JP2007265955A - Polymer electrolyte membrane, process for production thereof, polymer electrolyte, electrolyte composition, membrane-electrode assembly, and fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polymer electrolyte membrane capable of obtaining high ionic conductivity and stably obtaining high output even when humidifying of an electrolyte with auxiliaries is not conducted or humidifying is low. <P>SOLUTION: The electrolyte membrane is constituted of a block copolymer having an ion-conductive block. In the membrane, the ion-conductive block 12 forms ion-conductive domains 14 in a cylindrical shape arranged parallel to the direction of thickness d of the polymer electrolyte membrane. The ion-conductive block is made of a polymer having an ion exchange group. The ion exchange group is a sulfonic group, a carboxilic group, a phosphoric group, a phosphonic group, or a phosphonous group. The volume fraction of the ion-conductive block in the block copolymer is 5-30%. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a polymer electrolyte membrane suitable for a fuel cell having high ionic conductivity and having a small influence of humidity and temperature on the ionic conductivity, a method for producing the polymer electrolyte membrane, and membrane electrode bonding using the polymer electrolyte membrane Body and fuel cell.

  Fuel cells are classified into polymer electrolyte type, phosphoric acid type, alkali type, molten carbonate type, solid oxide type, and the like, depending on the type of electrolyte used. Among these, low-temperature operating fuel cells, particularly polymer electrolyte fuel cells, are less restricted in terms of materials constituting the fuel cells and can be reduced in size and weight. Therefore, it is expected to be applied to a portable small power source, an in-vehicle power source, and the like. In particular, for application as a small power source for portable devices, it is desired to further increase the output and reduce the size, and problems to be solved remain.

  The first problem is to increase the ionic conductivity and the strength of the electrolyte membrane. In the case of a polymer electrolyte fuel cell, it is common to use a polymer membrane such as a non-crosslinked perfluoro electrolyte represented by Nafion (registered trademark, manufactured by DuPont) or various hydrocarbon electrolytes as the electrolyte. It is. In order to increase the output of such a polymer electrolyte fuel cell, it is desirable that the ionic conductivity of the polymer membrane is high. In addition, since the fuel cell is generally used as a stack in which a large number of single cells are stacked, in order to reduce the size of the polymer electrolyte fuel cell, it is preferable that the thickness of the polymer membrane is small. The higher the strength of the polymer film, the better.

  However, since the distribution of ion exchange groups in the polymer membrane is generally random, the resistance increases when the density of ion exchange groups is small. Therefore, high ion conductivity cannot be obtained with a polymer membrane having a low density of ion exchange groups. On the other hand, if the density of ion exchange groups is increased, the ionic conductivity of the polymer membrane is increased. However, when the density of ion exchange groups in the polymer membrane increases, there is a problem that the membrane becomes water-soluble at some point and the strength of the polymer membrane decreases. That is, it is difficult for the polymer film to achieve both high ionic conductivity and high strength.

  In the conventional polymer electrolyte fuel cell, in order to solve this problem, a method for increasing the density of ion exchange groups while improving the strength and dimensional stability of the polymer membrane by combining and crosslinking has been proposed. Yes. For example, Patent Document 1 discloses a composite membrane in which an ion conductive polymer is impregnated into a porous support in which fibers are randomly oriented in order to improve the dimensional stability and handling suitability of a perfluoro-based electrolyte. Has been.

  Furthermore, in order to achieve both high ion conductivity and high strength, by fixing the introduction site of the ion conductive substance in the electrolyte membrane, even if the introduction amount of ion exchange groups is relatively small There have been proposed polymer electrolytes capable of obtaining high ionic conductivity.

  For example, Patent Document 2 discloses an electrolyte membrane having a membrane support having a communication hole penetrating in the thickness direction and an ion conductive material introduced into the communication hole. When a membrane support having a communication hole penetrating in the thickness direction is used as the porous support for introducing the ion conductive material, the introduction site of the ion conductive material is specified. Therefore, there is provided a polymer electrolyte membrane for a polymer electrolyte fuel cell that can provide high ion conductivity even when the amount of ion exchange groups introduced is relatively small.

  Patent Document 3 discloses an electrolyte membrane of a block copolymer composed of an ion conductive segment responsible for ion transport and a flexible and elastic elastomer segment (matrix segment) responsible for mechanical stability. Yes.

  The second problem is to make the electrolyte membrane resistant to dry out and the electrode resistant to flooding. Various materials are known as electrolyte membranes used in polymer electrolyte fuel cells, and all of these require water to exhibit ionic conductivity.

  Therefore, when the operating condition of the fuel cell becomes a dry condition, the water content of the electrolyte membrane decreases, so-called dryout occurs, which decreases the ionic conductivity, and causes a decrease in the output of the fuel cell.

  In conventional polymer electrolyte fuel cells, in order to solve this problem, it is common to use a method of replenishing the electrolyte membrane from the outside using an auxiliary machine. As a method for supplying moisture to the electrolyte membrane, specifically, a method of humidifying a reaction gas using a bubbler, a mist generator, etc., a method of directly injecting moisture into a reaction gas channel formed inside a separator, etc. It has been known.

  In the case of a polymer electrolyte fuel cell, water is generated by a cell reaction at the cathode. Further, when ions move from the anode side to the cathode side, water also moves to the cathode side by electroosmosis. Therefore, the moisture content is uneven in the electrolyte membrane. As a result, excess water tends to stay in the cathode, pores in the electrode are blocked with water, so-called flooding occurs, and the output of the fuel cell is reduced.

In addition, in order to suppress the deterioration of characteristics due to the moisture content unevenness in the electrolyte membrane, an electrolyte membrane that is not affected by the ionic conductivity due to humidity conditions is desired.
As a method for solving the above problem, Patent Document 4 discloses a block copolymer comprising a sulfonic acid group-containing block and a block not containing a sulfonic acid group as a polymer electrolyte membrane for a fuel cell. Yes. Specifically, a sulfonated aromatic polyethersulfone block copolymer comprising a hydrophilic segment having a sulfonic acid group introduced therein and a hydrophobic segment not having been introduced is used. It is described that the electrolyte membrane is excellent in water resistance because its ionic conductivity is equal to or higher than that of a polymer electrolyte into which sulfonic acid groups are randomly introduced, and the amount of water absorption is reduced. Has been. In addition, a polymer electrolyte with less influence of humidity and temperature on ion conductivity can be obtained.
Japanese Patent Laid-Open No. 6-231777 JP 2002-203576 A Japanese National Patent Publication No. 10-503788 JP 2003-031232 A

Each of the conventional techniques described above has the following problems.
First, in Patent Document 1, a composite membrane in which an ion conductive polymer is impregnated into a porous support in which fibers are randomly oriented is used as an electrolyte membrane. Therefore, since the pores in the porous support are randomly oriented, it is a part of the introduced ion exchange groups that contributes effectively to ion conduction. Therefore, in order to obtain high ionic conductivity, it is necessary to introduce a large amount of ionic conductive polymer into the porous support. However, in order to maintain the strength of the composite membrane, the porosity of the porous support cannot be increased too much. For this reason, there is a limit to increasing the ion conductivity using such a composite membrane.

  2ndly, in patent document 2, the introduction amount of an ion exchange group is provided by providing the film | membrane support body which has a communicating hole penetrated in the thickness direction, and the ion conductive substance introduced into the said communicating hole. Even if it is relatively small, relatively high ionic conductivity can be obtained. However, when the ion conductive material is immersed in the membrane support, the produced electrolyte membrane is a composite membrane consisting of two different materials, the ion conductive material membrane and the support. There is a possibility that the substance flows out due to moisture or expansion, and there is a problem in contact with the electrode and long-term durability of the fuel cell. In addition, even when the communication holes are modified with an ion conductive material, the ion exchange material introduced into the membrane support is sparse, so that the gas barrier property is poor, and the amount of ion exchange groups introduced is reduced. It is difficult to increase, and further improvement in ionic conductivity cannot be expected.

  Third, when the electrolyte is humidified using an auxiliary device, there are various components such as a water tank for storing humidifying water, a humidifier, and a condenser for collecting water discharged from the fuel cell. Necessary. Therefore, there is a problem that the entire fuel cell system is complicated and large. In addition, the humidification of the electrolyte using an auxiliary machine requires extra auxiliary machine power, which causes a decrease in power generation efficiency of the fuel cell. On the other hand, in the case of a polymer electrolyte fuel cell, as described above, water is generated by a cell reaction on the cathode side. If this generated water can be directly used for the humidification of the electrolyte, the humidification of the electrolyte by the auxiliary machine can be reduced or eliminated, and the entire fuel cell system can be reduced in size, weight and efficiency.

  However, conventional electrodes used in polymer electrolyte fuel cells are easy to discharge water staying in the electrodes, for example, by applying a water repellent treatment to the inner surface of the pores of the electrodes in order to suppress output reduction due to flooding. It is common. Therefore, the generated water cannot be used effectively. In addition, in order to operate stably, moisture management such as humidification by an auxiliary machine is necessary, which is a major obstacle in miniaturization of fuel cells.

  Fourthly, Patent Document 4 uses a sulfonated aromatic polyethersulfone block copolymer composed of a hydrophilic segment into which a sulfonic acid group is introduced and a hydrophobic segment into which the sulfonic acid group is not introduced. Thereby, the polymer electrolyte with little influence of humidity and temperature on ion conductivity can be obtained. However, such a block copolymer forms a microdomain by phase separation of a hydrophilic segment having a sulfonic acid group introduced therein and a hydrophobic segment not having a sulfonic acid group introduced therein, but its structure is suitable in all directions. Therefore, there is a limit to improving ion conduction efficiency.

  Microphase separation membranes made of block copolymers generally show regular microdomain arrangement within a narrow range (grain), but domain continuity is disrupted at the grain-grain boundary (grain boundary). Is done. In Patent Document 3, the ion conductive domain is divided by the elastomer matrix, but the ion conductive domain swells due to hydration accompanying humidification, and the domains contact each other even between the grain boundaries. Is disclosed to improve. However, under conditions of water shortage at the time of fuel cell start-up, high humidity non-humidification or low humidification conditions, these ion conductive domains are not hydrated, so the domains are separated and the ionic conductivity decreases. At the same time, the start-up characteristics and high-temperature output characteristics are expected to deteriorate.

  The present invention has been made in view of such background art, and the object of the best mode of the present invention is to obtain a high ionic conductivity, when the electrolyte is not humidified by an auxiliary machine, or when the humidity is low. It is an object of the present invention to provide a polymer electrolyte membrane capable of stably obtaining high output even in the case and a method for producing the same.

The object of the best mode of the present invention is to provide a low temperature operation type small fuel cell for portable equipment which can obtain high ion conductivity.
The object of the best mode of the present invention is to provide a polymer electrolyte, an electrolyte composition, and a membrane electrode assembly used in the above polymer electrolyte membrane and fuel cell.

