Biodegradable elastic photocured polyesters based on adipic acid, 4-hydroxycinnamic acid and poly(ε-caprolactone) diols

A novel series of photocurable biodegradable polyesters (CAC/PCL) were synthesized by a high-temperature solution polycondensation of poly(ε-caprolactone) (PCL) diols varying molecular weight (MW; 1250, 2000, 3000) and a diacyl chloride of 4,4′-(adipoyldioxy)dicinnamic acid (CAC) as a chain extender derived from adipic acid and 4-hydroxycinnamic acid. The resulting polyesters were photocured by the ultraviolet (UV) light irradiation (λ>280 nm) in order to prepare elastic polyester with enhanced thermal and mechanical properties. The effects of photocuring by the UV light irradiation on the thermal, tensile and hydrolytic properties of the CAC/PCL were examined. DSC indicated that the melting temperatures and the crystallinities are decreased by the photocuring. The tensile properties of the photocured CAC/PCL films depended on the MW of PCL-diols and photocured time. The CAC/PCL1250 films photocured for 10–60 min exhibited a strength-at-break of 3.1–4.7 MPa and an elongation-at-break of 640–1500%, and recovered very rapidly to the original size from 90 to 300% extension. Enzymatic degradation was performed in the phosphate buffer solution (pH 7.2) with Ps. cepacia lipase at 37 °C and evaluated by the weight loss. Non-photocured CAC/PCL films were degraded very rapidly and the weight loss after 3 h incubation was more than 60%. The weight loss of the photocured films decreased remarkably with increasing the photocuring time due to the increase of cross-linking density, while it increased with increasing the MW of PCL-diols. The photocured CAC/PCL1250 film is promising as a novel biodegradable elastomer for biomedical applications as well as environmental applications.