Proton conduction materials

Abstract

This disclosure provides a proton-conducting material that exhibits high proton conductivity even under non-humidified conditions and does not dissolve in water. The proton-conducting material comprises a polymer containing a proton source group and a polymer containing a proton channel, and at least one of the polymers containing the proton source group and the polymer containing the proton channel is a polymer containing an aromatic ring, at least a portion of which has a structure stacked by π-π interactions. Furthermore, the proton-conducting material comprises a polymer containing a proton source group and a proton channel, and the polymer containing the proton source group and the proton channel is a polymer having a main framework containing a proton source group and an aromatic ring and a cross-linked structure containing a proton channel, and at least a portion of which has a structure stacked by π-π interactions.

Description

Technical Field

[0001] This disclosure relates to a proton-conducting material that can be used in solid electrolyte membranes and the like for use in fuel cells. Background Technology

[0002] As solid electrolyte membranes used in fuel cells, perfluorosulfonic acid resin membranes such as Nafion (registered trademark, hereinafter the same) have traditionally been used. However, since the presence of water is essential for achieving high proton conductivity in perfluorosulfonic acid resin membranes, operation at temperatures below the boiling point of water (100°C) is required. Consequently, existing fuel cells using perfluorosulfonic acid resin membranes have incorporated humidification systems or temperature control systems to ensure adequate moisture levels, leading to issues related to the scaling up of fuel cell devices and increased costs.

[0003] In light of this situation, efforts have been made in recent years to develop a proton-conducting material that can be used under non-humidified conditions. For example, Patent Document 1 discloses an electrolyte membrane comprising a strong acid such as phosphoric acid and a basic polymer such as polybenzimidazole, which can be used under non-humidified conditions.

[0004] Furthermore, Patent Document 2 discloses a proton-conducting membrane comprising a block copolymer and a plasticizer as a non-volatile acidic substance, wherein the block copolymer has A blocks that aggregate with each other at the operating temperature to form structural domains and B blocks having proton-acceptable groups, and the B blocks bridge the structural domains.

[0005] On the other hand, as described in Patent Document 3, an ion conductor consisting of an inorganic porous membrane and an ionic liquid held on the inorganic porous membrane is also known as an electrolyte membrane that can be used under non-humidified conditions.

[0006] Prior technology documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2006-32275

[0009] Patent Document 2: Japanese Patent Application Publication No. 2020-68130

[0010] Patent Document 3: Japanese Patent Application Publication No. 2007-311311 Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] However, when the electrolyte membrane disclosed in Patent Documents 1 to 3 is used in a fuel cell, there is a problem that acid or ionic liquid will be released from the electrolyte membrane by generating water, which will make the operation of the fuel cell unstable and make the power generation performance easy to decrease.

[0013] This invention was made in view of the above-mentioned actual situation, and its main objective is to provide a proton-conducting material that has a high proton conductivity even under non-humidified conditions and does not dissolve in water.

[0014] Methods for solving problems

[0015] The proton-conducting material according to the first embodiment of this disclosure is characterized in that it contains a polymer containing a proton source group and a polymer containing a proton channel, and at least one of the polymers containing the proton source group and the polymers containing the proton channel is a polymer containing an aromatic ring, and at least a portion of the polymer containing the aromatic ring has a structure stacked by π-π interactions.

[0016] In the proton-conducting material according to the first embodiment of this disclosure, it may also be configured such that the polymer containing the proton source group contains at least one selected from styrene sulfonic acid polymers and perfluorosulfonic acid polymers.

[0017] In the proton-conducting material of the first embodiment of this disclosure, it may also be configured as a polymer containing at least one group selected from pyridyl, phenanthroline, and diazadibenzofuranyl as the polymer containing the proton channel.

[0018] In the proton-conducting material according to the first embodiment of this disclosure, it may also be configured to further contain polyethylene oxide as the polymer containing the proton channel.

[0019] The proton-conducting material according to the second embodiment of this disclosure is characterized in that it contains a polymer comprising a proton source group and a proton channel, wherein the polymer comprising the proton source group and the proton channel is a polymer having a main skeleton comprising a proton source group and an aromatic ring and a cross-linked structure comprising a proton channel, and at least a portion of the polymer comprising the proton source group and the proton channel has a structure formed by stacking through π-π interactions.

[0020] Invention Effects

[0021] According to this disclosure, a proton-conducting material that has high proton conductivity even under non-humidified conditions and does not dissolve in water can be provided. Attached Figure Description

[0022] Figure 1 A graph showing the proton conductivity at various temperatures is provided for comparison with the proton conduction membrane of Example 18 and the comparative conduction membrane of Comparative Example 2. Detailed Implementation

[0023] The proton-conducting material according to the first embodiment of this disclosure is characterized in that it contains a polymer containing a proton source group and a polymer containing a proton channel, and at least one of the polymers containing the proton source group and the polymers containing the proton channel is a polymer containing an aromatic ring, and at least a portion of the polymer containing the aromatic ring has a structure stacked by π-π interactions.

[0024] In the first embodiment of this disclosure, the polymer containing the proton source base is sometimes referred to as a "proton source polymer", and the polymer containing the proton channel is sometimes referred to as a "proton channel polymer".

[0025] The proton-conducting material according to the second embodiment of this disclosure is characterized in that it contains a polymer comprising a proton source group and a proton channel, wherein the polymer comprising the proton source group and the proton channel is a polymer having a main skeleton comprising a proton source group and an aromatic ring and a cross-linked structure comprising a proton channel, and at least a portion of the polymer comprising the proton source group and the proton channel has a structure formed by stacking through π-π interactions.

[0026] In the second embodiment of this disclosure, the polymer containing the proton source group and the proton channel is sometimes referred to as a "proton source crosslinked polymer".

[0027] Furthermore, the proton-conducting material involved in the second embodiment of this disclosure may further contain a polymer that contains a proton channel but does not contain a proton source group.

[0028] In the second embodiment of this disclosure, a polymer that contains a proton channel but does not contain a proton source group is sometimes referred to as a "proton channel polymer".

[0029] In either the first or second embodiment described above, the proton-conducting material of this disclosure exhibits high proton conductivity under non-humidified conditions. Because the proton-conducting material of this disclosure includes a proton source group that releases protons and a proton channel that coordinates protons, it exhibits proton conductivity even under non-humidified conditions.

[0030] In the first embodiment described above, the polymer formed by chemically bonding the proton source base or the proton channel has a structure that is stacked by π-π interactions, thereby forming a crystalline ordered structure in which protons can move easily. It is inferred that it has a conformation in which proton conduction pathways can be easily generated between the proton source base and the proton channel, and thus it is inferred that it has a high proton conductivity even under non-humidified conditions.

[0031] In the second embodiment described above, by giving the polymer having a main framework containing proton source groups and aromatic rings and a cross-linked structure containing proton channels a structure that is stacked by π-π interactions, a crystalline ordered structure in which protons can move easily is formed. It is inferred that the polymer has a conformation in which proton conduction pathways can be easily generated between the proton source groups in the main framework and the proton channels in the cross-linked structure. Therefore, it is inferred that the polymer has a high proton conductivity even under non-humidified conditions.

[0032] Furthermore, since in either the first or second embodiment described above, the proton source base and proton channel are chemically bonded to the polymer and thus do not dissolve in water, the proton-conducting material of this disclosure does not contain any components that dissolve in water. When the proton-conducting material of this disclosure is used in fuel cells or the like, since there is no dissolution relative to acids that generate water, the operation of the fuel cell is less likely to become unstable.

