Dresden 2009 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 6: Thin Films

CPP 6.10: Talk

Monday, March 23, 2009, 16:30–16:45, ZEU 160

Ion specific effects in thin aqueous films — •Natascha Schelero and Regine v. Klitzing — Stranski-Laboratorium, Institut für Chemie, TU Berlin, Germany

The specific effects of electrolytes are omnipresent in all systems and processes based on liquid water. For instance the question arises, why salty water is foaming in a more pronounced way than salt free water. Therefore, the effect of addition of different types of salt on the (de)stability and functionality of single thin aqueous films (foam films) is of interest.[1] Within this work the stability and the interactions between film surfaces is determined in a so-called thin film pressure balance (TFPB).This apparatus is normally used to investigate free-standing symmetrical foam films. In recent studies our group showed that a TFPB also can be used for the investigation of wetting films (air/ water/ solid)[2]. A great advantage of measurements of asymmetrical films is that one can modify the charge of both interfaces independently e.g. by charged polyelectrolytes. The stability of aqueous wetting films on a solid substrate depends on the charge of the substrate and on the ionic strength of the liquid. These results indicate that the force within a water film is controlled by electrostatic interactions[3] and give evidence for negative charges at the air/ water interface[1,4]. Further on, we will present a new insight into ion specific effects in foam films and wetting films. [1] K. Ciunel,et al. Langmuir 2005, 21, 4790 [2] R. v. Klitzing, Adv. Coll. Int. Sci. 2005, 114/115, 253 [3] K. Hänni-Ciunel, et al. Soft Materials, 2007, 5, 61 [4] K. Hänni-Ciunel, N. Schelero, R. v. Klitzing, Faraday Discussion, 2008, in press