Quasi-critical behaviour of "linear" and "nonlinear" dielectric permittivity in the isotropic phase of nematogens

Results are presented of dielectric permittivity and nonlinear dielectric e ffect (NDE) studies in the isotropic phase of n-pentylcyanobiphenyl (5CB). Both properties can be described by relations identical to those applied in critical binary solutions. For the isothermal, pressure and isobaric, temp erature paths approaching the nematic clearing point pretransitional anomal ies of dielectric permittivity and NDE are described by the same relations with critical exponents alpha = 0.5 and gamma = 1, respectively This substa ntiates the postulate of the isomorphism of critical phenomena in the isotr opic phase of nematogens. For tested "linear" and "nonlinear" changes of di electric permittivity the same values of the discontinuity of the isotropic nematic phase transition was obtained.