The effect of the donor unit on the optical properties of polymers

Article abstract of DOI:10.1016/j.orgel.2011.06.004

A series of donor-acceptor-donor (DAD) type π-conjugated monomers containing 10,11,12,13-tetrahydrodibenzo[a,c]phenazine moiety in the backbone as the acceptor unit and thiophene derivatives as the donor unit were prepared by Stille coupling. Thiophene, 3-hexyl thiophene and 3,4-ethylenedioxythiophene were used as the donor units to understand the effects of donor unit on electrochemical and optoelectronic properties of the resulting polymers. Electroactivity of monomers and redox behavior of their polymers were investigated by cyclic voltammetry. The presence of the strong electron-donating ethylenedioxy groups on the aromatic structure increased electron density on 2,7-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-10,11,12,13- tetrahydrodibenzo[a,c]phenazine (DTBP), thus the oxidation potential of DTBP shifts to a lower value than that of 2,7-bis(4-hexylthiophen-2-yl)-10,11,12,13- tetrahydrodibenzo[a,c] phenazine (HTBP) and 2,7-di(thiophen-2-yl)-10,11,12,13- tetrahydrodibenzo[a,c]phenazine (TTBP). The electronic band gaps, defined as the onset of the π-π transition, were found to be 2.5 eV for HTBP, 2.0 eV for DTBP and 2.2 eV for TTBP. Both of PDTBP and PTTBP films showed multi-color electrochromism and also fast switching times (<1 s) in the visible and NIR regions.

Full text of DOI:10.1016/j.orgel.2011.06.004

Organic Electronics 12 (2011) 1625–1631
Contents lists available at ScienceDirect
Organic Electronics
journal homepage: www.elsevier.com/locate/orgel
The effect of the donor unit on the optical properties of polymers
Elif Kose Unver a, Simge Tarkuc a,e, Yasemin Arslan Udum d, Cihangir Tanyeli a,
Levent Toppare a,b,c,
⇑
a Department of Chemistry, Middle East Technical University, 06531 Ankara, Turkey
b Department of Biotechnology, Middle East Technical University, 06531 Ankara, Turkey
c Department of Polymer Science and Technology, Middle East Technical University, 06531 Ankara, Turkey
d Institute of Science and Technology, Department of Advanced Technologies, Gazi University, 06570 Ankara, Turkey
e Opto-Electronic Materials, DelftChemTech, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 4 May 2011
Received in revised form 6 June 2011
Accepted 7 June 2011
Available online 30 June 2011
A
series of donor–acceptor–donor (DAD) type p-conjugated monomers containing
10,11,12,13-tetrahydrodibenzo[a,c]phenazine moiety in the backbone as the acceptor unit
and thiophene derivatives as the donor unit were prepared by Stille coupling. Thiophene,
3-hexyl thiophene and 3,4-ethylenedioxythiophene were used as the donor units to
understand the effects of donor unit on electrochemical and optoelectronic properties of
the resulting polymers. Electroactivity of monomers and redox behavior of their polymers
were investigated by cyclic voltammetry. The presence of the strong electron-donating
ethylenedioxy groups on the aromatic structure increased electron density on 2,7-bis
(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-10,11,12,13-tetrahydrodibenzo[a,c]phenazine
(DTBP), thus the oxidation potential of DTBP shifts to a lower value than that of 2,7-bis
(4-hexylthiophen-2-yl)-10,11,12,13-tetrahydrodibenzo[a,c] phenazine (HTBP) and 2,7-di
(thiophen-2-yl)-10,11,12,13-tetrahydrodibenzo[a,c]phenazine (TTBP). The electronic band
Keywords:
Electrochemical polymerization
Multichromism
Optical properties
gaps, defined as the onset of the p–
p⁄ transition, were found to be 2.5 eV for HTBP, 2.0 eV
for DTBP and 2.2 eV for TTBP. Both of PDTBP and PTTBP films showed multi-color electro-
chromism and also fast switching times (<1 s) in the visible and NIR regions.