  A polymer electrolyte membrane for solving the above problems is an electrolyte membrane made of a block copolymer having an ion conductive block, and the cylindrical domain of the ion conductive portion formed by the ion conductive block is an electrolyte membrane. It is arranged in parallel with the thickness direction.

It is preferable that the ion conductive block is made of a polymer having an ion exchange group.
The ion exchange group is preferably a sulfonic acid group, a carboxylic acid group, a phosphoric acid group, a phosphonic acid group or a phosphonous acid group.

It is preferable that the volume fraction of the ion conductive block in the block copolymer is 5% or more and 30% or less.
It is preferable that the repeating unit of the ion conductive block of the electrolyte made of the block copolymer includes at least one structure selected from the group represented by the following chemical formulas (1) to (3).

(Wherein R ¹ represents a hydrogen atom or a methyl group, and R ² represents an alkylene group or an arylene group.)

(In the formula, R ³ represents an alkylene group or an arylene group.)

(Wherein R ⁴ represents a hydrogen atom or a methyl group, R ⁵ and R ⁸ represent an alkylene group or an arylene group, R ⁶ and R ⁷ may be the same as or different from each other, and each represents a hydrogen atom or a carbon number of 1 To 3 organic groups.)

  A polymer electrolyte membrane for solving the above problems is a polymer electrolyte membrane comprising a block copolymer having a block exhibiting ionic conductivity and a block not exhibiting ionic conductivity. This is a polymer electrolyte membrane in which the volume fraction of the block exhibiting ionic conductivity in the polymer is 5% or more and 30% or less, and the molecular chain of the block not exhibiting ionic conductivity has a crosslinked structure. Such a crosslinked structure may be formed by a crosslinkable group of the polymer itself before crosslinking, or may be formed by using a crosslinking agent.

  In the polymer electrolyte membrane in which the molecular chain of the block that does not exhibit ion conductivity has a cross-linked structure, the cylindrical domain of the ion conductive portion formed by the ion conductive block is arranged in parallel with the thickness direction of the electrolyte membrane. It is preferable to become.

  A polymer electrolyte for solving the above problems is a polymer electrolyte membrane comprising a block copolymer having a block exhibiting ionic conductivity and a block not exhibiting ionic conductivity. The volume fraction of the block showing ion conductivity in the coalescence is 5% or more and 30% or less, and the repeating unit of the block showing no ion conductivity contains at least one crosslinkable group. It is a featured polymer electrolyte.

  An electrolyte composition for solving the above problems is a polymer electrolyte membrane comprising a block copolymer (A) having a block exhibiting ionic conductivity and a block not exhibiting ionic conductivity, The volume fraction of the block exhibiting ionic conductivity in the block copolymer is 5% or more and 30% or less, and the repeating unit of the block not exhibiting ionic conductivity contains at least one crosslinked structure. It contains a polymer electrolyte and (B) a radical generator.

The radical generator is preferably a photo radical generator.
The radical generator is preferably a thermal radical generator.
In addition, a method for producing a polymer electrolyte membrane for solving the above problems includes a step of forming a block copolymer having an ion conductive block, a cylinder formed by the ion conductive block of the formed block copolymer Characterized in that it has a step of forming ionic conductive portions arranged in parallel to the thickness direction of the electrolyte membrane by uniaxially orienting the domain-like domains.

  In addition, a method for producing a polymer electrolyte membrane for solving the above problems includes a step of forming a block copolymer having an ion conductive block, a cylinder formed by the ion conductive block of the formed block copolymer Characterized in that it has a step of uniaxially orienting the domain-like domains to form ion-conductive portions arranged in parallel with the thickness direction of the electrolyte membrane, and a step of cross-linking polymer side chains of blocks having no ion conductivity To do.

It is preferable that the cylindrical block domain formed by the ion conductive block is uniaxially oriented by applying heat treatment and an external field to the formed block copolymer.
Moreover, the membrane electrode assembly for solving the said subject is characterized by the electrode being arrange | positioned on both surfaces of said polymer electrolyte membrane.

The ion conductive portions of the polymer electrolyte membrane are preferably arranged in a direction substantially perpendicular to the electrode surface.
Moreover, the fuel cell for solving the said subject has a membrane electrode assembly by which the electrode is arrange | positioned on both surfaces of said polymer electrolyte membrane, It is characterized by the above-mentioned.

The ion conducting portions of the polymer electrolyte membrane are preferably arranged in a direction perpendicular to the electrode surface.
In the invention described above, it is preferable that the main chain of the block copolymer does not have an aromatic ring.

  According to a preferred embodiment of the present invention, ions are ionically separated by self-organizing phase-conducting ion conducting portions made of block copolymer ion conductive blocks in a matrix forming the membrane structure of the polymer electrolyte membrane. The influence of humidity and temperature on the conductivity is small, and high ionic conductivity is obtained.

  Furthermore, by providing a structure in which the ion conducting portions are oriented parallel to the thickness direction of the polymer electrolyte membrane, the ion conducting portions can be arranged in a uniaxial direction, thereby improving ion conduction efficiency. it can.

  Further, according to a preferred aspect of the present invention, in the fuel cell including the membrane electrode assembly in which the electrodes are joined to both surfaces of the polymer electrolyte membrane, the ion conducting portion is provided in parallel to the thickness direction of the electrolyte membrane. Since an electrolyte membrane having an oriented structure is used, the diffusion rate of water is improved. Part of the generated water at the electrode due to the battery reaction is returned to the electrolyte membrane by diffusion and reused for humidification of the electrolyte membrane. Therefore, by providing the structure in which the ion conducting portions are arranged in parallel to the thickness direction of the electrolyte membrane, the water in the electrolyte membrane can exist uniformly in the membrane.

  Therefore, even under low humidification conditions, the moisture content of the electrolyte membrane can be maintained at a level necessary for stable operation, a decrease in output can be suppressed, and a high output can be stably obtained. As a result, even when the electrolyte is not humidified by the auxiliary equipment or when the humidity is low, the amount of power generation is unlikely to decrease even when the moisture supply is insufficient, such as when the fuel cell is started, and the high output is stable over a long period of time. Thus, the fuel cell can be miniaturized.

  Thus, according to a preferred aspect of the present invention, high ionic conductivity can be obtained, and high output can be stably maintained over a long period of time even when the electrolyte is not humidified by an auxiliary device or when the humidification is low. The obtained polymer electrolyte membrane and a method for producing the polymer electrolyte membrane can be provided.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing an embodiment of the polymer electrolyte membrane of the present invention. In FIG. 1, a polymer electrolyte membrane (hereinafter also referred to as an electrolyte membrane) 10 is made of a block copolymer having an ion conductive block, and includes a matrix 11 of a membrane supporting portion and a cylindrical domain formed by the ion conductive block. Phase-separated into ionic conduction parts 12 made of ionic conduction parts 12 having a structure in which the ion conduction parts 12 are arranged in a cylindrical shape in the film thickness d direction.

  FIG. 2 is a block diagram showing an embodiment of the block copolymer of the present invention. The block copolymer 13 includes an ion conductive block (hereinafter also referred to as an ion conductive polymer) 12a made of an ion conductive polymer, and a matrix block (also called a matrix polymer) made of a matrix polymer that forms a matrix of a membrane support site. This is a copolymer consisting of 11a.

  The electrolyte membrane 10 has a structure in which an ion conducting portion 12 is arranged in a cylinder shape in a matrix 11. The diameter of the cylindrical domain 14 is not particularly limited, but those having a diameter of 1 nm to 100 nm are generally used.

  The diameter of the cylindrical domain 14 depends on the molecular weight of the ion conductive polymer and the molecular weight of the matrix polymer. Although there is no restriction | limiting in particular in the number average molecular weight of a block copolymer, A thing with Mn = 1,000-1,000,000 is generally used.

  Moreover, the ion conduction part 12 should just be orientated substantially parallel to the thickness direction of an electrolyte membrane at least, and the shape is not specifically limited. For example, the cylinder may be inclined at an angle of less than 90 ° with respect to the film thickness direction, but the inclination from the film thickness direction is preferably within 30 °, more preferably within 10 °. The cylinder may be linear or zigzag, but preferably has no branching portion. That is, the cylinder only needs to be oriented in a direction substantially parallel to the film thickness direction. The shape of the cross section of the ion conducting portion is not particularly limited as long as it is a shape expressed by microphase separation, such as a circle, an ellipse, and a wavy indeterminate shape.

  The block copolymer that forms the electrolyte membrane 10 includes an ion conductive polymer that forms the ion conductive block 12a and a matrix polymer that forms the matrix block 11a.

The material of the matrix polymer is not particularly limited as long as it can synthesize a block copolymer and can form a film structure.
As the matrix polymer, a general polymer having no ion exchange group, for example, a polymer synthesized from monomers such as an acrylate ester, a methacrylate ester, a styrene derivative, a conjugated diene, and a vinyl ester compound is used. Can be mentioned. Specific examples include polystyrene, polymethyl methacrylate, and trifluoroethyl methacrylate. In addition to these, monomers that form the matrix polymer include styrene, α-, o-, m-, p-alkyl, alkoxyl, halogen, haloalkyl, nitro, cyano, amide, ester-substituted products of styrene; 2,4-dimethylstyrene, paradimethylaminostyrene, vinylbenzyl chloride, vinylbenzaldehyde, indene, 1-methylindene, acenaphthalene, vinylnaphthalene, vinylanthracene, vinylcarbazole, 2-vinylpyridine, 4-vinylpyridine, 2- Polymerizable unsaturated aromatic compounds such as vinyl fluorene;
Alkyl (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl acrylate, n-butyl acrylate, 2-ethylhexyl (meth) acrylate, stearyl (meth) acrylate; methyl crotonic acid, crotonic acid Unsaturated monocarboxylic esters such as ethyl, methyl cinnamate and ethyl cinnamate; fluoroalkyl (meta) such as trifluoroethyl (meth) acrylate, pentafluoropropyl (meth) acrylate and heptafluorobutyl (meth) acrylate ) Acrylates; trimethylsiloxanyldimethylsilylpropyl (meth) acrylate, tris (trimethylsiloxanyl) silylpropyl (meth) acrylate, di (meth) acryloylpropyldimethylsilyl Siloxanyl compounds such as ether; hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate; dimethylaminoethyl (meth) acrylate Amine-containing (meth) acrylates such as diethylaminoethyl (meth) acrylate and t-butylaminoethyl (meth) acrylate; 2-hydroxyethyl crotonic acid, 2-hydroxypropyl crotonic acid, 2-hydroxypropyl cinnamate, etc. Hydroxyalkyl esters of unsaturated carboxylic acids; unsaturated alcohols such as (meth) allyl alcohol; unsaturated (mono) carboxylic acids such as (meth) acrylic acid, crotonic acid and cinnamic acid; (meth) acrylic Glycidyl acid, glycidyl α-ethyl acrylate, glycidyl α-n-propyl acrylate, glycidyl α-n-butyl acrylate, (meth) acrylic acid-3,4-epoxybutyl, (meth) acrylic acid-6,7 -Epoxyheptyl, α-ethylacrylic acid-6,7-epoxyheptyl, o-vinylbenzylglycidyl ether, m-vinylbenzylglycidylether, p-vinylbenzylglycidylether, (meth) acrylic acid-β-methylglycidyl, ( (Meth) acrylic acid-β-ethylglycidyl, (meth) acrylic acid-β-propylglycidyl, α-ethylacrylic acid-β-methylglycidyl, (meth) acrylic acid-3-methyl-3,4-epoxybutyl, ( Meth) acrylic acid-3-ethyl-3,4-epoxybutyl, (meth) acrylic Acid-4-methyl-4,5-epoxypentyl, (meth) acrylic acid-5-methyl-5,6-epoxyhexyl, (meth) acrylic acid-β-methylglycidyl, (meth) acrylic acid-3-methyl Epoxy group-containing (meth) acrylic acid esters such as 3,4-epoxybutyl; and their mono and diesters;
In addition, N-alkyl-substituted (meth) acrylamides such as N, N-dimethylacrylamide and N-isopropylacrylamide; N-methylolacrylamide, N-methylolmethacrylamide, N-vinylpyrrolidone, (anhydrous) maleic acid, fumaric acid, (Anhydrous) Unsaturated polycarboxylic acids (anhydrides) such as itaconic acid and citraconic acid, vinyl chloride, vinyl acetate and the like.

