title: Transformation from Globular to Cylindrical Mixed Micelles through Molecular Exchange that Induces Micelle Fusion.
abstract: Transformations between different micellar morphologies in solution induced by changes in composition, salt, or temperature are well-known phenomena; however, the understanding of the associated kinetic pathways is still limited. Especially for mixed surfactant systems, the micelles can take a very wide range of structures, depending on the surfactant packing parameter and other thermodynamic conditions. Synchrotron-based small-angle X-ray scattering (SAXS) in combination with fast mixing using a stopped-flow apparatus can give direct access to the structural kinetics on a millisecond time scale. Here, this approach is used to study the formation of cylindrical micelles after mixing two solutions with globular micelles of the nonionic surfactant dodecyl maltoside (DDM) and the anionic surfactant sodium dodecyl sulfate (SDS), respectively. Two separate processes were identified: (i) a transition in micellar shell structure, interpreted as exchange of surfactant molecules resulting in mixed globular micelles, and subsequently, (ii) fusion into larger, cylindrical structures.
authors.affiliation: Department of Chemistry and Interdisciplinary Nanoscience Center (iNANO), Aarhus University , Gustav Wieds Vej 14, DK-8000 Aarhus, Denmark.
authors.forename: Grethe V
authors.initials: GV
authors.lastname: Jensen
authors.affiliation: Department of Chemistry, University of Oslo , Postbox 1033 Blindern, NO-0315 Oslo, Norway.
authors.forename: Reidar
authors.initials: R
authors.lastname: Lund
authors.affiliation: ESRF-The European Synchrotron , 71 Avenue des Martyrs, F-38043 Grenoble, France.
authors.forename: Theyencheri
authors.initials: T
authors.lastname: Narayanan
authors.affiliation: Department of Chemistry and Interdisciplinary Nanoscience Center (iNANO), Aarhus University , Gustav Wieds Vej 14, DK-8000 Aarhus, Denmark.
authors.forename: Jan Skov
authors.initials: JS
authors.lastname: Pedersen
mesh_terms: D005960:Glucosides / Q000737:chemistry*; D007700:Kinetics; D008823:Micelles; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry*; D013501:Surface-Active Agents / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D005960:Glucosides; D008823:Micelles; D013501:Surface-Active Agents; D012967:Sodium Dodecyl Sulfate; C040358:dodecyl maltoside