Process for preparing unipolar cation-conducting ionomers from difluoro ionic monomers

Process for preparing an ionomer comprising at least repeating units UP corresponding to formula (II) below:

• in which
• M is an alkali metal cation, an alkaline-earth metal cation, a transition metal cation, a poor metal cation, an ammonium, a sulfonium or a phosphonium of valency m, with 1≤m≤3, m being an integer,
• Aa- is an anion chosen from a sulfonate anion, a sulfonimide anion of formula —SO2—N−—SO2R, an anion derived from a sulfonimide anion bearing at least two negative charges, and a carbanion of formula —SO2—C−R′R″, with 1≤a≤3, a being an integer,
• with R representing a fluorine atom;
• an optionally fluoro or perfluoro alkyl group, containing from 1 to 10 carbon atoms;
• an optionally fluoro or perfluoro alkoxy group, containing from 1 to 10 carbon atoms;
• a phenoxy group optionally substituted with an electron-withdrawing group X2;
• an optionally fluoro or perfluoro dialkyl ether group, containing from 1 to 10 carbon atoms;
• a thiocyanate group;
• an optionally substituted phenyl group;
• a nitrile group;
• an amino group of formula —NR1R2, in which R1 and R2 are chosen, independently of each other, from the following groups:
• an optionally fluoro or perfluoro alkyl group, containing from 1 to 5 carbon atoms, an alkyl group containing from 1 to 5 carbon atoms and bearing an electron-withdrawing group X3, an optionally fluoro or perfluoro dialkyl ether group, containing from 1 to 5 carbon atoms, and an electron-withdrawing group X4;
• a group —NR3 being chosen from a saturated heterocycle containing from 3 to 6 carbon atoms and an unsaturated heterocycle containing from 4 to 6 carbon atoms;
• an amide group of formula —NH—CO—R4 or —N(CH3)—CO—R4, in which R4 is an alkyl group containing from 1 to 3 carbon atoms;
• a sulfonamide group of formula —NH—SO2—R5 or —N(CH3)—SO2—R5, in which R5 is an alkyl group containing from 1 to 3 carbon atoms;
• a urethane group of formula —NH—CO2—R6 or —N(CH3)—CO2—R6, in which R6 is an alkyl group containing from 1 to 3 carbon atoms;
• a cyanamide group of formula NH—CN or N(R7)—CN, in which R7 is an alkyl group containing 1 to 3 carbon atoms;
• a dicyanamide group —N(CN)2;
• a tricyanomethyl group —C(CN)3;
• or a dicyanomethylene group of formula —CH(CN)2 or —CR8(CN)2, in which R9 is an alkyl group containing 1 to 3 carbon atoms,
• with R′ and R″ being chosen, independently of each other, from the following monovalent groups:
• a fluorine atom;
• a thiocyanate group;
• a nitrile group;
• a nitro group;
• a nitroso group of formula R9NO—, in which R9 is an alkyl group containing from 1 to 3 carbon atoms;
• a carbonyl group of formula —COR10 in which R10 is a perfluoro alkyl group containing from 1 to 5 carbon atoms;
• a sulfoxide group of formula —SOR11 in which R11 is an optionally fluoro or perfluoro alkyl group, containing from 1 to 5 carbon atoms or an optionally fluoro or perfluoro dialkyl ether group, containing from 1 to 5 carbon atoms;
• a sulfonyl group of formula —SO2R12 in which R12 is a fluorine atom, a thiocyanate group, a nitrile group, an optionally fluoro or perfluoro alkoxy group, containing from 1 to 5 carbon atoms, an optionally fluoro or perfluoro alkyl group, containing from 1 to 5 carbon atoms or an optionally fluoro or perfluoro dialkyl ether group, containing from 1 to 5 carbon atoms;
• a carboxylic ester group of formula —COOR13, in which R13 is an alkyl group containing from 1 to 5 carbon atoms;
• an amide group of formula —CONHR14 in which R14 is an alkyl group containing from 1 to 5 carbon atoms;
• an amide group of formula —CONR14R15 in which R14 and R15 are chosen, independently of each other, and R15 is an alkyl group containing from 1 to 5 carbon atoms;
• an optionally substituted phenyl group;
• or an optionally substituted phenoxy group, or
• with R′ and R″ being divalent groups such that the resulting carbanion radical —C−R′R″ forms an aromatic ring comprising from 5 to 6 carbon atoms and optionally one or more heteroatoms O or N, said aromatic ring being optionally substituted with one or more nitrile groups,
• 1≤n≤4, n being an integer,
• 0≤n′≤2, n′ being an integer,
• Z1 is chosen from a single bond, an oxygen atom, a sulfur atom, a group —S═O, a group —S(═O)2 and a phenyl group optionally substituted in the ortho position relative to one of the functions (CF2)n or (CF2)n′,
• Z2 is chosen from a single bond, an oxygen atom, a sulfur atom, a group —S═O, a group —S(═O)2 and a group —C═O, it being understood that when n′=0, Z2 is a single bond,
• E is an aromatic group comprising from 5 to 20 carbon atoms, it being understood that E comprises from 1 to 3 aromatic rings, and
• P is an alkylene oxide polymer chain,
• wherein said process comprises at least one step a) of polycondensation of at least one difluoro ionic monomer (I) with at least one alkylene oxide polymer P1 in basic medium, said difluoro ionic monomer corresponding to formula (I) below:
• in which:
• A, n, n′, Z1, Z2, E, m, a and M are as defined above, and
• T1 and T2 are fluorine atoms.