Design, synthesis and characterization of novel nitrogen- and sulfur-containing polymers with well-defined conjugated length

Article abstract of DOI:10.1039/b105628j

A series of novel nitrogen- and sulfur-containing conjugated polymers with well-defined conjugation length have been synthesized via an acid-induced self-polycondensation of functional monomers with methylsulfinyl groups. Synthesized polymers exhibit good

Full text of DOI:10.1039/b105628j

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Design, synthesis and characterization of novel nitrogen- and
sulfur-containing polymers with well-defined conjugated length
Kaizheng Zhu,*{ Lixiang Wang,* Xiabin Jing and Fosong Wang
State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied
Chemistry, Chinese Academy of Sciences, Changchun 130022, PR China.
E-mail: kzzhu@163.com or lixiang@ciac.jl.cn
Received 27th June 2001, Accepted 5th November 2001
First published as an Advance Article on the web 5th December 2001
A series of novel nitrogen- and sulfur-containing conjugated polymers with well-defined conjugation length
have been synthesized via an acid-induced self-polycondensation of functional monomers with methylsulfinyl
groups. Synthesized polymers exhibit good solubility in common solvents, such as CHCl3, THF, DMF, DMSO,
and NMP. With increased numbers of aminophenyl groups, these polymers have shown similar electrical
properties to polyaniline (PAn), and these are demonstrated by UV–vis spectroscopy and cyclic voltammetry
(CV) measurements on the polymers. The conductivity of preliminarily protonic-doped poly[phenylene sulfide-
alt-tetrakis(aniline)] (PPSTEA) is up to 1021 S cm21
.
Nitrogen- and/or sulfur-containing polymers are an important
group of electrically conductive polymers, such as polyaniline
(PAn), polypyrrole (PPy), polythiophene (PTh), and poly
(phenylene sulfide) (PPS).1–6 Among them PAn is especially
attractive, owning to its unique electrooptical properties and
market potential, good environmental stability, facility of
synthesis (chemical or electrochemical oxidation of aniline),
and cheapness of the monomer, etc.7 Thus, PAn offers the
promise of a relatively low-cost conducting (metallic) polymer
that is both stable and processable. To the best of our know-
ledge, although much effort has been applied to investigating
its synthesis, structure, properties, and application, PAn,
synthesized by chemical or electrochemical polymerization,
usually exhibits an ill-defined structure. Nevertheless, there still
exist some unsolved problems concerning its structure and
properties due to its complexity in molecular structure and
poor solubility in common organic solvents, which limits in-
depth investigations of the structure–property relationship and
of the conducting mechanism to some extent.
It should be mentioned that a challenging synthetic research
goal is to design new polyaniline derivatives with fixed
conjugation length and well-defined structures, as the ideal
polymer for identifying the conducting mechanism of common
PAn.
Recently, one of the authors proposed the simple combi-
nation of PPS and PAn to give poly(phenylene sulfide–
phenyleneamine) (PPSA),{ which is believed to be the first
hybrid structure of PPS–PAn and has promising electronic,
optical, and mechanical properties.8 This synthetic concept
was further extended to the design and synthesis of poly
(phenylene sulfide–phenyleneamine–phenyleneamine) (PPSAA)
by Mu¨llen.9 However, two alternating conjugated polymers
(PPSA and PPSAA) could not be doped to be conductive by
protonic acids, due to the too short iminophenylene segment in
their repeat unit.
synthetic concept towards poly(phenylene sulfide–trianiline)
(PPSTRA) and poly(phenylene sulfide–tetraaniline) (PPSTEA),
which containing one phenylene sulfide (PS) and three or four
iminophenylene segments in the repeat units, for determining
the shortest of conduction conjugation length of common PAn
to be conductive (Scheme 1). It is found that PPSTEA exhibits
remarkably close electronic properties to polyaniline, as
expected. The conductivity of a preliminary protonic-doping
test of PPSTEA is up to 1021 S cm21. Herein we will report
the details of synthesis and characterization for these new
polyaniline-derived polymers.
