RADICAL COPOLYMERIZATION OF 1,1-BIS(ETHOXYCARBONYL)-2-VINYLCYCLOPROPANE AND METHYL-METHACRYLATE ACCOMPANYING RING-OPENING AND CYCLIZATION

Radical copolymerization of 1,1-bis(ethoxycarbonyl)-2-vinyl cyclopropane (ECVCP) and methyl methacrylate (MMA) was carried out in the presence of 2,2'-azobis(isobutyronitrile) (AIBN) at 60-degrees-C in bulk or in chlorobenzene. Both the yields and molecular weights of the copolymers were lower than those of the homopolymers. Structural analysis of the copolymer suggested that radical copolymerization proceeded through ring opening followed by intramolecular cyclization. The copolymerization parameters were evaluated to be r1 =0.11, r2 = 21.49 and r1 = 0.11, r2 = 21.51 (M1, ECVCP; M2, MMA) by Fineman-Ross and nonlinear least-squares methods, respectively. From the examination of the electron density of the olefinic carbon of ECVCP and its related compounds calculated by a semiempirical molecular orbital method (PM3), it was confirmed that the substituents on the cyclopropane ring of the vinylcyclopropanes affected the reactivity of the olefinic groups less than those on 1,1-disubstituted ethylenes did. The degree of volume shrinkage on the copolymerization decreased as the content of ECVCP increased. A similar tendency was observed in the glass transition temperature (T(g)) of the copolymers.