Journal of Power Sources 160 (2006) 12041210

A polyvinyl alcohol/p-sulfonate phenem

an

sity, Crch Iarch

006

Abstract

Membran mer,conductivity ing aof the pheno oughvalue was st urreneffective in r ncreapermeation ductivthan that de transthat a high p 2006 Published by Elsevier B.V.

Keywords: Fuel cell; Membrane; Cross-linking; Acidbase complex; Methanol cross-over

1. Introdu

The prodevices sucfuel cell (Dmary goal.as chemicacrossover (in presencevital issues

As wideronment ishydrogen bcharged hyindicate thaalso lead toconductivitchannel str

CorresponE-mail ad

0378-7753/$doi:10.1016/jction

ton exchange membrane is a key component inh as the hydrogen fuel cell and the direct methanolMFC), where high proton conductivity is the pri-

However, preserving other membrane properties suchl stability in the acidic environment, low methanol

C.-S. Wu et al. / Journal of Power Sources 160 (2006) 12041210 1205

situations when such pairing was absent [9,10]. In the non-aqueous condition, proton conductivity reached 103 S cm1above 100 C. However, such materials suffered severely fromleaching ofmethanol sing of twoform a com[1115].

The preblend concalcohol) (Pphenolic rthe sulfonaforming acan lead todirectionalcase, a cov

moiety whwhich incmembranenot suffer fthe membrswelling wadvantageo(DMFC).

2. Experim

2.1. Memb

The memsolvent-casSHOWA],37% forma(DMSO) [Tsulfonic acthe formatithe procedwt.% of Pdissolved ugeneous sothe film bywere in thedried memdesired tem150 C, resenvironmen

2.2. Membrane characterization

The cooectro55].with-Elmin thaint

ater

mbraconc

ampighe7]:

= W

Wweds tool (

n ex

ionsingenviforge psoluprio

roton

proith

quenLABnce (

usinduRb)(.

etha

me

in a) wamethacedof ti

ranedex [tionthe small acid/base molecules in the presence of theolvent. Kerres et al. has also demonstrated that blend-or more polymers with acid and base functionality toposite membrane is one approach to achieve the goal

sent paper extends the acid and base polymerept by using a weak base polymer, poly(vinylVA) (1) (see below) with an acid source sulfonatedesin (s-Ph) (2). As the proton is shared betweente group and the hydroxyl (weak base) of PVAhydrogen bonded network, the acidbase pairingshort range ordered domains thus creating a highlyproton flow channel. Specifically for the presentalent bond is formed between the s-Ph and PVA

en the blend is dehydrated at elevated temperatures,reases the membrane strength. The cross-linkeddisplayed a strong self-standing property but doesrom loss of proton conductivity. Most importantly,ane shows decreased solvent uptake and reducedith increasing methanol concentration, which can beus for the application in direct methanol fuel cells

ental

rane preparation

branes used in the present study were prepared by at method. Poly(vinyl alcohol) (PVA) [MW = 80,000,phenol-4-sulfonic acid solution [Fluka, Germany],ldehyde solution [UCW, Taiwan], dimethyl sulfoxideEDIA, USA] were used as received. The phenol-4-

id and formaldehyde were used in a 1:1 mole ratio foron of sulfonated phenolic (s-Ph) resin by followingure described in the literature [16]. The appropriateVA and s-Ph were weighted respectively and thennder agitation in DMSO at 80 C. After that, homo-lutions were poured onto Teflon dishes to fabricatedrying at 80 C in a vacuum oven. The final productsform of films with thicknesses of 300400m. The

branes were heated for 2 h in a vacuum oven at theperature (herein termed curing ), i.e. 110, 130 andpectively. These films were stored under a dry argont prior to use.