Results and discussion
1. Polymer synthesis
The synthesis of these above polymers was based on the
Tsuchida route toward sulfur-linked polymer via an acid-
induced self-polycondensation of functional monomers with a
methylsulfinyl group and an aromatic group, which is
successful for the synthesis of PPSA and PPSAA.10
The synthesis of trianiline-containing monomer 15 was
started from the commercially available 4-bromothioanisole (8)
as shown in Scheme 2. 4-Bromo(methylsulfinyl)benzene (9) was
synthesized quantitatively by oxidizing 8 with Br2 in the
presence of wet, powdered silica gels.11 A modified Ullmann
reaction (K2CO3, CuI), starting from condensation of 9 and
N-acetylaniline (10), followed by the base hydrolysis of the
acetyl groups yielded the PPSA monomer 11 (4-methylsul-
finylphenyl(phenyl)amine). The iodo aromatic derivative 12
was prepared by iodination reaction of 11 with benzyltri-
methylammonium dichloroiodate (BTMA.ICl2). Compound
14 was obtained by the acetylation of 4-aminophenyl-
(phenyl)amine (13).12 Condensation of 12 and 14 by a similar
Ullmann reaction, base hydrolysis of the acetyl and reduction
of the TRA segment by phenylhydrazine resulted in the fully
reduced monomer 15.
In this paper our efforts have focused on the extension of this
The synthesis of tetraaniline-containing monomer 18 is
outlined in Scheme 3. The uncapped tetraaniline (TEA) 16 was
prepared in 90% yield from 13 by oxidative coupling with
ammonium persulfate (APS) in an acetone–HCl solution and
reduction with phenylhydrazine.13 Amine protected compound
17 was coupled with 9 and deprotection of the amino groups
{Current address: Institute of Materials Science, Zhongshan University,
Guangzhou 510275, PR China.
{The IUPAC names for these polymers are as follows: PPSA ~
poly(phenylene sulfide-alt-aniline), PPSAA ~ poly[phenylene sulfide-
alt-bis(aniline)], PPSTRA ~ poly[phenylene sulfide-alt-tris(aniline)]
and PPSTEA ~ poly[phenylene sulfide-alt-tetrakis(aniline)].
DOI: 10.1039/b105628j
J. Mater. Chem., 2002, 12, 181–187
This journal is # The Royal Society of Chemistry 2002
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Scheme 1 Typical novel nitrogen- and sulfur-containing polymers.
Scheme 3 Synthesis of PPSTEA monomer 18.
precipitated in methanol and further treated with phenylhy-
drazine to ensure the fully reduced state, the target polymers
were obtained as colorless solids in 90% yield. By a similar
polymerization procedure, PPDSA (7) was also prepared from
the polymerization of monomer 19.
Scheme 2 Synthesis of PPSTRA monomer 15.
with basic aqueous ethanol and reduction of the TEA segment
with phenylhydrazine gave the final fully reduced monomer 18
in good yield.
The diphenyl sulfide-containing monomer 19 was synthe-
sized via a similar Ullmann reaction by the condensation of 12
and benzenethiol according to Scheme 4.
The above monomers were self-condensed, respectively,
according to the modified Tsuchida route (Scheme 5).8 They
were added to methanesulfonic acid and stirred for 24 h at
room temperature under argon. The resulting viscous mixtures
were precipitated into an ice–water mixture and the resulting
green solids were washed with water. The polymer precursors
were dissolved in pyridine, and their pyridine solutions were
refluxed for 10 h to afford complete demethylation. After being
Scheme 4 Synthesis of PPDSA monomer 19.
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Fig. 2 13C NMR spectrum of tetraaniline-containing monomer 18.
Fig. 3 1H NMR spectra of PPSTRA (4) (a) and PPSTEA (5) (b).
amino protons of 4 and 5, respectively. Furthermore, the other
expected splitting of the aromatic proton signal is seen,
demonstrating the well-defined structure of the two polymers.
In Fig. 4 and Fig. 5 are shown the 13C NMR spectra of 4 and 5,
where only eight and ten aromatic carbons are observed, as
expected. A single strong IR signal at about 813 cm21 in the
region of aromatic C–H out-of-plane banding supports the 1,
4-linkage of the phenylene units in PPSTRA and PPSTEA. No
absorption bands attributed to the methyl, sulfoxide and
sulfone group are detected (see Fig. 6).
For the sake of comparison, we have also synthesized the
other two nitrogen- and sulfur-containing polymer PPSA (2)
and PPSAA (3), whose repeat units are combinations of PS and
aniline or bis(aniline). In contrast to PPS and PAn, PPSTRA
(4), PPSTEA (5), and PPDSA (7) were extremely soluble in
Scheme 5 Acid-induced synthesis of PPSTRA (4), PPSTEA (5), and
PPDSA (7).
