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 epsilon (s) in the isotropic phase, the longitudinal relaxation rimes tau (parallel to) and tau (parallel to), and the activation enthalpies DeltaH(is) and DeltaH(parallel to) on the number of carbon atoms in the alkyl chain n are analysed. A considerable increase in the retardation factor g = tau (parallel to)/tau (is) 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 (tau (parallel to) and DeltaH(parallel to)) indicate a hardening of this solid-like phase with shortening of the alkyl chain.