  From the viewpoint of easily forming a cylinder structure and controlling the orientation structure of the cylinder, the ion conductive polymer is preferably a substance having a low glass transition point (Tg). From the same viewpoint, the main chain of the ion conductive polymer is preferably an aliphatic hydrocarbon (the main chain does not have an aromatic ring). Here, the aliphatic hydrocarbon includes an aliphatic hydrocarbon in which a constituent atom is substituted with an atom or a group of atoms other than an aromatic ring. For example, the methylene group of the main chain may be substituted with an oxygen atom, NH group, carbonyl group, carboxyl group, amide group or the like. The main chain may have a substituted or unsubstituted alicyclic hydrocarbon group such as a maleimide structure having a cyclohexylene group. The main chain may have a double bond or a triple bond.

In addition, the film strength can be improved by using a functional group that can be cross-linked by light after film formation as described later.
The ion conductive polymer is not particularly limited as long as it has an ion exchange group and can synthesize a block copolymer. The amount of the ion exchange group may be any as long as it can form a cylinder structure.

  The ion conductive polymer constituting the ion conductive portion may be any polymer that can synthesize a block copolymer, and the ion exchange group contained therein is not particularly limited and may be arbitrarily selected depending on the purpose. Any one of sulfonic acid, carboxylic acid, phosphoric acid, phosphonic acid, and phosphonous acid is particularly preferably used. These polymers may contain one type of ion exchange group or two or more types of ion exchange groups.

  Preferred examples of the monomer having a sulfonic acid group include those obtained by adding a sulfonic acid group to the diene monomer or olefin monomer. Specifically, sulfonic acid (salt) group-containing styrene, sulfonic acid (salt) -containing (meth) acrylate, sulfonic acid (salt) -containing (meth) acrylamide, sulfonic acid (salt) group-containing butadiene, sulfonic acid (salt) Examples thereof include group-containing isoprene, sulfonic acid (salt) group-containing ethylene, and sulfonic acid (salt) group-containing propylene. Furthermore, in order to promote improvement in membrane strength, dimensional stability and phase separation structure of the electrolyte, fluorine introduced into these monomers, ethylenetetrafluoroethylenestyrenesulfonic acid, perfluorocarbonsulfonic acid, Perfluorocarbon phosphonic acid, trifluorostyrene sulfonic acid or the like may be used.

  Furthermore, the ion conductive polymer having a sulfonic acid group as an ion exchange group preferably includes a structure represented by the following chemical formulas (1) to (3) as a repeating unit. As a component constituting the ion conductive block, these structures can be used alone or two or more of them can be used together.

(Wherein R ¹ represents a hydrogen atom or a methyl group, and R ² represents an alkylene group or an arylene group.)

(In the formula, R ³ represents an alkylene group or an arylene group.)

(Wherein R ⁴ represents a hydrogen atom or a methyl group, R ⁵ and R ⁸ represent an alkylene group or an arylene group, R ⁶ and R ⁷ may be the same as or different from each other, and each represents a hydrogen atom or a carbon number of 1 To 3 organic groups.)

Specific examples of each substituent in the above chemical formulas (1) to (3) are shown below.
Examples of the alkylene group include a methylene group, an ethylene group, a propylene group, and a butylene group.
Examples of the arylene group include a phenylene group, a naphthylene group, and a biphenylene group.

Examples of the organic group having 1 to 3 carbon atoms include a methyl group, an ethyl group, an n-propyl group, and an iso-propyl group.
In the block copolymer, microdomains are formed by self-aggregation of each component, and phase separation is performed in a self-organized manner. However, unlike macro phase separation such as water and oil, each component is fixed in one polymer chain, so phase separation is regulated by the size of the molecule, and its size is several nanometers. From meter to 100 nanometers. Furthermore, the form of these phase separations changes into a spherical shape, a cylindrical shape, and a lamellar shape depending on the composition ratio and compatibility of each component, and the size of the microdomain can also be controlled by the chain length and compatibility. In the present invention, in order to form a cylindrical domain in the electrolyte membrane, the volume fraction of the ion conductive block in the block copolymer is preferably 5% or more and 30% or less.

  Such a block copolymer is formed from a solution and heat-treated at a temperature equal to or higher than the glass transition temperature (Tg) of both components (polymer) constituting the block copolymer, so that thermodynamic equilibrium is achieved at this temperature. Express microdomain structure (preparation of phase separation structure). Further, by adding an external field to this step, the microphase separation structure forms a structure arranged in a certain direction (uniaxial orientation). In the present invention, “external field” refers to an electric field, a magnetic field, a shear, and the like.For example, as a method of uniaxial orientation, an electric field, a magnetic field, a shear, etc. are performed while heat-treating the obtained polymer electrolyte membrane. By applying an external field, the ion conducting portion can be oriented in a uniaxial direction. In this case, as long as an external field is applied, the heat treatment may be performed at a temperature equal to or lower than Tg.

  In the present invention, “the structure in which the ion conducting portion 12 is arranged in a cylinder” means that the ion conducting portion has a film thickness due to induction of the microphase separation structure in the block copolymer composed of the ion conducting portion and the matrix portion. It means having a structure oriented in a uniaxial direction in a cylindrical shape in the direction. Specifically, after synthesizing a block copolymer having an ion conductive polymer, a phase separation structure is prepared by film formation and heat treatment, and then uniaxially oriented so that the ion conductive portion is aligned in the film thickness direction. An electrolyte membrane having a structure oriented in a shape is obtained. If uniaxial orientation can be achieved without applying an external field after film formation, of course, this uniaxial orientation treatment step is unnecessary.

  In this uniaxially oriented phase separation structure, the cylinder domains formed by the ion conducting portion are arranged substantially parallel to the film thickness direction. Therefore, even when the cylinder domains are not hydrated by humidification or the like, They are connected without interruption. Therefore, good start-up characteristics and high output characteristics can be stably obtained even under conditions of insufficient water at the time of fuel cell start-up, non-humidification or low humidification conditions.

The structure in which the ion conduction part is uniaxially oriented in a cylindrical shape is confirmed by cutting out an ultrathin section of the film, staining the section with RuO ₄ , and then observing the cross section of the film with a transmission electron microscope (hereinafter, TEM). be able to. Further, by observing the phase separation structure on the surface of the film with an atomic force microscope (hereinafter referred to as AFM), it is possible to confirm a structure in which the ion conducting portion is uniaxially oriented in a cylindrical shape.

  The composition ratio of the block copolymer having an ion conducting portion may be any composition ratio that can produce a cylindrical microphase separation structure. The form of the microphase separation structure such as the cylinder structure depends not only on the volume fraction value, but also on the compatibility parameters of both components constituting the block copolymer (referred to as the χ parameter in the art) and the degree of polymerization of both components. However, the volume fraction should be determined according to the chemical structure of the block copolymer used (compatibility of both blocks) and the degree of polymerization. Generally, it is contained in the block copolymer. The volume fraction of the ion-conductive block (IB) to be formed is 5% to 30%, preferably 10% to 30%. When the volume fraction of IB decreases (about 20% or less), the microphase separation structure becomes a spherical structure, but can be transferred to a cylinder structure by heat treatment and external field. In general, when the volume fraction of IB is less than 5%, it becomes difficult to form a phase separation structure. On the other hand, when the volume fraction of IB exceeds 30%, other phase separation forms (gyroids, lamellae, etc.) appear. To do. The volume fraction indicates the value of the volume fraction of each block chain constituting the block copolymer with respect to one molecular chain of the block copolymer. In addition, what is necessary is just to obtain | require the volume value of each block chain from molecular weight and specific gravity.

  Further, the molecular weight of the ion conductive polymer forming the block copolymer is generally about Mn = 2,000 or more and 500,000 or less, but is not limited to this range. The molecular weight of the matrix polymer is generally about Mn = 1,000 or more and 400,000 or less, but is not particularly limited.

  The method for synthesizing the block copolymer is not particularly limited and depends on the monomer type. For example, (1) after synthesizing an ion conductive polymer having an ion exchange group, the monomer to be a matrix polymer is copolymerized. , (2) After synthesizing the matrix polymer, copolymerize monomers that become ion-conductive polymers with ion-exchange groups, (3) Synthesize ion-conductive polymers and matrix polymers with ion-exchange groups, respectively (4) Synthesis of a block copolymer by polymer reaction and then introducing an ion exchange group after synthesizing the block copolymer.

  The method for synthesizing the block copolymer is not particularly limited as long as the block copolymer is obtained. For example, living polymerization or reaction of a hydrophobic segment prepolymer and a hydrophilic segment prepolymer having an ion exchange group is performed. Thus, a copolymer may be obtained and can be arbitrarily selected according to the application.

  Here, when the living polymerization method is used as a method for synthesizing the block copolymer, it is possible to synthesize the copolymer by freely controlling the degree of polymerization of the block chain. The living polymerization method includes various polymerization methods such as living anion polymerization, living cation polymerization, coordination polymerization, and living radical polymerization. Among these polymerization methods, the present invention is not particularly limited, but a living radical polymerization method is preferably used.

