Dresden 2009 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 6: Thin Films
CPP 6.11: Vortrag
Montag, 23. März 2009, 16:45–17:00, ZEU 160
Tuning of interactions in foam films from oppositely charged polyelectrolyte/surfactant mixtures — •Nora Kristen1, Vasile Simulescu1, Reinhard Miller2, and Regine v. Klitzing1 — 1Stranski-Laboratorium, TU Berlin, Berlin, Germany — 2Max Planck Institute of Colloids and Interfaces, Potsdam-Golm, Germany
Polyelectrolyte/surfactant mixtures in foams play an important role in many technical applications, e.g. in decalcification processes and cosmetics. In order to control the properties of the foam it is important to investigate single free-standing foam films. A quantitative measure of the interactions between the two opposing film interfaces is the disjoining pressure, which is the sum of repulsive electrostatic, attractive van der Waals and steric forces. The disjoining pressure as a function of film thickness is measured with a Thin Film Pressure Balance.
In this work we study the interactions between polyelectrolytes and surfactants in foam films at low surface charge. To tune the surface charge the concentration of negatively charged polyelectrolyte is varied. Starting with a cationic surfactant films with positively charged surfaces are formed. With the addition of more polyelectrolyte the surface charge is reduced and then reversed. Low and high polyelectrolyte concentrations induce the formation of thick Common Black Films but what happens at very low surface charges? Is a thin Newton Black Film formed or does the film break? Results on the stability of films with different polyelectrolytes are presented and compared with surface tension and elasticity measurements.The effect of polelectrolytes is compared to the influence of their monomers.