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
Electrochromism is defined as the reversible change in
transmittance and/or reflectance that is associated with
By virtue of their numerous applications, electrochro-
mic materials are currently attracting a great deal of inter-
est. There are many commercial applications of these
materials including anti-glare rear-view mirrors, electro-
chromic devices [1]. Electrochromism can be exploited in
a series of optical devices with potential use in various
applications, such as information display and storage, the
automotive industry (as rear view mirrors), and architec-
ture (as smart windows to control luminosity and save
energy through the control of sunlight transmission) [2].
an electrochemically induced oxidation–reduction reaction
[3]. The switching of redox states generates different elec-
tronic absorption bands. Electrochromism not only in-
cludes changes in the visible region, but also in the
ultraviolet (UV), infrared (IR), and even the microwave re-
gions of the spectrum [4–6].
Among the organic electrochromic materials, conduct-
ing polymers have received more attention because of
their additional advantages over inorganic compounds,
such as outstanding coloration efficiency [7], fast switching
ability [8,9], multiple colors with the same material
[7,10–12] and fine-tuning of the band gap (and the color)
through chemical structure modification [13–17].
Generally, there are three strategies that have been used
⇑
Corresponding author at: Department of Chemistry, Middle East
Technical University, 06531 Ankara, Turkey.
E-mail address: toppare@metu.edu.tr (L. Toppare).
1566-1199/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.orgel.2011.06.004

1626
E.K. Unver et al. / Organic Electronics 12 (2011) 1625–1631
to tune the electrochemical and the optical properties of
p
-
Varian Cary 5000 spectrophotometer. Minolta CS-100
conjugated polymers. The first is the increasing the conju-
gation length. An increase in the conjugation length results
in decreasing the band gap (Eg), limited by Peierls distor-
tion [18]. A second strategy is to change the electron den-
sity via incorporation of electron donating or withdrawing
groups onto the polymer. The third method is to modify
the steric interaction between repeat units within the
polymer backbone, using more planar systems result in
better orbital overlap, thereby lowering the band gap.
The fused-ring units allow fine-tuning of the polymer band
spectrophotometer
measurements.
was
used
for
colorimetry
2.3. Synthesis
2.3.1. 2,7-Dibromo-10,11,12,13-tetrahydrodibenzo[a,c]phena
zine (3)
2,7-Dibromophenanthrene-9,10-dione (300 mg, 0.82
mmol), ethanol (50 mL), catalytic amount PTSA and
cyclohexane-1,2-diamine (0.82 mmol) were placed in a
round-bottomed flask fitted with a condenser. The mixture
was heated under reflux. At the end of the reaction, cloudy
mixture was observed. Upon cooling, filtration of the
reaction mixture followed by washing with ethanol
afforded the desired product, 2,7-dibromo-10,11,12,13-
tetrahydrodibenzo[a,c]phenazine. To purify the dibromi-
nated compound, column chromatography was performed
over silica gel, eluting with 1:5 (CHCl3:Hexane).
gap due to the enhanced
p–p stacking between the
polymeric chains. Following this strategy, we previously
reported the synthesis of thienyl and ethylenedioxyben-
zene functionalized thieno[3,4-b]pyrazines [19] as precur-
sors to investigate the effect of changes in
p-conjugated
terthienyls on the electronic and optoelectronic properties
of the resulting polymers.
In an earlier work, a series of polymers with a conjugated
core building block containing dibenzo[a,c]phenazine
moietyas the acceptor unit and thiophene based donor units
were synthesized [20]. In the present study, three new
donor–acceptor–donor polymers with 10,11, 12,13-tetra-
hydrodibenzo[a,c]phenazine moiety as the acceptor unit
and thiophene, 3-hexyl thiophene and 3,4-ethylenedioxy-
thiophene as the donor units were synthesized. The effect
of replacing the 10,11,12,13-tetrahydrodibenzo[a,c]phena-
zine moiety with dibenzo[a,c]phenazine as the acceptor unit
on the electrochemical and spectroelectrochemical
properties of the resulting polymers were analyzed.
