RANDOM COPOLYMERIZATION OF EPSILON-CAPROLACTONE AND TRIMETHYLENE CARBONATE WITH RARE-EARTH CATALYSTS

Random copolymerization of trimethylene carbonate (TMC) with epsilon-c aprolactone (CL) catalyzed by rare earth chloride-epoxide or rare eart h isopropoxide has been investigated for the first time. It was found that in the presence of epoxide, rare earth chlorides have high activi ties for the copolymerization, giving high-molecular-weight random cop olymer P(CL-co-TMC) with a narrow molecular weight distribution. Light rare earth chloride-propylene oxide systems are more effective for th e copolymerization than heavy rare earth chloride-propylene oxide syst ems. For the rare earth chloride-epoxide catalyst system, epoxide is t he requisite component, and its amount affects the catalytic activity; while rare earth isopropoxide can catalyze the copolymerization alone . The preparative conditions of the copolymer with NdCl3-5PO system we re studied. The reactivity ratios of CL and TMC copolymerization with NdCl3-5PO determined by Fineman-Ross method are 1.60 for r(TMC) and 0. 72 for r(CL), respectively. The copolymers were characterized by H-1- and C-13-NMR, GPC, and DSC. The mechanism study shows that the rare ea rth alkoxide is the active species that initiates the ring opening cop olymerization of CL and TMC with acyl-oxygen bond cleavages of the mon omers. (C) 1997 John Wiley & Sons, Inc.