Formation of ionic liquid submicron particles. H-1 and F-19 nuclear magnetic resonance spectroscopic studies

We prepared novel ionic liquid submicron particles (ILSPs) in water by emulsifying the ionic liquid (IL) N-(2-methoxyethyl)-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr(12O1)TFSI), which is immiscible with water, with the nonionic surfactants Tween 20 and Span 80. The mean particle size and zeta potential of the ILSPs were about 580nm and -30mV, respectively. The ILSPs were characterized using H-1 and F-19 nuclear magnetic resonance (NMR) spectroscopic methods. The chemical shifts of the Pyr(12O1)(+) cation and TFSI- anion in the H-1 and F-19 NMR spectra of the ILSP suspension were consistent with those corresponding to pure Pyr(12O1)TFSI. This indicated that most of the Pyr(12O1)TFSI was still in the IL state in the ILSP suspension. In addition, H-1-H-1 nuclear Overhauser effect correlated spectroscopic measurements showed that the ILSP droplets contained Pyr(12O1)TFSI in the neat IL steric state even in the ILSP suspension, and Pyr(12O1)TFSI species localized in the droplet surfaces interacted with the hydrophobic acyl side chains of the surfactants. These NMR spectroscopic results show that the ILSPs formed an IL-in-water microemulsion in which droplets of neat Pyr(12O1)TFSI were surrounded by the two surfactants, that is, Tween 20 and Span 80. [GRAPHICS] .