Novel electroactive poly(arylene ether sulfone) copolymers containing pendant oligoaniline groups: Synthesis and properties

Article abstract of DOI:10.1002/pola.24584

We present a series of novel poly(arylene ether sulfone) copolymers containing pendant oligoaniline groups. A novel monomer containing oligoaniline, 2,6-difluorobenzoyl aniline tetramer (DFAT), was synthesized by reaction of 2,6-difluorobenzoyl chloride a

Full text of DOI:10.1002/pola.24584

Novel Electroactive Poly(arylene ether sulfone) Copolymers Containing
Pendant Oligoaniline Groups: Synthesis and Properties
DANMING CHAO,1 XIAOTENG JIA,1 HONGTAO LIU,1 LIBING HE,1 LILI CUI,1 CE WANG,1 ERIK B. BERDA2
1Alan G. MacDiarmid Institute, Jilin University, Changchun 130012, People’s Republic of China
2Department of Chemistry and Materials Science Program, University of New Hampshire, Durham, New Hampshire 03824
Received 12 November 2010; accepted 14 January 2011
DOI: 10.1002/pola.24584
Published online in Wiley Online Library (wileyonlinelibrary.com).
ABSTRACT: We present a series of novel poly(arylene ether sul-
fone) copolymers containing pendant oligoaniline groups. A
novel monomer containing oligoaniline, 2,6-difluorobenzoyl
aniline tetramer (DFAT), was synthesized by reaction of 2,6-
difluorobenzoyl chloride and parent aniline tetramer and incor-
porated into the aforementioned copolymers via direct copoly-
merization with 4,40-dichlorodiphenyl sulfone (DCDPS), and
4,40-isopropylidene diphenol (BPA) using N,N0-dimethylaceta-
mide as solvent. The structures of these copolymers were con-
firmed by FTIR, 1H NMR, and GPC. Spectral analysis of the
copolymers in different oxidation states was investigated via
UV-visible spectra. The copolymers exhibited outstanding ther-
mal stability and good solubility in various organic solvents.
Their electroactivity, explored with cyclic voltammetry, was
found to increase as the content of oligoaniline in the polymer
increased. The electric and dielectric properties of the copoly-
mers were also studied in detail. The electrochromic perform-
ance of the copolymers was investigated by electrochromic
photographs and transmittance spectra; the color of the co-
polymer thin films changes from grey (at 0.0 V), to green (at
0.4 V), to blue (at 0.6 V) and to pearl blue (at 1.0 V) and the
maximum transmittance change (DT) at 700 nm is 42.6%
C
V
(90.7% $ 48.1%).
2011 Wiley Periodicals, Inc. J Polym Sci
Part A: Polym Chem 49: 1605–1614, 2011
KEYWORDS: conducting polymers; copolymerization; electroac-
tive; electrochromic; oligoaniline; poly(arylene ether sulfone);
redox polymers
INTRODUCTION Conducting polymers continue to attract
great academic and industrial interest in the chemistry,
physics, engineering, and material science following the
work of Shirakawa and coworkers in the late 1970’s on the
conducting properties of polyacetylene.1 In recent years,
organic conducting polymers have been studied extensively
and have found promising applications in the fields of
organic field-effect transistors, photovoltaic cells, light emit-
ting diodes, and sensors.2–5 Polyaniline (PANI), one of the
most frequently investigated conducting polymers, has great
potential for advanced applications such as electrolumines-
cent, biosensors, electrochemical capacitors, chemical sensors
and electromagnetic interference shielding materials6–8 due
to its excellent environmental stability, ease of synthesis and
reversible acid/base doping/dedoping chemistry.9–12 How-
ever, PANI prepared by chemical and/or electrochemical
methods present a number of problems both in academic
research and industrial application.13,14 First, the ill-defined
molecular structure impeded the better understanding of the
structure-property correlations and the conducting mecha-
nism of PANI. Second, poor solubility, fusibility, and process-
ability restrict the practical application of PANI. Further, its
single functionality has severely limited the expansion of its
potential applicability.
In contrast to PANI, oligoanilines have already been investi-
gated thoroughly due to their structure regularity, good
electroactivity, excellent solubility, and excellent processabil-
ity.15–20 However, stability and mechanical properties of
oligoanilines are poor compared with those of the analogous
polymers. One of the most promising approaches is to pre-
pare functional polymers based on oligoanilines, with well-
defined molecular structure, as these should combine the
excellent solubility and processability inherent to the oligom-
ers with the mechanical benefits of a macromolecule. Consid-
erable effort has been devoted recently toward chemically
synthesizing polymers based on oligoanilines, such as graft,
alternating, and block-like polymers. Pron and coworkers21,22
copolymerized 3-octylthiophene with thiophene containing
tetra-aniline in the 3-position to prepare a hybrid copolymer,
which exhibits very interesting spectroscopic and electro-
chemical properties. Both of the oligoaniline side chains and
the polymer main chains could be doped consecutively. Poly-
mers with conjugated aniline oligomers in the main chains
have also been prepared by an acid-induced polycondensa-
tion.23 These polymers displayed good solubility in common
organic solvents and electrical conductivities up to 0.1 S/cm
upon doping with hydrochloric acid. Electroactive polyimides
derived from the bis-amino-terminated aniline trimer were
Correspondence to: C. Wang (E-mail: cwang@jlu.edu.cn)
C
V
Journal of Polymer Science Part A: Polymer Chemistry, Vol. 49, 1605–1614 (2011) 2011 Wiley Periodicals, Inc.
