Preparation of anion exchange membrane based on homogeneous quaternization of bromomethylated poly(arylene ether sulfone)

This article presented the synthetic and preparation route of quaternary ammonium functionalized anion exchange membranes (AEMs), which were derived from an engineering plastics polymer, poly(arylene ether sulfone) with 3,3′,5,5′‐tetramethyl‐4,4′‐dihydroxybipheny moiety (PAES‐TM). The benzylmethyl groups on the main‐chain of PAES‐TM were converted to the bromomethyl groups via a radical reaction, thereby avoiding complicated chloromethylation, which required carcinogenic reagents. The chemical structure of the bromomethylated PAES was characterized by ¹H NMR spectrum. Following a homogeneous quaternization with trimethylamine in the solution, a series of flexible and tough membranes were obtained by a solution casting and anion exchange process. The ion exchange capacity values were ranging from 1.03 to 1.37 meq g^?1. The properties of the membranes, including water uptake, hydroxide conductivity, and methanol permeability were evaluated in detail. The AEM showed a high conductivity above 10^?2 S cm^?1 at room temperature and extremely low methanol permeability of 4.16–4.94 × 10^?8 cm² s^?1. The high hydroxide conductivity of TMPAES‐140‐NOH could be attributed to the nano‐scale phase‐separated morphology in the membrane, which was confirmed by their transmission electron microscopy images. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40256.     

Imidazole/(HPO3)3‐doped sulfonated poly (ether ether ketone) composite membrane for fuel cells

A novel gel of imidazole/(HPO₃)₃ was synthesized and incorporated into sulfonated poly (ether ether ketone) (SPEEK) to fabricate composite proton exchange membranes. The composite membranes were characterized by alternating current impedance (AC), thermogravimetry (TG), differential scanning calorimetry (DSC), X‐ray diffraction (XRD), scanning electron microscope (SEM) and mechanical property test. Based on the electrochemical performance investigation, the proton conductivity of the membrane is intimately correlated with the temperature and the mass ratio of imidazole/(HPO₃)₃ in the composite. The SPEEK/imidazole/(HPO₃)₃?4 composite membrane (with 44.4 wt % of imidazole/(HPO₃)₃) has the optimized performance at 135°C. Mover, the strength of the composite membranes is almost comparable to that of Nafion membrane. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41946.     

Effect of phosphotungstic acid blending on properties of sulfonated poly(ether ether ketone)–poly(ethylene glycol) crosslinked membranes

This study shows the effect of phosphotungstic acid (PWA) blended into a sulfonated poly(ether ether ketone) (SPEEK) and poly(ethylene glycol) (PEG) crosslinked membrane on the membrane's electrochemical and mechanical properties. The PWA weight percentage was varied from 0 to 50%. All of the membranes were equilibrated with water at room temperature (27 °C) and elevated temperature (60 °C), and their properties were investigated. A scanning electron microscope with energy dispersive X‐ray was used to ascertain the tungsten concentration remaining in the membrane after water treatment. A systematic decrease in tungsten concentration was seen with the increase in the initial PWA percentage. The membrane blended with 10% PWA showed the best properties, having the highest conductivity (0.11 S cm^?1), mechanical strength, and chemical stability. Membranes with 10% PWA and without PWA were studied in a H₂/O₂ fuel cell. The membrane blended with 10% PWA gave 33% more power density than the membrane without PWA. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46667.     

Synergistic effect of aluminium phosphate and tungstophosphoric acid on the physicochemical properties of sulfonated poly ether ether ketone nanocomposite membrane

This study explores the synergistic effect of aluminium phosphate (ALP) nanoparticles and tungstophosphoric acid (TPA) on the physicochemical properties of sulfonated poly ether ether ketone (SPEEK) nanocomposite membranes. SPEEK/TPA/ALP nanocomposite containing optimum TPA (10 wt %) and varying ALP content (3–10 wt %) are fabricated to investigate the effect of ALP nanoparticles on membrane properties. Experimental results reveal that nanocomposite membrane containing 3 wt % ALP nanoparticles and 10 wt % TPA exhibits 3.3 and 18.8 times higher proton conductivity compared to 10 wt % TPA filled SPEEK composite membrane and reference SPEEK membrane. ALP nanoparticles help in retaining water within the membranes and thus 59.4% reduction in water desorption rate is achieved compared to SPEEK/TPA membrane. The leaching of TPA is reduced by 34.5% which helps in retaining membrane properties. Membranes are thermally stable up to 200°C. Microstructure of the composite films is investigated by scanning electron microscope. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42952.     