2 Polymer characterization
NMR spectra and elemental analyses verified the proposed
chemical structure of these synthesized monomers and poly-
1
mers. The H NMR spectrum of monomer 18 is given as an
example (Fig. 1). Four signals at d ~ 7.77, 7.84, 7.89, and
8.35 ppm are assigned to the four amino protons of 18; one
signal at 2.77 ppm is ascribed to the methyl proton linked with
the sulfinyl group. The relative intensities of the signals around
d ~ 6.78–7.58 ppm allow estimation of the other expected
splitting of the aromatic proton signals. In the 13C NMR
spectrum of 18 (Fig. 2), one signal at d ~ 43.1 ppm and twenty
signals at around d ~ 113.7–148.6 ppm are ascribed to the
methyl carbon and the other aromatic carbons, respectively.
1
The H NMR spectra of PPSTRA (4) and PPSTEA(5) are
shown in Fig. 3. Two signals at d ~ 7.87, 8.08 ppm (a) and
d ~ 7.76, 8.04 ppm (b) are attributed to the three and four
Fig. 4 13C NMR spectrum of PPSTRA (4).
Fig. 1 1H NMR spectrum of tetraaniline-containing monomer 18.
Fig. 5 13C NMR spectrum of PPSTEA (5).
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Fig. 7 UV–vis spectra of the fully reduced state of synthesized
polymers (20 uC, film coated onto Vycor): 2 (L1), 3 (L2), 4 (L3), 5
(L4) and 7 (L5).
Fig. 6 FTIR spectra of synthesized polymers: (a) 5, (b) 4, (c) 3, (d) 2
and (e) 7.
THF, DMF, DMSO and NMP, analogous to PPSA and
PPSAA. Molecular weights, reported in Table 1, were deter-
mined by gel-permeation chromatography (GPC) with uniform
polystyrene standards. From Table 1 we can see that PPSA has
the highest molecular weight of all the polymers. The greater
the number of aminophenyl groups, the lower the molecular
weight of the polymer. We explain this by the more sensitive
oxidative character of these monomers, but further investiga-
tions are under way.
Thermogravimetric analyses (TGA) of different nitrogen-
and sulfur-containing polymers show that polymers 4, 5 and
7 are stable up to 370 uC, 395 uC, and 320 uC in nitrogen
respectively. Differential scanning calorimetry (DSC) suggests
that 4, 5, and 7 possess glass transitions (Tg) of 114 uC, 112 uC,
and 90 uC, respectively, and no melting transition can be
detected. X-Ray diffraction patterns are all composed of a
diffuse peak at 2h ~ 18u, which along with the results of DSC,
indicates the amorphous nature of the synthesized polymers.
Fig. 8 UV–vis spectra of PPSTEA (5) at different oxidation states (20
uC, film coated onto Vycor): L1, in fully reduced state; L2, in partially
oxidized state; L3, in fully oxidized state; L4, doped with HCl.
3 Electronic properties of polymers
By UV–vis spectroscopic analysis, there were strong absorp-
tions at about 320 nm, assignable to the p–p* transition of
the aniline rings in neutral forms of 4, 5, and 7 (see Fig. 7).
When the fully reduced PPSTEA film was oxidized with iodine,
its color changed gradually from colorless to light green to
purple. Different colors were expected to correspond to
different states of oxidation, i.e., fully reduced, partially
oxidized and fully oxidized states. Correspondingly, the
UV–vis spectra of PPSTEA exhibited the following changes:
the peak at 320 nm was weakened and shifted slightly to shorter
wavelengths, there appeared a broad absorption at 580 nm
for partially oxidized PPSTEA (L2 in Fig. 8) and it moved
to 530 nm for fully oxidized PPSTEA (L3 in Fig. 8). It was
interesting that when partially oxidized PPSTEA film was
doped with hydrochloric acid, its color changed from purple to
green. As shown in Fig. 8 (L4), there appears a new peak at
about 420 nm and a very broad band centered at 800 nm. These
behaviors are consistent with that of common polymer
synthesized by chemical or electrochemical polymerization of
aniline, indicating that three oxidative states of PPSTEA could
be converted into each other and that PPSTEA could be doped
to a conductive state by protonic acids.14,15 (Scheme 6)
Cyclic voltammetry (CV) measurements were carried out in
acetonitrile solution at room temperature with 0.1 M tetra-
n-butylammonium perchlorate as supporting electrolyte. A
Table 1 Molecular weights of the synthesised polymers
d
Nn
Polymer
Mna,b/Da
Mwa,c/Da
Mw/Mn
2
3
4
5
7
56600
19000
9000
10600
6100
97800
42800
19700
20900
8300
1.73
2.25
2.80
1.97
1.36
285
65
23
22
20
aDetermined by gel-permeation chromatography (GPC) with uni-
form polystyrene standards and THF as solvent. bNumber-averaged
molecular weight. cWeight-averaged molecular weight. dNumber-
averaged degree of polymerization.
