Changes in Crystalline Morphology, Thermal, and Mechanical Properties with Hydrolytic Degradation of Immiscible Biodegradable PPDX/PCL Blends

Immiscible blends of high molecular weight commercial poly(p-dioxanone) (PPDX) and poly(epsilon-caprolactone) (PCL) were prepared by melt mixing in a wide composition range. The materials were exposed to a hydrolysis medium (phosphate buffer kept at a constant pH of 7.2) at 37 degrees C during 36 weeks. The change in weight of the samples as well as their thermal properties, morphology, spherulitic crystallization kinetics, and tensile properties were studied as a function of degradation time. As PCL does not experience weight loss during the entire degradation period explored here, weight loss was indicative of PPDX degradation only. The combined results Of calorimetry, spherulitic texture, and spherulite growth kinetics allowed Lis to establish that the PPDX component in the blends experiences a much faster degradation rate than in neat PPDX. Such increase in degradation rate Could be due to the larger surface area of PPDX component when it is dispersed in immiscible PCL. Nevertheless, the presence of PCL in the blends can extend the physical integrity of the samples in the degradation medium as well as their mechanical properties for longer periods of time as compared with neat PPDX. Therefore, the blends may be good candidates for replacing neat PPDX in specific applications requiring longer life time of the material. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 110: 3848-3858, 2008