Anion conductive aromatic copolymers from dimethylaminomethylated monomers: Synthesis, properties, and applications in alkaline fuel cells

Article abstract of DOI:10.1021/acs.macromol.6b00408

A novel series of anion conductive aromatic copolymers were synthesized from preaminated monomers (2,5-, 3,5-, or 2,4-dichloro-N,N-dimethylbenzylamine), and their properties were investigated for alkaline fuel cell applications. The targeted copolymers (QPE-bl-11a, -11b, and -11c) were synthesized via nickel-mediated Ullmann coupling polymerization, followed by quaternization and ion exchange reactions. Unlike the conventional method involving chloromethylation or bromination, this method provided copolymers with well-defined chemical structure. The hydrophilic components of the copolymers were composed of chemically stable phenylene main chain modified with high-density ammonium groups. Oligo(arylene ether sulfone ketone)s were employed as a hydrophobic block. QPE-bl-11a gave tough and bendable membranes by solution casting. The obtained membrane with the highest ion exchange capacity value (IEC = 2.47 mequiv g^-1) showed high hydroxide ion conductivity (130 mS cm^-1) in water at 80 °C. The QPE-bl-11a membrane showed reasonable alkaline stability in 1 M KOH aqueous solution for 1000 h at 60 °C. A platinum-free fuel cell was successfully operated with hydrazine as a fuel, the QPE-bl-11a as a membrane, and an electrode binder. The maximum power density of 380 mW cm^-2 was achieved at a current density of 1020 mA cm^-2 with O₂.

Full text of DOI:10.1021/acs.macromol.6b00408

Article
pubs.acs.org/Macromolecules
Anion Conductive Aromatic Copolymers from
Dimethylaminomethylated Monomers: Synthesis, Properties, and
Applications in Alkaline Fuel Cells
Ryo Akiyama,† Naoki Yokota,§ Eriko Nishino,∥ Koichiro Asazawa,∥ and Kenji Miyatake*,†,‡
‡
†Fuel Cell Nanomaterials Center and Clean Energy Research Center, University of Yamanashi, 4 Takeda, Kofu 400-8510, Japan
§Takahata Precision Japan Co. Ltd., 390 Maemada, Sakaigawa, Fuefuki, Yamanashi 406-0843, Japan
∥Frontier Technology R&D Division, Daihatsu Motor Co. Ltd., 3000 Ryuo, Gamo, Shiga 520-2593, Japan
S
* Supporting Information
ABSTRACT: A novel series of anion conductive aromatic
copolymers were synthesized from preaminated monomers
(2,5-, 3,5-, or 2,4-dichloro-N,N-dimethylbenzylamine), and
their properties were investigated for alkaline fuel cell
applications. The targeted copolymers (QPE-bl-11a, -11b,
and -11c) were synthesized via nickel-mediated Ullmann
coupling polymerization, followed by quaternization and ion
exchange reactions. Unlike the conventional method involving
chloromethylation or bromination, this method provided
copolymers with well-defined chemical structure. The hydrophilic components of the copolymers were composed of chemically
stable phenylene main chain modified with high-density ammonium groups. Oligo(arylene ether sulfone ketone)s were
employed as a hydrophobic block. QPE-bl-11a gave tough and bendable membranes by solution casting. The obtained
membrane with the highest ion exchange capacity value (IEC = 2.47 mequiv g−1) showed high hydroxide ion conductivity (130
mS cm−1) in water at 80 °C. The QPE-bl-11a membrane showed reasonable alkaline stability in 1 M KOH aqueous solution for
1000 h at 60 °C. A platinum-free fuel cell was successfully operated with hydrazine as a fuel, the QPE-bl-11a as a membrane, and
an electrode binder. The maximum power density of 380 mW cm−2 was achieved at a current density of 1020 mA cm−2 with O2.
chemical stability of AEMs under alkaline conditions. Kim et
al.16 and Ramani et al.17 reported independently that
degradation of quaternized poly(arylene ether)s main chain
was caused by the reaction with hydroxide ions on ether
linkages close to electron-withdrawing groups such as tethered
benzyltrimethylammonium groups. To solve this problem,
Hickner et al.18 have designed and synthesized comb-shaped
aromatic copolymers containing long alkyl side chains pendant
to the nitrogen-centered cationic group and revealed that these
membranes kept high ion conductivity in alkaline solution.
Holdcroft et al.19,20 also reported that AEMs containing
sterically hindered polybenzimidazolium showed high hydrox-
ide ion conductivity and stability. More recently, we have
developed aromatic copolymer (QPE-bl-9) membranes com-
posed of ammonium-functionalized phenylene (carbon−carbon
bonded) groups as the hydrophilic component. The QPE-bl-9
membrane showed high hydroxide ion conductivity (138 mS
cm−1) in hot water (80 °C) and reasonable alkaline stability for
1000 h in 1 M KOH aqueous solution at 40 °C.21 However,
chloromethylation reaction using chloromethyl methyl ether
(CMME) was required for the synthesis of QPE-bl-9. CMME is
INTRODUCTION
■
As an efficient and environmentally benign energy device, fuel
cells have received increasing attention.1 Especially, polymer
electrolyte fuel cells (PEFCs) using proton exchange
membranes (PEMs) are operable at moderate temperatures
and thus suitable for applications in stationary cogeneration
systems, portable devices, and electric vehicles.2 However, use
of strongly acidic PEMs requires expensive, exhaustible
precious metals (Pt) as electrocatalysts. To address this issue,
replacement of PEMs with anion exchange membranes
(AEMs) seems an attractive option. Under the basic conditions
of anion exchange membrane fuel cells (AEMFCs), abundant
metals, for example, Ni, Co, and Fe, can be used as
electrocatalysts.3−5 Moreover, the kinetics of the oxygen
reduction reaction is more favorable under alkaline than
under acidic conditions.
In the past decade, large numbers of highly conductive and
chemically stable AEMs were developed.6−11 Similar to PEMs
composed of aromatic block copolymers that exhibit high
proton conductivity due to their well-developed hydrophilic/
hydrophobic phase-separated morphology,12 we have attemp-
ted several investigations and developed multiblock poly-
(arylene ether)s having hydrophilic blocks with high density
ammonium groups to achieve high hydroxide ion conductiv-
ity.13−15 In contrast, further improvement is still required in
Received: February 25, 2016
Revised: June 6, 2016
© XXXX American Chemical Society
A
DOI: 10.1021/acs.macromol.6b00408
Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
2H), 7.33 (m, 1H). 13C NMR (125 MHz, CDCl3): δ 34.6, 37.8, 127.8,
128.6, 130.1, 130.7, 133.2, 137.7, 166.9. 2b was synthesized from 1b in
a manner similar to that of 2a. 3,5-Dichloro-N,N-dimethylbenzamide
known to possess carcinogenic activity and often accompany
unfavorable side reactions such as cross-linking. Furthermore, it
is rather difficult to achieve high chloromethylation degree
(defined as number of chloromethyl groups per phenylene
unit).
