4-(Furan-2-yl)phenyl-containing polydithienylpyrroles as promising electrodes for high contrast and coloration efficiency electrochromic devices

Article abstract of DOI:10.1016/j.orgel.2019.06.030

A 4-(furan-2-yl)phenyl-containing conjugated dithienylpyrrole (FPT) was prepared using a Paal-Knorr reaction and its homologous homopolymer (PFPT) and copolymers (P(FPT-co-DTC) and P(FPT-co-DTP)) were electrosynthesized. Spectroelectrochemical investigations displayed that PFPT film was saffron yellow (0 V) in a reduced state, yellowish-gray (1.0 V), light purple (1.2 V), and bluish-purple (1.4 V) in an oxidized state. P(FPT-co-DTC) film was green, grayish-green, grayish-blue, and bluish-purple from reduced to oxidized states. Electrochromic switching studies revealed the transmittance change (ΔT) of PFPT, P(FPT-co-DTC), and P(FPT-co-DTP) films were 22.7%, 44.8%, and 50.7% at 1320 nm, 906 nm, and 1212 nm, respectively, and the coloration efficiency (η) of PFPT, P(FPT-co-DTC), and P(FPT-co-DTP) films were estimated to be 181.8 cm² C^?1, 229.0 cm² C^?1, and 232.4 cm² C^?1 at 1320 nm, 906 nm, and 1212 nm, respectively. A P(FPT-co-DTP)/PProDOT-Et₂ ECD revealed a high ΔT (38.6% at 612 nm) and rapid switching time, whereas a PFPT/PProDOT-Et₂ ECD attained a high ΔT (33.3% at 590 nm), a high η (533.5 cm² C^?1 at 590 nm) and long-term reversible redox behaviors.

