High Adhesive Force, Wide Temperature Adaptability Thermochromic Ionogel Smart Window

Traditional thermochromic hydrogels have attracted much attention in the field of smart windows, but they still have some problems of temperature adaptability, such as easy freezing, water evaporation, etc. Here, a dynamic physically cross-linking network structure ionogel was constructed by an ionic liquid ([BMIm]+[BF4]−) with low vapor pressure, which has outstanding mechanical properties (670%, 89.5 kPa), antifreezing properties, and strong adhesion properties (under water and at high and low temperatures). Due to the repositionable phase separation caused by the internal hydrogen bonds, the ionogel exhibited transmittance changes of up to 72% in the range of 0 °C ∼ 60 °C, excellent optical stability, and thermochromic ability during the heating–cooling cycles. Furthermore, the ionogel was used as the active layer of the smart window, which could change the light transmittance of the window in real-time according to the outdoor temperature and then realize the indoor temperature adjustment to achieve the energy saving and emission reduction. This study provides a promising strategy for developing an ionogel smart window with wide temperature adaptability.