Dielectric relaxation and nematic potential of some nematogenic compounds

Component of epsilon(parallel to) of dielectric tensor has been studied in the nematic phase of three nematogenic compounds namely 6 OCB, 7 OCB and IPBOC. Using the relaxation data the nematic potential associated with the above molecules has been estimated based on Maier and Saupe mean field theory

Optical-Properties of Spherulites of Cholesteryl-Do-Decyl Carbonate

We report here some very interesting optical textures exhibited by a pure cholesterogenic compound viz., Cholesteryl-do-decyl carbonate. It also exhibits ringed spherulitic texture when crystallized at different temperatures. The observed ring spacing is found to increase with the increase of crystallization temperature and we were also able to determine Avarami's constants by studying the growth rate of these spherulites. Light scattering and optical diffraction studies have been carried out using optical textures exhibited by the sample. The local order parameters corresponding to untwisted nematic structure in the cholesteric layer has been estimated at various temperatures in the cholesteric phase using the measured refractive index and density data

Optical Effects from Spherulites in Polyethylene

The spherulites exhibited by polyethylene samples have an associated ring structure which gives rise to diffraction and other optical effects which are attributed to a periodic variation of the refractive index of the spherulites for light polarized transverse to the radial direction. The periodic and continuous variation of the refractive index is confirmed from sensitive interference experiments. The optical phenomena are illustrated with striking photographs

Static dielectric studies of some nematogenic compounds

Static dielectric constant studies of three nematogenic compounds, viz., 4'-(hexyloxy)-4 biphenyl carbonitrile, 4'-(heptyloxy)-4 biphenyl carbonitrile and 4-isothiocyanatophenyl 4-pentylbicyclo (2,2,2) octane 1-carboxylate, have been carried out and reported in this paper. The behaviour of the dielectric constants with temperature in these compounds have been explained in terms of the dipole moment