Proton conduction membrane and fuel cell that can be used at temperatures above 100°C

Abstract

To provide a proton conductive membrane that can be used at 100°C or higher, particularly an anhydrous proton conductive membrane that can be used in a medium temperature range of 100°C or higher and 150°C or lower, and a fuel cell.SOLUTION: A proton conductive membrane includes a polymer and a proton donating agent, the polymer includes a block copolymer having an A-B-A type unit in which an A block and a B block are covalently linked, the blocks are polymers each having a glass transition temperature (Tg) of 100°C or higher, and aggregate with each other to form a hard domain, the B block has a proton-accepting group and is swollen with the proton donating agent, and the B block bridges the domains of the A blocks.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a proton-conducting membrane that can be used at 100°C or higher, particularly an anhydrous proton-conducting membrane that can be used in a medium-temperature range of 100°C or higher and 150°C or lower, and a fuel cell.

Background Art

[0002] Patent Document 1 discloses a proton-conducting membrane that contains a crosslinked polymer and a plasticizer, wherein the crosslinked polymer has a proton-accepting group of 10 mol% or more of the repeating units constituting the crosslinked polymer, the plasticizer contains a proton-donating compound having a pKa of 2.5 or less, and is a viscoelastic solid in a temperature range of 50°C or higher and 120°C or lower. This proton-conducting membrane can exhibit high proton conductivity even in an anhydrous environment and can be used as a proton-conducting membrane in a fuel cell.

[0003] Patent Document 2 discloses a proton-conducting membrane that contains a polymer having a first part and a second part connected by a covalent bond, and a plasticizer. The first part aggregates with each other to form domains at the use temperature of the proton-conducting membrane, and the second part bridges between the domains. The second part has a proton-accepting group, and the plasticizer contains a proton-donating compound having a pKa of 2.5 or less, whereby the plasticizer penetrates into the second part and the glass transition temperature of the polymer is lower than that in the case where the plasticizer is not contained. This proton-conducting membrane can exhibit high proton conductivity even in a low-humidity or anhydrous environment and can be used as a proton-conducting membrane in a fuel cell.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention provides a new proton-conducting membrane and a fuel cell.

Means for Solving the Problems

[0006] The present invention for achieving the above object is as follows.

[0007] The present invention provides a new proton-conducting membrane and a fuel cell.

[0008] The present invention provides a new, particularly anhydrous proton-conducting membrane that can be used in a medium temperature range of 100°C or higher and 150°C or lower, and a fuel cell.

[0009] Item 1. A proton-conducting membrane, comprising a polymer and a proton donor, wherein the polymer includes a block copolymer having A-B-A type units in which an A block and a B block are covalently connected, the A block is a polymer having a glass transition temperature (Tg) of 100°C or higher, and aggregates with each other to form a hard domain, the B block has a proton-accepting group and is swollen by the proton donor, the B block bridges between the domains of the A block, and is usable at 100°C or higher, a proton-conducting membrane.

[0010] Item 2. The main chain of the block copolymer having the A-B-A type units except for the terminal portions, does not have a functional group that is easily decomposed by heat and / or does not have a functional group that is easily decomposed by an acid, the main chain, the proton-conducting membrane according to Item 1 above.

[0011] Item 3. The block copolymer having the A-B-A type unit is obtained by addition polymerization of monomers starting from one starting point, or two or more starting points, and is the proton conductive membrane according to Item 1 or 2 above.

[0012] Item 4. The block copolymer having the A-B-A type unit is produced by RAFT polymerization of the A block and the B block using a reversible addition-fragmentation chain transfer (RAFT) agent, and is the polymer which is the proton conductive membrane according to any one of Items 1 to 3 above.

[0013] Item 5. The RAFT agent is at least one thiocarbonylthio compound selected from the group consisting of dithioesters, dithiocarbamates, trithiocarbonates, and xanthates, and is the proton conductive membrane according to any one of Items 1 to 4 above.

[0014] Item 6. The RAFT agent has one trithiocarbonate unit having one site where polymerization can proceed such that a monomer is inserted between a sulfur atom and an adjacent carbon atom, and the A-B-A type unit can be synthesized by sequentially linking the A block, the B block, and the A block, or has two or more trithiocarbonate units each having one site where polymerization can proceed such that a monomer is inserted between a sulfur atom and an adjacent carbon atom, and the two or more trithiocarbonate units are hydrocarbon groups, and the block copolymer having the A-B-A type unit having a hydrocarbon group in the central part can be synthesized. Except for the terminal portions of the block copolymer having the A-B-A type unit, it does not contain a trithiocarbonate unit which is a residue of the RAFT agent. The proton conduction membrane according to any one of items 1 to 4, which is a RAFT agent.

[0015] Item 7. The proton conduction membrane according to any one of items 1 to 6, wherein the proton donor is a proton donor composed of at least one selected from the group consisting of sulfuric acid and phosphoric acid.

[0016] Item 8. The proton conduction membrane according to any one of items 1 to 7, wherein the A block is a block composed of at least one polymer selected from the group consisting of polystyrene-based polymers, polyacrylate-based polymers, polymethacrylate-based polymers, polyolefin-based polymers, polysulfone-based polymers, polyarylate-based polymers, polyetherketone-based polymers, polyetherimide-based polymers, polyphenylene sulfide-based polymers, polyphenylene ether-based polymers, polycarbonate-based polymers, polybenzimidazole-based polymers, and polyfluoroethylene-based polymers.

[0017] Item 9. The proton conduction membrane according to any one of items 1 to 8, wherein the proton-accepting group of the B block is a nitrogen-containing heterocyclic group.

[0018] Item 10. The proton conduction membrane according to item 9, wherein the nitrogen-containing heterocyclic group is at least one nitrogen-containing heterocyclic group selected from the group consisting of a pyridine ring group, an imidazole ring group, a pyrazole ring group, an imidazoline ring group, an oxazole ring group, a pyrimidine ring group, a pyrazine ring group, a triazole ring group, and a tetrazole ring group.

[0019] Item 11. The proton conduction membrane according to any one of items 1 to 8, wherein the repeating unit constituting the B block is a block composed of at least one monomer selected from the group consisting of vinyl-based monomers, ether-based monomers, ester-based monomers, amide-based monomers, and silicone-based monomers.

[0020] Item 12. The B block is a block composed of at least one polymer selected from the group consisting of vinyl polymers having a pyridine ring, vinyl polymers having an imidazole ring, vinyl polymers having a pyrazole ring, vinyl polymers having an imidazoline ring, vinyl polymers having an oxazole ring, vinyl polymers having a pyrimidine ring, vinyl polymers having a pyrazine ring, vinyl polymers having a triazole ring, and vinyl polymers having a tetrazole ring, and is the proton-conducting membrane according to any one of Items 1 to 8 above.

[0021] Item 13. The proton-conducting membrane according to any one of Items 1 to 12 above, which can be used in a medium temperature range of 100°C or higher and 150°C or lower.

[0022] Item 14. A method for producing a proton-conducting membrane, wherein the proton-conducting membrane contains a polymer and a proton donor, and includes a step of producing the polymer, the polymer including a block copolymer having A-B-A type units synthesized by addition polymerization of monomers starting from one starting point or two or more starting points, wherein the main chain of the block copolymer having A-B-A type units has no functional group that is easily decomposed by heat and / or no functional group that is easily decomposed by an acid, except at the terminal portions, wherein the A block is a polymer having a glass transition temperature (Tg) of 100°C or higher, and the A blocks aggregate with each other to form domains, wherein the B block is a polymer having a glass transition temperature (Tg) of 100°C or higher and having a proton-accepting group, wherein the polymer includes a block copolymer having A-B-A type units in which the A block and the B block are connected by a covalent bond, wherein the B block bridges between the domains of the A block, and the proton-conducting membrane can be used at 100°C or higher. Method for manufacturing a proton conductive membrane.

[0023] Item 15. A method for manufacturing a proton conductive membrane, wherein the proton conductive membrane contains a polymer and a proton donor, including a step of producing a polymer by subjecting an A block and a B block to RAFT polymerization using a reversible addition-fragmentation chain transfer (RAFT) agent, the RAFT agent having one trithiocarbonate unit having one site where polymerization can proceed such that a monomer is inserted between a sulfur atom and an adjacent carbon atom, or having two or more trithiocarbonate units each having one site where polymerization can proceed such that a monomer is inserted between a sulfur atom and an adjacent carbon atom, and a hydrocarbon group being between the two or more trithiocarbonate units, the A block being a polymer having a glass transition temperature (Tg) of 100°C or higher and aggregating with each other to form domains, the B block being a polymer having a glass transition temperature (Tg) of 100°C or higher and having a proton accepting group, the polymer including an A-B-A type block copolymer in which the A block and the B block are covalently connected, the B block bridging between domains of the A block, the proton conductive membrane being usable at 100°C or higher, Method for manufacturing a proton conductive membrane.

[0024] Item 16. A RAFT agent having one trithiocarbonate unit having one site where polymerization can proceed such that a monomer is inserted between the sulfur atom and the adjacent carbon atom is 4-[(2-carboxyethylsulfanylthiocarbonyl)sulfanyl]-4-cyanopentanoic acid, 2-{[(2-carboxyethyl)sulfanylthiocarbonyl]sulfanyl}propanoic acid, 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoic acid, 2-[(dodecylsulfanylthiocarbonyl)sulfanyl]propanoic acid, 2-(dodecylthiocarbonothioylthio)-2-methylpropanoic acid, methyl 2-(dodecylthiocarbonothioylthio)-2-methylpropanoate, 2-(dodecylthiocarbonothioylthio)propanoic acid, pentafluorophenyl 2-(dodecylthiocarbonothioylthio)-2-methylpropanoate, 3-azido-1-propanol 2-(dodecylthiocarbonothioylthio)-2-methylpropanoate, 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoic acid, methyl 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoate, N-hydroxysuccinimidyl 2-(dodecylthiocarbonothioylthio)-2-methylpropanoate, 3-[[(benzylthio)carbonothioyl]thio]propanoic acid, 2-cyano-2-propyldodecyl trithiocarbonate, 4-cyano-4-(phenylcarbonothioylthio)pentanoic acid, cyanomethyl[3-(trimethoxysilyl)propyl]trithiocarbonate, 3-butenyl-2-(dodecylthiocarbonothioylthio)-2-methylpropane, phthalimidomethylbutyl trithiocarbonate, 2-(2-alkoxyethylsulfanylthiocarbonylsulfanyl)propanoic acid, 4-((((2-carboxyethyl)thio)carbonothioyl)thio)-4-cyanopentanoic acid, 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanol, and cyanomethyldodecyl trithiocarbonate, or, The method for producing a proton-conducting membrane according to item 14 or 15 above, wherein the RAFT agent has two or more trithiocarbonate units each having a site where polymerization can proceed such that a monomer is inserted between the sulfur atom and the adjacent carbon atom, and the hydrocarbon group is present between the two or more trithiocarbonate units, is at least one trithiocarbonate selected from the group consisting of 1,4-phenylenebis(methylene)didodecylbis(carbonotrithioate), 1,4-phenylenebis(methylene)dibutylbis(carbonotrithioate), and 1,4-phenylenebis(methylene)dioctadecylbis(carbonotrithioate).

Advantages of the Invention

[0025] The present invention can provide a new proton-conducting membrane and a fuel cell.

[0026] The present invention can provide a new anhydrous proton-conducting membrane that can be used in a medium temperature range of 100°C or higher and 150°C or lower, in particular, and a fuel cell.

[0027] The proton-conducting membrane of the present invention can be suitably used as a proton-conducting membrane in a fuel cell, in particular.

Brief Description of the Drawings

[0028]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0029] (1) Proton conduction membrane The proton-conducting membrane of the present invention is, in particular, an anhydrous proton-conducting membrane that can be used in a medium temperature range of 100°C or higher and 150°C or lower, and is preferably used in fuel cells.

[0030] The proton-conducting membrane of the present invention contains a polymer and a proton donor, the polymer includes a block copolymer having A-B-A type units in which block A and block B are connected by a covalent bond, block A is a polymer with a glass transition temperature (Tg) of 100°C or higher, and in the proton donor, they aggregate with each other to form hard domains, block B has a proton-accepting group and is swollen by the proton donor, block B bridges between the domains of block A, and it is characterized in that it can be used at 100°C or higher.

[0031] Use temperature of the proton conduction membrane The proton-conducting membrane of the present invention can preferably be used in a medium temperature range of 100°C or higher and 150°C or lower.

[0032] The operating temperature of the proton-conducting membrane of the present invention is the temperature at which the proton-conducting membrane is used, and is preferably room temperature or higher, more preferably 50°C or higher, 60°C or higher, 70°C or higher, 80°C or higher, 90°C or higher, and even more preferably 100°C or higher. The operating temperature of the proton-conducting membrane of the present invention is preferably 200°C or lower, more preferably 150°C or lower, 140°C or lower, 130°C or lower, 120°C or lower, 110°C or lower. The proton-conducting membrane of the present invention is particularly an anhydrous proton-conducting membrane that can be used in a medium temperature range of 100°C or higher and 150°C or lower, and can be suitably used in fuel cells.

[0033] Polymer The proton-conducting membrane of the present invention contains a polymer.

[0034] In the proton-conducting membrane of the present invention, when the polymer having an A block (first part) and a B block (second part) connected by a covalent bond is a block copolymer, the A block of the block copolymer is referred to as the first part, and the B block of the block copolymer may be referred to as the second part.

[0035] The polymer includes a block copolymer having an A-B-A type unit in which an A block and a B block are connected by a covalent bond.

[0036] The block copolymer of the proton-conducting membrane of the present invention is a polymer having an A block (first part) and a B block (second part).

[0037] The domain of the proton-conducting membrane of the present invention refers to a part where the A block (first part) of the polymer aggregates by intermolecular forces other than covalent bonds, and is an aggregated part that can be reversibly changed between a glassy state and a molten state in response to changes in the environment such as temperature.

