Cationic polymerization of aliphatic cyclocarbonates

Numerous polymerizations of trimethylene carbonate (TMC) and neo-pentylene carbonate (NPC) were conducted in solution using methyl triflate as initiator. The polymerization mechanism was elucidated and rapid backbiting degradation along with the formation of ether groups was detected. When strong Lewis acids such as BF₃, SnCl₄ or SnBn₄ were used as initiators, much higher molecular weights were obtained, but the resulting polycarbonates still contained ether groups. BuSnCl₃ was found to be the most useful initiator yielding high molecular weight polycarbonates free of ether groups. However, in this case it is not clear, if a cationic mechanism or a coordination-insertion mechanism is involved.