Scheme 6 Different oxidation states of PPSTEA (5).
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highly conducting doped forms of polyaniline could be reached
by two completely different processes—protonic acid doping
and oxidative doping.16 The emeraldine base state is proto-
nically acid doped to the metallic regime by a process involving
no change in the number of electrons on the polymer chain; the
leucoemeraldine state, on the other hand, is oxidatively doped,
either chemically or electrochemically, by conventional redox
doping of the type found in other conducting polymers.17 As
we can obtain the conductive form of PPSTEA via a protonic
acid doping without changing the number of electrons of the
backbone in the sample, it is deduced that at least four
iminophenylene units are required for completing the insula-
tor–conductor transition of common polyaniline by doping
with protonic acid.
The sulfur atom has been regarding as inhibiting the
extensive conjugation along the polymer chain for PPSA
and PPSAA, and the charge transport has to proceed via a
‘hopping’ mechanism along several chains.8b,9 However, this is
not true for PPSTEA. This is because PPSTEA can complete
the protonic acid doping without changing the number of
polymer backbone, and the conductivity of a protonic acid or
iodine oxidative doping test is 2 orders higher than that of
tetraaniline. So we can envisage that the sulfur atom in the
polymer chain is not an inhibitor for furthering the conjugation
interaction. On the contrary, it may participate in the charge
transport to some extent. The actual reason for the lower
conductivity of PPSA, PPSAA, and PPSTRA should not be
ascribed to the interruption of the conjugation by sulfur, but to
the too short length of the phenylamine segments in the
repeated units. Further experiments on the confirming the
doping site (the actual site of quinone diimine in the repeat
unit), the charge transport, and the optimization of the doping
process in PPSTEA is in progress.
Fig. 9 Cyclic voltammogram of PPSTRA (L1) and PPSTEA film (L2):
20 uC, 0.1 M Bu4NClO4 in acetonitrile, voltage vs. Ag/AgCl, scan rates
50 mV s21
.
Conclusion
In conclusion, we have successfully synthesized a series of
novel nitrogen- and sulfur-containing conjugated polymers
poly(phenylene sulfide–trianiline) (PPSTRA) and poly(pheny-
lene sulfide–tetraaniline) (PPSTEA) whose repeat units are
the combination of one phenylene sulfide and tris(aniline) or
tetrakis(aniline) segments by using acid-induced polycon-
densation of 4-methylsulfinylphenyl capped trianiline and
4-methylsulfinylphenyl-capped tetraaniline. With the increase
in the number of aminophenyl groups, these polymers have
shown similar electrical properties to polyaniline (PAn). The
new conducting polymer PPSTEA, which represents the
first soluble conducting polyaniline analogue with a well-
defined structure, has high molecular weight, good solubility in
common organic solvents and good film-forming properties.
From the results on its protonic-doping reaction and con-
ductivity study, it is deduced that at least four iminophenylene
units (one benzenoid diamine and one quinone diimine) are
required for completing the insulator–conductor transition
of common polyaniline by doing with protonic acid. This
synthetic strategy appears to be general for developing novel
well-defined polyaniline analogues containing much longer
fixed conjugation lengths. Further studies in this regard are
currently under way in our laboratory.
Fig. 10 Cyclic voltammogram of PPSTEA–film: 20 uC, 1 M HCl,
voltage vs. SCE, scan rates 50 mV s21
three-electrode system was used; polymer film coated with Pt
as working electrode (id 0.8 mm); a Pt wire as a counter
electrode and Ag/AgCl as reference electrode. The CV curves
of PPSTEA and PPSTRA (Fig. 9) showed two main redox
peaks at 0.46 and 0.92 V, 0.59 and 0.84 V, respectively. After
over 50 cyclic scans, the redox peaks remained unchanged,
implying electrochemical reversibility and stability. Moreover,
the CV of PPSTEA film obtained by sweeping the potential
between 20.2 and 1.0 V in a blank (1 M HCl) medium is shown
in Fig. 10. It displayed two main redox peaks at 0.45 and 0.78 V
vs. SCE reference electrode.
Preliminary doping tests were carried out on free-standing
films or compressed powder pellets. The free-standing films
were cast from 0.5–1% w/w solutions of synthesized polymers
in chloroform. The conductivity was determined by the four-
probe technique. All these undoped synthesized polymers
are insulating with conductivity lower than 1029 S cm21
.
