Effect of stretching-induced changes in hydrodynamic screening on coil-stretch hysteresis of unentangled polymer solutions

TL;DR

This paper investigates how flow-induced chain stretching affects hydrodynamic screening and coil-stretch hysteresis in unentangled polymer solutions, revealing concentration-dependent effects that alter viscoelastic behavior.

Contribution

It combines experiments and simulations to show how stretching modifies hydrodynamic screening and hysteresis across different concentration regimes.

Findings

Hysteresis increases with concentration up to the critical overlap concentration.

Stretching enhances hydrodynamic screening in dilute solutions.

Flow modifies the concentration dependence of viscoelastic properties.

Abstract

Extensional rheometry and Brownian Dynamics simulations of flexible polymer solutions confirm predictions based on blob concepts that coil--stretch hysteresis in extensional flows increases with concentration, reaching a maximum at the critical overlap concentration $c^\ast$ before progressively vanishing in the semidilute regime. These observations demonstrate that chain stretching strengthens intermolecular hydrodynamic screening in dilute solutions, but weakens it in semidilute solutions. Flow can thus strongly modify the concentration dependence of viscoelastic properties of polymer solutions.