White solid (180 mg, 49%) IR
1598, 1479, 1427, 1371, 1323, 1263, 1197, 1074, 955,
898, 797, 733, 655, 526 cmꢀ1 1H-NMR (400 MHz CDCl3):
t = 3074, 2931, 1878,
.
d (ppm) 9.04 (d, 2H, J = 2.2 Hz), 8.12 (d, 2H, J = 8.7 Hz),
7.64 (dd, 2H, J = 8.7, 2.2 Hz), 3.08–3.10 (m, 4H), 1.99–2.02
(m, 4H) 13C-NMR (100 MHz, CDCl3):
d (ppm) 153.3,
137.4, 131.7, 131.4, 128.7, 127.6, 124.1, 122.1, 32.7, 22.8.
2.3.2. General procedure for the synthesis of 4, 5, 6 via Stille
coupling
2,7-Dibromo-10,11,12,13-tetrahydrodibenzo[a,c]phena-
zine (100 mg, 0.23 mmol), and tributylstannane compound
(0.92 mmol) were dissolved in anhydrous THF (80 ml), the
solution was purged with argon for 30 min and
Pd(PPh3)2Cl2 (40 mg, 0.057 mmol) was added at room tem-
perature. The mixture was refluxed over night under argon
atmosphere. The crude products were purified by column
chromatography using DCM – Hexane as the eluent.
2. Experimental
2.1. Materials
Dichloromethane (DCM), chloroform (CHCl3), hexane,
ethanol, N-bromosuccinimide (NBS), cyclohexane-1,2-
diamine, dichlorobis(triphenyl phosphine)palladium(II)
(Pd(PPh3)2Cl2), p-toluene sulfonic acid (PTSA) were pur-
chased from Sigma–Aldrich. Silica gel was purchased from
Merck and tetrahydrofuran (THF) was purchased from
Fisher Scienific UK Limited. Tributylstannane compounds
[21–23] and 2,7-dibromophenanthrene-9,10-dione [24]
were prepared according to literature method. THF was
dried and distilled over benzophenone–sodium under
nitrogen before use.
2.3.2.1. 2,7-Bis(4-hexylthiophen-2-yl)-10,11,12,13-tetrahydro
dibenzo[a,c] phenazine (4, HTBP). The crude product was
purified by column chromatography (DCM:Hexane 1:3)
to give 4, HTBP (82 mg, 58%) as pale yellow solid. IR
t
= 3055, 2925, 2852, 1611, 1460, 1371, 1323, 903, 810,
724, 580 cmꢀ1 1H-NMR (400 MHz CDCl3): d (ppm) 9.21
.
(s, 2H), 8.33 (d, 2H, J = 8.5 Hz), 7.79 (d, 2H, J = 8.5 Hz),
7.34 (s, 2H), 6.88 (s, 2H), 3.10–3.18 (m, 4H), 2.60 (t, 4H,
J = 7.6 Hz), 1.88–2.03 (m, 4H), 1.63 (p, 4H), 1.26–1.35 (m,
12H), 0.84 (t, 6H, J = 7.0 Hz) 13C-NMR (100 MHz, CDCl3): d
(ppm) 152.8, 144.8, 144.1, 138.9, 133.8, 130.4, 129.9,
126.6, 125.5, 123.4, 121.6, 120.2, 33.0, 32.0, 31.0, 30.8,
29.3, 23.2, 22.9, 14.4. HRMS m/z calcd for C40H44N2S2
617.3024 found 617.3046 [M+H]+.
2.2. Instrument
1H-NMR and 13C-NMR spectra of compounds were
recorded in CDCl3 using Bruker Spectrospin Avance DPX-
400 Spectrometer and chemical shifts were given relative
to tetramethylsilane. Voltalab 50 potentiostat was used
for the investigation of the redox behavior of monomers.
