Copolymers of aniline and 3-aminophenol derivatives with oligo(oxyethylene) side chains as novel water-soluble conducting polymers

Article abstract of DOI:10.1021/ma040070g

A novel water-soluble copolymer of aniline and aminophenol (AP) grafted with oligo(oxyethylene) (PEO) side chains (AP-g-PEO) was synthesized. The AP-g-PEO macromononer was prepared starting from an N-protected 3-aminophenol (protection group: tert-butoxycarbonyl) followed by the substitution of tosylated oligo(oxyethylene) on the hydroxide moiety of the AP and deprotection. Finally, AP-g-PEO was copolymerized with aniline at various feed mole ratios (AP-g-PEO/aniline), The copolymers and various intermediates were characterized by FTIR, MS, NMR, GPC, UV-vis, and chemical elemental analysis. The increase of the aniline content and the decrease of the PEO side chain length generated lower oligo(oxyethylene) grafted concentrations and solubilities in water but longer conjugation lengths and higher conductivities. Four AP-g-PEOs were prepared from four oligo(oxyethylene) methyl ethers with M_n = 164, 350, 750, and 2000. The poly((AP-g-PEO-750)-co-aniline) at a feed mole ratio of 3/1 was water-soluble and possessed a relatively high conductivity (0.12 S/cm). AP-g-PEOs were found to have low reactivities and to generate low homopolymerization degrees because of the torsional effects of the PEO side chains on the backbone of the copolymer. A possible copolymerization mechanism was suggested. Furthermore, the copolymers with high PEO content had lower oxidation and doping levels of their backbones, which were confirmed by X-ray photoelectron spectroscopy.

Full text of DOI:10.1021/ma040070g

6104
Macromolecules 2004, 37, 6104-6112
Copolymers of Aniline and 3-Aminophenol Derivatives with
Oligo(oxyethylene) Side Chains as Novel Water-Soluble Conducting
Polymers
F en gju n Hu a a n d Eli Ru ck en stein *
Department of Chemical and Biological Engineering, State University of New York at Buffalo,
Buffalo, New York 14260
Received April 6, 2004; Revised Manuscript Received May 25, 2004
ABSTRACT: A novel water-soluble copolymer of aniline and aminophenol (AP) grafted with oligo-
(oxyethylene) (PEO) side chains (AP-g-PEO) was synthesized. The AP-g-PEO macromononer was prepared
starting from an N-protected 3-aminophenol (protection group: tert-butoxycarbonyl) followed by the
substitution of tosylated oligo(oxyethylene) on the hydroxide moiety of the AP and deprotection. Finally,
AP-g-PEO was copolymerized with aniline at various feed mole ratios (AP-g-PEO/aniline). The copolymers
and various intermediates were characterized by FTIR, MS, NMR, GPC, UV-vis, and chemical elemental
analysis. The increase of the aniline content and the decrease of the PEO side chain length generated
lower oligo(oxyethylene) grafted concentrations and solubilities in water but longer conjugation lengths
and higher conductivities. Four AP-g-PEOs were prepared from four oligo(oxyethylene) methyl ethers
with Mn ) 164, 350, 750, and 2000. The poly((AP-g-PEO-750)-co-aniline) at a feed mole ratio of 3/1 was
water-soluble and possessed a relatively high conductivity (0.12 S/cm). AP-g-PEOs were found to have
low reactivities and to generate low homopolymerization degrees because of the torsional effects of the
PEO side chains on the backbone of the copolymer. A possible copolymerization mechanism was suggested.
Furthermore, the copolymers with high PEO content had lower oxidation and doping levels of their
backbones, which were confirmed by X-ray photoelectron spectroscopy.
In tr od u ction
conditions. A lower grafting degree, below 30%, was,
however, achieved through this “graft onto” process.23
Less attention was paid to the grafting of PEO side
chains to the phenyl ring, even though the modification
that occurs at nitrogen was expected to produce a higher
decrease of the conductivity than that which occurs at
a phenyl ring. Park et al.24 suggested a synthesis
strategy in which poly(ethyleneoxy)-3-aminobenzoate
was prepared by reacting 3-aminobenzoic acid with
trityl chloride, followed by the chlorination and esteri-
fication of the benzoic acid moiety. After deprotection
in acidic conditions, the resulted macromonomer could
be copolymerized with aniline. The presence of benzoic
acid or of its ester decreased the reactivity of the
macromonomer because of their electron-withdrawing
effect, resulting in a low-grafted copolymer (<35%).The
aniline derivatives with a short-chain alkoxyl grafted
on the phenyl ring, such as 2- or 3-methoxyaniline or
2- or 3-ethoxyaniline, were easily homopolymerized to
generate conducting polymers with conductivities as
high as that of polyaniline because the alkoxyl is an
electron donor.25 The homopolymerization of 2- or
3-aminophenol in acidic conditions has been also re-
ported.26 The low conductivity achieved, below 10-8
S/cm, might have been caused by the inductive effect of
the hydroxide moiety of the AP.
