Intramolecular charge transfer induced by deprotonation of hydroxyl groups in π-conjugated polymers with π-deficient aromatic rings

Article abstract of DOI:10.1016/j.reactfunctpolym.2010.11.014

π-Conjugated polymers consisting of p-phenylene (Ph) and 1,3,4-oxadiazole (Oz) or 4-octylphenyl-1,3,4-triazole (OctOz) rings [polymer-1: (Ph-Oz)_n and polymer-2: (Ph-OctTz)_n] and those consisting of 9,9-dihexyl-2,7-fluorene (Flu) and Oz or 1-(4-hydroxyphenyl)-1,3,4-triazole (HOPhTz) rings [polymer-3: (Ph-Oz-Py-Oz-Flu)_n and polymer-4: (Ph-HOPhTz-Py-HOPhTz-Flu)_n (Py = 2,5-pyridine)] were synthesized by polymerization promoted by polyphospholic acid and catalyzed by a Pd complex, respectively. Model compounds (model-1: Ph-Oz-Py-Oz-Ph, model-2: Ph-HOPhTz-Py-HOPhTz-Ph, and model-3: Ph-OctPhTz-Py-OctPhTz-Ph) were synthesized. The fact that the λ_max wavelengths of the polymers were longer than those of the model compounds suggests the expansion of the π-conjugation system along the polymer chain. The reaction of polymer-4 and model-2 with NaH caused the dehydration of the OH groups, which induced an intramolecular charge transfer (ICT) from the ONa group to the Tz ring. The ICT affected the optical properties of the polymers and the model compounds. The cast films of polymers obtained in this study underwent electrochemical reduction and oxidation.

Full text of DOI:10.1016/j.reactfunctpolym.2010.11.014

Reactive & Functional Polymers 71 (2011) 140–147
Contents lists available at ScienceDirect
Reactive & Functional Polymers
journal homepage: www.elsevier.com/locate/react
Intramolecular charge transfer induced by deprotonation of hydroxyl groups
in
p-conjugated polymers with p-deficient aromatic rings
⇑
Isao Yamaguchi , Hidehito Mitsuno
Department of Material Science, Faculty of Science and Engineering, Shimane University, 1060 Nishikawatsu, Matsue 690-8504, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
p
-Conjugated polymers consisting of p-phenylene (Ph) and 1,3,4-oxadiazole (Oz) or 4-octylphenyl-1,3,4-
Received 10 September 2010
Received in revised form 8 November 2010
Accepted 8 November 2010
Available online 20 November 2010
triazole (OctOz) rings [polymer-1: (Ph-Oz)n and polymer-2: (Ph-OctTz)n] and those consisting of 9,9-
dihexyl-2,7-fluorene (Flu) and Oz or 1-(4-hydroxyphenyl)-1,3,4-triazole (HOPhTz) rings [polymer-3:
(Ph-Oz-Py-Oz-Flu)n and polymer-4: (Ph-HOPhTz-Py-HOPhTz-Flu)n (Py = 2,5-pyridine)] were synthesized
by polymerization promoted by polyphospholic acid and catalyzed by a Pd complex, respectively. Model
compounds (model-1: Ph-Oz-Py-Oz-Ph, model-2: Ph-HOPhTz-Py-HOPhTz-Ph, and model-3: Ph-OctPhTz-
Py-OctPhTz-Ph) were synthesized. The fact that the kmax wavelengths of the polymers were longer than
Keywords:
Intramolecular charge transfer
Conjugated polymer
Triazole
those of the model compounds suggests the expansion of the
p-conjugation system along the polymer
chain. The reaction of polymer-4 and model-2 with NaH caused the dehydration of the OH groups, which
induced an intramolecular charge transfer (ICT) from the ONa group to the Tz ring. The ICT affected the
optical properties of the polymers and the model compounds. The cast films of polymers obtained in this
study underwent electrochemical reduction and oxidation.
Oxadiazole
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
occur more easily than that from the ONa group to the benzene ring.
According to this assumption,
sodium phenolato pendant group at the
show a smooth ICT from the ONa group to the
ring. Investigating the chemical properties of such
p
-conjugated polymers with a
-deficient aromatic ring
-deficient aromatic
-conjugated
Charge transfer (CT) type
much attention because of their potential use as materials for pho-
tovoltaic and electroluminescence devices [1–11]. Intramolecular
p
-conjugated polymers have received
p
p
p
CT (ICT) in
and electric properties; it can be caused by stimulating the
polymers with photo irradiation or heating [8]. -Conjugated poly-
mers that consist of either -excess or -deficient aromatic rings
p
-conjugated polymers significantly affects their optical
polymers can provide fundamental information for the develop-
ment of new emitting materials. In this study, triazole was used
p
as a
thermal stability, and facile N-substitution.
with -deficient aromatic rings such as triazole and oxadiazole
p-deficient aromatic ring because of its high electron affinity,
p
p
p
-Conjugated polymers
have been reported to cause ICT [4]. Thus, the introduction of a site
p
that sensitizes external stimuli to cause ICT and the formation of
have received considerable attention because of their strong blue
both p-excess and p-deficient aromatic rings in p-conjugated poly-
emission and high thermal stability [10,13–19]. However, to the
mers is a promising approach for the development of new CT-type
materials.
