Journal of Membrane Science 338 (2009) 5160

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Journal of Membrane Science

journa l homepage: www.e lsev ier .com

Novel s oximembr t t

Yonghui nxuLab of Function hnolog

a r t i c l

Article history:Received 11 SeReceived in reAccepted 7 ApAvailable onlin

Keywords:Poly(2,6-dime(PPO)Hybrid membAnion-exchanAlkaline memHeat treatmen

,4-phationethoximes, incltroll0.00

e eloandrinatells.

1. Introduction

The possibility of alkaline membrane fuel cells (AMFCs) hasevoked extensive interest in the recent years due to manyadvantagesenhancemeegories, easthe actual aconcerns inanion-exchbranes in ththe ammonconductivition (OH) (tthat of prottivity, the msome casestraditionalate precipitthat one of tbranes withand thermaexchange m[6]. Unfortu

CorresponE-mail add

from fulllment. Most of the conventional anion-exchange mem-branes (AEMs) are for other applications such as pervaporation,electrodialysis, electroanalysis, etc. [11,12]. They are characterizedand used in the halide form, such as Cl, Br and I form, rather than

0376-7388/$ doi:10.1016/j.m, including the restraint of methanol crossover, thent of catalyst efciency, the expanding of catalyst cat-iness of water management, etc. [14]. Debate as topplication is under way meanwhile and widely quotedclude the ion conductivity and stability of the alkalineange membranes (AAEMs) [5,6]. Instability of the mem-e alkaline forms is mainly due to the displacement ofium group by the OH anions [7,8], while the low iony is at least partly caused by the low mobility of hydroxylhe diffusion coefcient of OH ions is much lower than

ons in nearly all media [5]). To improve the ion conduc-embranes absorb alkali metal hydroxides (KOH, etc.) in[9,10], which will give rise to problems similar to the

alkaline fuel cells, especially the formation of carbon-ates in presence of CO2. Therefore, it has been agreedhe most imperative tasks at present is to develop mem-high conductivity as well as excellent physico-chemicall stabilities. Only then, aqueous-electrolyte-free anion-embrane alkaline fuel cell can become really feasiblenately, this task of developing suitable AAEMs is far

ding author. Tel.: +86 551 360 1587.ress: twxu@ustc.edu.cn (T. Xu).

in alkaline (OH) form. As to AAEMs (OH form anion-exchangemembranes) aimed for fuel cell usage, only a few studies have beencarried out. Among these, radiation-grafted (partially) uorinated-polymer-based AAEMs show superior performances [13,14]. Theyare physically and thermally stable, and have high conductivity. Butsome properties, such as erosion resistance and mechanical proper-ties, need further improvement. Besides, their price should be muchhigher than that of membranes based on non-uoropolymers.

Organicinorganic hybrids have the excellent potential of incor-porating the merits of inorganic components (such as goodmechanical strength, thermal and chemical stability) into theorganic matrix [1517], and so permit an ideal possibility of pro-viding the needed ion conducting membranes for fuel cells. Up tonow, the cation-exchange hybrid membranes have been frequentlyreported, in the hope of replacing the expensive peruorocarboncation-exchange membranes such as Naon [1820]. As for theanion-exchange hybrid membranes, much less work has been con-ducted [21], so that the AAEMs now utilized for AMFCs are almostall of organic polymeric materials.

In our previous work, hybrid membranes have been preparedbased on poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) and 3-aminopropyl-trimethoxysilane [22]. They have proper thermalstability and high content of anion exchange groups, includ-ing mainly primary and secondary amine groups and also some

see front matter 2009 Elsevier B.V. All rights reserved.emsci.2009.04.012ilica/poly(2,6-dimethyl-1,4-phenyleneanes for alkaline fuel cells: Effect of hea

Wu, Cuiming Wu, Tongwen Xu , Xiaocheng Lin, Yaal Membranes, School of Chemistry and Material Science, University of Science and Tec

e i n f o

ptember 2008vised form 4 April 2009ril 2009e 15 April 2009

thyl-1,4-phenylene oxide)

ranesge membranes (AEMs)brane fuel cell (AMFC)t

a b s t r a c t

A series of silica/poly(2,6-dimethyl-1prepared. PPO is modied by brominsolgel reaction with monophenyl tritreatment at 120140 C for different tchemical properties of the membranesand tensile property, can be easily conbranes have proper conductivity (up to(TS) can be higher than 20 MPa and thchemical stability in alkali conditionsmembranes based on (partially) uopotential application in alkaline fuel c/ locate /memsci

de) hybrid anion-exchangereatment

n Fuy of China, Jinzai Road 96#, Hefei 230026, PR China

enylene oxide) (PPO) anion exchange hybrid membranes are, hydroxylation and quaternization in sequence. Subsequentysilane (EPh) and tetraethoxysilane (TEOS), followed by heat, yields the hybrid membranes. Results show that the physico-uding ion exchange property, hydrophilicity, OH conductivityed by adjusting the heating temperature and time. The mem-85 S/cm) and favorable tensile properties. The tensile strengthngation at break (Eb) is in the range of 5.519.5%. Besides, thethermal stability are comparable to those of anion-exchangeed-polymer. Hence, the hybrid membranes are suitable for

2009 Elsevier B.V. All rights reserved.

52 Y. Wu et al. / Journal of Membrane Science 338 (2009) 5160

s from

quaternarynot be used(1) there isibility andto be usedgroups can[5]. In themembraneslane (EPh)proceduresity and thepropertiesby the heabe fully dismembranetigated by

+N(C2H5)3 B

2. Experim

2.1. Materia

Poly(2,6and Mw/Mcal Engineemolecular stetraethoxyand potassiwas used.

2.2. Bromin

Reactionin detail inchlorobenzwas subjecbromine. Ththe extent oat 135 C to

rouduct

ydrox

Brnd t2/g)

en imf KOHh, aniduah.

routduct

uaterScheme 1. The preparation procedures of silicapolymer hybrid membrane

ammonium groups. However, these membranes can-for AMFC application because of the following defects:a lack of homogeneity; (2) there is a lack of ex-

mechanical strength, and thus alumina plates haveas supports; (3) the primary and secondary aminemake little contribution to the OH conductivity

present work, free-standing anion-exchange hybridwere prepared from PPO, monophenyl triethoxysi-

and tetraethoxysilane (TEOS), and new methods andwere adopted to increase the exibility, homogene-

content of quaternary ammonium groups. As theof membranes prepared from PPO are greatly affectedt treatment [23], the impacts of heat treatment willcussed. Particularly, the impacts of heat treatment tos hydrophilicity and thermal properties will be inves-using the Br form and OH form membranes, i.e.,

R(BR form) and +N(C2H5)3

OH (OH form).

Thethe pro

2.3. H

PPOtion, a(119 cmand thratio ofor 24the resfor 24

Thethe pro

2.4. Qental

ls

-dimethyl-1,4-phenylene oxide) of Mw = 48,000 g/moln = 2.7 was obtained from the Institute of Chemi-ring of Beijing (China). Chlorobenzene was kept inieve before use. Bromine, monophenyl triethoxysilane,silane, toluene, dimethyl formamide (DMF), ethanolum hydroxide were of analytical grade. Deionized water

ation of PPO

procedure for bromination of PPO was describedour previous papers [24,25]. PPO was dissolved in

ene to form a 20% (w/v) solution and this solutionted to bromination by adding chlorobenzene-dilutede molar ratio of bromine to PPO was 1.5:1 to controlf bromination, and the reaction temperature was xedcontrol the substitution position (benzyl).

