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SUPPORTING INFORMATION

A New Graphene-modified Protic Ionic Liquid-based Composite Membrane for Solid Polymer Electrolytes Yun-Sheng Yea, Chi-Yung Tsenga, Wei-Chung Shena, Jing-Shiuan Wanga, Kuan-Jung Chena, Meng-Yao Chenga, John Ricka, Yao-Jheng Huangb, Feng-Chih Changb and Bing-Joe Hwanga* a

CORRESPONDING AUTHRO E-mail ADDRESS: Chemical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan.

[email protected] b

S1. Experimental Section

Institute of Applied Chemistry, National Chiao-Tung University, Hsin-Chu, Taiwan.

S1.1. Materials

Triethylamine (TEA) (Aldrich), acetic anhydride (Acros), 2,2’-Benzidinesulfonic acid (BDSA)

(Tokyo Kasei), m-Cresol (Wako Chem.), lithium bis(trifluoromethylsulfonyl) amide (Li+NTFSI-)

(Acros), sodium tetrafluoroborate (Na+BF4-) (Aldrich), dimethyl sulfoxide (DMSO) (Acros),

dimethylformamide (DMF) (Acros), propylene carbonate (PC) (Acros) and acetonitrile (AN)

(Acros) were used as received. Pyromellitic dianhydride (PMDA) (Aldrich), 4,4′ -(1,3-

Phenylenedioxy)dianiline (PDDA) (Aldrich) and oxydiphthalic dianhydride (ODPA) (Aldrich) were

dried in a vacuum oven at 150 ºC prior to use. 4,4‘-Diaminodiphenyl Ether-2,2‘-disulfonic Acid

(ODADS), poly(sodium 4-styrenesulfonate) (PSS) and 1-butyl-3-methylimidazolium

bis(trifluoromethane sulfone)imide (BMIm-NTFSI) were synthesized as previously reported.[9c, 23]

2,2’-Benzidinedisulfonic acid (BDSA) was washed with water and then dissolvent in water by

adding TEA. Acidification with 1M H2SO4 (aq) precipitated pure BDSA. The TEA form of 4,4‘-

Diaminodiphenyl Ether-2,2‘-disulfonic Acid (ODADS) and 2,2’-Benzidinesulfonic acid (BDSA)

were dispersed in ethanol at 60 ºC then TEA was added to achieve complete dissolution. After

cooling at 0 ºC overnight, the precipitate was filtered off, washed with ethanol, and dried under

vacuum.

Electronic Supplementary Material (ESI) for Journal of Materials ChemistryThis journal is © The Royal Society of Chemistry 2011

mailto:[email protected]�

S1.2. Characterization

FT-IR spectra were obtained with a Nicolet Avatar 320 FTIR spectrometer; 32 scans were collected

at a spectral resolution of 1 cm-1. The XPS measurements were performed with ESCA 2000

systhem (VG Microtech) using a monochromatized aluminum Kα anode. Wide-angle X-ray

diffraction (WAXD) 10 spectra were recorded for powdered samples using a Rigaku D/max-2500

type X-ray diffraction instrument. A DuPont Q100 thermo-gravimetric analyzer (TGA) was 25

utilized to investigate the thermal stability of the membranes; the samples (~10 mg) were heated

from ambient temperature to 850 °C under a nitrogen atmosphere at a heating rate of 20 ºC min-1

S1.3. Synthesis of Sulfonated Polyimide (SPI)

.

The molecular characteristics of poly(1-vinyl-3-butylimidazolium) bromide [PIL-(Br)] were

determined by gel permeation chromatography (GPC, Waters Breeze). Tetrahydrofuran (THF) was

used as an eluent, and the PS standard was used for calibration.

In a one-pot high temperature imidization process, control over the molecular weight and end group

functionality was achieved using stoichiometrically adjusted amounts of the monomers (Fig. S9). A

completely dried 150-mL four-neck flask was charged with PDDA (0.87 g, 2 mmol), BDSA (TEA

form) (3.72 g, 8 mmol) and m-cresol (68 mL) with stirring under an Ar flow. After the BDSA (TEA

form) had completely dissolved, PMDA (2.18 g, 10 mmol) and benzoic acid (1.75 g) were added.

The reaction mixture was heated at 80 °C for 6 h and the mixture heated at 180 °C for another 24 h.

The resulting polymer solution was precipitated into isopropanol (IPA). The polymer was filtered

off, purified through Soxhlet extraction with methanol overnight, and then dried at 120 °C in vacuo

for at least 24 h (yield: 90%). Sulfonated polyimide SPI (ODADS series) was synthesized and

purified using the same procedure, and BDSA and PMDA were replaced by ODADS and ODPA,

respectively (yield: 93%).


OSO

OO N

O

O

N

O

On m

SO3

SO3

OSO

OO NH2H2N +n

M-cresol180 oC

SO3

H2N + O

O

O

n+m O

O

OO3S

NH2

N+

N +

N

O

O

N+

N+

N

O

O

PMDA

BDSA

PDDA

SPI(PDDA-BDSA-PMDA)

SPI(PDDA-ODADS-ODPA)

OSO

O

O N

O

O

N

O

On m

OSO

OO NH2H2N +n

M-cresol180 oC

SO3

H2N + O

O

O

n+mO

N+

ODPAPDDAO3S

NH2

N+

ODADS

OO

O

O

ON

O

O

SO3

O

N+

O3S

N+

ON

O

O

Scheme. S1. Schematic representation of the preparation of the SPI Table S1. Characterization of SPI (PDDA-BDSA-PMDA) and SPI (PDDA-ODADS-ODPA)

a IEC calculated from DS. b

IEC measured with titration.

