Cyclopolymerization of Isopropenyl Acrylate and Methacrylate

Abstract

Radical polymerization of isopropenyl acrylate (IPA) and methacrylate (IPMA) was investigated at 60°C in benzene. The residual double bond in the polymers was determined to be mainly isopropenyl groups by spectroscopy and titrimetry. The decrease in the residual double bonds of polymers with decreasing initial monomer concentration can be explained in terms of an intramolecular chain monocyclization-bicyclization mechanism, in which the monocyclization took place between a growing polymer radical and the isopropenyl group of the penultimate monomer unit, and the bicyclization, between a monocyclized radical and the isopropenyl group of the terminal unit. The ratios of rate constants for the reactions of monocyclization and bicyclization over intermolecular propagation were evaluated to be 5.0 and 0.13 mol dm −3 for IPA and 0.26 and 0.06 mol dm−3 for IPMA, respectively. The effect of temperature on the overall rate of polymerization of IPA and on the amount of residual double bonds of poly(IPA) was examined. Copolymerization of styrene with these monomers gave apparent monomer reactivity ratios; r1(St)=0.23, r2(IPA)=0.79 and r1(St)=0.35, r2(IPMA)=0.60.