Robust and adhesive double-solvent phase change hydrogel with reversible transparency and shape memory for thermal management and information encryption

The excellent energy storage capacity of solid–liquid phase change materials has attracted considerable attention, but the vulnerability to leakage limits their applications. Therefore, the development of composite phase change materials has become a hot research topic in recent years. Therefore, a double-solvent (DS) phase change hydrogel (PCH) prepared by random copolymerization of acrylic acid (AA) and hydroxyethyl methacrylate (HEMA) with water and polyethylene glycol (PEG) as solvents was proposed. The phase transition enthalpies of melting and crystallization of the gel reached 116.2 J·g−1 and 113.5 J·g−1, respectively. PCH exhibits good morphological stability while storing thermal energy, which can effectively encapsulate phase change materials without leakage at high temperatures and be recyclable. PEG is used as both solvent and phase change part and the prepared gel reveals a high phase change material loading rate (76.2%), high breaking stress (4.7 MPa) and excellent compression resistance (1.2 MPa), superior to existing counterparts. The presence of a small amount of water in the system endows the gel with certain flexibility. Moreover, due to the solid–liquid phase transition behavior of PEG during temperature changes, PCHs possesses reversible adhesion and transparency, as well as shape memory properties. In addition, its low thermal conductivity and high energy storage efficiency make it perform well in the field of infrared stealth.