New Publication from Prof. Olmsted

Figure from Prof. Olmsted's paper showing a deviation in entanglement number for orthogonal interrupted shear in comparison to parallel interrupted shear. — The entanglement number Zk undergoes a remarkable non-monotonic behavior during orthogonal interrupted shear after a short delay time (bottom, blue curve), as the polymers reorient from pointing mainly left-right at early times to pointing mainly up-down at later times

Recently, Professor Peter Olmsted, Ph.D. and I(SM)² faculty member has put forward a new publication with Marco Cunha (University of Pennsylvania) and Mark Robbins (Johns Hopkins University). “Probing the nonequilibrium dynamics of stress, orientation, and entanglements in polymer melts with orthogonal interrupted shear simulations” appears in the 66^th volume of the Journal of Rheology. Polymer melts exhibit stress overshoot that has previously been shown to be smaller when sheared after partial relaxation. Professor Olmsted’s paper addresses simulations where the shear flow after the relaxation stage is orthogonal to the originally applied flow. The research demonstrates a larger stress overshoot under orthogonal interrupted shear that is not captured by current models, and differences in the average number of entanglements per chain and the average orientation at different scales along the chain. The authors suggest the complex behavior of entanglements is responsible for the larger stress overshoot and that the dynamics of entanglements might be better modeled with a tensorial measurement that can be coupled to orientation.