화학공학소재연구정보센터
Molecular Crystals and Liquid Crystals, Vol.548, 155-163, 2011
Study of Birefringence and Dielectric Properties and Determination of Dipole Moment of the Mesogen: 4-Cyano-4'-n-Octylbiphenyl as a Function of Temperature
Texture studies have been conducted on the above mesogen to confirm the transition temperatures and the various mesophases. Optical studies using He-Ne laser beam have been performed and refractive indices have been determined as a function of temperature by the application of Chatelain Wedge principle. From this principle, polarizability and orientational order parameter have been determined. The experimentally determined orientational order parameter is compared with theoretical Maier-Saupe values. To study the dielectric property, we have determined the parallel and perpendicular components of dielectric permittivities, i.e., epsilon(parallel to) and epsilon(perpendicular to) in the presence of magnetic field, and from dielectric anisotropy, polarizability, and order parameter, we have calculated effective dipole moment mu(eff) and angle of inclination beta of the axis of molecule with the director direction as a function of temperature. Dielectric studies of the sample have also been performed in the solution at various concentrations, and by extrapolating the values at infinite dilution, we have obtained isolated molecular dipole moment mu(iso). We have compared the values of mu(eff) and mu(iso) and have calculated correlation factor "g" that throws a light on nature of bonding of the molecules.