Branched poly(biphenylene-co-sulfone)ether ion exchange membranes containing perfluorocyclobutane groups for fuel cell applications

A series of branched poly(biphenylene-co-sulfone) ion exchange membranes containing perfluorocyclobutane groups were prepared for fuel cells. Two bifunctional trifluorovinyloxy-terminated monomers (sulfonable 4,4′-bis(trifluorovinyloxy)biphenyl and insulfonable 4,4′-sulfonyl-bis(trifluorovinyloxy)biphenyl) and a trifunctional trifluorovinyloxy-terminated branching agent (1,1,1-tris(4′-trifluorovinyloxyphenyl)ethane) were synthesized and terpolymerized via thermal [2π + 2π] cyclodimerization to obtain partially fluorinated and branched polymers containing 0–5 mol% of the branching agent. They were then postsulfonated by chlorosulfonic acid at room temperature, cast as membranes, and characterized to evaluate their electrochemical properties for fuel cell applications. As the branching agent content was increased, their polydispersity values highly increased, indicating they became highly branched. It was confirmed that higher branching agent content also increased the ion exchange capacity, water uptake, and proton conductivity of the branched ion exchange membranes containing perfluorocyclobutane groups. This indicates that their electrochemical properties can be easily controlled by the degree of branching. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48373.     

Synthesis and characterization of a new type of sulfonated poly(ether ether ketone ketone)s for proton exchange membranes

A novel series of sulfonated poly(ether ether ketone ketone)s (SPEEKKs) were prepared by aromatic nucleophilic polycondensation with different ratios of 1,3‐bis(3‐sodium sulfonate‐4‐fluorobenzoyl)benzene to 1,3‐bis(4‐fluorobenzoyl)benzene. ¹H‐NMR spectroscopy was used to confirm the degrees of sulfonation (DS) of the polymers. Thermal stabilities of the SPEEKKs in acid form were characterized by thermogravimetric analysis (TGA), which showed that SPEEKKs were excellently thermally stable at high temperatures. SPEEKK polymers can be easily cast into tough membranes. Both of proton conductivity and methanol diffusion coefficient have been tested in this article. Other properties of the SPEEKK membranes were investigated in detail. The results show that the SPEEKK membranes are promising in proton exchange membrane fuel cells (PEMFCs) application. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Sulfonated graphene oxide‐doped proton conductive membranes based on polymer blends of highly sulfonated poly(ether ether ketone) and sulfonated polybenzimidazole

Simultaneously improving the proton conductivity and mechanical properties of a polymer electrolyte membrane is a considerable challenge in commercializing proton exchange membrane fuel cells. In response, we prepared a new series of miscible polymer blends and thus the corresponding crosslinked membranes based on highly sulfonated poly(ether ether ketone) and sulfonated polybenzimidazole. The blended membranes showed more compact structures, due to the acid‐base interactions between the two constituents, and improved mechanical and morphological properties. Further efforts by doping sulfonated graphene oxide (s‐GO) forming composite membranes led to not only significantly elevated proton conductivity and electrochemical performance, but also better mechanical properties. Notably, the composite membrane with the filler content of 15 wt % exhibited a proton conductivity of 0.217 S cm^?1 at 80 °C, and its maximum power density tested by the H₂/air single PEMFC cell at room temperature reached 171 mW cm^?2, almost two and half folds compared with that of the native membrane. As a result, these polymeric membranes provided new options as proton exchange membranes for fuel‐cell applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46547.     

Montmorillonite‐reinforced sulfonated poly(phthalazinone ether sulfone ketone) nanocomposite proton exchange membranes for direct methanol fuel cells

To produce a composite membrane with high conductivity and low permeability, SPPESK with a degree of sulfonation of 101% was carefully selected for the preparation of montmorillonite (MMT)‐reinforced SPPESK using solution intercalation. The fundamental characteristics such as water uptake, swelling ratio, proton conductivity, methanol permeability, and mechanical properties of the composite membranes were studied. Water uptake is improved when organic MMT (OMMT) loading increase. The composite membranes with CTAB‐MMT loading of 4–0.5% show 0.143–0.150 S cm^?1 proton conductivity at 80°C, which approaches the value of Nafion112. In addition, methanol permeability was decreased to 6.29 × 10^?8 cm² s^?1 by the addition of 6 wt % OMMT. As a result, the SPPESK‐MMT composite membrane is a good candidate for use in direct methanol fuel cells. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39852.     

