Polymerization of vinylcyclopropanes

Abstract

Four geminally activated cyclopropanes, i.e., 1, 1-disubstituted 2-vinylcyclopropanes (VCP-XY), diethyl 1-vinylcyclopropane-1, 1-dicarboxylate (VCP-DCE), 2-vinylcyclopropane-1, 1-dicarbonitrile (VCP-DCN), ethyl c-cyano-2-vinylcyclopropanecarboxylate (VCP-CEN) and 1, 1-diphenyl-2-vinylcyclopropane (VCP-DPH), were synthesized, and the polymeri zation behavior and various chemical reactions of these vinlcyclopropane compounds were investigated. Those four vinylcyclopropane compounds showed quite different polymerization behavior depending on the employed polymerization systems. Radically VCP-DCE, VCP-CEN polymerized well and cleanly in 1,5-type ring-opening fashion giving the polymers of high molecular weights and copolymerized with common comonomers such as acrylonitrile and styrene. The polymers produced radically were confirmed to have structures of five carbon repeating unit in which the double bond is in trans configuration, and the polymers were soluble in common solvents and the solution-cast films were clear and flexible showing Tg values in the range of 25 to 40℃. VCP-DPh did not homopolymerize but copolymerized with acrylonitrile, styrene and maleic anhydride in low conversions. Formation of a cyclopropylcarbinyl radical and its subsequent isomerization to an allylcarbinyl radical, which is further stabilized by two substituents, are considered to be the mechanistic pathway for the 1, 5-type radical polymerization. With sodium cyanide VCP-DCN and VCP-CEN in N, N-dimethylformamide polymerized giving white powdery polymers in high conversions. VCP-DCN underwent polymerization with sodium cyanide at about 0℃ and VCP-CEN did at somewhat higher temperatures (ca. 15℃), and all the spectral data indicate that polymerization proceeded by mere ring-opening, resulting the polymers with pendent vinyl group. The polymer from VCP-CEN was soluble in common solvents such as acetone and chloroform but the polymer from VCP-DCN was only soluble in concentrated sulfuric ...