Fluoropolymers containing pendant groups with ionic bis(sulfonyl)imide moieties and perfluoroether end groups

Abstract

wherein Rf is a perfluoroether and X 1 and X 2 are independently cationic counterions. Also described are various articles, including catalyst inks, polymer electrolyte membranes, and membrane electrode assemblies, that include the fluoropolymers described herein, as well as methods for making the fluoropolymers. JPEG2023519957000021.jpg7115

Description

[Background technology]

[0001] A variety of fluoropolymers containing pendant ionic groups have been described (see, for example, U.S. Pat. No. 7,348,088). Such fluoropolymers are suitable for polymer electrolyte membranes in electrochemical fuel cells. Summary of the Invention

[0002] The industry would find advantage in fluoropolymers containing pendant groups having one or more ionic bis(sulfonyl)imide moieties and perfluoroether end groups that have improved properties such as high oxygen permeability.

[0003] In one embodiment, the compound of the formula: [ka] wherein Rf is a perfluoroether; and X 1 and X 2 are independently cationic counterions] Fluoropolymers are described that include pendant groups having the formula:

[0004] Also described are various articles including catalyst inks, polymer electrolyte membranes, and membrane electrode assemblies comprising the fluoropolymers described herein, as well as methods of making the fluoropolymers. DETAILED DESCRIPTION OF THE INVENTION

[0005] Described herein are fluoropolymers comprising pendant groups. At least some of the pendant groups comprise perfluoroether end groups. The pendant groups comprise one or more bis(sulfonyl)imide moieties and hydrogen ions (H + ).

[0006] The pendant groups of the fluoropolymer are typically of the formula: [ka] [In the formula, Rf is a perfluoroether, a is 0 or 1, c is 0, 1, or 2; b, e, and f are independently in the range of 2 to 6; d is 0, 1 or greater than 1; X 1 and X 2 are independently a cationic counterion (H + (including) It has.

[0007] In some embodiments, c is 1 or more than 1 (e.g., 2). When c is at least 1, b is independently an integer from 2 to 6. In some embodiments, b is less than 7, 6, 5, or 4. In some embodiments, b is 3.

[0008] In some embodiments, a and c are 0, d is 1 or greater than 1, and the pendant group has the formula: [ka] It has.

[0009] In some embodiments, d is typically 4, 3, or 2 or less.

[0010] In some embodiments, a, c, and d are each zero and the pendant group has the formula: -(OC e F 2e )-SO2-NX 1 -SO2-Rf.

[0011] In each of these embodiments, Rf is typically a single perfluoroether group having 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 perfluorinated carbon atoms, as well as any range derived from these integers. For example, the perfluoroether group can contain 3 to 6 perfluorinated carbon atoms. In some embodiments, Rf is a polyperfluoroether containing two perfluoroether groups, each of which independently contains 3 to 12 carbon atoms, as just described, as well as any range derived from these integers.

[0012] In some embodiments, e is 2, 3, 4, 5, or 6, as well as any range derived from these integers, such as from 2 to 4 or from 3 to 6.

[0013] In some embodiments, f is 2, 3, 4, 5, or 6, as well as any range derived from these integers, such as from 2 to 4 or from 3 to 6.

[0014] Fluoropolymers typically contain 5 mol % to 50 mol % of polymerized monomers having pendant groups comprising perfluoroether end groups, based on the total moles of polymerized monomers in the fluoropolymer. In some embodiments, the fluoropolymer contains at least 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 mol % of polymerized monomers having pendant groups comprising perfluoroether end groups. In some embodiments, the fluoropolymer contains less than 45, 40, 35, 30, or 25 mol % of polymerized monomers having pendant groups comprising perfluoroether end groups.

[0015] The fluoropolymer typically comprises polymerized monomers having other pendant groups that contain different end groups other than perfluoroether end groups. In some embodiments, the fluoropolymer further comprises pendant groups containing sulfonic acid (—SOH) end groups. In some embodiments, the fluoropolymer further comprises pendant groups containing sulfonamide (—SONH) end groups. The fluoropolymer typically comprises no more than 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 mol % of polymerized monomers having pendant groups containing different (e.g., sulfonic acid, sulfonamide) end groups other than perfluoroether end groups. Such other pendant groups containing different end groups other than perfluoroether end groups may or may not contain bis(sulfonyl)imide moieties. The relative proportions of the various moieties of the pendant groups can be determined by nuclear magnetic resonance (NMR) spectroscopy, as discussed in the Examples below.

[0016] The pendant groups are covalently bonded to the fluoropolymer backbone. The fluoropolymer backbone typically comprises polymerized (e.g., repeating) units of -[CF2-CF2]-. In a typical embodiment, at least 50 mol% of the polymerized (e.g., repeating) units of -[CF2-CF2]- are derived from the polymerization of tetrafluoroethylene (TFE). In some embodiments, the fluoropolymer comprises at least 50, 55, 60, 65, 70, 75, 80, 90, or 95 mol% of polymerized units of CF2=CF2, i.e., tetrafluoroethylene, based on the total moles of polymerized monomers of the fluoropolymer. The fluoropolymer backbone further comprises units of -[CF2-CF2]- derived from the polymerization of unsaturated groups of perfluorinated sulfonyl halide monomers. Each carbon atom of -[CF2-CF2]- is bonded to a pendant group as described herein.

[0017] A variety of other monomers can be used in preparing the fluoropolymers so long as they do not impair the desired properties (eg, oxygen permeability) of such fluoropolymers.

[0018] The fluoropolymer may be made by any suitable method.

[0019] One embodied method of preparing the fluoropolymer is described in more detail in the Examples, i) providing a first fluoropolymer intermediate comprising a fluoropolymer backbone and pendant groups terminating in sulfonyl halides (e.g., —SOF); ii) reacting the sulfonyl halide group of the first fluoropolymer intermediate with ammonia to form a sulfonamide ammonium salt, and ion-exchanging with an aprotic amine base (e.g., a tertiary amine such as triethylamine, (TEA)) to remove a proton from the ammonium to form the sulfonamide salt (e.g., —SONH - forming a second fluoropolymer intermediate terminated with TEAH+); iii) reacting the sulfonamide salt of the second fluoropolymer intermediate with a perfluorinated sulfonyl dihalide and an aprotic amine base (e.g., a tertiary amine) to form a bis(sulfonyl)imide sulfonyl halide (e.g., —SO - (TEAH + )SO2(CF2) f forming a third fluoropolymer intermediate terminated with SOF; iv) reacting the third fluoropolymer intermediate bis(sulfonyl)imide sulfonyl halide with ammonia to form a bis(sulfonyl)imide salt (e.g., —SON) terminated with an ammonium ion; - (TEAH + )SO2(CF2) f SO2NH(NH4 + forming a fourth fluoropolymer intermediate terminated with v) Optionally, purify the fourth fluoropolymer intermediate and ion exchange it to remove ammonium ions and convert the terminal sulfonamide to a neutralized form (e.g., —SONHSO(CF) f SO2NH2) or sulfonamide salts (-SO2NHSO2(CF2) which are reactive with aprotic amine bases (e.g., tertiary amines). fSO2NH - TEAH + ) and vi) reacting the optionally purified and ion-exchanged fourth fluoropolymer intermediate with an aprotic amine base (e.g., a tertiary amine) and a perfluoroether sulfonyl halide to covalently attach terminal perfluoroether groups; vii) optionally purifying and ion-exchanging the fluoropolymer of vi).

[0020] In some embodiments, the method further comprises repeating steps iii)-iv) and optionally v) before vi), where d in the above formula is the number of times steps ii) and iv) are performed.

[0021] In some embodiments where d is zero, steps i), ii), vi), and vii) are performed. In other words, steps 3-5 are omitted during the synthesis method when d is zero.

[0022] The pendant groups of the above fluoropolymer intermediates may further comprise perfluoroalkylene groups, perfluoroether groups, or combinations thereof. The perfluoroalkylene groups and / or perfluoroether groups may be present between the fluoropolymer backbone and the (e.g., first) bis(sulfonyl)imide group according to the various pendant group formulas described herein.

[0023] In some embodiments, the first fluoropolymer intermediate can be prepared by reacting tetrafluoroethylene (TFE) with an unsaturated perfluorinated sulfonyl halide (eg, fluoride) monomer.

