Distortion-sensitive insight into the pretransitional behavior of 4- n -octyloxy-4���-cyanobiphenyl (8OCB)

Results of studies of the static and dynamic dielectric properties in rod-like 4-n-octyloxy-4'-cyanobiphenyl (8OCB) with isotropic (I)���nematic (N)���smectic A (SmA)���crystal (Cr) mesomorphism, combined with measurements of the low-frequency nonlinear dielectric effect and heat capacity are presented. The analysis is supported by the derivative-based and distortion-sensitive transformation of experimental data. Evidence for the I���N and N���SmA pretransitional anomalies, indicating the influence of tricritical behavior, is shown. It has also been found that neither the N phase nor the SmA phase are uniform and hallmarks of fluid���fluid crossovers can be detected. The dynamics, tested via the evolution of the primary relaxation time, is clearly non-Arrhenius and described via ��(T) = ��c(T���TC)���phgr. In the immediate vicinity of the I���N transition a novel anomaly has been found: ���� ��� 1/(T ��� T*), where T* is the temperature of the virtual continuous transition and ���� is the excess over the 'background behavior'. Experimental results are confronted with the comprehensive Landau���de Gennes theory based modeling.