Controlling water adhesion on superhydrophobic surfaces with bi-functional polymers

Abstract

With an aim to control the surface hydrophobicity and water adhesion, as observed on various natural surfaces, novel 3,4-propylenedioxythiophene (ProDOT) monomers having one and two 3-trimethylsilylpropyl (TMS) groups were synthesized and subjected to electropolymerization to form surface coatings. The monomer ProDOT is employed owing to its tendency to form fibrous structures by electropolymerization [T. Darmanin, F. Guittard, Mater. Chem. Phys. 146 (2014) 6–11], whereas the TMS groups generate very low surface energies comparable to short chain fluorocarbons [N. M. Kovalchuk, et al., Colloids Surfaces A 604 (2020) 125277.]. It is shown that even though these two types of monomer lead to fibrous structures, the dimensions of the fibers as well as the wetting properties are different. The monomer with only a single TMS group (ProDOTSiMe3) generates extremely long nanofibers with only low surface roughness. The resulting surfaces have extremely high apparent contact angles (θw) up to 141.7° and strong water adhesion, similar to rose petals or gecko feet. On the other hand, the analogue with two TMS groups (ProDOT(SiMe3)2) forms short nanofibers but with extremely high surface roughness. The resulting surfaces are superhydrophobic with θw > 160° and ultra-low water adhesion (hysteresis and sliding angles < 1°), similar to lotus leaves. These results point to interesting applications offering control over water adhesion whilst maintaining high hydrophobicity.