The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
S. V. Bereza - One of the best experts on this subject based on the ideXlab platform.
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Properties of vinylpyrrolidone‐methyl methacrylate Statistical Copolymer in mixed solvents
Journal of Polymer Science Part C: Polymer Symposia, 2007Co-Authors: Z. H. Bakauova, E. A. Bekturov, S. V. BerezaAbstract:Intrinsic viscosities of fractions of the Statistical Copolymer of vinylpyrrolidone and methyl methacrylate (composition 42:58 mole percent) have been measured in the cross-selective solvents, benzene and methanol, in mixtures of these solvents, as well as in chloroform, a solvent for both polymer components, and in mixtures of chloroform with methanol. The dependence of the intrinsic viscosity on the composition of the mixed solvent exhibits a maximum reflecting the destruction of secondary structures that exist in the selective solvents. The temperature dependence of the intrinsic viscosity, which has a maximum around 50-60°C, has been studied in chlorobenzene between 10° and 100°C. The Mark-Houwink-Kuhn constants K and a, which do not change significantly with solvent composition, have been calculated. The values of the parameters Kθ and σ, which depend on solvent composition similarly to the intrinsic viscosity, have also been determined. The results indicate marked changes of macromolecular conformation from the hypercoiled structure in a selective solvent to the random coil in mixed and nonselective solvents.
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properties of vinylpyrrolidone methyl methacrylate Statistical Copolymer in mixed solvents
Journal of Polymer Science Part C: Polymer Symposia, 2007Co-Authors: Z. H. Bakauova, E. A. Bekturov, S. V. BerezaAbstract:Intrinsic viscosities of fractions of the Statistical Copolymer of vinylpyrrolidone and methyl methacrylate (composition 42:58 mole percent) have been measured in the cross-selective solvents, benzene and methanol, in mixtures of these solvents, as well as in chloroform, a solvent for both polymer components, and in mixtures of chloroform with methanol. The dependence of the intrinsic viscosity on the composition of the mixed solvent exhibits a maximum reflecting the destruction of secondary structures that exist in the selective solvents. The temperature dependence of the intrinsic viscosity, which has a maximum around 50-60°C, has been studied in chlorobenzene between 10° and 100°C. The Mark-Houwink-Kuhn constants K and a, which do not change significantly with solvent composition, have been calculated. The values of the parameters Kθ and σ, which depend on solvent composition similarly to the intrinsic viscosity, have also been determined. The results indicate marked changes of macromolecular conformation from the hypercoiled structure in a selective solvent to the random coil in mixed and nonselective solvents.
Diethelm Johannsmann - One of the best experts on this subject based on the ideXlab platform.
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glass transition induced by solvent desorption for Statistical mma nbma Copolymers influence of Copolymer composition
Polymer, 2001Co-Authors: A C Sabydubreuil, Béatrice Guerrier, Catherine Allain, Diethelm JohannsmannAbstract:Abstract An experimental study of the glass transition induced by solvent desorption has been performed for a series of Methyl methacrylate (MMA)/n-butyl methacrylate (nBMA) Statistical Copolymer films. The glass transition temperature of the dry homopolymers, PMMA and PnBMA, are, respectively, about 105 and 7°C above the temperature of the experiment, so that the glass transition domain can be analyzed in detail by varying the solvent concentration and the Copolymer composition. A strong coupling was found between drying dynamic and stress relaxation. In particular, the quantitative analysis of the desorption isotherms based on the Leibler–Sekimoto approach led to a bulk modulus K that increases as the proportion of nBMA increases, contrary to the behavior of dry annealed samples.
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Glass transition induced by solvent desorption for Statistical MMA/nBMA Copolymers — Influence of Copolymer composition
Polymer, 2001Co-Authors: A. C. Saby-dubreuil, Béatrice Guerrier, Catherine Allain, Diethelm JohannsmannAbstract:Abstract An experimental study of the glass transition induced by solvent desorption has been performed for a series of Methyl methacrylate (MMA)/n-butyl methacrylate (nBMA) Statistical Copolymer films. The glass transition temperature of the dry homopolymers, PMMA and PnBMA, are, respectively, about 105 and 7°C above the temperature of the experiment, so that the glass transition domain can be analyzed in detail by varying the solvent concentration and the Copolymer composition. A strong coupling was found between drying dynamic and stress relaxation. In particular, the quantitative analysis of the desorption isotherms based on the Leibler–Sekimoto approach led to a bulk modulus K that increases as the proportion of nBMA increases, contrary to the behavior of dry annealed samples.
Z. H. Bakauova - One of the best experts on this subject based on the ideXlab platform.
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Properties of vinylpyrrolidone‐methyl methacrylate Statistical Copolymer in mixed solvents
Journal of Polymer Science Part C: Polymer Symposia, 2007Co-Authors: Z. H. Bakauova, E. A. Bekturov, S. V. BerezaAbstract:Intrinsic viscosities of fractions of the Statistical Copolymer of vinylpyrrolidone and methyl methacrylate (composition 42:58 mole percent) have been measured in the cross-selective solvents, benzene and methanol, in mixtures of these solvents, as well as in chloroform, a solvent for both polymer components, and in mixtures of chloroform with methanol. The dependence of the intrinsic viscosity on the composition of the mixed solvent exhibits a maximum reflecting the destruction of secondary structures that exist in the selective solvents. The temperature dependence of the intrinsic viscosity, which has a maximum around 50-60°C, has been studied in chlorobenzene between 10° and 100°C. The Mark-Houwink-Kuhn constants K and a, which do not change significantly with solvent composition, have been calculated. The values of the parameters Kθ and σ, which depend on solvent composition similarly to the intrinsic viscosity, have also been determined. The results indicate marked changes of macromolecular conformation from the hypercoiled structure in a selective solvent to the random coil in mixed and nonselective solvents.