[0038] The intermolecular forces other than the covalent bond include, preferably, van der Waals forces, charge transfer forces, Coulomb forces, hydrophobic binding forces, hydrogen bonding forces, ionic bonding forces, coordination bonding forces, etc., or intermolecular forces such as combinations thereof. The intermolecular forces other than the covalent bond are not limited to these intermolecular forces.

[0039] In the present invention, at the use temperature of the proton conductive membrane, the domains formed by the aggregation of the A blocks (first parts) of the polymer are preferably in a glassy state, a crystalline state, or the like.

[0040] The glassy state refers to the amorphous state of a solid. Whether the domain is in a glassy state or a crystalline state can be determined by differential scanning calorimetry (DSC) measurement. More specifically, when an endothermic step is observed (a peak may also be observed), it is in a glassy state. When there is no endothermic step and only a sharp endothermic peak is observed, it is in a crystalline state.

[0041] The bridging of the proton conductive membrane of the present invention refers to a structure in which the B blocks (second parts) of the polymer bridge between the domains.

[0042] At the use temperature of the proton conductive membrane of the present invention, the A blocks (first parts) forming the domains and the B blocks (second parts) bridging them form a crosslinked structure as a whole.

[0043] As long as the effects of the present invention are not impaired, the polymer of the present invention preferably contains chemical crosslinking points (covalent crosslinking points), and more preferably is a polymer obtained by generating chemical crosslinking points after producing a proton conductive membrane composed only of physical crosslinking points.

[0044] Proton donor The proton conductive membrane of the present invention contains a proton donor (plasticizer).

[0045] The proton donor (plasticizer) contained in the proton-conducting membrane of the present invention preferably contains a proton-donating compound involved in proton transport, is miscible with the B block (second part) which is a polymer, and is sufficiently permeated.

[0046] The above-mentioned miscibility means that the respective molecules, that is, the molecules of the proton donor (plasticizer) and the B block (second part), are spontaneously mixed at the molecular level. The Gibbs energy of the above-mentioned mixing: ΔmixG means that it becomes a large negative value in absolute value.

[0047] ΔmixG (Gibbs energy of mixing) = ΔmixH - TΔmixS ΔmixH: Enthalpy of mixing ΔmixS: Entropy of mixing T: Absolute temperature at the time of mixing It is represented by.

[0048] If ΔmixH becomes a large negative value in absolute value and TΔmixS becomes a large positive value, then ΔmixG becomes a large negative value in absolute value, so it is well mixed at the molecular level. When a liquid proton donor (plasticizer) is used, a state in which the proton donor (plasticizer) and the B block (second part) are well miscible is realized.

[0049] The above-mentioned penetration is promoted by the fact that the ΔmixG of the penetration medium (usually a liquid) and the penetrated medium takes a large negative value in absolute value. Just by bringing the penetration medium into contact with the non-penetrating medium, the penetration medium spontaneously penetrates into the non-penetrating medium, realizing uniform mixing at the molecular level.

[0050] When the penetration medium is a proton donor (plasticizer) and the penetrated medium is the B block (second part) which is a polymer, usually the value of ΔmixG mainly depends on the magnitude of ΔmixS which becomes positive, but even if this becomes a negative value, it does not become a large absolute value. As a result, no large penetration occurs.

[0051] The proton-conducting membrane of the present invention has a B block (second part) which is a flexible polymer liable to undergo a conformational change, has a proton-accepting group, and the plasticizer preferably contains a proton-donating compound with a pKa of 2.5 or less.

[0052] The proton-conducting membrane of the present invention forms a pair that produces an ionic attractive interaction between the proton-accepting group of the B block (second part) and the proton-donating compound.

[0053] When considering the mixing of the B block (second part), which is a flexible polymer liable to undergo a conformational change, and the proton donor (plasticizer), due to the flexibility of the B block (second part), TΔmixS can achieve a moderately large positive value, so ΔmixG takes a negative value. Furthermore, since the B block (second part) and the proton donor (plasticizer) are a pair that generates heat when mixed, depending on the number of such pairs, ΔmixH takes a large negative value in absolute terms. Due to the contribution of this ionic attractive interaction, ΔmixG also becomes a large negative value in absolute terms, making it easier for the proton donor (plasticizer) to penetrate into the B block (second part).

[0054] Even after penetration, due to the contribution of the ionic attractive interaction between the proton-accepting group of the B block (second part) and the proton-donating compound in the proton donor (plasticizer), ΔmixG remains negative.

[0055] In the proton-conducting membrane of the present invention, the proton donor (plasticizer) does not naturally leach out.

[0056] The proton donor (plasticizer) can preferably lower the glass transition temperature of the polymer. In the proton-conducting membrane of the present invention, the glass transition temperature of the polymer corresponds to the glass transition temperature of the B block (second part) of the polymer.

[0057] The proton donor (plasticizer) contained in the proton conduction membrane of the present invention is preferably a proton donor composed of at least one selected from the group consisting of sulfuric acid and phosphoric acid.

[0058] Mechanism by which the proton conduction membrane exhibits its function The proton conduction membrane of the present invention is, in particular, an anhydrous proton conduction membrane that can be used in a medium temperature range of 100°C or higher and 150°C or lower, and can be suitably used in a fuel cell. The proton conduction membrane of the present invention can exhibit high proton conductivity even in a low humidity or anhydrous environment.

[0059] Using FIG. 1, the mechanism by which the proton conduction membrane of the present invention exhibits its function will be described.

[0060] The mechanism described below does not limit the proton conduction membrane of the present invention.

[0061] FIG. 1 is a schematic diagram for explaining the mechanism by which the proton conduction membrane of the present invention exhibits its function.

[0062] In the proton conduction membrane of the present invention, when the polymer having an A block (first part) and a B block (second part) connected by a covalent bond is a block copolymer, the A block of the block copolymer is referred to as the first part, and the B block of the block copolymer is referred to as the second part.

[0063] The proton conduction membrane of FIG. 1 includes a polymer having an A block (first part) and a B block (second part) connected by a covalent bond, and a proton donor (plasticizer).

[0064] The A blocks (first parts) aggregate with each other to form domains at the use temperature of the proton conduction membrane. In the proton conduction membrane, the B blocks (second parts) bridge between the domains formed by the A blocks (first parts).

[0065] The proton conduction membrane of the present invention thereby maintains its membrane shape.

[0066] The proton-conducting membrane of the present invention has the above structure. Since the A block (the first part) is on the nanometer order and is regularly and periodically arranged, it has a larger elongation at break and / or tensile strength compared to a proton-conducting membrane crosslinked by irregular and non-periodic covalent bonds.

[0067] The proton-conducting membrane of the present invention can preferably be produced by a solvent casting method, a spin coating method, or a hot melt method.

[0068] The proton-conducting membrane of the present invention can be made smoother and thinner compared to conventional proton-conducting membranes, and furthermore, enables large-area formation.

[0069] The proton donor (plasticizer) contained in the proton-conducting membrane of the present invention preferably contains a proton-donating compound with a pKa of 2.5 or less.

[0070] Protons are released from the proton-donating compound. When protons are released, the proton-donating compound becomes an anion. Since there are proton-accepting groups in the B block (the second part) of the polymer, some of the released protons bind to the proton-accepting groups. Accordingly, the proton-accepting groups in the B block (the second part) become cations.

[0071] As shown in FIG. 1, in the proton-conducting membrane of the present invention, ionic interactions occur between the anionized proton-donating compound, free protons, and cationized proton-accepting groups. Such ionic interactions exist throughout the entire membrane of the proton-conducting membrane, and free protons can move easily even in an anhydrous environment.

[0072] High proton conductivity can be imparted to the proton-conducting membrane of the present invention.

[0073] Since an ionic interaction acts between the anion and cation to be formed, preferably, a proton-donating compound having a pKa of 2.5 or less can stay within the membrane. A proton-donating compound (plasticizer), preferably having a pKa of 2.5 or less, hardly leaks or does not leak from the proton-conducting membrane of the present invention.

[0074] Due to the ionic interaction, the proton-donating agent (plasticizer) easily penetrates into the B block (second part).

[0075] By bringing the polymer and the plasticizer included in the proton-conducting membrane of the present invention into contact with each other, the proton-donating agent (plasticizer) spontaneously penetrates into the polymer to form a uniform mixed phase.

[0076] In the proton-conducting membrane of the present invention, even when the polymer and the proton-donating agent (plasticizer) coexist, the proton-donating agent (plasticizer) mainly penetrates into the B block (second part) of the polymer, and the state of the domain of the A block (first part) of the polymer is maintained.

[0077] As the penetration proceeds, that is, when the proton-donating agent (plasticizer) penetrates into the B block (second part) in a large amount, the glass transition temperature of the polymer decreases compared to the case where the proton-donating agent (plasticizer) is not included. Due to the decrease in the glass transition temperature of the polymer, the segmental motion of the polymer chain becomes active, and high proton conductivity can be imparted to the proton-conducting membrane of the present invention.

[0078] In FIG. 1, a proton-donating dibasic acid is depicted as the proton-donating compound. The proton-donating compound is not limited thereto.

[0079] In the proton-conducting membrane of the present invention, the polymer having an A block (first part) and a B block (second part) connected by a covalent bond is a block copolymer. In the proton-conducting membrane of the present invention, the polymer having an A block (first part) and a B block (second part) connected by a covalent bond is a block copolymer from the viewpoints of diversity of variations and ease of handling.

[0080] Regarding the proton-conducting membrane of the present invention, the polymer having an A block (first part) and a B block (second part) connected by a covalent bond is a block copolymer. The block copolymer has an A block and a B block.

[0081] Block copolymer The block copolymer has at least an A block (first part) and a B block (second part), and may contain a C block (third part) or a D block (fourth part).

[0082] A block (first part) The polymers constituting the A block are each a polymer containing the polymers listed below, and are polymers having a glass transition temperature of 100 °C or higher.

[0083] The glass transition temperature (Tg) of the present invention is a value obtained in accordance with JIS K 7121:2012 based on the DSC curve obtained by measuring at a heating rate of 10 °C / min.

[0084] In the proton-conducting membrane of the present invention, the A blocks aggregate with each other to form domains at the use temperature of the proton-conducting membrane.

[0085] The A block is a polymer having a glass transition temperature (Tg) of 100 °C or higher, and aggregates with each other to form hard domains.

[0086] The A block is not particularly limited as long as it aggregates with each other to form domains at the use temperature of the proton-conducting membrane.

[0087] In the present invention, the prefix "poly" refers to a polymer containing two or more monomers.

[0088] The A block contained in the proton conductive membrane of the present invention is preferably a block composed of at least one polymer selected from the group consisting of polystyrene-based polymers, polyacrylate-based polymers, polymethacrylate-based polymers, polyolefin-based polymers, polysulfone-based polymers, polyarylate-based polymers, polyether ketone-based polymers, polyether imide-based polymers, polyphenylene sulfide-based polymers, polyphenylene ether-based polymers, polycarbonate-based polymers, polybenzimidazole-based polymers, and polyfluoroethylene-based polymers. The A block is not limited thereto.

[0089] The polystyrene-based polymer is preferably a polymer having a styrene moiety of 50 mol% or more as a repeating unit. The polystyrene-based polymer preferably includes polystyrene, polyacetylstyrene, polyanisoylstyrene, polybenzoylstyrene, polybiphenylstyrene, polybromoethoxystyrene, polybromomethoxystyrene, polybromostyrene, polybutoxymethylstyrene, poly-tert-butylstyrene, polybutyrylstyrene, polychlorofluorostyrene, polychloromethylstyrene, polychlorostyrene, polycyanostyrene, polydichlorostyrene, polydifluorostyrene, polydimethylstyrene, polyethoxymethylstyrene, polyethoxystyrene, polyfluoromethylstyrene, polyfluorostyrene, polyiodostyrene, polymethoxycarbonylstyrene, polymethoxymethylstyrene, polymethylstyrene, polymethoxystyrene, polyperfluorostyrene, polyphenoxystyrene, polyphenylacetylstyrene, polyphenylstyrene, polypropoxystyrene, polytoluoylstyrene, polytrimethylstyrene, etc., and the glass transition temperature is 100 °C or higher. The polystyrene-based polymer is not limited thereto.

[0090] The polyacrylate polymer is preferably a polymer having an acrylate moiety of 50 mol% or more as a repeating unit. The polyacrylate polymer preferably includes polyacrylate adamantyl, polyacrylate - tert - butyl, polyacrylate - tert - butylphenyl, polyacrylate cyanoheptyl, polyacrylate cyanohexyl, polyacrylate cyanomethyl, polyacrylate cyanophenyl, polyacrylate fluoromethyl, polyacrylate methoxycarbonylphenyl, polyacrylate methoxyphenyl, polyacrylate naphthyl, polyacrylate pentachlorophenyl, polyacrylate phenyl, etc., and the glass transition temperature is 100°C or higher. The polyacrylate polymer is not limited to these.

[0091] The polymethacrylate polymer is preferably a polymer having a methacrylate moiety of 50 mol% or more as a repeating unit. The polymethacrylate polymer preferably includes polymethyl methacrylate, polyethyl methacrylate, polymethacrylonitrile, polyacrylate adamantyl, polybenzyl methacrylate, polyacrylate - tert - butyl, polyacrylate - tert - butylphenyl, polycycloethyl methacrylate, polycyanoethyl methacrylate, polycyanomethylphenyl methacrylate, polyacrylate cyanophenyl, polycyclobutyl methacrylate, polycyclodecyl methacrylate, polycyclododecyl methacrylate, polycyclobutyl methacrylate, polycyclohexyl methacrylate, polycyclooctyl methacrylate, polyfluoroalkyl methacrylate, polyglycidyl methacrylate, polyisobornyl methacrylate, polyisobutyl methacrylate, polyacrylate phenyl, polymethylsilyl methacrylate, polyxylenyl methacrylate, etc., and the glass transition temperature is 100°C or higher. The polymethacrylate polymer is not limited to these.

