Poly(arylene ether ether nitrile)s containing flexible alkylsulfonated side chains for polymer electrolyte membranes

A series of poly(arylene ether ether nitrile)s with different chain lengths of the alkylsulfonates (SPAEEN‐x: x refers number of the methylene units) are successfully synthesized for fuel cell applications. The polymers produced flexible and transparent membranes by solvent casting. The resulting membranes display a high thermal stability, oxidative stability, and higher proton conductivity than that of Nafion 117 at 80 °C and 95% relative humidity (RH). Furthermore, the SPAEEN‐12 with the longest alkylsulfonated side chain exhibits a higher proton conductivity at 30% RH than that of SPAEEN‐6 despite the lower IEC value, which indicates that the introduction of longer alkylsufonated side chains to the polymer main chain induces an efficient proton conduction by the formation of a well‐developed phase‐separated morphology. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 21–29     

Synthesis of sulfonated poly(imidoaryl ether sulfone) membranes for polymer electrolyte membrane fuel cells

New sulfonated poly(imidoaryl ether sulfone) copolymers derived from sulfonated 4,4′‐dichlorodiphenyl sulfone, 4,4′‐dichlorodiphenyl sulfone, and imidoaryl biphenol were evaluated as polymer electrolyte membranes for direct methanol fuel cells. The sulfonated membranes were characterized with Fourier transform infrared spectroscopy, thermogravimetric analysis, and proton nuclear magnetic resonance spectra. The state of water in the membranes was measured with differential scanning calorimetry, and the existence of free water and bound water was discussed in terms of the sulfonation level. The 10 wt % weight loss temperatures of these copolymers were above 470 °C, indicating excellent thermooxidative stability to meet the severe criteria of harsh fuel‐cell conditions. The proton conductivities of the membranes ranged from 3.8 × 10^?2 to 5 × 10^?2 S/cm at 90 °C, depending on the degree of sulfonation. The sulfonated membranes maintained the original proton conductivity even after a boiling water test, and this indicated the excellent hydrolytic stability of the membranes. The methanol permeabilities ranged from 1.65 × 10^?8 to 5.14 × 10^?8 cm²/s and were lower than those of other conventional sulfonated ionomer membranes, particularly commercial perfluorinated sulfonated ionomer (Nafion). The properties of proton and methanol transport were discussed with respect to the state of water in the membranes. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5620–5631, 2005     

Poly(arylene ether)s,poly(arylene thioether)s,and poly(arylene sulfone)s derived from a dihydroxy(imidoarylene) monomer

Novel poly(arylene ether)s, poly(arylene thioether)s, and poly(arylene sulfone)s were synthesized from the dihydroxy(imidoarylene) monomer 1 . The syntheses of poly(arylene ether)s were carried out in DMAc in the presence of anhydrous K₂CO₃ by a nucleophilic substitution reaction between the bisphenol and activated difluoro compounds. Poly(arylene thioether)s were synthesized according to the recently discovered one-pot polymerization reaction between a bis(N,N′-dimethyl-S-carbamate) and activated difluoro compounds in the presence of a mixture of Cs₂CO₃ and CaCO₃. The bis(N,N′-dimethyl-S-carbamate) 3 was synthesized by the thermal rearrangement reaction of bis(N,N′-dimethylthiocarbamate) 2 , which was synthesized from 1 by a phase-transfer catalyzed reaction. The poly(arylene thioether)s were further oxidized to form poly(arylene sulfone)s, which would be very difficult, if not impossible, to synthesize by other methods. All of the polymers described have extremely high T_gs and thermal stability as determined from DSC and TGA analysis. Poly(arylene sulfone)s have the highest T_gs and they are in the range of 298–361°C. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1201–1208, 1998     

Gas transport properties of novel poly(arylene ether ketone)s containing dibenzoylbiphenyl and benzonaphthone moieties

