Dielectric investigations in the nematic and hexatic smectic B phases of 4-hexyl-4′-[2-(4-isothiocyanatophenyl)ethyl]-1,1′-biphenyl

Abstract

Temperature-dependent dielectric characterization of 4-hexyl-4′-[2-(4-isothiocyanatophenyl)ethyl]-1,1′-biphenyl (HIEB), which exhibits smectic B and nematic phases, has been carried out over the frequency range of 1 Hz to 10 MHz for homeotropic and planar alignment of sample molecules. This compound shows positive dielectric anisotropy (Δε = ε _∥ − ε _⊥ > 0) in the nematic (N) phase. One mode of dielectric relaxation showing Arrhenius behaviour has been detected in the hexatic smectic B (SmB) phase. Various electrical parameters, namely, dielectric anisotropy, relaxation frequency and activation energy, have been determined in the N and SmB phases.

Keywords:

• dielectric permittivity
• hexatic phase
• dielectric relaxation
• dielectric anisotropy

Acknowledgements

Authors thank Prof. I.M.L. Das, in-charge, Impedance Spectroscopy Laboratory, Physics Department, Allahabad University, Allahabad, for providing dielectric measurement facility. We wish to thank Prof. S. Urban, Jagiellonian University, Krakow, Poland, for several fruitful discussions on experimental results. We are also grateful to Dr Ravindra Dhar for many useful discussions.