Lubrication Properties of Ammonium-Based Ionic Liquids Confined between Silica Surfaces Using Resonance Shear Measurements

Kamijo, Toshio; Arafune, Hiroyuki; Morinaga, Takashi; Honma, Saika; Sato, Takaya; Hino, Masaya; Mizukami, Masashi; Kurihara, Kazue

doi:10.1021/acs.langmuir.5b03354

Cited by 23 publications

(25 citation statements)

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“…[13] Their high thermal/oxidative stability, negligible volatility, low frictional properties, and facile tenability of these physicochemical properties by their molecular design, [14][15][16] which are the desired characteristics of swelling agents of low frictional gels. water) in the gels can easily evaporate to lose swelled state.…”

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confidence: 99%

Highly Robust and Low Frictional Double‐Network Ion Gel

Arafune

Honma

Morinaga

et al. 2017

Adv Materials Inter

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of proteoglycans and collagen fibrils with high water content (75-80 wt%) has attracted the lubrication with gel materials possessing high mechanical strength [4][5][6][7] and stable low friction. [8][9][10][11][12] These researches aim at shedding light on the gel properties and their potential application as artificial biomaterials.However, such advantages can hardly be realized for industrial uses since solvent (ex. water) in the gels can easily evaporate to lose swelled state. For this purpose, we focused on ionic liquids (ILs) to retain their swelled state. ILs are liquid salts fully composed of cations and anions, generally so-called when their melting temperature is lower than 100 °C. [13] Their high thermal/oxidative stability, negligible volatility, low frictional properties, and facile tenability of these physicochemical properties by their molecular design, [14][15][16] which are the desired characteristics of swelling agents of low frictional gels. In addition, demand for immobilizing ILs on solid surface with keeping their physicochemical properties to fabricate functional devices [17] have opened up the development of gel materials incorporating ILs, so-called as "ion gels" or "ionogels." [18] Ion gels can roughly be classified to physical or chemical gels. [18] In case of physical gels, cross-linking point of their polymer network is formed with relatively weak interaction like hydrophobic interaction, hydrogen bond, π−π interaction and so on, while chemical gels are cross-linked with covalently bonds. There have been several reports studying on tribological behavior of physical ion gels dispersed in ILs. [19][20][21] Espejo et al. characterized the tribological properties of a bucky gel with multiwalled carbon nanotube and 1-ethyl 3-methylimidazolium tosylate. [20] These combination at a tribopair of AISI 316L stainless steel and polycarbonate under 0.98 N at 0.1 m s −1 resulted in COF of 0.025, which is lower than that of a neat IL. In contrast, study on tribological properties of chemical ion gels with sheet-like morphology has not been reported in spite of their high mechanical strength and ease for immobilizing on solid devices.We have recently reported a lubrication system based on ILs and compatible polymer brushes grafted on a Si substrate showed efficient and robust lubrication. [22] They were composed of an ionic liquid, N, N-diethyl-N-(2-methoxyethyl)-N-methylammonium bis(trifluoromethylsulfonyl)imide (DEME-TFSI), and high density ionic liquid polymer brushes composed of the derivative of DEME-TFSI with a polymerizable group, Reducing friction is important to improve the lifetime and energy efficiency of mechanical systems. Since human joints with gel-like structure possess a coefficient of friction as low as 10 -3 , gel materials are recognized as a useful example for designing low frictional materials. Ion gels incorporating ionic liquids (ILs) as swelling agent is expected to be stable gel lubricant since high thermal stability and negligible volatility of ILs can maintain swelled sta...

