions.

Fluctuations, conformational asymmetry and block copolymer phase behaviour

DEFF Research Database (Denmark)

Bates, F.S.; Schulz, M.F.; Khandpur, A.K.

1994-01-01

Phase behaviour near the order-disorder transition (ODT) of 58 model hydrocarbon diblock copolymers, representing four different systems, is summarized. Six distinct ordered-state microstructures are reported, including hexagonally modulated lamellae (HML), hexagonally perforated layers (HPL) and...

Barriers to defect melting in chemo-epitaxial directed self-assembly of lamellar-forming diblock copolymer/homopolymer blends

Science.gov (United States)

Izumi, Kenichi; Kim, Bongkeun; Laachi, Nabil; Delaney, Kris T.; Carilli, Michael; Fredrickson, Glenn H.

2015-03-01

We investigate energy barriers and minimum energy paths (MEPs) for transitions from dislocation-pair defects to perfect lamellae in self-assembly of AB-diblock copolymer plus A- or B-homopolymer blends using self-consistent field theory (SCFT) and the numerical string method. For neutral substrates, all minimum energy paths discovered by the string method show two successive energy barriers. The two-barrier qualitative nature of the MEPs appears not to depend on the presence or absence of small amounts of homopolymer. For the first energy barrier, the barrier height shows pronounced increase with addition of A-homopolymer due to localization of A-homopolymer on the T-junction core of the dislocation. For chemo-epitaxially patterned substrates (stripes of A-attractive substrate alternating with neutral substrate), the presence of A-attractive stripes helps draw the system towards a perfect lamellar configuration, and energy barriers along the MEP are reduced, in some cases disappearing entirely. Our findings provide guidance on how the presence of homopolymer and chemo-epitaxial prepatterns affect the stability of defective morphologies.

Amphiphilic block copolymers for biomedical applications

Science.gov (United States)

Zupancich, John Andrew

Amphiphilic block copolymer self-assembly provides a versatile means to prepare nanoscale objects in solution. Control over aggregate shape is granted through manipulation of amphiphile composition and the synthesis of well-defined polymers offers the potential to produce micelles with geometries optimized for specific applications. Currently, polymer micelles are being investigated as vehicles for the delivery of therapeutics and attempts to increase efficacy has motivated efforts to incorporate bioactive ligands and stimuli-responsive character into these structures. This thesis reports the synthesis and self-assembly of biocompatible, degradable polymeric amphiphiles. Spherical, cylindrical, and bilayered vesicle structures were generated spontaneously by the direct dispersion of poly(ethylene oxide)-b-poly(gamma-methyl-ε-caprolactone) block copolymers in water and solutions were characterized with cryogenic transmission electron microscopy (cryo-TEM). The dependence of micelle structure on diblock copolymer composition was examined through the systematic variation of the hydrophobic block molecular weight. A continuous evolution of morphology was observed with coexistence of aggregate structures occurring in windows of composition intermediate to that of pure spheres, cylinders and vesicles. A number of heterobifunctional poly(ethylene oxide) polymers were synthesized for the preparation of ligand-functionalized amphiphilic diblock copolymers. The effect of ligand conjugation on block copolymer self-assembly and micelle morphology was also examined. An RGD-containing peptide sequence was efficiently conjugated to a set of well characterized poly(ethylene oxide)-b-poly(butadiene) copolymers. The reported aggregate morphologies of peptide-functionalized polymeric amphiphiles deviated from canonical structures and the micelle clustering, cylinder fragmentation, network formation, and multilayer vesicle generation documented with cryo-TEM was attributed to

Hierarchical self-assembly of two-length-scale multiblock copolymers

International Nuclear Information System (INIS)

Brinke, Gerrit ten; Loos, Katja; Vukovic, Ivana; Du Sart, Gerrit Gobius

2011-01-01

The self-assembly in diblock copolymer-based supramolecules, obtained by hydrogen bonding short side chains to one of the blocks, as well as in two-length-scale linear terpolymers results in hierarchical structure formation. The orientation of the different domains, e.g. layers in the case of a lamellar-in-lamellar structure, is determined by the molecular architecture, graft-like versus linear, and the relative magnitude of the interactions involved. In both cases parallel and perpendicular arrangements have been observed. The comb-shaped supramolecules approach is ideally suited for the preparation of nanoporous structures. A bicontinuous morphology with the supramolecular comb block forming the channels was finally achieved by extending the original approach to suitable triblock copolymer-based supramolecules.

Oxidation effect on templating of metal oxide nanoparticles within block copolymers

International Nuclear Information System (INIS)

Akcora, Pinar; Briber, Robert M.; Kofinas, Peter

2009-01-01

Amphiphilic norbornene-b-(norbornene dicarboxylic acid) diblock copolymers with different block ratios were prepared as templates for the incorporation of iron ions using an ion exchange protocol. The disordered arrangement of iron oxide particles within these copolymers was attributed to the oxidation of the iron ions and the strong interactions between iron oxide nanoparticles, particularly at high iron ion concentrations, which was found to affect the self-assembly of the block copolymer morphologies.

Diblock-copolymer-mediated self-assembly of protein-stabilized iron oxide nanoparticle clusters for magnetic resonance imaging.

Science.gov (United States)

Tähkä, Sari; Laiho, Ari; Kostiainen, Mauri A

2014-03-03

Superparamagnetic iron oxide nanoparticles (SPIONs) can be used as efficient transverse relaxivity (T2 ) contrast agents in magnetic resonance imaging (MRI). Organizing small (Doxide) diblock copolymer (P2QVP-b-PEO) to mediate the self-assembly of protein-cage-encapsulated iron oxide (γ-Fe2 O3 ) nanoparticles (magnetoferritin) into stable PEO-coated clusters. This approach relies on electrostatic interactions between the cationic N-methyl-2-vinylpyridinium iodide block and magnetoferritin protein cage surface (pI≈4.5) to form a dense core, whereas the neutral ethylene oxide block provides a stabilizing biocompatible shell. Formation of the complexes was studied in aqueous solvent medium with dynamic light scattering (DLS) and cryogenic transmission electron microcopy (cryo-TEM). DLS results indicated that the hydrodynamic diameter (Dh ) of the clusters is approximately 200 nm, and cryo-TEM showed that the clusters have an anisotropic stringlike morphology. MRI studies showed that in the clusters the longitudinal relaxivity (r1 ) is decreased and the transverse relaxivity (r2 ) is increased relative to free magnetoferritin (MF), thus indicating that clusters can provide considerable contrast enhancement. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Block copolymer adsorption from a homopolymer melt to an amine-terminated surface

Czech Academy of Sciences Publication Activity Database

Costa, A. C.; Composto, R. J.; Vlček, Petr; Geoghegan, M.

2005-01-01

Roč. 18, č. 2 (2005), s. 159-166 ISSN 1292-8941 R&D Projects: GA ČR GA203/01/0513 Grant - others:Americal Chemical Society, The Petroleum Research Fund(US) 38027/34081 Keywords : copolymer adsorption * neutron reflectometry * diblock copolymers Subject RIV: CD - Macromolecular Chemistry Impact factor: 2.503, year: 2005

Synthesis of an amphiphilic dendrimer-like block copolymer and its application on drug delivery

KAUST Repository

Wang, Shuaipeng

2014-10-27

Dendrimer-like amphiphilic copolymer is a kind of three-dimensional spherical structure polymer. An amphiphilic dendrimer-like diblock copolymer, PEEGE-G2-b-PEO(OH)12, constituted of a hydrophobic poly(ethoxyethyl glycidol ether) inner core and a hydrophilic poly(ethylene oxide) outer layer, has been successfully synthesized by the living anionic ring-opening polymerization method. The intermediates and targeted products were characterized with 1H NMR spectroscopy and gel permeation chromatography. The application on drug delivery of dendrimer-like diblock copolymer PEEGE-G2-b-PEO(OH)12 using DOX as a model drug was also studied. The drug loading content and encapsulation efficiency were found at 13.07% and 45.75%, respectively. In vitro release experiment results indicated that the drug-loaded micelles exhibited a sustained release behavior under acidic media.

Self-assembled structures of amphiphilic ionic block copolymers: Theory, self-consistent field modeling and experiment

NARCIS (Netherlands)

Borisov, O.V.; Zhulina, E.B.; Leermakers, F.A.M.; Muller, A.H.E.

2011-01-01

We present an overview of statistical thermodynamic theories that describe the self-assembly of amphiphilic ionic/hydrophobic diblock copolymers in dilute solution. Block copolymers with both strongly and weakly dissociating (pH-sensitive) ionic blocks are considered. We focus mostly on structural

Multiple ordered phases in a block copolymer melt

DEFF Research Database (Denmark)

Almdal, K.; Koppi, K.A.; Bates, F.S.

1992-01-01

A poly(ethylenepropylene)-poly(ethylethylene) (PEP-PEE) diblock copolymer containing 65% by volume PEP was investigated using small-angle neutron scattering (SANS) and rheological measurements. Four distinct phases have been identified as a function of temperature: three ordered phases at low...

Photoinitiated Polymerization-Induced Self-Assembly of Glycidyl Methacrylate for the Synthesis of Epoxy-Functionalized Block Copolymer Nano-Objects.

Science.gov (United States)

Tan, Jianbo; Liu, Dongdong; Huang, Chundong; Li, Xueliang; He, Jun; Xu, Qin; Zhang, Li

2017-08-01

Herein, a novel photoinitiated polymerization-induced self-assembly formulation via photoinitiated reversible addition-fragmentation chain transfer dispersion polymerization of glycidyl methacrylate (PGMA) in ethanol-water at room temperature is reported. It is demonstrated that conducting polymerization-induced self-assembly (PISA) at low temperatures is crucial for obtaining colloidal stable PGMA-based diblock copolymer nano-objects. Good control is maintained during the photo-PISA process with a high rate of polymerization. The polymerization can be switched between "ON" and "OFF" in response to visible light. A phase diagram is constructed by varying monomer concentration and degree of polymerization. The PGMA-based diblock copolymer nano-objects can be further cross-linked by using a bifunctional primary amine reagent. Finally, silver nanoparticles are loaded within cross-linked vesicles via in situ reduction, exhibiting good catalytic properties. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Conformation and structural changes of diblock copolymers with octopus-like micelle formation in the presence of external stimuli

Science.gov (United States)

Dammertz, K.; Saier, A. M.; Marti, O.; Amirkhani, M.

2014-04-01

External stimuli such as vapours and electric fields can be used to manipulate the formation of AB-diblock copolymers on surfaces. We study the conformational variation of PS-b-PMMA (polystyrene-block-poly(methyl methacrylate)), PS and PMMA adsorbed on mica and their response to saturated water or chloroform atmospheres. Using specimens with only partial polymer coverage, new unanticipated effects were observed. Water vapour, a non-solvent for all three polymers, was found to cause high surface mobility. In contrast, chloroform vapour (a solvent for all three polymers) proved to be less efficient. Furthermore, the influence of an additional applied electric field was investigated. A dc field oriented parallel to the sample surface induces the formation of polymer islands which assemble into wormlike chains. Moreover, PS-b-PMMA forms octopus-like micelles (OLMs) on mica. Under the external stimuli mentioned above, the wormlike formations of OLMs are able to align in the direction of the external electric field. In the absence of an electric field, the OLMs disaggregate and exhibit phase separated structures under chloroform vapour.

Conformation and structural changes of diblock copolymers with octopus-like micelle formation in the presence of external stimuli

International Nuclear Information System (INIS)

Dammertz, K; Saier, A M; Marti, O; Amirkhani, M

2014-01-01

External stimuli such as vapours and electric fields can be used to manipulate the formation of AB-diblock copolymers on surfaces. We study the conformational variation of PS-b-PMMA (polystyrene-block-poly(methyl methacrylate)), PS and PMMA adsorbed on mica and their response to saturated water or chloroform atmospheres. Using specimens with only partial polymer coverage, new unanticipated effects were observed. Water vapour, a non-solvent for all three polymers, was found to cause high surface mobility. In contrast, chloroform vapour (a solvent for all three polymers) proved to be less efficient. Furthermore, the influence of an additional applied electric field was investigated. A dc field oriented parallel to the sample surface induces the formation of polymer islands which assemble into wormlike chains. Moreover, PS-b-PMMA forms octopus-like micelles (OLMs) on mica. Under the external stimuli mentioned above, the wormlike formations of OLMs are able to align in the direction of the external electric field. In the absence of an electric field, the OLMs disaggregate and exhibit phase separated structures under chloroform vapour. (paper)

Shear instability of a gyroid diblock copolymer

DEFF Research Database (Denmark)

Eskimergen, Rüya; Mortensen, Kell; Vigild, Martin Etchells

2005-01-01

-induced destabilization is discussed in relation to analogous observations on shear-induced order-to-order and disorder-to-order transitions observed in related block copolymer systems and in microemulsions. It is discussed whether these phenomena originate in shear-reduced fluctuations or shear-induced dislocations....

Effect of Hydrophobic Chain Length on the Stability and Guest Exchange Behavior of Shell-Sheddable Micelles Formed by Disulfide-Linked Diblock Copolymers.

Science.gov (United States)

Fan, Haiyan; Li, Yixia; Yang, Jinxian; Ye, Xiaodong

2017-10-19

Reduction-responsive micelles hold enormous promise for application as drug carriers due to the fast drug release triggered by reducing conditions and high anticancer activity. However, the effect of hydrophobic chain length on the stability and guest exchange of reduction-responsive micelles, especially for the micelles formed by diblock copolymers containing single disulfide group, is not fully understood. Here, shell-sheddable micelles formed by a series of disulfide-linked copolymer poly(ethylene glycol)-b-poly(ε-caprolactone) (PEG-SS-PCL) containing the same chain length of PEG but different chain lengths of hydrophobic block PCL were prepared and well characterized. The influence of the chain length of hydrophobic PCL block on the stability and guest exchange of PEG-SS-PCL micelles was studied by the use of both dynamic laser light scattering (DLS) and fluorescence resonance energy transfer (FRET). The results show that longer PCL chains lead to a slower aggregation rate and guest exchange of micelles in the aqueous solutions containing 10 mM dithiothreitol (DTT). The cell uptake of the shell-sheddable PEG-SS-PCL micelles in vitro shows that the amount of internalization of dyes loaded in PEG-SS-PCL micelles increases with the chain length of hydrophobic PCL block investigated by flow cytometric analysis and confocal fluorescence microscopy.

Self-Assembly and Crystallization of Conjugated Block Copolymers

Science.gov (United States)

Davidson, Emily Catherine

This dissertation demonstrates the utility of molecular design in conjugated polymers to create diblock copolymers that robustly self-assemble in the melt and confine crystallization upon cooling. This work leverages the model conjugated polymer poly(3-(2'-ethyl)hexylthiophene) (P3EHT), which features a branched side chain, resulting in a dramatically reduced melting temperature (Tm 80°C) relative to the widely-studied poly(3-hexylthiophene) (P3HT) (Tm 200°C). This reduced melting temperature permits an accessible melt phase, without requiring that the segregation strength (chiN) be dramatically increased. Thus, diblock copolymers containing P3EHT demonstrate robust diblock copolymer self-assembly in the melt over a range of compositions and morphologies. Furthermore, confined crystallization in the case of both glassy (polystyrene (PS) matrix block) and soft (polymethylacrylate (PMA) matrix block) confinement is studied, with the finding that even in soft confinement, crystallization is constrained within the diblock microdomains. This success demonstrates the strategy of leveraging molecular design to decrease the driving force for crystallization as a means to achieving robust self-assembly and confined crystallization in conjugated block copolymers. Importantly, despite the relatively flexible nature of P3EHT in the melt, the diblock copolymer phase behavior appears to be significantly impacted by the stiffness (persistence length of 3 nm) of the P3EHT chain compared to the coupled amorphous blocks (persistence length 0.7 nm). In particular, it is shown that the synthesized morphologies are dominated by a very large composition window for lamellar geometries (favored at high P3EHT volume fractions); cylindrical geometries are favored when P3EHT is the minority fraction. This asymmetry of the composition window is attributed to impact of conformational asymmetry (the difference in chain stiffness, as opposed to shape) between conjugated and amorphous blocks

Formation of nanophases in epoxy thermosets containing amphiphilic block copolymers with linear and star-like topologies.

Science.gov (United States)

Wang, Lei; Zhang, Chongyin; Cong, Houluo; Li, Lei; Zheng, Sixun; Li, Xiuhong; Wang, Jie

2013-07-11

In this work, we investigated the effect of topological structures of block copolymers on the formation of the nanophase in epoxy thermosets containing amphiphilic block copolymers. Two block copolymers composed of poly(ε-caprolactone) (PCL) and poly(2,2,2-trifluoroethyl acrylate) (PTFEA) blocks were synthesized to possess linear and star-shaped topologies. The star-shaped block copolymer composed a polyhedral oligomeric silsesquioxane (POSS) core and eight poly(ε-caprolactone)-block-poly(2,2,2-trifluoroethyl acrylate) (PCL-b-PTFEA) diblock copolymer arms. Both block copolymers were synthesized via the combination of ring-opening polymerization and reversible addition-fragmentation chain transfer/macromolecular design via the interchange of xanthate (RAFT/MADIX) process; they were controlled to have identical compositions of copolymerization and lengths of blocks. Upon incorporating both block copolymers into epoxy thermosets, the spherical PTFEA nanophases were formed in all the cases. However, the sizes of PTFEA nanophases from the star-like block copolymer were significantly lower than those from the linear diblock copolymer. The difference in the nanostructures gave rise to the different glass transition behavior of the nanostructured thermosets. The dependence of PTFEA nanophases on the topologies of block copolymers is interpreted in terms of the conformation of the miscible subchain (viz. PCL) at the surface of PTFEA microdomains and the restriction of POSS cages on the demixing of the thermoset-philic block (viz. PCL).

Poly(Acrylic Acid-b-Styrene) Amphiphilic Multiblock Copolymers as Building Blocks for the Assembly of Discrete Nanoparticles

Science.gov (United States)

Greene, Anna C.; Zhu, Jiahua; Pochan, Darrin J.; Jia, Xinqiao; Kiick, Kristi L.

2011-01-01

In order to expand the utility of current polymeric micellar systems, we have developed amphiphilic multiblock copolymers containing alternating blocks of poly(acrylic acid) and poly(styrene). Heterotelechelic poly(tert-butyl acrylate-b-styrene) diblock copolymers containing an α-alkyne and an ω-azide were synthesized by atom transfer radical polymerization (ATRP), allowing control over the molecular weight while maintaining narrow polydispersity indices. The multiblock copolymers were constructed by copper-catalyzed azide-alkyne cycloaddition of azide-alkyne end functional diblock copolymers which were then characterized by 1H NMR, FT-IR and SEC. The tert-butyl moieties of the poly(tert-butyl acrylate-b-styrene) multiblock copolymers were easily removed to form the poly(acrylic acid-b-styrene) multiblock copolymer ((PAA-PS)9), which contained up to 9 diblock repeats. The amphiphilic multiblock (PAA-PS)9 (Mn = 73.3 kg/mol) was self-assembled by dissolution into tetrahydrofuran and extensive dialysis against deionized water for 4 days. The critical micelle concentration (CMC) for (PAA-PS)9 was determined by fluorescence spectroscopy using pyrene as a fluorescent probe and was found to be very low at 2 × 10-4 mg/mL. The (PAA-PS)9 multiblock was also analyzed by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The hydrodynamic diameter of the particles was found to be 11 nm. Discrete spherical particles were observed by TEM with an average particle diameter of 14 nm. The poly(acrylic acid) periphery of the spherical particles should allow for future conjugation of biomolecules. PMID:21552373

The melt rheological behavior of AB, ABA, BAB, and (AB)n block copolymers with monodisperse aramide segments

NARCIS (Netherlands)

Araichimani, A.; Dullaert, Konraad; Gaymans, R.J.

2009-01-01

The melt rheological behavior of segmented block copolymers with high melting diamide (A) hard segments (HS) and polyether (B) soft segments was studied. The block copolymers can be classified as B (monoblock), AB (diblock), ABA (triblock, diamide end segment), BAB (triblock, diamide mid-segment)

Tailored Design of Bicontinuous Gyroid Mesoporous Carbon and Nitrogen-Doped Carbon from Poly(ethylene oxide-b-caprolactone) Diblock Copolymers.

Science.gov (United States)

Chu, Wei-Cheng; Bastakoti, Bishnu Prasad; Kaneti, Yusuf Valentino; Li, Jheng-Guang; Alamri, Hatem R; Alothman, Zeid A; Yamauchi, Yusuke; Kuo, Shiao-Wei

2017-10-04

Highly ordered mesoporous resol-type phenolic resin and the corresponding mesoporous carbon materials were synthesized by using poly(ethylene oxide-b-caprolactone) (PEO-b-PCL) diblock copolymer as a soft template. The self-assembled mesoporous phenolic resin was found to form only in a specific resol concentration range of 40-70 wt % due to an intriguing balance of hydrogen-bonding interactions in the resol/PEO-b-PCL mixtures. Furthermore, morphological transitions of the mesostructures from disordered to gyroid to cylindrical and finally to disordered micelle structure were observed with increasing resol concentration. By calcination under nitrogen atmosphere at 800 °C, the bicontinuous mesostructured gyroid phenolic resin could be converted to mesoporous carbon with large pore size without collapse of the original mesostructure. Furthermore, post-treatment of the mesoporous gyroid phenolic resin with melamine gave rise to N-doped mesoporous carbon with unique electronic properties for realizing high CO 2 adsorption capacity (6.72 mmol g -1 at 0 °C). © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ionic Liquids As Self-Assembly Guide for the Formation of Nanostructured Block Copolymer Membranes

KAUST Repository

Madhavan, Poornima

2015-04-30

Nanostructured block copolymer membranes were manufactured by water induced phase inversion, using ionic liquids (ILs) as cosolvents. The effect of ionic liquids on the morphology was investigated, by using polystyrene-b-poly(4-vinyl pyridine) (PS-b-PV4P) diblock as membrane copolymer matrix and imidazolium and pyridinium based ILs. The effect of IL concentration and chemical composition was evident with particular interaction with P4VP blocks. The order of block copolymer/ILs solutions previous to the membrane casting was confirmed by cryo scanning electron microscopy and the morphologies of the manufactured nanostructured membranes were characterized by transmission and scanning electron microscopy. Non-protic ionic liquids facilitate the formation of hexagonal nanoporous block copolymer structure, while protic ILs led to a lamella-structured membrane. The rheology of the IL/block copolymer solutions was investigated, evaluating the storage and loss moduli. Most membranes prepared with ionic liquid had higher water flux than pure block copolymer membranes without additives.

Isotropic Lifshitz behavior in block copolymer-homopolymer blends

DEFF Research Database (Denmark)

Bates, F.S.; Maurer, W.; Lodge, T.P.

1995-01-01

A series of mixtures composed of a symmetric A-B diblock copolymer and a symmetric blend of A and B homopolymers was investigated by small-angle neutron scattering. Mean-field theory predicts that a line of lamellar-disorder transitions with wave-vector instability q* > 0 will meet a line of crit...

Meso-scale Modeling of Block Copolymers Self-Assembly in Casting Solutions for Membrane Manufacture

KAUST Repository

Moreno Chaparro, Nicolas

2016-01-01

Isoporous membranes manufactured from diblock copolymer are successfully produced at laboratory scale under controlled conditions. Because of the complex phenomena involved, membrane preparation requires trial and error methodologies to find

Supramolecular Assemblies from Poly(styrene-block-poly(4-vinylpyridine Diblock Copolymers Mixed with 6-Hydroxy-2-naphthoic Acid

Directory of Open Access Journals (Sweden)

Jean-François Gohy

2013-06-01

Full Text Available Supramolecular assemblies involving interaction of a small organic molecule, 2-hydroxy-6-Naphthoic acid (HNA, with poly(styrene-block-poly(4-vinylpyridine (PS-b-P4VP diblock copolymers are utilized to obtain micellar structures in solution, nanostructured thin films on flat substrates and, finally, nanoporous thin films. The formation of hydrogen bonds between HNA and the poly(4-vinylpyridine (P4VP blocks is confirmed by spectroscopic measurements. The accordingly P4VP/HNA hydrogen-bonded complexes are poorly soluble in 1,4-dioxane, resulting in the formation of micellar structures with a P4VP/HNA core and a polystyrene (PS corona. Those micelles have been spin-coated onto silicon wafers, resulting in nanostructured thin films consisting of P4VP/HNA dot-like features embedded in a PS matrix. The morphology of those films has been tuned by solvent annealing. Selective dissolution of HNA by methanol results in the formation of a nanoporous thin film. The P4VP/HNA nanodomains have been also cross-linked by borax, and the thin films have been further dissolved in a good solvent for PS, leading to micelles with a structure reminiscent of the thin films.

Liquid-crystalline side chain block copolymers - synthesis, morphology and LC behavior

NARCIS (Netherlands)

Arnold, M.; Poser, S.; Fischer, H.R.; Frank, W.; Utschick, H.

1994-01-01

Side-chain liq.-cryst. 2-hydroxyethyl methacrylate-styrene diblock copolymer (I) was prepd. by polymn. of 2-(trimethylsiloxy)ethyl methacrylate with styrene with further treatment with cholesteryl chloroformate. Morphol. and phase behavior of I were investigated. [on SciFinder (R)

Block copolymer-nanoparticle hybrid self-assembly

KAUST Repository

Hoheisel, Tobias N.; Hur, Kahyun; Wiesner, Ulrich B.

2015-01-01

© 2014 Published by Elsevier Ltd. Polymer-inorganic hybrid materials provide exciting opportunities as they may display favorable properties from both constituents that are desired in applications including catalysis and energy conversion and storage. For the preparation of hybrid materials with well-defined morphologies, block copolymer-directed nanoparticle hybrids present a particularly promising approach. As will be described in this review, once the fundamental characteristics for successful nanostructure formation at or close to the thermodynamic equilibrium of these nanocomposites are identified, the approach can be generalized to various materials classes. In addition to the discussion of recent materials developments based on the use of AB diblock copolymers as well as ABC triblock terpolymers, this review will therefore emphasize progress in the fundamental understanding of the underlying formation mechanisms of such hybrid materials. To this end, critical experiments for, as well as theoretical progress in the description of these nanostructured block copolymer-based hybrid materials will be discussed. Rather than providing a comprehensive overview, the review will emphasize work by the Wiesner group at Cornell University, US, on block copolymer-directed nanoparticle assemblies as well as their use in first potential application areas. The results provide powerful design criteria for wet-chemical synthesis methodologies for the generation of functional nanomaterials for applications ranging from microelectronics to catalysis to energy conversion and storage.

Investigations on the Phase Diagram and Interaction Parameter of Poly(styrene-b-1,3-cyclohexadiene) Copolymers

KAUST Repository

Misichronis, Konstantinos

2017-03-15

A series of linear diblock copolymers containing polystyrene (PS) and poly(1,3-cyclohexadiene) (PCHD) with high 1,4-microstructure (>87%) was synthesized by anionic polymerization and high vacuum techniques. Microphase separation in the bulk was examined by transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) and compared to computational analysis of the predicted morphological phase diagram for this system. Because of the high conformational asymmetry between PS and PCHD, these materials self-assemble into typical morphologies expected for linear diblock copolymer systems and atypical structures. Rheological measurements were conducted and revealed order–disorder transition temperatures (TODT), for the first time for PS-b-PCHD copolymers, resulting in a working expression for the effective interaction parameter χeff = 32/T – 0.016. Furthermore, we performed computational studies that coincide with the experimental results. These copolymers exhibit well-ordered structures even at high temperatures (∼260 °C) therefore providing a better insight concerning their microphase separation at the nanoscale which is important for their potential use in nanotechnology and/or nanolithography applications.

Investigations on the Phase Diagram and Interaction Parameter of Poly(styrene-b-1,3-cyclohexadiene) Copolymers

KAUST Repository

Misichronis, Konstantinos; Chen, Jihua; Imel, Adam; Kumar, Rajeev; Thostenson, James; Hong, Kunlun; Dadmun, Mark; Sumpter, Bobby G.; Kennemur, Justin G.; Hadjichristidis, Nikolaos; Mays, Jimmy W.; Avgeropoulos, Apostolos

2017-01-01

A series of linear diblock copolymers containing polystyrene (PS) and poly(1,3-cyclohexadiene) (PCHD) with high 1,4-microstructure (>87%) was synthesized by anionic polymerization and high vacuum techniques. Microphase separation in the bulk was examined by transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) and compared to computational analysis of the predicted morphological phase diagram for this system. Because of the high conformational asymmetry between PS and PCHD, these materials self-assemble into typical morphologies expected for linear diblock copolymer systems and atypical structures. Rheological measurements were conducted and revealed order–disorder transition temperatures (TODT), for the first time for PS-b-PCHD copolymers, resulting in a working expression for the effective interaction parameter χeff = 32/T – 0.016. Furthermore, we performed computational studies that coincide with the experimental results. These copolymers exhibit well-ordered structures even at high temperatures (∼260 °C) therefore providing a better insight concerning their microphase separation at the nanoscale which is important for their potential use in nanotechnology and/or nanolithography applications.

Ionization of amphiphilic acidic block copolymers.

Science.gov (United States)

Colombani, Olivier; Lejeune, Elise; Charbonneau, Céline; Chassenieux, Christophe; Nicolai, Taco

2012-06-28

The ionization behavior of an amphiphilic diblock copolymer poly(n-butyl acrylate(50%)-stat-acrylic acid(50%))(100)-block-poly(acrylic acid)(100) (P(nBA(50%)-stat-AA(50%))(100)-b-PAA(100), DH50) and of its equivalent triblock copolymer P(nBA(50%)-stat-AA(50%))(100)-b-PAA(200)-b-P(nBA(50%)-stat-AA(50%))(100) (TH50) were studied by potentiometric titration either in pure water or in 0.5 M NaCl. These polymers consist of a hydrophilic acidic block (PAA) connected to a hydrophobic block, P(nBA(50%)-stat-AA(50%))(100), whose hydrophobic character has been mitigated by copolymerization with hydrophilic units. We show that all AA units, even those in the hydrophobic block could be ionized. However, the AA units within the hydrophobic block were less acidic than those in the hydrophilic block, resulting in the preferential ionization of the latter block. The preferential ionization of PAA over that of P(nBA(50%)-stat-AA(50%))(100) was stronger at higher ionic strength. Remarkably, the covalent bonds between the PAA and P(nBA(50%)-stat-AA(50%))(100) blocks in the diblock or the triblock did not affect the ionization of each block, although the self-association of the block copolymers into spherical aggregates modified the environment of the PAA blocks compared to when PAA was molecularly dispersed.

Low Molecular Weight pDMAEMA-block-pHEMA Block-Copolymers Synthesized via RAFT-Polymerization: Potential Non-Viral Gene Delivery Agents?

Directory of Open Access Journals (Sweden)

Thomas Kissel

2011-03-01

Full Text Available The aim of this study was to investigate non-viral pDNA carriers based on diblock-copolymers consisting of poly(2-(dimethyl aminoethyl methacrylate (pDMAEMA and poly(2-hydroxyethyl methacrylate (pHEMA. Specifically the block-lengths and molecular weights were varied to determine the minimal requirements for transfection. Such vectors should allow better transfection at acceptable toxicity levels and the entire diblock-copolymer should be suitable for renal clearance. For this purpose, a library of linear poly(2-(dimethyl aminoethyl methacrylate-block-poly(2-hydroxyl methacrylate (pDMAEMA-block-pHEMA copolymers was synthesized via RAFT (reversible addition-fragmentation chain transfer polymerization in a molecular weight (Mw range of 17–35.7 kDa and analyzed using 1H and 13C NMR (nuclear magnetic resonance, ATR (attenuated total reflectance, GPC (gel permeation chromatography and DSC (differential scanning calorimetry. Copolymers possessing short pDMAEMA-polycation chains were 1.4–9.7 times less toxic in vitro than polyethylenimine (PEI 25 kDa, and complexed DNA into polyplexes of 100–170 nm, favorable for cellular uptake. The DNA-binding affinity and polyplex stability against competing polyanions was comparable with PEI 25 kDa. The zeta-potential of polyplexes of pDMAEMA-grafted copolymers remained positive (+15–30 mV. In comparison with earlier reported low molecular weight homo pDMAEMA vectors, these diblock-copolymers showed enhanced transfection efficacy under in vitro conditions due to their lower cytotoxicity, efficient cellular uptake and DNA packaging. The homo pDMAEMA115 (18.3 kDa self-assembled with DNA into small positively charged polyplexes, but was not able to transfect cells. The grafting of 6 and 57 repeating units of pHEMA (0.8 and 7.4 kDa to pDMAEMA115 increased the transfection efficacy significantly, implying a crucial impact of pHEMA on vector-cell interactions. The intracellular trafficking, in vivo transfection

Preparation of Water-soluble Polyion Complex (PIC Micelles Covered with Amphoteric Random Copolymer Shells with Pendant Sulfonate and Quaternary Amino Groups

Directory of Open Access Journals (Sweden)

Rina Nakahata

2018-02-01

Full Text Available An amphoteric random copolymer (P(SA91 composed of anionic sodium 2-acrylamido-2-methylpropanesulfonate (AMPS, S and cationic 3-acrylamidopropyl trimethylammonium chloride (APTAC, A was prepared via reversible addition-fragmentation chain transfer (RAFT radical polymerization. The subscripts in the abbreviations indicate the degree of polymerization (DP. Furthermore, AMPS and APTAC were polymerized using a P(SA91 macro-chain transfer agent to prepare an anionic diblock copolymer (P(SA91S67 and a cationic diblock copolymer (P(SA91A88, respectively. The DP was estimated from quantitative 13C NMR measurements. A stoichiometrically charge neutralized mixture of the aqueous P(SA91S67 and P(SA91A88 formed water-soluble polyion complex (PIC micelles comprising PIC cores and amphoteric random copolymer shells. The PIC micelles were in a dynamic equilibrium state between PIC micelles and charge neutralized small aggregates composed of a P(SA91S67/P(SA91A88 pair. Interactions between PIC micelles and fetal bovine serum (FBS in phosphate buffered saline (PBS were evaluated by changing the hydrodynamic radius (Rh and light scattering intensity (LSI. Increases in Rh and LSI were not observed for the mixture of PIC micelles and FBS in PBS for one day. This observation suggests that there is no interaction between PIC micelles and proteins, because the PIC micelle surfaces were covered with amphoteric random copolymer shells. However, with increasing time, the diblock copolymer chains that were dissociated from PIC micelles interacted with proteins.

Supramolecular self-assembly and opto-electronic properties of semiconducting block copolymers

NARCIS (Netherlands)

Boer, Bert de; Stalmach, Ulf; Hutten, Paul F. van; Melzer, Christian; Krasnikov, Victor V.; Hadziioannou, Georges

2001-01-01

With continuous and nanometre-scale interpenetrating phases of electron donor and acceptor components, a novel diblock copolymer, in which one block is poly(p-phenylene vinylene) (PPV) and the other is a C60-functionalized polystyrene, is designed to be an efficient photovoltaic material. The

Stability of monolayers and bilayers in a copolymer-homopolymer blend model

NARCIS (Netherlands)

Gennip, van Y.; Peletier, M.A.

2007-01-01

We study the stability of layered structures in a variational model for diblock copolymer- homopolymer blends. The main step consists of calculating the first and second derivative of a sharp-interface Ohta-Kawasaki energy for straight mono- and bilayers. By developing the interface perturbations in

A One-Step Route to CO2 -Based Block Copolymers by Simultaneous ROCOP of CO2 /Epoxides and RAFT Polymerization of Vinyl Monomers.

Science.gov (United States)

Wang, Yong; Zhao, Yajun; Ye, Yunsheng; Peng, Haiyan; Zhou, Xingping; Xie, Xiaolin; Wang, Xianhong; Wang, Fosong

2018-03-26

The one-step synthesis of well-defined CO 2 -based diblock copolymers was achieved by simultaneous ring-opening copolymerization (ROCOP) of CO 2 /epoxides and RAFT polymerization of vinyl monomers using a trithiocarbonate compound bearing a carboxylic group (TTC-COOH) as the bifunctional chain transfer agent (CTA). The double chain-transfer effect allows for independent and precise control over the molecular weight of the two blocks and ensures narrow polydispersities of the resultant block copolymers (1.09-1.14). Notably, an unusual axial group exchange reaction between the aluminum porphyrin catalyst and TTC-COOH impedes the formation of homopolycarbonates. By taking advantage of the RAFT technique, it is able to meet the stringent demand for functionality control to well expand the application scopes of CO 2 -based polycarbonates. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Organisation and shape of micellar solutions of block copolymers

Science.gov (United States)

Gaspard, J. P.; Creutz, S.; Bouchat, Ph.; Jérôme, R.; Cohen Stuart, M.

1997-02-01

Diblock copolymers of polymethacrylic acid sodium salt, forming the hair, and styrene derivatives have been studied in aqueous solutions by SANS and SAXS. The influence of both the chemical nature and the length of the hydrophobic bloxk on the size and shape of micelles have been investigated. The micellar core size is in agreement with the theoretical evaluation for copolymers with a short hydrophobic sequence. In contrast, in case of larger hydrophobic blocks, the measured size is incompatible with a star-like model. Various hypotheses are presented for the latter.

Novel Pentablock Copolymers as Thermosensitive Self-Assembling Micelles for Ocular Drug Delivery

Directory of Open Access Journals (Sweden)

Mitra Alami-Milani

2017-04-01

Full Text Available Many studies have focused on how drugs are formulated in the sol state at room temperature leading to the formation of in situ gel at eye temperature to provide a controlled drug release. Stimuli-responsive block copolymer hydrogels possess several advantages including uncomplicated drug formulation and ease of application, no organic solvent, protective environment for drugs, site-specificity, prolonged and localized drug delivery, lower systemic toxicity, and capability to deliver both hydrophobic and hydrophilic drugs. Self-assembling block copolymers (such as diblock, triblock, and pentablock copolymers with large solubility variation between hydrophilic and hydrophobic segments are capable of making temperature-dependent micellar assembles, and with further increase in the temperature, of jellifying due to micellar aggregation. In general, molecular weight, hydrophobicity, and block arrangement have a significant effect on polymer crystallinity, micelle size, and in vitro drug release profile. The limitations of creature triblock copolymers as initial burst release can be largely avoided using micelles made of pentablock copolymers. Moreover, formulations based on pentablock copolymers can sustain drug release for a longer time. The present study aims to provide a concise overview of the initial and recent progresses in the design of hydrogel-based ocular drug delivery systems.

Neutral, anionic, cationic, and zwitterionic diblock copolymers featuring poly(2-methoxyethyl acrylate) hydrophobic segments

DEFF Research Database (Denmark)

Javakhishvili, Irakli; Jankova Atanasova, Katja; Hvilsted, Søren

2013-01-01

-b-PDMAEMA while the betainisation of the latter provides zwitterionic diblock amphiphile PMEA-b-PDMAPS. Inspection of these macromolecular architectures by NMR spectroscopy and size exclusion chromatography (SEC) confirms a fairly high degree of control over the reactions emphasizing flexibility and precision...

Investigation of Universal Behavior in Symmetric Diblock Copolymer Melts

Science.gov (United States)

Medapuram, Pavani

Coarse-grained theories of dense polymer liquids such as block copolymer melts predict a universal dependence of equilibrium properties on a few dimensionless parameters. For symmetric diblock copolymer melts, such theories predict a universal dependence on only chieN and N¯, where chie is an effective interaction parameter, N is the degree of polymerization, and N¯ is a measure of overlap. This thesis focuses on testing the universal behavior hypothesis by comparing results for various properties obtained from different coarse-grained simulation models to each other. Specifically, results from pairs of simulations of different models that have been designed to have matched values of N¯ are compared over a range of values of chiN. The use of vastly different simulation models allows us to cover a vast range of chi eN ≃ 200 - 8000 that includes most of the experimentally relevant range. Properties studied here include collective and single-chain correlations in the disordered phase, block and chain radii of gyration in the disordered phase, the value of chieN at the order-disorder transition (ODT), the free energy per chain, the latent heat of transition, the layer spacing, the composition profile, and compression modulus in the ordered phase. All results strongly support the universal scaling hypothesis, even for rather short chains, confirming that it is indeed possible to give an accurate universal description of simulation models that differ in many details. The underlying universality becomes apparent, however, only if data are analyzed using an adequate estimate of chie, which we obtained by fitting the structure factor S( q) in the disordered state to predictions of the recently developed renormalized one-loop (ROL) theory. The ROL theory is shown to provide an excellent description of the dependence of S(q on chain length and thermodynamic conditions for all models, even for very short chains, if we allow for the existence of a nonlinear dependence of

Nanopatterning via Self-Assembly of a Lamellar-Forming Polystyrene-block-Poly(dimethylsiloxane Diblock Copolymer on Topographical Substrates Fabricated by Nanoimprint Lithography

Directory of Open Access Journals (Sweden)

Dipu Borah

2018-01-01

Full Text Available The self-assembly of a lamellar-forming polystyrene-block-poly(dimethylsiloxane (PS-b-PDMS diblock copolymer (DBCP was studied herein for surface nanopatterning. The DBCP was synthesized by sequential living anionic polymerization of styrene and hexamethylcyclotrisiloxane (D3. The number average molecular weight (Mn, polydispersity index (Mw/Mn and PS volume fraction (φps of the DBCP were MnPS = 23.0 kg mol−1, MnPDMS = 15.0 kg mol−1, Mw/Mn = 1.06 and φps = 0.6. Thin films of the DBCP were cast and solvent annealed on topographically patterned polyhedral oligomeric silsesquioxane (POSS substrates. The lamellae repeat distance or pitch (λL and the width of the PDMS features (dL are ~35 nm and ~17 nm, respectively, as determined by SEM. The chemistry of the POSS substrates was tuned, and the effects on the self-assembly of the DBCP noted. The PDMS nanopatterns were used as etching mask in order to transfer the DBCP pattern to underlying silicon substrate by a complex plasma etch process yielding sub-15 nm silicon features.

One-step routes from di- and triblock copolymer precursors to hydrophilic nanoporous poly(acrylic acid)-b-polystyrene

DEFF Research Database (Denmark)

Guo, Fengxiao; Jankova Atanasova, Katja; Schulte, Lars

2008-01-01

Nanoporous polystyrene with hydrophilic pores was prepared from di- and triblock copolymer precursors. The precursor material was either a poly(tert-butyl acryl ate)-b-polystyrene (PtBA-b-PS) diblock copolymer synthesized by atom transfer radical polymerization (ATRP) or a polydimethylsiloxane......-b-poly(tertbutyl acrylate)-b-polystyrene (PDMS-b-PtBA-b-PS) triblock copolymer synthesized by a combination of living anionic polymerization and ATRP. In the latter copolymer, PS was the matrix and mechanically stable component, PtBA was converted by acidic deprotection to hydrophilic poly(acrylic acid) (PAA) providing...

Distributions of chain ends and junction points in ordered block copolymers

International Nuclear Information System (INIS)

Mayes, A.M.; Johnson, R.D.; Russell, T.P.; Smith, S.D.; Satija, S.K.; Majkrzak, C.F.

1993-01-01

Chain configurations in ordered symmetric poly(styrene-b-methyl methacrylate) diblock copolymers were examined by neutron reflectively. In a thin-film geometry the copolymers organize into lamellar microdomains oriented parallel to the substrate surface. The copolymers organize into lamellar microdomains oriented parallel to the substrate surface. The copolymers were synthesized with small fractions of deuterated segments at either the chain ends or centers. This selective labeling permitted characterization of the spatial distribution of chain ends and junction points normal to the plane of the film. From the reflectivity analysis, the junction points are found to be confined to the PS/PMMA interfacial regions. The chain ends, however, are well distributed through their respective domains, exhibiting only a weak maximum in concentration at the center of the domains

Dual hydrophilic and salt responsive schizophrenic block copolymers – synthesis and study of self-assembly

NARCIS (Netherlands)

Vasantha, Vivek Arjunan; Jana, Satyasankar; Lee, Serina Siew Chen; Lim, Chin-Sing; Teo, Serena Lay Ming; Parthiban, Anbanandam; Vancso, Gyula J.

2015-01-01

A new class of dual hydrophilic diblock copolymers (BCPs) possessing poly(ethylene glycol) (PEG) and zwitterionic polysulfabetaine (PSB) was synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization. These BCPs formed schizophrenic micelles undergoing core–shell

Topology and Shape Control for Assemblies of Block Copolymer Blends in Solution

KAUST Repository

Moreno Chaparro, Nicolas; Nunes, Suzana Pereira; Peinemann, Klaus-Viktor; Calo, Victor M.

2015-01-01

We study binary blends of asymmetric diblock copolymers (AB/AC) in selective solvents with a mesoscale model. We investigate the morphological transitions induced by the concentration of the AC block copolymer and the difference in molecular weight between the AB and AC copolymers, when segments B and C exhibit hydrogen-bonding interactions. To the best of our knowledge, this is the first work modeling mixtures of block copolymers with large differences in molecular weight. The coassembly mechanism localizes the AC molecules at the interface of A and B domains and induces the swelling of the B-rich domains. The coil size of the large molecular weight block copolymer depends only on the concentration of the short block copolymer (AC or AB), regardless of the B–C interactions. However, the B–C interactions control the morphological transitions that occur in these blends.

Topology and Shape Control for Assemblies of Block Copolymer Blends in Solution

KAUST Repository

Moreno Chaparro, Nicolas

2015-10-27

We study binary blends of asymmetric diblock copolymers (AB/AC) in selective solvents with a mesoscale model. We investigate the morphological transitions induced by the concentration of the AC block copolymer and the difference in molecular weight between the AB and AC copolymers, when segments B and C exhibit hydrogen-bonding interactions. To the best of our knowledge, this is the first work modeling mixtures of block copolymers with large differences in molecular weight. The coassembly mechanism localizes the AC molecules at the interface of A and B domains and induces the swelling of the B-rich domains. The coil size of the large molecular weight block copolymer depends only on the concentration of the short block copolymer (AC or AB), regardless of the B–C interactions. However, the B–C interactions control the morphological transitions that occur in these blends.

