Dielectric spectroscopy in the alpha beta splitting region of glass transition in poly(ethyl methacrylate) and poly(n-butyl methacrylate): different evaluation methods and experimental conditions

Stability of the dielectric parameters in the alpha beta splitting region against methodical variations is demonstrated. The Williams product ansatz [expression] for correlation functions and an additive ansatz for dielectric functions are compared for poly(ethyl methacrylate). Both evaluation methods give a diminishing alpha intensity with increasing temperature, and a separate trace for the alpha relaxation different from both the secondary beta relaxation below and the high-temperature alpha process above the crossover. Furthermore, measurements on different poly(n-butyl methacrylate) samples and evaluation results of different experimentalists are compared. The intensity onset of the cooperative alpha relaxation, starting from zero at a characteristic temperature T sub on in the crossover region, and the parallel course of alpha and beta relaxations below T sub on , separated by about one frequency decade in an Arrhenius diagram, remain stable against measurement and evaluation variations.