Shear banding and the isotropic-to-nematic transition in wormlike micelles.
Using deuterium NMR spectroscopy in a Couette cell, we observe shear-induced nematic ordering in the concentrated wormlike-micelle system CTAB/D(2)O, and our results are qualitatively consistent with birefringence studies, and in exact quantitative agreement with the degree of order measured in neutron-diffraction measurements. The width of the nematic region depends on shear rate, as well as on the temperature proximity to the equilibrium isotropic-nematic transition. Comparison of the nematic order profiles with velocity profiles obtained under identical conditions shows quite clearly that the nematic state is not identifiable with a highly sheared, low viscosity layer, and we conclude that the process of shearing induces a nematic state of high viscosity, possibly associated with mesoscale ordering. We present a simple model in which transition from the high shear branch to the viscous nematic branch is counterbalanced by subsequent relaxation of nematic order.
Fischer
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Institute of Fundamental Sciences-Physics, Massey University, Palmerston North, New Zealand.
Callaghan
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PT
D001703:Biophysics / Q000295:instrumentation / Q000379:methods*; D017666:Deuterium Oxide / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008823:Micelles; D015233:Models, Statistical; D011108:Polymers / Q000737:chemistry; D013997:Time Factors
D008823:Micelles; D011108:Polymers; D017666:Deuterium Oxide