Patent Description:
Anion exchange polymers capable of forming anion-exchange membranes (AEMs) and ionomers (AEls) are provided for use in anion exchange membrane fuel cells (AEMFCs). More specifically, hydroxide exchange polymers are provided which are capable of forming hydroxide-exchange membranes (HEMs), and ionomers (HEls) for use in various applications such as hydroxide exchange membrane fuel cells (HEMFCs) and hydroxide exchange membrane electrolyzers (HEMEL).

Proton exchange membrane fuel cells (PEMFCs) are considered to be clean and efficient power sources. However, the high cost and unsatisfactory durability of catalysts are major barriers for large-scale commercialization of PEMFCs. By switching the polymer electrolyte from an "acidic" condition to a "basic" one, HEMFCs are able to work with non-precious metal catalysts and the catalysts are expected to be more durable. Other cheaper fuel cell components are also possible such as metal bipolar plates. <NPL>; <NPL>; <NPL>. However, currently available HEMs and HEls exhibit low alkaline/chemical stability, low hydroxide conductivity, high water uptake, and low mechanical integrity under dry conditions, especially after wet-dry cycles.

The biggest challenge for HEMs/HEls at present is achieving a high chemical stability at desired operation temperatures of <NUM> or more, and ideally <NUM> or more (e.g., in the presence of nucleophilic hydroxide ions). The most commonly encountered cationic functional groups (e.g., benzyl trimethyl ammonium and alkyl chain ammonium) can undergo a number of degradation processes in the presence of hydroxide ions nucleophiles by direct nucleophilic substitution and Hofmann elimination. Moreover, the polymer backbone of most base polymers for HEM/HEI applications (e.g., polysulfone and poly(phenylene oxide)) unavoidably contains ether linkages along the backbone, which makes the HEMs/HEIs potentially labile under high pH conditions. <NPL>; <NPL>. The strongly nucleophilic hydroxide ions attack these weak bonds and degrade the polymer backbone. Thus, alternative cationic groups, organic tethers, and polymer backbones are needed to enhance chemical stability of HEMs/HEls.

Another concern regarding current HEMs/HEls is their hydroxide conductivity. In comparison to Nafion, HEMs have intrinsically lower ionic conductivities under similar conditions, because the mobility of OH- is lower than that of H+. Greater ion-exchange capacity (IEC) is needed for HEMs/HEls to achieve greater hydroxide conductivity. However, high IEC usually leads to a membrane having high water uptake (i.e., a high swelling ratio), decreasing the morphological stability and mechanical strength of the membrane, especially after repeated wet-dry cycles. This highly swollen state when wet is a major reason for decreased flexibility and brittleness of HEMs when dry. The removal of the trade-off between high hydroxide conductivity and low water uptake has been a major setback in designing high-performance HEMs/HEls. Chemical cross-linking, physical reinforcement, side-chain polymerization, and blockcopolymer architecture have been tried to reduce water uptake while maintaining acceptable hydroxide conductivity, but these techniques bring challenging problems, e.g., reduced mechanical flexibility, decreased alkaline stability, and/or increased cost. <NPL>; <NPL>; <NPL>; <NPL>; <NPL>. Additionally, almost all side-chain or blockcopolymer HEMs are based on flexible aliphatic polymer chains due to limited available synthesis methods. As a result, the membranes still cannot provide morphological stability (low swell ratio) at high IECs and high temperature. <NPL>; <NPL>; <NPL>; <NPL>.

An additional obstacle to using HEMs is achievement of mechanical flexibility and strength in an ambient dry state. Most HEMs exhibit low mechanical strength and are very brittle in a completely dry state especially after being completely swollen. It is difficult to obtain and handle thin membranes that are large in size as needed for commercial use of HEMs. Without good mechanical properties, the ionomers cannot form and keep an adequate triple phase structure in the fuel cell electrode at high temperature, such as at or above <NUM>.

Another highly desirable feature of an HEI is that the polymer be soluble in a mixture of lower boiling alcohol and water but insoluble in pure alcohol or water so that the HEls can be readily incorporated into an electrode catalyst layer yet not be dissolved away by water or alcohol.

PEMFCs have recently been deployed as zero-emission power sources in commercially sold automobiles, with demonstrated long driving range and short refuelling time, which are two features preferred for customer acceptance. However, PEMFCs use platinum electrocatalysts and are not yet cost competitive with gasoline engines. Major approaches to PEMFC cost reduction include development of lowplatinum-loading, high power density membrane electrode assemblies (MEAs), and platinum-group-metal-free (PGM-free) cathode catalysts. A fundamentally different pathway to low cost fuel cells is to switch from PEMFCs to hydroxide exchange membrane fuel cells (HEMFCs) that, due to their basic operating environment, can work with PGM-free anode and cathode catalysts, and thus are potentially economically viable. To replace PEMFCs, however, HEMFCs have to provide a performance that matches PEMFC's, performance which in turn requires highly active anode and cathode catalysts as well as the highly chemically stable, ionically conductive, and mechanically robust hydroxide exchange membranes (HEMs)/hydroxide exchange ionomers (HEls) to build an efficient triple phase boundary and thus drastically improve the utilization of the catalyst particles and reduce the internal resistance.

HEMs/HEls are typically composed of organic cations tethered on a polymer backbone, with OH- being the balancing anion. A chemically stable HEM/HEI requires a stable organic cation and a stable polymer backbone. These hydroxide conductive organic cations have been obtained by introducing quaternary ammonium, imidazolium, guanidinium, phosphonium, sulfonium, ruthenium and cobaltocenium using chloromethylation of aromatic rings or bromination on the benzylic methyl groups of the polymers. Various polymer backbone structures-poly(olefins), poly(styrenes) poly(phenylene oxides), poly(phenylenes), poly(arylene ethers) -have been investigated recently. So far, most of HEMs/HEls based on traditional cation groups (such as benzyl trimethyl ammonium) and aromatic polymer backbones (such as polysulfone) have low alkaline/chemical stability, low hydroxide conductivity, high water uptake, and poor mechanical properties when dry.

Polymer backbones with ether linkages are generally vulnerable in alkaline medium and thus HEM/HEI having ether-free polymers backbones are highly desirable. Acid catalyzed hydroxylation reactions have been demonstrated to efficiently produce ether-free polymers backbones, and HEM/HEI with such backbones have proven to have good alkaline stability and mechanical properties.

<CIT> relates to the manufacture of anion exchange membranes based on polyaryl alkylenes.

Warshawsky A, et al. (<NPL>) relates to polyaryl crown ether alkylenes in the context of the manufacture of membranes.

To further enhance the alkaline stability of HEM/HEI under both high temperature and low relative humidity, cations other than the conventional ammonium cations are highly needed. Imidazolium cations, when properly substituted, have shown improved alkaline stability.

The scope of the invention is defined by the appended set of claims.

A polymer is provided which comprises structural units of Formulae (1A); (<NUM>'A); optionally (3A); and optionally (4A), wherein the structural units of Formulae (1A), (3A), (<NUM>'A) and (4A) have the structures:
<CHM>
<CHM>
<CHM>
and
<CHM>
wherein:.

An anion exchange polymer is also provided, which comprises a reaction product of a base and the polymer of the first aspect of this invention as described above, wherein the base comprises a hydroxide-, bicarbonate-, or carbonate-containing base.

A method of making an anion exchange polymer membrane comprising the anion exchange polymer is also provided. The method comprises:.

Another method of making an anion exchange polymer membrane comprising the anion exchange polymer is provided. The method comprises:.

An anion exchange membrane is also provided, optionally configured and sized to be suitable for use in a fuel cell, electrolyzer, electrodialyzer, solar hydrogen generator, flow battery, desalinator, sensor, demineralizer, water purifier, waste water treatment system, ion exchanger, or CO<NUM> separator, and the anion exchange membrane comprising the anion exchange polymer.

An anion exchange membrane fuel cell, electrolyzer, electrodialyzer, solar hydrogen generator, flow battery, desalinator, sensor, demineralizer, water purifier, waste water treatment system, ion exchanger, or CO<NUM> separator is also provided, the fuel cell, electrolyzer, electrodialyzer, solar hydrogen generator, flow battery, desalinator, sensor, demineralizer, water purifier, waste water treatment system, ion exchanger, or CO<NUM> separator comprising the anion exchange polymer.

Also provided is a reinforced electrolyte membrane, optionally configured and sized to be suitable for use in a fuel cell, electrolyzer, electrodialyzer, solar hydrogen generator, flow battery, desalinator, sensor, demineralizer, water purifier, waste water treatment system, ion exchanger, or CO<NUM> separator. The membrane comprises a porous substrate impregnated with the anion exchange polymer.

