Effect of Lateral Nitro Groups on the Properties of Sulfur-Ligated Twin Mesogens

The syntheses and the properties of new sulfurligated liquid crystalline sulfones, containing biphenyl units, as well as the influence of lateral nitro groups on their phase behaviour are described. Differential scanning calorimetry, optical polarizing microscopy and X-ray diffraction measurements reveal liquid crystalline properties for most of the synthesized bis(4-alkoxy-biphenyl-3-yl)sulfones ( 4 ). The mesomorphic behaviour of these compounds is compared with that of the corresponding nitro compounds 6 . The bis(4-alkoxy-6-nitrobiphenyl-3-yl)sulfones ( 6 ) are not mesogenic. The results demonstrate that lateral nitro groups introduced into the biphenyl unit, changing the length-breadth relation, depress the thermal stability and lead to the loss of the mesomorphic properties.