One-pot preparation of strong, tough, frost-resistant and recyclable organohydrogels via Hofmeister effect and its application for electronic devices

Abstract

Conductive hydrogels have shown a great potential in the field of flexible electronics. However, it is difficult to combine high strength and high toughness in conductive hydrogels prepared by conventional methods, which limits their applications in various fields. In this work, we pioneered a facile and cost-effective strategy to prepare soy protein isolate/poly(vinyl alcohol) (SPI/PVA) conductive hydrogels with high strength, toughness, low-temperature resistance, and recyclability by introducing all the salts into the prescuor solution directly. To solve the problem of unable to directly introducing high concentration Na₃Cit into the soy protein isolate/PVA solution, MgCl₂ was used to alleviate the strong salting-out effect of Na₃Cit. Thus the stable SPI/PVA/EG/MgCl₂/Na₃Cit complex solution was obtained and the SPI/PVA/EG/MgCl₂/Na₃Cit (SPEMS) organohydrogel was prepared by the freezing/thawing process. The optimum tensile strength of the SPEMS organohydrogel was 1.1±0.07 MPa, and the elongation at break was 701.3±23.67 %, respectively. Meanwhile, the ionic conductivity of the organohydrogel was as high as 1.7±0.01 S/m. Finally, the EG/H₂O binary solvent system endowed the organohydrogel with excellent low-temperature resistance (freezing point of −19.4 °C). The strain sensors assembled with SPEMS organohydrogels were characterized by high sensitivity (GF = 3.2, strain range from 20 %–500 %) and long-term stability. The flexible all-solid-state supercapacitor assembled with SPEMS organohydrogel as the electrolyte and activated carbon as the electrodes has a high area specific capacitance (113.76 mF/cm²) and good cycling stability (capacitance retention of 81.62 % after 1,000 charging and discharging cycles) at room temperature.