Considerable Proton Conductivity Research Articles

Interconnected hollow metal–organic framework network towards excellent proton transfer for proton exchange membrane

Interconnected hollow metal–organic framework (MOF) network (GO@HZIF-8) was designed as an efficient proton transfer accelerator in Nafion membrane. GO@HZIF-8 was constructed by in situ synthesis of ZIF-8 onto graphene oxide (GO) and succedent etching with tannic acid (TA). The hollow construction and surface TA functionalization of hollow ZIF-8 (HZIF-8) bestowed composite membrane with superior water retention. This was highly beneficial to the rapid proton transfer. Besides, the hollow construction could effectively reduce the proton transfer resistance onto GO@HZIF-8. More importantly, the interconnective architecture between HZIF-8 by the tethering function of GO and the interfacial hydrogen bond interaction between GO@HZIF-8 and Nafion resulted in connective proton transfer routes at GO@HZIF-8 surfaces and GO@HZIF-8/Nafion interfaces. These dramatically accelerated the proton transfer of GO@HZIF-8/Nafion composite membrane, enabling a considerable proton conductivity (PC) of 0.301 S cm−1 under 90 °C, 95 % RH, ∼1.33-fold greater than that of the pure Nafion membrane (RN). Moreover, the composite membrane exhibited a peak power density of 45.8 mW cm−2, ∼1.22-fold higher than that of RN. These results menifest that constructing hollow MOF network possesses grand prospect in the construction of high performance proton exchange membranes (PEMs).

Cyano crosslinked polybenzimidazole membranes containing 4,5-diazafluorene and pyridine for high temperature proton exchange membranes

Cross-linking is an effective way to enhance the mechanical strength of high-temperature proton exchange membranes (HTPEMs). In this study, a series of HTPEMs based on cyano-thermal cross-linked polybenzimidazole (C-PBPBI-xCN) were formulated and synthesized using cyano to achieve cross-linking via a simple heat treatment for the first time. The 4-fluorobenzonitrile was grafted onto the synthesized polybenzimidazole (PBI) containing 4,5-diazafluorene and pyridine, and the cyano-grafted PBI (PBPBI-xCN) membranes were then heat-treated to cross-link the cyano groups to improve the mechanical strength of PBI, resulting in HTPEMs with good mechanical properties without sacrificing considerable proton conductivity. The prepared cyano cross-linked membranes have high oxidative stability, thermal stability, mechanical strength and phosphoric acid retention properties. The proton conductivity of the C-PBPBI-3CN membrane achieved 52.8 mS cm−1 in an anhydrous environment at 180 °C, which is much higher than that of uncured PBPBI-xCN. The maximum output power density of the single cell based on the C-PBPBI-3CN reached 496.2 mW cm−2 at 140 °C.

Co-precipitation synthesis of a CeO2−SnO2 heterostructure electrolyte of low temperature solid oxide fuel cells

ABSTRACT Cerium dioxide (CeO2), especially doped cerium, is widely used as an electrolyte, while stannic oxide (SnO2) is known as a gas sensor material, but it is exceptionally new in solid-state ionics. In this work, a new semiconductor composite that consists of CeO2 and SnO2 was synthesized using a co-precipitation method and investigated for applications in solid oxide fuel cells (SOFCs). The as-prepared CeO2-SnO2 composite (n-n type) is employed as an electrolyte sandwiched between two Ni0.8Co0.15Al0.05LiO2-δ (NCAL) electrodes to fabricate fuel cells with a high power density of 1167 mW cm−2, accompanied by high open-circuit voltage (OCV) of 1.11 V at 550°C XRD, SEM, and HR-TEM analyses are employed to investigate the microstructure of the composites, illustrating that the as-prepared composite has particles of the nanometer size, without any other impurity phases. The electrical properties of the device are studied by EIS measurements. The results indicate that the synthesized CeO2-SnO2 composite exhibits higher ionic conductivity than that of the CeO2-SnO2 composite prepared by a dry grinding method. Considerable proton conductivity was also found for the CeO2-SnO2 composite. Interestingly, although two n-type semiconductor materials are composited for the electrolyte membrane, there is no short-circuit issue. Hence, the n-n heterojunction is proposed to explain the electron blocking mechanism.

