A new processable and fluorescent polydithienylpyrrole electrochrome with pyrene appendages

Article abstract of DOI:10.1016/j.electacta.2012.12.023

A new hybrid compound, namely 1-(pyren-3-yl)-2,5-di(thiophen-2-yl)-1H- pyrrole (SNS-P), was polymerized via both chemical and electrochemical methods. Chemically obtained soluble polydithienylpyrrole (c-PSNS-P) bearing pyrene appendages is a homogeneous and uniform polymer with a number averaged molecular weight of 15,200 g/mol. The polymer exhibits both multi-electrochromic and fluorescent properties. Upon oxidation, the color of electrochemically obtained polymer (e-PSNS-P) changes from yellowish orange to greenish yellow and to green/blue and finally to blue. In addition, the polymer induces yellowish orange (564 nm) and bright orange emission (613 nm) in solution and solid states, respectively.

Full text of DOI:10.1016/j.electacta.2012.12.023

Electrochimica Acta 90 (2013) 295–301
Contents lists available at SciVerse ScienceDirect
Electrochimica Acta
journal homepage: www.elsevier.com/locate/electacta
A new processable and fluorescent polydithienylpyrrole electrochrome with
pyrene appendages
a,∗
b
c
c
c
a,∗
Seha Tirke s¸ , Jetmire Mersini , Zahide Özta s¸ , Melek Pamuk Algi , Fatih Algi , Atilla Cihaner
a
Chemical Engineering and Applied Chemistry, Atılım Optoelectronic Materials and Solar Energy Laboratory (ATOMSEL), Atılım University, TR-06836 Ankara, Turkey
Department of Chemistry, Middle East Technical University, TR-06531 Ankara, Turkey
Laboratory of Organic Materials (LOM), C¸ anakkale Onsekiz Mart University, TR-17100 C¸ anakkale, Turkey
b
c
a r t i c l e i n f o
a b s t r a c t
Article history:
A new hybrid compound, namely 1-(pyren-3-yl)-2,5-di(thiophen-2-yl)-1H-pyrrole (SNS-P), was
Received 12 September 2012
Received in revised form 6 December 2012
Accepted 9 December 2012
Available online 19 December 2012
polymerized via both chemical and electrochemical methods. Chemically obtained soluble poly-
dithienylpyrrole (c-PSNS-P) bearing pyrene appendages is a homogeneous and uniform polymer with
a number averaged molecular weight of 15,200 g/mol. The polymer exhibits both multi-electrochromic
and fluorescent properties. Upon oxidation, the color of electrochemically obtained polymer (e-PSNS-P)
changes from yellowish orange to greenish yellow and to green/blue and finally to blue. In addition, the
polymer induces yellowish orange (564 nm) and bright orange emission (613 nm) in solution and solid
states, respectively.
Keywords:
Thiophene
Pyrrole
©
2012 Elsevier Ltd. All rights reserved.
Pyrene
Electrochromism
Fluorescence
1
. Introduction
of 2,6-diamidopyridine, which is a biologically important redox-
active molecule [31]. Furthermore, it was recently shown that a
chemiluminescent PSNS functionalized with luminol appendages
could be used for the detection of reactive oxygen species [32]. In
addition, by the help of fluorescent substituents like naphthalene
and fluorene, PSNS based polymers could exhibit both fluorescent
and electrochromic properties [13,36,37]. It was also shown that
the intrinsic properties could easily be controlled through rational
design of the backbone structures. Nonetheless, examples of pro-
cessable fluorescent and electrochromic polymeric materials based
on SNS unit have still been rare and newer ones are welcome. More-
over, SNS based materials can still be amplified to create viable
materials.
In this context, pyrene can also be a good candidate for the
functional SNS core since pyrene and its derivatives are valuable
fluorescent probes, which can be used in sensors [38–42], LEDs
[43,44], electrochromic [45], and transistors [46]. In spite of these
numerous applications of pyrene and derivatives, only a few ran-
dom copolymers of pyrene [47–50], have been reported, however,
regioregular polymeric systems with pyrene scaffold are uncom-
mon [51].
