Thermodynamic, optical and dielectric studies of the homologous members of columnar discotic compound Rufigallol hexa- n-alkoxylates

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Thermodynamic, optical texture and frequency dependent dielectric studies of re-synthesized discotic compounds Rufigallol hexa- n-alkoxylates (for n = 6, 7, 8, 9) having wide temperature range hexagonal columnar (col h) mesophase have been carried out. The mesophase and their transition temperatures have been determined by using polarizing microscope and differential scanning calorimetry. Dielectric permittivity parallel ( ε ||′) and perpendicular ( ε ⊥′) to column axis have been determined. Using these two sets of data, dielectric anisotropy (Δ ε′ = ε ||′ − ε ⊥′) has been obtained which has been found to be positive throughout the entire range of the col h mesophase for all of the four compounds of this series. No relaxation phenomenon has been observed in the frequency range of measurement i.e. 10 Hz to 10 MHz. The DC conductivity of these compounds has been found to be rather low (~ 10 − 10 to 10 − 11 S m − 1 ). All the dielectric parameters show odd-even effect with the variation of n.