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.
Here, with the aim of obtaining densely packed porous nanostructures of various shape using templateless electropolymerization in organic solvent (dichloromethane), original thieno[3,4-
b
]thiophene-based monomers with different substituents are studied. First of all, the adding of water in solution has a huge influence on the formation of porous structures because a much higher amount of gas (O
2
and/or H
2
) is released. Rigid substituents such as aromatic groups have a beneficial effect on the formation of nanotubular structures contrary to flexible ones such as alkyl chains. Special results are obtained with the pyrene substituent (Thieno-Pyr). With this monomer, coral-like structures are obtained. These structures are obtained by the formation first on long nanotubular structures and their sagging due to their weight. Then, the released gas is trapped inside these structures leading to huge craters. These exceptional surfaces could be used in the future in various potential applications such as in drug delivery, cell growth, sensors, optical devices or surface adhesion.
This article is part of the theme issue ‘Bioinspired materials and surfaces for green science and technology (part 2)’.
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