1
(2b): brown solid (85% yield). H NMR (500 MHz, CDCl3): δ 2.98
(s, 3H), 3.10 (s, 3H), 7.30 (m, 2H), 7.40 (m, 1H). 13C NMR (125
MHz, CDCl3): δ 35.1, 39.1, 125.3, 129.3, 135.0, 138.9, 168.2. In the
case of 2c, although the procedure was similar to that of 2a and 2b, the
product was obtained as a liquid. 2,4-Dichloro-N,N-dimethylbenza-
In this article, we report an advanced aromatic copolymer
AEMs synthesized from preaminated monomers (three
dichlorodimethylbenzylamines) as scaffold for ammonium
groups. The hydrophilic components are designed to have
high ammonium densities without linkages by heteroatoms
such as ether, sulfone, and ketone groups. By using dichloro-
dimethylbenzylamine monomers, quaternized ammonium
groups could be introduced on each phenylene ring (100%
degree of quaternization in the hydrophilic component).
Sequenced (arylene ether sulfone ketone) units were employed
as the hydrophobic block to afford good film forming capability.
Synthesis, hydroxide ion conductivity, mechanical and alkaline
stability, and platinum-free fuel cell performance of the AEMs
are described.
1
mide (2c): Orange liquid (96% yield). H NMR (500 MHz, CDCl3):
δ 2.87 (s, 3H), 3.13 (s, 3H), 7.24 (d, J = 8.1 Hz, 1H), 7.29−7.33 (m,
1H), 7.42 (s, 1H). 13C NMR (125 MHz, CDCl3): δ 34.7, 38.0, 127.6,
128.7, 129.4, 131.2, 134.8, 135.3, 167.4.
Synthesis of 2,5-Dichloro-N,N-dimethylbenzylamine (3a). A
500 mL one-neck round-bottomed flask equipped with a condenser, a
nitrogen purge, and a magnetic stirrer bar was charged with LAH (4.14
g, 109 mmol) and THF (250 mL). To this gray suspension, 2a (23.8 g,
109 mmol) in limited amounts was added. After stirring for 26 h under
reflux conditions, the reaction mixture was cooled to room
temperature and quenched by the Fieser method.22 Specifically, after
continuous additions of deionized water (4 mL), 15% aqueous sodium
hydroxide (4 mL), and deionized water (20 mL), and stirring for a
while, the resulting light gray precipitate was filtered and washed with
THF several times. Then, the filtrate was concentrated in a vacuum,
and the residue was purified by silica gel column chromatography
(eluent: EtOAc/hexane = 9/1) to afford desired amine 3a (17.3 g,
EXPERIMENTAL SECTION
■
Materials. 2,5-Dichlorobenzoic acid (>98.0%), 3,5-dichlorobenzoic
acid (>98.0%), 2,4-dichlorobenzoic acid (>95.0%), dimethylamine
hydrochloride (>99.0%), 4,4′-dichlorodiphenyl sulfone (ClPS,
>98.0%), 4,4′-dihydroxybenzophenone (DHBP, >98.0%), and 2,2′-
bipyridine (>99.0%) were purchased from TCI Co., Ltd., and used as
received. Dichloromethane (>99.5%), N,N-dimethylformamide (DMF,
>99.5%), trimethylamine (>99.0%), chloroform-d1 with 0.03% TMS
(CDCl3, 99.8% D), lithium aluminum hydride (LAH, >92.0%),
tetrahydrofuran (THF, >99.5%), sodium hydroxide (>97.0%), N,N-
dimethylacetamide (DMAc, >99.0%), toluene (>99.5%), potassium
carbonate (>99.5%), bis(1,5-cycloocatadiene)nickel(0) (Ni(cod)2,
>95.0%), 35−37 wt % hydrochloric acid, 1,1,2,2-tetrachloroethane
(TCE, >97.0%), iodomethane (>99.5%), dimethyl sulfoxide (DMSO,
>99.0%), potassium hydroxide (>86.0%), chloroform (>99.0%), N-
methyl-2-pyrrolidone (NMP, >99.0%), ethanol (>99.5%), 2-propanol
(>99.7%), dimethyl-d6 sulfoxide with 0.03% TMS (DMSO-d6, 99.9%
D), and potassium tetrachloroplatinate(II) (>95.0%) were purchased
from Kanto Chemical Co., Inc., and used as received. Oxalyl chloride
(>95.0%) was purchased from Wako Pure Chemical Industries, Ltd.,
and used as received. 1,1,2,2,-Tetrachloroethane-d2 (TCE-d2, 99% D)
was purchased from Across Organics and used as received. 50 wt %
Ni/C was purchased from Cataler Corporation and used as received.
NPC-2000 (Fe−N−C catalyst) was purchased from Pajarito Powder,
LLC, and used as received. 60 wt % hydrazine hydrate aqueous
solution was purchased from Otsuka-MGC Chemical Company, Inc.,
and used as received.
1
77% yield) as a light yellow liquid. H NMR (500 MHz, CDCl3): δ
2.30 (s, 6H), 3.49 (s, 2H) 7.16 (dd, J = 2.5, 8.4 Hz, 1H), 7.27 (d, J =
8.4 Hz, 1H), 7.46 (d, J = 2.5 Hz, 1H). 13C NMR (125 MHz, CDCl3):
δ 45.5, 60.4, 128.1, 130.4, 130.5, 132.3, 132.6, 138.4. 3b and 3c were
synthesized from 2b and 2c, respectively, in a similar manner to that of
3a. 3,5-Dichloro-N,N- dimethylbenzylamine (3b): colorless liquid
1
(61% yield). H NMR (500 MHz, CDCl3): δ 2.24 (s, 6H), 3.36 (s,
2H), 7.22 (d, J = 1.7 Hz, 2H), 7.25 (t, J = 1.7 Hz, 1H). 13C NMR (125
MHz, CDCl3): δ 45.3, 63.2, 127.1, 134.7, 142.7. 2,4-Dichloro-N,N-
1
dimethylbenzylamine (3c): light yellow liquid (76% yield). H NMR
(500 MHz, CDCl3): δ 2.28 (s, 6H), 3.49 (s, 2H), 7.22 (dd, J = 2.1, 8.2
Hz, 1H), 7.370 (d, J = 8.1 Hz, 1H), 7.372 (d, J = 2.1 Hz, 1H). 13C
NMR (125 MHz, CDCl3): δ 45.4, 60.1, 126.8, 129.1, 131.6, 133.1,
134.8, 135.1.
