High temperature creep behavior of phosphoric acid‐polybenzimidazole gel membranes

This work investigates the effects of polymer solids content and macromolecular structure on the high temperature creep behavior of polybenzimidazole (PBI) gel membranes imbibed with phosphoric acid (PA) after preparation via a polyphosphoric acid (PPA) mediated sol‐gel process Low‐solids, highly acid‐doped PBI membranes demonstrate outstanding fuel cell performance under anhydrous, ambient pressure, and high temperature (120–200 °C) operating conditions. However, PBI membranes are susceptible to creep under compressive loads at elevated temperatures, so their long‐term mechanical durability is a major concern. Here, we report results for the creep behavior of PBI membranes subject to compression at 180 °C. For para‐ and meta‐PBI homopolymers, increasing polymer solids content results in lower creep compliance and higher extensional viscosity, which may be rationalized by increasing chain density in the sol‐gel network. Comparing various homo‐ and copolymers at similar solids loading, differences in creep behavior may be rationalized in terms of chain–chain and chain‐solvent interactions that control macromolecular solubility and stiffness in the PA solvent. The results demonstrate the feasibility of improving the mechanical properties of PA‐doped PBI membranes by control of polymer solids content and rational design of PBI macromolecular structure. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1527–1538     

Synthesis and properties of a new fluorine‐containing polybenzimidazole for high‐temperature fuel‐cell applications

An amorphous, organosoluble, fluorine‐containing polybenzimidazole (PBI) was synthesized from 3,3′‐diaminobenzidine and 2,2‐bis(4‐carboxyphenyl)hexafluoropropane. The polymer was soluble in N‐methylpyrrolidinone and dimethylacetamide and had an inherent viscosity of 2.5 dL/g measured in dimethylacetamide at a concentration of 0.5 g/dL. The 5% weight loss temperature of the polymer was 520 °C. Proton‐conducting PBI membranes were prepared via solution casting and doped with different amounts of phosphoric acid. In the methanol permeability measurement, the PBI membranes showed much better methanol barrier ability than a Nafion membrane. The proton conductivity of the acid‐doped PBI membranes increased with increasing temperatures and concentrations of phosphoric acid in the polymer. The PBI membranes showed higher proton conductivity than a Nafion 117 membrane at high temperatures. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4508–4513, 2006     

Investigation of sequence isomer effects in AB‐polybenzimidazole polymers

In the present work, a unique series of random polybenzimidazole (PBI) copolymers consisting of the recently reported novel isomeric AB‐PBI (i‐AB‐PBI) and the well known AB‐PBI were synthesized. The i‐AB‐PBI incorporates additional linkages (2,2 and 5,5) in the benzimidazole sequence when compared with AB‐PBI. Random copolymers, varying in composition at 10 mol % increments, were synthesized to evaluate the effects of sequence isomerism in the polymer main chain without altering the fundamental chemical composition or functionality of a polymer chain consisting of 2,5‐benzimidazole units. Polymer solutions were prepared in polyphosphoric acid (PPA) and cast into membranes using the sol–gel PPA process. The resulting polymers were found to have high inherent viscosities (>2.0 dL/g) and showed elevated membrane proton conductivities (～0.2 S/cm) under anhydrous conditions at 180 °C. Fuel cell performance evaluations were conducted, and an average output voltage ranging from 0.5 to 0.60 V at 0.2 A/cm² was observed for hydrogen/air at an operational temperature of 180 °C without applied backpressure or humidification. Herein, we report for the first time glass transition (T_g) temperatures for AB‐PBI, i‐AB‐PBI, and an anomalous T_g effect for the series of randomized PBIs. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 619–628     

Synthesis and characterization of fluorine‐containing polybenzimidazole for proton conducting membranes in fuel cells