In this work we present the results from studies on novel poly(arylene ether ketone)s, including gas permeability, wide-angle x-ray diffraction (WAXD), and dynamic mechanical analysis (DMA). Poly(arylene ether ketone)s containing 2,2′- and 3,3′-dibenzoylbiphenyl (DBBP) moieties were characterized to study the effect of biphenyl substitution on gas transport properties. Gas permeabilities of naphthalene-containing poly(arylene ether ketone)s were also measured. Higher permeabilities were observed for polymers prepared with 6F-BPA, compared to 9,9-bis(4-hydroxyphenyl)fluorene (HPF). The naphthalene-containing polymers exhibited higher permeabilities than the DBBP polymers, except for a polymer having the 2,2′-DBBP and tetramethylbiphenyl moieties. Based on our work, and results reported in the literature, the 3,3′-DBBP polymers showed the lowest permeabilities for DBBP-containing poly-(arylene ether ketone)s. The low permeabilities are due to more efficiently packed chains brought on by greater flexibility of the backbone, compared to the other polymers studied. DMA studies confirmed the higher barriers to rotation which are believed to be responsible for 2,2′-DBBP polymers having similar selectivities compared to 3,3′-DBBP polymers. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 425–431, 1998     

Sulfonation of Novel Fluorine-containing Poly(arylene ether nitrile)s for Polymer Electrolyte Membranes

Sulfonation reaction of fluorine-containing poly(arylene ether nitrile) derived from 4-phenoxy-2,3,5,6-tetrafluorobenzonitrile (PTFB) and 2,2-bis(4-hydroxyphenyl)-1,1,1,3,3,3-hexafluoropropane (6FBA) by concentrated sulfuric acid at 30°C yielded quantitative introduction of one sulfonic group into phenoxy ring in the polymer at para-position with 68 mol% and at meta-position with 32 mol% due to the influence of fluorines at the ortho-positions of adjacent benzene ring. Membrane properties of the resulting polymer, thermal stability, proton conductivity and water uptake, were investigated for the application in fuel cells. While the membrane derived from the polymer showed similar level of proton conductivity at humidified condition to NAFION®112, its dimensional stability based on water uptake was lower than that of NAFION®112.     

The degradation mechanism of sulfonated poly(arylene ether sulfone)s in an oxidative environment

The degradation of sulfonated aromatic hydrocarbons based polymer electrolyte membranes is an important issue for fuel cell stability. However, its mechanism is relatively unclear. We have conducted accelerated radical tests and degradation product analysis for various sulfonated poly(arylene ether sulfone) (SPES) compounds. We evaluated the chemical durability of SPES, and observed its degradation mechanism under oxidative attack by hydrogen peroxide. Various SPES compounds were synthesized from 4,4′-biphenol, 4,4′-dihydroxy diphenyl sulfone, and 4,4′-dihydroxy benzophenone comonomers, and their physical properties were evaluated. SPES copolymerized with 4,4′-dihydroxy diphenyl sulfone had a higher durability towards oxidative attack compared with the other compounds studied, and SPES copolymerized with 4,4′-dihydroxy benzophenone exhibited the lowest durability.     

Polymer blend membranes of sulfonated poly(arylene ether ketone) for direct methanol fuel cell

The blend membranes of sulfonated poly(arylene ether ketone) (sPAEK) (IEC = 1.0 mequiv./g)/Nafion^® and the blend membranes of sPAEK (IEC = 1.0 mequiv./g)/sPAEK (IEC = 1.7 mequiv./g) were prepared. sPAEK with low IEC was introduced to reduce the methanol permeability through the membrane. Morphology, water uptake, proton conductivity and methanol permeability of the blend membranes were investigated by SEM, AFM, AC impedance spectroscopy and permeability measuring instrument. The cross-sections of blend membranes showed phase-separated morphologies. The effect of phase-separated morphology on the properties of blend membranes was investigated. The properties like water uptake, proton conductivity, and methanol permeability of sPAEK/Nafion^® blend membranes showed similar values with sPAEK and properties of sPAEK/sPAEK blend membranes showed intermediate values of two polymers due to the difference in morphology of the blend membranes. sPAEK/sPAEK blend membranes showed relatively high proton conductivity and lowered methanol permeability compared to Nafion^®. sPAEK/sPAEK blend membranes could be a competent substitution for Nafion^®.     