PPOBrof chlorobeume ratio oadded withaddition, thstirred for 3solution grof particleswas addedcontinued f

The routthe resultanwas also quabove. CorrPPOBrOHcursor for t

2.5. Prepar

For the pcursors (PPand EPh) wpoly(2,6-dimethyl-1,4-phenylene oxide) (PPO).

te of bromination is shown in step 1 of Scheme 1, andis signied as PPOBr.

ylation of PPOBr

was dissolved in chlorobenzene to form 0.21 g/mL solu-hen scraped on a glass plate to form a membrane. The membrane was cut into small pieces (24 cm2),mersed in excessive 0.5 mol/L KOH solution (the molar/PPOBr was 4). The reaction was carried out at 55 C

d then the product was taken out and rinsed to removel alkaline solution. Finally, the product was dried at 40 C

e of hydroxylation is shown in step 2 of Scheme 1, andis signied as PPOBrOH.

nization of PPOBrOH and PPOBrOH was dissolved at room temperature in the mixturenzene and DMF to form 0.045 g/mL solution. The vol-f chlorobenzene/DMF was 1:1.2. Then triethylamine wasthe molar ratio of benzyl group/triethylamine 1:3. Aftere temperature was raised to 40 C and the mixture wash. As the reaction proceeded, formerly homogeneous

adually became turbid, and after 3 h a large numberwere suspended in the solution. Hence, 8 mL ethanol

to get a homogeneous solution again. The reaction wasor 10 h.e of quaternization is shown in step 3 of Scheme 1, andt is signed as PPOBrOH(+). For comparison, PPOBr

aternized by following the same procedure as describedespondingly, the resultant was signed as PPOBr(+).(+) and PPOBr(+) would be used as the polymer pre-

he preparation of the hybrid membranes.

ation of the hybrid membranes

reparation of hybrid membranes, different polymer pre-OBrOH(+) or PPOBr (+)) and different silanes (TEOSere used. In the solution of PPOBrOH(+) or PPOBr(+)

Y. Wu et al. / Journal of Membrane Science 338 (2009) 5160 53

Table 1Molar ratio of silanes (TEOS and EPh) with respect to the phenyl groups of PPOBror PPOBrOH, for the preparation of hybrid membranes.

Membrane A B (B0B6) C A B C

PPOBr 1 1 1PPOBrOH 1 1 1 TEOS 0.25 0.125 0.25 0.125 EPh 0.125 0.25 0.125 0.25

as prepared in Section 2.4, TEOS, EPh, or TEOS + EPh (1:1, molarratio) were added, followed by adding 0.1 mol/L HCl. The molar ratioof TEOS, EPmolar ratiowas stirredat room tem

To studyTeon plateferent timethe rate of 5membranesand differerespectivelyfrom PPOBas A, B ancontinued tingly, which3 h, and 13and 140 Cthe last temmembranes

The routobtained m

2.6. Charac

1H NMRon a Brukeras solvent, aof the memtor 22, Bruk4000400 cmadzu TGA10 C/min.

To convemembranesperature, anthe absorbewere driedto absorb Cand thermaBr and OHon membraconducted o

The hydwere investwater uptaksimilar to pr

at 25 C for 2 days and weighed after removal of surface water.Then the samples were dried in a desiccator for a week (for OH

form samples) or 105 C for 6 h (for Br form samples), and nallyweighed. WR-Br or WR-OH was calculated as the relative weight gainper gram of the dry sample.

Ion exchange capacities (IECs) were measured in the mannersimilar to our previous works [26]. Dry membrane was accu-rately weighed and converted to Cl form in 1.0 mol/L NaCl for 2days. Excessive NaCl was washed off, and then the membrane wasimmersed in 0.5 mol/L Na2SO4 for 2 days. Anion exchange capac-ities were obtained by determining the amount of the exchangedCl through titration with 0.1 mol/L AgNO3.

appln alkonce27]:h. Thnd thurestreaas IEwas

e solcro

ed w). Thn antens

(Modhead. Tenecordmemr-pourreo inTheountontaT 30 (

odefrommpednce w

) con:

d

R isial-sef thell waeasuratur

Table 2Heat treatmen

Membrane

Heating time aHeating time aHeating time aHeating time ah, or TEOS + EPh to phenyl groups was 25%, while theof H2O:HCl:Si(OR) was 6:0.0108:1. The mixed solutionat 40 C for 24 h. Then it was cast onto Teon plate, driedperature for 3 days.the impacts of heat treatment, membranes on thewere further dried at different temperatures for dif-

s: (1) membranes were heated from 50 C to 120 C atC/h and kept at 120 C for 3 h. As shown in Table 1, sixwere obtained. The membranes from PPOBrOH(+)

nt silane(s) such as TEOS, TEOS + EPh and EPh weresigned as A, B and C. Correspondingly, the membranesr(+) and the silane(s) (TEOS and/or EPh) were signed

d C. (2) Seven pieces of membrane B were used ando heat. Seven membranes were obtained correspond-

were signed as B0 (125 C for 3 h), B1B5 (125 C for0 C for 110 h), and B6 (125 C for 3 h, 130 C for 10 hfor 3 h), as shown in Table 2. For convenience, onlyperature was used to describe the heat treatment of.e of solgel process is shown in step 4 of Scheme 1. Theembranes are in the Br form.

terizations

spectra of PPO, PPOBr and PPOBrOH were recordedDMX-300 NMR instrument at 300 Hz. CDCl3 was usednd tetramethylsilane as internal standard. FTIR spectrabranes were recorded using FTIR spectrometer (Vec-er) with a resolution of 2 cm1 and a spectral range ofm1. The thermal behavior was analyzed with a Shi--50H analyzer under air ow and with a heating rate of

rt the membranes from the Br form to the OH form,were immersed in 0.5 mol/L KOH for 16 h at room tem-d then washed with water for four times to remove

d alkaline solution completely. Finally, the membranesin a desiccator (at normal pressure, solid KOH was usedO2 in the air before drying) for a week. Water uptakel analysis were conducted on the membranes in both form, while the OH conductivity was determinednes in the OH form. The other characterizations weren membranes in the Br form.

rophilicities of membranes in both Br and OH formigated. Br form water uptake (WR-Br) and OH forme (WR-OH) were measured by following the proceduresevious papers [13,26]: samples were immersed in water

Forbility iwith ctance [2192days, aprocedbranessignedto IEC0alkalin

TheobservPHILIPnitroge

Thetestera cross25 mmwere r

Themal fououter cand twapart).was mgood cPGSTAstatic mrangestant iresistaion (OHequati

= LRW

wherepotentness othe cewas mtempe

t for the preparation of the hybrid membranes (membranes AC, A C , and B0B6).

