title: The impact of the structuring of hydrotropes in water on the mesoscale solubilisation of a third hydrophobic component.
abstract: In the present contribution, the pre-structuring of binary mixtures of hydrotropes and H2O 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/H2O and 2-propanol/H2O mixtures. Pre-structuring is most developed for binary 1-propanol/H2O and tert-butanol/H2O 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).
authors.affiliation: Institute of Inorganic Chemistry, University of Regensburg, 93040 Regensburg, Germany. arno.pfitzner@chemie.uni-regensburg.de.
authors.forename: Thomas
authors.initials: T
authors.lastname: Buchecker
authors.affiliation: Institute of Physical and Theoretical Chemistry, University of Regensburg, 93040 Regensburg, Germany. werner.kunz@chemie.uni-regensburg.de.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Krickl
authors.affiliation: Institute of Physical and Theoretical Chemistry, University of Regensburg, 93040 Regensburg, Germany. werner.kunz@chemie.uni-regensburg.de.
authors.forename: Robert
authors.initials: R
authors.lastname: Winkler
authors.affiliation: Institut Laue-Langevin, 6 rue Jules Horowitz, Grenoble Cedex 9, 38042, France.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Grillo
authors.affiliation: Institut de chimie séparative de Marcoule (ICSM), UMR 5257 (CEA, CNRS, UM, ENSCM), BP 17171, 30207 Bagnols-sur-Cèze, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Bauduin
authors.affiliation: Institute of Physical and Theoretical Chemistry, University of Regensburg, 93040 Regensburg, Germany. werner.kunz@chemie.uni-regensburg.de.
authors.forename: Didier
authors.initials: D
authors.lastname: Touraud
authors.affiliation: Institute of Inorganic Chemistry, University of Regensburg, 93040 Regensburg, Germany. arno.pfitzner@chemie.uni-regensburg.de.
authors.forename: Arno
authors.identifier: http://orcid.org/0000-0001-8653-7439
authors.initials: A
authors.lastname: Pfitzner
authors.affiliation: Institute of Physical and Theoretical Chemistry, University of Regensburg, 93040 Regensburg, Germany. werner.kunz@chemie.uni-regensburg.de.
authors.forename: Werner
authors.initials: W
authors.lastname: Kunz