[0024] In step iii) of the above synthesis, perfluorinated sulfonyl halide (eg, fluoride) monomers are also utilized.

[0025] In some embodiments, the unsaturated perfluorinated sulfonyl halide (e.g., fluoride) monomer has the following formula: CF2 = CF-(OC e F 2e )SO2F wherein e independently ranges from 2 to 6, as defined by the formula above. It has.

[0026] Suitable sulfonyl fluorides or chlorides are described in the literature, for example 1,1,2,2-tetrafluoroethyl-1,3-disulfonyl fluoride, 1,1,2,2,3,3-hexafluoropropyl-1,3-disulfonyl fluoride, 1,1,2,2,3,3,4,4-octafluorobutyl-1,4-disulfonyl fluoride, 1,1,2,2,3,3,4,4,5,5-perfluoropentyl Examples of suitable perfluorobutyl-1,5-disulfonyl chloride include 1,1,2,2-tetrafluoroethyl-1,2-disulfonyl chloride, 1,1,2,2,3,3-hexafluoropropyl-1,3-disulfonyl chloride, 1,1,2,2,3,3,4,4-octafluorobutyl-1,4-disulfonyl chloride, and 1,1,2,2,3,3,4,4,5,5-perfluoropentyl-1,5-disulfonyl chloride.

[0027] Perfluoroalkyl sulfonyl fluoride monomer can be prepared according to the procedure disclosed in WO 2004 / 060857.Polymerization can be carried out by first preparing a pre-emulsion of unsaturated perfluoroalkyl sulfonyl fluoride monomer in water using ammonium perfluorooctanoate (APFO) as emulsifier by high shear mixing using an Ultraturrax agitator.Then, the pre-emulsion can be reacted with TFE by adding initiator.In this embodiment, a and c in the above formula are zero.

[0028] In other embodiments where c is at least 1, the unsaturated perfluorinated sulfonyl halide (e.g., fluoride) monomer has the following formula: CF2 = CF-(OC b F 2b ) c (OC e F 2e )SO2F.

[0029] In one embodiment, b is 3 and e is 2.

[0030] In yet another embodiment where a is at least 1, the unsaturated perfluorinated sulfonyl halide (e.g., fluoride) monomer has the following formula: CF2=CF-(CF2) a (OC e F 2e )SO2F.

[0031] Starting monomers in which c is at least 1 or a is at least 1 are known in the literature (see U.S. Pat. No. 9,434,66792). In each of these formulas, F (i.e., fluoride) can alternatively be other halides, such as chloride.

[0032] In some embodiments, the first fluoropolymer intermediate is prepared from a single sulfonyl halide. In other embodiments, the first fluoropolymer intermediate is prepared from two or more sulfonyl halides. In some embodiments, step iii) utilizes a single disulfonyl halide. In other embodiments, step iii) utilizes two or more disulfonyl halides.

[0033] Aprotic amine bases can also be characterized as catalysts. Suitable aprotic amine catalytic bases include tertiary amines, pyridine, N,N-diisopropylethylamine (DIPEA, or Hunig's base), trialkylamines such as triethylamine, tripropylamine, and diazabicycloundecene (DBU).

[0034] The reaction can be carried out in a suitable (dry) polar aprotic solvent that is miscible, for example. Non-limiting examples of suitable polar aprotic solvents can include acetonitrile, tetrahydrofuran, N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), N-methylpyrrolidinone (NMP), tetrahydrofuran (THF), methyl tert-butyl ether (MTBE), and combinations thereof. The temperature suitable for preparing each fluoropolymer intermediate is described in the following examples.

[0035] In some embodiments, the fluoropolymer is formed into an aqueous dispersion. The purification and / or ion exchange step typically also includes dispersing the fluoropolymer intermediate in water or a water-miscible solvent mixture. The fluoropolymer can typically be dispersed in a solution of water and organic solvent at a concentration of at least 10, 15, 20, or 25 weight percent. In some embodiments, the dispersion can contain up to 30, 40, or 50 weight percent fluoropolymer dispersed in the solution of water and organic solvent. In some embodiments, higher concentrations can be produced by removing water and organic solvent from a dispersion with a low concentration of fluoropolymer. Examples of suitable organic solvents useful for preparing fluoropolymer dispersions of the copolymer include lower alcohols (e.g., methanol, ethanol, isopropanol, n-propanol), polyols (e.g., ethylene glycol, propylene glycol, glycerol), ethers (e.g., tetrahydrofuran and dioxane), diglyme, polyglycol ethers, ether acetates, acetonitrile, acetone, dimethylsulfoxide (DMSO), N,N-dimethylacetamide (DMA), ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, N,N-dimethylformamide (DMF), N-methylpyrrolidinone (NMP), dimethylimidazolidinone, butyrolactone, hexamethylphosphoric triamide (HMPT), isobutyl methyl ketone, sulfolane, and combinations thereof. In some embodiments, the fluoropolymer, water, and organic solvent may be heated to a temperature of about 250° C. In other embodiments, lower temperatures may be used in combination with pressure.

[0036] In some embodiments, prior to coagulation or spray drying (described below), the resulting fluoropolymer dispersion is refined to remove functional comonomers, anions, and / or cations by at least one of an anion or cation exchange process or ultrafiltration by tangential or cross-flow filtration. As used herein, the term "purify" refers to at least partial removal of impurities, regardless of whether the removal is complete. Anionic species that may constitute impurities include, for example, fluorides, anionic residues from surfactants and emulsifiers (e.g., perfluorooctanoate), residual compounds, and fluoropolymers having pendant groups lacking perfluoroether or polyperfluoroether end groups. However, it should be noted that it may be desirable not to remove ionic fluoropolymers containing pendant groups lacking perfluoroether end groups from the dispersion. Useful anion exchange resins typically comprise polymers (typically crosslinked) having multiple cationic groups (e.g., quaternary alkylammonium groups) paired with various anions (e.g., halides or hydroxides). When contacting with the fluoropolymer dispersion, the anionic impurities in the dispersion associate with the anion exchange resin. After the anion exchange step, the resulting anion-exchanged dispersion is separated from the anion exchange resin, for example, by filtration. Typically, a better yield is obtained when using a gel-type anion exchange resin than when using a macroporous anion exchange resin. Typically, the best yield is obtained by ultrafiltration, where the pore size of the filter membrane is small enough to retain the fluoropolymer but large enough to allow the solvent and impurities to pass through.

[0037] Examples of cationic impurities resulting from the above polymerization include alkali metal cations (e.g., Li + , Na + , K. + ), ammonium, quaternary alkylammonium, alkaline earth cations (e.g., Mg 2+ , Ca 2+ ), manganese cations (e.g., Mn 2+), and one or more of Group III metal cations. Useful cation exchange resins include polymers (typically crosslinked) with multiple pendant anionic or acidic groups, such as polysulfonates or polysulfonic acids, polycarboxylates, or polycarboxylic acids. The metal ion content of the copolymer can be measured by flame atomic absorption spectrometry after burning the copolymer and dissolving the residue in aqueous acid. For potassium as the analyte, the lower detection limit is typically less than 1 ppm.

[0038] Examples of useful sulfonic acid cation exchange resins include sulfonated styrene-divinylbenzene copolymers, sulfonated crosslinked styrene polymers, phenol-formaldehyde-sulfonic acid resins, and benzene-formaldehyde-sulfonic acid resins. Carboxylic acid cation exchange resins are organic acid cation exchange resins. Cation exchange resins are commercially available from a variety of sources. Cation exchange resins are generally commercially supplied in either their acid form or their sodium form. If the cation exchange resin is not in the acid form (i.e., the protonated form), it can be at least partially or completely converted to the acid form to avoid the introduction of other cations into the dispersion, which is generally undesirable. This conversion to the acid form can be achieved by means well known in the art, such as treatment with any suitable strong acid. In addition to removing impurities from the fluoropolymer dispersion, the cation exchange resin can also generate the acid form of the fluoropolymer pendant groups.

