Tough Hydrogels with Robust Wet Adhesion via Entropy-Driven Hydrogen Bond Reorganization

High-performance hydrogels for tissue repair should provide both mechanical reinforcement and interfacial adhesion. However, conventional strengthening strategies typically rely on hydrogen bonding within the network, whose inherent bonding energy and restricted configurational freedom intrinsically limit chain mobility at the interface, ultimately weakening wet adhesion. To overcome the strength-adhesion trade-off caused by hydrogen bond distribution, this study proposes an entropy-driven strategy that decouples the spatial distribution of hydrogen bonds to simultaneously achieve high bulk strength and robust wet adhesion. Starting from a conformationally disordered and high-entropy mixture, the hydrogen bonds then concentrate in the bulk through entropy-favored reconfiguration to strengthen the network. The bulk-interface energetic and conformational mismatch in turn triggers a localized phase separation, which reduces interfacial entropy to form a hydrogen bond-depleted nanoconfined water layer. This layer permits dynamic polymer-tissue hydrogen bonding, enabling robust wet adhesion without loss of bulk strength. The resulting hydrogel can rapidly conform to tissue surfaces, forming a high modulus structure (∼13 MPa) that withstands hydrostatic pressures up to 368 mmHg. It achieves sealing beyond physiological limits and maintains stable adhesion, demonstrating effective repair in models of skin injury, oral mucosal ulceration, and cardiac bleeding.