Study of the hydrolytic degradation of polydioxanone PPDX

The hydrolytic degradation of bioabsorbable polydioxanone (PPDX) was studied in a phosphate buffer solution, pH = 7.4, 37 degrees C. The degradation was evaluated by analyzing the changes in the elastic modulus and morphological changes. After 10 weeks, the weight loss, pH and molecular weight changes suggested diffusion of low molecular weight chain segments into the reaction medium as a consequence of the breaking of ester bonds in the material. The crystallinity (X-c) increased with hydrolysis time, indicating the first step of the degradation process. Modulus was found to decrease, indicating that chain scission proceeded in two steps: the first occurring in the amorphous regions of microfibrils and intermicrofibrillar space; the second in the crystalline regions, resulting in a lower stress value for the chain segments when submitted to external forces. Surface morphological changes suggest a heterogeneous degradation mechanism by layers. (C) 2000 Elsevier Science Ltd. All rights reserved.