Functional conjugated polymers have attracted considerable
attention since they are promising candidates to be amenable
for use in a variety of advanced technological applications such
as sensors [1–3], light emitting diodes [4,5], photovoltaic cells
[
6–8], transistors [9,10], electrochromic devices [11–13], and opti-
cal displays [14]. Especially, they have been thought as one of
the most useful electrochromic materials due to their multicolors
with the same material with a short response time under exter-
nal applied low potentials. Also, they exhibit high optical contrast
ratio between various redox states, high redox stability and long
cycle life under ambient conditions as well as processing onto large
area surfaces by spin and spray coatings [15] or roll-to-roll tech-
nique [16]. More importantly, all of these properties can be tuned
by structural design of the starting material [17–19].
Recently, significant effort has been devoted to design and
synthesize of novel, simple and effective functional and solution-
processable polymeric materials [17–23]. Among these materials,
dithienylpyrrole (SNS) is one of the most useful core units in
order to obtain materials with distinct properties [19,24–35]. For
instance, the flavin functionalized polydithienylpyrrole (PSNS) fab-
ricated by electrochemical methods could be used for the detection
Herein we wish to report the fluorescent and electrochromic
properties of a new processable polymer (PSNS-P), which is based
on SNS with a pyrene appandage; namely, 1-(pyren-3-yl)-2,5-
di(thiophen-2-yl)-1H-pyrrole (SNS-P). In this unique combination,
SNS unit provides low oxidation potential as well as electrochromic
features whereas pyrene appendage contributes with its fluores-
cence to this dual electrochromic and luminescent system. More
∗ Corresponding authors.
E-mail addresses: stirkes@atilim.edu.tr (S. Tirke s¸ ), cihaner@atilim.edu.tr
(
A. Cihaner).
0
013-4686/$ – see front matter © 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.electacta.2012.12.023

2
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S. Tirke s¸ et al. / Electrochimica Acta 90 (2013) 295–301
importantly, the polymer, PSNS-P, had a specific optical band gap
2.27 eV) to reflect and/or transmit the yellowish orange color in
the neutral state, and it could be switched to military green and
blue colors upon oxidation. Note that these colors are essential for
full color electrochromic device and display applications.
solution turned progressively dark brown with addition of oxi-
dizing agent). The mixture was stirred 48 h at room temperature.
It was then precipitated into methanol (100 mL). The precipitate
was filtered, redissolved in chloroform (100 mL), and stirred for
6 h with hydrazine monohydrate (4 mL) (the color of the solution
was turned from dark brown to dark orange after addition of the
hydrazine monohydrate). After evaporation, the concentrate was
precipitated into methanol (100 mL), the precipitate was filtered
through a Soxhlet thimble and purified via Soxhlet extraction for
48 h with methanol. The polymer was extracted with chloroform
and soluble and insoluble parts were obtained by 33% and 67%
yields, respectively.
(
2
. Experimental
All chemicals were purchased from Aldrich Chemical and used
as received unless otherwise noted. 0.1 M LiClO4 solution, dis-
solved separately in acetonitrile (ACN) and ethanol (EtOH), was
2
used as electrolyte solutions. A platinum disk (0.02 cm ) and a
platinum wire were used as working and counter electrodes,
respectively, as well as a Ag/AgCl reference and a Ag wire pseudo-
reference electrodes (calibrated externally using 10 mM solution
of ferrocene/ferrocenium couple which is an internal standard cal-
ibrated to be 0.44 V in ACN solution vs. Ag/AgCl, 0.44 V in ACN
solution vs. Ag wire and 0.44 V in EtOH solution vs. Ag wire). Repet-
itive cycling or constant potential electrolysis was used to obtain
the polymer films. Electro-optical properties were investigated by
using an indium tin oxide (ITO, Delta Tech. 8–12 ꢀ, 0.7 cm × 5 cm)
electrode as well as a platinum wire as counter electrode and
a Ag wire as a pseudoreference electrode. For the spectroelec-
trochemical measurements, the polymer film was coated on ITO
electrode via cyclic voltammetry or constant potential electrolysis
3. Results and discussion
Pyrene (1) was chosen as the starting material for the syn-
thesis of SNS-P. Nitration of 1 with Cu(NO3)2 in the presence of
acetic anhydride afforded nitropyrene 2, which was reduced with
hydrazine in the presence of Pd/C (10%) to give aminopyrene 3.
