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Sample records for azobenzene methacrylate block

  1. Photoinduced optical anisotropy in azobenzene methacrylate block copolymers: Influence of molecular weight and irradiation conditions

    DEFF Research Database (Denmark)

    Gimeno, Sofia; Forcen, Patricia; Oriol, Luis;

    2009-01-01

    The photoinduced anisotropy in a series of azomethacrylate block copolymers with different Molecular weights and azo contents has been investigated under several irradiation conditions. Depending on molecular weight and composition, different microstructures (disordered, lamellar, spherical) appe...

  2. PHOTORESPONSIVE BEHAVIOR OF AZOBENZENE-BASED (METH)ACRYLIC (CO)POLYMERS IN THIN-FILMS

    NARCIS (Netherlands)

    HAITJEMA, HJ; VONMORGEN, GL; TAN, YY; CHALLA, G

    1994-01-01

    The reversible photoisomerization and the thermal isomerization of azobenzene-based (Az.b.) groups covalently bound to (meth)acrylic (co)polymers were investigated in thin films. For the amorphous polymers it was found that a broad range of the thermal cis --> trans isomerization rates could be obta

  3. Micellization of quaternized poly(2-(dimethylamino)ethyl methacrylate)-block-poly(methyl methacrylate) copolymers in water

    OpenAIRE

    2001-01-01

    Micellization of a series of amphiphilic quaternized poly(2-(dimethylamino)ethyl methacrylate)-block-poly(methyl methacrylate) (PQDMAEMA-b-PMMA) copolymers has been studied in water. The alkyl halide used for the quaternization of the aminated block has an effect on the solution properties of the diblocks, that have been investigated by dynamic light scattering and surface tension measurements. When a short length alkyl halide is used, the diblock copolymers behave like traditional amphiphile...

  4. Block copolymer route towards poly(vinylidene fluoride)/poly(methacrylic acid)/nickel nanocomposites

    NARCIS (Netherlands)

    Voet, V.S.D.; Hermida-Merino, D.; Brinke, G. ten; Loos, K.

    2013-01-01

    PVDF-based block copolymers have been employed as precursors for the construction of PVDF/PMAA/Ni nanocomposites. New poly(tert-butyl methacrylate)-block-poly(vinylidene fluoride)-block-poly(tert-butyl methacrylate) (PtBMA-b-PVDF-b-PtBMA) triblock copolymers were synthesized via atom transfer radica

  5. Synthesis and aqueous solution properties of novel sugar methacrylate-based homopolymers and block copolymers.

    Science.gov (United States)

    Narain, Ravin; Armes, Steven P

    2003-01-01

    We report the facile preparation of a range of novel, well-defined cyclic sugar methacrylate-based polymers without recourse to protecting group chemistry. 2-Gluconamidoethyl methacrylate (GAMA) and 2-lactobionamidoethyl methacrylate (LAMA) were prepared directly by reacting 2-aminoethyl methacrylate with D-gluconolactone and lactobionolactone, respectively. Homopolymerization of GAMA and LAMA by atom transfer radical polymerization (ATRP) gave reasonably low polydispersities as judged by aqueous gel permeation chromatography. A wide range of sugar-based block copolymers were prepared using near-monodisperse macroinitiators based on poly(ethylene oxide) [PEO], poly(propylene oxide) [PPO], or poly(e-caprolactone) [PCL] and/or by sequential monomer addition of other methacrylic monomers such as 2-(diethylamino)ethyl methacrylate [DEA], 2-(diisopropylaminoethyl methacrylate [DPA], or glycerol monomethacrylate [GMA]. The reversible micellar self-assembly of selected sugar-based block copolymers [PEO23-GAMA50-DEA100, PEO23-LAMA30-DEA50, PPO33-GAMA50, and PPO33-LAMA50] was studied in aqueous solution as a function of pH and temperature using dynamic light scattering, transmission electron microscopy, surface tensiometry, and 1H NMR spectroscopy.

  6. Photoresponsive Azopolyester–PMMA Block Copolymers Obtained by Combination of ATRP, Polycondensation, and “Click” Chemistry

    DEFF Research Database (Denmark)

    Berges, Cristina; Javakhishvili, Irakli; Hvilsted, Søren

    2012-01-01

    Novel azobenzene‐containing block copolymers (BCs) with a polyester block bearing azobenzene moieties in the side chain and a poly (methyl methacrylate) (PMMA) block have been synthesized by the combination of atom transfer radical polymerization (ATRP), polycondensation, and “click” chemistry. T...

  7. An Observation on the Microphase Separation of Poly(methyl methacrylate)-block-Polystyrene Copolymer

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The phase behavior of a well-defined poly(methyl methacrylate)-b-polystyrene block copolymer was studied by transmission electron microscope.The results show that a microphase transition may have occurred in the copolymer film.A kind of lamellae and an ordered bicontinuous double-diamond morphology are observed clearly.The lamellar morphology reveals a larger period of about 400 nm.

  8. Structure-Properties Relationship in Proton Conductive Sulfonated Polystyrene-Polymethyl Methacrylate Block Copolymers.

    Science.gov (United States)

    Rubatat, Laurent; Li, Chaoxu; Dietsch, Herve; Nykainen, Antti; Ruokolainen, Janne; Mezzenga, Raffaele

    2009-03-01

    We report on the dependence of proton conductivity on the morphologies of sulfonated polystyrene-poly(methyl methacrylate) (sPS-PMMA) diblock copolymers. Three diblock copolymers of varying molecular weight and block volume fraction were studied, for each one several sulfonation degrees of the PS block were considered. The investigation of the morphologies of the self-assembled sPS-PMMA diblocks was carried out by means of small angle neutron scattering and transmission electron microscopy. Depending on molecular weight and sulfonation degrees, isotropic phase (ISO), lamellar phase (LAM), cylindrical hexagonal phase (HEX) and hexagonally perforated lamellae (HPL) were observed. Proton conductivity, normalized by the volume fraction of the conductive domains (formed by PS, sPS and water), was shown to rise monotonically with the following sequence of morphologies: ISO to HEX to HPL to LAM.

  9. Primer containing dimethylaminododecyl methacrylate kills bacteria impregnated in human dentin blocks

    Science.gov (United States)

    Chen, Chen; Cheng, Lei; Weir, Michael D; Lin, Nancy J; Lin-Gibson, Sheng; Zhou, Xue-Dong; Xu, Hockin HK

    2016-01-01

    Antibacterial dimethylaminododecyl methacrylate (DMADDM) was recently synthesized. The objectives of this study were to: (1) investigate antibacterial activity of DMADDM-containing primer on Streptococcus mutans impregnated into dentin blocks for the first time, and (2) compare the antibacterial efficacy of DMADDM with a previous quaternary ammonium dimethacrylate (QADM). Scotchbond Multi-Purpose (SBMP) bonding agent was used. DMADDM and QADM were mixed into SBMP primer. Six primers were tested: SBMP control primer P, P+2.5% DMADDM, P+5% DMADDM, P+7.5% DMADDM, P+10% DMADDM, and P+10% QADM. S. mutans were impregnated into human dentin blocks, and each primer was applied to dentin to test its ability to kill bacteria in dentinal tubules. Bacteria in dentin were collected via a sonication method, and the colony-forming units (CFU) and inhibition zones were measured. The bacterial inhibition zone of P+10% DMADDM was 10 times that of control primer (P0.1). In conclusion, antibacterial DMADDM-containing primer was validated to kill bacteria inside dentin blocks, possessing a much stronger antibacterial potency than the previous QADM. DMADDM-containing bonding agent was effective in eradicating bacteria in dentin, and its efficacy was directly proportional to DMADDM mass fraction. Therefore, DMADDM may be promising for use in bonding agents as well as in other restorative and preventive materials to inhibit bacteria. PMID:27811846

  10. Effect of block composition on thermal properties and melt viscosity of poly[2-(dimethylaminoethyl methacrylate], poly(ethylene oxide and poly(propylene oxide block co-polymers

    Directory of Open Access Journals (Sweden)

    2011-09-01

    Full Text Available To modify the rheological properties of certain commercial polymers, a set of block copolymers were synthesized through oxyanionic polymerization of 2-(dimethylaminoethyl methacrylate to the chain ends of commercial prepolymers, namely poly(ethylene oxide (PEO, poly(ethylene oxide-block-poly(propylene oxide-block-poly(ethylene oxide (PEO-PPO-PEO, and poly(propylene oxide (PPO. The formed block copolymers were analysed with size exclusion chromatography and nuclear magnetic resonance spectroscopy in order to confirm block formation. Thermal characterization of the resulting polymers was done with differential scanning calorimetry. Thermal transition points were also confirmed with rotational rheometry, which was primarily used to measure melt strength properties of the resulting block co-polymers. It was observed that the synthesised poly[2-(dimethylaminoethyl methacrylate]-block (PDM affected slightly the thermal transition points of crystalline PEO-block but the influence was stronger on amorphous PPO-blocks. Frequency sweeps measured above the melting temperatures for the materials confirmed that the pre-polymers (PEO and PEO-PPO-PEO behave as Newtonian fluids whereas polymers with a PDM block structure exhibit clear shear thinning behaviour. In addition, the PDM block increased the melt viscosity when compared with that one of the pre-polymer. As a final result, it became obvious that pre-polymers modified with PDM were in entangled form, in the melted state as well in the solidified form.

  11. Primer containing dimethylaminododecyl methacrylate kills bacteria impregnated in human dentin blocks

    Institute of Scientific and Technical Information of China (English)

    Chen Chen; Lei Cheng; Michael D Weir; Nancy J Lin; Sheng Lin-Gibson; Xue-Dong Zhou; Hockin HK Xu

    2016-01-01

    Antibacterial dimethylaminododecyl methacrylate (DMADDM) was recently synthesized. The objectives of this study were to:(1) investigate antibacterial activity of DMADDM-containing primer on Streptococcus mutans impregnated into dentin blocks for the first time, and (2) compare the antibacterial efficacy of DMADDM with a previous quaternary ammonium dimethacrylate (QADM). Scotchbond Multi-Purpose (SBMP) bonding agent was used. DMADDM and QADM were mixed into SBMP primer. Six primers were tested:SBMP control primer P, P+2.5%DMADDM, P+5%DMADDM, P+7.5%DMADDM, P+10%DMADDM, and P+10%QADM. S. mutans were impregnated into human dentin blocks, and each primer was applied to dentin to test its ability to kill bacteria in dentinal tubules. Bacteria in dentin were collected via a sonication method, and the colony-forming units (CFU) and inhibition zones were measured. The bacterial inhibition zone of P+10%DMADDM was 10 times that of control primer (Po0.05). CFU in dentin with P+10%DMADDM was reduced by three orders of magnitude, compared with control. DMADDM had a much stronger antibacterial effect than QADM, and antibacterial efficacy increased with increasing DMADDM concentration. Dentin shear bond strengths were similar among all groups (P40.1). In conclusion, antibacterial DMADDM-containing primer was validated to kill bacteria inside dentin blocks, possessing a much stronger antibacterial potency than the previous QADM. DMADDM-containing bonding agent was effective in eradicating bacteria in dentin, and its efficacy was directly proportional to DMADDM mass fraction. Therefore, DMADDM may be promising for use in bonding agents as well as in other restorative and preventive materials to inhibit bacteria.

  12. Azobenzene-functionalized cascade molecules

    DEFF Research Database (Denmark)

    Archut, A.; Vogtle, F.; De Cola, L.;

    1998-01-01

    Cascade molecules bearing up to 32 azobenzene groups in the periphery have been prepared from poly(propylene imine) dendrimers and N-hydroxysuccinimide esters. The dendritic azobenzene species show similar isomerization properties as the corresponding azobenzene monomers. The all-E azobenzene...

  13. Effects of block copolymer self-assembly on optical anisotropy in azobenzene-containing PS-b-PMMA films

    Science.gov (United States)

    Orofino, A. B.; Camezzana, M. F.; Galante, M. J.; Oyanguren, P. A.; Zucchi, I. A.

    2012-03-01

    Polystyrene-b-polymethylmethacrylate (PS-b-PMMA) was selected as the host for 4-(4-nitrophenylazo)aniline (Disperse Orange 3, DO3) based on a previous study of DO3/PMMA and DO3/PS binary blends. Selective location of DO3 into the PMMA block of the copolymer was expected during self-assembly of the block copolymer since a preferential interaction of DO3 with PMMA has been demonstrated. However, surface segregation of DO3 was found during the thermal annealing used to nanostructure the copolymer. To avoid this, a thermoplastic polymer (Azo-TP) was synthesized from the bulk reaction of DO3 and diglycidyl ether of bisphenol A (DGEBA). The choice of DGEBA as a co-reactant was an attempt to encourage the selective location of azo groups in the PMMA phase of PS-b-PMMA. An inspection of solutions of Azo-TP in PS and PMMA, corroborates the preferential affinity of Azo-TP for PMMA. The Azo-TP could be satisfactorily dissolved in PS-b-PMMA. We have investigated the growth and decay processes of the optically induced birefringence in films of PS-b-PMMA containing 12 wt% Azo-TP. The resulting materials showed a good photoinduced time response, high maximum birefringence and an elevated fraction of remnant anisotropy.

  14. Nanostructured Double Hydrophobic Poly(Styrene-b-Methyl Methacrylate) Block Copolymer Membrane Manufactured Via Phase Inversion Technique

    KAUST Repository

    Karunakaran, Madhavan

    2016-03-11

    In this paper, we demonstrate the formation of nanostructured double hydrophobic poly(styrene-b-methyl methacrylate) (PS-b-PMMA) block copolymer membranes via state-of-the-art phase inversion technique. The nanostructured membrane morphologies are tuned by different solvent and block copolymer compositions. The membrane morphology has been investigated using FESEM, AFM and TEM. Morphological investigation shows the formation of both cylindrical and lamellar structures on the top surface of the block copolymer membranes. The PS-b-PMMA having an equal block length (PS160K-b-PMMA160K) exhibits both cylindrical and lamellar structures on the top layer of the asymmetric membrane. All membranes fabricated from PS160K-b-PMMA160K shows an incomplete pore formation in both cylindrical and lamellar morphologies during the phase inversion process. However, PS-b-PMMA (PS135K-b-PMMA19.5K) block copolymer having a short PMMA block allowed us to produce open pore structures with ordered hexagonal cylindrical pores during the phase inversion process. The resulting PS-b-PMMA nanostructured block copolymer membranes have pure water flux from 105-820 l/m2.h.bar and 95% retention of PEG50K

  15. Photocontrol over the disorder-to-order transition in thin films of polystyrene-block-poly(methyl methacrylate) block copolymers containing photodimerizable anthracene functionality.

    Science.gov (United States)

    Chen, Wei; Wang, Jia-Yu; Zhao, Wei; Li, Le; Wei, Xinyu; Balazs, Anna C; Matyjaszewski, Krzysztof; Russell, Thomas P

    2011-11-02

    Reversible photocontrol over the ordering transition of block copolymers (BCPs) from a disordered state to an ordered state, namely the disorder-to-order transition (DOT), can be used to create long-range ordered nanostructures in self-assembled BCPs over macroscopic distances by photocombing, similar to the classic zone refining used to produce highly pure, large single crystals. Here, we have designed and synthesized an anthracene-functionalized tri-BCP containing deuterated polystyrene (d(8)-PS) and poly(methyl methacrylate) (PMMA) blocks, as well as a short middle block of poly(2-hydroxyethyl methacrylates) (PHEMA) that is randomly functionalized by anthracene. This tri-BCP maintains the order-to-disorder transition-type phase behavior of its parent d(8)-PS-b-PMMA di-BCPs. Under 365 nm UV irradiation, the junction between d(8)-PS and PMMA blocks is photocoupled through the anthracene photodimers, leading to a significant increase in the total molecular weight of the tri-BCP. As a consequence, when the tri-BCP is phase-mixed but close to the boundary of the ordering transition, it undergoes the DOT, as evidenced by small-angle neutron scattering and transmission electron microscopy. The tri-BCP could be reversibly brought through the DOT in thin films by taking advantage of photodimerization and thermal dissociation of anthracene. Currently, anthracene-functionalized d(8)-PS-b-PMMA BCP is one of the most promising candidates for the photocombing process to promote long-range laterally ordered nanostructures over macroscopic distances in a noninvasive manner.

  16. SYNTHESIS OF STYRENE-METHYL METHACRYLATE BLOCK COPOLYMER BY POLYAZOAMIDE AS INITIATOR

    Institute of Scientific and Technical Information of China (English)

    WANG Zhongyi; WEI Jeqing

    1996-01-01

    Polyazoamide(PAA) was used as initiator to prepare block copolymer P(MMA-b-St) by free radical polymerization. The fraction of block copolymer was about 50%. The structure of the block-copolymer was characterized by IR and the results of 1H-NMR and GPC showed that the content of the block and the molecular weight (-Mw) of the prepolymer and block copolymer could be controlled by varying the mol ratio of styrene/PAA and MMA/prepolymer. DSC and TEM results revealed that the block copolymer has two separated glass transition temperatures and phase separation within the domain structure.

  17. The effect of hydrophilic and hydrophobic block length on the rheology of amphiphilic diblock Polystyrene-b-Poly(sodium methacrylate) copolymers prepared by ATRP

    NARCIS (Netherlands)

    Raffa, Patrizio; Stuart, Marc C.A.; Broekhuis, Antonius A.; Picchioni, Francesco

    2014-01-01

    Following our previous investigation on the effect of molecular architecture on the rheology of Polystyrene-b-Poly(sodium methacrylate) copolymers (PS-b-PMAA), we consider here diblock PS-b-PMAA copolymers characterized by a different length of either the hydrophilic or the hydrophobic block. Variou

  18. Polystyrene-Poly(sodium methacrylate) Amphiphilic Block Copolymers by ATRP : Effect of Structure, pH, and Ionic Strength on Rheology of Aqueous Solutions

    NARCIS (Netherlands)

    Raffa, Patrizio; Brandenburg, Piter; Wever, Diego A. Z.; Broekhuis, Antonius A.; Picchioni, Francesco

    2013-01-01

    Three well-defined polystyrene-poly(sodium methacrylate) amphiphilic block copolymers characterized by different molecular architecture (diblock, triblock, and four-arm star) have been synthesized by ATRP. The rheology of their water solutions has been evaluated by measuring dynamic moduli and shear

  19. 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.

  20. Investigation of cross-linking poly(methyl methacrylate) as a guiding material in block copolymer directed self-assembly

    Science.gov (United States)

    Seidel, Robert; Rincon Delgadillo, Paulina; Ramirez-Hernandez, Abelardo; Wu, Hengpeng; Her, Youngjun; Yin, Jian; Nealey, Paul; de Pablo, Juan; Gronheid, Roel

    2014-03-01

    Directed self-assembly (DDSA) of block copolymers ((BCP) is attracting a growing amount of interest as a techhnique to expand traditional lithography beyond its current limits. It has reecently been demonstrated that chemoepitaxy can be used to successfully ddirect BCP assembly to form large arrays off high-density features. The imec DSA LiNe flow uses lithography and trim-etch to produce a "prepattern" of cross-linked polystyrene (PS) stripes, which in turn guide the formation of assembled BCPP structures. Thhe entire process is predicated on the preferential interaction of the respective BCP domains with particular regionss of the underlying prepattern. The use of polystyrene as the guiding material is not uniquely required, however, and in fact may not even be preferable. This study investigates an alternate chemistry -- crosslinked poly(methyl methacrylate), X-PMMA, -- as the underlying polymer mat, providing a route to higher auto-affinity and therefore a stronger guiding ability. In addition to tthe advantages of the chemistry under investigation, this study explores the broader theme of extending BCP DSA to other materials.

  1. The effect of hydrophilic and hydrophobic block length on the rheology of amphiphilic diblock Polystyrene-b-Poly(sodium methacrylate) copolymers prepared by ATRP.

    Science.gov (United States)

    Raffa, Patrizio; Stuart, Marc C A; Broekhuis, Antonius A; Picchioni, Francesco

    2014-08-15

    Following our previous investigation on the effect of molecular architecture on the rheology of Polystyrene-b-Poly(sodium methacrylate) copolymers (PS-b-PMAA), we consider here diblock PS-b-PMAA copolymers characterized by a different length of either the hydrophilic or the hydrophobic block. Various copolymers characterized by different PS or PMAA block length have been prepared by ATRP (kinetics is also discussed) and studied from the point of view of their rheological behaviour in water. To the best of our knowledge, this is the first systematic investigation concerning the effect of block length on the rheology of diblock polyelectrolytes. We found that the hydrophobic block length has small influence on the rheology. Surprisingly, the polymers with shortest PMAA blocks yield the strongest gels at high concentration. A simple model based on the classical theories of self-assembly and percolation of amphiphilic polymers has been here developed in order to explain the observed data.

  2. 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

    minority block of poly(methacrylic acid) (PMAA), microphase separate into spherical PMAA microdomains, either in disordered liquid-like state or body-centered-cubic (BCC) arrangement, at various annealing temperatures T, in the strong segregation regime SSR. We found that (i) the microphase separated state...... is favored over an anticipated molecularly homogenous state, (ii) the spherical microdomain morphology (with BCC symmetry) is favored over an anticipated hexagonally packed cylindrical morphology, (iii) the extent of the dissolution of short PMAA blocks in the PS material can be quantified, (iv......) the spherical microdomains are dilated, and (v) despite molecular-weight (and architectural) polydispersity, well-ordered BCC structures can be obtained....

  3. Can ionic liquid additives be used to extend the scope of poly(styrene)-block-poly(methyl methacrylate) for directed self-assembly?

    Science.gov (United States)

    Bennett, Thomas M.; Pei, Kevin; Cheng, Han-Hao; Thurecht, Kristofer J.; Jack, Kevin S.; Blakey, Idriss

    2014-07-01

    Directed self-assembly (DSA) is a promising approach for extending conventional lithographic techniques by being able to print features with critical dimensions under 10 nm. The most widely studied block copolymer system is polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA). This system is well understood in terms of its synthesis, properties, and performance in DSA. However, PS-b-PMMA also has a number of limitations that impact on its performance and hence scope of application. The primary limitation is the low Flory-Huggins polymer-polymer interaction parameter (χ), which limits the size of features that can be printed. Another issue with block copolymers in general is that specific molecular weights need to be synthesized to achieve desired morphologies and feature sizes. Here we explore blending ionic liquid (IL) additives with PS-b-PMMA to increase the χ parameter. ILs have a number of useful properties that include negligible vapor pressure, tunable solvent strength, thermal stability, and chemical stability. The blends of PS-b-PMMA with an IL selective for the PMMA block allowed the resolution of the block copolymer to be improved. Depending on the amount of additive, it is also possible to tune the domain size and the morphology of the systems. These findings may expand the scope of PS-b-PMMA for DSA.

  4. 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.

  5. Poly(Lactic Acid) Hemodialysis Membranes with Poly(Lactic Acid)-block-Poly(2-Hydroxyethyl Methacrylate) Copolymer As Additive: Preparation, Characterization, and Performance.

    Science.gov (United States)

    Zhu, Lijing; Liu, Fu; Yu, Xuemin; Xue, Lixin

    2015-08-19

    Poly(lactic acid) (PLA) hemodialysis membranes with enhanced antifouling capability and hemocompatibility were developed using poly(lactic acid)-block-poly(2-hydroxyethyl methacrylate) (PLA-PHEMA) copolymers as the blending additive. PLA-PHEMA block copolymers were synthesized via reversible addition-fragmentation (RAFT) polymerization from aminolyzed PLA. Gel permeation chromatography (GPC) and (1)H-nuclear magnetic resonance ((1)H NMR) were applied to characterize the synthesized products. By blending PLA with the amphiphilic block copolymer, PLA/PLA-PHEMA membranes were prepared by nonsolvent induced phase separation (NIPS) method. Their chemistry and structure were characterized with X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and atomic force microscopy (AFM). The results revealed that PLA/PLA-PHEMA membranes with high PLA-PHEMA contents exhibited enhanced hydrophilicity, water permeability, antifouling and hemocompatibility. Especially, when the PLA-PHEMA concentration was 15 wt %, the water flux of the modified membrane was about 236 L m(-2) h(-1). Its urea and creatinine clearance was more than 0.70 mL/min, lysozyme clearance was about 0.50 mL/min, BSA clearance was as less as 0.31 mL/min. All the results suggest that PLA-PHEMA copolymers had served as effective agents for optimizing the property of PLA-based membrane for hemodialysis applications.

  6. Custom CAD-CAM healing abutment and impression coping milled from a poly(methyl methacrylate) block and bonded to a titanium insert.

    Science.gov (United States)

    Proussaefs, Periklis

    2016-11-01

    This article describes a technique in which a custom-made computer-aided design and computer-aided manufacturing (CAD-CAM) healing abutment milled from a poly(methyl methacrylate) (PMMA) block is fabricated and bonded to a titanium metal insert. An impression is made during dental implant surgery, and the CAD-CAM custom-made healing abutment is fabricated before second-stage surgery while appropriate healing time is allowed for the dental implant to osseointegrate. The contours of the healing abutment are based on the contours of a tentatively designed definitive prosthesis. The healing tissue obtains contours that will be compatible with the contours of the definitive prosthesis. After the milling process is complete, a titanium metal insert is bonded to the healing abutment. Placement of the custom-made CAD-CAM healing abutment at second-stage surgery allows the tissue to obtain contours similar to those of the definitive prosthesis. A custom-made CAD-CAM impression coping milled from a PMMA block and with a titanium insert is used for the definitive impression after the soft tissue has healed. This technique allows guided soft tissue healing by using a custom-made CAD-CAM healing abutment and impression coping.

  7. Azobenzene-based inhibitors of human carbonic anhydrase II

    Directory of Open Access Journals (Sweden)

    Leander Simon Runtsch

    2015-07-01

    Full Text Available Aryl sulfonamides are a widely used drug class for the inhibition of carbonic anhydrases. In the context of our program of photochromic pharmacophores we were interested in the exploration of azobenzene-containing sulfonamides to block the catalytic activity of human carbonic anhydrase II (hCAII. Herein, we report the synthesis and in vitro evaluation of a small library of nine photochromic sulfonamides towards hCAII. All molecules are azobenzene-4-sulfonamides, which are substituted by different functional groups in the 4´-position and were characterized by X-ray crystallography. We aimed to investigate the influence of electron-donating or electron-withdrawing substituents on the inhibitory constant Ki. With the aid of an hCAII crystal structure bound to one of the synthesized azobenzenes, we found that the electronic structure does not strongly affect inhibition. Taken together, all compounds are strong blockers of hCAII with Ki = 25–65 nM that are potentially photochromic and thus combine studies from chemical synthesis, crystallography and enzyme kinetics.

  8. Structure control for fine tuning fluorescence emission from side-chain azobenzene polymers.

    Science.gov (United States)

    Smitha, P; Asha, S K

    2007-06-14

    New fluorescent azobenzene dyes and side-chain polymers have been synthesized and characterized and their photophysical properties studied. A series of azobenzene dyes having different fluorophores such as phenol (S1), phenylphenol (S2) and naphthol (S3) incorporated in them were synthesized. S2 had unusually high fluorescence with a quantum yield of phi f = 0.2 recorded in dichloromethane (DCM), whereas S1 and S3 were found to be weakly fluorescent. The azobenzene dyes were converted into methacrylate monomers having short ethyleneoxy spacers and then free radically polymerized. Phenylphenol-based azobenzene polymer (P2) continued to show fluorescence, whereas fluorescence was completely quenched in the case of phenol (P1)- and naphthol (P3)-based polymers. Phenylphenol, though twisted in the ground state is known to have a more planar geometry in the excited state--a factor that enables it to retain its fluorescence behavior even when it is incorporated as part of an azobenzene unit. In contrast, naphthol, which is a better fluorophore compared to phenylphenol, loses much of its emissive behavior upon coupling to the azobenzene unit. The extent of trans to cis photoisomerization in solution was very low (approximately 17%) for P2 after 30 min of continuous irradiation using 365 nm light, in contrast to approximately 40% for P1 under identical conditions. This is attributed to the steric repulsion brought about by the bulky phenylphenol units that restrict rotation. A 2-fold enhancement in fluorescence emission was observed for P2 upon irradiation by UV light at 360 nm, which relaxed to the original intensity in about 7 day's time. The higher emission of the cis azobenzenes is generally attributed to an inhibition of photoinduced electron transfer (PET) mechanism. The emission of P2 showed a concentration dependence which increased initially and then decreased in intensity with the formation of a new red-shifted peak at higher concentration due to aggregation

  9. Photoinduced micropattern in an azobenzene polymer film

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The micropattern observed in the amorphous azobenzene polymer film by degenerated four-wave mixing has been reported. Patterns with well-defined structures are examined with the scanning electron microscopy and the polarizing optical microscopy. It is demonstrated that the control of photoinduced micropattern in the azobenzene polymer film is possible by using appropriate polarized writing beams with total incident power exceeding a certain threshold.

  10. Unusual photoanisotropic alignment in amorphous azobenzene polymers

    DEFF Research Database (Denmark)

    Ramanujam, P.S.

    2015-01-01

    560 and 630nm, where the absorption is minimal, results in a possible uniaxial hedgehog arrangement of the molecules. Experiments performed with a dye laser, which can be tuned continuously between 560 and 630nm, are described. Not only azobenzene but also another photosensitive molecule...

  11. Photoinduced Deformation of Azobenzene Polyester Films

    DEFF Research Database (Denmark)

    Bublitz, D.; Helgert, M.; Fleck, B.;

    2000-01-01

    We investigate two types of azobenzene side-chain polyesters which have shown opposite behaviour in light-induced surface grating formation experiments. Thin films of these polymers prepared on a water surface undergo opposite changes of shape under the influence of polarized light. We propose...

  12. 76 FR 69659 - Methacrylic Acid-Methyl Methacrylate-Polyethylene Glycol Monomethyl Ether Methacrylate Graft...

    Science.gov (United States)

    2011-11-09

    ... AGENCY 40 CFR Part 180 Methacrylic Acid-Methyl Methacrylate-Polyethylene Glycol Monomethyl Ether... residues of methacrylic acid-methyl methacrylate- polyethylene glycol monomethyl ether methacrylate graft... permissible level for residues of methacrylic acid-methyl methacrylate-polyethylene glycol monomethyl...

  13. Gd@C82 metallofullerenes for neutron capture therapy—fullerene solubilization by poly(ethylene glycol-block-poly(2-(N, N-diethylaminoethyl methacrylate and resultant efficacy in vitro

    Directory of Open Access Journals (Sweden)

    Yukichi Horiguchi, Shinpei Kudo and Yukio Nagasaki

    2011-01-01

    Full Text Available Poly(ethylene glycol-block-poly(2-(N,N-diethylaminoethyl methacrylate (PEG-b-PAMA was found to solubilize fullerenes such as C60, and this technique was applied to metallofullerenes. Gd@C82 was easily dissolved in water in the presence of PEG-b-PAMA without any covalent derivatization, forming a transparent complex about 20–30 nm in diameter. Low cytotoxicity was confirmed in vitro. Neutron irradiation of cultured cells (colon-26 adenocarcinoma with Gd@C82-PEG-b-PAMA-complexed nanoparticles showed effective cytotoxicity, indicating the effective emission of gamma rays and internal conversion electrons produced from the neutron capture reaction of Gd. This result suggests a potentially valuable approach to gadolinium-based neutron capture therapy.

  14. Graphene oxide catalyzed cis-trans isomerization of azobenzene

    Directory of Open Access Journals (Sweden)

    Dongha Shin

    2014-09-01

    Full Text Available We report the fast cis-trans isomerization of an amine-substituted azobenzene catalyzed by graphene oxide (GO, where the amine functionality facilitates the charge transfer from azobenzene to graphene oxide in contrast to non-substituted azobenzene. This catalytic effect was not observed in stilbene analogues, which strongly supports the existence of different isomerization pathways between azobenzene and stilbene. The graphene oxide catalyzed isomerization is expected to be useful as a new photoisomerization based sensing platform complementary to GO-based fluorescence quenching methods.

  15. Cooperative Switching in Nanofibers of Azobenzene Oligomers

    Science.gov (United States)

    Weber, Christopher; Liebig, Tobias; Gensler, Manuel; Zykov, Anton; Pithan, Linus; Rabe, Jürgen P.; Hecht, Stefan; Bléger, David; Kowarik, Stefan

    2016-05-01

    Next-generation molecular devices and machines demand the integration of molecular switches into hierarchical assemblies to amplify the response of the system from the molecular level to the meso- or macro-scale. Here, we demonstrate that multi-azobenzene oligomers can assemble to form robust supramolecular nanofibers in which they can be switched repeatedly between the E- and Z-configuration. While in isolated oligomers the azobenzene units undergo reversible photoisomerization independently, in the nanofibers they are coupled via intermolecular interactions and switch cooperatively as evidenced by unusual thermal and kinetic behavior. We find that the photoisomerization rate from the Z-isomer to the E-isomer depends on the fraction of Z-azobenzene in the nanofibers, and is increased by more than a factor of 4 in Z-rich fibers when compared to E-rich fibers. This demonstrates the great potential of coupling individual photochromic units for increasing their quantum efficiency in the solid state with potential relevance for actuation and sensing.

  16. SYNTHESIS AND CHARACTERIZATION OF FOUR-ARMED BLOCK POLY(STYRENE-b-p-NITRO PHENYL METHACRYLATE) PREPARED BY THE ATRP METHOD

    Institute of Scientific and Technical Information of China (English)

    Cai-yuan Pan; Lei Tao; Ye Liu

    2002-01-01

    A novel tetrafunctional initiator, C[CH2O(CH2)3OOCCH(Br)CH3]4 (1), was synthesized through the reaction oftetraol with α-bromopropionyl chloride, and then was used as initiator of atom transfer radical polymerization (ATRP) in thepreparation of 4-armed polystyrene (PSt) with narrow polydispersity. The structure, molecular weight and molecular weightdistribution (MWD) of each arm were studied by 1H-NMR and GPC data of hydrolyzed products of the 4-armed PSt. TheATRP of St using 1/CuBr/bpy as initiator system is of "living" character based on the following evidence: narrow MWD,constant concentration of chain radical during the polymerization, control of molecular weight by the molar ratio of monomerconsumed to 1. The 4-armed poly(St-b-p-nitrophenyl methacrylate) [poly(St-b-NPMA)] was prepared by the ATRP ofNPMA using 4-armed PSt with terminal bromine as the initiator, and characterized by FT-IR, 1H-NMR spectra and GPCcurves. The micelles with PSt as core, and PNPMA as shell were formed by dropping DMSO into a solution of 4-armedpoly(St-b-NPMA) in DMF, as proved by laser light scatter (LLS) method.

  17. Optically induced surface relief phenomena in azobenzene polymers

    DEFF Research Database (Denmark)

    Holme, NCR; Nikolova, Ludmila; Hvilsted, Søren

    1999-01-01

    Azobenzene polymers and oligomers show intriguing surface relief features when irradiated with polarized laser light. We show through atomic force microscopic investigation of side-chain azobenzene polymers after irradiation through an amplitude mask that large peaks or trenches result depending ...

  18. Rewritable azobenzene polyester for polarization holographic data storage

    DEFF Research Database (Denmark)

    Kerekes, A; Sajti, Sz.; Loerincz, Emoeke;

    2000-01-01

    Optical storage properties of thin azobenzene side-chain polyester films were examined by polarization holographic measurements. The new amorphous polyester film is the candidate material for the purpose of rewritable holographic memory system. Temporal formation of anisotropic and topographic...... and erasing was tested. The ability of azobenzene polyester for rewriting was found satisfactory after many writing-erasing cycles....

  19. Synthesis of amphiphilic tri-block copolymer poly(vinylpyrrolidone)-b-poly(methyl methacrylate)-b-poly(vinylpyrrolidone) for the modification of polyethersulfone membrane

    Institute of Scientific and Technical Information of China (English)

    Sheng Qiang Nie; Fen Ran; Chao He; Peng Fei Zhao; Xiao Hong Wei; Jie Li; Chang Sheng Zhao

    2011-01-01

    Well-defined amphiphilic tri-block copolymer PVP-b-PMMA-b-PVP was prepared for the first time via successive reversible addition fragmentation chain transfer (RAFT) polymerization using carboxyl-terminated trithiocarbonate as the RAFT agent. The structure of the copolymer was characterized using FTTR, GPC and 1H NMR. The block copolymer could be directly blended with polyethersulfone (PES) as a macromolecule additive using N-methyl-2-pyrrolidone (NMP) as the solvent to prepare membranes. The water contact angles for the modified membranes decreased obviously, and therefore, the protein adsorption amount on the membrane surface decreased.

  20. The still unknown azobenzene - Wavelength dependent photoanisotropy in amorphous azobenzene polymers

    DEFF Research Database (Denmark)

    Ramanujam, P.S.; Jensen, Ole Bjarlin; Tidemand-Lichtenberg, Peter

    2013-01-01

    We demonstrate a new type of anisotropy in thin films of amorphous azobenzene polymers induced between 570 and 633 nm, where the absorbance in the film is on the order of 0.05. The anisotropy has a pronounced radial contribution. This observation points to an additional mechanism for the alignment...

  1. Grafting of poly[(methyl methacrylate)-block-styrene] onto cellulose via nitroxide-mediated polymerization, and its polymer/clay nanocomposite.

    Science.gov (United States)

    Karaj-Abad, Saber Ghasemi; Abbasian, Mojtaba; Jaymand, Mehdi

    2016-11-05

    For the first time, nitroxide-mediated polymerization (NMP) was used for synthesis of graft and block copolymers using cellulose (Cell) as a backbone, and polystyrene (PSt) and poly(methyl metacrylate) (PMMA) as the branches. For this purpose, Cell was acetylated by 2-bromoisobutyryl bromide (BrBiB), and then the bromine group was converted to 4-oxy-2,2,6,6-tetramethylpiperidin-1-oxyl group by a substitution nucleophilic reaction to afford a macroinitiator (Cell-TEMPOL). The macroinitiator obtained was subsequently used in controlled graft and block copolymerizations of St and MMA monomers to yield Cell-g-PSt and Cell-g-(PMMA-b-PSt). The chemical structures of all samples as representatives were characterized by FTIR and (1)H NMR spectroscopies. In addition, Cell-g-(PMMA-b-PSt)/organophilic montmorillonite nanocomposite was prepared through a solution intercalation method. TEM was used to evaluate the morphological behavior of the polymer-clay system. It was demonstrated that the addition of small percent of organophilic montmorillonite (O-MMT; 3wt.%) was enough to improve the thermal stability of the nanocomposite.

  2. Polarisation-sensitive optical elements in azobenzene polyesters and peptides

    DEFF Research Database (Denmark)

    Ramanujam, P.S.; Dam-Hansen, Carsten; Berg, Rolf Henrik;

    2006-01-01

    In this article, we describe fabrication of polarisation holographic optical elements in azobenzene polyesters. Both liquid crystalline and amorphous side-chain polyesters have been utilised. Diffractive optical elements such as lenses and gratings that are sensitive to the polarisation...... of the incident light have been fabricated with polarisation holography. Computer-generated optical elements and patterns have also been written with a single polarised laser beam. Recording of polarisation defects enabling easy visualisation is also shown to be feasible in azobenzene polyesters....

  3. Holographic Gratings in Azobenzene Side-Chain Polymethacrylates

    DEFF Research Database (Denmark)

    Andruzzi, Luisa; Altomare, Angelina; Ciardelli, Francesco

    1999-01-01

    Optical storage properties of thin unoriented liquid crystalline and amorphous side-chain azobenzene polymethacrylate films are examined by polarization holographic measurements. The investigated materials are free radical copolymers derived from two photochromic monomers, 6-(4-oxy-4'-cyanoazoben......Optical storage properties of thin unoriented liquid crystalline and amorphous side-chain azobenzene polymethacrylate films are examined by polarization holographic measurements. The investigated materials are free radical copolymers derived from two photochromic monomers, 6-(4-oxy-4...

  4. MORPHOLOGY STUDY OF A SERIES OF AZOBENZENE-CONTAINING SIDE-ON LIQUID CRYSTALLINE TRIBLOCK COPOLYMERS

    Institute of Scientific and Technical Information of China (English)

    Wei Deng; Annie Br(u)let; Pierre-antoine Albouy; Patrick Keller; Xiao-gong Wang; Min-hui Li

    2012-01-01

    A series of azobenzene containing side-on liquid crystalline ABA triblock copolymers were investigated.This triblock series possesses the same central liquid crystal block B and various lengths of the amorphous block A.Transmission electron microscopy (TEM),small angle X-rays and neutron scattering (SAXS and SANS) were used to study their morphologies.Aider annealing the samples over weeks at a temperature within the nematic temperature range of block B,different morphologies (disordered,lamellar,perforated layer and hexagonal cylinder) were observed by TEM.The alignment behavior of these azo triblock copolymers in the magnetic field for artificial muscle application,as well as the phase period and the order-disorder transition (ODT) were studied in situ by SANS.

  5. Photo-responsive and thermoreversible networks from the self-assembly of azobenzene-containing liquid crystal triblock copolymers (Conference Presentation)

    Science.gov (United States)

    Kurji, Zuleikha; Kornfield, Julia A.; Kuzyk, Mark G.

    2016-09-01

    We report the synthesis of azobenzene-containing coil-liquid crystal-coil triblock copolymers that can serve as mechano-optic actuators for applications that include non-invasively steering fiber optics. The coil (polystyrene) end-blocks phase segregate from the liquid crystal midblock forming of uniform and uniformly-spaced physical crosslinks, resulting in highly reproducible and thermoreversible networks by self-assembly. These polymers are elastic in the melt (at room temperature) and can be easily spun, coated or molded. Mechanical stretching results in a temporary monodomain alignment. Starting from identical triblock prepolymers (with polystyerene end blocks and 1,2-polybutadiene midblocks), a matched pair (azobenzene-containing, and non-azobenzene-containing) of liquid crystal triblock copolymers was synthesized. These triblocks were then be blended to prepare a series of elastomers with 0 to 5% azobenzene groups, while matching in nearly all other physical properties (cross-link density, modulus, birefringence, etc.), allowing the effect of concentration of photo-responsive groups to be unambiguously determined. Results will be presented that demonstrate this approach to independent control of optical density and photo-mechanical sensitivity.

  6. Synthesis and characterization of ferrocene containing block copolymers

    DEFF Research Database (Denmark)

    Chernyy, Sergey; Wang, Zhongli; Kirkensgaard, Jacob Judas Kain

    2017-01-01

    Narrowly dispersed diblock copolymers containing poly(methyl methacrylate) [PMMA] or poly(nonafluorohexyl methacrylate) [PF9MA] as the first block and poly(ferrocenylmethyl methacrylate) [PFMMA] as the second block, were prepared by anionic polymerization for the first time. Disordered bulk morph...

  7. Azobenzene-derived tris-β-diketonate lanthanide complexes: reversible trans-to-cis photoisomerization in solution and solid state.

    Science.gov (United States)

    Lin, Li-Rong; Wang, Xuan; Wei, Gao-Ning; Tang, Hui-Hui; Zhang, Hui; Ma, Li-Hua

    2016-10-14

    Novel azobenzene-derived β-diketonates (4,4,5,5,6,6,6-heptafluoro-1-azobenzene-1,3-hexanedione (LA), 4,4,5,5,6,6,6-heptafluoro-1-(4-dimethylamino)azobenzene-1,3-hexanedione (LB)) were designed and their complexes with lanthanide cations (La(3+), Eu(3+), Gd(3+), Yb(3+)) were prepared and characterized by (1)H NMR, FT-IR, and elemental analysis. Three of the complexes were crystallized successfully and identified by X-ray diffraction. It was significant to find that LA showed remarkably reversible trans-to-cis isomerization properties, however, LB, bearing an electron donor compared with LA, slowed down the isomerization to an extent. The presence of Ln(iii) enhanced the reversible trans-to-cis isomerization properties of both LA and LB a little upon photoirradiation in organic solvents, and amazingly increased the fatigue resistance. In addition, the complexes doped in polymethyl methacrylate (PMMA) films produced a similar phenomenon as well as when in solution. Theoretical calculations based on time dependent density functional theory (TD-DFT) were performed for geometry optimization and to determine the excitation energies of LA and LB to gain further insight into the electronic structure of the complexes, and the data were consistent with the experimental results. The excellent reversible photoisomerization properties of the newly designed Ln(iii) complexes can offer important advantages that will help with the further study of these materials to reach their full potential in applications such as molecular switching devices.

  8. Review of the recent progress in photoresponsive molecularly imprinted polymers containing azobenzene chromophores.

    Science.gov (United States)

    Wei, Yu-bo; Tang, Qian; Gong, Cheng-bin; Lam, Michael Hon-Wah

    2015-11-05

    Photoresponsive molecularly imprinted polymers (PMIPs) containing azobenzene have received wide research attention in recent years and made notable achievements. This article reviews the recent developments on PMIPs containing azobenzene. Topics include the following: (i) brief introduction of azobenzene, molecularly imprinted polymers, and PMIPs containing azobenzene; (ii) progress in functional monomers, cross-linkers, and polymerization conditions; (iii) preparation methods, properties, applications, as well as advantages and disadvantages of conventional PMIPs; (iv) substrate, preparation method, and applications of photoresponsive surface molecularly imprinted polymers; and (v) some perspectives for further development of PMIPs containing azobenzene.

  9. Approximate photochemical dynamics of azobenzene with reactive force fields.

    Science.gov (United States)

    Li, Yan; Hartke, Bernd

    2013-12-14

    We have fitted reactive force fields of the ReaxFF type to the ground and first excited electronic states of azobenzene, using global parameter optimization by genetic algorithms. Upon coupling with a simple energy-gap transition probability model, this setup allows for completely force-field-based simulations of photochemical cis→trans- and trans→cis-isomerizations of azobenzene, with qualitatively acceptable quantum yields. This paves the way towards large-scale dynamics simulations of molecular machines, including bond breaking and formation (via the reactive force field) as well as photochemical engines (presented in this work).

  10. Approximate photochemical dynamics of azobenzene with reactive force fields

    Science.gov (United States)

    Li, Yan; Hartke, Bernd

    2013-12-01

    We have fitted reactive force fields of the ReaxFF type to the ground and first excited electronic states of azobenzene, using global parameter optimization by genetic algorithms. Upon coupling with a simple energy-gap transition probability model, this setup allows for completely force-field-based simulations of photochemical cis→trans- and trans→cis-isomerizations of azobenzene, with qualitatively acceptable quantum yields. This paves the way towards large-scale dynamics simulations of molecular machines, including bond breaking and formation (via the reactive force field) as well as photochemical engines (presented in this work).

  11. Thermoforming polymethyl methacrylate.

    Science.gov (United States)

    Jagger, R G; Okdeh, A

    1995-11-01

    This study characterized a range of commercially available polymethyl methacrylate sheets with respect to molecular weight, residual monomer content, and glass transition temperature and then developed a thermoforming procedure that produced visually satisfactory thermoformed polymethyl methacrylate specimens. Molecular weight values of Perspex material were considerably greater than those of the other materials. All materials but Diakon had residual monomer concentrations of less than 1% and glass transition temperature values greater than 100 degrees C. Perspex material was selected for further investigation. It was necessary to preheat Perspex sheets in an oven at 160 degrees C for at least 30 minutes before heating and forming on the thermoforming apparatus to obtain acceptable specimens.

  12. Injectible bodily prosthetics employing methacrylic copolymer gels

    Science.gov (United States)

    Mallapragada, Surya K.; Anderson, Brian C.

    2007-02-27

    The present invention provides novel block copolymers as structural supplements for injectible bodily prosthetics employed in medical or cosmetic procedures. The invention also includes the use of such block copolymers as nucleus pulposus replacement materials for the treatment of degenerative disc disorders and spinal injuries. The copolymers are constructed by polymerization of a tertiary amine methacrylate with either a (poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) polymer, such as the commercially available Pluronic.RTM. polymers, or a poly(ethylene glycol) methyl ether polymer.

  13. A remarkably efficient azobenzene peptide for holographic information storage

    DEFF Research Database (Denmark)

    Rasmussen, P.H.; Ramanujam, P.S.; Hvilsted, S.

    1999-01-01

    A new family of proline-based azobenzene peptides (DNO) for holographic information storage is reported.:By use of polarization holography, it was found that gratings with extraordinarily high diffraction efficiency (up to 80%) can be recorded in hundreds of milliseconds in a similar to 13-mu m...

  14. Photoinduced Circular Anisotropy in Side-Chain Azobenzene Polyesters

    DEFF Research Database (Denmark)

    Nikolova, L.; Todorov, T.; Ivanov, M.;

    1997-01-01

    We report for the first time the inducing of large circular anisotropy in previously unoriented films of side-chain azobenzene polyesters on illumination with circularly polarized light at a wavelength of 488 nm. The circular dichroism and optical activity are measured simultaneously in real time...

  15. The Volume Holographic Optical Storage Potential in Azobenzene Containing Polymers

    DEFF Research Database (Denmark)

    Hvilsted, Søren; Sanchez, Carlos; Alcalá, Rafael

    2009-01-01

    Volume holographic data storage is one of the most promising techniques to improve both the storage capacity of devices and the transfer data rate. Among the materials proposed as storage data media, azobenzene containing polymers have received much attention. Some of their properties seem to be ...

  16. Photoinduced macroscopic chiral structures in a series of azobenzene copolyesters

    DEFF Research Database (Denmark)

    Nedelchev, L.; Nikolova, L.; Matharu, A.

    2002-01-01

    A study of the propagation of elliptically polarized light and the resulting formation of macroscopic chiral structures in a series of azobenzene side-chain copolyesters, in which the morphology is varied from liquid crystalline to amorphous, is reported. Real-time measurements are presented...

  17. Pattern Formation and Quasicrystal Structure in Azobenzene Polymer Film

    Institute of Scientific and Technical Information of China (English)

    XU Ze-Da; CAI Zhi-Gang; ZHANG Ling-Zhi; LIU Yan-Fa; YANG Jie; SHE Wei-Long; ZHOU Jian-Ying

    2000-01-01

    Pattern formation in azobenzene polymer film by degenerate four-wave mixing is reported. Island arrays with specific patterns are analyzed with scanning electron microscopy and polarizing optical microscopy. It is demonstrated that the control of photo-induced nanostructure sized micropattern in the nonlinear organic film is possible by using properly polarized writing beams with the total incident power exceeding a certain threshold.

  18. Geometry Control of Photo-induced Microstructures in an Azobenzene Polymer Film

    Institute of Scientific and Technical Information of China (English)

    Xu Ze-Da; LI Zhen; LIANG Li-Zhen; PENG Zhuo-Lun; CAI Zhi-Gang; ZHOU Jian-Ying; NINULESCU Valerica; ZHANG Ling-Zhi

    2001-01-01

    The mechanisms of photo-induced microstructures in an azobenzene polymer film are presented. They are based on the spatial periodic modulation of optical intensity and the photoisomerization of azobenzene molecules with the movement of main chains. Experiment and theory jointly point out the possibility of photo-inducing desired spatial microstructures in an azobenzene organic polymer via adequate optical lattices and adequately polarized ‘writing' beams.

  19. Polymer scaffolds bearing azobenzene - Potential for optical information storage

    DEFF Research Database (Denmark)

    Hvilsted, Søren; Ramanujam, P.S.

    2001-01-01

    The fundamental optical storage mechanism of the laser light addressable azobenzene moiety is briefly introduced. A modular and flexible synthesis design furnishes polyester matrices covalently integrating cyanoazobenzene in regularly spaced side chains. Thin films of these materials are particul......The fundamental optical storage mechanism of the laser light addressable azobenzene moiety is briefly introduced. A modular and flexible synthesis design furnishes polyester matrices covalently integrating cyanoazobenzene in regularly spaced side chains. Thin films of these materials...... are particularly well suited for holographic storage. Notable figures of merits of liquid crystalline polyesters are response time to blue-green laser light of the order of nanoseconds, storage capacity expressed as 5000 lines/mm, and high, permanent (almost nine years) diffraction efficiency of the order of 50...

  20. Threshold collision induced dissociation experiment for azobenzene and its derivatives

    Science.gov (United States)

    Rezaee, Mohammadreza; Compton, Robert

    In this study we investigated protonated azobenzene cation and properties of trans 2,2',6,6'-tetrafluoroazobenzene anion using the collision induced dissociation method and the results are compared with the results from ab initio electronic structure calculations. We measured the bond dissociation energies experimentally and found which theoretical quantum chemistry methods yield best results. Several high accuracy multi-level calculations such as CBS-QB3, G3 and G4 had been carried out to obtain reliable thermochemical information for azobenzene and several of its derivatives and their anion or cation. We also performed other experiments such as Raman spectroscopy to study these light sensitive molecules with promising applications such as photo-switching.

  1. Photophysical characteristics of polyaniline with photochromic azobenzene side groups

    Institute of Scientific and Technical Information of China (English)

    Feng Wei; Huang Kun; Wan Mei-Xiang

    2005-01-01

    Photochromic characteristics and optical molecular reorientation in conducting polymer such as polyaniline derivatives containing photochromic azobenzene moieties (PAPNPAPOA) in side chain are studied. Changes in the UV-vis absorption, refractive index, thickness, contact angle and morphology of these films after irradiation of a linearly polarized light with a wavelength of 365nm are measured. The trans-cis isomerization of PAPNPAPOA is proved irreversible even after withdrawing the UV light for a long time. That the structure of main-chain attends by the trans-cis isomerization of side-chain is confirmed by the absorption and the solution colour during the UV irradiation. These effects are discussed by taking the trans-cis isomerization of azobenzene into consideration.

  2. Azobenzene Modified Polymer Electrolyte Membrane for Ion Gating

    Science.gov (United States)

    Piedrahita, Camilo; Mballa, Mireille; He, Ruixuan; Kyu, Thein

    By virtue of ion concentration gradient across cell membranes, neuron cells are highly polarized driving electrical potential difference (e.g., Gibbs law). To regulate and control ion movement, living cells have specific channels with gates that are permeable to cations, enabling or excluding them via charge polarity and size. This mechanism for generating and transmitting signals from one neuron to another controls body movement via brain function. By virtue of trans-cis isomerization, azobenzene derivative (AZO) has been heavily sought for ion-gating in biological cells as a means of signal generation and transmission through nervous systems. In this work, PEM consisted of PEGDA/SCN/LiTFSI was modified with AZO derivatives for gating of lithium ions. At low concentrations of azobenzene of 3 wt Supported by NSF-DMR 1502543.

  3. Propagation of polarized light through azobenzene polyester films

    DEFF Research Database (Denmark)

    Nedelchev, L; Matharu, A; Nikolova, Ludmila;

    2002-01-01

    When elliptically polarized light of appropriate wavelength Corresponding to trans-cis-trans isomerisation process is incident on thin films of azobenzene polyesters, a helical structure is induced. We investigate the propagation of the exciting light beam (self-induced) as well as a probe light...... beam outside the absorption band through the polyester films. Investigations are carried out in one amorphous and one liquid crystalline polyester. We show that amorphous polyester after irradiation behaves like classical helical material....

  4. The Azobenzene Optical Storage Puzzle - Demands on the Polymer Scaffold?

    DEFF Research Database (Denmark)

    Hvilsted, Søren; Ramanujam, PS

    2001-01-01

    The basic mechanism of optical information storage utilizing the azobenzene photoaddressable moiety will briefly be introduced. A synthetically flexible polyester matrix covalently integrating cyanoazobenzene in regularly spaced side chains is particularly well suited for holographic storage...... of the nature of the main chain on polyester morphology and on the permanency of the induced anisotropy are discussed. Arguments for the design and methods of preparation of other very different polymer scaffolds supporting the cyanoazobenzene are elucidated. Whereas oligopeptides invariably form amorphous...

  5. The azobenzene optical storage puzzle - Demands on the polymer scaffold?

    DEFF Research Database (Denmark)

    Hvilsted, Søren; Ramanujam, P.S.

    2001-01-01

    The basic mechanism of optical information storage utilizing the azobenzene photoaddressable moiety will briefly be introduced. A synthetically flexible polyester matrix covalently integrating cyanoazobenzene in regularly spaced side chains is particularly well suited for holographic storage...... of the nature of the main chain on polyester morphology and on the permanency of the induced anisotropy are discussed. Arguments for the design and methods of preparation of other very different polymer scaffolds supporting the cyanoazobenzene are elucidated. Whereas oligopeptides invariably form amorphous...

  6. Physical processes in azobenzene polymers on irradiation with polarized light

    DEFF Research Database (Denmark)

    Holme, N.C.R.; Nikolova, L.; Norris, T.B.;

    1999-01-01

    . A transition route based on experimental results for the theoretically calculated energy level scheme is proposed. Physical observations of surface relief in thin films of azobenzene polymers when irradiated with polarized light are reported. These include two beam polarization holographic observations...... and single beam transmission measurements through a mask, followed by atomic force microscope and profiler investigations. It is concluded that none of the prevalent theories can explain all the observed facts....

  7. Slower processes of the ultrafast photo-isomerization of an azobenzene observed by IR spectroscopy

    NARCIS (Netherlands)

    Koller, F.O.; Sobotta, C.; Schrader, T.E.; Cordes, T.; Schreier, W.J.; Sieg, A.; Gilch, P.

    2007-01-01

    The photo-induced trans–cis isomerization of the azobenzene derivative 4-nitro-4'-(dimethylamino)azobenzene in polar solution was studied by femtosecond UV/Vis and IR spectroscopy. The UV/Vis experiment reveals two excited state processes; the slower one (1 ps) is the internal conversion to the grou

  8. Azobenzene side-chain liquid crystalline polyesters with outstanding optical storage properties

    DEFF Research Database (Denmark)

    Hvilsted, Søren; Pedersen, M; Holme, NCR

    1998-01-01

    on azobenzene, iii- the methylene main-chain segment length, and iv-the polyester molecular mass, all influence the optical storage properties. A general synthetic route to novel mesogenic azobenzene diols comprising parameters i and ii is outlined. Polyesters with molecular masses (parameter iv) up to 100...

  9. Reversible switching of electrical conductivity in an AOT-isooctane-water microemulsion via photoisomerization of azobenzene.

    Science.gov (United States)

    Bufe, Markus; Wolff, Thomas

    2009-07-21

    The electrical conductivity of microemulsions composed of aerosol OT (AOT), isooctane, and water as a function of temperature was studied in the absence and presence of azobenzene, and consequences of an in situ trans-cis photoisomerization of azobenzene were investigated. A conductivity onset upon raising the temperature of a water-in-oil microemulsion indicates percolation. Small amounts (0.1-5% w/w) of solubilized azobenzene induce higher percolation temperatures T(p) (by up to 19 K), and photoisomerization of azobenzene shifts T(p) back to values that may be below T(p) in the absence of azobenzene. Consequently, the microemulsion can be switched from nonconducting to conducting by exposing samples to UV-light at lambda > 310 nm, without varying temperature or composition. The effect reverts within several minutes after turning off the irradiation lamp through thermal reisomerization. By that, reversible switching of electrical conductivity is brought about.

  10. Azobenzene dye-coupled quadruply hydrogen-bonding modules as colorimetric indicators for supramolecular interactions

    Directory of Open Access Journals (Sweden)

    Yagang Zhang

    2012-04-01

    Full Text Available The facile coupling of azobenzene dyes to the quadruply hydrogen-bonding modules 2,7-diamido-1,8-naphthyridine (DAN and 7-deazaguanine urea (DeUG is described. The coupling of azobenzene dye 2 to mono-amido DAN units 4, 7, and 9 was effected by classic 4-(dimethylaminopyridine (DMAP-catalyzed peptide synthesis with N-(3-dimethylaminopropyl-N’-ethyl carbodiimide hydrochloride (EDC as activating agent, affording the respective amide products 5, 8, and 10 in 60–71% yield. The amide linkage was formed through either the aliphatic or aromatic ester group of 2, allowing both the flexibility and absorption maximum to be tuned. Azobenzene dye 1 was coupled to the DeUG unit 11 by Steglich esterification to afford the product amide 12 in 35% yield. Alternatively, azobenzene dye 16 underwent a room-temperature copper-catalyzed azide–alkyne Huisgen cycloaddition with DeUG alkyne 17 to give triazole 18 in 71% yield. Azobenzene coupled DAN modules 5, 8, and 10 are bright orange–red in color, and azobenzene coupled DeUG modules 12 and 18 are orange–yellow in color. Azobenzene coupled DAN and DeUG modules were successfully used as colorimetric indicators for specific DAN–DeUG and DAN–UPy (2-ureido-4(1H-pyrimidone quadruply hydrogen-bonding interactions.

  11. Correlation between the molecular structure and trans←→ cis isomerization characteristics of azobenzenes

    Institute of Scientific and Technical Information of China (English)

    HAN Mina; HONDA Takumu

    2012-01-01

    Photochemical and thermal isomerization of various azobenzenes was systematically investigated to understand the correlation between the molecular structure and trans←→cis isomerization characteristics of azobenzenes.A blue shift in π-π* absorption band of ortho-alkylated azobenzenes (1o and 2o) was observed together with a reduction in molar extinction coefficient (ε) in comparison with both meta-alkylated azobenzenes (4m and 5m) and 7p lacking the meta and ortho substituents.For ortho-alkylated azobenzene,photochemical trans-to-cis isomerization and thermal back cis-to-trans isomerization in solution occurred slowly when compared with 4m,5m and 7p.The half-life time of the cis form of 2o was found to be 380 h,which is about 8-50 times longer than those of comparable 4m,5m (43-13 h) and 7p (7h).Furthermore,comparison of the molecular structure and isomerization characteristics of azobenzene thiol (2oand 5m) self-assembled monolayers on flat gold surfaces indicates that the trans-to-cis photoconversion in monolayer systems is influenced by steric hindrance and strong intermolecular interaction between azobenzene units.

  12. Modification of nucleic acids by azobenzene derivatives and their applications in biotechnology and nanotechnology.

    Science.gov (United States)

    Li, Jing; Wang, Xingyu; Liang, Xingguo

    2014-12-01

    Azobenzene has been widely used as a photoregulator due to its reversible photoisomerization, large structural change between E and Z isomers, high photoisomerization yield, and high chemical stability. On the other hand, some azobenzene derivatives can be used as universal quenchers for many fluorophores. Nucleic acid is a good candidate to be modified because it is not only the template of gene expression but also widely used for building well-organized nanostructures and nanodevices. Because the size and polarity distribution of the azobenzene molecule is similar to a nucleobase pair, the introduction of azobenzene into nucleic acids has been shown to be an ingenious molecular design for constructing light-switching biosystems or light-driven nanomachines. Here we review recent advances in azobenzene-modified nucleic acids and their applications for artificial regulation of gene expression and enzymatic reactions, construction of photoresponsive nanostructures and nanodevices, molecular beacons, as well as obtaining structural information using the introduced azobenzene as an internal probe. In particular, nucleic acids bearing multiple azobenzenes can be used as a novel artificial nanomaterial with merits of high sequence specificity, regular duplex structure, and high photoregulation efficiency. The combination of functional groups with biomolecules may further advance the development of chemical biotechnology and biomolecular engineering.

  13. Temperature Dependence of Photoinduced Birefringence in an Azobenzene Polymer

    Institute of Scientific and Technical Information of China (English)

    XU Hong-Tao; WANG Chang-Shun; PAN Xu; ZHANG Xiao-Qiang; WANG Chuan-Yu; SUN Cun-Ying

    2007-01-01

    The photoinduced birefringence in an azobenzene polymer is investigated at different temperatures between -20℃ to 50℃. It is found that there is a peak value of photoinduced birefringence in the temperature dependence of the photoinduced birefringence under a certain pumping intensity. With the pump light in 90 mW/cm2,the peak value of the photoinduced birefringence appeared at about 0℃. The effect of temperature on the photoinduced birefringence is discussed using the competition mechanism between the photoinduced reorientation and the thermal random motion.

  14. Shapeshifting photoswitchable azobenzene compounds and their biological applications

    Science.gov (United States)

    Peddie, Victoria; Heng, Sabrina; Mustafa, Sanam; Thomas, Jacob; Hutchinson, Mark R.; Abell, Andrew D.

    2016-11-01

    The photoisomerisation of azobenzenes between trans and cis results in well-defined changes in geometry and a considerable change of polarity. Thus, incorporating an azobenezene into a bioactive compound provides an opportunity to control biological activity, with ideally one configuration being active and the other inactive. This can allow the role of a specific biomolecule to be probed in its native environment by controlling activity both spatially and temporally using light. Incorporating such a photoswitchable moiety into the structure of a known GRK2 inhibitor can generate photoswitchable inhibitors, which can be used to reversibly regulate the activity of GRK2, and hence GPRCs.

