EP4698589A1

EP4698589A1 - Polyphenylene ionomer for fuel cell or electrolysis cell application

Info

Publication number: EP4698589A1
Application number: EP24716409.8A
Authority: EP
Inventors: Matthew BOOHER; Emma LLOYD; Nicolas TREAT; Joel POLLINO
Original assignee: Syensqo Specialty Polymers USA LLC
Current assignee: Syensqo Specialty Polymers USA LLC
Priority date: 2023-04-19
Filing date: 2024-04-10
Publication date: 2026-02-25
Also published as: KR20260005917A; WO2024217947A1; CN121079345A

Abstract

The present invention relates to a polyphenylene ionomer (PPI) suitable to prepare membrane for use in fuel cell or electrolysis cell application operating in alkaline conditions. It also pertains to processes for preparing such polyphenylene ionomer and methods for preparing membranes thereof.

Description

Polyphenylene ionomer for fuel cell or electrolysis cell application

Reference to related applications

This application claims priority to U.S. provisional application 63/460376 - filed April 19^th, 2023 - and to European patent application No. 23180756.1 - filed June 21 ^st, 2023 the whole content of each of these applications being incorporated herein by reference for all purposes.

Technical Field

[0001] The present invention relates to a polyphenylene ionomer (PPI) suitable to prepare membrane for use in fuel cell or electrolysis cell application operating in alkaline conditions. It also pertains to processes for preparing such polyphenylene ionomer and methods for preparing membranes thereof.

Background Art

[0002] Anion exchange membranes (AEM) are key components of electrochemical devices such as fuel cells or electrolysis cells operating in alkaline conditions.

[0003] When compared with proton exchange membrane (PEM) technologies that operate in a highly acidic environment, an advantage provided by AEM based technology is the use of much less expensive non-Platinum Group Metals (PGM) electro catalysts and electrode components which greatly reduces the cost of the assembly.

[0004] Polyphenylenes exhibit excellent alkaline stability, therefore they are candidates of choice for manufacturing AEM.

[0005] Particularly when they are combined with alkaline stable functionality such as dialkyl piperidinium.

[0006] The use of polymers comprising phenylene repeating units has been disclosed in the art for the manufacture of ion-exchange membranes, which are actually dense films.

[0007] For example, US 7868124 (COMMISSARIAT A L'ENERGIE ATOMIQUE) discloses polymers comprising phenylene units, at least one of which bears a phenylene side group substituted with a perfluoro group or chain, which itself bears a -SO3H, -PO3H2 or-COOH group, and the use thereof to make proton exchange membranes (PEM) for fuel cell application.

[0008] Also, US 7888397 (SANDIA CORPORATION) discloses polyphenylene- based anion exchange membrane, made from casting dope solution of (co)polymer generally obtained by Diels-Alder polymerization. The synthesis of the copolymer requires non-readily available monomers and ion exchange capacity is moderate.

[0009] More recently, US 10290890 (University of Delaware) discloses poly(aryl piperidinium) polymers for use as anion exchange membrane material in fuel cell application. Those (co)polymers are generally obtained by Friedel- Crafts alkylation polymerization which requires some reactants such as trifluoroacetophenone to reach high enough molecular weights.

[0010] WO2021150994 (Rensselaer Polytechnic Institute) discloses polyaryl (co)polymers obtained by Friedel-Crafts alkylation polymerization for use as anion exchange membrane material in fuel cell application. Those (co)polymers also require some reactants such as trifluoroacetophenone to reach high enough molecular weights.

[0011] Finally, J. Power Sources, 2021, 506, 230184 discloses the synthesis of polyphenylene polymers bearing piperidinium moieties, through copolymerization of chloroaryl monomers:

[0012] The synthesis requires non-readily available monomers and stoichiometric amount of nickel catalyst. Piperidine group containing monomer is copolymerized and quaternization to piperidinium is further conducted by treating the resulting copolymer with iodomethane. Those polyphenylene polymers are further used to prepare anion exchange membranes for fuel cell application by solvent casting. Values of ionic conductivity measured at 80°C of the membranes in the Ch form are moderate.

Summary of invention [0013] The Applicant thus faced the problem of providing an ionomer that presents excellent alkaline stability and bears alkaline stable functionality capable of being responsible for anions transport.

[0014] Such ionomer should be obtained in high yield, achieving high molecular weight from the polymerization of easily available or commercially available monomers.

[0015] Such ionomer should be soluble in some organic solvents in order to prepare dope solutions or compositions useful to manufacture membranes e.g. by casting.

[0016] Such ionomer should also be suitable for preparing membranes with enhanced ion exchange capacity (I EC) and enhanced anion conductivity properties in order to be used for manufacturing AEM in fuel or electrolysis cells.

[0017] The Applicant also faced the problem of providing an ionomer having outstanding thermal properties, such that it can be used for preparing a membrane capable of working in demanding thermal conditions.

[0018] The Applicant also faced the problem of providing an ionomer having outstanding mechanical properties such that a self-standing membrane can be manufactured based on it.

[0019] The Applicant also faced the problem of providing an ionomer having outstanding mechanical properties such that a membrane having low thickness can be manufactured based on it.

[0020] The Applicant also faced the problem of providing a membrane having low water uptake.