[0092] A polyolefin-based polymer is a polymer having an olefin moiety of 50 mol% or more as a repeating unit. The polyolefin-based polymer preferably includes polyethylene, polypropylene, poly-α-olefin, etc., and the glass transition temperature is 100 °C or higher. The polyolefin-based polymer is not limited thereto.

[0093] A polysulfone-based polymer is preferably a polymer having a sulfone moiety of 50 mol% or more as a repeating unit. The polysulfone-based polymer preferably includes polyphenyl sulfone, polyether sulfone, polysulfone, etc., and the glass transition temperature is 100 °C or higher. The polysulfone-based polymer is not limited thereto.

[0094] A polyarylate-based polymer is preferably a polymer having an arylate moiety of 50 mol% or more as a repeating unit. The polyarylate-based polymer preferably includes polyarylate, etc., and the glass transition temperature is 100 °C or higher. The polyarylate-based polymer is not limited thereto.

[0095] A polyether ketone-based polymer is preferably a polymer having an ether ketone moiety of 50 mol% or more as a repeating unit. The polyether ketone-based polymer preferably includes polyether ketone, polyether ether ketone, polyether ketone ketone, polyether ether ketone ketone, etc., and the glass transition temperature is 100 °C or higher. The polyether ketone-based polymer is not limited thereto.

[0096] A polyether imide-based polymer is preferably a polymer having an ether imide moiety of 50 mol% or more as a repeating unit. The polyether imide-based polymer preferably includes polyether imide, etc., and the glass transition temperature is 100 °C or higher. The polyether imide-based polymer is not limited thereto.

[0097] The polyphenylene sulfide-based polymer is preferably a polymer having a polyphenylene sulfide moiety of 50 mol% or more as a repeating unit. The polyphenylene sulfide-based polymer preferably contains polyphenylene sulfide or the like, and has a glass transition temperature of 100°C or higher. The polyphenylene sulfide-based polymer is not limited thereto.

[0098] The polyphenylene ether-based polymer is preferably a polymer having a polyphenylene ether moiety of 50 mol% or more as a repeating unit. The polyphenylene ether-based polymer preferably contains polyphenylene ether or the like, and has a glass transition temperature of 100°C or higher. The polyphenylene ether-based polymer is not limited thereto.

[0099] The polycarbonate-based polymer is preferably a polymer having a carbonate moiety of 50 mol% or more as a repeating unit. The polycarbonate-based polymer is preferably polycarbonate or the like. The polycarbonate-based polymer is not limited thereto.

[0100] The polybenzimidazole-based polymer is preferably a polymer having a benzimidazole moiety of 50 mol% or more as a repeating unit. The polybenzimidazole-based polymer preferably contains polybenzimidazole or the like, and has a glass transition temperature of 100°C or higher. The polybenzimidazole-based polymer is not limited thereto.

[0101] The polyfluoroethylene-based polymer is preferably a polymer having a fluoroethylene moiety of 50 mol% or more as a repeating unit. The polyfluoroethylene-based polymer preferably contains polytetrafluoroethylene, poly(chlorotrifluoroethylene), poly(vinylidene fluoride), etc., and has a glass transition temperature of 100°C or higher. The polyfluoroethylene-based polymer is not limited to these.

[0102] In the present invention, the prefix "poly" refers to a polymer containing two or more monomers.

[0103] According to the operating temperature of the proton conductive membrane of the present invention, preferably, a material having a glass transition temperature or a melting temperature higher than the operating temperature of the proton conductive membrane is selected as the A block.

[0104] From the viewpoints of low miscibility with a proton donor (plasticizer) containing a proton donating compound, ease of handling, or low cost, the A block is preferably a polystyrene-based polymer.

[0105] B block (second part) The polymers constituting the B block are each a polymer containing the polymers listed below, and the glass transition temperature may be 100°C or higher or 100°C or lower.

[0106] The glass transition temperature (Tg) of the present invention is a value obtained in accordance with JIS K 7121:2012 based on a DSC curve obtained by measuring at a heating rate of 10°C / min.

[0107] In the proton conductive membrane of the present invention, the B block has a proton accepting group.

[0108] The B block has a proton accepting group and is swollen with a proton donor.

[0109] The B block bridges between the domains of the A block.

[0110] The proton accepting group is preferably a nitrogen-containing heterocyclic group.

[0111] The nitrogen-containing heterocyclic group is preferably at least one nitrogen-containing heterocyclic group selected from the group consisting of a pyridine ring group, an imidazole ring group, a pyrazole ring group, an imidazoline ring group, an oxazole ring group, a pyrimidine ring group, a pyrazine ring group, a triazole ring group, and a tetrazole ring group. The nitrogen-containing heterocyclic group is more preferably a nitrogen-containing heteroaromatic ring group, and still more preferably a pyridine ring group, an imidazole ring group, or the like.

[0112] The amount (number of moles) of proton-accepting groups per gram of the B block is not particularly limited. The amount (number of moles) of proton-accepting groups per gram of the B block is preferably 0.1 mmol / g or more, 0.5 mmol / g or more, 1.0 mmol / g or more, 2.5 mmol / g or more, or 5.0 mmol / g or more.

[0113] The amount (number of moles) of proton-accepting groups per gram of the B block is preferably 50 mmol / g or less, 40 mmol / g or less, 30 mmol / g or less, or 25 mmol / g or less from the viewpoint of facilitating the synthesis of the B block and ensuring the handleability of the resulting polymer.

[0114] The repeating unit constituting the B block is not particularly limited. The repeating unit constituting the B block is preferably composed of at least one monomer selected from the group consisting of vinyl monomers, ether monomers, ester monomers, amide monomers, and silicone monomers, or is derived from a monomer. The repeating unit constituting the B block is more preferably a monomer derived from a vinyl monomer because of its excellent availability and easy molecular modification.

[0115] In the present invention, the prefix "poly" refers to a polymer containing two or more monomers.

[0116] In the present invention, "(meth)acrylic acid" is a concept encompassing both acrylic acid and methacrylic acid. The same should be understood for "(meth)acrylate", "(meth)acrylamide", etc.

[0117] The polymer that can form the B block is preferably at least one polymer selected from the group consisting of vinyl polymers having a pyridine ring, vinyl polymers having an imidazole ring, vinyl polymers having a pyrazole ring, vinyl polymers having an imidazoline ring, vinyl polymers having an oxazole ring, vinyl polymers having a pyrimidine ring, vinyl polymers having a pyrazine ring, vinyl polymers having a triazole ring, and vinyl polymers having a tetrazole ring, and is a block composed of such polymers.

[0118] The polymer that can be the B block is not limited to these.

[0119] Vinyl polymers having a pyridine ring: poly(2-vinylpyridine), poly(4-vinylpyridine), etc.

[0120] Vinyl polymers having an imidazole ring: poly(1-vinylimidazole), poly(2-methyl-1-vinylimidazole), poly(2-vinylimidazole), poly(4-vinylimidazole), poly(2-phenyl-1-vinylimidazole), poly(1-vinylcarbazole), poly(2-(1H-imidazol-1-yl)ethyl (meth)acrylate), etc.

[0121] Vinyl polymers having a pyrazole ring: poly(1-vinylpyrazole), poly(3-vinylpyrazole), etc.

[0122] Vinyl polymers having an imidazoline ring: poly(1-vinyl-2-imidazoline), poly(1-vinyl-2-methylimidazoline), poly(2-vinyl-2-imidazoline), poly(2-(1H-imidazolin-1-yl)ethyl (meth)acrylate), etc.

[0123] Vinyl polymers having an oxazole ring: poly(2-phenyl-5-vinyl oxazole), etc.

[0124] Vinyl polymers having a pyrimidine ring: poly(5-vinylpyrimidine), poly(2,4-dichloro-6-vinylpyrimidine), etc.

[0125] Vinyl polymers having a pyrazine ring: poly(2-vinylpyrazine), poly(2,5-dimethyl-3-vinylpyrazine), poly(2-methyl-5-vinylpyrazine), etc.

[0126] Vinyl polymers having a triazole ring: poly(2,4-diamino-6-vinyltriazine), etc.

[0127] Vinyl polymers having a tetrazole ring: poly(1-vinyl-1H-tetrazole), poly(2-vinyl-2H-tetrazole), poly(5-vinyl-1H-tetrazole), poly(1-methyl-5-vinyl-1H-tetrazole), etc.

[0128] The polymers that can form the B block are more preferably poly(2-vinylpyridine), poly(4-vinylpyridine), poly(1-vinylimidazole), etc.

[0129] In the B block, from the viewpoint of ensuring a higher proton conductivity and further suppressing the leakage of the plasticizer by ionic interaction, the proton-accepting group is preferably present in a proportion of 10 mol% or more of the repeating units constituting the B block.

[0130] In the repeating units constituting the B block, the proportion of the proton-accepting group present is preferably 15 mol% or more, 20 mol% or more, 30 mol% or more, 40 mol% or more, 50 mol% or more, 60 mol% or more, 70 mol% or more, 80 mol% or more, 90 mol% or more, 95 mol% or more, 96 mol% or more, or 97 mol% or more.

[0131] In the repeating unit constituting the B block, the proportion of the proton-accepting group is preferably 99.5 mol% or less, 99 mol% or less, 98 mol% or less, 95 mol% or less, 90 mol% or less, 80 mol% or less, 70 mol% or less, 60 mol% or less, 50 mol% or less, 40 mol% or less, or 35 mol% or less.

[0132] The B block is combined with a proton donor (plasticizer) to form a proton-conducting membrane, thereby providing high molecular mobility.

[0133] The glass transition temperature (Tg) of the B block alone may be relatively high. If the glass transition temperature (Tg) of the B block is excessively high, the molecular mobility may not be sufficiently improved even after being mixed with a proton donor (plasticizer).

[0134] The glass transition temperature (Tg) of the B block is preferably 400 °C or less, 350 °C or less, 300 °C or less, or 250 °C or less, 200 °C or less, 150 °C or less, 100 °C or less, 50 °C or less, 0 °C or less.

[0135] The B block preferably has two or more glass transition temperatures. When the B block is mixed with a proton donor (plasticizer), this mixture has a low glass transition temperature. Accordingly, when the obtained proton-conducting membrane is used, the B block can maintain high molecular mobility. Furthermore, due to the presence of free protons, high proton conductivity can be achieved.

[0136] Arrangement of the block copolymer The sequence of the block copolymer composed of the A block and the B block is not particularly limited. The sequence of the block copolymer composed of the A block and the B block is preferably the following type.

[0137] AA···AABB···BBAA···AA: Triblock copolymer, also denoted as A-B-A type.

[0138] AA···AABB···BBAA···AABB···BB: A tetrablock copolymer, also denoted as A-B-A-B type.

[0139] From the perspective of more effectively exerting the effects of the present invention, the block copolymer is preferably an A-B-A type triblock copolymer composed of A blocks and B blocks.

[0140] An example of the A-B-A type triblock copolymer is Formula 1.

[0141]

Chemical formula

[0142] In the formula, p is preferably an integer of 2 or more, for example, 2 or more, 10 or more, 30 or more, 50 or more, 100 or more, 200 or more, 500 or more, 800 or more, 1,000 or more, 1,500 or more, or 2,000 or more. In the formula, p is preferably 20,000 or less, 15,000 or less, 10,000 or less, 8,000 or less, 5,000 or less, or 4,000.

[0143] In the formula, q is preferably an integer of 1 or more, for example, 1 or more, 5 or more, 15 or more, 25 or more, 50 or more, or 75 or more. In the formula, q is preferably 1,000 or less, 500 or less, 400 or less, 250 or less, or 150 or less.

[0144] As long as the effects of the present invention are not impaired, the block copolymer preferably further has other monomers or polymers different from the A blocks and B blocks.

[0145] In the proton conductive membrane of the present invention, the block copolymer preferably does not have residues such as initiators, coupling agents, and chain transfer agents used in the production of the block copolymer outside the polymer terminal portions.

[0146] The block copolymer contained in the proton conductive membrane of the present invention preferably has no residue of a chain transfer agent other than the polymer terminal portions.

[0147] An example of the case where the block copolymer further has a residue of a chain transfer agent is Formula 2. The present invention does not employ a polymer having a trithiocarbonate in the polymer central portion as represented by the following Formula 2.

[0148]

Chemical formula

[0149] In the formula, -R and -S-C(S)-S- are residues of a chain transfer agent.

[0150] In the formula, m is, for example, an integer of 1 or more and 10,000 or less.

[0151] In the formula, n is, for example, an integer of 1 or more and 1,000 or less.

[0152] In the proton conductive membrane of the present invention, preferably, the main chain of the block copolymer having the A-B-A type unit has no functional group that is easily decomposed by heat and / or has no functional group that is easily decomposed by an acid except for the terminal portions, and is the main chain.

[0153] In the proton conductive membrane of the present invention, preferably, the block copolymer having the A-B-A type unit is a block copolymer obtained by addition polymerization of monomers starting from one starting point or two or more starting points.

[0154] In the proton conductive membrane of the present invention, preferably, ​The block copolymer having the A-B-A type unit is produced by RAFT polymerization of the A block and the B block using a reversible addition-fragmentation chain transfer (RAFT) agent. It is a polymer.

[0155] In the proton conduction membrane of the present invention, preferably, The RAFT agent has one trithiocarbonate unit from which polymerization proceeds only from one sulfur atom, and by sequentially linking the A block, the B block, and the A block, a block copolymer having the A-B-A type unit can be synthesized, or has two or more trithiocarbonate units from which polymerization proceeds only from one sulfur atom, and a hydrocarbon group is present between the two or more trithiocarbonate units, and a block copolymer having the A-B-A type unit having a hydrocarbon group in the central part can be synthesized. Except for the terminal part of the block copolymer having the A-B-A type unit, it does not contain a trithiocarbonate unit which is a residue of the RAFT agent. It is a RAFT agent.

