Toughness and Thermoresponsive Hydrogel for Sandwich Smart Window with Adaptive Solar Modulation and Energy Saving
Huijie Guan, Yinghan Lu, Yijiang You, Shengxiang Gao, Li Liu, Guangfeng Wu
Abstract
Thermochromic hydrogels with self-regulating solar transmittance are gaining increasing attention due to their significant potential in the fields of smart windows and energy conservation. Smart windows incorporating viscosity-tough hydrogels as an interlayer exhibit enhanced advantages in resisting external forces. In this study, a tough and thermoresponsive composite hydrogel was developed by incorporating poly( N -isopropylacrylamide) nanoparticles (PNIPAM NPs) and W-doped VO 2 into a polyacrylamide-agar (PAM-Agar) double network hydrogel. Upon solar irradiation, thermochromism of PNIPAM NPs could regulate the visible light transmittance of the composite hydrogel and the photothermal effect of W-VO 2 contributes to the optical regulation and NIR shielding. The smart window, with the composite hydrogel as an interlayer, demonstrates excellent optical modulation capabilities, with a luminous transmittance ( T um (20 °C)) of 86.81%, high light modulation (Δ T um = 78.89%), a high solar modulation ( T sol ) of 83.59%, and a lower critical solution temperature (LCST) of 32.6 °C. The composite hydrogel’s superior toughness (0.215 MJ/m 3 ) also enhances the impact resistance of the smart window glass. Additionally, the adhesion between the hydrogel and the glass, with a maximum peeling force of up to 151 N/m (attributed to interactions between the amide groups and the silicon hydroxyl groups), was confirmed through a falling ball experiment. Moreover, the hydrogel exhibits a certain degree of thermal insulation, further promoting its utility in energy-saving applications. In conclusion, this study highlights the significant potential of such composite hydrogels in the development of smart windows for energy-efficient buildings.