Supertough and Biodegradable Poly(Lactic Acid) Blends with “Hard–Soft” Core–Shell Unsaturated Poly(ether-ester) through Self-Vulcanization

The development of a biodegradable material with super toughness while preserving its biodegradability poses a significant challenge. In this study, a series of biodegradable unsaturated multiblock poly(ether-ester) poly(butylene succinate-co-fumarate)-poly(ethylene glycol) (PBSFG) was synthesized and blended with polylactic acid (PLA). The impact of fumaric acid in PBSFG on the mechanical and degradation behavior of PLA/PBSFG blends was investigated. The results revealed that fumaric acid facilitated self-vulcanization of PBSFG, thereby leading to the formation of a “hard–soft” core–shell rubber phase within PLA. The core comprised the poly(butylene succinate-co-fumarate) (PBSF) segment, while the shell consisted of the PEG chain segment. The notched impact strength and elongation at break of PLA/PBSF20G blends showed significant improvements compared with pure PLA, with values of 76.1 kJ/m2 and 303.1%, respectively. These values are 24 and 101 times higher than those of pure PLA. Furthermore, enzymatic degradation experiments were conducted on the PLA/PBSFG blends, which demonstrated that the fumaric acid content significantly accelerated the degradation rate. The degradation rate of PLA/PBSF30G even surpassed that of pure PLA. Ultimately, this work successfully yielded fully degradable and supertough PLA blends.