Thermodynamic and electrical characteristics of the twisted grain boundary phases of 4-n-dodecyloxy-4′-(cholesteryloxycarbonyl-1-butyloxy) chalcone

Abstract

The investigated optically active dimeric compound, 4-n-dodecyloxy-4′-(cholesteryloxycarbonyl-1-butyloxy) chalcone, shows wide temperature ranges of two twisted grain boundary (TGB) phases, namely TGBA and TGBC*. The dielectric spectroscopy has been carried out for this compound in the frequency range of 1 Hz to 35 MHz for two different conditions of molecular anchoring. A relaxation mode has been detected in the TGBA and TGBC* phases for the planar anchoring of the molecules. This mode lies in the MHz region and has the characteristics of amplitude fluctuation of directors (soft mode). Results are supportive of the theory developed for the soft modes of TGBA and TGBC* phases. Dielectric anisotropy shows an unusual but characteristic (of TGB phases) variation with temperature.

Keywords:

• TGB phases
• dielectric permittivity and anisotropy
• dielectric strength
• relaxation frequency
• ionic conductivity

Acknowledgements

The authors thank the Department of Science and Technology, New Delhi, and the University Grants Commission, New Delhi, for providing financial assistance under various modes.