Engineering Supramolecular Composite Hydrogels via “pH‐Induced Ureidopyimidinone (UPy) Tautomerization” Strategy

Abstract Hydrogels are compelling materials for emerging applications including regenerative medicine, flexible electronics, and soft robotics; however, their mechanical weakness, time‐consuming fabrication, and end‐of‐life disposal pose significant challenges. Herein, a straightforward “pH‐induced tautomerization” strategy is presented for fabricating supramolecular composite hydrogels, which harness physical crosslinking mediated by ureidopyimidinone (UPy) tautomerism to construct a leaf‐like hierarchical meshing structures involving highly dynamic microphase‐separated domains. The resultant hydrogels achieve high mechanical properties, with an ultimate stress of 1.00 ± 0.09 MPa, a strain level of 4219.62 ± 56.32%, a toughness of 11.60 ± 0.29 MJ m −3 , and a fracture energy of 28.40 ± 0.76 KJ m −2 , which are 3.9‐20 times higher than those of conventional hydrogels with similar matrices. Beyond their superior mechanical properties, these hydrogels offer a remarkable combination of high compressive strength and exceptional ductility, ensuring superior puncture resistance. The uniform distribution of hydrogen bonds endows the material with outstanding fatigue resistance, dynamic self‐healing capabilities, and shape memory performance. Additionally, the physical crosslinking facilitates effortless recycling and regeneration, as the network can be disrupted through alkaline‐induced dissociation of hydrogen bonding and electrostatic repulsion. This “pH‐induced tautomerization” strategy offers a promising route for developing high‐performance, recyclable hydrogels for advanced applications.