Research ArticlePolybenzimidazole and Phosphonic Acid Groups-FunctionalizedPolyhedral Oligomeric Silsesquioxane Composite Electrolyte forHigh Temperature Proton Exchange Membrane

Sung-Kon Kim

Department of Materials Science and Engineering and Beckman Institute for Advanced Science and TechnologyUniversity of Illinois at Urbana-Champaign Urbana IL 61801 USA

Correspondence should be addressed to Sung-Kon Kim sk0903illinoisedu

Received 15 August 2016 Accepted 20 September 2016

Academic Editor Vincenzo Baglio

Copyright copy 2016 Sung-Kon Kim This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Here we report composite membrane consisting of poly[221015840-(m-phenylene)-551015840-(bibenzimidazole)] (PBI) and polyhedraloligomeric silsesquioxane functionalized with phosphonic acid groups (PO(OH)

2-POSS) for high temperature proton exchange

membrane sim7 phosphonic acid groups are incorporated into the phenyl rings of POSS via bromination in a high yield (sim93)followed by substitution of the bromine elements by phosphonate ester groups via a Pd(0) catalyzed PndashC coupling reactionPhosphonic acid groups are formed by the hydrolysis of the phosphonate ester groups in hydrobromic acid solution At a 50wtof PA content in the membranes PBIPO(OH)

2-POSS composite membrane shows larger proton conductivity of 32 times 10minus3 S cmminus1

than 28 times 10minus3 S cmminus1 of PBI membrane at 150∘C and anhydrous conditions owing to the multiple phosphonic acid groups ofPO(OH)

2-POSS that can function as proton transport medium at high temperature and low humidity conditions

1 Introduction

Phosphoric acid (PA)-doped polybenzimidazoles (PBIs)have gained great interests for proton exchange membrane(PEMs) due to their intrinsic attributes such as high protonconductivity (up to 200∘C) low gas permeability excellentoxidative and thermal stabilities and almost zero water dragcoefficient [1ndash5] In particular many attempts on PBI-basedorganicinorganic composites have been made to improvethe proton conductivity of PEMs that can operate at elevatedtemperature (generally 100ndash200∘C) and low humidity condi-tions Examples of inorganic components include silica(SiO2) [6 7] lithium hydrazinium sulfate (LiN

2H5SO4) [8]

zirconium phosphates (Zr(HPO4)2sdotnH2O) [9] zirconium

pyrophosphate (ZrP2O7) [10] phosphotungstic acid

(H3PW12O40sdotnH2O) [9] silicotungstic acid (H

4SiW12O40sdot

nH2O) [9] and boron phosphate (BPO

4) [11] all of which

have led to the improvement of electrochemical and physicalproperties of PBI electrolytes

Polyhedral oligomeric silsesquioxane (POSS) has beenintensively studied because of its well-defined three-dimen-sional nanoscale organicinorganic hybrid structure that

provides interesting opportunities for improving the physicaland mechanical properties of polymers due to filler effect[12 13]Thedevelopment of this compound as a nanobuildingblock is important to a variety of applications includingelectronics energy and biomedical engineering [13 14]In particular the properties of POSS can be tuned byincorporating various functionalities such as acrylates meth-acrylates alcohols amines carboxylic acids epoxides fluo-roalkyls halides and imides [13 15ndash18]

Phosphonic acid groups are attracting much attentionbecause of their high thermal hydrolytic and oxidativestabilities [19ndash22]They also undergo autodissociation due tointrinsically amphoteric character leading to the formation ofhydrogen bond network [23 24] and thus can participate inthe transport of protons from site to site without carriermolecules via Grotthuss-type mechanism [22 23 25] Thesedistinctive properties are of specific interest to proton con-ducting electrolytes that operate at high temperature andlow humidity conditions However it remains a significantchallenge to functionalize multiple phosphonic acid groupsto molecules (or macromolecular species) due to side reac-tions such as condensation and aggregation of phosphonic

Hindawi Publishing CorporationJournal of NanomaterialsVolume 2016 Article ID 2954147 7 pageshttpdxdoiorg10115520162954147

2 Journal of Nanomaterials

acid groups [26 27] In this study the phenyl rings of POSSwere functionalized with sim7 phosphonic acid groups viabromination followed by phosphonationThe functionalizedPOSS was incorporated with PBI for use in high temperaturePEMs

2 Experimental

21 Materials Bromine (Br2 gt995 Aldrich) tetrakis(tri-

phenylphosphine) palladium(0) (Pd(PPh3)4 990 Al-

drich) diethyl phosphate ((EtO)2POH 980 Aldrich)

triethylamine (TEA ge990 TCI) iso-octylphenyl polyhe-dral oligomeric silsesquioxane (termed as POSS here Hybridplastics) hydrobromic acid solution (HBr 470sim490 Dae-jung) sodium bisulfite (NaHSO

3 585 Daejung) iron (Fe

gt99 Aldrich) 331015840-diaminobenzidine (97 Tokyo KaseiTCI) poly(phosphoric acid) (PPA 116 H

3PO4 Junsei)

phosphorus pentoxide (97 Aldrich) and phosphoric acid(PA 85wtaqueous solutionAldrich)were used as receivedIsophthalic acid (99 Aldrich) was purified by recrystal-lization in ethanol to obtain white needlelike crystalsSolvents were distilled before use

22 Bromination of POSS (Br-POSS) Bromine-substitutedPOSS (Br-POSS) was synthesized as reported [28] Brieflyto a 500mL round-bottom flask equipped with magneticstirring bar was added POSS (100 g 935mmol) Fe (110 g197mmol) and 100mL of CH

2Cl2 Br2(361mL 701mmol)

was then added portion-wise and the solution was stirredfor 3 h at room temperature Subsequently 100mL of 10wtNaHSO

3aqueous solution was added to the solution to

remove residual Br2 The solution was then transferred to a

separatory funnel to extract the organic layer and thenwashed three times with distilled water The solvent wasremoved by using the rotary evaporator to produce a powderThe resulting powder was dissolved in ethyl acetate andprecipitated into 1000mL of methanol The precipitate wasobtained through filtering and then dried under vacuum togive a 108 g of final white powder (93) 1HNMR (500MHzDMSO-119889

6 ppm) 120575 795ndash645 (br C

6H5) 189ndash060 (m

C8H17) MALDI-TOF 119898119911 = 13758 14537 15346 16106

16885 17674 18463

23 Synthesis of PO(OEt)2-POSS A 100mL two-neck reactorequipped with nitrogen and condenser was charged with18mL of anhydrous dimethyl sulfoxide (DMSO) Br-POSS(300 g 179mmol) diethyl phosphite (459mL 359mmol)and TEA (500mL 359mmol) were added to the reactor andthe mixture was stirred for 10min Pd(PPh

3)4(207 g 179

mmol) was then injected into the reaction flask with highstream of nitrogen and the solution was heated for 72 h at100∘C After cooling to room temperature the solution wasprecipitated in distilled water (1000mL) The precipitate wasthen filtered and dried overnight in a vacuum oven to a givebrownish powder (86) 1H NMR (500MHz DMSO-119889

6

ppm) 120575 836ndash693 (br C6H5) 396ndash331 (br CH

2ndashO) 129ndash

019 (br CH3and C

8H17) 31P NMR (202MHz DMSO-119889

6

ppm) 120575 260

24 Synthesis of Poly[221015840-(m-phenylene)-551015840-(bibenzim-idazole)] (PBI) PPA (902 g) was charged into a 250mLthree-neck reactor equipped with a mechanical stirrernitrogen inlet and calcium chloride drying tube and heatedfor 30min at 150∘CDABI (278 g 130mmol) and IPA (216 g130mmol) were then added gradually and the solution wasstirred for 1 h at 150∘C under a slow nitrogen stream andmechanical stirring until it became a homogeneous solutionThe reaction temperature was raised to 200∘C After 30minphosphorus pentoxide (484 g 170mmol) was added and thereaction continued for 12 h at 200∘C with constant stirringusing a mechanical stirrer to obtain a very viscous darkbrown solution The reaction mixture was isolated into thepolymer in distilled water (1000mL) and the precipitate wasthen neutralized with an aqueous solution of NaHCO

3and

rinsed several times with distilled water to remove phosphatesalts It was dried overnight under vacuum The resultingpolymer was ground using a pulverizer (A11 basic IKA)and washed again to remove any residual phosphoric acidFinally the powder was dried at 70∘C in a vacuum oven for atleast 3 days (gt95) 1H NMR (500MHz DMSO-119889

6 ppm)

120575 914 (s 1H) 832 (d 2H) 800 (s 2H) 781 (d 2H) 762 (br3H)

25 Preparation of Composite Membranes 40 g of PBI pow-der and 10 g of PO(OEt)

2-POSS were dissolved in a 166 g of

NN-dimethylacetamide (DMAc) at 80∘C The mixed solu-tion was then spread onto a clean flat glass plate Thethickness of the solution was controlled using an adjustabledoctor blade and the casted solution was left to dry at80∘C for 12 h until no DMAc evaporation was noted Aftercooling to room temperature the obtained filmwas soaked indistilled water and peeled off the substrate The resulting filmwas dried using gel dryer at 60∘C for 1 h and then the filmwas further dried under vacuum for 12 h To convert POSSin phosphonated ester form (PO(OEt)

2-POSS) into that

in phosphonic acid form (PO(OH)2-POSS) the composite

membranes containing PO(OEt)2-POSS were soaked in con-

centrated HBr solution at reflux for 24 hThe composite filmswere thoroughly washed with distilled water several times toneutralize and to remove excess acid and then dried using geldryer at 60∘C for 1 h and then the film was further dried in avacuum oven for 12 hThe PBI and PO(OH

2)-POSS compos-

ite film obtainedwas weighed (1198821) and immersed in 1000mL

of the PA solution with 60wt concentration at 80∘C for 4 hThe PA-doped membrane was taken out of the PA solutionand then blotted with filter paper The membrane wasdried at 70∘C under vacuum for 2 days and weighed again(1198822) The weight difference (119882

2minus 1198821) was assumed to

be the weight of the absorbed PA The PA content of themembrane was then calculated as the weight percent (wt)of PA absorbed in the membrane using

PA content (wt) =(1198822minus1198821)

1198822

times 100 (1)

26 Characterization Matrix-assisted laser desorptionioni-zation time-of-flight mass spectroscopy (MALDI-TOFMS)

Journal of Nanomaterials 3

was recorded on a Voyager-DE STR BiospectrometryWorkstation (Applied Biosystems Inc) set in the positivereflection mode using dithranol as the matrix The MALDI-TOFMS instrument was equipped with a nitrogen laserwhich was emitting at 337 nm with a 3 ns pulse width The1H and 31P nuclear magnetic resonance (NMR) spectra werecollected on Bruker Avance 500 with a proton frequency of500MHz During the experiments deuterated dimethyl sul-foxide was used as the solvent and tetramethylsilane (TMS)was used as the internal standard Fourier transform infrared(FT-IR) spectra of dried membranes and powder sampleswere recorded in the attenuated total reflectance (ATR)mode in the frequency range of 4000sim650 cmminus1 on a Nicolet6700 instrument (Thermo Scientific USA) The spectrumwas recorded as the average of 32 scans with the resolution of8 cmminus1 Each of the samples was put in equal physical contactwith the sampling plate of the spectrometer accessory toavoid differences caused by pressure and penetration depthThe chemical composition and concentration of the materialwere determined by field-emission scanning electronmicroscopy (FE-SEM Carl Zeiss SUPRA 55VP) operated atan accelerating voltage of 15 kV and equipped with energy-dispersive spectroscopy (EDS) capabilities Proton conduc-tivity was measured using a four-point probe Impedancewas measured using a ZAHNER IM-6ex impedance analyzerin potentiostat mode with a perturbation amplitude of 10mVover frequencies of 1Hz to 1MHz Impedance at a controlledhumidity and temperature was measured fromNyquist plotsProton conductivity (120590) was calculated using 120590 = 119889119877119878where 119889 is the distance between the reference and sensingelectrodes and 119878 is the cross-sectional area (thickness timeswidth) of the doped membrane 1 cm times 5 cm membraneswere introduced to the conductivity cell and heated to 160∘Cand held for 30min Measurements were taken as the cellthen cooled to 100∘C in 10∘C steps

3 Results and Discussion

Iso-octylphenyl polyhedral oligomeric silsesquioxane whichwe term POSS here was brominated by a coupling reactionin high yield (ca 93) as reported (abbreviated as Br-POSS Figure 1) [28 29] and characterized by using MALDI-TOFMS 1HNMR and ATR FT-IR MALDI-TOFMS of Br-POSS shows a series of peaks separated by 79 amuof brominecentered at 1610119898119911 (Figure 2) It indicates that an averageof sim7 bromine elements per POSS was incorporated Thisobservation was further supported by 1HNMR spectra (Fig-ure 3) The bromination of POSS results in the broadeningof proton peaks associated with the phenyl rings of POSS(120575 = 81sim63 ppm) while the peaks of isooctyl moiety (120575lt 20 ppm) remain unchanged demonstrating that bromineelements are incorporated into the phenyl rings of POSSThe extent of bromine elements incorporated was calculatedby the comparison of integrals of proton peaks associatedwith the phenyl ring and the isooctyl moieties The averagenumber of the bromine elements per POSS determined by

1H NMR spectra was sim76 close to MALDI-TOFMS-determined value Figure 4 shows ATR FT-IR spectra of Br-POSSThe characteristic absorption band assigned to stretch-ing vibration for aromatic halogen compound appears at1009 cmminus1 The bands at 894 810 and 784 cmminus1 are alsoascribed to bromine-incorporated phenyl rings of POSS

The bromine elements of Br-POSS were substituted withphosphonate ester groups via a Pd(0) catalyzed PndashC cou-pling reaction which was carried out with diethyl phos-phite ((EtO)

2POH) and tetrakis(triphenylphosphine) palla-

dium(0) (Pd(PPh3)4) as a catalyst with trimethylamine (TEA)

[26 30 31] the resulting compound is named PO(OEt)2-

POSS (Figure 1) We observed the peaks of the CH2and CH

3

protons of phosphonate ester groups at 120575 = 380 and 115ppm respectively in 1H NMR spectra as a consequence ofsubstitution of phosphonate esters for bromine elements(Figure 3) [31] Figure 5 presents 31P NMR spectra ofPO(OEt)

2-POSS and diethyl phosphite a monomer used for

the substitution reaction The phosphorous signal associatedwith phosphonate ester units of PO(OEt

