Nonlinear rheology of confined polymer melts under oscillatory flow

We present a theory for nonlinear dynamics of confined polymer melts under oscillatory flow. Using a Rouse-like model of chains with finite extensibility, we calculate elastic and dissipative stresses and corresponding storage and loss moduli. The effect of bridges and surface slip are taken into account. Several features have been discovered: the storage modulus G' passes through a maximum with increasing strain amplitude in the range of intermediate frequencies, when adsorption is weak and surface slip is important; the elastic sigma' and dissipative sigma '' stresses and the corresponding moduli G' and G '' show a jump with increasing strain amplitude when polymer bridges between the surfaces are formed.