Résumé
Hydrotropes are added component in a formulation that allow efficient solubilisation of poorly miscible solutes in water, via formation of a nanostructured solution in dynamic equilibrium. Hydrotropes reduce surface tension, but unlike true surfactants do not form micelles on their own in water(Kunz, Holmberg, & Zemb, 2016). The most studied hydrotropes such as ethanol and tert-butylacohol, while in industrial formulation sodium salicylate and tosylate are used intensively. These two electrolytes are made of one big polarisable ion and one small hydrated counter-ion, thus responding to the general definition of antagonistic ion pair as defined by Onuki and co-workers(Onuki, Yabunaka, Araki, & Okamoto, 2016).In this talk, we will explore ternary phase diagrams obtained with salicylate. Unlike uncharged hydrotropes, there is no anomaly in calorific capacity or density in the water-rich pre-ouzo region, and therefore to “pre-ouzo effect”. Unlike non-electrolyte hydrotropes, the critical point lies on the solvent-rich side of the phase diagram. A very interesting region produces intense light and X-ray scattering scattering and lies near a crystallisation boundary. The loose aggregates produced are linked to an extraordinary fluid density anomaly , and preferential solubilisation entropy stabilizes small aggregates similar to DOLLOPS ten years ago in the case of calcium carbonate(Gebauer, Völkel, & Cölfen, 2008), and extensively used as the most efficient inorganic micro-gels in art preservation, according to methods developed by Baglioni and co-workers(Baglioni et al., 2014), and could be another examples of “solvent-swollen electrolytes inorganic micelles” as proposed by several groups studying electrolyte self-assembly. We propose that these dynamic colloidal aggregates are the missing species in the Pourbaix diagram used in geochemistry, electrochemistry and inorganic chemistry.Acknowldegement: The rench-Greman CNRS/MPG network NISI is acknowledged for support.References: Baglioni, P., Berti, D., Bonini, M., Carretti, E., Dei, L., Fratini, E., & Giorgi, R. (2014). Micelle, microemulsions, and gels for the conservation of cultural heritage. Advances in Colloid and Interface Science, 205, 361–371. http://doi.org/10.1016/j.cis.2013.09.008Gebauer, D., Völkel, A., & Cölfen, H. (2008). Stable Prenucleation Calcium Carbonate Clusters. Science (New York, N.Y.), 322(5909), 1819–1822. http://doi.org/10.1126/science.1164271Kunz, W., Holmberg, K., & Zemb, T. (2016). Hydrotropes. Current Opinion in Colloid & Interface Science, 22, 99–107. http://doi.org/10.1016/j.cocis.2016.03.005Onuki, A., Yabunaka, S., Araki, T., & Okamoto, R. (2016). Structure formation due to antagonistic salts. Current Opinion in Colloid & Interface Science, 22, 59–64. http://doi.org/10.1016/j.cocis.2016.02.007