High Dimensional Stability and Alcohol Resistance Aromatic Poly(aryl ether ketone) Polyelectrolyte Membrane Synthesis and Characterization

Crystallized sulfonated poly(arylene ether ketone) (Cr-SPAEK) materials constructed from dense sulfonated hydrophilic segments and crystalline poly(ether ketone) (PEK) hydrophobic backbone were designed. The membrane exhibited considerable proton conductivity and superb solvent resistance owing to its special phase morphology, the presence of a broad hydrophilic ion transport channel, and a crystalline hydrophobic matrix. The dense sulfonated hydrophilic segment provides excellent proton conductivity; the Cr-SPAEK-20 membrane exhibits higher proton-conducting ability than Nafion 117 in the temperature range of 20–100 °C; its proton conductivity reaches about 168 mS cm–1 at 100 °C. The crystalline PEK hydrophobic segment ensures superior solvent resistance and dimensional stability, guaranteeing the durability of the membrane in practical applications. The methanol permeability of Cr-SPAEK-20 is only one-eighth that of Nafion 117 when the test conditions are the same. The direct methanol fuel cell (DMFC), ...

A novel thermomechanically stable LaF3CsH5(PO4)2 composite electrolyte with high proton conductivity at elevated temperatures over 150 °C

Abstract A facile strategy is introduced to upgrade thermomechanical stability of the cesium pentahydrogen diphosphate (CPD), which is the most efficient inorganic electrolyte among all solid proton conductors, by constructing P OH•••F hydrogen bonds with lanthanum fluoride (LaF3). The optimal combination of the LaF3 CPD composite electrolyte is found to be 1:2 in a molar ratio (LaF3 CPD-2). LaF3 CPD-2 composite maintains robust solid state, even at a temperature up to 200 °C, which is 50 °C higher than the melting temperature of CPD. Meanwhile, the considerable proton conductivity of CPD is achieved in the LaF3 CPD-2 composite electrolyte due to the synergistic effect of the P OH•••F hydrogen bonds and the intrinsic proton conductive property of CPD. Last but not least, the LaF3 CPD-2 composite manifests excellent conductivity durability at 150 °C and low humidity condition with sizeable proton conductivity of 0.0262 S cm−1 after 60 h operation, implying that the LaF3 CPD composite could be a promising candidate for intermediate temperature proton conductors.

Thermodynamic and Kinetic Database for Hydration, Protonic Diffusion and Stability in Doped-BaHfO3 As High-Temperature Proton Conducting Electrolyte

Perovskite-type proton conducting materials is widely used as solid state electrolyte in Solid Oxide Fuel Cells (SOFCs), due to its excellent mechanical and thermodynamic stability and considerable proton conductivity. Developing novel materials via atomistic level simulation techniques is cost-effective and highly-efficient. In this abstract, we demonstrated the thermodynamic and kinetic database constructed for A and B-site doped BaHfO3, i.e. a novel proton-conducting perovskite system. We took advantage of ab-initio density functional theory calculations, transition state and diffusion theory, along with statistical thermodynamics. We successfully computed the key physical quantities relevant in hydration, proton conduction, and degradation process. The data obtained was analyzed through a data-science approach, by correlating computed quantities with intrinsic dopant properties, e.g. ionic radius, electro-negativity, etc. In the end, quantitative descriptors within fitting equations can be established for predicting unexplored dopants. This set of methods, including data-analytics, can be viewed as a standard way in constructing thermodynamic and kinetic database for other solid state ionic materials. Figure 1

