Hexaalkinylbenzol-Derivate, erste Kohlenwasserstoffe als neuartige columnar- oder nematischdiscotische Flüssigkristalle

Abstract

The first disc-shaped thermotropic liquid-crystalline hydrocarbons, the hexaalkynylbenzene derivatives 2 and 3, have been synthesized. These newly designed radial-symmetric mesogens contain the hexaethynylbenzene (2a, 2b) or the super-disc-like hexaphenylethynylbenzene unit (3b), respectively, as novel types of unsaturated «cores». These three hydrocarbons are monomesomorphic. The first two compounds (2a, 2b) exhibit very viscous and probably highly ordered columnar-discotic mesophases (not yet identified), whereas compound 3b shows enantiotropically the rarely observed fluid N_D nematic phase over a temperature range of about 16 K.