Stretchable and Self-Healing Graphene Oxide–Polymer Composite Hydrogels: A Dual-Network Design

Superior mechanical properties and self-healing are two hot topics in hydrogel science due to their tight relationship with the following potential application scopes. Most of the conventional hydrogels do not possess both features at the same time. Herein, we expand the recently proposed intertwined double-network mechanism and prepare a novel class of graphene oxide (GO)/poly(acryloyl-6-aminocaproic acid) (PAACA) composite hydrogels with enhanced mechanical properties and self-healing capability to pH stimulus. Without the use of any conventional organic cross-linkers, the double networks in GO/PAACA hydrogels are triggered by GO nanosheets and calcium ions as cross-linkers. For one thing, Ca2+ induces the formation of the 3D cross-linked network through coordination interactions with both oxygen-containing groups of GO nanosheets and polar groups of PAACA side chains. For another, powerful hydrogen-bonding network is simultaneously interconnected, attributed to the interactions of polar groups of PAACA side chains with both other polar groups of PAACA side chains and oxygen-containing groups of GO nanosheets.