(IR) sp[FTS-1minedPerkinmentswere m

2.3. W

MeferentThen sand wetion [1

uptake

whereresponmethan

2.4. Io

Theuated uargonstirredexchanNaOH(KHP)

2.5. P

Thegated wthe freAUTOresistaysis byThe co = (1/sample

2.6. M

Theformed(6 cm240 mlwas plperiodmembtive incalibrardination structure was investigated using infraredscopy on KBr using a BIO-RAD FT-IR spectrometerThe microstructure of the membranes was deter-a Varian 400 MHz solid-state NMR spectrometer. Aer TGA-7 series, was used to record TGA measure-e range of 30900 C. The weights of the samplesained in the range of 35 mg.

uptake and solvent uptake

ne samples were immersed in distilled water or dif-entrations of methanol and heated at 60 C for 2 h.les were dried in a vacuum oven at 80 C overnightd. The uptake was calculated using the follow equa-

wet WdryWdry

100%

t is the weight of the dry membrane and Wdry cor-the weight of the membrane soaked in water or

g), respectively.

change capacity (IEC)

exchange capacity (IEC) of the membranes was eval-a titration method [17]. The stored membranes in an

ronment were immersed in 1 M NaCl solution and6 h at 40 C. The protons released during the ionrocess were titrated with a 0.01N NaOH solution.tion was titrated with potassium hydrogen phthalater to use.

conductivity measurement

ton conductivity of these membranes were investi-a cell consisting of two stainless steel electrodes overcy range 1 MHz to 1 Hz, using frequency analyzer/PGSTAT 30 electrochemical instrument. The bulkRb) was determined from the equivalent circuit anal-ng a frequency response analyzer (FRA software).ctivity values () were calculated by the equation,t/A), where t is the thickness and A is the area of the

nol permeability measurement

thanol permeability of the membranes were per-permeation measuring device [18]. The membrane

s inserted between vessels A and B. A volume ofanol solution (50 vol.%) and 40 ml deionized waterin each vessels A and B, respectively. After a fixed

me, the amount of methanol that crossed through theand diffused to the vessel B was determined by refrac-ATAGO3T], comparing to a methanol concentrationcurve.

1206 C.-S. Wu et al. / Journal of Power Sources 160 (2006) 12041210

Fig. 1. (a) FTPVA and (e) p(b) 110, (c) 13

3. Results

The maiof s-Ph andof curing tproton con(IEC), and(3) the effeproton con

FTIR stus-Ph blendsatures (Fig(a), and sas-Ph and thblet peak a30003500assigned toIn pure s-P

have been assigned to S O and S O symmetric stretching,respectively. Upon blending s-Ph with PVA, the S O and S O

ing cterislayeen bH (

he penolpheneasen bens ins bePVAit i

eve00 cevidin FstretchcharacPh disphydrogfree Oing is tand phon theto incrbe evecontaiciationof theand sotion. Nat 33OH isarrow-IR spectra of (a) pure PVA, (b) 40, (c) 60 and (d) 80 wt.% s-Ph inure s-Ph. (b) FT-IR spectra of PVA60SP samples cured at (a) 80,0 and (d) 150 C.

and discussion

n issues to be examined in the membranes composedPVA are: (1) the degree of cross-linking as a function

emperature and s-Ph composition, (2) the change ofductivity as a function of ion exchange equivalentsolvent uptake for various s-Ph compositions, and

cts of cross-linking to the methanol permeability andductivity.dies were carried out on samples containing PVA and(Fig. 1a), and on samples cured at different temper-

. 1b). Fig. 1a displays the FT-IR spectra of pure PVAmples containing 40 (b), 60 (c) and 80 wt.% (d) ofe parent s-Ph (e). In pure PVA, we observed a dou-round 10001300 cm1 and a broad region aroundcm1. They are characteristic of PVA and have beenC O stretching and O H stretching, respectively.h, two peaks at 1030 cm1 and around 700 cm1

hydrogen bbe discusse

Curing tdisplays chat differentO H bandwith increasuggested aSO3 groupmight takewas not oc150 C [20150 C theoriginal va

