Sulfonated polyphenylene membranes comprising antioxidants and methods of use thereof

Abstract

Disclosed herein is a sulfonated polyphenylene membrane comprising a sulfonated polyphenylene polymer and an antioxidant, and a method for manufacturing the sulfonated polyphenylene membrane. The sulfonated polyphenylene membrane has applicability in electrochemical devices such as fuel cells, electrolyzers, dialyzers, hydrogen pumps, thermoelectrochemical hydrogen pumps, electrochemical hydrogen compressors, redox flow batteries, and other electrochemical devices.

Description

SULFONATED POLYPHENYLENE MEMBRANES COMPRISING ANTIOXIDANTS AND METHODS OF USE THEREOFCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Application No. 63 / 711,291, filed on October 24, 2024, the disclosure of which is hereby incorporated by reference in its entiretyFIELD OF INVENTION

[0002] The current invention pertains to membranes comprising sulfonated polyphenylene polymers and antioxidant(s), and methods for manufacturing such membranes. The sulfonated polyphenylene antioxidant membranes have applicability in electrochemical devices such as fuel cells, electrolyzers, dialyzers, hydrogen pumps, thermoelectrochemical hydrogen pumps, electrochemical hydrogen compressors, redox flow batteries, and other electrochemical devices.BACKGROUND

[0003] Proton Exchange Membrane Fuel Cells (PEMFCs) have emerged as promising candidates for clean energy production, owing to their high energy efficiency and minimal environmental impact. A PEMFC generally includes an anode, which is a hydrogen fuel, a cathode, to which oxygen is supplied, and a polymer electrolyte membrane disposed between two electrodes. Such a configuration is a membrane-electrode assembly (MEA). The reaction of a fuel cell for generating electricity is as follows: the hydrogen supplied to the anode is separated into a proton and electron, the proton moves toward the cathode through the membrane, and the electron moves to the cathode through an external circuit, such that oxygen molecules, the protons, and the electrons all react on the cathode to generate electricity and heat, and generating water (H2O) as a reaction by-product.

[0004] Here, the polymer electrolyte membrane serves to transfer the proton generated by the anode to the cathode, and serves as a diaphragm to preclude hydrogen, which is the fuel, from directly contacting oxygen.

[0005] The performance and durability of PEMFCs are significantly influenced by the presence of reactive oxygen species (ROS) generated during operation of the PEMFC. During the electrochemical reactions within PEMFCs, oxygen is typically supplied to the cathode, w here it undergoes reduction to form water molecules. However, this process canalso lead to the formation of ROS, such as superoxide radicals (O2’ ), hydrogen peroxide (H2O2), and hydroxyl radicals (*OH), each of which can cause oxidative damage to the proton exchange membrane (PEM) and catalyst layers, thereby deteriorating the performance and durability of PEMFCs, impacting membrane integrity.

[0006] This degradation not only leads to a decline in PEMFC performance but also necessitates frequent maintenance and replacement of components, thereby increasing the overall operational costs. Incorporating antioxidants into PEMFC systems presents a promising solution to mitigating oxidative degradation and prolonging the service life of PEMFCs.

[0007] Antioxidants play a pivotal role in scavenging ROS and preventing oxidative damage within PEMFCs. By neutralizing free radicals and inhibiting chain reactions initiated by ROS. antioxidants help maintain the structural integrity of PEMs and catalyst layers, thereby preserving the efficiency and longevity of PEMFCs. Furthermore, antioxidants can enhance the stability of electrocatalysts, mitigate membrane degradation, and reduce the occurrence of electrode poisoning, all of which contribute to improved PEMFC performance and durability

[0008] Several approaches can be employed to integrate antioxidants into PEMFC systems effectively. One approach involves doping PEMs with antioxidant compounds or incorporating antioxidant additives into the membrane electrode and catalyst layers.

[0009] The antioxidants can include a primary antioxidant having a radical scavenger or quencher function, a secondary antioxidant having a hydrogen peroxide decomposer function alone, or interchangeably use both the primary' and secondary’ antioxidant. The primary antioxidant can include phenolic antioxidants, monophenolicbisphenolic polymeric phenolic antioxidants, and amine-based antioxidants. The secondary antioxidant can include sulfur-based antioxidants and phosphorus antioxidants. Since polypropylene is oxidized more easily than polyethy lene, polypropylene can be used in combination with secondary antioxidants such as the phenolic antioxidants of 2,6-di-t-butyl-4-methylphenol (BHT) at 0,1% to 1,0%, dilauryl thiodi propionate, and distearyl thiodipropionate.

[0010] Representative primary antioxidants used in the perfluorinated sulfonic acid electrolyte membrane and ionomer for the fuel cell include cerium compounds such as cerium (HI) nitrate hexahydrate, cerium oxide, or ceria. Representative secondaryantioxidants include manganese antioxidants such as manganese oxide and transition metal catalyst such as platinum (Pt).

[0011] In the foregoing examples, however, when the metal salt form is used for the primary or secondary antioxidants, the metal ions are bonded to the terminus of the perfluorinated sulfonic acid ionomer sulfonic acid group and block the path through which the proton can move. Further, the particles at several ten to several hundred nano sizes of the metal or the metal oxide block the hydrated microchannel of the electrolyte membrane to inhibit proton movement. Therefore, generally, the use of metal salt or metal antioxidants can decrease proton conductivity, and hence function, of an electrolyte membrane.

[0012] In conventional practices, the incorporation of antioxidants into proton exchange membrane fuel cells (PEMFCs) involves blending metal ions or metal oxide nanoparticles into coating formulations. One significant drawback to this technique is the propensity for gelation and non-homogeneous distribution of particles within the PEM and electrode layers.

[0013] Gelation occurs when the antioxidant additives react with other components in the coating formulation, leading to the formation of gel-like structures. This gelation phenomenon can impede the uniform dispersion of antioxidants throughout the PEMFC, resulting in uneven protection against reactive oxygen species (ROS) and inconsistent performance across the cell.

[0014] Moreover, the non-homogeneous distribution of antioxidant particles within PEMFC layers can exacerbate oxidative degradation in localized regions, leaving other areas vulnerable to ROS-induced damage. This uneven distribution not only compromises the overall efficiency and durability of PEMFCs but also undermines their reliability in practical applications.

[0015] Therefore, a need exists to overcome the limitations of current antioxidant incorporation methods into PEMFC systems and to achieve uniform distribution and minimize gelation effects.SUMMARY

[0016] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summaryis not intended to identify key features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0017] In one aspect of the disclosure, provided herein is a sulfonated polyphenylene membrane comprising one or more sulfonated polyphenylene polymer and one or more antioxidant, wherein the sulfonated polyphenylene polymer comprises a polymer having a repeat unit (x) of Formula (I) as described herein.

[0018] In another aspect of the disclosure, provided herein is a method of making a multilayer sulfonated polyphenylene membrane through a layer-by-layer coating, comprising:(a) preparing a first solution comprising one or more sulfonated polyphenylene polymer as defined herein and at least one solvent:(b) applying the first solution onto a substrate to form a first wet layer;(c) drying the first wet layer at a temperature between about 40°C and about 70°C to produce a first sulfonated polyphenylene polymer layer;(d) preparing a second solution comprising one or more antioxidant as defined herein and at least one solvent:(e) applying the second solution onto the first sulfonated polyphenylene polymer layer to form a second wet layer;(f) drying the second wet layer between about 40°C and about 70°C to produce an antioxidant layer, thereby forming a composite membrane comprising the first sulfonated polyphenylene polymer layer and the antioxidant layer, wherein the antioxidant layer is in contact with the first sulfonated polyphenylene polymer layer;(g) applying the first solution or a third solution compnsing the same or different one or more sulfonated polyphenylene polymer as defined herein and at least one solvent onto the antioxidant layer to form a third wet layer;(h) drying the composite membrane with the third wet layer between about 40°C and about 70°C to produce a second sulfonated polyphenylene polymer layer, wherein the second sulfonated polyphenylene polymer layer is in direct contact with the antioxidant layer, and wherein the second sulfonated polyphenylene polymer layer is either identical to, or different from, the first sulfonated polyphenylene polymer layer.

[0019] In another aspect of the disclosure, provided herein is a method of making a multilayer sulfonated polyphenylene membrane through a layer-by-layer coating, comprising:(a) preparing a first solution comprising one or more antioxidant as defined herein and at least one solvent:(b) applying the first solution onto a substrate to form a first wet layer;(c) drying the substrate with the first wet layer between about 40°C and about 70°C to produce a first antioxidant layer;(d) preparing a second solution comprising one or more sulfonated polyphenylene polymer as defined herein and at least one solvent;(e) applying the second solution onto the first antioxidant layer to form a second wet layer;(I) drying the first antioxidant layer with the second wet layer between about 40°C and about 70°C to produce a first sulfonated polyphenylene polymer layer, thereby forming an intermediate membrane;(g) applying the first solution or a third solution comprising one or more antioxidant as defined herein and at least one solvent onto the first sulfonated polyphenylene polymer layer to form a third wet layer;(h) drying the intermediate membrane with the third wet layer between about 40°C and about 70°C to produce a second antioxidant layer, resulting in a final membrane; wherein the final membrane structure comprises, in sequence:(i) the first antioxidant layer.(ii) the first sulfonated polyphenylene polymer layer, and(iii) the second antioxidant layer; andwherein the first sulfonated polyphenylene polymer layer is in contact with the first antioxidant layer, wherein the second antioxidant layer is in contact with the first sulfonated polyphenylene polymer layer, andwherein the second antioxidant layer is either identical to, or different from, the first antioxidant layer.

[0020] In a further aspect of the disclosure, provided herein is a method of making a sulfonated polyphenylene membrane, comprising:(a) preparing a solution compnsing:(i) a sulfonated polyphenylene polymer,(ii) an antioxidant, and(iii) one or more solvent;(b) applying the solution to a substrate to form a wet layer; and(c) drying the substrate with the wet layer to form the sulfonated polyphenylene membrane,wherein the sulfonated polyphenylene polymer and the antioxidant are as described herein.

[0021] In yet another aspect of the disclosure, provided herein are methods of using the sulfonated polyphenylene antioxidant polymer membrane as described herein in an electrochemical device such as a fuel cell, electrolyzer, hydrogen pump, thermoelectrochemical hydrogen pump, electrochemical hydrogen compressor, or redox flow battery.

[0022] In an additional aspect of the disclosure, provided herein are electrochemical devices comprising the sulfonated polyphenylene antioxidant polymer membrane as described herein, wherein the electrochemical device is a fuel cell, electrolyzer, hydrogen pump, thermoelectrochemical hydrogen pump, electrochemical hydrogen compressor, redox flow battery, or other electrochemical devices.DESCRIPTION OF THE DRAWINGS

[0023] The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

[0024] FIG. 1 A shows an example layered sulfonated polyphenylene membrane, in accordance with embodiments described herein;

[0025] FIG. IB shows another example layered sulfonated polyphenylene membrane, wherein each layer has varying thickness throughout the layer, in accordance with embodiments described herein;

[0026] FIG. 1C shows an example asymmetrical layered sulfonated polyphenylene membrane, in accordance with embodiments described herein;

[0027] FIG. ID shows another example asymmetrical layered sulfonated polyphenylene membrane, in accordance with embodiments described herein;

[0028] FIG. IE shows an example symmetrical layered sulfonated polyphenylene membrane, in accordance with embodiments described herein;

[0029] FIG. 1 F shows an example sulfonated polyphenylene membrane including integrated sulfonated polyphenylene polymer layers and antioxidant layer, in accordance with embodiments described herein;

[0030] FIG. 2A shows an example layered sulfonated polyphenylene membrane including more than one set of alternating sulfonated polyphenylene polymer layers and antioxidant layers, in accordance with embodiments described herein;

[0031] FIG. 2B shows another example layered sulfonated polyphenylene membrane including more than one set of alternating sulfonated polyphenylene polymer layers and antioxidant layers, in accordance with embodiments described herein;

[0032] FIG. 2C shows an example composite sulfonated polyphenylene membrane including a porous reinforcement, in accordance with embodiments described herein; and

[0033] FIG. 3 shows an example composite sulfonated polyphenylene membrane including a layer of mixed sulfonated polyphenylene polymer and antioxidant, in accordance with embodiments described herein..DETAILED DESCRIPTION

[0034] To address the deficiencies of current PEMFC systems, the present disclosure provides a sulfonated polyphenylene polymer and antioxidant membrane.

[0035] Integration of antioxidants into PEMFC systems holds great potential for enhancing membrane performance, durability, and reliability. By mitigating the detrimental effects of ROS, antioxidants can preserve the structural integrity of PEMs and catalyst layers, thereby prolonging the service life of PEMFCs and reducing overall operational costs.

[0036] By synergistically combining the inherent oxidative resilience of the sulfonated polyphenylene backbone with antioxidants, the membranes disclosed herein can be fortified against oxidative damage, thereby extending their operational lifespan and bolstering durability in real-world applications. Additionally, the integration of antioxidants not only enhances safety margins under extreme conditions, such as fuel starvation or air bleeding, but also protects critical components within the membrane electrode assembly (MEA), including ionomers and catalysts, thus optimizing overall system performance and longevity,

[0037] Antioxidant incorporation offers significant potential for refining the properties and performance of sulfonated polyphenylene (SPP) PEMs through meticulousselection and incorporation. This strategic approach not only addresses current limitations but also pushes the boundaries of what can be achieved with sulfonated polyphenylene-based membranes, providing new avenues for improving efficiency and reliability in diverse applications within the fuel cell industry.

[0038] Sulfonated polyphenylene-based proton exchange membranes (PEMs) are promising alternatives to perfluorinated ionomers (PFSAs), such as Nafion®, for fuel cell applications. The hydrocarbon-based PEMs disclosed herein offer advantages such as low er cost, higher thermal stability and improved performance.

[0039] The SPP membranes disclosed herein demonstrated remarkable stability with negligible degradation even under accelerated oxidative degradation conditions using Fenton's reagent. This is a significant advantage over other hydrocarbon-based PEMs. which typically lack the oxidative stability of perfluorinated membranes like Nafion®.

[0040] Hydrocarbon-based ionomers such as the ionomers disclosed herein have greater thermal and oxidative stability than PFSAs and exhibit lower water transport properties. Greater thermal stability enhances fuel cell durability’ under strenuous fuel cell operating conditions. Lower water transport properties are advantageous under high temperature and low relative humidity fuel cell operating conditions, since the lo ’er water transport properties can increase water back-diffusion to the membrane and increase membrane hydration, which in turn lowers the cell resistance.

[0041] Sulfonated polyphenylene hydrocarbon (SPH) compositions demonstrate notable chemical stability and boast well-balanced characteristics suitable for solid polymer electrolyte membranes. Consequently, SPH membranes produced through casting SPH in suitable solvents exhibit chemical and electrochemical stability, robust mechanical strength, high ionic conductivity’, and effective electronic insulation.

[0042] The present disclosure provides methods of improving SPP PEM properties by incorporating antioxidants into the sulfonated polyphenylene membrane. For example, sulfonated polyphenylene membranes can be formed from sulfonated polyphenylene polymers mixed together with antioxidants. In another example, antioxidants are incorporated into membranes through a layer-by-layer (LbL) coating technique to integrate metal salt-based, complex-based, or particle-based antioxidants. This method involves sequentially depositing layers of polymer and antioxidants, ensuring uniform distribution, preventing polymer gelation, controlling release rates, optimizing material compatibility.and facilitating scalable production through versatile coating methods such as dip coating, spray coating, or roll-to-roll processing.

[0043] Multilayer coating leads to enhanced distribution of metal ions. With a multilayer coating, a metal salt-based antioxidant, for example, is incorporated into a distinct layer, ensuring a more uniform dispersion compared to blending, which can result in uneven distribution within the polymer matrix.

[0044] Multilayer coating also prevents polymer gelation Direct mixing of metal salts with certain polymers can induce gelation or crosslinking, increasing viscosity and potentially causing coating defects. By segregating the antioxidant layer from the polymer layer, these effects can be mitigated.

[0045] Multilayer coating additionally controls release and retention. The multilayer structure facilitates controlled release of the antioxidant and reduces undesirable leaching. Alternating polymer layers act as barriers, effectively retaining the antioxidant within the coating layer, prolonging its efficacy.

[0046] Multilayer coating further provides flexibility in composition. The layer-by-layer (LbL) or multi-layer coating approach allows independent optimization of the antioxidant layer and polymer layer, enabling selection of compatible materials and finetuning of coating properties.

[0047] Additionally, multilayer coating provides scalability and ease of application. Multilayer coatings are compatible with various application techniques such as dip coating, spray coating, or roll-to-roll processing, facilitating efficient large-scale production.

[0048] Incorporating antioxidants into PEMFC systems without compromising coating integrity or distribution uniformity represents a critical step toward enhancing the performance and durability of PEMFCs. The present disclosure is aimed at overcoming the challenges associated with antioxidant incorporation, accelerating the advancement of next-generation PEMFC technologies, and facilitating their widespread adoption in diverse applications.Definitions

[0049] The terminology used in the description of the invention herein is for the purpose of describing particular embodiments and is not intended to be limiting for the invention.

[0050] It is further appreciated that certain features of the disclosure, which are. for clarity, described in the context of separate embodiments, can also be provided in combination in a single embodiment. Conversely, various features of disclosure which are, for brevity, described in the context of a single embodiment, can also be provided separately or in any suitable subcombination.

[0051] The term "substituted" means that an atom or group of atoms formally replaces hydrogen as a "substituent" attached to another group. The term "substituted." unless otherwise indicated, refers to any level of substitution, e.g, mono-, di-, tri-, tetra-, penta-, or higher substitution, where such substitution is permitted (e.g., results in a stable compound). The substituents are independently selected, and substitution may be at any chemically accessible position. It is to be understood that substitution at a given atom is limited by valency.

[0052] When a group is unsubstituted, it can be referred to as the group name, for example alk l or aryl.

[0053] Substituents of polymers of the present disclosure are disclosed herein in groups or in ranges. It is specifically intended that the disclosure includes each and every-individual subcombination of the members of such groups and ranges. For example, the term "C1-6 alkyl" is specifically intended to individually disclose (without limitation) methyl, ethyl, C3 alkyl, C4 alkyl, C5 alkyl, and C6 alkyl, and to include linear or branched geometric isomers when such geometric isomers are possible. For example. C4alkyl can be n-butyl, sec-butyl, isobutyl, or tert-butyl.

[0054] It is further appreciated that certain features of the disclosure, which are, for clarity, described in the context of separate embodiments, can also be provided in combination in a single embodiment. Conversely, various features of the present disclosure that are, for brevity, described in the context of a single embodiment, can also be provided separately or in any suitable subcombination.

[0055] As used herein, the term "alkyl" refers to straight, branched, or cyclic hydrocarbon groups. In some embodiments, alkyl has 1 to 6 carbon atoms, 1 to 5 carbon atoms, 1 to 4 carbon atoms, 1 to 3 carbon atoms, 1 or 2 carbon atoms, or 1 carbon atom. Representative alkyl groups include methyl, ethyl, propyl (e.g., n-propyl, isopropyl, cyclopropyl), butyl (e.g., n-butyl, sec-butyl, isobutyl, tert-butyl, cyclobutyl), pentyl (e.g, n-pentyl, tert-pentyl, neopentyl, isopentyl, pentan-2-yl, pentan-3-yl. cyclopentyl), and hexyl (e.g, n-hexyl, geometric isomers, cyclohexyl) groups.

[0056] As used herein, the term "alkylene" refers to a linking alkyl group.

[0057] As used herein, the term "aryl" refers to an aromatic hydrocarbon group having 6 to 14 carbon atoms. Representative aryl groups include phenyl groups and naphthyl groups. In some embodiments, the term "aryl" includes monocyclic or polycyclic (e.g., having 2 or 3 fused rings) aromatic hydrocarbons such as, for example, phenyl, naphthyl, anthracenyl, phenanthrenyl. indanyl, and indenyl.