Electropolymerizations were carried out in a three-elec-
trode cell consisting of indium tin oxide (ITO, Delta tech-
2.3.2.2. 2,7-Bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-10,
11,12,13-tetrahydrodibenzo [a,c]phenazine (5, DTBP). The
crude product was purified by column chromatography
(DCM:Hexane 3:1) to give 5, DTBP (86 mg, 66%) as a yellow
nologies, 8–12
X
/cm2) coated glass as the working
solid. IR
t
= 3112, 2932, 1610, 1503, 1437, 1365, 1168,
electrode, platinum wire as the counter electrode, and Ag
wire as the pseudo-reference electrode (0.3 V vs Fc/Fc+).
UV–Vis-NIR spectra of the polymers were recorded on a
1071, 897, 810, 755, 605 cmꢀ1
.
1H-NMR (400 MHz CDCl3):
d (ppm) 9.31 (d, 2H, J = 1.8 Hz), 8.37 (d, 2H, J = 8.7 Hz), 7.99
(dd, 2H, J = 8.7, 1.8 Hz), 6.30 (s, 2H), 4.32–4.33 (m, 4H),

E.K. Unver et al. / Organic Electronics 12 (2011) 1625–1631
1627
4.22–4.24 (m, 4H), 3.10–3.16 (m, 4H), 1.97–1.99 (m, 4H).
13C-NMR (100 MHz, CDCl3): d (ppm) 151.3, 141.3, 137.7,
137.6, 131.1, 129.1, 128.1, 125.5, 121.8, 120.5, 116.6,
97.0, 63.8, 63.4, 31.8, 21.9. HRMS m/z calcd for
therene. With the help of one of them [24], it was
synthesized starting from phenanthrene-9,10-dione 1 in
the presence of NBS and concentrated H2SO4. Condensa-
tion reaction of 2 with cyclohexane-1,2-diamine afforded
3 in 49% yield, to obtain which reflux in EtOH for 5 h. To in-
crease the reaction yields, p-toluene sulfonic acid was uti-
lized as the catalyst. If the reaction medium is kept at room
temperature without catalyst, there is no aromatization in
the phenazine ring. However, this product is highly unsta-
ble and undergoes rearrangement with heat or light [25].
Finally, condensation product 3 was reacted with related
stannane compounds in the presence of Pd(PPh3)2Cl2 to
obtain target monomers 4 (HTBP), 5 (DTBP) and 6 (TTBP)
in moderate yields (58–66%).
C
32H24N2O4S2 565.1256 found 565.1250 [M+H]+.
2.3.2.3. 2,7-Di(thiophen-2-yl)-10,11,12,13-tetrahydrodibenzo
[a,c]phenazine (6, TTBP). The crude product was purified by
column chromatography (DCM:Hexane 5:1) to give 6, TTBP
(68 mg, 66%) as yellow solid. IR
t
= 3067, 2934, 1898, 1610,
1446, 1371, 1193, 1075, 903, 811, 696, 592 cmꢀ1
.
1H-NMR
(400 MHz CDCl3): d (ppm) 9.35 (d, 2H, J = 1.9 Hz), 8.49 (d,
2H, J = 8.5 Hz), 7.91 (dd, 2H, J = 8.5, 1.9 Hz), 7.53 (dd, 2H,
J = 3.5, 1.0 Hz), 7.30 (dd, 2H, J = 5.1, 1.0 Hz), 7.10 (dd, 2H,
J = 5.1, 3.5 Hz), 3.18–3.21 (m,4H), 2.02–2.05 (m, 4H). HRMS
m/z calcd for C28H20N2S2 449.1146 found 449.1139 [M+H]+.
3.2. Electropolymerization
The electrochemical behavior of HTBP, DTBP and TTBP
were investigated by cyclic voltammetry technique. Cyclic
voltammetry (CV) is a very useful method that reveals the
electroactivity of the compounds in concern. It also gives
evidence on the reversibility of the electron transfer
reactions during the electropolymerization. Electrochemi-
cal polymerizations of the monomers were studied via
CV in a solution of 10ꢀ2 M monomer on an ITO working
electrode.
