The copolymerization of methylmethacrylate and maleic anhydride

Abstract

A maximum is possible in the rate/composition curve for a copolymerization in which one monomer does not undergo homopolymerization and the termination reaction is diffusion controlled. The maximum can occur without any restriction on the value of the reactivity ratio, r 1, provided either that the propagation ratio k pab k pba satisfies certain conditions, or that the termination reaction is impeded by the introduction of the second monomer into the polymer chain. The copolymerization of methylmethacrylate and maleic anhydride in solution at 30°C (the total monomer concentration being maintained constant) has been shown to involve a diffusion-controlled termination step. The rate of termination decreases with increasing maleic anhydride content, as would be predicted if rearrangement of the conformations of the radical chain is the rate-determining step. The rate constant for addition of methylmethacrylate radicals to maleic anhydride is less than that for addition of maleic anhydride radicals to methylmethacrylate, as would be predicted on steric considerations. Accurate determination of the propagation rate constant, maleic anhydride radical plus methylmethacrylate, and of the hypothetical termination rate constant for a chain of maleic anhydride only, has not been possible in this study.