Thermotropic liquid crystals from a monosubstituted 2,2'-bipyridine

Unsymmetric functionalization of 5-bromo-2,2'-bipyridine and 5,5'-dibromo-2,2'-bipyridine with 4-n-alkoxyphenylethynyl leads to two new families of mesomorphic compounds. The smectic B, smectic A and nematic phases observed were studied by polarizing optical microscopy, differential scanning calorimetry and X-ray diffraction. The structural parameters of the smectic phases were determined. The internal structure of the smectic phases, particularly the range of the in-layer ordering of the molecules, was investigated as a function of temperature.