In order to obtain polycarbonates with adjustable degradation rates

the copolymer of trimethylene carbonate and 5-benzyloxy-trimethylene carbonate have been synthesized using lipase porcine pancreas as catalyst.The factors affecting the yield and molecular weights such as catalyst concentration

polymerization time and monomer feed ratio were investigated.Number-averaged Molecular weight of 3 000-18 000 of the resulting copolymer was obtained.The resulting copolymer composition exhibited good relation with the molar feed ratio of BTMC to TMC ranged from 1∶0.5 to 1∶10.When decreasing the enzyme concentration

the molecular weight of the copolymer increases with quantitative conversion under determined condition.Along with the reaction time

the M

n

is nearly unvaried whereas the yield increases during the posterior reaction stage.