Can Wormlike Micelle Stiffness by Estimated from Zero-Shear Viscosity? Experimental Investigation with a Model System and Specific Salt Interactions

Published

March 1, 2024

Author(s)

Nour S. Alawami, Kathleen Weigandt, Javen Weston

Abstract

The microstructure of wormlike micelles (WLM) directly affects the rheological properties of their solutions. Investigating the structure–property relationships of WLM has long been a popular topic for researchers who have developed theoretical and empirical models to describe their viscoelastic behavior. All these models rely on a collection of characteristic "length" parameters that are often difficult to estimate using relatively simple rheological tests. In particular, the micelle stiffness, as described by the persistence length, can be difficult to measure experimentally, while being very impactful on the bulk rheology of WLM solutions. Here, an array of inorganic salts (NaCl, LiCl, MgCl2, NaBr, NaI, and Na2SO4) have been used to induce wormlike micelle formation in an aqueous solution of the surfactant sodium lauryl ether sulfate. Ion dissociation/association with the surfactant head groups and the hydrogen bond network of the water alters the effective stiffness of the micelles, allowing for an estimation of the stiffness using three different methods: (1) small angle neutron scattering (SANS) measurements, (2) oscillatory rheological measurements, and (3) steady rheological measurements with a thermodynamic packing parameter model. Each of these methods are then compared and shown to be consistent with each other for the micelle solutions tested. The consistency of the results across all the measurements suggests that the approach used in this study, which estimates micelle parameters using steady shear rheology and a thermodynamic model, could provide a simpler and more accessible method for estimating micelle parameters in a wide range of surfactant systems.

Citation

Journal of Surfactants and Detergents

Volume

27

Issue

2

Pub Type

Journals

Download Paper

https://doi.org/10.1002/jsde.12719

Local Download

Keywords

Wormlike Micelles, Rheology, SANS

Citation

Alawami, N. , Weigandt, K. and Weston, J. (2024), Can Wormlike Micelle Stiffness by Estimated from Zero-Shear Viscosity? Experimental Investigation with a Model System and Specific Salt Interactions, Journal of Surfactants and Detergents, [online], https://doi.org/10.1002/jsde.12719, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=936263 (Accessed December 13, 2024)