Synthesis of novel chiral l-leucine grafted PEDOT derivatives with excellent electrochromic performances

Article abstract of DOI:10.1039/c4ra05075d

Two amino acid-functionalized poly(3,4-ethylenedioxythiophene) (PEDOT) derivatives, poly(N-(tert-butoxycarbonyl)-l-leucyl(3,4-ethylenedioxythiophene- 2′-yl)methylamide) (PEDOT-Boc-Leu) and poly(l-leucyl(3,4- ethylenedioxythiophene-2′-yl)methylamide) (PEDOT-Leu) were synthesized electrochemically via potentiostatic polymerization of corresponding monomers N-(tert-butoxycarbonyl)l-leucyl(3,4-ethylenedioxythiophene-2′-yl) methylamide (EDOT-Boc-Leu) and l-leucyl(3,4-ethylenedioxythiophene-2′-yl) methylamide (EDOT-Leu), which were synthesized by grafting Boc-l-leucine and l-leucine into a 3,4-ethylenedioxythiophene (EDOT) side chain. The electrochemical behaviors, structural characterization, circular dichroism, spectroscopic properties, surface morphology, electrochromic properties and thermal stabilities of PEDOT-Boc-Leu and PEDOT-Leu films were systematically investigated. These l-leucine grafted PEDOT derivatives displayed excellent reversible redox activities, rough and compact surface, and good thermal stability. The circular dichroism spectra suggested the chirality of these polymers. Importantly, the introduction of the l-leucine group enhanced the electrochromic properties of PEDOT and resulted in high contrast ratios (ΔT% = 49% at 600 nm for PEDOT-Boc-Leu) and high coloration efficiencies (431 cm² C^-1 at 960 nm for PEDOT-Leu). Satisfactory results implied that the obtained polymer films can probably be further developed in various applications, such as electrochromic devices, optical displays and chiral recognition.

Full text of DOI:10.1039/c4ra05075d

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Synthesis of novel chiral L-leucine grafted PEDOT
derivatives with excellent electrochromic
performances
Cite this: RSC Adv., 2014, 4, 35597
*
*
Dufen Hu,† Baoyang Lu,† Xuemin Duan, Jingkun Xu, Long Zhang, Kaixin Zhang,
Shimin Zhang and Shijie Zhen
Two amino acid-functionalized poly(3,4-ethylenedioxythiophene) (PEDOT) derivatives, poly(N-(tert-
butoxycarbonyl)-L-leucyl(3,4-ethylenedioxythiophene-20-yl)methylamide) (PEDOT–Boc–Leu) and poly-
(L-leucyl(3,4-ethylenedioxythiophene-20-yl)methylamide) (PEDOT–Leu) were synthesized electro-
chemically via potentiostatic polymerization of corresponding monomers N-(tert-butoxycar-
bonyl)L-leucyl(3,4-ethylenedioxythiophene-20-yl)methylamide (EDOT–Boc–Leu) and L-leucyl(3,4-
ethylenedioxythiophene-20-yl)methylamide (EDOT–Leu), which were synthesized by grafting Boc-L-
leucine and L-leucine into a 3,4-ethylenedioxythiophene (EDOT) side chain. The electrochemical
behaviors, structural characterization, circular dichroism, spectroscopic properties, surface morphology,
electrochromic properties and thermal stabilities of PEDOT–Boc–Leu and PEDOT–Leu films were
systematically investigated. These L-leucine grafted PEDOT derivatives displayed excellent reversible
redox activities, rough and compact surface, and good thermal stability. The circular dichroism spectra
suggested the chirality of these polymers. Importantly, the introduction of the L-leucine group enhanced
the electrochromic properties of PEDOT and resulted in high contrast ratios (DT% ¼ 49% at 600 nm for
PEDOT–Boc–Leu) and high coloration efficiencies (431 cm2 Cꢀ1 at 960 nm for PEDOT–Leu).
Satisfactory results implied that the obtained polymer films can probably be further developed in various
applications, such as electrochromic devices, optical displays and chiral recognition.
Received 29th May 2014
Accepted 28th July 2014
DOI: 10.1039/c4ra05075d
www.rsc.org/advances
chemical reactions.19 Kazuo Akagi and co-workers20–30 have
developed an electrochemical polymerization method with
Introduction
chiral nematic liquid crystal as an electrolyte, and successfully
use the method to produce unsubstituted chiral conducting
polymers. More recently, a series of new-generation chiral
conducting polymers have been designed and synthesized by
introducing chiral moiety into the side chains of conducting
polymers,31–34 which is a fashionable approach to obtain chiral
conducting polymers, and some promising applications are
presented.
Among various kinds of conducting polymers, poly(3,4-
ethylenedioxythiophene) (PEDOT) is one of representatives
and highly promising conducting polymers with versatile
properties such as high electrical conductivity, low band gap,
good redox activity, thermal stability, long-term stability, and
excellent transparency in the doped state.20,35 Also PEDOT is
applied in a variety of areas, such as electrolytic capacitors,36
printed wiring boards,37,38 ITO substitution,39 antistatic coat-
ings,40–42 electroluminescent lamps,43–45 organic solar cells,46,47
electrochromics,48–50 and so on.51,52 Unfortunately, PEDOT
shows poor photophysical property in the whole visible region
and chiral property,53 which limits its wide application as
optoelectronics and chiral materials. In comparison with
PEDOT, chiral PEDOT derivatives display chiroptical properties
Chiral conducting polymers, as an important branch of con-
ducting polymers, have been given lots of attention by many
researchers and are widely used in many areas such as chiral
sensors, chiral catalysts, and chromatographic separation of
enantiomeric drugs.1–3 Chiral conducting polymers not only
exhibit remarkable redox properties,4 pH switching capabilities,
relative ease of synthesis,5 and exceptional chiroptical perfor-
mance,6 but also show high electrical conductivity and good
environmental stability. Based on above advantages, chiral
conducting polymers are identied as possessing a great
number of exciting new potential applications,7 such as chiral
sensors,8 separation of enantiomers,9 electrochemical asym-
metric synthesis,10 and chiral catalysts.11 Up to date, several
methods have been proposed to prepare chiral conducting
polymers, including the polymerization of corresponding chiral
monomers,12–16 asymmetric selective polymerization,17,18 and
the introduction of a chiral group onto an achirality polymer via
School of Pharmacy, Jiangxi Science & Technology Normal University, Nanchang,
330013, P. R. China. E-mail: duanxuemin@126.com; xujingkun@tsinghua.org.cn;
Fax: +86-791-83823320; Tel: +86-791-88537967
† These authors contributed equally to this work.
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and helical structures and thus show signicant academic
research value and application prospect. Also, the electro-
chromic behavior of chiral PEDOT derivatives is superior to
other chiral p-conjugated polymers without electrochemical
activity.54 In addition, the chirality of the polymer can be
controlled by changing the polymer structures between the
doped and dedoped states through electrochemical doping and
dedoping processes.24 Yet to date, advanced work has been done
to study chiral PEDOT derivatives by different research
groups,15,20,21,24,55–59 but the design and synthesis of novel PEDOT
derivatives with extraordinary photophysical and excellent
chiral properties are still very necessary and signicant, which
apparently is a considerable challenge.
