Supporting Information Anion Conductive Block Poly(arylene ether)s: Synthesis, Properties, and Application in Alkaline Fuel Cells Manabu Tanaka, Keita Fukasawa, Eriko ishino, Susumu Yamaguchi, Koji Yamada, Hirohisa Tanaka, Byungchan Bae, Kenji Miyatake,*,, and Masahiro Watanabe*, Fuel Cell anomaterials Center and Clean Energy Research Center, University of Yamanashi, 4 Takeda, Kofu 400-8510, Japan Daihatsu Motor Co. Ltd., Frontier Technology R&D Division, 3000 Ryuo, Gamo, Shiga 520-2593, Japan miyatake@yamanashi.ac.jp (KM), m-watanabe@yamanashi.ac.jp (MW) S1
EXPERIMETAL SECTI Materials. 4,4 -Difluorodiphenyl sulfone (FPS) and 4,4 -dihydroxybenzophenone (DHBP) were purchased from TCI Inc. and crystallized from toluene. 9,9-Bis(4-hydroxyphenyl)fluorene (BHF) was purchased from TCI Inc. and used as received. Chloromethyl methyl ether (CMME), zinc chloride, trimethylamine aqueous solution (30 wt%), potassium carbonate, calcium carbonate, sodium hydroxide, potassium hydroxide, sodium bicarbonate, 1,1,2,2-tetrachloroethane (TCE), tetrahydrofurane (THF), toluene, methanol, chloroform, acetone, and,-dimethylformamide (DMF) were purchased from Kanto Chemical Co. and used as received.,-dimethyl acetamide (DMAc, organic synthesis grade, 99%) was purchased from TCI Inc. and dried over 3 A molecular sieves prior to use. Hydrazine hydrate aqueous solution (60 wt%) was supplied from tsuka Chemical Co., Ltd. Polymerization. Precursor multiblock poly(arylene ether)s (PEs) were prepared according to our previously reported method. 1,2 A typical polymerization procedure for PE-X16Y11, in which X represents the number of repeat units in the hydrophobic segment and Y represents the number of repeat units in the fluorene-containing (later hydrophilic) segment, was as follows. The hydrophobic oligomer was first synthesized. A 300 ml round-bottomed flask was charged with FPS (10.000 g, 39.331 mmol), DHBP (7.9300 g, 37.018 mmol), and potassium carbonate (13.589 g, 98.328 mmol). The polymerization reaction was carried out in 160 ml of DMAc and 40 ml of toluene with a Dean-Stark trap under nitrogen flow. The reaction temperature was maintained at 150 C for 3 h before the Dean-Stark trap was removed. The reaction was continued at 170 C for another 3 h under nitrogen flow to obtain a light yellow, viscous mixture. A small amount of FPS (0.5000 g, 1.9666 mmol) was added to the mixture to ensure end-capping of the oligomer with fluorine-containing terminal groups. The mixture was stirred at 170 C for 1 h, and poured into a large excess of hot water while hot. The precipitated crude oligomer was washed with deionized S2
water and methanol several times. After being collected with a glass filter (G2) and drying at 80 C under vacuum, the hydrophobic oligomer was obtained. The degree of polymerization of the hydrophobic oligomer was determined to be X = 8 from the integral ratio in the 1 H MR spectrum. The fluorene-containing oligomer was synthesized similarly to the hydrophobic oligomer. A 300 ml round-bottomed flask was charged with FPS (5.000 g, 19.666 mmol), BHF (7.7524 g, 22.124 mmol), and potassium carbonate (7.6444 g, 55.310 mmol). The polymerization reaction was carried out in 80 ml of DMAc and 20 ml of toluene with a Dean-Stark trap under nitrogen flow. The reaction temperature was maintained at 140 C for 2 h before the Dean-Stark trap was removed. The reaction was continued at 165 C for another 2 h under nitrogen flow, and then a small amount of BHF (0.3876 g, 1.1062 mmol) was added to ensure end-capping. After stirring the mixture at 165 C for 1 h, the oligomer was recovered and purified in a similar way to the above-mentioned hydrophobic oligomer. The degree of polymerization of the fluorene-containing oligomer was determined to be Y = 11 from the integral ratio in the 1 H MR spectrum. Block copolymerization was carried out as follows. The hydrophobic oligomer (7.4300 g, [-F] = 20.000 mmol), the fluorene-containing oligomer (6.7817 g, [-H] = 20.000 mmol), potassium carbonate (3.4553 g, 25.000 mmol), calcium carbonate (25.048 g, 250.00 mmol), DMAc (100 ml), and toluene (25 ml) were mixed in a 300 ml round-bottomed flask. The mixture was stirred at 145 C for 3 h under nitrogen flow before the Dean-Stark trap was removed. The polymerization was continued at 160 C for 5 h. The mixture was diluted with ca. 100 ml of DMAc at 160 C and poured dropwise into a large excess of hot water while hot. The crude product obtained was washed with deionized water and methanol several times. After being collected with a glass filter (G2) and drying at 80 C under vacuum, the multiblock copolymer was obtained as a white powder. The copolymer was dissolved in 400 ml of chloroform, and then 600 ml of acetone was slowly added into the solution to precipitate the copolymer with a narrower molecular weight distribution. The S3
