Synthesis and characterization of trifluoromethylated poly(ether-imidazole- imide)s based on unsymmetrical diamine bearing carbazole and imidazole chromophores in ionic liquids: Study of electrochemical properties by using nanocomposite electrode

Article abstract of DOI:10.1016/j.jfluchem.2012.06.011

A novel aromatic trifluoromethylated diamine containing various functional groups was synthesized and characterized by using different spectroscopic techniques. The diamine was polymerized with various dianhydrides in a green media of ionic liquid (IL) wi

Full text of DOI:10.1016/j.jfluchem.2012.06.011

Journal of Fluorine Chemistry 142 (2012) 29–40
Contents lists available at SciVerse ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
Synthesis and characterization of trifluoromethylated
poly(ether–imidazole–imide)s based on unsymmetrical diamine bearing
carbazole and imidazole chromophores in ionic liquids: Study of electrochemical
properties by using nanocomposite electrode
*
Mousa Ghaemy , Marjan Hassanzadeh, Mehdi Taghavi, Seyed Mojtaba Amini Nasab
Polymer Chemistry Research Laboratory, Department of Chemistry, University of Mazandaran, Babolsar 47416-95447, Islamic Republic of Iran
A R T I C L E I N F O
A B S T R A C T
Article history:
A novel aromatic trifluoromethylated diamine containing various functional groups was synthesized and
characterized by using different spectroscopic techniques. The diamine was polymerized with various
dianhydrides in a green media of ionic liquid (IL) without using NMP–pyridine–acetic anhydride. The
poly(ether–imidazole–imide) (PEII)s were obtained in good yields (80–96%) with moderate viscosity
(0.33–0.67 dL gꢀ1) in a shorter reaction time (10 h vs. 36 h) in IL. The resulting polymers were fully
characterized and their properties such as solubility, viscosity, crystallinity, thermal, photophysical, and
electrochemical behavior were investigated. They were amorphous and showed excellent solubility even
in common organic solvents, such as chloroform and m-cresol, with ability to form tough and flexible
films. The films were colorless and exhibited high optical transparency, with the UV cutoff wavelength in
the range 304–337 nm and the wavelength of 80% transparency in the range 375–400 nm. Furthermore,
they also possessed good thermal and thermo-oxidative stability with 10% weight loss temperatures
(T10%) in the range 441–528 8C in N2 atmosphere and in the range 382–494 8C in air. The glass transition
temperatures of all polyimides are in the range 204–302 8C.
Received 6 February 2012
Received in revised form 9 June 2012
Accepted 12 June 2012
Available online 26 June 2012
Keywords:
Ionic liquids
Trifluoromethylated polyimides
Solubility
Nanocomposite
Electrochemical oxidation
Thermal properties
Their electrochemical behavior was also studied by using adsorptive stripping cyclic voltammetry
and impedance spectroscopy on the multi-walled carbon nanotube-modified glassy carbon electrode.
ß 2012 Elsevier B.V. All rights reserved.
1. Introduction
resistance, and surface inertness [11–13]. During the past decade,
interests in these polymers have risen in response to increasing
Recently many organic synthesis and polycondensation
reactions were carried out in room temperature ionic liquids
(ILs) as an alternative to many volatile organic solvents [1–4].
There is a need in industry for the replacement of a large amount of
toxic solvents with eco-friendly and nonvolatile solvents for the
preparation of polyimides (PIs). Imidazolium based ILs have
attracted considerable commercial applications in phase transfer
catalysis, electrochemistry, extraction, polymerization, and as
substitutes for common volatile organic solvents [5–7]. The
‘‘green solvents’’ aspects of ILs are derived mainly from their
negligible vapor pressure, non-volatility and inflammability [8–
10]. Aromatic PIs constitute an important class of materials
because of their many desirable physicochemical and mechanical
characteristics, such as good thermal and hydrolytic stability,
excellent mechanical strength, low dielectric constant, wear
technological applications in a variety of fields such as aerospace,
automobile, and microelectronics. However, their applications
have been limited in some fields because of their insolubility in
common organic solvents and high melting points. Solubility of
the PIs has been targeted by several methods, such as introduction
of flexible linkage, bulky units in the polymer backbone, bulky
pendent substituents, or noncoplanar moieties. Among these
approaches, introduction of bulky pendants and heteroaromatic
rings into the polymer chains has provided not only enhanced
solubility but also good thermal stability and processability [14–
21]. There are reports of using imidazole and carbazole rings and
their derivatives into polymeric frameworks to improve the
solubility of the polymers, which have also been suggested as
promising photoconductive and photorefractive materials [22–
24]. PIs containing hexafluoroisopropylidene or trifluoromethyl
groups are of special interest due to enhanced solubility and
optical transparency together with a lower dielectric constant
which were attributed to low polarizability of the C–F bond and
increasing free volume. The trifluoromethylated PIs also provided
* Corresponding author. Tel.: +98 112 534 2353; fax: +98 112 534 2302.
E-mail address: ghaemy@umz.ac.ir (M. Ghaemy).
0022-1139/$ – see front matter ß 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jfluchem.2012.06.011

