FRICTION IN STRONGLY CONFINED POLYMER MELTS - EFFECT OF POLYMER BRIDGES

We propose a molecular theory of friction in confined polymer melts be tween atomically smooth surfaces, taking polymer bridges between the s urfaces into account. Using the activation friction model, we consider the bridge adsorption-desorption dynamics and calculate the macroscop ic friction force (the tangential stress) in the system as a function of the imposed velocity. We show that the bridges result in the regime where the friction force decreases with the increase of the imposed v elocity. The friction force passes through maximum and minimum values in the crossover range between linear and nonlinear regimes. We also i nvestigate the stability of sliding in the regime with decreasing fric tion force.