C-13-NMR STUDIES OF COMPOSITIONAL AND CONFIGURATIONAL SEQUENCE DISTRIBUTION IN ACRYLONITRILE-ETHYL METHACRYLATE COPOLYMERS

Acrylonitrile-ethyl methacrylate (A/E) copolymers of different monomer concentrations were prepared in bulk by free radical initiation. Copolymer composition was determined by nitrogen analysis and the comonomer reactivity ratios were determined by the method of Kelen-Tudos. C-13-NMR spectra of several acrylonitrile/ethyl methacrylate copolymers are discussed in terms of their triad monomer sequence and cotacticity. Terminal and penultimate reactivity ratios have been calculated using the observed monomer triad sequence distribution determined from C-13-NMR spectroscopy for individual samples. Triad sequence distribution was used to calculate dyad concentrations, probability parameters, number average sequence lenghts, and the comonomer mole fractions in the copolymers. The configurational sequence distributions in terms of all the 10 A-centered and 10 E-centered triad cotactic sequences have been determined and found to be in excellent agreement with those obtained using various cotactic probability parameters.