AC and AC B0 B1 B

t 120 C (h) 3 3 3 3t 125 C (h) 3 3 3t 130 C (h) 1 2t 140 C (h)ication in fuel cells, membrane should have enough sta-aline condition. Therefore, the membrane was treatedntrated alkaline solution to test their alkaline resis-membrane was immersed in 2 mol/L NaOH at 25 C foren, it was washed and immersed in 1 mol/L NaCl for 2e IEC of the membranes was measured with the sameas described above. To distinguish the IEC of the mem-

ted with alkaline solution and untreated, the former wasCt, and the latter was signed as IEC0. The ratio of IECtrecorded as a function of the immersion time in the

ution.ss-section morphologies of hybrid membranes wereith a scanning electron microscopy (XT30 ESEM-TMPe membranes were cryogenically fractured in liquidd then coated with gold before observation.ile properties were measured using an Instron universalel 1185) at 25 C with dumbbell shaped specimens atspeed of 25 mm/min, with an initial gauge length of

sile strength (TS) and elongation at break (Eb) valuesed.brane OH conductivity was measured using the nor-

int probe technique. The measuring cell (Telfon) has twont-carrying electrodes (stainless steel, at, 1 cm apart)ner potential-sensing electrodes (platinum, wire, 1 cmmembrane sample, 1 cm of width and 4 cm of length,ed on the cell; the screws were tightened to ensurect. The impedance was determined using an AutolabEco Chemie, Netherland, with FRA2 module) at galvano-with ac current amplitude of 0.1 mA over a frequency1 MHz to 50 Hz. The frequency corresponding to con-ance region was obtained using a Bode plot, and theas then obtained from a Nyquist plot. The hydroxyl

onductivity () is calculated according to the following

the membrane resistance, L is the distance betweennsing electrodes, and W and d are the width and thick-membrane, respectively. During the measurement,

s soaked in puried water. Hence, the conductivityred when the membrane was fully hydrated at roome.

2 B3 B4 B5 B6

3 3 3 33 3 3 34 6 10 10

3

54 Y. Wu et al. / Journal of Membrane Science 338 (2009) 5160

Fig. 1. 1H NMR spectra of PPO, PPOBr and PPOBrOH.

3. Results and discussion

3.1. 1H NMR and FTIR spectra

To comPPOBrOHThe characting to our pnew peak abenzyl subspeak intensof PPOBrthe peak inping of benof benzylOylation degintensity of

For memin the PPOreaction (tomembranes

Fig. 2. The FTImembrane B3,

band between 3100 cm1 and 3700 cm1, which is ascribed to thestretching vibration of OH groups from SiOH and benzylOHgroups, and maybe some absorbed water. The bands in the28503040 cm1 region and at 1465 cm1 are from the stretchingof CH3, Cis attributethe peaks aCOC and

From meing temperadsorptionloss of quatThe possiblternary amphenyl grouB0 to B6, thThis suggesdegree of si

3.2. Optimi

As mendecide theTEOS + EPhtion with P

tivelyo th

C wembra) (20of m2) M.08 m

e IECerented ter prn wtherenic pen aromvale

, memor thgreepare the chemical structure of PPO, PPOBr and, 1H NMR spectra were conducted and shown in Fig. 1.

eristic proton resonance signals of PPO are given accord-revious reports [24]. In the curve of PPOBr, there is at 4.4 ppm, which is due to the CH2Br groups. Thetitution ratio in PPOBr, as calculated from the relativeity of CH2Br and phenyl groups, is 86.5%. The curveOH is very similar to PPOBr except for an increase intensity at 4.4 ppm. The increase is due to the overlap-zylOH groups with CH2Br groups, because the peakH groups can appear in a wide range [28]. The hydrox-

ree of PPOBrOH, as calculated from the relative peakbenzylOH and phenyl groups, is 2.8%.brane preparation, the CH2Br and benzylOH groupsBrOH were subjected to quaternization and solgelgether with TEOS and EPh). FTIR spectra of the hybrid

were shown in Fig. 2. All the spectra show a large

respecundergB and(1) me(WR-BrWR-BrAC. ((1.882and th

DiffattribupolymreactioAC,inorgahydrogpared fand coHence[30]. Ftain deR spectra of (a) membrane B0, (b) membrane B1, (c) membrane B2, (d)(e) membrane B4, (f) membrane B5 and (g) membrane B6.

of swellingshows thatendure quahigh swellinafter the crsulfonatedhave strong(1) they hathe loss of sbe reduced.during IEC mserious. Beabout 2.8%,of benzylBIECs of memAC.

Membraing membrgood physicH2 and CH groups ( and ). The band at 1608 cm1d to the C C stretching vibration in phenyl groups;t 1190 cm1 and 10601140 cm1 are characteristic ofSiOSi stretching, respectively [29].mbrane B0 to B6, as the heating time prolongs and heat-

ature increases, the intensity of CH3, CH2 and CH(28503040 cm1) decreases. This indicates the gradualernary ammonium groups during the heat treatment.e mechanism of the loss is shown in Scheme 2: qua-monium groups can be degraded and crosslinked withps at high temperature [23]. Besides, from membranee peak of SiOSi (10601140 cm1) becomes clear.ts as the heat treatment strengthens, the crosslinkinglica increases accordingly.

zation of preparing conditions

tioned in Section 2.5, different silanes were used tosuitable conditions for membrane preparation: TEOS,mixture, or EPh was used to undergo the solgel reac-POBr(+), and membranes A, B and C were obtained,. When TEOS, TEOS + EPh mixture, or EPh was used to

e solgel reaction with PPOBrOH(+), membranes A,re obtained, respectively. Characterizations show that:nes AC have signicantly lower Br form water uptake

3667%) than membranes AC (all higher than 880%).embrane B is relatively low (217%) among membranesembranes AC have higher ion exchange capacities

mol/g) than membranes AC (1.701.95 mmol/g),of membrane B is the highest (2.08 mmol/g).

ces between membranes AC and AC are mainlyo the absence or presence of benzylOH groups in theecursor. PPOBr(+) is difcult to take part in the solgelith TEOS and/or EPh. Therefore, for the membranes

are few covalent bonds between their organic andhases. Only rather weak bonds such as van der Waals,nd ionic interactions exist. As for the membranes pre-PPOBrOH(+) (membranes AC), there exist both weaknt bonds between the organic and inorganic phases.

branes AC should have higher crosslinking degreee ion-exchange membranes based on PPOBr, a cer-of crosslinking is quite necessary for the enhancement

/corrosion resistance. For example, our previous workbase membrane of PPOBr without crosslinking cannotternization or sulfonation directly, for the product hasg degree and is like gel when fully hydrated. However,

osslinking of PPOBr (heated at 150 C for 2 h), it can besuccessfully [23]. Here in this work, as membranes ACer swelling resistance and corrosion resistance, hence,ve lower WR values; (2) during the IEC measurement,amples, especially quaternary ammonium groups, canAs for membranes AC, they have high swelling degreeeasurement, thus the loss of samples is relatively more

sides, the hydroxylation degree of PPOBrOH is onlyand thus has no signicant inuences on the contentr groups and the following quaternization. Hence, thebranes AC are a little higher than those of membranes

ne B has the low swelling degree but high IEC, indicat-ane prepared from mixed silanes (TEOS and EPh) haveal stabilities. This may be attributed to a combination

Y. Wu et al. / Journal of Membrane Science 338 (2009) 5160 55

Scheme 2. Mechanism of heat crosslinking for the h

of the properties of both silanes [31]: the phenyl group of EPhbrings favorable compatibility between the organic and inorganicphases; simultaneously, four alkoxy silicon groups of TEOS bringhigh crosslinking degree to the membrane.

