Bioinspired Nanotubular Structures by Soft-Template Electropolymerization: 3,4-(2,3-naphtylenedioxy)Thiophene Monomers Quenched to Form Dimers

Abstract

Preparing well-ordered nanotubes on materials surface is a great of interest in many applications. Bio-inspired and theoretical approaches show that porous structures such as nanotubes are key parameters for both surface hydrophobicity and water adhesion. Here, a very easy soft-template electropolymerization approach is used to form nanotubular structures, followed by a bioinspired strategy to control the wetting properties. Fully conjugated monomers based on 3,4-(2,3- naphtylenedioxy)thiophene (NaphDOT) core grafted with many rigid aromatic groups such as phenyl, naphthalene, pyrene, pyrrole, were synthesized. Then, electropolymerization is carried out with these monomers, followed by surface and morphologies characterization of corresponding polymers. We show that even if just dimers are formed by electropolymerization, the resulting polymer can be sufficiently insoluble to form structured films. 3,4-(2,3-naphtylenedioxy)thiophene (NaphDOT) is chosen as a judicious example, due to strong <i>π</i>-stacking interactions, and also their capacity to form nanotubular structures by soft template-electropolymerization in the presence of water (H<sub>2</sub>O). Here, different substituents, polymerizable or not, are grafted on the 2-position of thiophene. Films are formed with all the studied substituents. Nanotubular structures are especially observed with the following substituents: hydroxyl, pyrene and pyrrole, but in the presence of H<sub>2</sub>O. We study also their influence on the surface hydrophobicity.