SYNTHESIS AND PROPERTIES OF AROMATIC POLYESTERS WHITH CARDED FRAGMENTS

Polyethers are of great interest for various industries due to a complex of valuable properties, such as heat resistance, fire resistance, high strength, etc. Carded polymers occupy a special place among polymers with increased heat resistance, containing in the main polymer chain at least one element that is part of the lateral cyclic grouping. The presence of such fragments increases the glass transition temperature and heat resistance, which allows the copolymers to be operated at higher temperatures without changing the physico-mechanical parameters. For crystalline polymers, the presence of cardo fragments leads to better solubility in organic solvents. One of the promising ways of synthesizing heat-resistant polymeric materials is based on the use of aromatic compounds such as 3,3-bis (4'-hydroxyphenyl) phthalide, 3-chloro-3- (diphenyloxyd-4'-yl) phthalide, 3- chloro-3- (diphenylsulfide-4'-yl) phthalide, 9,9-bis (4'-hydroxyphenyl) fluorene, 9,9-bis (4'-hydroxyphenyl) anthrone-10, 2-phenyl-3,3- Bis (4'-hydroxyphenyl) phthalimidine and the like. At present, the worldwide problem of the release of toxic waste into the environment is aggravated, which causes irreversible climatic changes. To solve this problem, it was proposed to develop solid fuel cells based on polymeric proton-exchange membranes. Thus, polymer membranes must satisfy a number of requirements: to provide minimal ohmic losses, to possess considerable proton conductivity, mechanical strength, thermal stability and to have limited solubility in organic solvents. Polymer membranes with carded fragments in the main chain satisfy all the requirements. In the presented review features of synthesis and properties of copolymers on the basis of polysulfones, polyether ketones, polyetherimides with carded fragments are considered.Forcitation:Shakhmurzova K.T., Kurdanova Zh.I., Zhansitov A.A., Baiykaziev A.E., Khashirova S.Yu., Pakhomov S.I., Ligidov M.Kh.Synthesis and properties of aromatic polyesters whith carded fragments. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 6. P. 28-39.

Proton Conductance of a Superior Water-Stable Metal-Organic Framework and Its Composite Membrane with Poly(vinylidene fluoride).

Proton-exchange membranes (PEMs) as separators have important technological applications in electrochemical devices, including fuel cells, electrochemical sensors, electrochemical reactors, and electrochromic displays. The composite membrane of a proton-conducting metal-organic framework (MOF) and an organic polymer combines the unique physical and chemical nature of the polymer and the high proton conductivity of the MOF, bringing together the best of both components to potentially fabricate high-performance PEMs. In this study, we have investigated the proton-transport nature of a zirconium(IV) MOF, MOF-808 (1). This superior-water-stability MOF shows striking proton conductivity with σ = 7.58 × 10-3 S·cm-1 at 315 K and 99% relative humidity. The composite membranes of 1 and poly(vinylidene fluoride) (PVDF) have further been fabricated and are labeled as 1@PVDF-X, where X represents the mass percentage of 1 (as X%) in 1@PVDF-X and X = 10-55%. The composite membranes exhibit good mechanical features and durability for practical application and a considerable proton conductivity of 1.56 × 10-4 S·cm-1 in deionized water at 338 K as well. Thus, the composite membranes show promising applications as alternative PEMs in diverse electrochemical devices.

Copolymerization of 4-(3,4-diamino-phenoxy)-benzoic acid and 3,4-diaminobenzoic acid towards H3PO4-doped PBI membranes for proton conductor with better processability

A series of copolymers, which can also be regarded as ABPBIs containing phenoxyl in the main chain, were synthesized by copolymerization of two kinds of self-polycondensation monomers: 3,4-diaminobenzoic acid (DABA) and 4-(3,4-diamino-phenoxy)-benzoic acid (DPBA). The phenoxyl-containing ABPBIs exhibit better processability and acid stability than original ABPBI, despite their affinities towards acid decrease with the addition of phenoxyl moieties. By adjusting the phenoxyl content of the polymer, we made a tradeoff between acid doping levels and proton conductivity, with mechanical properties. The optimal polymer therein, PO-AB-50 (50 M percentages of DPBA in total monomers), exhibits considerable proton conductivity (53.47mS/cm at 160°C) and tensile strength (1.9MPa) after doped with phosphoric acid. In addition, the oxidation stability, water uptake and swell ratio properties of the polymers were also improved with the introduction of phenoxyl moieties.