The film of the fully reduced PPSTEA doped with iodine
had a conductivity of 1022 S cm21. When the partially oxi-
dized PPSTEA was doped with hydrochloric acid (HCl), its
conductivity is estimated to be 1021 S cm21. In the same way,
Experimental
doped tetraaniline (16) had a conductivity of 1023 S cm21
.
General
However, the effects on the electrical conductivity of protonic
doping of other polymers such as PPSAA and PPSTRA have
turned out to be disappointing. It has not been possible to
obtain any conducting films through this type of doping
method. Furthermore, the same results were obtained from the
oxidatively doped films of these leucoemeraldine-like samples,
by treating them with iodine or bromine. It is well known that
Commercial reagents were used without further purification
unless specially noted. Solvents were purified, dried, and
degassed according to standard procedures. All synthesis was
1
carried out under argon. H NMR and 13C NMR data were
obtained on Varian Unity Inova 400 MHz and Bruker AC-F
80 MHz spectrometers. The chemical shifts were calibrated
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from tetramethylsilane (TMS). FT-IR spectra were recorded
on a Bio-Rad FTS-135 (USA) using KBr pellets. UV–Vis
spectra were recorded using a Varian Cray 50 type spectro-
meter. Gel permeation chromatograms (GPC) were obtained
on a Waters 510, polystyrene as standard and THF as eluent at
a 1.0 mL min21 flow rate. Cyclic voltammetry (CV) measure-
ments were done in a three electrode system using a platinum
microelectrode as working electrode, Pt wire as counter
electrode and Ag/AgCl or saturated calomel electrode (SCE)
as reference, and potentiostat configuration from EG&G 283
Princeton Applied Research. C, H, N and S elemental analysis
were recorded on Bio-Rad Co’s elemental analytical instru-
ment. Differential scanning calorimetric (DSC) and thermal
gravimetric analysis (TGA) were recorded on Perkin-Elmer
DSC-7 and Perkin-Elmer TGA-7, temperature increase rate: 10
uC min21 under N2 or air.
glacial acetic acid (10 mL) was added dropwise to a solution
of fully reduced uncapped tetraaniline (16) (5.8 g, 16 mmol)
in glacial acetic acid (70 mL) under argon. After the addition
was complete, the mixture was heated to 70 uC and stirred for
an additional 6 h. The glacial acetic acid was removed by
distillation under reduced pressure. By column chromato-
graphy (SiO2, acetone–EtOAc ~ 1 : 4 as eluent, Rf ~ 0.35) 17
was obtained as a colorless solid.
N,N’,N@,N--Tetraacetyl-uncapped tetraaniline (17). Yield
6.1 g (70%); mp 155 uC. 1H NMR (400 MHz, CDCl3)
d(ppm) 2.05(s, 12H, H3CCO), 7.20–7.26(m, 17H, aromatic
H). Anal. Calcd for C32H30N4O4: C, 71.91; H, 5.62; N, 10.45.
Found: C, 71.79; H, 5.78; N, 10.37%.
N-Phenyl-N,N’-(1,4-phenylene)diacetamide (14). Yield 4.3 g
(75%); mp 135 uC. 1H NMR (80 MHz, CDCl3) d(ppm)
2.00(s, 6H, COCH3), 7.20–7.26(m, 9H, aromatic H). Anal.
Calcd for C16H16N2O2: C, 71.64; H, 5.97; N, 10.45. Found: C,
71.59; H, 6.05; N, 10.37%.
Synthesis
4-Bromo(methylsulfinyl)benzene (9). Dry silica gel (60 g) was
placed in a 250 mL round bottomed flask containing a
magnetic stirring bar and a loosely fitted rubber septum. Water
(30 g) was added to the vigorously stirred silica gel. After
complete addition of the water, stirring continued until a free
flowing powder was obtained. CH2Cl2 (100 mL) was added to
the flask. A solution of 4-bromothioanisole (50 mmol, 10.1 g)
in CH2Cl2 was added to the stirred heterogeneous mixture. A
solution of Br2 (2.70 mL, 52 mmol) in CH2Cl2 (5 mL) was
added dropwise from a syringe to the mixture. The color of the
Br2 disappeared instantly. The mixture was stirred at RT
for 10 min. During this period complete disappearance of
4-bromothioanisole was confirmed by TLC (SiO2, EtOAc–
hexane ~ 4 : 1, Rf ~ 0.45). The mixture was then filtered
through a sintered glass funnel, the solid residue was washed
with CH2Cl2 (100 mL) and the washings were added to the
filtrate. Removal of the solvent from the CH2Cl2 solution
under vacuum gave pure sulfoxide (9) 10.9 g (99% yield) as a
colorless solid (mp 86 uC). 1H NMR (400 MHz, CDCl3)
d(ppm) 2.73(s, 3H, SOCH3), 7.52(d, 2H, aromatic H), 7.64(d,
2H, aromatic H). Anal. Calcd for C7H7SOBr: C, 38.37; H, 3.20;
S, 14.62. Found: C, 38.21; H, 3.27; S, 14.56%.
