Effect of conjugated core building block dibenzo[a,c]phenazine unit on π-conjugated electrochromic polymers: Red-shifted absorption

Article abstract of DOI:10.1002/pola.23935

A comparative investigation was undertaken for the electrosynthesis and electrochemical properties of three different electroactive polymers having a conjugated core building block, dibenzo[a,c]phenazine. A series of monomers has been synthesized as regards to thiophene based units; thiophene, 3-hexyl thiophene, and 3,4-ethylenedioxythiophene. The effects of different donor substituents on the polymers' electrochemical properties were examined by cyclic voltammetry. Introducing highly electron-donating (ethylene dioxy) group to the monomer enables solubility while also lowering the oxidation potential. The planarity of the monomer unit enhances π-stacking and consequently lowering the E_g from 2.4 eV (PHTP) to 1.7 (PTBP). Cyclic voltammetry and spectroelectrochemical measurements revealed that 2,7-bis(4-hexylthiophen-2-yl) dibenzo[a,c]phenazine (HTP) and 2,7-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5- yl)dibenzo[a,c]phenazine (TBP) possessed electrochromic behavior. The colorimetry analysis revealed that while PTBP have a color change from red to blue, PHTP has yellow color at neutral state and blue color at oxidized state. Hence the presence of the phenazine derivative as the acceptor unit causes a red shift in the polymers' absorption to have a blue color.

Full text of DOI:10.1002/pola.23935

Effect of Conjugated Core Building Block Dibenzo[a,c]phenazine Unit on
p-Conjugated Electrochromic Polymers: Red-Shifted Absorption
1
1
2
1
1,*
ELIF KOSE UNVER, SIMGE TARKUC, YASEMIN ARSLAN UDUM, CIHANGIR TANYELI, LEVENT TOPPARE
1
Department of Chemistry, Middle East Technical University, Ankara 06531, Turkey
2
Department of Advanced Technologies, Institute of Science and Technology, Gazi University, Ankara 06570, Turkey
Received 15 December 2009; accepted 14 January 2010
DOI: 10.1002/pola.23935
Published online in Wiley InterScience (www.interscience.wiley.com).
ABSTRACT: A comparative investigation was undertaken for the
electrosynthesis and electrochemical properties of three differ-
ent electroactive polymers having a conjugated core building
block, dibenzo[a,c]phenazine. A series of monomers has been
synthesized as regards to thiophene based units; thiophene, 3-
hexyl thiophene, and 3,4-ethylenedioxythiophene. The effects
of different donor substituents on the polymers’ electrochemi-
cal properties were examined by cyclic voltammetry. Introduc-
ing highly electron-donating (ethylene dioxy) group to the
monomer enables solubility while also lowering the oxidation
potential. The planarity of the monomer unit enhances p-stack-
measurements revealed that 2,7-bis(4-hexylthiophen-2-yl)di-
benzo[a,c]phenazine (HTP) and 2,7-bis(2,3-dihydrothieno[3,4-
b][1,4]dioxin-5-yl)dibenzo[a,c]phenazine (TBP) possessed elec-
trochromic behavior. The colorimetry analysis revealed that
while PTBP have a color change from red to blue, PHTP has
yellow color at neutral state and blue color at oxidized state.
Hence the presence of the phenazine derivative as the acceptor
unit causes a red shift in the polymers’ absorption to have a
blue color. VC 2010 Wiley Periodicals, Inc. J Polym Sci Part A:
Polym Chem 48: 1714–1720, 2010
ing and consequently lowering the E
g
from 2.4 eV (PHTP) to
KEYWORDS: conducting polymers; conjugated materials; dibenzo-
1.7 (PTBP). Cyclic voltammetry and spectroelectrochemical
phenazine; electrochemistry; electrochromism; redox polymers
INTRODUCTION The design and synthesis of new p-conjugated
polymers attract great attention in the field of organic semicon-
ductors due to their potential applications in electrochromic
are generally even more highly colored and opaque than their
neutral counterparts.
