Experimental Section

9,9-Bis(hydroxyphenyl)fluorene (BHF) (> 97%, TCI), dimethylamine (> 40wt%, Kanto Chemical), formic acid (35-37wt%, Kanto Chemical), tetrahydrofuran (Kanto Chemical), ethanol (97%, Kanto Chemical), decafluorobiphenyl (DFBP) (> 98%, TCI), hexafluorobisphenol A (HFBPA) (> 98%, TCI), toluene dehydrated (> 99.5%, Kanto Chemical), chloromethyl methyl ether (CMME) (> 94%, Kanto Chemical), 0.5 M zinc chloride in tetrahydrofuran solution (Aldrich), 1,1,2,2-tetrachloroethane (TCE) (> 98%, Kanto Chemical), 45wt% trimethylamine aqueous solution (Aldrich), and iodomethane (Kanto Chemical) were used as received. N,N-Dimethylacetamide (DMAc) (> 99%, Kanto Chemical) was dried over molecular sieves 4 Å at least 1 day before use. Potassium carbonate (Kanto Chemical) was dried in a vacuum oven at least 12 h before use. Other chemicals were of commercially available grade and used as received.

Synthesis of Hydrophobic Oligomer 1

A typical procedure for the hydrophobic oligomer 1 is as follows. A three-necked flask with a nitrogen inlet and a Dean-Stark trap was charged with HFBPA (1.09 g, 3.24 mmol), K2CO3 (1.12 g, 8.11 mmol), DMAc (7.5 mL), and toluene (3 mL). The mixture was heated at 160 °C for 3 h for azeotropic dehydration in nitrogen atmosphere. The mixture was cooled down to room temperature. DFBP (1.00 g, 2.99 mmol) in DMAc (2.5 mL) solution was added to the mixture. The reaction was carried out at 50 °C for 3 h. After the reaction, the mixture was poured into a large excess of deionized water. The resulting precipitate was collected by filtration. The

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crude product was washed with hot water and hot methanol several times, and dried at 60 °C in a vacuum oven to obtain oligomer 1 in 93% yield. In a similar manner, hydrophobic oligomers with different chain lengths and end groups were synthesized by changing the feed ratio of the comonomers.

Synthesis of Hydrophilic Precursor Oligomer 2

A typical procedure for the hydrophilic precursor oligomer 2 for QPE-bl-3 is as follows. A three-necked flask with a nitrogen inlet and a Dean-Stark trap was charged with BHF (1.18 g, 3.36 mmol), K2CO3 (1.04 g, 7.50 mmol), DMAc (7.5 mL), and toluene (3 mL). The mixture was heated at 160 °C for 3 h for azeotropic dehydration in nitrogen atmosphere. The mixture was cooled down to room temperature. DFBP (1.00 g, 2.99 mmol) in DMAc (2.5 mL) solution was added to the mixture. The reaction was carried out at 60 °C for 3 h. Then, additional BHF (0.12 g, 0.34 mmol) was added to ensure the end-capping reaction. After the reaction for another 1 h, the mixture was poured into a large excess of deionized water. The resulting precipitate was collected by filtration. The crude product was washed with hot water and hot methanol several times, and dried at 60 °C in a vacuum oven to obtain oligomer 2 in 89% yield. In a similar manner, hydrophilic precursor oligomers with different chain lengths were synthesized by changing the feed ratio of the comonomers.

Synthesis of Block Copolymers of PE-bl-3

A typical procedure for the block copolymerization is as follows (PE-bl-3). A three-necked flask with a nitrogen inlet was charged with hydrophobic oligomer 1 (0.74 g, 0.22 mmol), hydrophilic precursor oligomer 2 (1.85 g, 0.22 mmol), K2CO3

(0.046 g, 0.33 mmol), and DMAc (15 mL). The polymerization reaction was carried out at 60 °C for 6 h. After the reaction, the mixture was poured into a large excess

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of deionized water. The resulting precipitate was washed with hot water and hot methanol several times, and dried at 60 °C in a vacuum oven to obtain PE-bl-3 in 87% yield. In a similar manner, PE-bl-3 M2 and M4 were synthesized from 3 and 4, respectively.