Paal–Knorr reaction of aminopyrene 3 with 4 in the presence of
catalytic amount of PTSA in Dean–Stark trap provided the target
compound in 92% yield. SNS-P initially characterized on the basis
1
13
of H, C NMR and FTIR analysis, which firmly established the
structure.
in 0.1 M LiClO /EtOH. In order to break in the polymer film, it was
The electronic absorption and emission spectra of SNS-P, SNS
[54] and pyrene were given in Fig. 1. The absorption spectrum of
SNS unit consisted of two broad bands centered at around 230 nm
and 330 nm (␲–␲*). On the other hand, absorption spectrum of
pyrene had six different sets of bands centered at 241 nm, 263 nm,
275 nm, 308 nm, 321 nm and 337 nm. However, the absorption
spectrum of SNS-P contained all the absorption bands of each units
(SNS and pyrene), as expected. It was noted that the emission of
both SNS and pyrene were blue, whereas SNS-P emitted yellowish
light.
The electrochemical behavior of the SNS-P was investigated in
an electrolyte solution containing 0.1 M TBAPF6 dissolved in ACN
solution. As shown in Fig. 2, during anodic scan, the monomer
exhibits a lower oxidation peak of 0.89 V vs. Ag/AgCl than its
main components: pyrene (1.41 V vs. Ag/AgCl) and SNS (1.12 V vs.
Ag/AgCl) units. It confirmed that a strong electronic interaction
exists between the HOMO levels of the pyrene and the SNS units.
This indicated that attempted oxidation of the monomer at this low
potential would result in polymerization through SNS units without
disturbing and the cleavage of the pyrene unit. Similar results were
also observed in the cases of fluorene and naphthalene derived SNS
monomers [37].
On that basis, the electropolymerization was performed via
cyclic voltammetry technique between 0.0 V and 1.00 V, but inter-
estingly the monomer did not give the corresponding polymer on
the surface of the electrode in acetonitrile, ACN, solution. It was
also the case when dichloromethane, DCM, was used as a solvent.
Most probably, the product was quite soluble in these solvents and
the electrodeposition did not take place at all. For that reason, the
electropolymerization was carried out in 0.1 M LiClO4 dissolved in
EtOH, which had a suitable potential range (from 0.0 V to 1.0 V) for
the polymerization (Fig. 3b). SNS-P monomer underwent polymer-
ization easily during repetitive cycles between 0.0 V and 0.85 V vs.
Ag wire. Fig. 3a shows a characteristic signature of the formation of
an electroactive polymer film; after first cycle, a new redox couple
started to appear and intensified after each cycle (Scheme 1).
Electrochemically obtained polymer film, e-PSNS-P, on ITO
(Scheme 2) shows a reversible redox couple with a half wave of
0.44 V vs. Ag/AgCl (Fig. 4a) in a monomer free electrolyte solu-
4
switched between 0.0 and 0.90 V in a monomer-free electrolytic
solution. Electroanalytical measurements were performed using
a Gamry PCI4/300 potentiostat–galvanostat. The electro-optical
spectra were monitored on a Specord S 600 spectrometer (standard
◦
illuminator D65, field of width 5 observer) and color space was
given by the International Commission of Illumination with lumi-
nance (L*), hue (a*), and intensity (b*). Platinum cobalt DIN ISO
6
21, iodine DIN EN 1557, and Gardner DIN ISO 6430 are the refer-
ences of colorimetric measurements. FTIR spectra were recorded
on Nicolet 510 FTIR with an attenuated total reflectance (ATR).
GPC analysis of the polymer was carried out with Polymer Labo-
ratories PL-GPC 220 instrument. Thermal gravimetric analysis was
done via PerkinElmer Pyris 1 TGA under nitrogen atmosphere with
◦
1
0 C/min heating rate. The synthesis of 2, 3 [52] and 4 [53] were
carried out according to published procedures.
2.1. Synthesis of SNS-P (5)
A solution of 100 mg (0.4 mmol) 1,4-di(thiophen-2-yl)butane-
1
,4-dione (4), 90 mg (0.4 mmol) amino pyrene (3) and 3 mg
p-toluenesulfonic acid in 50 mL dry toluene were heated under
reflux in a Dean–Stark apparatus until all the starting materials
were consumed. The flask was cooled and the solvent was removed
under reduced pressure. The residue was filtered through a short
pad of silica gel by eluting with CH Cl /hexane (1:1, v/v) to give
2
2
analytically pure SNS-P (160 mg, 0.369 mmol) as brown solid in
◦
1
9
8
2% yield. M.p. 239–240 C; H NMR (400 MHz, CDCl ): ı/ppm:
3
.22–8.18 (m, 2H), 8.15–8.10 (m, 3H), 8.02–7.95 (m, 3H), 7.56 (d,
J = 10 Hz, 1H), 6.76 (s, 2H), 6.75 (dd, J = 5.0–1.0 Hz, 2H), 6.52 (dd,
J = 5.0–3.6 Hz, 2H), 6.34 (dd, J = 3.6–1.0 Hz, 2H); 13C NMR (100 MHz,
CDCl ): ı/ppm: 134.8, 132.1, 131.5, 131.1, 131.0, 130.8, 129.3, 128.6,
3
1
1
28.1, 127.3, 126.7, 126.5, 125.9, 125.1, 124.9, 124.4, 123.7, 123.6,
22.1, 109.8.
