Dielectric Relaxation Processes in Ethanol/Water Mixtures
S. Schrödle, R. Buchner and W. Kunz
J. Chem. Phys. B108 (2004) 6281-6287
Abstract
Precise complex permittivity spectra over the frequency range 0.15 <=n/GHz <= 89 GHz
are reported for monodisperse (EGn,1 <= n <= 6) and polydisperse (PEG174, PEG300, PEG400) oligo(ethylene glycol)s at 25 °C. Up to about 20 GHz, the
relaxation behaviour of all samples can be reasonably described with empirical functions that reflect a broad and
asymmetric relaxation time distribution, like the Havriliak-Negami function. However, these functions deviate
systematically at higher frequencies and do not allow one to rationalize the concentration dependence of the
spectra on dilution in dichloromethane or when going from the diol to the corresponding dimethyl ether. It is shown
that a coherent description can be achieved by using a superposition of Debye-type relaxation processes. This
approach allows the separation of end-group effects connected with the relaxation of the hydrogen bond network
from intramolecular dipole relaxation processes caused by the reorientation of chain segments.
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