The Copolymerization of Carbon Dioxide and [2-(3,4-Epoxycyclohexyl)ethyl]trimethoxysilane Catalyzed by (Salen)CrCl. Formation of a CO2 Soluble Polycarbonate

The copolymerization of 2-(3,4-epoxycyclohexyl)ethyl-trimethoxysilane and carbon dioxide catalyzed by (salen)CrIIICl (H2salen = N,Nʹbis(3,5-di-tert-butylsalicylidene)-1,2-ethylenediimine) with 2.5 equiv of N-MeIm as cocatalyst affords a polycarbonate devoid of polyether linkages, along with only a trace quantity of cyclic carbonate. The presence of the trimethoxysilane functionality in the epoxide not only provided the reactant monomer and product copolymer high solubility in liquid carbon dioxide but also provided the ability to cross-link the copolymer and thereby greatly alter the physical properties of the thus formed polycarbonate. In addition, the enhanced solubility of the copolymer in liquid CO2 furnishes a ready means of removing the highly colored metal catalyst from the polycarbonate product.