  The slip behavior of polydimethylsiloxane (PDMS) polymer melts flowing on
non-adsorbing surfaces made of short non-entangled PDMS chains densely
end-grafted to silica has been characterized. For high enough shear rates,
constant slip lengths proportional to the bulk fluid viscosity have been
observed, in agreement with Navier's interfacial equation, and demonstrating
that the interfacial Navier's friction coefficient is a local quantity,
independent of the polymer molecular weight. Comparing the interfacial shear
stresses deduced from these measured slip lengths to available friction stress
measured for crosslinked PDMS elastomers, we directly compared the interfacial
melt or elastomer friction coefficient to the monomer-monomer friction.
