Dual-Responsive Hydrogels with Three-Stage Optical Modulation for Smart Windows

Abstract

Since room temperature management consumes a large amount of building energy, thermochromic smart windows have been extensively used for temperature regulation and energy management. However, the development of the smart window is still limited by its simple thermochromic performance, unreasonable thermochromic temperature, and the lack of additional stimulation conditions. In this work, a dual-responsive hydrogel was developed by introducing sodium dodecyl sulfate (SDS) and sodium chloride into the cross-linking network of poly(N-isopropylacrylamide) (PNIPAM) and polyacrylamide (PAM) for energysaving and privacy protection. By controlling the temperature from low (<15 °C) to medium (15−28 °C) to high (>28 °C), the dual-responsive hydrogel achieved a reversible three-stage transition of opaque−transparent−translucent. The hydrogel exhibited a satisfactory solar modulation ability (T lum = 80.3%, ΔT sol,15−18°C = 72.9%, ΔT sol,18−35°C = 42.7%) and effective IR and UV shielding at high (or low) temperatures. Moreover, compared with traditional windows, smart windows made of dual-responsive hydrogels could offer better thermal insulation and heat preservation. The electrochromic properties of the dual-responsive hydrogel presented a facile strategy to meet the needs of different situations. The dual-responsive hydrogel features energy-saving, privacy protection, three-stage optical modulation, and multistimulus responsiveness, making it an ideal smart window candidate.

Integrated Thermoelectric Design Inspired by Ionic Liquid Microemulsion-Based Gel with Regulatable Dual-Temperature Responsiveness

“…Unexpectedly, it also appeared dual-temperature responsiveness (Figure B). As illustrated in Figure S3, we speculated that low-temperature opacity of the hydrogel was attributed to the settling of Tween 20 into the dense 3D network of the hydrogel. , Correspondingly, the transparent mode was ascribed to the increased solubility of Tween 20 with the temperature elevated. After that, when the temperature rose above the cloud point, the hydrogen bonds between H 2 O molecules and poly­(oxyethylene) hydrophilic (abbreviated EO) headgroups of Tween 20 were broken, resulting in the impairment of hydrophilicity, so the hydrogel reverted to opaque once again. , In addition, sample SA-L gel composed by Tween 20 and LiCl (Figure B) revealed that LiCl further reduced the higher/lower critical transition temperature (abbreviated U/LCTT) of hydrogel and significantly narrowed the transparency temperature range owing to its salting-out effect, which can decrease the cloud points of nonionic surfactants by reducing the solubility of hydrophobic chains and disrupting the hydrogen bond between H 2 O molecules and oxygen atoms of EO headgroups. , Interestingly, IL microemulsion-based gel containing the same concentration of Tween 20 (sample ME in Figure B) not only owned dual-temperature responsiveness but also exhibited a significantly wider transparent temperature range.…”

“…As illustrated in Figure S3, we speculated that low-temperature opacity of the hydrogel was attributed to the settling of Tween 20 into the dense 3D network of the hydrogel. 32,56 Correspondingly, the transparent mode was ascribed to the increased solubility of Tween 20 with the temperature elevated.…”

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

“…p) Comparison with previous work. [5,15,23,25,31,[42][43][44][45][46][47][48][49][50][51][52][53][54][55]. change when the resistance increases and the current decreases.…”

Hydrogel, the Next‐Generation Electrolyte for Electrochromic Devices

“…In addition to being used as photochromic and electrochromic bifunctional hydrogel, the PAM hydrogel containing specified additives also exhibited three‐stage optical modulation properties for smart windows. Dai et al [ 33 ] constructed a dual‐responsive hydrogel by applying sodium dodecyl sulfate and sodium chloride into the cross‐linking network of poly(N‐isopropylacrylamide) and PAM for energy‐saving and privacy protection ( Figure a). The dual‐responsive hydrogel realized a reversible three‐stage transition between opaque, transparent, and translucent.…”