As the basic composition unit of macromolecular protein,
chiral amino acids are not only biologically important to life but
also play crucial roles as chiral auxiliaries and building blocks
in organic synthesis.60 Furthermore, all nature amino acids
show excellent biocompatibility, low toxicity, efficient and quick
biodegradability, which is benecial for the fabrication of
sensing platform. Hence, the natural amino acids can be used
as the ideal chiral materials for the design and synthesis of
chiral PEDOTs by attaching onto their side chain.61
Syntheses
20-Azidomethyl-3,4-ethylenedioxythiophene (EDOT–MeN3).64
Under a nitrogen atmosphere, EDOT–MeCl (0.17 g, 0.9 mmol)
and NaN3 (0.08 g, 1.2 mmol) were dissolved in DMF (10 mL) and
stirred at 120 ꢁC for 17 h. Aer cooling, 10 mL H2O was added.
Then the mixture was extracted with ethyl acetate (5 ꢂ 15 mL).
The organic phases were combined and extracted with H2O (3 ꢂ
15 mL) and brine (1 ꢂ 15 mL), dried with anhydrous MgSO4,
and ltered. Aer evaporation of the solvent, the remaining
crude product was isolated by ash chromatography (silica gel,
petroleum ether–ethyl acetate, 10/1, v/v) to give 0.16 g of a light
1
yellow oil (yield 91%). H NMR (400 MHz, CDCl3, ppm): d 6.37
(dd, J1 ¼ 3.6 Hz, J2 ¼ 11.2 Hz, 2H), 4.03–4.34 (m, 3H), 3.47–3.60
(m, 2H).
20-Aminomethyl-3,4-ethylenedioxythiophene
(EDOT–
MeNH2).65 EDOT–MeN3 (0.20 g, 1 mmol) and PPh3 (0.29 g, 1.1
mol) in a molar ration of 1 : 1.1 were dissolved in 4.5 mL THF
and stirred at 50 ꢁC. Then, NaOH (4.5 mL, 2 M) was added
dropwise, and the reaction mixture was stirred overnight. The
reaction mixture was allowed to cool to room temperature. Aer
evaporation of THF, 2 M HCl solution was used to control the
pH below 3. Then the aqueous layer was extracted with CH2Cl2
and the combined organic layers were discarded. 1 M NaOH
solution was added to adjust the pH of aqueous layer to 8. The
aqueous layer was extracted with CH2Cl2 and the combined
organic layers were dried with anhydrous MgSO4. Aer evapo-
ration of the solvent, the remaining crude product was isolated
by ash chromatography (silica gel, dichloromethane–meth-
In this work, L-leucine was chosen as the side chain moiety
onto EDOT through covalent bonding. Two novel PEDOT
derivatives,
poly(N-(tert-butoxycarbonyl)-L-leucyl(3,4-ethyl-
enedioxythiophene-20-yl) methylamide) (PEDOT–Boc–Leu) and
poly(L-leucyl(3,4-ethylenedioxythiophene-20-yl)methylamide)
(PEDOT–Leu), were electrosynthesized for the rst time through
the electropolymerization of corresponding EDOT derivatives of
N-(tert-butoxycarbonyl)-L-leucyl(3,4-ethylenedioxythiophene-20-yl)-
methylamide (EDOT–Boc–Leu) and L-leucyl(3,4-ethyl-
enedioxythiophene-20-yl)methylamide (EDOT–Leu), which were
synthesized by acylation reaction. The electrochemical
behavior, structural characterization, circular dichroism, solu-
bility, spectroscopic properties, thermal stabilities, and surface
morphology of as-prepared PEDOT–Boc–Leu and PEDOT–Leu
lms and their electrochromic properties were investigated in
detail.
1
anol, 20/1, v/v) to give 0.15 g of a colorless oil (yield 87%). H
NMR (400 MHz, CDCl3, ppm): d 6.35 (d, J ¼ 4 Hz, 2H), 3.99–4.24
(m, 3H), 2.96–3.03 (m, 2H), 1.52 (s, 2H).
N-(tert-Butoxycarbonyl)-L-leucine (N-Boc-L-Leu). A solution of
(Boc)2O (2.59 g, 11.87 mmol) in dioxane (9 mL) was added to an
ice-cold solution of L-leucine (1.31 g, 10.00 mmol) in 1 M NaOH
(20 mL) with stirring at ꢀ5 C. Aer 30 min, then the mixture
ꢁ
was stirred for over 14 h at to room temperature. The mixture
was concentrated to half its original volume by rotary evapora-
tion, cooled in ice, and acidied pH to 2–3 by slow addition of
1 M NaHSO4. Finally, the solution was extracted with acetic
ether (3 ꢂ 20 mL), the combined organic layers were dried with
anhydrous MgSO4, and concentrated to give 1.86 g of a colorless
solid (yield 51%).
Experimental section
Materials
EDOT–Boc–Leu. EDOT–MeNH2 (0.37 g, 2.16 mmol), EDC
(0.47 g, 2.38 mmol), and HOBT (0.03 g, 0.22 mmol) were dis-
solved in CH2Cl2 (15 mL) with stirring while being cooled in an
ice bath. A solution of N-Boc-L-Leu (0.55 g, 0.24 mmol) in CH2Cl2
(5 mL) was added slowly. Aer stirring for 1 h, the ice bath was
removed and the reaction was performed with continued stir-
ring at room temperature for another 16 h. Subsequently, the
colorless reaction solution was washed with 1 M HCl (3 ꢂ 30
mL), a saturated solution of NaHCO3 (3 ꢂ 30 mL), and then with
saturated brine (1 ꢂ 30 mL), respectively. The organic layer was
dried with anhydrous MgSO4. The solvent was removed under
reduced pressure and the remaining crude product was isolated
by ash chromatography (silica gel, petroleum ether–ethyl
acetate, 2/1, v/v) to give 0.79 g of a colorless solid (yield 95%).
L-Leucine (99%), triphenylphosphine (PPh3, 99%), sodium
azide (NaN3, 99%); N3-dimethylpropane-1,3-diamine (EDC,
99%), N-hydroxybenzotrizole (HOBT, 99%), triuoroacetic acid
(TFA, 99%), and di-tert-butyl dicarbonate ((Boc)2O, 99%) were
purchased from Aladdin Chemistry Co. Ltd. and dimethyl
sulfoxide (DMSO, AR) was purchased from Tianjin Bodi
Chemicals Co., Ltd. All above of reagents were used as received.
Dichloromethane (CH2Cl2, AR; Tianjin Damao Chemical
Reagent Factory) was puried by distillation over calcium
hydride
before
used.
Tetra-n-butylammonium
hexa-
uorophosphate (Bu4NPF6, 99%; Acros Organics) was dried
ꢁ
under vacuum at 60 C for 24 h before used. 20-Chloromethyl-
3,4-ethylenedioxythiophene (EDOT–MeCl) was prepared in
accordance with Duan et al.62,63
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[a]20 ¼ ꢀ14.87ꢁ. lH NMR (400 MHz, DMSO-d6, ppm): d 8.10 (t, J Vertex 70 Fourier spectrometer with samples in KBr pellets.
