Environment-responsive coatings with recoverable in-air superamphiphobicity and underwater superoleophobicity

Abstract Creating a surface that is simultaneously amphiphobic in air and oleophobic in water is energy unfavorable. To overcome this counterintuitive scientific problem, we demonstrate a general approach for construction of environment-responsive coatings made of perfluorinated surfactant substituted polyelectrolyte multilayers (PEMs). Sum frequency generation (SFG) vibrational spectroscope indicates that in an air environment, the film coatings orderly protrude their hydrophobic perfluorinated tails into air to decrease surface energy, giving rise to amphiphobicity with water and hexadecane contact angles (CAs) of ~114° and ~65° respectively on flat substrates. When the coated substrates are placed in water, the coatings will undergo a reconfiguration, the perfluorinated chains of the coatings instantaneously migrate and embed themselves into the film bulk to optimize their surface energy, leaving hydrophilic portions and positively charged groups exposed at the film-water interface (confirmed by surface zeta potential, XPS and SFG), which leads to an underwater oleophobicity with hexadecane CA of ~147°. By applying the coatings on roughed substrates, e.g., fabrics, both superamphiphobicity and underwater superoleophobicity were achieved with in-air water and hexadecane CAs of ~155° and ~152°, and underwater hexadecane CA of ~169°, respectively. Moreover, the coatings with these special wettabilities exhibit a good self-healing performance upon both plasma-induced surface decomposition and salt treatment. These coatings may bring in new insights of surface wettability and offer great potential in self-cleaning, anti-oil-fouling both in air and water (especially for aquatic devices working in oil spill situations).