Self-healable, super tough graphene oxide-poly(acrylic acid) nanocomposite hydrogels facilitated by dual...

Here we propose a facile, one-pot in situ free radical polymerization strategy to prepare self-healable, super tough graphene oxide (GO)-poly(acrylic acid) (PAA) nanocomposite hydrogels by using Fe³⁺ ions as a cross-linker. The 3-dimensional network structure of the GO-PAA nanocomposite hydrogels is facilitated by dual cross-linking effects through dynamic ionic interactions: (i) the first cross-linking points are Fe³⁺ ions creating ionic cross-linking among PAA chains; (ii) the second cross-linking points are GO nanosheets linking PAA chains through Fe³⁺ coordination. When the GO-PAA nanocomposite hydrogels are under stretching conditions, the ionic interactions among PAA chains can dynamically break and recombine to dissipate energy, while the GO nanosheets coordinated to the PAA chains maintain the configuration of the hydrogels and work as stress transfer centers transferring the stress to the polymer matrix. In this regard, the GO-PAA nanocomposite hydrogels exhibit superior toughness (tensile strength = 777 kPa, work of extension = 11.9 MJ m^-3) and stretchability (elongation at break = 2980%). Furthermore, after being treated at 45 °C for 48 h, the cut-off GO-PAA nanocomposite hydrogels exhibit good self-healing properties (tensile strength = 495 kPa, elongation at break = 2470%). The self-healable, super tough GO-PAA nanocomposite hydrogels lay a basis for developing advanced soft materials holding potential applications in modern biomedical engineering and technology.