The stick-slip transition in highly entangled poly( styrene-butadiene) melts

We study the interfacial slippage of highly viscous polymer melts in a plane Couette cell by combining stress measurements and optical determination of sliding velocities (Fluorescence Recovery After Photobleaching). This enables us to observe the apparition of stick-slip instabilities in a narrow shear rate range whose limits are governed by the molecular characteristics of both the bulk and surface anchored polymer chains. A qualitative interpretation of these results will be given in terms of extraction and re-entanglement of the surface anchored chains from the bulk ones as well as a necessary criterion for the apparition of these instabilities. Experiments exploring the kinetics of the stick-slip regime appear to be a simple and promising way to investigate interfacial dynamics and to estimate the characteristic times involved. (C) 2001 Elsevier Science B.V. All rights reserved.