[0058] As used herein, the term "arylene" refers to a linking aryl group. For example, the term "phenylene" refers to a linking phenyl group.

[0059] As used herein, the term "aralkyl” refers to an alkyl group as defined herein, with an aryl group as defined herein, substituted for one of the alkyl hydrogen atoms. A representative aralkyl group is a benzyl group.

[0060] As used herein, the term "aralkylene" refers to a linking aralkyl group.

[0061] As used herein, the term "heteroaryl" refers to a 5- to 10-membered aromatic monocyclic or bicyclic ring containing 1 to 4 heteroatoms selected from O, S, and N. Representative 5- or 6-membered aromatic monocyclic ring groups include pyridine, pyrimidine, pyridazine, furan, thiophene, thiazole, oxazole, and isooxazole. Representative 9- or 10-membered aromatic bicyclic ring groups include benzofuran, benzothiophene, indole, pyranopyrrole, benzopyran, quinoline, benzocyclohexyl, and naphthyridine.

[0062] As used herein, the term "heteroarylene" refers to a linking heteroaryl group.

[0063] As used herein, the term "heteroaralkyl" refers to an alkyl group as defined herein with a heteroaryl group as defined herein substituted for one of the alkyl hydrogen atoms. For example, a representative heteroaralkyl group is an alkylpyridyl group

[0064] As used herein, the term "heteroaralkylene" refers to a linking heteroaralkyl group.

[0065] As used herein, the term "halogen" or "halo" refers to fluoro, chloro, bromo, and iodo groups. "Halogen" or "halo" can refer to the entire set of fluoro, chloro, bromo, and iodo groups, or to a subset of halogen atoms, e.g., fluoro, chloro, and bromo; chloro, bromo, and iodo: and any other combination or subcombination of halogen atoms.

[0066] As used herein, the term "heteroatomic" or "heteroatomic groups" refers to one or more heteroatom, wherein the one or more heteroatom is selected from N, O, and S.

[0067] As used herein, the term "copolymer" refers to a polymer that is the result of polymerization of two or more different monomeric units. The number and the nature of each monomeric unit can be separately controlled in a copolymer. The copolymercomprises at least one monomeric unit that is ionomeric, and at least one monomeric unit that is not ionomeric, or is uncharged. The ionomeric monomers in the copolymer can be the same or can be different The uncharged monomers in the copolymer can be the same or can be different.

[0068] As used herein, the term "repeat unit" corresponds to the smallest monomeric unit or constitutional unit, the repetition of which constitutes a macromolecule (or polymer or block). The monomeric unit of a polymer refers to a group of atoms in a monomer, comprising a part of the polymer chain, together with its pendant atoms or groups of atoms. The monomeric unit is a repeating unit within a chain. The monomeric unit can also refer to an end group on a polymer chain. For example, the monomeric unit of polyethylene glycol can be -CH2CH2O- corresponding to a repeating unit, or -CH2CH2OH corresponding to an end group. As used herein, the term "end group" refers to a repeating unit, or monomeric unit, with only one attachment to a polymer chain, located at the end of a polymer.

[0069] The repeat units can be disposed in a purely random, an alternating random, a regular alternating, a statistical, a regular block, or a random block configuration unless expressly stated to be otherwise

[0070] As used herein, the term "random copolymer" is a copolymer having an irregular mixture of two or more monomeric units. The distribution of the monomeric units throughout the polymer can be a statistical distribution, or approach a statistical distribution, of the repeat units. In some embodiments, the distribution of one or more of the monomeric unit is favored A purely random configuration can, for example, be: x x y z x y y z y z z z... or y z x y z y z x x.... An alternating random configuration can be: x y x z. y x y z y x z..., and a regular alternating configuration can be: x y z x y z x y z....

[0071] As used herein, the term "statistical copolymer" is a copolymer having a composition of monomeric units as determined by the mole percent of monomeric units used to generate the polymer. For example, in a statistical copolymer comprising 90% ionomeric monomer and 10% uncharged monomer, the resulting polymer is expected to consist of about 90% ionomeric monomer units and about 10% uncharged monomer units. A statistical polymer comprises an average composition ratio of x and y monomer units.

[0072] A regular block configuration (i.e., a block copolymer) has the following example configuration when comprising 3 different monomeric units (x. y. and z) for the block:... x x x y y y z z z x x x.., while a random block configuration has the followinggeneral example configuration of, for example:...x x x zz zxx x y y y y z z zx xx z z z z or for example,...x-x-x-y-y-y-y-x-x-x-y-y-y-x-x-x-x-y-y-y.... A block copolymer comprises blocks of 3 or more of the same monomeric units.

[0073] As used herein, the term "cationic" refers to a moiety that is positively charged, or ionizable to a positively charged moiety under chemical or acidic conditions relative to the pKa of an atom. Examples of cationic moieties include, for example, ammonium, iminium, imidazolium, o.xazolium, thiazolium groups, etc.

[0074] As used herein, the term "integrated" refers to one layer incorporated to a depth within another layer. Integrated layers are not immiscible, or are not conterminous. For example, when two layers integrate, one layer is embedded within another layer to an extent. The integration can be on the nanoscale level, wherein one layer is embedded within the other layer by a few nanometers to up to a thousand nanometers. The integration can be on the microscale level, wherein one layer is embedded within the other layer by one micrometer to up to a thousand micrometers. When layers are integrated, they can be integrated through a gradient, wherein as the permeation of one composition is deeper into the other layer, the concentration decreases. For example, two layers can be integrated wherein the one or more antioxidant permeates the polyphenylene polymer layer wherein the antioxidant concentration decreases as the antioxidant permeates, or is deeper, into the thickness of the polyphenylene polymer layer. Alternatively, when layers are integrated, they can be integrated homogeneously wherein as the permeation of one composition is deeper into the other layer, the concentration essentially does not change. For example, two layers can be integrated wherein the one or more antioxidant permeates the polyphenylene polymer layer wherein the antioxidant concentration essentially does not change as the antioxidant permeates, or is deeper, into the thickness of the polyphenylene polymer layer.

[0075] As used herein, the term "conterminous" refers to two layers that are not integrated, or that are immiscible. Layers that are conterminous, or are immiscible, share a common boundary but the composition of each layer does not integrate within the composition of the other layer. Conterminous layers can have a straight or linear boundary, or can have a curved or irregularly shaped boundary.

[0076] As used in the description of the invention and the appended claims, the singular forms "a", "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0077] As used herein, the term "about" can be understood to include values within 10% of the stated value. For example, a temperature of "about 40°C" means the temperature is 40 ± 4 °C. Otherwise stated, the temperature is 36°C to 44°C. In another example, about 50-90% stands for about 50% to about 90%, and means 50 ± 5% (e.g., 45%-55%) to 90 ± 9% (e.g, 81-99%).[00781 It is further intended that the compounds of the present disclosure are stable. As used herein, "stable" refers to a compound that is sufficiently robust to survive isolation to a useful degree of purity from a reaction mixture.

[0079] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the present disclosure and relevant art, and should not be interpreted in an idealized or overly formal sense unless expressly so defined herein.Membranes

[0080] In some aspects, disclosed herein are sulfonated polyphenylene membranes, comprising one or more sulfonated polyphenylene polymer and one or more antioxidant, wherein the sulfonated polyphenylene polymer comprises a repeat unit (x) of Formula (I) as described herein.

[0081] In some embodiments, the sulfonated polyphenylene membrane is layered. In some embodiments, the sulfonated polyphenylene membrane comprises a mixture of one or more sulfonated polyphenylene polymer and one or more antioxidant. The mixture can be homogeneous throughout the membrane, or can be heterogeneous throughout the membrane.

[0082] In some embodiments wherein the sulfonated polyphenylene membrane comprises a mixture of one or more sulfonated polyphenylene polymer and one or more antioxidant, the mixture is homogeneous wherein the antioxidant is about evenly dispersed throughout the entire thickness of the membrane, is about evenly dispersed throughout the entire x- and y- plane of the membrane, or is about evenly dispersed throughout both the entire thickness and the x- and y- plane of the membrane. In some embodiments, the antioxidant is evenly dispersed throughout about 90% to about 100% of the thickness ofthe membrane. In some embodiments, the antioxidant is evenly dispersed throughout about 90% to about 100% of the x- and y -plane of the membrane. In some embodiments, the anti oxidant is evenly dispersed throughout about 90% to about 100% of both the x- and y-plane of the membrane and the thickness of the membrane.

[0083] In some embodiments, the even dispersion is throughout part of the x- and y- plane of the membrane, throughout part of the thickness of the membrane, or throughout part of both the x- and y- plane of the membrane and the thickness of the membrane. In some embodiments, the antioxidant is evenly dispersed throughout about 50% to about 90% of the thickness of the membrane. In some embodiments, the antioxidant is evenly dispersed throughout about 50% to about 90% of the x- and -plane of the membrane. In some embodiments, the antioxidant is evenly dispersed throughout about 50% to about 90% of both the thickness of the membrane and the x- and y-plane of the membrane.

[0084] In some embodiments wherein the sulfonated polyphenylene membrane comprises a mixture of one or more sulfonated polyphenylene polymer and one or more antioxidant, the mixture is heterogeneous wherein the antioxidant is unevenly dispersed throughout the entire thickness of the membrane, is unevenly dispersed throughout the entire x- and y- plane of the membrane, or is unevenly dispersed throughout both the entire thickness and the x- and y - plane of the membrane. In some embodiments, the antioxidant is unevenly dispersed throughout about 90% to about 100% of the thickness of the membrane. In some embodiments, the antioxidant is unevenly dispersed throughout about 90% to about 100% of the x- and y-plane of the membrane. In some embodiments, the antioxidant is unevenly dispersed throughout about 90% to about 100% of both the x- and y-plane of the membrane and the thickness of the membrane.

[0085] In some embodiments, the uneven dispersion is throughout part of the x-and y- plane of the membrane, throughout part of the thickness of the membrane, or throughout part of both the x- and y- plane of the membrane and the thickness of the membrane. In some embodiments, the antioxidant is unevenly dispersed throughout about 50% to about 90% of the thickness of the membrane. In some embodiments, the antioxidant is unevenly dispersed throughout about 50% to about 90% of the x- and y-plane of the membrane. In some embodiments, the antioxidant is unevenly dispersed throughout about 50% to about 90% of both the thickness of the membrane and the x- and y-plane of the membrane. In some embodiments wherein the sulfonated polyphenylene membrane comprises a mixture of one or more sulfonated polyphenylene polymer and one or moreantioxidant, the membrane comprises about 80% to about 99% of' the sulfonated polyphenylene polymer and about 1% to about 20% of the one or more antioxidant. In some embodiments wherein the sulfonated polyphenylene membrane comprises a mixture of one or more sulfonated polyphenylene polymer and one or more antioxidant, the membrane comprises about 80% to about 99.5% of the sulfonated polyphenylene polymer and about 0.5% to about 20% of the one or more antioxidant. In some embodiments wherein the sulfonated polyphenylene membrane comprises a mixture of one or more sulfonated polyphenylene polymer and one or more antioxidant, the membrane comprises about 80% to about 99.9% of the sulfonated polyphenylene polymer and about 0.1% to about 20% of the one or more antioxidant.

[0086] In some embodiments, the sulfonated polyphenylene membrane comprises layers. In some embodiments, the one or more sulfonated polyphenylene polymer is in the form of a layer. In some embodiments, the one or more antioxidant is in the form of a layer. In some embodiments, the membrane comprises alternating layers of the one or more sulfonated polyphenylene polymer layer and the one or more antioxidant layer. In some embodiments, the membrane comprises combined layers of the one or more sulfonated polyphenylene polymer layer and combined layers of the one or more antioxidant layer. Such combined layers mean two or more layers of the same composition in contact with each other. For example, the membrane can comprise a combined layer of sulfonated polyphenylene polymer wherein the membrane comprises a first sulfonated polyphenylene polymer layer, a second sulfonated polyphenylene polymer layer, and additional layers of the sulfonated polyphenylene polymers as desired. Additionally, the membrane can comprise a combined layer of antioxidant wherein the membrane comprises a first antioxidant layer, a second antioxidant layer, and additional layers of the antioxidant as desired. In an example, the membrane comprises a first sulfonated polyphenylene polymer layer and a second sulfonated polyphenylene polymer layer to form a combined sulfonated polyphenylene polymer layer, an antioxidant layer, and a third sulfonated polyphenylene polymer layer and a fourth sulfonated polyphenylene polymer layer to form a second combined sulfonated polyphenylene polymer layer. In another example, the membrane comprises a first sulfonated polyphenylene polymer layer and a second sulfonated polyphenylene polymer layer to form a combined sulfonated polyphenylene polymer layer, a first antioxidant layer and a second antioxidant layer to form a combined antioxidant layer, and a third sulfonated polyphenylene polymer layer and a fourthsulfonated polyphenylene polymer layer to form a second combined sulfonated polyphenylene polymer layer. Each compositional layer of the combined layers can be 1 to 8 layers of sulfonated polyphenylene polymer or 1 to 8 layers of antioxidant.

[0087] In some embodiments, the membrane comprises between 1 and 10 sulfonated polyphenylene polymer layers. In some embodiments, the membrane comprises between 1 and 6 sulfonated polyphenylene polymer layers. In some embodiments, the membrane comprises between 1 and 4 sulfonated polyphenylene polymer layers. In some embodiments, the membrane comprises 1 or 2 sulfonated polyphenylene polymer layers. In the foregoing, the layers can be combined layers.

[0088] In some embodiments, the membrane comprises between 1 and 10 antioxidant layers. In some embodiments, the membrane comprises between 1 and 6 antioxidant layers. In some embodiments, the membrane comprises between 1 and 4 antioxidant layers. In some embodiments, the membrane comprises 1 or 2 antioxidant layers. In the foregoing, the layers can be combined layers.

[0089] In some embodiments, the membrane comprises between 1 and 4 sulfonated polyphenylene polymer layers and between 1 and 4 antioxidant layers. In some embodiments, the membrane comprises 1 or 2 sulfonated polyphenylene polymer layers and 1 or 2 antioxidant layers. In some embodiments, the membrane comprises between 1 and 4 sulfonated polyphenylene polymer layers and I or 2 antioxidant layers. In some embodiments, the membrane comprises 1 or 2 sulfonated polyphenylene polymer layers and between 1 and 4 antioxidant layers.

[0090] In some embodiments, each layer of the antioxidant layers is in contact with I or 2 layers of the sulfonated polyphenylene polymer layers. In some embodiments, each combined layer of the antioxidant layers is in contact with 1 or 2 layers of the sulfonated polyphenylene polymer layers. In some embodiments, each layer of the antioxidant layers is in contact with 1 or 2 combined layers of the sulfonated polyphenylene polymer layers. In some embodiments, each combined layer of the antioxidant layers is in contact with 1 or 2 combined layers of the sulfonated polyphenylene polymer layers.

[0091] In some embodiments, each layer of the sulfonated polyphenylene polymer layers is in contact with 1 or 2 layers of the antioxidant layers. In some embodiments, each combined layer of the sulfonated polyphenylene polymer layers is in contact with 1 or 2 layers of the antioxidant layers. In some embodiments, each layer of the sulfonated polyphenylene polymer layers is in contact with 1 or 2 combined layers of the antioxidantlayers. In some embodiments, each combined layer of the sulfonated polyphenylene polymer layers is in contact with 1 or 2 combined layers of the antioxidant layers.

[0092] In some embodiments wherein the layers are in contact, the contact between the layers forms an interface.

[0093] In some embodiments, the layers at the interface are conterminous. For example, when two layers are conterminous, the composition of each layer is not integrated, or is segregated, and the contact between the layers exists essentially only between, or at, the surfaces of each layer.

[0094] In some embodiments, the layers at the interface are integrated. Integration can enhance the overall performance and stability of the membrane. Integration occurs when the composition of one layer is embedded to an extent within the other layer. For example, the one or more antioxidant can be integrated, or embedded, within the sulfonated polyphenylene polymer layer. In another example, the one or more sulfonated polyphenylene polymer can be integrated, or embedded, within the antioxidant layer.

[0095] The extent of integration between the antioxidant and polymer layers can vary depending on several factors, including the nature of the antioxidant layer. The integration, or mixing behavior, between layers is significantly influenced by the type of antioxidant used. For example, with organic antioxidant lay ers, the mixing is primarily dictated by the solubility of the molecular antioxidant in the sulfonated polyphenylene layer. With inorganic metal salt- or complex-based antioxidant layers, the mixing is affected by the solubility of the salt or complex in the solution from which the polyphenylene layer was formed. If the antioxidant is in the form of nanoparticles, the mixing is dictated by nanoparticle interface interactions.

[0096] Additional factors affecting integration can include polymer-antioxidant compatibility, processing conditions, and molecular characteristics. Regarding polymer-antioxidant compatibility, the chemical compatibility between the sulfonated polyphenylene polymer and antioxidant molecules influences how well the compositions mix at the interface. Regarding processing conditions, the temperature, pressure, and mixing methods during fabrication can affect the degree, or extent, of integration. Regarding molecular characteristics, the size, shape, and polarity of both the sulfonated polyphenylene polymer and antioxidant molecules play a role in the ability of one composition to integrate within the layer of the other composition.

[0097] The optimal degree of integration depends on the specific application of the membrane and the desired properties of the membrane. For example, a conterminous interface can be preferred for certain functional requirements. In another example, extensive integration can be beneficial for maximizing antioxidant effectiveness and membrane stability.[00981 In some embodiments, the integration is on a nanoscale level wherein one layer is embedded within the other layer by about 3 nm to about 1,000 nm In some embodiments, one layer is embedded within the other layer by about 3 nm to about 500 nm. In some embodiments, one layer is embedded within the other layer by about 10 nm to about 100 nm. In some embodiments, one layer is embedded within the other layer by about 100 nm to about 1,000 nm.

[0099] In some embodiments, the integration is on a microscale level wherein one layer is embedded within the other layer by about 1 µm to about 1,000 µm. In some embodiments, one layer is embedded within the other layer by about 1 µm to about 500 µm. In some embodiments, one layer is embedded within the other layer by about 1 µm to about 100 µm. In some embodiments, one layer is embedded within the other layer by about 1 µm to about 10 µm.

[0100] In some embodiments, the integration is homogeneous wherein as one composition is integrated into the other layer, the concentration essentially remains the same throughout the integration at the interface between two layers. For example, two layers can be integrated wherein the one or more antioxidant permeates the polyphenylene polymer layer wherein the antioxidant concentration essentially does not change as the antioxidant permeates, or is deeper, into the thickness of the polyphenylene polymer layer. In another example, two layers can be integrated wherein the one or more sulfonated polyphenylene polymer permeates the antioxidant layer wherein the sulfonated polyphenylene polymer concentration essentially does not change as the sulfonated polyphenylene polymer permeates, or is deeper, into the thickness of the antioxidant layer.

[0101] In some embodiments, the integration occurs as a gradient wherein as one composition is integrated into the other layer, the concentration decreases as the one composition is integrated deeper into the other layer. For example, two layers can be integrated wherein the one or more antioxidant permeates the polyphenylene polymer layer wherein the antioxidant concentration decreases as the antioxidant permeates, or is deeper, into the thickness of the polyphenylene polymer layer. In another example, two layers canbe integrated wherein the one or more sulfonated polyphenylene polymer permeates the antioxidant layer wherein the sulfonated polyphenylene polymer concentration decreases as the sulfonated polyphenylene polymer permeates, or is deeper, into the thickness of the antioxidant layer.

[0102] In some embodiments, the antioxidant membrane has a total thickness of about 1 pm to about 5 pm.

[0103] In some embodiments, the one or more sulfonated polyphenylene polymer layer together comprises about 75% to about 99% of the total thickness of the antioxidant membrane.

[0104] In some embodiments, the one or more antioxidant layer together comprises about 1% to about 25% of the total thickness of the antioxidant membrane.

[0105] In some embodiments, each layer of the one or more sulfonated polyphenylene polymer layer has a thickness of between about 5 pm and about 100 pm.

