High-pressure and molecular weight variation of electrical relaxation in poly(ethylene oxide)

Publisher Website
Google Scholar
Abstract
Vacuum audio frequency complex admittance measurements have been performed on poly(ethylene oxide) using a fully automated dielectric spectrometer. Measurements have been made over the temperature range 5.5–320 K for molecular weights from 1.85×104 to 4×106. The γ relaxation is essentially unchanged over the range of molecular weights studied. This represents evidence against assigning the γ relaxation to the motion of end groups. Next, previously reported data for the γ relaxation are reanalyzed using a reduced plot. The activation volume is found to be 3–4 cm3/mol in good agreement with the previous work and the small value implies that the relaxation is associated with the motion of very small segments of the polymer chain. Next, the relaxation associated with the glass transition αa is only observed in temperature for some samples but is observed in both frequency and temperature for others. The strength of αa decreases monotonically as molecular weight decreases. Finally, αa was studied up to pressures of about 0.2 GPa for 5×106 molecular weight material. The results for the shift of αa with pressure are in qualitative agreement with recent theories.