Addition polymerization of 2-aryl- and 2-ethoxycarbonyl-1-methlenecyclopropanes promoted by nickel complexes

[Ni(pi-C3H5)Br](2) initiates addition polymerization of 2-aryl-1-methylenecyclopropanes and 2-ethoxycarbonyl-1-methlenecyclopropane, affording the polymers hawing cyclopropylidene groups. The H-1 and C-13 NMR spectra of the polymers indicate well-regulated head-to-tail linkage of the monomer units. Quenching of polymerization of 2-phenyl-1-methylenecyclopropane by D2O forms the polymer with -CH2D terminal group, which is more consistent with 1,2-insertion of the monomer to the Ni-carbon bond than 2,1-insertion. GPC of the polymer of 2-phenyl-1-methlenecyclopropane prepared at -40degreesC shows M-n = 29 000 (M-w/M-n = 1.59) based on polystyrene standards. Molecular weight of the polymers of 2-aryl-1-methylenecyclopropane increases with the electron-withdrawing substituent of the aromatic group of the monomer. DSC and TG analyses of the polymer of 2-aryl-1-methylenecyclopropane show glass transition at the temperature range 153-178degreesC and 5% weight loss due to thermal decomposition at 352-361degreesC. The polymer of 2-ethoxycarbonyl-1-methylenecyloprapane has lower T-g and T-d(5).