Polymerization of lactides and lactones. IV. Ring-opening polymerization of epsilon-caprolactone by rare earth phenyl compounds

Ring-opening polymerization of epsilon-caprolactone (CL) has been initiated with rare earth phenyl compounds in both bulk and solution. These rare ear th phenyl initiators can give polycaprolactone (PCL) with high yield and hi gh molecular weight. The polymerization mechanism is through a coordination -deprotonation-insertion process, by which the monomer inserts on the Ln-O bond of rare earth enolate. The efficiency of rare earth phenyl compounds f or CL is high. The effects of reaction conditions, such as reaction time, r eaction temperature, and monomer/initiator molar ratio, on the polymerizati on are discussed. The polymer was characterized by FTIR, H-1-NMR. (C) 1999 John Wiley & Sons, Inc.