Stretchable, Low-Hysteresis, and Recyclable Ionogel by Ionic Liquid Catalyst and Mixed Ionic Liquid-Induced Phase Separation

Stretchable ionogels are rapidly emerging as ideal materials for the construction of flexible ionotronics and soft machines. However, current ionogels suffer from low stretchability and large hysteresis, existing unstable signals at large deformations, and repetitive actions. Here, we propose a simple strategy based on mixed ionic liquid (IL)-induced phase separation to fabricate highly stretchable, tough, and low-hysteresis ionogels by dissolving poly(vinyl alcohol) (PVA) in IL mixture of 1-allyl-3-methylimidazolium chloride and 1-ethyl-3-methylimidazolium ethyl sulfate. The cross-linking network microstructures with special nanophase separated domains endow the ionogel with a high stretchability (1030%) and toughness (0.21 MJ/m3), which are 4.0 and 13.5 times that of the PVA ionogel synthesized in 1-allyl-3-methylimidazolium chloride with H2SO4. The low mechanical hysteresis characteristic of these ionogels is evidenced by cyclic tensile and compressive stress–strain curves. Moreover, the ultralow PVA content (3–8%) and typical sea-island microstructure endow the ionogel with superior room-temperature ionic conductivities (up to 1.8 mS/cm) and lower activation energies. Importantly, these ionogels show excellent recyclability and reprocessability due to the dissociation and recombination of the acetylated covalent cross-linking with the acidic IL catalyst. Potential applications of these resilient ionogels as flexible strain and pressure sensors for detecting the dynamic deformations under cyclic loading are further demonstrated.