Thermodynamics of coil-hyperbranched poly(styrene-b-acrylated epoxidized soybean oil) block copolymers

Science.gov (United States)

Lin, Fang-Yi; Hohmann, Austin; Hernández, Nacú; Cochran, Eric

Here we present the phase behavior of a new type of coil-hyperbranched diblock copolymer: poly(styrene- b-acrylated epoxidized soybean oil), or PS-PAESO. PS-PAESO is an example of a biorenewable thermoplastic elastomer (bio-TPE). To date, we have shown that bio-TPEs can be economical commercial substitutes for their petrochemically derived analogues--such as poly(styrene- b-butadiene- b-styrene) (SBS)--in a range of applications including pressure sensitive adhesives and bitumen modification. From a polymer physics perspective, PS-PAESO is an interesting material in that it couples a linear coil-like block with a highly branched block. Thus in contrast to the past five decades of studies on linear AB diblock copolymers, coil-hyperbranched block copolymers are relatively unknown to the community and can be expected to deviate substantially from the standard ``universal'' phase behavior in the AB systems. To explore these new materials, we have constructed a library of PS-PAESO materials spanning a range of molecular weight and composition values. The phase transition behavior and the morphology information will be interpreted by isochronal temperature scanning in dynamic shear rheology, small angle X-ray scattering and the corresponding transmission electron microscopy.

Synthesis of an amphiphilic dendrimer-like block copolymer and its application on drug delivery

KAUST Repository

Wang, Shuaipeng; Song, Xiaowan; Feng, Xiaoshuang; Chen, Peng; Qian, Jiasheng; Xia, Ru; Miao, Jibin

2014-01-01

. The application on drug delivery of dendrimer-like diblock copolymer PEEGE-G2-b-PEO(OH)12 using DOX as a model drug was also studied. The drug loading content and encapsulation efficiency were found at 13.07% and 45.75%, respectively. In vitro release experiment

Lamellar Microdomains of Block-Copolymer-Based Ionic Supramolecules Exhibiting a Hierarchical Self-Assembly

DEFF Research Database (Denmark)

Ayoubi, Mehran Asad; Almdal, Kristoffer; Zhu, Kaizheng

2014-01-01

(Cn; n = 8, 12, and 16) trimethylammonium counterions (i.e., side chains) at various ion (pair) fractions X [i.e., counterion/side-chain grafting density; X = number of alkyl counterions (i.e., side chains) per acidic group of the parent PMAA block] these L-b-AC ionic supramolecules exhibit...... a spherical-in-lamellar hierarchical self-assembly. For these systems, (1) the effective Flory-Huggins interaction parameter between L- and AC-blocks chi'(Cn/x) was extracted, and (2) analysis of the lamellar microdomains showed that when there is an increase in X, alkyl counterion (i.e., side chain) length l......Based on a parent diblock copolymer of poly(styrene)-b-poly(methacrylic acid), PS-b-PMAA, linear-b-amphiphilic comb (L-b-AC) ionic supramolecules [Soft Matter 2013, 9, 1540-1555] are synthesized in which the poly(methacrylate) backbone of the ionic supramolecular AC-block is neutralized by alkyl...

Photodegradable neutral-cationic brush block copolymers for nonviral gene delivery.

Science.gov (United States)

Hu, Xianglong; Li, Yang; Liu, Tao; Zhang, Guoying; Liu, Shiyong

2014-08-01

We report on the fabrication of a photodegradable gene-delivery vector based on PEO-b-P(GMA-g-PDMAEMA) neutral-cationic brush block copolymers that possess cationic poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) brushes for DNA compaction, poly(ethylene oxide) (PEO) as a hydrophilic block, and poly(glycidyl methacrylate) (PGMA) as the backbone. The PEO-b-P(GMA-g-PDMAEMA) copolymers were synthesized through the combination of reversible addition-fragmentation transfer (RAFT) polymerization and postmodification. A photocleavable PEO-based macroRAFT agent was first synthesized; next, the PEO-b-PGMA block copolymer was prepared by RAFT polymerization of GMA; this was followed by a click reaction to introduce the RAFT initiators on the side chains of the PGMA block; then, RAFT polymerization of DMAEMA afforded the PEO-b-P(GMA-g-PDMAEMA) copolymer. The obtained neutral-cationic brush block copolymer could effectively complex plasmid DNA (pDNA) into nanoparticles at an N/P ratio (i.e., the number of nitrogen residues per DNA phosphate) of 4. Upon UV irradiation, pDNA could be released owing to cleavage of the pDNA-binding cationic PDMAEMA side chains as well as the nitrobenzyl ester linkages at the diblock junction point. In addition, in vitro gene transfection results demonstrated that the polyplexes could be effectively internalized by cells with good transfection efficiency, and the UV irradiation protocol could considerably enhance the efficiency of gene transfection. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Resonant soft x-ray GISAXS on block copolymer films

Science.gov (United States)

Wang, Cheng; Araki, T.; Watts, B.; Ade, H.; Hexemer, A.; Park, S.; Russell, T. P.; Schlotter, W. F.; Stein, G. E.; Tang, C.; Kramer, E. J.

2008-03-01

Ordered block copolymer thin films may have important applications in modern device fabrication. Current characterization methods such as conventional GISAXS have fixed electron density contrast that can be overwhelmed by surface scattering. However, soft x-rays have longer wavelength, energy dependent contrast and tunable penetration, making resonant GISAXS a very promising tool for probing nanostructured polymer thin films. Our preliminary investigation was performed using PS-b-P2VP block copolymer films on beam-line 5-2 SSRL, and beam-line 6.3.2 at ALS, LBNL. The contrast/sensitivity of the scattering pattern varies significantly with photon energy close to the C K-edge (˜290 eV). Also, higher order peaks are readily observed, indicating hexagonal packing structure in the sample. Comparing to the hard x-ray GISAXS data of the same system, it is clear that resonant GISAXS has richer data and better resolution. Beyond the results on the A-B diblock copolymers, results on ABC block copolymers are especially interesting.

SANS and SAXS study of block copolymer/homopolymer mixtures

International Nuclear Information System (INIS)

Hasegawa, Hirokazu; Tanaka, Hideaki; Hashimoto, Takeji; Han, C.C.

1991-01-01

The lateral and vertical components of the radius of gyration for a single block copolymer chain and those of a single homopolymer 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). The homopolymers whose molecular weights are much smaller than that of the corresponding chains of the block copolymers were used so that the homopolymers were uniformly solubilized in the corresponding microdomains. The SANS result suggests that the homopolymer chains in the microdomain space as well as the block copolymer chains 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. On 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. (orig.)

Photoconductivity enhancement and charge transport properties in ruthenium-containing block copolymer/carbon nanotube hybrids.

Science.gov (United States)

Lo, Kin Cheung; Hau, King In; Chan, Wai Kin

2018-04-05

Functional polymer/carbon nanotube (CNT) hybrid materials can serve as a good model for light harvesting systems based on CNTs. This paper presents the synthesis of block copolymer/CNT hybrids and the characterization of their photocurrent responses by both experimental and computational approaches. A series of functional diblock copolymers was synthesized by reversible addition-fragmentation chain transfer polymerizations for the dispersion and functionalization of CNTs. The block copolymers contain photosensitizing ruthenium complexes and modified pyrene-based anchoring units. The photocurrent responses of the polymer/CNT hybrids were measured by photoconductive atomic force microscopy (PCAFM), from which the experimental data were analyzed by vigorous statistical models. The difference in photocurrent response among different hybrids was correlated to the conformations of the hybrids, which were elucidated by molecular dynamics simulations, and the electronic properties of polymers. The photoresponse of the block copolymer/CNT hybrids can be enhanced by introducing an electron-accepting block between the photosensitizing block and the CNT. We have demonstrated that the application of a rigorous statistical methodology can unravel the charge transport properties of these hybrid materials and provide general guidelines for the design of molecular light harvesting systems.

[Complex formation between alpha-chymotrypsin and block copolymers based on ethylene and propylene oxide, induced by high pressure].

Science.gov (United States)

Topchieva, I N; Sorokina, E M; Kurganov, B I; Zhulin, V M; Makarova, Z G

1996-06-01

A new method of formation of non-covalent adducts based on an amphiphilic diblock copolymer of ethylene and propylene oxides with molecular mass of 2 kDa and alpha-chymotrypsin (ChT) under high pressure, has been developed. The composition of the complexes corresponds to seven polymer molecules per one ChT molecule in the pressure range of 1.1 to 400 MPa. The complexes fully retain the catalytic activity. Kinetic constants (Km and kcat) for enzymatic hydrolysis of N-benzoyl-L-tyrosine ethyl ester catalyzed by the complexes are identical with the corresponding values for native ChT. Analysis of kinetics of thermal inactivation of the complexes revealed that the constant of the rate of the slow inactivation step is markedly lower than for ChT.

"Non-equilibrium" block copolymer micelles with glassy cores: a predictive approach based on theory of equilibrium micelles.

Science.gov (United States)

Nagarajan, Ramanathan

2015-07-01

Micelles generated in water from most amphiphilic block copolymers are widely recognized to be non-equilibrium structures. Typically, the micelles are prepared by a kinetic process, first allowing molecular scale dissolution of the block copolymer in a common solvent that likes both the blocks and then gradually replacing the common solvent by water to promote the hydrophobic blocks to aggregate and create the micelles. The non-equilibrium nature of the micelle originates from the fact that dynamic exchange between the block copolymer molecules in the micelle and the singly dispersed block copolymer molecules in water is suppressed, because of the glassy nature of the core forming polymer block and/or its very large hydrophobicity. Although most amphiphilic block copolymers generate such non-equilibrium micelles, no theoretical approach to a priori predict the micelle characteristics currently exists. In this work, we propose a predictive approach for non-equilibrium micelles with glassy cores by applying the equilibrium theory of micelles in two steps. In the first, we calculate the properties of micelles formed in the mixed solvent while true equilibrium prevails, until the micelle core becomes glassy. In the second step, we freeze the micelle aggregation number at this glassy state and calculate the corona dimension from the equilibrium theory of micelles. The condition when the micelle core becomes glassy is independently determined from a statistical thermodynamic treatment of diluent effect on polymer glass transition temperature. The predictions based on this "non-equilibrium" model compare reasonably well with experimental data for polystyrene-polyethylene oxide diblock copolymer, which is the most extensively studied system in the literature. In contrast, the application of the equilibrium model to describe such a system significantly overpredicts the micelle core and corona dimensions and the aggregation number. The non-equilibrium model suggests ways to

Thermoresponsive behavior of block copolymers of PEO and PNIPAm with different architecture in aqueous solutions: a study by NMR, FTIR, DSC and quantum-chemical calculations

Czech Academy of Sciences Publication Activity Database

Spěváček, Jiří; Konefal, Rafal; Dybal, Jiří; Čadová, Eva; Kovářová, Jana

2017-01-01

Roč. 94, September (2017), s. 471-483 ISSN 0014-3057 R&D Projects: GA ČR(CZ) GA15-13853S Institutional support: RVO:61389013 Keywords : thermoresponsive polymer * diblock copolymer PEO-b-PNIPAm * y-shape triblock copolymer PEO-b-(PNIPAm)2 Subject RIV: CD - Macromolecular Chemistry OBOR OECD: Polymer science Impact factor: 3.531, year: 2016

Shear-induced Long Range Order in Diblock Copolymer Thin Films

Science.gov (United States)

Ding, Xuan; Russell, Thomas

2007-03-01

Shear is a well-established means of aligning block copolymer micro-domains in bulk; cylinder-forming block copolymers respond by orienting cylinder axes parallel to the flow direction, and macroscopic specimens with near-single-crystal texture can be obtained. A stepper motor is a brushless, synchronous electric motor that can divide a full rotation into a large number of steps. With the combination of a stepper motor and several gear boxes in our experiment, we can control the rotating resolution to be as small as 1 x10-4 degree/step. Also, with the help of a customized computer program we can control the motor speed in a very systematical way. By changing parameters such as the weight (or the uniform pressure) and the lateral force we can carry on experiment to examine the effect of lateral shear on different polymer systems such as PS-b-PEO (large χ) and PS-b-P2VP (small χ).

Spontaneous Evolution of Nanostructure in Composite Films Consisting of Mixtures of Two Different Block Copolymer Micelles

Science.gov (United States)

Kim, Sehee; Char, Kookheon; Sohn, Byeong-Hyeok

2010-03-01

Diblock copolymers consisting of two immiscible polymer blocks covalently bonded together form various self-assembled nanostructures such as spheres, cylinders, and lamellae in bulk phase. In a selective solvent, however, they assemble into micelles with soluble corona brushes and immiscible cores. Both polystyrene-poly(4-vinylpyridine) (PS-b-P4VP) and polystyrene-poly(2-vinylpyridine) (PS-b-P2VP) diblock copolymers form micelles with PS coronas and P4VP or P2VP cores in a PS selective solvent (toluene). By varying the mixture ratio between PS-b-P4VP and PS-b-P2VP, composite films based on the micellar mixtures of PS-b-P4VP and PS-b-P2VP were obtained by spin-coating, followed by the solvent annealing with tetrahydrofuran (THF) vapor. Since THF is a solvent for both PS and P2VP blocks and, at the same time, a non-solvent for the P4VP block, PS-P2VP micelles transformed to lamellar multilayers while PS-P4VP micelles remained intact during the THF annealing. The spontaneous evolution of nanostructure in composite films consisting of lamellae layers with BCP micelles were investigated in detail by cross-sectional TEM and AFM.

Comparison of the pharmacological and biological properties of HPMA copolymer-pirarubicin conjugates: A single-chain copolymer conjugate and its biodegradable tandem-diblock copolymer conjugate

Czech Academy of Sciences Publication Activity Database

Etrych, Tomáš; Tsukigawa, K.; Nakamura, H.; Chytil, Petr; Fang, J.; Ulbrich, Karel; Otagiri, M.; Maeda, H.

2017-01-01

Roč. 106, 30 August (2017), s. 10-19 ISSN 0928-0987 R&D Projects: GA ČR(CZ) GA15-02986S; GA MŠk(CZ) LQ1604; GA MŠk(CZ) ED1.1.00/02.0109 Grant - others:AV ČR,Japan Society for the Promotion of Science(CZ) JSPS-16-05 Program:Bilaterální spolupráce Institutional support: RVO:61389013 Keywords : pirarubicin * PHPMA conjugate * tandem-diblock PHPMA conjugate Subject RIV: FR - Pharmacology ; Medidal Chemistry OBOR OECD: Pharmacology and pharmacy Impact factor: 3.756, year: 2016

Design of block copolymer membranes using segregation strength trend lines

KAUST Repository

Sutisna, Burhannudin

2016-05-18

Block copolymer self-assembly and non-solvent induced phase separation are now being combined to fabricate membranes with narrow pore size distribution and high porosity. The method has the potential to be used with a broad range of tailor-made block copolymers to control functionality and selectivity for specific separations. However, the extension of this process to any new copolymer is challenging and time consuming, due to the complex interplay of influencing parameters, such as solvent composition, polymer molecular weights, casting solution concentration, and evaporation time. We propose here an effective method for designing new block copolymer membranes. The method consists of predetermining a trend line for the preparation of isoporous membranes, obtained by computing solvent properties, interactions and copolymer block sizes for a set of successful systems and using it as a guide to select the preparation conditions for new membranes. We applied the method to membranes based on poly(styrene-b-ethylene oxide) diblocks and extended it to newly synthesized poly(styrene-b-2-vinyl pyridine-b-ethylene oxide) (PS-b-P2VP-b-PEO) terpolymers. The trend line method can be generally applied to other new systems and is expected to dramatically shorten the path of isoporous membrane manufacture. The PS-b-P2VP-b-PEO membrane formation was investigated by in situ Grazing Incident Small Angle X-ray Scattering (GISAXS), which revealed a hexagonal micelle order with domain spacing clearly correlated to the membrane interpore distances.

Ion Correlation Effects in Salt-Doped Block Copolymers

Science.gov (United States)

Brown, Jonathan R.; Seo, Youngmi; Hall, Lisa M.

2018-03-01

We apply classical density functional theory to study how salt changes the microphase morphology of diblock copolymers. Polymers are freely jointed and one monomer type favorably interacts with ions, to account for the selective solvation that arises from different dielectric constants of the microphases. By including correlations from liquid state theory of an unbound reference fluid, the theory can treat chain behavior, microphase separation, ion correlations, and preferential solvation, at the same coarse-grained level. We show good agreement with molecular dynamics simulations.

Structure-directing star-shaped block copolymers: supramolecular vesicles for the delivery of anticancer drugs.

Science.gov (United States)

Yang, Chuan; Liu, Shao Qiong; Venkataraman, Shrinivas; Gao, Shu Jun; Ke, Xiyu; Chia, Xin Tian; Hedrick, James L; Yang, Yi Yan

2015-06-28

Amphiphilic polycarbonate/PEG copolymer with a star-like architecture was designed to facilitate a unique supramolecular transformation of micelles to vesicles in aqueous solution for the efficient delivery of anticancer drugs. The star-shaped amphipilic block copolymer was synthesized by initiating the ring-opening polymerization of trimethylene carbonate (TMC) from methyl cholate through a combination of metal-free organo-catalytic living ring-opening polymerization and post-polymerization chain-end derivatization strategies. Subsequently, the self-assembly of the star-like polymer in aqueous solution into nanosized vesicles for anti-cancer drug delivery was studied. DOX was physically encapsulated into vesicles by dialysis and drug loading level was significant (22.5% in weight) for DOX. Importantly, DOX-loaded nanoparticles self-assembled from the star-like copolymer exhibited greater kinetic stability and higher DOX loading capacity than micelles prepared from cholesterol-initiated diblock analogue. The advantageous disparity is believed to be due to the transformation of micelles (diblock copolymer) to vesicles (star-like block copolymer) that possess greater core space for drug loading as well as the ability of such supramolecular structures to encapsulate DOX. DOX-loaded vesicles effectively inhibited the proliferation of 4T1, MDA-MB-231 and BT-474 cells, with IC50 values of 10, 1.5 and 1.0mg/L, respectively. DOX-loaded vesicles injected into 4T1 tumor-bearing mice exhibited enhanced accumulation in tumor tissue due to the enhanced permeation and retention (EPR) effect. Importantly, DOX-loaded vesicles demonstrated greater tumor growth inhibition than free DOX without causing significant body weight loss or cardiotoxicity. The unique ability of the star-like copolymer emanating from the methyl cholate core provided the requisite modification in the block copolymer interfacial curvature to generate vesicles of high loading capacity for DOX with significant

Formation of nanoscale networks: selectively swelling amphiphilic block copolymers with CO2-expanded liquids.

Science.gov (United States)

Gong, Jianliang; Zhang, Aijuan; Bai, Hua; Zhang, Qingkun; Du, Can; Li, Lei; Hong, Yanzhen; Li, Jun

2013-02-07

Polymeric films with nanoscale networks were prepared by selectively swelling an amphiphilic diblock copolymer, polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP), with the CO(2)-expanded liquid (CXL), CO(2)-methanol. The phase behavior of the CO(2)-methanol system was investigated by both theoretical calculation and experiments, revealing that methanol can be expanded by CO(2), forming homogeneous CXL under the experimental conditions. When treated with the CO(2)-methanol system, the spin cast compact PS-b-P4VP film was transformed into a network with interconnected pores, in a pressure range of 12-20 MPa and a temperature range of 45-60 °C. The formation mechanism of the network, involving plasticization of PS and selective swelling of P4VP, was proposed. Because the diblock copolymer diffusion process is controlled by the activated hopping of individual block copolymer chains with the thermodynamic barrier for moving PVP segments from one to another, the formation of the network structures is achieved in a short time scale and shows "thermodynamically restricted" character. Furthermore, the resulting polymer networks were employed as templates, for the preparation of polypyrrole networks, by an electrochemical polymerization process. The prepared porous polypyrrole film was used to fabricate a chemoresistor-type gas sensor which showed high sensitivity towards ammonia.

Non-Classical Order in Sphere Forming ABAC Tetrablock Copolymers

Science.gov (United States)

Zhang, Jingwen; Sides, Scott; Bates, Frank

2013-03-01

AB diblock and ABC triblock copolymers have been studied thoroughly. ABAC tetrablock copolymers, representing the simplest variation from ABC triblock by breaking the molecular symmetry via inserting some of the A block in between B and C blocks, have been studied systematically in this research. The model system is poly(styrene-b-isoprene-b-styrene-b-ethylene oxide) (SISO) tetrablock terpolymers and the resulting morphologies were characterized by nuclear magnetic resonance, gel permeation chromatography, small-angle X-ray scattering, transmission electron microscopy, differential scanning calorimetry and dynamic mechanical spectroscopy. Two novel phases are first discovered in a single component block copolymers: hexagonally ordered spherical phase and tentatively identified dodecagonal quasicrystalline (QC) phase. In particular, the discovery of QC phase bridges the world of soft matters to that of metals. These unusual sets of morphologies will be discussed in the context of segregation under the constraints associated with the tetrablock molecular architecture. Theoretical calculations based on the assumption of Gaussian chain statistics provide valuable insights into the molecular configurations associated with these morphologies. the U.S. Department of Energy, Basic Energy Sciences, Division of Materials Science and Engineering, under contract number DEAC05-00OR22725 with UT-Battelle LLC at Oak Ridge National Lab.

Well-defined Polymethylene-Based Co/Terpolymers by Combining Anthracene/Maleimide Diels-Alder Reaction with Polyhomologation

KAUST Repository

Hadjichristidis, Nikolaos; Alkayal, Nazeeha

2015-01-01

A novel strategy towards well-defined polymethylene-based co/terpolymers, by combining anthracene/maleimide Diels-Alder reaction with polyhomologation, is presented. For the synthesis of diblock copolymers the following approach was applied: a

Polymer brushes on nanoparticles: their positioning in and influence on block copolymer morphology.

Science.gov (United States)

Kim, Bumjoon

2007-03-01

Polymers brushes grafted to the nanoparticle surface enable the precise positioning of particles within a block copolymer matrix by determining the compatibility of nanoparticles within a polymeric matrix and modifying the interfacial properties between polymers and inorganic nanoparticle. Short thiol terminated polystyrene (PS-SH), poly(2-vinylpyridine) (P2VP-SH) and PS-r-P2VP with the molecular weight (Mn) of 3 kg/mol were used to control the location of Au nanoparticles over PS-b-P2VP diblock copolymer template. We will discuss further the approach of varying the areal chain density (σ) of PS-SH brushes on the PS coated particles, which utilizes the preferential wetting of one block of a copolymer (P2VP) on the Au substrate. Such favorable interaction provides the strong binding of Au particles to the PS/P2VP interface as σ of PS chains on the Au particle decreases. We find that at σ above a certain value, the nanoparticles are segregated to the center of the PS domains while below this value they are segregated to the interface. The transition σ for PS-SH chains (Mn = 3.4 kg/mol) is 1.3 chains/nm^2 but unexpectedly scales as Mn-0.55 as Mn is varied from 1.5 to 13 kg/mol. In addition, we will discuss changes in block copolymer morphology that occur as the nanoparticle volume fraction (φ) is increased for nanoparticles that segregate to the domain center as well as those that segregate to the interface, the latter behaving as nanoparticle surfactants. Small φ of such surfactants added to lamellar diblock copolymers lead initially to a decrease in lamellar thickness, a consequence of decreasing interfacial tension, up to a critical value of φ beyond which the block copolymer adopts a bicontinuous morphology. I thank my collaborators G. H. Fredrickson, J. Bang, C. J. Hawker, and E. J. Kramer as well as funding by the MRL as UCSB from the NSF-MRSEC-Program Award DMR05-20418.

Combinatorial Study of Surface Pattern Formation in Thin Block Copolymer Films

International Nuclear Information System (INIS)

Smith, Archie P.; Douglas, Jack F.; Meredith, J. Carson; Amis, Eric J.; Karim, Alamgir

2001-01-01

Surface pattern formation in diblock copolymer films is investigated as a function of film thickness h and molecular mass M . Smooth films are observed for certain h ranges centered about multiples of the lamellar thickness L 0 , and we attribute this effect to an increase in the surface chain density with h in the outer brushlike copolymer layer. We also observe apparently stable labyrinthine surface patterns for other h ranges, and the average size of these patterns is found to scale as λ∼L -2.5 0 . Hole and island patterns occur for h ranges between those of the labyrinthine patterns and the smooth regions, and their size similarly decreases with L 0 and M

Thermally Stable Gold Nanoparticles with a Crosslinked Diblock Copolymer Shell

Science.gov (United States)

Jang, Se Gyu; Khan, Anzar; Hawker, Craig J.; Kramer, Edward J.

2010-03-01

The use of polymer-coated Au nanoparticles prepared using oligomeric- or polymeric-ligands tethered by Au-S bonds for incorporation into block copolymer templates under thermal processing has been limited due to dissociation of the Au-S bond at T > 100^oC where compromises their colloidal stability. We report a simple route to prepare sub-5nm gold nanoparticles with a thermally stable polymeric shell. An end-functional thiol ligand consisting of poly(styrene-b-1,2&3,4-isoprene-SH) is synthesized by anionic polymerization. After a standard thiol ligand synthesis of Au nanoparticles, the inner PI block is cross-linked through reaction with 1,1,3,3-tetramethyldisiloxane. Gold nanoparticles with the cross-linked shell are stable in organic solvents at 160^oC as well as in block copolymer films of PS-b-P2VP annealed in vacuum at 170^oC for several days. These nanoparticles can be designed to strongly segregate to the PS-P2VP interface resulting in very large Au nanoparticle volume fractions φp without macrophase separation as well as transitions between lamellar and bicontinuous morphologies as φp increases.

Sulfonated amphiphilic block copolymers : synthesis, self-assembly in water, and application as stabilizer in emulsion polymerization

Science.gov (United States)

Jiguang Zhang; Matthew R. Dubay; Carl J. Houtman; Steven J. Severtson

2009-01-01

Described is the synthesis of diblock copolymers generated via sequential atom transfer radical polymerization (ATRP) of poly(n-butyl acrylate) (PnBA) followed by chain augmentation with either sulfonated poly(2-hydroxyethyl methacrylate) (PHEMA) or poly(2-hydroxyethyl acrylate) (PHEA) blocks. ATRP of PHEMA or PHEA from PnBA macroinitiator was conducted in acetone/...

Design, Synthesis and Characterization of Polyethylene-Based Macromolecular Architectures by Combining Polyhomologation with Powerful Linking Chemistry

KAUST Repository

Alkayal, Nazeeha

2016-01-01

synthetic route towards well-defined polymethylene-based co/terpolymers, by combining the anthracene/maleimide Diels–Alder reaction with polyhomologation, is presented. For the synthesis of diblock copolymers the following approach was applied: (a) synthesis

Aqueous-Based Fabrication of Low-VOC Nanostructured Block Copolymer Films as Potential Marine Antifouling Coatings.

Science.gov (United States)

Kim, Kris S; Gunari, Nikhil; MacNeil, Drew; Finlay, John; Callow, Maureen; Callow, James; Walker, Gilbert C

2016-08-10

The ability to fabricate nanostructured films by exploiting the phenomenon of microphase separation has made block copolymers an invaluable tool for a wide array of coating applications. Standard approaches to engineering nanodomains commonly involve the application of organic solvents, either through dissolution or annealing protocols, resulting in the release of volatile organic compounds (VOCs). In this paper, an aqueous-based method of fabricating low-VOC nanostructured block copolymer films is presented. The reported procedure allows for the phase transfer of water insoluble triblock copolymer, poly(styrene-block-2 vinylpyridine-block-ethylene oxide) (PS-b-P2VP-b-PEO), from a water immiscible phase to an aqueous environment with the assistance of a diblock copolymeric phase transfer agent, poly(styrene-block-ethylene oxide) (PS-b-PEO). Phase transfer into the aqueous phase results in self-assembly of PS-b-P2VP-b-PEO into core-shell-corona micelles, which are characterized by dynamic light scattering techniques. The films that result from coating the micellar solution onto Si/SiO2 surfaces exhibit nanoscale features that disrupt the ability of a model foulant, a zoospore of Ulva linza, to settle. The multilayered architecture consists of a pH-responsive P2VP-"shell" which can be stimulated to control the size of these features. The ability of these nanostructured thin films to resist protein adsorption and serve as potential marine antifouling coatings is supported through atomic force microscopy (AFM) and analysis of the settlement of Ulva linza zoospore. Field trials of the surfaces in a natural environment show the inhibition of macrofoulants for 1 month.

Self-Assembly of Nanoparticle Mixtures in Diblock Copolymers: Multiscale Molecular Modeling

Czech Academy of Sciences Publication Activity Database

Malý, Marek; Posocco, P.; Pricl, S.; Fermeglia, M.

2008-01-01

Roč. 47, č. 15 (2008), s. 5023-5038 ISSN 0888-5885 Grant - others:NMP3(XE) CT/2006/033304 Institutional research plan: CEZ:AV0Z40720504 Keywords : copolymers * nanoparticles * dissipative particle dynamics Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.895, year: 2008

The Self-Assembly of Copolymers with One Hydrophobic and One Polyelectrolyte Block in Aqueous Media: A Dissipative Particle Dynamics Study.

Czech Academy of Sciences Publication Activity Database

Lísal, Martin; Limpouchová, Z.; Procházka, K.

2016-01-01

Roč. 18, č. 24 (2016), s. 16127-16136 ISSN 1463-9076 R&D Projects: GA ČR(CZ) GA13-02938S Institutional support: RVO:67985858 Keywords : amphiphilic diblock copolymers * hybrid olymeric micelles * simulations Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.123, year: 2016

Flory-Huggins parameter χ, from binary mixtures of Lennard-Jones particles to block copolymer melts

International Nuclear Information System (INIS)

Chremos, Alexandros; Nikoubashman, Arash; Panagiotopoulos, Athanassios Z.

2014-01-01

In this contribution, we develop a coarse-graining methodology for mapping specific block copolymer systems to bead-spring particle-based models. We map the constituent Kuhn segments to Lennard-Jones particles, and establish a semi-empirical correlation between the experimentally determined Flory-Huggins parameter χ and the interaction of the model potential. For these purposes, we have performed an extensive set of isobaric–isothermal Monte Carlo simulations of binary mixtures of Lennard-Jones particles with the same size but with asymmetric energetic parameters. The phase behavior of these monomeric mixtures is then extended to chains with finite sizes through theoretical considerations. Such a top-down coarse-graining approach is important from a computational point of view, since many characteristic features of block copolymer systems are on time and length scales which are still inaccessible through fully atomistic simulations. We demonstrate the applicability of our method for generating parameters by reproducing the morphology diagram of a specific diblock copolymer, namely, poly(styrene-b-methyl methacrylate), which has been extensively studied in experiments

Flory-Huggins parameter χ, from binary mixtures of Lennard-Jones particles to block copolymer melts

Energy Technology Data Exchange (ETDEWEB)

Chremos, Alexandros, E-mail: achremos@imperial.ac.uk [Department of Chemical Engineering, Centre for Process Systems Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ (United Kingdom); Nikoubashman, Arash, E-mail: arashn@princeton.edu; Panagiotopoulos, Athanassios Z. [Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544 (United States)

2014-02-07

In this contribution, we develop a coarse-graining methodology for mapping specific block copolymer systems to bead-spring particle-based models. We map the constituent Kuhn segments to Lennard-Jones particles, and establish a semi-empirical correlation between the experimentally determined Flory-Huggins parameter χ and the interaction of the model potential. For these purposes, we have performed an extensive set of isobaric–isothermal Monte Carlo simulations of binary mixtures of Lennard-Jones particles with the same size but with asymmetric energetic parameters. The phase behavior of these monomeric mixtures is then extended to chains with finite sizes through theoretical considerations. Such a top-down coarse-graining approach is important from a computational point of view, since many characteristic features of block copolymer systems are on time and length scales which are still inaccessible through fully atomistic simulations. We demonstrate the applicability of our method for generating parameters by reproducing the morphology diagram of a specific diblock copolymer, namely, poly(styrene-b-methyl methacrylate), which has been extensively studied in experiments.

Superhydrophobic surfaces of electrospun block copolymer fibers with low content of fluorosilicones

International Nuclear Information System (INIS)

Tian, Xiaoping; Yi, Lingmin; Meng, Xiaomei; Xu, Kai; Jiang, Tengteng; Lai, Dongzhi

2014-01-01

A series of well-defined poly[methyl(3,3,3-trifluoropropyl)siloxane]-b-poly(methyl methacrylate) (PMTFPS-b-PMMA) diblock copolymers with low content of PMTFPS were synthesized by atom transfer radical polymerization (ATRP) of MMA from PMTFPS macroinitiators (PMTFPS-Br). The polymerization result reveals that the ATRP of MMA from PMTFPS-Br is fist-order with respect to MMA under different polymerization conditions, demonstrating a typical characteristic of living polymerization. The results also show that PMTFPS-b-PMMA diblock copolymers can exhibit a total surface tension (γ S ) varying from 25.28 mN/m to 21.87 mN/m with the change of PMTFPS contents from 2.6 wt% to 22.2 wt%. Moreover, the water contact angles of electrospun PMTFPS-b-PMMA surfaces could be higher than 150° with water roll-off angles less than 10°, which denotes a superhydrophobic property. However, the electronspinning conditions, especially the concentration of spinning solution, would have important effect on the surface morphology, surface composition and wetting behavior of electrospun films. It was found that bead-free fibers with uniform diameter as well as good superhydrophobic property could be prepared on condition that the polymer concentration of spinning solution was as high as 32 wt% in the mixed solvent of DMF and THF.

Synthesis and conformational characterization of functional di-block copolymer brushes for microarray technology

Energy Technology Data Exchange (ETDEWEB)

Di Carlo, Gabriele; Damin, Francesco [Institute of Chemistry of Molecular Recognition, National Research Council of Italy, Via M. Bianco 9, 20131 Milano (Italy); Armelao, Lidia [ISTM-CNR and INSTM, Department of Chemistry, University of Padova, Via F. Marzolo 1, 35131 Padova (Italy); Maccato, Chiara [Department of Chemistry and INSTM, University of Padova, Via F. Marzolo 1, 35131 Padova (Italy); Unlu, Selim [Department of Electrical and Computer Engineering, Boston University, St. Mary Street 8, Boston, MA 02215 (United States); Department of Biomedical Engineering, Boston University, St. Mary Street 8, Boston, MA 02215 (United States); Spuhler, Philipp S. [Department of Biomedical Engineering, Boston University, St. Mary Street 8, Boston, MA 02215 (United States); Chiari, Marcella, E-mail: marcella.chiari@icrm.cnr.it [Institute of Chemistry of Molecular Recognition, National Research Council of Italy, Via M. Bianco 9, 20131 Milano (Italy)

2012-02-01

Surface initiated polymerization (SIP) coupled with reversible addition-fragmentation chain transfer polymerization (RAFT) was used to functionalize microarray glass slides with block polymer brushes. N,N-dimethylacrylamide (DMA) and N-acryloyloxysuccinimide (NAS) (graft-poly[DMA-b-(DMA-co-NAS)]) brushes, with di-block architecture, were prepared from a novel RAFT chain transfer agent bearing a silanating moiety (RAFT silane) directly anchored onto the glass surfaces. Conformational characterization of the coatings was performed by Self Spectral Interference Fluorescence Microscopy (SSFM), an innovative technique that describes the location of a fluorescent DNA molecule relative to a surface with sub-nanometer accuracy. X-ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscopy (SEM) were used to characterize the coatings composition and morphology.

Synthesis and conformational characterization of functional di-block copolymer brushes for microarray technology

International Nuclear Information System (INIS)

Di Carlo, Gabriele; Damin, Francesco; Armelao, Lidia; Maccato, Chiara; Unlu, Selim; Spuhler, Philipp S.; Chiari, Marcella

2012-01-01

Surface initiated polymerization (SIP) coupled with reversible addition-fragmentation chain transfer polymerization (RAFT) was used to functionalize microarray glass slides with block polymer brushes. N,N-dimethylacrylamide (DMA) and N-acryloyloxysuccinimide (NAS) (graft-poly[DMA-b-(DMA-co-NAS)]) brushes, with di-block architecture, were prepared from a novel RAFT chain transfer agent bearing a silanating moiety (RAFT silane) directly anchored onto the glass surfaces. Conformational characterization of the coatings was performed by Self Spectral Interference Fluorescence Microscopy (SSFM), an innovative technique that describes the location of a fluorescent DNA molecule relative to a surface with sub-nanometer accuracy. X-ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscopy (SEM) were used to characterize the coatings composition and morphology.

Thermoresponsive self-assembly of nanostructures from a collagen-like peptide-containing diblock copolymer.

Science.gov (United States)

Luo, Tianzhi; He, Lirong; Theato, Patrick; Kiick, Kristi L

2015-01-01

Temperature-triggered formation of nanostructures with distinct biological activity offers opportunities in selective modification of matrices and in drug delivery. Toward these ends, diblock polymers comprising poly(diethylene glycol methyl ether methacrylate) (PDEGMEMA) conjugated to a triple helix-forming collagen-like peptide were produced. Triggered by the collapse of the thermoresponsive domain above its LCST, the conjugate undergoes a reversible transition in aqueous solution to form well-defined nanovesicles with diameters of approximately 100 nm, with a transition temperature of 37 °C. The incorporation of CLP domains in these nanostructures may offer opportunities for the selective targeting of collagen-containing matrices. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The effect of film thickness and molecular structure on order and disorder in thin films of compositionally asymmetric block copolymers

Science.gov (United States)

Mishra, Vindhya

Directed self-assembly of thin film block copolymers offer a high throughput-low cost route to produce next generation lithographic devices, if one can bring the defect densities in the self assembled patterns below tolerance limits. However, the ability to control the nanoscale structure or morphology in thin film block copolymers presents challenges due to confinement effects on equilibrium behavior. Using structure characterization techniques such as grazing incidence small angle X-ray scattering (GISAXS), transmission electron and atomic force microscopy as well as self-consistent field theory, we have investigated how film thickness, annealing temperature and block copolymer structure affects the equilibrium behavior of asymmetric block copolymer films. Our studies have revealed the complicated dependence of order-disorder transitions, order-order transitions and symmetry transitions on film thickness. We found that the thickness dependent transition in the packing symmetry of spherical morphology diblock copolymers can be suppressed by blending with a small amount of majority block homopolymer, which allowed us to resolve the driving force behind this transition. Defect densities in, and the order-disorder transition temperature of, thin films of graphoepitaxially aligned diblock copolymer cylinders showed surprising sensitivity to the microdomain spacing. Methods to mitigate defect formation in thin films have been identified. The challenge of quantification of structural order in these systems was overcome using GISAXS, which allowed us to study the phenomena of disordering in two and three dimensions. Through studies on block copolymers which exhibit an order-order transition in bulk, we found that that subtle differences in the packing frustration of the spherical and cylindrical phases as well as the higher configurational entropy of free chain ends at the surface can drive the equilibrium configuration in thin films away from the stable bulk structure

Rapid transitions between defect configurations in a block copolymer melt.

Science.gov (United States)

Tsarkova, Larisa; Knoll, Armin; Magerle, Robert

2006-07-01

With in situ scanning force microscopy, we image the ordering of cylindrical microdomains in a thin film of a diblock copolymer melt. Tracking the evolution of individual defects reveals elementary steps of defect motion via interfacial undulations and repetitive transitions between distinct defect configurations on a time scale of tens of seconds. The velocity of these transitions suggests a cooperative movement of clusters of chains. The activation energy for the opening/closing of a connection between two cylinders is estimated.

Solubilization of Phenol Derivatives in Polymer Micelles Formed by Cationic Block Copolymer

Directory of Open Access Journals (Sweden)

Irma Fuentes

2017-01-01

Full Text Available The aggregation of cationic block copolymers formed by polystyrene (PS and poly(ethyl-4-vinylpyridine (PS-b-PE4VP was studied in aqueous solution. Diblock copolymers of PS and poly(4-vinylpyridine were synthesized by sequential anionic polymerization using BuLi as initiator. Subsequently, the 4-vinylpyridine units were quaternized with ethyl bromide to obtain cationic PS-b-PE4VP block copolymers with different quaternization degree. The self-aggregation of cationic block copolymers was studied by fluorescence probing, whereas the morphology and size of polymer micelles were determined by transmission electronic microscopy. Results indicate that spherical micelles with sizes lower than 100 nm were formed, whereas their micropolarity decreases with increasing quaternization degree. The partition of phenols between the micellar and aqueous phase was studied by using the pseudo-phase model, and the results show that the partition coefficients increase with increasing length of the side alkyl chain and are larger for star micelles. These results are discussed in terms of three-region model.

Thermosensitive Self-Assembling Block Copolymers as Drug Delivery Systems

Directory of Open Access Journals (Sweden)

Giovanni Filippo Palmieri

2011-04-01

Full Text Available Self-assembling block copolymers (poloxamers, PEG/PLA and PEG/PLGA diblock and triblock copolymers, PEG/polycaprolactone, polyether modified poly(Acrylic Acid with large solubility difference between hydrophilic and hydrophobic moieties have the property of forming temperature dependent micellar aggregates and, after a further temperature increase, of gellifying due to micelle aggregation or packing. This property enables drugs to be mixed in the sol state at room temperature then the solution can be injected into a target tissue, forming a gel depot in-situ at body temperature with the goal of providing drug release control. The presence of micellar structures that give rise to thermoreversible gels, characterized by low toxicity and mucomimetic properties, makes this delivery system capable of solubilizing water-insoluble or poorly soluble drugs and of protecting labile molecules such as proteins and peptide drugs.

Synthesis and Functionalization of Poly(ethylene oxide-b-ethyloxazoline) Diblock Copolymers with Phosphonate Ions

OpenAIRE

Chen, Alfred Yuen-Wei

2013-01-01

Poly(ethylene oxide) (PEO) and poly(2-ethyl-2-oxazoline) (PEOX) are biocompatible polymers that act as hydrophilic "stealth" drug carriers. As block copolymers, the PEOX group offers a wider variety of functionalization. The goal of this project was to synthesize a poly(ethylene oxide)-b-poly(2-ethyl-2-oxazoline) (PEO-b-PEOX) block copolymer and functionalize pendent groups of PEOX with phosphonic acid. This was achieved through cationic ring opening polymerization (CROP) of 2-...

The effect of copolymers on the interfaces in incompatible homopolymers blend: Molecular dynamics study

Science.gov (United States)

Ryu, Jiho; Lee, Won Bo

2015-03-01

Using molecular dynamics simulations the effect of copolymers as compatibilizer for reducing interfacial tension and enhancement of interfacial adhesion at the interface of thermodynamic unfavorable homopolymers blend is studied with block- and graft-copolymers. We have calculated local pressure tensor of system along the axis perpendicular to interface, varying bending potential energy of one part, which consist of just one kind of beads, of copolymer chain to examine the effect of stiffness of surfactin molecules. Here we consider symmetric diblock copolymer (f =1/2) having 1/2 N make of beads of type A and the other part made of beads of type B, and graft copolymer having backbone linear chain consist of 1/2 N beads of type of A and branched with two side-chain consist of 1/4 N beads of type B. All simulations were performed under the constant NPT ensemble at T* =1, ρ* ~0.85. Also we studied changes of effect of copolymers with increasing pairwise repulsive interaction potential between two beads of types A and B while homopolymers chain length are fixed, N =30. Chemical and Biomolecular Engineering, Sogang University, Seoul, South Korea.

First detection of lamella-gyroid-cylinder phase transition of neat polyethylene-poly(ethylene oxide) diblock copolymers on the basis of synchrotron WAXD/SAXS and infrared/Raman spectral measurements

International Nuclear Information System (INIS)

Weiyu, Cao; Tashiro, Kohji; Hanesaka, Makoto; Takeda, Shinichi; Masunaga, Hiroyasu; Sasaki, Sono; Takata, Masaki

2009-01-01

The phase transition behaviour of polyethylene-b-poly(ethylene oxide) (PE-b-PEO) diblock copolymer with relatively short chain lengths has been studied on the basis of temperature dependent infrared and Raman spectral measurements and synchrotron WAXD/SAXS simultaneous measurements, from which the concrete structural changes were deduced successfully from the various levels of molecular chain conformation, chain packing mode and higher-order structure. The higher-order structure has been found to transform between lamella, perforated lamella, gyroid, cylinder and sphere structures. The inner structural changes occurring in the polyethylene and poly(ethylene oxide) parts have been related with these morphological changes. The morphological transition from lamella to gyroid occurs with keeping the crystalline state of polyethylene parts. This apparently curious transition can be interpreted reasonably by assuming the thermally-activated chain motion in the crystal lattice, which may play an important role as a trigger to induce the morphological change from lamella to gyroid. This idea was supported by the measurement of half-width of Raman anti-symmetric CH 2 stretching band sensitive to the thermal mobility of alkyl chains.

Influence of copolymer architectures on adhesion and compatibilization of polymers at interfaces

Science.gov (United States)

Guo, Lantao

Adhesion and compatibilization of immiscible homopolymers by a variety of copolymer architectures were studied. The work is arranged into 5 chapters: In Chapter 1, an introduction to recent studies on improvement of adhesion and compatibilization of polymer blends using copolymers was made including the advantages and shortcomings of interfacial reinforcement by a diblock copolymer architecture. Emphasis is on the novel ways to improve adhesion at polymer interfaces by a variety of copolymer architectures, including physical entanglement and chemical modification and chemical bonding. In Chapter 2, a series of Polystyrene-Poly(methyl methacrylate) (PS-PMMA) graft copolymers were introduced to modify the PS and PMMA homopolymer interface and was found to increase the interfacial fracture toughness to a large extent, depending on the detailed architectural variables such as the graft number per chain, the lengths of the backbone and the grafts, and the total molecular weights of the graft copolymers. It was also found that there was an optimal number of grafts per chain which can be interpreted based on the graft length and inter-branch length of the backbone of the copolymer. Effect of in-situ grafting via a chemical reaction between Polystyrene-Poly(vinyl phenol) (PS-PSOH) and oxazoline containing Styrene-Acrylonitril (SAN) was also discussed compared with the physical grafting of a graft copolymer of different structural parameters. In Chapter 3, hydrogen bonding was utilized to toughen the interface between PS and PAA poly(acrylic acid)) or PMMA using a random copolymer architecture of Polystyrene-Poly(vinyl pyridine) (PS-PVP). It was shown that random copolymer architecture is not only economically feasible due to its low cost of producing but also very effective on adhesion because it not only overcomes the issue of micelle formation which is an unavoidable situation in the diblock and graft cases but the enhancement of adhesion is much higher utilizing a H

Pressure jump kinetics of disorder to BCC ordering in diblock copolymer micelles in a selective solvent

Czech Academy of Sciences Publication Activity Database

Liu, Y.; Spring, J. D.; Steinhart, Miloš; Bansil, R.