[0156] Usefulness of the proton conduction membrane of the present invention For a solid electrolyte membrane for a fuel cell, high catalytic activity is required, and an electrolyte membrane that can be used at about 100°C to 150°C is demanded.

[0157] In a conventional proton conduction membrane made of an A-B-A type block polymer, as the A block, there is a part that aggregates to form a domain, and as the B block, there is a part that has a proton acceptor group (such as a pyridine ring group) and swells in a proton donor to bridge between domains, and the temperature at which it can be used as a membrane is less than 100°C.

[0158] In a conventional A-B-A type polymer chain, residues derived from a RAFT agent formed in the polymerization process remain, and the residue portion tends to be thermally unstable. When a conventional proton-conducting membrane is used at a high temperature, the polymer chain is broken, and the membrane strength cannot be maintained at 100 °C or higher. When a conventional proton-conducting membrane is used at a temperature of 100 °C or higher, it tends to be difficult to maintain its shape, strength, etc.

[0159] The proton-conducting membrane of the present invention particularly has a proton donor and an A-B-A type block polymer. The A block is a portion that aggregates in the proton donor, and the B block is a portion having a proton acceptor group. Compared with the prior art, particularly, both the A block and the B block have a glass transition temperature (Tg) of 100 °C or higher, and further, except for the terminal portions of the block polymer chains, residues of the RAFT agent used in the polymerization process are not contained.

[0160] The proton-conducting membrane of the present invention is particularly characterized in that, firstly, an A-B-A type block polymer is synthesized by a polymerization method in which no residues enter except for the terminal portions of the polymer, and secondly, a copolymer having a glass transition temperature (Tg) of about 100 °C to 150 °C is employed for the A block and the B block.

[0161] In the proton-conducting membrane of the present invention, firstly, an A-B-A type block polymer is produced by a polymerization method in which no residues enter except for the terminal portions of the polymer. In the polymerization process of the present invention, by using a specific RAFT agent (reversible addition-fragmentation chain transfer agent), the molecular weight distribution of the polymer can be narrowly controlled, and the control of the polymer terminal is also easy. In the polymerization process, the preferably used RAFT agent has one trithiocarbonate unit having one site where polymerization can proceed such that a monomer is inserted between a sulfur atom and an adjacent carbon atom, or has two or more trithiocarbonate units each having one site where polymerization can proceed such that a monomer is inserted between a sulfur atom and an adjacent carbon atom, and the two trithiocarbonate units are RAFT agents that do not contain a chemically stable hydrocarbon group such as an ester, an ether, an amide, etc. between the units.

[0162] In the proton-conducting membrane of the present invention, secondly, in the polymerization step, preferably, as the A block and the B block, a copolymer having a glass transition temperature (Tg) of about 100°C to 150°C is preferably employed. As the A block, preferably, poly(4-tert-butylstyrene) (Tg: 150°C) is used, and as the B block, poly(4-vinylpyridine) (Tg: 150°C) is used. The proton-conducting membrane of the present invention can be preferably used at 100°C to 150°C.

[0163] (2) Method for manufacturing a proton conduction membrane Method for manufacturing a proton conduction membrane (1) The proton-conducting membrane of the present invention contains a polymer and a proton donor.

[0164] The manufacturing method (1) of the proton-conducting membrane of the present invention includes a step of producing the polymer including a block copolymer having an A-B-A type unit in which monomers are addition-polymerized from one starting point or two or more starting points.

[0165] The main chain of the block copolymer having the A-B-A type unit does not have a functional group that is easily decomposed by heat and / or does not have a functional group that is easily decomposed by an acid, except for the terminal portions.

[0166] The A block is a polymer having a glass transition temperature (Tg) of 100°C or higher, and aggregates with each other to form domains.

[0167] The B block is a polymer having a glass transition temperature (Tg) of 100°C or higher and has a proton-accepting group.

[0168] The polymer includes a block copolymer having an A-B-A type unit in which the A block and the B block are connected by a covalent bond.

[0169] The B block bridges between the domains of the A block.

[0170] The proton conduction membrane can be used at 100°C or higher.

[0171] A process for producing the polymer, comprising polymerizing monomers starting from one starting point or two or more starting points to obtain a block copolymer having A-B-A type units The process is a process for synthesizing a block copolymer having A-B-A type units by sequentially linking an A block, a B block, and an A block.

[0172] The main chain of the block copolymer having A-B-A type units has no functional group that is easily decomposed by heat and / or no functional group that is easily decomposed by an acid, except at the terminal portions.

[0173] The main chain is preferably linked by a carbon-carbon single bond.

[0174] The A block is a polymer having a glass transition temperature (Tg) of 100°C or higher, and aggregates with each other to form domains.

[0175] The A block is preferably a styrene-based polymer.

[0176] The B block is a polymer having a glass transition temperature (Tg) of 100°C or higher and has a proton accepting group.

[0177] The B block is preferably a vinylpyridine-based polymer.

[0178] The polymer includes a block copolymer having A-B-A type units in which the A block and the B block are covalently linked.

[0179] The B block bridges between the domains of the A block.

[0180] Method for manufacturing a proton conduction membrane (2) The proton conduction membrane of the present invention includes a polymer and a proton donor.

[0181] The method for producing a proton-conducting membrane (2) includes a step of producing a polymer by subjecting an A block and a B block to RAFT polymerization using a reversible addition-fragmentation chain transfer (RAFT) agent. The method for producing a proton-conducting membrane (2) includes a step of producing a polymer by subjecting an A block and a B block to RAFT polymerization using a reversible addition-fragmentation chain transfer (RAFT) agent.

[0182] The RAFT agent has two or more trithiocarbonate units, and a hydrocarbon group is present between the two or more trithiocarbonate units.

[0183] The A block is a polymer having a glass transition temperature (Tg) of 100°C or higher, and the A blocks aggregate with each other to form domains.

[0184] The B block is a polymer having a glass transition temperature (Tg) of 100°C or higher and has a proton-accepting group.

[0185] The polymer includes a block copolymer having A-B-A type units in which the A block and the B block are covalently linked.

[0186] The B block bridges between the domains of the A block.

[0187] The proton-conducting membrane can be used at 100°C or higher.

[0188] The method for producing a proton-conducting membrane (2) includes a step of producing a polymer by subjecting an A block and a B block to RAFT polymerization using a reversible addition-fragmentation chain transfer (RAFT) agent.

[0189] The RAFT agent has two or more trithiocarbonate units, and a hydrocarbon group is present between the two or more trithiocarbonate units.

[0190] The RAFT agent is preferably at least one trithiocarbonate selected from the group consisting of 4-[(2-carboxyethylsulfanylthiocarbonyl)sulfanyl]-4-cyanopentanoic acid, 2-{[(2-carboxyethyl)sulfanylthiocarbonyl]sulfanyl}propanoic acid, 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoic acid, 2-[(dodecylsulfanylthiocarbonyl)sulfanyl]propanoic acid, 2-(dodecylthiocarbothioylthio)-2-methylpropanoic acid, methyl 2-(dodecylthiocarbothioylthio)-2-methylpropanoate, 2-(dodecylthiocarbothioylthio)propanoic acid, pentafluorophenyl 2-(dodecylthiocarbothioylthio)-2-methylpropanoate, 3-azido-1-propanol 2-(dodecylthiocarbothioylthio)-2-methylpropanoate, 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoic acid, methyl 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoate, N-hydroxysuccinimidyl 2-(dodecylthiocarbothioylthio)-2-methylpropanoate, 3-[[(benzylthio)carbonothioyl]thio]propanoic acid, 2-cyano-2-propyldodecyltrithiocarbonate, 4-cyano-4-(phenylcarbonothioylthio)pentanoic acid, cyanomethyl[3-(trimethoxysilyl)propyl]trithiocarbonate, 3-butenyl-2-(dodecylthiocarbothioylthio)-2-methylpropane, phthalimidomethylbutyltrithiocarbonate, 2-(2-alkoxyethylsulfanylthiocarbonylsulfanyl)propanoic acid, 4-((((2-carboxyethyl)thio)carbonothioyl)thio)-4-cyanopentanoic acid, 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanol, and cyanomethyldodecyltrithiocarbonate 1,4-phenylenebis(methylene)didodecylbis(carbonotrithioate), 1,4-phenylenebis(methylene)dibutylbis(carbonotrithioate), and 1,4-phenylenebis(methylene)dioctadecylbis(carbonotrithioate).

[0191] The A block is a polymer with a glass transition temperature (Tg) of 100 °C or higher, and aggregates with each other to form domains.

[0192] The A block is preferably a styrene-based polymer.

[0193] The B block has a proton-accepting group and is preferably a vinylpyridine-based polymer.

[0194] The polymer includes an A-B-A type block copolymer in which the A block and the B block are connected by a covalent bond.

[0195] The B block bridges between the domains of the A block.

[0196] Synthesis of the block copolymer The method for synthesizing the block copolymer having the A block and the B block is not particularly limited as long as it is an addition polymerization such as anionic polymerization, cationic polymerization, or radical polymerization.

[0197] The method for synthesizing the block copolymer having the A block and the B block preferably uses the following method.

[0198] Preferably, in the presence of a small amount of a polymerization initiator, a RAFT agent (reversible addition-fragmentation chain transfer agent) and a monomer constituting the A block (or B block) are polymerized, and then isolated and purified to synthesize a macro RAFT agent containing the A block (or B block).

[0199] Next, the block copolymer having the A block and the B block is synthesized by polymerizing the macro RAFT agent and the monomer constituting the B block (or A block) in the presence of a small amount of a polymerization initiator.

[0200] In the proton-conducting membrane of the present invention, preferably, the block copolymer having the A-B-A type unit is a block copolymer obtained by addition polymerization of monomers from one starting point or two or more starting points.

[0201] Polymerization initiator The polymerization initiator is preferably an azo radical polymerization initiator, a peroxide radical polymerization initiator, or the like.

[0202] Azo radical polymerization initiators: azobisisobutyronitrile (AIBN), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), dimethyl 2,2'-azobisisobutyrate, etc.

[0203] Peroxide radical polymerization initiators: benzoyl peroxide, t-butyl hydroperoxide, cumene hydroperoxide, etc.

[0204] The polymerization initiator is not limited to these.

[0205] RAFT agent (reversible addition-fragmentation chain transfer agent) In the proton-conducting membrane of the present invention, for example, the block copolymer having the A-B-A type unit is a polymer produced by RAFT polymerization of the A block and the B block using a reversible addition-fragmentation chain transfer (RAFT) agent.

[0206] In the proton-conducting membrane of the present invention, for example, the RAFT agent has one trithiocarbonate unit having one site where polymerization can proceed such that a monomer is inserted between a sulfur atom and an adjacent carbon atom, and by sequentially linking the A block, the B block, and the A block, a block copolymer having the A-B-A type unit is synthesized, or It has two or more trithiocarbonate units each having one site where polymerization can proceed such that a monomer is inserted between a sulfur atom and an adjacent carbon atom, a hydrocarbon group is present between the two or more trithiocarbonate units, and it has the above A-B-A type unit having a hydrocarbon group at the center, and a block copolymer is synthesized. It is a RAFT agent that does not contain a trithiocarbonate unit which is a residue of the RAFT agent except at the terminal of the block copolymer having the A-B-A type unit.

[0207] Having two sites where polymerization can proceed such that a monomer is inserted between a sulfur atom and an adjacent carbon atom Chemical structure of the RAFT agent having one trithiocarbonate unit R-S-C(=S)-S-R The R takes, for example, a chemical structure of the same functional group.

[0208] When using the RAFT agent, polymerization proceeds from two sulfur atoms of the trithiocarbonate unit to both sides, and a compound having the following structure is produced.

[0209] R-polymer-S-C(=S)-S-polymer-R A trithiocarbonate unit remains as a residue at the center of the polymer, and in a medium temperature range of about 100 °C to 150 °C, it tends not to withstand use as a proton conductive membrane.

[0210] Having one site where polymerization can proceed such that a monomer is inserted between a sulfur atom and an adjacent carbon atom RAFT agent having two (or more) trithiocarbonate units R1-S-C(=S)-S-R2-S-C(=S)-S-R3 The R1 and R3 preferably take a chemical structure of the same functional group.

[0211] When using the RAFT agent, polymerization does not proceed from the S adjacent to R1 and the S adjacent to R3, and a compound having the following structure is produced.

[0212] R1-S-C(=S)-S-polymer-R2-polymer-S-C(=S)-S-R3 The -S-C(=S)-S-R3 and R1-S-C(=S)-S- at the terminal part may peel off.

[0213] R2 is resistant to heat, acids, etc., is not strongly affected by the polymer, and can withstand use as a proton conduction membrane in a medium temperature range of about 100°C to 150°C.

[0214] The present invention is not limited to RAFT polymerization. Generally, a synthesis method in which a residue that is weak to heat, acids, etc. enters the central part of the polymer is not preferable. For example, when synthesizing by a coupling method, those having ester or ether sites are not preferable in the present invention.

[0215] Preferred RAFT agent Preferably, the RAFT agent includes thiocarbonylthio compounds such as dithioesters, dithiocarbamates, trithiocarbonates, and xanthates.

[0216] Preferably, the RAFT agent is bis(n-octylmercaptopropyl)disulfide, 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoic acid, 2-(dodecylthiocarbonothioylthio)-2-methylpropionic acid, S,S'-bis(α,α'-dimethyl-α''-acetic acid)trithiocarbonate, 2-cyano-2-propyl dodecyl trithiocarbonate, 4-cyano-4-(phenylcarbonothioylthio)pentanoic acid, cyanomethyl dodecyl trithiocarbonate, 2-cyano-2-propyl benzodithionate, 1,4-phenylene bis(methylene) didodecyl bis(carbonotrithioate), 1,4-phenylene bis(methylene) dibutyl bis(carbonotrithioate), and 1,4-phenylene bis(methylene) dioctadecyl bis(carbonotrithioate), etc.

