Impact of Solvent Structuring in Water/ tert-Butanol Mixtures on the Assembly of Silica Nanoparticles to Aerogels.

Soft matter structuring is a useful tool for the preparation of well-structured inorganic materials. Here, we report a strategy using a structured solvent based on binary mixtures as a directing agent for silica nanoparticles in aerogel elaboration. Binary mixtures involving water/ethanol and water/ tert-butanol have been respectively chosen as representatives of unstructured and structured solvents. The water/alcohol/TEOS systems were effectively characterized as surfactant-free microemulsions. The enhanced solvent structuring, however, disappears upon the reaction with TEOS, and assembly is directed by solvent structuring found in the binary mixtures. For the first time, the influence of solvent composition on the sol-gel reaction was investigated with respect to the reaction rate and the structuring behavior thanks to dynamic light scattering (DLS), small- and wide-angle X-ray scattering (SWAXS), and transmission electron microscopy (TEM) experiments. The silica nanoparticles aggregate in a different manner depending on the solvent composition, which allows the change in the morphology, the degree of interconnection, and the surface area of the resulting material. Silica nanoparticles with a very high surface area of up to 2000 m2/g can be obtained by this approach.