Alternating copolymerization of α-methylstyrene and maleic anhydride

Alternating copolymers of α-methylstyrene (α-MeSt) and maleic anhydride (MAn) were prepared by free-radical-initiated polymerization in bulk, benzene, or butanone as solvents. By applying the generalized model described by Shirota and co-workers, the reactivity ratios k_1c/k₁₂ and k_2c/k₂₁ were calculated from the change of copolymerization rate with monomer feed at constant total monomer concentration. From the equation R_p = R_p(f) + R_p(CT) were calculated R_p(f) and R_p(CT), and it was found that in benzene the reaction proceeds predominantly by the addition of CT-complex monomers, while in butanone, cross propagation of free monomers predominates. Termination occurs predominantly by homotermination of α-MeSt macro free radicals, k_t22, although the cross termination k_t21 is also operative.