Issue 14, 2021

Near-surface rheology and hydrodynamic boundary condition of semi-dilute polymer solutions

Abstract

Understanding confined flows of complex fluids requires simultaneous access to the mechanical behaviour of the liquid and the boundary condition at the interfaces. Here, we use evanescent wave microscopy to investigate near-surface flows of semi-dilute, unentangled polyacrylamide solutions. By using both neutral and anionic polymers, we show that monomer charge plays a key role in confined polymer dynamics. For solutions in contact with glass, the neutral polymers display chain-sized adsorbed layers, while a shear-rate-dependent apparent slip length is observed for anionic polymer solutions. The slip lengths measured at all concentrations collapse onto a master curve when scaled using a simple two-layer depletion model with non-Newtonian viscosity. A transition from an apparent slip boundary condition to a chain-sized adsorption layer is moreover highlighted by screening the charge with additional salt in the anionic polymer solutions. We anticipate that our study will be a starting point for more complex studies relating the polymer dynamics at interfaces to their chemical and physical composition.

Graphical abstract: Near-surface rheology and hydrodynamic boundary condition of semi-dilute polymer solutions

Article information

Article type
Paper
Submitted
27 Nov. 2020
Accepted
02 Marts 2021
First published
03 Marts 2021

Soft Matter, 2021,17, 3765-3774

Near-surface rheology and hydrodynamic boundary condition of semi-dilute polymer solutions

G. Guyard, A. Vilquin, N. Sanson, S. Jouenne, F. Restagno and J. D. McGraw, Soft Matter, 2021, 17, 3765 DOI: 10.1039/D0SM02116D

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