We propose a simple experimental procedure based on the cloud point measurement of a non-ionic surfactant as a tool for (i) estimating the super-chaotropic behaviour of polyoxometalates (POMs) and for (ii) establishing a classification of POMs according to their affinity towards polar surfaces.

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).

In the last decadeo rganic-inorganic hybrid materials have becomeessential in materials science as they combine properties of both buildingb locks. Nowadays the main routes for their synthesis involve electrostatic coupling, covalent grafting, and/or solvente ffects. In this field, polyoxometalates (POMs) have emerged as interesting inorganic functional buildingb locks due to their outstanding properties. In the present work the well-known a-Keggin polyoxometalate, a-PW 12 O 40 3À (PW), is shown to form hybrid crystalline materials with industrial (neutral) polyethylene glycol oligomers (PEG) under mild conditions, that is, in aqueous medium and at room temperature. The formation of these materials originates from the spontaneous self-assembly of PW with EO x ,( EO = ethylene oxide)w ith at least four EO units (x > 4). The PW-PEG nanoassemblies, made of aP OM surrounded by about two PEG oligomers, are stabilized by electrostatic repulsions betweent he negatively charged PW anions.A ddition of NaCl, aimed at screening the inter-nanoassembly repulsions,i nduces aggregation and formationo f hybrid crystalline materials. Single-crystal analysiss howed ah igh selectivity of PW towards EO 5 -EO 6 oligomers from PEG200, which is made of am ixture of EO 3-8 .T herefore, ag eneral "soft" route to produce POM-organic composites is proposed here through the controlo fe lectrostatic repulsions between spontaneously formed nanoassemblies in water.H owever, this rational design of new POM hybrid (crystalline) materials with hydrophilic blocks, using such as imple mixing procedureo ft he components, requires ad eep understanding of the molecular interactions.