Frequency dependent conductivity in polymers and other disordered materials

Experimental data of the ac conductivity in polymers and other disordered materials are discussed in terms of theoretical models, especially with respect to a common universal behaviour, as proposed by Summerfield. Two parameters can be extracted from such an analysis, the frequency exponents=0.69±0.04, describing the behaviour at higher frequencies, and a model dependent factorA, ranging between 10^–2 and 10^–5, that characterizes the crossover from frequency independent values to an ac conductivity increasing with frequency like ₅.Dedicated to Professor Harry Thomas on the occasion of his 60th birthday