Recently, many studies concerning the environmental impact of ionic liquids (ILs) have shown that despite their unique properties and clear advantages in an ever wide range of applications and processes, ILs are not intrinsically green. In a search for biodegradable and low toxicity, a new type of ILs has been developed, the deep eutectic solvents (DESs). In this context, the aim of this work is to provide accurate densities, viscosities, and refractive indices for DESs prepared using cholinium chloride as the hydrogen bond acceptor and several carboxylic acids (levulinic, glutaric, malonic, oxalic, and glycolic) as the hydrogen bond donors. The impact of two different synthetic methodologies, heating and grinding, in the thermophysical properties of the prepared DESs was assessed. The obtained DESs were analyzed using NMR spectroscopy, FTIR, and electrospray ionization mass spectrometry in order to check their structures and purities. Thermophysical properties, densities, viscosities, and refractive indices were rationalized in terms of the chemical structure of the prepared DESs. The effect of the presence of water in the thermophysical properties of the compounds was also evaluated. Finally, comparisons between the DESs and the corresponding ILs are presented.

Density and viscosity data for six pyridinium-based ionic liquids combined with the bis[(trifluoromethyl)sulfonyl]amide anion were measured at atmospheric pressure in the (278 to 363) K temperature range. The fundamental aim of this work is to study the effect of the structure of the pyridinium-based cation, namely, its alkyl chain length and structural isomers, and the position of the second alkyl substitution on the measured properties. Albeit many studies exist on the physical properties of ionic liquids in what concerns the nature of the anion and the length of the cation alkyl side chain, the effect of structural and positional isomerism on those properties is much less known. In additionsand since small amounts of water influence the phase equilibrium and thermophysical properties of ionic liquidsswater-saturated ionic liquid samples were also studied in the (298 to 363) K temperature range. The Vogel-Tammann-Fulcher (VTF) method was applied to describe the viscosity data, and novel group contribution parameters are proposed for the ionic liquid cations presented here, thus broadening its applicability.

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This work explores the possibility of increasing the ionicity of ionic liquids via the solubilization of inorganic salts in their midst. The resulting purely ionic media-distinct ionic liquid plus inorganic salt mixtures-are liquid in an extensive concentration range and can be aptly denominated High Ionicity Ionic Liquids (HIILs).