Cyclopolymerization of Isopropenyl Acrylate and Methacrylate

Abstract

ABSTRACT:Radical polymerization of isopropenyl acrylate (IPA) and methacrylate (IPMA) was investigated at 60oC 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.O.l3 moldm -J for IPA and 0.26 and 0.06 mol dm -J 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; r 1 (St)=0.23, r2(IPA)=0.79 and r1(St)=0.35, riiPMA)=0.60.KEY WORDS Cyclopolymerization I Monocyclization I Bicyclization Isopropenyl Acrylate I Isopropenyl Methacrylate I Copolymerization Monomer Reactivity Ratio I Although cyclopolymerizations of vinyl /3-substituted acrylates 1 -4 and isopropenyl ethyl maleate 5 as unsymmetrical 1, 5-dienes were conducted to lead to the formation of polymers containing y-lactone or/and /3-lactone units along the main chain, those of vinyl acrylate (VA), methacrylate (VMA), and achloroacrylate (VCA) gave the polymers containing {}-lactone or larger cyclic units. 6 • 7 The mechanism of cyclopolymerization of VA, VMA, and VCA has been studied. 7 The suggested propagation reactions are intermolecular addition of a polymer radical to the aery! or a-substituted aery! group of monomers, intramolecular monocyclization of a polymer radical with the vinyl group of a penultimate monomer unit, and intramolecular bicyclization of a monocyclized radical with the vinyl group of a polymer end. The effect of the a-substituent of aery! residues on the degree of cyclization was evident in the monocyclization tendency which decreased with increasing size of the a-substituent of aery! residues.In this article, cyclopolymerizations of isopropenyl acrylate (IPA) and methacrylate (IPMA) are described in order to evaluate the effect of a-methyl substituent of the vinyl residue on the intramolecular cyclization reactions. The effect of temperature on the degree of cyclization of poly(IPA) was examined. In addition, copolymerization of styrene with IPA and IPMA was carried out to see which olefinic group of dienes would participate in the intermolecular propagation. 631