Synthesis of PE-bl-11. ClPS-terminated telechelic oligomers 4
were synthesized according to the literature23 (see Supporting
Information). A typical procedure for PE-bl-11 is as follows (X = 4,
3a, m:n = 1:12). A 100 mL three-neck round-bottomed flask equipped
with a condenser, a nitrogen purge, a Dean−Stark trap, and a magnetic
stirrer bar was charged with oligomer 4 (482 mg, 0.123 mmol), 2,2′-
bipyridine (600 mg, 3.84 mmol), dichloromonomer 3a (311 mg, 1.52
mmol), toluene (5 mL), and DMAc (10 mL). The mixture was stirred
at 170 °C for 2 h to remove water. Then, after removal of toluene and
cooling to 80 °C, Ni(cod)2 (1.00 g, 3.64 mmol) was added, and the
reaction was continued at the same temperature for 19 h After cooling
to room temperature and diluting with additional DMAc (10 mL), the
resulting mixture was poured into a 200 mL of concentrated
hydrochloric acid to afford the light yellow precipitate. The resulting
solid was collected by filtration, washed with deionized water,
potassium carbonate aqueous solution, deionized water, and methanol
successively and dried at 60 °C under reduced pressure overnight to
Synthesis of 2,5-Dichloro-N,N-Dimethylbenzamide (2a). A
500 mL one-neck round-bottomed flask equipped with a magnetic
stirrer bar was charged with 2,5-dichlorobenzoic acid (1a; 22.4 g, 117
mmol) and dichloromethane (200 mL). To this suspension was added
a solution of oxalyl chloride (16.8 g, 132 mmol) in dichloromethane
(66 mL) followed by DMF (10 drops). After stirring for 6 h, full
1
1
conversion of starting carboxylic acid was confirmed by the H NMR
afford PE-bl-11 as a light yellow solid (423 mg, 84% yield). From H
spectrum. Next, after cooling with an ice bath, to this acyl halide
solution was added dimethylamine hydrochloride (18.9 g, 232 mmol)
followed by triethylamine (50 mL, 359 mmol) slowly. After the ice
bath was removed, the mixture was stirred at room temperature for a
further 24 h and diluted with deionized water. After separation of the
two layers, the aqueous layer was extracted with dichloromethane.
Then, the combined organic layers were washed with 1 M
hydrochloric acid, saturated sodium hydrogen carbonate aqueous
solution, and deionized water and concentrated in vacuo. By addition
of hexane to the residue, a light brown solid was formed. The resulting
solid was filtered, washed with hexane, and dried at 60 °C under
NMR spectrum, the ratio of m to n was calculated as 1.0 to 7.6.
Preparation of QPE-bl-11. A typical procedure for PE-bl-11 is as
follows (X = 4, 3a, m:n = 1:12). A 20 mL vial equipped with a
magnetic stirrer bar was charged with obtained PE-bl-11 (359 mg,
0.801 mmol; amount of nitrogen) and DMAc (3.5 mL). To this
solution, iodomethane (249 μL, 4.00 mmol) was added. After stirring
for 48 h, the reaction mixture was diluted with additional DMAc (3
mL) and poured into a 100 mL of deionized water to afford the light
yellow precipitate. The obtained crude product was washed with
deionized water several times and dried at 60 °C under reduced
pressure overnight to afford QPE-bl-11 in iodide ion form as a light
orange solid (428 mg). From the 1H NMR spectrum, the ratio of m to
n was calculated as 1.0 to 4.8. The obtained QPE-bl-11 (300 mg) was
1
reduced pressure to afford desired amide 2a (23.8 g, 93% yield). H
NMR (500 MHz, CDCl3): δ 2.88 (s, 3H), 3.13 (s, 3H), 7.24−7.31 (m,
B
DOI: 10.1021/acs.macromol.6b00408
Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
Scheme 1. Synthesis of Dichloromonomers 3
Scheme 2. Synthesis of Oligomer 4, PE-bl-11(4)a and QPE-bl-11(4)a
dissolved in DMSO (3 mL) and then cast onto a flat glass plate.
Drying the solution at 50 °C gave a QPE-bl-11 membrane (50−60 μm
thick). The membrane was treated with 1 M KOH aqueous solution at
40 °C for 48 h. The membrane was washed and soaked in degassed
deionized water for 1 day to obtain the QPE-bl-11 membrane in
hydroxide ion form.
conductivity cell attached to an ac impedance spectroscopy system.
Water uptake was measured at room temperature. The oxidative
stability of the membrane was evaluated by treating the sample with
hot Fenton’s reagent (3.5% H2O2 containing 2 ppm FeSO4 at 80 °C)
for 8 h.
Temperature dependence of the storage moduli (E′), loss moduli
(E″), and tan δ (E″/E′) of QPE-bl-11(4)a membranes in iodide ion
forms was carried at 60% relative humidity (RH) from room
temperature to 95 °C at a heating rate of 1 °C min−1. RH dependence
of E′, E″, and tan δ was carried out at 80 °C from ca. 0 to 90% RH at a
humidification rate of 1% RH min−1. Details on these measurements
are described in the Supporting Information.
Preparation of Catalyst-Coated Membrane (CCM) with QPE-
bl-11(4)a and Fuel Cell Operation. A mixture of 50 wt % Ni/C
(0.060 g) and DMF/2-propanol (1/1 by weight, 1.5 g) was sonicated
with a TAITEC VP-50 ultrasonic homogenizer for 10 min. A 2.0 wt %
QPE-bl-11(4)a (IEC = 1.95 mequiv g−1, 0.33 g as polymer weight)
solution in DMF/2-propanol (1/1 by weight) was added to the
mixture. The mixture was sonicated for 3 min and stirred with an IKA
VIBRAX VXR basic shaker for 15 min. The slurry obtained was
sprayed onto one side of QPE-bl-11(4)a membrane (IEC = 1.95
mequiv g−1, 80 μm thick, 16 cm2) at 50 °C to form the anode catalyst
layer. The coated area was 4.0 cm2. Then, NPC-2000 (0.050 g) and
DMF/2-propanol (1/1 by weight, 2.0 g) were sonicated with a Sharp
UT-206 (37 kHz) for 60 min. A 2.0 wt % QPE-bl-11a (IEC = 1.95
1
Measurements. H and 13C NMR spectra were recorded using
CDCl3, TCE-d2, or DMSO-d6 as a solvent. Apparent molecular
weights were estimated by gel permeation chromatography (GPC)
calibrated with standard polystyrene (PS) samples. DMF containing
0.01 M LiBr was used as eluent. For transmission electron microscopic
(TEM) observation, the membranes were ion-exchnaged with
tetrachloroplatinate ions. The stained membranes were embedded in
epoxy resin, sectioned to 50 nm thickness, and placed on a copper
grids. Ion exchange capacity (IEC) was determined by titration. The
membrane samples in iodide ion forms were treated with 1 M KOH
aqueous solution at 40 °C for 48 h, and the resulting membranes in
hydroxide ion forms were neutralized with 1 M hydrochloric acid. The
membrane samples in chloride ion forms (ca. 50 mg) were immersed
in 12.5 mL of 0.1 M sodium nitrate aqueous solution for 24 h. The
amount of Cl− released from the membranes was measured by
titration with 0.01 M silver nitrate aqueous solution using potassium
chromate as an indicator and sodium hydrogen carbonate as a pH
adjuster. The hydroxide ion conductivity of the membranes was
measured in degassed and deionized water using a four-probe
C
DOI: 10.1021/acs.macromol.6b00408
Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
1
Figure 1. H NMR spectra of (a) oligomer 4 (X = 4), (b) PE-bl-11(4)a, and (c) QPE-bl-11(4)a (m:n = 1:12).
mequiv g−1, 1.3 g as polymer weight) solution in DMF/2-propanol (1/
the desired dichloromonomers 3 in high yields. All these
compounds were well-characterized by 1H NMR and 13C NMR
spectra (Figures S1−S6).
