Microphase separation induced polyzwitterionic ionogel with tough, highly conductive, self-healing and shape-memory properties for wearable electrical devices

Ionogels have aroused much attention due to their unique advantages for constructing wearable devices. However, integrating the properties of strong toughness, high ion conductivity, self-healing and shape-memory into one ionogel is still challenging. Herein, we develop a polyzwitterionic ionogel through the copolymerization of zwitterionic [2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) (SBMA) and acrylamide (AAm) in ionic liquid (IL) of 1-ethyl-3-methylimidazolium ethyl sulfate (EMIES). The facile ability to engage in hydrogen bonds for poly acrylamide (PAM) segments makes them easily aggregated in EMIES, resulting in the formation of polymer-rich domains. In contrast, poly[2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) (PSBMA) segments combined with EMIES form solvent-rich phase due to their good compatibility. Therefore, interpenetrating phase-separated structure is produced during the polymerization. The polymer-rich phase can dissipate energy and provide high strength, while the solvent-rich phase enables the ionogel with large stretchability. Besides, the zwitterionic groups on PSBMA can provide separate and continuous ion conductive pathways, facilitating the ion transport. Attributing to the synergy of phase separation and zwitterionic feature, the resulting ionogel presents balanced mechanical and electrical properties with high toughness of 2.7 MJ/m3 and ion conductivity of 1.3 mS/cm, as well as desirable self-healing ability. The resulting PSBMA/PAAm ionogel demonstrated excellent performance as a temperature and strain sensor. Remarkably, the ionogel possessed outstanding shape-memory property, making the ionogel can fix on the human joint or object with nonzero Gaussian curvature and maintains the sensing functions. Therefore, the morphing ionogel based sensor displays huge versatilities and potentials on detecting the signals variations for the objects with sophisticated geometries.