Phase Change Emulsion Gel for Smart Windows With Bidirectional Light Regulating and Energy Storage Based on Refractive Index Matching

ABSTRACT The growing demand for green, low‐carbon, and sustainable development has driven the advancement of window materials that integrate adaptive light modulation with energy conservation for residential and industrial buildings. This paper presented a systematic strategy using a phase change emulsion gel to construct smart windows capable of thermal energy storage and release. Based on the thermoresponsive behavior of hydroxypropyl methylcellulose (HPMC) as the matrix, combined with the solid–liquid phase change of the oil phase and a refractive index matching mechanism between the water and oil phase, the smart glass achieved bidirectional coordinated tunability in transmittance, haze, and thermal management with a high enthalpy of 96.56 J g −1 . Within the operating temperature range from 24°C to 40°C, the total transmittance remained consistently above 85 %, while the haze can be continuously adjusted from 3.98 % to 78.98 % in response to ambient temperature. Prototype validation in residential/office buildings and agricultural facilities demonstrated broad adaptability and scalability, indicating strong potential to support the green and sustainable transformation of the construction sector.