Dielectric studies on two compounds exhibiting first and second order smectic Ad - Nematic transitions

Abstract

The influence of the order of the smectic A to nematic transition (A-N) on the behaviour of the static dielectric permittivity was investigated by studying 4-cyano- phenyl 4'-n-decyloxybenzoate (CP10OB) and 4-cyanophenyl 4'-n-undecyloxybenzoate (CP11OB). In the case of the former which exhibits a second order A-N transition, ε, ει as well as Δε are seen to show a change of slope at the transition while in case of the latter compound which has a first order A-N transition a small jump is seen. These studies show that the change in the order of the A-N transition manifests in the dielectric properties of the materials.