Microscopic theory for the fast flow of polymer melts

We develop a theory of fast flows of entangled polymer melts incorporating the process of convective constraint release (CCR) as a local rearrangement of the entanglement tubes. Using a new formalism that simultaneously captures reptation, fluctuation motion of the chain, and Rouse motion of its tube, we show that the spurious maximum of shear stress as a function of shear rate, predicted by the original Doi-Edwards theory and other treatments of CCR, may be removed. The single chain (SANS) structure factor in shear flow is also predicted and compared to hitherto unexplained experimental data. The stress maximum is retained in the case of living polymeric micelles.