Dynamic Percolation and Swollen Behavior of Nanodroplets in 1‑Ethyl-3-methylimidazolium Trifluoromethanesulfonate/Triton X‑100/Cyclohexane Microemulsions

Microemulsions comprising an ionic liquid (IL), 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([emim]­[OTf]), as the polar component, Triton X-100 as a surfactant, and cyclohexane as the nonpolar medium were prepared and characterized. Conductivity and dynamic viscosity data were critically analyzed to confirm dynamic percolation among the droplets that are in continuous motion, aggregation, and fission. The transition from oil-continuous phase to bicontinuous phase was observed at the conductance and viscosity percolation thresholds and sharp changes in the values of conductivity and dynamic viscosity could be identified. Dynamic light scattering measurements revealed swelling of the droplets, which varied within the hydrodynamic diameter range of 10–100 nm. Diffusivity of the droplets suggested less Brownian movement with increased amount of the IL. Moreover, changes in the droplet sizes and diffusivity with increase in IL content supported dynamic percolation within the systems

Binary Protic Ionic Liquid Mixtures as a Proton Conductor: High Fuel Cell Reaction Activity and Facile Proton Transport

Binary mixtures of two protic ionic liquids (PILs), namely, diethylmethylammonium hydrogensulfate ([dema]­HSO₄) and diethylmethylammonium bis­(trifluoromethanesulfonyl)­amide ([dema]­[NTf₂]), were prepared by mixing in various weight ratios for prospective use as fuel cell electrolytes. The binary mixtures showed significantly higher electrochemical activity compared with the constituent pure PILs, and the activity changed depending on the composition of the mixtures. Specifically, the open circuit potential (OCP) for a H₂ | O₂ cell using a binary electrolyte consisting of 56 wt % [dema]­[NTf₂] was 1.03 V vs a reversible hydrogen electrode (RHE), whereas the values were 0.90 and 0.77 V for pure [dema]­HSO₄ and [dema]­[NTf₂], respectively, under similar conditions. The electrochemical activity of the binary mixtures was interpreted by comparing their molecular characteristics inferred from Fourier transform infrared (FT-IR) and ¹H NMR spectroscopy with those of the constituent PILs. The binary systems showed enhanced electrochemical activity, possibly due to anion/proton exchange through the formation of hydrogen bonds of varying strengths via the N–H bond. The anion/proton exchange appears to average the N–H bond strength to render it suitable for fuel cell reactions. Bulk physicochemical properties such as thermal properties, viscosity, ionic conductivity, and ionicity were also measured precisely. The results of the pulsed gradient spin echo (PGSE) NMR and Walden plot collectively suggest that the Grotthuss mechanism in addition to the vehicle mechanism contributes to proton transport in the binary systems, possibly due to the coexistence of [dema] cation and HSO₄^– anion, whereas the vehicle mechanism is dominant for pure [dema]­[NTf₂]