Alex Lubnin - The Microstructure of Poly(isobutylene-co-p-methylstyrene) by NMR Spectroscopy

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Journal of Macromolecular Science - Pure and Applied Chemistry, Vol. A32, No. 11, pp. 1809-1830 (1995)


The microstructure of isobutylene-p-methylstyrene (IB-pMeSt) copolymer was studied by NMR spectroscopy.  1H- and 13C-NMR spectra were used to obtain overall copolymer compns.  13C-NMR signals were assigned in terms of triad monomer sequences, and triad distributions were obtained over a wide copolymer compn. range.  According to statistical tests, the IB-pMeSt copolymerization cannot be described by zero- (Bernoullian) or first-order Markov models because reactivity ratios rIB and rpMeSt were found to change with the monomer feed compn.  Addnl. insight into the microstructure of IB-pMeSt copolymers was gained by calcg. sequence nos., run nos., and sequence lengths from triad distributions.  Further, the Kelen-Tuedoes plot showed a distinct curvature indicating that the Kelen-Tuedoes method, applied over the entire monomer feed compn. range, cannot give meaningful reactivity ratios for this monomer pair.  Evidently the simple two-parameter Mayo-Lewis model is inadequate to describe the IB-pMeSt copolymn. system.

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