The miand PVA ispolarizatiotaining 40marized inintensity anby the follo

M(t) =M

By this anarelaxation tdently, andcarbon direincreases w60 wt.%. Sthe hydroxincrease ofdipolar intecan originatance or froharacteristic of s-Ph grows while the C O stretchingtic of PVA decrease. The O H stretching region in s-d two peaks, which have previously been identified asonded OH (3100 cm1) and non-hydrogen bonded3400 cm1) [19]. It is known that hydrogen bond-rimary driving force for the miscibility between PVAic resin [19]. With the presence of the sulfonate groupolic, inter-molecular hydrogen bonding, is expectedand the miscibility between the two polymers wouldtter. However, the region from 3000 to 3500 cm1formation from a multitude of hydrogen bond asso-tween the aromatic sulfonate and the hydroxyl group

and within the s-Ph and within the PVA moieties,s too broad to allow for unambiguous quantifica-rtheless, a gradual shift of the PVA OH (locatedm1), towards 3100 cm1 of the hydrogen bondedent with increasing s-Ph content as indicated by theig. 1a. More direct evidence of the inter-molecularonding comes from solid-state NMR studies, as willd later.he sample leads to changes in these features. Fig. 1bange in FTIR spectra of the PVA60SP samples curedtemperatures. Negligible changes are found in the

region but intensities of S O and S O peaks decreasesing annealing temperature. The reduced SO3 signalsromatic de-sulfonation or cross-linking between thes of the phenolic resin and the hydroxyls of PVAplace. Although possible, substantial de-sulfonationcurring until the temperature was raised to above]. As evident in Fig. 1b, after annealing sample atSO3 concentration dropped substantially from the

lue prior to heating.scibility and the hydrogen bonding between s-Ph

best illustrated by the 13C solid-state NMR cross-n dynamics. The 13C NMR spectra for samples con-and 60 wt.% s-Ph at different contact times are sum-Fig. 2. The relationships between the magnetizationd cross-polarization contact time can be describedwing equation:

0

[exp

(tT H1

) exp

(tTCH

)]

1TCHT H1

lysis, the cross polarization time TCH and the protonime in the rotating frame T1 can be derived indepen-the results are summarized in Table 1. The TCH for

ctly attached to the sulfonic acid group ( = 128 ppm),hen the s-Ph concentration increases from 40 to

imilarly, TCH for the methine carbon attached toyl group ( = 68 ppm) shows the reverse trend. TheTCH is known to be associated with the reduction ofraction between carbon and hydrogen nuclei, whichte either from a lengthening carbon hydrogen dis-m an increasing molecular re-orientation. Since the

C.-S. Wu et al. / Journal of Power Sources 160 (2006) 12041210 1207

Fig. 2. (a) The 13C solid-state NMR spectra of PVA/40 wt.% s-Ph at differentcontact times. (b) The 13C solid-state NMR spectra of PVA/60 wt.% s-Ph atdifferent contact times.

Table 1Cross-polarization dynamics for the individual carbons as indicated in structure(1) and (2) in PVA40SP and PVA60SPPeak number ppm TCH (s)

PVA40SP PVA60SP

2 116 4783, 4 128 695 4445, 6 38 3279 29897 68 331 408

CH is fixed due to covalent nature, the decrease in TCH is thusgauging the decrease of the molecular motion. The results there-fore, suggest a rise of motion in the s-Ph moiety and a restrictionof molecular reorientation in the PVA segment upon blending.The two moieties must be in close proximity with intimatemiscibility in order to produce the observed effect. A plausi-ble acidbase interaction between PVA and s-Ph is depicted inScheme 1 where bi-functional hydrogen bonding is establishedbetween s-Ph and PVA.

This structure does not include the configurations of the intra-molecular hydrogen bonding within s-Ph and within PVA.

Fig. 3 scontainingincrease wiapproaches101 S cmcorrelatedthe conducthe case fosuggests thwater.

