title: Water-AOT-alkylbenzene microemulsions: influence of alkyl chain length on structure and percolation behavior.
abstract: We study the percolation behavior of the water-in-oil (w/o) droplet phase of AOT (sodium bis[2-ethylhexyl] sulfosuccinate)-based microemulsions with different alkylbenzenes (toluene, ethylbenzene, butylbenzene or octylbenzene) as oil phase. We use microemulsions of varying composition with molar water to surfactant ratios 0≤W≤ 50 and droplet (water plus surfactant) volume fractions 10%≤φ≤50%. Using dielectric spectroscopy, a percolation transition is observed in w/o microemulsions with butylbenzene or octylbenzene. With increasing molecular weight of the alkylbenzene, the percolation temperature T(P) decreases. The structure of the microemulsions is determined by small angle X-ray scattering (SAXS). With increasing molar weight of the alkylbenzene, the stability range of the L(2) droplet phase extends to higher W. The larger amount of solubilizable water can be related to variable oil penetration of the AOT monolayer, which affects the spontaneous curvature of the surfactant shell.
authors.affiliation: Institut für Festkörperphysik, Technische Universität Darmstadt, 64289 Darmstadt, Germany. markus.appel@fkp.physik.tu-darmstadt.de
authors.forename: Markus
authors.initials: M
authors.lastname: Appel
authors.forename: Tinka Luise
authors.initials: TL
authors.lastname: Spehr
authors.forename: Robert
authors.initials: R
authors.lastname: Wipf
authors.forename: Bernd
authors.initials: B
authors.lastname: Stühn