NONLINEAR RHEOLOGY OF CONFINED POLYMER MELTS UNDER OSCILLATORY FLOW

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