30
M. Ghaemy et al. / Journal of Fluorine Chemistry 142 (2012) 29–40
Scheme 1. Synthesis of target diamine.
other merits such as good thermal and low moisture absorption
[25–27].
shown in Scheme 1. Condensation of 4,40-dimethoxy benzyl with
aqueous HBr and glacial acetic acid was applied for the synthesis of
compound 1. The compound 2 was synthesized by nucleophilic
aromatic substitution reaction of 4,40-dihydroxy benzil with 2-
chloro-5-nitrobenzotrifluoride. The reaction between compound 2
and 9-ethyl-carbazole-2-carbaldehyde in ammonium acetate
which is a well known synthetic method for preparation of
imidazole ring was used to synthesize the compound 3. The
catalytic hydrogenation of dinitro groups in compound 3 into the
corresponding diamine was accomplished by using hydrazine
hydrate in ethanol in the presence of a catalytic amount of Pd/C.
The purity of all compounds was checked by thin-layer chroma-
tography using ethylacetate/n-hexane mixture. The structure of
diamine 4 was confirmed by elemental analysis, FT-IR, and 1H and
13C NMR spectroscopy. The FT-IR spectrum of compound 3 showed
absorption bands at 1546 and 1349 cmꢀ1 due to asymmetric and
symmetric –NO2 stretching vibrations. After reduction, absorption
peaks related to NO2 groups disappeared and new bands at 3478
and 3373 cmꢀ1 due to N–H stretching were observed. The 1H NMR
spectrum of diamine 4 in Fig. 1 and the assigned protons given in
the experimental section has confirmed that the nitro groups were
completely transformed into the amine groups by the high field
shift of the aromatic protons and by the characteristic resonance of
two different kind of protons: NH2 protons at 5.47 and 5.52 ppm
and N–H of imidazole ring at 12.5 ppm. The 13C NMR spectrum of
diamine 4 in Fig. 2 showed 32 different carbon atoms for the
aromatic segment and heterocyclic ring. The chemical shift in the
upfield region (14.23 and 37.56 ppm) is ascribed to the resonance
of aliphatic methyl group. Also, there are four quartet peaks
because of the heteronuclear 13C–19F coupling. The large quartet
centered at about 123 ppm is due to the –CF3 carbons. The one-
bond C–F coupling constant in this case is about 270 Hz. The CF3-
attached carbon also shows a clear quartet centered at about
122 ppm with a smaller coupling constant of about 32 Hz due to
two-bond C–F coupling. These quartet signals corroborate the
presence of CF3 group in the synthesized compounds. Thus, all the
spectroscopic data obtained by 13C NMR and DEPT techniques
were in good agreement with the expected chemical structures.
Carbon nanotubes (CNTs) with high stiffness and tensile
strength have received enormous attention for the composites
with desired mechanical properties [28], and also in electrochem-
istry mainly due to their electrocatalytic effects and ability to
promote electron transfer reactions [29]. The modification of
electrode substrates with CNTs for use in analytical sensing
provides better surface property and more enhanced sensitivity
due to excellent chemical and electrical properties of CNTs.
Electrochemical oxidation of polymers in various conditions can be
a pattern of their stability. The polymer stability is estimated by its
potential of oxidation. By using electrochemical studies, the
determinant bonds in the polymer structures, which are responsi-
ble for polymer oxidation, can be recognized and the ability of
different monomer structures on polymer stability can be
characterized [30–32].
In this paper, we wish to report a convenient and environmen-
tally benign green route for the synthesis of novel high-
performance PEIIs by using imidazolium-based ILs under one-
step classical heating conditions. Therefore, a new aromatic and
unsymmetrical diamine, 4,40-(((2-(9-ethyl-carbazol-2-yl)-1H-im-
idazole-4,5-diyl)bis(4,1-phenylene))bis
(oxy))bis(3-(trifluoro-
methyl)aniline), bearing polar CF3 groups, ether linkage, bulky
imidazole and carbazole rings was designed and successfully
synthesized. This diamine was used for the synthesis of novel PEIIs
in view of improving their solubility with outstanding thermal
stability. These collective functional groups of highly polar CF3
groups along with flexibility, unsymmetrical, and bulky pendant in
the polymer backbone were expected to decrease the regularity of
polymer chains, increasing the distance between the chains and
weaken the intermolecular interaction of the chains. Therefore, as
a result of higher barrier potential for free rotation, increasing
interaction with polar solvent molecules and presence of
chromophore would afford polymers with useful solubility,
thermal and photophysical properties.
2. Results and discussion
2.1. Synthesis and characterization of diamine (4)
2.2. Polymers synthesis and characterization
A new diamine, 4,40-(4,40-(2-(9-ethylcarbazol-2-yl)-1H-imid-
azole-4,5-diyl)bis(4,1 phenylene))bis(oxy)bis(3-(trifluoromethy-
l)aniline), was synthesized according to the synthetic route and
Polycondensation in NMP/Py/Ac2O, is one of the effective
methods for the synthesis of aromatic PIs. However, because of the
usage of such aggressive solvents, partial hydrolysis of formed

M. Ghaemy et al. / Journal of Fluorine Chemistry 142 (2012) 29–40
31
Fig. 1. 1H NMR spectrum of diamine (4) in DMSO-d6.
polymers during their isolation and purification complicates this
process as well. For the advancement of ecological safety and
improvement of technological ability of this process, IL solvents
based on the imidazolium cations were used as a reaction medium.
The reaction proceeded efficiently in ILs allowing PEII synthesis by
direct polycondensation of dianhydride and diamines without
using NMP, Ac2O and pyridine (Py). Room temperature ILs,
predominantly those based on substituted imidazolium cations
which can be prepared simply from the commercially available
starting materials, N-trimethylsilylimidazole and alkyl halides,
were used in this investigation [10,33]. Thus, different symmetrical
1,3-dialkylimidazolium ILs bearing Brꢀ, PFꢀ and BFꢀ anions,
polymers. In order to find out the effect of ILs nature on the yield
and viscosity of the polymer, the synthesis of PEII 1 was carried out
in different imidazolium type ILs at a reaction temperature. IL
needs to be liquid and thermally stable near the reaction
temperature and a good solvent for initial monomers and the
resulting polymers. These ILs were all very viscose liquids at room
temperature. Therefore, the choice of polycondensation tempera-
ture (130 8C) was being determined by the viscosity of the ILs and
solubility of the diamine 4 and the corresponding polymers.
Although PEII 1 was soluble in all used ILs, but as alkyl chain in IL
increased the yield and viscosity of the polymer decreased. This
may be due to the decrease of polarity of IL as a result of increase in
the alkyl chain which explains the lower mobility of polymer
chains in longer alkyl chain of ILs. The polymer PEII 1 with the
highest yield and viscosity was obtained when [1,3-(Pr)2im]Br was
4
6
shown in Table 1, were prepared and used as polycondensation
agent. These ILs are soluble in the polar solvents such as water and
methanol, which allowed the complete isolation of obtained
Fig. 2. 13C NMR spectra of diamine (4) in DMSO-d6: (A) DEPT and (B) normal.

