Copolymerizations Of Carbon Dioxide And Epoxides

Since 1969,the carbon dioxide(CO2) and epoxides copolymerization was reported by Inoue, this reaction became one of the most popular research topics. Zn Et2/H2 O was employed as catalyst in the beginning, which was of low activity and selectivity. More and more catalysts were developed for CO2 and epoxides copolymerization. Among these catalysts, Salen Co catalyst was popular due to its activity and selectivity.In our work, Salph Co catalyst was employed in CO2 and propylene oxide(PO) copolymerization. Salph Co catalyst was ignore in CO2 and PO copolymerization. In early research, Salph Co catalyst showed low selectivity in CO2 and PO copolymerization, lots of cyclic carbonate was obtained. Although this catalyst was developed for CO2 and PO copolymerization by Coates, it was finally employed in poly propylene copolymerization. The Salph Co catalyst was paramagnetic and conjugated, as the 1H NMR results proved. We guess that the Co center was in a special status: between Co(II) and Co(III). And the X-group linked to the Co center seemed important. With DNP group, the Salph Co catalyst was highly active and selective. Even at as high as 60 oC, the copolymerization of CO2 and PO was stable: 100% carbonate was obtained.As the 13 C NMR spectroscopy showed, the copolymer contained near 99% head-to-tail linkages. The copolymer showed an enhanced glass transition temperature of 43.5 oC,which was 5-10 oC higher than common PPC. In general, it was hard to obtain stereoselective copolymer with high molecular weight under such low reaction temperature. The copolymerizations under low temperature often showed low TOFs, the conversion of monomer was also low, which finally led to low molecular weight of the polymer. Although the TOF in our work was also low at 0 oC, with a particular high conversation of PO(60%), we have obtained high molecular weight PPC(Mn = 100,000).