Phosphoric acid doped sulfonated poly(tetra phenyl isoquinoline ether sulfone) copolymers for high temperature proton exchange membrane potential application

Phosphoric acid-doped sulfonated poly(tetra phenyl isoquinoline ether sulfone)s (PA-SPTPIESs) were successfully synthesized for high temperature proton exchange membrane. Poly(tetra phenyl ether ketone sulfone)s (PTPEKS) were prepared from 1,2-bis(4-fluorobenzoyl)-3,4,5,6-tetraphenyl benzene (BFBTPB) and bis(4-fluorohenyl) sulfone with bis(4-hydroxyphenyl) sulfone. The synthesis of the poly(tetra phenyl isoquinoline ether sulfone)s (PTPIESs), was carried out via an intramolecular ring-closure reaction of dibenzoylbenzene of PTPEKS with benzylamine. The sulfonated poly(tetra phenyl isoquinoline ether sulfone)s (SPTPIESs) were obtained by following sulfonation with concentrated sulfuric acid and doped by phosphoric acid. Different contents of sulfonated unit on PTPIESs (8, 12, 16 mol% of BFBTPB) and PA-SPTPIESs were studied by FT-IR, ¹H NMR spectroscopy, and thermogravimetric analysis (TGA). Strong acid–base interaction effect between poly benzisoquinoline (PBI) and sulfonic acid groups formed ionic crosslinking network between polymer chains. The ion exchange capacity (IEC) and proton conductivity of PA-SPTPIESs were evaluated with degree of sulfonation and doping of phosphoric acid.     

Preparation and properties of phosphoric acid doped sulfonated poly(tetra phenyl phthalazine ether sulfone) copolymers for high temperature proton exchange membrane application

Phosphoric acid-doped sulfonated poly(tetra phenyl phthalazine ether sulfone) (PA-SPTPPES) copolymers were successfully synthesized by the 4,4′-dihydroxydiphenylsulfone with 1,2-bis(4-fluorobenzoyl)-3,4,5,6-tetraphenylbenzene (BFBTPB) and 4,4′-difluorodiphenylsulfone in sulfolane. Poly(tetra phenyl phthalazine ether sulfone)s (PTPPESs) were prepared via an intramolecular ring-closure reaction of dibenzoylbenzene of precursor and hydrazine. The sulfonated poly(tetra phenyl phthalazine ether sulfone) (SPTPPES) membranes were obtained by sulfonation under concentrated sulfuric acid, and followed phosphoric acid-doped by immersion in phosphoric acid. Different contents of doped and sulfonated unit of PA-SPTPPES (10, 15, 20 mol% of BFBTPB) were studied by FT-IR, ¹H NMR spectroscopy, and thermo gravimetric analysis (TGA). The ion exchange capacity (IEC) and proton conductivity of SPTPPESs and PA-SPTPPESs were evaluated with increase of degree of sulfonation and doping level. The PA-SPTPPESs membranes exhibit proton conductivities (80 °C, relative humidity 30%) of 41.3 ∼ 74.1 mS/cm and the maximum power densities of PA-SPTPPES 10, 15, and 20 were about 294, 350, and 403 mW/cm².     

Sulfonated poly(ether sulfone) electrolytes structured with mesonaphthobifluorene graphene moiety for PEMFC

Sulfonated poly(ether sulfone)s containing a mixture of cis and trans mesonaphthobifluorene moiety were synthesized, and their properties were characterized. The mesonaphthobifluorene graphene moiety contained 6 phenyl rings and was conjugated together to form planar sheets of sp²-bonded carbon. Poly(arylene ether sulfone)s containing a mixture of cis and trans tetraphenyl ethylene units were synthesized by polycondensation, and converted into graphene by intramolecular Friedel–Craft cyclization with Lewis acid (FeCl₃). The sulfonation was taken selectively on mesonaphthobifluorene units with concentrated sulfuric acid. The structural properties of the sulfonated polymers were investigated by ¹H NMR spectroscopy. The membranes were studied with regard to ion exchange capacity (IEC), water uptake, and proton conductivity.     

