Synthesis And Biodegradability Of Aromatic/Aliphatic Copolyesters

In order to obtain a biodegradable polymer material with satisfactory thermaI properties,new series copolyesters,poly(hexylene terephthalale-co-lactide)(PHTL).and poly(4,4'-isopropylidenediphenyl terephthalate)-co-poly(hexylene terephthalate)-co-polylactide(PBHTL),were synthesized via direct polycondensation transesteri-fication from terephthaloyl dichloride,bisphenol-A,1,6-hexanediol,and oligo(lacticacid).These copolyesters were characterized by proton nuclear magnetic resonance(1H NMR),differential scanning calorimetry(DSC),thermogravimetry(TG)and wide-angle X-ray scattering(WAXS).Their melting temperature(T_m),melting heat of fusion(△H_m),glass-transition temperature(T_g),and thermal decomposition temperalure(T_d)(1.5 wt％)were obtained.By using the relative integral areas of me dyad peaks in 1H NMR spectrum of copolyesters PHTL,the sequence lengths of the hexylene terephthalate(n_HT)and 1actide(n_LA)units in the resultant copolyesters are 3.5 and 1.5.Compared to poly(hexylene terephthalate)(PHT),PHTL has lower Tm but higher T_g due to the incorporation of aliphatic unit into the main chains.ThePBHTL shows two-step thermal decomposition,which is correspoilding to segment of 4,4'-isopropylidenediphenyl terephthalale(BAT)and segments of hexylerie terephthalate(HT)and lactide(LA).Due to the incorporation of flexible aliphatic unit into the main chains,PBHTL has lower T_g,and shows enhanced hydrolytic degradability under a physiological conditions with increasing lactide and hexylene moieties.The copolyester PHTL and PBHTL underwent significant hydrolytic degradation at 37℃in a phosphate buffer solution.The weigth loss of PBHT82L8 copolyester consisting lO mol％BAT unit,82 mol％HT unit and 8 mol％LAurlit,is almost 22％after 5 weeks degradation.Encouraging results on biocompatibility were receiVed by initial studies of cell growth on the surface of copolyester PBHTL films.