Experimental determination of the shear, rotational, and coupling viscosities for p-n-hexyl-cyanobiphenyl.
In soft condensed materials consisting of molecules with form anisotropy, the translation and rotation interact with each other. Not only the shear and rotational viscosities but also the coupling viscosity are necessary to theoretically describe the molecular motion under coupling between the different degrees of freedom. In this paper, we report on the determination of all three viscosities with our experimental techniques. We obtained the absolute values for p-n-hexyl-cyanobiphenyl (6CB) in the isotropic phase. The experimental techniques used are the optical-beating spectroscopy of depolarized light scattering and the measurement of birefringence induced by capillary waves. The coupling strength is given in the form 2 micro2/etanu for the former and micro/nu for the latter; from this we determined the absolute values of eta, nu, and micro. The coupling viscosity was found to be responsible for the critical behavior of the coupling effect reported previously.
Hirano
T
T
Institute of Industrial Science, University of Tokyo, 4-6-1, Komaba, Meguro-ku, Tokyo 153-8505, Japan. hirano22@iis.u-tokyo.ac.jp
Sakai
K
K