Based on these observations, PPOBrOH was selected, andmixed silanes of EPh + TEOS were used for the membrane prepa-ration. In the following work, membrane B was used for studyingthe impacts of heat treatment. From 125 C to 140 C, seven mem-branes were obtained: membrane B0 (125 C for 3 h), membranesB1B5 (130 C for 110 h) and membrane B6 (140 C for 3 h).

3.3. Ion exchange capacity

Ion exchand the resthe heatingfrom 2.12 m140 C, its IEternary ammmore rapidl

From thewith a heatabove 185

IEC results sa long heatiat 140 C. Tbe considerduration.

As the (panion-exchfor comparuorinatedshow the Ivalues of th

Fig. 3. Br forcapacities (IEC

3.4. Water

For the Awhen the mOH form [halide ionsbranes hydform (WR-Bresults wereuorinatedB2B5 weremembranes

From Firanere inc78.5%ses frranes2) Th

rrespan sthe Ohat, ahe mrepo

[22ransf, vart. (3)es, blowlOH

aftedecr

r signnd hct, angrou

raneydro

kalin

applem

roupationange capacities of membranes B0B6 were measured,ults were shown in Fig. 3. From membrane B0 to B5, astime prolongs at 130 C, IEC values generally decreasemol/g to 1.27 mmol/g. For membrane B6, after heated atC value is only 0.76 mmol/g, indicating most of its quar-onium groups lose. Hence, the membrane decomposes

y at 140 C.analysis of TGA (which will be discussed in Section 3.6),

ing rate of 10 C/min, membranes begin to decomposeC (short-term thermal stability). However, both FTIR anduggest membranes decompose gradually at 130 C afterng time (110 h, long-term thermal stability), especiallyherefore, the thermal stabilities of membranes shoulded from two aspects: heating temperature and heating

artially) uorinated-polymer-based AAEMs (OH formange membranes) have high performances in AMFCs,ison, IECs of membranes B2B5 and the (partially)

-polymer-based AAEMs are shown in Table 3. ResultsEC values of hybrid membranes are nearly twice thee (partially) uorinated-polymer-based AAEMs.

membperatufrom 1decreamembment. (the coform cB0 in tcates tform, tof theI formto be tmationaccounincreasmore sall thethough

Theto theilongs acompaphenylmembtheir h

3.5. Al

Foris the mnium gdegradm (WR-Br) and OH form water uptakes (WR-OH), and ion exchanges) of membranes B0B6.

C2H5 N+(

and

(C2H5)3N+ybrid membranes.

uptake (WR)

EMs, their swelling degree should be much enhancedembranes are changed from the halide form to the

14], for OH ions have much higher hydrophilicity than. To compare the impacts of heat treatment to mem-rophilicity, the values of water uptake (including Br

r) and OH form WR (WR-OH)) were compared and thealso shown in Fig. 3. For comparison with the (partially)

-polymer-based AAEMs, WR-OH values of membranesalso shown in Table 3. Results show that the hybridgenerally have higher WR-OH values.

g. 3, three conclusions can be deduced: (1) fromB0 to B6, as the heating time prolongs and heating tem-reases, WR decreases dramatically. The WR-Br decreases(membrane B0) to 2.0% (membrane B6), and the WR-OH

om more than 1000% to 34%. This indicates hydrophilicgradually become hydrophobic during the heat treat-e WR-OH is generally more than three times higher thanonding WR-Br. For example, membrane B0 in the Br

ill keep dimensional stability in water, while membraneH form is like a gel when fully hydrated. This indi-fter the transformation from the Br form to the OH

embranes hydrophilicity increases signicantly. Mostrted AEMs are in the halide form, such as Cl, Br or27]. For application in AMFCs, these membranes haveormed to the OH form. Therefore, during the transfor-iation of hydrophilicity should be seriously taken intoAs the heating time prolongs and heating temperature

oth the WR-OH and WR-Br decrease, but WR-OH decreasesy from membrane B3 (133%) to B6 (34%). This indicates

form membranes have favorable hydrophilicity, evenr heated at 140 C.ease in membranes hydrophilicity is mainly attributedicant decrease in IECs. Besides, as the heating time pro-eating temperature increases, silica network becomesd the crosslinking between quaternary ammonium andps is strengthened too, as shown in Fig. 2. Hence, fromB0 to B6, their crosslinking degree increases, and thusphilicity decreases.

e resistance (effect of alkaline solution on the IECs)

ication in fuel cells, a widely quoted concern with AEMsbrane stability in the OH form [5]. Quaternary ammo-s are relatively unstable in alkaline condition since theirmay occur through direct nucleophilic displacement:C2H5)2 OHC2H5OH + (C2H5)2N

CH2 OH(C2H5)3N + HO CH2

56 Y. Wu et al. / Journal of Membrane Science 338 (2009) 5160

Table 3Comparisons between the hybrid membranes and the (partially) uorinated-polymer-based AEMs (all the properties are of membranes in the OH form unless specicallymentioned).

Membranes Hybrid membranes B2B5 Membranes in Ref [32] Membranes in Refs. [14,36]

Composition PPOBrOH(+)/SiO2 Grafted (partiIEC (mmol/g) 1.272.05a 0.71.0WR (%) 45.2325.9 IDT (C) 135144 155160Duration in alkaline solution 2 mol/L NaOH within 68 h 1 mol/L KOH wMechanical properties 20.324.5 MPa, and 5.313.7%d; elastic and strong Brittle, or elasThickness (m) 85110 6095Conductivity (S/cm) 0.0010.0085 0.02

a IEC values of the hybrid membranes in the Br form.b IDT values of uorinated-polymer-based AEMs in the Cl form.c The used membrane sample is PVDF-based AAEMs. PVDF is a type of partially uorinated-polymer,d Tensile strength (TS) and elongation at break (Eb) of the hybrid membranes in the Br form.

or Hofmann elimination [5]:

CH3 CH2 N+(C2H5)2 OHCH2 = CH +(C2H5)2N +HOH

To investigate the alkaline resistance, membranes with properWR-OH, i.e., membranes B2B5 were selected and immersed in2 mol/L NaOH solution. The ratio of IECt (membrane treated withalkaline solution) to IEC0 (membrane untreated) was recorded as afunction of the immersion time. The results were shown in Fig. 4.

All the lines drop rapidly in the initial 028 h, then level off inthe followinof unstableinitial partaccount forhighest unscomponentaged aftermay be lostthe membrSimultaneoily due to tloss and degslowly.

