  The temperature dependence of the hydrodynamic boundary condition between a
PDMS melt and two different non-attractive surfaces made of either an OTS
(octadecyltrichlorosilane) self-assembled monolayer (SAM) or a grafted layer of
short PDMS chains has been characterized. A slip length proportional to the
fluid viscosity is observed on both surfaces. The slip temperature dependence
is deeply influenced by the surfaces. The viscous stress exerted by the polymer
liquid on the surface is observed to follow exactly the same temperature
dependences as the friction stress of a cross-linked elastomer sliding on the
same surfaces. Far above the glass transition temperature, these observations
are rationalized in the framework of a molecular model based on activation
energies: increase or decrease of the slip length with increasing temperatures
can be observed depending on how the activation energy of the bulk viscosity
compares to that of the interfacial Navier's friction coefficient.
