Biodegradable Polymers from 5-Hydroxylevulinic Acid: 1. Synthesis and Characterization of Poly(5-hydroxylevulinic acid)

As an attempt to synthesize new biodegradable polymers from renewable cellulose resources, melt polycondensation of 5-hydroxylevulinic acid (5-HLA) was reported for the first time. The resulting product, poly (5-hydroxylevulinic acid) (PHLA), was synthesized and characterized with GPC, FTIR, H-1 NMR and DSC. The in vitro degradation behaviors in phosphate-buffered saline (PBS) and in deionized water (DW) were also examined. The molecular weight of PHLA is not high (several 1,000s), but it possesses unordinary high glass transition temperature (as high as 120 degrees C). This is very different from existing aliphatic polyesters that usually have T(g)s lower than 60 degrees C. The high T-g is attributed to the formation of inter-and/or intramolecular hydrogen bonds due to a characteristic keto-enol tautomerism equilibrium in the polymer structure. PHLA readily degraded hydrolytically in aqueous media.