[0021] All those problem and more are solved by the polyphenylene ionomer of the present invention which is a polyphenylene ionomer [polymer (PPI)] comprising :

(i) at least one recurring unit (R_Pi) represented by the following formula:

wherein Ri and R2 are each independently selected from the list consisting of C1-C18 alkyl groups or represent together a C4-C8 alkanediyl group forming a cyclic moiety, and wherein X^s is a counter anion;

(ii) at least one recurring unit (R_PP) selected from the group of recurring units represented by the following formula: wherein R3, R4, Rs and Re are each independently selected from the list consisting of hydrogen, alkyl, aryl, alkoxy, aryloxy, alkylketone, arylketone, fluoroalkyl, fluoroaryl, bromoalkyl, bromoaryl, chloroalkyl, chloroaryl, alkylsulfone, arylsulfone, alkylamide, arylamide, alkylnitrile, arylnitrile, alkylester, arylester, fluorine, chlorine, and bromine, with the proviso that R3, R4, Rs and Re do not simultaneously represent hydrogen;

(iii) optionally at least one recurring unit (R_pm) selected from the group of recurring units represented by the following formula: wherein R7, Rs, R9 and R10 are each independently selected from the list consisting of hydrogen, alkyl, aryl, alkoxy, aryloxy, alkylketone, arylketone, fluoroalkyl, fluoroaryl, bromoalkyl, bromoaryl, chloroalkyl, chloroaryl, alkylsulfone, arylsulfone, alkylamide, arylamide, alkylnitrile, arylnitrile, alkylester, arylester, fluorine, chlorine, and bromine; and iv) optionally at least one recurring unit selected from the group of recurring units represented by the following formulae: wherein Rn and R12 are each independently selected from the list consisting of C1-C18 optionally fluorinated alkyl groups and optionally substituted aryl groups, or represent together a Cs-Cs alkanediyl group forming a cyclic moiety, or represent together an optionally substituted biphenyldiyl group forming a cyclic moiety.

[0022] Thus, in a second aspect, the present invention relates to a method for preparing the polyphenylene ionomer [polymer (PPI)] according to the invention, comprising the following steps of:

1 -copolymerization of:

(i) at least one monomer (M_Pi) represented by the following formula: wherein Ri and R2 are each independently selected from the list consisting of C1-C18 alkyl groups or represent together a C4-C8 alkanediyl group forming a cyclic moiety, and wherein Z is selected from the group consisting of Cl, Br and I;

(ii) at least one monomer (M_PP) represented by the following formula: wherein R3, R4, Rs and Re are each independently selected from the list consisting of hydrogen, alkyl, aryl, alkoxy, aryloxy, alkylketone, arylketone, fluoroalkyl, fluoroaryl, bromoalkyl, bromoaryl, chloroalkyl, chloroaryl, alkylsulfone, arylsulfone, alkylamide, arylamide, alkylnitrile, arylnitrile, alkylester, arylester, fluorine, chlorine, and bromine, with the proviso that R3, R4, Rs and Re do not simultaneously represent hydrogen;

(iii) optionally at least one monomer (M_pm) represented by the following formula: wherein R7, Rs, R9 and R10 are each independently selected from the list consisting of hydrogen, alkyl, aryl, alkoxy, aryloxy, alkylketone, arylketone, fluoroalkyl, fluoroaryl, bromoalkyl, bromoaryl, chloroalkyl, chloroaryl, alkylsulfone, arylsulfone, alkylamide, arylamide, alkylnitrile, arylnitrile, alkylester, arylester, fluorine, chlorine, and bromine; and

(iv) optionally at least one monomer selected from the group of monomers represented by the following formulae: wherein Rn and R12 are each independently selected from the list consisting of C1-C18 optionally fluorinated alkyl groups and optionally substituted aryl groups, or represent together a Cs-Cs alkanediyl group forming a cyclic moiety, or represent together an optionally substituted biphenyldiyl group forming a cyclic moiety; wherein Y is selected from the group consisting of Cl, Br and I; and 2-optionally exchanging counter anion Z^e for counter anion X^s.

[0023] In a third aspect, the present invention relates to a method for preparing the polyphenylene ionomer [polymer (PPI)] according to the invention, comprising the following steps of:

1 -copolymerization of:

(i) at least one monomer (Mpni) represented by the following formula: wherein R13 is selected from the list consisting of C1-C18 alkyl groups;

(ii) at least one monomer (M_PP) represented by the following formula: wherein R3, R4, Rs and Re are each independently selected from the list consisting of hydrogen, alkyl, aryl, alkoxy, aryloxy, alkylketone, arylketone, fluoroalkyl, fluoroaryl, bromoalkyl, bromoaryl, chloroalkyl, chloroaryl, alkylsulfone, arylsulfone, alkylamide, arylamide, alkylnitrile, arylnitrile, alkylester, arylester, fluorine, chlorine, and bromine, with the proviso that R3, R4, Rs and Re do not simultaneously represent H;

(iv) optionally at least one monomer selected from the group of monomers represented by the following formulae:

wherein Rn and R12 are each independently selected from the list consisting C1-C18 optionally fluorinated alkyl groups and optionally substituted aryl groups, or represent together a Cs-Cs alkanediyl group forming a cyclic moiety, or represent together an optionally substituted biphenyldiyl group forming a cyclic moiety; wherein Y is selected from the group consisting of Cl, Br and I; and 2-quaternization of the resulting copolymer.

[0024] The present invention also relates to a liquid composition (LC) comprising the polyphenylene ionomer [polymer (PPI)] according to the invention and a liquid medium (L).

[0025] The present invention still relates to a solid composition (SC) comprising the polyphenylene ionomer [polymer (PPI)] according to the invention.

[0026] A further object of the present invention is an article comprising the polyphenylene ionomer [polymer (PPI)] and more particularly an anion exchange membrane (AEM), an electrocatalytic layer (EL) or a membrane electrode assembly (MEA).

[0027] Still another object of the present invention is a process for manufacturing the article according to the invention from the liquid composition (LC) or from the solid composition (SC).

