Exceptionally Strong Effect of Small Structural Variations in Functionalized 3,4-Phenylenedioxythiophenes on the Surface Nanostructure and Parahydrophobic Properties of Their Electropolymerized Films

Abstract

Electropolymerization of electron-rich aromatics/heteroaromatics to form conducting polymers is an easy and powerful technique to form surfaces of different nanostructures and hydrophobicity/wettability. Understanding the factors governing the growth of the polymer nanostructures and controlling the surface morphology are the big challenges for the surface and materials science. In this paper, we report the design and synthesis of a series of 3,4-phenylenedioxythiophenes (PheDOTs) substituted at the benzene ring with 2-naphthylmethyl-, 1-naphthylmethyl-, and 9-anthracenylmethyl-groups (2Na-PheDOT, 1Na-PheDOT, and 9Ant-PheDOT). They have been electropolymerized in either potentiostatic or potentiodynamic conditions to form the polymer surfaces of different morphologies. Even small changes in the structure of PheDOT monomers by varying the side groups (2-/1-naphthyl- or 9-anthracenyl-) result in the formation of very different polymer surface nanostructures: from monodirectionally growing (one-dimensional) vertically aligned nanotubes for 2Na-PheDOT to ribbonlike nanostructures (two-dimensional) for 1Na-PheDOT, and a mixture of these two structures for 9Ant-PheDOT. Moreover, the surfaces of the p­[2Na-PheDOT] polymer, electrodeposited from the monomer 2Na-PheDOT and the dimer (2Na-PheDOT) 2 (which have different solubilities and the reactivities on electropolymerization, but formally lead to the polymer of the same chemical structure), show very different nanostructures. In contrast to 2Na-PheDOT, which forms vertically aligned nanotubes of the polymer on the surface, the polymerization of (2Na-PheDOT) 2 leads to spherical particles [three-dimensional (3D)] when Bu4NClO4 is used as an electrolyte and a membrane structure with spherical holes (3D) in the case of more hydrophobic Bu4NPF6. The importance of water for gas bubble formation (O2 and H2) during electropolymerization and creation of the surface nanostructures has been demonstrated and discussed. The formation of these different nanostructures is accompanied by different wettability of the surface, from hydrophilic (with an apparent water droplet contact angle of θw ∼ 40–70°) to highly hydrophobic (θw up to 129–134°). The sticky, parahydrophobic surface formed from 1Na-PheDOT showed high adhesion to water, with no water droplets moving after inclination of the surface to 90° (rose-petal effect).

A bioinspired strategy for designing well-ordered nanotubular structures by templateless electropolymerization of thieno[3,4- b ]thiophene-based monomers

“…With this strategy, the base structure of the polymerizing monomer is much more critical, as the monomer and polymer directly stabilize gas bubbles formed in solution. Owing to their rigidity and π-stacking interactions, monomers based on 3,4-phenylenedioxythiophene (PheDOT), 3,4-naphtalenedioxythiophene (NaphDOT) and thienothiophene are excellent candidates to develop nanoporous structures from electropolymerization in organic solvents, and this has been demonstrated for CH 2 Cl 2 as solvent [30][31][32][33][34][35][36]. Within this subset of potential monomers for in situ electropolymerization, thieno [3,4b]thiophene derivatives are particularly interesting as they have exceptional opto-electronic properties.…”

Tunable Nanoporous Structures with Rose Petal Effect by Soft‐Template Electropolymerization of Benzotrithiophene Monomers

“…The soft-template electropolymerization was reported as a very nice strategy to prepare on substrates ordered porous structures such as nanotubes. [20][21][22][23][24][25][26][27][28][29][30][31] The electropolymerization of pyrrole directly in water (H 2 O) was very studied in the literature. [20][21][22][23][24] Depending on the deposition method it is possible to form on the substrate gas bubbles (O 2 and/or H 2 ) acting as soft-template for the growth of nanotubes.…”

“…Because most of the monomers are not soluble in water, this process was pursued in organic solvent. [25][26][27][28][29][30][31] In organic solvent, H 2 O can be added in solution for releasing on the substrate gas bubbles acting also as soft-template for the preparation of porous structures and H 2 O content as a huge influence, especially on the numbers of nanotubes. The influence of H 2 O content was determined by comparing the results obtained in dichloromethane (CH 2 Cl 2 ) and in dichloromethane saturated with water, called (CH 2 Cl 2 + H 2 O).…”

Soft-template electropolymerization of 3,4-(2,3-naphtylenedioxy)thiophene-2-acetic acid esters favoring dimers: Controlling the surface nanostructure by side ester groups

“…It also represents a special interest for softtemplate electropolymerization due to its strong ability to form highly ordered porous nanostructures such as vertically aligned nanotubes, probably due to -stacking interactions favoring the deposition in a preferential direction [44,45]. Electropolymerization of PheDOT derivatives, R-PheDOT, was shown to form rich pallet of surface nanostructures of the polymer films depending on the functional group substitution at the benzene ring [59,60]. The naphthalenefused analog of EDOT, 3,4-(2,3-naphtylenedioxy)thiophene (NaphDOT), has proven to be an exceptional monomer for soft-template electropolymerization, forming extremely ordered nanotubular polymeric structures on the electrode surface [43,44].…”