THE SCALING OF THE DIELECTRIC ALPHA-RELAXATION IN LOW-MOLECULAR GLASS-FORMING SYSTEMS AND POLYMERS

By measuring the complex dielectric function over 15 decades in frequency, the scaling of the cc-relaxation is evaluated for several glass-forming liquids including low-molecular weight materials (propylene carbonate, propylene glycol and glycerol) and a polymer melt (poly(propylene glycol), PPG). The temperature dependence of the mean relaxation time and of the relaxation strength of the relaxation function display two dynamical regions being separated by a crossover temperature. Several of observed findings are essentially not in accordance with predictions of the mode-coupling theory for supercooled liquids. In the case if PPG, it has been shown that small and large scale motions decouple from the alpha-process at different temperatures below the crossover temperature.