Synthesis and characterization of sulfonated polyphosphazene-graft-polystyrene copolymers for proton exchange membranes

A novel series of polyphosphazene-graft-polystyrene (PP-g-PS) copolymers were successfully prepared by atom transfer radical polymerization (ATRP) of styrene monomers and brominated poly(bis(4-methylphenoxy)phosphazene) macroinitiator. The graft density and the graft length could be regulated by changing the bromination degree of the macroinitiator and the ATRP reaction time, respectively. The PP-g-PS copolymers readily underwent a regioselective sulfonation reaction, which occurred preferentially at the polystyrene sites, producing the sulfonated PP-g-PS copolymers with a range of ion exchange capacities. The resulting sulfonated PP-g-PS membranes prepared by solution casting showed high water uptake, low water swelling and considerable proton conductivity. They also exhibited good oxidative stability and high resistance to methanol crossover. Morphological studies of the membranes by transmission electron microscopy showed clear nanophase-separated structures resulted from hydrophobic polyphosphazene backbone and hydrophilic polystyrene sulfonic acid segments, indicating the formation of proton transferring tunnels. Therefore, these sulfonated copolymers may be candidate materials for proton exchange membranes in direct methanol fuel cell (DMFC) applications.

Effect of operating temperature on the behavior of promising SPEEK/cSMM electrolyte membrane for DMFCs

The behavior of sulfonated poly (ether ether ketone) (SPEEK) with different degrees of sulfonation (DS) (60–76%) blended with charged surface modifying macromolecule (cSMM) at different operating temperatures as an electrolyte membrane for direct methanol fuel cell (DMFC) application has been studied. A good DMFC electrolyte membrane should possess high proton conductivity and low methanol permeability. In this work, the fabricated SPEEK/cSMM membranes were compared with pure SPEEK and commercial Nafion 112 membranes in terms of water uptake, proton conductivity, and methanol permeability at temperature range of room to 80°C. The water uptake of SPEEK/cSMM membranes increased with the temperature and it was higher than that of SPEEK and Nafion 112 membranes; however newly fabricated membranes with 68% and 76% DS were dissolved at high temperatures although showed the same trend at lower temperatures. In agreement with the result of water uptake, proton conductivity of SPEEK/cSMM membranes also increased with temperature and was higher as compared to the corresponding SPEEK membranes; however it was still lower than that of Nafion 112. The methanol permeability values of the SPEEK/cSMM membranes were lower at different temperatures as compared to corresponding SPEEK and Nafion 112 at the same condition. Owing to considerable proton conductivity and lower methanol permeability values, SPEEK60/cSMM exhibited the highest overall performance than other tested membranes at 60°C. These results indicated that SPEEK60/cSMM membrane is promising to be used as a polymer electrolyte membrane in direct methanol fuel cell.

