Synthesis of High-Toughness Polyesters Using Xylose and Lactic Acid and Analysis of Their Biodegradability

The production of plastic materials consumes a large amount of petroleum resources, leading to the depletion of these resources and environmental problems associated with plastic disposal. Recently, the demand for sustainable bioplastics has increased, necessitating an appealing strategy for the development of bioplastics using sustainable raw materials, including inedible resources that degrade rapidly under mild conditions. In this study, poly(alkylene xylosediglyoxylates)-co-poly(lactic acid) (PAX-co-PLA) is synthesized from xylose and lactic acid, which can be conditioned from inedible resources through a two-step condensation process. The thermal stability and mechanical properties can be tuned by changing the compositions of the copolymers. Among the PAX-co-PLA, PEX-co-PLA exhibits a high Tg (glass transition temperature) of 106 °C and PHX-co-PLA exhibits an elongation at a break of 106 ± 4%. The biodegradability is evaluated, focusing on neat PHX and PHX-co-PLA, which exhibit high toughness. Both exhibit significant disintegration in the compost. Neat PHX and PHX-co-PLA exhibit biodegradability by BOD (biological oxygen demand) of 14% and 13% in seawater, respectively. Furthermore, PHX-co-PLA exhibits a contact angle (76.2 ± 1.7°) comparable to that of PLA, retains its shape for 2 weeks in water at 20 °C, and shows improved water resistance compared to neat PHX. With its thermoformability, water resistance, and partial biodegradability, PAX-co-PLA is expected to have wide applications and address environmental issues, including the reduction in microplastic pollution.