Full text of DOI:10.1016/j.orgel.2019.06.030

Accepted Manuscript
4-(Furan-2-yl)phenyl-containing polydithienylpyrroles as promising electrodes for high
contrast and coloration efficiency electrochromic devices
Wen-Hsin Wang, Jui-Cheng Chang, Tzi-Yi Wu
PII:
S1566-1199(19)30325-8
DOI:
https://doi.org/10.1016/j.orgel.2019.06.030
ORGELE 5318
Reference:
To appear in: Organic Electronics
Received Date: 21 March 2019
Revised Date: 19 June 2019
Accepted Date: 23 June 2019
Please cite this article as: W.-H. Wang, J.-C. Chang, T.-Y. Wu, 4-(Furan-2-yl)phenyl-containing
polydithienylpyrroles as promising electrodes for high contrast and coloration efficiency electrochromic
devices, Organic Electronics (2019), doi: https://doi.org/10.1016/j.orgel.2019.06.030.
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ACCEPTED MANUSCRIPT
Graphical Abstract
100
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0
O
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n
PFPT
PFPT/PProDOT-Et2 ECD
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Time (s)
A PFPT/PProDOT-Et2 ECD attained a high ∆T (33.3% at 590 nm) and a high
η
(533.5 cm2 C–1 at 590 nm).
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4-(Furan-2-yl)phenyl-containing polydithienylpyrroles as
promising electrodes for high contrast and coloration
efficiency electrochromic devices
Wen-Hsin Wanga, Jui-Cheng Changb, Tzi-Yi Wua,*
a Department of Chemical and Materials Engineering, National Yunlin University of
Science and Technology, Yunlin 64002, Taiwan, ROC
b Bachelor Program in Interdisciplinary Studies, National Yunlin University of Science
and Technology, Yunlin 64002, Taiwan, ROC
* Correspondence: wuty@yuntech.edu.tw.
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ABSTRACT
A 4-(furan-2-yl)phenyl-containing conjugated dithienylpyrrole (FPT) was
prepared using a Paal-Knorr reaction and its homologous homopolymer (PFPT) and
copolymers (P(FPT-co-DTC) and P(FPT-co-DTP)) were electrosynthesized.
Spectroelectrochemical investigations displayed that PFPT film was saffron yellow (0
V) in a reduced state, yellowish-gray (1.0 V), light purple (1.2 V), and bluish-purple
(1.4 V) in an oxidized state. P(FPT-co-DTC) film was green, grayish-green,
grayish-blue, and bluish-purple from reduced to oxidized states. Electrochromic
switching studies revealed the transmittance change (∆T) of PFPT, P(FPT-co-DTC),
and P(FPT-co-DTP) films were 22.7%, 44.8%, and 50.7% at 1320 nm, 906 nm, and
1212 nm, respectively, and the coloration efficiency (η) of PFPT, P(FPT-co-DTC), and
P(FPT-co-DTP) films were estimated to be 181.8 cm2 C-1, 229.0 cm2 C-1, and 232.4
cm2 C-1 at 1320 nm, 906 nm, and 1212 nm, respectively. A
P(FPT-co-DTP)/PProDOT-Et2 ECD revealed a high ∆T (38.6% at 612 nm) and rapid
switching time, whereas a PFPT/PProDOT-Et2 ECD attained a high ∆T (33.3% at 590
nm), a high
η
(533.5 cm2 C–1 at 590 nm) and long-term reversible redox behaviors.
Keywords: 4-(furan-2-yl)phenyl, spectroelectrochemistry, electrochromic switching,
electrochromic device, long-term cycling stability
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1. Introduction
Electrochromic materials have taken an interest in academic scientists due to their
promising applications as electrochromic car window film, auto-dimming rear-view
mirror and light adjusting sunglasses [1]. In the past two decades, both organic
materials (diphthalocyanine, viologen, tetrathiafulvalene, and conjugated polymer) and
inorganic materials (WO3, V2O5, NiO, IrO2, and MoO3) materials have been developed
to be used in electrochromic devices. Although inorganic electrochromic materials
present considerable benefits regarding their high optical contrast and electrical
durability, organic electrochromic materials show some benefits over inorganic
electrochromic materials due to their fast electrochromic switching, high coloration
efficiency, ease of processing and multicolor electrochromism, etc [2]. Recently,
interest has focused on the research of conjugated polymers as organic electrochromic
materials in ECDs [3]. Polythiophene [4,5], polyimides [6,7], polyindoles [8],
polycarbazole [9-12], poly(3,4-ethylenedioxythiophene) (PEDOT) [13],
poly(3,4-propylenedioxythiophene) (PProDOT) [14], polytriphenylamine [15,16], and
polyaniline [17] have been applied widely in various organic electrochromic devices.
Among these conjugated polymers, polythiophenes have been extensively studied due
to their good redox reversibility, attractive optoelectronic properties and high electrical
and environmental stability. PEDOT and PProDOT are common derivatives of
polythiophenes, which comprise two electron-donating atoms on 3,4-positions of
polythiophenes. PEDOT and PProDOT show lower onset oxidation potentials than
those of polythiophenes [18]. Moreover, important optoelectronic properties of PEDOT
and PProDOT are low transmissivity at their reduced state and high transmissivity at
their oxidized state, which are known as reduced state blue organic electrochromic
materials [19]. Polydithienylpyrroles (PSNS) and their derivatives are also most
promising polythiophenes derivatives, the onset oxidation potentials (0.7 V vs.
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Ag/AgCl [20]) of PSNS derivatives are less than those of polythiophenes, PEDOT, and
PProDOT. Low onset oxidation potential leads PSNS derivatives to have high-lying
HOMOs and can be oxidized facilely during redox processes. Ak et al. reported the
synthesis and electrochromic characterization of a dithienylpyrrole based copolymer
(P(TPVB-co-EDOT)), the copolymer revealed high transmittance change (75% at 1000
nm), satisfactory switching response, and reasonable stability [21]. Ozkut and Cihaner
et al. synthesized a conjugated copolymer (P(EDOT-co-1)) using electropolymerization,
P(EDOT-co-1) revealed five color variations ranging from dark purple, purple, gray,
green to cyan. Moreover, P(EDOT-co-1) displayed a high ∆T (41%), a high
η
(258 cm2
C–1), and fast switching time (1.4 s) [22]. On the other hand, furan is a donor unit, the
incorporation of furan unit in polymer backbone is beneficial for enhancing the hole
transporting ability of polymer. 3,6-di(2-thienyl)carbazole (DTC) and
dithieno[3,2-b:2’,3’-d]pyrrole (DTP) units reveal similar structures to dithienylpyrroles.
However, DTP unit presents a fused-ring thiophene and a conjugated planar ring
structures, which enhances effective conjugation length and red-shifts the UV-vis
absorption spectra [23].
So far, the incorporation of a 4-(furan-2-yl)phenyl group into the pyrrole unit of
dithienylpyrrole and the investigation of electrochromic behaviors of its corresponding
polymer films have not been carried out yet. In the present work,
4-(furan-2-yl)phenyl-containing PFPT, P(FPT-co-DTC), and P(FPT-co-DTP) films are
employed as the anodically coloring materials in dual type ECDs, and a
poly(3,4-(2,2-diethylpropylenedioxy)thiophene) (PProDOT-Et2) film is employed as
the cathodically coloring material in dual type ECDs. The electrochromic behaviors
and color–bleach kinetics of PFPT, P(FPT-co-DTC), and P(FPT-co-DTP) films and
spectroelectrochemistry, redox stabilities, and optical memory of their corresponding
ECDs are investigated exhaustively.
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2. Experimental
2.1. Materials
Furan, 4-nitroaniline, isoamyl nitrite, and other starting chemicals were purchased
from Aldrich, Acros, Tokyo Chemical Industry (TCI), Merck, and used as received.
The monomer (ProDOT-Et2) of cathodic layer and 1-ethyl-3-propylimidazolium
bis(trifluoromethanesulfonyl)imide ([EPI+][TFSI–]) were prepared in accordance with
previously published methods [24-26]. Anodic polymer films were either prepared
potentiodynamically with a potential range of -1.0 V to 1.8 V or potentiostatically at
0.9 V on conductive glasses. The reference electrode used in the preparation of
polymer films is an Ag/AgCl electrode. P(FPT-co-DTC) and P(FPT-co-DTP) films
were coated using a feed molar ratio of either FPT/DTC or FPT/DTP at 1/1. The length
and width of electrochromic electrodes are 1.5 and 1 cm, respectively.
2.2. Synthesis of 2-(4-nitrophenyl)furan (Scheme 1)
A 100 mL round-bottomed flask equipped with a magnetic mixer was charged with
furan (2.04 g, 30 mmol), 4-nitroaniline (2.76 g, 20 mmol), isoamyl nitrite (3.51 g, 30
mmol), and 120 mL acetonitrile (ACN). The solution was stirred for 7 h at 25 oC. After
evaporating off ACN, the remaining product was purified using a column
chromatography on silica with an eluent (dichloromethane/hexane = 1/4). Yield: 61%.
1H NMR (700 MHz, DMSO-d6): δ 8.27 (d, 2H, phenyl-H), 7.95 (d, 3H, phenyl-H and
Fu-H), 7.32 (d, 1H, Fu-H), 6.71 (dd, 1H, Fu-H). 13C NMR (125 MHz, DMSO-d6): δ
110.4, 113.0, 124.1, 124.5, 136.1, 145.4, 146.0, 151.1. Elem. anal. calcd. for C10H7NO3:
C, 63.49%; H, 3.73%; N, 7.40%. Found: C, 63.31%; H, 3.66%; N, 7.28%.
2.3. Synthesis of 4-(furan-2-yl)aniline
A 100 mL round-bottomed flask equipped with a magnetic mixer was charged with
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2-(4-nitrophenyl)furan (0.95 g, 5 mmol), NH2NH2·H2O (0.15 g, 3 mmol), 5 mg Pd/C,
and 15 mL EtOH, and the solution was stirred for a day under reflux. After evaporating
off EtOH under reduced pressure, the remaining product was purified using a column
chromatography on silica with an eluent (dichloromethane/hexane = 1/1). Yield: 74 %.
1H NMR (700 MHz, DMSO-d6): δ 7.56 (d, 1H, Fu-H), 7.35 (d, 2H, phenyl-H), 6.58 (d,
2H, phenyl-H), 6.53 (d, 1H, Fu-H), 6.47 (dd, 1H, Fu-H), 5.29 (s, 2H, phenyl-NH2-).
13C NMR (125 MHz, DMSO-d6): δ 101.8, 111.8, 114.1, 118.8, 124.8, 140.9, 148.5,
154.6. Elem. anal. calcd. for C10H9NO: C, 75.45 %; H, 5.70 %; N, 8.80 %. Found: C,
75.27%; H, 5.63%; N, 8.71%.
2.4. Synthesis of 1-(4-(furan-2-yl)phenyl)-2,5-di(thiophen-2-yl)-pyrrole (FPT)
A 100 mL round-bottomed flask equipped with a magnetic mixer was charged with
1,4-di(2-thienyl)-1,4-butanedione (2.1 mmol, 0.53 g), 4-(furan-2-yl)aniline (6.3 mmol,
1 g), 22 mL toluene, and 12 mg p-TSA, and the solution was stirred for 18 h at 110 °C.
After evaporating off toluene using a rotavapor, the remaining product was purified
using a column chromatography on silica with an eluent (dichloromethane/hexane =
1/2). Yield: 63 %. 1H-NMR (700 MHz, DMSO-d6)：δ 7.82 (d, 3H, Fu-H and phenyl-H),
7.39 (d, 2H, phenyl-H), 7.29 (d, 2H, Th-H), 7.11 (d, 1H, Fu-H), 6.88 (dd, 2H, Th-H),
6.72 (d, 2H, Th-H), 6.65 (dd, 1H, Fu-H), 6.58 (d, 2H, Py-H). 13C NMR (125 MHz,
DMSO-d6): δ 107.4, 109.7, 112.4, 124.2, 124.4, 125.0, 127.2, 129.8, 130.7, 131.3,
134.0, 136.6, 143.7, 152.0. Elem. anal. calcd. for C22H15NOS2: C, 70.75%; H, 4.05%;
N, 3.75%. Found: C, 70.58%; H, 3.97%; N, 3.62%.
2.5. Fabrication of ECDs
Dual type PFPT/PProDOT-Et2, P(FPT-co-DTC)/PProDOT-Et2, and
P(FPT-co-DTP)/PProDOT-Et2 ECDs were fabricated by sandwiching the electrolyte
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layer between two complementary polymer films. The anodic polymer layers were
PFPT, P(FPT-co-DTC), and P(FPT-co-DTP) films, the cathodic polymer layer was a
PProDOT-Et2 film, and the electrolyte layer was an [EPI+][TFSI–]/PVdF-HFP
composite electrolyte, which was prepared based on our previous works [26]. The
anodic and cathodic coloring layers were coated on indium tin oxide (ITO) substrates
at 0.9 and +1.4 V, respectively.
2.6. Spectroelectrochemical and electrochemical properties
Spectroelectrochemical characteristics of polymer films and ECDs were measured
using a UV-Vis-NIR spectrophotometer (JASCO V-670) and an electrochemical
analyzer (CHI660a). The electrochemical cell for electrochemical measurements
includes an ITO glass as working electrode (WE), a platinum wire as counter electrode
(CE), Ag/AgCl as reference electrode (RE), and the electrodes are immersed in 0.1 M