Polyaniline has been extensively studied in the past
20 years, as one of the important conducting polymers,
because of its thermal stability and high conductivity.1-4
However, this polymer was found to have low solubili-
ties in the common solvents and poor processability.
Numerous investigations have been carried out for the
improvement of the solubility and processability by
introducing various side chains such as alkyl,5 alkoxy,6
benzyl,7 and aryl8 substituents either at the aromatic
ring or at nitrogen. The grafted side chains in these
aniline derivatives increased the solubility of the PANI
backbones. Water-soluble poly(aniline derivatives) could
be also prepared by the direct polymerization of water-
soluble aniline derivative monomers containing a sul-
fonic acid moiety at the phenyl ring or nitrogen.9-13 The
withdrawing effect of the sulfonic group caused, how-
ever, difficulties in homopolymerization and also de-
creased the conductivity. The copolymerizations of
sulfonated aniline and aniline have been successfully
carried out.14-18 Another pathway was the modification
of the backbone of polyaniline through grafting water-
soluble side chains at either the ring or nitrogen. A
typical example is the directly sulfonated polyaniline
(SPAN) reported by Epstein et al.19 A decrease of the
conductivity because of the withdrawing effect was
observed.19-21 Yamaguchi et al. prepared PANI grafted
with hydrophilic poly(ethylene oxide) (PEO) through a
“graft from” process, in which a ring-opening polymer-
ization of an epoxide occurred on the active anionic
nitrogens of the PANI backbone.22 Wang et al. grafted
PEO chains to the active anionic nitrogens of PANI via
a direct attachment under very strict experimental
In previous papers, we reported the preparation of a
water-soluble polydiphenylamine (PDPA) with poly-
(ethylene oxide) (PEO) grafted onto the nitrogens of the
PDPA backbone.27 The grafting was achieved by sub-
stituting the tosyloyl end group of PEO-tosylate with
an amine of the PDPA under mild conditions. The
resulted PDPA-g-PEO with a comb-shaped architecture
became soluble in organic solvents, such as chloroform
or tetrahydrofuran, and even became water-soluble for
PEO side chains of molecular weight Mn ) 2000. The
* To whom correspondence should be addressed. Tel (716) 645-
2911 ext 2214; fax (716) 645-3822; e-mail feaeliru@acsu.buffalo.edu.
10.1021/ma040070g CCC: $27.50 © 2004 American Chemical Society
Published on Web 07/09/2004

Macromolecules, Vol. 37, No. 16, 2004
Copolymers of Aniline and 3-Aminophenol Derivatives 6105
Sch em e 1. Syn th esis P a th w a y of Cop olym er s of AP -g-P EO a n d An ilin e
Am in o P r otectin g Rea ction . 3-Aminophenol (0.1 mol), di-
tert-butyldicarbonate (0.1 mol), and 40 mL of DMF were
introduced into a round flask under a nitrogen atomosphere.
The system was subjected to intensive magnetic stirring for a
few minutes and then cooled to 0 °C in an ice-water bath. A
triethylamine (0.105 mol) solution in DMF (40 mL) was added
dropwise within 1 h. The reaction lasted an additional 12 h at
0 °C. Further, 300 mL of chloroform and 100 mL of water were
introduced to generate two layers. The pH of the top layer (the
water phase) was carefully adjusted, using a 0.1 N HCl
aqueous solution, at pH ) 7, and extracted with chloroform
three times (30 mL each time). The combined chloroform
phases were first washed with a saturated NaHCO3 aqueous
solution and then washed with water until neutral. The
chloroform solution was dried with Na2SO4, and the solvent
was evaporated on a rotary evaporator. A light brown solid,
N-protected aminophenol (AP-Boc), was obtained with an yield
of 89%. 1H NMR (CDCl3) δ ) 7.01-6.10 (1,3-Ph, 4 H), 4.57
(-OH, 1H), 3.66 (-NH2, 2 H). Anal. Calcd for C11H15O3N: C,
63.15; H, 7.18; O, 22.97; N, 6.70. Found: C, 63.12; H, 7.16; O,
22.99; N, 6.73. MS (m/z): 209.1.
PEO-grafted polyaniline can be employed as battery
material and biomaterial.28-31
In the present paper, an N-protected aniline deriva-
tive was first prepared by reacting 3-aminophenol (AP)
with tert-butoxycarbonyl (t-Boc) as a temporary protect-
ing group.32 The protection was followed by the grafting
of an oligo(oxyethylene) side chain at the 3-position by
substituting the tosyloyl end group of tosylate oligo-
(oxyethylene) with the hydroxide moiety of the AP under
mild conditions31,33 to generate AP-Boc-g-PEO. Further,
the AP-Boc-g-PEO was deprotected with trifluoroacetic
acid (TFA) to obtain an aniline macromonomer possess-
ing an oligo(oxyethylene) side chain at the 3-position
(AP-g-PEO), which was (co)polymerized via chemical
oxidation in the presence of 1.2 N HCl aqueous solution
(see Scheme 1). The molecular structures of the amino-
protected oligomers and copolymers were characterized
by FTIR, MS, NMR, GPC, and elemental chemical
analysis. Furthermore, the oxidation levels of these
copolymers upon doping or undoping were examined by
X-ray photoelectron spectroscopy (XPS).
