Synthesis and characterization of octafluorinated 1,2-(4,4′-dialkoxyaryl)acetylene monomers and 1,4-bis[(4′,4′-dialkoxyphenyl)ethynyl]benzene dimers

Abstract

The symmetrically octafluorinated 1,2-bis(2,3,5,6,-tetrafluoro-4-n-alkoxyphenyl)acetylene (n= 7–9) monomers and symmetrically octafluorinated 1,4-bis[(2,3,5,6-tetrafluoro-4-n-alkoxyphenyl)ethynyl]benzene (n= 3–9, 12) dimers have been prepared by a Pd-catalysed coupling reaction from the starting material, 1-pentafluorophenyl-2-trimethylsilylacetylene. Textural observation by polarising microscopy showed that the monomers were not liquid crystalline, but that the dimers exhibited enantiotropic nematic liquid crystallinity. The effect of the symmetrical tetrafluoro-substitution of phenyl groups on the mesomorphic behaviour are also discussed.