copolymer was dissolved in DMAc, reprecipitated from hot water, and washed with deionized water and methanol several times. The pure multiblock copoly(arylene ether), PE-X16Y11, was collected with a glass filter (G2) and dried at 80 C in a vacuum oven. Chloromethylation of Multiblock Copoly(arylene ether)s. A typical procedure for the chloromethylation reaction was as follows. A 50 ml pressure glass bottle was charged with PE-X16Y11 (1.0000 g, [fluorene unit] = 1.0374 mmol) and TCE (20 ml), and placed in a combinatorial reaction system (L-CS Pres., MRITEX Inc.). After stirring the mixture at 35 C for 30 min to ensure dissolution of the copolymer, zinc chloride (0.1414 g, 1.0374 mmol) in 1.0 ml THF solution and CMME (3.3408 g, 41.496 mmol) were added into the mixture. The reaction was carried out at 35 C for 120 h to obtain a yellow mixture. The mixture was diluted with ca. 20 ml of TCE and poured dropwise into a large excess of methanol. The crude product was washed with deionized water and methanol several times. After being collected with a glass filter (G2) and drying at 80 C under vacuum, the chloromethylated copolymer, CMPE-X16Y11, was obtained as a white powder. Membrane Preparation and Quaternization. The chloromethylated copolymer, CMPE-X16Y11 (1.000 g) was dissolved in 25 ml of TCE and the solution was filtered with a 0.45 µm PTFE membrane filter. The filtrate was cast onto a flat glass plate and dried on a hot plate at 60 C overnight under ambient conditions to give a 50 ± 5 µm thick, transparent, tough membrane. The membrane was immersed in a 30 wt% trimethylamine aqueous solution at room temperature for 2 days for the quaternization reaction. The resulting quaternized copolymer membrane was washed with water several times and immersed in a 1 M sodium hydroxide aqueous solution at room temperature for 2 days to convert the counter anions from chloride to hydroxide ions. The quaternized copoly(arylene ether) (QPE-X16Y11) membrane obtained was washed with deionized water several times and stored in a closed vessel filled with deionized water. S4
Measurements. 1 H MR spectra, molecular weight (gel permeation chromatography (GPC)), water uptake, and ion conductivity were measured as previously reported. 3,4 For scanning transmission electron microscopic (STEM) observations, the membrane samples were stained (ion-exchanged) with tungstate ions by immersing in 1.0 M sodium tungstate aqueous solution, rinsing with deionized water, and drying in a vacuum oven for 12 h. The stained samples were embedded in epoxy resin and sectioned to yield 90 nm thick samples using a Leica microtome Ultracut UCT and placed on copper grids. Images were taken on a Hitachi HD-2300C STEM using an accelerating voltage of 200 kv. Stress versus strain curves were obtained for samples cut into a dumbbell shape (DI-53504-S3, 35 mm 6 mm (total) and 12 mm 2 mm (test area)). Measurement was conducted at 60% RH and 80 C at a stretching speed of 10 mm/min. Thermal and hydrothermal stability tests of the QPE membranes were performed at a typical fuel cell operating temperature (80 C). Small pieces of QPE-X16Y11 (IEC = 1.65 or 1.75 meq/g) membranes were placed in vials filled with hot water or air, respectively. The vials were sealed and maintained at 80 C for 500 h. Changes in chemical structure after these tests were investigated by 1 H MR spectra. Fabrication of Membrane/Electrode Assembly (MEA) and Fuel Cell peration. A 100 mg portion of i powder (Inco, type 210H, 0.2-0.5 µm) was mixed with 0.96 ml of isopropanol, 0.24 ml of THF and 0.2 ml of 2 wt% anionic ionomer in THF solution (Tokuyama, A3). The mixture was sonicated for 5 min and mixed by a ball mill with Zr 2 beads (ikkato Corporation, diameter = 2.0 mm) for 15 min. The slurry obtained was sprayed onto a QPE-X16Y11 membrane (IEC = 1.93 meq/g, thickness (under ambient conditions) = 57 µm) to form the anode. For the cathode, the catalyst slurry was prepared from Co-polypyrrole (PPy)-C (Hokko Chemical Industry Co., Ltd.) powder and sprayed onto the other side of the membrane in a similar way to that described above. The loaded amounts of the catalysts were ca. 2.5 mg/cm 2 of i for the anode and ca. 0.2 mg/cm 2 of S5
