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SYSO: Symposium Self-organizing Surfaces and Interfaces

SYSO 3: Self-Organizing Surfaces and Interfaces - Posters

SYSO 3.13: Poster

Mittwoch, 25. März 2009, 17:30–19:30, P3

Influence of Polymers on polarizability and structure of microemulsion droplets — •Robert Wipf, Sebastian Jaksch, Bernd Stühn, and Björn Kuttich — TU Darmstadt, Experimentelle Physik kondensierter Materie, 64289 Darmstadt, Germany

Water-in-oil microemulsions are thermodynamically stable mixtures of water droplets in a continuous oil phase. The droplets are stabilized by a monomolecular layer of amphiphilic surfactant molecules. The investigated microemulsion consists of water and decane with sodium bis(2-ethylhexyl)sulfosuccinate (AOT) as ionic surfactant. We determine the structure of this system by SAXS showing spherical structure. The conductivity of such systems exhibits a steep increase when volume fraction or temperature increase above a critical value. This behavior can be understood as dynamic percolation. In the dielectric spectrum of a microemulsion, as a heterogeneous system, an interfacial polarization, known as Maxwell-Wagner-Sillars effect, was observed. In the high frequency regime a further relaxation occurs, which can be attributed to the sodium and AOT moiety ions. This relaxation depends strongly on the water content of the droplets as well as their interaction. Adding PEO to the water core leads to an extra polymer shell on the inner side of the droplet interface. Its influence on percolation temperature and structure can be observed by dielectric spectroscopy and SAXS. Adding the amphiphilic triblock copolymer PEO-PI-PEO at low droplet volume fraction decorates the droplets. This decreases attractive interaction among the droplets as we observe in dielectric and SAXS measurements.