12-17 June 2000, University of Leipzig, Germany

High Resolution Magic Angle Spinning (HRMAS) provides a powerful tool for the study of molecules bound to solid supports like resins or polymers, or soft materials such as lipids or physiological tissues. The averaging of the residual dipole interactions leads to spectra are of nearly liquid state quality. We show that HRMAS can also be applied in the case of the template surfactants in mesoporous silica gels before the final calcination step. Leaving the surfactants inside the pores could provide new applications in the domain of mesoporous materials, linked to the chemical properties of the organic part of the gels. HRMAS could help to fully characterize those materials during the various steps of synthesis. 29Si, 13C or 1H MAS NMR are valuable characterization methods for calcined and non-calcined silica materials. However, solid state MAS NMR yields limited information about the surfactants or adsorbed molecules, owing to non-quantitative low-resolution spectra. High resolution spectra have been obtained by adding an appropriate solvent. 1D and 2D NMR experiments allowed a more detailed investigation of the surfactants and their interactions with the silica surface. Recoupling of the static dipolar interaction by rotational resonance experiments was performed between protons belonging to different types of surfactants. The results obtained by HRMAS for two types of silica gels will be presented.