LiClO4/ACN electrolyte. The onset potential of oxidation was estimated using the first
CV cycle.
3. Results and discussion
3.1. Electrochemical polymerization
Fig. 1 shows the cyclic voltammetric curves for the repeated scanning
electropolymerization of FPT, DTC, and DTP monomers and their mixtures. As the
voltammetric curves increased with increasing number of cycles, the PFPT,
P(FPT-co-DTC), and P(FPT-co-DTP) films could be seen on the ITO
transparent conductive glass, demonstrating the polymer films were coated on the ITO
conductive substrate [27]. As presented in Fig. 1, the onset oxidation potential of FPT,
DTC, and DTP were 0.74, 0.82, and 0.80 V, respectively. The onset oxidation potential
disparity of these monomers is less than 0.1 V, implying the copolymerization of FPT
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and DTC (or DTP) was feasible. Moreover, the onset oxidation potential of FPT was
less than those of DTC and DTP, indicating that 4-(furan-2-yl)phenyl-containing
dithienylpyrrole was easier to oxidize than either the DTC or DTP. Figs. 1(d) and 1(e)
showed the cyclic voltammetric experiments using mixtures of two monomers ((FPT +
DTC) and (FPT + DTP)) in solutions. Obviously, the oxidation peaks, reduction peaks,
and cyclic voltammetric wave-shapes of P(FPT-co-DTC) and P(FPT-co-DTP) films
were different to those of PFPT, PDTC, and PDTP films, which indicated copolymer
films were electrodeposited on ITO substrates. The schemes of
coelectropolymerization were displayed in Scheme 2.
The PFPT film was scanned in monomer-free 0.1 M LiClO4/ACN
solution at different sweep rates. As shown in Fig. 2, PFPT film exhibited well-defined
redox processes. A linear increase in the anodic and cathodic currents as a function of
the scanning rates indicated that the electroactive species migrated during the redox
process were non-diffusional controlled and PFPT film was bounded to the ITO
electrode tightly [28].
3.2. Spectral analysis of polymer films
Fig. 3 showed the UV-visible-NIR spectra of PFPT, P(FPT-co-DTC), and
P(FPT-co-DTP) films at various potentials. PFPT film revealed an absorption shoulder
at 407 nm, which could be ascribed to the π–π* transition of PFPT film. When the
applied voltages increased gradually, the absorbance of π–π* transition bands
weakened gradually and polaron and bipolaron bands emerged and heightened at
around 590 and 1320 nm [29]. P(FPT-co-DTC) film shows similar π–π* transition
shoulder at 406 nm, the polaron and bipolaron peaks shift to 906 nm. However, the
π–π* transition absorption band of P(FPT-co-DTP) film shifted bathochromically
to 472 nm in [EPI+][TFSI–] solution, implying the dithieno[3,2-b:2’,3’-d]pyrrole unit of
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P(FPT-co-DTP) backbone displayed satisfactory π-conjugation across fused thiophene
rings [30]. The polaron (or bipolaron) band of P(FPT-co-DTP) film shifted
bathochromically to 1212 nm.
Table 1 revealed the electrochromic images and L*, a*, b* values of PFPT,
P(FPT-co-DTC), and P(FPT-co-DTP) films at various potentials in [EPI+][TFSI–]
solution. PFPT film was saffron yellow (0 V) in a reduced state, yellowish-gray (1.0 V),
light purple (1.2 V), and bluish-purple (1.4 V) in an oxidized state. P(FPT-co-DTC)
and P(FPT-co-DTP) films displayed four color variations from reduced to oxidized
states. P(FPT-co-DTC) film was green, grayish-green, grayish-blue, and bluish-purple
at 0, 1.0, 1.2, and 1.4 V, respectively. P(FPT-co-DTP) film was brass, gray,
grayish-blue, and blue at 0, 0.8, 1.0, and 1.2 V, respectively. The CIE chromaticity
charts of PFPT, P(FPT-co-DTC), and P(FPT-co-DTP) films in an ionic liquid solution
in reduced and oxidized states are shown in Fig. S1 (in supplementary information).
The optical band gap (Eg) of PFPT film calculated using the onset wavelength of
the π-π* transition peak was 2.26 eV [31]. Table 2 summarizes the comparison of Eg
with reported polymer films, PFPT film shows comparable Eg to those reported for
P(TPHA) [32] and PSNS-iProP [33]. However, the Eg of PFPT film is smaller than
those reported for PSNS-Fc [34] and P(SNS-pyrene) [35], which can be ascribed to the
incorporations of ferrocene and pyrene as the anchored group of PSNS derivatives
increasing the Eg significantly. The oxidation onset potential of PFPT (vs. Ag/AgCl)
was 0.74 V, the EFOC value determined from ferrocene/ferrocenium (Fc/Fc+) (vs.
Ag/AgCl) was 0.57 V, and the Eonset(ox) (vs. EFOC) was estimated as 0.17 V. The HOMO
energy level of PFPT calculated from the Eonset(ox) and the energy level of the Fc/Fc+
couple (4.8 eV below the vacuum level (zero eV)) [36,37] was taken as –4.97 eV. The
LUMO energy level of PFPT relative to the vacuum level was estimated to be –2.71
eV.
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3.3. Color–bleach kinetics of polymer films
The potentials of PFPT, P(FPT-co-DTC), and P(FPT-co-DTP) films were
interchanged between 0 (the reduced state) and 1.0 V (the oxidized state) with a time
interval of 5 s in a solution. The dynamic electrochromic switching profiles of the three
films in an ionic liquid are displayed in Fig. 4, and their coloration and bleaching
switching times (τc and τb) estimated at 90% of entire transmittance change and
calculated at various cycles are listed in Table S1 (in supplementary information). The
τc and τb of three polymer films at various cycles and wavelengths were estimated to be
1.71-2.46 s in an ionic liquid solution.
The transmittance variations between the reduced and oxidized states of the PFPT,
P(FPT-co-DTC), and P(FPT-co-DTP) films were 22.7%, 44.8%, and 50.7% at 1320
nm, 906 nm, and 1212 nm, respectively, at the first cycle. The ∆T of P(FPT-co-DTC)
and P(FPT-co-DTP) films in near-infrared region increased significantly compared to
that of PFPT film in an ionic liquid solution, implying DTC- and DTP-containing
copolymers displayed higher ∆T in the near-infrared zone than that of PFPT
homopolymer. The transmittance variations for the PFPT, P(FPT-co-DTC), and
P(FPT-co-DTP) films in the near-infrared zone are larger than those in UV-Vis zone,
this can be attributed to the formation of significant charge carriers upon doping. Table
2 lists the comparison of transmittance change with the reported polymer films in
electrolytes. PFPT film reveals a higher ∆Tmax than those reported for P(TPHA) at 334
nm [32], PSNS-iProP at 646 nm [33], and P(SNS-pyrene) at 349 nm [35]. However,
the ∆Tmax of PFPT film is lower than that of PSNS-Fc at 356 nm [34].
The discrepancy of optical density (∆OD) at specific wavelength can be calculated
using the following formula,
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Tox
∆OD = log(
) ,
(1)
Tred
where Tox and Tred denote the transmittance at oxidized and reduced states, respectively.
As presented in Table 2, the PFPT film displayed higher
PSNS-iProP at 646 nm [33].
∆OD than that reported for
Another crucial parameter of electrochromic polymer films is coloration
efficiency (
η
), which can be determined from the following formula:
∆OD
η
=
, (2)
Qd
where Qd represents the injected/ejected electronic charge per unit electrode area. As
shown in Table 2, the
[EPI+][TFSI–] were estimated to be 181.8 cm2 C-1 at 1320 nm, 229.0 cm2 C-1 at 906 nm,
and 232.4 cm2 C-1 at 1212 nm, respectively. Although PFPT displayed lower
ηmax of PFPT, P(FPT-co-DTC), and P(FPT-co-DTP) films in
η
max than
than
those of P(FPT-co-DTC) and P(FPT-co-DTP) films, PFPT film presented higher
η
those reported for PSNS-iProP at 646 nm [33] and P(SNS-pyrene) at 349 nm [35].
3.4. Spectroelectrochemical behaviors of ECDs
Figs. 5(a), 5(b), and 5(c) exhibit the UV-Vis spectra of dual type
PFPT/PProDOT-Et2, P(FPT-co-DTC)/PProDOT-Et2, and
P(FPT-co-DTP)/PProDOT-Et2 ECDs at several potentials. PFPT/PProDOT-Et2,
P(FPT-co-DTC)/PProDOT-Et2, and P(FPT-co-DTP)/PProDOT-Et2 ECDs presented
precise absorption shoulders or peaks at ca. 407, 406, and 472 nm at 0 V, respectively,
which were in agreement with the π–π* transition of PFPT, P(FPT-co-DTC), and
P(FPT-co-DTP) films in neutral states. In the circumstance, the PProDOT-Et2 layer
was classified as in an oxidized state and presented no conspicuous characteristic peak
in the UV-Vis zone [38]. An increase of applied voltage resulted in the oxidation of
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anodically coloring layers and the reduction of the cathodically coloring layers.
Accordingly, absorption peaks of ECDs started to appear at 586-612 nm, the
preeminent color of three ECDs was dark blue at a voltage
≥ +1.2 V as displayed in
Table 3. Fig. S2 (in supplementary information) exhibited the chromaticity diagrams of
these dual type ECDs at -0.4 and 1.2 V.
3.5. Color–bleach kinetics of ECDs
As presented in Fig. 6, the color–bleach kinetics of PFPT/PProDOT-Et2,
P(FPT-co-DTC)/PProDOT-Et2, and P(FPT-co-DTP)/PProDOT-Et2 ECDs were
interchanged between − 0.2 (the bleached state) and +1.2 V (the colored state) with a
time interval of 5 s. The τc and τb of these ECDs estimated at various cycles are
summarized in Table 4, which were shorter than those of their corresponding polymer
films in solutions. This can be ascribed to the ECDs showed short distance between
working and counter electrodes [39]. Furthermore, the ∆Tmax of PFPT/PProDOT-Et2,
P(FPT-co-DTC)/PProDOT-Et2, and P(FPT-co-DTP)/PProDOT-Et2 ECDs as shown in
Table 4 were 33.3, 29.9, and 37.5%, respectively, from −0.2 V (the bleached state) to
+1.2 V (the colored state). Therefore, the ECD employing P(FPT-co-DTP) as an
anodically coloring film displayed the highest
∆Tmax among the three ECDs.
As listed in Table 5, the
η
of ECDs were 533.5, 340.0, and 855.9 cm2 C-1 for
PFPT/PProDOT-Et2 ECD at 590 nm, P(FPT-co-DTC)/PProDOT-Et2 ECD at 586 nm,
and P(FPT-co-DTP)/PProDOT-Et2 ECD at 612 nm, respectively. Hence, the ECD
employing a P(FPT-co-DTP) anodically coloring film revealed the highest
η
, and a
P(FPT-co-DTC) anodically coloring film displayed the lowest
η among the three
ECDs.
As shown in Table 5, the ∆Tmax and η of PFPT/PProDOT-Et2,
P(FPT-co-DTC)/PProDOT-Et2, and P(FPT-co-DTP)/PProDOT-Et2 ECDs were
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compared with previous reported works. PFPT/PProDOT-Et2 ECD displayed higher
∆
Tmax than those reported for P(TPHA-co-EDOT)/PEDOT [32], PBTC/PEDOT [40],
PBEC/PEDOT [40], and PBDO/PProDOT-Et2 ECDs [41]. Moreover,
PFPT/PProDOT-Et2 ECD obtained a higher than those reported for PBTC/PEDOT
η
[40], PBEC/PEDOT [40], and PBDO/PProDOT-Et2 ECDs [41].
3.6. Open-circuit memory of ECDs
The transmittance-time profiles of PFPT/PProDOT-Et2,
P(FPT-co-DTC)/PProDOT-Et2, and P(FPT-co-DTP)/PProDOT-Et2 ECDs in different
electrochromic states were measured at 590, 586 and 612 nm, respectively. The applied
potentials in bleached and colored states are 1 s during each 200 s time interval. As
shown in Fig. 7, the transmittance changes were less than 3% in bleached (−0.2 V) and
colored (+1.2 V) states of the three ECDs, revealing that these ECDs had adequate
optical memory.
3.7. Electrochemical stability of ECDs
The electrochemical cycling stability of ECDs scanned between -1.0 V and +1.8 V is
carried out using CV [42]. As displayed in Fig. 8, the electrochemical activity of
PFPT/PProDOT-Et2, P(FPT-co-DTC)/PProDOT-Et2, and
P(FPT-co-DTP)/PProDOT-Et2 ECDs was 93.7%, 96.0%, and 94.1%, respectively, after
scanning between -1.0 V and +1.8 V for 500 cycles. 90.9%, 95.6%, and 93.1% of
electrochemical activity was maintained after 1000 cycles for PFPT/PProDOT-Et2,
P(FPT-co-DTC)/PProDOT-Et2, and P(FPT-co-DTP)/PProDOT-Et2 ECDs, respectively.
The electrochemical activities of PFPT/PProDOT-Et2, P(FPT-co-DTC)/PProDOT-Et2,
and P(FPT-co-DTP)/PProDOT-Et2 ECDs at 500th cycle are larger than those reported
for imidazole-containing polymer (P1)/PEDOT ECD (stability = 81.3% at 500th cycle)
13