Semi-interpenetrating polymer networks based-on end-group crosslinked fluorine-containing polyimide via click chemistry

The reinforced composite membranes based on Nafion® membranes attract a lot of attention as proton exchange membrane (PEM) for polymer electrolyte membrane fuel cells (PEMFCs). Fluorine-containing polyimide (FPI), end-capped with alkynyl, is synthesized from 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), 2,2′-bis(trifluoromethyl)- 4,4′-diaminobiphenyl (TFMB), and 3-aminophenylacetylene (APA). The chemical structure of FPI is characterized by 1H-NMR. The reinforced composite membrane based-on semi-interpenetrating polymer network (semi-IPN) is prepared via solution casting of FPI and Nafion®212, and crosslinking thereafter. During the membrane preparation, alkynyl in FPI reacts with azide and itself via click chemistry and addition polymerization. The water uptake, swelling ratio, mechanical properties, thermal behavior, proton conductivity, and oxidative stability of the composite membranes are investigated. Compared to Nafion®212, the composite membrane shows improved thermal stability, mechanical properties, and dimensional stability. The tensile strength of the composite membranes is in the range of 35.0–55.6MPa, which is much higher than that of Nafion®212 membrane. The composite membranes show considerable proton conductivity from 2.0×10−2Scm−1 to 9.9×10−2Scm−1 at a temperature range from 30°C to 100°C, depending on FPI content.

Polyelectrolyte based on tetra-sulfonated poly(arylene ether)s for direct methanol fuel cell

A series of tetra-sulfonated poly(arylene ether)s are prepared from a new tetra-sulfonated difluoride monomer and commercial 4,4′-difluorobenzophenone and 4,4′-(hexafluoroisopropylidene)diphenol via polycondensation process. With the content of tetra-sulfonated monomer raising from 15% to 35% in difluoride monomer, sulfonated polymers with ion exchange capacity (IEC) ranging from 0.92 to 1.66 mequiv g−1 are obtained. The high thermal stable polymer owns the glass transition temperature higher than 190 °C and onset decomposition temperature higher than 300 °C. The polymers exhibit good solubility in dimethylacetamide (DMAc) and the tough, flexible and transparent films are obtained by solution casting method. These membranes exhibit suitable proton conductivity, low methanol permeability and excellent dimensional stability. The membrane with IECE = 1.81 mequiv g−1 shows considerable proton conductivity (84 mS cm−1) and swelling ration (only 8.6%) under fully hydrated state at 100 °C. Their excellent performance is attributed to distinct phase separation between hydrophilic and hydrophobic morphology, which is observed by TEM. This work demonstrates that the strategy of combining locally high densities hydrophilic segment with fluorine-containing hydrophobic segment in a polymer chain can balance on proton conduction and dimensional stability efficiently. Furthermore, these membranes own much lower methanol permeability and higher selectivity than Nafion.

Concentrated sulfonated poly (ether sulfone)s as proton exchange membranes

A novel bisphenol monomer containing concentrated electron rich phenyls is synthesized, which provides a locally and densely postsulfonation sites. Based on this monomer, a series of new sulfonated poly (ether sulfone)s (SPESs) are successfully obtained by nucleophilic substitution reaction, followed by postsulfonation using concentrated sulfuric acid. All the polymer membranes are readily prepared by solvent casting and exhibit excellent thermal stability and mechanical properties. As ion exchange capacity (IEC) ranging from 0.98 to 1.66 mequiv g−1, the polymers afford considerable proton conductivity and water absorption. SPES-3 with IEC = 1.66 mequiv g−1 shows equal proton conductivity (0.131 S cm−1) to Nafion 117 at 100 °C under fully hydrated state. At low IEC level (IEC = 0.92 mequiv g−1), SPES-1 also exhibits higher conductivity (>10−2 S cm−1) than some earlier reported sulfonated random polymers. Their excellent performance is attributed to the internal structure of the polymers, which formed distinct phase separation between hydrophilic and hydrophobic moiety observed by SAXS. A combination of high proton conductivities, moderate water uptake, suitable mechanical properties and low swelling ratios for some of the obtained SPES indicates that they are good candidate materials for proton exchange membranes (PEMs).