[0106] In some embodiments, each layer of the one or more antioxidant layer has a thickness of about 1 pm to about 5 pm.Sulfonated Polyphenylene Polymer Compositions

[0107] In some embodiments, the sulfonated polyphenylene polymer comprises a repeat unit (x) of Formula (I), wherein Formula (I) has the structure:(I),wherein:R1A, R1B, R1C, R1D, R1E, R1F are independently aryl or heteroaryl, each unsubstituted or substituted with 1, 2. 3, 4, or 5 substituents independently selected from C]_6alkyl, halo, nitro, cyano, SO3-X+, PO32~2X+, and COO X+;R1Gand R1Hare independently H, aryl, or heteroaryl, wherein said aryl and heteroaryl are each unsubstituted or substituted with 1, 2, 3. 4, or 5 substituentsindependently selected from Cj.6 alkyl, halo, nitro, cyano, SO3'X+, PO32'2X+, and COO X+;A] is aiylene, heteroaiylene. aralkylene. or heteroaralkylene, each unsubstituted or substituted with 1, 2, 3, or 4 substituents independently selected from halo, nitro, cyano, aryl, and heteroaryl;AT is absent, arylene, or heteroaiylene, wherein said arylene and heteroaiylene are each unsubstituted or substituted with 1. 2, 3, or 4 substituents independently selected from halo, nitro, cyano, aryl, and heteroaryl;Lj is an unsubstituted or substituted linking heteroatom, arylene, heteroarylene, aralkylene. or heteroaralkylene, wherein said aylene. heteroarylene, aralkylene, and heteroaralkylene are each unsubstituted or substituted with 1, 2, 3. or 4 substituents independently selected from C[.6alkyl, halo, nitro, cyano, aiyl, and heteroaryl:L2and L3are independently absent, arylene, or heteroaiylene, wherein said aiylene and heteroaiylene are each unsubstituted or substituted with 1, 2, 3, or 4 substituents independently selected from Cj.g alkyl, halo, nitro, cyano, aryl, and heteroaryl; and X+is H+, a cation, an alkali metal ion. or [N(RA)(RB)(RC)(RD)]+wherein RA, Rg. Rc, and RDare independently H, CA6alkyl, aryl, or heteroaryl.[0108| In some embodiments, the sulfonated polyphenylene polymer comprises a repeat unit (x) of Formula (I), wherein Formula (I) has the structure:(I),wherein:R1A, Rig,R-IFareindependently aryl or heteroaryl, each unsubstituted or substituted with 1, 2. 3, 4, or 5 substituents independently selected from C]_6alkyl, halo, nitro, cyano, SO3"X+, PO32"2X+, and COO"X+;R1Gand R1Hare independently H, aryl, or heteroaryl, wherein said aryl and heteroaryl are each unsubstituted or substituted with 1, 2, 3. 4, or 5 substituentsindependently selected from C1-6alkyl, halo, nitro, cyano, SO3-X+, PO32'2X+, and COO X+;A] is arylene, heteroarylene. aralkylene. or heteroaralkylene, each unsubstituted or substituted with 1, 2, 3, or 4 substituents independently selected from halo, nitro, cyano, aryl, and heteroaryl;AT is absent, arylene, or heteroarylene, wherein said arylene and heteroarylene are each unsubstituted or substituted with 1. 2, 3, or 4 substituents independently selected from halo, nitro, cyano, aryl, and heteroaryl;Lj is an unsubstituted or substituted linking heteroatom, arylene, heteroarylene, aralkylene. or heteroaralkylene, wherein said arylene, heteroarylene. aralkylene, and heteroaralkylene are each unsubstituted or substituted with 1, 2, 3. or 4 substituents independently selected from C[.6alkyl, halo, nitro, cyano, aryl, and heteroaryl:L2and L3are independently absent, arylene, or heteroarylene, wherein said arylene and heteroarylene are each unsubstituted or substituted with 1, 2, 3, or 4 substituents independently selected from Cj.g alkyl, halo, nitro, cyano, aryl, and heteroaryl;X+is H+, a cation, an alkali metal ion. or [N(RA)(RB)(RC)(RD)]+wherein RA, RB. Rc, and RDare independently IT, C1-6alkyl, aryl, or heteroaryl; andprovided that the repeating unit of Formula (I) is not(A).

[0109] In some embodiments, the sulfonated polyphenylene polymer comprises a repeat unit (x) of Formula (I), wherein Formula (I) has the structure:wherein:RIA, RIB,RIRID,R1E>ANC’R1Fareindependently aryl or heteroaryl, each unsubstituted or substituted with 1, 2. 3, 4, or 5 substituents independently selected from Cj.6 alkyl, halo, nitro, cyano, SO3’X+, PO32“2X+, and COO X+, and provided that at least two of RiA, R1B, R1C,RID,RIE, and R ip are independently aryl or heteroaryl substituted with 1, 2. 3, 4, or 5 substituents independently selected from SO3~X+, PO32"2X’, and COO" X+;R1Gand R1Hare independently H, aryl, or heteroaryl, wherein said aryl and heteroaryl are each unsubstituted or substituted with 1, 2, 3, 4, or 5 substituents independently selected from C1-6alkyl, halo, nitro, cyano, SO3-X+, PO32-2X+, and COO-X+;Aj is arylene, heteroarylene, aralkylene, or heteroaralkylene, each unsubstituted or substituted with 1. 2, 3, or 4 substituents independently selected from halo, nitro, cyano, aryl, and heteroarykA2is absent, arylene, or heteroarylene, wherein said arylene and heteroarylene are each unsubstituted or substituted with 1, 2, 3, or 4 substituents independently selected from halo, nitro, cyano, aryl, and heteroaryl;L; is an unsubstituted or substituted linking heteroatom, arylene, heteroarylene, aralkylene, or heteroaralkylene, wherein said arylene, heteroarylene, aralkylene, and heteroaralkylene are each unsubstituted or substituted with 1, 2, 3. or 4 substituents independently selected fromalkyl, halo, nitro, cyano, aryl, and heteroarykL2and L3are independently absent, arylene, or heteroarylene, wherein said arylene and heteroarylene are each unsubstituted or substituted with 1, 2, 3, or 4 substituents independently selected from C1-6alkyl, halo, nitro, cyano, aryl, and heteroaryl; and X+is H+, a cation, an alkali metal ion, or [N(RA)(RB)(RC)(RD)]+wherein RA, RB, RC, and RDare independently H, C1-6alkyl, aryl, or heteroaryl.

[0110] In some embodiments, the sulfonated polyphenylene polymer comprises a repeat unit (x) of Formula (1), wherein Formula (1) has the structure:R1A, R1B, R1C, R1D, R1E, and R1Fare independently aryl or heteroaryl, each unsubstituted or substituted with 1, 2, 3, 4, or 5 substituents independently selected from C1-6alkyl, halo, nitro, cyano, SO3-X+, PO32"2X+, and COO X+, and provided that at least two of R1A, R1B, R1C, R1D, R1E, and R1Eare independently aryl or heteroaryl substituted with 1, 2, 3, 4, or 5 substituents independently selected from SO3‘X+, PO32"2X+, and COO" X+;R1Gand R1Hare independently H, aryl, or heteroaryl, wherein said aryl and heteroaryl are each unsubstituted or substituted with 1, 2, 3, 4, or 5 substituents independently selected from C1-6alkyl, halo, nitro, cyano, SO3-X+, PO32-2X+, and COO-X+;A1is arylene, heteroarylene, aralkylene, or heteroaralkylene, each unsubstituted or substituted with 1, 2, 3, or 4 substituents independently selected from halo, nitro, cyano, ary l, and heteroaryl;A2is absent, arylene, or heteroarylene, wherein said arylene and heteroarylene are each unsubstituted or substituted with 1, 2, 3, or 4 substituents independently selected from halo, nitro, cyano, aryl, and heteroaryl;L1is an unsubstituted or substituted linking heteroatom, arylene, heteroarylene, aralkylene, or heteroaralkylene, wherein said arylene, heteroarylene, aralkylene, and heteroaralkylene are each unsubstituted or substituted with 1, 2, 3, or 4 substituents independently selected from C1-6alkyl, halo, nitro, cyano, aryl, and heteroaryl;L2and L3are independently absent, arylene, or heteroarylene, wherein said arylene and heteroarylene are each unsubstituted or substituted with 1, 2, 3, or 4 substituents independently selected from C1-6alkyl, halo, nitro, cyano, aryl, and heteroaryl;X+ is H+, a cation, an alkali metal ion, or [N(RA)(Rg)(Rc)(RD)]+wherein RA, RB, R(2, and RQ are independently H, Cj.g alky l, ary l, or heteroaryl; andprovided that the repeating unit of Formula (I) is not

[0111] In some embodiments of the sulfonated polyphenylene polymer, A1is unsubstituted or substituted arylene, wherein the substituted arylene is substituted with 1.2, 3, or 4 substituents independently selected from halo, nitro, cyano, aryl, and heteroaryl, and A2is absent.

[0112] In some embodiments of the sulfonated polyphenylene polymer, L1is naphthalenylene, phenylene, or C1-6alkyl-substituted phenylene, and L2and L3are independently absent or phenylene, and wherein when present, each phenylene is unsubstituted or substituted with 1, 2, 3, or 4 substituents independently selected from C1-6alkyl and halo.

[0113] In some embodiments, the sulfonated polyphenylene polymer further comprises a. hydrophobic polyphenylene repeat unit (y) of Formula (II) to form a polyphenylene copolymer, wherein Formula (II) has the structure:anwherein:R2A, R2B, R2C, R2D, R2E, and R2Fare independently aryl or heteroaryl, each unsubstituted or substituted with 1, 2, 3, 4, or 5 substituents independently selected from C1-6alkyl, halo, nitro, and cyano;R2Gand R2Hare independently H, aryl, or heteroaryl, wherein said aryl and heteroaryl are each unsubstituted or substituted with 1, 2, 3, 4, or 5 substituents independently selected from C1-6alkyl, halo, nitro, and cyano;B1is arylene, heteroarylene, aralkylene, or heteroaralkylene, each unsubstituted or substituted with 1, 2, 3, or 4 substituents independently selected from C1-6alkyl, halo, nitro, cyano, aryl, and heteroaryl;B2is absent, arylene, or heteroarylene, wherein said arylene and heteroarylene are each unsubstituted or substituted with 1, 2, 3, or 4 substituents independently selected from C1-6alkyl, halo, nitro, cyano, aryl, and heteroaryl;L| is an unsubstituted or substituted linking heteroatom, arylene, heteroarylene, aralkylene, or heteroaralkylene, wherein said arylene, heteroarylene, aralkylene, and heteroaralkylene are each unsubstituted or substituted with 1, 2, 3, or 4 substituents independently selected from C1-6alkyl, halo, nitro, cyano, aryl, and heteroaryl;L2and Lj are independently absent, arylene, or heteroarylene, wherein said arylene and heteroarylene are each unsubstituted or substituted with 1, 2, 3, or 4 substituents independently selected from C1-6alkyl, halo, nitro, cyano, aryl, and heteroaryl; and X+is H+, a cation, an alkali metal ion, or [N(RA)(RB)(RC)(RD)]+wherein RA, RB, RC, and RDare independently H, C1-6alkyl, aryl, or heteroaryl.

[0114] In some embodiments, the polyphenylene copolymer has a structure of Formula (III):(III),wherein:R]A, RIB, R]C> RJD- R-1E,RIFareindependently aryl or heteroaryl, each unsubstituted or substituted with 1, 2, 3, 4, or 5 substituents independently selected from Ci-6 alkyl, halo, nitro, cyano, SO3’X+, PO2’2X+. and COO'X+;R2A, R2B, R2C, R2D, R2E, and R2Fare independently aryl or heteroaryl, each unsubstituted or substituted with 1, 2, 3, 4, or 5 substituents independently selected from C1-6alkyl, halo, nitro, and cyano;R1Gand RIH are independently II, aryl, or heteroaryl, wherein said aryl and heteroaryl are each unsubstituted or substituted with 1, 2, 3, 4, or 5 substituents independently selected from Cj. alkyl, halo, nitro, cyano, SO ’X+, PO322X+, and COO X+;R2Gand R2Hare independently H, aryl, or heteroaryl, wherein said aryl and heteroaryl are each unsubstituted or substituted with 1, 2, 3, 4, or 5 substituents independently selected from C1-6alkyl, halo, nitro, and cyano;A] and Bj are independently arylene, heteroarylene, aralkylene, or heteroaralkyl ene, each unsubstituted or substituted with 1, 2, 3, or 4 substituents independently selected from C1-6alkyl, halo, nitro, cyano, aryl, and heteroaryl;A2and B2are independently absent, arylene, or heteroarylene, wherein said arylene and heteroarylene are each unsubstituted or substituted with 1, 2. 3, or 4 substituents independently selected from C1-6alkyl, halo, nitro, cyano, aryl, and heteroaryl;Lj is an unsubstituted or substituted linking heteroatom, arylene, heteroarylene, aralkylene, or heteroaralkylene, wherein said arylene, heteroarylene, aralkylene, and heteroaralkylene are each unsubstituted or substituted with 1. 2, 3, or 4 substituents independently selected from C1-6alkyl, halo, nitro, cyano, aryl, and heteroaryl;L2and L3are each independently absent, arylene, or heteroarylene, wherein said arylene and heteroarylene are each unsubstituted or substituted with 1, 2, 3, or 4 substituents independently selected from C]_6alkyl, halo, nitro, cyano, aryl, and heteroaryl; andX+is H+, a cation, an alkali metal ion, or [N(RA)(RB)(RC)(RD)]+wherein RA, RB, RC, and RDare independently H, C1-6alkyl, aryl, or heteroaryl.

[0115] In some embodiments, in the copolymer of structure (III), at least two of R], RIB RICE R]D’ RIE? and RIFafeindependently aryl or heteroaiyl substituted with 1, 2, 3, 4. or 5 substituents independently selected from SO3'X+, PO32-2X+, and COO’X+

[0116] In some embodiments, the polyphenylene copolymer has a structure ofR3, R4, R5, and Rg are independently selected from H, SC>3’X+, PO2-2X+, and COO-X+:R7, Rg, R9, and R] 0are independently selected from H. C|_6alkyl, halo, nitro, and cyano;A1and B1are independently arylene, heteroarylene, aralkylene, or heteroaralkylene, each unsubstituted or substituted with 1, 2, 3, or 4 substituents independently selected from C1-6alkyl, halo, nitro, cyano, aryl, and heteroaryl;A2and B2are independently absent, arylene, heteroarylene, aralkylene, or heteroaralkylene, wherein said arylene, heteroarylene, aralkylene, or heteroaralkylene are each unsubstituted or substituted with 1, 2, 3, or 4 substituents independently selected from C1-6alkyl, halo, nitro, cyano, aryl, and heteroaryl;Lj is an unsubstituted or substituted linking heteroatom, arylene, heteroarylene, aralkylene. or heteroaralkylene, wherein said arylene, heteroarylene. aralkylene, and heteroaralkylene are each unsubstituted or substituted with 1. 2, 3, or 4 substituents independently selected from C1-6alkyl, halo, nitro, cyano, aryl, and heteroaryl;L2and L3 are each independently absent, arylene, or heteroarylene, wherein said arylene and heteroarylene are each unsubstituted or substituted with 1, 2. 3, or 4 substituents independently selected from C1-6alkyl, halo, nitro, cyano, aryl, and heteroaryl; andX+is H+, a cation, an alkali metal ion, or [N(RA)(RB)(RC)(RD)]+wherein RA, RB, RC, and RDare independently H, C1-6alkyl, aryl, or heteroaryl.

[0117] In some embodiments, A1, B1, or both A1and B1are independently arylene, unsubstituted or substituted with 1, 2, 3, or 4 substituents independently selected from C1-6alkyl, halo, nitro, cyano, aryl, and heteroaryl; and A2, B2, or both A2and B2are absent.

[0118] In some embodiments, L1is naphthalenylene, phenylene, or C1-6alkyl-substituted phenylene, and L2and L3are each independently absent or phenylene, wherein when present, each phenylene is unsubstituted or substituted with 1, 2, 3, or 4 substituents independently selected from C1-6alkyl and halo, and wherein Lj of Formula (I) is the same or different from Lj of Formula (II), L2of Formula (I) is the same or different from L2of Formula (II), and L of Formula (I) is the same or different from L3of Formula (II).

[0119] In some embodiments, the sulfonated polyphenylene polymer membraneforming composition further comprises a branching comonomerwherein Mj is selected from an unsubstituted or substituted linking atom, arylene, heteroary iene, aralkylene, heteroaralkyl ene, and combinations thereof, wherein the linking atom, arylene, heteroarylene, aralkylene, and heteroaralkylene are each unsubstituted or substituted with 1, 2, or 3 substituents independently selected from Cj_6alkyl, halo, nitro, cyano, ary l, and heteroaryl.

[0120] In some embodiments,is bound through at least 3 covalent bonds, and is selected from the group consisting of:

[0121] In some embodiments, the sulfonated polyphenylene polymer membraneforming composition has a branched structure of Formula (V):(V),wherein P1and P2are both a repeat unit (x) of Formula (I), or are independently selected from a repeat unit (x) of Formula (I) and a repeat unit (y) of Formula (II); and R1A, R1B, R1C, R1D, R1E, R1F, R1G, R1H, A1and A2are as described for Formula (I)

[0122] In some embodiments, the ratio of a repeat unit (z) to the sum of a repeat unit (x), P1and P2of Formula (V) (i.e., z / (x+P1+P2)) is less than 0.2.

[0123] In some embodiments, each L1, L2, and L3when present, and each L2and L3when present, are independently selected from:-31-wherein X+is H+, a cation, an alkali metal ion, or [N(RA)(RB)(RC)(RD)]+wherein RA, RB, RC, and RDare independently H, C1-6alkyl, aryl, or heteroaryl.wherein X+is H, a cation, an alkali metal ion, or [N(RA)(Rg)(Rt^)(RD)]+wherein RA, Rg, Rg, and RQ are independently H, Cgg alkyl, aryl, or heteroaryl.

[0126] In some embodiments, the repeat unit (y) of Formula (II) is selected from:

[0127] In some embodiments, the repeat unit (y) of Formula (II) is selected from:

[0128] In some embodiments, the mole percent of the repeat unit (x) is about 59% to about 99%, and the mole percent of the repeat unit (y) is about 41% to about 1%. In some embodiments, the mole percent of the repeat unit (x) is about 79% to about 99%, and the mole percent of the repeat unit (y) is about 21% to about 1%. In some embodiments, the mole percent of the repeat unit (x) is about 85% to about 95%, and the mole percent of the repeat unit (y) is about 15% to about 5%.

[0129] In some embodiments, the mole percent of the repeat unit (x) is about 90%, and the mole percent of the repeat unit (y) is about 10%.

[0130] In some embodiments, the polyphenylene copolymer is a random copolymer comprising a random distribution of the repeat units (x) and (y).

[0131] In some embodiments, the polyphenylene copolymer is a statistical copolymer comprising an average composition ratio of the repeat units (x) and (y).

[0132] In some embodiments, the polyphenylene copolymer is a block copolymer, wherein:the repeat unit (x) is an integer from 3 to 100,the repeat unit (y) is an integer from 3 to 100; andwherein a mole ratio of the first block to the second block ranges from 1:99 to 99: 1.

[0133] In some embodiments, the sulfonated polyphenylene polymer comprises between about 1 wt% and about 50 wt% of the membrane-forming composition, between about 5 wt% and about 25 wt% of the membrane-forming composition, or between about 5 wt% and about 15 wt% of the membrane-forming composition.

[0134] In some embodiments, the membrane-forming composition has a shear viscosity (at 10 s-1shear rate) less than about 5,000 centi Poise (cP).Antioxidants

[0135] In some embodiments, the one or more antioxidant comprises one or more metal salt-based antioxidant, one or more complex-based antioxidant, one or more particlebased antioxidant, or a combination thereof.

