Silica M41S formation mechanism

Pinnavaia etal. used neutral alkylamines as templates to form disordered mesoporous silica, named hexagonal molecular sieves (HMS). The S°I° formation mechanism was proposed between neutral amine micelles (S°) and neutral inorganic precursors (1°). The interactions between S° and 1° were assumed to be hydrogen bonding. The resulting HMS has a worm-like pore structure, with thicker framework walls and smaller X-ray scattering domain sizes compared to M41S. 

This review of the proposed M 41S formation mechanism will address the issues of how M 41S materials formed, factors controlling this formation and principles of phase selection/transformation. The concepts concerning M41S formation have been formulated based on the studies involving silica (or aluminosilicate)-cationic surfactant systems. Their extension to other compositions will be discussed at the end of this section. As M41S materials are always prepared in the presence of amphiphiles (surfactants), it is safe to conclude that surfactant molecules play a vital role in their formation. Furthermore, the M41S materials... 

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