The newly synthesized perfluoropolyether (PFPE) ionic liquid whose terminal group is an ammonium salt with a carboxylic\nacid has better frictional properties when compared to the conventional PFPEs. Stick-slip motion was not observed even for the\nsmooth surface for the modified PFPE tape. The friction is almost independent of the PFPE structure, but depends on the amine\nstructures. The ammonium salt being tightly anchored to the rubbing surface covers uniformly, which leads to better lubricity. The\nhigher dispersive interaction of the hydrophobic group of the amine is endowed with a compensating friction reduction. Steric\nhindrance of the hydrophilic group causes a high friction. Based on these findings, a saturated long chain ammonium salt is the\nbest selection. Moreover, the modified PFPEs are dissolved in alcohol and hexane, which makes practical use convenient without\nany environmental problems. These ionic lubricants invented around 1987 have been used for magnetic tapes for about a quarter\ncentury because of their good lubricity and are reviewed in this paper.
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