The effect of solvent on the styrene-acrylonitrile copolymerization

The copolymerization of styrene and acrylonitrile has been examined in acetonitrile and toluene and in bulk. All the systems display a significant penultimate unit effect. The comparison of the bulk system with these involving toluene and acetonitrile reveals a relatively small solvent effect. The bulk and toluene systems behave very similarly in the high styrene region (Xs > 0.3), while the bulk and acetonitrile systems behave very similarly in the high acrylonitrile region (Xs < 0.3). The solvents, therefore, behave as effective analogues of styrene and acrylonitrile, which are the "solvents" in the bulk copolymerization. The relationships between the copolymer compositions and triad fractions for the polymers prepared in each system have been assessed for evidence consistent with partitioning of monomer between polymer and solvent phases. Similar relationships were found for the triads independent of the solvent, a result which may be indicative of a "bootstrap" effect