Effects of orientation and mobility of surface modifiers on the selectivity and efficiency of chemical interactions at selected chemically modified surfaces.

Abstract

Several surfaces chemically modified with a variety of surface modifiers have been studied using chromatographic, nuclear magnetic resonance, and computational techniques. The goal was to determine the effect of modifier structure on the solvation, selectivity, and efficiency of chemical interactions occurring at chemically modified surfaces. Oleyldimethylchlorosilane has been synthesized and bonded to silica to determine the effect of a conformational change at the center of the chain on the behavior of the entire surface. It has been shown with these studies that the configuration of the modifier plays an important role in determining the selectivity of chemical interactions at modified surfaces. By comparison with phospholipid bilayers, of the structure, solvation and dynamics of alkylmodified silicas has been achieved. Octyldimethylsilyl- and octadecyldimethylsilyl-modified silicas have been further reacted with t-butyltrichlorosilane, t-butyldimethylchlorosilane and trimethylchlorosilane to determine both the utility of t-butyltrichlorosilane as an end-capping reagent and the extent to which solvation of the near-surface region affects the performance of these surfaces. It was shown that the orientation and solvation of modifiers at the near surface has a profound effect on the selectivity and efficiency of chemical interactions at the surface. Sepharose gels modified with iminodiacetic acid have been studied by titrimetric and spectroscopic means. A model compound has been synthesized and characterized in solution. The results have led to a better understanding of the behavior of chelating agents at sepharose surfaces and the effects of immobilization on the behavior of ligands at a surface. Finally, quartz crystalline microbalances modified with physisorbed polymer layers have been studied by correspondence analysis. In this case, it has been shown that the polymer backbone of the modifying agent plays an important role in determining the selectivity of the modified surfaces. Together these studies have led to a more complete understanding of the effects of the structure and solvation of modified surfaces on the selectivity and efficiency of chemical interactions occurring at those surfaces. These observations apply to interactions occurring at chromatographic stationary phases and to interactions at chemically modified surfaces in general.