I. A study of solution copolymerization of maleic anhydride and vinyl monomers. II. A study of the effect of additives on the stability of polystyrene and model compounds

The role of solvents on solution copolymerization of maleic anhydride with styrene, and with esters of acrylic or methacrylic acids was studied and correlated with Hildebrand-Scatchard's solubility parameter values (6). It was observed that copolymers were readily obtained in either heterogeneous or homogeneous phases. When the solubility parameter values of the solvent and copolymer were similar, homogeneous solution copolymerization was observed. When solubility parameter values of the polymer and solvent differ by more than 1.46, the copolymer precipitated. Copolymerization could be changed from heterogeneous to homogeneous by either varying the solubility parameter value of the solvent or comonomer, or by the addition of chain-transfer agents. The relative rates of copolymerization were greater in the heterogeneous systems than in the homogeneous systems. In the former, the relative rate and the degree of polymerization decreased as the difference between the solubility parameter values of the solvent and copolymer increased. The original product from the heterogeneous system was assumed to be essentially a monodispersed living polymer which continued to propagate in the gel stage of the precipitate. This living polymer was used as a seed to initiate the polymerization of fresh monomers in the absence of regular free radical initiator. The new block copolymers obtained are characterized by viscometry, pyrolysis gas chromatography and infrared spectroscopy.