AO-resistant shape memory polyimide/silica composites with excellent thermal stability and mechanical properties

Shape memory polyimide/silica (PI/silica) composites with atomic oxygen resistance, good thermal stability and mechanical properties are synthesized by co-condensation of poly(amic acid) terminated with (3-aminopropy)triethoxysilane (APTES) and tetraethoxysliane (TEOS) via a sol-gel method. The silica networks formed in the hybrid films act not only as permanent crosslink points, but as atomic oxygen (AO) resistant moieties. The results show that the PI/silica composite films possess high thermal decomposition temperature (T-d > 550 degrees C), high glass transition temperature (T-g > 265 degrees C) as well as good shape fixation ratio (R-f > 98%) and shape recovery ratio (R-r > 90%). The mechanical properties, surface topography and shape memory performance of PI/silica composite films were evaluated before and after AO irradiation in simulated space environment. Compared to pristine PI, the mechanical properties, surface topography, and shape memory performances of PI-SiO2-15 were less affected by AO exposure, which results from the silica protective layer formed on the composite film surface, indicating good AO-resistant ability of PI/silica composite films. This work may provide a strategy toward the design of promising shape memory materials for applications in the field of severe conditions.