32
M. Ghaemy et al. / Journal of Fluorine Chemistry 142 (2012) 29–40
Table 1
The influence of IL cation and anion upon yield and molecular weight (
h
inh) of PEII 1.
IL
a
Polymer
PEII 1
IL structure
Yield (%)
76
hinh
[1,3-Isopropyl2im]Br
[1,3-Propyl2im]Br
[1,3-Butyl2im]Br
[1,3-Pentyl2im]Br
[1,3-Hexyl2im]Br
[1,3-Heptyl2im]Br
[1,3-Butyl2im]BF4
[1,3-Butyl2im]PF6
0.52
0.67
0.64
0.55
0.44
0.43
0.41
0.33
PEII 1
PEII 1
PEII 1
PEII 1
PEII 1
PEII 1
PEII 1
96
89
83
79
81
68
64
a
Measured at a concentration of 0.5 g/dL in NMP at 25 8C.
used as the reaction media, as shown in Table 1, and this IL was also
selected for the synthesis of other PEIIs. As far as anions were
concerned, the best results were achieved in ILs with Brꢀ. The
optimum time of polycondensation was determined by measuring
the yield and viscosity of PEII 1 in the selected IL and temperature,
the results were shown in Fig. 3. Therefore all of the PEIIs (1–4)
were prepared in two different reaction conditions; in direct
polycondensation reactions by using NMP/Py/Ac2O and by using
only IL of [1,3-(Pr)2im]Br. The results in Table 2 demonstrated the
beneficial effect of using IL in the synthesis of PEIIs in addition to
other useful properties such as non-volatility and reusability of ILs.
Furthermore, removal of some chemicals (e.g. NMP, Py and Ac2O)
which are essential in conventional direct polycondensation and
also longer period of time (36 h vs. 10 h) increases the cost of
polymerization as well as the environmental pollution which all
together are the desired aspects for energy saving. The PEIIs were
obtained as light brown powders with good yields, 81–96% after
extraction with refluxing methanol for 24 h to remove low fraction
oligomers, and their inherent viscosities were in the range of 0.37–
0.67 dL gꢀ1 indicating medium molecular weights. The aforemen-
tioned results can serve as evidence that ILs are the effective
alternative to the previously used aggressive and toxic media.
Because of their nature the ILs have very low vapor pressure and
are characterized by the absence of strong acid or alkaline
Table 2
Product yields and solubility of PEII 1–PEII 5.
Code
Solvent
Yield (%)
hinh (dL/g)a
DMAc
DMF
NMP
DMSO
Py
DO
CHCl3
CH3CN
m-cresol
PEII 1
PEII 2
PEII 3
PEII 4
PEII 5
PEII 1a
PEII 2a
PEII 3a
PEII 4a
PEII 5a
96
94
91
81
94
91
88
84
80
90
0.67
0.51
0.65
0.37
0.67
0.58
0.46
0.61
0.33
0.55
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
+
ꢁ
ꢁ
ꢁ
+
ꢁ
–
+
++
++
++
++
+
+
–
++
+
ꢁ
–
++
++
–
ꢁ
ꢁ
–
++
++
ꢁ
+
–
++
+
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
–
++
+
ꢁ
–
++
++
++
++
ꢁ
ꢁ
++
++
++, soluble at room temperature; +, soluble on heating at 60 8C; ꢁ, partially soluble on heating at 60 8C; –, insoluble on heating at 60 8C. PEII 1–PEII 5 and PEII 1a–PEII 5a were
synthesized in IL and NMP/Ac2O/Py media, respectively.
a
Measured at a polymer concentration of 0.5 g/dL in NMP at 30 8C.

M. Ghaemy et al. / Journal of Fluorine Chemistry 142 (2012) 29–40
33
Fig. 3. Optimum conditions for the synthesis of PEII 1 in IL.
properties; therefore, the risk of polymer’s hydrolysis at the
isolation along with the necessity of its thorough purification are
no longer relevant. The polymer structures were confirmed by
elemental analysis, FT-IR and 1H NMR spectroscopic techniques.
The characteristic absorption bands of the five-membered imide
ring appeared at 1785 and 1723 cmꢀ1, corresponding to asym-
metric and symmetric C55O stretching, at 1375 cmꢀ1 related to C–
N stretching, and at 1094 and 763 cmꢀ1 because of imide ring
deformation. The 1H NMR spectrum of PEII 1 in DMSO-d6, Fig. 4,
showed peaks of aromatic protons at 7.06–8.85 ppm and N–H
imidazole proton at 12.61 ppm, all of which were well assigned to
the supposed chemical structure and no peaks attributable to amic
acids were detected. The integration ratio of these peaks also
agreed with the structure. The elemental analysis values generally
agreed with the calculated values for the proposed structures of
polymers.
2.3. X-ray diffraction of the PEIIs
The crystallinity of the prepared PEIIs as powder samples was
examined by WAXD analysis with graphite-monochromatized
Fig. 4. 1H NMR spectrum of PEII 1 in DMSO-d6.
Fig. 5. X-ray diffraction patterns of PEIIs.

34
M. Ghaemy et al. / Journal of Fluorine Chemistry 142 (2012) 29–40
Fig. 6. UV–vis and fluorescence spectrum of diamine (4) and PEII 1–PEII 5.
Table 3
Optical properties data of PEII 1–PEII 5.
Polymer
labs (nm)a
lem (nm)a
labs (nm)a
lem (nm)a
Ff (%)b
Film thickness (
m
m)
l0 (nm)c
Transparency (%)d
PEII 1
PEII 2
PEII 3
PEII 4
PEII 5
321
327
308
301
308
455
470
446
431
443
324
333
315
302
313
463
474
451
433
447
0.10
0.12
0.09
0.25
0.15
51
60
57
55
51
326
337
321
304
318
87
85
86
87
88
Polymer concentration of 0.20 g/dL in NMP.
a
UV–vis and fluorescence spectra of the PEIIs in solution (a) and film (b), respectively.
b
c
Fluorescence quantum yield relative to 10ꢀ5 M quinine sulfate in 1 N H2SO4 (aq) (
Ff = 0.55) as a standard.
Cut-off wavelength.
d
Transparency at 400 nm.
Cu K
a
radiation and with 2
u
ranging from 0 to 508. The WAXD
other PEIIs. It should be noted that good solubility in low-boiling
point solvents is critical for preparing objects at a relatively low
processing temperature which is desirable for advanced micro-
electronics manufacturing applications.
patterns of these polymers showed an amorphous nature and the
results were shown in Fig. 5. The amorphous nature of the PEIIs can
be attributed to their unsymmetrical structural units and the bulky
CF3 groups, which reduced the intra- and interpolymer chain
interactions, resulting in loose polymer chain packaging and
aggregates. Therefore, the amorphous nature of the resulting PEIIs
would endow them a good solubility.
2.5. Photophysical properties
The UV–vis absorption and fluorescence spectra of diamine
(2 ꢂ 10ꢀ5 M) and PEIIs (0.2 g/dL) in dilute NMP solution were
shown in Fig. 6 and the extracted data were tabulated in Table 3.
The diamine and PEIIs exhibited strong UV–vis absorption bands
with maxima at 302 nm and in the range of 301–327 nm,
2.4. Solubility
The solubility of the resulting PEIIs was investigated in 5% (w/v)
in different organic solvents, and the results were tabulated in
Table 2. These polymers exhibited good solubility behavior in polar
aprotic solvents such as NMP, N,N-dimethylacetamide (DMAc),
N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and
even in less polar solvents like pyridine and m-cresol, but showed
poorer solubility in dioxane (DO) and chloroform (CHCl3) due to
the low value of dielectric constant of these solvents. The good
solubility of these PEIIs might be attributed to the unsymmetrical
structure of the diamine, introduction of the flexible ether linkages
and the bulky pendant of carbazole and CF3 groups in the polymer
backbone which decreased the interaction between polymer
chains and loosen their packing efficiency, resulting in the increase
of free volume in the polymers and easier diffusion of solvent
molecules. On the other hand, the unsymmetrical structure could
result in the random orientation in consecutive repeating units
along the polymer main chain, which are naturally different in
rigidity and degree of bending and lead to backbone randomiza-
tion. This backbone randomization should also make a contribu-
tion to the high solubility of these polymers. In addition, the
solubility varies depending upon the dianhydride used. PEIIs
synthesized from aliphatic dianhydride (PEII 4) exhibited good
solubility behavior in Py and m-cresol in comparison with the
respectively, assignable mainly to the
transitions. A slightly red shift is observed in the spectra of PEIIs
p–p* and also n–p*
Fig. 7. Transmission UV–vis absorption spectra of PEII 1–PEII 5 films.

