About this Event
3700 O'Hara Street, Pittsburgh, PA 15261
Title: Thin-Film Properties and Applications for a Novel Fluorinated Ionic Liquid
Abstract: Fluoropolymers have been favored in widespread use for a variety of coating applications, especially in specially-wettable surfaces and as thin-film lubricants. For example, surfaces that are more wettable to water than to oils are highly desired for use in oil/water separation enhancement, detergent-free cleaning, and anti-fogging coatings. Unfortunately, such surfaces are rare, typically consisting of fluoropolymer coatings with multi-step modification processes. Moreover, reported surfaces are often only mildly effective and are degrading in oleophobicity with time. The tunable nature of ionic liquids (ILs) makes them an attractive coating alternative, offering endless possibilities for customization and optimization by controlling the functional groups on the organic ion substituents. For this, a functionalized ionic liquid coating (dubbed “HFILOH”) with highly fluorinated alkyl segments was developed to promote a high degree of oleophobicity on Si substrates due to the high fluorination, while maintaining a water contact angle (WCA) below 10°. The coating is only about one nanometer thick and shows robust oleophobicity over at least 48 hours of continuous exposure. However, while the coating has the desired properties, the mechanism for this hydrophilic/oleophobic behavior remains unclear and the is even disputed in literature. The most widely cited mechanisms are coating penetration based on size-exclusion, or stimulus-sensitive rearrangement of the coating. Aim 1 of this proposal is to gather experimental evidence to either support or deny the penetration mechanism by observing time-dependent effects of testing liquids with varied molecular sizes and shapes.
Another application where HFILOH is a promising alternative is lubrication of computer storage media. Media lubricants are essential to the reliability and function of hard disk drives (HDDs). In addition to a low coefficient of friction (CoF), a good media lubricant should have surface-bonding capabilities with low surface tension for self-healing properties, high thermal stability for heat-assisted magnetic recording (HAMR), and a low monolayer thickness to minimize head media spacing (HMS). Traditionally, the state-of-the-art lubricants have been functionalized perfluoropolyethers (PFPEs). However, the bulky molecular size of these polymer-based lubricants is a limiting factor in the reduction of the HMS. In addition to the aforementioned customizability, ILs are a promising replacement due to their high thermal stability and relatively small size. Previous work has demonstrated the tribological performance of HFILOH, displaying a CoF comparable to that of the PFPE Ztetraol, but with a lower surface tension and a thinner effective coating. These results show strong potential for the next-generation HDD lubricant, but production scale-up potential is currently limited by the existing synthesis procedures which are plagued by low yield and low purity. This proposal will aim to scale up production of high-purity HFILOH to a marketable quantity while minimizing the material and environmental costs associated with the large waste streams that result from the low yield synthesis. This work will be completed in two parts. Aim 2 will focus on adjusting reaction conditions, including time, temperature, and stoichiometry, to achieve high purity HFILOH in significantly higher yields. Then, with the understanding gained from Aim 2, Aim 3 will be to scale-up production of the high purity HFILOH by up to 200x in order to meet potential market needs, either through linear batch scaling, or by converting from batch to semi-continuous synthesis. Altogether, this research should result in larger-scale production of HFILOH that is high quality and ready for implementation as the next HDD lubricant.
Committee:
Dr. Lei Li, Chair
Department of Chemical and Petroleum Engineering, University of Pittsburgh
Dr. Susan Fullerton
Department of Chemical and Petroleum Engineering, University of Pittsburgh
Dr. Sachin Velankar
Department of Chemical and Petroleum Engineering, University of Pittsburgh
Dr. Haitao Liu
Department of Chemistry, University of Pittsburgh
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