2012-01-01

Roč. 45, č. 22 (2012), s. 9147-9154 ISSN 0024-9297 Institutional support: RVO:61389013 Keywords : X-ray-scattering * block-copolymer * triblock copolymer Subject RIV: CD - Macromolecular Chemistry Impact factor: 5.521, year: 2012

Activated Porous Carbon Spheres with Customized Mesopores through Assembly of Diblock Copolymers for Electrochemical Capacitor.

Science.gov (United States)

Tang, Jing; Wang, Jie; Shrestha, Lok Kumar; Hossain, Md Shahriar A; Alothman, Zeid Abdullah; Yamauchi, Yusuke; Ariga, Katsuhiko

2017-06-07

A series of porous carbon spheres with precisely adjustable mesopores (4-16 nm), high specific surface area (SSA, ∼2000 m 2 g -1 ), and submicrometer particle size (∼300 nm) was synthesized through a facile coassembly of diblock polymer micelles with a nontoxic dopamine source and a common postactivation process. The mesopore size can be controlled by the diblock polymer, polystyrene-block-poly(ethylene oxide) (PS-b-PEO) templates, and has an almost linear dependence on the square root of the degree of polymerization of the PS blocks. These advantageous structural properties make the product a promising electrode material for electrochemical capacitors. The electrochemical capacitive performance was studied carefully by using symmetrical cells in a typical organic electrolyte of 1 M tetraethylammonium tetrafluoroborate/acetonitrile (TEA BF 4 /AN) or in an ionic liquid electrolyte of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF 4 ), displaying a high specific capacitance of 111 and 170 F g -1 at 1 A g -1 , respectively. The impacts of pore size distribution on the capacitance performance were thoroughly investigated. It was revealed that large mesopores and a relatively low ratio of micropores are ideal for realizing high SSA-normalized capacitance. These results provide us with a simple and reliable way to screen future porous carbon materials for electrochemical capacitors and encourage researchers to design porous carbon with high specific surface area, large mesopores, and a moderate proportion of micropores.

Fluids density functional theory and initializing molecular dynamics simulations of block copolymers

Science.gov (United States)

Brown, Jonathan R.; Seo, Youngmi; Maula, Tiara Ann D.; Hall, Lisa M.

2016-03-01

Classical, fluids density functional theory (fDFT), which can predict the equilibrium density profiles of polymeric systems, and coarse-grained molecular dynamics (MD) simulations, which are often used to show both structure and dynamics of soft materials, can be implemented using very similar bead-based polymer models. We aim to use fDFT and MD in tandem to examine the same system from these two points of view and take advantage of the different features of each methodology. Additionally, the density profiles resulting from fDFT calculations can be used to initialize the MD simulations in a close to equilibrated structure, speeding up the simulations. Here, we show how this method can be applied to study microphase separated states of both typical diblock and tapered diblock copolymers in which there is a region with a gradient in composition placed between the pure blocks. Both methods, applied at constant pressure, predict a decrease in total density as segregation strength or the length of the tapered region is increased. The predictions for the density profiles from fDFT and MD are similar across materials with a wide range of interfacial widths.

Ordered CdSe nanoparticles within self-assembled block copolymer domains on surfaces.

Science.gov (United States)

Zou, Shan; Hong, Rui; Emrick, Todd; Walker, Gilbert C

2007-02-13

Hierarchical, high-density, ordered patterns were fabricated on Si substrates by self-assembly of CdSe nanoparticles within approximately 20-nm-thick diblock copolymer films in a controlled manner. Surface-modified CdSe nanoparticles formed well-defined structures within microphase-separated polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) domains. Trioctylphosphine oxide (TOPO)-coated CdSe nanoparticles were incorporated into PS domains and polyethylene glycol-coated CdSe nanoparticles were located primarily in the P2VP domains. Nearly close-packed CdSe nanoparticles were clearly identified within the highly ordered patterns on Si substrates by scanning electron microscopy (SEM). Contact angle measurements together with SEM results indicate that TOPO-CdSe nanoparticles were partially placed at the air/copolymer interface.

Synthesis of photoactuating acrylic thermoplastic elastomers containing diblock copolymer-grafted carbon nanotubes

Czech Academy of Sciences Publication Activity Database

Ilčíková, M.; Mrlík, M.; Sedláček, T.; Šlouf, Miroslav; Zhigunov, Alexander; Koynov, K.; Mosnáček, J.

2014-01-01

Roč. 3, č. 10 (2014), s. 999-1003 ISSN 2161-1653 R&D Projects: GA TA ČR TE01020118 Institutional support: RVO:61389013 Keywords : photoactuating nanocomposite * carbon nanotubes * copolymer Subject RIV: CD - Macromolecular Chemistry Impact factor: 5.764, year: 2014

Aggregation behavior of doubly thermoresponsive polysulfobetaine-b-poly(N-isopropylacrylamide) diblock copolymers

Czech Academy of Sciences Publication Activity Database

Vishnevetskaya, N. S.; Hildebrand, V.; Niebuur, B.-J.; Grillo, I.; Filippov, Sergey K.; Laschewsky, A.; Müller-Buschbaum, P.; Papadakis, C. M.

2016-01-01

Roč. 49, č. 17 (2016), s. 6655-6668 ISSN 0024-9297 R&D Projects: GA ČR(CZ) GC15-10527J Institutional support: RVO:61389013 Keywords : polymer * thermoresponsive * block copolymer Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 5.835, year: 2016

Biomimetic synthesis of calcium carbonate bilayers interfaced by a diblock copolymer template

NARCIS (Netherlands)

Goos, J.A.C.M.; Vo, C.D.; Dey, A.; Hoogen, van den C.J.; Lousberg, N.J.H.G.M.; Hendrix, M.M.R.M.; Tirelli, N.; With, de G.; Sommerdijk, N.A.J.M.

2012-01-01

The synthesis of a new class of hybrid materials with two differently oriented layers of calcite at adjacent sides of an organic template is demonstrated. A Langmuir monolayer of the amphiphilic block copolymer poly(butyl acrylate)-b-poly(hydroxypropyl acrylate) directs the formation of a first

Comparing blends and blocks: Synthesis of partially fluorinated diblock polythiophene copolymers to investigate the thermal stability of optical and morphological properties

Directory of Open Access Journals (Sweden)

Pierre Boufflet

2016-10-01

Full Text Available The microstructure of the active blend layer has been shown to be a critically important factor in the performance of organic solar devices. Block copolymers provide a potentially interesting avenue for controlling this active layer microstructure in solar cell blends. Here we explore the impact of backbone fluorination in block copolymers of poly(3-octyl-4-fluorothiophenes and poly(3-octylthiophene (F-P3OT-b-P3OT. Two block co-polymers with varying block lengths were prepared via sequential monomer addition under Kumada catalyst transfer polymerisation (KCTP conditions. We compare the behavior of the block copolymer to that of the corresponding homopolymer blends. In both types of system, we find the fluorinated segments tend to dominate the UV–visible absorption and molecular vibrational spectral features, as well as the thermal behavior. In the block copolymer case, non-fluorinated segments appear to slightly frustrate the aggregation of the more fluorinated block. However, in situ temperature dependent Raman spectroscopy shows that the intramolecular order is more thermally stable in the block copolymer than in the corresponding blend, suggesting that such materials may be interesting for enhanced thermal stability of organic photovoltaic active layers based on similar systems.

Comb-like amphiphilic polypeptide-based copolymer nanomicelles for co-delivery of doxorubicin and P-gp siRNA into MCF-7 cells

Energy Technology Data Exchange (ETDEWEB)

Suo, Aili, E-mail: ailisuo@mail.xjtu.edu.cn [Department of Oncology, The First Affiliated Hospital of Xi' an Jiaotong University, Xi' an 710061 (China); Qian, Junmin, E-mail: jmqian@mail.xjtu.edu.cn [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Zhang, Yaping; Liu, Rongrong; Xu, Weijun [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Wang, Hejing [Department of Oncology, The First Affiliated Hospital of Xi' an Jiaotong University, Xi' an 710061 (China)

2016-05-01

A comb-like amphiphilic copolymer methoxypolyethylene glycol-graft-poly(L-lysine)-block-poly(L-phenylalanine) (mPEG-g-PLL-b-Phe) was successfully synthesized. To synthesize mPEG-g-PLL-b-Phe, diblock copolymer PLL-b-Phe was first synthesized by successive ring-opening polymerization of α-amino acid N-carboxyanhydrides followed by the removal of benzyloxycarbonyl protecting groups, and then mPEG was grafted onto PLL-b-Phe by reductive amination via Schiff's base formation. The chemical structures of the copolymers were identified by {sup 1}H NMR. mPEG-g-PLL-b-Phe copolymer had a critical micelle concentration of 6.0 mg/L and could self-assemble in an aqueous solution into multicompartment nanomicelles with a mean diameter of approximately 78 nm. The nanomicelles could encapsulate doxorubicin (DOX) through hydrophobic and π–π stacking interactions between DOX molecules and Phe blocks and simultaneously complex P-gp siRNA with cationic PLL blocks via electrostatic interactions. The DOX/P-gp siRNA-loaded nanomicelles showed spherical morphology, possessed narrow particle size distribution and had a mean particle size of 120 nm. The DOX/P-gp siRNA-loaded nanomicelles exhibited pH-responsive release behaviors and displayed accelerated release under acidic conditions. The DOX/P-gp siRNA-loaded nanomicelles were efficiently internalized into MCF-7 cells, and DOX released could successfully reach nuclei. In vitro cytotoxicity assay demonstrated that the DOX/P-gp siRNA-loaded nanomicelles showed a much higher cytotoxicity in MCF-7 cells than DOX-loaded nanomicelles due to their synergistic killing effect and that the blank nanomicelles had good biocompatibility. Thus, the novel comb-like mPEG-g-PLL-b-Phe nanomicelles could be a promising vehicle for co-delivery of chemotherapeutic drug and genetic material. - Highlights: • Comb-like amphiphilic copolymer mPEG-g-PLL-b-Phe was successfully synthesized. • Polypeptide-based copolymer could self-assemble into

Superhydrophobic surfaces of electrospun block copolymer fibers with low content of fluorosilicones

Energy Technology Data Exchange (ETDEWEB)

Tian, Xiaoping [Key Laboratory of Advanced Textile Materials and Manufacturing Technology, Ministry of Education, Zhejiang Sci-Tech University, Hangzhou 310018 (China); Engineering Research Center for Eco-Dyeing and Finishing of Textiles, Ministry of Education, Zhejiang Sci-Tech University, Hangzhou 310018 (China); Yi, Lingmin, E-mail: lmyi@zstu.edu.cn [Key Laboratory of Advanced Textile Materials and Manufacturing Technology, Ministry of Education, Zhejiang Sci-Tech University, Hangzhou 310018 (China); Engineering Research Center for Eco-Dyeing and Finishing of Textiles, Ministry of Education, Zhejiang Sci-Tech University, Hangzhou 310018 (China); Department of Chemical Engineering and Materials Science, Stevens Institute of Technology, Hoboken, NJ 07030 (United States); Meng, Xiaomei; Xu, Kai [Key Laboratory of Advanced Textile Materials and Manufacturing Technology, Ministry of Education, Zhejiang Sci-Tech University, Hangzhou 310018 (China); Engineering Research Center for Eco-Dyeing and Finishing of Textiles, Ministry of Education, Zhejiang Sci-Tech University, Hangzhou 310018 (China); Jiang, Tengteng; Lai, Dongzhi [Key Laboratory of Advanced Textile Materials and Manufacturing Technology, Ministry of Education, Zhejiang Sci-Tech University, Hangzhou 310018 (China)

2014-07-01

A series of well-defined poly[methyl(3,3,3-trifluoropropyl)siloxane]-b-poly(methyl methacrylate) (PMTFPS-b-PMMA) diblock copolymers with low content of PMTFPS were synthesized by atom transfer radical polymerization (ATRP) of MMA from PMTFPS macroinitiators (PMTFPS-Br). The polymerization result reveals that the ATRP of MMA from PMTFPS-Br is fist-order with respect to MMA under different polymerization conditions, demonstrating a typical characteristic of living polymerization. The results also show that PMTFPS-b-PMMA diblock copolymers can exhibit a total surface tension (γ{sub S}) varying from 25.28 mN/m to 21.87 mN/m with the change of PMTFPS contents from 2.6 wt% to 22.2 wt%. Moreover, the water contact angles of electrospun PMTFPS-b-PMMA surfaces could be higher than 150° with water roll-off angles less than 10°, which denotes a superhydrophobic property. However, the electronspinning conditions, especially the concentration of spinning solution, would have important effect on the surface morphology, surface composition and wetting behavior of electrospun films. It was found that bead-free fibers with uniform diameter as well as good superhydrophobic property could be prepared on condition that the polymer concentration of spinning solution was as high as 32 wt% in the mixed solvent of DMF and THF.

Theoretical study of the self-assembly of Janus Bottlebrush Polymers from A-Branch-B Diblock Macromonomers

Science.gov (United States)

Gadelrab, Karim; Alexander-Katz, Alfredo; LaboratoryTheoretical Soft Materials Team

The self-assembly of block copolymers BCP has provided an impressive control over the nanoscale structure of soft matter. While the main focus of the research in the field has been directed towards simple linear diblocks, the development of advanced polymer architecture provided improved performance and access to new structures. In particular, bottlebrush BCPs (BBCPs) have interesting characteristics due to their dense functionality, high molecular weight, low levels of entanglement, and tendency to efficiently undergo rapid bulk phase separation. In this work, we are interested in theoretically studying the self-assembly of Janus-type ``A-branch-B'' BBCPs where A and B blocks can phase separate with the bottlebrush polymer backbone serving as the interface between the two blocks. Hence, the polymer backbone adds an extra constraint on the equilibrium spacing between neighboring linear diblock chains. In this regard, the segment length of the backbone separating the AB junctions has a direct effect of the observed domain spacing and effective segregation strength of the AB blocks. We employ self-consistent field theoretic SCFT simulations to capture the effect of volume fraction of different constituents and construct a phase diagram of the accessible morphologies of these BBCPs.

Meso-scale Modeling of Block Copolymers Self-Assembly in Casting Solutions for Membrane Manufacture

KAUST Repository

Moreno Chaparro, Nicolas

2016-05-01

Isoporous membranes manufactured from diblock copolymer are successfully produced at laboratory scale under controlled conditions. Because of the complex phenomena involved, membrane preparation requires trial and error methodologies to find the optimal conditions, leading to a considerable demand of resources. Experimental insights demonstrate that the self-assembly of the block copolymers in solution has an effect on the final membrane structure. Nevertheless, the complete understanding of these multi-scale phenomena is elusive. Herein we use the coarse-grained method Dissipative Particle Dynamics to study the self-assembly of block copolymers that are used for the preparation of the membranes. To simulate representative time and length scales, we introduce a framework for model reduction of polymer chain representations for dissipative particle dynamics, which preserves the properties governing the phase equilibria. We reduce the number of degrees of freedom by accounting for the correlation between beads in fine-grained models via power laws and the consistent scaling of the simulation parameters. The coarse-graining models are consistent with the experimental evidence, showing a morphological transition of the aggregates as the polymer concentration and solvent affinity change. We show that hexagonal packing of the micelles can occur in solution within different windows of polymer concentration depending on the solvent affinity. However, the shape and size dispersion of the micelles determine the characteristic arrangement. We describe the order of crew-cut micelles using a rigid-sphere approximation and propose different phase parameters that characterize the emergence of monodisperse-spherical micelles in solution. Additionally, we investigate the effect of blending asymmetric diblock copolymers (AB/AC) over the properties of the membranes. We observe that the co-assembly mechanism localizes the AC molecules at the interface of A and B domains, and induces

High-frequency ultrasound-responsive block copolymer micelle.

Science.gov (United States)

Wang, Jie; Pelletier, Maxime; Zhang, Hongji; Xia, Hesheng; Zhao, Yue

2009-11-17

Micelles of a diblock copolymer composed of poly(ethylene oxide) and poly(2-tetrahydropyranyl methacrylate) (PEO-b-PTHPMA) in aqueous solution could be disrupted by high-frequency ultrasound (1.1 MHz). It was found that, upon exposure to a high-intensity focused ultrasound (HIFU) beam at room temperature, the pH value of the micellar solution decreased over irradiation time. The infrared spectroscopic analysis of solid block copolymer samples collected from the ultrasound irradiated micellar solution revealed the formation of carboxylic acid dimers and hydroxyl groups. These characterization results suggest that the high-frequency HIFU beam could induce the hydrolysis reaction of THPMA at room temperature resulting in the cleavage of THP groups. The disruption of PEO-b-PTHPMA micelles by ultrasound was investigated by using dynamic light scattering, atomic force microscopy, and fluorescence spectroscopy. On the basis of the pH change, it was found that the disruption process was determined by a number of factors such as the ultrasound power, the micellar solution volume and the location of the focal spot of the ultrasound beam. This study shows the potential to develop ultrasound-sensitive block copolymer micelles by having labile chemical bonds in the polymer structure, and to use the high-frequency HIFU to trigger a chemical reaction for the disruption of micelles.

Shear induced structures of soft colloids: Rheo-SANS experiments on kinetically frozen PEP-PEO diblock copolymer micelles

International Nuclear Information System (INIS)

Stellbrink, J; Lonetti, B; Rother, G; Willner, L; Richter, D

2008-01-01

We investigated the effect of external steady shear on dilute to concentrated solutions of PEP-PEO diblock copolymer micelles (soft colloids). The degree of softness in terms of particle interactions (intermolecular softness) and deformability of the individual particle (intramolecular softness) was varied by changing the ratio between hydrophobic and hydrophilic blocks from symmetric (1:1, hard sphere-like) to very asymmetric (1:20, star-like). We performed in situ rheology and small angle neutron scattering experiments (Rheo-SANS) to relate macroscopic flow properties to microscopic structural changes. The rheology data qualitatively show the same behavior for both types of micelles: (i) a divergence of the zero shear viscosity η 0 at a critical concentration φ c approximately following a Vogel-Fulcher-Tammann law and (ii) close to this liquid-solid transition a shear rate dependent viscosity which can be described by the Carreau function with an asymptotic power law η(γ-dot) ∼ γ-dot -0.4 starting at a critical shear rate γ-dot c . Rheo-SANS experiments in the liquid phase close to φ c were extended into the strong shear thinning region for both types of micelles at φ/φ c ∼0.8 and γ-dot red =γ-dot/γ-dot c approx. 10. In our Rheo-SANS data we observe a rather controversial influence of external shear on the structural properties of the two different micellar systems. With increasing shear rate the symmetric, hard sphere-like micelles show a decreasing structure factor S(Q) but a shear rate independent interparticle distance. The asymmetric, star-like micelles show an increase in S(Q) and an increase of the interparticle distance, both in the flow and vorticity direction. This unexpected behavior can be rationalized by a shear induced elongation and tilt of the star-like micelles along the flow direction as predicted by recent MD simulations (Ripoll et al 2006 Phys. Rev. Lett. 96 188302)

Self-assembly behavior of well-defined polymethylene-block-poly(ethylene glycol) copolymers in aqueous solution

KAUST Repository

Alkayal, Nazeeha

2016-09-22

A series of well-defined amphiphilic polymethylene-b-poly(ethylene glycol) (PM-b-PEG) diblock copolymers, with different hydrophobic chain length, were synthesized by combining Diels-Alder reaction with polyhomologation. The successful synthetic procedure was confirmed by size-exclusion chromatography (SEC) and 1H NMR spectroscopy. These block copolymers self-assembled into spherical micelles in aqueous solutions and exhibit low critical micelle concentration (CMC) of 2–4 mg/mL, as determined by fluorescence spectroscopy using pyrene as a probe. Measurements of the micelle hydrodynamic diameters, performed by dynamic light scattering (DLS), cryo-transmission electron microscopy (cryo-TEM) and atomic force microscopy (AFM), revealed a direct dependence of the micelle size from the polymethylene block length.

Non-surface activity and micellization behavior of cationic amphiphilic block copolymer synthesized by reversible addition-fragmentation chain transfer process.

Science.gov (United States)

Ghosh, Arjun; Yusa, Shin-ichi; Matsuoka, Hideki; Saruwatari, Yoshiyuki

2011-08-02

Cationic amphiphilic diblock copolymers of poly(n-butylacrylate)-b-poly(3-(methacryloylamino)propyl)trimethylammonium chloride) (PBA-b-PMAPTAC) with various hydrophobic and hydrophilic chain lengths were synthesized by a reversible addition-fragmentation chain transfer (RAFT) process. Their molecular characteristics such as surface activity/nonactivity were investigated by surface tension measurements and foam formation observation. Their micelle formation behavior and micelle structure were investigated by fluorescence probe technique, static and dynamic light scattering (SLS and DLS), etc., as a function of hydrophilic and hydrophobic chain lengths. The block copolymers were found to be non-surface active because the surface tension of the aqueous solutions did not change with increasing polymer concentration. Critical micelle concentration (cmc) of the polymers could be determined by fluorescence and SLS measurements, which means that these polymers form micelles in bulk solution, although they were non-surface active. Above the cmc, the large blue shift of the emission maximum of N-phenyl-1-naphthylamine (NPN) probe and the low micropolarity value of the pyrene probe in polymer solution indicate the core of the micelle is nonpolar in nature. Also, the high value of the relative intensity of the NPN probe and the fluorescence anisotropy of the 1,6-diphenyl-1,3,5-hexatriene (DPH) probe indicated that the core of the micelle is highly viscous in nature. DLS was used to measure the average hydrodynamic radii and size distribution of the copolymer micelles. The copolymer with the longest PBA block had the poorest water solubility and consequently formed micelles with larger size while having a lower cmc. The "non-surface activity" was confirmed for cationic amphiphilic diblock copolymers in addition to anionic ones studied previously, indicating the universality of non-surface activity nature.

Nanosized amorphous calcium carbonate stabilized by poly(ethylene oxide)-b-poly(acrylic acid) block copolymers.

Science.gov (United States)

Guillemet, Baptiste; Faatz, Michael; Gröhn, Franziska; Wegner, Gerhard; Gnanou, Yves

2006-02-14

Particles of amorphous calcium carbonate (ACC), formed in situ from calcium chloride by the slow release of carbon dioxide by alkaline hydrolysis of dimethyl carbonate in water, are stabilized against coalescence in the presence of very small amounts of double hydrophilic block copolymers (DHBCs) composed of poly(ethylene oxide) (PEO) and poly(acrylic acid) (PAA) blocks. Under optimized conditions, spherical particles of ACC with diameters less than 100 nm and narrow size distribution are obtained at a concentration of only 3 ppm of PEO-b-PAA as additive. Equivalent triblock or star DHBCs are compared to diblock copolymers. The results are interpreted assuming an interaction of the PAA blocks with the surface of the liquid droplets of the concentrated CaCO3 phase, formed by phase separation from the initially homogeneous reaction mixture. The adsorption layer of the block copolymer protects the liquid precursor of ACC from coalescence and/or coagulation.

Adsorption of non-ionic ABC triblock copolymers: Surface modification of TiO2 suspensions in aqueous and non-aqueous medium

Science.gov (United States)

Lerch, Jean-Philippe; Atanase, Leonard Ionut; Riess, Gérard

2017-10-01

A series of non-ionic ABC triblock copolymers, such as poly(butadiene)-b-poly(2-vinylpyrridine)-b-poly(ethylene oxide) (PB-P2VP-PEO) were synthesized by sequential anionic polymerizations. For these copolymers comprising an organo-soluble PB and a water-soluble PEO block, their P2VP middle block has been selected for its anchoring capacity on solid surfaces. The adsorption isotherms on TiO2 were obtained in heptane and in aqueous medium, as selective solvents. In both of these cases, the P2VP middle block provides the surface anchoring, whereas PB and PEO sequences are acting as stabilizing moieties in heptane and water respectively. By extension to ABC triblock copolymers of the scaling theory developed for diblock copolymers, the density of adsorbed chains could be correlated with the molecular characteristics of the PB-P2VP-PEO triblock copolymers. From a practical point a view, it could be demonstrated that these copolymers are efficient dispersing agents for the TiO2 pigments in both aqueous and non-aqueous medium.

Synthesis and quaternization of nitroxide-terminated poly(4-vinylpyridine-co-acrylonitrile) macroinitiators and related diblock copolymers

Czech Academy of Sciences Publication Activity Database

Poláková, Lenka; Lokaj, Jan; Holler, Petr; Starovoytova, Larisa; Pekárek, Michal; Štěpánek, Petr

-, 065 (2010), s. 1-10 ISSN 1618-7229 R&D Projects: GA ČR GESON/06/E005; GA ČR GA203/07/0659 Institutional research plan: CEZ:AV0Z40500505 Keywords : 4-vinylpyridine-acrylonitrile copolymers * block copolymers * nitroxide-mediated radical polymerization Subject RIV: CD - Macromolecular Chemistry Impact factor: 0.574, year: 2010 http://www.e-polymers.org/journal/papers/lpolakova_240710.pdf

Investigation of a new thermosensitive block copolymer micelle: hydrolysis, disruption, and release.

Science.gov (United States)

Pelletier, Maxime; Babin, Jérôme; Tremblay, Luc; Zhao, Yue

2008-11-04

Thermosensitive polymer micelles are generally obtained with block copolymers in which one block exhibits a lower critical solution temperature in aqueous solution. We investigate a different design that is based on the use of one block bearing a thermally labile side group, whose hydrolysis upon heating shifts the hydrophilic-hydrophobic balance toward the destabilization of block copolymer micelles. Atom transfer radical polymerization was utilized to synthesize a series of diblock copolymers composed of hydrophilic poly(ethylene oxide) (PEO) and hydrophobic poly(2-tetrahydropyranyl methacrylate) (PTHPMA). We show that micelles of PEO-b-PTHPMA in aqueous solution can be destabilized as a result of the thermosensitive hydrolytic cleavage of tetrahydropyranyl (THP) groups that transforms PTHPMA into hydrophilic poly(methacrylic acid). The three related processes occurring in aqueous solution, namely, hydrolytic cleavage of THP, destabilization of micelles, and release of loaded Nile Red (NR), were investigated simultaneously using 1H NMR, dynamic light scattering, and fluorescence spectroscopy, respectively. At 80 degrees C, the results suggest that the three events proceed with a similar kinetics. Although slower than at elevated temperatures, the disruption of PEO-b-PTHPMA micelles can take place at the body temperature (approximately 37 degrees C), and the release kinetics of NR can be adjusted by changing the relative lengths of the two blocks or the pH of the solution.

„Schizophrenic” micelles from doubly thermoresponsive polysulfobetaine-b-poly(N-isopropylmethacrylamide) diblock copolymers

Czech Academy of Sciences Publication Activity Database

Vishnevetskaya, N. S.; Hildebrand, V.; Niebuur, B.-J.; Grillo, I.; Filippov, Sergey K.; Laschewsky, A.; Müller-Buschbaum, P.; Papadakis, C. M.

2017-01-01

Roč. 50, č. 10 (2017), s. 3985-3999 ISSN 0024-9297 R&D Projects: GA ČR(CZ) GC15-10527J Keywords : self-assembly * block copolymers * UCST Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry Impact factor: 5.835, year: 2016

Two-dimensional phase separated structures of block copolymers on solids

Science.gov (United States)

Sen, Mani; Jiang, Naisheng; Endoh, Maya; Koga, Tadanori; Ribbe, Alexander

The fundamental, yet unsolved question in block copolymer (BCP) thin films is the self-organization process of BCPs at the solid-polymer melt interface. We here focus on the self-organization processes of cylinder-forming polystyrene-block-poly (4-vinylpyridine) diblock copolymer and lamellar-forming poly (styrene-block-butadiene-block-styrene) triblock copolymer on Si substrates as model systems. In order to reveal the buried interfacial structures, the following experimental protocols were utilized: the BCP monolayer films were annealed under vacuum at T>Tg of the blocks (to equilibrate the melts); vitrification of the annealed BCP films via rapid quench to room temperature; subsequent intensive solvent leaching (to remove unadsorbed chains) with chloroform, a non-selective good solvent for the blocks. The strongly bound BCP layers were then characterized by using atomic force microscopy, scanning electron microscopy, grazing incidence small angle X-ray scattering, and X-ray reflectivity. The results showed that both blocks lie flat on the substrate, forming the two-dimensional, randomly phase-separated structure irrespective of their microdomain structures and interfacial energetics. Acknowledgement of financial support from NSF Grant (CMMI -1332499).

Polyethylene-Based Tadpole Copolymers

KAUST Repository

Alkayal, Nazeeha; Zhang, Zhen; Bilalis, Panayiotis; Gnanou, Yves; Hadjichristidis, Nikolaos

2017-01-01

Novel well-defined polyethylene-based tadpole copolymers ((c-PE)-b-PS, PE: polyethylene, PS: polystyrene) with ring PE head and linear PS tail are synthesized by combining polyhomologation, atom transfer radical polymerization (ATRP), and Glaser

Polyethylene-Based Tadpole Copolymers

KAUST Repository

Alkayal, Nazeeha

2017-02-15

Novel well-defined polyethylene-based tadpole copolymers ((c-PE)-b-PS, PE: polyethylene, PS: polystyrene) with ring PE head and linear PS tail are synthesized by combining polyhomologation, atom transfer radical polymerization (ATRP), and Glaser coupling reaction. The -OH groups of the 3-miktoarm star copolymers (PE-OH)-b-PS, synthesized by polyhomologation and ATRP, are transformed to alkyne groups by esterification with propiolic acid, followed by Glaser cyclization and removal of the unreacted linear with Merrifield\\'s resin-azide. The characterization results of intermediates and final products by high-temperature size exclusion chromatography, H NMR spectroscopy, and differential scanning calorimetry confirm the tadpole topology.

Manipulating Interfaces through Surface Confinement of Poly(glycidyl methacrylate)-block-poly(vinyldimethylazlactone), a Dually Reactive Block Copolymer

International Nuclear Information System (INIS)

Lokitz, Bradley S.; Wei, Jifeng; Hinestrosa Salazar, Juan P.; Ivanov, Ilia N.; Browning, James B.; Ankner, John Francis; Kilbey, S. Michael II; Messman, Jamie M.

2012-01-01

The assembly of dually reactive, well-defined diblock copolymers incorporating the chemoselective/functional monomer, 4,4-dimethyl-2-vinylazlactone (VDMA) and the surface-reactive monomer glycidyl methacrylate (GMA) is examined to understand how competition between surface attachment and microphase segregation influences interfacial structure. Reaction of the PGMA block with surface hydroxyl groups not only anchors the copolymer to the surface, but limits chain mobility, creating brush-like structures comprising PVDMA blocks, which contain reactive azlactone groups. The block copolymers are spin coated at various solution concentrations and annealed at elevated temperature to optimize film deposition to achieve a molecularly uniform layer. The thickness and structure of the polymer thin films are investigated by ellipsometry, infrared spectroscopy, and neutron reflectometry. The results show that deposition of PGMA-b-PVDMA provides a useful route to control film thickness while preserving azlactone groups that can be further modified with biotin-poly(ethylene glycol)amine to generate designer surfaces. The method described herein offers guidance for creating highly functional surfaces, films, or coatings through the use of dually reactive block copolymers and postpolymerization modification.

Colloids from oppositely charged polymers: reversibility and surface activity

NARCIS (Netherlands)

Hofs, P.S.

2009-01-01

The research described in this thesis concerns the formation, solution properties, and adsorption of polyelectrolyte complexes composed of at least one diblock copolymer with a neutral and a charged block and either an oppositely charged homopolyelectrolyte or a diblock copolymer, with a neutral

SYNTHESIS OF BLOCK COPOLYMER BY INTEGRATED LIVING ANIONIC POLYMERIZATION-ATOM TRANSFER RADICAL POLYMERIZATION (ATRP)

Institute of Scientific and Technical Information of China (English)

Bing Liu; Feng Liu; Ning Luo; Sheng-kang Ying; Qing Liu

2000-01-01

Alpha-trichloroacetoxy terminated polystyrene oligomer (PS-CH2CH2OCOCCl3) and poly-(styrene-b-butadiene)oligomer [P(S-b-B)-CH2CH2OCOCCl3)] were synthesized by living anionic polymeri-zation using n-butyllithium as initiator.Then the PS-CH2CH2OCOCCl3 (PS-Cl3) or P(S-b-B)-CH2CH2O-COCCl3 (PSB-Cl3) was used as the macroinitiator in the polymerization of (meth)acrylates in the presence of CuX/bpy. AB diblock and ABC triblock copolymers were prepared by the integrated living anionic polymerization (LAP)-atom transfer radical polymerization (ATRP). The structures of the PSB-Cl3 and the P(S-b-MMA) were identified by FTIR and 1H-NMR spectrum, respectively. A new way to design block copolymers (the combination of LAP and ATRP) was developed.

Organization of Gold Nanorods in Cylinder-Forming Block Copolymer Films

Science.gov (United States)

Jian, Guoquian; Riggleman, Robert; Composto, Russell

2012-02-01

The addition of gold nanorods (AuNRs) to copolymer films can impart unique optical and electrical properties. To take full advantage of this system, the AuNRs must be dispersed in a self-organizing copolymer that directs the orientation of the anisotropic particle. In the present work, AuNRs with aspect ratio 3.6 (8 nm x 29 nm) are grafted with poly(2-vinyl pyridine) (P2VP) brushes and dispersed in a cylindrical forming diblock copolymer of polystyrene-b-P2VP (180K-b-77K, 29.6 wt% P2VP). Films are spun cast and solvent annealed in chloroform to produce a perpendicular cylindrical morphology at the surface. Using TEM and UV-ozone etching combined with AFM, the AuNRs are well dispersed and co-locate (top down view) with the P2VP cylinders, ˜50nm diameter. However, the AuNRs mainly lie parallel to the surface indicating that they likely locate at the junction created at the intersection between P2VP cylinders and P2VP brush layer adjacent to the silicon oxide surface. Self-consistent field calculations of the Au:PS-b-P2VP morphology as well as the effect of adding P2VP homopolymer to the nanocomposite will be discussed.

Diblock Terpolymers Are Tunable and pH Responsive Vehicles To Increase Hydrophobic Drug Solubility for Oral Administration.

Science.gov (United States)

Tale, Swapnil; Purchel, Anatolii A; Dalsin, Molly C; Reineke, Theresa M

2017-11-06

Synthetic polymers offer tunable platforms to create new oral drug delivery vehicles (excipients) to increase solubility, supersaturation maintenance, and bioavailability of poorly aqueous soluble pharmaceutical candidates. Five well-defined diblock terpolymers were synthesized via reversible addition-fragmentation chain transfer polymerization (RAFT) and consist of a first block of either poly(ethylene-alt-propylene) (PEP), poly(N-isopropylacrylamide) (PNIPAm), or poly(N,N-diethylaminoethyl methacrylate) (PDEAEMA) and a second hydrophilic block consisting of a gradient copolymer of N,N-dimethylacrylamide (DMA) and 2-methacrylamidotrehalose (MAT). This family of diblock terpolymers offers hydrophobic, hydrophilic, or H-bonding functionalities to serve as noncovalent sites of drug binding. Drug-polymer spray dried dispersions (SDDs) were created with a model drug, probucol, and characterized by differential scanning calorimetry (DSC). These studies revealed that probucol crystallinity decreased with increasing H-bonding sites available in the polymer. The PNIPAm-b-P(DMA-grad-MAT) systems revealed the best performance at pH 6.5, where immediate probucol release and effective maintenance of 100% supersaturation was found, which is important for facilitating drug solubility in more neutral conditions (intestinal environment). However, the PDEAEMA-b-P(DMA-grad-MAT) system revealed poor probucol dissolution at pH 6.5 and 5.1. Alternatively, at an acidic pH of 3.1, a rapid and high dissolution profile and effective supersaturation maintenance of up to 90% of the drug was found, which could be useful for triggering drug release in acidic environments (stomach). The PEP-b-P(DMA-grad-MAT) system showed poor performance (only ∼20% of drug solubility at pH 6.5), which was attributed to the low solubility of the polymers in the dissolution media. This work demonstrates the utility of diblock terpolymers as a potential new excipient platform to optimize design parameters for

Nanostructured Polysulfone-Based Block Copolymer Membranes

KAUST Repository

Xie, Yihui

2016-05-01

The aim of this work is to fabricate nanostructured membranes from polysulfone-based block copolymers through self-assembly and non-solvent induced phase separation. Block copolymers containing polysulfone are novel materials for this purpose providing better mechanical and thermal stability to membranes than polystyrene-based copolymers, which have been exclusively used now. Firstly, we synthesized a triblock copolymer, poly(tert-butyl acrylate)-b-polsulfone-b-poly(tert-butyl acrylate) through polycondensation and reversible addition-fragmentation chain-transfer polymerization. The obtained membrane has a highly porous interconnected skin layer composed of elongated micelles with a flower-like arrangement, on top of the graded finger-like macrovoids. Membrane surface hydrolysis was carried out in a combination with metal complexation to obtain metal-chelated membranes. The copper-containing membrane showed improved antibacterial capability. Secondly, a poly(acrylic acid)-b-polysulfone-b-poly(acrylic acid) triblock copolymer obtained by hydrolyzing poly(tert-butyl acrylate)-b-polsulfone-b-poly(tert-butyl acrylate) formed a thin film with cylindrical poly(acrylic acid) microdomains in polysulfone matrix through thermal annealing. A phase inversion membrane was prepared from the same polymer via self-assembly and chelation-assisted non-solvent induced phase separation. The spherical micelles pre-formed in a selective solvent mixture packed into an ordered lattice in aid of metal-poly(acrylic acid) complexation. The space between micelles was filled with poly(acrylic acid)-metal complexes acting as potential water channels. The silver0 nanoparticle-decorated membrane was obtained by surface reduction, having three distinct layers with different particle sizes. Other amphiphilic copolymers containing polysulfone and water-soluble segments such as poly(ethylene glycol) and poly(N-isopropylacrylamide) were also synthesized through coupling reaction and copper0-mediated

Micelles and gels of oxyethylene-oxybutylene diblock copolymers in aqueous solution: The effect of oxyethylene-block length

DEFF Research Database (Denmark)

Derici, L.; Ledger, S.; Mai, S.M.

1999-01-01

and in aqueous 0.2 mol dm(-3) K(2)SO(4)), yielding the micellar association numbers, the hydrodynamic and thermodynamic radii, and related expansion factors. Micellar parameters were also obtained by small-angle neutron scattering (SANS) for solutions of a similar copolymer, E(86)B(10), in water, i......Block copolymer E(90)B(10) (E = oxyethylene, B = oxybutylene) was synthesised and characterised by gel permeation chromatography and (13)C NMR spectroscopy. Dynamic light scattering (DLS) and static light scattering (SLS) were used to characterise the micelles in solution (both in water...... of water in the micelle core. Moderately concentrated solutions of copolymer E(90)B(10) were studied in the gel state by small-angle X-ray scattering (SAXS) in tandem with rheology (oscillatory shear). Values for the dynamic elastic modulus (G') of the gels significantly exceeded 10(4) Pa across the range...

Morphology of polymer-based films for organic photovoltaics

OpenAIRE

Ruderer, Matthias A.

2012-01-01

In this thesis, polymer-based films are examined for applications in organic photovoltaics. Polymer-fullerene, polymer-polymer and diblock copolymer systems are characterized as active layer materials. The focus is on experimental parameters influencing the morphology formation of the active layer in organic solar cells. Scattering and imaging techniques provide a complete understanding of the internal structure on different length scales which is compared to spectroscopic and photovoltaic pr...

Ion transport properties of mechanically stable symmetric ABCBA pentablock copolymers with quaternary ammonium functionalized midblock

Energy Technology Data Exchange (ETDEWEB)

Ertem, S. Piril [Department of Polymer Science and Engineering, University of Massachusetts Amherst, 120 Governors Drive Amherst Massachusetts 01003; Caire, Benjamin R. [Department of Chemical and Biological Engineering, Colorado School of Mines, Golden Colorado 80401; Tsai, Tsung-Han [Department of Polymer Science and Engineering, University of Massachusetts Amherst, 120 Governors Drive Amherst Massachusetts 01003; Zeng, Di [Department of Polymer Science and Engineering, University of Massachusetts Amherst, 120 Governors Drive Amherst Massachusetts 01003; Vandiver, Melissa A. [Department of Chemical and Biological Engineering, Colorado School of Mines, Golden Colorado 80401; Kusoglu, Ahmet [Energy Conversion Group, Energy Technologies Area, Lawrence Berkeley National Laboratory, Berkeley California 94720; Seifert, Soenke [Energy Conversion Group, Energy Technologies Area, Lawrence Berkeley National Laboratory, Berkeley California 94720; Hayward, Ryan C. [Department of Polymer Science and Engineering, University of Massachusetts Amherst, 120 Governors Drive Amherst Massachusetts 01003; Weber, Adam Z. [Energy Conversion Group, Energy Technologies Area, Lawrence Berkeley National Laboratory, Berkeley California 94720; Herring, Andrew M. [Department of Chemical and Biological Engineering, Colorado School of Mines, Golden Colorado 80401; Coughlin, E. Bryan [Department of Polymer Science and Engineering, University of Massachusetts Amherst, 120 Governors Drive Amherst Massachusetts 01003; Liberatore, Matthew W. [Department of Chemical Engineering Department, University of Toledo, 2801 W Bancroft Street MS305 Toledo Ohio 43606

2017-02-07

Anion exchange membranes (AEMs) are a promising class of materials for applications that require selective ion transport, such as fuel cells, water purification, and electrolysis devices. Studies of structure–morphology–property relationships of ion-exchange membranes revealed that block copolymers exhibit improved ion conductivity and mechanical properties due to their microphase-separated morphologies with well-defined ionic domains. While most studies focused on symmetric diblock or triblock copolymers, here, the first example of a midblock quaternized pentablock AEM is presented. A symmetric ABCBA pentablock copolymer was functionalized to obtain a midblock brominated polymer. Solution cast films were then quaternized to obtain AEMs with resulting ion exchange capacities (IEC) ranging from 0.4 to 0.9 mmol/g. Despite the relatively low IEC, the polymers were highly conductive (up to 60 mS/cm Br2 at 90 8C and 95%RH) with low water absorption (<25 wt %) and maintained adequate mechanical properties in both dry and hydrated conditions. Xray scattering and transmission electron microscopy (TEM) revealed formation of cylindrical non-ionic domains in a connected ionic phase.

Small angle X-ray scattering study of thermodynamic and conformational changes in ion-containing symmetric diblock copolymers

Energy Technology Data Exchange (ETDEWEB)

Gunkel, Ilja [Max Planck Institute of Microstructure Physics, Halle (Germany); Institute of Physics, Martin Luther University Halle Wittenberg, Halle (Germany); Thurn-Albrecht, Thomas [Institute of Physics, Martin Luther University Halle Wittenberg, Halle (Germany)

2010-07-01

We present temperature-dependent SAXS measurements on two different symmetric block copolymers with added salt (lithiumtriflate, LiCF{sub 3}SO{sub 3}). For both studied systems, polystyrene-b-poly-2-vinylpyridine (PS-b-P2VP) and Polystyrene-b-Polyethyleneoxide (PS-b-PEO), the salt selectively dissolved in one block leading to large increases of the order-disorder transition temperatures (T{sub ODT}). In addition, the lamellar thickness of these ion-containing block copolymers nontrivially changed above a certain salt concentration - in PS-b-P2VP the lamellae became thicker whereas their thickness decreased in PS-b-PEO. Using basic arguments of the thermodynamics of block copolymers we were able to separate the ion-induced increase of T{sub ODT} due to a higher incompatibility between the different blocks from changes in the thickness of the lamellae at T{sub ODT} resulting from changes in the conformation of the ion-containing blocks.

New approach in synthesis, characterization and release study of pH-sensitive polymeric micelles, based on PLA-Lys-b-PEGm, conjugated with doxorubicin

International Nuclear Information System (INIS)

Efthimiadou, E. K.; Tapeinos, C.; Bilalis, P.; Kordas, G.

2011-01-01

Amphiphilic block copolymers are well established as building blocks for the preparation of micellar drug carriers. The functional polymer micelles possess several advantages, such as high drug efficiency, targeted delivery, and minimized cytotoxicity. The synthesis of block copolymers using nano-structured templates has emerged as a useful and versatile approach for preparing drug carriers. Here, we report the synthesis of a smart polymeric compound of a diblock PLA-Lys-b-PEG copolymer containing doxorubicin. We have synthesized functionalized diblock copolymers, with lysinol, poly(lactide) and monomethoxy poly(ethylene glycol) via thermal ring-opening polymerization and a subsequent six-step substitution reaction. A variety of spectroscopic methods were employed here to verify the product of our synthesis. 1 H-Nuclear magnetic resonance and Fourier transform infrared studies validated the expected synthesis of copolymers. Doxorubicin is chemically loaded into micelles, and the ex vitro release can be evaluated either in weak acidic or in SBF solution by UV–vis spectroscopy. Dynamic light scattering, thermo gravimetric analysis, and size exclusion chromatography have also been used.

In-situ visualization and order quantification of symmetric diblock copolymer directed self-assembly

International Nuclear Information System (INIS)

Salaün, M.; Le Gallic, M.; Picard, E.; Zelsmann, M.

2013-01-01

In this work, atomic force microscopy (AFM) investigations of lamellar PS-b-PMMA block copolymer layers are performed during the self-assembly process. These in-situ experiments are made on both un-patterned planar substrates and topographical substrates (graphoepitaxy experiments) at different temperatures and for different durations. Image processing software is used to produce AFM movies of the same location on the sample and to measure polymer micro-phase domain lengths versus annealing time. We observed that micro-domain formation starts after only a few minutes of heating. On planar substrates, the micro-domain length evolution with time (t) is in accordance with the literature, following a power law ∼ t 0.29 . On the other hand, in substrate channels and in conditions used, we show that the domain length dependence follows a two-step process. Initially, the system adopts a similar kinetic dependence as that of the planar substrate, but at longer times, drastically reduced time dependence is observed due to the topographical confinement of the domains. - Highlights: ► Live atomic force microscopy of block copolymer directed self-assembly is performed. ► Values of polymer self-assembly kinetic in topographical trenches are measured. ► Opens the way to a better understanding of graphoepitaxy order nucleation and growth

Thermo-reversible supramolecular hydrogels of trehalose-type diblock methylcellulose analogues.

