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 cyclopropa ne (ECVCP) and methyl methacrylate (MMA) was carried out in the presen ce of 2,2'-azobis(isobutyronitrile) (AIBN) at 60-degrees-C in bulk or in chlorobenzene. Both the yields and molecular weights of the copolym ers were lower than those of the homopolymers. Structural analysis of the copolymer suggested that radical copolymerization proceeded throug h ring opening followed by intramolecular cyclization. The copolymeriz ation 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 leas t-squares methods, respectively. From the examination of the electron density of the olefinic carbon of ECVCP and its related compounds calc ulated by a semiempirical molecular orbital method (PM3), it was confi rmed that the substituents on the cyclopropane ring of the vinylcyclop ropanes 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 s imilar tendency was observed in the glass transition temperature (T(g) ) of the copolymers.