1 by weight) was added to the mixture and stirred with an IKA
VIBRAX VXR basic shaker for 15 min. The slurry obtained was
sprayed onto the other side of the membrane in a similar manner to
the anode catalyst layer to form the cathode catalyst layer. The loaded
amounts of the catalysts were 2.6 mg cm−2 for Ni as the anode and 1.3
mg cm−2 for NPC-2000 as the cathode. The CCM was pressed at 3.3
MPa at room temperature for 30 s. The CCM was treated with 1.0 M
KOH aqueous solution at room temperature overnight for the ion
exchange to the hydroxide ion form. The CCM was sandwiched by
two gas diffusion layer (Freidenburg H1410 carbon cloth for the
anode, and GTI carbon cloth with microporous layer for the cathode)
and two bipolar plates. Point symmetric serpentine flow fields were
used. A fuel cell was operated at 60 °C supplying a mixture of 1.0 M
KOH and 10 wt % hydrazine aqueous solution to the anode at a flow
rate of 1.3 × current (A) mL min−1 (minimum flow rate was 1.0 mL
min−1) and humidified oxygen or air to the cathode at a flow rate of
500 mL min−1. The operating pressure was set at 10 kPa for the
cathode.
Synthesis of QPE-bl-11. The quaternized block copoly-
mers QPE-bl-11 were synthesized as shown in Scheme 2.
Initially, the ClPS-terminated telechelic hydrophobic oligomers
4 were synthesized by nucleophilic substitution polymerization
of DHBP and slight excess of ClPS using potassium carbonate
as a base in DMAc solution. The chain lengths were controlled
by the feed monomer ratios. The chemical structure of 4 was
1
characterized by H NMR spectra (Figure 1a and Figure S7).
The numbers of repeat units of 4 calculated from the integral
1
ratios in the H NMR spectra were in good agreement with
those expected from the feed monomer ratios (Table 1). On
Table 1. Molecular Weight of Oligomers 4
a
b
c
d
e
e
X
X
X
Mn (kDa) Mn (kDa) Mw (kDa) Mw/Mn
RESULTS AND DISCUSSION
■
2
2.5
5.1
8.2
3.9
7.1
1.4
2.5
3.8
1.9
3.3
5.7
4.1
7.3
2.1
2.2
2.5
Synthesis of Dichloromonomers 3. Three types of
dichloromonomers 3 in which substitution positions were
different were synthesized as shown in Scheme 1. First,
commercially available dichlorobenzoic acids 1 were converted
to amides 2 via chlorination24 followed by the reaction with
dimethylamine hydrochloride in one pot. Then, the resulting
amides 2 were reduced by LAH under reflux conditions to give
4
8
12.5
13.9
a
b
Calculated from the feed comonomer ratio. Determined by 1H
NMR spectra. Calculated from Mn (GPC). Calculated from X
(NMR). Determined by GPC analyses (calibration with polystyrene
standards).
c
d
e
D
DOI: 10.1021/acs.macromol.6b00408
Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
Table 2. Properties of PE-bl-11 and QPE-bl-11
PE-bl-11
a
a
b
c
c
b
bd
IEC (mequiv g−1
)
,
X
monomer
m:n
m:n
yield (%)
Mn (kDa)
Mw (kDa)
Mw/Mn
QPE-bl-11 m:n
e
2
3a
3a
3a
3a
3a
3b
3c
3c
3a
3a
1:3
1:6
1:6
1:1.6
1:4.9
1:3.7
1:7.6
1:9.6
1:4.7
1:3.0
1:4.7
1:5.9
1:15.5
90
86
70
84
79
92
83
87
86
70
10.4
18.1
29.4
27.5
19.2
26.5
22.4
11.9
20.6
18.7
77.0
126
7.4
7.0
5.0
4.7
12.2
9.9
3.7
3.8
4.7
4.0
1:1.9
1:4.4
1:3.7
1:5.3
1:9.7
1.19 (1.06)
2
4
4
4
4
4
4
8
8
2.15 (2.12)
1.29 (1.79)
1.62 (2.56)
2.47 (2.62)
1.77 (1.54)
1.09 (1.15)
148
1:12
1:18
1:6
129
235
f
262
−
1:6
82.5
44.6
96.9
74.2
1:3.2
1:3.2
1:5.7
1:9.6
f
1:9
1.32 (− )
1:12
1:24
1.23 (1.36)
1.81 (1.96)
a
b
c
Calculated from the feed ratio. Determined by 1H NMR spectra. Determined by GPC analyses (calibrated with polystyrene standards).
d
e
f
Calculated as QPE-bl-11 (OH− form). Values in parentheses were determined by titration. Not determined.
Figure 2. Structure of PE-bl-9 and QPE-bl-9 containing similar hydrophilic structure as that of QPE-bl-11.
the other hand, the numbers of repeat units of 4 calculated
from Mn determined by gel permeation chromatography
(GPC) analyses (Figure S8, calibrated with polystyrene
standards) were higher than those calculated from the
dimethyl groups was used for estimation of the composition
(ratio of m to n) in PE-bl-11s. When 3a and 3c were used, the
composition of these monomers incorporated in the copoly-
mers was relatively low compared with the feed amounts. Only
ca. 50−60% of the monomers used were introduced in the
copolymers. This was presumably because of the steric
hindrance of ortho-substituents in the monomers. On the
other hand, for less hindered 3b, the copolymer composition
was higher (ca. 80%). Compared with trisubstituted dichlor-
omonomers 3, simple m- and p-dichlorobenzenes were more
reactive and the introduction of those monomers was
quantitative. In fact, when Ullmann coupling reaction of
oligomer 4 and dichlorobenzenes was carried out under the
same reaction conditions as for PE-bl-11, the ratio of
oligophenylene moieties was the same as the feed ratio
(Scheme S1 and Figure S11).
