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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 1: Focus: Amphiphilic Systems I

CPP 1.5: Vortrag

Montag, 23. März 2009, 12:00–12:15, ZEU 222

Switching of Electrical Conductivity in Microemulsions — •Thomas Wolff and Markus Bufe — Technische Universität Dresden, Physikalische Chemie, 01062 Dresden

Microemulsions exhibit three types of macroscopically monophasic solutions structures: water droplets in oil (w/o), oil droplets in water (o/w), and bicontinuous (sponge-like. In the latter two structures water forms a continuous phase. As a consequence these two structures show electrical conductivity in contrast to w/o. Transitions between the solutions states can be achieved by varying composition or temperature. The onset of electrical conductivity in conductivity versus temperature curves can be taken as the percolation temperature indicating the transition o/w - bicontinuous.

We have reported systems in which percolation temperatures are influenced by the presence of certain solubilizates. Photochemically reactive solubilizates allow isothermal switching of conductivity (without turning a mechanical contact), provided photoeduct and photoproduct induce different percolation temperatures. The solubilizates thus act as large response triggers for varying the solution structure. However, the systems described so far [1 and refences therein] allow switching in one way only, i.e. from conductive to non-conductive or vice versa.

Here we present AOT systems, in which thermally reversible photoreactions of solubilizates are used, so that the conductivity can be switched on under light (e.g. at daytime) and disappears in the dark (e.g. at night).

[1] M. Bufe, T. Wolff, Phys. Chem. Chem. Phys. 8 (2006) 4222-4227