Identification of relaxation processes in pure polyethylene oxide (PEO) films by the dielectric permittivity and electric modulus formalisms

The ac-impedance of bulk-like films of pure polyethylene oxide (PEO) polymer was measured as a function of frequency f in the range 0.1 to 10(7) Hz at various constant temperatures T (155 - 330 K). The as-measured data were analyzed by electric permittivity and modulus formalisms to unveil which dielectric and conductive relaxation processes were responsible for their relaxation behavior below/above glass transition temperature T-g of pure PEO polymer. At T > T-g, none of the alpha-, beta-, or gamma-relaxations could be inferred for studied pure PEO films from frequency variation of measured imaginary part epsilon"(f, T) of complex dielectric permittivity (epsilon) over tilde (f, T), as low-frequency losses masked real dielectric contribution to the measured e"(f, T) at low frequencies and high temperatures. However, at T < T-g, a broad, relaxation process has been observed in the high-frequency part of their isothermal epsilon"(f, T) - f spectra, which can be related to the beta- or gamma-dielectric relaxation process. Nonlinear regressions of the measured epsilon"(f, T) -f data for T < T-g yielded moral fits to a simple addition of a Havriliak-Negami function, and a Bergman-loss Kohlrausch-Williams-Watts-type function, with the relaxation time tau(max)(T) obtained from Havriliak-Negami-fitting parameters, was found to follow a thermally activated Arrhenius-like relaxation behavior. Conversely, representation of the imaginary part M"(f, T > T-g) -f spectra of complex electric modulus (M) over tilde (f) = 1/(epsilon) over tilde (f) was found to depict 2 overlapped relaxation processes, which were detached well by a nonlinear regression of a simple superposition of 2 different M"(f) expressions having the form of the universal Bergman loss function, where it was found that the relaxation time is also thermally activated.