Two new kinds of fluorine‐containing polybenzimidazoles (PBI), poly(2,2′‐(tetrafluoro‐p‐phenylene)‐5,5′‐bibenzimidazole) and poly(2,2′‐tetradecafluoroheptylene‐5,5′‐bibenzimidazole), were synthesized by condensation polymerization of 3,3′‐diaminobenzidine and perfluoroterephthalic acid (or perfluoroazelaic acid), with polyphosphoric acid as solvent. Thermogravimetric analysis results show that the fluorine‐containing polymers synthesized exhibit promising thermal stability. The film‐forming properties of the fluorine‐containing polymers are improved over nonfluorinated PBI. The introduction of fluorine into the backbone of the polymers has significant positive affection on their chemical oxidation stability demonstrated by Fenton test. Compared with poly(2,2′‐(m‐phenylene)‐5,5′‐bibenzimidazole)/phosphoric acid (PA) composite membrane, the resulting fluorinated membranes with a same PA doping level exhibit better flexibility and higher proton conductivity. The maximum proton conductivity gained is 3.05 × 10^?2 S/cm at 150 °C with a PA doping level of 7. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2115–2122, 2010     

Sulfonated polybenzimidazoles: Proton conduction and acid–base crosslinking

A series of soluble, benzimidazole‐based polymers containing sulfonic acid groups (SuPBI) has been synthesized. SuPBI membranes resist extensive swelling in water but are poor proton conductors. When blended with high ion exchange capacity (IEC) sulfonated poly(ether ether ketone) (SPEEK), a polymer that has high proton conductivity but poor mechanical integrity, ionic crosslinks form reducing the extent of swelling. The effect of sulfonation of PBI on crosslinking in these blends was gauged through comparison with nonsulfonated analogs. Sulfonic acid groups present in SuPBI compensate for acid groups involved in crosslinking, thereby increasing IEC and proton conductivity of the membrane. When water uptake and proton conductivity were compared to the IEC of blends containing either sulfonated or nonsulfonated PBI, no noticeable distinction between PBI types could be made. Comparisons were also made between these blends and pure SPEEK membranes of similar IEC. Blend membranes exhibit slightly lower maximum proton conductivity than pure SPEEK membranes (60 vs. 75 mS cm^?1) but had significantly enhanced dimensional stability upon immersion in water, especially at elevated temperature (80 °C). Elevated temperature measurements in humid environments show increased proton conductivity of the SuPBI membranes when compared with SPEEK‐only membranes of similar IEC (c.f. 55 for the blend vs. 42 mS cm^?1 for SPEEK at 80 °C, 90% relative humidity). © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3640–3650, 2010     

Preparation and characterization of polybenzimidazole membranes prepared by gelation in phosphoric acid

Phosphoric acid doped poly (2, 2′‐(m‐phenylene)‐5, 5′‐bibenzimidazole) (PBI) membranes were prepared by dissolving PBI powders in 85% phosphoric acid at 190–200°C and then promoting gelation of the PBI by cooling the solutions to ?18°C. The extent of acid doping of the PBI membranes was controlled by immersing the membrane in aqueous phosphoric acid solutions of different concentrations (acid de‐doping). The process of the acid de‐doping was faster than acid doping of membrane cast from N,N‐dimethylacetamide (DMAc). The de‐doping process caused shrinkage of the PBI membrane and thus an increase in the membrane strength due to the packing of PBI chains according to the X‐ray diffraction analysis. The tensile stress and proton conductivity of the obtained PBI membranes with different acid doping levels were measured. For a PBI (η_IV: 0.58 dL · g^?1) membrane with an acid doping level of 7.0 (molar number of doped acid per mole repeat unit of PBI), the stress at break and proton conductivity at 120°C without humidification were 2.6 MPa and 5.1 × 10^?2 S · cm^?1, respectively. These results were comparable to those of the membranes cast from PBI solutions in DMAc. Copyright © 2009 John Wiley & Sons, Ltd.     

Comparative investigation of novel PBI blend ionomer membranes from nonfluorinated and partially fluorinated poly arylene ethers