Various techniques have been developed in recent years for the living radical polymerization method, and examples include the following.
For example, Macromol. Chem. Rapid Commun. 1982, Vol. 3, page 133, Iniferter polymerization, Macromolecules, 1994, Vol. 27, page 7228 using a radical scavenger such as a nitroxide compound, Journal of・ The American Chemical Society (J. Am. Chem. Soc.), 1995, Vol. 117, p. 5614, as an initiator and transition metal complex as a catalyst. “RAFT: Reversible Addition-Fragment” shown in “Atom Transfer Radical Polymerization (ATRP)”, Macromolecules, 1998, Vol. 31, p. 5559 application chain transfer polymerization "and the like. By using such a polymerization method, various vinyl monomers can be polymerized.

  One embodiment of the present invention is a polymer electrolyte of a block copolymer in which a polymerizable functional group is contained in a side chain of a matrix polymer 11a that forms a matrix of an electrolyte membrane support site. After forming the block copolymer, the polymerizable functional group is reacted to crosslink only the matrix portion 11 that does not exhibit ionic conductivity, thereby forming an electrolyte membrane that improves the mechanical strength of the entire membrane. be able to. As a specific crosslinking method, a composition comprising (A) a matrix polymer containing a polymerizable functional group in the side chain and (B) a radical generator is prepared, and after such a composition is formed into a film, photoreaction or What is necessary is just to bridge | crosslink, when the radical generate | occur | produced from the radical generating agent of (B) component by thermal reaction reacts and cures between the polymerizable functional groups of the side chain of (A) component between molecules.

  The matrix polymer (A) having a polymerizable functional group in the side chain has an ethylenically unsaturated group that is one or more polymerizable functional groups in one molecule, and a photoreaction or thermal reaction after film formation. The polymer is not particularly limited as long as it is a polymer that can react and cure with radicals generated from the component (B) to form a crosslinked product.

  Examples of the polymerizable functional group of such a compound include a functional group having an ethylenically unsaturated group such as a vinyl group or a (meth) acryl group and reacting by a radical polymerization mechanism. By introducing a structure having a polymerizable functional group in the polymer side chain in this way, the cross-linking reaction proceeds between the matrix polymer side chains after film formation, so that the mechanical properties can be significantly improved and the film characteristics can be expressed. it can.

  The radical polymerizable ethylenically unsaturated group contained in these polymer side chains may contain any functional group derived from a radical polymerizable monomer. Examples of the skeleton of such radical polymerizable monomer include styrene, α- Vinyl aromatic monomers such as methylstyrene, 2-vinylpyridine and 4-vinylpyridine, acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, methyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, ethyl acrylate Butyl acrylate, isooctyl acrylate, octadecyl acrylate, cyclohexyl acrylate, tetrahydrofurfuryl methacrylate, phenyl acrylate, phenethyl acrylate, benzyl methacrylate, β-cyanoethyl acrylate Of α, β-unsaturated carboxylic acids and their derivatives, such as rate, maleic anhydride, diethyl itaconate, acrylamide, methacrylonitrile and N-butylacrylamide, carboxylic acids such as vinyl acetate and vinyl 2-ethylhexanoate Examples thereof include vinyl halides such as vinyl esters, vinyl chloride and vinylidene chloride, N-vinyl compounds such as N-vinyl pyrrolidone, N-vinyl caprolactam and N-vinyl carbazole, and vinyl ketones such as methyl vinyl ketone.

  The method for introducing a polymer side chain of these ethylenically unsaturated groups is not particularly limited, and a monomer containing an ethylenically unsaturated group in the side chain may be polymerized. Unsaturated groups may be introduced. However, when a block polymer is synthesized by radical polymerization, the side chain reacts with the ethylenically unsaturated group in the side chain during the synthesis of the block polymer. More preferably, an ethylenically unsaturated group is introduced into the polymer side chain later.

  The radical polymerization initiator as the component (B) refers to a compound that generates radicals by light, heat, or both, and initiates and accelerates polymerization of the side chain ethylenically unsaturated group of the component (A). . As the radical generator according to the present invention, a known photopolymerization initiator or thermal polymerization initiator can be selected and used.

  As such radical photopolymerization initiator, known compounds can be used, for example, benzoins such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isobutyl ether; acetophenone, 2,2-diethoxy- 2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 1,1-dichloroacetophenone, 2-hydroxy-2-methyl-phenylpropan-1-one, diethoxyacetophenone, 1-hydroxycyclohexyl phenyl ketone, 2 Such as -benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one Anthraquinones such as 2-ethylanthraquinone, 2-tertiarybutylanthraquinone, 2-chloroanthraquinone and 2-amylanthraquinone; thioxanthones such as 2,4-diethylthioxanthone, 2-isopropylthioxanthone and 2-chlorothioxanthone; Ketals such as acetophenone dimethyl ketal and benzyl dimethyl ketal; benzophenones such as benzophenone, 4-benzoyl-4'-methyldiphenyl sulfide and 4,4'-bismethylaminobenzophenone; 2,4,6-trimethylbenzoyldiphenyl Phosphine oxides, phosphine oxides such as bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, 2,4,6-tris (monochloromethyl)- -Triazine, 2,4,6-tris (dichloromethyl) -s-triazine, 2,4,6-tris (trichloromethyl) -s-triazine, 2-methyl-4,6-bis (trichloromethyl) -s -Although s-triazines, such as a triazine, are mentioned, It does not specifically limit to these.

  In addition to these photopolymerization initiators, thermal radical polymerization initiators such as various organic peroxides and azo compounds may be added in consideration of curing using heat treatment after film formation. The type of these thermal polymerization initiators can be appropriately selected according to the heat treatment temperature after film formation. For example, organic oxides include di-tertbutyl peroxide, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane, 2,5, -dimethyl-2,5-di (tert-butylperoxy). ) Hexin-3,3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxonane, 1,1,3,3-tetramethylbutyl hydroperoxide, diisopropylbenzene monohydroperoxide , Tert-butyl hydroperoxide, tert-amyl hydroperoxide, dicumyl peroxide, tert-butyl cumyl peroxide, diisopropylbenzene monohydroperoxide, di (tert-butylperoxyisopropyl) benzene and the like are preferably used.

  By forming a film from a composition solution comprising such a block copolymer having (A) an ethylenically unsaturated group in the side chain and (B) a radical generator, and crosslinking the matrix block 11a, the film strength is increased. In addition to improving the structure, the structure in which the block copolymer is phase-separated in a self-organized manner can be fixed, and by stabilizing the cylindrical proton conduction structure in the membrane, stable proton conduction performance is exhibited. be able to.

  Specifically, a coating film is first formed on the substrate surface with the composition solution. At this time, as a coating method, a coating means such as a spin coating method, a dipping method, a roll coating method, a spray method, or a casting method can be used. The polymer electrolyte membrane of the present invention in which the matrix portion not exhibiting ionic conductivity is cross-linked can also improve ionic conduction by uniaxially orienting the cylinder structure formed by microphase separation. The polymer electrolyte membrane before cross-linking is subjected to uniaxial orientation of the microphase-separated structure by applying an external field such as an electric field while heat-treating to form ion conducting portions arranged in a cylindrical shape in the film thickness direction. Furthermore, the electrolyte membrane in which the matrix block is cross-linked can be formed by a step in which the oriented electrolyte membrane is cross-linked by generating radicals by light irradiation or heating.

Irradiation light in the light irradiation process includes i-line having a wavelength of 365 nm, h-line having a wavelength of 404 nm, g-line having a wavelength of 436 nm, ultraviolet light from a wide wavelength light source such as a xenon lamp, KrF excimer laser having a wavelength of 248 nm, and ArF excimer laser having a wavelength of 193 nm. And the like, and may be selected according to the chemical structure of the radical generator (B), but ultraviolet light and visible light are preferred. The illuminance is preferably 0.1 mW / cm ² or more and 100 mW / cm ² or less, although it depends on the irradiation wavelength.

  On the other hand, when the radical is generated from the (B) radical generator by heating, it is preferable to use a radical generator that decomposes at a temperature higher than the heating temperature at the time of forming the phase separation structure of the block copolymer. When a radical generator that generates radicals at a low temperature is used, cross-linking occurs before the ion conducting portions are arranged in a cylinder shape in the film thickness direction, and thus a uniaxially oriented electrolyte membrane may not be formed.

  By the way, in order to crosslink only the matrix part 11 which does not show ion conductivity, it is also possible to use a crosslinking agent. In this case, a cross-linking agent can be used regardless of whether the block copolymer side chain contains an ethylenically unsaturated group or not. In the former case, the crosslinking agent is chemically bonded to the ethylenically unsaturated group on the side chain of the block copolymer through a covalent bond, so that the phase separation structure is stabilized and the mechanical strength is improved. In the latter case, due to the presence of the block copolymer in the dense network structure formed by the crosslinking agent, the mobility of the polymer chain is constrained by the network, the structure is stabilized, and the mechanical strength is improved. Is also achieved.

  As the crosslinking agent, those containing two or more ethylenically unsaturated groups exhibiting radical polymerizability in the molecule are preferably used. There is no restriction | limiting in particular as a polymeric compound which has an ethylenically unsaturated group, A well-known polymeric compound can be used. For example, examples of compounds having two ethylenically unsaturated groups in the molecule are ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, neopentyl glycol Di (meth) acrylate, 1,3-dioxolane di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, glycerin di (meth) acrylate, polyethylene oxide di (meth) acrylate, polypropylene oxide di (meth) Acrylate, tricyclodecane dimethylol di (meth) acrylate, bisphenol A di (meth) acrylate, polyoxyethylenated bisphenol A di (meth) acrylate, polyoxyethylenated bisphenol F di (meth) acrylate , Polyoxyethylenated bisphenol S di (meth) acrylate, polyoxypropylenated bisphenol A di (meth) acrylate, polyoxypropylenated bisphenol F di (meth) acrylate, polyoxypropylenated bisphenol S di (meth) acrylate, methylene Examples thereof include bisacrylamide, N, N′-acryloylethylenediamine, N, N′-acryloylpropylenediamine, divinylbenzene, diallyl phthalate, allyl acrylate, and allyl methacrylate.

  Examples of compounds having three ethylenically unsaturated groups in the molecule include trimethylolpropane triacrylate, pentaerythritol triacrylate, polyoxyethylenated trimethylolpropane triacrylate, polyoxypropylenated trimethylolpropane triacrylate, N , N ′, N ″ -trihydroxyethyl-1,3,5, triazine-2,4,6, trione triacrylate, glycerol triacrylate, polyoxyethylenated glycerol triacrylate, trimethylolpropane trimethacrylate, pentaerythritol tri And methacrylate.

  Examples of compounds having 4 or more ethylenically unsaturated groups in the molecule include pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, polyhydroxy oligoester polyacrylate, poly Examples thereof include hydroxy oligo urethane polyacrylate, pentaerythritol tetramethacrylate, ditrimethylolpropane tetramethacrylate, dipentaerythritol hexamethacrylate, polyhydroxy oligoester polymethacrylate, and the like.

