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Investigation of dynamics in BMIM TFSA ionic liquid through variable temperature and pressure NMR relaxometry and diffusometry.
- Source :
-
Journal of the Electrochemical Society [J Electrochem Soc] 2017; Vol. 164 (8), pp. H5189-H5196. - Publication Year :
- 2017
-
Abstract
- A comprehensive variable temperature, pressure and frequency multinuclear ( <superscript>1</superscript> H, <superscript>2</superscript> H, and <superscript>19</superscript> F) magnetic resonance study was undertaken on selectively deuterated 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide (BMIM TFSA) ionic liquid isotopologues. This study builds on our earlier investigation of the effects of increasing alkyl chain length on diffusion and dynamics in imidazolium-based TFSA ionic liquids. Fast field cycling <superscript>1</superscript> H T <subscript>1</subscript> data revealed multiple modes of motion. Through calculation of diffusion coefficient (D) values and activation energies, the low- and high-field regimes were assigned to the translational and reorientation dynamics respectively. Variable-pressure <superscript>2</superscript> H T <subscript>1</subscript> measurements reveal site-dependent interactions in the cation with strengths in the order MD <subscript>3</subscript> > CD <subscript>3</subscript> > CD <subscript>2</subscript> , indicating dissimilarities in the electric field gradients along the alkyl chain, with the CD <subscript>2</subscript> sites having the largest gradient. Additionally, the α saturation effect in T <subscript>1</subscript> vs. P was observed for all three sites, suggesting significant reduction of the short-range rapid reorientational dynamics. This reduction was also deduced from the variable pressure <superscript>1</superscript> H T <subscript>1</subscript> data, which showed an approach to saturation for both the methyl and butyl group terminal methyl sites. Pressure-dependent D measurements show independent motions for both cations and anions, with the cations having greater D values over the entire pressure range.
Details
- Language :
- English
- ISSN :
- 0013-4651
- Volume :
- 164
- Issue :
- 8
- Database :
- MEDLINE
- Journal :
- Journal of the Electrochemical Society
- Publication Type :
- Academic Journal
- Accession number :
- 30034028
- Full Text :
- https://doi.org/10.1149/2.0301708jes