Anti-swelling P(DAC-co-NaSS-co-VDT) polyampholyte hydrogel with solvent displacement and salinity enhanced wet strength and adhesion

Polyampholyte (PA) hydrogels in general possess excellent mechanical properties, but their underwater applications are largely limited due to swelling induced dramatically reduced strength and poor wet adhesion, especially in high salinity environments. Here, we report our approach to fabricating an anti-swelling poly(acryloyloxyethyltrimethyl ammonium chloride (DAC)-co-sodium p-styrenesulfonate (NaSS)-co-2-Vinyl-4,6-diamino-1,3,5-triazine (VDT), or P(DAC-co-NaSS-co-VDT), PA hydrogel by introducing multi-hydrogen bonding capable functional VDT moieties into the DAC/NaSS coexisting and cation/anion ratio easily tunable PA network. The mechanical properties of the P(DAC-co-NaSS-co-VDT) hydrogel in bulk and at interface were controllable with dimethyl sulfoxide (DMSO)/H2O solvent displacement and Hofmeister effect in a wide salinity range, exhibiting maximum tensile strength, Young's modulus, and wet adhesion toughness of 7.6 MPa, 200 MPa, and 350 J m−2, respectively. The anti-swelling and strong P(DAC-co-NaSS-co-VDT) PA hydrogel developed in this work may find great potential in underwater sensing and sewage treatment as well as for many biomedical applications.