title: Clouding in fatty acid dispersions for charge-dependent dye extraction.
abstract: The clouding phenomenon in non-ionic surfactant systems is a common feature that remains rare for ionic detergents. Here, we show that fatty acid (negatively charged) systems cloud upon cooling hot dispersions depending on the concentration or when adding excess guanidine hydrochloride. The clouding of these solutions yields the formation of enriched fatty acid droplets in which they exhibit a polymorphism that depends on the temperature: upon cooling, elongated wormlike micelles transit to rigid stacked bilayers inside droplets. Above this transition temperature, droplets coalesce yielding a phase separation between a fatty acid-rich phase and water, allowing extraction of dyes depending on their charge and lipophilicity. Positively charged and zwitterionic dyes were sequestered within the droplets (and then in the fatty acid-rich upper phase) whereas the negatively charged ones were found in both phases. Our results show an additional case of negatively charged surfactant which exhibit clouding phenomenon and suggest that these systems could be used for extracting solutes depending on their charge and lipophilicity.
authors.affiliation: UMR 1332, biologie et pathologie du fruit, INRA, centre de Bordeaux, 33883 Villenave d'Ornon, France.
authors.forename: David
authors.initials: D
authors.lastname: Garenne
authors.affiliation: Université de Bordeaux, Centre de Recherche Paul-Pascal, CNRS, Av. A. Schweitzer, 33600 Pessac, France.
authors.forename: Laurence
authors.initials: L
authors.lastname: Navailles
authors.affiliation: Université de Bordeaux, Centre de Recherche Paul-Pascal, CNRS, Av. A. Schweitzer, 33600 Pessac, France.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Nallet
authors.affiliation: Institute of Chemistry and Biology of Membranes and Nano-objects, UMR 5248, CNRS, Université de Bordeaux, Institut Polytechnique Bordeaux, F-33600 Pessac, France.
authors.forename: Axelle
authors.initials: A
authors.lastname: Grélard
authors.affiliation: Institute of Chemistry and Biology of Membranes and Nano-objects, UMR 5248, CNRS, Université de Bordeaux, Institut Polytechnique Bordeaux, F-33600 Pessac, France.
authors.forename: Erick J
authors.initials: EJ
authors.lastname: Dufourc
authors.affiliation: UMR 1332, biologie et pathologie du fruit, INRA, centre de Bordeaux, 33883 Villenave d'Ornon, France. Electronic address: jean-paul.douliez@bordeaux.inra.fr.
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Douliez
mesh_terms: D004396:Coloring Agents / Q000737:chemistry / Q000302:isolation & purification*; D005227:Fatty Acids / Q000737:chemistry*; D019791:Guanidine / Q000737:chemistry; D010316:Particle Size; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry
chemical_list: D004396:Coloring Agents; D005227:Fatty Acids; D013501:Surface-Active Agents; D019791:Guanidine
keywords: Compartments; Dye sequestration; Fatty acid; Self-assembly; Surfactant clouding