Reactivities of monomers towards the phenyl radical

Abstract

Labelled benzoyl peroxide has been used to initiate at 60°C polymerizations of styrene, methyl methacrylate and vinyl acetate in the presence of dimethylformamide; the relative numbers of benzoyloxy and phenyl end-groups have been determined in the polymers. The effects of dimethylformamide upon the balance between the two types of end-group can be explained if there is a significant primary radical transfer between that substance and the phenyl radical. It is possible to compare the reactivities of monomers towards the phenyl radical using the primary radical transfer process as the reference reaction. At 60°C the relative values of the velocity constants for the addition of the phenyl radical to styrene, methyl methacrylate and vinyl acetate are 1.0, 1.7 and 0.08 respectively. It is confirmed that the reactions of the phenyl radical are little affected by polar factors.