Hydration Lubrication: The Macromolecular Domain

Jahn, Sabrina; Klein, Jacob

doi:10.1021/acs.macromol.5b00327

Cited by 136 publications

(96 citation statements)

References 160 publications

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“…This lubrication mechanism was emphasized and discussed in two seminal publications by Raviv, Klein and Laurat, 45,46 and more recently in a perspective article by Jahn and Klein. 47 The double-chained cationic surfactant didodecyldimethylammonium bromide adsorbs strongly onto the highly negatively charged mica surface to form a bilayer structure. In SFA experiments it has been demonstrated that this surfactant bilayer has sufficient cohesion to withstand shear under high loads, and the friction force was found to be so small that it could not be measured with the very accurate and sensitive SFA tribometer.…”

Section: Amphiphilic Moleculesmentioning

confidence: 99%

Synergies in lubrication

Dédinaité

Claesson

2017

Phys. Chem. Chem. Phys.

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To slide surfaces against each other with application of a minimum force and minimum wear has been important since ancient times, and it remains equally important today. The use of oil-soluble lubricants is widely spread in technology, whereas living organisms have developed water-soluble lubricants to facilitate sliding motions. In this perspective article we focus on water-based lubrication in the boundary lubrication regime, and particularly lubrication synergies. This focus has, of course, found inspiration from the outstanding lubrication properties of synovial joints. It has ignited significant amount of research, mostly aimed at answering the question: Which molecule is the magic biolubricant? Different research groups have advocated different answers, and the debate has been intensive. In this article we argue that the question in itself is inappropriate. The relevant question is rather the following: How do molecules work in synergy to provide superior lubrication?

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Section: Amphiphilic Moleculesmentioning

confidence: 99%

Synergies in lubrication

Dédinaité

Claesson

2017

Phys. Chem. Chem. Phys.

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“…[1a, 2] These tightly bound water molecules render the polyelectrolyte chains highly swelled in water, [2,3] and are believed to be the major mechanism for their promising applications such as underwater oil repellency, [4] antifouling, [1b, 5] oil/water separation, [6] and lubrication. [7] Of all polyelectrolytes,t he zwitterionic ones exhibit excellent hydrophilicity and hydration strength by integrating both positive and negative ionic groups. [1a, 8] Upon contact with hydrophobic oil, the polyelectrolyte surfaces,l ike most polar surfaces with high surface energy, will reorient their ionic groups inwards to lower the surface free energy,l eading to evident loss of surface hydrophilicity and wettability alteration.…”

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Long‐Range Hydrophilic Attraction between Water and Polyelectrolyte Surfaces in Oil

et al. 2016

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The outstanding water wettability and the capability of polyelectrolyte surfaces to spontaneously clean oil fouling are determined by their wetting mechanism in the surrounding medium. Here, we have quantified the nanomechanics between three types of polyelectrolyte surfaces (i.e. zwitterionic, cationic, and anionic) and water or oil drops using an atomic force microscope (AFM) drop probe technique, and elucidated the intrinsic wetting mechanisms of the polyelectrolyte surfaces in oil and water media. The measured forces between oil drops and polyelectrolyte surfaces in water can be described by the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Surprisingly, strong long-range attraction was discovered between polyelectrolyte surfaces and water drops in oil, and the strongest interaction was measured for the polyzwitterion. This unexpected long-range "hydrophilic" attraction in oil could be attributed to a strong dipolar interaction because of the large dipole moment of the polyelectrolytes. Our results provide new nanomechanical insights into the development of novel polyelectrolyte-based materials and coatings for a wide range of engineering, bioengineering, and environmental applications.

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Investigation of Superlubricity Achieved by Polyalkylene Glycol Aqueous Solutions

Wang

Liu

2016

Adv Materials Inter

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and investigated the fl uidity of hydration layers [26][27][28] to better understand the frictional behaviors in biological systems. Previously, our group reported different kinds of liquid superlubricity, e.g., boric acid with glycerol, [ 29 ] phosphoric acid, [ 30 ] as well as glycerol, [ 31 ] polyhydroxy alcohol solutions, [ 32 ] ethylene glycol, [ 33 ] and silicone oil [ 34 ] by running-in with an acid solution. However, the widespread application of these lubricating fl uids in industry is limited by the production of hydrogen ions and the high dependence on water content in these systems.Polyalkylene glycols (PAGs), a type of synthetic lubricants, are the copolymers from any combination of different alkylene oxides, typically of ethylene oxide (EO) and propylene oxide (PO). [ 35 ] Their high-temperature stability, low pour point, and high viscosity index are highly suited for the normal operation of mechanical equipment, for example, ore crushers, cement kilns, and steel roller bearings. In addition, most PAGs are biodegradable and some of them are even food-grade accredited, which means they satisfy the demands necessary for application in the agriculture, forestry, mining, and food-manufacturing industries. [ 35,36 ] By controlling the mixing ratio of EO/PO, the chemical structure of PAG allows for high-strength hydrogen bonding; thus, the solubility of PAG will be adjusted accordingly. [35][36][37] The presence of oxygen atoms in the polymer backbone results in the highly polar PAG being able to absorb onto the contact surface. As such, they have been widely applied in the textile industry, for household cleaners and polishes, and metal cutting. [ 36,38 ] In present work, considering that PAGs have a good hydration and adsorption capacity, we investigated the tribological properties of these aqueous solutions. Using various weight fractions of PAG, the friction coeffi cient was recorded in both droplet and full immersion states. As a result, ultralow friction coeffi cient can be achieved using a wide range of concentration. The contact region after test and the hydration state of PAG chains were analyzed to determine the mechanism of the superlubricity phenomenon in this system. Because of its superior lubrication property and the stable state of the system under ambient conditions, the application of this environmentally friendly solution, such as bearing and joint lubricating systems, was proposed to save energy via the reduction of friction, and prevent pollution from lubricant leakage.Ultralow friction coeffi cient ( µ ) of a polyalkylene glycol (PAG) aqueous solution obtained in both droplet state (40 µL) and full immersion state after a running-in period. Here, two key factors in achieving the superlubricity state ( µ < 0.01) demonstrated: the low shearing strength of the hydrated layer and the presence of a suitable amount of free water molecules. In the initial running-in period, a decrease in contact pressure contributes to the formation of elastohydrodynamic behavior of fl uid. The hydrogen-bon...

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Hydration Lubrication: The Macromolecular Domain

Cited by 136 publications

References 160 publications

Synergies in lubrication

Synergies in lubrication

Long‐Range Hydrophilic Attraction between Water and Polyelectrolyte Surfaces in Oil

Investigation of Superlubricity Achieved by Polyalkylene Glycol Aqueous Solutions

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