A novel quaternized poly(ether sulfone) membrane for alkaline fuel cell application

A new type of poly(ether sulfone)‐based self‐aggregated anion exchange membrane (AEM) was successfully synthesized and used in H₂/O₂ fuel cell applications. The self‐aggregated structural design improves the effective mobility of OH^? ion and increases the ionic conductivity of AEM. Proton nuclear magnetic resonance and Fourier transform infrared spectroscopy spectra confirm successful chloromethylation and quaternization in the poly(ether sulfone). Thermogravimetric analysis curves show the self‐aggregated membrane was thermally stable up to 180 °C. The AEM also has excellent mechanical properties, with tensile strength 53.5 MPa and elongation at break 47.6% under wet condition at room temperature. The performance of H₂/O₂ single fuel cell at 30 °C showed the maximum power density of 162 mW cm^?2. These results show that the self‐aggregated quaternized poly(ether sulfone) membrane is a potential candidate for alkaline fuel cell applications. Copyright © 2014 John Wiley & Sons, Ltd.     

Poly(arylene ether sulfone) with tetra(quaternary ammonium) moiety in the polymer repeating unit for application in solid alkaline exchange membrane fuel cells

Poly(arylene ether sulfone)s with tetra(quaternary ammonium) hydroxide groups in the repeating unit of the polymer main chain were prepared for solid alkaline exchange membrane fuel cells. We synthesized a novel monomer with four amine groups which were derivatized to ammonium functional groups. Using this monomer, we easily synthesized poly(arylene ether sulfone)s which conduct hydroxyl ions. This direct synthetic method can control the exact amount of quaternary ammonium hydroxide groups in the polymer structure. The polymers were characterized by NMR, thermogravimetric analysis, water uptake, conductivity, and cell performance. In a solid alkaline exchange membrane fuel cell test, a maximum power output of 77 mW cm⁻² was achieved using hydrogen and oxygen.     

Proton conducting hybrid membrane electrolytes of sulfonated poly(ether sulfone)s and poly(ether sulfone)s containing metallophthalocyanine

A role of metallophthalocyanine (MPc) as an anti-oxidizing agent of polymer membrane and an accelerating agent of proton conductivity was discussed. The poly(ether sulfone)s bearing MPc (Ni, Co and Fe), PMPc were prepared by two-step reaction from phenolphthalein and fumaronitrile and followed reaction with metal (II) chloride (Ni, Co and Fe) and 1,2-dicyanobenzene in quinoline. The sulfonated polymer was synthesized by condensation polymerization using 1,2-bis(4-hydroxyphenyl)-1,2-diphenyl ethylene, bis(4-fluorophenyl) sulfone and followed by sulfonation reaction with concentrated sulfuric acid. A series of hybrid membranes (H–Ni, H–Co and H–Fe) were prepared from a mixture of the sulfonated copolymer and PMPcs in dimethylacetamide (DMAc). The structural properties of the synthesized polymers were studied by ¹H-NMR spectroscopy and FT-IR. The membrane properties were investigated by measurements of ion exchange capacity (IEC), water uptake, and proton conductivity, chemical degradation test, and atomic force microscopy (AFM) analysis. The cell performance of the membranes was compared with those of normal sulfonated poly(ether sulfone)s and Nafion.     