2.2. Chemical polymerization of SNS-P (5)
Compound SNS-P (80 mg, 0.186 mmol) was dissolved in chloro-
form (30 mL). A solution of anhydrous FeCl3 (254.2 mg, 0.93 mmol)
in nitromethane was added dropwise over a period of 45 min to the
stirred monomer at room temperature (the bright yellow monomer
tion containing 0.1 M TBAPF /ACN and this value was smaller than
6
fluorene (0.54 V) and naphthalene (0.56–0.61 V) analogs [37]. The

S. Tirke s¸ et al. / Electrochimica Acta 90 (2013) 295–301
297
Fig. 1. (a) Absorption and (b) emission spectra of SNS-P, SNS and pyrene in chloroform.
polymer film was firmly coated on ITO electrode and it exhibited
a non-diffusional redox behavior, which was confirmed by a linear
relationship of peak current intensities as a function of scan rates
acceptable stability since it retains 63% of its electroactivity after
two thousands of switching between its redox states.
As shown in Fig. 6a, the IR spectrum of SNS-P shows strong
− −1
1
(
Fig. 4b).
It was observed that chemically and electrochemically obtained
peaks at 691 cm and 3107 cm (for ␣-hydrogens of thiophene
−
1
−1
rings), 793 cm (for ␤-hydrogens of pyrrole ring) and 843 cm
ꢀ
−
polymers, c-PSNS-P and e-PSNS-P, were both soluble in com-
mon organic solvents like tetrahydrofuran (THF), DCM, chloroform,
toluene, N,N-dimethylformamide and dimethylsulphoxide, which
clearly suggested that they all could easily be processed over sur-
faces via spin coating, spraying, and printing techniques.
Stability and robustness of the polymer film, on the other hand,
are quite important parameters to be amenable for use in appli-
cations. In order to reveal the stability of the polymer film, it
was switched between its redox states under ambient conditions
without purging the electrolyte solution with an inert gas (in
the presence of the air) via a square wave potential method by
(for ␤/␤ -hydrogens of thiophene rings). The intensity of the peak at
1
−1
691 cm decreased and the peak at 3107 cm disappeared com-
pletely, which corresponded to the coupling at ␣-position, while
other peaks still appeared as expected in the c-PSNS-P polymer
spectrum. This also confirmed that the polymerization proceeds
through alpha position of the thiophene units. On the other hand,
−
1
except for the peak at 3040 cm , which was attributed to the C
H
stretching of pyrene unit [55], it was very difficult to prove the
presence of pyrene units in the polymer backbone under the light
of FTIR information. At this point, the absorption spectrum of the
polymer was taken into account. When compared to the monomer,
3
.0 s intervals. Stability of the polymer film was also checked via
cyclic voltammetry. Fig. 5 shows that the polymer film had an
Fig. 3. (a) Electropolymerization of SNS-P on ITO electrode in 0.1 M LiClO4/EtOH at
100 mV/s by potential scanning to give e-PSNS-P. (b) Cyclic voltammogram of the
monomer-free electrolyte solution containing 0.1 M LiClO4/EtOH.
Fig. 2. Cyclic voltammograms of (a) SNS-P, (b) SNS and (c) pyrene in 0.1 M TBAPF6
in ACN on Pt electrode at a scan rate of 100 mV/s vs. Ag/AgCl.

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S. Tirke s¸ et al. / Electrochimica Acta 90 (2013) 295–301
Scheme 1. Synthesis of SNS-P (5).
Scheme 2. Electrochemical and chemical polymerization of SNS-P.
the spectrum apparently confirmed the presence of pyrene units,
since the absorption bands lower than 350 nm belong to the pyrene
unit in both spectra and a broad band centered at 450 nm can be
easily attributed to the c-PSNS-P polymeric chain (Fig. 6b).
