An Introduction to Ionic Liquids

doi:10.1002/9783527340033.ch1

Cited by 9 publications

(6 citation statements)

References 89 publications

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“…However, the applications of ILs based on metal halide anions are limited due to their high moisture sensitivity. For instance, chloroaluminate tends to hydrolyze forming HCl, which has corrosive properties [60]. In the following decade, ILs significantly evolved into air-and water-stable forms when Wilkes and Zaworotko [61] reported, for the first time, species including the cation 1-ethyl- ).…”

Section: Electrochemical Properties Of Ionic Liquidsmentioning

confidence: 99%

The roles of ionic liquids as new electrolytes in redox flow batteries

Ortiz-Martínez

Gómez‐Coma

Pérez

et al. 2020

Separation and Purification Technology

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Section: Electrochemical Properties Of Ionic Liquidsmentioning

confidence: 99%

The roles of ionic liquids as new electrolytes in redox flow batteries

Ortiz-Martínez

Gómez‐Coma

Pérez

et al. 2020

Separation and Purification Technology

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“…In the last two decades, technological developments in the transportation sector, which resulted in vehicle electri cation, together with growing demands for enhancing sustainable development have brought about a need for "green" lubricants with improved functionalities. As highlighted by several reviews [24][25][26][27][28] ionic liquids (ILs), which are ionic compounds with melting temperature below 373 K [29], have gained wide interest as potential alternative lubricants able to meet the requirements of next-generation tribological systems. The attractive physico-chemical properties of ILs, such as high thermal stability, low ammability, low vapor pressure, and high degree of chemical tunability [30][31][32][33], combines with their strong interaction with material surfaces owing to their ionic nature, which has opened novel paths for tailoring their lubricity by controlling the structure of the IL boundary layers [34][35][36][37][38][39][40].…”

Section: Introductionmentioning

confidence: 99%

Linking Molecular Structure and Lubrication Mechanisms in Tetraalkylammonium Orthoborate Ionic Liquids

2023

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While ionic liquids (ILs) have gained wide interest as potential alternative lubricants able to meet the requirements of next-generation tribological systems owing to their unique physico-chemical properties and promising lubricating behavior, our understanding of the mechanisms by which ILs reduce friction and/or wear is still elusive. Here, we combine macroscale tribological experiments with surface-analytical measurements to shed light on the lubrication mechanisms of a class of halogen-free ILs, namely tetraalkylammonium orthoborate ILs, at steel/steel sliding contacts. The tribological results indicate an improvement of the friction-reducing properties of these ILs as the length of the alkyl chains attached to ammonium cations increases. Ex situ X-ray photoelectron spectroscopy analyses provide further evidence for the dependence of the lubrication mechanism of tetraalkylammonium orthoborate ILs on the IL structure. In the case of tetraalkylammonium orthoborate ILs with asymmetric ammonium cations containing a long alkyl chain, no sacri cial tribo lms were formed on steel surfaces, thus suggesting that the friction-reducing ability of these ILs originates from their propensity to undergo a pressure-induced morphological change at the sliding interface that leads to the generation of a lubricious, solid-like layered structure. Conversely, the higher friction response observed in tribological tests performed with tetraalkylammonium orthoborate ILs containing more symmetric ammonium cations and short alkyl chains is proposed to be due to the inability of this IL to create a transient interfacial layer owing to the reduced van der Waals interactions between the cationic alkyl chains. The resulting hard/hard contact between the sliding surfaces is proposed to lead to the cleavage of boron-oxygen bonds in the presence of water to form species that then adsorb onto the steel surface, including trivalent borate esters and oxalic acid from the decomposition of orthoborate anions, as well as tertiary amines from the degradation of alkylammonium cations induced by hydroxides released during the orthoborate decomposition reaction. The results of this work not only establish links between the molecular structure of a class of halogen-free ILs, their lubricating performance, and lubrication mechanism, but also provide evidence for the existence of multiple mechanisms underpinning the promising lubricating properties of ILs in general.

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“…Ionic liquids (ILs) are a special class of chemical compounds that consist of ions and commonly refer to organic salts with a low melting point [ 1 ]. The combination of exclusive properties of ionic liquids, such as extremely low vapor pressure, high polarity and thermal stability, has been a major incentive behind their study as solvents and electrolytes in synthesis [ 2 , 3 , 4 ], catalysis [ 2 , 5 , 6 ], electrochemistry [ 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 ], extraction and separation chemistry [ 4 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ] and in many other applications [ 22 , 23 , 24 , 25 , 26 ].…”

Section: Introductionmentioning

confidence: 99%

Machine Learning Quantitative Structure–Property Relationships as a Function of Ionic Liquid Cations for the Gas-Ionic Liquid Partition Coefficient of Hydrocarbons

Toots

Sild

Leis

et al. 2022

IJMS

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Ionic liquids (ILs) are known for their unique characteristics as solvents and electrolytes. Therefore, new ILs are being developed and adapted as innovative chemical environments for different applications in which their properties need to be understood on a molecular level. Computational data-driven methods provide means for understanding of properties at molecular level, and quantitative structure–property relationships (QSPRs) provide the framework for this. This framework is commonly used to study the properties of molecules in ILs as an environment. The opposite situation where the property is considered as a function of the ionic liquid does not exist. The aim of the present study was to supplement this perspective with new knowledge and to develop QSPRs that would allow the understanding of molecular interactions in ionic liquids based on the structure of the cationic moiety. A wide range of applications in electrochemistry, separation and extraction chemistry depends on the partitioning of solutes between the ionic liquid and the surrounding environment that is characterized by the gas-ionic liquid partition coefficient. To model this property as a function of the structure of a cationic counterpart, a series of ionic liquids was selected with a common bis-(trifluoromethylsulfonyl)-imide anion, [Tf2N]−, for benzene, hexane and cyclohexane. MLR, SVR and GPR machine learning approaches were used to derive data-driven models and their performance was compared. The cross-validation coefficients of determination in the range 0.71–0.93 along with other performance statistics indicated a strong accuracy of models for all data series and machine learning methods. The analysis and interpretation of descriptors revealed that generally higher lipophilicity and dispersion interaction capability, and lower polarity in the cations induces a higher partition coefficient for benzene, hexane, cyclohexane and hydrocarbons in general. The applicability domain analysis of models concluded that there were no highly influential outliers and the models are applicable to a wide selection of cation families with variable size, polarity and aliphatic or aromatic nature.

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An Introduction to Ionic Liquids

Cited by 9 publications

References 89 publications

The roles of ionic liquids as new electrolytes in redox flow batteries

The roles of ionic liquids as new electrolytes in redox flow batteries

Linking Molecular Structure and Lubrication Mechanisms in Tetraalkylammonium Orthoborate Ionic Liquids

Machine Learning Quantitative Structure–Property Relationships as a Function of Ionic Liquid Cations for the Gas-Ionic Liquid Partition Coefficient of Hydrocarbons

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