Biomedical Engineering Reference
In-Depth Information
From an electrochemical point of view the properties such
as extended potential window, relatively high viscosity, ionic
conductivity, electrochemical, and thermal stability are important
when ILs are used in electrochemistry. Since ILs have quite broad
electrochemical windows combined with high stability [34, 35],
it is possible to use them at high potentials and to characterize
doping abilities of synthesized films of conducting polymers
(especially on the negative side of the potential scale). The relatively
low nucleophilicity of ILs is also an advantage. In the synthesis of
conducting polymers, the yield of polymerization is in some cases
enhanced due to higher viscosities of ILs than of conventional
solvents [51]. Table 3.1 summarizes some of the physical properties
of ILs used in electrochemistry.
3.3 ELECTROPOLYMERIZATION OF
CONDUCTING POLYMERS IN IONIC
LIQUIDS
Synthesis of conducting polymers is usually conducted in organic
solvents such as acetonitrile (ACN) or tetrahydrofuran (THF)
[41-43]. However, these solvents are highly volatile and toxic. First
attempts to use ILs for synthesis of conducting polymers were
made in the 1980s and the beginning of the 1990s. The commonly
known conducting polymers such as poly(para-phenylene) (PPP)
[44, 45], polypyrole (PPy) [46], polyaniline (PANI) [47], and
polythiophene (PTh) [48] were electrochemically polymerized in
chloroaluminate ILs. Because of several factors, such as moisture
sensitivity of chloroaluminates producing HCl that enhanced the
decomposition of the formed film and difficulties in processability
of the film, moisture-stable ILs based on PF
anions
were introduced. Up to date PTh, PPy, PEDOT, PANI, and PPP have
been synthesized in these ILs.
The synthesis of PPy in ILs was extensively studied by the
Wallace group [49, 50]. They used [BMIM][PF
-
, BF
-
, or Tf
N
-
6
4
2
] and [BMP][Tf
N]
6
2
in their polymerization studies. In the case of [BMIM][PF
], the
6
 
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