Durable, superoleophobic polymer–nanoparticle composite surfaces with re-entrant geometry via solvent-induced phase transformation

Abstract

Superoleophobic plastic surfaces are useful in a wide variety of applications including anti-fouling, self-cleaning, anti-smudge, and low-drag. Existing examples of superoleophobic surfaces typically rely on poorly adhered coatings or delicate surface structures, resulting in poor mechanical durability. Here, we report a facile method for creating re-entrant geometries desirable for superoleophobicity via entrapment of nanoparticles in polycarbonate surfaces. Nanoparticle incorporation occurs during solvent-induced swelling and subsequent crystallization of the polymer surface. The resulting surface was found to comprise of re-entrant structures, a result of the nanoparticle agglomerates acting as nucleation points for polymer crystallization. Examples of such surfaces were further functionalized with fluorosilane to result in a durable, super-repellent surface. This method of impregnating nanoparticles into polymer surfaces could prove useful in improving the anti-bacterial, mechanical, and liquid-repellent properties of plastic devices.

Why re-entrant surface topography is needed for robust oleophobicity

“…Nanoparticles incorporated deeper into the polymer would have a less significant effect on the surface topography [58]. This re-entrant surface, once fluorinated, was found to be repellent towards both hexadecane and water [58]. (Online version in colour.)…”

“…In order to make their material truly superoleophobic, Brown & Bhushan [58] added reentrant topography. To accomplish this, nanoparticles were added to the acetone solvent during the solvent-induced phase transformation of polycarbonate.…”

Super-Amphiphobic Coating System Incorporating Functionalized Nano-Al2O3 in Polyvinylidene Fluoride (PVDF) with Enhanced Corrosion Resistance

“…The re-entrant surface is a geometry where the surface asperities create an overhang or "liquid sagging" [17]. Example of re-entrant phenomena is the surface of the gills of a standing mushroom, inverse trapezoidal, and the bottom half of a sphere [13].…”

Selective separation of oil and water with mesh membranes by capillarity

“…Note that as oils do not give surfaces in which θ smooth N 90°t his approach will not work for producing superoleophobic surfaces. However, this can be achieved using surfaces engineered to have a reentrant structure [14,15]. In membrane separation processes it is important to recognize that air is not present at the interface, that is, both of the fluid phases are liquids, and the desired properties are obtained when the wetting liquid penetrates the surface roughness, as air does in the Cassie state described above.…”