3. Results and discussion
3.1. Synthesis of monomers
Syntheses of the monomers are depicted Scheme 1. In
literature, there are a number of methods [25–28] for the
synthesis of 2,7-dibromophenanthrene-9,10-dione 2 start-
ing from phenanthrene-9,10-dione or 2,7-dibromophenan-
Scheme 1. The synthetic route of the monomers. (a) NBS, conc. H2SO4, rt, 3h (b) Cyclohexane-1,2-diamine, PTSA, EtOH, reflux, 5h (c–e) Pd(PPh3)2Cl2,
stannanes(tributyl(4-hexylthiophen-2-yl)stannane)(c), tributyl(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)stannane(d) and tributyl(thiophen-2-yl)stannane(e),
dry THF, overnight reflux.

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E.K. Unver et al. / Organic Electronics 12 (2011) 1625–1631
Fig. 1. Cyclic voltammogram of (a) PHTBP (b) PDTBP (c) PTTBP in DCM (for PDTBP, DCM/ACN(5/95)) solution containing 0.1 M TBAPF6, scan rate
100 mV sꢀ1
.
Cyclic voltammograms showed both an irreversible
oxidation wave corresponding to the oxidation of the
monomers and the reversible redox couple for the
polymers (Fig. 1). While the monomer oxidation potential
of DTBP was observed at 0.97 V, they were at 1.28 V for
HTBP and >1.3 V for TTBP. Comparing the onsets of mono-
mer oxidation, DTBP was much more easily oxidized than
both HTBP and TTBP. The presence of electron-donating
ethylene-dioxy bridge on EDOT units lowers the oxidation
potential compared to those of thiophene and 3-hexyl thi-
ophene substituted monomers. The oxidation peak poten-
tials of polymers vary from 0.83 to 1.16 V vs Ag wire
pseudo reference electrode, whereas the reduction peak
potentials were in a range of 0.70–1.00 V. As the cyclic scan
proceeded, intensities of anodic and cathodic currents of
the polymer films gradually increased, indicating the pres-
ence of a conductive polymer on the electrode.
resulting oligomer, thereby the polymer film grows on
the surface of electrode.
3.3. Spectroelectrochemistry
Polymers were prepared by repetitive potential-sweep
anodic oxidation of the corresponding monomers HTBP
and TTBP on ITO coated glass slides in DCM. For DTBP, a
DCM/ACN mixture (5:95) was utilized with 0.1 M TBAPF6
at a scan rate 100 mV sꢀ1. After electropolymerization,
the polymer coated electrode was washed with acetonitrile
to remove unreacted monomer. To investigate spectro-
scopic changes, UV–Vis-NIR spectrophotometer was used
in a monomer free system. The spectra of polymers were
recorded continuously versus time while applying a con-
stant potential. Fig. 2 illustrates the optoelectrochemistry
of PHTBP, PDTBP and PTTBP. Stepwise oxidation of the
PHTBP shows the fading of absorbance at 395 nm which
Our previous work where dibenzo[a,c]phenazine
moiety was used as the acceptor unit, 2,7-di(thiophen-2-
yl)dibenzo[a,c]phenazine (TTP) did not produce an adher-
ent thin polymer film on ITO-coated electrode surface
[19]. Introduction of alkyl bridge on the backbone of
belongs to p–
p⁄ transition. As polymer film gets oxidized,
typical evolution of peaks at 620 nm and 1500 nm oc-
curred corresponding to polaronic and bipolaronic bands,
respectively. The band gap of PHTBP, onset of the
p–
p⁄
p-conjugated system leads to obtain a polymer film on
transition for the neutral polymer was calculated as
the surface of working electrode. It seems like that the
presence of alkyl bridge enhanced the solubility of the
2.5 eV using the absorption band centered at 395 nm. The
absorbance assigned to
p–
p⁄ transition for PDTBP is at

E.K. Unver et al. / Organic Electronics 12 (2011) 1625–1631
1629
Fig. 2. Spectroelectrochemical spectra of (a) PHTBP with applied potential between +0.4 and +1.3 V in DCM/TBAPF6 (b) PDTBP with applied potential
between ꢀ0.1 and +1.2 V in ACN/DCM/TBAPF6 (c) PTTBP with applied potential between 0.0 and +1.2 V in DCM/TBAPF6.
