SYNTHESIS, CHARACTERIZATION, BIODEGRADATION, AND DRUG-DELIVERY APPLICATION OF BIODEGRADABLE LACTIC GLYCOLIC ACID OLIGOMERS .1. SYNTHESIS AND CHARACTERIZATION

A series of oligomers or low molecular weight polymers of lactic and/o r glycolic acid has been synthesized with different molar ratios of la ctic to glycolic acid. These oligomers have been characterized with re spect to oligomer composition, molecular weight, intrinsic viscosity, crystallinity, melting temperature, and glass transition temperature. The polymerization conditions for the lactic/glycolic acid oligomer sy ntheses were as follows: 180-220 degrees C, 5 mm Hg, 5 h, and 0.1 wt% of catalyst (antimony oxide) concentration. The polymeric compositions correlated to the feed ratios of lactic to glycolic acid. The molecul ar weight of the oligomers ranged from 895.8 +/- 48.7 to 1368.0 +/- 0 D with the intrinsic viscosity ranging from 0.0513 to 0.0814 dl g(-1). The lactic/glycolic acid oligomers were found to be amorphous. The gl ass transition temperatures of the lactic/glycolic acid oligomers were lower than physiological temperature.