In this study, a new family of donor–acceptor–donor polymer
with phenazine moieties as the core building block was syn-
thesized (Scheme 1). The reason behind the choice of this
approach is that a fully conjugated phenazine backbone
allows planarity while donor moieties tune the solubility and
electrochromic properties of the resulting polymers.
1
2
displays, light emitting diodes (LEDs), and photovoltaic de-
3
–5
vices.
by the electrochemical doping/dedoping process offer a broad
The color changes induced in p-conjugated polymers
6,7
set of new materials for electrochromic applications. The major
advantage of these organic based materials is that their electro-
chromic properties can be tuned through chemical structure
modification. Besides structural variations on the monomer
repeat via substitution of functional groups, the design of new
precursor structures allows a significant reduction of the band
8,9
EXPERIMENTAL
Materials
10,11
Dichloromethane (DCM), ethanol, N-bromosuccinimide (NBS),
dimethylsulfoxide (DMSO), phenanthrene-9,10-dione, diami-
nobenzene, dichlorobis(triphenylphosphine)palladium (II),
and para-toluene sulfonic acid (PTSA) were purchased from
gap energy (Eg).
In designing low band gap systems, the
methodologies that can be used to synthesize polymers with E
g
less than 2 eV are controlling bond-alternation, creating highly
planar systems, inducing order by interchain effects, resonance
effects along the polymer backbone, and using donor-acceptor
Sigma-Aldrich. Chloroform (CHCl ) concentrated sulfuric acid
3
12–14
and silica gel (70–230 mesh) were purchased from Merck,
while tetrahydrofuran (THF) was purchased from Fisher Sci-
entific U.K. Limited. Tributylstannane compounds were syn-
thesized according to previously described methods. THF
was dried and distilled over benzophenone-sodium under
nitrogen before use.
effects.
In more planar systems, better orbital overlap leads
to a lowering of the band gap. The reduction in E has been
g
ascribed to an increased contribution of the quinoid structure,
1
5
brought about by fused benzene ring. Due to the deviation
from the planarity and the interring twisting on polymer, new
electronic states are formed resulting in shifts in the optical
absorptions to longer wavelength. These polymers are gener-
ally colored both in the neutral, nonconducting, and doped,
conducting states. The oxidatively doped conducting polymers
Instrument
1
13
H NMR and C NMR spectra were recorded with a Bruker
Spectrospin Avance DPX-400 Spectrometer at 400 MHz and
Correspondence to: L. Toppare (E-mail: toppare@metu.edu.tr)
Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 48, 1714–1720 (2010) V
2010 Wiley Periodicals, Inc.
C
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ARTICLE
SCHEME 1 Chemical structures of
TTP, HTP, and TBP.
chemical shifts (d) were determined relative to tetramethylsi-
lane as the internal standard. Electropolymerization was per-
formed with a Voltalab 50 potentiostat in a three-electrode cell
consisting of indium tin oxide doped glass slide (ITO) as the
working electrode, platinum wire as the counter electrode, and
Ag wire as the pseudo-reference electrode. Varian Cary 5000
spectrophotometer was used to perform the spectroelectro-
chemical studies of the polymers. Colorimetry measurements
were performed via Minolta CS-100 spectrophotometer. HRMS
data was acquired at the Center for Genomics, University at
Albany, Rensselaer, NY on QSTAR XL and ESI -Q-TOF II (Waters,
Milford, MA, USA). Samples were dissolved in 100 lL CH Cl .
was purged with argon for 30 min and dichlorobis(triphenyl
phosphine)palladium(II) (40 mg, 0.057 mmol) was added at
room temperature. The mixture was refluxed for 15 h under
argon atmosphere. A yellow solid was observed in the reac-
tion medium. Solvent was filtered to remove the solvent. The
solid was washed with dichloromethane to obtain gold like
yellow solid (73 mg, 71%).