Su bstitu tion Rea ction of Tosyla ted Oligo(oxyeth yl-
en e) (P EO-Tos) to th e Hyd r oxid e Moiety of th e P h en ol
of AP -Boc. AP-Boc (0.050 mol), potassium tert-butylate (0.050
mol), and dry THF (250 mL) were introduced into a round flask
under a dry nitrogen atmosphere and subjected to intensive
stirring. PEO-Tos with controlled oxyethylene chain length
(PEO-150, PEO-350, PEO-750, and PEO-2000) was prepared
via the tosylation of the oligo(oxyethylene) methyl ether with
tosyol chloride as reported in a previous paper.27 PEO-Tos
(0.055 mol) was dissolved in 50 mL of THF, and this solution
was added dropwise to the flask. The system was subjected to
intensive stirring for 3 days. The mixture became light red,
and a precipitate appeared, indicating the start of grafting.
Dichloromethane (300 mL) and 100 mL of water were intro-
duced to generate two layers. The top layer (the water phase)
was extracted with dichloromethane three times (30 mL each
time), and the extracted oil phase was combined with the
previous dichloromethane phase. The total oil phase was
Exp er im en ta l Section
Ma ter ia ls. 3-Aminophenol (99%), aniline (99%), di-tert-
butyldicarbonate (97%), hydrochloric acid (37 wt %), am-
monium persulfate (98 wt %), trifluoroacetic acid (TFA, 99%),
triethylamine (99 wt %), p-toluenesulfonyl chloride (99+ wt
%), and potassium tert-butylate (>95 wt %) were purchased
from Aldrich and used without further purification. Oligo-
(oxyethylene) methyl ethers with different molecular weights,
such as tri(ethylene glycol) monomethyl ether (PEO-150, Mn
) 164) and poly(ethylene oxide) methyl ethers (PEO-350 (Mn
) 350), PEO-750 (Mn ) 750), and PEO-2000 (Mn ) 2000)) were
also purchased from Aldrich and used without further puri-
fication. The solvents, dimethylformamide (DMF), diethyl
ether, and tetrahydrofuran (THF) from Aldrich and dichloro-
methane and chloroform from Fisher, were of HPLC purity.

6106 Hua and Ruckenstein
Macromolecules, Vol. 37, No. 16, 2004
washed with water three times (100 mL each time) and dried
with Na2SO4. The dichloromethane was removed on a rotary
evaporator. Further purification was carried out via a chro-
matographic method. A light brown liquid, namely AP-Boc-g-
PEO, was thus obtained with an yield of about 70%.
Dep r ot ect in g R ea ct ion of AP -Boc-g-P E O a n d Co-
p olym er iza tion w ith An ilin e. AP-Boc-g-PEO (0.030 mol),
TFA (0.060 mol), and dichloromethane (40 mL) were intro-
duced into a round flask equipped with a condensor, subjected
to intensive stirring, and its temperature raised to 40 °C. The
reaction lasted 2 h at 40 °C, after which the solvent and the
excess of TFA were removed on a rotary evaporator under high
vacuum at a temperature <30 °C. A brown liquid, AP-g-PEO,
was obtained with a yield of 98%.
AP-g-PEO and aniline, with feed mole ratios of AP-g-PEO/
aniline of 10/1, 6/1, 3/1, 1/1, or 1/2, and a total concentration
of 1.2 N were dissolved in 45 mL of 1.2 N HCl aqueous solution
with intensive stirring, and the system was cooled to 5 °C.
Ammonium persulfate (0.010 mol) dissolved in 1.2 N HCl
aqueous solution (15 mL) was added dropwise into the flask.
The color of the mixture changed slowly from brown to green,
indicating the beginning of copolymerization. After 18 h, a
green precipitate was separated using a supercentrifuge
(Dupont, RC-5) at 3500 rpm for 30 min. The green particles
of the copolymers were washed with water several times until
no red supernatant was identified. Further purifications of the
HCl-doped copolymers were carried out through dissolution-
precipitation in diethyl ether. The yields were 32, 57, 62, 67,
and 75% for feed mole ratios of 10/1, 6/1, 3/1, 1/1, and 1/2,
respectively. The dedoping was carried out through the
neutralization of the above HCl-doped copolymers with a 1.0
N NH4OH aqueous solution. A blue solid was obtained with
an yield above 90% in all cases.
The homopolymerization of AP-g-PEOs was also carried out
for comparison purposes. The yield was in all cases below 37%.