HEMs/HEIs formed from polymers with various pendant cationic groups and having intrinsic hydroxide conduction channels have been discovered which simultaneously provide improved chemical stability, conductivity, water uptake, good solubility in selected solvents, mechanical properties, and other attributes relevant to HEM/HEI performance. The attachment of the pendant side chains to the rigid aromatic polymer backbone of the polymer which is free of ether bonds allows fine tuning of the mechanical properties of the membrane and incorporation of alkaline stable cations, such as imidazoliums, phosphoniums and ammoniums, and provides enhanced stability to the polymer. HEMs/HEIs formed from these polymers exhibit superior chemical stability, anion conductivity, decreased water uptake, good solubility in selected solvents, and improved mechanical properties in an ambient dry state as compared to conventional HEM/HEIs. The inventive HEMFCs exhibit enhanced performance and durability at relatively high temperatures.

As a first aspect of the invention, a polymer is provided which comprises structural units of Formulae (1A); (<NUM>'A); optionally (3A); and optionally (4A), wherein the structural unit of Formulae (1A), (3A), (<NUM>'A) and (4A) have the structures:
<CHM>
<CHM>
<CHM>
and
<CHM>
wherein:.

The quaternary ammonium or phosphonium group has the formula (5A):
<CHM>.

The nitrogen-containing heterocyclic group is an optionally substituted pyrrole, pyrroline, pyrazole, pyrazoline, imidazole, imidazoline, triazole, pyridine, triazine, pyrazine, pyridazine, pyrimidine, azepine, quinoline, piperidine, pyrrolidine, pyrazolidine, imidazolidine, azepane, isoxazole, isoxazoline, oxazole, oxazoline, oxadiazole, oxatriazole, dioxazole, oxazine, oxadiazine, isoxazolidine, morpholine, thiazole, isothiazole, oxathiazole, oxathiazine, or caprolactam, wherein each substituent is independently alkyl, alkenyl, alkynyl, aryl, or aralkyl.

Preferably, the nitrogen-containing heterocyclic group is unsaturated such as pyrrole, pyrroline, pyrazole, pyrazoline, imidazole, imidazoline, triazole, pyridine, triazine, pyrazine, pyridazine, pyrimidine, azepine, or quinoline, and each substitutable position of the heterocycle is substituted independently with alkyl (e.g., methyl, ethyl, propyl, n-butyl) or aryl groups (e.g., phenyl with alkyl substituents).

The nitrogen-containing heterocyclic group can comprise an imidazolium having the formula (6A):
<CHM>
wherein: R<NUM>, R<NUM>, R<NUM>, and R<NUM> are each independently hydrogen, halide, alkyl, alkenyl, alkynyl or aryl, and the alkyl, alkenyl, alkynyl or aryl are optionally substituted with halide. Preferably, R<NUM> is <NUM>,<NUM>,<NUM>-alkylphenyl, and R<NUM>, R<NUM>, and R<NUM> are each independently C<NUM>-C<NUM> alkyl. An example of an imidazole as the nitrogen-containing heterocycle is <NUM>-butyl-<NUM>-mesityl-<NUM>,<NUM>-dimethyl-<NUM>H-imidazole-imidazole which has the formula:
<CHM>.

The structural unit of Formulae (3A) has the structure:
<CHM>
wherein n is <NUM>, <NUM>, <NUM> or <NUM>; R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, and R<NUM> are each independently hydrogen, halide, alkyl, alkenyl, alkynyl or aryl, and the alkyl, alkenyl, alkynyl or aryl are optionally substituted with halide; and wherein R<NUM> and R<NUM> are optionally linked to form a five membered ring optionally substituted with halide or alkyl.

For example, in the structural unit of formula (3A), at least one of R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, and R<NUM> can be halide or aryl, and the aryl can be optionally substituted with halide.

As another example, in the structural unit of formula (3A), R<NUM> and R<NUM> can be linked to form a five membered ring optionally substituted with halide or alkyl.

The structural unit of formula (3A) can be derived from an aromatic monomer comprising biphenyl, para-terphenyl, meta-terphenyl, para-quaterphenyl, <NUM>,<NUM>-dimethyl-<NUM>-fluorene, or benzene.

The structural unit of formula (<NUM>'A) has the structure:
<CHM>
wherein R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, and R<NUM> are each independently hydrogen, halide, alkyl, alkenyl, alkynyl or aryl, and the alkyl, alkenyl, alkynyl or aryl are optionally substituted with halide. The benzo ring shown in formula (<NUM>'A) as dashed lines and the R<NUM> group can be present or absent. If the benzo ring shown in formula (<NUM>'A) as dashed lines is absent, then the R<NUM> group is absent since the benzo ring of the structural unit would be bivalent. If the benzo ring shown in formula (<NUM>'A) as dashed lines is present, then the R<NUM> group is present since the benzo ring having the R<NUM> group would be monovalent.

For example, the structural unit can be derived from a dibenzo-<NUM>-crown-<NUM> polyether as in formula (<NUM>'A-<NUM>) wherein m' and n' are <NUM>, a dibenzo-<NUM>-crown-<NUM> polyether as in formula (<NUM>'A-<NUM>) wherein m' is <NUM> and n' is <NUM>, a dibenzo-<NUM>-crown-<NUM> polyether as in formula (<NUM>'A-<NUM>) wherein m' and n' are <NUM>, or a dibenzo-<NUM>-crown-<NUM> polyether as in formula (<NUM>'A-<NUM>) wherein m' and n' are <NUM>, and R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, and R<NUM> are as defined for formula (<NUM>'A):
<CHM>
or a benzo-<NUM>-crown-<NUM> polyether as in formula (<NUM>'A-<NUM>) wherein m' and n' are <NUM>, and R<NUM> and R<NUM> are as defined for formula (<NUM>'A):
<CHM>.

For example, in the structural unit of any of formulae (<NUM>'A)-(<NUM>'A-<NUM>), R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, and R<NUM>, if present, can be hydrogen or halide.

The structural unit of formula (<NUM>'A-<NUM>) can be derived from the respective dibenzo-crown ether wherein R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, and R<NUM> are each hydrogen. Dibenzo-<NUM>-crown-<NUM> polyether can be made from catechol and bis(chloroethyl) ether as described by <NPL>, and is commercially available. Dibenzo-<NUM>-crown-<NUM> polyether, dibenzo-<NUM>-crown-<NUM> polyether, and dibenzo-<NUM>-crown-<NUM> polyether are also commercially available.

The structural unit of formula (<NUM>'A-<NUM>) can be derived from benzo-<NUM>-crown-<NUM> polyether wherein R<NUM> and R<NUM> are each hydrogen. Benzo-<NUM>-crown-<NUM> polyether is commercially available.

The optional structural unit of Formula (4A) has the structure:
<CHM>
wherein each R<NUM> is independently alkyl, alkenyl, alkynyl, or a substituent having the formula (4B):
<CHM>
and the alkyl, alkenyl, or alkynyl are optionally substituted with fluoride; R<NUM>, R<NUM>, R<NUM>, R<NUM>, and R<NUM> are each independently hydrogen, halide, alkyl, alkenyl, alkynyl or aryl, and the alkyl, alkenyl, alkynyl or aryl are optionally substituted with halide.

For example, in the structural unit of formula (4A), R<NUM> can be alkyl, alkenyl, or alkynyl, and the alkyl, alkenyl, or alkynyl can be optionally substituted with fluoride.

As another example, in the structural unit of formula (4A), R<NUM> can be the substituent of formula (4B) and at least one of R<NUM>, R<NUM>, R<NUM>, R<NUM> and R<NUM> can be halide or aryl, and the aryl can be optionally substituted with fluoride.

As yet another example, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, and R<NUM> can each independently be hydrogen, or alkyl optionally substituted with fluoride, and R<NUM> can be alkyl optionally substituted with fluoride or the substituent of formula (4B).

In other instances, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, and R<NUM> can each independently be hydrogen, methyl, ethyl, propyl, butyl, pentyl, or hexyl, or methyl, ethyl, propyl, butyl, pentyl, or hexyl optionally substituted with fluoride, and R<NUM> can be methyl, ethyl, propyl, butyl, pentyl, or hexyl optionally substituted with fluoride or the substituent of formula (4B).

A sum of the mole fractions of the structural unit of Formula (1A) and Formula (4A) in the polymer can be about equal to a sum of the mole fractions of the structural units of Formulae (3A) and (<NUM>'A) in the polymer, and the ratio of the mole fraction of the structural unit of Formula (1A) in the polymer to the sum of the mole fractions of the structural units of Formulae (3A) and (<NUM>'A) in the polymer can be from about <NUM> to <NUM>.

A mole ratio of a sum of the mole fractions of the structural unit of Formula (1A) and Formula (4A) to a sum of the mole fractions of Formulae (3A) and (<NUM>'A) in the polymer can be from about <NUM>:<NUM> to about <NUM>:<NUM>, and the ratio of the mole fraction of the structural unit of Formula (1A) to the sum of the mole fractions of the structural units of Formulae (3A) and (<NUM>'A) can be from about <NUM> to <NUM>.

