Comparison between interpretations of dielectric behavior of poly(vinyl acetate) by the coupling model and the Havriliak–Negami equation

Abstract

Comparison has been made between the Kohlrausch–Williams–Watts (KWW) function and the Havriliak–Negami (HN) equation in order to examine which is more suitable for describing dielectric relaxation behavior reported recently for poly(vinyl acetate). The measured complex permittivity is fitted satisfactorily by the KWW function as well as the HN equation over a frequency range of −2≤log( f/f m )≤2, where f m is the frequency of maximum dielectric loss. Temperature dependence of the Kohlrausch relaxation time τ* obtained experimentally is also explained by the coupling model, which gives τ*=[(1−n)ω n c τ0]1/(1−n), over a wide temperature region including the region below the glass transition temperature. The value of ω c is determined as 7.2×109 s− 1, which is quite reasonable compared to the predicted value. No anomalous dielectric behavior was found in the glass transition region. This is not true of the results obtained with the HN equation.