Ch a r a cter iza tion . Proton (1H) NMR, MS, UV-vis absorp-
tion, and FTIR measurements have been carried out on a 400
MHz INOVA-400, Mass Spectroscope (PHI 7200 model), a
Thermo Spectronic Genesys-6, and a Perkin-Elmer FTIR 1760,
respectively. The NMR solutions were prepared by dissolving
the polymer in deuterated water or deuterated chloroform (5
g/L). Gel permeation chromatography (GPC, Waters) was used
to evaluate the molecular weights of the homopolymers and
copolymers on the basis of a polystyrene calibration curve. The
GPC was equipped with three 30 cm long columns filled with
a Waters Styragel, a Waters HPLC 515 pump, and a Waters
410 RI detector. The GPC measurements have been carried
out using DMF as eluent at 60 °C, at a flow rate of 1.0 mL/
min and 1.0 cm/min chart speed.
F igu r e 1. FTIR spectra of (a) PEO-750-Tos, (b) AP-Boc, (c)
AP-Boc-g-PEO-750, and (d) poly(AP-g-PEO-750)-co-aniline) (3/
1).
The chemical elemental analysis of the polymer samples was
carried out on a Perkin-Elmer model 2400 C, H, N analyzer.
The chlorine and sulfur contents were determined by the
oxygen flask method. The room temperature conductivities of
the compressed pellets of the various copolymers were deter-
mined using the conventional four-point method. The surface
elemental analysis of compressed disks was carried out on a
VG ESCA/SIMSLAB MK II with a Mg KR radiation source
(1253.6 eV). Each copolymer sample was first dissolved in
DMF, and subsequently DMF was removed using a rotary
evaporator. The solid sample was dried under high vacuum
at room temperature for at least 7 days under a nitrogen atmo-
sphere and ground into a powder which was compressed into
a disk (of thickness around 1 mm) between two Teflon films.
Resu lts a n d Discu ssion
Syn th esis a n d Ch a r a cter iza tion . The copolymers
of aminophenol with oligo(oxyethylene) side chains at
the 3-position of the phenyl ring (AP-g-PEO) and aniline
were prepared via the successive four steps of Scheme
1. The t-Boc-N-protected aminophenol (AP-Boc) was
grafted via substitution with tosylated oligo(oxyethyl-
ene) (PEO-Tos-150, PEO-Tos-350, PEO-Tos-750, or PEO-
Tos-2000 prepared from PEO-150 (Mn ) 164), PEO-350
F igu r e 2. MS spectrum of AP-Boc-g-PEO-750.
(Mn ) 350), PEO-750 (Mn ) 750), and PEO-2000 (Mn )
2000), respectively) to generate the corresponding oli-
gomer (AP-Boc-g-PEO). Figure 1 presents the FTIR
spectra of PEO-750-Tos (spectrum a), AP-Boc (spectrum

Macromolecules, Vol. 37, No. 16, 2004
Copolymers of Aniline and 3-Aminophenol Derivatives 6107
1
F igu r e 3. (A) H NMR spectra of (a) 3-aminophenol, (b) AP-Boc, (c) AP-Boc-g-PEO-750, (d) AP-g-PEO-750, and (e) poly((AP-g-
PEO)-co-aniline) (3/1) in CDCl3, 5 g/L. (B) Two expanded 1H NMR spectra of (b) AP-Boc and (c) AP-Boc-g-PEO-750 in CDCl3, 5
g/L.

6108 Hua and Ruckenstein
Macromolecules, Vol. 37, No. 16, 2004
F igu r e 4. 1H NMR spectra of copolymers in D2O, 5 g/L: (a) poly((AP-g-PEO-750)-co-aniline) (3/1), (b) poly((AP-g-PEO-750)-co-
aniline) (1/1), and (c) poly((AP-g-PEO-350)-co-aniline) (3/1).
b), and AP-Boc-g-PEO-750 (spectrum c); the character-
istic peak of the hydroxide moiety at 3300 cm-1 disap-
peared in AP-Boc-g-PEO-750 because of the formation
of an ether bond after substitution, and the ether bond
peaks (C-O-C) of the PEO side chains and of the
phenoxyl (dC-O-C) appeared around 1108 cm-1 as a
tons of the amide (-CONH-) and methyl (-CH3) of the
t-Boc, respectively) disappeared. The signals due to the
protons of the phenyl ring were shifted upfield because
the deshielding effect caused by the tert-butoxycarbonyl
was no longer present. The main peaks in the MS
spectrum after deprotection were found to differ from
those of AP-g-Boc-g-PEO-750 (see Figure 2) by 108 Da,
corresponding exactly to the molecular weight of the
t-Boc moiety.
