Many ionic liquids (ILs) are composed of interpenetrating polar and apolar networks. These nanoscale networks are sustained by different local intermolecular and electrostatic interactions and are predicted to differ in their physical properties by orders of magnitude. Nonetheless, it is commonplace for the physical properties of ILs to be described by bulk parameters, such as the bulk dynamic viscosity. This study addresses the limitations of using bulk parameter descriptions in nanostructured ILs by applying the Saffman-Delbrück model to interpret the self-diffusion coefficient of ions within the homologous series of [C_nmim][NTf₂] ILs. We demonstrate that pulsed field gradient NMR spectroscopy can effectively probe the relative viscosities of polar/charged and apolar networks within these pure ILs. Our calculated polar viscosities show good agreement with literature simulations. Our approach provides valuable insights into the local viscoelastic environments within nanostructured media. This work not only contributes to the understanding of mass and charge transport in ILs but also offers a new experimental perspective for studying structured fluids more broadly.

中文翻译：

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离子扩散揭示了纳米结构离子液体中的异质粘度


许多离子液体 （IL） 由相互穿穿的极性和非极性网络组成。这些纳米级网络由不同的局部分子间和静电相互作用维持，并且预计它们的物理性质会相差几个数量级。尽管如此，IL 的物理性质通常由本体参数（例如本体动态粘度）来描述。本研究通过应用 Saffman-Delbrück 模型来解释 [C_nmim][NTf₂] IL 同源系列中离子的自扩散系数，解决了在纳米结构 IL 中使用体参数描述的局限性。我们证明脉冲场梯度 NMR 波谱可以有效地探测这些纯 IL 中极性/带电和非极性网络的相对粘度。我们计算的极性粘度与文献模拟结果具有良好的一致性。我们的方法为纳米结构介质中的局部粘弹性环境提供了有价值的见解。这项工作不仅有助于理解 IL 中的质量和电荷传输，还为更广泛地研究结构化流体提供了新的实验视角。