[0039] The fluoropolymer typically has an equivalent weight (EW) of at least 600, 700, 750, or 800 g / equivalent. In some embodiments, the fluoropolymer has an equivalent weight (EW) greater than 800, more typically greater than 900, and more typically greater than 1000. In some embodiments, the fluoropolymer typically has an equivalent weight (EW) less than 1200, and more typically less than 1100. Equivalent weight can be determined according to the test methods described in the examples.

[0040] In some preferred embodiments, portions of the fluoropolymer backbone and pendant groups are selected to provide high oxygen permeability.

[0041] Oxygen permeability can be determined by at least two methods described in the Examples: Oxygen permeability can vary depending on relative humidity and temperature.

[0042] In some embodiments, the fluoropolymer has a viscosity of at least 1.1E-13 (i.e., 1.1×10) at 80° C. at 25% relative humidity. -13 ) (determined by Test Method 1). In some embodiments, the electrochemical oxygen permeability of the fluoropolymer at 80°C and 25% relative humidity is at least 1.5E-13 or 2E-13. In some embodiments, the electrochemical oxygen permeability of the fluoropolymer at 80°C and 50% relative humidity is at least 1.5E-13, 2.0E-13, or 2.5E-13. In some embodiments, the electrochemical oxygen permeability of the fluoropolymer at 80°C and 100% relative humidity is at least 2.1E-13, 2.2E-13, 2.3E-13, 2.4E-13, 2.5E-13, 2.6E-13, 2.7E-13, 2.8E-13, or 2.9E-13 at 80°C and 100% relative humidity. In some embodiments, the electrochemical oxygen permeability is 2E-12, 1E-12, 9E-13, 8E-13, 7E-13, 6E-13, 5E-13, 4E-13, or 3E-13 or less at 80° C. and 25%, 50%, or 100% relative humidity. In some embodiments, the electrochemical oxygen permeability is 2.9E-13, 2.8E-13, or 2.7E-13 or less at 80° C. and 50% relative humidity. In some embodiments, the electrochemical oxygen permeability is 2.6E-13, 2.5E-13, 2.4E-13, or 2.3E-13 or less at 80° C. and 50% relative humidity.

[0043] In some embodiments, the fluoropolymer has a permeability coefficient for oxygen transmission (determined by Test Method 2) at 23°C and zero relative humidity of at least 8.5E-15. In some embodiments, the fluoropolymer has a permeability coefficient for oxygen transmission of at least 9E-15, 9.5E-15, or 1E-14. In some embodiments, the permeability coefficient for oxygen transmission is 1E-13, 9E-14, 8E-14, 7E-14, 6E-14, 5E-14, 4E-14, 3E-14, 2E-14, or 1.5E-14 or less.

[0044] In some preferred embodiments, moieties of the fluoropolymer backbone and pendant groups are selected to provide high electrical conductivity, as determined by the test methods described in the Examples. Conductivity can vary depending on relative humidity and temperature. In some embodiments, the fluoropolymer has a conductivity of at least 0.001 Siemens / cm, 0.005 Siemens / cm, or 0.010 Siemens / cm (S / cm) at 25% relative humidity and 80°C. In some embodiments, the fluoropolymer has a conductivity of at least 0.001 S / cm, 0.005 S / cm, 0.010 S / cm, 0.020 S / cm, 0.030 S / cm, 0.040 S / cm, or 0.050 S / cm at 50% relative humidity and 80°C. In some embodiments, the fluoropolymer has a conductivity of at least 0.001 S / cm, 0.005 S / cm, 0.010 S / cm, 0.020 S / cm, 0.030 S / cm, 0.040 S / cm, 0.050 S / cm, 0.10 S / cm, 0.15 S / cm, 0.20 S / cm, or 0.25 S / cm at 90% relative humidity and 80°C.

[0045] Fluoropolymers can exhibit various combinations of oxygen permeability and conductivity just described.

[0046] The high oxygen permeability in the copolymers disclosed herein can be useful, for example, to improve the efficiency of fuel cells.

[0047] The copolymers of the present disclosure may be useful, for example, in the manufacture of catalyst inks and polymer electrolyte membranes for use in fuel cells or other electrolysis cells. A membrane electrode assembly (MEA) is the central element of a proton exchange membrane fuel cell, such as a hydrogen fuel cell. A fuel cell is an electrochemical cell that produces usable electricity by catalytically combining a fuel, such as hydrogen, with an oxidant, such as oxygen. A typical MEA contains a polymer electrolyte membrane (also known as an ion conductive membrane (ICM)) that functions as a solid electrolyte. One specific type of ICM is a proton exchange membrane (PEM). One side of the ICM or PEM contacts an anode electrode layer, and the opposite side contacts a cathode electrode layer. Each electrode layer contains an electrochemical catalyst, typically comprising platinum metal. Gas diffusion layers (GDLs) facilitate gas transport to and from the anode and cathode electrode materials to conduct electrical current. The GDL is also sometimes called a fluid transport layer (FTL) or diffuser / current collector (DCC). The anode and cathode electrode layers may be applied to the GDL in the form of a catalyst ink, and the resulting coated GDL is sandwiched between PEMs to form a five-layer MEA. Alternatively, the anode and cathode electrode layers may be applied to both sides of the PEM in the form of a catalyst ink, and the resulting catalyst-coated membrane (CCM) is sandwiched between two GDLs to form a five-layer MEA. Details regarding the preparation of catalyst inks and their use in membrane assemblies can be found, for example, in U.S. Patent Publication No. 2004 / 0107869 (Velamakanni et al.). In a typical PEM fuel cell, protons are formed at the anode by the oxidation of hydrogen and transported across the PEM to the cathode to react with oxygen, generating electrical current through an external circuit connecting the electrodes. PEMs form a durable, non-porous, non-conductive mechanical barrier between the reactant gases, yet still allow H + It allows ions to pass through easily.

[0048] The copolymers of the present disclosure may be useful as PEMs and / or for preparing catalyst ink compositions. In some embodiments, the copolymers (e.g., as components of the fluoropolymer dispersions described above) can be combined with catalyst particles (e.g., metal particles or carbon-supported metal particles). A variety of catalysts may be useful. Typically, carbon-supported catalyst particles are used. Typical carbon-supported catalyst particles contain 30% to 95% by weight carbon and 5% to 70% by weight of a catalytic metal, typically platinum for the cathode and platinum or platinum and ruthenium in a 2:1 weight ratio for the anode. However, other metals, such as gold, silver, palladium, iridium, rhodium, iron, cobalt, nickel, chromium, tungsten, manganese, vanadium, and alloys thereof, may also be useful. To produce an MEA or CCM, the catalyst may be applied to the PEM by any suitable means, including both manual and mechanical methods, such as hand brushing, notch bar coating, fluid bearing die coating, wire wound rod coating, slot fed knife coating, three-roll coating, or decal transfer. Coating may be accomplished in a single application or multiple applications. Advantageously, copolymers according to the present disclosure may be useful for producing a catalyst layer by a single coating application. The catalyst ink may be applied directly to the PEM or GDL, or the catalyst ink may be applied to a transfer substrate, dried, and then applied as a decal to the PEM or FTL.

[0049] In some embodiments, the catalyst ink comprises a copolymer disclosed herein at a concentration of at least 10, 15, or 20 wt % and up to 30 wt %, based on the total weight of the catalyst ink. In some embodiments, the catalyst ink comprises catalyst particles in an amount of at least 10, 15, or 20 wt % and up to 50, 40, or 30 wt %, based on the total weight of the catalyst ink. The catalyst particles can be added to a fluoropolymer dispersion prepared as described above in any of the embodiments. The resulting catalyst ink can be mixed, for example, with heating. The percentage of solids in the catalyst ink can be selected, for example, to obtain desired rheological properties. Examples of suitable organic solvents useful for inclusion in the catalyst ink include lower alcohols (e.g., methanol, ethanol, isopropanol, n-propanol), polyols (e.g., ethylene glycol, propylene glycol, glycerol), ethers (e.g., tetrahydrofuran and dioxane), diglyme, polyglycol ethers, ether acetates, acetonitrile, acetone, dimethylsulfoxide (DMSO), N,N dimethylacetamide (DMA), ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, N,N-dimethylformamide (DMF), N-methylpyrrolidinone (NMP), dimethylimidazolidinone, butyrolactone, hexamethylphosphoric triamide (HMPT), isobutyl methyl ketone, sulfolane, and combinations thereof. In some embodiments, the catalyst ink contains 0% to 50% by weight of a lower alcohol and 0% to 20% by weight of a polyol. Additionally, the ink may contain 0% to 2% of a suitable dispersant.

