Nonlinear shear flow experiments suggest no missing physics in slip-link models of entangled polymer melts*

The idea that the dynamics of concentrated, high-molecular weight polymers are largely governed by entanglements is now widely accepted and typically interpreted through the tube model. However, recent work has shown that tube models can not predict the maximum strain, of polymer melts under start-up of shear flow at high Rouse-Weissenberg numbers. Based on these observations it has been suggested that there are physics missing in the tube theory. Here, we show that the slip-link model can predict all the features observed in start-up of shear experiments for melts and solutions of various chemistries (PS, PI, PBD, SBR) and for various numbers of entanglements. Specifically
we use the the open-source GPU implementation of the clustered fixed slip-link model, and perform simulations for the startup of shear flow for melts with 14 and 30 entanglements. We find that the maximum strain depends weakly on the number of entanglements and that it does not necessarily follow a single power law, in agreement with data. Moreover, a master curve is obtained for the shear stress normalized by its peak value vs. strain normalized by its value at the maximum stress, also in agreement with experiments.