1
comonomer compositions and the H NMR spectra, probably
because of the rigid-rod-like main chain structure as discussed
in our previous report.23
PE-bl-11(4)a was prepared from oligomer 4 (X = 4) and
dichloromonomer 3a by nickel-mediated Ullmann coupling
reaction.21,23,25−31 First, the effects of solvent were investigated
in Ullmann coupling reaction using 3a (Table S1) to find that
DMAc gave better results (slightly higher molecular weight of
the product with closer copolymer composition to the feed
ratio) than DMSO. Then, using DMAc as the solvent, several
types of PE-bl-11s were synthesized by changing the reaction
conditions, such as chain length of 4 (X = 2, 4, or 8),
monomers 3a−c and feed amount (Table 2). As a result, PE-bl-
11s were obtained in reasonable yields (Table 2). The PE-bl-
11s obtained were soluble in several organic solvents such as
chloroform, TCE, NMP, DMF, and DMAc. The molecular
weights of PE-bl-11s determined by GPC were Mn = 10.4−29.4
kDa and Mw = 74.2−262 kDa (Table 2). Polydispersity indexes
were relatively high (Mw/Mn = 3.7−12.2). Mw of PE-bl-11s
were smaller than those of PE-bl-9s which contained no
dimethylaminomethylene groups (Figure 2).21 The results
indicate that the dichloromonomers 3 are less reactive in the
Ullmann coupling reaction than m- and p-dichlorobenzenes.
On the other hand, whereas PE-bl-9s afforded the bimodal
peaks in the GPC curves, GPC profiles of PE-bl-11s were
unimodal as shown in Figure S9, suggesting the formation of
the copolymers with no or little oligomers composed solely of
the dichloromonomers 3.
While the quaternization of PE-bl-11 was first conducted
using iodomethane in DMAc solution, it was revealed that there
were big differences in the solubility among the QPE-bl-11s. In
the case of PE-bl-11(4)a derived from 3a, the light yellow
precipitate was obtained after the addition of the quaternization
reaction mixture into a deionized water. Isolated QPE-bl-
1
11(4)a could be analyzed by H NMR spectrum (Figure 1c),
and the quaternization was confirmed from the integration of
the methyl groups. The molecular weight measurement of the
resulting QPE-bl-11 was unavailable because of the strong
interactions with the GPC column. In the case of PE-bl-11(4)b
derived from 3b, the reaction with iodomethane in DMAc
solution provided gel-like insoluble product. Therefore, PE-bl-
11(4)b membrane was immersed in 5% (v/v) iodomethane
ethanol solution. The resulting QPE-bl-11(4)b was insoluble in
both DMSO-d6 and TCE-d2. In the case of QPE-bl-11(4)c
derived from 3c, the product could not be recovered because of
no precipitation after the addition of the reaction mixture into a
deionized water. In this case, the reaction mixture was directly
cast onto a flat glass plate. This quaternized QPE-bl-11(4)c
The chemical structure of PE-bl-11s was characterized by 1H
1
NMR spectra (Figure 1b and Figure S10). In the H NMR
spectra, although dimethylamine moiety was confirmed, the
peak of benzylic methylene groups was very broad and not
suitable for quantitative analyses. Therefore, the peak of
1
membrane was analyzed by H NMR spectrum (Figure S12).
E
DOI: 10.1021/acs.macromol.6b00408
Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
Figure 3. TEM images of (a) QPE-bl-11(2)a (IEC = 1.19 mequiv g−1), (b) QPE-bl-11(4)a (IEC = 1.29 mequiv g−1), (c) QPE-bl-11(8)a (IEC =
1.23 mequiv g−1), (d) QPE-bl-11(4)b (IEC = 1.77 mequiv g−1), and (e) QPE-bl-11(4)c (IEC = 1.09 mequiv g−1) membranes stained with
tetrachloroplatinate ions.
Casting from a DMSO solution of QPE-bl-11(4)a derived
from 3a afforded yellow, transparent, and bendable membranes
(Figure S13). While QPE-bl-11(4)b and QPE-bl-11(4)c
membranes (m:n = 1:6) were also transparent and flexible,
QPE-bl-11(4)b membrane was orange. QPE-bl-11(4)c with
high IEC (1.32 mequiv g−1) was unsuccessful and gave a brittle
membrane. The IEC values were also measured by titration,
which were comparable to or slightly higher than those
tion and that the morphology was dependent on the
hydrophobic block length. The phase separation was larger
for QPE-bl-11a(4) than for QPE-bl-9 probably due to the
differences in the quaternization procedure; QPE-bl-11 was
quaternized in solution and then cast to the membrane, while
QPE-bl-9 was quaternized as a membrane.21 It is noticeable that
the morphology was not practically affected by the IEC value as
confirmed in the three QPE-bl-11(4)a membranes with
different IEC values (1.29, 1.62, and 2.47 mequiv g−1; see
Figures S14a, S14b, and S14c). Compared to QPE-bl-11(4)a,
QPE-bl-11(4)b and QPE-bl-11(4)c membranes having the
same number of hydrophobic repeat units (X) exhibited less
developed phase separation containing smaller spherical
domains (ca. 1−2 nm in diameter, Figures 3d and 3e),
implying that the substitution positions of ammonium groups
and the main chain in the hydrophilic component affected the
self-aggregation properties.
Water uptake and hydroxide ion conductivity of the QPE-bl-
11a, -11b, and -11c membranes were measured at room
temperature and 30 °C, respectively, and are plotted in Figure 4
as a function of the IEC. The general trend is that the water
uptake and conductivity both increase as increasing IEC value.
QPE-bl-11a membranes exhibited higher water uptake than that
of QPE-bl-9 membranes, reflecting the above-mentioned
morphology. QPE-bl-11b membrane exhibited much lower
water uptake and hydroxide ion conductivity than those of
QPE-bl-11a membranes presumably because of the different
quaternization procedure for QPE-bl-11b membrane (see
1
estimated from the H NMR spectra (Table 2).
Morphology and Properties of QPE-bl-11 Membrane.
QPE-bl-11 membranes were ion exchanged from iodide ions to
tetrachloroplatinate ions for TEM observation. The membranes
2−
were reddish brown and somewhat less flexible in PtCl4
forms. Figure 3 shows the cross-sectional TEM images of
selected samples of QPE-bl-11a, -11b, and -11c membranes.
The dark areas represent hydrophilic domains containing
stained (ion-exchanged) ammonium groups, and the bright
areas represent hydrophobic domains composed of the polymer
main chains. The QPE-bl-11 membranes showed hydrophilic/
hydrophobic phase-separated morphology. While QPE-bl-
11(2)a membrane contained minute spherical domains (ca.