2)-POSS is shifted

downfield by sim17 ppm as compared to that of diethyl phos-phite because of the substitution reaction ATR FT-IR spec-tra also provide the information regarding the substitutionreaction (Figure 4) The phosphoryl linkage (P=O) stretch-ing appears at around 1680 cmminus1 The bands at 1048 and1023 cmminus1 are assigned to PminusOminusC absorptions of the estergroup and the band at 949 cmminus1 is attributed to PminusOminusCvibrations [27 31] SEMEDSmeasurement was conducted toverify substitution from bromine elements to phosphonateester groups (Figure 6) No notable peaks of bromine ele-ments are observed A single peak of phosphorus appears atsim21 keV and its intensity is comparable with that of sil-icon at sim19 keV Assuming that the substitution occurredcompletely the number of phosphorous elements per POSSshould be sim7 which is the same with that of silicon ofPOSS Accordingly the atomic weight ratio of phosphorusto silicon for PO(OEt)

2-POSS determined through EDS is

unity supporting the assumption that bromine elements werecompletely substituted by phosphonate ester groups

Following the protocol we and others have exploredpoly[221015840-(m-phenylene)-551015840-(bibenzimidazole)] (PBI) wassynthesized by a condensation polymerization and fabricatedinto a freestanding membrane through a solution castingmethod commonly used which was also applied to the fab-rication of PBIPO(OEt)

2-POSS composite membrane The

phosphonate ester units of PO(OEt)2-POSS were readily

converted into the phosphonic acid ones denoted asPO(OH)

2-POSS by hydrolysis in hydrobromic acid (HBr)

solution as demonstrated in Figure 1 In addition in ATR FT-IR spectra the characteristic bands associated with phospho-nate ester groups of PO(OEt)

2-POSS disappear implying the

substitution of phosphonic acids for phosphonate esters(Figure 4) More importantly PO(OEt)

2-POSS is soluble in

organic solvents such asDMSOandDMAcwhile its solubilitydecreases significantly once the hydrolysis is performedwhich is most likely due to strong hydrogen bond networkformed between phosphonic acid groups [31 32] Due tosuch dissolution issue of PO(OH)

2-POSS in organic solvents

4 Journal of Nanomaterials

O

O

O

O

O

O O

OOO

OOO

OOO

OOO

OO

OOO O

O O

O

O

O

OO

O OO

OO

O

OO

Si

Si Si

Si

SiSi

SiSi

OO

OO O

OO

O

O

OO

OSi

Si Si

Si

SiSi

SiSi

O

O

OO

O OO

OO

O

OO

Si

Si Si

Si

SiSi

SiSi

OO

OO O

OO

O

O

OO

OSi

Si Si

Si

SiSi

SiSi

PP

P

P

P

P

PP

P

P

P

P

PP

HO

HOHO

HOHO

HO

HO

OH

OH

OH

OHOH OH

OH

Br

Br

Br

Br

Br

Br Br

POSS

Br2Fe

CH2Cl2 RT 3h

(EtO)2POHPd(PPh3)4TEA

DMSO 100∘C

Br-POSS

PO(OEt)2-POSS PO(OH)2-POSS

HBr

Reflux

Figure 1 Synthesis of phosphonic acids-functionalized POSS

1400 1500 1600 1700 1800 19001300Mass (mz)

of substituted Br elements = 7

Figure 2 MALDI-TOFMS of Br-POSS

PO(OEt)2-POSS which is soluble in DMAc was mixed with

PBI for freestanding film formation prior to hydrolysis Thedoping of the composite membrane in 60wt PA solutionimparts proton conducting capability of the membrane ThePA content absorbed in the membranes is sim50wt

Figure 7 shows the proton conductivities of the PA-dopedmembranes with temperature ranging from 100 to 150∘Cunder anhydrous conditions Not surprisingly the protonconductivity increases with increasing temperature an obser-vation common to all studies on PA-doped PBI derivativemembranes [5 25 33ndash36] In particular PBIPO(OH)

2-POSS

composite membrane provides greater proton conductivity32 times 10minus3 S cmminus1 than PBI membrane (28 times 10minus3 S cmminus1) at

Br-POSS

POSS

8 6 4 2 010Chemical shift (ppm)

OO

O

Si

P

PO(OEt)2-POSS

Figure 3 1HNMR spectra of POSS Br-POSS and PO(OEt)2-POSS

a given temperature The conductivity against temperatureexhibits the Arrhenius behavior (120590 = 120590

0exp(minus119864

119886119877119879) where

1205900is the preexponential factor and 119864

119886is the activation energy

Journal of Nanomaterials 5

10481023

Br-POSS

7848108941009

Tran

smitt

ance

(au

)

POSS

1680

949

PO(OEt)2-POSS

PO(OH)2-POSS

1500 1200 9001800Wavenumber (cmminus1)

Figure 4 ATR FT-IR spectra of POSS Br-POSS PO(OEt)2-POSS

and PO(OH)2-POSS

Diethyl phosphite

PO(OEt)2-POSS

40 30 20 10 050Chemical shift (ppm)

Figure 5 31P NMR spectra of diethyl phosphite and PO(OEt)2-

POSS

for the proton conduction) indicating that proton conduc-tion in the membrane follows a proton-hopping dominantmechanism (Grotthuss-type mechanism) as reported byother reports [33 34 37] We thus speculate that sim7 phos-phonic acid groups of PO(OH)

2-POSS provide a better

pathway for proton conduction as they bridge the apparentgap between PAs (andor PA and PBI) via the hoppingmechanism

4 Conclusions

In summary we succeeded in functionalizing POSS with sim7phosphonic acid groups Following brominationsim7 bromineelements of POSS were substituted with phosphonate estergroups which were further hydrolyzed into phosphonic acidgroups in hydrobromic acid solution The solubility of thePOSS significantly decreased after the hydrolysis whichmight be due to hydrogen bond network formed betweenphosphonic acids The functionalized PO(OH)

2-POSS was

hybridized with PBI and the composite was fabricated intofreestanding membrane followed by doping in PA solution

Cou

nts (

au)

C-K120572

Si-K120572 P-K120572

O-K120572 Pd-L120572

2 4 6 8 100X-ray energy (keV)

Figure 6 SEMEDS spectroscopy of PO(OEt)2-POSS

PBI

PBIPO(OH)2-POSS

minus25

minus20

minus15

minus10

minus05

00

05

ln(120590

T) (

KSmiddotcm

minus1 )

25 26 27241000T (Kminus1)

Figure 7 Proton conductivities of PA-doped PBI and PBIPO(OH)

2-POSS membranes with temperature ranging from 100 to

150∘C under anhydrous conditions PA content of the membranes isca 50wt

The PA-doped composite membrane retains proton conduc-tivity greater than that of PBI membrane at high temperatureover 100∘C and low humidity conditions We conclude thatphosphonic acids-functionalized POSS as a filler providesconsiderable increase in proton conducting capability ofpolymer electrolyte operating at high temperature

Competing Interests

The author declares that there are no competing interestsregarding the publication of this paper

References

[1] J S Wainright J-T Wang D Weng R F Savinell and M LittldquoAcid-doped polybenzimidazoles a new polymer electrolyterdquoJournal of the Electrochemical Society vol 142 no 7 pp L121ndashL123 1995

6 Journal of Nanomaterials

[2] J Weber K-D Kreuer J Maier and A Thomas ldquoProtonconductivity enhancement by nanostructural control of po-ly(benzimidazole)-phosphoric acid adductsrdquo AdvancedMateri-als vol 20 no 13 pp 2595ndash2598 2008

[3] Q Li R He J O Jensen and N J Bjerrum ldquoPBI-based poly-mer membranes for high temperature fuel cellsmdashpreparationcharacterization and fuel cell demonstrationrdquo Fuel Cells vol 4no 3 pp 147ndash159 2004

[4] L Xiao H Zhang E Scanlon et al ldquoHigh-temperaturepolybenzimidazole fuel cell membranes via a sol-gel processrdquoChemistry of Materials vol 17 no 21 pp 5328ndash5333 2005

[5] S-K Kim T-H Kim J-W Jung and J-C Lee ldquoPolyben-zimidazole containing benzimidazole side groups for high-temperature fuel cell applicationsrdquo Polymer vol 50 no 15 pp3495ndash3502 2009

[6] E Quartarone PMustarelli A Carollo S Grandi AMagistrisand C Gerbaldi ldquoPBI composite and nanocomposite mem-branes for PEMFCs the role of the fillerrdquo Fuel Cells vol 9 no3 pp 231ndash236 2009

[7] P Mustarelli A Carollo S Grandi et al ldquoComposite proton-conducting membranes for PEMFCsrdquo Fuel Cells vol 7 no 6pp 441ndash446 2007

[8] J-W Jung S-K Kim and J-C Lee ldquoPreparation of polybenz-imidazolelithium hydrazinium sulfate composite membranesfor high-temperature fuel cell applicationsrdquo MacromolecularChemistry and Physics vol 211 no 12 pp 1322ndash1329 2010

[9] R He Q Li G Xiao and N J Bjerrum ldquoProton conductivityof phosphoric acid doped polybenzimidazole and its compos-ites with inorganic proton conductorsrdquo Journal of MembraneScience vol 226 no 1-2 pp 169ndash184 2003

[10] T-H Kim T-W Lim Y-S Park K Shin and J-C Lee ldquoProton-conducting zirconiumpyrophosphatepoly(25-benzimidazole)composite membranes prepared by a PPA direct castingmethodrdquo Macromolecular Chemistry and Physics vol 208 no21 pp 2293ndash2302 2007

[11] S M J Zaidi ldquoPreparation and characterization of compositemembranes using blends of SPEEKPBI with boron phosphaterdquoElectrochimica Acta vol 50 no 24 pp 4771ndash4777 2005

[12] S-W Kuo and F-C Chang ldquoPOSS related polymer nanocom-positesrdquo Progress in Polymer Science vol 36 no 12 pp 1649ndash1696 2011

[13] D B Cordes P D Lickiss and F Rataboul ldquoRecent develop-ments in the chemistry of cubic polyhedral oligosilsesquiox-anesrdquo Chemical Reviews vol 110 no 4 pp 2081ndash2173 2010

[14] D-G Kim J Shim J H Lee S-J Kwon J-H Baik andJ-C Lee ldquoPreparation of solid-state composite electrolytesbased on organicinorganic hybrid star-shaped polymer andPEG-functionalized POSS for all-solid-state lithium batteryapplicationsrdquo Polymer vol 54 no 21 pp 5812ndash5820 2013

[15] K J Shea and D A Loy ldquoBridged polysilsesquioxanesMolecular-engineered hybrid organic-inorganic materialsrdquoChemistry of Materials vol 13 no 10 pp 3306ndash3319 2001

[16] J D Lichtenhan Y A Otonari and M J Carr ldquoLinear hybridpolymer building blocks methacrylate-functionalized poly-hedral oligomeric silsesquioxane monomers and polymersrdquoMacromolecules vol 28 no 24 pp 8435ndash8437 1995

[17] M Takeda K Kuroiwa M Mitsuishi and J Matsui ldquoSelf-assembly of amphiphilic POSS anchoring a short organic tailwith uniform structurerdquo Chemistry Letters vol 44 no 11 pp1560ndash1562 2015

[18] S-Y Kuwahara K Yamamoto and J-I Kadokawa ldquoSynthesis ofamphiphilic polyhedral oligomeric silsesquioxane having ahydrophobic fluorescent dye group and its formation of fluo-rescent nanoparticles in waterrdquo Chemistry Letters vol 39 no10 pp 1045ndash1047 2010

[19] D D Jiang Q Yao M A McKinney and C A Wilkie ldquoTGAFTIR studies on the thermal degradation of some polymericsulfonic and phosphonic acids and their sodium saltsrdquo PolymerDegradation and Stability vol 63 no 3 pp 423ndash434 1999

[20] M Schuster T Rager A Noda K D Kreuer and J MaierldquoAbout the choice of the protogenic group in PEM separatormaterials for intermediate temperature low humidity opera-tion a critical comparison of sulfonic acid phosphonic acid andimidazole functionalized model compoundsrdquo Fuel Cells vol 5no 3 pp 355ndash365 2005

[21] A Kaltbeitzel S Schauff H Steininger et al ldquoWater sorptionof poly(vinylphosphonic acid) and its influence on protonconductivityrdquo Solid State Ionics vol 178 no 7ndash10 pp 469ndash4742007

[22] B Lafitte and P Jannasch ldquoPolysulfone ionomers functionalizedwith benzoyl(difluoromethylenephosphonic acid) side chainsfor proton-conducting fuel-cell membranesrdquo Journal of PolymerScience Part A Polymer Chemistry vol 45 no 2 pp 269ndash2832007

[23] R Tayouo G David B Ameduri J Roziere and S RoualdesldquoNew fluorinated polymers bearing pendant phosphonic acidgroups Proton conducting membranes for fuel cellrdquo Macro-molecules vol 43 no 12 pp 5269ndash5276 2010

[24] E Labalme G David P Buvat J Bigarre and T BoucheteauldquoNew hybrid membranes based on phosphonic acid function-alized silica particles for PEMFCrdquo Journal of Polymer SciencePart A Polymer Chemistry vol 50 no 7 pp 1308ndash1316 2012

[25] S-K Kim S-W Choi W S Jeon et al ldquoCross-linkedbenzoxazine-benzimidazole copolymer electrolyte membranesfor fuel cells at elevated temperaturerdquo Macromolecules vol 45no 3 pp 1438ndash1446 2012

[26] K Jakoby K V Peinemann and S P Nunes ldquoPalladium-catalyzed phosphonation of polyphenylsulfonerdquoMacromolecu-lar Chemistry and Physics vol 204 no 1 pp 61ndash67 2003

[27] B Lafitte and P Jannasch ldquoPhosphonation of polysulfonesvia lithiation and reaction with chlorophosphonic acid estersrdquoJournal of Polymer Science Part A Polymer Chemistry vol 43no 2 pp 273ndash286 2005

[28] MDGuiver O Kutowy and JWApSimon ldquoFunctional grouppolysulphones by bromination-metalationrdquo Polymer vol 30no 6 pp 1137ndash1142 1989

[29] C M Brick R Tamaki S-G Kim et al ldquoSpherical poly-functional molecules using poly(bromophenylsilsesquioxane)sas nanoconstruction sitesrdquo Macromolecules vol 38 no 11 pp4655ndash4660 2005

