Abstract
To obtain a biodegradable polymer material with satisfactory thermal properties, higher elongation and modulus of elasticity, a series of biodegradable aliphatic/aromatic co-polyesters, poly(hexylene terephthalate-co-lactide) (PHTL), was synthesized via melt polycondensation from dimethyl terephthalate (DMT), 1,6-hexanediol (HDO) and oligo(lactic acid) (OLA) in the presence of titanium (IV) butoxide. The resulting co-polyesters were characterized by proton nuclear magnetic resonance (1H-NMR), differential scanning calorimetry, thermogravimetry and wide-angle X-ray scattering, and their melting temperature, melting heat of fusion, glass-transition temperature (T g) and thermal decomposition temperature (T m) (1.5 wt%) were obtained. Only one T g and two T m values were observed for all samples, and were found to decrease gradually with increase of lactide moieties. By using the relative integral areas of the dyad peaks in the 1H-NMR spectrum of co-polyesters PHTL, the sequence lengths of the hexylene terephthalate (n HT) units in the resultant co-polyesters are 3.5. The PHTL co-polyesters exhibited a pronounced hydrolytic degradability, which increase with the content in lactide units. 1H-NMR analysis of the residue left by evaporation of the mother solution after hydrolytic degradation revealed that the degradation products consisted mostly of lactide and hexylene terephthalate blocks.