NONLINEAR ELASTICITY AND FRICTION OF LIQUID-CRYSTALLINE POLYMER MONOLAYERS

In the present paper we consider nonlinear elasticity and friction of grafted persistent chains, which are highly stretched in the normal to the surface direction due to orientational interactions. We examine t he normal and the lateral forces both in equilibrium and under shear s liding when the monolayer is confined by a bare surface. We show that in the confined monolayer in equilibrium the tilted orientation of the director becomes stable. In the sliding regime the friction force pas ses through a maximum value. The additional normal force in the slidin g regime, when the distance between the surfaces is fixed, is also con sidered. We show that this force is attractive for small velocities an d becomes repulsive for high velocities after the friction force passe s through the maximum value. (C) 1998 American Institute of Physics.