Lipase-catalyzed polymerization of diethyl carbonate and diol to aliphatic poly(alkylene carbonate)

Diethyl carbonate (DEC) and diols, such as 1,3-propanediol and 1,4-butanediol, were polymerized by a lipase at a temperature between 40 and 80°C to yield the corresponding aliphatic polycarbonates in a successive two-step polymerization. Bulk polymerization, especially at a temperature between 70 and 75°C, and preferably using immobilized lipase from Candida antarctica (Novozym 435) gave polycarbonates with weight-average molecular weights of 40000. An excess amount of DEC, preferably a 3-fold molar ratio to the diols, was needed for the polycondensation reaction of DEC and the diols. This was due to the partial degradation of both DEC and the carbonate moieties of the polymer chain by the lipase.