[0028] Finally, the present invention also pertains to a fuel cell or an electrolysis cell comprising the article of the invention. Description of embodiments

[0029] The polyphenylene ionomer of the present invention is a polyphenylene ionomer [polymer (PPI)] comprising :

(i) at least one recurring unit (R_Pi) represented by the following formula: wherein Ri and R2 are each independently selected from the list consisting of C1-C18 alkyl groups or represent together a C4-C8 alkanediyl group forming a cyclic moiety, and wherein X^s is a counter anion;

(iii) optionally at least one recurring unit (R_pm) selected from the group of recurring units represented by the following formula: wherein R7, Rs, R9 and R10 are each independently selected from the list consisting of hydrogen, alkyl, aryl, alkoxy, aryloxy, alkylketone, arylketone, fluoroalkyl, fluoroaryl, bromoalkyl, bromoaryl, chloroalkyl, chloroaryl, alkylsulfone, arylsulfone, alkylamide, arylamide, alkylnitrile, arylnitrile, alkylester, arylester, fluorine, chlorine, and bromine; and iv) optionally at least one recurring unit selected from the group of recurring units represented by the following formulae: wherein R11 and R12 are each independently selected from the list consisting of C1-C18 optionally fluorinated alkyl groups and optionally substituted aryl groups, or represent together a Cs-Cs alkanediyl group forming a cyclic moiety, or represent together an optionally substituted biphenyldiyl group forming a cyclic moiety.

[0030] R1 and R2 may be methyl groups.

[0031] Advantageously, X can be selected from the group consisting of OH, Cl, Br and I.

[0032] Even more advantageously, R1 and R2 are methyl groups and X is OH. [0033] Preferably, recurring unit (R_PP) is represented by the following formula:

[0034] Advantageously, Ri and R2 are methyl groups, X is selected from the group consisting of OH, Cl, Br and I and the recurring unit (R_PP) is represented by the following formula:

[0035] Optionally, the ionomer of the present invention comprises at least one recurring unit (R_pm).

[0036] The ionomer of the present invention may comprise at least one recurring unit (R_pm) of formula :

[0037] Recurring unit (R_pm) may have formula :

[0038] Alternatively, recurring unit (R_pm) may have formula :

[0039] The ionomer of the present invention may further comprise at least one recurring unit selected from the recurring units of formulae :

[0040] In some preferred embodiments, the ionomer of the present invention comprises at least one recurring unit of formula :

[0041] In some preferred embodiments, the polyphenylene ionomer according to the invention essentially consists or consists of:

(i) at least one recurring unit (R_Pi) represented by the following formula: wherein Ri and R2 are each independently selected from the list consisting C1-C18 alkyl groups or represent together a C4-C8 alkanediyl group forming a cyclic moiety, wherein X© is a counter anion; and

(ii) at least one recurring unit (R_PP) represented by the following formula:

[0042] The polyphenylene ionomer according to the invention may essentially consists or consists of:

(i) at least one recurring unit (R_Pi) represented by the following formula: wherein Ri and R2 are methyl groups , wherein X^s is a counter anion selected from the list consisting of OH, Cl,

Br and I; and

(ii) at least one recurring unit (R_PP) represented by the following formula:

[0043] By essentially consisting, is meant that the polyphenylene ionomer according to the invention comprises less than 5 mol % based on the total number of moles of all the recurring units, of recurring units different from the recurring units of (i) and (ii) as above described, preferably less than 2 mol % and more preferably less than 1 mol %.

[0044] Generally, the polyphenylene ionomer (PPI) according to the invention comprises at least about 30 mole percent, preferably at least 40 mole percent and more preferably at least 50 mole percent, based on the total moles number of all the recurring units, of recurring units (R_Pi) represented by the following formula : wherein Ri and R2 are each independently selected from the list consisting of C1-C18 alkyl groups or represent together a C4-C8 alkanediyl group forming a cyclic moiety, and wherein X^s is a counter anion.

[0045] By knowing the molar composition of the polyphenylene ionomer (PPI) according to the invention, it is possible to calculate the ion-exchange capacity (I EC) expressed in mmol of ionic species per gram of ionomer.

[0046] Ion exchange capacity represents the relative amount of cationic groups attached onto the ionomer that will be responsible for the transport of negatively charged ions through a membrane made from said ionomer.

[0047] I EC can be measured e.g. by titration using techniques well known by the person skilled in the art.

[0048] Another object of the present invention relates to a method for preparing the polyphenylene ionomer [polymer (PPI)] according to anyone of the preceding Claims, comprising the following steps of:

1- copolymerization of:

wherein Rn and R12 are each independently selected from the list consisting of C1-C18 optionally fluorinated alkyl groups and optionally substituted aryl groups, or represent together a Cs-Cs alkanediyl group forming a cyclic moiety, or represent together an optionally substituted biphenyldiyl group forming a cyclic moiety; wherein Y is selected from the group consisting of Cl, Br and I; and 2- optionally exchanging counter anion Z^e for counter anion X^s.

[0049] The monomer (M_Pi) can be prepared e.g. by the method described in Journal of Power Sources, 2021 , 506, 230184 which is a Friedel-Crafts alkylation:

[0050] Co-monomers are commercially available or can be synthesized by any person skilled in the art.

[0051] In step 1 , the copolymerization is generally performed with phenylene monomers bearing Y groups selected from the group consisting of Cl, Br and I. Good results were obtained with Y being Cl. [0052] The copolymerization is generally conducted under an inert atmosphere in the presence of a liquid medium. Generally phenylene monomers and resulting polyphenylene ionomer are soluble in said liquid medium.