Co-PPy-C for the cathode, respectively. The catalyst-coated membrane was pressed at 9 MPa for 30 s at 80 C to ensure tight contact between the catalyst layers and the membrane. The MEA thus prepared, with a geometric electrode area of 4.41 cm 2, was mounted in a single cell and treated with 1.0 M potassium hydroxide aqueous solution at a flow rate of 2 ml/min for 2 h at 80 C for the ion-exchange of the membrane to the hydroxide form. The fuel cell was operated at 80 C while supplying a mixture of 1.0 M potassium hydroxide and 5.0 wt% hydrazine aqueous solution to the anode at a flow rate of 2 ml/min and humidified oxygen or air (26 %RH) to the cathode at a flow rate of 500 ml/min. The operating pressure was set at 20 kpa for both electrodes. Serpentine and comb-shaped flow fields were used for the anode and the cathode, respectively. (1) Bae, B.; Yoda, T.; Miyatake, K.; Uchida, H.; Watanabe, M. Angew. Chem. Int. Ed. 2010, 49, 317-320. (2) Bae, B.; Miyatake, K.; Watanabe, M. Macromolecules 2010, 43, 2684-2691. (3) Tanaka, M.; Koike, M.; Miyatake, K.; Watanabe, M. Macromolecules 2010, 43, 2657-2659. (4) Tanaka, M.; Koike, M.; Miyatake, K.; Watanabe, M. Polym. Chem. 2011, 2, 99-106. S6
Complete reference 3. (3) Borup, R.; Meyers, J.; Pivovar, B.; Kim, Y.-S.; Mukundan, R.; Garland,.; 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.; ta, K.; gumi, Z.; Miyata, S.; ishikata, A.; Siroma, Z.; Uchimoto, Y.; Yasuda, K.; Kimijima, K.; Iwashita,. Chem. Rev. 2007, 107, 3904-3951. S7
Figure S1. 1 H MR spectra of (a) hydrophobic oligomer (X16) and (b) fluorene-containing oligomer (Y11). Figure S2. TEM image of QPE-X22Y11 (IEC = 0.89 meq/g) stained with tungstate ions. Figure S3. Possible degradation mechanisms of AEMs. Figure S4. 1 H MR spectra of QPE-X16Y11 (IEC = 1.65 meq/g) (a) before and (b) after long-term stability tests in hot water at 80 C for 500 h. Figure S5. 1 H MR spectra of QPE-X16Y11 (IEC = 1.75 meq/g) (a) before and (b) after long-term stability tests in hot air at 80 C for 500 h. Figure S6. 1 H MR spectra of QPE-X8Y8 (IEC = 1.26 meq/g) (a) before and after long-term conductivity tests in (b) hot water at 80 C for 5000 h. Table S1. Molecular weight of hydrophobic and fluorene-containing oligomers. S8
(a) F a b c d b' a' S C S F 16 CDCl 3 a c b d b' a' (b) e f H g' S h' g H h i' j' j i 11 k' l' k l CDCl 3 f i k h e g l j h' g' Figure S1. 1 H MR spectra of (a) hydrophobic oligomer (X16) and (b) fluorene-containing oligomer (Y11). S9
Figure S2. TEM image of QPE-X22Y11 (IEC = 0.89 meq/g) stained with tungstate ions. S10
1) H H 2) H 3 C H Stevens Rearragement H 2 H 3) H 3 C H H 2 4) H 3 C H Sommelet-Hauser rearrangement H 2 Figure S3. Possible degradation mechanisms of AEMs. S11
a b c d e f S C 16 S g H h o m i k H p n l h l g h 11 k j n DMS acetone (a) a,c,h,h b,d,f k,k e,g,g j,i,i l,l m,n m,n H2 o,p (b) 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 ppm Figure S4. 1 H MR spectra of QPE-X16Y11 (IEC = 1.65 meq/g) (a) before and (b) after long-term stability tests in hot water at 80 C for 500 h. S12
a b c d e f S C 16 S g H h o m i k H p n l h l g h 11 k j n DMS (a) a,c,h,h b,d,f k,k e,g,g j,i,i l,l m,n m,n H2 o,p acetone (b) 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 ppm Figure S5. 1 H MR spectra of QPE-X16Y11 (IEC = 1.75 meq/g) (a) before and (b) after long-term stability tests in hot air at 80 C for 500 h. S13
a b c d e f S C 8 S g H h o m i k H p n l h l g h 8 k j n DMS o,p (a) a,c,h,h b,d,f k,k e,g,g j,i,i l,l m,n m,n H2 acetone (b) 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 ppm Figure S6. 1 H MR spectra of QPE-X8Y8 (IEC = 1.26 meq/g) (a) before and after long-term conductivity tests in (b) hot water at 80 C for 5000 h. S14
Table S1. Molecular weight of hydrophobic and fluorene-containing oligomers. Expected btained btained ligomer oligomer length oligomer length a oligomer length b M n (kg/mol) M w (kg/mol) M w /M n X8 8 8 11 5,000 12,200 2.5 X16 16 16 33 14,700 29,500 2.0 X22 32 22 38 16,500 52,900 3.2 Y8 8 8 8.8 5,300 13,100 2.5 Y11 16 11 9.3 5,600 12,400 2.2 Y23 32 23 19 10,800 19,100 1.8 a Estimated from the 1 H MR spectra. b Estimated from the GPC data. S15