JP2008078130A - Polymer electrolyte membrane, manufacturing method therefor, and evaluation method of the proton conductivity of the polymer electrolyte membrane - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polymer electrolyte membrane having superior proton conductivity in its thickness direction. <P>SOLUTION: The polymer electrolyte membrane, preferably, contains a polymer compound containing an ionic segment having an ionic functional group and non-ionic segment having substantially no ionic functional group, and the phase containing ionic segments and the phase containing non-ionic segments are phase-separated, and in the surface region thereof, the change in the amount of ionic segment from the surface toward the interior decreases substantially monotonically. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a polymer electrolyte membrane, a method for producing the same, and a method for evaluating proton conductivity of the polymer electrolyte membrane.

  Conventionally, as a polymer electrolyte for use in a polymer electrolyte fuel cell, perfluorosulfonic acid-based materials such as Nafion (registered trademark) having proton conductivity can impart excellent characteristics to the fuel cell. It has been known.

  However, since conventional polymer electrolytes may be difficult to use at high temperatures and are very expensive, the development of polymer electrolyte membranes that can eliminate these disadvantages has become active. Among these, polymer electrolytes in which sulfonic acid groups are introduced into aromatic polyethers having excellent heat resistance and high film strength are promising. As such polymer electrolytes, for example, polymer electrolyte membranes such as sulfonated polyether ketone (Patent Document 1) and sulfonated polyethersulfone (Patent Documents 2 and 3) have been proposed.

In addition, a polymer electrolyte membrane for a fuel cell is required to have high proton conductivity in order to obtain high output. As a method for increasing the proton conductivity of a polymer electrolyte membrane, a method for increasing a phase having an ionic functional group such as a sulfonic acid group is generally known. Among these, it is known that a polymer electrolyte membrane having a microphase separation structure is less affected by humidity and has high proton conductivity (Patent Document 4).
Japanese National Patent Publication No. 11-502249 Japanese Patent Laid-Open No. 10-45913 Japanese Patent Laid-Open No. 10-21944 Japanese Patent Laid-Open No. 2003-3232

  By the way, in recent years, further improvement in output has been demanded for fuel cells. In order to obtain higher output, it is preferable that the proton conductivity in the film thickness direction is particularly high in the polymer electrolyte membrane. However, it has been difficult for the conventional polymer electrolyte to obtain a polymer electrolyte membrane having excellent proton conductivity in the film thickness direction.

  Therefore, the present invention has been made in view of such circumstances, and an object thereof is to provide a polymer electrolyte membrane having proton conductivity excellent in the film thickness direction. It is another object of the present invention to provide a method for producing such a polymer electrolyte membrane of the present invention and a method for evaluating proton conductivity of the polymer electrolyte membrane.

  In order to achieve the above object, the present inventors have conducted extensive research. As a result, the proton conductivity in the film thickness direction is determined when the ionic functional group has a specific distribution state in the film thickness direction in the surface area of the film. As a result, the present invention has been completed.

  That is, the polymer electrolyte membrane of the present invention is a polymer electrolyte membrane containing a polymer compound containing an ionic segment having an ionic functional group and a nonionic segment substantially having no ionic functional group. , A phase containing many ionic segments and a phase containing many nonionic segments are separated, and in at least one surface region, the change in the amount of ionic segments from the surface side toward the inner side is substantially It is a characteristic monotonous decrease.

  Thus, if the ionic segments are distributed in the surface region so as to substantially monotonously decrease in the depth direction, the conduction of ions in the film thickness direction in this region becomes good, and the film also in the whole film. Proton conductivity in the thickness direction is improved. On the other hand, if the amount of ionic segments in the surface region increases toward the inner side, or if there is a large change including both increases and decreases, proton conduction is disadvantageous, resulting in a film thickness direction. A sufficiently high proton conductivity cannot be obtained.

Here, the change in the amount of the ionic segment is “substantially monotonically decreasing”. The amount of the ionic segment tends to decrease as a whole toward the inside, and all depth positions This means that the amount of the ionic segment in is not greatly deviated from the above-mentioned decreasing tendency. Therefore, as long as the above-described decreasing tendency is maintained, the inner side may have a portion where the amount of ionic segments is larger than the front side. Further, the “surface region” refers to a region near at least one surface of the polymer electrolyte membrane. For example, it is preferable that the depth in terms of SiO ₂ in the X-ray spectroscopic measurement described later is a region up to 4 nm. Specifically, an actual depth region from the surface to 1000 nm is preferable.

  The distribution of ionic segments in the surface region can be grasped by, for example, signal intensity obtained by X-ray photoelectron spectroscopy (hereinafter abbreviated as “XPS”) measurement. That is, the polymer electrolyte membrane of the present invention is a polymer electrolyte membrane containing a polymer compound containing an ionic segment having an ionic functional group and a nonionic segment substantially having no ionic functional group. The phase is separated into a phase containing many ionic segments and a phase containing many nonionic segments, and the intensity of a specific signal selected from signals derived from ionic segments by XPS is A, When the intensity of a specific signal selected from signals derived from sex segments is B, the change in the value represented by A / (A + B) from the surface side to the inside side is substantially in at least one surface region. It may be characterized by a monotonous decrease.

