Synthesis and properties of new three-ring phenylacetylene liquid crystals containing the cyclohexyl unit

Abstract

Two series of new three-ring phenylacetylene liquid crystals were synthesized and their physical properties were evaluated. These liquid crystal materials show only a nematic phase, high clearing points and good solubilities. The compounds containing two cyclohexyl rings exhibit moderate birefringence (Dn) values of around 0.14, while those containing one cyclohexyl ring show a broad nematic phase range and high Dn of around 0.33.

An improved practical Pd/C‐catalyzed Sonogashira cross‐coupling reaction for the synthesis of liquid crystals of trans‐cyclohexyltolans

“…In recent years, we have been interested in the synthesis of trans ‐cyclohexyltolan‐type liquid crystals, which have the properties of low viscosity coefficients, higher phase transition temperature and higher optical anisotropy (Δ n ),4–7 by the Sonogashira cross‐coupling reaction of 1‐iodo‐4‐( trans ‐4‐alkylcyclohexyl)benzene with aromatic terminal alkynes catalyzed by Pd(PPh 3 ) 4 or PdCl 2 (PPh 3 ) 2 with CuI as co‐catalyst in both the academic and industrial settings 8–10. One of the most important topics in our research group is the development of an alternative catalyst system which aims to suppress side reactions, improve liquid crystal quality, and decrease production cost.…”