The Experts below are selected from a list of 211578 Experts worldwide ranked by ideXlab platform
Meenakshi Malhotra - One of the best experts on this subject based on the ideXlab platform.
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compositional assignments and Sequence Distribution of vinylidene chloride methyl acrylate copolymers using one and two dimensional nmr spectroscopy
Macromolecules, 1996Co-Authors: A S Brar, Meenakshi MalhotraAbstract:The microstructure of vinylidene chloride−methyl acrylate copolymers prepared by a photopolymerization process using uranyl ion as photosensitizer is analyzed by one- and two-dimensional NMR spectroscopy. Sequence Distribution was calculated from 13C{1H} NMR spectra of the copolymers. A 13C distortionless enhancement by polarization transfer spectrum was used to differentiate between the resonance signals of methoxy and methylene units in the copolymer. Comonomer reactivity ratios were determined using Kelen−Tudos and the nonlinear error in variables methods. The Sequence Distribution of vinylidene chloride- and methyl acrylate-centered triads determined from 13C{1H} NMR spectra of copolymers is in good agreement with triad concentrations calculated from statistical model and Monte Carlo simulation methods. 2D heteronuclear single quantum correlation and correlated spectroscopy spectrum was used to analyze the complex 1H NMR spectrum.
Issa Katime - One of the best experts on this subject based on the ideXlab platform.
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Poly(4-vinylpyridine)/poly(vinyl acetate-co-vinyl alcohol) blends: effect of Sequence Distribution on miscibility
Polymer, 1995Co-Authors: Josér. Isasi, Luis C. Cesteros, Issa KatimeAbstract:Abstract The miscibility of blends of poly(4-vinylpyridine) (P4VP) with blocky copolymers of vinyl alcohol/vinyl acetate (ACA) of different compositions has been investigated and compared to that of the blends with random ACA copolymers. The miscibility window found in both cases is narrower for the blocky ACA blends, indicating the influence of the comonomer Sequence Distribution. Fourier transform infra-red spectroscopy shows a lower level of pyridinehydroxy hydrogen-bonding interactions in the case of blends with blocky ACA copolymers. Cloud point curves have been obtained from optical microscopy measurements for several P4VP/ACA blends. Finally, the binary interaction model including the influence of the copolymer Sequence Distribution has been applied using Balazs and Cantow—Schulz approximations.
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Hydrogen Bonding and Sequence Distribution in Poly(vinyl acetate-co-vinyl alcohol) Copolymers
Macromolecules, 1994Co-Authors: José Ramón Isasi, Luis C. Cesteros, Issa KatimeAbstract:The correlation between hydrogen-bonding self-association and Sequence Distribution in different poly(vinyl acetate-co-vinyl alcohol) copolymers (ACA) of different degrees of hydrolysis and Sequence Distributions has been studied by infrared and NMR spectroscopy. For ACA copolymers, quasi-random Distributions are obtained by acid alcoholysis, blocker Distributions by saponification, and intermediate Distributions by acombined method, as shown by 13 C NMR. FTIR spectroscopy has pointed out that hydrogen-bonding Distribution in ACA copolymers strongly depends on Sequence Distribution. For block copolymers, hydroxyl-hydroxyl self-association is preferred
A S Brar - One of the best experts on this subject based on the ideXlab platform.
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compositional assignments and Sequence Distribution of vinylidene chloride methyl acrylate copolymers using one and two dimensional nmr spectroscopy
Macromolecules, 1996Co-Authors: A S Brar, Meenakshi MalhotraAbstract:The microstructure of vinylidene chloride−methyl acrylate copolymers prepared by a photopolymerization process using uranyl ion as photosensitizer is analyzed by one- and two-dimensional NMR spectroscopy. Sequence Distribution was calculated from 13C{1H} NMR spectra of the copolymers. A 13C distortionless enhancement by polarization transfer spectrum was used to differentiate between the resonance signals of methoxy and methylene units in the copolymer. Comonomer reactivity ratios were determined using Kelen−Tudos and the nonlinear error in variables methods. The Sequence Distribution of vinylidene chloride- and methyl acrylate-centered triads determined from 13C{1H} NMR spectra of copolymers is in good agreement with triad concentrations calculated from statistical model and Monte Carlo simulation methods. 2D heteronuclear single quantum correlation and correlated spectroscopy spectrum was used to analyze the complex 1H NMR spectrum.
Bernard Wiegert - One of the best experts on this subject based on the ideXlab platform.
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Sequence Distribution of the methyl methacrylate ethyl acrylate copolymer by 13c n m r spectroscopy
Polymer, 1997Co-Authors: Giao Nguyen, Marek Matlengiewicz, D Nicole, Michel Swistek, Bernard WiegertAbstract:Abstract A method for characterizing triad and pentad Distribution by 13 C n.m.r. spectroscopy has been developed and applied for an acrylate-methacrylate copolymer for which the chemical shifts of the homopolymers were sufficiently separated to observe mixed Sequences up to pentads. Calculation of the intensity was performed applying Markov-Bernoulli statistics while the chemical shift for each Sequence was calculated by a separately developed incremental method. Based on these data, the carbonyl signal was simulated yielding very good agreement at the triad level and satisfactory agreement at the pentad level. © 1997 Elsevier Science Ltd.
Ching-hsuan Lin - One of the best experts on this subject based on the ideXlab platform.
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Sequence Distribution and thermal properties of poly(butylene naphthalate terephthalate)
Journal of Polymer Research, 1997Co-Authors: Chun-shan Wang, Ching-hsuan LinAbstract:Poly(butylene naphthalate terephthalate) (PBNT) copolyesters were synthesized from bis(4-hydroxybutyl) terephthalate (BHBT) and bis(4-hydroxybutyl) naphthalate (BHBN) as starting materials. BHBT and BHBN were either homopolymerized or copolymerized at 260∼270 °C in the presence of titanium tetrabutoxide (TBT) as a catalyst to provide PBNT with various compositions. The copolyesters were characterized using inherent viscosity, X-ray, d.s.c., t.g.a. and ^1H NMR. The composition and Sequence Distribution of the copolyesters was determined from ^1H NMR spectra. The copolyesters exhibited a degree of randomness of about 1, indicating that the reactivity of BHBT and BHBN was almost the same. X-ray and d.s.c. showed PBNT copolyesters to be crystalline polymers. T.g.a. kinetics showed PBNT copolyesters to exhibit higher degradation activation energy, that is, better thermal stability, than PBTs.