[30] M Kalek and J Stawinski ldquoPd(0)-catalyzed phosphorus-carbon bond formation Mechanistic and synthetic studieson the role of the palladium sources and anionic additivesrdquoOrganometallics vol 26 no 24 pp 5840ndash5847 2007

[31] K Miyatake and A S Hay ldquoNew poly(arylene ether)s withpendant phosphonic acid groupsrdquo Journal of Polymer SciencePart A Polymer Chemistry vol 39 no 21 pp 3770ndash3779 2001

[32] J Parvole and P Jannasch ldquoPolysulfones grafted with poly(vin-ylphosphonic acid) for highly proton conducting fuel cellmembranes in the hydrated and nominally dry staterdquo Macro-molecules vol 41 no 11 pp 3893ndash3903 2008

Journal of Nanomaterials 7

[33] R Bouchet and E Siebert ldquoProton conduction in acid dopedpolybenzimidazolerdquo Solid State Ionics vol 118 no 3-4 pp 287ndash299 1999

[34] A Bozkurt W H Meyer and G Wegner ldquoPAAimidazol-based proton conducting polymer electrolytesrdquo Journal of PowerSources vol 123 no 2 pp 126ndash131 2003

[35] S-KKimTKo S-WChoi et al ldquoDurable cross-linked copoly-mer membranes based on poly(benzoxazine) and poly(25-benzimidazole) for use in fuel cells at elevated temperaturesrdquoJournal of Materials Chemistry vol 22 no 15 pp 7194ndash72052012

[36] S-K Kim K-H Kim J O Park et al ldquoHighly durable poly-mer electrolyte membranes at elevated temperature cross-linked copolymer structure consisting of poly(benzoxazine)andpoly(benzimidazole)rdquo Journal of Power Sources vol 226 pp346ndash353 2013

[37] H-S Lee A Roy O Lane and J E McGrath ldquoSynthesisand characterization of poly(arylene ether sulfone)-b-polyben-zimidazole copolymers for high temperature low humidityproton exchange membrane fuel cellsrdquo Polymer vol 49 no 25pp 5387ndash5396 2008

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NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

2 Journal of Nanomaterials

acid groups [26 27] In this study the phenyl rings of POSSwere functionalized with sim7 phosphonic acid groups viabromination followed by phosphonationThe functionalizedPOSS was incorporated with PBI for use in high temperaturePEMs

2 Experimental

21 Materials Bromine (Br2 gt995 Aldrich) tetrakis(tri-

phenylphosphine) palladium(0) (Pd(PPh3)4 990 Al-

drich) diethyl phosphate ((EtO)2POH 980 Aldrich)

triethylamine (TEA ge990 TCI) iso-octylphenyl polyhe-dral oligomeric silsesquioxane (termed as POSS here Hybridplastics) hydrobromic acid solution (HBr 470sim490 Dae-jung) sodium bisulfite (NaHSO

3 585 Daejung) iron (Fe

gt99 Aldrich) 331015840-diaminobenzidine (97 Tokyo KaseiTCI) poly(phosphoric acid) (PPA 116 H

3PO4 Junsei)

phosphorus pentoxide (97 Aldrich) and phosphoric acid(PA 85wtaqueous solutionAldrich)were used as receivedIsophthalic acid (99 Aldrich) was purified by recrystal-lization in ethanol to obtain white needlelike crystalsSolvents were distilled before use

22 Bromination of POSS (Br-POSS) Bromine-substitutedPOSS (Br-POSS) was synthesized as reported [28] Brieflyto a 500mL round-bottom flask equipped with magneticstirring bar was added POSS (100 g 935mmol) Fe (110 g197mmol) and 100mL of CH

2Cl2 Br2(361mL 701mmol)

was then added portion-wise and the solution was stirredfor 3 h at room temperature Subsequently 100mL of 10wtNaHSO

3aqueous solution was added to the solution to

remove residual Br2 The solution was then transferred to a

separatory funnel to extract the organic layer and thenwashed three times with distilled water The solvent wasremoved by using the rotary evaporator to produce a powderThe resulting powder was dissolved in ethyl acetate andprecipitated into 1000mL of methanol The precipitate wasobtained through filtering and then dried under vacuum togive a 108 g of final white powder (93) 1HNMR (500MHzDMSO-119889

6 ppm) 120575 795ndash645 (br C

6H5) 189ndash060 (m

C8H17) MALDI-TOF 119898119911 = 13758 14537 15346 16106

16885 17674 18463

23 Synthesis of PO(OEt)2-POSS A 100mL two-neck reactorequipped with nitrogen and condenser was charged with18mL of anhydrous dimethyl sulfoxide (DMSO) Br-POSS(300 g 179mmol) diethyl phosphite (459mL 359mmol)and TEA (500mL 359mmol) were added to the reactor andthe mixture was stirred for 10min Pd(PPh

3)4(207 g 179

mmol) was then injected into the reaction flask with highstream of nitrogen and the solution was heated for 72 h at100∘C After cooling to room temperature the solution wasprecipitated in distilled water (1000mL) The precipitate wasthen filtered and dried overnight in a vacuum oven to a givebrownish powder (86) 1H NMR (500MHz DMSO-119889

6

ppm) 120575 836ndash693 (br C6H5) 396ndash331 (br CH

2ndashO) 129ndash

019 (br CH3and C

8H17) 31P NMR (202MHz DMSO-119889

6

ppm) 120575 260

24 Synthesis of Poly[221015840-(m-phenylene)-551015840-(bibenzim-idazole)] (PBI) PPA (902 g) was charged into a 250mLthree-neck reactor equipped with a mechanical stirrernitrogen inlet and calcium chloride drying tube and heatedfor 30min at 150∘CDABI (278 g 130mmol) and IPA (216 g130mmol) were then added gradually and the solution wasstirred for 1 h at 150∘C under a slow nitrogen stream andmechanical stirring until it became a homogeneous solutionThe reaction temperature was raised to 200∘C After 30minphosphorus pentoxide (484 g 170mmol) was added and thereaction continued for 12 h at 200∘C with constant stirringusing a mechanical stirrer to obtain a very viscous darkbrown solution The reaction mixture was isolated into thepolymer in distilled water (1000mL) and the precipitate wasthen neutralized with an aqueous solution of NaHCO

3and

rinsed several times with distilled water to remove phosphatesalts It was dried overnight under vacuum The resultingpolymer was ground using a pulverizer (A11 basic IKA)and washed again to remove any residual phosphoric acidFinally the powder was dried at 70∘C in a vacuum oven for atleast 3 days (gt95) 1H NMR (500MHz DMSO-119889

6 ppm)

120575 914 (s 1H) 832 (d 2H) 800 (s 2H) 781 (d 2H) 762 (br3H)

25 Preparation of Composite Membranes 40 g of PBI pow-der and 10 g of PO(OEt)

2-POSS were dissolved in a 166 g of

NN-dimethylacetamide (DMAc) at 80∘C The mixed solu-tion was then spread onto a clean flat glass plate Thethickness of the solution was controlled using an adjustabledoctor blade and the casted solution was left to dry at80∘C for 12 h until no DMAc evaporation was noted Aftercooling to room temperature the obtained filmwas soaked indistilled water and peeled off the substrate The resulting filmwas dried using gel dryer at 60∘C for 1 h and then the filmwas further dried under vacuum for 12 h To convert POSSin phosphonated ester form (PO(OEt)

2-POSS) into that

in phosphonic acid form (PO(OH)2-POSS) the composite

membranes containing PO(OEt)2-POSS were soaked in con-

centrated HBr solution at reflux for 24 hThe composite filmswere thoroughly washed with distilled water several times toneutralize and to remove excess acid and then dried using geldryer at 60∘C for 1 h and then the film was further dried in avacuum oven for 12 hThe PBI and PO(OH

2)-POSS compos-

ite film obtainedwas weighed (1198821) and immersed in 1000mL

of the PA solution with 60wt concentration at 80∘C for 4 hThe PA-doped membrane was taken out of the PA solutionand then blotted with filter paper The membrane wasdried at 70∘C under vacuum for 2 days and weighed again(1198822) The weight difference (119882

2minus 1198821) was assumed to

be the weight of the absorbed PA The PA content of themembrane was then calculated as the weight percent (wt)of PA absorbed in the membrane using

PA content (wt) =(1198822minus1198821)

1198822

times 100 (1)

26 Characterization Matrix-assisted laser desorptionioni-zation time-of-flight mass spectroscopy (MALDI-TOFMS)

Journal of Nanomaterials 3

was recorded on a Voyager-DE STR BiospectrometryWorkstation (Applied Biosystems Inc) set in the positivereflection mode using dithranol as the matrix The MALDI-TOFMS instrument was equipped with a nitrogen laserwhich was emitting at 337 nm with a 3 ns pulse width The1H and 31P nuclear magnetic resonance (NMR) spectra werecollected on Bruker Avance 500 with a proton frequency of500MHz During the experiments deuterated dimethyl sul-foxide was used as the solvent and tetramethylsilane (TMS)was used as the internal standard Fourier transform infrared(FT-IR) spectra of dried membranes and powder sampleswere recorded in the attenuated total reflectance (ATR)mode in the frequency range of 4000sim650 cmminus1 on a Nicolet6700 instrument (Thermo Scientific USA) The spectrumwas recorded as the average of 32 scans with the resolution of8 cmminus1 Each of the samples was put in equal physical contactwith the sampling plate of the spectrometer accessory toavoid differences caused by pressure and penetration depthThe chemical composition and concentration of the materialwere determined by field-emission scanning electronmicroscopy (FE-SEM Carl Zeiss SUPRA 55VP) operated atan accelerating voltage of 15 kV and equipped with energy-dispersive spectroscopy (EDS) capabilities Proton conduc-tivity was measured using a four-point probe Impedancewas measured using a ZAHNER IM-6ex impedance analyzerin potentiostat mode with a perturbation amplitude of 10mVover frequencies of 1Hz to 1MHz Impedance at a controlledhumidity and temperature was measured fromNyquist plotsProton conductivity (120590) was calculated using 120590 = 119889119877119878where 119889 is the distance between the reference and sensingelectrodes and 119878 is the cross-sectional area (thickness timeswidth) of the doped membrane 1 cm times 5 cm membraneswere introduced to the conductivity cell and heated to 160∘Cand held for 30min Measurements were taken as the cellthen cooled to 100∘C in 10∘C steps

3 Results and Discussion

Iso-octylphenyl polyhedral oligomeric silsesquioxane whichwe term POSS here was brominated by a coupling reactionin high yield (ca 93) as reported (abbreviated as Br-POSS Figure 1) [28 29] and characterized by using MALDI-TOFMS 1HNMR and ATR FT-IR MALDI-TOFMS of Br-POSS shows a series of peaks separated by 79 amuof brominecentered at 1610119898119911 (Figure 2) It indicates that an averageof sim7 bromine elements per POSS was incorporated Thisobservation was further supported by 1HNMR spectra (Fig-ure 3) The bromination of POSS results in the broadeningof proton peaks associated with the phenyl rings of POSS(120575 = 81sim63 ppm) while the peaks of isooctyl moiety (120575lt 20 ppm) remain unchanged demonstrating that bromineelements are incorporated into the phenyl rings of POSSThe extent of bromine elements incorporated was calculatedby the comparison of integrals of proton peaks associatedwith the phenyl ring and the isooctyl moieties The averagenumber of the bromine elements per POSS determined by

1H NMR spectra was sim76 close to MALDI-TOFMS-determined value Figure 4 shows ATR FT-IR spectra of Br-POSSThe characteristic absorption band assigned to stretch-ing vibration for aromatic halogen compound appears at1009 cmminus1 The bands at 894 810 and 784 cmminus1 are alsoascribed to bromine-incorporated phenyl rings of POSS

The bromine elements of Br-POSS were substituted withphosphonate ester groups via a Pd(0) catalyzed PndashC cou-pling reaction which was carried out with diethyl phos-phite ((EtO)

2POH) and tetrakis(triphenylphosphine) palla-

dium(0) (Pd(PPh3)4) as a catalyst with trimethylamine (TEA)

[26 30 31] the resulting compound is named PO(OEt)2-

POSS (Figure 1) We observed the peaks of the CH2and CH

3

protons of phosphonate ester groups at 120575 = 380 and 115ppm respectively in 1H NMR spectra as a consequence ofsubstitution of phosphonate esters for bromine elements(Figure 3) [31] Figure 5 presents 31P NMR spectra ofPO(OEt)

2-POSS and diethyl phosphite a monomer used for

the substitution reaction The phosphorous signal associatedwith phosphonate ester units of PO(OEt

2)-POSS is shifted

downfield by sim17 ppm as compared to that of diethyl phos-phite because of the substitution reaction ATR FT-IR spec-tra also provide the information regarding the substitutionreaction (Figure 4) The phosphoryl linkage (P=O) stretch-ing appears at around 1680 cmminus1 The bands at 1048 and1023 cmminus1 are assigned to PminusOminusC absorptions of the estergroup and the band at 949 cmminus1 is attributed to PminusOminusCvibrations [27 31] SEMEDSmeasurement was conducted toverify substitution from bromine elements to phosphonateester groups (Figure 6) No notable peaks of bromine ele-ments are observed A single peak of phosphorus appears atsim21 keV and its intensity is comparable with that of sil-icon at sim19 keV Assuming that the substitution occurredcompletely the number of phosphorous elements per POSSshould be sim7 which is the same with that of silicon ofPOSS Accordingly the atomic weight ratio of phosphorusto silicon for PO(OEt)

2-POSS determined through EDS is

unity supporting the assumption that bromine elements werecompletely substituted by phosphonate ester groups

Following the protocol we and others have exploredpoly[221015840-(m-phenylene)-551015840-(bibenzimidazole)] (PBI) wassynthesized by a condensation polymerization and fabricatedinto a freestanding membrane through a solution castingmethod commonly used which was also applied to the fab-rication of PBIPO(OEt)

2-POSS composite membrane The

phosphonate ester units of PO(OEt)2-POSS were readily

converted into the phosphonic acid ones denoted asPO(OH)

2-POSS by hydrolysis in hydrobromic acid (HBr)

solution as demonstrated in Figure 1 In addition in ATR FT-IR spectra the characteristic bands associated with phospho-nate ester groups of PO(OEt)

2-POSS disappear implying the

substitution of phosphonic acids for phosphonate esters(Figure 4) More importantly PO(OEt)

