Dresden 2006 – scientific programme
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CPP: Chemische Physik und Polymerphysik
CPP 24: POSTER Microfluidics
CPP 24.11: Poster
Thursday, March 30, 2006, 17:00–19:00, P2
Polymer Droplets on Soft, Brush-Coated Substrates — •Torsten Kreer1, Claudio Pastorino2, Kurt Binder2, and Marcus Mueller3 — 1Institut Charles Sadron, 6 rue Baussingault, 67083 Strasbourg Cedex, France — 2Institut fuer Physik, WA331, Johannes-Gutenberg-Universitaet, 55099 Mainz, Germany — 3Institut fuer theoretische Physik, Georg-August-Universitaet, 37077 Goetingen, Germany
Brushes are soft, elastically deformable substrates exhibiting a rich wetting behavior and additional dissipation mechanisms for the motion of droplets. We study thin polymer films and droplets on brushes by NEMD simulation using a DPD thermostat. The brushes consist of chemically identical polymers as the droplets.
The properties of the interface between the brush and the melt of identical molecules in equilibrium and under shear are dominated by universal entropic effects. Upon increasing the grafting density the free polymers are expelled from the brush and a brush-melt interface gradually builds up. Molecular conformations and the overlap between brush and melt are studied for different grafting densities. The slip length of the melt on the brush substrate is extracted from the velocity profiles and adopts large positive values for low grafting densities, but decreases and becomes negative for dense, autophobic brushes.
At high grafting density the polymer melt forms droplets (autophobic dewetting). Nanoscopic polymer droplets driven by volume forces (e.g. inclined plane or centrifugal forces) are investigated. The steady state at which the droplet moves at constant velocity is discussed.