In this study, the properties of novel acid-base blend membranes from polybenzimidazole PBI and self-prepared sulfonated nonfluorinated and partially fluorinated arylene main chain polymers from the polymer classes of aromatic polyethers, polyetherketones, polyethersulfones, and polyphosphine oxides are comparatively discussed. The aims of this study were to (1) determine the influence of the chemical structure of the polymers on their thermal and chemical stabilities and to identify polymeric structures having stabilities as high as possible, and (2) determine the effect of the addition of PBI to sulfonated arylene ionomers in terms of improving of their chemical, thermal, and dimensional stabilities. The working hypothesis of the study was that partially fluorinated arylene main-chain ionomers should have better chemical and thermal stabilities than the F-free ionomers, due to the much higher stability of C F bonds, compared to that of C H bonds. Improved procedures have been used for the polycondensation reactions, by applying an excess of K₂CO₃ deprotonation compound; the use of a dehydration agent like toluene or benzene was not required. Further, reactions could be performed at lower temperatures than is usually required for such polycondensation reactions; most of the polycondensations were made in a temperature range between 80 and 130 °C. The following properties of the polymers and blend membranes have been determined: proton conductivity, water uptake, swelling, thermal stability including thermal stability of sulfonic acid groups and of the polymer backbone, and oxidative stability by H₂O₂ treatment. The result of these investigations was that polymers containing fluorinated building blocks and/or phosphine oxide building blocks had the best stabilities. Selected acid-base blend membranes were made from PBI and these aromatic polymers showed proton conductivities of up to 0.1 S/cm, water uptake values of not more than 40%, and starting temperatures for SO₃H group splitting-off approaching 290 °C. Moreover, PBI-sulfonated polymer blend membranes showed much less weight loss after H₂O₂ treatment than does the sulfonated polymers alone, indicating a radical attack-stabilizing effect of PBI. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2311–2326, 2006     

Polybenzimidazoles tethered with N‐phenyl 1,2,4‐triazole units as polymer electrolytes for fuel cells

Polybenzimidazole (PBI) polymers tethered with N‐phenyl 1,2,4‐triazole (NPT) groups were prepared from a newly synthesized aromatic diacid, 3′‐(4‐phenyl‐4H‐1,2,4‐triazole‐3,5‐diyl) dibenzoic acid (PTDBA). The obtained polymers show superior thermal and chemical stability and good solubility in many aprotic solvents. The inherent viscosities of all polymers were around 1 dL/g. They exhibit high thermal stability with initial decomposition temperature ranging from 515 to 530 °C, high glass transition temperature ranging from 375 to 410 °C, and good mechanical properties with tensile stress in the range of 66–98 MPa and modulus 1897–2600 MPa. XRD analysis indicates that these polymers are amorphous in nature. Physicochemical properties such as water and phosphoric acid‐uptake, oxidative stability, and proton conductivity of membranes of these polymers have also been determined. The proton conductivity ranged from 4.7 × 10^?3 to 1.8 × 10^?2 S cm^?1 at 175 °C in dry conditions. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2289–2303, 2009     

Polymer electrolyte membranes by in situ polymerization of poly(ethylene carbonate‐co‐ethylene oxide) macromonomers in blends with poly(vinylidene fluoride‐co‐hexafluoropropylene)

Salt‐containing membranes based on polymethacrylates having poly(ethylene carbonate‐co‐ethylene oxide) side chains, as well as their blends with poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP), have been studied. Self‐supportive ion conductive membranes were prepared by casting films of methacrylate functional poly(ethylene carbonate‐co‐ethylene oxide) macromonomers containing lithium bis(trifluorosulfonyl)imide (LiTFSI) salt, followed by irradiation with UV‐light to polymerize the methacrylate units in situ. Homogenous electrolyte membranes based on the polymerized macromonomers showed a conductivity of 6.3 × 10^?6 S cm^?1 at 20 °C. The preparation of polymer blends, by the addition of PVDF‐HFP to the electrolytes, was found to greatly improve the mechanical properties. However, the addition led to an increase of the glass transition temperature (T_g) of the ion conductive phase by ～5 °C. The conductivity of the blend membranes was thus lower in relation to the corresponding homogeneous polymer electrolytes, and 2.5 × 10^?6 S cm^?1 was recorded for a membrane containing 10 wt % PVDF‐HFP at 20 °C. Increasing the salt concentration in the blend membranes was found to increase the T_g of the ion conductive component and decrease the propensity for the crystallization of the PVDF‐HFP component. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 79–90, 2007     

Synthesis of novel polybenzimidazoles with pendant amino groups and the formation of their crosslinked membranes for medium temperature fuel cell applications