The mole ratio of the sum of the mole fractions of the structural unit of Formula (1A) and Formula (4A) to the sum of the mole fractions of Formulae (3A) and (<NUM>'A) in the polymer can be from about <NUM>:<NUM> to about <NUM>:<NUM>.

A second aspect of the invention is an anion exchange polymer which comprises a reaction product of a base and any one of the polymers as described above in the first aspect of the invention, wherein the base comprises a hydroxide-, bicarbonate-, or carbonate-containing base.

Preferably, the hydroxide-containing base is sodium hydroxide or potassium hydroxide; the bicarbonate-containing base such is sodium bicarbonate or potassium bicarbonate; or the carbonate-containing base is sodium carbonate or potassium carbonate.

Representative anion exchange polymers (first six polymers not according to the invention) include the following wherein x is <NUM>-<NUM>:
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>.

An imidazolium tethered-poly(aryl alkylene) polymer or imidazolium tethered-poly(aryl-crown ether-alkylene) polymer not being part of the invention can be an hydroxide exchange polymer comprising a poly(aryl alkylene) or poly(aryl-crown ether-alkylene) backbone free of ether linkages, and having: water uptake of not more than <NUM>% based on the dry weight of the polymer when immersed in pure water at <NUM>; or hydroxide conductivity in pure water at <NUM> of at least <NUM>/cm. Also, a polymer not being part of the invention can be: stable to degradation (as evidenced by no change in the <NUM>H NMR spectra) when immersed in <NUM> potassium hydroxide at <NUM> for <NUM>,<NUM> hours; stable to degradation (as evidenced by no change in the<NUM>H NMR spectra) when immersed in <NUM> potassium hydroxide at <NUM> for <NUM> hours; stable to degradation (as evidenced by no change in the <NUM>H NMR spectra) when kept at relative humidity of <NUM>% and <NUM>% at <NUM> for <NUM> hours; insoluble in pure water and isopropanol at <NUM>, but soluble in a <NUM>/<NUM> mixture by weight of water and ethanol at <NUM>. Also, a polymer not being part of the invention can have a tensile strength of at least <NUM> MPa and/or elongation at break of at least <NUM>%.

Uptake of the imidazolium tethered-poly(aryl-crown ether-alkylene) polymer not being part of the invention can be no more than <NUM>% when the polymer is crosslinked with a crosslinking agent or is chemically bound to a membrane. For example, the water uptake of polycrownether-CF3-TMA (also known as PCE-C5-QA-<NUM>) of Example <NUM> was <NUM>% and of poly(aryl-crown ether-alkylene) -CF3-IM of Example <NUM> was about <NUM>% when measured, but can be decreased by crosslinking or chemically binding the polymer to a membrane.

Crosslinking agents for use in crosslinking any of the polymers described herein include, for example, dibromoalkanes (dibromohexanes, dibromobutane), diiodoalkanes (diiodohexanes, diiodobutane), and ammonium cationcontaining dibromoalkanes and diiodoalkanes.

The imidazolium tethered-poly(aryl alkylene) polymer or imidazolium tethered-poly(aryl-crown ether-alkylene) polymer not being part of the invention can be an hydroxide exchange polymer comprising an imidazolium-tethered poly(aryl alkylene) or poly(aryl-crown ether-alkylene) backbone free of ether linkages, and having a peak power density of at least <NUM> mW/cm<NUM> when the polymer is used as an hydroxide exchange membrane of an hydroxide exchange membrane fuel cell and is loaded at <NUM>% as an hydroxide exchange ionomer in cathodic and anodic catalyst layers of the fuel cell, the fuel cell having <NUM>Pt cm-<NUM> PtRu/C on anode, <NUM>Pt cm-<NUM> PtRu/C on cathode and test conditions being hydrogen flow rate of <NUM>/min, oxygen flow rate of <NUM>/min, cell temperature of <NUM>, and anode and cathode humidifier temperature at <NUM>, and <NUM>, respectively.

Preferably, the aryl linkages of the imidazolium tethered-poly(aryl alkylene) polymer backbone free of ether linkages comprise p-phenyl, and the alkylene linkages comprise hydroxide bicarbonate, or carbonate anions, or a combination thereof. The imidazolium tethered-poly(aryl-crown ether-alkylene) polymer backbone free of ether linkages also preferably comprises dibenzo-<NUM>-crown-<NUM>, dibenzo-<NUM>-crown-<NUM> polyether, dibenzo-<NUM>-crown-<NUM> polyether, or dibenzo-<NUM>-crown-<NUM> polyether.

The aryl linkages of the imidazolium tethered-poly(aryl alkylene) polymer backbone can be derived, for example, from biphenyl, para-terphenyl, meta-terphenyl, para-quaterphenyl, <NUM>,<NUM>-dimethyl-<NUM>-fluorene, or benzene monomers. The imidazolium tethered-poly(aryl-crown ether-alkylene) polymer backbone free of ether linkages can be derived, for example, from dibenzo-<NUM>-crown-<NUM>, dibenzo-<NUM>-crown-<NUM> polyether, dibenzo-<NUM>-crown-<NUM> polyether, or dibenzo-<NUM>-crown-<NUM> polyether.

The alkylene linkages of the imidazolium tethered-poly(aryl alkylene) backbone are derived from <NUM>-bromo-<NUM>,<NUM>,<NUM>-trifluoroheptan-<NUM>-one monomers.

The imidazolium tethered-poly(aryl alkylene) polymer backbone or imidazolium tethered-poly(aryl-crown ether-alkylene) polymer backbone can further comprise <NUM>,<NUM>,<NUM>-trifluoroethylbenzene linkages derived from <NUM>,<NUM>,<NUM>-trifluoroacetophenone monomer, or trifluoromethyl methylene linkages derived from trifluoromethyl ketone monomer, such as <NUM>,<NUM>, <NUM>-trifluoropropane linkages derived from <NUM>,<NUM>,<NUM>-trifluoroacetone.

A third aspect of the invention is a method of making an anion exchange polymer membrane comprising the anion exchange polymer in the second aspect of the invention. The method comprises: reacting the cation-functionalized trifluoroketone monomer, the optional trifluoromethyl ketone monomer, the crown ether monomer, and the optional aromatic monomer in the presence of an organic solvent and a polymerization catalyst to form a cation-functionalized intermediate polymer; and dissolving the cation-functionalized intermediate polymer in a solvent to form a polymer solution; and casting the polymer solution to form a polymer membrane; and exchanging anions of the polymer membrane with hydroxide, bicarbonate, or carbonate ions or a combination thereof to form the anion exchange polymer membrane.

For example, a cation-functionalized trifluoroketone monomer such as an imidazolium functionalized <NUM>-bromo-<NUM>,<NUM>,<NUM>-trifluoroheptan-<NUM>-one, an optional trifluoromethyl ketone monomer such as <NUM>,<NUM>,<NUM>-trifluoroacetophenone or <NUM>,<NUM>,<NUM>-trifluoroacetone, and an aromatic monomer such as benzene, biphenyl, p-terphenyl, m-terphenyl or p-quaterphenyl or a crown ether monomer such as dibenzo-<NUM>-crown-<NUM>, dibenzo-<NUM>-crown-<NUM> polyether, dibenzo-<NUM>-crown-<NUM> polyether, or dibenzo-<NUM>-crown-<NUM> polyether can be placed in a stirred container and dissolved or dispersed into an organic solvent. A polymerization catalyst in a solvent can then be added dropwise over up to <NUM> minutes at -<NUM> to <NUM>. Thereafter, the reaction is continued at this temperature for about <NUM> to about <NUM> hours. The resulting solution is poured slowly into an aqueous solution of ethanol. The solid obtained is filtered, washed with water and immersed in <NUM> K2CO3 at room temperature for about <NUM> to <NUM> hours. Finally, the product is filtered, washed with water and dried completely under vacuum to form a cation-functionalized polymer. The cation functionalized polymer is then subjected to anion exchange, for example in <NUM> KOH for hydroxide exchange, at about <NUM> to <NUM> for about <NUM> to <NUM> hours, followed by washing and immersion in DI water for about <NUM> to <NUM> hours under an oxygen-free atmosphere to remove residual KOH.

A representative reaction scheme for the third aspect of the invention is shown below, wherein R<NUM>, R<NUM>, R<NUM>, R<NUM>, and R<NUM> are each independently hydrogen, alkyl, alkenyl, phenyl or alkynyl, and the alkyl, alkenyl, phenyl or alkynyl are optionally substituted with a halide; R<NUM> is phosphonium or nitrogen-containing heterocycle; n is the number of repeat units in the polymer; q is <NUM>-<NUM>; and x is <NUM>-<NUM>:
<CHM>
<CHM>.