[0050] In some embodiments, the copolymers of the present disclosure may be useful for producing polymer electrolyte membranes. The copolymers may be formed into polymer electrolyte membranes by any suitable method, including casting, molding, and extrusion. Typically, the membranes are cast from a fluoropolymer dispersion (e.g., as described above in any of the embodiments), followed by drying and / or annealing. The copolymers may also be cast from a suspension. Any suitable casting method may be used, including bar coating, spray coating, slit coating, and brush coating. After formation, the membrane may be annealed, typically at temperatures above 120°C, more typically above 130°C, and most typically above 150°C. In some embodiments of the method according to the present disclosure, the polymer electrolyte membrane can be obtained by obtaining the copolymer in a dispersion of the fluoropolymer, optionally purifying the dispersion by ion exchange purification, and concentrating the dispersion to produce the membrane. Typically, when a fluoropolymer dispersion is used to form the membrane, the concentration of the copolymer is advantageously high (e.g., at least 20, 30, or 40 weight percent). In many cases, water-miscible organic solvents are added to promote film formation. Examples of water-miscible solvents include lower alcohols (e.g., methanol, ethanol, isopropanol, n-propanol), polyols (e.g., ethylene glycol, propylene glycol, glycerol), ethers (e.g., tetrahydrofuran and dioxane), acetic acid ethers, acetonitrile, acetone, dimethyl sulfoxide (DMSO), N,N-dimethylacetamide (DMA), ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, N,N-dimethylformamide (DMF), N-methylpyrrolidinone (NMP), dimethylimidazolidinone, butyrolactone, hexamethylphosphoric triamide (HMPT), isobutyl methyl ketone, sulfolane, and combinations thereof.

[0051] The present disclosure provides a membrane electrode assembly including at least one of a catalyst ink including a copolymer of the present disclosure or a polymer electrolyte membrane including a copolymer of the present disclosure. The catalyst ink and the polymer electrolyte membrane may use the same or different copolymers. In some embodiments, the catalyst ink includes a copolymer of the present disclosure and the polymer electrolyte membrane includes a conventional copolymer (e.g., one that does not include the pendant groups described herein).

[0052] In some embodiments of the polymer electrolyte membrane of the present disclosure, at least one salt of cerium, manganese, or ruthenium, or one or more cerium oxide or zirconium oxide compounds, is added to the acid form of the copolymer prior to membrane formation. Typically, the cerium, manganese, or ruthenium salt and / or cerium oxide or zirconium oxide compound is thoroughly mixed with or dissolved in the copolymer to achieve a substantially uniform dispersion.

[0053] The cerium, manganese, or ruthenium salts can contain any suitable anion, including chloride, bromide, hydroxide, nitrate, sulfonate, acetate, phosphate, and carbonate. More than one anion may be present. Other salts may be present, including salts containing other metal cations or ammonium cations. Once cation exchange occurs between the transition metal salt and the acid form of the ionomer, it may be desirable to remove the acid formed by the combination of the liberated proton with the anion of the original salt. Therefore, it may be useful to use an anion that generates a volatile or soluble acid, such as chloride or nitrate. The manganese cation is preferably Mn 2+ , Mn 3+ , and Mn 4+ may be in any suitable oxidation state, including, but most typically, Mn 2+ The ruthenium cation is Ru 3+ and Ru 4+ may be in any suitable oxidation state, including, but most typically, Ru 3+ The cerium cation is Ce 3+and Ce 4+ Without intending to be bound by theory, the cerium, manganese, or ruthenium cations may be in any suitable oxidation state, including H from the anionic groups of the polymer electrolyte. + It is believed that the cations exchange with the ions and associate with these anionic groups, thereby remaining in the polymer electrolyte. Furthermore, it is believed that polyvalent cerium, manganese, or ruthenium cations may form ionic bridges between the anionic groups of the polymer electrolyte, further enhancing the stability of the polymer. In some embodiments, the salt may exist in a solid form. The cations may exist in a combination of two or more forms, including solvated cations, cations associated with bound anionic groups of the polymer electrolyte membrane, and cations bound to salt precipitates. The amount of salt added is typically 0.001 to 0.5 charge equivalents, more typically 0.005 to 0.2, more typically 0.01 to 0.1, and more typically 0.02 to 0.05, based on the molar amount of acid functional groups present in the polymer electrolyte. Further details regarding the combination of anionic copolymers with cerium, manganese, or ruthenium cations can be found in US Pat. Nos. 7,575,534 and 8,628,871 (each to Frey et al.).

[0054] Useful cerium oxide compounds may contain cerium in the (IV) oxidation state, the (III) oxidation state, or both, and may be crystalline or amorphous. Cerium oxide may be, for example, CeO or CeO. Cerium oxide may be substantially free of metallic cerium or may contain metallic cerium. Cerium oxide compounds may or may not contain other metal elements. Examples of mixed metal oxide compounds containing cerium oxide include solid solutions such as zirconia-ceria and multicomponent oxide compounds such as barium cerate. While not intending to be bound by theory, it is believed that cerium oxide may strengthen the polymer by chelation and the formation of crosslinks between the bound anionic groups. The amount of cerium oxide compound added is typically 0.01 to 5 weight percent, more typically 0.1 to 2 weight percent, and more typically 0.2 to 0.3 weight percent, based on the total weight of the copolymer. The cerium oxide compound is typically present in an amount of less than 1 vol. %, more typically less than 0.8 vol. %, and more typically less than 0.5 vol. %, based on the total volume of the polymer electrolyte membrane. The cerium oxide may be particles of any suitable size, in some embodiments, from 1 nm to 5000 nm, from 200 nm to 5000 nm, or from 500 nm to 1000 nm. Further details regarding polymer electrolyte membranes containing cerium oxide compounds can be found in U.S. Pat. No. 8,367,267 (Frey et al.).

[0055] The polymer electrolyte membrane may have a thickness of up to 90 micrometers, up to 60 micrometers, or up to 30 micrometers in some embodiments. A thinner membrane may offer less resistance to ions passing through. When used in fuel cells, this results in cooler operation and a greater usable energy output.

[0056] In some embodiments, the copolymers of the present disclosure may be imbibed into a porous support matrix in the form of a thin membrane, typically having a thickness of up to 90 micrometers, up to 60 micrometers, or up to 30 micrometers. Any suitable method for imbibing the copolymer into the pores of the support matrix can be used, including overpressure, vacuum, wicking, and liquid immersion. Any suitable support matrix can be used. Typically, the support matrix is ​​non-conductive. Typically, the support matrix is ​​composed of a fluoropolymer, which is more typically perfluorinated. Typical matrices include porous polytetrafluoroethylene (PTFE), such as biaxially expanded PTFE webs. In another embodiment, fillers (e.g., fibers) can be added to the polymer to reinforce the membrane.

[0057] To produce an MEA, a GDL may be applied to either side of the CCM by any suitable means. Any suitable GDL may be used in the practice of the present disclosure. Typically, the GDL is composed of a sheet material containing carbon fiber. Typically, the GDL is a carbon fiber structure selected from woven and nonwoven carbon fiber structures. Carbon fiber structures that may be useful in the practice of the present disclosure include Toray™ carbon paper, SpectraCarb™ carbon paper, AFN™ nonwoven carbon cloth, and Zoltek™ carbon cloth. The GDL may be coated or impregnated with a variety of materials, including carbon particle coatings, hydrophilic treatments, and hydrophobic treatments such as coating with polytetrafluoroethylene (PTFE).

[0058] In use, an MEA according to the present disclosure is typically sandwiched between two rigid plates known as distribution plates, also known as bipolar plates (BPPs) or monopolar plates. Like GDLs, distribution plates are typically electrically conductive. They are typically fabricated from carbon composite, metal, or plated metal materials. The distribution plate distributes reactant or product fluids to and from the MEA electrode surfaces through one or more fluid-conducting channels typically cut, milled, molded, or stamped into the surface facing the MEA. These channels are sometimes referred to as flow fields. The distribution plate is termed a "bipolar plate" because it can distribute fluids to and from two consecutive MEAs in a stack, with one side directing fuel to the anode of the first MEA while the other side directs oxidant to the cathode of the next MEA (and removes product water). Alternatively, the distribution plate may have channels on only one side to distribute fluid to or from the MEA on only that side, and this plate is sometimes called a "monopolar plate." A typical fuel cell stack contains multiple MEAs stacked alternately with bipolar plates.

