Polarization-diffusion effect on the dispersion of N- and αα-dielectric relaxation modes

In this paper, the contribution of polarization diffusion on the dispersion of the electric susceptibility in polymeric materials, that exhibits normal (N-) relaxation at low frequencies and segmental or alpha (αα-) relaxation at high frequencies, is studied. Polarization diffusion is locally established when the viscoelastic relaxation couples to the relaxation of a dipolar system. In order to formulate this diffusion process, it was proposed a physical description based on a system of two coupled equations to express the viscoelastic and dielectric relaxations, and the coupling between them is introduced by considering spatial inhomogeneities. The complex polarization-diffusion coefficient and the wave number as frequency function are obtained considering two parameters, which were evaluated using a diffusive model for the N- and αα-dielectric modes, respectively, for several polymeric systems.