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Berlin 2008 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 4: Colloidal Fluids

CPP 4.2: Talk

Monday, February 25, 2008, 14:45–15:00, C 264

Charged colloids at water interfaces — •Martin Oettel1, Alvaro Dominguez2, Derek Frydel3, and Siegfried Dietrich31Mainz University, Germany — 2University of Seville, Spain — 3Max-Planck-Institute for Metals Research Stuttgart, Germany

The effective interactions of colloids trapped at fluid interfaces exhibit qualitatively new features when compared to the ones in colloidal bulk solutions. Electrostatic interactions which are exponentially screened in ionic solvents become longer–ranged and dipole–like at interfaces between water and a nonpolar medium (usually taken to be air or oil). We show (within Poisson-Boltzmann theory) that charge renormalization makes the effective electrostatic repulsion weakly dependent on the surface charge density on the water side and independent on the salt concentration in the high charge density limit [1]. This is in stark contrast to expectations from linear Debye-Hückel theory which has been used frequently to interpret experimental results. Furthermore, inhomogeneities of colloid surface charge or an anisotropic colloid shape affect the effective interaction only in subleading terms which asymptotically decay faster than the leading dipolar interaction which is isotropic in the interface plane [2].
D. Frydel, S. Dietrich, and M. Oettel, Phys. Rev. Lett. 99, 118302 (2007).
A. Dominguez, D. Frydel, and M. Oettel, arxiv:0706.3977.

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