Electrical Behaviour of Twist Grain Boundary Phases of 4-n-dodecyloxy-4'-(cholesteryloxycarbonyl-1-butyloxy) chalcone

ABSTRACT

There are only few compounds, which have shown wide temperature range twist grain boundary (TGB) phases. One such compound is the cholesterol derived, 4-n-dodecyloxy-4'-(cholesteryloxycarbonyl-1-butyloxy) chalcone, which shows a wide temperature range TGBA (~ 11 °C) and TGBC* (~ 19 °C). In the present work, we are reporting the temperature and frequency dependence of the dielectric parameters of the above compound for two different conditions of molecular anchoring i.e. planar and homeotropic. The dielectric studies have been carried out in the frequency range of 1 Hz to 35 MHz. In homeotropically aligned sample, the experimental dielectric spectra display a feeble relaxation mode in TGBA and TGBC* phases in MHz frequency range. Planar oriented molecules show a soft mode like relaxation due to the tilt fluctuation of molecules in MHz region for both the TGB phases and support theoretical formulation for the soft mode relaxation of the TGB phases. Various dielectric parameters have been determined for the two TGB phases of the above mentioned compound.

Keywords:

Chiral liquid crystals, Liquid crystal dimers, TGB phases, Dielectric relaxation spectroscopy, Dielectric strength slopes, Rotational viscosity.