These polymerizable compounds having an ethylenically unsaturated group may be used alone as a crosslinking agent or may be used in combination of two or more.
The cross-linking agent preferably has a structure that can be localized in a hydrophobic segment (non-ion conductive matrix segment), and preferably has a hydrophobic chemical structure. Among the above, as a highly hydrophobic crosslinking agent, for example, 1,6-hexanediol di (meth) acrylate, tricyclodecane dimethylol di (meth) acrylate, bisphenol A di (meth) acrylate, polyoxyethylenation Bisphenol A di (meth) acrylate, polyoxyethylenated bisphenol F di (meth) acrylate, polyoxyethylenated bisphenol S di (meth) acrylate, polyoxypropylenated bisphenol A di (meth) acrylate, polyoxypropylene bisphenol F Di (meth) acrylate, polyoxypropylenated bisphenol S di (meth) acrylate, divinylbenzene, polyoxypropylenated trimethylolpropane triacrylate, triazine-2,4,6, trionto Although acrylate, and the like without limitation.

  In addition to the two components that make up the block copolymer, the membrane after the addition of the crosslinker as the third component has a hydrophilic segment (ion conductive block) and the crosslinker is localized in the matrix segment. The volume fraction of the hydrophobic segment (matrix block + crosslinker) varies from the volume fraction of the original block copolymer. Therefore, in order to obtain a desired film nanostructure (such as a cylinder), the volume fraction of the original block copolymer and the amount of the crosslinking agent to be added may be adjusted.

  Next, the operation of the electrolyte membrane according to the embodiment of the present invention will be described. The electrolyte membrane in the present invention has a structure in which an ion conducting portion made of an ion conducting polymer and a matrix polymer constituting the membrane are phase separated. Therefore, in the ionic conduction part, the ratio that effectively contributes to ionic conduction is high, and since the ionic conduction part contains a lot of water even at low humidity, the electrolyte membrane has high ionic conductivity and little influence of humidity. Can be obtained. In addition, since the matrix polymer does not change its shape due to the moisture content of the membrane, it is excellent in dimensional stability and can have both high strength and high ionic conductivity.

  Further, in the electrolyte membrane, the ion conduction portion is oriented in a direction substantially parallel to the film thickness direction of the electrolyte membrane, so that the ion migration path between the electrodes provided on both sides of the electrolyte membrane is the shortest ion movement path. Will be connected. Therefore, the ion conduction efficiency is further improved and high ion conduction is obtained. Further, the diffusion rate of water in the ion conducting portion is improved, and water generated at the cathode can be quickly and uniformly distributed in the membrane. Thereby, drying of a film | membrane can be suppressed also under low humidification, and the ionic conductivity characteristic independent of humidity can be acquired.

  By disposing an electrode on the above-described polymer electrolyte membrane of the present invention, a membrane / electrode assembly which is one embodiment of the present invention can be produced. This membrane electrode assembly is composed of the polymer electrolyte of the present invention and catalyst electrodes (anode and cathode) facing each other with the catalyst electrolyte sandwiched therebetween, and the catalyst layer has a catalyst layer formed on the gas diffusion layer. The method for producing the joined body is not particularly limited, and a known technique can be used. For example, platinum, platinum-ruthenium alloy, or a catalyst obtained by dispersing and supporting fine particles thereof on a carrier such as carbon is used as a catalyst. The gas diffusion electrode can be directly formed on the polymer electrolyte membrane, the gas diffusion electrode and the polymer electrolyte membrane can be hot-pressed, or the method can be produced by bonding with an adhesive solution.

  Moreover, a fuel cell can be produced by a known technique using the polymer electrolyte membrane of the present invention and the membrane electrode assembly. An example of the configuration of the fuel cell includes a configuration including the membrane electrode assembly, a pair of separators sandwiching the membrane electrode assembly, a current collector attached to the separator, and a packing. The anode pole side separator is provided with an anode pole side opening, and is supplied with gas fuel or liquid fuel of alcohols such as hydrogen and methanol. On the other hand, the cathode pole side separator is provided with a cathode pole side opening, and is supplied with an oxidant gas such as oxygen gas or air. In the case of a passive type fuel cell, the separator on the oxidant gas side may be omitted.

  An example of the fuel cell unit formed in this way is shown in FIG. In addition, it is also possible to provide a gas flow path such as foam metal instead of the separator or between the separator and the gas diffusion layer.

  By producing a fuel cell using the polymer electrolyte membrane, a high output can be stably obtained over a long period of time even when the electrolyte is not humidified by an auxiliary machine or when the humidity is low. The battery can be downsized. In addition, when the polymer electrolyte membrane in which the matrix of the present invention is cross-linked is used, its mechanical strength and dimensional stability are improved, so that swelling of the membrane due to moisture can be suppressed, and as a fuel cell using methanol as a direct fuel. Since permeation of methanol can be suppressed, it can be suitably used.

EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited only to these Examples. First, various polymers were synthesized by the following procedure.
Synthesis example 1
Synthesis of polystyrene sulfonic acid-b-polystyrene (BP-2) [b represents a block copolymer. ]
In a 20 ml Schlenk tube, 5.5 g of styrene sulfonic acid ethyl ester, 30 μl of 1-bromoethylbenzene (1-Bromoethyl-benzene), 5.5 g of dimethylformamide, 1,1,4,7,10,10-hexamethyltriethylenetetramine 85 μl of (1,1,4,7,10,10-hexanemethyltetramine) and 45 mg of CuBr catalyst were added, and the mixed solution was purged with nitrogen for dissolved oxygen, and then polymerized at 100 ° C. for 5 hours. This was reprecipitated in toluene to obtain polymer a. When the molecular weight of polymer a was measured by gel permeation chromatography (GPC) measurement using DMF as a solvent, Mn (number average molecular weight) was 24,200.

  Then, in a 20 ml Schlenk tube, 1.5 g of styrene monomer, 0.5 g of polymer a, 1.5 g of dimethylformamide, 10 μl of 1,1,4,7,10,10-hexamethyltriethylenetetramine and 5 mg of CuBr catalyst were added, and 110 Polymerization was carried out at 5 ° C. for 5 hours to obtain a block copolymer BP-1 (polystyrenesulfonic acid ethyl ester-b-polystyrene). When the molecular weight of the block copolymer BP-1 was measured by gel permeation chromatography (GPC) measurement using DMF as a solvent, Mn was 82,100.

  Furthermore, 1.5M ammonium carbonate aqueous solution and dimethylformamide were added to the obtained block copolymer BP-1, and the mixture was heated to reflux to deprotect the ethyl ester, and the desired block copolymer polystyrene sulfonic acid-b-polystyrene. (BP-2) was obtained. The volume fraction of polystyrene sulfonic acid in BP-2 was 29%. The structural formula of this block copolymer BP-2 is shown below.

Synthesis example 2
Synthesis of polystyrene sulfonic acid-b-poly (trifluoroethyl methacrylate) (BP-4)
To a 20 ml Schlenk tube, 5.5 g of styrene sulfonic acid ethyl ester, 30 μl of 1-bromoethylbenzene, 5.5 g of dimethylformamide, 85 μl of 1,1,4,7,10,10-hexamethyltriethylenetetramine and 45 mg of CuBr catalyst are added. Then, after replacing the dissolved oxygen with nitrogen, this mixed solution was polymerized at 100 ° C. for 5 hours. This was reprecipitated in toluene to obtain a polymer b. When the molecular weight of the polymer b was measured by gel permeation chromatography (GPC) using DMF as a solvent, Mn was 24,200.

  Next, in a 20 ml Schlenk tube, 3.0 g of trifluoroethyl methacrylate, 1.0 g of polymer b, 3.0 g of dimethylformamide, 16 μl of 1,1,4,7,10,10-hexamethyltriethylenetetramine, CuBr catalyst 11. 7 mg was added, and polymerization was performed at 110 ° C. for 3 hours to obtain a block copolymer BP-3 (polystyrenesulfonic acid ethyl ester-b-polytrifluoromethacrylate trifluoroethyl). When the molecular weight of the block copolymer BP-3 was measured by gel permeation chromatography (GPC) measurement using DMF as a solvent, Mn was 81,420.

  Furthermore, 1.5M ammonium carbonate aqueous solution and dimethylformamide were added to the obtained block copolymer BP-3, and the mixture was refluxed with heating to deprotect the ethyl ester, and the target block copolymer polystyrene sulfonic acid-b-poly Trifluoroethyl methacrylate (BP-4) was obtained. The volume fraction of polystyrene sulfonic acid in BP-4 was 27%. The structural formula of this block copolymer BP-4 is shown below.

Synthesis example 3
Synthesis of polystyrene sulfonic acid-b-polymethyl methacrylate (BP-6)
To a 20 ml Schlenk tube, 8 g of styrene monomer, 51 μl of 1-bromoethylbenzene, 202 μl of 1,1,4,7,10,10-hexamethyltriethylenetetramine and 100 mg of CuBr catalyst are added, and this mixed solution is replaced with nitrogen. Then, polymerization was carried out at 110 ° C. for 2 hours. This was diluted with toluene and then reprecipitated in methanol to obtain polymer c. When the molecular weight of the polymer c was measured by gel permeation chromatography (GPC) measurement using DMF as a solvent, Mn was 19,100.

  Next, 2.0 g of methyl methacrylate, 1.0 g of polymer c, 4 ml of anisole, 19.5 μl of 1,1,4,7,10,10-hexamethyltriethylenetetramine and 14.3 mg of CuBr catalyst are added to a 20 ml Schlenk tube. Polymerization was carried out at 80 ° C. for 10 hours to obtain a block copolymer BP-5 (polymethyl methacrylate-b-polystyrene). When the molecular weight of the block copolymer BP-5 was measured by gel permeation chromatography (GPC) measurement using dimethylformamide as a solvent, Mn was 68,520.

  Furthermore, 5 g of dioxane was added to the reaction vessel, and 0.5 g of anhydrous sulfuric acid was added thereto while keeping the internal temperature at 25 ° C., and the mixture was stirred for 2 hours to obtain an anhydrous sulfuric acid-dioxane complex. In another reaction vessel, 1.3 g of block copolymer BP-5 was dissolved in 4.0 g of 1-tetrahydrofuran. In this, an anhydrous sulfuric acid-dioxane complex was added keeping the internal temperature at 25 ° C., and the mixture was stirred for 2 hours to sulfonate only polystyrene, and BP-6 (polystyrene sulfonic acid-b-polymethyl methacrylate) was obtained. Obtained. The volume fraction of polystyrene sulfonic acid in BP-6 was 29%. The structural formula of this block copolymer BP-6 is shown below.

