Synthesis of laterally substituted alpha-methylstilbene-tolane liquid crystals

Abstract

Three series of alpha-methylstilbene-tolane liquid crystals, 4-[2-(4-alkylphenyl)-1-ethynyl]-4'-fluoro-alpha-methylstilbene (3a-3e), 4-[2-(4-alkylphenyl)-1-ethynyl]-2'-methyl-4'-fluoro-alpha-methylstilbene (4a-4e) and 4-[2-(4-alkylphenyl)-1-ethynyl]-3'-methyl-4'-fluoro-alpha-methylstilbene (5a-5e), were synthesized and their phase transition temperatures characterized. All the alpha-methylstilbene-tolane liquid crystals exhibit an enantiotropic nematic phase. Compounds 5a-5e, which contain a lateral methyl group at the 3 position of the middle phenyl ring, display low melting points, a wide nematic range and a small enthalpy of fusion. Their potential applications for displays and laser-beam steering are noted.