Contribution to the mechanism of copolymerization of phenylvinyl alkyl ethers and thioethers with maleic anhydride

The equilibrium constants of the charge-transfer complex monomers of phenylvinyl alkyl ethers (I) and thioethers (II) with maleic anhydride (MAn) were determined by the transformed Benessi—Hildebrand NMR method, and it was found that the bulkiness of alkyl groups had no significant influence on the equilibrium constant. The rate of copolymerization, however, was largely dependent on the bulkiness of the alkyl groups in the phenylvinyl alkyl ether series. The rate of copolymerization of I (R = Et; sec-Bu) and II (R = Et; sec-Bu) with MAn was proportional to the square root of AIBN concentration, and intrinsic viscosity of poly-I (R = Et)-co-MAn was proportional to the reciprocal square root of AIBN concentration. Spontaneous copolymerization did not occur, but I (R = Et) copolymerizes with MAn in the presence of oxygen; II did not copolymerize with MAn in the presence of oxygen; nor in the presence of peroxide initiators. In the copolymerization of I (R = Et) and MAn, it was found that molecular weight increases with conversion. By applying the generalized model described by Shirota and co-workers, the reactivity ratios k_1c/k₁₂ and k_2c/₂₁ for copolymerization of I (R = Et) and II (R = Et) with MAn were calculated from the change of copolymerization rate with monomer feed at constant total monomer concentration.