Thermally induced flexible phase change hydrogels for solar thermal storage and human thermal management

Hydrated salt is widely used for solar energy utilization and thermal management due to its phase change properties. However, its practical application is limited by issues such as leakage, phase separation, and supercooling, which require urgent attention. To address these challenges, a novel approach was proposed by synthesizing a photothermal phase change hydrogel using sodium acetate trihydrate as the phase change material, graphene oxide as the photothermal agent, and acrylamide and konjac glucomannan as the support structure. The hydrogel's three-dimensional network effectively reduces the likelihood of salt leakage and suppresses supercooling to a range of 1.2–3.1℃. The photothermal conversion efficiency of the phase change hydrogel can reach 89.7% due to high light absorption performance of graphene oxide. Hydrogels with phase change properties have an energy storage density of 179.2 J/g. As hydrated salts undergo a solid–liquid transition, phase change hydrogels experience a dramatic change in stiffness due to the temperature shift. Due to the existence of a three-dimensional network structure, a continuous and effective heat transfer path is formed inside the hydrogel, which presents thermal conductivity of 0.868 W/(m·k). The unique properties of phase change hydrogels pave a new avenue for personal thermal management and solar energy utilization.