Tough and conductive PVA-based double-network ionic hydrogels for flexible sensors

Hydrogels have been widely used for fabricating flexible sensors. However, it still remains a significant challenge to construct conductive hydrogels with excellent mechanical properties. This work presents a type of double-network (DN) hydrogels composed of poly(vinyl alcohol) (PVA) and poly(ionic liquids) (PILs), which are prepared through repetitive freezing/thawing process. Taking advantage of the coordination between carboxyl groups and Fe 3+ ions, the mechanical properties of the DN hydrogels are enhanced after treated with Fe 3+ ions. The influence of dosage of PILs and Fe 3+ ions on the mechanical properties and conductivities of DN hydrogels is investigated. The DN hydrogel P(AVIM-AA) 1 /PVA-Fe 3+ 4 , which is prepared under optimal conditions, shows high tensile strength (1.75 MPa), elongation at break (375 %), and toughness (2.75 MJ m −3 ). P(AVIM-AA) 1 /PVA-Fe 3+ 4 also displays a good conductivity of 0.65 S m −1 and a high sensing sensitivity with a gauge factor of 2.766, indicating its potential application as flexible sensors.