[0136] In some embodiments, the one or more antioxidant comprises one or more metal salt-based antioxidant.

[0137] In some embodiments, the one or more antioxidant comprises a cerium salt.

[0138] In some embodiments, the metal salt-based antioxidant is selected from the group consisting of cerium hydrogen phosphate (CeHPO^, cerium(III) nitrate hexahydrate (Ce(NO3)3'6H?. O), cerium(III) chloride (CeCh), cerium(III) sulfate (Ce2(SO4)s), cerium(III) acetate (CetCjJ-IaGb.)?,), cerium(III) carbonate (Cej^COa)?), zinc chloride (ZnCE), zinc sulfate (ZnSCh), zinc acetate (ZntCfH-iO-h). manganese chloride (MiiCh), manganese sulfate (MnSC ), manganese acetate (Mnf ZHsOa^), copper sulfate (CuSCh), copper chloride (C11CI2), copper acetate (CutXZHaCh^), nickel chloride (NiCL>), nickel sulfate (N1SO4). nickel acetate (NiiCbHjt h). cobalt chloride (C0CI2). cobalt sulfate (C0SO4), cobalt acetate (Co CzHaCb ), sodium selenite (NazSeCh), sodium selenate (NaaSeOr), selenious acid (HfSeOu. aluminum(III) chloride (AlCls), aluminum nitrate (AlfNOsJs), tin(II) chloride (SnCh), and combinations thereof.

[0139] In some embodiments, the one or more antioxidant comprises one or more complex-based antioxi dant.

[0140] In some embodiments, the one or more antioxidant comprises a cerium complex.

[0141] In some embodiments, the complex-based antioxidant is selected from the group consisting of cenum(III) picolinate, cerium(III) bis(picolinate), cenum(lll) bis(bipyridyl), cerium(III) 1,10-phenanthroline, cerium(III) 2,2'-bipyridyl-5,5'-dicarboxvlate, cerium(III) 2,2'-bipyridyl, cerium(III) 3,4-dimethylpyridine, ceriura(III) imidazole, cenum(III) pyrazole, cerium(III) tetrapyridyl, zinc picolinate, zinc monomethionme, zinc gluconate. copper(II) picolinate, copper(II) 1,10-phenanthroline, copper(II) bisphosphonate, copper(II) gluconate, copper(II) hydroxyqumoline, nickel(II) picolinate, nickel(II) acetylacetonate, nickel(II) 1,10-phenanthroline, nickel(II) salicylate, nickel(II) glycinate, nickel(II) ethylenediaminetetraacetic acid, cobalt(II) picolinate, cobalt(II) 1,10-phenanthroline, cobalt(II) gluconate. cobalt(II) salicylate, cobalt(II) ethylenedi aminetetraacetic acid. iron(Il) picolinate, iron(ll) bisphosphonate, iron(II) 1,10-phenanthroline, iron(II) gluconate, iron(II) salicylate, potassium ferricyanide, ferric hexacyanoferrate(lll), and combinations thereof.

[0142] In some embodiments, the complex-based antioxidant comprises a 1,10-phenanthroline complex, wherein the 1,10-phenanthroline is unsubstituted or substituted with 1, 2, 3, 4, 5, or 6 substituents independently selected from Cj-g alkyl, aryl, heteroaryl, ketone (=0), -S0wX+, and sulfonic acid (-SO H). Examples of such substituted 1,10-phenanthroline include 5,6-Dimethyl- 1, 1 O-phenanthroline; 4,7-Diphenyl-l, 1 -phenanthroline; 2,9-Diphenyl- 1, 10-phenanthrolme; 2,9-Dimethyl- 1, 10-phenanthroline; 2.9-Dimethyl-4,7-diphenyl-l,10-phenanthroline-3,8-disulfomc acid: and 4,7-Diphenyl- 1.10-phenanthroline, 2,9-dimethyl disulfonate.

[0143] In some embodiments, the one or more antioxidant comprises one or more particle-based antioxidant.

[0144] In some embodiments, the particle-based antioxidant is selected from the group consisting of metal oxide, cerium oxide (CeCh), zinc oxide (ZnO), nickel oxide (NiO), copper(II) oxide (CuO), copper(I) oxide (Cu2O). manganese dioxide (MnC ), titanium dioxide (TiCh), zirconi um-doped cerium oxide (CeCh-ZrCh), lanthanum-doped cerium oxide (CeCh-LaaO?), praseodymium-doped cerium oxide (CeCh-PnCh), gadolini um-doped cerium oxide (CeO2.-Gd2. O3), yttri um-doped cerium oxide (CeOz-YzO.y), copper-doped cerium oxide (CeCh-CuO). iron-doped cerium oxide (CeO2-Fe2O3). nickel-doped cerium oxide (CeCh-NiO), cobalt-doped cerium oxide (CeCh-CoO). manganese-doped cerium oxide (CeOz-MnO?.), tin-doped cerium oxide (CeCh-SnO?), and combinations thereof,

[0145] In some embodiments, the particle-based antioxidant is a metal oxide. In some embodiments, the particle-based antioxidant is cerium oxide (CeO2).

[0146] In some embodiments, the one or more antioxidant comprises cerium oxide (CeO2). In some embodiments, the cerium oxide is a nanoparticle.

[0147] In some embodiments, the one or more antioxidant further comprises an organic phenolic compound

[0148] In some embodiments, the organic phenolic compound is selected from the group consisting of vitamin E, quercetin, resveratrol, polyphenol, pentaery thrityl tetra-di-t-butyl hydroxyhydrocinnamate, octadecyl di-t-butyl-4-hydroxyhydrocinnamate, ethylene bis(oxyethylene) bis-(3-(5-tert-butyl-4-hydroxy-m-tolyl)-propionate), pentaerythritol tetrakis[3-[3,5-di-tert-butyl-4-hydroxyphenyl]propionate, and combinations thereof.

[0149] In some embodiments, the one or more antioxidant comprises a fluoroalkyl phosphonic acid, a bisphosphonic acid, Trolox-bisphosphonate, pyndoxal-5'-bisphosphonate, and combinations thereof.

[0150] In some embodiments, the one or more antioxidant further comprises a polymer antioxidant. For example, phenolic antioxidants, similar to the commercially available antioxidants found in BASF®'s Irganox* Series (e.g., Irganox® 1010 and Irganox® 1076) may be incorporated into the polymeric structure. Light stabilizing moieties comprising hindered amine light stabilizers (HALS), similar to BASF®'s Tinuvin® Series, may also be integrated to provide dual functionality'. The present disclosure provided herein may include both phosphite and phenolic-based polymeric antioxidants, similar to commercially available Clanant®'s Hostanox® series polymers. Flexibility in application using phosphite and phenolic- based polymeric antioxidants, similar to that of Cytec®'s Cyanox® products, allows for its use with the present disclosure. The polymeric antioxidants of the present disclosure may incorporate structural elements analogous to those found in Adeka®'s Ultra® Series, Kraton®'s Paqell® line, or Eastman® Chemical's Epolene® range. The foregoing examples illustrate some commercially available polymeric antioxidants that are useful in the present disclosure, without limiting the invention to these specific embodiments.

[0151] In some embodiments, the one or more antioxidant comprises cerium hydrogen phosphate (CellPO^).

[0152] In some embodiments, the one or more antioxidant further comprises an inorganic oxide. In some embodiments, the inorganic oxide is fumed silica (SiCL). In some embodiments, fumed silica is also included for water management in a high-temperature environment (e.g., between 80°C and 160°C).

[0153] In some embodiments, the one or more antioxidant further comprises an organic compound. In some embodiments, the organic compound is tetraethyl orthosilicate (TOS). In some embodiments, the TOS is included to form particles to enhance adherence to the framework. In some embodiments, TOS is also included for waler management in a high-temperature environment (e.g., between 80°C and 160°C).

[0154] In some embodiments, the one or more antioxidant further comprises a metal-organic frameworks (MOF),

[0155] In some embodiments, the one or more antioxidant further comprises polyhedral oligomeric silsesquioxanes (POSS). In some embodiments, the POSS is sulfonated POSS (sPOSS)Metal Oxide Antioxidants

[0156] In some embodiments, the one or more antioxidant comprises a metal oxide, wherein the metal oxide, described by Chemical Formula (I):MO2-p(I),comprises M, which can be a transition metal or a rare-earth metal, adjusted for electrical neutrality' by P through oxygen vacancies. In some embodiments, the metal (M) of the metal oxide is selected from the group consisting of zirconium (Zr), cerium (Ce), samarium (Sm), gadolinium (Gd), terbium (Tb), tin (Sn), niobium (Nb), tantalum, and titanium (Ti).

[0157] In some embodiments, the one or more antioxidant comprises a mixture of more than one metal oxides, wherein the metal oxides are selected from the group consisting of zirconium oxide (ZrO2), cerium oxide (CeO2), samarium oxide (Sm2O3). gadolinium oxide (Gd2O3), terbium oxide (Tb^O ), and tin oxide (SnO2). For example, the antioxidant can be a mixture of tin oxide (SnCh) and cerium oxide (CeO?).

[0158] In some embodiments, the one or more antioxidant is selected from the group consisting of cerium oxide (CeCh), zinc oxide (ZnO), nickel oxide (NiO), copper(II) oxide (CuO). copper® oxide (Cu2O), manganese dioxide (MnCh), titanium dioxide (Ti O2), niobium oxide (Nb2O3, NbO, anchor NbO2), tantalum oxide (Ta C®, potassium octatitanate (K2Ti80jy and / or K2Ti60j 3). and combinations thereof.

[0159] In some embodiments, niobium oxide and tantalum oxide is individually included for water management in a high-temperature environment (e.g., between 80°C and 160°C).

[0160] In some embodiments, the one or more metal oxide is a particle. In some embodiments, the one or more metal oxide is a fiber. In some embodiments, the metal oxide particles are doped with one or more metal. For example, the antioxidant can be cerium oxide doped with tin (Sn). The tin-doped cerium oxide can be suitably obtained by substituting at least a portion of cerium(IV) ions (Ce4) in the cerium oxide with tin ions (Sn2+and / or Sn4 +).

[0161] In some embodiments, the one or more antioxidant is selected from the group consisting of zirconium-doped cerium oxide (CeCh-ZrCh), lanthanum-doped cerium oxide (CeO2.-La2. O3), praseodymium-doped cerium oxide (CeO2-Pr2. O3), gadolinium-doped cerium oxide (CeO2-Gd2Os), yttrium-doped cerium oxide (CeCh-Y2O3), copper-doped cerium oxide (CeCh-CuO), iron-doped cerium oxide (CeO2-Fe2Os), mckel-doped cerium oxide (CeCh-NiO), cobalt-doped cerium oxide (CeO?-CoO). manganese-doped cerium oxide (CeCh-MnCh), tin-doped cerium oxide (CeCh-SnCh), and combinations thereof.

[0162] In some embodiments, the one or more antioxidant comprises one or more metal oxide and one or more metal oxide doped with one or more metal.

[0163] In some embodiments, the one or more antioxidant comprising the metal oxide, metal ion, or a combination thereof, further comprises a polymer.

[0164] In some embodiments, the polymer is selected from the group consisting of ethyl cellulose, hydroxypropyl methyl cellulose, carboxymethyl cellulose, polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), poly(methyl methacrylate) (PMMA), poly(acrylic acid) (PAA), poly(4-vinylpyridine) (P4VP), chitosan, polyvinyl alcohol (PVA). polyvinyl phenol, poly vinyl phosphonic acid (PVPA), and combinations thereof.

[0165] In some embodiments, the metal oxide is supported on a substrate. In some embodiments, the substrate is selected from the group consisting of titanium dioxide (T1O2), silicon dioxide (S1O2), zirconium oxide (ZrCh), cerium oxide (CeCh), cerium zirconium oxide (CeZrOr), gadolinium-doped cerium oxide (CeO2.-Gd2. O3), carbon, and combinations thereof,

[0166] In some embodiments, the metal oxide is supported on carbon. Other supports with antioxidant properties suitable for fuel cells are also applicable.

[0167] In some embodiments, the metal oxide is a crystallite. The crystallite size of the metal oxide typically ranges from about 1 nm to 100 nm. Smaller sizes have the potential to increase solubility and affect long-term stability, while larger sizes can reduce antioxidant effectiveness. Measurement of crystallite size is typically conducted using X-ray diffraction (XRD)

[0168] In some embodiments, the metal oxide is a component of an agglomerate, wherein the agglomerate size is about 1 pm or less. Additionally, the average particle diameter of the metal oxide agglomerate is 1 pm or less. Such diameter can ensure effectivedispersion within the sulfonated polyphenylene electrolyte membrane, with smaller diameters preferred for uniform distnbution.

[0169] In some embodiments, the one or more antioxidant comprising the metal oxide further comprises an organic compound. In some embodiments, the metal oxide is a particle, and the organic compound is on the surface of the metal oxide particle.[01701 In some embodiments, the organic compound comprises a functional group selected from the group consisting of a sulfonic acid (-SO3H). carboxylic acid (-COOH). alcohol (-OH), ether (-O-), amino (-NH2), amide (-CONH2), and combinations thereof.

[0171] In some embodiments, the organic compound is selected from the group consisting of citric acid, oxalic acid, stearic acid, p-toluenesulfonic acid, methanesulfonic acid, 4-hydroxybutanesulfonic acid, 3-hydroxypropanesulfonic acid, propanesulfonic acid, butylsulfonic acid, ethanol, isopropanol, polyvinyl alcohol (PVA), polyethylene glycol (PEG), crown ethers, caffeic acid, ferulic acid, vanillic acid, protocatechuic acid, 1,2-dihydroxybenzene, 2-hydroxybenzoic acid, 4-(2-aminoethyl)benzene-l,2-diol (dopamine), polydopamine, ethylenediamine, triethylamine, acrylamide, N, N-dimethyl formamide, ethanol amine, triethanol amine, 3-aminopropyltnmethoxysilane (APTMS), and combinations thereof.Methods

[0172] The membrane-forming composition can be prepared by dissolving sulfonated polyphenylene in a suitable solvent or solvent blend as disclosed herein, followed by thorough mixing. In some embodiments, the membrane-forming composition is applied to one or both surface of a substrate (such as film, glass, or metal) to form the membrane on the substrate

[0173] The membrane-forming composition is a liquid solution or mixture at room temperature, and the solution is pourable. As used herein, pourable means that the solution has a shear viscosity less than about 100,000 cP at processing temperature, particularly less than about 10,000 cP, and more particularly less than about 5,000 cP at 10 s-1shear rate Processing temperature was typically carried out at about 20°C to about 25°C. However, higher or lower temperatures may be used instead.

[0174] In an aspect of this disclosure, provided herein is a method of making a sulfonated polyphenylene membrane through a layer-by-layer coating, comprising:(a) preparing a first solution comprising one or more sulfonated polyphenylene polymer as defined herein and one or more solvent;(b) applying the first solution onto a substrate to form a first wet layer;(c) drying the first wet layer at a temperature between about 40°C and about 70°C to produce a first sulfonated polyphenylene polymer layer;(d) preparing a second solution comprising one or more antioxidant as defined herein and one or more solvent;(e) applying the second solution onto the first sulfonated polyphenylene polymer layer to form a second wet layer;(f) drying the second wet layer between about 40°C and about 70°C to produce an antioxidant layer, thereby forming a composite membrane comprising the first sulfonated polyphenylene polymer layer and the antioxidant layer, wherein the antioxidant layer is in contact with the first sulfonated polyphenylene polymer layer;(g) applying the first solution or a third solution comprising the same or different one or more sulfonated polyphenylene polymer as defined herein and one or more solvent onto the antioxidant layer to form a third wet layer;(h) drying the composite membrane with the third wet layer between about 40°C and about 70°C to produce a second sulfonated polyphenylene polymer layer, wherein the second sulfonated polyphenylene polymer layer is in direct contact with the antioxidant layer, and wherein the second sulfonated polyphenylene polymer layer is either identical to, or different from, the first sulfonated polyphenylene polymer layer.

[0175] FIG. 1A shows an example layered sulfonated polyphenylene membrane 101, including sulfonated polyphenylene polymer layers 1 and 3 and an antioxidant layer 2, in accordance with embodiments described herein. In some embodiments, the layers are cast atop a substrate 10.

[0176] FIG. IB shows an example layered sulfonated polyphenylene membrane 102, including sulfonated polyphenylene polymer layers 1 and 3 and an antioxidant layer 2, wherein each layer has varying thickness throughout the layer, in accordance with embodiments described herein. In some embodiments, the layers are cast atop a substrate 10.

[0177] FIG. 1C shows an example asymmetrical layered sulfonated polyphenylene membrane 103, including sulfonated polyphenylene polymer layers 1 and 3 and an antioxidant layer 2, wherein the sulfonated polyphenylene polymer layers 1 and 3 havedifferent thicknesses, in accordance with embodiments described herein. In some embodiments, the layers are cast atop a substrate 10.

[0178] FIG IF shows an example sulfonated polyphenylene membrane 106, including integrated sulfonated polyphenylene polymer layers 1' and 3' and an integrated antioxidant layer 2', wherein the integrated sulfonated polyphenylene polymer layers 1’ and 3' are embedded to an extent within the integrated antioxidant layer 2; and the integrated antioxidant layer 2' is embedded to an extent within the integrated sulfonated polyphenylene polymer layers 1' and 3', in accordance with embodiments described herein. In some embodiments, the layers are cast atop a substrate 10.

[0179] In some embodiments, the method further comprises repeating steps (d) through (h) one or more time to form additional alternating layer of sulfonated polyphenylene polymer and antioxidant.

[0180] In some embodiments, the method further comprises:(i) coating the second sulfonated polyphenylene polymer layer of the membrane with a solution comprising one or more antioxidant as defined herein and one or more solvent;(j) heating the coated membrane at a temperature between about 40°C and about 70°C to form a membrane comprising a second antioxidant layer, wherein the second antioxidant layer is in contact with the second sulfonated polyphenylene polymer layer, and is the same as, or different from, the first antioxidant layer;(k) coating the second antioxidant layer with a solution comprising one or more sulfonated polyphenylene polymer as defined herein and one or more solvent, wherein said sulfonated polyphenylene polymer solution is in contact with the second antioxidant layer, and is the same as, or different from, the sulfonated polyphenylene polymer solution used to prepare the first or second sulfonated polyphenylene polymer layers: and(l) heating the coated membrane at a temperature between about 40°C and about 70°C to form a membrane comprising:(i) the first sulfonated polyphenylene polymer layer,(ii) the first antioxidant layer,(iii) the second sulfonated polyphenylene polymer layer,(iv) the second antioxidant layer, and(v) a third sulfonated polyphenylene polymer layer.

[0181] In some embodiments, the sulfonated polyphenylene membrane comprises up to 10 sulfonated polyphenylene polymer layers and up to 9 antioxidant layers.

[0182] FIG 2A shows an example layered sulfonated polyphenylene membrane 201, including two alternating antioxidant layers 2 and 4 in between alternating sulfonated polyphenylene polymer layers 1, 3, and 5, in accordance with embodiments described herein. In some embodiments, the layers are cast atop a substrate 10.

[0183] In some embodiments, the heating steps (c), (f). (h), (j), and (1) are performed for a duration ranging from about 1 minute to about 24 hours.

[0184] In some embodiments, the antioxidant solution used in step (i) is the same as the antioxidant solution used in step (e).

[0185] In some embodiments, the antioxidant solution used in step (i) is different from the antioxidant solution used in step (e).

[0186] In some embodiments, the sulfonated polyphenylene polymer solution used in step (k) is the same as the sulfonated polyphenylene polymer solution used in step (a) and / or step (g).

[0187] In some embodiments, the sulfonated polyphenylene polymer solution used in step (k) is different from the sulfonated polyphenylene polymer solution used in step (a) and / or step (g).

