PROPYLENE-OXIDE HOMOPOLYMERIZATION AND COPOLYMERIZATION WITH CARBON-DIOXIDE BY GAMMA-ALUMINA-SUPPORTED ZINC COORDINATION CATALYSTS

Propylene oxide was homopolymerized and copolymerized with carbon dioxide in the presence of catalysts based on ethylzinc phenoxide or ethylzinc 1-phenoxy-2-propoxide and/or diethylzinc and gamma-alumina as a support. The propylene oxide homopolymerization yielded poly(propylene oxide) with an average molecular weight of about 20 x 10(3), and consisting of the prevailing amorphous fraction and the crystalline fraction. The copolymerization of propylene oxide and carbon dioxide produced poly (propylene carbonate) with an average molecular weight of about 30 x 10(3) and was accompanied by the formation of propylene carbonate. The polymeric products obtained were characterized by means of elemental analysis, IR, UV, H-1-NMR and C-13-NMR spectroscopy, and molecular weight determinations. On the basis of these studies, especially those concerning the polymer end-groups and the chain microstructure:, a possible structure of the active sites in gamma-alumina-supported zinc: coordination catalysts and a possible mechanism of the initiation and propagation reactions in propylene oxide homopolymerization and copolymerization with carbon dioxide are presented.