High-Frequency Shear Viscoelastic Study of Cyanobiphenyl Series in the Smectic A and Nematic Mesophases

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Abstract
The temperature dependence of the shear viscosity η′ and the shear elasticity G ′ for homeotropically aligned liquid crystals, cyanobiphenyl series, 7CB, 8CB, 9CB, and 10CB at 10, 30, and 50 MHz was determined by use of the piezoelectric composite resonator method. In the vicinity of the phase transition points, the temperature dependences of η′ and G ′ show characteristic behaviors corresponding to the phase transition types; in particular, it is found that the dependence of G ′ shows an inflection point at the nematic-smectic A transition temperature. Arrhenius plots of η′ are linear with an activation energy of 2.3× 104 Jmol-1 on the isotropic, nematic, and smectic A phases except in the neighborhood of the phase transition points. The results of frequency dependence suggest the existence of the fiequency dispersion.