Smooth Transparent Omniphobic Coatings with Remarkable Liquid Repellence

Abstract

leaf (Nelumbo), superhydrophobic surfaces with a contact angle > 150° and low roll-off angles < 10°, have shown remarkable properties such as selfcleaning (so-called lotus effect), [1,2] antibiofouling [3] and anti-corrosion. [10,11] The surfaces rely on air pockets trapped in the micro-/nano-hierarchical structures to diminish the contact between the surface and the liquid to be repelled (Cassie-Baxter state). However, the composite solid/air interface design of these surfaces is metastable. Extreme conditions such as high pressure, high temperature, and abrasion cause loss of the super repellent properties, when the air is removed from the textured surfaces. Slippery liquid-infused porous surfaces (SLIPS) were developed as an alternative to superhydrophobic surfaces to address these limitations. [12][13][14] The mobility of the lubricant that is infused into the micro-/nanoporous structures allows liquid drops on the surface to easily slide off. These surfaces have shown exceptional omniphobicity, self-healing, [12] selfcleaning, [15] and antifouling properties. [15] However, like the air layer in superhydrophobic surfaces, the lubricant layer can be removed either by evaporation or replacement with other liquids and once the lubrication layer is lost and the solid surface is exposed, the material loses its slippery properties.Liquid repellent surfaces are of high interest in various fields like protective coatings and droplet manipulation due to their outstanding properties from self-cleaning to anti-fouling. Most reported surfaces rely on the fabrication of micro/-nanostructured surfaces, the infusion of porous surfaces with immiscible lubricants, or the grafting of monolayers with low surface energy to achieve repellence of various liquids. However, these methods are limited in terms of their durability and long-term stability. Here, the fabrication of smooth, transparent fluorinated poly (perfluoroalkyl methacrylate) coatings via UV-initiated radical polymerization in a simple one-step procedure is reported. The resulting surfaces show very low surface energies of down to 7 mN m −1 , low contact angle hysteresis below 5°, very good repellence towards various liquids with different polarities as well as self-cleaning and anti-graffiti ability. The fabricated coatings can be applied to various substrates from glass slides to microfiber cloths. This demonstrates that they outperform common commercially available fluorinated coatings, such as, for example, Hyflon AD 40L S, in terms of liquid repellence and their performance in real-world applications.

Enhancing oil repellency of electron beam‐grafted polyethylene terephthalate fabric with 2‐(perfluorohexyl) ethyl acrylate monomer via pre‐irradiation

“…Fluorinated monomers with four or six fluorinated carbons in the side chain are replaced with C8‐based fluorinated monomers. However, fluorinated fluoroalkyl groups with shorter side chains are less crystalline, and thus exhibit higher surface molecular mobility 35,38,39 . Consequently, carbonyl groups (–COO–), which are polar groups in fluoroalkyl groups, are exposed on the surface when in contact with water 35,36 .…”

“…However, fluorinated fluoroalkyl groups with shorter side chains are less crystalline, and thus exhibit higher surface molecular mobility. 35,38,39 Consequently, carbonyl groups (-COO-), which are polar groups in fluoroalkyl groups, are exposed on the surface when in contact with water. 35,36 It has been reported that copolymers with fluorinated monomers and alkyl acrylate monomers prepared to suppress the surface molecular mobility of fluoroalkyl groups improve the water repellency of polymeric substrates.…”

Mechanochemical Activation of Silicone for Large-Scale Fabrication of Anti-Biofouling Liquid-like Surfaces

“…The resulting surface resembles a liquid-like layer with nanoscopic thickness. This strategy involves poly­(dimethylsiloxane) (PDMS), alkylchlorosilanes, and perfluorinated polyether covalently grafted to the surface for high repellency against liquids with a broad range of surface tension. − The high mobility of these flexible chains allows them to act as a liquid-like lubricating layer against other liquids. ,− Being only a few nanometers in thickness, the grafted layers exhibit low or no light scattering, rendering them transparent and preserving the appearance of the coated surfaces. ,, Therefore, this strategy is increasingly becoming the choice for many groups to prepare liquid-repellent coatings. ,,− Due to their covalent grafting to the substrate, the grafted layers exhibit excellent resistance to mechanical abrasion and are not easily affected by contact with liquids. However, the time-consuming preparation procedures, specific application methods such as vacuum systems, and the use of chemicals such as acids in the fabrication process limit the utilization of liquid-like surfaces in practical applications.…”

“…2,24−28 Being only a few nanometers in thickness, the grafted layers exhibit low or no light scattering, rendering them transparent and preserving the appearance of the coated surfaces. 18,29,30 Therefore, this strategy is increasingly becoming the choice for many groups to prepare liquid-repellent coatings. 17,19,31−36 mechanical abrasion and are not easily affected by contact with liquids.…”