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X-Ray Diffraction and Resonance Shear Measurement on Nano-Confined Ionic Liquids


X-ray diffraction measurement at the SPring-8 synchrotron was employed to investigate the structures of two types of imidazolium-based ionic liquids (ILs), 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C4mim][NTF2]) and 1-butyl-3-methylimidazolium tetrafluoroborate ([C4mim][BF4]), confined between silica surfaces by varying the surface separation distances of ca. 500 nm (bulk liquid), ca. 10 nm, and ca. 2 nm (hard wall thickness). The obtained diffraction profiles and intensities were discussed by considering the structures and properties of the nano-confined ILs between silica surfaces investigated by the resonance shear meassurement (RSM) and molecular dynamic simulation (MD) in our previous reports. The [C4mim][NTf2] showed two diffraction peaks at q = 8.8 nm-1 (spacing d = 0.71 nm) and at q = 14.0 nm-1 (spacing d = 0.45 nm) at the greatest distance (D = ca. 500 nm), which were assigned to the interval between the same ions (anion-anion or cation-cation) within the polar network of [C4mim][NTf2] and the interval between the neighboring anion-cation, respectively. The positions of these two peaks remained the same at D = ca.10 nm and at the hard wall (D = ca.2 nm) and their intensity factor increased, indicating that both the cation and anion existed in the same layer. This result was consistent with the checker board structure of [C4mim][NTf2] on the silica surface computer simulated in our previous studies. On the other hand, the [C4mim][BF4] showed a peak at q = 15.4 nm-1 (spacing d = 0.41 nm) corresponding to the anion-cation interval at the greatest distance (D = ca.500 nm). This peak became broader and weaker at D = ca.12 nm and at D = ca. 2 nm.

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Publication details

The article was received on 24 Dec 2017, accepted on 23 Feb 2018 and first published on 08 Mar 2018

Article type: Paper
DOI: 10.1039/C7CP08611C
Citation: Phys. Chem. Chem. Phys., 2018, Accepted Manuscript
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    X-Ray Diffraction and Resonance Shear Measurement on Nano-Confined Ionic Liquids

    K. Tomita, M. Mizukami, S. Nakano, N. Ohta, N. Yagi and K. Kurihara, Phys. Chem. Chem. Phys., 2018, Accepted Manuscript , DOI: 10.1039/C7CP08611C

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