Synthesis of CMPE-bl-3

A typical procedure for the chloromethylation reaction of PE-bl-3 is as follows.

A flask was charged with PE-bl-3 (1.00 g, 0.22 mmol) and TCE (26.7 mL). In a glove box charged with nitrogen, excess of CMME (7.0 mL, 97.7 mmol) and ZnCl2 (2.4 mL, 1.22 mmol) were added to the mixture. The reaction was carried out at 50 °C for 48 h in the sealed flask. After the reaction, the mixture was poured into a large excess of MeOH. The resulting precipitate was washed with hot methanol several times, and dried at 40 °C in a vacuum oven to obtain CMPE-bl-3 in 98% yield.

Membrane Preparation and Quaternization of CMPE-bl-3

CMPE-bl-3 (1.00 g) was dissolved in TCE (10 mL) and filtered. The filtrate was cast on a flat glass plate and heated at 60 °C for 4 h to dryness to obtain a CMPE-bl-3 membrane (ca. 50 μm thick). The resulting membrane was immersed in a large excess of 45 wt% TMA aqueous solution at room temperature for 48 h. The membrane was washed with and stored in degassed water.

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Scheme 2-1. Synthesis of QPE-bl-3.

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Synthesis of 9,9-Bis(3-dimethylaminomethyl-4-hydroxyphenyl)fluorene (BHF-M2)

A one-necked flask was charged with BHF (4.00 g, 11.4 mmol), ethanol (24 mL), formaldehyde (6.0 mL, 79.9 mmol), and dimethylamine (7.2 mL, 57.07 mmol). The mixture was stirred at 40 °C for 24 h. The resulting precipitate was collected by filtration. The crude product was washed with hot methanol and water several times, and dried at 40 °C in a vacuum oven to obtain BHF-M2 in 83% yield. ¹H NMR (500 MHz, TCE-d2, δ in ppm): 6.65-6.67 (2H, d, Ha), 7.00-7.02 (4H, d, Hb), 7.26-7.29 (2H, t, Hd), 7.34-7.38 (4H, m, Hc,e), 7.74-7.76 (2H, d, Hf), 3.72 (4H, s, Hi), 2.25 (12H, s, Hj).

Synthesis of 9,9-Bis(3,5-bis(dimethylaminomethyl)4-hydroxyphenyl)fluorene (BHF-M4)

A one-necked flask was charged with BHF (4.00 g, 11.4 mmol), tetrahydrofuran (24 mL), formaldehyde (6.0 mL, 79.9 mmol), and dimethylamine (7.2 mL, 57.07 mmol). The mixture was stirred at 50 °C for 24 h. The resulting precipitate was collected by filtration. The crude product was washed with hot methanol and water several times, and dried at 40 °C in a vacuum oven to obtain BHF-M4 in 91% yield.

1H NMR (500 MHz, TCE-d2, δ in ppm): 6.75-6.77 (2H, s, Hb), 7.21-7.38 (3H, m, Hc, d, e), 7.74-7.76 (1H, d, Hf) , 3.71 (8 H, s, Hi), 2.24 (24 H, s, Hj).

Scheme 2-2 Synthesis of (a) BHF-M2 and (b) BHF-M4.

(a)

(b)

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Scheme 2-3. Synthesis of QPE-bl-3 M2 and M4.

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Synthesis of Hydrophilic Precursor Oligomer 3

A typical procedure for the hydrophilic precursor oligomer 3 for QPE-bl-3 M2 is as follows. A three-necked flask with a nitrogen inlet was charged with BHF M2 (1.42 g, 4.27 mmol), DFBP (1.58 g, 3.42 mmol), K2CO3 (1.18 g, 8.54 mmol), and DMAc (15 mL). The reaction was carried out at 60 °C for 6 h. Then, additional DFBP (0.16 g, 0.34 mmol) was added to ensure the end-capping reaction. After the reaction for another 1 h, the mixture was poured into a large excess of deionized water. The resulting precipitate was collected by filtration. The crude product was washed with hot water and hot methanol several times, and dried at 60 °C in a vacuum oven to obtain oligomer 3 in 84% yield. In a similar manner, hydrophilic precursor oligomers 3 with different chain length were synthesized by changing the feed ratio of the comonomers.