2-POSS is soluble in

organic solvents such asDMSOandDMAcwhile its solubilitydecreases significantly once the hydrolysis is performedwhich is most likely due to strong hydrogen bond networkformed between phosphonic acid groups [31 32] Due tosuch dissolution issue of PO(OH)

2-POSS in organic solvents

4 Journal of Nanomaterials

O

O

O

O

O

O O

OOO

OOO

OOO

OOO

OO

OOO O

O O

O

O

O

OO

O OO

OO

O

OO

Si

Si Si

Si

SiSi

SiSi

OO

OO O

OO

O

O

OO

OSi

Si Si

Si

SiSi

SiSi

O

O

OO

O OO

OO

O

OO

Si

Si Si

Si

SiSi

SiSi

OO

OO O

OO

O

O

OO

OSi

Si Si

Si

SiSi

SiSi

PP

P

P

P

P

PP

P

P

P

P

PP

HO

HOHO

HOHO

HO

HO

OH

OH

OH

OHOH OH

OH

Br

Br

Br

Br

Br

Br Br

POSS

Br2Fe

CH2Cl2 RT 3h

(EtO)2POHPd(PPh3)4TEA

DMSO 100∘C

Br-POSS

PO(OEt)2-POSS PO(OH)2-POSS

HBr

Reflux

Figure 1 Synthesis of phosphonic acids-functionalized POSS

1400 1500 1600 1700 1800 19001300Mass (mz)

of substituted Br elements = 7

Figure 2 MALDI-TOFMS of Br-POSS

PO(OEt)2-POSS which is soluble in DMAc was mixed with

PBI for freestanding film formation prior to hydrolysis Thedoping of the composite membrane in 60wt PA solutionimparts proton conducting capability of the membrane ThePA content absorbed in the membranes is sim50wt

Figure 7 shows the proton conductivities of the PA-dopedmembranes with temperature ranging from 100 to 150∘Cunder anhydrous conditions Not surprisingly the protonconductivity increases with increasing temperature an obser-vation common to all studies on PA-doped PBI derivativemembranes [5 25 33ndash36] In particular PBIPO(OH)

2-POSS

composite membrane provides greater proton conductivity32 times 10minus3 S cmminus1 than PBI membrane (28 times 10minus3 S cmminus1) at

Br-POSS

POSS

8 6 4 2 010Chemical shift (ppm)

OO

O

Si

P

PO(OEt)2-POSS

Figure 3 1HNMR spectra of POSS Br-POSS and PO(OEt)2-POSS

a given temperature The conductivity against temperatureexhibits the Arrhenius behavior (120590 = 120590

0exp(minus119864

119886119877119879) where

1205900is the preexponential factor and 119864

119886is the activation energy

Journal of Nanomaterials 5

10481023

Br-POSS

7848108941009

Tran

smitt

ance

(au

)

POSS

1680

949

PO(OEt)2-POSS

PO(OH)2-POSS

1500 1200 9001800Wavenumber (cmminus1)

Figure 4 ATR FT-IR spectra of POSS Br-POSS PO(OEt)2-POSS

and PO(OH)2-POSS

Diethyl phosphite

PO(OEt)2-POSS

40 30 20 10 050Chemical shift (ppm)

Figure 5 31P NMR spectra of diethyl phosphite and PO(OEt)2-

POSS

for the proton conduction) indicating that proton conduc-tion in the membrane follows a proton-hopping dominantmechanism (Grotthuss-type mechanism) as reported byother reports [33 34 37] We thus speculate that sim7 phos-phonic acid groups of PO(OH)

2-POSS provide a better

pathway for proton conduction as they bridge the apparentgap between PAs (andor PA and PBI) via the hoppingmechanism

4 Conclusions

In summary we succeeded in functionalizing POSS with sim7phosphonic acid groups Following brominationsim7 bromineelements of POSS were substituted with phosphonate estergroups which were further hydrolyzed into phosphonic acidgroups in hydrobromic acid solution The solubility of thePOSS significantly decreased after the hydrolysis whichmight be due to hydrogen bond network formed betweenphosphonic acids The functionalized PO(OH)

2-POSS was

hybridized with PBI and the composite was fabricated intofreestanding membrane followed by doping in PA solution

Cou

nts (

au)

C-K120572

Si-K120572 P-K120572

O-K120572 Pd-L120572

2 4 6 8 100X-ray energy (keV)

Figure 6 SEMEDS spectroscopy of PO(OEt)2-POSS

PBI

PBIPO(OH)2-POSS

minus25

minus20

minus15

minus10

minus05

00

05

ln(120590

T) (

KSmiddotcm

minus1 )

25 26 27241000T (Kminus1)

Figure 7 Proton conductivities of PA-doped PBI and PBIPO(OH)

2-POSS membranes with temperature ranging from 100 to

150∘C under anhydrous conditions PA content of the membranes isca 50wt

The PA-doped composite membrane retains proton conduc-tivity greater than that of PBI membrane at high temperatureover 100∘C and low humidity conditions We conclude thatphosphonic acids-functionalized POSS as a filler providesconsiderable increase in proton conducting capability ofpolymer electrolyte operating at high temperature

Competing Interests

The author declares that there are no competing interestsregarding the publication of this paper

References

[1] J S Wainright J-T Wang D Weng R F Savinell and M LittldquoAcid-doped polybenzimidazoles a new polymer electrolyterdquoJournal of the Electrochemical Society vol 142 no 7 pp L121ndashL123 1995

6 Journal of Nanomaterials

[2] J Weber K-D Kreuer J Maier and A Thomas ldquoProtonconductivity enhancement by nanostructural control of po-ly(benzimidazole)-phosphoric acid adductsrdquo AdvancedMateri-als vol 20 no 13 pp 2595ndash2598 2008

[3] Q Li R He J O Jensen and N J Bjerrum ldquoPBI-based poly-mer membranes for high temperature fuel cellsmdashpreparationcharacterization and fuel cell demonstrationrdquo Fuel Cells vol 4no 3 pp 147ndash159 2004

[4] L Xiao H Zhang E Scanlon et al ldquoHigh-temperaturepolybenzimidazole fuel cell membranes via a sol-gel processrdquoChemistry of Materials vol 17 no 21 pp 5328ndash5333 2005

[5] S-K Kim T-H Kim J-W Jung and J-C Lee ldquoPolyben-zimidazole containing benzimidazole side groups for high-temperature fuel cell applicationsrdquo Polymer vol 50 no 15 pp3495ndash3502 2009

[6] E Quartarone PMustarelli A Carollo S Grandi AMagistrisand C Gerbaldi ldquoPBI composite and nanocomposite mem-branes for PEMFCs the role of the fillerrdquo Fuel Cells vol 9 no3 pp 231ndash236 2009

[7] P Mustarelli A Carollo S Grandi et al ldquoComposite proton-conducting membranes for PEMFCsrdquo Fuel Cells vol 7 no 6pp 441ndash446 2007

[8] J-W Jung S-K Kim and J-C Lee ldquoPreparation of polybenz-imidazolelithium hydrazinium sulfate composite membranesfor high-temperature fuel cell applicationsrdquo MacromolecularChemistry and Physics vol 211 no 12 pp 1322ndash1329 2010

[9] R He Q Li G Xiao and N J Bjerrum ldquoProton conductivityof phosphoric acid doped polybenzimidazole and its compos-ites with inorganic proton conductorsrdquo Journal of MembraneScience vol 226 no 1-2 pp 169ndash184 2003

[10] T-H Kim T-W Lim Y-S Park K Shin and J-C Lee ldquoProton-conducting zirconiumpyrophosphatepoly(25-benzimidazole)composite membranes prepared by a PPA direct castingmethodrdquo Macromolecular Chemistry and Physics vol 208 no21 pp 2293ndash2302 2007

[11] S M J Zaidi ldquoPreparation and characterization of compositemembranes using blends of SPEEKPBI with boron phosphaterdquoElectrochimica Acta vol 50 no 24 pp 4771ndash4777 2005

[12] S-W Kuo and F-C Chang ldquoPOSS related polymer nanocom-positesrdquo Progress in Polymer Science vol 36 no 12 pp 1649ndash1696 2011

[13] D B Cordes P D Lickiss and F Rataboul ldquoRecent develop-ments in the chemistry of cubic polyhedral oligosilsesquiox-anesrdquo Chemical Reviews vol 110 no 4 pp 2081ndash2173 2010

[14] D-G Kim J Shim J H Lee S-J Kwon J-H Baik andJ-C Lee ldquoPreparation of solid-state composite electrolytesbased on organicinorganic hybrid star-shaped polymer andPEG-functionalized POSS for all-solid-state lithium batteryapplicationsrdquo Polymer vol 54 no 21 pp 5812ndash5820 2013

[15] K J Shea and D A Loy ldquoBridged polysilsesquioxanesMolecular-engineered hybrid organic-inorganic materialsrdquoChemistry of Materials vol 13 no 10 pp 3306ndash3319 2001

[16] J D Lichtenhan Y A Otonari and M J Carr ldquoLinear hybridpolymer building blocks methacrylate-functionalized poly-hedral oligomeric silsesquioxane monomers and polymersrdquoMacromolecules vol 28 no 24 pp 8435ndash8437 1995

[17] M Takeda K Kuroiwa M Mitsuishi and J Matsui ldquoSelf-assembly of amphiphilic POSS anchoring a short organic tailwith uniform structurerdquo Chemistry Letters vol 44 no 11 pp1560ndash1562 2015

[18] S-Y Kuwahara K Yamamoto and J-I Kadokawa ldquoSynthesis ofamphiphilic polyhedral oligomeric silsesquioxane having ahydrophobic fluorescent dye group and its formation of fluo-rescent nanoparticles in waterrdquo Chemistry Letters vol 39 no10 pp 1045ndash1047 2010

[19] D D Jiang Q Yao M A McKinney and C A Wilkie ldquoTGAFTIR studies on the thermal degradation of some polymericsulfonic and phosphonic acids and their sodium saltsrdquo PolymerDegradation and Stability vol 63 no 3 pp 423ndash434 1999

[20] M Schuster T Rager A Noda K D Kreuer and J MaierldquoAbout the choice of the protogenic group in PEM separatormaterials for intermediate temperature low humidity opera-tion a critical comparison of sulfonic acid phosphonic acid andimidazole functionalized model compoundsrdquo Fuel Cells vol 5no 3 pp 355ndash365 2005

[21] A Kaltbeitzel S Schauff H Steininger et al ldquoWater sorptionof poly(vinylphosphonic acid) and its influence on protonconductivityrdquo Solid State Ionics vol 178 no 7ndash10 pp 469ndash4742007

[22] B Lafitte and P Jannasch ldquoPolysulfone ionomers functionalizedwith benzoyl(difluoromethylenephosphonic acid) side chainsfor proton-conducting fuel-cell membranesrdquo Journal of PolymerScience Part A Polymer Chemistry vol 45 no 2 pp 269ndash2832007

[23] R Tayouo G David B Ameduri J Roziere and S RoualdesldquoNew fluorinated polymers bearing pendant phosphonic acidgroups Proton conducting membranes for fuel cellrdquo Macro-molecules vol 43 no 12 pp 5269ndash5276 2010

[24] E Labalme G David P Buvat J Bigarre and T BoucheteauldquoNew hybrid membranes based on phosphonic acid function-alized silica particles for PEMFCrdquo Journal of Polymer SciencePart A Polymer Chemistry vol 50 no 7 pp 1308ndash1316 2012

[25] S-K Kim S-W Choi W S Jeon et al ldquoCross-linkedbenzoxazine-benzimidazole copolymer electrolyte membranesfor fuel cells at elevated temperaturerdquo Macromolecules vol 45no 3 pp 1438ndash1446 2012

[26] K Jakoby K V Peinemann and S P Nunes ldquoPalladium-catalyzed phosphonation of polyphenylsulfonerdquoMacromolecu-lar Chemistry and Physics vol 204 no 1 pp 61ndash67 2003

[27] B Lafitte and P Jannasch ldquoPhosphonation of polysulfonesvia lithiation and reaction with chlorophosphonic acid estersrdquoJournal of Polymer Science Part A Polymer Chemistry vol 43no 2 pp 273ndash286 2005

[28] MDGuiver O Kutowy and JWApSimon ldquoFunctional grouppolysulphones by bromination-metalationrdquo Polymer vol 30no 6 pp 1137ndash1142 1989

[29] C M Brick R Tamaki S-G Kim et al ldquoSpherical poly-functional molecules using poly(bromophenylsilsesquioxane)sas nanoconstruction sitesrdquo Macromolecules vol 38 no 11 pp4655ndash4660 2005

[30] M Kalek and J Stawinski ldquoPd(0)-catalyzed phosphorus-carbon bond formation Mechanistic and synthetic studieson the role of the palladium sources and anionic additivesrdquoOrganometallics vol 26 no 24 pp 5840ndash5847 2007

[31] K Miyatake and A S Hay ldquoNew poly(arylene ether)s withpendant phosphonic acid groupsrdquo Journal of Polymer SciencePart A Polymer Chemistry vol 39 no 21 pp 3770ndash3779 2001

[32] J Parvole and P Jannasch ldquoPolysulfones grafted with poly(vin-ylphosphonic acid) for highly proton conducting fuel cellmembranes in the hydrated and nominally dry staterdquo Macro-molecules vol 41 no 11 pp 3893ndash3903 2008

Journal of Nanomaterials 7

[33] R Bouchet and E Siebert ldquoProton conduction in acid dopedpolybenzimidazolerdquo Solid State Ionics vol 118 no 3-4 pp 287ndash299 1999

[34] A Bozkurt W H Meyer and G Wegner ldquoPAAimidazol-based proton conducting polymer electrolytesrdquo Journal of PowerSources vol 123 no 2 pp 126ndash131 2003

[35] S-KKimTKo S-WChoi et al ldquoDurable cross-linked copoly-mer membranes based on poly(benzoxazine) and poly(25-benzimidazole) for use in fuel cells at elevated temperaturesrdquoJournal of Materials Chemistry vol 22 no 15 pp 7194ndash72052012

[36] S-K Kim K-H Kim J O Park et al ldquoHighly durable poly-mer electrolyte membranes at elevated temperature cross-linked copolymer structure consisting of poly(benzoxazine)andpoly(benzimidazole)rdquo Journal of Power Sources vol 226 pp346ndash353 2013

[37] H-S Lee A Roy O Lane and J E McGrath ldquoSynthesisand characterization of poly(arylene ether sulfone)-b-polyben-zimidazole copolymers for high temperature low humidityproton exchange membrane fuel cellsrdquo Polymer vol 49 no 25pp 5387ndash5396 2008

