Relationships between conductivity and local topology in heterocyclic polymer networks

The low frequency complex dielectric relaxation above the glass transition temperature T(g) for a series of well-characterized heterocyclic polymer networks has been analyzed in terms of the electric moduli formalism. It was established that the contribution of ionic conductivity to the electric modulus can be quantitatively separated from the alpha relaxation by using a combination of two Havriliak-Negami (HN) functions. A strong correlation between the mechanisms of both conductivity and segmental mobility was inferred from the similarity of the shape of the HN function for conductivity relaxation to those for the main relaxation. This correlation is further supported by the similarity of the temperature dependencies of the relevant relaxation times corresponding to both processes. The overwhelming contribution of the preexponents D0 in the Arrhenius behavior of the apparent diffusion coefficients can be explained by considering a model implying decreased mean free paths of the diffusing elements and lower activation entropies of diffusion for polymer networks with higher apparent network densities.