Dielectric Relaxation Processes in Ethanol/Water Mixtures
Dielectric Relaxation Processes in Ethanol/Water Mixtures
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DOI：
10.1021/jp035255o
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发表时间：
2004-05
影响因子：
2.9
通讯作者：
Takaaki Sato;R. Buchner
中科院分区：
文献类型：
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作者：
Takaaki Sato;R. Buchner
在0.1≤ν/GHz≤-89频率范围内，利用0.1≤ν/GHz≤-25中的TDR和13≤ν/GHz≤-89中的波导干涉仪，在25°C下测量了乙醇-水混合物的复介电谱，其中XEA=0.04，0.08，0.11，0.18，0.3，0.5，0.7，0.9和1.0。在0.3≤XEA≤1.0时，三步松弛模型被证明是最合适的。除了主要的低频过程(j=1)的科尔-−-科尔驰豫外，当XEA=0到1时，它的驰豫时间τ1显著地增加，当XEA=0时，需要两个额外的德拜项(j=2和3)，驰豫时间分别为τ2≈10ps和τ3≈1−2ps。考虑到纯液体的驰豫机制，这些高频过程可以有效地归结为链结构末端(j=2)的单氢键乙醇单体的运动和翻转。
We have determined the complex dielectric spectra of ethanol/water mixtures at 25 °C for the nine molar fractions of ethanol, XEA = 0.04, 0.08, 0.11, 0.18, 0.3, 0.5, 0.7, 0.9, and 1.0, in the frequency range 0.1 ≤ ν/GHz ≤ 89 using TDR in 0.1 ≤ ν/GHz ≤ 25 and waveguide interferometers in 13 ≤ ν/GHz ≤ 89. At 0.3 ≤ XEA ≤ 1.0, a three-step relaxation model turns out to be most appropriate. Besides a Cole−Cole relaxation for the dominating low-frequency process (j = 1), assigned to the cooperative dynamics of the H-bond system, which exhibits a pronounced increase of its relaxation time, τ1, when going from XEA = 0 to 1, two additional Debye terms (j = 2 and 3) with the relaxation times of τ2 ≈ 10 ps and τ3 ≈ 1−2 ps are required to reproduce the high-frequency part of the spectrum. In view of the well-established relaxation mechanisms of pure liquids, these high-frequency processes can be validly assigned to the motion of singly H-bonded ethanol monomers at the ends of the chain structure (j = 2) and the flipp...