Science.gov (United States)

Yamagami, Mao; Kamitakahara, Hiroshi; Yoshinaga, Arata; Takano, Toshiyuki

2018-03-01

This paper describes the design and synthesis of new trehalose-type diblock methylcellulose analogues with nonionic, cationic, and anionic cellobiosyl segments, namely 1-(tri-O-methyl-cellulosyl)-4-[β-d-glucopyranosyl-(1→4)-β-d-glucopyranosyloxymethyl]-1H-1,2,3-triazole (1), 1-(tri-O-methyl-cellulosyl)-4-[(6-amino-6-deoxy-β-d-glucopyranosyl)-(1→4)- 6-amino-6-deoxy-β-d-glucopyranosyloxymethyl]-1H-1,2,3-triazole (2), and 4-(tri-O-methyl-cellulosyloxymethyl)-1-[β-d-glucopyranuronosyl-(1→4)-β-d-glucopyranuronosyl]-1H-1,2,3-triazole (3), respectively. Aqueous solutions of all of the 1,2,3-triazole-linked diblock methylcellulose analogues possessed higher surface activities than that of industrially produced methylcellulose and exhibited lower critical solution temperatures, that allowed the formation of thermoresponsive supramolecular hydrogels at close to human body temperature. Supramolecular structures of thermo-reversible hydrogels based on compounds 1, 2, and 3 were investigated by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Detailed structure-property-function relationships of compounds 1, 2, and 3 were discussed. Not only nonionic hydrophilic segment but also ionic hydrophilic segments of diblock methylcellulose analogues were valid for the formation of thermo-reversible supramolecular hydrogels based on end-functionalized methylcellulose. Copyright © 2017 Elsevier Ltd. All rights reserved.

Phase Behavior of Binary Blends of AB+AC Block Copolymers with compatible B and C blocks

Science.gov (United States)

Pryamitsyn, Victor; Ganesan, Venkat

2012-02-01

Recently the experimental studies of phase behavior of binary blends of PS-b-P2VP and PS-b-PHS demonstrated an interesting effect: blends of symmetric PS-b-P2VP and shorter symmetric (PS-b-PHS) formed cylindrical HEX and spherical BCC phases, while each pure component formed lamellas. The miscibility of P2VP and PHS is caused by the hydrogen bonding between P2VP and PHS,which can be described as a negative Flory ?-parameter between P2VP and PHS. We developed a theory of the microphase segregation of AB+AC blends of diblock copolymers based on strong stretching theory. The main result of our theory is that in the copolymer brush-like layer formed by longer B chain and shorter C chains, the attraction between B and shorter C chains causes relative stretching of short C chains and compression of longer B chains. The latter manifests in an excessive bending force towards the grafting surface (BC|AA interface). Such bending force causes a transition from a symmetric lamella phase to a HEX cylinder or BCC spherical phases with the BC phase being a ``matrix'' component. In a blend of asymmetric BCC sphere forming copolymers (where B and C segments are the minor components), such bending force may unfold BCC spherical phase to a HEX cylinder phase, or even highly uneven lamella phases.

Well-defined block copolymers for gene delivery to dendritic cells: probing the effect of polycation chain-length.

Science.gov (United States)

Tang, Rupei; Palumbo, R Noelle; Nagarajan, Lakshmi; Krogstad, Emily; Wang, Chun

2010-03-03

The development of safe and efficient polymer carriers for DNA vaccine delivery requires mechanistic understanding of structure-function relationship of the polymer carriers and their interaction with antigen-presenting cells. Here we have synthesized a series of diblock copolymers with well-defined chain-length using atom transfer radical polymerization and characterized the influence of polycation chain-length on the physico-chemical properties of the polymer/DNA complexes as well as the interaction with dendritic cells. The copolymers consist of a hydrophilic poly(ethylene glycol) block and a cationic poly(aminoethyl methacrylate) (PAEM) block. The average degree of polymerization (DP) of the PAEM block was varied among 19, 39, and 75, with nearly uniform distribution. With increasing PAEM chain-length, polyplexes formed by the diblock copolymers and plasmid DNA had smaller average particle size and showed higher stability against electrostatic destabilization by salt and heparin. The polymers were not toxic to mouse dendritic cells (DCs) and only displayed chain-length-dependent toxicity at a high concentration (1mg/mL). In vitro gene transfection efficiency and polyplex uptake in DCs were also found to correlate with chain-length of the PAEM block with the longer polymer chain favoring transfection and cellular uptake. The polyplexes induced a modest up-regulation of surface markers for DC maturation that was not significantly dependent on PAEM chain-length. Finally, the polyplex prepared from the longest PAEM block (DP of 75) achieved an average of 20% enhancement over non-condensed anionic dextran in terms of uptake by DCs in the draining lymph nodes 24h after subcutaneous injection into mice. Insights gained from studying such structurally well-defined polymer carriers and their interaction with dendritic cells may contribute to improved design of practically useful DNA vaccine delivery systems. Copyright 2009 Elsevier B.V. All rights reserved.

Morphology and Surface Energy of a Si Containing Semifluorinated Di-block Copolymer Thin Films.

Science.gov (United States)

Shrestha, Umesh; Clarson, Stephen; Perahia, Dvora

2013-03-01

The structure and composition of an interface influence stability, adhesiveness and response to external stimuli of thin polymeric films. Incorporation of fluorine affects interfacial energy as well as thermal and chemical stability of the layers. The incompatibility between the fluorinated and non-fluorinated blocks induces segregation that leads to long range correlations where the tendency of the fluorine to migrate to interfaces impacts the surface tension of the films. Concurrently Si in a polymeric backbone enhances the flexibility of polymeric chains. Our previous studies of poly trifluoro propyl methyl siloxane-polystyrene thin films with SiF fraction 0.03-0.5 as a function of temperature have shown that the SiF block drives layering parallel to the surface of the diblock. Here in we report the structure and interfacial energies of SiF-PS in the plane of the films, as a function of the volume fraction of the SiF block obtained from Atomic Force microscopy and contact angle measurement studies. This work is supported by NSF DMR - 0907390

High-concentration graphene dispersion stabilized by block copolymers in ethanol.

Science.gov (United States)

Perumal, Suguna; Lee, Hyang Moo; Cheong, In Woo

2017-07-01

This article describes a comprehensive study for the preparation of graphene dispersions by liquid-phase exfoliation using amphiphilic diblock copolymers; poly(ethylene oxide)-block-poly(styrene) (PEO-b-PS), poly(ethylene oxide)-block-poly(4-vinylpyridine) (PEO-b-PVP), and poly(ethylene oxide)-block-poly(pyrenemethyl methacrylate) (PEO-b-PPy) with similar block lengths. Block copolymers were prepared from PEO using the Steglich coupling reaction followed by reversible addition-fragmentation chain transfer (RAFT) polymerization. Graphite platelets (G) and reduced graphene oxide (rGO) were used as graphene sources. The dispersion stability of graphene in ethanol was comparatively investigated by on-line turbidity, and the graphene concentration in the dispersions was determined gravimetrically. Our results revealed that the graphene dispersions with PEO-b-PVP were much more stable and included graphene with fewer defects than that with PEO-b-PS or PEO-b-PPy, as confirmed by turbidity and Raman analyses. Gravimetry confirmed that graphene concentrations up to 1.7 and 1.8mg/mL could be obtained from G and rGO dispersions, respectively, using PEO-b-PVP after one week. Distinctions in adhesion forces of PS, VP, PPy block units with graphene surface and the variation in solubility of the block copolymers in ethanol medium significantly affected the stability of the graphene dispersion. Copyright © 2017 Elsevier Inc. All rights reserved.

Intradomain phase transitions in flexible block copolymers with self-aligning segments

Science.gov (United States)

Burke, Christopher J.; Grason, Gregory M.

2018-05-01

We study a model of flexible block copolymers (BCPs) in which there is an enlthalpic preference for orientational order, or local alignment, among like-block segments. We describe a generalization of the self-consistent field theory of flexible BCPs to include inter-segment orientational interactions via a Landau-de Gennes free energy associated with a polar or nematic order parameter for segments of one component of a diblock copolymer. We study the equilibrium states of this model numerically, using a pseudo-spectral approach to solve for chain conformation statistics in the presence of a self-consistent torque generated by inter-segment alignment forces. Applying this theory to the structure of lamellar domains composed of symmetric diblocks possessing a single block of "self-aligning" polar segments, we show the emergence of spatially complex segment order parameters (segment director fields) within a given lamellar domain. Because BCP phase separation gives rise to spatially inhomogeneous orientation order of segments even in the absence of explicit intra-segment aligning forces, the director fields of BCPs, as well as thermodynamics of lamellar domain formation, exhibit a highly non-linear dependence on both the inter-block segregation (χN) and the enthalpy of alignment (ɛ). Specifically, we predict the stability of new phases of lamellar order in which distinct regions of alignment coexist within the single mesodomain and spontaneously break the symmetries of the lamella (or smectic) pattern of composition in the melt via in-plane tilt of the director in the centers of the like-composition domains. We further show that, in analogy to Freedericksz transition confined nematics, the elastic costs to reorient segments within the domain, as described by the Frank elasticity of the director, increase the threshold value ɛ needed to induce this intra-domain phase transition.

Coalescence in an interface-modified polymer blend as studied by light-scattering measurements

DEFF Research Database (Denmark)

Søndergaard, K.; Lyngaae-Jørgensen, Jørgen

1996-01-01

the requirement is the BC to reside at the interface. In the present study the block chain lengths were chosen shorter than the corresponding homopolymers as a starting point. For selected model systems it was found that symmetrical diblock copolymers with phi(bc) greater than or equal to 1% were most effective......The influence of B-B diblock copolymers on coalescence in A:B blends has been studied by rheo-optical measurements and electron microscopy. Divergent criteria and experimental evidence appear in the literature on the block copolymer (BC) molecular weight (M(W)) and volume fraction (phi(bc)) when...... is discussed based on various mechanisms: shear-induced mutual compatibility between components, squeeze-out/drainage of the interfacial layer, frictional pull-out of BC chains, collision-induced entrapment of BC between interfaces, encapsulation of the BC based on the concept of elastic interfacial curvature....

Synthesis of Diblock Codendrimer by Double Click Chemistry

Energy Technology Data Exchange (ETDEWEB)

Lee, Jae Wook; Han, Seung Choul; Ji, Won Ho [Dong-A Univ., Busan (Korea, Republic of); Jin, Sungho [Pusan National Univ., Busan (Korea, Republic of); Kim, Ji Hyeon [Gachon Univ., Seongnam (Korea, Republic of)

2012-12-15

Efficient double click methods for the synthesis of diblock codendrimers were developed. The synthetic strategy involved the sequential click reactions between an alkyne and an azide. The short core building block, 1,4-diazidobutane, was chosen to serve as the azide functionalities for dendrimer growth via click reactions with the alkyne-functionalized PAMAM dendrons as hydrophilic dendron and alkyne-functionalized Frechet-type dendrons as hydrophobic dendron. The structure of diblock codendrimers was confirmed by {sup 1}H and {sup 13}C NMR spectroscopy, IR spectroscopy, mass spectrometry, and GPC analysis.

Synthesis of Diblock Codendrimer by Double Click Chemistry

International Nuclear Information System (INIS)

Lee, Jae Wook; Han, Seung Choul; Ji, Won Ho; Jin, Sungho; Kim, Ji Hyeon

2012-01-01

Efficient double click methods for the synthesis of diblock codendrimers were developed. The synthetic strategy involved the sequential click reactions between an alkyne and an azide. The short core building block, 1,4-diazidobutane, was chosen to serve as the azide functionalities for dendrimer growth via click reactions with the alkyne-functionalized PAMAM dendrons as hydrophilic dendron and alkyne-functionalized Frechet-type dendrons as hydrophobic dendron. The structure of diblock codendrimers was confirmed by 1 H and 13 C NMR spectroscopy, IR spectroscopy, mass spectrometry, and GPC analysis

Tuning of Block Copolymer Membrane Morphology through Water Induced Phase Inversion Technique

KAUST Repository

Madhavan, Poornima

2016-06-01

Isoporous membranes are attractive for the regulation and detection of transport at the molecular level. A well-defined asymmetric membranes from diblock copolymers with an ordered nanoporous membrane morphologies were fabricated by the combination of block copolymer self-assembly and non-solvent-induced phase separation (NIPS) technique. This is a straightforward and fast one step procedure to develop integrally anisotropic (“asymmetric”) membranes having isoporous top selective layer. Membranes prepared via this method exhibit an anisotropic cross section with a thin separation layer supported from underneath a macroporous support. These membrane poses cylindrical pore structure with ordered nanopores across the entire membrane surfaces with pore size in the range from 20 to 40 nm. Tuning the pore morphology of the block copolymer membranes before and after fabrication are of great interest. In this thesis, we first investigated the pore morphology tuning of asymmetric block copolymer membrane by complexing with small organic molecules. We found that the occurrence of hydrogen-bond formation between PS-b-P4VP block copolymer and –OH/ –COOH functionalized organic molecules significantly tunes the pore morphology of asymmetric nanoporous membranes. In addition, we studied the complexation behavior of ionic liquids with PS-b-P4VP block copolymer in solutions and investigated their effect on final membrane morphology during the non-solvent induced phase separation process. We found that non-protic ionic liquids facilitate the formation of hexagonal nanoporous block copolymer structure, while protic ionic liquids led to a lamella-structured membrane. Secondly, we demonstrated the catalytic activity of the gold nanoparticle-enhanced hollow fiber membranes by the reduction of nitrophenol. Also, we systematically investigated the pore morphology of isoporous PS-b-P4VP using 3D imaging technique. Thirdly, we developed well-distributed silver nanoparticles on the

Adsorption of Poly(ethylene oxide)-Poly(lactide) Copolymers. Effects of Composition and Degradation.

Science.gov (United States)

Muller, Dries; Carlsson, Fredrik; Malmsten, Martin

2001-04-01

The effect of chemical degradation of two diblock copolymers of poly(ethylene oxide) (E) and poly(lactide) (L), E(39)L(5) and E(39)L(20), on their adsorption at silica and methylated silica was investigated with in situ ellipsometry. Steric stablization of polystyrene dispersions was investigated in relation to degradation. Hydrolysis of the poly(lactide) block of the copolymers was followed at different temperatures and pH by using HPLC to measure the occurrence of lactic acid in solution. The block copolymers were quite stable in pH-unadjusted solution at low temperature, whereas degradation was facilitated by increasing temperature or lowering of the pH. Lower degradation rates of E(39)L(20) where observed at low temperature in comparison with those of E(39)L(5), whereas the degradation rates of the copolymers were quantitatively similar at high temperature. The adsorption of the copolymers at methylated silica substrates decreased with increasing degree of degradation due to the reduction in the ability of hydrophobic block to anchor the copolymer layer at the surface. At silica the adsorption initially increased with increasing degradation, particularly for E(39)L(20) due to deposition of aggregates onto the surface. After extensive degradation the adsorption of the copolymers at both silica and methylated silica resembled that of the corresponding poly(ethylene oxide) homopolymer. Overall, it was found that the eventual reduction in adsorption occurred at a lower degree of degradation for E(39)L(5) than for E(39)L(20). Mean-field calculations showed a reduced anchoring for the block copolymers with decreasing poly(lactide) block length at hydrophobic surfaces. In accordance with this finding, it was observed that polystyrene dispersions were stabilized by E(39)L(20) or E(39)L(5) in a way that depended on both the lactide block length and the degree of degradation. Upon degradation of the hydrophobic block, stabilization of the polystyrene dispersions was

Simultaneous tuning of chemical composition and topography of copolymer surfaces: micelles as building blocks.

Science.gov (United States)

Zhao, Ning; Zhang, Xiaoyan; Zhang, Xiaoli; Xu, Jian

2007-05-14

A simple method is described for controlling the surface chemical composition and topography of the diblock copolymer poly(styrene)-b-poly(dimethylsiloxane)(PS-b-PDMS) by casting the copolymer solutions from solvents with different selectivities. The surface morphology and chemical composition were characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively, and the wetting behavior was studied by water contact angle (CA) and sliding angle (SA) and by CA hysteresis. Chemical composition and morphology of the surface depend on solvent properties, humidity of the air, solution concentration, and block lengths. If the copolymer is cast from a common solvent, the resultant surface is hydrophobic, with a flat morphology, and dominated by PDMS on the air side. From a PDMS-selective solvent, the surface topography depends on the morphology of the micelles. Starlike micelles give rise to a featureless surface nearly completely covered by PDMS, while crew-cut-like micelles lead to a rough surface with a hierarchical structure that consists partly of PDMS. From a PS-selective solvent, however, surface segregation of PDMS was restricted, and the surface morphology can be controlled by vapor-induced phase separation. On the basis of the tunable surface roughness and PDMS concentration on the air side, water repellency of the copolymer surface could be tailored from hydrophobic to superhydrophobic. In addition, reversible switching behavior between hydrophobic and superhydrophobic can be achieved by exposing the surface to solvents with different selectivities.

Novel Polymers Based on Atom Transfer Radical Polymerization of 2-Methoxyethyl Acrylate

DEFF Research Database (Denmark)

Bednarek, Melania; Jankova Atanasova, Katja; Hvilsted, Søren

2007-01-01

macroinitiators, however, for the latter the controlled conditions were somehow difficult to maintain. The amphiphilic behavior of the diblock copolymers lead to phase separation resulting in two glass transition temperatures as detected by DSC. Contact angle (Y) investigations with water on PMEA, PMMA...

Apertureless near-field vibrational imaging of block-copolymer nanostructures with ultrahigh spatial resolution.

Science.gov (United States)

Raschke, Markus B; Molina, Leopoldo; Elsaesser, Thomas; Kim, Dong Ha; Knoll, Wolfgang; Hinrichs, Karsten

2005-10-14

Nanodomains formed by microphase separation in thin films of the diblock copolymers poly(styrene-b-2-vinylpyridine) (PS-b-P2VP) and poly(styrene-b-ethyleneoxide) (PS-b-PEO) were imaged by means of infrared scattering-type near-field microscopy. When probing at 3.39 mum (2950 cm(-1)), contrast is obtained due to spectral differences between the C--H stretching vibrational resonances of the respective polymer constituents. An all-optical spatial resolution better than 10 nm was achieved, which corresponds to a sensitivity of just several thousand C--H groups facilitated by the local-field enhancement at the sharp metallic probe tips. The results demonstrate that infrared spectroscopy with access to intramolecular dimensions is within reach.

Synthesis of defined polyhedral oligosilsesquioxane-containing diblock and triblock methacrylate copolymers by atom transfer radical polymerization

Czech Academy of Sciences Publication Activity Database

Janata, Miroslav; Sikora, Antonín; Látalová, Petra; Čadová, Eva; Raus, Vladimír; Matějka, Libor; Vlček, Petr

2013-01-01

Roč. 128, č. 6 (2013), s. 4294-4301 ISSN 0021-8995 R&D Projects: GA ČR GAP106/12/0844; GA ČR GAP108/12/1459 Institutional support: RVO:61389013 Keywords : copolymers * nanostructured polymers * radical polymerization Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.640, year: 2013

Improving proton conduction pathways in di- and triblock copolymer membranes: Branched versus linear side chains

Science.gov (United States)

Dorenbos, G.

2017-06-01

Phase separation within a series of polymer membranes in the presence of water is studied by dissipative particle dynamics. Each polymer contains hydrophobic A beads and hydrophilic C beads. Three parent architectures are constructed from a backbone composed of connected hydrophobic A beads to which short ([C]), long ([A3C]), or symmetrically branched A5[AC][AC] side chains spring off. Three di-block copolymer derivatives are constructed by covalently bonding an A30 block to each parent architecture. Also three tri-blocks with A15 blocks attached to both ends of each parent architecture are modeled. Monte Carlo tracer diffusion calculations through the water containing pores for 1226 morphologies reveal that water diffusion for parent architectures is slowest and diffusion through the di-blocks is fastest. Furthermore, diffusion increases with side chain length and is highest for branched side chains. This is explained by the increase of water pore size with , which is the average number of bonds that A beads are separated from a nearest C bead. Optimization of within the amphiphilic parent architecture is expected to be essential in improving proton conduction in polymer electrolyte membranes.

Cellulose-based graft copolymers prepared by simplified electrochemically mediated ATRP

Directory of Open Access Journals (Sweden)

P. Chmielarz

2017-02-01

Full Text Available Brush-shaped block copolymer with a dual hydrophilic poly(acrylic acid-block-poly(oligo(ethylene glycol acrylate (PAA-b-POEGA arms was synthesized for the first time via a simplified electrochemically mediated ATRP (seATRP under both constant potential electrolysis and constant current electrolysis conditions, utilizing only 30 ppm of catalyst complex. The polymerization conditions were optimized to provide fast reactions while employing low catalyst concentrations and preparation of cellulose-based brush-like copolymers with narrow molecular weight distributions. The results from proton nuclear magnetic resonance (1H NMR spectral studies support the formation of cellulose-based graft (copolymers. It is expected that these new polymer brushes may find application as pH- and thermo-sensitive drug delivery systems.

Fabrication of platinum nanoparticles in aqueous solution and solid phase using amphiphilic PB-b-PEO copolymer nanoreactors

International Nuclear Information System (INIS)

Hoda, Numan; Budama, Leyla; Çakır, Burçin Acar; Topel, Önder; Ozisik, Rahmi

2013-01-01

Graphical abstract: TEM image of Pt nanoparticles produced by reducing by NaBH 4 within PB-b-PEO micelles in aqueous media (scale bar 1 nm). - Highlights: • Pt nanoparticles were synthesized within amphiphilic diblock copolymer micelles. • The effects of reducing agents and precursor dose on Pt np size were investigated. • The effect on fabrication of Pt np by reducing in aqueous and solid phases was compared. • The size of nanoparticles was about 1.4 nm for all doses and reducing agents types. - Abstract: Fabrication of Pt nanoparticles using an amphiphilic copolymer template in aqueous solution was achieved via polybutadiene-block-polyethyleneoxide copolymer micelles, which acted as nanoreactors. In addition, Pt nanoparticles were synthesized using hydrogen gas as the reducing agent in solid state for the first time to compare against solution synthesis. The influences of loaded precursor salt amount to micelles and the type of reducing agent on the size of nanoparticles were investigated through transmission electron microscopy. It was found that increasing the ratio of precursor salt to copolymer and using different type of reducing agent, even in solid phase reduction, did not affect the nanoparticle size. The average size of Pt nanoparticles was estimated to be 1.4 ± 0.1 nm. The reason for getting same sized nanoparticles was discussed in the light of nucleation, growth process, stabilization and diffusion of nanoparticles within micelles

A Stepwise "Micellization-Crystallization" Route to Oblate Ellipsoidal, Cylindrical, and Bilayer Micelles with Polyethylene Cores in Water

Energy Technology Data Exchange (ETDEWEB)

Yin, Ligeng; Lodge, Timothy P; Hillmyer, Marc A [UMM

2012-11-26

Micellar polymorphism from block copolymers has been well documented, but most attention has focused on noncrystalline hydrophobic systems. We have investigated the micellization in water of model diblock copolymers with semicrystalline polyethylene (PE) as the core-forming component. Poly(N,N-dimethylacrylamide)–polyethylene (AE) diblock copolymers were synthesized by a combination of anionic and RAFT polymerizations. The bulk nanostructures were probed by small-angle X-ray scattering (SAXS) and AE diblock copolymers were found to be moderately segregated at 140 °C. Dispersions of AE amphiphiles in water were prepared by direct dissolution at 120 °C (i.e., above the melting transition of PE) followed by cooling to 25 °C. By manipulating the composition of AE diblock copolymers, discrete structures with oblate ellipsoidal, cylindrical, and bilayer morphologies were produced, as evidenced in cryogenic transmission electron microscopy (cryo-TEM). The self-assembled aggregates were also studied by small-angle neutron scattering (SANS) and dilute solution rheology. The semicrystalline nature of the nanostructures was further revealed by differential scanning calorimetry (DSC) and wide-angle X-ray scattering (WAXS). A stepwise “micellization–crystallization” process was proposed as the micelle formation mechanism, as supported by the existence of similar nanostructures at 120 °C using SANS. This strategy holds promise for a general protocol toward the production of giant wormlike micelles and vesicles with semicrystalline polymeric cores.

Silicon containing copolymers

CERN Document Server

Amiri, Sahar; Amiri, Sanam

2014-01-01

Silicones have unique properties including thermal oxidative stability, low temperature flow, high compressibility, low surface tension, hydrophobicity and electric properties. These special properties have encouraged the exploration of alternative synthetic routes of well defined controlled microstructures of silicone copolymers, the subject of this Springer Brief. The authors explore the synthesis and characterization of notable block copolymers. Recent advances in controlled radical polymerization techniques leading to the facile synthesis of well-defined silicon based thermo reversible block copolymers?are described along with atom transfer radical polymerization (ATRP), a technique utilized to develop well-defined functional thermo reversible block copolymers. The brief also focuses on Polyrotaxanes and their great potential as stimulus-responsive materials which produce poly (dimethyl siloxane) (PDMS) based thermo reversible block copolymers.

The effect of heat treatment on the internal structure of nanostructured block copolymer films

Energy Technology Data Exchange (ETDEWEB)

Sepe, A; Hoppe, E T; Jaksch, S; Magerl, D; Zhong, Q; Papadakis, C M [Technische Universitaet Muenchen, Physikdepartment, Fachgebiet Physik weicher Materie/Lehrstuhl fuer funktionelle Materialien, James-Franck-Strasse 1, 85747 Garching (Germany); Perlich, J [HASYLAB at DESY, Notkestrasse 85, 22603 Hamburg (Germany); Posselt, D [IMFUFA, Department of Science, Systems and Models, Roskilde University, PO Box 260, 4000 Roskilde (Denmark); Smilgies, D-M, E-mail: papadakis@tum.de [Cornell High Energy Synchrotron Source (CHESS), Wilson Laboratory, Cornell University, Ithaca, NY 14853 (United States)

2011-06-29

We report on the temperature dependence of the nanostructure of thin block copolymer films, as studied using in situ grazing-incidence small-angle x-ray scattering (GISAXS). We focus on spin-coated poly(styrene-b-butadiene) diblock copolymer thin films featuring lamellae perpendicular to the substrate. In situ GISAXS measurements elucidate the structural changes during heat treatment at temperatures between 60 and 130 {sup 0}C. Thermal treatment below 100 {sup 0}C does not destroy the perpendicular lamellar order. In contrast, treatment between 105 and 120 {sup 0}C leads to a broad distribution of lamellar orientations which only partially recovers upon subsequent cooling. Treatment at 130 {sup 0}C leads to severe changes of the film structure. We attribute the change of behavior at 100 {sup 0}C to the onset of the glass transition of the polystyrene block and the related increase of long-range mobility. Our results indicate that the perpendicular lamellar orientation for high molar mass samples is not stable under all conditions.

Lamplighter model of a random copolymer adsorption on a line

Directory of Open Access Journals (Sweden)

L.I. Nazarov

2014-09-01

Full Text Available We present a model of an AB-diblock random copolymer sequential self-packaging with local quenched interactions on a one-dimensional infinite sticky substrate. It is assumed that the A-A and B-B contacts are favorable, while A-B are not. The position of a newly added monomer is selected in view of the local contact energy minimization. The model demonstrates a self-organization behavior with the nontrivial dependence of the total energy, E (the number of unfavorable contacts, on the number of chain monomers, N: E ~ N^3/4 for quenched random equally probable distribution of A- and B-monomers along the chain. The model is treated by mapping it onto the "lamplighter" random walk and the diffusion-controlled chemical reaction of X+X → 0 type with the subdiffusive motion of reagents.

Solution small-angle x-ray scattering as a screening and predictive tool in the fabrication of asymmetric block copolymer membranes

KAUST Repository

Dorin, Rachel Mika; Marques, Debora S.; Sai, Hiroaki; Vainio, Ulla; Phillip, William A.; Peinemann, Klaus; Nunes, Suzana Pereira; Wiesner, Ulrich B.

2012-01-01

Small-angle X-ray scattering (SAXS) analysis of the diblock copolymer poly(styrene-b-(4-vinyl)pyridine) in a ternary solvent system of 1,4-dioxane, tetrahydrofuran, and N,N-dimethylformamide, and the triblock terpolymer poly(isoprene-b-styrene-b-(4-vinyl)-pyridine) in a binary solvent system of 1,4-dioxane and tetrahydrofuran, reveals a concentration-dependent onset of ordered structure formation. Asymmetric membranes fabricated from casting solutions with polymer concentrations at or slightly below this ordering concentration possess selective layers with the desired nanostructure. In addition to rapidly screening possible polymer solution concentrations, solution SAXS analysis also predicts hexagonal and square pore lattices of the final membrane surface structure. These results suggest solution SAXS as a powerful tool for screening casting solution concentrations and predicting surface structure in the fabrication of asymmetric ultrafiltration membranes from self-assembled block copolymers. (Figure presented) © 2012 American Chemical Society.

Solution small-angle x-ray scattering as a screening and predictive tool in the fabrication of asymmetric block copolymer membranes

KAUST Repository

Dorin, Rachel Mika

2012-05-15

Small-angle X-ray scattering (SAXS) analysis of the diblock copolymer poly(styrene-b-(4-vinyl)pyridine) in a ternary solvent system of 1,4-dioxane, tetrahydrofuran, and N,N-dimethylformamide, and the triblock terpolymer poly(isoprene-b-styrene-b-(4-vinyl)-pyridine) in a binary solvent system of 1,4-dioxane and tetrahydrofuran, reveals a concentration-dependent onset of ordered structure formation. Asymmetric membranes fabricated from casting solutions with polymer concentrations at or slightly below this ordering concentration possess selective layers with the desired nanostructure. In addition to rapidly screening possible polymer solution concentrations, solution SAXS analysis also predicts hexagonal and square pore lattices of the final membrane surface structure. These results suggest solution SAXS as a powerful tool for screening casting solution concentrations and predicting surface structure in the fabrication of asymmetric ultrafiltration membranes from self-assembled block copolymers. (Figure presented) © 2012 American Chemical Society.

Merging Bottom-Up with Top-Down: Continuous Lamellar Networks and Block Copolymer Lithography

Science.gov (United States)

Campbell, Ian Patrick

Block copolymer lithography is an emerging nanopatterning technology with capabilities that may complement and eventually replace those provided by existing optical lithography techniques. This bottom-up process relies on the parallel self-assembly of macromolecules composed of covalently linked, chemically distinct blocks to generate periodic nanostructures. Among the myriad potential morphologies, lamellar structures formed by diblock copolymers with symmetric volume fractions have attracted the most interest as a patterning tool. When confined to thin films and directed to assemble with interfaces perpendicular to the substrate, two-dimensional domains are formed between the free surface and the substrate, and selective removal of a single block creates a nanostructured polymeric template. The substrate exposed between the polymeric features can subsequently be modified through standard top-down microfabrication processes to generate novel nanostructured materials. Despite tremendous progress in our understanding of block copolymer self-assembly, continuous two-dimensional materials have not yet been fabricated via this robust technique, which may enable nanostructured material combinations that cannot be fabricated through bottom-up methods. This thesis aims to study the effects of block copolymer composition and processing on the lamellar network morphology of polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) and utilize this knowledge to fabricate continuous two-dimensional materials through top-down methods. First, block copolymer composition was varied through homopolymer blending to explore the physical phenomena surrounding lamellar network continuity. After establishing a framework for tuning the continuity, the effects of various processing parameters were explored to engineer the network connectivity via defect annihilation processes. Precisely controlling the connectivity and continuity of lamellar networks through defect engineering and

Synthesis and characterization of sugar-based methacrylates and their random copolymers by ATRP

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G. Acik

2017-10-01

Full Text Available Various sugar-based methacrylate monomers have been prepared and randomly copolymerized with methyl methacrylate (MMA using classical atom transfer radical polymerization (ATRP. Firstly, four different sugar-based methacrylates are synthesized by two-step method: (i etherification of protected monosaccharides with epichlorohydrin and (ii following ring-opening reaction of obtained epoxides with methacrylic acid (MAA in the presence of triethylamine. Next, these monomers are copolymerized with MMA via ATRP at 90 °C to obtain corresponding random copolymers. The molecular weights of the copolymers are determined by both GPC (gel permeation chromatography and 1H-NMR (nuclear magnetic resonance spectroscopy analyses and found as 10600~16800 and 12200~18500 g/mol, respectively. Moreover, the copolymer compositions are also determined by 1H-NMR analysis using characteristic signals of the monomers and found as about 94.1~97.8%, which are good agreement with feeding ratio. In addition, the glass transition temperatures of copolymers are found as 101.2~102.9 °C by changing type and composition of sugar-based methacrylate monomers. Overall, a series of well-defined random copolymers comprising different sugar-based methacrylates and methyl methacrylates were successfully synthesized by classical ATRP method.

Intradomain Textures in Block Copolymers: Multizone Alignment and Biaxiality

Science.gov (United States)

Prasad, Ishan; Seo, Youngmi; Hall, Lisa M.; Grason, Gregory M.

2017-06-01

Block copolymer (BCP) melt assembly has been studied for decades, focusing largely on self-organized spatial patterns of periodically ordered segment density. Here, we demonstrate that underlying the well-known composition profiles (i.e., ordered lamella, cylinders, spheres, and networks) are generic and heterogeneous patterns of segment orientation that couple strongly to morphology, even in the absence of specific factors that promote intra or interchain segment alignment. We employ both self-consistent field theory and coarse-grained simulation methods to measure polar and nematic order parameters of segments in a freely jointed chain model of diblock melts. We show that BCP morphologies have a multizone texture, with segments predominantly aligned normal and parallel to interdomain interfaces in the respective brush and interfacial regions of the microdomain. Further, morphologies with anisotropically curved interfaces (i.e., cylinders and networks) exhibit biaxial order that is aligned to the principal curvature axes of the interface.

Diketopyrrolopyrrole-diketopyrrolopyrrole-based conjugated copolymer for high-mobility organic field-effect transistors

KAUST Repository

Kanimozhi, Catherine K.

2012-10-10

In this communication, we report the synthesis of a novel diketopyrrolopyrrole-diketopyrrolopyrrole (DPP-DPP)-based conjugated copolymer and its application in high-mobility organic field-effect transistors. Copolymerization of DPP with DPP yields a copolymer with exceptional properties such as extended absorption characteristics (up to ∼1100 nm) and field-effect electron mobility values of >1 cm 2 V -1 s -1. The synthesis of this novel DPP-DPP copolymer in combination with the demonstration of transistors with extremely high electron mobility makes this work an important step toward a new family of DPP-DPP copolymers for application in the general area of organic optoelectronics. © 2012 American Chemical Society.

Creating surfactant nanoparticles for block copolymer composites through surface chemistry.

Science.gov (United States)

Kim, Bumjoon J; Bang, Joona; Hawker, Craig J; Chiu, Julia J; Pine, David J; Jang, Se Gyu; Yang, Seung-Man; Kramer, Edward J

2007-12-04

A simple strategy to tailor the surface of nanoparticles for their specific adsorption to and localization at block copolymer interfaces was explored. Gold nanoparticles coated by a mixture of low molecular weight thiol end-functional polystyrene (PS-SH) (Mn = 1.5 and 3.4 kg/mol) and poly(2-vinylpyridine) homopolymers (P2VP-SH) (Mn = 1.5 and 3.0 kg/mol) were incorporated into a lamellar poly(styrene-b-2-vinylpyridine) diblock copolymer (PS-b-P2VP) (Mn = 196 kg/mol). A library of nanoparticles with varying PS and P2VP surface compositions (FPS) and high polymer ligand areal chain densities was synthesized. The location of the nanoparticles in the PS-b-P2VP block copolymer was determined by transmission electron microscopy. Sharp transitions in particle location from the PS domain to the PS/P2VP interface, and subsequently to the P2VP domain, were observed at FPS = 0.9 and 0.1, respectively. This extremely wide window of FPS values where the polymer-coated gold nanoparticles adsorb to the interface suggests a redistribution of PS and P2VP polymers on the Au surface, inducing the formation of amphiphilic nanoparticles at the PS/P2VP interface. In a second and synthetically more challenging approach, gold nanoparticles were covered with a thiol terminated random copolymer of styrene and 2-vinylpyridine synthesized by RAFT polymerization. Two different random copolymers were considered, where the molecular weight was fixed at 3.5 kg/mol and the relative incorporation of styrene and 2-vinylpyridine repeat units varied (FPS = 0.52 and 0.40). The areal chain density of these random copolymers on Au is unfortunately not high enough to preclude any contact between the P2VP block of the block copolymer and the Au surface. Interestingly, gold nanoparticles coated by the random copolymer with FPS = 0.4 were dispersed in the P2VP domain, while those with FPS = 0.52 were located at the interface. A simple calculation for the adsorption energy to the interface of the nanoparticles

Visualization of the distribution of surface-active block copolymers in PDMS-based coatings

DEFF Research Database (Denmark)

Noguer, A. Camós; Latipov, R.; Madsen, F. B.

2018-01-01

the distribution and release of these block copolymers from PDMS-based coatings has been previously reported. However, the distribution and behaviour of these compounds in the bulk of the PDMS coating are not fully understood. A novel fluorescent-labelled triblock PEG-b-PDMS-b-PEG copolymer was synthesized...... results in non-specific protein adsorption and wettability issues. Poly(ethylene glycol)-based surface-active block copolymers and surfactants have been added to PDMS coatings and films to impart biofouling resistance and hydrophilicity to the PDMS surface with successful results. Information regarding...

Nanoparticles based on novel amphiphilic polyaspartamide copolymers

International Nuclear Information System (INIS)

Craparo, Emanuela Fabiola; Teresi, Girolamo; Ognibene, Maria Chiara; Casaletto, Maria Pia; Bondi, Maria Luisa; Cavallaro, Gennara

2010-01-01

In this article, the synthesis of two amphiphilic polyaspartamide copolymers, useful to obtain polymeric nanoparticles without using surfactants or stabilizing agents, is described. These copolymers were obtained starting from α,β-poly-(N-2-hydroxyethyl)-dl-aspartamide (PHEA) by following a novel synthetic strategy. In particular, PHEA and its pegylated derivative (PHEA-PEG 2000 ) were functionalized with poly(lactic acid) (PLA) through 1,1'-carbonyldiimidazole (CDI) activation to obtain PHEA-PLA and PHEA-PEG 2000 -PLA graft copolymers, respectively. These copolymers were properly purified and characterized by 1 H-NMR, FT-IR, and Size Exclusion Chromatography (SEC) analyses, which confirmed that derivatization reactions occurred. Nanoparticles were obtained from PHEA-PLA and PHEA-PEG 2000 -PLA graft copolymers by using the high pressure homogenization-solvent evaporation method, avoiding the use of surfactants or stabilizing agents. Polymeric nanoparticles were characterized by dimensional analysis, before and after freeze-drying process, and Scanning Electron Microscopy (SEM). Zeta potential measurements and X-ray Photoelectron Spectroscopy (XPS) analysis demonstrated the presence of PEG and/or PHEA onto the PHEA-PEG 2000 -PLA and PHEA-PLA nanoparticle surface, respectively.

Differences in the adsorption behaviour of poly(ethylene oxide) copolymers onto model polystyrene nanoparticles assessed by isothermal titration microcalorimetry correspond to the biological differences.

Science.gov (United States)

Stolnik, S; Heald, C R; Garnett, M G; Illum, L; Davis, S S

2005-01-01

The adsorption behaviour of a tetrafunctional copolymer of poly (ethylene oxide)-poly (propylene oxide) ethylene diamine (commercially available as Poloxamine 908) and a diblock copolymer of poly (lactic acid)-poly (ethylene oxide) (PLA/PEG 2:5) onto a model colloidal drug carrier (156 nm sized polystyrene latex) is described. The adsorption isotherm, hydrodynamic thickness of the adsorbed layers and enthalpy of the adsorption were assessed. The close similarity in the conformation of the poly (ethylene oxide) (PEO) chains (molecular weight 5,000 Da) in the adsorbed layers of these two copolymers was demonstrated by combining the adsorption data with the adsorbed layer thickness data. In contrast, the results from isothermal titration microcalorimetry indicated a distinct difference in the interaction of the copolymers with the polystyrene colloid surface. Poloxamine 908 adsorption to polystyrene nanoparticles is dominated by an endothermic heat effect, whereas, PLA/PEG 2:5 adsorption is entirely an exothermic process. This difference in adsorption behaviour could provide an explanation for differences in the biodistribution of Poloxamine 908 and PLA/PEG 2:5 coated polystyrene nanoparticles observed in previous studies. A comparison with the interaction enthalpy for several other PEO-containing copolymers onto the same polystyrene colloid was made. The results demonstrate the importance of the nature of the anchoring moiety on the interaction of the adsorbing copolymer with the colloid surface. An endothermic contribution is found when an adsorbing molecule contains a poly (propylene oxide) (PPO) moiety (e.g. Poloxamine 908), whilst the adsorption is exothermic (i.e. enthalpy driven) for PEO copolymers with polylactide (PLA/PEG 2:5) or alkyl moieties.

Monolithic route to efficient dye-sensitized solar cells employing diblock copolymers for mesoporous TiO 2

KAUST Repository

Nedelcu, Mihaela; Guldin, Stefan; Orilall, M. Christopher; Lee, Jinwoo; Hü ttner, Sven; Crossland, Edward J. W.; Warren, Scott C.; Ducati, Caterina; Laity, Pete R.; Eder, Dominik; Wiesner, Ulrich; Steiner, Ullrich; Snaith, Henry J.

2010-01-01

We present a material and device based study on the fabrication of mesoporous TiO2 and its integration into dye-sensitized solar cells. Poly(isoprene-block-ethyleneoxide) (PI-b-PEO) copolymers were used as structure directing agents for the sol-gel based synthesis of nanoporous monolithic TiO2 which was subsequently ground down to small particles and processed into a paste. The TiO2 synthesis and the formation of tens of micrometre thick films from the paste is a scalable approach for the manufacture of dye sensitised solar cells (DSCs). In this study, we followed the self-assembly of the material through the various processing stages of DSC manufacture. Since this approach enables high annealing temperatures while maintaining porosity, excellent crystallinity was achieved. Internal TiO 2 structures ranging from the nanometre to micrometre scale combine a high internal surface area with the strong scattering of light, which results in high light absorption and an excellent full-sun power conversion efficiency of up to 6.4% in a robust, 3 μm thick dye-sensitized solar cell. © 2010 The Royal Society of Chemistry.

Distinct Adsorption Configurations and Self-Assembly Characteristics of Fibrinogen on Chemically Uniform and Alternating Surfaces including Block Copolymer Nanodomains

Science.gov (United States)

2015-01-01

Understanding protein–surface interactions is crucial to solid-state biomedical applications whose functionality is directly correlated with the precise control of the adsorption configuration, surface packing, loading density, and bioactivity of protein molecules. Because of the small dimensions and highly amphiphilic nature of proteins, investigation of protein adsorption performed on nanoscale topology can shed light on subprotein-level interaction preferences. In this study, we examine the adsorption and assembly behavior of a highly elongated protein, fibrinogen, on both chemically uniform (as-is and buffered HF-treated SiO2/Si, and homopolymers of polystyrene and poly(methyl methacrylate)) and varying (polystyrene-block-poly(methyl methacrylate)) surfaces. By focusing on high-resolution imaging of individual protein molecules whose configurations are influenced by protein–surface rather than protein–protein interactions, fibrinogen conformations characteristic to each surface are identified and statistically analyzed for structural similarities/differences in key protein domains. By exploiting block copolymer nanodomains whose repeat distance is commensurate with the length of the individual protein, we determine that fibrinogen exhibits a more neutral tendency for interaction with both polystyrene and poly(methyl methacrylate) blocks relative to the case of common globular proteins. Factors affecting fibrinogen–polymer interactions are discussed in terms of hydrophobic and electrostatic interactions. In addition, assembly and packing attributes of fibrinogen are determined at different loading conditions. Primary orientations of fibrinogen and its rearrangements with respect to the underlying diblock nanodomains associated with different surface coverage are explained by pertinent protein interaction mechanisms. On the basis of two-dimensional stacking behavior, a protein assembly model is proposed for the formation of an extended fibrinogen network

Preparation and self-assembly behavior of polystyrene-block-poly (dimethylaminoethyl methacrylate amphiphilic block copolymer using atom transfer radical polymerization

Directory of Open Access Journals (Sweden)

2008-03-01

Full Text Available Asymmetric and semi-symmetric amphiphilic diblock copolymers polystyrene-block-poly (dimethylaminoethyl methacrylate (PS-b-PDMAEMA with the same PS block length of 62 repeat units and quite short (3 repeat units or equivalent (47 repeat units length of PDMAEMA have been prepared simply by varying the ratio of the bromine-terminated macroinitiator polystyrene (PS-Br to DMAEMA using atom transfer radical polymerization (ATRP. The chemical structures and compositions of the PS-b-PDMAEMA block copolymers are studied by nuclear magnetic resonance (NMR spectroscopy, gel permeation chromatography (GPC, and elementary analysis (EA. The self-assembly behaviors of copolymers in N,N-dimethyl formamide (DMF with different pH and dioxane/water binary solvent mixture by direct dissolution method (DD, are studied by transmission electron microscopy (TEM, electron diffracting analysis (EDA, and energy-dispersive analysis of X-rays (EDAX techniques. Transmission electron microscopy results suggest that asymmetric block copolymer PS62-b-PDMAEMA3 (the numbers in the form of footnotes represent repeated units of each monomer in the copolymer can form spherical core-shell micelles, large compound reverse micelles (LCRMs, hexagonal/rhombic phases, reverse hexagonal/rhombic phases, vesicles, reverse vesicles and necklace-like reverse micelles, controlled by common or selective solvent and pH, while most of the aggregates of semi-symmetric PS62-b-PDMAEMA47 are simply spherical, such as spherical core-shell micelles and reverse spherical core-shell micelles, besides hexagonal/rhombic phases. All above structures are controlled by three components of the free energy of aggregation: core-chain stretching, interfacial energy and intercoronal chain interaction.

