Strong and tough hydrogels enabled by progressive enhancement of polymer networks

Despite the unique properties, the hydrogels' weak mechanical properties have severely limited their practical applications, and it remains great challenging to simultaneously enhance the strength, toughness and fracture energy of hydrogels. Herein, we develop strong yet tough polyvinyl alcohol (PVA) hydrogels via the synergy of wet-annealing and Hofmeister effect. The macromolecular chain engineered multiscale strengthening and toughening are achieved. The densified polymeric network, increased crystallinity and enhanced hydrogen bonding interaction enables the PVA hydrogels to have outstanding mechanical properties. The tensile strength, toughness and fracture energy of the resultant hydrogels can reach as high as 21.4 MPa, 182.3 MJ/m3 and 56.8 KJ/m2, respectively. This study provides a new avenue to effectively tune the macromolecular chain conformation and hence improve the comprehensive mechanical properties of gel materials.