Transition anionic complex in trihexyl(tetradecyl)phosphonium-bis(oxalato)borate ionic liquid – revisited

Shimpi, Manishkumar R.; Rohlmann, Patrick; Shah, Faiz Ullah; Glavatskih, Sergei; Antzutkin, Oleg N.

doi:10.1039/d0cp05845a

Cited by 21 publications

(15 citation statements)

References 55 publications

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“…The high conductivity of EMIM-TFSI can be attributed to the less bulky ions compared to the phosphonium ILs, therefore allowing for better ionic mobility, combined with a higher degree of ion dissociation. The conductivity values for P-BOB and P-BMB are also in good agreement with previously reported data [45,46].…”

Section: Resultssupporting

confidence: 92%

“…P-BEHP was selected because of its high popularity in tribological research [47]. In addition to these, EMIM-TFSI was studied as comparison because of its reported conductivity [48] being multiple orders of magnitude higher than that reported for the orthoborate ILs, P-BOB and P-BMB [45,46]. This choice of ILs provides a big range of additive conductivity to evaluate the proposed methodology.…”

Section: Greasesmentioning

confidence: 99%

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On Electric Conductivity of Greases

Reddy

Shah

Leckner³

et al. 2022

Preprint

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The development of new lubricant systems compatible with modern e-drive conditions, including stray voltages and currents, has gained momentum in recent years. One of the strategies being widely evaluated to achieve these goals is the development of conductive lubricants. Greases, however, have a complex architecture which renders measurement and analysis of their electrical properties challenging; this has severely limited the implementation of the strategy for this class of materials. In this work, a measurement methodology implementing electrochemical impedance spectroscopy to evaluate the electrical properties of grease samples is introduced. Compared to the commonly used conductivity meters, this method, through its multi-frequency alternating current (AC) impedance measurement approach, is able to effectively distinguish the separate contributions of the bulk and the sample-electrode interface to the measured electrical response. Thus, the bulk conductivity of a range of greases with different electrical properties could be obtained independently of their interfacial behavior at the electrode. The temperature dependent bulk conductivity of lithium complex grease doped with different ionic liquids and non-ionic solids (copper and graphite) has accordingly been evaluated and the rather different conductivity mechanisms explained. Bulk ionic conductivity of neat ionic liquids has also been measured using a liquid sample specific electrochemical cell, which aids in the interpretation of the ionic liquid based greases.

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Section: Resultssupporting

confidence: 92%

Section: Greasesmentioning

confidence: 99%

On Electric Conductivity of Greases

Reddy

Shah

Leckner³

et al. 2022

Preprint

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“…The two commercially available ILs, P-BMPP, trihexyltetradecylphosphonium bis(2,4,4-trimethylpentyl)phosphinate, and P-BEHP, trihexyltetradecylphosphonium bis(2-ethylhexyl)phosphate, were procured from CYTEC Industries Ltd. (now part of Solvay S.A.) and Iolitec Ionic Liquids Technologies GmbH, respectively. The two boron-based ILs, P-BOB, trihexyltetradecylphosphonium bis-(oxalato)borate, 73 and P-BMB, trihexyltetradecylphosphonium bis-(mandelato)borate, 58 were synthesized by our collaborators at Luleå University of Technology.…”

Section: ■ Materials and Methodsmentioning

confidence: 99%

“…All of the studied ILs have a quaternary phosphonium cation decorated with four long alkyl chains. Two of the ILs contain orthoborate anions and have been custom-synthesized using previously reported procedures. , The other two ILs are commercially available, containing phosphinate and phosphate anions. In addition to studying the presence of ionic boundary films, the tribological performance in rolling (with mild sliding) and reciprocating sliding conditions were investigated.…”

Section: Introductionmentioning

confidence: 99%

Micro- to Nano- and from Surface to Bulk: Influence of Halogen-Free Ionic Liquid Architecture and Dissociation on Green Oil Lubricity

Reddy

Munavirov

Pilkington

et al. 2021

ACS Sustainable Chem. Eng.

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Four nonhalogenated ionic liquids (ILs) based on the same phosphonium cation are investigated in terms of the anion suitability for enhancing the lubricity of a biodegradable oil. For all test conditions, typical for industrial machine components, the lubrication is shown to be governed by nonsacrificial films formed by the physisorption of ionic species on the tribo-surfaces. The anionic structure appears to have an important role in the formation of friction modifying films. The orthoborate ILs exhibit the formation of robust ionic boundary films, resulting in reduced friction and better wear protection. On the contrary, the surface adsorption of phosphinate and phosphate ILs appears to antagonistically disrupt the intrinsic lubrication properties of the biodegradable oil, resulting in high friction and wear. Through additional investigations, it is postulated that the higher dissociation of orthoborate ILs in the biodegradable oil allows the formation of hierarchical and electrostatically overscreened layer structures with long-range order, whereas the ILs with phosphate and phosphinate anions exhibit low dissociation in biodegradable oil, possibly due to the ion pairs being surrounded by a hydrocarbon halo, which presumably results in weak adsorption to form a mixed interfacial layer with no long-range order.

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“…The ionic liquids were prepared as described previously (PBMB and PBScB 40 , PBOB 57 ) with spectroscopic and physical data matching that reported. Prior to use, these ionic liquids were dried under vacuum to constant weight and were found to be < 100 ppm water using Karl-Fischer titrimetry.…”

Section: Methodsmentioning

confidence: 99%

The effect of anion architecture on the lubrication chemistry of phosphonium orthoborate ionic liquids

Munavirov

Black

Shah

et al. 2021

Sci Rep

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Phosphonium ionic liquids with orthoborate anions have been studied in terms of their interfacial film formation, both physisorbed and sacrificial from chemical breakdown, in sheared contacts of varying harshness. The halogen-free anion architecture was varied through (i) the heteronuclear ring size, (ii) the hybridisation of the constituent atoms, and (iii) the addition of aryl functionalities. Time of Flight-Secondary Ion Mass Spectrometry analysis revealed the extent of sacrificial tribofilm formation allowing the relative stability of the ionic liquids under tribological conditions to be determined and their breakdown mechanisms to be compared to simple thermal decomposition. Overall, ionic liquids outperformed reference oils as lubricants; in some cases, sacrificial films were formed (with anion breakdown a necessary precursor to phosphonium cation decomposition) while in other cases, a protective, self-assembly lubricant layer or hybrid film was formed. The salicylate-based anion was the most chemically stable and decomposed only slightly even under the harshest conditions. It was further found that surface topography influenced the degree of breakdown through enhanced material transport and replenishment. This work thus unveils the relationship between ionic liquid composition and structure, and the ensuing inter- and intra-molecular interactions and chemical stability, and demonstrates the intrinsic tuneability of an ionic liquid lubrication technology.

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Transition anionic complex in trihexyl(tetradecyl)phosphonium-bis(oxalato)borate ionic liquid – revisited

Abstract: It was found that Li[BOB]·nH2O salts were not readily suitable for the synthesis of high-purity orthoborate-based tetraalkylphosphonium ionic liquids, as exemplified here for trihexyl(tetradecyl)phosphonium bis(oxalato)borate, [P6,6,6,14][BOB]: Along with [BOB]-, a...

Cited by 21 publications

References 55 publications

On Electric Conductivity of Greases

On Electric Conductivity of Greases

Micro- to Nano- and from Surface to Bulk: Influence of Halogen-Free Ionic Liquid Architecture and Dissociation on Green Oil Lubricity

The effect of anion architecture on the lubrication chemistry of phosphonium orthoborate ionic liquids

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