Optical Patterning of Photosensitive Thin Film Silica Mesophases

Photosensitive films incorporating molecular photoacid generators compartmentalized within a silica-surfactant mesophase were prepared by an evaporationinduced self-assembly process. UV-exposure promoted localized acid-catalyzed siloxane condensation, enabling selective etching of unexposed regions, thereby serving as a cresistIess’ technique to prepare patterned mesoporous silica. We also demonstrated an optically-defined mesophase transformation (hexagonal+ tetragonal) and patterning of . refractive index and wetting behavior. Spatial control of structure and function on the macroand mesoscales is of interest for sensor arrays, nano-reactors, photonic and fluidic devices, and low dielectric constant films. More importantly, it extends the capabilities of conventional lithography from spatially defining the presence or absence of film to ;patial control of film structure and function. Since the discovery of surfactant-templating procedures to prepare ordered mesoporous silicas (l), films have been identified as a promising application. Thin film silica mesophases have been prepared at solid-liquid (2) and liquid-vapor interfaces (3), and by spin-coating (4, 5), and dip-coating (6, 7). These procedures have been combined with soft lithographic techniques