Lubrication of starch in ionic liquid-water mixtures: Soluble carbohydrate polymers form a boundary film on hydrophobic surfaces.
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 ≥60wt%. In 65wt% EMIMAc, a small amount of soluble starch (0.33wt%) 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. 2nm) 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.
Australian Research Council Centre of Excellence in Plant Cell Walls, The University of Queensland, Brisbane, Qld 4072, Australia; School of Chemical Engineering, The University of Queensland, Brisbane, Qld 4072, Australia. Electronic address: gleb.yakubov@uq.edu.au.
Gleb E
GE
Yakubov
Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Brisbane, Qld 4072, Australia; Key Laboratory of Chemical and Biological Transformation Processes, School of Chemistry and Chemical Engineering, Guangxi University for Nationalities, Nanning 530006, China.
Lei
L
Zhong
Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, Brisbane, Qld 4072, Australia.
Ming
M
Li
School of Chemical Engineering, The University of Queensland, Brisbane, Qld 4072, Australia.
Michael W
MW
Boehm
Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Brisbane, Qld 4072, Australia.
Fengwei
F
Xie
Ian Wark Research Institute, University of South Australia, Mawson Lakes Campus, Mawson Lakes, SA 5095, Australia.
David A
DA
Beattie
School of Chemical Engineering, The University of Queensland, Brisbane, Qld 4072, Australia; Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Brisbane, Qld 4072, Australia.
Peter J
PJ
Halley
Australian Research Council Centre of Excellence in Plant Cell Walls, The University of Queensland, Brisbane, Qld 4072, Australia; School of Chemical Engineering, The University of Queensland, Brisbane, Qld 4072, Australia.
Jason R
JR
Stokes
D004129:Dimethylpolysiloxanes / Q000737:chemistry; D020724:Elastomers / Q000737:chemistry; D057927:Hydrophobic and Hydrophilic Interactions; D007093:Imidazoles / Q000737:chemistry; D052578:Ionic Liquids / Q000737:chemistry*; D012995:Solubility; D013213:Starch / Q000737:chemistry*; D013499:Surface Properties; D013696:Temperature; D014867:Water / Q000737:chemistry*
D004129:Dimethylpolysiloxanes; D020724:Elastomers; D007093:Imidazoles; D052578:Ionic Liquids; D014867:Water; C013830:baysilon; D013213:Starch; C518739:1-ethyl-3-methylimidazolium
1-Ethyl-3-methylimidazolium acetate (PubChem CID: 11658353); Amylose; Boundary friction; Ionic liquid; Lubrication; Starch; Suspension