Preparation and degradation of L-lactide and ε-caprolactone homo and copolymer films

L-Lactide and c-caprolactone homo and copolymers were synthesized by ring-opening polymerization using stannous octoate, as the catalyst. The number and weight average molecular weights, and polydispersity indices were in the range of 30,000-35,000, 52,000-56,000, and 1.53-1.86, respectively. All polymers were semicrystalline, as indicated by DSC. The LLA/CL ratio in the final copolymer was 60/40, as obtained by H-1-NMR. Polymeric films (120 pm) were prepared by solvent casting, using chloroform as the solvent and drying in air. Degradation of these films was investigated in aqueous media with or without the presence of a microorganism (Pseudomonas putida) for 60 days. We followed the degradation by measuring the changes in the molecular weights and distribution, and also changes in mechanical properties. Molecular weights decreased with time, but there was no significant changes in the molecular weight distributions. There were significant changes in the mechanical behavior of the films. They became much less flexible, even brittle and mechanically weaker in 60 days. The changes were more pronounced in the case of copolymer film. We observed almost no effect of micro-organisms on either molecular weights or mechanical properties. (C) 2002 Elsevier Science Ltd. All rights reserved.