Figure 1c also contains a typical FTIR spectrum of
neutralized poly(AP-g-PEO-750-co-aniline) prepared for
a feed mole ratio of AP-g-PEO-750/aniline ) 3/1. The
characteristic vibrations at 1585 and 1490 cm-1 can be
assigned to the stretching vibrations of the quinoid and
benzenoid rings, respectively, indicating the generation
of conjugation along the backbone (oxidated state). Its
NMR spectrum (CDCl3, spectrum e of Figure 3A)
displays two groups of signals at 8.00-7.00 and 4.00-
3.00 ppm, which can be assigned to the protons of the
phenyl ring of polyaniline main chain and the oxyalkyl
protons of PEO side chains, respectively. However, in
deuterated water (D2O), the signals due to the protons
of the phenyl ring became weak. Particularly for the
copolymer prepared from a feed mole ratio of 1/1, these
signals could be hardly identified (see Figure 4). This
is probably related to the aggregation of the hydrophobic
polyaniline backbones in water.27
Cop olym er iza tion of AP -g-P EOs a n d An ilin e.
The copolymerization of aniline derivatives and aniline
has been investigated because most derivatives with
side chains attached either to the phenyl ring or to the
nitrogen have low reactivities because of the torsional
and electronic withdrawing effects of the side groups.
The methoxy- or ethoxyaniline can homopolymerize as
aniline because the methoxy or ethyoxy moieties are
electron donors, thus almost complementing the loss of
reactivity due to the torsional effects. Table 1 shows that
the poly(2-methoxyaniline) (poly(o-anisidine)) and poly-
aniline exhibit comparable polymerization degrees (153.0
multipeak. The carbonyl vibration peak at 1734 cm-1
,
which can be assigned to t-Boc, is still present in the
two compounds, indicating that the t-Boc was not
eliminated during substitution. Figure 2 displays a
typical MS spectrum of AP-Boc-g-PEO-750 (ESI MS),
where the values of the main molecular ionic peaks in
the MS spectra reflect the following formula:
where n is the number of ethylene oxides in the oligo-
(oxyethylene) side chains. Furthermore, in the 1H NMR
spectra (CDCl3, Figure 3A), the signals in the range
8.0-6.0 ppm of the phenyl rings of AP-Boc or AP-Boc-
g-PEO-750 were shifted downfield compared with those
of 3-aminophenol because of the deshielding effect
caused by the tert-butoxycarbonyl. The characteristic
signal at 1.44 ppm, which can be assigned to the protons
of methane of t-Boc, remained almost the same in the
two cases (spectra b and c in Figure 3A), indicating that
the protecting groups were not lost during substitution.
In Figure 3B of the expanded NMR spectra of AP-Boc
and AP-Boc-g-PEO-750, the protons of the phenyl ring
could be assigned to the chemical formula inserted. The
signals at 4.18, 3.65, and 3.41 ppm can be assigned to
the protons of phenoxymethylene, the oxyethylene, and
oxymethyl of the PEO side chains, respectively. The
NMR spectrum of AP-g-PEO-750 obtained after depro-
tection (spectrum d of Figure 3A) shows that the signals
at 7.10 ppm (peak i) and 1.40 ppm (peak j) present in
AP-Boc-g-PEO-750 (which can be assigned to the pro-

Macromolecules, Vol. 37, No. 16, 2004
Copolymers of Aniline and 3-Aminophenol Derivatives 6109
Ta ble 1. P h ysica l P a r a m eter s of th e Cop olym er s of AP -g-P EOs a n d An ilin e
AP-g-PEO/
aniline,a feed
mole ratio
Mn
AP-g-PEO/
aniline in
PEO wt
fraction in
copolymerd
HCl concn,
temp
(polymerization
conductivity,
S/cme
name
degree)b
copolymer (y/x)c
polyaniline
poly(o-anisidine)
poly (AP-g-PEO-150)
poly (AP-g-PEO-350)
poly (AP-g-PEO-750)
poly (AP-g-PEO-2000)
poly((AP-g-PEO-750)-co-aniline)
poly((AP-g-PEO-750)-co-aniline)
poly((AP-g-PEO-750)-co-aniline)
poly((AP-g-PEO-750)-co-aniline)
poly((AP-g-PEO-750)-co-aniline)
poly((AP-g-PEO-150)-co-aniline)
poly((AP-g-PEO-350)-co-aniline)
poly((AP-g-PEO-2000)-co-aniline)
1.2 N, 5 °C
1.2 N, 5 °C
3.0 N, 5 °C
3.0 N, 5 °C
3.0 N,5 °C
3.0 N, 5 °C
1.2 N, 5 °C
1.2 N, 5 °C
1.2 N, 5 °C
1.2 N, 5 °C
1.2 N, 5 °C
1.2 N, 5 °C
1.2 N, 5 °C
3.0 N, 5 °C
15760 (169.5)
18970 (153.0)
9550 (36.4)
11350 (24.0)
5675 (6.50)
4.57
3.53
2.34 × 10-3
5.43 × 10-5
<10-7
<10-7
7.4 × 10-5
4.8 × 10-4
0.12
12060 (5.7)
9650 (13.7)
10/1
6/1
3/1
1/1
1/2
3/1
3/1
3/1
4.0
3.2
1.7
0.7
0.44
2.4
2.0
0.4
0.850
0.845
0.821
0.757
0.702
0.504
0.693
0.858
20460 (30.4)
56450 (98.6)
41690 (102.7)
40630 (125.1)
27590 (126.9)
37480 (112.1)
26540 (17.6)
0.30
0.83
0.67
0.44
<10-7
a
b
AP-g-PEOs denote aminophenol derivatives with various oligo(oxyethylene) side chains at the 3-position of 3-aminophenol. Number-
average molecular weights of the neutralized polymers were determined by GPC on the basis of a PS calibration curve; using DMF as
eluent at a rate of 1 mL/min and at 60 °C. The polymerization degree is expressed as DPn ) (Mn,GPC × (1 + (y/x)))/((y/x) × Mn,AP-g-PEO
+
Mn,aniline - 2). c The mole ratio of AP-g-PEO/aniline in copolymer, y/x, was determined from Table 3 via chemical elemental analysis, i.e.,
d
y/x ) (C/N - 6)/(7 - C/N + (Mn - 31)/22)), where Mn,AP-g-PEO is the molecular weight of the oligo(oxyethylene). PEO weight fraction
was calculated from footnote c using the expression (Mn,AP-g-PEO × (y/x))/((Mn,AP-g-PEO + 109) × (y/x) + 91). e Conductivities of polymeric
compressed pellets determined via the four-point method. Each polymer was dried under vacuum for at least 7 days before the measurement
and ground into a powder which was further compressed into a disk.
