Effect of TiO2 on the Pore Structure of SiO2-PDMS Ormosils

Abstract

In this work, pore structure evolution of Ormosils containing TBT (Tetrabutyl titanate) has been characterized by means of mercury porosimetry, nitrogen adsorption and helium pycnometry. These ormosils have been prepared by the sol-gel method by the reaction of TEOS (tetraethoxysilane), PDMS (polydimethylsiloxane, silanol terminated) and TBT under acid-catalyzed conditions. The addition of TiO2 increases the volume and specific surface of secondary micropores and at the same time decreases the corresponding volumes of mesopores and macropores. The presence of TiO2 gives also a continuous decreasing in the pore connectivity being 9.7 for the ormosil without TiO2 and 4.4 for that of the higher concentration of TiO2. However, the pore length shows a significant decrease with the first addition of TiO2 changing from 9.1 to 2.2 at the higher TiO2 concentration. Pore volumes show a decrease as the TiO2 concentration is increased in the ormosil. On the other hand, density increases and porosity decreases with the TiO2 concentration. These results are in accordance with the presence of TiO2 nanoparticles in the ormosil and the size of such nanoparticles increases with the TiO2 concentration. Fractal constant has a low value, close to 2, for all different samples meaning that these ormosils can be considered as low surface roughness materials.