Degradation characteristics of poly(ε-caprolactone)-based copolymers and blends

The hydrolytic degradation of various bioresorbable copolymers and blends derived from epsilon-caprolatcone, D,L-lactide and poly(ethylene glycol) (PEG) was investigated at 37 degrees C in a pH 7.4 phosphate buffer. Poly(epsilon-caprolatcone) (PCL) followed a slow degradation profile due to its hydrophobicity and crystallinity. The hydrophilicity and degradability of the materials can be improved by copolymerization with PEG and/or poly-(D,L-lactide) (PLA). Homogenous degradation was shown in the cases of PCL, PCL/PEG copolymers and their blends, whereas PLA-containing copolymers followed a heterogenous degradation due to internal autocatalysis. It was also shown that PCL-based materials gradually turned to PCL-enriched residues during degradation due to preferential hydrolysis of PLA segments and to diffusion of soluble species such as PLA oligomers and detached PEG blocks bearing short PLA segments. The results are discussed in comparison with literature data. (c) 2006 Wiley Periodicals, Inc.