Ordering fluctuations in a shear-banding wormlike micellar system
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Ordering fluctuations in a shear-banding wormlike micellar system. / Angelico, R.; Rossi, C. Oliviero; Ambrosone, L.; Palazzo, G.; Mortensen, Kell; Olsson, U.
I: Physical Chemistry Chemical Physics, Bind 12, Nr. 31, 2010, s. 8856-8862.Publikation: Bidrag til tidsskrift › Tidsskriftartikel › Forskning › fagfællebedømt
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TY - JOUR
T1 - Ordering fluctuations in a shear-banding wormlike micellar system
AU - Angelico, R.
AU - Rossi, C. Oliviero
AU - Ambrosone, L.
AU - Palazzo, G.
AU - Mortensen, Kell
AU - Olsson, U.
PY - 2010
Y1 - 2010
N2 - 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 , 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 P2 and the angular deviation from the vorticity axis as determined from the scattering peaks. The periods of the oscillations were not found to depend on imposed . 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.
AB - 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 , 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 P2 and the angular deviation from the vorticity axis as determined from the scattering peaks. The periods of the oscillations were not found to depend on imposed . 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.
KW - Faculty of Science
KW - Materials
KW - Small-angle scattering
KW - Micelles
KW - shear-band
U2 - 10.1039/B926152D
DO - 10.1039/B926152D
M3 - Journal article
VL - 12
SP - 8856
EP - 8862
JO - Physical Chemistry Chemical Physics
JF - Physical Chemistry Chemical Physics
SN - 1463-9076
IS - 31
ER -
ID: 32146527