Kerr effect studies of the isotropic-smectic phase transition of liquid crystalline 4-nitrophenyl 4-n-alkoxybenzoates

The static and dynamic pretransitional behaviour at the isotropic-smectic A phase transition was investigated by the electric Kerr effect and compared with the behaviour at the isotropic-nematic phase transition. Close above the smectic A-isotropic transition temperature a strong divergence and a deviation from the behaviour according to the Landau – de Gennes model (which was upheld far from the clearing temperature) was observed for both the Kerr constant and the Kerr relaxation time. The Kerr relaxation times near the smectic A-isotropic phase transition exceed that of the isotropic-nematic transition by more than a factor of 4 which is due to the existence of quasi smectic cybotactic groups in the isotropic phase.