Nanoparticulate TiO sub(2)-Supported Double Metal Cyanide Catalyst for the Copolymerization of CO sub(2) with Propylene Oxide

A titanium oxide supported double metal cyanide (TiO sub(2)-DMC) was found to be a highly active catalyst for the reaction of CO sub(2) with propylene oxide to polyethercarbonates, which are useful polymer building blocks for polyurethane applications. The catalyst was prepared by coprecipitation of potassium hexacyanocobaltate(III) and titanium(IV) ethoxide with an excess amount of ZnCl sub(2) under slightly acidic conditions. The TiO sub(2)-DMC catalyst provided excellent selectivity to the polymer (>97%) and outstanding productivity (>500 g sub(polymer)/g sub(catalyst)). The TiO sub(2)-support enhanced the Lewis acidity of the DMC catalyst, which facilitated activation of the epoxide and adjusted the binding strength of the polymer chain to the surface of the catalyst. CO sub(2) is utilized as a renewable resource in the copolymerization with epoxides to polyethercarbonates. The excellent chemoselectivity of the nanoparticulate TiO sub(2)-supported double metal cyanide catalyst is rationalized by the Lewis acidity of the TiO sub(2) support. The polyethercarbonate is characterized by a large fraction of carbonate linkages in segments with a nonalternating sequence of co-monomers.