Designing Nanoporous Membranes through Templateless Electropolymerization of Thieno[3,4-b]thiophene Derivatives with High Water Content

Abstract

In this work, we present the synthesis of original thieno[3,4- b ]thiophene monomers with rigid substituents (e.g., perfluorinated chains, and aromatic groups) and demonstrate the ability to prepare nanotubular and nanoporous structures via templateless, surfactant-free electropolymerization in organic solvents (dichloromethane). For the majority of synthesized monomers, including a significant amount of water in the electropolymerization solvent leads to the formation of nanoporous membranes with tunable size and surface hydrophobicity. If water is not included in the electropolymerization solvent, most of the surfaces prepared are relatively smooth. Tests with different water contents show that the formation of nanoporous membranes pass through the formation of vertically aligned nanotubes and that the increase in water content induces an increase in the number of nanotubes while their diameter and height remain unchanged. An increase in surface hydrophobicity is observed with the formation of nanopores up to ≈300 nm in diameter, but as the nanopores further increase in diameter, the surfaces become more hydrophilic with an observed decrease in the water contact angle. These materials and the ease with which they can be fabricated are extremely interesting for applications in separation membranes, opto-electronic devices, as well as for sensors.

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

“…84,85 Very recently, we have studied the influence of water on the surface morphology of electrodeposited polymers from thieno-[3,4-b]thiophene derivatives. 86,87 It has been demonstrated that with a significant amount of water in dichloromethane (dichloromethane saturated with water vs commercial dichloromethane), the surface morphology is drastically changed, e.g., from densely packed spherical particles to nanoporous membrane structures (with pores of d ∼ 100−300 nm) 86 or from smooth or treelike surfaces to hollow spherical or coral-like structures. 87 This is likely due to the formation of a large amount gas bubbles (O 2 and H 2 ) during electropolymerization in the dichloromethane/water system.…”

Designing Tunable Omniphobic Surfaces by Controlling the Electropolymerization Sites of Carbazole‐Based Monomers

“…[33] The water content of the polymerization solvent also plays a huge part in the morphology of the resulting nanostructures, increasing their porosity. [34,35] The water indeed reacts during electropolymerization forming gas bubbles that can act as a softtemplate for the polymer deposition. It has been recently demonstrated that reverse micelles are formed in the electropolymerization solvent, and that these micelles also participate to the formation of a soft template, leading to porous nanostructures.…”

Templateless Electrodeposition of Conducting Polymer Nanotubes on Mesh Substrates

“…Indeed, the nanotube formation is highly affected by H 2 O content because it changes the amount of released O 2 and/or H 2 bubbles. Indeed, the influence of H 2 O was already studied in the literature, [ 29,31 ] for example, by adding different amount of H 2 O and it was shown that the increase in H 2 O can often increase the number of nanotubes or other porous structures. [ 31 ]…”

“…Very recently, by a judicious choice in monomer and H 2 O content, the templateless electropolymerization process in organic solvent such as dichloromethane (CH 2 Cl 2 ) has been proposed as an efficient method to prepare extremely well‐controlled porous nanostructures such as vertically aligned nanotubes. [ 26–33 ] Trace H 2 O naturally present in solution are responsible for the formation of gas bubbles (O 2 and/or H 2 ). The method does not require any acid or surfactant but the monomer has to play the role of the surfactant in stabilizing gas bubbles during electropolymerization.…”

“…In the first one, substituted monomers of the thieno[3,4‐ b ]thiophene family are selected for their capacity to form nanotubular structures. [ 30–33 ] Three substituents of different hydrophobicity are chosen: pyrene, perfluorobutyl (C 4 F 9 ), and perfluorooctyl (C 8 F 17 ) chains. In the second strategy, a thieno[3,4‐ b ]thiophene monomer with a functional hydroxyl group (OH) is first electropolymerized before to graft perfluorinated chains by simple esterification reaction.…”