¼ 7.6 Hz, 1H), 6.90 (s, 1H), 6.56 (d, J ¼ 2.8 Hz, 2H), 4.18 (d, J ¼ 12 Ultraviolet-visible (UV-vis) spectra were measured with a Perkin-
Hz, 2H), 3.84–3.92 (m, 2H), 3.36 (d, J ¼ 17.6 Hz, 2H), 1.58 (s, 1H), Elmer Lambda 900 ultraviolet-visible-near-infrared spectro-
1.35–1.43 (m, 11H), 0.85 (t, J ¼ 7.2 Hz, 6H).
photometer. Optical rotation determination was performed on
EDOT–Leu.66 EDOT–Boc–Leu (0.80 g, 2.08 mmol) was dis- Anton Paar MCP 200 polarimeter. Fluorescence spectra of the
solved in CH2Cl2 (38 mL) with stirring while being cooled in an monomers and polymers were determined with an F-4500
ice bath. A solution of TFA (2 mL) in CH2Cl2 (2 mL) was added uorescence spectrophotometer (Hitachi). Thermogravimetric
slowly. Aer 4–5 h, the pH of the mixture was adjusted to (TG) and differential thermogravimetric (DTG) analyses were
basicity with a saturated solution of NaHCO3. Then the mixture performed with a Pyris Diamond TG/DTA thermal analyzer
was extracted with CH2Cl2 (3 ꢂ 120 mL), and saturated brine (Perkin-Elmer). Circular dichroism (CD) was measured with
(3 ꢂ 120 mL), respectively. The organic layer was dried with JASCO Corp., J-810, Rev. 1.00. Scanning electron microscopy
anhydrous MgSO4. The solvent was removed under reduced (SEM) measurements were taken using Sigma cold eld emis-
pressure and the remaining crude product was isolated by ash sion scanning electron microscope. The addition of solutions to
chromatography (silica gel, dichloromethane–methanol, 32/1, the cell was performed with the Finnpipette (Labsystems, Hel-
v/v) to give 0.38 g of a colorless solid (yield 64%). [a]20
¼
sinki, Finland). The temperature was controlled with a type
ꢀ10.88ꢁ. lH NMR (400 MHz, CDCl3, ppm): d 7.70 (s, 1H), 6.25 (s, HHS thermostat (Shanghai, China).
2H), 4.11–4.20 (m, 2H), 3.81–3.88 (m, 1H), 3.33–3.60 (m, 3H),
Spectroelectrochemical measurements were carried out to
1.62–1.66 (m, 2H), 1.44 (s, 2H), 1.23–1.31 (m, 1H), 0.83–0.89 (m, consider absorption spectra of these polymer lms under
6H).
applied potentials. The spectroelectrochemical cell consisted of
a quartz cell, a reference electrode of Ag/AgCl electrode,
an auxiliary electrode of Pt wire, and a working electrode of
polymer lm modied indium tin oxide (ITO) glass. All
measurements were carried out in the supporting electrolyte of
CH2Cl2–Bu4NPF6 (0.10 M).
Electrochemical measurements
Electrochemical synthesis and examinations were performed
in a one-compartment cell with the use of Model 263A
potentiostat-galvanostat (EG&G Princeton Applied Research)
under a computer control. The three electrodes of the
working electrode, the reference electrode, and the counter
electrode were all platinum (Pt) wires with a diameter of
0.5 mm, which were placed 5 mm apart in the transverse
direction during the measurements (Scheme 1). Besides, to
obtain a sufficient amount of polymer for characterization,
the Pt sheets with a surface area of 10 and 12 cm2 each
(10 mm apart) were employed as working and counter elec-
trodes, respectively. The Pt wire electrode directly immersed
in the solution served as the reference electrode and it
also revealed sufficient stability during the experiments.
Electrodes mentioned above were carefully polished with
abrasive paper (1500 mesh), and ultrasonic cleaned by water
and acetone successively before each examination. All
experiments were carried out under a slight argon over-
pressure. Finally, the polymer lms were dried at 60 ꢁC under
vacuum for 24 h. The PEDOT–Boc–Leu lm was prepared in
CH2Cl2–Bu4NPF6 (0.10 M) containing 0.01 M EDOT–Boc–Leu
and characterized electrochemically in monomer-free
CH2Cl2–Bu4NPF6 (0.10 M). The PEDOT–Leu lm was
prepared in CH2Cl2–Bu4NPF6 (0.10 M) containing 5% TFA
and 0.01 M EDOT–Leu and characterized electrochemically in
monomer-free CH2Cl2–Bu4NPF6 (0.10 M) containing 5% TFA.
Both PEDOT–Boc–Leu and PEDOT–Leu lms were dedoped
by 25% ammonia for three days. Aer dedoping, their color
both changed to brownish yellow.
The optical density (DOD) at the specic wavelength (lmax
)
was determined by %T value of electrochemically oxidized and
reduced lms, using the following equation:67
DOD ¼ log(Tox/Tred
)
(1)
The coloration efficiency (CE) is dened as the relation
between the injected/ejected charge as a function of electrode
area (Qd) and the change in optical density (DOD) at the specic
dominant wavelength (lmax) as illustrated by the following eqn
(2):68
CE ¼ DOD/Qd
(2)
Characterization
NMR spectra were recorded on a Bruker AV 400 NMR spec-
trometer with d6-DMSO or CDCl3 as the solvent and tetrame-
thylsilane as an internal standard (TMS, singlet, chemical shi:
Scheme 1 The three-electrode system employed for electrochemical
0.0 ppm). Infrared spectra (IR) were recorded using Bruker polymerization and tests.
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Electrochemical polymerization of EDOT–Boc–Leu and
EDOT–Leu
Results and discussion
Syntheses of monomers
The polymers were electrosynthesized in CH2Cl2–Bu4NPF6 (0.10
M) system containing 0.01 M monomers (5% TFA were added to
the monomer of EDOT–Leu mixture solutions). The addition of
TFA during the electrochemical polymerization of EDOT–Leu
could suppress the oxidation of amino group, and decreased the
onset oxidation potential of corresponding monomer. As seen
in Fig. 1, all the CVs showed similar characteristics to those of
other inherently conducting polymers, which indicated that the
polymerization proceeded easily even at low monomer
concentrations. The two insets in Fig. 1 showed onset oxidation
potentials of EDOT–Boc–Leu (at 1.5 V) and EDOT–Leu (at 0.6 V).
In the rst cycle of CVs, the current density on the reverse
scan was higher than that on the forward scan (in the region
of ꢀ0.70 V to 1.6 V (EDOT–Boc–Leu) and ꢀ0.45 V to 0.45 V
(EDOT–Leu)). In comparison with the two gures, the formation
of this loop could be explained as the characteristics of nucle-
ation process.72–75 In Fig. 1A, during the oxidative scan, two
oxidation peaks appeared at 0.42 V and 1.24 V, also three
reduction peaks appeared at 0.26 V, 0.43 V and 0.91 V. And in
Fig. 1B, the redox peaks were two relatively wide peaks. All these
peaks were attributed to the p-doping/dedoping processes of
PEDOT–Boc–Leu and PEDOT–Leu lms formed in previous
scans. Upon sequential cycles, the redox currents increased,
implying that the formation of an electroactive and conductive
layer on the Pt electrode surface (light-blue to blue-black as the
deposit thickened) was gradually increasing. Moreover, the
broad redox waves of the as-formed PEDOT–Boc–Leu and
PEDOT–Leu lms could be ascribed to the wide distribution of
the polymer chain length or the version of conductive species
on the polymer main chain from the dedoped state to polarons,
from polarons to bipolarons, and nally from bipolarons to the
metallic state.76 The potential shi of the current wave
maximum provided information about the increase of the
electrical resistance of the polymer lms and the overpotential
needed to overcome this resistance.
