Standard methods for characterizations of structure and hydrolytic degradation of aliphatic/aromatic copolyesters

Aliphatic/aromatic copolyesters, which possess good mechanical property and degradability, are of immense interest. Standard characterization techniques for the copolymer structure and degradation behaviors have been developed. The techniques are applied to examine hydrolytic degradation of poly(ethylene terephthalate-co-lactic acid) in a phosphate buffer solution (pH 7.2) at 60 °C. The weight loss of the copolymer and pH of the medium as a function of time are examined. 1H NMR spectra provide information on microstructure and molecular weight of the samples, where deviations of the results from the actual values are observed, due to low solubility of the copolymer. More accurate results are obtained from TGA and FTIR experiments, as the samples are characterized in bulk. Insight into degradation mechanisms of the copolymer is derived from FTIR spectra. The content of aromatic esters in the soluble degraded species is determined from UV-Vis spectroscopy. These standard methods can be applied to various types of degradable aliphatic/aromatic copolyesters, which are essential in property assessment and determination of their potential applications.