Generall(028 h), thB2 > B3 or Bclose to eachmembranes

Fig. 4. Alkalinof the exposur

(more thansolution. Thmore damaare damagehigher. Thelarger in thestage as the

The ratirapidly at alkaline sol

re thrid mrm. D

mmoe (p

ranesstag

mmoranesatede))-b

erma

hermapp

sirab80

due tctrodec

he habetw

lossaramhermg 28192 h. This indicates membranes contain a partquaternary ammonium groups. Calculated from the

of lines, the unstable quaternary ammonium groups1732% of the total ones, and membrane B5 has the

table ones. These unstable groups may come from thes which are insufciently crosslinked or partly dam-the heat treatment. Insufciently crosslinked groupsmore easily due to membrane swelling, especially for

anes with high swelling degree (such as membrane B2).usly, partly damaged groups are decomposed more eas-he degradation in strong alkaline solution. After theradation of these groups, membranes decompose more

y speaking, after the fast decomposition in the rst stagee ratio (IECt/IEC0) is in the following order: membrane4 > B5 in the second stage (2896 h), then the ratios are

other in the third stage (96192 h). This indicates that ifare immersed in alkaline solution for long enough time

compathe hybOH fonary awith thmembsecondnary amembuorinuorid

3.6. Th

3.6.1. TFor

are de(abovelossesthe elebilitiesfrom tencesweightbility p(IDT), te resistances of membranes B2B5: the ratios of IECt/IEC0, as a functione time to 2 mol/L NaOH at 25 C.

ature at 5%in Figs. 5 anOH form,Td-OH. Correas IDTBr, inselected forin Table 4.

Fig. 5(a)100 C, for tin air. As meheat treatmloss beforeare all highally) uorinated-polymer Grafted uorinated-polymer0.771.0848.254.4200290b

ithin 48 hc Stable in alkaline conditiontic and strong Lack of physical strength and stability

86880.010.017

and its full name is poly(vinylidene uoride) ([CH2CF2]n).

100 h), they would have similar resistance to alkalineough membranes with stronger heat treatment containged components (more quarternary ammonium groupsd during heat treatment), their crosslinking degree is

refore, the decomposing rates of these membranes arerst and second stages, but become smaller in the thirdcomplete decomposition of unstable components.

o (IECt/IEC0) of some reported AEMs also decreasesrst, but then decreases more slowly in concentrated

ution [27]. However, there is still no standard method toe alkaline resistance of AEMs. For application in AMFCs,

embranes in the Br form have to be transformed to theuring the transformation, most of the unstable quater-

nium groups should be lost. Therefore, for comparisonartially) uorinated-polymer-based AAEMs, the hybrid

in the OH form can be considered to degrade in thee (within 68 h), i.e., after the loss of unstable quater-nium groups (Table 3). Results show that the hybridhave comparable alkaline resistance with the partially

-polymer-based AAEMs, such as PVDF (poly(vinylideneased AAEMs [32].

l stability (TGA analysis)

al stabilities of membranes in the halide (Br) formlication in AMFCs, AEMs with high thermal stabilityle, since operation of AMFCs at elevated temperatureC [33]) would not only reduce thermodynamic voltageo pH difference across the membrane but also improvekinetics [5]. However, for most of AEMs, thermal sta-rease signicantly when the membranes are changedlide form to the OH form [5]. To compare the differ-een these two forms of the hybrid membranes, theirbehaviors were studied by TGA analysis. Thermal sta-eters, including the initial decomposition temperatureal degradation temperature (Td, dened as the temper-weight loss) can be determined from TGA thermogramsd 6. To distinguish the Td of membranes in the Br and

the former is signed as Td-Br, and the latter is signed asspondingly, IDT of membranes in the Br form is signedthe OH form is signed as IDTOH. Membranes B2B5 are

the thermal analysis, and the results are summarized

shows that some samples begin to lose weight beforehey absorbed a small amount of water when preservedmbranes B2B5 were heated at 130 C for 210 h duringent, in the determination of IDTBr and Td-Br, the weight130 C is neglected. The IDTBr values of the membraneser than 185 C, and their Td-Br values are in the range of

Y. Wu et al. / Journal of Membrane Science 338 (2009) 5160 57

Fig. 5. (a) TGAform with the

208227 C(partially) to 194 C [13non-uorintemperatur[34,35]. Frothe IDTBr va(membraneThis is reasincreases asincreasing t

Table 4TGA analysis r

Membrane

IDTBr (C)a

Td-Br (C)b

Td-OH (C)Thickness (mConductivity (

a IDT is thegrams. The sub

b The thermwhich the weithe anion form

To clarify the thermal degradation behavior, DrTGA results areplotted in Fig. 5(b). The samples generally possess ve weightloss peaks. As mentioned above, the primary degradation at lowtemperature is caused by the evaporation of absorbed water. Thesecondary degradation (190280 C) is due to the decomposition ofammonium groups. The third degradation (320365 C) is ascribedto the decomposition of CH2 groups. The fourth degradation(390435 C) is due to the degradation of CH3 groups. The lastdegradation (470575 C) is corresponding to the decompositionof polymer chains and phenyl groups.

3.6.2. Thermal stabilities of membranes in the alkaline (OH)form

The thermal stabilities of membranes B2B5 in the OH formwere investigated by TGA analysis and the diagrams obtained areshown in Fig. 6(a).

ably, all the samples begin to lose weight (11.815.3%) before, and continue to lose weight as the temperature rises. This ise samples in the OH form are highly hydrophilic, and afternsformation from the Br form to the OH form, the samplesnly dried in a desiccator for a week. Hence, much water stills in the samples. Therefore, in the determination of Td-OH ofples, the weight loss before 100 C is neglected. The Td-OH

are collected in Table 4.IDTOH values of the samples are difcult to be accurately

ted as the lines drop rapidly all along. However, weight lossesNot100 Cbecausthe trawere oremainthe samvalues

Theestimaand (b) DrTGA thermograms of the hybrid membranes in the Br

heating rate of 10 C/min under air ow.

. These values are close to the corresponding ones of theuorinated-polymer-based AEMs (Cl form, IDT is equal]), and higher than those of a number of other reported

ated-polymer electrolyte membranes for low or high-e fuel cell applications (IDT below or up to about 150 C)m membrane B2 to B5, as the heating time increases,lues increase from 185.8 C (membrane B2) to 202.6 CB5), and Td-Br values increase from 208.1 C to 227.7 C.onable because the membranes crosslinking degreethe heating time increases, and thus resulting in the

hermal stabilities.

esults, thickness and OH conductivity values of membranes B2B5.

B2 B3 B4 B5

185.8 188.0 198.5 202.6208.1 214.2 223.1 227.7156.6 156.2 168.7 170.1

) 110 99 85 98S/cm) 0.0085 0.0059 0.0010

initial decomposition temperature determined from TGA thermo-script indicates the anion form of the hybrid membranes.al degradation temperatures (Td) are dened as the temperature atght loss reaches 5 wt% in TGA thermograms. The subscript indicatesof the hybrid membranes.

Fig. 6. (a) TGAwith the heatiand (b) DrTGA thermograms of the hybrid membranes in OH formng rate of 10 C/min under air ow.

58 Y. Wu et al. / Journal of Membrane Science 338 (2009) 5160

brane

of membranmembranescantly highIDTBr: memstabilities.

To clarifplotted in Fform (Fig. 5Fig. 6(b). Thnium groupnew peak, wthe membrhybrid mem(partially) in Table 3.