1
H NMR (400 MHz, d6-DMF) (Fig. 1): d (ppm) 9.83 (d, 2H, J
¼
1.6 Hz), 9.10 (d, 2H, J ¼ 8.3 Hz), 8.64 (dd, 2H, J ¼ 6.4, 3.2
Hz), 8.47 (d, 2H, J ¼ 8.3 Hz), 8.26 (dd, 2 H, J ¼ 6.4, 3.2 Hz),
.06 (d, 2H, J ¼ 3.3 Hz), 7.93 (d, 2H, J ¼ 5.0 Hz), 7.50 (t, 2H,
J ¼ 5.0, 3.3 Hz) HRMS m/z calcd for (C H N S ) 445.0833;
8
2
2
2
8 16 2 2
found 445.0814 [MþH]þ.
Synthesis
,7-Dibromophenanthrene-9,10-dione: (2)
2
2,7-Bis(4-hexylthiophen-2-yl)dibenzo[a,c]
NBS (1.795 g, 10.09 mmol) was added to a well stirred solu-
tion of phenanthrene-9,10-dione 1 (1 g, 4.80 mmol) in 98%
H SO and stirred at room temperature for 3 h. The mixture
phenazine: (5, HTP)
,7-Dibromodibenzo[a,c]phenazine (100 mg, 0.23 mmol), and
2
2
4
20
tributyl(4-hexylthiophen-2-yl)stannane
(418 mg, 0.92
was poured on crushed ice. The orange product was filtered
off and washed with cold water. It was recrystallized in
mmol) were dissolved in anhydrous THF (150 mL), the solu-
tion was purged with argon for 30 min and dichlorobis(tri-
phenyl phosphine)palladium(II) (40 mg, 0.057 mmol) was
added at room temperature. The mixture was refluxed for
1
6–18
ꢀ
1
DMSO.
(1.31 g, 75%) M.P. 326.8 C (by DSC). H NMR
(
400MHz d -DMSO): d (ppm) 8.25 (d, 2H, J ¼ 8.4 Hz), 8.09
6
(d, 2H, J ¼ 1.9 Hz), 7.96 (dd, 2H, J ¼ 8.4, 1.9 Hz).
14 h under argon atmosphere. Solvent was evaporated under
vacuum and the crude product was purified by column chro-
matography over silica gel, eluting with 1:2 (chloroform: hex-
ane) to give a yellow solid (96 mg, 64%).
1
2
,7-Dibromodibenzo[a,c]phenazine: (3)
2,7-Dibromophenanthrene-9,10-dione (300 mg, 0.82 mmol)
and diaminobenzene (88.64 mg, 0.82 mmol) were dissolved
in ethanol. Catalytic amount PTSA was added in the solution.
The mixture was refluxed for 5 h. A yellow colored cloudy
mixture was observed. Filtration of the reaction mixture fol-
lowed by washing with ethanol afforded the product as an
yellow solid (310 mg, 86%). H NMR (400 MHz, CDCl ): d
H NMR (400 MHz, CDCI ) (Fig. 2): d (ppm) 9.44 (s, 2H),
3
8.35 (d, 2H, J ¼ 8.4 Hz), 8.29 (dd, 2H, J ¼ 6.4, 3.3 Hz), 7.87
(d, 2H, J ¼ 8.4), 7.79 (dd, 2H, J ¼ 6.4, 3.3 Hz), 7.40 (s, 2H),
6.91 (s, 2H), 2.63 (t, 4H, J ¼ 7.6 Hz), 1.66 (m, 4H), 1.32 (m,
1
13
3
12 H), 0.85 (t, 6H, J ¼ 6.8 Hz), C NMR (100 MHz, CDCl ): d
3
(
ppm) 9.46 (d, 2H, J ¼ 2.2 Hz), 8.29 (m, 4 H), 7.83 (m, 4H)
(ppm) 144.9, 143.8, 142.6, 142.5, 134.4, 130.9, 130.8, 130.1,
129.8, 127.9, 125.6, 123.7, 122.9, 120.5, 32.0, 31.0, 30.8,
29.4, 22.9, 14.4.
1
3
3
C NMR (100 MHz, CDCI ): d (ppm) 142.7, 133.7, 132.2,
130.8, 130.4, 129.8, 129.4, 124.9, 123.2, 100.3.
