(573d) Distributions of Molecular Conformation in Flowing Solutions of Semidilute Polymers

Polymer dynamics are important to a wide range of solution processing methods, such as printing and coating. Despite the ubiquity of these methods in both polymer industry and research, the connection between the applied processing flows and molecular conformation is not well understood. For many applications, however, the out-of-equilibrium conformations of polymers that arise in these processes can heavily impact the eventual material properties. Furthermore, in these same applications it is important to understand semi-dilute polymer systems where polymer chains are interpenetrating and thus modifying their dynamics. A major challenge in the field is to thus understand the distribution of polymer conformations in semidilute solutions during fluid flows. We have recently developed a new method to study the out-of-equilibrium behavior of polymer molecules in non-dilute systems using Brownian Dynamics simulations, where we have greatly accelerated the calculation of the hydrodynamic interactions that play a key role in polymer solution dynamics. We apply this method to a number of steady-state, start-up, and relaxation experiments in planar elongational flow to show how non-dilute polymer chains interact during these processes and give rise to multiple populations of molecular conformations. We explore the role of hydrodynamics and concentration on the existence of molecular 'hooks' and other coupled molecular motions that alter the stretching and fluctuating state of the polymers under an applied strain and strain rate.