[0053] The liquid medium is generally anhydrous.

[0054] Just for the sake of example, the liquid medium can be selected from polar aprotic solvents and preferably selected in the group consisting of N- methyl-pyrrolidone (NMP), dimethyl acetamide (DMAc), dimethylformamide (DMF), dimethylsulfoxide (DMSO), tetrahydrofuran (THF), methyl-5-dimethylamino-2-methyl-5-oxopentanoate (commercially available under the tradename Rhodialsov Polarclean®), triethylphosphate (TEP) and mixtures thereof.

[0055] A catalytic system well known by the person skilled in the art is generally used to ensure the reductive coupling reaction between the phenylene monomers.

[0056] For example, nickel-catalyzed coupling reactions have been described in several U.S. Patents, including U.S. Patents 5,227,457; 5,886,130; and 5,824,744; the disclosures of which are incorporated fully herein by reference.

[0057] Generally, this method uses a nickel catalyst to couple dihaloaryl species in conjunction with a triphenylphosphine (TPP) ligand and a zinc metal reducing agent in a polar aprotic solvent such as N, N-dimethyl acetamide DMAc or (NMP) N-methylpyrolidone. Such a reaction can be represented as follows, where Y is a substituent and X is a halogen:

[0058] The above described method can produce commercial quantities of substituted polyphenylenes.

[0059] The reaction mixture is generally filtered e.g. through a plug of Celite and then coagulated into a non-solvent of the polyphenylene ionomer such as methanol. The polyphenylene ionomer can be further recovered by filtration. [0060] The resulting copolymer can be treated with methanol containing 5% HCI, filtered, and washed with methanol thoroughly to remove excess of zinc dust.

[0061] In step 2, exchanging counter anion Z⁰ for counter anion X^s is generally performed by any techniques well known by the person skilled in the art. Just for the sake of example, polyphenylene ionomer bearing I^s can be ion-exchanged with Cl⁰ by soaking for several hours, typically for 2 hours, in saturated NaCI solution before being washed with fresh deionized water for several hours, typically for 2 hours, to remove any excess NaCI.

[0062] Still another object of the present invention relates to a method for preparing the polyphenylene ionomer [polymer (PPI)] according to the invention, comprising the following steps of: T-copolymerization of:

(i) at least one monomer (M_pni) represented by the following formula: wherein R13 is selected from the list consisting of C1-C18 alkyl groups;

(ii) at least one monomer (M_PP) represented by the following formula: wherein R3, R4, Rs and Re are each independently selected from the list consisting of hydrogen, alkyl, aryl, alkoxy, aryloxy, alkylketone, arylketone, fluoroalkyl, fluoroaryl, bromoalkyl, bromoaryl, chloroalkyl, chloroaryl, alkylsulfone, arylsulfone, alkylamide, arylamide, alkylnitrile, arylnitrile, alkylester, arylester, fluorine, chlorine, and bromine, with the proviso that R3, R4, Rs and Re do not simultaneously represent H; (iii) optionally at least one monomer (M_pm) represented by the following formula: wherein R7, Rs, R9 and R10 are each independently selected from the list consisting of hydrogen, alkyl, aryl, alkoxy, aryloxy, alkylketone, arylketone, fluoroalkyl, fluoroaryl, bromoalkyl, bromoaryl, chloroalkyl, chloroaryl, alkylsulfone, arylsulfone, alkylamide, arylamide, alkylnitrile, arylnitrile, alkylester, arylester, fluorine, chlorine, and bromine; and

(iv) optionally at least one monomer selected from the group of monomers wherein R11 and R12 are each independently selected from the list consisting C1-C18 optionally fluorinated alkyl groups and optionally substituted aryl groups, or represent together a Cs-Cs alkanediyl group forming a cyclic moiety, or represent together an optionally substituted biphenyldiyl group forming a cyclic moiety; wherein Y is selected from the group consisting of Cl, Br and I; and 2’-quaternization of the resulting copolymer.

[0063] Step T is generally performed in the same conditions as those depicted above for step 1.

[0064] The resulting copolymer can be treated with methanol containing 5% HCI, filtered, and washed with methanol thoroughly to remove excess of zinc dust. Accordingly, the amine groups of the resulting copolymer might be in the form of hydrochloride salt. [0065] Neutralization of the hydrochloride salt form can be made by treating with a base, e.g. aqueous NaOH, the copolymer in solution in NMP to recover the amine groups, as represented in the scheme below:

[0066] In step 2’, quaternization of the amine groups of the resulting copolymer from step T, can be performed e.g. by treating the copolymer with alkyl halide, generally in solution. Just for the sake of example, copolymer in solution in NMP can be treated by an excess of methyl iodide at room temperature e.g. at 30°C for quaternization, as represented in the scheme below:

[0067] Another object of the present invention pertains to a liquid composition (LC) comprising the polyphenylene ionomer [polymer (PPI)] according to the invention and a liquid medium (L).

[0068] The liquid medium (L) preferably comprises at least one organic solvent.

