The effect of ε-caproyl/d,l-lactyl unit composition on the hydrolytic degradation of poly(d,l-lactide-ran-ε-caprolactone)-poly(ethylene glycol)-poly(d,l-lactide-ran-ε-caprolactone)

The degradation of P(DLAX-ran-CLY)-b-PEG-b-P(DLAX-ran-CLY)s ( P(DLAX-ran-CLY): Poly(d,l-lactide-ran-ε-caprolactone), PEG: Poly(ethylene glycol), X: d,l-lactyl unit fraction, Y: ε-caproyl unit fraction) is investigated. The fraction of DLA in the both end blocks is varied while the overall molecular weight and molecular weight of PEG are kept constant. DSC, XRD and GPC are employed to track the degradation process up to 200 days. Also the change in the surface and cross-sectional morphology is provided by SEM micro-photographs. The result of water absorption and weight loss characterization reveals that the incorporation of DLA in the polyester block could be an effective tool to facilitate degradation as well as water absorption. By tracking the change of molecular weight and polydispersity, chain scission and transport or removal of degraded product from the specimen were found to play a complex role in overall degradation.