[0188] In another aspect of this disclosure, provided herein is a method of making a sulfonated polyphenylene membrane through a layer-by-layer coating, comprising:(a) preparing a first solution comprising one or more antioxidant as defined herein and one or more solvent;(b) applying the first solution onto a substrate to form a first wet layer;(c) drying the substrate with the first wet layer between about 40°C and about 70°C to produce a first antioxidant layer;(d) preparing a second solution comprising one or more sulfonated polyphenylene polymer as defined herein and one or more solvent;(e) applying the second solution onto the first antioxidant layer to form a second wet layer;(f) drying the first antioxidant layer with the second wet layer between about 40°C and about 70°C to produce a first sulfonated polyphenylene polymer layer, thereby forming an intermediate membrane;(g) applying the first solution or a third solution comprising one or more antioxidant as defined herein and one or more solvent onto the first sulfonated polyphenylene polymer layer to form a third wet layer;(h) drying the intermediate membrane with the third wet layer between about 40°C and about 70 C to produce a second antioxidant layer, resulting m a final membrane; wherein the final membrane structure comprises, in sequence:(i) the first antioxidant layer,(li) the first sulfonated polyphenylene polymer layer, and(iii) the second antioxidant layer; andwherein the first sulfonated polyphenylene polymer layer is in contact with the first antioxidant layer, wherein the second antioxidant layer is in contact with the first sulfonated polyphenylene polymer layer, andwherein the second antioxidant layer is either identical to, or different from, the first antioxidant layer.

[0189] In some embodiments, the method further comprises repeating steps (d) through (h) one or more times to form additional alternating layers of sulfonated polyphenylene polymer and antioxidant.[01901 In some embodiments, the method further comprises:(i) coating the second antioxidant layer of the membrane with a solution comprising one or more sulfonated polyphenylene polymer and one or more solvent;(j) heating the coated membrane at a temperature between about 40°C and about 70°C to form a membrane comprising a second sulfonated polyphenylene polymer layer, wherein the second sulfonated polyphenylene polymer layer is in contact with the second antioxidant layer:(k) coating the second sulfonated polyphenylene polymer layer with a solution comprising antioxidant as defined herein and one or more solvent, wherein said antioxidant solution is the same as, or different from, the antioxidant solution used to prepare the first and / or second antioxidant layers; and(l) heating the coated membrane at a temperature between about 40°C and about 70 C to form a membrane comprising;(i) the first antioxidant layer.(ii) the first sulfonated polyphenylene polymer layer,(iii) the second antioxidant layer,(iv) the second sulfonated polyphenylene polymer layer, and(v) a third antioxidant layer,wherein:the third antioxidant layer is in contact with the second sulfonated polyphenylene polymer layer, andthe third antioxidant layer is the same as, or different from, the first and / or second antioxidant layers.

[0191] FIG. ID shows an example asymmetrical layered sulfonated polyphenylene membrane 104, including a sulfonated polyphenylene polymer layer 1 and antioxidant layers 2 and 4, wherein the antioxidant layers 2 and 4 have different thicknesses, in accordance with embodiments described herein. In some embodiments, the layers are cast atop a substrate 10.

[0192] FIG. IE shows an example symmetrical layered sulfonated polyphenylene membrane 105, including a sulfonated polyphenylene polymer layer 1 and antioxidant layers 2 and 4, wherein the antioxidant layers 2 and 4 have the same thicknesses, in accordance with embodiments described herein. In some embodiments, the layers are cast atop a substrate 10.

[0193] In some embodiments, the sulfonated polyphenylene membrane comprises up to 9 sulfonated polyphenylene polymer layers and up to 10 antioxidant layers.

[0014] FIG. 2B shows an example layered sulfonated polyphenylene membrane 202, including two alternating sulfonated polyphenylene polymer layers 1 and 3 in between alternating antioxidant layers 2, 4, and 6, in accordance with embodiments described herein. In some embodiments, the layers are cast atop a substrate 10.

[0195] In some embodiments, the heating steps (c). (f), (h). (j), and (1) are performed for a duration ranging from about 1 minute to about 24 hows.

[0196] In some embodiments, the sulfonated polyphenylene polymer solution used in step (i) is the same as the sulfonated polyphenylene polymer solution used in step (e).

[0197] In some embodiments, the sulfonated poly phenylene poly mer solution used in step (i) is different from the sulfonated polyphenylene polymer solution used in step (e)

[0198] In some embodiments, the antioxidant solution used in step (k) is the same as the antioxidant solution used in step (a) and / or step (g).

[0199] In some embodiments, the antioxidant solution used in step (k) is different from the antioxidant solution used in step (a) and / or step (g).

[0200] In some embodiments, the method further comprises:(a) contacting a solution comprising one or more sulfonated polyphenylene pol mer as defined herein and one or more solvent with a first surface of a porous scaffold reinforcement, wherein said porous scaffold reinforcement has a first surface and a second surface;(b) heating the porous scaffold reinforcement and the sulfonated polyphenylene polymer solution in contact with the first surface;(c) contacting the second surface of the porous scaffold reinforcement with a solution comprising one or more sulfonated polyphenylene polymer as defined herein and one or more solvent; and(d) heating the porous scaffold reinforcement and the sulfonated polyphenylene polymer solution in contact with the second surface, thereby forming a reinforced sulfonated polyphenylene polymer layer,wherein the sulfonated polyphenylene polymer solution in contact with the first surface of the porous scaffold reinforcement is the same as, or is different from, the sulfonated polyphenylene polymer solution in contact with the second surface of the porous scaffold reinforcement.

[0201] In some embodiments, the sulfonated polyphenylene polymer solution in contact with the first surface of the porous scaffold reinforcement is the same as the sulfonated polyphenylene polymer solution in contact with the second surface of the porous scaffold reinforcement.

[0202] In other embodiments, the sulfonated polyphenylene polymer solution in contact with the first surface of the porous scaffold reinforcement is different from the sulfonated polyphenylene polymer solution in contact with the second surface of the porous scaffold reinforcement.

[0203] FIG. 2C shows an example composite sulfonated polypheny lene membrane 203, including sulfonated polyphenylene polymer layers 1 and 3, an antioxidant layer 2, and a porous reinforcement 7, in accordance with embodiments described herein. In some embodiments, the layers are cast atop a substrate 10.

[0204] In some embodiments, the method further comprises repeating steps (a) through (d) one or more time to build up multiple layers of reinforced sulfonated polyphenylene polymer.

[0205] In some embodiments, the method further comprises repeating the foregoing steps (a) through (h) of the layer-by-layer coating one or more time to build upmultiple layers of' the sulfonated polyphenylene polymer and the antioxidant on the porous scaffold reinforcement.

[0206] In some embodiments, heating steps (b) and (d) are performed at a temperature ranging from about 40°C to about 70°C.

[0207] In some embodiments, heating steps (b) and (d) are performed for a duration ranging from about 1 minute to about 24 hours.

[0208] In some embodiments, the method further comprises applying pressure during one or both of heating step (b) and (d) to enhance the integration of the sulfonated polyphenylene polymer into the porous scaffold reinforcement.

[0209] In some embodiments, the reinforced sulfonated polyphenylene polymer layer formed is incorporated into the membrane structure described in the foregoing embodiments, either as a replacement for one of the sulfonated polyphenylene polymer layers or as an additional layer.

[0210] In yet another aspect of this disclosure, provided herein is a method of making a sulfonated polyphenylene membrane, comprising:(a) preparing a solution compnsing:(i) one or more sulfonated polyphenylene polymer as descnbed herein, (ii) one or more antioxidant as described herein, and(iii) one or more solvent:(b) applying the solution to a substrate to form a wet layer; and(c) drying the substrate with the wet layer to form the sulfonated polyphenylene membrane

[0211] FIG. 3 shows an example composite sulfonated polyphenylene membrane 301, including a layer 8 of sulfonated polyphenylene polymer and antioxidant, wherein the sulfonated polyphenylene polymer and the antioxidant are mixed as a single composition and no interface exists between them within the layer, in accordance with embodiments described herein. In some embodiments, the layer is cast atop a substrate 10.

[0212] In some embodiments, the method further comprises:(a) contacting a solution comprising one or more sulfonated polyphenylene polymer as defined herein, one or more antioxidant as defined herein, and one or more solvent, with a first surface of a porous scaffold reinforcement, wherein said porous scaffold reinforcement has a first surface and a second surface;(b) heating the porous scaffold reinforcement and the solution in contact with the first surface:(c) contacting the second surface of the porous scaffold reinforcement with a solution comprising one or more sulfonated polyphenylene polymer as defined herein, one or more antioxidant as defined herein, and one or more solvent: and(d) heating the porous scaffold reinforcement and the solution in contact with the second surface, thereby forming a reinforced sulfonated polyphenylene polymer layer, wherein the solution in contact with the first surface of the porous scaffold reinforcement is the same as, or is different from, the solution in contact with the second surface of the porous scaffold reinforcement.

[0213] In some embodiments, the method further comprises repeating steps (a) through (d) one or more time to build up multiple layers of reinforced sulfonated polyphenylene polymer.

[0214] In some embodiments, heating steps (b) and (d) are performed at a temperature ranging from about 40°C to about 70°C.

[0215] In some embodiments, heating steps (b) and (d) are performed for a duration ranging from about 1 minute to about 24 hours.

[0216] In some embodiments, the method further comprises applying pressure during one or both of heating step (b) and (d) to enhance the integration of the sulfonated polyphenylene polymer into the porous scaffold reinforcement.

[0217] In some embodiments, the porous scaffold reinforcement comprises a material selected from the group consisting of polytetrafluoroethylene (PTFE), expanded polytetrafluoroethylene (ePTFE), polypropylene, polyethylene, polyester, nylon, polysulfone, polybenzimidazole (PBI), poly etheretherketone (PEEK), and combinations thereof.

[0218] In some embodiments, the reinforced sulfonated polyphenylene polymer layer formed is incorporated into the membrane structure described in the foregoing embodiments, either as a replacement for one of the sulfonated polyphenylene polymer layers or as an additional layer.

[0219] In some embodiments, the method further comprises applying pressure during one or more of the heating step to enhance layer adhesion and / or integration.

[0220] In some embodiments, the substrate is selected from the group consisting of glass, metal, ceramic, polymer, and combinations thereof.

[0221] In some embodiments, the sulfonated polyphenylene polymer solution comprises a solvent selected from the group consisting of butanone, pentanone, cyclopentanone, hexanone, cyclohexanone, heptanone, cycloheptanone, propanol, butanol, pentanol, hexanol, cyclohexanol, octanol, decanol, dodecanol, propanediol, butanediol, pentanediol, hexanediol, octanediol, decanediol, dodecanediol, glycerol, ethylene glycol, l-methoxy-2-propanol, dipropylene glycol methyl ether, ethyl lactate, glycerol triacetin, y-butyrolactone, 8-valerolactone, E-caprolactone, and combinations thereof.

[0222] In some embodiments, the antioxidant solution comprises a solvent selected from the group consisting of butanone, pentanone, cyclopentanone, hexanone, cyclohexanone, heptanone. cycloheptanone, propanol, butanol, pentanol, hexanol, cyclohexanol, octanol, decanol, dodecanol, propanediol, butanediol, pentanediol, hexanediol, octanediol, decanediol, dodecanediol, glycerol, ethylene glycol, 1 -methoxylpropanol, dipropylene glycol methyl ether, ethyl lactate, gl cerol triacetin, y-butyrolactone, 5-valerolactone, e-caprolactone, and combinations thereof.

[0223] In some embodiments, the concentration of antioxidant in the antioxidant solution ranges from about 0.1 wt% to about 20 wt%.

[0224] In some embodiments, the concentration of sulfonated polyphenylene polymer in the sulfonated polyphenylene polymer solution ranges from about 1 wt% to about 30 wt%.

[0225] In some embodiments, the method further comprises adding one or more additive to the antioxidant solution, to the sulfonated polyphenylene polymer solution, or to both the antioxidant solution and the sulfonated polyphenylene polymer solution, wherein the additives are selected from the group consisting of plasticizers, polymers (e.g.. polyethylene glycol (PEG), polypropylene glycol (PPG) sulfonated polystyrene, polyvinyl alcohol, polystyrene, cellulosic ethers, etc.), and combinations thereof.

[0226] In some embodiments, the in-plane (x, y direction) swelling upon hydration is less than about 25%. In some embodiments, the in-plane (x. y direction) swelling upon hydration is about 1% to about 10%.

[0227] In some embodiments, the heating comprises heating at a temperature below 120°C. In some embodiments, the heating comprises heating at a temperature between about 40’C and about 120 C, between about 60°C and about 120°C, or between about 80 C and about 120 C.

[0228] Various drying techniques such as warm air, hot air, low humidity air, vacuum drying, or exposure to far-infrared radiation or electron beams can be employed to dry the coating layer. Typically, drying temperatures fall within the range of 30°C to 120°C, with drying times ranging from 1 minute to 1 hour, depending on the solvent type. For instance, drying could occur at temperatures of 50°C to 90°C for a duration of 1 to 30 minutes, or even as short as 1 to 10 minutes.

[0229] Following drying, the residual amount of high-boiling-point solvent in the coated membrane is ideally 10 wt% or less. Specifically, both low-boiling-point and high-boiling-point solvents are ideally 3 wt% or less in the coated separator. In some cases, after drying, no low-boiling-point solvent may remain, while the high-boiling-point solvent may still be present in quantities of 10 wt% or less within the membrane.[02301 The organic solvent remaining in the dried coating layer of the present invention may have a boiling point higher than 150°C.

[0231] In some embodiments, the sulfonated polyphenylene polymer solution has a viscosity' less than about 5,000 cP, or between about 50 cP and about 5000 cP.Ball-milled Metal Oxide Particles

[0232] In a further aspect, this disclosure provides a method for manufacturing ultrafine metal oxide powders, comprising:(a) selecting a metal oxide as disclosed herein;(b) mixing the metal oxide with an organic additive to form a mixture; and (c) milling the mixture for about 0.5 hour to about 48 hours to form an ultrafine powder, wherein the ultrafine powder comprises particles of about 1 nm to about 200 nm.

[0233] The milling of the mixture can occur m a rotary ball mill such as a Planetary Ball Mill at 200 to 600 rpms. V arying various ball milling parameters enables particles of various target size ranges to be prepared.

[0234] Particle size in ball milling can be controlled by systematically adjusting key parameters, including milling time, milling speed, ball-to-powder ratio (BPR), ball size, ball material, and the choice between wet and dry milling conditions. For instance, to process coarse particles larger than 100 pm, larger milling balls, shorter milling times, and lower speeds are used. To obtain fine particles in the I pm to 100 pm range, a combination of ball sizes, moderate to high speeds, and longer milling times is employed, with wet milling being preferred for sizes approaching 1 pm. Nanoparticles smaller than 100 nmrequire small milling balls, high speeds, extended milling times, and typically wet milling conditions, often with the addition of process control agents to prevent agglomeration. By carefully adjusting these variables, particles with desired size distributions and properties can be produced.

[0235] In some embodiments, the organic additive is an organic compound. In some embodiments, the organic compounds used in the ball-milling process contact, or become attached to, the surface of the particles.

[0236] Metal oxide powders of specific sizes can be synthesized by ball-milling metal oxides with organic compounds containing functional groups like sulfonic acid (-SO3H), carboxylic acid (-COOH), alcohol (-OH), ether (-O-), amino (-NH2), amide (-CONH2). others, and combinations thereof. For example, the organic compound is selected from the group consisting of citric acid, oxalic acid, stearic acid, p-toluenesulfonic acid, methanesulfonic acid, 4-hydroxybutanesulfonic acid, 3-hydroxypropanesulfonic acid, propanesulfonic acid, butylsulfonic acid, ethanol, isopropanol, polyvinyl alcohol, polyethylene glycol, crown ethers, caffeic acid, ferulic acid, vanillic acid, protocatechuic acid, 1,2-dihydroxybenzene, 2-hydroxybenzoic acid, 4-(2-aminoethyl)benzene-l,2-diol (dopamine), polydopamine, ethylenediamine, triethylamine, acrylamide, N, N-dimethylformamide, ethanol amine, triethanol amine, 3-aminopropyltrimethoxysilane (APTMS). and combinations thereof.

[0237] The particles can be characterized using a comprehensive suite of analytical techniques. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) are effective for visualizing particle morphology' and size distribution. X-ray Diffraction (XRD) provides insights into crystalline structure and phase composition. Dynamic Light Scattering (DLS) can quantify particle size distribution, while the Brunauer-Emmett-Teller (BET) method measures specific surface area. Chemical composition can be analyzed with Energy Dispersive X-ray Spectroscopy' (EDS), and surface chemistry can be examined using X-ray Photoelectron Spectroscopy (XPS). Additionally. Fourier Transform Infrared Spectroscopy (FTIR) can be employed to identify chemical bonds and functional groups on the particle surfaces.

[0238] In some embodiments, the organic additive is a polymer. In some embodiments, the polymer used in the ball-milling process contact, or become attached to, the surface of the particles.

[0239] In some embodiments, the polymer is selected from the group consisting of ethyl cellulose, hydroxypropyl methylcellulose, carboxymethyl cellulose, polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), poly(methyl methacrylate) (PMMA), poly(acrylic acid) (PAA), poly(4-vinylpyridine) (P4VP), chitosan, polyvinyl alcohol (PVA), polyvinyl phenol, poly vinyl phosphonic acid (PVPA), and combinations thereof.

[0240] Ball-milling enables the production of particles within target size ranges.

[0241] Various organic compounds and polymers are utilized to prepare metal oxide powders with specific characteristics through ball-milling processes.

[0242] The selection of the appropriate organic compound or polymer depends on several factors. These include the desired particle size, as different compounds can influence particle size differently. The surface functionality provided by the organic compound is crucial, as it imparts specific surface properties to the metal oxide particles. Compatibility with the metal oxide is also a consideration, ensuring that the chosen compound or polymer does not induce undesirable reactions during synthesis.

[0243] Ball-milling offers an approach to producing nano-crystalline materials (C. C. Koch, "Synthesis of Nanostructured Materials by Mechanical Milling: Problems and Opportunities", Nano Structured Materials, Vol 9. pp 13-22, 1997). Unlike other methods, ball-milling achieves nano-materials through the structural breakdown of coarser-grained crystals and aggregates through severe plastic deformation. The quality of the final product can be controlled by milling energy, time, and temperature. Achieving particle sizes of a few-nanometers diameter requires extended processing times (several hours for small batches).Porous Scaffold

[0244] In some embodiments, the porous scaffold reinforcement is formed from a plurality of nanofibers.

[0245] In some embodiments, the plurality of nanofibers ranges from about 1 pm to about 50 pm in length.

[0246] In some embodiments, the plurality of nanofibers comprises a non-ionically conducting aiyl-based polymer, a non-ionically conducting heteroatyl-based polymer, a non-ionically conducting heterocyclic-based polymer, a non-ionically conducting alkyl-based polymer, or combinations thereof, and wherein the non-ionically conducting aryl-based polymer, non-ionically conducting heteroaryl-based polymer, non-ionically conducting heterocyclic-based polymer, non-ionically conducting alkyl-based polymer, or combinations thereof are independently unsubstituted or substituted with alkyl groups, heteroatomic groups, or combinations thereof.

[0247] In some embodiments, the plurality of nanofibers comprises one or more polymer building blocks selected from the group consisting of: polysulfone (PSU). polyimide (PI), polyphenylene oxide (PPO), polyphenylene sulfoxide (PPSO), polyphenylene sulfide (PPS), polyphenylene sulfide sulfone (PPS / SO), polyparaphenylene (PPP), polyphenylduinoxaline (PPQ), polyarylketone (PK) polyethersulfone (PES), poly etherethersulfone (PEES). polyarylsulfone, polyarylethersulfone (PAS), polyphenylene sulfone (PPSU). polyphenylenesulfone (PPSO), polyetherketone (PEK), poly etheretherketone (PEEK), polyetherketone-ketone (PEKK), poly ether etherketoneketone (PEEKK) polyetherketoneetherketone-ketone (PEKEKK) polymers, polyphenylene sulfide (PPS), polyarylate. liquid crystal polymer (LCP), polytetrafluoroethylene (PTFE), polypropylene (PP), polyethylene (PE), polyester, polyamide, polystyrene, polyvinyl chloride (PVC), poly benzoxazole (PBO), poly benzothiazole (PBT), polybenzimidazole (PBI), polyamide (PA), polyimide (PI), glass fiber, cellulose, aramid, polypara-pheny lene terephthalamide (PPTA), and a combination thereof.