Synthesis example 4
Synthesis of polystyrene sulfonic acid-r-polystyrene (RP-2) [r represents a random copolymer. ]
To a 20 ml Schlenk tube, 2.5 g of styrenesulfonic acid ethyl ester, 4.5 g of styrene monomer, 2.5 g of dimethylformamide, and 60 mg of azoisobutyronitrile were added, and polymerization was carried out at 100 ° C. for 2 hours. This was reprecipitated in toluene to obtain a random copolymer (RP-1). When the molecular weight of RP-1 was measured by gel permeation chromatography (GPC) measurement using DMF as a solvent, Mn was 100,000.

  Furthermore, 1.5 M ammonium carbonate aqueous solution and dimethylformamide were added to the obtained random copolymer RP-1, heated to reflux, ethyl ester was deprotected, and the desired random copolymer polystyrene sulfonic acid-r-polystyrene. (RP-2) was obtained. The volume fraction of polystyrene sulfonic acid in RP-2 was 28%.

Example 1
The block copolymer BP-2 having a sulfonic acid group as an ion exchange group obtained in Synthesis Example 1 was dissolved in dimethylformamide so as to have a solid concentration of 20 wt%, and a film having a thickness of 30 μm was formed on the Pt substrate by dip coating. Was deposited. Further, the Pt substrate was sandwiched on this substrate so as to be Pt / BP-2 / Pt, an electric field was applied so as to be 40 V / μm, and heating was performed at 160 ° C. for 10 hours to produce an electrolyte membrane. The AFM observation result on the electrolyte membrane surface is shown in FIG.

  As apparent from FIG. 3, a dot-like pattern was observed on the film surface. The volume fraction of polystyrene sulfonic acid sites in BP-2 is 27%, and it is known that polystyrene sulfonic acid, which is an ion conducting part, forms a cylindrical microdomain structure in the body volume fraction. In other words, the dot-like pattern observed on the film surface means a cross section of the cylinder structure, and the cylinder structure formed by the ion conducting portion is uniaxially oriented parallel to the thickness direction of the electrolyte membrane. Admitted.

The obtained electrolyte membrane was pressed against the platinum plate from both sides, and the resistance of the electrolyte membrane was measured by an alternating current two-terminal method with a frequency of 1 kHz. As a result, the ionic conductivity at a temperature of 50 ° C. and a relative humidity of 50% was 0.02 S · cm ^−. It was ¹ .

Example 2
BP-4 obtained in Synthesis Example 2 was dissolved in dimethylformamide so as to have a solid content concentration of 20 wt%, and a film having a thickness of 30 μm was formed on the Pt substrate by dip coating. Further, the Pt substrate was sandwiched on this substrate so as to be Pt / BP-4 / Pt, an electric field was applied so as to be 40 V / μm, and heating was performed at 160 ° C. for 10 hours to produce an electrolyte membrane. As a result of performing AFM observation on the surface of the electrolyte membrane, a microphase-separated structure in which the ion conducting portion was uniaxially oriented parallel to the thickness direction of the electrolyte membrane was recognized.

The obtained electrolyte membrane was pressed against the platinum plate from both sides, and the resistance of the electrolyte membrane was measured by an alternating current two-terminal method with a frequency of 1 kHz. As a result, the ionic conductivity at a temperature of 50 ° C. and a relative humidity of 50% was 0.02 S · cm ^−. It was ¹ .

Example 3
BP-6 obtained in Synthesis Example 3 was dissolved in dimethylformamide so as to have a solid content concentration of 20 wt%, and a film having a thickness of 30 μm was formed on the Pt substrate by dip coating. Further, the Pt substrate was sandwiched on this substrate so as to be Pt / BP-6 / Pt, an electric field was applied so as to be 40 V / μm, and heating was performed at 160 ° C. for 10 hours to produce an electrolyte membrane. As a result of performing AFM observation on the surface of the electrolyte membrane, a microphase-separated structure in which the ion conducting portion was uniaxially oriented parallel to the thickness direction of the electrolyte membrane was recognized.

As a result of pressing the platinum plate from both sides of the obtained electrolyte membrane and measuring the resistance of the electrolyte membrane by an AC two-terminal method with a frequency of 1 kHz, the ionic conductivity at a temperature of 50 ° C. and a relative humidity of 50% is 0.03 S · cm ^−. It was ¹ .

Comparative Example 1
BP-2 obtained in Synthesis Example 1 was dissolved in dimethylformamide so as to have a solid content concentration of 20 wt%, and a film having a thickness of 30 μm was formed on the Pt substrate by dip coating, and 5 ° C. on a hot plate at 70 ° C. Dried for minutes. This film is a film that has not been subjected to long-time heat treatment and alignment treatment by an external field. As a result of performing AFM observation on the surface of the obtained electrolyte membrane, it was confirmed that the ion conducting portion and the matrix portion were randomly separated in a sea-island structure.

As a result of pressing the platinum plate from both sides of the obtained electrolyte membrane and measuring the resistance of the electrolyte membrane by an alternating current two-terminal method with a frequency of 1 kHz, the ionic conductivity at a temperature of 50 ° C. and a relative humidity of 50% is 0.005 S · cm ^−. It was ¹ .

Comparative Example 2
BP-2 obtained in Synthesis Example 1 was dissolved in dimethylformamide so as to have a solid content concentration of 20 wt%, and a film having a thickness of 30 μm was formed on the Pt substrate by dip coating. Further, this substrate was heated at 160 ° C. for 10 hours to produce an electrolyte membrane. This film is a film that is only heat-treated without applying an external field. As a result of performing AFM observation on the surface of the obtained electrolyte membrane, it was confirmed that the ion conducting portion and the matrix portion were randomly separated in a sea-island structure.

As a result of pressing the platinum plate from both sides of the obtained electrolyte membrane and measuring the resistance of the electrolyte membrane by an alternating current two-terminal method with a frequency of 1 kHz, the ionic conductivity at a temperature of 50 ° C. and a relative humidity of 50% is 0.007 S · cm ^−. It was ¹ .

Comparative Example 3
RP-2 obtained in Synthesis Example 4 was dissolved in dimethylformamide so as to have a solid content concentration of 20 wt%, and a 30 μm-thick film was produced on a Pt substrate by dip coating to obtain an electrolyte film. This film is not a block copolymer but a film made of a random copolymer. The surface of the obtained electrolyte membrane was observed by AFM, but no phase separation structure was confirmed.

As a result of pressing the platinum plate from both sides of the obtained electrolyte membrane and measuring the resistance of the electrolyte membrane by an alternating current two-terminal method with a frequency of 1 kHz, the ionic conductivity at a temperature of 50 ° C. and a relative humidity of 50% is 0.001 S · cm ^−. It was ¹ .

Synthesis example 5
Synthesis of a block copolymer (BP-8) comprising a sulfonic acid-containing block containing a structure represented by the formula (1) as a repeating unit and a polystyrene block, 0.3 mmol of copper bromide, pentamethyldiethylenetriamine under a nitrogen atmosphere 0.3 mmol, methyl 2-bromopropionate 0.3 mmol, and tert-butyl acrylate (tBA) 45 mmol were mixed, and after replacing the dissolved oxygen with nitrogen, the reaction was performed at 70 ° C. The reaction was carried out while confirming the polymerization rate by gas chromatography, and the reaction was stopped by quenching with liquid nitrogen. As a result of confirming the molecular weight of the obtained poly tBA by GPC, it was Mn = 13,600 and Mw / Mn = 1.07.

  Subsequently, 0.4 mmol of poly tBA having bromine at the end, 0.4 mmol of copper (I) bromide, 0.4 mmol of hexamethyltriethylenetetraamine, and 800 mmol of styrene were mixed and purged with nitrogen. After the reaction at 100 ° C., the reaction was stopped by quenching with liquid nitrogen. After purification by reprecipitation into methanol, the molecular weight of the obtained PtBA-b-PSt (BP-7) was confirmed by GPC. As a result, Mn = 75,700 and Mw / Mn = 1.18. From these results, the molecular weight of each block was calculated to be 13,600 for the PtBA block and 62,100 for the PSt block, and agreed well with the composition ratio of both blocks determined from the peak integrated value ratio of 1H-NMR.

  Then, the resulting block copolymer BP-7 was mixed with trifluoroacetic acid (5 equivalents relative to the tert-butyl group) in tetrahydrofuran (THF) at room temperature to deprotect the tert-butyl group of the PtBA segment. Reaction was carried out to convert to carboxylic acid to obtain polyacrylic acid-b-polystyrene (PAA-b-PSt). Further, PAA-b-PSt is dissolved in THF, sodium hydride (10 equivalents relative to the carboxylic acid) and 1,3-propane sultone (20 equivalents relative to the carboxylic acid) are added, heated to reflux, and PAA By performing sulfonation of the segment, a block copolymer (BP-8) having the target structural formula (1) having a sulfonic acid group as an ion exchange group as one component was obtained. The volume fraction of the sulfonic acid-containing block in BP-8 was 23%. The structural formula of this block copolymer BP-8 is shown below.

Synthesis Example 6
Synthesis of a block copolymer (BP-10) comprising a sulfonic acid-containing block containing a structure represented by the formula (2) as a repeating unit and polyhexafluoroisopropyl acrylate, under a nitrogen atmosphere, 0.6 mmol of copper bromide, Hexamethyltriethylenetetraamine (0.6 mmol), 1-bromoethylbenzene (0.3 mmol), and tert-butoxystyrene (tBOS) (30 mmol) were mixed. After replacing the dissolved oxygen with nitrogen, the reaction was carried out at 110 ° C. The reaction was carried out while confirming the polymerization rate by gas chromatography, and the reaction was stopped by quenching with liquid nitrogen. As a result of confirming the molecular weight of the obtained poly tBOS by GPC, it was Mn = 10,300 and Mw / Mn = 1.12.

  Then, bromine-terminated poly tBOS 0.4 mmol, copper (I) bromide 0.4 mmol, pentamethyldiethylenetriamine 0.4 mmol, 1,1,1,3,3,3-hexafluoroisopropyl 100 mmol of acrylate (HFIPA) was dissolved and mixed in trifluorotoluene / anisole (2/1, v / v) as a solvent and purged with nitrogen. After the reaction at 90 ° C., the reaction was stopped by quenching with liquid nitrogen. After purification by reprecipitation into methanol, the molecular weight of the obtained PtBOS-b-PHFIPA (BP-9) was confirmed by GPC. As a result, Mn = 48,100 and Mw / Mn = 1.22. From these results, the molecular weight of each block was calculated to be 10,300 for the PtBOS block and 37,800 for the PHFIPA block, and was in good agreement with the composition ratio of both blocks determined from the peak integrated value ratio of 1H-NMR.