[0059] Another type of electrochemical device is an electrolytic cell, which uses electricity to produce chemical change or chemical energy. One example of an electrolytic cell is a chloralkali membrane battery, in which an aqueous sodium chloride solution is electrolyzed by an electric current between an anode and a cathode. The electrolyte is separated into anolyte and catholyte portions by a membrane that is exposed to harsh conditions. In a chloralkali membrane battery, corrosive sodium hydroxide collects in the catholyte portion, hydrogen gas is produced in the cathode portion, and chlorine gas is produced from the sodium chloride-rich anolyte portion at the anode. The copolymers of the present disclosure may be useful, for example, in the manufacture of catalyst inks and electrolyte membranes for use in chloralkali membrane batteries or other electrolytic cells.

[0060] The copolymers according to the present disclosure may also be useful as binders for electrodes in other electrochemical cells (e.g., lithium-ion batteries). To fabricate an electrode, powdered active components may be dispersed in a solvent with the copolymer and coated onto a metal foil substrate or current collector. The resulting composite electrode contains the powdered active components in a polymer binder adhered to a metal substrate. Active materials useful for fabricating negative electrodes include conductive powders such as main group element alloys and graphite. Examples of active materials useful for fabricating negative electrodes include oxides (tin oxide), carbon compounds (e.g., artificial graphite, natural graphite, amorphous graphite, expanded graphite, and flake graphite), silicon carbide compounds, silicon oxide compounds, titanium sulfide, and boron carbide compounds. Active materials useful for fabricating positive electrodes include lithium compounds, such as Li 4 / 3 Ti 5 / 3 O4, LiV3O8, LiV2O5, LiCo 0.2 Ni 0.8 O2, LiNiO2, LiFePO4, LiMnPO4, LiCoPO4, LiMn2O4, and LiCoO2, etc. The electrode may also include a conductive diluent and an adhesion promoter.

[0061] Electrochemical battery cells (e.g., lithium ion batteries) containing the copolymers disclosed herein as a binder or solid polymer electrolyte can be fabricated by placing at least one each of a positive electrode and a negative electrode in contact with the electrolyte. Typically, a microporous separator impregnated with a liquid electrolyte can be used to prevent direct contact between the negative and positive electrodes. The copolymers disclosed herein can be suitable to function as both an electrolyte and a separator. When the electrodes are externally connected, lithiation and delithiation can occur in the electrodes, generating an electric current.

[0062] The electrochemical cells can be useful as rechargeable batteries and can be used in a variety of devices, including portable computers, tablet displays, personal digital assistants, mobile phones, motor-driven devices (e.g., personal or household appliances and vehicles), appliances, lighting devices (e.g., flashlights), and heating devices. One or more of the electrochemical cells can be combined to provide a battery pack. The present invention includes the following aspects. (1) the following formula: [ka] [In the formula, Rf is a perfluoroether, a is 0 or 1, c is 0 or 1; b, e, and f are independently in the range of 2 to 6; d is 0, 1, or greater than 1; X 1 and X 2 are independently cationic counterions] 1. A fluoropolymer comprising a pendant group represented by: (2) a and c are 0, d is at least 1, and the pendant group has the formula: [ka] Item 1. The fluoropolymer according to item 1, having (3) The fluoropolymer according to item 1 or 2, wherein Rf is a perfluoroether having 3 to 12 perfluorinated carbon atoms. (4)X 1 and X 2 4. The fluoropolymer according to any one of items 1 to 3, wherein is hydrogen. (5) a, c, and d are each zero and the pendant group has the formula: -(OC e F 2e )-SO 2 -NX 1 -SO 2 -Rf 5. The fluoropolymer according to any one of items 1 to 4, having: (6) The fluoropolymer according to any one of items 1 to 5, wherein the fluoropolymer further comprises up to 10 mol% of pendant groups comprising at least one bis(sulfonyl)imide moiety and an end group selected from sulfonic acid and sulfonamide. (7) The fluoropolymer according to any one of items 1 to 6, wherein the fluoropolymer comprises 5 mol % to 50 mol % of the pendant groups. (8) The fluoropolymer is 50 mol% to 95 mol% of -[CF 2 -CF 2 8. The fluoropolymer according to any one of items 1 to 7, comprising a main chain containing polymerized units of ]-. (9) The fluoropolymer is at least i) 1.1E-13 at 25% relative humidity, ii) 1.5E-13 at 50% relative humidity; iii) 2.2E-13 at 100% relative humidity, or 9. The fluoropolymer according to any one of items 1 to 8, having an electrochemical oxygen permeability coefficient at 80°C of the combination thereof. (10) The fluoropolymer according to any one of items 1 to 9, wherein the fluoropolymer has an oxygen permeability coefficient of at least 8.5E-15 at 23°C and zero relative humidity. (11) The fluoropolymer is at least i) 0.001 S / cm, 0.005 S / cm, or 0.010 S / cm at 25% relative humidity; ii) 0.010S / cm, 0.020S / cm, 0.030S / cm, 0.040S / cm, 0.050S / cm at 50% relative humidity; iii) 0.050 S / cm, 0.10 S / cm, 0.15 S / cm, 0.20 S / cm, 0.25 S / cm at 90% relative humidity, or 11. The fluoropolymer according to any one of items 1 to 10, having a combination thereof and an ionic conductivity at 80°C. (12) A fluoropolymer comprising a pendant group comprising one or more ionic bis(sulfonyl)imide moieties and a terminal perfluoroether group, wherein the fluoropolymer has an oxygen permeability coefficient according to item 9 or 10. (13) The fluoropolymer according to any one of items 1 to 12, wherein the fluoropolymer is dispersed in an organic solvent. (14) The fluoropolymer according to any one of items 1 to 13, wherein the fluoropolymer is dispersed in an aqueous solvent or a mixture of water and a water-miscible organic solvent. (15) A catalyst ink comprising the fluoropolymer according to any one of items 1 to 14. (16) A polymer electrolyte membrane prepared from the fluoropolymer according to any one of items 1 to 14. (17) A membrane electrode assembly comprising at least one of the catalyst ink according to item 15 or the polymer electrolyte membrane according to item 16. (18) A method for producing a fluoropolymer, comprising: i) providing a first fluoropolymer intermediate comprising a fluoropolymer backbone and pendant groups terminated with sulfonyl halides; ii) reacting the sulfonyl halide group of the first fluoropolymer intermediate with ammonia to ion exchange with an aprotic amine base and remove a proton from the ammonium to form a second fluoropolymer intermediate terminated with a sulfonamide salt; iii) reacting the sulfonamide salt of the second fluoropolymer intermediate with a perfluorinated disulfonyl halide and an aprotic amine base to form a third fluoropolymer intermediate terminated with a bis(sulfonyl)imide sulfonyl halide; iv) reacting the bis(sulfonyl)imide sulfonyl halide of the third fluoropolymer intermediate with ammonia to form a fourth fluoropolymer intermediate terminated with a bis(sulfonyl)imide salt that terminates with an ammonium ion; v) optionally purifying and ion-exchanging the fourth fluoropolymer intermediate to remove the ammonium ions and convert the terminal sulfonamide to a neutralized form or sulfonamide salt that is reactive with aprotic amine bases; vi) reacting the optionally purified and ion-exchanged fourth fluoropolymer intermediate with an aprotic amine base and a perfluoroether sulfonyl halide to covalently attach terminal fluoropolymer perfluoroether groups; vii) optionally purifying and ion-exchanging the fluoropolymer of vi); A method comprising: (19) The method according to item 18, further comprising repeating steps ii) to v) before vi), wherein d is the number of times steps ii) to v) are performed. (20) The method according to item 18 or 19, wherein the pendant group of the fluoropolymer intermediate of i) further comprises a perfluoroalkyl group, a perfluoroether group, or a combination thereof between the fluoropolymer backbone and the bis(sulfonyl)imide group. (21) The method according to any one of items 18 to 20, wherein the fluoropolymer is one described in any one of items 1 to 12. [Example]

[0063] Unless otherwise stated or readily apparent from the context, all parts, percentages, ratios, etc. in the examples and elsewhere in this disclosure are by weight.