Synthesis of multi-block poly(arylene ether sulfone) copolymer membrane with pendant quaternary ammonium groups for alkaline fuel cell

A series of multi-block poly(arylene ether sulfone)s are synthesized via the copolymerization of bis(4-hydroxyphenol) sulfone, 3,3′, 5,5′-tetramethylbiphenol and 4,4′-difluorodiphenyl sulfone. The resulting multi-block copolymers are brominated by using N-bromosuccinmide (NBS) as bromination reagent. The bromomethylated copolymer is solution cast to form clear, creasable films, and subsequent soaking of these films in aqueous trimethylamine to give benzyltrimethylammonium groups. The anion exchange membranes obtained by the solution hydroxide exchange with aqueous sodium hydroxide show varying degrees of ionic conductivity depending on their ion exchange capacity. The highest hydroxide conductivity 0.029 S cm⁻¹ is achieved with the QBPES-40 membrane having IEC value of 1.62 mequiv g⁻¹ at room temperature and 100% RH. The obtained anion exchange membranes also have good mechanical properties and dimensional stability, which greatly facilitates the preparation of a MEA and the cell operation.     

Solvent processible, high-performance partially fluorinated copoly(arylene ether) alkaline ionomers for alkaline electrodes

A solvent processable, low water uptake, partially fluorinated copoly(arylene ether) functionalized with pendant quaternary ammonium groups (QAPAE) was synthesized and uses as the ionomer in alkaline electrodes on fuel cells. The quaternized polymers containing fluorinated biphenyl groups were synthesized via chloromethylation of copoly(arylene ether) followed by amination with trimethylamine. The resulting ionomers were very soluble in polar, aprotic solvents. Highly aminated ionomers had conductivities approaching 10 mS cm⁻¹ at room temperature. Compared to previous ionomers based on quaternized poly(arylene ether sulfone) (QAPSF) with similar ion exchange capacity (IEC), the water uptake of QAPAE was significantly less due to the hydrophobic octafluoro-biphenyl groups in the backbone. The performance of the fuel cell electrodes made with the QAPAE ionomers was evaluated as the cathode on a hybrid AEM/PEM fuel cell. The QAPAE alkaline ionomer electrode with IEC = 1.22 meq g⁻¹ had superior performance to the electrodes prepared with QAPSF, IEC = 1.21 meq g⁻¹ at 25 and 60 °C in a H₂/O₂ fuel cell. The peak power densities at 60 °C were 315 mW cm⁻² for QAPAE electrodes and 215 mW cm⁻² for QAPSF electrodes.     

Anion conductive tetra-sulfonium hydroxides poly(fluorenylene ether sulfone) membrane for fuel cell application

A series of anion exchange membranes of poly (fluorenylene ether sulfone) containing tertiary sulfonium hydroxide-functionalized fluorenyl groups were synthesized by sequential polycondensation, chloromethylation, substitution with dimethyl sulfide and ion exchange. They showed excellent solubility in polar aprotic solvents. Consequently, flexible and tough alkaline membranes with varying ionic contents were obtained by an anion exchange of tertiary sulfonium chloride polymers with 1.0 M KOH at room temperature. Different levels of substitution were performed to achieve high ionic conductivity as well as upholding the membranes’ mechanical stability. The tertiary sulfonium membranes demonstrated lower water uptake compared to quaternary ammonium membrane. High hydroxide ion conductivity was achieved up to 18.3 mS cm^?1 at 80 °C with the membrane of the highest ion exchange capacity (IEC, 1.51 mmol g^?1). The resulting alkaline polymers were characterized by ¹H NMR, FT-IR, thermogravimetric analysis (TGA), water uptake, IEC, atomic force microscopic (AFM) images.     

Synthesis and characterization of sulfonated poly (arylene ether ketone sulfone) block copolymers containing multi-phenyl for PEMFC