General procedure for the coupling reaction of amides and
4-bromo(methylsulfinyl)benzene (modified Goldberg reaction)
The synthesis of 4-(methylsulfinyl)phenyl capped tetraaniline
18 was used as an example. Monomer 18 was prepared in the
following procedure: a 50 mL round bottomed flask was
charged with a Teflon-covered magnetic bar and a thoroughly
ground mixture of 17 (5.0 g, 9.3 mmol), 4-bromo(methylsul-
finyl)benzene (9) (2.1 g, 9.3 mmol), K2CO3 (1.6 g) and CuI
(0.6 g), 18-crown-6 (0.2 g). The reaction was allowed to proceed
at 180 uC under argon for 24 h. The resulting highly viscous
mixture was taken up in CH2Cl2 and continuously washed with
1 M HCl, NH4OH and brine then dried with anhydrous
Na2SO4. The combined solvent was removed by distillation
under reduced pressure and the residue was chromatographed
over silica (EtOAc–MeOH ~ 4 : 1 as eluent, Rf ~ 0.4). After
the combined solvent was distilled under reduced pressure, the
residue was dissolved in ethanol (100 mL) containing KOH
(4.5 g) and heated to reflux for 6 h. The purple solution was
cooled and poured into 500 mL of water. The precipitate was
filtered off over a G4 sintered glass funnel and reduced with
phenylhydrazine and recrystallized from toluene. 18 was
obtained as a light blue crystalline solid.
Preparation of uncapped tetraaniline (16). The uncapped
tetraaniline (TEA) was prepared from 4-aminophenyl(phenyl)-
amine (13) by means of a modified MacDiarmid method, i.e.,
oxidative coupling by ammonium persulfate (APS) in an
acetone–HCl solution. 4-Aminophenyl(phenyl)amine (5.5 g,
30 mmol) was dissolved in a mixture of acetone (250 mL) and
aqueous HCl (200 mL, 2.0 M). The solution was cooled in an
ice–salt bath. (NH4)2S2O8 (APS) (5.5 g, 24 mmol) dissolved in
50 mL H2O–acetone (1 : 1 ~ v/v) mixture solution was added
dropwise into the solution. After about 15 min, the color of the
solution changed to blue. The reaction solution was stirred
vigorously for an additional 4–5 h. The solid product was
collected by filtration through a G4 sintered glass funnel under
a reduced pressure, and was washed with 1.0 M HCl and
acetone. The product was treated with 1.0 M aqueous NH3,
and filtered. The remaining solid was washed with distilled
water until the filtrate became neutral. Upon drying at 40 uC
overnight under vacuum, a brown powder was obtained. It was
reduced by phenylhydrazine in ethanol solution. 9.8 g (90%
yield) light blue powder (fully reduced state 16) was obtained.
m/z (MALDI-TOF MS): 367 (Mz). Anal. Calcd for C24H18N4:
C, 79.56; H, 4.97; N, 15.47. Found: C, 79.44; H, 5.07 N,
15.45%.
4-(Methylsulfinyl)phenyl-capped tetraaniline (18). Yield 2.3 g
(50%); mp 197 uC. 1H NMR (400 MHz, DMSO-d6) d(ppm)
2.77(s, 3H, SOCH3), 6.79–7.57(m, 21H, aromatic H), 7.77(s,
1H, NH), 7.84(s, 1H, NH), 7.89(s, 1H, NH), 8.35(s, 1H, NH);
13C NMR (400 MHz, DMSO-d6) d(ppm) 43.17, 113.73, 114.67,
115.30, 116.46, 117.98, 118.87, 119.43, 120.74, 122.65, 125.66,
129.14, 129.45, 132.70, 134.82, 136.26, 137.14, 138.55, 140.45,
145.57, 148.70. Anal. Calcd for C31H28N4SO: C, 73.81; H, 5.56;
N, 11.11; S, 6.35. Found: C, 73.66; H, 5.66; N, 11.08; S, 6.32%.
m/z (MALDI-TOF MS): 505 (Mz).