NOVEL ELECTROACTIVE POLY(ARYLENE ETHER SULFONE), CHAO ET AL.
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JOURNAL OF POLYMER SCIENCE PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
also reported by Wei and coworkers24 Novel poly(methacry-
lamide)s containing oligoaniline side chains were prepared
by free radical polymerization and its redox behaviors were
investigated.25 Many electrochromic polyamides, reported by
Wang and coworkers,26 were prepared by the condensation
polymerization between amine-capped oligoaniline and acyl
chlorides such as isophthaloyl dichloride, terephthaloyl chlo-
ride, and azelaoyl chloride. A series of novel electroactive
block copolymers with bioactive properties was synthesized
by coupling an electroactive carboxyl-capped aniline penta-
mer with two bioactive bihydroxyl-capped polymers via a
condensation reaction.27–29 In addition, electroactive poly
(aryl ether) materials with oligoanilines in the main chains
have been reported in our group,30–32 and the materials syn-
thesized by polycondensation or oxidative coupling polymer-
ization displayed excellent thermal stability.
hydroxide) and stirred for 12 h. Then it was filtered and
washed with distilled water for several times, followed by
drying in vacuum. Finally, the PAT was reduced to the
leucoemeraldine oxidation state. Yield: 94%. MALDI-TOF-MS:
m/z calculated for C24H22N4 ¼ 366.5. Found 366.6.
FTIR (KBr, cmꢂ1): 3390 (s, tNH), 3020 (m, tCH), 1600 and
1527 (s, tC¼C of benzenoid rings), 1305 (s, tCAN), 815 (m,
d
CH), 746 (m, dCH), 692 (m, dCH). 1H NMR (d6-DMSO): d ¼
7.78 (s, 1H, due to H4), d ¼ 7.68 (s, 1H, due to H3), d ¼ 7.43
(s, 1H, due to H2), d ¼ 7.12 (t, 2H, due to H6), d ¼ 6.87 (m,
12H, due to H8), d ¼ 6.65 (t, 1H, due to H5), d ¼ 6.51(d, 2H,
due to H7), d ¼ 4.62 (s, 2H, due to H1).
Synthesis of DFAT
A solution of 5.28 g (30 mmol) 2,6-difluorobenzoyl chloride
in 120 mL of dry methylene chloride was added dropwise
over a period of 5 h to a stirring mixture of PAT (11.35 g, 31
mmol) and triethylamine (12 mL) in 300 mL of methylene
chloride. The reaction, carried out in an atmosphere of dry
nitrogen to avoid oxidation of PAT, proceeded readily
at room temperature, with the formation of a grey solution.
Following the addition of the solution of 2,6-difluorobenzoyl
chloride, the resulting mixture was stirred for 1 h. The prod-
uct, filtered from the mixture, was subsequently washed
with methylene chloride two times, filtered and dried under
dynamic vacuum at 45 ꢀC for 24 h. The grey powder was
obtained in 85% yield. MALDI-TOF-MS: m/z calculated for
Polymers containing pendant oligoanilines are of interest
because the large side groups should simultaneously
decrease molecular mobility and enhance solubility. The
electrical, electrochemical and mechanical properties can be
easily modified by adjusting the feed percent through copoly-
merization.25 We chose poly(arylene ether sulfone)s as the
main chain to attach the pendant olidoanilines. Poly(arylene
ether sulfone)s materials are a family of high-performance
engineering plastics with excellent properties, such as film
formation, thermal and dimensional stability. Functional poly
(arylene ether sulfone)s have been well studied as proton
exchange membranes, gas-separated membranes, adhesives
and optical materials.33–35 Herein, we describe the synthesis
of a new monomer, 2,6-difluorobenzoyl aniline tetramer
(DFAT) and its facile incorporation into poly(arylene ether
sulfone) backbones, yielding copolymers with oligoaniline
side chains. The properties of these copolymers, such as
organic solubility, thermal stability, electroactivity, electrical
conductivity, dielectric properties and electrochromic per-
formance are also described in detail.
C
31H24F2N4O ¼ 506.5. Found 506.6.
