Berlin 2008 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 14: Membranes
CPP 14.4: Talk
Tuesday, February 26, 2008, 15:45–16:00, C 230
Polyelectrolyte-surfactant interactions in foam films — •Nora Kristen1, Vasile Simulescu1,2, and Regine v. Klitzing1 — 1Stranski-Laboratorium, Institut für Chemie, Technische Universität Berlin, Str. d. 17.Juni 124, 10623 Berlin — 2West University Timisoara, 300223 Timisoara, Rumania
Interactions between polyelectrolytes and surfactants in foams are of interest for many technical applications, e.g. in cleaning processes. Foam consists of many single free-standing films; to investigate these foam films a so called Thin Film Pressure Balance (TFPB) is used. With this apparatus disjoining pressure isotherms are measured (disjoining pressure vs. film thickness).
Depending on the charge combination of the surfactant and the polyelectrolyte, two different types of films can be formed: either a Common black Film (CBF, mainly stabilized by electrostatic forces) or a Newton Black Film (NBF, mainly stabilized by steric forces).
The addition of polyelectrolytes affects the interactions within the foam due to complexation between the surfactant and the polyelectrolyte at the surfaces. With a cationic surfactant like C(n)TAB a film with positive charged surfaces is formed. After addition of negative polyelectrolyte, the charge at the surface is reversed. In both cases, a CBF is formed due to the electrostatic repulsion of the two interfaces. But what happens at isoelectric point of the surface charge: Is a NBF formed or does the film break? The addition of very low polyelectrolyte concentrations leads to a low net surface charge. Therefore the stability of films with a low polyelectrolyte concentration is investigated.