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Journal of Nanomaterials 3

was recorded on a Voyager-DE STR BiospectrometryWorkstation (Applied Biosystems Inc) set in the positivereflection mode using dithranol as the matrix The MALDI-TOFMS instrument was equipped with a nitrogen laserwhich was emitting at 337 nm with a 3 ns pulse width The1H and 31P nuclear magnetic resonance (NMR) spectra werecollected on Bruker Avance 500 with a proton frequency of500MHz During the experiments deuterated dimethyl sul-foxide was used as the solvent and tetramethylsilane (TMS)was used as the internal standard Fourier transform infrared(FT-IR) spectra of dried membranes and powder sampleswere recorded in the attenuated total reflectance (ATR)mode in the frequency range of 4000sim650 cmminus1 on a Nicolet6700 instrument (Thermo Scientific USA) The spectrumwas recorded as the average of 32 scans with the resolution of8 cmminus1 Each of the samples was put in equal physical contactwith the sampling plate of the spectrometer accessory toavoid differences caused by pressure and penetration depthThe chemical composition and concentration of the materialwere determined by field-emission scanning electronmicroscopy (FE-SEM Carl Zeiss SUPRA 55VP) operated atan accelerating voltage of 15 kV and equipped with energy-dispersive spectroscopy (EDS) capabilities Proton conduc-tivity was measured using a four-point probe Impedancewas measured using a ZAHNER IM-6ex impedance analyzerin potentiostat mode with a perturbation amplitude of 10mVover frequencies of 1Hz to 1MHz Impedance at a controlledhumidity and temperature was measured fromNyquist plotsProton conductivity (120590) was calculated using 120590 = 119889119877119878where 119889 is the distance between the reference and sensingelectrodes and 119878 is the cross-sectional area (thickness timeswidth) of the doped membrane 1 cm times 5 cm membraneswere introduced to the conductivity cell and heated to 160∘Cand held for 30min Measurements were taken as the cellthen cooled to 100∘C in 10∘C steps

3 Results and Discussion

Iso-octylphenyl polyhedral oligomeric silsesquioxane whichwe term POSS here was brominated by a coupling reactionin high yield (ca 93) as reported (abbreviated as Br-POSS Figure 1) [28 29] and characterized by using MALDI-TOFMS 1HNMR and ATR FT-IR MALDI-TOFMS of Br-POSS shows a series of peaks separated by 79 amuof brominecentered at 1610119898119911 (Figure 2) It indicates that an averageof sim7 bromine elements per POSS was incorporated Thisobservation was further supported by 1HNMR spectra (Fig-ure 3) The bromination of POSS results in the broadeningof proton peaks associated with the phenyl rings of POSS(120575 = 81sim63 ppm) while the peaks of isooctyl moiety (120575lt 20 ppm) remain unchanged demonstrating that bromineelements are incorporated into the phenyl rings of POSSThe extent of bromine elements incorporated was calculatedby the comparison of integrals of proton peaks associatedwith the phenyl ring and the isooctyl moieties The averagenumber of the bromine elements per POSS determined by

1H NMR spectra was sim76 close to MALDI-TOFMS-determined value Figure 4 shows ATR FT-IR spectra of Br-POSSThe characteristic absorption band assigned to stretch-ing vibration for aromatic halogen compound appears at1009 cmminus1 The bands at 894 810 and 784 cmminus1 are alsoascribed to bromine-incorporated phenyl rings of POSS

The bromine elements of Br-POSS were substituted withphosphonate ester groups via a Pd(0) catalyzed PndashC cou-pling reaction which was carried out with diethyl phos-phite ((EtO)

2POH) and tetrakis(triphenylphosphine) palla-

dium(0) (Pd(PPh3)4) as a catalyst with trimethylamine (TEA)

[26 30 31] the resulting compound is named PO(OEt)2-

POSS (Figure 1) We observed the peaks of the CH2and CH

3

protons of phosphonate ester groups at 120575 = 380 and 115ppm respectively in 1H NMR spectra as a consequence ofsubstitution of phosphonate esters for bromine elements(Figure 3) [31] Figure 5 presents 31P NMR spectra ofPO(OEt)

2-POSS and diethyl phosphite a monomer used for

the substitution reaction The phosphorous signal associatedwith phosphonate ester units of PO(OEt

2)-POSS is shifted

downfield by sim17 ppm as compared to that of diethyl phos-phite because of the substitution reaction ATR FT-IR spec-tra also provide the information regarding the substitutionreaction (Figure 4) The phosphoryl linkage (P=O) stretch-ing appears at around 1680 cmminus1 The bands at 1048 and1023 cmminus1 are assigned to PminusOminusC absorptions of the estergroup and the band at 949 cmminus1 is attributed to PminusOminusCvibrations [27 31] SEMEDSmeasurement was conducted toverify substitution from bromine elements to phosphonateester groups (Figure 6) No notable peaks of bromine ele-ments are observed A single peak of phosphorus appears atsim21 keV and its intensity is comparable with that of sil-icon at sim19 keV Assuming that the substitution occurredcompletely the number of phosphorous elements per POSSshould be sim7 which is the same with that of silicon ofPOSS Accordingly the atomic weight ratio of phosphorusto silicon for PO(OEt)

2-POSS determined through EDS is

unity supporting the assumption that bromine elements werecompletely substituted by phosphonate ester groups

Following the protocol we and others have exploredpoly[221015840-(m-phenylene)-551015840-(bibenzimidazole)] (PBI) wassynthesized by a condensation polymerization and fabricatedinto a freestanding membrane through a solution castingmethod commonly used which was also applied to the fab-rication of PBIPO(OEt)

2-POSS composite membrane The

phosphonate ester units of PO(OEt)2-POSS were readily

converted into the phosphonic acid ones denoted asPO(OH)

2-POSS by hydrolysis in hydrobromic acid (HBr)

solution as demonstrated in Figure 1 In addition in ATR FT-IR spectra the characteristic bands associated with phospho-nate ester groups of PO(OEt)

2-POSS disappear implying the

substitution of phosphonic acids for phosphonate esters(Figure 4) More importantly PO(OEt)

2-POSS is soluble in

organic solvents such asDMSOandDMAcwhile its solubilitydecreases significantly once the hydrolysis is performedwhich is most likely due to strong hydrogen bond networkformed between phosphonic acid groups [31 32] Due tosuch dissolution issue of PO(OH)

2-POSS in organic solvents

4 Journal of Nanomaterials

O

O

O

O

O

O O

OOO

OOO

OOO

OOO

OO

OOO O

O O

O

O

O

OO

O OO

OO

O

OO

Si

Si Si

Si

SiSi

SiSi

OO

OO O

OO

O

O

OO

OSi

Si Si

Si

SiSi

SiSi

O

O

OO

O OO

OO

O

OO

Si

Si Si

Si

SiSi

SiSi

OO

OO O

OO

O

O

OO

OSi

Si Si

Si

SiSi

SiSi

PP

P

P

P

P

PP

P

P

P

P

PP

HO

HOHO

HOHO

HO

HO

OH

OH

OH

OHOH OH

OH

Br

Br

Br

Br

Br

Br Br

POSS

Br2Fe

CH2Cl2 RT 3h

(EtO)2POHPd(PPh3)4TEA

DMSO 100∘C

Br-POSS

PO(OEt)2-POSS PO(OH)2-POSS

HBr

Reflux

Figure 1 Synthesis of phosphonic acids-functionalized POSS

1400 1500 1600 1700 1800 19001300Mass (mz)

of substituted Br elements = 7

Figure 2 MALDI-TOFMS of Br-POSS

PO(OEt)2-POSS which is soluble in DMAc was mixed with

PBI for freestanding film formation prior to hydrolysis Thedoping of the composite membrane in 60wt PA solutionimparts proton conducting capability of the membrane ThePA content absorbed in the membranes is sim50wt

Figure 7 shows the proton conductivities of the PA-dopedmembranes with temperature ranging from 100 to 150∘Cunder anhydrous conditions Not surprisingly the protonconductivity increases with increasing temperature an obser-vation common to all studies on PA-doped PBI derivativemembranes [5 25 33ndash36] In particular PBIPO(OH)

2-POSS

composite membrane provides greater proton conductivity32 times 10minus3 S cmminus1 than PBI membrane (28 times 10minus3 S cmminus1) at

Br-POSS

POSS

8 6 4 2 010Chemical shift (ppm)

OO

O

Si

P

PO(OEt)2-POSS

Figure 3 1HNMR spectra of POSS Br-POSS and PO(OEt)2-POSS

a given temperature The conductivity against temperatureexhibits the Arrhenius behavior (120590 = 120590

0exp(minus119864

119886119877119879) where

1205900is the preexponential factor and 119864

119886is the activation energy

Journal of Nanomaterials 5

10481023

Br-POSS

7848108941009

Tran

smitt

ance

(au

)

POSS

1680

949

PO(OEt)2-POSS

PO(OH)2-POSS

1500 1200 9001800Wavenumber (cmminus1)

Figure 4 ATR FT-IR spectra of POSS Br-POSS PO(OEt)2-POSS

and PO(OH)2-POSS

Diethyl phosphite

PO(OEt)2-POSS

40 30 20 10 050Chemical shift (ppm)

Figure 5 31P NMR spectra of diethyl phosphite and PO(OEt)2-

POSS

for the proton conduction) indicating that proton conduc-tion in the membrane follows a proton-hopping dominantmechanism (Grotthuss-type mechanism) as reported byother reports [33 34 37] We thus speculate that sim7 phos-phonic acid groups of PO(OH)

2-POSS provide a better

pathway for proton conduction as they bridge the apparentgap between PAs (andor PA and PBI) via the hoppingmechanism

4 Conclusions

In summary we succeeded in functionalizing POSS with sim7phosphonic acid groups Following brominationsim7 bromineelements of POSS were substituted with phosphonate estergroups which were further hydrolyzed into phosphonic acidgroups in hydrobromic acid solution The solubility of thePOSS significantly decreased after the hydrolysis whichmight be due to hydrogen bond network formed betweenphosphonic acids The functionalized PO(OH)

2-POSS was

hybridized with PBI and the composite was fabricated intofreestanding membrane followed by doping in PA solution

Cou

nts (

au)

C-K120572

Si-K120572 P-K120572

O-K120572 Pd-L120572

2 4 6 8 100X-ray energy (keV)

Figure 6 SEMEDS spectroscopy of PO(OEt)2-POSS

PBI

PBIPO(OH)2-POSS

minus25

minus20

minus15

minus10

minus05

00

05

ln(120590

T) (

KSmiddotcm

minus1 )

25 26 27241000T (Kminus1)

Figure 7 Proton conductivities of PA-doped PBI and PBIPO(OH)

2-POSS membranes with temperature ranging from 100 to

150∘C under anhydrous conditions PA content of the membranes isca 50wt

The PA-doped composite membrane retains proton conduc-tivity greater than that of PBI membrane at high temperatureover 100∘C and low humidity conditions We conclude thatphosphonic acids-functionalized POSS as a filler providesconsiderable increase in proton conducting capability ofpolymer electrolyte operating at high temperature

Competing Interests

The author declares that there are no competing interestsregarding the publication of this paper

References

[1] J S Wainright J-T Wang D Weng R F Savinell and M LittldquoAcid-doped polybenzimidazoles a new polymer electrolyterdquoJournal of the Electrochemical Society vol 142 no 7 pp L121ndashL123 1995

6 Journal of Nanomaterials

[2] J Weber K-D Kreuer J Maier and A Thomas ldquoProtonconductivity enhancement by nanostructural control of po-ly(benzimidazole)-phosphoric acid adductsrdquo AdvancedMateri-als vol 20 no 13 pp 2595ndash2598 2008

[3] Q Li R He J O Jensen and N J Bjerrum ldquoPBI-based poly-mer membranes for high temperature fuel cellsmdashpreparationcharacterization and fuel cell demonstrationrdquo Fuel Cells vol 4no 3 pp 147ndash159 2004

[4] L Xiao H Zhang E Scanlon et al ldquoHigh-temperaturepolybenzimidazole fuel cell membranes via a sol-gel processrdquoChemistry of Materials vol 17 no 21 pp 5328ndash5333 2005

[5] S-K Kim T-H Kim J-W Jung and J-C Lee ldquoPolyben-zimidazole containing benzimidazole side groups for high-temperature fuel cell applicationsrdquo Polymer vol 50 no 15 pp3495ndash3502 2009

[6] E Quartarone PMustarelli A Carollo S Grandi AMagistrisand C Gerbaldi ldquoPBI composite and nanocomposite mem-branes for PEMFCs the role of the fillerrdquo Fuel Cells vol 9 no3 pp 231ndash236 2009

[7] P Mustarelli A Carollo S Grandi et al ldquoComposite proton-conducting membranes for PEMFCsrdquo Fuel Cells vol 7 no 6pp 441ndash446 2007

[8] J-W Jung S-K Kim and J-C Lee ldquoPreparation of polybenz-imidazolelithium hydrazinium sulfate composite membranesfor high-temperature fuel cell applicationsrdquo MacromolecularChemistry and Physics vol 211 no 12 pp 1322ndash1329 2010

[9] R He Q Li G Xiao and N J Bjerrum ldquoProton conductivityof phosphoric acid doped polybenzimidazole and its compos-ites with inorganic proton conductorsrdquo Journal of MembraneScience vol 226 no 1-2 pp 169ndash184 2003

[10] T-H Kim T-W Lim Y-S Park K Shin and J-C Lee ldquoProton-conducting zirconiumpyrophosphatepoly(25-benzimidazole)composite membranes prepared by a PPA direct castingmethodrdquo Macromolecular Chemistry and Physics vol 208 no21 pp 2293ndash2302 2007

[11] S M J Zaidi ldquoPreparation and characterization of compositemembranes using blends of SPEEKPBI with boron phosphaterdquoElectrochimica Acta vol 50 no 24 pp 4771ndash4777 2005

[12] S-W Kuo and F-C Chang ldquoPOSS related polymer nanocom-positesrdquo Progress in Polymer Science vol 36 no 12 pp 1649ndash1696 2011

[13] D B Cordes P D Lickiss and F Rataboul ldquoRecent develop-ments in the chemistry of cubic polyhedral oligosilsesquiox-anesrdquo Chemical Reviews vol 110 no 4 pp 2081ndash2173 2010

