Poly(ethylene oxide) Mushrooms Adsorbed at Silica-Ionic Liquid Interfaces Reduce Friction

Area of Science:

• Tribology
• Materials Science
• Surface Chemistry

Background:

• Ionic liquids (ILs) are promising lubricants due to their unique properties.
• Understanding polymer adsorption at IL interfaces is crucial for optimizing lubrication.

Purpose of the Study:

• Investigate the adsorbed layer conformation and lubricity of polyethylene oxide (PEO) on ionic liquid (IL)-silica interfaces.
• Determine the effect of PEO molecular weight on friction reduction in ILs.

Main Methods:

• Colloid probe atomic force microscopy (AFM) was used to study PEO adsorption.
• Normal force curves and friction measurements were performed on propylammonium nitrate (PAN) and 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) ILs.

Main Results:

• Adsorbed PEO layers exhibited steric interactions consistent with the mushroom model.
• PEO significantly reduced friction compared to pure ILs.
• Lubricity increased with increasing PEO molecular weight (35, 100, and 300 kDa).

Conclusions:

• Adsorbed polymer layers enhance the lubricating properties of ILs.
• Friction is governed by intermolecular interactions within entangled polymer chains.
• PEO is effective in reducing friction while preserving IL functionality as lubricants.