[0217] The RAFT agent is not limited to these.

[0218] The RAFT agent is preferably at least one trithiocarbonate selected from the group consisting of 4-[(2-carboxyethylsulfanylthiocarbonyl)sulfanyl]-4-cyanopentanoic acid, 2-{[(2-carboxyethyl)sulfanylthiocarbonyl]sulfanyl}propanoic acid, 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoic acid, 2-[(dodecylsulfanylthiocarbonyl)sulfanyl]propanoic acid, 2-(dodecylthiocarbonothioylthio)-2-methylpropanoic acid, methyl 2-(dodecylthiocarbonothioylthio)-2-methylpropanoate, 2-(dodecylthiocarbonothioylthio)propanoic acid, pentafluorophenyl 2-(dodecylthiocarbonothioylthio)-2-methylpropanoate, 3-azido-1-propanol 2-(dodecylthiocarbonothioylthio)-2-methylpropanoate, 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoic acid, methyl 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoate, N-hydroxysuccinimidyl 2-(dodecylthiocarbonothioylthio)-2-methylpropanoate, 3-[[(benzylthio)carbonothioyl]thio]propanoic acid, 2-cyano-2-propyldodecyltrithiocarbonate, 4-cyano-4-(phenylcarbonothioylthio)pentanoic acid, cyanomethyl[3-(trimethoxysilyl)propyl]trithiocarbonate, 3-butenyl-2-(dodecylthiocarbonothioylthio)-2-methylpropane, phthalimidomethylbutyltrithiocarbonate, 2-(2-alkoxyethylsulfanylthiocarbonylsulfanyl)propanoic acid, 4-((((2-carboxyethyl)thio)carbonothioyl)thio)-4-cyanopentanoic acid, 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanol, and cyanomethyldodecyltrithiocarbonate, 1,4-phenylenebis(methylene)didodecylbis(carbonotrithioate), 1,4-phenylenebis(methylene)dibutylbis(carbonotrithioate), and 1,4-phenylenebis(methylene)dioctadecylbis(carbonotrithioate).

[0219] By appropriately selecting the RAFT agent, the sequence of the target block copolymer can be synthesized.

[0220] Average degree of polymerization of the A block and the B block The average degree of polymerization of the A block is not particularly limited.

[0221] The average degree of polymerization of the A block is preferably 2 or more, 10 or more, 30 or more, 50 or more, 100 or more, or 150 or more. If the average degree of polymerization of the A block is 2 or more, the A blocks tend to aggregate with each other to form domains at the use temperature of the proton conductive membrane.

[0222] The average degree of polymerization of the A block is preferably 2,000 or less, 1,000 or less, 800 or less, 500 or less, or 300 or less. If the average degree of polymerization of the A block is 10,000 or less, it is easy to handle as a sample.

[0223] For example, in the case of an A-B-A type triblock copolymer, the average degree of polymerization of the A block is the value of the total average degree of polymerization of the components of the A blocks included.

[0224] The average degree of polymerization of the B block is not particularly limited.

[0225] The average degree of polymerization of the B block is preferably 2 or more, 10 or more, 30 or more, 50 or more, 100 or more, 200 or more, 500 or more, 800 or more, 1,000 or more, 1,500 or more, or 2,000 or more. If the average degree of polymerization of the B block is 2 or more, it is easy to form a more uniform mixed phase when mixed with a plasticizer.

[0226] The average degree of polymerization of the B block is preferably 20,000 or less, 15,000 or less, 10,000 or less, 8,000 or less, 5,000 or less, or 4,000. If the average degree of polymerization of the B block is 20,000 or less, it is easy to adjust the acidity or basicity of the proton conductive membrane.

[0227] In the present invention, the average degree of polymerization can be determined by the 1H-NMR method.

[0228] Proton donor (plasticizer) The proton donor (plasticizer) contained in the proton conductive membrane of the present invention preferably contains a proton donating compound involved in proton transport, is well dissolved in the B block (second part) which is a polymer, and is sufficiently penetrated.

[0229] The proton donor (plasticizer) contained in the proton conductive membrane of the present invention preferably contains a proton donating compound having a pKa of 2.5 or less, 2.3 or less, 2.1 or less, 2.0 or less, 1.0 or less, 0.0 or less, -1.0 or less, or -2.0 or less. The proton donor (plasticizer) contains a proton donating compound having a high acidity and a compound having a high tendency to release protons.

[0230] In the present invention, pKa is the acid dissociation constant in water at 25°C, and for a compound that dissociates in multiple steps such as sulfuric acid or phosphoric acid, it is the value pKa1 in the first-step dissociation.

[0231] For example, the pKa of sulfuric acid is -3.0 and the pKa of phosphoric acid is 1.83 (Reference: "Chemical Handbook", 5th revised edition, The Chemical Society of Japan, pp. II-332-333, "Evans group pKa table, Harvard University").

[0232] The proton donating compound is preferably an organic acid such as sulfuric acid, phosphoric acid, ethanedisulfonic acid, or 4-hydroxybenzene-1,3-bis(sulfonic acid). The proton donating compound is more preferably one or more selected from sulfuric acid and phosphoric acid.

[0233] The proton donating compound preferably has a boiling point or decomposition temperature high enough not to volatilize or decompose at the use temperature of the proton conductive membrane. From this viewpoint, the boiling point or decomposition temperature of the proton donating compound is preferably above 120°C, 150°C or higher, or 200°C or higher.

[0234] The proton-donating compound contained in the proton donor is preferably one or more proton-donating compounds selected from the group consisting of sulfuric acid and phosphoric acid, and is sulfuric acid or phosphoric acid. The boiling point of sulfuric acid is about 290 °C (decomposition). The boiling point of phosphoric acid is about 213 °C (decomposition).

[0235] The proton donor (plasticizer) is preferably composed of only the proton-donating compound or is composed of the proton-donating compound and other plasticizers.

[0236] Preferably, a plasticizer having no other proton-donating property is used in combination. The plasticizer having no other proton-donating property is preferably polyalkylene glycol, polyvinyl ether, polyol ester, etc.

[0237] When the total mass of the plasticizer is 100 parts by mass, the usage ratio of the other plasticizer is preferably 50 parts by mass or less, 30 parts by mass or less, 10 parts by mass or less, 5 parts by mass or less, or 1 part by mass or less, or no other plasticizer is used at all.

[0238] In the present invention, the alkylene group is a concept including a methylene group, an alkylmethylene group, and a dialkylmethylene group.

[0239] Molar ratio of the proton-donating compound to the proton-accepting group The molar ratio of the proton-donating compound to the proton-accepting group (proton-donating compound / proton-accepting group) is not particularly limited.

[0240] The molar ratio of the proton-donating compound to the proton-accepting group (proton-donating compound / proton-accepting group) is preferably 1.0 or more, 1.1 or more, 1.3 or more, 1.4 or more, 1.5 or more, 1.6 or more, 1.7 or more, 1.8 or more, 1.9 or more, 2.0 or more, 2.1 or more, 2.2 or more, 2.3 or more, 2.4 or more, 2.5 or more, 2.6 or more, 2.7 or more, 2.8 or more, 2.9 or more, 3.0 or more, 3.1 or more, 3.4 or more, 3.5 or more, 3.6 or more, 3.7 or more, 3.8 or more, 3.9 or more, 4.0 or more, 4.1 or more, 4.2 or more, or 4.3 or more from the viewpoint of ensuring the function of the proton-donating compound as a plasticizer.

[0241] The upper limit of the molar ratio is not particularly limited. The upper limit of the molar ratio is preferably 10.0 or less, 9.0 or less, 8.5 or less, 8.0 or less, 7.5 or less, 7.0 or less, 6.5 or less, 6.0 or less, 5.5 or less, 5.0 or less, 4.5 or less, 4.4 or less, or 4.3 or less from the viewpoint of maintaining the film strength and ensuring the stability as a film.

[0242] Ratio of the block copolymer to the proton donor (plasticizer) From the viewpoint of enhancing the molecular mobility of the obtained proton-conducting film and obtaining sufficiently high proton conductivity, the usage ratio of the proton-donating agent (plasticizer) with respect to a total of 100 parts by mass of the block copolymer and the proton-donating agent (plasticizer) is preferably 50 parts by mass or more, 60 parts by mass or more, 65 parts by mass or more, 70 parts by mass or more, 75 parts by mass or more, or 80 parts by mass or more.

[0243] From the viewpoint of maintaining the film strength and ensuring the stability as a film, the usage ratio of the proton-donating agent (plasticizer) with respect to a total of 100 parts by mass of the block copolymer and the proton-donating agent (plasticizer) is 90 parts by mass or less, 85 parts by mass or less, 82 parts by mass or less, 80 parts by mass or less, 75 parts by mass or less, 70 parts by mass or less, or 65 parts by mass or less.

[0244] In the present invention, the total number of moles of protons that can be donated by a proton-donating agent (plasticizer), preferably a proton-donating compound having a pKa of 2.5 or less, is preferably greater than the total number of moles of protons that can be accepted by the proton-accepting group.

[0245] Properties of the proton conduction membrane Morphology of the proton conduction membrane The proton-conducting membrane of the present invention can be used at 100°C or higher, and in particular, can be used in a medium-temperature range of 100°C or higher and 150°C or lower. The proton-conducting membrane of the present invention is preferably an anhydrous proton-conducting membrane and can be suitably used in a fuel cell.

[0246] The proton-conducting membrane of the present invention is preferably a viscoelastic solid in the temperature range of 100°C or higher.

[0247] The viscoelastic solid is a solid having viscosity and elasticity, meaning a solid that does not exhibit fluidity and maintains its shape. A substance that is a viscoelastic solid has the property that when a stress is applied to cause a small deformation, the stress with respect to the deformation becomes maximum immediately after the deformation and decreases with the passage of time, but finally becomes a constant value that is not zero. A substance that is a viscoelastic solid has the property that when the stress that deforms it in that state is removed, the deformation becomes smaller and, in some cases, returns to its original shape.

[0248] In the proton-conducting membrane of the present invention, the proton-donating agent (plasticizer) contains a proton-donating compound and donates protons to become anionized. The proton-accepting group of the B block accepts protons to become cationized, whereby an electrostatic interaction acts between the proton-donating compound of the proton-donating agent (plasticizer) and the proton-accepting group of the B block, and the proton-donating compound as the proton-donating agent (plasticizer) remains in the proton-conducting membrane.

[0249] Due to the above action, the proton-conducting membrane as a whole can maintain a viscoelastic solid state.

[0250] Such a viscoelastic solid promotes molecular motion within the proton conduction membrane due to its characteristic mechanical properties (flexibility), and thereby promotes proton conductivity.

[0251] Thickness of the proton conduction membrane The proton conduction membrane of the present invention is excellent in formability and can be formed into a film by a hot melt method, a solvent casting method, etc. Therefore, it can be made thinner than conventional proton conduction membranes.

[0252] The film thickness of the proton conduction membrane of the present invention is preferably 1.00 mm or less, 0.90 mm or less, 0.80 mm or less, 0.75 mm or less, 0.73 mm or less, 0.72 mm or less, 0.71 mm or less, 0.70 mm or less, 0.68 mm or less, 0.65 mm or less, 0.60 mm or less, 0.55 mm or less, 0.50 mm or less, 0.45 mm or less, 0.40 mm or less, 0.35 mm or less, 0.30 mm or less, 0.28 mm or less, 0.25 mm or less, 0.23 mm or less, or 0.20 mm or less.

[0253] This film thickness is preferably 0.05 mm or more, or 0.10 mm or more.

[0254] Glass transition temperature of the proton conduction membrane The proton conduction membrane of the present invention contains a block copolymer and a proton donor (plasticizer), and thus exhibits high molecular mobility as a whole. The high molecular mobility of the proton conduction membrane can be evaluated by the fact that the glass transition temperature (Tg) is low.

[0255] In the proton conduction membrane of the present invention, along with the high molecular mobility of the introduced proton donor (plasticizer) itself, the glass transition temperature (Tg) of the mixture composed of the B block (the second part) and the proton donor (plasticizer) is low.

[0256] The proton conduction membrane of the present invention can maintain molecular mobility even at low temperatures, and thus can obtain high proton conductivity.

[0257] The glass transition temperature (Tg) of the proton-conducting membrane is preferably equal to or lower than the lower limit value of the operating temperature of the proton-conducting membrane, more preferably lower than room temperature, lower than 5°C, 2°C or lower, 0°C or lower, -20°C or lower, -40°C or lower, -60°C or lower, -65°C or lower, -70°C or lower, -75°C or lower, -80°C or lower, -84°C or lower, -85°C or lower, or lower than -85°C.

[0258] The glass transition temperature (Tg) of the present invention is a value obtained in accordance with JIS K 7121:2012 based on the DSC curve obtained by measuring at a heating rate of 10°C / min.

[0259] Proton conductivity of the proton conduction membrane The proton-conducting membrane of the present invention exhibits high proton conductivity in a low-humidity or anhydrous environment.

[0260] The proton conductivity of the proton-conducting membrane of the present invention is preferably 0.003 S / cm or higher, 0.0032 S / cm or higher, 0.005 S / cm or higher, 0.010 S / cm or higher, 0.014 S / cm or higher, 0.015 S / cm or higher, 0.030 S / cm or higher, 0.040 S / cm or higher, 0.050 S / cm or higher, 0.075 S / cm or higher, 0.080 S / cm or higher, 0.090 S / cm or higher, or 0.095 S / cm or higher in a low-humidity or anhydrous environment at 50°C.

[0261] The proton conductivity of the proton-conducting membrane of the present invention is preferably 0.010 S / cm or higher, 0.020 S / cm or higher, 0.030 S / cm or higher, 0.050 S / cm or higher, 0.075 S / cm or higher, 0.100 S / cm or higher, 0.125 S / cm or higher, 0.150 S / cm or higher, 0.175 S / cm or higher, or 0.200 S / cm or higher in a low-humidity or anhydrous environment at 120°C.

