Mixed Debye-type liquids studied by dielectric, shear mechanical, nuclear magnetic resonance, and near-infrared spectroscopy
Mixed Debye-type liquids studied by dielectric, shear mechanical, nuclear magnetic resonance, and near-infrared spectroscopy
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DOI：
10.1016/j.jnoncrysol.2014.07.018
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发表时间：
2015-01-01
影响因子：
3.5
通讯作者：
Boehmer, R.
中科院分区：
文献类型：
--
作者：
Bauer, S.;Moch, K.;Boehmer, R.
一元醇类化合物的类德拜过程一直是研究的热点，介电谱法是研究该类化合物的主要方法。然而，一些其他的技术是有用的解开这些超分子液体的动力学。关于纯一羟基醇的最新综述，见R。博默角盖纳鲁河里切特，物理代表（接受）。在此背景下，本文主要涉及混合物涉及一元醇使用各种实验方法。给出的例子包括混合物上的介电谱，其显示了与结构弛豫分离的小德拜过程。对于另一种混合物，它表明，时间尺度的电介质和德拜过程的流变签名相吻合。利用同位素标记绘制出的旋转动力学的两个组件的二元混合物的1-丁醇（BuOH）和1-溴丁烷（BuBr）使用自旋晶格弛豫核磁共振（NMR）光谱。虽然BuOH中的羟基运动在BuBr的混合物后变得更快，但烷基溴动力学实际上与组合物无关。两次和四次受激回波NMR实验表明，在BuOH-BuBr混合物的动态交换是类似的过冷液体没有德拜过程，因此它不提供一个合理的理解对称加宽的结构介电损耗峰在此和相关的混合物。最后，纯的和混合的一元醇在宽的温度范围内记录的近红外光谱的波长依赖的导数分析表明，氢网络的重排不同低于和高于约250 K。(c)2014爱思唯尔有限公司版权所有。
Monohydroxy alcohols have been in the focus of scientific research for a long time and their Debye (-like) process was studied predominantly using dielectric spectroscopy. However, a number of other techniques are useful to unravel the dynamics of these supramolecular liquids. For a recent review on neat monohydroxy alcohols, see R. Bohmer, C. Gainaru, R. Richert, Phys. Rep, (accepted). On this background the present article deals mostly with mixtures involving monohydroxy alcohols using various experimental methods. Examples given include dielectric spectroscopy on a mixture which shows a small Debye process well separated from the structural relaxation. For another mixture it is demonstrated that the time scales of the dielectric and the rheological signatures of the Debye process coincide. Isotope labeling is exploited to map out the rotational dynamics of both components in binary mixtures of 1-butanol (BuOH) and 1-bromobutane (BuBr) using spin-lattice relaxation nuclear magnetic resonance (NMR) spectroscopy. While the hydroxyl motion in BuOH becomes faster upon admixture of BuBr, the alkyl bromide dynamics is virtually independent of composition. Two-time and four-time stimulated-echo NMR experiments show that the dynamic exchange in a BuOH-BuBr mixture is similar to that of supercooled liquids devoid of a Debye process and hence it does not provide a rationale to understand the symmetric broadening of the structural dielectric loss peak in this and related mixtures. Finally, a wavelength dependent derivative analysis of near-infrared spectra recorded for pure and mixed monohydroxy alcohols over wide temperature ranges shows that the rearrangement of the hydrogen network differs below and above about 250 K. (c) 2014 Elsevier B.V. All rights reserved.