Highly Conductive, Transparent, Adhesive, and Self-Healable Ionogel Based on a Deep Eutectic Solvent with Widely Adjustable Mechanical Strength.

Ionogels have attracted intensive attentions as promising flexible conductive materials. However, simultaneous integration of excellent mechanical properties, high conductivity, outstanding self-healing ability, and strong adhesiveness is still challenging. Here, an ingenious composition design is proposed to address this long-standing challenge of ionogels. High-performance PEI/PAA/CMC ionogels, consist of a loosely cross-linked poly(acrylic acid) (PAA) network, dynamically cross-linked network based on polycationic polyethyleneimine (PEI) and polyanionic PAA, and carboxymethyl cellulose (CMC) reinforcing filler, are formed in a deep eutectic solvent (DES) composed of choline chloride and urea. Benefiting from the loose PAA network and dynamic noncovalent interactions, ionogels with both highly enhanced mechanical robustness and excellent conductivity are obtained at high loading of DES, overcoming the strength-ductility/conductivity trade-off dilemma. By adjusting PEI/PAA mass ratio, the tensile strength and strain of PEI/PAA/CMC ionogels are effectively controlled in a wide range of 0.15-7.9 MPa and 232-1161%, respectively, while maintaining the desirable conductivity of ≈10 -4 S cm -1 . Besides, healed tensile strength over 2.1 MPa and adhesion strength up to 0.2 MPa are achieved for the PEI 0.06 /PAA 0.25 /CMC 0.01 ionogel. The delicate design strategy provides a feasible approach to prepare ionogels with outstanding comprehensive performance, which have potential for applications in flexible electronics.