A steady-state dependence of slip velocity on shear stress at polymer/
solid surfaces is derived from a molecular model that includes effects
of drag on polymer chains, disentanglement, and detachment and reatta
chment of chains from the solid surface. The dependence includes two t
urning points and thus a region where slip velocity is a multivalued f
unction of shear stress. This behavior is consistent with experimental
observations of abrupt and hysteretic transitions between regimes of
small and large slip. Parameters involved in the model are estimated a
nd a reasonable comparison with experiment is obtained. (C) 1998 The S
ociety of Rheology. [S0148-6055(98)01106-7].