Non-linear rheology of lamellar liquid crystals |
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Authors: | C -Y D Lu P Chen Y Ishii S Komura T Kato |
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Institution: | (1) Department of Chemistry, National Taiwan University, 106 Taipei, Taiwan;(2) Department of Physics and Center for Complex Systems, National Central University, 320 Jung-li, Taiwan;(3) Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, 192-0397 Tokyo, Japan |
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Abstract: | We measure the non-linear relation between the shear stress and shear rate in the lyotropic lamellar phase of C12E5 /water system. The measured shear thinning exponent changes with the surfactant concentration. A simple rheology theory of
a lamellar or smectic phase is proposed with a prediction
∼ σ3/2 , where
is the shear rate and σ is the shear stress. We consider that the shear flow passed through the defect structure causes the
main dissipation. As the defect line density varies with the shear rate, the shear thinning arises. The defect density is
estimated by the dynamic balance between the production and annihilation processes. The defect production is caused by the
shear-induced layer undulation instability. The annihilation occurs through the shear-induced defect collision process. Further
flow visualization experiment shows that the defect texture correlates strongly with the shear thinning exponent. |
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Keywords: | 61 30 Jf Defects in liquid crystals 83 60 Fg Shear rate dependent viscosity 61 72 Lk Linear defects: dislocations disclinations |
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