Dynamics of Imidazolium Ionic Liquids from a Combined Dielectric Relaxation and Optical Kerr Effect Study: Evidence for Mesoscopic Aggregation
Dynamics of Imidazolium Ionic Liquids from a Combined Dielectric Relaxation and Optical Kerr Effect Study: Evidence for Mesoscopic Aggregation
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DOI：
10.1021/ja903315v
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发表时间：
2009-08-12
影响因子：
15
通讯作者：
Wynne, Klaas
中科院分区：
文献类型：
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作者：
Turton, David A.;Hunger, Johannes;Wynne, Klaas
我们已经测量了1，3-二烷基咪唑基室温离子液体（RTIL）[emim][BF 4]，[emim][DCA]和[bmim][DCA]的分子间动力学在25 ℃从低于1 GHz到10 THz的超快光学克尔效应（OKE）光谱和介电弛豫光谱（DRS）增强时域太赫兹和远红外FTIR光谱。这种协调一致的方法允许对相对无特征的太赫兹区域进行更详细的分析，其中较高频率的扩散模式与振动和分子间振动强烈重叠。最感兴趣的是，虽然，是一个强烈的低频（亚α）松弛，我们表明是根据最近的模拟，报告了从聚集体或集群结构，解释了这些液体的异常和不方便的高粘度所产生的介观结构。
We have measured the intermolecular dynamics of the 1,3-dialkylimidazolium-based room-temperature ionic liquids (RTILs) [emim][BF4], [emim][DCA], and [bmim][DCA] at 25 degrees C from below 1 GHz to 10 THz by ultrafast optical Kerr effect (OKE) spectroscopy and dielectric relaxation spectroscopy (DRS) augmented by time-domain terahertz and far-infrared FTIR spectroscopy. This concerted approach allows a more detailed analysis to be made of the relatively featureless terahertz region, where the higher frequency diffusional modes are strongly overlapped with librations and intermolecular vibrations. Of greatest interest though, is an intense low frequency (sub-alpha) relaxation that we show is in accordance with recent simulations that have reported mesoscopic structure arising from aggregates or clusters-structure that explains the anomalous and inconveniently high viscosities of these liquids.