Simultaneously improved strength and toughness in κ-carrageenan/polyacrylamide double network hydrogel via synergistic interaction.

Hybrid double network (DN) hydrogels have been fabricated by combining a physically cross-linked κ-carrageenan network, where various cations were used as cross-linker, with a covalently cross-linked polyacrylamide (PAAm) network. Compared to monovalent K+ and divalent Ca2+ cations, the presence of K+/Ca2+ mixture cations produced a well interconnected porous structure due to the synergistic effect, which simultaneously improved the strength and toughness of the resulting DN hydrogel. A model has been proposed considering the dissociation asynchronism of double-helical aggregates, which well interpret the fracture process and toughening mechanism of the K+/Ca2+-cross-linked κ-carrageenan/PAAm DN hydrogel. Moreover, the synergistic effect of K+/Ca2+ mixture cations also improved the recovery efficiency at room temperature and self-healing ability of DN hydrogel. The strategy of synergistic interaction presented here provides an alternative view for the fabrication of hybrid DN hydrogels with desirable mechanical performance and functional property.