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 Dietrich3 — 1Mainz 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.