Synthesis of Hydrophilic Precursor Oligomer 4

A typical procedure for the hydrophilic precursor oligomer 4 for QPE-bl-3 M4 is as follows. A three-necked flask with a nitrogen inlet was charged with BHF M4 (1.00 g, 2.99 mmol), DFBP (1.09 g, 3.24 mmol), K2CO3 (1.12 g, 8.11 mmol), and DMAc (20 mL). The reaction was carried out at 60 °C for 6 h. Then, additional DFBP (0.11 g, 0.32 mmol) was added to ensure the end-capping reaction. After the reaction, the mixture was poured into a large excess of deionized water. The resulting precipitate was collected by filtration. The crude product was washed with hot water and hot methanol several times, and dried at 60 °C in a vacuum oven to obtain oligomer 4 in 87% yield. In a similar manner, hydrophilic precursor oligomers 4 with different chain length were synthesized by changing the feed ratio of the

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comonomers.

Synthesis of Block Copolymers of PE-bl-3 M2 and M4.

A typical procedure for the block copolymerization is as follows (PE-bl-3 M2).

A three-necked flask with a nitrogen inlet was charged with hydrophobic oligomer 1 (0.14 g, 0.02 mmol), hydrophilic precursor oligomer 3 (0.36 g, 0.02 mmol), K2CO3

(0.006 g, 0.04 mmol), and DMAc (5 mL). The polymerization reaction was carried out at 60 °C for 8 h. After the reaction, the mixture was poured into a large excess of deionized water. The resulting precipitate was washed with hot water and hot methanol several times, and dried at 60 °C in a vacuum oven to obtain PE-bl-3 M2 in 89% yield. In a similar manner, PE-bl-3 M4 were synthesized from 1 and 4, respectively.

Quaternization and Membrane Preparation of QPE-bl-3 M2 and M4.

A typical procedure for the quarternization reaction of QPE-bl-3 M2 is as follows.

A one-necked flask was charged with PE-bl-3 M2 (1.00 g, 0.59 mmol of dimethylbenzylamine groups), CH3I (0.20 g, 1.42 mmol) and DMAc (10 mL). The reaction was carried out at 40 °C for 24 h in a sealed flask. After the reaction, the mixture was cast on a flat glass plate and heated at 60 °C for 4 h to obtain a QPE-bl-3 M2 membrane (ca. 50 μm thick). In a similar manner, 3 M2s and PE-bl-3 M4s with different copolymer compositions were quaternized.

Exchange of Counter Ions of the Quarternized Membranes

The quaternized membranes were immersed in a large excess of 1 M KOH at

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room temperature for 48 h. The membranes were washed with and stored in degassed water.

Measurements

1H and ¹⁹F NMR spectra were obtained on a JEOL JNM-ECA/ECX500 using CDCl3 for BHF-M4, 1, 2, 3, and PE-bl-3s, and deuterated 1,1,2,2-tetrachloroethane (TCE-d2) for BHF-M2, CMPE-bl-3s, PE-bl-3 M2s, and PE-bl-3 M4s, and DMSO-d6

for QPE-bl-3s, QPE-bl-3 M2s, and QPE-bl-3 M4s as solvents and tetramethylsilane (TMS) as an internal reference. Molecular weight was measured with a gel permeation chlomatography (GPC) equipped with a Jasco 805 UV detector, a Shodex SB-803 HQ column for oligomers and a Shodex K-805L for polymers using DMF containing 0.01 M LiBr as eluent. Molecular weights were calibrated with standard polystyrene samples. For transmission electron microscopic (TEM) observation, membrane samples were stained with tetrachloroplatinate ions by ion exchange of the ammonium groups in a 0.5 M K2[PtCl4] aqueous solution, rinsed with deionized water, and dried in a vacuum oven at 40 °C for 8 h. The stained membranes were embedded in epoxy resin, sectioned to 50 nm thickness with a Leica microtome Ultracut UCT, and placed on copper grids. Images were taken on a Hitachi H-9500 transmission electron microscope with an acceleration voltage of 200 kV.