Sulfonated multi-block copolymers (SMBPs) were successfully synthesized from precursors of hydrophilic and hydrophobic block oligomers. The hydrophilic block oligomer was synthesized using 1,2-bis(4-fluorobenzoyl)-3,4,5,6-tetraphenylbenzene (BFBTPB) and 4,4′-(2,2-diphenylethenylidene) diphenol (DHTPE). The hydrophobic block oligomer was prepared by bis(4-hydroxyphenyl) sulfone and bis(4-fluorophenyl) sulfone. The sulfonation was taken selectively on hydrophilic block segment as well as para position of the pendant phenyl groups with concentrated sulfuric acid. To control the IEC the stoichiometry mole ratios were changed with hydrophilic blocks of 10, 13 and 17 mol%. The structural properties of SMBPs were studied by FT-IR, ¹H NMR spectroscopy, thermogravimetric analysis (TGA), and atomic force microscope (AFM). The water uptakes were 9.7–42.3% at 30 °C and 14.3%–70.4% at 80 °C with changing the ion exchange capacities. The resulted ion exchange capacities (IEC) were 1.09–1.63 meq./g. The highest power density of a fuel cell using SMBP 17 (IEC = 1.63 meq./g) and Nafion 211 was 0.41 and 0.45 W/cm², respectively, at 0.6 V.     

Anion-exchange membranes composed of quaternized-chitosan derivatives for alkaline fuel cells

A series of quaternized-chitosan derivatives (QCDs) with various degrees of quaternization was synthesized using glycidyltrimethylammonium chloride as a main quaternized reagent. These QCDs were then processed into hydroxide—form quaternary ammonium salts with aqueous potassium hydroxide solutions. The resultant hydroxide—form QCD gels were further crosslinked into anion-exchange membranes using ethylene glycol diglycidyl ether. The crosslinking density, crystallinity, swelling index, ion exchange capacity, ionic conductivity and thermal stability of the crosslinked membranes were subsequently investigated. It was found that properties of crosslinked membranes were modulated mainly by the degree of quaternization and crosslinking density of membranes. Some membranes exhibited promising characteristics and had the potential for applications in alkaline polymer electrolyte fuel cells in considering their integrative properties.     

Synthesis and characterization of pendant propane sulfonic acid on phenylene based copolymers by superacid-catalyzed reaction

A series of phenylene based polyelectrolytes were synthesized from 2,2′-biphenol, biphenyl and isatin by superacid catalyzed polyhydroxyalkylation reactions. Grafted sulfonated polymers were synthesized by substitution reaction with 3-bromopropane sulfonic acid potassium salt. These polymers have all carbon–carbon structure on polymer backbone without ether linkage. Particularly, the flexible sulfoalkyl groups were attached to a 2,2′-biphenol unit and formed grafting structure which afforded better stability due to less reactive towards nucleophilic substitution reaction, and good proton mobility because of well phase separation. The structure properties of the synthesized polymers were investigated by ¹H NMR spectroscopy. The membranes were studied by ion exchange capacity (IEC), water uptake, dimensional stability, proton conductivity, and cell performance. The chemical deterioration test was performed by Fenton reagent, and compared with normal sulfonated poly(ether sulfone)s and Nafion.     

Comparison of alkaline fuel cell membranes of random & block poly(arylene ether sulfone) copolymers containing tetra quaternary ammonium hydroxides

A series of modified anion conductive block poly(arylene ether sulfone) copolymer membranes containing a selective substituted unit, 15%, 20% and 25% 4,4′-(2,2-diphenylethenylidene) diphenol, were prepared for use in alkaline fuel cells. The anion exchange membranes were synthesized by first introducing chloromethyl groups. Quaternary ammonium groups could then be added to the tetra-phenyl ethylene units, followed by subsequent ion exchange. The tetra quaternary ammonium hydroxide polymers showed high molecular weights and exhibited high solubility in polar aprotic solvents. The block copolymer membrane showed higher ionic conductivity (21.37 mS cm⁻¹) than the random polymer membrane of similar composition (17.91 mS cm⁻¹). The membranes showed good chemical stability in 1.0 M KOH solution at 60 °C. They were characterized by ¹H NMR, FT-IR, TGA and measurements of ion exchange capacity, water uptake and ionic conductivity.     

