Enzymatic degradation of poly(propylene carbonate) and poly(propylene carbonate-co-ɛ-caprolactone) synthesized via CO2 fixation

Poly(propylene carbonate) (PPC) and poly(propylene carbonate-co-ɛ-caprolactone) (PPCCL) were synthesized via the zinc glutarate catalyzed copolymerization of carbon dioxide (CO2) and propylene oxide (PO) without and with ɛ-caprolactone (CL), respectively. In addition, poly(ɛ-caprolactone) (PCL) was prepared via the homopolymerization of CL with the aid of methyl triflate catalyst. The polymer products were characterized in terms of their chemical compositions, molecular weights, and thermal properties. Films of these polymers were tested with a series of enzymes (four different families and a total of 18 enzymes) in a phosphate buffer in order to characterize their enzymatic degradabilities. This is the first report demonstrating that PPC films exhibit positive enzymatic degradability with Rhizopus arrhizus lipase, esterase/lipase ColoneZyme A, and Proteinase K. Moreover, PPCCL films exhibited positive enzymatic degradability with most of the enzymes utilized in our study, and thus PPCCL has an enzymatic degradability comparable to that of PCL. In particular, the PPCCL films exhibit excellent enzymatic degradability with Pseudomonas lipase, Rhizopus arrhizus lipase, and esterase/lipase ColoneZyme A. Considering its excellent enzymatic degradability, the PPCCL terpolymer has potential biomedical applications. In conclusion, ZnGA-catalyzed copolymerizations of CO2 and PO with or without CL are chemical fixation processes of CO2 that can be used to produce enzyme-degradable aliphatic polymers.