1−2 nm in diameter, Figure 3a), QPE-bl-11(4)a and QPE-bl-
11(8)a membranes with longer X exhibited more developed
phase separation containing larger hydrophilic domains (ca. 5−
10 nm in width, Figures 3b and 3c). (Note that they share a
similar IEC value.) The results suggest that the hydrophilic
components were sequenced to a certain extent although the
dichloromonomer 3 was used for the semiblock copolymeriza-
F
DOI: 10.1021/acs.macromol.6b00408
Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
membrane preparation and quaternization procedures, the
existence of polar functional groups (sulfone and ketone) and
the lack of fluorine groups would be accountable for high water
absorbability of QPE-bl-11a membranes. The QPE-bl-11a with
longer hydrophobic chain length exhibited higher water
absorbability probably because of more developed phase
separated morphology. The hydroxide ion conductivity and
its dependence on the IEC value were similar between QPE-bl-
9 and QPE-bl-11a membranes. Compared to QPE-bl-9
membranes which exhibited a jump in the conductivity at λ =
ca. 18 (Figure 6), QPE-bl-11a membranes exhibited approx-
Figure 4. (a) Water uptake (room temperature) and (b) hydroxide
ion conductivity (30 °C) of QPE-bl-11 and QPE-bl-9 membranes as a
function of IEC.
above). The water uptake was then replotted as the number of
absorbed water molecules per ammonium group (λ) in Figure
5, which further supports the higher water absorbability of
QPE-bl-11a membranes than QPE-bl-9 membranes. The λ
value increased as increasing IEC for QPE-bl-11a membranes,
while the λ value was nearly constant and independent of IEC
for QPE-bl-9 membranes. In addition to the differences in the
Figure 6. Hydroxide ion conductivity of QPE-bl-11 and QPE-bl-9
membranes at 30 °C as a function of λ at room temperature.
imate linear increase of the conductivity to the IEC value. The
results imply that the absorbed water was more efficiently
utilized for the hydroxide ion conductivity for QPE-bl-9
membranes than for QPE-bl-11a membranes. This discussion
is not contradictory to higher water uptake behavior of the
QPE-bl-11a membranes (vide supra) derived from less
hydrophobic (non-fluorinated) main chain structure. Unlike
the water uptake behavior, the hydroxide ion conductivity
seemed less dependent on the hydrophobic chain length.
The hydroxide ion conductivity of the QPE-bl-11 mem-
branes showed Arrhenius-type temperature dependence at least
up to 80 °C as shown in Figure 7. The apparent activation
energies calculated from the slopes were ca. 12−17 kJ mol−1,
parallel to the reported values for AEMs,14,15,30,32,33 indicating
that hydrated hydroxide ions are involved in the ion conducting
mechanism. The QPE-bl-11(4)a membrane (IEC = 1.62
mequiv g−1) showed high conductivity comparable to that of
QPE-bl-9 membrane with similar IEC (1.76 mequiv g−1). The
hydroxide ion conductivity of QPE-bl-11a membranes
increased with increasing IEC value, and the QPE-bl-11(4)a
with the highest IEC (2.47 mequiv g−1) achieved a value of 130
mS cm−1 at 80 °C. This conductivity is among the highest for
aromatic polymer based anion exchange membranes.
One of the major problems associated with anion exchange
membranes is a poor alkaline stability. The alkaline stability of
the QPE-bl-11(4)a (IEC = 1.29, 1.62, and 2.47 mequiv g−1, I−
Figure 5. λ of QPE-bl-11 and QPE-bl-9 membranes as a function of
IEC. λ values were calculated from the data in Figure 4a and IEC
values.
G
DOI: 10.1021/acs.macromol.6b00408
Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
slight chemical and morphological degradations could have
caused significant loss in the hydroxide ion conductivity.
1
In contrast, H NMR spectrum of the higher IEC (2.47
mequiv g−1) QPE-bl-11(4)a membrane showed decrease in
methyl peaks of the trimethylammonium groups (Figure S17).
1
From the H NMR spectrum in Figure S17, it was estimated
that ca. 28% of the ammonium groups was lost. This severer
chemical degradation of the higher IEC membrane must be
related with higher water uptake and swelling. It should be
noted that QPE-bl-11(4)a membranes (1.62 and 2.47 mequiv
g−1) showed higher hydroxide ion conductivity than that of
QPE-bl-9 membrane (1.97 mequiv g−1) after 500 h alkaline
stability test.
Oxidation stability is critical for anion exchange membranes
to the applications in fuel cells. As an accelerated test, QPE-bl-
11(4)a (IEC = 1.95 mequiv g−1) was treated with hot Fenton’s
reagent. After 8 h, the post-test membrane retained its shape
and bendability. The remaining weight, IEC, and hydroxide ion
conductivity were 105%, 95%, and 96%, respectively, indicating
high oxidative stability of the QPE-bl-11 membrane.
As a mechanical stability test, dynamic mechanical analysis
(DMA) was carried out for the membranes in iodide ion form.
The storage moduli (E′), loss moduli (E″), and tan δ (E″/E′)
of QPE-bl-11(4)a membranes in I− forms was measured at 60%
RH as a function of temperature up to 95 °C (Figure 9). The
storage moduli and loss moduli of QPE-bl-11(4)a membranes
were nearly constant from room temperature to 95 °C. The
IEC seemed a minor factor to affect these properties.
Compared to QPE-bl-9 membrane, QPE-bl-11 membranes
exhibited slightly higher storage and loss moduli. Three QPE-
bl-11(4)a membranes did not show detectable peaks in the
E″and tan δ curves, implying that they did not exhibit a glass
transition behavior under the tested conditions.
Figure 7. Temperature dependence of hydroxide ion conductivities of
QPE-bl-11 derived from 3a and QPE-bl-9 membranes in water.
form) membranes were evaluated at 60 °C in 1 M KOH
aqueous solution (Figure 8). The conductivity of lower IEC
Humidity dependence of E′, E″, and tan δ of QPE-bl-11(4)a
was also measured at 80 °C (Figure S19). Similar to the
temperature dependence, QPE-bl-11a membranes showed
higher storage and loss moduli than those of QPE-bl-9
membrane. The loss moduli decreased as increase in the
humidity for all the membranes due to the increased water
absorption.
Figure 8. Change of ion conductivity of QPE-bl-11(4)a (IEC = 1.29,
1.62, and 2.47 mequiv g−1) and QPE-bl-9 (IEC = 1.97 mequiv g−1)
membranes at 60 °C in 1 M KOH aqueous solution. The membranes
were used in iodide ion form to avoid the effect of CO2 from the air.
An MEA (membrane electrode assembly) was prepared
using QPE-bl-11(4)a (IEC = 1.95 mequiv g−1) as membrane
and electrode binders (note that this copolymer was specially
prepared in a larger scale for fuel cell experiments and thus is
not included in Table 2 and the above discussion). The fuel cell
was operable with hydrazine aqueous solution as a fuel at 60 °C
(Figure 10). The open circuit voltage (OCV) was relatively
high at 0.78 V (with air) and 0.79 V (with O2), indicating low
hydrazine permeability of the membrane. The fuel cell
exhibited the maximum power density of 380 mW cm−2 at a
current density of 1020 mA cm−2 with O2 and 172 mW cm−2 at
452 mA cm−2 with air. The ohmic resistance was ca. 200 mΩ
cm2 for both conditions, which was higher than that (100 mΩ
cm2) calculated from the hydroxide ion conductivity (80 mS
cm−1 at 60 °C in water) and the thickness (80 μm) of the
membrane, presumably because of the contact resistance
between QPE-bl-11(4)a membrane and the catalyst layers.
