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

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.