FTIR (KBr, cmꢂ1): 3369 (s, tNH), 3299 (s, tNH), 1657 (vs,
C¼O), 1600(s, tC¼C of benzenoid rings), 1525 (vs, tC¼C of
t
benzenoid rings), 1303 (s, tCAN), 1008(m, dCF), 817 (m, dCH),
746 (m, dCH), 692 (m, dCH). 1H NMR (d6-DMSO): d ¼ 10.51
(s, 1H, due to H1), d ¼ 7.80 (s, 1H, due to H4), d ¼ 7.77 (s,
1H, due to H3), d ¼ 7.65 (s, 1H, due to H2), d ¼ 7.56 (t, 1H,
due to H9), d ¼ 7.48 (d, 2H, due to H7), d ¼ 7.23 (t, 2H, due
to H6), d ¼ 7.14 (t, 2H, due to H8), d ¼ 6.96 (m, 12H, due to
EXPERIMENTAL
H
10), d ¼ 6.68(t, 1H, due to H5).
Materials
2,6-difluorobenzoyl chloride and N-phenyl-p-phenylenedi-
amine were purchased from Aldrich. 4,40-dichlorodiphenyl
sulfone and 4,40-isopropylidene diphenol were purchased
Synthesis of Electroactive Poly(arylene ether sulfone)
Copolymers (PES-S-AT)
ꢀ
from Shanghai Chemical Factory. K2CO3 was dried at 110 C
A typical synthesis procedure of PES-S-AT-40, where 40
refers to the feed percent of DFAT, was as follows. A mixture
of DMAc (30 mL), toluene (10 mL), anhydrous potassium
carbonate (1.423 g), DFAT (2.026 g, 4 mmol), 4,40-dichlorodi-
phenyl sulfone (1.723 g, 6 mmol), and 4,40-isopropylidene
diphenol (2.283 g, 10 mmol) were added to a 100 mL three-
necked round-bottom flask and heated to reflux under nitro-
gen with magnetic stirring for 2 h to remove the water by
azeotropic distillation with toluene, and then the toluene
was removed. The mixture was heated to reflux for 8 h to
ensure the completion of the reaction. The solution was
cooled to room temperature and poured into 400 mL water,
which yielded a grey precipitate. The precipitate was washed
with water and ethanol several times, filtered and dried
for 24 h before used. All other reagents were obtained from
commercial sources and used as received without further pu-
rification. Distilled and deionized water was used. Optically
transparent indium-tin oxide (ITO) glass substrates (Reintech
electronic technologies, Beijing) with dimensions of 4.0 cm
ꢁ 0.6 cm ꢁ 0.07 cm were used for electrochromic thin films
electrode.
Synthesis of Parent Aniline Tetramer (PAT)
The parent aniline tetramer in emeraldine state was synthe-
sized by oxidative coupling of N-phenyl-p-phenylenediamine
in the presence of ferric chloride hexahydrate as an oxidant
according to the method of Zhang et al.36 The obtained PAT
(5.0 g) was dispersed into a stirring mixture solution
(30 mL of hydrazine hydrate in 400 mL of 1.0 M ammonium
ꢀ
under dynamic vacuum at 45 C for 48 h Yield: 90%.
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ARTICLE
Preparation of the Poly(arylene ether sulfone)
Thermal Properties
Copolymers in Emeraldine State Doped with HCl
Differential scanning calorimeter (DSC) measurements were
performed on a Mettler Toledo DSC821eꢀ instrument at a
The obtained polymers (0.5 g) was dispersed into a stirring
mixture solution (ammonium persulfate in 30 mL of 1.0 M
HCl) and stirred for 5 h. The mol quantity of ammonium
persulfate corresponds to that of each PES-S-AT-x. Then the
mixture was filtered using a Buchner funnel and water aspi-
rator, and the filter cake was washed with distilled water for
several times, followed by drying under dynamic vacuum at
50 ꢀC for 24 h. Finally, the doped copolymers were proved
in the emeraldine oxidation state by UV-Vis spectra.
ꢀ
heating rate of 10 C/min from 50 to 300 C under nitrogen.
The glass-transition temperatures (Tg) of the copolymers
were reported as the midpoint of the step transition in the
second heating run. A Perkin-Elmer PYRIS 1 TGA was used
to investigate the thermal stability of the copolymers in the
temperature range from 100 to 700 ꢀC at a rate of 10.0 ꢀC
minꢂ1 under nitrogen protection.
Electrochemical Activity
The cyclic voltammetry (CV) was performed with a CHI
660A Electrochemical Workstation (CH Instruments) in a
conventional three-electrode cell, by using thin films cast
from DMAc solutions onto a g-c electrode. The film was
cycled at 1.0 M H2SO4 aqueous solution in the range from
ꢂ100 mV to þ1000 mV.
Fabrication of Electrochromic Electrodes
The ITO substrates were cleaned ultrasonically in the etha-
nol for 5 min and in the deionized water for another 3 min.
Then the ITO substrates dried in the air. Take PES-S-AT-100
copolymer as an example: the polymer (0.03 g) was
dissolved in DMAc (1 mL) to form a blue solution, and fil-
tered through 0.2-lm poly(tetrafluoroethylene) syringe filter.
Then the copolymer films were spin-coated onto the ITO
substrates by the DMAc solution of PES-S-AT-100. The spin-
coating process was firstly 500 rpm for 5 s and then 1000
rpm for 30 s. Before electrochromic measurements, a copper
tape (1.0 cm ꢁ 0.5 cm) was applied to the top edge of ITO
substrates as the bus bar.