490 nm and this transition was observed at 430 for PTTBP.
The band gap of PDTBP was calculated as 2.0 eV and that of
PTTBP was calculated as 2.2 eV using the wavelength value
the visible region (Table 1, colors refer to polymer thick-
nesses between 0.5 and 1 microns). Polymers of PDTBP
and PTTBP have the ability to achieve multi-colors with
small structural modifications. Multicolored electrochro-
mism observed in a polymer is a promising property since
these types of materials can be utilized as active layers in
many device applications especially in the information
technologies. On the other hand, PHTBP film changes from
a yellow neutral state to a blue oxidized state.
PDTBP is orange in its neutral state. Upon oxidation, the
orange color of the polymer turns into brown. Further oxi-
dation results in purple. A gray color was observed when
+0.7 V potential was applied. When the potential is further
increased the polymer turns into a blue color.
at the onset of the p–
p⁄ transition. The difference in band
gap, 0.5 eV, between PHTBP and PDTBP can be explained
by distortion of backbone planarity. Presence of alkyl
chains at the b-position of thiophene ring causes steric
interactions between repeat units within the polymer
backbone, resulting in decreasing
p orbital overlap.
The
p–
p⁄ transition for 10,11,12,13-tetrahydrodi-
benzo[a,c]phenazine containing polymers takes place at
an higher energy than those of the dibenzo[a,c]phenazine
derivatives [20]. Introduction of alkyl bridge on the back-
bone of
to deviation from the planarity, resulting in decreasing
-orbital overlap, thereby the absorption band of
p-conjugated system instead of aromatic unit leads
The color of the PTTBP film is yellow in its neutral state.
Its color switches from yellow to greenish brown due to
further oxidation. When +0.9 V potential is applied, the
polymer turns into gray. Further oxidation causes blue
color.
p
p–
p⁄
transition shifts to shorter wavelength.
3.4. Colorimetry
Color and luminance (L) changes were monitored as the
potential was increased. According to the CIE (Commission
Internationale de I’Eclairage) system of colorimetry, the
color is made up of three attributes; luminance (Y), hue
(x), and saturation (y).
3.5. Electrochemical switching
Electrochromic switching studies were carried out to
obtain changes in the transmittance (optical contrast). A
square-wave potential step method coupled with optical
spectroscopy is used to obtain the switching times and
the contrast for these polymers. For that matter, polymer
Polymers of PDTBP and PTTBP reveal several distinct
colors since the polaron bands of the polymers are still in

1630
E.K. Unver et al. / Organic Electronics 12 (2011) 1625–1631
Table 1
Electronic and electrochromic properties of the polymers.
Polymer
PHTBP
kmax (nm)
Redox state
Y
x
y
Color
Eg (eV)
395
Neutral
Oxidized
Neutral
Half Ox.
Half Ox.
Half Ox
Oxidized
Neutral
Oxidized
99.9
48.7
38.9
32.9
32.7
34,8
34.8
79.8
62.5
49.9
44.6
0.320
0.258
0.4S9
0.437
0.376
0316
0.209
0.353
0.353
0.321
0.2S0
0.366
0.297
0.398
0398
0.385
0.329
0.219
0.397
0.399
0.363
0.312
Yellow
Blue
2.5
PDTBP
490
Orange
Brown
Purple
Dark gray
Blue
Yellow
Gray
Brown
Blue
2.0
PTTBP
430
2.2
Fig. 3. Electrochromic switching, optical absorbance change monitored (a) at 395, 620 and 1500 nm for PHTBP between +0.4 and +1.3 V (b) at 490, 610 and
1320 nm for PDTBP between ꢀ0.1 and +1.2 V (c) at 430, 550 and 1270 nm for PTTBP between 0.0 and +1.2 V.
Table 2
Switching properties of polymers.
