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

Abstract

Ionogels have aroused great attention due to their unique advantages for constructing wearable devices. However, the mechanical properties and ion conductivity of ionogels are often negatively correlated in current research. Furthermore, integrating advanced functionalities such as self-healing and shape–memory into a robust and conductive ionogel remains challenging. Herein, we developed a polyzwitterionic ionogel through the copolymerization of zwitterionic [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl) (SBMA) and acrylamide (AAm) in the ionic liquid (IL) 1-ethyl-3-methylimidazolium ethyl sulfate (EMIES). The facile ability of the polyacrylamide (PAM) segments to engage in hydrogen bonds 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 a solvent-rich phase due to their good compatibility. Therefore, an 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 an ionogel with high stretchability. Additionally, the zwitterionic groups on PSBMA can provide separate and continuous ion conductive pathways, facilitating ion transport. The resulting ionogel presents balanced mechanical and electrical properties with a high toughness of 2.7 MJ m⁻³ and ion conductivity of 1.3 mS cm⁻¹, as well as desirable self-healing ability, which are attributed to the synergy of its phase separation and zwitterionicity. The resulting PSBMA/PAAm ionogel demonstrated excellent performance as a temperature and strain sensor. Remarkably, the ionogel possessed outstanding shape–memory properties, making the ionogel able to be fixed on a human joint or object with nonzero Gaussian curvature and maintain the sensing functions. Therefore, the morphing ionogel-based sensor displays huge versatility and potential for detecting the signal variations for objects with sophisticated geometries.