A new synthesis of mesoporous MSU-X silica controlled by a two-step pathway

In the field of micelle templated structures (MTS), the MSU-X family of mesoporous silica is obtained by using nonionic poly(ethylene oxide)-based surfactants. We show that the microstructure of these materials is highly dependent on the initial pH conditions and that a first assembly step, using a mild acidity, which allowed us to obtain a stable solution containing micellar hybrid objects made of both surfactant micelles and small silica oligomers, can be determined in the 2-4 pH range. The second step of the synthesis consists of the condensation of the silica particles and can be performed in two different ways. Either the pH of the stable solution is increased to neutral values or small amounts of fluoride are added. With the second method both the nanostructure and the particle morphology are better controlled. This novel two-step synthesis leads in addition to hexagonal pore framework when assembly molecules such as Tween 60 or block copolymer Pluronic P123 are used as assembly agents.