F igu r e 5. UV-vis spectra of (a) neutralized PANI, (b)
neutralized poly(o-anisidine), (c) neutralized poly((AP-g-PEO-
F igu r e 6. UV-vis spectra of (a) neutralized PANI, (b)
750)-co-aniline) (3/1), (d) neutralized poly(2-aminophenol), and
(e) neutralized poly(AP-g-PEO-750) (all in DMF).
neutralized poly((AP-g-PEO-750)-co-aniline) (1/2), (c) neutral-
ized poly((AP-g-PEO-750)-co-aniline) (1/1), (d) neutralized poly-
((AP-g-PEO-750)-co-aniline) (3/1), and (e) neutralized poly((AP-
g-PEO-750)-co-aniline) (6/1) (all in DMF).
and 169.5, respectively). The UV-vis spectra of PANI
and poly(o-anisidine) (spectra a and b of Figure 5)
exhibit two absorbance peaks at 320 and 640 nm, which
can be assigned to the π-π* transition of the benzenoid
and the exciton transition of the quinoid rings, respec-
tively. They show that their conjugations and conduc-
tivities are comparable. The UV-vis spectrum of poly-
((AP-g-PEO-750)-co-aniline) (3/1) has a peak at 605 nm,
which was blue-shifted in comparison with PANI, and
a lower area integral, indicating a lower conjugation.
Four AP-g-PEOs with various PEO side chains (Mn,PEO
) 164, 350, 750, and 2000) were homopolymerized under
acidic conditions and produced low molecular weight
homopolymers and low conductivities (<10-3 S/cm). The
polymerization degree decreased with increasing PEO
side chain length, indicating that the reactivity of AP-
g-PEOs has decreased in the same direction (see Table
1). Using AP-g-PEO-750 as an example, the UV-vis
spectrum (Figure 5, spectrum e) of polyAP-g-PEO-750
provided a very weak peak around 600 nm in the
neutralized state and a very low conductivity (<10-7
S/cm) in the HCl-doped state. However, the copoly-
merization between AP-g-PEO-750 and aniline with a
feed mole ratio of 3/1 could produce high molecular
weight copolymers (polymerization degree ) 98.6). The
mole ratio AP-g-PEO-750/aniline in the copolymers
increased from 0.44 to 4.0 with increasing feed mole
ratio of AP-g-PEO-750/aniline from 1/2 to 10/1, and the
conductivity decreased in the same direction. In Figure
6, the blue shift compared to PANI increased with
increasing feed mole ratio; i.e., the peak at 640 nm of
the polyaniline was shifted to 595 nm for poly((AP-g-
PEO-750)-co-aniline) at a feed mole ratio ) 6/1, along
with a decrease in the area integral, indicating a
decrease of conjugation. Furthermore, the GPC traces
of these copolymers (Figure 7) demonstrated that their
molecular weight varied with the feed mole ratio. (The
number-average molecular weights are listed in Table

6110 Hua and Ruckenstein
Macromolecules, Vol. 37, No. 16, 2004
F igu r e 7. GPC traces of neutralized polymers: (a) poly(AP-
g-PEO-750), (b) polyaniline, (c) poly((AP-g-PEO-750)-co-aniline)
(6/1), (d) poly((AP-g-PEO-750)-co-aniline) (1/1), (e) poly((AP-
g-PEO-350)-co-aniline) (3/1), and (f) poly((AP-g-PEO-750)-co-
aniline (3/1).
F igu r e 8. UV-vis spectra of (a) neutralized poly((AP-g-PEO-
150)-co-aniline) (3/1), (b) neutralized poly((AP-g-PEO-350)-co-
aniline) (3/1), (c) neutralized poly((AP-g-PEO-750)-co-aniline)
(3/1), and (d) neutralized poly((AP-g-PEO-2000)-co-aniline) (3/
1) (all in DMF).