[0033] Furthermore, while the electrolyte membranes disclosed in Patent Documents 1 to 3 can be used under non-humidified conditions, they tend to exhibit decreased proton conductivity in the mid-to-low temperature range below 100°C, and the electrolyte membrane disclosed in Patent Document 2 is difficult to use in high-temperature ranges due to its low glass transition temperature. Therefore, when using the electrolyte membranes disclosed in Patent Documents 1 to 3, it is difficult to maintain high proton conductivity over a wide temperature range. In contrast, in the preferred embodiment of the proton-conducting material disclosed herein, high proton conductivity can be achieved over a wide temperature range under non-humidified conditions. Since the polymer structure is stabilized through π-π interactions or cross-linking, it is difficult for structural transfer of the polymer due to temperature changes to occur, thus indicating a high proton conductivity over a wide temperature range. When a proton-conducting membrane with high proton conductivity over a wide temperature range under non-humidified conditions is used in a fuel cell, the humidification system or temperature control system introduced into the fuel cell device can be further simplified or eliminated, thus achieving a revolutionary reduction in the cost of the fuel cell device.

[0034] Furthermore, in this disclosure, "no humidification" refers to an environment with a humidity level below 5% RH.

[0035] Furthermore, in this disclosure, the aromatic ring can be either an aromatic hydrocarbon ring or an aromatic heterocycle.

[0036] Furthermore, in this disclosure, the "~" in the numerical range refers to the range that includes the values ​​recorded before and after it as the lower limit and the upper limit.

[0037] The first and second embodiments of the proton-conducting material disclosed herein will be described in detail below.

[0038] First Implementation Method

[0039] The proton-conducting material involved in the first embodiment of this disclosure contains a proton source polymer and a proton channel polymer, and at least one of the proton source polymer and the proton channel polymer is a polymer containing an aromatic ring, and at least a portion of the polymer containing the aromatic ring has a structure stacked by π-π interactions.

[0040] In the first embodiment of this disclosure, the proton source polymer and the proton channel polymer are different polymers. The proton source polymer preferably does not contain a proton channel, and the proton channel polymer preferably does not contain a proton source group.

[0041] (Proton source polymer)

[0042] In this disclosure, the proton source group is not particularly limited to any group capable of releasing a proton. Examples of proton source groups include sulfonic acid groups (-SO3H), carboxyl groups (-COOH), hydroxyl groups (-OH), thiols (-SH), imidazole groups, and benzimidazole groups. Among these groups, sulfonic acid groups are preferred from the perspective of improving proton conductivity. As proton source groups that readily form a stacked structure realized by π-π interactions, proton source groups containing aromatic rings, such as imidazole groups and benzimidazole groups, are preferred, for example.

[0043] From the perspective of improving the proton conductivity of proton-conducting materials, the aforementioned proton-source polymer can also be a polymer in which the content of structural units derived from monomers containing proton source groups in 100 parts by mass of all structural units is preferably 90 parts by mass or more, more preferably 95 parts by mass or more, and is composed of structural units derived from monomers containing proton source groups.

[0044] The proton source polymer can be either a hydrocarbon organic polymer or a perfluorinated organic polymer. Furthermore, in this disclosure, the hydrocarbon organic polymer can also contain heteroatoms, and the perfluorinated organic polymer can also contain heteroatoms other than fluorine.

[0045] In proton-source hydrocarbon polymers, structural units derived from monomers containing proton-source groups include, for example, those derived from monomers such as 4-styrenesulfonic acid, 4-vinylbenzoic acid, 2-vinylbenzoic acid, 4-vinylphenol, 2-vinylphenol, 1-vinylimidazolium, 2-vinylimidazolium, 4-vinylimidazolium, 4-(1H-imidazol-1-yl)styrene, 2-vinyl-1H-benzimidazole, 1-vinyl-1H-benzimidazole, and 4-(1H-benzi[d]imidazol-1-yl)styrene. Furthermore, in this disclosure, structural units derived from styrenesulfonic acid also include substances hydrogenated after polymerization of salts such as sodium styrenesulfonate.

[0046] From the perspective of improving the proton conductivity of proton-conducting materials, styrene sulfonate polymers are preferred as hydrocarbon proton source polymers. In this disclosure, styrene sulfonate polymers refer to polymers containing structural units derived from styrene sulfonate.

[0047] The aforementioned styrene sulfonic acid polymer may also be a polystyrene sulfonic acid in which the content of structural units derived from styrene sulfonic acid in 100 parts by mass of all structural units is preferably 90 parts by mass or more, more preferably 95 parts by mass or more, and is composed of structural units derived from styrene sulfonic acid.

[0048] In the case where the above-mentioned styrene sulfonic acid polymers contain structural units derived from monomers other than styrene sulfonic acid, other monomers may include, for example, styrene, substituted styrene having substituents other than sulfonic acid groups, vinylfluorene, dibenzofuran, 4,5-diazabenzofuran, etc.

[0049] Although the number-average molecular weight Mn of the aforementioned styrene sulfonic acid polymers is not particularly limited, it is preferably 4,000 to 10,000, more preferably 5,000 to 9,000, and even more preferably 6,000 to 8,000. Because when the number-average molecular weight Mn of the aforementioned styrene sulfonic acid polymers is within the above range, proton source groups are easily aggregated and proton conduction pathways are readily generated, thus easily improving the proton conductivity of the proton-conducting material.

[0050] As a hydrocarbon proton source polymer that readily forms structures stacked through π-π interactions, a hydrocarbon proton source polymer containing an aromatic ring can be used, for example. Preferably, a polymer containing structural units derived from at least one selected from vinylimidazole, 4-(1H-imidazol-1-yl)styrene, and vinylbenzimidazole is used. The content of structural units derived from vinylimidazole, 4-(1H-imidazol-1-yl)styrene, or vinylbenzimidazole in this polymer is preferably 90 parts by mass or more, more preferably 95 parts by mass or more, and may also be 100 parts by mass out of 100 parts by mass of all structural units.

[0051] Although the number-average molecular weight Mn of the above-mentioned hydrocarbon proton source polymers containing aromatic rings is not particularly limited, it is preferably 1,000 to 100,000.

[0052] Perfluorinated proton source polymers are polymers composed of perfluorinated carbon containing proton source groups in the main chain or side chains, and may further contain heteroatoms. From the perspective of improving the proton conductivity of proton-conducting materials, it is preferable that the proton source groups are contained in the side chains.

[0053] From the perspective of improving the proton conductivity of proton-conducting materials, perfluoropolymers containing sulfonic acid groups are preferred as proton source polymers. More preferably, perfluorosulfonic acid polymers containing sulfonic acid groups in their side chains are preferred. Particularly preferred are perfluorosulfonic acid polymers having a main chain composed of perfluoroalkylene groups and side chains derived from perfluoroethylene ethers substituted with sulfonic acid groups. Examples of suitable perfluorosulfonic acid polymers include Nafion (registered trademark, manufactured by DuPont) and Aquivion (registered trademark, manufactured by Solvay). Nafion (registered trademark) is a copolymer of tetrafluoroethylene and perfluoro[2-(fluorosulfonylethoxy)propyl vinyl ether].

[0054] From the perspective of improving the proton conductivity of the proton-conducting material, the aforementioned proton source polymer preferably contains at least one selected from the aforementioned styrene sulfonic acid polymers and the aforementioned perfluorosulfonic acid polymers.

[0055] On the other hand, when the proton channel polymer contained in the proton conduction material does not contain an aromatic ring, the proton source polymer is preferably a proton source polymer that readily forms a stacked structure realized by π-π interactions. Preferably, it contains a polymer containing a structural unit derived from at least one of vinylimidazole, 4-(1H-imidazol-1-yl)styrene and vinylbenzimidazole.

[0056] (Proton channel polymer)

[0057] In this disclosure, the proton channel is not specifically limited to any structure capable of coordinating with a proton. Examples of structures that can serve as proton channels include pyridyl, phenanthroline, diazadibenzofuranyl, polyoxyalkylene, primary or secondary amino groups, amide groups, and amide bonds.