Synthesis and thermal properties of poly(arylene ether ketone)s containing phthalazinone moieties

A series of novel poly(arylene ether ketone)s were synthesized from the reaction of hydroquinone and 4-(4-hydroxyphenyl)-2,3-phthalazin-1-one with 4,4′-difluorobenzophenone in N-cyclohexylpyrrolidinone containing anhydrous potassium carbonate. The polymers exhibited high glass transition temperatures together with excellent thermooxidative stability. The chain structure of these polymers was studied by means of differential scanning calorimetry (DSC), wide-angle X-ray diffraction techniques (WAXD), and matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS). The experimental results indicated that these “as-made” copoly(aryleneketone)s containing hydroquinone moieties exhibited a block chain structure with segments which mainly consisted of hydroquinone and 4,4′-difluorobenzophenone. These chain segments resulted in crystallites in the polymers although they are thermodynamically unstable. The polymers showed thermal properties comparable to commercial PEEK, but the conditions for synthesis are much milder. The glass transition temperatures and solubilities of the copoly(arylene ketone)s tended to increase with increasing phthalazinone moiety content, while the crystallite melting points and crystallinity appeared to decrease. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1781–1788, 1999     

Synthesis of thermally crosslinkable fluorine‐containing poly(arylene ether ketone)s—II. Propargyl ether terminated poly(arylene ether ketone)s

Novel thermally crosslinkable fluorine‐containing poly(arylene ether ketone)s comprised of 2,3,5, 6‐tetrafluoro‐1,4‐phenylene moiety were synthesized by the termination of polymer chain ends with propargyl ether groups in order to improve solvent resistance. Crosslinking reaction occurred over 250°C through the formation of both chromen ring and polyene structure. This structure change brought about not only the outstanding solvent resistance but also the increase in glass transition temperature (T_g). The cured films also exhibited excellent thermal stability, transparency and hydrophobicity derived from fluorine atoms. Copyright © 2004 John Wiley & Sons, Ltd.     

Sulfonated poly(aryl ether ether ketone ketone)s containing fluorinated moieties as proton exchange membrane materials

A series of sulfonated poly(aryl ether ether ketone ketone)s statistical copolymers with high molecular weights were synthesized via an aromatic nucleophilic substitution polymerization. The sulfonation content (SC), defined as the number of sulfonic acid groups contained in an average repeat unit, could be controlled by the feed ratios of monomers. Flexible and strong membranes in sodium sulfonate form could be prepared by the solution casting method, and readily transformed to their proton forms by treating them in 2 N sulfuric acid. The polymers showed high T_gs, which increased with an increase in SC. Membranes prepared from the present sulfonated poly(ether ether ketone ketone) copolymers containing the hexafluoroisopropylidene moiety (SPEEKK‐6F) and copolymers containing the pendant 3,5‐ditrifluoromethylphenyl moiety (SPEEKK‐6FP) had lower water uptakes and lower swelling ratios in comparison with previously prepared copolymers containing 6F units. All of the polymers possessed proton conductivities higher than 1 × 10^?2 S/cm at room temperature, and proton conductivity values of several polymers were comparable to that of Nafion at high relative humidity. Their thermal stability, oxidative stability, and mechanical properties were also evaluated. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2299–2310, 2006     

Free volume in glassy poly(arylene ether ketone)s

Amorphous polyarylene ether ketones were examined in the glassy state by positron annihilation lifetime spectroscopy (PALS) and in the melt by standard rheological techniques. Specimens were well-characterized fractions of two isomeric structures. PALS clearly shows that the polymer with meta linkages in its backbone contains larger voids (> 0.25 nm radius). Thus despite their similar bulk densities, the two materials must pack very differently on a local scale. On the other hand, the free volumes inferred from the WLF treatment of melt viscosity data are practically identical in both materials ca. 4% at T_g. The comparison between techniques sheds some light on the distribution of free volume. © 1992 John Wiley & Sons, Inc.     

Highly proton conducting proton‐exchange membranes based on fluorinated poly(arylene ether ketone)s with octasulfonated segments

A new bisphenol monomer containing a pair of electron‐rich tetra‐arylmethane units was designed and synthesized. Based on this monomer, along with commercial 4,4′‐(hexafluoroisopropylidene)diphenol A and 4,4′‐difluorobenzophenone, a series of novel poly(arylene ether ketone)s containing octasulfonated segments of varying molar percentage (x) (6F‐SPAEK‐x) were successfully synthesized by polycondensation reactions, followed by sulfonation. Tough, flexible, and transparent membranes, exhibiting excellent thermal stabilities and mechanical properties were obtained by casting. 6F‐SPAEK‐x samples exhibited appropriate water uptake and swelling ratios at moderate ion exchange capacities (IECs) and excellent proton conductivities. The highest proton conductivity (215 mS cm⁻¹) is observed for hydrated 6F‐SPAEK‐15 (IEC = 1.68 meq g⁻¹) at 100 °C, which is more than 1.5 times that of Nafion 117. Furthermore, the 6F‐SPAEK‐10 membrane exhibited comparable proton conductivity (102 mS cm⁻¹) to that of Nafion 117 at 80 °C, with a relatively low IEC value (1.26 meq g⁻¹). Even under 30% relative humidity, the 6F‐SPAEK‐20 membrane (2.06 meq g⁻¹) showed adequate conductivity (2.1 mS cm⁻¹) compared with Nafion 117 (3.4 mS cm⁻¹). The excellent comprehensive properties of these membranes are attributed to well‐defined nanophase‐separated structures promoted by strong polarity differences between highly ionized and fluorinated hydrophobic segments. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 25–37     