The results imply that the optimization of the CCM
preparation method could result in better fuel cell performance.
(1.29 mequiv g−1) QPE-bl-11(4)a membrane jumped from 1.8
to 68 mS cm−1 within 24 h due to the ion exchange reaction
from iodide ion to more conductive hydroxide ion. Then, the
conductivity decreased gradually with time and maintained 23
mS cm−1, 34% of the peak conductivity, after 1000 h. The post-
test membrane was not so ductile as the pristine membrane.
1
Since there were only minor changes confirmed in the H
NMR spectrum and TEM image (Figures S15 and S18), the
degradation during the alkaline stability test involved the main
chain scission and decomposition of the ammonium groups.
The same tendency was also observed for the middle IEC (1.62
mequiv g−1) QPE-bl-11(4)a membrane. In this case, the
conductivity dropped after 500 h, and only 1.6% of the peak
1
conductivity was maintained after 1000 h. However, the H
NMR spectra of the post-test QPE-bl-11(4)a membranes did
not imply serious chemical degradation (Figure S16). These
results indicate that the lack of heteroatom linkages in the
hydrophilic components improved the alkaline stability and that
CONCLUSIONS
We have developed a series of quaternized aromatic copolymers
(QPE-bl-11s) from chlorine-terminated oligo(arylene ether
■
H
DOI: 10.1021/acs.macromol.6b00408
Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
Figure 10. (a) Cell voltage, power density, and (b) ohmic resistance as
a function of current density of direct hydrazine fuel cell with QPE-bl-
11(4)a as membrane and electrode binders at 60 °C.
water. In addition, it was revealed that QPE-bl-11(4)a
membranes were more stable than QPE-bl-9 membrane
under alkaline stability test. Lack of heteroatoms linkages
contributed to improving the chemical stability of the polymer
main chains, however, trimethylbenzylammonium groups
decomposed under harsh alkaline conditions. A platinum-free
fuel cell with hydrazine as a fuel, the QPE-bl-11(4)a as a
membrane, and electrode binder was successfully operated. The
maximum power density of 380 mW cm−2 was achieved at a
current density of 1020 mA cm−2 with O2.
ASSOCIATED CONTENT
* Supporting Information
■
Figure 9. DMA of QPE-bl-11(4)a (IEC = 1.29, 1.62, and 2.47 mequiv
g−1) and QPE-bl-9 (IEC = 1.97 mequiv g−1) membranes at 60% RH.
S
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.macro-
mol.6b00408.
sulfone ketone)s and three types of dimethylamine-containing
dichloromonomers 3 in which substitution positions were
different. Bendable membranes were obtained from the
copolymers of well-controlled chemical structure and high
ammonium density. From the TEM observation, it was found
that the hydrophilic components of QPE-bl-11a were
sequenced to a certain extent although the dichloromonomer
3a was used for the semiblock copolymerization and that the
morphology was dependent on the hydrophobic block length
rather than the IEC value. The water uptake and hydroxide ion
conductivity of QPE-bl-11a membranes both increased as
increasing IEC value. This trend was different from that of
QPE-bl-9 membranes containing similar hydrophilic structure
but less ammonium density. The high local ion concentration
(or high ammonium density) of QPE-bl-11a contributed to
high hydroxide ion conductivity. As a result, QPE-bl-11(4)a
membrane with highest IEC (2.47 mequiv g−1) exhibited
significantly high conductivity of 130 mS cm−1 at 80 °C in
1H and 13C NMR spectra of compounds 2 and 3, H
1
NMR spectra and GPC profiles of oligomer 4, 1H NMR
spectra of PE-bl-11 and QPE-bl-11, TEM images of
QPE-bl-11(4)a, DMA of QPE-bl-11(4)a and QPE-bl9
membranes at 80 °C as a function of RH (PDF)
AUTHOR INFORMATION
Corresponding Author
*E-mail miyatake@yamanashi.ac.jp; Tel +81 552208707; Fax
+81 552208707 (K.M.).
■
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
This work was partly supported by CREST, Japan Science and
Technology Agency (JST) and the Ministry of Education,
■
I
DOI: 10.1021/acs.macromol.6b00408
Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
(19) Thomas, O. D.; Soo, K. J. W. Y; Peckham, T. J.; Kulkarni, M. P.;
Holdcroft, S. A Stable Hydroxide-Conducting Polymer. J. Am. Chem.
Soc. 2012, 134, 10753−10756.
Culture, Sports, Science and Technology (MEXT) Japan
through a Grant-in-Aid for Scientific Research (26289254).
(20) Wright, A. G.; Holdcroft, S. Hydroxide-Stable Ionenes. ACS
Macro Lett. 2014, 3, 444−447.
REFERENCES
■
(21) Yokota, N.; Shimada, M.; Ono, H.; Akiyama, R.; Nishino, E.;
Asazawa, K.; Miyake, J.; Watanabe, M.; Miyatake, K. Aromatic
Copolymers Containing Ammonium-Functionalized Oligophenylene
Moieties as Highly Anion Conductive Membranes. Macromolecules
2014, 47, 8238−8246.
(22) Fieser, L. F.; Fieser, M. Reagents for Organic Synthesis; Wiley:
New York, 1967; Vol. 1, pp 581−595.
(23) Miyahara, T.; Hayano, T.; Matsuno, S.; Watanabe, M.;
Miyatake, K. Sulfonated Polybenzophenone/Poly(arylene ether)
Block Copolymer Membranes for Fuel Cell Applications. ACS Appl.
Mater. Interfaces 2012, 4, 2881−2884.
(1) Steele, B. C. H.; Heinzel, A. Materials for fuel-cell technologies.
Nature 2001, 414, 345−352.
(2) Borup, R.; Meyers, J.; Pivovar, B.; Kim, Y. S.; Mukundan, R.;
Garland, N.; Myers, D.; Wilson, M.; Garzon, F.; Wood, D.; Zelenay,
P.; More, K.; Stroh, K.; Zawodzinski, T.; Boncella, J.; McGrath, J. E.;
Inaba, M.; Miyatake, K.; Hori, M.; Ota, K.; Ogumi, Z.; Miyata, S.;
Nishikata, A.; Siroma, Z.; Uchimoto, Y.; Yasuda, K.; Kimijima, K.;
Iwashita, N. Scientific Aspects of Polymer Electrolyte Fuel Cell
Durability and Degradation. Chem. Rev. 2007, 107, 3904−3951.
(3) Varcoe, J. R.; Slade, R. C. T. Prospects for Alkaline Anion-
Exchange Membranes in Low Temperature Fuel Cells. Fuel Cells 2005,
5, 187−200.
