Photo- and bio-degradation of poly(ester-urethane)s films based on poly[(R)-3-Hydroxybutyrate] and poly(ε-Caprolactone) blocks

Biodegradable segmented poly(ester-urethane)s derived from telechelic dihydroxy-poly[(R)-3-hydroxybutyrate], acting as hard segments, and poly(ε-caprolactone)-diols, acting as soft segments, using 1,6-hexamethylene diisocyanate, as non toxic connecting agent, were synthesized. The copolymers were characterized with regard to their molecular weight by GPC and their main thermal transitions by DSC. These copolymers as well as PHB were exposed to UV-irradiation for different time intervals and the changes in the chemical structure were analyzed by FTIR spectroscopy. Under our experimental conditions, it was found that the increase of irradiation time was accompanied by increase of the proportion of the gel fraction and the decrease of the intrinsic viscosity of the soluble fraction of the investigated copolymers. The biodegradability of PHB and poly(ester-urethane) sample containing ~40 wt% PHB before and after UV-irradiation was investigated under soil burial. The results showed that the photolysis in air prior to biodegradation increased the rate of degradation.