3.7. Morph

Since therties, memprolongs anshow that mbranes B0 aand B6, as s

Membrasilica partica few smalbrane is stilparticles ansilica particnary ammotime prolonstability atwhen the tepens betwemembrane

nsile

mectioned inremem mees deffe

agedfectsse ofFig. 7. SEM micrographs of the cross-sections (a) membrane B0, (b) mem

es B4 and B5 are lower than those of other investigated, indicating that membranes B4 and B5 have signi-

er thermal stabilities. This conrms to the tendency ofbranes with longer heating time have higher thermal

y the thermal degradation behavior, DrTGA results areig. 6(b). Compared with the DrTGA of samples in the Br

(b)), a new peak in the range of 135180 C appears ine new peak is ascribed to the decomposition of ammo-s (OH form). IDTOH can be roughly estimated from thehich is in the range of 135144 C. The Td-OH values of

anes are in the range of 156170 C, indicating that the

3.8. Te

Theelongacollectmeasu

FroEb valuby twois damtwo efdecreabranes have comparable thermal stabilities with theuorinated-polymer-based AAEMs [14,32,36], as shown

ology of hybrid membranes

e heat treatment has great impact on membrane prop-brane structure should be changed as the heating timed heating temperature increases. SEM micrographsembranes B0B4 are similar. Therefore, images of mem-

nd B3 are selected for comparison with membranes B5hown in Fig. 7.nes B0 and B3 are compact and dense, and no signicantles can be observed. For membrane B5, though there arel holes with their diameter less than 1m, the mem-l homogenous. However, membrane B6 has some larged holes in the range of 14m, and also has many smallles less than 1m. This suggests that though the quater-nium groups are gradually decomposed as the heatinggs, membranes framework can still keep dimensionaltemperatures ranging from 120 C to 130 C. However,mperature further rises to 140 C, phase separation hap-en the organic and inorganic phases, and the damage ofs structure becomes more serious.

branes stremembraneTS values.

Comparmembranes

Fig. 8. The tenB3, (c) membrane B5 and (d) membrane B6.

properties

hanical strength was measured as tensile strength andat break. The measured values of membranes B0B5 are

Fig. 8. Membrane B6 is too brittle to be taken for thent.mbrane B0 to B5, TS values are around 2024 MPa, but

ecrease dramatically from 19.5% to 5.3%. This is causedcts: as the heating time prolongs, membranes structuregradually, but its crosslinking degree increases. Both theenhance membranes brittleness, thus lead to the sharpexibility. The damage of structure also reduces mem-

ngth, but the increase of crosslinking degree enhancess strength. Hence, the hybrid membranes have similar

ed with some reported organic membranes [37,38], ourhave acceptable tensile properties with higher TS but

sile strength (TS) and elongation at break (Eb) of membranes B0B5.

Y. Wu et al. / Journal of Membrane Science 338 (2009) 5160 59

a little lower Eb values. Besides, tensile properties of ion-exchangemembranes, especially the membranes with high charge densities,are always sensitive to humidity [3]. Therefore, during operation infuel cells, membranes can show better tensile properties when pre-served at hiwas immersured TS valhumidity haincrease me

Mechanalso compaAAEMs (Tabelastic andor higher m

3.9. Membr

The thiclisted in Taobtained duThe conduc0.00100.00those of somvalues are spolymer-badue to twoto quaternizgroups in thliteratures [with CH2N[44], quaterhave higherbranes is loform salts.exposed tocarbonationlead to sevetion, membBr form tbefore testi0.0116 S/cmation of dirwidely percof partiallyable.

From meically fromtwo main r1.87 mmol/AMFC applitivity as hi(from 133.8the hydratithe preparaity and highto be contruorinatedare hydroppolymers arserious prob(membraneTherefore, ptial for conthat heat trof the memable.

4. Conclusions

Anion exchange hybrid membranes based on poly(2,6-dimethyl-1,4-phenylene oxide) were prepared through bromination, hydrox-

, quxysileatment ooperred.he herm wrm w; IECthe

tionraneseralhen

mbrae resratur170ach urangaree (p

ranesalinence athe p

ing tbe d

s theeme

near

wled

s job(No.m ofcatioA07

B623

enc

es

SCsMs

sBrBrBr

Br(

Br

OHgh humidity. To examine this deduction, membrane B5sed in water for about 10 min before testing. The mea-ue was 23.6 MPa, while Eb value was 7.0%. This indicatess no signicant impact to membranes strength, but canmbranes exibility signicantly.

ical strength of membranes B2B5 (Br form) isred with that of (partially) uorinated-polymer-basedle 3). Besides, membranes B2B5 in the OH form are

strong. Hence, the hybrid membranes have comparableechanical strength.

ane conductivity

kness and conductivity values of membranes B2B5 areble 4. For membrane B2, no conductivity value can be

e to its high swelling degree (WR-OH is up to 325%).tivity values of membranes B3B5 are in the range of85 S/cm, which are comparable with or higher thane AAEMs [39,40], as shown in Table 3. However, these

ignicantly lower than those of (partially) uorinated-sed AAEMs [3,4143]. The lower conductivity maybemain reasons: (1) in our work, triethylamine was usede CH2Br groups of PPOBr, and so the ion conductinge membranes are CH2N+(C2H5)3Br groups. In other3,32,36], trimethylamine was used to get membranes+(CH3)3Cl groups. According to previous researches

nary amine groups CH2N+R3 with R of longer chainresistance. Hence, the conductivity value of our mem-wer; (2) the formation of bicarbonate and carbonateBefore the conductivity test, AAEM samples had beenair for some time, and the CO2 (in the air) would cause

of the samples [43]. The carbonation effect wouldrely decreased conductivities [3]. To prove this deduc-rane B3 was selected. After the transformation from

o OH form, the membrane was preserved in waterng. The obtained conductivity value was increased to(while original value is 0.0085 S/cm). During the oper-

ect methanol fuel cells, carbonation of the AAEM is aeived problem [3]. Therefore, the conductivity valuescarbonated AAEMs (membranes B2B5) are also valu-

mbrane B3 to B5, conductivity values decrease dramat-0.0085 S/cm to 0.0010 S/cm. This can be attributed toeasons: one is the signicant decrease of IECs (fromg to 1.27 mmol/g). As has been reported, for practicalcation, it is essential to maximize IEC to get conduc-gh as possible [5]. Another is the decrease of WR-OH% to 45.2%), for the conductivity always depends on

on degree to a great extent [31,45]. Therefore, duringtion of AAEMs, to get both enough dimensional stabil-

OH conductivity, membranes hydrophilicity needsolled in a proper range. For the reported (partially)

