Dielectric spectroscopy of T-shaped blue-phase-III liquid crystal

Abstract

Dielectric relaxation spectra of a liquid crystalline (LC) material showing blue-phase-III (BPIII) for a considerably large temperature regime consisting of T-shaped molecules are investigated. A low frequency relaxation mode is observed in the isotropic phase (I) as well as in BPIII of the investigating material which is attributed to the short axis rotation of the T-shaped molecules. The outcome of the temperature and dc bias field variation of dielectric strength (Δε) and relaxation frequency (ν(c)) in the vicinity of the I-BPIII transition is also discussed. The temperature dependence of ν(c) in BPIII with a minor deviation from Arrhenius activities in the fluctuation-dominated nonlinear region (FDNLR) is found to follow the unusual thermal behavior of the activation energy (E(A)). The growth of pretransitional fluctuations is found to be nonlinear in the vicinity of the I-BPIII transition. A moderate growth of transition fluctuation commences from the value of the exponent α(eff)=0.38/°C, which is obtained by an exponential variation of ν(c) with respect to temperature in BPIII. Observed dynamic phenomenon in the vicinity of the I-BPIII transition regions is explained on the basis of the Landau-de Gennes and Maier-Saupe Theories.