Highly Stretchable, Mechanically Strong, Tough, and Self-Recoverable Nanocomposite Hydrogels by Introducing Strong Ionic Coordination Interactions

In this study, the authors report a novel class of super tough nanocomposite hydrogels with physically dual-crosslinking effects (DC hydrogels) through introducing strong ionic coordination interactions. Herein, graphene oxide (GO) nanosheets and iron (Fe3+) ions act as physical cross-linkers. GO nanosheets trigger the formation of the first cross-linking points through hydrogen bonding with poly(acrylamide-co-acrylic acid) (p(AAm-co-AAc)) chains, while the second cross-linking points are formed by strong ionic coordination interactions between Fe3+ ions and -COO(-)groups of p(AAm-co-AAc) chains. The optimal tough DC hydrogel displays superstretchability (approximate to 20.8 times), remarkable tensile strength (approximate to 3.7 MPa), high toughness (approximate to 48.71 MJ m(-3)), good self-recovery property (approximate to 84.1% toughness recovery within 4 h without any external stimuli) and fatigue resistance. In summary, this study opens up a new avenue to design and fabricate highly tough hydrogels with outstanding comprehensive properties by the synergistic effects of nanocomposite and dual-crosslinked hydrogels.