[0248] In some embodiments, the plurality of nanofibers is woven; stretched; drawn; made by electrospinning; or wet-laid or dry' -laid into a scaffold, sheet, or mat.

[0249] In some embodiments, the porous scaffold reinforcement is formed from one or more woven material. The one or more woven material is selected from woven PEEK, woven PAEK, woven PPS, woven polyarylate or liquid crystal polymer (LCP), woven PTFE, woven PP, woven PE, woven polyester, woven polyamide, and a combination thereof.

[0250] In some embodiments, the porous scaffold reinforcement is formed from one or more stretched material. The one or more stretched material is selected from expanded PE, expanded PTFE. expanded PP, expanded PMP, expanded polystyrene, expanded PVC, and a combination thereof.

[0251] In some embodiments, the porous scaffold reinforcement is formed from one or more electrospun material. The one or more electrospun material is selected fromelectrospun PBI. electrospun PI, electrospun PEEK, electrospun PPS, electrospun PPSU, electrospun polyamide, and a combination thereof.

[0252] In some embodiments, the porous scaffold reinforcement is formed from one or more non-woven material. The one or more non-woven material is selected from wet-laid polyphenylene sulfide (PPS), wet-laid polybenzimidazole (PBI), wet-laid polyimide, wet-laid polyester, wet-laid glass fiber, wet-laid cellulose, dry-laid aramid, dry-laid polyethylene, dry-laid polypropylene, dry-laid polyester, and a combination thereof.

[0253] In some embodiments, the porous scaffold reinforcement is formed from one or more wet-laid material.

[0254] In some embodiments, the porous scaffold reinforcement is formed from one or more dry laid material.

[0255] In some embodiments, the porous scaffold reinforcement has a pore diameter ranging from about 0,05 pm to about 10 pm, from about 0.05 pm to about 8 pm, from about 0.05 pm to about 6 pm, from about 0.1 pm to about 10 pm, from about 0.5 pm to about 10 pm, from about 1 pm to about 10 pm, from about 0.1 pm to about 8 pm, or from about 0.2 pm to about 6 pm.

[0256] In some embodiments, the porous scaffold reinforcement has a porosity range from about 40% to about 95%, from about 50% to about 95%, from about 60% to about 95%, from about 70% to about 95%, from about 80% to about 95%. from about 40% to about 90%, from about 40% to about 85%, from about 50% to about 90%, or from about 60% to about 90%.

[0257] In some embodiments, the porous scaffold reinforcement is heat treated, pressure treated, plasma treated, or a combination thereof, pnor to contacting the sulfonated polyphenylene polymer membrane-forming composition.

[0258] In some embodiments, the porous scaffold reinforcement has a thickness of less than about 100 pm, of less than about 80 pm, of less than about 70 pm, of less than about 60 pm, of less than about 50 pm, of less than about 40 pm, of less than about 30 pm, of less than about 20 pm, of less than about 10 pm, of between about I pm and about 100 pm, of between about I pm and about 90 pm, of between about 1 pm and about 80 pm, of between about 1 pm and about 70 pm, of between about 1 pm and about 60 pm, of between about 1 pm and about 50 pm, of between about 1 pm and about 40 pm, of between about I pm and about 30 pm, of between about I pm and about 20 pm, of between about I pm and about 10 pm, or of between about 5 pm and about 20 pm

[0259] In some embodiments, the porous scaffold is chosen to balance mechanical stability, gas diffusion, and ionic conductivity. The support’s porosity and thickness are carefully engineered to optimize these properties. Accordingly, the porous support typically exhibits a porosity of at least 30%, with an ideal range between about 30% and about 80%. This level of porosity ensures adequate pathways for gas diffusion and ion transport while maintaining structural integrity. The pores within the support structure typically range from hundreds of nanometers to a few micrometers in size, allowing for efficient mass transport of reactants and products.

[0260] The support can be designed as either a continuous polymer sheet or a woven / non-woven fabric. The thickness of the support is a critical parameter that affects both mechanical strength and ion transport. For supports with moderate to high porosity (about 30% to about 80%). the thickness typically ranges from about 5 pm to about 50 pm. This range provides a good balance between structural support and minimal resistance to ion and gas transport. In cases where the porosity is lower (below about 30%), the support is preferably made thinner, ranging from about 1 um to about 5 pm. This reduced thickness compensates for the lower porosity by enhancing the impregnation of the ion-exchange polymer and improving overall ionic conductivity. The thinner structure ensures that the lower porosity does not significantly impede ion transport through the membrane.

[0261] For higher porosities between about 50% and about 75%, with pore sizes ranging from about 0.1 pm to about 1 pm, the support thickness can be increased to between about 5 pm and about 20 pm. This increased thickness provides the necessary mechanical robustness to counteract the potential weakness introduced by high porosity. At the same time, the larger pores and higher overall porosity facilitate effective gas diffusion and ion transport within the fuel cell structure. With regards to porosity, pore size, and thickness, one having skill in the art can optimize the porous support to achieve the desired balance of mechanical strength, gas permeability, and ionic conductivity in PEM fuel cells. This optimization is crucial for enhancing overall fuel cell performance and durability.

[0262] In some embodiments, the reinforced sulfonated polyphenylene polymer membrane has a thickness of between about 5 pm and about 150 pm, of between about 5 pm and about 120 pm, of between about 5 pm and about 110 pm, of between about 5 pm and about 100 pm, of between about 5 pm and about 90 pm, of between about 5 pm and about 80 pm, of between about 5 pm and about 70 pm, of between about 5 pm and about60 pin, of between about 5 pm and about 50 pm, of between about 5 pm and about 40 pm, of less than about 100 pm, of less than about 50 pm, or of less than about 40 pm.

[0263] In some embodiments, the reinforced sulfonated polyphenylene polymer membrane has a thickness, and the porous scaffold reinforcement comprises at least about 20% of the thickness of the reinforced sulfonated polyphenylene polymer membrane, or of between about 20% and about 90% of the thickness of the reinforced sulfonated polyphenylene polymer membrane.

[0264] In some embodiments, the reinforced sulfonated polyphenylene polymer membrane has a thickness, and the porous scaffold reinforcement is distributed through at least about 50% of the thickness of the polyphenylene polymer membrane, through at least about 60% of the thickness of the polyphenylene polymer membrane, through at least about 70% of the thickness of the polyphenylene polymer membrane, through at least about 80% of the thickness of the polyphenylene polymer membrane, through at least about 90% of the thickness of the polyphenylene polymer membrane, through about 50% to about 95% of the thickness of the polyphenylene polymer membrane, through about 60% to about 95 % of the thickness of the polyphenylene polymer membrane, through about 70% to about 95% of the thickness of the polyphenylene polymer membrane, or through about 80% to about 95% of the thickness of the polyphenylene polymer membrane.

[0265] In some embodiments, the weight ratio of the sulfonated polyphenylene polymer membrane-forming composition to the porous scaffold reinforcement is greater than about 70:30, is about 75:25 or greater, is about 80:20 or greater, is about 85:15 or greater, is about 90:10 or greater, or is about 95:5 or greater.Uses of the Sulfonated Polyphenylene Antioxidant Membranes

[0266] In another aspect of the disclosure, provided herein is a fuel cell membraneelectrode assembly, comprising:(a) a hydrogen electrode to which hydrogen gas is supplied:(b) an oxygen electrode to which an oxidizer gas is supplied; and(c) a sulfonated polyphenylene polymer membrane or reinforced sulfonated polyphenylene polymer membrane, comprising the sulfonated polyphenylene polymer membrane-forming composition as defined herein, located between the hydrogen and oxygen electrodes.

[0267] In yet another aspect of the disclosure, provided herein is an electrolyzer membrane-electrode assembly, comprising:(a) a hydrogen evolution electrode configured for the evolution of hydrogen gas; (b) an oxygen evolution electrode configured for the evolution of oxygen gas; and (c) a sulfonated polyphenylene polymer membrane or reinforced sulfonated polyphenylene polymer membrane, comprising the sulfonated polyphenylene polymer membrane-forming composition as defined herein, located between the hydrogen and oxygen evolution electrodes.

[0268] In yet another aspect of the disclosure, provided herein is a hydrogen pump or thermoelectrochemical hydrogen pump membrane-electrode assembly, comprising:(a) a hydrogen electrode configured to receive and split hydrogen gas;(b) a secondary’ hydrogen electrode to which protons are transmitted and the hydrogen is reformed, and(c) a sulfonated polyphenylene polymer membrane or reinforced sulfonated polyphenylene polymer membrane, comprising the sulfonated polyphenylene polymer membrane-forming composition as defined herein, located between the hydrogen electrode and the secondary hydrogen electrode.

[0269] In yet another aspect of the disclosure, provided herein is a method of using the sulfonated polyphenylene polymer membrane or reinforced sulfonated polyphenylene polymer membrane disclosed herein, in an electrochemical device such as a fuel cell, electrolyzer, hydrogen pump, thermoelectrochemical hydrogen pump, electrochemical hydrogen compressor, or redox flow battery.

[0270] In yet another aspect of the disclosure, provided herein is a sulfonated polyphenylene polymer membrane produced by any of the methods disclosed herein, or reinforced polyphenylene polymer membrane produced by any of the methods disclosed herein, for use in an electrochemical device selected from a fuel cell, electrolyzer, hydrogen pump, thermoelectrochemical hydrogen pump, electrochemical hydrogen compressor, redox flow battery, or other electrochemical devices.

[0271] In yet another aspect of the disclosure, provided herein is an electrochemical device comprising the sulfonated polyphenylene polymer membrane produced by any of the methods disclosed herein, or reinforced sulfonated polyphenylene polymer membrane produced by’ any of the methods disclosed herein, wherein the electrochemical device is a fuel cell, electrolyzer, hydrogen pump, thermoelectrochemical hydrogen pump,electrochemical hydrogen compressor, redox flow battery, or other electrochemical devices.

[0272] In a further aspect of the disclosure, provided herein is an electrochemical device comprising the sulfonated polyphenylene membrane as defined herein, wherein the electrochemical device is a fuel cell, electrolyzer, hydrogen pump, thermoelectrochemical hydrogen pump, electrochemical hydrogen compressor, redox flow battery, or other electrochemical devices.EXAMPLESMaterials and Methods

[0273] The film-forming compositions and membrane compositions described herein were prepared using sulfonated polyphenylene random copolymers as described herein. The polymers are characterized as having an ion exchange capacity between 2.8 and 3.2. Antioxidant materials were used without any further purification or treatment. For measuring conductivity, membranes were first conditioned by hydrating the membrane in DI water for 24 hours before the measurement. Conductivity was measured in a two-electrode through-plane configuration. Cells were constructed with 1 cm x I cm pieces of membrane that were subjected to AC impedance spectroscopy using a Solartron 1260 frequency response analyzer. A 100 mV sinusoidal AC potential operating over a frequency range of 10 MHz to 1,000 MHz was utilized The raw data was fitted to a Randles equivalent circuit to obtain the membrane ionic resistance, from which the proton conductivity was calculated using the electrode separation distance and cross-sectional area of the membrane.Example 1Comparative Sulfonated Polypheny lene Polymer Membrane

[0274] A membrane-forming composition was prepared by dissolving a sulfonated polyphenylene polymer at 7 wt% in a solvent mixture. The membrane-forming composition was cast as a thin film onto a polyester substrate and the solvent was subsequently evaporated at room temperature to obtain one layer of sulfonated polyphenylene polymer membrane with a dry thickness of 15 pm. After drying. a second layer of the same membrane-forming composition was cast on top of the first layer and thesolvent evaporated at room temperature to obtain a total membrane thickness of 29 pm. The through-plane conductivity of the membrane was measured to be 126 ± 3 mS / cm.Example 2Sulfonated Polyphenylene Polymer Antioxidant Membrane[02751 A membrane-forming composition was prepared by dissolving a sulfonated polyphenylene polymer at 7 wt% in a solvent mixture. The membrane-forming composition was cast as a thin film onto a polyester substrate and the solvent was subsequently evaporated at room temperature to obtain one layer of sulfonated polyphenylene polymer membrane with a dry thickness of 15 pm. An antioxidant layerforming composition was prepared by dissolving Ce(NO3)3·6H2O at 0.2 wl% in tert-butyl alcohol. The antioxidant layer-forming composition was cast as a thin film, of 250 pm wet thickness, on top of the first sulfonated polyphenylene polymer layer and the solvent evaporated at room temperature. After drying, a second layer of the sulfonated polyphenylene polymer membrane-forming composition was cast on top of the antioxidant layer and the solvent evaporated at room temperature to form a sulfonated polyphenylene antioxidant membrane with total thickness of 29 pm. The through-plane conductivity of this membrane was measured to be 119 ± 4 mS / cm. This example demonstrates that a metal salt-based antioxidant can be incorporated into a sulfonated polyphenylene antioxidant membrane without significant change to the conductivity.Example 3Sulfonated Polyphenylene Polymer Antioxidant Membrane

[0276] A membrane-forming composition was prepared by dissolving a sulfonated polyphenylene polymer at 7 wt% in a solvent mixture. The membrane-forming composition was cast as a thin film onto a polyester substrate and the solvent was subsequently evaporated at room temperature to obtain one layer of sulfonated polyphenylene polymer membrane with a dry thickness of 15 pm. An antioxidant layerforming composition was prepared by dispersing CeCh nanoparticles via sonication at 0.2 wt% in tert-butyl alcohol. The antioxidant layer-forming composition was cast as a thin film, of 250 pm wet thickness, on top of the first sulfonated polyphenylene polymer layer and the solvent evaporated at room temperature. After drying, a second layer of the sulfonated polyphenylene polymer membrane-forming composition was cast on top of theantioxidant layer and the solvent evaporated at room temperature to form a sulfonated polyphenylene antioxidant membrane with total thickness of 29 pm. The through-plane conductivity of the resulting membrane was measured to be 121 ± 5 mS / cm. This example demonstrates that a metal oxide particle-based antioxidant can be incorporated into a sulfonated polyphenylene antioxidant membrane without significant change to the conductivity.Example 4Sulfonated Polyphenylene Polymer Antioxidant Membrane

[0277] A membrane-forming composition was prepared by dissolving a sulfonated polyphenylene polymer at 7 wt% in a solvent mixture. The membrane-forming composition was cast as a thin film onto a polyester substrate and the solvent was subsequently evaporated at room temperature to obtain one layer of sulfonated polyphenylene polymer membrane with a dry thickness of 15 pm. An antioxidant layerforming composition was prepared by separately dissolving Ce(NO3)3·6H2O at 0.2 wt% in tert-butyl alcohol and dispersing CeO2nanoparticles via sonication at 0.2 wt% in tert-butyl alcohol. These two antioxidant compositions were then mixed in equal volumes to form a new antioxidant layer-forming composition containing both a metal salt and metal oxide. The antioxidant layer-forming composition was cast as a thin film, of 250 pm wet thickness, on top of the first sulfonated polyphenylene polymer layer and the solvent evaporated at room temperature. After drying, a second layer of the sulfonated polyphenylene polymer membrane-forming composition was cast on top of the antioxidant layer and the solvent evaporated at room temperature to form a sulfonated polyphenylene antioxidant membrane with total thickness of 30 pm The through-plane conductivity of this membrane was measured to be 123 ± 3 mS / cm. This example demonstrates that a mixture of antioxidant types, a metal salt and metal oxide in this example, can be deposited simultaneously as a single interlayer within a sulfonated polyphenylene antioxidant membrane without sacrificing conductivity.Example 5Sulfonated Polyphenylene Polymer Antioxidaent Membrane

[0278] A membrane-forming composition was prepared by dissolving a sulfonated polyphenylene polymer at 7 wt% in a solvent mixture. The membrane-forming composition was cast as a thin film onto a polyester substrate and the solvent was subsequently evaporated at room temperature to obtain one layer of sulfonated polyphenylene polymer membrane with a dry thickness of 6 pm. An antioxidant layerforming composition was prepared by dissolving Ce(NO3)3·6H2O at 0.2 wt% in tert-butyl alcohol. The antioxidant layer-forming composition was cast as a thin film, of 180 pm wet thickness, on top of the first sulfonated polyphenylene polymer layer and the solvent evaporated at room temperature. After drying, subsequent alternating layers of sulfonated polyphenylene polymer and antioxidant were cast to form a sulfonated polyphenylene antioxidant membrane with 4 layers of sulfonated polyphenylene and 3 layers of antioxidant. The total thickness of this resulting membrane was 20 pm. The through-plane conductivity of this membrane was measured to be 111 ± 7 mS / cm. This example demonstrates that the sulfonated polyphenylene antioxidant membrane can be comprised of multiple alternating layers of sulfonated polyphenylene and antioxidant layers without sacrificing conductivity.Example 6Sulfonated Polyphenylene Polymer Antioxidant Membrane

[0279] A membrane-forming composition was prepared by dissolving a sulfonated polyphenylene polymer at 7 wt% in a solvent mixture. The membrane-forming composition was cast as a thin film onto a polyester substrate and the solvent was subsequently’ evaporated at room temperature to obtain one layer of sulfonated polyphenylene polymer membrane with a dry thickness of 15 pm. An antioxidant layerforming composition was prepared by dissolving Ce(NO3)3·6H2O at 0.2 wt% and ethyl cellulose at 1 wt% in tert-butyl alcohol. The antioxidant layer-forming composition was cast as a thin film, of 180 pm wet thickness, on top of the first sulfonated polyphenylene polymer layer and the solvent evaporated at room temperature. After drying, a second layer of the sulfonated polyphenylene polymer membrane-forming composition was cast on top of the antioxidant layer and the solvent evaporated at room temperature to form a sulfonated polyphenylene antioxidant membrane with total thickness of 31 pm The through-planeconductivity of this membrane was measured to be 118 ± 5 mS / cm. This example demonstrates that the antioxidant can optionally be blended with another polymer and cast as a composite interlayer within the sulfonated polyphenylene antioxidant membrane.Example 7Sulfonated Polyphenylene Polymer Antioxidant Membrane

[0280] A membrane-forming composition was prepared by dissolving a sulfonated polyphenylene polymer at 6.3 wt% in a solvent mixture. The membrane-forming composition was cast as a thin film onto a polyester substrate and the solvent was subsequently evaporated at room temperature to obtain one layer of sulfonated polyphenylene polymer membrane with a dry thickness of 15 pm. An antioxidant layerforming composition was prepared by dissolving niobium oxide at 0.7 wt% in a mixture of C2to C4alcohols and water. The antioxidant layer-forming composition was cast as a thin film, of about 180 pm wet thickness, on top of the polyester substrate as a monolithic single pass film with a total thickness of about 15 pm to 20 pm. The through-plane conductivity of this membrane was measured to be 103 ± 3 mS / cm. This example demonstrates that the antioxidant can be used as a composite interlayer within a sulfonated polyphenylene antioxidant membrane.Example 8Sulfonated Polyphenylene Polymer Antioxidant Membrane

[0281] A membrane-forming composition was prepared by dissolving a sulfonated polyphenylene polymer at 6.3 wt% in a solvent mixture. The membrane-forming composition was cast as a thin film onto a polyester substrate and the solvent was subsequently evaporated at room temperature to obtain one layer of sulfonated polyphenylene polymer membrane with a dry' thickness of 15 pm. An antioxidant layerforming composition was prepared by dissolving potassium octatitanate (K^Ti^O ) at 0.7 wt% in a mixture of C2to C4alcohols and water. The antioxidant layer-forming composition was cast as a thin film, of about 180 µm wet thickness, on top of the polyester substrate as a monolithic single pass membrane with a total thickness of about 15 pm to 20 pm. The through-plane conductivity of this membrane was measured to be 80 ± 3 mS / cm. This example demonstrates that various antioxidant types, a metal oxide in this example.can be used as a composite interlayer within a sulfonated polyphenylene antioxidant membrane.Example 9Polymer Conductivity

[0282] While illustrative embodiments have been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention.

