Silicon dioxide surface modified with cholesterol derivatives

The major aim of the presented work was focused on the preparation and characterization of surface architecture of home-made packing materials for liquid chromatography and related techniques. Four stationary phases were synthesized on the basis of the same batch of silica gel. Two of them were obtained using compounds possessing liquid crystalline properties, one consisted of alkylamide ligands and one was conventionally prepared hydrocarbonaceous material. Properties of the silica matrix as well as the preparation of phases were discussed. Various physicochemical techniques were applied for the characterization of the surface of obtained packings. The progress of the modification reactions was confirmed by elemental analysis, which allowed calculation of the surface coverage density with bonded ligands. Created undersurface structure was examined by means of the solid-state NMR and FT-IR spectroscopy. Thermal analysis revealed the presence of phase transitions. The chromatographic experiments were designed and performed to prove the evidence of the non-homogenous nature of the surface of the packing materials and to create a relative hydrophobicity scale.