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

trans-4-Methacryloyloxyazobenzene/styrene (M/S) copolymers of different monomer concentrations were prepared by solution polymerization using benzoyl peroxide as initiator. The copolymer composition was determined from the percent nitrogen content in the copolymers. The methyl carbons of M- and quaternary carbon of S-centered resonances were used for determining the sequences in terms of the distribution of M- and S-centered triads. The sequence distribution of M- and S-centered triads determined from 13C{1H}-NMR spectra of the copolymer are in good agreement with triad concentration calculated from statistical model. The comonomer reactivity ratios, determined by both Kelen–Tudos and non-linear error in variables method are rM=1.02±0.12, rS=0.55±0.07; rM=1.02 and rS=0.54, respectively. 13C distortionless enhancement by polarization transfer spectrum was used to differentiate the resonance signals of M- and S-methylene and methine carbon units of S. Assignments to the methylene resonance signals have been assigned up to the tetrad levels using two dimensional (2D) heteronuclear single quantum correlation experiments. Homonuclear 2D total correlation spectroscopy NMR spectrum was used to ascertain the various compositional and configurational sequence of the copolymer.