A series of new polybenzimidazoles (PBIs) with pendant amino groups have been synthesized via condensation polymerization of 5‐aminoisophthalic acid (APTA), isophthalic acid (iPTA), and 3,3′diaminobenzidine (DAB) in polyphosphoric acid at 190 °C for 20 h. The molar ratios between APTA and iPTA were controlled at 1:0, 2:1, 1:1, and 1:2, respectively, and the copolymerization reactions were carried out via both random and sequenced manners. The resulting polymers showed good solubility in some organic solvents such as dimethylsulfoxide (DMSO) and N,N‐dimethylacetamide (DMAc). The pendant amino groups of the PBIs were utilized to react with two kinds of crosslinkers, 1,3‐dibromopropane and ethylene glycol diglycidyl ether, to yield various crosslinked membranes. The crosslinked membranes generally showed good mechanical properties even at high‐phosphoric acid (PA) doping levels, whereas the uncrosslinked membranes highly swelled or even dissolved in PA. Fenton's test revealed that the crosslinked PBI membranes had excellent radical oxidative stability. The proton conductivities of the PA‐doped crosslinked membranes increased with an increase in temperature and high‐proton conductivity up to 0.14 S/cm at 0% relative humidity at 170 °C was achieved. The membranes with high PA‐doping levels, good mechanical properties, and high‐proton conductivities have been successfully developed. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009     

Partially fluorinated and ammonium‐functionalized terpolymers: Effect of aliphatic groups on the properties of anion conductive membranes

Synthesis and properties of a series of ammonium‐containing terpolymers (QPAF‐3) as anion conductive membranes are reported. The QPAF‐3s composed of perfluoroalkylene, alkylene, and ammonium‐functionalized phenylene groups without heteroatom linkages in the main chain were synthesized via nickel‐mediated polycondensation reaction, followed by chloromethylation, quaternization, and ion exchange reactions. Self‐standing, bendable membranes were obtained by solution casting. The QPAF‐3 membrane with optimized terpolymer composition and ion exchange capacity (1.46 meq g^?1) showed high hydroxide ion conductivity (123 mS cm^?1 in water at 80 °C). The alkaline stability test in 1 M KOH for 1000 h at 80 °C and the post‐test analysis with IR spectra and tensile strength suggested that ammonium groups were likely to be decomposed while the polymer main chain was chemically more robust. The presence of the alkylene groups in the terpolymers lowered solubility, glass transition temperature, and elongation property of the resulting membranes. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 1442–1450     

Polybenzimidazole‐based block copolymers: From monomers to membrane electrode assemblies for high temperature polymer electrolyte membrane fuel cells

In this study, PBI‐based block copolymers were developed and their performance as membranes in high temperature polymer electrolyte membrane fuel cells was evaluated. This type of block copolymer consists of “phosphophilic” PBI and “phosphophobic” non‐PBI segments. The final properties of such block copolymers strongly depended on the length of the individual blocks and their chemical structures. In a systematic approach, a series of various block copolymers was synthesized and characterized both in terms of ex situ properties (e.g., proton conductivity, phosphoric acid uptake, swelling behavior) and in situ fuel cell tests. A very poor membrane‐electrode interface limited the performance of the membrane electrode assemblies, but was remarkably improved in power output, stability, and long‐term durability by treating the electrode interface with a fluorinated PBI derivative. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1831–1843     

Phosphoric acid‐doped imidazolium ionomers with enhanced stability for anhydrous proton‐exchange membrane applications

Phosphoric acid‐doped crosslinked proton‐conducting membranes with high anhydrous proton conductivity, and good chemical stability in phosphoric acid were synthesized and characterized. The synthetic procedure of the acid‐doped composite membranes mainly involves the in situ crosslinking of polymerizable monomer oils (styrene and acrylonitrile) and vinylimidazole, and followed by the sulfonation of pendant imidazole groups with butanesultone, and further doped with phosphoric acid. The resultant phosphoric acid‐doped composite electrolyte membranes are flexible and show high thermal stability and high‐proton conductivity up to the order of 10^?2 S cm^?1 at 160 °C under anhydrous conditions. The phosphoric acid uptake, swelling degree, and proton conductivity of the composite membranes increase with the vinylimidazole content. The resultant composite membranes also show good oxidative stability in Fenton's reagent (at 70 °C), and quite good chemical stability in phosphoric acid (at 160 °C). The properties of the prepared electrolyte membranes indicate their promising prospects in anhydrous proton‐exchange membrane applications. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013 , 51, 1311–1317     

