In the present contribution, the pre-structuring of binary mixtures of hydrotropes and HO is linked to the solubilisation of poorly water miscible compounds. We have chosen a series of short-chain alcohols as hydrotropes and benzyl alcohol, limonene and a hydrophobic azo-dye (Disperse Red 13) as organic compounds to be dissolved. A very weak pre-structuring is found for ethanol/HO and 2-propanol/HO mixtures. Pre-structuring is most developed for binary 1-propanol/HO and tert-butanol/HO mixtures and supports the bicontinuity model of alcohol-rich and water-rich domains as already postulated by Anisimov et al. Such a pre-structuring leads to a high solubilisation power for poorly water miscible components (limonene and Disperse Red, characterized by high octanol/water partition coefficients, log(P) values of 4.5 and 4.85), whereas a very weak pre-structuring leads to a high solubilisation power for slightly water miscible components (benzyl alcohol). This difference in solubilisation power can be linked to (i) the formation of mesoscale structures in the cases of ethanol and 2-propanol and (ii) the extension of pre-structures in the cases of 1-propanol and tert-butanol. Three different solubilisation mechanisms could be identified: bulk solubilisation, interface solubilisation and a combination of both. These supramolecular structures in binary and ternary systems were investigated by small-and-wide-angle X-ray and neutron scattering, dynamic light scattering and conductivity measurements (in the presence of small amounts of salt).

The initial definition of hydrotropy by Neuberg in 1916 describes a hydrotrope as a molecule which enhances the solubilization of hydrophobic substances in water. Sodium dodecyl sulfate (SDS) and sodium xylene sulfonate (SXS) are typical representatives fulfilling this old definition. They are either surfactants with a critical micellar concentration (CMC) or hydrotropes in the current sense of the term, showing a minimum hydrotrope concentration (MHC), respectively. In the present contribution, we consider the antagonistic salt PPhCl as a hydrotrope. Surface tension measurements and solubilization experiments on a hydrophobic dye confirm the solubilization behavior of PPhCl, which is in-between the one of SDS and SXS. With the help of scattering techniques (DLS, SLS, SAXS), NMR and conductivity measurements, we show that in contrast to SDS as a hydrotrope with an inherent CMC, PPhCl does not exhibit mesoscale aggregation. Therefore, PPhCl can be classified rather as a hydrotrope in the modern sense, with an inherent MHC just as SXS.

The synthesis of organotriethoxysilanes by click chemistry was studied using the recyclable, multidentate catalyst [Cu(C18tren)]Br. For the evaluation, alkyne precursors containing some of the more common organic functions were reacted with a triethoxy silyl group containing azide. The procedure allowed the isolation of the desired products in high yields and high purity. Especially remarkable is the facility of the catalyst removal by simple filtration and evaporation. The catalyst is concluded to be ideal for the synthesis of moisture sensitive organotriethoxysilanes.

Soft matter structure 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 directing agent for silica nanoparticles in aerogel elaboration. Binary mixtures involving water/EtOH and water/tert-butanol have been respectively chosen as representatives of unstructured and structured solvents. The systems water/alcohol/TEOS were effectively characterized as surfactant free microemulsions. The enhanced solvent structuring, however, disappears upon the reaction of TEOS and assembly is directed by solvent structuring found in the binary. 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 allow changing the morphology, degree of interconnection and surface area of the resulting material. Silica nanoparticles with very high surface area up to 2000 m 2 /g can be obtained by this approach.