M. Ghaemy et al. / Journal of Fluorine Chemistry 142 (2012) 29–40
35
Fig. 9. TGA curves of PEII 1–PEII 5 under N2 and air at 10 8C/min.
Fig. 8. DSC curves of PEII 1–PEII 5 under N2 at 10 8C/min.
increasing flexibility of the polymers backbone. PEII 4, obtained
from bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride,
showed the lowest Tg because of the presence of flexible ether
linkage between the phthalimide units. PEII 1, derived from
pyromellitic dianhydride, exhibited the highest Tg because of
having rigid polymer backbone. The Tg values of these polymers are
lower than analogous PEIIs (Tg, 240–306 8C, which suggests that
the nonlinear structure in the polymer backbone decreased the
intermolecular interactions in these polymers, thus led to lower Tg
values [35]. Thermal stability of PEIIs was evaluated by TGA in N2
and air atmosphere at a heating rate 10 8C/min and the curves are
shown in Fig. 9. The T10% values of the PEIIs were in the range 441–
528 and 382–494 8C in N2 and air, respectively, and the amount of
residue at 800 8C in N2 was up to 60%. As can be seen in Table 4,
thermal stability of these polymers based on the T10% values and
the amount of remained char at 800 8C is higher in N2 atmosphere
than those obtained in air. This difference can be due to thermal
oxidation of the polymer sample at high temperature in air which
resulted in thermal breakdown of polymer chains. It is concluded
from Table 4 data that PEIIs with the aliphatic unit in the backbone
such as PEII 4 and PEII 5 (or PEII 4a and PEII 5a) exhibited higher
difference in thermal stability, or lower thermal stability, when
comparing T10% in air and in N2. Comparing the T10% of polymers in
Table 4, it is observed that introduction of aliphatic trifluoromethyl
decrease thermal stability of polymer at high temperatures in N2 or
in air. According to the results reported by other researchers [19],
in comparison with the absorption spectrum of the diamine which
can be due to expansion of conjugation system. Figs. 6a and 7
depict the UV–vis absorption and transmittance spectra of
trifluoromethylated PEIIs films (50
the data were listed in Table 3. The cut-off wavelength (
m
m thick), respectively, and
0) values
l
of the PEII films ranged from 302 nm to 333 nm, and the optical
transmittance values at 400 nm are higher than 80%. These PEIIs
with CF3 pendants have smaller l0 values and higher optical
transparency. These polymers also show color from pale yellow to
colorless in nature. A possible explanation is that the bulky and
strong electron-withdrawing CF3 group in the diamine structure is
presumably effective in decreasing the intermolecular and
intramolecular charge–transfer complexes (CTC) between polymer
chains as a result of steric hindrance and the inductive effect. The
maximum emission (lmax(em)) of the diamine in NMP solution
(2 ꢂ 10ꢀ5 mol Lꢀ1) was observed at 449 nm. The Fluorescence
spectra of PEIIs in NMP solutions (0.2 g/dL) and in solid state
exhibited high-intensity maximum around 470 nm for aromatic
PEIIs (PEII 2) and 432 nm for the aliphatic PEII (PEII 4), respectively.
To measure the fluorescence quantum yields (
solutions (0.2 g/dL) in NMP were prepared. A 0.1 N solution of
quinine in H2SO4 ( f = 0.55) was used as reference according to the
literature [34]. The f values were 0.35 for the diamine, 0.25 for the
Ff), dilute polymer
F
F
aliphatic PEII and 0.09–0.12 for the aromatic PEIIs. The blue shift
and higher fluorescence quantum yield of the aliphatic PEII 4
compared with the aromatic PEIIs could be attributed to reduced
conjugation and capability of charge–transfer complex formation
by the aliphatic dianhydride with the electron-donating diamine
moiety in comparison to the stronger electron-accepting aromatic
dianhydrides.
Table 4
Thermal properties of PEII 1–PEII 5.
Polymer
Tg (8C)a
T10% (8C)b
T10% (8C)c
Char yieldd
LOI (%)e
PEII 1
PEII 2
PEII 3
PEII 4
PEII 5
PEII 1a
PEII 2a
PEII 3a
PEII 4a
PEII 5a
302
272
290
204
253
294
269
288
204
250
528
495
499
441
472
511
469
477
440
463
494
435
472
382
415
486
418
459
382
402
67
50
61
32
43
61
41
52
32
39
44
37
42
30
35
42
34
38
30
33
2.6. Thermal properties
DSC and TGA were applied to evaluate the thermal properties of
the PEIIs. The DSC and TGA curves of the PEIIs are shown in Figs. 8
and 9, respectively, and thermal analysis data from the original
curves were summarized in Table 4. The absence of melting peak in
DSC thermograms and the results from X-ray patterns supported
the generally amorphous nature of the PEIIs. The amorphous
nature of these polymers can be attributed to their asymmetric
structural unit and bulky pendent group which decreased the intra
and inter-chain interactions, resulting in loose polymer chain
packaging and aggregates. The Tg values of the PEIIs are in the
range of 204–302 8C. As we expected, the Tg values depended on
the structure of the dianhydride component and decreased with
PEII 1–PEII 5 and PEII 1a–PEII 5a were synthesized in IL and NMP/Py/Ac2O media,
respectively.
a
Tg was recorded in DSC at 10 8C/min in N2.
Temperature at which 10% weight loss was recorded by TGA in N2.
b
c
Temperature at which 10% weight loss was recorded by TGA in air.
d
Percentage weight of char remained of TGA analysis at 800 8C in N2.
Limiting oxygen index percent evaluating at char yield 800 8C.
e