Polymer
PHTBP
PDTBP
PTTBP
kmax (nm)
Switching time (s)
395
1.7
620
1 5
1500
1.8
490
0.8
610
0.7
1320
06
430
2.3
550
0.5
1270
0.5
films were switched between their neutral and oxidized
states with a time interval of 5 s to monitor their stability,
optical contrasts and switching times both in visible and
NIR regions. The results were displayed in Fig. 3 where
transmittance–time profiles of the polymers were
recorded during double step spectrochronoamperometry.

E.K. Unver et al. / Organic Electronics 12 (2011) 1625–1631
1631
[9] A. Kumar, D.M. Welsh, M.C. Morvant, F. Piroux, K.A. Abboud, J.R.
Reynolds, Conducting poly(3,4-alkylenedioxythiophene) derivatives
as fast electrochromics with high-contrast ratios, Chem. Mater. 10
(1998) 896.
In Near-IR region, PTTBP film has the maximum contrast
ratio (% T) as 64% at 1270 nm. The corresponding data
are given in Fig. 3.
D
[10] G. Sonmez, H.B. Sonmez, C.K.F. Shen, F. Wudl, Red, green, and blue
colors in polymeric electrochromics, Adv. Mater. 16 (2004) 1905.
[11] B.C. Thompson, P. Schottland, K. Zong, J.R. Reynolds, In situ
colorimetric analysis of electrochromic polymers and devices,
Chem. Mater. 12 (2000) 1563.
[12] B.C. Thompson, P. Schottland, G. Sonmez, J.R. Reynolds, In situ
colorimetric analysis of electrochromic polymer films and devices,
Synth. Met. 119 (2001) 333.
The switching time from oxidized state to reduced state
of an electrochromic polymer is yet another important
parameter to determine its potential application in electro-
chromic windows. The time required for full oxidized state
from full reduced state is defined as the response time. The
switching time data for polymers are given in Table 2.
[13] G. Sonmez, C.K.F. Shen, Y. Rubin, F. Wudl, A. Red, Green, and blue
(RGB) polymeric electrochromic device (PECD): the dawning of the
PECD era, Angew. Chem. Int. Edit. 43 (2004) 1498.
[14] I. Schwendeman, R. Hickman, G. Sonmez, P. Schottland, K. Zong,
D. Welsh, J.R. Reynolds, Enhanced contrast dual polymer
electrochromic devices, Chem. Mater. 14 (2002) 3118.
4. Conclusion
A series of
p-conjugated monomers based on 10,11,
12,13-tetrahydrodibenzo[a,c]phenazine as the acceptor
unit was synthesized to understand the effects of donor
strength on the optoelectronic and redox properties of
the electropolymerized materials. Multicolored polymers
from PDTBP and PTTBP were successfully synthesized via
electrochemical methods. Spectroelectrochemical studies
and electrochromic characterization demonstrated that
the polymer containing EDOT unit in the polymer back-
bone not only decreased the band gap (Eg) but also
enhanced the electrochromic properties such as optical
contrast, switching time and multicolor properties. The
polymer films with their electrochromic property, compar-
atively fast switching time and high optical contrast, are
expected to be useful for practical use in smart windows.
[15] G. Sonmez, C.K.F. Shen, Y. Rubin, F. Wudl, The unusual effect of
bandgap lowering by C60 on a conjugated polymer, Adv. Mater. 17
(2005) 897.
[16] F. Ozyurt, E.G. Gunbas, A. Durmus, L. Toppare, Processable and
multichromic polymer of bis-3-hexylthiophene substituted 4-tert-
butylphenyl quinoxaline, Org. Electron. 9 (2008) 296.
[17] H.S. Nalwa, Handbook of Organic Conductive Molecules and
Polymers, John Wiley and Sons, New York, 1997.
[18] C.Q. Wu, Y.G. Zhang, H.Q. Lin, Peierls bond distortion in substituted
polyacetylenes, Synth. Met. 119 (2001) 219.
[19] S. Tarkuc, E.K. Unver, Y.A. Udum, C. Tanyeli, L. Toppare, The effect of
changes in
p-conjugated terthienyl systems using thienyl and
ethylenedioxybenzene
functionalized thieno[3,4b] pyrazine
precursors: multicolored low band gap polymers, Electrochim.