[0058] In these structures, the proton channel, which is easy to form a stacked structure realized by π-π interaction and easy to improve proton conductivity, is preferably at least one group selected from pyridyl, phenanthroline, and diazadibenzofuranyl, wherein more preferably, it is at least one group selected from 2-pyridyl, 1,10-phenanthroline, and 4,5-diazadibenzofuranyl.

[0059] Furthermore, in this disclosure, 1,10-phenanthrolinel refers to the group represented by the following chemical formula (1), and 4,5-diazadibenzofuranl refers to the group represented by the following chemical formula (2). Additionally, in chemical formulas (1) and (2), * represents a bond.

[0060] Chemical Formula 1

[0061]

[0062] From the perspective of improving the proton conductivity of proton-conducting materials, the aforementioned proton channel polymer can also be a polymer in which the content of structural units derived from monomers containing proton channels in 100 parts by mass of all structural units is preferably 90 parts by mass or more, more preferably 95 parts by mass or more, and is composed of structural units derived from monomers containing proton channels.

[0063] The aforementioned proton channel polymers can also be hydrocarbon organic polymers.

[0064] Among the aforementioned proton channel polymers, structural units derived from monomers containing proton channels include, for example, structural units derived from monomers such as 2-vinylpyridine, 4-vinylpyridine, polyethylene glycol diacrylate, and polyethylene glycol dimethacrylate, as well as 1,10-phenanthroline and 4,5-diazadibenzofuran.

[0065] As a proton channel polymer that readily forms a layered structure achieved through π-π interactions and readily improves the proton conductivity of proton-conducting materials, a proton channel polymer containing an aromatic ring can be used. Preferably, a polymer containing structural units derived from 2-vinylpyridine and at least one structural unit selected from 1,10-phenanthroline and 4,5-diazadibenzofurane is used. Preferably, at least one selected from poly(2-vinylpyridine), poly(1,10-phenanthroline), and poly(4,5-diazadibenzofurane) is used. Here, for each of poly(2-vinylpyridine), poly(1,10-phenanthroline), and poly(4,5-diazadibenzofurane), the content of the structural unit derived from 2-vinylpyridine, 1,10-phenanthroline, and 4,5-diazadibenzofurane should be at least 90 parts by mass of all structural units per 100 parts by mass, more preferably at least 95 parts by mass, and may also be 100 parts by mass.

[0066] In cases where poly(2-vinylpyridine), poly(1,10-phenanthroline), and poly(4,5-diazabenzifune) contain structural units derived from other monomers, such other monomers include, for example, styrene, substituted styrene, vinylfluorene, dibenzofune, 4,5-diazabenzifune, etc.

[0067] In addition, poly(1,10-phenanthroline) without other structural units is a polymer represented by the following chemical formula (1'), and poly(4,5-diazadibenzofuran) without other structural units is a polymer represented by the following chemical formula (2').

[0068] Chemical formula 2

[0069]

[0070] Although the number-average molecular weight Mn of poly(2-vinylpyridine) is not particularly limited, it is preferably 300 to 3000, more preferably 400 to 2500, and even more preferably 500 to 2000. Since the 2-pyridine groups are easily aggregated through π-π interactions when the number-average molecular weight Mn of poly(2-vinylpyridine) is within the above range, and proton conduction pathways are easily generated, it is easy to improve the proton conductivity of the proton-conducting material.

[0071] While the number-average molecular weight Mn of poly(1,10-phenanthroline) is not particularly limited, when the above-mentioned styrene sulfonic acid polymer is used as the proton source polymer, a molecular weight of 700 to 1500 is preferred, more preferably 800 to 1300, further preferably 900 to 1100, and especially preferably 1000. On the other hand, when the above-mentioned perfluorosulfonic acid polymer is used as the proton source polymer, a molecular weight of 7000 to 15000 is preferred, more preferably 8000 to 13000, further preferably 9000 to 11000, and especially preferably 10000. Since the number-average molecular weight Mn of poly(1,10-phenanthroline) is within the above range, the 1,10-phenanthroline groups are easily aggregated through π-π interactions, thereby easily generating proton conduction pathways, and thus easily improving the proton conductivity of the proton-conducting material.

[0072] In addition, poly(1,10-phenanthroline) can be synthesized, for example, with reference to W. Yang and T. Nakano, Chem. Commun., 2015, 51, pp. 17269-17272.

[0073] The number-average molecular weight (Mn) of poly(4,5-diazadibenzofuran) is preferably 800–2400, more preferably 1000–2000, even more preferably 1400–1800, and particularly preferably 1600. When the number-average molecular weight (Mn) of poly(4,5-diazadibenzofuran) is within the above range, the 4,5-diazadibenzofuran groups readily aggregate through π-π interactions, thereby easily generating proton conduction pathways. Therefore, it is easy to improve the proton conductivity of the proton-conducting material.

[0074] In addition, poly(4,5-diazadibenzofuran) can be synthesized, for example, with reference to the 63rd Annual Conference on Polymer Science (Publication No. 1Pa007).

[0075] Furthermore, as a proton channel polymer, polyepoxide is preferred from the perspective of improving the durability of proton conduction materials, and polyethylene oxide is even more preferred.

[0076] As a proton channel polymer, it is preferable to combine a proton channel polymer containing at least one group selected from pyridyl, phenanthrene-linyl, and diazadibenzofuranyl, with a polyepoxide, as a combination, from the perspective of improving both the proton conductivity and durability of the proton-conducting material. Based on the proton-conducting material with improved durability by including polyepoxide, a proton-conducting membrane with excellent flexibility can be provided, and large-area thin-film processing of the proton-conducting membrane can be achieved.

[0077] Furthermore, the proton-conducting material according to the first embodiment of this disclosure may be a proton-source polymer containing a polymer that forms a stacked structure realized by π-π interactions, or it may be a proton-channel polymer containing only polyoxyalkylene.

[0078] While the number-average molecular weight (Mn) of polyethylene oxide is not particularly limited, it is preferably 300 to 600,000, more preferably 500 to 550,000, and even more preferably 600 to 510,000. Regarding polyethylene oxide, when the number-average molecular weight (Mn) is above the lower limit mentioned above, it has a superior effect on improving the durability of the proton-conducting material, and when the number-average molecular weight (Mn) is below the upper limit mentioned above, it suppresses the decrease in the proton conductivity of the proton-conducting material.

[0079] In the first embodiment of this disclosure, preferred combinations for achieving particularly high proton conductivity in the combination of proton source polymer and proton channel polymer include, for example, combinations containing a styrene sulfonate polymer as the proton source polymer and poly(4,5-diazadibenzofuran) as the proton channel polymer; combinations containing a styrene sulfonate polymer as the proton source polymer and poly(2-vinylpyridine) as the proton channel polymer; combinations containing a styrene sulfonate polymer as the proton source polymer and poly(1,10-phenanthroline) with a number average molecular weight Mn of 900 to 1100 as the proton channel polymer; and combinations containing a perfluorosulfonate polymer as the proton source polymer and poly(1,10-phenanthroline) with a number average molecular weight Mn of 9000 to 11000 as the proton channel polymer. Among these combinations, the combination that is preferred because of its particularly high proton conductivity at high temperatures is one that contains a styrene sulfonic acid polymer as the proton source polymer and a poly(4,5-diazadibenzofuran) polymer as the proton channel polymer.

[0080] Furthermore, considering the high proton conductivity and excellent durability, among the preferred combinations described above, a combination containing polyethylene oxide as the proton polymer channel is further preferred. Specifically, considering the particularly high proton conductivity at high temperatures and the combination of high proton conductivity and excellent durability, a combination containing a styrene sulfonate polymer as the proton source polymer and poly(4,5-diazadibenzofuran) and polyethylene oxide as the proton channel polymer is preferred.