Using the amino group/carboxyl group of amino acids to form
amide or ester bond are two main approaches to introduce
amino acids into EDOT side chain. We have ever attempted to
the synthesis of L-alanine-modied EDOT through esterication
of 20-hydroxymethyl-3,4-ethylenedioxythiophene (EDOT–MeOH)
with L-alanine.61 Unfortunately, aer removing the Boc group on
L-alanine, the obtained monomer will be hydrolyzed in short
time due to the existence of its own amino group. Hence,
another route was explored to efficiently synthesize EDOT–Leu
in this work (Scheme 2). Firstly, EDOT–N3 was synthesized
based on a versatile intermediate of EDOT–MeCl, and then
EDOT–MeNH2 was obtained by reducing azide group of EDOT–
N3.69,70 EDOT–Boc–Leu was made according to the steps
described by McTiernan et al.71 Subsequently, a common
organic acid of TFA was chosen to remove Boc group on the
EDOT–Boc–Leu to get EDOT–Leu monomer.
Potentiostatic synthesis was employed to prepare PEDOT–
Boc–Leu and PEDOT–Leu lms. Considering the overall factors
affecting the quality of the formed lms, such as moderate
Scheme 2 Efficient synthesis routes for EDOT–Boc–Leu and EDOT–
Leu.
Fig. 1 CVs of EDOT–Boc–Leu (A) in CH2Cl2–Bu4NPF6 (0.1 M) and EDOT–Leu (B) in CH2Cl2–Bu4NPF6 (0.1 M) containing 5% TFA. Monomers
concentration: 0.01 M. Potential scan rate: 100 mV sꢀ1
.
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Fig. 2 IR spectra of monomers and polymers: EDOT–Boc–Leu (A-a), doped PEDOT–Boc–Leu (A-b), dedoped PEDOT–Boc–Leu (A-c), EDOT–
Leu (B-a), doped PEDOT–Leu (B-b) and dedoped PEDOT–Leu (B-c).
polymerization rate, negligible over oxidation, regular double bond was not destroyed during electrochemical
morphology, and good adherence against the working elec- polymerization.
trode, the selected applied potential were 1.60 V and 0.75 V for
All results conrmed that the structures of EDOT–Boc–Leu
the electropolymerization of EDOT–Boc–Leu and EDOT–Leu, and EDOT–Leu were not destroyed during the electrochemical
respectively.
polymerization process. Moreover, the augmented width and
shis of these bands from the monomer to polymer manifested
the occurrence of the electrochemical polymerization. The
broadening of the IR bands in the experimental spectra was due
to the resulting product composed of oligomers with wide chain
dispersity. The vibrational peaks of the oligomers with different
polymerization degrees had different IR shis. These peaks
overlapped one another and produced broad band with hyper-
structures. Furthermore, there were chemical defects on the
polymer chains, which resulted from the inevitable over oxida-
tion of the polymers. This also contributed to the band broad-
ening of IR spectra.77
Infrared spectra
Vibrational spectra can provide much structural information for
conducting polymers, especially for insoluble and infusible
polymers. A comparison of the evolution of the vibrational
modes appearing in conducting polymers and in some simpler
related molecules acting as references usually facilitates the
interpretation of the experimental absorption spectra. IR
spectra of the monomer (a), the doped (b) and dedoped (c)
polymers were illustrated in Fig. 2. From these gures, no
apparent difference was found between the IR spectra of the
doped and dedoped polymers, which mainly due to the auto-
Thermal analysis
matic dedoping process of polymers, concerning dopant The thermal stability of conducting polymers is very essential
removal. The details of the band assignments of monomers, parameter for their potential applications. It is known that the
doped polymers and dedoped polymers were given in Table 1. skeletal decomposition temperatures of conducting polymers
The peak at 3110 cmꢀ1 for EDOT–Boc–Leu (Fig. 2A) was are usually low, generally reported to be lower than 600 K, which
produced by C–H vibration of the 2,5-positions in the thiophene hinders the practical uses of these polymers in various elds.78
ring. This peak was retained in the monomer (Fig. 2A) but To investigate the thermal stability of PEDOT–Boc–Leu and
disappeared in the electrochemical polymerized samples PEDOT–Leu lms, TG and DTG experiments were performed
(Fig. 2A and B). This indicated that the electropolymerization of under a nitrogen stream at a heating rate of 10 K minꢀ1. As
EDOT occurred at the 2,5-positions of the thiophene ring. From shown in Fig. 3, it could be clearly observed that there were
Fig. 2 and Table 1, the C]O stretching vibration existed in the three-step weight losses for two polymers. The polymers initially
spectra of monomers and polymers, indicating that the C]O underwent a small weight decrease (about 5.79% for PEDOT–
Table 1 Assignments of IR Spectra of monomers (EDOT–Boc–Leu and EDOT–Leu) and polymers (PEDOT–Boc–Leu and PEDOT–Leu)
EDOT–Boc–Leu
Band (cmꢀ1
EDOT–Leu
)
Assignment
Band (cmꢀ1
)
Assignment
3115 (a), 1684 (a), 1553 (a), 1174 (a);
3127 (b), 1725 (b), 1513 (b), 1198 (b);
1641 (c), 1507 (c), 1298 (c)
N–H stretching vibration
3325 (a), 3428 (b), 3303 (c)
N–H stretching vibration
1728 (a), 1726 (b), 1647 (c)
C]O stretching vibration
1655 (a), 1656 (b), 1647 (c)
C]O stretching vibration
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Boc–Leu, and 7.34% for PEDOT–Leu) at relatively low temper-
ature (from 286 to 410 K), which may be attributed to evapo-
ration of trace water in the polymers. As the temperature
increasing, a more pronounced weight loss step (about 43.84%
for PEDOT–Boc–Leu) was observed for 410 K < T # 698 K, which
may be caused by the Boc protected L-leucine group oxidizing
decomposition of the skeletal PEDOT–Boc–Leu side chain
structure. And for PEDOT–Leu (about 49.23% at 410 K < T # 705
K), the result may be caused by the L-leucine group oxidizing
decomposition of the skeletal PEDOT–Leu side chain structure.
With the gradual increasing of the temperature, weight went on
losing (about 14.74% for PEDOT–Boc–Leu, and 11.96% for
PEDOT–Leu), which were essentially due to the oxidizing
decomposition of the skeletal PEDOT–Boc–Leu and PEDOT–Leu
backbone chain structures. As seen in Fig. 3A and B, the
residual weight of PEDOT–Boc–Leu (about 35.63%) and
PEDOT–Leu (about 31.47%) lms, also indicated the high
thermal stability of PEDOT–Boc–Leu and PEDOT–Leu lms.
Simultaneously, the DTG curves showed that the corresponding
maximal decomposition occurred at 620 K (PEDOT–Boc–Leu
lm), and at 615 K (PEDOT–Leu lm). Based on above discus-
sion, both PEDOT–Boc–Leu and PEDOT–Leu exhibited good
thermal stabilities.
