Ring-opening Polymerization Of Adipic Anhydride Or Ethylene Carbonate Catalyzed By Rare Earth Complexes: The Synthesis, Degradation And Biocompatibility Research

In recent years, biodegradable polymeric materials have been used for drug delivery, bone and cartilage repairing, tissue engineering. Compared to nonbiodegradable polymers, they have favorable advantages. That is, they do not need to be taken out and can degrade into small molecules in body. Biodegradable polymers are the most potential materials for biomedical applications. In this paper, recent developments of biopolymers were reviewed. Novel biodegradable polymers, polyanhydrides and aliphatic polycarbonate have been developed since 1980s'. These materials are highly biocompatible, demonstrated by tissue response and toxicological study. In addition, they show surface-eroding behavior, thus provide a sustained release rate over a long period of time, and the rate is adjustable. So these materials are very promising in biomedical applications. This paper presented an outline of recent researches and clinical applications of these polymers.Lanthanum tris(2,6-di-tert-butyl-4-methylphenolate) was applied to catalyze the ROP of AA and the copolymerization of AA with CL. Various conditions were examined. The copolymer structures are identified by GPC, ~1H NMR and DSC. Only PAA/PDTC or PAA/ PTMC blends were obtained by the copolymerization of AA and DTC or TMC.The ring-opening copolymerization of adipic anhydride with propylene oxide has been carried out using yttrium triflates as a catalyst. Poly(propylene adipate) could be synthesized by controlling the copolymerization conditions. Poly(AA-alt-PO) with M_n=4,400, could be synthesized. The copolymerization procedure was tracked by ~1H NMR analysis and was found that the mechanism is very complex.The ring-opening copolymerization of ethylene carbonate (EC) with (CL) was carried out using Ln(DBMP)3 as a single component catalyst. Copolymers containing 22.0% EC contents with high molecular weights (up to 23.97×10~4) and moderate molecular weight distributions (between 1.66 and 2.03) were synthesized at room temperature. Compared with homopoly(ε-caprolactone), the copolymers with EC units (22.0%) exhibited higher glass transition temperatures (-35.6℃), lower melting temperatures (44.5℃) and greatly enhanced elongation at break (2383%) based on dynamic mechanic analysis. The crystallinities of the copolymers decreased with the increasing EC molar percentage in the products.PAA/PCL-b-PAA, PAA/PDTC and PAA/PTMC blends were prepared by in situ copolymerization and solution blending methods. The matrices were degraded in vitro. PAA degraded fast within 24 h. Porous membranes were remained. It is founded the membranes of the matrices prepared by in situ polymerization have more regular cavities.Poly(CL-co-EC)s were proved as a suitable and biocompatible copolymer with the changeable physico-mechanical properties. Biocompatibility tests of the copolymers showed that they good cell adhesion, growth viability, morphology and mitochondrial activity of L929 cells. Hemolysis test and muscle transplantation approved poly(CL-co-EC)s could be used as biocompatible material.