Proton exchange membranes based on semi-interpenetrating polymer networks of Nafion ® and poly(vinylidene fluoride) via radiation crosslinking

A new method to prepare proton exchange membranes based on semi-interpenetrating polymer networks (semi-IPN) of Nafion ® and poly(vinylidene fluoride) (PVDF) via radiation crosslinking was proposed. The tensile strength, degree of crosslinking, water uptake, and swelling ratio of the composite membranes were studied. Compared to the recast Nafion ® 212 membrane, the composite membranes show much better mechanical properties and improved dimensional stability. The tensile strength of the composite membranes ranges from 34.3 MPa to 53.4 MPa, which is higher than that of the recast Nafion ® 212 membrane (23.9 MPa). The dimensional stability of the composite membranes also increases with increasing PVDF content in the membranes. The composite membranes show considerable proton conductivity even at 100–120 °C. The membrane containing 40% PVDF shows the highest proton conductivity of 3.37 × 10 −2 S/cm at 115 °C. These properties make them a great potential in polymer electrolyte membrane fuel cells (PEMFC).

Novel polyaromatic ionomers with large hydrophilic domain and long hydrophobic chain targeting at highly proton conductive and stable membranes

A novel dihydroxyl monomer bearing 18 electron rich phenyl rings were synthesized and polymerized with other monomers bearing electron deficient phenyl rings to give dense and selective sites in macromolecules for post-sulfonation, which was successfully conducted in ClSO3H/CH2Cl2 solution at room temperature in a subsequential step. The chemical structures were confirmed by 1H NMR and FT-IR spectra. The ionic exchange capacity (IEC) was controlled to be from 0.65 to 1.21 mequiv g−1 to afford considerable proton conductivity. Distinct phase separation was observed in the resulting membranes from SAXS profiles. The SPAEK-5 with an IEC of 1.21 mequiv g−1 gave better proton conductivity than Nafion 117 at all tested temperatures under 100% relative humidity. The membranes exhibited an exceeding stability when immersing in Fenton's reagent (3 wt.% H2O2 + 2 ppm FeSO4) at 80 °C. These properties make them promising candidates for electrochemical applications.

Semi-interpenetrating polymer networks of Nafion ® and fluorine-containing polyimide with crosslinkable vinyl group

Fluorine-containing polyimide with crosslinkable vinyl group (FPI) was synthesized from 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), 2,2′-bis(trifluoromethyl)-4,4′-diaminobiphenyl (PFMB), and 4-amino styrene (AS). The reinforced composite membranes based on semi-interpenetrating polymer networks (semi-IPN) were prepared via solution casting of FPI and Nafion ®212, and crosslinking thereafter. The water uptake, swelling ratio, mechanical properties, thermal behavior, proton conductivity, and oxidative stability of the composite membranes were investigated. Compared with the recast Nafion ® 212, the composite membrane shows better mechanical properties and improved dimensional stability. The tensile strength of the composite membranes ranges from 39.0 MPa to 80.0 MPa, which is higher than that of the recast Nafion ® 212 membrane (26.6 MPa). The dimensional stability of the composite membranes increases with increasing FPI content in the membranes, whereas the proton conductivity decreases. The composite membranes show considerable proton conductivity from 2.0 × 10 −2 S cm −1 to 8.9 × 10 −2 S cm −1 at a temperature from 30 °C to 100 °C, depending on the FPI contents. The composite membranes with semi-IPN from FPI and Nafion ®212 have considerable high proton conductivity, excellent mechanical properties, thermal and dimensional stabilities.

Bridging the analog and digital worlds with linear ICs : L. Altman. Electronics, 5 June (1972), p. 83

