Ultrafast fabrication of deep eutectic solvent flexible ionic gel with high-transmittance, freeze-resistant and conductivity by frontal polymerization.

As a common flexible sensing device, gels are widely used in electronic skin, personalized health monitoring, and smart manufacturing. However, gel suffers from temperature sensitivity, long polymerization times or thickness limitations. Deep eutectic solvents (DESs) have abundant hydrogen bond networks and low saturated vapor pressure, which can accelerate the frontal polymerization of ionic gels, and overcome the temperature sensitivity problem. Here, we showed how choline chloride (ChCl)-glycerol (Gly) DES can be used to create ionic gels with different properties and functions by combining them with different monomers (acrylamide (AM), acrylic acid (AA) and itaconic acid (IA)). Subsequently, we revealed the rapid gelation mechanism of PAM-ChCl-Gly ionic gel from multiple perspectives by density functional theory and molecular dynamics simulation, which was then applied to flexible sensing. The experimental results showed that the PAM-ChCl-Gly ionic gel had excellent tensile properties, high transparency, self-adhesion and stability. In addition, its gelation time was only 90 s without heating. ChCl-Gly DES offered a plentiful and stable hydrogen bonding network. PAM-ChCl-Gly ionic gels can detect tiny pressure and strain changes, making them suitable for flexible sensing. This greatly enriched the theoretical research foundation of DES-based ionic gels and broadened their application areas.