ACCEPTED MANUSCRIPT
[43] and PBTC/PEDOT ECD (stability = 92% at 500th cycle) [40]. The
results indicate that the anodically coloring films are potential for using in ECDs.
4. Conclusions
Three 4-(furan-2-yl)phenyl-containing conjugated polydithienylpyrroles (PFPT,
P(FPT-co-DTC), and P(FPT-co-DTP)) were electrosynthesized on conductive ITO
glass using potentiodynamic and potentiostatic depositions. The polymer films
displayed reversible redox behaviors and multichromic properties. P(FPT-co-DTP)
film displayed conspicuous color variations ranging from brass, gray, grayish-blue to
blue. Electrochromic switching studies of polymer films revealed that P(FPT-co-DTP)
film attained a higher ∆Tmax (50.7%) and η
max (232.4 cm2 C–1) at 1212 nm than those of
PFPT and P(FPT-co-DTC) films. Moreover, three dual-type ECDs based on three
anodically coloring materials and a cathodically coloring material were fabricated.
PFPT/PProDOT-Et2 ECD realized high
∆Tmax (33.3%), ∆ODmax (53.4%) and η (533.5
cm2 C–1). In addition, PFPT/PProDOT-Et2, P(FPT-co-DTC)/PProDOT-Et2, and
P(FPT-co-DTP)/PProDOT-Et2 ECDs displayed short switching time (≤1.03 s) and
long-term electrochemical cycling stability. Owing to the promising outcomes, the
three anodically coloring materials are potential candidates as electrochromic layers for
ECDs.
References
[1] C.G. Granqvist, P.C. Lansåker, N.R. Mlyuka, G.A. Niklasson, E. Avendaño, Solar
Energy Mater. Solar Cells 93 (2008) 2032.
[2] E. Rustaml, S. Goker, S. Tarkuc, Y.A. Udum, L. Toppare, J. Electrochem. Soc. 162
(2015) G75.
[3] S.-H. Hsiao, Y.-P. Huang, Dyes Pigm. 158 (2018) 368.
[4] K. Lin, S. Zhang, H. Liu, Y. Zhao, Z. Wang, J. Xu, Int. J. Electrochem. Sci. 10
(2015) 7720.
[5] B. Gadgil, P. Damlin, E. Dmitrieva, T. Ääritalo, C. Kvarnström, RSC Adv. 5 (2015)
42242.
14

