Highly Fluorinated Ionic Liquid Films as Nanometer-Thick Media Lubricants for Hard Disk Drives

Ionic liquids (ILs) are promising candidates for the next-generation nanometer-thick lubricants in hard disc drives (HDDs) because of their excellent physiochemical properties and low monolayer (ML) thicknesses. However, the commercially available ILs have higher surface tension and higher friction than the state-of-the-art perfluoropolyether (PFPE) lubricant. In the current study, a fluorinated IL (FIL) lubricant, which contains cations with highly fluorinated alkyl chains, has been successfully synthesized. The surface tension of FIL is comparable to that of PFPE, which is ideal for enhancing the tribological performance of the FIL lubricant. The thermogravimetric analysis results showed that FIL has higher thermal stability than PFPE Ztetraol. Atomic force microscopy revealed that because of the intrinsically smaller molecular size of FIL, the ML thickness is only ∼50% of that of Ztetraol, which is expected to induce a lower lubricant thickness and higher areal density. Compared to the commercially available ILs, reduced friction of the nanometer-thick FIL lubricant on carbon overcoat was also achieved because of its intrinsically lower surface tension. Our results demonstrate that FIL has great potential for application as the next-generation media lubricant in HDDs.