Lignin-incorporated PVA/chitosan hydrogels with highly enhanced toughness and rigidity through a non-covalent crosslinking strategy

Supramolecular hydrogels assembled through dynamic non-covalent interactions are renowned for their reversible reorganizability, yet often suffer from inadequate mechanical strength. In this work, sulfonated lignin serving as a reversible interfacial mediator was used to establish dynamic non-covalent bonds throughout the network, which allow for energy dissipation and structural reconfiguration under stress. The soaking strategy employing a saturated lignin solution effectively augments the crosslinking density and dramatically increases the network compactness of the resulted hydrogel. Through structural engineering design at the molecular to micro-nanoscale, the optimized hydrogel exhibits exceptional overall performance. It achieves a tensile strength of 36.5 ± 2 MPa, a Young's modulus of 19.4 ± 1.25 MPa, and a toughness of 86.1 ± 7.4 MJ/m 3 , representing dramatic increases of 67, 191, and 174 times, respectively, compared to the poly (vinyl alcohol)/chitosan hydrogel. These results suggest a synergistic enhancement of both rigidity and toughness. Mechanistic insights into the interface revealed that the sulfonate groups in lignin play a pivotal role in enhancing the crosslinking density, primarily by significantly improving interfacial viscoelasticity and fostering strong molecular-level interactions. This interfacial design strategy provides a promising structural engineering approach for developing high-performance supramolecular hydrogels, with the potential applications in various fields, including soft engineering and structural composites.