Membrane Ion exchange capacity (meq/g)

Calculated IECth Titrationi IECa tit IECb

tit/IECth (%)

SPI (PDDA-BDSA-PMDA) 2.49 2.31 92.8

SPI (PDDA-ODADS-ODPA) 2.14 2.01 93.9


S2. FT-IR spectrum of graphene oxide

There are four main peaks centered at 1052, 1402 and 1738 cm-1. The peak at 1052 cm-1 arises from

epoxy (-O-) groups. The peak at 1738 cm-1 corresponds to the vibrational mode of the ketone (-

C=O) groups. The peak observed at 1402 cm-1

3500 3000 2500 2000 1500 1000 500

PIL(BF4)-G

PIL(NTFSI)-G

PSS-G

so2SO2-N c-o

c-o

Wavenumber (cm-1)

c=oc=c so2

BF4

GO

R-G

(b)

200 300 400 500 600200 300 400 500 600200 300 400 500 600200 300 400 500 600

Abs

orba

nce

PSS-G

R-G

GO

PIL( BF4) -G

wavelength (nm)

PIL(NTFSI)-G

(a)

is assigned to a C-O vibrational mode.

Fig. S1. (a) UV and (b) FT-IR spectra of GO, reduced GO (R-G), and an organic phase suspension of PSS-G, PIL(NTFSI)-G and PIL(BF4)-G.


292 290 288 286 284 282 280

epoxidehydroxyl C-OH

Carboxyl C=O

C-O

Binding Energy (eV)

C-C(A) GO

Inte

nsity

290 288 286 284 282 280

Binding Energy (eV)

Inte

nsity

(B) R-G

C-C

Fig. S2. (a) Carbon 1s XPS profile of GO and (b) R-G; comparison of XPS profile (c) PSS-G, (d) PIL(NTFSI)-G and (e) PIL(BF4)-G.


200 400 600 800

0

20

40

60

80

100

PIL(BF4) PIL(NTFSI)

Wei

ght (

%)

Temperature (o C)

PSS

200 400 600 800

40

60

80

100

Wei

ght (

%)

Temperature (o C)

GO G PSS-G PIL(NTFSI)-G PIL(BF4)-G

26.4 %24.4 %

(a) (b)

Fig. S3. TGA curves of (a) GO, R-G and modified graphene; (b) TGA curves of pure PSS, PIL(NTFSI) and PIL(BF4

10 20 30 40 50

Rel

ativ

e In

tens

ity

2 theta (degree)

1. GO2. RG3. PSS-G4. PIL(NTFSI)-G5. PIL(BF4)-G

1

2

3

5

4

).

Fig. S4. XRD curves of the GO, R-G, PSS-G, PIL(NTFSI)-G and PIL(BF4

)-G.


Fig. S5. Photographs of (1) - (3) correspond to DMSO dispersion of the GO (0.25 mg ml-1

) mixed with PIL-NTFSI, SPI and PSS and the weight ratio of the polymer to GO was 10; photographs of (4) - (6) correspond to (1) - (3) after being mixed with BMIm-NTFSI of 2.5 mg by shaking vigorously and then depositing for 30 min.

Fig. S6. Photographs of (1) - (5) correspond to BMIm-NTFSI dispersion of the (1) PIL(NTFSI)-G, (2) PIL(BF4)-G, (3) PSS-G, (4) R-G and (5) GO (0.25 mg ml-1).


88

Fig. S7. Ionic conductivities as a function of temperature of SPI/PIL(NTFSI)-G/PIL membranes in anhydrous conditions.

Fig. S8. The ionic conductivities of membranes incorporating the same amounts of PIL(NTFSI)-G (0.5 wt %) with various ratios of IL (50 ~ 80 wt%).


99

0.00.10.20.30.40.50.60.70.80.9

0.000

0.001

0.002

0.003

0.004

Ioni

c co

nduc

tivity

(S c

m-1

)

PIL(NTFSI)-G loading (wt%)

SPI (PDDA-BDSA-PMDA)

SPI (PDDA-ODADS-ODPA)

3.6 times

3.9 times

Fig. S9 The ionic conductivities of membranes incorporating the same amount of PIL(NTFSI)-G (0.5 wt %) with various ratios of PIL (50 ~ 80 wt%).

Fig. S10 TGA curves of SPI/PIL(NTFSI)-G/PIL composite membranes.


1010

REFERENCES AND NOTES

1. (a) Ye, Y.-S.; Cheng, M.-Y.; Tseng, J.-Y.; Liang, G.-W.; Rick, J.; Huang, Y.-J.; Chang,

F.-C.; Hwang, B.-J., New Proton Conducting Membranes with High Retention of Protic

Ionic Liquids. Journal of Materials Chemistry 2011; (b) Ye, Y.-S.; Chen, W.-Y.; Huang, Y.-

J.; Cheng, M.-Y.; Yen, Y.-C.; Cheng, C.-C.; Chang, F.-C., Preparation and

characterization of high-durability zwitterionic crosslinked proton exchange membranes.

Journal of Membrane Science 2010, 362 (1-2), 29-37; (c) Fang, J.; Guo, X.; Harada, S.;

Watari, T.; Tanaka, K.; Kita, H.; Okamoto, K.-i., Novel Sulfonated Polyimides as

Polyelectrolytes for Fuel Cell Application. 1. Synthesis, Proton Conductivity, and Water

Stability of Polyimides from 4,4‘-Diaminodiphenyl Ether-2,2‘-disulfonic Acid.

Macromolecules 2002, 35 (24), 9022-9028.


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