New dimensions in salt–solvent mixtures: a 4th evolution of ionic liquids

Abstract

In the field of ionic liquids (ILs) it has long been of fundamental interest to examine the transition from salt-in-solvent behaviour to pure liquid-salt behaviour, in terms of structures and properties. At the same time, a variety of applications have beneficially employed IL-solvent mixtures as media that offer an optimal set of properties. Their properties in many cases can be other than as expected on the basis of simple mixing concepts. Instead, they can reflect the distinct structural and interaction changes that occur as the mixture passes through the various stages from pure coulombic medium, to "plasticised" coulombic medium, into a meso-region where distinct molecular and ionic domains can co-exist. Such domains can persist to quite a high dilution into the salt-in-solvent regime and their presence manifests itself in a number of important synergistic interaction effects in diverse areas such as membrane transport and corrosion protection. Similarly, the use of ionic liquids in synthetic processes where there is a significant volume fraction of molecular species present can produce a variety of distinct and unexpected effects. The range of these salt-solvent mixtures is considerably broader than just those based on ionic liquids, since there is only minor value in the pure salt being a liquid at the outset. In other words, the extensive families of organic and metal salts become candidates for study and use. Our perspective then is of an evolution of ionic liquids into a broader field of fundamental phenomena and applications. This can draw on an even larger family of tuneable salts that exhibit an exciting combination of properties when mixed with molecular liquids.

Impact of some pyrrolidinium ionic liquids on copper dissolution behavior in acidic environment: experimental, morphological and theoretical insights

“…[16][17][18] In general, ILs are organic salts in its liquid state with low melting point below 100 C, consisting of organic cations as ammonium, imidazolium, pyridinium, piperidinium, sulfonium, phosphonium or pyrrolidinium and inorganic anions such as uoride, chloride, bromide or cyanide. 19 Their intrinsic physicochemical features, like good solvent transport, excellent electrical conductivity, and electrochemical activity make them potential candidates in physisorption and chemisorption studies. 20 Some ILs have surface activity, like surfactants and able to form micelles and reducing wetting interfacial tension of aggressive solutions that support surface wetting and adsorption.…”

“…Org sol + xH 2 O / Org ads + H 2 O sol (19) where, x is the number of H 2 O molecules substituted. Thus, it is assumed that the metal surface charge is governed by the corrosion potential of surface (E corr ) described by the potential of zero charge which affect the adsorption potential of compounds on copper surface (PZC) E q ¼ 0, hence affecting the overall inhibition process.…”

Influence of Carboxylate Anions on Phase Behavior of Choline Ionic Liquid Mixtures

“…These properties can be tailored by variation of the composition of cations and anions [1]. Even more variability is offered by using mixtures of ILs, an option that is considered the fourth evolution of ILs [2]. In this contribution, we deal with mixtures of choline carboxylate ILs.…”

“…We anticipate that these mixtures will widen the application range of this class of ILs. We see potential applications in the medical [3] and environmental fields [1] where these systems offer a combination of low toxicity, adjustable solvation properties, and tunable ionic conductivity [2].…”

Hydrogen‐Bonding‐Driven Ion‐Pair Formation in Protic Ionic Liquid Aqueous Solution

“…The experimental values of conductivity, viscosity, and surface tension would deviate from the ideal values when ion pairs were formed . As a result, the properties and functions of PIL solutions are not always predictable based on simple mixing rules, and anion moieties usually play important roles . Therefore, fundamental and structural investigation into ion pairs is one essential feature for understanding properties of PILs solutions.…”