Preparation of Nanostructured Organic-Inorganic Hybrid Materials Using Supercritical Fluid Technology

The effects of surface treatment of nanometric titanium dioxide (TiO2) powder with octyltriethoxysilane on the hydrophobicity of the inorganic nanoparticles have been investigated. Thermogravimetric analysis (TGA), attenuated total reflection infrared spectroscopy (ATR-IR.), laser scattering and specific BET-surface area and pore volume measurements were used as characterization techniques. The TiO2 nanoparticles were treated with solutions of supercritical carbon dioxide (scCO(2)) as solvent and silane molecules. A thermal resistant polysiloxane structure was formed on the TiO2 surface. The mesoporosity of the aggregates of TiO2 was preserved after the supercritical silanization process. The dispersibility of TiO2 in an organic hydrophobic phase (petroleum) was enhanced after the surface treatment. Optimization and modelling of the silanization process in scCO(2) media was performed using experimental design. Reaction pressure (P), temperature (T) and processing time (t) were chosen as potential variables that may influence the process. A two-level full factorial design involving 2(3) experiments was carried out to extract information concerning significant effects and interactions. Results showed that changes in the values of the process variables lead to variations in particle size distribution and porosity of the silanized samples. (C) Koninklijke Brill NV, Leiden, 2009