Dielectric studies of the 4-n-alkyl-4'-thiocyanatobiphenyl (nBT) homologous series (n=2-10) in the isotropic and E phases

Results of the dielectric studies of nine members of the nBT (4-n-alkyl-4'-thiocyanatobiphenyl, n= 2-10) homologous series in the crystal E (E) and isotropic (I) phases are presented. The dependence of the static permittivity ∊s in the isotropic phase, the longitudinal relaxation times τis and τ∥, and the activation enthalpies ΔH is and ΔH ∥ on the number of carbon atoms in the alkyl chain n are analysed. A considerable increase in the retardation factor g= τ∥/τis with decreasing n is observed. The results are compared with those obtained for similar two-ring homologous series. The parameters characterizing the molecular rotations around the short axis in the E phase (τ∥ and ΔH ∥) indicate a hardening of this solid-like phase with shortening of the alkyl chain.