Enzyme-catalyzed Polymerization And Characterization Of Lactones

In this paper PPL were selected as catalyst after the sieve of enzymes and different kinds of biodegradable polylactones were successfully synthesized with it. The mechanism of enzyme-catalyzed polymerization was investigated and the reaction conditions were optimized. The copolymerization of caprolactone with other monomers was also studied.In the study of polymerization of caprolactone, effects of polymerization time, temperature, solvent and amounts of enzymes were investigated. The results indicated that under given polymerization temperature and amounts of enzymes, the molecular weight of polycaprolactone would enhance with increasing polymerization time and finally reached a fixed value. However, the molecular weight of polycaprolactone might decrease slightly if polymerization time was too long. The conversion of caprolactone was increased with increasing polymerization time and interestingly, there seem to be an accelerating period of polymerization. Under given polymerization time and amounts of enzymes, the molecular weight and conversion of polycaprolactone were increased with higher polymerization temperature. Under given polymerization time and temperature, the more enzyme used, the higher the molecular weight of polycaprolactone was. The solvent was one important factor of polymerization whose effects were complicated. The mechanism of enzyme-catalyzed polymerization was also put forward.In the study of polymerization of butyrolactone, effects of polymerization time and amounts of enzymes were investigated. The results indicated that under given polymerization temperature and amounts of enzymes, the conversion of butyrolactone was increased with increasing polymerization time. Under given polymerization time and temperature, the more enzyme used, the higher the molecular weight of polybutyrolactone was.In the study of copolymerization of lactones, the possibility of copolymerization of caprolactone and other monomers was explored and several copolymers were synthesized. Effects of polymerization time and composition of monomers were investigated. The results indicated that under given polymerization temperature and amounts of enzymes, the conversions of caprolactone and succinic anhydride wereSffii^^^i^ftifei inenhanced with increasing polymerization time and the conversion of succinic anhydride was much higher than that of caprolactone. With more succinic anhydride monomer used, the content of succinic anhydride unit in the copolymer increased, which was higher than that of succinic anhydride in monomer.The paper provides necessary experimental and theoretical foundation for the further studies of enzyme-catalyzed lactone ring-opening polymerization.