ACCEPTED MANUSCRIPT
[6] S.-H. Hsiao, W.-K. Liao, G.-S. Liou, Polymers 9 (2017) 511.
[7] S.-H. Hsiao, Y.-Z. Chen, J. Electroanal. Chem. 799 (2017) 417.
[8] C.W. Kuo, T.Y. Wu, M.W. Huang, J. Taiwan Inst. Chem. Eng. 68 (2016) 481.
[9] C.W. Kuo, P.Y. Lee, Polymers 9 (2017) 518.
[10] B. Hu, X. Zhang, J. Liu, X. Chen, J. Zhao, L. Jin, Synth. Met. 228 (2017) 70.
[11] F.B. Koyuncu, S. Koyuncu, E. Ozdemir, Org. Electron. 12 (2011) 1701.
[12] B. Hu, X. Lv, J. Sun, G Bian, M. Ouyang, Z. Fu, P. Wang, C. Zhang, Organ.
Electron. 14 (2013) 1521.
[13] S. Ertan, A. Cihaner, Dyes Pigm. 149 (2018) 437.
[14] C.-W. Kuo, T.-L. Wu, Y.-C. Lin, J.-K. Chang, H.-R. Chen, T.-Y. Wu, Polymers 8
(2016) 368.
[15] L. Ji, Y.Y. Dai, S.M. Yan, X.J. Lv, C. Su, L.H. Xu, Y.K. Lv, M. Ouyang, Z. Chen,
C. Zhang, Sci. Rep. 6 (2016) 30068.
[16] C.-W. Kuo, J.-C. Chang, P.-Y. Lee, T.-Y. Wu, Y.-C. Huang, Materials 11 (2018)
1895.
[17] C.W. Kuo, B.K. Chen, W.B. Li, L.Y. Tseng, T.Y. Wu, C.G. Tseng, H.R. Chen, Y.C.
Huang, J. Chin. Chem. Soc. 61 (2014) 563.
[18] N. Atılgan, A. Cihaner, A.M. Önal, React. Funct. Polym. 70 (2010) 244.
[19] T.Y. Wu, J.L. Li, RSC Adv. 6 (2016) 15988.
[20] Y.S. Su, J.C. Chang, T.Y. Wu, Polymers 9 (2017) 114.
[21] T. Soganci, H.C. Soyleyici, M. Ak, H. Cetisli, J. Electrochem. Soc. 163 (2016)
H59.
[22] E. Tutuncu, M.I. Ozkut, B. Balci, H. Berk, A. Cihaner, Eur. Polym. J. 110 (2019)
233.
[23] S. Kumar, K.R.J. Thomas, C.-T. Li, K.-C. Ho, Org. Electron. 26 (2015) 109.
[24] D.M. Welsh, A. Kumar, E.W. Meijer, J.R. Reynolds, Adv. Mater. 11 (1999) 1379.
[25] T.Y. Wu, B.K. Chen, L. Hao, K.F. Lin, I.W. Sun, J. Taiwan Inst. Chem. Eng. 42
(2011) 914.
[26] T.Y. Wu, J.W. Liao, C.Y. Chen, Electrochim. Acta 150 (2014) 245.
[27] S.H. Hsiao, H.M. Wang, RSC Adv. 6 (2016) 43470.
[28] T.Y. Wu, H.H. Chung, Polymers 8 (2016) 206.
[29] J. Xu, Q. Ji, L. Kong, H. Du, X. Ju, J. Zhao, Polymers 10 (2018) 450.
[30] S. Mabrouk, M. Zhang, Z. Wang, M. Liang, B. Bahrami, Y. Wu, J. Wu, Q. Qiao, S.
Yang, J. Mater. Chem. A 6 (2018) 7950.
[31] T.Y. Wu, R.B. Sheu, Y. Chen, Macromolecules 37 (2004) 725.
[32] S. Tarkuc, M. Ak, E. Onurhan, L. Toppare, J. Macromol. Sci. Pure Appl. Chem.
45
(2008) 164.
[33] K.H. Chang, H.P. Wang, T.Y. Wu, I.W. Sun, Electrochim. Acta 119 (2014) 225.
[34] Z. Bicil, P. Camurlu, B. Yucel, B. Becer, J. Polym. Res. 20 (2013) 228.
[35] N. Guven, P. Camurlu, B. Yucel, Polym. Int. 64 (2015) 758.
[36] M.H. Tsao, T.Y. Wu, H.P. Wang, I.W. Sun, S.G. Su, Y.C. Lin, C.W. Chang, Mater.
Lett. 65 (2011) 583.
[37] T.Y. Wu, M.H. Tsao, F.L. Chen, S.G. Su, C.W. Chang, H.P. Wang, Y.C. Lin, W.C.
Ou-Yang, I.W. Sun, Int. J. Mol. Sci. 11 (2010) 329.
[38] Y.S. Su, T.Y. Wu, Polymers 9 (2017) 284.
15

