Formation of a continuous mesoporous silica film with fully aligned mesochannels on a glass substrate

A continuous mesoporous silica film with uniaxially aligned hexagonal mesochannels was formed on a silica glass substrate using a rubbing-treated thin polyimide coating on the substrate. Polyimide which has a hexamethylene group per the repeating unit: as a part of the main chain was used. The mesostructured silica film was grown on the polyimide-coated substrate through the hydrolysis of tetraethoxysilane under acidic conditions in the presence of hexadecyltrimethylammonium chloride. X-ray diffraction experiments show that the hexagonal mesochannels in the film run parallel to the substrate surface and are aligned normal to the rubbing direction with a very narrow distribution of +/-6 degrees. The hexagonal arrangement of the mesochannels over the whole film thickness was proved by cross-sectional transmission electron microscopy. This highly preferred alignment of the mesochannels is caused by strong interactions between the surfactant tail groups and the polymer chains.