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O: Oberflächenphysik

O 18: Grenzfl
äche fest-flüssig

O 18.5: Talk

Tuesday, March 12, 2002, 12:15–12:30, H44

Layering Transitions and Density Fluctuations in Thin Liquid Films — •Thomas Becker, Anke Klingner, and Frieder Mugele — University of Ulm, Dept. of Applied Physics, Albert Einstein Allee 11, D-89069 Ulm

We used a modified surface forces apparatus (SFA) with 2-dimensional image acquisition to study layering transitions in thin liquid films confined between two freshly cleaved mica sheets. For octamethylcyclotetrasiloxane (OMCTS) we observed four subsequent layering transitions. In contrast to previous experiments with undecanol [1, 2], the boundary line between the areas of initial and of final film thickness remains smooth during the transition. As the film thickness decreases, the average speed of the boundary line decreases, too. From the latter, we infer the relative increase of the friction coefficient. We also analyzed fluctuations of transmission in metastable layers, which can be converted to fluctuations of the film’s optical thickness. From these measurements, we derived an upper limit for the amplitude of density fluctuations in our 2D OMCTS films. [1] F.Mugele, M.Salmeron, Phys. Rev. Lett. 84(25), 2000 [2] S.Zilberman et al., Phys. Rev. E 63(5),2001