A fourth aspect of the invention is a method of making an anion exchange polymer membrane comprising the anion exchange polymer in the second aspect of the invention. The method comprises: reacting the halogenated trifluoroketone monomer, the optional trifluoromethyl ketone monomer, the crown ether monomer, and the optional aromatic monomer in the presence of an organic solvent and a polymerization catalyst to form a halogen-functionalized polymer; and reacting the halogen-functionalized polymer with the tertiary phosphane compound or the nitrogen-containing heterocycle or a salt thereof in the presence of an organic solvent to form a cation-functionalized polymer; and dissolving the cation-functionalized polymer in a solvent to form a polymer solution; and casting the polymer solution to form a polymer membrane; and exchanging anions of the polymer membrane with hydroxide, bicarbonate, or carbonate ions or a combination thereof to form the anion exchange polymer membrane.

For example, a halogenated trifluoroketone monomer such as <NUM>-bromo-<NUM>,<NUM>,<NUM>-trifluoroheptan-<NUM>-one, an optional trifluoromethyl ketone monomer such as <NUM>,<NUM>,<NUM>-trifluoroacetophenone or <NUM>,<NUM>,<NUM>-trifluoroacetone, and an aromatic monomer such as benzene, biphenyl, p-terphenyl, m-terphenyl or p-quaterphenyl or crown ether monomer such as dibenzo-<NUM>-crown-<NUM>, dibenzo-<NUM>-crown-<NUM> polyether, dibenzo-<NUM>-crown-<NUM> polyether, or dibenzo-<NUM>-crown-<NUM> polyether can be placed in a stirred container and dissolved or dispersed into an organic solvent. A polymerization catalyst in a solvent can then be added dropwise over up to <NUM> minutes at -<NUM> to <NUM>. Thereafter, the reaction is continued at this temperature for about <NUM> to about <NUM> hours. The resulting solution is poured slowly into an aqueous solution of ethanol. The solid obtained is filtered, washed with water and immersed in <NUM> K2CO3 at room temperature for about <NUM> to <NUM> hours. Finally, the product is filtered, washed with water and dried completely under vacuum to form a halogen-functionalized polymer.

The halogen functionalized polymer is then placed in a stirred container with the quaternary phosphonium compound or the nitrogen-containing heterocycle or a salt thereof such as a functionalized imidazole and dissolved or dispersed into an organic solvent. The reaction is continued at a temperature of about <NUM> to <NUM> for about <NUM> to about <NUM> hours. The resulting solution is then cast to form a polymer membrane. The polymer membrane is then subjected to anion exchange, for example in <NUM> KOH for hydroxide exchange, at about <NUM> to <NUM> for about <NUM> to <NUM> hours, followed by washing and immersion in DI water for about <NUM> to <NUM> hours under an oxygen-free atmosphere to remove residual KOH.

A representative reaction scheme for the fourth aspect of the invention is shown below, wherein R<NUM>, R<NUM>, R<NUM>, R<NUM>, and R<NUM> are each independently hydrogen, alkyl, alkenyl, phenyl or alkynyl, and the alkyl, alkenyl, phenyl or alkynyl are optionally substituted with a halide; R<NUM> is a quaternary ammonium or phosphonium group or nitrogen-containing heterocyclic group as defined in the first aspect of the invention; n is the number of repeat units in the polymer; q is <NUM>-<NUM>; and x is <NUM>-<NUM>:
<CHM>
<CHM>
<CHM>.

A fifth aspect of the invention is an anion exchange membrane, optionally configured and sized to be suitable for use in a fuel cell, electrolyzer, electrodialyzer, solar hydrogen generator, flow battery, desalinator, sensor, demineralizer, water purifier, waste water treatment system, ion exchanger, or CO<NUM> separator, and comprising the anion exchange polymer of the second aspect of the invention.

The anion exchange polymer can be made into reinforced hydroxide exchange membranes as described below. Such reinforced hydroxide exchange membranes can be prepared by a method which comprises wetting a porous substrate in a liquid to form a wetted substrate; dissolving the poly(aryl alkylene) polymer in a solvent to form a homogeneous solution; applying the solution onto the wetted substrate to form the reinforced membrane; drying the reinforced membrane; and exchanging anions of the reinforced membrane with hydroxide ions to form the reinforced hydroxide exchange polymer membrane. The solution can be applied to the wetted substrate by any known membrane formation technique such as casting, spraying, or doctor knifing.

The resulting reinforced membrane can be impregnated with the poly(aryl alkylene) polymer multiple times if desired by wetting the reinforced membrane again and repeating the dissolving, casting and drying steps.

The polymerization catalyst used in forming the polymer can comprise trifluoromethanesulfonic acid, pentafluoroethanesulfonic acid, heptafluoro-<NUM>-propanesulfonic acid, trifluoroacetic acid, perfluoropropionic acid, heptafluorobutyric acid, or a combination thereof.

Each of the organic solvents used in the any of the above methods can be independently selected from polar aprotic solvents (e.g., dimethyl sulfoxide, <NUM>-methyl-<NUM>-pyrrolidinone, <NUM>-methyl-<NUM>-pyrrolidone, <NUM>-methyl-<NUM>-pyrrolidone, or dimethylformamide) or other suitable solvents including, but are not limited to, methylene chloride, trifluoroacetic acid, trifluoromethanesulfonic acid, chloroform, <NUM>,<NUM>,<NUM>,<NUM>-tetrachloroethane, dimethylacetamide or a combination thereof.

The solvent in the dissolving step can comprise methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol, a pentanol, a hexanol, dimethyl sulfoxide, <NUM>-methyl-<NUM>-pyrrolidone, dimethylformamide, chloroform, ethyl lactate, tetrahydrofuran, <NUM>-methyltetrahydrofuran, water, phenol, acetone, or a combination thereof.

The liquid used to wet the porous substrate can be a low boiling point solvent such as a lower alcohol (e.g., methanol, ethanol, propanol, isopropanol) and/or water. Preferably, the liquid is anhydrous ethanol.

Additional aspects of the invention are described below.

An anion exchange membrane such as a hydroxide exchange membrane is also provided. The membrane is configured and sized to be suitable for use in a fuel cell, electrolyzer, electrodialyzer, solar hydrogen generator, flow battery, desalinator, sensor, demineralizer, water purifier, waste water treatment system, ion exchanger, or CO<NUM> separator, and comprises any of the poly(aryl alkylene) polymers as described herein.

A reinforced electrolyte membrane such as a reinforced hydroxide exchange membrane is also provided to increase the mechanical robustness of the anion exchange membrane for stability through numerous wet and dry cycles (relative humidity cycling) in a fuel cell. The membrane is configured and sized to be suitable for use in a fuel cell, electrolyzer, electrodialyzer, solar hydrogen generator, flow battery, desalinator, sensor, demineralizer, water purifier, waste water treatment system, ion exchanger, or CO<NUM> separator, and comprises a porous substrate impregnated with any of the poly(aryl alkylene) polymers as described herein. Methods for preparing reinforced membranes are well known to those of ordinary skill in the art such as those disclosed in <CIT>and <CIT>.

The porous substrate can comprise a membrane comprised of polytetrafluoroethylene, polypropylene, polyethylene, poly(ether ketone), polyaryletherketone, imidazolium-tethered poly(aryl alkylene), imidazole -tethered poly(aryl alkylene), polysulfone, perfluoroalkoxyalkane, or a fluorinated ethylene propylene polymer, or other porous polymers known in the art such as the dimensionally stable membrane from Giner for use in preparing reinforced membranes for fuel cells. Such porous substrates are commercially available, for example, from W. Gore & Associates.

The porous substrate can have a porous microstructure of polymeric fibrils. Such substrates comprised of polytetrafluoroethylene are commercially available. The porous substrate can comprise a microstructure of nodes interconnected by fibrils.

The interior volume of the porous substrate can be rendered substantially occlusive by impregnation with the poly(aryl alkylene) polymer as described herein.

The porous substrate can have a thickness from about <NUM> micron to about <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM> microns. Preferably, the porous substrate has a thickness from about <NUM> microns to about <NUM> microns, or from about <NUM> microns to about <NUM> microns.

Polymers of the invention having high water uptake are useful as ionomers in electrolyzers or fuel cells if the polymers are adhered to a catalyst layer so as not to be washed away during operation of the electrolyzer or fuel cell. Adherence can be achieved by chemically binding the polymer to a membrane or catalyst layer within the electrolyzer or fuel cell, or by crosslinking the polymer with crosslinkers such as those described above. For example, functional groups on a polymer of the invention such as bromoalkyl groups can be reacted with functional groups on a membrane, such as amine groups, to bind the polymer ionomer to the membrane.

When polymers of the invention are used as a membrane, it is preferred that the water uptake of the polymer ranges from about <NUM> to about <NUM>% to maintain the mechanical strength of the membrane.