Cross-liboth the IEplayed in Fat temperat

Scheme 1. The probable acidbase interactions betwhows the IEC and conductivity values for samplesa different wt.% of s-Ph. Both IEC and conductivityth increasing s-Ph content. Notice that the IEC value3.0 mmole g1 with the conductivity reaching nearly1 for pure s-Ph. The proton conductivity is highly

with the increase of the sulfonate group. Notice thattivity at high IEC values does not taper off, as wasund in most proton conducting membranes, whiche majority of sulfonate groups are fully accessible to

nking of the matrix by annealing the sample alteredC and proton conductivity. Both properties are dis-ig. 4 for membranes (PVA60SP, 60 wt.% s-Ph) curedures 110, 130 and 150 C. The changes are relativelyeen PVA and s-Ph.

1208 C.-S. Wu et al. / Journal of Power Sources 160 (2006) 12041210

Fig. 3. Ion exchange capacity (IEC) and conductivity at different wt.% of s-Phin PVA polymer.

small below 110 C, but a significant drop is found when thecuring temperature is raised above 130 C. From ambient tem-perature to 130 C the IEC dropped from 2.0 to 1.5 mmole g1,consistent with the drop of the SO3 concentration, measuredfrom the IR. However, the conductivity dropped more to wellbelow the 102 S cm1 level after annealing at 130 C. Simi-larly, the IEC value of the sample PVA60SP cured at 150 Cis located in between that of PVA20SP and PVA40SP, but itsconductivity does not reflect the fair IEC value and shows two

Fig. 4. Ion ecured at diffe

Fig. 5. Water uptake and proton conductivity as a function of curing temperaturefor samples of different composition.

orders lessremains higthat local mthe sulfonathis polyment conducreorientatioductivity. Tdifferent am

The amtransport sterms of protion of the cwt.% of s-included. Ithe water u

ang, a suare

f SOate end (23 atrule

ntialt the

Table 2The IEC, wat

Samples

PVAPVA20SP (17PVA40SP (6:PVA50SP (4:PVA60SP (3:PVA60SPPVA60SPPVA80SP (1:SP

* The parenxchange capacity (IEC) and conductivity of PVA60SP samples

The ch130 Cuptaketion osulfonPVA aof SOcan besubstapendenrent temperature. does not oc

er uptake, and proton conductivity for various PVA/s-Ph compositions

Curing temperature (C) IEC (mmole g1) W.U.

:1)* 0.28 50.11) 0.88 113.61) 1.54 160.61) 2.02 173.9

110 1.67 121.9130 1.50 49.8

1) 2.66 366.2 3.10

thesis is the monomer ratio between vinyl alcohol vs. phenol-4-sulfonic.conductivity. The significance of the fact that the IECh but the conductivity becomes much lower suggestsotion, especially the degree of free re-orientation ofte group is critical to proton transfer. Manipulatinger microstructure, which can either create more flu-ting channel connectivity or increases the SO3 freen are other means to be exploited to improve the con-he conductivity and IEC values for other samples ofount of s-Ph are summarized in Table 2.

ount of solvent that was required to initiate protonerved to measure the efficiency of the membrane inton transport. Fig. 5 shows the water uptake as a func-uring temperature for samples containing a different

Ph. For comparison, the conductivity data are alsot is clear that as the curing temperature is increased,ptake decreases and the conductivity decreases also.e is small, but when the temperature is increased tobstantial decrease both in the conductivity and water

observed. Possible reasons for this are: (1) the reduc-3 due to the formation of a covalent cross-linkingster structure (see Scheme 1) between p-s-Ph and) the loss of SO3 concentration due to disintegrationtemperatures above 130 C. The second possibilityd out since the IEC values are not decreased before adrop of conductivity is observed. Furthermore, inde-rmal gravimetric analysis showed that de-sulfonation

cur until 150 C.

