The paper presents the results of measurements of the linear dielectric properties of the compounds from the homologous series of alkylcyanobiphenyls $({\mathrm{C}}_n{\mathrm{H}}_{2n+1}\mathrm{PhPhCN},$ $n\mathrm{CB})$ in the vicinity of the first order transition (from the isotropic liquid to the crystalline phase) of nonmesogenic $n\mathrm{CB}\mathrm{’}\mathrm{s}$ $(n=2\mathrm{}–4)$ and the weakly first order transition (from the isotropic liquid to the nematic phase) of 5CB. The experimental method for the separation of the critical part of the static permittivity derivative and the activation energy for rotation of the mesogenic molecules, in the vicinity of weakly first order phase transition, is proposed. It is shown that the critical temperature dependence of the permittivity and the activation energy can be described with a function of $(T-T^{*}{)}^{-\alpha }$ type, with the same values of the temperature of virtual transition of the second order ${(T}^{*})$ and the critical exponent $\left(\alpha \right).\mathrm{}$

• Received 3 December 2002

DOI:https://doi.org/10.1103/PhysRevE.67.041705