2
,7-Di(thiophen-2-yl)dibenzo[a,c]phenazine: (4, TTP)
2,7-Bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)
dibenzo[a,c]phenazine: (6, TBP)
2,7-Dibromodibenzo[a,c]phenazine (100 mg, 0.23 mmol)
2,7-Dibromodibenzo[a,c]phenazine (100 mg, 0.23 mmol) and
1
9
tributyl(thiophen-2-yl)stannane (343.33 mg, 0.92 mmol)
were dissolved in anhydrous THF (150 mL). The solution
21
and tributyl(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)stannane
EFFECT OF CONJUGATED CORE BUILDING BLOCK, UNVER ET AL.
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JOURNAL OF POLYMER SCIENCE: PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
1
FIGURE 1 H NMR spectrum of 2,7-di(thiophen-2-yl)dibenzo[a,c]phenazine (TTP). [Color figure can be viewed in the online issue,
which is available at www.interscience.wiley.com.]
(
396.7 mg, 0.92 mmol) were dissolved in anhydrous THF (150
3.3 Hz), 8.11 (dd, 2H, J ¼ 8.5, 2.0 Hz), 7.79 (dd, 2H, J ¼ 6.5,
13
mL), the solution was purged with argon for 30 min and
dichlorobis(triphenyl phosphine)palladium(II) (40 mg, 0.057
mmol) was added at room temperature. The mixture was
refluxed for 12 h under argon atmosphere. Solvent was evapo-
rated under vacuum and the crude product was purified by
column chromatography over silica gel, eluting with 2:1
3.3 Hz), 6.36 (s, 2H), 4.39 (m, 4H), 4.27 (m, 4H) C NMR
(100 MHz, CDCl ): d (ppm) 141.4, 141.2, 141.0, 137.8, 131.6,
3
129.3, 129.0, 128.5, 128.4, 126.9, 122.1, 121.8, 116.1, 97.3,
63.8, 63.4. HRMS m/z calcd for (C H N O S ) 561.0943;
3
2 20 2 4 2
found 561.0961 [MþH]þ (Fig. 4).
(
chloroform:hexane) to give a brownish orange solid (85 mg,
RESULTS AND DISCUSSION
6
6 %).
Synthesis
1
H NMR (400 MHz, CDCI ) (Fig. 3): d (ppm) 9.59 (d, 2H, J ¼
Scheme 2 shows the way, the monomers were prepared
using phenanthrene-9,10-quinone as the starting material.
3
2.0 Hz), 8.43 (d, 2H, J ¼ 8.5 Hz), 8.31 (dd, 2H, J ¼ 6.5,
1
FIGURE
2
H
NMR spectrum of
2
,7-bis(4-hexylthiophen-2-yl)diben-
zo[a,c]phenazine (HTP). [Color fig-
ure can be viewed in the online
issue, which is available at www.
interscience.wiley.com.]
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ARTICLE
1
FIGURE 3 H NMR spectrum of 2,7-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)dibenzo[a,c]phenazine (TBP). [Color figure can be
viewed in the online issue, which is available at www.interscience.wiley.com.]
1
6
According to a method in literature, phenanthrene-9,10-
quinone was brominated by treatment with NBS in concen-
trated H
aminobenzene gave 2,7-dibromodibenzo[a,c]phenazine in
good yield (86%). Stannylation of 3-hexyl thiophene, ethyle-
nedioxythiophene (EDOT), and thiophene was achieved by
addition of equimolar strong base, n-BuLi followed by addi-
2 4
SO . The condensation reaction takes place between
,7-dibromophenanthrene-9,10-quinone 5 with the 1,2-di-
2
2
2,23
tion of Bu SnCl. Finally, Stille coupling,
was used to
3
attach donor moieties to the acceptor phenazine unit to give
the desired monomers in satisfactory yields (64–71%).
Electrochemistry
Electroactivities of monomers were investigated using cyclic
voltammetry. Analysis of TTP showed poor film-forming ability
FIGURE 4 HRMS data for (a) TTP (b) TBP.
SCHEME 2 Synthetic route to monomers.
