Tailoring physical machinery and biodegradation properties of unsaturated polyesters through manipulation of synthesis and curing conditions

Unsaturated polyesters, in particular unsaturated polyesters with low volatility or without styrene, are gaining increasing importance in gel coatings, adhesives and molding resins. However, the cured unsaturated polyesters are usually described as non-degradable polyesters, which will lead to environmental and safety problems. In this paper, a kind of unsaturated copolyester with different binary acid composition, named poly (butylene succinate-co-butylene itaconic) (PBISx), was synthesized. Then, a photo-curable polyester(CPBIS) which can degrade under certain conditions was obtained by thiol - ene click reaction without adding styrene curing agent. The physical properties of unsaturated polyester PBISx can be effectively controlled by changing the ratio of raw materials, such as T g from - 23.7 o C to - 45.2 o C, Xc from 38% to 14%, and T m from 109.6 °C to 74.9 °C. It was found that CPBIS completely lost its degradability in lipase when its gel rate exceeded 98%. However, CPBIS could be degraded in GSH regardless of the gel rate, and lipase resumed its degradation in the GSH/lipase mixture, and the degradation rate reached 12% at 70h, attributed to the selective degradation of C-S-C bond by GSH and the secondary degradation of ester bond by lipase.