Abstract: Bimetallic catalysts were prepared from a zinc salt, triethylaluminum, and an active proton containing compound.The catalysts were studied for the alternating copolymerization of carbon dioxide with propylene oxide giving poly (propylene carbonate). As a cocatalyst, polymer containing carboxyl groups was superior to water.The catalytic activities of the systems depended on the type of zinc salts,the molar ratio of catalyst's components, and the mixing procedure of the components. It is considered that there exists certain cooperative effect from two metals and a possible structure of the active center was proposed.

Key words: Copolymerization of carbon dioxide with propylene oxide, Bimetallic catalyst system, Carboxyl containing polymer