Influence of the Silane Coupling Agent and of the Temperature of Deposition on the Structure of the Silica Surface Layer

Silane molecules are widely used in literature as coupling agents for the synthesis of composites that involve oxide surfaces (generally glass, silica films or particles). Promising applications are described in many different fields, such as the low cost deposition of transparent conductive layers (like indium thin oxide) on glass[1], the encapsulation of silica particles in polymeric materials to enhance the mechanical properties or the stabilization of oxide suspensions in organic matrixes[2]. Here, vapor phase chemisorptions of different silanes on silica substrates were studied at different temperature (70 – 150 °C). The silane chemisorption was realized both on glass slide and on micrometric silica powders. Silanes with different chemical nature were employed, comparing fluorinated and un-fluorinated molecules. The quality of the layer was tested by an original combination of spectroscopic, electrochemical and surface characterization techniques. Solid state nuclear magnetic resonance (CP-MAS NMR) provides information about the grafting mode of the silane on the surface [3], whereas water contact angle, electrochemical (CV and impedance) and FTIR measurements give information about the role played by the nature of the coupling agents and the growth conditions of the surface layer on the final structure.