Fig. 4 CD spectra of the doped PEDOT–Boc–Leu (a) and dedoped
PEDOT–Boc–Leu (b), doped PEDOT–Leu (c) and dedoped PEDOT–
Leu (d). The polymers were dissolved in DMSO.
dedoped PEDOT–Boc–Leu had their peaks in the long wave-
length. Meanwhile, compared with the doped PEDOT–Boc–Leu,
it could be observed that the chirality of the dedoped sample
was enhanced. For PEDOT–Leu, the reasons of the polymer
main chains to take a helically twisted structure and their peaks
in the long wavelength were that the amino group on amino
acid chains may form hydrogen bonds with the nitrogen of
amide on other polymer unions or the carbonyl of amide might
form hydrogen bonds with the amino group of other polymer
unions. And different from PEDOT–Boc–Leu, compared with
the doped PEDOT–Leu, the dedoped one had another kind of
enhanced CD intensity. These results demonstrated that the
main chains of polymers took helically twisted structures under
the introduction of the chiral amino acid side chains, and the
dedoping processes were helpful to enhance the chirality of
polymers. The chirality of the polymer weakened as the twisting
CD spectra of polymer lms
CD is one of the most interesting properties of chiral conduct-
ing polymers, as well as the linearly polarized dichroism. The
CD of conjugated polymers originating from their chiral struc-
ture requires no macroscopic alignment of the polymers. Fig. 4
showed CD spectra of PEDOT–Boc–Leu and PEDOT–Leu lms.
The CD peaks of all polymers from 280 nm to 320 nm were due
to the single chirality of amino acid chain. A chiral carbon on
the dioxane ring of EDOT was racemic before polymerization.
Therefore, the polymers should not have peaks in the long
wavelength. But for PEDOT–Boc–Leu, the oxygen of carbonyl on
Boc group may form hydrogen bonds with the nitrogen of
amide on other polymer unions or the carbonyl of amide may
form hydrogen bonds with the amino group of amino acids on
other polymer unions, which will induce the main chains of
polymers to take a helically twisted structure and the doped and
degree decreased.20 At the same time, the distance between the
ꢀ
polymer main chains was expanded because the dopants (PF6
)
were intercalated into the main chains. The increase of inter-
chain distance weakened the helical p-stacking, causing a
decrease in CD intensity.
Fig. 3 TG/DTG curves of dedoped PEDOT–Boc–Leu (A) and dedoped PEDOT–Leu (B) films.
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polymer sequence.79 These spectral results conrmed the
occurrence of electrochemical polymerization among the
monomer and the formation of a conjugated polymer with
broad molar mass distribution (Fig. 6).
UV-vis and uorescent spectra
PEDOT–Boc–Leu lm was prepared from CH2Cl2–Bu4NPF6 in
the doped state with dark brown color. While PEDOT–Leu lm
was prepared in CH2Cl2–Bu4NPF6 containing 5% TFA were in
the doped state with dark brown color. When they were dedo-
ped by 25% ammonia for three days, their color both changed to
brownish yellow. It was very interesting that both dedoped
PEDOT–Boc–Leu and PEDOT–Leu lms were partly soluble in
many common organic solvents, such as acetonitrile, DMSO,
dichloromethane, tetrahydrofuran, and chloroform, etc.
UV-vis spectra of the monomers and corresponding polymer
lms dissolved in DMSO were illustrated in Fig. 5. The mono-
mer of EDOT–Boc–Leu showed a characteristic absorption peak
at 273 nm (Fig. 5A-a), while the spectra of the doped and
dedoped PEDOT–Boc–Leu lms showed two much broader
absorptions with their maximum at 566 nm (Fig. 5A-b) and 560
nm (Fig. 5A-c), respectively. In comparison, EDOT–Leu mono-
mer presented a characteristic absorption peak at 266 nm
(Fig. 5B-a) and the doped PEDOT–Leu lm showed absorption
at 570 nm (Fig. 5B-b) and the dedoped PEDOT–Leu lm pre-
sented absorption at 560 nm (Fig. 5B-c). The overall absorption
of PEDOT–Boc–Leu tailed off to more than 700 nm (Fig. 5A and
B). Generally, longer wavelength in spectra indicated longer
Surface morphology
SEM was carried out in order to study the surface morphology of
the as-prepared conducting polymer lms. There were obvious
differences in surface morphology of the doped/dedoped
PEDOT–Boc–Leu lms. The doped PEDOT–Boc–Leu lm
surface was consisted of well-separated globules in the magni-
cation image and the diameter of most globules was less than
1 nm (Fig. 7a), which was in contrast to the smooth surface of
the pristine ITO electrode. Moreover, the globular humps were
found to have irregular shape in the magnication image and
some particles presented in Fig. 7a. However, in Fig. 7b, the
dedoped PEDOT–Boc–Leu lm appeared to be isolated parti-
cles, quite spherical, and their sizes were also less than 1 nm in
diameter. This result may be attributed to the intercalation of
ꢀ
dopants such as PF6 into the interchains of PEDOT–Boc–Leu
ꢀ
lm in the doped state, while in the dedoped state PF6 cou-
terions were removed during the dedoping procedure. In
Fig. 7c, PEDOT–Leu lm in the doped state had a homogeneous,
Fig. 5 UV-vis spectra of monomers and polymers: EDOT–Boc–Leu (A-a), doped PEDOT–Boc–Leu (A-b), dedoped PEDOT–Boc–Leu (A-c),
EDOT–Leu (B-a), doped PEDOT–Leu (B-b) and dedoped PEDOT–Leu (B-c). Solvent: DMSO.
Fig. 6 Fluorescence spectra of monomers and polymers: EDOT–Boc–Leu (A-a), dedoped PEDOT–Boc–Leu (A-b), EDOT–Leu (B-a), and
dedoped PEDOT–Leu (B-b). Solvent: DMSO.
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was clearly seen that modied electrodes represented steady-
state and broad redox peaks in selected electrolytes. This
might be ascribed to the presence of slow diffusion of the
counterions inside the lms, changes of the lms capacitance,
and a wide distribution of the polymer chain length resulting
from coupling defects distributed statically.81 The peak current
densities were linearly proportional to the potential scanning
rates (inset in Fig. 8), indicating that the redox processes were
non-diffusional and the electroactive polymer lms were well
adhered to the working electrodes surface. Furthermore, the
conversion between conducting (doped) and insulating (dedo-
ped) state was no signicant decomposition, which implied the
materials had high redox stability.
Spectroelectrochemical properties of PEDOT–Boc–Leu and
PEDOT–Leu lms
Spectroelectrochemical studies of PEDOT–Boc–Leu and
PEDOT–Leu lms were performed to evaluate their electronic
properties and band gaps, and to elucidate the effect of amino
acid substitution on the electronic properties of PEDOT. As
shown in Fig. 9, the electrooptical properties of the polymer
lms were investigated using the changes of electronic
absorption spectra at various applied voltages. PEDOT–Boc–Leu
and PEDOT–Leu lms were electrosynthesized directly on ITO
glasses, and a home-made electrochemical cell was built from a
commercial UV-vis cuvette. The cell was placed in the optical
path of the sample light beam in a ultraviolet-visible-near
infrared (UV-vis-NIR) spectrophotometer, which allowed us to
acquire electronic absorption spectra under potential control in
CH2Cl2–Bu4NPF6 (0.1 M) solution. As each potential was step-
ped, the absorption in the visible regime began to decrease,
whereas that in the NIR regime increased, indicating the crea-
tion of lower energy charge carriers at the expense of p–p*
transition.82,83 The spectroelectrochemistry of PEDOT–Boc–Leu
lm upon oxidation was presented in Fig. 9A as a series of UV-
Fig. 7 SEM photographs of PEDOT–Boc–Leu and PEDOT–Leu films
deposited electrochemically on ITO electrode; doped and dedoped
PEDOT–Boc–Leu (a and b); doped and dedoped PEDOT–Leu (c and
d).
compact and smooth morphology. Simultaneously, the lm of
PEDOT–Leu in the dedoped state showed a swollen morphology
(Fig. 7d). These differences between the doped and dedoped
polymer lms were mainly due to the migration of counter
anions out of the polymer lms and their gradual solubility
from the electrode to the solution during the dedoping
processes,80 which broke the relatively smooth surfaces of
doped polymer lms.