EFFECT OF CONJUGATED CORE BUILDING BLOCK, UNVER ET AL.
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JOURNAL OF POLYMER SCIENCE: PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
oxidation started at a slightly higher potential (þ1.2 V vs the
Ag wire pseudo-reference electrode). As expected, the oxida-
tion of HTP was observed at higher potential than that of
TBP due to the difference in electronic nature of the external
moieties (3-hexyl thiophene and EDOT). Upon repeated scan-
ning the increasing current response of the polymer redox
process illustrates that electrochemical polymerization is pro-
ceeding on the electrode surface to form an electroactive poly-
mer film. During the anodic scans polymer oxidations were
observed at þ1.0 V for PTBP and þ1.17 V for PHTP. Reduc-
tion peaks of the polymers were at þ0.77 V for PTBP and
þ0.93 V for PHTP vs the same reference electrode (Table 1).
Cyclic voltammograms were obtained at different scan rates
to test the mass transfer on the electrode (Fig. 6). Anodic
and cathodic peak currents reveal a linear relationship as a
function of scan rate for both polymers, which proves that
the films were well-adhered and electroactive. The linear
increase of the current upon incrementing the scan also indi-
cates that the electrochemical processes are not diffusion
limited and are quasi-reversible even at high scan rates.
Spectroelectrochemical Studies
To probe the electronic structure of the polymers and examine
the optical changes upon doping, spectroelectrochemical anal-
yses were performed. For that matter, polymer films were de-
-
2
posited on ITO-coated glass slides from 1.10 M monomer
solutions in 0.1 M TBAPF /DCM. The optical changes were
6
investigated by UV-Vis-NIR spectroscopy in a monomer-free
TBAPF /DCM solution via applying different voltages. Fig. 7
6
reveals spectroelectrochemistry and corresponding colors of
PTBP and PHTP at their reduced and oxidized states.
FIGURE 5 Repeated potential scan electropolymerization of (a)
Oxidation of an electrochromic material produces radical cat-
ions (polarons) and further oxidation produces dications
6
TBP and (b) HTP at 100 mV/s in 0.1 M TBAPF /DCM on the ITO
electrode.
(
bipolarons), allowing new electronic transition thereby
changing absorption spectra. As seen from the spectroelec-
trochemical series, upon stepwise oxidation of all the poly-
mers, the absorption of p-p* transitions decreased while
those of the polaron and bipolaron peaks increased.
The absorption assigned to p-p* transition for PTBP is at
580 nm. The band gap of the polymer was calculated as
1.7 eV from the onset of the p-p* transition. As the potential
applied to the film increases, the broad absorption peaks at
about 580 and 1230 nm, which correspond to polaron and
bipolaron species, respectively, also increase. Presence of
alkyl chains at the b-position of thiophene ring has influence
on the electronic structure of the p-conjugated system where
in dichloromethane (DCM), acetonitrile (ACN), benzonitrile,
and tetrahydrofuran (THF). Hence, this polymer was not
good enough to produce films with a sufficient quality for
electrochromic studies. Figure 5 shows the cyclic voltammo-
grams corresponding to the potentiodynamic polymerization
of TBP and HTP by application of consecutive potential
scans. In each case, the first cycle shows an irreversible an-
odic wave corresponding to the oxidation of the monomer.
Subsequent cycling leads to a new redox system associated
with the oxidation and reduction of the polymer deposited
on the electrode surface.
Cyclic voltammograms of TBP and HTP were obtained in
dichloromethane (DCM) containing 0.1 M tetrabutylammo-
TABLE 1 CV Data and Calculated HOMO and LUMO Energies
nium hexafluorophosphate (TBAPF ) with a scan rate of
for the Polymers
6
1
00 mV/s. Electropolymerization of TBP was performed
Oxidation
Energy Level
(eV)
using multiple scan voltammetry between þ0.4 V and
þ1.3 V on ITO electrode. TBP monomer started to get oxi-
dized at þ1.1 V vs the Ag wire pseudo-reference electrode
Potential (V)
Bandgap (eV)
op
E
ox
E
onset,ox
E
g
HOMO
LUMO
(
0.35 V vs SCE) during the first anodic sweep. The redox
behavior of HTP was studied by scanning the potential
between þ0.3 V and þ1.4 V. For HTP monomer, the onset of
PTBP
PHTB
1.0
ꢁ0.45
0.58
1.7
2.4
ꢁ4.35
ꢁ5.33
ꢁ2.65
ꢁ2.93
1.17
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ARTICLE
0
8
0
.273). PHTP film changed from a yellow neutral state (Y:
21; x: 0.352; y: 0.386) to a blue oxidized state (Y: 538; x:
.263; y: 0.309).
