Strong and tough fully physically crosslinked double network hydrogels with tunable mechanics and high self-healing performance

Suffering weak mechanical properties, hydrogels are generally limited for high load-bearing applications. Herein, chitosan and poly(acrylic acid) (PAA) are employed as double networks (DN), and metal-coordination and chain entanglement are exploited as dual crosslinks to develop fully physically crosslinked DN hydrogels. In spite of the non-covalent crosslinking, the hydrogel exhibits impressive tensile properties (3.7 +/- 0.12 MPa) and toughness (1200 +/- 50% of elongation at break and 2.8 x 10(3) J m(-2) of fracture energy). In addition, good fatigue resistance and self-recovery performance are achieved for the hydrogel because of their supramolecular nature. Notably, the DN hydrogel display good self-healing property with recovered fracture stress and strain of 1.4 MPa and similar to 700%, respectively. The results indicate that the supramolecular design proposed in this work can bring more benefits for wide applications of hydrogel.