Copolymerization of 2-vinylcyclopropane-1,1-dicarbonitrile

Abstract

To investigate the radical polymerization behavior of substituted vinylcyclopropanes, 2-vinylcyclopropane-1,1-dicarbonitrile was prepared from 1,4-dibromo-2-butene and malononitrile, and its copolymerization with various common comonomers including alkyl vinyl ethers were carried out radically. Copolymerizations of 2-vinylcyclopropane-1,1-dicarbonitrile (VCP-DCN) with AIBN as initiator were carried out in neat or in solution at 60℃. Structure and composition of the resulting copolymers were determined by NMR and IR spectra. Under these conditions, VCP-DCN copolymerized well with vinyl acetate, methyl acrylate, and acrylonitrile by 1,5-fashion. Maleic anhydride which does not homopolymerize radically did not copolymerize with VCP-DCN. Interesting to observe was the copolymerization of VCP-DCN with alkyl vinyl ethers. Radical copolymerization of VCP-DCN with alkyl vinyl ethers yielded the copolymers which were surprisingly rich in alkyl vinyl ethers rather than expected one-to-one alternating copolymers or the copolymer rich in VCP-DCN. During the copolymerization reaction usually amber color developed. The copolymers, formed were soluble in various common solvents and the inherent viscosity was 0.2-0.3 dl/g. Another striking feature of the copolymer structure revealed by spectra was that the copolymers do not possess any unsaturation which would result if VCP-DCN copolymerize in 1,5-fashion. Since the copolymers showed strong absorption band at $2230cm^{-1}$ indicating the presence of nitrile groups, it was postulated that VCP-DCN is incorporated into copolymers by 1,2-type polymerization leaving cyclopropane ring intact. To interpret what we have observed we proposed a cationic polymerization mechanism in which radicals promote the formation of initiating electron donor-acceptor complex. In the proposed mechanism the primary radicals formed by decomposition of radical initiators first react with VCP-DCN to form a radical which has two geminal nitrile grou...