[0081] In the first embodiment of this disclosure, the mass ratio of the proton source polymer to the proton channel polymer is appropriately adjusted to improve proton conductivity according to the type of each polymer. Although not particularly limited, the content of the proton channel polymer is typically 1 to 15 parts by mass relative to 100 parts by mass of the proton source polymer, preferably 2 to 10 parts by mass. When the content of the proton channel polymer relative to the proton source polymer is within the above range, it is easy to achieve a conformation that facilitates the formation of a proton conduction path between the proton source group and the proton channel, thus easily improving proton conductivity.

[0082] In the case where the combination of a styrene sulfonic acid polymer as a proton source polymer and poly(4,5-diazadibenzofuran) as a proton channel polymer is present, the content of poly(4,5-diazadibenzofuran) relative to 100 parts by mass of the styrene sulfonic acid polymer is preferably 1 to 15 parts by mass, and more preferably 3 to 10 parts by mass.

[0083] In the case where the proton source polymer contains a styrene sulfonic acid polymer and the proton channel polymer contains poly(4,5-diazadibenzofuran), and further contains polyethylene oxide, the content of poly(4,5-diazadibenzofuran) is preferably 1 to 5 parts by mass, more preferably 2 to 4 parts by mass, and even more preferably 3 parts by mass, relative to 100 parts by mass of the styrene sulfonic acid polymer; and the content of polyethylene oxide is preferably 8 to 12 parts by mass, more preferably 9 to 11 parts by mass, and even more preferably 10 parts by mass.

[0084] In the case where the proton source polymer contains a styrene sulfonic acid polymer and the proton channel polymer contains poly(2-vinylpyridine), the content of poly(2-vinylpyridine) relative to 100 parts by mass of the styrene sulfonic acid polymer is preferably 8 to 12 parts by mass, more preferably 9 to 11 parts by mass, and even more preferably 10 parts by mass.

[0085] In the case where the proton source polymer contains a styrene sulfonic acid polymer and the proton channel polymer contains poly(1,10-phenanthroline) with a number average molecular weight Mn of 900 to 1100, the content of poly(1,10-phenanthroline) relative to 100 parts by mass of the styrene sulfonic acid polymer is preferably 1 to 5 parts by mass, more preferably 1 to 3 parts by mass, and even more preferably 2 parts by mass.

[0086] In the case where the proton channel polymer contains a perfluorosulfonic acid polymer and a poly(1,10-phenanthroline) with a number average molecular weight Mn of 9,000 to 11,000, the content of poly(1,10-phenanthroline) relative to 100 parts by mass of the perfluorosulfonic acid polymer is preferably 8 to 12 parts by mass, more preferably 9 to 11 parts by mass, and even more preferably 10 parts by mass.

[0087] Furthermore, when the proton source polymer contains at least one selected from styrene sulfonic acid polymers and perfluorosulfonic acid polymers, and the proton channel polymer contains at least one selected from poly(2-vinylpyridine) and poly(1,10-phenanthroline), and further contains a combination of polyethylene oxide, the content of polyethylene oxide relative to 100 parts by mass of the proton source polymer is preferably 8 to 12 parts by mass, more preferably 9 to 11 parts by mass, and even more preferably 10 parts by mass.

[0088] (Physical properties)

[0089] In the proton-conducting material according to the first embodiment of this disclosure, at least a portion of the polymer containing aromatic rings has a structure formed by stacking through π-π interactions.

[0090] The polymers in proton-conducting materials have a structure formed by stacking layers through π-π interactions, for example, enabling... 1 Confirmation can be made using H-NMR spectroscopy or ultraviolet absorption spectroscopy.

[0091] Specifically, the method described in T. Nakano and T. Yade, Journal of the American Chemical Society, 2003, 125, pp. 15474-15484 can be used.

[0092] In the proton-conducting material according to the first embodiment of this disclosure, the proton-conducting material can be configured such that, by containing at least one of the above-mentioned proton source polymer and proton channel polymer, which contains an aromatic ring and is prone to forming a structure stacked by π-π interactions, at least a portion of the polymer containing the aromatic ring has a structure stacked by π-π interactions.

[0093] The proton-conducting material according to the first embodiment of this disclosure can achieve a proton conductivity of 10 mS / cm or more in the thickness direction of the film-forming proton-conducting material at 25°C and without humidification, preferably 20 mS / cm or more, and more preferably 30 mS / cm or more.

[0094] The form of the proton-conducting material involved in the first embodiment of this disclosure is not particularly limited; for example, it can also be in the form of a film, that is, it can also be a proton-conducting membrane. The proton-conducting membrane can, for example, be used as a solid electrolyte membrane in a fuel cell.

[0095] Although the thickness of the proton conduction membrane is appropriately adjusted according to the application and is not particularly limited, it can be set to, for example, 0.1 to 5.0 mm.

[0096] (Manufacturing method)

[0097] The method for manufacturing the proton-conducting material according to the first embodiment of this disclosure is not particularly limited as long as it is a method that can obtain the proton-conducting material described above. For example, the proton-conducting material according to the first embodiment of this disclosure can be manufactured by a method that includes a step of obtaining a mixture containing a proton source polymer, a proton channel polymer, and a solvent, and a step of removing the solvent from the mixture.

[0098] The solvent used in the above mixture is appropriately selected according to the type of polymer and is not particularly limited. For example, water, organic solvents, or mixtures thereof can be used. The above mixture can be obtained, for example, by mixing a solution obtained by dissolving a proton source polymer in a solvent and a solution obtained by dissolving a proton channel polymer in a solvent. In this case, it is preferable to select the solvent in a way that ensures uniform mixing of these solutions; for example, water, alcohol, or mixtures thereof are preferred. Methanol is typically used as an alcohol.

[0099] When the proton-conducting material is in the form of a film, in the process of removing the solvent from the above-mentioned mixture, for example, the mixture can be dried into a film by using a drop casting method, thereby producing a film-shaped proton-conducting material.

[0100] The method for removing solvent from the above mixture is not particularly limited. For example, the solvent can also be removed by drying at room temperature or, for example, on a hot plate set to 60°C in air.

[0101] Second Implementation Method

[0102] The proton-conducting material according to the second embodiment of this disclosure contains a proton-source crosslinked polymer. The proton-source crosslinked polymer is a polymer having a main framework containing a proton source group and an aromatic ring, and a crosslinked structure containing a proton channel. At least a portion of the proton-source crosslinked polymer has a structure formed by stacking through π-π interactions.

[0103] The aforementioned proton-source crosslinked polymer is inferred to be crosslinked by using a crosslinked structure containing proton channels to crosslink the main framework containing the proton source group and the aromatic ring, and has a three-dimensional structure, thereby easily forming a structure that is stacked by utilizing π-π interactions.

[0104] As described above, the proton-conducting material according to the second embodiment of this disclosure exhibits high proton conductivity even under non-humidified conditions. Furthermore, the proton-conducting material according to the second embodiment of this disclosure maintains excellent durability by giving the proton source crosslinked polymer a crosslinked structure. Therefore, the proton-conducting material according to the second embodiment of this disclosure provides a proton-conducting membrane that exhibits both high proton conductivity and excellent durability, and maintains high proton conductivity for a longer period due to suppression of degradation over time. Moreover, the proton-conducting material according to the second embodiment of this disclosure has excellent flexibility, enabling the large-area thin-film fabrication of the proton-conducting membrane.

[0105] (Proton-source cross-linked polymer)

[0106] In the second embodiment of this disclosure, the proton source crosslinking polymer used is a polymer having a main framework comprising a proton source group and an aromatic ring, and a crosslinking structure comprising a proton channel; it may also be a hydrocarbon organic polymer. Regarding the proton source group, as in the first embodiment described above, the proton source group preferred in the first embodiment is also preferred in the second embodiment.

[0107] From the perspective of improving the proton conductivity of proton-conducting materials, the aforementioned proton-source crosslinked polymer can also be such that, in 100 parts by mass of all structural units of the main framework, the content of structural units derived from monomers containing proton source groups is preferably 90 parts by mass or more, more preferably 95 parts by mass or more, and the main framework is a polymer framework composed of structural units derived from monomers containing proton source groups.