Sch em e 2. A P ossible Cop olym er iza tion Mech a n ism
with different side chains and the same feed mole ratio
exhibited a blue shift in the UV-vis spectra, i.e., the
peak at 625 nm of poly((AP-g-PEO-150)-co-aniline) (3/
1) becoming 595 nm for poly((AP-g-PEO-2000)-co-
aniline) (3/1) (see Figure 8).
Solu bility. The solubility of the copolymers was
dramatically improved by the grafting with oligo(oxy-
ethylene) (Table 2). The copolymers prepared from AP-
g-PEO-750 and aniline in the range of feed mole ratios
1/1 to 10/1 can dissolve in most commercial organic polar
solvents. The poly((AP-g-PEO-750)-co-aniline) (3/1) ex-
hibited a high water solubility and a relatively high
conductivity (0.12 S/cm).
Su r fa ce Elem en ta l An a lysis of th e Cop olym er s.
The copolymers were also examined using X-ray photo-
electron spectroscopy (XPS). In Table 3, the surface and
bulk elemental stoichiometries of the copolymers pre-
pared from various feed mole ratios are listed. The
carbon and oxygen contents obtained by XPS were
higher than those provided by the chemical elemental
analysis, mostly because of the contamination of the
surface (the adsorbed carbon dioxide), which occurs in
any XPS analysis.34 Figure 9 presents the wide-scale
XPS spectra of the HCl-doped and neutralized polymers.
They exhibited binding energies around 284, 398, and
533 eV, which can be assigned to C 1s, N 1s, and O 1s,
respectively. The peaks due to S 2p and Cl 2p at 167
and 199 eV, respectively, could be hardly identified in
the neutralized polymers, indicating that the chloride
ions and the tosyol groups have been completely re-
moved. Of course, the chloride peak appeared after HCl
doping.
It should be noted that the C, N, and O cores are
present in several energetic states which involve dif-
ferent components upon doping or dedoping (see Table
4). The oxidation and doping levels of the copolymers
can be determined by analyzing the N 1s core levels.35
In the XPS data analysis, the Shirley background was
subtracted before the curve fitting.36 The AugerScan
Demo software was employed for curve fitting. The
experimental spectra were fit into components of Gauss-
ian-Lorentzian line shape. The component composi-
tions were determined from the ratios among the area
1.) The polymerization degrees of the copolymers pre-
pared at the feed mole ratios of 1/2, 1/1, 3/1, 6/1, and
10/1 were 125.1, 102.7, 98.6, 30.4, and 13.7, respectively.
As the feed mole ratio increased, the backbone length
became shorter and possessed a lower conjugation. The
grafted PEO-750 side chain of AP-g-PEO-750 provided
a steric barrier which weakened the polaron formation
under oxidation conditions, and as a result, the reactiv-
ity decreased. The higher diffusion barriers generated
by the longer side chains regarding the propagation of
the radical species decreased the rate of growth of the
chains. Indeed, for the same feed mole ratio, the
polymerization degree decreased as the oligo(oxyethyl-
ene) side chain length increased (see Table 1) because
of the decreased reactivity of AP-g-PEO with longer side
chains. A possible copolymerization mechanism via
chemical oxidation under acidic conditions is suggested
in Scheme 2. The copolymers resulted from AP-g-PEOs

Macromolecules, Vol. 37, No. 16, 2004
Copolymers of Aniline and 3-Aminophenol Derivatives 6111
Ta ble 2. Solu bility of th e Va r iou s Cop olym er s in Neu tr a lized Sta tea
neutralized polymers
polyaniline
poly(o-anisidine)
poly (AP-g-PEO-150)
poly (AP-g-PEO-350)
poly (AP-g-PEO-750)
poly (AP-g-PEO-2000)
poly((AP-g-PEO-750)-co-aniline) (10/1)
poly((AP-g-PEO-750)-co-aniline) (6/1)
poly((AP-g-PEO-750)-co-aniline) (3/1)
poly((AP-g-PEO-750)-co-aniline) (1/1)
poly((AP-g-PEO-750)-co-aniline) (1/2)
poly((AP-g-PEO-150)-co-aniline) (3/1)
poly((AP-g-PEO-350)-co-aniline) (3/1)
poly((AP-g-PEO-2000)-co-aniline) (3/1)
NMP
THF
chloroform
DMF
water
S
S
S
S
S
S
S
S
S
S
S
S
S
S
I
I
S
S
S
S
S
S
S
S
S
S
S
S
S
S
I
I
SS
PS
S
S
S
S
S
PS
SS
SS
PS
S
PS
PS
S
S
S
S
S
S
S
PS
PS
S
S
S
S
S
S
PS
SS
PS
S
PS
PS
S
S
S
a
Keywords: S ) soluble up to 1.0g/L, stable for 1 month; I ) insoluble; SS ) slightly soluble, precipitation after 1 day, with a colored
supernatant; PS ) partially soluble, no precipitation within 1 week, but precipitation by centrifugation at 7000 rpm for 10 min.
