Long-term atomic oxygen resistant polyimide films containing carborane nanocage structure in the main chains

•Carborane nanocage structure was used for modification of AO resistance.•Carborane-containing PI nanocomposite films achieved both high thermal stability and AO resistance.•More denser passivation layer formed, eliminating the volume shrinkage phenomenon prevalent in POSS-PI films.•The mechanism of “self-healing” characteristic of PI nanocomposite films during AO irradiation was proposed.