[0262] Water content of the proton conduction membrane The proton-conducting membrane of the present invention exhibits high proton conductivity even when it does not contain water in the membrane. When the total mass of the membrane is 100 parts by mass, the water content of the proton-conducting membrane is preferably 1 part by mass or less, 0.1 part by mass or less, 0.01 part by mass or less, or 0.001 part by mass or less.

[0263] Fabrication of the proton conduction membrane The proton-conducting membrane of the present invention can preferably be produced by introducing a proton donor (plasticizer) into a block copolymer. The introduction of the proton donor (plasticizer) into the block copolymer is not particularly limited.

[0264] The introduction of the proton donor (plasticizer) into the block copolymer is preferably carried out by the following steps (i) to (iv).

[0265] Step (i) (i) A step of dissolving or dispersing the block copolymer in a solvent to prepare a solution or dispersion of the block copolymer.

[0266] The solvent to be used is preferably a solvent that evaporates relatively easily, more preferably a volatile solvent. The solvent is preferably an alcohol-based solvent such as methanol or ethanol; an ether-based solvent such as dimethyl ether, diethyl ether, or tetrahydrofuran; an ester-based solvent such as ethyl acetate; a pyridine-based solvent such as pyridine; water, and a mixed solvent thereof, etc. The solvent is not limited to these.

[0267] Step (ii) (ii) A step of removing the solvent from the solution or dispersion of the block copolymer obtained in step (i) to form a block copolymer membrane.

[0268] The means for removing the solvent is not particularly limited. The means for removing the solvent is preferably evaporation at room temperature or by heating. Appropriately, operations such as drying are preferably added.

[0269] Step (iii) (iii) Dissolving or dispersing a proton donor (plasticizer) in a solvent to prepare a solution or dispersion of the proton donor (plasticizer).

[0270] The solvent used is preferably selected from polar solvents having a high affinity for the block copolymer and the proton donor (plasticizer) and being stable to strong acids. The solvent used is preferably a solvent that evaporates relatively easily. The solvent used is preferably an alcohol-based solvent such as water, methanol, ethanol; an ether-based solvent such as dimethyl ether, diethyl ether, tetrahydrofuran; etc. The solvent used is not limited to these.

[0271] The amount of the solvent used is preferably 500 parts by mass or more, 750 parts by mass or more, 1,000 parts by mass or more, 1,250 parts by mass or more, or 1,500 parts by mass or more with respect to a total of 100 parts by mass of the proton donor (plasticizer) and the block copolymer film obtained in step (ii).

[0272] The amount of the solvent used is preferably 5,000 parts by mass or less, 4,500 parts by mass or less, 4,000 parts by mass or less, 3,500 parts by mass or less, or 3,000 parts by mass or less with respect to a total of 100 parts by mass of the proton donor (plasticizer) and the block copolymer film obtained in step (ii).

[0273] Step (iv) (iv) Immersing the block copolymer film obtained in step (ii) in the solution or dispersion of the proton donor (plasticizer) prepared in step (iii), and removing the solvent to obtain the proton conductive film of the present invention.

[0274] The means for removing the solvent is not particularly limited. The means for removing the solvent is preferably evaporation at room temperature or by heating. Appropriate operations such as drying are added to the means for removing the solvent.

[0275] The proton-conducting membrane of the present invention is preferably formed into a film shape by a method such as a casting method or a pressing method before removing the solvent in the step (iv). Alternatively, after passing through the step (iv), it is preferably carried out by a method such as a hot melt method.

[0276] Preferred method for manufacturing a proton conduction membrane 1 (Figure 2) As a preferred first embodiment of the method for producing the proton-conducting membrane of the present invention, it is a method for producing an A-B-A type block polymer by a polymerization method in which no residue is contained other than the terminal portion of the polymer.

[0277] RAFT agent (reversible addition-fragmentation chain transfer agent): By using a RAFT agent, the molecular weight distribution can be narrowed and the control of the polymer terminal is easy. A RAFT agent having two or more trithiocarbonate units is used, and a hydrocarbon group that is chemically stable is provided between the two or more trithiocarbonate units.

[0278] It is not preferable that esters, ethers, amides, etc. are contained between the units.

[0279] The proton-conducting membrane of the present invention can be used at 100°C to 150°C.

[0280] Preferred method for manufacturing a proton conduction membrane 2 (Figure 3) As a preferred second embodiment of the method for producing the proton-conducting membrane of the present invention, it is a method for producing an A-B-A type block polymer by a polymerization method in which a copolymer having a glass transition temperature (Tg) of 100°C to 150°C is adopted for the A block and the B block.

[0281] Preferred A block: poly(4-tert-butylstyrene) (Tg: 150°C) Preferred B block: poly(2-vinylpyridine) (Tg: 100°C), poly(4-vinylpyridine) (Tg: 150°C) The proton-conducting membrane of the present invention can be used at 100°C to 150°C.

[0282] (3) Fuel cell The fuel cell of the present invention has the proton conductive membrane of the present invention.

[0283] The fuel cell of the present invention preferably has a laminate in which a fuel electrode side separator having a fuel flow path, a fuel electrode side catalyst layer, the proton conductive membrane of the present invention, an air electrode side catalyst layer, and an air electrode side separator having an air flow path are laminated in this order.

[0284] The fuel cell of the present invention preferably has a laminate in which a fuel electrode side separator having a fuel flow path, a fuel electrode side gas diffusion layer, a fuel electrode side catalyst layer, the proton conductive membrane of the present invention, an air electrode side catalyst layer, an air electrode side gas diffusion layer, and an air electrode side separator having an air flow path are laminated in this order.

Example

[0285] Hereinafter, the present invention will be described in detail in the form of examples.

[0286] The following examples do not limit the use of the present invention in any way.

[0287] (1) Example 1 Fabrication of the proton-conductive electrolyte membrane of Example 1 In Example 1, the following Scheme 1 was followed.

[0288] First step As an aba triblock copolymer in which a trithiocarbonate (S-C(=S)-S)) group, which is a RAFT agent residue, does not exist in the central part of the molecular chain but exists at both ends and has a glass transition temperature (Tg) higher than 100°C, poly(4-tert-butylstyrene)-b-poly(2-vinylpyridine)-b-poly(4-tert-butylstyrene) (hereinafter, also referred to as "BPB triblock copolymer") was synthesized.

[0289] Second step The proton-conductive electrolyte membrane of Example 1 was prepared by swelling the BPB triblock copolymer membrane (hereinafter also simply referred to as "BPB membrane") with sulfuric acid (H2SO4) (a proton donor (plasticizer)).

[0290] At both ends of BPB, B is an abbreviation of poly(4-tert-butylstyrene), and at the operating temperature of the proton-conductive electrolyte membrane, they aggregate with each other to form a glassy domain, which is the a block of the present invention. Also, the central P is an abbreviation of poly(2-vinylpyridine), which is the b block of the present invention.

[0291]

Chemical formula

[0292] (1-1) First step Step 1-1 The unpurified 2-vinylpyridine monomer was purified by passing it through a column filled with basic alumina.

[0293] Next, the purified 2-vinylpyridine monomer, RAFT agent, and azobisisobutyronitrile (AIBN) were weighed out in amounts of 49 g (0.47 mol), 187 mg (0.269 mmol), and 13 mg (0.073 mmol) respectively, and a solution was prepared by mixing them in a round-bottom flask with a cock.

[0294] Next, nitrogen gas was bubbled through for 55 minutes, and polymerization was carried out at 80 °C using an oil bath at normal pressure while stirring at 500 rpm.

[0295] After 2 hours, the polymerization reaction was completely stopped by immersing the flask in liquid nitrogen.

[0296] As the RAFT agent, 1,4-phenylenebis(methylene) didodecyl bis(carbonotrithioate) was used.

[0297] The molar ratio of the 2-vinylpyridine monomer to the RAFT agent was approximately 1730:1.

[0298] Chloroform (good solvent) was added to the reaction solution to prepare a polymer solution of approximately 8% by mass.

[0299] Subsequently, the polymer solution was dropped into approximately 1200 mL of hexane (poor solvent) to precipitate a powdery polymer (crude poly(2-vinylpyridine)).

[0300] Subsequently, the obtained polymer was separated by suction filtration and thoroughly dried by vacuum drying. Then, it was dissolved again in chloroform and dropped into hexane to precipitate the polymer.

[0301] The operation of precipitating the polymer was performed three times in total to remove unreacted monomers and low molecular weight oligomers, and purified poly(2-vinylpyridine) was obtained.

[0302] Subsequently, the purified poly(2-vinylpyridine) was dissolved in deuterated chloroform to prepare a solution of approximately 2% by mass, and the number-average degree of polymerization was determined by proton nuclear magnetic resonance spectroscopy ( 1 1H-NMR) method.

[0303] The number-average degree of polymerization was 1180, and the number-average molecular weight was approximately 120,000.

[0304] Subsequently, the purified polystyrene was dissolved in tetrahydrofuran (THF) to prepare a solution of approximately 0.3% by mass, and the molecular weight distribution (Mw / Mn) was determined by gel permeation chromatography (GPC). Standard polystyrene was used for molecular weight calibration.

[0305] As a result, Mw / Mn = 1.73. The eluent was THF, the flow rate was 1 mL / min, and the measurement was carried out with two TSK-GEL columns GMH HR -M connected in series manufactured by Tosoh Corporation.

[0306] Step 1-2 The purified poly(2-vinylpyridine) obtained in the above step 1-1 has RAFT agent residues introduced at both of its ends. Using this as a macro-RAFT agent (since it is a RAFT agent with a large molecular weight, it is called a "macro-RAFT agent"), polymerization with 4-tert-butylstyrene monomer was carried out.

[0307] The 4-tert-butylstyrene monomer was purified by mixing a hexane solution of n-butyl-sec-butylmagnesium (concentration 0.7 M) in a volume amount that is one-tenth of the monomer, stirring for about 1 hour, and then passing it through an alumina column.

[0308] Next, the purified 4-tert-butylstyrene monomer, macro-RAFT agent, AIBN, and N,N-dimethylformamide (DMF) were weighed out in amounts of 9.53 g (0.0595 mol), 10.0 g (0.0810 mmol), 1.4 mg (0.0081 mmol), and 9.4 g respectively, and a solution was prepared by mixing them in a round-bottom flask with a stopper.

[0309] Next, nitrogen gas was bubbled through for 25 minutes, and polymerization was carried out while stirring at 120 °C and 500 rpm using an oil bath at normal pressure.

[0310] After 4.5 hours, the polymerization reaction was completely stopped by immersing the flask in liquid nitrogen.

[0311] The molar ratio of the 4-tert-butylstyrene monomer to the macro-RAFT agent was approximately 735:1.

[0312] Chloroform was added to the reaction solution to prepare a polymer solution of approximately 8% by mass.

[0313] Next, the polymer solution was dropped into approximately 300 mL of acetonitrile to precipitate a powdery BPB triblock copolymer crude product.

[0314] Next, the obtained polymer was separated by decantation and dried sufficiently by vacuum drying. After that, it was dissolved again in chloroform and dropped into hexane to precipitate the polymer.

[0315] The operation of precipitating the polymer was carried out three times in total to remove unreacted monomers and low molecular weight oligomers, and a purified BPB triblock copolymer was obtained.

[0316] The purified BPB triblock copolymer of Example 1 is also referred to as BPB-1.

[0317] BPB-1 was dissolved in deuterated chloroform to prepare a solution of about 2% by mass, 1 and the average degree of polymerization was determined by the 1H-NMR method.

[0318] The average degree of polymerization of the total of the a-block (B-block) components was 227, the average degree of polymerization of the b-block (P-block) components was 1180, and the number average molecular weight of the whole was about 160,000.

[0319] The density of poly(4-tert-butylstyrene) is 0.94 g / cm 3 , and since the density of poly(2-vinylpyridine) is 1.14 g / cm3, the volume fraction of poly(4-tert-butylstyrene) in BPB-1 was 26%.

[0320] BPB-1 was dissolved in THF to prepare a solution of about 0.5% by mass, and when Mw / Mn was determined by GPC, Mw / Mn = 1.64. The eluent was THF, the flow rate was 1 mL / min, and the measurement was carried out with two TSK-GEL columns GMH HR -M manufactured by Tosoh Corporation connected in series.

[0321] (1-2) Second step About 1 g of the obtained BPB-1 was dissolved in about 10 g of a pyridine solvent.

[0322] Next, the solution was poured into a container made of perfluoroalkoxyalkane (hereinafter referred to as PFA) (inner diameter 4 cm), and left standing at 50 °C for about X days to evaporate the volatile solvent (pyridine).

[0323] Next, using a vacuum dryer, it was dried at 50 °C for about 1 day to completely remove the volatile solvent, and a BPB-1 film was obtained.

[0324] A solution prepared by dissolving 0.89 g of concentrated sulfuric acid (97%) in 20 mL of a mixed solvent of water and methanol (weight ratio 1:1) was poured into a PFA container (inner diameter 4 cm), and 269 mg of the BPB-1 film was immersed therein. It was left standing at 40 °C for about 2 days to evaporate the volatile solvents (water and methanol).

[0325] Thereafter, using a vacuum dryer, it was dried at 50 °C for about 2 days to completely remove the volatile solvent, and a BPB-1 / H2SO4 film (1.13 g, thickness 0.60 mm) obtained by swelling the BPB-1 film with H2SO4 (a proton donor (plasticizer)) was used as the proton-conductive electrolyte membrane of Example 1.

[0326] In the proton-conductive electrolyte membrane of Example 1, the weight ratio of BPB-1 to H2SO4 was 24:76, and the molar ratio of sulfuric acid to the pyridyl group (i.e., the pyridine ring group) was 4.3.