Electrochromic Performance
The electrochromic electrodes coated by PES-S-AT were
applied a constant potential of 0, 0.2, 0.4, 0.5, 0.6, 0.8, and
1.0 V versus Ag/AgCl in the 0.5 M H2SO4 for 400 s. Then
the electrochromic electrodes were rinsed with deionized
water and dried by N2 blewing. Subsequently, the change
of color and transmittance were monitored with a digital
camera (Canon, IXUS130) and UV-2501 PC Spectrometer
(SHIMADZU).
Measurement
Electric and Dielectric Properties
Mass spectroscopy (MS) was performed on an AXIMA-CFR
laser desorption ionization flying time spectrometer (COM-
PACT). Fourier-transform infrared spectra (FTIR) measure-
ments were recorded on a BRUKER VECTOR 22 Spectro-
meter by averaging 128 scans at a solution of 4 cmꢂ1 in the
range of 4000–400 cmꢂ1. The nuclear magnetic resonance
spectra (NMR) of PAT, DFAT and PES-S-AT in deuterated
dimethyl sulfoxide (DMSO) were run on a BRUKER-500 spec-
trometer to determine the chemical structure and tetra-
methylsilane was used as the internal standard. The
number-average molecular weight (Mn), weight-average mo-
lecular weight (Mw), and molecular weight distribution of
PES-S-AT were measured with a gel permeation chromatog-
raphy (GPC) instrument equipped with a Shimadzu GPC-
802D gel column and SPD-M10AVP detector with N,N0 -dime-
The electrical conductivity of the copolymers at room tem-
perature (RT) was measured by a four-probe method using a
2182 Nanovoltmeter and 2400 Sourcemeter as the current
source. Three samples of each copolymer were tested and
the conductivity of each sample was measured four times at
different current values. The average of 12 measurements
was taken as the conductivity of the copolymer. The formula
Iꢁ24:4
used for calculating conductivity is as follows: r ¼
.
Uꢁdꢁh
Where r, I, V, d, and h are conductivity (S cmꢂ1), current (A)
set, voltage (V) measured, the width (mm) and thickness
(mm) of the sample.
Dielectric spectroscopy was performed using a QuadTech
1920 LCR meter. Measurements of the capacitance(C) over
the range of 0.1 kHz to 1 MHz were carried out with the
pressure compressed circular pellets of the pristine material,
ꢃ1 cm in diameter with a thickness of 0.4 mm. The dielec-
thylformamide as an eluent at a flow rate of 1 mL minꢂ1
.
Calibration was accomplished with monodispersed polysty-
rene (PS) standards. Inherent viscosity was determined on
an Ubbelohde viscometer in thermostatic container with the
polymer concentration of 0.5 g/dL in NMP at 25 ꢀC. The
composition of PES-S-AT copolymer were calculated from the
results of elemental analysis. The weight percentages of
carbon, hydrogen, nitrogen and sulfur in the samples were
measured by a Flash Ea 1112 elemental analysis instrument.
tric constant (e0) were calculated from capacitance using the
4Cd
following equation: e0 ¼
, where d is the thickness and D
pD2E0
is the diameter of the sample, and E0, the permittivity of the
free space, is 8.854 ꢁ 10ꢂ12 F/m.
RESULTS AND DISCUSSION
Synthesis and Characterization of Monomers
The synthetic route of PAT and DFAT is outlined in Scheme
1. According to a well-established synthetic method,30 PAT
was successfully synthesized by oxidative coupling of N-phe-
nyl-p-phenylenediamine using ferric chloride hexahydrate as
an oxidant, followed by reduction using hydrazine hydrate in
1.0 M ammonium hydroxide. DFAT was prepared by the
Spectrascopic Properties
UV-vis spectra were performed on UV-2501 PC Spectrometer
(SHIMADZU) in DMF. Initial solution of PES-S-AT in the
lecoemeraldine oxidation state was quite dilute (around 0.05
mg mLꢂ1).
NOVEL ELECTROACTIVE POLY(ARYLENE ETHER SULFONE), CHAO ET AL.
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JOURNAL OF POLYMER SCIENCE PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
SCHEME 1 Synthesis of parent aniline tetramer (PAT) and 2,6-difluorobenzoyl aniline tetramer (DFAT).
