| A novel synthetic approach used to produce covalently bonded silica-based chromatographic stationary phases is described and discussed. The compound 4-methoxyphenyl 4-allyloxybenzoate (MPAB), known to develop liquid crystalline properties when immobilized onto a polysiloxane backbone, has been bonded to a silica support. Similarly, the liquid crystalline compound cholesteryl 10-undecenoate has also been bonded to such a support. In both the cases, the procedure involves the preparation of a silica intermediate containing stable silicon hydride (silane) surface species, followed by the catalytic addition of these species to the terminal vinyl group present in both esters. Spectroscopic and thermoanalytical evaluation techniques were used to characterize the structure of the modified silica. Diffuse reflectance infrared spectroscopy (DRIFT), differential scanning calorimetry (DSC), electron spectroscopy for chemical analysis (ESCA), and carbon analysis were used to evaluate the modified silica. |