  15. Structure dependence of photochromism and thermochromism of azobenzene-functionalized polythiophenes

    Directory of Open Access Journals (Sweden)

    2007-07-01

    Full Text Available Two novel azobenzene-functionalized polythiophenes, poly[4-((4-(phenylazophenoxybutyl-3-thienylacetate] (P4 and the copolymer of 3-hexylthiophene and 4-((4-(phenylazophenoxybutyl-3-thienylacetate (COP64 have been synthesized. The structure dependence of photoluminescence features and thermochromic behaviors of both azobenzene-functionalized polymers was investigated. The results show that polymer structure has a strong influence on the conformation and optical properties of the resulting polythiophene derivatives. The photochemical control of photoluminescence property was achieved with homopolymer P4 using photoactive azobenzene side chains.

  16. Quantum theory and experimental studies of absorption spectra and photoisomerization of azobenzene polymers

    DEFF Research Database (Denmark)

    Pedersen, Thomas Garm; Ramanujam, P.S.; Johansen, P.M.;

    1998-01-01

    The microscopic properties of azobenzene chromophores are important for a correct description of optical storage systems based on photoinduced anisotropy in azobenzene polymers. A quantum model of these properties is presented and verified by comparison to experimental absorption spectra for trans...... and cis isomers of cyano methoxy azobenzene. In addition, the trans --> cis quantum efficiency is measured, and hence the combined experimental and theoretical work allows one to determine the essential molecular properties, including magnitude and anisotropy of the absorption cross section and various...

  17. Conformational Dynamics of o-Fluoro-Substituted Z-Azobenzene.

    Science.gov (United States)

    Rastogi, S K; Rogers, R A; Shi, J; Gao, C; Rinaldi, P L; Brittain, W J

    2015-11-20

    A conformational analysis of o-fluoro Z-azobenzene reveals a slight preference for aromatic C-F/π interaction. Density functional theory (DFT) indicates that the conformation with a C-F/π interaction is preferred by approximately 0.3-0.5 kcal/mol. Ground-state conformations were corroborated with X-ray crystallography. (Z)-Azobenzene (Z-AB) with at least one o-fluoro per ring displays (19)F-(19)F through-space (TS) coupling. 2D J-resolved NMR was used to distinguish through-bond from TS coupling ((TS)JFF). (TS)JFF decreases as the temperature is lowered and the multiplets coalesce into broad singlets. We hypothesize that the coalescence temperature (Tc) corresponds to the barrier for phenyl rotation. The experimentally determined barrier of 8-10 kcal/mol has been qualitatively verified by DFT where transition states with a bisected geometry were identified with zero-point energies of 6-9 kcal/mol relative to ground state. These values are significantly higher that values estimated from previous theoretical studies but lie within a reasonable range for phenyl rotation in hydrocarbon systems.

  18. An Optimized Glutamate Receptor Photoswitch with Sensitized Azobenzene Isomerization.

    Science.gov (United States)

    Gascón-Moya, Marta; Pejoan, Arnau; Izquierdo-Serra, Mercè; Pittolo, Silvia; Cabré, Gisela; Hernando, Jordi; Alibés, Ramon; Gorostiza, Pau; Busqué, Félix

    2015-10-16

    A new azobenzene-based photoswitch, 2, has been designed to enable optical control of ionotropic glutamate receptors in neurons via sensitized two-photon excitation with NIR light. In order to develop an efficient and versatile synthetic route for this molecule, a modular strategy is described which relies on the use of a new linear fully protected glutamate derivative stable in basic media. The resulting compound undergoes one-photon trans-cis photoisomerization via two different mechanisms: direct excitation of its azoaromatic unit and irradiation of the pyrene sensitizer, a well-known two-photon sensitive chromophore. Moreover, 2 presents large thermal stability of its cis isomer, in contrast to other two-photon responsive switches relying on the intrinsic nonlinear optical properties of push-pull substituted azobenzenes. As a result, the molecular system developed herein is a very promising candidate for evoking large photoinduced biological responses during the multiphoton operation of neuronal glutamate receptors with NIR light, which require accumulation of the protein-bound cis state of the switch upon repeated illumination.

  19. Azobenzene C-Nucleosides for Photocontrolled Hybridization of DNA at Room Temperature.

    Science.gov (United States)

    Goldau, Thomas; Murayama, Keiji; Brieke, Clara; Asanuma, Hiroyuki; Heckel, Alexander

    2015-12-01

    Herein, we report the reversible light-regulated destabilization of DNA duplexes by using azobenzene C-nucleoside photoswitches. The incorporation of two different azobenzene residues into DNA and their photoswitching properties are described. These new residues demonstrate a photoinduced destabilization effect comparable to the widely applied D-threoninol-linked azobenzene switch, which is currently the benchmark. The photoswitches presented herein show excellent photoswitching efficiencies in DNA duplexes - even at room temperature - which are superior to commonly used azobenzene-based nucleic acid photoswitches. In addition, these photoswitching residues exhibit high thermal stability and excellent fatigue resistance, thus rendering them one of the most efficient candidates for the regulation of duplex stability with light.

  20. Theoretical Investigation of Nonlinear Optical Properties of Organic and Transition Metal Hybrid Azobenzene Dendrimers

    Institute of Scientific and Technical Information of China (English)

    LIU Cai-Ping; LIU Ping; WU Ke-Chen

    2008-01-01

    In this work, we report a theoretical exploration of the responses of organic azo-benzene dendrimers. The polarizabilities, the first and second hyperpolarizabilities of the azobenzene monomers (GO), and the first, second and third generation (G1, G2 and G3, respectively) are investigated by semi-empirical methods. The calculated results show that the nonlinear optical (NLO)properties of these organic dendrimers are mainly determined by the azobenzene chromospheres.Additionally, the values of β and γ increase almost in proportion to the number of chromophores. On the other hand, two types of transition metal hybrid azobenzene dendrimers (core-hybrid and branch-end hybrid according to the sites combined with transition metals) are simulated and discussed in detail in the framework of time-dependent density functional theory (TDDFT). The calculated results reveal that the NLO responses of these metal dendrimers distinctly varied as a result of altering the charge transfer transition scale and the excitation energies.

  1. Azobenzene Polyesters Used as Gate‐Like Scaffolds in Nanoscopic Hybrid Systems

    DEFF Research Database (Denmark)

    Bernardos, Andrea; Mondragón, Laura; Javakhishvili, Irakli

    2012-01-01

    The synthesis and characterisation of new capped silica mesoporous nanoparticles for on‐command delivery applications is reported. Functional capped hybrid systems consist of MCM‐41 nanoparticles functionalised on the external surface with polyesters bearing azobenzene derivatives and rhodamine B...

  2. The ground and excited state electron affinities of cytosine and trans-azobenzene

    Science.gov (United States)

    Chen, Edward C. M.; Herder, Charles; Chen, Edward S.

    2007-06-01

    The electron capture detector, reduction potential, electron transfer and photon methods of determining electron affinities are compared. The adiabatic electron affinities are (in eV): t-azobenzene(O 2), 1.578(5); t-azobenzene, 1.378(5); cytosine, 1.043(5) from anion photoelectron spectra. The largest or ground state value for trans-azobenzene and an excited state electron affinity for cytosine, 0.70 eV are also determined by reduction potentials. Other excited state energies are (in eV): t-azobenzene, 0.328(5), 0.589(5), 0.690(5), 0.768(5), 0.954(5), 1.038(5), 1.150(5), 1.275(5) and cytosine, 0.089(5), 0.098(5), 0.198(5), 0.235(5). The cytosine values are consistent with electron transport and radiation damage and repair in DNA.

  3. Copolymerization of Styrene with Dodecyl Methacrylate and Octadecyl Methacrylate

    OpenAIRE

    Vidović, Elvira; SARIĆ, Karla; JANOVIĆ, Zvonimir

    2002-01-01

    Styrene (Sty) was copolymerized with dodecyl methacrylate (DDMA) and with octadecyl methacrylate (ODMA) in toluene solution using 2,2'-azobis(isobutyronitrile) (AIBN) as a free radical initiator over a wide composition and conversion range. The copolymer composi-tion was determined from NMR spectra. The copolymerization reactivity ratios were found to be r1 = 0.52 (Sty) and r2 = 0.42 (DDMA) for the Sty-DDMA system, and r1 = 0.58 (Sty) and r2 = 0.45 (ODMA) for the Sty-ODMA system, showing a te...

  4. Irradiance and Temperature Dependence of Photo-Induced Orientation in Two Azobenzene-Based Polymers

    Science.gov (United States)

    1998-06-23

    and Almeria Natansohn* Department of Chemistry, Queen’s University, Kingston, Ontario, K7L 3N6 Paul Rochon Department of Physics, Royal Military...1. IRRADIANCE AND TEMPERATURE DEPENDENCE OF PHOTO-INDUCED ORIENTATION IN TWO AZOBENZENE-BASED POLYMERS Dennis Hore and Almeria Natansohn...IRRADIANCE AND TEMPERATURE DEPENDENCE OF PHOTO-INDUCED ORIENTATION IN TWO AZOBENZENE-BASED POLYMERS Dennis Hore and Almeria Natansohn Department of

  5. Fluorinated Azobenzenes for Shape-Persistent Liquid Crystal Polymer Networks.

    Science.gov (United States)

    Iamsaard, Supitchaya; Anger, Emmanuel; Aßhoff, Sarah Jane; Depauw, Alexis; Fletcher, Stephen P; Katsonis, Nathalie

    2016-08-16

    Liquid crystal polymer networks respond with an anisotropic deformation to a range of external stimuli. When doped with molecular photoswitches, these materials undergo complex shape modifications under illumination. As the deformations are reversed when irradiation stops, applications where the activated shape is required to have thermal stability have been precluded. Previous attempts to incorporate molecular switches into thermally stable photoisomers were unsuccessful at photogenerating macroscopic shapes that are retained over time. Herein, we show that to preserve photoactivated molecular deformation on the macroscopic scale, it is important not only to engineer the thermal stability of the photoswitch but also to adjust the cross-linking density in the polymer network and to optimize the molecular orientations in the material. Our strategy resulted in materials containing fluorinated azobenzenes that retain their photochemical shape for more than eight days, which constitutes the first demonstration of long-lived photomechanical deformation in liquid-crystal polymer networks.

  6. Light scattering of thin azobenzene side-chain polyester layers

    DEFF Research Database (Denmark)

    Kerekes, Á.; Lörincz, E.; Ramanujam, P.S.;

    2002-01-01

    Light scattering properties of liquid crystalline and amorphous azobenzene side-chain polyester layers used for optical data storage were examined by means of transmissive scatterometry. Comparative experiments show that the amorphous polyester has significantly lower light scattering...... characteristics than the liquid crystalline polyester. The amorphous samples have negligible polarization part orthogonal to the incident beam. the liquid crystalline samples have relative high orthogonal polarization part in light scattering, The light scattering results can be used to give a lower limit...... for the domain size in thin liquid crystalline polyester layers being responsible for the dominant light scattering. The characteristic domain Sizes obtained from the Fourier transformation of polarization microscopic Pictures confirm these values....

  7. Antimicrobial azobenzene compounds and their potential use in biomaterials

    Science.gov (United States)

    Sessa, L.; Concilio, S.; Iannelli, P.; De Santis, F.; Porta, A.; Piotto, S.

    2016-04-01

    We recently synthesized a class of active compounds with azobenzene structure [1] and lowest in silico toxicity values. The antimicrobial activity of these molecules and their thermal stability are very promising and indicate that they may have interesting and therapeutically significant applications. This work aims to develop new materials with antibacterial and antifungal activity inserting different percentages of synthetic antimicrobial azo compounds in commercial polymer matrices. We realized thin films using solvent casting and melt compounding techniques. The obtained materials retained the proprieties of the pure matrices. This means that azo dye dissolved in the matrix does not influence the thermal behavior and the morphology of the material. Tested films exhibited the capability to inhibit biofilms formation of S. aureus and C. albicans. Spectrophotometric investigation of the azo compound released from the polymer matrices confirmed that the realized materials might be interesting for biomedical tools, antibacterial surfaces, and films for active packaging.

  8. Photomechanical Bending of Azobenzene-Based Photochromic Molecular Fibers

    Directory of Open Access Journals (Sweden)

    Riku Matsui

    2013-03-01

    Full Text Available Microfibers composed of azobenzene-based photochromic amorphous molecular materials, namely low molecular-mass photochromic materials with a glass-forming property, could be fabricated. These fibers were found to exhibit mechanical bending motion upon irradiation with a laser beam. In addition, the bending direction could be controlled by altering the polarization direction of the irradiated light without changing the position of the light source or the wavelength of the light. In-situ fluorescence observation of mass transport induced at the surface of the fiber doped with CdSe quantum dots suggested that the bending motions were related with the photoinduced mass transport taking place near the irradiated surface of the fiber.

  9. Photochromic switching of the DNA helicity induced by azobenzene derivatives

    Science.gov (United States)

    Deiana, Marco; Pokladek, Ziemowit; Olesiak-Banska, Joanna; Młynarz, Piotr; Samoc, Marek; Matczyszyn, Katarzyna

    2016-06-01

    The photochromic properties of azobenzene, involving conformational changes occurring upon interaction with light, provide an excellent tool to establish new ways of selective regulation applied to biosystems. We report here on the binding of two water-soluble 4-(phenylazo)benzoic acid derivatives (Azo-2N and Azo-3N) with double stranded DNA and demonstrate that the photoisomerization of Azo-3N leads to changes in DNA structure. In particular, we show that stabilization and destabilization of the B-DNA secondary structure can be photochemically induced in situ by light. This photo-triggered process is fully reversible and could be an alternative pathway to control a broad range of biological processes. Moreover, we found that the bicationic Azo-3N exhibited a higher DNA-binding constant than the monocationic Azo-2N pointing out that the number of positive charges along the photosensitive polyamines chain plays a pivotal role in stabilizing the photochrome-DNA complex.

  10. Azobenzene-based supramolecular polymers for processing MWCNTs

    Science.gov (United States)

    Maggini, Laura; Marangoni, Tomas; Georges, Benoit; Malicka, Joanna M.; Yoosaf, K.; Minoia, Andrea; Lazzaroni, Roberto; Armaroli, Nicola; Bonifazi, Davide

    2012-12-01

    Photothermally responsive supramolecular polymers containing azobenzene units have been synthesised and employed as dispersants for multi-walled carbon nanotubes (MWCNTs) in organic solvents. Upon triggering the trans-cis isomerisation of the supramolecular polymer intermolecular interactions between MWCNTs and the polymer are established, reversibly affecting the suspensions of the MWCNTs, either favouring it (by heating, i.e. cis --> trans isomerisation) or inducing the CNTs' precipitation (upon irradiation, trans --> cis isomerisation). Taking advantage of the chromophoric properties of the molecular subunits, the solubilisation/precipitation processes have been monitored by UV-Vis absorption spectroscopy. The structural properties of the resulting MWCNT-polymer hybrid materials have been thoroughly investigated via thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and atomic force microscopy (AFM) and modelled with molecular dynamics simulations.Photothermally responsive supramolecular polymers containing azobenzene units have been synthesised and employed as dispersants for multi-walled carbon nanotubes (MWCNTs) in organic solvents. Upon triggering the trans-cis isomerisation of the supramolecular polymer intermolecular interactions between MWCNTs and the polymer are established, reversibly affecting the suspensions of the MWCNTs, either favouring it (by heating, i.e. cis --> trans isomerisation) or inducing the CNTs' precipitation (upon irradiation, trans --> cis isomerisation). Taking advantage of the chromophoric properties of the molecular subunits, the solubilisation/precipitation processes have been monitored by UV-Vis absorption spectroscopy. The structural properties of the resulting MWCNT-polymer hybrid materials have been thoroughly investigated via thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and atomic force microscopy

  11. SYNTHESIS AND CHARACTERIZATION OF STAR-SHAPED POLY ( ε-CAPROLACTONE ) -b-POLY ( 2-HYDROXYETHYL METHACRYLATE) BLOCK COPOLYMER%星型两亲性聚己内酯-b-聚甲基丙烯酸(2-羟乙酯)嵌段共聚物的合成和表征

    Institute of Scientific and Technical Information of China (English)

    王蓓蕾; 涂松; 邱永兵; 陈元维; 罗祥林

    2011-01-01

    通过开环聚合(ROP)和原子转移自由基聚合(ATRP)制备了一类新型的两亲性嵌段共聚物——六臂星形聚(ε-已内酯)-b-聚甲基丙烯酸(2-羟乙酯)(6sPCL-b-PHEMA).6sPCL-b-PHEMA通过三步反应合成:(1)双季戊四醇开环聚合ε-己内酯的合成6sPCL;(2)以2-溴异丁基酰溴封端星形聚合物制备大分子引发剂6sPCL-Br;(3)采用溴化亚铜[Cu(I) Br]和2,2'-联吡啶(Bpy)催化甲基丙烯酸(2-羟乙酯)(HEMA)单体聚合合成具有不同亲疏水链段比的6sPCL-b-PHEMA.通过核磁氢谱(1H-NMR)和红外光谱(FT-IR)对共聚物的化学结构进行表征,确认合成了目标产物.利用示差扫描量热仪(DSC)对其热性能并利用接触角测量仪对材料的膜的亲水性进行了研究,结果表明,PCL与HEMA进行共聚以后,可以降低PCL的结晶性并提高聚合物的亲水性,随着HEMA在共聚物中含量的增加,这种趋势更加明显.%The six-arm star-shaped amphiphilic block copolymers poly ( ε-caprolactone ) -b-poly ( 2-hydroxyethyl methacrylate ) ( 6sPCL-b-PHEMA ) were prepared by a combination of ring-opening polymerization ( ROP) and atom transfer radical polymerization ( ATRP). The synthesis procedure was composed of three step reactions;First,6sPCL homopolymers were prepared via ring-opening polymerization of ^-caprolactone by using dipentaerythritol with 6 hydroxyl functional groups as an initiator; Second,6sPCL was functionalized to get macroinitiator 6sPCL-Br for ATRP; Third, atom transfer radical polymerization of 2-hydroxyethyl methacrylate (HEMA) from the macroinitiator 6sPCL-Br was conducted by using copper ( I ) bromide ( Cu(I)Br) and 2,2'-bipyredine (Bpy) as catalyze system to synthesize the star block copolymer 6sPCL-6-PHEMA. Molecular structure of 6sPCL-6-PHEMA was confirmed by1 H nuclear magnetic resonance (1H-NMR) and Fourier transform infrared ( FTIR) spectroscopy. Thermal behavior and hydrophilicity of obtained 6sPCL-6-PHEMA were measured by DSC and water contact

  12. Preparation and Photochemical Behavior of a Cationic Azobenzene Dye-Montmorillonite Intercalation Compound

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Montmorillonite/cationic azobenzene dye(p-(δ-triethylammoniobutoxy)-p'-methyl-azobenzene bromide) intercalation compounds were prepared by the conventional ion exchange method. As compared with that of pure cationic azo-dye, the thermal stability of the intercalated dye was greatly enhanced, and the absorption band corresponding to azobenzene group in intercalated dye shifted towards longer wave length by 38 nm. This could be ascribed to the strong conjugation of cationic azo-dye supramolecular order structure(J cluster) confined in a nanoscale space of montmorillonite interlayer gallery. UV/vis spectra data show that the intercalated azo dye in the montmorillonite interlayer space exhibited reversible trans-to-cis photoisomerization and daylight cis-to-trans back reaction. FTIR indicates the successful intercalation of cationic azo-dye into the montmorillonite interlayer.

  13. Synthesis and Site-Specific Incorporation of Red-Shifted Azobenzene Amino Acids into Proteins.

    Science.gov (United States)

    John, Alford A; Ramil, Carlo P; Tian, Yulin; Cheng, Gang; Lin, Qing

    2015-12-18

    A series of red-shifted azobenzene amino acids were synthesized in moderate-to-excellent yields via a two-step procedure in which tyrosine derivatives were first oxidized to the corresponding quinonoidal spirolactones followed by ceric ammonium nitrate-catalyzed azo formation with the substituted phenylhydrazines. The resulting azobenzene-alanine derivatives exhibited efficient trans/cis photoswitching upon irradiation with a blue (448 nm) or green (530 nm) LED light. Moreover, nine superfolder green fluorescent protein (sfGFP) mutants carrying the azobenzene-alanine analogues were expressed in E. coli in good yields via amber codon suppression with an orthogonal tRNA/PylRS pair, and one of the mutants showed durable photoswitching with the LED light.

  14. Light propagation through photoinduced chiral structures in azobenzene-containing polymers

    DEFF Research Database (Denmark)

    Nedelchev, L; Nikolova, L; Todorov, T;

    2001-01-01

    We investigate light propagation through azobenzene-containing polymers with photoinduced chiral structures. The structures have large pitch but the Mauguin condition is not fulfilled. The eigenmodes are shown to be elliptical and their ellipticity is determined by the ellipticity e(o) of the exc......We investigate light propagation through azobenzene-containing polymers with photoinduced chiral structures. The structures have large pitch but the Mauguin condition is not fulfilled. The eigenmodes are shown to be elliptical and their ellipticity is determined by the ellipticity e...

  15. Photo-Induced Magnetic Anisotropy of Polymer Film Containing Azobenzene Organic Free Radical Group

    Institute of Scientific and Technical Information of China (English)

    徐则达; 张勇; 陈小芳; 范星河; 宛新华; 周其凤

    2003-01-01

    The forward degenerate four-wave mixing geometry was employed to induce microstructure in an organic free radical azobenzene polymer film. Before irradiated with Ar+ laser beams (λ = 514.5 nm), the azobenzene organic free radical polymer exhibits magnetic isotropic measured by superconducting quantum interference device. After photo-induced microstructure, the polymer film becomes magnetic anisotropy. When the applied magnetic field H = 50 Gauss, the magnetization along the normal direction of the polymer film is Mz = 5.5 × 10-5 emu/g,which is larger than Mx = 4.1 × 10-5 emu/g in the direction parallel to the polymer film.

  16. Effects of Laser-Induced Heating on the Photoinduced Birefringence in Azobenzene-Side-Chain Copolymer

    Institute of Scientific and Technical Information of China (English)

    杨军; 明海; 章江英; 王沛; 郎建英; 鲁拥华; 刘剑; 张其锦

    2003-01-01

    The photoinduced birefringence was observed in the polymer poly[2-(4-(4-cyanophenyl) diazenyl phenyloxy) ethoxyl methacrylatel with a cw 532nm laser. The azobenzene polymer character has been studied under the conditions of various illuminating time and light intensities. By analysing the processes of reorientation, the effect of laser-induced heating has been introduced to the buildup of photoinduced birefringence in azobenzene-side-chain copolymer. The curves for the buildup of birefringence were fitted with a modified function, i.e., biexponential curves and Gaussian curves. The relationship among all the parameters has also been presented. With the modified fitting function, we obtain a better fitting result.

  17. Surface relief measurements in side-chain azobenzene polyesters with different substituents

    DEFF Research Database (Denmark)

    Helgert, M.; Wenke, L.; Hvilsted, Søren;

    2001-01-01

    Light-induced surface modification of a series of liquid-crystalline side-chain azobenzene polyesters which have the same main- and side-chain structure but eleven different substituents on the azobenzene is investigated. Using a transmission mask as well as single focused beams we show...... that the formation of the surface relief is dependent on the substituents. In both experiments irradiation with p-polarized light generates peaks for the CN, CF3, CH3 and F substituents, while fur a Cl substituent valleys art: observed. Also s-polarized light is found to produce surface deformations. An amorphous...

  18. Photoregulated potassium ion permeation through dihexadecyl phosphate bilayers containing azobenzene and stilbene surfactants

    Energy Technology Data Exchange (ETDEWEB)

    Lei, Y.; Hurst, J.K. [Washington State Univ., Pullman, WA (United States). Dept. of Chemistry

    1999-05-11

    Photoresponsive asymmetrically organized systems based upon small unilamellar dihexadecyl phosphate (DHP) vehicles were constructed by entrapping high concentrations of potassium ion within the vesicular aqueous core and incorporating either an amphiphilic trans-azobenzene-containing phosphate monoester or an amphiphilic trans-stilbene-containing carboxylic acid into its membrane structure. Spectroscopic measurements indicated that the azobenzene derivative was molecularly dispersed in the hydrocarbon phase of the vesicle and that the extent of aggregation of the membrane-localized stilbene derivative was minor. Thermal K{sup +} leak rates from the doped vesicles were very low, with calculated permeability coefficients (P) of {approximately}4 {times} 10{sup {minus}12} cm/s at 40 C for DHP vesicles containing 5.5 mol % of the trans-azobenzene derivative and {approximately}1.5 {times} 10{sup {minus}11} cm/s at 38 C for vesicles containing 5.5 mol % of the trans-stilbene derivative; for comparison, P {approx_equal} 2 {times} 10{sup {minus}12} cm/s for undoped vesicles at 40 C. Photoexcitation of the azobenzene-doped vesicles at 360 nm caused >90% trans {r_arrow} cis photoisomerization over the measured temperature range (25--40 C), with complete reversion to the trans isomer upon photoexcitation at 450 nm. Photoexcitation of deoxygenated suspensions of the stilbene-doped vesicles at 315 nm gave {approximately}80% conversion to the cis isomer in the photostationary state, which was not reversible. At 25 C, K{sup +} leak rates for the isomeric azobenzene-doped vesicles were nearly identical; at 40 C, K{sup +} leakage for the DHP vesicles containing the cis-azobenzene isomer corresponded to P {approx_equal} 2 {times} 10{sup {minus}11} cm/s, 5-fold greater than that of the trans isomer. In trans {r_arrow} cis {r_arrow} trans photocycling experiments, K{sup +} leak rates alternately increased and decreased, indicating that the vesicles remained intact. At 40 C, K

  19. 40 CFR 721.10153 - Modified methyl methacrylate, 2-hydroxyethyl methacrylate polymer (generic).

    Science.gov (United States)

    2010-07-01

    ...-hydroxyethyl methacrylate polymer (generic). 721.10153 Section 721.10153 Protection of Environment...-hydroxyethyl methacrylate polymer (generic). (a) Chemical substance and significant new uses subject to... methacrylate polymer (PMN P-08-6) is subject to reporting under this section for the significant new...

  20. H-aggregation of azobenzene-substituted amphiphiles in vesicular membranes

    NARCIS (Netherlands)

    Kuiper, JM; Engberts, JBFN

    2004-01-01

    Photochemical switching has been studied of double-tailed phosphate amphiphiles containing azobenzene units in both tails in aqueous vesicular dispersions and in mixed vesicular systems with 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). Since the ease of switching depends on the strength of the b

  1. Synthesis of Novel Amphiphilic Azobenzenes and X-ray Scattering Studies of Their Langmuir Monolayers

    DEFF Research Database (Denmark)

    Sørensen, Thomas Just; Kjær, Kristian; Breiby, Dag Werner;

    2008-01-01

    . At the air-water interface, the amphiphilic azobenzenes form noncrystalline but stable Langmuir films that display an unusual reversible monolayer collapse close to 35 mN/m. The structures and phase transitions were studied by X-ray reflectivity (XR) and grazing-incidence X-ray diffraction, both utilizing...

  2. Synthesis of azobenzene-containing liquid crystalline gelator for use in liquid crystal gels

    Institute of Scientific and Technical Information of China (English)

    Guang Wang; Xiao Liang Zhao; Yue Zhao

    2008-01-01

    A liquid crystalline gelator containing the azobenzene chromophore was synthesized for the first time; it was used to form self-assembled network in nematic liquid crystals resulting in liquid crystal gels with distinct features.? 2008 Guang Wang. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

  3. Synthesis and characterization of conjugated polymer containing azobenzene and oxadiazole units

    Institute of Scientific and Technical Information of China (English)

    Yue Zhang; Shi Jun Yu; Lu Wang; Cong Li

    2009-01-01

    A novel conjugated polymer containing azobenzene and oxadiazole units was synthesized through multi-step synthesis.The structures and properties of monomer and polymer were characterized and evaluated with IR,1H NMR,UV,TGA and GPC,respectively.Polymer with long side chain of alkoxy shows good solubility,thermal stability and photoisomerization property.

  4. Surface Organization, Light-Driven Surface Changes, and Stability of Semifluorinated Azobenzen Polymers

    Energy Technology Data Exchange (ETDEWEB)

    Paik,M.; Krishnan, S.; You, F.; Li, X.; Hexemer, A.; Ando, Y.; Kang, S.; Fischer, D.; Kramer, E.; Ober, C.

    2007-01-01

    A series of polymers with 4-perfluoroalkyl-modified azobenzene side groups was investigated for its light-induced changes in surface properties. The ultraviolet (UV) light activated trans to cis isomerization of the azobenzene group, and the influence of molecular order and orientation on this process were studied using near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and water contact angle measurements. Light-induced molecular reorganization in the near-surface region was studied by NEXAFS using in situ UV irradiation of polymer thin films. Differential scanning calorimetry and wide-angle X-ray scattering studies showed that sufficiently long fluoroalkyl groups formed well-ordered smectic mesophases in the bulk, as well as on the surface, which was evidenced by NEXAFS. The disruption of mesogen packing by photoisomerization was found to be influenced by the fluoroalkyl segment length. Surfaces with perfluorohexyl and perfluorooctyl groups that showed high orientational order were also highly resistant to light-induced changes. In such cases, the trans-cis isomerization resulted in greater lowering of the azobenzene phenyl ring order parameters than the perfluoroalkyl order parameters. UV exposure caused reorientation of the phenyl rings of the azobenzene group, but the terminal perfluoroalkyl segments remained more or less ordered.

  5. Photoisomerization quantum yield of azobenzene-modified DNA depends on local sequence.

    Science.gov (United States)

    Yan, Yunqi; Wang, Xin; Chen, Jennifer I L; Ginger, David S

    2013-06-05

    Photoswitch-modified DNA is being studied for applications including light-harvesting molecular motors, photocontrolled drug delivery, gene regulation, and optically mediated assembly of plasmonic metal nanoparticles in DNA-hybridization assays. We study the sequence and hybridization dependence of the photoisomerization quantum yield of azobenzene attached to DNA via the popular d-threoninol linkage. Compared to free azobenzene we find that the quantum yield for photoisomerization from trans to cis form is decreased 3-fold (from 0.094 ± 0.004 to 0.036 ± 0.002) when the azobenzene is incorporated into ssDNA, and is further reduced 15-fold (to 0.0056 ± 0.0008) for azobenzene incorporated into dsDNA. In addition, we find that the quantum yield is sensitive to the local sequence including both specific mismatches and the overall sequence-dependent melting temperature (Tm). These results serve as design rules for efficient photoswitchable DNA sequences tailored for sensing, drug delivery, and energy-harvesting applications, while also providing a foundation for understanding phenomena such as photonically controlled hybridization stringency.

  6. Influence of UV irradiation on the blue and red light photoinduced processes in azobenzene polyesters

    DEFF Research Database (Denmark)

    Rodríguez, F.J.; Sánchez, C.; Villacampa, B.

    2004-01-01

    Birefringence induced in a series of liquid crystalline side-chain azobenzene polyesters with different substituent groups was investigated under irradiation with 488 and 633 nm linearly polarized lights. Two different initial conditions have been used: the effect of a previous irradiation with U...

  7. Effect of heat and film thickness on a photoinduced phase transition in azobenzene liquid crystalline polyesters

    DEFF Research Database (Denmark)

    Sanchez, C; Alcala, R; Hvilsted, Søren

    2003-01-01

    The liquid crystal to isotropic phase transition induced with 488 nm light in films of liquid crystalline azobenzene polyesters has been studied as a function of temperature, light intensity, and film thickness. That phase transition is associated with the photoinduced trans-cis-trans isomerizati...

  8. High diffraction efficiency polarization gratings recorded by biphotonic holography in an azobenzene liquid crystalline polyester

    DEFF Research Database (Denmark)

    Sánchez, C; Alcalá, R; Hvilsted, Søren

    2001-01-01

    High diffraction efficiencies have been achieved with polarization gratings recorded in thin films of an azobenzene side-chain liquid crystalline polyester by means of biphotonic processes. Efficiency values up to 30% have been reached after an induction period of 300 s and subsequent evolution w...

  9. Biphotonic holographic gratings in azobenzene polyesters: Surface relief phenomena and polarization effects

    DEFF Research Database (Denmark)

    Sánchez, C.; Alcalá, R.; Hvilsted, Søren

    2000-01-01

    Biphotonic holographic gratings have been recorded in a side-chain azobenzene liquid crystalline polyester using a blue incoherent source and a He-Ne laser. Intensity gratings and the appearance of surface relief have been observed when two linearly polarized beams from a He-Ne laser are made to ...

  10. Synthesis and Conformation of Substituted Chiral Binaphthyl-Azobenzene Cyclic Dyads with Chiroptical Switching Capabilities

    Directory of Open Access Journals (Sweden)

    Masuki Kawamoto

    2011-02-01

    Full Text Available Optically active binaphthyl-azobenezene cyclic dyads were synthesized to develop a photochromic switching molecule. Azobenezene moieties were cis-trans isomerized by photoirradiation. As a reflection of the structural change, the specific optical rotation and circular dichroism underwent significant shifts. Under certain conditions, the positive-negative and zero-positive (or zero-negative signals were reversed. Optical rotation may potentially be applied in noise-cancelling nondestructive photoswiches. The conformations were studied by experimental and theoretical methods. The results revealed that the helical chirality, (P or (M, of the cis-azobenzene moiety was induced by intramolecular axial chirality. The twist direction depended on the axial chirality as well as the azobenzene linkage position to the binaphthyls, but was independent of the identity of substituted groups. 2,2’-Linked-(R-binaphthyl was found to induce cis-(P-azobenzene, whereas symmetrically 7,7’-linked-(R-binaphthyl was found to induce cis-(M-azobenzene.

  11. Diffraction from polarization holographic gratings with surface relief in side-chain azobenzene polyesters

    DEFF Research Database (Denmark)

    Naydenova, I; Nikolova, L; Todorov, T;

    1998-01-01

    We investigate the polarization properties of holographic gratings in side-chain azobenzene polyesters in which an anisotropic grating that is due to photoinduced linear and circular birefringence is recorded in the volume of the material and a relief grating appears on the surface. A theoretical...

  12. Theoretical model of photoinduced anisotropy in liquid-crystalline azobenzene side-chain polyesters

    DEFF Research Database (Denmark)

    Pedersen, Thomas Garm; Johansen, Per Michael; Holme, N.C.R.;

    1998-01-01

    A theoretical framework for the temporal behavior of photoinduced anisotropy in liquid-crystalline azobenzene side-chain polyesters is constructed. The domain structure of the material is taken into account and inter molecular interactions are included through a mean-field description. Photoinduced...

  13. Azobenzene-based surface patterns revisited: New insights with new materials? (Conference Presentation)

    Science.gov (United States)

    Priimagi, Arri

    2016-09-01

    This contribution focuses on a relatively old topic of azobenzene photomechanics, namely the photoinduced surface patterning. The phenomenon was demonstrated alreay in 1995, yet it has not redeemed its promise as a simple, one-step patterning method that could challenge the more conventional microfabrication techniques. However, inspired by recent advances in fabrication techniques, materials development, and theoretical modelling, the field is going through a revival from both fundamental and applied perspectives. (i) How much (or how little) azobenzene needed in order to create the surface patterns? (ii) What is the maximum size of objects that can be moved with light? (iii) Can one pattern crystalline materials? (iv) Under what conditions ss the patterning process light-reversible? These questions will herein be addressed via four case studies, all employing supramolecular materials where non-covalent intermolecular interactions are used to attach the azobenzenes into a passive host matrix. All azobenzene-based material movements are triggered by photoisomerization and are therefore inherently related to one another, and therefore we believe our observations to provide useful insights also for photomobile materials and photomechanical actuation.

  14. pH-sensitive methacrylic copolymer gels and the production thereof

    Science.gov (United States)

    Mallapragada, Surya K.; Anderson, Brian C.

    2007-05-15

    The present invention provides novel gel forming methacrylic blocking copolymers that exhibit cationic pH-sensitive behavior as well as good water solubility. The copolymers are constructed by polymerization of a tertiary amine methacrylate with either a (poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) polymer, such as the commercially available Pluronic.RTM. polymers, or a poly(ethylene glycol)methyl ether polymer. The polymers may be used for drug and gene delivery, protein separation, as structural supplements, and more.

  15. Formation of Anisotropic Block Copolymer Gels

    Science.gov (United States)

    Liaw, Chya Yan; Shull, Kenneth; Henderson, Kevin; Joester, Derk

    2011-03-01

    Anisotropic, fibrillar gels are important in a variety of processes. Biomineralization is one example, where the mineralization process often occurs within a matrix of collagen or chitin fibers that trap the mineral precursors and direct the mineralization process. We wish to replicate this type of behavior within block copolymer gels. Particularly, we are interested in employing gels composed of cylindrical micelles, which are anisotropic and closely mimic biological fibers. Micelle geometry is controlled in our system by manipulating the ratio of molecular weights of the two blocks and by controlling the detailed thermal processing history of the copolymer solutions. Small-Angle X-ray Scattering and Dynamic Light Scattering are used to determine the temperature dependence of the gel formation process. Initial experiments are based on a thermally-reversible alcohol-soluble system, that can be subsequently converted to a water soluble system by hydrolysis of a poly(t-butyl methacrylate) block to a poly (methacrylic acid) block. MRSEC.

  16. 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

    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 ...

  17. Theoretical study of solvent effects on the ground and low-lying excited free energy surfaces of a push-pull substituted azobenzene.

    Science.gov (United States)

    Corchado, Jose C; Sánchez, M Luz; Fdez Galván, Ignacio; Martín, M Elena; Muñoz-Losa, Aurora; Barata-Morgado, Rute; Aguilar, Manuel A

    2014-10-30

    The ground and low-lying excited free energy surfaces of 4-amino-4'-cyano azobenzene, a molecule that has been proposed as building block for chiroptical switches, are studied in gas phase and a variety of solvents (benzene, chloroform, acetone, and water). Solvent effects on the absorption and emission spectra and on the cis-trans thermal and photo isomerizations are analyzed using two levels of calculation: TD-DFT and CASPT2/CASSCF. The solvent effects are introduced using a polarizable continuum model and a QM/MM method, which permits one to highlight the role played by specific interactions. We found that, in gas phase and in agreement with the results found for other azobenzenes, the thermal cis-trans isomerization follows a rotation-assisted inversion mechanism where the inversion angle must reach values close to 180° but where the rotation angle can take almost any value. On the contrary, in polar solvents the mechanism is controlled by the rotation of the CN═NC angle. The change in the mechanism is mainly related to a better solvation of the nitrogen atoms of the azo group in the rotational transition state. The photoisomerization follows a rotational pathway both in gas phase and in polar and nonpolar solvents. The solvent introduces only small modifications in the nπ* free energy surface (S1), but it has a larger effect on the ππ* surface (S2) that, in polar solvents, gets closer to S1. In fact, the S2 band of the absorption spectrum is red-shifted 0.27 eV for the trans isomer and 0.17 eV for the cis. In the emission spectrum the trend is similar: only S2 is appreciably affected by the solvent, but in this case a blue shift is found.

  18. PHOTOINDUCED HOLOGRAPHIC PHASE GRATINGS BURIED IN AZOBENZENE SIDE-CHAIN POLYMER FILMS WITH A CHIRAL GROUP

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    An optically active polymer (PM1) containing azobenzene moieties with a chiral group (s-2-methyl-butyl) was synthesized by homopolymerization of monomer, 4-[2-(methacryloyloxy)ethyloxy]-4'-(s-2-methyl-1-butyloxycarbonyl)azobenzene, using the free radical polymerization method. The polymer dissolved in tetrahydrofuran (THF) could be easily processed into high optical quality films. The optical anisotropy of the polymer films was investigated by polarizing optical microscopy (POM). The experimental results showed that irradiation with a circularly polarized beam could align the orientation of the molecules in the polymer films. Moreover, the holographic phase gratings of photo-induced polymer films were detected by atomic force microscopy (AFM) and POM. In comparison with polymer containing no chiral group, it was found from the preliminary measurement of the photo-induced holographic phase gratings that PM1 containing a chiral group could form holographic phase gratings buried in the films.

  19. Novel azobenzene-phthalocyanine dyads——design of photo-modulated J-aggregation

    Institute of Scientific and Technical Information of China (English)

    NIU LiHong; ZHONG Cheng; CHEN ZiHui; ZHANG Zhi; LI ZhongYu; ZHANG FuShi; TANG YingWu

    2009-01-01

    Based on the J-aggregation mechanism of α-aryl/alkoxy-subetituted zinc phthalocyanines(Pcs) in non-coordinating solvents, two novel azobenzene-phthalocyanine dyads (3-azo-ZnPc and 4-azo-ZnPc) were synthesized with the aim of developing Pc compounds whose ability to form J-aggregation could be photo-modulated. It was found that 3-azo-ZnPc in chloroform could be effectively photo-controlled in a wide range. This phenomenon could be explained by the changes in the geometry and dipole moment of azobenzene during the photo-isomerization process. 4-azo-ZnPc did not have this ability at all, with or without UV light illumination. The positions of the oxygen atoms to which the aryl/alkoxy substitution was attached relatively were found important in determining the aggregation ability.

  20. Orientation of azobenzene molecules in polymer films induced by all-optical poling

    Institute of Scientific and Technical Information of China (English)

    Xiaoxia Zhong(钟晓霞); Shouyu Luo(罗售余); Xiuqin Yu(虞秀琴); Qu Li(李劬); Yingli Chen(陈英礼); Yu Sui(隋郁); Jie Yin(印杰)

    2003-01-01

    A model of the alignment of azobenzene molecules in polymer film induced by all-optical poling is proposedand verified by experiment. We found that when the writing beams of frequencies ω and 2ω are both linearlypolarized with their polarization directions parallel to each other, azobenzene molecules tend to reorientto the direction perpendicular to the writing beams polarization. At the end of the writing process, moremolecules orient to the direction perpendicular to the writing beams polarization than those which orientto the parallel direction. The alignment of molecules parallel or perpendicular to the polarization of thewriting beams is characteristic of polarity or no polarity, respectively. The alignment of molecules alongthe polarization of writing beams results in the second order nonlinearity in the polymer film. Accordingto the model, a new method to improve the optical poling efficiency is put forward.

  1. Cis-trans isomerisation of azobenzenes studied by laser-coupled NMR spectroscopy and DFT calculations.

    Science.gov (United States)

    Wazzan, Nuha A; Richardson, Patricia R; Jones, Anita C

    2010-07-30

    In a combined experimental and computational study of a group of para-substituted azobenzenes, the effects of substituents and solvent on the kinetics of thermal cis-to-trans isomerisation have been examined and the success of DFT calculations in predicting kinetic parameters assessed. Mono-substituted species are predicted to isomerise by inversion in both non-polar and polar solvent, whereas for push-pull azobenzenes the mechanism is predicted to change from inversion to rotation on going from non-polar to polar solvent. Computed free energies of activation qualitatively reproduce experimental trends but do not quantitatively predict the kinetics of cis-trans isomerisation. The polarisable continuum model of solvation fails to predict the experimentally observed influence of solvent on the entropy of activation.

  2. Recent advances towards azobenzene-based light-driven real-time information-transmitting materials

    Directory of Open Access Journals (Sweden)

    Jaume García-Amorós

    2012-07-01

    Full Text Available Photochromic switches that are able to transmit information in a quick fashion have attracted a growing interest within materials science during the last few decades. Although very fast photochromic switching materials working within hundreds of nanoseconds based on other chromophores, such as spiropyranes, have been successfully achieved, reaching such fast relaxation times for azobenzene-based photochromic molecular switches is still a challenge. This review focuses on the most recent achievements on azobenzene-based light-driven real-time information-transmitting systems. Besides, the main relationships between the structural features of the azo-chromophore and the thermal cis-to-trans isomerisation, the kinetics and mechanism are also discussed as a key point for reaching azoderivatives endowed with fast thermal back-isomerisation kinetics.

  3. Photoinduced reversible switching of porosity in molecular crystals based on star-shaped azobenzene tetramers.

    Science.gov (United States)

    Baroncini, Massimo; d'Agostino, Simone; Bergamini, Giacomo; Ceroni, Paola; Comotti, Angiolina; Sozzani, Piero; Bassanetti, Irene; Grepioni, Fabrizia; Hernandez, Taylor M; Silvi, Serena; Venturi, Margherita; Credi, Alberto

    2015-08-01

    The development of solid materials that can be reversibly interconverted by light between forms with different physico-chemical properties is of great interest for separation, catalysis, optoelectronics, holography, mechanical actuation and solar energy conversion. Here, we describe a series of shape-persistent azobenzene tetramers that form porous molecular crystals in their E-configuration, the porosity of which can be tuned by changing the peripheral substituents on the molecule. Efficient E→Z photoisomerization of the azobenzene units takes place in the solid state and converts the crystals into a non-porous amorphous melt phase. Crystallinity and porosity are restored upon Z→E isomerization promoted by visible light irradiation or heating. We demonstrate that the photoisomerization enables reversible on/off switching of optical properties such as birefringence as well as the capture of CO2 from the gas phase. The linear design, structural versatility and synthetic accessibility make this new family of materials potentially interesting for technological applications.

  4. Preparation of a cationic azobenzene dye-montmorillonite intercalation compound and its photochemical behavior

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Montmorillonite/cationic azobenzene dye (GTL) intercalation compounds were prepared by the conventional ion exchange method. As compared with that of pure GTL, the thermal stability of the intercalated GTL was greatly enhanced, and the absorption band corresponding to azobenzene group in intercalated GTL shifted towards a longer wavelength by 55 nm, which could be ascribed to the strong conjugation of GTL supramolecular order structure (J cluster) confined in a nanoscale space of montmorillonite interlayer gallery. The microstructures of the resulting intercalation compounds could be successfully controlled by varying the amount of dye loaded as evidenced by the basal spacing of the intercalation compounds. The intercalated azo dye in the montmorillonite interlayer space exhibited reversible trans-to-cis photoisomerization and thermal cis-to-trans reaction. FTIR proved the successful intercalation of GTL into the silicate layer.

  5. Cyclometalated platinum(II) with ethynyl-linked azobenzene ligands: an original switching mode.

    Science.gov (United States)

    Savel, Paul; Latouche, Camille; Roisnel, Thierry; Akdas-Kilig, Huriye; Boucekkine, Abdou; Fillaut, Jean-Luc

    2013-12-28

    The photophysical properties of 6-phenyl-2,2'-bipyridyl platinum(ii) complexes bearing different σ-alkynyl-linked azobenzene ancillary ligands were investigated. These complexes exhibited strong, broad, structureless charge-transfer bands in the visible region, which were red-shifted when the electron-donating ability of the para substituent on the azo-acetylide ligand increased. When excited at the charge-transfer absorption band, the complexes exhibited weak green emission, which was assigned to a triplet metal-to-ligand charge transfer/interligand charge transfer emission ((3)MLCT/(3)L'LCT). The presence of an amino substituent in the azobenzene moiety opened the possibility of protonation, which led to the formation of an azonium based derivative and resulted in drastic perturbations of the molecular orbitals and photophysical properties of the Pt-acetylide complex. These studies are fully supported by DFT and TD-DFT calculations.

  6. Mechanized azobenzene-functionalized zirconium metal-organic framework for on-command cargo release

    Science.gov (United States)

    Meng, Xiangshi; Gui, Bo; Yuan, Daqiang; Zeller, Matthias; Wang, Cheng

    2016-01-01

    Stimuli-responsive metal-organic frameworks (MOFs) have gained increasing attention recently for their potential applications in many areas. We report the design and synthesis of a water-stable zirconium MOF (Zr-MOF) that bears photoresponsive azobenzene groups. This particular MOF can be used as a reservoir for storage of cargo in water, and the cargo-loaded MOF can be further capped to construct a mechanized MOF through the binding of β-cyclodextrin with the azobenzene stalks on the MOF surface. The resulting mechanized MOF has shown on-command cargo release triggered by ultraviolet irradiation or addition of competitive agents without premature release. This study represents a simple approach to the construction of stimuli-responsive mechanized MOFs, and considering mechanized UiO-68-azo made from biocompatible components, this smart system may provide a unique MOF platform for on-command drug delivery in the future. PMID:27493996

  7. Compound grating structures in photonic crystals for resonant excitation of azobenzene

    DEFF Research Database (Denmark)

    Jahns, Sabrina; Kallweit, Christine; Adam, Jost;

    -difference time-domain (FDTD) calculations for determination of resonance positions and electric field strengths in compound grating structures. By superimposing two single-period gratings a photonic crystal can be designed supporting multiple guided mode resonances suitable to switch azobenzenes between...... is small and thus a high excitation light intensity is required. We investigate the enhancement of the local energy density using periodically nanostructured surfaces in a high refractive index material. Such photonic crystals support quasi-guided modes visible as resonances in the reflection as well...... as in the transmission light spectrum. These guided modes have field contributions decaying exponentially in the near field of the photonic crystal. Azobenzene immobilized on the photonic crystal surface will experience a significantly increased light intensity compared to non-resonant surfaces. We performed finite...

  8. Low Driving Voltage and Analysis of Azobenzene Polymer Doped Liquid Crystal Grating

    Institute of Scientific and Technical Information of China (English)

    SONG Jing; LIU Yong-Gang; MA Ji; XUAN Li

    2006-01-01

    We mix azobenzene polymer and liquid crystal in certain ratio. Then the mixture is injected into cells. Nonlinearly photoinduced birefringence takes place when linearly polarized ultraviolet is applied with the pattern photomask covering on the cells, which results in the formation of azobenzene polymer doped liquid crystalgrating. The obtained grating is characterized by an optical microscope and a He-Ne laser. The results indicate that the samples have clear grating structure, and the diffraction efficiencies can be modulated by electric field. The sample driving voltage is 0.6 V/μm. It is lower than the driving voltage of holographic polymer dispersed liquid crystal transmission grating and could be matched with the driving integrated circuit.

  9. Metal nanoparticle - block copolymer composite assembly and disassembly

    NARCIS (Netherlands)

    Li, Z.H.; Sai, H.; Warren, S.C.; Kamperman, M.M.G.; Arora, H.; Gruner, S.M.; Wiesner, U.

    2009-01-01

    Ligand-stabilized platinum nanoparticles (Pt NPs) were self-assembled with poly(isoprene-block-dimethylaminoethyl methacrylate) (PI-b-PDMAEMA) block copolymers to generate organic-inorganic hybrid materials. High loadings of NPs in hybrids were achieved through usage of N,N-di-(2-(allyloxy)ethyl)-N-

  10. Synthesis and characterization of amphiphilc block copolymer poly(methyl acrylic acid)-block-polytetrahydrofuran

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Under the specially designated condition the polymerization of both tetrahydrofuran (THF) and tert-butyl methacrylate (tBMA) is a living one. The diblock copolymer, poly(tert-butyl methacrylate)-block-polytetrahydrofuran (PtBMA-b-PTHF), was successfully synthesized by means of the coupling reaction of living cationic PTHF+, SbF6- with living anionic PtBMA-, Li+. LiCl, which has a beneficial effect on the molecular weight distribution (MWD) in the anionic polymerization of (meth)acrylates, hinders the coupling reaction of living chains and cannot be used in the preparation of tBMA precursor. The hydrolysis of the aforementioned diblock copolymer under acid condition results in the amphiphilic diblock copolymer, i.e. poly(methyl acrylic acid)-block-polytetra- hydrofuran (PMAA-b-PTHF). The diblock copolymers were characterized with GPC and IR.

  11. Trans-cis photoisomerization of azobenzene by n→π* excitation:A semiclassical dynamics study

    Institute of Scientific and Technical Information of China (English)

    Shuai Yuan; Wei Feng Wu; Yusheng Dou; Jian She Zhao

    2008-01-01

    A realistic dynamics simulation study is reported for the trans-cis photoisomerization of azobenzene triggered by the n→π*excitation and the results show that the formation of cis isomer follows the rotational motion around the N=N bond.The simulation find that the CNN bond angle bending vibrations also play a significant role in the vibronic coupling between the HOMO and LUMO,which essentially leads a nonadiabatic transition of the molecule to the electronic ground state.

  12. Influence of the substituent on azobenzene side-chain polyester optical storage materials

    DEFF Research Database (Denmark)

    Pedersen, M; Hvilsted, Søren; Holme, NCR;

    1999-01-01

    , chloro, and bromo. C-13 NMR spectroscopic and molecular mass investigations substantiate good film forming characteristics. The optical storage performance of thin polyester films are investigated through polarization holography. The resulting diffraction efficiency is mapped and discussed as a function...... of irradiation power and exposure time. Polytetradecanedioates with cyano-, nitro-, methyl-, fluoro-, or trinuoromethyl-azobenzene reach more than 50% diffraction efficiency. Investigations of anisotropy induced at different temperatures reveal that the polyesters are only photosensitive in a narrow temperature...

  13. 40 CFR 721.9492 - Polymers of styrene, cyclohexyl methacrylate and substituted methacrylate.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Polymers of styrene, cyclohexyl... Significant New Uses for Specific Chemical Substances § 721.9492 Polymers of styrene, cyclohexyl methacrylate...) The chemical substances identified generically as polymers of styrene, cyclohexyl methacrylate...

  14. Molecularly Engineered Azobenzene Derivatives for High Energy Density Solid-State Solar Thermal Fuels.

    Science.gov (United States)

    Cho, Eugene N; Zhitomirsky, David; Han, Grace G D; Liu, Yun; Grossman, Jeffrey C

    2017-03-15

    Solar thermal fuels (STFs) harvest and store solar energy in a closed cycle system through conformational change of molecules and can release the energy in the form of heat on demand. With the aim of developing tunable and optimized STFs for solid-state applications, we designed three azobenzene derivatives functionalized with bulky aromatic groups (phenyl, biphenyl, and tert-butyl phenyl groups). In contrast to pristine azobenzene, which crystallizes and makes nonuniform films, the bulky azobenzene derivatives formed uniform amorphous films that can be charged and discharged with light and heat for many cycles. Thermal stability of the films, a critical metric for thermally triggerable STFs, was greatly increased by the bulky functionalization (up to 180 °C), and we were able to achieve record high energy density of 135 J/g for solid-state STFs, over a 30% improvement compared to previous solid-state reports. Furthermore, the chargeability in the solid state was improved, up to 80% charged from 40% charged in previous solid-state reports. Our results point toward molecular engineering as an effective method to increase energy storage in STFs, improve chargeability, and improve the thermal stability of the thin film.

  15. Photo Induced Membrane Separation for Water Purification and Desalination Using Azobenzene Modified Anodized Alumina Membranes.

    Science.gov (United States)

    Fujiwara, Masahiro; Imura, Tatsuki

    2015-06-23

    Water purification and desalination to produce end-use water are important agendas in 21st century, because the global water shortage is becoming increasingly serious. Those processes using light energy, especially solar energy, without the consumption of fossil fuels are desired for creating sustainable society. For these earth-friendly water treatments, nanoporous materials and membranes are expected to provide new technologies. We have reported before that the repetitive photo isomerization of azobenzene groups between the trans and cis isomers induced by the simultaneous irradiation of UV and visible lights accelerates the molecular movement of nearby molecules in nanoporous materials. After further studies, we recently found that the permeation of water through azobenzene modified anodized alumina membranes as a photo responsive nanoporous membrane was achieved by the simultaneous irradiation of UV and visible lights, while no water penetration occurred under no light, only single UV or visible light. The photo induced permeation of water was promoted by the vaporization of water with the repetitive photo isomerization of azobenzene. This membrane permeation achieved the purification of water solutions, because dye molecules and a protein dissolved in aqueous solutions were not involved in the photo induced penetrated water. When 3.5% of sodium chloride solution as model seawater was employed for this membrane separation, the salt content of the permeated water was less than 0.01% to accomplish the complete desalination of seawater.

  16. Tuning the optical emission of MoS{sub 2} nanosheets using proximal photoswitchable azobenzene molecules

    Energy Technology Data Exchange (ETDEWEB)

    Li, Juan [Physik Department and NIM, Walter Schottky Institute, Technische Universität München, Am Coulombwall 4, Garching D-85748 (Germany); Physik Department E20, Technische Universität München, James-Franck-St. 1, Garching D-85748 (Germany); Wierzbowski, Jakob; Ceylan, Özlem; Klein, Julian; Anh, Tuan Le; Meggendorfer, Felix; Finley, Jonathan J.; Margapoti, Emanuela, E-mail: emanuela.margapoti@wsi.tum.de [Physik Department and NIM, Walter Schottky Institute, Technische Universität München, Am Coulombwall 4, Garching D-85748 (Germany); Nisic, Filippo; Dragonetti, Claudia [Dipartimento di Chimica, Università degli Studi di Milano and UdR dell' INSTM di Milano, Via Golgi 19, I-20133 Milano (Italy); Palma, Carlos-Andres; Barth, Johannes V. [Physik Department E20, Technische Universität München, James-Franck-St. 1, Garching D-85748 (Germany)

    2014-12-15

    We report photoluminescence measurements performed on monolayer- and two-layer-MoS{sub 2} placed on two types of mixed self-assembled monolayers (mSAMs) of photoswitchable azobenzene molecules. The two mSAMs differ via the electronegative character of the azobenzene derivatives. Thin layers of a transition metal dichalcogenide—MoS{sub 2}—were mechanically exfoliated on mSAM to allow for direct interaction between the molecules and the MoS{sub 2} layers. When the MoS{sub 2} nanosheet is in contact with the electropositive azobenzene molecules in trans configuration, an emission side band at lower energies and at low excitation powers suggest n-type doping. The photoisomerization of the molecules from trans to cis configuration lowers the doping, quenching the side band and enhancing the overall PL efficiency by a factor of ∼3. Opposite results were observed with the chlorinated, more electronegative molecules, exhibiting a reversed trend in the PL efficiency between trans and cis, but with an overall larger intensity. The type of doping induced by the two types of mSAMs was determined by Kelvin probe force microscopy technique.

  17. Microscopic theory of light-induced deformation in amorphous side-chain azobenzene polymers.

    Science.gov (United States)

    Toshchevikov, V; Saphiannikova, M; Heinrich, G

    2009-04-16

    We propose a microscopic theory of light-induced deformation of side-chain azobenzene polymers taking into account the internal structure of polymer chains. Our theory is based on the fact that interaction of chromophores with the polarized light leads to the orientation anisotropy of azobenzene macromolecules which is accompanied by the appearance of mechanical stress. It is the first microscopic theory which provides the value of the light-induced stress larger than the yield stress. This result explains a possibility for the inscription of surface relief gratings in glassy side-chain azobenzene polymers. For some chemical architectures, elongation of a sample demonstrates a nonmonotonic behavior with the light intensity and can change its sign (a stretched sample starts to be uniaxially compressed), in agreement with experiments. Using a viscoplastic approach, we show that the irreversible strain of a sample, which remains after the light is switched off, decreases with increasing temperature and can disappear at certain temperature below the glass transition temperature. This theoretical prediction is also confirmed by recent experiments.

  18. Femtosecond pump-probe photoionization-photofragmentation spectroscopy of azobenzene cation

    Institute of Scientific and Technical Information of China (English)

    HO; JrWei

    2010-01-01

    We report the studies of ultrafast dynamics of azobenzene cations using femtosecond photoionization-photofragmentation spectroscopy. In our experiment,a femtosecond pump pulse first prepares an ensemble of azobenzene cations via photoionization of neutrals. A delayed probe pulse then brings the evolving ionic system to higher states that ultimately undergo ion fragmentation. The dynamics is followed by monitoring either the parent-ion depletion or fragment-ion formation as a function of the pump-probe delay time. The observed transients for azobenzene cations are characterized by a constant ion depletion modulated by a rapidly damped oscillatory signal with a period of about 1 ps. Theoretical calculations suggest that the oscillation arises from a vibration motion along the twisting inversion coordinate involving displacements in CNNC and phenyl-ring torsions. The oscillation is damped rapidly with a time constant of about 1.2 ps,suggesting that energy dissipation from the active mode to bath modes takes place on this time scale.

  19. Synthesis and characterization of dicyclopalladated complexes of azobenzene derivatives by experimental and computational methods.

    Science.gov (United States)

    Babić, Darko; Curić, Manda; Molcanov, Kresimir; Ilc, Gregor; Plavec, Janez

    2008-11-17

    A series of doubly cyclopalladated complexes of azobenzene and its unsymmetrical substituted derivatives, namely, {LPdCl(mu-AZB)LPdCl}, where AZB is azobenzene, 4-methylazobenzene, 4-aminoazobenzene, or 4-(dimethylamino)-4'-nitroazobenzene, while L is N,N-dimethylformamide, dimethylsulfoxide, or pyridine, have been prepared. Their structural and spectroscopic properties were determined by X-ray diffraction analysis as well as by (1)H NMR, IR, UV-vis, and fluorimetric studies. Experimental results were rationalized by quantum chemical calculations. Crystal structures of several complexes have been resolved, and for the first time, it was demonstrated that the cyclopalladation may take place at the azobenzene aromatic ring having the strong electron-withdrawing substituent at the para position. In all cases, the metalated carbon and N,N-dimethylformamide or dimethylsulfoxide ligands are mutually trans, whereas the pyridine ligands are in the cis arrangement. cis/trans isomerism in the isolated compounds is explained by comparing the calculated energies of isomeric structures. All of the complexes absorb strongly in the visible region, and according to time-dependent density functional theory calculations, most of the absorptions can be attributed to intraligand pi --> pi* or metal-to-ligand charge-transfer transitions. The fluorescence emission was observed for the complexes with 4-aminoazobenzene or 4-(dimethylamino)-4'-nitroazobenzene. The aromaticity of palladacycles is evaluated by several aromaticity indices and related to relevant experimental findings.

  20. Optical Input/Electrical Output Memory Elements based on a Liquid Crystalline Azobenzene Polymer.

    Science.gov (United States)

    Mosciatti, Thomas; Bonacchi, Sara; Gobbi, Marco; Ferlauto, Laura; Liscio, Fabiola; Giorgini, Loris; Orgiu, Emanuele; Samorì, Paolo

    2016-03-01

    Responsive polymer materials can change their properties when subjected to external stimuli. In this work, thin films of thermotropic poly(metha)acrylate/azobenzene polymers are explored as active layer in light-programmable, electrically readable memories. The memory effect is based on the reversible modifications of the film morphology induced by the photoisomerization of azobenzene mesogenic groups. When the film is in the liquid crystalline phase, the trans → cis isomerization induces a major surface reorganization on the mesoscopic scale that is characterized by a reduction in the effective thickness of the film. The film conductivity is measured in vertical two-terminal devices in which the polymer is sandwiched between a Au contact and a liquid compliant E-GaIn drop. We demonstrate that the trans → cis isomerization is accompanied by a reversible 100-fold change in the film conductance. In this way, the device can be set in a high- or low-resistance state by light irradiation at different wavelengths. This result paves the way toward the potential use of poly(metha)acrylate/azobenzene polymer films as active layer for optical input/electrical output memory elements.

  1. Rock blocks

    OpenAIRE

    Turner, W.

    2007-01-01

    Consider representation theory associated to symmetric groups, or to Hecke algebras in type A, or to q-Schur algebras, or to finite general linear groups in non-describing characteristic. Rock blocks are certain combinatorially defined blocks appearing in such a representation theory, first observed by R. Rouquier. Rock blocks are much more symmetric than general blocks, and every block is derived equivalent to a Rock block. Motivated by a theorem of J. Chuang and R. Kessar in the case of sym...

  2. Mass spectrometric identification of an azobenzene derivative produced by smectite-catalyzed conversion of 3-amino-4-hydroxyphenylarsonic acid

    Science.gov (United States)

    Wershaw, R. L.; Rutherford, D.W.; Rostad, C.E.; Garbarino, J.R.; Ferrer, I.; Kennedy, K.R.; Momplaisir, G.-M.; Grange, A.

    2003-01-01

    The compound 3-amino-4-hydroxyphenylarsonic acid (3-amino-HPAA) reacts with smectite to form a soluble azobenzene arsonic acid compound. This reaction is of particular interest because it provides a possible mechanism for the formation of a new type of arsenic compound in natural water systems. 3-Amino-HPAA is a degradation product excreted by chickens that are fed rations amended with roxarsone. Roxarsone is used to control coccidial intestinal parasites in most of the broiler chickens grown in the United States. The structure of the azobenzene arsonic acid compound was first inferred from negative-ion and positive-ion low-resolution mass-spectrometric analyses of the supernatant of the smectite suspension. Elemental composition of the parent ion determined by high-resolution positive-ion mass spectrometric measurements was consistent with the proposed structure of the azobenzene arsonic acid compound. Published by Elsevier Science B.V.