Preparation and characterization of grafted propane sulfonic acid polyphenylene membrane via superacid-catalyzed reaction

A series of polyphenylene-based polyelectrolytes were synthesized from 2,2'-biphenol, and isatin by superacid catalyzed polyhydroxyalkylation reactions. Grafted sulfonated polyphenylenes were synthesized via K₂CO₃ catalyzed condensation reaction with 3-bromopropane sulfonic acid potassium salt. These polymers have all carbon–carbon linkages without any ether linkage on polymer backbone, which were not attacked by nucleophiles (H₂O, hydrogen peroxide, hydroxide anion and radical). Particularly, chemical modification to flexible sulfoalkyl groups implanted to a biphenol unit afforded better stability due to less reactive towards nucleophilic substitution reaction, and good proton mobility because of well phase separation. The structural properties of the synthesized polymers were investigated by ¹H NMR spectroscopy. The membranes were studied by ion exchange capacity (IEC), water uptake, dimensional stability as well as proton conductivity assessment. The chemical degradation test was performed by Fenton's reagent, and compared with the usual sulfonated poly(ether sulfone)s and Nafion.     

Studies of sulfonated polyphenylene containing fluorine moiety via nickel catalyzed C–C coupling polymerization

The synthesis of polyphenylenes containing fluorine moiety (PPTF), their functionalization with sulfonic acid groups, and the measurement of apposite parameters for PEMs are described. The polymers were prepared by Ni-catalyzed carbon–carbon coupling reaction of -(2,2,2-trifluoro-1-phenylethylidene)-bis(4-chlorobenzene) (TFPECB) and 2,5-dichlorobenzophenone, followed by sulfonation reaction with chlorosulfuric acid. These polymers have all carbon–carbon linkages without any ether linkage on the polymer backbone, which was not attacked by nucleophiles (H₂O, hydrogen peroxide, hydroxide anion and radical), and sulfuric acid groups were selectively attached to the side phenyl rings of the TFPECB unit. A series of membranes was studied by ¹H NMR spectroscopy, ion exchange capacity (IEC), water uptake, and proton conductivity. The membranes' degradation was tested with Fenton reagent and compared with normal sulfonated poly(ether sulfone)s and Nafion.     

Increased microbial fuel cell performance using quaternized poly ether ether ketone anionic membrane electrolyte for electricity generation

A high-performance hydroxide exchange membrane was prepared by the chloromethylation and quaternization of Poly ether ether ketone (PEEK) for microbial fuel cell applications. The study reports on the synthesis of a novel quaternized poly ether ether ketone (QPEEK) membrane and subsequent utilization of the ionomer as an anion exchange membrane (AEM). The structural characterization of chloromethylation and quaternization of PEEK was confirmed by FT-IR and ₁H¹ NMR spectroscopy and the morphologies were viewed by scanning electron microscopy. The effects of oxygen crossover and specific substrate crossover on cathode potential were also studied in detail. The investigation of QPEEK with the commercially available AEM (AMI-7001) revealed that the QPEEK shows excellent static properties, i.e. ion-exchange capacity, water uptake, thickness, etc.; and kinetic properties, i.e. diffusion permeability and better durability over 250 days. Power density obtained from an MFC containing the QPEEK-AEM produced higher value (60 W/m³) than the commercial AMI-7001 AEM (52 W/m³). This study shows that QPEEK could be used as an efficient and a cost effective AEM for an MFC.     

