Preparation of Microporous Hybrid Materials by Thermal Removal of Sterically Hindered Carbosilane Side Groups

The preparation of hybrid porous materials by condensation of poly(dimethyl-co-methyl)siloxanes functionalized with side units: i.e., templating –RC(SiMe₃)₃ [R = (CH₂)₅, (CH₂)₂SiMe₂], and reactive –Si(OEt)₃, of random distribution along the main chain is described. Tetrabutylammonium salts, tetrabutylammonium hydroxide and tetrabutylammonium fluoride were chosen as the catalytic system. The relationship between the steric hindrance of the carbosilane template, the type of n-Bu₄N⁺ catalyst and the structure of cross-linked materials was investigated. It was found that bulky carbosilane substituents can block formation of the porous structure in the cross-linked material. The type of interaction between Si(OEt)₃ and the catalyst seems to be an equally important factor for 3D structure formation. Controlled thermolysis of the cross-linked materials, performed in order to remove carbosilane units by thermal degradation, allowed for the formation of porous materials having high specific surface area.