Multi‐Solvent‐Induced Gradient Aggregation Rendered Superstrong, Tough, Stretchable, and Fatigue‐Resistant Lignin‐Based Supramolecular Hydrogels

A hydrogel that is expected as a biomedical load‐bearing material remains a substantial challenge. In this work, a multi‐solvent‐induced gradient aggregation state strategy is developed to construct lignin‐based supramolecular hydrogels that feature superstrong, tough, stretchable, and fatigue‐resistant properties. The multi‐solvent high‐temperature annealing induces the gradient crystallization of polyvinyl alcohol and the self‐assembly of lignin. The interior strong hydrogen‐binding and the external weak non‐covalent‐binding forms a gradient aggregation state microstructure and compact macrostructure, where lignin acts as an interfacial molecular bridge. By sharing interconnection points to collaboratively dissipate energy, the developed hydrogels demonstrate high modulus (74.4 MPa), toughness (90 MJ m−3), tear (34,000 J m−2), tensile (24.8 MPa), and compressive strength (60 MPa). Moreover, such lignin‐based supramolecular hydrogels also exhibit extraordinary fatigue resistance, biocompatibility, and reactive oxygen species scavenging activity. This gradient non‐covalent conjoined‐network caused by multi‐solvent high‐temperature annealing provides a new design strategy and potential for developing biomaterials that mimic biomedical load‐bearing materials (e.g., natural tendons and ligaments).