From the viewpoint of electrochromic devices and display appli-
cations, spectroelectrochemical properties of the electrochromic
polymer must be examined for various redox states by using the
changes in the electronic absorption spectra under applied var-
ious potentials. As shown in Fig. 7, the e-PSNS-P film coated on
ITO exhibited a wide absorption band centered at 450 nm (2.76 eV)
in its neutral state and the polymer band gap (Eg) was found
from its commencement on the low energy end as 2.27 eV, which
was in agreement with precedent PSNS analogs [37]. Upon oxida-
tion, valence-conduction band (␲–␲* transition) at 450 nm started
to diminish and a new absorption band appeared at 790 nm,
corresponding to the formation of the charge carriers, and this
band started to intensify with increasing doping. During oxida-
tion, the polymer film induced a color change from yellowish
orange (L = 76.10, a* = 6.91, b* = 65.41) to military green (L = 62.76,
a* = −9.24, b* = 14.47). Fig. 7 also showed how the color of the
polymer film could be tuned by applying different potentials. In
addition, the memory study showed that the polymer film was
mostly stable in its neutral state when compared to its oxidized
state. Oxidized polymer film slowly turned into pseudo-oxidized
state with open circuit potential under ambient conditions.
Fig. 4. (a) Scan rate dependence of PSNS-P film on an ITO electrode in 0.1 M
TBAPF6/ACN at different scan rates vs. Ag/AgCl: (i) 20 mV/s, (ii) 40 mV/s, (iii)
Fig. 5. Electrochemical stability of e-PSNS-P on an ITO electrode in 0.1 M
TBAPF6/ACN after 2000 switching by a square wave potential method with a 3 s
interval at each redox state. ia: anodic peak current, ic: cathodic peak current. Cyclic
voltammograms represent the behavior of the polymer film after a certain number
of switching.
6
0 mV/s, (iv) 80 mV/s, (v) 100 mV/s, (vi) 120 mV/s, (vii) 140 mV/s, (viii) 160 mV/s,
(
(
ix) 180 mV/s, and (x) 200 mV/s. (b) Relationship of anodic (ia) and cathodic current
ic) peaks as a function of scan rate for e-PSNS-P film in 0.1 M TBAPF6/ACN.

S. Tirke s¸ et al. / Electrochimica Acta 90 (2013) 295–301
299
Fig. 6. (a) FTIR spectra of SNS-P, pyrene and c-PSNS-P. (b) UV–vis spectra of SNS-P and c-PSNS-P in DCM solution.
2
One of the important parameters for device application is
switching time, which is the time elapsed between two differ-
ent colors under applied potentials. For this process, square-wave
potential method was used to record the percent transmittance
between 0.0 and 0.80 V with switching time intervals of 10, 5, 3,
film was calculated as 219.6 cm /C at 450 nm with a response time
of 0.7 s.
Along with the electrochemical stability, optical stability is
another key parameter for electrochromic devices and display
applications. Therefore, c-PSNS-P was switched between its redox
states via square wave potential method for 3 s time intervals under
ambient conditions. It was noted that 60% of the optical activity pre-
served after two thousand cycles, which indicated that the polymer
was a promising candidate for use in electrochromic devices and
display applications.
2
, and 1 s. As shown in Fig. 8, the polymer film exhibited 16.7%
of transmittance at 450 nm with a response time of 0.57 s. When
the switching time was changed from 10 s to 1 s, the polymer film
retained its electro-optical properties with no appreciable changes.
For example, when it was switched in 1 s, only about 1.2% at 450 nm
(
4.7% at 950 nm)optical contrast change was observed. The col-
Like spectroelectrochemical properties of the electrochemically
obtained polymer film, electrochromic properties of the chemi-
cally obtained polymer were also elucidated for different redox
states by using the changes in absorption spectra after the addi-
oration efficiency (at 95% of the full contrast after which point the
naked eyes could not sense the changes in the color) of the PSNS-P
tion of various amounts of SbCl5 and N H5OH solutions as oxidizing
2
and reducing agents, respectively. The polymer could be switched
chemically and reversibly many times between its redox states and
the spectacular color changes could be nicely observed upon chem-
ical switching (Fig. 9). As shown in Fig. 9a, the intensity of peak at
Fig. 8. Chronoabsoptometry experiments for e-PSNS-P film on ITO in 0.1 M
TBAPF6/ACN while the polymers were switched in different time intervals (10, 5,
3, 2, 1 s) between redox states.