[0064] [Table 1]

[0065] Film Coating Method Films were prepared using an Automatic Film Applicator (AFA) 1132N drawdown machine (TCQ Sheen, Metamora, MI) set at a speed of 50 mm / sec for the total coating distance. The drawdown machine coating surface was placed on a glass plate (12 inches × 17 inches × 1 / 8 inches, 30.5 cm × 43.2 cm × 0.32 cm) and a 2 mil (51 micrometer) silicone-coated polyethylene terephthalate (PET) release liner. The glass and liner were cleaned of any debris with isopropyl alcohol (IPA). Both the release liner and plate were secured under the drawdown mechanism by built-in clips. A 4-inch (10.2 cm) milled coating notch bar square (Gardco, Paul N. Gardner Co., Pompano Beach, FL) was placed on the silicone-coated PET release liner, and the fluoropolymer dispersion was poured onto the front of the notch bar, and the ionomer dispersion was coated at the set speed and distance. The release liner was taped at all four corners to prevent it from rising in the forced air oven. The glass plate with the release liner and coating was removed from the drawdown machine, covered with an aluminum pan to prevent debris from falling into the coating, and placed on a ceramic support mounted on a metal wire shelf in a forced air oven (Despatch, Minneapolis, MN) set at 120°C for 30 minutes. The release liner and coating thereon were removed from the glass, placed in an aluminum pan covered with another aluminum pan, and returned to the oven set at 140°C for 15 minutes. The temperature was increased to 160°C and held for 10 minutes. The film was cooled and characterized by micrometer measurements.

[0066] Test Method Determination of sulfonamide content The sulfonamide content of the resulting polymer dispersions was measured by a nuclear magnetic resonance spectrometer (obtained from Bruker Corp, Billerica, MA under the trade designation "BRUKER A500 NMR") after the polymers were dried and dispersed in perdeuterated solvents MeOD or DMSO-d6, and showed sulfonamides associated with sulfonyl fluoride, sulfonamide, bis(sulfonyl)imide, and sulfonic acid functional groups found between -107 ppm and -126 ppm. 19 The F spectra were calculated by comparing the CF2 peak incorporation.

[0067] Melt Flow Index The melt flow index (MFI) of the as-prepared polymer, reported in g / 10 min, was measured according to the procedure described in DIN EN ISO 1133-1 using a Goettfert MPD, MI-Robo, M14 melt indexer (Buchen, Germany) at a substrate weight of 5.0 kg and a temperature of 265° C. The MFI was obtained using a standardized extrusion die with a diameter of 2.1 mm and a length of 8.0 mm.

[0068] Proton conductivity The dried films were evaluated using a standard in-plane, four-point probe conductance apparatus with platinum electrodes. The cells were electrically connected to a potentiostat (Model 273, Princeton Applied Research, Oak Ridge, TN) and an Impedance / Gain Phase Analyzer (Solartron SI 1260, Ametek Inc., Oak Ridge, TN). AC impedance measurements were performed using ZPLOT and ZVIEW software (Scribner Associates Inc., Southern Pines, NC). Temperature and relative humidity (RH) were controlled with a constant humidity oven (model 1000H, Test Equity, Moorpark, CA). The test method selected an initial condition of 70% RH with a set temperature of 80°C, then gradually decreased the RH to 25% RH and then increased up to 90% RH. Each condition was maintained for 90 minutes. Conductivity, in Siemens / cm (S / cm), is reported at various humidities as humidity increases.

[0069] Equivalent weight (EW) determination by titration of bulk films Approximately 0.5 g to 0.7 g of the dried film was weighed and added to 50 g of 1 M NaCl (aq). The film was ion-exchanged for over 4 hours with gentle agitation by rolling or shaking in a bottle. The HCl produced was titrated with 0.03 M NaOH to determine the ion-exchange capacity of a known mass of film.

[0070] Oxygen Permeability Coefficient - Test Method 1 Oxygen permeability measurements of dried ionomer films were carried out according to the method described in Zhang et al. (J. Electrochem. Soc, 160, F616, 2013) using the materials and parameters described below.

[0071] [Table 2]

[0072] Iridium oxide (IrOx) dispersed at 30 wt% on graphitized carbon (Tanaka) was used as the anode material. Both the anode ink and the cathode ink were prepared by mixing the ingredients in the table below. In each case, the ink was prepared in a nitrogen inerted enclosure. Water was added first to the catalyst, followed by additional solvent and ionomer solution.

[0073] [Table 3]

[0074] The catalyst ink was mixed by combining all ingredients and then ball milling for 48 hours using 6 mm ceramic ZrO2 beads (from Glen Mills Inc., Clifton, NJ). Using 3M Company's in-house pilot-scale production line, anode and cathode electrodes were coated onto 1 mil polyethylene terephthalate (PET) film containing a silicone release surface and dried at a maximum temperature of 145°C. The ionomer membrane to be tested was placed between the cathode and anode catalyst layer decals prepared above, with the liner on the outside of the structure and the catalyst facing the ionomer membrane, as is common in the industry. The structure was hot-laminated using a heated steel 6-inch (15.2 cm) diameter roller heated to 325°F (163°C) at a roller speed of 1.2 ft / min (0.37 m / s) with 100 pounds per square inch (0.69 MPa) of air pressure applied to the laminator drum. The silicone coated PET release liner was removed from the construction immediately after lamination to form the CCM.

[0075] Assembling for testing at the single cell fuel test station.

[0076] The CCM was mounted between two GDLs, with four serpentine graphite flow fields and a gasket selected to provide 10% compression to the gas diffusion layers, for a 50 cm 2The test cell was directly installed in a single fuel cell (obtained from Fuel Cell Technologies, Albuquerque, NM under the trade designation "50 cm2 CELL HARDWARE" (50SCH)). After assembly, the test cell was connected to a test station (obtained from Fuel Cell Technologies, Inc. under the trade designation "SINGLE FUEL CELL TEST STATION"). A supply of hydrogen gas was provided to the anode side, and air was supplied to the cathode side. The test station was used to control the applied cell voltage or current density. All tests described below were performed on the same electrochemical cell, using the same type of ion exchange membrane and cathode configuration.

[0077] The data were used to generate the necessary corrections for electrical shorts across the membrane, membrane thickness, and water pressure, as described in Zhang et al. The resulting data were then used to extrapolate oxygen permeability in mol cm s. -1 ·cm -2 kPa -1 This method refines the bulk film O2 permeability measurements described by Zhang et al. to best achieve repeatable and stable data for multiple membrane types. The key difference from the Zhang method was that the Pt oxygen reduction reaction (ORR) cathode electrode was modified to contain more Pt and more active Pt. Thus, 0.4 mg Pt / cm2 on a Ketjen carbon electrode. 2 NECC SA50BK platinum was used.

[0078] Oxygen permeability coefficient - Test method 2 The dried films, still on their backings, were cut into 4-inch (10.2 cm) diameter circular samples using an AccuCut die and an AccuCut MARKIV mechanical press (Omaha, NE), followed by 5 cm (10.2 cm) diameter circular samples using an adhesive-backed aluminum mask (TM Electronics, Inc., Davens, Massachusetts, PML-800815). 2The area was masked (masked on both sides). The mask was first applied to the air-open side of the film, holding one side of the film against the coated release liner substrate. A weighted roller was used to apply pressure to the mask to ensure a good seal around the active area of ​​the sample. The release liner was then removed, and a second mask was applied in alignment with the first mask, and a weighted roller was again used to ensure a good seal between the mask and the sample. The oxygen permeation analyzer (8001L Oxygen Permeation Analyzer, Systech Illinois Instruments Company, Johnsburg, IL) was calibrated with 88.6 ppm O2 in N2 calibration gas (Oxygen Services Company, SG3 00LG025, certified, St. Paul, MN) or calibrated against a film with a certified oxygen transmission rate (OTR) value. The masked sample was mounted in the cell, and two samples were run per test. Vacuum grease (Apiezon, Manchester, UK) was then applied around the periphery of each cell to ensure a good seal between the sample and the nitrogen side of the instrument. Ultra-high purity oxygen (99.996%, Oxygen Services Company, SG3 00MG003) test gas and ultra-high purity nitrogen (99.999%, Oxygen Services Company, NIT 304UHP) carrier gas were obtained from Oxygen Services Company. Measurements began after tubing purging and leak checking to ensure the cell was properly sealed. Transmittance was sampled at 20-minute intervals, and the test was stopped when a change in OTR of 1% or less was determined by the instrument between the sampling intervals. The resulting OTR value provided by the instrument was proportional to the sample thickness (cm). 厚さ ), test area of ​​the sample

number

number

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[0079] Comparative example A (CE-A) It is a copolymer having the following structure:

[0080] The copolymer had an equivalent weight of 798 g / mol, 19.2 mol % polymerized sulfonate-functional monomer and 80.8 mol % polymerized tetrafluoroethylene comonomer.

