Synthesis of Aliphatic Polycarbonates via theRing-opening Polymerization of Ethylene Carbonate Catalyzed by Ionic Liquid

摘要

@@1.Introduction Aliphatic polycarbonates (APC) has being found wide appilications in polyurethane and surfactant industries because of good biocompatibility and biodegradability. The new process of urea alcoholysis does not rely on the petroleum product (epoxide) and replaces poisonous phosgene to prepare five-membered cyclic carbonate, so it is meaningful to study on the ring-opening polymerization (ROP) of five-membered cyclic carbonate to prepare APC via a green environment protection way. However, cyclic carbonates of the smallest ring (five-membered) e.g ethylene carbonate (EC) hardly undergo ROP in contrast to six-and seven-membered cyclic carbonates. The reason is that molecular structure of five-membered ring is more stable than that of multi-membered ring. The ROP of EC proceeds above 200°C without catalyst, and involves decarbonation which results in the formation of aliphatic poly(ethylene ether carbonate) (APEC) with contents of EC units below 50 tool%. The synthesis of APEC has been reported in the presence of Lewis acids, transesterification catalysts and bases as initiators or as polymerization catalysts[4], but the reactions needed long time with serious decarbonation. Recently, the use of room temperature ionic liquids as either solvents or catalysts has been the subject of considerable attentions because of the prospects for "green" catalysis.