Structural Evolution during the Synthesis of Mesoporous Silica in Fatty Acid/Aminoalkoxysilane/Water Systems

Abstract

We report on the phase behavior and structural evolution during the early stages of silica templating using surfactant liquid crystals in aminoalkoxysilane/lauric acid/water systems. Specific aminoalkoxysilanes are used so that hydrolysis and condensation reactions are slow enough to follow the changes in the early stages of mesoporous silica formation without the need for very sophisticated techniques. A lyotropic lamellar phase that swells with water is present in the early stages of the system and develops into kinetically correlated siliceous phases with preservation of morphology. Moreover, lyotropic and siliceous phases coexist at a certain time. Hydrolysis and condensation of alkoxysilane groups cause microstructural changes in the lyotropic lamellar phase, as monitored by in situ small-angle X-ray scattering and infrared spectroscopy measurements. Although the changes in the initial lamellar phase depend on the nature of the alkoxysilane groups, the final siliceous phases show similar correlation ...