Vinyl polymerization. LXXIX. Effect of the alkyl group on the radical polymerization of alkyl methacrylates

The effect of the alkyl group on the rates of polymerization of alkyl methacrylates initiated by α,α′‐azobisisobutyronitrile in benzene at 60°C. has been investigated. The rate of polymerization increased with increasing length of the alkyl group. This has already been attributed to the increased steric effect of the alkyl group in the termination process. In the present study, it was proved that the viscosities of alkyl methacrylate monomers increased with increasing length of the alkyl group, and that overall polymerization rate constants were inversely proportional to the viscosities. Accordingly, the above result might be explained by an increase in the contribution of the diffusioncontrolled termination with increasing length of the alkyl group in alkyl methacrylate.