Immobilization of multifunctional silsesquioxane cage on precipitated silica supports

Synthesis of octakis({3-glycidoxypropyl}dimethylsiloxy) octasilsesquioxane (G-POSS) was carried out based on a reaction involving the hydrosilylation of allyl glycidyl ether with octakis(dimethylsiloxy) octasilsesquioxane, using Karstedt’s catalyst and toluene. SiO₂/POSS hybrid systems were obtained via a method of immobilization by evaporation of the solvent, using hydrated or spherical silica obtained by precipitation in an aqueous or emulsion environment. The surface of the SiO₂ was modified using octakis({3-glycidoxypropyl}dimethylsiloxy) octasilsesquioxane (G-POSS). The effectiveness of the modification of the obtained hybrid materials was verified using Fourier transform infrared spectroscopy and nuclear magnetic resonance (²⁹Si and ¹³C CP MAS NMR). The tests showed that the interactions between the silica support and the modifier are of the nature of chemical adsorption. In addition a mechanism was proposed for the interactions between silica and oligosilsesquioxane. To test the final effect, the hybrid systems were subjected to morphological evaluation (transmission electron microscopy). Parameters of porous structure of the products were also determined: the specific surface area, pore diameter and pore volume. Thermal stability was tested for the pure silsesquioxane cage, the initial silica supports and the resulting systems. Elemental analysis was also carried out to determine the effect of surface modification on the degree of coverage with a particular POSS compound.