Ionic conducting membranes based on new sulfonated poly(arylene ether ketone)s for fuel cell applications

The synthesis and characterization of new di‐ and tetra‐sulfonated ether diketone monomers are described. From these monomers, a wide series of sulfonated poly(arylene ether ketone)s (SPAEK) are synthesized by varying the sulfonic acid repartition along the polymer backbones. Their chemical structures are thoroughly characterized by NMR. From these polymers tough membranes are obtained from solution casting method and their water uptake, ionic conductivity, and water/gas permeation properties are determined and compared with those of Nafion membrane. Preliminary fuel cell tests show that SPAEK membranes are promising candidates for fuel cell application. This work brings new insights concerning the beneficial effects of introducing densely sulfonated monomers in a polyarylether macromolecular structure along with fluorinated groups improving conductivity while reducing unwanted excessive swelling. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 771–777     

Side-Chain Sulfonated Poly(arylene ether)s for Fuel Cell Applications

Summary: Poly(arylene ether sulfone)s of high molecular weight and narrow molecular weight distribution were obtained by melt polycondensation of 4,4′-difluorodiphenyl- sulfone and trimethylsilylethers of 4,4′-dihydroxydiphenylsulfone and phenylhydroquinone using CsF as catalyst. Although a block-like structure of the polymers could be expected from the course of reaction, only a single T_g ranging from 190 °C to 230 °C could be detected by DSC and which depended on the copolymer composition. Contrary to the sulfonation of similar poly(ether ether ketone)s the poly(arylene ether sulfone)s here reported were sulfonated both in the side chain and the main chain. Nonetheless the sulfonated poly(arylene ether sulfone)s showed high hydrolytic stability in water at 130 °C.     

Synthesis and characterization of hydrophilicity-controlled poly(arylene ether sulfone) copolymers with phenolphthalein-based carboxylic acid groups for separation membrane applications

Abstract

Hydrophilicity-controlled poly(arylene ether sulfone) copolymers with phenolphthalein-based carboxylic acid groups (PES-COOH-X) were synthesized via direct copolymerization by adjusting the feed molar ratio. The chemical structures of the obtained copolymers were confirmed by ¹H nuclear magnetic resonance (NMR) spectroscopy. The copolymers showed good solubility in common aprotic solvents and exhibited excellent mechanical properties. The water contact angles of the obtained copolymers could be reduced by approximately 52% from 92.1° to 44.2° with increasing content of phenolphthalein-derived monomer, 2-[bis(4-hydroxyphenyl)methyl] benzoic acid (PPH-COOH), in the feed molar ratio. A series of PES-COOH-X membranes was prepared via a conventional immersion precipitation phase inversion method. The effects of the monomer feed molar ratio on the morphology, hydrophilicity, pure water flux, and water uptake of the prepared membranes were investigated. The results showed that the pure water flux of the PES-COOH-X membranes was significantly enhanced by almost a factor of two as compared to the pristine PES membrane. From the water contact angle data, it was identified that the hydrophilicity of the membranes was increased rapidly with increasing PPH-COOH content in the membranes. These hydrophilicity-controlled poly(arylene ether sulfone) copolymers may be considered as good candidates for separation membrane materials.     

聚醚砜醚酮的合成与性能

以4,4′-二羟基二苯砜和4,4′-二氟二苯酮为单体, 通过溶液缩聚合成了聚醚砜醚酮(PESEK), 其分子结构相当于聚醚砜(PES)与聚醚醚酮(PEEK)的交替共聚物. 在共聚物分子中, 存在砜基、醚基和酮基, 整个结构单元形成了大共轭体系, 聚合物属无定形聚合物, 玻璃化转变温度(Tg)为198 ℃, 介于PEEK和PES的Tg之间, 其热稳定性和加工性能优于PES, 而力学性能与PES接近.     