Structure, viscoelasticity, and interfacial dynamics of a model polymeric bicontinuous microemulsion

Energy Technology Data Exchange (ETDEWEB)

Hickey, Robert J.; Gillard, Timothy M.; Irwin, Matthew T.; Lodge, Timothy P.; Bates, Frank S. (UMM)

2016-01-01

We have systematically studied the equilibrium structure and dynamics of a polymeric bicontinuous microemulsion (BμE) composed of poly(cyclohexylethylene) (PCHE), poly(ethylene) (PE), and a volumetrically symmetric PCHE–PE diblock copolymer, using dynamic mechanical spectroscopy, small angle X-ray and neutron scattering, and transmission electron microscopy. The BμE was investigated over an 80 °C temperature range, revealing a structural evolution and a rheological response not previously recognized in such systems. As the temperature is reduced below the point associated with the lamellar-disorder transition at compositions adjacent to the microemulsion channel, the interfacial area per chain of the BμE approaches that of the neat (undiluted) lamellar diblock copolymer. With increasing temperature, the diblock-rich interface swells through homopolymer infiltration. Time–temperature-superposed linear dynamic data obtained as a function of frequency show that the viscoelastic response of the BμE is strikingly similar to that of the fluctuating pure diblock copolymer in the disordered state, which we associate with membrane undulations and the breaking and reforming of interfaces. This work provides new insights into the structure and dynamics that characterize thermodynamically stable BμEs in the limits of relatively weak and strong segregation.

Ultrafast Self-Assembly of Sub-10 nm Block Copolymer Nanostructures by Solvent-Free High-Temperature Laser Annealing.

Science.gov (United States)

Jiang, Jing; Jacobs, Alan G; Wenning, Brandon; Liedel, Clemens; Thompson, Michael O; Ober, Christopher K

2017-09-20

Laser spike annealing was applied to PS-b-PDMS diblock copolymers to induce short-time (millisecond time scale), high-temperature (300 to 700 °C) microphase segregation and directed self-assembly of sub-10 nm features. Conditions were identified that enabled uniform microphase separation in the time frame of tens of milliseconds. Microphase ordering improved with increased temperature and annealing time, whereas phase separation contrast was lost for very short annealing times at high temperature. PMMA brush underlayers aided ordering under otherwise identical laser annealing conditions. Good long-range order for sub-10 nm cylinder morphology was achieved using graphoepitaxy coupled with a 20 ms dwell laser spike anneal above 440 °C.

The Influence of Charged Species on the Phase Behavior, Self-Assembly, and Electrochemical Performance of Block Copolymer Electrolytes

Science.gov (United States)

Thelen, Jacob Lloyd

lithium metal anode. The increase in the specific energy of a battery upon replacing a graphite anode with lithium metal can offset the losses in performance due to the poor ion conduction of SPEs. However, BCEs that enable the use of a lithium anode and have improved performance would represent a major breakthrough for the development of high capacity batteries. The electrochemical performance of BCEs has a complex relationship with the nature of the microphase separated domains, which is not well-understood. The objective of this dissertation is to provide fundamental insight into the nature of microphase separation and self-assembly of block copolymer electrolytes. Specifically, I will focus on how the ion-polymer interactions within a diverse set of BCEs dictate nanostructure. Combining such insight with knowledge of how nanostructure influences ion motion will enable the rational design of new BCEs with enhanced performance and functionality. In order to facilitate the study of BCE nanostructure, synchrotron-based X-ray scattering techniques were used to study samples over a wide range of length-scales under conditions relevant to the battery environment. The development of the experimental aspects of the X-ray scattering techniques, as well as an improved treatment of scattering data, played a pivotal role in the success of this work. The dissemination of those developments will be the focus of the first section. The thermodynamic impact of adding salt to a neutral diblock copolymer was studied in a model BCE composed of a low molecular weight SEO diblock copolymer mixed with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), a common salt used in lithium batteries. In neutral block copolymers (BCPs), self-assembly is a thermodynamically driven process governed by a balance between unfavorable monomer contacts and the entropy of mixing. When the enthalpic and entropic contributions to free energy are similar in magnitude, a block copolymer can undergo a thermally

Patchy micelles based on coassembly of block copolymer chains and block copolymer brushes on silica particles.

Science.gov (United States)

Zhu, Shuzhe; Li, Zhan-Wei; Zhao, Hanying

2015-04-14

Patchy particles are a type of colloidal particles with one or more well-defined patches on the surfaces. The patchy particles with multiple compositions and functionalities have found wide applications from the fundamental studies to practical uses. In this research patchy micelles with thiol groups in the patches were prepared based on coassembly of free block copolymer chains and block copolymer brushes on silica particles. Thiol-terminated and cyanoisopropyl-capped polystyrene-block-poly(N-isopropylacrylamide) block copolymers (PS-b-PNIPAM-SH and PS-b-PNIPAM-CIP) were synthesized by reversible addition-fragmentation chain transfer polymerization and chemical modifications. Pyridyl disulfide-functionalized silica particles (SiO2-SS-Py) were prepared by four-step surface chemical reactions. PS-b-PNIPAM brushes on silica particles were prepared by thiol-disulfide exchange reaction between PS-b-PNIPAM-SH and SiO2-SS-Py. Surface micelles on silica particles were prepared by coassembly of PS-b-PNIPAM-CIP and block copolymer brushes. Upon cleavage of the surface micelles from silica particles, patchy micelles with thiol groups in the patches were obtained. Dynamic light scattering, transmission electron microscopy, and zeta-potential measurements demonstrate the preparation of patchy micelles. Gold nanoparticles can be anchored onto the patchy micelles through S-Au bonds, and asymmetric hybrid structures are formed. The thiol groups can be oxidized to disulfides, which results in directional assembly of the patchy micelles. The self-assembly behavior of the patchy micelles was studied experimentally and by computer simulation.

Dissipative Particle Dynamics Study of Electrostatic Self-Assembly in Aqueous Mixtures of Copolymers Containing One Neutral Water-Soluble Block and One Either Positively or Negatively Charged Polyelectrolyte Block

Czech Academy of Sciences Publication Activity Database

Šindelka, K.; Limpouchová, Z.; Lísal, Martin; Procházka, K.

2014-01-01

Roč. 47, č. 17 (2014), s. 6121-6134 ISSN 0024-9297 R&D Projects: GA ČR(CZ) GA13-02938S; GA MŠk LH12020 Grant - others:GA ČR(CZ) GAP106/12/0143; GA MŠMT(CZ) LK21302; GA MŠMT(CZ) LM2010005; GA MŠMT(CZ) CZ. 1.05/3.2.00/08.0144 Institutional support: RVO:67985858 Keywords : monte-carlo simulations * molecular-dynamics * diblock copolymer Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 5.800, year: 2014

PCL-PDMS-PCL copolymer-based microspheres mediate cardiovascular differentiation from embryonic stem cells

Science.gov (United States)

Song, Liqing

Poly-epsilon-caprolactone (PCL) based copolymers have received much attention as drug or growth factor delivery carriers and tissue engineering scaffolds due to their biocompatibility, biodegradability, and tunable biophysical properties. Copolymers of PCL and polydimethylsiloxane (PDMS) also have shape memory behaviors and can be made into thermoresponsive shape memory polymers for various biomedical applications such as smart sutures and vascular stents. However, the influence of biophysical properties of PCL-PDMS-PCL copolymers on stem cell lineage commitment is not well understood. In this study, PDMS was used as soft segments of varying length to tailor the biophysical properties of PCL-based co-polymers. While low elastic modulus (affected cardiovascular differentiation of embryonic stem cells, the range of 60-100 MPa PCL-PDMS-PCL showed little influence on the differentiation. Then different size (30-140 mum) of microspheres were fabricated from PCL-PDMS-PCL copolymers and incorporated within embryoid bodies (EBs). Mesoderm differentiation was induced using bone morphogenetic protein (BMP)-4 for cardiovascular differentiation. Differential expressions of mesoderm progenitor marker KDR and vascular markers CD31 and VE-cadherin were observed for the cells differentiated from EBs incorporated with microspheres of different size, while little difference was observed for cardiac marker alpha-actinin expression. Small size of microspheres (30 mum) resulted in higher expression of KDR while medium size of microspheres (94 mum) resulted in higher CD31 and VE-cadherin expression. This study indicated that the biophysical properties of PCL-based copolymers impacted stem cell lineage commitment, which should be considered for drug delivery and tissue engineering applications.

Chain length dependence of the helix orientation in Langmuir-Blodgett monolayers of alpha-helical diblock copolypeptides

NARCIS (Netherlands)

Nguyen, Le-Thu T.; Ardana, Aditya; Vorenkamp, Eltjo J.; ten Brinke, Gerrit; Schouten, Arend J.

2010-01-01

The effect of chain length on the helix orientation of alpha-helical diblock copolypeptides in Langmuir and Langmuir-Blodgett monolayers is reported for the first time. Amphiphilic diblock copolypeptides (PLGA-b-PMLGSLGs) of poly(alpha-L-glutamic acid) (PLGA) and

A poly(ether-ester) copolymer for the preparation of nanocarriers with improved degradation and drug delivery kinetics

International Nuclear Information System (INIS)

Gagliardi, M.; Bertero, A.; Bardi, G.; Bifone, A.

2016-01-01

This paper reports the synthesis and the physicochemical, functional and biological characterisations of nanocarriers made of a novel di-block biodegradable poly(ether-ester) copolymer. This material presents tunable, fast biodegradation rates, but its products are less acidic than those of other biosorbable polymers like PLGA, thus presenting a better biocompatibility profile and the possibility to carry pH-sensitive payloads. A method for the production of monodisperse and spherical nanoparticles is proposed; drug delivery kinetics and blood protein adsorption were measured to evaluate the functional properties of these nanoparticles as drug carriers. The copolymer was labelled with a fluorescent dye for internalisation tests, and rhodamine B was used as a model cargo to study transport and release inside cultured cells. Biological tests demonstrated good cytocompatibility, significant cell internalisation and the possibility to vehiculate non-cell penetrating moieties into endothelial cells. Taken together, these results support the potential use of this nanoparticulate system for systemic administration of drugs. - Highlights: • We propose a novel biodegradable nanocarrier for intracellular drug delivery. • Biodegradation rates can be finely tuned by controlling copolymer composition. • Degradation products are less acidic, thus enabling delivery of pH-sensitive cargoes. • We demonstrate intracellular delivery of a non-cell-penetrating model drug. • No significant membrane damage by the polymer nanocarriers is observed.

A poly(ether-ester) copolymer for the preparation of nanocarriers with improved degradation and drug delivery kinetics

Energy Technology Data Exchange (ETDEWEB)

Gagliardi, M., E-mail: mariacristina.gagliardi@iit.it [Center for Micro Bio-Robotics @SSSA, Istituto Italiano di Tecnologia, Viale Rinaldo Piaggio 34, 56025 Pontedera (Italy); Bertero, A. [Department of Biology, Unit of Cellular and Developmental Biology, University of Pisa, S.S.12 Abetone e Brennero 4, 56127 Pisa (Italy); Center for Neuroscience and Cognitive Systems @UNITN, Istituto Italiano di Tecnologia, Corso Bettini 31, 38068 Rovereto (Italy); Bardi, G. [Center for Bio-Molecular Nanotechnologies @UniLe, Istituto Italiano di Tecnologia, Via Barsanti, 73010 Arnesano (Italy); Bifone, A. [Center for Neuroscience and Cognitive Systems @UNITN, Istituto Italiano di Tecnologia, Corso Bettini 31, 38068 Rovereto (Italy)

2016-02-01

This paper reports the synthesis and the physicochemical, functional and biological characterisations of nanocarriers made of a novel di-block biodegradable poly(ether-ester) copolymer. This material presents tunable, fast biodegradation rates, but its products are less acidic than those of other biosorbable polymers like PLGA, thus presenting a better biocompatibility profile and the possibility to carry pH-sensitive payloads. A method for the production of monodisperse and spherical nanoparticles is proposed; drug delivery kinetics and blood protein adsorption were measured to evaluate the functional properties of these nanoparticles as drug carriers. The copolymer was labelled with a fluorescent dye for internalisation tests, and rhodamine B was used as a model cargo to study transport and release inside cultured cells. Biological tests demonstrated good cytocompatibility, significant cell internalisation and the possibility to vehiculate non-cell penetrating moieties into endothelial cells. Taken together, these results support the potential use of this nanoparticulate system for systemic administration of drugs. - Highlights: • We propose a novel biodegradable nanocarrier for intracellular drug delivery. • Biodegradation rates can be finely tuned by controlling copolymer composition. • Degradation products are less acidic, thus enabling delivery of pH-sensitive cargoes. • We demonstrate intracellular delivery of a non-cell-penetrating model drug. • No significant membrane damage by the polymer nanocarriers is observed.

Synthesis of diblock copolymers comprising poly(2-vinylpyridine-co-acrylonitrile) and polystyrene blocks by nitroxide-mediated radical polymerization

Czech Academy of Sciences Publication Activity Database

Lokaj, Jan; Poláková, Lenka; Holler, Petr; Starovoytova, Larisa; Štěpánek, Petr; Diat, O.

2007-01-01

Roč. 105, č. 3 (2007), s. 1616-1622 ISSN 0021-8995 R&D Projects: GA ČR GESON/03/E001 Institutional research plan: CEZ:AV0Z40500505 Keywords : 2-vinylpyridine-acrylonitrile copolymers * nitroxide-mediated radical copolymerization * chain extension Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.008, year: 2007

A 3x1 integrated pyroelectric sensor based on VDF/TrFE copolymer

NARCIS (Netherlands)

Setiadi, D.; Setiadi, D.; Sarro, P.M.; Regtien, Paulus P.L.

1996-01-01

This paper presents an integrated pyroelectric sensor based on a vinylidene fluoride¿trifluoroethylene (VDF/TrFE) copolymer. A silicon substrate that contains field-effect transistor (FET) readout electronics is coated with the VDF/TrFE copolymer film using a spin-coating technique. On-chip poling

High-Tg Polynorbornene-Based Block and Random Copolymers for Butanol Pervaporation Membranes

Science.gov (United States)

Register, Richard A.; Kim, Dong-Gyun; Takigawa, Tamami; Kashino, Tomomasa; Burtovyy, Oleksandr; Bell, Andrew

Vinyl addition polymers of substituted norbornene (NB) monomers possess desirably high glass transition temperatures (Tg); however, until very recently, the lack of an applicable living polymerization chemistry has precluded the synthesis of such polymers with controlled architecture, or copolymers with controlled sequence distribution. We have recently synthesized block and random copolymers of NB monomers bearing hydroxyhexafluoroisopropyl and n-butyl substituents (HFANB and BuNB) via living vinyl addition polymerization with Pd-based catalysts. Both series of polymers were cast into the selective skin layers of thin film composite (TFC) membranes, and these organophilic membranes investigated for the isolation of n-butanol from dilute aqueous solution (model fermentation broth) via pervaporation. The block copolymers show well-defined microphase-separated morphologies, both in bulk and as the selective skin layers on TFC membranes, while the random copolymers are homogeneous. Both block and random vinyl addition copolymers are effective as n-butanol pervaporation membranes, with the block copolymers showing a better flux-selectivity balance. While polyHFANB has much higher permeability and n-butanol selectivity than polyBuNB, incorporating BuNB units into the polymer (in either a block or random sequence) limits the swelling of the polyHFANB and thereby improves the n-butanol pervaporation selectivity.

Langmuir monolayers of non-ionic polymers: Equilibrium of metastability? Case study of PEO and its PPO-PEO diblock copolymers

NARCIS (Netherlands)

Deschenes, L.; Saint-Germain, F.; Lyklema, J.

2015-01-01

Stability and reorganization in Langmuir films of PEO in PEO homopolymers and PPO–PEO block copolymers were investigated using film balance measurements. The apparent fractional losses of EO segments transferred into the subphase resulting from successive compression–expansion cycles have been

Biosynthesis and characterization of diblock copolymer of p(3-hydroxypropionate)-block-p(4-hydroxybutyrate) from recombinant Escherichia coli

DEFF Research Database (Denmark)

Tripathi, Lakshmi; Wu, Linping; Meng, Dechuan

2013-01-01

Poly(4-hydroxybutyrate) (P4HB) is a highly elastic polymer, whereas poly(3-hydroxypropionate) (P3HP) is a polymer with enormous tensile strength. This study aimed to biosynthesize a block copolymer consisting of soft P4HB block with a strong P3HP block to gain unique and excellent material proper...

Self-assembly in poly(dimethylsiloxane)-poly(ethylene oxide) block copolymer template directed synthesis of Linde type A zeolite.

Science.gov (United States)

Bonaccorsi, Lucio; Calandra, Pietro; Kiselev, Mikhail A; Amenitsch, Heinz; Proverbio, Edoardo; Lombardo, Domenico

2013-06-11

We describe the hydrothermal synthesis of zeolite Linde type A (LTA) submicrometer particles using a water-soluble amphiphilic block copolymer of poly(dimethylsiloxane)-b-poly(ethylene oxide) as a template. The formation and growth of the intermediate aggregates in the presence of the diblock copolymer have been monitored by small-angle X-ray scattering (SAXS) above the critical micellar concentration at a constant temperature of 45 °C. The early stage of the growth process was characterized by the incorporation of the zeolite LTA components into the surface of the block copolymer micellar aggregates with the formation of primary units of 4.8 nm with a core-shell morphology. During this period, restricted to an initial time of 1-3 h, the core-shell structure of the particles does not show significant changes, while a subsequent aggregation process among these primary units takes place. A shape transition of the SAXS profile at the late stage of the synthesis has been connected with an aggregation process among primary units that leads to the formation of large clusters with fractal characteristics. The formation of large supramolecular assemblies was finally verified by scanning electron microscopy, which evidenced the presence of submicrometer aggregates with size ranging between 100 and 300 nm, while X-ray diffraction confirmed the presence of crystalline zeolite LTA. The main finding of our results gives novel insight into the mechanism of formation of organic-inorganic mesoporous materials based on the use of a soft interacting nanotemplate as well as stimulates the investigation of alternative protocols for the synthesis of novel hybrid materials with new characteristics and properties.

Polymersomes from dual responsive block copolymers: drug encapsulation by heating and acid-triggered release.

Science.gov (United States)

Qiao, Zeng-Ying; Ji, Ran; Huang, Xiao-Nan; Du, Fu-Sheng; Zhang, Rui; Liang, De-Hai; Li, Zi-Chen

2013-05-13

A series of well-defined thermoresponsive diblock copolymers (PEO45-b-PtNEAn, n=22, 44, 63, 91, 172) were prepared by the atom transfer radical polymerization of trans-N-(2-ethoxy-1,3-dioxan-5-yl) acrylamide (tNEA) using a poly(ethylene oxide) (PEO45) macroinitiator. All copolymers are water-soluble at low temperature, but upon quickly heating to 37 °C, laser light scattering (LLS) and transmission electron microscopy (TEM) characterizations indicate that these copolymers self-assemble into aggregates with different morphologies depending on the chain length of PtNEA and the polymer concentration; the morphologies gradually evolved from spherical solid nanoparticles to a polymersome as the degree of polymerization ("n") of PtNEA block increased from 22 to 172, with the formation of clusters with rod-like structure at the intermediate PtNEA length. Both the spherical nanoparticle and the polymersome are stable at physiological pH but susceptible to the mildly acidic medium. Acid-triggered hydrolysis behaviors of the aggregates were investigated by LLS, Nile red fluorescence, TEM, and (1)H NMR spectroscopy. The results revealed that the spherical nanoparticles formed from PEO45-b-PtNEA44 dissociated faster than the polymersomes of PEO45-b-PtNEA172, and both aggregates showed an enhanced hydrolysis under acidic conditions. Both the spherical nanoparticle and polymersome are able to efficiently load the hydrophobic doxorubicin (DOX), and water-soluble fluorescein isothiocyanate-lysozyme (FITC-Lys) can be conveniently encapsulated into the polymersome without using any organic solvent. Moreover, FITC-Lys and DOX could be coloaded in the polymersome. The drugs loaded either in the polymersome or in the spherical nanoparticle could be released by acid triggering. Finally, the DOX-loaded assemblies display concentration-dependent cytotoxicity to HepG2 cells, while the copolymers themselves are nontoxic.

A Comprehensive Systematic Study on Thermoresponsive Gels: Beyond the Common Architectures of Linear Terpolymers

Directory of Open Access Journals (Sweden)

Anna P. Constantinou

2017-01-01

Full Text Available In this study, seven thermoresponsive methacrylate terpolymers with the same molar mass (MM and composition but various architectures were successfully synthesized using group transfer polymerization (GTP. These terpolymers were based on tri(ethylene glycol methyl ether methacrylate (TEGMA, A unit, n-butyl methacrylate (BuMA, B unit, and 2-(dimethylaminoethyl methacrylate (DMAEMA, C unit. Along with the more common ABC, ACB, BAC, and statistical architectures, three diblock terpolymers were also synthesized and investigated for the first time, namely (ABC, A(BC, and B(AC; where the units in the brackets are randomly copolymerized. Two BC diblock copolymers were also synthesized for comparison. Their hydrodynamic diameters and their effective pKas were determined by dynamic light scattering (DLS and hydrogen ion titrations, respectively. The self-assembly behavior of the copolymers was also visualized by transmission electron microscopy (TEM. Both dilute and concentrated aqueous copolymer solutions were extensively studied by visual tests and their cloud points (CP and gel points were determined. It is proven that the aqueous solution properties of the copolymers, with specific interest in their thermoresponsive properties, are influenced by the architecture, with the ABC and A(BC ones to show clear sol-gel transition.

Polymeric bicontinuous microemulsions

DEFF Research Database (Denmark)

Bates, F.S.; Maurer, W.W.; Lipic, P.M.

1997-01-01

High molecular weight block copolymers can be viewed as macromolecular surfactants when blended with thermodynamically incompatible homopolymers. This Letter describes the formation of polymeric bicontinuous microemulsions in nurtures containing a model diblock copolymer and two homopolymers. Alt...

Inner Stucture of Thin Films of Lamellar Poly(styrene-em>b>-butadiene) Diblock Copolymers as revealed by Grazing-Incidence Small-Angle Scattering

DEFF Research Database (Denmark)

Busch, Peter; Posselt, Dorthe; Smilgies, Detlef-Matthias

2007-01-01

The lamellar orientation in supported, thin films of poly(styrene-b-butadiene) (P(S-b-B)) depends on block copolymer molar mass. We have studied films from nine block copolymer samples with molar masses between 13.9 and 183 kg/mol using grazing-incidence small-angle X-ray scattering (GISAXS) and ...... quantitatively in the framework of our recently developed distorted-wave Born approximation model (Busch, P.; et al. J. Appl. Crystallogr. 2006, 39, 433). The results cannot be explained from enthalpic considerations alone but point to the importance of entropic factors....

PEO-related block copolymer surfactants

DEFF Research Database (Denmark)

Mortensen, K.

2001-01-01

Non-ionic block copolymer systems based on hydrophilic poly(ethylene oxide) and more hydrophobic co-polymer blocks are used intensively in a variety of industrial and personal applications. A brief description on the applications is presented. The physical properties of more simple model systems...... of such PEG-based block copolymers in aqueous suspensions are reviewed. Based on scattering experiments using either X-ray or neutrons, the phase behavior is characterized, showing that the thermo-reversible gelation is a result of micellar ordering into mesoscopic crystalline phases of cubic, hexagonal...

In vitro degradation of nanoparticles prepared from polymers based on DL-lactide, glycolide and poly(ethylene oxide)

NARCIS (Netherlands)

Zweers, M.L.T.; Engbers, G.H.M.; Grijpma, Dirk W.; Feijen, Jan

2004-01-01

Nanoparticles of poly(DL-lactic acid) (PDLLA), poly(DL-lactic-co-glycolic acid) (PLGA) and poly(ethylene oxide)–PLGA diblock copolymer (PEO–PLGA) were prepared by the salting-out method. The in vitro degradation of PDLLA, PLGA and PEO–PLGA nanoparticles in PBS (pH 7.4) at 37 °C was studied. The

Polyether based segmented copolymers with uniform aramid units

NARCIS (Netherlands)

Niesten, M.C.E.J.

2000-01-01

Segmented copolymers with short, glassy or crystalline hard segments and long, amorphous soft segments (multi-block copolymers) are thermoplastic elastomers (TPE’s). The hard segments form physical crosslinks for the amorphous (rubbery) soft segments. As a result, this type of materials combines

Morphological and physical characterization of poly(styrene-isobutylene-styrene) block copolymers and ionomers thereof

Science.gov (United States)

Baugh, Daniel Webster, III

Poly(styrene-isobutylene-styrene) block copolymers made by living cationic polymerization using a difunctional initiator and the sequential monomer addition technique were analyzed using curve-resolution software in conjunction with high-resolution GPC. Fractional precipitation and selective solvent extraction were applied to a representative sample in order to confirm the identity of contaminating species. The latter were found to be low molecular weight polystyrene homopolymer, diblock copolymer, and higher molecular weight segmented block copolymers formed by intermolecular electrophilic aromatic substitution linking reactions occurring late in the polymerization of the styrene outer blocks. Solvent-cast films of poly(styrene-isobutylene-styrene) (PS-PIB-PS) block copolymers and block ionomers were analyzed using small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). Four block copolymer samples with center block molecular weights of 52,000 g/mol and PS volume fractions (o sbPS) ranging from 0.17 to 0.31 were studied. All samples exhibited hexagonally packed cylinders of PS within the PIB matrix. Cylinder spacing was in the range 32 to 36 nm for most samples, while cylinder diameters varied from 14 to 21 nm. Porod analysis of the scattering data indicated the presence of isolated phase mixing and sharp phase boundaries. PS-PIB-PS block copolymers and ionomers therefrom were analyzed using dynamic mechanical analysis (DMA) and tensile testing. The study encompassed five block copolymer samples with similar PIB center blocks with molecular weights of approx52,000 g/mol and PS weight fractions ranging from 0.127 to 0.337. Ionomers were prepared from two of these materials by lightly sulfonating the PS outer blocks. Sulfonation levels varied from 1.7 to 4.7 mol % and the sodium and potassium neutralized forms were compared to the parent block copolymers. Dynamic mechanical analysis (DMA) of the block copolymer films indicated the existence

Highly filled biocomposites based on ethylene-vinyl acetate copolymer and wood flour

Science.gov (United States)

Shelenkov, P. G.; Pantyukhov, P. V.; Popov, A. A.

2018-05-01

Recently, there is a great interest in the world to biodegradable materials based on synthetic polymers in a composition with natural fillers. Highly filled polymer composite materials based on various grades of synthetic block copolymer of ethylene vinyl acetate with wood flour were under investigation. Five grades of ethylene-vinyl acetate copolymer differing in the content of vinyl acetate groups and a melt flow index were used in this work in order to find the best one for highly filled biocomposites. Wood flour content in biocomposites was 50, 60, 70 weight %. The rheological and physico-mechanical characteristics of the resulting biocomposites were studied.

Poly(ortho-phenylenediamine-co-aniline) based copolymer with improved capacitance

Science.gov (United States)

Olmedo-Martínez, Jorge L.; Farías-Mancilla, Bárbara I.; Vega-Rios, Alejandro; Zaragoza-Contreras, E. Armando

2017-10-01

A poly(ortho-phenylenediamine-co-aniline) copolymer is synthesized via the oxidative route, using a 1:1 M ratio of aniline to ortho-phenylenediamine (oPDA) and ammonium persulfate as the oxidizing agent. Infrared spectroscopy indicates that the copolymer contains the functional groups typically present in polyaniline and poly(ortho-phenylenediamine); whereas UV-vis-NIR spectroscopy shows that the copolymer adopts a phenazine-type structure. Cyclic voltammetry evidences the copolymer synthesis, as a redox peak at -65 mV, different from those exhibited by polyaniline (160 mV and 600 mV) or poly(o-phenylenediamine) (-240 mV) is observed. Finally, electrochemical impedance spectroscopy and the charge/discharge test provide support to propose the copolymer application in electrodes for supercapacitors.

Flexible control of cellular encapsulation, permeability, and release in a droplet-templated bifunctional copolymer scaffold.

Science.gov (United States)

Chen, Qiushui; Chen, Dong; Wu, Jing; Lin, Jin-Ming

2016-11-01

Designing cell-compatible, bio-degradable, and stimuli-responsive hydrogels is very important for biomedical applications in cellular delivery and micro-scale tissue engineering. Here, we report achieving flexible control of cellular microencapsulation, permeability, and release by rationally designing a diblock copolymer, alginate-conjugated poly(N-isopropylacrylamide) (Alg-co-PNiPAM). We use the microfluidic technique to fabricate the bifunctional copolymers into thousands of mono-disperse droplet-templated hydrogel microparticles for controlled encapsulation and triggered release of mammalian cells. In particular, the grafting PNiPAM groups in the synthetic cell-laden microgels produce lots of nano-aggregates into hydrogel networks at elevated temperature, thereafter enhancing the permeability of microparticle scaffolds. Importantly, the hydrogel scaffolds are readily fabricated via on-chip quick gelation by triggered release of Ca 2+ from the Ca-EDTA complex; it is also quite exciting that very mild release of microencapsulated cells is achieved via controlled degradation of hydrogel scaffolds through a simple strategy of competitive affinity of Ca 2+ from the Ca-Alginate complex. This finding suggests that we are able to control cellular encapsulation and release through ion-induced gelation and degradation of the hydrogel scaffolds. Subsequently, we demonstrate a high viability of microencapsulated cells in the microgel scaffolds.

Tuning of the Morphology and Optoelectronic Properties of ZnO/P3HT/P3HT- b-PEO Hybrid Films via Spray Deposition Method.

Science.gov (United States)

Wang, Kun; Bießmann, Lorenz; Schwartzkopf, Matthias; Roth, Stephan V; Müller-Buschbaum, Peter

2018-06-20

The self-assembly of amphiphilic diblock copolymers yields the possibility of using them as a template for tailoring the film morphologies of sol-gel chemistry-derived inorganic electron transport materials, such as mesoporous ZnO and TiO 2 . However, additional steps including etching and backfilling are required for the common bulk heterojunction fabrication process when using insulating diblock copolymers. Here, we use the conducting diblock copolymer poly(3-hexylthiophene)- block-poly(ethylene oxide) (P3HT- b-PEO) in which P3HT acts as charge carrier transport material and light absorber, whereas PEO serves as a template for ZnO synthesis. The initial solution is subsequently spray-coated to obtain the hybrid film. Scanning electron microscopy and grazing-incidence small-angle X-ray scattering measurements reveal a significant change in the morphology of the hybrid films during deposition. Optoelectronic properties illustrate the improved charge separation and charge transfer process. Both the amount of the diblock copolymer and the annealing temperature play an important role in tuning the morphology and the optoelectronic properties. Hybrid films being sprayed from a solution with the ratio of ω ZnO , ω P3HT , and ω P3HT- b-PEO of 2:1:1 and subsequent annealing at 80 °C show the most promising morphology combined with an optimal photoluminescence quenching. Thus, the presented simple, reagent- and energy-saving fabrication method provides a promising approach for a large-scale preparation of bulk heterojunction P3HT/ZnO films on flexible substrates.

Styrene-Based Copolymer for Polymer Membrane Modifications

OpenAIRE

Harsha Srivastava; Harshad Lade; Diby Paul; G. Arthanareeswaran; Ji Hyang Kweon

2016-01-01

Poly(vinylidene fluoride) (PVDF) was modified with a styrene-based copolymer. The crystalline behavior, phase, thermal stability, and surface morphology of the modified membranes were analyzed. The membrane surface roughness showed a strong dependence on the styrene-acrylonitrile content and was reduced to 34% for a PVDF/styrene-acrylonitrile blend membrane with a 40/60 ratio. The thermal and crystalline behavior confirmed the blend miscibility of both polymers. It was observed in X-ray diffr...

Associative, thermodynamic and thermo-kinetics behavior of di- and triblock copolymers of oxyethylene and oxybutylene in aqueous media

International Nuclear Information System (INIS)

Khan, Abbas; Siddiq, Mohammad

2014-01-01

Highlights: • Associative, thermodynamic and thermo-kinetics behavior was investigated. • Micellization of these copolymer is spontaneous, endothermic and entropy driven. • Micelles are spherical in shape and their nature depends on temperature. • Fusion/fission mechanism dominates over unimer entry/expulsion for micellar dynamics. • Micellar parameters depend on temperature and on the delicate hydrophobic–hydrophilic balance of the blocks. - Abstract: The associative, thermodynamic and thermo-kinetics properties of a diblock E 90 B 10 and three triblock copolymers based on polyoxyethylene and polyoxybutylene of the type E m B 10 E m water have been studied by surface tensiometry, light scattering and temperature-jump stopped-flow techniques. The data from surface tension was helpful to detect the critical micelle concentration (CMC) as well as to calculate the thermodynamic parameters of micellization. Dynamic light scattering (DLS) was employed to obtain the values of hydrodynamic radii (R h ), volume (υ h ) and hydrodynamic expansion parameter (δ h ) of the micelle at different temperatures. Similarly, static light scattering (SLS) measurements made us enable to find out various micellar parameters such as; weight-average molar (M w ), association number (N w ), thermodynamic radius (R t ), thermodynamic volume (υ t ), anhydrous volume (υ a ) and thermodynamic expansion parameter (δ t ) of the micelles. Likewise, the kinetics of micellar aggregation/dynamic was also investigated by using temperature-jump stopped-flow technique in the temperature range of 20–50 °C

Effect of side chain position on solar cell performance in cyclopentadithiophene-based copolymers

International Nuclear Information System (INIS)

Lee, Sang Kyu; Seo, Jung Hwa; Cho, Nam Sung; Cho, Shinuk

2012-01-01

The photovoltaic properties of a series of low band-gap conjugated copolymers, in which alkyl side chains were substituted at various positions, were investigated using donor–acceptor (D–A) conjugated copolymers consisting of a cyclopentadithiophene derivative and dithienyl-benzothiadiazole. The base polymer, which has no alkyl side chains, yielded promising power conversion efficiency of 3.8%. Polymers with alkyl side chains, however, exhibited significantly decreased performance. In addition, the effects of processing additive became negligible. The results indicate that substituted side chains, which were introduced to improve solubility, critically affected the optical and electronic properties of D–A conjugated copolymers. Furthermore, the position of the side chain was also very important for controlling the morphological properties of the D–A conjugated copolymers. - Highlights: ► Effect of side chain position on solar cell performance was investigated. ► Polymer without alkyl chains yielded promising power conversion efficiency of 3.8%. ► Position of side chains critically affected the optical and electronic properties.

Drug delivery system design and development for boron neutron capture therapy on cancer treatment

International Nuclear Information System (INIS)

Sherlock Huang, Lin-Chiang; Hsieh, Wen-Yuan; Chen, Jiun-Yu; Huang, Su-Chin; Chen, Jen-Kun; Hsu, Ming-Hua

2014-01-01

We have already synthesized a boron-containing polymeric micellar drug delivery system for boron neutron capture therapy (BNCT). The synthesized diblock copolymer, boron-terminated copolymers (Bpin-PLA-PEOz), consisted of biodegradable poly(D,L-lactide) (PLA) block and water-soluble polyelectrolyte poly(2-ethyl-2-oxazoline) (PEOz) block, and a cap of pinacol boronate ester (Bpin). In this study, we have demonstrated that synthesized Bpin-PLA-PEOz micelle has great potential to be boron drug delivery system with preliminary evaluation of biocompatibility and boron content. - Highlights: • Herein, we have synthesized boron-modified diblock copolymer. • Bpin-PLA-PEOz, which will be served as new boron containing vehicle for transporting the boron drug. • This boron containing Bpin-PLA-PEOz micelle was low toxicity can be applied to drug delivery

Morphologies of precise polyethylene-based acid copolymers and ionomers

Science.gov (United States)

Buitrago, C. Francisco

Acid copolymers and ionomers are polymers that contain a small fraction of covalently bound acidic or ionic groups, respectively. For the specific case of polyethylene (PE), acid and ionic pendants enhance many of the physical properties such as toughness, adhesion and rheological properties. These improved properties result from microphase separated aggregates of the polar pendants in the non-polar PE matrix. Despite the widespread industrial use of these materials, rigorous chemical structure---morphology---property relationships remain elusive due to the inevitable structural heterogeneities in the historically-available acid copolymers and ionomers. Recently, precise acid copolymers and ionomers were successfully synthesized by acyclic diene metathesis (ADMET) polymerization. These precise materials are linear, high molecular weight PEs with pendant acid or ionic functional groups separated by a precisely controlled number of carbon atoms. The morphologies of nine precise acid copolymers and eleven precise ionomers were investigated by X-ray scattering, solid-state 13C nuclear magnetic resonance (NMR) and differential scanning calorimetry (DSC). For comparison, the morphologies of linear PEs with pseudo-random placement of the pendant groups were also studied. Previous studies of precise copolymers with acrylic acid (AA) found that the microstructural precision produces a new morphology in which PE crystals drive the acid aggregates into layers perpendicular to the chain axes and presumably at the interface between crystalline and amorphous phases. In this dissertation, a second new morphology for acid copolymers is identified in which the aggregates arrange on cubic lattices. The fist report of a cubic morphology was observed at room and elevated temperatures for a copolymer functionalized with two phosphonic acid (PA) groups on every 21st carbon atom. The cubic lattice has been identified as face-centered cubic (FCC). Overall, three morphology types have been

Poly(ethylene oxide)–Poly(propylene oxide)-Based Copolymers for ...

African Journals Online (AJOL)

Amphiphilic poly(ethylene oxide)–poly(propylene oxide) (PEO–PPO)-based copolymers are thermoresponsive materials having aggregation properties in aqueous medium. As hydrosolubilizers of poorly water-soluble drugs and improved stability of sensitive agents, these materials have been investigated for improvement ...

The plumber's nightmare: a new morphology in block copolymer-ceramic nanocomposites and mesoporous aluminosilicates.

Science.gov (United States)

Finnefrock, Adam C; Ulrich, Ralph; Toombes, Gilman E S; Gruner, Sol M; Wiesner, Ulrich

2003-10-29

A novel cubic bicontinuous morphology is found in polymer-ceramic nanocomposites and mesoporous aluminosilicates that are derived by an amphiphilic diblock copolymer, poly(isoprene-b-ethylene oxide) (PI-b-PEO), used as a structure-directing agent for an inorganic aluminosilicate. Small-angle X-ray scattering (SAXS) was employed to unambiguously identify the Im(-)3m crystallographic symmetry of the materials by fitting individual Bragg peak positions in the two-dimensional X-ray images. Structure factor calculations, in conjunction with results from transmission electron microscopy, were used to narrow the range of possible structures consistent with the symmetry and showed the plumber's nightmare morphology to be consistent with the data. The samples are made by deposition onto a substrate that imposes a strain field, generating a lattice distortion. This distortion is quantitatively analyzed and shown to have resulted in shrinkage of the crystallites by approximately one-third in a direction perpendicular to the substrate, in both as-made composites and calcined ceramic materials. Finally, the observation of the bicontinuous block-copolymer-derived hybrid morphology is discussed in the context of a pseudo-ternary morphology diagram and compared to existing studies of ternary phase diagrams of amphiphiles in a mixture of two solvents. The calcined mesoporous materials have potential applications in the fields of catalysis, separation technology, and microelectronics.

Well-defined Polymethylene-Based Co/Terpolymers by Combining Anthracene/Maleimide Diels-Alder Reaction with Polyhomologation

KAUST Repository

Hadjichristidis, Nikolaos

2015-05-26

A novel strategy towards well-defined polymethylene-based co/terpolymers, by combining anthracene/maleimide Diels-Alder reaction with polyhomologation, is presented. For the synthesis of diblock copolymers the following approach was applied: a) synthesis of α-anthracene-ω-hydroxy- polymethylene by polyhomologation using tri (9-anthracene-methyl propyl ether) borane as initiator, b) synthesis of furan-protected-maleimide-terminated poly (ε-caprolactone) or polyethylene glycol and c). Diels-Alder reaction between the anthracene and maleimide-terminated polymers. In the case of triblock terpolymers the α-anthracene-ω-hydroxy-polymethylene was used as macroinitiator for the ring-opening polymerization of D, L-lactide to afford an anthracene-terminated PM-b-PLA copolymer, followed by Diels-Alder reaction with furan-protected maleimide-terminated poly (ε-caprolactone) or polyethylene glycol to give the triblock terpolymers. All intermediate and final products were characterized by SEC, 1H NMR, UV-VIS spectroscopy and DSC.

About morphology in ethylene-propylene(-diene) copolymers-based latexes

NARCIS (Netherlands)

Tillier, D.L.; Meuldijk, J.; Hoehne, G.W.H.; Frederik, P.M.; Regev, O.; Koning, C.E.

2005-01-01

Coatings and engineering plastics often require high impact strength. This property can be achieved with tougheners. For the present paper, core-shell impact modifiers were synthesized using ethylene–propylene copolymers (EPM), ethylene–propylene-diene copolymers (EPDM) or a mixture of both types

A new method to analyze copolymer based superplasticizer traces in cement leachates.

Science.gov (United States)

Guérandel, Cyril; Vernex-Loset, Lionel; Krier, Gabriel; De Lanève, Michel; Guillot, Xavier; Pierre, Christian; Muller, Jean François

2011-03-15

Enhancing the flowing properties of fresh concrete is a crucial step for cement based materials users. This is done by adding polymeric admixtures. Such additives have enabled to improve final mechanicals properties and the development of new materials like high performance or self compacting concrete. Like this, the superplasticizers are used in almost cement based materials, in particular for concrete structures that can have a potential interaction with drinking water. It is then essential to have suitable detection techniques to assess whether these organic compounds are dissolved in water after a leaching process or not. The main constituent of the last generation superplasticizer is a PolyCarboxylate-Ester copolymer (PCE), in addition this organic admixture contains polyethylene oxide (free PEO) which constitutes a synthesis residue. Numerous analytical methods are available to characterize superplasticizer content. Although these techniques work well, they do not bring suitable detection threshold to analyze superplasticizer traces in solution with high mineral content such as leachates of hardened cement based materials formulated with superplasticizers. Moreover those techniques do not enable to distinguish free PEO from PCE in the superplasticizer. Here we discuss two highly sensitive analytical methods based on mass spectrometry suitable to perform a rapid detection of superplasticizer compounds traces in CEM I cement paste leachates: MALDI-TOF mass spectrometry, is used to determine the free PEO content in the leachate. However, industrial copolymers (such as PCE) are characterized by high molecular weight and polymolecular index. These two parameters lead to limitation concerning analysis of copolymers by MALDI-TOFMS. In this study, we demonstrate how pyrolysis and a Thermally assisted Hydrolysis/Methylation coupled with a triple-quadrupole mass spectrometer, provides good results for the detection of PCE copolymer traces in CEM I cement paste

Directed Self-Assembly of Triblock Copolymer on Chemical Patterns for Sub-10-nm Nanofabrication via Solvent Annealing.

Science.gov (United States)

Xiong, Shisheng; Wan, Lei; Ishida, Yoshihito; Chapuis, Yves-Andre; Craig, Gordon S W; Ruiz, Ricardo; Nealey, Paul F

2016-08-23

Directed self-assembly (DSA) of block copolymers (BCPs) is a leading strategy to pattern at sublithographic resolution in the technology roadmap for semiconductors and is the only known solution to fabricate nanoimprint templates for the production of bit pattern media. While great progress has been made to implement block copolymer lithography with features in the range of 10-20 nm, patterning solutions below 10 nm are still not mature. Many BCP systems self-assemble at this length scale, but challenges remain in simultaneously tuning the interfacial energy atop the film to control the orientation of BCP domains, designing materials, templates, and processes for ultra-high-density DSA, and establishing a robust pattern transfer strategy. Among the various solutions to achieve domains that are perpendicular to the substrate, solvent annealing is advantageous because it is a versatile method that can be applied to a diversity of materials. Here we report a DSA process based on chemical contrast templates and solvent annealing to fabricate 8 nm features on a 16 nm pitch. To make this possible, a number of innovations were brought in concert with a common platform: (1) assembling the BCP in the phase-separated, solvated state, (2) identifying a larger process window for solvated triblock vs diblock BCPs as a function of solvent volume fraction, (3) employing templates for sub-10-nm BCP systems accessible by lithography, and (4) integrating a robust pattern transfer strategy by vapor infiltration of organometallic precursors for selective metal oxide synthesis to prepare an inorganic hard mask.

Double-brush Langmuir-Blodgett monolayers of alpha-helical diblock copolypeptides

NARCIS (Netherlands)

Nguyen, Le-Thu T.; Vorenkamp, Eltjo J.; Daumont, Christophe J. M.; ten Brinke, Gerrit; Schouten, Arend J.; Vukovic, Ivana; Loos, Katja

2010-01-01

The synthesis of amphiphilic diblock copolypeptides consisting of poly(alpha-L-glutamic acid) (PLGA) and poly(gamma-methyl-L-glutamate-ran-gamma-stearyl-L-glutamate) with 30 mol % of stearyl substituents (PMLGSLG) and their monolayer behavior at the air-water interface have been studied.

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

International Nuclear Information System (INIS)

Torikai, Naoya; Mogi, Yasuhiro; Matsushita, Yushu; Noda, Ichiro; Han, C.C.

1993-01-01

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 (S H ) and 2-vinylpyridine homopolymer (P H ) 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)

Mechanism-Based Enhanced Delivery of Drug-Loaded Targeted Nanoparticles for Breast Cancer Therapy

Science.gov (United States)

2014-02-01

hydrophilic polymeric segments (block ionomers) were used for the synthesis of nanogels. Polymethacrylic acid (PMA) and polyglutamic acid (PGA) were used...Fabrication of the nanogels involves condensation of diblock copolymers of poly(ethylene oxide) (PEG) and poly(carboxylic acid ) by divalent metal cations into...theoretical extent of cross-linking. The theoretical extent of cross-linking has been controlled by the ratio of amine functional groups to carboxylic acid

Micellizationa and Gelation of Water Soluable Thermo-and Light-sensitive Block Copolymer Investigated by SANS

Science.gov (United States)

He, Lilin; Hu, Bin; Zhao, Bin

2015-03-01

Here we present an extensive small-angle neutron scattering (SANS) characterization of micellization and gelation of PEO-b-P(TEGEA-co-NBA) in deuterated water in a wide range of temperatures and concentrations before and after the removal of o-nitrobenzyl group by UV irradiation. Scattering data analysis indicated that unimers predominated in the solutions at low temperatures and concentrations. The polymer self-assembled into micelles with the P(TEGEA-co-NBA) block packed into the core and PEO forming the corona layer. A core-shell model was used to fit SANS data and obtain sizes and scattering length densities. Structural parameters such as the aggregation numbers, the radius of gyration of the chains in the shell region, the number of water molecules in the both regions were determined. The structural information combined with the rheological data were used to describe the phase behaviors of the diblock copolymer in aqueous solution.

