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Vinyl Polymers (vinyl + polymer)

Distribution by Scientific Domains
Polymers and Materials Science100%

Selected Abstracts

Origin of Bends in Unperturbed Vinyl Polymers: An Illustration with Polystyrene

MACROMOLECULAR THEORY AND SIMULATIONS, Issue 7 2007
Yergou B. Tatek
Abstract Previous experimental works have shown that dendronized vinyl polymers exhibit bends when adsorbed onto a surface. Two different mechanisms are believed to be responsible for the formation of these bends. These mechanisms are the temperature dependent random fluctuations of torsional bond states on one hand, and the intramolecular interactions due to the randomness in the stereochemical sequence of side chains on the other hand. Investigation of the amplitude and scope of the above mechanisms has been made by studying the conformational space of PS chains via RIS based Monte Carlo sampling. It was found that at low temperature bend formation is due to tacticity, whereas it was thermally driven at high temperature. The existence of a transition temperature between these two bend formation modes was demonstrated. It was also shown that for atactic chains, the maximum of bend formation occurs at Pm,,,0.7. [source]

Starch- graft -(synthetic copolymer) latexes initiated with Ce4+ and stabilized by amylopectin

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2007
Hank De Bruyn
Abstract A method is presented for synthesizing surfactant-free latexes comprising starch- graft -(vinyl polymer) starting with a suspension of amylopectin, either native or modified, then using cerium(IV) with either potassium persulfate or glucose to create grafting sites on the starch. Latex particles comprising polystyrene, poly(styrene- co -(n -butyl acrylate)) and poly(vinyl acetate) grafted onto high molecular weight amylopectin were developed, with up to 80% of the starch effectively grafted to the particles. These latexes were colloidally stable against electrolyte (several months in 4 M NaCl). Reaction rates of Ce4+ with simple sugars and polysaccharides were investigated, as well as the gelation mechanism of the latex. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4185,4192, 2007 [source]

Synthesis and properties of organic/inorganic hybrid nanoparticles prepared using atom transfer radical polymerization

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008
Tzong-Liu Wang
Abstract The synthesis of organic/inorganic hybrid materials was conducted by atom transfer radical polymerization (ATRP) of styrene and methyl methacrylate (MMA) from the surface of silica colloids. Colloidal initiators were prepared by the functionalization of silica nanoparticles with (3-(2-bromoisobutyryl)propyl) dimethylethoxysilane (BIDS). Well-defined polymer chains were grown from the nanoparticle surfaces to yield individual particles composed of a silica core and a well-defined outer polystyrene (PS) or poly(methyl methacrylate) (PMMA) layer. Fourier transform infrared (FTIR) and solid state 13C and 29Si-NMR spectroscopy confirmed the successful modification of nanosilica surfaces. Subsequent grafting of polymers on silica surfaces by ATRP was also performed with success based on FTIR and NMR data. Scanning electron microscopy (SEM) and silicon mapping showed both hybrid materials were homogeneous dispersion systems. Energy dispersive X-ray spectrometer (EDS) analysis indicated that the BIDS initiator was covalently attached on surfaces of silica nanoparticles and ATRP of styrene and MMA were accomplished. Thermogravimetric analysis (TGA) results displayed higher thermal stabilities for both nanohybrids in comparison with the linear-type vinyl polymers. Contact angle measurements revealed the nanomaterials character for both silica-based hybrid materials. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

Origin of Bends in Unperturbed Vinyl Polymers: An Illustration with Polystyrene

MACROMOLECULAR THEORY AND SIMULATIONS, Issue 7 2007
Yergou B. Tatek
Abstract Previous experimental works have shown that dendronized vinyl polymers exhibit bends when adsorbed onto a surface. Two different mechanisms are believed to be responsible for the formation of these bends. These mechanisms are the temperature dependent random fluctuations of torsional bond states on one hand, and the intramolecular interactions due to the randomness in the stereochemical sequence of side chains on the other hand. Investigation of the amplitude and scope of the above mechanisms has been made by studying the conformational space of PS chains via RIS based Monte Carlo sampling. It was found that at low temperature bend formation is due to tacticity, whereas it was thermally driven at high temperature. The existence of a transition temperature between these two bend formation modes was demonstrated. It was also shown that for atactic chains, the maximum of bend formation occurs at Pm,,,0.7. [source]

Chain Conformations in the Crystalline Field of Syndiotactic Vinyl Polymers Deriving from 1,3-Diene Monomers.

MACROMOLECULAR THEORY AND SIMULATIONS, Issue 8 2004
Analysis by Molecular Mechanics
Abstract Summary: Conformational energy calculations on the chain conformation in the crystalline field have been performed for various syndiotactic vinyl polymers deriving from 1,3-diene monomers. Energy maps as a function of the independent torsion angles have evidenced for all the polymers minima corresponding to highly extended and to helical chains. Energy minimizations as a function of all the internal parameters for the s(2/1)2 and tcm symmetries have allowed the evaluation of the energy differences between chains having the two symmetries and the prediction of the values of the conformational parameters for each polymer. The results have been compared with the experimental data reported in the literature for some of the studied polymers. Conformational energy map of sPBD12. [source]