SYNTHESIS OF ORIENTED FILMS OF MESOPOROUS SILICA ON MICA

POROUS inorganic solids find,vide application in, for example, catalys is and separation technologies. One of the most promising routes to su ch materials exploits cooperative interactions between a supramolecula r organic template and inorganic precursor molecules to create an orde red porous solid(1-7). This general approach offers considerable flexi bility, and has led to materials with a wide range of bulk morphologie s and controlled pore diameters spanning several orders of magnitude(8 -10). From a technological point of view, the preparation of such mate rials in the form of mesoporous thin films is desirable, but attempts to achieve this aim have been largely unsuccessful, resulting in disor dered materials(11), Here we report the synthesis of thin (similar to 0.2-1.0 mu m) ordered films of mesoporous silica on freshly cleaved mi ca substrates. The films are stable on removal from the substrate. We propose a model to explain the formation of these films, in which the surface structure and reactivity of the mica substrate controls the or ientation of the micellar precursor species, which in turn imposes ord er on the resulting solid film.