reaction between 2,6-difluorobenzoyl chloride and PAT in
the presence of triethylamine at a yield of 85%. The synthe-
sized PAT and DFAT were fully characterized by MALDI-TOF
adjacent to the sulfone groups (H11) appeared at high fre-
quency area (around 7.86 ppm) because of the strong elec-
tron-drawing effects. Furthermore, the signal of H8 exhibits
triplet at 7.14 ppm in the 1H NMR spectrum of DFAT, but it
appears doublet at 6.66 ppm in the 1H NMR spectrum of
PES-S-AT copolymers, which confirms that the fluorine
groups have been completely reacted to the hydroxyl groups
during the nucleophilic polymercondensation reaction. The
integral area ratio of H11 to H15, obtained from the 1H NMR
spectrum, are given in Table 1. Then the value of x in the
PES-S-AT-x are 19.6, 38.8, 58.0, 78.7, and 100, deduced from
the integral area ratio of H11 to H15. Typical elemental analy-
sis for PES-S-AT-x are shown in Table 1, as are the ratio of
1
spectra, FTIR, and H NMR spectroscopy. Figure 1 illustrates
the 1H NMR spectra of PAT and DFAT in DMSO-d6. The1H
NMR spectra clearly reveal that the primary aromatic amino
groups (NH2) have been completely transformed into acyl-
amino groups (ACOANHA) by the low-field shift of the pro-
ton H1 and H7. The relative intensities and expected splitting
of the aromatic proton signal is also seen, demonstrating the
well-defined structure of PAT and DFAT.
Synthesis and Characterization PES-S-AT Copolymers
The synthetic routes for preparation of poly(arylene ether
sulfone) copolymers with pendant oligoaniline groups are
depicted in Scheme 2. All the polymerizations proceeded
homogeneously by K2CO3-mediated nucleophilic aromatic
polymercondensation using 4,40-isopropylidene diphenol as
bisphenol monomer. Copolymers with different pendants
ratio could be obtained by adjusting the feed of DFAT to
4,40-dichlorodiphenyl sulfone. The reaction temperature was
1
Sulfur to Nitrogen. The data of H NMR and elemental analy-
sis verifies that the PES-S-AT copolymers have been synthe-
sized according to expectation, which indicate that the DFAT
has the similar reaction activity to 4,40-dichlorodiphenyl sul-
fone in K2CO3-mediated nucleophilic aromatic polymercon-
densation reaction. The number average molecular weight
(Mn) and the polydispersity index of the copolymers,
obtained by GPC, are presented in Table 2.
ꢀ
first controlled at 140 C to remove the water by azeotropic
distillation with toluene, and then increased to 163 ꢀC to
accomplish polymerization.
The chemical structures of PES-S-AT copolymers were con-
1
firmed by FTIR, H NMR spectroscopy and GPC. FTIR spectra
of PES-S-AT copolymers (Fig. 2) showed the characteristic
absorption bonds around 3394 cmꢂ1 corresponding to N–H
stretching vibration, around 2930 cmꢂ1 based on C-H
stretching vibration of methyl groups and around 1650 cmꢂ1
due to C¼¼O stretching vibration in aryl carbonyl groups. The
vibration at around 1600 cmꢂ1 and 1504 cmꢂ1 is attributed
to the stretching vibration of C¼C in the benzene rings, and
the peak at 1235 cmꢂ1 can be assigned to the stretching
vibration of C-O-C of the aryl ether linkages. The bands at
1454 cmꢂ1(tC¼¼C), 1294 cmꢂ1(tCAN), 1049 cmꢂ1(dCH), and
748 cmꢂ1(dCH), based on the structure of oligoaniline, were
found to increase as the concentration of oligoaniline in the
polymer increased. And the bands at 1149 cmꢂ1(tO¼S¼O),
1105 cmꢂ1(dCH), and 559 cmꢂ1(dCH), attributed to the vibra-
tion of diphenylsulfone segments, decrease as the concentra-
tion of oligoaniline in the polymer increased. The 1H NMR
spectra of PES-S-AT copolymers are shown in Figure 3. The
signals at d ¼ 10.24, 7.73, 7.67, 7.59 ppm are attributed to
the amino protons and the signals around d ¼ 1.68–1.50
ppm are ascribed to the methyl protons. Aromatic protons
FIGURE 1 1H NMR spectra of PAT and DFAT.
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ARTICLE
SCHEME 2 Synthesis of PAE-S-AT-x
copolymers. (x represents the oligo-
anilines mole percent of the
copolymers).
These copolymers were obtained in almost quantitative
yields, with inherent viscosities in the range of 0.12–0.18
dL/g, as shown in Table 2. It is too low compared with that
of ordinary polymers, because the bulky pendant groups in
chemical structure impede the interchain entanglement to
some extent. The PES-S-AT copolymers exhibited outstanding
solubility in polar solvents such as THF, NMP, DMAc, DMF
and DMSO (Table 3). During the solubility test, an interesting
phenomenon was found: the copolymers with high ratio of
FIGURE 2 FTIR spectra of the PAE-S-AT copolymers. [Color fig-
ure can be viewed in the online issue, which is available at
wileyonlinelibrary.com.]
FIGURE 3 1H NMR spectra of PAE-S-AT copolymers. [Color fig-
ure can be viewed in the online issue, which is available at
wileyonlinelibrary.com.]
NOVEL ELECTROACTIVE POLY(ARYLENE ETHER SULFONE), CHAO ET AL.
