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.