Ta ble 3. Su r fa ce a n d Bu lk Elem en ta l Stoich iom etr ies of th e Neu tr a lized Cop olym er s of AP -g-P EOs a n d An ilin e
copolymers
poly(o-anisidine)
poly(AP-g-PEO-750)-co-aniline) (6/1)
poly((AP-g-PEO-750)-co-aniline) (3/1)
poly((AP-g-PEO-750)-co-aniline) (1/1)
poly((AP-g-PEO-750)-co-aniline) (1/2)
atomic ratio in the bulka
atomic ratio on the surfaceb
C7.38H9.03O1.05N1.00Cl0.01S0.00
C31.70H59.87O13.20N1.00Cl0.00S0.00
C27.20H49.87O10.91N1.00Cl0.00S0.00
C19.86H31.29O7.10N1.00Cl0.00S0.01
C16.29H24.54O5.20N1.00Cl0.01S0.00
C13.13O2.42N1.00Cl0.00S0.00
C38.70O19.02N1.00Cl0.01S0.03
C34.57O16.10N1.00Cl0.00S0.00
C25.20O10.61N1.00Cl0.01S0.03
C20.70O7.90N1.00Cl0.01S0.01
a
b
Determined by chemical elemental analysis. Each polymer was dried for at least 7 days under vacuum and ground into a powder,
followed by compression as a disk. The disk surface concentrations were determined by XPS.
Ta ble 4. Elem en t An a lysis of a Typ ica l HCl-Dop ed
Cop olym er P oly((AP -g-P EO-750)-co-a n ilin e) (3/1) by XP S
element
(orbital)
possible
components
binding
energy (eV)
FWHM
(eV)a
component
conc, %
N 1s
dN-
398.20
399.41
400.83
402.31
199.00
1.09
1.86
2.68
2.95
1.5
2.3
53.3
36.7
7.7
-NH-
-N+-
-N+H-
Cl-
Cl 2p
100
a
FWHM denotes the full width at half-maximum of the fitted
peak.
(o-anisidine). This indicates that in the copolymer the
chain conformation produced a lower conjugation be-
cause of the higher steric barrier of the PEO side chains.
Thus, the doping level was depressed, and the electron
delocalization was weakened along the backbone. In this
case, a lower conductivity was expected, which is
consistent with the UV-vis results presented above. In
a series of parallel XPS experiments, a decrease of the
doping level was observed with increasing graft side
chain length and feed mole ratio AP-g-PEO/aniline.
F igu r e 9. XPS spectra of copolymers: (a) neutralized poly-
(o-anisidine), (b) neutralized poly((AP-g-PEO-750)-co-aniline)
(3/1), (c) neutralized poly((AP-g-PEO-750)-co-aniline) (1/1), (d)
neutralized poly((AP-g-PEO-350)-co-aniline (1/2), (e) neutral-
ized poly(AP-g-PEO-750), and (f) HCl-doped poly((AP-g-PEO-
750)-co-aniline) (3/1).
Con clu sion s
integrals of the fitted peaks. Figure 10 presents the core
XPS spectra of N 1s of HCl-doped poly((AP-g-PEO-750)-
co-aniline) (3/1) and HCl-doped poly(o-anisidine). The
N 1s core has four fitted components for the core levels
of 398.20, 399.41, 400.83, and 402.31 eV of Figure 10a,
listed in Table 4. They can be assigned to the undoped
imine and amine, doped imine, and positively charged
amine, with the component concentrations 2.3, 53.3,
36.7, and 7.7%, respectively.23,35,37 The doping level
attained was 44.4%, which is much lower than the
62.4% of the HCl-doped poly(o-anisidine). (Its four N 1s
core components have the compositions of 2.8, 34.8, 53.6,
and 8.8% in Figure 10b.) The total oxidation level of
39.0% of the HCl-doped poly((AP-g-PEO-750)-co-aniline)
(3/1) is much lower than the 56.4% of HCl-doped poly-
A simple synthetic strategy to prepare various soluble
and processable copolymers of aniline and a macro-
monomer, aminophenol, grafted with various oligo-
(oxyethylene) side chains at the 3-position (AP-g-PEOs),
was developed. The copolymerization and copolymer
compositions were changed using various feed mole
ratios AP-g-PEO/aniline and oligo(oxyethylene) side
chain lengths. By increasing the aniline content of the
feed mole ratio or decreasing the side chain length of
PEO, the copolymerization produced longer chain co-
polymers with higher conjugation and conductivity. The
copolymer of poly((AP-g-PEO-750-co-aniline) with a feed
mole ratio of 3/1 was water-soluble and exhibited a
relatively high conductivity (0.12 S/cm).

6112 Hua and Ruckenstein
Macromolecules, Vol. 37, No. 16, 2004
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