Advanced

Effect of ionic strength on the rheological behavior of aqueous cetyltrimethylammonium p-toluene sulfonate solutions

Torres, Miguel F.; Gonzalez, Juan M.; Rojas, Mario R.; Muller, Alejandro J.; Saez, A. Eduardo; Löf, David LU and Schillén, Karin LU (2007) In Journal of Colloid and Interface Science 307(1). p.221-228
Abstract
The influence of ionic environment on the rheological properties of aqueous cetyltrimethylammonium p-toluene sulfonate (CTAT) solutions has been studied under three different flow fields: simple shear, opposed-jets flow and porous media flow. Emphasis was placed in the experiments on a range of CTAT concentration in which wormlike micelles were formed. It is known that these solutions exhibit shear thickening in the semi-dilute regime, which has been explained in terms of the formation of shear-induced, cooperative structures involving wormlike micelles. In simple shear flow, the zero shear viscosity exhibits first an increase with salt addition followed by a decrease, while the critical shear rate for shear thickening increases sharply at... (More)
The influence of ionic environment on the rheological properties of aqueous cetyltrimethylammonium p-toluene sulfonate (CTAT) solutions has been studied under three different flow fields: simple shear, opposed-jets flow and porous media flow. Emphasis was placed in the experiments on a range of CTAT concentration in which wormlike micelles were formed. It is known that these solutions exhibit shear thickening in the semi-dilute regime, which has been explained in terms of the formation of shear-induced, cooperative structures involving wormlike micelles. In simple shear flow, the zero shear viscosity exhibits first an increase with salt addition followed by a decrease, while the critical shear rate for shear thickening increases sharply at low salt contents and tends to saturate at relatively high ionic strengths. The results are explained in terms of a competition between micellar growth induced by salt addition and changes in micellar flexibility caused by ionic screening effects. Dynamic light scattering results indicate that micelles grow rapidly upon salt addition but eventually achieve a constant size under static conditions. These observations suggest that the wormlike micelles continuously grow with salt addition, but, as they become more flexible due to electrostatic screening, the wormlike coils tend to adopt a more compact conformation. The trends observed in the apparent viscosities measured in porous media flows seem to confirm these hypotheses-but viscosity increases in the shear thickening region-and are magnified by micelle deformation induced by the elongational nature of the local flow in the pores. In opposed-jets flow, the solutions have a behavior that is close to Newtonian, which suggests that the range of strain rates employed makes the flow strong enough to destroy or prevent the formation of cooperative micellar structures. (c) 2006 Published by Elsevier Inc. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
porous media flow, extensional flow, CTAT, shear-thickening
in
Journal of Colloid and Interface Science
volume
307
issue
1
pages
221 - 228
publisher
Elsevier
external identifiers
  • wos:000243570400029
  • scopus:33847055120
ISSN
1095-7103
DOI
10.1016/j.jcis.2006.11.002
language
English
LU publication?
yes
id
083b5844-bc31-4075-bea2-e54ab59edbd4 (old id 676589)
date added to LUP
2008-01-02 14:27:55
date last changed
2017-08-27 04:11:41
@article{083b5844-bc31-4075-bea2-e54ab59edbd4,
  abstract     = {The influence of ionic environment on the rheological properties of aqueous cetyltrimethylammonium p-toluene sulfonate (CTAT) solutions has been studied under three different flow fields: simple shear, opposed-jets flow and porous media flow. Emphasis was placed in the experiments on a range of CTAT concentration in which wormlike micelles were formed. It is known that these solutions exhibit shear thickening in the semi-dilute regime, which has been explained in terms of the formation of shear-induced, cooperative structures involving wormlike micelles. In simple shear flow, the zero shear viscosity exhibits first an increase with salt addition followed by a decrease, while the critical shear rate for shear thickening increases sharply at low salt contents and tends to saturate at relatively high ionic strengths. The results are explained in terms of a competition between micellar growth induced by salt addition and changes in micellar flexibility caused by ionic screening effects. Dynamic light scattering results indicate that micelles grow rapidly upon salt addition but eventually achieve a constant size under static conditions. These observations suggest that the wormlike micelles continuously grow with salt addition, but, as they become more flexible due to electrostatic screening, the wormlike coils tend to adopt a more compact conformation. The trends observed in the apparent viscosities measured in porous media flows seem to confirm these hypotheses-but viscosity increases in the shear thickening region-and are magnified by micelle deformation induced by the elongational nature of the local flow in the pores. In opposed-jets flow, the solutions have a behavior that is close to Newtonian, which suggests that the range of strain rates employed makes the flow strong enough to destroy or prevent the formation of cooperative micellar structures. (c) 2006 Published by Elsevier Inc.},
  author       = {Torres, Miguel F. and Gonzalez, Juan M. and Rojas, Mario R. and Muller, Alejandro J. and Saez, A. Eduardo and Löf, David and Schillén, Karin},
  issn         = {1095-7103},
  keyword      = {porous media flow,extensional flow,CTAT,shear-thickening},
  language     = {eng},
  number       = {1},
  pages        = {221--228},
  publisher    = {Elsevier},
  series       = {Journal of Colloid and Interface Science},
  title        = {Effect of ionic strength on the rheological behavior of aqueous cetyltrimethylammonium p-toluene sulfonate solutions},
  url          = {http://dx.doi.org/10.1016/j.jcis.2006.11.002},
  volume       = {307},
  year         = {2007},
}