INORGANIC MONOLAYERS FORMED AT AN ORGANIC TEMPLATE - A LANGMUIR-BLODGETT ROUTE TO MONOLAYER AND MULTILAYER FILMS OF ZIRCONIUM OCTADECYLPHOSPHONATE

Single-layer and multilayer films of zirconium octadecylphosphonate have been prepared on silicon oxide surfaces and characterized by Langmuir-Blodgett (LB) transfer data, contact angle, ATR-FTIR, XPS, ellipsometry and X-ray diffraction. The deposition method uses a preformed, organized organic template for assembling the inorganic lattice by combining LB and self-assembly (SA) techniques. First, an LB template of octadecylphosphonic acid is formed on an octadecyltrichlorosilane-covered substrate, then Zr4+ ions are ''self-assembled''from solution. A capping octadecylphosphonic acid LB monolayer is added to complete the bilayer. Transfer of the phosphonic acid is continuous with transfer ratios ranging between 1.1 and 1.2. Contact angle measurements on a completed bilayer give an advancing contact angle of 112 +/- 1-degrees. The asymmetric methylene (nu(a)(CH2)) band of the template layer appears at 2918 cm-1 and possesses a fwhm of 20 cm-1 indicating that an all-trans, close-packed template is formed. The frequency and shape of the nu(a)(CH2) band remain unchanged in the progression from the template layer to bilayer to multilayers. XPS analysis of the zirconated LB template shows a 1:1 ratio of Zr:P, while bilayer and multilayer films possess a Zr:P ratio of 1:2 consistent with the stoichiometry observed in solid zirconium phosphonate. Ellipsometry shows a layer-by-layer increase in film thickness corresponding to a bilayer thickness of 51 angstrom, while X-ray diffraction reveals a d spacing of 52 angstrom and thus demonstrates the layered nature of the films. The zirconium phosphonate films are quite insoluble in both water and organic solvents.