Bioinspired surfaces with strong water adhesion from electrodeposited poly(thieno[3,4-b]thiophene) with various branched alkyl chains

In this original work, we wanted to prepare surfaces with both high hydrophobicity and strong water adhesion, as observed on rose petals or gecko foot. The surfaces are prepared by electropolymerization and using thieno[3,4-b]thiophene monomers with various branched alkyl chains. Here, branched alkyl chains are used to their lower hydrophobic properties compared to linear alkyl chains and fluorinated chains. It is observed a change from structured to smooth when the branched alkyl chain length increases. Using short branched alkyl chains, the surfaces are mainly composed of wrinkles and nanoparticles displaying high hydrophobicity (theta w up to 134.9 degrees) combined with strong water adhesion, as observed on rose petals even if theta w is less important. Dynamic contact angle measurements show that their water adhesion is extremely strong and water droplets remain stuck on them. By adding H2O in the solvent (CH2Cl2+H2O), it is possible to release gas bubbles (H-2 and/or O-2) in-situ leading to more porous surfaces but here it is observed an increase of surface hydrophilicity. These original polymer surfaces have potential applications in water harvesting systems or oil/water separation membranes, for example.