best of our knowledge, there has been no research on
polymers that shows ICT caused by the reaction of the polymers
with NaH. In this study, -conjugated polymers consisting of
9,9-dihexyl-2,7-fluorene groups and 1,3,4-oxadiazole (Oz) or 4-
hydroxyphenyl-1,3,4-triazole (HOPh-Tz) rings, which generate an
electron-donating ONa group through treatment with a base, were
synthesized. The triazole ring located between two benzene rings at
the 2,5-positions has been reported to be orthogonal to them [20],
which reduces the steric crowding between the phenylene rings at-
p-conjugated
Recently, polyphenoles with oligo(p-phenylene) pendant groups
and their significant solvatochromism after the deprotonation of
the OH group for the polymers with NaH were reported [12]. In
other words, the emission color of the deprotonated polymers can
be tuned by solvents. The wavelength at which the emission peak
was observed shifted to a longer wavelength with an increase in
the donor number (DN) of the solvents. These phenomena were
attributed to ICT from the ONa group to the adjacent benzene rings.
p
tached to triazole and effectively limits the -conjugation range. In
p
ICT from the ONa group to the
p-deficient aromatic ring should
this study, to obtain polymers with a long p-conjugation system, a
2,5-pyridine (Py) ring was placed between the Oz and Tz rings in
the polymer main chain. The Py ring can reduce the steric crowding
with the Oz and Tz rings because the number of o-H atoms in the Py
ring is less than that in the p-phenylene ring.
⇑
Corresponding author.
E-mail address: iyamaguchi@riko.shimane-u.ac.jp (I. Yamaguchi).
1381-5148/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.reactfunctpolym.2010.11.014

I. Yamaguchi, H. Mitsuno / Reactive & Functional Polymers 71 (2011) 140–147
141
The synthesis and optical, electrochemical, and thermal proper-
ties of CT-type -conjugated polymers with -deficient Tz or Oz
rings and the corresponding model compounds are reported.
collected by filtration, and dried under vacuum to obtain monomer-
2 as a white powder (1.3 g, 86%). 1H NMR (400 MHz, DMSO-d6): d
10.1 (s, 1H), 9.89 (s, 1H), 8.44 (s, 1H), 7.95 (d, J = 8.4 Hz, 1H), 7.83
(dd, J = 2.0 Hz and 8.4 Hz, 1H), 7.60–7.63 (m, 4H), 7.35 (d,
J = 8.0 Hz, 4H), 7.26 (d, J = 8.4 Hz, 2H), 7.15 (d, J = 8.4 Hz, 2H),
6.82 (d, J = 8.8 Hz, 2H), 6.74 (d, J = 8.4 Hz, 2H). 13C NMR
(100 MHz, DMSO-d6): d 159.3, 158.0, 154.3, 152.1, 150.0, 148.0,
145.3, 131.6, 130.3, 129.3, 129.2, 126.6, 126.1, 125.9, 125.3,
123.5, 118.7, 117.8, 116.7, 116.7, 116.5, 115.9, 115.7, 115.0,
114.5, 111.3. Calcd for C33H21N7Br2O2ꢀ0.4H2O: C, 56.03; H, 2.99;
N, 13.86. Found; C, 55.77; H, 3.22; N, 13.42.
p
p
2. Experimental
2.1. General
Solvents were dried, distilled, and stored under nitrogen. Subse-
quently, 1, 2, and 3 were synthesized according to the literature
[21]. Other reagents were purchased and used without further
purification. Reactions were carried out with standard Schlenk
techniques under nitrogen.
2.5. Synthesis of model-2
IR and NMR spectra were recorded on a JASCO FT/IR-660 PLUS
spectrophotometer with a KBr pellet and a JEOL AL-400 spectrom-
eter, respectively. Elemental analysis was conducted on a Yana-
gimoto MT-5 CHN corder. UV–vis and PL spectra were obtained
by a JASCO V-560 spectrometer and a JASCO FP-6200, respectively.
Quantum yields were calculated by using a diluted ethanol solu-
tion of 7-dimethylamino-4-methylcoumarin as the standard. Cyc-
lic voltammetry was performed in a DMSO solution containing
0.10 M [Et4N]BF4 with a Hokuto Denko HSV-110. Pt plate and Ag
wire were used as working and counter electrodes and reference
electrode, respectively. TGA curves were obtained by a Rigaku
Thermo plus TG8120. The ground-state geometries of model com-
pounds were optimized with the Gaussian 09 computer program at
the density functional theory (DFT) level using the B3LYP/6-31G*
functional [22].
Model-2 was synthesized using a procedure similar to that used
for monomer-2. 1H NMR (400 MHz, DMSO-d6): d 10.1 (s, 1H), 9.85
(s, 1H), 8.45 (s, 1H), 7.95 (d, J = 8.0 Hz, 1H), 7.83 (dd, J = 2.4 Hz
and 8.0 Hz, 1H), 7.39–7.42 (m, 10H), 7.25 (d, J = 8.8 Hz, 2H), 7.14
(d, J = 8.8 Hz, 2H), 6.82 (d, J = 8.8 Hz, 2H), 6.74 (d, J = 8.8 Hz, 2H).