  3. Photo-induced morphological winding and unwinding motion of nanoscrolls composed of niobate nanosheets with a polyfluoroalkyl azobenzene derivative.

    Science.gov (United States)

    Nabetani, Yu; Takamura, Hazuki; Uchikoshi, Akino; Hassan, Syed Zahid; Shimada, Tetsuya; Takagi, Shinsuke; Tachibana, Hiroshi; Masui, Dai; Tong, Zhiwei; Inoue, Haruo

    2016-06-16

    Photo-responsive nanoscrolls can be successfully fabricated by mixing a polyfluoroalkyl azobenzene derivative and a niobate nanosheet, which is exfoliated from potassium hexaniobate. In this study, we have found that the photo-responsive nanoscroll shows a morphological motion of winding and unwinding, which is basically due to the nanosheet sliding within the nanoscroll, by efficient photo-isomerization reactions of the intercalated azobenzene in addition to the interlayer distance change of the nanoscrolls. The relative nanosheet sliding of the nanoscroll is estimated to be ca. 280 nm from the AFM morphology analysis. The distance of the sliding motion is over 20 times that of the averaged nanosheet sliding in the azobenzene/niobate hybrid film reported previously. Photo-responsive nanoscrolls can be expected to be novel photo-activated actuators and artificial muscle model materials.

  4. Photo-orientation of azobenzene-containing liquid-crystalline materials by means of domain structure rearrangement.

    Science.gov (United States)

    Bogdanov, Alexey V; Vorobiev, Andrey Kh

    2013-11-07

    A novel mechanism of photo-orientation of azobenzene-containing liquid-crystalline materials is proposed. This mechanism is based on the notion of photochemically induced domain rearrangement driven by destabilization of liquid-crystalline phase in light absorbing domains due to photochemical formation of non-mesogenic cis-azobenzene moieties. The experimental evidence of photoinduced movement of a domain boundary is presented, and the velocity of this movement is measured. A mathematical model for photo-orientation of a polydomain azobenzene-containing material is formulated. The values of model parameters for a liquid-crystalline azopolymer have been measured in separate experiments. Theoretical predictions demonstrate quantitative agreement with the experimental observations.

  5. Block-Copolymer-Assisted Solubilization of Carbon Nanotubes and Exfoliation Monitoring Through Viscosity

    NARCIS (Netherlands)

    Cotiuga, Irina; Picchioni, Francesco; Agarwal, Uday S.; Wouters, Daan; Loos, Joachim; Lemstra, Piet J.

    2006-01-01

    The use of the block copolymers polystyrene-block-poly(ethylene oxide) and poly(methyl methacrylate)-block-poly(ethylene oxide) is described to assist the direct solubilization of single-walled carbon nanotubes (SWNTs) into water under ultrasonic irradiation. As compared to surfactants and homopolym

  6. The synthesis and characterization of 2-mercaptoethyl methacrylate

    Directory of Open Access Journals (Sweden)

    Knežević Marija

    2005-01-01

    Full Text Available The synthesis of 2-mercaptoethyl methacrylate from methacrylic acid and 2-mercaptoethanol by etherification using acetyl chloride as catalyst was optimized. The purity of the obtained product was controlled by gas chromatography and its identity confirmed by H-NMR and FTIR spectroscopy. 2-Mercapto-ethyl methacrylate could find application as a chain transfer agent in radical polymerizations.

  7. Fabrication of narrow surface relief features in a side-chain azobenzene polyester with a scanning near-field microscope

    DEFF Research Database (Denmark)

    Ramanujam, P.S.; Holme, N. C. R.; Pedersen, M.;

    2001-01-01

    We show that it is possible to fabricate topographic submicron features in a side-chain azobenzene polyester with a scanning near-field optical microscope, Through irradiation at a wavelength of 488 run at intensity levels of 12 W/cm(2), topographic features as narrow as 240 nm and as high as 6 nm...... have been reproducibly recorded in a thin film of the polyester. These observations are consistent with the fact that at low intensities peaks are produced evolving into formation of trenches at high intensities in the case of amorphous side-chain azobenzene polyesters. This may find applications...

  8. Vibrational spectra study of phosphorus dendrimer containing azobenzene units on the surface

    Science.gov (United States)

    Furer, V. L.; Vandyukov, A. E.; Majoral, J. P.; Caminade, A. M.; Kovalenko, V. I.

    2013-08-01

    The FTIR and FT Raman spectra of the first generation dendrimers, possessing oxybenzaldehyde (G1) or oxyphenylazobenzaldehyde (G2) terminal groups and sodium 4-[4-oxyphenyl)azo]-benzaldehyde (SOAB) were studied. The structural optimization and normal mode analysis were performed for dendrimer G2 on the basis of the density functional theory (DFT). These calculations gave the frequencies of vibrations, infrared intensities and Raman scattering activities for the E- and Z-forms of azobenzene unit. The energy differences between the E- and Z-forms are 12.62 and 25.16 kcal/mol for SOAB and G2. The calculated in gas phase dipole moments for the E- and Z-forms are equal to 20.86, 18.28 D (SOAB) and 7.56, 8.88 D (G2). The calculated geometrical parameters and harmonic vibrational frequencies are predicted in a good agreement with the experimental data. It was found that dendrimer G2 molecule has a concave lens structure with planar sbnd Osbnd C6H4sbnd CHdbnd Nsbnd N(CH3)Pdbnd S and sbnd Osbnd C6H4sbnd Ndbnd Nsbnd C6H4sbnd CHdbnd O fragments and slightly non-planar cyclotriphosphazene core. The experimental IR and Raman spectra of dendrimer G2 were interpreted by means of potential energy distributions. Relying on DFT calculations a complete vibrational assignment is proposed. The strong band 1598 cm-1 in the IR spectra show marked changes of the optical density in dependence of substituents in the aromatic ring. The differences in the IR and Raman spectra of SOAB and G2 for the E- and Z-forms of azobenzene units were cleared up. During structural isomerization of azobenzene units, redistribution of band intensities appears to a much higher extent than frequency shifts.

  9. Substrate-Controlled Transformation of Azobenzenes to Indazoles and Indoles via Rh(III)-Catalysis.

    Science.gov (United States)

    Cai, Shangjun; Lin, Songyun; Yi, Xiangli; Xi, Chanjuan

    2017-01-06

    Rh(III)-catalyzed substrate-controlled transformation of azobenzenes to indazoles and 2-acyl (NH) indoles is achieved via C-H functionalization. Generally, good functional groups tolerance, satisfying yields, and excellent regio-selectivity are achieved in this reaction. Mechanistically, the reaction with acrylates undergoes β-hydride elimination, while the reaction with vinyl ketones or acrylamides undergoes nucleophilic addition. Copper acetate was supposed to play different roles in the β-hydride elimination to furnish indazoles and nucleophilic addition of C-Rh bond to deliver 2-acyl (NH) indoles.

  10. Azobenzene-functionalized carbon nanotubes as high-energy density solar thermal fuels.

    Science.gov (United States)

    Kolpak, Alexie M; Grossman, Jeffrey C

    2011-08-10

    Solar thermal fuels, which reversibly store solar energy in molecular bonds, are a tantalizing prospect for clean, renewable, and transportable energy conversion/storage. However, large-scale adoption requires enhanced energy storage capacity and thermal stability. Here we present a novel solar thermal fuel, composed of azobenzene-functionalized carbon nanotubes, with the volumetric energy density of Li-ion batteries. Our work also demonstrates that the inclusion of nanoscale templates is an effective strategy for design of highly cyclable, thermally stable, and energy-dense solar thermal fuels.

  11. Second- and third-order nonlinearities of novel push-pull azobenzene polymers.

    Science.gov (United States)

    El Ouazzani, Hasnaa; Iliopoulos, Konstantinos; Pranaitis, Mindaugas; Krupka, Oksana; Smokal, Vitaliy; Kolendo, Aleksey; Sahraoui, Bouchta

    2011-03-10

    In this work, the second- and third-order nonlinear optical response of spin-deposited thin films of three different push-pull side chain azobenzene polymers is investigated by the second- and third-harmonic Maker fringes techniques using 30 ps laser pulses at a fundamental wavelength of 1064 nm. Measurements were carried out before and after aligning the chromophores by corona poling of the films, while different polarization configurations have been utilized. Strong dependence of the response upon the structure of the systems has been found, which is related to the different charge transfer within the molecules. The reported findings are compared with already published results.

  12. Second-order nonlinear optical properties of mexylaminotriazine-functionalized glass-forming azobenzene derivatives

    Science.gov (United States)

    Umezawa, Hirohito; Jackson, Matthew; Lebel, Olivier; Nunzi, Jean-Michel; Sabat, Ribal Georges

    2016-10-01

    The second-order nonlinear optical coefficients of thin films of mexylaminotriazine-functionalized azobenzene molecular glass derivatives were measured using second harmonic generation. The thin films were poled using a custom corona poling set-up and the second harmonic light from a pulsed 1064-nm laser was detected. Four out of the six tested compounds showed optical nonlinearity and a maximum coefficient of 75 pm/V was obtained. The time dependence of the nonlinear coefficients was studied under ambient light and under dark; the second harmonic generation intensity stayed constant for thiazole-containing derivatives while a significant decay was measured for the other compounds.

  13. Optical and Physical Applications of Photocontrollable Materials: Azobenzene-Containing and Liquid Crystalline Polymers

    Directory of Open Access Journals (Sweden)

    Takashi Fukuda

    2012-01-01

    Full Text Available Photocontrol of molecular alignment is an exceptionally-intelligent and useful strategy. It enables us to control optical coefficients, peripheral molecular alignments, surface relief structure, and actuation of substances by means of photoirradiation. Azobenzene-containing polymers and functionalized liquid crystalline polymers are well-known photocontrollable materials. In this paper, we introduce recent applications of these materials in the fields of mechanics, self-organized structuring, mass transport, optics, and photonics. The concepts in each application are explained based on the mechanisms of photocontrol. The interesting natures of the photocontrollable materials and the conceptual applications will stimulate novel ideas for future research and development in this field.

  14. Synthesis and Characterization of Nonsymmetric Liquid Crystal Dimer Containing Biphenyl and Azobenzene Moiety

    Directory of Open Access Journals (Sweden)

    S. Sandy Subala

    2013-01-01

    Full Text Available Calamitic liquid crystalline dimer containing azobenzene moiety and a decyloxy biphenyl linked by flexible spacers {4-[7-(4′-decyloxy-biphenyl-4-yloxy-alkyloxy]-phenyl}-(4-decyl-phenyl-diazene has been synthesized and characterized by spectroscopic methods. The transition temperatures and phase behaviours were studied by Differential Scanning Calorimeter (DSC and Polarizing Optical Microscope (POM. The synthesized compounds exhibited enantiotropic liquid crystal phase with higher spacer display nematic and smectic C phases while lower spacer shows nematic and smectic A phases.

  15. Azobenzene Modified Imidacloprid Derivatives as Photoswitchable Insecticides: Steering Molecular Activity in a Controllable Manner

    Science.gov (United States)

    Xu, Zhiping; Shi, Lina; Jiang, Danping; Cheng, Jiagao; Shao, Xusheng; Li, Zhong

    2015-10-01

    Incorporating the photoisomerizable azobenzene into imidacloprid produced a photoswitchable insecticidal molecule as the first neonicotinoid example of remote control insecticide performance with spatiotemporal resolution. The designed photoswitchable insecticides showed distinguishable activity against Musca both in vivo and in vitro upon irradiation. Molecular docking study further suggested the binding difference of the two photoisomers. The generation of these photomediated insecticides provides novel insight into the insecticidal activity facilitating further investigation on the functions of insect nicotinic acetylcholine receptors and opens a novel way to control and study insect behavior on insecticide poisoning using light.

  16. Ab initio calculation of the electronic spectrum of azobenzene dyes and its impact on the design of optical data storage materials

    DEFF Research Database (Denmark)

    Åstrand, Per-Olof; Ramanujam, P.S.; Hvilsted, Søren

    2000-01-01

    Electronic excitation energies of 16 azobenzene dyes have been calculated by ab initio methods within the second-order polarization propagator approximation (SOPPA). Good agreement with expriment is found for the lowest singlet and triplet states for both the trans- and cis-azobenzene molecules......, the experimental singlet π → π* transitions are reproduced for a set of azobenzene dyes with different electron donor and acceptor groups and the correct shifts in excitation energy are obtained for the different substituents. It has also been demonstrated that ab initio methods can be used to determine suitable...... candidates for azo components used in materials for data storage....

  17. METHACRYLATE AND ACRYLATE ALLERGY IN DENTAL STUDENTS.

    Directory of Open Access Journals (Sweden)

    Maya Lyapina

    2013-09-01

    Full Text Available A multitude of acrylic monomers is used in dentistry, and when dental personnel, patients or students of dental medicine become sensitized, it is of great importance to identify the dental ;acrylic preparations to which the sensitized individual can be exposed. Numerous studies confirm high incidence of sensitization to (meth acrylates in dentatal professionals, as well as in patients undergoing dental treatment and exposed to resin-based materials. Quite a few studies are available aiming to evaluate the incidence of sensitization in students of dental medicineThe purpose of the study is to evaluate the incidence of contact sensitization to some (meth acrylates in students of dental medicine at the time of their education, in dental professionals (dentists, nurses and attendants and in patients, the manifestation of co-reactivity.A total of 139 participants were included in the study, divided into four groups: occupationally exposed to (methacrylates and acrylic monomers dental professionals, 3-4 year-of-education students of dental medicine, 6th year–of-education students of dental medicine and patients with suspected or established sensitization to acrylates, without occupational exposure. All of them were patch-tested with methyl methacrylate (MMA, triethyleneglycol dimethacrylate (TREGDMA, ethyleneglycol dimethacrylate (EGDMA, 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy phenyl]propane (bis-GMA, 2-hydroxyethyl methacrylate (2-HEMA, and tetrahidrofurfuril metacrylate. The overall sensitization rates to methacrylates in the studied population are comparative high – from 25.9% for MMA to 31.7% for TREGDMA. Significantly higher incidence of sensitization in the group of 3-4 course students compared to the one in the group of dental professionals for MMA and TREGDMA was observed. Highest was the incidence of sensitization to ethyleneglycol dimethacrylate, BIS-GMA, 2-HEMA and tetrahydrofurfuryl methacrylate in the group of patients, with

  18. Preparation and characterization of star ABC triblock copolymer of ethylene oxide,styrene and methyl methacrylate

    Institute of Scientific and Technical Information of China (English)

    黄骏廉; 黄晓宇; 胡文兵; 楼文奎

    1997-01-01

    A universally significant method,which combines the anionic polymerization with photoinduced charge transfer polymerization,for preparation of soluble star ABC triblock copolymer of ethylene oxide,styrene and methyl methacrylate,was described.The poly(ethylene oxide) (PEO) block was formed by initiation of phenoxy an-ions using p-aminophenol protected by Schiff’s base as the parent compound Then the charge transfer system composed of PEO chains with deprotected-amino end groups and benzophenone initiated the polymerization of styrene and methyl metnacrylate sequentially under UV irradiation.The formed star triblock copolymer of styrene,ethylene oxide and methyl methacrylate could be purified by thin-layer chromatography (TLC) and characterized by IR,1H NMR,GPC (gel permeation chromatogrphy) and PGC (pyrolysis gas chromatography).

  19. Synthesis and Characterization of Polyphosphazenes Modified with Hydroxyethyl Methacrylate and Lactic Acid

    Directory of Open Access Journals (Sweden)

    Evelyn Carolina Martínez Ceballos

    2013-01-01

    Full Text Available Poly(dichlorophosphazene was prepared by melt ring-opening polymerization of the hexachlorocyclotriphosphazene. Poly[bis(2-hydroxyethyl-methacrylate-phosphazene] and poly[(2-hydroxyethyl-methacrylate-graft-poly(lactic-acid-phosphazene] were obtained by nucleophilic condensation reactions at different concentrations of the substituents. The properties of the synthesized copolymers were assessed by FTIR, 1H-NMR and 31P-NMR, thermal analysis (DSC-TGA, and electron microscopy (SEM. The copolymers have a block structure and show two Tg's below room temperature. They are stable up to a temperature of 100°C. The type of the substituents attached to the PZ backbone determines the morphology of the polymers.

  20. Photoswitching of azobenzene-containing self-assembled monolayers as a tool for control over silicon surface electronic properties

    Science.gov (United States)

    Malyar, Ivan V.; Titov, Evgenii; Lomadze, Nino; Saalfrank, Peter; Santer, Svetlana

    2017-03-01

    We report on photoinduced remote control of work function and surface potential of a silicon surface modified with a photosensitive self-assembled monolayer consisting of chemisorbed azobenzene molecules (4-nitroazobenzene). It was found that the attachment of the organic monolayer increases the work function by hundreds of meV due to the increase in the electron affinity of silicon substrates. The change in the work function on UV light illumination is more pronounced for the azobenzene jacketed silicon substrate (ca. 250 meV) in comparison to 50 meV for the unmodified surface. Moreover, the photoisomerization of azobenzene results in complex kinetics of the work function change: immediate decrease due to light-driven processes in the silicon surface followed by slower recovery to the initial state due to azobenzene isomerization. This behavior could be of interest for electronic devices where the reaction on irradiation should be more pronounced at small time scales but the overall surface potential should stay constant over time independent of the irradiation conditions.

  1. Remarkable enhancement of the photoreactivity of a polyfluoroalkyl azobenzene derivative in an organic-inorganic nano-layered microenvironment.

    Science.gov (United States)

    Ramakrishnan, Vivek; Yamamoto, Daisuke; Sasamoto, Shin; Shimada, Tetsuya; Nabetani, Yu; Tachibana, Hiroshi; Inoue, Haruo

    2014-11-21

    Organic-inorganic hybrids composed of polyfluoroalkyl azobenzene surfactant (abbreviated as C3F-Azo-C6H) and inorganic layered compounds are able to undergo reversible three-dimensional morphology changes such as interlayer space changes and nanosheet sliding in a giant scale due to reversible trans-cis isomerization of the azobenzene moiety upon photo-irradiation. In this paper, we have systematically studied the relationship between the layered hybrid microstructures of C3F-Azo-C6H-clay and their photoreactivity for understanding the mechanism of the photo-induced morphology change. The photoreactivity was found to be very much affected by the surrounding microenvironments. As compared with it in solution, the cis-trans photo-isomerization in C3F-Azo-C6H-clay nano-layered film was substantially enhanced with the quantum yield exceeding unity (Φ = 1.9), while the trans-cis isomerization was rather retarded. The corresponding hydrocarbon analogue of the azobenzene surfactant (C3H-Azo-C6H) did not show such an enhancement. The enhancement was discussed in terms of a cooperative effect among adjacent azobenzene moieties along with polyfluoroalkyl chains and the inorganic clay nanosheet to prevent a dissipation of the excess energy being liberated during the photo-isomerization within the nano-layered microenvironment.

  2. Molecular design of super hydrogelators: understanding the gelation process of azobenzene-based sugar derivatives in water

    NARCIS (Netherlands)

    Kobayashi, Hideki; Friggeri, Arianna; Koumoto, Kazuya; Amaike, Masato; Shinkai, Seiji; Reinhoudt, David N.

    2002-01-01

    As an attempt to rationally design aqueous organogelators, a bolaamphiphilic azobenzene derivative (1) bearing two sugar groups was synthesized. Compound 1 formed a gel in water even at concentrations as low as 0.05 wt % (0.65 mM). Spectroscopic studies and electron-micrographic observations have cl

  3. Temperature- and Photocontrolled Unfolding/Folding of a Triple-Helical Azobenzene-Stapled Collagen Peptide Monitored by Infrared Spectroscopy.

    Science.gov (United States)

    Lorenz, Lisa; Kusebauch, Ulrike; Moroder, Luis; Wachtveitl, Josef

    2016-05-04

    The triple-helical structure of a model collagen peptide possessing azobenzene-derived clamps integrated in all three strands as side-chain-to-side-chain crosslinks is analyzed by IR spectroscopy in comparative thermal excursion experiments with the triple helix of a typical reference collagen peptide consisting of only glycine-proline-hydroxyproline repeats. By exploiting the known stabilizing effects of aqueous alcoholic solvents on the unique collagen fold, deuterated ethylene glycol/water (1:1) is used as a solvent to investigate the effect of the light-switchable trans/cis-azobenzene clamp on the stability of the triple helix in terms of H/D exchange rates and thermal unfolding. Results of this comparative analysis clearly reveal only a minor destabilization of the triple helix by the hydrophobic azobenzene moieties compared to the reference collagen peptide as reflected by a lower midpoint of the thermal unfolding and higher rates of H/D exchange. However, it also reveals that the driving force exerted by the trans-to-cis photoisomerization of the azobenzene moieties is insufficient for unfolding of the compact triple-helical collagen fold. Only temperature-dependent untightening of this fold with heating results in a reversible photomodulated unfolding and refolding of the azo-collagen peptide into the original triple helix.

  4. An analysis of the anisotropic and topographic gratings in a side-chain liquid crystalline azobenzene polyester

    DEFF Research Database (Denmark)

    Holme, N.C.R.; Nikolova, L.; Ramanujam, P.S.;

    1997-01-01

    We have examined in detail the formation of surface relief structures in azobenzene polyesters formed by polarization holography with orthogonally circularly polarized laser beams, We show that it is possible to separate the contribution to the diffraction efficiency into an anisotropic part...

  5. 10,000 optical write, read, and erase cycles in an azobenzene sidechain liquid-crystalline polyester

    DEFF Research Database (Denmark)

    Holme, NCR; Ramanujam, P.S.; Hvilsted, Søren

    1996-01-01

    We show far what is believed to he the first time that it is possible tu generate 10,000 rapid write, read, and erase cycles optically in an azobenzene sidechain liquid-crystalline polyester. We do this by exposing the film alternately to visible light from an argon laser at 488 nm and ultraviolet...

  6. Photo-Reversible Supramolecular Hydrogels Assembled by α-Cyclodextrin and Azobenzene Substituted Poly(acrylic acid)s

    NARCIS (Netherlands)

    Wang, Mingwei; Zhang, Xiaojun; Li, Li; Wang, Junyou; Wang, Jie; Ma, Jun; Yuan, Zhenyu; Lincoln, Stephen F.; Guo, Xuhong

    2016-01-01

    Photo-reversible supramolecular hydrogels based on the mixture of α-cyclodextrin (α-CD) and azobenzene (Azo) substituted poly(acrylic acid) s were prepared. Effects of substitution degree of Azo, polymer concentration and tethered chain length on the reversible sol-gel transition of these mixture

  7. OPTICAL PHASE CONJUGATION RESPONSE OF PHOTOINDUCED POLYMER FILMS CONTAINING AZOBENZENE MOIETIES WITH CHIRAL GROUP

    Institute of Scientific and Technical Information of China (English)

    Ze-da Xu; Yong Zhang; Xing-he Fan; Xin-hua Wan; Qi-feng Zhou

    2002-01-01

    An optically active monomer containing azobenzene moieties with chiral group (s-2-methyl-butyl), 4-[2-(methacryloyloxy)ethyloxy]-4'-(s-2-methyl-1-butyloxycarbonyl) azobenzene (M1) was synthesized. Polymer (PM1) possessing optical phase conjugated response was obtained by homopolymerization of the optically active monomer (M1) using free radical polymerization. The polymer was very soluble in common solvents and good optical quality films could be easily fabricated by spin coating. The optical phase conjugated responses of the polymer PM1 were measured by degenerate four-wave mixing (DFWM). In comparison with polymer containing no chiral group, it was found from the preliminary measurement of photoisomeric change that optical phase conjugated response of the PM1 in the long-range order hexagonal symmetry microstructure could be easily controlled by choosing the appropriate polarization direction of the irradiating beams (514.5 nm) and the irradiating number, presumably due to the chiral group in the PM1 molecular structure. For the case of the polymer investigated here, a chiral group side chain was introduced to increase optical phase conjugated response intensity with different polarization directions of the irradiating beams, which aims originally at searching for a new photoactive material.

  8. Fluorescence modulation of cadmium sulfide quantum dots by azobenzene photochromic switches.

    Science.gov (United States)

    Javed, Hina; Fatima, Kalsoom; Akhter, Zareen; Nadeem, Muhammad Arif; Siddiq, Muhammad; Iqbal, Azhar

    2016-02-01

    We have investigated the attachment of azobenzene photochromic switches on the modified surface of cadmium sulfide (CdS) quantum dots (QDs). The modification of CdS QDs is done by varying the concentration of the capping agent (mercaptoacetic acid) and NH3 in order to control the size of the QDs. The X-ray diffraction studies revealed that the crystallite size of CdS QDs ranged from 6 to 10 nm. The azobenzene photochromic derivatives bis(4-hydroxybenzene-1-azo)4,4'(1,1' diphenylmethane) (I) and 4,4'-diazenyldibenzoic acid (II) were synthesized and attached with surface-modified CdS QDs to make fluorophore-photochrome CdS-(I) and CdS-(II) dyad assemblies. Upon UV irradiation, the photochromic compounds (I) and (II) undergo a reversible trans-cis isomerization. The photo-induced trans-cis transformation helps to transfer photo-excited electrons from the conduction band of the CdS QDs to the lowest unoccupied molecular orbital of cis isomer of photochromic compounds (I) and (II). As a result, the fluorescence of CdS-(I) and CdS-(II) dyads is suppressed approximately five times compared to bare CdS QDs. The fluorescence modulation in such systems could help to design luminescent probes for bioimaging applications.

  9. NANOSTRUCTURES OF FUNCTIONAL BLOCK COPOLYMERS

    Institute of Scientific and Technical Information of China (English)

    Guojun Liu

    2000-01-01

    Nanostructure fabrication from block copolymers in my group normally involves polymer design, synthesis, selfassembly, selective domain crosslinking, and sometimes selective domain removal. Preparation of thin films with nanochannels was used to illustrate the strategy we took. In this particular case, a linear triblock copolymer polyisopreneblock-poly(2-cinnamoylethyl methacrylate)-block-poly(t-butyl acrylate), PI-b-PCEMA-b-PtBA, was used. Films, 25 to50μm thick, were prepared from casting on glass slides a toluene solution of PI-b-PCEMA-b-PtBA and PtBA homopolymer,hPtBA, where hPtBA is shorter than the PtBA block. At the hPtBA mass fraction of 20% relative to the triblock or the total PtBA (hPtBA and PtBA block) volume fraction of 0.44, hPtBA and PtBA formed a seemingly continuous phase in the matrix of PCEMA and PI. Such a block segregation pattern was locked in by photocrosslinking the PCEMA domain. Nanochannels were formed by extracting out hPtBA with solvent. Alternatively, larger channels were obtained from extracting out hPtBA and hydrolyzing the t-butyl groups of the PtBA block. Such membranes were not liquid permeable but had gas permeability constants ~6 orders of magnitude higher than that of low-density polyethylene films.

  10. Population Blocks.

    Science.gov (United States)

    Smith, Martin H.

    1992-01-01

    Describes an educational game called "Population Blocks" that is designed to illustrate the concept of exponential growth of the human population and some potential effects of overpopulation. The game material consists of wooden blocks; 18 blocks are painted green (representing land), 7 are painted blue (representing water); and the remaining…

  11. Dimensional accuracy of thermoformed polymethyl methacrylate.

    Science.gov (United States)

    Jagger, R G

    1996-12-01

    Thermoforming of polymethyl methacrylate sheet is used to produce a number of different types of dental appliances. The purpose of this study was to determine the dimensional accuracy of thermoformed polymethyl methacrylate specimens. Five blanks of the acrylic resin were thermoformed on stone casts prepared from a silicone mold of a brass master die. The distances between index marks were measured both on the cast and on the thermoformed blanks with an optical comparator. Measurements on the blanks were made again 24 hours after processing and then 1 week, 1 month, and 3 months after immersion in water. Linear shrinkage of less than 1% (range 0.37% to 0.52%) was observed 24 hours after removal of the blanks from the cast. Immersion of the thermoformed specimens in water resulted in an increase in measured dimensions, but after 3 months' immersion these increases were still less than those of the cast (range 0.07% to 0.18%). It was concluded that it is possible to thermoform Perspex polymethyl methacrylate accurately.

  12. Preparation of mesoporous SiO2@azobenzene-COOH chemoselective nanoprobes for comprehensive mapping of amino metabolites in human serum.

    Science.gov (United States)

    Li, Hua; Qin, Qian; Qiao, Lizhen; Shi, Xianzhe; Xu, Guowang

    2015-06-30

    A novel type of mesoporous SiO2@H4/D4 tagged azobenzene-COOH chemoselective nanoprobe was developed for comprehensive mapping of amino metabolites in complex biological samples with high specificity and sensitivity.

  13. Zitongdong Block

    Institute of Scientific and Technical Information of China (English)

    1996-01-01

    @@ The Zitongdong Block (Eastern Zitong Block) is located in the northwest of the Sichuan Basin. Tectonically, it is situated in the east part of Zitong Depression, southeast of mid-Longmenshan folded and faulted belt( as shown on Fig. 8 ), covering an area of 1 730 km2. The traffic is very convenient, the No. 108 national highway passes through the north of the block. Topographically, the area belongs to low hilly land at the elevation of 500-700 m.

  14. Periodontal repair in dogs: histologic observations of guided tissue regeneration with a prostaglandin E1 analog/methacrylate composite.

    Science.gov (United States)

    Trombelli, L; Lee, M B; Promsudthi, A; Guglielmoni, P G; Wikesjö, U M

    1999-06-01

    This report describes observations of healing following guided tissue regeneration (GTR) including surgical implantation of the prostaglandin E1 analog misoprostol with calcium-layered methacrylate particles. Critical size, supra-alveolar periodontal defects were surgically created around the 3rd and 4th mandibular premolar teeth in 4 beagle dogs. Wound management included soaking with a 24 microg/ml misoprostol solution and implantation of the misoprostol/methacrylate composite. One jaw quadrant per animal was prepared for GTR using expanded polytetrafluoroethylene membranes. The gingival flaps were coronally advanced and sutured to submerge the teeth. The tissues covering the surgical sites daily received topical misoprostol in an oral adhesive over the 4-week healing interval. Upon euthanasia, tissue blocks were prepared for histometric analysis of regeneration of alveolar bone and cementum, root resorption and ankylosis. The defect area underneath the membrane and the density of methacrylate particles were recorded for the GTR defects. The methacrylate particles appeared encapsulated in a dense connective tissue without signs of an inflammatory reaction, some in contact to newly formed bone. Alveolar bone regeneration height averaged (+/-SD) 1.2+/-1.0 and 1.0+/-0.6 mm for GTR and non-GTR defects, respectively. Corresponding values for bone regeneration area were 1.3+/-1.0 and 0.7+/-0.5 mm2. Cementum regeneration was confined to the apical aspect of the defects. Small areas of root resorption and ankylosis were observed for all teeth. Bone regeneration area correlated positively to the defect area and negatively to the density of methacrylate particles in the GTR defects. The histologic observations suggest that the methacrylate composite has marginal potential to promote bone and cementum regeneration under provisions for GTR.

  15. SYNTHESIS AND PROPERTIES OF A NEW AZOBENZENE SIDE-CHAIN POLYMER CONTAINING A TEMPO RADICAL

    Institute of Scientific and Technical Information of China (English)

    Yong Zhang; Ze-da Xu; Xing-he Fan; Xiao-fang Chen; Xin-hua Wan; Qi-feng Zhou

    2002-01-01

    To allow anisotropies of optical properties in a magnetic field, nitroxide radical is introduced into the ortho-position of the phenylene ring in the side chain. A new azobenzene side-chain polymer (TEMPO-PAZ) containing TEMPOradical was synthesized. The polymer has a good solubility in organic solvents. The ESR spectrum of the polymer indicatedthree absorption lines characteristic of TEMPO radical. The optical phase conjugated responses (I4) of the polymer filmswere investigated by degenerate four-wave mixing (DFWM). The experimental results showed that optical phase conjugatedresponse of the TEMPO-PAZ could be easily controlled by choosing the appropriate direction of magnetic field presumablydue to the nitroxide radical in the TEMPO-PAZ molecular structure. For the polymer investigated here, the nitroxide radicalwas introduced to increase optical phase conjugated response intensity in a magnetic field, aiming originally at searching fora new photo-active organic magnetic multifunctional materials.

  16. Magnetic and optical bistability in tetrairon(III) single molecule magnets functionalized with azobenzene groups.

    Science.gov (United States)

    Prasad, Thazhe Kootteri; Poneti, Giordano; Sorace, Lorenzo; Rodriguez-Douton, Maria Jesus; Barra, Anne-Laure; Neugebauer, Petr; Costantino, Luca; Sessoli, Roberta; Cornia, Andrea

    2012-07-21

    Tetrairon(III) complexes known as "ferric stars" have been functionalized with azobenzene groups to investigate the effect of light-induced trans-cis isomerization on single-molecule magnet (SMM) behaviour. According to DC magnetic data and EPR spectroscopy, clusters dispersed in polystyrene (4% w/w) exhibit the same spin (S = 5) and magnetic anisotropy as bulk samples. Ligand photoisomerization, achieved by irradiation at 365 nm, has no detectable influence on static magnetic properties. However, it induces a small but significant acceleration of magnetic relaxation as probed by AC susceptometry. The pristine behaviour can be almost quantitatively recovered by irradiation with white light. Our studies demonstrate that magnetic and optical bistability can be made to coexist in SMM materials, which are of current interest in molecular spintronics.

  17. Near-field lithography on the azobenzene polymer liquid crystal films

    Institute of Scientific and Technical Information of China (English)

    Douguo Zhang; Jian Liu; Zebo Zhang; Li Cao; Anlian Pan; Pei Wang; Yonghua Lu; Ming Bai; Jun Yang; Lin Tang; Jiangying Zhang; Hai Ming; Qijin Zhang

    2005-01-01

    @@ In this article, we reported near-field research on azobenzene polymer liquid crystal films using scanning near-field optical microscopy (SNOM). Optical writing and subsequently topographic reading of the patterns with subwavelength resolution were carried out in our experiments. Nanometer scale dots and lines were successfully fabricated on the films and the smallest dot diameter is about 120 nm. The width of the line fabricated is about 250 nm. This method is also a choice for nanolithography. The mechanism of the surface deformation on the polymer films was briefly analyzed from the viewpoint of gradient force in the optical near field. The intensity distribution of the electric field near the tip aperture was numerically simulated using finite-difference time-domain (FDTD) method and the numerical simulation results were consistent with the experimental results.

  18. New Azobenzene Dye Colorimetric and Ratiometric Chemosensors for Mercury(Ⅱ)Ion

    Institute of Scientific and Technical Information of China (English)

    GUO Min; XUE wei; GUAN Mingyun; SUN Jianhua; YIN Gui

    2009-01-01

    A new series of azobenzene dyes,which possessed colorimetric and ratiometric recognition to Hg2+ based on the mechanism of internal charge transfer(ICT),was developed and characterized.The molecules involving azo and imino functional groups can coordinate with Hg2+ to result in a large blue shift from 453 to 363 nm corresponding to a notable color change from orange to pale yellow in aqueous methanol solution(H2O/CH3OH = 1/4,V/V),which can be applied to naked eye detection of Hg2+.The sensitivity,selectivity and binding mode of the sensors to Hg2+ were investigated by UV-Vis spectroscopy.

  19. Investigation of Methacrylic Acid at High Pressure Using Neutron Diffraction

    DEFF Research Database (Denmark)

    Marshall, William G.; Urquhart, Andrew; Oswald, Iain D. H.

    2015-01-01

    This article shows that pressure can be a low-intensity route to the synthesis of polymethacrylic acid. The exploration of perdeuterated methacrylic acid at high pressure using neutron diffraction reveals that methacrylic acid exhibits two polymorphic phase transformations at relatively low press...

  20. Regulation of substituent groups on morphologies and self-assembly of organogels based on some azobenzene imide derivatives

    Science.gov (United States)

    Jiao, Tifeng; Wang, Yujin; Zhang, Qingrui; Zhou, Jingxin; Gao, Faming

    2013-04-01

    In this paper, new azobenzene imide derivatives with different substituent groups were designed and synthesized. Their gelation behaviors in 21 solvents were tested as novel low-molecular-mass organic gelators. It was shown that the alkyl substituent chains and headgroups of azobenzene residues in gelators played a crucial role in the gelation behavior of all compounds in various organic solvents. More alkyl chains in molecular skeletons in present gelators are favorable for the gelation of organic solvents. Scanning electron microscopy and atomic force microscopy observations revealed that the gelator molecules self-assemble into different aggregates, from wrinkle, lamella, and belt to fiber with the change of solvents. Spectral studies indicated that there existed different H-bond formations between amide groups and conformations of methyl chains. The present work may give some insight to the design and character of new organogelators and soft materials with special molecular structures.

  1. Voltage-controlled nonvolatile molecular memory of an azobenzene monolayer through solution-processed reduced graphene oxide contacts.

    Science.gov (United States)

    Min, Misook; Seo, Sohyeon; Lee, Sae Mi; Lee, Hyoyoung

    2013-12-23

    The solution-processed fabrication of an azobenzene (ABC10) monolayer-based nonvolatile memory device on a reduced graphene oxide (rGO) electrode is successfully accomplished. Trans--cis isomerizations of ABC10 between two rGO electrodes in a crossbar device are controlled by applied voltage. An rGO soft-contact top electrode plays an important role in the conformational-change-dependent conductance switching process of an ABC10 monolayer.

  2. Large work function shift of gold induced by a novel perfluorinated azobenzene-based self-assembled monolayer.

    Science.gov (United States)

    Crivillers, Núria; Osella, Silvio; Van Dyck, Colin; Lazzerini, Giovanni M; Cornil, David; Liscio, Andrea; Di Stasio, Francesco; Mian, Shabbir; Fenwick, Oliver; Reinders, Federica; Neuburger, Markus; Treossi, Emanuele; Mayor, Marcel; Palermo, Vincenzo; Cacialli, Franco; Cornil, Jérôme; Samorì, Paolo

    2013-01-18

    Tune it with light! Self-assembled monolayers on gold based on a chemisorbed novel azobenzene derivative with a perfluorinated terminal phenyl ring are prepared. The modified substrate shows a significant work function increase compared to the bare metal. The photo-conversion between trans and cis isomers chemisorbed on the surface shows great perspectives for being an accessible route to tune the gold properties by means of light.

  3. Synthesis of Poly(methacrylic acid)-functionalized SBA-15 and its Adsorption of Phenol in Aqueous Media

    Energy Technology Data Exchange (ETDEWEB)

    Vo, Vien; Kim, Heejun; Kim, Hayeong; Kim, Youngmee; Kim, Sung Jin [Ewha Womans Univ., Seoul (Korea, Republic of)

    2013-12-15

    Poly(methacrylic acid)-functionalized SBA-15 silicas (denoted as P-x-PMA/SBA-15 where x is molar ratio of TSPM/(TEOS+TSPM) in percentage in the initial mixture) were synthesized by co-condensation of tetraethoxysilane and varying contents of 3-(trimethoxysilyl)propyl methacrylate in acidic medium with the block copolymer Pluronic 123 as a structure directing agent and then polymerization by methacrylic acid in the presence of ammonium persulfate as an initiator. The functionalized materials were characterized by PXRD, TEM, SEM, IR, and N{sub 2} adsorption-desorption at 77 K. The investigation of phenol adsorption in aqueous solution on the materials showed that the poly(methacrylic acid)-functionalized mesoporous silicas possess strong adsorption ability for phenol with interaction of various kinds of hydrogen bonds. The adsorption data were fitted to Langmuir isotherms and the maximum adsorption capacity of the three functionalized materials P-5-PMA/SBA-15, P-10-PMA/SBA-15, and P-15-PMA/SBA-15 to be 129.37 mg/g, 187.97 mg/g, and 78.43 mg/g, respectively, were obtained. The effect of the pH on phenol adsorption was studied.

  4. From the N-Heterocyclic Carbene-Catalyzed Conjugate Addition of Alcohols to the Controlled Polymerization of (Meth)acrylates.

    Science.gov (United States)

    Ottou, Winnie Nzahou; Bourichon, Damien; Vignolle, Joan; Wirotius, Anne-Laure; Robert, Fredéric; Landais, Yannick; Sotiropoulos, Jean-Marc; Miqueu, Karinne; Taton, Daniel

    2015-06-22

    Among various N-heterocyclic carbenes (NHCs) tested, only 1,3-bis(tert-butyl)imidazol-2-ylidene (NHC(tBu) ) proved to selectively promote the catalytic conjugate addition of alcohols onto (meth)acrylate substrates. This rather rare example of NHC-catalyzed 1,4-addition of alcohols was investigated as a simple means to trigger the polymerization of both methyl methacrylate and methyl acrylate (MMA and MA, respectively). Well-defined α-alkoxy poly(methyl (meth)acrylate) (PM(M)A) chains, the molar masses of which could be controlled by the initial [(meth)acrylate]0/[ROH]0 molar ratio, were ultimately obtained in N,N-dimethylformamide at 25 °C. A hydroxyl-terminated poly(ethylene oxide) (PEO-OH) macro-initiator was also employed to directly access PEO-b-PMMA amphiphilic block copolymers. Investigations into the reaction mechanism by DFT calculations revealed the occurrence of two competitive concerted pathways, involving either the activation of the alcohol or that of the monomer by NHC(tBu) .

  5. Zitongxi Block

    Institute of Scientific and Technical Information of China (English)

    1996-01-01

    @@ Zitongxi Block (Western Zitong Block), is located in Zitong County, northwest of Sichuan Province (as shown on Fig. 8 ). Geologically. it is situated in the Zitong Depression, southwest of the middle Longmenshan faulted and folded belt, covering an area of 1 830 km2. Transportation is very convenient. A crisscross network of highways run through the block and the Baocheng railway is nearby. The climate is moderate. Most area belongs to hilly land with the elevation of 500-600 m.The Tongjiang River runs across the area.

  6. Molecular characteristics of a fluorescent chemosensor for the recognition of ferric ion based on photoresponsive azobenzene derivative

    Science.gov (United States)

    Chi, Zhen; Ran, Xia; Shi, Lili; Lou, Jie; Kuang, Yanmin; Guo, Lijun

    2017-01-01

    Metal ion recognition is of great significance in biological and environmental detection. So far, there is very few research related to the ferric ion sensing based on photoresponsive azobenzene derivatives. In this work, we report a highly selective fluorescent "turn-off" sensor for Fe3 + ions and the molecular sensing characteristics based on an azobenzene derivative, N-(3,4,5-octanoxyphenyl)-N‧-4-[(4-hydroxyphenyl)azophenyl]1,3,4-oxadiazole (AOB-t8). The binding association constant was determined to be 6.07 × 103 M- 1 in ethanol and the stoichiometry ratio of 2:2 was obtained from Job's plot and MS spectra. The AOB-t8 might be likely to form the dimer structure through the chelation of ferric ion with the azobenzene moiety. Meanwhile, it was found that the photoisomerization property of AOB-t8 was regulated by the binding with Fe3 +. With the chelation of Fe3 +, the regulated molecular rigidity and the perturbed of electronic state and molecular geometry was suggested to be responsible for the accelerated isomerization of AOB-t8 to UV irradiation and the increased fluorescence lifetime of both trans- and cis-AOB-t8-Fe(III). Moreover, the reversible sensing of AOB-t8 was successfully observed by releasing the iron ion from AOB-t8-Fe(III) with the addition of citric acid.

  7. Uptake of isoprene, methacrylic acid and methyl methacrylate into aqueous solutions of sulfuric acid and hydrogen peroxide

    Institute of Scientific and Technical Information of China (English)

    Ze Liu; Maofa Ge; Weigang Wang

    2012-01-01

    Multiphase acid-catalyzed oxidation by hydrogen peroxide has been suggested to be a potential route to secondary organic aerosol formation from isoprene and its gas-phase oxidation products,but the lack of kinetics data significantly limited the evaluation of this process in the atmosphere.Here we report the first measurement of the uptake of isoprene,methacrylic acid and methyl methacrylate into aqueous solutions of sulfuric acid and hydrogen peroxide.Isoprene cannot readily partition into the solution because of its high volatility and low solubility,which hinders its further liquid-phase oxidation.Both methacrylic acid and methyl methacrylate can enter the solutions and be oxidized by hydrogen peroxide,and steady-state uptake was observed with the acidity of solution above 30 wt.% and 70 wt.%,respectively.The steady-state uptake coefficient of methacrylic acid is much larger than that of methyl methacrylate for a solution with same acidity.These observations can be explained by the different reactivity of these two compounds caused by the different electron-withdrawing conjugation between carboxyl and ester groups.The atmospheric lifetimes were estimated based on the calculated steady-state uptake coefficients.These results demonstrate that the multiphase acid-catalyzed oxidation of methacrylic acid plays a role in secondary organic aerosol formation,but for isoprene and methyl methacrylate,this process is not important in the troposphere.

  8. Chengzikou Block

    Institute of Scientific and Technical Information of China (English)

    1996-01-01

    @@ Chengzikou Block is located in the north of Hekou district, Dongying City, Shandong Province, adjacent to Bohai Bay. It can be geographically divided into three units: onshore, transitional zone and offshore ultrashallow zone, totally covering an area of 470 km2. The southern onshore area is low and gentle in topography;the northern shallow sea is at water depths of 2-8 m below sea level, and the transitional zone occupies more than 60% of the whole block. The climate belongs to temperate zone with seasonal wind. Highways are welldeveloped here, and the traffic is very convenient. The Chengzikou Block is about 80 km away from Dongying City and 290 km from Jinan City in the south. The northern offshore area of the block is 160 km away from Longkou port in the east and only 38 km away in the west from Zhuangxi port.

  9. Longmenshan Block

    Institute of Scientific and Technical Information of China (English)

    1996-01-01

    @@ Longmenshan Block is located in Jiange County of Jiangyou City in the northwest of Sichuan Basin. covering an area of 2 628 km2. Geologically, it is situated in the Mid-Longmenshan fault and fold belt, neighbouring Zitong Depression in its southeast. There are mountains surrounding its northwest , the rest area being hilly land,with the elevation of 500-700 m. The BaoCheng railway and the No. 108 highway run through the block, the traffic is very convenient.

  10. RAFT Copolymerization of Glycidyl Methacrylate and N,N-Dimethylaminoethyl Methacrylate

    Institute of Scientific and Technical Information of China (English)

    曹俊; 张丽芬; 潘向强; 程振平; 朱秀林

    2012-01-01

    In this work, copolymerization of two functional monomers, glycidyl methacrylate (GMA) and N,N-dimethylaminoethyl methacrylate (DMAEMA), was firstly carried out via reversible addition-fragmentation chain transfer (RAFT) polymerization successfully. The copolymerization kinetics was investigated under the molar ratio of n[GMA+DMAEMA]o/n[AIBN]o/n[CPDN]o=300/1/3 at 60℃. The copolymerization showed typical "living" features such as first-order polymerization kinetics, linear increase of molecular weight with monomer conversion and narrow molecular weight distribution. The reactivity ratios of GMA and DMAEMA were calculated by the extended Kelen-Tudos linearization methods. The epoxy group of the copolymer PGMA-co-PDMAEMA remained intact under the conditions of RAFT copolymerization and could easily be post-modified by ethylenedia- mine. Moreover, the modified copolymer could be used as a gene carrier.

  11. Self-assembling Characteristics of Amphiphilic Star Block Copolymers with a Polyelectrolyte Shell

    Institute of Scientific and Technical Information of China (English)

    S.Strandman; A.Zarembo; V.Aseyev; S.J.Butcher; H.Tenhu

    2007-01-01

    1 Results Amphiphilic block copolymers are capable of forming supramolecular assemblies resembling those observed in nature,such as spherical micelles,worm micelles,and vesicles.Changing the solvent composition,ionic strength or pH of the polymer solution may induce the self-assembly of block copolymers or trigger the transition between the geometries of noncovalent assemblies.In the current work,we have synthesised starlike amphiphilic block copolymers having hydrophobic poly(methyl methacrylate),PMMA,...

  12. Biocompatible Bacterial Cellulose-Poly(2-hydroxyethyl methacrylate Nanocomposite Films

    Directory of Open Access Journals (Sweden)

    Andrea G. P. R. Figueiredo

    2013-01-01

    Full Text Available A series of bacterial cellulose-poly(2-hydroxyethyl methacrylate nanocomposite films was prepared by in situ radical polymerization of 2-hydroxyethyl methacrylate (HEMA, using variable amounts of poly(ethylene glycol diacrylate (PEGDA as cross-linker. Thin films were obtained, and their physical, chemical, thermal, and mechanical properties were evaluated. The films showed improved translucency compared to BC and enhanced thermal stability and mechanical performance when compared to poly(2-hydroxyethyl methacrylate (PHEMA. Finally, BC/PHEMA nanocomposites proved to be nontoxic to human adipose-derived mesenchymal stem cells (ADSCs and thus are pointed as potential dry dressings for biomedical applications.

  13. Biocompatible Bacterial Cellulose-Poly(2-hydroxyethyl methacrylate) Nanocomposite Films

    Science.gov (United States)

    Figueiredo, Andrea G. P. R.; Figueiredo, Ana R. P.; Alonso-Varona, Ana; Fernandes, Susana C. M.; Palomares, Teodoro; Rubio-Azpeitia, Eva; Barros-Timmons, Ana; Silvestre, Armando J. D.; Pascoal Neto, Carlos; Freire, Carmen S. R.

    2013-01-01

    A series of bacterial cellulose-poly(2-hydroxyethyl methacrylate) nanocomposite films was prepared by in situ radical polymerization of 2-hydroxyethyl methacrylate (HEMA), using variable amounts of poly(ethylene glycol) diacrylate (PEGDA) as cross-linker. Thin films were obtained, and their physical, chemical, thermal, and mechanical properties were evaluated. The films showed improved translucency compared to BC and enhanced thermal stability and mechanical performance when compared to poly(2-hydroxyethyl methacrylate) (PHEMA). Finally, BC/PHEMA nanocomposites proved to be nontoxic to human adipose-derived mesenchymal stem cells (ADSCs) and thus are pointed as potential dry dressings for biomedical applications. PMID:24093101

  14. Chadong Block

    Institute of Scientific and Technical Information of China (English)

    1996-01-01

    @@ The Chadong Block, located in the east of Qaidam Basin, Qinghai Province, covers an area of 12 452 km2. It is bounded by Kunlum Mountains in the south and the northwest is closely adjacent to Aimunike Mountain.Rivers are widely distributed, which always run in NWSE direction, including the Sulunguole, Qaidam and Haluwusu Rivers. The traffic condition is good, the Qinghai-Tibet highway stretching through the whole area and the Lan-Qing railway, 20-50 km away from the block, passing from north to west. A lot of Mongolia minority people have settled there, of which herdsmen always live nearby the Qaidam River drainage area.

  15. Photoinduced formation of an azobenzene-based CD-active supramolecular cyclic dimer.

    Science.gov (United States)

    Sogawa, Hiromitsu; Terada, Kayo; Miyagi, Yu; Shiotsuki, Masashi; Inai, Yoshihito; Masuda, Toshio; Sanda, Fumio

    2015-04-27

    A series of new photo-responsive amino acid-derived azobenzenedicarboxylic acid derivatives (S)-1 a-e were synthesized. Compound (S)-1 a in the trans form exhibited no circular dichroism (CD) signal in DMF under ambient conditions, whereas intense Cotton effects were observed upon UV irradiation, indicating the formation of a chiral supramolecular structure in the cis form. The CD signals disappeared when trifluoroacetic acid (TFA) was added to the solution. The ester counterpart [(S)-1 a'] showed no CD signal. Hydrogen bonding between the carboxy groups seemed necessary for constructing the supramolecular structure. The kinetic studies of cis to trans isomerization of (S)-1 a demonstrated that the formation of a chiral supramolecule enhances the stability of the cis-azobenzene structure. The ESI mass spectrum of stilbenedicarboxylic acid (S)-4, an analogue of (S)-1 b, confirmed the formation of a dimer. A theoretical CD study revealed that (S)-1 a in the cis form should be present as a cyclic chiral dimer.

  16. Conformal Electroplating of Azobenzene-Based Solar Thermal Fuels onto Large-Area and Fiber Geometries.

    Science.gov (United States)

    Zhitomirsky, David; Grossman, Jeffrey C

    2016-10-05

    There is tremendous growth in fields where small functional molecules and colloidal nanomaterials are integrated into thin films for solid-state device applications. Many of these materials are synthesized in solution and there often exists a significant barrier to transition them into the solid state in an efficient manner. Here, we develop a methodology employing an electrodepositable copolymer consisting of small functional molecules for applications in solar energy harvesting and storage. We employ azobenzene solar thermal fuel polymers and functionalize them to enable deposition from low concentration solutions in methanol, resulting in uniform and large-area thin films. This approach enables conformal deposition on a variety of conducting substrates that can be either flat or structured depending on the application. Our approach further enables control over film growth via electrodepsition conditions and results in highly uniform films of hundreds of nanometers to microns in thickness. We demonstrate that this method enables superior retention of solar thermal fuel properties, with energy densities of ∼90 J/g, chargeability in the solid state, and exceptional materials utilization compared to other solid-state processing approaches. This novel approach is applicable to systems such as photon upconversion, photovoltaics, photosensing, light emission, and beyond, where small functional molecules enable solid-state applications.

  17. Application of peptide nucleic acids containing azobenzene self-assembled electrochemical biosensors in detecting DNA sequences

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Hybridization of peptide nucleic acids probe containing azobenzene (NH2-TNT4, N-PNAs) with DNA was performed by covalently immobilizing of NH2-TNT4 in sequence on the 3-mercaptopropionic acid self-assembled monolayer modified gold electrode with the helps of N-(3-dimethylaminopropy1)-N’-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS), and the hybrid was coded as N-PNAs/DNA. Using [Fe(CN)6]4-/3- (1:1) as the electrochemical indicator, the electrochemical properties of the N-PNAs self-assembled monolayer (N-PNAs-SAMs) and N-PNAs/DNA hybridization system under the conditions of before and after UV light irradiation were characterized with cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectra (EIS). Results showed that the redox currents decreased with the increase of irradiation time, suggesting that the ability of the charge transfer on the electrode surface was weakened and the conformation of hybrid system had been changed, and the control of PNAs/DNA hybridization could be realized by UV light irradiation.

  18. Photochromic molecular gyroscope with solid state rotational states determined by an azobenzene bridge.

    Science.gov (United States)

    Commins, Patrick; Garcia-Garibay, Miguel A

    2014-02-21

    We describe the synthesis, characterization, photochemical isomerization, and rotational dynamics of a crystalline molecular gyroscope containing an azobenzene bridge (trans-2) that spans from one end of the stator to other, with the intention of exploring its function as a molecular brake. While single crystal X-ray diffraction analysis of a photochemically inactive dichloromethane solvate was used to confirm the molecular and packing structures of trans-2, a nanocrystalline pseudopolymorph was shown to be photoactive, and it was analyzed by powder X-ray diffraction (PXRD), scanning electron microscopy, and variable temperature solid state (2)H NMR before and after photoisomerization. It was shown that the nanocrystalline suspension irradiated with λ = 340 nm reaches a photostationary state with 34% of cis-isomer, as compared to that observed in solution where the corresponding value is 74%. Line shape analysis of solid state (2)H NMR spectra of a phenylene-d4 isotopologue, obtained as a function of temperature, indicated that rotation in crystals of the trans-2 isomer, with a mean activation energy of 4.6 ± 0.6 kcal/mol and a pre-exponential factor exp(29.4 ± 1.7), is ten times faster than that of samples containing the cis-2 isomer, which has a higher mean activation energy of 5.1 ± 0.6 kcal/mol and a lower pre-exponential factor of exp(27.9 ± 1.3).

  19. Size Switchable Supramolecular Nanoparticle Based on Azobenzene Derivative within Anionic Pillar[5]arene

    Science.gov (United States)

    Zhang, Cai-Cai; Li, Sheng-Hua; Zhang, Cui-Fang; Liu, Yu

    2016-11-01

    A photo/thermal-switchable supramolecular nanoparticles assembly has been constructed based on an inclusion complex between anionic pillar[5]arene 2C-WP5A and azobenzene derivative Azo-py-OMe (G). The novel anionic pillar[5]arene-based host-guest inclusion complexation was investigated by the 1H NMR titration, 2D ROESY and isothermal titration microcalorimetry (ITC) showing high association constant (Ka) of (2.60 ± 0.06) × 104 M‑1 with 1:1 binding stoichiometry. Furthermore, the supramolecular nanoparticles assembly can be conveniently obtained from G and a small amount of 2C-WP5A in aqueous solution, which was so-called “host induced aggregating (HIA)”. The size and morphology of the supramolecular nanoparticles assembly were characterized by TEM and DLS. As a result of the photo/thermal-isomerization of G included in the cavity of 2C-WP5A, the size of these nanoparticles could reversibly change from ~800 nm to ~250 nm, which could switch the solution of this assembly from turbid to clear.

  20. Study on the prediction of visible absorption maxima of azobenzene compounds

    Institute of Scientific and Technical Information of China (English)

    LIU Jun-na; CHEN Zhi-rong; YUAN Shen-feng

    2005-01-01

    The geometries of azobenzene compounds are optimized with B3LYP/6-311 G* method, and analyzed with nature bond orbital, then their visible absorption maxima are calculated with TD-DFT method and ZINDO/S method respectively. The results agree well with the observed values. It was found that for the calculation of visible absorption using ZINDO/S method could rapidly yield better results by adjusting OWFπ-π (the relationship between π-π overlap weighting factor) value than by the TD-DFT method. The method of regression showing the linear relationship between OWFπ-π and BLN-N (nitrogen-nitrogen bond lengths) as OWFπ-π=-8.1537+6.5638BLN-N, can be explained in terms of quantum theory, and also be used for prediction of visible absorption maxima of other azobenzne dyes in the same series. This study on molecules' orbital geometry indicates that their visible absorption maxima correspond to the electron transition from HOMO (the highest occupied molecular orbital) to LUMO (the lowest unoccupied molecular orbital).

  1. Synthesis of organic-inorganic hybrid azobenzene materials for the preparation of nanofibers by electrospinning

    Science.gov (United States)

    Bućko, Aleksandra; Zielińska, Sonia; Ortyl, Ewelina; Larkowska, Maria; Barille, Regis

    2014-12-01

    The new photochromic hybrid materials containing different mole fractions of highly photoactive 4-[(E)-[4-[ethyl(2-hydroxyethyl)amino]phenyl]azo]-N-(4-methylpyrimidin-2-yl)benzenesulfonamide (SMERe) were prepared by a low temperature sol-gel process. The guest-host systems with triethoxyphenylsilane matrix were obtained. These materials were used to form thin transparent films by a spin-coating technique. Then the ability of thin hybrid films to reversible trans-cis photoisomerization under illumination was investigated using ellipsometry and UV-Vis spectroscopy. The reversible changes of refractive index of the films under illumination were in the range of 0.005-0.056. The maximum absorption of these materials was located at 462-486 nm. Moreover, the organic-inorganic azobenzene materials were used to form nanofibers by electrospinning using various parameters of the process. The microstructure of electrospun fibers depended on sols properties (e.g. concentration and viscosity of the sols) and process conditions (e.g. the applied voltage, temperature or type of the collector) at ambient conditions. The morphology of obtained nanofibers was analyzed by an optical microscopy and scanning electron microscopy. In most instances, the beadless fibers were obtained. The wettability of the surface of electrospun fibers deposited on glass substrates was investigated.

  2. Optical storage in azobenzene-containing epoxy polymers processed as Langmuir Blodgett films

    Energy Technology Data Exchange (ETDEWEB)

    Fernández, Raquel; Mondragon, Iñaki [‘Materials - Technologies’ Group, Department of Chemical and Environmental Engineering, Polytechnic School, Universidad País Vasco/Euskal Herriko Unibertsitatea, Pza Europa 1, 20018 Donostia-San Sebastián (Spain); Sanfelice, Rafaela C.; Pavinatto, Felippe J.; Oliveira, Osvaldo N. [Instituto de Física de São Carlos, Universidade de São Paulo, Av. Trabalhador São Carlense, 400, Centro, CEP 13560-970, São Carlos (Brazil); Oyanguren, Patricia [Institute of Materials Science and Technology (INTEMA), University of Mar del Plata and National Research Council (CONICET), J. B. Justo 4302, 7600 Mar del Plata (Argentina); Galante, María J., E-mail: galant@fi.mdp.edu.ar [Institute of Materials Science and Technology (INTEMA), University of Mar del Plata and National Research Council (CONICET), J. B. Justo 4302, 7600 Mar del Plata (Argentina)

    2013-04-01

    In this study, azocopolymers containing different main-chain segments have been synthesized with diglycidyl ether of bisphenol A (DGEBA, DER 332, n = 0.03) and the azochromophore Disperse Orange 3 (DO3) cured with two monoamines, viz. benzylamine (BA) and m-toluidine (MT). The photoinduced birefringence was investigated in films produced with these azopolymers using the spin coating (SC) and Langmuir Blodgett (LB) techniques. In the LB films, birefringence increased with the content of azochromophore and the film thickness, as expected. The nanostructured nature of the LB films led to an enhanced birefringence and faster dynamics in the writing process, compared to the SC films. In summary, the combination of azocopolymers and the LB method may allow materials with tuned properties for various optical applications, including in biological systems were photoisomerization may be used to trigger actions such as drug delivery. Highlights: ► Langmuir Blodgett (LB) films of epoxy-based azopolymers were obtained and analyzed. ► Optical properties of LB and spin coated (SC) films were compared. ► Azo content, structure, laser power and number of layers were main factors studied. ► LB films had larger free volume for the azobenzenes isomerization than SC. ► LB films led to higher birefringence and faster dynamics compared to SC.

  3. Photocontrol of Voltage-Gated Ion Channel Activity by Azobenzene Trimethylammonium Bromide in Neonatal Rat Cardiomyocytes.

    Directory of Open Access Journals (Sweden)

    Sheyda R Frolova

    Full Text Available The ability of azobenzene trimethylammonium bromide (azoTAB to sensitize cardiac tissue excitability to light was recently reported. The dark, thermally relaxed trans- isomer of azoTAB suppressed spontaneous activity and excitation propagation speed, whereas the cis- isomer had no detectable effect on the electrical properties of cardiomyocyte monolayers. As the membrane potential of cardiac cells is mainly controlled by activity of voltage-gated ion channels, this study examined whether the sensitization effect of azoTAB was exerted primarily via the modulation of voltage-gated ion channel activity. The effects of trans- and cis- isomers of azoTAB on voltage-dependent sodium (INav, calcium (ICav, and potassium (IKv currents in isolated neonatal rat cardiomyocytes were investigated using the whole-cell patch-clamp technique. The experiments showed that azoTAB modulated ion currents, causing suppression of sodium (Na+ and calcium (Ca2+ currents and potentiation of net potassium (K+ currents. This finding confirms that azoTAB-effect on cardiac tissue excitability do indeed result from modulation of voltage-gated ion channels responsible for action potential.

  4. Quantitative Structure-activity Relationships for Anaerobic Biodegradation of Substituted Azobenzenes

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xiao-yi; ZHU Huai-wu; LUO Shi-xia; WANG Zheng-wu; XIAO Han

    2004-01-01

    The degradation rates of the azo-bonds of a series of substituted azobenzenes caused by anaerobic sludge digestion were determined by measuring the biggest change of the absorption peak area of the UV-Vis spectra of the anaerobic sludge system before and after degradation. The electronic structure of the molecules was calculated by using the quantum chemistry semiempirical method AM1. The research on the correlation between the biodegradability of the azo-bond and the molecular structure descriptors has led to the following results. (1) There is an obvious relationship between the degradation rate D and the difference Δqπ in π-charge density of the azo-bond. (2) The different substituents in the molecules result in a wave pattern of π-charge distribution and the increasing of the flowability of π-electron. A good flowability of the π-charge favors the reduction between electron contributing azo groups. (3) The effect of the substituents on the π-electron system depends on the electromerization of the substituents in combination with the conjugated systems.

