Non-linear dielectric effects in polymers and glass-forming liquids

Non-linear dielectric effects are examined for polar polymers and glass-forming liquids with special interest on their relaxation phenomena. We made measurements of the linear and non-linear complex permittivities on the frequency domain by means of Fourier decomposition of the dielectric response induced by a sinusoidal electric field. It is shown that non-linear complex permittivities exhibit a relaxation in a form of an extended Havriliak-Negami function. The relaxation strengths give the equilibrium polarization expanded in odd powers of the electric field. Combined knowledge about the linear and third non-linear relaxation strengths allows estimates of the number density and the moment of equivalent free dipoles. It also leads to prediction of the saturation polarization imparted by poling.