Structural Investigations of a Non Calamitic Shaped Liquid Crystalline Compound Showing Unusual Phases

Abstract

X-ray diffraction, birefringence, density and static dielectric permittivity measurements were performed on a calamitic hockey stick shaped mesogen. In addition to SmA phase, this compound exhibits two tilted mesophases – the SmC, synclinic and the SmC_a, anticlinic phase. From x-ray diffraction and birefringence data, the orientational order parameters have been determined. The order parameters values drop at the SmC – SmC_a phase boundary. Possible cause for the drop in the order parameter values has been discussed. Interestingly, it has been found that the dielectric anisotropy of this compound changes from positive to negative values in the SmCa phase.

Keywords:

• Dielectric anisotropy
• hockey shaped molecule
• optical birefringence
• orientational order parameter
• x-ray diffraction

Acknowledgment

We gratefully acknowledge financial support from Department of Science and Technology, New Delhi (Project No: SR/S2/CMP-20/2005 and SR/S2/CMP-29/2007).