DIELECTRIC BEHAVIOR OF N(P-OCTYLOXYBENZYLIDENE) P-TOLUIDINE (OBT) IN NEMATIC MESOPHASE AT RADIO FREQUENCIES

Dielectric permittivity and loss have been measured in the frequency range 0.5-3.5 MHz in nematic and isotropic phases of OBT. Measurements in the nematic region with a magnetic field greater than saturation value acting parallel to the rf electric field exhibit a Debye type dispersion of ε∥ with relaxation frequency 5.3 MHz at 71°C and activation energy of 27.0 kcal/mole. The results can be explained on the basis of the molecular rotation about a transverse axis occurring under hindering nematic potential. Measurements also indicate that OBT behaves as a positive dielectric material at low frequencies and a negative dielectric material at higher frequencies. © 1979 American Institute of Physics.