A new sulfonated poly(ether sulfone) hybrid with low humidity dependence for high‐temperature proton exchange membrane fuel cell applications

A new sulfonated poly(ether sulfone) (PES) hybrid with low humidity dependence was prepared based on a new synthesized PES and Udel as a commercial PES. The PES was synthesized based on a pyridine containing diol which is able to change between pyridine and pyridinium salt forms during the cell performance (acidic condition) and facilitate proton transfer. The presence of nitrogen group increases inter and intramolecular interactions in the membrane and enhance proton hopping mechanism. Thermogravimetrical analysis of PES hybrid shows good thermal stability. Proton conductivity measurements were evaluated on a fuel cell test station, showing that the membrane has better performance under lower humidity (relative humidity = 60%) compare to the fully hydrated condition (relative humidity = 100%). The results reveal that proton transfer might be mainly accomplished through proton hopping mechanism at higher temperatures. The membrane also shows significant proton conductivity at 120 °C (about 6.6 mS cm^?1 at RH = 30%). © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45342.     

Highly selective sulfonated poly(vinylidene fluoride‐co‐hexafluoropropylene)/poly(ether sulfone) blend proton exchange membranes for direct methanol fuel cells

Proton exchange membranes (PEMs) based on blends of poly(ether sulfone) (PES) and sulfonated poly(vinylidene fluoride‐co‐hexafluoropropylene) (sPVdF‐co‐HFP) were prepared successfully. Fabricated blend membranes showed favorable PEM characteristics such as reduced methanol permeability, high selectivity, and improved mechanical integrity. Additionally, these membranes afford comparable proton conductivity, good oxidative stability, moderate ion exchange capacity, and reasonable water uptake. To appraise PEM performance, blend membranes were characterized using techniques such as Fourier transform infrared spectroscopy, AC impedance spectroscopy; atomic force microscopy, and thermogravimetry. Addition of hydrophobic PES confines the swelling of the PEM and increases the ultimate tensile strength of the membrane. Proton conductivities of the blend membranes are about 10^?3 S cm^?1. Methanol permeability of 1.22 × 10^?7cm² s^?1 exhibited by the sPVdF‐co‐HFP/PES10 blend membrane is much lower than that of Nafion‐117. AFM studies divulged that the sPVdF‐co‐HFP/PES blend membranes have nodule like structure, which confirms the presence of hydrophilic domain. The observed results demonstrated that the sPVdF‐co‐HFP/PES blend membranes have promise for possible usage as a PEM in direct methanol fuel cells. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43907.     

Performance of the sulfonated poly ether ether ketone proton exchange membrane modified with sulfonated polystyrene and phosphotungstic acid for microbial fuel cell applications

In this research, the preparation of low cost proton exchange membranes (PEMs) based on sulfonated poly ether ether ketone (SPEEK) for application in the microbial fuel cells (MFCs) is studied. Sulfonated polystyrene (SPS) and phosphotungstic acid (PWA) were employed to improve the performance of PEM through the creation of more proton pathways. At first, the sulfonation of PEEK and polystyrene were performed through two modified methods to obtain uniform and high degree of sulfonation (DS) of the polymers and then, the PEMs were prepared through the solution casting method. Accordingly, the formation of uniform skin layer was confirmed by the SEM micrographs. Blending the aforementioned additives to the SPEEK polymer solution significantly enhanced the proton conductivity, water uptake and durability of the modified membranes. The proton conductivities of SPEEK/SPS and SPEEK/PWA membranes at additive/SPEEK weight ratio of 0.15 were 45.3% and 26.2% higher than that of the commercial Nafion117 membrane, respectively. Moreover, the degradation times for the abovementioned modified membranes were 140 and 350 min which indicated satisfactory oxidation stability. Besides, the aforementioned membranes exhibited two times more water uptake compared to the neat SPEEK membrane. Finally, SPEEK/SPS and SPEEK/PWA membranes produced 68% and 36% higher maximum power in the MFC, compared to the commercial Nafion117 membrane. Therefore, the fabricated PEMs are potentially suitable alternatives to be used in the fuel cell applications.     

