As there was no report on the degradation properties of poly(p-dioxanone)(PPDO) with molecular weight above 2.0×105

and most studies on PPDO were carried out using monofilament suture of poly(p-dioxanone) as model in previous reports

so it was interesting to study the behavior of PPDO with higher molecular weight in other solid form

such as plates and bars.The in vitro-hydrolytic degradation of high molecular weight poly(p-dioxanone)

(Mν＝2.8×105) was studied by the changes of weight retention

water absorption

pH value

intrinsic viscosity

tensile strength

break elongation

thermal properties

crystalline structure and the morphology of PPDO bars in phosphate buffered saline (PBS) (pH 7.44) at 37℃ for 8 weeks.During 8 weeks degradation in PBS

the PPDO samples exhibit obvious changes in their morphology

thermal properties

mechanical properties and degradation behaviors.It was found that the weight loss and water absorption increased slightly

at the same time pH almost maintained original value while the significant decrease of molecular weight was observed.The surface micrographs of PPDO samples showed that microcracks grew with the hydrolytic degradation.The glass transition temperature (Tg) of samples decreased notably

while the degree of crystallinity (Dc) increased and the original crystalline structure substantially remained.The samples lost their tensile strengths and breaking elongation almost completely after 6 weeks of degradation.The results suggested that the PPDO bars with high molecular weight exhibited much smaller degradation rate in vitro hydrolytic degradation.