Strong and Tough Double‐network Hydrogels With Modulus Compatibility and Reinforced Interfacial Interactions

The double‐network strategy is a classic approach for preparing the hydrogels with high mechanical performance. However, the poor modulus compatibility between the rigid and soft polymers causes rigid network stress concentration and irreversible fracture, thus ultimately limiting hydrogels applicability. Here, we propose a strategy to fabricate strong and tough double‐network hydrogel by regulating modulus compatibility and reinforcing interfacial interactions between poly(vinyl alcohol) and cellulose nanofibers. The introduction of tannic acid not only enables decrease of modulus of CNF rigid network within the double‐network hydrogel, but also reinforces the noncovalent interactions between the double networks, leading to the improvement of mechanical properties. The resulted hydrogel exhibits an extremely high tensile strength of 39.7 ± 1.7 MPa and an outstanding toughness of 155.2 ± 2.5 MJ m −3 . Furthermore, the double‐network hydrogel has excellent fracture energy, fatigue resistance and biocompatibility. This work provides a practical avenue to design strong and tough hydrogels that can be exploited for biomedical application.