[14] D-G Kim J Shim J H Lee S-J Kwon J-H Baik andJ-C Lee ldquoPreparation of solid-state composite electrolytesbased on organicinorganic hybrid star-shaped polymer andPEG-functionalized POSS for all-solid-state lithium batteryapplicationsrdquo Polymer vol 54 no 21 pp 5812ndash5820 2013

[15] K J Shea and D A Loy ldquoBridged polysilsesquioxanesMolecular-engineered hybrid organic-inorganic materialsrdquoChemistry of Materials vol 13 no 10 pp 3306ndash3319 2001

[16] J D Lichtenhan Y A Otonari and M J Carr ldquoLinear hybridpolymer building blocks methacrylate-functionalized poly-hedral oligomeric silsesquioxane monomers and polymersrdquoMacromolecules vol 28 no 24 pp 8435ndash8437 1995

[17] M Takeda K Kuroiwa M Mitsuishi and J Matsui ldquoSelf-assembly of amphiphilic POSS anchoring a short organic tailwith uniform structurerdquo Chemistry Letters vol 44 no 11 pp1560ndash1562 2015

[18] S-Y Kuwahara K Yamamoto and J-I Kadokawa ldquoSynthesis ofamphiphilic polyhedral oligomeric silsesquioxane having ahydrophobic fluorescent dye group and its formation of fluo-rescent nanoparticles in waterrdquo Chemistry Letters vol 39 no10 pp 1045ndash1047 2010

[19] D D Jiang Q Yao M A McKinney and C A Wilkie ldquoTGAFTIR studies on the thermal degradation of some polymericsulfonic and phosphonic acids and their sodium saltsrdquo PolymerDegradation and Stability vol 63 no 3 pp 423ndash434 1999

[20] M Schuster T Rager A Noda K D Kreuer and J MaierldquoAbout the choice of the protogenic group in PEM separatormaterials for intermediate temperature low humidity opera-tion a critical comparison of sulfonic acid phosphonic acid andimidazole functionalized model compoundsrdquo Fuel Cells vol 5no 3 pp 355ndash365 2005

[21] A Kaltbeitzel S Schauff H Steininger et al ldquoWater sorptionof poly(vinylphosphonic acid) and its influence on protonconductivityrdquo Solid State Ionics vol 178 no 7ndash10 pp 469ndash4742007

[22] B Lafitte and P Jannasch ldquoPolysulfone ionomers functionalizedwith benzoyl(difluoromethylenephosphonic acid) side chainsfor proton-conducting fuel-cell membranesrdquo Journal of PolymerScience Part A Polymer Chemistry vol 45 no 2 pp 269ndash2832007

[23] R Tayouo G David B Ameduri J Roziere and S RoualdesldquoNew fluorinated polymers bearing pendant phosphonic acidgroups Proton conducting membranes for fuel cellrdquo Macro-molecules vol 43 no 12 pp 5269ndash5276 2010

[24] E Labalme G David P Buvat J Bigarre and T BoucheteauldquoNew hybrid membranes based on phosphonic acid function-alized silica particles for PEMFCrdquo Journal of Polymer SciencePart A Polymer Chemistry vol 50 no 7 pp 1308ndash1316 2012

[25] S-K Kim S-W Choi W S Jeon et al ldquoCross-linkedbenzoxazine-benzimidazole copolymer electrolyte membranesfor fuel cells at elevated temperaturerdquo Macromolecules vol 45no 3 pp 1438ndash1446 2012

[26] K Jakoby K V Peinemann and S P Nunes ldquoPalladium-catalyzed phosphonation of polyphenylsulfonerdquoMacromolecu-lar Chemistry and Physics vol 204 no 1 pp 61ndash67 2003

[27] B Lafitte and P Jannasch ldquoPhosphonation of polysulfonesvia lithiation and reaction with chlorophosphonic acid estersrdquoJournal of Polymer Science Part A Polymer Chemistry vol 43no 2 pp 273ndash286 2005

[28] MDGuiver O Kutowy and JWApSimon ldquoFunctional grouppolysulphones by bromination-metalationrdquo Polymer vol 30no 6 pp 1137ndash1142 1989

[29] C M Brick R Tamaki S-G Kim et al ldquoSpherical poly-functional molecules using poly(bromophenylsilsesquioxane)sas nanoconstruction sitesrdquo Macromolecules vol 38 no 11 pp4655ndash4660 2005

[30] M Kalek and J Stawinski ldquoPd(0)-catalyzed phosphorus-carbon bond formation Mechanistic and synthetic studieson the role of the palladium sources and anionic additivesrdquoOrganometallics vol 26 no 24 pp 5840ndash5847 2007

[31] K Miyatake and A S Hay ldquoNew poly(arylene ether)s withpendant phosphonic acid groupsrdquo Journal of Polymer SciencePart A Polymer Chemistry vol 39 no 21 pp 3770ndash3779 2001

[32] J Parvole and P Jannasch ldquoPolysulfones grafted with poly(vin-ylphosphonic acid) for highly proton conducting fuel cellmembranes in the hydrated and nominally dry staterdquo Macro-molecules vol 41 no 11 pp 3893ndash3903 2008

Journal of Nanomaterials 7

[33] R Bouchet and E Siebert ldquoProton conduction in acid dopedpolybenzimidazolerdquo Solid State Ionics vol 118 no 3-4 pp 287ndash299 1999

[34] A Bozkurt W H Meyer and G Wegner ldquoPAAimidazol-based proton conducting polymer electrolytesrdquo Journal of PowerSources vol 123 no 2 pp 126ndash131 2003

[35] S-KKimTKo S-WChoi et al ldquoDurable cross-linked copoly-mer membranes based on poly(benzoxazine) and poly(25-benzimidazole) for use in fuel cells at elevated temperaturesrdquoJournal of Materials Chemistry vol 22 no 15 pp 7194ndash72052012

[36] S-K Kim K-H Kim J O Park et al ldquoHighly durable poly-mer electrolyte membranes at elevated temperature cross-linked copolymer structure consisting of poly(benzoxazine)andpoly(benzimidazole)rdquo Journal of Power Sources vol 226 pp346ndash353 2013

[37] H-S Lee A Roy O Lane and J E McGrath ldquoSynthesisand characterization of poly(arylene ether sulfone)-b-polyben-zimidazole copolymers for high temperature low humidityproton exchange membrane fuel cellsrdquo Polymer vol 49 no 25pp 5387ndash5396 2008

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

4 Journal of Nanomaterials

O

O

O

O

O

O O

OOO

OOO

OOO

OOO

OO

OOO O

O O

O

O

O

OO

O OO

OO

O

OO

Si

Si Si

Si

SiSi

SiSi

OO

OO O

OO

O

O

OO

OSi

Si Si

Si

SiSi

SiSi

O

O

OO

O OO

OO

O

OO

Si

Si Si

Si

SiSi

SiSi

OO

OO O

OO

O

O

OO

OSi

Si Si

Si

SiSi

SiSi

PP

P

P

P

P

PP

P

P

P

P

PP

HO

HOHO

HOHO

HO

HO

OH

OH

OH

OHOH OH

OH

Br

Br

Br

Br

Br

Br Br

POSS

Br2Fe

CH2Cl2 RT 3h

(EtO)2POHPd(PPh3)4TEA

DMSO 100∘C

Br-POSS

PO(OEt)2-POSS PO(OH)2-POSS

HBr

Reflux

Figure 1 Synthesis of phosphonic acids-functionalized POSS

1400 1500 1600 1700 1800 19001300Mass (mz)

of substituted Br elements = 7

Figure 2 MALDI-TOFMS of Br-POSS

PO(OEt)2-POSS which is soluble in DMAc was mixed with

PBI for freestanding film formation prior to hydrolysis Thedoping of the composite membrane in 60wt PA solutionimparts proton conducting capability of the membrane ThePA content absorbed in the membranes is sim50wt

Figure 7 shows the proton conductivities of the PA-dopedmembranes with temperature ranging from 100 to 150∘Cunder anhydrous conditions Not surprisingly the protonconductivity increases with increasing temperature an obser-vation common to all studies on PA-doped PBI derivativemembranes [5 25 33ndash36] In particular PBIPO(OH)

2-POSS

composite membrane provides greater proton conductivity32 times 10minus3 S cmminus1 than PBI membrane (28 times 10minus3 S cmminus1) at

Br-POSS

POSS

8 6 4 2 010Chemical shift (ppm)

OO

O

Si

P

PO(OEt)2-POSS

Figure 3 1HNMR spectra of POSS Br-POSS and PO(OEt)2-POSS

a given temperature The conductivity against temperatureexhibits the Arrhenius behavior (120590 = 120590

0exp(minus119864

119886119877119879) where

1205900is the preexponential factor and 119864

119886is the activation energy

Journal of Nanomaterials 5

10481023

Br-POSS

7848108941009

Tran

smitt

ance

(au

)

POSS

1680

949

PO(OEt)2-POSS

PO(OH)2-POSS

1500 1200 9001800Wavenumber (cmminus1)

Figure 4 ATR FT-IR spectra of POSS Br-POSS PO(OEt)2-POSS

and PO(OH)2-POSS

Diethyl phosphite

PO(OEt)2-POSS

40 30 20 10 050Chemical shift (ppm)

Figure 5 31P NMR spectra of diethyl phosphite and PO(OEt)2-

POSS

for the proton conduction) indicating that proton conduc-tion in the membrane follows a proton-hopping dominantmechanism (Grotthuss-type mechanism) as reported byother reports [33 34 37] We thus speculate that sim7 phos-phonic acid groups of PO(OH)

2-POSS provide a better

pathway for proton conduction as they bridge the apparentgap between PAs (andor PA and PBI) via the hoppingmechanism

4 Conclusions

In summary we succeeded in functionalizing POSS with sim7phosphonic acid groups Following brominationsim7 bromineelements of POSS were substituted with phosphonate estergroups which were further hydrolyzed into phosphonic acidgroups in hydrobromic acid solution The solubility of thePOSS significantly decreased after the hydrolysis whichmight be due to hydrogen bond network formed betweenphosphonic acids The functionalized PO(OH)

2-POSS was

hybridized with PBI and the composite was fabricated intofreestanding membrane followed by doping in PA solution

Cou

nts (

au)

C-K120572

Si-K120572 P-K120572

O-K120572 Pd-L120572

2 4 6 8 100X-ray energy (keV)

Figure 6 SEMEDS spectroscopy of PO(OEt)2-POSS

PBI

PBIPO(OH)2-POSS

minus25

minus20

minus15

minus10

minus05

00

05

ln(120590

T) (

KSmiddotcm

minus1 )

25 26 27241000T (Kminus1)

Figure 7 Proton conductivities of PA-doped PBI and PBIPO(OH)

2-POSS membranes with temperature ranging from 100 to

150∘C under anhydrous conditions PA content of the membranes isca 50wt

The PA-doped composite membrane retains proton conduc-tivity greater than that of PBI membrane at high temperatureover 100∘C and low humidity conditions We conclude thatphosphonic acids-functionalized POSS as a filler providesconsiderable increase in proton conducting capability ofpolymer electrolyte operating at high temperature

Competing Interests

The author declares that there are no competing interestsregarding the publication of this paper

References

[1] J S Wainright J-T Wang D Weng R F Savinell and M LittldquoAcid-doped polybenzimidazoles a new polymer electrolyterdquoJournal of the Electrochemical Society vol 142 no 7 pp L121ndashL123 1995

6 Journal of Nanomaterials

[2] J Weber K-D Kreuer J Maier and A Thomas ldquoProtonconductivity enhancement by nanostructural control of po-ly(benzimidazole)-phosphoric acid adductsrdquo AdvancedMateri-als vol 20 no 13 pp 2595ndash2598 2008

[3] Q Li R He J O Jensen and N J Bjerrum ldquoPBI-based poly-mer membranes for high temperature fuel cellsmdashpreparationcharacterization and fuel cell demonstrationrdquo Fuel Cells vol 4no 3 pp 147ndash159 2004

[4] L Xiao H Zhang E Scanlon et al ldquoHigh-temperaturepolybenzimidazole fuel cell membranes via a sol-gel processrdquoChemistry of Materials vol 17 no 21 pp 5328ndash5333 2005

[5] S-K Kim T-H Kim J-W Jung and J-C Lee ldquoPolyben-zimidazole containing benzimidazole side groups for high-temperature fuel cell applicationsrdquo Polymer vol 50 no 15 pp3495ndash3502 2009

[6] E Quartarone PMustarelli A Carollo S Grandi AMagistrisand C Gerbaldi ldquoPBI composite and nanocomposite mem-branes for PEMFCs the role of the fillerrdquo Fuel Cells vol 9 no3 pp 231ndash236 2009

[7] P Mustarelli A Carollo S Grandi et al ldquoComposite proton-conducting membranes for PEMFCsrdquo Fuel Cells vol 7 no 6pp 441ndash446 2007

[8] J-W Jung S-K Kim and J-C Lee ldquoPreparation of polybenz-imidazolelithium hydrazinium sulfate composite membranesfor high-temperature fuel cell applicationsrdquo MacromolecularChemistry and Physics vol 211 no 12 pp 1322ndash1329 2010

[9] R He Q Li G Xiao and N J Bjerrum ldquoProton conductivityof phosphoric acid doped polybenzimidazole and its compos-ites with inorganic proton conductorsrdquo Journal of MembraneScience vol 226 no 1-2 pp 169ndash184 2003

[10] T-H Kim T-W Lim Y-S Park K Shin and J-C Lee ldquoProton-conducting zirconiumpyrophosphatepoly(25-benzimidazole)composite membranes prepared by a PPA direct castingmethodrdquo Macromolecular Chemistry and Physics vol 208 no21 pp 2293ndash2302 2007

[11] S M J Zaidi ldquoPreparation and characterization of compositemembranes using blends of SPEEKPBI with boron phosphaterdquoElectrochimica Acta vol 50 no 24 pp 4771ndash4777 2005

[12] S-W Kuo and F-C Chang ldquoPOSS related polymer nanocom-positesrdquo Progress in Polymer Science vol 36 no 12 pp 1649ndash1696 2011

[13] D B Cordes P D Lickiss and F Rataboul ldquoRecent develop-ments in the chemistry of cubic polyhedral oligosilsesquiox-anesrdquo Chemical Reviews vol 110 no 4 pp 2081ndash2173 2010