13C NMR (100 MHz, DMSO-d6): d 158.4, 157.8, 154.9, 153.1,
151.9, 148.0, 147.2, 136.3, 129.7, 129.4, 129.3, 128.4, 126.9,
126.1, 125.2, 123.7, 116.4, 115.6. Calcd for C33H23N7O2ꢀ0.3H2O: C,
71.42; H, 4.29; N, 17.67. Found; C, 71.50; H, 4.11; N, 17.39.
2.6. Synthesis of model-3
Model-3 was synthesized using a procedure similar to that used
for monomer-1. 1H NMR (400 MHz, DMSO-d6): d 8.51 (s, 8H),8.24
(d, J = 7.6 Hz, 4H), 7.82 (d, J = 7.6 Hz, 2H), 7.70 (t, J = 8.0 Hz, 4H),
7.30 (s, 4H), 2.64 (t, J = 8.0 Hz, 4H), 1.61 (t, J = 8.0 Hz, 4H), 1.24–
1.30 (m, 20H), 0.83 (t, J = 7.2 Hz, 6H). 13C NMR (100 MHz, DMSO-
d6): d169.2, 166.8, 149.3, 138.9, 132.9, 132.7, 132.5, 131.1, 130.7,
127.8, 122.2, 120.3. Calcd for C33H23N7O2ꢀ0.6H2O: C, 70.73; H,
4.35; N, 17.50. Found; C, 70.90; H, 4.60; N, 17.88.
2.2. Synthesis of monomer-1
1 (0.11 g, 0.20 mmol) was dissolved in polyphospholic acid
(PPA) (20 mL) at 140 °C. After the solution was stirred at that tem-
perature for 72 h, it was poured in water (300 mL). The resulting
precipitate was collected by filtration, washed with water and
methanol, and dissolved in DMSO at 100 °C. When the DMSO solu-
tion was cooled to room temperature, a gray solid was precipitated
from the solution. The precipitate was collected by filtration,
washed with methanol, and dried under vacuum to obtain mono-
mer-1 as a white powder (0.077 g, 73%). 1H NMR (400 MHz, CDCl3):
d 9.47 (s, 1H), 8.72 (d, J = 6.8 Hz, 1H), 8.47 (d, J = 8.4 Hz, 1H), 8.06–
8.11 (m, 4H), 7.84 (d, J = 8.0 Hz, 4H). 13C NMR (100 MHz, CDCl3): d
155.3, 144.3, 141.6, 140.1, 138.9, 135.2, 131.8, 131.3, 130.1, 128.5,
128.2, 124.3, 122.6, 122.3, 109.5. Calcd for C21H11N5Br2O2ꢀ0.5H2O:
C, 47.22; H, 2.26; N, 13.11. Found: C, 47.20; H, 2.65; N, 12.75.
2.7. Synthesis of polymer-1
Terephthaloyl chloride (1.0 g, 5.0 mmol) was added to an NMP
solution (100 mL) of terephthalic dihydrazide (0.97 g, 5.0 mmol)
by portions over 2 h in an ice bath. The reaction solution was stir-
red at 0 °C for 2 h and at room temperature for 50 h and was
poured in water (500 mL). The resulting precipitate was washed
with acetone (200 mL) two times, collected by filtration, and dried
under vacuum to obtain a precursor polymer (1.61 g, 100%). The
precursor polymer (0.81 g, 2.5 mmol) was dissolved in PPA
(100 mL). The reaction solution was stirred at 175 °C for 72 h and
poured in water (500 mL). The resulting precipitate was washed
with methanol (300 mL) and dried under vacuum to obtain poly-
mer-1 as a light brown powder (0.39 g, 54%). 1H NMR (400 MHz,
D2SO4): d 8.80. Calcd for C16H8N4O2ꢀ0.5H2O: C, 64.65; H, 3.05; N,
18.85. Found; C, 64.48; H, 3.18; N, 18.64.
2.3. Synthesis of model-1
Model-1 was synthesized using a procedure similar to that used
for monomer-1. 1H NMR (400 MHz, DMSO-d6): d 9.54 (s, 1H), 8.78
(dd, J = 2.0 Hz and 8.0 Hz, 1H), 8.53 (d, J = 8.4 Hz, 1H), 8.19 (dd,
J = 6.0 Hz and 9.2 Hz, 4H), 7.66–7.69 (m, 6H). 13C NMR (100 MHz,
DMSO-d6): d 165.3, 146.6, 136.7, 136.1, 132.3, 129.5, 128.8, 128.1,
127.8, 127.1, 125.7, 125.5, 123.9, 123.4, 123.2, 122.6, 122.3, 121.1,
119.7, 118.9, 117.4. Calcd for C21H13N5O2ꢀ0.5H2O: C, 67.02; H,
3.75; N, 18.61. Found; C, 66.89; H, 4.01; N, 18.25.
2.8. Synthesis of polymer-2
2.4. Synthesis of monomer-2
A mixture of polymer-1 (0.32 g, 1.1 mmol) and 4-octylaniline
(1.3 g, 10 mmol) was stirred at 170 °C for 72 h and poured in water
(500 mL). The resulting precipitate was washed with methanol
(300 mL) two times, collected by filtration, and dried under vac-
uum to obtain polymer-2 as a light brown powder (0.47 g, 64%).
