DIELECTRIC AND OPTICAL STUDIES OF HOMOLOGOUS SERIES OF BICYCLO[2,2,2]OCTANE DERIVATIVES WITH -NCS TERMINAL GROUP

The static dielectric constants and the optical birefringence for four members of the homologous series of bicyclo[2,2,2]octane derivatives with -NCS terminal group (pentyl to octyl) have been measured as a fun ction of temperature. From the dielectric anisotropy, the optical bire fringence as well as the polarized absorption spectra of the dichroic dye dissolved in the liquid crystalline host the order parameter has b een determined. The results obtained by using various experimental met hods have been compared with those calculated from the Maier-Saupe mea n field theory. It has been found that the order parameter for tile su ccessive homologues shows alternation similar to that exhibited for th e nematic-isotropic transition temperature.