title: Isothermal behavior of the Soret effect in nonionic microemulsions: size variation by using different n-alkanes.
abstract: In this work we investigate the thermodiffusion behavior of microemulsion droplets of the type H2O/n-alkane/C12E5 (pentaethylene glycol monododecyl ether) using the n-alkanes: n-octane, n-decane, n-dodecane, and n-tetradecane. In order to determine the thermodiffusion behavior of these microemulsion droplets, we apply the infrared thermal diffusion forced Rayleigh scattering (IR-TDFRS) technique. We measure the Soret coefficient (ST) as function of the structure upon approaching the emulsification failure boundary (efb) and as a function of the radius of the spherical o/w microemulsion droplets close to the efb. By varying the chain length of the n-alkanes, we are able to study the thermodiffusion behavior of spherical o/w microemulsion droplets of different sizes at the same temperature. In the investigated range a linear dependence of the Soret coefficient as function of the radius was found. By use of a proposed relationship between the Soret coefficient and the temperature dependence of the interfacial tension, the transition layer l could be determined for the first time. Additionally, small angle neutron scattering (SANS) experiments are performed to determine the size and to prove that the shape of the microemulsion droplets is spherical close to the efb. Accordingly, the scattering curves could be quantitatively described by a combination of a spherical core-shell form factor and sticky hard sphere structure factor.
authors.affiliation: ICS-Soft Condensed Matter, Forschungszentrum Jülich GmbH , D-52428 Jülich, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Naumann
authors.forename: Sascha
authors.initials: S
authors.lastname: Datta
authors.forename: Thomas
authors.initials: T
authors.lastname: Sottmann
authors.forename: Bastian
authors.initials: B
authors.lastname: Arlt
authors.forename: Henrich
authors.initials: H
authors.lastname: Frielinghaus
authors.forename: Simone
authors.initials: S
authors.lastname: Wiegand
mesh_terms: D000473:Alkanes / Q000737:chemistry*; D004655:Emulsions; D008956:Models, Chemical; D015394:Molecular Structure; D033363:Neutron Diffraction; D053838:Scattering, Small Angle; D013501:Surface-Active Agents / Q000737:chemistry*; D013696:Temperature; D014867:Water
chemical_list: D000473:Alkanes; D004655:Emulsions; D013501:Surface-Active Agents; D014867:Water