Synthesis and characterization of novel functionalized polylactides with pendent hydroxyl arms

A class of polyesters have been synthesized by the ring-opening copolymerization of dl-lactide (DLLA) and RS-benzyloxyethyl-β-malolactonate (MABE) using different monomer feeding doses. The compositions and structures of poly(dl-lactide-co-RS-benzyloxyethyl-β-malolactonate) (poly(DLLA-co-MABE)) were determined by 1H and 13C NMR measurements. GPC measurement showed that the molecular weight of the copolymers decreased as the MABE content increases. After catalytic hydrogenation of the benzyl ether functions, the desired copolymers with pendent hydroxyl arms, poly(dl-lactide-co-RS-hydroxyethyl-β-malolactonate) (poly(DLLA-co-MAHE)), were recovered. Thermal properties of poly(DLLA-co-MABE) and poly(DLLA-co-MAHE) copolymers were examined by differential scanning calorimetry (DSC) measurement. Single glass transition temperature appeared in the DSC spectra, which confirmed that the copolymers were true copolymers and not blends. The hydrophilicity of poly(DLLA-co-MAHE) copolymer was tunable, which increased with the increase in MAHE content. Furthermore, the hydrolytic degradation of poly(DLLA-co-MAHE) material was investigated and the results showed that faster degradation was observed in the copolymer film containing more MAHE content.