Electro-optic and molecular relaxation behaviour of fluoro substituted achiral unsymmetrical four-ring bent-core mesogen

Abstract

Electro-optic and molecular relaxation studies in a new achiral unsymmetrical four-ring bent-core mesogen are presented in this study. The compound consists of a laterally fluoro-substituted 3,4′-disubstituted biphenyl unit with an ester linkage between the two phenyl rings as the central unit. The mesomorphic properties were characterised by polarising optical microscopy and differential scanning calorimetry. The compound exhibited enantiotropic B₇–B_x phase sequence. The electro-optic studies revealed a bistable switching from planar to a homeotropic state under an electric field in B₇ phase. Further memory effect was observed between planar and homeotropic textures after the removal of electric field in B₇ phase. Temperature dependent permittivity studies as a function of frequency revealed that the molecular relaxation increases with the increasing temperature in B₇ phase than in B_x phase.

Keywords:

• bent-core mesogens
• electro-optical studies
• memory effect
• relaxation phenomenon

Acknowledgement

Financial assistance provided by Department of Science and Technology, Department of Atomic Energy, Naval Research Board and University Grants commission India is gratefully acknowledged. Authors wish to thanks the reviewer for comments and valuable suggestions.