pH-Driven Wetting Switchability of Electrodeposited Superhydrophobic Copolymers of Pyrene Bearing Acid Functions and Fluorinated Chains

A smart stimuli responsive surface is fabricated by the subsequent electro-copolymerization of pyrene monomers followed by a basic and acid treatment, respectively. Copolymers of fluorinated pyrenes and pyreneacetic acid were produced with different molar concentration of each monomer (0, 25, 50, 75 and 100% of Py-nF6 vs. Py-COOH) by an electrochemical process. Two different perfluorinated pyrenes containing ester and amide groups are used to reach superhydrophobic properties. The relation of those bonds with the final properties of the surface is reported. The pH-sensitive group of the Py-COOH allows the surfaces to be reversibly switched from superhydrophobic (w > 150o and very low hysteresis) to a hydrophilic behavior (w < 90o). The amide and ester bonds influence the recovery of the original wettability after both basic and acid treatment. If the fluorinated homopolymer with ester bonds is insensitive to basic and acid treatment due to its superhydrophobic properties with ultra-low water adhesion, the recovery of the original wettability for the copolymers is much more important with amide bonds due to their lower pH-sensitivity. This strategy offers the opportunity to access superhydrophobic films with switchable wettability by a simple pH treatment. The films showed to be a good tool to use towards biological applications as bacterial-resistant film when superhydrophobic or bacterial-adherent film when hydrophilic, for example.