Atomic layer deposition assisted pattern transfer technology for ultra-thin block copolymer films

Energy Technology Data Exchange (ETDEWEB)

Chen, Wenhui; Luo, Jun; Meng, Lingkuan; Li, Junjie; Xiang, Jinjuan; Li, Junfeng; Wang, Wenwu; Chen, Dapeng; Ye, Tianchun; Zhao, Chao

2016-08-31

As an emerging developing technique for next-generation lithography, directed self-assembly (DSA) of block copolymer (BCP) has attracted numerous attention and has been a potential alternative to supplement the intrinsic limitations of conventional photolithography. In this work, the self-assembling properties of a lamellar diblock copolymer poly(styrene-b-methylmethacrylate) (PS-b-PMMA, 22k-b-22k, L{sub 0} = 25 nm) on Si substrate and an atomic layer deposition (ALD)-assisted pattern transfer technology for the application of DSA beyond 16/14 nm complementary metal oxide semiconductor (CMOS) technology nodes, were investigated. Firstly, two key processing parameters of DSA, i.e. annealing temperatures and durations of BCP films, were optimized to achieve low defect density and high productivity. After phase separation of BCP films, self-assembling patterns of low defect density should be transferred to the substrate. However, due to the nano-scale thickness and the weak resistance of BCP films to dry etching, it is nearly impossible to transfer the BCP patterns directly to the substrate. Therefore, an ALD-based technology was explored in this work, in which deposited Al{sub 2}O{sub 3} selectively reacts with PMMA blocks thus hardening the PMMA patterns. After removing PS blocks by plasma etching, hardened PMMA patterns were left and transferred to underneath SiO{sub 2} hard mask layer. Using this patterned hard mask, nanowire array of 25 nm pitch were realized on Si substrate. From this work, a high-throughput DSA baseline flow and related ALD-assisted pattern transfer technique were developed and proved to have good capability with the mainstream CMOS technology. - Highlights: • Optimization on self-assembly process for high productivity and low defectivity • Enhancement of etching ratio and resistance by atomic layer deposition (ALD) • A hard mask was used for pattern quality improvement and contamination control.

Poly(ether amide) segmented block copolymers with adipicacid based tetra amide segments

NARCIS (Netherlands)

Biemond, G.J.E.; Feijen, Jan; Gaymans, R.J.

2007-01-01

Poly(tetramethylene oxide)-based poly(ether ester amide)s with monodisperse tetraamide segments were synthesized. The tetraamide segment was based on adipic acid, terephthalic acid, and hexamethylenediamine. The synthesis method of the copolymers and the influence of the tetraamide concentration,

Investigating Block-Copolymer Micelle Dynamics for Tunable Cargo Delivery

Science.gov (United States)

Li, Xiuli; Kidd, Bryce; Cooksey, Tyler; Robertson, Megan; Madsen, Louis

Block-copolymer micelles (BCPMs) can carry molecular cargo in a nanoscopic package that is tunable using polymer structure in combination with cargo properties, as well as with external stimuli such as temperature or pH. For example, BCPMs can be used in targeted anticancer drug delivery due to their biocompatibility, in vivo degradability and prolonged circulation time. We are using NMR spectroscopy and diffusometry as well as SANS to investigate BCPMs. Here we study a diblock poly(ethylene oxide)-b-(caprolactone) (PEO-PCL) that forms spherical micelles at 1% (w/v) in the mixed solvent D2O/THF-d8. We quantify the populations and diffusion coefficients of coexisting micelles and free unimers over a range of temperatures and solvent compositions. We use temperature as a stimulus to enhance unimer exchange and hence trigger cargo release, in some cases at a few degrees above body temperature. We present evidence for dominance of the insertion-expulsion mechanism of unimer exchange in these systems, and we map phase diagrams versus temperature and solvent composition. This study sheds light on how intermolecular interactions fundamentally affect cargo release, unimer exchange, and overall micelle tunability.

Precision design of ethylene- and polar-monomer-based copolymers by organometallic-mediated radical polymerization

Science.gov (United States)

Kermagoret, Anthony; Debuigne, Antoine; Jérôme, Christine; Detrembleur, Christophe

2014-03-01

The copolymerization of ethylene with polar monomers is a major challenge when it comes to the manufacture of materials with potential for a wide range of commercial applications. In the chemical industry, free-radical polymerization is used to make a large proportion of such copolymers, but the forcing conditions result in a lack of fine control over the architecture of the products. Herein we introduce a synthetic tool, effective under mild experimental conditions, for the precision design of unprecedented ethylene- and polar-monomer-based copolymers. We demonstrate how an organocobalt species can control the growth of the copolymer chains, their composition and the monomer distribution throughout the chain. By fine tuning the ethylene pressure during polymerization and by exploiting a unique reactive mode of the end of the organometallic chain, novel block-like copolymer structures can be prepared. This highly versatile synthetic platform provides access to a diverse range of polymer materials.

Structural Transformation of Diblock Copolymer/Homopolymer Assemblies by Tuning Cylindrical Confinement and Interfacial Interactions.

Science.gov (United States)

Xu, Jiangping; Wang, Ke; Liang, Ruijing; Yang, Yi; Zhou, Huamin; Xie, Xiaolin; Zhu, Jintao

2015-11-17

In this study, we report the controllable structural transformation of block copolymer/homopolymer binary blends in cylindrical nanopores. Polystyrene-b-poly(4-vinylpyridine)/homopolystyrene (SVP/hPS) nanorods (NRs) can be fabricated by pouring the polymers into an anodic aluminum oxide (AAO) channel and isolated by selective removal of the AAO membrane. In this two-dimensional (2D) confinement, SVP self-assembles into NRs with concentric lamellar structure, and the internal structure can be tailored with the addition of hPS. We show that the weight fraction and molecular weight of hPS and the diameter of the channels can significantly affect the internal structure of the NRs. Moreover, mesoporous materials with tunable pore shape, size, and packing style can be prepared by selective solvent swelling of the structured NRs. In addition, these NRs can transform into spherical structures through solvent-absorption annealing, triggering the conversion from 2D to 3D confinement. More importantly, the transformation dynamics can be tuned by varying the preference property of surfactant to the polymers. It is proven that the shape and internal structure of the polymer particles are dominated by the interfacial interactions governed by the surfactants.

Associative, thermodynamic and thermo-kinetics behavior of di- and triblock copolymers of oxyethylene and oxybutylene in aqueous media

Energy Technology Data Exchange (ETDEWEB)

Khan, Abbas [Department of Chemistry, Abdul Wali Khan University, Mardan 23200 (Pakistan); Department of Chemistry, Quaid-I-Azam University, Islamabad 45320 (Pakistan); Siddiq, Mohammad, E-mail: m_sidiq12@yahoo.com [Department of Chemistry, Quaid-I-Azam University, Islamabad 45320 (Pakistan)

2014-11-10

Highlights: • Associative, thermodynamic and thermo-kinetics behavior was investigated. • Micellization of these copolymer is spontaneous, endothermic and entropy driven. • Micelles are spherical in shape and their nature depends on temperature. • Fusion/fission mechanism dominates over unimer entry/expulsion for micellar dynamics. • Micellar parameters depend on temperature and on the delicate hydrophobic–hydrophilic balance of the blocks. - Abstract: The associative, thermodynamic and thermo-kinetics properties of a diblock E{sub 90}B{sub 10} and three triblock copolymers based on polyoxyethylene and polyoxybutylene of the type E{sub m}B{sub 10}E{sub m} water have been studied by surface tensiometry, light scattering and temperature-jump stopped-flow techniques. The data from surface tension was helpful to detect the critical micelle concentration (CMC) as well as to calculate the thermodynamic parameters of micellization. Dynamic light scattering (DLS) was employed to obtain the values of hydrodynamic radii (R{sub h}), volume (υ{sub h}) and hydrodynamic expansion parameter (δ{sub h}) of the micelle at different temperatures. Similarly, static light scattering (SLS) measurements made us enable to find out various micellar parameters such as; weight-average molar (M{sub w}), association number (N{sub w}), thermodynamic radius (R{sub t}), thermodynamic volume (υ{sub t}), anhydrous volume (υ{sub a}) and thermodynamic expansion parameter (δ{sub t}) of the micelles. Likewise, the kinetics of micellar aggregation/dynamic was also investigated by using temperature-jump stopped-flow technique in the temperature range of 20–50 °C.

Synthesis of Well-defined Amphiphilic Block Copolymers by Organotellurium-Mediated Living Radical Polymerization (TERP).

Science.gov (United States)

Kumar, Santosh; Changez, Mohammad; Murthy, C N; Yamago, Shigeru; Lee, Jae-Suk

2011-10-04

Low-molecular weight amphiphilic diblock copolymers, polystyrene-block-poly (2-vinylpyridine) (PS-b-P2VP), and (P2VP-b-PS) with different block ratios were synthesized for the first time via organotellurium-mediated living radical polymerization (TERP). For both the homo- and block copolymerizations, good agreement between the theoretical, and experimental molecular weights was found with nearly 100% yield in every case. The molecular weight distribution for all the samples ranged between 1.10 and 1.24, which is well below the theoretical lower limit of 1.50 for a conventional free radical polymerization. Furthermore, a very simple approach to producing highly dense arrays of titania nanoparticles (TiO2 ) is presented using a site-selective reaction of titanium tetraisopropoxide within the P2VP domains of micellar film of P2VP-b-PS in toluene through the sol-gel method. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Use of Radioactive Marker as a Tool to Evaluate the Drug Release in Plasma and Particle Biodistribution of Block Copolymer Nanoparticles

Directory of Open Access Journals (Sweden)

Sharon Johnstone

2011-01-01

Full Text Available Diblock copolymer nanoparticles encapsulating a paclitaxel prodrug, Propac 7, have been used to demonstrate the usefulness of a nonmetabolizable radioactive marker, cholesteryl hexadecyl ether (CHE, to evaluate nanoparticle formulation variables. Since CHE did not exchange out of the nanoparticles, the rate of clearance of the CHE could be used as an indicator of nanoparticle stability in vivo. We simultaneously monitored prodrug circulation and carrier circulation in the plasma and the retention of CHE relative to the retention of prodrug in the plasma was used to distinguish prodrug release from nanoparticle plasma clearance. Nanoparticles labelled with CHE were also used to evaluate accumulation of nanoparticles in the tumour. This marker has provided relevant data which we have applied to optimise our nanoparticle formulations.

Effect of Areal Density of Polymer Chains on Gold Nanoparticles on Nanoparticle Location in a Block Copolymer Template

Science.gov (United States)

Kim, B. J.; Bang, J.; Hawker, C. J.; Kramer, E. J.

2006-03-01

It is well established that one block of a copolymer can interact preferentially with an inorganic substrate to produce wetting and domain orientation. We take advantage of this preferential interaction to control the location of 2.5 nm diameter Au nanoparticles coated with short thiol-terminated polystyrene (Mn=3.4 kg/mol) chains (PS-SH) in a symmetric poly(styrene-b-2 vinyl-pyridine) (PS-b-P2VP) diblock copolymer (Mn=196 kg/mol) by changing the areal density σ of the PS-SH on the Au. If σ >= 1.6 chains/nm^2, the preferential interaction between the P2VP of the PS-b-P2VP and the Au surface is screened and the Au localizes in the center of the PS domains. If σ <= 1.4 chains/nm^2 , the Au particles are localized at the PS-P2VP interface. Au nanoparticles coated with thiol terminated P2VP (Mn=3 kg/mol) localize in the center of the P2VP domain of the PS-P2VP over the entire range of σ, demonstrating the localization of the PS coated Au nanoparticles at the interface at low values of σ is due to the unscreened Au-P2VP interaction.

Structuring of Interface-Modified Polymer Blends

DEFF Research Database (Denmark)

Lyngaae-Jørgensen, Jørgen

1999-01-01

The paper treats the case where blends of polystyrene (PS), poly (dimethylsiloxane) (PDMS) and a diblock copolymer of PS and PDMS are used as model materials. This modelsystem is predicted to be "stable" in discrete blends in simple shear flow. Stable in the sence that the block copolymer can not...

Graphene oxide-enhanced sol-gel transition sensitivity and drug release performance of an amphiphilic copolymer-based nanocomposite

Science.gov (United States)

Hu, Huawen; Wang, Xiaowen; Lee, Ka I; Ma, Kaikai; Hu, Hong; Xin, John H.

2016-01-01

We report the fabrication of a highly sensitive amphiphilic copolymer-based nanocomposite incorporating with graphene oxide (GO), which exhibited a low-intensity UV light-triggered sol-gel transition. Non-cytotoxicity was observed for the composite gels after the GO incorporation. Of particular interest were the microchannels that were formed spontaneously within the GO-incorporated UV-gel, which expedited sustained drug release. Therefore, the present highly UV-sensitive, non-cytotoxic amphiphilic copolymer-based composites is expected to provide enhanced photothermal therapy and chemotherapy by means of GO’s unique photothermal properties, as well as through efficient passive targeting resulting from the sol-gel transition characteristic of the copolymer-based system with improved sensitivity, which thus promises the enhanced treatment of patients with cancer and other diseases. PMID:27539298

Influence of the content of hard segments on the properties of novel urethane-siloxane copolymers based on a poly(ε-caprolactone-b-poly(dimethylsiloxane-b-poly(ε- caprolactone triblock copolymer

Directory of Open Access Journals (Sweden)

Antić Vesna V.

2011-01-01

Full Text Available A series of novel thermoplastic urethane-siloxane copolymers (TPUSs based on a α,ω-dihydroxy-[poly(ε-caprolactone-bpoly( dimethylsiloxane-b-poly(ε-caprolactone] (α,ω-dihydroxy-PCLPDMS- PCL triblock copolymer, 4,4?-methylenediphenyl diisocyanate (MDI and 1,4-butanediol (BD was synthesized. The effects of the content (9-63 wt. % of hard urethane segments and their degree of polymerization on the properties of the segmented TPUSs were investigated. The structure, composition and hard segment degree of polymerization of the hard segments were examined using 1H- and quantitative 13C-NMR spectroscopy. The degree of crystallinity of the synthesized copolymers was determined using wide-angle X-ray scattering (WAXS. The surface properties were evaluated by measuring the water contact angle and water absorption. In the series of the TPUSs, the average degree of polymerization of the hard segments was varied from 1.2 to 14.4 MDI-BD units. It was found that average values from 3.8 to 14.4 MDI-BD units were effective segment lengths for crystallization of hard segments, which resulted in an increase in the degree of microphase separation of the copolymers. Spherulite-like superstructures were observed in copolymer films by scanning electron microscopy (SEM, which are believed to arise from the crystallization of the hard segments and/or PCL segments, depending on the content of the hard segments. The surface of the copolymers became more hydrophobic with increasing weight fraction of PDMS. The synthesized copolymers based on a PCL-PDMS-PCL segment showed good thermal stability, which increased with increasing content of soft PDMS segments, as was confirmed by the value of the starting temperature of thermal degradation.

Diketopyrrolopyrrole-diketopyrrolopyrrole-based conjugated copolymer for high-mobility organic field-effect transistors

KAUST Repository

Kanimozhi, Catherine K.; Yaacobi-Gross, Nir; Chou, Kang Wei; Amassian, Aram; Anthopoulos, Thomas D.; Patil, Satish P.

2012-01-01

In this communication, we report the synthesis of a novel diketopyrrolopyrrole-diketopyrrolopyrrole (DPP-DPP)-based conjugated copolymer and its application in high-mobility organic field-effect transistors. Copolymerization of DPP with DPP yields a

Non-Invasive Nanodiagnostics of Cancer (NINOC)

Science.gov (United States)

2010-04-01

tested. CONCLUSIONS Well-defined diblock copolymers of poly(ethylene glycol) and polymethacrylic acid (PEG-b-PMA) with aldehyde functionality were...treatment of cancer, tumor-specific targeting has been proposed using a variety of targeting moieties such as folic acid , transferrin, RGD-peptides...tert-butyl and PEG groups (Table 1). In order to obtain the final block copolymer 6, the hydrolysis of copolymer 5 was carried out in the acidic

Highly Efficient One-Pot Synthesis of COS-Based Block Copolymers by Using Organic Lewis Pairs.

Science.gov (United States)

Yang, Jia-Liang; Cao, Xiao-Han; Zhang, Cheng-Jian; Wu, Hai-Lin; Zhang, Xing-Hong

2018-01-31

A one-pot synthesis of block copolymer with regioregular poly(monothiocarbonate) block is described via metal-free catalysis. Lewis bases such as guanidine, quaternary onium salts, and Lewis acid triethyl borane (TEB) were equivalently combined and used as the catalysts. By using polyethylene glycol (PEG) as the macromolecular chain transfer agent (CTA), narrow polydispersity block copolymers were obtained from the copolymerization of carbonyl sulfide (COS) and propylene oxide (PO). The block copolymers had a poly(monothiocarbonate) block with perfect alternating degree and regioregularity. Unexpectedly, the addition of CTA to COS/PO copolymerization system could dramatically improve the turnover frequency (TOF) of PO (up to 240 h -1 ), higher than that of the copolymerization without CTA. In addition, the conversion of CTA could be up to 100% in most cases, as revealed by ¹H NMR spectra. Of consequence, the number-average molecular weights ( M n s) of the resultant block copolymers could be regulated by varying the feed ratio of CTA to PO. Oxygen-sulfur exchange reaction (O/S ER), which can generate randomly distributed thiocarbonate and carbonate units, was effectively suppressed in all of the cases in the presence of CTA, even at 80 °C. This work presents a versatile method for synthesizing sulfur-containing block copolymers through a metal-free route, providing an array of new block copolymers.

An atomic force microscopy study on the transition from mushrooms to octopus surface ''micelles'' by changing the solvent quality

NARCIS (Netherlands)

Stamouli, A.; Pelletier, E.; Koutsos, V; van der Vegte, E.W.; Hadziioannou, G

1996-01-01

Atomic force microscopy (AFM) is used to study the behavior of a diblock copolymer onto a solid surface while the solvent quality is changed. In a first step, the copolymer poly(2-vinylpyridine)/polystyrene (P2VP/PS) is adsorbed onto mica from a selective solvent (the PS block is well solvated and

Preservation of beech and spruce wood by allyl alcohol-based copolymers

International Nuclear Information System (INIS)

Solpan, Dilek; Gueven, Olgun

1999-01-01

Allyl alcohol (AA), acrylonitrile (AN), methyl methacrylate (MMA), monomers and monomer mixtures AA+AN, AA+MMA were used to conserve and consolidate Beech and Spruce. After impregnation, copolymerisation and polymerisation were accomplished by gamma irradiation. The fine structure of wood+polymer(copolymer) composites was investigated by Scanning Electron Microscopy (SEM). It was observed that copolymer obtained from AA+MMA monomer mixture showed the optimum compatibility. The compressional strength and Brinell Hardness Numbers determined for untreated and treated wood samples indicated that the mechanical strength of wood+copolymer composites was increased. It was found that the mechanical strength of the wood samples containing the AA+MMA copolymer was higher than the others. In the presence of P(AA/MMA), at highest conversion, the compressive strength perpendicular to the fibres in Beech and Spruce increased approximately 100 times. The water uptake capacity of wood+copolymer composites was observed to decrease by more than 50% relative to the original samples, and biodegradation did not take place

Ibuprofen-loaded microspheres based on a co-polymer of Eudragit ...

African Journals Online (AJOL)

The objective of this study was to encapsulate ibuprofen in microspheres based on a co-polymer of Eudragit® RS100 and RL100 with a view to achieving a controlled release of the incorporated drug. The microparticles were prepared by an o/o emulsion-solvent evaporation method using varying polymer ratios and ...

Enhanced Bioactivity of α-Tocopheryl Succinate Based Block Copolymer Nanoparticles by Reduced Hydrophobicity.

Science.gov (United States)

Palao-Suay, Raquel; Aguilar, María Rosa; Parra-Ruiz, Francisco J; Maji, Samarendra; Hoogenboom, Richard; Rohner, Nathan A; Thomas, Susan N; Román, Julio San

2016-12-01

Well-structured amphiphilic copolymers are necessary to obtain self-assembled nanoparticles (NPs) based on synthetic polymers. Highly homogeneous and monodispersed macromolecules obtained by controlled polymerization have successfully been used for this purpose. However, disaggregation of the organized macromolecules is desired when a bioactive element, such as α-tocopheryl succinate, is introduced in self-assembled NPs and this element must be exposed or released to exert its action. The aim of this work is to demonstrate that the bioactivity of synthetic NPs based on defined reversible addition-fragmentation chain transfer polymerization copolymers can be enhanced by the introduction of hydrophilic comonomers in the hydrophobic segment. The amphiphilic terpolymers are based on poly(ethylene glycol) (PEG) as hydrophilic block, and a hydrophobic block based on a methacrylic derivative of α-tocopheryl succinate (MTOS) and small amounts of 2-hydroxyethyl methacrylate (HEMA) (PEG-b-poly(MTOS-co-HEMA)). The introduction of HEMA reduces hydrophobicity and introduces "disorder" both in the homogeneous blocks and the compact core of the corresponding NPs. These NPs are able to encapsulate additional α-tocopheryl succinate (α-TOS) with high efficiency and their biological activity is much higher than that described for the unmodified copolymers, proposedly due to more efficient degradation and release of α-TOS, demonstrating the importance of the hydrophilic-hydrophobic balance. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Virus-Assembled Flexible Electrode-Electrolyte Interfaces for Enhanced Polymer-Based Battery Applications

Directory of Open Access Journals (Sweden)

Ayan Ghosh

2012-01-01

Full Text Available High-aspect-ratio cobalt-oxide-coated Tobacco mosaic virus (TMV- assembled polytetrafluoroethylene (PTFE nonstick surfaces were integrated with a solvent-free polymer electrolyte to create an anode-electrolyte interface for use in lithium-ion batteries. The virus-assembled PTFE surfaces consisted primarily of cobalt oxide and were readily intercalated with a low-molecular-weight poly (ethylene oxide (PEO based diblock copolymer electrolyte to produce a solid anode-electrolyte system. The resulting polymer-coated virus-based system was then peeled from the PTFE backing to produce a flexible electrode-electrolyte component. Electrochemical studies indicated the virus-structured metal-oxide PEO-based interface was stable and displayed robust charge transfer kinetics. Combined, these studies demonstrate the development of a novel solid-state electrode architecture with a unique peelable and flexible processing attribute.

Structure of micelles formed by highly asymmetric polystyrene-b-polydimethylsiloxane and polystyrene-b-poly[5-(N,N-diethylamino)isoprene] diblock copolymers

Czech Academy of Sciences Publication Activity Database

Giacomelli, F. C.; Riegel, I. C.; Štěpánek, Petr; Petzhold, C. L.; Ninago, M. D.; Satti, A. J.; Ciolino, A. E.; Villar, M. A.; Schmidt, V.; Giacomelli, C.

2010-01-01

Roč. 26, č. 18 (2010), s. 14494-14501 ISSN 0743-7463 R&D Projects: GA ČR GA202/09/2078 Grant - others:AV ČR(CZ) ASCR/CONICET 2012CZ006 Institutional research plan: CEZ:AV0Z40500505 Keywords : dynamic light-scattering * block-copolymers * selective solvent Subject RIV: BO - Biophysics Impact factor: 4.269, year: 2010

Inorganic Nanoparticle Induced Morphological Transition for Confined Self-Assembly of Block Copolymers within Emulsion Droplets.

Science.gov (United States)

Zhang, Yan; He, Yun; Yan, Nan; Zhu, Yutian; Hu, Yuexin

2017-09-07

Recently, it has been reported that the incorporation of functional inorganic nanoparticles (NPs) into the three-dimensional (3D) confined self-assembly of block copolymers (BCPs) creates the unique nanostructured hybrid composites, which can not only introduce new functions to BCPs but also induce some interesting morphological transitions of BCPs. In the current study, we systematically investigate the cooperative self-assembly of a series of size-controlled and surface chemistry-tunable gold nanoparticles (AuNPs) and polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) diblock copolymer within the emulsion droplets. The influences of the size, content, and surface chemistry of the AuNPs on the coassembled nanostructures as well as the spatial distribution of AuNPs in the hybrid particles are examined. It is found that the size and content of the AuNPs are related to the entropic interaction, while the surface chemistry of AuNPs is related to the enthalpic interaction, which can be utilized to tailor the self-assembled morphologies of block copolymer confined in the emulsion droplets. As the content of PS-coated AuNPs increases, the morphology of the resulting AuNPs/PS-b-P2VP hybrid particles changes from the pupa-like particles to the bud-like particles and then to the onion-like particles. However, a unique morphological transition from the pupa-like particles to the mushroom-like particles is observed as the content of P4VP-coated AuNPs increases. More interestingly, it is observed that the large AuNPs are expelled to the surface of the BCP particles to reduce the loss in the conformational entropy of the block segment, which can arrange into the strings of necklaces on the surfaces of the hybrid particles.

Fast & scalable pattern transfer via block copolymer nanolithography

DEFF Research Database (Denmark)

Li, Tao; Wang, Zhongli; Schulte, Lars

2015-01-01

A fully scalable and efficient pattern transfer process based on block copolymer (BCP) self-assembling directly on various substrates is demonstrated. PS-rich and PDMS-rich poly(styrene-b-dimethylsiloxane) (PS-b-PDMS) copolymers are used to give monolayer sphere morphology after spin-casting of s......A fully scalable and efficient pattern transfer process based on block copolymer (BCP) self-assembling directly on various substrates is demonstrated. PS-rich and PDMS-rich poly(styrene-b-dimethylsiloxane) (PS-b-PDMS) copolymers are used to give monolayer sphere morphology after spin...... on long range lateral order, including fabrication of substrates for catalysis, solar cells, sensors, ultrafiltration membranes and templating of semiconductors or metals....

Dynamic actuation of glassy polymersomes through isomerization of a single azobenzene unit at the block copolymer interface

Science.gov (United States)

Molla, Mijanur Rahaman; Rangadurai, Poornima; Antony, Lucas; Swaminathan, Subramani; de Pablo, Juan J.; Thayumanavan, S.

2018-06-01

Nature has engineered exquisitely responsive systems where molecular-scale information is transferred across an interface and propagated over long length scales. Such systems rely on multiple interacting, signalling and adaptable molecular and supramolecular networks that are built on dynamic, non-equilibrium structures. Comparable synthetic systems are still in their infancy. Here, we demonstrate that the light-induced actuation of a molecularly thin interfacial layer, assembled from a hydrophilic- azobenzene -hydrophobic diblock copolymer, can result in a reversible, long-lived perturbation of a robust glassy membrane across a range of over 500 chemical bonds. We show that the out-of-equilibrium actuation is caused by the photochemical trans-cis isomerization of the azo group, a single chemical functionality, in the middle of the interfacial layer. The principles proposed here are implemented in water-dispersed nanocapsules, and have implications for on-demand release of embedded cargo molecules.

Self-assembled structures in d8-polystyreneblock- polyisoprene/polystyrene blends in the weak segregation regime: SAXS and TEM study

Czech Academy of Sciences Publication Activity Database

Holoubek, Jaroslav; Baldrian, Josef; Hromádková, Jiřina; Steinhart, Miloš

2009-01-01

Roč. 58, č. 7 (2009), s. 762-774 ISSN 0959-8103 R&D Projects: GA ČR GA202/09/2078; GA ČR GESON/06/E005 Institutional research plan: CEZ:AV0Z40500505 Keywords : diblock copolymers * homopolymer/copolymer blends * SAXS Subject RIV: CD - Macromolecular Chemistry Impact factor: 2.137, year: 2009

Complexation of Polyelectrolyte Micelles with Oppositely Charged Linear Chains.

Science.gov (United States)

Kalogirou, Andreas; Gergidis, Leonidas N; Miliou, Kalliopi; Vlahos, Costas

2017-03-02

The formation of interpolyelectrolyte complexes (IPECs) from linear AB diblock copolymer precursor micelles and oppositely charged linear homopolymers is studied by means of molecular dynamics simulations. All beads of the linear polyelectrolyte (C) are charged with elementary quenched charge +1e, whereas in the diblock copolymer only the solvophilic (A) type beads have quenched charge -1e. For the same Bjerrum length, the ratio of positive to negative charges, Z +/- , of the mixture and the relative length of charged moieties r determine the size of IPECs. We found a nonmonotonic variation of the size of the IPECs with Z +/- . For small Z +/- values, the IPECs retain the size of the precursor micelle, whereas at larger Z +/- values the IPECs decrease in size due to the contraction of the corona and then increase as the aggregation number of the micelle increases. The minimum size of the IPECs is obtained at lower Z +/- values when the length of the hydrophilic block of the linear diblock copolymer decreases. The aforementioned findings are in agreement with experimental results. At a smaller Bjerrum length, we obtain the same trends but at even smaller Z +/- values. The linear homopolymer charged units are distributed throughout the corona.

Synthesis of block copolymers derived from N-trityl-(S)-serine and pyrene end-labeled poly(methyl methacrylate) or poly(N-isopropylacrylamide) via ATRP

International Nuclear Information System (INIS)

Buruiana, Emil C.; Podasca, Viorica; Buruiana, Tinca

2012-01-01

A new monomer bearing N-trityl-L-serine methyl ester in structure, methacryloyloxyethyl carbamoyloxy–N-trityl methyl serine (MTS), was prepared to be further polymerized by atom transfer radical polymerization (ATRP) with pyrene-endcapped poly(methyl methacrylate) (Py–PMMA–Br) or poly(N-isopropylacrylamide) (Py–PNIPA–Br). The resulting block copolymers, poly(methyl methacrylate–block–methacryloyloxyethyl carbamoyloxy–N-trityl methyl serine) (Py–PMMA–b–PMTS) and poly(N-isopropylacrylamide–block–methacryloyloxyethyl carbamoyloxy–N-trityl methyl serine (Py–PNIPA–b–PMTS) were characterized by 1 H ( 13 C) NMR, ultraviolet, FTIR and fluorescence spectroscopy, thermal analysis, differential scanning calorimetry (DSC), atomic force microscopy (AFM), scanning electron microscopy (SEM), and gel permeation chromatography (GPC) measurements. The chemical composition in Py–PMMA–b–PMTS was estimated from the 1 H NMR analysis that indicated a ratio of the repeating units of 46:19 (MMA:MTS). For the Py–PNIPA–b–PMTS the composition rate in the copolymer was 61:25 (NIPA:MTS). Quenching of the pyrene species with N,N-diethylaniline, nitrobenzene, nitrophenol, potassium iodide, p-nitrotoluene and tetracyanoquinodimethane (TCNQ) in DMF solution excited at 348 nm was evidenced, more efficiently being nitrophenol and TCNQ. In this case, the monomer emission at 388–409 nm underwent a significant decrease caused of an electron transfer from the electron-reach photoexcited pyrene molecule to the electron-deficient quenchers. - Highlights: ► Diblock copolymers combine the fluorescence of pyrene–PMMA (PNIPA) with the characteristics of PMTS. ► Such copolymers could be used for nitroderivatives detecting. ► UV/vis and fluorescence measurements give a good correlation for LCST of Py–PNIPA–Br.

Synthesis of block copolymers derived from N-trityl-(S)-serine and pyrene end-labeled poly(methyl methacrylate) or poly(N-isopropylacrylamide) via ATRP

Energy Technology Data Exchange (ETDEWEB)

Buruiana, Emil C., E-mail: emilbur@icmpp.ro [Petru Poni Institute of Macromolecular Chemistry, 41A Gr. Ghica Voda Alley 700487, Iasi (Romania); Podasca, Viorica; Buruiana, Tinca [Petru Poni Institute of Macromolecular Chemistry, 41A Gr. Ghica Voda Alley 700487, Iasi (Romania)

2012-10-15

A new monomer bearing N-trityl-L-serine methyl ester in structure, methacryloyloxyethyl carbamoyloxy-N-trityl methyl serine (MTS), was prepared to be further polymerized by atom transfer radical polymerization (ATRP) with pyrene-endcapped poly(methyl methacrylate) (Py-PMMA-Br) or poly(N-isopropylacrylamide) (Py-PNIPA-Br). The resulting block copolymers, poly(methyl methacrylate-block-methacryloyloxyethyl carbamoyloxy-N-trityl methyl serine) (Py-PMMA-b-PMTS) and poly(N-isopropylacrylamide-block-methacryloyloxyethyl carbamoyloxy-N-trityl methyl serine (Py-PNIPA-b-PMTS) were characterized by {sup 1}H ({sup 13}C) NMR, ultraviolet, FTIR and fluorescence spectroscopy, thermal analysis, differential scanning calorimetry (DSC), atomic force microscopy (AFM), scanning electron microscopy (SEM), and gel permeation chromatography (GPC) measurements. The chemical composition in Py-PMMA-b-PMTS was estimated from the {sup 1}H NMR analysis that indicated a ratio of the repeating units of 46:19 (MMA:MTS). For the Py-PNIPA-b-PMTS the composition rate in the copolymer was 61:25 (NIPA:MTS). Quenching of the pyrene species with N,N-diethylaniline, nitrobenzene, nitrophenol, potassium iodide, p-nitrotoluene and tetracyanoquinodimethane (TCNQ) in DMF solution excited at 348 nm was evidenced, more efficiently being nitrophenol and TCNQ. In this case, the monomer emission at 388-409 nm underwent a significant decrease caused of an electron transfer from the electron-reach photoexcited pyrene molecule to the electron-deficient quenchers. - Highlights: Black-Right-Pointing-Pointer Diblock copolymers combine the fluorescence of pyrene-PMMA (PNIPA) with the characteristics of PMTS. Black-Right-Pointing-Pointer Such copolymers could be used for nitroderivatives detecting. Black-Right-Pointing-Pointer UV/vis and fluorescence measurements give a good correlation for LCST of Py-PNIPA-Br.

RAFT Aqueous Dispersion Polymerization of N-(2-(Methacryloyloxy)ethyl)pyrrolidone: A Convenient Low Viscosity Route to High Molecular Weight Water-Soluble Copolymers.

Science.gov (United States)

Cunningham, Victoria J; Derry, Matthew J; Fielding, Lee A; Musa, Osama M; Armes, Steven P

2016-06-28

RAFT solution polymerization of N -(2-(methacryoyloxy)ethyl)pyrrolidone (NMEP) in ethanol at 70 °C was conducted to produce a series of PNMEP homopolymers with mean degrees of polymerization (DP) varying from 31 to 467. Turbidimetry was used to assess their inverse temperature solubility behavior in dilute aqueous solution, with an LCST of approximately 55 °C being observed in the high molecular weight limit. Then a poly(glycerol monomethacylate) (PGMA) macro-CTA with a mean DP of 63 was chain-extended with NMEP using a RAFT aqueous dispersion polymerization formulation at 70 °C. The target PNMEP DP was systematically varied from 100 up to 6000 to generate a series of PGMA 63 -PNMEP x diblock copolymers. High conversions (≥92%) could be achieved when targeting up to x = 5000. GPC analysis confirmed high blocking efficiencies and a linear evolution in M n with increasing PNMEP DP. A gradual increase in M w / M n was also observed when targeting higher DPs. However, this problem could be minimized ( M w / M n RAFT aqueous dispersion polymerization of NMEP was approximately four times faster than the RAFT solution polymerization of NMEP in ethanol when targeting the same DP in each case. This is perhaps surprising because both 1 H NMR and SAXS studies indicate that the core-forming PNMEP chains remain relatively solvated at 70 °C in the latter formulation. Moreover, dissolution of the initial PGMA 63 -PNMEP x particles occurs on cooling from 70 to 20 °C as the PNMEP block passes through its LCST. Hence this RAFT aqueous dispersion polymerization formulation offers an efficient route to a high molecular weight water-soluble polymer in a rather convenient low-viscosity form. Finally, the relatively expensive PGMA macro-CTA was replaced with a poly(methacrylic acid) (PMAA) macro-CTA. High conversions were also achieved for PMAA 85 -PNMEP x diblock copolymers prepared via RAFT aqueous dispersion polymerization for x ≤ 4000. Again, better control was achieved when

Melt-processable hydrophobic acrylonitrile-based copolymer systems with adjustable elastic properties designed for biomedical applications.

Science.gov (United States)

Cui, J; Trescher, K; Kratz, K; Jung, F; Hiebl, B; Lendlein, A

2010-01-01

Acrylonitrile-based polymer systems (PAN) are comprehensively explored as versatile biomaterials having various potential biomedical applications, such as membranes for extra corporal devices or matrixes for guided skin reconstruction. The surface properties (e.g. hydrophilicity or charges) of such materials can be tailored over a wide range by variation of molecular parameters such as different co-monomers or their sequence structure. Some of these materials show interesting biofunctionalities such as capability for selective cell cultivation. So far, the majority of AN-based copolymers, which were investigated in physiological environments, were processed from the solution (e.g. membranes), as these materials are thermo-sensitive and might degrade when heated. In this work we aimed at the synthesis of hydrophobic, melt-processable AN-based copolymers with adjustable elastic properties for preparation of model scaffolds with controlled pore geometry and size. For this purpose a series of copolymers from acrylonitrile and n-butyl acrylate (nBA) was synthesized via free radical copolymerisation technique. The content of nBA in the copolymer varied from 45 wt% to 70 wt%, which was confirmed by 1H-NMR spectroscopy. The glass transition temperatures (Tg) of the P(AN-co-nBA) copolymers determined by differential scanning calorimetry (DSC) decreased from 58 degrees C to 20 degrees C with increasing nBA-content, which was in excellent agreement with the prediction of the Gordon-Taylor equation based on the Tgs of the homopolymers. The Young's modulus obtained in tensile tests was found to decrease significantly with rising nBA-content from 1062 MPa to 1.2 MPa. All copolymers could be successfully processed from the melt with processing temperatures ranging from 50 degrees C to 170 degrees C, whereby thermally induced decomposition was only observed at temperatures higher than 320 degrees C in thermal gravimetric analysis (TGA). Finally, the melt processed P

Characteristic of natural rubber latex-methyl metha-crylate copolymer in mineral lubricant base oil

International Nuclear Information System (INIS)

Meri Suhartini; Rahmawati

2010-01-01

Natural rubber latex-methyl methacrylate copolymer was diluted in xylene, then diluted in four types of lubricant base oil with concentrations of 0.25%, 1%, 5%, and 10%. The mixed solutions were analyzed to obtain kinematics viscosity, viscosity index, density, ash content, metal content, flash point, shear stability and total alkali number. The viscosity index of sample, increased by adding the copolymer solution. The results showed that lubricant base oil of High Viscosity index (HVI) 60 and mixed HVI 60: HVI 650 gave optimum viscosity index. The higher concentration of polymer added into base lubricant oil, the higher viscosity index obtained. The shear stability test showed that the kinematics viscosity of sample decreased 6.5% after 60 minutes of treatment test. (author)

Triblock copolymers based on epsilon-caprolactone and trimethylene carbonate for the 3D printing of tissue engineering scaffolds

NARCIS (Netherlands)

Guney, Aysun; Malda, Jos; Dhert, Wouter J. A.; Grijpma, Dirk W.

Background: Biodegradable PCL-b-PTMC-b-PCL triblock copolymers based on trimethylene carbonate (TMC) and epsilon-caprolactone (CL) were prepared and used in the 3D printing of tissue engineering scaffolds. Triblock copolymers of various molecular weights containing equal amounts of TMC and CL were

Triblock copolymers based on ε-caprolactone and trimethylene carbonate for the 3D printing of tissue engineering scaffolds

NARCIS (Netherlands)

Güney, Aysun; Malda, Jos; Dhert, Wouter J A; Grijpma, Dirk W

BACKGROUND: Biodegradable PCL-b-PTMC-b-PCL triblock copolymers based on trimethylene carbonate (TMC) and ε-caprolactone (CL) were prepared and used in the 3D printing of tissue engineering scaffolds. Triblock copolymers of various molecular weights containing equal amounts of TMC and CL were

Triblock copolymers based on ε-caprolactone and trimethylene carbonate for the 3D printing of tissue engineering scaffolds

NARCIS (Netherlands)

Güney, Aysun; Malda, Jos; Dhert, Wouter J.A.; Grijpma, Dirk W.

2017-01-01

Background: Biodegradable PCL-b-PTMC-b-PCL triblock copolymers based on trimethylene carbonate (TMC) and ε-caprolactone (CL) were prepared and used in the 3D printing of tissue engineering scaffolds. Triblock copolymers of various molecular weights containing equal amounts of TMC and CL were

CO2 permeation properties of poly(ethylene oxide)-based segmented block copolymers

NARCIS (Netherlands)

Husken, D.; Visser, Tymen; Wessling, Matthias; Gaymans, R.J.

2010-01-01

This paper discusses the gas permeation properties of poly(ethylene oxide) (PEO)-based segmented block copolymers containing monodisperse amide segments. These monodisperse segments give rise to a well phase-separated morphology, comprising a continuous PEO phase with dispersed crystallised amide

Amphiphilic copolymers for fouling-release coatings

DEFF Research Database (Denmark)

Noguer, Albert Camós; Olsen, Stefan Møller; Hvilsted, Søren

of the coatings [9,10,11]. This work shows the effect of an amphiphilic copolymer that induces hydrophilicity on the surface of the silicone-based fouling release coatings. The behaviour of these copolymers within the coating upon immersion and the interaction of these surface-active additives with other...

pH-Responsive Tumor-Targetable Theranostic Nanovectors Based on Core Crosslinked (CCL Micelles with Fluorescence and Magnetic Resonance (MR Dual Imaging Modalities and Drug Delivery Performance

Directory of Open Access Journals (Sweden)

Sidan Tian

2016-06-01

Full Text Available The development of novel theranostic nanovectors is of particular interest in treating formidable diseases (e.g., cancers. Herein, we report a new tumor-targetable theranostic agent based on core crosslinked (CCL micelles, possessing tumor targetable moieties and fluorescence and magnetic resonance (MR dual imaging modalities. An azide-terminated diblock copolymer, N3-POEGMA-b-P(DPA-co-GMA, was synthesized via consecutive atom transfer radical polymerization (ATRP, where OEGMA, DPA, and GMA are oligo(ethylene glycolmethyl ether methacrylate, 2-(diisopropylaminoethyl methacrylate, and glycidyl methacrylate, respectively. The resulting diblock copolymer was further functionalized with DOTA(Gd (DOTA is 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrakisacetic acid or benzaldehyde moieties via copper(I-catalyzed alkyne-azide cycloaddition (CuAAC chemistry, resulting in the formation of DOTA(Gd-POEGMA-b-P(DPA-co-GMA and benzaldehyde-POEGMA-b-P(DPA-co-GMA copolymers. The resultant block copolymers co-assembled into mixed micelles at neutral pH in the presence of tetrakis[4-(2-mercaptoethoxyphenyl]ethylene (TPE-4SH, which underwent spontaneous crosslinking reactions with GMA residues embedded within the micellar cores, simultaneously switching on TPE fluorescence due to the restriction of intramolecular rotation. Moreover, camptothecin (CPT was encapsulated into the crosslinked cores at neutral pH, and tumor-targeting pH low insertion peptide (pHLIP, sequence: AEQNPIYWARYADWLFTTPLLLLDLALLVDADEGTCG moieties were attached to the coronas through the Schiff base chemistry, yielding a theranostic nanovector with fluorescence and MR dual imaging modalities and tumor-targeting capability. The nanovectors can be efficiently taken up by A549 cells, as monitored by TPE fluorescence. After internalization, intracellular acidic pH triggered the release of loaded CPT, killing cancer cells in a selective manner. On the other hand, the nanovectors labeled with DOTA

An amphiphilic graft copolymer-based nanoparticle platform for reduction-responsive anticancer and antimalarial drug delivery

Science.gov (United States)

Najer, Adrian; Wu, Dalin; Nussbaumer, Martin G.; Schwertz, Geoffrey; Schwab, Anatol; Witschel, Matthias C.; Schäfer, Anja; Diederich, François; Rottmann, Matthias; Palivan, Cornelia G.; Beck, Hans-Peter; Meier, Wolfgang

2016-08-01

Medical applications of anticancer and antimalarial drugs often suffer from low aqueous solubility, high systemic toxicity, and metabolic instability. Smart nanocarrier-based drug delivery systems provide means of solving these problems at once. Herein, we present such a smart nanoparticle platform based on self-assembled, reduction-responsive amphiphilic graft copolymers, which were successfully synthesized through thiol-disulfide exchange reaction between thiolated hydrophilic block and pyridyl disulfide functionalized hydrophobic block. These amphiphilic graft copolymers self-assembled into nanoparticles with mean diameters of about 30-50 nm and readily incorporated hydrophobic guest molecules. Fluorescence correlation spectroscopy (FCS) was used to study nanoparticle stability and triggered release of a model compound in detail. Long-term colloidal stability and model compound retention within the nanoparticles was found when analyzed in cell media at body temperature. In contrast, rapid, complete reduction-triggered disassembly and model compound release was achieved within a physiological reducing environment. The synthesized copolymers revealed no intrinsic cellular toxicity up to 1 mg mL-1. Drug-loaded reduction-sensitive nanoparticles delivered a hydrophobic model anticancer drug (doxorubicin, DOX) to cancer cells (HeLa cells) and an experimental, metabolically unstable antimalarial drug (the serine hydroxymethyltransferase (SHMT) inhibitor (+/-)-1) to Plasmodium falciparum-infected red blood cells (iRBCs), with higher efficacy compared to similar, non-sensitive drug-loaded nanoparticles. These responsive copolymer-based nanoparticles represent a promising candidate as smart nanocarrier platform for various drugs to be applied to different diseases, due to the biocompatibility and biodegradability of the hydrophobic block, and the protein-repellent hydrophilic block.Medical applications of anticancer and antimalarial drugs often suffer from low aqueous

Anionic polymerization and polyhomologation: An ideal combination to synthesize polyethylene-based block copolymers

KAUST Repository

Zhang, H.; Alkayal, N.; Gnanou, Yves; Hadjichristidis, Nikolaos

2013-01-01

A novel one-pot methodology combining anionic polymerization and polyhomologation, through a "bridge" molecule (BF3OEt 2), was developed for the synthesis of polyethylene (PE)-based block copolymers. The anionically synthesized macroanion reacts

Quasi-Block Copolymers Based on a General Polymeric Chain Stopper.