  5. Two-photon brightness of azobenzene photoswitches designed for glutamate receptor optogenetics.

    Science.gov (United States)

    Carroll, Elizabeth C; Berlin, Shai; Levitz, Joshua; Kienzler, Michael A; Yuan, Zhe; Madsen, Dorte; Larsen, Delmar S; Isacoff, Ehud Y

    2015-02-17

    Mammalian neurotransmitter-gated receptors can be conjugated to photoswitchable tethered ligands (PTLs) to enable photoactivation, or photoantagonism, while preserving normal function at neuronal synapses. "MAG" PTLs for ionotropic and metabotropic glutamate receptors (GluRs) are based on an azobenzene photoswitch that is optimally switched into the liganding state by blue or near-UV light, wavelengths that penetrate poorly into the brain. To facilitate deep-tissue photoactivation with near-infrared light, we measured the efficacy of two-photon (2P) excitation for two MAG molecules using nonlinear spectroscopy. Based on quantitative characterization, we find a recently designed second generation PTL, L-MAG0460, to have a favorable 2P absorbance peak at 850 nm, enabling efficient 2P activation of the GluK2 kainate receptor, LiGluR. We also achieve 2P photoactivation of a metabotropic receptor, LimGluR3, with a new mGluR-specific PTL, D-MAG0460. 2P photoswitching is efficiently achieved using digital holography to shape illumination over single somata of cultured neurons. Simultaneous Ca(2+)-imaging reports on 2P photoswitching in multiple cells with high temporal resolution. The combination of electrophysiology or Ca(2+) imaging with 2P activation by optical wavefront shaping should make second generation PTL-controlled receptors suitable for studies of intact neural circuits.

  6. Genotoxicity of a variety of azobenzene and aminoazobenzene compounds in the hepatocyte/DNA repair test and the Salmonella/mutagenicity test.

    Science.gov (United States)

    Mori, H; Mori, Y; Sugie, S; Yoshimi, N; Takahashi, M; Ni-i, H; Yamazaki, H; Toyoshi, K; Williams, G M

    1986-04-01

    Genotoxicity of 39 azo dye compounds of azobenzenes, aminoazobenzenes, and diaminoazobenzenes was examined in the hepatocyte primary culture/DNA repair test. Azobenzene (AzB) and 3,3'- or 4,4'-substituted azobenzenes such as (CH3)2AzB, (CH2OH)2AzB, (CH2OCOCH3)2AzB, and (CH2Cl)2AzB did not generate DNA repair, indicating lack of genotoxicity of these compounds. In contrast, all of 24 aminoazobenzenes, including those of unknown carcinogenicity, i.e., 3'-methyl-4-aminoazobenzene, 3'-CH2OH-aminoazobenzene, 3'-hydroxymethyl-N-methyl-4-aminoazobenzene, 3'-COOH-methylaminoazobenzene, 4'-formyl-N,N-dimethyl-4-aminoazobenzene, 3'-CH2Cl-dimethylaminoazobenzene, 4'-CH2Cl-dimethylaminoazobenzene, and 2'-, 3'-, or 4'-CH2OCOCH3-dimethylaminoazobenzene, elicited DNA repair synthesis. A positive DNA repair response was obtained for the 3 of 6 tested diaminoazobenzenes, i.e., N'-acetyl-N'-methyl-4-amino-dimethylaminoazobenzene, N'-acetyl-N'-methyl-4-amino-methylaminoazobenzene, and N'-acetyl-N'-methyl-4-amino-N-acetyl-methylaminoazobenzene, which are known to be carcinogenic. These results indicate that the amino group is functional for the expression of genotoxicity of azobenzene compounds. Twenty-one azobenzenes of these 3 classes were also examined for their mutagenicity in the Salmonella/mutagenicity assay. These results were almost identical with those of the DNA repair test except for several azo dyes such as AzB and 4,4'-(CH2Oacetyl)2AzB of the azobenzenes and N'-acetyl-4-amino-dimethylaminoazobenzene and N'-acetyl-N-methyl-4-amino-N-acetyl methylaminoazobenzene of the diaminoazobenzenes.

  7. Methacrylate-based monolithic layers for planar chromatography of polymers.

    Science.gov (United States)

    Maksimova, E F; Vlakh, E G; Tennikova, T B

    2011-04-29

    A series of macroporous monolithic methacrylate-based materials was synthesized by in situ free radical UV-initiated copolymerization of functional monomers, such as glycidyl methacrylate (GMA), butyl methacrylate (BuMA), 2-aminoethyl methacrylate (AEMA), 2-hydroxyethyl methacrylate (HEMA) and 2-cyanoethyl methacrylate (CEMA), with crosslinking agent, namely, ethylene glycol dimethacrylate (EDMA). The materials obtained were applied as the stationary phases in simple and robust technique - planar chromatography (PLC). The method of separation layer fabrication representing macroporous polymer monolith bound to the specially prepared glass surface was developed and optimized. The GMA-EDMA and BuMA-EDMA matrixes were successfully applied for the separation of low molecular weight compounds (the mixture of several dies), as well as poly(vinylpyrrolidone) and polystyrene homopolymers of different molecular weights using reversed-phase mechanism. The materials based on copolymers AEMA-HEMA-EDMA and CEMA-HEMA-EDMA were used for normal-phase PLC separation of 2,4-dinitrophenyl amino acids and polystyrene standards.

  8. MOLECULAR MUTAGENESIS INDUCED BY GLYCIDYL METHACRYLATE

    Institute of Scientific and Technical Information of China (English)

    高惠兰; 左谨; 谢大英; 方福德

    1994-01-01

    Glycidyl methacrylate(GMA)is a recently recognized mutagen.In order to explore the mutagenicity and mechanism of GMA,plasmid pBR322 was used for in vitro binding,mutant screening,restriction enzyme map-ping,and DNA sequencing.To explore the mechanism by which an initial premutational event is converted into a stable heritable mutation,pBR322 and GMA-bound pBR322 were transformed into E.coli HB101,and the follow-ing results were obtainge:1)GMA-bound pBR322 induced phenotype changes in competent cells.Two stable and heritable mutants were isolated (ApRTcS and ApSTcR).2)When restriction enzyme mapping was used to analyze the mutant ApRTcS,four of seven maps showed changes,but no large DNA insertion or deletion were observed.3)The frequency of deletion and insertion forms counted about 10%.Sequence specificity and hot spot regions were evident in the sequence analysis of mutated plasmid.The above results indicate that the premutagenic lesions of plasmid induced by GMA can be converted into point mutatons in vivo.

  9. Chlorhexidine-releasing methacrylate dental composite materials.

    Science.gov (United States)

    Leung, Danny; Spratt, David A; Pratten, Jonathan; Gulabivala, Kishor; Mordan, Nicola J; Young, Anne M

    2005-12-01

    Light curable antibacterial, dental composite restoration materials, consisting of 80 wt% of a strontium fluoroaluminosilicate glass dispersed in methacrylate monomers have been produced. The monomers contained 40-100 wt% of a 10 wt% chlorhexidine diacetate (CHXA) in hydroxyethylmethacrylate (HEMA) solution and 60-0 wt% of a 50/50 mix of urethane dimethacrylate (UDMA) and triethyleneglycol dimethacrylate (TEGDMA). On raising HEMA content, light cure polymerisation rates decreased. Conversely, water sorption induced swelling and rates of diffusion controlled CHXA release from the set materials increased. Experimental composites with 50 and 90 wt% of the CHXA in HEMA solution in the monomer were shown, within a constant depth film fermentor (CDFF), to have slower rates of biofilm growth on their surfaces between 1 and 7 days than the commercial dental composite Z250 or fluoride-releasing dental cements, Fuji II LC and Fuji IX. When an excavated bovine dentine cylinder re-filled with Z250 was placed for 10 weeks in the CDFF, both bacteria and polymers from the artificial saliva penetrated between the material and dentine. With the 50 wt% experimental HEMA/CHXA formulation, this bacterial microleakage was substantially reduced. Polymer leakage, however, still occurred. Both polymer and bacterial microleakage were prevented with a 90 wt% HEMA/CHXA restoration in the bovine dentine due to swelling compensation for polymerisation shrinkage in combination with antibacterial release.

  10. Properties of mixed-crystalline organic material prepared by zone levelling IV. Melting properties and excess enthalpies of (trans-azobenzene + trans-stilbene)

    NARCIS (Netherlands)

    Bouwstra, J.A.; Leeuw, V.V. de; Miltenburg, J.C.

    1985-01-01

    Homogeneous mixed crystals of (trans-azobenzene + trans-stilbene) were prepared. Molar heat capacities of the pure substances and the mixed crystals were determined at temperatures from 300 to 400 K. The melting temperatures and molar enthalpies of fusion were measured for trans-stilbene and trans-a

  11. Atomic force and optical near-field microscopic investigations of polarization holographic gratings in a liquid crystalline azobenzene side-chain polyester

    DEFF Research Database (Denmark)

    Ramanujam, P.S.; Holme, N.C.R.; Hvilsted, S.

    1996-01-01

    Atomic force and scanning near-field optical microscopic investigations have been carried out on a polarization holographic grating recorded in an azobenzene side-chain Liquid crystalline polyester. It has been found that immediately following laser irradiation, a topographic surface grating...

  12. Dethreading of a Photoactive Azobenzene-Containing Molecular Axle from a Crown Ether Ring: A Computational Investigation.

    Science.gov (United States)

    Tabacchi, Gloria; Silvi, Serena; Venturi, Margherita; Credi, Alberto; Fois, Ettore

    2016-06-17

    Pseudorotaxanes formed by a dibenzo[24]crown-8 ring (R) and a dialkylammonium axle bearing either two E- or two Z-azobenzene units (EE-A or ZZ-A) revealed useful for the construction of light-powered molecular machines and motors, as they provide the opportunity of photocontrolling self-assembly/disassembly processes. The potential energies profiles for the dethreading of these complexes have been investigated by adopting a combination of first-principles molecular dynamics, metadynamics and quantum-chemical geometry optimization approaches. While the dethreading of the EE-A axle is associated with a monotonic energy increase, for that of the ZZ-A axle a transition state and an intermediate structure, in which the components are still threaded together, are found. The rate determining step for the dethreading of the ZZ axle has a higher energy barrier than that of the EE axle, in agreement with the experimental kinetic data. Moreover, the results suggest that the elliptic shape of the ring cavity is important for discriminating between the E and Z terminal azobenzene during dethreading.

  13. A Light-Responsive Self-Assembly Formed by a Cationic Azobenzene Derivative and SDS as a Drug Delivery System

    Science.gov (United States)

    Geng, Shengyong; Wang, Yuzhu; Wang, Liping; Kouyama, Tsutomu; Gotoh, Toshiaki; Wada, Satoshi; Wang, Jin-Ye

    2017-01-01

    The structure of a self-assembly formed from a cationic azobenzene derivative, 4-cholesterocarbonyl-4‧-(N,N,N-triethylamine butyloxyl bromide) azobenzene (CAB) and surfactant sodium dodecyl sulfate (SDS) in aqueous solution was studied by cryo-TEM and synchrotron radiation small-angle X-ray scattering (SAXS). Both unilamellar and multilamellar vesicles could be observed. CAB in vesicles were capable to undergo reversible trans-to-cis isomerization upon UV or visible light irradiation. The structural change upon UV light irradiation could be catched by SAXS, which demonstrated that the interlamellar spacing of the cis-multilamellar vesicles increased by 0.2-0.3 nm. Based on this microstructural change, the release of rhodamine B (RhB) and doxorubicin (DOX) could be triggered by UV irradiation. When incubated NIH 3T3 cells and Bel 7402 cells with DOX-loaded CAB/SDS vesicles, UV irradiation induced DOX release decreased the viability of both cell lines significantly compared with the non-irradiated cells. The in vitro experiment indicated that CAB/SDS vesicles had high efficiency to deliver loaded molecules into cells. The in vivo experiment showed that CAB/SDS vesicles not only have high drug delivery efficiency into rat retinas, but also could maintain high drug concentration for a longer time. CAB/SDS catanionic vesicles may find potential applications as a smart drug delivery system for controlled release by light.

  14. Through-space (19)F-(19)F spin-spin coupling in ortho-fluoro Z-azobenzene.

    Science.gov (United States)

    Rastogi, Shiva K; Rogers, Robert A; Shi, Justin; Brown, Christopher T; Salinas, Cindy; Martin, Katherine M; Armitage, Jacob; Dorsey, Christopher; Chun, Gao; Rinaldi, Peter; Brittain, William J

    2016-02-01

    We report through-space (TS) (19)F-(19)F coupling for ortho-fluoro-substituted Z-azobenzenes. The magnitude of the TS-coupling constant ((TS) JFF ) ranged from 2.2-5.9 Hz. Using empirical formulas reported in the literature, these coupling constants correspond to non-bonded F-F distances (dFF) of 3.0-3.5 Å. These non-bonded distances are significantly smaller than those determined by X-ray crystallography or density functional theory, which argues that simple models of (19)F-(19)F TS spin-spin coupling solely based dFF are not applicable. (1)H, (13)C and (19)F data are reported for both the E and Z isomers of ten fluorinated azobenzenes. Density functional theory [B3YLP/6-311++G(d,p)] was used to calculate (19) F chemical shifts, and the calculated values deviated 0.3-10.0 ppm compared with experimental values.

  15. A Light-Responsive Self-Assembly Formed by a Cationic Azobenzene Derivative and SDS as a Drug Delivery System

    Science.gov (United States)

    Geng, Shengyong; Wang, Yuzhu; Wang, Liping; Kouyama, Tsutomu; Gotoh, Toshiaki; Wada, Satoshi; Wang, Jin-Ye

    2017-01-01

    The structure of a self-assembly formed from a cationic azobenzene derivative, 4-cholesterocarbonyl-4′-(N,N,N-triethylamine butyloxyl bromide) azobenzene (CAB) and surfactant sodium dodecyl sulfate (SDS) in aqueous solution was studied by cryo-TEM and synchrotron radiation small-angle X-ray scattering (SAXS). Both unilamellar and multilamellar vesicles could be observed. CAB in vesicles were capable to undergo reversible trans-to-cis isomerization upon UV or visible light irradiation. The structural change upon UV light irradiation could be catched by SAXS, which demonstrated that the interlamellar spacing of the cis-multilamellar vesicles increased by 0.2–0.3 nm. Based on this microstructural change, the release of rhodamine B (RhB) and doxorubicin (DOX) could be triggered by UV irradiation. When incubated NIH 3T3 cells and Bel 7402 cells with DOX-loaded CAB/SDS vesicles, UV irradiation induced DOX release decreased the viability of both cell lines significantly compared with the non-irradiated cells. The in vitro experiment indicated that CAB/SDS vesicles had high efficiency to deliver loaded molecules into cells. The in vivo experiment showed that CAB/SDS vesicles not only have high drug delivery efficiency into rat retinas, but also could maintain high drug concentration for a longer time. CAB/SDS catanionic vesicles may find potential applications as a smart drug delivery system for controlled release by light. PMID:28051069

  16. Degree of conversion and leached monomers of urethane dimethacrylate-hydroxypropyl methacrylate-based dental resin systems.

    Science.gov (United States)

    Zhang, Meng; Puska, Mervi A; Botelho, Michael G; Säilynoja, Eija S; Matinlinna, Jukka P

    2016-01-01

    The degree of conversion (DC) and monomer leaching of three experimental urethane dimethacrylate (UEDMA)-hydroxypropyl methacrylate (HPMA)-based resin systems were studied. Three experimental resins (E1: 70.6 wt% UEDMA + 27.4 wt% HPMA, E2: 80.6 wt% UEDMA + 17.4 wt% HPMA, E3: 90.6 wt% UEDMA + 7.4 wt% HPMA) and one control resin [C: 70.6 wt% bis-phenol A glycidyl methacrylate (bis-GMA) + 27.4 wt% methyl methacrylate (MMA)] were prepared. For the DC test, cylindrical specimens [1.5 mm (h) × 6 mm (d)] were scanned with an ATR-FTIR instrument before and after light-curing (n = 5). For the monomer leaching test, block-shaped specimens [5.67 mm (l) × 2.00 mm (w) × 2.00 mm (h)] were light-cured (n = 6), stored in a 75% ethanol:water solution for 3 days, and then analyzed with HPLC. The UEDMA-HPMA-based experimental groups showed higher DC (62-78%) than the bis-GMA-MMA-based control group (58-66%), and the DC decreased as the UEDMA content increased (P < 0.05). Amongst the four groups, E3 exhibited the lowest leaching of both mono methacrylate (0.1% HPMA) and dimethacrylate (<0.043% UEDMA) monomers after 30 or 40 s of curing. The UEDMA-HPMA-based resins, therefore, exhibited higher DC and less monomer leaching compared to the bis-GMA-MMA-based resin. (J Oral Sci 58, 15-22, 2016).

  17. Investigation of the homogeneity of methacrylate allergens in commercially available patch test preparations

    DEFF Research Database (Denmark)

    Mose, Kristian Fredløv; Andersen, Klaus Ejner; Christensen, Lars Porskjaer

    2013-01-01

    The homogeneity of methacrylates in commercial patch test preparations has not yet been investigated. Inhomogeneous patch test preparations may give rise to false-negative or false-positive patch test results in patients suspected of having methacrylate allergy....

  18. GLYCOL METHACRYLATE EMBEDDING OF ALGINATE-POLYLYSINE MICROENCAPSULATED PANCREATIC-ISLETS

    NARCIS (Netherlands)

    FRITSCHY, WM; GERRITS, PO; WOLTERS, GHJ; PASMA, A; VANSCHILFGAARDE, R

    1995-01-01

    A method for processing and embedding alginate-polylysine microencapsulated pancreatic tissue in glycol methacrylate resin (GMA) is described. Fixation in 4% phosphate buffered formaldehyde, processing in ascending concentrations of glycol methacrylate monomer and embedding in Technovit 7100 results

  19. Final report of the safety assessment of methacrylate ester monomers used in nail enhancement products.

    Science.gov (United States)

    2005-01-01

    Methacrylate ester monomers are used in as artificial nail builders in nail enhancement products. They undergo rapid polymerization to form a hard material on the nail that is then shaped. While Ethyl Methacrylate is the primary monomer used in nail enhancement products, other methacrylate esters are also used. This safety assessment addresses 22 other methacrylate esters reported by industry to be present in small percentages as artificial nail builders in cosmetic products. They function to speed up polymerization and/or form cross-links. Only Tetrahydrofurfuryl Methacrylate was reported to the FDA to be in current use. The polymerization rates of these methacrylate esters are within the same range as Ethyl Methacrylate. While data are not available on all of these methacrylate esters, the available data demonstrated little acute oral, dermal, or i.p. toxicity. In a 28-day inhalation study on rats, Butyl Methacrylate caused upper airway irritation; the NOAEL was 1801 mg/m3. In a 28-day oral toxicity study on rats, t-Butyl Methacrylate had a NOAEL of 20 mg/kg/day. Beagle dogs dosed with 0.2 to 2.0 g/kg/day of C12 to C18 methacrylate monomers for 13 weeks exhibited effects only in the highest dose group: weight loss, emesis, diarrhea, mucoid feces, or salivation were observed. Butyl Methacrylate (0.1 M) and Isobutyl Methacrylate (0.1 M) are mildly irritating to the rabbit eye. HEMA is corrosive when instilled in the rabbit eye, while PEG-4 Dimethacrylate and Trimethylolpropane Trimethacrylate are minimally irritating to the eye. Dermal irritation caused by methacrylates is documented in guinea pigs and rabbits. In guinea pigs, HEMA, Isopropylidenediphenyl Bisglycidyl Methacrylate, Lauryl Methacrylate, and Trimethylolpropane Trimethacrylate are strong sensitizers; Butyl Methacrylate, Cyclohexyl Methacrylate, Hexyl Methacrylate, and Urethane Methacrylate are moderate sensitizers; Hydroxypropyl Methacrylate is a weak sensitizer; and PEG-4 Dimethacrylate and

  20. Fictitious crack modelling of polymethyl methacrylate porous material

    NARCIS (Netherlands)

    Jimenez Pique, E.; Dortmans, L.J.M.G.; With, G. de

    2002-01-01

    Fracture tests were performed on a granular polymethyl methacrylate porous material used as a mould for white were castings. Two types of sample geometry (single-edge notch beam and wedge opening load) and two types of environment (dry at room temperature and in water at 45°C) were used and the forc

  1. Cytotoxicity evaluation of methacrylate- and silorane-based composite resins

    Directory of Open Access Journals (Sweden)

    Gulsah Goktolga Akin

    2012-10-01

    Full Text Available

    Objectives: The objective of this study was to investigate and compare the cytotoxic effects of four composite resin materials with different content.

    Material and Methods: Two traditional methacrylate-based (Clearfil AP-X, RefleXions, as well as a self-adhering methacrylate-based (Vertise Flow and a silorane-based (Filtek Silorane composite resin were tested in the experiment. Ten cylindrical specimens were made of each material, using a mould (2mm. thick and 8 mm. in diameter. An agar diffusion method was employed, and cytotoxicity rankings were determined using lysis index scores. For statistical analysis, Kruskal-Wallis and Mann-Whitney U-tests were used.

    Results: Amongst the composite resins, the silorane-based composite was found to be less cytotoxic than the methacrylate-based composite resins, which all had the same cytotoxicity ranking.

    Conclusions: The silorane-based composite resin was considered more biocompatible than the methacrylate-based composite resins.

  2. Allergic contact dermatitis to methacrylates in ECG electrode dots.

    Science.gov (United States)

    Lyons, Georgina; Nixon, Rosemary

    2013-02-01

    Acrylates are used widely in acrylic nails, dental restorative materials, paint, varnish, printing ink, adhesives, glue, orthopaedic prostheses, bone cement and diathermy pads. This is the first case of allergic contact dermatitis to methacrylates in electrocardiogram electrode dots reported in the literature.

  3. Synthesis of acrylates and methacrylates from coal-derived syngas

    Energy Technology Data Exchange (ETDEWEB)

    Spivey, J.J.; Gogate, M.R.; Jang, B.W.L. [Bechtel, San Francisco, CA (United States)] [and others

    1995-12-31

    Acrylates and methacrylates are among the most widely used chemical intermediates in the world. One of the key chemicals of this type is methyl methacrylate. Of the 4 billion pounds produced each year, roughly 85% is made using the acetone-cyanohydrin process, which requires handling of large quantities of hydrogen cyanide and produces ammonium sulfate wastes that pose an environmental disposal challenge. The U.S. Department of Energy and Eastman Chemical Company are sharing the cost of research to develop an alternative process for the synthesis of methyl methacrylate from syngas. Research Triangle Institute is focusing on the synthesis and testing of active catalysts for the condensation reactions, and Bechtel is analyzing the costs to determine the competitiveness of several process alternatives. Results thus far show that the catalysts for the condensation of formaldehyde and the propionate are key to selectively producing the desired product, methacrylic acid, with a high yield. These condensation catalysts have both acid and base functions and the strength and distribution of these acid-base sites controls the product selectivity and yield.

  4. Stereocomplex Formation of Atactic Poly(methyl methacrylate)

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Stereocomplexes formed in atactic poly(methyl methacrylate) (a-PMMA) films cast form different solvents were studied by means of Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). The growth of stereocomplex was a function of annealing temperature and annealing time, respectively.

  5. Synthesis and Characterization of Carboxymethylcellulose-Methacrylate Hydrogel Cell Scaffolds

    Directory of Open Access Journals (Sweden)

    Andreia Ribeiro

    2010-08-01

    Full Text Available Many carbohydrates pose advantages for tissue engineering applications due to their hydrophilicity, degradability, and availability of chemical groups for modification. For example, carboxymethylcellulose (CMC is a water-soluble cellulose derivative that is degradable by cellulase. Though this enzyme is not synthesized by mammalian cells, cellulase and the fragments derived from CMC degradation are biocompatible. With this in mind, we created biocompatible, selectively degradable CMC-based hydrogels that are stable in routine culture, but degrade when exposed to exogenous cellulase. Solutions of CMC-methacrylate and polyethylene glycol dimethacrylate (PEG-DM were co-crosslinked to form stable hydrogels; we found that greater CMC-methacrylate content resulted in increased gel swelling, protein diffusion and rates of degradation by cellulase, as well as decreased gel shear modulus. CMC-methacrylate/PEG-DM gels modified with the adhesive peptide RGD supported fibroblast adhesion and viability. We conclude that hydrogels based on CMC-methacrylate are suitable for bioengineering applications where selective degradability may be favorable, such as cell scaffolds or controlled release devices.

  6. Controlled/"Living" Radical Polymerization of (-)-Menthyl Methacrylate

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The atom transfer radical polymerization(ATRP) of (-)-menthyl methacrylate((-)-MnMA) mediated by CuCl/bipyridine and ethyl 2-bromopropionate or 1-phenylethyl bromide in THF system has been studied. The dependence of the specific rotation on molecular weight and the CD of Poly((-)-MnMA) thus obtained was investigated.

  7. Reverse Atom Transfer Radical Polymerization of (-)-Menthyl Methacrylate

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The reverse atom transfer radical polymerization(RATRP) of (-)-menthyl methacrylate ((-)-MnMA) with AIBN(AIBN/CuCl2/bipyridine(bipy) or (-)sparteine((-)Sp) =1/2/4) initiating system in THF has been studied. The dependence of the specific rotation on molecular weight was investigated.

  8. Triazene UV-triggered photogeneration of silver/gold nanoparticles in block copolymer templates

    Energy Technology Data Exchange (ETDEWEB)

    Melinte, Violeta; Chibac, Andreea; Buruiana, Tinca; Hitruc, Gabriela; Buruiana, Emil C., E-mail: emilbur@icmpp.ro [Petru Poni Institute of Macromolecular Chemistry, Polyaddition and Photochemistry Department (Romania)

    2015-10-15

    This article describes an attractive way to in situ create noble metal nanoparticles in block copolymer matrixes through the UV-triggered photodecomposition of the photolabile triazene units without the use of any conventional reducing agent. The poly(isodecyl methacrylate-co-triazene urethane methacrylate) random copolymer containing pendent photocleavable triazene junctions (COP-1) was synthesized under RAFT conditions and subsequently employed as macroinitiator to obtain a block copolymer, namely poly(isodecyl methacrylate-co-triazene urethane methacrylate)-block-poly(acrylic acid) (COP-2). The photogeneration of silver/gold metal nanoparticles (NPs) from noble metal precursors (1 wt% AgNO{sub 3} or AuBr{sub 3} metal salts) induced through the UV decomposition of triazene units with the formation of some radical active species was monitored in solution and thin films. The in situ growth of Ag/Au nanostructures into polymer matrixes for which the light is a key element has been confirmed by UV spectroscopy and TEM analysis. The TEM images allowed the visualization of the silver NPs (sizes of 4–16 nm in COP-1 and of 2–6 nm in COP-2) as well as of the gold NPs (sizes between 10 and 20 nm in COP-1 and from 15 to 25 nm in COP-2), which are mainly spherical in shape, even though there is some triangular or hexagonal gold nanoparticles.

  9. Polymerization contraction and conversion of light-curing BisGMA-based methacrylate resins.

    Science.gov (United States)

    Venhoven, B A; de Gee, A J; Davidson, C L

    1993-09-01

    The aim of this study was to investigate the polymerization contraction and the conversion of light-curing methacrylate resins based on bisphenol-A bis(2-hydroxypropyl)methacrylate (BisGMA) diluted with triethylene glycol dimethyacrylate (TEGDMA), methyl methacrylate (MMA), hydroxypropyl methacrylate (HPMA) or (+/-)-2-ethylhexyl methacrylate (EHMA). The contraction measurements were carried out with a linometer, a simple device to determine true linear polymerization contraction of liquid monomers at ambient temperature. The contraction increased with the amount of diluting monomer. The estimated conversion of the BisGMA-TEGDMA, calculated using the contraction, is consistent with literature values. The BisGMA-HPMA mixtures showed high conversions at moderate contraction.

  10. Structure-property relationships of symmetrical and asymmetrical azobenzene derivatives as gelators and their self-assemblies.

    Science.gov (United States)

    Balamurugan, Rathinam; Kai-Ming, Wu; Chien, Chih-Chieh; Liu, Jui Hsiang

    2014-11-28

    Two different series of symmetrical and asymmetrical azobenzenes containing terminal cholesteryl/adamantyl derivatives (SAC/SAA and AAC) with varying spacer lengths (alkyl chains) have been developed. The gelation and aggregation of these derivatives were studied relative to structural motifs, spacer lengths, solvent affinity, temperatures and light conditions. Among these derivatives, the cholesteryl derivatives that have short alkyl chains (derivatives with longer alkyl chains (11 spacer) and adamantyl derivatives did not possess this ability. Self-assembled fibrous structures were constructed by gelators with short alkyl chains (derivatives, respectively. However, the cholesteryl derivative without a spacer (AAC0) did not exhibit any liquid crystalline phase but acted as an efficient gelator relative to the other gelators in this study.

  11. Optical properties of azobenzene-functionalized self-assembled monolayers: Intermolecular coupling and many-body interactions

    Science.gov (United States)

    Cocchi, Caterina; Moldt, Thomas; Gahl, Cornelius; Weinelt, Martin; Draxl, Claudia

    2016-12-01

    In a joint theoretical and experimental work, the optical properties of azobenzene-functionalized self-assembled monolayers (SAMs) are studied at different molecular packing densities. Our results, based on density-functional and many-body perturbation theory, as well as on differential reflectance (DR) spectroscopy, shed light on the microscopic mechanisms ruling photo-absorption in these systems. While the optical excitations are intrinsically excitonic in nature, regardless of the molecular concentration, in densely packed SAMs intermolecular coupling and local-field effects are responsible for a sizable weakening of the exciton binding strength. Through a detailed analysis of the character of the electron-hole pairs, we show that distinct excitations involved in the photo-isomerization at low molecular concentrations are dramatically broadened by intermolecular interactions. Spectral shifts in the calculated DR spectra are in good agreement with the experimental results. Our findings represent an important step forward to rationalize the excited-state properties of these complex materials.

  12. Reflection Band Control of Inverse Opal Film with Photoresponse Properties of Push-Pull Type Azobenzene LC Polymers

    Directory of Open Access Journals (Sweden)

    Sunnam Kim

    2008-01-01

    Full Text Available DcAz2Mc and DR1Mc molecules having push-pull type of azobenzene groups are synthesized, and their photo-orientational behaviors are investigated in the polymer system. In order to understand the relationship between a molecular structure and its physical properties, electronic structure calculation is computationally carried out. Regarding to their photo response properties, the copolymers of poly(DcAz2Mc-co-M6PBMe and poly(DR1Mc-co-M6PBMe are infiltrated into inverse opal films, and Bragg reflection shifts are observed under photostimuli. When the linearly polarized light is irradiated, Bragg reflection bands are shifted to the longer wavelength region as reflective index increases.

  13. Azobenzene liquid crystalline materials for efficient optical switching with pulsed and/or continuous wave laser beams.

    Science.gov (United States)

    Hrozhyk, Uladzimir A; Serak, Svetlana V; Tabiryan, Nelson V; Hoke, Landa; Steeves, Diane M; Kimball, Brian R

    2010-04-12

    This study compares optical switching capabilities of liquid crystal (LC) materials based on different classes of azobenzene dyes. LCs based on molecules containing benzene rings with nearly symmetrical pi-pi conjugation respond more efficiently to a cw beam than to a nanosecond laser pulse and maintain the changes induced by the beam for tens of hours. Using azo dye molecules containing two benzene rings with push-pull pi-pi conjugation we demonstrate high photosensitivity to both a cw beam as well as nanosecond laser pulse with only 1 s relaxation of light-induced changes in material properties. Even faster, 1 ms restoration time is obtained for azo dye molecules containing hetaryl (benzothiazole) ring with enhanced push-pull pi-pi conjugation. These materials respond most efficiently to pulsed excitation while discriminating cw radiation.

  14. Synthesis of molecularly imprinted organic-inorganic hybrid azobenzene materials by sol-gel for radiation induced selective recognition of 2,4-dichlorophenoxyacetic acid

    Science.gov (United States)

    Shuai Jiang, Guang; An Zhong, Shi; Chen, Lan; Blakey, Idriss; Whitaker, Andrew

    2011-02-01

    A novel photoresponsive functional monomer bearing a siloxane polymerisable group and azobenzene moieties was synthesized. This monomer was then used to prepare photoresponsive molecularly imprinted polymers (MIP), which have specific binding sites for 2,4-dichlorophenoxyacetic acid (2,4-D) through hydrogen bonding moieties. The binding affinity of the imprinted recognition sites was switchable by alternate irradiations with ultraviolet and visible light, suggesting that azobenzene groups located inside the binding sites could be used as chemical sensors and the trans-cis isomerization could regulate the affinity for the 2,4-D. In addition, the concentration of the 2,4-D was able to be quantified by monitoring the trans-to-cis photoisomerization rate constant.

  15. Adhesion of Escherichia coli on to a series of poly(methacrylates) differing in charge and hydrophobicity

    OpenAIRE

    Harkes, G; Feijen, J.; DANKERT, J

    1991-01-01

    The adhesion of three Escherichia coli strains on to six poly(methacrylates) differing in hydrophobicity and surface charge was measured as a function of time under laminar flow conditions. Polymers used were poly(methy) methacrylate) (PMMA), poly(hydroxyethy) methacrylate) (PHEMA) and copolymers of MMA or HEMA with either 15% methacrylic acid (MAA) or 15% trimethylaminoethyl methacrylate-HCl salt (TMAEMA-CI). Bacterial and polymer surfaces were characterized by means of water contact angles ...

  16. 石墨烯/偶氮杂化材料研究进展%Progress on graphene/azobenzene hybrid materials

    Institute of Scientific and Technical Information of China (English)

    王东瑞; 王晓工

    2012-01-01

    Graphene, a true two dimensional nanomaterial with the layer thickness of one atom, has showed many outstanding properties and aroused tremendous research enthusiasm. Azobenzene-containing polymers and other materials have also attracted considerable attention because of the unique photoresponsive properties. Graphene/ azobenzene hybrids materials can combine interesting properties of graphere and azobenzene-containing materials and have been studied in authors and other laboratories in recent years. This review highlighted some recent research progresses in this area. The content of this article included the preparations of graphene/azobenzene hybrids materials through surface-grafting of azo polymers, covalent-bonding modification with low-molecular-weight azo compounds and electrostatic layer-by-layer deposition. The photoresponsive properties and application in the electronchemical energy storage device of the materials were also reviewed in some detail.%石墨烯作为一种新型二维平面纳米材料,表现出许多优异的物理性质.含偶氮苯的化合物和聚合物作为功能材料具有独特的光响应性质.将石墨烯的特性与偶氮材料的光响应性相结合,有望发展一类具有卓越性能的新型光电功能材料.本文总结了石墨烯/偶氮杂化材料这一研究方向的最新进展,重点介绍了杂化材料的制备、表征和光电功能性质等,并简要展望了这类材料的发展前景.

  17. A New Biindenylidenedione Compound with Two Azobenzene Units:Synthesis and Photochromic Behavior Both in Solution and in the Solid State

    Institute of Scientific and Technical Information of China (English)

    LIU Juyan; HAN Jie; WANG Juanyu; PANG Meili; MENG Jiben

    2009-01-01

    A new photochromic biindenylidenedione compound bearing two azobenzene units was synthesized and characterized by means of 1H NMR,13C NMR,ESI-MS and elemental analysis.The photochromic and photo-induced radical properties were investigated by means of UV-Vis and electron spin resonance spectroscopy,respectively.The results showed that the title compound exhibited photochromic behavior with good fatigue resistances both in solution and in the solid state.

  18. Ultrasound guided supraclavicular block.

    LENUS (Irish Health Repository)

    Hanumanthaiah, Deepak

    2013-09-01

    Ultrasound guided regional anaesthesia is becoming increasingly popular. The supraclavicular block has been transformed by ultrasound guidance into a potentially safe superficial block. We reviewed the techniques of performing supraclavicular block with special focus on ultrasound guidance.

  19. Symmetrical trimeric star-shaped mesogens based on 1,3,5-trisubstituted benzene incorporating Schiff base and azobenzene fragments as the peripheral units: Synthesis and mesomorphic properties

    Indian Academy of Sciences (India)

    Guan-Yeow Yeap; Yew-Hong Ooi; Nozomi Uchida; Masato M Ito

    2014-05-01

    Two series of symmetrical three-armed star-shaped mesogens based on 1,3,5-trihydroxybenzene as a core unit, interconnecting three Schiff base or azobenzene moieties via oxymethylene spacers have been synthesized and characterized by spectroscopic techniques. Every member in these series possesses either chlorine (Cl) or bromine (Br) terminal atom, with different alkyl spacer length (CH2 whereby ranging from 3 to 6). Their thermal stability and mesomorphic properties are investigated by employing DSC and POM. The dependence of phase transition in relation to the alkyl spacer length is shown by both series. These star-shaped mesogens exhibit only nematic and smectic phases. The difference between the two series lies on the structure of linking group in the peripheral units (-CH=N- for series PSB-X- and -N=N- for series PAZ-X-). Therefore, a comparison study of the mesomorphic properties between these two series of star-shaped mesogens is discussed whereby the azobenzene-basedmesogens are thermally more stable than the Schiff base counterpart. In addition, soft crystalline phase is observed for the azobenzene-based star-shaped mesogens possessing hexyl alkyl spacer.

  20. Langmuir-Blodgett mono- and multilayers of preformed poly(octadecyl methacrylate)s, 2. Structural studies by IR spectroscopy and small-angle X-ray scattering

    NARCIS (Netherlands)

    Arndt, Thomas; Schouten, Arend Jan; Schmidt, Günther F.; Wegner, Gerhard

    1991-01-01

    Langmuir-Blodgett (LB) mono- and multilayers of preformed atactic and isotactic poly(octadecyl methacrylate)s were studied on gold surfaces and silicon wafers. The average orientation of the carbonyl bond of the ester group was found to be about 50° with respect to the normal to the substrate, and t

  1. SYNTHESIS OF METHACRYLATES FROM COAL-DERIVED SYNGAS

    Energy Technology Data Exchange (ETDEWEB)

    Jang, B.W.L.; Spivey, J.J.; Gogate, M.R.; Zoeller, J.R.; Colberg, R.D.; Choi, G.N.

    1999-12-01

    Research Triangle Institute (RTI), Eastman Chemical Company, and Bechtel have developed a novel process for synthesis of methyl methacrylate (MMA) from coal-derived syngas, under a contract from the US Department of Energy/Fossil Energy Technology Center (DOE/FETC). This project has resulted in five US patents (four already published and one pending publication). It has served as the basis for the technical and economic assessment of the production of this high-volume intermediate from coal-derived synthesis gas. The three-step process consists of the synthesis of a propionate from ethylene carbonylation using coal-derived CO, condensation of the propionate with formaldehyde to form methacrylic acid (MAA); and esterification of MAA with methanol to yield MMA. The first two steps, propionate synthesis and condensation catalysis, are the key technical challenges and the focus of the research presented here.

  2. Physical properties of agave cellulose graft polymethyl methacrylate

    Energy Technology Data Exchange (ETDEWEB)

    Rosli, Noor Afizah; Ahmad, Ishak; Abdullah, Ibrahim; Anuar, Farah Hannan [Polymer Research Centre (PORCE), School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi Selangor (Malaysia)

    2013-11-27

    The grafting polymerization of methyl methacrylate and Agave cellulose was prepared and their structural analysis and morphology were investigated. The grafting reaction was carried out in an aqueous medium using ceric ammonium nitrate as an initiator. The structural analysis of the graft copolymers was carried out by Fourier transform infrared and X-ray diffraction. The graft copolymers were also characterized by field emission scanning electron microscopy (FESEM). An additional peak at 1732 cm{sup −1} which was attributed to the C=O of ester stretching vibration of poly(methyl methacrylate), appeared in the spectrum of grafted Agave cellulose. A slight decrease of crystallinity index upon grafting was found from 0.74 to 0.68 for cellulose and grafted Agave cellulose, respectively. Another evidence of grafting showed in the FESEM observation, where the surface of the grafted cellulose was found to be roughed than the raw one.

  3. Physical properties of agave cellulose graft polymethyl methacrylate

    Science.gov (United States)

    Rosli, Noor Afizah; Ahmad, Ishak; Abdullah, Ibrahim; Anuar, Farah Hannan

    2013-11-01

    The grafting polymerization of methyl methacrylate and Agave cellulose was prepared and their structural analysis and morphology were investigated. The grafting reaction was carried out in an aqueous medium using ceric ammonium nitrate as an initiator. The structural analysis of the graft copolymers was carried out by Fourier transform infrared and X-ray diffraction. The graft copolymers were also characterized by field emission scanning electron microscopy (FESEM). An additional peak at 1732 cm-1 which was attributed to the C=O of ester stretching vibration of poly(methyl methacrylate), appeared in the spectrum of grafted Agave cellulose. A slight decrease of crystallinity index upon grafting was found from 0.74 to 0.68 for cellulose and grafted Agave cellulose, respectively. Another evidence of grafting showed in the FESEM observation, where the surface of the grafted cellulose was found to be roughed than the raw one.

  4. Solid coatings deposited from liquid methyl methacrylate via Plasma Polymerization

    Science.gov (United States)

    Wurlitzer, Lisa; Maus-Friedrichs, Wolfgang; Dahle, Sebastian

    2016-09-01

    The polymerization of methyl methacrylate via plasma discharges is well known today. Usually, plasma-enhanced chemical vapor deposition (PECVD) is used to deposit polymer coatings. Solid coatings are formed out of the liquid phase from methyl methacrylate via dielectric barrier discharge. The formation of the coating proceeds in the gas and the liquid phase. To learn more about the reactions in the two phases, the coatings from MMA monomer will be compared to those from MMA resin. Finally, attenuated total reflection infrared spectroscopy, confocal laser scanning microscopy and X-ray photoelectron spectroscopy are employed to characterize the solid coatings. In conclusion, the plasma enhanced chemical solution deposition is compared to the classical thermal polymerization of MMA.

  5. States of Water in Hydrogels Containing with Glyceryl Methacrylate

    Institute of Scientific and Technical Information of China (English)

    LI Qin-hua; LIU Li; HUANG Zhi-rong; LIN Dong-qing

    2014-01-01

    Hydrogel materials were prepared by thermopolymerization with different content of glyceryl methacrylate and hydroxyethyl methacrylate. The different states of water in swelling hydrogels were described and studied by differential scanning calorimetry (DSC). It was found that the hydrophilicity of GMA was stronger than HEMA, the water content and bound water of GMA hydrogel are higher than HEMA hydrogel. With the increase of GMA content, the content of free water in hydrogel increased. When GMA content was lower than 50%, the increase of GMA content also increased the content of bound water; but when GMA content was higher than 50%, the increase of GMA content decreased the content of bound water, which was caused by the chain hydrogen bond formed on the GMA chain with hydroxyl group each other.

  6. Penile enlargement with methacrylate injection: is it safe?

    Directory of Open Access Journals (Sweden)

    Fabio Cesar Miranda Torricelli

    Full Text Available CONTEXTPenis size is a great concern for men in many cultures. Despite the great variety of methods for penile augmentation, none has gained unanimous acceptance among experts in the field. However, in this era of minimally invasive procedure, injection therapy for penile augmentation has become more popular. Here we report a case of methacrylate injection in the penis that evolved with penile deformity and sexual dysfunction. This work also reviews the investigation and management of this pathological condition.CASE REPORTA 36-year-old male sought medical care with a complaint of penile deformity and sexual dysfunction after methacrylate injection. The treatment administered was surgical removal. Satisfactory cosmetic and functional results were reached after two months.CONCLUSIONSThere is a need for better structured scientific research to evaluate the outcomes and complication rates from all penile augmentation procedures.

  7. Gelatin methacrylate microspheres for controlled growth factor release.

    Science.gov (United States)

    Nguyen, Anh H; McKinney, Jay; Miller, Tobias; Bongiorno, Tom; McDevitt, Todd C

    2015-02-01

    Gelatin has been commonly used as a delivery vehicle for various biomolecules for tissue engineering and regenerative medicine applications due to its simple fabrication methods, inherent electrostatic binding properties, and proteolytic degradability. Compared to traditional chemical cross-linking methods, such as the use of glutaraldehyde (GA), methacrylate modification of gelatin offers an alternative method to better control the extent of hydrogel cross-linking. Here we examined the physical properties and growth factor delivery of gelatin methacrylate (GMA) microparticles (MPs) formulated with a wide range of different cross-linking densities (15-90%). Less methacrylated MPs had decreased elastic moduli and larger mesh sizes compared to GA MPs, with increasing methacrylation correlating to greater moduli and smaller mesh sizes. As expected, an inverse correlation between microparticle cross-linking density and degradation was observed, with the lowest cross-linked GMA MPs degrading at the fastest rate, comparable to GA MPs. Interestingly, GMA MPs at lower cross-linking densities could be loaded with up to a 10-fold higher relative amount of growth factor than conventional GA cross-linked MPs, despite the GA MPs having an order of magnitude greater gelatin content. Moreover, a reduced GMA cross-linking density resulted in more complete release of bone morphogenic protein 4 and basic fibroblast growth factor and accelerated release rate with collagenase treatment. These studies demonstrate that GMA MPs provide a more flexible platform for growth factor delivery by enhancing the relative binding capacity and permitting proteolytic degradation tunability, thereby offering a more potent controlled release system for growth factor delivery.

  8. POLYMERIZATION OF BUTYL METHACRYLATE BY IRON PYRIDINEBISIMINE COMPLEXES

    Institute of Scientific and Technical Information of China (English)

    Jing-yu Liu; Yan-guo Li; Yi Zheng; Yue-sheng Li

    2005-01-01

    Fe(Ⅱ) pyridinebisimine complexes activated with trialkylaluminium or modified methylaluminoxane (MMAO) as catalysts were employed for the polymerization of butyl methacrylate (BMA). Polymer yields, catalytic activities and molecular weights as well as molecular weight distributions of BMA can be controlled over a wide range by varying the reaction parameters such as cocatalyst, A1/Fe molar ratio, monomer/catalyst molar ratio, monomer concentration and reaction yield could reach 99.1% under optimum condition.

  9. Multifunctional methacrylate-based coatings for glass and metal surfaces

    Science.gov (United States)

    Pospiech, Doris; Jehnichen, Dieter; Starke, Sandra; Müller, Felix; Bünker, Tobias; Wollenberg, Anne; Häußler, Liane; Simon, Frank; Grundke, Karina; Oertel, Ulrich; Opitz, Michael; Kruspe, Rainer

    2017-03-01

    In order to prevent freshwater biofouling glass and metal surfaces were coated with novel transparent methacrylate-based copolymers. The multifunctionality of the copolymers, such as adhesion to the substrate, surface polarity, mechanical long-term stability in water, and ability to form metal complexes was inserted by the choice of suitable comonomers. The monomer 2-acetoacetoxy ethyl methacrylate (AAMA) was used as complexing unit to produce copper(II) complexes in the coating's upper surface layer. The semifluorinated monomer 1H,1H,2H,2H-perfluorodecyl methacrylate was employed to adjust the surface polarity and wettability. Comprehensive surface characterization techniques, such as X-ray photoelectron spectroscopy (XPS) and contact angle measurements showed that surface compositions and properties can be easily adjusted by varying the concentrations of the comonomers. The formation of copper(II) complexes along the copolymer chains and their stability against washing out with plenty of water was proven by XPS. Copolymers containing semifluorinated comonomers significantly inhibited the growth of Achnanthidium species. Copolymers with copper-loaded AAMA-sequences were able to reduce both the growth of Achnanthidium spec. and Staphylococcus aureus.

  10. Block Cipher Analysis

    DEFF Research Database (Denmark)

    Miolane, Charlotte Vikkelsø

    Block ciphersarecryptographicprimitivesthatoperateon fixed sizetexts(blocks). Mostdesigns aim towards secure andfastencryption oflarge amounts ofdata. Block ciphers also serve as the building block of a number of hash functions and message authentication codes(MAC).Thetask of cryptanalysisisto en...... on small scale variants of AES. In the final part of the thesis we present a new block cipher proposal Present and examine its security against algebraic and differential cryptanalysis in particular.......Block ciphersarecryptographicprimitivesthatoperateon fixed sizetexts(blocks). Mostdesigns aim towards secure andfastencryption oflarge amounts ofdata. Block ciphers also serve as the building block of a number of hash functions and message authentication codes(MAC).Thetask of cryptanalysisisto...... ensurethat no attack violatesthe securitybounds specifiedbygeneric attack namely exhaustivekey search and table lookup attacks. This thesis contains a general introduction to cryptography with focus on block ciphers and important block cipher designs, in particular the Advanced Encryption Standard...

  11. A tri-block copolymer templated synthesis of gold nanostructures.

    Science.gov (United States)

    Falletta, Ester; Ridi, Francesca; Fratini, Emiliano; Vannucci, Chiara; Canton, Patrizia; Bianchi, Sabrina; Castelvetro, Valter; Baglioni, Piero

    2011-05-01

    Stable ultra-small gold nanoparticles have been synthesized in aqueous phase by using a tri-block copolymer (BMB) as a templating agent consisting of two PEG-methylacrylate chains (B blocks) anchored to a poly(methacrylic) moiety containing a trithiocarbonate unit (M block). The effect of the BMB/Au molar ratios on the final particle size, shape and monodispersity has been investigated. The synthesized nanosols have been characterized by means of Visible Absorption, Small Angle X-ray Scattering (SAXS), and Transmission Electron Microscopy (TEM). Results clearly indicate that the polymer plays a key role in determining the size and shape of gold particles, from fractal-like structures to monodisperse spherical particles with a mean diameter of about 3 nm. The aggregation behavior of these nanostructures has been characterized both in solution (SAXS) as well as on mica substrate (AFM) and has been proven to be driven by the polymer to gold concentration ratio.

  12. Nanostructured photovoltaic materials using block polymer assemblies

    Science.gov (United States)

    Mastroianni, Sarah Elizabeth

    Despite its potential as an abundant, sustainable alternative to non-renewable energy sources, solar energy currently is underutilized. Photovoltaics, which convert energy from sunlight into electricity, commonly are made from inorganic semiconductor materials that require expensive manufacturing and processing techniques. Alternatively, organic materials can be used to produce flexible and lightweight organic photovoltaic (OPV) devices, which can be prepared using solution-based processing techniques. However, OPV devices are limited by low efficiencies and short lifetimes compared to their inorganic counterparts. In OPV systems, charge carriers are generated in the active layer via the separation of excitons (electron-hole pairs) at interfaces between donor and acceptor materials. Because excitons have a limited diffusion length (˜10 nm), they may recombine before reaching a donor-acceptor interface if domain sizes are large. This exciton recombination can limit device efficiency; thus, the design parameters for improved active layer morphologies include large interfacial areas, small size scales, and continuous conducting pathways. Currently, most OPV devices are prepared by blending donor and acceptor materials in bulk heterojunction (BHJ) devices, often resulting in non-ideal, process-dependent morphologies. Alternatively, the self-assembly of block polymers (BP)s offers a reproducible means to generate nanostructured active layers. The work presented in this dissertation examines the synthetic approaches to preparing BPs containing different electroactive materials: non-conjugated, amorphous poly(vinyl-m-triphenylamine) [PVmTPA] and conjugated poly(3-alkythiophene) [P3AT] p-type materials as well as fullerene-based n-type materials. The synthesis and self-assembly of a model poly(methyl methacrylate)- b-PVmTPA system is presented. This work was extended to synthesize PVmTPA BPs with complementary poly(methyl methacrylate- co-hydroxyethyl methacrylate) [P

  13. Evaluation of bond strength of silorane and methacrylate based restorative systems to dentin using different cavity models

    Directory of Open Access Journals (Sweden)

    Stephano Zerlottini Isaac

    2013-09-01

    Full Text Available OBJECTIVE: The aim of this in vitro study was to evaluate the microtensile bond strength (µTBS to dentin of two different restorative systems: silorane-based (P90, and methacrylate-based (P60, using two cavity models. MATERIAL AND METHODS: Occlusal enamel of 40 human third molars was removed to expose flat dentin surface. Class I cavities with 4 mm mesial-distal width, 3 mm buccal-lingual width and 3 mm depth (C-factor=4.5 were prepared in 20 teeth, which were divided into two groups (n=10 restored with P60 and P90, bulk-filled after dentin treatment according to manufacturer's instructions. Flat buccal dentin surfaces were prepared in the 20 remaining teeth (C-factor=0.2 and restored with resin blocks measuring 4x3x3 mm using the two restorative systems (n=10. The teeth were sectioned into samples with area between 0.85 and 1.25 mm2 that were submitted to µTBS testing, using a universal testing machine (EMIC at speed of 0.5 mm/min. Fractured specimens were analyzed under stereomicroscope and categorized according to fracture pattern. Data were analyzed using ANOVA and Tukey Kramer tests. RESULTS: For flat surfaces, P60 obtained higher bond strength values compared with P90. However, for Class I cavities, P60 showed significant reduction in bond strength (p0.05, or between Class I Cavity and Flat Surface group, considering P90 restorative system (p>0.05. Regarding fracture pattern, there was no statistical difference among groups (p=0.0713 and 56.3% of the fractures were adhesive. CONCLUSION: It was concluded that methacrylate-based composite µTBS was influenced by cavity models, and the use of silorane-based composite led to similar bond strength values compared to the methacrylate-based composite in cavities with high C-factor.

  14. EFFECT OF 2—HYDROXYETHYL METHACRYLATE ON SEMIBATCH EMULSIFIER—FREE EMULSION COPOLYMERIZATION OF METHYL METHACRYLATE AND BUTYL ACRYLATE

    Institute of Scientific and Technical Information of China (English)

    GUOTianying; SONGMoudao; 等

    1999-01-01

    The semibatch emulsifier-free emulsion copolymerization of methyl methacrylate (MMA) and butyl acrylate(BA) in the presence of 2-hydroxyethyl methacrylate(HEMA) initiated by K2S2O8(PSP) was studied.The latex particles can maintain an appreciable stability during the emulsifier-free emulsion copolymerization of MMA and BA in the presence of HEMA.The average particle diameter increase with an increase of total solids content,HEMA content,PSP content,ionic strength of the system and monomer feed rate,and decrease with the monomer feed ration from 3/1 (MMA/BA:molar ration).to 1/3.The stability of this reaction system is improved by adding HEMA as nonionic comonomer,High solids content (50%) latex with monodisperse particle can be obtained using this process.

  15. PEGYLATED SINGLE-WALLED CARBON NANOTUBES WITH GELABLE BLOCK COPOLYMERS

    Institute of Scientific and Technical Information of China (English)

    Cheng Zhang; Wen Zhu; Lei Gao; Yong-ming Chen

    2011-01-01

    Functional amphiphilic block copolymer poly(ethylene glycol)-block-poly[(3-(triethoxysilyl)propyl methacrylate)-co-(1-pyrene-methyl) methacrylate], PEG113-b-P(TEPM26-co-PyMMA4),was synthesized via atom transfer radical polymerization (ATRP) initiated by monomethoxy capped poly(ethylene glycol) bromoisobutyrate.This polymer exhibited strong ability to disperse and exfoliate single-walled carbon nanotubes (SWNTs) in different solvents due to the adhesion of pyrene units to surface of SWNTs.In aqueous solution,the PTEPM segments that were located on the nanotube surfaces with the pyrene units could be gelated and,as a result,the silica oxide networks with PEG coronas were formed on the surface of nanotubes,which ensured the composites with a good dispersibility and stability.Furthermore,functional silane coupling agents,3-mercaptopropyltrimethoxysilane and 3-aminopropyltriethoxysilane,were introduced during dispersion of SWNTs using the block copolymers.They were co-gelated with PTEPM segments,and the -SH and -NH2 functionalitieswere introduced into the silica oxide coats respectively.

  16. SYNTHESIS OF POLY(METHYL METHACRYLATE)-graft-POLYSTYRENE BY ATOM TRANSFER RADICAL POLYMERIZATION

    Institute of Scientific and Technical Information of China (English)

    Sheng-min Gong; Qun-sheng Li; Yan Shi; Zhi-feng Fu; Shu-ke Jiao; Wan-tai Yang

    2003-01-01

    The radical copolymerization of methyl methacrylate and 2-hydroxyethyl methacrylate was carried out via atom complex. This polymerization proceeds in a living fashion with controlled molecular weight and low polydispersity. The obtained copolymer was esterified with 2-bromoisobutylryl bromide yielding a macroinitiator, poly(methyl methacrylate-co-2-hydroxyethyl methacrylate-co-2-(2-bromoisobutyryloxy)ethyl methacrylate), and its structure was characterized by 1HNMR. This macroinitiator was used for ATRP of styrene to synthesize poly(methyl methacrylate)-grafi-polystyrene. The molecular weight of graft copolymer increased with the monomer conversion, and the polydispersity remained relatively low.The individual grafted polystyrene chains were cleaved from the macroinitiator backbone by hydrolysis and the hydrolyzed product was characterized by 1H-NMR and GPC.

  17. Concomitant sensitization to glutaraldehyde and methacrylic monomers among dentists and their patients

    OpenAIRE

    Maya Grigorievna Lyapina; Maria Dencheva; Assya Krasteva-Panova; Mariana Tzekova-Yaneva; Mariela Deliverska; Angelina Kisselova-Yaneva

    2016-01-01

    Background: A multitude of methacrylic monomers is used in dentistry. Glutaraldehyde (G) is used in dental practice and consumer products as a broad-spectrum antimicrobial agent. The purpose of our study is to evaluate the frequency and the risk of concomitant sensitization to some methacrylic monomers (methyl methacrylate (MMA), triethyleneglycol dimethacrylate (TEGDMA), ethyleneglycol dimethacrylate (EGDMA), 2,2-bis-[4-(2-hydroxy-3-methacrylo-xypropoxy)phenyl]-propane (Bis-GMA), 2-hydroxy-e...

  18. Light-induced reversible modification of the work function of a new perfluorinated biphenyl azobenzene chemisorbed on Au (111)

    Science.gov (United States)

    Masillamani, Appan Merari; Osella, Silvio; Liscio, Andrea; Fenwick, Oliver; Reinders, Federica; Mayor, Marcel; Palermo, Vincenzo; Cornil, Jérôme; Samorì, Paolo

    2014-07-01

    We describe the synthesis of a novel biphenyl azobenzene derivative exhibiting: (i) a protected thiol anchoring group in the α-position to readily form self-assembled monolayers (SAMs) on Au surfaces; and (ii) a terminal perfluorinated benzene ring in the ω-position to modify the surface properties. The design of this molecule ensured both an efficient in situ photoswitching between the trans and cis isomers when chemisorbed on Au(111), due to the presence of a biphenyl bridge between the thiol protected anchoring group and the azo dye, and a significant variation of the work function of the SAM in the two isomeric states, induced by the perfluorinated phenyl head group. By exploiting the light responsive nature of the chemisorbed molecules, it is possible to dynamically modify in situ the work function of the SAM-covered electrode, as demonstrated both experimentally and by quantum-chemical calculations, revealing changes in work function up to 220 meV. These findings are relevant for tuning the work function of metallic electrodes, and hence to dynamically modulate charge injection at metal-semiconductor interfaces for organic opto-electronic applications.We describe the synthesis of a novel biphenyl azobenzene derivative exhibiting: (i) a protected thiol anchoring group in the α-position to readily form self-assembled monolayers (SAMs) on Au surfaces; and (ii) a terminal perfluorinated benzene ring in the ω-position to modify the surface properties. The design of this molecule ensured both an efficient in situ photoswitching between the trans and cis isomers when chemisorbed on Au(111), due to the presence of a biphenyl bridge between the thiol protected anchoring group and the azo dye, and a significant variation of the work function of the SAM in the two isomeric states, induced by the perfluorinated phenyl head group. By exploiting the light responsive nature of the chemisorbed molecules, it is possible to dynamically modify in situ the work function of

  19. Preparation of Pickering double emulsions using block copolymer worms.

    Science.gov (United States)

    Thompson, Kate L; Mable, Charlotte J; Lane, Jacob A; Derry, Mathew J; Fielding, Lee A; Armes, Steven P

    2015-04-14

    The rational formulation of Pickering double emulsions is described using a judicious combination of hydrophilic and hydrophobic block copolymer worms as highly anisotropic emulsifiers. More specifically, RAFT dispersion polymerization was utilized to prepare poly(lauryl methacrylate)-poly(benzyl methacrylate) worms at 20% w/w solids in n-dodecane and poly(glycerol monomethacrylate)-poly(2-hydroxypropyl methacrylate)-poly(benzyl methacrylate) worms at 13% w/w solids in water by polymerization-induced self-assembly (PISA). Water-in-oil-in-water (w/o/w) double emulsions can be readily prepared with mean droplet diameters ranging from 30 to 80 μm using a two-stage approach. First, a w/o precursor emulsion comprising 25 μm aqueous droplets is prepared using the hydrophobic worms, followed by encapsulation within oil droplets stabilized by the hydrophilic worms. The double emulsion droplet diameter and number of encapsulated water droplets can be readily varied by adjusting the stirring rate employed during the second stage. For each stage, the droplet volume fraction is relatively high at 0.50. The double emulsion nature of the final formulation was confirmed by optical and fluorescence microscopy studies. Such double emulsions are highly stable to coalescence, with little or no change in droplet diameter being detected over storage at 20 °C for 10 weeks as judged by laser diffraction. Preliminary experiments indicate that the complementary o/w/o emulsions can also be prepared using the same pair of worms by changing the order of homogenization, although somewhat lower droplet volume fractions were required in this case. Finally, we demonstrate that triple and even quadruple emulsions can be formulated using these new highly anisotropic Pickering emulsifiers.

  20. Investigation of Complexation of Linear Poly(N-vinyl-2-pyrrolidone with Poly(methacrylic acid-co-methyl methacrylate Gel

    Directory of Open Access Journals (Sweden)

    Guoqin Liu

    2011-01-01

    Full Text Available The contraction of poly(methacrylic acid-co-methyl methacrylate (P(MAA-co-MMA gel induced by complexation with linear poly(N-vinyl-2-pyrrolidone (PVP is quite different from that of poly(acrylic acid (PAA or poly(methacrylic acid (PMAA gel. It was found that the concentration of PVP has a strong effect on the complexation with P(MAA-co-MMA gel. When PVP was introduced into the P(MAA-co-MMA network, its dynamic mechanic properties vary greatly between complexed and uncomplexed networks. It had the following results: (1 the higher modulus ratio; (2 a slight contraction of gel.

  1. Small-angle neutron scattering from mixtures of sodium dodecyl sulfate and a cationic, bolaform surfactant containing azobenzene.

    Science.gov (United States)

    Hubbard, F Pierce; Santonicola, Gabriella; Kaler, Eric W; Abbott, Nicholas L

    2005-07-05

    This paper reports on the microstructures formed in aqueous solutions containing mixtures of sodium dodecyl sulfate (SDS) and a photosensitive, bolaform surfactant, bis(trimethylammoniumhexyloxy)azobenzene dibromide (BTHA). By using quasi-elastic light scattering and small-angle neutron scattering, we determined that aqueous solutions containing SDS and the trans isomer of BTHA (0.1 wt % total surfactant, 15 mol % BTHA, 85 mol % SDS) form vesicles with average hydrodynamic diameters of 1350 +/- 50 angstroms and bilayer thicknesses of 35 +/- 2 angstroms. The measured bilayer thickness is consistent with a model of the vesicle bilayer in which the trans isomer of BTHA spans the bilayer. Upon illumination with UV light, the BTHA underwent photoisomerization to produce a cis-rich photostationary state (80% cis isomer). We measured this photoisomerization to drive the reorganization of vesicles into cylindrical aggregates with cross-sectional radii of 19 +/- 3 angstroms and average hydrodynamic diameters of 240 +/- 50 angstroms. Equilibration of the cis-rich solution in the dark at 25 degrees C for 12 h or illumination of the solution with visible light leads to the recovery of the trans-rich photostationary state of the solution and the reformation of vesicles, thus demonstrating the potential utility of this system as the basis of a tunable fluid.