ACCEPTED MANUSCRIPT
[39] C.-W. Kuo, J.-C. Chang, P.-Y. Lee, T.-Y. Wu, Y.-C. Huang, Materials 11 (2018)
1895.
[40] L. Kong, Z. Wang, J. Zhao, J. Xu, Int. J. Electrochem. Sci. 10 (2015) 982.
[41] T.Y. Wu, Y.S. Su, J. Electrochem. Soc. 162 (2015) G103.
[42] C.W. Kuo, T.Y. Wu, S.C. Fan, Coatings 8 (2018) 102.
[43] G. Xu, J. Zhao, J. Liu, C. Cui, Y. Hou, Y. Kong, J. Electrochem. Soc. 160 (2013)
G149.
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Table 1. Electrochromic images and L*, a*, b* values of homopolymer and copolymer
films at various potentials in [EPI+][TFSI–].
Polymer films
E/V
Photographs
L *a
a *
b *
0
PFPT
82.51
80.68
77.66
74.24
78.51
67.95
58.21
56.35
81.89
85.48
84.46
82.93
1.63
-1.07
-1.28
-0.72
-5.31
-6.53
-1.13
-0.23
15.77
-0.94
-1.93
-2.4
33.23
24.1
1.0
1.2
1.4
0
15.7
9.29
P(FPT-co-DTC)
43.56
16.26
-2.72
-7.15
18.07
1.99
1.0
1.2
1.4
0
P(FPT-co-DTP)
0.8
1.0
1.2
-4.97
-7.18
a L* represents the lightness, and a* and b* denote the color channels.
Table 2. Comparisons of ∆Tmax and ηmax for several polymer films.
max / cm2 C-1
---
---
167.4
169
181.8
229.0
232.4
Polymer films
P(TPHA)
PSNS-Fc
PSNS-iProP
P(SNS-pyrene)
PFPT
P(FPT-co-DTC)
P(FPT-co-DTP)
Electrolyte
0.1 M LiCIO4/ACN
LiCIO4/ACN
Eg / eV
∆Tmax / %
Ref.
32
34
33
35
λ
/ nm
∆ODmax / %
η
334
356
646
349
2.27
2.61
2.28
3.36
2.26
---
11
---
---
7.7
---
21.1
53.4
47.8
27.1
15.5
20.28
22.7
44.8
50.7
0.1 M TBABF4/ethanol
0.1 M LiCIO4/ACN
[EPI+][TFSI–]
1320
906
1212
This work
This work
This work
[EPI+][TFSI–]
[EPI+][TFSI–]
---
17

