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"Polymer droplets on top of a brush of chemically identical molecules: Autophobic dewetting and motion of droplets under external force on a soft substrate"
M. Müller, C. Pastorino, T. Kreer, K. Binder and L. Gonzalez MacDowell
Proc. of the "231st American Chemical Society (ACS) National Meeting", Atlanta, Georgia, USA, March 26-30, 2006.
ACS Abstracts 231, PMSE 416 (2006)
Brushes are soft, elastically deformable substrates giving rise to a rich wetting behavior and additional molecular dissipation mechanisms for the motion of droplets. We study thin polymer films and droplets on flat brush-covered substrates by non-equilibrium molecular dynamics simulation of a coarse-grained bead-spring model. The brush consists of identical polymers as the droplets. 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 in equilibrium and under shear. The velocity profile across a thin polymer film is investigated. The slip length adopts large positive values (perfect slip) for low grafting densities, but decreases and becomes negative for densely grafted, autophobic brushes. At high grafting density the polymer melt dewets from the brush and forms droplets. Nanoscopic polymer droplets driven by volume forces are investigated in their steady state.
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