Carboxymethyl Cellulose Enhanced Polymeric Form Stable Phase Change Materials with Reversible Transparency for Energy Storage

The rapid advancement of phase change material (PCM) has spurred numerous innovations, such as the use of reversible optical properties of solid–liquid phase change materials in the manufacturing of optical devices. However, these materials often exhibit poor stability and low heat storage performance. Here, a method for producing cellulose-based phase change gel (PCG) is proposed. The addition of carboxymethyl cellulose (CMC) significantly increased the tensile strength of the phase change gel postmelting, resulting in a remarkable 1131% increase compared with that of the CMC-free gels. Within this gel, poly(ethylene glycol) (PEG) is embedded as a phase change filler in a dual network cross-linked by hydroxyethyl methacrylate (HEMA) and CMC, preventing leaks and enhancing shape stability. The maximum enthalpy values for melting and solidification reach 90.6 and 88.4 J/g, respectively. The resulting gel exhibits a high degree of haze that effectively prevents glare, resulting in optical transparency changes ranging from about 25 to 78% during phase transitions. The preparation process of these phase change gels involves no toxic or harmful solvents, ensuring an environmentally friendly and straightforward approach. This expands research opportunities in phase change materials for intelligent optical devices, thermal energy management, and beyond.