Polymerization of lactides and lactones - 5. Ring-opening polymerization of epsilon-caprolactone and DL-lactide by rare earth 2-methylphenyl samarium

Ring-opening homopolymerization and copolymerization of epsilon-caprolacton e and lactide have been initiated with rare earth 2-methylphenyl samarium i n bulk. The initiator can give high yield and high molecular weight polymer . The polymerization mechanism is suggested as 'coordination-deprotonation- insertion', by which the monomer is inserted on the Ln-O bond of rare earth enolate. The effects of reaction conditions, such as reaction time, reacti on temperature, monomer/initiator molar ratio on the polymerization have be en discussed. The polymer was characterized by FTIR and H-1-NMR. (C) 1999 E lsevier Science Ltd. All rights reserved.