Dielectric relaxations in a few binary mixtures of p-methoxybenzylidene–p′-n-butylaniline and a nematogenic or nonmesogenic compound

Dielectric relaxations in a few binary mixtures, which are in nematic state, of p-methoxybenzylidene–p′-n-butylaniline (MBBA) and other components were studied in the frequency range 300Hz–4 MHz. One of the components added was p-ethoxybenzylidene–p′-cyanoaniline (EBCA), a nematogenic compound, which formed a eutectic mixture with MBBA. Others were p-n-butylaniline and chloroform, nonmesogenic compounds. The low frequency relaxations were observed in all samples. The relaxation time increased by adding EBCA to MBBA, while decreased by adding p-n-butylaniline and chloroform to MBBA. The activation enthalpy for the low frequency relaxation and the activation enthalpy for viscosity of the isotropic phase had a maximum near the eutectic mixing ratio (cE). By examining the above dielectric results by the Meier–Saupe theory, it was concluded that both long range– and short range–intermolecular interactions in nematic phase increase anomalously near cE.