Fig. 7. (a) Electronic absorption spectra and the colors of the e-PSNS-P on ITO in
0
.1 M TBAPF6/ACN at various applied potentials between 0.0 V and 0.85 V.

3
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S. Tirke s¸ et al. / Electrochimica Acta 90 (2013) 295–301
pack so tightly in the amorphous solid phase. Probably, this situa-
tion mainly prevents quenching in the solid phase as in the case
of the solution. On the other hand, it is also possible that solu-
tion and solid states of the polymer do not induce any considerable
changes in the electronic level. Thus, both leads to emissive states.
The bathochromic shift of the emission wavelength was probably
due to the ␲–␲ stacking in the solid phase.
The number average molecular weight, Mn, of chemically
obtained polymer was determined utilizing gel permeation chro-
matography (GPC) by using polystyrene as the standard and THF as
the eluent and it was found to be as 15,200 g/mol. It could be easily
concluded that the polymer chain consisted of approximately 35
repeating SNS-P units.
The thermal stability is one of the important keys for a polymer
in order to find a chance to be used in optoelectronic devices since
the polymer must be thermally robust during metal vapor depo-
sition like in PLED and solar cell applications. Therefore, thermal
behavior was investigated via thermogravimetric analysis (TGA).
◦
Up to 400 C, the polymer is robust and it losses approximately
4
Fig. 9. (a) Electronic absorption spectra of c-PSNS-P during chemical oxidation by
SbCl5. (b) Electronic absorption spectra of neutral and oxidized c-PSNS-P.
% of its weight. Upon further heating, the polymer film starts to
decompose and at the end of heating it can be concluded that the
polymer film is thermally very robust since it totally lost 34% of its
weight at 991 C under nitrogen atmosphere, which confirms that
4
50 nm began to alleviate slowly with the addition of SbCl5 solu-
◦
tion, and a new absorption band started to intensify at 790 nm,
which corresponded to the formation of the charge carriers. Further
addition of SbCl5 resulted in the formation of a new band at 900 nm
along with the band at 790 nm. During this process, the color of
the c-PSNS-P changed from orange/yellow to yellow/green and to
green/blue and finally to blue. The data suggested that there was no
degradation in the polymer structure when it was switched chem-
ically, since the absorption bands below 370 nm were still present
in the spectrum of the polymer (Fig. 9b).
The polymer (c-PSNS-P) was fluorescent and it exhibited a maxi-
mum wavelength of 564 nm resulting in yellowish orange emission
in DCM solution. Interestingly, the polymer was also fluorescent in
the solid state. Note that organic compounds with emissions in the
solid state are rare, since even bright organic fluorophores pack
very tightly in the crystalline state or amorphous solid phase (as
thin films), leading to very significant quenching [56–58]. c-PSNS-
P exhibited reddish orange emission (613 nm) in the solid state
c-PSNS-P can be a promising candidate to be amenable for use in
optoelectronic devices.
4. Conclusion
To conclude, a new dithienylpyrrole based material (SNS-P)
with pyrene appendage was designed, synthesized and charac-
terized. This combination provided a novel processable polymer
electrochrome (e-PSNS-P), which can be switched from yellowish
orange color in the neutral state to military green and blue col-
ors upon application of the voltage pulses. Furthermore, the colors
could reversibly be switched on and off chemically with the addi-
tion of SbCl5 and N H5OH. Note that these colors are essential for
2
full color electrochromic device and display applications. Interest-
ingly, c-PSNS-P was emissive in both solution (yellowish orange)
and the solid states (red). The electrochemical and thermal stability
of the material indicated that PSNS-P was an excellent candidate
for electrochromic applications. Work along this line is currently
underway in our laboratories.
(
Fig. 10). Although it is expected that the polymer chains would be
much closer in the solid phase when compared to solution phase
due to ␲–␲ stacking, it is assumed that the polymer chains do not
Acknowledgments
The authors gratefully acknowledge the financial support
from the Scientific and Technical Research Council of Turkey
(TUBITAK), Atilim University (ATÜ-ALP-1011-02, ATÜ-BAP-1011-
0
5), C¸ anakkale Onsekiz Mart University and The Turkish Academy
of Sciences (TÜBA). Z. Ö. is indebted to TUBITAK for the scholarship
and M.P.A. is indebted to TUBA for a graduate fellowship.
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