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Ultrafast dynamics of ionic liquids in colloidal dispersion

Abstract

Ionic liquid (IL)- surfactant complexes have significance both in applications and fundamental research, but their underlying dynamics are not well understood. We apply polarization-controlled two-dimensional infrared spectroscopy (2D-IR) to study the dynamics of [BMIM][SCN]/ surfactant/ solvent model systems. We examine the effect of the choice of surfactants and solvent, and the IL-to-surfactant ratio (W-value), with a detailed analysis of the orientation and structural dynamics of each system. Different surfactants create very different environments for the entrapped ILs, ranging from a semi-static micro-environment to a fluxional environment that evolves even faster than the bulk IL. The oil-phase also clearly affects the microscopic dynamics. The anisotropy decay for entrapped ILs completes within 10~ps, which is similar to free thiocyanate ion in water, while a significant reorientation-induced spectral diffusion (RISD) effect is observed. The entrapped ionic liquid are highly dynamic for all W-values, and no core-shell structure is observed. We hypothesize that, instead of an ionic liquid-reverse micelle (IL-RM), the microscopic structure of this system is small colloidal dispersions or pairs of IL and surfactants. A detailed analysis of the polarization-controlled 2D-IR spectra of AOT system reveals a potential ion-exchange mechanism

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Publication details

The article was received on 02 Jul 2017, accepted on 02 Nov 2017 and first published on 03 Nov 2017


Article type: Paper
DOI: 10.1039/C7CP04441K
Citation: Phys. Chem. Chem. Phys., 2017, Accepted Manuscript
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    Ultrafast dynamics of ionic liquids in colloidal dispersion

    Z. Ren, J. Kelly, C. P. Gunathilaka, T. Brinzer, S. Dutta, C. A. Johnson, S. Mitra and S. Garrett-Roe, Phys. Chem. Chem. Phys., 2017, Accepted Manuscript , DOI: 10.1039/C7CP04441K

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