Dual-covalently-crosslinked polycationic elastomers with mitigated residual deformation and enhanced ionic conductivity for multifunctional flexible electronics

Stretchable ionic conductors have attracted extensive attention in flexible electronics due to their inherent flexibility and tunable conductivity. To effectively overcome the drawbacks of ionogels (liquid spill) and solvent-free ionic elastomers (poor ductility), we report a novel design strategy for ionic conductors by employing the molecular weight differences of crosslinkers to construct a rigid-flexible network structure with dual crosslinking points in polycationic elastomers (PCEs). Benefiting from the grafting of ionic liquids onto the polymer backbone, PCEs effectively mitigate the adverse effects of ionic liquids leakage and phase separation. By optimizing the balance between dynamic and covalent crosslinks, the dual-covalently-crosslinked polycationic elastomer (DC-PCE) exhibits significantly reduced hysteresis (7.22%, 54.88% lower than that of the single-crosslinker polycationic elastomer (SC-PCE)) and a 27.8% higher ionic conductivity. When configured as a strain sensor, DC-PCE demonstrates low-hysteresis force-electric response, coupled with a broad strain working range (2%-300%), maintaining signal stability even after 3000 cycles of tensile testing. The flexible electronic based on DC-PCE can sensitively detect and distinguish both large body movements and subtle skin deformations, while showing great promise in posture recognition for soft robots.