Heterogeneity-related dynamics in isotropic n-pentylcyanobiphenyl.

The evolution of the dielectric relaxation time tau(T) and its strong electric field related counterpart tau(fluct).(T) in the isotropic phase of rodlike liquid crystalline n-pentylcyanobiphenyl (5CB) is discussed. For the tau(fluct).(T) a strong pretransitional increase on approaching the virtual critical point located at deltaT = 1.1 K below isotropic nematic clearing temperature T(IN) is shown. The linearized derivative analysis applied to test the evolution of tau(T) revealed a sequence of Vogel-Fulcher-Tammann based dynamical domains, for which the fragility increases enormously on approaching T(IN). The similar analysis focused on testing the "critical" mode-coupling theory behavior showed superior features of such description. A strong asymmetric broadening of the dielectric loss curves is also discussed.