Suitable examples of organic solvents are:

- aliphatic hydrocarbons including, more particularly, the paraffins such as, in particular, pentane, hexane, heptane, octane, nonane, decane, undecane, dodecane or cyclohexane, and naphthalene and aromatic hydrocarbons and more particularly aromatic hydrocarbons such as, in particular, benzene, toluene, xylenes, cumene, petroleum fractions composed of a mixture of alkylbenzenes;

- aliphatic or aromatic halogenated hydrocarbons including more particularly, perchlorinated hydrocarbons such as, in particular, tetrachloroethylene, hexachloroethane;

- partially chlorinated hydrocarbons such as dichloromethane, chloroform, 1 ,2-dichloroethane, 1 , 1 ,1 -trichloroethane, 1 , 1 ,2,2-tetrachloroethane, pentachloroethane, trichloroethylene, 1 -chlorobutane, 1 ,2-dichlorobutane, monochlorobenzene, 1 ,2-dichlorobenzene, 1 ,3-dichlorobenzene, 1 ,4- dichlorobenzene, 1 ,2,4-trichlorobenzene or mixture of different chlorobenzenes;

- aliphatic, cycloaliphatic or aromatic ether oxides, more particularly, diethyl oxide, dipropyl oxide, diisopropyl oxide, dibutyl oxide, methylterbutyl ether, dipentyl oxide, diisopentyl oxide, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether benzyl oxide; dioxane, tetrahydrofuran (THF);

- dimethylsulfoxide (DMSO);

- glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether;

- glycol ether esters such as ethylene glycol methyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate;

- alcohols, including polyhydric alcohols, such as methyl alcohol, ethyl alcohol, diacetone alcohol, ethylene glycol;

- ketones such as acetone, methylethylketone, methylisobutyl ketone, diisobutylketone, cyclohexanone, isophorone;

- linear or cyclic esters such as isopropyl acetate, n-butyl acetate, methyl acetoacetate, dimethyl phthalate, y-butyrolactone;

- linear or cyclic carboxamides such as N,N-dimethylacetamide (DMAc), N,N-diethylacetamide, dimethylformamide (DMF), diethylformamide or N- methyl-2-pyrrolidone (NMP);

- organic carbonates for example dimethyl carbonate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, ethylmethyl carbonate, ethylene carbonate, vinylene carbonate;

- phosphoric esters such as trimethyl phosphate, triethyl phosphate (TEP); - ureas such as tetramethyl urea, tetraethylurea;

- methyl-5-dimethylamino-2-methyl-5-oxopentanoate (commercially available under the tradename Rhodialsov Polarclean®).

[0069] Preferably, said at least one organic solvent is selected from polar aprotic solvents and even more preferably in the group consisting of: N-methyl- pyrrolidone (NMP), dimethyl acetamide (DMAc), dimethylformamide (DMF), dimethylsulfoxide (DMSO), tetrahydrofuran (THF), methyl-5- dimethylamino-2-methyl-5- oxopentanoate (commercially available under the tradename Rhodialsov Polarclean®) and triethylphosphate (TEP).

[0070] Good results were obtained with dimethylsulfoxide (DMSO) as organic solvent.

[0071] The liquid composition (LC) generally comprises at least 3 wt. %, preferably at least 5 wt. % and more preferably at least 10 wt.%, based on the total weight of said liquid composition (LC), of polyphenylene ionomer [polymer (PPI)].

[0072] Besides, the liquid composition (LC) generally comprises at most 40 wt. %, preferably at most 30 wt. % and more preferably at most 20 wt.%, based on the total weight of said liquid composition (LC), of polyphenylene ionomer [polymer (PPI)].

[0073] The liquid composition (LC) may optionally comprise additional ingredients such as stabilizer or radical scavenger.

[0074] Still another object of the present invention pertains to a solid composition (SC) comprising the polyphenylene ionomer [polymer (PPI)] according to the invention.

[0075] The solid composition (SC) may be composed of polyphenylene ionomer (PPI) or may optionally comprise additional ingredients such as stabilizer, radical scavenger, plasticizing agent or processing aid.

[0076] The solid composition (SC) generally comprises at least 90 wt. %, preferably at least 95 wt. % and more preferably at least 99 wt.%, based on the total weight of said solid composition (SC), of polyphenylene ionomer [polymer (PPI)].

[0077] The present invention also relates to an article comprising the polyphenylene ionomer [polymer (PPI)] according to the invention. [0078] Preferably, the article according to the invention is an anion exchange membrane (AEM), an electrocatalytic layer (EL) or a membrane electrode assembly (MEA).

[0079] In a first embodiment the article is an anion exchange membrane (AEM) for a fuel or electrolysis cell application, herein referred to also as a “membrane”.

[0080] Membranes can be obtained from liquid composition (LC) according to the invention using techniques known in the art, such as impregnation, casting, coating, e.g. roller coating, gravure coating, reverse roll coating, dip coating, spray coating.

[0081] Therefore, another object of the present invention is a process for manufacturing the article according to the invention, comprising the impregnation, casting or coating of the liquid composition (LC).

[0082] Solid composition (SC) may advantageously be converted into membranes by conventional extrusion techniques.

[0083] Accordingly, another object of the present invention is a process for manufacturing the article according to the invention, comprising extrusion of the solid composition (SC).

[0084] The membranes may optionally be reinforced, for instance by lamination of the extruded membrane from the solid composition (SC) to a suitable reinforcing support or by impregnation of the liquid composition (LC) onto a porous support. Suitable supports may be made from a wide variety of components. The porous supports may be made from hydrocarbon polymers such as woven or non-woven polyolefin membranes, e.g. polyethylene or polypropylene, or polyesters, e.g. polyethylene terephthalate). Porous supports of fluorinated polymers are generally preferred for use in fuel cell applications because of their high chemical inertia. Biaxially expanded PTFE porous supports (otherwise known as ePTFE membranes) are among preferred supports. These supports are notably commercially available under trade names GORE-TEX®, TETRATEX®.

[0085] When the polyphenylene ionomer (PPI), in the membrane, is in the I© form, it can be exchanged to Cl© form by soaking the membrane for several hours, typically for 2 hours, in saturated NaCI solution before being washed with fresh deionized water for several hours, typically for 2 hours, to remove any excess NaCI.