[0327] (1-3) Evaluation Measurement of the glass transition temperature (Tg) Regarding the sample of the proton-conductive electrolyte membrane of Example 1 obtained above, differential scanning calorimetry (DSC) measurement was performed in the temperature range of -85 °C to 200 °C under the condition of a heating rate of 10 °C / min in accordance with JIS K 7121:2012, and the DSC thermogram of Figure 5 was obtained, and two Tg values were observed.

[0328] One of the Tg values was -76 °C, which was lower than the operating temperature of the proton-conductive membrane (for example, in the range of room temperature or higher and 150 °C or lower), and this was considered to be derived from the mixed phase of the b block (P block) and H2SO4 (a proton donor (plasticizer)).

[0329] Another Tg is derived from the a-block (B-block) and is 148°C, which is higher than the operating temperature of the proton conduction membrane (e.g., a temperature of 150°C or lower).

[0330] Therefore, it was suggested that the proton-conductive electrolyte membrane of Example 1 can be used as a membrane even at a high temperature of 100°C or higher and 150°C or lower.

[0331] AC impedance measurement An AC impedance measurement was performed on a sample of the proton-conductive electrolyte membrane of Example 1 using a platinum mesh with a thickness of 0.1 mm as an electrode.

[0332] A sample of the proton-conductive electrolyte membrane of Example 1 cut into strip shape (thickness 0.58 mm, width 2.44 mm, length approximately 1 mm) was sandwiched between a pair of electrodes arranged opposite to each other with an electrode distance of 0.70 cm. The sample sandwiched between the electrodes was placed in a small environmental test chamber SH-242 (manufactured by Espec Corporation) and dried for 1 hour or more under the conditions of a temperature of 140°C and a relative humidity of substantially 0%RH.

[0333] A professional temperature and humidity meter testo635-2 (manufactured by Testo) was used to measure the temperature and relative humidity.

[0334] At a temperature of 125°C and a relative humidity of substantially 0%RH, using a potentiostat / galvanostat VSP-300 (manufactured by BioLogic), with a voltage of 50 mV and the frequency changed in the range from 10 6 Hz to 10 0 Hz, an AC impedance measurement was performed under non-humidified conditions.

[0335] At the point where the resistance value of the membrane was read from the intersection with the real axis in the Nyquist plot, it was 2.2×10 2 Ω.

[0336] The proton conductivity of the sample of this proton-conductive electrolyte membrane was determined by the following formula (1) and was 0.23 S / cm. This result represents a very high proton conductivity comparable to that of a humidified Nafion (registered trademark) membrane.

[0337] Proton conductivity = distance between electrodes / (thickness of membrane × width of membrane × resistance value) (1)

[0338] Next, when AC impedance measurement was performed under the measurement conditions of a temperature of 110°C and a relative humidity of substantially 0%RH, the resistance value in the frequency region where the absolute value of the resistance value became substantially constant was 2.6×10 2 Ω, and the proton conductivity was 0.19 S / cm.

[0339] When AC impedance measurement was performed under the measurement conditions of a temperature of 95°C and a relative humidity of substantially 0%RH, the resistance value in the frequency region where the absolute value of the resistance value became substantially constant was 3.1×10 2 Ω, and the proton conductivity was 0.16 S / cm.

[0340] When AC impedance measurement was performed under the measurement conditions of a temperature of 80°C and a relative humidity of substantially 0%RH, the resistance value in the frequency region where the absolute value of the resistance value became substantially constant was 4.0×10 2 Ω, and the proton conductivity was 0.12 S / cm.

[0341] When AC impedance measurement was performed under the measurement conditions of a temperature of 65°C and a relative humidity of substantially 0%RH, the resistance value in the frequency region where the absolute value of the resistance value became substantially constant was 5.3×10 2 Ω, and the proton conductivity was 0.092 S / cm.

[0342] When AC impedance measurement was performed under the measurement conditions of a temperature of 50°C and a relative humidity of substantially 0%RH, the resistance value in the frequency region where the absolute value of the resistance value became substantially constant was 7.5×10 2 Ω, and the proton conductivity was 0.066 S / cm.

[0343] The measurement conditions were set as follows: AC impedance measurement was carried out at a temperature of 35°C and a relative humidity of substantially 0%RH. The absolute value of the resistance was 1.1×10 3 Ω in the frequency range where the absolute value of the resistance became almost constant, and the proton conductivity was 0.043 S / cm.

[0344] The measurement conditions were set as follows: AC impedance measurement was carried out at a temperature of 20°C and a relative humidity of 2.9%RH. The absolute value of the resistance was 1.9×10 3 Ω in the frequency range where the absolute value of the resistance became almost constant, and the proton conductivity was 0.026 S / cm.

[0345] The measurement results of the proton conductivity of Example 1 are shown in Table 1 and Figure 4.

[0346] In Figure 4, it is represented by ● and a solid line.

[0347] The proton-conducting electrolyte membrane of Example 1 had a poly(4-tert-butylstyrene) component with a Tg of 100°C or higher, and yet, a tendency was observed that the proton conductivity increased with the increase in temperature. This is considered to be due to the fact that the molecular mobility of the proton-conducting mixed phase in the pseudo-fluid state increased with the increase in temperature, and as a result, the proton conductivity was improved.

[0348] (2) Example 2 In Example 2, the following Scheme 2 was followed.

[0349] First step A BPB triblock copolymer in which the trithiocarbonate (S-C(=S)-S)) group, which is the RAFT agent residue, does not exist in the central part of the molecular chain but exists only at one end was synthesized.

[0350] Second step The proton-conducting electrolyte membrane of Example 2 was prepared by swelling the BPB membrane with H2SO4.

[0351]

Chemical formula

[0352] (2-1) First step Step 1-1 The 4-tert-butylstyrene monomer, RAFT agent, azobisisobutyronitrile (AIBN), and diethylbenzene, which were purified in the same manner as in Step 1-2 of Example 1, were weighed out in amounts of 8.8 g (0.055 mol), 188 mg (0.516 mmol), 8.4 mg (0.0515 mmol), and 8.7 g, respectively, and a solution was prepared by mixing them in a round-bottom flask with a stopper.

[0353] Next, bubbling was carried out with nitrogen gas for 65 minutes, and polymerization was carried out at 130 °C using an oil bath under normal pressure while stirring at 500 rpm.

[0354] After 6 hours, the polymerization reaction was completely stopped by immersing the flask in liquid nitrogen.

[0355] As the RAFT agent, 2-(dodecylthiocarbonothioylthio)-2-methylpropanoic acid was used.

[0356] The molar ratio of the 4-tert-butylstyrene monomer to the RAFT agent was approximately 107:1.

[0357] The reaction solution was dropped into about 100 mL of solmix (poor solvent) to precipitate a powdery polymer (crude poly(4-tert-butylstyrene)).

[0358] The obtained polymer was separated by decantation, thoroughly dried by vacuum drying, then dissolved in chloroform (good solvent), and dropped into solmix to precipitate the polymer.

[0359] The operation of precipitating the polymer was carried out three times in total to remove unreacted monomers and low-molecular oligomers, and purified poly(4-tert-butylstyrene) was obtained.

[0360] In the same manner as in Example 1, 1 when H-NMR measurement and GPC measurement were carried out, it was found that the average degree of polymerization of this purified poly(4-tert-butylstyrene) was 71, the average molecular weight was about 11,000, and Mw / Mn was 1.4.

[0361] Step 1-2 In the purified poly(4-tert-butylstyrene) obtained in Step 1-1, a RAFT agent residue is introduced at its terminal end. Using this as a macro-RAFT agent, polymerization with a 2-vinylpyridine monomer was carried out.

[0362] 2-Vinylpyridine was purified in the same manner as in Step 1-1 of Example 1, and 14.6 g (0.139 mol), 0.792 g (0.0695 mmol), and 3.3 mg (0.021 mmol) of the purified 2-vinylpyridine monomer, macro-RAFT agent, and AIBN were weighed out respectively, and a solution was prepared by mixing them in a round-bottom flask with a cock.

[0363] Then, bubbling was carried out with nitrogen gas for 30 minutes, and polymerization was carried out while stirring at 80 °C and 500 rpm using an oil bath at normal pressure.

[0364] After 3.5 hours, the polymerization reaction was completely stopped by immersing the flask in liquid nitrogen.

[0365] The molar ratio of the 2-vinylpyridine monomer to the macro-RAFT agent was approximately 2000:1.

[0366] Chloroform was added to the reaction solution to prepare a polymer solution of about 8% by mass.

[0367] Next, the polymer solution was dropped into about 450 mL of acetonitrile to precipitate a crude product of poly(4-tert-butylstyrene)-b-poly(2-vinylpyridine) diblock copolymer (hereinafter also referred to as "BP diblock copolymer").

[0368] The obtained polymer was separated by decantation and thoroughly dried by vacuum drying. Then, it was dissolved in chloroform again and dropped into acetonitrile to precipitate the polymer.

[0369] The operation of precipitating the polymer was carried out three times in total to remove unreacted monomers and low-molecular oligomers, and a purified BP diblock copolymer was obtained.

[0370] This purified BP diblock copolymer is also referred to as "BP-1".

[0371] 1 At the place where 1H-NMR measurement and GPC measurement were carried out, the average degree of polymerization of the entire first a block (B block) component of BP-1 was 71, the average degree of polymerization of the second b block (P block) component was 818, the overall number-average molecular weight was about 97,000, and Mw / Mn = 1.8.

[0372] Step 1-3 In the purified BP-1 obtained in the above-described step 1-2, a RAFT agent residue is introduced at its end. As a macro-RAFT agent, polymerization with 4-tert-butylstyrene monomer was carried out again.

[0373] Using the macro-RAFT agent obtained in step 1-2 as the RAFT agent and using DMF and diethylbenzene as the solvents, 4-tert-butylstyrene was polymerized in the same manner as in step 1-1.

[0374] The molar ratio of 4-tert-butylstyrene monomer to the macro-RAFT agent was approximately 300:1.

[0375] The crude product was purified in the same manner as in step 1-2 to obtain a BPB triblock copolymer. The purified BPB triblock copolymer of Example 2 is also referred to as "BPB-2".

[0376] 1Where H-NMR measurement and GPC measurement were carried out, the average degree of polymerization of the entire a-block component of BPB-2 was 219, the average degree of polymerization of the b-block component was 818, the number-average molecular weight of the whole was about 121,000, and Mw / Mn = 1.8.

[0377] (2-2) Second step In the same manner as in Example 1, a BPB-2 film was swollen with H2SO4 to prepare a proton-conductive electrolyte membrane (also referred to as "BPB-2 / H2SO4 membrane", thickness 1.0 mm).

[0378] The weight ratio of BPB-2 to H2SO4 was 25:75, and the molar ratio of sulfuric acid to pyridyl groups was 4.5, obtaining almost the same results as in Example 1.

[0379] (2-3) Evaluation Measurement of the glass transition temperature Where DSC measurement of the proton-conductive electrolyte membrane was carried out in the same manner as in Example 1, the DSC thermogram of Fig. 5 was obtained, and Tg was observed at -84 °C and 151 °C.

[0380] The former (Tg at -84 °C) is lower than the use temperature of the proton-conductive membrane (for example, in the range of room temperature or higher and 150 °C or lower), and this is considered to be derived from the mixed phase of the b-block (P-block) and H2SO4.

[0381] The latter (Tg at 151 °C) is derived from the a-block (B-block) and was higher than the use temperature of the proton-conductive membrane (for example, a temperature of 140 °C or lower).

[0382] Therefore, it was suggested that the proton-conductive electrolyte membrane of Example 2 can be used as a membrane even at high temperatures of 100 °C or higher.

[0383] AC impedance measurement AC impedance measurement was carried out in the same manner as in Example 1, and the proton conductivity under non-humidified conditions was measured.

[0384] The measurement results of the proton conductivity of Example 2 are shown in Table 1 and Fig. 4.

[0385] In FIG. 4, it is represented by ■ and a broken line.

[0386] Under non-humidified conditions and in the temperature range of 20°C to 140°C, it was found that the proton conductive membrane of Example 2 exhibited a conductivity of 0.022 to 0.23 S / cm, showing a proton conductivity as high as that of the proton conductive electrolyte membrane of Example 1.

[0387] (3) Comparative Example 1 In Comparative Example 1, an attempt was made to prepare a proton conductive electrolyte membrane of Comparative Example 1 by swelling the diblock copolymer, BP-1, obtained in Step 1-2 of Example 2 with H2SO4.

[0388] The weight ratio of BPB-2 to H2SO4 was 21:79, and the molar ratio of sulfuric acid to pyridyl groups was 4.5, obtaining a mixing ratio almost equal to that of Example 1.

[0389] In the BPB triblock copolymer of Example 2, the molecular chains of the P block bridge between the isolated hard domains composed of the B component. However, in the BP diblock copolymer of Comparative Example 1, the molecular chains of the P block cannot bridge between the isolated hard domains composed of the B component, so it is considered that it cannot be used as a membrane at 100°C or higher.

[0390] (4) Comparative Example 2 In Comparative Example 2, the following Scheme 3 was followed.

[0391] Except for using a styrene monomer instead of a 4-tert-butylstyrene monomer, in substantially the same manner as in Example 1, a polystyrene-b-poly(2-vinylpyridine)-b-polystyrene (hereinafter, also referred to as "SPS triblock copolymer") in which the trithiocarbonate group, which is a RAFT agent residue, does not exist at the central part of the molecular chain but exists at both ends was synthesized (the total number average degree of polymerization of S is 307, the number average degree of polymerization of P is 1180, the total number average molecular weight is 155,000, Mw / Mn = 1.6, φ S = 22%, hereinafter, referred to as "SPS-1").

[0392] By swelling this SPS-1 film with H2SO4, the proton-conductive electrolyte membrane of Comparative Example 2 was prepared.

[0393] The weight ratio of SPS-1 to H2SO4 was 23:77, and the molar ratio of sulfuric acid to pyridyl groups was 4.4, and a molar ratio almost equal to that of Example 2 was obtained.

