ABSTRACT

Abbreviations ......................................................................................................... 134 4.1 Introduction .................................................................................................. 135 4.2Membrane Synthesis ..................................................................................... 136

4.2.1Requirements for PEMs .................................................................... 136 4.2.2Polymer Synthetic Methods .............................................................. 137

4.2.2.1 Postsulfonation of Aromatic Polymers .............................. 137 4.2.2.2 Direct Copolymerization of Sulfonated Monomers........... 138

4.2.3Membrane Formation ....................................................................... 140 4.3Membrane Characterization ......................................................................... 141

4.3.1Spectral Studies (IR, NMR) ............................................................. 141 4.3.2 Morphological Studies (AFM, TEM, X-Ray) ................................... 143 4.3.3 Physical Properties (Solubility, Viscosity,

Thermal Stability, and Mechanical Properties) ................................ 147 4.3.4Ion Exchange Capacity, Water Uptake, and Swelling Ratio ............. 148

4.3.4.1Ion Exchange Capacity ...................................................... 148 4.3.4.2 Water Uptake ..................................................................... 149 4.3.4.3 Swelling Ratio .................................................................... 151

4.3.5Proton Conductivity .......................................................................... 151 4.3.6Chemical Stability ............................................................................ 152

4.3.6.1Hydrolytic Stability ............................................................ 152 4.3.6.2 Oxidative Stability ............................................................. 156

4.4 Membrane Conducting Mechanism .............................................................. 156 4.4.1Proton Conduction Mechanism ........................................................ 156

4.5Membrane Applications of PEMs for Fuel Cells .......................................... 157 4.5.1Problems of Aromatic PEMs ............................................................ 157 4.5.2 Recent Developments of Aromatic SPESs ....................................... 157

4.5.2.1Multiblock Copolymers ..................................................... 158 4.5.3Locally and Densely Sulfonated Polymers ....................................... 167 4.5.4SPES with High IEC Values and High Free Volume ....................... 174 4.5.5SPES with Pendant Peruoroalkyl Sulfonic Acids .......................... 179 4.5.6 Cross-Linked SPES .......................................................................... 186

6F-BPA 4,4′-(Hexauoroisopropylidene)diphenol AFM Atomic force microscope BNSHSulfonated binaphthyl-based poly(arylene ether sulfone) BPBiphenyl BPSBiphenyl-based poly(arylene ether sulfone) BPSH Randomly sulfonated biphenyl-based poly(arylene ether sulfone) CM1-Ethynyl-2,4-diuorobenzene DCDPS4,4′-Dichlorodiphenylsulfone DFBPDecauorobiphenyl DMADynamic mechanical analysis DMAc Dimethylacetamide DMFDimethylformamide DMFCDirect methanol fuel cell DMSODimethyl sulfoxide DSDegree of sulfonation ESPSN Sulfonated poly(phenylene sul–de nitrile) EWEquivalent weight FTIRFourier transform infrared spectrometry HFBHexauorobenzene HSPSulfonated poly(arylene ether sulfone) IEC Ion exchange capacity MB Multiblock sulfonated-uorinated poly(arylene ether sulfone) MEAMembrane electrode assembly MPM(HPO4)2 · nH2O (M = Sn, Zr, Ti) MW Molecular weight NMPN-Methylpyrrolidone NMRNuclear magnetic resonance NSNanosheet PEEKK Poly(ether ether ketone ketone) PEFC Polymer electrolyte fuel cells PEMProton exchange membrane PEMFCProton exchange membrane fuel cell PESPoly(ether sulfone) PES-Br Poly(oxy-4,4′-(3,3′-dibromobiphenylene)-oxy-4,4′-diphenylsulfone) PES-PSA Peruorosulfonated poly(arylene ether sulfone) PPMAPhosphorus pentoxide-methanesulfonic acid PPOPoly(propylene oxide)

4.5.7 Composite-Type SPESs .................................................................... 193 4.5.8 Thermally Annealed SPESs ............................................................. 195

4.6Chapter Summary ......................................................................................... 196 Acknowledgment ................................................................................................... 196 References .............................................................................................................. 197

PSA-K Potassium 1,1,2,2-tetrauoro-2-(1,1,2,2-tetrauoro-2-iodoethoxy)ethane sulfonate

RHRelative humidity SAXSSmall-angle x-ray scattering SDCDPS3,3′-Disulfonate-4,4′-dichlorodiphenylsulfone SFM Scanning force microscope SHQ Potassium 2,5-dihydroxybenzenesulfonate s-MWNTSulfonated multiwalled carbon nanotubes SnPSn(HPO4)2 · nH2O SPES Sulfonated poly(ether sulfone) SPESKSulfonated poly(arylene ether sulfone ketone) SPSUSulfonated poly(sulfone) STEMScanning transmission electron microscope TEM Transmission electron microscope TGA Thermogravimetric analysis WAXSWide-angle x-ray scattering WUWater uptake XESPSNCross-linked sulfonated poly(phenylene sul–de nitrile) XRD X-ray diffraction

Ever-increasing energy consumption is inescapable for progress in human society. Mostoftheenergy weusetodayisprovided bythecombustion offossilfuels. However, fossilfuelcombustion hasresultedinairpollutionandglobalwarming, whichaffects allliving thingsonearth.Inaddition,thedepletionoffossilfuelreserves isagreatconcern.Thesehealthandenvironmental concernscallfornew technologies for energy conversion and power generation that are more ef–cient and environmentallyfriendly. Fuelcellsareoneofthepromisingfuturepower sourcesdue totheiradvantages suchashighef–ciency, highenergy density, quietoperation,and environmental friendliness.Amongthem,thepolymerelectrolytefuelcells(PEFCs) areconsideredtobethemostpromisingpower sourceforportableandautomotive applicationsinwhichprotonexchange membranes(PEMs)playanimportantrole inPEFCs,whichareresponsiblefortheprotontransferfromtheanodetothecathodeandtheentirefuelcellperformance.Currently, peruorinatedpolymers,suchas Na–on® or Flemion®, are the state-of-the-art materials because of their good physical andchemicalstabilitiesalongwithahighprotonconductivity underawiderangeof relative humidity (RH) at moderate operating temperatures (Figure 4.1) [1,2].