Customizing oil-wettability in air—without affecting extreme water repellency

Abstract

Lotus leaf inspired superhydrophobic interfaces strongly repel the aqueous phase—but inherently display super-oil-affinity in air. However, superamphiphobic interfaces repel both the aqueous phase and the oil/oily phase strongly, due to their contact angles of above 150°. The fundamental criteria for optimizing such distinct super liquid wettabilities are different. Thus, in the past, distinct synthetic approaches were adopted to achieve these two different types of liquid-repellent interfaces for different prospective and relevant applications. Here, in this communication, a rapid and scalable spray deposition process is introduced for tailoring different oil-wettabilities in air, without perturbing the superhydrophobicity. An appropriate dilution of a reaction mixture of strategically selected two small molecules that readily reacted through the 1,4 conjugate addition reaction provided a facile basis for customizing oil wettability—starting from superoleophilicity to superoleophobicity, keeping intact the super water repellence. The synthesized superhydrophobic and superamphiphobic interfaces remained efficient for sustaining exposures of various practically relevant physical manipulations and abrasions and chemically complex aqueous phases. Furthermore, both the superhydrophobic and superamphiphobic interfaces were successfully extended for comparing the oil/water separation, anti-fouling and self-cleaning performances. Such a simple and common synthetic approach for preparing extremely water repellent interfaces that have differences in oil-wettability in air would be useful for practically relevant outdoor applications.