The poly(aryl alkylene) polymers or poly(aryl-crown ether-alkylene) polymers can be used in HEMFCs such as a typical fuel cell <NUM> as shown in <FIG> illustrates a typical fuel cell <NUM> with an anode portion <NUM> (illustrated on the left) and a cathode portion <NUM> (illustrated on the right) which are separated by an electrolyte membrane <NUM>. The electrolyte membrane <NUM> can be any membrane comprising any of the poly(aryl alkylene) polymers or poly(aryl-crown ether-alkylene) polymers as described herein, and can be a reinforced membrane. Supporting members are not illustrated. The anode portion carries out an anode half-reaction which oxidizes fuel releasing electrons to an external circuit and producing oxidized products. The cathode portion carries out a cathode half-reaction which reduces an oxidizer consuming electrons from the external circuit. The gas diffusion layers (GDLs) <NUM> and <NUM> serve to deliver the fuel <NUM> and oxidizer <NUM> uniformly across the respective catalyst layers <NUM> and <NUM>. Charge neutrality is maintained by a flow of ions from the anode to the cathode for positive ions and from cathode to anode for negative ions. The dimensions illustrated are not representative, as the electrolyte membrane is usually selected to be as thin as possible while maintaining the membrane's structural integrity.

In the case of the illustrated hydroxide exchange membrane fuel cell (HEMFC), the anode half-reaction consumes fuel and OH- ions and produces waste water (as well as carbon dioxide in the case of carbon containing fuels). The cathode half reaction consumes oxygen and produces OH- ions, which flow from the cathode to the anode through the electrolyte membrane. Fuels are limited only by the oxidizing ability of the anode catalyst and typically include hydrogen gas, methanol, ethanol, ethylene glycol, and glycerol. Preferably, the fuel is H2 or methanol. Catalysts are usually platinum (Pt), silver (Ag), or one or more transition metals, e.g., Ni. In the case of a PEMFC, the anode half-reaction consumes fuel and produces H+ ions and electrons. The cathode half reaction consumes oxygen, H+ ions, and electrons and produces waste water, and H+ ions (protons) flow from the anode to the cathode through the electrolyte membrane.

It can, therefore, be appreciated how an electrolyte membrane made from a poly(aryl alkylene) polymer or poly(aryl-crown ether-alkylene) polymer significantly improves fuel cell performance. First, greater fuel cell efficiency requires low internal resistance, and therefore, electrolyte membranes with greater ionic conductivity (decreased ionic resistance) are preferred. Second, greater power requires greater fuel cell currents, and therefore, electrolyte membranes with greater ion-current carrying capacity are preferred. Also, practical electrolyte membranes resist chemical degradation and are mechanically stable in a fuel cell environment, and also should be readily manufactured.

The poly(aryl alkylene) polymers or poly(aryl-crown ether-alkylene) polymers can be used in HEMELs such as an electrolyzer <NUM> as shown in <FIG> illustrates an electrolyzer <NUM> with an anode portion <NUM> (illustrated on the left) and a cathode portion <NUM> (illustrated on the right) which are separated by an electrolyte membrane <NUM>. The electrolyte membrane <NUM> can be any membrane comprising any of the poly(aryl alkylene) polymers or poly(aryl-crown ether-alkylene) polymers as described herein, and can be a reinforced membrane. Supporting members are not illustrated. The anode portion carries out an anode half-reaction which oxidizes ions releasing electrons to an external circuit and producing oxidized products. The cathode portion carries out a cathode half-reaction which reduces an oxidizer consuming electrons from the external circuit. The gas diffusion layers (GDLs) <NUM> and <NUM> serve to release the oxidizer <NUM> and fuel <NUM> uniformly across the respective catalyst layers <NUM> and <NUM>. Charge neutrality is maintained by a flow of ions from the anode to the cathode for positive ions and from cathode to anode for negative ions. The dimensions illustrated are not representative, as the electrolyte membrane is usually selected to be as thin as possible while maintaining the membrane's structural integrity.

In the case of the illustrated hydroxide exchange membrane fuel cell (HEMFC), the anode half-reaction consumes OH- ions and produces oxygen. The cathode half reaction consumes water and produces hydrogen and OH- ions, which flow from the cathode to the anode through the electrolyte membrane. Fuels are limited only by the oxidizing ability of the cathode catalyst and typically include hydrogen gas, methanol, ethanol, ethylene glycol, and glycerol. Preferably, the fuel is H<NUM> or methanol. Catalysts are usually platinum (Pt), silver (Ag), or one or more transition metals, e.g., Ni.

It can, therefore, be appreciated how an electrolyte membrane made from a poly(aryl alkylene) polymer or poly(aryl-crown ether-alkylene) polymer significantly improves electrolyzer performance. First, greater electrolyzer efficiency requires low internal resistance, and therefore, electrolyte membranes with greater ionic conductivity (decreased ionic resistance) are preferred. Second, greater fuel production requires greater electrolyzer currents, and therefore, electrolyte membranes with greater ion-current carrying capacity are preferred. Also, practical electrolyte membranes resist chemical degradation and are mechanically stable in an electrolyzer environment, and also should be readily manufactured.

Although a principal application for the poly(aryl alkylene) polymers or poly(aryl-crown ether-alkylene) polymers is for energy conversion such as in use in anion exchange membranes, hydroxide exchange membranes, anion exchange membrane fuel cells, and hydroxide exchange membrane fuel cells, the anion/hydroxide exchange ionomers and membranes can be used for many other purposes such as use in fuel cells (e.g., hydrogen/alcohol/ammonia fuel cells); electrolyzers (e.g., water/carbon dioxide/ammonia electrolyzers), electrodialyzers; ion-exchangers; solar hydrogen generators; desalinators (e.g., desalination of sea/brackish water); demineralizers (e.g., demineralization of water); water purifiers (e.g., ultra-pure water production); waste water treatment systems; concentration of electrolyte solutions in the food, drug, chemical, and biotechnology fields; electrolysis (e.g., chlor-alkali production and H2/O2 production); energy storage (e.g., super capacitors, metal air batteries and redox flow batteries); sensors (e.g., pH/RH sensors); and in other applications where an anion-conductive ionomer is advantageous.

Having described the invention in detail, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims.

The following non-limiting examples are provided to further illustrate the present invention.

An imidazolium-tethered poly(aryl alkylene) polymer was prepared from <NUM>-bromo-<NUM>,<NUM>,<NUM>-trifluoroheptan-<NUM>-one, <NUM>,<NUM>,<NUM>-trifluoroacetone and biphenyl (referred to as BP-CF3-IM-x, wherein x is the mole ratio of <NUM>-bromo-<NUM>,<NUM>,<NUM>-trifluoroheptan-<NUM>-one to biphenyl and is from <NUM> to <NUM>). BP-CF3-IM-x was prepared by three major steps: (<NUM>) synthesis of a bromide-functionalized polymer, (<NUM>) synthesis of an imidazolium-functionalized polymer, and (<NUM>) membrane casting and hydroxide exchange. The reaction scheme is depicted below, wherein n is the number of repeat units in the polymer:
<CHM>.

Other BP-CF3-IM-x membranes are prepared by using different mole ratios of <NUM>-bromo-<NUM>,<NUM>,<NUM>-trifluoroheptan-<NUM>-one to biphenyl.

Increasing the temperature also enhances the hydroxide conductivity of the membrane samples.

An imidazolium-tethered poly(aryl alkylene) polymer was prepared from <NUM>-bromo-<NUM>,<NUM>,<NUM>-trifluoroheptan-<NUM>-one, <NUM>,<NUM>,<NUM>-trifluoroacetone and p-terphenyl (referred to as TP-CF3-IM-x, wherein x is the mole ratio of <NUM>-bromo-<NUM>,<NUM>,<NUM>-trifluoroheptan-<NUM>-one to p-terphenyl and is from <NUM> to <NUM>). TP-CF3-IM-x was prepared by three major steps: (<NUM>) synthesis of a bromide-functionalized polymer, (<NUM>) synthesis of an imidazolium-functionalized polymer, and (<NUM>) membrane casting and hydroxide exchange. The reaction scheme is depicted below, wherein n is the number of repeat units in the polymer:
<CHM>.