[14] D-G Kim J Shim J H Lee S-J Kwon J-H Baik andJ-C Lee ldquoPreparation of solid-state composite electrolytesbased on organicinorganic hybrid star-shaped polymer andPEG-functionalized POSS for all-solid-state lithium batteryapplicationsrdquo Polymer vol 54 no 21 pp 5812ndash5820 2013

[15] K J Shea and D A Loy ldquoBridged polysilsesquioxanesMolecular-engineered hybrid organic-inorganic materialsrdquoChemistry of Materials vol 13 no 10 pp 3306ndash3319 2001

[16] J D Lichtenhan Y A Otonari and M J Carr ldquoLinear hybridpolymer building blocks methacrylate-functionalized poly-hedral oligomeric silsesquioxane monomers and polymersrdquoMacromolecules vol 28 no 24 pp 8435ndash8437 1995

[17] M Takeda K Kuroiwa M Mitsuishi and J Matsui ldquoSelf-assembly of amphiphilic POSS anchoring a short organic tailwith uniform structurerdquo Chemistry Letters vol 44 no 11 pp1560ndash1562 2015

[18] S-Y Kuwahara K Yamamoto and J-I Kadokawa ldquoSynthesis ofamphiphilic polyhedral oligomeric silsesquioxane having ahydrophobic fluorescent dye group and its formation of fluo-rescent nanoparticles in waterrdquo Chemistry Letters vol 39 no10 pp 1045ndash1047 2010

[19] D D Jiang Q Yao M A McKinney and C A Wilkie ldquoTGAFTIR studies on the thermal degradation of some polymericsulfonic and phosphonic acids and their sodium saltsrdquo PolymerDegradation and Stability vol 63 no 3 pp 423ndash434 1999

[20] M Schuster T Rager A Noda K D Kreuer and J MaierldquoAbout the choice of the protogenic group in PEM separatormaterials for intermediate temperature low humidity opera-tion a critical comparison of sulfonic acid phosphonic acid andimidazole functionalized model compoundsrdquo Fuel Cells vol 5no 3 pp 355ndash365 2005

[21] A Kaltbeitzel S Schauff H Steininger et al ldquoWater sorptionof poly(vinylphosphonic acid) and its influence on protonconductivityrdquo Solid State Ionics vol 178 no 7ndash10 pp 469ndash4742007

[22] B Lafitte and P Jannasch ldquoPolysulfone ionomers functionalizedwith benzoyl(difluoromethylenephosphonic acid) side chainsfor proton-conducting fuel-cell membranesrdquo Journal of PolymerScience Part A Polymer Chemistry vol 45 no 2 pp 269ndash2832007

[23] R Tayouo G David B Ameduri J Roziere and S RoualdesldquoNew fluorinated polymers bearing pendant phosphonic acidgroups Proton conducting membranes for fuel cellrdquo Macro-molecules vol 43 no 12 pp 5269ndash5276 2010

[24] E Labalme G David P Buvat J Bigarre and T BoucheteauldquoNew hybrid membranes based on phosphonic acid function-alized silica particles for PEMFCrdquo Journal of Polymer SciencePart A Polymer Chemistry vol 50 no 7 pp 1308ndash1316 2012

[25] S-K Kim S-W Choi W S Jeon et al ldquoCross-linkedbenzoxazine-benzimidazole copolymer electrolyte membranesfor fuel cells at elevated temperaturerdquo Macromolecules vol 45no 3 pp 1438ndash1446 2012

[26] K Jakoby K V Peinemann and S P Nunes ldquoPalladium-catalyzed phosphonation of polyphenylsulfonerdquoMacromolecu-lar Chemistry and Physics vol 204 no 1 pp 61ndash67 2003

[27] B Lafitte and P Jannasch ldquoPhosphonation of polysulfonesvia lithiation and reaction with chlorophosphonic acid estersrdquoJournal of Polymer Science Part A Polymer Chemistry vol 43no 2 pp 273ndash286 2005

[28] MDGuiver O Kutowy and JWApSimon ldquoFunctional grouppolysulphones by bromination-metalationrdquo Polymer vol 30no 6 pp 1137ndash1142 1989

[29] C M Brick R Tamaki S-G Kim et al ldquoSpherical poly-functional molecules using poly(bromophenylsilsesquioxane)sas nanoconstruction sitesrdquo Macromolecules vol 38 no 11 pp4655ndash4660 2005

[30] M Kalek and J Stawinski ldquoPd(0)-catalyzed phosphorus-carbon bond formation Mechanistic and synthetic studieson the role of the palladium sources and anionic additivesrdquoOrganometallics vol 26 no 24 pp 5840ndash5847 2007

[31] K Miyatake and A S Hay ldquoNew poly(arylene ether)s withpendant phosphonic acid groupsrdquo Journal of Polymer SciencePart A Polymer Chemistry vol 39 no 21 pp 3770ndash3779 2001

[32] J Parvole and P Jannasch ldquoPolysulfones grafted with poly(vin-ylphosphonic acid) for highly proton conducting fuel cellmembranes in the hydrated and nominally dry staterdquo Macro-molecules vol 41 no 11 pp 3893ndash3903 2008

Journal of Nanomaterials 7

[33] R Bouchet and E Siebert ldquoProton conduction in acid dopedpolybenzimidazolerdquo Solid State Ionics vol 118 no 3-4 pp 287ndash299 1999

[34] A Bozkurt W H Meyer and G Wegner ldquoPAAimidazol-based proton conducting polymer electrolytesrdquo Journal of PowerSources vol 123 no 2 pp 126ndash131 2003

[35] S-KKimTKo S-WChoi et al ldquoDurable cross-linked copoly-mer membranes based on poly(benzoxazine) and poly(25-benzimidazole) for use in fuel cells at elevated temperaturesrdquoJournal of Materials Chemistry vol 22 no 15 pp 7194ndash72052012

[36] S-K Kim K-H Kim J O Park et al ldquoHighly durable poly-mer electrolyte membranes at elevated temperature cross-linked copolymer structure consisting of poly(benzoxazine)andpoly(benzimidazole)rdquo Journal of Power Sources vol 226 pp346ndash353 2013

[37] H-S Lee A Roy O Lane and J E McGrath ldquoSynthesisand characterization of poly(arylene ether sulfone)-b-polyben-zimidazole copolymers for high temperature low humidityproton exchange membrane fuel cellsrdquo Polymer vol 49 no 25pp 5387ndash5396 2008

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Journal of Nanomaterials 5

10481023

Br-POSS

7848108941009

Tran

smitt

ance

(au

)

POSS

1680

949

PO(OEt)2-POSS

PO(OH)2-POSS

1500 1200 9001800Wavenumber (cmminus1)

Figure 4 ATR FT-IR spectra of POSS Br-POSS PO(OEt)2-POSS

and PO(OH)2-POSS

Diethyl phosphite

PO(OEt)2-POSS

40 30 20 10 050Chemical shift (ppm)

Figure 5 31P NMR spectra of diethyl phosphite and PO(OEt)2-

POSS

for the proton conduction) indicating that proton conduc-tion in the membrane follows a proton-hopping dominantmechanism (Grotthuss-type mechanism) as reported byother reports [33 34 37] We thus speculate that sim7 phos-phonic acid groups of PO(OH)

2-POSS provide a better

pathway for proton conduction as they bridge the apparentgap between PAs (andor PA and PBI) via the hoppingmechanism

4 Conclusions

In summary we succeeded in functionalizing POSS with sim7phosphonic acid groups Following brominationsim7 bromineelements of POSS were substituted with phosphonate estergroups which were further hydrolyzed into phosphonic acidgroups in hydrobromic acid solution The solubility of thePOSS significantly decreased after the hydrolysis whichmight be due to hydrogen bond network formed betweenphosphonic acids The functionalized PO(OH)

2-POSS was

hybridized with PBI and the composite was fabricated intofreestanding membrane followed by doping in PA solution

Cou

nts (

au)

C-K120572

Si-K120572 P-K120572

O-K120572 Pd-L120572

2 4 6 8 100X-ray energy (keV)

Figure 6 SEMEDS spectroscopy of PO(OEt)2-POSS

PBI

PBIPO(OH)2-POSS

minus25

minus20

minus15

minus10

minus05

00

05

ln(120590

T) (

KSmiddotcm

minus1 )

25 26 27241000T (Kminus1)

Figure 7 Proton conductivities of PA-doped PBI and PBIPO(OH)

2-POSS membranes with temperature ranging from 100 to

150∘C under anhydrous conditions PA content of the membranes isca 50wt

The PA-doped composite membrane retains proton conduc-tivity greater than that of PBI membrane at high temperatureover 100∘C and low humidity conditions We conclude thatphosphonic acids-functionalized POSS as a filler providesconsiderable increase in proton conducting capability ofpolymer electrolyte operating at high temperature

Competing Interests

The author declares that there are no competing interestsregarding the publication of this paper

References

[1] J S Wainright J-T Wang D Weng R F Savinell and M LittldquoAcid-doped polybenzimidazoles a new polymer electrolyterdquoJournal of the Electrochemical Society vol 142 no 7 pp L121ndashL123 1995

6 Journal of Nanomaterials

[2] J Weber K-D Kreuer J Maier and A Thomas ldquoProtonconductivity enhancement by nanostructural control of po-ly(benzimidazole)-phosphoric acid adductsrdquo AdvancedMateri-als vol 20 no 13 pp 2595ndash2598 2008

[3] Q Li R He J O Jensen and N J Bjerrum ldquoPBI-based poly-mer membranes for high temperature fuel cellsmdashpreparationcharacterization and fuel cell demonstrationrdquo Fuel Cells vol 4no 3 pp 147ndash159 2004

[4] L Xiao H Zhang E Scanlon et al ldquoHigh-temperaturepolybenzimidazole fuel cell membranes via a sol-gel processrdquoChemistry of Materials vol 17 no 21 pp 5328ndash5333 2005

[5] S-K Kim T-H Kim J-W Jung and J-C Lee ldquoPolyben-zimidazole containing benzimidazole side groups for high-temperature fuel cell applicationsrdquo Polymer vol 50 no 15 pp3495ndash3502 2009

[6] E Quartarone PMustarelli A Carollo S Grandi AMagistrisand C Gerbaldi ldquoPBI composite and nanocomposite mem-branes for PEMFCs the role of the fillerrdquo Fuel Cells vol 9 no3 pp 231ndash236 2009

[7] P Mustarelli A Carollo S Grandi et al ldquoComposite proton-conducting membranes for PEMFCsrdquo Fuel Cells vol 7 no 6pp 441ndash446 2007

[8] J-W Jung S-K Kim and J-C Lee ldquoPreparation of polybenz-imidazolelithium hydrazinium sulfate composite membranesfor high-temperature fuel cell applicationsrdquo MacromolecularChemistry and Physics vol 211 no 12 pp 1322ndash1329 2010

[9] R He Q Li G Xiao and N J Bjerrum ldquoProton conductivityof phosphoric acid doped polybenzimidazole and its compos-ites with inorganic proton conductorsrdquo Journal of MembraneScience vol 226 no 1-2 pp 169ndash184 2003

[10] T-H Kim T-W Lim Y-S Park K Shin and J-C Lee ldquoProton-conducting zirconiumpyrophosphatepoly(25-benzimidazole)composite membranes prepared by a PPA direct castingmethodrdquo Macromolecular Chemistry and Physics vol 208 no21 pp 2293ndash2302 2007

[11] S M J Zaidi ldquoPreparation and characterization of compositemembranes using blends of SPEEKPBI with boron phosphaterdquoElectrochimica Acta vol 50 no 24 pp 4771ndash4777 2005

[12] S-W Kuo and F-C Chang ldquoPOSS related polymer nanocom-positesrdquo Progress in Polymer Science vol 36 no 12 pp 1649ndash1696 2011

[13] D B Cordes P D Lickiss and F Rataboul ldquoRecent develop-ments in the chemistry of cubic polyhedral oligosilsesquiox-anesrdquo Chemical Reviews vol 110 no 4 pp 2081ndash2173 2010

[14] D-G Kim J Shim J H Lee S-J Kwon J-H Baik andJ-C Lee ldquoPreparation of solid-state composite electrolytesbased on organicinorganic hybrid star-shaped polymer andPEG-functionalized POSS for all-solid-state lithium batteryapplicationsrdquo Polymer vol 54 no 21 pp 5812ndash5820 2013

[15] K J Shea and D A Loy ldquoBridged polysilsesquioxanesMolecular-engineered hybrid organic-inorganic materialsrdquoChemistry of Materials vol 13 no 10 pp 3306ndash3319 2001

[16] J D Lichtenhan Y A Otonari and M J Carr ldquoLinear hybridpolymer building blocks methacrylate-functionalized poly-hedral oligomeric silsesquioxane monomers and polymersrdquoMacromolecules vol 28 no 24 pp 8435ndash8437 1995

[17] M Takeda K Kuroiwa M Mitsuishi and J Matsui ldquoSelf-assembly of amphiphilic POSS anchoring a short organic tailwith uniform structurerdquo Chemistry Letters vol 44 no 11 pp1560ndash1562 2015

[18] S-Y Kuwahara K Yamamoto and J-I Kadokawa ldquoSynthesis ofamphiphilic polyhedral oligomeric silsesquioxane having ahydrophobic fluorescent dye group and its formation of fluo-rescent nanoparticles in waterrdquo Chemistry Letters vol 39 no10 pp 1045ndash1047 2010

[19] D D Jiang Q Yao M A McKinney and C A Wilkie ldquoTGAFTIR studies on the thermal degradation of some polymericsulfonic and phosphonic acids and their sodium saltsrdquo PolymerDegradation and Stability vol 63 no 3 pp 423ndash434 1999

[20] M Schuster T Rager A Noda K D Kreuer and J MaierldquoAbout the choice of the protogenic group in PEM separatormaterials for intermediate temperature low humidity opera-tion a critical comparison of sulfonic acid phosphonic acid andimidazole functionalized model compoundsrdquo Fuel Cells vol 5no 3 pp 355ndash365 2005

[21] A Kaltbeitzel S Schauff H Steininger et al ldquoWater sorptionof poly(vinylphosphonic acid) and its influence on protonconductivityrdquo Solid State Ionics vol 178 no 7ndash10 pp 469ndash4742007

[22] B Lafitte and P Jannasch ldquoPolysulfone ionomers functionalizedwith benzoyl(difluoromethylenephosphonic acid) side chainsfor proton-conducting fuel-cell membranesrdquo Journal of PolymerScience Part A Polymer Chemistry vol 45 no 2 pp 269ndash2832007