  2. Assessing computationally efficient isomerization dynamics: Delta-SCF density-functional theory study of azobenzene molecular switching

    CERN Document Server

    Maurer, Reinhard J; 10.1063/1.3664305

    2012-01-01

    We present a detailed comparison of the S0, S1 (n -> \\pi*) and S2 (\\pi -> \\pi*) potential energy surfaces (PESs) of the prototypical molecular switch azobenzene as obtained by Delta-self-consistent-field (Delta-SCF) Density-Functional Theory (DFT), time-dependent DFT (TD-DFT) and approximate Coupled Cluster Singles and Doubles (RI-CC2). All three methods unanimously agree in terms of the PES topologies, which are furthermore fully consistent with existing experimental data concerning the photo-isomerization mechanism. In particular, sum-method corrected Delta-SCF and TD-DFT yield very similar results for S1 and S2, when based on the same ground-state exchange-correlation (xc) functional. While these techniques yield the correct PES topology already on the level of semi-local xc functionals, reliable absolute excitation energies as compared to RI-CC2 or experiment require an xc treatment on the level of long-range corrected hybrids. Nevertheless, particularly the robustness of Delta-SCF with respect to state c...

  3. Light-induced reversible modification of the work function of a new perfluorinated biphenyl azobenzene chemisorbed on Au (111).

    Science.gov (United States)

    Masillamani, Appan Merari; Osella, Silvio; Liscio, Andrea; Fenwick, Oliver; Reinders, Federica; Mayor, Marcel; Palermo, Vincenzo; Cornil, Jérôme; Samorì, Paolo

    2014-08-07

    We describe the synthesis of a novel biphenyl azobenzene derivative exhibiting: (i) a protected thiol anchoring group in the α-position to readily form self-assembled monolayers (SAMs) on Au surfaces; and (ii) a terminal perfluorinated benzene ring in the ω-position to modify the surface properties. The design of this molecule ensured both an efficient in situ photoswitching between the trans and cis isomers when chemisorbed on Au(111), due to the presence of a biphenyl bridge between the thiol protected anchoring group and the azo dye, and a significant variation of the work function of the SAM in the two isomeric states, induced by the perfluorinated phenyl head group. By exploiting the light responsive nature of the chemisorbed molecules, it is possible to dynamically modify in situ the work function of the SAM-covered electrode, as demonstrated both experimentally and by quantum-chemical calculations, revealing changes in work function up to 220 meV. These findings are relevant for tuning the work function of metallic electrodes, and hence to dynamically modulate charge injection at metal-semiconductor interfaces for organic opto-electronic applications.

  4. Toward Spatiotemporally Controlled Synthesis of Photoresponsive Polymers: Computational Design of Azobenzene-Containing Monomers for Light-Mediated ROMP.

    Science.gov (United States)

    Zhou, Qunfei; Fursule, Ishan; Berron, Brad J; Beck, Matthew J

    2016-09-15

    Density functional theory calculations have been used to identify the optimum design for a novel, light-responsive ring monomer expected to allow spatial and temporal control of ring-opening metathesis polymerization (ROMP) via light-mediated changes in ring strain energy. The monomer design leverages ring-shaped molecules composed of 4,4'-diaminoazobenzene (ABn) closed by alkene-α,ω-dioic acid linkers. The atomic geometries, formation enthalpies and ring strain energies of azobenzene (AB)-containing rings with various length linkers have been calculated. The AB(2,2) monomer is identified as having optimal properties for light-mediated ROMP, including high thermodynamic stability, low ring strain energy (RSE) with cis-AB, and high RSE with trans-AB. Time-dependent DFT calculations have been used to explore the photoisomerization mechanism of isolated AB and AB-containing rings, and calculations show that trans-to-cis and cis-to-trans photoisomerization of the optimal AB(2,2) ring molecule can be achieved with monochromatic green and blue light, respectively. The AB(2,2) monomer identified here is expected to allow precise, reversible, spatial and temporal light-mediated control of ROMP through AB photoisomerization, and to have promising potential applications in the fabrication of patterned and/or responsive AB-containing polymer materials.

  5. Molecular structure and vibrational and chemical shift assignments of 3'-chloro-4-dimethylamino azobenzene by DFT calculations.

    Science.gov (United States)

    Toy, Mehmet; Tanak, Hasan

    2016-01-05

    In the present work, a combined experimental and theoretical study on ground state molecular structure, spectroscopic and nonlinear optical properties of azo compound 3'-chloro-4-dimethlamino azobenzene are reported. The molecular geometry, vibrational wavenumbers and the first order hyperpolarizability of the title compound were calculated with the help of density functional theory computations. The optimized geometric parameters obtained by using DFT (B3LYP/6-311++G(d,p)) show good agreement with the experimental data. The vibrational transitions were identified based on the recorded FT-IR spectra in the range of 4000-400cm(-1) for solid state. The (1)H isotropic chemical shifts with respect to TMS were also calculated using the gauge independent atomic orbital (GIAO) method and compared with the experimental data. Using the TD-DFT method, electronic absorption spectra of the title compound have been predicted, and good agreement is determined with the experimental ones. To investigate the NLO properties of the title compound, the polarizability and the first hyperpolarizability were calculated using the density functional B3LYP method with the 6-311++G(d,p) basis set. According to results, the title compound exhibits non-zero first hyperpolarizability value revealing second order NLO behavior. In addition, DFT calculations of the title compound, molecular electrostatic potential and frontier molecular orbitals were also performed at 6-311++G(d,p) level of theory.

  6. Synthesis, optical and thermal behaviour of palladium(II) complexes with 4-(4-alkoxy-2-hydroxybenzylideneamino)azobenzene

    Indian Academy of Sciences (India)

    Boon-Teck Heng; Guan-Yeow Yeap; Daisuke Takeuchi

    2013-11-01

    A series of new Pd(II) complexes derived from the reaction of palladium acetate with 4-(4-alkoxy-2-hydroxybenzylideneamino)azobenzene having the flexible terminal chain of OCH2+1, in which n are even numbers ranging from 8 to 16, has been successfully synthesized. The physical measurement and spectroscopic techniques (FTIR and 1H-NMR) reveal that the Pd(II) complexes possess the Pd-N and Pd-O coordination modes in which the central Pd(II) adopts square-planar geometry. The observation under the polarized light shows that all the ligands and Pd(II) complexes exhibit enantiotropic mesophases. The ligands with -octyloxy and -decyloxy flexible chains exhibit the nematic (N) and smectic A (SmA) phases whilst the Pd(II) complexes show exclusive SmA phase. The SmA phase observed in Pd(II) complexes can be supported by the presence of focal conic fan-shaped texture with the presence of curved lines which are prominent during the cooling process. On the other hand, the comparison studies show that Pd(II) complexes possess exceptional higher phase transition temperatures as compared to the corresponding Cu(II) and Ni(II) complexes.

  7. 含手性碳偶氮苯化合物的合成及其光致变色性能%Synthesis and Photochromic Properties of Azobenzene Compounds Containing Chiral Carbon

    Institute of Scientific and Technical Information of China (English)

    陈思; 谢孔良

    2009-01-01

    Two novel azobenzene compounds containing ehiral carbon, 4-(formic acid ethyl lactate ester)-4'-N, N-bi-methyl azobenzene and 4-(formic acid ethyl lactate ester)- 4'- N, N-bi-methyl bi-azobenzene, had been synthesized by reactions of sulfonyl chlorination and esterfication. The azobenzene compounds containing chiral carbon were characterized and detected by paper chromatography method and Infrared (IR) spectrum. The Ultraviolet-visible light (UV-Vis) spectrum results showed that the two compunds have good photochromism properties and the chiral carbon had significant effect on UV-Vis spectrum. Research shows that single-azobenzene structure of the compound has larger transformation in the absorption spectrum than bi-azobenzene structure of the compound.%采用重氮化偶合反应合成得到偶氮苯染料母体,再经酰氯化、酯化反应合成出两种新型的含手性碳的偶氮苯化合物4-甲酸乳酸乙酯酯基-4'-N,N-二甲基偶氮苯和4-甲酸乳酸乙酯酯基-4'-N,N-二甲基双偶氮苯,并用纸色谱、傅里叶红外(IR)光谱进行了监测和表征.经紫外一可见光(UV-Vis)光谱测试表明两种化合物显示出良好的光致变色性能,与母体化合物的对比可以看出,接入手性碳后光致变色光谱表现出明显的变化,且单偶氮结构的化合物要比双偶氮结构的化合物光致变色光谱明显.

  8. Microindentation of Polymethyl Methacrylate (PMMA Based Bone Cement

    Directory of Open Access Journals (Sweden)

    F. Zivic

    2011-12-01

    Full Text Available Characterization of polymethyl methacrylate (PMMA based bone cement subjected to cyclical loading using microindentation technique is presented in this paper. Indentation technique represents flexible mechanical testing due to its simplicity, minimal specimen preparation and short time needed for tests. The mechanical response of bone cement samples was studied. Realised microindentation enabled determination of the indentation testing hardness HIT and indentation modulus EIT of the observed bone cement. Analysis of optical photographs of the imprints showed that this technique can be effectively used for characterization of bone cements.

  9. Deterioration of polymethyl methacrylate dentures in the oral cavity.

    Science.gov (United States)

    Matsuo, Hiroshi; Suenaga, Hanako; Takahashi, Masatoshi; Suzuki, Osamu; Sasaki, Keiichi; Takahashi, Nobuhiro

    2015-01-01

    Polymethyl methacrylate (PMMA)-made prostheses used in the oral cavity were evaluated by multimodal assessment in order to elucidate the biodeterioration of PMMA. In used dentures (UD), the micro-Vickers hardness of the polished denture surface and denture basal surface was lower than that of the torn surface (pPMMA deteriorated during long-term use in the oral cavity in terms of hardness and volatile content with component alteration, and suggests the involvement of biodeterioration, possibly due to saliva and oral microbiota.

  10. Femtosecond laser induced porosity in poly-methyl methacrylate

    Energy Technology Data Exchange (ETDEWEB)

    Baset, Farhana, E-mail: fbaset@gmail.com; Villafranca, Ana, E-mail: avillafr@uottawa.ca; Guay, Jean-Michel, E-mail: guay_jeanmichel@hotmail.com; Bhardwaj, Ravi, E-mail: ravi.bhardwaj@uottawa.ca

    2013-10-01

    We show that femtosecond laser ablation of poly-methyl methacrylate (PMMA) induces porosity within the ablation crater that increases with pulse energy/fluence and number of laser shots. For deeper craters the porosity evolves into 3D honeycomb like structure on the sidewalls. Using imaging technique, we show that the porous area fraction decreases with pulse energy while the pore size distribution peaks at a pore area of 0.037 μm{sup 2} at higher energies. In line ablation, the pore size increases with the speed at which the laser focus is moved.

  11. Synthesis of methacrylate monomers with antibacterial effects against S. mutans.

    Science.gov (United States)

    He, Jingwei; Söderling, Eva; Österblad, Monica; Vallittu, Pekka K; Lassila, Lippo V J

    2011-11-23

    A series of polymerizable quaternary ammonium compounds were synthesized with the aim of using them as immobilized antibacterial agents in methacrylate dental composites, and their structures were characterized by FT-IR, (1)H-NMR, and (13)C-NMR analysis. Their antibacterial activities against the oral bacterium Streptococcus mutans were evaluated in vitro by a Minimum Inhibitory Concentration test, and the results showed that 2-dimethyl-2-hexadecyl-1-methacryloxyethyl ammonium iodide (C16) had the highest antibacterial activity against S. mutans, and 2-dimethyl-2-pentyl-1-methacryloxyethyl ammonium iodide (C5) and 2-dimethyl-2-octyl-1-methacryloxyethyl ammonium iodide (C8) did not show any inhibition.

  12. Surface Roughening of Polystyrene and Poly(methyl methacrylate in Ar/O2 Plasma Etching

    Directory of Open Access Journals (Sweden)

    Amy E. Wendt

    2010-12-01

    Full Text Available Selectively plasma-etched polystyrene-block-poly(methyl methacrylate (PS-b-PMMA diblock copolymer masks present a promising alternative for subsequent nanoscale patterning of underlying films. Because mask roughness can be detrimental to pattern transfer, this study examines roughness formation, with a focus on the role of cross-linking, during plasma etching of PS and PMMA. Variables include ion bombardment energy, polymer molecular weight and etch gas mixture. Roughness data support a proposed model in which surface roughness is attributed to polymer aggregation associated with cross-linking induced by energetic ion bombardment. In this model, RMS roughness peaks when cross-linking rates are comparable to chain scissioning rates, and drop to negligible levels for either very low or very high rates of cross-linking. Aggregation is minimal for very low rates of cross-linking, while very high rates produce a continuous cross-linked surface layer with low roughness. Molecular weight shows a negligible effect on roughness, while the introduction of H and F atoms suppresses roughness, apparently by terminating dangling bonds. For PS etched in Ar/O2 plasmas, roughness decreases with increasing ion energy are tentatively attributed to the formation of a continuous cross-linked layer, while roughness increases with ion energy for PMMA are attributed to increases in cross-linking from negligible to moderate levels.

  13. Preparation of Novel Poly(hydroxyethyl methacrylate-co-glycidyl methacrylate-Grafted Core-Shell Magnetic Chitosan Microspheres and Immobilization of Lactase

    Directory of Open Access Journals (Sweden)

    Wendy Katiyo

    2013-06-01

    Full Text Available Poly(hydroxyethyl methacrylate-co-glycidyl methacrylate-grafted magnetic chitosan microspheres (HG-MCM were prepared using reversed-phase suspension polymerization method. The HG-MCM presented a core-shell structure and regular spherical shape with poly(hydroxyethyl methacrylate-co-glycidyl methacrylate grafted onto the chitosan layer coating the Fe3O4 cores. The average diameter of the magnetic microspheres was 10.67 μm, within a narrow size distribution of 6.6–17.4 μm. The saturation magnetization and retentivity of the magnetic microspheres were 7.0033 emu/g and 0.6273 emu/g, respectively. The application of HG-MCM in immobilization of lactase showed that the immobilized enzyme presented higher storage, pH and thermal stability compared to the free enzyme. This indicates that HG-MCM have potential applications in bio-macromolecule immobilization.

  14. Glycol methacrylate embedding for light microscopy : Basic principles and trouble-shooting

    NARCIS (Netherlands)

    Gerrits, PO; Horobin, RW

    1996-01-01

    Acrylic resin mixtures are now widely used as embedding media for the preparation of tissue sections. Most of these mixtures are based on 2-hydroxyethyl methacrylate (glycol methacrylate, GMA). Resin embedding preserves tissue components far better than paraffin, celloidin or frozen sections. The pr

  15. Synthesis, characterization and gold loading of polystyrene-poly(pyridyl methacrylate) core–shell latex systems

    NARCIS (Netherlands)

    Oláh, Attila; Hempenius, Mark A.; Vancso, G. Julius

    2004-01-01

    In this research, novel 3-(2-pyridyl)propyl methacrylate and 3-(3-pyridyloxy)propyl methacrylate monomers were synthesized and emulsion polymerized on colloidal polystyrene seeds, resulting in core–shell latex systems. The cores and the core–shell particles were characterized by static light scatter

  16. 21 CFR 177.2000 - Vinylidene chloride/methyl acrylate/methyl methacrylate polymers.

    Science.gov (United States)

    2010-04-01

    ... methacrylate polymers. 177.2000 Section 177.2000 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF...: POLYMERS Substances for Use as Basic Components of Single and Repeated Use Food Contact Surfaces § 177.2000 Vinylidene chloride/methyl acrylate/methyl methacrylate polymers. The vinylidene chloride/methyl...

  17. Blends of poly (vinylidene fluoride) with stereoregular poly (akyl methacrylate) s

    NARCIS (Netherlands)

    Roerdink, Eize

    1980-01-01

    This thesis describes various aspects of polymer-polymer blends of poly (vinylidene fluoride) (PVF2) with stereoregular poly (alkyl methacrylate)s, like mutual miscibility, nature and size of the interactions between the complementary polymers, Lower Critical Solution Temperature (LCST) behaviour, c

  18. Shrinkage kinetics of a methacrylate- and a silorane-based resin composite: effect on marginal integrity

    NARCIS (Netherlands)

    Gregor, L.; Bortolotto, T.; Feilzer, A.J.; Krejci, I.

    2013-01-01

    Purpose: To evaluate the relation between the linear displacement (LD), shrinkage force (SF) and marginal adaptation of a methacrylate- and a silorane-based composite. Materials and Methods: The LD and SF of 8 samples made of Filtek Supreme XT (methacrylate-based composite) and Filtek Silorane (silo

  19. Langmuir monolayer and Langmuir-Blodgett films formed by a melamine-headed azobenzene-derived amphiphile: interfacial assembly affected by host-guest interaction.

    Science.gov (United States)

    Xu, Weihong; Wang, Yanhua; Xiao, Yunxia; Liu, Fang; Lu, Guo-Yuan

    2009-04-09

    A novel azobenzene-derived amphiphile with a melamine head, 2Azo-2C12H2-melamine, has been synthesized. pi-A isotherm measurements displayed that this amphiphile is able to form a stable Langmuir monolayer on both pure water and barbituric acid (BA)- or thymine (T)-containing subphases. The collapse surface pressure and limiting molecular area of its Langmuir monolayer on pure water are 40 mN/m and 0.56 nm2, respectively. However, when barbituric acid or thymine was introduced into the subphase, the corresponding pi-A isotherms of the monolayers exhibited a lower collapse surface pressure (22 mN/m for BA, 21 mN/m for T) and smaller limiting molecular area (0.54 nm2 for BA and 0.52 nm2 for T). UV-vis and FT-IR studies of the LB films formed by 2Azo-2C12H25-melamine have also been carried out. The results indicated that the LB films of 2Azo-2C12H25-melamine deposited from pure water undergo distinct collapse of the H-aggregate upon UV irradiation, while the LB films deposited from a BA- or T-containing subphase retain the H-aggregate. The host-guest-interaction-induced blockage of azobenzene photoisomerization should be responsible for the stabilized H-aggregate. A 1:1 host/guest binding mode to form a linear supramolecular polymeric chain has been proposed in the Langmuir monolayers formed on a BA- or T-containing subphase. The current results suggest that the host-guest interaction should be an effective means to manipulate the interfacial assembly of azobenzene-derived amphiphiles.

  20. Electrical induction and optical erasure of birefringence in the isotropic liquid phase of a dichiral azobenzene liquid-crystalline compound (Presentation Recording)

    Science.gov (United States)

    Yamamoto, Takahiro; Nishiyama, Isa

    2015-10-01

    Liquid crystal is a representative soft matter, which has physical properties between those of conventional liquid and those of crystal in a temperature range above a melting point. A liquid-crystal display (LCD) employs the response of the liquid-crystal alignment to the electric field and is a key device of an information display. For common LCDs, the precise control of the initial alignment of LC molecules is needed so that a good dark state, thus a high contrast ratio, can be obtained. If the birefringence can be induced in the liquid phase by the application of electric field, it is of great use as a material for the LCD application. In this study, we will report a unique property of dichiral azobenzene liquid crystals: an electric induction of birefringence in a liquid phase of an antiferroelectric dichiral azobenzene liquid crystal. The optically isotropic texture changes into the homogenous birefringent texture by the application of the in-plane electric field above the clearing temperature of the liquid crystal. We find that one of the possible reasons of the induction of the birefringence in the isotropic phase is the electrically-induced increase of the phase transition temperature between the antiferroelectric liquid-crystalline and "liquid" phases, i.e., increase in the clearing temperature. The resulting birefringence can be disappeared by the irradiation of UV light, due to the photoinduced isomerization of the azobenzene compound, thus dual control of the birefringent structure, by the irradiation of light and/or by the application of the electric field, is achieved.

  1. Right- and Left-Handed Helices, What is in between? Interconversion of Helical Structures of Alternating Pyridinedicarboxamide/m-(phenylazo)azobenzene Oligomers.

    Science.gov (United States)

    Tao, Peng; Parquette, Jon R; Hadad, Christopher M

    2012-12-11

    Some unnatural polymers/oligomers have been designed to adopt a well-defined, compact, three-dimensional folding capability. Azobenzene units are common linkages in these oligomer designs. Two alternating pyridinedicarboxamide/m-(phenylazo)azobenzene oligomers that can fold into both right- and left-handed helices were studied computationally in order to understand their dynamical properties. Helical structures were shown to be the global minima among the many different conformations generated from the Monte Carlo simulations, and extended conformations have higher potential energies than compact ones. To understand the interconversion process between right- and left-handed helices, replica-exchange molecular dynamic (REMD) simulations were performed on both oligomers, and with this method, both right- and left-handed helices were successfully sampled during the simulations. REMD trajectories revealed twisted conformations as intermediate structures in the interconversion pathway between the two helical forms of these azobenzene oligomers. This mechanism was observed in both oligomers in current study and occurred locally in the larger oligomer. This discovery indicates that the interconversion between helical structures with different handedness goes through a compact and partially folded structure instead of globally unfold and extended structure. This is also verified by the nudged elastic band (NEB) calculations. The temperature weighted histogram analysis method (T-WHAM) was applied on the REMD results to generate contour maps of the potential of mean force (PMF). Analysis showed that right- and left-handed helices are equally sampled in these REMD simulations. In large oligomers, both right- and left-handed helices can be adopted by different parts of the molecule simultaneously. The interconversion between two helical forms can occur in the middle of the helical structure and not necessarily at the termini of the oligomer.

  2. Thermal degradation behavior of methyl methacrylate derived copolymer.

    Science.gov (United States)

    Kaya, Esin; Kurt, Adnan; Er, Mustafa

    2012-11-01

    A novel copolymer of 2-hydroxy-3-menthyloxy-1-(4-methoxyphenyl)-3-oxopropyl methacrylate (HMOPMA) and methyl methacrylate (MMA), [poly(HMOPMA-co-MMA)], was synthesized by free radical polymerization. The percentages of HMOPMA and MMA units obtained in the copolymer composition were 19% and 81%, respectively. The solubility parameter of poly(HMOPMA-co-MMA) was found to be 10.3 cal(1/2) cm(-3/2) by turbidimetric titration method. Thermal degradation mechanism and activation energies for initial decomposition process under non-isothermal conditions were determined by integral approximation methods from the thermogravimetric study. The decomposition activation energies of poly(HMOPMA-co-MMA) using Kissinger and Flyn-Wall-Ozawa methods were calculated as 119.99 kJ/mol and 125.34 kJ/mol, respectively. The study of kinetic equations showed that the reaction mechanism of decomposition process in the conversion range studied progressed with D1 mechanism, one-dimensional diffusion of deceleration type of solid state mechanism.

  3. Anti-Biofouling Effect of PEG-Grafted Block Copolymer Synthesized by RAFT Polymerization.

    Science.gov (United States)

    Kim, Seon-Mi; Han, Sang Suk; Kim, A Young; Choi, Beom-Jin; Paik, Hyun-Jong; Lee, Inwon; Park, Hyun; Chun, Ho Hwan; Cho, Youngjin; Hwang, Do-Hoon

    2015-10-01

    Poly(glycidyl methadrylate-block-styrene) (PGMA-b-PS), a block copolymer consisting of glycidyl methacrylate and styrene, was synthesized via reversible addition-fragmentation chain transfer living polymerization. The synthesized PGMA-b-PS was then grafted with low-molecular-weight polyethylene glycol (PEG) via epoxy ring opening to give PGMA-g-PEG-b-PS, which was evaluated as an anti-biofouling coating material. As a preliminary test for the anti-biofouling effect, a protein adsorption experiment was performed on the synthesized block copolymer surface. The block copolymers were spin-coated onto silicon wafers, and protein adsorption experiments were carried out using fluorescein isothiocyanate conjugate-labeled bovine serum albumin. The fluorescence intensity of the protein adsorbed on the block copolymer surface was compared with that of a polystyrene film as a reference. The synthesized PGMA-g-PEG-b-PS film showed much lower fluorescence intensity than that of the PS film.

  4. Total Spinal Block after Thoracic Paravertebral Block.

    Science.gov (United States)

    Beyaz, Serbülent Gökhan; Özocak, Hande; Ergönenç, Tolga; Erdem, Ali Fuat; Palabıyık, Onur

    2014-02-01

    Thoracic paravertebral block (TPVB) can be performed with or without general anaesthesia for various surgical procedures. TPVB is a popular anaesthetic technique due to its low side effect profile and high analgesic potency. We used 20 mL of 0.5% levobupivacaine for a single injection of unilateral TPVB at the T7 level with neurostimulator in a 63 year old patient with co-morbid disease who underwent cholecystectomy. Following the application patient lost consciousness, and was intubated. Haemodynamic instability was normalised with rapid volume replacement and vasopressors. Anaesthetic drugs were stopped at the end of the surgery and muscle relaxant was antagonised. Return of mucle strenght was shown with neuromuscular block monitoring. Approximately three hours after TPVB, spontaneous breathing started and consciousness returned. A total spinal block is a rare and life-threatening complication. A total spinal block is a complication of spinal anaesthesia, and it can also occur after peripheral blocks. Clinical presentation is characterised by hypotension, bradicardia, apnea, and cardiac arrest. An early diagnosis and appropriate treatment is life saving. In this case report, we want to present total spinal block after TPVB.

  5. Modeling of a Buss-Kneader as a Polymerization Reactor for Acrylates. Part II: Methyl Methacrylate Based Resins

    NARCIS (Netherlands)

    Troelstra, E.J; van Dierendonck, L.L.; Janssen, L.P.B.M.; Renken, A.

    2002-01-01

    The Buss-Kneader has proven to be a suitable reactor for the polymerization of acrylates. In this second part, the polymerization of methyl methacrylate and the ter-polymerization of methyl methacrylate (MMA), hydroxyethyl methacrylate and n-butylmethacrylate is carried out in a pilot Buss-Kneader.

  6. Adhesion of Escherichia coli on to a series of poly(methacrylates) differing in charge and hydrophobicity

    NARCIS (Netherlands)

    Harkes, G.; Feijen, J.; Dankert, J.

    1991-01-01

    The adhesion of three Escherichia coli strains on to six poly(methacrylates) differing in hydrophobicity and surface charge was measured as a function of time under laminar flow conditions. Polymers used were poly(methy) methacrylate) (PMMA), poly(hydroxyethy) methacrylate) (PHEMA) and copolymers of

  7. Generalized Block Failure

    DEFF Research Database (Denmark)

    Jönsson, Jeppe

    2015-01-01

    Block tearing is considered in several codes as a pure block tension or a pure block shear failure mechanism. However in many situations the load acts eccentrically and involves the transfer of a substantial moment in combination with the shear force and perhaps a normal force. A literature study...... yield lines around the block leads to simple interaction formulas similar to other interaction formulas in the codes.......Block tearing is considered in several codes as a pure block tension or a pure block shear failure mechanism. However in many situations the load acts eccentrically and involves the transfer of a substantial moment in combination with the shear force and perhaps a normal force. A literature study...

  8. Fluorosilicone multi-block copolymers tethering quaternary ammonium salt groups for antimicrobial purpose

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Fang; Qin, Xiaoshuai; Li, Yancai; Ren, Lixia; Zhao, Yunhui, E-mail: zhaoyunhui@tju.edu.cn; Yuan, Xiaoyan

    2015-08-30

    Highlights: • QAS-containing fluorosilicone multi-block copolymers were synthesized. • The block length of PHFBMA in the copolymers was tailored via RAFT polymerization. • Surface roughness of the copolymers decreased with the increased PHFBMA content. • A certain length of PHFBMA block enhanced C−N{sup +} percentage on the surface. - Abstract: Symmetrically structured fluorosilicone multi-block copolymers containing poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and poly(hexafluorobutyl methacrylate) (PHFBMA) were sequentially synthesized via reversible addition–fragmentation chain transfer polymerization, using a polydimethylsiloxane (PDMS) chain transfer agent with dithiocarbonate groups at both ends. Then, the CBABC-type block copolymers were quaternized with n-octyliodide to tether quaternary ammonium salt (QAS) groups in the PDMAEMA blocks for the antimicrobial use. The obtained fluorosilicone copolymers showed clear variations in the C-N{sup +} composition and surface morphology on their films depending on the content of the PHFBMA blocks, which were characterized by X-ray photoelectron spectroscopy and atomic force microscopy, respectively. The results indicated that the symmetrical CBABC structure favored PDMS and QAS tethered blocks migrating to the film surface. With the mass percentage of the PHFBMA increased from 0 to 32.5%, the surface roughness of the copolymer film decreased gradually with a tendency to form a smooth surface. Owing to the surface properties, fluorosilicone multi-block copolymers containing a certain amount of PHFBMA with higher C-N{sup +} content and relatively smooth morphology demonstrated obvious antimicrobial activity against Gram-positive bacteria, Bacillus subtilis and Gram-negative bacteria, Escherichia coli. The functionalized multi-block copolymers based on fluorosilicone and QAS groups would have potential applications in antimicrobial coatings.

  9. Radiation-grafted polymers for biomaterial applications. I. 2-hydroxyethyl methacrylate: ethyl methacrylate grafting onto low density polyethylene films

    Energy Technology Data Exchange (ETDEWEB)

    Cohn, D.; Hoffman, A.S.; Ratner, B.D.

    1984-08-01

    Studies were conducted on the radiation grafting of 2-hydroxyethyl methacrylate (HEMA) and ethyl methacrylate (EMA) by the mutual irradation technique onto low density polyethylene. Four different solution concentrations were used, and radiation doses ranged from 0.03 to 0.50 Mrad. Four copolymer compositions having different HEMA:EMA ratios were also studied using two total monomer concentrations. The kinetics of the grafting process demonstrated by the two monomers were basically different. While EMA showed a typical diffusion-controlled kinetic pattern, HEMA exhibited a more complex behavior, the main features of which were an induction period, a slight autoacceleration and a significant drop in graft level after a maximum is reached. The difference in behavior was interpreted in terms of partitioning of monomers into the polyethlene substrate. The surface topography of the grafted films was studied by means of scanning electron microscopy. A mechanism based on osmotic cell formation was suggested for the HEMA graft system. The copolymer systems investigated showed that the graft reaction is faster in the initial stages for higher percentages of EMA in the monomer mixtures; as grafting proceeds the trend is reversed. 24 references, 16 figures, 2 tables.

  10. Poly(2-hydroxyethyl methacrylate-co-dodecyl methacrylate-co-acrylic acid): synthesis, physico-chemical characterisation and nafcillin carrier.

    Science.gov (United States)

    Zecheru, Teodora; Rotariu, Traian; Rusen, Edina; Mărculescu, Bogdan; Miculescu, Florin; Alexandrescu, Laura; Antoniac, Iulian; Stancu, Izabela-Cristina

    2010-10-01

    In the present study polymeric microbeads of poly(2-hydroxyethyl methacrylate-co-dodecyl methacrylate-co-acrylic acid) or p(HEMA-co-dDMA-co-AA) were synthesised and characterized through FT-IR and scanning electron microscopy (SEM); their swelling behavior against saline solution was explored and their in vitro cytotoxicity was evaluated. Further, in order to elucidate kinetic aspects regarding the ternary system p(HEMA-co-dDMA-co-AA), a mathematical model of the reactivity ratios of the comonomers in the terpolymer has been conceived and analyzed. An intensified tendency of AA units accumulation in the copolymer has been noticed, in spite of HEMA units, while dDMA conserves in the copolymer the fraction from the feed. Three compositions have been selected for nafcillin-loading and their in vitro release capacity was evaluated. The compositions of 80:10:10 and 75:10:15 M ratios appear suitable for further in vivo testing, in order to be used as drug delivery systems in the treatment of different osseous diseases.

  11. Structural characterization of a poly(methacrylic acid)-poly(methyl methacrylate) copolymer by nuclear magnetic resonance and mass spectrometry.

    Science.gov (United States)

    Giordanengo, Rémi; Viel, Stéphane; Hidalgo, Manuel; Allard-Breton, Béatrice; Thévand, André; Charles, Laurence

    2009-11-03

    Mass spectrometry (MS) and nuclear magnetic resonance (NMR) have been combined to achieve the complete microstructural characterization of a poly(methacrylic acid)-poly(methyl methacrylate) (PMAA-PMMA) copolymer synthesized by nitroxide-mediated polymerization. Various PMAA-PMMA species could be identified which mainly differ in terms of terminaisons. 1H and 13C NMR experiments revealed the structure of the end-groups as well as the proportion of each co-monomer in the copolymers. These end-group masses were further confirmed from m/z values of doubly charged copolymer anions detected in the single stage mass spectrum. In contrast, copolymer composition derived from MS data was not consistent with NMR results, obviously due to strong mass bias well known to occur during electrospray ionization of these polymeric species. Tandem mass spectrometry could reveal the random nature of the copolymer based on typical dissociation reactions, i.e., water elimination occurred from any two contiguous MAA units while MAA-MMA pairs gave rise to the loss of a methanol molecule. Polymer backbone cleavages were also observed to occur and gave low abundance fragment ions which allowed the structure of the initiating end-group to be confirmed.

  12. Structural characterization of a poly(methacrylic acid)-poly(methyl methacrylate) copolymer by nuclear magnetic resonance and mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Giordanengo, Remi [Universites Aix-Marseille I, II et III - CNRS, UMR 6264: Laboratoire Chimie Provence, Spectrometries Appliquees a la Chimie Structurale, F-13397 Marseille (France); Viel, Stephane [Aix-Marseille Universite - CNRS, UMR 6263: Institut des Sciences Moleculaires de Marseille, Chimiometrie et Spectrometries, F-13397 Marseille (France); Hidalgo, Manuel; Allard-Breton, Beatrice [ARKEMA, Centre de Recherche Rhone Alpes, Rue Henri Moissan, F-69493 Pierre-Benite (France); Thevand, Andre [Universites Aix-Marseille I, II et III - CNRS, UMR 6264: Laboratoire Chimie Provence, Spectrometries Appliquees a la Chimie Structurale, F-13397 Marseille (France); Charles, Laurence, E-mail: laurence.charles@univ-provence.fr [Universites Aix-Marseille I, II et III - CNRS, UMR 6264: Laboratoire Chimie Provence, Spectrometries Appliquees a la Chimie Structurale, F-13397 Marseille (France)

    2009-11-03

    Mass spectrometry (MS) and nuclear magnetic resonance (NMR) have been combined to achieve the complete microstructural characterization of a poly(methacrylic acid)-poly(methyl methacrylate) (PMAA-PMMA) copolymer synthesized by nitroxide-mediated polymerization. Various PMAA-PMMA species could be identified which mainly differ in terms of terminaisons. {sup 1}H and {sup 13}C NMR experiments revealed the structure of the end-groups as well as the proportion of each co-monomer in the copolymers. These end-group masses were further confirmed from m/z values of doubly charged copolymer anions detected in the single stage mass spectrum. In contrast, copolymer composition derived from MS data was not consistent with NMR results, obviously due to strong mass bias well known to occur during electrospray ionization of these polymeric species. Tandem mass spectrometry could reveal the random nature of the copolymer based on typical dissociation reactions, i.e., water elimination occurred from any two contiguous MAA units while MAA-MMA pairs gave rise to the loss of a methanol molecule. Polymer backbone cleavages were also observed to occur and gave low abundance fragment ions which allowed the structure of the initiating end-group to be confirmed.

  13. Analytical strategy for the molecular weight determination of random copolymers of poly(methyl methacrylate) and poly(methacrylic acid).

    Science.gov (United States)

    Giordanengo, Rémi; Viel, Stéphane; Hidalgo, Manuel; Allard-Breton, Béatrice; Thévand, André; Charles, Laurence

    2010-06-01

    Molecular weight characterization of random amphiphilic copolymers currently represents an analytical challenge. In particular, molecules composed of methacrylic acid (MAA) and methyl methacrylate (MMA) as the repeat units raise issues in commonly used techniques. The present study shows that when random copolymers cannot be properly ionized by MALDI, and hence detected and measured in MS, one possible analytical strategy is to transform them into homopolymers, which are more amenable to this ionization technique. Then, by combining the molecular weight of the so-obtained homopolymers, as measured by MS, with the relative molar proportion of the MMA and MMA units, as given by (1)H NMR spectrum, one can straightforwardly estimate the molecular weight of the initial copolymer. A methylation reaction was performed to transform MAA-MMA copolymer samples into PMMA homopolymers, using trimethylsilyldiazomethane as a derivatization agent. Weight average molecular weight (M(w)) parameters of the MAA-MMA copolymers could then be derived from M(w) values obtained for the methylated MAA-MMA molecules by MALDI, which were also validated by pulsed gradient spin echo (PGSE) NMR. An alkene function in one of the studied copolymer end-groups was also shown to react with the methylation agent, giving rise to MMA-like polymeric by-products characterized by tandem mass spectrometry and which could be avoided by adjusting the amount of the trimethylsilyldiazomethane in the reaction medium.

  14. Synthesis of poly (methyl methacrylate)-b-polystyrene with high molecular weight by DPE seeded emulsion polymerization and its application in proton exchange membrane.

    Science.gov (United States)

    Wang, Wenwen; Zhang, Hepeng; Geng, Wangchang; Gu, Junwei; Zhou, Yanyang; Zhang, Junping; Zhang, Qiuyu

    2013-09-15

    In this article, we present poly (methyl methacrylate)-b-polystyrene (PMMA-b-PS) with different block ratios and high molecular weight, which was synthesized by environmentally friendly seeded emulsion polymerization with 1,1-diphenylethylene (DPE) as a chain transfer agent. Polymerization kinetics in the first and second stage was investigated. Stable latex and homogeneous latex particles were obtained with the characterization of laser light scattering (LLS) and transmission electron microscopy (TEM). SEC and (1)H NMR revealed the successful preparation of block copolymers with high molecular weight and two different block ratios. The morphology of microphase separation of block copolymer thin films was investigated by AFM, and long-range order lamellar morphology was observed after vapor-annealing. The block copolymer with block ratio of almost 1:1 and higher molecular weight than that of previous PMMA-b-PS was sulfonated with acetyl sulfate, and the sulfonation was confirmed by FTIR, (1)H NMR, and TGA. Then, the sulfonated PMMA-b-PS was casted as membranes. The electrochemical impedance spectroscopy displayed that membranes possessed favorable proton conductivity and fine dimensional stability, and they could be candidates as proton exchange membranes.

  15. Well-defined ABA- and BAB-type block copolymers of PDMAEMA and PCL

    DEFF Research Database (Denmark)

    Bruce, Carl; Javakhishvili, Irakli; Fogelstrom, Linda

    2014-01-01

    Triblock copolymers of ABA- and BAB-type consisting of poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA, A) and poly(epsilon-caprolactone) (PCL, B) have successfully been prepared. PDMAEMA-b-PCL-b-PDMAEMA (ABA) and PCL-b-PDMAEMA-b-PCL (BAB) were synthesised by a combination of ring...... as the outer block (ABA), the inherent crystallinity of PCL was destroyed while with PCL as the outer block (BAB), the degree of crystallinity was in the same proximity as for a PCL homopolymer....

  16. Block copolymer/ferroelectric nanoparticle nanocomposites

    Science.gov (United States)

    Pang, Xinchang; He, Yanjie; Jiang, Beibei; Iocozzia, James; Zhao, Lei; Guo, Hanzheng; Liu, Jin; Akinc, Mufit; Bowler, Nicola; Tan, Xiaoli; Lin, Zhiqun

    2013-08-01

    Nanocomposites composed of diblock copolymer/ferroelectric nanoparticles were formed by selectively constraining ferroelectric nanoparticles (NPs) within diblock copolymer nanodomains via judicious surface modification of ferroelectric NPs. Ferroelectric barium titanate (BaTiO3) NPs with different sizes that are permanently capped with polystyrene chains (i.e., PS-functionalized BaTiO3NPs) were first synthesized by exploiting amphiphilic unimolecular star-like poly(acrylic acid)-block-polystyrene (PAA-b-PS) diblock copolymers as nanoreactors. Subsequently, PS-functionalized BaTiO3 NPs were preferentially sequestered within PS nanocylinders in the linear cylinder-forming polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymer upon mixing the BaTiO3 NPs with PS-b-PMMA. The use of PS-b-PMMA diblock copolymers, rather than traditional homopolymers, offers the opportunity for controlling the spatial organization of PS-functionalized BaTiO3 NPs in the PS-b-PMMA/BaTiO3 NP nanocomposites. Selective solvent vapor annealing was utilized to control the nanodomain orientation in the nanocomposites. Vertically oriented PS nanocylinders containing PS-functionalized BaTiO3 NPs were yielded after exposing the PS-b-PMMA/BaTiO3 NP nanocomposite thin film to acetone vapor, which is a selective solvent for PMMA block. The dielectric properties of nanocomposites in the microwave frequency range were investigated. The molecular weight of PS-b-PMMA and the size of BaTiO3 NPs were found to exert an apparent influence on the dielectric properties of the resulting nanocomposites.Nanocomposites composed of diblock copolymer/ferroelectric nanoparticles were formed by selectively constraining ferroelectric nanoparticles (NPs) within diblock copolymer nanodomains via judicious surface modification of ferroelectric NPs. Ferroelectric barium titanate (BaTiO3) NPs with different sizes that are permanently capped with polystyrene chains (i.e., PS-functionalized BaTiO3NPs) were

  17. BLOCK H-MATRICES AND SPECTRUM OF BLOCK MATRICES

    Institute of Scientific and Technical Information of China (English)

    黄廷祝; 黎稳

    2002-01-01

    The block H-matrices are studied by the concept of G-functions, several concepts of block matrices are introduced. Equivalent characters of block H-matrices are obtained. Spectrum localizations claracterized by Gfunctions for block matrices are got.

  18. Block TERM factorization of block matrices

    Institute of Scientific and Technical Information of China (English)

    SHE Yiyuan; HAO Pengwei

    2004-01-01

    Reversible integer mapping (or integer transform) is a useful way to realize Iossless coding, and this technique has been used for multi-component image compression in the new international image compression standard JPEG 2000. For any nonsingular linear transform of finite dimension, its integer transform can be implemented by factorizing the transform matrix into 3 triangular elementary reversible matrices (TERMs) or a series of single-row elementary reversible matrices (SERMs). To speed up and parallelize integer transforms, we study block TERM and SERM factorizations in this paper. First, to guarantee flexible scaling manners, the classical determinant (det) is generalized to a matrix function, DET, which is shown to have many important properties analogous to those of det. Then based on DET, a generic block TERM factorization,BLUS, is presented for any nonsingular block matrix. Our conclusions can cover the early optimal point factorizations and provide an efficient way to implement integer transforms for large matrices.

  19. Optimization of glycol methacrylate embedding of large specimens in neurological research. Study of rat skull-brain specimens after implantation of polyester meshes.

    Science.gov (United States)

    Quester, Ralf; Knifka, Jutta; Schröder, Roland

    2002-01-15

    Advances in neuroscience require better anatomical knowledge of neuronal architecture and structural details. Optimal embedding techniques are the basis for precise morphometric studies in section series as well as for the evaluation of tissue specimens or implants of differing hardness. There are very few methods for preparing large specimens by resin embedding, although resins such as polyethylene glycol (PEG) and methyl methacrylate (MMA) are presently in use. However, these methods have proven to be laborious and sometimes unsatisfactory for serial sectioning. While glycol methacrylate embedding (GMA) is suitable for smaller specimens, it results in inadequate infiltration and polymerization in blocks larger than 1 x 1 x 0.2 cm. We present an improved technique using GMA, which permits both standardized embedding of 4 x 2 x 2 cm blocks and preparation of section series. This method was developed for preserving skull-brain specimens from rats with polyester-mesh implants. The excellent preservation of cellular details allowed the assessment of local tissue reaction to foreign-body material in situ. Advantages of this method are: (1) No toxic catalysts or solvents are used (as opposed to MMA and current GMA processes); (2) Laborious routines in stretching and mounting of sections are not necessary (in contrast to PEG and MMA); (3) No deplastination is required before staining (in contrast to PEG and MMA); (4) Excellent morphologic preservation of various tissue is achieved.

  20. Radiation synthesis of nanosilver nanohydrogels of poly(methacrylic acid)

    Science.gov (United States)

    Gupta, Bhuvanesh; Gautam, Deepti; Anjum, Sadiya; Saxena, Shalini; Kapil, Arti

    2013-11-01

    Nanosilver nanohydrogels (nSnH) of poly(methacrylic acid) were synthesized and stabilized using gamma irradiation. The main objective of this study was to develop silver nanoparticles and to evaluate the antimicrobial activity. Radiation helps in the polymerization, crosslinking and reduction of silver nitrate as well. Highly stable and uniformly distributed silver nanoparticles have been obtained within hydrogel network by water in oil nanoemulsion polymerization and were evaluated by dynamic light scattering (DLS) and transmission electron microscopy (TEM) respectively. TEM showed almost spherical and uniform distribution of silver nanoparticles through the hydrogel network. The mean size of silver nanoparticles ranging is 10-50 nm. The nanohydrogels showed good swelling in water. Antibacterial studies of nSnH suggest that it can be a good candidate as coating material in biomedical applications.

  1. Poly(hydroxyethyl methacrylate) based networked solid polymer electrolyte.

    Science.gov (United States)

    Lee, A-Ran; Kim, Young-Deok; Lee, Sang-Keol; Jo, Nam-Ju

    2013-10-01

    Solid polymer electrolytes (SPEs) have good safety for lithium battery compared to liquid electrolytes, but they have low ionic conductivity. To solve the problem, the polymer-in-salt system was introduced which has higher ionic conductivity than salt-in-polymer system. However, polymer-in-salt system has disadvantages that are poor mechanical properties with increasing salt concentration. In this study, networked polymer electrolytes consisting of poly(hydroxyethyl methacrylate) (P(HEMA)), lithium triflate (LiCF3SO3, LiTf) and hydrochloric acid (HCl) were prepared. And the electrochemical and mechanical properties of P(HEMA) based SPEs were investigated by using ac impedance analyzer and universal testing machine, respectively.

  2. Preparation and modification of itaconic anhydride–methyl methacrylate copolymers

    Directory of Open Access Journals (Sweden)

    MILOS B. MILOVANOVIC

    2007-12-01

    Full Text Available The free radical copolymerisation of itaconic anhydride and methyl methacrylate in solution was studied at 60 °C. The copolymer composition was determined by 1H-NMR spectroscopy and the obtained monomer reactivity ratios were calculated, rITA = 1.35±0.11; rMMA = 0.22±0.22 (by the Fineman–Ross method and rITA = 1.27±0.38; rMMA = 0.10±0.05 (by the Mayo–Lewis method. The synthesised copolymers were modified by reaction with di-n-butyl amine. The copolymer composition after amidation was determined by elemental analysis via the nitrogen content. Amidation of the anhydride units in the copolymers with di-n-butyl amine resulted in complete conversion to itaconamic acid.

  3. Synthesis, characterization and photoinduced curing of polysulfones with (methacrylate functionalities

    Directory of Open Access Journals (Sweden)

    Cemil Dizman

    2010-06-01

    Full Text Available The UV-curable telechelic polysulfones with (methacrylate functionalities were synthesized by condensation polymerization and subsequent esterification. The final polymers and intermediates at various stages were characterized by 1H NMR, FT-ATR, and GPC. The oligomeric films prepared from the appropriate solutions containing these telechelics and 2,2-dimethoxy-2-phenylacetophenone (DMPA as the photoinitiator undergo rapid polymerization upon irradiation forming insoluble networks. The photo-curing behavior was investigated by photo-DSC and the effects of the molecular weight of the polysulfone precursor and type of functionality on the rate of polymerization and conversion were evaluated. Thermal properties of the photochemically cured films were studied by differential scanning calorimeter (DSC and thermal gravimetric analysis (TGA.

  4. DIMENSIONAL STABILITY OF METHYL METHACRYLATE HARDENED HYBRID POPLAR WOOD

    Directory of Open Access Journals (Sweden)

    Wei-Dan Ding,

    2011-11-01

    Full Text Available This study examines the dimensional stability of fast-growing poplar clones wood after treatment by impregnation with methyl methacrylate (MMA. Six hybrid poplar clones from one plantation in Quebec were sampled. The effects of hardening with MMA on density as well as longitudinal, radial, tangential, and volumetric swelling properties (S, water uptake capacity (D, anti-swelling efficiency (ASE, and water repellent efficiency (WRE after soaking were investigated. Hardening treatment increased the density of all poplar woods by 1.2 to 1.6 and decreased the inner water migration rate during soaking. S and D values of hardened woods were significantly lower than those of controls, depending on the clone type. ASE and WRE values suggested that incorporating MMA effectively improved the dimensional stability of poplar wood at the early soaking stage, but was less effective in the long term.

  5. Synthesis of Methacrylate Monomers with Antibacterial Effects Against S. Mutans

    Directory of Open Access Journals (Sweden)

    Jingwei He

    2011-11-01

    Full Text Available A series of polymerizable quaternary ammonium compounds were synthesized with the aim of using them as immobilized antibacterial agents in methacrylate dental composites, and their structures were characterized by FT-IR, 1H-NMR, and 13C-NMR analysis. Their antibacterial activities against the oral bacterium Streptococcus mutans were evaluated in vitro by a Minimum Inhibitory Concentration test, and the results showed that 2-dimethyl-2-hexadecyl-1-methacryloxyethyl ammonium iodide (C16 had the highest antibacterial activity against S. mutans, and 2-dimethyl-2-pentyl-1-methacryloxyethyl ammonium iodide (C5 and 2-dimethyl-2-octyl-1-methacryloxyethyl ammonium iodide (C8 did not show any inhibition.

  6. Effect of trans-cis photoisomerization on phase equilibria and phase transition of liquid-crystalline azobenzene chromophore and its blends with reactive mesogenic diacrylate.

    Science.gov (United States)

    Kim, Namil; Li, Quan; Kyu, Thein

    2011-03-01

    Photoisomerization-induced phase transition of neat liquid-crystalline azobenzene chromophore (LCAC) and its effect on phase diagrams of its mixtures with reactive mesogenic diacrylate monomer (RM257) have been investigated experimentally and theoretically. Upon irradiation with ultraviolet light, the nematic phase of LCAC transformed to isotropic, while the crystal phase showed corrugated textures on the surface (i.e., ripples). The phase-transition temperatures and corresponding morphologies of the blends have been investigated by means of differential scanning calorimetry and optical microscopy. A theoretical phase diagram of a binary nematic and crystalline system was constructed by self-consistently solving the combined free energies of Flory-Huggins, Maier-Saupe, and phase-field theory. The calculation revealed various coexistence regions such as nematic + liquid (N₁ + L₂), crystal + liquid (Cr₁ + L₂), crystal + nematic (Cr₁ + N₂), and crystal + crystal (Cr₁ + Cr₂) over a broad range of compositions including the single-phase nematic (N₁, N₂) of the corresponding constituents. The calculated liquidus lines were in good accord with the depressed mesophase-isotropic transition points. The present paper demonstrates the effect of trans-cis photoisomerization on the mesophase transitions of neat LCAC and the phase diagram of LCAC-RM257 as well as on the ripple formation (i.e., periodic undulation) on the azobenzene crystals.

  7. Photoinduced dichroism and optical anisotropy in a liquid-crystalline azobenzene side chain polymer caused by anisotropic angular distribution of trans and cis isomers

    Science.gov (United States)

    Blinov, Lev M.; Kozlovsky, Mikhail V.; Ozaki, Masanori; Skarp, Kent; Yoshino, Katsumi

    1998-10-01

    Photochromism has been studied for two comb-like liquid-crystalline copolymers (I) and (II) containing azobenzene chromophores in their side chains. In a smectic glass phase of both copolymers, upon short-time irradiation by UV light, long-living cis isomers are observed. Both copolymers manifest the photoinduced anisotropy, the physical mechanisms of which seem to be quite different. In spin-coated films of polymer (II), the origin of the anisotropy is a strong stable dichroism, which is due to an enrichment and depletion of the chosen angular direction, correspondingly, with trans and cis isomers of the azobenzene chromophores. Polymer (I) manifests no dichroism at all, and its induced optical anisotropy may be accounted for by a rather slow chromophore reorientation. In copolymer (II) a considerable reorientation of the mesogenic groups also occurs as a secondary phenomenon at the stage of the cis isomer formation only. This observation shed more light on the general process of the light-induced molecular reorientation in polymers, liquid crystals, and Langmuir-Blodgett films, which is of great importance for holographic information recording.

  8. Azobenzene mesogens mediated preparation of SnS nanocrystals encapsulated with in-situ N-doped carbon and their enhanced electrochemical performance for lithium ion batteries application

    Science.gov (United States)

    Wang, Meng; Zhou, Yang; Duan, Junfei; Chen, Dongzhong

    2016-09-01

    In this work, azobenzene mesogen-containing tin thiolates have been synthesized, which possess ordered lamellar structures persistent to higher temperature and serve as liquid crystalline precursors. Based on the preorganized tin thiolate precursors, SnS nanocrystals encapsulated with in-situ N-doped carbon layer have been achieved through a simple solventless pyrolysis process with the azobenzene mesogenic thiolate precursor served as Sn, S, N, and C sources simultaneously. Thus prepared nanocomposite materials as anode of lithium ion batteries present a large specific capacity of 604.6 mAh·g-1 at a current density of 100 mA·g-1, keeping a high capacity retention up to 96% after 80 cycles, and display high rate capability due to the synergistic effect of well-dispersed SnS nanocrystals and N-doped carbon layer. Such encouraging results shed a light on the controlled preparation of advanced nanocomposites based on liquid crystalline metallomesogen precursors and may boost their novel intriguing applications. Project supported by the National Natural Science Foundation of China (Grant No. 21574062) and the Huaian High-Technology Research Institute of Nanjing University, China (Grant No. 2011Q1).

  9. Lesson Thirteen Trifascicular Block

    Institute of Scientific and Technical Information of China (English)

    鲁端; 王劲

    2005-01-01

    @@ A complete trifascicular block would result in complete AV block. The idio ventricular rhythm has a slower rate and a wide QRS complex because the pacemaker is located at the peripheral part of the conduction system distal to the sites of the block1. Such a rhythm may be difficult to differentiate from bifascicular or bundle branch block combined with complete block at a higher level such as the AV node or His bundle2. Besides a slower ventricular rate, a change in the morphology of the QRS complex from a previous known bifascicular pattern would be strongly suggestive of a trifascicular origin of the complete AV block3. A His bundle recording is required for a definitive diagnosis, however.

  10. Polyglycidyl methacrylate based immunoaffinity cryogels for insulin adsorption

    Energy Technology Data Exchange (ETDEWEB)

    Memmedova, Türkan; Armutcu, Canan; Uzun, Lokman, E-mail: lokman@hacettepe.edu.tr; Denizli, Adil

    2015-07-01

    Immunoaffinity chromatography (IAC) is a kind of bioaffinity chromatography which used antibodies or antibody-related molecules as the stationary phase. IAC is used by many applications for analytical, clinical and diagnostic purposes, particularly preferring in analytical purposes on one-step separation and purification of target compounds. Moreover, immunoaffinity chromatography is used in antibody enrichment and separation of cells. IAC columns are usually applied in the antibody experiments due to powerful and selective binding of antibodies and/or their target antigens. Antigen or antibody molecules could be immobilized to the solid support. Therefore, target antibody or cell is purified. Specific bioligands can be immobilized directly on glycidyl based polymeric material with simple acid–base catalyst. In this study, polyglycidyl methacrylate based therefore cryogels were prepared and anti-insulin antibodies were immobilized on porous surface of cryogels. Swelling test, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and scanning electron microscopy (SEM) were conducted to characterize cryogels developed. To optimize separation conditions, effects of pH, initial insulin concentration, flow rate, salt concentration, contact time and temperature on insulin adsorption capacity were examined. The results indicated that the immunoaffinity cryogel developed here could be classified as good alternative with prominent properties such as high reusability and cost-friendly adsorbent and would be one of the primary reports for immunoaffinity purification of insulin molecules in not only lab-scale but also for industrial purposes. - Highlights: • Polyglycidyl methacrylate based cryogels developed as stationary phase • Immunoaffinity cryogels for reusable and cost-friendly insulin adsorption • Increase in worldwide prevalence of diabetes, type 1 or 2 • An exponential increase in the demand on insulin market • Guiding researchers for not

  11. Vascular responsiveness to dimethylaminoethyl methacrylate and its degradation products.

    Science.gov (United States)

    Abebe, Worku; Maddux, William F; Schuster, George S; Lewis, Jill B

    2003-07-01

    The increasing use of acrylate-based resins in dentistry has raised questions about the biocompatibility of these substances with oral tissues. The focus of the present investigation was to assess the responsiveness of blood vessels to the resin polymerization accelerating agent dimethylaminoethyl methacrylate (DMAEMA) and its degradation products dimethylethanolamine (DME) and methacrylic acid (MAA), using the rat aortic ring preparation as a tissue model. DMAEMA induced concentration-dependent relaxation of norepinephrine (NE)-contracted aortic rings with and without endothelium. N-nitro-L-arginine methyl ester (L-NAME) selectively inhibited the endothelium-dependent relaxation induced by DMAEMA, suggesting the release of nitric oxide from the endothelium by DMAEMA. Both indomethacin and glybenclamide attenuated the vasorelaxation elicited by DMAEMA in the presence as well as in the absence of endothelium, providing evidence for the role of vasorelaxant prostanoid(s) and K(ATP) channel activation in the responses observed. On the other hand, while MAA was without any apparent effect on the rat aorta, DMAEMA at high and DME at relatively low concentrations caused contraction of the tissues with and without endothelium in the absence of NE. The DME-induced contraction was inhibited by indomethacin, suggesting the involvement of contractile arachidonic acid metabolite(s) in the action of DME. This observation was supported by the findings of increased thromboxane A(2) (TXA(2)) production in aortic rings incubated with DME. Taken together, the data suggest that both DMAEMA and its degradation product, DME, are vasoactive, inducing vasorelaxation and contraction by various mechanisms that may involve the release of nitric oxide from the endothelium, the activation of smooth muscle K(ATP) channels, and the generation of vasorelaxant prostanoid(s) and TXA(2). These effects may play a role in tissue homeostasis and certain adverse conditions associated with the use of

  12. Blocked Urethral Valves

    Science.gov (United States)

    ... Blocked Urethral Valves Health Issues Listen Español Text Size Email Print Share Blocked Urethral Valves Page Content Article Body Urine leaves the bladder through a tube called the urethra, which in boys passes through the penis. Rarely, small membranes form across the urethra in ...

  13. Types of Heart Block

    Science.gov (United States)

    ... P wave as it normally would. If an electrical signal is blocked before it reaches the ventricles, they won't contract and pump blood to the lungs and the rest of the body. Second-degree heart block is divided into two ...

  14. Related Drupal Nodes Block

    NARCIS (Netherlands)

    Van der Vegt, Wim

    2010-01-01

    Related Drupal Nodes Block This module exposes a block that uses Latent Semantic Analysis (Lsa) internally to suggest three nodes that are relevant to the node a user is viewing. This module performs three tasks. 1) It periodically indexes a Drupal site and generates a Lsa Term Document Matrix. Inde

  15. The Block Neighborhood

    CERN Document Server

    Arrighi, Pablo

    2010-01-01

    We define the block neighborhood of a reversible CA, which is related both to its decomposition into a product of block permutations and to quantum computing. We give a purely combinatorial characterization of the block neighborhood, which helps in two ways. First, it makes the computation of the block neighborhood of a given CA relatively easy. Second, it allows us to derive upper bounds on the block neighborhood: for a single CA as function of the classical and inverse neighborhoods, and for the composition of several CAs. One consequence of that is a characterization of a class of "elementary" CAs that cannot be written as the composition of two simpler parts whose neighborhoods and inverse neighborhoods would be reduced by one half.

  16. Fabrication of 3D Microfluidic Devices by Thermal Bonding of Thin Poly(methyl methacrylate) Films

    KAUST Repository

    Perez, Paul

    2012-07-01

    The use of thin-film techniques for the fabrication of microfluidic devices has gained attention over the last decade, particularly for three-dimensional channel structures. The reasons for this include effective use of chip volume, mechanical flexibility, dead volume reduction, enhanced design capabilities, integration of passive elements, and scalability. Several fabrication techniques have been adapted for use on thin films: laser ablation and hot embossing are popular for channel fabrication, and lamination is widely used for channel enclosure. However, none of the previous studies have been able to achieve a strong bond that is reliable under moderate positive pressures. The present work aims to develop a thin-film process that provides design versatility, speed, channel profile homogeneity, and the reliability that others fail to achieve. The three building blocks of the proposed baseline were fifty-micron poly(methyl methacrylate) thin films as substrates, channel patterning by laser ablation, and device assembly by thermal-fusion bonding. Channel fabrication was characterized and tuned to produce the desired dimensions and surface roughness. Thermal bonding was performed using an adapted mechanical testing device and optimized to produce the maximum bonding strength without significant channel deformation. Bonding multilayered devices, incorporating conduction lines, and integrating various types of membranes as passive elements demonstrated the versatility of the process. Finally, this baseline was used to fabricate a droplet generator and a DNA detection chip based on micro-bead agglomeration. It was found that a combination of low laser power and scanning speed produced channel surfaces with better uniformity than those obtained with higher values. In addition, the implemented bonding technique provided the process with the most reliable bond strength reported, so far, for thin-film microfluidics. Overall, the present work proved to be versatile

  17. SYNTHESIS AND PROPERTIES OF IER FROM 2—HYDROXYETHYL METHACRYLATE

    Institute of Scientific and Technical Information of China (English)

    WANGJiaxing; HANYujian; 等

    1993-01-01

    This paper introduced the synthesis and properties of IER based on 2-hydroxyethyl methacrylate.The derivatives containing DEAE-,CM-,SO3H groups were prepared and their uses in biochemistry were studies.

  18. Biomimetic potential of some methacrylate-based copolymers: a comparative study.

    Science.gov (United States)

    Zecheru, Teodora; Filmon, Robert; Rusen, Edina; Mărculescu, Bogdan; Zerroukhi, Amar; Cincu, Corneliu; Chappard, Daniel

    2009-11-01

    Preparation of new biocompatible materials for bone recovery has consistently gained interest in the last few decades. Special attention was given to polymers that contain negatively charged groups, such as phosphate, carboxyl, and sulfonic groups toward calcification. This present paper work demonstrates that other functional groups present also potential application in bone pathology. New copolymers of 2-hydroxyethyl methacrylate with diallyldimethylammonium chloride (DADMAC), glycidyl methacrylate (GlyMA), methacrylic acid (MAA), 2-methacryloyloxymethyl acetoacetate (MOEAA), 2-methacryloyloxyethyltriethylammonium chloride (MOETAC), and tetrahydrofurfuryl methacrylate (THFMA) were obtained. The copolymers were characterized by FTIR, swelling potential, and they were submitted to in vitro tests for calcification and cytotoxicity evaluation. GlyMA and MOETAC-containing copolymers show promising results for further in vivo mineralization tests, as a potential alternative to the classical bone grafts, in bone tissue engineering.

  19. Polymerization of sodium methacrylate induced by irradiation; Polimerizacion del metacrilato de sodio inducida por la irradiacion

    Energy Technology Data Exchange (ETDEWEB)

    Galvan S, A. [Instituto Nacional de Investigaciones Nucleares, Gerencia de Ciencias Basicas, A.P. 18-1027, 11801 Mexico D.F. (Mexico)

    1998-07-01

    This work has two objectives, first: it is pretended to localize the lines of carbon links in its IR spectra, and second: following the polymerization of sodium methacrylate according to that it is irradiated with gamma rays. (Author)

  20. Radical Polymerization of Vinyl Acetate and Methyl Methacrylate Using Organochromium Initiators Complexed with Macrocyclic Polyamines

    Science.gov (United States)

    1994-06-30

    METHYL METHACRYLATE USING ORGANOCHROMIUM REA NTS COMPLEXED WITH MACROCYCLIC A• by Daniela Mardare, Scott Gaynor, Krzysztof Matyjaszewski DTIC Published... Daniela Mardare, Scott Gaynor, Krzysztof Matyjaszewski 7. PERFORMING ORGANIZATION NAME(S) AND ADORESS(ES) a. PERFORMING ORGANIZATION Carnegie Mellon

  1. Wireless Connection between Guide Wires and Bone Cement: Extravasated Methyl Methacrylate Mimicking a Retained Guide Wire

    Directory of Open Access Journals (Sweden)

    Kevin C. Ching

    2013-01-01

    Full Text Available We present the case of a 56-year-old double lung transplant recipient with chest pain who underwent an attempted endovascular retrieval of what was described as a retained guide wire in the azygos vein. After successfully grasping the tip, the object further migrated to the right pulmonary artery complicating the retrieval. It was realized that the “wire” was extravasated methyl methacrylate from a recent percutaneous kyphoplasty. This is believed to be the first report of attempted endovascular retrieval of extravasated methyl methacrylate in the azygos system. We include the details of this case and briefly review the current literature on the management of extravasated methyl methacrylate from vertebral augmentation procedures. Extravasated methyl methacrylate in the venous system is a common finding after vertebral augmentation procedures and any radiopaque stripe arising from a cemented vertebral body should be first described as probable cement leakage.

