Boundary lubricity of phosphonium bisoxalatoborate ionic liquids

Rohlmann, Patrick; Watanabe, Seiya; Shimpi, Manishkumar R.; Leckner, Johan; Rutland, Mark W.; Harper, Jason B.; Glavatskih, Sergei

doi:10.1016/j.triboint.2021.107075

Cited by 13 publications

(18 citation statements)

References 62 publications

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“…This behaviour is akin to that seen for PBOB under different conditions, 33 noting that the presence of an aryl group will introduce additional surface self-assembly constraints.…”

Section: Effects Of Ionic Liquid Structure On Lubrication and Tribo Lm Formationmentioning

confidence: 60%

“…In contrast to the pure oils, the friction coe cients are now, albeit weakly, systematic with the viscosity of the liquids, which implies either a larger surface separation, a lower roughness, or both. It is thus reasonable to infer that the conditions most probably correspond to the boundary lubrication regime with the surfaces separated by boundary lms; 33 the nature of these lms will be discussed subsequently.…”

Section: Effects Of Ionic Liquid Structure On Lubrication and Tribo Lm Formationmentioning

confidence: 99%

“…Currently lacking is an understanding of (i) the manner in which phosphonium ionic liquids facilitate lubrication, (ii) the mechanism of their breakdown, and, particularly, (iii) the relationship of the structure of the ionic liquid components to both of the above. On point (i), both traditional sacri cial tribo lms 32 and ionic boundary layers 33 have been invoked to explain the tribological properties of ionic liquids. Where referred to, breakdown of ionic liquids has focussed upon the cation of the ionic liquid and the resulting decomposition products.…”

Section: Introductionmentioning

confidence: 99%

“…The trihexyl(tetradecyl)phosphonium cation was chosen due to it signi cant stability and preliminary data demonstrating the lubricity of an ionic liquid based on this cation. 33 The three anions were based on boron centres; boronbased compounds are well recognized by the tribological community for reducing wear and friction. [34][35][36] The selected orthoborate structures ensure that the compounds are liquid at room temperature (cf.…”

Section: Introductionmentioning

confidence: 99%

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The Effect of Anion Architecture on the Lubrication Chemistry of Phosphonium Orthoborate Ionic Liquid

Munavirov

Black

Shah

et al. 2021

Preprint

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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. ToF-SIMS 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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“…This behaviour is akin to that seen for PBOB under different conditions, 33 noting that the presence of an aryl group will introduce additional surface self-assembly constraints.…”

Section: Effects Of Ionic Liquid Structure On Lubrication and Tribo Lm Formationmentioning

confidence: 60%

Section: Effects Of Ionic Liquid Structure On Lubrication and Tribo Lm Formationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

The Effect of Anion Architecture on the Lubrication Chemistry of Phosphonium Orthoborate Ionic Liquid

Munavirov

Black

Shah

et al. 2021

Preprint

Self Cite

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show abstract

“…Currently lacking is an understanding of (i) the manner in which phosphonium ionic liquids facilitate lubrication, (ii) the mechanism of their breakdown, and, particularly, (iii) the relationship of the structure of the ionic liquid components to both of the above. On point (i), both traditional sacrificial tribofilms 32 and ionic boundary layers 33 have been invoked to explain the tribological properties of ionic liquids. Where referred to, breakdown of ionic liquids has focussed upon the cation of the ionic liquid and the resulting decomposition products.…”

Section: Introductionmentioning

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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Molecular Architecture Effects on Bulk Nanostructure in Bis(Orthoborate) Ionic Liquids

Hammond,

Bousrez,

Mehler

et al. 2023

Small

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A series of 19 ionic liquids (ILs) based on phosphonium and imidazolium cations of varying alkyl‐chain lengths with the orthoborate anions bis(oxalato)borate [BOB]−, bis(mandelato)borate, [BMB]− and bis(salicylato)borate, [BScB]−, are synthesized and studied using small‐angle neutron scattering (SANS). All measured systems display nanostructuring, with 1‐methyl‐3‐n‐alkyl imidazolium‐orthoborates forming clearly bicontinuous L3 spongelike phases when the alkyl chains are longer than C6 (hexyl). L3 phases are fitted using the Teubner and Strey model, and diffusely‐nanostructured systems are primarily fitted using the Ornstein‐Zernicke correlation length model. Strongly‐nanostructured systems have a strong dependence on the cation, with molecular architecture variation explored to determine the driving forces for self‐assembly. The ability to form well‐defined complex phases is effectively extinguished in several ways: methylation of the most acidic imidazolium ring proton, replacing the imidazolium 3‐methyl group with a longer hydrocarbon chain, substitution of [BOB]− by [BMB]−, or exchanging the imidazolium for phosphonium systems, irrespective of phosphonium architecture. The results suggest there is only a small window of opportunity, in terms of molecular amphiphilicity and cation:anion volume matching, for the formation of stable extensive bicontinuous domains in pure bulk orthoborate‐based ILs. Particularly important for self‐assembly processes appear to be the ability to form H‐bonding networks, which offer additional versatility in imidazolium systems.

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Boundary lubricity of phosphonium bisoxalatoborate ionic liquids

Cited by 13 publications

References 62 publications

The Effect of Anion Architecture on the Lubrication Chemistry of Phosphonium Orthoborate Ionic Liquid

The Effect of Anion Architecture on the Lubrication Chemistry of Phosphonium Orthoborate Ionic Liquid

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

Molecular Architecture Effects on Bulk Nanostructure in Bis(Orthoborate) Ionic Liquids

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