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properties of vinylpyrrolidone methyl methacrylate Statistical Copolymer in mixed solvents
Journal of Polymer Science Part C: Polymer Symposia, 2007Co-Authors: Z. H. Bakauova, E. A. Bekturov, S. V. BerezaAbstract:Intrinsic viscosities of fractions of the Statistical Copolymer of vinylpyrrolidone and methyl methacrylate (composition 42:58 mole percent) have been measured in the cross-selective solvents, benzene and methanol, in mixtures of these solvents, as well as in chloroform, a solvent for both polymer components, and in mixtures of chloroform with methanol. The dependence of the intrinsic viscosity on the composition of the mixed solvent exhibits a maximum reflecting the destruction of secondary structures that exist in the selective solvents. The temperature dependence of the intrinsic viscosity, which has a maximum around 50-60°C, has been studied in chlorobenzene between 10° and 100°C. The Mark-Houwink-Kuhn constants K and a, which do not change significantly with solvent composition, have been calculated. The values of the parameters Kθ and σ, which depend on solvent composition similarly to the intrinsic viscosity, have also been determined. The results indicate marked changes of macromolecular conformation from the hypercoiled structure in a selective solvent to the random coil in mixed and nonselective solvents.
Hind Ali Alghamdi - One of the best experts on this subject based on the ideXlab platform.
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Antibacterial Activity of Tannic Acid and Tannic Acid/Amphiphilic Cationic Polymer Mixtures
Asian Journal of Chemistry, 2020Co-Authors: Fatimah M. Alzahrani, Michelle Webb, Stephen G. Yeates, Hind Ali AlghamdiAbstract:In this study, the antibacterial activity of tannic acid/amphiphilic cationic polymer (poly{2-[(methacryloyloxy)ethyl]trimethyl-ammonium chloride}, PMADQUAT) and tannic acid mixtures was examined on the strains of Gram-positive (S. aureus) and Gram-negative (E. coli CI2, E. coli K12, Klebsiella pneumonia and P. aeruginosa) bacteria. Tannic acid exhibited the antibacterial activity against all the studied bacterial strains. The ester linkage between glucose and gallic acid is vital for the antimicrobial activity of tannic acid. Tannic acid inhibited the growth of S. aureus and E. coli K12 (1 wt%) and reduced the growth of P. aeruginosa to 23%. Mixing cationic polymers having different structures (Statistical Copolymer, homopolymer and diblock polymer) with tannic acid lead to an increase in antibacterial activity of tannic acid and the stability and clarity of mixtures was higher than that of a pure tannic acid solution. Tannic acid/diblock polymer and tannic acid/homopolymer mixtures (0.1 wt%) were excellent for inhibiting the growth of planktonic E. coli K12 bacteria, and a low concentration (0.0001 wt%) of tannic acid/diblock polymer reduced its growth to 19%. By contrast, the tannic acid/Statistical polymer mixture (0.0001 wt%) was excellent for inhibiting the growth of Gram-positive S. aureus bacteria.
A.b. Holmes - One of the best experts on this subject based on the ideXlab platform.
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Luminescence properties of a PPV-based Statistical Copolymer with glyme-like side groups
Synthetic Metals, 2001Co-Authors: Jorge Morgado, Franco Cacialli, Richard H. Friend, Beng Sim Chuah, H. Rost, S.c. Moratti, A.b. HolmesAbstract:The orange emitting Statistical Copolymer, poly[2,5-bis(dimethyloctylsilyl)-1,4-phenylene vinylene)]-co-[2,5-bis(trisethoxy-methoxy)-1,4-phenylene vinylene)], has a photoluminescence efficiency of about 17%. Light-emitting diodes with calcium cathodes exhibit luminances up to 1300 cd/m 2 with an efficiency of 0.5 cd/A. ITO/Copolymer+lithium triflate/Al devices exhibit typical light-emitting electrochemical cell behaviour.
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Light-Emitting Devices Based on a Poly(p-phenylenevinylene) Statistical Copolymer with Oligo(ethylene oxide) Side Groups
Macromolecules, 2001Co-Authors: Jorge Morgado, Franco Cacialli, Richard H. Friend, Beng Sim Chuah, H. Rost, A.b. HolmesAbstract:We present the photo- and electroluminescence properties of the Statistical Copolymer, poly[2,5-bis(dimethyloctylsilyl)-1,4-phenylenevinylene)]-co-[2,5-bis(triethoxymethoxy)-1,4-phenylenevinylene)], BDMOS-co-BTEM-PPV, designed to combine the high efficiency of BDMOS-PPV, with the ion-coordinating ability of BTEM-PPV. We find that the photoluminescence efficiency is increased to about 17%, from 8.8% for BTEM-PPV. Single-layer light-emitting diodes with calcium (aluminum) cathodes exhibit luminances up to 1300 (10) cd/m2 with an efficiency of ≈0.5 (0.01) cd/A. ITO/BDMOS-co-BTEM-PPV:LiTf (8 wt %)/Al devices display behavior typical of light-emitting electrochemical cells, LECs, with efficiencies up to 0.03 cd/A. These results show that this Statistical Copolymer approach is successful at improving the photoluminescence efficiency, while also granting sufficient ion coordination for LEC applications.
