Strong anti-polyelectrolyte zwitterionic hydrogels with superior self-recovery, tunable surface friction, conductivity, and antifreezing properties

Abstract Salt-responsive hydrogels, have great potential in electrochemical devices and marine-related applications. But so far most of these hydrogels swell in water while shrink in salt solution. Herein, based on a special zwitterionic monomer, 3-(1-(4-vinylbenzyl)-1H-imidazol-3-ium-3-yl)propane-1-sulfonate (VBIPS), tough double-network hydrogels showing strong anti-polyelectrolyte effect were designed. The hydrogel was prepared by one-pot copolymerization of VBIPS and N-(2-Hydroxyethyl) acrylamide in the presence of sodium alginate. The double-network showed good mechanical properties and excellent recoverability. These hydrogels with salt-response exhibited shrinkage, opaque, and high surface friction in water, but swelled, camouflage, and high lubrication in salt solution. Meanwhile, after complexing with multivalent cations, the hydrogels not only maintained the initial flexibility, but also largely decreased the freezing point to −60 °C. Besides, the interesting electrochemical behavior of polyzwitterions offered the hydrogels showing high ionic conductivity both at room temperature and ultra-low temperature, which greatly broadened the applications to extreme conditions.