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

N-vinyl-2-pyrrolidone/acrylonitrile (V/A) copolymers of different compositi ons were prepared by free radical solution polymerization in DMF using benz oyl peroxide as an initiator. The composition of the copolymers was determi ned by using quantitative C-13(H-1)-NMR spectra. The methine carbon of V- a nd A-centered resonances were used for the determination of the sequence di stribution of V- and A-centered triads. The sequence distribution of V- and A-centered triads determined from C-13(H-1)-NMR spectra of the copolymers are in pood agreement with the triad concentration calculated from the Alfr ey-Mayo statistical model. The comonomer reactivity ratios, determined by b oth 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 respect ively. Two-dimensional (HC)-H-1-C-13-heteronuccear single quantum correlati on spectroscopy was used to assign the aliphatic protons in the H-1-NMR spe ctrum. Total correlated spectroscopy was used to assign the various H-1-H-1 coupling in the copolymers. (C) 2001 Elsevier Science Ltd. All rights rese rved.