Structural Relaxation and Anharmonicity in Polymer Electrolytes: Effect of the Thermal History

The effects of the storage at room temperature of PEO-KSCN polymer electrolytes have been studied by differential scanning calorimetry (DSC) and dynamical mechanical analysis. It has been revealed that, over the explored time interval, the annealing causes small variations in the anharmonic and relaxation properties of the samples, which are to be ascribed to changes in the relative amount of the phases building up the structure. The elastic and anelastic characteristics show a well-defined dependence on the degree of crystallinity of the polymer, which grows slightly with increasing annealing time. The application of a simplified version of a quasi-harmonic model and of the Kolrausch-Williams-Watts stretched exponential function permits to describe the temperature behaviour of the elastic modulusE? and to obtain an anharmonicity parameter characterizing the polymeric system.