Quasi-Critical Behaviour of “Linear” and “Nonlinear” Dielectric Permittivity in the Isotropic Phase of Nematogens

Abstract

Results are presented of dielectric permittivity and nonlinear dielectric effect (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, temperature paths approaching the nematic clearing point pretransitional anomalies of dielectric permittivity and NDE are described by the same relations with critical exponents α ≈ 0.5 and γ = 1, respectively This substantiates the postulate of the isomorphism of critical phenomena in the isotropic phase of nematogens. For tested “linear” and “nonlinear” changes of dielectric permittivity the same values of the discontinuity of the isotropic — nematic phase transition was obtained.

Key Words:

• Pretransitional effect
• nematic
• nonlinear dielectric effect
• dielectric permittivity
• critical behaviour