The hydroxide ion conductivities of the membranes were measured in degassed, deionized water (18 MΩ cm) at 30, 40, 60, and 80 °C using a four-probe conductivity cell attached with AC impedance spectroscopy (Solartoron 1255B, Solartron Inc.) Ion conducting resistances (R (Ω)) were determined from the impedance plots obtained in the frequency range from 1 to 10⁵ Hz. The hydroxide ion conductivity

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(σ (S/cm)) was calculated from the equation σ = (l / A × R), where l (cm) is the distance between inner two probes and A (cm²) is the conducting area. Water uptake (ΔW (%)) measurement was carried out in degassed, deionized water at room temperature for 24 h. Drying the membranes in a vaccum oven at 60 °C for 8 h provided a dry weight (Wd (g)). Wet weight (Ww (g)) was measured after wiping off the surface water carefully with tissue paper. The water uptake of the membranes was calculated from the equation, ΔW(%) = (Ww - Wd) / Wd × 100.

Dynamic mechanical analysis (DMA) was carried out with an ITK DVA-225 dynamic viscoelastic analyzer. Relative humidity (RH) dependence of storage modulus (E' (Pa)), loss modules (E'' (Pa)), and tan δ at 80 °C was obtained for the membranes (5 mm × 30 mm) at a humidification rate of 1 %RH min^-1 from 0% to 90%.

Gas permeability was measured with a GTR-XFYC gas permeation measurement apparatus equipped with a Yanaco G2700T gas chloromatography and a Porapak-Q column and a TCD detector. Argon and helium were used as carrier gases for the measurement of hydrogen and oxygen, respectively. Gas permeation coefficient, Q (cm³ (STD) cm/cm² s cmHg) was calculated by the following equations, Q = 273/T

× 1/A × B × 1/t × l × 1/(76-PH2O) where T (K) is the absolute temperature of the cell, A (cm²) is the permeation area, B (cm³) is the amount of permeated test gas, t (s) is the sampling time, l (cm) is the thickness of the membrane and PH2O (cmHg) is the water vapor pressure. The measurement was carried out at 80 °C and 30, 60, and 90% RH.

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Preparation of Catalyst Coated Membrane (CCM)

A zirconia pot was charged with platinum catalysts supported on carbon black (TEC10E50E, Tanaka Kikinzoku Kogyo Co., ltd.), water, and 1-propanol. The mixture was stirred with a ball mill at 270 rpm for 30 min. Commercially available anion conductive ionomer Tokuyama AS-4 (AS-4 / carbon black = 0.8 by weight) was added to the mixture, which was stirred for another 30 min to obtain the catalyst ink. The obtained ink was sprayed on both sides of the QPE-bl-3 membrane (x5y10, IEC = 1.7 meq/g, 62 μm thick in hydroxide ion form) by pulse-swirl-spray technique.

The loading amount of Pt was 0.22 g/cm² for the anode and 0.20 g/cm² for the cathode, respectively. The obtained catalyst-coated membrane (CCM) was pressed at 10 kf/cm² at room temperature for 3 min.

Fuel Cell Operation

The CCM was sandwiched by two gas diffusion layers (25BC, SGL Carbon Group Co., ltd.) and mounted into a single cell in which the electrode area was 4.41 cm². The flow fields were serpentine and comb-shaped for the anode and the cathode, respectively. The fuel cell was pre-operated at 40 °C and 30 mA/cm² for 3 h. The fuel cell was operated with fully humidified (100% RH) hydrogen and oxygen at 40

°C. The flow rate was set at 100 mL/min for both gases.

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