Biomimetic, strong, and tough hydrogels by integrating cellulose nanocrystals into polymer networks

Natural resilin represents one of the most famous biological materials with outstanding mechanical properties, which is the high resilience. Until now, the fabrication of hydrogels with high resilience to mimic resilin is still a challenge. Herein, a strategy is developed for the preparation of strong, tough, and high resilient hydrogels. Ceric ion/hydroxyl redox initiated graft polymerization of polyacrylamide is applied to integrate cellulose nanocrystals into the chemical networks of hydrogels. With the addition of N, N′-methylene bisacrylamide as chemical cross-linker, polymer networks with cellulose nanocrystals as net-points formed. Chemically bonded cellulose nanocrystals provide hydrogels with high strength and toughness. After mechanical pretreatment, the optimized polymer networks further provide the hydrogels with high resilience (∼92%). Moreover, the mechanical properties of high resilient hydrogels can be finely tuned via adjusting the N, N′-methylene bisacrylamide or cellulose nanocrystals contents, providing the opportunities to prepared hydrogel with high strength, high toughness, and high resilience that mimic different kind of elastic proteins.