Acta 55 (2010) 7254.
[20] E.K. Unver, S. Tarkuc, Y.A. Udum, C. Tanyeli, L. Toppare, Effect of
conjugated core building block dibenzo[a,c]phenazine unit on p-
conjugated electrochromic polymers: red-shifted absorption, J.
Polym. Sci., Part A: Polym. Chem. 48 (2010) 1714.
[21] J.T. Pinhey, E.G. Roche, The chemistry of organolead(IV)
tricarboxylates. Synthesis and electrophilic heteroarylation
reactions of 2- and 3-thienyl-, and 2- and 3-furyl-lead
tricarboxylates, J. Chem. Soc. Perkin Trans. 1 (1988) 2415.
[22] E. Bundgaard, F.C. Kreb, A comparison of the photovoltaic response
of head-to-head and head-to-tail coupled poly{(benzo-2,1,3-
References
[1] V. Seshadri, J. Padilla, H. Bircan, B. Radmard, R. Draper, M. Wood, T.F.
Otero, G.A. Sotzing, Optimization, preparation, and electrical short
evaluation for 30 cm2 active area dual conjugated polymer
electrochromic windows, Org. Electron. 8 (2007) 367.
[2] M. De Paoli, W.A. Gazotti, Electrochemistry, polymers and opto-
electronic devices: a combination with a future, J. Braz. Chem. Soc.
13 (2002) 410.
[3] R.J. Mortimer, Organic electrochromic materials, Electrochim. Acta
44 (1999) 2971.
[4] T.L. Rose, S. D’Antonio, M.H. Jillson, A.B. Kon, R. Suresh, F. Wang, A
microwave shutter using conductive polymers, Synth. Met. 85
(1997) 1439.
[5] Y.A. Udum, A. Durmus, E.G. Gunbas, L. Toppare, Both p- and n-type
dopable polymer toward electrochromic applications, Org. Electron.
9 (2008) 501.
[6] P. Topart, P. Hourquebie, Infrared switching electroemissive devices
based on highly conducting polymers, Thin Solid Films 352 (1999)
243.
[7] G. Sonmez, H. Meng, F. Wudl, Organic polymeric electrochromic
devices: polychromism with very high coloration efficiency, Chem.
Mater. 16 (2004) 574.
[8] S.A. Sapp, G.A. Sotzing, J.R. Reynolds, High contrast ratio and fast-
switching dual polymer electrochromic devices, Chem. Mater. 10
(1998) 2101.
thiadiazol-4,7-diyl)-(dihexyl)[2,20]dithiophene-5,50-diyl},
Bull. 55 (2005) 157.
Polym.
[23] E. Kim, M. Kim, K. Kim, Diarylethenes with intramolecular donor–
acceptor structures for photo-induced electrochemical change,
Tetrahedron 62 (2006) 6814.
[24] M. Hanif, P. Lu, M. Li, Y. Zheng, Z. Xie, Y. Ma, D. Li, Synthesis,
characterization, electrochemistry and optical properties of a novel
phenanthrenequinone-alt-dialkylfluorene conjugated copolymer, J.
Polym. Int. 56 (2007) 1507.
[25] M. Putala, N.K. Pustet, A. Mannschreck, Diastereoselective reaction
of (MP)-pentahelicene-7,8-dione with trans-cyclohexane-1,2-
diamine, thermal and photochemical transformations of its
product, Tetrahedron Asymmetr. 12 (2001) 3333.
[26] B. He, H. Tian, Y. Geng, F. Wang, K. Mullen, Facile synthesis of 9,10-
diarylphenanthrenes and poly(9,10-diarylphenanthrenes), Org. Lett.
10 (2008) 773.
[27] F. Dewhurst, P. Shah, Iodination of fluorenone by N-iodosuccinimide,
J. Chem. Soc. C 11 (1969) 1503.
[28] J. Gautrot, P. Hodge, M. Helliwell, J. Raftery, D. Cupertino, Synthesis
of electron-accepting polymers containing phenanthra-9,10-
quinone units, J. Mater. Chem. 19 (2009) 4148.