Aromatic polyimides have been extensively used in the manufacturing of spacecrafts and air engines due to their excellent thermal and mechanical properties.Polyimides are usually employed as the matrix resins of carbon(or quartz)fiber-reinforced composites for structural or sub-structural applications,or as the thermal control shielding films and the solar cell substrate in satellite,as the solar sail membranes in space vehicles etc.However,there will be a big problem when polyimide materials are serviced in the low-earth-orbit(LEO)environment(100-1000 km in altitude)where the atomic oxygen(AO)can seriously erode the surface of most orgainc materials,resulting in the polymer degradation with mass loss.