[0081] Films of CE-A were prepared by redispersing the ionomer in aqueous methanol to produce a 40% solids dispersion of the ionomer. The ionomer dispersion was coated onto a 2 mil (51 micrometer) polyimide liner (KAPTON, available from DuPont, Wilmington, DE) at a constant flow rate, using a coating die and a line speed of approximately 1 meter / min, at a target dry thickness of 30 micrometers, using a pilot-scale coater manufactured by Hirano Techsheet Co., Ltd. (Nara, Japan) with four drying zones arranged sequentially in the downweb direction and set at 50°C, 100°C, 120°C, and 145°C, respectively. The film was then subjected to a second heat treatment at 200°C for 10 minutes. Electrical conductivity and oxygen permeability measurements (described in the test methods) were performed on the film.

[0082] Preparation of fluoropolymers containing pendant groups with bis(sulfonyl)imide moieties and perfluoroether end groups. i) Preparation of the First Fluoropolymer Intermediate, FSO2-Terminated Pendant Groups FSO2C4F8OCF=CF2 was prepared as described in U.S. Patent No. 6,624,328. Tetrafluoroethylene and FSO2C4F8OCF=CF2 were copolymerized as described in U.S. Patent No. 7,348,088. The resulting FSO2-terminated fluoropolymer intermediate had an equivalent weight of 798 g / mol, 19.2 mol% polymerized FSO2C4F8OCF=CF2 monomer and 80.8 mol% polymerized tetrafluoroethylene comonomer, and a melt flow index of 32 g / 10 min at 265 °C and 5 kg mass. Fluoropolymer with a particle size of <1 mm obtained by sieving through a wire mesh was used in subsequent reactions. In the subsequent reaction step, the number of moles of polymerized tetrafluoroethylene comonomer (80.8 mol%) and the number of moles of polymerized FSO2C4F8OCF=CF2 monomer (19.2 mol%) remained the same. However, as described in the conventional reaction schemes, the covalent attachment of various moieties increases the molecular weight of most of the pendant groups.

[0083] ii) a second fluoropolymer intermediate, -SONH - Preparation of TEAH+ terminal pendant groups Intermediate fluoropolymer 1 was functionalized using a larger-scale version of the process of Example PE1 of U.S. Pat. No. 9,419,300, in which intermediate fluoropolymer 1 was converted to a sulfonamide-functionalized polymer of similar composition with side chains having a 13:1 ratio of sulfonamide (-SO2NH2) to sulfonic acid (SO3H) functionality by NMR. However, in this process, the sulfonamide ammonium intermediate was reacted with triethylamine and slowly heated under reduced pressure to remove ammonia. The dispersion was dried on a PTFE release liner at 85°C in a nitrogen-inerted vacuum oven and then used in subsequent reactions. The product was the anionic triethylammonium salt of a polymer nominally having the structure shown below.

[0084] iii) a third fluoropolymer intermediate, -SON - (TEAH + )SO2C3F6SO2F Preparation of terminal pendant groups A dry 3 L glass reactor equipped with an air-driven stirrer, addition funnel, septum, and nitrogen supply was charged with 235 g of dried intermediate fluoropolymer 2, followed by 311.78 g of dry TEA via cannula through the septum. While cooling over an ice-water bath, stirring was initiated and 953 g of ACN was added. The mixture was stirred fast enough to suspend the polymer particles in the reaction mixture, and the temperature was monitored with a thermocouple. 325.75 g of PPDSF was transferred to the addition funnel, and the addition was initiated once the reaction mixture reached 3 °C. The total amount was added dropwise over 20 min, maintaining the reaction temperature at 4 °C. The mixture was stirred and allowed to slowly warm to room temperature overnight. The polymer swelled, making the suspension very elastic. The total suspension was diluted to 3 L with ACN, which again thickened with swollen polymer. Heating in an 80 °C bath condensed a small amount of polymer. The thick suspension was transferred in portions to neat toluene, while preventing the condensed polymer mass from undergoing further process steps, ensuring that the condensed polymer mass precipitated from solution and the toluene-to-swollen polymer suspension volume ratio was at least 3:1. The solids were then placed in a 1-gallon (3.8 L) jug and washed in 50% (w / w) toluene for 24 hours to extract any remaining ACN. The polymer and wash solvent slurry was rotary evaporated at 43°C and dynamic vacuum in approximately 340 g batches to remove the solvent, producing 221.14 g of -SON. - (TEAH + The SO2C3F6SO2F terminated fluoropolymer intermediate was collected. The nominal formula is shown below. [ka]

[0085] iv) Preparation of the fourth fluoropolymer intermediate, -SO2NHSO2C3F6SO2NH2 terminal pendant group To a dry, nitrogen-inerted 1 L stirred reactor (Parr Company, Moline, IL) was added 70.5 g of intermediate fluoropolymer 3, which had been frozen in liquid nitrogen and ground with a mortar and pestle until a fine powder was obtained. The vessel was evacuated using a rotary vane pump. 438.7 g of ACN was added via cannula, and the reactor was cooled in an isopropyl alcohol-dry ice bath. When the reaction mixture reached -10 °C, 102 g of liquid ammonia was rapidly added via zip-tube transfer. The temperature naturally rose to 3 °C over 5 minutes, after which it was rapidly cooled and the reaction was stirred on the cold bath and allowed to slowly warm to room temperature overnight. The reactor was evacuated for 30 minutes, and the reaction mixture was poured into a round-bottom flask (RBF).

[0086] v) optional purification and ion exchange of cations 250 mL of 2 M LiOH (aq) was added, and the water and triethylamine were removed by rotary evaporation to recover 61.75 g of solids. Over two dispersion runs, all solids were loaded into a stirred 600 mL Parr reactor and dispersed in DI HO with 5 equivalents of dissolved LiOH·HO at 250 RPM for 2 hours at 250 °C to yield a 6.89 wt% solids dispersion. The dispersion was filtered through a 1-micrometer glass microfiber syringe filter (4524T, Pall Corporation, Port Washington, NY) and then purified by tangential flow filtration. The aqueous dispersion was then ion-exchanged over Amberlite IR 120H+ ion-exchange resin. The dispersions were combined, and the ionomer dispersion was washed by diafiltration through a hollow fiber tangential flow filtration (TFF) module (S02-S050-05-N, PS / 50 kD, Spectrum, Inc., Rancho Dominguez, CA) at an equal volume of 500 mL and 20 psig backpressure. Washing with 1000 mL of DI HO followed by 4 L of 50 / 50 MeOH / HO (w / w) added 50 mL of 2 M LiOH (aq) in one portion to the retentate after the first 500 mL of MeOH / HO was added. The aqueous methanol was then washed with 2 volumes of DI HO. A 10 wt. % dispersion was obtained for bulk collection, with the lower wt. % wash of the filtration system collected separately. A polycarbonate column (2.55 cm (r) x 65 cm (h)) was packed approximately halfway (1.8 mol acid sites) with Amberlite resin. The resin was washed with 20 L of DI HO before ion-exchanging the polymer dispersion. The ionomer dispersion and filtration system wash were passed over the resin in a single pass and collected as a dispersion with a pH of 0-1 (colorimetric pH paper, 8880-1, Ricca Chemical Co., Arlington, TX). The acidic polymer was collected and dried in a forced air oven to remove water at approximately 60 °C, yielding 50.55 g of the final protonated sulfonamide-terminated polymer. The acidic form of intermediate fluoropolymer 4 was prepared according to the supplementary information in J. Am. Chem. Soc. 2019, 141, 13547-13561. 19It was characterized by F NMR. 19 As determined by F NMR, the side chain chemistry included 8.5 mol% sulfonic acid terminated side chains (-SO3H), 6.0 mol% sulfonamide terminated side chains (-SON2NH2), and 85.5 mol% (-SON2NHSO2C3F6SON2NH2) terminated side chains. In other words, of the 19.2 mol% total polymerized monomers having pendant sulfonyl fluorides of the first fluoropolymer intermediate, 16.4 mol% were (-SON2NHSO2C3F6SON2NH2) terminated here, while 1.6 mol% were (-SO3H) terminated and 1.2 mol% were (-SON2NH2) terminated, with respect to the total fluoropolymer. The nominal structure is shown below. [ka]

