Rheological consequences of wet and dry friction in a dumbbell model with hydrodynamic interactions and internal viscosity

TL;DR

This study investigates how internal viscosity and hydrodynamic interactions affect the rheological behavior of dilute polymer solutions using a dumbbell model, revealing their distinct influences on transient and steady shear flow properties.

Contribution

It provides new insights into the separate roles of solvent-mediated friction and internal viscosity on polymer rheology through detailed simulations.

Findings

Hydrodynamic interactions significantly affect stress jump and transient viscometric functions.

Internal viscosity influences zero-shear rate viscometrics and mimics rigid behavior at high values.

Steady-shear properties depend on finite extensibility and differ from rigid dumbbell predictions.

Abstract

The effect of fluctuating internal viscosity and hydrodynamic interactions on a range of rheological properties of dilute polymer solutions is examined using a finitely extensible dumbbell model for a polymer. Brownian dynamics simulations are used to compute both transient and steady state viscometric functions in shear flow. The results enable a careful differentiation of the influence, on rheological properties, of solvent-mediated friction from that of a dissipative mechanism that is independent of solvent viscosity. In particular, hydrodynamic interactions have a significant influence on the magnitude of the stress jump at the inception of shear flow, and on the transient viscometric functions, but a negligible effect on the steady state viscometric functions at high shear rates. Zero-shear rate viscometric functions of free-draining dumbbells remain essentially independent of the internal viscosity parameter, as predicted by the Gaussian approximation, but the inclusion of hydrodynamic interactions induces a dependence on both the hydrodynamic interaction and the internal viscosity parameter. Large values of the internal viscosity parameter lead to linear viscoelastic predictions that mimic the behavior of rigid dumbbell solutions. On the other hand, steady-shear viscometric functions at high shear rates differ in general from those for rigid dumbbells, depending crucially on the finite extensibility of the dumbbell spring.