Engineering Self‐Adaptive Multi‐Response Thermochromic Hydrogel for Energy‐Saving Smart Windows and Wearable Temperature‐Sensing

Abstract Buildings account for ≈40% of the total energy consumption. In addition, it is challenging to control the indoor temperature in extreme weather. Therefore, energy‐saving smart windows with light regulation have gained increasing attention. However, most emerging base materials for smart windows have disadvantages, including low transparency at low temperatures, ultra‐high phase transition temperature, and scarce applications. Herein, a self‐adaptive multi‐response thermochromic hydrogel (PHC‐Gel) with dual temperature and pH response is engineered through “one‐pot” integration tactics. The PHC‐Gel exhibits excellent mechanical, adhesion, and electrical conductivity properties. Notably, the low critical solubility temperature (LCST) of PHC‐Gel can be regulated over a wide temperature range (20–35 °C). The outdoor practical testing reveals that PHC‐Gel has excellent light transmittance at low temperatures and radiation cooling performances at high temperatures, indicating that PHC‐Gel can be used for developing energy‐saving windows. Actually, PHC‐Gel‐based thermochromic windows show remarkable visible light transparency ( T lum ≈ 95.2%) and solar modulation (△ T sol ≈ 57.2%). Interestingly, PHC‐Gel has superior electrical conductivity, suggesting that PHC‐Gel can be utilized to fabricate wearable signal‐response and temperature sensors. In summary, PHC‐Gel has broad application prospects in energy‐saving smart windows, smart wearable sensors, temperature monitors, infant temperature detection, and thermal management.