A novel design strategy for triple-network structure hydrogels with high-strength, tough and self-healing properties

In this study, we prepared a novel triple-network (TN) structure hydrogel composed of polyacrylic acid (PAA), agar and polyvinyl alcohol (PVA). The obtained TN hydrogel has a superior mechanical property as well as self-healing property feature. In the TN hydrogel system, PAA-Fe3+ polymer mainly providing hydrogel self-healing properties by the ionic coordinates between COO− and Fe3+ as the first network, while, agar and PVA polymers gel mainly providing hydrogel high mechanical properties as the second and third network. The structure of TN the hydrogel can be controlled by adjusting the content of Fe3+ and composition in the three polymers. When 1.5 wt% Fe3+ in the TN hydrogels, the PAA/Agar/PVA TN hydrogels possess high mechanical strength, the fracture strain and fracture stress were 497% and 450 kPa, respectively, and the compression strength reached up to 1337 kPa under the compression deformation of 80%. Besides, the TN hydrogels exhibited excellent self-healing ability, when healed 72% at tensile stress and 84% at tensile strain after 24 h without adding any solvent or additive. The research offers a novel design strategy to improve mechanical strength and self-healing ability of hydrogels by controlling the compositions and interactions in the three networks. [Display omitted] •A novel strategy was proposed to improve mechanical strength of hydrogel.•The hydrogel possessed good mechanical strength and self-healing properties.•The self-healing mechanism of the hydrogel is schematically illustrated.•The self-healing and mechanical strength of hydrogels can be controlled.