Dielectric and viscous properties of mesogenic n-nonylcyanobiphenyl (9CB).

Static and dynamic linear dielectric properties and shear viscosity of freely flowing 9CB in the isotropic (I), nematic (N) and smectic A (S(A)) phases were investigated. Pretransitional effects observed in the vicinity of the I to N phase transition manifest themselves as anomalies in the temperature dependence of the static permittivity, the rotational diffusion exponent and the activation energy of molecules rotating around their short axis. As a presmectic effect, a jump in the temperature dependence of the shear viscosity of freely flowing nematic 9CB is observed at about 0.5 °C before the transition to the S(A) phase.