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Table 3. Electrochromic images and L*, a*, and b* values of PFPT/PProDOT-Et2,
P(FPT-co-DTC)/PProDOT-Et2, and P(FPT-co-DTP)/PProDOT-Et2 ECDs.
ECDs
E/V
Photoimages
L*
a*
0.2
b*
PFPT
/PProDOT-Et2
-0.4
78.4
17.82
-8.07
-16.23
-20.22
37
0.6
0.8
1.2
-0.4
0.4
0.6
0.8
1.2
-0.4
0
64.26
58.56
55.7
1.02
1.63
3.59
-8.16
P(FPT-co-DTC)/
PProDOT-Et2
73.25
57.74
50.41
-5.6
13.91
3.57
-4.09
43.81
40.63
73.33
75.88
69.75
64.3
-2.93
0.21
-6.28
-11.51
14.83
13.06
-4.4
P(FPT-co-DTP)/
PProDOT-Et2
13.82
4.55
0.4
0.6
0.8
1.2
-0.49
-0.23
-14.5
58.63
54.55
-1.4
-23.77
-30.05
4.66
18

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Table 4. The transmittance changes and switching time of ECDs.
Cycle
No.
Optical contrast/%
τ/s
Stability
(100 cyc)
ECDs
λ/nm
Tb
Tc
τc
τb
∆
T
1
50
100
1
50
100
1
50
100
1
50
100
1
46.1
46.3
46.8
45.3
44.8
44.5
49.4
50.0
48.3
---
---
---
55.7
55.5
55.4
12.8
13.2
13.7
15.4
15.1
15.0
11.9
11.4
11.3
---
---
---
26.6
26.8
26.9
33.3
33.1
33.1
29.9
29.7
29.5
37.5
38.6
37.0
31.3
26.8
24.9
29.2
28.7
28.5
1.01
0.87
0.93
0.86
0.93
0.97
1.03
0.96
0.96
0.96
0.96
0.99
1.05
1.06
1.04
0.89
0.87
0.87
0.95
0.94
0.90
0.84
0.91
0.91
0.99
0.96
0.97
1.03
1.01
1.00
PFPT/PProDOT-Et2
590
99.4%
98.7%
98.7%
79.5%
97.6%
P(FPT-co-DTC)/
PProDOT-Et2
586
612
592
591
P(FPT-co-DTP)/
PProDOT-Et2
a
PDTC/PProDOT-Et2
PDTP/PProDOT-Et2
50
100
a Reference 38.
Table 5. Electrochromic parameters of ECDs.
Ref.
32
40
40
41
ECDs
∆Tmax / % ∆ODmax / %
λ
/ nm
611
580
616
586
590
586
612
592
591
η
/ cm2 C–1
---
120
399
437.5
533.5
340.0
855.9
345.2
324.1
P(TPHA-co-EDOT)/PEDOT
PBTC/PEDOT
23
---
26.3
20.1
32.3
33.3
29.9
38.6
31.3
29.2
---
---
PBEC/PEDOT
PBDO/PProDOT-Et2
PFPT/PProDOT-Et2
37.6
53.4
47.2
61.8
35.6
32.2
This study
This study
This study
38
P(FPT-co-DTC)/PProDOT-Et2
P(FPT-co-DTP)/PProDOT-Et2
PDTC/PProDOT-Et2
PDTP/PProDOT-Et2
This study
19

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(a)
(d)
0.6
0.4
0.2
0.0
-0.2
3
FPT
FPT + DTC
2
1
0
-1
-2
-1.0
-0.5
0.0
0.5
1.0
1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
Potential (V) vs. Ag/AgCl sat's KCl
Potential (V) vs. Ag/AgCl sat's KCl
(b)
(e)
3
1.0
0.8
0.6
0.4
0.2
0.0
-0.2
-0.4
FPT + DTP
DTC
2
1
0
-1
-2
-1.0
-0.5
0.0
0.5
1.0
1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
Potential (V) vs. Ag/AgCl sat's KCl
E / V vs. Ag/AgCl sat's KCl
(c)
0.8
DTP
0.6
0.4
0.2
0.0
-0.2
-0.4
-1.0
-0.5
0.0
0.5
1.0
1.5
E / V vs. Ag/AgCl sat's KCl
Figure 1. Electrosyntheses of (a) 2 mM FPT, (b) 2 mM DTC, (c) 2 mM DTP, (d) 2 mM
FPT + 2 mM DTC, (e) 2 mM FPT + 2 mM DTP in 0.1 M LiClO4/ACN (scan rate: 100
mV s-1).
20

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(a)
(b)
0.4
0.2
0.3
Ipa
Ipc
0.2
0.1
0.0
0.0
25 mV s-1
-0.1
50 mV s-1
-0.2
-0.4
100 mV s-1
150 mV s-1
-0.2
200 mV s-1
-0.3
0
50
100
150
200
-1.0
-0.5
0.0
0.5
1.0
1.5
Scan rate (mV s-1
)
Potential (V) vs. Ag/AgCl sat's KCl
Figure 2. (a) The i-V curves of PFPT film at different scan rates in 0.1 M LiClO4/ACN;
(b) the relationship of scan rates vs. anodic and cathodic peak current densities of PFPT
film in 0.1 M LiClO4/ACN.
21

