FINE-STRUCTURE IN THE PARAMETERS OF DIELECTRIC AND VISCOELASTIC RELAXATIONS

A new method for the analysis of dielectric or viscoelastic data, the calculation of the fine structure in relaxation parameters, is describ ed. The dielectric case is worked out in detail. Use is made of the pa rtial derivatives of the dielectric constant with respect to temperatu re and frequency. It is shown how the fine structure in activation ene rgy and frequency factor (Arrhenius) or, equivalently, the fine struct ure in activation enthalpy and activation entropy (Eyring) can be extr acted from the data using these derivatives. Results of simulations us ing a Cole-Cole distribution in frequency factors and a Gaussian distr ibution in activation energies are discussed. The values of both relax ation parameters are accurately deconvoluted with the fine-structure m ethod. Finally, some experimental results for rigid poly(vinyl chlorid e) are presented. The typical behavior at the alpha- and beta-transiti ons is discussed. An additional effect is observed at temperatures clo se to the alpha-transition or the structural transition from the glass y to the rubbery state. This effect offers an interesting tool for a n early frequency-independent assessment of the glass-rubber transition.