Isomeric structure of styrene-acrylonitrile and styrene-methylcrylate copolymer pyrolysis products

Gas chromatographic retention indices of pyrolysis products of styrene-acrylonitrile and styrene-methylacrylate copolymers were measured on two columns prepared with different stationary phases. A retention index against retention index diagram proved to be useful to define the composition of product molecules, as the points of homologous series form straight lines. We identified the isomeric structure of dimers and trimers consisting of two kind of monomer units by comparing their retention indices. This comparison was based on the determination of the retention index increments of cyano, methoxy-carbonyl and phenyl groups bounded to primary, secondary or olefinic carbon atom. The isomeric structures of styrene-acrylonitrile dimers and trimers were confirmed by mass spectroscopy.