Pure Physical‐Crosslinked High‐Strength Thermochromic Hydrogel for Smart Window and Energy Conservation

Abstract Thermochromic smart windows have attracted widespread attention in the field of solar modulation and building energy conservation. However, current materials of smart windows are still confronted with challenges, including low integrated luminous transmittance (T_lum), low solar energy modulation (ΔT_sol), weak mechanical properties, and invariable critical transition temperature (τ_c). Herein, hydrophobic polyether side chains, that can reversibly undergo adjustable temperature‐triggered hydrophobic association, are introduced to thermochromic hydrogels for the first time. Due to the reversible phase separation, the obtained hydrogels demonstrate high T_lum (92.69%), high ΔT_sol (82.15%), widely adjustable τ_c and fast transition rate (<4 s). Furthermore, the adjustable τ_c of hydrogel is independent of component changes, attributed to the rearrangement of physical‐crosslinked chain segments at various temperatures. Moreover, strong hydrogen bond and high entanglement endow the hydrogel with outstanding mechanical properties (tensile strength >0.45 MPa, elongation >440%). The results of simulation investigations in different cities illustrate that the hydrogels have excellent solar modulation and temperature regulation capabilities. Meanwhile, the thermochromic hydrogel possesses remarkable 3D‐printability and real‐time state monitoring capability, meeting the requirements of different climates and practical application. Therefore, the strategy proposed in this work provides innovative insights for thermochromic hydrogel smart windows and building energy conservation.