36
M. Ghaemy et al. / Journal of Fluorine Chemistry 142 (2012) 29–40
Fig. 10. SEM image of a graphite layer (a), graphite layer with MWCNTs (b) and PEII 1-modified carbon nanotubes paste electrode (c).
polyimides containing trifluoromethyl showed higher or compa-
rable thermal stability than non-fluorinated polyimides. Char yield
can be used as criteria for evaluating limiting oxygen index (LOI) of
the polymers in accordance with Van Krevelen and Hoftyzer
equation [36]. LOI = 17.5 + 0.4 CR where CR = char yield. The char
yield determines the flame retardency of a polymer. If it has a
higher retardency, then it has greater tendency to self-extinguish a
flame. The T10 values in N2 and air and the LOI values calculated
based on their char yields at 800 8C were given in Table 4. The data
from thermal analysis indicated that the resulting polymers
exhibited fairly high thermal stability. This explains that introduc-
tion of strong electron negativity of –CF3 groups might have
enhanced the polarity of the polymer, which should restrict the
movement of polymer-link and led to better thermal stability
[37,38].
2.7. SEM characterization
Fig. 10 shows typical SEM images of carbon paste electrode
(CPE), multiwall carbon nanotubes paste electrode (MWCNTPE)
and MWCNTPE modified with PEIIs. It can be seen that on the
surface of CPE (Fig. 10a), the layer of irregular and isolated flakes of
graphite powder was present. After MWCNTs added to the carbon
paste matrix, it can be seen in Fig. 10b that MWCNTs were
distributed on the electrode with special three-dimensional
structure, indicating that the MWCNTs were successfully modified
Fig. 11. Cyclic voltammograms of the monomer, PEII 1 with modified CPE (a and b), cyclic voltammograms of the PEII 2 without and with modified CPE (c and d) at a scan rate
of 100 mV/s.

M. Ghaemy et al. / Journal of Fluorine Chemistry 142 (2012) 29–40
37
3. Conclusions
A novel trifluoromethyl-substituted diamine bearing imidazole
and carbazole rings with an asymmetric molecular structure, 4,40-
(4,40-(2-(9-ethyl-carbazol-2-yl)-1H-imidazole-4,5-diyl)bis(4,1-
phenylene))bis(oxy) bis(3-(trifluoromethyl)aniline), has been suc-
cessfully synthesized from readily available reagents. The diamine
was polymerized with several aromatic and aliphatic dianhydrides
via a conventional two-stage method including poly(amic acid)
formation and chemical imidization in NMP solvent and a single-
stage method in IL without using chemical imidization agents. In
general, the results demonstrated the beneficial effects of using IL
media in the synthesis of these PEIIs, such as good yields and
moderate viscosity, shorter period of reaction time, not being
needed to remove some chemicals (e.g. NMP, Py and Ac2O), non-
volatility and reusability, as well as the environmental pollution.
Because of the presence of polar CF3 and aryl ether groups along
the polymer backbone together with the asymmetric structure of
the repeating unit, these amorphous polymers exhibited excellent
solubility in many organic solvents and could be solution cast into
transparent tough films. They also showed high thermal stability
with high optical transparency. Therefore, these PEIIs may be
considered as promising processable high temperature materials
for applications in microelectronic and optical devices.
Fig. 12. Nyquist diagrams of the multiwall carbon nanotubes paste electrode
modified with monomer (a) and PEII 1 (b) in PBS (pH 7.0).
on the MWCNTPE. Also, it can be clearly seen in Fig. 10c that the
polymer has been dispersed in modified electrode.
4. Experimental
2.8. Electrochemical investigation
4.1. Materials
The main object of this investigation was to study the
electrochemical behavior of these PEIIs. Imidazol group can be
oxidized at a suitable potential in electrochemical process [39].
Fig. 11A(a) shows cyclic voltammogram of multiwall carbon
paste electrode modified with the diamine. An oxidation peak at
potential ꢃ700 mV can be seen with low current which is
related to the imidazol ring in the diamine structure. Fig. 11A(b)
shows cyclic voltammogram of the polymer (PEII 1) paste with
carbon used as electrode. As can be seen in this figure, there is a
large oxidation current which can be attributed to the oxidation
of imidazole rings in the polymer chains. The effect of MWCNTs
on the oxidation peak current and peak potential was studied
and the cyclic voltammograms for the polymer–carbon paste
electrode were compared, in Fig. 11B, with the voltammogram
of the electrode paste with MWCNT. As can be seen in these
figures, addition of MWCNTs into the polymer carbon paste
matrix increases the oxidation peak current and decreases the
potential. This phenomenon is related to the unique electro-
chemical properties of CNTs with polymer and carbon paste as
electrode [40,41]. MWCNTs will definitely improve the char-
acteristics of electrochemical oxidation of polymer. Electro-
chemical impedance spectroscopy (EIS) was also employed to
investigate the oxidation of the diamine and PEIIs at the surface
of carbon nanotubes paste electrode. Fig. 12(a) and (b) compares
the Nyquist diagram of the multiwall carbon nanotubes paste
electrode modified with diamine and PEII 1 in phosphate buffer
solution (PBS) (pH = 7.0), respectively. Under these conditions,
charge transfer resistance (Rct) is the only element that has a
simple physical meaning describing how fast the rate of charge
transfer is during the oxidation of imidazol groups. It is known
that the amount of Rct has reverse relationship with electro-
chemical activity of the species. In fact, with increasing
electrochemical oxidation peak current, the value of Rct
decreased [41]. The Rct values for the diamine and PEIIs were
All starting materials and reagents were purchased from either
Merck or Fluka (Germany) through a local agency. N-methyl-2-
pyrrolidinone (NMP) and pyridine (Py) were purified by distillation
˚
under reduced pressure over calcium hydride and stored over 4 A
molecular sieves. Dianhydrides such as 3,30,4,40-benzophenone
tetracarboxylic dianhydride, pyromellitic dianhydride, 4,40-oxy-
diphthalic anhydride and bicyclo[2.2.2]oct-7-ene-2, 3, 5, 6-
tetracarboxylic dianhydride were dried in a vacuum oven at
110 8C for 5 h. Phosphate buffer (sodium dihydrogen phosphate
and disodum monohydrogen phosphate plus sodium hydroxide,
0.1 mol Lꢀ1) solution with pH = 7.0 value was used. Spectrally
graphite powder (particle size <50
m
m), multiwall carbon
m)),
nanotubes (>90%, MWCNTs, d ꢂ l = (70–90 nm) ꢂ (5–9
m
and high viscosity paraffin (d = 0.88 kg/L) were purchased (Fluka)
and used for preparation of carbon paste electrodes.
4.2. Measurements
Proton and carbon nuclear magnetic resonance (1H NMR and
13C NMR) spectra were recorded on a 400 MHz Bruker (Ettlingen,
Germany) instrument using DMSO-d6 as solvent and tetramethyl
silane as an internal standard. Elemental analyses performed by a
CHN-600 Leco elemental analyzer. Melting point (uncorrected)
was measured with a Barnstead Electrothermal engineering LTD
9200 apparatus. Inherent viscosities (at a concentration of 0.5 g/
dL) were measured with an Ubbelohde suspended-level viscome-
ter at 25 8C using NMP as solvent. Qualitative solubility was
determined using 0.05 g of the polymer in 0.5 mL of solvent.
Thermogravimetric analysis (TGA) was performed with the DuPont
Instruments (TGA 951) analyzer well equipped with a PC at a
heating rate of 10 8C/min under N2 and air atmosphere (5, 10, 15
and 20 8C/min) and in the temperature range of 25–650 8C.
Differential scanning calorimeter (DSC) was recorded on a Perkin
Elmer pyris 6 DSC under nitrogen atmosphere at a heating rate of
10 8C/min. Glass-transition temperatures (Tg) values were read at
the middle of the transition in heat capacity and were taken from
the second heating scan after cooling from 350 8C at a cooling rate
found 110 K
V and 95 KV (Fig. 12 curves (a) and (b)),
respectively. It is interesting to note that the result obtained
with EIS is very similar to those obtained from cyclic
voltammetry.