Claims

CLAIMSThe embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A sulfonated polyphenylene membrane, comprising one or more sulfonated polyphenylene polymer and one or more antioxidant, wherein the sulfonated polyphenylene polymer comprises a repeat unit (x) of Formula (I):(I),wherein:R1A, R1B, R1C, R1D, R1E,RIFareindependently aryl or heteroaryl, each unsubstituted or substituted with 1, 2, 3. 4, or 5 substituents independently selected from Cj.g alky 1. halo, nitro, cyano. SOvX+, PC>32’2X+, and COO X+;R1Gand R1Hare independently H, aryl, or heteroaryl, wherein said aryl and heteroaryl are each unsubstituted or substituted -with 1, 2, 3, 4, or 5 substituents independently selected fromalkyl, halo, nitro, cyano. SO3-X+, PO32-2X+, and COO-X+;Aj is arylene, heteroarylene, aralkylene. or heteroaralkylene, each unsubstituted or substituted with 1. 2, 3, or 4 substituents independently selected from halo, nitro, cyano, aryl, and heteroarykA2is absent, arylene, or heteroarylene, wherein said arylene and heteroarylene are each unsubstituted or substituted with 1, 2, 3, or 4 substituents independently selected from halo, nitro, cyano, aryl, and heteroaryl;L] is an unsubstituted or substituted linking heteroatom, arylene, heteroarylene, aralkylene, or heteroaralkylene, wherein said arylene, heteroaiylene, aralkylene, and heteroaralkylene are each unsubstituted or substituted with 1, 2, 3, or 4 substituents independently selected from Cj.g alkyl, halo, nitro, cyano, ary l, and heteroaryl;L2and L- are independently absent, arylene, or heteroarylene, wherein said arylene and heteroarylene are each unsubstituted or substituted with 1, 2, 3, or 4 substituents independently selected from Cj.6alkyl, halo, nitro, cyano, aryl, and heteroaryl; and X+is H+, a cation, an alkali metal ion, or [N(RA)(RB)(RC)(RD)]+wherein RA, RB, RC, and RDare independently H, C1-6alkyl, aryl, or heteroaryl.

2. The sulfonated polyphenylene membrane of Claim 1, wherein the one or more sulfonated polyphenylene polymer is in the form of a layer, and the one or more antioxidant is in the form of a layer.

3. The sulfonated polyphenylene membrane of Claim 1 or 2, wherein the membrane comprises one to ten sulfonated polyphenylene polymer layers.

4. The sulfonated polyphenylene membrane of any one of Claims 1-3. wherein the membrane comprises one to ten antioxidant layers.

5. The sulfonated polyphenylene membrane of any one of Claims 1-4, wherein the membrane comprises one to four sulfonated polyphenylene polymer layers and one to four antioxidant layers.

6. The sulfonated polyphenylene membrane of any one of Claims 1-5, wherein the membrane comprises one or two sulfonated polyphenylene polymer layers and one or two antioxidant layers.

7. The sulfonated polyphenylene membrane of any one of Claims 2-6, wherein the membrane comprises alternating layers of the polyphenylene polymer layers and the antioxidant layers.8 The sulfonated polyphenylene membrane of any one of Claims 2-7, wherein each layer of the antioxidant layers is in contact with one or two layers of the sulfonated polyphenylene polymer layers, and wherein the contact between the layers forms an interface.

9. The sulfonated polyphenylene membrane of any one of Claims 2-8, wherein each layer of the sulfonated polyphenylene polymer layers is in contact with one or two layers of the antioxidant layers, and wherein the contact between the layers forms an interface.

10. The sulfonated polyphenylene membrane of Claim 8 or 9, wherein the sulfonated polyphenylene polymer layer and the antioxidant layer are integrated at the interface or are conterminous at the interface.

11. The sulfonated polyphenylene membrane of Claim 10, wherein at the interface, the sulfonated polyphenylene polymer layer and the antioxidant layer are integrated by about 0.1 um to about 1 pm or are integrated by about 1 pm to about 10 pm.

12. The sulfonated polyphenylene membrane of Claim 10 or 11, wherein at the interface, the sulfonated polyphenylene polymer layer and the antioxidant layer are integrated through a gradient, are integrated through a homogeneous concentration, or are integrated by a combination thereof.

13. The sulfonated polyphenylene membrane of Claim 1, wherein the membrane comprises a mixture of the one or more sulfonated polyphenylene polymer and the one or more antioxidant.

14. The sulfonated polyphenylene membrane of Claim 1 or 13, wherein the membrane comprises about 80% to about 99.9% of the one or more sulfonated polyphenylene polymer and about 0.1% to about 20% of the one or more antioxidant.

15. The sulfonated polyphenylene membrane of any one of Claims 1-14, wherein Aj is unsubstituted or substituted arylene, wherein the substituted arylene is substituted with 1, 2, 3, or 4 substituents independently selected from halo, nitro, cyano, and, and heteroaryl, and A2is absent.

16. The sulfonated polyphenylene membrane of any one of Claims 1-15, wherein L] is naphthalenylene, phenylene, or Cpg alkyl-substituted phenylene, and L2and L3are independently absent or phenylene, and wherein when present, each phenylene is unsubstituted or substituted with 1, 2, 3, or 4 substituents independently selected from C|_6alkyl and halo.

17. The sulfonated polyphenylene membrane of any one of Claims 1-16. wherein the sulfonated polyphenylene polymer layer further comprises a hydrophobic polyphenylene repeat unit (y) of Formula (II) to form a polyphenylene copolymer, wherein Formula (II) has the structure:(11),wherein:R2A, R2B,R2Fare independently aryl or heteroaryl, each unsubstituted or substituted with 1, 2, 3, 4, or 5 substituents independently selected from C1-6alkyl, halo, nitro, and cyano;R2G and R2H are independently H, aryl, or heteroaryl, wherein said aryl and heteroaryl are each unsubstituted or substituted with 1, 2, 3.

4. or 5 substituents independently selected from Cj.g alkyl, halo, nitro, and cyano;B1is arylene, heteroarylene, aralkylene, or heteroaralkylene, each unsubstituted or substituted with 1, 2, 3, or 4 substituents independently selected from C1-6alkyl, halo, nitro, cyano, aiyl, and heteroaryl;B2is absent, arylene, or heteroarylene, wherein said arylene and heteroarylene are each unsubstituted or substituted with 1, 2, 3, or 4 substituents independently selected from C1-6alkyl, halo, nitro, cyano, aryl, and heteroaryl;Lj is an unsubstituted or substituted linking heteroatom, arylene, heteroarylene, aralkylene, or heteroaralkylene, wherein said arylene, heteroarylene, aralkylene. and heteroaralkyl ene are each unsubstituted or substituted with 1, 2, 3, or 4 substituents independently selected from C1-6alkyl, halo, nitro, cyano, aryl, and heteroaryl;L2and I..-, are independently absent, arylene, or heteroarylene, wherein said aiylene and heteroarylene are each unsubstituted or substituted with 1, 2. 3, or 4 substituents independently selected from C1-6alkyl, halo, nitro, cyano, aryl, and heteroaryl; and X+is H+, a cation, an alkali metal ion, or [N(RA)(RB)(RC)(RD)]+wherein RA, RB, RC, and RDare independently H, C1-6alkyl, aryl, or heteroaryl.

18. The sulfonated polyphenylene membrane of Claim 17, wherein the polyphenylene copolymer has a structure of Formula (III):(Ill),wherein:R1A, R1B,KID- R-IE>an<^ ^-IFareindependently ar I or heteroaryl, each unsubstituted or substituted with 1.

2. 3, 4, or 5 substituents independently selected from C].g alkyl, halo, nitro, cyano, SOj’X1. PO2"2X+, and COO"X+;R2A, R2B, R2C, R2D, R2E, and R2Fare independently aryl or heteroaryl, each unsubstituted or substituted with 1, 2, 3, 4, or 5 substituents independently selected from C1-6alkyl, halo, nitro, and cyano;R1Gand R1Hare independently H, aryl, or heteroaryl, wherein said aryl and heteroaryl are each unsubstituted or substituted with 1, 2, 3, 4, or 5 substituents independently selected from C].6alkyl, halo, nitro, cyano, SO3’X+, PO2’2X+, and COO X+;R2Gand R2H are independently H, aryl, or heteroaryl, wherein said aryl and heteroaryl are each unsubstituted or substituted with 1, 2, 3, 4, or 5 substituents independently selected from C1-6alkyl, halo, nitro, and cyano;Aj and Bj are independently arylene, heteroarylene, aralkylene, or heteroaralkylene, each unsubstituted or substituted with 1, 2, 3. or 4 substituents independently selected from Cj.6 alkyl, halo, nitro, cyano, aryl, and heteroaryl;A2and B2are independently absent, arylene, or heteroarylene, wherein said arylene and heteroarylene are each unsubstituted or substituted with 1, 2, 3, or 4 substituents independently selected from Cj.6 alkyl, halo, nitro, cyano, aryl, and heteroaryl;Lj is an unsubstituted or substituted linking heteroatom, arylene, heteroarylene. aralkylene, or heteroaralkylene, wherein said arylene, heteroarylene, aralkylene, and heteroaralkylene are each unsubstituted or substituted with 1. 2, 3, or 4 substituents independently selected from C1-6alkyl, halo, nitro, cyano, aryl, and heteroaryl;L2and L are each independently absent, arylene, or heteroarylene, wherein said arylene and heteroarylene are each unsubstituted or substituted with 1, 2. 3, or 4 substituents independently selected fromalkyl, halo, nitro, cyano, aryl, and heteroaryl; andX+is H+, a cation, an alkali metal ion. or [N(RA)(RB)(RC)(RD)]+wherein RA, RB, RC, and RDare independently H, C1-6alkyl, aryl, or heteroaryl.

19. The sulfonated polyphenylene membrane of Claim 17 or 18, wherein the polyphenylene copolymer has a structure of Formula (IV):(iv),wherein:R3, R4, R5, and Rg are independently selected from H, SO ’X+, PO32'2X+, and COO X+;R7, Rg, Rq. and R]0are independently selected from H, Cj_g alkyl, halo, nitro, and cyano;A1and B1are independently arylene, heteroarylene, aralkylene, or heteroaralkylene, each unsubstituted or substituted with 1, 2, 3, or 4 substituents independently selected from Cj.g alkyl, halo, nitro, cyano, aryl, and heteroaryl;A2and B2are independently absent, arylene, heteroarylene, aralkylene, or heteroaralkylene, wherein said arylene, heteroarylene, aralkylene, or heteroaralkylene, are each unsubstituted or substituted with 1, 2, 3, or 4 substituents independently selected from Cj.6alkyl, halo, nitro, cyano, aryl, and heteroaryl;L] is an unsubstituted or substituted linking heteroatom, arylene, heteroarylene, aralkylene, or heteroaralkylene, wherein said arylene, heteroarylene, aralkylene, and heteroaralkylene are each unsubstituted or substituted with 1, 2, 3, or 4 substituents independently selected from Cgg alkyl, halo, nitro, cyano, aryl, and heteroaryl;L2and L3are each independently absent, arylene, or heteroarylene, wherein said arylene and heteroarylene are each unsubstituted or substituted with 1. 2, 3, or 4 substituents independently selected from Cyg alkyl, halo, nitro, cyano, ary l, and heteroaryl; andX+is H+, a cation, an alkali metal ion, or [N(RA)(RB)(RC)(RD)]+wherein RA, RB, RC, and RDare independently H, C1-6alkyl, aryl, or heteroaryl.

20. The sulfonated polyphenylene membrane of any one of Claims 17-19, wherein A;, Bj, or both A1and B1are independently arylene, unsubstituted or substituted with 1. 2, 3, or 4 substituents independently selected from Cy6alkyl, halo, nitro, cyano, aryl, and heteroaryl; and A2, B2, or both A2and B2are absent.

21. The sulfonated polyphenylene membrane of any one of Claims 17-20, wherein L1is naphthalenylene, phenylene, or C1-6alkyl-substituted phenylene, and L2and L3are each independently absent or phenylene, wherein when present, each phenylene is unsubstituted or substituted with 1, 2, 3, or 4 substituents independently selected from C1-6alkyl and halo, and wherein L1of Formula (I) is the same or different from L1of Formula (II), L2of Formula (I) is the same or different from L2of Formula (II), and L3of Formula (I) is the same or different from L3of Formula (II).

22. The sulfonated polyphenylene membrane of any one of Claims 1 -21, further comprising a branching comonomerwherein M1is selected from an unsubstituted or substituted linking atom, arylene, heteroarylene, aralkylene, heteroaralkyl ene, and combinations thereof, wherein the linking atom, arylene, heteroarylene, aralkylene, and heteroaralkylene are each unsubstituted or substituted whh 1, 2, or 3 substituents independently selected from C1-6alkyl, halo, nitro, cyano, aryl, and heteroaryl.

23. The sulfonated polyphenylene membrane of Claim 22, wherein M1is bound through at least 3 covalent bonds, and wherein Mj is selected from the group consisting of24. The sulfonated polyphenylene membrane of Claim 22 or 23, having a branched structure of Formula (V):(V),wherein P] and P2are both a repeat unit (x) of Formula (I), or are independently selected from a repeat unit (x) of Formula (I) and a repeat unit (y) of Formula (II).

25. The sulfonated polyphenylene membrane of Claim 24, wherein the ratio of a repeat unit (z) to the sum of a repeat unit (x), P1;and P2of Formula (V) (i.e, z / (x+P1+P2)) is less than 0.2.

26. The sulfonated polyphenylene membrane of any one of Claims 1-25, wherein each L3. L2. and Lj of -T^-L-r-L!- when present, and each L3and L2of -L ~L2-- Mj- when present, are independently selected from:

27. The sulfonated polyphenylene membrane of any one of Claims 1-26. wherein the repeat unit (x) of Formula (I) is selected from:wherein X+is H+, a cation, an alkali metal ion, or [N(RA)(RB)(RC)(RD)]+wherein RA, RB, RC, and RDare independently H, C1-6alkyl, aryl, or heteroaryl.

28. The sulfonated polyphenylene membrane of any one of Claims 1-27, wherein the repeat unit (x) of Formula (I) is selected from:Rc, and RQ are independently H,alkyl, aryl, or heteroaryl.

29. The sulfonated polyphenylene membrane of any one of Claims 17-28, wherein the repeat unit (y ) of Formula (II) is selected from:

30. The sulfonated polyphenylene membrane of any one of Claims 17-29, wherein the repeat unit (y) of Formula (II) is selected from:

31. The sulfonated polyphenylene membrane of any one of Claims 17-30, wherein the mole percent of the repeat unit (x) is about 59% to about 99%, and the mole percent of the repeat unit (y ) is about 41% to about 1%.

32. The sulfonated polyphenylene membrane of any one of Claims 17-31. wherein the mole percent of the repeat unit (x) is about 90%. and the mole percent of the repeat unit (y) is about 10%.

33. The sulfonated polyphenylene membrane of any one of Claims 17-32, wherein the polyphenylene copolymer is a random copolymer comprising a random distribution of the repeat units (x) and (y).

34. The sulfonated polyphenylene membrane of any one of Claims 17-32, wherein the polyphenylene copolymer is a statistical copolymer comprising an average composition ratio of the repeat units (x) and (y ).

35. The sulfonated polyphenylene membrane of any one of Claims 17-32, wherein the polyphenylene copolymer is a block copolymer, wherein:the repeat unit (x) is an integer from 3 to 100,the repeat unit (y) is an integer from 3 to 100; andwherein a mole ratio of the first block to the second block ranges from 1:99 to 99:1.

36. The sulfonated polyphenylene membrane of any one of Claims 1-35, wherein the one or more antioxidant comprises a metal oxide, wherein a metal (M) of the metal oxide is selected from the group consisting of zirconium (Zr), cerium (Ce), samarium (Sm). gadolinium (Gd), terbium (Tb), tin (Sn), niobium (Nb), tantalum, and titanium (Ti).

37. The sulfonated polyphenylene membrane of any one of Claims 1-36, wherein the one or more antioxidant comprises a mixture of metal oxides, wherein the metal oxides are selected from the group consisting of zirconium oxide, cerium oxide, samarium oxide, gadolinium oxide, terbium oxide, and tin oxide.

38. The sulfonated polyphenylene membrane of any one of Claims 1-37, wherein the one or more antioxidant comprises one or more metal oxides doped with one or more metal.

39. The sulfonated polyphenylene membrane of Claim 38, wherein the metal (M) and the metal (M) of the metal oxide are independently selected from the group consisting of zirconium (Zr), cerium (Ce). samarium (Sm), gadolinium (Gd), terbium (Tb). and tin (Sn).

40. The sulfonated polyphenylene membrane of any one of Claims 36-39, wherein the metal oxide is supported on a substrate, and the substrate is selected from the group consisting of titanium dioxide (TiCh), silicon dioxide (SiO 2), zirconium oxide (Z1O2), cerium oxide (CeCh), cerium zirconium oxide (CeZrO4), gadolini um-doped cerium oxide (CeC -GdzCh), carbon, and combinations thereof.

41. The sulfonated polyphenylene membrane of any one of Claims 36-39, wherein the metal oxide is particle-based, fiber-based, or a combination thereof.

42. The sulfonated polyphenylene membrane of any one of Claims 1-35, wherein the one or more antioxidant comprises one or more metal salt-based antioxidant, one or more complex-based antioxidant, one or more particle-based antioxidant, or a combination thereof.

43. The sulfonated polyphenylene membrane of any one of Claims 1-42. wherein the one or more antioxidant comprises a cerium salt or cerium complex44. The sulfonated polyphenylene membrane of Claim 42 or 43, wherein the metal salt-based antioxidant is selected from the group consisting of cerium hydrogen phosphate (CeHPO4), cenum(III) nitrate hexahydrate (Ce(NO3)3·6H2O), cerium(III) chloride (CeCl?), cerium(III) sulfate (Ce2(SO4)?), cerium(III) acetate (CetCzThO?)}), cerium(III) carbonate (Cez COj)?). zinc chloride (ZnCb), zinc sulfate (ZnSCh), zinc acetate (Zn(C2H3O2)2), manganese chloride (MnCb), manganese sulfate (MnSCri), manganese acetate (MnfCzHjChfi), copper sulfate (CuSOfi, copper chloride (CuCh). copper acetate (CulCzHsOz)?), nickel chloride (NiCh), nickel sulfate (NiSOfi, nickel acetate (NifCzl zM cobalt chloride (C0CI2), cobalt sulfate (COSOJ), cobalt acetate (Co(C2l-LO2) ), sodium selenite (NazSeO?), sodium selenate (NazSeO<), selenious acid (HzSeOa), aluminum(III) chloride (Aids), aluminum nitrate (Al(NO3)s), tin(II) chloride (SnCh), and combinations thereof.

45. The sulfonated polyphenylene membrane of Claim 42 or 43. wherein the complex-based antioxidant is selected from the group consisting of cerium(lll) picolinate, cerium(III) bis(picolinate), cerium(lll) bis(bipyridyl), cerium(III) 1.10-phenanthrolme, cerium(III) 2,2'-bipyridyl-5,5’-dicarboxylate, cerium(III) 2,2'-bipyridyl, cerium(III) 3,4-dimethylpyridine, cenum(III) imidazole, cerium(lll) pyrazole, cerium(lll) tetrapyridyl, zinc picolinate, zinc monomethionine, zinc gluconate, copper(II) picolinate, copper(II) 1.10-phenanthroline, copper(II) bisphosphonate, copper(II) gluconate, copper(II) hydroxy quinoline, nickel(II) picolinate, nickel(II) acetylacetonate, nickel(II) 1,10-phenanthroline, nickel(II) salicylate, nickel(II) glycinate, nickel(II) ethylenediaminetetraacetic acid, cobalt(II) picolinate, cobalt(II) 1,10-phenanthroline, cobalt(ll) gluconate, cobalt(ll) salicylate, cobalt(II) ethylenediaminetetraacetic acid, iron(ll) picolinate, iron(II) bisphosphonate, iron(ll) 1,10-phenanthroline, iron(ll) gluconate, iron(II) salicylate, potassium ferricyanide, ferric hexacyanoferrate(III), and combinations thereof.