[0108] Furthermore, based on the fact that it is easy to form a structure that is stacked through π-π interactions and easy to improve the proton conductivity of the proton-conducting material, the above-mentioned proton-source crosslinked polymer can also be such that, in 100 parts by mass of all structural units of the main framework, the content of structural units derived from monomers containing proton source groups and aromatic rings is preferably 90 parts by mass or more, more preferably 95 parts by mass or more, and the main framework is a polymer framework composed of structural units derived from monomers containing proton source groups and aromatic rings.

[0109] Furthermore, in the second embodiment of this disclosure, the mass of the main backbone and the mass of the cross-linked structure in the proton-source cross-linked polymer are respectively derived from the mass of the structure of the compound forming the main backbone and the mass of the structure of the compound forming the cross-linked structure, and can be calculated based on the mass of each compound used in the synthesis of the polymer.

[0110] In the aforementioned proton-source crosslinked polymers, structural units that are part of the main backbone and originate from monomers containing proton source groups and aromatic rings can be listed as structural units derived from monomers such as 4-styrenesulfonic acid, 4-vinylbenzoic acid, 2-vinylbenzoic acid, 4-vinylphenol, 2-vinylphenol, 1-vinylimidazole, 2-vinylimidazole, 4-vinylimidazole, 4-(1H-imidazol-1-yl)styrene, 2-vinyl-1H-benzimidazole, and 1-vinyl-1H-benzimidazole.

[0111] From the perspective that it is easy to form a structure stacked through π-π interactions and to easily improve the proton conductivity of the proton-conducting material, a backbone derived from a styrene sulfonic acid polymer is preferred. In the second embodiment, the preferred manner for the styrene sulfonic acid polymer that forms the backbone, including the content of structural units derived from styrene sulfonic acid and the number-average molecular weight, is the same as that used in the first embodiment described above.

[0112] The cross-linked structure of proton-source cross-linked polymers is a cross-linked structure containing proton channels. This cross-linked structure can be formed through covalent bonds, through intermolecular forces other than covalent bonds, or through a known cross-linking agent. Examples of intermolecular forces other than covalent bonds include van der Waals forces, charge-movement forces, Coulomb forces, hydrophobic bonds, hydrogen bonds, ionic bonds, coordination bonds, or combinations thereof.

[0113] As a structure that forms the proton channel included in the above-described crosslinking structure, for example, the same structure as that described in the first embodiment above can be listed, wherein preferably, at least one selected from primary or secondary amino groups, amide groups, and amide bonds.

[0114] The aforementioned crosslinked structure can also be a crosslinked structure formed by a crosslinking agent containing proton channels. Although the crosslinking agent used in forming the aforementioned crosslinked structure only needs to contain at least one structure that serves as a proton channel, from the point of view of improving proton conductivity, it is preferable to contain a structure that serves as a proton channel or more, and more preferably a structure that serves as a proton channel.

[0115] Although the aforementioned cross-linked structure formed by covalent bonds is not particularly limited, cross-linked structures formed by cross-linking agents such as N,N'-methylenebisacrylamide are preferred, for example.

[0116] The aforementioned cross-linked structure, formed by covalent bonds, can be formed by copolymerizing the monomer or macromonomer that forms the main framework with a cross-linking agent. Although the copolymer obtained by the above copolymerization can be any of random copolymers, block copolymers, and graft copolymers, random copolymers are preferred from the perspective of improving proton conductivity.

[0117] Furthermore, when a water-soluble crosslinking agent such as N,N'-methylenebisacrylamide is used as the crosslinking agent to form the aforementioned crosslinking structure, for example, hydrogenation can be carried out after copolymerizing a salt such as sodium styrene sulfonate with the water-soluble crosslinking agent in water, thereby obtaining a proton-source crosslinked polymer in which a crosslinking structure derived from a water-soluble crosslinking agent is introduced into the main backbone derived from a styrene sulfonic acid polymer. Since sodium styrene sulfonate has higher polymerizability than styrene sulfonic acid, it is easier to form a main backbone of the desired molecular weight by using sodium styrene sulfonate in the polymerization reaction.

[0118] Even among water-soluble crosslinking agents, N,N'-methylenebisacrylamide is particularly preferred from the perspective of easily improving the proton conductivity and durability of proton-conducting materials.

[0119] Of the aforementioned cross-linked structures formed by intermolecular forces other than covalent bonds, those formed by hydrogen bonding are preferred. Examples of cross-linked structures containing proton channels and formed by hydrogen bonding include cross-linked structures derived from diamino compounds such as alkylene diamines having 1 to 6 carbon atoms, such as 1,6-diaminohexane (DAH) and 1,2-ethylenediamine (DAE). Cross-linked structures derived from diamino compounds can be formed, for example, by mixing a polymer that will serve as the main backbone with a diamino compound in solution.

[0120] Although the molecular weight of the crosslinking agent used in the formation of the above crosslinking structure is not particularly limited, it is preferably 30 to 300, more preferably 50 to 200, and even more preferably 60 to 160, from the point of view that it is easy to improve the proton conductivity and durability of the proton-conducting material.

[0121] Furthermore, from the perspective of easily improving the proton conductivity and durability of the proton-conducting material, it is preferable that the above-mentioned crosslinked structure has proton channels at both ends of the straight-chain alkylene groups.

[0122] The number of carbon atoms in the aforementioned straight-chain alkylene groups is preferably 1 to 10, and more preferably 1 to 6.

[0123] As for the aforementioned proton-source crosslinked polymers, from the perspective of obtaining proton-conducting materials with high proton conductivity and excellent durability, polymers having a main framework derived from styrene sulfonate polymers and a crosslinking structure derived from N,N'-methylenebisacrylamide, polymers having a main framework derived from styrene sulfonate polymers and a crosslinking structure derived from 1,6-diaminohexane, and polymers having a main framework derived from styrene sulfonate polymers and a crosslinking structure derived from 1,2-ethylenediamine are preferred. Among these, from the perspective of obtaining particularly high proton conductivity over a wide temperature range, polymers having a main framework derived from styrene sulfonate polymers and a crosslinking structure derived from N,N'-methylenebisacrylamide are more preferred.

[0124] In the above-mentioned proton source crosslinked polymer, the content of the crosslinked structure is appropriately adjusted in a way that improves the proton conductivity of the proton-conducting material. Although not particularly limited, it is usually 1 to 15 parts by mass relative to 100 parts by mass of the main skeleton, preferably 1 to 10 parts by mass.

[0125] When the content of the cross-linked structure containing proton channels relative to the main skeleton containing proton source groups and aromatic rings is within the above range, it is easy to form a conformation that easily generates proton conduction pathways between proton source groups and proton channels, thus easily improving proton conductivity.

[0126] In the polymer having a main backbone derived from styrene sulfonic acid polymers and a crosslinking structure derived from N,N'-methylenebisacrylamide, the content of the crosslinking structure relative to 100 parts by mass of the main backbone is preferably 1 to 7 parts by mass, and more preferably 1 to 5 parts by mass.

[0127] In a polymer having a backbone derived from styrene sulfonic acid polymers and a crosslinked structure derived from 1,6-diaminohexane, 1 to 7 parts by mass are preferred, and more preferably 1 to 5 parts by mass.

[0128] In polymers having a backbone derived from styrene sulfonic acid polymers and a crosslinking structure derived from 1,2-ethylenediamine, 1 to 7 parts by mass are preferred, and more preferably 3 to 5 parts by mass.

