Tough supramolecular hydrogels with excellent self-recovery behavior mediated by metal-coordination interaction

Based on the strategy of dynamic metal-coordination for improving mechanical properties, a further ideal was taken to prepare the tough hydrogels with the combination of self-crosslinking monomer and metal-coordination complexes. Herein, a series of hydrogels of poly(acrylamide-co-acrylic acid-co-N-hydroxymethyl acrylamide) (P(AM-co-AAc-co-NMAM)) consisting the chemical crosslinking induced by NMAM units and the physical crosslinking derived from the coordination complexes of carboxyl-Fe3+ were prepared. The molecular structure was investigated with the ATR-FTIR, Raman and UV-vis spectra. These hydrogels with different water content of 57-93% possess good mechanical performances. The optimal hydrogels possess high tensile strength (8.56 MPa), prominent modulus (15.5 MPa), remarkable toughness (37.85 MJ/m(3)) and superb tearing energy (7062 J/m(2)). The tough hydrogels also display excellent self-recovery (95% toughness recovery within 50 min), pH-triggered healing, shape memory and plasticity abilities. These hydrogels having high strength and toughness may broaden range of potential applications in load-bearing soft actuators, flexible electronics, etc.