Imidazolium-Based Ionic Liquid Exhibiting Dual Hydrophilic and Oleophobic Properties without Polar End Groups

Abstract

Simultaneously hydrophilic and oleophobic surfaces offer substantial advantages for applications such as antifogging, self-cleaning, and oil–water separation. It remains challenging to engineer such surfaces without requiring polar functional groups. This study introduces HFIL, a novel ionic liquid (IL) coating that achieves simultaneous hydrophilic and oleophobic properties via a one-step dip-coating process without relying on polar functional groups. Key findings show that, despite the bulk form of HFIL having a high hexadecane contact angle (HCA) of 74.1° and an even higher water contact angle (WCA) of 87.6°, the IL forms a stable monolayer on high-energy surfaces exhibiting a much lower WCA of approximately 40° with minimal change to the HCA. Washing tests demonstrate that, even without the polar functional groups, there is a non-zero bonded thickness upon which the oleophobicity is comparable to polytetrafluorethylene (PTFE). These properties highlight HFIL’s potential for durable applications in antifouling, antifogging, and environmental separation technologies, where selective liquid interactions are essential. This work contributes to a broader understanding of IL-based surface modifications, advancing the development of high-performance coatings.