Electrochromic Switching Studies
The stability and switching time upon electrochromic switch-
ing of the polymer films between their neutral and oxidized
forms were monitored in the visible and NIR regions. The
switching time, which is defined as the time required for
95% of the full change in absorption was estimated by
applying a square-wave potential coupled with optical spec-
troscopy. In this experiment, the potential was set at an ini-
tial potential for a given period of time (5s), and was
stepped to a second potential for the same period of time
(
5s) before being switched back to the initial potential.
During the experiment, the transmittance (%T) at
%
different wavelengths was measured with a UV-Vis-NIR
spectrophotometer.
To allow a comparison of the polymers, the results of these
switching studies for PTBP and PHTP are shown in Figure 8.
PTBP revealed impressing switching times of 0.4 s at 470
nm and 0.6 s at 580 nm while switching the applied poten-
tial between þ0.4 V and þ1.3 V. This switching ability per-
sists for over 3000 cycles. The percent transmittance
between neutral and oxidized states was found to be 22%
for 470 nm and 8% for 580 nm. At 1230 nm PTBP films
show an optical contrast of 50% with a fast switching time
FIGURE 6 Cyclic voltammograms of (a) PTBP and (b) PHTP in 0.1
M TBAPF /DCM at scan rates of 100, 150,200, 250, and 300 mV/s.
6
the onset of the p-p* transition shifts to shorter wavelength.
PHTP exhibits a larger E value (2.4 eV) than PTBP.
g
The different structures of the polymers due to the differen-
ces in donor moiety affect not only the monomer oxidation
and the polymer redox couple potentials but also the maxi-
mum absorption wavelengths of the corresponding transi-
tion. The introduction of alkyl substituents on polymer
causes steric hindrance, resulting in less order and less con-
jugation by the blue shift in absorption spectra and the
increase in polymer’ band gap.
The color changes were further investigated by colorimetry
using the CIE 1931 Yxy color space to define color precisely.
PTBP becomes red (Y: 176; x: 0.395; y: 0.337) in the neutral
state, while its oxidized state is blue (Y: 204; x: 0.251; y:
FIGURE 7 p-Doping spectroelectrochemistry of (a) PTBP and
(b) PHTP films on an ITO-coated glass slide in monomer-free,
0.1
6
M TBAPF /DCM electrolyte-solvent couple at applied
potentials.
EFFECT OF CONJUGATED CORE BUILDING BLOCK, UNVER ET AL.
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JOURNAL OF POLYMER SCIENCE: PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
achieves 17% at 380 nm, 38% at 610 nm and 54% at
400 nm.
1
Authors gratefully thank TUBA grant. Two of us (E.K.U., S.T.)
acknowledge TUBITAK-Department of Science Fellowships
and Grant Program.
REFERENCES AND NOTES
1
Sonmez, G.; Meng, H.; Zhang, Q.; Wudl, F. Adv Funct Mater
003, 13, 726–731.
2
2
Kraft, A.; Grimsdale, A. C.; Holmes, A. B. Angew Chem Int Ed
Engl 1998, 37, 403–428.
3
Huynh, W. U.; Dittmer, J. J.; Alivisatos, A. P. Science 2002,
95, 2425–2427.
2
4
Liang, C. W.; Su, W. F.; Wang, L. Appl Phys Lett 2009, 95,
33303–133305.
