A Short-Chain Multibranched Perfluoroalkyl Thiol for More Sustainable Hydrophobic Coatings

Abstract

Perfluorocarbons (PFCs) have proven to be very efficient in building up omniphobic surfaces because of the peculiar properties of fluorine atoms. However, due to their environmental impact and bioaccumulative potential, perfluorinated surfactants with chains longer than six carbon atoms have been banned, and other alternatives had to be found. Herein, we demonstrate the possibility to build omniphobic self-assembled monolayers (SAMs) using a multibranched fluorinated thiol (BRFT) bearing ultrashort fluorinated alkyl groups, surrounding a hydrocarbon polar core. This unique design allows us to multiply the number of fluorine atoms in the molecule (27 F atoms per molecule), affording a high fluorine density on the surface and a low surface free energy. Moreover, the presence of four ether bonds in the core may hasten molecular degradation in the environment because of the cleavage of such bonds in physiological conditions, thus overcoming bioaccumulation issues. BRFT may effectively represent a valuable substitute of long-chain perfluoroalkyl thiols. In fact, BRFT SAMs show the same hydrophobic and oleophobic performances of standard linear perfluoroalkyl thiols (such as 1H,1H,2H,2H-perfluorodecanethiol, PFDT), giving rise to more stable surfaces with a better frictional behavior. Superhydrophobicity was also observed with SAMs grown on nanostructured Cu/Ag surfaces. Our results have proven the ability of short-chain multibranched fluorous molecules to behave as suitable replacements for long-chain perfluoroalkanes in the field of surface coatings. Our molecules may be applied to various surfaces because of the available multiple choice of linker chemistry.

Hydrophobin‐Coated Solid Fluorinated Nanoparticles for 19F‐MRI

“…As recently reported by some of us, a highly fluorinated branched thiol, F 27 ‐SH ( Figure a), was able to self‐assemble on gold (Au) surfaces forming a highly ordered and robust monolayer with interesting non‐wetting properties towards both water and oil. [ 14 ] Since the molecular structure of F 27 ‐SH closely resembles that of PERFECTA, a fluorinated thiol monolayer on planar surface was used as a model substrate. The ability of HFBII to adsorb on such a surface was evaluated measuring the static water contact angles (WCAs, Table 1 , Figure S1, Supporting Information), before and after its exposure to a HFBII aqueous solution.…”

Applying an Oleophobic/Hydrophobic Fluorinated Polymer Monolayer Coating from Aqueous Solutions

“…Many different surface-coating strategies have been developed to make oleophobic coatings, such as layer-by layer assembly (LbL), , sol–gel approaches, , and self-assembled monolayers (SAMs). − Even though considerable technological advancements have been made in this field, the environmental friendliness and the sustainability of fluorinated coatings remain major issues that limit their applications. As already stated, fluorocarbon-based materials, especially long perfluoroalkanes, are highly stable and can bioaccumulate. − Furthermore, upon their eventual breakdown, their degradation products, such as perfluorooctanoic acid , and perfluorooctanesulphonate have been shown to be toxic.…”

Robust hydrophobic gold, glass and polypropylene surfaces obtained through a nanometric covalently bound organic layer

“…20 Dichiarante et al recently described the use of multibranched peruoroalkyl thiol compounds and 1H,1H,2H,2H-peruorodecanethiol to develop hydrophobic gold surfaces. 21 Static contact angles of ca. 110 were measured, which marginally decreased (<10%) over two weeks.…”