Ion Diffusion Reveals Heterogeneous Viscosity in Nanostructured Ionic Liquids.

Many ionic liquids (ILs) are composed of interpenetrating polar and apolar networks. These nanoscale networks are sustained by different local intermolecular and electrostatic interactions and are predicted to differ in their physical properties by orders of magnitude. Nonetheless, it is commonplace for the physical properties of ILs to be described by bulk parameters, such as the bulk dynamic viscosity.

Lipid Membrane Flexibility in Protic Ionic Liquids.

Here, we determine by neutron spin echo spectrometry (NSE) how the flexibility of egg lecithin vesicles depends on solvent composition in two protic ionic liquids (PILs) and their aqueous mixtures. In combination with small-angle neutron scattering (SANS), dynamic light scattering (DLS), and fluorescent probe microscopy, we show that the bending modulus is up to an order of magnitude lower than in water but with no change in bilayer thickness or nonpolar chain composition. This effect is attributed to the dynamic association and exchange of the IL cation between the membrane and bulk liquid, which has the same origin as the underlying amphiphilic nanostructure of the IL solvent itself.

Aqueous choline amino acid deep eutectic solvents.

We have investigated the structure and phase behavior of biocompatible, aqueous deep eutectic solvents by combining choline acetate, hydrogen aspartate, and aspartate amino acid salts with water as the sole molecular hydrogen bond donor. Using contrast-variation neutron diffraction, interpreted via computational modeling, we show how the interplay between anion structure and water content affects the hydrogen bond network structure in the liquid, which, in turn, influences the eutectic composition and temperature. These mixtures expand the current range choline amino acid ionic liquids under investigation for biomass processing applications to include higher melting point salts and also explain how the ionic liquids retain their desirable properties in aqueous solution.

Amphiphilic nanostructure in choline carboxylate and amino acid ionic liquids and solutions.

The liquid structures of six choline carboxylate/amino acid ionic liquids (bio-ILs) and their mixtures with water and various n-alkanols have been investigated by small-angle X-ray scattering (SAXS). The ILs exhibit long-range amphiphilic nanostructure comprised of polar and apolar domains that can be controlled by choice of anion, and which is tolerant to water dilution. Mixtures with n-alkanols can lead to marked changes in domain size and ordering.

DTAB micelle formation in ionic liquid/water mixtures is determined by ionic liquid cation structure.

Hypothesis: The high CMCs and low aggregation numbers of ionic micelles in the extreme electrolyte environment of ionic liquids (ILs) seem to be at odds with the effect of dilute aqueous electrolytes, which lower CMCs and promote elongated micelles. We hypothesise that the driving force for micellisation in ILs is determined by their underlying amphiphilic nanostructure, and that this can be controlled by mixing with water.

Experiments: CMCs and micelle sizes of dodecyltrimethylammonium bromide (DTAB) are determined in mixed solvents comprising water and the ionic liquids ethylammonium nitrate (EAN), ethanolammonium nitrate (EtAN), and propylammonium nitrate (PAN) over a wide composition range.