Electrochemistry of PEDOT–Boc–Leu and PEDOT–Leu lms
For insight into the electroactivity of the obtained polymer vis-NIR absorbance curves and the corresponding colors of
lms, the electrochemical behavior of PEDOT–Boc–Leu and electrochemically prepared lms correlated with electrode
PEDOT–Leu lms-modied electrodes were investigated by potentials. In view of the overall situation, for PEDOT–Boc–Leu,
cyclic voltammetry in monomer-free CH2Cl2–Bu4NPF6 (Fig. 8). It the trend of absorbance curves and the position of absorbance
Fig. 8 CVs of PEDOT–Boc–Leu (A) and PEDOT–Leu (B, containing 5% TFA) films in CH2Cl2–Bu4NPF6 (0.1 M) at a potential scan rates of 25, 50,
100, 150, 200, 250, and 300 mV sꢀ1. The films were obtained by CV. Inset: plots of redox peak current densities vs. potential scan rates. jp is the
peak current densities, jp,a and jp,c denote the anodic and the cathodic peak current densities, respectively.
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Fig. 9 Spectroelectrochemistry for PEDOT–Boc–Leu (A) in CH2Cl2–Bu4NPF6 (0.1 M) and PEDOT–Leu (B) in CH2Cl2–Bu4NPF6 (0.1 M) containing
5% TFA as applied potentials between ꢀ1.0 V and 1.0 V on ITO coated glass. (a) ꢀ1.0 V, (b) ꢀ0.9 V, (c) ꢀ0.8 V, (d) ꢀ0.7 V, (e) ꢀ0.6 V, (f) ꢀ0.5 V, (g)
ꢀ0.4 V, (h) ꢀ0.3 V, (i) ꢀ0.2 V, (j) ꢀ0.1 V, (k) 0.0 V, (l) 0.1 V, (m) 0.2 V, (n) 0.3 V, (o) 0.4 V, (p) 0.5 V, (q) 0.6 V, (r) 0.7 V, (s) 0.8 V, (t) 0.9 V, (u) 1.0 V.
Fig. 10 Photographs of PEDOT–Boc–Leu and PEDOT–Leu films deposited electrochemically on ITO electrode; doped and dedoped PEDOT–
Boc–Leu (a and b); doped and dedoped PEDOT–Leu (c and d).
peaks were very similar to PEDOT. Stepwise oxidation of the Furthermore, comparable to the corresponding PEDOT, the
polymer (increasing applied voltage from ꢀ1.0 to 1.0 V) showed lower band gap of PEDOT–Leu led to a lower trapping of elec-
the fading of absorbance at 600 nm and typical evolution of trons and facilitates better electron injection from the contact,
peaks at more than 730 nm.84 In the dedoped form, the lm so that PEDOT–Leu lm required low potentials for the elec-
exhibited strong absorption at the wavelength around 600 nm, trochromic switching.
approximately the same as that of PEDOT, but it was almost
obvious at the wavelength more than 710 nm. The band gap
(extracted from the onset of the p–p* transition) for the dedo-
ped polymer was calculated as 1.67 eV using the absorption
band centered at 745 nm, which was comparable to the reported
optical band gap of parent PEDOT (1.6 eV). This implied that
the pendant amino acid group had little inuence on the elec-
tronic properties of PEDOT.
For a comparative study, the spectral changes of PEDOT–Leu
were presented in Fig. 9B. The neutral form of the PEDOT–Leu
showed a distinct p–p* transition at 600 nm. Further oxidation
of the polymer lms, a new absorption band were observed
around 950 nm due to the formation of bipolarons.
Electrochromic switching of PEDOT–Boc–Leu and PEDOT–
Leu lms
As-prepared PEDOT–Boc–Leu and PEDOT–Leu lms had
favorable electrochromic properties compared with PEDOT.
Namely, PEDOT–Boc–Leu and PEDOT–Leu lms in the doped
state were dark blue and blue (Fig. 10A and C), respectively.
When they were dedoped by electrochemical method, their
colors changed to purple and pink (Fig. 10B and D). As seen in
Fig. 10A and B, doped and dedoped PEDOT–Boc–Leu lms
clearly exhibited helical structures, which were due to the
function chiral amino acid group. In order to gain further
insight into their electrochromic properties, the optical
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Fig. 11 Electrochromic switching and optical absorbance monitored at 600 nm (A) for PEDOT–Boc–Leu recorded during double step spec-
trochronoamperometry between ꢀ0.8 V and 0.6 V and at 600 nm (B) and 960 nm (C) for PEDOT–Leu between ꢀ1.0 V and 1.0 V for a switching
time of 10 s.
Table 2 Electrochromic parameters for PEDOT–Boc–Leu and PEDOT–Leu
Response time (s)
Coloration efficiency
Polymer
Wavelength/nm
Tred/%
Tox/%
DT/%
Oxidation
Reduction
(cm2 Cꢀ1
)
PEDOT–Boc–Leu
PEDOT–Leu
600
600
960
4
10
45
53
53
27
49
43
18
2.3
2.2
4.2
2.5
5.8
5.8
163
351
431
switching studies were investigated using a square wave slowly than the reduction of the doped form (bleaching step)
potential step method coupled with optical spectroscopy known due to the difference in charge transport rates between the two
as chronoabsorptometry in a monomer-free solution. The states. However, the results about PEDOT–Boc–Leu and
electrochromic parameters, such as optical contrast ratio PEDOT–Leu lms were not conrm to typical result in this
(OD%), response time and coloration efficiency of the polymer experiment. The response required to attain 95% of total
lms were explored by increment and decrement in the trans- transmittance difference was found to be 2.3 s at 600 nm for
mittance with respect to time at the specic absorption wave- PEDOT–Boc–Leu and 2.2 s at 600 nm for PEDOT–Leu from the
length of 600 nm for PEDOT–Boc–Leu and 600 and 960 nm for dedoped state to the doped state, while from the doped state to
PEDOT–Leu (Fig. 11B and C). The potentials switched stepwise the dedoped state, the response time was 2.5 s at 600 nm for
between doped and dedoped states with a residence time of 10 PEDOT–Boc–Leu and 5.8 s at 600 nm for PEDOT–Leu,
s. The optical contrast ratio, response time and coloration effi- respectively.
ciency of PEDOT–Boc–Leu and PEDOT–Leu lms were
summarized in Table 2.
The optical contrast ratios of PEDOT–Boc–Leu between
Conclusions
dedoped (at ꢀ0.8 V) and doped states (at 0.6 V) were found to be
Chiral EDOT–Boc–Leu and EDOT–Leu were rstly synthesized
by some readily synthesized steps and electropolymerized for
the preparation of corresponding chiral polymers in CH2Cl2-
Bu4NPF6 (0.1 M) system. A series of characterizations were
systematically tested for monomers and polymers. The obtained
chiral PEDOT–Boc–Leu and PEDOT–Leu lms showed good
redox activity, excellent surface structure and high thermal
stability. PEDOT side chain in the presence of chiral amino acid
group can induce helical structure of PEDOT. In addition,
PEDOT–Boc–Leu and PEDOT–Leu lms showed favorable elec-
trochromic performances compared with PEDOT, with high
optical contrast ratio (49% at 600 nm for PEDOT–Boc–Leu),
high coloration efficiency (431 cm2 Cꢀ1 for PEDOT–Leu) and
good optical stability. It is believed that PEDOT–Boc–Leu and
PEDOT–Leu lms will be promising candidates for multifunc-
tional polymeric materials in electrochromic devices, chiral
recognition and optical displays. The introduction of chiral
moieties into PEDOT was demonstrated to be a useful approach
for the synthesis of optically active PEDOT derivatives.
