SYNTHESIS OF ORGANIC ELECTROACTIVE MATERIALS IN IONIC LIQUIDS - Electrochemical Nanofabrication: Principles and Applications - page 121

enhancement over the conventional organic solvents was connected
with the increased electrochemical stability of the film during
potential cycling and more distinct reduction peaks were observed.
Figure 3.2 shows cyclic voltammograms of PPy films made in
different ILs and propylene carbonate (PC). All the films are cycled
in PC/TBAPF electrolyte. It was found that films obtained in both

studied ILs are electrochemically more active than the films made
in PC. A possible explanation for the increased electrochemical
activity may be connected with the higher amount of dopant ions
in the films made in ILs than in PC/salt solution. Additionally
films obtained in ILs were observed to be smoother and more
compact when compared with films made in conventional organic
solvents. Fuchigami and coworkers studied the use of [EMIM][OTf ]
(OTf=CF

6

) in electrosynthesis of PPy [51]. Polymerization rate
as well as the doping level (determined by elemental analysis) was
improved when compared with the case when ACN was used as the
solvent. The electrochemical polymerization process was also more
reproducible in [EMIM][OTf ] than in organic solvents as indicated
by the smaller standard deviation of the thickness of the film
obtained in [EMIM][OTf ]. Recently Deepa et al. made morphological
studies of PPy films electropolymerized in [EMIM][OTf] confirming
the previous observations of decrease in polymer surface roughness
[52]. The enhancement in polymerization yield and rate in [EMIM]
[OTf ] may be explained by its high viscosity [53]. Since the diffusion
of the formed radicals and the oligomers from the electrode surface
is slower in highly viscous media, and therefore, the concentration
of the reaction products at the electrode interface is increased, the
material deposition is increased as well. A new interesting method
of PPy synthesis was presented by Han et al. where polyelectrolyte-
functionalized IL (PEFIL) has been used [54]. PEFIL (imidazolium
based) was functionalized with poly(styrenesulfonate). The reaction
was performed in aqueous solution of the monomer. The surface of
the working electrode was covered by highly viscous PEFIL, which
assisted the polymerization of PPy by donating anions. This method
provided the way for electrolyte free electrosynthesis of PPy films
with sufficient electroactivity.

SO

-

3 3