Synthesis and properties of hyperbranched polybenzimidazoles via A2 + B3 approach

Hyperbranched polybenzimidazoles (HBPBIs) were successfully synthesized by condensation polymerization of 1,3,5‐benzenetricarboxylic acid (BTA) and 3,3′‐diaminobenzidine (DAB) in polyphosphoric acid (PPA) at 190 °C. Different monomer addition manners and molar ratios resulted in different polymers, that is, simultaneous addition of BTA and DAB with the molar ratio of 1:1 (manner 1) gave carboxyl‐terminated HBPBI (HBPBI‐1), whereas the addition of BTA portion‐wise to DAB solution in PPA with the molar ratio of DAB:BTA = 2:1 (manner 2) yielded amine‐terminated HBPBI (HBPBI‐2). The free carboxyl and amino groups of HBPBI‐1 and HBPBI‐2 could further react with o‐diaminobenzene and benzoic acid, respectively, to form the chemically modified polymers. Except HBPBI‐2, all the HBPBIs showed good solubility in some organic solvents (e.g., dimethyl sulfoxide and N,N‐dimethylacetamide). Thermogravimetric analysis measurement revealed that HBPBIs except HBPBI‐1 had high thermal stability (>450 °C). HBPBI membranes with good mechanical properties were obtained by crosslinking treatment of partially chemically modified HBPBIs with terephthaldehyde (TPA) during the film cast process. The HBPBI membranes had high phosphoric acid uptake and the phosphoric acid‐doped HBPBI‐6 (40% o‐diamino groups were reacted with benzoic acid) membrane showed higher tensile strength than the acid‐doped commercial PBI despite the higher doping level of the former. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1150–1158, 2007     

Effect of crosslinking on the properties of partially fluorinated anion exchange membranes

A series of crosslinked, ammonium‐functionalized, and partially fluorinated copolymers have been prepared and evaluated as anion exchange membranes. In order to investigate the effect of crosslinking on the membrane properties, precursor copolymers containing chloromethyl groups were crosslinked with various aliphatic diamines followed by quaternization with monoamines. Crosslinking was effective in lowering water absorbability at no expense of high hydroxide ion conductivity of the membranes. By tuning the degree of crosslinking (20 mol %) and crosslinker chain length (C6 and C8), the highest ion conductivity of 73 mS/cm (at 80°C in water) was achieved. Furthermore, alkaline stability of the membranes was also improved by the crosslinking; the remaining ion conductivity after the stability test (in 1 M potassium hydroxide at 80°C) was 8.2 mS/cm (after 1000 h) for the C6 crosslinked membrane and 1 mS/cm (after 500 h) for the uncrosslinked membrane, respectively. The ammonium groups attached with the crosslinkers seemed more alkaline stable than the uncrosslinked benzyltrimethylammonium groups, while the polymer main chain was intact under the harsh alkaline conditions. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 1059–1069     

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     

Transport properties of thermally responsive anion exchange membranes containing N‐isopropylacrylamide in electrodialysis

Anion exchange membranes containing N‐isopropylacrylamide as a component were prepared, and their electrochemical properties were examined. The membranes were crosslinked with ethylene glycol dimethacrylate and contained weakly basic or strongly basic anion exchange groups. The dependence of electrochemical properties of the membranes (electrical resistance, transport number of anions, water content, and reduced osmotic flux) on temperature was completely different from those of the anion exchange membrane without N‐isopropylacrylamide. For example, the reduced osmotic flux decreased with increasing temperature until 40°C, and the transport number of chloride ions increased with increasing temperature from 25.0°C, although those of the conventional membrane monotonously increased or decreased. The transport numbers of various anions relative to chloride ions in electrodialysis were evaluated at a different temperature. Although the transport numbers between anions did not change appreciably in the conventional membrane with temperature, those of the anion exchange membranes with N‐isopropylacrylamide changed with a temperature dependent on the hydration degree of anions: permeation of less‐hydrated anions such as nitrate and bromide ions compared with chloride ions increased with increasing temperature, and that of strongly hydrated anions such as sulfate and fluoride ions decreased with increasing temperature. This is based on the increase or decrease in uptake of the anions in the membrane with the change in temperature because hydrophilicity of the membranes changes with temperature due to the apparent aggregation of isopropyl groups in the membranes. And the change in electrochemical properties and transport numbers of various anions relative to chloride ions with temperature was completely reversible with increasing or decreasing temperature. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 793–804, 1999     