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JOURNAL OF POLYMER SCIENCE PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
TABLE 1 The Elemental Analysis and 1H NMR Data of the PAE-S-AT Copolymers
Polymer
C (wt %)
H (wt %)
N (wt %)
S (wt %)
neSxp
ncSal
R
H
H
Xexp
Xcal
20.0
11
15
N
N
PAE-S-AT-20
PAE-S-AT-40
PAE-S-AT-60
PAE-S-AT-80
PAE-S-AT-100
75.08
76.52
77.70
78.72
79.54
5.12
5.25
5.33
5.41
5.51
2.20
4.09
5.64
6.93
8.03
5.24
3.56
2.19
1.02
0.00
1.041
0.380
0.170
0.064
0.000
1.000
0.375
0.166
0.063
0.000
0.536
0.408
0.280
0.142
0.000
19.6
38.8
40.0
60.0
58.0
78.7
80.0
100.0
100.0
nS , molar ratio of sulfur to nitrogen; R
H
H
11 , integral area ratio of H11 to H15 from the 1H NMR spectra; X, the amount of oligoaniline side groups; exp,
N
experimental data; cal, calculated data. 15
pendants (such as PES-S-AT-100, PES-S-AT-80) possess excel-
lent solubility in acetone, while the copolymers with low
ratio of pendants (such as PES-S-AT-20, PES-S-AT-40) possess
good solubility in the solvent of methylene chloride and
chloroform. The exciting solubility of PES-S-AT copolymers in
the common organic solvent makes this an attractive system
for both academic research and industrial applications.
perature, and is liable to decompose first. The results
demonstrate that the PES-S-AT copolymers had good thermal
stability and higher degradation temperature.
Spectroscopic Properties
Take PES-S-AT-100 copolymer as an example: a sample was
dissolved in DMAc solution followed by the addition of trace
amount of (NH4)2S2O8. The solution gradually turned to dark
blue and finally purple upon being oxidized. This process
was monitored by UV-vis spectra with time intervals about 4
mins; the obtained UV-vis spectra are presented in Figure 5.
First, two absorption peaks at 287 nm and 330 nm were
observed, which are associated with pAp* transition transi-
tions in the benzoid rings. When slow oxidation took place,
the absorption peak at 330 nm started to undergo a blue
shift (from 330 nm to 306 nm) while decreasing in intensity,
and the UV–vis spectra showed a new absorption peak at
about 570 nm. This is assigned to exciton-type transition
between the HOMO orbital of the benzoid ring and the
LUMO orbital of the quinoid ring and continually increased
in intensity. When its intensity reached the maximum, the
PAE-S-AT copolymer was in the emeraldine oxidation state
with parent aniline tetramer segment containing one quinoid
rings (Scheme 3). With further oxidization of PES-S-AT co-
polymer, all the absorption peaks decreased and the absorp-
tion peak at 570 nm began to undergo a red shift to
655 nm. Finally the absorption in the range of 400 nm and
Thermal Properties
The thermal properties of PES-S-AT copolymers were eval-
uated by their Tg and Td data (Table 2) measured by DSC
and TGA, respectively. The Tg of the PES-S-AT copolymers
decreased from 166 ꢀC to 150 ꢀC as the concentration of
pendants in the polymer increased, which attribute to the
bulky pendant groups in chemical structure hindering inter-
chain interaction. The thermal stability of the synthesized
PES-S-AT copolymers was studied under identical drying and
heating conditions. The typical TGA curves are shown in
Figure 4. The process of loss weight undergoes only one
step beginning at 300 ꢀC for the decomposition of main
chain. Table 2 gave the 5 and 10% weight loss temperatures
of the obtained copolymers. It indicates that the PES-S-AT
copolymers have good thermal resistance compared with
usual PANI materials.37 Moreover, the copolymers with low
ratio of pendants (such as PES-S-AT-20, PES-S-AT-40) possess
better thermal stability, because the oligoaniline segment is
not as stable as the other aromatic segment under high tem-
TABLE 2 The Basic Properties of the PAE-S-AT Copolymers
ga
Tg
Td5
Td10
(ꢀC)
rf
b
c
d
e
Polymer
(dL/g)
(ꢀC)
(ꢀC)
Mn
Mw/Mn
(S/cm)
PAE-S-AT-20
PAE-S-AT-40
PAE-S-AT-60
PAE-S-AT-80
PAE-S-AT-100
a
0.18
0.15
0.15
0.15
0.12
166
159
156
152
150
438
410
400
404
377
459
436
433
432
417
29,300
10,300
37,400
13,700
9,600
2.57
3.06
2.33
1.86
1.47
5.96 ꢁ 10ꢂ7
1.12 ꢁ 10ꢂ6
4.73 ꢁ 10ꢂ6
8.27 ꢁ 10ꢂ6
2.36 ꢁ 10ꢂ5
Inherent viscosity was determined on an Ubbelohde viscometer in thermostatic container with the poly-
mer concentration of 0.5 g/dL in NMP at 25 ꢀC.
b
Glass transition temperature by DSC.
c
5% Weight-loss temperatures were detected at a heating rate of 10 ꢀC/min, in nitrogen.
d
10% Weight-losses temperatures were detected at a heating rate of 10 ꢀC/min in nitrogen.
e
The number-average molecular weight and molecular weight distribution were measured with a gel per-
meation chromatography with DMF as an eluent at a flow rate of 1 mL/min.
f
The electric conductivity of the copolymers doped with HCl in emeraldine oxidation state was measured
by a four-probe method.
