Dielectric Relaxation in Nematic and Isotropic Phases of p-Azoxyphenetole (PAP)

Abstract

Dielectric relaxation studies of the isotropic and nematic phases of 4,4'-n-diethoxyazoxybenzene (PAP) have been carried out in the radio and microwave frequency ranges. In the nematic phase two substantially different relaxation processes, with relaxation times τ_‖ ∼ 10⁻⁸ sec and τ_‖ ∼ 10⁻¹¹ sec, have been detected. They are connected with the reorientational motions of molecules around their short and long axes, respectively. The dielectric permittivity extrapolated to very high frequencies is markedly greater than the squared refractive index. This indicates that there might be additional relaxation process in the infra-red region. The relaxation spectrum of the isotropic phase is broad and the most probable relaxation time τ₀ = 2 · 10⁻¹¹ sec.