One-Pot Synthesis of Soft, Shape-Stable and Conductive Phase Change Hydrogels

Abstract

Phase change materials are extensively utilized in construction and solar energy sectors. In this study, a soft, shape-stable and conductive phase change hydrogel (PCH) was developed by incorporating sodium sulfate hydrate into polyacrylamide (PAM) hydrogel. Within the PCH, sodium sulfate serves as the phase change component, adsorbed within the pores of the hydrogel, while the PAM crosslinking network provides a stable framework. An outer dense layer prevents the phase change salt from expanding outward, thus avoiding phase separation. The PCH exhibits a phase transition enthalpy of approximately 150J/g and a phase transition temperature ranging from 25-32°C. After adding sodium chloride, the phase transition temperature can be maintained between 20-25 ℃, which is more suitable for human body cooling. Remarkably, the phase change properties of PCH remain unaltered even after 500 phase transition cycles. A 150g piece of phase change hydrogel is sufficient to meet the cooling requirements of outdoor workers (in temperatures above 30°C) for 1.25 to 1.5 hours, making it suitable for prolonged human body cooling in hightemperature environments. Moreover, the stable PCH is easily customizable and retains the softness characteristic of hydrogels. Its unique phase transition capability also endows the hydrogel with exceptional electrochemical properties. The comprehensive and outstanding performance of phase change hydrogels holds tremendous potential for future applications.