(%) (nH2O/SO3) Conductivity (S cm1) 5.92 105

7 98.33 1.20 1027 71.55 3.54 1022 57.95 5.26 1021 47.75 4.84 1023 40.66 3.76 1025 18.44 8.59 104

76.55 8.57 102 1.97 101

C.-S. Wu et al. / Journal of Power Sources 160 (2006) 12041210 1209

Table 3Permeability and the /D value of PVA/SP membranes

Samples

PVA20SPPVA20SPPVA20SPPVA40SPPVA40SPPVA60SPPVA60SPNafion 117

Table 2ues for samsome sampcussion, thcalculatedses in the fi

Based omonomer (5.5 A, andstretched cphenolic anwhere the from s-Ph iunit in thethat a singThe ratio wsince the ction is apprbears the cevidence ofthe TGA rest decompof either s-consist ofto the polhow the chtions of thrand methan

Table 3with increawater molewith increacompositioIn this casevent uptakeproton tranthe formatto acidic suduction). TPVA40SP)conductionexcess, theincreases sIn this case

Solvent uptake and conductivity at different methanol vol.% for (a)P and (b) PVA60SP cured at 130 C.

rane. These important results suggest that proton trans-an aqueous environment can be activated by less than 40

molecules surrounding each sulfonate group (the lowerf water is not yet determined). It also raises the point thatroperly structured conduction environment and channeltivity (e.g. by forming the polymer-complex), a favor-oton transport condition is achieved by the least amounter. For the pure s-Ph sample (IEC value exceeds 3.1), therane swells severely in water and the conductivity cannotsured correctly.membrane faces the greatest challenge in a concentratedol solution, where the possibility of swelling weakens the

rane properties and the crossover effect limits its functionFCs [2123]. Fig. 6a and b show the variation of thet uptake as a function of methanol concentration for theCuringtemperature (C)

Methanol permeability(cm2 s1)

/P (104)

1.81 106 0.66110 7.19 107130 1.73 107

4.08 106 0.87110 2.09 106 0.53

5.34 106 0.91130 4.84 107 0.37

2.80 106 0.82

summarizes the IEC, water uptake, conductivity val-ples containing 20, 40, 50, 60 and 80 wt.% s-Ph andles cured at 110 and 130 C. For convenience of dis-e monomer mole ratio for s-PH and vinyl alcoholfrom the weight fraction is also included in parenthe-rst column.n a simple geometric calculation from the size of thethe separation between adjacent sulfonate groups isfor vinyl alcohols, it is 1.9 A) and by assuming a

onformation, it is estimated the pairing of sulfonated vinyl alcohol monomers occurs at a 1:3 mole ratio,polymer-complex can be formed, i.e. the sulfonates forming hydrogen bonding with every fourth PVAfully stretched arrangement. It is highly plausible

le s-Ph chain can pair with a multiple PVA chain.hen the polymer-complex occurs may be smaller

hains are not fully stretched. Although this calcula-oximate, it can be expected that the sample PVA60SPlosest composition to the polymer-complex. Directsuch polymer-complex formation is derived from

esults, which shows PVA60SP that bears the high-osition temperature near 550 C. When the amountPh or PVA exceeds this mole ratio, the system willisolated s-Ph or isolated PVA domains, in additionymer-complex. It becomes interesting to examineange of polymer composition, which alters the frac-ee domains, can influence the proton conductivity,ol permeation.shows that the water uptake and IEC value increasese of s-Ph concentration. However, (the number ofcules available per sulfonate group) value decreasessing s-Ph concentration and is lowest at the 3:1 ration (PVA60SP) where the polymer-salt is expected.

