A NEW CHAIN EXTENSION REACTION ON POLY(LACTIC-GLYCOLIC ACID) (PLGA) THERMAL OLIGOMERS LEADING TO HIGH-MOLECULAR-WEIGHT PLGA-BASED POLYMERICPRODUCTS

A novel and effective chain-extension procedure for obtaining high-mol ecular-weight PLGA-based bioerodible polymers is described. This proce dure consists in a polycondensation reaction between PLGA thermal olig omers of average molecular weight 1000-3000 and bischlorofomates of ei ther simple diols or a,alpha,omega-bis-hydroxylated oligomers, such as polyethyleneglycols or bis-hydroxy terminated poly-epsilon-caprolacto nes. In the latter case, multiblock copolymers are obtained. By varyin g the nature and the length of the starting diol, as well as the lacti c/glycolic acid molar ratio in the starting PLGA oligomer, products wi th widely different physicochemical properties can be synthesized. In particular, dissolution times in aqueous media can be tuned within an ample range, from a few days to several months. This provides exceptio nal opportunities for designing products whose properties are tailored in view of specific applications in the biomedical held. (C) 1998 SCI .