Biodegradable liquid crystalline polyesters of hydroxyphenylalkanoic acids: Synthesis and in vitro degradation studies of poly[3-(4-oxyphenyl)propionate-co-4-oxybenzoate]

Liquid crystalline copolyester of 3-(4-hydroxyphenyl)propionic acid (HPPA) of natural origin with 4-hydroxybenzoic acid (HBA) was synthesized by direc t acidolytic polycondensation of the pure acetoxy derivatives of the monome rs. The copolyesters were characterized by IR and NMR spectroscopy and by v iscosity, TGA, DSC and PLM measurement. The HPPA/HBA50:50 copolyester showe d birefringence with nematic schlieren texture above 220 degreesC with melt processability. The in vitro hydrolytic degradability of the polyesters wa s studied by noting water absorption in buffer solutions of pH 7 and 10 at 30 and 60 degreesC. The degradation observed at 30 degreesC and pH 7 was 0. 7 wt%, in the case of HPPA/HBA50:50 copolyester after 340 hours. At pH 10 a nd at 60 degreesC, the degradation reached 2.75 wt% after 340 hours. The de gradation was also proven by DSC, TGA, WAXD, and SEM techniques. The result s indicated considerable degradation compared to commercial Vectra(R).