1H NMR (400 MHz, D2SO4): d 9.31 (4H), 7.94–8.54 (4H). Calcd for
CaCl2 (2.0 g, 18.0 mmol) was added to an NMP (30 mL) solution
of monomer-1 (1.1 g, 2.1 mmol) and p-anisidine (3.7 g, 30 mmol).
After the reaction mixture was stirred at 175 °C for 96 h, the sol-
vent was removed under vacuum. The resulting solid was dis-
solved in methanol (30 mL) and the solution was refluxed for
72 h. The precipitate from the solution was washed with methanol,
C44H50N6: C, 79.72; H, 7.69; N, 12.68. Found: C, 78.99; H, 7.00; N,
12.15.

142
I. Yamaguchi, H. Mitsuno / Reactive & Functional Polymers 71 (2011) 140–147
2.9. Synthesis of polymer-3
formation from the oxadiazole ring to the triazole ring accompa-
nied by hydrolysis of the OCH3 group to yield monomer-2 and
model-2, respectively (Scheme 1c). The reaction 3 with p-octylani-
line at a 1:2 molar ratio in the presence of PPA yielded model-3
(Scheme 1d). These synthesis results are summarized in Table 1.
The polymerization of terephthaloyl chloride with 1,4-benzene
dihydrazide followed by treatment with PPA yielded polymer-1
Monomer-1 (0.26 g, 0.50 mmol) and 9,9-dihexyl-2,7-diboronic
acid trimethylene ester (0.25 g, 0.50 mmol) were dissolved in
20 mL of dry NMP under N2. To the solution were added K2CO3(aq)
(2.0 M, 4 mL; N2 bubbled before use) and Pd(PPh3)4 (0.058 g,
0.050 mmol). After the mixture was stirred for 72 h at 100 °C, the
solvent was removed under vacuum. The resulting solid was
washed with water and acetone. Polymer-3 was collected by filtra-
tion, dried under vacuum, and obtained as a light brown powder
(0.34 g, 97%). 1H NMR (400 MHz, DMSO-d6): d 7.71–8.34 (17H),
2.13 (4H), 1.07 (12H), 0.74 (10H). Calcd for C46H43N5O2ꢀ0.5H2O:
C, 78.16; H, 6.27; N, 9.91. Found: C, 77.84; H, 6.15; N, 10.09.
Table 1
Synthesis results and optical properties.
Yield,
%
g
sp/c,
Absorption, nm
PL, nm
dL gꢁl
In
In film
solution
2.10. Synthesis of polymer-4
Monomer-
1
Monomer-
2
Model-1
Model-2
Model-3
86
86
–
–
–
–
–
–
–
–
Polymer-4 was synthesized using a procedure similar to that
used for polymer-3.
87
79
65
–
–
–
325c
308c
324c
–
–
–
410c
1H NMR (400 MHz, DMSO-d6): d 8.49 (1H), 7.66–7.90 (14H),
7.08–7.16 (5H), 6.78–6.85 (5H), 2.12 (4H), 1.06 (12H), 0.74 (10H).
Calcd for C58H53N7O2ꢀH2O: C, 77.57; H, 6.17; N, 10.92. Found: C,
77.90; H, 5.89; N, 10.61.
390c
349, 368,
387c
Polymer-1
Polymer-2
54
64
–
346d
347d
–
407d
2.02a
364,
380f
–
407d
g
g
Polymer-3
Polymer-4
97
93
1.24b
1.71b
345e
357
407 (408)
407 (542)
3. Results and discussion
359
(357)e
3.1. Synthesis
In conc. H2SO4 at 30 °C (c = 0.10 g dLꢁ1).
In NMP at 30 °C (c = 0.10 g dLꢁ1).
In NMP.
a
b
c
d
e
f
The reaction of 4-bromobenzoyl chloride and benzoyl chloride
with 2,5-pyridine dihydrazide at a 2:1 molar ratio followed by
treatment with thionyl chloride yielded nonomer-1 and model-1,
respectively (Scheme 1a and b). The reaction of nonomer-1 and
model-1 with p-anisidine in the presence of CaCl2 caused the trans-
In conc. H2SO4.
In NMP. kmax value after treatment with NaH was shown in parenthesis.
Shoulder peak.
In NMP. kem value after treatment with NaH was shown in parenthesis.
g
O
O
O
O
O
O
C Cl
O
H
H
H H
H H
+
H N N C Ar C N NH
R
C N N C Ar C N N C
R
2 R
(a)
2
2
R = Br, Ar =
: 1
: 2
: 3
N
N
R = H, Ar =
R = H, Ar =
O
O
O
O
N N
O
N N
H H
H H
PPA
R
C N N C Ar C N N C
R
R
R
Ar
R
(b)
(c)
O
R = Br, Ar =
R = H, Ar =
: monomer-1
: model-1
N
N
N N
N N
N
N N
O
N N
+ 2
CaCl
2
Ar
R
R
Ar
R
H N
OCH
3
2
N
O
OH
OH
R = Br, Ar =
: monomer-2
: model-2
N
R = H, Ar =
N
O
O
O
O
N N
N
N N
H H
C N N C
H H
C N N C
PPA
+ 2
(d)
H N
C H
8 17
2
N
C H
C H
8 17
8
17
model-3
Scheme 1. Synthesis of monomers and model compounds.

