高分子量聚对二氧环己酮体外降解研究

对高分子量(Mν=2.8×105)的聚对二氧环己酮条状样品在37℃磷酸缓冲溶液(PBS)中的降解行为进行了研究,通过定期观察其吸水率与质量损失,pH,特性黏数,降解过程中样品形态与晶体结构,热力学性能与机械性能的改化,发现此高分子量的聚对二氧环己酮在体外降解过程中质量损失与吸水率变化不大,但分子量下降明显,同时样品表面缺陷逐渐增加;结晶度与玻璃化温度随之改变,但其晶体结构基本保持不变;到第6周时,其力学强度基本消失.证明高分子量PPDO具有较慢的降解速度,显示出很好的稳定性.

STUDY ON HYDROLYTIC DEGRADATION OF POLY(p-DIOXANONE) WITH HIGH MOLECULAR WEIGHT IN VITRO

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),(M_ν=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(T_g)of samples decreased notably,while the degree of crystallinity(D_c)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.