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.
Li et al. (Wed,) studied this question.