I. Yamaguchi, H. Mitsuno / Reactive & Functional Polymers 71 (2011) 140–147
143
O
O
O
C Cl
O
O
C
O
O
O
H
H
H H
C N N C
H H
C N N
+
n
n
(a) Cl C
H N N C
C N NH
2
2
n
O
C
O
O
O
H H
N N
N N
O
H H
C N N C
C N N
O
n
PPA
n
polymer-1
N N
N N
N
H2N
OC8H17
PPA
polymer-1
(b)
N
n
C H
C H
8
8
17
poly1m7er-2
Scheme 2. Synthesis of polymers consisted of p-phenylene and oxadiazole or triazole rings.
Table 2
Solubility of monomers, model compounds, and polymersa.
polymer-1
CHCI3
DMF
DMSO
NMP
CF3COOH
H2SO4
Monomer-1
Monomer-2
Model-1
Model-2
Model-3
Polymer-1
Polymer-2
Polymer-3
Polymer-4
ꢁ
ꢁ
++
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
++
++
++
++
ꢁ
++
++
++
++
ꢁ
++
++
++
++
ꢁ
++
++
++
++
++
ꢁ
++
++
++
++
++
++
++
++
++
polymer-4
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
++
ꢁ
++
+
++
+
++
++
++
a
++: soluble, +: partly soluble, ꢁ: insoluble.
ν(O-H)
model-2
(Scheme 2a). The reaction of polymer-1 with 4-octylaniline caused
the conversion from the Oz ring to the Tz ring to yield polymer-2
(Scheme 2b). The conversion of the oxazole rings in monomer-1,
model-1, and polymer-1 to the triazole rings in monomer-2,
model-2, and polymer-2 requires an excess amount of amine because
of the low reaction efficiency. The solubilities of the obtained mono-
mers, model compounds, and polymers are summarized in Table 2.
Polymer-1 and polymer-2 were soluble in acidic solvents such as
trifluoroacetic acid and sulfuric acid but insoluble in organic
solvents.
ν(O-H)
model-3
To obtain polymers soluble in non-acidic organic solvents, the
Pd-complex-catalyzed polymerization of monomer-1 and mono-
mer-2 with 9,9-dihexyl-2,7-diboronic acid trimethylene ester was
carried out and resulted in yields of 97% and 93% for polymer-3
and polymer-4, respectively (Scheme 3). Polymer-3 was completely
soluble in polar organic solvents such as N,N-dimethylformamide
(DMF), dimethyl sulfoxide (DMSO), and N-methyl-2-pyrollidone
(NMP), whereas polymer-4 was partly soluble in these solvents.
4000
3000
2000
1500
1000
500
-1
wave number/ cm
Fig. 1. IR spectra of polymer-1, polymer-4, model-2, and model-3.
N N
O
N N
O
O
O
O
O
Pd(PPh3)4
K2CO3(aq)
+
+
monomer-1
monomer-2
B
H C
B
N
n
C H
13
6
6
13
C H
H
H
C
C
6
13
13
6
polymer-3
N N
N
N N
N
O
O
O
O
Pd(PPh3)4
K2CO3(aq)
B
H C
B
N
n
13
C H
6
13
6
13
C H
6
13
6
OH
OH
polymer-4
Scheme 3. Synthesis of polymers with 9,9-dihexyl-2,7-fluorene and oxadiazole or triazole rings.

144
I. Yamaguchi, H. Mitsuno / Reactive & Functional Polymers 71 (2011) 140–147
The intrinsic viscosities for a sulfuric acid solution of polymer-2
the p-phenylene protons were larger than those of the pyridine pro-
tons because the phenylene rings are close to the ONa group. The
peak corresponding to the OH protons of polymer-4 was not ob-
served in the 1H NMR spectrum. The reason for the disappearance
is unclear. However, the peaks corresponding to the benzene and
pyridine protons in polymer-4 shifted to high magnetic field posi-
tions after treatment with NaH because of the generation of the elec-
tron-donating ONa groups, as shown in Fig. 3b. These results support
thepresenceof OH groupsin polymer-4. Additionally, thepresenceof
OH groups in polymer-4 is supported by the fact that IR absorption
and NMP solutions of polymer-3 and polymer-4 at a concentration
of 0.10 g dLꢁ1 were 2.02, 1.24, and 1.71 dL gꢁ1, respectively. GPC
measurements could not be carried out because of the low solubil-
ities of the polymers in the eluent.
3.2. IR and NMR spectra
Fig. 1 depicts the IR spectra of polymer-1, polymer-4, model-2,
and model-3. The disappearance of the peak corresponding to
(C@O) in the IR spectra of polymer-1 and model-3 suggests that
that can be assigned to m(OAH) of model-2 and polymer-4 was ob-
served at the same wave number, as mentioned above.
m
the triazole ring formation reaction proceeded to completion. The
IR spectrum of polymer-4 resembles that of model-2. The broad
absorption at around 3100 cmꢁ1 was assigned to
m(OAH) of the
3.3. UV–vis and PL spectra
hydrogen bonding OH groups in polymer-4 and model-2.