(<NUM>) Synthesis of a bromide-functionalized polymer (TP-CF3-Br-<NUM>). To a <NUM> three-necked flask equipped with overhead mechanical stirrer, <NUM>-bromo-<NUM>,<NUM>,<NUM>-trifluoroheptan-<NUM>-one (<NUM>, <NUM> mmol) and p-terphenyl (<NUM>, <NUM> mmol) were dissolved into methylene chloride (<NUM>). Trifluoromethanesulfonic acid (TFSA) (<NUM>) was then added dropwise over <NUM> minutes at <NUM>. Thereafter, the reaction was continued at this temperature for <NUM> hours. The resulting viscous, brown solution was poured slowly into ethanol. The precipitated solid was filtered, washed with water and immersed in <NUM> K<NUM>CO<NUM> at room temperature for <NUM> hours. Finally, the product was filtered, washed with water and dried completely at <NUM> under vacuum. The yield of the polymer was nearly <NUM>%. <NUM>H NMR (CDCl<NUM>, δ, ppm): <NUM> (H<NUM>, <NUM>), <NUM> (H<NUM>, <NUM>), <NUM> (H<NUM>, <NUM>), <NUM> (H<NUM>, <NUM>), <NUM> (H<NUM>, <NUM>), <NUM> (H<NUM>, <NUM>), <NUM> (H<NUM>, <NUM>), <NUM> (H<NUM>, <NUM>) (<FIG>). (<NUM>) Synthesis of imidazolium-functionalized polymer (TP-CF3-IM-<NUM>). To a <NUM> one-necked flask equipped with magnetic bar, the bromide-functionalized polymer (<NUM>, <NUM> mmol) and the functionalized imidazole (<NUM>, <NUM> mmol) were added into NMP (<NUM>). The solution was stirred over <NUM> hours <NUM>. The resulting yellow solution was used to cast a membrane. The membrane was washed consequently three times with hydrochloride solution (PH = <NUM>) and DI water, and dried completely at <NUM> under vacuum. The yield of the polymer TP-CF3-IM-x was almost <NUM>%. <NUM> NMR (DMSO-d6, δ, ppm): <NUM> (H13, <NUM>), <NUM> (H1, <NUM>), <NUM> (H2, <NUM>), <NUM> (H3, <NUM>), <NUM>-<NUM> (H4, <NUM>), <NUM>-<NUM> (H5, H6, H12, <NUM>), <NUM> (H7, <NUM>), <NUM>-<NUM> (H8, H9, H10, <NUM>), <NUM> (H11, <NUM>) (<FIG>). (<NUM>) TP-CF3-IM-x membrane casting and hydroxide exchange. Membrane was prepared by dissolving the TP-CF3-IM-x polymer (<NUM>) in NMP (<NUM>) and casting on a clear glass plate at <NUM> for <NUM> hours. The membrane (in bromide form) was peeled off from a glass plate in contact with deionized (DI) water. The membrane in hydroxide form was obtained by ion exchange in <NUM> KOH at <NUM> for <NUM> hours, followed by washing and immersion in DI water for <NUM> hours under argon to remove residual KOH. (<NUM>) Water uptake and hydroxide conductivity. When x =<NUM>, TP-CF3-IM-<NUM> has conductivity of <NUM>/cm at <NUM>. It has low water uptake and dimensional swelling ratio in bicarbonate form (as shown in Table <NUM>) in pure water from <NUM> to <NUM>.

(<NUM>) Hydroxide exchange membrane fuel cell (HEMFC) performance. Although TP-CF3-IM-x polymer membranes are expected to have superior chemical stability, hydroxide conductivity, low water uptake, good solubility and mechanical properties, the most practical evaluation of these materials is their performance in HEMFC single cells as an HEI in the catalyst layer and as the HEM. Membrane-electrode assemblies (MEAs) can be fabricated by depositing <NUM><NUM> electrode onto both sides of a TP-CF3-IM-x polymer membrane with a robotic sprayer (Sono-Tek ExactaCoat). The electrode ink is prepared by adding <NUM> of catalyst (Tanaka Kikinzoku Kogyo, or TKK, <NUM>% Pt on high-surface-area C) and a desired amount of ionomer (a TP-CF3-IM-x polymer, prepared by dissolving the BP-CF3-IM-x polymer in a water and isopropanol mixture) to <NUM> of water and <NUM> of isopropanol, followed by sonicating for <NUM> hour. The catalyst loading is <NUM>Pt cm-<NUM> PtRu/C on anode, <NUM>Pt cm-<NUM> PtRu/C on cathode. The sandwich is completed by adding a rubber gasket, a GDL (SGL25CC), and a graphite flow field (ElectroChem) to each side of the MEA. Performance is characterized with a fuel cell test system equipped with a back pressure module (Scribner 850e)( Materials: TP100-CF3-IM-<NUM> membrane, ionomer loading of <NUM> %, catalyst: <NUM>Pt cm-<NUM> PtRu/C on anode, <NUM>Pt cm-<NUM> PtRu/C on cathode. Test conditions: <NUM>, anode humidifier temperature: <NUM>, cathode anode humidifier temperature: <NUM>, H<NUM> flow rate: <NUM>/min, O<NUM> flow rate: <NUM>/min. Normally, the cell is activated for <NUM> minutes at <NUM> mA/cm<NUM> and another <NUM> minutes at <NUM> mA/cm<NUM>. After activation, performance is recorded by scanning current. Results are shown in Figure <NUM>. (<NUM>) Hydroxide exchange membrane electrolyzer (HEMEL) performance. Although TP-CF3-IM-x polymer membranes are expected to have superior chemical stability, hydroxide conductivity, low water uptake, good solubility and mechanical properties, the most practical evaluation of these materials is their performance in HEMEL cells as an HEI in the catalyst layer and as the HEM. Membrane-electrode assemblies (MEAs) were fabricated by depositing <NUM><NUM> electrode onto both sides of a TP-CF3-IM-x polymer membrane with a robotic sprayer (Sono-Tek ExactaCoat). The electrode ink was prepared by adding <NUM> of catalyst (Tanaka Kikinzoku Kogyo, or TKK, <NUM>% Pt on high-surface-area C) and a desired amount of ionomer (a TP-CF3-IM-x polymer, prepared by dissolving the TP-CF3-IM-x polymer in a water and ethanol mixture) to <NUM> of water and <NUM> of ethanol, followed by sonicating for <NUM> hour. The catalyst loading was <NUM> Pt/cm<NUM>. Pt-coated Ti plate and TGP-H-<NUM> Toray carbon paper (<NUM>% wet proofing) were the gas diffusion layers for the anode and cathode sides, respectively. The cell and de-ionized water temperatures were kept at a constant temperature. Performance was characterized with an Arbin testing system (Materials: TP100-CF3-IM-<NUM> membrane, ionomer loading of <NUM> %, catalyst: <NUM>Pt cm-<NUM> Pt/C on anode, <NUM> cm-<NUM> IrO<NUM> on cathode. Test conditions: <NUM> for water and electrolyzer, water flow rate: <NUM>/min. Normally, the cell was activated for <NUM> minutes at <NUM> mA/cm<NUM> and another <NUM> minutes at <NUM> mA/cm<NUM>. After activation, performance was recorded by scanning current. Results are shown in Figure <NUM>.

Another imidazolium-tethered poly (aryl alkylene) polymer is prepared from <NUM>-bromo-<NUM>,<NUM>,<NUM>-trifluoroheptan-<NUM>-one, <NUM>,<NUM>,<NUM>-trifluoroacetone and m-terphenyl (referred to as mTP-CF3-IM-x, wherein x is the mole ratio of <NUM>-bromo-<NUM>,<NUM>,<NUM>-trifluoroheptan-<NUM>-one to biphenyl and is from <NUM> to <NUM>). mTP-CF3-IM-x is prepared by three major steps similar to that of TP-CF3-IM-x: (<NUM>) synthesis of a bromide-functionalized polymer, (<NUM>) synthesis of a imidazolium-functionalized polymer, and (<NUM>) membrane casting and hydroxide exchange. The reaction scheme is depicted below, wherein n is the number of repeat units in the polymer:
<CHM>.

Another method of preparing the BP-CF3-IM-x polymer of Example <NUM> is from the reaction of imidazolium functionalized <NUM>-bromo-<NUM>,<NUM>,<NUM>-trifluoroheptan-<NUM>-one, <NUM>,<NUM>,<NUM>-trifluoroacetone and biphenyl (referred to as BP-CF3-IM-x, wherein x is the mole ratio of imidazolium functionalized <NUM>-bromo-<NUM>,<NUM>,<NUM>-trifluoroheptan-<NUM>-one to biphenyl and is from <NUM> to <NUM>). BP-CF3-IM-x is prepared by two major steps: (<NUM>) synthesis of an imidazolium-functionalized polymer, and (<NUM>) membrane casting and hydroxide exchange. The reaction scheme is depicted below, wherein n is the number of repeat units in the polymer:
<CHM>.

Another method of preparing the TP-CF3-IM-x polymer of Example <NUM> is from the reaction of imidazolium functionalized <NUM>-bromo-<NUM>,<NUM>,<NUM>-trifluoroheptan-<NUM>-one, <NUM>,<NUM>,<NUM>-trifluoroacetone and p-terphenyl (referred to as TP-CF3-IM-x, wherein x is the mole ratio of imidazolium functionalized <NUM>-bromo-<NUM>,<NUM>,<NUM>-trifluoroheptan-<NUM>-one to p-terphenyl and is from <NUM> to <NUM>). TP-CF3-IM-x is prepared by two major steps: (<NUM>) synthesis of an imidazolium-functionalized polymer, and (<NUM>) membrane casting and hydroxide exchange. The reaction scheme is depicted below, wherein n is the number of repeat units in the polymer:
<CHM>.