Preparation of a new type of ion‐exchange membrane based on sulfonated poly(ether ether ketone ketone)s

Novel sulfonated poly(ether ether ketone ketone)s were prepared directly by nucleophilic polycondensation. They showed excellent thermal stability and good solubility and could be easily cast into tough membranes. The sulfonated membranes showed swelling of 16.08–26.71% and an ion‐exchange capacity of 1.01–1.57. The transport properties of different cations (H⁺, Na⁺, and K⁺) of membranes based on these polymers were evaluated. The potential for ion‐exchange membranes looks good. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2481–2486, 2005     

A convenient crosslinking method for sulfonated poly(ether ether ketone) membranes via friedel–crafts reaction using 1,6‐dibromohexane and aluminum trichloride

In this study, sulfonated poly(ether ether ketone) (SPEEK) was very efficiently crosslinked via a Friedel–Craft reaction using 1,6‐dibromohexane and AlCl₃. The resulting crosslinked SPEEK (c‐SPEEK) membranes exhibited improved dimensional stability, thermal and chemical stability, and mechanical strength with slight reduction in the elongation. The methanol permeability was reduced by approximately two orders of magnitude by the crosslinking reaction. The proton conductivities of c‐SPEEK membranes were greater than Nafion‐212 in the temperature range of 30–90°C. Overall, this new crosslinking method can be conveniently and efficiently applicable to most aromatic hydrocarbon polymer membranes. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40695.     

Proton exchange membranes based on poly(vinylidene fluoride) and sulfonated poly(ether ether ketone)

Blend membranes were obtained by solution casting from poly(vinylidene fluoride) (PVDF) and sulfonated poly(ether ether ketone) (SPEEK) in N,N-dimethylacetamide (DMAc). DSC and XRD were used to characterize the structure of the blend membranes. The effect of PVDF content on the membrane properties was investigated. The methanol permeability, water uptake and the swelling ratio of blend membranes decreased with the increase of PVDF content. Though the proton conductivity decreased upon the addition of PVDF, they were still comparable to that of Nafion^® 117 membrane. Higher selectivities were also found for most blend membranes in comparison with Nafion^® 117 membrane. The effect of methanol concentration on solution uptake, swelling ratio and methanol permeability of the blend membranes was also studied.     

Proton exchange membranes based on modified sulfonated poly(ether ether ketone) membranes with chemically in situ polymerized polypyrrole

Sulfonated poly(ether ether ketone) (SPEEK) membranes were modified with chemically in situ polymerized polypyrrole (PPy). The effects of temperature and methanol concentration on the solution uptake and the swelling ratio of SPEEK/PPy membranes were investigated. The solution uptake and the swelling ratio of the membranes decreased upon the incorporation of PPy. When the methanol concentration increased, both the solution uptake and the swelling ratio increased to a maximum, and then decreased. FT-IR, XRD, DSC and TGA were used to characterize the modified membranes. The methanol permeability of modified SPEEK membranes decreased upon the incorporation of PPy, and higher selectivity values were found for SPEEK/PPy membranes in comparison with pure SPEEK and Nafion^® 117 membranes.     

Synthesis and properties of sulfonated poly(phosphazene)‐graft‐poly(styrene‐co‐N‐benzylmaleimide) copolymers via atom transfer radical polymerization for proton exchange membrane

A series of sulfonated poly(phosphazene)‐graft‐poly(styrene‐co‐N‐benzylmaleimide) (PP‐g‐PSN) copolymers were prepared via atom transfer radical polymerization (ATRP), followed by regioselective sulfonation which occurred preferentially at the poly(styrene‐co‐N‐benzylmaleimide) sites. The structures of these copolymers were confirmed by Fourier transform infrared (FTIR) spectroscopy, ¹H‐NMR, and ³¹P‐NMR, respectively. The resulting sulfonated PP‐g‐PSN membranes showed high water uptakes (WUs), low water swelling ratios (SWs), low methanol permeability coefficients, and proper proton conductivities. In comparison with non‐grafting sulfonated poly(bis(phenoxy)phosphazene) (SPBPP) membrane previously reported, the present membranes displayed higher proton conductivity, significantly improved the thermal and oxidative stabilities. Transmission electron microscopy (TEM) observation showed clear phase‐separated structures resulting from the difference in polarity between the hydrophobic polyphosphazene backbone and hydrophilic sulfonated poly(styrene‐co‐N‐benzylmaleimide) side chains, indicating effective ionic pathway in these membranes. The results showed that these materials were promising candidate materials for proton exchange membrane (PEM) in direct methanol fuel cell (DMFC) applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42251.     