Fig. 2 depicts the 1H NMR spectra of polymer-1, polymer-2, and
model-3 in CF3COOD. The peak assignments are indicated in the fig-
ure. The peaks corresponding to the protons of the benzene rings at
the 2,5-positions of the triazole ring in polymer-2 were observed at
higher magnetic field positions than in polymer-1. Thus, the elec-
tron negativity of the triazole ring is lower than that of the oxadi-
azole ring [23]. The peaks corresponding to the protons of the
benzene rings and hexyl groups in polymer-2 were observed at al-
most the same positions as those in model-3.
Fig. 4 depicts the UV–vis spectra of model-2 and polymer-4 in
N-methyl-2-pyrrolidone (NMP) before and after the addition of
an excess amount of NaH. The wavelength at which the absorption
maximum (kmax) for polymer-4 was observed was longer than that
of model-2, suggesting that the p-conjugation system of polymer-4
expanded along the polymer chain. The kmax values for model-2 and
polymer-4 barely changed after the deprotonation of the OH
groups. However, new broad absorptions appeared in the ranges
of 370–430 and 400–480 nm in the UV–vis spectra for model-3
and polymer-4, respectively.
The kmax value for the NMP solution of polymer-4 was larger
than that for the sulfuric acid solution of polymer-2. These observa-
tions correspond to the smaller number of o-protons in the 2,5-
pyridine ring, which reduced the twisting of the polymer chain.
However, the kmax value for the cast film of polymer-2 (364 nm)
was larger than that for polymer-4 (359 nm). These observations
Fig. 3 depicts the 1H NMR spectraof model-2 and polymer-4 before
and after the deprotonation of the OH groups with NaH in DMSO-d6.
The peak integral between the aromatic and aliphatic protons sup-
ports the structures of the polymer and model compound. The peaks
corresponding to the OH groups of model-2 disappeared after
treatment with NaH, suggesting that the deprotonation proceeded
to completion. The benzene and pyridine protons in model-2 shifted
to high magnetic field positions after the deprotonation because of
the generation of electron-donating ONa groups. The peak shifts of
correspond to the assumption that polymer-2 forms a
p-stacked
structure in film. The fact that the powder X-ray diffraction
Fig. 2. 1H NMR spectra of polymer-1, polymer-2, and model-3 in CF3COOD.

I. Yamaguchi, H. Mitsuno / Reactive & Functional Polymers 71 (2011) 140–147
145
Fig. 3. 1H NMR spectra of model-2 and polymer-4 before and after the deprotonation of the OH groups with NaH in DMSO-d6.
polymer-4
1.2
1.0
deprotonated
model-2
polymer-4 deprotonated
model-2
polymer-4
model-2
0.8
0.6
0.4
0.2
0
deprotonated
polymer-4
deprotonated
model-2
250
300
350
400
450
500
300
350
400
450
500
550
600
650
700
Wavelength/ nm
Wavelength/ nm
Fig. 4. UV–vis spectra of model-2 and polymer-4 in NMP before and after the
addition of an excess amount of NaH.
Fig. 5. PL spectra of model-2 and polymer-4 in NMP before and after the addition of
an excess amount of NaH.
(XRD) pattern of polymer-2 showed peaks at 8.6ꢀ and 21.3ꢀ in
contrast to the broad XRD pattern of polymer-4 supports the occur-
rence of
p-stacking for polymer-2 in film. Rigid p-conjugated poly-
mers with long alkyl side chains have been reported to form

146
I. Yamaguchi, H. Mitsuno / Reactive & Functional Polymers 71 (2011) 140–147
p-stacked structures, which causes a bathochromic shift of kmax
[24–30].
1.68
polymer-3
Fig. 5 depicts the photoluminescence (PL) spectra of model-2 and
1.5
1.0
0.5
polymer-4 in N-methyl-2-pyrrolidone (NMP) before and after the
addition of an excess amount of NaH. The PL peak positions of mod-
el-2 and polymer-4 in NMP shifted to longer wavelengths with the
deprotonation of the OH groups. The degrees of bathochromic shift
(Dkem) in the PL peak positions for model-2 and polymer-4 were
-2.0 -1.5
-0.5
-0.5
-1.0
125 and 135 nm, respectively. The kem position of polyphenylene
withthehydroxy[1,10;40,100]terphenylunit(polymer-5(OH))hasbeen
reported to shift by 110 nm to a longer wavelength after the depro-
tonation of the OH group in DMF [12].
0.5
1.0
1.5
-1.24
-1.27
-1.63
polymer-4
0.49
0.28
I
0.1
-0.1
-0.2
-0.3
-2.0
-1.5
-1.0
OH
ONa
H
0.5
1.0
/ V
1.5
-1.89
E
n
13
n
C H
C H
6 13
H
C
C
13 6
6
13
6
-1.55
polymer-5(OH),
λem = 412 nm in
DMF (DN = 26.6)
polymer-5(ONa),
λem = 522 nm in
DMF (DN = 26.6)
-2.33
The fact that the
Dkem value in polymer-4 was larger than that in
Fig. 6. Cyclic voltammograms for the cast films of polymer-3 and polymer-4 in an
acetonitrile solution (0.10 M) of [Et4N]BF4. The scan rate was 50 mV sꢁ1
polymer-5 ( kem = 110 nm) apparently corresponds to the assump-
D
.
tion that the charge transfer from the ONa group to the electron-
accepting triazole ring occurs more easily than that from the
ONa group to the adjacent benzene rings. The PL peak position of
polymer-3 (408 nm) was essentially the same as that of polymer-4
(407 nm). However, the PL peak position of polymer-3 was almost
unchanged by the treatment with NaH. This result confirms that
the bathochromic shift in the PL peak position of polymer-4 after
treatment with NaH can be attributed to the formation of the
vs. Ag+/Ag corresponding to the electrochemical oxidation of the
2,7-diphenylfluorene unit. However, the corresponding reduction
(p-dedoping) peak did not appear in the cyclic voltammograms,
likely because of the formation of a stable adduct between the
electrochemically oxidized polymer and BFꢁ4 . Electrochemically oxi-
dized p-conjugated polymers have been reported to form stable ad-
ducts with BFꢁ4 during cyclic voltammetry measurements [32]. The
electrochemical reaction was accompanied by electrochromism.
