The foreword to this special issue of the Journal dedicated to Professor Kenneth R. Seddon provides an account of his distinguished career and his pioneering work in the field of ionic liquids.

Progress and challenges in addressing the fundamental issues in ionic liquid chemistry are discussed, including the broadening scope of mixture systems that form part of this field, thermal stability, biodegradation, nomenclature, ion pairing, and electrochemical properties.

[C₄mim]PF₆ shows a complex phase behaviour and several phases have been reported so far. Among them, the structure and dynamics for α, β, and γ have been well investigated and the phase behaviour is strongly associated with the cation conformational change.

(Io)nanofluids are very interesting materials for heat transfer processes. They combine the specific properties of ionic liquids (i.e. low vapour pressure), and enhanced thermophysical properties (in particular thermal conductivity) caused by the dispersed nanoparticles. The mechanism and modelling of thermal conductivity are a particular consideration in this work.

We present the application of imidazolium-based surface-active ionic liquids as ligands and optional reaction media in iridium-catalyzed water oxidations and report a strong influence of ionic liquid concentration in water on the catalytic performance.

Photo-excitation dynamics of ionic liquids composed of dicyanoaurate(i) have been studied by ultrafast time-resolved luminescence spectroscopy. The low energy band of the dual luminescence bands showed a dynamic shift with time depending on the cation species and excitation wavelength. The shift is discussed in relation to the oligomer formation of anions in the ionic liquids.

Palladium nanoparticles were prepared in functionalized ionic liquids by magnetic sputtering. The shape and size of the nanoparticles are related to the structure/organisation of ionic liquids used.

The homogeneous strong base catalyst-free acylation of cellulose using 2,2,2-trifluoroethyl ester as the acyl donor in an ionic liquid, [P_1ME][OAc] as the solvent has been accomplished.

Imidazolium-based ILs showed a higher dissolution ability for bovine insulin amyloid aggregates than ammonium-based ILs for all concentrations of x (x = 0–30 mol-% IL). The mechanisms of dissolution by ILs across a broad IL concentration range for insulin amyloid aggregates is described.

Multiple crystallization pathways of 1-ethyl-3-methylimidazolium nitrate, [C₂mim][NO₃], were switched at the bifurcation pressure (P_B). P_B was determined by the high pressure-inherent conformer (P′) of C₂mim⁺ anion.

The structural fluctuation and mixing state of aqueous solutions of tetrabutylphosphonium trifluoroacetate, ([P_4,4,4,4]CF₃COO), which exhibits a lower-critical-solution-temperature-type phase transition, were investigated. The relationship between the mesoscopic fluctuations and the macroscopic phase transition was clarified by drawing a contour map of the fluctuations on the phase diagram.

Several mixtures of ionic liquids, playing roles in both cellulose dissolution and catalysis, were synthesised. Cellulose etherification was performed in these IL mixtures. The proportion of propoxy cellulose exceeded 2.5 after 24 h.

The structural features of IL binary mixtures have been investigated through ¹H NMR, FT-IR, thermogravimetric, and solvatochromic measurements.

A range of hydrogels incorporating ionic liquids and a redox couple are investigated for use in thermoelectrochemical cells.

The electroreduction of TNT and DNT in the presence of oxygen, moisture (humidity), and other nitroaromatic compounds is studied. Although currents for TNT were unaffected by oxygen, DNT currents were significantly affected. Humid environments were found to have a large effect on the voltammetry for both compounds. Importantly, DNT and TNT could be separately identified and quantified in a mixture.

Inexpensive Brønsted-acidic ionic liquids based on nitrogen bases and sulfuric acid, suitable for industrial-scale catalysis, as reaction media and catalysts for the Beckmann rearrangement of cyclohexanone oxime to ϵ-caprolactam are reported. The advantages of the proposed method are a high conversion of oxime with very good selectivity after 15 min of reaction and omission of the neutralisation step.

A polar liquid zwitterion with a small volume of water dissolves cytochrome c stably, compared with an analogous ionic liquid.

In this study, the interactions between tetrabutylphosphonium carboxylates and water were assessed by thermodynamic measurements. Densities, ρ, viscosities, η, and enthalpies of mixing, Δ_mixH, of binary [P_{4 4 4 4}][C_nCOO]–water mixtures (with n = 1, 2 or 7) were determined at atmospheric pressure as a function of temperature.

We report the photocontrollable micelle–cluster transition of an ABC triblock copolymer in an ionic liquid. With decreasing temperature, the triblock copolymer changes its self-assembled structure from micelles into clusters due to the aggregation of photo- and thermoresponsive blocks. Under UV irradiation, the micelles form clusters at lower temperatures than that in the dark.