title: Conductivity in nonpolar media: experimental and numerical studies on sodium AOT-hexadecane, lecithin-hexadecane and aluminum(III)-3,5-diisopropyl salicylate-hexadecane systems.
abstract: The conductivity behavior of doped hydrocarbon systems is studied by applying impedance spectroscopy. In the case of 3,5-diisopropyl salicylato aluminum (III) the charge carriers are formed by dissociation of the compound and their concentration is proportional to the square root of the solute concentration. In hydrocarbon systems that consist of micelle forming compounds (sodium AOT/ lecithin) a linear dependence of charge carrier concentration on solute concentration is observed in the concentration regime where micelles are present. The conduction mechanisms are studied by numerical solution of a Poisson-Nernst-Planck system that describes the charge transport. We follow two different approaches to extract the degree of micelle dissociation from the impedance data. Firstly, by computing the response of a linear approximation of the Poisson-Nernst-Planck model, and secondly by computing the fully nonlinear response from direct numerical simulations using finite elements. For high and moderate frequencies both approaches agree very well with the experimental data. For small frequencies the response becomes nonlinear and the concept of impedance fails. Furthermore, the numerically computed values for the degree of dissociation are of the same order of magnitude as the values obtained with classical formulas, but still differ by a factor of about 1/3. The direct numerical simulation allows new insight into the conduction mechanisms for different frequency regimes.
authors.affiliation: Institute of Particle Technology, University of Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: Jochen
authors.initials: J
authors.lastname: Schmidt
authors.forename: Rodolphe
authors.initials: R
authors.lastname: Prignitz
authors.forename: Dirk
authors.initials: D
authors.lastname: Peschka
authors.forename: Andreas
authors.initials: A
authors.lastname: Münch
authors.forename: Barbara
authors.initials: B
authors.lastname: Wagner
authors.forename: Eberhard
authors.initials: E
authors.lastname: Bänsch
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Peukert
mesh_terms: D000473:Alkanes / Q000737:chemistry*; D000535:Aluminum / Q000737:chemistry*; D004553:Electric Conductivity; D054709:Lecithins / Q000737:chemistry*; D008823:Micelles; D008962:Models, Theoretical; D012459:Salicylates / Q000737:chemistry*; D013696:Temperature
chemical_list: D000473:Alkanes; D054709:Lecithins; D008823:Micelles; D012459:Salicylates; D000535:Aluminum; C007932:n-hexadecane