Wang Li-Min, Shahriari Shervin, Richert Ranko
Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604, USA.
J Phys Chem B. 2005 Dec 15;109(49):23255-62. doi: 10.1021/jp054542k.
With the recognition that the Debye-type dielectric relaxation of liquid monohydroxy alcohols does not reflect the structural relaxation dynamics associated with the viscous flow and the glass transition, its behavior upon dilution is expected to differ from that of real alpha-processes. We have investigated the Debye-type dielectric relaxation of binary alcohol/alkane mixtures across the entire concentration range in the supercooled regimes. The focus is on 2-ethyl-1-hexanol in two nonpolar liquids, 3-methylpentane and squalane, which are more fluid and more viscous than the alcohol, respectively. The Debye relaxation is found to occur only for alcohol mole fractions x > 0.2 and is always accompanied by a non-Debye relaxation originating from the alcohol component. Prior to its complete disappearance, the Debye relaxation is subject to broadening. We observe that the Debye dynamics of 2-ethyl-1-hexanol is accelerated in the more fluid 3-methylpentane, while the more viscous squalane leads to longer Debye relaxation times. The present experiments also provide evidence that the breakdown of the Debye relaxation amplitude does not imply the absence of hydrogen-bonded structures.
随着人们认识到液态单羟基醇的德拜型介电弛豫并不反映与粘性流动和玻璃化转变相关的结构弛豫动力学，其在稀释时的行为预计会与真实的α过程不同。我们研究了二元醇/烷烃混合物在过冷状态下整个浓度范围内的德拜型介电弛豫。重点是2-乙基-1-己醇在两种非极性液体3-甲基戊烷和角鲨烷中的情况，这两种液体分别比该醇更易流动和更粘稠。发现仅当醇的摩尔分数x>0.2时才会出现德拜弛豫，并且总是伴随着源自醇组分的非德拜弛豫。在德拜弛豫完全消失之前，它会变宽。我们观察到，在更易流动的3-甲基戊烷中，2-乙基-1-己醇的德拜动力学加快，而更粘稠的角鲨烷则导致德拜弛豫时间更长。目前的实验还提供了证据，表明德拜弛豫幅度的下降并不意味着不存在氢键结构。