38
M. Ghaemy et al. / Journal of Fluorine Chemistry 142 (2012) 29–40
of 10 8C/min. Ultraviolet–visible and fluorescence emission spectra
were recorded on a Cecil 5503 (Cecil Instruments, Cambridge, UK)
and Perkin-Elmer LS-3B spectrophotometers (Norwalk, CT, USA)
(slit width = 2 nm), respectively, using a dilute polymer solution
(0.20 g/dL) in DMSO. X-ray powder diffraction patterns were
solution. After 30 min of stirring at room temperature, the
mixture was heated at 110 8C for 6 h and then was poured in
100 mL distilled water. The yellow precipitate was filtered off and
dried in a vacuum oven at 80 8C. Yield: 93% (2.9 g) and m. p: 157–
160 8C.
recorded by an X-ray diffractometer (GBC MMA instrument) with
˚
FT-IR (KBr) at cmꢀ1: 3045 (aromatic C–H); 1621 (C55O); 1482
(C55C); 1534, 1353 (NO2); 1268 (C–O) stretching. 1H NMR
Be-filtered Cu K (1.5418 A) operating at 35.4 kV and 28 mA. The 2
u
scanning range was set between 48 and 508 at a scan rate of 0.058/s.
Cyclic voltammetry (CV) was performed in an analytical system,
micro-Autolab, potentiostat/galvanostat connected to a three-
electrode cell, Metrohm Model 663 VA stand, linked with a
computer (Pentium IV, 2.67 GHz) and with micro-Autolab
software. The prepared electrodes with CNTs and polymers were
characterized by scanning electron microscopy (SEM; Seron Tech.
AIS 2100). All the voltammetric measurements were performed
using an Autolab PGSTAT 302N, potentiostat/galvanostat (Utrecht,
The Netherlands) connected to a three-electrode cell, Metrohm
(400 MHz, DMSO-d6,): d 7.41 (d, 4H, Ar-H, J = 8.0 Hz), 7.46 (d,
2H, Ar-H, J = 8.0 Hz), 8.08 (d, 4H, Ar-H, J = 8.0 Hz), 8.54 (dd, 2H, Ar-
H, J = 8.0 Hz), 8.57 (d, 2H, Ar-H, J = 2.8 Hz).
4.4.3. 2-(4,5-bis(4-(4-nitro-2-(trifluoromethyl)phenoxy)phenyl)-1H-
imidazol-2-yl)-9-ethyl carbazole (3)
Into a 100 mL round-bottomed two-necked flask equipped with
a condenser, a magnetic stirring bar and a nitrogen gas inlet tube, a
mixture of 9-ethyl-carbazole-2-carbaldehyde (1.11 g, 0.005 mol),
compound
2 (3.1 g, 0.005 mol), ammonium acetate (2.7 g,
(Herisau, Switzerland) Model 663 VA stand, linked with
a
0.035 mol), and glacial acetic acid (25 mL) was refluxed for 14 h.
Upon cooling, the yellow precipitate was collected by filtration and
washed with a mixture of ethanol/water (50/50, v/v) and dried in a
vacuum oven at 80 8C. Yield: 91% (3.75 g) and m. p.: 170–173 8C.
FT-IR (KBr) at cmꢀ1: 3473 (NH, imidazole ring); 3062 (aromatic
C–H); 2904 (aliphatic C–H); 1612 (C55N); 1586 (C55C), 1546, 1349
computer (Pentium IV, 1200 MHz) and with Autolab software. A
platinum wire was used as the auxiliary electrode. Modified
multiwall carbon nanotubes paste electrode (MWCNTPE) and Ag/
AgCl/KClsat were used as the working and reference electrodes,
respectively. For impedance measurements, a frequency range of
100 kHz to 0.1 Hz was employed. The AC voltage amplitude used
was 5 mV, and the equilibrium time was 10 min. The electrode
prepared with carbon nanotubes was characterized by scanning
electron microscopy (SEM) (Seron Tech. AIS 2100). A digital pH/
mV-meter (Metrohm model 710) was applied for pH measure-
ments.
(NO2); 1278 (C–N), 1237 (C–O–C). 1H NMR (400 MHz, DMSO-d6,):
d
1.36 (t, 3H, CH3), 4.50 (q, 2H, CH2), 7.19 (d, 2H, Ar-H, J = 8.0 Hz),
7.23 (d, 2H, Ar-H, J = 8.0 Hz), 7.27 (t, 1H, Ar-H, J = 8.0 Hz), 7.36 (d,
2H, Ar-H, J = 8.0 Hz), 7.50 (t, 1H, Ar-H, J = 8.0 Hz), 7.66 (d, 2H, Ar-H,
J = 8.0 Hz), 7.73 (d, 2H, Ar-H, J = 8.0 Hz), 7.77 (d, 2H, Ar-H,
J = 8.0 Hz), 8.19 (d, 1H, Ar-H, J = 8.0 Hz), 8.24 (dd, 1H, Ar-H,
J = 8.0 Hz), 8.48 (d, 2H, Ar-H, J = 2.8 Hz), 8.55 (dd, 2H, Ar-H,
J = 8.0 Hz), 8.87 (d, 1H, Ar-H, J = 1.6 Hz), 12.57 (s, 1H, N–H
imidazole ring). Anal. Calcd. for C43H27N5O6F6 (823 g/mol): C,
62.69%; H, 3.28%; N, 8.50%. Found: C, 62.66%; H, 3.30%; N, 8.50%.