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ARTICLE
TABLE 3 The Solubility of the PAE-S-AT Copolymers in the Different Solvents
Acetonitrile
CH2Cl2
CHCl3
Acetone
THF
DMF
DMAc
PAE-S-AT-20
PAE-S-AT-40
PAE-S-AT-60
PAE-S-AT-80
PAE-S-AT-100
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
þ
þꢂ
ꢂ
ꢂ
ꢂ
þ
ꢂ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
ꢂ
þꢂ
ꢂ
ꢂ
þꢂ
þ
þ
The solubility of the PAE-S-AT-X was determined with 5% solid content at 25 ꢀC; þ, soluble; þꢂ, partially
soluble; ꢂ, insoluble.
800 nm disappeared, which showed that the PES-S-AT copoly-
mer has reached in the pernigraniline oxidation state. The
chemical oxidation process of PES-S-AT-100 copolymer is sim-
ilar to that of polymer bearing oligoaniline groups. However,
the absorption peak at 570 nm of PES-S-AT copolymers
undergoes a red shift when it transform from emeraldine oxi-
dation state to pernigraniline oxidation state, which is con-
trast to that of polyaniline, oligoaniline and oligoaniline-con-
taining polymers.30,38,39 The phenomenon indicates that the
bandgap between the HOMO and LUMO of the polymers
should decrease when it transform from emeraldine oxidation
state to pernigraniline oxidation state, which would be
caused by the unique chemical structure. Further studies in
the regard are currently underway.
working electrode, prepared using the identical volume with
the same concentration, were used to evaluate the electroac-
tivity. In the cyclic voltammetry of the PES-S-AT copolymers,
two pairs of redox peaks appear with oxidation peaks at 330
and 530 mV in that of PES-S-AT-100 and PES-S-AT-80, which
are shift slightly compared with DFAT due to the difference
of molecular structure. But in the cyclic voltammetry of PES-
S-AT-(60, 40, 20), only one pair of redox peaks appear with
oxidation peaks around 530 mV, owing to the weak electro-
activity caused by the lower concentration of oligoaniline. In
addition, the maximum current value of each copolymer was
found to increase as the pendant concentration in the poly-
mer increased.
Electrical and Dielectric Properties
Electrochemical Activity
Electrical conductivity of the doped copolymers in emeral-
dine oxidative state at room temperature are between 2.36
ꢁ 10ꢂ5 and 5.96 ꢁ 10ꢂ7 S cmꢂ1and increase as the concen-
tration of oligoaniline in the polymer increased. However, the
conductivity of the obtained copolymers are much lower
than that for the HCl-doped polyaniline (1.0 S cmꢂ1) and
parent aniline tetramer (3.0 ꢁ 10ꢂ3 S cmꢂ1). This is attrib-
uted to the rigidity of the backbone precluding aggregation
of the aniline tetramers into a continuous conducting region.
Figure 6 shows the cyclic voltammetry of the synthesized
PES-S-AT-(100, 80, 60, 40, 20) copolymers and DFAT
obtained in 1.0 M H2SO4 aqueous solution using Ag/Agþ as
the reference electrode with a scan rate of 100 mV sꢂ1. A
THF solution of PES-S-AT copolymers and DFAT was cast on
the g-c working electrode and was evaporated to form a thin
solid film. Under these conditions, the cyclic voltammetry of
DFAT shows two pairs of redox peaks with oxidation peaks
at 320, and 520 mV, respectively. It indicated that DFAT pos-
sess three oxidation states, that is, Leucoemeraldine, Emeral-
dine, and Pernigraniline (Scheme 3), which is similar to poly-
aniline.26 The films of the PES-S-AT copolymers on the g-c
Recently, we have prepared a kind of high dielectric constant
material using polymers with oligoaniline in the main
chain,40,41 which would solves phase separation, migration,
and extraction problems existing in traditional high dielectric
constant PANI/polymer blends.42–44 Although dielectric
properties of polymers with oligoaniline in the main chain
were well documented, the dielectric properties of polymers
with oligoaniline as the pendants have been rarely reported.
Measurements of the dielectric response over the range of
0.1 kHz to 1 MHz were carried out with pressure com-
pressed pellets of polymers; then gold electrodes were sput-
tered on the two surfaces of the pellets to form electrodes.
Figure 7 demonstrates the variation of dielectric constant
with frequency for pristine PES-S-AT copolymers, and doped
PES-S-AT copolymers in the emeraldine oxidative state (HCl-
treated) at room temperature. In the insert graph of Figure
7, it reveals that pristine PES-S-AT copolymers gave e0 values
around 3.3 detected at a frequency of 0.1 kHz, and then
decreased to 2.5 as the frequency was increased to 1 MHz,
respectively. The diagram illustrates that pristine PES-S-AT
copolymers possess dielectric constant corresponding to that
FIGURE 4 TGA thermograms of the PAE-S-AT copolymers in
N2.
