Kerr-effect investigations in a nematic liquid crystal

In this paper we report the dc Kerr constant and the pretransitional temperature of a polar nematic liquid crystal 4-(trans-4'-4'-n-pentylcyclohexy)-benzonitrile (PCH-5). The observed second-order pretransitional temperature T* from our measurements is found to be 1.2 ^∘{}C below the first-order nematic to isotropic transition temperature. The dependence of the Kerr constant on (T-T*{)}^{{{-}}1}$ is found to be in good agreement with the predictions of the Landau--de Gennes model. The highest value of the Kerr constant observed at 632.8 nm is found to be 9.737×{}10^-11 m V^-2, corresponding to a temperature of 55.3 ^∘{}C.