Joint double-network hydrogels with excellent mechanical performance

Based on the tough double-network hydrogel, a further crosslinked DN network hydrogel was developed and named joint double network (JDN) hydrogel. The JDN hydrogel consisting of ionically cross-linked sodium alginate (SA) as the first network, the chemically cross-linked poly (acrylamide-acrylic acid) (PAMAAc) as the second network and both of them combined together by ferric ions. As a result, SA/PAMAAc-Fe3+ hydrogels exhibited high mechanical strength with tensile stress of 1.26 MPa and tensile strain of 653%. Ultraviolet-visible spectroscopy, rheological and swelling tests also illustrated that the JDN structure greatly improved the mechanical properties of hydrogels because of close integration of internal networks. Moreover, the SA/PAMAAc-Fe3+ JDN hydrogel also owned high water content of 85%, free-plasticity, and excellent electrical property, which allowed it to be easily molded various shapes for tough electronic devices, flexible electrodes, and wearable equipment.