  Hydrodynamic slip of Newtonian liquids is a new phenomenon, the origin of
which is not yet clarified. There are various direct and indirect techniques to
measure slippage. Here we describe a method to characterize the influence of
slippage on the shape of rims surrounding growing holes in thin polymer films.
Atomic force microscopy is used to study the shape of the rim; by analyzing its
profile and applying an appropriate lubrication model we are able to determine
the slip length for polystyrene films. In the experiments we study polymer
films below the entanglement length that dewet from hydrophobized (silanized)
surfaces. We show that the slip length at the solid/liquid interface increases
with increasing viscosity. The correlation between viscosity and slip length is
dependent on the type of silanization. This indicates a link between the
molecular mechanism of the interaction of polymer chains and silane molecules
under flow conditions that we will discuss in detail.
