Copolymerization of carbon dioxide and some oxiranes by organoaluminium catalysts

Carbon dioxide was copolymerized with methyloxirane and 7‐oxabicyclo[4.1.0]heptane using triethylaluminium as a catalyst component. Factors to control the copolymer composition were sought on the basis of an assumed copolymerization mechanism. Compared to nonpolar solvents, ethereal solvents were found to increase the carbon dioxide content in the copolymer obtained by the triethylaluminium/water system, giving a fraction with almost alternating sequence. The addition of a Lewis base, especially treiphenylphosphine, to triethylaluminium was also useful to get copolymers of high carbon dioxide content. The coincidence of these results with the expectation from the assumed copolymerization scheme clearly indicates that the copolymerization proceeds through a coordinated anionic mechanism.