Compositional and structural analysis of PELA biodegradable block copolymers degrading under in vitro conditions.

This paper describes an investigation of the in vitro degradation of some polyethylene oxide/polylactic acid block copolymers. It has been found that the faster the degradation, the more basic the incubation medium and, as expected, the higher the temperature. The addition of enzyme proved to have no effect. This study shows that some polyethylene oxide/polylactic acid copolymers exhibit a steady increase in polylactic acid content, as degradation proceeds. This behaviour was attributed to the solubilization effect of the hydrophilic polyethylene oxide chains on the extraction of polyethylene oxide/polylactic acid-degrading fragments. Our findings indicate that polylactic acid blocks are cleaved randomly, the lactoyl end unit playing no special role. In accordance with data published for other biodegradable polymers, the crystallinity of polyethylene oxide/polylactic acid increases as degradation proceeds.