Science.gov (United States)

Sanguramath, Rajashekharayya A; Nealey, Paul F; Shenhar, Roy

2016-07-11

Quasi-block copolymers (q-BCPs) are block copolymers consisting of conventional and supramolecular blocks, in which the conventional block is end-terminated by a functionality that interacts with the supramolecular monomer (a "chain stopper" functionality). A new design of q-BCPs based on a general polymeric chain stopper, which consists of polystyrene end-terminated with a sulfonate group (PS-SO3 Li), is described. Through viscosity measurements and a detailed diffusion-ordered NMR spectroscopy study, it is shown that PS-SO3 Li can effectively cap two types of model supramolecular monomers to form q-BCPs in solution. Furthermore, differential scanning calorimetry data and structural characterization of thin films by scanning force microscopy suggests the existence of the q-BCP architecture in the melt. The new design considerably simplifies the synthesis of polymeric chain stoppers; thus promoting the utilization of q-BCPs as smart, nanostructured materials. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis and immobilization of polystyreneb-polyvinyltriethoxysilane micelles

KAUST Repository

Zhu, Saisai; Zhu, Hui; Xia, Ru; Feng, Xiaoshuang; Chen, Peng; Qian, Jiasheng; Cao, Ming; Yang, Bin; Miao, Jibin; Su, Lifen; Song, Changjiang

2018-01-01

Diblock copolymers polystyrene-block-polyvinyltriethoxysilane (PS-b-PVTES) were synthesized via atom transfer radical polymerization (ATRP), which self-assembled into spherical micelles in solvent of THF-methanol mixtures. The self

Synthesis of Fluorinated Amphiphilic Block Copolymers Based on PEGMA, HEMA, and MMA via ATRP and CuAAC Click Chemistry

OpenAIRE

Erol, Fatime Eren; Sinirlioglu, Deniz; Cosgun, Sedat; Muftuoglu, Ali Ekrem

2014-01-01

Synthesis of fluorinated amphiphilic block copolymers via atom transfer radical polymerization (ATRP) and Cu(I) catalyzed Huisgen 1,3-dipolar cycloaddition (CuAAC) was demonstrated. First, a PEGMA and MMA based block copolymer carrying multiple side-chain acetylene moieties on the hydrophobic segment for postfunctionalization was carried out. This involves the synthesis of a series of P(HEMA-co-MMA) random copolymers to be employed as macroinitiators in the controlled synthesis of P(HEMA-co-M...

Synthesis, characterizations and biocompatibility of novel biodegradable star block copolymers based on poly[(R)-3-hydroxybutyrate] and poly(epsilon-caprolactone)

DEFF Research Database (Denmark)

Wu, Linping; Wang, Liang; Wang, Xiaojuan

2010-01-01

Star block copolymers based on poly[(R)-3-hydroxybutyrate] (PHB) and poly(epsilon-caprolactone) (PCL), termed SPHBCL, were successfully synthesized with structural variation on arm numbers and lengths via coupling reactions and ring opening polymerizations. Arm numbers 3, 4 and 6 of SPHBCL were...... weights of the SPHBCL due to the discrepancy of star copolymer structures. The melting temperature of SPHBCL decreased with increasing degree of branching. Thermal decomposition temperature was revealed to be lower than that of linear block copolymer LPHBCL counterparts based on PHB and PCL. Films made...... from various SPHBCL copolymers had different porous or networking surface morphology, and all possessed improved biocompatibility in terms of less blood clotting and more osteoblast cell growth compared with their corresponding homopolymers PHB and PCL. Among them, it was found, however, that the 4-arm...

Amphiphilic copolymers based on PEG-acrylate as surface active water viscosifiers : Towards new potential systems for enhanced oil recovery

NARCIS (Netherlands)

Raffa, Patrizio; Broekhuis, Antonius A.; Picchioni, Francesco

2016-01-01

With the purpose of investigating new potential candidates for enhanced oil recovery (EOR), amphiphilic copolymers based on Poly(ethylene glycol) methyl ether acrylate (PEGA) have been prepared by Atom Transfer Radical Polymerization (ATRP). A P(PEGA) homopolymer, a block copolymer with styrene

Graphene oxide stabilized by PLA-PEG copolymers for the controlled delivery of paclitaxel.

Science.gov (United States)

Angelopoulou, A; Voulgari, E; Diamanti, E K; Gournis, D; Avgoustakis, K

2015-06-01

To investigate the application of water-dispersible poly(lactide)-poly(ethylene glycol) (PLA-PEG) copolymers for the stabilization of graphene oxide (GO) aqueous dispersions and the feasibility of using the PLA-PEG stabilized GO as a delivery system for the potent anticancer agent paclitaxel. A modified Staudenmaier method was applied to synthesize graphene oxide (GO). Diblock PLA-PEG copolymers were synthesized by ring-opening polymerization of dl-lactide in the presence of monomethoxy-poly(ethylene glycol) (mPEG). Probe sonication in the presence of PLA-PEG copolymers was applied in order to reduce the hydrodynamic diameter of GO to the nano-size range according to dynamic light scattering (DLS) and obtain nano-graphene oxide (NGO) composites with PLA-PEG. The composites were characterized by atomic force microscopy (AFM), thermogravimetric analysis (TGA), and DLS. The colloidal stability of the composites was evaluated by recording the size of the composite particles with time and the resistance of composites to aggregation induced by increasing concentrations of NaCl. The composites were loaded with paclitaxel and the in vitro release profile was determined. The cytotoxicity of composites against A549 human lung cancer cells in culture was evaluated by flow cytometry. The uptake of FITC-labeled NGO/PLA-PEG by A549 cells was also estimated with flow cytometry and visualized with fluorescence microscopy. The average hydrodynamic diameter of NGO/PLA-PEG according to DLS ranged between 455 and 534 nm, depending on the molecular weight and proportion of PLA-PEG in the composites. NGO/PLA-PEG exhibited high colloidal stability on storage and in the presence of high concentrations of NaCl (far exceeding physiological concentrations). Paclitaxel was effectively loaded in the composites and released by a highly sustained fashion. Drug release could be regulated by the molecular weight of the PLA-PEG copolymer and its proportion in the composite. The paclitaxel

Triblock copolymers based on ε-caprolactone and trimethylene carbonate for the 3D printing of tissue engineering scaffolds.

Science.gov (United States)

Güney, Aysun; Malda, Jos; Dhert, Wouter J A; Grijpma, Dirk W

2017-05-09

Biodegradable PCL-b-PTMC-b-PCL triblock copolymers based on trimethylene carbonate (TMC) and ε-caprolactone (CL) were prepared and used in the 3D printing of tissue engineering scaffolds. Triblock copolymers of various molecular weights containing equal amounts of TMC and CL were prepared. These block copolymers combine the low glass transition temperature of amorphous PTMC (approximately -20°C) and the semi-crystallinity of PCL (glass transition approximately -60°C and melting temperature approximately 60°C). PCL-b-PTMC-b-PCL triblock copolymers were synthesized by sequential ring opening polymerization (ROP) of TMC and ε-CL. From these materials, films were prepared by solvent casting and porous structures were prepared by extrusion-based 3D printing. Films prepared from a polymer with a relatively high molecular weight of 62 kg/mol had a melting temperature of 58°C and showed tough and resilient behavior, with values of the elastic modulus, tensile strength and elongation at break of approximately 120 MPa, 16 MPa and 620%, respectively. Porous structures were prepared by 3D printing. Ethylene carbonate was used as a crystalizable and water-extractable solvent to prepare structures with microporous strands. Solutions, containing 25 wt% of the triblock copolymer, were extruded at 50°C then cooled at different temperatures. Slow cooling at room temperature resulted in pores with widths of 18 ± 6 μm and lengths of 221 ± 77 μm, rapid cooling with dry ice resulted in pores with widths of 13 ± 3 μm and lengths of 58 ± 12 μm. These PCL-b-PTMC-b-PCL triblock copolymers processed into porous structures at relatively low temperatures may find wide application as designed degradable tissue engineering scaffolds. In this preliminary study we prepared biodegradable triblock copolymers based on 1,3-trimethylene carbonate and ε-caprolactone and assessed their physical characteristics. Furthermore, we evaluated their potential as melt-processable thermoplastic

Loess clay based copolymer for removing Pb(II) ions

International Nuclear Information System (INIS)

He, Yu-Feng; Zhang, Ling; Wang, Rong-Min; Li, Hui-Ru; Wang, Yan

2012-01-01

Highlights: ► The loess clay based copolymer was prepared using functional monomers. ► Characterization of the polymer adsorbent and the raw material were carried out. ► The adsorption behavior of the complex for Pb(II) ions was evaluated. ► The removal rate of Pb(II) got to 99% and the adsorption capacity got to 356.9 mg/g. - Abstract: Functional monomers, such as acrylic acid and 2-hydroxyethyl methacrylate were supported into loess clay in situ polymerization, which afforded loess clay based copolymer (LC/PAAHM), a new kind of polymer adsorbent for removing Pb(II) ions from aqueous solution. Characterization of the polymer adsorbent was carried out by different sophisticated methods, such as Fourier transformation infrared spectrometry (FTIR), scanning electron microscopy (SEM), X-ray diffractometry (XRD), thermogravimetric analysis (TGA), and Zetasizer. Batch experiments were carried out to evaluate the factors affecting the removal efficiency, in which the pH, the adsorbent dosage, temperature and initial Pb(II) concentration all found in positive relevance to the increase of Pb(II) removal efficiency. The removal rate of Pb(II) got to 99% at room temperature and the adsorption capacity got to 356.9 mg/g. The pseudo-first-order and pseudo-second-order kinetic models were applied to test the experimental data, and Langmuir and Freundlich models have been applied to study the adsorption equilibrium, respectively.

Targeted drug delivery nanosystems based on copolymer poly(lactide)-tocopheryl polyethylene glycol succinate for cancer treatment

International Nuclear Information System (INIS)

Ha, Phuong Thu; Nguyen, Hoai Nam; Do, Hai Doan; Phan, Quoc Thong; Thi, Minh Nguyet Tran; Nguyen, Xuan Phuc; Thi, My Nhung Hoang; Le, Mai Huong; Nguyen, Linh Toan; Bui, Thuc Quang; Phan, Van Hieu

2016-01-01

Along with the development of nanotechnology, drug delivery nanosystems (DDNSs) have attracted a great deal of concern among scientists over the world, especially in cancer treatment. DDNSs not only improve water solubility of anticancer drugs but also increase therapeutic efficacy and minimize the side effects of treatment methods through targeting mechanisms including passive and active targeting. Passive targeting is based on the nano-size of drug delivery systems while active targeting is based on the specific bindings between targeting ligands attached on the drug delivery systems and the unique receptors on the cancer cell surface. In this article we present some of our results in the synthesis and testing of DDNSs prepared from copolymer poly(lactide)-tocopheryl polyethylene glycol succinate (PLA-TPGS), which carry anticancer drugs including curcumin, paclitaxel and doxorubicin. In order to increase the targeting effect to cancer cells, active targeting ligand folate was attached to the DDNSs. The results showed copolymer PLA-TPGS to be an excellent carrier for loading hydrophobic drugs (curcumin and paclitaxel). The fabricated DDNSs had a very small size (50–100 nm) and enhanced the cellular uptake and cytotoxicity of drugs. Most notably, folate-decorated paclitaxel-loaded copolymer PLA-TPGS nanoparticles (Fol/PTX/PLA-TPGS NPs) were tested on tumor-bearing nude mice. During the treatment time, Fol/PTX/PLA-TPGS NPs always exhibited the best tumor growth inhibition compared to free paclitaxel and paclitaxel-loaded copolymer PLA-TPGS nanoparticles. All results evidenced the promising potential of copolymer PLA-TPGS in fabricating targeted DDNSs for cancer treatment. (paper)

Targeted drug delivery nanosystems based on copolymer poly(lactide)-tocopheryl polyethylene glycol succinate for cancer treatment

Science.gov (United States)

Thu Ha, Phuong; Nguyen, Hoai Nam; Doan Do, Hai; Thong Phan, Quoc; Nguyet Tran Thi, Minh; Phuc Nguyen, Xuan; Nhung Hoang Thi, My; Huong Le, Mai; Nguyen, Linh Toan; Quang Bui, Thuc; Hieu Phan, Van

2016-03-01

Along with the development of nanotechnology, drug delivery nanosystems (DDNSs) have attracted a great deal of concern among scientists over the world, especially in cancer treatment. DDNSs not only improve water solubility of anticancer drugs but also increase therapeutic efficacy and minimize the side effects of treatment methods through targeting mechanisms including passive and active targeting. Passive targeting is based on the nano-size of drug delivery systems while active targeting is based on the specific bindings between targeting ligands attached on the drug delivery systems and the unique receptors on the cancer cell surface. In this article we present some of our results in the synthesis and testing of DDNSs prepared from copolymer poly(lactide)-tocopheryl polyethylene glycol succinate (PLA-TPGS), which carry anticancer drugs including curcumin, paclitaxel and doxorubicin. In order to increase the targeting effect to cancer cells, active targeting ligand folate was attached to the DDNSs. The results showed copolymer PLA-TPGS to be an excellent carrier for loading hydrophobic drugs (curcumin and paclitaxel). The fabricated DDNSs had a very small size (50-100 nm) and enhanced the cellular uptake and cytotoxicity of drugs. Most notably, folate-decorated paclitaxel-loaded copolymer PLA-TPGS nanoparticles (Fol/PTX/PLA-TPGS NPs) were tested on tumor-bearing nude mice. During the treatment time, Fol/PTX/PLA-TPGS NPs always exhibited the best tumor growth inhibition compared to free paclitaxel and paclitaxel-loaded copolymer PLA-TPGS nanoparticles. All results evidenced the promising potential of copolymer PLA-TPGS in fabricating targeted DDNSs for cancer treatment.

SYNTHESIS AND CHARACTERIZATION OF NOVEL BIPOLAR PPV-BASED COPOLYMER CONTAINING TRIAZOLE AND CARBAZOLE UNITS

Institute of Scientific and Technical Information of China (English)

Ze Liu; Li-xiang Wang; Xia-bin Jing; Fo-song Wang

2001-01-01

Two new blue light-emitting PPV-based conjugated copolymers containing both an electron-withdrawing unit (triazole-TAZ) and electron-rich moieties (carbazole-CAR and bicarbazole-BCAR) were prepared by Wittig condensation polymerization between the triazole diphosphonium salt and the corresponding dialdehyde monomers. Their structures and properties were characterized by FT-IR, TGA, DSC, UV-Vis, PL spectroscopy and electrochemical measurements. The resulting copolymers are soluble in common organic solvents and thermally stable with a Ts of 147C for TAZ-CAR-PPV and of 157C for TAZ-BCAR-PPV. The maximum photoluminescence wavelengths of TAZ-CAR-PPV and TAZ-BCAR-PPV film appear at 460 nm and 480 nm, respectively. Cyclic voltammetry measurement demonstrates that TAZ-BCAR-PPV has good electrochemical reversibility, while TAZ-CAR-PPV exhibits the irreversible redox process. The triazole unit was found to be an effective π-conjugation interrupter and can play the rigid spacer role in determining the emission colour of the resulting copolymer.

Side-chain amino-acid-based pH-responsive self-assembled block copolymers for drug delivery and gene transfer.

Science.gov (United States)

Kumar, Sonu; Acharya, Rituparna; Chatterji, Urmi; De, Priyadarsi

2013-12-10

Developing safe and effective nanocarriers for multitype of delivery system is advantageous for several kinds of successful biomedicinal therapy with the same carrier. In the present study, we have designed amino acid biomolecules derived hybrid block copolymers which can act as a promising vehicle for both drug delivery and gene transfer. Two representative natural chiral amino acid-containing (l-phenylalanine and l-alanine) vinyl monomers were polymerized via reversible addition-fragmentation chain transfer (RAFT) process in the presence of monomethoxy poly(ethylene glycol) based macro-chain transfer agents (mPEGn-CTA) for the synthesis of well-defined side-chain amino-acid-based amphiphilic block copolymers, monomethoxy poly(ethylene glycol)-b-poly(Boc-amino acid methacryloyloxyethyl ester) (mPEGn-b-P(Boc-AA-EMA)). The self-assembled micellar aggregation of these amphiphilic block copolymers were studied by fluorescence spectroscopy, atomic force microscopy (AFM) and scanning electron microscopy (SEM). Potential applications of these hybrid polymers as drug carrier have been demonstrated in vitro by encapsulation of nile red dye or doxorubicin drug into the core of the micellar nanoaggregates. Deprotection of side-chain Boc- groups in the amphiphilic block copolymers subsequently transformed them into double hydrophilic pH-responsive cationic block copolymers having primary amino groups in the side-chain terminal. The DNA binding ability of these cationic block copolymers were further investigated by using agarose gel retardation assay and AFM. The in vitro cytotoxicity assay demonstrated their biocompatible nature and these polymers can serve as "smart" materials for promising bioapplications.

Investigation of some copolymers based on acrylic salts as circulation loss control agents

Directory of Open Access Journals (Sweden)

Ahmed Mohamed Alsabagh

2013-12-01

The prepared copolymers were investigated as loss circulation control materials by measuring different filtration parameters such as; spurt loss, fluid loss and permeability plugging tester value according to the American Petroleum Institute (API standard. From the obtained data, it was found that the 0.6% from the poly[PA-co-AM](0.4:0.6 exhibited the best results of the filtration parameters among the other copolymers. At the same time all the studied copolymers enhanced the rheological properties of the drilling mud. These results were discussed on the light of the swelling capacity of the copolymers.

Data on glycerol/tartaric acid-based copolymer containing ciprofloxacin for wound healing applications

Directory of Open Access Journals (Sweden)

E. De Giglio

2016-06-01

Full Text Available This data article is related to our recently published research paper “Exploiting a new glycerol-based copolymer as a route to wound healing: synthesis, characterization and biocompatibility assessment", De Giglio et al. (Colloids and Surfaces B: Biointerfaces 136 (2015 600–611 [1]. The latter described a new copolymer derived from glycerol and tartaric acid (PGT. Herein, an investigation about the PGT-ciprofloxacin (CIP interactions by means of Fourier Transform Infrared Spectroscopy (FT-IR acquired in Attenuated Total Reflectance (ATR mode and Differential Scanning Calorimetry (DSC was reported. Moreover, CIP release experiments on CIP-PGT patches were performed by High Performance Liquid Chromatography (HPLC at different pH values.

Bio-inspired synthesis of hybrid silica nanoparticles templated from elastin-like polypeptide micelles

Science.gov (United States)

Han, Wei; MacEwan, Sarah R.; Chilkoti, Ashutosh; López, Gabriel P.

2015-07-01

The programmed self-assembly of block copolymers into higher order nanoscale structures offers many attractive attributes for the development of new nanomaterials for numerous applications including drug delivery and biosensing. The incorporation of biomimetic silaffin peptides in these block copolymers enables the formation of hybrid organic-inorganic materials, which can potentially enhance the utility and stability of self-assembled nanostructures. We demonstrate the design, synthesis and characterization of amphiphilic elastin-like polypeptide (ELP) diblock copolymers that undergo temperature-triggered self-assembly into well-defined spherical micelles. Genetically encoded incorporation of the silaffin R5 peptide at the hydrophilic terminus of the diblock ELP leads to presentation of the silaffin R5 peptide on the coronae of the micelles, which results in localized condensation of silica and the formation of near-monodisperse, discrete, sub-100 nm diameter hybrid ELP-silica particles. This synthesis method, can be carried out under mild reaction conditions suitable for bioactive materials, and will serve as the basis for the development and application of functional nanomaterials. Beyond silicification, the general strategies described herein may also be adapted for the synthesis of other biohybrid nanomaterials as well.The programmed self-assembly of block copolymers into higher order nanoscale structures offers many attractive attributes for the development of new nanomaterials for numerous applications including drug delivery and biosensing. The incorporation of biomimetic silaffin peptides in these block copolymers enables the formation of hybrid organic-inorganic materials, which can potentially enhance the utility and stability of self-assembled nanostructures. We demonstrate the design, synthesis and characterization of amphiphilic elastin-like polypeptide (ELP) diblock copolymers that undergo temperature-triggered self-assembly into well

Synthesis and immobilization of polystyreneb-polyvinyltriethoxysilane micelles

KAUST Repository

Zhu, Saisai

2018-01-31

Diblock copolymers polystyrene-block-polyvinyltriethoxysilane (PS-b-PVTES) were synthesized via atom transfer radical polymerization (ATRP), which self-assembled into spherical micelles in solvent of THF-methanol mixtures. The self-assembled micelles were immobilized by cross-linking reaction of VTES in a shell layer of micelles. The chemical structures of block copolymers and morphology of micelles were characterized in detail. It was found that the size of immobilized micelles was strongly affected by the copolymer concentration, composition of mixture solvent, and block ratios.

Dynamics of chain exchange between self-assembled diblock copolymer micelles of poly(ethylene oxide)-block-polylactide studied by direct nonradiative excitation energy transfer

Czech Academy of Sciences Publication Activity Database

Popelka, Štěpán; Machová, Luďka; Rypáček, František; Špírková, Milena; Štěpánek, M.; Matějíček, P.; Procházka, K.

2005-01-01

Roč. 70, č. 11 (2005), s. 1811-1828 ISSN 0010-0765 R&D Projects: GA AV ČR IAA4050202; GA AV ČR IAA400500505 Institutional research plan: CEZ:AV0Z40500505 Keywords : block copolymers * self-assembly * micelles Subject RIV: CD - Macromolecular Chemistry Impact factor: 0.949, year: 2005

PVDF-based copolymers, terpolymers and their multi-component material systems for capacitor applications

Science.gov (United States)

Chu, Baojin

Miniature of power electronics, scaling-down of microelectronics and other electrical and electronic systems, and development of many technologies (such as hybrid vehicles or implantable heart defibrillators) require capacitors with high energy density to improve the weight and volume efficiency of the whole system. Various capacitor technologies are investigated to meet the requirements of developing future technologies. Among these technologies, polymer film capacitor technology is one of the most promising. Besides high energy density, polymer-based capacitors possess the merits of high power density, low loss, high reliability (self-healing), easy processing, and feasibility (in size, shape and energy level). Due to the ferroelectricity of polyvinylidene fluoride (PVDF)-based polymers, they exhibit much higher polarization response under an electric field, in comparison with other linear dielectric polymers for capacitor applications. The maximum polarization level of PVDF-based polymers can be as high as 0.1 C/m2 and the breakdown field can be higher than 600 MV/m. An estimated energy density of around 30 J/cm3 can be expected in this class of materials. However, this value is much higher than the energy density that can be achieved in the PVDF homopolymer and the poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) copolymers due to the polarization hysteresis in these polymers. Therefore, in this thesis, PVDF-based polymer materials were investigated and developed to approach this expected energy density by various strategies. An energy density of higher than 24 J/cm 3, which is close to the predicted value, was found in PVDF-based copolymers. Recently, the poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)) terpolymer was developed in Prof. Qiming Zhang's group. Previous works have shown that incorporation of CTE into P(VDF-TrFE) copolymers, in which bulky CFE acts as a defect, could convert the copolymer into relaxor

Synthesis of Fluorinated Amphiphilic Block Copolymers Based on PEGMA, HEMA, and MMA via ATRP and CuAAC Click Chemistry

Directory of Open Access Journals (Sweden)

Fatime Eren Erol

2014-01-01

Full Text Available Synthesis of fluorinated amphiphilic block copolymers via atom transfer radical polymerization (ATRP and Cu(I catalyzed Huisgen 1,3-dipolar cycloaddition (CuAAC was demonstrated. First, a PEGMA and MMA based block copolymer carrying multiple side-chain acetylene moieties on the hydrophobic segment for postfunctionalization was carried out. This involves the synthesis of a series of P(HEMA-co-MMA random copolymers to be employed as macroinitiators in the controlled synthesis of P(HEMA-co-MMA-block-PPEGMA block copolymers by using ATRP, followed by a modification step on the hydroxyl side groups of HEMA via Steglich esterification to afford propargyl side-functional polymer, alkyne-P(HEMA-co-MMA-block-PPEGMA. Finally, click coupling between side-chain acetylene functionalities and 2,3,4,5,6-pentafluorobenzyl azide yielded fluorinated amphiphilic block copolymers. The obtained polymers were structurally characterized by 1H-NMR, 19F-NMR, FT-IR, and GPC. Their thermal characterizations were performed using DSC and TGA.

Preparation, characterization, and in vitro activity evaluation of triblock copolymer-based polymersomes for drugs delivery

Science.gov (United States)

Besada, Lucas N.; Peruzzo, Pablo; Cortizo, Ana M.; Cortizo, M. Susana

2018-03-01

Polymersomes are polymer-based vesicles that form upon hydration of amphiphilic block copolymers and display high stability and durability, due to their mechanical and physical properties. They have hydrophilic reservoirs as well as thick hydrophobic membranes; allowing to encapsulate both water-soluble bioactive agent and hydrophobic drugs. In this study, poly ethylene glycol (PEG3350 and PEG6000) were used as hydrophilic part and poly(vinyl benzoate) (PVBz) as hydrophobic block to synthesize amphiphilic triblock copolymers (PVBz- b-PEG- b-PVBz). Different proportions of hydrophilic/hydrophobic part were assayed in order to obtain polymersomes by solvent injection method. For the synthesis of the copolymers, the initial block of PEG was derived to obtain a macroinitiator through a xanthate functional group (PEGX3 or PEGX6) and the polymerization of vinyl benzoate was carried out through reversible addition-fragmentation chain transfer polymerization (RAFT). The structure of PEGX and copolymers was confirmed by Infrared, 1H-NMR and UV-Vis spectrometry, while the average molecular weight (Mw) and polydispersity index (PI) were determined by size exclusion chromatography (SEC). The structures adopted by the copolymers in aqueous solution by self-assembly were investigated using transmission electron microscopy (TEM), dynamic light scattering (DLS) and small-angle X-ray scattering (SAXS). Both techniques confirm that polymersomes were obtained for a fraction of hydrophilic block ( f) ≈ 35 ± 10%, with a diameter of 38.3 ± 0.3 nm or 22.5 ± 0.7 nm, as determined by TEM and according to the M w of the precursor block copolymer. In addition, we analyzed the possible cytotoxicity in view of its potential application as biomedical nanocarrier. The results suggest that polymersomes seem not induce cytotoxicity during the periods of time tested.

Design, synthesis, and characterization of lightly sulfonated multigraft acrylate-based copolymer superelastomers

Energy Technology Data Exchange (ETDEWEB)

Misichronis, Konstantinos [Univ. of Tennessee, Knoxville, TN (United States). Dept. of Chemistry; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical Sciences Division; Wang, Weiyu [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Science (CNMS); Cheng, Shiwang [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical Sciences Division; Wang, Yangyang [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Science (CNMS); Shrestha, Umesh [Univ. of Tennessee, Knoxville, TN (United States). Dept. of Chemistry; Dadmun, Mark D. [Univ. of Tennessee, Knoxville, TN (United States). Dept. of Chemistry; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical Sciences Division; Mays, Jimmy W. [Univ. of Tennessee, Knoxville, TN (United States). Dept. of Chemistry; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical Sciences Division; Saito, Tomonori [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical Sciences Division

2018-01-29

Multigraft copolymer superelastomers consisting of a poly(n-butyl acrylate) backbone and polystyrene side chains were synthesized and the viscoelastic properties of the non-sulfonated and sulfonated final materials were investigated using extensional rheology (SER3). The non-linear viscoelastic experiments revealed significantly increased true stresses (up to 10 times higher) after sulfonating only 2–3% of the copolymer while the materials maintained high elongation (<700%). The linear viscoelastic experiments showed that the storage and loss modulus are increased by sulfonation and that the copolymers can be readily tuned and further improved by increasing the number of branching points and the molecular weight of the backbone. Here, in this way, we show that by tuning not only the molecular characteristics of the multigraft copolymers but also their architecture and chemical interaction, we can acquire thermoplastic superelastomer materials with desired viscoelastic properties.

Solid radiation curable polyene compositions containing liquid polythiols and solid styrene-allyl copolymer based polyenes

International Nuclear Information System (INIS)

Morgan, C.R.

1977-01-01

Novel styrene-allyl alcohol copolymer based solid polyene compositions which when mixed with liquid polythiols can form solid curable polyene-polythiol systems are claimed. These solid polyenes, containing at least two reactive carbon-to-carbon unsaturated bonds, are urethane or ester derivatives of styrene-allyl alcohol copolymers. The solid polyenes are prepared by treating the hydroxyl groups of a styrene-allyl alcohol copolymer with a reactive unsaturated isocyanate, e.g., allyl isocyanate or a reactive unsaturated carboxylic acid, e.g., acrylic acid. Upon exposure to a free radical generator, e.g., actinic radiation, the solid polyene-polythiol compositions cure to solid, insoluble, chemically resistant, cross-linked polythioether products. Since the solid polyene-liquid polythiol composition can be cured in a solid state, such a curable system finds particular use in preparation of coatings, imaged surfaces such as photoresists, particularly solder-resistant photoresists, printing plates, etc

Tadpole-Shaped POSS-Based Copolymers and the Aggregation Behavior at Air/Water Interface

Directory of Open Access Journals (Sweden)

Lin Zhu

2018-01-01

Full Text Available The aggregation behavior of three tadpole-shaped Polyhedral oligomeric silsesquioxane (POSS based block copolymers using different blocks poly(methyl methacrylate (PMMA and poly(trifluoroethyl methacrylate (PTFEMA with different block sequence and ratio (POSS-PTFEMA161-b-PMMA236, POSS-PMMA277-b-PTFEMA130, and POSS-PMMA466-b-PTFEMA172 was investigated on the air-water interface. The interfacial rheology of three block copolymers was studied by surface pressure isotherm, compression modulus measurements, and compression and expansion hysteresis analysis on the Langmuir trough. The block sequence and ratio play a great role in self-assembly behavior at the interface. Based on surface pressure isotherm analysis, a thin film with low elasticity was achieved for the POSS-PTFEMA161-b-PMMA236. Moreover, for the block copolymer with same segment sequence (POSS-PMMA2-b-PTFEMA, the thin film compression capability is increased with increasing the PMMA ratio. The morphology of the deposited LB thin film was illustrated by atomic force microscopy (AFM and X-ray photoelectron spectroscopy (XPS. We observed that a thin film was composed by crater-shaped quasi-2D micelles for POSS-PTFEMA-b-PMMA, while it was proved that only flaky texture was observed for both POSS-PMMA277-b-PTFEMA130 and POSS-PMMA466-b-PTFEMA172. The thickness and area of flaky aggregates were greatly related to PMMA ratio. The different interface self-assembly structure evolution was proposed based on the interfacial rheology and thin film morphology studies.

Microstructural evolution during tensile deformation of polypropylenes

International Nuclear Information System (INIS)

Dasari, A.; Rohrmann, J.; Misra, R.D.K.

2003-01-01

Tensile deformation processes occurring at varying strain rates in high and low crystallinity polypropylenes and ethylene-propylene di-block copolymers have been investigated by scanning electron microscopy. This is examined for both long and short chain polymeric materials. The deformation processes in different polymeric materials show striking dissimilarities in spite of the common propylene matrix. Additionally, the deformation behavior of long and their respective short chain polymers was different. Deformation mechanisms include crazing/tearing, wedging, ductile ploughing, fibrillation, and brittle fracture. The different modes of deformation are depicted in the form of strain rate-strain diagrams. At a constant strain rate, the strain to fracture follows the sequence: high crystallinity polypropylenes< low crystallinity polypropylenes< ethylene-propylene di-block copolymers, indicative of the trend in resistance to plastic deformation

Dynamics of Block Copolymer Nanocomposites

Energy Technology Data Exchange (ETDEWEB)

Mochrie, Simon G. J.

2014-09-09

A detailed study of the dynamics of cadmium sulfide nanoparticles suspended in polystyrene homopolymer matrices was carried out using X-ray photon correlation spectroscopy for temperatures between 120 and 180 °C. For low molecular weight polystyrene homopolymers, the observed dynamics show a crossover from diffusive to hyper-diffusive behavior with decreasing temperatures. For higher molecular weight polystyrene, the nanoparticle dynamics appear hyper-diffusive at all temperatures studied. The relaxation time and characteristic velocity determined from the measured hyper-diffusive dynamics reveal that the activation energy and underlying forces determined are on the order of 2.14 × 10-19 J and 87 pN, respectively. We also carried out a detailed X-ray scattering study of the static and dynamic behavior of a styrene– isoprene diblock copolymer melt with a styrene volume fraction of 0.3468. At 115 and 120 °C, we observe splitting of the principal Bragg peak, which we attribute to phase coexistence of hexagonal cylindrical and cubic double- gyroid structure. In the disordered phase, above 130 °C, we have characterized the dynamics of composition fluctuations via X-ray photon correlation spectroscopy. Near the peak of the static structure factor, these fluctuations show stretched-exponential relaxations, characterized by a stretching exponent of about 0.36 for a range of temperatures immediately above the MST. The corresponding characteristic relaxation times vary exponentially with temperature, changing by a factor of 2 for each 2 °C change in temperature. At low wavevectors, the measured relaxations are diffusive with relaxation times that change by a factor of 2 for each 8 °C change in temperature.

Multiblock copolymers synthesized in aqueous dispersions using multifunctional RAFT agents

NARCIS (Netherlands)

Bussels, R.; Bergman-Göttgens, C.M.; Meuldijk, J.; Koning, C.E.

2005-01-01

Triblock copolymers were synthesized in aqueous dispersions in two polymerization steps using a low molar mass difunctional dithiocarbamate-based RAFT agent, and in merely one polymerization step using a macromolecular difunctional dithiocarbamate-based RAFT agent. Segmented block copolymers

Dissipative Particle Dynamics Study of the pH-Dependent Behavior of Poly(2-vinylpyridine)-block-poly(ethylene oxide) Diblock Copolymer in Aqueous Buffers

Czech Academy of Sciences Publication Activity Database

Posel, Zbyšek; Limpouchová, Z.; Šindelka, K.; Lísal, Martin; Procházka, K.

2014-01-01

Roč. 47, č. 7 (2014), s. 2503-2514 ISSN 0024-9297 R&D Projects: GA ČR GCP205/11/J043 Grant - others:GA ČR(CZ) GAP106/12/0143 Institutional support: RVO:67985858 Keywords : monte-carlo simulations * union-type micelles * block-copolymer Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 5.800, year: 2014

Morphology-properties relationship on nanocomposite films based on poly(styrene-block-diene-block-styrene copolymers and silver nanoparticles

Directory of Open Access Journals (Sweden)

2011-02-01

Full Text Available A comparative study on the self-assembled nanostructured morphology and the rheological and mechanical properties of four different triblock copolymers, based on poly(styrene-block-diene-block-styrene and poly(styrene-block-diene-block-styrene matrices, and of their respective nanocomposites with 1 wt% silver nanoparticles, is reported in this work. In order to obtain well-dispersed nanoparticles in the block copolymer matrix, dodecanethiol was used as surfactant, showing good affinity with both nanoparticles and the polystyrene phase of the matrices as predicted by the solubility parameters calculated based on Hoftyzer and Van Krevelen theory. The block copolymer with the highest PS content shows the highest tensile modulus and tensile strength, but also the smallest elongation at break. When silver nanoparticles treated with surfactant were added to the block copolymer matrices, each system studied shows higher mechanical properties due to the good dispersion and the good interface of Ag nanoparticles in the matrices. Furthermore, it has been shown that semiempirical models such as Guth and Gold equation and Halpin-Tsai model can be used to predict the tensile modulus of the analyzed nanocomposites.

Bacterial resistance of self-assembled surfaces using PPOm-b-PSBMAn zwitterionic copolymer - concomitant effects of surface topography and surface chemistry on attachment of live bacteria.

Science.gov (United States)

Hsiao, Sheng-Wen; Venault, Antoine; Yang, Hui-Shan; Chang, Yung

2014-06-01

Three well-defined diblock copolymers made of poly(sulfobetaine methacrylate) (poly(SBMA)) and poly(propylene oxide) (PPO) groups were synthesized by atom transfer radical polymerization (ATRP) method. They were physically adsorbed onto three types of surfaces having different topography, including smooth flat surface, convex surface, and indented surface. Chemical state of surfaces was characterized by XPS while the various topographies were examined by SEM and AFM. Hydrophilicity of surfaces was dependent on both the surface chemistry and the surface topography, suggesting that orientation of copolymer brushes can be tuned in the design of surfaces aimed at resisting bacterial attachment. Escherichia coli, Staphylococcus epidermidis, Streptococcus mutans and Escherichia coli with green fluorescent protein (E. coli GFP) were used in bacterial tests to assess the resistance to bacterial attachment of poly(SBMA)-covered surfaces. Results highlighted a drastic improvement of resistance to bacterial adhesion with the increasing of poly(SBMA) to PPO ratio, as well as an important effect of surface topography. The chemical effect was directly related to the length of the hydrophilic moieties. When longer, more water could be entrapped, leading to improved anti-bacterial properties. The physical effect impacted on the orientation of the copolymer brushes, as well as on the surface contact area available. Convex surfaces as well as indented surfaces wafer presented the best resistance to bacterial adhesion. Indeed, bacterial attachment was more importantly reduced on these surfaces compared with smooth surfaces. It was explained by the non-orthogonal orientation of copolymer brushes, resulting in a more efficient surface coverage of zwitterionic molecules. This work suggests that not only the control of surface chemistry is essential in the preparation of surfaces resisting bacterial attachment, but also the control of surface topography and orientation of antifouling

Conformation of single block copolymer chain in two-dimensional microphase-separated structure studied by scanning near-field optical microscopy.

Science.gov (United States)

Sekine, Ryojun; Aoki, Hiroyuki; Ito, Shinzaburo

2009-05-21

The localization and orientation of the symmetric diblock copolymer chain in a quasi-two-dimensional microphase-separated structure were studied by scanning near-field optical microscopy (SNOM). In the monolayer of poly(isobutyl methacrylate)-block-poly(octadecyl methacrylate) (PiBMA-b-PODMA), the individual PiBMA subchains were directly observed by SNOM, and the center of mass (CM) and orientational angle relative to the phase interface were examined at the single chain level. It was found that the position of the CM and the orientation of the PiBMA subchain in the lamellar structure were dependent on the curvature of the PiBMA/PODMA interface. As the interface was bent toward the objective chain, the block chain preferred the CM position closer to the domain center, and the conformation was strongly oriented perpendicularly to the domain interface. With increase of the curvature, the steric hindrance among the block chain increases, resulting in the stretched conformation.

Renewable poly(δ-decalactone based block copolymer micelles as drug delivery vehicle: in vitro and in vivo evaluation

Directory of Open Access Journals (Sweden)

Kuldeep K. Bansal

2018-03-01

Full Text Available Polymers from natural resources are attracting much attention in various fields including drug delivery as green alternatives to fossil fuel based polymers. In this quest, novel block copolymers based on renewable poly(δ-decalactone (PDL were evaluated for their drug delivery capabilities and compared with a fossil fuel based polymer i.e. methoxy-poly(ethylene glycol-b-poly(ε-caprolactone (mPEG-b-PCL. Using curcumin as a hydrophobic drug model, micelles of PDL block copolymers with different orientation i.e. AB (mPEG-b-PDL, ABA (PDL-b-PEG-b-PDL, ABC (mPEG-b-PDL-b-poly(pentadecalactone and (mPEG-b-PCL were prepared by nanoprecipitation method. The size, drug loading and curcumin stability studies results indicated that mPEG-b-PDL micelles was comparable to its counterpart mPEG-b-PCL micelles towards improved delivery of curcumin. Therefore, mixed micelles using these two copolymers were also evaluated to see any change in size, loading and drug release. Drug release studies proposed that sustained release can be obtained using poly(pentadecalactone as crystalline core whereas rapid release can be achieved using amorphous PDL core. Further, mPEG-b-PDL micelles were found to be non-haemolytic, up to the concentration of 40 mg/mL. In vivo toxicity studies on rats advised low-toxic behaviour of these micelles up to 400 mg/kg dose, as evident by histopathological and biochemical analysis. In summary, it is anticipated that mPEG-b-PDL block copolymer micelles could serve as a renewable alternative for mPEG-b-PCL copolymers in drug delivery applications.

Olefin–Styrene Copolymers

OpenAIRE

Nunzia Galdi; Antonio Buonerba; Leone Oliva

2016-01-01

In this review are reported some of the most relevant achievements in the chemistry of the ethylene–styrene copolymerization and in the characterization of the copolymer materials. Focus is put on the relationship between the structure of the catalyst and that of the obtained copolymer. On the other hand, the wide variety of copolymer architecture is related to the properties of the material and to the potential utility.

Synthesis by ATRP of poly(ethylene-co-butylene)-block-polystyrene, poly(ethylene-co-butylene)-block-poly(4-acetoxystyrene) and its hydrolysis product poly(ethylene-co-butylene)-block-poly(hydroxystyrene)

DEFF Research Database (Denmark)

Jankova, Katja; Kops, Jørgen; Chen, Xianyi

1999-01-01

Diblock copolymers of poly(ethylene-co-butylene) and polystyrene or poly(4-acetoxystyrene) are synthesized by atom transfer radical polymerization (ATRP) using a 2-bromopropionic ester macroinitiator prepared from commercial monohydroxyl functional narrow dispersity hydrogenated polybutadiene...

Hydrophilic segmented block copolymers based on poly(ethylene oxide) and monodisperse amide segments

NARCIS (Netherlands)

Husken, D.; Feijen, Jan; Gaymans, R.J.

2007-01-01

Segmented block copolymers based on poly(ethylene oxide) (PEO) flexible segments and monodisperse crystallizable bisester tetra-amide segments were made via a polycondensation reaction. The molecular weight of the PEO segments varied from 600 to 4600 g/mol and a bisester tetra-amide segment (T6T6T)

Solid polymer electrolytes based on alternating copolymers of vinyl ethers with methoxy oligo(ethyleneoxy)ethyl groups and vinylene carbonate

International Nuclear Information System (INIS)

Itoh, Takahito; Fujita, Katsuhito; Inoue, Kentaro; Iwama, Hiroki; Kondoh, Kensaku; Uno, Takahiro; Kubo, Masataka

2013-01-01

Graphical abstract: - Highlights: • Synthesis of alternating copolymers of vinyl ethers and vinylene carbonate. • Preparation of polymer electrolytes based on the alternating copolymers with LiTFSI. • Structure-property relationship for alternating copolymers-based electrolytes. • Interfacial stability between polymer electrolytes with lithium metal electrode. - Abstract: Alternating copolymers (poly(1a-g-alt-VC)) of vinyl ethers with various methoxy oligo(ethyleneoxy)ethyl groups and vinylene carbonate (VC) were prepared, and the thermal and electrochemical properties of their polymer electrolytes with LiTFSI and interfacial stability between the polymer electrolyte and Li metal electrode were investigated. T g 's increased linearly with salt contents, and decreased with an increase in the chain length of methoxy oligo(ethyleneoxy)ethyl groups in the vinyl ethers at constant salt concentration. The slopes of T g vs. [Li]/[O] were identical, independent of the polymer structure. The ionic conductivities of the polymer electrolytes increased with increasing the side-chain ethyleneoxy (EO) unit length of the vinyl ether unit in the alternating copolymers, and also their temperature dependences became relatively smaller in the polymer electrolytes having longer EO units in the vinyl ethers. The highest ionic conductivity, 1.2 × 10 −4 S/cm at 30 °C, was obtained in the alternating copolymer with a side-chain EO unit length of 23.5 in the vinyl ether unit. Ion transport coupled with the segmental motion of the polymer is dominant in these polymer electrolytes. Interfacial resistance increased gradually with contact time, indicative of the formation of passivation films on the Li metal electrode. These polymer electrolytes are thermally stable and have large electrochemical windows of use

Blends of Styrene-Butadiene-Styrene Triblock Copolymer with Random Styrene-Maleic Anhydride Copolymers

NARCIS (Netherlands)

Piccini, Maria Teresa; Ruggeri, Giacomo; Passaglia, Elisa; Picchioni, Francesco; Aglietto, Mauro

2002-01-01

Blends of styrene-butadiene-styrene triblock copolymer (SBS) with random styrene-maleic anhydride copolymers (PS-co-MA), having different MA content, were prepared in a Brabender Plastigraph mixer. The presence of polystyrene (PS) blocks in the SBS copolymer and the high styrene content (93 and 86

Core–Shell Structure and Aggregation Number of Micelles Composed of Amphiphilic Block Copolymers and Amphiphilic Heterografted Polymer Brushes Determined by Small-Angle X-ray Scattering

Energy Technology Data Exchange (ETDEWEB)

Szymusiak, Magdalena; Kalkowski, Joseph; Luo, Hanying; Donovan, Alexander J.; Zhang, Pin; Liu, Chang; Shang, Weifeng; Irving, Thomas; Herrera-Alonso, Margarita; Liu, Ying (JHU); (IIT); (UIC)

2017-08-31

A large group of functional nanomaterials employed in biomedical applications, including targeted drug delivery, relies on amphiphilic polymers to encapsulate therapeutic payloads via self-assembly processes. Knowledge of the micelle structures will provide critical insights into design of polymeric drug delivery systems. Core–shell micelles composed of linear diblock copolymers poly(ethylene glycol)-b-poly(caprolactone) (PEG-b-PCL), poly(ethylene oxide)-b-poly(lactic acid) (PEG-b-PLA), as well as a heterografted brush consisting of a poly(glycidyl methacrylate) backbone with PEG and PLA branches (PGMA-g-PEG/PLA) were characterized by dynamic light scattering (DLS) and small-angle X-ray scattering (SAXS) measurements to gain structural information regarding the particle morphology, core–shell size, and aggregation number. The structural information at this quasi-equilibrium state can also be used as a reference when studying the kinetics of polymer micellization.

