Physics of Trapped Macromolecular Chains from Surface Force Apparatus Dynamic Measurements

We present experimental data of the rheological behavior of a polymer melt in a confined state. The polymer is adsorbed on the surfaces of the cell of a dynamic surface force apparatus. We analyze the variations of the zero-shear viscosity and the steady-state compliance with the separation of the surfaces by using a model of nonuniform medium. The viscosity of the adsorbed layers is about three times as much as in the melt, whereas their compliance increases by a factor of some thousands. Those results are described in terms of length distribution of the loops and tails and of their interconnection with the free chains. The impact of possible sliding motions either at the surfaces or between tethered and free chains is rejected in our experiment.