Characteristic dielectric parameters of columnar discotic hexa-n-alkoxyanthraquinones

Temperature-dependent dielectric spectroscopy of resynthesized discotic compounds, rufigallol hexa-n-alkoxylates for n = 6, 7, 8, 9 having wide temperature range (>70°C) hexagonal columnar mesophase has been carried out in the frequency range of 10 Hz to 10 MHz. The mesophase and their transition temperatures have been determined by using polarizing microscope and differential scanning calorimeter. Dielectric permittivity parallel (ε′||) and perpendicular (ε′⊥) to column have been determined. Using these data, dielectric anisotropy (Δε = ε′|| - ε′⊥) has been found to be positive throughout the entire range of the Colh phase for all of the four compounds of this series. No relaxation phenomenon is found in the frequency range of 10 Hz to 10 MHz. The DC conductivity of these compounds has been found to be rather low (∼10-10-10-11 S-m-1). All the electrical parameters show odd-even effect with the variation of n.