[0129] (Proton channel polymer)

[0130] The proton-conducting material according to the second embodiment of this disclosure may also contain a proton channel polymer. Furthermore, the proton channel polymer used in the second embodiment preferably does not contain a proton source group. Examples of proton channel polymers used in the second embodiment include those identical to those used in the first embodiment described above. Preferably, the proton channel polymer used in the second embodiment is selected from at least one of poly(2-vinylpyridine), poly(1,10-phenanthroline), and poly(4,5-diazadibenzofuran), with poly(4,5-diazadibenzofuran) being more preferred.

[0131] In the second embodiment, the preferred number-average molecular weight Mn of poly(2-vinylpyridine), poly(1,10-phenanthroline), and poly(4,5-diazadibenzofuran) is the same as that of the first embodiment described above.

[0132] In the case where the proton-conducting material according to the second embodiment of this disclosure also contains a proton channel polymer, the content of the proton channel polymer is usually 1 to 10 parts by mass relative to 100 parts by mass of the main skeleton containing the above-mentioned proton source group and aromatic ring, preferably 1 to 5 parts by mass.

[0133] (Physical properties)

[0134] In the proton-conducting material according to the second embodiment of this disclosure, at least a portion of the aforementioned proton source crosslinked polymer has a structure formed by stacking through π-π interactions. This situation, where the polymers in the proton-conducting material have a structure formed by stacking through π-π interactions, can be confirmed by the same method as in the first embodiment described above.

[0135] The proton-conducting material according to the second embodiment of this disclosure can achieve a proton conductivity of 10 mS / cm or more in the thickness direction of the film-forming proton-conducting material at 25°C and without humidification, preferably 20 mS / cm or more, and more preferably 30 mS / cm or more.

[0136] The morphology of the proton-conducting material involved in the second embodiment of this disclosure is the same as that in the first embodiment described above.

[0137] (Manufacturing method)

[0138] The method for manufacturing the proton-conducting material according to the second embodiment of this disclosure is not particularly limited as long as it is a method that can obtain the above-mentioned proton-conducting material.

[0139] As a method for manufacturing a proton-conducting material containing a main framework having a proton source group and an aromatic ring and a cross-linked structure having a proton channel formed by covalent bonds, for example, the following method can be listed: copolymerizing a monomer or macromonomer forming the main framework with a cross-linking agent, and then hydrogenating it as needed to obtain a proton-source cross-linked polymer, and shaping the obtained proton-source cross-linked polymer into a desired shape.

[0140] Although the above copolymerization can be any of random copolymerization, block copolymerization, and graft copolymerization, random copolymerization is preferred from the perspective of easily obtaining proton-source crosslinked polymers with high proton conductivity.

[0141] As a method for manufacturing a proton-conducting material containing a polymer having a main framework comprising a proton source group and an aromatic ring and a cross-linked structure comprising a proton channel formed by intermolecular forces other than covalent bonds, a method can be listed as follows: a proton-source cross-linked polymer is obtained by adding a cross-linking agent that forms the cross-linked structure to a solution formed by dissolving the polymer that will become the main framework and mixing the solution; and a mixture of the obtained proton-source cross-linked polymer, a proton channel polymer added as needed, and a solvent is prepared, thereby removing the solvent from the mixture.

[0142] Here, the mixture can also be a solution obtained by simply dissolving the proton source cross-linked polymer in a solvent.

[0143] The solvent used in the above mixture is appropriately selected according to the type of polymer or crosslinking agent and is not particularly limited. For example, water, organic solvents, or mixtures thereof can be used. The above mixture can be obtained, for example, by mixing a solution obtained by dissolving a proton source crosslinking polymer in a solvent and a solution obtained by dissolving a proton channel polymer in a solvent. In this case, it is preferable to select the solvent in a way that ensures uniform mixing of these solutions; for example, water, alcohol, or mixtures thereof are preferred. Methanol is typically used as an alcohol.

[0144] The method for removing the solvent from the mixture and the method for forming it into a film are the same as the method for manufacturing the proton-conducting material described in the first embodiment above.

[0145]

Example

[0146] The present disclosure is further described below by way of examples, but the present disclosure is not limited to the manner of these examples.

[0147] In addition, the thickness of the proton conduction membranes obtained in the various embodiments and the comparative conduction membranes obtained in the various comparative examples were measured using a micrometer (Mitutoyo Corp., model: CLM1-15QM).

[0148] [Comparative Example 1]

[0149] A comparative conductive film of Comparative Example 1 with film thicknesses shown in Table 1 was obtained by drop casting a solution of polystyrene sulfonic acid (Mn7000) onto a stainless steel electrode with a diameter of 5 mm.

[0150] [Example 1]

[0151] A water-alcohol solution obtained by dissolving polystyrene sulfonic acid (Mn7000) and a methanol solution obtained by dissolving poly(4,5-diazadibenzofuran) (Mn1600) were mixed in the amounts shown in Table 1, with the mass ratio of polystyrene sulfonic acid to poly(4,5-diazadibenzofuran) as indicated. The resulting mixture was then drop-cast onto a 5 mm diameter stainless steel electrode to form a film, thereby obtaining the proton-conducting membrane of Example 1 with the film thickness shown in Table 1.

[0152] [Examples 2-5]

[0153] Except that in Example 1, the proton-conducting membranes of Examples 2 to 5 were obtained in the same manner as in Example 1, except that the proton channel polymers shown in Table 1 were used instead of poly(4,5-diazadibenzofuran), and the amount of each solution added was varied as needed in such a way as the mass ratio of polystyrene sulfonic acid to proton channel polymers was the value shown in Table 1.

[0154] [Comparative Example 2]

[0155] The Nafion membrane (product name: NR212, manufactured by Chemours, membrane thickness 0.31 mm), which is a perfluorosulfonic acid resin, was used as the comparative conductive membrane of Comparative Example 2.

[0156] [Example 6]

[0157] A suspension of Nafion and an aqueous-alcohol solution containing dissolved poly(1,10-phenanthroline) (Mn10000) were mixed in the amounts shown in Table 1 at a Nafion to poly(1,10-phenanthroline) mass ratio, thereby obtaining a mixture. Using the obtained mixture, the proton-conducting membrane of Example 6 with the membrane thickness shown in Table 1 was obtained by the same method as in Example 1.

[0158] [Example 7]

[0159] A water-alcohol solution obtained by dissolving polystyrene sulfonic acid (Mn7000), a methanol solution obtained by dissolving poly(4,5-diazadibenzofuran) (Mn1600), and a methanol solution obtained by dissolving polyethylene oxide (Mn600) were mixed in the amounts shown in Table 2, with the mass ratio of polystyrene sulfonic acid to poly(4,5-diazadibenzofuran) to polyethylene oxide being as shown. Using the obtained mixture, the proton-conducting membrane of Example 7 with the membrane thickness shown in Table 2 was obtained by the same method as in Example 1.

[0160] [Examples 8-10]

[0161] Except that in Example 7, polyoxyethylene with the number average molecular weight shown in Table 2 was used instead of polyoxyethylene (Mn600), the proton conduction membranes of Examples 8 to 10 were obtained in the same manner as in Example 7.

[0162] [Example 11]

[0163] In a water-alcohol solution obtained by dissolving polystyrene sulfonic acid (Mn7000), 1,6-diaminohexane was added in amounts equal to the mass ratio of polystyrene sulfonic acid to 1,6-diaminohexane shown in Table 3, and the mixture was prepared to obtain a mixture. Using the obtained mixture, the proton-conducting membrane of Example 11 with the membrane thickness shown in Table 3 was obtained by the same method as in Example 1.

[0164] [Examples 12-13]

[0165] Except for changing the amount of 1,6-diaminohexane added in Example 11 by using the mass ratio of polystyrene sulfonic acid to 1,6-diaminohexane as shown in Table 3, the proton conduction membranes of Examples 12 and 13 were obtained in the same manner as in Example 11.

