On the silica edge, an NMR point of view

‘‘The properties of amorphous silicas of high specific surface area, from the smallest colloidal particles to macroscopic gels, depend largely on the chemistry of the surface of the solid phase’’ [1]. Silicas are useful for numerous applications. The most recent application is certainly their use in the tire manufacturing process (Energy Tires of Michelin Cie). As styrene-butadiene rubber compatibility with an organophobic silica is questionable contrarily with carbon black, it was necessary to investigate the surface composition to adapt it to such application. To do this, different methods have to be used. Infra-red spectrometry was the first physical method to demonstrate the existence of single and/or associated hydroxyls groups (Fig. 1). More recently solid state NMR was not only able to identify geminal, the existence of which was sometimes debated, but also single or associated hydroxyls.