4-Methylsulfinylphenyl(phenyl)amine (11). Yield 3.43 g (75%);
1
mp 135 uC. H NMR (400 MHz, CDCl3) d(ppm) 2.71(s, 3H,
SOCH3), 6. 80(s, 1H, NH), 7.05–7.07(t, 1H), 7.10–7.12(d, 2H),
7.14–7.16(d, 2H), 7.31–7.35(t, 2H), 7.51–7.53(d, 2H); 13C NMR
(400 MHz, DMSO-d6) d(ppm) 43.28, 115.91, 118.94, 121.72,
125.94, 129.85, 135.57, 142.84, 147.23. Anal. Calcd for
C13H13NSO: C, 67.50; H, 5.66; N, 6.06; S, 13.86. Found: C,
67.59; H, 5.70; N, 6.00; S, 13.93%.
Preparation of (4-iodophenyl)(4-methylsulfinylphenyl)amine
(12). To a solution of 4-methylsulfinylphenyl(phenyl)amine
(2.3 g, 10 mmol) in dichloromethane–methanol (50 mL–20 mL),
General procedure for the acetylation of uncapped oligoaniline
The synthesis of 17 was used as an example for the acetylation
of uncapped oligoaniline. Acetic anhydride (7.3 g, 70 mmol) in
benzyltrimethylammonium
(3.8 g, 10.5 mmol) and calcium carbonate (1.1 g) were added
dichloroiodate
(BTMA.ICl2)
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in one portion. The mixture was stirred for 16 h at room
temperature, during which the color of the solution gradually
changed from yellow to light brown. Excess calcium carbonate
was filtered and the filtrate was concentrated; then, the
obtained residue was extracted with ether. The ether layer
was continual washed with 10% NaHSO3 and brine, then dried
with anhydrous Na2SO4 and evaporated under vacuum to give
light gray crystals (from 1 : 3 methanol–water). Yield 3.4 g
(95%); mp 153 uC. 1H NMR (80 MHz, CDCl3) d(ppm)
2.70(s, 3H, SOCH3), 5.82(s, 1H, NH), 6.83(d, 2H), 7.03(d,
2H), 7.55(d, 2H), 7.61(d, 2H). Anal. Calcd for C13H12NSOI: C,
43.70; H, 3.36; N, 3.92; S, 8.96. Found: C, 43.21; H, 3.50; N,
3.86; S, 8.85%.
Poly[phenylene sulfide-alt-tris(aniline)] (PPSTRA) (4). Yield
0.35 g (89%). 1H NMR (400 MHz, DMSO-d6) d(ppm) 6.97–
6.99(d, 4H), 7.06–7.11(m, 8H), 7.29–7.26(d, 4H), 7.87(s, 1H,
NH), 8.08(s, 2H, NH); 13C NMR (400 MHz, DMSO-d6)
d(ppm) 115.23, 117.79, 121.01, 123.31, 132.56, 134.50, 138.58,
144.89. Anal. Calcd for C24H19N3S: C, 75.59; H, 4.99; N, 11.02;
S, 8.40. Found: C, 74.80; H, 5.18; N, 10.96; S, 8.32%.
Poly(phenylene sulfide-alt-aniline) (PPSA) (2). Yield 0.19 g
(91%). 1H NMR (400 MHz, DMSO-d6) d(ppm) 7.13–7.15(d,
4H), 7.29–7.31(d, 4H), 8.55(s, 1H, NH); 13C NMR (400 MHz,
DMSO-d6) d(ppm) 118.12, 125.81, 132.71, 142.83. Anal. Calcd
for C12H9NS: C, 72.35; H, 4.65; N, 7.04; S, 16.06; Found: C,
74.41; H, 4.71; N, 6.92; S, 16.26%.
4-Methylsulfinylphenyl-capped trianiline (15). With the same
procedure used for 18, 15 was obtained by the condensation of
compounds 12 and 14. Yield 1.2 g (30%); mp 150 uC. 1H NMR
(400 MHz, DMSO-d6) d(ppm) 2.78(s, 3H, SOCH3), 6.82(t, 1H),
7.04–7.17(m, 12H), 7.26–7.30(t, 4H), 7.40–7.43(t, 2H), 7.56–
7.65(m, 2H), 7.92–7.95(d, 1H), 8.37(s, 2H, NH), 8.70(s, 1H,
NH). Anal. Calcd for C25H23N3SO: C, 72.64; H, 5.57; N, 10.17;
S, 7.75. Found: C, 72.38; H, 5.70; N, 10.11; S, 7.71%.