  2. Kinetic measurement of esterase-mediated hydrolysis for methacrylate monomers used in dental composite biomaterials

    Science.gov (United States)

    Russo, Karen Ann

    Methacrylate-based monomers are routinely used in medical biomaterials. Monomers undergo polymerization reactions to form the solid resin. These polymerization reactions can be incomplete thus making unpolymerized monomer available for possible biodistribution. Understanding the fate of these monomers is essential not only for their toxicological profile but also for development of future biomaterials. Aromatic methacrylate-based monomers included in this study were bisphenol A dimethacrylate and bisphenol A diglycidyl dimethathacrylate; aliphatic methacrylate monomers were 2-hydroxyethyl methacrylate and triethyleneglycol dimethacrylate. These compounds contain ester moieties thought to be susceptible to esterase-mediated hydrolysis. The hypothesis was that the ester bond of the methacrylate monomers can be hydrolyzed by esterases and these reactions would occur in a measurable, time-dependent manner confirmed by specific Michaelis-Menten kinetic relationships. Including aliphatic and aromatic methacrylate monomers in this work allowed for structure-based comparisons. In vitro enzymolysis of the test compounds by acetylcholinesterase and cholesterol esterase was performed in buffered solutions. The hydrolysis reactions were monitored by high performance liquid chromatography with ultraviolet detection. The disappearance of parent compound and appearance of hydrolysis products were quantitated. The aromatic methacrylate monomers, bisphenol A dimethacrylate and bisphenol A diglycidyl dimethacrylate, were resistant to acetylcholine esterase hydrolysis but were converted by cholesterol esterase. The putative xenoestrogen, bisphenol A, was identified as a hydrolysis product from bisphenol A dimethacrylate conversion. Cholesterol esterase induced hydrolysis of bisphenol A diglycidyl dimethacrylate yielded a Km value of 1584 muM and Vmax of 14 muM min-1. Triethyleneglycol was converted by both esterases with calculated Km values of 394 and 1311 muM for acetylcholine

  3. Preparation and evaluation of poly(alkyl methacrylate-co-methacrylic acid-co-ethylene dimethacrylate) monolithic columns for separating polar small molecules by capillary liquid chromatography

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Shu-Ling; Wu, Yu-Ru; Lin, Tzuen-Yeuan; Fuh, Ming-Ren, E-mail: msfuh@scu.edu.tw

    2015-04-29

    Highlights: • Methacrylic acid (MAA) was used to increase hydrophilicity of polymeric monoliths. • Fast separation of phenol derivatives was achieved in 5 min using MAA-incorporated column. • Separations of aflatoxins and phenicol antibiotics were achieved using MAA-incorporated column. - Abstract: In this study, methacrylic acid (MAA) was incorporated with alkyl methacrylates to increase the hydrophilicity of the synthesized ethylene dimethacrylate-based (EDMA-based) monoliths for separating polar small molecules by capillary LC analysis. Different alkyl methacrylate–MAA ratios were investigated to prepare a series of 30% alkyl methacrylate–MAA–EDMA monoliths in fused-silica capillaries (250-μm i.d.). The porosity, permeability, and column efficiency of the synthesized MAA-incorporated monolithic columns were characterized. A mixture of phenol derivatives is employed to evaluate the applicability of using the prepared monolithic columns for separating small molecules. Fast separation of six phenol derivatives was achieved in 5 min with gradient elution using the selected poly(lauryl methacrylate-co-MAA-co-EDMA) monolithic column. In addition, the effect of acetonitrile content in mobile phase on retention factor and plate height as well as the plate height-flow velocity curves were also investigated to further examine the performance of the selected poly(lauryl methacrylate-co-MAA-co-EDMA) monolithic column. Moreover, the applicability of prepared polymer-based monolithic column for potential food safety applications was also demonstrated by analyzing five aflatoxins and three phenicol antibiotics using the selected poly(lauryl methacrylate-co-MAA-co-EDMA) monolithic column.

  4. Barrier layers against oxygen transmission on the basis of electron beam cured methacrylated gelatin

    Science.gov (United States)

    Scherzer, Tom

    1997-08-01

    The development of barrier layers against oxygen transmission on the basis of radiation-curable methacrylated gelatin will be reported. The electron beam cured gelatin coatings show an extremely low oxygen permeability and a high resistance against boiling water. Moreover, the methacrylated gelatins possess good adhesion characteristics. Therefore, they are suited as barrier adhesives in laminates for food packaging applications. If substrate foils from biodegradable polymers are used, the development of completely biodegradable packaging materials seems to be possible.

  5. Miscibility of Methylmethacrylate-co-methacrylic Acid Polymer with Magnesium, Zinc, and Manganese Sulfonated Polystyrene Ionomers

    OpenAIRE

    ALKAN, Cemil; YURTSEVEN, Nebahat; ARAS, Leyla

    2005-01-01

    The miscibility of methyl methacrylate-co-methacrylic acid polymer (MMA-MAA) with metal neutralized sulfonated polystyrene ionomers was investigated by viscometry, differential scanning calorimetry (DSC), and Fourier transform infrared radiation spectroscopy (FTIR) techniques. Polystyrene (PS) was sulfonated by acetic anhydride and sulfuric acid and the sulfonation degree was found to be 2.6 mole percent, and 2.6 mole percent sulfonated polystyrene was neutralized by Mg, Zn, and Mn sa...

  6. Grafting of Chitosan and Chitosantrimethoxylsilylpropyl Methacrylate on Single Walled Carbon Nanotubes-Synthesis and Characterization

    OpenAIRE

    2010-01-01

    Acid functionalized single walled carbon nanotubes (CNTs) were grafted to chitosan by first reacting the oxidized CNTs with thionyl chloride to form acyl-chlorinated CNTs. This product was subsequently dispersed in chitosan and covalently grafted to form CNT-chitosan. CNT-chitosan was further grafted onto 3-trimethoxysilylpropyl methacrylate by free radical polymerization conditions, to yield CNT-g-chitosan-g-3-trimethoxysilylpropyl methacrylate (TMSPM), hereafter referred to as CNT-chitosan-...

  7. Metal Nanoparticle/Block Copolymer Composite Assembly and Disassembly.

    Science.gov (United States)

    Li, Zihui; Sai, Hiroaki; Warren, Scott C; Kamperman, Marleen; Arora, Hitesh; Gruner, Sol M; Wiesner, Ulrich

    2009-01-01

    Ligand-stabilized platinum nanoparticles (Pt NPs) were self-assembled with poly(isoprene-block-dimethylaminoethyl methacrylate) (PI-b-PDMAEMA) block copolymers to generate organic-inorganic hybrid materials. High loadings of NPs in hybrids were achieved through usage of N,N-di-(2-(allyloxy)ethyl)-N-3-mercaptopropyl-N-3-methylammonium chloride as the ligand, which provided high solubility of NPs in various solvents as well as high affinity to PDMAEMA. From NP synthesis, existence of sub-1 nm Pt NPs was confirmed by high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) images. Estimations of the Pt NP ligand head group density based on HAADF-STEM images and thermogravimetric analysis (TGA) data yielded results comparable to what has been found for alkanethiol self-assembled monolayers (SAMs) on flat Pt {111} surfaces. Changing the volume fraction of Pt NPs in block copolymer-NP composites yielded hybrids with spherical micellar, wormlike micellar, lamellar and inverse hexagonal morphologies. Disassembly of hybrids with spherical, wormlike micellar, and lamellar morphologies generated isolated metal-NP based nano-spheres, cylinders and sheets, respectively. Results suggest the existence of powerful design criteria for the formation of metal-based nanostructures from designer blocked macromolecules.

  8. SYNTHESIS OF METHYL METHACRYLATE FROM COAL-DERIVED SYNGAS

    Energy Technology Data Exchange (ETDEWEB)

    Makarand R. Gogate; James J. Spivey; Joseph R. Zoeller; Richard D. Colberg; Gerald N. Choi

    1999-07-19

    Research Triangle Institute (RTI), Eastman Chemical Company, and Bechtel collectively are developing a novel three-step process for the synthesis of methyl methacrylate (MMA) from coal-derived syngas that consists of the steps of synthesis of a propionate, its condensation with formaldehyde to form methacrylic acid (MAA), and esterification of MAA with methanol to produce MMA. The research team has completed the research on the three-step methanol-based route to MMA. Under an extension to the original contract, we are currently evaluating a new DME-based process for MMA. The key research need for DME route is to develop catalysts for DME partial oxidation reactions and DME condensation reactions. During the April-June quarter(04-06/99) the first in-situ formaldehyde generation from DME and condensation with methyl propionate is demonstrated and the results are summarized. The supported niobium catalyst shows better condensation activity, but supported tungsten catalyst has higher formaldehyde selectivity. The project team has also completed a 200-hour long term test of PA-HCHO condensation over 30% Nb{sub 2}O{sub 5}/SiO{sub 2}. Three activity cycles and two regeneration cycles were carried out. 30% Nb{sub 2}O{sub 5}/SiO{sub 2} showed similar MAA yields as 10% Nb{sub 2}O{sub 5}/SiO{sub 2} at 300 C. However, the deactivation appears to be slower with 30% Nb{sub 2}O{sub 5}/SiO{sub 2} than 10% Nb{sub 2}O{sub 5}/SiO{sub 2}. An detailed economic analysis of PA-HCHO condensation process for a 250 million lb/yr MMA plant is currently studied by Bechtel. Using the Amoco data-based azeotropic distillation model as the basis, an ASPEN flow sheet model was constructed to simulate the formaldehyde and propionic acid condensation processing section based on RTI's design data. The RTI MAA effluent azeotropic distillation column was found to be much more difficult to converge. The presence of non-condensible gases along with the byproduct DEK (both of which were not presented

  9. Precise Synthesis of Block Polymers Composed of Three or More Blocks by Specially Designed Linking Methodologies in Conjunction with Living Anionic Polymerization System

    Directory of Open Access Journals (Sweden)

    Akira Hirao

    2013-07-01

    Full Text Available This article reviews the successful development of two specially designed linking methodologies in conjunction with a living anionic polymerization system for the synthesis of novel multiblock polymers, composed of three or more blocks, difficult to be synthesized by sequential polymerization. The first methodology with the use of a new heterofunctional linking agent, 2-(4-chloromethylphenylethyldimethylchlorosilane (1, was developed for the synthesis of multiblock polymers containing poly(dimethylsiloxane (PDMS blocks. This methodology is based on the selective reaction of the chain-end silanolate anion of living PDMS, with the silyl chloride function of 1, and subsequent linking reaction of the resulting ω-chain-end-benzyl chloride-functionalized polymer with either a living anionic polymer or living anionic block copolymer. With this methodology, various multiblock polymers containing PDMS blocks, up to the pentablock quintopolymer, were successfully synthesized. The second methodology using an α-phenylacrylate (PA reaction site was developed for the synthesis of multiblock polymers composed of all-vinyl polymer blocks. In this methodology, an α-chain-end-PA-functionalized polymer or block copolymer, via the living anionic polymerization, was first prepared and, then, reacted with appropriate living anionic polymer or block copolymer to link the two polymer chains. As a result, ACB (BCA, BAC (CAB, (ABn, (ACn, ABA, ACA, BCB, and ABCA multiblock polymers, where A, B, and C were polystyrene, poly(2-vinylpyridine, and poly(methyl methacrylate segments, could be successfully synthesized. The synthesis of triblock copolymers, BAB, CAC, and CBC, having molecular asymmetry in both side blocks, was also achieved. Furthermore, the use of living anionic polymers, derived from many other monomers, categorized as either of styrene, 2-vinylpyridine, or methyl methacrylate in monomer reactivity, in the linking methodology enabled the number of

  10. Preparation of photoresponse azobenzene polymer by ATRP%原子转移自由基聚合法制备偶氮苯聚合物

    Institute of Scientific and Technical Information of China (English)

    刘长玲; 王怀宇; 宋岩

    2016-01-01

    偶氮苯类聚合物具有光响应性,在信息储存、光电子、分子开关等领域得到了很好的应用。采用原子转移自由基聚合法,以三羟甲基丙烷为核制备引发剂,以偶氮苯为单体合成三臂聚偶氮苯星形聚合物。通过红外光谱仪、核磁共振氢谱仪对聚合物的结构进行表征,结果表明已成功地合成出目标产物。通过GPC(凝胶渗透色谱仪)对其相对分子质量及其分布进行测试,表明合成出的聚合物符合“活性-可控”聚合特征。利用紫外-可见分光光度计测定聚偶氮苯的紫外吸收,结果表明具有光照射下的构型反转。%Azobenzene polymers have photoresponsive property and get very good application in fields of information storage, photonics, molecular switch etc. The azobenzene star polymer with three- arm was pre⁃pared by atom transfer radical polymerization (ATRP), using the trimethyolpropane as the initiator of nuclear preparation, and azobenzene as the monomer. The structure of polymers were characterized by the infrared spectroscopy (FTIR), hydrogen nuclear magnetic resonance spectrometer (1H- NMR), which showed that the target product was successful y synthesized. The molecular weight and the molecular weight distribution of the polymer was measured by gel permeation chromatograph (GPC), and the results showed that the synthe⁃sized polymer agreed with the "reactive- control able" characteristics. The result of UV spectrophotometer ab⁃sorption of polyazobenzene showed the configuration inversion under light radiation.

  11. Composition and solution properties of fluorinated block copolymers and their surface structures in the solid state

    Institute of Scientific and Technical Information of China (English)

    NI HuaGang; XUE DongWu; WANG XiaoFang; ZHANG Wei; WANG XinPing; SHEN ZhiQuan

    2009-01-01

    A series of diblock copolymers composed of methyl methacrylate and 2-perfluorooctylethyl methacry-late (PMMA144-b-PFMAn) with various PFMA block lengths were prepared by atom transfer radical po-lymerization (ATRP). The surface structures and properties of these polymers in the solid state and in solution were investigated using contact angle measurement, X-ray photoelectron spectroscopy (XPS), sum frequency generation (SFG) vibrational spectroscopy, surface tension and dynamic laser light scattering (DLS). It was found that with increasing PFMA block length, water and oil repellency de-creased, the ratio of F/C increased with increasing film depth, and the degree of ordered packing of the perfluoroalkyl side chains at the surface decreased. When the number of PFMA block units reached 10, PMMA segments were detected at the copolymer surface, which was attributed to the PFMA block length affecting molecular aggregation structure of the copolymer in the solution and the interfacial structure at the air/liquid interface, which in turn affects surface structure formation during solution solidification. The results suggest that copolymer solution properties play an important role in struc-ture formation on the solid surface.

  12. Preparation and icephobic properties of polymethyltrifluoropropylsiloxane-polyacrylate block copolymers

    Science.gov (United States)

    Li, Xiaohui; Zhao, Yunhui; Li, Hui; Yuan, Xiaoyan

    2014-10-01

    Five polymethyltrifluoropropylsiloxane (PMTFPS)-polyacrylate block copolymers (PMTFPS-b-polyacrylate) were synthesized by free radical polymerization of methyl methacrylate, n-butyl acrylate and hydroxyethyl methacrylate using PMTFPS macroazoinitiator (PMTFPS-MAI) in range of 10-50 mass percentages. The morphology, surface chemical composition and wettability of the prepared copolymer films were investigated by transmission electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and water contact angle measurement. Delayed icing time and ice shear strength of the films were also detected for the icephobic purpose. The surface morphologies of the copolymers were different from those of the bulk because of the migration of the PMTFPS segments to the air interface during the film formation. Maximal delayed icing time (186 s at -15 °C) and reduction of the ice shear strength (301 ± 10 kPa) which was significantly lower than that of polyacrylates (804 ± 37 kPa) were achieved when the content of PMTFPS-MAI was 20 wt%. The icephobicity of the copolymers was attributed primarily to the enrichment of PMTFPS on the film surface and synergistic effect of both silicone and fluorine. Thus, the results show that the PMTFPS-b-polyacrylate copolymer can be used as icephobic coating materials potentially.

  13. [Studies of dental methacrylic resin. (Part 8) Flexural and impact adhesive strength of self-curing methacrylic resin to cross-linked polymethyl methacrylate resins (author's transl)].

    Science.gov (United States)

    Hirasawa, T; Hirabayashi, S; Harashima, I

    1981-10-01

    Heat-curing methacylic resins cross-linked with three kinds of dimethacrylates, i.e. EDMA, tri-EDMA and nona-EDMA, were prepared, and the flexural and the impact adhesive strength of the dough moulding type and the pour type self-curing methacrylic resins to them were examined. The results obtained were as follows. (1) The flexural and the impact adhesive strength of the pour type self-curing resin were higher and more stable than those of the dough moulding type one. (2) The flexural and the impact adhesive strength of self-curing resins to cross-linked adherent resins rised in order of nona-EDMA greater than tri-EDMA greater than EDMA in the range of higher concentration of cross-linking agents. This tendency was marked for the pour type resin. (3) When the dough moulding type resin was used as adhesive resin, to adherent resin cross-linked with EDMA or tri-EDMA which had relatively short chain, the respective adhesive strength of that decreased with increasing the concentration of cross-linking agent. While, to adherent resin cross-linked with nona-EDMA, which had relatively long and more flexible chain, the respective adhesive strength of the dough moulding type resin increased with increasing the concentration of cross-linking agent. (4) When the pour type resin was used as adhesive resin, to adherent resin cross-linked with EDMA or tri-EDMA, the respective adhesive strength of that showed the maximum at the concentration near 2 to 5 mole% and decreased with increasing the concentration. While, to adherent resin cross-linked with nona-EDMA, the flexural adhesive strength of the pour type resin was approximately constant without the effect of the concentration, but the impact adhesive strength of that increased with increasing the concentration. (5) The flexural adhesive strength of the dough moulding and the pour type resin under the wet condition decreased about 30 to 60% compared with under the dry condition, but the percentage of the falling for the impact

  14. Block copolymer battery separator

    Science.gov (United States)

    Wong, David; Balsara, Nitash Pervez

    2016-04-26

    The invention herein described is the use of a block copolymer/homopolymer blend for creating nanoporous materials for transport applications. Specifically, this is demonstrated by using the block copolymer poly(styrene-block-ethylene-block-styrene) (SES) and blending it with homopolymer polystyrene (PS). After blending the polymers, a film is cast, and the film is submerged in tetrahydrofuran, which removes the PS. This creates a nanoporous polymer film, whereby the holes are lined with PS. Control of morphology of the system is achieved by manipulating the amount of PS added and the relative size of the PS added. The porous nature of these films was demonstrated by measuring the ionic conductivity in a traditional battery electrolyte, 1M LiPF.sub.6 in EC/DEC (1:1 v/v) using AC impedance spectroscopy and comparing these results to commercially available battery separators.

  15. Hawaii Census 2000 Blocks

    Data.gov (United States)

    U.S. Environmental Protection Agency — This data layer represents Census 2000 demographic data derived from the PL94-171 redistricting files and SF3. Census geographic entities include blocks, blockgroups...

  16. Steroidal neuromuscular blocking agents

    NARCIS (Netherlands)

    Wierda, JMKH; Mori, K; Ohmura, A; Toyooka, H; Hatano, Y; Shingu, K; Fukuda, K

    1998-01-01

    Since 1964 approximately 20 steroidal neuromuscular blocking agents have been evaluated clinically. Pancuronium, a bisquaternary compound designed on the drawingboard, was the first steroidal relaxant introduced into clinical practice worldwide in the 1970's. Although a major improvement, pancuroniu

  17. Superalloy Lattice Block Structures

    Science.gov (United States)

    Nathal, M. V.; Whittenberger, J. D.; Hebsur, M. G.; Kantzos, P. T.; Krause, D. L.

    2004-01-01

    Initial investigations of investment cast superalloy lattice block suggest that this technology will yield a low cost approach to utilize the high temperature strength and environmental resistance of superalloys in lightweight, damage tolerant structural configurations. Work to date has demonstrated that relatively large superalloy lattice block panels can be successfully investment cast from both IN-718 and Mar-M247. These castings exhibited mechanical properties consistent with the strength of the same superalloys measured from more conventional castings. The lattice block structure also accommodates significant deformation without failure, and is defect tolerant in fatigue. The potential of lattice block structures opens new opportunities for the use of superalloys in future generations of aircraft applications that demand strength and environmental resistance at elevated temperatures along with low weight.

  18. Manufacture of poly(methyl methacrylate) microspheres using membrane emulsification.

    Science.gov (United States)

    Bux, Jaiyana; Manga, Mohamed S; Hunter, Timothy N; Biggs, Simon

    2016-07-28

    Accurate control of particle size at relatively narrow polydispersity remains a key challenge in the production of synthetic polymer particles at scale. A cross-flow membrane emulsification (XME) technique was used here in the preparation of poly(methyl methacrylate) microspheres at a 1-10 l h(-1) scale, to demonstrate its application for such a manufacturing challenge. XME technology has previously been shown to provide good control over emulsion droplet sizes with careful choice of the operating conditions. We demonstrate here that, for an appropriate formulation, equivalent control can be gained for a precursor emulsion in a batch suspension polymerization process. We report here the influence of key parameters on the emulsification process; we also demonstrate the close correlation in size between the precursor emulsion and the final polymer particles. Two types of polymer particle were produced in this work: a solid microsphere and an oil-filled matrix microcapsule.This article is part of the themed issue 'Soft interfacial materials: from fundamentals to formulation'.

  19. Carboxybetaine methacrylate oligomer modified nylon for circulating tumor cells capture.

    Science.gov (United States)

    Dong, Chaoqun; Wang, Huiyu; Zhang, Zhuo; Zhang, Tao; Liu, Baorui

    2014-10-15

    Circulating tumor cells (CTC) capture is one of the most effective approaches in diagnosis and treatment of cancers in the field of personalized cancer medicine. In our study, zwitterionic carboxybetaine methacrylate (CBMA) oligomers were grafted onto nylon via atomic transfer random polymerization (ATRP) which would serve as a novel material for the development of convenient CTC capture interventional medical devices. The chemical, physical and biological properties of pristine and modified nylon surfaces were assessed by Fourier transform infrared spectra, atomic force microscope, water contact angle measurements, X-ray photoelectron spectroscopy, protein adsorption, platelet adhesion, and plasma recalcification time (PRT) determinations, etc. The results, including the significant decrease of proteins adsorption and platelets adhesion, as well as prolonged PRTs demonstrated the extraordinary biocompatibility and blood compatibility of the modified surface. Furthermore, we showed that upon immobilization of anti-epithelial cell adhesion molecular (anti-EpCAM) antibody onto the CBMA moiety, the modified nylon surface can selectively capture EpCAM positive tumor cells from blood with high efficiency, indicating the potential of the modified nylon in the manufacture of convenient interventional CTC capture medical devices.

  20. Poly(methyl methacrylate) films for organic vapour sensing

    CERN Document Server

    Capan, R; Hassan, A K; Tanrisever, T

    2003-01-01

    Optical constants and fabrication parameters are investigated using surface plasmon resonance (SPR) studies on spun films of poly(methyl methacrylate) (PMMA) derivatives in contact with two different dielectric media. A value of 1.503 for the refractive index of PMMA films produced from a solution having concentration of 1 mg ml sup - sup 1 at the speed of 3000 rpm is in close agreement with the data obtained from ellipsometric measurements. The film thickness shows a power-law dependence on the spin speed but the thickness increases almost linearly with the concentration of the spreading solution. These results are in good agreement with the hydrodynamic theory for a low-viscosity and highly volatile liquid. On the basis of SPR measurements under dynamic conditions, room temperature response of PMMA films to benzene vapours is found to be fast, highly sensitive and reversible. The sensitivity of detection of toluene, ethyl benzene and m-xylene is much smaller than that of benzene.

  1. Strengthening of Poly Methyl Methacrylate (PMMA) through Electron Irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, Sung Ho; Lim, Hyung San; Ha, Jun Mok; Cho, Sung Oh [KAIST, Daejeon (Korea, Republic of)

    2015-05-15

    Poly Methyl Methacrylate (PMMA) was previously known to show the deteriorating mechanical properties when irradiated with electrons. This is true for low electron irradiation does, but it was found, through experimentation, that at high irradiation dose, PMMA demonstrates improved mechanical properties. With enough electron irradiation dose, the scissions can form new links amongst one another to achieve stability that surpasses that of the PMMA in pre-irradiation treatment state. With higher irradiation dosage and beam strength, hardness of irradiated PMMA could be increased to a much greater extent. Electrons with 50keV of energy can only penetrate around 30 μm of PMMA, thus increasing the beam energy could potentially allow for hardening of not just the surface of the PMMA samples, but the whole samples themselves. Furthermore, Pencil Hardness Test is a method to roughly analyze a material's hardness and does not provide an accurate feedback on the mechanical properties of the material of interest. Hence, a more thorough and effective method of measuring data from the use of equipment such as IZOD Impact Tester, Strain-Stress Tester and Haze Meter will be utilized in the future.

  2. In vivo genotoxicity assessment of acrylamide and glycidyl methacrylate.

    Science.gov (United States)

    Dobrovolsky, Vasily N; Pacheco-Martinez, M Monserrat; McDaniel, L Patrice; Pearce, Mason G; Ding, Wei

    2016-01-01

    Acrylamide (ACR) and glycidyl methacrylate (GMA) are structurally related compounds used for making polymers with various properties. Both chemicals can be present in food either as a byproduct of processing or a constituent of packaging. We performed a comprehensive evaluation of ACR and GMA genotoxicity in Fisher 344 rats using repeated gavage administrations. Clastogenicity was measured by scoring micronucleated (MN) erythrocytes from peripheral blood, DNA damage in liver, bone marrow and kidneys was measured using the Comet assay, and gene mutation was measured using the red blood cell (RBC) and reticulocyte Pig-a assay. A limited histopathology evaluation was performed in order to determine levels of cytotoxicity. Doses of up to 20 mg/kg/day of ACR and up to 250 mg/kg/day of GMA were used. ACR treatment resulted in DNA damage in the liver, but not in the bone marrow. While ACR was not a clastogen, it was a weak (equivocal) mutagen in the cells of bone marrow. GMA caused DNA damage in the cells of bone marrow, liver and kidney, and induced MN reticulocytes and Pig-a mutant RBCs in a dose-dependent manner. Collectively, our data suggest that both compounds are in vivo genotoxins, but the genotoxicity of ACR is tissue specific.

  3. Structures of Silk Fibers Grafted with Hexafluorobutyl Methacrylate

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The relationship between the graft yield and the effect of hexafluorobutyl methacrylate graft treatment on the structural changes of the silk fibers was studied on the basis of the results of scanning electron micrograph photographs (SEM), infrared spectroscopy (IR), Raman spectrum,wide-angle X-ray diffraction patterns (WAXD), nuclear magnetic resonance(NMR) and amion acid analysis. The results showed that the crystalline regions of grafted fibers were hardly affected and the fiber fission occurred on the cross sections of grafted fibers. The surface of fibers was covered with a high polymer film. The Raman spectrum showed there was little change in the conformation of grafted fibers which mainly remained β-sheet conformation. The IR of the grafted silk fibers showed new absorption of bands occurred which belonged to the stretching-vibrationabsorption-peak bands of VC=O and VC-F of aliphatic ester species. The CF3-,-CF2- and -CFH- structures of grafted silk macromdlecule were verified in the NMR spectrum.The amion acid analysis indicated fluoride monomers were inclined to graft with TYR,ARG and GLU of silk fibers.

  4. Anisotropic properties of aligned SWNT modified poly (methyl methacrylate) nanocomposites

    Indian Academy of Sciences (India)

    Weixue Li; Qing Wang; Jianfeng Dai

    2006-06-01

    The poly (methyl methacrylate) (PMMA)/single-walled carbon nanotube (SWNT) composites with good uniformity, dispersion and alignment of SWNT were fabricated in an improved figuration process. The semidried mixture was stretched along one direction at a drawing ratio of 50 before it was dried, and then folded along the same direction stretching repeatedly for 100 times. The transmission electron microscopic (TEM) observation demonstrated that SWNT in the PMMA/SWNT composite tends to align in the stretching direction owing to a torque exerting on it in the stretching process. The electrical and mechanical properties of PMMA/SWNT composite were studied as a function of SWNT orientation and concentration. The aligned SWNT modified PMMA/SWNT composite presented highly anisotropic properties. The experimental results showed that the electrical conductivity and mechanical properties of composite rise with the increase of SWNT concentration, and that composite films showed higher conductivity and higher mechanical draw ratios along the stretched direction than perpendicular to it. The thermogravimetric analysis (TGA) revealed that embedding the SWNTs into the PMMA matrix also improves the thermal stability of the composite.

  5. Electrochemical impedance spectroscopy study of a surface confined redox reaction: The reduction of azobenzene on mercury in the absence of diffusion

    Energy Technology Data Exchange (ETDEWEB)

    Prieto, Francisco, E-mail: dapena@us.es [Department of Physical Chemistry, University of Seville, c/Profesor Garcia Gonzalez no 2, 41012 Seville (Spain); Rueda, Manuela; Hidalgo, Jose; Martinez, Elisa; Navarro, Inmaculada [Department of Physical Chemistry, University of Seville, c/Profesor Garcia Gonzalez no 2, 41012 Seville (Spain)

    2011-09-30

    The kinetics of azobenzene reduction on mercury electrodes in the absence of diffussional mass transport is studied by electrochemical impedance spectroscopy (EIS) in acetic acid/acetate buffered solutions at different pH values. Cyclic voltammetry experiments confirm the absence of diffusion effects and provide the values of the surface equilibrium potential. The analysis of the impedance frequency spectrums at every potential within the faradaic region conforms well the model and provides the global rate constant of the process, k{sub f}. The potential dependence of k{sub f} suggests the existence of an EE mechanism, with two electron transfers controlling the overall rate. The kinetic parameters of every step are obtained and their pH dependences clarify the role played by the protonation steps.

  6. Remarkable pH-responsive polypropylene microfiltration membrane through surface entrapment of poly(2-(diethylamino) ethyl methacrylate)-containing macromolecules by ATRP method.

    Science.gov (United States)

    Jiang, Ping; Li, Duxin; Liu, Yuejun; Zhang, Xiuju; Lai, Dengwang

    2013-03-01

    Polypropylene (PP) microfiltration membrane were functionalized with an adsorption/surface entrapment process, using block copolymers with poly(n-butyl acrylate) (PBA) as anchor block being capable to tether the pH-responsive block poly(2-(diethylamino) ethyl methacrylate) (PDEA) to the surface, Homopolymer and Block copolymer synthesis was investigated by atom transfer radical polymerization (ATRP) using PMDETA, CuBr and ethyl acetate. These polymers were characterized by 1H NMR and GPC. Copolymer of PDEA with polybutylacrylate (PBA) was selected as best suitable modifier. Models related to the underlying deswelling/entrapment process which leads to fixation of the modifier were considered. Surface properties were analyzed by ATR-FTIR spectroscopy and water contact angle measurements, which confirmed the presence of modifier and a strong improvement of surface and pore wettability. The structure of membranes was evaluated using Polarized Optical Microscopy. Furthermore the pH-sensitive properties of modified PP membranes were verified by pH-dependence of water permeability which due to protonation/deprotonation and volume phase transition of PDEA around the pH 6-6.9.

  7. Thin-Film Behavior of Poly(methyl methacrylates). 3. Epitaxial Crystallization in Thin Films of Isotactic Poly(methyl methacrylate) Using Crystalline Langmuir-Blodgett Layers

    NARCIS (Netherlands)

    Brinkhuis, R.H.G.; Schouten, A.J.

    1992-01-01

    A procedure is introduced using monolayer crystallized films of isotactic poly(methyl methacrylate) (i-PMMA) to induce crystallization in amorphous films of i-PMMA. Use of the Langmuir-Blodgett films as surface crystallization nuclei permits the preparation of highly crystalline films with thickness

  8. Surface modification of silk fibroin fibers with poly(methyl methacrylate) and poly(tributylsilyl methacrylate) via RAFT polymerization for marine antifouling applications

    Energy Technology Data Exchange (ETDEWEB)

    Buga, Mihaela-Ramona [National Research and Development Institute for Cryogenics and Isotopic Technologies, ICIT Rm. Valcea, 240050 Rm. Valcea, Uzinei 4, CP7, Raureni, Valcea (Romania); Zaharia, Cătălin, E-mail: zaharia.catalin@gmail.com [Advanced Polymer Materials Group, University Politehnica of Bucharest, 1-7, Gh. Polizu Street, Sector 1, 011061 Bucharest (Romania); Bălan, Mihai [National Research and Development Institute for Cryogenics and Isotopic Technologies, ICIT Rm. Valcea, 240050 Rm. Valcea, Uzinei 4, CP7, Raureni, Valcea (Romania); Bressy, Christine [Université de Toulon, MAPIEM, EA 4323, 83957 La Garde (France); Ziarelli, Fabio [Fédération des Sciences Chimiques de Marseille, CNRS-FR1739, Spectropole, 13397 Marseille (France); Margaillan, André [Université de Toulon, MAPIEM, EA 4323, 83957 La Garde (France)

    2015-06-01

    In this study, silk fibroin surface containing hydroxyl and aminogroups was firstly modified using a polymerizable coupling agent 3-(trimethoxysilyl) propyl methacrylate (MPS), in order to induce vinyl groups onto the fiber surface. The reversible addition–fragmentation chain transfer (RAFT)-mediated polymerization of methyl methacrylate (MMA) and tributylsilyl methacrylate (TBSiMA) through the immobilized vinyl bond on the silk fibroin surface in the presence of 2-cyanoprop-2-yl dithiobenzoate (CPDB) as chain-transfer agent and 2,2′-azobis(isobutyronitrile) (AIBN) as initiator was conducted in toluene solution at 70 °C for 24 h. The structure and properties of the modified fiber were characterized by Fourier Transform Infrared Spectroscopy, {sup 13}C, {sup 29}Si Nuclear Magnetic Resonance (NMR) spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), confirming the presence of the coupling molecule and the methacrylate groups onto the silk fibroin fiber surface. Molecular weight distributions were assessed by triple detection size exclusion chromatography (TD-SEC) in order to verify the livingness of the polymerization. - Highlights: • SF surface containing hydroxyl and amino groups was firstly modified with MPS. • RAFT polymerizations of MMA and TBSiMA were studied. • TD-SEC was used to verify the livingness of the RAFT polymerization. • The grafted polymer chains enhance the thermal stability of the SF fibers. • The grafted fibers could be potentially promising candidates as antifouling agents.

  9. Influence of solvent on micellar morphologies of semifluorinated block copolymers.

    Science.gov (United States)

    Lee, Min Young; Kim, Sang Jae; Jeong, Yeon Tae; Kim, Joo Hyun; Gal, Yeong-Soon; Lim, Kwon Taek

    2009-12-01

    The influence of solvents on micellar architectures of block copolymers composed of poly(1H,1H-dihydroperfluorooctyl methacrylate) and poly(ethylene oxide) was investigated. In this study, binary solvents with desired proportions were chosen, which had remarkable influence on the morphology of the resulting micelles. With simple adjusting the composition of the binary solvent of chloroform and trichlorofluoromethane, interesting shapes of micelle-like aggregates, such as core-shell, cylinder, worm-like and inverted micelles were formed with sizes of 15, 70, 30 and 250 nm, respectively. In the case of methanol/water system, core-shell spheres and vesicles were produced by varying the proportion of the contents. The morphologies were also tuned to honeycomb-like and bowl-shaped micelles as well as large planar lamellae with holes in DMF and water binary solvent.

  10. Gelation of photopolymerized hyaluronic acid grafted with glycidyl methacrylate

    Energy Technology Data Exchange (ETDEWEB)

    Prado, S.S.; Weaver, J.M.; Love, B.J., E-mail: bjlove@umich.edu

    2011-12-01

    Experiments have tracked the ambient gelation of a series of hydrophilic hyaluronic acid (HA) resins grafted with glycidyl methacrylate (GM) and photopolymerized as a function of dose. The resin mixtures range in GMHA concentration between 0.5 and 1.5% w/w in phosphate buffered saline (PBS). Illuminated at 20 mW/cm{sup 2}, the dynamic viscosity ({eta}(t)) has been tracked and characterized using the Boltzmann log-sigmoidal model. A gelled viscosity of {approx} 10 Pa s was determined at 0.5% w/w which rose to {approx} 50 Pa s at or above 1% w/w. More curing agent marginally increased the gel viscosity at each concentration. Time constants associated with viscosity advancement were shortest at [GMHA] = 1.0%; higher concentrations are attributed with lower quantum efficiency when illuminated. Subsequent frequency sweeps replicated already published work using similar GHMA concentrations in PBS. G' values ranged from 100 to 500 Pa over the formulation range with expected sensitivity to GMHA and curing agent concentration. Overall, the sigmoidal model represented this advancing viscosity data well, and further analysis of the physical significance of these model parameters may help in understanding photopolymerization of this complicated formulation more broadly. Highlights: {yields} The ambient dynamic viscosity of photopolymerized GMHA gels has been measured. {yields} 2 physical parameters and two time constants were extracted from the sigmoidal model. {yields} Higher crosslinker content for a fixed GMHA concentration led to higher gel viscosity. {yields} The time to toggle between the initial and final viscosity ranged between 5 and 10 s. {yields} Dynamic frequency sweep tests on cured gels also revealed G' values between 100 and 500 Pa.

  11. Assessment of methyl methacrylate genotoxicity by the micronucleus test.

    Science.gov (United States)

    Araújo, Amarildo Mariano de; Alves, Guilherme Rodrigues; Avanço, Guilherme Trevisan; Parizi, José Luiz Santos; Nai, Gisele Alborghetti

    2013-01-01

    The aim of this study was to evaluate the genotoxic potential of methyl methacrylate (MMA) vapor by simulating standard occupational exposure of 8 hours per day and using the micronucleus test. We used 32 adult male Wistar rats divided into three groups: A - 16 rats exposed to MMA for 8 hours a day, B - Eight rats receiving single subcutaneous doses of cyclophosphamide on the first day of the experiment (positive control), C - Eight rats receiving only water and food ad libitum (negative control). Eight rats from group A and all of the rats from groups B and C were sacrificed 24 hours after beginning the experiment (acute exposure in group A). The remaining animals in group A were sacrificed 5 days after the experiment began (repeated exposure assessment in group A, simulating occupational exposure 40 hours/week). Femoral bone marrow was collected from each rat at the time of sacrifice for use in the micronucleus test. Two slides were completed per animal and were stained with Giemsa staining. Two thousand polychromatic erythrocytes were counted per animal. The Kruskal-Wallis test followed by a multiple comparisons test (Dunn test) was used for statistical analysis. The median number of micronuclei was 7.00 in the group exposed to MMA for 1 day, 2.00 in the group exposed to MMA for 5 days, 9.00 in the group exposed to cyclophosphamide (positive control) and 0.756 in the negative control group (p < 0.0001). MMA was genotoxic when measured after 1 day of exposure but was not evidently genotoxic after 5 days.

  12. Silver-polysaccharide nanocomposite antimicrobial coatings for methacrylic thermosets.

    Science.gov (United States)

    Travan, Andrea; Marsich, Eleonora; Donati, Ivan; Benincasa, Monica; Giazzon, Marta; Felisari, Laura; Paoletti, Sergio

    2011-01-01

    Bisphenol A glycidylmethacrylate (BisGMA)/triethyleneglycol dimethacrylate (TEGDMA) thermosets are receiving increasing attention as biomaterials for dental and orthopedic applications; for both these fields, bacterial adhesion to the surface of the implant represents a major issue for the outcome of the surgical procedure. Moreover, the biological behaviour of these materials is influenced by their ability to establish proper interactions between their surface and the eukaryotic cells of the surrounding tissues, which is important for good implant integration. The aim of this work was to develop an antimicrobial non-cytotoxic coating for methacrylic thermosets by means of a nanocomposite material based on a lactose-modified chitosan and antibacterial silver nanoparticles. The coating was characterized by UV-vis spectrophotometry, optical microscopy, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). In vitro tests were employed for a biological characterization of the material: antimicrobial efficacy tests were carried out with both Gram+ and Gram- strains. Osteoblast-like cell-lines, primary human fibroblasts and adipose-derived stem cells, were used for LDH cytotoxicity assays and Alamar blue cell proliferation assays. Cell morphology and distribution were evaluated by SEM and confocal laser scanning microscopy. In vitro results showed that the nanocomposite coating is effective in killing both bacterial strains and that this material does not exert any significant cytotoxic effect towards tested cells, which are able to firmly attach and proliferate on the surface of the coating. Such biocompatible antimicrobial polymeric films containing silver nanoparticles may have good potential for surface modification of medical devices, especially for prosthetic applications in orthopedics and dentistry.

  13. Right bundle branch block

    DEFF Research Database (Denmark)

    Bussink, Barbara E; Holst, Anders Gaarsdal; Jespersen, Lasse;

    2013-01-01

    AimsTo determine the prevalence, predictors of newly acquired, and the prognostic value of right bundle branch block (RBBB) and incomplete RBBB (IRBBB) on a resting 12-lead electrocardiogram in men and women from the general population.Methods and resultsWe followed 18 441 participants included.......5%/2.3% in women, P Right bundle branch block was associated with significantly.......60-1.62). The presence of IRBBB was not associated with any adverse outcome.ConclusionIn this cohort study, RBBB and IRBBB were two to three times more common among men than women. Right bundle branch block was associated with increased cardiovascular risk and all-cause mortality, whereas IRBBB was not. Contrary...

  14. Mechanical Properties of Surface-Charged Poly(Methyl Methacrylate as Denture Resins

    Directory of Open Access Journals (Sweden)

    Sang E. Park

    2009-01-01

    Full Text Available The aim of this study was to examine the mechanical properties of a new surface-modified denture resin for its suitability as denture base material. This experimental resin is made by copolymerization of methacrylic acid (MA to poly(methyl methacrylate (PMMA to produce a negative charge. Four experimental groups consisted of Orthodontic Dental Resin (DENTSPLY Caulk as a control and three groups of modified PMMA (mPMMA produced at differing ratios of methacrylic acid (5 : 95, 10 : 90, and 20 : 80 MA : MMA. A 3-point flexural test using the Instron Universal Testing Machine (Instron Corp. measured force-deflection curves and a complete stress versus strain history to calculate the transverse strength, transverse deflection, flexural strength, and modulus of elasticity. Analysis of Variance and Scheffe Post-test were performed on the data. Resins with increased methacrylic acid content exhibited lower strength values for the measured physical properties. The most significant decrease occurred as the methacrylic acid content was increased to 20% mPMMA. No significant differences at P<.05 were found in all parameters tested between the Control and 5% mPMMA.

  15. Facile Fabrication of Gradient Surface Based on (meth)acrylate Copolymer Films

    Science.gov (United States)

    Zhang, Y.; Yang, H.; Wen, X.-F.; Cheng, J.; Xiong, J.

    2016-08-01

    This paper describes a simple and economic approach for fabrication of surface wettability gradient on poly(butyl acrylate - methyl methacrylate) [P (BA-MMA)] and poly(butyl acrylate - methyl methacrylate - 2-hydroxyethyl methacrylate) [P (BA-MMA-HEMA)] films. The (meth)acrylate copolymer [including P (BA-MMA) and P (BA-MMA-HEMA)] films are hydrolyzed in an aqueous solution of NaOH and the transformation of surface chemical composition is achieved by hydrolysis in NaOH solution. The gradient wetting properties are generated based on different functional groups on the P (BA-MMA) and P (BA-MMA-HEMA) films. The effects of both the surface chemical and surface topography on wetting of the (meth)acrylate copolymer film are discussed. Surface chemical composition along the materials length is determined by XPS, and surface topography properties of the obtained gradient surfaces are analyzed by FESEM and AFM. Water contact angle system (WCAs) results show that the P (BA-MMA-HEMA) films provide a larger slope of the gradient wetting than P (BA-MMA). Moreover, this work demonstrates that the gradient concentration of chemical composition on the poly(meth) acrylate films is owing to the hydrolysis processes of ester group, and the hydrolysis reactions that have negligible influence on the surface morphology of the poly(meth) acrylate films coated on the glass slide. The gradient wettability surfaces may find broad applications in the field of polymer coating due to the compatibility of (meth) acrylate polymer.

  16. Effect of block length on the self-assembly of end-capping perfluoroalkyl moieties on the polymer surface

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Most research on copolymers with fluorinated monomers has focused on the relationship between fluorinated monomer content and the corresponding surface structure. However,the influence of the non-fluorinated block on the surface structure of the copolymer film is unknown. Various molecular weight poly(butyl methacrylates) (PBMA) end-capped with 2-perfluorooctylethyl methacrylate (FMA) units (PBMA-ec-FMA) have been synthesized by atom transfer radical polymerization (ATRP). The effect of the PBMA block length on the surface structure and properties of the polymers both in the solid state and in solution was investigated using various techniques. X-ray photoelectron spectroscopy (XPS),sum frequency generation (SFG) vibrational spectroscopy and X-ray diffraction (XRD) analyses indicated that longer PBMA blocks enhanced both the enrichment of the fluorinated moieties and the order of the packing orientation of the perfluoroalkyl side chains on the surface. This enhancement was attributed mainly to the molecular aggregate structure of the end-capped polymers with long PBMA blocks in the solution and to the interfacial structure at the air/liquid interface,which favors the -(CF2)7CF3 moieties self-assembling on the polymer surface during film formation. This observation suggests that the polyacrylate block structure in fluorinated diblock copolymers,in addition to the fluorinated monomer content,plays an important role in structure formation on the solid surface.

  17. Magnetothermally responsive star-block copolymeric micelles for controlled drug delivery and enhanced thermo-chemotherapy.

    Science.gov (United States)

    Deng, Li; Ren, Jie; Li, Jianbo; Leng, Junzhao; Qu, Yang; Lin, Chao; Shi, Donglu

    2015-06-07

    Magnetothermally responsive drug-loaded micelles were designed and prepared for cancer therapy. These specially designed micelles are composed of the thermo-responsive star-block copolymer poly(ε-caprolactone)-block-poly(2-(2-methoxyethoxy)ethyl methacrylate-co-oligo(ethylene glycol)methacrylate) and Mn, Zn doped ferrite magnetic nanoparticles (MZF-MNPs). The thermo-responses of 6sPCL-b-P(MEO2MA-co-OEGMA) copolymers were shown to be dependent on the MEO2MA to OEGMA ratio. The lower critical solution temperature (LCST) of the star-block copolymers was controlled at 43 °C by adjusting the feed molar ratios of MEO2MA/OEGMA at 92 : 8. With the anti-tumor drug doxorubicin (DOX) self-assembling into the carrier system, the thermo-responsive micelles exhibited excellent temperature-triggered drug release behavior. In vitro cytotoxicity results showed high biocompatibility of the polymer micelles. Efficient cellular proliferation inhibition by the drug-loaded micelles was found on the HepG2 cells under different treatments. The thermo-responsive polymer micelles are promising for controlled drug delivery in tumor therapy under an alternating magnetic field.

  18. Poly(DL-lactide)-b-poly(N,N-dimethylamino-2-ethyl methacrylate): synthesis, characterization, micellization behavior in aqueous solutions, and encapsulation of the hydrophobic drug dipyridamole.

    Science.gov (United States)

    Karanikolopoulos, Nikos; Zamurovic, Miljana; Pitsikalis, Marinos; Hadjichristidis, Nikos

    2010-02-08

    We synthesized a series of well-defined poly(dl-lactide)-b-poly(N,N-dimethylamino-2-ethyl methacrylate) (PDLLA-b-PDMAEMA) amphiphilic diblock copolymers by employing a three-step procedure: (a) ring-opening polymerization (ROP) of dl-lactide using n-decanol and stannous octoate, Sn(Oct)(2), as the initiating system, (b) reaction of the PDLLA hydroxyl end groups with bromoisobutyryl bromide, and (c) atom transfer radical polymerization, ATRP, of DMAEMA with the newly created bromoisobutyryl initiating site. The aggregation behavior of the prepared block copolymers was investigated by dynamic light scattering and zeta potential measurements at 25 degrees C in aqueous solutions of different pH values. The hydrophobic drug dipyridamole was efficiently incorporated into the copolymer aggregates in aqueous solutions of pH 7.40. High partition coefficient values were determined by fluorescence spectroscopy.

  19. Contaminated soil concrete blocks

    NARCIS (Netherlands)

    Korte, de A.C.J.; Brouwers, H.J.H.; Limbachiya, Mukesh C.; Kew, Hsein Y.

    2009-01-01

    According to Dutch law the contaminated soil needs to be remediated or immobilised. The main focus in this article is the design of concrete blocks, containing contaminated soil, that are suitable for large production, financial feasible and meets all technical and environmental requirements. In ord

  20. Effects of Block Scheduling

    Directory of Open Access Journals (Sweden)

    William R. Veal

    1999-09-01

    Full Text Available This study examined the effects of a tri-schedule on the academic achievement of students in a high school. The tri-schedule consists of traditional, 4x4 block, and hybrid schedules running at the same time in the same high school. Effectiveness of the schedules was determined from the state mandated test of basic skills in reading, language, and mathematics. Students who were in a particular schedule their freshman year were tested at the beginning of their sophomore year. A statistical ANCOVA test was performed using the schedule types as independent variables and cognitive skill index and GPA as covariates. For reading and language, there was no statistically significant difference in test results. There was a statistical difference mathematics-computation. Block mathematics is an ideal format for obtaining more credits in mathematics, but the block format does little for mathematics achievement and conceptual understanding. The results have content specific implications for schools, administrations, and school boards who are considering block scheduling adoption.

  1. Concrete Block Pavements

    Science.gov (United States)

    1983-03-01

    1967, Cedergren 1974, Federal Highway .’,U .. V,47 -’":: 37 Administration 1980). Block pavements have essentially the same prob- lems with moisture...Vicksburg, Miss. Cedergren , H. R. 1974. Drainage of Highway and Airfield Pavements, John Wiley and Sons, New VOk. I Cement and Concrete Association

  2. Block That Pain!

    Science.gov (United States)

    ... along with the National Institute of Dental and Craniofacial Research (NIDCR) and the National Institute of General Medical Sciences (NIGMS). This finding shows that a specific combination of two molecules can block only pain-related neurons. It holds the promise of major ...

  3. Superparamagnetic poly(methyl methacrylate) nanoparticles surface modified with folic acid presenting cell uptake mediated by endocytosis

    Science.gov (United States)

    Feuser, Paulo Emilio; Jacques, Amanda Virtuoso; Arévalo, Juan Marcelo Carpio; Rocha, Maria Eliane Merlin; dos Santos-Silva, Maria Claudia; Sayer, Claudia; de Araújo, Pedro H. Hermes

    2016-04-01

    The encapsulation of superparamagnetic nanoparticles (MNPs) in polymeric nanoparticles (NPs) with modified surfaces can improve targeted delivery and induce cell death by hyperthermia. The goals of this study were to synthesize and characterize surface modified superparamagnetic poly(methyl methacrylate) with folic acid (FA) prepared by miniemulsion polymerization (MNPsPMMA-FA) and to evaluate their in vitro cytotoxicity and cellular uptake in non-tumor cells, murine fibroblast (L929) cells and tumor cells that overexpressed folate receptor (FR) β, and chronic myeloid leukemia cells in blast crisis (K562). Lastly, hemolysis assays were performed on human red blood cells. MNPsPMMA-FA presented an average mean diameter of 135 nm and a saturation magnetization (Ms) value of 37 emu/g of iron oxide, as well as superparamagnetic behavior. The MNPsPMMA-FA did not present cytotoxicity in L929 and K562 cells. Cellular uptake assays showed a higher uptake of MNPsPMMA-FA than MNPsPMMA in K562 cells when incubated at 37 °C. On the other hand, MNPsPMMA-FA showed a low uptake when endocytosis mechanisms were blocked at low temperature (4 °C), suggesting that the MNPsPMMA-FA uptake was mediated by endocytosis. High concentrations of MNPsPMMA-FA showed hemocompatibility when incubated for 24 h in human red blood cells. Therefore, our results suggest that these carrier systems can be an excellent alternative in targeted drug delivery via FR.

  4. pH-responsive layer-by-layer films of zwitterionic block copolymer micelles

    OpenAIRE

    Demirel, Adem Levent; Yusan, Pelin; Tuncel, İrem; Bütün, Vural; Erel-Goktepe, İrem

    2014-01-01

    We report a strategy to incorporate micelles of poly[3-dimethyl (methacryloyloxyethyl) ammonium propane sulfonate]-block-poly[2-(diisopropylamino) ethyl methacrylate] (beta PDMA-b-PDPA) into electrostatic layer-by-layer (LbL) films. We obtained micelles with pH-responsive PDPA-cores and zwitterionic bPDMA-coronae at pH 8.5 through pH-induced self-assembly of bPDMA-b-PDPA in aqueous solution. To incorporate bPDMA-b-PDPA micelles into LbL films, we first obtained a net electrical charge on bPDM...

  5. Fabrication of Bioactive Surfaces by Functionalization of Electroactive and Surface-Active Block Copolymers

    Directory of Open Access Journals (Sweden)

    Omotunde Olubi

    2014-08-01

    Full Text Available Biofunctional block copolymers are becoming increasingly attractive materials as active components in biosensors and other nanoscale electronic devices. We have described two different classes of block copolymers with biofuctional properties. Biofunctionality for block copolymers is achieved through functionalization with appropriate biospecific ligands. We have synthesized block copolymers of electroactive poly(3-decylthiophene and 2-hydroxyethyl methacrylate by atom transfer radical polymerization. The block copolymers were functionalized with the dinitrophenyl (DNP groups, which are capable of binding to Immunoglobulin E (IgE on cell surfaces. The block copolymers were shown to be redox active. Additionally, the triblock copolymer of α, ω-bi-biotin (poly(ethylene oxide-b-poly (styrene-b-poly(ethylene oxide was also synthesized to study their capacity to bind fluorescently tagged avidin. The surface-active property of the poly(ethylene oxide block improved the availability of the biotin functional groups on the polymer surfaces. Fluorescence microscopy observations confirm the specific binding of biotin with avidin.

  6. Effects of surfactants on the properties of mortar containing styrene/methacrylate superplasticizer.

    Science.gov (United States)

    Negim, El-Sayed; Kozhamzharova, Latipa; Khatib, Jamal; Bekbayeva, Lyazzat; Williams, Craig

    2014-01-01

    The physical and mechanical properties of mortar containing synthetic cosurfactants as air entraining agent are investigated. The cosurfactants consist of a combination of 2% dodecyl benzene sodium sulfonate (DBSS) and either 1.5% polyvinyl alcohol (PVA) or 1.5% polyoxyethylene glycol monomethyl ether (POE). Also these cosurfactants were used to prepare copolymers latex: styrene/butyl methacrylate (St/BuMA), styrene/methyl methacrylate (St/MMA), and styrene/glycidyl methacrylate (St/GMA), in order to study their effects on the properties of mortar. The properties of mortar examined included flow table, W/C ratio, setting time, water absorption, compressive strength, and combined water. The results indicate that the latex causes improvement in mortar properties compared with cosurfactants. Also polymer latex containing DBSS/POE is more effective than that containing DBSS/PVA.

  7. Synthesis and characterization of methacrylate matrix resin bearing o-nitrobenzyl group

    Institute of Scientific and Technical Information of China (English)

    郭玲香; 管婧; 林保平; 杨洪

    2015-01-01

    The matrix polymer PTBCHNB bearing o-nitrobenzyl group was successfully synthesized by copolymerization of tertiary-butyl methacrylate (TBMA), cyclohexyl methacrylate (CHMA) and o-nitrobenzyl methacrylate (NBMA) via reversible addition fragmentation chain transfer (RAFT) polymerization method. PTBCHNB was characterized by FTIR, 1HNMR, GPC and DSC. After UV irradiation, the o-nitrobenzyl groups of PTBCHNB were photocleaved and the resulting carboxyl groups were highly alkali soluble, and PTBCHNB was converted to PCHIBMA bearing carboxyl groups. So, the matrix polymer could be etched by mild alkali solution with no requirements of photoacid generators and other diverse additives. The photocleavable behaviors of PTBCHNB were determined by FTIR, 1H NMR and TGA analysis. The resist formulated with PTBCHNB and cast in THF solution showed square pattern of 10 μm×10 μm using a mercury-xenon lamp in a contact printing mode and tetramethyl-ammonium hydroxide aqueous solution as a developer.

  8. Using click chemistry to modify block copolymers and their morphologies

    Science.gov (United States)

    Wollbold, Johannes

    Microphase separated block copolymers (BCPs) are emerging as promising templates and scaffolds for the fabrication of nanostructured materials. To achieve the desired nanostructures, it is necessary to establish convenient approaches to control the morphology of BCPs. It remains challenging to induce morphological transitions of BCPs via external fields. Click chemistry, especially alkyne/azide click chemistry, has been widely used to synthesize novel functionalized materials. Here, we demonstrate that alkyne/azide click chemistry can be used as an efficient approach to chemically modify BCPs and therefore induce morphological transitions. Alkyne-functionalized diblock copolymers (di-BCPs) poly(ethylene oxide)- block-poly(n-butyl methacrylate-random-propargyl methacrylate) (PEO-b-P(nBMA-r-PgMA)) have been successfully synthesized. When the di-BCP is blended with an azide additive Rhodamine B azide and annealed at elevated temperatures, click reaction occurs between the two components. With the Rhodamine B structure attached to the polymer backbone, the di-BCP shows dramatic change in the interactions between the two blocks and the volume fraction of each block. As a result, morphological transitions, such as disorder-to-order transitions (DOTs) and order-to-order transitions (OOTs), are observed. The reaction kinetics and morphology evolution during the click chemistry induced DOTs have been investigated by in-situ and ex-situ characterizations, and fast kinetics properties are observed. Microphase separated morphologies after the DOTs or OOTs are dictated by the composition of neat di-BCPs and the mole ratio between the alkyne and azide groups. The DOTs of PEO-b-P(nBMA-r-PgMA) di-BCPs induced by alkyne/azide click chemistry have also been achieved in thin film geometries, with comparable kinetics to bulk samples. The orientation of the microdomains is dependent on the grafting density of Rhodamine B structure as well as film thickness. At higher grafting densities

  9. Free radical (co)polymerization of methyl methacrylate and styrene in room temperature ionic liquids

    Science.gov (United States)

    Zhang, Hongwei

    Conventional free radical polymerizations were carried out in a variety of room temperature ionic liquids (RTILs). Generally, methyl methacrylate (MMA) and styrene (St) were used as typical monomers to compare the polymerization behavior both in RTILs and in common volatile organic compound solvents (VOCs). In most cases, it was observed that both yields and molecular weights are enhanced in the RTIL. While we believe the "diffusion-controlled termination" mechanism makes the termination of the radical propagating chains difficult due to the highly viscous nature of RTIL, other researchers have suggested that the rapid polymerization rates are due to the high polarity of these reaction media. By employing more than a dozen RTILs with a wide range of anions and cations, we attempted to correlate the viscosity and polarity of the RTILs with the molecular weights and polymerization rates. This correlation was not successful, suggesting that other parameters may also play a role in affecting the polymerization behavior. Other kinds of polymerizations have also been attempted including nitroxide-mediated living radical polymerizations of St and MMA in 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF6), and redox initiation system initiated polymerization of MMA through redox pair formed by cation of trihexyl-tetradecyl-phosphonium bis(2,4,4-trimethylpentyl) phosphinate ([H3TDP] [(PM3) 2P]) and BPO. The formation of PSt-b-PMMA by sequential monomer addition through the standard free radical polymerization mechanism, using BPO as initiator, can be realized in [BMIM]PF6 due to the insolubility of polymerized first block---PSt in [BMIM]PF6. The macroradicals wrapped inside the chain coils have prolonged lifetimes because of the diminished termination, which allow some of these radicals to initiate polymerization of MMA at room temperature to form diblock copolymer. Solvents effects on reactivity ratios for free radical statistical copolymerization have been

  10. Investigation of dairy cattle ease of movement on new methyl methacrylate resin aggregate floorings.

    Science.gov (United States)

    Franco-Gendron, N; Bergeron, R; Curilla, W; Conte, S; DeVries, T; Vasseur, E

    2016-10-01

    Freestall dairy farms commonly present issues with cattle slips and falls caused by smooth flooring and manure slurry. This study examined the effect of 4 new methyl methacrylate (MMA) resin aggregate flooring types (1-4) compared with rubber (positive) and concrete (negative control) on dairy cow (n=18) ease of movement when walking on straight and right-angled corridors. Our hypothesis was that cow ease of movement when walking on the MMA surfaces would be better than when walking on traction milled concrete, and at least as good as when walking on rubber. Cattle ease of movement was measured using kinematics, accelerometers, and visual observation of gait and associated behaviors. Stride length, swing time, stance time, and hoof height were obtained from kinematic evaluation. Acceleration and asymmetry of variance were measured with accelerometers. Locomotion score and behaviors associated with lameness, such as arch back, head bob, tracking up, step asymmetry, and reluctance to bear weight were visually observed. Stride length, swing time, stance time, and the number of steps taken were the only variables affected by flooring type. Differences between flooring types for these variables were tested using a generalized linear mixed model with cow as a random effect, week as a random block factor, and flooring type as a fixed effect. Multiple comparisons with a Scheffé adjustment were done to analyze differences among flooring types. Stride length was 0.14 m longer (better) on rubber when compared with concrete, and 0.11 and 0.17 m shorter on MMA 1 and 2 compared with rubber. On MMA 3 and 4, stride length did not differ from either rubber or concrete. Swing time was 0.04 s shorter (worse) on MMA 1 than on rubber, but did not differ from any other flooring. Stance time was 0.18 s longer (worse) on MMA 2 when compared with rubber, but it did not differ from any other treatment. The number of steps was higher on MMA 4 compared with rubber (4.57 vs. 3.95 steps), but

  11. Macroporous poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) resins-Versatile immobilization supports for biocatalysts

    NARCIS (Netherlands)

    Miletic, Nemanja; Vukovic, Zorica; Nastasovic, Aleksandra; Loos, Katja; Miletić, Nemanja; Vuković, Zorica; Nastasović, Aleksandra

    2009-01-01

    Crosslinked macroporous hydrophilic poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate)s [abbreviated poly(GMA-co-EGDMA)] with identical chemical structure (60% of glycidyl methacrylate) but with varied average pore sizes (from 30 to 560 nm), specific surface areas (from 13.2 to 106.0 m(2)

  12. Influence of cyclodextrin on the solubility and the polymerization of (methacrylated Triton® X-100

    Directory of Open Access Journals (Sweden)

    Melanie Kemnitz

    2012-12-01

    Full Text Available Triton® X-100 (poly(ethylene glycol tert-octylphenyl ether was (methacrylated and polymerized in the absence and presence of randomly methylated β-cyclodextrin (RAMEB-CD. Triton®-polymers that were polymerized with RAMEB-CD in water were compared with polymers that were synthesized in organic solvents after the addition of RAMEB-CD. The polymers were characterized by 1H NMR and FTIR spectroscopy, matrix-assisted laser desorption ionization mass spectrometry (MALDI-TOF MS, dynamic light scattering (DLS, gel-permeation chromatography (GPC and turbidity measurements. Additionally, the viscosity change of the methacrylic homopolymer with RAMEB-CD was evaluated.

  13. Production of microencapsulate glycidyl methacrylate with melamine formaldehyde resin shell materials

    Science.gov (United States)

    Bel, T.; Ulku, G.; Kizilcan, N.; Cimenoglu, H.; Yahya, N.; Baydogan, N.

    2016-11-01

    This study gives some information about the preparation of Glycidyl Methacrylate (GMA) microcapsules with Melamine Formaldehyde (MF) resin as a shell material (MF-GMA). Melamine formaldehyde resin containing hydroxyl groups was synthesized in the first step. Second step includes the addition of GMA monomer along with Sodium Dodecyl Benzenesulfonate (SDBS) and Polyvinyl Alcohol (PVA) aqueous solution for getting emulsible solution. The resultant MF-GMA microcapsules had good enclosing performance and thermal stability. The characteristic properties and the morphology of microencapsulated Glycidyl Methacrylate were examined by using FTIR analysis and their morphology was investigated by using optical microscope.

