Lubrication of starch in ionic liquid–water mixtures: Soluble carbohydrate polymers form a boundary film on hydrophobic surfaces. (20th November 2015)

• Record Type: Journal Article
• Authors: Yakubov, Gleb E.; Zhong, Lei; Li, Ming; Boehm, Michael W.; Xie, Fengwei; Beattie, David A.; Halley, Peter J.; Stokes, Jason R.
• Is Part Of: Carbohydrate polymers. Volume 133(2015)
• Page Start: 507
• Page End: 516
• Publication Date: 2015-11-20
• Subjects: 1-Ethyl-3-methylimidazolium acetate (PubChem CID: 11658353); Starch -- Lubrication -- Ionic liquid -- Amylose -- Boundary friction -- Suspension; Polysaccharides -- Periodicals; Polysaccharides -- Periodicals; Polysaccharides -- Périodiques; Electronic journals; 547.78
• DOI: 10.1016/j.carbpol.2015.06.087
• Languages: English
• ISSNs: 0144-8617

Abstract

Highlights: Soluble starch polymers enhance lubrication of ionic liquid–water solvents. A fraction of starch is highly soluble in 1-ethyl-3-methylimidazolium acetate. Small amount of soluble starch reduces the boundary friction coefficient. This low-friction is associated with a nanometre thick film formed from the amylose. The presence of dissolved amylose enhances the lubrication of starch suspensions. Abstract: Soluble starch polymers are shown to enhance the lubrication of ionic liquid–water solvent mixtures in low-pressure tribological contacts between hydrophobic substrates. A fraction of starch polymers become highly soluble in 1-ethyl-3-methylimidazolium acetate (EMIMAc)–water solvents with ionic liquid fraction ≥60 wt%. In 65 wt% EMIMAc, a small amount of soluble starch (0.33 wt%) reduces the boundary friction coefficient by up to a third in comparison to that of the solvent. This low-friction is associated with a nanometre thick film (ca. 2 nm) formed from the amylose fraction of the starch. In addition, under conditions where there is a mixture of insoluble starch particles and solubilised starch polymers, it is found that the presence of dissolved amylose enhances the lubrication of starch suspensions between roughened substrates. These findings open up the possibility of utilising starch biopolymers, as well as other hydrocolloids, for enhancing the performance of ionic liquid lubricants.