Preparation And Properties Of Biodegradable Aliphatic Polycarbonate Research

Biodegradable polycarbonates are a class of important biomedical materials. Aliphatic polycarbonates have surface erosion property and good biocompatibility and biodegradability because they decompose into carbon dioxide and neutral diols after degradation. Various main chain structures and functional pendent groups enable biodegradable polycarbonates to possess versatile physiochemical and biological properties in order to meet needs in biomedical applications. Nowadays, they have been extensively used as bioabsorbable sutures, bone fixing materials and drug controlled release carriers.An new aliphatic polycarbonate poly [(propylene oxide)-co-(carbon dioxide)-co-(maleic anhydride)] (PPCMA) was successfully synthesized by the terpolymerization of carbon dioxide(CO₂) , propylene oxide(PO), and maleic anhydride(MA), using a polymer supported bimetallic complex as catalyst. The resulting terpolymers were characteristic by FTIR, ¹H-NMR, ¹³ C-NMR measurements. Because of the existence of the ester unit, the hydrophilicity and non-enzymatic degradability of PPCMA was found to be much better than that of PPC. With increasing MA content, the hydrophilicity and non-enzymatic degradability of PPCMA were improved. The hydrophile mass fraction was as high as 15．1% and the weight loss reached 26．78% after 8 weeks while the content of MA was 29．45%. The change of the molecular weight was inapparent and little acidic substance was released during the degradation process.Thermal properties and kinetics of thermal degradation of PPCMA were studied in this paper. The result showed that the glass transition temperatures and degradation temperatures of the terpolymers were much higher than that of PPC. It was found that the apparent activation energy of themal degradation was 78．44～81．04 KJ/mol and the themal degradation kept to A₂ nucleation and growth of Sigmoidal mechanism.The PPCMA-glucose microcapsules were prepared by the water-in-oil-in-water multiple-emulsion method. The factors, which could obviously impact on the carried-drug capability of PPCMA, were studied systematically. The PPCMA-glucose microspheres were obtained with smooth and spherical surface. The glucose release test revealed that the glucose release speed of the PPCMA-glucose microcapsules in pH=7．4 PBS was more quickly than that in pH=1．0 KCl-HCl. The glucose release speed of the PPCMA-glucose microcapsules was much faster than that of PPC-glucose in pH=7．4 PBS.