Comb-shaped sulfonated poly(aryl ether sulfone) proton exchange membrane for fuel cell applications

Structure design is the primary strategy to acquire suitable ionomers for preparing proton exchange membranes (PEMs) with excellent performance. A series of comb-shaped sulfonated fluorinated poly(aryl ether sulfone) (SPFAES) membranes are prepared from sulfonated fluorinated poly(aryl ether sulfone) polymer (SPFAE) and sulfonated poly(aryl ether sulfone) oligomer (SPAES-Oligomer). Chemical structures of the comb-shaped membranes are verified by ¹H nuclear magnetic resonance (NMR) and Fourier transform infrared (FT-IR) spectra. The comb-shaped SPFAES membranes display more continuous hydrophilic domains for ion transfer, because the abundant cations and flexible side-chains structure possess higher mobility and hydrophilicity, which show significantly improved proton conductivity, physicochemical stability, mechanical property compared to the linear SPFAE membranes. In a H₂/O₂ single-cell test, the SPFAES-1.77 membrane achieves a higher power density of 699.3 mW/cm² in comparison with Nafion® 112 (618.0 mW/cm²) at 80 °C and 100% relative humidity. This work offers a promising example for the synthesis of highly branched polymers with flexible comb-shaped side chains for high-performance PEMs.     

Hyperbranched-linear poly(ether sulfone) blend films for proton exchange membranes

Hyperbranched poly(ether sulfone) polymers having sulfonyl chloride end-groups is blended at up to 30 w% with linear poly(ether ether ether sulfone)s and a two-phase system is generated via spinodal decomposition upon drying from a DMAc solution. Conversion of the end-groups from sulfonyl chloride to sulfonic acid is accomplished using 16 M H₂SO₄ that is also believed to introduce additional sulfonic acid groups at the interface of the linear polymer. The blend films before and after conversion to sulfonic acid have similar tensile strengths as films composed of solely linear polymer (yield stress >40 MPa and Young's modulus >3 GPa m). These films are designed to test the viability of hyperbranched polymers as fuel cell membranes. Proton conductivities of up to 0.03 S cm⁻¹ are observed at 80 °C and 90% R.H indicating a good potential for use of hyperbranched polymers as a proton conduction material.     

Studies of sulfonated polyphenylene membranes containing benzophenone moiety for PEMFC

The sulfonated polyphenylenes containing benzophenone structure (sulfonated Parmax 1200, S-Parmax) were prepared by sulfonation reaction of Parmax 1200 with 30% fuming sulfuric acid, and degree of sulfonation was controlled by sulfonation reaction time. These polymers have all carbon structure without ether linkages that have the possibility of attack by nucleophiles (made by PEMFC operating system). The polyphenylene structure of Parmax provides a stiff and resistant backbone, whereas the pendant benzoyl group enables the solubility of the material, and also provides sites for chemical modifications. The structure properties of the synthesized polymers were investigated by ¹H NMR spectroscopy. The membranes were studied by ion exchange capacity (IEC), water uptake, and proton conductivity. These membranes deterioration test was performed by Fenton reagent, and compared with normal sulfonated poly(ether sulfone)s and Nafion. The power densities of membranes were performed by single cell.     

Role of post-sulfonation of poly(ether ether sulfone) in proton conductivity and chemical stability of its proton exchange membranes for fuel cell

Commercially available poly(ether ether sulfone), PEES, was directly sulfonated using concentrated sulfuric acid at low temperatures by minimizing degradation during sulfonation. The sulfonation reaction was performed in the temperature range of 5–25 °C. Sulfonated polymers were characterized by FTIR, ¹H NMR spectroscopy and ion exchange capacity (IEC) measurements. Degradation during sulfonation was investigated by measuring intrinsic viscosity, glass transition temperature and thermal decomposition temperature of sulfonated polymers. Sulfonated PEES, SPEES, membranes were prepared by solvent casting method and characterized in terms of IEC, proton conductivity and water uptake. The effect of sulfonation conditions on chemical stability of membranes was also investigated via Fenton test. Optimum sulfonation condition was determined to be 10 °C with conc. H₂SO₄ based on the characteristics of sulfonated polymers and also the chemical stability of their membranes. SPEES membranes exhibited proton conductivity up to 185.8 mS cm⁻¹ which is higher than that of Nafion 117 (133.3 mS cm⁻¹) measured at 80 °C and relative humidity 100%.