Electrodeposition of Polypyrenes with Tunable Hydrophobicity, Water Adhesion, and Fluorescence Properties

The control in surface hydrophobicity and water adhesion is extremely important for various applications in water harvesting, oil/water separation membrane, energy systems or biosensing, for example. Here, for the first time we show that the use of fluorescent monomers such as pyrene with various substituents differing by their hydrophobicity, size, or rigidity/flexibility can lead to surfaces with tunable hydrophobicity, water adhesion and fluorescence properties by a direct electropolymerization process. Seven original monomers with fluoroalkyl, alkyl, phenyl, adamantyl, and triethylene glycol substituents were synthesized and studied. The surface roughness is highly dependent on the substituent, and it seems that the fluorescence, although complex, correlates with the surface roughness. Superhydrophobic properties and highly oleophobic properties are obtained using fluoroalkyl chains due to the presence of nanostructured microparticles. In comparison to the structured absorption and emission bands of pyrene monomers, the pyrene polymers (oligomers) exhibit a broad structureless spectral shape both in absorption and in emission, which seems to be due to pyrene oligomerization and aggregation. This work is a first tentative attempt to combine superhydrophobic and fluorescent properties using an innovative strategy and opens new doors to explore in this domain.