  Using Couette and Poiseuille flow, we extract the temperature dependence of
the slip length, $\delta$, from molecular dynamics simulations of a
coarse-grained polymer model in contact with an attractive, corrugated surface.
$\delta$ is dictated by the ratio of bulk viscosity and surface mobility. At
weakly attractive surfaces, a lubrication layer forms, $\delta$ is large and
increases upon cooling. Close to the glass transition temperature, $T_ g$, very
large slip lengths are observed. At a more attractive surface, a``stick y
surface layer" is build up, which gives rise to a small slip length. Upon cool
ing, $\delta$ decreases at high temperatures, passes through a minimum and
grows upon approaching $T_g$. At strongly attractive surfaces, the Navier-slip
condit ion fails to describe Couette and Poiseuille flow simultaneously. The
simulation results are corroborated by a schematic, two-layer model suggesting
that the ob servations do not depend on the details of the computational model.