[0394] In the context of SPS, the Ss at both ends are abbreviations for polystyrene.

[0395]

Chemical formula

[0396] (4-1) Evaluation Measurement of the glass transition temperature When DSC measurement of the proton-conductive electrolyte membrane was performed in the same manner as in Example 1, the DSC thermogram of Fig. 6 was obtained, and Tg was observed at -83°C and 100°C.

[0397] Both are lower than the operating temperature of the proton-conductive membrane (for example, in the range of room temperature or higher and 150°C or lower).

[0398] The former (Tg of -83°C) is considered to be derived from the mixed phase of Block B and H2SO4.

[0399] The latter (Tg of 100°C) is considered to be derived from Block A.

[0400] It is considered that the proton-conductive electrolyte membrane of Comparative Example 2 cannot sufficiently maintain its membrane shape at high temperatures of 100°C or higher.

[0401] (5) Comparative Example 3 In Comparative Example 3, the following Scheme 4 was followed.

[0402] First step As an ABA triblock copolymer in which a trithiocarbonate group, which is a RAFT agent residue, is present in the central block of the molecular chain, polystyrene-b-poly(4-vinylpyridine)-b-polystyrene (hereinafter, also referred to as " 4 the "S

[0403] Second step S 4 PS triblock copolymer membrane" (simply also referred to as the "S 4 PS membrane").) was synthesized by swelling the PS triblock copolymer membrane with H2SO4 to prepare the proton conductive electrolyte membrane of Comparative Example 3.

[0404] S 4 In the context of S 4 PS, the central

[0405]

Chemical formula

[0406] (5-1) First step Step 1-1 The styrene monomer, RAFT agent, and azobisisobutyronitrile (AIBN) purified in the same manner as in Step 1-2 of Example 1 were weighed out at 9.1 g (0.088 mol), 136 mg (0.262 mmol), and 5.1 mg (0.0311 mmol), respectively, and a solution was prepared by mixing them in a round-bottom flask with a cock.

[0407] Then, bubbling was performed with nitrogen gas for 40 minutes, and polymerization was carried out at 130 °C and 500 rpm with stirring using an oil bath at normal pressure.

[0408] After 4 hours, the polymerization reaction was completely stopped by immersing the flask in liquid nitrogen.

[0409] As the RAFT agent, S,S'-bis(α,α'-dimethyl-α''-acetic acid) trithiocarbonate was used.

[0410] The molar ratio of the styrene monomer to the RAFT agent was approximately 333:1.

[0411] THF (good solvent) was added to the reaction solution to prepare a polymer solution of approximately 8% by mass.

[0412] The polymer solution was dropped into approximately 700 mL of methanol (poor solvent) to precipitate a powdery polymer (crude polystyrene).

[0413] The obtained polymer was separated by suction filtration and thoroughly dried by vacuum drying. Then, it was dissolved again in THF and dropped into methanol to precipitate the polymer.

[0414] The operation of precipitating the polymer was performed three times in total to remove unreacted monomers and low molecular weight oligomers, and purified polystyrene was obtained.

[0415] In the same manner as in Example 1 1 Where H-NMR measurement and GPC measurement were performed, it was found that the average degree of polymerization of this purified polystyrene was 149, the average molecular weight was approximately 15,000, and Mw / Mn was 1.2.

[0416] Step 1-2 The purified polystyrene obtained in Step 1-1 has a RAFT agent residue introduced at its terminal end. Using this as a macro RAFT agent, polymerization with 4-vinylpyridine monomer was carried out.

[0417] 4-Vinylpyridine was purified in the same manner as in Step 1-1 of Example 1. 39 g (0.37 mol), 0.917 g (0.0611 mmol), and 30.2 mg (0.184 mmol) of the purified 4-vinylpyridine monomer, macro RAFT agent, and AIBN were weighed out respectively and mixed in a round-bottom flask with a stopper to prepare a solution.

[0418] Then, bubbling was carried out with nitrogen gas for 40 minutes, and polymerization was carried out while stirring at 80 °C and 500 rpm using an oil bath at normal pressure.

[0419] After 40 minutes, the polymerization reaction was completely stopped by immersing the flask in liquid nitrogen.

[0420] The molar ratio of the 4-vinylpyridine monomer to the macro RAFT agent was approximately 5670:1.

[0421] Chloroform was added to the reaction solution to prepare a polymer solution of approximately 8% by mass.

[0422] This polymer solution was dropped into approximately 1500 mL of hexane to precipitate a crude purified S 4 PS triblock copolymer.

[0423] The obtained polymer was separated by suction filtration and sufficiently dried by vacuum drying. Then, it was dissolved again in chloroform and dropped into hexane to precipitate the polymer.

[0424] The operation of precipitating the polymer was carried out three times in total to remove unreacted monomers and low molecular weight oligomers, and a purified S 4 PS triblock copolymer was obtained.

[0425] The purified S 4 PS triblock copolymer of Comparative Example 3 is also referred to as "S 4 PS-1".

[0426] 1 Where H-NMR measurement and GPC measurement were carried out, the average degree of polymerization of the entire a-block (S-block) component of S 4 PS-1 was 149, the average degree of polymerization of the b-block ( 4 P-block) component was 1270, the number average molecular weight of the whole was about 149,000, and Mw / Mn = 1.7.

[0427] (5-2) Second step In the same manner as in Example 1, S4 The PS-1 membrane was swollen with H2SO4 to prepare a proton-conductive electrolyte membrane (also referred to as "S4PS-1 / H2SO4 membrane", with a thickness of about 0.7 mm).

[0428] S 4 The weight ratio of PS-1 to H2SO4 was 20:80, and the molar ratio of sulfuric acid to pyridyl groups was 4.9, obtaining almost the same as in Example 1.

[0429] (6) Tables 1 and 2

[0430]

Table 1

[0431]

Table 2

[0432] (7) Summary of the examples Example 1 is an example using a bifunctional RAFT agent.

[0433] Example 2 is a method for synthesizing an A-B-A triblock copolymer in three steps of A, B, and A sequentially. According to the method of Example 2, no degradable residues enter the central part of the polymer.

[0434] In the proton-conductive membrane of the present invention, the central part of the polymer does not have residues that are easily decomposed by heat, acid, etc., and the end block of the polymer has a glass transition temperature of about 150°C. The proton-conductive membrane of the present invention is a polymer electrolyte membrane composed of the triblock polymer of the polymer, and exhibits a high conductivity (~0.1 S / cm) in the medium temperature range (100°C to 150°C) under non-humidified conditions.

[0435] In the proton-conductive membrane of the present invention, the mid-block of the polymer has a basic group and is dissolved in a strongly acidic liquid electrolyte, and the end block of the polymer is not dissolved in the strongly acidic liquid electrolyte.

Claims

1. A proton conductive membrane comprising: a polymer and a proton donor; the polymer includes a block copolymer having A-B-A type units in which an A block and a B block are connected by a covalent bond; the A block is a polymer having a glass transition temperature (Tg) of 100 °C or higher, and aggregates with each other to form a hard domain; the B block has a proton accepting group and is swollen by the proton donor; the B block bridges between domains of the A block; the block copolymer having the A-B-A type units is a polymer produced by RAFT polymerization of the A block and the B block using a reversible addition-fragmentation chain transfer (RAFT) agent; the RAFT agent is: 4-[(2-carboxyethylsulfanylthiocarbonyl)sulfanyl]-4-cyanopentanoic acid, 2-{[(2-carboxyethyl)sulfanylthiocarbonyl]sulfanyl}propanoic acid, 2-[(dodecylsulfanylthiocarbonyl)sulfanyl]propanoic acid, methyl 2-(dodecylthiocarbonothioylthio)-2-methylpropionate, 2-(dodecylthiocarbonothioylthio)propanoic acid, 2-(dodecylthiocarbonothioylthio)-2-methylpropanoic acid, pentafluorophenyl 2-(dodecylthiocarbonothioylthio)-2-methylpropionate, 3-azido-1-propanol 2-(dodecylthiocarbonothioylthio)-2-methylpropionate, methyl 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoate, N-hydroxysuccinimidyl 2-(dodecylthiocarbonothioylthio)-2-methylpropionate, 3-[[(benzylthio)carbonothioyl thio]propanoic acid, cyanomethyl [3-(trimethoxysilyl)propyl]trithiocarbonate, 3-butenyl 2-(dodecylthiocarbonothioylthio)-2-methylpropane, phthalimidomethyl butyltrithiocarbonate, 2-(2-alkoxyethylsulfanylthiocarbonylsulfanyl)propanoic acid, 4-((((2-carboxyethyl)thio)carbonothioyl)thio)-4-cyanopentanoic acid, and 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanol; 1,4-Phenylenebis(methylene)didodecylbis(carbonotrithioate), 1,4-phenylenebis(methylene)dibutylbis(carbonotrithioate), and 1,4-phenylenebis(methylene)dioctadecylbis(carbonotrithioate); At least one trithiocarbonate selected from the group consisting of; A proton-conducting membrane that can be used at 100°C or higher.

2. The main chain of the block copolymer having the A-B-A type unit has no functional group that is easily decomposed by heat and no functional group that is easily decomposed by acid, except at the terminal portions. The proton-conducting membrane according to Claim 1.

3. The proton donor is a proton donor composed of at least one selected from the group consisting of sulfuric acid and phosphoric acid. The proton-conducting membrane according to Claim 1 or 2.

4. The A block is a block composed of at least one polymer selected from the group consisting of polystyrene-based polymers, polyacrylate-based polymers, polymethacrylate-based polymers, polyolefin-based polymers, polysulfone-based polymers, polyarylate-based polymers, polyetherketone-based polymers, polyetherimide-based polymers, polyphenylene sulfide-based polymers, polyphenylene ether-based polymers, polycarbonate-based polymers, polybenzimidazole-based polymers, and polyfluoroethylene-based polymers. The proton-conducting membrane according to any one of Claims 1 to 3.

5. The proton-accepting group possessed by the B block is a nitrogen-containing heterocyclic group. The proton-conducting membrane according to any one of Claims 1 to 3.

6. The nitrogen-containing heterocyclic group is at least one nitrogen-containing heterocyclic group selected from the group consisting of a pyridine ring group, an imidazole ring group, a pyrazole ring group, an imidazoline ring group, an oxazole ring group, a pyrimidine ring group, a pyrazine ring group, a triazole ring group, and a tetrazole ring group. The proton-conducting membrane according to Claim 5.

7. The repeating unit constituting the B block is a block composed of at least one monomer selected from the group consisting of vinyl-based monomers, ether-based monomers, ester-based monomers, amide-based monomers, and silicone-based monomers. The proton-conducting membrane according to any one of Claims 1 to 3.

8. The B block is a block composed of at least one polymer selected from the group consisting of a vinyl polymer having a pyridine ring, a vinyl polymer having an imidazole ring, a vinyl polymer having a pyrazole ring, a vinyl polymer having an imidazoline ring, a vinyl polymer having an oxazole ring, a vinyl polymer having a pyrimidine ring, a vinyl polymer having a pyrazine ring, a vinyl polymer having a triazole ring, and a vinyl polymer having a tetrazole ring. The proton-conducting membrane according to any one of claims 1 to 3.

9. The proton-conducting membrane according to any one of claims 1 to 8, which can be used in a medium temperature range of 100°C or higher and 150°C or lower.

10. A method for producing a proton-conducting membrane, wherein the proton-conducting membrane contains a polymer and a proton donor, including a step of producing a polymer by subjecting an A block and a B block to RAFT polymerization using a reversible addition-fragmentation chain transfer (RAFT) agent. The RAFT agent is 4-[(2-carboxyethylsulfanylthiocarbonyl)sulfanyl]-4-cyanopentanoic acid, 2-{[(2-carboxyethyl)sulfanylthiocarbonyl]sulfanyl}propanoic acid, 2-[(dodecylsulfanylthiocarbonyl)sulfanyl]propanoic acid, methyl 2-(dodecylthiocarbonothioylthio)-2-methylpropionate, 2-(dodecylthiocarbonothioylthio)propanoic acid, 2-(dodecylthiocarbonothioylthio)-2-methylpropanoic acid, 2-(dodecylthiocarbonothioylthio)-2-methylpropanoic acid pentafluorophenyl ester, 2-(dodecylthiocarbonothioylthio)-2-methylpropanoic acid 3-azido-1-propanol ester, methyl 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoate, 2-(dodecylthiocarbonothioylthio)-2-methylpropanoic acid N-hydroxysuccinimidyl, 3-[[(benzylthio)carbonothioyl Thiopropionic acid, cyanomethyl [3-(trimethoxysilyl)propyl] trithiocarbonate, 3-butenyl-2-(dodecylthiocarbonothioylthio)-2-methylpropane, phthalimidomethylbutyl trithiocarbonate, 2-(2-alkoxyethylsulfanylthiocarbonylsulfanyl)propionic acid, 4-((((2-carboxyethyl)thio)carbonothioyl)thio)-4-cyanopentanoic acid, and 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanol; At least one trithiocarbonate selected from the group consisting of 1,4-phenylenebis(methylene)didodecylbis(carbonotrithioate), 1,4-phenylenebis(methylene)dibutylbis(carbonotrithioate), and 1,4-phenylenebis(methylene)dioctadecylbis(carbonotrithioate); The A block is a polymer having a glass transition temperature (Tg) of 100°C or higher, and they aggregate with each other to form domains. The B block is a polymer having a glass transition temperature (Tg) of 100°C or higher and has a proton-accepting group. The polymer includes an ABA-type block copolymer in which the A block and the B block are covalently connected. The B block bridges between the domains of the A block. The proton-conducting membrane can be used at 100°C or higher. Method for producing a proton-conducting membrane. The method for producing a proton-conducting membrane according to claim 10, wherein the main chain of the block copolymer having the ABA-type unit does not have a functional group that is easily decomposed by heat or an acid, except at the terminal portions.

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