[0166] [Example 14]

[0167] A water-alcohol solution obtained by dissolving polystyrene sulfonic acid (Mn7000) and a methanol solution obtained by dissolving poly(4,5-diazadibenzofuran) (Mn1600) and 1,6-diaminohexane were mixed in the amounts shown in Table 3, with the mass ratio of polystyrene sulfonic acid to poly(4,5-diazadibenzofuran) to 1,6-diaminohexane being as shown in Table 3, thereby obtaining a mixture. Using the obtained mixture, the proton-conducting membrane of Example 14 with the membrane thickness shown in Table 3 was obtained by the same method as in Example 1.

[0168] [Examples 15-16]

[0169] The proton-conducting membranes of Examples 15 and 16 were obtained in the same manner as in Examples 12 and 13, except that 1,2-ethylenediamine was used instead of 1,6-diaminohexane in Examples 12 and 13.

[0170] [Example 17]

[0171] The proton-conducting membrane of Example 17 was obtained in the same manner as in Example 14, except that 1,2-ethylenediamine was used instead of 1,6-diaminohexane in Example 14.

[0172] [Example 18]

[0173] The proton-conducting membrane of Example 18 was obtained in Scheme 1 below by setting the amount of N,N'-methylenebisacrylamide (MBAA) added to be 1 part by mass relative to 100 parts by mass of polystyrene sulfonic acid.

[0174] Specifically, N,N'-methylenebisacrylamide was added to a 2 mol / L (2 M) aqueous solution of sodium 4-styrene sulfonate, and 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide] was further added as a water-soluble initiator. The mixture was then reacted at 86 °C to obtain a random copolymer gel of sodium 4-styrene sulfonate and N,N'-methylenebisacrylamide. The obtained copolymer gel was then immersed in 3 M hydrochloric acid, washed with water, and vacuum dried for 24 hours to obtain the proton-conducting membrane of Example 18.

[0175] Chemical formula 3

[0176] <Option 1>

[0177]

[0178] [Example 19]

[0179] Except that the amount of N,N'-methylenebisacrylamide added in Example 18 was changed to 5 parts by mass relative to 100 parts by mass of polystyrene sulfonic acid, the proton conduction membrane of Example 19 was obtained in the same manner as in Example 18.

[0180] [evaluate]

[0181] Measurement of proton conductivity

[0182] The conductivity measurement battery was placed in the tank of a small environmental tester (Espec, model: SH-242), and the results were obtained using an impedance analyzer (YHP, model: 4194A) as shown in Tables 1-4. Figure 1The characteristic impedance was measured under the recorded temperature, without humidification, and with a frequency scan range of 100 Hz to 1 MHz. The real component of the Nyquist plot of the characteristic impedance, which is the point where the capacitance component is minimized, was taken as the measured value (Rm). The film thickness (d) and electrode area (S) of the sample were used as the impedance characteristic (Ru) when the measuring cable was short-circuited, and the conductivity (σ) in the film thickness direction was calculated according to the following formula (unit: S / cm).

[0183] σ=d / {(Rm-Ru)×S}

[0184] <Durability>

[0185] The proton conduction membranes obtained in Examples 1, 2, 7 to 19 were observed by visual inspection after being heated to 110°C and after being stored at room temperature for an extended period of time. The durability of the proton conduction membranes was evaluated according to the following evaluation criteria.

[0186] (Durability evaluation criteria)

[0187] A: The membrane will not degrade whether it is heated or stored at room temperature for an extended period of time.

[0188] B: Although the membrane did not degrade after being stored at room temperature for a short time, it will degrade after being heated or stored at room temperature for a long time.

[0189] C: The membrane will degrade after being stored at room temperature for a short period of time.

[0190] Table 1

[0191] Table 1

[0192]

[0193] Table 2

[0194] Table 2

[0195]

[0196] Table 3

[0197] Table 3

[0198]

[0199] Table 4

[0200] Table 4

[0201]

[0202] In addition, the abbreviations in Tables 1 to 4 are as follows.

[0203] • PSS: Polystyrene sulfonic acid (Mn7000)

[0204] • Nafion: Nafion (registered trademark) (Product Code: NR212, manufactured by DuPont)

[0205] • Poly(DADBF): Poly(4,5-diazadibenzofuran) (Mn1600) • Poly(2VPy)500: Poly(2-vinylpyridine) (Mn500)

[0206] • Poly(Phen)1000: Poly(1,10-phenanthroline)(Mn1000)

[0207] • Poly(Phen)10000: Poly(1,10-phenanthroline)(Mn10000)

[0208] • PEO600: Polyethylene oxide (Mn600)

[0209] • PEO3000: Polyethylene oxide (Mn3000)

[0210] • PEO46000: Polyethylene oxide (Mn46000)

[0211] • PEO510000: Polyethylene oxide (Mn510000)

[0212] ·DAH: 1,6-Diaminohexane

[0213] DAE: 1,2-Ethylenediamine

[0214] ·MBAA: N,N'-methylenebisacrylamide

[0215] <Water Resistance>

[0216] The water resistance of the proton-conducting membrane obtained in Example 18 was evaluated by methods A and B described below.

[0217] (Method A)

[0218] Approximately 100 mg of the proton-conducting membrane obtained in Example 18 was cut off to prepare a sample. The sample weighed 92.85 mg. After immersing the sample in water at 80°C for one hour, air-drying for 4 days, and further vacuum drying for 24 hours, the sample weighed 90.14 mg, resulting in an observed weight reduction of 2.9% (2.7] mg.

[0219] The aforementioned weight reduction is considered to be due to errors caused by insufficient drying of the measured sample, which is sufficiently small compared to existing proton-conducting membranes, or errors based on mechanical losses caused by small-scale experiments. Therefore, it is clear that the proton-conducting membrane obtained in Example 18 has high water resistance and does not dissolve in water.

[0220] (Method B)

[0221] The proton-conducting membrane obtained in Example 18 was cut to prepare a sample. The sample was immersed in water at room temperature (25°C) for 24 hours to allow it to swell, and the swollen sample was weighed to be 6160 mg. The swollen sample was further immersed in water at 80°C for 1 hour and weighed to be 6950 mg, thus observing a weight increase of 12.8% (790 mg).

[0222] The aforementioned weight increase is presumed to be due to insufficient swelling of the sample before immersion in water at 80°C. Therefore, it is clear that the proton-conducting membrane obtained in Example 18 has high water resistance, meaning it will not dissolve in water even after being sufficiently swollen with water.

[0223] In addition, Figure 1 The results of proton conductivity measurements for the proton-conducting membrane obtained in Example 18 under unhumidified conditions with 5% RH within a temperature range of -20°C to 150°C are shown, as well as the results of proton conductivity measurements for the comparative conductive membrane of Comparative Example 2 under unhumidified conditions with 5% RH within a temperature range of -20°C to 150°C within a temperature range of 5% RH. Additionally, in Figure 1 In the figure, the horizontal axis represents 1000 / T (T is the measurement temperature (K)), and the vertical axis represents the proton conductivity (S / cm).

[0224] The proton-conducting membranes obtained in Examples 1-10 shown in Tables 1 and 2 are proton-conducting materials according to the first embodiment of this disclosure. They contain polystyrene sulfonic acid or Nafion (registered trademark) as proton source polymers, and poly(4,5-diazadibenzofuran), poly(2-vinylpyridine), or poly(1,10-phenanthroline) as proton channel polymers. Since these proton channel polymers have proton channels containing aromatic rings that readily form a stacked structure through π-π interactions, at least a portion of the proton channel polymers in the proton-conducting membranes obtained in Examples 1-10 have a stacked structure through π-π interactions.

[0225] The proton-conducting membranes obtained in Examples 1 to 10, which are the proton-conducting materials according to the first embodiment of this disclosure, have a proton conductivity of up to 10 mS / cm or more under conditions of 25°C and without humidification, thereby increasing the proton conductivity compared with the polystyrene sulfonic acid membrane of Comparative Example 1 and the Nafion membrane of Comparative Example 2.

