A Polyimide Nanocomposite from Octa(aminophenyl)silsesquioxane

Octaaminophenylsilsesquioxane (OAPS) can serve as a nanosized building block for the construction of materials with nanometer control of the periodicity of the organic and inorganic components and bonding between components. We describe here the synthesis of a prototypical three-dimensional polyimide by reaction of OAPS with pyromellitic dianhydride (PMDA). Model studies with phthalic anhydride provided useful cure conditions. Thus, stoichiometrically correct OAPS/PMDA nanocomposites were obtained following curing of NMP and DMF reaction solutions at lower temperatures and then to >350 °C/N₂ under vacuum. The resulting materials offer thermal stabilities in air and N₂ of >500 °C (5% mass loss temperature) and char yields >75%/N₂. X-ray powder patterns indicate that the resulting materials are completely amorphous, as might be expected from the extreme rigidity of the organic tethers linking cube vertexes that will prevent long-range ordering from occurring during curing. These materials hold promise for high compressive strength applications.