The yellow cast film of the polymer changed to reddish brown after
electrochemical oxidation. The cyclic voltammogram of polymer-3
showed two peaks at –1.24 and –1.63 V vs. Ag+/Ag corresponding
to the electrochemical reduction of the oxadiazole and pyridine
rings, respectively. As depicted in Fig. 6b, two peaks corresponding
to the electrochemical oxidation of the two OH groups in polymer-4
were observed at 0.28 and 0.49 V vs. Ag+/Ag. The cyclic voltammo-
gram of polymer-4 showed two peaks at –1.55 and –2.23 V vs. Ag+/
Ag corresponding to the electrochemical reduction of the triazole
and pyridine rings, respectively, which were coupled with the peaks
at –1.27 and -1.89 V vs. Ag+/Ag, respectively. The results show that
the cathodic potential of the peak corresponding to the electro-
chemical reduction of the pyridine ring of polymer-4 was higher
than that of polymer-3 due to the lower electronic negativity of
the triazole ring compared to the oxadiazole ring.
ONa group. The PL intensities of model-2
mer-4 = 0.006) after deprotonation were considerably lower
than those of model-2 ( = 0.21) and polymer-4 ( = 0.35) before
deprotonation because of the ICT in the deprotonated species. ICT
in -conjugated polymers has been reported to reduce their PL
(U = 0.004) and poly-
(U
U
U
p
emission efficiencies [31].
3.4. Computational calculations
To obtain information on the ICT in model-2 and polymer-4 after
deprotonation of the OH groups, the molecular orbitals of model-
4(OH) and model-4(ONa) were compared with computational
calculations at the density functional theory (DFT) level. Model-
4(OH) and model-4(ONa) with symmetric structures are suitable
for rapid calculations.
N N
N
N N
N
N N
N
N N
N
3.6. Thermal properties
ONa
ONa
OH
OH
Fig. S2 shows TGA curves of polymer-3 and polymer-4. The
weight loss of the polymers in the range of 80–300 °C corresponds
to the thermal loss of hydrated water in the polymers. Polymer-4
started a gradual weight loss due to the thermal decomposition
of the polymer chain at 300 °C and 95% weight of the polymer
caused thermal decomposition at 600 °C. In contrast, polymer-3
showed a high thermal stability. Approximately 50% of the weight
of the polymer remained at 600 °C. The higher thermal stability of
polymer-3 appeared to be due to its rigid structure.
model-4(ONa)
model-4(OH)
Fig. S1 shows the calculated HOMOs of model-4(OH) and model-
4(ONa). In the case of model-4(ONa), there are distributed electrons
between the triazole ring and the phenolate ring. In contrast, there
are no distributed electrons between the triazole ring and the phe-
nolate ring in model-4(OH). These observations support the
assumption that ICT between the phenolate ring and the triazole
ring occurred in the deprotonated species.
3.5. Cyclic voltammograms
4. Conclusion
Fig. 6 depicts cyclic voltammograms for the cast films of poly-
mer-3 and polymer-4. Polymer-3 showed an anodic peak at 1.68 V
p
-Conjugated polymers with Oz and HOPhTz groups were ob-
tained by polymerization promoted by polyphospholic acid and

I. Yamaguchi, H. Mitsuno / Reactive & Functional Polymers 71 (2011) 140–147
147
[8] B.C. Thompson, Y.G. Kim, T.D. MaMarley, J.R. Reynolds, J. Am. Chem. Soc. 128
(2006) 12714.
[9] A. Iraqi, G.W. Barker, D.F. Pickup, React. Funct. Polym. 66 (2006) 195.
[10] H. Wang, Z. Li, B. Huang, Z. Jiang, Y. Liang, H. Wang, J. Qin, G. Yu, Y. Liu, Y. Song,
React. Funct. Polym. 66 (2006) 993.
[11] C. Winder, N.S. Sariciftci, J. Mater. Chem. 14 (2004) 1077.
[12] I. Yamaguchi, K. Goto, M. Sato, Macromolecules 42 (2009) 7836.
[13] Y.-S. Kim, D.G. Kim, N.Y. Kwon, H.J. Kim, M.S. Choi, M. Lee, T.S. Lee, React.
Funct. Polym. 70 (2010) 223.
[14] J. Choi, B. Lee, J.H. Kim, Synth. Met. 159 (2009) 1922.
[15] C.S. Wu, Y. Chen, Macromolecules 42 (2009) 3729.
[16] J.H. Kim, H.S. Lee, Synth. Met. 157 (2007) 1040.
