Sequence determination of N-vinyl-2-pyrrolidone/acrylonitrile copolymers by NMR spectroscopy

Abstract

N-vinyl-2-pyrrolidone/acrylonitrile (V/A) copolymers of different compositions were prepared by free radical solution polymerization in DMF using benzoyl peroxide as an initiator. The composition of the copolymers was determined by using quantitative 13 C{ 1 H}-NMR spectra. The methine carbon of V- and A-centered resonances were used for the determination of the sequence distribution of V- and A-centered triads. The sequence distribution of V- and A-centered triads determined from 13 C{ 1 H}-NMR spectra of the copolymers are in good agreement with the triad concentration calculated from the Alfrey–Mayo statistical model. The comonomer reactivity ratios, determined by both the Kelen-Tudos and the non-linear error in variable methods are r V=0.06±0.005, r A=0.46±0.019; r V=0.06 and r A=0.46 respectively. Two-dimensional 1 H– 13 C-heteronuclear single quantum correlation spectroscopy was used to assign the aliphatic protons in the 1 H-NMR spectrum. Total correlated spectroscopy was used to assign the various 1 H– 1 H coupling in the copolymers.