Reactivities of some organozinc initiators for copolymerization of carbon dioxide and propylene oxide

Abstract

Abstract Copolymerization of carbon dioxide (CO 2 ) and propylene oxide (PO) was carried out by using diethylzinc/water and diethylzinc/methanol catalyst systems. A remarkable amount of polycarbonate was obtained using the former system, but hardly any polymer was formed with the latter catalyst. The difference between these two systems was examined in relation to the elementary processes of the copolymerization. Both the catalysts react with CO 2 to produce XZnOCOOR, where X = OCH 3 for the diethylzinc/methanol system and X = (OZn) n OH or (OZn) n C 2 H 5 for the diethylzinc/water system. The reactivity of XZnOCOOR with PO depends on X and the difference between the two systems can be explained by the presence or absence of repeating ZnO bonds. Diethylzinc/primary amine systems produced copolymers while diethylzinc/secondary amine systems were inefficient yielding only small quantities of polymer. This can also be explained by the presence or absence of repeating ZnNR bonds.