[0086] Similarly, when the polyphenylene ionomer (PPI), in the membrane, is in the I© form or Cl© form, it can be exchanged to OH© form by soaking the membrane for several hours in saturated NaOH.

[0087] In a second embodiment the article of the invention is an electrocatalytic layer (EL).

[0088] Electrocatalytic layers may advantageously be prepared starting from a liquid composition (LC) according to the invention further comprising catalyst particles. Said liquid compositions are generally referred to as “catalytic inks”. Typical catalyst particles comprise an active compound selected among metals like iron, manganese, cobalt, nickel, platinum, ruthenium, gold, palladium, rhodium, iridium, osmium; their electro conductive oxides and alloys. The active compound is generally supported on a suitable material, herein called “carrier”, which is preferably electrically conductive. The carrier is advantageously chosen from carbon powder, for instance carbon black.

[0089] The amount of catalyst particles (including the carrier, if any) in the catalytic ink is generally of at least 1 wt% based on the total weight of the catalytic ink. Preferably, it is of at least 3 wt% and more preferably of at least 5wt %. The amount of catalyst particles (including the carrier, if any) in the catalytic ink is advantageously of at most 50 wt% based on the total weight of the catalytic ink, preferably of at most 40 wt% and more preferably of at most 30 wt%.

[0090] The electrocatalytic layers (EL) may for instance be prepared by screen printing or solution coating the catalyst ink on the surface of an anion exchange membrane (AEM).

[0091] In a third embodiment the article is a membrane electrode assembly (MEA). The membrane electrode assembly comprises a membrane having first and second surface, a first electrocatalytic layer (EL) adhered to said first surface and a second electrocatalytic layer (EL) adhered to said second surface, wherein at least one of said membrane, said first or second electrocatalytic layers comprises the polyphenylene ionomer as defined above.

[0092] The present invention finally relates to a fuel cell or an electrolysis cell comprising the article of the invention.

[0093] All definitions and preferences defined previously within the context of the polyphenylene ionomer (PPI) or of the process for its preparation apply to the compositions (LC) and (SC) as well as to any article containing said polyphenylene ionomer (PPI).

[0094] The invention will be herein after illustrated in greater detail by means of the Examples contained in the following Experimental Section; the Examples are merely illustrative and are by no means to be interpreted as limiting the scope of the invention.

Experimental Section

[0095] Figure

[0096] Figure 1 : ¹H NMR spectrum of polyphenylene ionomer of example 2 with targeted I EC value of 1.70

[0097] RAW MATERIALS

2,5-dichlorobenzophenone was supplied by Byelen Chemicals. Bis(triphenylphosphine)nickel dichloride was obtained from Alfa Aesar. Zinc dust was supplied by Umicore.

Methyl iodide, methanol (MeOH) and trifluoromethanesulfonic (triflic acid) were supplied by ThermoFisher scientific.

Chlorobenzene, N-methyl-4-piperidone, 1 ,3-dichlorobenzene, triphenylphosphine, potassium iodide, dichloromethane (DCM), anhydrous N-methylpyrrolidone (NMP), dimethylsulfoxide (DMSO) and Dimethylacetamide (DMAC) were obtained from Sigma Aldrich.

4, 4-bis(4-chlorophenyl)-1 -methylpiperidine and 4,4-bis(4-chlorophenyl)-

1 , 1 -dimethylpiperidin-1 -ium iodide were prepared as described below.

[0098] Monomer synthesis [0099] Monomer synthesis was adapted from Journal of Power Sources, 2021, 506, 230184 and conducted as represented on the following reaction

[00100] In a round-bottom flask equipped with mechanical stirring, were added under nitrogen atmosphere, 0.22 mol (25.0 g) of 1-methyl-4-piperidone was added to the flask with 166.25 mL (0.662 mol) of chlorobenzene, and to this solution was added 477 mL of trifluoromethanesulfonic acid. This mixture was left under stirring for 6 h at 0°C in a water/ice bath and then for 12 h at 30°C. The resulting solution was basified by adding 2 M aq. NaOH and extracted with dichloromethane. The organic phase was washed with deionized water and brine and then dried with anhydrous Na2SO4. After removal of the solvent under reduced pressure, the crude product was purified by column chromatography over silica gel using MeOH/DCM (v/v, 1/10) as the eluent to obtain 4,4-bis(4-chlorophenyl)-1- methylpiperidine as a viscous oil with a yield of 81% (57.25 g, 0.179 mol).

[00101] In an amber coated round-bottom flask equipped with mechanical stirring, were added under nitrogen atmosphere, 0.08 mol (25.62 g) of 4,4-bis(4- chlorophenyl)-1-methylpiperidine, 50mL dichloromethane and 15mL (0.24 mol) of methyl iodide. The solution was stirred during 12h at room temperature for quaternization. 4,4-bis(4-chlorophenyl)-1 , 1 - dimethylpiperidin-1-ium iodide was recovered by removal of the excess of methyl iodide and of dichloromethane under reduced pressure. Finally, white crystalline solid was obtained by recrystallization from anhydrous ethanol.