[0226] Furthermore, the proton conduction membranes obtained in Examples 1 to 10 do not dissolve in water because the proton source groups and proton channels are bonded to the polymer by covalent bonds. Therefore, the proton conduction membranes obtained in Examples 1 to 10 are products that do not contain components that dissolve in water.

[0227] Furthermore, in Example 1 shown in Table 1, it is shown that the proton-conducting material according to the first embodiment of this disclosure, which contains a styrene sulfonic acid polymer as the proton source polymer and poly(4,5-diazadibenzofuran) as the proton channel polymer, has extremely high proton conductivity even at high temperatures under non-humidified conditions.

[0228] Based on the comparison between Examples 1-2 and Examples 7-10 shown in Table 2, it is evident that the proton-conducting material of the first embodiment of this disclosure, which further contains polyethylene oxide as a proton channel polymer, improves durability while suppressing the decrease in proton conductivity.

[0229] The proton-conducting membranes obtained in Examples 11-19 shown in Tables 3 and 4 are proton-conducting materials according to the second embodiment of this disclosure. They have a main framework derived from polystyrene sulfonic acid as a main framework containing a proton source group and an aromatic ring, and contain a proton-source crosslinked polymer with a crosslinked structure derived from 1,6-diaminohexane, 1,2-ethylenediamine or N,N'-methylenebisacrylamide as a crosslinked structure containing a proton channel. At least a portion of the proton-source crosslinked polymer has a structure stacked by π-π interactions.

[0230] The proton-conducting membranes obtained in Examples 11-19, which are the proton-conducting materials involved in the second embodiment of this disclosure, also have a proton conductivity of up to 10 mS / cm or more under conditions of 25°C and without humidification, thereby increasing the proton conductivity compared with the polystyrene sulfonic acid membrane of Comparative Example 1 and the Nafion membrane of Comparative Example 2.

[0231] Furthermore, in the proton conduction membranes obtained in Examples 11-19, the proton source groups are covalently bonded to the main framework, and the proton channels are covalently bonded to the cross-linked structure or the proton channel polymer. Since the cross-linked structure is chemically bonded to the main framework, the proton source groups and the proton channels do not dissolve in water. Therefore, the proton conduction membranes obtained in Examples 11-19 do not contain any components that dissolve in water.

[0232] Furthermore, the proton-conducting membranes obtained in Examples 11-19 not only have high proton conductivity but also excellent durability.

[0233] Furthermore, in Example 18 shown in Table 4, it was demonstrated that the proton-conducting material according to the second embodiment of this disclosure, containing a proton-source crosslinked polymer with a main backbone derived from styrene sulfonic acid polymers and a crosslinking structure derived from N,N'-methylenebisacrylamide, exhibits high proton conductivity and excellent durability even at high temperatures and under non-humidified conditions. Furthermore, regarding the proton-conducting membrane obtained in Example 18, it was confirmed that it showed almost no change even after being stored at room temperature for 3 days, thereby suppressing degradation over time.

[0234] Furthermore, it is shown that, regarding the proton-conducting membrane obtained in Example 18, the above-described evaluation of water resistance resulted in high water resistance.

[0235] In addition, according to Figure 1 The results shown demonstrate that the proton-conducting membrane obtained in Example 18 exhibits high proton conductivity over a wide temperature range and under non-humidified conditions.

[0236] Furthermore, since the comparative conductive membrane in Comparative Example 2 is a Nafion membrane, its proton conductivity is insufficient under non-humidified conditions. In the comparative conductive membrane of Comparative Example 2, as... Figure 1 As shown, the reason why the proton conductivity increases with higher temperature is inferred to be due to the glass transition temperature of the Nafion film in Comparative Example 2 being 109°C, which increases molecular mobility. Furthermore, in addition to the possibility that trace amounts of moisture may not have been completely removed, the possibility that the proton conductivity on the surface may increase due to the thinning of the film thickness and decrease in resistance at high temperatures is also considered. In the measurement unit where surface pressure was applied, there is a possibility that the film softens and its thickness decreases at high temperatures.

[0237] Thus, the proton-conducting material disclosed herein is a proton-conducting material that has a high proton conductivity even under non-humidified conditions and does not dissolve in water, and can be appropriately used as an electrolyte material for a catalyst layer used in a fuel cell or as a solid electrolyte membrane used in a fuel cell.

Claims

1. A proton-conducting material, wherein, The proton-conducting material comprises a polymer containing a proton source group and a polymer containing a proton channel, and at least one of the polymers containing the proton source group and the polymers containing the proton channel is a polymer containing an aromatic ring, and at least a portion of the polymer containing the aromatic ring has a structure formed by stacking through π-π interactions. The polymer containing the proton source group is a styrene sulfonic acid polymer. As the polymer containing proton channels, it contains poly(4,5-diazadibenzo-p-ethylene) with a number average molecular weight of 1000-2000 in a ratio of 1 to 15 parts by mass relative to 100 parts by mass of the styrene sulfonate polymer. The poly(4,5-diazadibenzofuran) is a polymer composed solely of structural units derived from 4,5-diazadibenzofuran.

2. The proton-conducting material as described in claim 1, wherein, The styrene sulfonic acid polymer contains 1 to 5 parts by mass of poly(4,5-diazadibenzofuran) with a number average molecular weight Mn of 1,000 to 2,000, relative to 100 parts by mass of the styrene sulfonic acid polymer, and also contains 8 to 12 parts by mass of polyethylene oxide with a number average molecular weight Mn of 600 to 510,000, relative to 100 parts by mass of the styrene sulfonic acid polymer.

3. A proton-conducting material, wherein, The proton-conducting material comprises a polymer containing a proton source group and a polymer containing a proton channel, and at least one of the polymers containing the proton source group and the polymers containing the proton channel is a polymer containing an aromatic ring, and at least a portion of the polymer containing the aromatic ring has a structure formed by stacking through π-π interactions. The polymer containing the proton source group is a styrene sulfonic acid polymer. As the polymer containing proton channels, it contains poly(2-vinylpyridine) with a number average molecular weight (Mn) of 500 to 2000 in a ratio of 8 to 12 parts by mass relative to 100 parts by mass of the styrene sulfonic acid polymer. The poly(2-vinylpyridine) is a polymer composed solely of structural units derived from 2-vinylpyridine.

4. A proton-conducting material, wherein, The proton-conducting material comprises a polymer containing a proton source group and a polymer containing a proton channel, and at least one of the polymers containing the proton source group and the polymers containing the proton channel is a polymer containing an aromatic ring, and at least a portion of the polymer containing the aromatic ring has a structure formed by stacking through π-π interactions. The polymer containing the proton source group is a styrene sulfonic acid polymer. As the polymer containing proton channels, it contains poly(1,10-phenanthroline) with a number average molecular weight of 900-1100 in a ratio of 1 to 3 parts by mass relative to 100 parts by mass of the styrene sulfonate polymer. The poly(1,10-phenanthroline) is a polymer composed solely of structural units derived from 1,10-phenanthroline.

5. A proton-conducting material, wherein, The proton-conducting material comprises a polymer containing a proton source group and a polymer containing a proton channel, and at least one of the polymers containing the proton source group and the polymers containing the proton channel is a polymer containing an aromatic ring, and at least a portion of the polymer containing the aromatic ring has a structure formed by stacking through π-π interactions. The polymer containing the proton source group is a perfluorosulfonic acid polymer. As the polymer containing proton channels, it contains poly(1,10-phenanthroline) with a number average molecular weight (Mn) of 9000-11000 in a ratio of 8-12 parts by mass relative to 100 parts by mass of the perfluorosulfonic acid polymer. The poly(1,10-phenanthroline) is a polymer composed solely of structural units derived from 1,10-phenanthroline.

6. The proton-conducting material according to any one of claims 1, 3 to 5, wherein, The polymer containing the proton channels further contains polyethylene oxide.

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