Synthesis of l-Lactide via Degradation of Various Telechelic Oligomeric Poly(l-lactic acid) Intermediates

Abstract

Hydroxyl-terminated telechelic oligomeric poly(l-lactic acid), namely t-OPLLA-(OH)n (n = 2, 3, 4), and carboxyl-terminated telechelic oligomeric poly(l-lactic acid), namely t-OPLLA-(COOH)2, were respectively synthesized by the copolymerization of l-lactic acid with comonomers 1,4-butanediol, glycerol, pentaerythritol, and succinic acid, while the normal oligomeric(l-lactic acid), namely OPLLA, was obtained through the self-polymerization. The effects of the type and amount of comonomer as well as the molecular weight of starting oligomer on both the generation of l-lactide and the molecular weight of residual oligomer were examined. It was found that the selectivity to l-lactide for the degradation of t-OPLLA-(OH)n (91.7–93.56%) was slightly larger and that for the t-OPLLA-(COOH)2 was almost unchanged, relative to that for the degradation of OPLLA (90.3%). Both the yield of crude lactide and reaction rate for the degradation of t-OPLLA-(OH)n were higher, and those for t-OPLLA-(COOH)2 were lower than for t...