Abstract: Double metal cyanide/rare earth metal complex was used to catalyze the copolymerization between propylene oxide and carbon dioxide. It was found that the catalytic activity was much higher than that using rare earth ternary catalyst alone. The method could produce resultant polymer with average relative molecular mass above 1.0×105 using the as-prepared catalyst with less than 2% propylene carbonate by product, which was remarkably decreased from over 10% mass fraction using the rare earth ternary catalyst alone. The effects of complex catalyst component, including the category of rare earth metal, the molar ratio of n(Y)/n(Zn), the acidity of the ligand of rare earth metal salt, as well as the reaction pressure and reaction time on the copolymerization were investigated. It was found that Y(CCl3COO)3 could improve catalytic activity of double metal cyanide, when n(Y)/n(Zn)=6 and reaction time was 4 h, compared with the double metal cyanide, the catalytic activity was increased by 31.5% while the carbonate unit content in the polymer was reduced. Our results indicate that the rare earth metal complexes only activated the complexation of propylene oxide, and the catalytic process still followed that of the double metal cyanide complex.

Key words: rare earth complex, double metal cyanide complex, copolymerization, carbon dioxide, propylene oxide, propylene carbonate