Dielectric Relaxations in Polyoxymethylene and Polyethylene Oxide

Abstract

Dielectric properties in the frequency range 10-1 to 106 c/s are studied above 100°C for polyoxymethylene (POM) and above -32°C for polyethylene oxide (PEO). In case of POM, a dielectric dispersion which corresponds to the mechanical α dispersion in its frequency and temperature position is observed and is assigned to the crystalline phase. The relaxation strength Δε of this dispersion increases with increasing crystallinity and, when compared at a constant crystallinity, Δε is larger and the relaxation time is longer for the sample of larger lamella thickness. This behavior follows qualitatively the prediction of Okano's theory of the crystalline dispersion. The magnitude of Δε, however, is larger than the theoretical one by the order of three. Several possible origins of this discrepancy are suggested. In case of PEO, the primary dispersion which comes from segmental motion in the amorphous phase is observed. The relaxation strength of the dispersion agrees well with theory. Dispersion maps of the two polymers compiled from existing literatures as well as the present study are presented.