Molecular based prediction of the extensional rheology of high molecular weight polystyrene dilute solutions: A hi-fidelity Brownian dynamics approach

Abstract

A highly efficient Brownian dynamics algorithm for simulation of bead-spring chain micromechanical models that utilizes the Krylov framework and the semi-implicit predictor-corrector scheme is used to study the behavior of dilute solutions of high molecular weight polystyrene in uniaxial extensional flow. The influence of key parameters, namely, appropriate inclusion of hydrodynamic interactions (HI) and excluded volume (EV), the level of fine-graining, and the flow strength on the observed extensional hardening of the dilute solutions over a broad molecular weight range is considered. Specifically, it is demonstrated that the combination of HI and successive fine-graining results in very good predictions of rheological properties of solutions containing 1.95, 3.9, and 10.2 × 106 molecular weight macromolecules. However, for the highest molecular weight system, namely, 20 × 106, some level of discrepancy between experiment and the simulation results is observed. Finally, the incorporation of EV in order to predict material functions that are more consistent with the measurements for the highest molecular weight macromolecule solution is discussed.