Fig. 6.PVA60S

membport inwaterlimit ofor a pconnec

able prof watmembbe mea

Themethanmembin DMsolven, complete acidbase pairing has prevented high sol-, but the chain mobility is still sufficient to supportsport. In addition, the full miscibility also preventedion of localized water clusters that have no accesslfonate groups (thus not contributing towards con-his is the case when PVA is in excess (PVA20SP,

, where is high but fewer protons are available for. On the other hand, in PVA80SP when s-Ph is inIEC approaches 2.66 mmole g1, the value again

ubstantially and the proton conductivity is also high., however the substantial water uptake weakens the

PVA60SP mat temperatare also incFig. 6a, theincrease inis also deccomparisoncan be founno longer i

Contracmethanol cembrane before (Fig. 6a) and after (Fig. 6b) curingure of 130 C. The solvent uptake data for Nafion 117luded in Fig. 6a for comparison. As observed fromswelling ratio decreases from 150 to 130% with anmethanol concentration. Although the conductivity

reased, the value is of the order of 102 S cm1. Inwith Nafion 117, a severe swelling to about 100%d with increasing methanol concentration, where it

s a free-standing film.tion of the cross-linked matrix with increasingontent, and thus the reduced methanol permeabil-

1210 C.-S. Wu et al. / Journal of Power Sources 160 (2006) 12041210

ity compared to that with the conventional Nafion membrane, isa valuable property of the present membrane. With these merits,the material is applied not only to fuel cells but also to separationmembranes and applications in concentrated alcohol conditions.In the case of Nafion, methanol shows a higher affinity with theether groups of the side chains, and gradually dissolves into theotherwiseof an arommatic grouuptake of mcation indimembranethe membrtrasted witabout the sthe membrlinked struc30 vol.% mproton con

Table 3 sability for sat 110 andmeability idropped onthat cross-lHowever, tumn of Tabratio is higcross-linkinpermeationpolymer-cobetween hiIn both cas

4. Conclu

Althougapplicationdesign empacceptor poPVA base102 S cm110 C, covAlthough tleading to ativity valueto Nafion, ature, the cushowed a rmethanol cpermeabilition and wicross-over

the reduced solvent uptake as well as to the higher membraneselectivity towards water. Although both methanol permeationand proton conductivity are lower compared to Nafion, theconductivity/permeability ratio of 0.97 for the PVA/s-Ph 40:60composition is actually higher than that determined for Nafion.The results illustrate the importance of tailoring the structure

otona po

lizedng mncreainkeucetiont me

wled

ionah wo

nce

. KreNodatanab. Kre

Yama. Kre. He

H. Me. Wan96) 7. Waitende94).YamaYamaerres

249erres

erres

erres

114. KerZhou67.iao,. Jun(200

. ChuVoge327Li,649

Ioroi,lid-St. Ari

apotohydrophobic PVdF or PTFE backbone. In the caseatic side chain, the solubility parameter of the aro-p is different from that of methanol, and repels theethanol, compared to that of water. NMR quantifi-

cated that the composition of methanol inside theis less than that in the solution and suggests that

ane favors water uptake over methanol. This is con-h Nafion where the methanol concentration remainsame in the membrane as it is in the fuel stream. Forane cured at 130 C (Fig. 6b), the covalently cross-ture has effectively reduced the methanol uptake. Atethanol, the solvent uptake falls to around 32%. Theductivity dropped to below the 103 S cm1 level.ummarizes the results including the methanol perme-amples containing a different wt.% of s-Ph and curing

130 C. With increasing s-Ph, the methanol per-ncreased slightly. But after curing, the permeabilitye order from 106 to 107 cm2 s1, which suggestedinking has effectively reduced methanol permeation.he proton conductivity is also reduced. The last col-le 3 indicates that the conductivity/permeability (/P)her for membranes without curing, which suggestsg has suppressed more conductivity than methanol. The two samples PVA40SP and PVA60SP where themplex is most abundant, displayed the best balance

gh proton conductivity and low methanol permeation.es, the /P ratio was higher than Nafion.

sions

h far from being ideal for a membrane for fuel cells, the current results unveil a plausible structuralloying both a proton donor polymer and a protonlymer. The membranes composed of s-Ph acid and

displayed good proton conductivity, of the order of1 at ambient temperatures. Upon cross-linking abovealent links between PVA and s-Ph were established.

his sacrificed a certain amount of sulfonate groups,slight reduction of proton conductivity, this conduc-was still at the 102 S cm1 level. In sharp contrastnd other polymer electrolytes disclosed in the litera-rrent membrane (both before and after cross-linking)eduction of methanol solvent uptake with increasingoncentration. These films have been found to show aty of 107 cm2 s1 with increase of s-Ph concentra-th increasing curing temperature. The low methanol(lower methanol permeation value) is attributed to

of a prtion ofbe reareduciwith icross-lthe redconven

presen

Ackno

Natresearc

Refere

[1] K.D[2] A.