4.3. Ionic liquids synthesis
All room temperature ILs were prepared according to the
procedures reported in the literatures [10,33]. The structure of the
prepared ILs was given in Table 1, and they were all very viscose
liquids at room temperature.
4.4.4. 4,40-(4,40-(2-(9-ethylcarbazol-2-yl)-1H-imidazole-4,5-
diyl)bis(4,1-phenylene)) bis(oxy)bis(3-(trifluoromethyl) aniline) (4)
Into a 100 mL round-bottomed two-necked flask equipped with
4.4. Monomer synthesis
a magnete stirring bar, a mixture of compound 3 (4.10 g,
0.005 mol) and Pd/C (0.1 g, 10%) were dispersed in 50 mL ethanol.
The suspension was heated to reflux, and then 6 mL hydrazine
monohydrate was added slowly to the mixture. After a further 8 h
of reflux, the solution was filtered hot to remove Pd/C, and the
filtrate was cooled to precipitate white crystals. The product was
collected by filtration and dried in a vacuum oven at 80 8C. Yield:
86% (3.26 g) and m.p.: 155–157 8C.
The following synthetic steps were used to synthesis the target
diamine, as outlined in Scheme 1.
4.4.1. Synthesis of 4,40-dihydroxy benzyl (1)
Into a 100 mL round-bottomed two-necked flask equipped with
a magnetic stirrer bar and a reflux condenser, 4,40-dimethox-
ybenzil (2 g, 0.0075 mmol), aqueous HBr (15 mL, 48%) and glacial
acetic acid (15 mL) were placed. The reaction mixture was refluxed
for 24 h, after cooling to room temperature, was poured into
100 mL water. Ethyl acetate was added to the mixture to give two
phases of which the organic phase containing the product was
separated and dried over magnesium sulfate for 12 h. The solvent
was removed under reduced pressure and the obtained yellow
precipitate was washed thoroughly with water and then dried in a
vacuum oven at 80 8C. Yield: 94% (1.7 g) and m.p.: 229–231 8C. FT-
IR (KBr) at cmꢀ1: 3400 (OH phenol), 3045 (C–H aromatic), 1646
FT-IR (KBr) at cmꢀ1: 3478, 3373 (NH2), 3462 (N–H imidazole
ring), 3051 (C–H aromatic), 2912 (aliphatic C–H); 1628 (C55N),
1597 (C55C), 1286 (C–N) and 1214 (C–O–C). 1H NMR (400 MHz,
DMSO-d6,):
d 1.35 (t, 3H, CH3), 4.47 (q, 2H, CH2), 5.47 (s, 2H, NH2),
5.52 (s, 2H, NH2), 6.82–6.99 (m, 10H, Ar-H), 7.25 (t, 1H, Ar-H), 7.47
(t, 1H, Ar-H), 7.49 (d, 2H, Ar-H, J = 8.0 Hz), 7.56 (d, 2H, Ar-H,
J = 8.0 Hz), 7.64 (d, 1H, Ar-H, J = 8.0 Hz), 7.70 (d, 1H, Ar-H,
J = 8.0 Hz), 8.15 (d, 1H, Ar-H, J = 8.0 Hz), 8.21 (dd, 1H, Ar-H,
J = 8.4 Hz), 8.82 (d, 1H, Ar-H, J = 1.6 Hz), 12.51 (s, 1H, N-H imidazole
ring). 13C NMR (400 MHz, DMSO-d6,
d): 1 (14.23), 2 (37.56), 3
(C55O), 1576 (C55C), 1223 (C–O). 1H NMR (400 MHz, DMSO-d6,):
d
(109.71), 4 (109.83), 5 (111.16), 6 (115.51), 7 (115.97), 8 (116.36,
117.00, 117.08 and 117.58), 9 (119.09), 10 (119.59), 11 (120.71), 12
(121.68, 121.98, 122.09 and 122.26), 13 (122.70, 125.41, 125.42
and 128.63), 14 (122.73), 15 (123.57), 16 (123.98), 17 (124.55), 18
(126.03), 19 (126.49), 20 (127.04), 21 (128.83), 22 (130.37), 23
(130.46), 24 (131.90), 25 (136.42), 26 (139.92), 27 (140.49), 28
(142.32), 29 (142.96), 30 (146.19, 146.54 and 146.90), 31 (157.47),
6.91–6.95 (d, 4H, J = 8.0 Hz), 7.73–7.77 (d, 4H, J = 8.0 Hz), 10.84 (s,
2H).
4.4.2. Synthesis of 1, 2-bis(4-(4-nitro-2-
(trifluoromethyl)phenoxy)phenyl)ethane-1,2-dione (2)
Into a 100 mL round-bottomed two-necked flask equipped
with a magnetic stirrer bar and a reflux condenser, 4,40-dihydroxy
benzil (1.21 g, 0.005 mol) and 1-chloro-4-nitro-2-(trifluoro-
methyl)benzene (2.25 g, 0.01 mol) were dissolved in 10 mL DMAc,
and potassium carbonate (1.38 g, 0.01 mol) was added to the
32 (158.49). DEPT Technique (400 MHz, DMSO-d6, d): 1 (14.22), 2
(37.56), 3 (109.71), 4 (109.84), 5 (111.15), 7 (115.97), 8 (116.35,
116.99, 117.08 and 117.58), 9 (119.09), 10 (119.59), 11 (120.71), 15
(123.58), 16 (123.99), 19 (126.49), 21 (128.83), 22 (130.37), 24

