A Presentation of Ionic Liquids as Lubricants: Some Critical Comments

Abstract

Ionic liquids (ILs) are liquid materials at room temperature with an ionic intrinsic nature. The electrostatic interactions therefore play a pivotal role in dictating their inner structure, which is then expected to be far from the traditional pattern of classical simple liquids. Therefore, the strength of such interactions and their long-range effects are responsible for the ionic liquid high viscosity, a fact that itself suggests their possible use as lubricants. More interestingly, the possibility to establish a wide scenario of possible interactions with solid surfaces constitutes a specific added value in this use. In this framework, the ionic liquid complex molecular structure and the huge variety of possible interactions cause a complex aggregation pattern which can depend on the presence of the solid surface itself. Although there is plenty of literature focusing on the lubricant properties of ionic liquids and their applications, the aim of this contribution is, instead, to furnish to the reader a panoramic view of this exciting problematic, commenting on interesting and speculative aspects which are sometimes neglected in standard works and trying to furnish an enriched vision of the topic. The present work constitutes an easy-to-read critical point of view which tries to interact with the imagination of readers, hopefully leading to the discovery of novel aspects and interconnections and ultimately stimulating new ideas and research.

The Application of Ionic Liquids in the Lubrication Field: Their Design, Mechanisms, and Behaviors

“…In addition to potential corrosive properties, most ILs are much more expensive to manufacture than common lubricants. The current production technology mainly reduces the reaction steps of IL synthesis by establishing effective synthesis schemes, and even realizes one-step synthesis to make ILs more economically viable [55]. Using ILs as additives is another effective strategy to make ILs more economically viable, which has To sum up, both the interface behaviors of ILs (physical adsorption, chemical reaction and the contact angle between the ions and the surface) and the materials of frictional pairs will affect the lubrication effect of ILs.…”

Confined ionic liquids films under shear: The importance of the chemical nature of the solid surface

“…Those properties are desirable for applications as lubricants or as additives to conventional surfactants, where the liquid is simultaneously subject to high temperatures, high loads, and high shear, requiring a characterization of how intermolecular structure and the physical properties, especially the viscosity, change under those conditions. 4,5,6,7,8 The lubricant coating of an ionic liquid over a solid surface can be as thin as 10 nm. 8,9,10 If a Coeutte flow is produced in the film confined between movable surfaces, even relatively low velocities applied on the covered surface can induce extraordinarily high shear rates.…”

Potential Applications of Ionic Liquids in Dentistry: A Narrative Review

“…The earliest application of IL was as a propellant in warfare 6. Later, it was used as energetic materials 7, lubricants 8, disinfectants 9, and surfactants 10.…”