1
5
Lin, Y. Y.; Chu, T. H.; Li, S. S.; Chuang, C. H.; Chang, C. H.;
Su, W. F.; Chang, C. P.; Chu, M. W.; Chen, C. W. J Am Chem
Soc 2009, 131, 3644–3649.
6
Udum, Y. A.; Yildiz, E.; Gunbas, G.; Toppare, L. J Polym Sci
Part A: Polym Chem 2008, 46, 3723–3731.
7
Rosseinsky, D. R.; Mortimer, R. J. Adv Mater 2001, 13,
83–793.
7
8
Roncali, J. Chem Rev 1992, 92, 711–738.
9
Durmus, A.; Gunbas, G. E.; Toppare, L. Chem Mater 2007, 19,
247–6251.
6
1
0 Zoombelt, A. P.; Gilot, J.; Wienk, M. M.; Janssen, R. A. J.
Chem Mater 2009, 21, 1663–1669.
1 Mishra, S. P.; Palai, A. K.; Srivastava, R.; Kamalasanan, M.
N.; Patri, M. J Polym Sci Part A: Polym Chem 2009, 47,
FIGURE 8 (a) Electrochromic switching and optical absorption
1
change monitored at 470, 580, and 1230 nm for PTBP in 0.1 M
TBAPF
tion change monitored at 380, 610, and 1400 nm for PHTP in
.1 M TBAPF /DCM. [Color figure can be viewed in the online
6
/DCM. (b) Electrochromic switching and optical absorp-
6
514–6525.
1
2 Roncali, J. Chem Rev 1997, 97, 173–205.
0
6
issue, which is available at www.interscience.wiley.com.]
13 Salzner, U. J Phys Chem B 2002, 106, 9214–9220.
4 Berlin, A.; Zotti, G.; Zecchin, S.; Schiavon, G.; Vercelli, B.;
Zanelli, A. Chem Mater 2004, 16, 3667–3676.
1
of approximately 1 s. PHTP was switched between þ0.3 V
and þ1.4 V. The optical contrasts were found to be 17% at
1
5 McCullough, R. D. Adv Mater 1998, 10, 93–116.
380 nm and 38% at 610 nm. The switching times were cal-
1
6 Hanif, M.; Lu, P.; Li, M.; Zheng, Y.; Xie, Z.; Ma, Y.; Li, D.; Li,
culated as 2.5 s at 380 nm and 1.8 s at 610 nm. About 1 s
was required for PHTP films to accomplish an optical con-
trast of 54% at 1400 nm. The switching ability of PHTP lasts
for only a little over 400 cycles.
J. Polym Int 2007, 56, 1507–1513.
17 Dewhurst, F.; Shah, P. K. J. J Chem Soc 1969, 1503–
1504.
1
8 He, B.; Tian, H.; Geng, Y.; Wang, F.; Muellen, K. Org Lett
CONCLUSIONS
2
008, 10, 773–776.
A series of monomers differing by the electron-donating
groups along the backbone have been synthesized and char-
acterized. Introduction of highly electron-donating (ethylene
dioxy unit) group to the monomer not only leads to good
solubility, but also a lower oxidation potential. The planarity
of the monomer unit allows for a better packing of the
monomer chains, thus enhancing p-stacking and conse-
1
9 Xia, Y.; Luo, J.; Deng, X.; Li, X.; Li, D.; Zhu, X.; Yang, W.;
Cao, Y. Macromol Chem Phys 2006, 207, 511–520.
2
0 Hou, Q.; Zhou, Q.; Zhang, Y.; Yang, W.; Yang, R.; Cao, Y.
Macromolecules 2004, 37, 6299–6305.
21 Zhu, S. S.; Swager, T. M. J Am Chem Soc 1997, 119,
1
2568–12577.
22 Milstein, D.; Stille, J. K.
636–3638.
quently lowering the E from 2.4 eV (PHTP) to 1.7 (PTBP).
g
J Am Chem Soc 1978, 100,
3
The optical contrasts for PTBP were calculated as 22% at
470 nm, 8% at 580 nm, and 50% at 1230 nm. PHTP
23 Stille, J. K. Angew Chem Int Ed Engl 1986, 25, 508–524.
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