Dielectric Investigations of Induced Twist Grain Boundary Phases in the Binary Mixtures of Cholesteryl Benzoate and Di-Heptyloxyazoxybenzene

The binary mixtures of Di-heptyloxyazoxybenzene (HOAB) and Cholesteryl Benzoate (ChB) show the longest ever temperature range of TGBA and TGBC* phases for ChB concentration 25 and 18 mole percent respectively. Comprehensive dielectric studies of these two binary mixtures have been carried out in the frequency range of 1 Hz to 10 MHz for different condition of molecular anchoring. Both mixtures show negative dielectric anisotropy (Δ ϵ′ = ϵ‖′−ϵ⊥′ < 0) in all the mesophases. One mode of dielectric relaxation showing Arrhenius behavior has been detected in N*, TGBA and TGBC* phases for the homeotropic aligned sample for both mixtures. This mode corresponds to rotation of molecules about their short axes. Planar oriented molecules of TGBC* and SmC* phase show a mode of relaxation presumably due to same reason as stated above. Various electrical parameter viz. dielectric anisotropy, relaxation frequency, dielectric strength, activation energy have been determined for TGB phases.