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Ordering fluctuations in a shear-banding wormlike micellar system

Angelico, R.; Rossi, C. Oliviero; Ambrosone, L.; Palazzo, G.; Mortensen, K. and Olsson, Ulf LU (2010) In Physical Chemistry Chemical Physics 12(31). p.8856-8862
Abstract
We present a first investigation about the non-linear flow properties and transient orientational-order fluctuations observed in the shear-thinning lecithin-water-cyclohexane wormlike micellar system at a concentration near to the zero-shear isotropic-nematic phase transition. From rheological measurements the stress plateau was found shifted to very low values of the applied shear rate (gamma)over dot, compared to most of the concentrated living polymer systems reported in the literature. Rheo-small angle neutron scattering (Rheo-SANS) experiments performed in the flow-vorticity plane revealed periodical fluctuations of both the order parameter P-2 and the angular deviation phi from the vorticity axis as determined from the scattering... (More)
We present a first investigation about the non-linear flow properties and transient orientational-order fluctuations observed in the shear-thinning lecithin-water-cyclohexane wormlike micellar system at a concentration near to the zero-shear isotropic-nematic phase transition. From rheological measurements the stress plateau was found shifted to very low values of the applied shear rate (gamma)over dot, compared to most of the concentrated living polymer systems reported in the literature. Rheo-small angle neutron scattering (Rheo-SANS) experiments performed in the flow-vorticity plane revealed periodical fluctuations of both the order parameter P-2 and the angular deviation phi from the vorticity axis as determined from the scattering peaks. The periods of the oscillations were not found to depend on imposed (gamma)over dot. A theoretical model was also developed to explain the oscillatory dynamics of the shear-induced nematic order parameter in terms of the presence of standing waves of the director orientation profile along the circumference of the Couette cell. The experimental results of the periodic order parameter fluctuations together with their theoretical modelling shed significant new insights on the shear banding phenomenon, particularly its microscopic mechanism. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Physical Chemistry Chemical Physics
volume
12
issue
31
pages
8856 - 8862
publisher
Royal Society of Chemistry
external identifiers
  • wos:000280514800020
  • scopus:77955102894
ISSN
1463-9084
DOI
10.1039/b926152d
language
English
LU publication?
yes
id
b50f98d5-6750-44d1-a3fa-f51d2039c2dd (old id 1677778)
date added to LUP
2010-09-21 11:22:40
date last changed
2018-07-15 03:58:51
@article{b50f98d5-6750-44d1-a3fa-f51d2039c2dd,
  abstract     = {We present a first investigation about the non-linear flow properties and transient orientational-order fluctuations observed in the shear-thinning lecithin-water-cyclohexane wormlike micellar system at a concentration near to the zero-shear isotropic-nematic phase transition. From rheological measurements the stress plateau was found shifted to very low values of the applied shear rate (gamma)over dot, compared to most of the concentrated living polymer systems reported in the literature. Rheo-small angle neutron scattering (Rheo-SANS) experiments performed in the flow-vorticity plane revealed periodical fluctuations of both the order parameter P-2 and the angular deviation phi from the vorticity axis as determined from the scattering peaks. The periods of the oscillations were not found to depend on imposed (gamma)over dot. A theoretical model was also developed to explain the oscillatory dynamics of the shear-induced nematic order parameter in terms of the presence of standing waves of the director orientation profile along the circumference of the Couette cell. The experimental results of the periodic order parameter fluctuations together with their theoretical modelling shed significant new insights on the shear banding phenomenon, particularly its microscopic mechanism.},
  author       = {Angelico, R. and Rossi, C. Oliviero and Ambrosone, L. and Palazzo, G. and Mortensen, K. and Olsson, Ulf},
  issn         = {1463-9084},
  language     = {eng},
  number       = {31},
  pages        = {8856--8862},
  publisher    = {Royal Society of Chemistry},
  series       = {Physical Chemistry Chemical Physics},
  title        = {Ordering fluctuations in a shear-banding wormlike micellar system},
  url          = {http://dx.doi.org/10.1039/b926152d},
  volume       = {12},
  year         = {2010},
}