Ultratough Organic–Inorganic Bicontinuous Network Hydrogel via Crosslinking Liquid‐Like Inorganic Ionic Clusters With Polymer Chains

ABSTRACT Mechanically robust hydrogels hold great promise in structural engineering and materials fields. However, high strength and high toughness are usually mutually exclusive, and simultaneously achieving both properties in a hydrogel remains challenging. Inspired by the structural design of double‐network hydrogels and nano‐reinforcement strategies, herein, we develop an ultratough hydrogel featuring an organic–inorganic bicontinuous network structure. Specifically, liquid‐like calcium phosphate clusters (CPC) and polyvinyl alcohol (PVA) molecular chains are crosslinked at the ionic–molecular level to form an organic–inorganic bicontinuous network, which imparts the resulting PVA/CPC hydrogel with outstanding mechanical properties (tensile strength: 32.89 ± 4.67 MPa, toughness: 108.50 ± 19.27 MJ m ^{− 3} ), surpassing those of most existing high‐performance hydrogels. Furthermore, the PVA/CPC hydrogel demonstrates exceptional energy absorption and dissipation capabilities, enduring 100 000 cycles of stretching in water without fracture, thus exhibiting remarkable fatigue resistance. Damaged PVA/CPC hydrogel can be repaired via organic–inorganic re‐crosslinking. These superior mechanical properties provide a solid foundation for the large‐scale application of the PVA/CPC hydrogel in soft robotics, energy‐absorbing cushioning materials. The proposed organic–inorganic crosslinking strategy, based on liquid‐like inorganic ionic clusters and polymer chains, offers a promising approach for producing high‐performance bicontinuous network structural materials.