(4) Lu, S.; Pan, J.; Huang, A.; Zhuang, L.; Lu, J. Alkaline polymer
electrolyte fuel cells completely free from noble metal catalysts. Proc.
Natl. Acad. Sci. U. S. A. 2008, 105, 20611−20614.
(5) Yu, E. H.; Wang, X.; Krewer, U.; Li, L.; Scott, K. Direct oxidation
alkaline fuel cells: from materials to systems. Energy Environ. Sci. 2012,
5, 5668−5680.
(24) Ghosh, K.; Saha, I. Triphenylamine-based simple chemosensor
for selective fluorometric detection of fluoride, acetate and
dihydrogenphosphate ions in different solvents. J. Inclusion Phenom.
Mol. Recognit. Chem. 2011, 70, 97−107.
(25) Ullmann, F.; Bielecki, J. Ueber Synthesen in der Biphenylreihe.
Ber. Dtsch. Chem. Ges. 1901, 34, 2174−2185.
(26) Fanta, P. E. The Ullmann Synthesis of Biaryls. Chem. Rev. 1946,
38, 139−196.
(6) Couture, G.; Alaaeddine, A.; Boschet, F.; Ameduri, B. Polymeric
materials as anion-exchange membranes for alkaline fuel cells. Prog.
Polym. Sci. 2011, 36, 1521−1557.
́
(27) Hassan, J.; Sevignon, M.; Gozzi, C.; Schulz, E.; Lemaire, M.
Aryl−Aryl Bond Formation One Century after the Discovery of the
Ullmann Reaction. Chem. Rev. 2002, 102, 1359−1469.
(7) Merle, G.; Wessling, M.; Nijmeijer, K. Anion exchange
membranes for alkaline fuel cells: A review. J. Membr. Sci. 2011,
377, 1−35.
(28) Ueda, M.; Ichikawa, F. Synthesis of aromatic poly(ether
ketone)s by nickel-catalyzed coupling polymerization of aromatic
dichlorides. Macromolecules 1990, 23, 926−930.
(8) Hickner, M. A.; Herring, A.; Coughlin, E. B. Anion Exchange
Membranes: Current Status and Moving Forward. J. Polym. Sci., Part
B: Polym. Phys. 2013, 51, 1727−1735.
(29) Yamamoto, T.; Morita, A.; Miyazaki, Y.; Maruyama, T.;
Wakayama, H.; Zhou, Z.-H.; Nakamura, Y.; Kanbara, T.; Sasaki, S.;
Kubota, K. Preparation of π-conjugated poly(thiophene-2,5-diyl),
poly(p-phenylene), and related polymers using zerovalent nickel
complexes. Linear structure and properties of the π-conjugated
polymers. Macromolecules 1992, 25, 1214−1223.
(9) Miyake, J.; Watanabe, M.; Miyatake, K. Ammonium-function-
alized poly(arylene ether)s as anion-exchange membranes. Polym. J.
2014, 46, 656−663.
(10) Valade, D.; Boschet, F.; Ameduri, B. Grafting Polymerization of
Styrene onto Alternating Terpolymers Based on Chlorotrifluoro-
ethylene, Hexafluoropropylene, and Vinyl Ethers, and Their
Modification into Ionomers Bearing Ammonium Side-Groups. J.
Polym. Sci., Part A: Polym. Chem. 2010, 48, 5801−5811.
(11) Valade, D.; Boschet, F.; Ameduri, B. Random and Block
Styrenic Copolymers Bearing Both Ammonium and Fluorinated Side-
Groups. J. Polym. Sci., Part A: Polym. Chem. 2011, 49, 4668−4679.
(12) Elabd, Y. A.; Hickner, M. A. Block Copolymers for Fuel Cells.
Macromolecules 2011, 44, 1−11.
(13) Tanaka, M.; Fukasawa, K.; Nishino, E.; Yamaguchi, S.; Yamada,
K.; Tanaka, H.; Bae, B.; Miyatake, K.; Watanabe, M. Anion Conductive
Block Poly(arylene ether)s: Synthesis, Properties, and Application in
Alkaline Fuel Cells. J. Am. Chem. Soc. 2011, 133, 10646−10654.
(14) Yokota, N.; Ono, H.; Miyake, J.; Nishino, E.; Asazawa, K.;
Watanabe, M.; Miyatake, K. Anion Conductive Aromatic Block
Copolymers Containing Diphenyl Ether or Sulfide Groups for
Application to Alkaline Fuel Cells. ACS Appl. Mater. Interfaces 2014,
6, 17044−17052.
(30) Ono, H.; Miyake, J.; Shimada, S.; Uchida, M.; Miyatake, K.
Anion exchange membranes composed of perfluoroalkylene chains
and ammonium-functionalized oligophenylenes. J. Mater. Chem. A
2015, 3, 21779−21788.
(31) Miyake, J.; Mochizuki, T.; Miyatake, K. Effect of the Hydrophilic
Componentin Aromatic Ionomers:Simple Structure Provides Im-
proved Properties as Fuel Cell Membranes. ACS Macro Lett. 2015, 4,
750−754.
(32) Ono, H.; Miyake, J.; Bae, B.; Watanabe, M.; Miyatake, K.
Synthesis and Properties of Partially Fluorinated Poly(arylene ether)
Block Copolymers Containing Ammonium Groups as Anion
Conductive Membranes. Bull. Chem. Soc. Jpn. 2013, 86, 663−670.
(33) Ren, X.; Price, S. C.; Jackson, A. C.; Pomerantz, N.; Beyer, F. L.
Highly Conductive Anion Exchange Membrane for High Power
Density Fuel-Cell Performance. ACS Appl. Mater. Interfaces 2014, 6,
13330−13333.
(15) Shimada, M.; Shimada, S.; Miyake, J.; Miyatake, K.; Uchida, M.
Anion Conductive Aromatic Polymers Containing Fluorenyl Groups:
Effect of the Position and Number of Ammonium Groups. J. Polym.
Sci., Part A: Polym. Chem. 2016, 54, 935−944.
(16) Fujimoto, C.; Kim, D.-S.; Hibbs, M.; Wrobleski, D.; Kim, Y. S.
Backbone stability of quaternized polyaromatics for alkaline membrane
fuel cells. J. Membr. Sci. 2012, 423−424, 438−449.
(17) Arges, C. A.; Ramani, V. Two-dimensional NMR spectroscopy
reveals cation-triggered backbone degradation in polysulfone-based
anion exchange membranes. Proc. Natl. Acad. Sci. U. S. A. 2013, 110,
2490−2495.
(18) Li, N.; Leng, Y.; Hickner, M. A.; Wang, C.-Y. Highly Stable,
Anion Conductive, Comb-Shaped Copolymers for Alkaline Fuel Cells.
J. Am. Chem. Soc. 2013, 135, 10124−10133.
J
DOI: 10.1021/acs.macromol.6b00408
Macromolecules XXXX, XXX, XXX−XXX