Development of ferroelectric liquid crystals with low birefringence

ABSTRACT

We propose an approach for development of ferroelectric liquid crystals (FLC) with low birefringence Δn. Two basic principles have been used to get lowering of Δn: selection of molecules with short chains of conjugation as components for achiral matrix and averaging of local refractive indices by FLC helical structure. FLC mixtures with low birefringence (0.07 < Δn < 0.10 at wavelength 589.3 nm of sodium line) were elaborated and investigated. They consist of an achiral matrix including both nematic and smectic liquid crystal components and of phenylpyrimidine derivatives as chiral dopants. The materials developed can be used for all basic electro-optical FLC modes such as surface stabilised FLC (SSFLC), deformed helix ferroelectrics (DHF) and electrically suppressed helix (ESH). The mixtures developed allow to reduce the FLC cells chromatic retardance variation due to the weaker birefringence dispersion as compared with the known FLC materials to date.

Graphical Abstract

KEYWORDS:

• Ferroelectric liquid crystal
• phenacyl esters
• Demus ester
• chains of conjugation
• birefringence

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The work was partially supported by the Russian Foundation for Basic Research (RFBR) grants: No. 16-02-00441-a and No. 16-29-14012 -ofi-m. S. Torgova is grateful to Politecnico di Torino for financial support. A. Strigazzi acknowledges support from the MEPhI Academic Excellence Project (Contract No. 02.a03.21.0005).