Low-Frequency Dielectric Investigations of Smectic-C Tilt Angle

Low-frequency dielectric studies are carried out to determine the molecular tilt in liquid crystalline smectic-C phase in some of the schiff base n(p-n-alkoxybenzylidene) p-n-alkyl anilines viz., nO.m compounds. The influence of smectic-C thermal range, thermal fluctuations and range of smectic-A phase and the odd-even effect in a homologous series are investigated for the equilibrium smectic-C tilt angle value. The growth of tilt angle as relevant order parameter is discussed in the context of de Gennes critical model and other mean field models. Order parameter exponent β supports the de Gennes model characterised by long range gauge invariance of tilt order fluctuations over smectic layers. The observed smectic-C thermal span and the value of maximum tilt angle are found to agree with McMillan molecular model.