The effect of lateral fluorination on the properties of phenyl-tolane liquid crystals

Abstract

Multifluorinated phenyl-tolane liquid crystals were synthesised by two steps cross-coupling reactions, and their structures were confirmed by nuclear magnetic resonance (NMR), mass spectra (MS) and infrared spectrometry (IR). All of these compounds show only nematic phase, and their melting points decrease dramatically with the introduction of lateral fluorine atom. The physical properties of the compounds were also evaluated. The extrapolated birefringence of the compounds are at the range of 0.32-0.37 at 589 nm, and the dielectric anisotropies exist between 3.1 and 20.6, and the rotational viscosities are as low as 63.7-130.7 mPa·s. With the increase of lateral fluorine substituents in the benzene ring, the Δε value increases tremendously while the clearing points, birefringence and rotational viscosity decrease. These compounds show good solubilities and are favourable to form eutectic mixtures. The effect of lateral fluorine atoms at different region of the core on the dielectric anisotropy and mesophase is also discussed.

Difluorovinyl Liquid Crystal Diluters Improve the Electro-Optical Properties of High-∆n Liquid Crystal Mixture for AR Displays

“…As we know, there is little research on the regulation of elastic constants. Liquid crystal chemists [ 21 , 32 , 33 ] often employ various molecular engineering strategies to synthesize many LC compounds with large ∆ ε , then LC physicists utilize these LC compounds to prepare LC mixtures with large ∆ ε [ 34 ]. These large-∆ ε LC mixtures can be used to reduce the working voltage of LC devices, meanwhile realizing the energy savings and consumption reduction in all kinds of LC devices.…”

“…Tolane liquid crystals as the representative of large π-conjugated structures [ 19 , 20 ] show the performance advantages of high ∆ n and low viscosity, which are suitable as high-∆ n components. The lateral fluorine substituent not only decreases the melting point and increases the ∆ ε [ 21 ], but is also utilized to widen the nematic phase temperature range of LCs [ 22 ]. Accordingly, fluorinated liquid crystals are usually optimized as large ∆ ε components.…”

Dielectric and optical anisotropy enhanced by 1,3-dioxolane terminal substitution on tolane-liquid crystals

“…The birefringence (Dn) values were measured at 20 1C by an Abbe refractometer using a 589 nm wavelength light source in a mixed liquid crystal (NR-5336LA). The dielectric anisotropies (De) of the liquid crystal monomers were measured at 20 1C in the host mixture 15 by an electrical constants instrument (EC-1, TOYO Corporation, Japan).…”

High birefringence liquid crystals with a wide temperature range and low melting point for augmented reality displays

“…[31][32][33] Lateral fluorine substituents and terminal polar groups are utilized to obtain electrical regulatory components with large dielectric anisotropy (De) and low T m . 34,35 LC diluters containing an olefin terminal group have been reported to display low T m and rotational viscosity (g 1 ). 36 Wide-temperature modulation components with a high clearing point (T c ) and relatively low T m are realized with three-ring molecular structures.…”