Ferroelectric and antiferroelectric liquid crystalline phases in some pyridine carboxylic acid derivatives
The synthesis and mesomorphic properties of two series of compounds viz.(S)-(+)-4-(1-methylheptyloxy)phenyl 4′-(6″-alkoxypyridine-3-carbonyloxy)benzoates and (S)-(+)-l-methylheptyl4-[4′-(6″-alkoxypyridine-3-carbonyloxy)benzoyloxy]-benzoates are reported; the homologues of the former series exhibit smectic A and smectic C* phases while the derivatives of the latter series show rich polymesomorphism including the antiferroelectric phase. The mesophases have been characterised by using optical polarising microscopy and differential scanning calorimetric methods. Some physical properties such as the spontaneous polarisation, helical pitch, tilt angle and relative permittivity of two derivatives have also been investigated.