A series of tetra-sulfonated poly(arylene ether)s are prepared from a new tetra-sulfonated difluoride monomer and commercial 4,4′-difluorobenzophenone and 4,4′-(hexafluoroisopropylidene)diphenol via polycondensation process. With the content of tetra-sulfonated monomer raising from 15% to 35% in difluoride monomer, sulfonated polymers with ion exchange capacity (IEC) ranging from 0.92 to 1.66 mequiv g−1 are obtained. The high thermal stable polymer owns the glass transition temperature higher than 190 °C and onset decomposition temperature higher than 300 °C. The polymers exhibit good solubility in dimethylacetamide (DMAc) and the tough, flexible and transparent films are obtained by solution casting method. These membranes exhibit suitable proton conductivity, low methanol permeability and excellent dimensional stability. The membrane with IECE = 1.81 mequiv g−1 shows considerable proton conductivity (84 mS cm−1) and swelling ration (only 8.6%) under fully hydrated state at 100 °C. Their excellent performance is attributed to distinct phase separation between hydrophilic and hydrophobic morphology, which is observed by TEM. This work demonstrates that the strategy of combining locally high densities hydrophilic segment with fluorine-containing hydrophobic segment in a polymer chain can balance on proton conduction and dimensional stability efficiently. Furthermore, these membranes own much lower methanol permeability and higher selectivity than Nafion.

Line drivers are not limited to computer systems : D. Pippenger. EDN/EEE, 15 March (1972), p. 44

A series of tetra-sulfonated poly(arylene ether)s are prepared from a new tetra-sulfonated difluoride monomer and commercial 4,4′-difluorobenzophenone and 4,4′-(hexafluoroisopropylidene)diphenol via polycondensation process. With the content of tetra-sulfonated monomer raising from 15% to 35% in difluoride monomer, sulfonated polymers with ion exchange capacity (IEC) ranging from 0.92 to 1.66 mequiv g−1 are obtained. The high thermal stable polymer owns the glass transition temperature higher than 190 °C and onset decomposition temperature higher than 300 °C. The polymers exhibit good solubility in dimethylacetamide (DMAc) and the tough, flexible and transparent films are obtained by solution casting method. These membranes exhibit suitable proton conductivity, low methanol permeability and excellent dimensional stability. The membrane with IECE = 1.81 mequiv g−1 shows considerable proton conductivity (84 mS cm−1) and swelling ration (only 8.6%) under fully hydrated state at 100 °C. Their excellent performance is attributed to distinct phase separation between hydrophilic and hydrophobic morphology, which is observed by TEM. This work demonstrates that the strategy of combining locally high densities hydrophilic segment with fluorine-containing hydrophobic segment in a polymer chain can balance on proton conduction and dimensional stability efficiently. Furthermore, these membranes own much lower methanol permeability and higher selectivity than Nafion.

Charge induced instability in 709 operational amplifiers : J. R. Haberer and J. J. Bart. 10 th IEEE Annual Proceedings, Reliability Physics 1972, p. 106

A series of tetra-sulfonated poly(arylene ether)s are prepared from a new tetra-sulfonated difluoride monomer and commercial 4,4′-difluorobenzophenone and 4,4′-(hexafluoroisopropylidene)diphenol via polycondensation process. With the content of tetra-sulfonated monomer raising from 15% to 35% in difluoride monomer, sulfonated polymers with ion exchange capacity (IEC) ranging from 0.92 to 1.66 mequiv g−1 are obtained. The high thermal stable polymer owns the glass transition temperature higher than 190 °C and onset decomposition temperature higher than 300 °C. The polymers exhibit good solubility in dimethylacetamide (DMAc) and the tough, flexible and transparent films are obtained by solution casting method. These membranes exhibit suitable proton conductivity, low methanol permeability and excellent dimensional stability. The membrane with IECE = 1.81 mequiv g−1 shows considerable proton conductivity (84 mS cm−1) and swelling ration (only 8.6%) under fully hydrated state at 100 °C. Their excellent performance is attributed to distinct phase separation between hydrophilic and hydrophobic morphology, which is observed by TEM. This work demonstrates that the strategy of combining locally high densities hydrophilic segment with fluorine-containing hydrophobic segment in a polymer chain can balance on proton conduction and dimensional stability efficiently. Furthermore, these membranes own much lower methanol permeability and higher selectivity than Nafion.