Ruiz-Martín M D, Qureshi N, González M A, Ollivier J, Frick B, Farago B
Institut Laue-Langevin, 71 Avenue des Martyrs, CS 20156, 38042 Grenoble Cedex 9, France.
J Chem Phys. 2022 Feb 28;156(8):084505. doi: 10.1063/5.0082088.
We present a systematic study on the effect of water on the microscopic dynamics of 1-butyl-3-methylimidazolium tetrafluoroborate by means of quasielastic neutron scattering. By mixing the ionic liquid with either heavy or light water, the different contributions to the quasielastic broadening could be identified and treated separately. This study was performed at room temperature, which is more than 15 °C above the demixing line. Our results show that even small amounts of water accelerate the diffusion mechanisms considerably. While samples with small water percentage reveal a diffusion process confined within ionic liquid nanodomains, an admixture of more than 15 wt. % water relieves the confinement. Furthermore, the presence of two water species was identified: one behaving as free water, whereas the other was interpreted as a component bound to the ionic liquid motion. Based on the fact that water preferentially binds to the BF anion, which itself has a negligible contribution to the scattered intensity, our experiments reveal unprecedented information about the microscopic anion dynamics.
我们通过准弹性中子散射对水对1-丁基-3-甲基咪唑四氟硼酸盐微观动力学的影响进行了系统研究。通过将离子液体与重水或轻水混合，可以识别并分别处理对准弹性展宽的不同贡献。这项研究是在室温下进行的，该温度比混合线高出15°C以上。我们的结果表明，即使少量的水也会显著加速扩散机制。水含量低的样品显示出扩散过程局限于离子液体纳米域内，而水含量超过15 wt.% 的混合物则解除了这种限制。此外，还识别出了两种水物种：一种表现为自由水，而另一种被解释为与离子液体运动相关的成分。基于水优先与BF阴离子结合这一事实，而BF阴离子本身对散射强度的贡献可忽略不计，我们的实验揭示了有关微观阴离子动力学的前所未有的信息。
