Addition Polymerization of 2-Aryl- and 2-Ethoxycarbonyl-1-methylenecyclopropanes Promoted by Nickel Complexes

Abstract

[ Ni(π-C 3 H 5 )Br] 2 initiates addition polymerization of 2-aryl-1-methylenecyclopropanes and 2-ethoxycarbonyl-1-methylenecyclopropane, affording the polymers having cyclopropylidene groups. The 1 H and 13 C 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 D 2 O forms the polymer with −CH 2 D 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-methylenecyclopropane prepared at −40 °C 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 153−178 °C and 5% weight loss due to thermal decomposition at 352−361 °C. The polymer of 2-ethoxycarbonyl-1-methylenecylopropane has lower T g and T d 5 .