Hierarchical structural double network hydrogel with high strength, toughness, and good recoverability

Hierarchical structural double network hydrogel (H-DN gel) was fabricated by inducing ferric coordination crosslinkers in the second network of PAMPS/P(AAm–AAc) double network hydrogel. Investigations of the tensile and compressive properties indicated that the H-DN gel exhibited a dramatic enhancement in the Young's modulus, tensile ultimate strength, toughness, compressive modulus and stress, compared to traditional double network hydrogels. H-DN hydrogel exhibited good recoverability that remained at ∼70% of the initial dissipated energy after resting at 60 °C for 15 min. Finally, scanning electron microscopy (SEM) revealed that the amount of embedded micro-network structures in H-DN gel became more intensive and the walls got thicker.