49% at 600 nm (Fig. 11A). For PEDOT–Leu, the transmittance
differences at different wavelengths were measured using a UV-
vis-NIR spectrophotometer as the applied potential between
ꢀ1.0 V and 1.0 V. The optical contrast ratios of PEDOT–Leu
were showed to be 43% at 600 nm and 18% at 960 nm
(Fig. 11B and C).
The CE is also an important characteristic for electrochromic
materials and obtained for a certain amount of the charge
injected in the polymer as a function of the change in optical
density. In this study, CE was measured as 163 cm2 Cꢀ1 (at 600
nm) for PEDOT–Boc–Leu, while for PEDOT–Leu, the CE was
calculated for 351 cm2 Cꢀ1 at 600 nm and 431 cm2 Cꢀ1 at 960
nm. Compared with PEDOT (183 cm2 Cꢀ1),70 the CE of PEDOT–
Leu was much higher. Response time is also an important
parameter for a polymer since it indicates the speed of ions
moving into the polymer chains during the doping process.
Typically, for most electrochromic conducting polymers, the
oxidation of the dedoped form (coloration step) proceeds more
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24 H. Goto and K. Akagi, Macromolecules, 2005, 38, 1091–1098.
25 M. Goh, M. Kyotani and K. Akagi, J. Am. Chem. Soc., 2007,
129, 8519–8527.
26 T. Mori, T. Sato, M. Kyotani and K. Akagi, Macromolecules,
2009, 42, 1817–1823.
27 T. Mori, M. Kyotani and K. Akagi, Macromolecules, 2010, 43,
8363–8372.
28 M. Goh, T. Matsushita, M. Kyotani and K. Akagi,
Macromolecules, 2007, 40, 4762–4771.
Acknowledgements
The authors would like to acknowledge the nancial support of
this work by the National Natural Science Foundation of China
(51263010, 51303073, 51272096), Natural Science Foundation
of Jiangxi Province (20122BAB216011, 20142BAB206028,
20142BAB216029), Jiangxi Science and Technology Normal
University (YC2013-X03).
29 S. Matsushita, B. Yan, S. Yamamoto, Y. S. Jeong and K. Akagi,
Angew. Chem., Int. Ed., 2014, 53, 1659–1663.
Notes and references
1 T. Nakano and Y. Okamoto, Chem. Rev., 2001, 101, 4013– 30 J. Park, M. Goh and K. Akagi, Macromolecules, 2014, 47,
4038.
2784–2795.
2 J. J. L. M. Cornelissen, A. E. Rowan, R. J. M. Nolte and 31 D. Iarossi, A. Mucci, F. Parenti, L. Schenetti, R. Seeber,
N. A. J. M. Sommerdijk, Chem. Rev., 2001, 101, 4039–4070.
3 R. J. M. Nolte, Chem. Soc. Rev., 1994, 23, 11–19.
C. Zanardi, A. Forni and M. Tonelli, Chem.–Eur. J., 2001, 7,
676–685.
4 L. A. P. Kane-Maguire and G. G. Wallace, Chem. Soc. Rev., 32 M. Lemaire, D. Delabouglise, R. Garreau, A. Guy and
2010, 39, 2545–2576.
J. Roncali, J. Chem. Soc., Chem. Commun., 1988, 658–661.
5 P. A. McCarthy, J. Y. Huang, S. M. Yang and H. L. Wang, 33 D. Kotkar, V. Joshi and P. K. Ghosh, J. Chem. Soc., Chem.
Langmuir, 2002, 18, 259–263.
Commun., 1988, 917–918.
6 J. Deng, C. Zhou and N. H. Song, Macromolecules, 2009, 42, 34 M. M. Bouman, E. E. Havinga, R. A. J. Janssen and
6865–6872. E. W. Meijer, Mol. Cryst. Liq. Cryst., 1994, 256, 439–448.
7 H. F. Chow and M. K. Ng, Tetrahedron: Asymmetry, 1996, 7, 35 (a) Bayer AG, Eur. Patent 339 340 1988; (b) F. Jonas and
2251–2262.
L. Schrader, Synth. Met., 1991, 41, 831–836; (c) G. Heywang
and F. Jonas, Adv. Mater., 1992, 4, 116; (d) I. Winter,
C. Reece, J. Hormes, G. Heywang and F. Jonas, Chem.
Phys., 1995, 194, 207–213; (e) Bayer AG, Robert Bosch
GmbH, German Patent DE 19 627069, 1998; (f) Bayer AG,
German Patent DE 19 627071, 1998.
8 M. Kaniewska, T. Sikora, R. Kataky and M. Trojanowicz, J.
Biochem. Biophys. Methods, 2008, 70, 261–1267.
9 J. C. Ramos, R. M. Souto-Maior and M. Navarro, Polymer,
2006, 47, 8095–8100.
10 M. Schwientek, S. Pleus and C. H. Hamann, J. Electroanal.
Chem., 1999, 461, 94–101.
36 (a) F. Jonas, G. Heywang, W. Schmidtberg, J. Heinze and M.
Dietrich, Prior, April 22, 1988, 339-340, (Bayer AG); (b) F.
Jonas and G. Heywang, Prior, April 30, 1988, 340-512,
(Bayer AG); (c) F. Jonas and G. Heywang, Electrochim. Acta,
1994, 39, 1345–1347.
´
11 J. Papillon, E. Schulz, S. Gelinas, J. Lessard and M. Lemaire,
Synth. Met., 1998, 96, 155–160.
12 (a) B. M. W. Langeveld-Voss, R. A. J. Janssen and
E. W. Meijer, J. Mol. Struct., 2000, 521, 285–301; (b)
F. Babudri, D. Colangiuli, L. D. Bari, G. M. Farinola, 37 G.-D. Wolf and F. Jonas, DE 19637018, (Bayer AG), Prior,
O. H. Omar, F. Naso and G. Pescitelli, Macromolecules,
2006, 39, 5206–5212.
13 P. Emiel, A. Delmotte, R. A. J. Janssen and E. W. Meijer, Adv.
Mater., 1997, 9, 493–496.
September 12, 1996.
38 J. Hupe, W. Kronenberg, J. Kickelhain and D. Maier, EP
1191127, (Enthone-OMI, LPKF Laser & Electronics AG),
Prior, September 26, 2000.
14 H. Goto and K. Akagi, Synth. Met., 2001, 119, 165–166.
15 (a) H. Goto, J. Polym. Sci., Part A: Polym. Chem., 2007, 45,
39 K. Neyts, A. Real, M. Marescaux, S. Mladenovski and
J. Beeckman, J. Appl. Phys., 2008, 103, 093113.
2085–2090; (b) H. Goto, Y. S. Jeong and K. Akagi, 40 F. Jonas, W. Kra and B. Muys, Macromol. Symp., 1995, 100,
Macromol. Rapid Commun., 2005, 26, 164–167.
169.
16 B. Y. Lu, J. K. Xu, Y. Z. Li, C. C. Liu, R. R. Yue and X. X. Sun, 41 F. Jonas and J. T. Morrison, Synth. Met., 1997, 85, 1397–1398.
