Liquid crystal templates of mesoporous silica materials

The paper considers the mesophases of lyotropic liquid crystals and their role in creating the scaffold of mesoporous silica materials. It was in 1992 that a Mobil Research group disclosed a method to produce silica particles having a regular network of pores with hexagonal and cubic symmetries. The method was proposed as based on a liquid-crystal 'templating' mechanism. Since the symmetries resulting from the templating of silica scaffolds are those observed in the mesophases of lyotropic liquid crystals, the Mobil Research group supposed the presence of a mesophase directly in a stage of the templating mechanism. Here we discuss the method as it was reported in 1992 and what is today defined as a true liquid-crystal templating approach. It will be stressed that, in any case, the templating is a surfactant-assisted method, that can be better defined as supramolecular templating method. The template mainly happens in the form of a modified Stöber process. In this framework, the cubic phases of liquid crystals will be analyzed in depth. The related surfaces with zero mean curvature (gyroids) will by discussed through a Ginzburg-Landau model.