Flame‐Retardant Host–Guest Films for Efficient Thermal Management of Cryogenic Devices

Abstract Phase change materials hold tremendous potential for thermal energy storage and temperature management due to their high latent heat and chemical stability. However, the manufacture of flame‐retardant, form‐stable phase change films working under a cryogenic environment remains difficult. Herein, an organic polydopamine‐aramid nanofiber (PANF) aerogel film with a limiting oxygen index (LOI) of 32 is applied as a host to confine a unique phase change guest material (i.e., deep eutectic solvent, DES) to fabricate PANF‐DES host–guest flame‐retardant cryogenic phase change films. The PANF aerogel film is prepared through the in situ polymerization of dopamine within the aramid nanofiber hydrogel film, exhibiting a high specific surface area of 289 m 2 g −1 . The cryogenic phase change material is a ternary DES composed of ammonium chloride (NH 4 Cl), ethylene glycol (Eg), and deionized water (H 2 O). The as‐prepared PANF‐DES host–guest films with the phase transition temperature of −21 °C and melting enthalpy of 225 J g −1 can withstand fire for 60 s without naked flame, and the peak of heat release rate (pkHRR) is only 26.0 MJ kg −1 . This study opens the way for developing ultra‐low flammable phase change composite films, as well as shows great potential applications for thermal management in cryogenic devices.