Enhanced strength and toughness of κ-carrageenan/polyacrylic acid physical double-network hydrogels by dual cross-linking of the first network

Double network (DN) hydrogels with high strength and toughness have been developed as promising materials. In this paper, we prepared a novel κ-carrageenan/polyacrylic acid (κ-CG/PAA) DN hydrogel with excellent mechanical performances, which was achieved by dual cross-linking of the stiff first network. The obtained DN-1.956-0.1-2-15 hydrogels exhibited exceptional mechanical properties with fracture tensile stress of 2.53 MPa, fracture strain of 1381.91% and toughness of 13.40 MJ/m3. The results showed that dual cross-linking of κ-CG (double-helical junctions and metal coordination bonds) was conductive to high strength and toughness. Moreover, due to their totally physically cross-linking structures, the hydrogels showed 67% recovery of toughness after 2 min. Furthermore, the DN hydrogels showed self-healing capability, shape-memory ability, as well as excellent cytocompatibility and biodegradability. Such a designed DN hydrogel realizes the essential integration of improved mechanical properties, good biocompatibility and biodegradation for developing a desired scaffold material for potential tissue engineering applications.