Siloxane-TiO2 Hybrid Nanocomposites. The structure of the hydrophobic layer

Anatase-brookite titanium dioxide nanoparticles are derivatized with two commercial trifunctional siloxanes by a mild impregnation method. The filmed titania nanoparticles are characterized by X-ray diffraction, N-2 adsorption at subcritical temperatures (BET and BJH methods), and contact angle determinations. Starting from siloxane contents of 9%, the particles show highly hydrophobic properties (contact angle around 140-150 degrees), complete buoyancy over water, and excellent self-cleaning properties. Solid-state Si-29 cross-polarization magic angle spinning nuclear magnetic resonance (Si-29 CP/MAS NMR) is used to investigate the mode of attachment of the siloxane molecules to the TiO2 surface. The combination of these results with X-ray photoelectron spectroscopy and attenuated total reflectance Fourier transform infrared spectroscopy provides unique information on the structure of the chemisorbed siloxane layer. The siloxane groups covalently attached to the TiO2 surface may serve as powerful linkers for different functionalities.