Hydrogen network fluctuations of associating liquids: Dielectric relaxation of ethylene glycol oligomers and their mixtures with water

Abstract

Complex dielectric spectra of ethylene glycol and of various derivatives as well as of mixtures of water with an ethylene glycol oligomer and with a poly(ethylene glycol) dimethyl ether oligomer have been measured. The spectra can be well represented by a Cole-Cole [Cole and Cole, J. Chem. Phys. 9, 341 (1941)] spectral function. The extrapolated low frequency (static) permittivity of this function has been evaluated to yield the effective dipole orientation correlation factor of the liquids. The relaxation time of the ethylene glycols displays a characteristic dependence upon the ratio of concentrations of hydrogen bond donating and accepting groups, indicating two opposing effects. With increasing availability of hydrogen bonding sites effects of association and also of dynamical destabilization increase. Both effects exist also in the mixture of water with the oligomers. They are discussed in terms of a wait-and-switch model of dipole reorientation in associating liquids. Another feature in the dependence of the dielectric relaxation time of poly(ethylene glycol)/water mixtures upon mixture composition has been tentatively assigned to precritical demixing behavior of the binary liquids in some temperature range.

Muon studies of Li+ diffusion in LiFePO4 nanoparticles of different polymorphs

“…The results obtained for ethylene glycol compare well with previously reported values. 44 Note that the errors quoted in our data are systematic errors of around AE1% associated with the simple quasi-static model 41 used to model the aperture admittance of the coaxial probe to convert microwave reectance data into complex permittivity values. We nd that both solvents have large measured values of 3 2 , conrming their effectiveness as microwave absorbers.…”

Effects of Solvent Polarity on Li-ion Diffusion in Polymer Electrolytes: An All-Atom Molecular Dynamics Study with Charge Scaling

“…The calculated ε p value for neat PEO at P 1.00 in Figure 1 a is in good agreement with the reported experimental values in the literature (ε ∼ 4–5). 16 , 47 − 49 Adding salt to the PEO matrix reduces the dielectric constant as the reorientation of the solvent is significantly hindered. From Figure 1 a, one can see that the solvent polarity of a system was enhanced by scaling up the charge on the polymer.…”

Molecular Interactions in Poly(ethylene glycol)–Water Mixtures at Various Temperatures: Density and Isentropic Compressibility Study

“…Fewer water links between polymers are obviously required upon addition of water in order to reach the structure of smallest volume. We note that association of the pure protic solvent is nicely reflected by the dielectric relaxation time, which is substantially larger for triethylene glycol monoethyl ether (t = 87 ps) than for tetraethylene glycol dimethyl ether (t = 15 ps, 25 8C [38] ). Addition of water is accompanied by a rearrangement of the hydrogen-bonding network.…”

“…[38] This maximum, however, is located at Y m w = 0.15, corresponding to a water molecule to ether oxygen atom concentration ratio C w /C e = 0.44. This ratio means that the dielectric relaxation time peaks when about one water molecule is available to bridge two ether oxygen atoms.…”