The effect of fluorine or chlorine substitution on mesomorphic properties of ferroelectric nematic liquid crystals

TL;DR

This study explores how fluorine and chlorine substitutions affect the mesomorphic and ferroelectric properties of nematic liquid crystals, introducing novel molecular designs and observing unique phase behaviors and surface anchoring effects.

Contribution

It presents new molecular structures with halogen substituents, including the first use of chlorine in ferroelectric nematogens, and analyzes their phase behavior and ferroelectric properties.

Findings

Halogen substitution influences ferroelectric nematic phase stability.

Chlorine substitution introduces unique ferroelectric properties.

Surface anchoring shows strong polar character in the NF phase.

Abstract

Ferroelectric nematic phase (NF) represents an attractive and foremost field of liquid crystals, combining fluidity with ferroelectricity. NF materials exhibit large polarization values and remarkable non-linear optical properties. We have designed an original molecular structure with halogen substituents in the position of an electron donating group. In a prolonged molecular core, such a modification led to the presence of the ferroelectric nematic phase (NF) below the nematic one. Besides, an application of Cl atom in the molecular core of one of the presented materials has been utilized for the first time for ferroelectric nematogens. We have examined mesogenic behaviour and ferroelectric characteristics of the NF phase. In the NF phase for the cell with antiparallel rubbing, we have detected a textural transformation, which evidences strong polar character of anchoring at the surfaces. The presented results provide valuable insight into the design of ferroelectric nematic liquid crystalline compounds.