Another method of preparing the m-TP-CF3-IM-x of Example <NUM> is from the reaction of imidazolium functionalized <NUM>-bromo-<NUM>,<NUM>,<NUM>-trifluoroheptan-<NUM>-one, <NUM>,<NUM>,<NUM>-trifluoroacetone and m-terphenyl (referred to as mTP-CF3-IM-x, wherein x is the mole ratio of imidazolium functionalized <NUM>-bromo-<NUM>,<NUM>,<NUM>-trifluoroheptan-<NUM>-one to m-terphenyl and is from <NUM> to <NUM>). mTP-CF3-IM-x is prepared by two major steps: (<NUM>) synthesis of an imidazolium-functionalized polymer, and (<NUM>) membrane casting and hydroxide exchange. The reaction scheme is depicted below, wherein n is the number of repeat units in the polymer:
<CHM>.

An imidazolium-tethered poly(crown ether) polymer was prepared from <NUM>-bromo-<NUM>,<NUM>,<NUM>-trifluoroheptan-<NUM>-one, <NUM>,<NUM>,<NUM>-trifluoroacetone and dibenzo-<NUM>-crown-<NUM> (referred to as PCE-C5-IM-x, wherein x is the mole ratio of <NUM>-bromo-<NUM>,<NUM>,<NUM>-trifluoroheptan-<NUM>-one to dibenzo-<NUM>-crown-<NUM> and is from <NUM> to <NUM>). PCE-C5-IM-x was prepared by three major steps: (<NUM>) synthesis of a bromide-functionalized polymer, (<NUM>) synthesis of an imidazolium-functionalized polymer, and (<NUM>) membrane casting and hydroxide exchange. The reaction scheme is depicted below, wherein n is the number of repeat units in the polymer:
<CHM>.

Synthesis of a bromide-functionalized polymer (PCE-C5-Br-<NUM>). To a <NUM> three-necked flask equipped with overhead mechanical stirrer, dibenzo-<NUM>-crown-<NUM> (<NUM>, <NUM> mmol) and <NUM>-bromo-<NUM>,<NUM>,<NUM>-trifluoroheptan-<NUM>-one (<NUM>, <NUM> mmol) were suspended into chloroform (<NUM>). TFSA (<NUM>) was then added dropwise slowly at -<NUM>. Thereafter, the reaction was continued at <NUM> for <NUM>. The resulting viscous solution was poured slowly into ethanol. The white fibrous solid was filtered, washed with water and immersed in <NUM> K2CO3 at <NUM> for <NUM>. Finally, the white fibrous product was filtered, washed with water and dried completely at <NUM> under vacuum. The yield of the polymer was <NUM>%. <NUM>H NMR (CDCl<NUM>, δ, ppm): <NUM>-<NUM> (<NUM>), <NUM>-<NUM> (<NUM>), <NUM>(<NUM>), <NUM> (<NUM>), <NUM> (<NUM>), <NUM> (<NUM>), <NUM> (<NUM>) (see <FIG>).

Synthesis of imidazolium-functionalized polymer (PCE-C5-IM-Br-<NUM>) To a <NUM> one-necked flask equipped with magnetic bar, the bromide-functionalized polymer (<NUM>, <NUM> mmol) and the imidazole (<NUM>, <NUM> mmol) were added into DMSO (<NUM>). The solution was stirred over <NUM> hours <NUM>. The resulting yellow solution was used to cast a membrane. The membrane was washed consequently three times with hydrochloride solution (pH <NUM>) and DI water, and dried completely at <NUM> under vacuum. The yield of the polymer PCE-C5-IM-Br-<NUM> was <NUM>%. <NUM> NMR (DMSO-d6, δ, ppm): <NUM> (<NUM>), <NUM>-<NUM> (<NUM>), <NUM>-<NUM> (<NUM>), <NUM> (<NUM>), <NUM>-<NUM> (<NUM>), <NUM> (<NUM>), <NUM>-<NUM> (<NUM>), <NUM>-<NUM>(<NUM>), <NUM> (<NUM>) (see <FIG>).

PCE-C5-IM OH-<NUM> membrane casting and hydroxide exchange. Membrane was prepared by dissolving the PCE-C5-IM-Br-<NUM> polymer (<NUM>) in NMP (<NUM>) and casting on a clear glass plate at <NUM> for <NUM> hours. The membrane (in bromide form) was peeled off from a glass plate in contact with deionized (DI) water. The membrane in hydroxide form was obtained by ion exchange in <NUM> KOH at <NUM> for <NUM> hours, followed by washing and immersion in DI water for <NUM> hours under argon to remove residual KOH.

Another imidazolium-tethered poly (crown ether) polymer is prepared from <NUM>-bromo-<NUM>,<NUM>,<NUM>-trifluoroheptan-<NUM>-one, <NUM>,<NUM>,<NUM>-trifluoroacetone and dibenzo-<NUM>-crown-<NUM> (referred to as PCE-C5-IM-x, wherein x is the mole ratio of <NUM>-bromo-<NUM>,<NUM>,<NUM>-trifluoroheptan-<NUM>-one to dibenzo-<NUM>-crown-<NUM> and is from <NUM> to <NUM>). PCE-C5-IM-x is prepared by three major steps similar to that of PCE-C5-IM-<NUM>: (<NUM>) synthesis of a bromide-functionalized polymer, (<NUM>) synthesis of an imidazolium-functionalized polymer, and (<NUM>) membrane casting and hydroxide exchange. The reaction scheme is depicted below, wherein n is the number of repeat units in the polymer.

Another method of preparing the PCE-C5-IM-x of Example <NUM> is from the reaction of imidazolium functionalized <NUM>-bromo-<NUM>,<NUM>,<NUM>-trifluoroheptan-<NUM>-one, <NUM>,<NUM>,<NUM>-trifluoroacetone and dibenzo-<NUM>-crown-<NUM> (referred to as PCE-C5-IM-x, wherein x is the mole ratio of imidazolium functionalized <NUM>-bromo-<NUM>,<NUM>,<NUM>-trifluoroheptan-<NUM>-one to PCE-C5-IM-x and is from <NUM> to <NUM>). PCE-C5-IM-x is prepared by two major steps: (<NUM>) synthesis of an imidazolium-functionalized polymer, and (<NUM>) membrane casting and hydroxide exchange. The reaction scheme is depicted below, wherein n is the number of repeat units in the polymer:
<CHM>.

A quaternary ammonium-tethered poly(crown ether) polymer was prepared from <NUM>-bromo-<NUM>,<NUM>,<NUM>-trifluoroheptan-<NUM>-one and dibenzo-<NUM>-crown-<NUM> (referred to as PCE-C5-QA-x, wherein x is the mole ratio of <NUM>-bromo-<NUM>,<NUM>,<NUM>-trifluoroheptan-<NUM>-one to dibenzo-<NUM>-crown-<NUM> and is from <NUM> to <NUM>). PCE-C5-QA-x was prepared by three major steps: (<NUM>) synthesis of a bromide-functionalized polymer, (<NUM>) synthesis of a quaternary ammonium-functionalized polymer, and (<NUM>) membrane casting and hydroxide exchange. The reaction scheme is depicted below, wherein n is the number of repeat units in the polymer:
<CHM>.

A quaternary ammonium-tethered poly(crown ether) polymer was prepared from <NUM>-bromo-<NUM>,<NUM>,<NUM>-trifluoroheptan-<NUM>-one, <NUM>,<NUM>,<NUM>-trifluoroacetone and dibenzo-<NUM>-crown-<NUM> (referred to as PCE-C5-IM-x, wherein x is the mole ratio of <NUM>-bromo-<NUM>,<NUM>,<NUM>-trifluoroheptan-<NUM>-one to dibenzo-<NUM>-crown-<NUM> and is from <NUM> to <NUM>). PCE-C5-QA-x is prepared by three major steps: (<NUM>) synthesis of a bromide-functionalized polymer, (<NUM>) synthesis of a quaternary ammonium-functionalized polymer, and (<NUM>) membrane casting and hydroxide exchange. The reaction scheme is depicted below, wherein n is the number of repeat units in the polymer:
<CHM>.

