(557h) Novel Highly Fluorinated Ionic Liquids As Media Lubricants

Nanometer-thick lubricants are critical to the reliability of nano- and micro-electromechanical systems (NEMS/MEMS) and hard disc drives (HDDs). Ionic liquids (ILs) are promising candidates for next-generation media lubricants because of their excellent physical properties, e.g., high thermal stability, small molecular size, layering molecular structure when confined on solid, and low cost. However, our previous research showed that IL lubricant has higher friction and higher surface energy than the state-of-the-art lubricant, i.e., perfluoropolyether (PFPE), which raises concerns for their application as media lubricants. In the current study, a novel IL lubricant with highly fluorinated imidazolium cations (FIL) was successfully synthesized. The surface energy of FIL significantly reduced to a value comparable to the surface energy of PFPE Z-dol. The thermogravimetric analysis (TGA) results indicated that FIL has higher thermal stability than PFPE Z-tetraol, which is highly desirable in lubrication. The surface roughness results, which are characterized by atomic force microscopy (AFM), demonstrated that the monolayer (ML) thickness of FIL is only ~50% of that of Z-tetraol, which is induced by the intrinsically small molecular size of FIL. The low ML thickness of FIL provides the opportunity to scale down the thickness of the nanometer-thick films and thus increase the areal density. The friction coefficient of the nanometer-thick FIL, however, is slightly higher than that of the PFPE, which can be attributed to the extremely low bonded ratio of the FIL lubricant on the solid substrate. The addition of functional end-groups in the molecular structure is expected to enhance the bonding of the FIL lubricant on the media surface, and further reduce the friction.