SEQUENCE DETERMINATION OF ACRYLONITRILE (ETHYL ACRYLATE) COPOLYMERS BY C-13-NMR SPECTROSCOPY AND CORRELATION WITH GLASS-TRANSITION TEMPERATURE

Acrylonitrile-(ethyl acrylate) copolymers of various compositions were prepared by bulk polymerization using benzoyl peroxide as initiator. Copolymer compositions were determined by elemental analyses; monomer reactivity ratios were determined using a nonlinear least square errors in variables model which gave more reliable value of r1 and r2. Terminal and penultimate reactivity ratios have been calculated using the observed monomer triad sequence distribution determined from (C{H})-C-13-H-1-NMR spectra. The triad sequence distribution was used to calculate diad concentrations, conditional probability parameters and number-average sequence lengths in the copolymers. The observed triad sequence concentrations determined from (C{H})-C-13-H-1-NMR spectra agreed well with those calculated from reactivity ratios. Glass transition temperatures of various copolymers determined from DSC agreed well with those obtained from diad concentrations.