Wa[3] K.D[4] M.[5] K.D[6] H.G

W.[7] J.T

(19[8] J.S

Ex(19

[9] M.[10] M.[11] J. K

243[12] J. K[13] J. K[14] J. K

144[15] J.A[16] W.

55[17] J. Q[18] D.H

106[19] P.P[20] C.

320[21] Q.

489[22] T.

So[23] A.S

Chconduction channel (in the present case, by forma-lymer-complex) when high proton conductivity canwith less water. Such a structure is also effective inethanol uptake where the swelling ratio decreasesse of methanol concentration. Contraction of the

d matrix with increasing methanol content, and thusd methanol permeability compared to that with theal Nafion membrane, is a valuable property of thembrane.

gment

l Science Council provides funding to carryout thisrk under the contract no. NSC 932811M 008017.

s

uer, Solid State Ionics 136 (2000) 149160., Md.A.B.H. Susan, K. Kudo, S. Mitsushima, K. Hayamizu, M.e, J. Phys. Chem. B 107 (2003) 40244033.uer, J. Membr. Sci. 185 (2001) 2939.da, I. Honma, Electrochim. Acta 50 (2005) 28372841.uer, Chem. Mater. 8 (1996) 610.rz, K.D. Kreuer, J. Maier, G. Scharfenberger, M.F.H. Schuster,yer, Electrochim. Acta 48 (2003) 21652171.g, J.S. Wainright, R.F. Savinell, M. Litt, J. Appl. Electrochem. 2651.nright, J.T. Wang, R.F. Savinell, M. Litt, H. Moaddel, C. Rogers,d Abs., The Electrochem. Soc. Spring Meeting, San Francisco 94

da, I. Honma, Chem. Phys. Chem. 5 (2004) 724728.da, I. Honma, Electrochim. Acta 40 (2003) 24112415., A. Ullrich, F. Meier, T. Haring, Solid State Ionics 125 (1999)., W. Cui, US Patent No. 6,300,381 (2001)., W. Cui, US Patent No. 6,194,474 (2001)., W. Cui, W. Zhang, J. Polym. Sci: Part A: Polym. Chem. 36 (1998)48.res, J. Membr. Sci. 185 (2001) 327., M. Yoshino, H. Kita, K. Okamoto, J. Membr. Sci. 217 (2003)

T. Hamaya, T. Okada, Chem. Mater. 17 (2005) 24132421.g, S.Y. Cho, D.H. Peck, D.R. Shin, J.S. Kim, J. Power Sources2) 173177.

, H.-D. Wu, Polymer 41 (2000) 101109.l, J. Meier-Haack, A. Taeger, D. Lehmann, Fuel Cell 4 (2004).R. He, J.O. Jensen, N.J. Bjerrum, Chem. Mater. 15 (2003)15.K. Kuraoda, K. Yasuda, T. Yazawa, Y. Miyazaki, Electrochem.

ate Lett. 7 (2004) A394A396.co, V. Baglio, P. Creti, A. Di Blasi, V. Antonucci, J. Brunea, A.t, A. Bozzi, J. Schoemans, Power Sources 123 (2003) 107115.

A polyvinyl alcohol/p-sulfonate phenolic resin composite proton conducting membraneIntroductionExperimentalMembrane preparationMembrane characterizationWater uptake and solvent uptakeIon exchange capacity (IEC)Proton conductivity measurementMethanol permeability measurement

Results and discussionConclusionsAcknowledgmentReferences