Synthesis, characterization and biodegradability of aliphatic polyesters from cyclic diacetalized galactose

Abstract

The use of carbohydrate derivatives for polymer synthesis has attracted much attention not only because of the huge abundance and renewable character of these resources, but also due to the degradable and biocompatible behavior that can be expected for such polymers. The cyclic monomer dimethyl 2,4:3,5-di-O-methylene galactarate, which was synthesized from galactaric acid, has several attractive features linked to its rigidity, chirality, non-toxicity and hydrophilicity. Aliphatic homopolyesters poly(alkylene 2,4:3,5-di-O-methylene galactarate)s were prepared from dimethyl 2,4:3,5-di-O-methylene galactarate and the aliphatic α,ω-diols 1,6- hexanediol; 1,8-octanediol; 1,10-decanediol and 1,12-dodecanediol; and were characterized by NMR, FT-IR, viscosimetry and GPC. According to the asymmetric constitution of the galactarate unit, these polyesters displayed optical activity in solution. The thermal behavior, mechanical properties and biodegradability of these polyesters were evaluated and compared with those displayed by their homologues dimethyl adipatederived homopolyesters. All poly(alkylene 2,4:3,5-di-O-methylene galactarate)s and poly(alkylene adipate)s from synthesis were semicrystalline. Glass transition temperatures of poly(alkylene 2,4:3,5-di-Omethylene galactarate)s were higher than those observed for poly(alkylene adipate)s. The introduction of ring acetal groups improved the thermal stability and caused an increase in the elastic modulus and the tensile strength of the polyesters, and produced a reduction in the elongation at break at the same time. Finally, the degradation study revealed that poly(alkylene 2,4:3,5-di-O-methylene galactarate)s were biodegradable polyesters, and that they degraded faster than poly(alkylene adipate)s.