[0087] vi) Preparation of perfluoroether-terminated fluoropolymers A 1 L glass pressure vessel was charged with a large stir bar (Fisherbrand 14-513-55, oval, Fisher Scientific, Waltham, MA) and 50.55 g of the acid form of intermediate fluoropolymer 4. A rubber septum was attached to the top of the vessel, and N2 (g) was allowed to flow in and out through a syringe needle. 54.28 g of dry TEA (471283-100 mL, Sigma Aldrich, St. Louis, MO) was charged to the reactor via cannula, followed by 257.48 g of ACN in the same manner. The mixture was allowed to soak in the reagents for 24 minutes to neutralize and swell the polymer to the triethylammonium form. See the structure below. [ka]

[0088] 97.61 g of CF3CF2OC4F8SO2F (DF-MV4S) was added rapidly with stirring, resulting in an observable exotherm. The pressure vessel was capped and heated in a silicone oil bath heated by a heater coil (Mange SF100, 1 kW at 115 V) controlled by a temperature controller (Model 410A, J-KEM Scientific, St. Louis, MO) set at 60 V output on a hotplate-stir plate (VWR, Radnor, PA) to stir the mixture. The bath was maintained at 60 °C, and after 15 minutes of stirring at ambient conditions, the reactor was placed in the bath. As the polymer reacted and swelled, the mixture became more difficult to stir. After 35 minutes, the stir bar was replaced with a larger octagonal stir bar to allow for proper mixing. The reaction mixture was stirred overnight and appeared homogeneous and clear orange-brown. Stirring the mixture for another day allowed the apparent viscosity to increase. Stirring and heating continued for a total of 19 days. The polymer dispersion was cooled and slowly decanted from the reaction flask into 1 L of toluene, stirring with a metal disperser blade at 400 RPM. The polymer precipitated as a faint white-tan solid, leaving behind a dark orange solvent. The precipitate was filtered through a glass-fritted funnel (Whatman GF-B, GE Healthcare UK Limited, Buckinghamshire, UK). The solvent was further evaporated in a forced-air oven at 70 °C for 17.25 h, after which a crust layer formed and not all of the toluene evaporated. The polymer was swelled in 250 mL of nPA in a 2 L RBF and treated with 10 equivalents of LiOH from 2 M LiOH (aq) and an additional 250 mL of nPA to further swell the polymer. The TEA was removed under dynamic vacuum on a rotary evaporator at 60 °C. The bulk solvent was removed (dried to 376.77 g of swollen gel) and 754.56 g of 60 / 40 nPA / H2O (w / w) solvent was added.The gel and dispersed polymer mixture was divided in half, and each aliquot was processed in a shear mixer (SL2T Laboratory Mixer-Emulsifier, Silverson, Buckinghamshire, England) at 5000 RPM or less for 5 minutes to break down the undispersed polymer through a 5 mm sieve. It was then processed with an ultrasonic probe (Ultrasonic Processor, Ace Glass Inc., Vineland, NJ) at half-maximum amplitude for 5 minutes and full-maximum amplitude for 3 minutes to obtain a cloudy, pale yellow, viscous dispersion with no visible gel. Finally, the dispersion was processed for an additional 5 minutes in a shear mixer fitted with a 1 mm sieve. The dispersion was heated on a hotplate stirrer (RCT basic, IKA Werke, Wilmington, NC) at agitation setting 4 and temperature setting 100. After 30 minutes, the dispersion temperature reached 46.8°C, and fine LiOH salts could be observed as a suspension during mixing. The mixture was diluted with 200 mL of 70 / 30 EtOH / HO (w / w) and poured into a 2 L bottle for TFF purification of salts and small molecule by-products. The two dispersions were concentrated and added to one 2 L bottle to an equal process volume of 1 L, and diafiltration was initiated using a total of 5 L of 70 / 30 EtOH / HO (w / w) wash solvent to obtain the dispersion of fluoropolymer with Li+ counterion in 70 / 30 EtOH / HO (w / w) shown below. Polymer sample was dried under nitrogen and dispersed in MeOD. 19 F NMR was obtained and showed a final fluoropolymer side chain composition with about 91.7% perfluoroalkyl ether terminated side chains (as shown below), and 8.3% terminations with -SO3Li. [ka]

[0089] The dispersion and filtration system wash were collected and eluted with approximately 10 equivalents of Amberlite IR-120 H beads pre-rinsed with 4 gallons of DI HO to dissolve the Li counterions. +The entire collection was rotary evaporated to remove bulk solvent under dynamic vacuum at 40°C, and final dried under warm flowing N2(g) to give 59.96 g (0.040 mol, 87.1% yield) of the resulting fluoropolymer shown below. [ka]

[0090] Preparation of perfluoroether-terminated fluoropolymer dispersions A dispersion was prepared by dispersing approximately 5 g of perfluoroether-terminated fluoropolymer in 60 / 40 nPA / HO (w / w) solvent by rotating in a 60 mL bottle equipped with a stir bar to increase agitation until dispersed. The dispersion was 10.5 wt% solids.

[0091] The 10.50 wt% solids dispersion was coated onto a release liner with a 25 mil (0.64 mm) wetting gap as shown in the film coating method, and the solid film was used in a titration analysis to determine the equivalent weight of the perfluoroether-terminated fluoropolymer. After equivalent weight (EW) determination by titration using the bulk film method, two aliquots of two separate samples were titrated, each with an average equivalent weight of 783.4 g / mol.

[0092] The 10.50 wt. % solids dispersion was degassed in the same solvent-rich environment in a desiccator at slightly reduced pressure for several hours and then coated onto a release liner at a 25 mil (0.64) wet gap as shown in the film coating method. The coated film was characterized as being 29 micrometers dry and completely intact with no surface defects. The film was analyzed in mol·cm·s according to the electrochemical and OTR methods described above. -1 ·cm -2 kPa -1 The films were characterized for oxygen permeability in units of 0.015 MPa. The ionic conductivity of the films was also measured. The results are shown in the table below.

[0093]

Table 4

[0094]

Table 5

Claims

1. The following formula: 【Chemistry 2】 [In the formula, Rf is a perfluoroether; e and f independently range from 2 to 6; d is 1 or greater than 1; X １ and X ２ are independently cationic counterions.

1. A fluoropolymer comprising a pendant group represented by:

2. 10. The fluoropolymer of claim 1, wherein Rf is a perfluoroether having from 3 to 12 perfluorinated carbon atoms.

3. X １ and X ２ The fluoropolymer of claim 1 wherein is hydrogen.

4. 4. The fluoropolymer of claim 1, further comprising up to 10 mol % of pendant groups comprising at least one bis(sulfonyl)imide moiety and an end group selected from sulfonic acid and sulfonamide.

5. 4. The fluoropolymer of any one of claims 1 to 3, wherein the fluoropolymer comprises from 5 mol % to 50 mol % of the pendant groups.

6. The fluoropolymer is 50 mol % to 95 mol % of -[CF ２ -CF ２ 6. The fluoropolymer according to claim 1, comprising a main chain containing polymerized units of the formula:

7. The fluoropolymer of any one of claims 1 to 6, wherein the fluoropolymer is dispersed in an organic solvent, an aqueous solvent, or a mixture of water and a water-miscible organic solvent.

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