Enhancing the degradability of poly(lactic acid) through the introduction of main-chain thionoester linkages by ring-opening copolymerization

Abstract Poly(lactic acid) (PLA) is often used as a sustainable alternative to petrochemical-based single-use plastics, but its slow degradation can lead to waste accumulation in the environment. To address this problem, we modified the backbone structure of PLA by replacing some carbonyl oxygen atoms with sulfur atoms to impart weaker thionoester linkages. Thiocarbonyl L-lactide was copolymerized with lactide to synthesize copolymers with varying molecular weights and thionoester incorporation. The thermal properties and aqueous stability of the resulting copolymers were studied, and their selective degradation in response to specific stimuli was evaluated. This copolymerization approach represents a modular strategy for yielding degradable aliphatic polyesters that are potentially amenable to industrial use.