Zn2+-coordinated hierarchical dynamic crosslinking in phenolized lignin-based polyurethane elastomers: mechanical self-reinforcement and dynamic adaptability enhancement

Abstract

Lignin-based polyurethane elastomers (LPUes) offer a sustainable alternative to petroleum-derived counterparts yet often suffer from a trade-off between mechanical strength and dynamic reversibility. In this work, a multi-level dynamic crosslinking network comprising dynamic phenol-carbamate bonds, metal-coordination bonds, and hydrogen bonds was innovatively constructed by introducing Zn²⁺ into phenolized lignin-based polyurethane elastomers (Zn-LPUes). The resulting Zn-LPUes achieve an optimal balance of high mechanical performance and dynamic functionality. The optimized sample exhibits a tensile strength of 42.8 MPa, an elongation at break of 1569%, and a toughness of 270.5 MJ m⁻³. Notably, mechanical training efficiently induces and stabilizes chain orientation, resulting in a 50.4% tensile strength enhancement to 64.5 MPa. The hierarchical dynamic bonding enables excellent reprocessability, with 97.4% tensile strength retention after two hot-pressing cycles and over 80% retention after five cycles. Moreover, such Zn-LPUes demonstrate efficient near-infrared (NIR)-triggered self-healing, recovering 74.8% of tensile strength and 93.4% of elongation at break after 20 min of irradiation. This work provides a viable strategy to reconcile mechanical robustness with dynamic reversibility in sustainable elastomers, advancing the development of high-performance biomass-derived materials.