Issue 16, 2022

Transition to the viscoelastic regime in the thinning of polymer solutions

Abstract

In this study, we investigate the transition between the Newtonian and the viscoelastic regimes during the pinch-off of droplets of dilute polymer solutions and discuss its link to the coil-stretch transition. The detachment of a drop from a nozzle is associated with the formation of a liquid neck that causes the divergence of the local stress in a vanishingly small region. If the liquid is a polymer solution, this increasing stress progressively unwinds the polymer chains, up to a point where the resulting increase in the viscosity slows down drastically the thinning. This threshold to a viscoelastic behavior corresponds to a macroscopic strain rate. In the present study, we characterize the variations of with respect to the polymer concentration and molar weight, to the solvent viscosity, and to the nozzle size, i.e., the weight of the drop. We provide empirical scaling laws for these variations. We also analyze the thinning dynamics at the transition and show that it follows a self-similar dynamics controlled by the time scale [small epsi, Greek, dot above]c−1. This characteristic time is different and always shorter than the relaxation time of the polymer.

Graphical abstract: Transition to the viscoelastic regime in the thinning of polymer solutions

Supplementary files

Article information

Article type
Paper
Submitted
09 Feb 2022
Accepted
26 Mar 2022
First published
30 Mar 2022

Soft Matter, 2022,18, 3147-3156

Transition to the viscoelastic regime in the thinning of polymer solutions

S. Rajesh, V. Thiévenaz and A. Sauret, Soft Matter, 2022, 18, 3147 DOI: 10.1039/D2SM00202G

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