Proton‐conductive membranes based on blends of polyimides

We prepared novel proton‐conductivity membranes based on blends of sulfonated polyimides. The blend membranes were prepared from a sulfonated homopolyimide and a sulfonated copolyimide with a solvent‐casting method. The proton conductivities of the blend membranes were measured as functions of the temperature with four‐point‐probe electrochemical impedance spectroscopy. The conductivity of the membranes strongly depended on the sulfonated homopolyimide content and increased with an increase in the content. The proton conductivity of all the blended membranes indicated a higher value than that determined in Nafion at 80 °C, and this may mean that the proton transfer in the blend membranes is responsible for the ionic channels induced by the hydrophobic and hydrophilic domains. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1325–1332, 2007     

Highly alkaline stable anion exchange membranes from nonplanar polybenzimidazole with steric hindrance backbone

The anion exchange membranes (AEMs) with both high ionic conductivity and alkali stability are always the research focus of the AEM fuel cells. Here, a novel nonplanar polymer for AEMs manufacture, mPBI‐TP‐x‐R, with excellent hydroxide stability and satisfactory processability is reported for the first time. The serial mPBI‐TP‐x resins with steric hindrance were prepared by copolymerization among 3,3′,4,4′‐tetraaminobiphenyl, isophthalic acid and tetraphenyl‐terephthalic acid (TP) in different ratios under microwave condensation. The copolymers mPBI‐TP‐x were quaternized at N1/N3‐sites of benzimidazole unit in backbone with alkyl groups (R?CH₃, C₂H₅, n‐C₃H₇, or n‐C₄H₉) to prepare soluble ionomers, and the corresponding membranes in hydroxyl ion form were prepared by a solution casting method and subsequent ion‐exchange process. The chemical structure of all membranes was characterized using FTIR and ¹H NMR spectroscopy. The properties of ion exchange capacity, water uptake, swelling ratio, tensile strength, ionic conductivity, and alkaline stability were measured. Among the prepared membranes, the mPBI‐TP‐15%‐(n‐Bu) exhibited the excellent alkaline stability (only degradation ca. 5% under 1M NaOH aqueous solution at 60 °C for 800 h) and satisfactory OH^? conductivity (46.66 mS/cm at 80 °C). The current research provides a useful exploration to commercial application of alkaline fuel cell. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 1087–1096     

Liquid crystalline supramolecular crosslinked polymer complexes of ditopic rylenebisimides and P4VP

Perylenebisimide and naphthalenebisimide (PBI‐PDP and NBI‐PDP) end functionalized with pentadecyl phenol is designed as ditopic hydrogen bonding acceptors to form supramolecular crosslinked network with poly(4‐vinyl pyridine) (P4VP). The pristine PBI‐PDP has been grown as single crystals from DCM‐MeOH (dichloromethane‐methanol) mixture at room temperature, which revealed a P21 space group. Noticeably, the pentadecyl alkyl chain shields the aromatic perylene core on both sides resulting in the absence of π–π interaction in single‐crystal assembly. The naphthalenebisimide derivative exhibits thermotropic liquid crystalline behavior, while both the molecules exhibits lyotropic liquid crystalline phases in tetrahydrofuran (THF), which were characterized using a combination of differential scanning calorimeter, X‐ray diffraction, and polarized light microscopy. The hydrogen‐bonded complex of both the rylenebisimides with P4VP preserves the mesomorphic properties in THF. The electron transport mobility measured by space charge limited current measurements reveals a two orders of magnitude increase in the charge transport in the P4VP complex compared to that of the pristine molecule. The average electron mobility obtained is μ _e,avg: 10^?3 cm²/Vs for P4VP‐PBI compared to μ _e,avg: 10^?5 cm²/Vs for pristine PBI derivative. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 951–959