[17] H.H. Sun, C.Y. Mei, Q.G. Zhou, Z. Lin, D.G. Ma, L.X. Wang, X.B. Jing, F.S. Wang, J.
Polym. Sci. Part A Polym. Chem. 44 (2006) 3469.
catalyzed by a Pd complex. The expansion of the
p-conjugation
system of the polymers along the polymer chain was confirmed
by the results showing that the kmax wavelengths of the polymers
were longer than those of the corresponding model compounds.
The reaction of the polymer with HOPhTz groups with NaH caused
the deprotonation of the OH groups, which led to ICT from the ONa
group to the Tz ring. The ICT affected the optical properties of the
polymer. The absorption and PL peak positions of the deprotonated
polymer shifted toward longer wavelengths compared with the
polymer before deprotonation. The cast films of the polymers ob-
tained in this study underwent electrochemical reduction and oxi-
dation. The results obtained in this study indicate that the ICT
[18] S.-H. Chen, Y. Chen, Macromolecules 38 (2005) 53.
[19] S. Janietz, J. Barche, A. Wedel, D. Sainova, Macromol. Chem. Phys. 205 (2004)
1916.
[20] S.-H. Chen, C.-S. Shiau, L.-R. Tsai, Y. Chen, Polymer 47 (2006) 8436.
[21] P.M. Hergenrother, Macromolecules 3 (1970) 10.
caused by the deprotonation of an OH group with a base in p-con-
jugated polymers is a useful phenomenon for the development of
new functional materials.
[22] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman,
J.A. Montgomery Jr., T. Vreven, K.N. Kudin, J.C. Burant, J.M. Millam, S.S. Iyengar,
J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G.A.
Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa,
M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J.E. Knox,
H.P. Hratchian, J.B. Cross, C. Adamo, J. Jaramillo, R. Gomperts, R.E. Stratmann,
O. Yazyev, A.J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, P.Y. Ayala, K.
Morokuma, G.A. Voth, P. Salvador, J.J. Dannenberg, V.G. Zakrzewski, S.
Dapprich, A.D. Daniels, M.C. Strain, O. Farkas, D.K. Malick, A.D. Rabuck, K.
Raghavachari, J.B. Foresman, J.V. Ortiz, Q. Cui, A.G. Baboul, S. Clifford, J.
Cioslowski, B.B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R.L.
Martin, D.J. Fox, T. Keith, M.A. Al-Laham, C.Y. Peng, A. Nanayakkara, M.
Challacombe, P.M. W. Gill, B. Johnson, W. Chen, M. W. Wong, C. Gonzalez, J.A.
Pople, Gaussian 03, Revision A.1, Gaussian, Inc., Pittsburgh, 2003.
[23] E. Jansson, P.C. Jha, H. Agren, Chem. Phys. 330 (2006) 166.
[24] T. Yamamoto, B.-L. Lee, Macromolecules 35 (2002) 2993.
[25] T. Yasuda, Y. Sakai, S. Aramaki, T. Yamamoto, Chem. Mater. 17 (2005) 6060.
[26] T. Yamamoto, A. Mahmut, M. Abe, S. Kuroda, T. Imase, S. Sasaki, J. Polym. Sci.
Part B Polym. Phys. 43 (2005) 2219.
Acknowledgment
The authors wish to thank Dr. H. Shiratori in their department
for help with DFT measurements.
Appendix A. Supplementary material
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.reactfunctpolym.2010.11.014.
References
[1] R. Po, M. Maggini, N. Camaioni, J. Phys. Chem. C 114 (2010) 695.
[2] F. Laquai, Y. Park, J. Kim, T. Basche, Macromol. Rapid Commun. 30 (2009) 1203.
[3] T. Umeyama, T. Takamatsu, N. Tezuka, Y. Matano, Y. Araki, T. Wada, O.
Yoshikawa, T. Sagawa, S. Yoshikawa, H. Imahori, J. Phys. Chem. C 113 (2009)
10798.
[4] T. Morikita, T. Yasuda, T. Yamamoto, React. Funct. Polym. 68 (2008) 1483.
[5] S. Wakim, B.R. Aich, Y. Tao, M. Leclerc, Polym. Rev. 48 (2008) 432.
[6] A. Cravino, Poym. Int. 56 (2007) 943.
[27] T. Yamamoto, S. Otsuka, K. Namekawa, H. Fukumoto, I. Yamaguchi, T. Fukuda,
N. Asakawa, T. Yamanobe, T. Shiono, Z. Cai, Polymer 47 (2006) 6038.
[28] T. Yasuda, K. Namekawa, T. Iijima, T. Yamamoto, Polymer 48 (2007) 4375.
[29] T. Morikita, I. Yamaguchi, T. Yamamoto, Adv. Mater. 13 (2001) 1862.
[30] R.S. Ashraf, E. Klem, J. Polym. Sci. Part A Polym. Chem. 43 (2005) 6445.
[31] X. Zhang, A.S. Shetty, S.A. Jenekhe, Macromolecules 32 (1999) 7422.
[32] M. Ranger, M. Leclerc, Can. J. Chem. 76 (1998) 1571.
[7] R. Gomez, D. Veldman, R. Blanco, C. Seoane, J.L. Segura, R.A.J. Janssen,
Macromolecules 40 (2007) 2760.