Dresden 2017 – wissenschaftliches Programm
CPP 62.4: Vortrag
Donnerstag, 23. März 2017, 15:45–16:00, ZEU 255
Influence of surfactants in forced dynamic dewetting — •Günter. K. Auernhammer, Franziska Henrich, Daniela Fell, Dorota Linke, and Hans-Jürgen Butt — MPI Polymer Research, Mainz, Germany
In this work we show that the forced dynamic dewetting of surfactant solutions depends sensitively on the surfactant concentration.
Anionic, cationic and nonionic surfactants with critical micelle concentrations (CMCs) spanning four orders of magnitude were used.
The receding contact angle in water decreased with increasing velocity. This decrease was strongly enhanced when adding surfactant, even at surfactant concentrations of 10% of the critical micelle concentration (1).
Plots of the receding contact angle- versus-velocity almost superimpose when being plotted at the same relative concentration (concentration/ CMC). Thus the rescaled concentration is the dominating property for dynamic dewetting. The charge of the surfactants did not play a role, excluding electrostatic effects. The change in contact angle can be interpreted by local surface tension gradients, i.e. Marangoni stresses, close to the three-phase contact line. The decrease of dynamic contact angles with velocity follows two regimes. Despite the existence of Marangoni stresses close to the contact line, for a dewetting velocity above 1–10 mm s−1 the hydrodynamic theory is able to describe the experimental results for all surfactant concentrations. Flow profiles at different length scales support the hydrodynamic interpretation of the governing mechanism.
(1) F. Henrich, et al. Soft Matter 12 (2016): 7782 - 7791.