A flexible phase change gel with complementary regulation of haze and supercooling degree by hydroxyethyl cellulose and cellulose nanocrystals for light and thermal management

The phase change gel offers temperature regulation capability. • HEC and CNC synergistically regulate optical properties and lowered supercooling. • The gel exhibites thermal responsiveness in both optical and mechanical properties. • Smart windows from the gel are used for energy saving and daylight simulation. With the increasing demands for sustainable development and visual comfort, smart window materials integrating light regulation and energy conservation have experienced rapid advancement. This paper presented a strategy based on hydroxyethyl methacrylate (HEMA) free radical polymerization to prepare phase-change gels for smart windows, which combine thermal energy storage with light regulation functions. Utilizing polyethylene glycol (PEG) as the energy storage component, leveraging its thermally responsive solid-liquid phase change characteristics, and incorporating the complementary effects of sulfonated cellulose nanocrystals (SCNC) on optical properites and hydroxyethyl cellulose (HEC) on supercooling degree, the regulation of transmittance and haze was achieved, with an enthalpy of melting reaching 103.11 J g −1 . Within the operating temperature ranging from melting point to 40 ℃, the transmittance consistently remained above 80% with increasing SCNC addition, while the haze can be adjusted from 1.06% to 91.06%. EnergyPlus simulation results demonstrated that the smart window achieved an annual energy saving rate of 13.89% in Phoenix, while providing soft indoor lighting, offering significant potential for green and sustainable transformation in the construction industry. Download: Download high-res image (365KB) Download: Download full-size image