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 beta 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.