Core–Shell Structure and Aggregation Number of Micelles Composed of Amphiphilic Block Copolymers and Amphiphilic Heterografted Polymer Brushes Determined by Small-Angle X-ray Scattering

Energy Technology Data Exchange (ETDEWEB)

Szymusiak, Magdalena [Department; Kalkowski, Joseph [Department; Luo, Hanying [Department; Donovan, Alexander J. [Department; Zhang, Pin [Department; Liu, Chang [Department; Shang, Weifeng [Department; Irving, Thomas [Department; Herrera-Alonso, Margarita [Department; Liu, Ying [Department; Department

2017-08-16

A large group of functional nanomaterials employed in biomedical applications, including targeted drug delivery, relies on amphiphilic polymers to encapsulate therapeutic payloads via self-assembly processes. Knowledge of the micelle structures will provide critical insights into design of polymeric drug delivery systems. Core–shell micelles composed of linear diblock copolymers poly(ethylene glycol)-b-poly(caprolactone) (PEG-b-PCL), poly(ethylene oxide)-b-poly(lactic acid) (PEG-b-PLA), as well as a heterografted brush consisting of a poly(glycidyl methacrylate) backbone with PEG and PLA branches (PGMA-g-PEG/PLA) were characterized by dynamic light scattering (DLS) and small-angle X-ray scattering (SAXS) measurements to gain structural information regarding the particle morphology, core–shell size, and aggregation number. The structural information at this quasi-equilibrium state can also be used as a reference when studying the kinetics of polymer micellization.

Facile Synthesis of Magnetic Copolymer Microspheres Based on Poly(glycidyl methacrylate-co-N-isopropylacrylamide/Fe3O4 by Suspension Photopolymerization

Directory of Open Access Journals (Sweden)

Siti Zulaikha Mazlan

2014-01-01

Full Text Available Magnetic copolymer based on poly(glycidyl methacrylate-co-N-isopropylacrylamide microspheres was prepared by 2,2-dimethoxy-2-phenylacetophenone- (DMPP- photo initiated and poly(vinyl alcohol- (PVA- stabilized single step suspension photopolymerization. The effect of chemical interaction, morphology, and thermal properties by adding 0.1% w/v Fe3O4 in the copolymer was investigated. Infrared analysis (FTIR showed that (C=C band disappeared after copolymerization, indicating that the magnetic copolymer microspheres were successfully synthesized and two important bands at 908 cm−1 and 1550 cm−1 appear. These are associated with the epoxy group stretching of GMA and secondary amide (N–H/C–H deformation vibration of NIPAAm in magnetic microspheres. The X-ray diffraction (XRD result proved the incorporation of Fe3O4 nanoparticles with copolymer microspheres as peak of Fe3O4 was observed. Morphology study revealed that magnetic copolymer exhibited uniform spheres and smoother appearance when entrapped with Fe3O4 nanoparticles. The lowest percentage of Fe3O4 nanoparticles leached from the copolymer microspheres was obtained at pH 7. Finally, thermal property of the copolymer microspheres was improved by adding a small amount of Fe3O4 nanoparticles that has been shown from the thermogram.

Methacrylate-Based Copolymers for Polymer Optical Fibers

Directory of Open Access Journals (Sweden)

Daniel Zaremba

2017-01-01

Full Text Available Waveguides made of poly-methyl-methacrylate (PMMA play a major role in the homogeneous distribution of display backlights as a matrix for solid-state dye lasers and polymer optical fibers (POFs. PMMA is favored because of its transparency in the visible spectrum, low price, and well-controlled processability. Nevertheless, technical drawbacks, such as its limited temperature stability, call for new materials. In this work, the copolymerization technique is used to modify the properties of the corresponding homopolymers. The analytical investigation of fourteen copolymers made of methyl-methacrylate (MMA or ethyl-methacrylate (EMA as the basis monomer is summarized. Their polymerization behaviors are examined by NMR spectroscopy with subsequent copolymerization parameter evaluation according to Fineman-Ross and Kelen-Tüdös. Therefore, some r-parameter sets are shown to be capable of copolymerizations with very high conversions. The first applications as high-temperature resistant (HT materials for HT-POFs are presented. Copolymers containing isobornyl-methacrylate (IBMA as the comonomer are well-suited for this demanding application.

Novel Injectable Pentablock Copolymer Based Thermoresponsive Hydrogels for Sustained Release Vaccines.

Science.gov (United States)

Bobbala, Sharan; Tamboli, Viral; McDowell, Arlene; Mitra, Ashim K; Hook, Sarah

2016-01-01

The need for multiple vaccinations to enhance the immunogenicity of subunit vaccines may be reduced by delivering the vaccine over an extended period of time. Here, we report two novel injectable pentablock copolymer based thermoresponsive hydrogels made of polyethyleneglycol-polycaprolactone-polylactide-polycaprolactone-polyethyleneglycol (PEG-PCL-PLA-PCL-PEG) with varying ratios of polycaprolactone (PCL) and polylactide (PLA), as single shot sustained release vaccines. Pentablock copolymer hydrogels were loaded with vaccine-encapsulated poly lactic-co-glycolic acid nanoparticles (PLGA-NP) or with the soluble vaccine components. Incorporation of PLGA-NP into the thermoresponsive hydrogels increased the complex viscosity of the gels, lowered the gelation temperature, and minimized the burst release of antigen and adjuvants. The two pentablock hydrogels stimulated both cellular and humoral responses. The addition of PLGA-NP to the hydrogels sustained immune responses for up to 49 days. The polymer with a higher ratio of PCL to PLA formed a more rigid gel, induced stronger immune responses, and stimulated effective anti-tumor responses in a prophylactic melanoma tumor model.

A pH- and temperature-responsive bioresorbable injectable hydrogel based on polypeptide block copolymers for the sustained delivery of proteins in vivo.

Science.gov (United States)

Turabee, Md Hasan; Thambi, Thavasyappan; Duong, Huu Thuy Trang; Jeong, Ji Hoon; Lee, Doo Sung

2018-02-27

Sustained delivery of protein therapeutics is limited owing to the fragile nature of proteins. Despite its great potential, delivery of proteins without any loss of bioactivity remains a challenge in the use of protein therapeutics in the clinic. To surmount this shortcoming, we report a pH- and temperature-responsive in situ-forming injectable hydrogel based on comb-type polypeptide block copolymers for the controlled delivery of proteins. Polypeptide block copolymers, composed of hydrophilic polyethylene glycol (PEG), temperature-responsive poly(γ-benzyl-l-glutamate) (PBLG), and pH-responsive oligo(sulfamethazine) (OSM), exhibit pH- and temperature-induced sol-to-gel transition behavior in aqueous solutions. Polypeptide block copolymers were synthesized by combining N-carboxyanhydride-based ring-opening polymerization and post-functionalization of the chain-end using N-hydroxy succinimide ester activated OSM. The physical properties of polypeptide-based hydrogels were tuned by varying the composition of temperature- and pH-responsive PBLG and OSM in block copolymers. Polypeptide block copolymers were non-toxic to human embryonic kidney cells at high concentrations (2000 μg mL -1 ). Subcutaneous administration of polypeptide block copolymer sols formed viscoelastic gel instantly at the back of Sprague-Dawley (SD) rats. The in vivo gels exhibited sustained degradation and were found to be bioresorbable in 6 weeks without any noticeable inflammation at the injection site. Anionic characteristics of hydrogels allow efficient loading of a cationic model protein, lysozyme, through electrostatic interaction. Lysozyme-loaded polypeptide block copolymer sols readily formed a viscoelastic gel in vivo and sustained lysozyme release for at least a week. Overall, the results demonstrate an elegant approach to control the release of certain charged proteins and open a myriad of therapeutic possibilities in protein therapeutics.

Synthesis and characterization of polyester copolymers based on poly(butylene succinate) and poly(ethylene glycol)

International Nuclear Information System (INIS)

Zhou, Xiao-Ming

2012-01-01

A series of polyester copolymers was synthesized from 1,4-succinic acid with 1,4-butanediol and poly(ethylene glycol) through a two-step process of esterification and polycondensation in this article. The composition and physical properties of copolyesters were investigated via GPC, 1 HNMR, DSC and PLM. The copolymer composition was in good agreement with that expected from the feed composition of the reactants. The melting temperature (T m ), crystallization temperature (T c ), and crystallinity (X c ) of these copolyesters decreased gradually as the content of PEG unit increased. Otherwise, experimental results also showed that the contents of PEG in copolymers had an effect on the molecular weight, distribution, thermal properties, hydrolysis degradation properties, and crystalline morphology of polyester copolymers. - Graphical abstract: The composition of polyester copolymer was determined from the 1 H NMR spectra using the relative intensities of the proton peaks. As a sample, the 1 H NMR spectrum of polyester copolymer with 10 mol% of PEG is shown in Fig. 2: CO-(CH 2 ) 2 -CO; O-CH 2 - and C-(CH 2 ) 2 -C from the SA and BD unit at δ2.59; δ 4.08 and δ1.67; O-(CH 2 CH 2 ) n -O from the PEG unit at δ 3.61. The molar composition of polyester copolymer was measured as the area ratio of δ3.61/(δ4.08 + δ1.67) peak. The PEG unit is incorporated into the copolymers in an amount of about 9.12mol% less than that of the feed proportion. These results showed that the composition of the copolymers is in good agreement with that expected from the feed proportion. Highlights: ► The introduction of PEG unit changed the flexibility of PBS main chain. ► PEG unit did not alter the crystal form of PBS in copolymers. ► PEG unit hindered the formation of ring-banded spherulite morphology in copolymers. ► The copolyesters had good in vitro degradation performance. ► The composition ratio of PEG unit can adjust the in vitro degradation performance.

Main-chain supramolecular block copolymers.

Science.gov (United States)

Yang, Si Kyung; Ambade, Ashootosh V; Weck, Marcus

2011-01-01

Block copolymers are key building blocks for a variety of applications ranging from electronic devices to drug delivery. The material properties of block copolymers can be tuned and potentially improved by introducing noncovalent interactions in place of covalent linkages between polymeric blocks resulting in the formation of supramolecular block copolymers. Such materials combine the microphase separation behavior inherent to block copolymers with the responsiveness of supramolecular materials thereby affording dynamic and reversible materials. This tutorial review covers recent advances in main-chain supramolecular block copolymers and describes the design principles, synthetic approaches, advantages, and potential applications.

Rheological Behavior of Entangled Polystyrene-Polyhedral Oligosilsesquioxane (POSS) Copolymer

National Research Council Canada - National Science Library

Wu, Jian; Mather, Patrick T; Haddad, Timothy S; Kim, Gyeong-Man

2006-01-01

...: random copolymers of polystyrene (PS) and styryl-based polyhedral oligosilsesquioxane (POSS), R7(Si8O12)(C6H4CH=CH2), with R = isobutyl (iBu). A series of styrene-styryl POSS random copolymers with 0, 6, 15, 30, 50 wt...

Realization of an integrated VDF/TrFE copolymer-on-silicon pyroelectric sensor

NARCIS (Netherlands)

Setiadi, D.; Setiadi, D.; Regtien, Paulus P.L.; Sarro, P.M.

1995-01-01

An integrated pyroelectric sensor based on a vinylidene fluoride trifluoroethylene (VDF/TrFE) copolymer is presented. A silicon substrate that contains FET readout electronics is coated with the VDF/TrFE copolymer film using a spin-coating technique. On-chip poling of the copolymer has been applied

Electrical and optical properties of diketopyrrolopyrrole-based copolymer interfaces in thin film devices.

Science.gov (United States)

Adil, Danish; Kanimozhi, Catherine; Ukah, Ndubuisi; Paudel, Keshab; Patil, Satish; Guha, Suchi

2011-05-01

Two donor-acceptor diketopyrrolopyrrole (DPP)-based copolymers (PDPP-BBT and TDPP-BBT) have been synthesized for their application in organic devices such as metal-insulator semiconductor (MIS) diodes and field-effect transistors (FETs). The semiconductor-dielectric interface was characterized by capacitance-voltage and conductance-voltage methods. These measurements yield an interface trap density of 4.2 × 10(12) eV⁻¹ cm⁻² in TDPP-BBT and 3.5 × 10¹² eV⁻¹ cm⁻² in PDPP-BBT at the flat-band voltage. The FETs based on these spincoated DPP copolymers display p-channel behavior with hole mobilities of the order 10⁻³ cm²/(Vs). Light scattering studies from PDPP-BBT FETs show almost no change in the Raman spectrum after the devices are allowed to operate at a gate voltage, indicating that the FETs suffer minimal damage due to the metal-polymer contact or the application of an electric field. As a comparison Raman intensity profile from the channel-Au contact layer in pentacene FETs are presented, which show a distinct change before and after biasing.

Amphiphilic glycosylated block copolypeptides as macromolecular surfactants in the emulsion polymerization of styrene

NARCIS (Netherlands)

Jacobs, Jaco; Gathergood, N.; Heuts, J.P.A.; Heise, A.

2015-01-01

Diblock copolymers consisting of poly(L-phenyl alanine) and poly(benzyl-L-glutamate) or poly(CBZ-L-lysine), respectively, were synthesized via sequential NCA polymerization. After deprotection, subsequent partial glycosylation of the glutamic acid and lysine units with galactosamine hydrochloride or

Volume holographic storage and multiplexing in blends of PMMA and a block methacrylic azopolymer, using 488 nm light pulses in the range of 100 ms to 1 s

DEFF Research Database (Denmark)

Forcen, Patricia; Oriol, Luis; Sanchez, Carlos

2008-01-01

Blends of polymethylmethacrylate (PMMA) and diblock methacrylic azopolymers have been investigated for holographic storage with short light pulses. Transmission electron microscopy measurements show that the dilution of the block copolymer in PMMA changes the microstructure from a lamellar to a s...

A novel diblock copolymer of (monomethoxy poly [ethylene glycol]-oleate with a small hydrophobic fraction to make stable micelles/polymersomes for curcumin delivery to cancer cells

Directory of Open Access Journals (Sweden)

Erfani-Moghadam V

2014-11-01

effect of the prepared nanostructures. Apoptosis induction was observed in a dose-dependent manner after curcumin-loaded mPEG-OA treatments. Two common self-assembling structures, micelles and polymersomes, were observed by atomic force microscopy and dynamic light scattering, and the abundance of each structure was dependent on the concentration of the diblock copolymer. The mPEG-OA micelles had a very low CMC (13.24 µM or 0.03 g/L. Moreover, atomic force microscopy and dynamic light scattering showed that the curcumin-loaded mPEG-OA polymersomes had very stable structures, and at concentrations 1,000 times less than the CMC, at which the micelles disappear, polymersomes were the dominant structures in the dispersion with a reduced size distribution below 150 nm. Overall, the results from these tests revealed that this nanocarrier can be considered as an appropriate drug delivery system for delivering curcumin to cancer cells. Keywords: anticancer agent, nanocarrier, encapsulation, bioavailability, apoptosis, critical micelle concentration

Synthesis of ABA Tri-Block Co-Polymer Magnetopolymersomes via Electroporation for Potential Medical Application

Directory of Open Access Journals (Sweden)

Jennifer Bain

2015-12-01

Full Text Available The ABA tri-block copolymer poly(2-methyloxazoline–poly(dimethylsiloxane–poly(2-methyloxazoline (PMOXA–PDMS–PMOXA is known for its capacity to mimic a bilayer membrane in that it is able to form vesicular polymersome structures. For this reason, it is the subject of extensive research and enables the development of more robust, adaptable and biocompatible alternatives to natural liposomes for biomedical applications. However, the poor solubility of this polymer renders published methods for forming vesicles unreproducible, hindering research and development of these polymersomes. Here we present an adapted, simpler method for the production of PMOXA–PDMS–PMOXA polymersomes of a narrow polydispersity (45 ± 5.8 nm, via slow addition of aqueous solution to a new solvent/polymer mixture. We then magnetically functionalise these polymersomes to form magnetopolymersomes via in situ precipitation of iron-oxide magnetic nanoparticles (MNPs within the PMOXA–PDMS–PMOXA polymersome core and membrane. This is achieved using electroporation to open pores within the membrane and to activate the formation of MNPs. The thick PMOXA–PDMS–PMOXA membrane is well known to be relatively non-permeable when compared to more commonly used di-block polymer membranes due a distinct difference in both size and chemistry and therefore very difficult to penetrate using standard biological methods. This paper presents for the first time the application of electroporation to an ABA tri-block polymersome membrane (PMOXA–PDMS–PMOXA for intravesicular in situ precipitation of uniform MNPs (2.6 ± 0.5 nm. The electroporation process facilitates the transport of MNP reactants across the membrane yielding in situ precipitation of MNPs. Further to differences in length and chemistry, a tri-block polymersome membrane structure differs from a natural lipid or di-block polymer membrane and as such the application and effects of electroporation on this type of

Synthesis of a gamma irradiation grafted polytetrafluoroethylene (PTFE) based olefinic copolymer

International Nuclear Information System (INIS)

Ferreto, Helio Fernando Rodrigues

2006-01-01

The extrusion of linear low density polyethylene (LLDPE) is limited by a process related defect known as 'melt fracture' or 'sharkskin', which is a surface defect of the extruded polymer. This defect results in a product with a rough surface that lacks luster and in alterations of specific surface properties. The aim of this study was to obtain a recycled polytetrafluoroethylene polymer with an olefin that could improve the extrudability of the LLDPE. The copolymer was obtained by irradiating recycled PTFE in an inert atmosphere followed by the addition of an olefinic monomer to graft the latter in the polymeric matrix (PTFE). After a certain time of contact, the copolymer was heat treated to permit recombination and elimination of the radicals, both in a reactive and/or inert atmosphere. Three olefinic monomers were used, namely; acetylene, ethylene and 1,3-butadiene. The 1,3-butadiene monomer was found to be more effective with respect to grafting. The specimens were studied using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and differential thermogravimetry (DTG). 0.2-2.0 wt% of the copolymer that was obtained was mixed with LLDPE. The rheological properties of the mixture were determined with a torque rheometer. The results indicated that the process used rendered a copolymer which when added to LLDPE, improved the extrusion process and eliminated the defect 'melt fracture'. (author)

Metallo-supramolecular block copolymer micelles

NARCIS (Netherlands)

Gohy, J.M.W.

2009-01-01

Supramolecular copolymers have become of increasing interest in recent years in the search for new materials with tunable properties. In particular, metallo-supramolecular block copolymers in which metal-ligand complexes are introduced in block copolymer architectures, have known important progress,

Renewable Pentablock Copolymers Containing Bulky Natural Rosin for Tough Bioplastics

Science.gov (United States)

Rahman, Md Anisur; Ganewatta, Mitra S.; Lokupitiya, Hasala N.; Liang, Yuan; Stefik, Morgan; Tang, Chuanbing

Renewable polymers have received significant attention due to environmental concerns on petrochemical counterparts. One of the most abundant natural biomass is resin acids. However, most polymers derived from resin acids are low molecular weight and brittle because of the high chain entanglement molecular weight resulted from the bulky hydrophenanthrene pendant group. It is well established that the brittleness can be overcome by synthesizing multi-block copolymers with low entanglement molecular weight components. We investigated the effects of chain architecture and microdomain orientation on mechanical properties of both tri and pentablock copolymers. We synthesized rosin-containing A-B-A-B-A type pentablock and A-B-A type triblock copolymers to improve their mechanical properties. Pentablock copolymers showed higher strength and better toughness as compared to triblock copolymers, both superior to homopolymers. The greater toughness of pentablock copolymers is due to the presence of the rosin based midblock chains that act as bridging chains between two polynorbornene blocks.

Nano-emulsion based on acrylic acid ester co-polymer derivatives as an efficient pre-tanning agent for buffalo hide

OpenAIRE

El-Monem, Farouk Abd; Hussain, Ahmed I.; Nashy, EL-Shahat H.A.; El-Wahhab, Hamada Abd; Naser, Abd El-Rahman M.

2014-01-01

Acrylic copolymer nanoemulsions were prepared based on methyl methacrylate (MMA) and butyl acrylate (BA). The prepared acrylic copolymer emulsions were characterized using solid content, rheological properties, molecular weight, MFFT and TEM. The prepared polymers were used as pre-tanning of the depickled hide to enhance the physico-mechanical properties of tanned leather. The key parameters which affect exhaustion and fixation of chrome tan as well as shrinkage temperature of the tanned leat...

Distribution of short block copolymer chains in Binary Blends of Block Copolymers Having Hydrogen Bonding

Science.gov (United States)

Kwak, Jongheon; Han, Sunghyun; Kim, Jin Kon

2014-03-01

A binary mixture of two block copolymers whose blocks are capable of forming the hydrogen bonding allows one to obtain various microdomains that could not be expected for neat block copolymer. For instance, the binary blend of symmetric polystyrene-block-poly(2-vinylpyridine) copolymer (PS-b-P2VP) and polystyrene-block-polyhydroxystyrene copolymer (PS-b-PHS) blends where the hydrogen bonding occurred between P2VP and PHS showed hexagonally packed (HEX) cylindrical and body centered cubic (BCC) spherical microdomains. To know the exact location of short block copolymer chains at the interface, we synthesized deuterated polystyrene-block-polyhydroxystyrene copolymer (dPS-b-PHS) and prepared a binary mixture with PS-b-P2VP. We investigate, via small angle X-ray scattering (SAXS) and neutron reflectivity (NR), the exact location of shorter dPS block chain near the interface of the microdomains.

Highly conductive side chain block copolymer anion exchange membranes.

Science.gov (United States)

Wang, Lizhu; Hickner, Michael A

2016-06-28

Block copolymers based on poly(styrene) having pendent trimethyl styrenylbutyl ammonium (with four carbon ring-ionic group alkyl linkers) or benzyltrimethyl ammonium groups with a methylene bridge between the ring and ionic group were synthesized by reversible addition-fragmentation radical (RAFT) polymerization as anion exchange membranes (AEMs). The C4 side chain polymer showed a 17% increase in Cl(-) conductivity of 33.7 mS cm(-1) compared to the benzyltrimethyl ammonium sample (28.9 mS cm(-1)) under the same conditions (IEC = 3.20 meq. g(-1), hydration number, λ = ∼7.0, cast from DMF/1-propanol (v/v = 3 : 1), relative humidity = 95%). As confirmed by small angle X-ray scattering (SAXS), the side chain block copolymers with tethered ammonium cations showed well-defined lamellar morphologies and a significant reduction in interdomain spacing compared to benzyltrimethyl ammonium containing block copolymers. The chemical stabilities of the block copolymers were evaluated under severe, accelerated conditions, and degradation was observed by (1)H NMR. The block copolymer with C4 side chain trimethyl styrenylbutyl ammonium motifs displayed slightly improved stability compared to that of a benzyltrimethyl ammonium-based AEM at 80 °C in 1 M NaOD aqueous solution for 30 days.

Nanostructure of polymer monolayer and polyelectrolyte brush at air/water interface by X-ray and neutron reflectometry

CERN Document Server

Matsuoka, H; Matsumoto, K

2003-01-01

The nanostructure of amphiphilic diblock copolymer monolayer on water was directly investigated by in situ X-ray and neutron reflectivity techniques. The diblock copolymer consists of polysilacyclobutane, which is very flexible, as a hydrophobic block and polymethacrylic acid, an anionic polymer, as a hydrophilic block. The polymers with shorter hydrophilic segment formed a very smooth and uniform monolayer with hydrophobic layer on water and dense hydrophilic layer under the water. But the longer hydrophilic segment polymer formed three-layered monolayer with polyelectrolyte brush in addition to hydrophobic and dense hydrophilic layers. The dense hydrophilic layer is thought to be formed to avoid a contact between hydrophobic polymer layer and water. Its role is something like a 'carpet'. An additional interesting information is that the thickness of the 'carpet layer' is almost 15A, independent the surface pressure and hydrophilic polymer length. Highly quantitative information was obtained about the nanost...

Anionic polymerization and polyhomologation: An ideal combination to synthesize polyethylene-based block copolymers

KAUST Repository

Zhang, H.

2013-08-07

A novel one-pot methodology combining anionic polymerization and polyhomologation, through a "bridge" molecule (BF3OEt 2), was developed for the synthesis of polyethylene (PE)-based block copolymers. The anionically synthesized macroanion reacts with the "bridge" molecule to afford a 3-arm star (trimacromolecular borane) which serves as an initiator for the polyhomologation. 2013 The Royal Society of Chemistry.

Effect of furan π-bridge on the photovoltaic performance of D-A copolymers based on bi(alkylthio-thienyl)benzodithiophene and fluorobenzotriazole

Institute of Scientific and Technical Information of China (English)

Tinghai Yan; Haijun Bin; Yankang Yang; Lingwei Xue; Zhi-Guo Zhang; Yongfang Li

2017-01-01

The medium band gap donor-acceptor（D-A） copolymer J61 based on bi（alkylthio-thienyl）benzodithiophene as donor unit and fluorobenzotriazole as acceptor unit and thiophene as π-bridge has demonstrated excellent photovoltaic performance as donor material in nonfullerene polymer solar cells（PSCs） with narrow bandgap n-type organic semiconductor ITIC as acceptor.For studying the effect of π-bridges on the photovoltaic performance of the D-A copolymers,here we synthesized a new D-A copolymer J61-F based on the same donor and acceptor units as J61 but with furan π-bridges instead of thiophene.J61-F possesses a deeper the highest occupied molecular orbital（HOMO） level at-5.45 eV in comparison with that（-5.32 eV） of J61.The non-fullerene PSCs based on J61-F:ITIC exhibited a maximum power conversion efficiency（PCE） of 8.24%with a higher open-circuit voltage(Voc) of 0.95 V,which is benefitted from the lower-lying HOMO energy level of J61-F donor material.The results indicate that main chain engineering by changing π-bridges is another effective way to tune the electronic energy levels of the conjugated D-A copolymers for the application as donor materials in non-fullerene PSCs.

Effect of furan n-bridge on the photovoltaic performance of D-A copolymers based on bi(alkylthio-thienyl)benzodithiophene and fluorobenzotriazole

Institute of Scientific and Technical Information of China (English)

Tinghai Yan; Haijun Bin; Yankang Yang; Lingwei Xue; Zhi-Guo Zhang; Yongfang Li

2017-01-01

The medium band gap donor-acceptor (D-A) copolymer J61 based on bi(alkylthio-thienyl)benzodithiophene as donor unit and fluorobenzotriazole as acceptor unit and thiophene as π-bridge has demonstrated excellent photovoltaic performance as donor material in nonfullerene polymer solar cells (PSCs) with narrow bandgap n-type organic semiconductor ITIC as acceptor.For studying the effect of π-bridges on the photovoltaic performance of the D-A copolymers,here we synthesized a new D-A copolymer J61-F based on the same donor and acceptor units as J61 but with furan π-bridges instead ofthiophene.J61-F possesses a deeper the highest occupied molecular orbital (HOMO) level at-5.45 eV in comparison with that (-5.32 eV) of J61.The non-fullerene PSCs based on J61-F:ITIC exhibited a maximum power conversion efficiency (PCE) of 8.24％ with a higher open-circuit voltage (Voo) of 0.95 V,which is benefitted from the lower-lying HOMO energy level of J61-F donor material.The results indicate that main chain engineering by changing π-bridges is another effective way to tune the electronic energy levels of the conjugated D-A copolymers for the application as donor materials in non-fullerene PSCs.

Generating nanoparticles containing a new 4-nitrobenzaldehyde thiosemicarbazone compound with antileishmanial activity

International Nuclear Information System (INIS)

Aparecida Britta, Elizandra; Conceição da Silva, Cleuza; Forti Rubira, Adley; Vataru Nakamura, Celso; Borsali, Redouane

2016-01-01

Thiosemicarbazones are an important class of compounds that have been extensively studied in recent years, mainly because of their broad profile of pharmacological activity. A new 4-nitrobenzaldehyde thiosemicarbazone compound (BZTS) that was derived from S-limonene has been demonstrated to have significant antiprotozoan activity. However, the hydrophobic characteristic of BZTS limits its administration and results in low oral bioavailability. In the present study, we proposed the synthesis of nanoparticle-based block copolymers that can encapsulate BZTS, with morphological evaluation of the nanoparticle suspensions being performed by transmission and cryo-transmission electronic microscopy. The mean particle sizes of the nanoparticle suspensions were determined by static light and dynamic light scattering (SLS/DLS), and the hydrodynamic radius (Rh) was determined using the Stokes-Einstein equation. The zeta potential (ζ) and polydispersity index (PDI) were also determined. The entrapment encapsulation efficiency of the BZTS nanoparticles was measured by ultraviolet spectrophotometry. In vitro activity of BZTS nanoparticle suspensions against intracellular amastigotes of Leishmania amazonensis and cytotoxic activity were also evaluated. The results showed the production of spherical nanoparticles with varied sizes depending on the hydrophobic portion of the amphiphilic diblock copolymers used. Significant concentration-dependent inhibitory activity against intracellular amastigotes was observed, and low cytotoxic activity was demonstrated against macrophages. - Highlights: • The spherical nanoparticles were obtained using distinct diblock copolymers. • BZTS was successfully encapsulated in the nanoparticles. • BZTS nanoparticle suspensions presented activity in Leishmania amazonensis.

Generating nanoparticles containing a new 4-nitrobenzaldehyde thiosemicarbazone compound with antileishmanial activity

Energy Technology Data Exchange (ETDEWEB)

Aparecida Britta, Elizandra [Programa de Pós-Graduação em Ciências Farmacêuticas, Universidade Estadual de Maringá (Brazil); Conceição da Silva, Cleuza; Forti Rubira, Adley [Departamento de Química, Universidade Estadual de Maringá (Brazil); Vataru Nakamura, Celso, E-mail: cvnakamura@uem.br [Programa de Pós-Graduação em Ciências Farmacêuticas, Universidade Estadual de Maringá (Brazil); Borsali, Redouane, E-mail: borsali@cermav.cnrs.fr [Centro de Pesquisas em Macromoléculas Vegetais, CERMAV, Grenoble (France)

2016-12-01

Thiosemicarbazones are an important class of compounds that have been extensively studied in recent years, mainly because of their broad profile of pharmacological activity. A new 4-nitrobenzaldehyde thiosemicarbazone compound (BZTS) that was derived from S-limonene has been demonstrated to have significant antiprotozoan activity. However, the hydrophobic characteristic of BZTS limits its administration and results in low oral bioavailability. In the present study, we proposed the synthesis of nanoparticle-based block copolymers that can encapsulate BZTS, with morphological evaluation of the nanoparticle suspensions being performed by transmission and cryo-transmission electronic microscopy. The mean particle sizes of the nanoparticle suspensions were determined by static light and dynamic light scattering (SLS/DLS), and the hydrodynamic radius (Rh) was determined using the Stokes-Einstein equation. The zeta potential (ζ) and polydispersity index (PDI) were also determined. The entrapment encapsulation efficiency of the BZTS nanoparticles was measured by ultraviolet spectrophotometry. In vitro activity of BZTS nanoparticle suspensions against intracellular amastigotes of Leishmania amazonensis and cytotoxic activity were also evaluated. The results showed the production of spherical nanoparticles with varied sizes depending on the hydrophobic portion of the amphiphilic diblock copolymers used. Significant concentration-dependent inhibitory activity against intracellular amastigotes was observed, and low cytotoxic activity was demonstrated against macrophages. - Highlights: • The spherical nanoparticles were obtained using distinct diblock copolymers. • BZTS was successfully encapsulated in the nanoparticles. • BZTS nanoparticle suspensions presented activity in Leishmania amazonensis.

Microencapsulated n-octadecane with different methylmethacrylate-based copolymer shells as phase change materials for thermal energy storage

International Nuclear Information System (INIS)

Qiu, Xiaolin; Li, Wei; Song, Guolin; Chu, Xiaodong; Tang, Guoyi

2012-01-01

Microcapsules containing n-octadecane with different methylmethacrylate (MMA (methyl methacrylate))-based copolymer shells were fabricated by a suspension-like polymerization. Butyl acrylate (BA), butyl methacrylate (BMA), lauryl methacrylate (LMA) and stearyl methacrylate (SMA) were employed as monomers to copolymerize with MMA. Pentaerythritol tetraacrylate (PETRA) was employed as a crosslinking agent. The (microencapsulted phase change materials) MicroPCMs were characterized using Fourier transformed infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). Thermal properties and thermal resistances of MicroPCMs were investigated by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA), respectively. Phase change enthalpies and PCM contents of MicroPCMs increased with the length decreasing of the side chain of the monomers. The n-octadecane content of as much as 77.3% can be obtained in the crosslinked MicroPCMs with P(MMA-co-BMA) as shell, and accompanied by the highest melting enthalpy (173.7 J/g) and crystallization enthalpy (174.4 J/g). Heat capacities of crosslinked MicroPCMs are higher than those of their uncrosslinked counterparts. The crosslinked MicroPCMs exhibit significantly greater thermal stabilities compared with their uncrosslinked counterparts and the n-ontadecane bulk. The crosslinked MicroPCMs with P(MMA-co-SMA) displays the highest thermal resistance temperature up to 255 °C. Therefore, MicroPCMs with MMA-based copolymer as shells, especially crosslinked copolymer shells, show excellent potentials for thermal energy storage. -- Highlights: ► n-Octadecane was encapsulated with methylmethacrylate(MMA)-based copolymer shells. ► n-Octadecane content of Microcapsules increased with length decreasing of side chain of monomers. ► Microcapsule with P(MMA-co-butyl methacrylate) has the highest latent heat. ► Microcapsule with P(MMA-co-stearyl methacrylate) has the greatest thermal stability.

Synthesis and self-assembling of responsive polysaccharide-based copolymers in aqueous media

Energy Technology Data Exchange (ETDEWEB)

Marques, Nivia do N.; Balaban, Rosangela de C. [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil); Halila, Sami; Borsali, Redouane, E-mail: borsali@cermav.cnrs.fr, E-mail: halila@cermav.cnrs.fr [Centre de Recherche sur les Macromolecules Vegetales (CERMAV), Grenoble (France)

2015-07-01

This work reports the synthesis and the thermoresponsive self-assembly behavior of carboxymethylcellulose-g-JeffamineM2070 and carboxymethylcellulose-g-JeffamineM600 copolymers in aqueous media. They were prepared through the grafting of two different types of amino-terminated poly(ethylene oxide-co-propylene oxide) chains onto the carboxylate groups of carboxymethylcellulose, by using water-soluble carbodiimide derivative and N-hydroxysuccinimide as coupling reagents. The grafting efficiency was confirmed by infrared and the degree of substitution by {sup 1}H NMR integrations. The salt effect on cloud point temperature was evaluated into different solvents (Milli-Q water, 0.5M NaCl, synthetic sea water (SSW) and 0.5M K{sub 2}CO{sub 3}) by UV-Vis and dynamic light scattering (DLS) measurements. Both copolymers showed lower cloud point temperature in 0.5M K2CO3 than in 0.5M NaCl and in SSW, which was attributed to the higher ionic strength for K{sub 2}CO{sub 3} combined to the ability of CO{sub 3}{sup 2-} to decrease polymer-water interactions. Copolymers chains displayed higher hydrodynamic radii than CMC precursor at 25 and 60 °C in saline solutions, and self-associations changed as a function of the environment and copolymer composition. (author)

Synthesis and self-assembling of responsive polysaccharide-based copolymers in aqueous media

International Nuclear Information System (INIS)

Marques, Nivia do N.; Balaban, Rosangela de C.; Halila, Sami; Borsali, Redouane

2015-01-01

This work reports the synthesis and the thermoresponsive self-assembly behavior of carboxymethylcellulose-g-JeffamineM2070 and carboxymethylcellulose-g-JeffamineM600 copolymers in aqueous media. They were prepared through the grafting of two different types of amino-terminated poly(ethylene oxide-co-propylene oxide) chains onto the carboxylate groups of carboxymethylcellulose, by using water-soluble carbodiimide derivative and N-hydroxysuccinimide as coupling reagents. The grafting efficiency was confirmed by infrared and the degree of substitution by "1H NMR integrations. The salt effect on cloud point temperature was evaluated into different solvents (Milli-Q water, 0.5M NaCl, synthetic sea water (SSW) and 0.5M K_2CO_3) by UV-Vis and dynamic light scattering (DLS) measurements. Both copolymers showed lower cloud point temperature in 0.5M K2CO3 than in 0.5M NaCl and in SSW, which was attributed to the higher ionic strength for K_2CO_3 combined to the ability of CO_3"2"- to decrease polymer-water interactions. Copolymers chains displayed higher hydrodynamic radii than CMC precursor at 25 and 60 °C in saline solutions, and self-associations changed as a function of the environment and copolymer composition. (author)

Rheological Behavior of Entangled Polystyrene-Polyhedral Oligosilsesquioxane (POSS) Copolymer (Postprint)

National Research Council Canada - National Science Library

Wu, Jian; Mather, Patrick T; Haddad, Timothy S; Kim, Gyeong-Man

2006-01-01

...: random copolymers of polystyrene (PS) and styryl-based polyhedral oligosilsesquioxane (POSS), R7(Si8O12)(C6H4CH=CH2), with R = isobutyl (iBu). A series of styrene-styryl POSS random copolymers with 0, 6, 15, 30, 50 wt...

Mechano-responsive hydrogels crosslinked by reactive block copolymer micelles

Science.gov (United States)

Xiao, Longxi

Hydrogels are crosslinked polymeric networks that can swell in water without dissolution. Owing to their structural similarity to the native extracelluar matrices, hydrogels have been widely used in biomedical applications. Synthetic hydrogels have been designed to respond to various stimuli, but mechanical signals have not incorporated into hydrogel matrices. Because most tissues in the body are subjected to various types of mechanical forces, and cells within these tissues have sophisticated mechano-transduction machinery, this thesis is focused on developing hydrogel materials with built-in mechano-sensing mechanisms for use as tissue engineering scaffolds or drug release devices. Self-assembled block copolymer micelles (BCMs) with reactive handles were employed as the nanoscopic crosslinkers for the construction of covalently crosslinked networks. BCMs were assembled from amphiphilic diblock copolymers of poly(n-butyl acrylate) and poly(acrylic acid) partially modified with acrylate. Radical polymerization of acrylamide in the presence of micellar crosslinkers gave rise to elastomeric hydrogels whose mechanical properties can be tuned by varying the BCM composition and concentration. TEM imaging revealed that the covalently integrated BCMs underwent strain-dependent reversible deformation. A model hydrophobic drug, pyrene, loaded into the core of BCMs prior to the hydrogel formation, was dynamically released in response to externally applied mechanical forces, through force-induced reversible micelle deformation and the penetration of water molecules into the micelle core. The mechano-responsive hydrogel has been studied for tissue repair and regeneration purposes. Glycidyl methacrylate (GMA)-modified hyaluronic acid (HA) was photochemically crosslinked in the presence of dexamethasone (DEX)-loaded crosslinkable BCMs. The resultant HA gels (HAxBCM) contain covalently integrated micellar compartments with DEX being sequestered in the hydrophobic core. Compared

The radiation crosslinking of ethylene copolymers

International Nuclear Information System (INIS)

Burns, N.M.

1979-01-01

The enhanced radiation crosslinking tendency of ethylene-vinyl acetate and ethylene-ethyl acrylate copolymers over ethylene homopolymer is proportional to the comonomer content. This is caused by an increase in the amorphous polymer content and by structure-related factors. The copolymers crosslink by a random process that for ethylene-vinyl acetate copolymer involves some crosslinking through the acetoxy group of the comonomer. While knowledge of the process for the crosslinking of ethylene-ethyl acrylate copolymer is less certain, it is currently believed to occur primarily at the branch point on the polymer backbone. Data relating comonomer content and the molecular weight of the copolymers to the radiation crosslinking levels realized were developed to aid in resin selection by the formulator. Triallyl cyanurate cure accelerator was found to be less effective in ethylene-vinyl acetate copolymer than in homopolymer and to have no effect on gel development in ethylene-ethyl acrylate copolymer. (author)

Improvements of fill factor in solar cells based on blends of polyfluorene copolymers as electron donors

International Nuclear Information System (INIS)

Gadisa, Abay; Zhang, Fengling; Sharma, Deepak; Svensson, Mattias; Andersson, Mats R.; Inganaes, Olle

2007-01-01

The photovoltaic characteristics of solar cells based on alternating polyfluorene copolymers, poly(2,7-(9,9-dioctyl-fluorene)-alt-5,5-(4',7'-di-2-thienyl-2',1',3' -benzothia diazole)) (APFO-3), and poly(2,7-(9,9-didodecyl-fluorene)-alt-5,5-(4',7'-di-2-thienyl-2',1',3' -benzothiadiazole)) (APFO-4), blended with an electron acceptor fullerene molecule [6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM), have been investigated and compared. The two copolymers have the same aromatic backbone structure but differ by the length of their alkyl side chain. The overall photovoltaic performance of the solar cells is comparable irrespective of the copolymer used in the active layer. However, the fill factor (FF) values of the devices are strongly affected by the copolymer type. Higher FF values were realized in solar cells with APFO-4 (with longer alkyl side chain)/PCBM bulk heterojunction active layer. On the other hand, devices with blends of APFO-3/APFO-4/PCBM were found to render fill factor values that are intermediate between the values obtained in solar cells with APFO-3/PCBM and APFO-4/PCBM active film. Upon using APFO-3/APFO-4 blends as electron donors, the cell efficiency can be enhanced by about 16% as compared to cells with either APFO-3 or APFO-4. The transport of holes in each polymer obeys the model of hopping transport in disordered media. However, the degree of energetic barrier against hopping was found to be larger in APFO-3. The tuning of the photovoltaic parameters will be discussed based on studies of hole transport in the pure polymer films, and morphology of blend layers. The effect of bipolar transport in PCBM will also be discussed

Synthesis and characterization of novel curing agents for surface coatings based on acrylamide copolymers

International Nuclear Information System (INIS)

Patel, N. V.; Parmar, R. J.; Parmar, J. S.

2003-01-01

The acrylamide based curing agents were prepared form methyl methacrylate-acrylamide copolymers by further methylolation and subsequent etherification with butanol. These were characterized for their various physico-chemical characteristics. Various sets of these ACAs were blended with hydroxyl functional acrylic resin to prepare the staving compared with the conventional melamine-formaldehyde based curing agent containing compositions. The films were also characterized thermogravimetric analysis and IR-spectra. The result reveals that the properties of certain compositions based on ACAs were remarkably better than those of conventional melamine-formaldehyde based curing agent based coatings

Bactericidal and Hemocompatible Coating via the Mixed-Charged Copolymer.

Science.gov (United States)

Fan, Xiao-Li; Hu, Mi; Qin, Zhi-Hui; Wang, Jing; Chen, Xia-Chao; Lei, Wen-Xi; Ye, Wan-Ying; Jin, Qiao; Ren, Ke-Feng; Ji, Jian

2018-03-28

Cationic antibacterial coating based on quaternary ammonium compounds, with an efficient and broad spectrum bactericidal property, has been widely used in various fields. However, the high density of positive charges tends to induce weak hemocompatibility, which hinders the application of the cationic antibacterial coating in blood-contacting devices and implants. It has been reported that a negatively charged surface can reduce blood coagulation, showing improved hemocompatibility. Here, we describe a strategy to combine the cationic and anionic groups by using mixed-charged copolymers. The copolymers of poly (quaternized vinyl pyridine- co- n-butyl methacrylate- co-methacrylate acid) [P(QVP- co- nBMA- co-MAA)] were synthesized through free radical copolymerization. The cationic group of QVP, the anionic group of MAA, and the hydrophobic group of nBMA were designed to provide bactericidal capability, hemocompatibility, and coating stability, respectively. Our findings show that the hydrophilicity of the copolymer coating increased, and its zeta potential decreased from positive charge to negative charge with the increase of the anionic/cationic ratio. Meanwhile, the bactericidal property of the copolymer coating was kept around a similar level compared with the pure quaternary ammonium copolymer coating. Furthermore, the coagulation time, platelet adhesion, and hemolysis tests revealed that the hemocompatibility of the copolymer coating improved with the addition of the anionic group. The mixed-charged copolymer combined both bactericidal property and hemocompatibility and has a promising potential in blood-contacting antibacterial devices and implants.

Fabrication of Hyperbranched Block-Statistical Copolymer-Based Prodrug with Dual Sensitivities for Controlled Release.

Science.gov (United States)

Zheng, Luping; Wang, Yunfei; Zhang, Xianshuo; Ma, Liwei; Wang, Baoyan; Ji, Xiangling; Wei, Hua

2018-01-17

Dendrimer with hyperbranched structure and multivalent surface is regarded as one of the most promising candidates close to the ideal drug delivery systems, but the clinical translation and scale-up production of dendrimer has been hampered significantly by the synthetic difficulties. Therefore, there is considerable scope for the development of novel hyperbranched polymer that can not only address the drawbacks of dendrimer but maintain its advantages. The reversible addition-fragmentation chain transfer self-condensing vinyl polymerization (RAFT-SCVP) technique has enabled facile preparation of segmented hyperbranched polymer (SHP) by using chain transfer monomer (CTM)-based double-head agent during the past decade. Meanwhile, the design and development of block-statistical copolymers has been proven in our recent studies to be a simple yet effective way to address the extracellular stability vs intracellular high delivery efficacy dilemma. To integrate the advantages of both hyperbranched and block-statistical structures, we herein reported the fabrication of hyperbranched block-statistical copolymer-based prodrug with pH and reduction dual sensitivities using RAFT-SCVP and post-polymerization click coupling. The external homo oligo(ethylene glycol methyl ether methacrylate) (OEGMA) block provides sufficient extracellularly colloidal stability for the nanocarriers by steric hindrance, and the interior OEGMA units incorporated by the statistical copolymerization promote intracellular drug release by facilitating the permeation of GSH and H + for the cleavage of the reduction-responsive disulfide bond and pH-liable carbonate link as well as weakening the hydrophobic encapsulation of drug molecules. The delivery efficacy of the target hyperbranched block-statistical copolymer-based prodrug was evaluated in terms of in vitro drug release and cytotoxicity studies, which confirms both acidic pH and reduction-triggered drug release for inhibiting proliferation of He

Structure and stability of complex coacervate core micelles with lysozyme

NARCIS (Netherlands)

Lindhoud, Saskia; de Vries, Renko; Norde, Willem; Cohen Stuart, Martien A.

Encapsulation of enzymes by polymers is a promising method to influence their activity and stability. Here, we explore the use of complex coacervate core micelles for encapsulation of enzymes. The core of the micelles consists of negatively charged blocks of the diblock copolymer PAA(42)PAAm(417)

Engineering with macromolecules : from supramolecular chemistry to defined nanomaterials

NARCIS (Netherlands)

Lohmeijer, B.G.G.; Gohy, J.M.W.; Schubert, U.S.

2003-01-01

By uniting concepts from polymer chem. and supramol. chem. we present a new approach for the prepn. of functional nano-materials. Amphiphilic diblock and triblock copolymers were constructed in such a way that a bisterpyridine ruthenium complex acts as the linker between the two constituting blocks.