Novel sulfonated poly(ether ether ketone ketone) derived from bisphenol S

A series of sulfonated poly(ether ether ketone ketone)s derived from bisphenol S were prepared by nucleophilic polycondensation. They showed high thermal resistance and good solubility. Most of the polymers were easily cast into tough membranes. The swelling of the membranes (6.02–16.02%) was lower than that of Nafion membranes, and the ion‐exchange capacity of the membranes (0.67–1.44) was higher than that of Nafion membranes. The proton conductivity of the membranes was 0.022–0.125 s/cm. They could be used as proton‐exchange membranes in fuel cells. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1569–1574, 2004     

Investigation on structure and properties of anion exchange membranes based on tetramethylbiphenol moieties containing copoly(arylene ether)s

Quaternary ammonium functionalized poly(arylene ether)s (QPAEs) containing 2,2′,6,6′‐tetramethylbiphenol moieties were designed and successfully synthesized via nucleophilic substitution polycondensation, bromination, quaternization and alkalization. The structure, water uptake, ion exchange capacities (IECs), hydroxide ion conductivities, and mechanical properties, as well as thermal and chemical stabilities of obtained QPAEs membranes were investigated. The QPAE‐a membrane with IEC value of 0.98 meq g^?1 demonstrated the highest ion conductivity (47.4 mS cm^?1) at 80°C. The ion transport activation energy (E_a) of QPAEs membranes varied from 8.57 to 19.95 kJ mol^?1. After chemical stability test conditioned in 1M NaOH at 60°C for 7 days, the QPAEs membranes except QPAE‐c (IEC = 0.88 meq g^?1) still exhibited high hydroxide ion conductivities (over 15 mS cm^?1) and acceptable tensile strength (～10 MPa). These properties indicate that the ionomers membranes are potential candidates for anion exchange membranes in anion exchange membrane fuel cells. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41525.     

Preparation and characterization of proton exchange membrane based on polyphosphoric acid modified by PVDF‐HFP

A polyphosphoric acid functionalized proton exchange membrane (PEM) was prepared by a ring opening reaction using the epoxycyclohexylethyltrimethoxysilane (EHTMS) and amino trimethylene phosphonic acid (ATMP) as raw materials and was modified by poly(vinylidene fluoride)–hexafluoro propylene (PVDF‐HFP). The structure of the membranes was characterized by Fourier transform infrared and scanning electron microscopy. The X‐ray photoelectron spectroscopy explores the content of the elements in the membrane related to the ion exchange capacity value. The membranes’ properties including water uptake, swelling ratio, proton conductivity, and hydrolysis stability were studied. Performance tests show that when ATMP/EHTMS = 1/5, conductivity of the PVDF‐HFP modified PEMs increased from 0.83 × 10^?4 S cm^?1 at 20 °C to 9.53 × 10^?3 S cm^?1 at 160 °C, the swelling ratio of membranes decreased from 2.71% to 2.13%. The results indicate that the introduction of F atoms is beneficial to increase the proton conductivity and the dimensional stability. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46737.     

Stable anion exchange membranes derived from fluorinated poly(aryl ethers) with quaternized fluorene units for fuel cell applications

A series of fluorinated poly(aryl ethers) containing benzyltrimethyl quaternary ammonium functionalized fluorene units (QPFAE) are synthesized via condensation polymerization, chloromethylation, and quaternization. Ionomer structure and the ion exchange capacity are confirmed by ¹H‐nuclear magnetic resonance spectroscopy. Other characterization techniques such as Fourier transform infrared spectroscopy, atomic force microscopy, thermogravimetric analysis, gel permeation chromatography, electrochemical impedance spectroscopy, Fenton, water‐swelling, and hydrolytic aging tests are used to evaluate the physicochemical properties of the as‐prepared QPFAE membranes. For the QPFAE membranes with ion exchange capacity of 0.95–1.94 mmol/g, they displayed low water uptake and methanol permeability (4.59–26.1 × 10⁻⁸ cm²/s at 25 °C), fairly good dimensional stability, high mechanical toughness, as well as fine thermal‐oxidative‐hydrolytic stability and ion conductivity at least 10 mS/cm. The membranes also showed clear hydrophilic/hydrophobic phase‐separation morphology. Furthermore, the QPFAE membranes could endure harsh basic conditions (1–4 mol/L NaOH solution) at 60 and 80 °C at least 240 h, keeping rather high mechanical toughness and ion conduction capability during the aging test. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46301.