Effect of topological constraints in semidilute polymer solutions under planar extensional flow

Polymer solution dynamics and rheology are relevant to a wide range of processing methods. Developing an understanding of the polymer conformational dynamics and the emergent material properties is challenging because of the interplay of hydrodynamic interactions (HI), excluded volume, and topological constraints driven by concentration and polymer architecture. This is particularly true in extensional flow, which strongly deforms the polymers from their equilibrium conformations. Using a new technique for rapid Brownian dynamics (BD) simulation which we call the iterative conformational averaging (CA) method, we investigate the dynamics and rheology of linear, comb, and ring polymer solutions at concentrations increasing from the dilute limit into the semidilute regime. We apply step strain rate planar extensional flow and quantify the dynamics in startup, at steady state, and after flow cessation via conformational distributions and the polymer contribution to extensional viscosity. We show that flow enhances intermolecular HI and topological interactions, resulting in transient intermolecular entanglements. We investigate the effect of these constraints on polymer stretching and the transient solution stress.