[23] R Tayouo G David B Ameduri J Roziere and S RoualdesldquoNew fluorinated polymers bearing pendant phosphonic acidgroups Proton conducting membranes for fuel cellrdquo Macro-molecules vol 43 no 12 pp 5269ndash5276 2010

[24] E Labalme G David P Buvat J Bigarre and T BoucheteauldquoNew hybrid membranes based on phosphonic acid function-alized silica particles for PEMFCrdquo Journal of Polymer SciencePart A Polymer Chemistry vol 50 no 7 pp 1308ndash1316 2012

[25] S-K Kim S-W Choi W S Jeon et al ldquoCross-linkedbenzoxazine-benzimidazole copolymer electrolyte membranesfor fuel cells at elevated temperaturerdquo Macromolecules vol 45no 3 pp 1438ndash1446 2012

[26] K Jakoby K V Peinemann and S P Nunes ldquoPalladium-catalyzed phosphonation of polyphenylsulfonerdquoMacromolecu-lar Chemistry and Physics vol 204 no 1 pp 61ndash67 2003

[27] B Lafitte and P Jannasch ldquoPhosphonation of polysulfonesvia lithiation and reaction with chlorophosphonic acid estersrdquoJournal of Polymer Science Part A Polymer Chemistry vol 43no 2 pp 273ndash286 2005

[28] MDGuiver O Kutowy and JWApSimon ldquoFunctional grouppolysulphones by bromination-metalationrdquo Polymer vol 30no 6 pp 1137ndash1142 1989

[29] C M Brick R Tamaki S-G Kim et al ldquoSpherical poly-functional molecules using poly(bromophenylsilsesquioxane)sas nanoconstruction sitesrdquo Macromolecules vol 38 no 11 pp4655ndash4660 2005

[30] M Kalek and J Stawinski ldquoPd(0)-catalyzed phosphorus-carbon bond formation Mechanistic and synthetic studieson the role of the palladium sources and anionic additivesrdquoOrganometallics vol 26 no 24 pp 5840ndash5847 2007

[31] K Miyatake and A S Hay ldquoNew poly(arylene ether)s withpendant phosphonic acid groupsrdquo Journal of Polymer SciencePart A Polymer Chemistry vol 39 no 21 pp 3770ndash3779 2001

[32] J Parvole and P Jannasch ldquoPolysulfones grafted with poly(vin-ylphosphonic acid) for highly proton conducting fuel cellmembranes in the hydrated and nominally dry staterdquo Macro-molecules vol 41 no 11 pp 3893ndash3903 2008

Journal of Nanomaterials 7

[33] R Bouchet and E Siebert ldquoProton conduction in acid dopedpolybenzimidazolerdquo Solid State Ionics vol 118 no 3-4 pp 287ndash299 1999

[34] A Bozkurt W H Meyer and G Wegner ldquoPAAimidazol-based proton conducting polymer electrolytesrdquo Journal of PowerSources vol 123 no 2 pp 126ndash131 2003

[35] S-KKimTKo S-WChoi et al ldquoDurable cross-linked copoly-mer membranes based on poly(benzoxazine) and poly(25-benzimidazole) for use in fuel cells at elevated temperaturesrdquoJournal of Materials Chemistry vol 22 no 15 pp 7194ndash72052012

[36] S-K Kim K-H Kim J O Park et al ldquoHighly durable poly-mer electrolyte membranes at elevated temperature cross-linked copolymer structure consisting of poly(benzoxazine)andpoly(benzimidazole)rdquo Journal of Power Sources vol 226 pp346ndash353 2013

[37] H-S Lee A Roy O Lane and J E McGrath ldquoSynthesisand characterization of poly(arylene ether sulfone)-b-polyben-zimidazole copolymers for high temperature low humidityproton exchange membrane fuel cellsrdquo Polymer vol 49 no 25pp 5387ndash5396 2008

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

6 Journal of Nanomaterials

[2] J Weber K-D Kreuer J Maier and A Thomas ldquoProtonconductivity enhancement by nanostructural control of po-ly(benzimidazole)-phosphoric acid adductsrdquo AdvancedMateri-als vol 20 no 13 pp 2595ndash2598 2008

[3] Q Li R He J O Jensen and N J Bjerrum ldquoPBI-based poly-mer membranes for high temperature fuel cellsmdashpreparationcharacterization and fuel cell demonstrationrdquo Fuel Cells vol 4no 3 pp 147ndash159 2004

[4] L Xiao H Zhang E Scanlon et al ldquoHigh-temperaturepolybenzimidazole fuel cell membranes via a sol-gel processrdquoChemistry of Materials vol 17 no 21 pp 5328ndash5333 2005

[5] S-K Kim T-H Kim J-W Jung and J-C Lee ldquoPolyben-zimidazole containing benzimidazole side groups for high-temperature fuel cell applicationsrdquo Polymer vol 50 no 15 pp3495ndash3502 2009

[6] E Quartarone PMustarelli A Carollo S Grandi AMagistrisand C Gerbaldi ldquoPBI composite and nanocomposite mem-branes for PEMFCs the role of the fillerrdquo Fuel Cells vol 9 no3 pp 231ndash236 2009

[7] P Mustarelli A Carollo S Grandi et al ldquoComposite proton-conducting membranes for PEMFCsrdquo Fuel Cells vol 7 no 6pp 441ndash446 2007

[8] J-W Jung S-K Kim and J-C Lee ldquoPreparation of polybenz-imidazolelithium hydrazinium sulfate composite membranesfor high-temperature fuel cell applicationsrdquo MacromolecularChemistry and Physics vol 211 no 12 pp 1322ndash1329 2010

[9] R He Q Li G Xiao and N J Bjerrum ldquoProton conductivityof phosphoric acid doped polybenzimidazole and its compos-ites with inorganic proton conductorsrdquo Journal of MembraneScience vol 226 no 1-2 pp 169ndash184 2003

[10] T-H Kim T-W Lim Y-S Park K Shin and J-C Lee ldquoProton-conducting zirconiumpyrophosphatepoly(25-benzimidazole)composite membranes prepared by a PPA direct castingmethodrdquo Macromolecular Chemistry and Physics vol 208 no21 pp 2293ndash2302 2007

[11] S M J Zaidi ldquoPreparation and characterization of compositemembranes using blends of SPEEKPBI with boron phosphaterdquoElectrochimica Acta vol 50 no 24 pp 4771ndash4777 2005

[12] S-W Kuo and F-C Chang ldquoPOSS related polymer nanocom-positesrdquo Progress in Polymer Science vol 36 no 12 pp 1649ndash1696 2011

[13] D B Cordes P D Lickiss and F Rataboul ldquoRecent develop-ments in the chemistry of cubic polyhedral oligosilsesquiox-anesrdquo Chemical Reviews vol 110 no 4 pp 2081ndash2173 2010

[14] D-G Kim J Shim J H Lee S-J Kwon J-H Baik andJ-C Lee ldquoPreparation of solid-state composite electrolytesbased on organicinorganic hybrid star-shaped polymer andPEG-functionalized POSS for all-solid-state lithium batteryapplicationsrdquo Polymer vol 54 no 21 pp 5812ndash5820 2013

[15] K J Shea and D A Loy ldquoBridged polysilsesquioxanesMolecular-engineered hybrid organic-inorganic materialsrdquoChemistry of Materials vol 13 no 10 pp 3306ndash3319 2001

[16] J D Lichtenhan Y A Otonari and M J Carr ldquoLinear hybridpolymer building blocks methacrylate-functionalized poly-hedral oligomeric silsesquioxane monomers and polymersrdquoMacromolecules vol 28 no 24 pp 8435ndash8437 1995

[17] M Takeda K Kuroiwa M Mitsuishi and J Matsui ldquoSelf-assembly of amphiphilic POSS anchoring a short organic tailwith uniform structurerdquo Chemistry Letters vol 44 no 11 pp1560ndash1562 2015

[18] S-Y Kuwahara K Yamamoto and J-I Kadokawa ldquoSynthesis ofamphiphilic polyhedral oligomeric silsesquioxane having ahydrophobic fluorescent dye group and its formation of fluo-rescent nanoparticles in waterrdquo Chemistry Letters vol 39 no10 pp 1045ndash1047 2010

[19] D D Jiang Q Yao M A McKinney and C A Wilkie ldquoTGAFTIR studies on the thermal degradation of some polymericsulfonic and phosphonic acids and their sodium saltsrdquo PolymerDegradation and Stability vol 63 no 3 pp 423ndash434 1999

[20] M Schuster T Rager A Noda K D Kreuer and J MaierldquoAbout the choice of the protogenic group in PEM separatormaterials for intermediate temperature low humidity opera-tion a critical comparison of sulfonic acid phosphonic acid andimidazole functionalized model compoundsrdquo Fuel Cells vol 5no 3 pp 355ndash365 2005

[21] A Kaltbeitzel S Schauff H Steininger et al ldquoWater sorptionof poly(vinylphosphonic acid) and its influence on protonconductivityrdquo Solid State Ionics vol 178 no 7ndash10 pp 469ndash4742007

[22] B Lafitte and P Jannasch ldquoPolysulfone ionomers functionalizedwith benzoyl(difluoromethylenephosphonic acid) side chainsfor proton-conducting fuel-cell membranesrdquo Journal of PolymerScience Part A Polymer Chemistry vol 45 no 2 pp 269ndash2832007

[23] R Tayouo G David B Ameduri J Roziere and S RoualdesldquoNew fluorinated polymers bearing pendant phosphonic acidgroups Proton conducting membranes for fuel cellrdquo Macro-molecules vol 43 no 12 pp 5269ndash5276 2010

[24] E Labalme G David P Buvat J Bigarre and T BoucheteauldquoNew hybrid membranes based on phosphonic acid function-alized silica particles for PEMFCrdquo Journal of Polymer SciencePart A Polymer Chemistry vol 50 no 7 pp 1308ndash1316 2012

[25] S-K Kim S-W Choi W S Jeon et al ldquoCross-linkedbenzoxazine-benzimidazole copolymer electrolyte membranesfor fuel cells at elevated temperaturerdquo Macromolecules vol 45no 3 pp 1438ndash1446 2012

[26] K Jakoby K V Peinemann and S P Nunes ldquoPalladium-catalyzed phosphonation of polyphenylsulfonerdquoMacromolecu-lar Chemistry and Physics vol 204 no 1 pp 61ndash67 2003

[27] B Lafitte and P Jannasch ldquoPhosphonation of polysulfonesvia lithiation and reaction with chlorophosphonic acid estersrdquoJournal of Polymer Science Part A Polymer Chemistry vol 43no 2 pp 273ndash286 2005

[28] MDGuiver O Kutowy and JWApSimon ldquoFunctional grouppolysulphones by bromination-metalationrdquo Polymer vol 30no 6 pp 1137ndash1142 1989

[29] C M Brick R Tamaki S-G Kim et al ldquoSpherical poly-functional molecules using poly(bromophenylsilsesquioxane)sas nanoconstruction sitesrdquo Macromolecules vol 38 no 11 pp4655ndash4660 2005

[30] M Kalek and J Stawinski ldquoPd(0)-catalyzed phosphorus-carbon bond formation Mechanistic and synthetic studieson the role of the palladium sources and anionic additivesrdquoOrganometallics vol 26 no 24 pp 5840ndash5847 2007

[31] K Miyatake and A S Hay ldquoNew poly(arylene ether)s withpendant phosphonic acid groupsrdquo Journal of Polymer SciencePart A Polymer Chemistry vol 39 no 21 pp 3770ndash3779 2001

[32] J Parvole and P Jannasch ldquoPolysulfones grafted with poly(vin-ylphosphonic acid) for highly proton conducting fuel cellmembranes in the hydrated and nominally dry staterdquo Macro-molecules vol 41 no 11 pp 3893ndash3903 2008

Journal of Nanomaterials 7

[33] R Bouchet and E Siebert ldquoProton conduction in acid dopedpolybenzimidazolerdquo Solid State Ionics vol 118 no 3-4 pp 287ndash299 1999

[34] A Bozkurt W H Meyer and G Wegner ldquoPAAimidazol-based proton conducting polymer electrolytesrdquo Journal of PowerSources vol 123 no 2 pp 126ndash131 2003

[35] S-KKimTKo S-WChoi et al ldquoDurable cross-linked copoly-mer membranes based on poly(benzoxazine) and poly(25-benzimidazole) for use in fuel cells at elevated temperaturesrdquoJournal of Materials Chemistry vol 22 no 15 pp 7194ndash72052012

[36] S-K Kim K-H Kim J O Park et al ldquoHighly durable poly-mer electrolyte membranes at elevated temperature cross-linked copolymer structure consisting of poly(benzoxazine)andpoly(benzimidazole)rdquo Journal of Power Sources vol 226 pp346ndash353 2013

[37] H-S Lee A Roy O Lane and J E McGrath ldquoSynthesisand characterization of poly(arylene ether sulfone)-b-polyben-zimidazole copolymers for high temperature low humidityproton exchange membrane fuel cellsrdquo Polymer vol 49 no 25pp 5387ndash5396 2008

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Journal of Nanomaterials 7

[33] R Bouchet and E Siebert ldquoProton conduction in acid dopedpolybenzimidazolerdquo Solid State Ionics vol 118 no 3-4 pp 287ndash299 1999

[34] A Bozkurt W H Meyer and G Wegner ldquoPAAimidazol-based proton conducting polymer electrolytesrdquo Journal of PowerSources vol 123 no 2 pp 126ndash131 2003

[35] S-KKimTKo S-WChoi et al ldquoDurable cross-linked copoly-mer membranes based on poly(benzoxazine) and poly(25-benzimidazole) for use in fuel cells at elevated temperaturesrdquoJournal of Materials Chemistry vol 22 no 15 pp 7194ndash72052012

[36] S-K Kim K-H Kim J O Park et al ldquoHighly durable poly-mer electrolyte membranes at elevated temperature cross-linked copolymer structure consisting of poly(benzoxazine)andpoly(benzimidazole)rdquo Journal of Power Sources vol 226 pp346ndash353 2013

[37] H-S Lee A Roy O Lane and J E McGrath ldquoSynthesisand characterization of poly(arylene ether sulfone)-b-polyben-zimidazole copolymers for high temperature low humidityproton exchange membrane fuel cellsrdquo Polymer vol 49 no 25pp 5387ndash5396 2008

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CeramicsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CompositesJournal of

NanoparticlesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Biomaterials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MetallurgyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

MaterialsJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Nano

materials

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofNanomaterials