The synthesis and mesomorphic properties of 2,2′,3-tri- and 2,2′,3,3′-tetra-fluoro-1,1′∶4′,1″-terphenyls for high dielectric biaxiality ferroelectric liquid crystal mixtures

Abstract

Liquid crystalline 1,1Ј : 4Ј,1Љ-terphenyls with three and four lateral fluoro substituents and alkyl or alkoxy substituents in the 4-and 4Ј-positions have been synthesised. Synthetic strategies employed were convergent and involved the use of arylboronic acids and aryl halides in palladium-catalysed cross-coupling reactions. These syntheses are of particular interest because issues of selective metallation (at positions ortho to a fluoro substituent) and selective coupling reactions (bromo versus iodo sites) are involved, not all of which proceed as expected. All the trifluoroterphenyls and most of the tetrafluoroterphenyls generate the smectic C phase, the phase stability and temperature range of which were found to be highly dependent upon the relative lengths of the two terminal chains. The 2,2Ј,3and 2,2Ј,3,3Ј-patterns of lateral fluoro substitution in 1,1Ј : 4Ј,1Љ-terphenyls generate materials of high lateral dipole and enable the formulation of ferroelectric mixtures with a high dielectric biaxiality which is very important in τV minimum driving schemes.

Synthesis and physical properties of difluoroterphenyl ferroelectric liquid crystal with mixed alkenyloxy‐ester terminal ends

“…The group reported that the larger this distance, the larger is the possibility of the formation of a ferroelectric liquid crystal [13]. Trifluorination and tetrafluorination of such cores have also recently been reported [14][15][16].…”

The Fascinating Influence of Fluoro Substituents on the Synthesis and Properties of Liquid Crystals

“…The inherently high liquid crystal phase stability of terphenyls allows for the introduction of a third lateral fluoro substituent, and still generates a smectic C phase to a usefully high temperature (compound 33). When next to the original two fluoro substituents, the third fluoro substituent enhances the dielectric anisotropy, and yet the viscosity is reduced [25].…”

Banana‐shaped and other bent‐core liquid crystals

“…During the late 1980s and early 1990s, much research was conducted in the area of generating materials for ferroelectric applications, and one of the largest programmes involved the synthesis of ferroelectric host materials and chiral dopants to generate ferroelectric mixtures of high dielectric biaxiality [49][50][51][52][53][54][55][56]. In order to achieve this goal host materials of very high negative dielectric anisotropy were required, and this was best achieved by the use of materials with two lateral fluoro substituents inherently fixed on one side of the molecule (e.g., compound 47) [49].…”