Electrochim. Acta, 2010, 55, 2391–2397.
42 F. Jonas and K. Lerch, Kunststoffe, 1997, 87, 1401–1402.
17 T. Tsuruta, S. Inoue and F. J. Furukawa, Macromol. Chem., 43 M. Huppauff, R. Sybrichs and A. Gehring, DE 19757874,
1965, 84, 298–299. (Bosch GmbH), Prior, December 12, 1997.
18 P. E. Ebert and C. C. Price, J. Polym. Sci., 1959, 34, 157–160. 44 H. Andriessen, EP 1 231 251 A1, (Agfa-Gevaert), Prior, August
¨
19 E. Yashima, K. Maeda and Y. Okamoto, Nature, 1999, 399,
14, 2002.
449–451.
45 A. Saito, JP 2002 124391 A2, (Seiko Precision Inc.), Prior,
August 8, 2000.
20 Y. S. Jeong and K. Akagi, Macromolecules, 2011, 44, 2418–
2426.
46 E. L. Williams, G. E. Jabbour, Q. Wang, S. E. Shaheen,
D. S. Ginley and E. A. Schiff, Appl. Phys. Lett., 2005, 87,
223504.
21 S. Matsushita, Y. S. Jeong and K. Akagi, Chem. Commun.,
2013, 49, 1883–1890.
22 H. Goto and K. Akagi, Macromol. Rapid Commun., 2004, 25, 47 J.-G. Chen, H.-Y. Wie and K.-C. Ho, Sol. Energy Mater. Sol.
1482–1486.
Cells, 2007, 91, 1472–1477.
23 H. Goto and K. Akagi, Chem. Mater., 2006, 18, 255–262.
This journal is © The Royal Society of Chemistry 2014
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RSC Advances
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48 D. M. Welsh, L. J. Kloeppner, L. Madrigal, M. R. Pinto, 67 C. L. Gaupp, D. M. Welsh, R. D. Rauh and J. R. Reynolds,
B. C. Thompson, K. S. Schanze, K. A. Abboud, D. Powell
and J. R. Reynolds, Macromolecules, 2002, 35, 6517–6525.
49 A. Cirpan, A. A. Argun, C. R. G. Grenier, B. D. Reeves and
J. R. Reynolds, J. Mater. Chem., 2003, 13, 2422–2428.
Chem. Mater., 2002, 14, 3964–3970.
68 B. D. Reeves, C. R. G. Grenier, A. A. Argun, A. Cirpan,
T. D. McCarley and J. R. Reynolds, Macromolecules, 2004,
37, 7559–7569.
50 P. Schottland, K. Zong, C. L. Gaupp, B. C. Thompson, 69 V. Coessens, Y. Nakagawa and K. Matyjaszewski, Polym.
C. A. Thomas, I. Giurgiu, R. Hickman, K. A. Abboud and
Bull., 1998, 40, 135–142.
J. R. Reynolds, Macromolecules, 2000, 33, 7051–7061.
70 W. S. Mungall, G. L. Greene, G. A. Heavner and
R. L. Letsinger, J. Org. Chem., 1975, 40, 1659–1662.
71 C. D. McTiernan and M. Chahma, Synth. Met., 2011, 161,
1532–1536.
¨
¨
51 T. G. Backlund, H. G. O. Sandberg, R. Osterbacka, H. Stubb,
¨
¨
T. Makela and S. Jussila, Synth. Met., 2005, 148, 87–91.
52 G. C. Schmidt, M. Bellmann, B. Meier, M. Hambsch,
¨
K. Reuter, H. Kempa and A. C. Hubler, Org. Electron., 2010, 72 A. J. Downard and D. A. Pletcher, J. Electroanal. Chem., 1986,
11, 1683–1687. 206, 139–145.
53 R. M. Walczak and J. R. Reynolds, Adv. Mater., 2006, 18, 73 A. J. Downard and D. A. Pletcher, J. Electroanal. Chem., 1986,
1121–1131. 206, 147–152.
54 S. Matsushita, Y. S. Jeong and K. Akagi, Chem. Commun., 74 R. E. Nole and D. Pletcher, J. Electroanal. Chem., 1987, 227,
2013, 49, 1883–1890. 229–235.
55 K. Kawabata and H. Goto, J. Mater. Chem., 2012, 22, 23514– 75 H. Randriamahazaka, V. Noel and C. Chevrot, J. Electroanal.
¨
23524.
Chem., 1999, 472, 103.
56 Y. Sulaiman and R. Kataky, Analyst, 2012, 137, 2386–2393.
57 K. Kawabata, M. Takeguchi and H. Goto, Macromolecules,
2013, 46, 2078–2091.
58 K. Kawabata and H. Goto, J. Mater. Chem., 2012, 22, 23514–
23524.
76 M. Zhou and J. Heinze, Electrochim. Acta, 1999, 44, 1733–
1748.
77 J. X. Zhang, C. Liu, G. Q. Shi and Y. F. Zhao, J. Polym. Sci., Part
B: Polym. Phys., 2005, 43, 241–251.
78 B. Y. Lu, S. Chen, J. Wang, J. K. Xu, X. M. Duan and M. S. Pei,
Chin. J. Chem., 2012, 30, 1177–1184.
59 H. Goto and K. Kawabata, Polym. Chem., 2011, 2, 1098–1106.
60 J. C. Xiao, J. L. Xu, S. Cui, H. B. Liu, S. Wang and Y. L. Li, Org. 79 H. J. Bowley, D. L. Gerrard, W. F. Maddams and M. R. Paton,
Lett., 2008, 10, 645–648. Makromol. Chem., 1985, 186, 695–705.
61 B. Y. Lu, Y. Lu, Y. P. Wen, X. M. Duan, J. K. Xu, S. Chen and 80 B. Y. Lu, J. Yan, J. K. Xu, S. Y. Zhou and X. J. Hu,
L. Zhang, Int. J. Electrochem. Sci., 2013, 8, 2826–2841. Macromolecules, 2010, 43, 4599–4608.
62 L. Zhang, Y. P. Wen, Y. Y. Yao, X. M. Duan, J. K. Xu and 81 G. Inzelt, M. Pineri, J. W. Schultze and M. A. Vorotyntsev,
X. Q. Wang, J. Appl. Polym. Sci., 2013, 130, 2660–2670. Electrochim. Acta, 2000, 45, 2403–2421.
63 J. L. Segura, R. Gomez, E. Reinold and P. Bauerle, Org. Lett., 82 C. W. Chang, G. S. Liou and S. H. Hsiao, J. Mater. Chem.,
2005, 7, 2345–2348. 2007, 17, 1007–1015.
64 A. E. Daugaard and S. Hvilsted, Macromolecules, 2008, 41, 83 B. Y. Lu, S. J. Zhen, S. M. Zhang, J. K. Xu and G. Q. Zhao,
4321–4327. Polym. Chem., 2014, 5, 4896–4908.
65 W. S. Mungall, G. L. Greene, G. A. Heavner and 84 Y. C. Kunga and S. H. Hsiao, J. Mater. Chem., 2010, 20, 5481–
´
R. L. Letsinger, J. Org. Chem., 1975, 40, 1659–1662.
5492.
66 N. A. Nikolic and P. Beak, Org. Syn. Coll., 1997, 74, 23–28.
35608 | RSC Adv., 2014, 4, 35597–35608
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