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 facile one-pot, microwave-assisted synthesis of novel functionalized arylenedioxythiophenes as promising building blocks for conjugated polymers with tuneable electronic properties is presented.
Controlling the surface structures of conducting polymers is extremely important for various applications not only because of their unique optoelectronic properties but also owing to the wetting properties of these materials. Using a templateless electropolymerization approach, we report the formation of porous polymer nanostructures from a series of 3,4-(1,2-phenylenedioxy)(PheDOT) derivatives with electronwithdrawing side groups (Cl, CN, CF 3 , SO 2 CH 3 ). In this templateless electropolymerization, trace water present in solution is sufficient to produce gas bubbles (O 2 and H 2 ) and, as a consequence, to form the porous nanostructures with a tendency to form nanotubes on the surface. We show that the substituents in PheDOT play an important role to control the porous nanostructures and, as a consequence, the surface hydrophobicity. Using 3,4-(1,3-propylenedioxy)type (ProDOT) derivative F 4 -BnDOT, the formation of densely packed nanofibers was demonstrated, and these are not a result of the presence of trace water. In this case, the surfaces are even more hydrophobic than for PheDOT-based polymers, displaying extremely high apparent water contact angles (q w = 138-1448) and strong water adhesion. Such surfaces from electropolymerized conducting polymers could be used in a number of technological applications, e.g. self-cleaning surfaces, micropatterning, water harvesting and microfluid systems.
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