-polymer-based AAEMs [1314,32,36], their substrateshobic (partially) uorinated-polymer, and hydrophilice grafted on their surfaces. Therefore, swelling is not alem. For the homogenous OH form hybrid membraness B2B5), they always show high swelling degrees.roper IECs and high crosslinking degrees are essen-trol on swelling. Through our research, it is showneatment can be an effective way to control swellingbranes. Heating at 130 C for 46 h is the most desir-

ylationtriethoheat trtreatmand prcompa

As tBr foOH foto 34%thoughelongamembare genpens w

Mealkalintempeof 156can rein thebraneswith thmembble alkresista

Forincludneed tosuch aimprovin the

Ackno

ThiChinaPrograof EduKJ20082009C

Nom

CodPPOEPhTEOAMFAAE

AEMPPOPPOPPO

PPOWRWR-WR-aternization, and solgel reaction with monophenylane (EPh) or/and tetraethoxysilane (TEOS), followed byent at 120140 C for different times. The effects of heatn membranes properties were systematically studied,

ties of membranes in the Br form and OH form were

ating time prolongs and heating temperature increases,ater uptake (WR-Br) decreases from 178% to 2%, whileater uptake (WR-OH) decreases from more than 1000%

s decrease from 2.12 mmol/g to 0.76 mmol/g. Besides,tensile strength remains in the range of 2024 MPa, theat break decreases from 19% to 5%. SEM images showtreated at temperatures ranging from 120 C to 130 C

ly compact and homogenous, but phase separation hap-membrane is treated at 140 C.nes treated at 130 C for 210 h have relatively highistance and thermal stabilities: the thermal degradatione of membranes in the OH form (Td-OH) is in the rangeC, and the initial decomposition temperature (IDTOH)p to 144 C. Membranes have the conductivity valuese of 0.00100.0085 S/cm. Therefore, the hybrid mem-suitable for potential application in AMFCs. Comparedartially) uorinated-polymer-based AAEMs, the hybrid

have higher IECs and mechanical strength, compara-resistance and thermal stabilities, but lower swelling

nd OH conductivity.ractical application in AMFCs, more characterizations,

he methanol crossover and especial the fuel cell test,eveloped; some properties need to be further improved,swelling resistance and OH conductivity. The above

nt is underway in our laboratory and will be reportedfuture.

gements

was supported in part by Natural Science Foundation of20636050), Specialized Research Fund for the Doctoral

Higher Education(No. 200803580015), Foundationsnal Committee of Anhui Province (Nos. ZD2008002,

2) and National Basic Research Program of China (No.403).

lature

Full name or meaningpoly(2,6-dimethyl-1,4-phenylene oxide)monophenyl triethoxysilanetetraethoxysilanealkaline membrane fuel cellsalkaline anion-exchange membranes, or OH formanion-exchange membranesanion-exchange membranesPPO after bromination

OH PPO after bromination, and then hydroxylationOH(+) PPO after bromination, hydroxylation, andthen quaternization

+) PPO after bromination, and then quaternizationwater uptakeBr form water uptakeOH form water uptake

60 Y. Wu et al. / Journal of Membrane Science 338 (2009) 5160

IECs ion exchange capacitiesIECs membranes treated with alkaline solutionIECs membranes untreated with alkaline solutionIDT initial decomposition temperatureIDTBr IDT of membranes in the Br formIDTOH IDT of membranes in the OH formTd the temperature at 5% weight lossTd-Br Td of membranes in the Br formTd-OHTSEb

References

[1] J.R. VarcexchangeElectroch

[2] E.H. Yu, Kexchange

[3] J.R. Varcoley, Polyexchangemetal-cat(2007) 26

[4] K. Matsuofuel cells2731.

[5] J.R. Varcolow temp

[6] Y. Wang,line memkinetic ad

[7] A.A. Zagoexchange(2002) 15

[8] V. Neagubase anio463.

[9] E. Agel, J.for alkalin

[10] E. Agel, J.in alkalin

[11] T. Uragamdration omembranmolecule

[12] S. Sachdepolystyre(2008) 94

[13] T.N. DankmembranChem. 13

[14] H. Hermchloridesubsequeof the exp147163.

[15] G.R. PedrAdv. Mate

[16] D. NystrHighly-ormodied

[17] Y.M. Chenaggregate(2006) 74

[18] P. Jannascmer elec102.

[19] J.L. ZhangH.J. Wang891.

[20] V.K. Shahi, Highly charged proton-exchange membrane: sulfonated poly(ethersulfone)silica polyelectrolyte composite membranes for fuel cells, Solid StateIonics 177 (2007) 33953404.

[21] R.K. Nagarale, G.S. Gohil, V.K. Shahi, R. Rangarajan, Preparation oforganicinorganic composite anion-exchange membranes via aqueous disper-sion polymerization and their characterization, J. Colloid Interface Sci. 287(2005) 198206.

[22] S.L. Zhang, T.W. Xu, C.M. Wu, Synthesis and characterizations of novel, positivelycharged hybrid membranes from poly(2,6-dimethyl-1,4-phenylene oxide), J.Membr. Sci. 269 (2006) 142151.

[23] D. Wu, R.Q. Fu, T.W. Xu, L. Wu, W.H. Yang, A novel proton-conductive mem-brane with reduced methanol permeability prepared from bromomethylated

y(2,6-dimethyl-1,4-phenylene oxide) (BPPO), J. Membr. Sci. 310 (2008)530. Xu,

mbran01) 15. Tangmbranion anmbr. S. Wu,rid mppl. Po. Kommbranembr. Mo

ible, mMeer

. Wu,ridsethac

035hi, C.J.s: prem. MKim, Wation i. 238 (. Daniationre portoica,

polyepchemionmaocom94.

Popalls with.T. Slafted a597.i, Z.Mym. J.ark, H

with(2006. Yangpolym

atsuparatiin alkVarco

mbranchem.ilpi, Mon-ex08) 18anagine fueTd of membranes in the OH formtensile strengthelongation at break

oe, R.C.T. Slade, An electron-beam-grafted ETFE alkaline anion-membrane in metal-cation-free solid-state alkaline fuel cells,

em. Commun. 8 (2006) 839843.. Scott, Development of direct methanol alkaline fuel cells using anionmembranes, J. Power Sources 137 (2004) 248256.e, R.C.T. Slade, E.L.H. Yee, S.D. Poynton, D.J. Driscoll, D.C. Apper-

(ethylene-co-tetrauoroethylene)-derived radiation-grafted anion-membrane with properties specically tailored for application in

ion-free alkaline polymer electrolyte fuel cells, Chem. Mater. 19862693.ka, Y. Iriyama, T. Abe, M. Matsuoka, Z. Ogumi, Alkaline direct alcoholusing an anion exchange membrane, J. Power Sources 150 (2005)

e, R.C.T. Slade, Prospects for alkaline anion-exchange membranes inerature full cells, Fuel Cells 5 (2005) 187200.L. Li, L. Hu, L. Zhuang, J.T. Lu, B.Q. Xu, A feasibility analysis for alka-brane direct methanol fuel cell: thermodynamic disadvantages versusvantages, Electrochem. Commun. 5 (2003) 662666.rodni, D.L. Kotova, V.F. Selemenev, Infrared spectroscopy of ionresins: chemical deterioration of the resins, React. Funct. Polym. 537., I. Bunia, I. Plesca, Ionic polymers VI. Chemical stability of strongn exchangers in aggressive media, Polym. Degrad. Stabil. 70 (2000)

Bouet, J.F. Fauvarque, Characterization and use of anionic membranese fuel cells, J. Power Sources 101 (2001) 267274.