NOVEL ELECTROACTIVE POLY(ARYLENE ETHER SULFONE), CHAO ET AL.
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JOURNAL OF POLYMER SCIENCE PART A: POLYMER CHEMISTRY DOI 10.1002/POLA
FIGURE 5 UV–vis spectra monitoring the chemical oxidation of the PAE-S-AT-100 with time intervals about 4 mins. (a): from the
leucoemeraldine oxidation state to the emeraldine oxidation state; (b): from the emeraldine oxidation state to the pernigrailine oxi-
dation state. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]
of traditional polymers. After doping with HCl, the PES-S-AT
copolymers in the emeraldine oxidative state have enhanced
dielectric constants at frequency between 0.1 kHz and 1
MHz. Such as, PES-S-AT-100 copolymer possesses e0 values of
78.05, 11.96, and 5.49 at frequencies of 0.1 kHz, 10 kHz,
and 1 MHz, respectively. And it displays the dielectric con-
stant of the copolymers decreased significantly with the
increase of frequency. The phenomena and mechanism of
this dielectric behavior is similar to that of electroactive
polymers as previously reported.40,41 Moreover, the dielectric
constants of PES-S-AT copolymers were found to decrease as
the pendant concentration in the polymer decreased.
would likewise occur at the oligoaniline linkages of poly-
mers; hence, the PES-S-AT copolymers were subsequently
analyzed for their abilities to exhibit electrochromic
characteristics.
Spectroelectrochemical measurements were performed on
PES-S-AT-100 copolymer by increasing the potential from 0.0
to 1.0 V and in conjunction with the acquisition of UV-vis
spectral data. The typical electrochromic photographs are
shown in Figure 8. The material underwent a drastic color
change from grey (at 0.0 V), to green (at 0.4 V), to blue (at
0.6 V) and to pearl blue (at 1.0 V) during the oxidation pro-
cess. The transmittance spectra in Figure 9 shows that the
ITO electrode decorated with PES-S-AT-100 copolymer gives
a good electrochromic performance. The maximum transmit-
tance change (DT) at 700 nm is 42.6% [90.7% (at 0.0 V) $
48.1% (at 0.6 V)]. Moreover, the copolymer thin films exhibit
stronger adherence to the ITO glass substrates and better
repetition of redox behaviors than polyaniline. Although
similar results were obtained for other copolymers (PES-S-
Electrochromic Studies
It is well established that the ability of a polymer to exhibit
a rapid color change in different redox states is important
for the electrochromic applications. Among various electro-
chromic polymers, polyaniline is particularly attractive due
to its unique optical properties and high environmental sta-
bility.45,46 In addition, the transformation of oxidation states
is highly repetitive under low driving potential, and its color
contrast is high in the visible light region. It was envisioned
that the oxidation states transformation and color change
FIGURE 6 Cyclic voltammograms of the PAE-S-AT copolymers
with a scan rate of 100 mV sꢂ1 (insert: cyclic voltammetry of
DFAT with a scan rate of 100 mV sꢂ1). [Color figure can be viewed
in the online issue, which is available at wileyonlinelibrary.com.]
SCHEME 3 Molecular structures of DFAT at various oxidation
states.
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ARTICLE
FIGURE 9 Optical transmittance of PES-S-AT-100/ITO electro-
des in 0.5 M H2SO4 at different potentials (vs. Ag/AgCl) for 400
s. [Color figure can be viewed in the online issue, which is
available at wileyonlinelibrary.com.]
FIGURE 7 Frequency dependence of dielectric constant of PAE-
S-AT copolymers in pristine form and emeraldine oxidation
state with HCl-doped form, respectively. [Color figure can be
viewed in the online issue, which is available at wileyonlinelibrary.
com.]
the good solubility, processability, electroactivity, thermal sta-
bility, dielectric and electrochromic properties, the PES-S-AT
copolymers have great potential for foreseen applications,
such as antistatic coatings, wave-absorbing materials, elec-
trochromic devices, and thin films in electronic applications,
etc.
AT-20, -40, -60, -80), only slight color change and maximum
transmittance change (DT) (700 nm) were observed, which
is in accord with the decreased percentage of oligoanilines.
This work is supported in part by the National 863 Project (No.
2007AA03Z324), National 973 Project (No. 2007CD936203),
and NSFC grants (No. 20674027 and 50873045).
CONCLUSIONS
We have synthesized a series of novel copolymers of poly
(arylene ether sulfone) with oligoaniline groups as pendants
by nucleophilic polymercondensation reaction. The synthe-
sized copolymers PES-S-AT exhibit a broad and strong
absorption in visible region, good solubility in the organic
solvents and excellent thermal stability. Furthermore, the
electroactivity, electric and dielectric properties of the PES-S-
AT copolymers were investigated in detail. Preliminary stud-
ies on electrochromic properties of PES-S-AT copolymers
afforded the electrochromic electrode with an obvious color
change and maximum transmittance change of 42.6%. Given
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