Stick-Slip Transition at Polymer Melt/Solid Interfaces

A striking superfluidlike stick-slip transition is studied and semiquantitatively analyzed for a series of highly entangled linear polyethylene melts subjected to capillary flow. The observed violation of the law of the stick hydrodynamic boundary condition is significant and unambiguous, and can be conveniently characterized by an extrapolation length $b$. It is shown that $b$ at the transition is independent of temperature and sharply increases with molecular weight in confirmation with a simple scaling relation introduced by de Gennes.