  Next, the obtained block copolymer BP-9 was added to 8.6N hydrobromic acid (tert-butoxy group) using trifluorotoluene / 1,4-dioxane (1/1, v / v) as a solvent. 3 equivalents) at 60 ° C. to carry out deprotection reaction of the tert-butoxy group of the PtBOS segment to convert it into phenol to obtain polyvinylphenol-b-polyhexafluoroisopropyl acrylate (PVPh-b-PHFIPA). It was. Further, PVPh-b-PHFIPA is dissolved in THF, sodium hydride (10 equivalents with respect to the hydroxyl group) and 1,4-butane sultone (20 equivalents with respect to phenol) are added, heated to reflux, and the sulfone of the PVPh segment is added. As a result, a block copolymer (BP-10) having a target structural formula (2) having a sulfonic acid group as an ion exchange group as one component was obtained. The volume fraction of the sulfonic acid-containing block in BP-10 was 26%. The structural formula of this block copolymer BP-10 is shown below.

Synthesis example 7
Synthesis of a block polymer (BP-12) comprising a sulfonic acid-containing block containing a structure represented by the formula (3) as a repeating unit and polytrifluoroethyl methacrylate, in a nitrogen atmosphere, 0.2 mmol of copper chloride, hexamethyl After mixing 0.4 mmol of triethylenetetraamine, 0.2 mmol of 2-ethylbromoisobutyrate, 30 mmol of dimethylaminoethyl methacrylate (DMAMA), and replacing the dissolved oxygen with nitrogen, the reaction was carried out at 40 ° C. . The reaction was carried out while confirming the polymerization rate by gas chromatography, and the reaction was stopped by quenching with liquid nitrogen. As a result of confirming the molecular weight of the obtained polyDMAMA by GPC, it was Mn = 12,200 and Mw / Mn = 1.24.

  Subsequently, the obtained polyDMAMA 0.3 mmol, copper (I) bromide 0.3 mmol, 4,4-dinonyl-2,2-bipyridyl 0.6 mmol, 2,2,2-trifluoroethyl methacrylate ( 200 mmol of TFEMA) was dissolved and mixed in trifluorotoluene / dimethylformamide (1/1, v / v) as a solvent and purged with nitrogen. After the reaction at 80 ° C., the reaction was stopped by quenching with liquid nitrogen. After purification by reprecipitation into methanol, the molecular weight of the obtained PDMAMA-b-PTFEMA (BP-11) was confirmed by GPC. As a result, Mn = 64,600 and Mw / Mn = 1.21. From these results, the molecular weight of each block was calculated to be 12,200 for the PDMAMA block and 52,400 for the PTFEMA block, and was in good agreement with the composition ratio of both blocks obtained from the peak integration value ratio of 1H-NMR.

  Next, 1,3-propane sultone (2 equivalents to the DMAMA unit) was added to the obtained block copolymer BP-11 using trifluorotoluene / THF (1/1, v / v) as a solvent, and 40 A block copolymer (BP-12) having the target structural formula (3) having sulfonic acid as an ion exchange group as one component was obtained by reacting at 0 ° C. and sulfonating the PDMAMA segment. The volume fraction of the sulfonic acid-containing block in BP-12 was 28%. The structural formula of this block copolymer BP-12 is shown below.

Example 4
In this example, an electrolyte membrane was produced from a block copolymer having the formula (1) as a repeating unit of an ion conducting portion. BP-8 obtained in Synthesis Example 5 was dissolved in propylene glycol methyl ether acetate so as to have a solid concentration of 15 wt%, and a film having a thickness of 25 μm was formed on the Pt substrate by dip coating. Next, the substrate was sandwiched between Pt substrates in a sandwich structure so as to be Pt / BP-8 / Pt, and an electric field was applied at 100 ° C. for 30 hours at 30 V / μm. As a result of performing AFM observation on the surface of the electrolyte membrane, a microphase-separated structure in which the ion conducting portion was uniaxially oriented parallel to the thickness direction of the electrolyte membrane was recognized.

The obtained electrolyte membrane was pressed against the platinum plate from both sides, and the resistance of the electrolyte membrane was measured by an alternating current two-terminal method with a frequency of 1 kHz. As a result, the ionic conductivity at a temperature of 50 ° C. and a relative humidity of 50% was 0.04 S · cm ^−. It was ¹ .

Example 5
In this example, an electrolyte membrane was prepared from a block copolymer having the formula (2) as a repeating unit of an ion conducting portion. BP-10 obtained in Synthesis Example 6 was dissolved in dimethylformamide so as to have a solid content concentration of 17 wt%, and a film having a thickness of 25 μm was formed on the Pt substrate by dip coating. Further, sandwiched between Pt substrate and Pt / BP-10 / Pt by a sandwich structure on this substrate, and an electric field was applied for 10 hours at 140 ° C. to 40 V / μm. As a result of performing AFM observation on the surface of the electrolyte membrane, a microphase-separated structure in which the ion conducting portion was uniaxially oriented parallel to the thickness direction of the electrolyte membrane was recognized.

The obtained electrolyte membrane was pressed against the platinum plate from both sides, and the resistance of the electrolyte membrane was measured by an alternating current two-terminal method with a frequency of 1 kHz. As a result, the ionic conductivity at a temperature of 50 ° C. and a relative humidity of 50% was 0.05 S · cm ^−. It was ¹ .

Example 6
In this example, an electrolyte membrane was prepared from a block copolymer having the formula (3) as a repeating unit of an ion conducting portion. BP-12 obtained in Synthesis Example 7 was dissolved in propylene glycol methyl ether acetate so as to have a solid content concentration of 22 wt%, and a film having a thickness of 30 μm was formed on the Pt substrate by dip coating. Further, this substrate was sandwiched between Pt substrates so as to be Pt / BP-12 / Pt, and an electric field was applied for 10 hours at 140 ° C. so as to be 40 V / μm. As a result of performing AFM observation on the surface of the electrolyte membrane, a microphase-separated structure in which the ion conducting portion was uniaxially oriented parallel to the thickness direction of the electrolyte membrane was recognized.

The obtained electrolyte membrane was pressed against the platinum plate from both sides, and the resistance of the electrolyte membrane was measured by an alternating current two-terminal method with a frequency of 1 kHz. As a result, the ionic conductivity at a temperature of 50 ° C. and a relative humidity of 50% was 0.04 S · cm ^−. It was ¹ .

Synthesis example 8
Synthesis of a polymer having a structure represented by the formula (3) as an ion conductive block, and a block polymer (BP-14) in which a polymerizable functional group is introduced into a side chain of a matrix polymer as a block that does not exhibit ion conductivity Under a nitrogen atmosphere, 0.35 mmol of copper chloride, 0.7 mmol of hexamethyltriethylenetetraamine, 0.35 mmol of 2-ethylbromoisobutyrate, and 40 mmol of dimethylaminoethyl methacrylate (DMAMA) were mixed. After replacing the dissolved oxygen, the reaction was carried out at 40 ° C. The reaction was carried out while confirming the polymerization rate by gas chromatography, and the reaction was stopped by quenching with liquid nitrogen. As a result of confirming the molecular weight of the obtained polyDMAMA by GPC, it was Mn = 9,400 and Mw / Mn = 1.29.

  Subsequently, the obtained polyDMAMA 0.3 mmol, copper (I) bromide 0.25 mmol, 4,4-dinonyl-2,2-bipyridyl 0.5 mmol, 2- (trimethylsilyloxy) ethyl methacrylate (TMSOMA) 200 mmol was dissolved and mixed in dimethylformamide as a solvent and purged with nitrogen. After the reaction at 70 ° C., the reaction was stopped by quenching with liquid nitrogen. After purification by reprecipitation in methanol, the molecular weight of the obtained PDMAMA-b-PTMSOMA (BP-13) was confirmed by GPC. As a result, Mn = 58,300 and Mw / Mn = 1.27. From these results, the molecular weight of each block was calculated to be 9,400 for the PDMAMA block and 48,900 for the PTMOMA block, and was in good agreement with the composition ratio of both blocks determined from the peak integrated value ratio of 1H-NMR.

  Next, the obtained BP-13 was dissolved in THF and mixed with a 6N aqueous hydrochloric acid solution at room temperature to deprotect the trimethylsilyl group, thereby converting the side chain of the PTMSOMA block into a hydroxyl group. The obtained product was dissolved in THF and reacted with acrylic acid chloride in the presence of triethylamine to introduce an acrylic group that is a polymerizable functional group into a block side chain that does not exhibit ionic conductivity.

  Furthermore, the block copolymer with an acrylic group introduced in the side chain was added 1,3-propane sultone (2 equivalents to the DMAMA unit) using THF as a solvent and reacted at 40 ° C. to sulfonate the PDMAMA segment. To obtain a block copolymer (BP-14) containing a block in which an acrylic group is introduced into the side chain of the matrix polymer that contains the structural formula (3) as an ion conductive component and does not exhibit ion conductivity. It was. The volume fraction of the sulfonic acid-containing block in BP-14 was 25%. The structural formula of this block copolymer BP-14 is shown below.

Example 7
In this example, an electrolyte composition comprising a block copolymer having the formula (3) as a repeating unit of an ionic conduction part and having a polymerizable functional group in a block that does not exhibit ionic conductivity, and a thermal radical generator. This is an example in which an electrolyte membrane in which the matrix portion was cross-linked after being prepared and formed was formed.

  An electrolyte composition was prepared by dissolving 25 parts by weight of BP-14 obtained in Synthesis Example 8 and 100 parts by weight of dimethylformamide so that dicumyl peroxide was 8 parts by weight as a thermal radical generator.

  A film having a film thickness of 25 μm was formed on the Pt substrate by dip coating from this composition solution. Further, the substrate was heated at 110 ° C. for 10 hours to produce an electrolyte membrane. This film is a film in which a matrix portion not showing ion conductivity is cross-linked by performing a heat treatment without applying an external field. When infrared spectroscopic (IR) measurement of the film after heat treatment was performed, the peak (1615 cm-1) derived from the acrylic group of the polymer side chain that existed after film formation disappeared, indicating that the crosslinking reaction had progressed. confirmed. Moreover, as a result of performing AFM observation of the obtained electrolyte membrane surface, it was recognized that the ion conduction part and the matrix site | part were phase-separated disorderly by the sea island structure.

As a result of pressing the platinum plate from both sides of the obtained electrolyte membrane and measuring the resistance of the electrolyte membrane by an alternating current two-terminal method with a frequency of 1 kHz, the ionic conductivity at a temperature of 50 ° C. and a relative humidity of 50% is 0.008 S · cm ^−. It was ¹ .

  Further, when the film hardness was measured by a nanoindentation method (manufactured by Elionix, ENT-1100), the uncrosslinked film of Example 4 was 0.2 GPa, whereas the crosslinked film of this example was Was 0.7 GPa, and it was confirmed that the mechanical strength was improved.

Example 8
In this example, an electrolyte composition comprising a block copolymer having a polymerizable functional group in a block having formula (3) as a repeating unit of an ionic conduction part and not exhibiting ionic conductivity, and a photoradical generator. By applying an electric field after forming the film, an ion conductive part forms a microphase-separated structure uniaxially oriented parallel to the thickness direction of the electrolyte film, and an electrolyte film in which the matrix part is cross-linked is formed. This is a manufactured example.