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(a)
(b)
(c)
0 V
0.6 V
0.8 V
1.2 V
1.4 V
1.8 V
0.6
0.4
0.2
0.0
590 nm
1320 nm
407 nm
400
800
1200
1600
Wavelength (nm)
1.2
1.0
0.8
0.6
0.4
0.2
0 V
0.4 V
0.6 V
1.0 V
1.2 V
1.4 V
906 nm
406 nm
400
800
1200
1600
Wavelength (nm)
0.6
0 V
1212 nm
0.4 V
0.6 V
0.8 V
1.0 V
1.2 V
1.4 V
0.5
0.4
0.3
0.2
0.1
472 nm
400
800
1200
1600
Wavelength (nm)
Figure 3. UV-Vis-NIR spectra of (a) PFPT, (b) P(FPT-co-DTC), and (c)
P(FPT-co-DTP) films at various potentials in [EPI+][TFSI-].
22

ACCEPTED MANUSCRIPT
(a)
100
80
60
40
20
0
PFPT at 1320 nm
Tb (0 V)
Tc (1.0 V)
100
150
200
250
(b)
Time (s)
100
80
60
40
20
0
P(FPT-co-DTC) at 906 nm
Tb (0 V)
Tc (1.0 V)
100
150
200
250
(c)
Time (s)
100
80
60
40
20
0
P(FPT-co-DTP) at 1212 nm
Tb (0 V)
Tc (1.0 V)
100
150
200
250
Time (s)
Figure 4. Transmittance-time profiles of (a) PFPT, (b) P(FPT-co-DTC), and (c)
P(FPT-co-DTP) films in an ionic liquid with a time interval between bleached and
colored states of 5 s.
23

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(a)
0.8
0.6
0.4
0.2
590 nm
-0.4 V
0 V
0.2 V
0.4 V
0.6 V
0.8 V
1.0 V
1.2 V
407 nm
400
600
800
1000
1200
1400
Wavelength (nm)
(b)
0.7
0.6
0.5
0.4
0.3
0.2
0.1
406 nm
(b)
-0.4 V
-0.2 V
0 V
0.2 V
0.4 V
0.6 V
0.8 V
1.0 V
1.2 V
588 nm
400
600
800
1000
1200
1400
Wavelength (nm)
(c)
0.8
0.6
0.4
0.2
0.0
-0.4 V
-0.2 V
0 V
0.2 V
0.4 V
0.6 V
0.8 V
1.0 V
1.2 V
612 nm
472 nm
400
600
800
1000
1200
1400
Wavelength (nm)
Figure 5. UV-Vis spectra of (a) PFPT/PProDOT-Et2, (b) P(FPT-co-DTC)/PProDOT-Et2,
and (c) P(FPT-co-DTP)/PProDOT-Et2 ECDs at different voltages.
24

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(a)
100
80
60
40
20
0
Tb (-0.2 V)
Tc (1.2 V)
200
250
300
350
400
Time (s)
(b)
100
80
60
40
20
0
Tb (-0.2 V)
Tc (1.2 V)
200
250
300
350
400
Time (s)
(c)
100
80
60
40
20
0
Tb (-0.2 V)
Tc (1.2 V)
200
250
300
350
400
Time (s)
Figure 6. Electrochromic switching of (a) PFPT/PProDOT-Et2 ECD at 590 nm, (b)
P(FPT-co-DTC)/PProDOT-Et2 ECD at 586 nm, and (c) P(FPT-co-DTP)/PProDOT-Et2
ECD at 612 nm with a time interval of 5 s. The ECDs were switched between − 0.2 V
and +1.2 V.
25

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(a)
100
80
60
40
20
0
-0.2 V
1.2 V
0
200
400
600
800
1000
1200
Time (s)
(b)
100
80
60
40
20
0
-0.2 V
1.2 V
0
200
400
600
800
1000
1200
Time (s)
(c)
100
-0.2 V
1.2 V
80
60
40
20
0
0
200
400
600
800
1000
1200
Time (s)
Figure 7. Open circuit memory of (a) PFPT/PProDOT-Et2 ECD measured at 590 nm,
(b) P(FPT-co-DTC)/PProDOT-Et2 ECD measured at 586 nm, and (c)
P(FPT-co-DTP)/PProDOT-Et2 ECD monitored at 612 nm.
26

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(a)
(b)
(c)
0.15
0.10
0.05
0.00
-0.05
-0.10
-0.15
1st cycle
500th cycle
1000th cycle
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Potential (V) vs. Ag/AgCl sat's KCl
0.2
1st cycle
500th cycle
1000th cycle
0.1
0.0
-0.1
-0.2
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Potential (V) vs. Ag/AgCl sat's KCl
0.15
0.10
0.05
0.00
-0.05
-0.10
-0.15
1st cycle
500th cycle
1000th cycle
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Potential (V) vs. Ag/AgCl sat's KCl
Figure 8. Cyclic voltammograms of (a) PFPT/PProDOT-Et2, (b)
P(FPT-co-DTC)/PProDOT-Et2, and (c) P(FPT-co-DTP)/PProDOT-Et2 ECDs at the
first, 500th, and 1000th cycles.
27

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NH2
NO2
O
CH3CN
O
O
O2N
N
+
+
O
H2N NH2 H2O
Pd/C
O
O
O2N
H2N
1
O
O
O
O
S
S
PTSA
+
H2N
toluene
S
N
S
1
FPT
Scheme 1. The synthetic procedures of FPT monomer.
O
O
electrochemical
polymerization
S
N
S
S
N
S
n
PFPT
FPT
O
O
H
N
H
electrochemical
polymerization
N
+
S
S
S
N
S
S
S
S
N
S
m
n
FPT
DTC
P(FPT-co-DTC)
O
O
electrochemical
polymerization
C6H13
C6H13
C6H13
C6H13
+
N
N
S
N
S
S
N
S
S
S
S
S
m
n
P(FPT- -DTP)
DTP
FPT
co
Scheme 2. The electrosynthesized schemes of PFPT, P(FPT-co-DTC) and
P(FPT-co-DTP).
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