Highly flexible and compressible polyimide/silica aerogels with integrated double network for thermal insulation and fire-retardancy.

• Polyimide/silica (PSi) aerogel with integrated double network and anisotropic structure was fabricated. • The PSi aerogel could withstand 500 cyclic compression test in the radial direction with a high silica content of 60 wt%. • The PSi aerogel exhibited ultra-low thermal conductivity of 21.2 mW m⁻¹ K⁻¹ in the radial direction. • The PSi aerogel exhibited structure integrity when subjected to a flame of a propane/butane blowlamp (∼1200 °C). The materials with thermal insulating and fire-retardant properties are highly demanded for architectures to improve the energy efficiency. The applications of conventional inorganic insulating materials such as silica aerogels are restricted by their mechanical fragility and organic insulating materials are either easily ignitable or exhibit unsatisfactory thermal insulation performance. Here, we report an organic/inorganic composite aerogel with integrated double network structure, in which silica constituent homogeneously distribute in the anisotropic polyimide nanofiber aerogel matrix and strong interfacial effect is formed between two components. The integrated binary network endows the polyimide/silica composite aerogels with outstanding compressibility and flexibility even with a high inorganic content of 60%, which can withstand 500 cyclic fatigue tests at a compressive strain of 50% in the radial direction. The resulting composite aerogel exhibits a combination of outstanding insulating performance with a low thermal conductivity (21.2 mW m⁻¹ K⁻¹) and excellent resistance to a 1200 °C flame without disintegration. The high-performance polyimide/silica aerogels can decrease the risk brought by the collapse of reinforced concrete structures in a fire, demonstrating great potential as efficient building materials. [Display omitted] [ABSTRACT FROM AUTHOR]