Synthesis of poly(L-lactic-co-glycolic acid) telechelic prepolymers by direct melt polycondensation, and their characterization

Abstract

A series of L-lactic/glycolic acid polymers (PLLGAc) differing in molar ratios of L-lactic (L-LAc) to glycolic (GAc) acid and of relatively low molecular weights [Mn(theor) = 4000] were synthesized by direct melt polycondensation in the presence of 1,4-butanediol and sulfuric acid as a molecular weight regulator and catalyst, respectively. The characterization experiments (FT-IR, 1H NMR) demonstrated a good correlation between the polymer compositions and the ratios of L-LAc and GAc in the feed. The DSC studies of the prepolymers indicated that the melting point as well as degree of crystallinity of PLLGAc decreased with the increase in the molar fraction of GA units in the copolymer. The glass transition temperatures of the polymers varied from 29 to 45 C degrees, depending on the polymer composition. The alkaline hydrolyzability (0.1 M NaOH, 37 C degrees) of the polymers is strongly affected by GA content in PLLGAc. With increasing GA content in the prepolymer, weight loss of a sample becomes faster.