Influence of water in the reaction of γ-aminopropyltriethoxysilane with silica gel. A Fourier-transform infrared and cross-polarisation magic-angle-spinning nuclear magnetic resonance study

Abstract

Silica gel has been modified with y-arninopropyltriethoxysilane under varying conditions, controlling the influence of water in the different modification stages. Diffuse reflectance infrared Fourier-transform (DRIFT) spectra revealed the influence of surface water in the reaction stage and of air humidity in the curing stage. These results were confirmed and refined by 29Si and ' 3C cross-polarisation magic-angle-spinning nuclear magnetic resonance (CPMASNMR) spectroscopy. Combining the results of both techniques, four modification structures present on the silica surface are proposed, depending on the conditions used.

The mechanism for the controlled synthesis of highly dispersed vanadia supported on silica SBA-15

“…These studies have shown that the presence of surface water strongly influences the resulting structure of the adsorbed APTS [36]. Depending on the amount of water exposure during the modification stages of silica (pretreatment, reaction, curing), different structures were formed.…”

“…These XPS results show that the majority of APTMS molecules were in their bidentate form with a contribution from monodentate APTMS. Previously, the influence of surface water in the reaction of APTS with silica gel was studied extensively using 29 Si NMR and DRIFTS [36]. It was shown that hydrolysis of the alkoxy groups was prevented and mainly bidentate but no polymerized (tridentate) APTS was formed, when all modification stages, the silica pretreatment, the reaction of silica with APTS, as well as the curing stage were performed under dry/vacuum conditions.…”

Analytical Applications of Silica-Modified Electrodes -A Comprehensive Review

“…The most commonly used organosilane-modified substrate is silica gel coated with aminopropyltriethoxysilane [128][129][130][131]. It found applications in chromatography, trace-metal concentration, composite synthesis and protein immobilization [129].…”

Development and characterization of polymer-grafted ceramic membranes for solvent nanofiltration

“…SRNF membranes show a high potential in chemical synthesis as the recovery of homogeneous catalysts from reaction products [93] [94][95][96][97][98]. Many of the reactions where these catalysts are used are performed in solvents, resulting in extensive and usually destructive separations.…”

“…in toluene) condensation and hydrolysis between one or more functional groups of neighboring silane molecules mainly occurs on the surface with minimal intercondensation between silane molecules in the bulk phase [85,89,92]. For these multifunctional silanes, silylation occurs by hydrolysis of one or more of the chloro or alkoxy groups by water, which is preadsorbed on the support surface [89,91,93], present in the solvent (traces of humidity) [93,94] or provided by a post-silylation curing [93], followed by releasing of hydrochloric acid (HCl) or an alcohol (CH 3 OH or CH 3 CH 2 OH) for chloroor alkoxysilanes, respectively (equation 1). In a second step the hydrolyzed silane is adsorbed via hydrogen bonding and reacts with the surface OH group to form a M-O-Si bond via a condensation reaction (equation 2):…”