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 a gainst methodical variations is demonstrated. The Williams product ansatz f or correlation functions and an additive ansatz for dielectric functions ar e compared for poly(ethyl methacrylate). Both evaluation methods give a dim inishing a intensity with increasing temperature, and a separate trace for the alpha relaxation different from both the secondary beta relaxation belo w and the high-temperature a process above the crossover. Furthermore, meas urements on different poly(n-butyl methacrylate) samples and evaluation res ults of different experimentalists are compared. The intensity onset of the cooperative a relaxation, starting from zero at a characteristic temperatu re T-on in the crossover region, and the parallel course of alpha and beta relaxations below T-on, separated by about one frequency decade in an Arrhe nius diagram, remain stable against measurement and evaluation variations.