  22 parts by weight of BP-14 obtained in Synthesis Example 8 and 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one (Irgacure 369; (Specialty Chemicals) was dissolved in 100 parts by weight of propylene glycol methyl ether acetate so as to be 5 parts by weight to prepare an electrolyte composition.

A film having a thickness of 20 μm was formed on the Pt substrate by dip coating from this composition solution. The substrate was sandwiched between Pt substrates so as to be Pt / BP-14 / Pt, and an electric field was applied at 70 ° C. for 6 hours so as to be 40 V / μm. Subsequently, the i-line was exposed to irradiation light to perform a crosslinking reaction of the matrix polymer side chain. When infrared spectroscopy (IR) measurement of the film after light irradiation was performed, the peak (1615 cm ⁻¹ ) derived from the acrylic group of the polymer side chain that existed after the film formation disappeared, indicating that the crosslinking reaction had progressed. confirmed. Further, as a result of AFM observation of the electrolyte membrane surface, a microphase separation structure in which the ion conducting portion was uniaxially oriented parallel to the thickness direction of the electrolyte membrane was recognized.

As a result of pressing the platinum plate from both sides of the obtained electrolyte membrane and measuring the resistance of the electrolyte membrane by an AC two-terminal method with a frequency of 1 kHz, the ionic conductivity at a temperature of 50 ° C. and a relative humidity of 50% is 0.03 S · cm ^−. It was ¹ .

  Further, when the film hardness was measured by a nanoindentation method (manufactured by Elionix, ENT-1100), the uncrosslinked film of Example 4 was 0.2 GPa, whereas the crosslinked film of this example was Was 0.6 GPa, and it was confirmed that the mechanical strength was improved.

Example 9
An example of a method for producing a membrane electrode assembly and a fuel cell is shown below.
HiSPEC1000 (registered trademark, manufactured by Johnson & Massey) was used as the catalyst powder, and Nafion solution (registered trademark, manufactured by DuPont) was used as the electrolyte solution. First, a mixed dispersion of catalyst powder and electrolyte solution was prepared, and a film was formed on a PTFE sheet using a doctor blade method to prepare a catalyst sheet. Next, the produced catalyst sheet was hot-press-transferred on the electrolyte membrane subjected to the uniaxial orientation treatment of BP-14 obtained in Example 8 at 150 ° C. and 9.8 MPa (100 kgf / cm ² ) by a decal method. A membrane electrode assembly was produced. Further, the membrane electrode assembly was sandwiched between carbon cross electrodes (manufactured by E-TEK), and then clamped by sandwiching with a current collector to produce a fuel cell as shown in FIG.

Using the prepared fuel cell, hydrogen gas was injected into the anode side at an injection rate of 300 ml / min, air was supplied to the cathode side, the cell outlet pressure was atmospheric pressure, the relative humidity was 50% for both the anode and cathode, and the cell temperature was The temperature was 50 ° C. When a discharge test was performed at a current density of 400 mA / cm ² , the initial cell potential was 540 mV. As a result of confirming the stability of the battery output performance, the cell potential after the operation for one week or more was hardly changed from 99% of the initial value, and the output was stable.

Comparative Example 4
A fuel cell was produced and operated under the same conditions as in Example 9 except that the electrolyte membrane made of the random copolymer RP-2 obtained in Synthesis Example 4 was used, and the stability of the battery output performance was confirmed. One week later, the cell potential was 50% of the initial cell potential, and the output was greatly reduced.

Example 10
In this example, a block copolymer having the formula (1) as a repeating unit of an ionic conduction part and an electrolyte composition composed of a photo radical generator and a crosslinking agent were prepared, and an electric field was applied after film formation. This is an example in which an electrolyte membrane in which a microphase separation structure is formed in which the ion conducting portion is uniaxially oriented parallel to the thickness direction of the electrolyte membrane and the matrix portion is crosslinked.

  25 parts by weight of BP-8 obtained in Synthesis Example 5, 7 parts by weight of polyoxypropylenated bisphenol A diacrylate as a crosslinking agent, and 2-benzyl-2-dimethylamino-1- (4-morpholine as a photo radical generator Rinophenyl) -butan-1-one (Irgacure 369; manufactured by Ciba Specialty Chemicals) was dissolved in 100 parts by weight of propylene glycol methyl ether acetate so as to be 5 parts by weight to prepare an electrolyte composition.

A film having a thickness of 30 μm was formed on the Pt substrate by dip coating from this composition solution. A Pt substrate was sandwiched on this substrate so as to be Pt / BP-8 + crosslinking agent / Pt, and an electric field was applied at 70 ° C. for 6 hours so as to be 40 V / μm. Subsequently, the i-line was exposed to irradiation light to perform a crosslinking reaction of the matrix polymer side chain. Infrared spectroscopy (IR) measurement of the film after light irradiation revealed that the cross-linking reaction proceeded because the peak (1613 cm ⁻¹ ) derived from the acrylic group contained in the cross-linking agent present after film formation disappeared. It was confirmed. Further, as a result of AFM observation of the electrolyte membrane surface, a microphase separation structure in which the ion conducting portion was uniaxially oriented parallel to the thickness direction of the electrolyte membrane was recognized.

As a result of pressing the platinum plate from both sides of the obtained electrolyte membrane and measuring the resistance of the electrolyte membrane by an AC two-terminal method with a frequency of 1 kHz, the ionic conductivity at a temperature of 50 ° C. and a relative humidity of 50% is 0.03 S · cm ^−. It was ¹ .

  Further, when the film hardness was measured by a nanoindentation method (manufactured by Elionix, ENT-1100), the uncrosslinked film of Example 4 was 0.2 GPa, whereas the crosslinked film of this example was Was 1.0 GPa, and it was confirmed that the mechanical strength was improved.

  The polymer electrolyte membrane according to a preferred embodiment of the present invention has a high ion conductivity, and can stably obtain a high output without humidifying the electrolyte by an auxiliary device. It can be used for fuel cells.

It is a schematic block diagram which shows one Embodiment of the polymer electrolyte membrane of this invention. It is a block diagram which shows one Embodiment of the block copolymer of this invention. It is an AFM image of the micro phase separation structure which the block copolymer of this invention forms. It is a schematic block diagram which shows an example of the unit of the fuel cell of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Polymer electrolyte membrane 11 Matrix 12 Ion conduction part 14 Cylindrical domain 13 Block copolymer 12a Ion conductive block (ion conductive polymer)
11a Matrix block (matrix polymer)
21 Polymer electrolyte membrane 22a, 22b Catalyst layer 23a, 23b Gas diffusion layer 24a, 24b Separator 25a, 25b Current collector 26 Packing

Claims (19)

  An electrolyte membrane made of a block copolymer having an ion conductive block, wherein the cylindrical domain of the ion conductive portion formed by the ion conductive block is arranged in parallel with the thickness direction of the electrolyte membrane. A characteristic polymer electrolyte membrane.   The polymer electrolyte membrane according to claim 1, wherein the ion conductive block is made of a polymer having an ion exchange group.   2. The polymer electrolyte membrane according to claim 1, wherein the volume fraction of the ion conductive block in the block copolymer is 5% or more and 30% or less.   2. The polymer electrolyte membrane according to claim 1, wherein the main chain of the block copolymer does not have an aromatic ring. The repeating unit of the ion conductive block of the electrolyte made of the block copolymer includes at least one structure selected from the group represented by the following chemical formulas (1) to (3). 1. The polymer electrolyte membrane according to 1.
(Wherein R ¹ represents a hydrogen atom or a methyl group, and R ² represents an alkylene group or an arylene group.)
(In the formula, R ³ represents an alkylene group or an arylene group.)
(Wherein R ⁴ represents a hydrogen atom or a methyl group, R ⁵ and R ⁸ represent an alkylene group or an arylene group, R ⁶ and R ⁷ may be the same as or different from each other, and each represents a hydrogen atom or a carbon number of 1 To 3 organic groups.)   A polymer electrolyte membrane comprising a block copolymer having a block showing ionic conductivity and a block showing no ionic conductivity, wherein the volume fraction of the block showing the ionic conductivity in the block copolymer 5 to 30%, and a molecular chain of a block that does not exhibit ionic conductivity has a crosslinked structure.   The block showing ion conductivity forms a cylindrical domain of an ion conductive part, and the cylindrical domain is arranged in parallel with the thickness direction of the electrolyte membrane. Polymer electrolyte membrane.   The polymer electrolyte membrane according to claim 6, wherein the main chain of the block copolymer does not have an aromatic ring.   A polymer electrolyte membrane comprising a block copolymer having a block showing ionic conductivity and a block showing no ionic conductivity, wherein the volume fraction of the block showing the ionic conductivity in the block copolymer 5 to 30%, and the polymer electrolyte is characterized in that at least one crosslinkable group is contained in the repeating unit of the block that does not exhibit ionic conductivity.   The polymer electrolyte according to claim 9, wherein the main chain of the block copolymer does not have an aromatic ring.   (A) A polymer electrolyte membrane comprising a block copolymer having a block exhibiting ionic conductivity and a block not exhibiting ionic conductivity, wherein the block exhibiting ionic conductivity in the block copolymer A polymer electrolyte having a volume fraction of 5% or more and 30% or less and containing at least one cross-linked structure in the repeating unit of the block not exhibiting ionic conductivity, and (B) a radical generator An electrolyte composition characterized by that.   The electrolyte composition according to claim 11, wherein the main chain of the block copolymer does not have an aromatic ring.   Step of forming a block copolymer having an ion conductive block, ion conduction in which the cylindrical domain formed by the ion conductive block of the formed block copolymer is uniaxially aligned and arranged in the thickness direction of the electrolyte membrane A method for producing a polymer electrolyte membrane comprising the step of forming a portion.   14. The method for producing a polymer electrolyte membrane according to claim 13, further comprising a step of crosslinking the polymer side chain of the block having no ion conductivity.   14. The method for producing a polymer electrolyte membrane according to claim 13, wherein the formed block copolymer is subjected to a heat treatment and an external field to uniaxially align the cylindrical domain formed by the ion conductive block. .   A membrane electrode assembly, wherein electrodes are arranged on both surfaces of the polymer electrolyte membrane according to claim 1.   The membrane electrode assembly according to claim 16, wherein the ion conductive portions of the polymer electrolyte membrane are arranged in a direction perpendicular or substantially perpendicular to the electrode surface.   A fuel cell comprising at least a membrane electrode assembly in which electrodes are arranged on both surfaces of the polymer electrolyte membrane according to claim 1 and a current collector.   19. The fuel cell according to claim 18, wherein the ion conducting portions of the polymer electrolyte membrane are arranged in a direction perpendicular or substantially perpendicular to the electrode surface.