Study of interactions between silicate species and surfactant micelles in the synthesis of organized mesoporous materials

Abstract

We report investigations into silicate/surfactant assembly in the preliminary stages of the formation of ordered mesoporous siliceous MCM-41 materials. These materials were obtained in the presence of cetyltrimethylammonium bromide (C.TAB) or chloride (C.TAC) as surfactants by decreasing the pH of clear basic silicate solutions (waterglass solution or octameric silicate species Si 8 O 20 8− ). The influence of the surfactant molecules on the nature of silicate species was studied by 29 Si liquid state NMR spectroscopy. Pyrene time-resolved fluorescence quenching experiments were used to characterize surfactant micelles in the presence of silicate species and/or NaOH. The results obtained suggest that interactions between silicate species and surfactant micelles are weak in the precursor solution. The absence of any organization in the system prior to precipitation seems to indicate that the most important step in the process is the formation of siliceous prepolymers.