M. Ghaemy et al. / Journal of Fluorine Chemistry 142 (2012) 29–40
39
Scheme 2. Polycondensation reactions of the diamine with different dianhydrides.
(131.90). Anal. Calcd. for C43H31N5O2F6 (763 g/mol): C, 67.62%; H,
4.06%; N, 9.17%. Found: C, 67.59%; H, 4.10%; N, 9.16%.
4.5.2.1. PEII 1. 96% yield, FT-IR (KBr, cmꢀ1): 3435 (NH imidazole),
3072 (C–H aromatic), 1781, 1722 (C55O imide), 1608 (C55N
imidazole), 1475 (C55C), 1370 (C–N) and 1250 (C–O). 1H NMR
4.5. Polymer synthesis
(DMSO-d6): d 1.36 (t, 3H, CH3), 4.48 (q, 2H, CH2), 7.06–8.84 (m,
23H, Ar-H), 12.61 (s, 1H, N–H imidazole ring). Anal. Calcd. (%) for
(C53H29F6N5O6)n: C, 67.30; H, 3.07; N, 7.41. Found: C, 67.22; H,
3.15; N, 7.39.
4.5.1. Method I: direct polycondensation using NMP/Py/Ac2O
The following general procedure was used for the preparation
of all PEIIs. A 100 mL three-necked round-bottomed flask equipped
with a condenser, a magnetic stirrer bar, a nitrogen gas inlet tube
and a calcium chloride drying tube was charged with 1 mmol
(0.51 g) diamine and 10 mL dry NMP and the mixture was stirred at
4.5.2.2. PEII 2. 94% yield, FT-IR (KBr, cmꢀ1): 3447 (NH imidazole),
3052 (C–H aromatic), 1782, 1725 (C55O imide), 1605 (C55N
imidazole), 1483 (C55C), 1372 (C–N) and 1239 (C–O). 1H NMR
room temperature for 0.5 h. Thereafter, 1 mmol of
a
dried
(DMSO-d6): d 1.42 (t, 3H, CH3), 4.51 (q, 2H, CH2), 7.26–8.93 (m,
dianhydride was added and the mixture was stirred at room
temperature for 24 h, forming a viscous solution of poly(amic acid)
(PAA) in NMP. The chemical imidization of PAA was carried out by
adding 3 mL of a mixture of acetic anhydride/pyridine (6/4, v/v)
into the solution while stirring at room temperature for 1 h. The
mixture was then stirred at 130 8C for 12 h to yield a homogeneous
polymer solution, which was poured slowly into methanol to yield
a precipitate that was collected by filtration, washed thoroughly
with hot methanol and dried at 80 8C in a vacuum oven overnight.
The yields were in the range of 80–91%.
27H, Ar-H), 12.75 (s, 1H, N–H imidazole ring). Anal. Calcd. (%) for
(C60H33F6N5O7)n: C, 68.64; H, 3.15; N, 6.67. Found: C, 68.60; H,
3.19; N, 6.66.
4.5.2.3. PEII 3. 91% yield, FT-IR (KBr, cmꢀ1): 3448 (NH imidazole),
3056 (C–H aromatic), 1784, 1725 (C55O imide), 1603 (C55N
imidazole), 1498 (C55C), 1370 (C–N) and 1248 (C–O). 1H NMR
(DMSO-d6):
d 1.31 (t, 3H, CH3), 4.44 (q, 2H, CH2), 7.07–8.57 (m,
27H, Ar-H), 12.58 (s, 1H, N–H imidazole ring). Anal. Calcd. (%) for
(C59H33F6N5O7)n: C, 68.27; H, 3.18; N, 6.75. Found: C, 68.26; H,
3.19; N, 6.73.
4.5.2. Method II: direct polycondensation using ILs
The following general procedure, as illustrated in Scheme 2, was
used for the preparation of PEIIs from the diamine and various
aliphatic and aromatic dianhydrides.
4.5.2.4. PEII 4. 81% yield, FT-IR (KBr, cmꢀ1): 3447 (NH imidazole),
3056 (C–H aromatic), 2957 (C–H aliphatic), 1786, 1721 (C55O imide),
1605 (C55N imidazole), 1497 (C55C), 1369 (C–N) and 1261 (C–O). 1H
In a 50 mL round-bottomed three-necked flask equipped with a
dropping funnel, a reflux condenser and a magnetic stirrer bar,
1 mmol (0.51 g) diamine, 1 mmol tetracarboxylic acid dianhydride
and 3 g of IL were stirred at room temperature for 10 min. The
temperature was gradually elevated to 180 8C under an inert gas
atmosphere and reaction mixture was held at such temperature
and stirring for 10 h. An additional 0.5 g IL was added to the
mixture. As the reaction proceeded, the solution became viscous.
The reaction mixture was then cooled to room temperature and the
resulting polymers were precipitated in 100 mL methanol. The
precipitate was filtered and washed with hot water, and then was
further purified by washing with refluxing methanol for 24 h in a
Soxhlet apparatus to remove the low molecular weight oligomers.
NMR (DMSO-d6): d 1.36 (t, 3H, CH3), 2.34 (m, 2H, CH2), 2.66 (m, 4H,
CH), 4.48 (q, 2H, CH), 6.71 (m, 2H, C55CH), 7.02–8.68 (m, 21H, Ar-H),
12.56 (s, 1H, N–H imidazole ring). Anal. Calcd. (%) for (C55H35F6N5O6)n:
C, 67.69; H, 3.59; N, 7.18. Found: C, 67.66; H, 3.61; N, 7.18.
4.5.2.5. PEII 5. 94% yield, FT-IR (KBr, cmꢀ1): 3432 (NH imidazole),
3047 (C–H aromatic), 1784, 1723 (C55O imide), 1600 (C55N
imidazole), 1497 (C55C), 1368 (C–N) and 1254 (C–O). 1H NMR
(DMSO-d6):
d 1.32 (t, 3H, CH3), 4.44 (q, 2H, CH2), 7.11–8.65 (m,
27H, Ar-H), 12.66 (s, 1H, N–H imidazole ring). Anal. Calcd. (%) for
(C61H33F12N5O6)n: C, 63.16; H, 2.85; N, 6.04. Found: C, 63.02; H,
2.96; N, 6.01.
4.6. Preparation of electrode
The inherent viscosity (hinh) of the resulting PEIIs was between
0.37–0.67 dL gꢀ1, measured at a concentration of 0.5 g/dL in NMP
at 25 8C. The above procedure was used for the preparation of all
PEIIs given bellow.
The PEIIs containing imidazol-derivative is electrochemical
active and insoluble in aqueous solutions, thus it can be simply

40
M. Ghaemy et al. / Journal of Fluorine Chemistry 142 (2012) 29–40
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We wish to express our gratitude to the Research Affairs
Division of University of Mazandaran (UMZ), Babolsar (Iran), for
partial financial support.
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