Hybrid fluoropolymer composites

1. A process for manufacturing a polymer electrolyte membrane, said process comprising:

(i) providing a composition [composition (C1)] comprising:

at least one fluoropolymer [polymer (F)] comprising recurring units derived from at least one fluorinated monomer [monomer (F)] and at least one hydrogenated monomer comprising at least one hydroxyl group [monomer (OH)],

at least one metal compound [compound (M1)] of formula (I):

X 4-m AY m   (I)

wherein m is an integer from 1 to 3, A is a metal selected from the group consisting of Si, Ti and Zr, Y is a hydrolysable group and X is a hydrocarbon group comprising at least one —N═C═O functional group,

a liquid medium [medium (L)],

an electrolyte medium comprising at least one metal salt [medium (E)], and

optionally, at least one metal compound [compound (M2)] of formula (II):

X′ 4-m′ A′Y′ m′   (II)

wherein m′ is an integer from 1 to 4, A′ is a metal selected from the group consisting of Si, Ti and Zr, Y′ is a hydrolysable group and X′ is a hydrocarbon group, optionally comprising at least one functional group different from the —N═C═O functional group;

(ii) reacting at least a fraction of the hydroxyl groups of the monomer (OH) of said polymer (F) with at least a fraction of said compound (M1) and, optionally, at least a fraction of said compound (M2) thereby providing a composition [composition (C2)] comprising at least one grafted fluoropolymer [polymer (F-g)] comprising recurring units derived from at least one fluorinated monomer [monomer (F)] and at least one hydrogenated monomer [monomer (HH)], said monomer (HH) comprising:

at least one pendant side chain comprising an end group of formula —O—C(O)—NH—Z-AY m X 3-m (M1-g), wherein m, Y, A, X have the same meaning as defined above and Z is a hydrocarbon group, optionally comprising at least one —N═C═O functional group, and

optionally, at least one pendant side chain comprising an end group of formula —O-A′Y′ m′-1 X′ 4-m′ (M2-g), wherein m′, Y′, A′, X′ have the same meaning as defined above;

(iii) hydrolysing and/or condensing the end groups of formula —O—C(O)—NH—Z-AY m X 3-m (M1-g) and, optionally, the end groups of formula —O-A′Y′ m′-1 X′ 4-m′ (M2-g) of the polymer (F-g) thereby providing a composition [composition (C3)] comprising at least one fluoropolymer hybrid organic/inorganic composite [polymer (F-h)];

(iv) processing into a polymer electrolyte membrane the composition (C3) provided in step (iii); and

(v) drying the polymer electrolyte membrane provided in step (iv).

2. The process according to claim 1 , wherein the medium (E) comprises at least one metal salt and at least one organic carbonate.

3. The process according to claim 1 , wherein the medium (E) comprises at least one metal salt, at least one ionic liquid and, optionally, at least one organic carbonate.

4. The process according to claim 1 , wherein the metal salt is selected from the group consisting of MeI, Me(PF 6 ) n , Me(BF 4 ) n , Me(ClO 4 ) n , Me(bis(oxalato)borate) n (Me(BOB) n ), MeCF 3 SO 3 , Me[N(CF 3 SO 2 ) 2 ] n , Me[N(C 2 F 5 SO 2 ) 2 ] n , Me[N(CF 3 SO 2 )(R F SO 2 )] n with R F being C 2 F 5 , C 4 F 9 , CF 3 OCF 2 CF 2 , Me(AsF 6 ) n , Me[C(CF 3 SO 2 ) 3 ] n , Me 2 S n , wherein Me is a metal, and n is the valence of said metal.

5. The process according to claim 1 , wherein under step (i) the polymer (F) is obtainable by polymerization of at least one monomer (F) and at least one monomer (OH).

6. The process according to claim 1 , wherein under step (i) the polymer (F) further comprises recurring units derived from at least one hydrogenated monomer [monomer (H)] different from the monomer (OH).

7. The process according to claim 1 , wherein under step (i) the monomer (OH) of the polymer (F) is selected from the group consisting of (meth)acrylic monomers of formula (III) and vinylether monomers of formula (IV):

wherein each of R 1 , R 2 and R 3 , equal to or different from each other, is independently a hydrogen atom or a C 1 -C 3 hydrocarbon group, and R X is a C 1 -C 5 hydrocarbon moiety comprising at least one hydroxyl group.

8. The process according to claim 1 , wherein under step (i) the polymer (F) is selected from the group consisting of:

polymers (F-1) comprising recurring units derived from vinylidene fluoride (VDF), at least one monomer (OH) and, optionally, at least one monomer (F) different from VDF, and

polymers (F-2) comprising recurring units derived from at least one per(halo)fluoromonomer selected from tetrafluoroethylene (TFE) and chlorotrifluoroethylene (CTFE), at least one monomer (H) selected from ethylene, propylene and isobutylene, and at least one monomer (OH), optionally comprising one or more additional monomers.

9. The process according to claim 8 , wherein the polymer (F-1) comprises:

(a) at least 60% by moles of vinylidene fluoride (VDF);

(b) optionally, from 0.1% to 15% by moles of at least one monomer (F) selected from vinyl fluoride (VF 1 ), chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), tetrafluoroethylene (TFE), trifluoroethylene (TrFE), perfluoromethylvinylether (PMVE); and

(c) from 0.01% to 20% by moles of at least one monomer (OH) of formula (III) as defined in claim 7 .

10. The process according to claim 1 , wherein the compound (M1) is of formula (I-A):

R A 4-m A(OR B ) m   (I-A)

wherein m is an integer from 1 to 3, A is a metal selected from the group consisting of Si, Ti and Zr, R A , equal to or different from each other and at each occurrence, is a C 1 -C 12 hydrocarbon group comprising at least one —N═C═O functional group and R B , equal to or different from each other and at each occurrence, is a C 1 -C 5 linear or branched alkyl group, preferably R B being a methyl or ethyl group.

11. The process according to claim 1 , wherein under step (i) the composition (C) further comprises at least one condensation catalyst.