Alpha-Hydroxy Acid Based Biodegradable Polymers Poly(L-Lactide) And Polydepsipeptides
Poly(L-lactide), PLLA, is a poly-alpha-hydroxy acid which has been investigated extensively for possible use as a biodegradable polyester in medicine. Methods for the synthesis of L-Lactic acid polymers include polycondensation of L-Lactic acid, ring opening polymerization of L-Lactic acid anhydrosulphite and L-Lactic acid O-carboxyanhydride. In a study on the polymerization kinetics, the crude polymerization products obtained at different reaction times were analyzed for their monomer content by 200 MhzH NMR spectroscopy, while the purified PLLA samples were characterized by combined GPC-LALLS measurements. The polymerization reaction of L-Lactide in the bulk appeared to be first order in monomer and first order in initiator. An interesting class of biodegradable polymers is the polydepsipeptides, polymers composed of alpha-amino acid and alpha-hydroxy acid residues. After penetration of water into the polymer matrix, degradation starts through a bulk hydrolysis of ester bonds and the molecular weight decreases.