A NOVEL RARE-EARTH COORDINATION CATALYST FOR POLYMERIZATION OF BIODEGRADABLE ALIPHATIC LACTONES AND LACTIDES

A novel rare earth coordination system composed of lanthanide trifluor oacetates Ln(CF3COO)(3) (Ln = Y, Yb, Nd, Tm, Ho, La, Pr) and triisobut ylaluminium Al(i-Bu)(3) was used as catalyst for the polymerization of epsilon-caprolactone (CL), D,L-lactide (DLLA) and their copolymerizat ion. The influence of temperature, time and catalyst concentration on polymerization yields and molecular weights of the polyesters have bee n studied. It was shown that the ring-opening polymerization of cyclic esters catalysed by Ln(CF3COO)(3)/Al(i-Bu)(3) has some living charact er and the molecular weight of the polyester could be controlled by ad justing the molar ratio of monomer to catalyst. The DLLA/CL copolymer was synthesized by sequential addition of monomers and the structure o f the copolyester was characterized by GPC, NMR and DSC. (C) 1998 SCI.