Bouet, J.F. Fauvarque, H. Yassir, The use of a solid polymer electrolytee fuel cells, Ann. Chim. Sci. Mater. 26 (2001) 5968.i, T. Katayama, T. Miyata, H. Tamura, T. Shiraiwa, A. Higuchi, Dehy-f an ethanol/water azeotrope by novel organicinorganic hybrides based on quaternized chitosan and tetraethoxysilane biomacro-

s 5 (2004) 15671574.va, R.P. Ram, J.K. Singh, A. Kumar, Synthesis of anion exchange

ne membranes for the electrolysis of sodium chloride, AIChE J. 540949.s, R.C.T. Slade, J.R. Varcoe, Alkaline anion-exchange radiation-graftedes for possible electrochemical application in fuel cells, J. Mater.(2003) 712721.

an, R.C.T. Slade, J.R. Varcoe, The radiation-grafting of vinylbenzylonto poly(hexauoropropylene-co-tetrauoroethylene) lms withnt conversion to alkaline anion-exchange membranes: optimisationerimental conditions and characterization, J. Membr. Sci. 218 (2003)

o, Hybrid organicinorganic materialsin search of synergic activity,r. 13 (2001) 163174.m, P. Antoni, E. Malmstrm, M. Johansson, M. Whittaker, A. Hult,dered hybrid organicinorganic isoporous membranes from polymernanoparticles, Macromol. Rapid Commun. 26 (2005) 524528., J.Z. Du, M. Xiong, K. Zhang, H. Zhu, Gelation inside block copolymers and organic/inorganic nanohybrids, Macromol. Rapid Commun. 27

pol522

[24] T.Wme(20

[25] B.BmenatMe

[26] C.MhybJ. A

[27] E.NmeJ. M

[28] M.Mexand

[29] Y.Hhyb-m358

[30] Y. SrialChe

[31] Y.J.meSci

[32] T.Nradatu

[33] D. Sontro

[34] I. Hnan83

[35] M.tor

[36] R.Cgra585

[37] Y. LPol

[38] I. Pites18

[39] C.Cite

[40] K. MPreuse

[41] J.R.Metro

[42] A. Fani(20

[43] H. Ybra1750.h, Recent developments in high-temperature proton conducting poly-trolyte membranes, Curr. Opin. Colloid Interface Sci. 8 (2003) 96

, Z. Xie, J.J. Zhang, Y.H. Tang, C.J. Song, T. Navessin, Z.Q. Shi, D.T. Song,, High temperature PEM fuel cells, J. Power Sources 160 (2006) 872

[44] T.W. Xu,anion excphenylen

[45] S.H. Kwabrane forcell, Solid.W.H. Yang, Fundamental studies of a new series of anion exchangees: membrane preparation and characterization, J. Membr. Sci. 1909166.

, T.W. Xu, M. Gong, W.H. Yang, A novel positively charged asymmetryes from poly(2,6-dimethyl-1,4-phenylene oxide) by benzyl bromi-d in situ amination: membrane preparation and characterization, J.ci. 248 (2005) 119125.Y.H. Wu, T.W. Xu, Y.X. Fu, Novel anion-exchange organicinorganic

embranes prepared through solgel reaction and UV/thermal curing,lym. Sci. 107 (2008) 18651871.

kova, D.F. Stamatialis, H. Strathmann, M. Wessling, Anion-exchangees containing diamines: preparation and stability in alkaline solution,

. Sci. 244 (2004) 2534.jtahedi, E. Akbarzadeh, R. Shari, M.S. Abaee, Lithium bromide as a

ild, and recyclable reagent for solvent-free cannizzaro, tishchenko,weinPonndorfVerley reactions, Org. Lett. 9 (2007) 27912793.C.M. Wu, M. Gong, T.W. Xu, New anion exchanger organicinorganicand membranes from a copolymer of glycidylmethacrylate andryloxypropyl trimethoxy silane, J. Appl. Polym. Sci. 102 (2006)

89.Seliskar, Optically transparent polyelectrolytesilica composite mate-

paration, characterization, and application in optical chemical sensing,ater. 9 (1997) 821829.

.C. Choi, S.I. Woo, W.H. Hong, Proton conductivity and methanol per-n NaonTM/ORMOSIL prepared with various organic silanes, J. Membr.2004) 213222.ks, R.C.T. Slade, J.R. Varcoe, Comparison of PVDF- and FEP-based-grafted alkaline anion-exchange membranes for use in low temper-table DMFCs, J. Mater. Chem. 12 (2002) 33713373.L. Ogier, L. Akrour, F. Alloin, J.-F. Fauvarque, Anionic membrane basedichlorhydrin matrix for alkaline fuel cell: synthesis, physical and elec-

cal properties, Electrochim. Acta 53 (2007) 15961603., S. Nomura, H. Nakajima, Protonic conducting organic/inorganicposites for polymer electrolyte membrane, J. Membr. Sci. 185 (2001)

, X.M. Du, Inorganicorganic copolymers as solid state ionic conduc-grafted anions, Electrochim. Acta 40 (1995) 23052308.

de, J.R. Varcoe, Investigations of conductivity in FEP-based radiation-lkaline anion-exchange membranes, Solid State Ionics 176 (2005)

. Huang, Y.D. Lv, Electrospinning of nylon-6,66,1010 terpolymer, Eur.42 (2006) 16961704..G. Peng, D.W. Gidley, S. Xue, T.J. Pinnavaia, Epoxy-silica mesocompos-enhanced tensile properties and oxygen permeability, Chem. Mater.

) 650656., Synthesis and characterization of the cross-linked PVA/TiO2 compos-er membrane for alkaline DMFC, J. Membr. Sci. 288 (2007) 5160.

oka, S. Chiba, Y. Iriyama, T. Abe, M. Matsuoka, K. Kikuchi, Z. Ogumi,on of anion-exchange membrane by plasma polymerization and itsaline fuel cells, Thin Solid Films 516 (2008) 33093313.e, M. Beillard, D.M. Halepoto, J.P. Kizewski, S. Poynton, R.C.T. Slade,e and electrode materials for alkaline membrane fuel cells, J. Elec-Soc. Trans. 16 (2008) 18191834.. Boccia, H.A. Gasteiger, Pt-free cathode catalyst performance in H2/O2

change membrane fuel cells (AMFCs), J. Electrochem. Soc. Trans. 16351845., K. Fukuta, Anion exchange membrane and ionomer for alkaline mem-l cells (AMFCs), J. Electrochem. Soc. Trans. 16 (2008) 257262.Z.M. Liu, W.H. Yang, Fundamental studies of a new series of

hange membranes: membrane prepared from poly(2,6-dimethyl-1,4-e oxide) (PPO) and trimethylamine, J. Membr. Sci. 249 (2005) 183191.k, T.H. Yang, C.S. Kimb, K.H. Yoon, Naon/mordenite hybrid mem-high-temperature operation of polymer electrolyte membrane fuelState Ionics 160 (2003) 309315.

Novel silica/poly(2,6-dimethyl-1,4-phenylene oxide) hybrid anion-exchange membranes for alkaline fuel cells: Effect of heat treatmentIntroductionExperimentalMaterialsBromination of PPOHydroxylation of PPO-BrQuaternization of PPO-Br-OH and PPO-BrPreparation of the hybrid membranesCharacterizations

Results and discussion1H NMR and FTIR spectraOptimization of preparing conditionsIon exchange capacityWater uptake (WR)Alkaline resistance (effect of alkaline solution on the IECs)Thermal stability (TGA analysis)Thermal stabilities of membranes in the halide (Br-) formThermal stabilities of membranes in the alkaline (OH-) form

Morphology of hybrid membranesTensile propertiesMembrane conductivity

ConclusionsAcknowledgementsReferences