Poly[bis(phenylene sulfide)-alt-aniline] (PPDSA) (7). Yield
0.28 g (89%). 1H NMR (400 MHz, DMSO-d6) d(ppm) 7.17–
7.42(12H, aromatic H), 8.71(s, 1H, NH); 13C NMR (400 MHz,
DMSO-d6) d(ppm) 117.43, 119.80, 125.11, 132.50, 134.58,
142.41. Anal. Calcd for C18H13NS2: C, 70.36; H, 4.23; N, 4.56;
S, 20.85. Found: C, 70.08; H, 4.52; N, 4.50; S, 20.65%.
Acknowledgement
(4-Methylsulfinylphenyl)(4-phenylthiophenyl)amine (19). A
50 mL round bottomed flask was charged with a Teflon-
covered magnetic bar and a thoroughly ground mixture of 12
(2.1 g, 6 mmol), thiophenol (1.0 g, 9 mmol), K2CO3 (1.5 g), and
DMF (10 mL). The reaction was allowed to proceed at 135 uC
under argon for 16 h. After cooling to room temperature, the
resulting mixture was poured into water (200 mL), extracted
with CH2Cl2 and continuously washed with dilute KOH
solution and brine, then dried with anhydrous Na2SO4. The
combined solvent was removed by distillation under reduced
pressure and the residue was purified by chromatography over
silica (EtOAc–acetone ~ 4 : 1 as eluent, Rf ~ 0.4). 19 was
obtained as colorless crystals. Yield 1.8 g (90%); mp 157 uC. 1H
NMR (400 MHz, CDCl3) d(ppm) 2.77(s, 3H, SOCH3), 6.12(s,
1H, NH), 7.09(d, 2H,), 7.14(d, 2H), 7.27(m, 5H), 7.37(d, 2H),
7.54(d, 2H). Anal. Calcd for C19H17NS2O: C, 67.27; H, 5.01; N,
4.13; S, 18.88. Found: C, 67.01; H, 5.40; N, 4.11; S, 18.80%.
The work was financially supported by the NSFC (29725410
and 29992530) and CAS (KJ 951-A1-501-01). We are very
grateful to Mrs Rong Hua for performing the GPC experi-
ments and Dr Zaicheng Sun for helpful discussions.
References
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A. G. MacDiarmid and A. J. Epstein, in Conjugated Polymeric
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General procedure for the preparation of polymers 2, 4, 5, and 7
by the acid-induced self-condensation of corresponding
monomers with methylsulfinyl as functional groups
The polymerization of the tetraaniline-containing monomer 18
was used as an example. A 25 mL round bottomed flask was
charged with a Teflon-covered magnetic bar and 8 mL of
methanesulfonic acid was added. Monomer 18 (0.5 g, 1 mmol)
was added at RT and stirred for 24 h under argon. The
resulting highly viscous mixture was precipitated into an ice–
water mixture and filtered off, washed with water, and dried
under reduced pressure to obtain the precursor.
A 100 mL, round bottomed flask was charged with a Teflon-
covered magnetic bar, the above precursor and pyridine
(25 mL) were added. The mixture was refluxed for 6 h under
argon. After cooling, the clear solution was poured into cold
methanol (300 mL) and stirred for 2 h. The polymer was
filtered off, washed with water and methanol, reduced with
phenylhydrazine in THF, then reprecipitated in methanol and
dried under reduced pressure to obtain the fully reduced
structure 5.
8
9
J. Leununger, J. Uebe, J. Salbeck, L. Gherghel, C. Wang and
K. Mu¨llen, Synth. Met., 1999, 100, 19.
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17 (a) J. Chiang and A. G. MacDiarmid, Synth. Met., 1986, 13, 183;
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Materials, ed. W. R. Salaneck, I. Lundstrom and B. Ranby,
Oxford, New York, 1993, p. 73.
Poly[phenylene sulfide-alt-tetrakis(aniline)] (PPSTEA) (5).
Yield 0.42 g (90%). 1H NMR (400 MHz, DMSO-d6) d(ppm)
6.97–7.25(m, 20H, aromatic H), 7.76(s, 2H, NH), 8.04(s, 2H,
NH); 13C NMR (400 MHz, DMSO-d6) d(ppm) 116.54, 118.68,
120.50, 122.94, 126.08, 133.83, 136.20, 139.08, 141.57, 146.79.
Anal. Calcd for C30H24N4S: C, 76.27; H, 5.08; N, 11.87; S, 6.78.
Found: C, 75.74; H, 5.20; N, 11.82; S, 6.75%.
J. Mater. Chem., 2002, 12, 181–187
187