Effects of temperature and dissolved LiClO$_{4}$ on the viscoelastic and dynamic properties of poly(ethylene oxide), (PEO) melts

The physical properties of poly(ethylene oxide) (PEO) melts and PEO/LiClO$_{4}$ complexes are of major importance for understanding the mechanism and dynamics of lithium-ion transport in polymer electrolytes. We used a fiber-optic coupled triple-pass Fabry-Perot interferometer to study the Brillouin light scattering spectra of PEO melts and PEO melt/LiClO$_{4}$ solutions for various salt concentrations and in the temperature range from the melting point up to 180$^{\circ}$C. We report the measured Brillouin line-shifts and line-widths. A relaxation process was identified in the gigahertz frequency range and was studied in detail. The ``mapping'' of the relaxation in the frequency--temperature--concentration parameter space yields important information about the local segment dynamics of the polymer chain, which has a direct effect on the transport of the charge carriers in the polymer electrolyte.