  14. Oxidative Esterification of Methacrolein to Methyl Methacrylate over Supported Palladium Catalyst

    Institute of Scientific and Technical Information of China (English)

    Wei ZHAO; Wei Guo CHENG; Zeng Xi LI; Lei WANG; Xiang Ping ZHANG; Suo Jiang ZHANG

    2006-01-01

    Supported palladium catalysts, which were used in the oxidative esterification of methacrolein to methyl methacrylate, have been prepared with different carriers and Pd precursors.Experimental results revealed that Pd catalysts with γ-Al2O3 support and Na2PdCl4 precursor showed good performance. Pd catalyst modified with Pb and Mg indicated that Pd-Mg bimetallic catalyst exhibited considerably higher activity and Pd-Pb exhibited both higher activity and selectivity. 92.27% methacrolein conversion and 90.57% methyl methacrylate selectivity were obtained on Pd-Pb-Mg catalyst.

  15. Modification of polyethylene films by radiation grafting of glycidyl methacrylate and immobilization of {beta}-cyclodextrin

    Energy Technology Data Exchange (ETDEWEB)

    Nava-Ortiz, C.A.B. [Departamento de Quimica de Radiaciones y Radioquimica, Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Circuito Exterior, Ciudad Universitaria, Mexico DF 04510 (Mexico); Burillo, G. [Departamento de Quimica de Radiaciones y Radioquimica, Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Circuito Exterior, Ciudad Universitaria, Mexico DF 04510 (Mexico)], E-mail: burillo@nucleares.unam.mx; Bucio, E. [Departamento de Quimica de Radiaciones y Radioquimica, Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Circuito Exterior, Ciudad Universitaria, Mexico DF 04510 (Mexico); Alvarez-Lorenzo, C. [Departamento de Farmacia y Tecnologia Farmaceutica, Facultad de Farmacia, Universidad de Santiago de Compostela, 15782 Santiago de Compostela (Spain)

    2009-01-15

    Glycidyl methacrylate was grafted onto polyethylene films using a preirradiation method with {gamma} rays. The effect of absorbed dose, monomer concentration, and reaction time on the degree of grafting was determined. The grafted samples were verified by FTIR-ATR spectroscopy. {beta}-Cyclodextrin was immobilized onto polypropylene modified with glycidyl methacrylate, and the ability of the cavities of {beta}-cyclodextrin to form inclusion complexes was demonstrated using the typically organic compound approach with m-toluic acid (3-MBA) as a probe.

  16. Investigation of nanocomposites made with poly(methacrylic acid-co-methyl methacrylate)/poly(N-vinyl-2-pyrrolidone)/multi-walled carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Guoqin, Liu; Wei, Miao [College of Material Science and Engineering, Henan University of Technology (China); Lin-Jian, Shangguan, E-mail: mikepolymer@126.com [School of Mechanical Engineering, North China University of Water Conservancy and Electric Power (China)

    2014-06-01

    Poly(methacrylic acid-co-methyl methacrylate) (P(MAA-co-MMA)) was prepared in the presence of poly(N-vinyl-2-pyrrolidone) (PVP) and multi-walled carbon nanotubes (MWNTs) via ultrasonic assisted solution free radical polymerization, i.e., P(MAA-co-MMA)/PVP/MWNTs nanocomposites. The morphology, glassy-state storage modulus, thermal behavior and swelling characteristics of P(MAA-co-MMA)/PVP/MWNTs nanocomposites were investigated. Scanning electron micrographs (SEM) revealed that MWNTs at low concentration could be uniformly dispersed into P(MAA-co-MMA)/PVP blends. With increasing MWNTs weight fraction, the average glassy-state modulus, glass transition temperatures and decomposition temperature of the nanocomposites increased, but their swelling characteristics decreased. (author)

  17. Recovery from blocking between outcomes.

    Science.gov (United States)

    Wheeler, Daniel S; Miller, Ralph R

    2005-10-01

    Contemporary associative learning research largely focuses on cue competition phenomena that occur when 2 cues are paired with a common outcome. Little research has been conducted to investigate similar phenomena occurring when a single cue is trained with 2 outcomes. Three conditioned lick suppression experiments with rats assessed whether treatments known to alleviate blocking between cues would also attenuate blocking between outcomes. In Experiment 1, conditioned responding recovered from blocking between outcomes when a long retention interval was interposed between training and testing. Experiment 2 obtained recovery from blocking between outcomes when the blocking outcome was extinguished after the blocking treatment. In Experiment 3, a recovery from blocking between outcomes occurred when a reminder stimulus was presented in a novel context prior to testing. Collectively, these studies demonstrate that blocking of outcomes, like blocking of cues, appears to be caused by a deficit in the expression of an acquired association.

  18. SUPERFICIAL CERVICAL PLEXUS BLOCK

    Directory of Open Access Journals (Sweden)

    Komang Mega Puspadisari

    2014-01-01

    Full Text Available Superficial cervical plexus block is one of the regional anesthesia in  neck were limited to thesuperficial fascia. Anesthesia is used to relieve pain caused either during or after the surgery iscompleted. This technique can be done by landmark or with ultrasound guiding. The midpointof posterior border of the Sternocleidomastoid was identified and the prosedure done on thatplace or on the level of cartilage cricoid.

  19. Managing access block.

    Science.gov (United States)

    Cameron, Peter; Scown, Paul; Campbell, Donald

    2002-01-01

    There is pessimism regarding the ability of the Acute Health Sector to manage access block for emergency and elective patients. Melbourne Health suffered an acute bed crisis in 2001 resulting in record ambulance diversions and emergency department (ED) delays. We conducted an observational study to reduce access block for emergency patients whilst maintaining elective throughput at Melbourne Health. This involved a clinician-led taskforce using previously proven principles for organisational change to implement 51 actions to improve patient access over a three-month period. The primary outcome measures were ambulance diversion, emergency patients waiting more than 12 hours for an inpatient bed, elective throughput and theatre cancellations. Despite a reduction in multi-day bed numbers all primary objectives were met, ambulance diversion decreased to minimal levels, 12-hour waits decreased by 40% and elective throughput was maintained. Theatre cancellations were also minimised. We conclude that access block can be improved by clinician-led implementation of proven process improvements over a short time frame. The ability to sustain change over the longer term requires further study.

  20. Reversible molecular switching at a metal surface: A case study of tetra- tert-butyl-azobenzene on Au(1 1 1)

    Science.gov (United States)

    Wolf, Martin; Tegeder, Petra

    2009-06-01

    Molecular switches represent a fascinating class of functional molecules, whose properties can be reversibly changed between different molecular states by excitation with light or other external stimuli. Using surface science concepts like self assembly to align such molecules in a well-defined geometry at solid surfaces, new functional properties may arise, which are relevant for different fields like, e.g., molecular electronics, sensing or biocompatible interfaces. For a microscopic understanding of molecular switching at surfaces, it is essential to obtain detailed knowledge on the underlying elementary processes, for instance the excitation mechanism in photoinduced switching. Here we present a case study of a specifically designed azobenzene derivative on a metal surface, namely tetra- tert-butyl-azobenzene (TBA) adsorbed on Au(1 1 1), which is so far one of the best studied system for which reversible conformational changes have been demonstrated. TBA/Au(1 1 1) can thus be viewed as model system in order to gain deeper insights into molecular switching processes at metal surfaces. We have studied the photoinduced and thermally activated reversible switching of TBA in direct contact with a Au(1 1 1) surface using two-photon photoemission (2PPE) and high-resolution electron energy loss spectroscopy (HREELS). The trans/cis-isomerization of TBA is accompanied by reversible changes in the geometrical and electronic structure of the molecules, allowing to gain mechanistic and quantitative insight into the switching process. In particular, the cross sections for the photoisomerization, the ratio between the cis- and trans-TBA in the photostationary state, and the activation energy for the thermally induced cis→trans reaction have been determined and are found to be strongly reduced compared to the corresponding quantities in the liquid phase. Furthermore, the mechanism of optical excitation and molecular switching of TBA on Au(1 1 1) has been identified to arise

  1. Development of mesalazine pellets coated with methacrylic-derived polymer

    Directory of Open Access Journals (Sweden)

    Simone Cristina Déo

    2011-03-01

    Full Text Available Mesalazine (5-ASA is the standard drug for the treatment of inflammatory bowel disease (IBD due to its local effect on intestinal and colonic mucosa. The effective and safe treatment of this disease requires more efficient delivery of the active substance to its site of action. The focus of this study was the use of multiparticulate systems, a modified release form in which the drug is divided into several functional subunits of release in the form of granules or pellets. When these forms are administered, they are rapidly disintegrated, distributing their content throughout the gastrointestinal tract. The aim of this study was to develop and evaluate a multiparticulate system consisting of pellets coated with polymer for pH-dependent release, derived from methacrylic acid and incorporated into the tablet dosage form of mesalazine as a model drug. The extrusion-spheronisation technique was used, resulting in smooth and spherical pellets with uniform size distribution, which were coated in fluidized bed using Opadry® Enteric 94K28327 containing Eudragit® S100 as the agent regulating drug release. The dissolution profile of coated pellets showed good control of drug release from the polymer at the two levels of coating evaluated (8% and 10%, but only the 10% coated pellets were statistically similar to Asalit® 400 mg.A mesalazina (5-ASA tem se apresentado como fármaco padrão para o tratamento da doença inflamatória intestinal (DII devido ao seu efeito local na mucosa intestinal e colônica. A terapia efetiva e segura desta doença requer a chegada da substância ativa ao seu local de ação com maior eficiência. Nessa busca, tem se destacado o uso de Sistemas Multiparticulados, forma farmacêutica de liberação modificada, em que o fármaco está dividido em várias subunidades funcionais de liberação, sob a forma de grânulos ou péletes, que quando administrados, são rapidamente desintegrados distribuindo seu conteúdo por todo trato

  2. Block Transfer Handbook: Constructing and Negotiating Block Transfer Agreements.

    Science.gov (United States)

    Finlay, Finola

    The purpose of this handbook is to provide resources for institutions or articulation committees who are engaged in the task of investigating the feasibility of block transfer agreements. Block transfer is the process whereby a block of credits is granted to students who have successfully completed a certificate, diploma, or cluster of courses…

  3. Wettability and ζ potentials of a series of methacrylate polymers and copolymers

    NARCIS (Netherlands)

    Hogt, A.H.; Gregonis, D.E.; Andrade, J.D.; Kim, S.W.; Dankert, J.; Feijen, J.

    1985-01-01

    Polymers and copolymers of different methacrylates were synthesized and coated on glass slides. The surfaces of the polymer films were characterized by their water contact angles and potentials using the Wilhelmy plate technique and streaming potential measurements, respectively. From contact-angle

  4. Recent Origin of the Methacrylate Redox System in Geobacter sulfurreducens AM-1 through Horizontal Gene Transfer.

    Science.gov (United States)

    Arkhipova, Oksana V; Meer, Margarita V; Mikoulinskaia, Galina V; Zakharova, Marina V; Galushko, Alexander S; Akimenko, Vasilii K; Kondrashov, Fyodor A

    2015-01-01

    The origin and evolution of novel biochemical functions remains one of the key questions in molecular evolution. We study recently emerged methacrylate reductase function that is thought to have emerged in the last century and reported in Geobacter sulfurreducens strain AM-1. We report the sequence and study the evolution of the operon coding for the flavin-containing methacrylate reductase (Mrd) and tetraheme cytochrome с (Mcc) in the genome of G. sulfurreducens AM-1. Different types of signal peptides in functionally interlinked proteins Mrd and Mcc suggest a possible complex mechanism of biogenesis for chromoproteids of the methacrylate redox system. The homologs of the Mrd and Mcc sequence found in δ-Proteobacteria and Deferribacteres are also organized into an operon and their phylogenetic distribution suggested that these two genes tend to be horizontally transferred together. Specifically, the mrd and mcc genes from G. sulfurreducens AM-1 are not monophyletic with any of the homologs found in other Geobacter genomes. The acquisition of methacrylate reductase function by G. sulfurreducens AM-1 appears linked to a horizontal gene transfer event. However, the new function of the products of mrd and mcc may have evolved either prior or subsequent to their acquisition by G. sulfurreducens AM-1.

  5. Recent Origin of the Methacrylate Redox System in Geobacter sulfurreducens AM-1 through Horizontal Gene Transfer.

    Directory of Open Access Journals (Sweden)

    Oksana V Arkhipova

    Full Text Available The origin and evolution of novel biochemical functions remains one of the key questions in molecular evolution. We study recently emerged methacrylate reductase function that is thought to have emerged in the last century and reported in Geobacter sulfurreducens strain AM-1. We report the sequence and study the evolution of the operon coding for the flavin-containing methacrylate reductase (Mrd and tetraheme cytochrome с (Mcc in the genome of G. sulfurreducens AM-1. Different types of signal peptides in functionally interlinked proteins Mrd and Mcc suggest a possible complex mechanism of biogenesis for chromoproteids of the methacrylate redox system. The homologs of the Mrd and Mcc sequence found in δ-Proteobacteria and Deferribacteres are also organized into an operon and their phylogenetic distribution suggested that these two genes tend to be horizontally transferred together. Specifically, the mrd and mcc genes from G. sulfurreducens AM-1 are not monophyletic with any of the homologs found in other Geobacter genomes. The acquisition of methacrylate reductase function by G. sulfurreducens AM-1 appears linked to a horizontal gene transfer event. However, the new function of the products of mrd and mcc may have evolved either prior or subsequent to their acquisition by G. sulfurreducens AM-1.

  6. Enthalpy of mixing of methacrylic acid with organic solvents at 293 K

    Science.gov (United States)

    Sergeev, V. V.

    2016-03-01

    The enthalpies of mixing of binary systems of methacrylic acid with acetonitrile, benzene, hexane, 1,2-dichloroethane, and acetic acid are measured calorimetrically at 293 K and atmospheric pressure. The enthalpy of mixing of all the studied binary systems is positive over the range of concentrations.

  7. Polymerization of Methyl Methacrylate with Samarocene Complex Supported on Mesoporous Silica

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Samarocene complex was supported on a series of mesoporous silica with various pore sizes. Polymerization of methyl methacrylate (MMA) by these catalysts provide highly syndiotactic PMMAs with higher molecular weights compared with those obtained by solution polymerization with homogeneous catalyst system.

  8. Polymorphism and polymerisation of acrylic and methacrylic acid at high pressure

    DEFF Research Database (Denmark)

    Oswald, Iain D. H.; Urquhart, Andrew J.

    2011-01-01

    The polymorphism and polymerisation of two related acids have been investigated under high pressure conditions. Acrylic acid crystallises as a new polymorph at 0.65 GPa whilst methacrylic acid crystallises in a new polymorph at a higher pressure of 1.5 GPa. Both these new polymorphs exhibit similar...

  9. Cosolvency-Induced Switching of the Adhesion between Poly(methyl methacrylate) Brushes

    NARCIS (Netherlands)

    Yu, Y.; Kieviet, B.D.; Kutnyanszky, E.; Vancso, G.J.; Beer, de S.

    2015-01-01

    We present a simple method to reversibly switch the adhesive force between two surfaces that are decorated with poly(methyl methacrylate) (PMMA) graft polymers. By employment of a PMMA/isopropanol/water or a PMMA/ethanol/water cosolvent system, we can tune the swelling of the brushes. In pure isopro

  10. Refractive microlenses produced by excimer laser machining of poly(methyl methacrylate)

    DEFF Research Database (Denmark)

    Jensen, Martin Frøhling; Krühne, Ulrich; H., L.;

    2005-01-01

    A method has been developed whereby refractive microlenses can be produced in poly (methyl methacrylate) by excimer laser irradiation at λ = 248 nm. The lenses are formed by a combined photochemical and thermal process. The lenses are formed as depressions in the substrate material (negative foca...

  11. Photopolymerization-Induced Two-Beam Coupling and Light-Induced Scattering in Polymethyl Methacrylate

    Institute of Scientific and Technical Information of China (English)

    LI Wei; GAO Feng; TANG Bai-Quan; Christian Pruner; ZHANG Xin-Zheng; SHI Yan-Li; XU Jing-Jun; QIAO Hai-Jun; WU Qiang; Romano A. Rupp; LOU Ci-Bo; WANG Zhen-Hua

    2008-01-01

    @@ Light amplification due to two-beam coupling is realized in doped polymethyl methacrylate (PMMA) glasses. A coupling gain as large as 14 cm-1 is obtained. The dynamic behaviour of absorption and light-induced scattering due to the process of photopolymerization are also studied. The results show that the amplification and its dynamic process enable possible applications of PMMA in optical devices.

  12. Textural properties of poly(glycidyl methacrylate) : acid-modified bentonite nanocomposites

    NARCIS (Netherlands)

    Zunic, M.; Milutinovic-Nikolic, A.; Nastasovic, A.; Vukovic, Z.; Loncarevic, D.; Vukovic, I.; Loos, K.; ten Brinke, G.; Jovanovic, D.; Sharma, Bhaskar; Ubaghs, Luc; Keul, Helmut; Höcker, Hartwig; Loontjens, Ton; Benthem, Rolf van; Žunić, M.; Milutinović-Nikolić, A.; Nastasović, A.; Vuković, Z.; Lončarević, D.; Vuković, I.; Jovanović, D.

    2013-01-01

    The aim of this study was to obtain enhanced textural properties of macroporous crosslinked copolymer poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) by synthesizing nanocomposites with acid-modified bentonite. Nanocomposites were obtained by introducing various amounts of acid-modifie

  13. A novel epoxy methacrylate resin containing phthalazinone moiety for UV coatings

    Institute of Scientific and Technical Information of China (English)

    Yan Kou; Jin Yan Wang; Xi Gao Jian

    2007-01-01

    A novel phthalazinone modified epoxy acrylate resin for the high temperature resistant ultravioet (UV) curable coating was synthesized. The methacrylated epoxy resins obtained were utilized to UV radiation curing by taking 2.5% (wt%) of photoinitiator in combination with 20% (wt%) of diluent, and generated the interpenetraring polymer networks. The cured film had good thermal and chemical stability.

  14. Characterization of methyl methacrylate grafting onto preirradiated biodegradable lignocellulose fiber by gamma-radiation.

    Science.gov (United States)

    Khan, Ferdous

    2005-01-14

    Gamma-radiation-induced graft copolymerization of methyl methacrylate onto natural lignocellulose (jute) fiber was carried out by the preirradiation method in an aqueous medium by using octylphenoxy-polyethoxyethanol as an emulsifier. The different factors that influenced the graft copolymer reaction process were investigated. In the case of radiation-dose-dependent grafting, samples irradiated in the presence of air produced up to 73% graft weight compared to 53% obtained in the case of irradiation in a nitrogen environment. By assuming Arrhenius reaction kinetics, the activation energy (E(a)) of the grafting reaction process was evaluated for different reaction temperatures. Moreover, the graft copolymer reaction was controlled by incorporating a homopolymer-inhibiting agent and three different chain-transfer agents in the reaction medium. The mechanical and thermal properties of jute fiber 'as received' and jute-graft-poly(methyl methacrylate) were also investigated. The results showed that the percentage of grafting with jute fiber has a significant effect on the properties. The kinetic parameters were evaluated from TGA thermograms by using Broido's method in the temperature range 240-350 degrees C. Scanning electron micrographs show that the structural changes on the surface of jute fibers were induced by graft copolymerization of methyl methacrylate monomer. Fiber-fiber surface friction was measured in terms of the average maximum load and the kinetic friction. SEM of jute-graft-poly(methyl methacrylate).

  15. ON COPOLYMERIZATION KINETICS OF N-VINYL PYRROLIDONE METHYL METHACRYLATE AT HIGH CONVERSION

    Institute of Scientific and Technical Information of China (English)

    WEN Jianyie; Sun Yishi

    1988-01-01

    In this work, Fourier transform infrared spectroscopy was used to study the copolymerization kinetics of N-vinyl pyrrolidone-methyl methacrylate (VPMMA) at high conversion. Through computer simulation,copolymerization rate equation based on the free volume theory, diffusion theory and modified MH model was established. The activation energy of copolymerization was also estimated.

  16. Graft Copolymerization of Methyl Methacrylate Monomer onto Starch and Natural Rubber Latex Initiated by Gamma Irradiation

    Directory of Open Access Journals (Sweden)

    S. Iskandar

    2011-04-01

    Full Text Available To obtain the degradable plastic, the graft copolymerization of methyl methacrylate onto starch and natural rubber latex was conducted by a simultaneous irradiation technique. Gamma-ray from cobalt-60 source was used as the initiator. The grafted copolymer of starch-polymethyl methacrylate and the grafted copolymer of natural rubber-polymethyl methacrylate were mixed in the blender, and dried it in the oven. The dried grafted copolymer mixture was then molded using hydraulic press machine. The effect of irradiation dose, composition of the grafted copolymer mixture, film forming condition and recycle effect was evaluated. The parameters observed were tensile strength, gel fraction and soil burial degradability of grafted copolymer mixture. It was found that the tensile strength of grafted copolymer mixture increased by -ray irradiation. Increasing of the grafted copolymer of natural rubber-polymethyl methacrylate content, the gel fraction and tensile strength of the grafted copolymer mixture increased. The tensile strength of the grafted copolymer mixture was increased from 18 MPa to 23 MPa after recycled (film forming reprocessed 3 times. The grafted copolymer mixture was degraded completely after soil buried for 6 months

  17. Morphology and film formation of poly(butyl methacrylate)-polypyrrole core-shell latex particles

    NARCIS (Netherlands)

    Huijs, F; Lang, J

    2000-01-01

    Core-shell latex particles made of a poly(butyl methacrylate) (PBMA) core and a thin polypyrrole (PPy) shell were synthesized by two-stage polymerization. In the first stage, PBMA latex particles were synthesized in a semicontinuous process by free-radical polymerization. PBMA latex particles were l

  18. Controlled release of cortisone drugs from block copolymers synthetized by ATRP

    Science.gov (United States)

    Valenti, G.; La Carta, S.; Mazzotti, G.; Rapisarda, M.; Perna, S.; Di Gesù, R.; Giorgini, L.; Carbone, D.; Recca, G.; Rizzarelli, P.

    2016-05-01

    Diseases affecting posterior eye segment, like macular edema, infection and neovascularization, may cause visual impairment. Traditional treatments, such as steroidal-drugs intravitreal injections, involve chronic course of therapy usually over a period of years. Moreover, they can require frequent administrations of drug in order to have an adequately disease control. This dramatically reduce patient's compliance. Efforts have been made to develop implantable devices that offer an alternative therapeutic approach to bypass many challenges of conventional type of therapy. Implantable drug delivery systems (DDS) have been developed to optimize therapeutic properties of drugs and ensure their slow release in the specific site. Polymeric materials can play an essential role in modulating drug delivery and their use in such field has become indispensable. During last decades, acrylic polymers have obtained growing interest. Biocompatibility and chemical properties make them extremely versatile, allowing their use in many field such as biomedical. In particular, block methacrylate copolymer with a balance of hydrophilic and hydrophobic properties can be suitable for prolonged DDS in biomedical devices. In this work, we focused on the realization of a system for controlled and long term release of betamethasone 17,21-dipropionate (BDP), a cortisone drug, from methacrylic block copolymers, to be tested in the treatment of the posterior eye's diseases. Different series of methyl methacrylate/hydroxyethyl methacrylate (MMA/HEMA) block and random copolymers, with different monomer compositions (10-60% HEMA), were synthetized by Atom Transfer Radical Polymerization (ATRP) to find the best hydrophilic/hydrophobic ratio, able to ensure optimal kinetic release. Copolymer samples were characterized by NMR spectroscopy (1H-NMR, 13C-NMR, CosY), SEC, TGA and DSC. Monitoring of drug release from films loaded with BDP was carried out by HPLC analysis. Evaluation of different kinetic

  19. Demographic Data - MDC_Block

    Data.gov (United States)

    NSGIC GIS Inventory (aka Ramona) — A polygon feature class of Miami-Dade Census 2000 Blocks. Census blocks are areas bounded on all sides by visible and/or invisible features shown on a map prepared...

  20. Habitat Blocks and Wildlife Corridors

    Data.gov (United States)

    Vermont Center for Geographic Information — Habitat blocks are areas of contiguous forest and other natural habitats that are unfragmented by roads, development, or agriculture. Vermonts habitat blocks are...

  1. Porous block nanofiber composite filters

    Energy Technology Data Exchange (ETDEWEB)

    Ginley, David S.; Curtis, Calvin J.; Miedaner, Alexander; Weiss, Alan J.; Paddock, Arnold

    2016-08-09

    Porous block nano-fiber composite (110), a filtration system (10) and methods of using the same are disclosed. An exemplary porous block nano-fiber composite (110) includes a porous block (100) having one or more pores (200). The porous block nano-fiber composite (110) also includes a plurality of inorganic nano-fibers (211) formed within at least one of the pores (200).

  2. Properties of blocked linear systems.

    Science.gov (United States)

    Chen, Weitian; Anderson, Brian D O; Deistler, Manfred; Filler, Alexander

    2012-10-01

    This paper presents a systematic study on the properties of blocked linear systems that have resulted from blocking discrete-time linear time invariant systems. The main idea is to explore the relationship between the blocked and the unblocked systems. Existing results are reviewed and a number of important new results are derived. Focus is given particularly on the zero properties of the blocked system as no such study has been found in the literature.

  3. Appropriate schemata and building blocks

    Institute of Scientific and Technical Information of China (English)

    Yang Haijun; Li Minqiang

    2005-01-01

    Appropriate schemata as a novel concept to characterize building blocks are introduced, and then, the traits of appropriate schemata are presented. The effects of building blocks by search operators are analyzed. Hence, the experiments on RR-8X8 are employed to verify that appropriate schemata construct the building blocks. The validity of appropriate schemata and building blocks from the views of theory and practice is presented.

  4. Blocking the Hawking radiation

    DEFF Research Database (Denmark)

    Autzen, M.; Kouvaris, C.

    2014-01-01

    grows after its formation (and eventually destroys the star) instead of evaporating. The fate of the black hole is dictated by the two opposite mechanics, i.e., accretion of nuclear matter from the center of the star and Hawking radiation that tends to decrease the mass of the black hole. We study how...... the assumptions for the accretion rate can in fact affect the critical mass beyond which a black hole always grows. We also study to what extent degenerate nuclear matter can impede Hawking radiation due to the fact that emitted particles can be Pauli blocked at the core of the star....

  5. Preparation and icephobic properties of polymethyltrifluoropropylsiloxane–polyacrylate block copolymers

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xiaohui; Zhao, Yunhui [School of Materials Science and Engineering, and Tianjin Key Laboratory of Composite and Functional Materials, Tianjin University, Tianjin 300072 (China); Li, Hui [School of Chemistry and Chemical Engineering, Shandong Key Laboratory of Fluorine Chemistry and Chemical Engineering Materials, University of Jinan, Jinan 250022 (China); Yuan, Xiaoyan, E-mail: xyuan28@yahoo.com [School of Materials Science and Engineering, and Tianjin Key Laboratory of Composite and Functional Materials, Tianjin University, Tianjin 300072 (China)

    2014-10-15

    Highlights: • PMTFPS–b-polyacrylate copolymers in five different compositions were synthesized. • Enrichment of PMTFPS amounts at the surface made high F/Si value. • Icing delay time was related to the surface roughness. • Ice shear strength was decreased by the synergistic effect of silicone and fluorine. - Abstract: Five polymethyltrifluoropropylsiloxane (PMTFPS)–polyacrylate block copolymers (PMTFPS–b-polyacrylate) were synthesized by free radical polymerization of methyl methacrylate, n-butyl acrylate and hydroxyethyl methacrylate using PMTFPS macroazoinitiator (PMTFPS-MAI) in range of 10–50 mass percentages. The morphology, surface chemical composition and wettability of the prepared copolymer films were investigated by transmission electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and water contact angle measurement. Delayed icing time and ice shear strength of the films were also detected for the icephobic purpose. The surface morphologies of the copolymers were different from those of the bulk because of the migration of the PMTFPS segments to the air interface during the film formation. Maximal delayed icing time (186 s at −15 °C) and reduction of the ice shear strength (301 ± 10 kPa) which was significantly lower than that of polyacrylates (804 ± 37 kPa) were achieved when the content of PMTFPS-MAI was 20 wt%. The icephobicity of the copolymers was attributed primarily to the enrichment of PMTFPS on the film surface and synergistic effect of both silicone and fluorine. Thus, the results show that the PMTFPS–b-polyacrylate copolymer can be used as icephobic coating materials potentially.

  6. Property Blocks: Games and Activities.

    Science.gov (United States)

    Humphreys, Alan, Ed.; Dailey, Jean, Ed.

    This pamphlet describes the property blocks produced by MINNEMAST, and discusses their use in the development of thinking processes. Classification systems, including block diagrams and tree diagrams, are discussed. Sixteen classroom activities and eleven games which use the blocks are described. Suggestions to the teacher for further reading are…

  7. Undergraduate Prosthodontics Students’ Knowledge of Working With Methyl Methacrylate at Shahid Sadoughi Medical University in 2014

    Directory of Open Access Journals (Sweden)

    Lotfikamran

    2016-06-01

    Full Text Available Background The toxicity of the methyl methacrylate monomer is an ongoing concern in dentistry. Therefore, those who are involved with this substance need to be cognizant of how to work with it. Objectives This study aimed to evaluate the level of working knowledge about methyl methacrylate among undergraduate prosthodontics students at Shahid Sadoughi university in 2014. Materials and Methods In this descriptive cross-sectional study, the knowledge level of 54 undergraduate prosthodontics students, who had passed the last 2 years of their education, was assessed via a 13-question survey related to methyl methacrylate. Each correct answer was assigned 2 points, and the total sum of right answers was used to measure the knowledge level of each participant. In order to analyze the study data, SPSS16 was used to apply an ANOVA test, t-test, and Pearson correlation coefficient. Results The mean level of individuals’ knowledge in regard to working with methyl methacrylate was 14.74 ± 5.03, with a domain variance of 0 to 22. A significant relationship was observed between age-related knowledge level mean and education level (P = 0.001, though no relationship was confirmed in regard to knowledge mean and gender (P < 0.286. Moreover, there was a reverse insignificant relationship between the students’ total average and their knowledge level (P = 0.715. Conclusions The study results demonstrated that undergraduate prosthodontics students in their last two years of study had an average knowledge of working with methyl methacrylate. Therefore, health education should focus more on working with dentistry substances, in order to enhance the knowledge level of the targeted students.

  8. Mechanisms of Action of (Methacrylates in Hemolytic Activity, in Vivo Toxicity and Dipalmitoylphosphatidylcholine (DPPC Liposomes Determined Using NMR Spectroscopy

    Directory of Open Access Journals (Sweden)

    Seiichiro Fujisawa

    2012-01-01

    Full Text Available We investigated the quantitative structure-activity relationships between hemolytic activity (log 1/H50 or in vivo mouse intraperitoneal (ip LD50 using reported data for α,β-unsaturated carbonyl compounds such as (methacrylate monomers and their 13C-NMR β-carbon chemical shift (δ. The log 1/H50 value for methacrylates was linearly correlated with the δCβ value. That for (methacrylates was linearly correlated with log P, an index of lipophilicity. The ipLD50 for (methacrylates was linearly correlated with δCβ but not with log P. For (methacrylates, the δCβ value, which is dependent on the π-electron density on the β-carbon, was linearly correlated with PM3-based theoretical parameters (chemical hardness, η; electronegativity, χ; electrophilicity, ω, whereas log P was linearly correlated with heat of formation (HF. Also, the interaction between (methacrylates and DPPC liposomes in cell membrane molecular models was investigated using 1H-NMR spectroscopy and differential scanning calorimetry (DSC. The log 1/H50 value was related to the difference in chemical shift (ΔδHa (Ha: H (trans attached to the β-carbon between the free monomer and the DPPC liposome-bound monomer. Monomer-induced DSC phase transition properties were related to HF for monomers. NMR chemical shifts may represent a valuable parameter for investigating the biological mechanisms of action of (methacrylates.

  9. Phase behavior for the poly(alkyl methacrylate)+supercritical CO{sub 2}+DME mixture at high pressures

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Yong-Seok; Chio, Sang-Won; Byun, Hun-Soo [Chonnam National University, Yeosu (Korea, Republic of)

    2016-01-15

    The phase behavior curves of binary and ternary system were measured for poly(alkyl methacrylate) in supercritical CO{sub 2}, as well as for the poly(alkyl methacrylate)+dimethyl ether (DME) (or 1-butene) in CO{sub 2}. The solubility curves are reported for the poly(alkyl methacrylate)+DME in supercritical CO{sub 2} at temperature from (300 to 465) K and a pressure from (3.66 to 248) MPa. Also, The high-pressure static-type apparatus of cloud-point curve was tested by comparing the measured phase behavior data of the poly(methyl methacrylate) [PMMA]+CO{sub 2}+20.0 and 30.4 wt% methyl methacrylate (MMA) system with literature data of 10.4, 28.8 and 48.4 wt% MMA concentration. The phase behavior data for the poly(alkyl methacrylate)+CO{sub 2}+DME mixture were measured in changes of the pressure-temperature (p, T) slope and with DME concentrations. Also, the cloud-point pressure for the poly(alkyl methacrylate)+1- butene solution containing supercritical CO{sub 2} shows from upper critical solution temperature (UCST) region to lower critical solution temperature (LCST) region at concentration range from (0.0 to 95) wt% 1-butene at below 455 K and at below 245MPa.

  10. Supramolecular Phase-Selective Gelation by Peptides Bearing Side-Chain Azobenzenes: Effect of Ultrasound and Potential for Dye Removal and Oil Spill Remediation

    Directory of Open Access Journals (Sweden)

    Jürgen Bachl

    2015-05-01

    Full Text Available Phase selective gelation (PSG of organic phases from their non-miscible mixtures with water was achieved using tetrapeptides bearing a side-chain azobenzene moiety. The presence of the chromophore allowed PSG at the same concentration as the minimum gelation concentration (MGC necessary to obtain the gels in pure organic phases. Remarkably, the presence of the water phase during PSG did not impact the thermal, mechanical, and morphological properties of the corresponding organogels. In the case of miscible oil/water mixtures, the entire mixture was gelled, resulting in the formation of quasi-hydrogels. Importantly, PSG could be triggered at room temperature by ultrasound treatment of the mixture or by adding ultrasound-aided concentrated solution of the peptide in an oil-phase to a mixture of the same oil and water. Moreover, the PSG was not affected by the presence of salts or impurities existing in water from natural sources. The process could be scaled-up, and the oil phases (e.g., aromatic solvents, gasoline, diesel fuel recovered almost quantitatively after a simple distillation process, which also allowed the recovery and reuse of the gelator. Finally, these peptidic gelators could be used to quantitatively remove toxic dyes from aqueous solutions.

  11. Supramolecular Phase-Selective Gelation by Peptides Bearing Side-Chain Azobenzenes: Effect of Ultrasound and Potential for Dye Removal and Oil Spill Remediation

    Science.gov (United States)

    Bachl, Jürgen; Oehm, Stefan; Mayr, Judith; Cativiela, Carlos; Marrero-Tellado, José Juan; Díaz Díaz, David

    2015-01-01

    Phase selective gelation (PSG) of organic phases from their non-miscible mixtures with water was achieved using tetrapeptides bearing a side-chain azobenzene moiety. The presence of the chromophore allowed PSG at the same concentration as the minimum gelation concentration (MGC) necessary to obtain the gels in pure organic phases. Remarkably, the presence of the water phase during PSG did not impact the thermal, mechanical, and morphological properties of the corresponding organogels. In the case of miscible oil/water mixtures, the entire mixture was gelled, resulting in the formation of quasi-hydrogels. Importantly, PSG could be triggered at room temperature by ultrasound treatment of the mixture or by adding ultrasound-aided concentrated solution of the peptide in an oil-phase to a mixture of the same oil and water. Moreover, the PSG was not affected by the presence of salts or impurities existing in water from natural sources. The process could be scaled-up, and the oil phases (e.g., aromatic solvents, gasoline, diesel fuel) recovered almost quantitatively after a simple distillation process, which also allowed the recovery and reuse of the gelator. Finally, these peptidic gelators could be used to quantitatively remove toxic dyes from aqueous solutions. PMID:26006247

  12. Supramolecular phase-selective gelation by peptides bearing side-chain azobenzenes: effect of ultrasound and potential for dye removal and oil spill remediation.

    Science.gov (United States)

    Bachl, Jürgen; Oehm, Stefan; Mayr, Judith; Cativiela, Carlos; Marrero-Tellado, José Juan; Díaz, David Díaz

    2015-05-22

    Phase selective gelation (PSG) of organic phases from their non-miscible mixtures with water was achieved using tetrapeptides bearing a side-chain azobenzene moiety. The presence of the chromophore allowed PSG at the same concentration as the minimum gelation concentration (MGC) necessary to obtain the gels in pure organic phases. Remarkably, the presence of the water phase during PSG did not impact the thermal, mechanical, and morphological properties of the corresponding organogels. In the case of miscible oil/water mixtures, the entire mixture was gelled, resulting in the formation of quasi-hydrogels. Importantly, PSG could be triggered at room temperature by ultrasound treatment of the mixture or by adding ultrasound-aided concentrated solution of the peptide in an oil-phase to a mixture of the same oil and water. Moreover, the PSG was not affected by the presence of salts or impurities existing in water from natural sources. The process could be scaled-up, and the oil phases (e.g., aromatic solvents, gasoline, diesel fuel) recovered almost quantitatively after a simple distillation process, which also allowed the recovery and reuse of the gelator. Finally, these peptidic gelators could be used to quantitatively remove toxic dyes from aqueous solutions.

  13. Dark conglomerate phases of azobenzene derived bent-core mesogens - relationships between the molecular structure and mirror symmetry breaking in soft matter.

    Science.gov (United States)

    Alaasar, Mohamed; Prehm, Marko; Brautzsch, Marcel; Tschierske, Carsten

    2014-10-07

    New 4-bromoresorcinol based bent-core molecules with peripheral fluoro substituted azobenzene wings have been synthesized and the liquid crystalline self-assembly was investigated by differential scanning calorimetry (DSC), optical polarizing microscopy (POM), electro-optic studies and X-ray diffraction (XRD). A new type of optically isotropic mesophase composed of chiral domains with opposite handedness (dark conglomerate phases, DC phases) is observed, which for some homologues with medium alkyl chain length is stable down to ambient temperature. It is proposed that these DC phases are formed by helical twisted nano-domains of limited size and composed of the crystallized aromatic cores which are separated by the disordered alkyl chains. This structure is distinct from the previously known soft helical nano-filament phases (HNF phases, B4 phases) formed by extended crystalline nano-filaments and also distinct from the fluid sponge phases composed of deformed fluid layers. Comparison with related bent-core molecules having H, F, Cl, I, CH3 and CN groups in the 4-position at the resorcinol core, either with or without additional peripheral fluorines, provided information about the effects of these substituents on the tendency to form DC phases. Based on these relationships and by comparison with the minimum energy conformations obtained by DFT calculations a hypothesis is provided for the formation of DC phases depending on the molecular structure.

  14. Effects of gomisin A on the promotor action and serum bile acid concentration in hepatocarcinogenesis induced by 3'-methyl-4-dimethylamino-azobenzene.

    Science.gov (United States)

    Miyamoto, K; Hiramatsu, K; Ohtaki, Y; Kanitani, M; Nomura, M; Aburada, M

    1995-10-01

    The effects of gomisin A, a lignan component of Schizandra fruits, on the promotion stage of hepatocarcinogenesis initiated by 3'-methyl-4-dimethylamino-azobenzene (3'-MeDAB) in male Donryu rats were investigated. When different types of tumor promotors, phenobarbital (PB) and deoxycholic acid (DCA), were administered for 5 weeks after initiation by 3'-MeDAB, preneoplastic alterations in the liver, determined by glutathione S-transferase placental form (GST-P), were markedly increased. Gomisin A significantly inhibited the increase in number and size of GST-P positive foci, regardless of the promotor. This lignan inhibited the increase in serum bile acid concentration by administration of DCA, but hardly influenced the serum bile acids in the PB-combined group. These results suggest that the inhibitory effect of gomisin A on the promotive action of DCA is based on improving bile acid metabolism, but regarding the action of PB, the effect could not be elucidated from the metabolism of bile acids.

  15. Nanofabrication of SERS device by an integrated block-copolymer and nanoimprint lithography method.

    Energy Technology Data Exchange (ETDEWEB)

    Nealey, Paul (University of Wisconsin); Liu, Charlie (University of Wisconsin); Skinner, Jack L.; Yang, Elaine; Steinhaus, Charles A.; Yang, Chu-Yeu Peter

    2010-05-01

    The integration of block-copolymers (BCPs) and nanoimprint lithography (NIL) presents a novel and cost-effective approach to achieving nanoscale patterning capabilities. The authors demonstrate the fabrication of a surface-enhanced Raman scattering device using templates created by the BCP-NIL integrated method. The method utilizes a poly(styrene-block-methyl methacrylate) cylindrical-forming diblock-copolymer as a masking material to create a Si template, which is then used to perform a thermal imprint of a poly(methyl methacrylate) (PMMA) layer on a Si substrate. Au with a Cr adhesion layer was evaporated onto the patterned PMMA and the subsequent lift-off resulted in an array of nanodots. Raman spectra collected for samples of R6G on Si substrates with and without patterned nanodots showed enhancement of peak intensities due to the presence of the nanodot array. The demonstrated BCP-NIL fabrication method shows promise for cost-effective nanoscale fabrication of plasmonic and nanoelectronic devices.

  16. A new drug carrier: Magnetite nanoparticles coated with amphiphilic block copolymer

    Institute of Scientific and Technical Information of China (English)

    CHANG Yu; BAI YunPeng; TENG Bao; Li ZhaoLong

    2009-01-01

    This paper reports on the synthesis and characterization of 4 nm magnetite nanoparticles coated with amphiphilic block copolymers of poly(ethyl methacrylate)-b-poly(2-hydroxyethyl methacrylate) (PEMA-b-PHEMA) by surface-initiated atom transfer radical polymerization (ATRP), which can act as new po-tential carriers for hydrophobic targeted drug delivery. Vibrating sample magnetometer analysis indi-cated that the magnetite nanoparticles were superparamagnetic at room temperature. Thermogravim-etric analysis (TGA) was applied to studying the property of surface of magnetite nanoparticles, and the surface density of macromolecules was calculated. The grafting density of oleic acid, BrMPA and PEMA was 5.8, 3.9, 0.16 chain/nm2 respectively, which indicates that the initiation efficiency decreases due to the influence of large space of oleic acid molecules. In vitro progesterone and (-)-isoproterenol hy-drochloride release in phosphate buffered saline (PBS) at pH 7.0 and 37℃ was conducted in order to demonstrate the function of drug loading and release. The results showed that the amount of drug carried into the core-shell Fe3O4@PEMA-b-PHEMA depends on the length of hydrophobic segment of block copolymer. The release of progesterone (37% after 22 h in our previous work) was compared with the release of (-)-isoproterenol hydrochloride (80% after 50 min), demonstrating that the strong hy-drophobic interaction between hydrophobic segment and drug can effectively control the release of hydrophobic drugs.

  17. Synthesis of PMMA-b-PU-b-PMMA tri-block copolymers through ARGET ATRP in the presence of air

    Directory of Open Access Journals (Sweden)

    P. Krol

    2013-03-01

    Full Text Available ARGET (activators regenerated by electron transfer ATRP (atom transfer radical polymerization has been successfully performed (in flasks fitted with rubber septa without the need for use of Schlenk line in the presence of limited amount of air and with a very small (370 ppm amount of copper catalyst together with an appropriate reducing agent Cu(0. Novelty of this work is that the poly(methyl methacrylate-block-polyurethane-block-poly(methyl methacrylate triblock copolymers were synthesized for the first time through ARGET ATRP, by using tertiary bromine-terminated polyurethane as a macroinitiator (MBP-PU-MBP, CuBr2 or CuCl2 as a catalyst and N,N,N',N",N"-pentamethyldiethylenetriamine (PMDETA or 2,2'-bipyridine (Bpy as a complexing agent. As the polymerization time increases, both the monomer conversion and ln([M]0/[M] increased and the molecular weight of copolymer increases linearly with increasing conversion. Theoretical number-average molecular weight (Mn, th of the tri-block copolymers was found to be comparable with number-average molecular weight determined by GPC analyses (Mn, GPC. These results indicate that the formation of the tri-block copolymers was through atom transfer radical polymerization mechanism. 1H and 13C NMR spectral methods were employed to confirm chemical structures of synthesized macroinitiator and tri-block copolymers. Mole percentage of PMMA in the tri-block copolymers was calculated using 1H NMR spectroscopy and was found to be comparable with the GPC results. Additionally, the studies of surface properties (confocal microscopy and SFE of tri-block copolymer coatings confirmed the presence of MMA segments.

  18. Humanoid by ROBO-BLOCK

    Science.gov (United States)

    Niimi, Hirofumi; Koike, Minoru; Takeuchi, Seiichi; Douhara, Noriyoshi

    2007-12-01

    Humanoid by ROBO-BLOCK (robot block system) and the rational formula of robots were proposed. ROBO-BLOCK is composed of servo motors, the parts for servomotor rotor, the brackets for servomotor fixation, the board parts and the controllers. A robot can be assembled easily by ROBO-BLOCK. Meanwhile, it is convenient when the structure of the robot can be described easily as a character. The whole structure of the robot is expressed as rational formula of the robot to show molecule structure in chemistry. ROBO-BLOCK can be useful for not only the research but also the education. Creative student experiment was done in the college of industrial technology.

  19. Mushroom-shaped Morphology Formed in Thin Films of Cylinder-forming Block Copolymer

    Institute of Scientific and Technical Information of China (English)

    GONG Yu-mei; SONG Jing-chuan; ZHANG Gui-xia

    2011-01-01

    The morphology of the film of polystyrene-block-poly(methyl methacrylate)(PS-b-PMMA) block copolymer having polystyrene(PS) cylinder forming composition spin-coated on a neutral brush modified silicon substrate has been investigated in this report. A mushroom-shaped morphology formed in the film with one period to two periods(L0-2L0) in thickness, which was spin-coated under a low humidity condition(RH ca.13%) and then thermally annealed at an extreme high temperature(230 ℃). The results suggest that the spin-coating condition together with the confinement conditions plays a crucial role in the interesting morphology formation.

  20. DESIGN AND SYNTHESIS OF NOVEL CHIRAL IONIC LIQUIDS AND THEIR APPLICATION IN FREE RADICAL POLYMERIZATION OF METHYL METHACRYLATE

    Institute of Scientific and Technical Information of China (English)

    Hong-yang Ma; Xin-hua Wan; Xiao-fang Chen; Qi-feng Zhou

    2003-01-01

    Two new chiral ionic liquids, 1-((-)-menthoxycarbonylmethylene)-3-methylimidazolium hexafluorophosphate and l-((-)-menthoxycarbonylmethylene)-3-hexadecylimidazolium hexafluorophosphate, were designed and prepared. Their chemical structures were characterized by 1H-NMR. Reverse atom transfer radical polymerization of methyl methacrylate(MMA) in these two ionic liquids was carried out using AIBN/CuC12/bipy as the initiating system. The resultant well-defined polymethyl methacrylate (PMMA) was employed as a macroinitiator to induce the atom transfer radical polymerization of menthyl methacrylate (MnMA) in chlorobenzene, which yielded a PMMA-b-PMnMA diblock copolymer with narrow polydispersity.

  1. THE COMPATIBILITY OF BLENDS OF POLY(VINYL CHLORIDE) OR CHLORINATED POLY(VINYL CHLORIDE) WITH POLY(METHYL METHACRYLATE)

    Institute of Scientific and Technical Information of China (English)

    WANG Qingguo; CHENG Rongshi

    1988-01-01

    IR spectral shifts of carbonyl vibrational absorption for ethyl acetate, which acts analogically as the structural unit of poly(methyl methacrylate), in cyclohexane, chloroform, chlorinated paraffins, poly(vinyl chloride) and chlorinated poly(vinyl chloride) were measured. The results suggest that there are specific interactions between the carbonyl groups and the chlorinated hydrocarbons which could be responsible for the apparent compatibility of poly(vinyl chloride) -poly(methyl methacrylate) and chlorinated poly(vinyl chloride) -poly(methyl methacrylate) blends. Additionally, the effects of the preparation mode of blend films on phase separation and observed compatibility are discussed.

  2. Spintronics: Conceptual Building Blocks

    Science.gov (United States)

    Ansermet, J.-Ph.

    The purpose of this introduction to spintronics is to provide some elementary description of its conceptual building blocks. Thus, it is intended for a newcomer to the field. After recalling rudimentary descriptions of spin precession and spin relaxation, spin-dependent transport is treated within the Boltzmann formalism. This suffices to introduce key notions such as the spin asymmetry of the conductivities in the two-current model, the spin diffusion length, and spin accumulation. Two basic mechanisms of spin relaxation are then presented, one arising from spin-orbit scattering and the other from electron-magnon collisions. Finally, the action of a spin-polarized current on magnetization is presented in a thermodynamics framework. This introduces the notion of spin torque and the characteristic length scale over which the transverse spin polarization of conduction electron decays as it is injected into a magnet.

  3. Photovoltaic building blocks

    DEFF Research Database (Denmark)

    Hanberg, Peter Jesper; Jørgensen, Anders Michael

    2014-01-01

    it directcompetitive with fossil energy sources a further reduction is needed. By increasing the efficiency of the solar cells one gain an advantage through the whole chain of cost. So that per produced Watt of power less material is spent, installation costs are lower, less area is used etc. With an average...... efficiency of about 15% for commercial Silicon solar cells there is still much to gain. DTU Danchip provides research facilities, equipment and expertise for the building blocks that comprises fabricating the efficient solar cell. In order to get more of the sun light into the device we provide thin film......Photovoltaics (PV), better known as solar cells, are now a common day sight on many rooftops in Denmark.The installed capacity of PV systems worldwide is growing exponentially1 and is the third most importantrenewable energy source today. The cost of PV is decreasing fast with ~10%/year but to make...

  4. Celiac ganglia block

    Energy Technology Data Exchange (ETDEWEB)

    Akinci, Devrim [Department of Radiology, Hacettepe University School of Medicine, Sihhiye, 06100 Ankara (Turkey); Akhan, Okan [Department of Radiology, Hacettepe University School of Medicine, Sihhiye, 06100 Ankara (Turkey)]. E-mail: oakhan@hacettepe.edu.tr

    2005-09-01

    Pain occurs frequently in patients with advanced cancers. Tumors originating from upper abdominal viscera such as pancreas, stomach, duodenum, proximal small bowel, liver and biliary tract and from compressing enlarged lymph nodes can cause severe abdominal pain, which do not respond satisfactorily to medical treatment or radiotherapy. Percutaneous celiac ganglia block (CGB) can be performed with high success and low complication rates under imaging guidance to obtain pain relief in patients with upper abdominal malignancies. A significant relationship between pain relief and degree of tumoral celiac ganglia invasion according to CT features was described in the literature. Performing the procedure in the early grades of celiac ganglia invasion on CT can increase the effectiveness of the CGB, which is contrary to World Health Organization criteria stating that CGB must be performed in patients with advanced stage cancer. CGB may also be effectively performed in patients with chronic pancreatitis for pain palliation.

  5. Atomic Basic Blocks

    Science.gov (United States)

    Scheler, Fabian; Mitzlaff, Martin; Schröder-Preikschat, Wolfgang

    Die Entscheidung, einen zeit- bzw. ereignisgesteuerten Ansatz für ein Echtzeitsystem zu verwenden, ist schwierig und sehr weitreichend. Weitreichend vor allem deshalb, weil diese beiden Ansätze mit äußerst unterschiedlichen Kontrollflussabstraktionen verknüpft sind, die eine spätere Migration zum anderen Paradigma sehr schwer oder gar unmöglich machen. Wir schlagen daher die Verwendung einer Zwischendarstellung vor, die unabhängig von der jeweils verwendeten Kontrollflussabstraktion ist. Für diesen Zweck verwenden wir auf Basisblöcken basierende Atomic Basic Blocks (ABB) und bauen darauf ein Werkzeug, den Real-Time Systems Compiler (RTSC) auf, der die Migration zwischen zeit- und ereignisgesteuerten Systemen unterstützt.

  6. Evaluation of a new biocompatible poly(N-(morpholino ethyl methacrylate)-based copolymer for the delivery of ruthenium oligonucleotides, targeting HPV16 E6 oncogene.

    Science.gov (United States)

    Reschner, Anca; Shim, Yong Ho; Dubois, Philippe; Delvenne, Philippe; Evrard, Brigitte; Marcélis, Lionel; Moucheron, Cécile; Kirsch-De Mesmaeker, Andrée; Defrancq, Eric; Raes, Martine; Piette, Jacques; Collard, Laurence; Piel, Géraldine

    2013-08-01

    This study investigates the use of a new biocompatible block copolymer poly(2-(dimethylamino)ethyl methacrylate-N-(morpholino)ethyl methacrylate (PDMAEMA-b-PMEMA) for the delivery of a particular antisense oligonucleotide targeting E6 gene from human papilloma virus. This antisense oligonucleotide was derivatized with a polyazaaromatic Ru(II) complex which, under visible illumination, is able to produce an irreversible crosslink with the complementary targeted sequence. The purpose of this study is to determine whether by the use of a suitable transfection agent, it is possible to increase the efficiency of the antisense oligonucleotide targeting E6 gene, named Ru-P-4. In a recent study, we showed that Oligofectamine transfected Ru-P-4 antisense oligonucleotide failed to inhibit efficiently the growth of cervical cancer cell line SiHa, contrarily to the Ru-P-6 antisense oligonucleotide, another sequence also targeting the E6 gene. The ability of PDMAEMA-b-PMEMA to form polyplexes with optimal physicochemical characteristics was investigated first. Then the ability of the PDMAEMA-b-PMEMA/Ru-P-4 antisense oligonucleotide polyplexes to transfect two keratinocyte cell lines (SiHa and HaCat) and the capacity of polyplexes to inhibit HPV16+ cervical cancer cell growth was evaluated. PDMAEMA-b-PMEMA base polyplexes at the optimal molar ratio of polymer nitrogen atoms to DNA phosphates (N/P), were able to deliver Ru-P-4 antisense oligonucleotide and to induce a higher growth inhibition in human cervical cancer SiHa cells, compared to other formulations based on Oligofectamine.

  7. Effect of temperature on the interfacial behavior of a polystyrene-b-poly(methyl methacrylate) diblock copolymer at the air/water interface.

    Science.gov (United States)

    Seo, Yongsok; Cho, Chung Yeon; Hwangbo, Minyoung; Choi, Hyoung Jin; Hong, Soon Man

    2008-03-18

    Monolayers of a polystyrene-poly(methyl methacrylate) (PS-PMMA) diblock copolymer at the air-water interface were studied by measuring the surface pressure-area isotherms at several temperatures. Langmuir film balance experiments and atomic force microscopy showed that the diblock copolymer molecules formed surface micelles. In the plot of the surface pressure versus surface area per repeating unit, the monolayer changed from the gas phase to the liquid expanded phase at lower surface pressure for systems at low temperature compared to those at high temperature. In addition, a plateau, corresponding to the transition from the liquid expanded to liquid condensed phase, appeared in that plot at lower surface pressure for systems with a higher subphase (water) temperature. Hysteresis was observed in the compression-expansion cycle process. Increasing the subphase temperature alleviated this hyteresis gap, especially at low surface pressures. The minimum in the plot of the surface pressure versus surface area per repeating unit in the expansion process (which arises from the transition) and the transition plateau appeared more vividly at higher water temperature. These dynamic experimental results show that PS-PMMA diblock copolymers, in which both blocks are insoluble in water, do not form complicated entanglements in two-dimensional space. Although higher water temperature provided more entropy to the chains, and thus more conformational freedom, it did not change the surface morphology of the condensed film because both blocks of PS-PMMA are insoluble in water.

  8. (2,6-DIPHENYL) PHENYL METHACRYLATE .2. RADICAL COPOLYMERIZATION WITH METHYL-METHACRYLATE - THE T(G)S OF ITS COPOLYMERS WITH AN ADDENDUM ON THE POLYMERIZATION OF (2,6-DIPHENYL) PHENYL ACRYLATE

    NARCIS (Netherlands)

    TAN, YY; VANEKENSTEIN, GORA

    1994-01-01

    The radical copolymerization of (2,6-diphenyl) phenyl methacrylate (1) with methyl methacrylate in DMF with AIBN at 70-degrees-C has the reactivity rators r1 = 0.071 and r2 = 1.42, from which Q1 = 1.45 and e(l) = 1.20. The copolymers had M(n) s in the range of 10,000-40,000 and T(g) s ranging from 4

  9. Effect of cyclic loading on microleakage of silorane based composite compared with low shrinkage methacrylate-based composites

    Directory of Open Access Journals (Sweden)

    Hamid Kermanshah

    2016-01-01

    Conclusion: Silorane did not provide better marginal seal than the low shrinkage methacrylate-based composites (except Aelite. In addition, cyclic loading did not affect the marginal microleakage of evaluated composite restorations .

  10. Large Block Test Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Lin, W

    2001-12-01

    This report documents the Large-Block Test (LBT) conducted at Fran Ridge near Yucca Mountain, Nevada. The LBT was a thermal test conducted on an exposed block of middle non-lithophysal Topopah Spring tuff (Tptpmn) and was designed to assist in understanding the thermal-hydrological-mechanical-chemical (THMC) processes associated with heating and then cooling a partially saturated fractured rock mass. The LBT was unique in that it was a large (3 x 3 x 4.5 m) block with top and sides exposed. Because the block was exposed at the surface, boundary conditions on five of the six sides of the block were relatively well known and controlled, making this test both easier to model and easier to monitor. This report presents a detailed description of the test as well as analyses of the data and conclusions drawn from the test. The rock block that was tested during the LBT was exposed by excavation and removal of the surrounding rock. The block was characterized and instrumented, and the sides were sealed and insulated to inhibit moisture and heat loss. Temperature on the top of the block was also controlled. The block was heated for 13 months, during which time temperature, moisture distribution, and deformation were monitored. After the test was completed and the block cooled down, a series of boreholes were drilled, and one of the heater holes was over-cored to collect samples for post-test characterization of mineralogy and mechanical properties. Section 2 provides background on the test. Section 3 lists the test objectives and describes the block site, the site configuration, and measurements made during the test. Section 3 also presents a chronology of events associated with the LBT, characterization of the block, and the pre-heat analyses of the test. Section 4 describes the fracture network contained in the block. Section 5 describes the heating/cooling system used to control the temperature in the block and presents the thermal history of the block during the test

  11. Electron Transfer of Myoglobin Immobilized in Au Electrodes Modified with a RAFT PMMA-Block-PDMAEMA Polymer

    Directory of Open Access Journals (Sweden)

    Carla N. Toledo

    2014-01-01

    Full Text Available Myoglobin was immobilized with poly(methyl methacrylate-block-poly[(2-dimethylaminoethyl methacrylate]PMMA-block-PDMAEMA polymer synthesized by reversible addition-fragmentation chain transfer technique (RAFT. Cyclic voltammograms gave direct and slow quasireversible heterogeneous electron transfer kinetics between Mb-PMMA-block-PDMAEMA modified electrode and the redox center of the protein. The values for electron rate constant (Ks and transfer coefficient (α were 0.055±0.01·s−1 and 0.81±0.08, respectively. The reduction potential determined as a function of temperature (293–328 K revealed a value of reaction center entropy of ΔS0 of 351.3±0.0002 J·mol−1·K−1 and enthalpy change of -76.8±0.1 kJ·mol−1, suggesting solvent effects and charge ionization atmosphere involved in the reaction parallel to hydrophobic interactions with the copolymer. The immobilized protein also exhibits an electrocatalytical response to reduction of hydrogen peroxide, with an apparent Km of 114.7±58.7 μM. The overall results substantiate the design and use of RAFT polymers towards the development of third-generation biosensors.

  12. Dimensional Reduction for Conformal Blocks

    CERN Document Server

    Hogervorst, Matthijs

    2016-01-01

    We consider the dimensional reduction of a CFT, breaking multiplets of the d-dimensional conformal group SO(d+1,1) up into multiplets of SO(d,1). This leads to an expansion of d-dimensional conformal blocks in terms of blocks in d-1 dimensions. In particular, we obtain a formula for 3d conformal blocks as an infinite sum over 2F1 hypergeometric functions with closed-form coefficients.

  13. Preparation and surface modification of magnetic poly(methyl methacrylate) microspheres

    Institute of Scientific and Technical Information of China (English)

    YANG Chengli; GUAN Yueping; XING Jianmin; LIU Junguo; AN Zhentao; LIU Huizhou

    2004-01-01

    A novel method for preparation of magnetic polymer microspheres by spraying suspension polymerization (SSP) was developed. Relatively uniform magnetic poly(methyl methacrylate) microspheres were prepared by the spraying suspension polymerization (SSP)using methyl methacrylate (MMA) as monomer, divinylbenzene (DVB) as cross-linking agent,benzoyl peroxide (BPO) as initiator and polyvinyl alcohol (PVA) as stabilizer in the presence of hydrophobic Fe3O4 magnetic fluid. The microspheres prepared were modified by surface chemical reaction. The magnetic properties and morphology of the microspheres were examined by SEM and VSM respectively. The active functional groups of microspheres were examined by infrared spectra. The results showed that microspheres with saturation magnetization of 16.8emu/g showed distinct superparamagnetic characteristics and the magnetic microspheres with a size of 10 μm were relatively uniform.

  14. PREPARATION OF POLY(METHYL METHACRYLATE)/LAYERED DOUBLE HYDROXIDES NANOCOMPOSITES via in situ SOLUTION POLYMERIZATION

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    An exfoliated layered double hydroxides/poly(methyl methacrylate) (LDHs/PMMA) nanocomposite was prepared by in situ solution polymerization of methyl methacrylate (MMA) in the presence of 4-vinylbenzenesulfonate intercalated LDHs(MgAl-VBS LDHs). MgAl-VBS LDHs was prepared by the ion exchange method, and the structure and composition of the MgAl-VBS LDHs were determined by X-ray diffraction (XRD), infrared spectroscopy and elemental analysis. XRD and transmission electron microscopy (TEM) were employed to examine the structure of LDHs/PMMA nanocomposite. It was indicated that the LDHs layers were well exfoliated and dispersed in the PMMA matrix. The grafting of PMMA onto LDHs was confirmed by the extraction result and the weight fraction of grafted PMMA increased as the weight fraction of LDHs in the nanocomposites increased.

  15. Effect of epoxidation on 30% poly(methyl methacrylate)-grafted natural rubber polymer electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Nazir, Khuzaimah; Aziz, Ahmad Fairoz [Faculty of Applied Sciences, Universiti Teknologi MARA, 40450 Shah Alam, Selangor (Malaysia); Adam, Nurul Ilham [Faculty of Applied Sciences, Universiti Teknologi MARA, KampusTapah, 35400 Tapah Road, Tapah, Perak (Malaysia); Yahya, Muhd Zu Azhan [Faculty of Defence Sciences and Technology, Universiti Pertahanan Nasional Malaysia, Kem Sungai Besi, 57000 Kuala Lumpur (Malaysia); Ali, Ab Malik Marwan [Institute of Science, Universiti Teknologi MARA, 40450 Shah Alam, Selangor (Malaysia)

    2015-08-28

    Epoxidized 30% poly(methyl methacrylate)-grafted natural rubber (EMG 30) as a polymer host in solid polymer electrolytes (SPEs) has been investigated. EMG30 was synthesized via performicepoxidation method onto 30% poly(methyl methacrylate)-grafted natural rubber (MG30) and the formations of epoxy group were discussed. The EMG30 were characterized by proton nuclear magnetic resonance ({sup 1}HNMR) to investigate their chemical structure and differential scanning calorimeter to determine their crystallinity. A new peak in {sup 1}HNMR spectra (2.71 ppm) confirmed the appearance of epoxy group. SPE based on EMG30 doped with 40 wt% LiCF{sub 3}SO{sub 3} show the highest conductivity. The complexation between EMG30 and LiCF{sub 3}SO{sub 3} were confirmed by attenuated total reflection Fourier transform infrared (ATR-FTIR)

  16. Fabrication slab waveguide based polymethyl methacrylate (PMMA) with spin coating method

    Science.gov (United States)

    Andriawan, Alan; Pramono, Yono Hadi; Masoed, Asnawi

    2016-11-01

    Fabrication and characterization slab waveguide based polymethyl methacrylate (PMMA) has been carried out. Slab waveguide fabrication done by the spin coating method. Slab waveguide fabrication process carried out by the rotational speed of 1000, 2000, and 3000 rpm respectively played for 10 seconds. Then the slab waveguides heated using a hot plate. Heating process starting from room temperature then increased 5°C to 70°C with a 5 minute warm-up time interval. From the results of characterization fabricated slab waveguides to determine the film thickness is made. Then made observations on the waveguide by passing the light beam He-Ne laser on the thin layer through a single mode optical fiber. From the results of characterization is known that the fabrication of a slab waveguide with a layer thickness of 166 μm. From this research it is known that polymethyl methacrylate (PMMA) can be used as a waveguide with a spin coating method.

