Lactic Acid and Ricinoleic Acid Based Copolyesters

Abstract

Copolyesters based on purified ricinoleic (RA) and lactic (LA) acids with different RA:LA ratios were synthesized by thermal polycondensation and by transesterification of high molecular weight poly(lactic acid) (PLA) with ricinoleic acid and repolyesterification. Thermal polycondensation resulted in random P(LA−RA) copolyesters of molecular weights between 2000 and 8000 with the polymers containing 20% or more RA were liquid at room temperature. Transesterification of high molecular weight PLA with pure ricinoleic acid and repolymerization of those oligomers by condensation resulted in multiblock P(PLA−RA) copolyesters of molecular weights between 6000 and 14000. Polymers containing 50% RA were liquid at room temperature. 1H NMR spectroscopy analysis coupled with information from DSC allowed determination of the polymer structure. Polymers prepared by thermal polycondensation are random copolymers (h > 1), while the copolymers prepared by transesterification have a multiblock character (h < 1). The LA nu...