Epimerization of isotactic polystyrene

Shepherd, L. T.; Chen, Teng Ko; Harwood, H. James

doi:10.1007/bf00284418

Cited by 29 publications

(11 citation statements)

References 9 publications

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“…6c) is similar to that of free‐radically synthesized polystyrene in the aliphatic region, except that the resonances are shifted downfield by approximately 0.5 ppm 38. Both free‐radically38 synthesized and atactic39 polystyrene exhibit broad resonances at approximately 1.5 ppm due to C H 2 , and at approximately 2.0 due to C H . In contrast, the C H mm triad resonance of isotactic polystyrene appears as a well‐defined pentad at approximately 2.2 ppm,39, 40 and the C H rr triad resonance of syndiotactic polystyrene appears as a well‐defined pentad at approximately 1.9 ppm 40.…”

Section: Resultsmentioning

confidence: 60%

“…The spectrum of PPFS (Fig. 6c) is similar to that of free‐radically synthesized polystyrene in the aliphatic region, except that the resonances are shifted downfield by approximately 0.5 ppm 38. Both free‐radically38 synthesized and atactic39 polystyrene exhibit broad resonances at approximately 1.5 ppm due to C H 2 , and at approximately 2.0 due to C H .…”

Section: Resultsmentioning

confidence: 75%

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Synthesis, isolation, and thermal behavior of polybutadiene grafted with poly(2,3,4,5,6‐pentafluorostyrene)

Paz-Pazos

Pugh

2005

J. Polym. Sci. A Polym. Chem.

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2,3,4,5,6-Pentafluorostyrene (PFS) was copolymerized with polybutadiene (PB) in tetrahydrofuran using benzoyl peroxide as the initiator at 50, 60, and 80 8C. The copolymerizations follow typical radical polymerization kinetics and behavior. The grafting parameters were evaluated as a function of monomer conversion, initiator concentration, and/or temperature by gel permeation chromatography of directly injected copolymerization mixtures. The grafting efficiencies and grafting ratios are most consistent with a system that terminates by combination and whose graft sites are generated by hydrogen abstraction of allylic radicals by primary initiator radicals. Pure graft copolymers were isolated by extracting unreacted PB into hexanes and PPFS homopolymer into acetone. The similarity of the glass transition temperatures of the PPFS grafts and the corresponding extracted PPFS homopolymers confirms that their lengths are approximately equal. V V C 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2874-2891, 2005

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Section: Resultsmentioning

confidence: 60%

Section: Resultsmentioning

confidence: 75%

Synthesis, isolation, and thermal behavior of polybutadiene grafted with poly(2,3,4,5,6‐pentafluorostyrene)

Paz-Pazos

Pugh

2005

J. Polym. Sci. A Polym. Chem.

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“…Depending on the NMR field strength, stereochemically different sequences of five or more monomer units can be distinguished. The methine proton resonances occur in two general areas, and it has been shown in studies on partially epimerized isotactic PS that the lower field methine proton resonance area is due to mm stereosequences [164]. Copyright (1996) of American Chemical Society) 7.3 Coupling with 1 H-NMR them completely.…”

Section: Analysis Of Microstructure Of Polystyrene [154]mentioning

confidence: 99%

Multidimensional HPLC of Polymers

Pasch

Trathnigg

2013

Springer Laboratory

110

130

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“…Solvent CDC13 , 10 wt/volo/o, 55 oc; pulse width 90°, number of scans[4][5][6][7][8][9][10][11][12][13][14][15][16] Effect of pulse repetition time on relative peak intensity and observed tacticity for radically prepared PMMA by 500 MHz 1 H NMR.…”

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confidence: 99%

Stereochemistry of Polymers

Hatäda

Kitayama

2004

NMR Spectroscopy of Polymers

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When a polymer has stereochemical isomerism within the chain, its properties often depend on the stereochemical structure. Thus the analysis of the stereochemistry of polymers is important and NMR spectroscopy has been the most valuable tool for this purpose. Definition of TacticityIn polymers of vinyl monomers CH 2 =CH-X or vinylidene monomers CH 2 =CXY, the main-chain carbons having substituent group(s) are termed "pseudo-asymmetric" since, if the chain ends are disregarded, such carbons do not have the four different substituents necessary to qualify for being truly asymmetric. Nevertheless, they have the possibility of relative handedness. The simplest regular arrangements along a chain are the isotactic structure, in which all the substituents are located on the same side of the zigzag plane representing the chain stretched out in an all-trans conformation. The structure is often represented by a "rotated Fischer projection" in which the main-chain skeleton is represented by a horizontal line (Eq. 3.1). RNK. Hatada et al., NMR Spectroscopy of Polymers © Springer-Verlag Berlin Heidelberg 2004 74 3 Stereochemistry of PolymersFor a vinyl polymer, two types of diads should be considered, which are designated as meso (m) and racemo (r). Using these notations, a sequence in an isotactic polymer can be represented as -mmmmmm-and that in a syndiotactic polymer as -rrrrrrrr-. In reality, however, purely isotactic or syndiotactic polymers are rarely obtainable but the extent of regularity is always the question to be analyzed. Tacticity [1] is the term used for defining such stereochemical features of polymers. 1

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Epimerization of isotactic polystyrene

Cited by 29 publications

References 9 publications

Synthesis, isolation, and thermal behavior of polybutadiene grafted with poly(2,3,4,5,6‐pentafluorostyrene)

Synthesis, isolation, and thermal behavior of polybutadiene grafted with poly(2,3,4,5,6‐pentafluorostyrene)

Multidimensional HPLC of Polymers

Stereochemistry of Polymers

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