聚醚砜酮的磺化及其在异丁烯低聚反应中的应用

Concentrated homogeneous mineral acids have been widely used as catalysts in industrial processes for several decades. These catalysts are corrosive to the apparatus, and there are large volumes of chemically reactive waste stream that are difficult to deal with[1]. In order to solve these problems, investigators have replaced these mineral acids with solid acid catalysts. Besides inorganic solid acid catalysts such as zeolite, solid organic polymeric resins containing acid groups, especially sulfuric acid resins such as Amberlyst[2], have attracted much attention. Compared with most inorganic acid catalysts, they have the advantages of their potentially high acidity, controllable surface area and porosity[3]. This article reports a novel sulfonated poly(phthalazinone ether sulfone ketone) (S-PPESK) resin and its application to isobutene oligomerization. S-PPESK exhibits high catalytic activity and excellent dimerization selectivity.     

Sulfonated carbon nanotubes/sulfonated poly(ether sulfone ether ketone ketone) composites for polymer electrolyte membranes

A series of composite membranes consisting of sulfonated carbon nanotubes (sCNTs) and sulfonated poly(ether sulfone ether ketone ketone) were successfully fabricated via the solution casting method. The chemical structure, as well as the long‐term stability of the sCNTs in different solvents, was investigated by Fourier transform infrared (FTIR) analysis and solubility experiment, respectively. The morphology, tensile strength, proton conductivity, and methanol permeability of the composite membranes were also investigated. The scanning electron microscope (SEM) observation indicated the good dispersion of the carbon nanotubes in polymer matrix as well as the strong interfacial bonding between the sulfonated poly(ether sulfone ether ketone ketone) (SPESEKK) matrix and sCNTs. The addition of either pristine carbon nanotubes or modified carbon nanotubes significantly enhanced the tensile strength of the SPESEKK membrane. The proton conductivity of the SPESEKK membrane increased while the methanol permeability decreased as the sCNTs content increased, showing a strong interaction between the modified nanotubes and SPESEKK. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis and characterization of poly(arylene ether ketone)s bearing pendant sulfonic acid groups for proton exchange membrane materials

A bisphenol monomer (2,5‐dimethoxy)phenylhydroquinone was prepared and further polymerized to obtain poly(arylene ether ketone) copolymers containing methoxy groups. After demethylation and sulfobutylation, a series of novel poly(arylene ether ketone)s bearing pendant sulfonic acid group (SPAEKs) with different sulfonation content were obtained. The chemical structures of all the copolymers were analyzed by ¹H NMR and ¹³C NMR spectra. Flexible and tough membranes with reasonably good mechanical properties were prepared. The resulting side‐chain‐type SPAEK membranes showed good dimensional stability, and their water uptake and swelling ratio were lower than those of conventional main‐chain‐type SPAEK membranes with similar ion exchange capacity. Proton conductivities of these side‐chain‐type sulfonated copolymers were higher than 0.01 S/cm and increased gradually with increasing temperature. Their methanol permeability values were in the range of 1.97 × 10^?7–5.81 × 10^?7 cm²/s, which were much lower than that of Nafion 117. A combination of suitable proton conductivities, low water uptake, low swelling ratio, and high methanol resistance for these side‐chain‐type SPAEK films indicated that they may be good candidate material for proton exchange membrane in fuel cell applications. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Radiation degradation of poly(arylene ether ketone)s

The resistance of five poly(arylene ether ketone)s with related chemical structures to degradation by ionizing radiation has been studied by ESR spectroscopy and yields of volatile products. All of the polymers showed high resistance to radiation with low yields of radicals after irradiation in vacuum at 77 K (when up to 84% of the radicals were identified as radical anions) and much lower yields at 300 K. The yields of volatile products were much less than reported for poly(arylene sulfone)s [1, 2]. Methyl substitution on a main-chain aromatic ring decreased the radiation resistance, but methane only comprised 10% of the volatile products from the methyl-substituted polymers. A polymer containing an isopropylidene group in the main chain and a substituent aromatic carbonyl showed significantly decreased radiation resistance. Extremely low radical yields were obtained after irradiation in air at 300 K, contrary to many polymers. XPS analysis showed an increase in C–O bonds on the surface after irradiation in air.