One- and two-dimensional NMR studies on the compositional sequence and themicrostructure of trans-4-methacryloyloxyazobenzene/styrene copolymers

trans-4-Methacryloyloxyazo benzene/styrene (M/S) copolymers of different mo nomer concentrations were prepared by solution polymerization using benzoyl peroxide as initiator. The copolymer composition was determined from the p ercent nitrogen content in the copolymers. The methyl carbons of M- and qua ternary carbon of S-centered resonances were used for determining the seque nces in terms of the distribution of M- and S-centered triads. The sequence distribution of M- and S-centered triads determined from C-13{H-1}-NMR spe ctra of the copolymer are in good agreement with triad concentration calcul ated from statistical model. The comonomer reactivity ratios, determined by both Kelen-Tudos and non-linear error in variables method are r(M) = 1.02 +/- 0.12, r(S) = 0.55 +/- 0.07; r(M) = 1.02 and r(S) = 0.54, respectively. C-13 distortionless enhancement by polarization transfer spectrum was used to differentiate the resonance signals of M- and S-methylene and methine ca rbon units of S. Assignments to the methylene resonance signals have been a ssigned up to the tetrad levels using two dimensional (2D) heteronuclear si ngle quantum correlation experiments. Homonuclear 2D total correlation spec troscopy NMR spectrum was used to ascertain the Various compositional and c onfigurational sequence of the copolymer. (C) 2001 Elsevier Science Ltd. Al l rights reserved.