[00102] Copolymers synthesis

[00103] Example 1 : Co-polymerization of 1,3-dichlorobenzene and 2,5- dichlorobenzophenone

[00104] The process was adapted from US 5,886,130. All materials were charged to the reaction vessel within an inert atmosphere (nitrogen) dry glovebox. To a 3-neck 100 mL jacketed round-bottom flask equipped with a mechanical stir shaft were added bis(triphenylphosphine)nickel chloride (0.810 g, 1.239 mmol), potassium iodide, triphenylphosphine, 2,5- dichlorobenzophenone (7.777 g, 30.97 mmol), 1 ,3-dichlorobenzene (4.552 g, 30.97 mmol), activated zinc dust, and anhydrous N-methylpyrrolidone (52 mL). Once sealed with rubber septa within the glovebox, the flask was brought out, connected to a recirculating heater/chil ler, and connected to a low flow nitrogen purge. The mixture was heated over a period of 1 hour to 70°C and stirred overnight. The following day, the mixture was pressure filtered through a plug of Celite and then coagulated into 500mL of methanol and filtered. The resulting polymer was treated with methanol containing 5% HCI, filtered, and washed with methanol thoroughly.

[00105] Examples 2-5 : Co-polymerization of 4,4-bis(4-chlorophenyl)-1,1- dimethylpiperidin-1-ium iodide and 2,5-dichlorobenzophenone

[00106] Example 2

[00107] Made according to the procedure for synthesis example 1 with 9.799 g 2,5-dichlorobenzophenone (39.02 mmol) and 10.593 g 4,4-bis(4- chlorophenyl)-1 ,1-dimethylpiperidin-1-ium iodide (22.92 mmol) and 110 mL of anhydrous N-methylpyrrolidone. The targeted IEC was 1.70. Calculated IEC using ¹H NMR was 1.73 (see table 1).

[00108] Example 3 [00109] Made according to the procedure for synthesis example 1 with 9.176 g

2,5-dichlorobenzophenone (36.54 mmol) and 11.736 g g 4,4-bis(4- chlorophenyl)-1 , 1 -dimethylpiperidin-1-ium iodide (25.39 mmol) 114 mL of anhydrous N-methylpyrrolidone. The targeted lEC was 1.85. Calculated IEC using ¹H NMR was 1.85 (see table 1).

[00110] Example 4

[00111] Made according to the procedure for synthesis example 1 with 8.555 g

2,5-dichlorobenzophenone (34.07 mmol) and 12.883 g 4,4-bis(4- chlorophenyl)-1 , 1 -dimethylpiperidin-1-ium iodide (27.87 mmol) 118 mL of anhydrous N-methylpyrrolidone. The targeted IEC was 2.00. Calculated IEC using ¹H NMR was 1.99 (see table 1).

[00112] Example s

[00113] Made according to the procedure for synthesis example 1 with 6.999 g

2,5-dichlorobenzophenone (27.87 mmol) and 15.745 g 4,4-bis(4- chlorophenyl)-1 , 1 -dimethylpiperidin-1-ium iodide (34.07 mmol) 118 mL of anhydrous N-methylpyrrolidone. The targeted IEC was 2.33. Calculated IEC using ¹H NMR was 2.33 (see table 1).

[00114] Molecular weight determination

[00115] Measurements were performed at 45°C using two Agilent PLgel 5 pm, MiniMix-D (250 x 4.6mm) columns coupled with one Agilent PLgel 5 pm, MiniMix-D Guard (50 x 4.6mm) column and a UV detection set at 270 nm. The mobile phase was composed of dimethylacetamide (DMAc) and the flow rate was of 0.3 mL/min. 5pL samples were injected, calibration was obtained with polystyrene standards. Mw is weight-average molar mass, expressed in g/mol.

[00116] Theoretical Ion Exchange Capacity (IEC) Calculation

[00117] Theoretical IEC was calculated for each copolymer using ¹H NMR in DMSO. Four types of protons, as represented on the scheme below, can be distinguished using ¹H NMR: [00118] Comparison of the known number of aromatic protons in each recurring unit (8 protons) to the observed number of aliphatic protons for signal 4, enables calculation of recurring unit composition in mole percent using the following equation, taking into account that expected number of 4 protons is 6 when m = 0 and n = 1 , and that number of observed protons is given by the integration of signal assigned to 4 protons on ¹H NMR spectrum:

Obseiwd 4 protons - - x 100% = mole % diplxwfldimetitylprperldBitum Exp®ted 4 protons

[00119] Accordingly, in the ¹H NMR spectrum of copolymer reported in Figure 1 (Target I EC = 1.70) :

2.27

- x 100% = 37.8 mole % Diphenyldimethylpiperidinium 6

[00120] From the molar ratio of recurring units, an average recurring unit molecular weight is calculated (based on the OH- form), 218.55 g/mol for the previous example with m = 0.622 and n = 0.378. With this information, one skilled in the art can calculate ion exchange capacity, as shown below:

[00121] Membrane casting

[00122] Membranes were prepared by dissolving each polymer in DMSO within the range of (10-12 weight %) at 100-120°C. The pale yellow dope solution was filtered, poured onto a warmed glass plate, and cast into a thin film using a doctor blade. The glass plate was immediately transferred to a pre-heated oven at 70°C, under nitrogen atmosphere, and left for 4 hours without vacuum until tack-free. After 4 hours, the temperature was increased to 120°C and the film was annealed under vacuum for 16-18 hours. Following the annealing step, the films were removed from the glass plate by immersing in room temperature deionized water.

[00123] Membrane ion-exchanging

[00124] Prior to chloride conductivity measurement, the membranes were ion- exchanged for 2 hours in saturated NaCI solution and then washed twice with fresh deionized water for 2 hours to remove any excess NaCI and recover Ch form.

