Synthesis and mesomorphic properties of mesogens containing (4-polyfluoroalkoxy-2,3,5,6-tetrafluorophenyl)ethynyl groups

Due to the activation of fluorine atoms in aromatic rings by four other fluorine atoms and a 4-ethynyl bond, polyfluoroalkoxy chains can be introduced into aromatic rings by direct nucleophilic substitution reaction using potassium carbonate as base to prepare 4-polyfluoroalkoxy-2,3,5,6-tetrafluorophenylacetylenes. Seven compounds containing (4-polyfluoroalkoxy-2,3,5,6-tetrafluorophenyl)ethynyl groups have been prepared by catalytic reaction using bis(triphenylphosphine)palladium dichloride and copper(I) iodide as catalysts. Mesomorphic properties of target compounds were investigated by optical polarizing microscopy and differential scanning calorimetry (DSC). Mesophases were devalued by highly fluorinated alkoxy terminal chains compared with similar compounds whose terminal chains were not highly fluorinated.