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

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.