The true liquid crystal approach to mesoporous silica

Liquid crystalline phases, consisting of nonionic surfactant and water, are exploited as templates for the synthesis of inorganic nanostructures. In this approach the aqueous domains of a lyotropic liquid crystal phase function as a confining medium, in which the polymerisation of a water-soluble precursor takes place without destroying the nanostructure. Conducting the prepration of mesoporous silica in a lyotropic liquid crystal phase has considerable advantages over previous routes towards mesoporous ceramic oxides. (i) The nanostructure of the solid can be predicted a priori by knowing the phase structure of the liquid crystal before solidification, (ii) this approach allows the use of nonionic surfactants as templates, (iii) the progress of the reaction can be observed by a variety of methods, such as polarised light optical microscopy, X-ray diffraction, and deuterium NMR spectroscopy, all of which are noninvasive. The synthesis and a new way of monitoring the temporal evolution of the inorganic nanostructure using deuterium NMR spectroscopy are described. The results show unambiguously that the lyotropic liquid crystal phase acts as a template for the nanostructure.