Thermally driven memory flexible phase change hydrogel for solar energy efficient building thermal management

Sodium sulfate decahydrate (SSD), as a typical inorganic phase change material (PCM), can be used to improve solar energy utilization efficiency and thermal management. However, its inherent problems of leakage, phase separation and strong rigidity severely limit its practical application. In this work, a phase change hydrogel with shape remembering behavior and high photothermal conversion capability was designed using konjac glucan and acrylamide copolymer as supporting material, SSD as PCM, and hydrothermal carbon (HTC) as photothermal converter and thermal conductive filler. In view of the hydrogel hydrophilic cross-linked 3D network, good compatibility with SSD, can effectively solve the problem of SSD high temperature leakage, SSD packaging efficiency up to 90.4 wt%. At the same time, HTC forms a continuous and effective photothermal conversion and thermal conductivity path with the help of the 3D network of hydrogel, and the phase change hydrogel shows excellent photothermal conversion performance and thermal conductivity (0.89–1.11 W m⁻¹ K⁻¹). In addition, the phase change hydrogels exhibited excellent thermally driven shape memory behavior (385 s) and mechanical strength up to 0.67 MPa. This provides a new feasible way to construct green buildings instead of air conditioning for winter insulation.