Dual-Cross-Linked Biobased Degradable Poly(lactic acid) Elastomers with High Toughness and Thermal Stability

Poly(lactic acid) (PLA)-based elastomers (PLAEs) have gained significant attention as sustainable materials due to their biomass-derived origin and biodegradability. However, their inherent brittleness and low thermal stability severely limit practical applications. Inspired by the hierarchical architecture of spider silk, the dual-cross-linking strategy was adopted to simultaneously enhance the toughness and thermal stability while preserving biodegradability by introducing tannic acid (TA) and isophthalic dihydrazide (IPDH) into PLAEs. TA promoted a high cross-linking density of molecular chains to enhance the thermal stability, while IPDH induced the formation of high-density hydrogen bonds to serve as energy-dissipating phases to achieve remarkable toughness. The PLAEs prepared with dual chain extenders (PLAE-TI) exhibit a high glass transition temperature of −6.1 °C, which is approximately 15 °C higher than that of the PLAE without chain extenders (PLAE-0). Furthermore, PLAE-TI demonstrates significantly enhanced mechanical properties with a tensile strength of 45.4 MPa and toughness of 71.5 MJ/m³, corresponding to 5.6-fold and 2.0-fold improvements over PLAE-0, respectively. This bioinspired hierarchical architecture not only resolves the long-standing trade-off but also endows multifunctionality, including antibacterial activity, UV shielding, and controlled degradability, offering the potential for low-waste and environmentally friendly preparation in scalable applications of biomedical devices and flexible electronics.