Berlin 2001 – wissenschaftliches Programm

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CPP: Chemische Physik und Polymerphysik

CPP 1: Special Symposium: Molecular Dynamics in Confined Geometries

CPP 1.7: Fachvortrag

Montag, 2. April 2001, 17:15–17:45, 3010

Interactions between polyelectrolytes and surfactants in free-standing black films — •Regine v. Klitzing, Branko Kolaric, and Jose Luis Toca-Herrera — Iwan-N.-Stranski-Institut, TU Berlin, Strasse des 17. Juni 112, 10623 Berlin

Free-standing aqueous surfactant films give the opportunity to study the interactions between two opposing air/liquid interfaces. The sum of interactions between the film surfaces is determined quantitatively by the disjoining pressure (disjoining pressure in dependence vs. film thickness) and is measured by varying the outer pressure in a so-called thin film balance. Pressure measurements at surfactant films containing polyelectrolytes will be presented, and analyzed in terms of current theories. The addition of polyelectrolytes leads to a stepwise thinning in the film thickness which is due to a mesoscopic ordering of the polyelectrolyte chains. The polyelectrolyte/surfactant interactions do not influence the jump size, but the total film thickness and film stability. In dependence on the surface charge and the polymer charge a transition from a Common Black Film (CBF, thickness determined by DLVO forces) to a Newton Black Film (NBF, thickness determined by steric forces) can be induced or avoided. This has a decisive effect on the film stability. Fluorescence measurements at films containing dye-labled polyelectrolytes give first qualitative informations about the amount of polyelectrolytes in CBF and NBF.