Doubly Reversible Thermochromic and Thermoresponsive Photoluminescent Ionogels with High Stretchability, Low Hysteresis, and Excellent Thermomechanical Stability

Abstract

Stretchable ionogels with thermoresponsive capabilities are garnering substantial attention owing to their potential applications in the fields of smart displays, soft robotics, and wearable ionotronics. Nevertheless, the application of traditional thermoresponsive ionogels in complex scenes remains a challenge because of the single response mechanism and poor thermomechanical stability. Herein, a simple strategy for the construction of high-stretchable and low-hysteresis ionogels with doubly reversible thermochromic and thermoresponsive photoluminescent properties is proposed. Taking advantage of the synergistic effect of poly(hydroxyethyl acrylate) (PHEA) and polyethylene glycol monomethyl ether (mPEG) in the ionic liquid (IL), doubly reversible thermochromic ionogels with both upper critical solution temperature (UCST) and lower critical solution temperature (LCST) phase behaviors are prepared. Simultaneously, doubly reversible thermoresponsive multiple photoluminescent behaviors are realized by the confined-domain cross-link-enhanced emission (CEE) effect. The synergistic effect of hierarchical micro/nanophase-separated structures and entanglement of polymer chains endow the ionogel with high stretchability (1070%), low hysteresis (<3.0%), outstanding temperature tolerance (−80–300 °C), excellent ionic conductivity (up to 2.57 mS/cm), and extraordinary thermomechanical stability (25–200 C). Ionogel-based wearable thermo-mechano-multimodal sensors can detect various human motions sensitively, showing great promise in multifunctional wearable ionotronics.