Fast-responsive ionogel with switchable conductivity triggered by photothermal effect

Abstract

This study has developed a photothermal-responsive smart ionogel that achieves rapid conductivity switching through the incorporation of graphene. The gel is constructed with a double-network structure composed of poly(styrene-b-ethylene oxide-b-styrene) (PS-PEO-PS) block copolymer and ionic liquids 1-(4-vinylbenzyl)-3-butylimidazolium bis(trifluoromethylsulfonyl)imide ([VBBIM][NTf₂]) / 1,3-dimethylimidazolium bis(trifluoro-methanesulfonyl)imide ([MMI][NTf₂]), where graphene serves dual functions of photothermal conversion and electrical conduction. Under illumination, graphene induces a phase transition in [MMI][NTf₂] (Tm = 22 °C), enabling the gel to respond as quickly as within 16 seconds, with conductivity increasing up to tenfold (from 3.19 × 10⁻⁵ to 3.06 × 10⁻⁴ S·m⁻¹) and reversible modulation. After optimizing the doping concentration (0.3 wt%), the material exhibits excellent mechanical properties (tensile strength of 42 kPa) alongside high conductivity (1.74 × 10⁻⁴ S·m⁻¹), a 2.6-fold enhancement in near-infrared absorption, and significantly improved thermal stability. This strategy provides new insights for the development of fast-responding, conductivity-controllable flexible electronic materials.