Cooperative self-assembly processes of inorganic species and amphiphilic molecules have experienced major advances over the past six years. The ability to design these materials with spatially controlled combinations of different mesophases or compositions, and therefore different properties, would greatly enhance their utility as nanofunctional surfaces.
We present a simple lithographic procedure, which allows a deliberate control of structure and properties of a meso-ordered silica film through optical mediation. This nanostructural lithography process exploits the pH sensitivity of supra-molecular self-assembly which allows spatial control over mesophases in the thin film and a selective etching capability. Through the addition of a photoacid generator in the coating sol along with surfactant and silica source, dip coating results in continuous, ordered photosensitive films. Exposure to UV light through a mask produces local pH changes, inducing mesostructural phase transitions and an increase in the acidcatalyzed siloxane condensation rate in the exposed regions. Two surfactant systems, CTAB (CH3(CH2)15N+(CH3)3Br–) and Brij 56 (CH3(CH2)15(OCH2CH2)10OH) have been studied. X-ray diffraction, transmission and scanning electron microscopy, optical microscopy, ellipsometry, MAS-NMR and atomic force microscopy are used to characterize the patterned nanostructured surfaces.