[00125] Measurement of Ionic Conductivity (Cl form)

[00126] The in-plane ionic conductivity (o in mS/cm) of each membrane (6mm x 30mm) was measured using a BekkTech four-point probe platinum electrode (BT-512) conductivity test system with an Ivium potentiostat. Measurements were collected under fully hydrated conditions. The test cell, containing the secured membrane, was immersed in ultra-pure deionized water at 80°C and equilibrated for 15 minutes prior to measurement. The ionic conductivity was calculated according to the following equation

[00127] where L is the distance between the two inner platinum wires (0.425 cm), R is the resistance of the membrane in Q, and W and T are the width and thickness of the membrane in centimeters. Resistance was measured using a linear voltage sweep (Start 0 V : Range -10 mV to 10 mV : Scan rate 500 mV/s: E step 1 mV).

[00128] Results

[00129] Some features of the prepared membranes are reported in Table 1 .

*Data from the supplier.

[00130] As can be seen in Table 1 , the polyphenylene ionomers according to the examples 2-5 have high molecular weights. Moreover, those high molecular weight can be combined with high IEC.

[00131] The good correlation between targeted value and calculated values, shows that IEC can easily be tuned by setting the comonomers ratio during the copolymerization process. Values as high as 2.33 mmol/g while maintaining high molecular weight can be achieved.

[00132] Membranes obtained using the polyphenylene ionomer according to the examples 2-5 are self-standing membranes.

[00133] It can be seen from table 1 that the membranes according the examples 2- 5, under Ch form, show higher ionic conductivity at 80°C than commercially available self-standing membranes such as Fumasep® FAA- 3-50 and PiperlON also under Ch form.

[00134] Surprisingly, membranes according the examples 3-4 show higher ionic conductivity at 80°C than commercially available self-standing membranes despite the fact that they have lower IEC than the later.

Claims

Claim 1 . Polyphenylene ionomer [polymer (PPI)] comprising:

Claim 2. Polyphenylene ionomer [polymer (PPI)] according to claim 1 , wherein the recurring unit (R_PP) is represented by the following formula:

Claim 3. Polyphenylene ionomer according to Claim 1 or 2 wherein recurring unit (R_Pm) is selected from those of formula:

Claim 4. Polyphenylene ionomer according to Claim 1 or 2, essentially consisting or consisting of:

(i) at least one recurring unit (R_Pi) represented by the following formula: wherein Ri and R2 are each independently selected from the list consisting C1- C alkyl groups or represent together a C4-C8 alkanediyl group forming a cyclic moiety, wherein X^s is a counter anion; and

(ii) at least one recurring unit (R_PP) represented by the following formula:

Claim 5. Polyphenylene ionomer according to any one of Claims 1 to 4, wherein X is selected from the group consisting of OH, Cl, Br and I.

Claim 6. Polyphenylene ionomer according to any one of Claims 1 to 5, wherein Ri and R2 are methyl groups and X is OH.

Claim 7. Polyphenylene ionomer (PPI) according to any one of Claims 1 to 6, comprising at least about 30 mole percent, preferably at least 40 mole percent and more preferably at least 50 mole percent, based on the total mole number of recurring units, of recurring units (R_Pi) represented by the following formula: wherein R1 and R2 are each independently selected from the list consisting of C1-C18 alkyl groups or represent together a C4-C8 alkanediyl group forming a cyclic moiety, and wherein X^s is a counter anion.

Claim 8. Method for preparing the polyphenylene ionomer [polymer (PPI)] according to any one of the preceding Claims, comprising the following steps of:

1 -copolymerization of: (i) at least one monomer (M_Pi) represented by the following formula: wherein Ri and R2 are each independently selected from the list consisting of C1-C18 alkyl groups or represent together a C4-C8 alkanediyl group forming a cyclic moiety, and wherein Z is selected from the group consisting of Cl, Br and I;

(iii) optionally at least one monomer (M_pm) represented by the following formula: wherein R7, Rs, R9 and R10 are each independently selected from the list consisting of hydrogen, alkyl, aryl, alkoxy, aryloxy, alkylketone, arylketone, fluoroalkyl, fluoroaryl, bromoalkyl, bromoaryl, chloroalkyl, chloroaryl, alkylsulfone, arylsulfone, alkylamide, arylamide, alkylnitrile, arylnitrile, alkylester, arylester, fluorine, chlorine, and bromine; and (iv) optionally at least one monomer selected from the group of monomers represented by the following formulae: wherein R11 and R12 are each independently selected from the list consisting of C1-C18 optionally fluorinated alkyl groups and optionally substituted aryl groups, or represent together a Cs-Cs alkanediyl group forming a cyclic moiety, or represent together an optionally substituted biphenyldiyl group forming a cyclic moiety; wherein Y is selected from the group consisting of Cl, Br and I; and

2-optionally exchanging counter anion Z^e for counter anion X^s.

Claim 9. Method for preparing the polyphenylene ionomer [polymer (PPI)] according to any one of Claims 1 to 7, comprising the following steps of: 1 ’-copolymerization of:

Claim 10. A liquid composition (LC) comprising the polyphenylene ionomer [polymer (PPI)] according to any one of claims 1 to 7 and a liquid medium (L).

Claim 11. A solid composition (SC) comprising the polyphenylene ionomer [polymer (PPI)] according to any one of claims 1 to 7.

Claim 12. An article comprising the polyphenylene ionomer [polymer (PPI)] according to any one of claims 1 to 7.

Claim 13. The article according to claim 12, which is an anion exchange membrane (AEM), an electrocatalytic layer (EL) or a membrane electrode assembly (MEA).

Claim 14. A process for manufacturing the article according to claim 12 or 13, comprising the impregnation, casting or coating of the liquid composition (LC) of claim 10.

Claim 15. A process for manufacturing the article according to claim 12 or 13, comprising extrusion of the solid composition (SC) of claim 11.

Claim 16. A fuel cell or an electrolysis cell comprising the article of claim 12 or 13.