46. The sulfonated polyphenylene membrane of Claim 42, 43, or 45, wherein the complex-based antioxidant comprises a 1,10-phenanthroline complex, wherein the 1.10-phenanthroline is unsubstituted or substituted with 1, 2, 3, 4, 5, or 6 substituents independently selected from Cj_6alkyl, aryl, heteroaryl, ketone (=0), -SO3"X+, and sulfonic acid (-SO3H).

47. The sulfonated polyphenylene membrane of Claim 42 or 43, wherein the particle-based antioxidant is selected from the group consisting of metal oxide, cerium oxide (CeOz), zinc oxide (ZnO), nickel oxide (NiO), copper(II) oxide (CuO), copper(I) oxide (Cu20), manganese dioxide (MnOz), titanium dioxide (T1O2), niobium oxide (Nb2O5, NbO. and / or NbO2), tantalum oxide (Ta2O5). potassium octatitanate (K2Ti8O!7and / or K2Ti6O13), zirconium-doped cerium oxide (CeOz-ZrOz), lanthanum-doped cerium oxide (CeCh-LazOa), praseodymium-doped cerium oxide (CeOz-PrzCh), gadolimum-doped cerium oxide (CeOz-GdzCh), yttrium-doped cerium oxide (CeOz-YzOi), copper-doped cerium oxide (CeOz-CuO), iron-doped cerium oxide (CeOz-FezOz). nickel-doped cerium oxide (CeOz-NiO), cobalt-doped cerium oxide (CeOz-CoO), manganese-doped cerium oxide (CeOz-MnOz), tin-doped cerium oxide (CeOz-SnOz), and combinations thereof.

48. The sulfonated polyphenylene membrane of any one of Claims 36-41 or 43, wherein the metal oxide is cerium oxide (CeO2).

49. The sulfonated polyphenylene membrane of any one of Claims 1-41, wherein the one or more antioxidant comprises cerium oxide (CeO?).

50. The sulfonated polyphenylene membrane of Claim 48 or 49, wherein the cerium oxide is a nanoparticle.

51. The sulfonated polyphenylene membrane of any one of Claims 41 or 47-50, wherein the one or more antioxidant comprising the metal oxide further comprises an organic compound, and wherein the organic compound is on the surface of the metal oxide particle.

52. The sulfonated polyphenylene membrane of Claim 51, wherein the organic compound comprises a functional group selected from the group consisting of a sulfonic acid (-SO3H), carboxylic acid (-COOH), alcohol (-OH), ether (-O-), amino (-NH2), amide (-CONH7), and combinations thereof.

53. The sulfonated polyphenylene membrane of Claim 51 or 52, wherein the organic compound is selected from the group consisting of citric acid, oxalic acid, stearic acid, p-toluenesulfomc acid, methanesulfonic acid, 4-hydroxybutanesulfonic acid, 3-hydroxy propanesulfonic acid, propanesulfonic acid, butylsulfonic acid, ethanol, isopropanol, polyvinyl alcohol (PVA), polyethylene glycol (PEG), crown ethers, caffeic acid, ferulic acid, vanillic acid, protocatechuic acid, 1,2-dihydroxybenzene, 2-hydroxybenzoic acid. 4-(2-aminoethyl)benzene-l,2-dioI (dopamine), polydopamine, ethylenediamine, triethylamine, acrylamide, N, N-dimethylformamide, ethanol amine, triethanol amine, 3-aminopropyltrimethoxysilane (APTMS), and combinatfions thereof.

54. The sulfonated polyphenylene membrane of any one of Claims 36-53, wherein the one or more antioxidant comprising the metal oxide, metal ion, or a combination thereof further comprises a polymer.

55. The sulfonated polyphenylene membrane of Claim 54, wherein the polymer is selected from the group consisting of ethyl cellulose, hydroxypropyl methylcellulose, carboxymethyl cellulose, polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), poly(methyl methacrylate) (PMMA), poly(aciylic acid) (PAA), poly(4-vinylpyridine) (P4VP), chitosan, polyvinyl alcohol (PVA), polyvinyl phenol, poly' vinyl phosphonic acid (PVP A), and combinations thereof.

56. The sulfonated polyphenylene membrane of any one of Claims 36-55, wherein the metal oxide is a crystallite, and the crystallite size is between about 1 nm and about 100 nm.

57. The sulfonated polyphenylene membrane of any one of Claims 36-56, wherein the metal oxide is a component of an agglomerate, and wherein the agglomerate size is about 1 pm or less.

58. The sulfonated polyphenylene membrane of any one of Claims 1-57, wherein the one or more antioxidant further comprises an organic phenolic compound.

59. The sulfonated polyphenylene membrane of Claim 58, wherein the organic phenolic compound is selected from the group consisting of vitamin E, quercetin, resveratrol, polyphenol, pentaerythrityl tetra-di-t-butyl hydroxyhydrocinnamate, octadecyl di-t-butyl-4-hydroxyhydrocinnamate, ethylene bis(oxy ethylene) bis-(3-(5-tert-butyl-4-hydroxy-m-tolyl)-propi onate). pentaerythritol tetraIds[3-[3,5-di-tert-butyl-4-hydroxy phenyl] propionate, and combinations thereof.

60. The sulfonated polyphenylene membrane of any one of Claims 1-59, wherein the one or more antioxidant comprises a fluoroalkyl phosphonic acid, a bisphosphonic acid. Trolox-bisphosphonate, pyridoxal-5'-bisphosphonate, and combinations thereof.

61. The sulfonated polyphenylene membrane of any one of Claims 1-60, wherein the one or more antioxidant comprises cerium hydrogen phosphate (CeIIPO4).

62. The sulfonated polyphen lene membrane of any one of Claims 1-61, wherein the one or more antioxidant further comprises an inorganic oxide,63. The sulfonated polyphenylene membrane of Claim 62, wherein the inorganic oxide is fumed silica (SiO2).

64. The sulfonated polyphenylene membrane of any one of Claims 1-63, wherein the one or more antioxidant further comprises an organic compound.

65. The sulfonated polyphenylene membrane of Claim 64, wherein the organic compound is tetraethyl orthosilicate.

66. The sulfonated polyphenylene membrane of any one of Claims 1-65, wherein the one or more antioxidant further comprises a metal-organic framework.

67. The sulfonated polyphenylene membrane of any one of Claims 1-66, wherein the one or more antioxidant further comprises polyhedral oligomeric silsesquioxanes (POSS).

68. The sulfonated polyphenylene membrane of Claim 67. the POSS is sulfonated POSS (sPOSS).-SO-69. The sulfonated polyphenylene membrane of any one of Claims 1-68, wherein the antioxidant layer has a total thickness of about 1 pm to about 5 pm.

70. The sulfonated polyphenylene membrane of any one of Claims 2-12 or 15-69, wherein the sulfonated polyphenylene polymer layers together comprise about 75% to about 99% of the total thickness of the sulfonated polyphenylene membrane.

71. The sulfonated polyphenylene membrane of Claim 69 or 70, wherein the one or more antioxidant layer together comprise about 1% to about 25% of the total thickness of the antioxidant membrane.

72. The sulfonated polyphenylene membrane of any one of Claims 2-12 or 15- 71. wherein each layer of the one or more sulfonated polyphenylene polymer layer has a thickness of between about 5 pm and about 100 pm.

73. The sulfonated polyphenylene membrane of any one of Claims 2-12 or 15- 72, wherein each layer of the one or more antioxidant layer has a thickness of about 1 pm to about 5 pm.

74. The sulfonated polyphenylene membrane of any one of Claims 1 -73, further comprising a porous scaffold reinforcement.

75. The sulfonated polyphenylene membrane of Claim 74, wherein the porous scaffold reinforcement comprises a material selected from the group consisting of polytetrafluoroethylene (PTFE). expanded polytetrafluoroethylene (ePTFE). polypropylene, polyethylene, polyester, nylon, polysulfone, polybenzimidazole (PBl), poly etheretherketone (PEEK), and combinations thereof.

76. A method of making a sulfonated polyphenylene membrane through a layer-by-layer coating, comprising:(a) preparing a first solution comprising one or more sulfonated polyphenylene polymer as defined by any one of Claims 1 and 15-35 and one or more solvent;(b) applying the first solution onto a substrate to form a first wet layer;(c) drying the first wet layer at a temperature between about 40°C and about 70°C to produce a first sulfonated polyphenylene polymer layer;(d) preparing a second solution comprising one or more antioxidant as defined by any one of Claims 36-68 and one or more solvent;(e) applying the second solution onto the first sulfonated polyphenylene polymer layer to form a second wet layer;(f) drying the second wet layer between about 40°C and about 70°C to produce an antioxidant layer, thereby forming a composite membrane comprising the first sulfonated polyphenylene polymer layer and the antioxidant layer, wherein the antioxidant layer is in contact with the first sulfonated polyphenylene polymer layer;(g) applying the first solution or a third solution comprising the same or different one or more sulfonated polyphenylene polymer as defined by any one of Claims 1 and 15-35 and one or more solvent onto the antioxidant layer to form a third wet layer;(h) drying the composite membrane with the third wet layer between about 40°C and about 70°C to produce a second sulfonated polyphenylene polymer layer and thereby forming a membrane, wherein the second sulfonated polyphenylene polymer layer is in contact with the antioxidant layer, and wherein the second sulfonated polyphenylene polymer layer is either identical to, or different from, the first sulfonated polyphenylene polymer layer.

77. The method of Claim 76, further comprising:(i) coating the second sulfonated polyphenylene polymer layer of the membrane with a solution comprising one or more antioxidant as defined by any one of Claims 36-68 and one or more solvent;(j) heating the coated membrane at a temperature between about 40°C and about 70°C to form a membrane comprising a second antioxidant layer, wherein the second antioxidant layer is in contact with the second sulfonated polyphenylene polymer layer;(k) coating the second antioxidant layer with a solution comprising one or more sulfonated polyphenylene polymer as defined by any one of Claims 1 and 15-35 and one or more solvent, wherein said sulfonated polyphenylene polymer solution is the same as, or different from, the sulfonated polyphenylene polymer solution used to prepare the first or second sulfonated polyphenylene polymer layers; and(l) heating the coated membrane at a temperature between about 40°C and about 70°C to form a membrane comprising:(i) the first sulfonated polyphenylene polymer layer,(ii) the first antioxidant layer,(iii) the second sulfonated polyphenylene polymer layer,(iv) the second antioxidant layer, and(v) a third sulfonated polyphenylene polymer layer,wherein:the third sulfonated polyphenylene polymer layer is in contact with the second antioxidant layer, andthe third sulfonated polyphenylene polymer layer is the same as, or different from, the first or second sulfonated polyphenylene polymer layers.

78. The method of Claim 77, further comprising:repeating the steps of Claim 77 to form up to 10 sulfonated polyphenylene polymer layers and 9 antioxidant layers.

79. A method of making a sulfonated polyphenylene membrane through a layer-by-layer coating, comprising:(a) preparing a first solution comprising one or more antioxidant as defined by any one of Claims 36-68 and one or more solvent;(b) applying the first solution onto a substrate to form a first wet layer;(c) drying the substrate with the first wet layer between about 40°C and about 70°C to produce a first antioxidant layer;(d) preparing a second solution comprising one or more sulfonated polyphenylene polymer as defined by any one of Claims 1 and 15-35 and one or more solvent;(e) applying the second solution onto the first antioxidant layer to form a second wet layer;(f) drying the first antioxidant layer with the second wet layer between about 40°C and about 70°C to produce a first sulfonated polyphenylene polymer layer, thereby forming an intermediate membrane;(g) applying the first solution or a third solution comprising one or more antioxidant as defined by any one of Claims 36-68 and one or more solvent onto the first sulfonated polyphenylene polymer layer to form a third wet layer;(h) drying the intermediate membrane with the third wet layer between about 40°C and about 70°C to produce a second antioxidant layer, resulting in a final membrane; wherein the final membrane structure comprises, in sequence:(i) the first antioxidant layer,(ii) the first sulfonated polyphenylene polymer layer, and(iii) the second antioxidant layer; andwherein the first sulfonated polyphenylene polymer layer is in contact with the first antioxidant layer, wherein the second antioxidant layer is in contact with the first sulfonated polyphenylene polymer layer, andwherein the second antioxidant layer is either identical to, or is different from, the first antioxidant layer.

80. The method of Claim 79. further comprising:(i) coating the second antioxidant layer of the membrane with a solution comprising one or more sulfonated polyphenylene polymer as defined by any one of Claims 1 and 15-35 and one or more solvent;(j) heating the coated membrane at a temperature between about 40°C and about 70°C to form a membrane comprising a second sulfonated polyphenylene polymer layer, wherein the second sulfonated polyphenylene polymer layer is in contact with the second antioxidant layer;(k) coating the second sulfonated polyphenylene polymer layer with a solution comprising one or more antioxidant as defined by any one of Claims 36-68 and one or more solvent, wherein said antioxidant solution is the same as, or different from, the antioxidant solution used to prepare the first and / or second antioxidant layers; and(l) heating the coated membrane at a temperature between about 40°C and about 70°C to form a membrane comprising:(i) the first antioxidant layer,(ii) the first sulfonated polyphenylene polymer layer,(iii) the second antioxidant layer,(iv) the second sulfonated polyphenylene polymer layer, and (v) a third antioxidant layer,wherein:the third antioxidant layer is in contact with the second sulfonated polyphenylene polymer layer, and the third antioxidant layer is the same as, or different from, the first and / or second antioxidant layers.

81. The method of Claim 80, further comprising:repeating the steps of Claim 80 to form up to 10 antioxidant layers and 9 sulfonated polyphenylene polymer layers.

82. The method of any one of Claims 76-81, further comprising:(a) contacting the sulfonated polyphenylene polymer solution with a first surface of a porous scaffold reinforcement having a first surface and a second surface;(b) heating the porous scaffold reinforcement and the sulfonated polyphenylene polymer solution in contact with the first surface;(c) contacting the second surface of the porous scaffold reinforcement with a solution comprising one or more sulfonated polyphenylene polymer as defined by any one of Claims 1 and 15-35 and one or more solvent; and(d) heating the porous scaffold reinforcement and the sulfonated polyphenylene polymer solution in contact with the second surface, thereby forming a reinforced sulfonated polyphenylene polymer layer,wherein the sulfonated polyphenylene polymer solution in contact with the first surface of the porous scaffold reinforcement is the same as, or is different from, the sulfonated polyphenylene polymer solution in contact with the second surface of the porous scaffold reinforcement.

83. A method of making a sulfonated poly phenylene membrane, comprising: (a) preparing a solution comprising:(i) one or more sulfonated polyphenylene polymer as defined by any one of Claims 1 and 15-35,(ii) one or more antioxidant as defined by any one of Claims 36-68, and (iii) one or more solvents;(b) applying the solution to a substrate to form a wet layer; and(c) drying the substrate with the wet layer to form a sulfonated polyphenylene membrane.

84. The method of Claim 83. further comprising:(a) contacting a solution comprising one or more sulfonated polyphenylene polymer as defined by any one of Claims 1 and 15-35, one or more antioxidant as defined by any one of Claims 36-68, and one or more solvent, with a first surface of a porous scaffold reinforcement, wherein said porous scaffold reinforcement has a first surface and a second surface;(b) heating the porous scaffold reinforcement and the solution in contact with the first surface;(c) contacting the second surface of the porous scaffold reinforcement with a solution comprising one or more sulfonated polyphenylene polymer as defined by any one of Claims 1 and 15-35, one or more antioxidant as defined by any one of Claims 36-68, and one or more solvent; and(d) heating the porous scaffold reinforcement and the solution in contact with the second surface, thereby forming a reinforced sulfonated polyphenylene polymer layer.wherein the solution in contact with the first surface of the porous scaffold reinforcement is the same as, or is different from, the solution in contact with the second surface of the porous scaffold reinforcement.

85. The method of any one Claims 76-84, wherein the one or more solvents is selected from the group consisting of butanone, pentanone, cyclopentanone, hexanone, cyclohexanone, heptanone. cycloheptanone, propanol, butanol, pentanol, hexanol, cyclohexanol, octanol, decanol, dodecanol, propanediol, butanediol, pentanediol, hexanediol, octanediol, decanediol, dodecanedi ol, glycerol, ethylene glycol, l-methoxy-2-propanol, dipropylene glycol methyl ether, ethyl lactate, glycerol triacetin, y-butyrolactone, 5-valerolactone, and s-caprolactone86. A method for manufacturing ultrafine metal oxide powders, comprising: (a) selecting the metal oxide of any one of Claims 36-41 or 47-68;(b) mixing the metal oxide with an organic additive to form a mixture; and (c) milling the mixture for about 0.5 hour to about 48 hours, to form an ultrafine powder, wherein the ultrafme powder comprises particles of about 1 nm to about 200 nm.

87. The method of any one of Claims 76-86, wherein an in-plane (x, y direction) swelling upon hydration is less than about 10%.

88. The method of any one of Claims 76-87, wherein the heating comprises heating at a temperature below 120 C.

89. The method of any one of Claims 76-88, wherein the sulfonated polyphenylene polymer solution has a viscosity less than about 5,000 cP.

90. A fuel cell membrane-electrode assembly, comprising;(a) a hydrogen electrode to which hydrogen gas is supplied:(b) an oxygen electrode to which an oxidizer gas is supplied; and(c) a sulfonated poly phenylene membrane as defined in any one of Claims 1-75, located between the hydrogen and oxygen electrodes.

91. An electrolyzer membrane-electrode assembly, comprising:(a) a hydrogen evolution electrode configured for the evolution of hydrogen gas; (b) an oxygen evolution electrode configured for the evolution of oxygen gas; and (c) a sulfonated polyphenylene membrane as defined in any one of Claims 1-75, located between the hydrogen and oxygen evolution electrodes92. A hydrogen pump or thermoelectrochemical hydrogen pump membraneelectrode assembly, comprising:(a) a hydrogen electrode configured to receive and split hydrogen gas;(b) a secondary hydrogen electrode to which protons are transmitted and the hydrogen is reformed; and(c) a sulfonated polyphenylene membrane as defined in any one of Claims 1-75, located between the hydrogen electrode and the secondary hydrogen electrode.

93. A method of using the sulfonated polyphenylene membrane as defined by any one of Claims 1-75 in an electrochemical device such as a fuel cell, electrolyzer, hydrogen pump, thermoelectrochemical hydrogen pump, electrochemical hydrogen compressor, or redox flow battery’.

94. The sulfonated polyphenylene membrane produced by the method of anyone of Claims 76-89 for use in an electrochemical device selected from a fuel cell, electrolyzer, hydrogen pump, thermoelectrochemical hydrogen pump, electrochemical hydrogen compressor, redox flow battery, or other electrochemical devices,95. An electrochemical device comprising the sulfonated polyphenylene membrane produced by the method of any one of Claims 76-89, wherein the electrochemical device is a fuel cell, electrolyzer, hydrogen pump, thermoelectrochemical hydrogen pump, electrochemical hydrogen compressor, redox flow battery’, or other electrochemical devices.

96. An electrochemical device comprising the sulfonated polyphenylene membrane as defined in any one of Claims 1-75, wherein the electrochemical device is a fuel cell, electrolyzer, hydrogen pump, thermoelectrochemical hydrogen pump, electrochemical hydrogen compressor, redox flow battery, or other electrochemical devices.

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