  17. Preparation of poly (methyl methacrylate)/nanometer calcium carbonate composite by in-situ emulsion polymerization

    Institute of Scientific and Technical Information of China (English)

    史建明; 包永忠; 黄志明; 翁志学

    2004-01-01

    Methyl methacrylate (MMA) emulsion polymerization in the presence of nanometer calcium carbonate (nano-CaCO3) surface modified with (-methacryloxypropyltrimethoxysilane (MPTMS) was carried out to prepare poly (methyl methacrylate) (PMMA)/nano-CaCO3 composite. The reaction between nano-CaCO3 and MPTMS, and the grafting of PMMA onto nano-CaCO3 were confirmed by infrared spectrum. The grafting ratio and grafting efficiency of PMMA on nano-CaCO3 modified with MPTMS were much higher than that on nano-CaCO3 modified with stearic acid. The grafting ratio of PMMA increased as the weight ratio between MMA and nano-CaCO3 increased, while the grafting efficiency of PMMA decreased. Transmission electron micrograph showed that nano-CaCO3 covered with PMMA was formed by in-situ emulsion polymerization.

  18. Structure and properties of hybrid poly(2-hydroxyethyl methacrylate)/SiO2 monoliths

    DEFF Research Database (Denmark)

    Ji, Xiangling; Jiang, Shichun; Qiu, Xuepeng

    2003-01-01

    Abstract: Hybrid poly(2-hydroxyethyl methacrylate) (PHEMA)/SiO2 monoliths were synthesized via a sol-gel process of the precursor tetraethyl orthosilicate (TEOS) and the in situ free-radical polymerization of 2-hydroxyethyl methacrylate (HEMA). The weight ratio of the starting chemicals, TEOS...... to HEMA, was varied between 100/0 and 0/100. Structural analysis was performed by IR and NMR. The NMR results indicated that the introduction of PHEMA in the silica networks gave rise to a lower degree of condensation of TEOS. The resulting monoliths showed more than 75% transmittance in the visible...... related to some degree of chemical crosslinking between the polymer and the silica moiety, which would greatly improve the thermal stability of such hybrid monoliths compared with a pure PHEMA....

  19. Stable Poly(methacrylic acid Brush Decorated Silica Nano-Particles by ARGET ATRP for Bioconjugation

    Directory of Open Access Journals (Sweden)

    Marcello Iacono

    2015-08-01

    Full Text Available The synthesis of polymer brush decorated silica nano-particles is demonstrated by activator regeneration by electron transfer atom transfer radical polymerization (ARGET ATRP grafting of poly(tert-butyl methacrylate. ATRP initiator decorated silica nano-particles were obtained using a novel trimethylsiloxane derivatised ATRP initiator obtained by click chemistry. Comparison of de-grafted polymers with polymer obtained from a sacrificial initiator demonstrated good agreement up to 55% monomer conversion. Subsequent mild deprotection of the tert-butyl ester groups using phosphoric acid yielded highly colloidal and pH stable hydrophilic nano-particles comprising approximately 50% methacrylic acid groups. The successful bio-conjugation was achieved by immobilization of Horseradish Peroxidase to the polymer brush decorated nano-particles and the enzyme activity demonstrated in a conversion of o-phenylene diamine dihydrochloride assay.

  20. The application of methacrylate resin and the derivation as restorative material of damaged tooth tissue

    Directory of Open Access Journals (Sweden)

    Adioro Soetojo

    2007-12-01

    Full Text Available The application of methacrylate resin and the derivation (composite resin and dentin bonding in clinical conservative dentistry has been widely developed. This material could be used to restore class I-V cavity with good aesthetic due to the compatible color with tooth. Composite resin adhesion hydrophobically in enamel that is due to mechanic retention in the form of resin tags which penetrates into enamel porosity. Meanwhile hydrophilic dentin bonding adhesion due to the chemical reaction between functional groups of amino collagen with carbonyl in dentin bonding forming amide binding. In addition mechanical retention in which dentin bonding penetrating into nano inter fibrilar cavity then polymerized. The success of methacrylate resin adhesion restoration is decided by enamel porosity, wetting character of resin, wetting contact angle, good etching acid, optimal humidity of tooth surface, the accuracy of dentist during filling is done etc.

  1. The Intermetallic Catalysts for Oxidative Esterification of Methacrolein to Methyl Methacrylate

    Institute of Scientific and Technical Information of China (English)

    DONG Hai-feng; LI Zeng-xi; WANG Zheng-ping; ZHAO Wei; DIAO Yan-yan; ZHANG Suo-jiang

    2006-01-01

    A series of supported intermetallic Pb-Pb catalysts were prepared with the impregnation method by changing the support (silica, molecular sieve or γ-alumina) and the pore size. The chemical states of the two metals were characterized by XPS analysis, the process for producing methyl methacrylate based on the direct oxidative esterification of methacrolein with methanol in the presence of oxygen was performed in a slurry reactor with the above-mentioned catalysts. The influence of the calcination temperature and the kinds of support as well as the pore size on catalytic activity had been extensively investigated. Under the conditions of temperature at 80 ℃, catalyst 3.8% (ω) and the reaction time 2 h, the conversion rate of methacrolein reached 85%, the selectivity and the yield of methyl methacrylate were 90% and 76.5%, respectively.

  2. The Competing Effects of Hyaluronic and Methacrylic Acid in Model Contact Lenses.

    Science.gov (United States)

    Weeks, Andrea; Subbaraman, Lakshman N; Jones, Lyndon; Sheardown, Heather

    2012-01-01

    The aim of this study was to determine the influence of hyaluronic acid (HA) on lysozyme sorption in model contact lenses containing varying amounts of methacrylic acid (MAA). One model conventional hydrogel (poly(2-hydroxyethyl methacrylate) (pHEMA)) and two model silicone hydrogels (pHEMA, methacryloxypropyltris(trimethylsiloxy)silane (pHEMA TRIS) and N,N-dimethylacrylamide, TRIS (DMAA TRIS)) lens materials were prepared with and without MAA at two different concentrations (1.7 and 5%). HA, along with dendrimers, was loaded into these model contact lens materials and then cross-linked with 1-ethyl-3-(3-dimethylamino propyl)-carbodiimide (EDC). Equilibrium water content (EWC), advancing water contact angle and lysozyme sorption on these lens materials were investigated. In the HA-containing materials, the presence (P contact angles (P contact lens materials. Hydrogel materials that contain HA have tremendous potential as hydrophilic, protein-resistant contact lens materials.

  3. Synthesis and characterization of in situ prepared poly (methyl methacrylate) nanocomposites

    Indian Academy of Sciences (India)

    Shahzada Ahmad; Sharif Ahmad; S A Agnihotry

    2007-02-01

    Hybrid materials, which consist of organic–inorganic materials, are of profound interest owing to their unexpected synergistically derived properties. These hybrid materials replaced the pristine polymers due to their higher strength and stiffness in the recent years. In the present work, studies concerning the preparation of poly (methyl methacrylate) (PMMA), PMMA/SiO2, and PMMA/TiO2 nanocomposites are reported. These nanocomposite polymers were synthesized by means of free radical polymerization of methyl methacrylate using benzoyl peroxide as an initiator in a water medium. Further `sol–gel’ transformation based hydrolysis and condensation of Ti and Si alkoxides were used to prepare the inorganic phase during the polymerization process of MMA.

  4. Separation of heavy metals from water by functionalized glycidyl methacrylate poly (high internal phase emulsions).

    Science.gov (United States)

    Huš, Sebastjan; Kolar, Mitja; Krajnc, Peter

    2016-03-11

    Removal of silver, lead and cadmium ions from both model solutions and real contaminated water was achieved, in a flow through manner, by using highly porous functionalized poly(glycidyl methacrylate) materials, prepared by the polymerisation of high internal phase emulsions (polyHIPE), with significant sorption differences between metals allowing for selective removal. PolyHIPEs, initially prepared from glycidyl methacrylate as a functional monomer, were functionalized with pentaerythritol tetrakis(3-mercaptopropionate), 1,9-nonanedithiol and 2-aminobenzenethiol via the epoxy ring opening on the polymer supports and applied in a flow-through manner via encasements into dedicated disk holders. Capacity of 21.7mg Ag per gram of polymer was found for 1,9-nonanedithiol functionalized polymers, while the capacity was decreasing with the decreasing ionic radius of the metal; the dynamics of sorption also depended on metal ion size and furthermore on the thiol used for the polymer functionalization.

  5. High Molecular Weight Thermally Stable Poly (Sodium Methacrylate / Magnetites Nanocomposites Via Emulsion Polymerization

    Directory of Open Access Journals (Sweden)

    Rasha A. El-Ghazawya,

    2014-04-01

    Full Text Available Core/shell type magnetite nanocomposites (MN were synthesized using sodium methacrylate (NMA monomer. Functionalized and bare magnetite nanoparticles were prepared by conventional co-precipitation method giving particles with 3-10 nm in diameter. Microemulsion polymerization was used for constructing core/shell structure with magnetite nanoparticles as core and poly (sodium methacrylate as shell. Chemical structure and morphology of the synthesized PNMA/magnetite nanocomposites were investigated using FTIR and TEM, respectively. The synthesized nanocomposites show effective encapsulation of different treated magnetite nanoparticles in the polymer matrix and exhibited good thermal stability. Such magnetite nanocomposites with high molecular weight and thermal stability have potential application in enhanced oil recovery application.

  6. Double-bond-containing polyallene-based triblock copolymers via phenoxyallene and (meth)acrylate

    Science.gov (United States)

    Ding, Aishun; Lu, Guolin; Guo, Hao; Huang, Xiaoyu

    2017-03-01

    A series of ABA triblock copolymers, consisting of double-bond-containing poly(phenoxyallene) (PPOA), poly(methyl methacrylate) (PMMA), or poly(butyl acrylate) (PBA) segments, were synthesized by sequential free radical polymerization and atom transfer radical polymerization (ATRP). A new bifunctional initiator bearing azo and halogen-containing ATRP initiating groups was first prepared followed by initiating conventional free radical homopolymerization of phenoxyallene with cumulated double bond to give a PPOA-based macroinitiator with ATRP initiating groups at both ends. Next, PMMA-b-PPOA-b-PMMA and PBA-b-PPOA-b-PBA triblock copolymers were synthesized by ATRP of methyl methacrylate and n-butyl acrylate initiated by the PPOA-based macroinitiator through the site transformation strategy. These double-bond-containing triblock copolymers are stable under UV irradiation and free radical circumstances.

  7. STUDY ON CASTOR OIL POLYURETHANE/POLY (METHYL METHACRYLATE) AB CROSSLINKED POLYMERS

    Institute of Scientific and Technical Information of China (English)

    DU Ying; HAN Xiaozu; LIU Wenzhong

    1991-01-01

    Castor oil polyurethane/poly(methyl methacrylate) AB crosslinked polymers (ABCP) were synthesized by free radical copolymerization of MMA and vinyl-terminated castor oil polyurethane which was obtained from isocyanate-terminated castor oil polyurethane and hydroxyethyl methacrylate.The mechanical properties, transition and relaxation, as well as compatibility and morphology of the ABCP were investigated by changing the component. The results show that the ABCP is a semicompatible system and the compatibility of the two components decreases with increasing content of the hard segment. The mechanical and damping properties of the ABCP are obviously superior to that of their homopolymers. The damping value is mainly controlled by crosslink density of the ABCP but the Tg value by component.

  8. Experimental and theoretical investigation of the complexation of methacrylic acid and diisopropyl urea

    Science.gov (United States)

    Pogány, Peter; Razali, Mayamin; Szekely, Gyorgy

    2017-01-01

    The present paper explores the complexation ability of methacrylic acid which is one of the most abundant functional monomer for the preparation of molecularly imprinted polymers. Host-guest interactions and the mechanism of complex formation between methacrylic acid and potentially genotoxic 1,3-diisopropylurea were investigated in the pre-polymerization solution featuring both experimental (NMR, IR) and in silico density functional theory (DFT) tools. The continuous variation method revealed the presence of higher-order complexes and the appearance of self-association which were both taken into account during the determination of the association constants. The quantum chemical calculations - performed at B3LYP 6-311 ++G(d,p) level with basis set superposition error (BSSE) corrections - are in agreement with the experimental observations, reaffirming the association constants and justifying the validity of computational investigation of such systems. Furthermore, natural bond orbital analysis was carried out to appraise the binding properties of the complexes.

  9. Common blocks for ASQS(12

    Directory of Open Access Journals (Sweden)

    Lorenzo Milazzo

    1997-05-01

    Full Text Available An ASQS(v is a particular Steiner system featuring a set of v vertices and two separate families of blocks, B and G, whose elements have a respective cardinality of 4 and 6. It has the property that any three vertices of X belong either to a B-block or to a G-block. The parameter cb is the number of common blocks in two separate ASQSs, both defined on the same set of vertices X . In this paper it is shown that cb ≤ 29 for any pair of ASQSs(12.

  10. Methylation of acidic moieties in poly(methyl methacrylate-co-methacrylic acid) copolymers for end-group characterization by tandem mass spectrometry.

    Science.gov (United States)

    Giordanengo, Rémi; Viel, Stéphane; Hidalgo, Manuel; Allard-Breton, Béatrice; Thévand, André; Charles, Laurence

    2010-07-30

    The complete structural characterization of a copolymer composed of methacrylic acid (MAA) and methyl methacrylate (MMA) units was achieved using tandem mass spectrometry. In a first step, collision-induced dissociation (CID) of sodiated MAA-MMA co-oligomers allowed us to determine the co-monomeric composition, the random nature of the copolymer and the sum of the end-group masses. However, dissociation reactions of MAA-based molecules mainly involve the acidic pendant groups, precluding individual characterization of the end groups. Therefore, methylation of all the acrylic acid moieties was performed to transform the MAA-MMA copolymer into a PMMA homopolymer, for which CID mainly proceeds via backbone cleavages. Using trimethylsilyldiazomethane as a derivatization agent, this methylation reaction was shown to be complete without affecting the end groups. Using fragmentation rules established for PMMA polymers together with accurate mass measurements of the product ions and knowledge of reagents used for the studied copolymer synthesis, a structure could be proposed for both end groups and it was found to be consistent with signals obtained in nuclear magnetic resonance spectra.

  11. Preparation and characterization of pH-sensitive and antifouling poly(vinylidene fluoride) microfiltration membranes blended with poly(methyl methacrylate-2-hydroxyethyl methacrylate-acrylic acid).

    Science.gov (United States)

    Ju, Junping; Wang, Chao; Wang, Tingmei; Wang, Qihua

    2014-11-15

    Functional terpolymer of poly(methyl methacrylate-2-hydroxyethyl methacrylate-acrylic acid) (P(MMA-HEMA-AA)) was synthesized via a radical polymerization method. The terpolymer could be directly blended with poly(vinylidene fluoride) (PVDF) to prepare the microfiltration (MF) membranes via phase separate process. The synthesized polymers were characterized by Fourier transform infrared (FTIR), the nuclear magnetic resonance proton spectra ((1)H NMR). The membrane had the typical asymmetric structure and the hydrophilic side chains tended to aggregate on the membrane surface. The surface enrichment of amphiphilic copolymer and morphology of MF membranes were characterized by Fourier transform infrared attenuated total reflection spectroscopy (FTIR-ATR) and scanning electron microscopy (SEM). The contact angle (CA) and water uptake were also tested to assess the hydrophilicity and wetting characteristics of the polymer surface. The water filtration properties were measured. It was found the modified membranes showed excellent pH-sensitivity and pH-reversibility behavior. Furthermore, the hydrophilicity of the blended membranes increased, and the membranes showed good protein antifouling property.

  12. A Novel Method for Preparing Approximately Micron-sized Polymethyl Methacrylate Microspheres with Clear Surface

    Institute of Scientific and Technical Information of China (English)

    Di Qiang WANG; Bai Ling LIU; Jie HU; Xiao Qin LIN; Min ZHANG

    2004-01-01

    Polymethyl methacrylate (PMMA) microspheres with clear surface and diameter close to 1 μm were synthesized by newly soap-free emulsion polymerization. The results showed that the presence of ethanol and NaCl made the increase of diameter and distribution, while the presence of toluene could avoid the problem of the increase of distribution, resulting a harvest of PMMA microspheres with a diameter close to 1 μm.

  13. IN VITRO WEAR RESISTANCE OF THREE TYPES OF POLYMETHYL METHACRYLATE DENTURE TEETH

    OpenAIRE

    Katia Rodrigues Reis; Gerson Bonfante; Luiz Fernando Pegoraro; Paulo Cesar Rodrigues Conti; Pedro Cesar Garcia de Oliveira; Osvaldo Bazzan Kaizer

    2008-01-01

    The wear resistance of denture teeth is important to the longevity of removable prostheses of edentulous patients. The ability of denture teeth to maintain a stable occlusal relationship over time may be influenced by this property. The purpose of this in vitro study was to evaluate the wear resistance of polymethyl methacrylate (PMMA) denture teeth based on their chemical composition when opposed by a ceramic antagonist. The maxillary canines (n=10) of 3 PMMA denture teeth (Trubyte Biotone, ...

  14. AGING OF ADHESIVE INTERFACES TREATED WITH BENZALKONIUM CHLORIDE AND BENZALKONIUM METHACRYLATE

    OpenAIRE

    Sabatini, Camila; Pashley, David H.

    2015-01-01

    Inhibition of endogenous dentin matrix metalloproteinases (MMPs) within incompletely infiltrated hybrid layers can contribute to the preservation of resin-dentin bonds. This study evaluated the bond stability of interfaces treated with benzalkonium chloride (BAC) and benzalkonium methacrylate (MBAC), and its inhibitory properties in dentin MMP activity. Single-component adhesive ALL-BOND UNIVERSAL, modified with BAC or MBAC in concentrations of 0, 0.5, 1.0 and 2.0% was used for microtensile b...

  15. STEREOREGULARITY OF POLY (METHYL METHACRYLATE) OBTAINED WITH CHIRAL ANIONIC COMPLEX INITIATOR

    Institute of Scientific and Technical Information of China (English)

    CHEN Chuanfu; REN Changyu; XI Fu

    1995-01-01

    The stereoregular polymerization of methyl methacrylate (MMA) have been investigated with chiral anionic complex initiator[FlLi-(-)SP]in toluene,THF and toluene/THF [1/1(v/v)].The tacticities of PMMAs obtained in the three solvents have been found to be mainly a syndiotactic triads (s-PMMA)with content of 72.3,67.7 and 71.4% ,respectively.

  16. Electrical conduction mechanism of polyvinyl chloride (PVC)–polymethyl methacrylate (PMMA) blend film

    Indian Academy of Sciences (India)

    R S Gulalkari; Y G Bakale; D K Burghate; V S Deogaonkar

    2007-09-01

    The electrical conduction mechanism in polyvinyl chloride (PVC)–polymethyl methacrylate (PMMA) blend film has been studied at various temperatures in the range 313 K to 353 K. The results are presented in the form of – characteristics. Analysis has been made in the light of Poole–Frenkel, Fowler–Nordheim, Schottky, log() vs. plots and Arrhenius plots. It is observed that, Schottky–Richardson mechanism is primarily responsible for the observed conduction.

  17. Radiation-grafting of ethylene glycol dimethacrylate (EGDMA) and glycidyl methacrylate (GMA) onto silicone rubber

    Science.gov (United States)

    Flores-Rojas, G. G.; Bucio, E.

    2016-10-01

    Silicone rubber (SR) was modified with a graft of ethylene glycol dimethacrylate (EGDMA) and glycidyl methacrylate (GMA) using either gamma-radiation or azobisisobutyronitrile (AIBN). The graft efficiency was evaluated as a function of monomer concentration, absorbed dose, reaction temperature, and concentration of AIBN. The hydrophilicity of the grafted films was measured by contact angle and their equilibrium swelling time in ethanol. Additional characterization by infrared (FTIR-ATR) spectroscopy, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) is also reported.

  18. Durability of Poly(Methyl Methacrylate) Lenses Used in Concentrating Photovoltaic Technology (Revised) (Presentation)

    Energy Technology Data Exchange (ETDEWEB)

    Miller, D. C.; Carloni, J. D.; Pankow, J. W.; Gjersing, E. L.; To, B.; Packard, C. E.; Kennedy, C. E.; Kurtz, S. R.

    2012-01-01

    Concentrating photovoltaic (CPV) technology recently gained interest based on its expected low levelized cost of electricity, high efficiency, and scalability. Many CPV systems employ Fresnel lenses composed of poly(methyl methacrylate) (PMMA) to obtain a high optical flux density on the cell. The optical and mechanical durability of these lenses, however, is not well established relative to the desired surface life of 30 years. Our research aims to quantify the expected lifetime of PMMA in key market locations (FL, AZ, and CO).

  19. Effect of histological processing and methacrylate sectioning on the area of gill tissue in teleost

    Directory of Open Access Journals (Sweden)

    AL. Cruz

    Full Text Available Deformation of biological tissues may occur during histological processing and results in loss of accuracy when quantitative information about cells, tissues and organs is necessary. In this study, the gill tissue from armored catfish (Pterygoplichthys anisitsi was quantified in each step of processing using the stereological principles. During processing for glycol methacrylate embedding, gill tissue from shrinks significantly but regains its original dimensions after sectioning.

  20. Microleakage of silorane- and methacrylate-based class V composite restorations.

    Science.gov (United States)

    Krifka, Stephanie; Federlin, Marianne; Hiller, Karl-Anton; Schmalz, Gottfried

    2012-08-01

    The marginal integrity of class V restorations in a silorane- and a group of methacrylate-based composite resins with varying viscosities was tested in the present study. Different adhesives (OptiBond FL, KerrHawe; AdheSE One, Vivadent; or Silorane System Adhesive, 3M ESPE) were applied to 168 standardized class V cavities. The cavities (n = 12) were filled with a wide range of different viscous composite resins: Filtek Silorane, 3M ESPE; els and els flow, Saremco; Tetric EvoCeram and Tetric EvoFlow, Vivadent; Grandio, Voco; and Ultraseal XT Plus, Ultradent. Microleakage of the restoration was assessed by dye penetration (silver staining) on multiple sections with and without thermocycling and mechanical loading (TCML: 5,000 × 5-55°C; 30 s/cycle; 500,000 × 72.5 N, 1.6 Hz). Data were statistically analyzed with the Mann-Whitney U test and the Error Rates Method (ERM). The silorane-based composite resin yielded the lowest dye penetration after TCML. Microleakage of methacrylate-based composite restorations, in general (ERM), was statistically significantly influenced by the adhesive system, Moreover, dye penetration at enamel margins was significantly lower than dye penetration at dentin margins. The chemical basis of composite resins and adjacent tooth substance seems to strongly influence marginal sealing of class V restorations for methacrylate-based materials. Moreover, the steps of dental adhesives used affected marginal integrity. The silorane-based composite resin evaluated in the present study exhibits the best marginal seal. The three-step adhesive yielded better marginal sealing than the one-step adhesive for methacrylate-based class V composite restorations.

  1. Eikonalization of Conformal Blocks

    CERN Document Server

    Fitzpatrick, A Liam; Walters, Matthew T; Wang, Junpu

    2015-01-01

    Classical field configurations such as the Coulomb potential and Schwarzschild solution are built from the $t$-channel exchange of many light degrees of freedom. We study the CFT analog of this phenomenon, which we term the `eikonalization' of conformal blocks. We show that when an operator $T$ appears in the OPE $\\mathcal{O}(x) \\mathcal{O}(0)$, then the large spin $\\ell$ Fock space states $[TT \\cdots T]_{\\ell}$ also appear in this OPE with a computable coefficient. The sum over the exchange of these Fock space states in an $\\langle \\mathcal{O} \\mathcal{O} \\mathcal{O} \\mathcal{O} \\rangle$ correlator build the classical `$T$ field' in the dual AdS description. In some limits the sum of all Fock space exchanges can be represented as the exponential of a single $T$ exchange in the 4-pt correlator of $\\mathcal{O}$. Our results should be useful for systematizing $1/\\ell$ perturbation theory in general CFTs and simplifying the computation of large spin OPE coefficients. As examples we obtain the leading $\\log \\ell$...

  2. Adductor Canal Block versus Femoral Nerve Block and Quadriceps Strength

    DEFF Research Database (Denmark)

    Jæger, Pia Therese; Nielsen, Zbigniew Jerzy Koscielniak; Henningsen, Lene Marianne;

    2013-01-01

    : The authors hypothesized that the adductor canal block (ACB), a predominant sensory blockade, reduces quadriceps strength compared with placebo (primary endpoint, area under the curve, 0.5-6 h), but less than the femoral nerve block (FNB; secondary endpoint). Other secondary endpoints were...

  3. UV-cured methacrylic membranes as novel gel-polymer electrolyte for Li-ion batteries

    Science.gov (United States)

    Nair, J. R.; Gerbaldi, C.; Meligrana, G.; Bongiovanni, R.; Bodoardo, S.; Penazzi, N.; Reale, P.; Gentili, V.

    In this paper, we report the synthesis and characterisation of novel methacrylic based polymer electrolyte membranes for lithium batteries. The method adopted for preparing the solid polymer electrolyte was the UV-curing process, which is well known for being easy, low cost, fast and reliable. It consists of a free radical photo polymerisation of poly-functional monomers: Bisphenol A ethoxylate (15 EO/phenol) dimethacrylate (BEMA) was chosen, as it can readily form flexible 3D networks and has long poly-ethoxy chains which can enhance the movement of Li +-ions inside the polymer matrix. The preliminary results reported here refer to systems where LiPF 6 solutions swelled the preformed polymer membranes. The tests on the conductivity, stability and cyclability of the membranes put in evidence the importance of the polymerisation in presence of mono-methacrylates acting as reactive diluents. Good values of ionic conductivity have been found, especially at ambient temperature. Much better results can be expected by choosing an appropriate mono-methacrylate to modify the polymeric membrane properties and by modifying the methodology of Li +-ions incorporation inside the polymer matrix.

  4. Fabrication and Characterization of Magnetoresponsive Electrospun Nanocomposite Membranes Based on Methacrylic Random Copolymers and Magnetite Nanoparticles

    Directory of Open Access Journals (Sweden)

    Ioanna Savva

    2012-01-01

    Full Text Available Magnetoresponsive polymer-based fibrous nanocomposites belonging to the broad category of stimuli-responsive materials, is a relatively new class of “soft” composite materials, consisting of magnetic nanoparticles embedded within a polymeric fibrous matrix. The presence of an externally applied magnetic field influences the properties of these materials rendering them useful in numerous technological and biomedical applications including sensing, magnetic separation, catalysis and magnetic drug delivery. This study deals with the fabrication and characterization of magnetoresponsive nanocomposite fibrous membranes consisting of methacrylic random copolymers based on methyl methacrylate (MMA and 2-(acetoacetoxyethyl methacrylate (AEMA (MMA-co-AEMA and oleic acid-coated magnetite (OA·Fe3O4 nanoparticles. The AEMA moieties containing β-ketoester side-chain functionalities were introduced for the first time in this type of materials, because of their inherent ability to bind effectively onto inorganic surfaces providing an improved stabilization. For membrane fabrication the electrospinning technique was employed and a series of nanocomposite membranes was prepared in which the polymer content was kept constant and only the inorganic (OA·Fe3O4 content varied. Further to the characterization of these materials in regards to their morphology, composition and thermal properties, assessment of their magnetic characteristics disclosed tunable superparamagnetic behaviour at ambient temperature.

  5. Autonomous healing materials based on epoxidized natural rubber and ethylene methacrylic acid ionomers

    Science.gov (United States)

    Arifur Rahman, Md; Penco, Maurizio; Peroni, Isabella; Ramorino, Giorgio; Janszen, Gerardus; Di Landro, Luca

    2012-03-01

    The development of autonomous healing material has an enormous scientific and technological interest. In this context, this research work deals with the investigation of autonomous healing behavior of epoxidized natural rubber (ENR) and its blends with ethylene methacrylic acid ionomers. The autonomous healing behavior of ENR and its blends containing two different ionomers [poly(ethylene-co-methacrylic acid sodium salt) (EMNa) and poly(ethylene-co-methacrylic acid zinc salt) (EMZn)] has been studied by ballistic puncture tests. Interestingly, EMNa/ENR blends exhibit complete healing just after the ballistic test but EMZn/ENR blends do not show full self-repairing. The healing efficiency has been evaluated by optical microscopy and a depressurized air-flow test. The healing mechanism has been investigated by characterizing thermal and mechanical properties of the blends. The chemical structure studied by FTIR and thermal analysis show that the ion content of ionomers and functionality of ENR has a significant influence on the self-healing behavior.

  6. Study of sodium dodecyl sulfate-poly(propylene oxide) methacrylate mixed micelles.

    Science.gov (United States)

    Bastiat, Guillaume; Grassl, Bruno; Khoukh, Abdel; François, Jeanne

    2004-07-01

    Sodium dodecyl sulfate (SDS)-poly(propylene oxide) methacrylate (PPOMA) (of molecular weight M(w) = 434 g x mol(-1)) mixtures have been studied using conductimetry, static light scattering, fluorescence spectroscopy, and 1H NMR. It has been shown that SDS and PPOMA form mixed micelles, and SDS and PPOMA aggregation numbers, N(ag SDS) and N(ag PPOMA), have been determined. Total aggregation numbers of the micelles (N(ag SDS) + N(ag PPOMA)) and those of SDS decrease upon increasing the weight ratio R = PPOMA/SDS. Localization of PPOMA inside the mixed micelles is considered (i) using 1H NMR to localize the methacrylate function at the hydrophobic core-water interface and (ii) by studying the SDS-PPO micellar system (whose M(w) = 400 g x mol(-1)). Both methods have indicated that the PPO chain of the macromonomer is localized at the SDS micelle surface. Models based on the theorical prediction of the critical micellar concentration of mixed micelles and structural model of swollen micelles are used to confirm the particular structure proposed for the SDS-PPOMA system, i.e., the micelle hydrophobic core is primarily composed of the C12 chains of the sodium dodecyl sulfate, the hydrophobic core-water interface is made up of the SDS polar heads as well as methacrylate functions of the PPOMA, the PPO chains of the macromonomer are adsorbed preferentially on the surface, i.e., on the polar heads of the SDS.

  7. Effect of light on self-assembly of aqueous mixtures of sodium dodecyl sulfate and a cationic, bolaform surfactant containing azobenzene.

    Science.gov (United States)

    Hubbard, F Pierce; Abbott, Nicholas L

    2007-04-24

    We report light and small-angle neutron scattering measurements that characterize microstructures formed in aqueous surfactant solutions (up to 1.0 wt % surfactant) containing mixtures of sodium dodecyl sulfate (SDS) and the light-sensitive bolaform surfactant, bis(trimethylammoniumhexyloxy)azobenzene dibromide (BTHA) as a function of composition, equilibration time, and photostationary state (i.e., solutions rich in cis-BTHA or trans-BTHA). We observed formation of vesicles in both SDS-rich and trans-BTHA-rich regions of the microstructure diagram, with vesicles present over a particularly broad range of compositions for trans-BTHA-rich solutions. Illumination of mixtures of BTHA and SDS with a broadband UV light source leads to formation of photostationary states where the fraction of BTHA present as cis isomer (75-80% cis-BTHA) is largely independent of the mixing ratio of SDS and BTHA. For a relatively limited set of mixing ratios of SDS and BTHA, we observed UV illumination of SDS-rich vesicles to result in the reversible transformation of the vesicles to micellar aggregates and UV illumination of BTHA-rich vesicles to result in irreversible precipitation. Surprisingly, however, for many mixtures of trans-BTHA and SDS that formed solutions containing vesicles, illumination with UV light (which was confirmed to lead to photoisomerization of BTHA) resulted in only a small decrease in the number of vesicles in solution, relatively little change in the sizes of the remaining vesicles, and coexistance of the vesicles with micelles. These observations are consistent with a physical model in which the trans and cis isomers of BTHA present at the photostationary state tend to segregate between the different microstructures coexisting in solution (e.g., vesicles rich in trans-BTHA and SDS coexist with micelles rich in cis-BTHA and SDS). The results presented in this paper provide guidance for the design of light-tunable surfactants systems.

  8. QSPR models for prediction of the soil sorption coefficient (log KOC) values of 209 polychlorinated trans-azobenzenes (PCt-ABs).

    Science.gov (United States)

    Wilczyńska-Piliszek, Agata J; Piliszek, Sławomir; Falandysz, Jerzy

    2012-01-01

    The values of the soil sorption coefficient (K(OC)) have been computed for 209 environmentally relevant trans polychlorinated azobenzenes (PCABs) lacking experimental partitioning data. The quantitative structure-property relationship (QSPR) approach and artificial neural networks (ANN) predictive ability used in models based on geometry optimalization and quantum-chemical structural descriptors, which were computed on the level of density functional theory (DFT) using B3LYP functional and 6-311++G** basis set and of the semi-empirical quantum chemistry method for property parameterization (PM6) of the molecular orbital package (MOPAC). An experimentally available data on physical and chemical properties of PCDD/Fs and PCBs were used as reference data for the QSPR models and ANNs predictions in this study. Both calculation methods gave similar results in term of absolute log K(OC) values, while the PM6 model generated in the MOPAC was a much more efficient compared to the DFT model in GAUSSIAN. The estimated values of log K(OC) varied between 4.93 and 5.62 for mono-, 5.27 and 7.46 for di-, 6.46 and 8.09 for tri-, 6.65 and 9.11 for tetra-, 6.75 and 9.68 for penta-, 6.44 and 10.24 for hexa-, 7.00 and 10.36 for hepta-, 7.09 and 9.82 octa-, 8.94 and 9.71 for nona-Ct-ABs, and 9.26 and 9.34 for deca-Ct-AB. Because of high log K(OC) values PCt-ABs could be classified as compounds with high affinity to the particles of soil, sediments and organic matter.

  9. Poly(amic acid)s and their poly(amide imide) counterparts containing azobenzene moieties: Characterization, imidization kinetics and photochromic properties

    Energy Technology Data Exchange (ETDEWEB)

    Konieczkowska, Jolanta [Centre of Polymer and Carbon Materials, Polish Academy of Sciences, 34 M. Curie-Sklodowska Str., 41-819 Zabrze (Poland); Institute of Chemistry, University of Silesia, 9 Szkolna Str., 40-006 Katowice (Poland); Janeczek, Henryk [Centre of Polymer and Carbon Materials, Polish Academy of Sciences, 34 M. Curie-Sklodowska Str., 41-819 Zabrze (Poland); Kozanecka-Szmigiel, Anna, E-mail: annak@if.pw.edu.pl [Faculty of Physics, Warsaw University of Technology, 75 Koszykowa Str., 00-662 Warszawa (Poland); Schab-Balcerzak, Ewa, E-mail: eschab-balcerzak@cmpw-pan.edu.pl [Centre of Polymer and Carbon Materials, Polish Academy of Sciences, 34 M. Curie-Sklodowska Str., 41-819 Zabrze (Poland)

    2016-09-01

    We report on a series of novel photochromic poly(amide imide)s and their poly(amic acid) precursors bearing azobenzene chromophores as the side groups. The chemical structures of the polymers were designed so that they exhibited an enhanced thermal stability combined with a large and stable birefringence photogenerated by light of the wavelengths belonging to a wide spectral range. The polymers possessed rigidly attached azochromophores in the content of either one or two per a repeating unit, which in the latter case differed in their structures. The imidization kinetics of the poly(amic acid)s was investigated by differential scanning calorimetry and the kinetic parameters were estimated using Ozawa and Kissinger methods. Measurements of the selected physical properties of the polymers, such as solubility, supramolecular structure, linear absorption, thermal stability, glass transition and photochromic response were performed and used for determination of the structure-property relations. The measurements of photochromic properties showed a very efficient generation of optical anisotropy upon blue and violet irradiation, for both the poly(amide imide)s containing two different chromophores in the repeating unit and for their precursors. For these poly(amide imide)s and for their precursors an exceptionally slow decrease in the photoinduced optical anisotropy in the dark was also observed. - Highlights: • Three azopoly(amide imide)s were obtained from azopoly(amic acid)s. • Chosen physicochemical properties and photochromic responses were measured. • Desired optical response was found for polymers with two azo-dyes in repeating unit. • Structure-property relations were shown.

  10. Block Transfer Agreement Evaluation Project

    Science.gov (United States)

    Bastedo, Helena

    2010-01-01

    The objective of this project is to evaluate for the British Columbia Council on Admissions and Transfer (BCCAT) the effectiveness of block transfer agreements (BTAs) in the BC Transfer System and recommend steps to be taken to improve their effectiveness. Findings of this study revealed that institutions want to expand block credit transfer;…

  11. Four-block beam collimator

    CERN Multimedia

    1977-01-01

    The photo shows a four-block collimator installed on a control table for positioning the alignment reference marks. Designed for use with the secondary beams, the collimators operated in vacuum conditions. The blocks were made of steel and had a standard length of 1 m. The maximum aperture had a square coss-section of 144 cm2. (See Annual Report 1976.)

  12. OPAL Various Lead Glass Blocks

    CERN Multimedia

    These lead glass blocks were part of a CERN detector called OPAL (one of the four experiments at the LEP particle detector). OPAL uses some 12 000 blocks of glass like this to measure particle energies in the electromagnetic calorimeter. This detector measured the energy deposited when electrons and photons were slowed down and stopped.

  13. Block storage subsystem performance analysis

    CERN Document Server

    CERN. Geneva

    2016-01-01

    You feel that your service is slow because of the storage subsystem? But there are too many abstraction layers between your software and the raw block device for you to debug all this pile... Let's dive on the platters and check out how the block storage sees your I/Os! We can even figure out what those patterns are meaning.

  14. Synthesis of chemically cross-linked polyvinyl alcohol-co-poly (methacrylic acid) hydrogels by copolymerization; a potential graft-polymeric carrier for oral delivery of 5-fluorouracil

    OpenAIRE

    Muhammad Usman Minhas; Mahmood Ahmad; Liaqat Ali; Muhammad Sohail

    2013-01-01

    Background of the Study The propose of the present work was to develop chemically cross-linked polyvinyl alcohol-co-poly(methacrylic acid) hydrogel (PVA-MAA hydrogel) for pH responsive delivery of 5-Fluorouracil (5-FU). Methods PVA based hydrogels were prepared by free radical copolymerization. PVA has been cross-linked chemically with monomer (methacrylic acid) in aqueous medium, cross-linking agent was ethylene glycol di-methacrylate (EGDMA) and benzoyl peroxide was added as reaction initia...

  15. Removal of Co(II), Cu(II) and Pb(II) ions by polymer based 2-hydroxyethyl methacrylate: thermodynamics and desorption studies

    OpenAIRE

    Omid Moradi; Behrooz Mirza; Mehdi Norouzi; Ali Fakhri

    2012-01-01

    Abstract Removal thermodynamics and desorption studies of some heavy metal ions such as Co(II), Cu(II) and Pb(II) by polymeric surfaces such as poly 2-hydroxyethyl methacrylate (PHEMA) and copolymer 2-hydroxyethyl methacrylate with monomer methyl methacrylate P(MMA-HEMA) as adsorbent surfaces from aqueous single solution were investigated with respect to the changes in pH of solution, adsorbent composition, contact time and temperature in the individual aqueous solution. The linear correlatio...

  16. Composition and solution properties of fluorinated block copolymers and their surface structures in the solid state

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    A series of diblock copolymers composed of methyl methacrylate and 2-perfluorooctylethyl methacry-late(PMMA144-b-PFMAn) with various PFMA block lengths were prepared by atom transfer radical po-lymerization(ATRP).The surface structures and properties of these polymers in the solid state and in solution were investigated using contact angle measurement,X-ray photoelectron spectroscopy(XPS),sum frequency generation(SFG) vibrational spectroscopy,surface tension and dynamic laser light scattering(DLS).It was found that with increasing PFMA block length,water and oil repellency de-creased,the ratio of F/C increased with increasing film depth,and the degree of ordered packing of the perfluoroalkyl side chains at the surface decreased.When the number of PFMA block units reached 10,PMMA segments were detected at the copolymer surface,which was attributed to the PFMA block length affecting molecular aggregation structure of the copolymer in the solution and the interfacial structure at the air/liquid interface,which in turn affects surface structure formation during solution solidification.The results suggest that copolymer solution properties play an important role in struc-ture formation on the solid surface.

  17. Conformal Nets II: Conformal Blocks

    Science.gov (United States)

    Bartels, Arthur; Douglas, Christopher L.; Henriques, André

    2017-03-01

    Conformal nets provide a mathematical formalism for conformal field theory. Associated to a conformal net with finite index, we give a construction of the `bundle of conformal blocks', a representation of the mapping class groupoid of closed topological surfaces into the category of finite-dimensional projective Hilbert spaces. We also construct infinite-dimensional spaces of conformal blocks for topological surfaces with smooth boundary. We prove that the conformal blocks satisfy a factorization formula for gluing surfaces along circles, and an analogous formula for gluing surfaces along intervals. We use this interval factorization property to give a new proof of the modularity of the category of representations of a conformal net.

  18. Plasticizer-free microspheres for ionophore-based sensing and extraction based on a methyl methacrylate-decyl methacrylate copolymer matrix

    Energy Technology Data Exchange (ETDEWEB)

    Peper, Shane; Ceresa, Alan; Qin Yu; Bakker, Eric

    2003-12-19

    Plasticizer-free methyl methacrylate-decyl methacrylate (MMA-DMA) microspheres were prepared under mild, non-reactive conditions using a high-throughput particle generator. The particles were perfectly smooth and monodisperse, with a particle diameter of approximately 10.0 {mu}m. In order to evaluate the suitability of the polymer as a matrix for bulk extraction processes, lipophilic sensing components were incorporated into the particles. Particles contained either a H{sup +}-selective chromoionophore (ETH 5294) only (type 1), or a K{sup +}-selective ionophore (BME-44), anionic sites (NaTFPB), and ETH 5294 (type 2). Type 1 particles responded according to an anion-proton coextraction mechanism and demonstrated Hofmeister selectivity by showing a preference for more lipophilic sample anions (ClO{sub 4}{sup -}>NO{sub 3}{sup -}>Cl{sup -}). Particles of type 2 functioned by way of an ion-exchange equilibrium and demonstrated a functional response for K{sup +}, with a dynamic range from 10{sup -1}-10{sup -4} M K{sup +}. These particles also exhibited selectivity comparable to that previously reported for analogous particles made from bis(2-ethylhexyl sebacate) (DOS)-plasticized poly(vinyl chloride) (PVC) and DMA-DOS. In addition, the behavior of both types1 and 2 particles was in agreement with analogous thin film optical sensors (optodes) prepared from MMA-DMA. With the advent of ionophore-based plasticizer-free microspheres a wide variety of ions may potentially be assessed using various popular bead-based sensing strategies, such as lab-on-a-chip technologies, bundled optical fiber arrays, and flow cytometry, without experiencing the deleterious effects resultant of plasticizer leaching.

  19. Amphiphilic star block copolymers as gene carrier Part I: Synthesis via ATRP using calix[4]resorcinarene-based initiators and characterization

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Anna; Xue, Yan; Wei, Dafu [Shanghai Key Laboratory of Advanced Polymeric Materials, Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); Guan, Yong, E-mail: yguan@ecust.edu.cn [Shanghai Key Laboratory of Advanced Polymeric Materials, Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); Xiao, Huining [Department of Chemical Engineering, University of New Brunswick, Fredericton, New Brunswick, Canada E3B 5A3 (Canada)

    2013-01-01

    In this work, a cationic star polymer [poly(2-dimethylamino)ethyl methacrylate (PDMAEMA)] was prepared via atom transfer radical polymerization (ATRP), using brominated calix[4]resorcinarene as an initiator. Hydrophobic moieties, methyl methacrylate (MMA) and butyl acrylate (BA), were further incorporated via 'one-pot' method. Well-defined eight-armed star block copolymers bearing hydrophilic blocks inside and hydrophobic blocks outside were synthesized. The molecular weight, particle size, electrophoretic mobility and apparent charge density were determined by gel permeation chromatography (GPC), dynamic light scattering (DLS), phase analysis light scattering (PALS) and colloidal titration, respectively. The zeta potentials and apparent charge densities of the products exhibited the characteristics of polyelectrolyte. The incorporation of hydrophobic moieties generated electrostatic screening effect. The as-synthesized amphiphilic star copolymer is promising as a thermo-sensitive gene carrier for gene therapy. Highlights: Black-Right-Pointing-Pointer Amphiphilic cationic star block copolymers with well-controlled structures were prepared via ATRP. Black-Right-Pointing-Pointer The molecular structures and properties of the initiator and copolymers were systematically characterized. Black-Right-Pointing-Pointer The products exhibited the positive charged character, and hydrophobic moieties generated electrostatic screening effect.

  20. Antimicrobial films obtained from latex particles functionalized with quaternized block copolymers.

    Science.gov (United States)

    Alvarez-Paino, Marta; Juan-Rodríguez, Rafael; Cuervo-Rodríguez, Rocío; Tejero, Rubén; López, Daniel; López-Fabal, Fátima; Gómez-Garcés, José L; Muñoz-Bonilla, Alexandra; Fernández-García, Marta

    2016-04-01

    New amphiphilic block copolymers with antimicrobial properties were obtained by atom transfer radical polymerization (ATRP) and copper catalyzed cycloaddition following two approaches, a simultaneous strategy or a two-step synthesis, which were proven to be very effective methods. These copolymers were subsequently quaternized using two alkyl chains, methyl and butyl, to amplify their antimicrobial properties and to investigate the effect of alkyl length. Antimicrobial experiments in solution were performed with three types of bacteria, two gram-positive and one gram-negative, and a fungus. Those copolymers quaternized with methyl iodide showed better selectivities on gram-positive bacteria, Staphylococcus aureus and Staphylococcus epidermidis, against red blood cells, demonstrating the importance of the quaternizing agent chosen. Once the solution studies were performed, we prepared poly(butyl methacrylate) latex particles functionalized with the antimicrobial copolymers by emulsion polymerization of butyl methacrylate using such copolymers as surfactants. The characterization by various techniques served to test their effectiveness as surfactants. Finally, films were prepared from these emulsions, and their antimicrobial activity was studied against the gram-positive bacteria. The results indicate that the antimicrobial efficiency of the films depends not only on the copolymer activity but also on other factors such as the surface segregation of the antimicrobial agent to the interface.

  1. Sol-gel titanium dioxide blocking layers for dye-sensitized solar cells: electrochemical characterization.

    Science.gov (United States)

    Kavan, Ladislav; Zukalova, Marketa; Vik, Ondrej; Havlicek, David

    2014-04-14

    Compact, thin TiO2 films are grown on F-doped SnO2 (FTO) by dip-coating from precursor solutions containing poly(hexafluorobutyl methacrylate) or hexafluorobutyl methacrylate as the structure-directing agents. The films are quasi-amorphous, but crystallize to TiO2 (anatase) upon heat treatment at 500 °C in air. Cyclic voltammetry experiments performed using Fe(CN)6(3-/4-) or spiro-OMeTAD as model redox probes selectively indicate the pinholes, if any, in the layer. The pinhole-free films on FTO represent an excellent rectifying interface at which no anodic faradaic reactions occur in the depletion state. The flat-band potentials of the as-grown films are upshifted by 0.2-0.4 V against the values predicted for a perfect anatase single-crystal surface, but they still follow the Nernstian pH dependence. The optimized buffer layer is characterized by a combination of quasi-amorphous morphology (which is responsible for the blocking function) and calcination-induced crystallinity (which leads to fast electron injection and electron transport in the conduction band). The latter manifests itself by a reversible charging of the chemical capacitance of TiO2 in its accumulation state. The capacitive-charging capability and pinhole formation significantly depend on the post-deposition heat treatment.

  2. MarineMineralsProgramBlocks

    Data.gov (United States)

    Bureau of Ocean Energy Management, Department of the Interior — This data set contains OCS block outlines and delineated polygons in ESRI ArcGIS shape file format for the BOEM Gulf of Mexico Region that contain sediment resources...

  3. Hawaii Census 2000 Block Groups

    Data.gov (United States)

    U.S. Environmental Protection Agency — This data layer represents Census 2000 demographic data derived from the PL94-171 redistricting files and SF3. Census geographic entities include blocks, blockgroups...

  4. Left bundle-branch block

    DEFF Research Database (Denmark)

    Risum, Niels; Strauss, David; Sogaard, Peter;

    2013-01-01

    The relationship between myocardial electrical activation by electrocardiogram (ECG) and mechanical contraction by echocardiography in left bundle-branch block (LBBB) has never been clearly demonstrated. New strict criteria for LBBB based on a fundamental understanding of physiology have recently...

  5. Multi-block and path modelling procedures

    DEFF Research Database (Denmark)

    Høskuldsson, Agnar

    2008-01-01

    The author has developed a unified theory of path and multi-block modelling of data. The data blocks are arranged in a directional path. Each data block can lead to one or more data blocks. It is assumed that there is given a collection of input data blocks. Each of them is supposed to describe one...

  6. 基于偶氮苯的超分子凝胶材料的研究进展%Progress in supramolecular gels based on azobenzene

    Institute of Scientific and Technical Information of China (English)

    杨润苗; 董观秀; 赵德建; 杨雁玲; 刘玉海

    2015-01-01

    Stimulus-responsive gels based on azobenzene,which can dynamically respond to external stimuli,have attracted considerable attention,since it can provide a broad range of tunable parameters, wavelength,intensity,and duration. The progress in supramolecular gels,which were classified into supramolecular organogel,supramolecular hydrogels,organi-inorganic hybrid supramolecular gel system,was reviewed in recent three years. The review focuses on the molecular size and shape of gelator,analyzes the role of supramolecular self-assembly driving force and the structural form by self-assembly. Finally,the application of gel systems in the field of optical switch,drug release and biological material was prospected.%基于偶氮苯的光响应型凝胶对光刺激可以保证连续性和精确性感知,并在刺激过程中有显著的响应行为性,是目前研究最多的光响应材料之一。本文将含偶氮苯的凝胶体系分成超分子有机凝胶、超分子水凝胶、超分子凝胶体系和有机无机杂化型体系,较系统地综述了近三年来基于偶氮苯的光响应型超分子凝胶的结构特点和研究进展。重点阐述了凝胶因子的分子大小和形态,涵盖了小分子、树枝状大分子、嵌段共聚物、超支化分子等;分析了发挥自组装驱动力的超分子之间的作用,涵盖了氢键、静电相互作用、π-π作用、疏水效应等;总结了自组装聚集形态的构造,涵盖了胶束、囊泡、纤维束、纳米棒等;最后展望了各类凝胶体系在光控开关、药物释放、生物材料等领域的应用前景。

  7. Influence of strain rate on fracture behavior of poly(methyl methacrylate)

    Institute of Scientific and Technical Information of China (English)

    赵荣国; 陈朝中

    2008-01-01

    The effect of strain rate on fracture behavior of poly(methyl methacrylate) was investigated.The uniaxial tensile rupture tests for the poly(methyl methacrylate) samples were carried out at different strain rates at ambient temperature.It is found that the elastic modulus of the material increases with increasing strain rate,while the elongation is reversal with strain rate.Simultaneously,there exists a critical strain rate within which the stress-strain curves overlap one another,and beyond which the curves depart from each other.The amount of energy added to the system due to work done by the imposed load was calculated,and the strain energy stored in the material at each strain rate was calculated by the current stress integral with respect to strain.The complementary strain energy,which is the difference between the work and the strain energy,was obtained and was considered to supply the surface energy to create a new crack surface in the polymeric material.It is found that the work done by the imposed load,which is needed for the fracture of poly(methyl methacrylate) sample,decreases with increasing strain rate,and the strain energy decreases with strain rate as well,which demonstrates that the polymeric material at high strain rate is easier to fracture than that at low strain rate.As the strain rate increases,the fracture mode changes from ductile,semi-ductile to brittle mode.The complementary strain energy almost sustains a constant at any strain rate.The density of surface energy,which characterizes the energy per unit area needed for creating crack surface,is a strain rate-independent material constant.

  8. Addition of silver nanoparticles reduces the wettability of methacrylate and silorane-based composites

    Directory of Open Access Journals (Sweden)

    Shahin Kasraei

    2012-12-01

    Full Text Available Incorporation of silver nanoparticles into composite resins is recommended for their reported antibacterial properties, but this incorporation can affect the wettability of such materials. Therefore, this study evaluated the effect of nano-silver addition to silorane-based and methacrylate-based composites on their contact angle. Nano-silver particles were added to Z250 (methacrylate-based and P90 (silorane-based composites at 0.5% and 1% by weight. The control group had no additions. SEM-EDX analysis was performed to confirm the homogeneity of the nano-silver distribution. Seventy-two composite discs were prepared and standardized to the identical surface roughness values, and then distributed randomly into 6 groups containing 12 samples each (N = 12. Two random samples from each group were observed by atomic force microscopy. Distilled water contact angle measurements were performed for the wettability measurement. Two-way ANOVA, followed by the Tukey-HSD test, with a significance level of 5%, were used for data analysis. It was observed that wettability was significantly different between the composites (p = 0.0001, and that the addition of nano-silver caused a significant reduction in the contact angle (p = 0.0001. Wettability varied depending on the concentration of the nano silver (p = 0.008. Silorane-based composites have a higher contact angle than methacrylate-based composites. Within the limitations of this study, it can be concluded that the addition of 0.5% nano-silver particles to the composites caused a decrease in the contact angle of water.

  9. Utilization of Methacrylates and Polymer Matrices for the Synthesis of Ion Specific Resins

    Energy Technology Data Exchange (ETDEWEB)

    Czerwinski, Kenneth [Univ. of Nevada, Las Vegas, NV (United States)

    2013-10-29

    Disposal, storage, and/or transmutation of actinides such as americium (Am) will require the development of specific separation schemes. Existing efforts focus on solvent extraction systems for achieving suitable separation of actinide from lanthanides. However, previous work has shown the feasibility of ion-imprinting polymer-based resins for use in ion-exchange-type separations with metal ion recognition. Phenolic-based resins have been shown to function well for Am-Eu separations, but these resins exhibited slow kinetics and difficulties in the imprinting process. This project addresses the need for new and innovative methods for the selective separation of actinides through novel ion-imprinted resins. The project team will explore incorporation of metals into extended frameworks, including the possibility of 3D polymerized matrices that can serve as a solid-state template for specific resin preparation. For example, an anhydrous trivalent f-element chain can be formed directly from a metal carbonate, and methacrylic acid from water. From these simple coordination complexes, molecules of discrete size or shape can be formed via the utilization of coordinating ligands or by use of an anionic multi-ligand system incorporating methacrylate. Additionally, alkyl methyl methacrylates have been used successfully to create template nanospaces, which underscores their potential utility as 3D polymerized matrices. This evidence provides a unique route for the preparation of a specific metal ion template for the basis of ion-exchange separations. Such separations may prove to be excellent discriminators of metal ions, even between f-elements. Resins were prepared and evaluated for sorption behavior, column properties, and proton exchange capacity.

  10. Determination of thermodynamic properties of poly(cyclohexyl methacrylate)by inverse gas chromatography

    Institute of Scientific and Technical Information of China (English)

    Ismet KAYA; Cigdem Yigit PALA

    2014-01-01

    In this work,some thermodynamic properties of poly( cyclohexyl methacrylate)were studied by inverse gas chromatography( IGC). For this purpose,the polymeric substance was coated on Chromosorb W and which was filled into a glass column. The retention times(tr)of the probes were determined from the interactions of poly(cyclohexyl methacrylate)with n-pentane,n-hexane,n-heptane,n-octane,n-decane, methanol,ethanol,2-propanol,butanol,acetone,ethyl methyl ketone,benzene,toluene and o-xylene by IGC technique. Then,the specific volume(V0g)was determined for each probe molecule. By using(1/T;lnV0g) graphics,the glass transition temperature of poly( cyclohexyl methacrylate)was found to be 373 K. The adsorp-tion heat under the glass transition temperature(ΔH a ),and partial molar heat of sorption above the glass tran-sition(ΔHS1 ),partial molar free energy of sorption(ΔGS1 )and partial molar entropy of sorption(ΔSS1 )belong-ing to sorption for every probe were calculated. The partial molar heat of mixing at infinite dilution(ΔH∞1 ), partial molar free energy of mixing at infinite dilution(ΔG∞1 ),Flory-Huggins interaction parameter(χ∞12 )and weight fraction activity coefficient(a1/w1)∞ values of polymer-solute systems were calculated at different col-umn temperatures. The solubility parameters(δ2 )of the polymer were obtained by IGC technique.

  11. 通过阴离子型和阳离子型活性链的偶合反应合成甲基丙烯酸甲酯-四氢呋喃嵌段共聚物%Synthesis of Poly (methyl methacrylate)-biock-polytetrahydrofuran by Coupling of Cationic and Anionic Living Chains

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The diblock copolymer poly (methyl methacrylate)-block-polytetrahydrofuran (PMMA-bPTHF) was successfully synthesized by means of the coupling reaction of living cationic PTHF+,SbF-6 and living anionic PMMA-,Li+.Lithium chloride,which is frequently used as a ligand in the polymerization of (meth)acrylates,obstructs the coupling reaction between the anionic and the cationic precursors due to the combination of the chlorine anion with the PTHF cation.Thus,the anionic polymerization should be carried out in the absence of LiCl.

  12. Radiation synthesis of acrylamide/N,N-(dimethylamino) ethyl methacrylate grafted onto low density polyethylene films

    Science.gov (United States)

    Abdel Ghaffar, A. M.

    2011-02-01

    Radiation-induced graft copolymerization of acrylamide/N,N-(dimethylamino) ethyl methacrylate (AAm/DMAEMA) onto low density polyethylene films was carried out. The effect of grafting conditions such as solvent type and comonomer composition were studied. Characterization of the prepared films was investigated by Fourier transform infrared. Some selected properties such as thermal stability and swelling behavior were determined. It was found that grafting efficiency, swelling behavior and thermal stability increased with increasing DMAEMA content. Scanning electron microscopy was used for predicting the change in surface morphology via the grafted films. The improvement in properties of the prepared films make it possible to use them in some practical applications.

  13. Bacterial Adhesion and Surface Roughness for Different Clinical Techniques for Acrylic Polymethyl Methacrylate

    OpenAIRE

    2016-01-01

    This study sought to assess the effect of different surface finishing and polishing protocols on the surface roughness and bacterial adhesion (S. sanguinis) to polymethyl methacrylates (PMMA). Fifty specimens were divided into 5 groups (n = 10) according to their fabrication method and surface finishing protocol: LP (3 : 1 ratio and laboratory polishing), NF (Nealon technique and finishing), NP (Nealon technique and manual polishing), MF (3 : 1 ratio and manual finishing), and MP (3 : 1 ratio...

  14. Thermal response of polystyrene/poly methyl methacrylate (PS/PMMA) polymeric blends

    Science.gov (United States)

    Mathur, Vishal; Sharma, Kananbala

    2016-12-01

    The present paper reports the investigationsto evaluate thermal behavior of polystyrene/poly methyl methacrylate (PS/PMMA) polymeric blends, prepared at different compositions through solution casting method. The glass transition temperatures have been obtained using dynamic mechanical analyzer. Simultaneous measurements of temperature dependentthermal transport properties (thermal conductivity and thermal diffusivity) have been made using Hot Disk Thermal Constants Analyzer based on transient plane source. The study reveals that blending of PS with PMMA leads to different phase morphologies corresponding to different composition range which further affects the thermal performance of respective blends.

  15. Thick methacrylate sections devoid of lost caps simplify stereological quantifications based on the optical fractionator design

    DEFF Research Database (Denmark)

    Andersen, Stine Hasselholt; Lykkesfeldt, Jens; Larsen, Jytte Overgaard

    2015-01-01

    Abstract In neuroscience, the optical fractionator technique is frequently used for unbiased cell number estimations. Although unbiased in theory, the practical application of the technique is often biased by the necessity of introducing a guard zone at one side of the disector to counter lost caps...... methacrylate) sections were inspected for lost caps to evaluate the possibility of whole section thickness counting with the optical fractionator technique and hippocampal granular cell nucleoli density differences along the z-axis were assessed with a z-axis analysis. No lost caps were found in the examined...

  16. Femtosecond laser fabrication of tubular waveguides in poly(methyl methacrylate).

    Science.gov (United States)

    Zoubir, Arnaud; Lopez, Cedric; Richardson, Martin; Richardson, Kathleen

    2004-08-15

    Femtosecond laser direct writing is employed for the fabrication of buried tubular waveguides in bulk poly(methyl methacrylate). A novel technique using selective chemical etching is presented to resolve the two-dimensional refractive-index profile of the fabrication structures. End-to-end coupling in the waveguides reveals a near-field intensity distribution that results from the superimposition of several propagating modes with different azimuthal symmetries. Mode analysis of the tubular waveguides is performed using the finite-difference method, and the possible propagating mode profiles are compared with the experimental data.

  17. Far infrared-assisted encapsulation of filter paper strips in poly(methyl methacrylate) for proteolysis.

    Science.gov (United States)

    Chen, Qiwen; Bao, Huimin; Zhang, Luyan; Chen, Gang

    2016-02-01

    Filter paper strips were enclosed between two poly(methyl methacrylate) plates to fabricate paper-packed channel microchips under pressure in the presence of far infrared irradiation. After the enclosed paper strip was oxidized by periodate, trypsin was covalently immobilized in them to fabricate microfluidic proteolysis bioreactor. The feasibility and performance of the unique bioreactor were demonstrated by digesting BSA and lysozyme. The results were comparable to those of conventional in-solution proteolysis while the digestion time was significantly reduced to ∼18 s. The suitability of the microfluidic paper-based bioreactors to complex proteins was demonstrated by digesting human serum.

  18. Kinetics and mechanism of polymerization of methyl methacrylate initiated by stibonium ylide

    Indian Academy of Sciences (India)

    A K Srivastava; Ajey Kumar Chaurasia

    2004-01-01

    Homopolymerization of methyl methacrylate (MMA) was carried out in the presence of triphenylstibonium 1,2,3,4-tetraphenyl-cyclopentadienylide as an initiator in dioxane at 65°C ± 0·1°C. The system follows non-ideal radical kinetics ( ∝ [M]1.4 [I]0.44) due to primary radical termination as well as degradative chain-transfer reaction. The overall activation energy and average value of $k_{p}^{2}/k_{t}$ were 64 kJ mol-1 and 0.173 × 10-3 l mol-1 s-1 respectively.

  19. Low-weight Impact Behaviour of Carbon Fibre Reinforced Methyl Methacrylate Nanocomposites

    Directory of Open Access Journals (Sweden)

    Virginija Jankauskaitė

    2015-06-01

    Full Text Available Inthis study, the carbon fibre reinforced methyl methacrylate (CF/MMA compositetoecap for safety shoes was manufactured to increase the energy absorptioncapacity during impact. Different types of nanofillers such as organic andinorganic nanotubes, unmodified and organically modified nanoclays were appliedto modify matrix impact properties. The drop-weight impact tests of thenanocomposite toecap were performed with respect to nanofiller nature andcarbon fibre stacking sequence. It was found that the most influence on thestiffness and impact damage of the carbon fibre methyl methacrylatenanocomposite toecaps besides stacking sequence show organic and inorganic nanotubesor unmodified nanoclay.DOI: http://dx.doi.org/10.5755/j01.ms.21.2.7075

  20. Thermal response of polystyrene/poly methyl methacrylate (PS/PMMA) polymeric blends

    Science.gov (United States)

    Mathur, Vishal; Sharma, Kananbala

    2016-02-01

    The present paper reports the investigationsto evaluate thermal behavior of polystyrene/poly methyl methacrylate (PS/PMMA) polymeric blends, prepared at different compositions through solution casting method. The glass transition temperatures have been obtained using dynamic mechanical analyzer. Simultaneous measurements of temperature dependentthermal transport properties (thermal conductivity and thermal diffusivity) have been made using Hot Disk Thermal Constants Analyzer based on transient plane source. The study reveals that blending of PS with PMMA leads to different phase morphologies corresponding to different composition range which further affects the thermal performance of respective blends.