Rapid viscous flow of a nematic liquid crystal in the vicinity of the nematic-smectic A transition |
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Authors: | A. V. Zakharov A. A. Vakulenko |
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Affiliation: | (1) Institute for Problems of Mechanical Engineering, Russian Academy of Sciences, Bol’shoi pr. 61, Vasil’evskii Ostrov, St. Petersburg, 199178, Russia |
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Abstract: | The resistance to shear flow is investigated theoretically for polar liquid crystals, such as 4-n-octyl-4′-and 4-n-octyloxy-4′-cyanobiphenyls. It is established that the lowest resistance to shear flow at temperatures in the vicinity of the nematic-smectic A phase transition point T NA is observed when the nematic director is oriented perpendicular to both the flow velocity vector and the flow velocity gradient. The three Miesowicz shear viscosity coefficients ηi (i=1–3) at temperatures close to the phase transition temperature (tens of millikelvins from T NA ) and far from this transition are calculated in the framework of the Ericksen-Leslie theory. The decrease in the viscosity coefficients in the order η2>η1>η 3 is explained by the fact that fluctuations of the local smectic order in the nematic phase lead to a singular behavior of the viscosity coefficient η2, whereas the other two viscosity coefficients η1 and η3 are not affected by order parameter fluctuations. |
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