We study the interfacial slippage of highly viscous polymer melts in a plan
e Couette cell by combining stress measurements and optical determination o
f sliding velocities (Fluorescence Recovery After Photobleaching). This ena
bles us to observe the apparition of stick-slip instabilities in a narrow s
hear rate range whose limits are governed by the molecular characteristics
of both the bulk and surface anchored polymer chains. A qualitative interpr
etation of these results will be given in terms of extraction and re-entang
lement of the surface anchored chains from the bulk ones as well as a neces
sary criterion for the apparition of these instabilities. Experiments explo
ring the kinetics of the stick-slip regime appear to be a simple and promis
ing way to investigate interfacial dynamics and to estimate the characteris
tic times involved. (C) 2001 Elsevier Science B.V. All rights reserved.