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confidence: 99%

Highly Robust and Low Frictional Double‐Network Ion Gel

Arafune

Honma

Morinaga

et al. 2017

Adv Materials Inter

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“…RSM was performed using an in-house resonance shear system based on an SFA [22], as shown schematically in Figure 1. The experimental setup and procedures for RSM are described in detail in a previous publication [21].…”

Section: Rsm For Nanoscale Properties Of Ilsmentioning

confidence: 99%

“…This means that [DEME][TFSI] remained between the silica surfaces at the separation of 2.5 nm, and the coupling of the upper and lower surfaces became stronger with the increased applied load. 4 ] confined between the silica surfaces at various separation distances under an applied load N. Resonance curves for AS and SC are also shown [22]. Solid lines denote the best fit curves to a physical model [27].…”

Section: Progress and Developments In Ionic Liquidsmentioning

confidence: 99%

“…However, the relationship between these nanoscale properties and the macrolubrication properties is still not fully understood even for the same surface and ILs. Motivated by this problem, we have recently used resonance shear measurement (RSM) to show that some ILs form a layered structure in the nanoscale space created by the sliding surface [21,22]. We also revealed that a nanostructure consisting of only several IL layers had a large influence on macroscale friction.…”

Section: Introductionmentioning

confidence: 99%

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Behavior of Ionic Liquids Under Nanoconfinement Greatly Affects Actual Friction

Kamijo¹,

Arafune²,

Morinaga³

et al. 2017

Progress and Developments in Ionic Liquids

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Ionic liquids (ILs) are organic salts consisting of anions and cations that exist as liquids at room temperature. ILs exhibit many attractive properties such as negligible volatility, low flammability, and relatively high thermal stability. These properties can be varied in a controlled fashion through systematic changes in the molecular structure of their constituent ions. Some recent studies have aimed to use ILs as new lubricant materials. However, the behavior of ILs as lubricants on the sliding interfaces has not been elucidated. In this chapter, we describe the nano-and macrolubrication properties of some ILs with different types of anions using resonance shear measurement (RSM) and conventional ball-on-plate-type tribotests, respectively. This study reveals that the properties observed by RSM for nanoscale systems can provide important insights for the study of the friction coefficients (macrolubrication properties) obtained by tribotests.

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“…to reduce wear), it could negatively affect the lubrication in macro, micro and nano-devices. 16,30,46,64 nanostructures assembled at room temperature on a variety of solid insulating substrates influence the electric properties of the IL layers, by means of a combined morphological and electrical analysis by AFM. We have shown that a conductive to insulating transition accompanies the surface-induced liquid to solid-like structural transition of solid-supported ILs, with a marked reduction of the dielectric constant compared to the bulk phase.…”

Section: Introductionmentioning

confidence: 99%

Surface confinement induces the formation of solid-like insulating ionic liquid nanostructures

Bovio¹,

Milani²,

Podestà

2017

Preprint

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We report on the modification of the electric properties of the imidazolium-based [BMIM][NTf2] ionic liquid upon surface confinement in the sub-monolayer regime. Solid-like insulating nanostructures of [BMIM][NTf2] spontaneously form on a variety of insulating substrates, at odd with the liquid and conductive nature of the same substances in the bulk phase. A systematic spatially resolved investigation by atomic force microscopy of the morphological, mechanical and electrical properties of [BMIM][NTf2] nanostructures showed that this liquid substance rearranges into lamellar nanostructures with a high degree of vertical order and enhanced resistance to mechanical compressive stresses and very intense electric fields, denoting a solid-like character. The morphological and structural reorganization has a profound impact on the electric properties of supported [BMIM][NTf2] islands, which behave like insulator layers with a relative dielectric constant between 3 and 5, comparable to those of conventional ionic solids, and significantly smaller than those measured in the bulk ionic liquid. These results suggest that in the solid-like ordered domains confined either at surfaces or inside the pores of the nanoporous electrodes of photo-electrochemical devices, the ionic mobility and the overall electrical properties can be significantly perturbed with respect to the bulk liquid phase, which would likely influence the<br>performance of the devices.<br>

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Lubrication Properties of Ammonium-Based Ionic Liquids Confined between Silica Surfaces Using Resonance Shear Measurements

Cited by 23 publications

References 30 publications

Highly Robust and Low Frictional Double‐Network Ion Gel

Highly Robust and Low Frictional Double‐Network Ion Gel

Behavior of Ionic Liquids Under Nanoconfinement Greatly Affects Actual Friction

Surface confinement induces the formation of solid-like insulating ionic liquid nanostructures

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