Sodium lignosulfonate doped polyvinyl alcohol-based hydrogel conductive composites based on ion-specific effects with continuously tunable mechanical properties and excellent conductive sensing properties

Hydrogels have great application prospects in the fields of bionics, soft tissue probes, and motion detection, etc. However, the high water content and loose cross-linker structure of hydrogels lead to weak mechanical properties, which limits their application and development. Therefore, in this study, sodium lignosulfonate doped polyvinyl alcohol hydrogels (PVA/LS) were constructed using polyvinyl alcohol as the matrix and sodium lignosulfonate as the filler; the hydrogels were also treated with different ionic solutions to construct ion-responsive hydrogels (PVA/LS/ION); and ion-conducting hydrogels (PVA/LS/CL) were constructed by the change of the concentration of sodium chloride (NaCl) solution. The hydrophilicity of the polyvinyl alcohol (PVA) molecular chain was changed by different ions, resulting in either water absorption (salting in) or dehydration (salting out), and the hydrogel mechanical properties could be adjusted over a wide range (tensile strength: 77 kPa ∼ 3.26 MPa; elongation at break: 290 ∼ 870%; modulus: 24 ∼ 563 kPa; toughness: 96 kJ/m3 ∼ 14.1 MJ/m3). In addition, the hydrogels have good conductivity regulation (1.09 ∼ 2.72 S/m) and sensing properties, with GF values up to 1.23, and sensitive and stable strain sensing properties. This work provides useful insights into the application of ion-specific effects to the field of hydrogels.