Berlin 2012 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 36: Wetting, Micro and nanofluidics I
CPP 36.2: Vortrag
Donnerstag, 29. März 2012, 15:30–15:45, C 264
Influence of surfactant concentration and transport on forced dynamic wetting — •Daniela Fell1,2, Ngamjarassrivichai Pawanrat1,3, Manos Anyfantakis1, Elmar Bonaccurso2, Hans-Jürgen Butt1, and Günter K. Auernhammer1 — 1Max Planck Institute for Polymer Research, Mainz, Germany — 2Center of Smart Interfaces, Darmstadt, Germany — 3Chulalongkorn University, Bangkok, Thailand
We study the influence of surfactants as well as their local and non-local transport processes on dynamic contact angles in a rotating drum setup. Therefore contact angles of surfactant solutions at concentrations well below the critical micelle concentration (cmc) are measured as a function of wetting/dewetting velocity. Surface transport of surfactant is hindered by the axis holding the cylinder. Changing the filling height from half filled to slightly below or above the axis removes this hindrance. For blocking surface as well as bulk transport an additional metallic barrier is added to a half filled bath.
With increasing surfactant concentration the receding contact angle decreased. Stronger surfactants (low cmc) show a larger decrease of the contact angle than weaker ones. Additionally, at a constant concentration the receding contact angle decreased when increasing the hindrance to surfactant transport. Dynamic contact angles are therefore not only influenced by short-range effects like Marangoni stresses, but also by long-range transport processes like diffusion and advection between regions close to the advancing and receding contact lines.