Environmental biodegradability of hydrolysable polyesters from renewable resources

The predicted growth in plastic demand and the targets for global CO₂ emission reductions require a transition to replace fossil-based feedstock for polymers and a transition to closed-loop recyclable, and in some cases to, biodegradable polymers. Renewable resources could be carbon “already above the ground”, including biomass, CO₂, and recycled fossil based materials. Additionally, the first two resources provide opportunities for alternative building blocks for polymer synthesis and subsequently could provide better properties (e.g. incorporate environmental biodegradability as a design feature). Polyesters have the potential to be recycled by both mechanical and chemical processes. Therefore, using (environmentally) biodegradable polyesters could help to smooth the transition from the current scenario (with leaks to the environment) to a future circular economy (with most plastics recycled). Moreover, (co-)polyesters provide a wide range of applications with (to some extent) tuneable physical and thermal properties by variation of (chemical) structures and compositions as well as biodegradability.
The biodegradation of novel hydrolysable polyesters (i.e. poly(lactic-co-glycolic acid) (PLGA, good barrier properties) and Poly(isosorbide oxalate) (PISOX, high T_g) copolyesters) was investigated and the underlying mechanisms with an emphasis on structure-biodegradability/hydrolysis relationships was discussed. Generally, they show biodegradability comparable to (or even better than) that of cellulose under the same conditions (in soil and marine environment) except PISOX copolymers with 1,4-cyclohexanedimethanol and terephthalic acid as third and fourth comonomer. Meanwhile, the methodology that make (bio)degradability studies as part of a materials development process economical and, at the same time, time-efficient and of high scientific quality was presented.