SYNTHESIS AND CHARACTERIZATION OF OCTAFLUORINATED 1,2-(4,4'-DIALKOXYARYL)ACETYLENE MONOMERS AND 1,4-BIS[(4',4''-DIALKOXYPHENYL)ETHYNYL]BENZENE DIMERS

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.