Ultralight, highly flexible in situ thermally crosslinked polyimide aerogels with superior mechanical and thermal protection properties via nanofiber reinforcement

Advanced thermal-insulation materials for human use in high-temperature and ultra-low-temperature environments have received extensive attention. However, facile synthesis of aerogels with excellent mechanical and thermal properties via freeze-drying or electrospinning alone is still challenging. We hypothesized that a polyimide aerogel with high mechanical strength and good thermal-insulation performance and suitability for various applications at high and low temperatures could be prepared facilely using a simple and novel preparation strategy that combines electrospinning, freeze-drying, and in situ thermal crosslinking.Polyamideimide (PAI) nanofibers loaded with bismaleimide (BMI) were electrospun and dispersed into a polyamic acid aqueous solution. PAI/BMI-nanofiber-reinforced polyimide (IBNR-PI) aerogels with an interpenetrating network structure were prepared by freeze-drying and heat treatment.The IBNR-PI aerogels possessed extremely low volume density (26 mg cm-3) and high porosity (94.92%). Most importantly, they showed high tensile strength and good compressive fatigue resistance with plastic deformation of only 7% after 1000 compression cycles. The aerogels also showed a significantly low thermal conductivity (30.06 mW m-1 K-1) and excellent thermal insulation over a wide temperature range. Thus, the IBNR-PI aerogels are excellent candidates for thermal-insulation materials at high and low temperatures.