NONLINEARITY AND NON-EXPONENTIALITY OF PRIMARY RELAXATIONS

The glass transformation range of supercooled liquids and amorphous polymers is characterized by a number of unusual properties such as structural state dependence as well as non-Debye and non-Arrhenius behaviors. It is shown how the latter phenomenon, quantified in terms of the fragility index m, is related to the associated spectral width in the linear response regime and to the non-linearity of the enthalpy relaxation for a diverse variety of glass-forming materials.