The term "suitable substituent," as used herein, is intended to mean a chemically acceptable functional group, preferably a moiety that does not negate the activity of the inventive compounds. Such suitable substituents include, but are not limited to halo groups, perfluoroalkyl groups, perfluoroalkoxy groups, alkyl groups, alkenyl groups, alkynyl groups, hydroxy groups, oxo groups, mercapto groups, alkylthio groups, alkoxy groups, aryl or heteroaryl groups, aryloxy or heteroaryloxy groups, aralkyl or heteroaralkyl groups, aralkoxy or heteroaralkoxy groups, HO-(C=O)-groups, heterocylic groups, cycloalkyl groups, amino groups, alkyl - and dialkylamino groups, carbamoyl groups, alkylcarbonyl groups, alkoxycarbonyl groups, alkylaminocarbonyl groups, dialkylamino carbonyl groups, arylcarbonyl groups, aryloxycarbonyl groups, alkylsulfonyl groups, and arylsulfonyl groups. Those skilled in the art will appreciate that many substituents can be substituted by additional substituents.

The term "alkyl," as used herein, refers to a linear, branched or cyclic hydrocarbon radical, preferably having <NUM> to <NUM> carbon atoms (i.e., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> carbons), and more preferably having <NUM> to <NUM> carbon atoms. Alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, iso-butyl, secondary-butyl, and tertiary-butyl. Alkyl groups can be unsubstituted or substituted by one or more suitable substituents.

The term "alkenyl," as used herein, refers to a straight, branched or cyclic hydrocarbon radical, preferably having <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> carbons, more preferably having <NUM> to <NUM> carbon atoms, and having one or more carbon-carbon double bonds. Alkenyl groups include, but are not limited to, ethenyl, <NUM>-propenyl, <NUM>-propenyl (allyl), iso-propenyl, <NUM>-methyl-<NUM>-propenyl, <NUM>-butenyl, and <NUM>-butenyl. Alkenyl groups can be unsubstituted or substituted by one or more suitable substituents, as defined above.

The term "alkynyl," as used herein, refers to a straight, branched or cyclic hydrocarbon radical, preferably having <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> carbons, more preferably having <NUM> to <NUM> carbon atoms, and having one or more carbon-carbon triple bonds. Alkynyl groups include, but are not limited to, ethynyl, propynyl, and butynyl. Alkynyl groups can be unsubstituted or substituted by one or more suitable substituents, as defined above.

The term "aryl" or "ar," as used herein alone or as part of another group (e.g., aralkyl), means monocyclic, bicyclic, or tricyclic aromatic radicals such as phenyl, naphthyl, tetrahydronaphthyl, indanyl and the like; optionally substituted by one or more suitable substituents, preferably <NUM> to <NUM> suitable substituents, as defined above. The term "aryl" also includes heteroaryl.

"Arylalkyl" or "aralkyl" means an aryl group attached to the parent molecule through an alkylene group. The number of carbon atoms in the aryl group and the alkylene group is selected such that there is a total of about <NUM> to about <NUM> carbon atoms in the arylalkyl group. A preferred arylalkyl group is benzyl.

The term "cycloalkyl," as used herein, refers to a mono, bicyclic or tricyclic carbocyclic radical (e.g., cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclopentenyl, cyclohexenyl, bicyclo[<NUM>. <NUM>]heptanyl, bicyclo[<NUM>. <NUM>]octanyl and bicyclo[<NUM>. <NUM>]nonanyl, etc.); optionally containing <NUM> or <NUM> double bonds. Cycloalkyl groups can be unsubstituted or substituted by one or more suitable substituents, preferably <NUM> to <NUM> suitable substituents, as defined above.

The term "-ene" as used as a suffix as part of another group denotes a bivalent radical in which a hydrogen atom is removed from each of two terminal carbons of the group, or if the group is cyclic, from each of two different carbon atoms in the ring. For example, alkylene denotes a bivalent alkyl group such as ethylene (-CH2CH2-) or isopropylene (-CH2(CH3)CH2-). For clarity, addition of the -ene suffix is not intended to alter the definition of the principal word other than denoting a bivalent radical. Thus, continuing the example above, alkylene denotes an optionally substituted linear saturated bivalent hydrocarbon radical.

The term "ether" as used herein represents a bivalent (i.e., difunctional) group including at least one ether linkage (i.e., -O-).

The term "heteroaryl," as used herein, refers to a monocyclic, bicyclic, or tricyclic aromatic heterocyclic group containing one or more heteroatoms (e.g., <NUM> to <NUM> heteroatoms) selected from O, S and N in the ring(s). Heteroaryl groups include, but are not limited to, pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl, thienyl, furyl, imidazolyl, pyrrolyl, oxazolyl (e.g., <NUM>,<NUM>-oxazolyl, <NUM>,<NUM>-oxazolyl), thiazolyl (e.g., <NUM>,<NUM>-thiazolyl, <NUM>,<NUM>-thiazolyl), pyrazolyl, tetrazolyl, triazolyl (e.g., <NUM>,<NUM>,<NUM>-triazolyl, <NUM>,<NUM>,<NUM>-triazolyl), oxadiazolyl (e.g., <NUM>,<NUM>,<NUM>-oxadiazolyl), thiadiazolyl (e.g., <NUM>,<NUM>,<NUM>-thiadiazolyl), quinolyl, isoquinolyl, benzothienyl, benzofuryl, and indolyl. Heteroaryl groups can be unsubstituted or substituted by one or more suitable substituents, preferably <NUM> to <NUM> suitable substituents, as defined above.

The term "hydrocarbon" as used herein describes a compound or radical consisting exclusively of the elements carbon and hydrogen.

The term "substituted" means that in the group in question, at least one hydrogen atom bound to a carbon atom is replaced with one or more substituent groups such as hydroxy (-OH), alkylthio, phosphino, amido (-CON(RA)(RB), wherein RA and RB are independently hydrogen, alkyl, or aryl), amino(-N(RA)(RB), wherein RA and RB are independently hydrogen, alkyl, or aryl), halo (fluoro, chloro, bromo, or iodo), silyl, nitro (-NO2), an ether (-ORA wherein RA is alkyl or aryl), an ester (-OC(O)RA wherein RA is alkyl or aryl), keto (-C(O)RA wherein RA is alkyl or aryl), heterocyclo, and the like. When the term "substituted" introduces or follows a list of possible substituted groups, it is intended that the term apply to every member of that group. That is, the phrase "optionally substituted alkyl or aryl" is to be interpreted as "optionally substituted alkyl or optionally substituted aryl. " Likewise, the phrase "alkyl or aryl optionally substituted with fluoride" is to be interpreted as "alkyl optionally substituted with fluoride or aryl optionally substituted with fluoride.

The term "tethered" means that the group in question is bound to the specified polymer backbone. For example, an imidazolium-tethered poly (aryl alkylene) polymer is a polymer having imidazolium groups bound to a poly (aryl alkylene) polymer backbone.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

Claim 1:
A polymer comprising structural units of Formulae (1A); (<NUM>'A); optionally (3A); and optionally (4A), wherein the structural units of Formulae (1A), (3A), (<NUM>'A) and (4A) have the structures:
<CHM>
<CHM>
<CHM>
<CHM>
wherein:
R<NUM> are each independently a quaternary ammonium or phosphonium group or a nitrogen-containing heterocyclic group or a salt thereof, the quaternary ammonium or phosphonium group having the formula (5A):
<CHM>
and the nitrogen-containing heterocyclic group being an optionally substituted pyrrole, pyrroline, pyrazole, pyrazoline, imidazole, imidazoline, triazole, pyridine, triazine, pyrazine, pyridazine, pyrimidine, azepine, quinoline, piperidine, pyrrolidine, pyrazolidine, imidazolidine, azepane, isoxazole, isoxazoline, oxazole, oxazoline, oxadiazole, oxatriazole, dioxazole, oxazine, oxadiazine, isoxazolidine, morpholine, thiazole, isothiazole, oxathiazole, oxathiazine, or caprolactam, wherein each substituent is independently alkyl, alkenyl, alkynyl, aryl, or aralkyl;
R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, R<NUM>, and R<NUM> are each independently hydrogen, halide, alkyl, alkenyl, alkynyl or aryl, and the alkyl, alkenyl, alkynyl or aryl are optionally substituted with halide, and wherein R<NUM> and R<NUM> are optionally linked to form a five membered ring optionally substituted with halide or alkyl;
each R<NUM> is independently alkyl, alkenyl, alkynyl, or a substituent having formula (4B):
<CHM>
and the alkyl, alkenyl, or alkynyl are optionally substituted with fluoride;
R<NUM> and R<NUM> are each independently alkylene;
R<NUM>, R<NUM>, R<NUM>, R<NUM>, and R<NUM> are each independently alkyl, alkenyl, or alkynyl;
q is <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>; m is <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM>;
n is <NUM>, <NUM>, <NUM> or <NUM>;
each m' and each n' is independently <NUM>, <NUM> or <NUM>;
each n' is independently <NUM>, <NUM> or <NUM>;
X- is an anion; and
Z is P when the structural unit of formula (3A) is present in the polymer but the structural unit of formula (<NUM>'A) is not present in the polymer, and Z is N or P when the structural unit of formula (<NUM>'A) is present in the polymer.