Fluidlike behavior of dielectric permittivity in a wide range of temperature above and below the nematic-isotropic transition - art. no. 052701

Singular behavior of the static dielectric permittivity of n-alkyloxycyanob iphenyls (CnH2n+1O-Ph-Ph-C = N, n = 6, 7) was studied above and below the n ematic clearing point (T1-N). On approaching the clearing point, the evolut ion of principal components of the nematic permittivity tensor, epsilon (pa rallel to) and epsilon (perpendicular to), is described by the order parame ter exponent beta approximate to0.25. The mean value of the nematic permitt ivity epsilon (mean) = (epsilon (parallel to) + 2 epsilon (perpendicular to ))/3 exhibits a singular behavior similar to that observed in the isotropic phase and that for the diameter of the coexistence curve in binary mixture s. The derivative of experimental data d epsilon (iso)(T)/dT and d epsilon (mean)(T)/dT shows the specific-heat-like behavior with universal exponents alpha = alpha' approximate to 0.5. Results obtained confirm the hypothesis of the fluidlike, pseudospinodal, and tricritical behavior of the isotropi c to nematic phase transition. [A. Drozd-Rzoska, Phys. Rev. E 59, 5556 (199 9)].