Further, the signal intensity described above at each depth position, while gradually removing the surface by sputtering using a C ₆₀ ion, it is preferably determined by performing XPS measurement on each surface. That is, the change in the value represented by A / (A + B) described above is that A / with respect to the sputtering time t when sputtering using C ₆₀ ions and measurement of the value represented by A / (A + B) are repeated. This is a change in the value of (A + B). This is because the change in the value represented by A / (A + B) is at each time point t with respect to the elapsed time t when sputtering using C ₆₀ ions is performed in the direction from the surface toward the inside. In other words, it is a change in the value represented by A / (A + B) obtained on the surface.

The “substantially monotonous decrease” described above can be confirmed by, for example, a correlation coefficient between t and a value represented by A / (A + B). That is, in the surface region, the value of A / (A + B) is measured every time a time of 0.1 nm or more and 0.5 nm or less in terms of SiO ₂ has elapsed from the start of sputtering, and from the first time to any n-th time When the correlation coefficient between t obtained by the measurement of A and the value represented by A / (A + B) is obtained, all correlation coefficients obtained when n is 4 or more are negative. It is preferable to be “substantially monotonically decreasing”. When the value of A / (A + B) is changed so as to satisfy such a condition, the polymer electrolyte membrane more reliably has good proton conductivity in the film thickness direction.

  In addition, the specific signal derived from the ionic segment or the nonionic segment is preferably the following signal. That is, the specific signal selected from the signals derived from the ionic segments is preferably a signal that is not observed from the main nonionic segments. The specific signal selected from the signals derived from the nonionic segments is preferably a signal that is not observed from the main ionic segments.

  Thus, the specific signal used for measuring each signal intensity more accurately reflects the content of ionic or nonionic segments. In order to obtain this effect better, it is more preferable that each specific signal is selected so as to satisfy both of the above conditions. The “main ionic segment” described above refers to the type with the highest ratio among the segments classified as the ionic segment, and the “main nonionic segment” has the same definition. The signal that is not observed from the main ionic segment or the nonionic segment is preferably a signal that is not observed from a segment that occupies 50% by weight or more of each segment, and is observed from a segment that occupies 70% by weight or more. More preferably, the signal is not used.

  The polymer electrolyte membrane of the present invention is a polymer electrolyte membrane containing a polymer compound containing an ionic segment having an ionic functional group and a nonionic segment substantially having no ionic functional group. Phase separated into a phase rich in ionic segments and a phase rich in nonionic segments, and a layered portion having a concentration of the nonionic segments substantially higher than the overall average in the surface region. Even if it is characterized by not having, it is preferable.

  Since such a polymer electrolyte membrane does not have a layered portion having a higher concentration of nonionic segments than the whole in its surface region, proton conduction in the thickness direction is rarely inhibited. Therefore, the polymer electrolyte membrane of the present invention has a characteristic that proton conductivity in the thickness direction is good.

  The polymer compound constituting the polymer electrolyte membrane of the present invention is preferably an aromatic polymer compound. Such a compound is excellent in proton conductivity and can improve proton conductivity in the film thickness direction.

［式中、Ａｒ^１は、芳香環に直接結合したイオン性官能基を置換基として少なくとも有する２価の芳香族基を示し、Ｘ^１は、直接結合、オキシ基、チオキシ基、カルボニル基又はスルホニル基を示す。］ It is preferable that the aromatic polymer compound includes a structural unit represented by the following general formula (1) because it can exhibit particularly excellent proton conductivity.

[Wherein Ar ¹ represents a divalent aromatic group having at least an ionic functional group directly bonded to an aromatic ring as a substituent, and X ¹ represents a direct bond, an oxy group, a thioxy group, a carbonyl group or a sulfonyl group. Indicates a group. ]

  The polymer compound is particularly preferably a block copolymer having the ionic segment and the nonionic segment. Since such a block copolymer is likely to cause phase separation between a phase containing many ionic segments and a phase containing many nonionic segments when a polymer electrolyte membrane is formed, the polymer of the present invention It is effective as a constituent material of the electrolyte membrane.

［式中、Ａｒ^１１は、芳香環に直接結合したイオン性官能基を置換基として少なくとも有する２価の芳香族基を示し、Ｘ^１１は、直接結合、オキシ基、チオキシ基、カルボニル基又はスルホニル基を示す。ｄは２以上の整数である。］ More specifically, in this block copolymer, the ionic segment preferably has a structure represented by the following general formula (2).

[In the formula, Ar ¹¹ represents a divalent aromatic group having at least an ionic functional group directly bonded to an aromatic ring as a substituent, and X ¹¹ represents a direct bond, an oxy group, a thioxy group, a carbonyl group or a sulfonyl group. Indicates a group. d is an integer of 2 or more. ]

［式中、Ｘ^１２は、直接結合、オキシ基、チオキシ基、カルボニル基又はスルホニル基を示し、Ｒ^１は、それぞれ独立に、水素原子、炭素数１〜２０のアルキル基、炭素数１〜２０のアルコキシ基、炭素数６〜２０のアリール基、炭素数６〜２０のアリールオキシ基又は炭素数２〜２０のアシル基を示し、Ｊ^１はイオン性官能基を示し、ｐ及びｑはそれぞれ独立に１又は２であり、ｄは２以上の整数である。］ In particular, when the ionic segment has a structure represented by the following general formula (3a) or the following general formula (3b), it tends to exhibit excellent proton conductivity.

[Wherein, X ¹² represents a direct bond, an oxy group, a thioxy group, a carbonyl group or a sulfonyl group, and each R ¹ independently represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or 1 to 20 carbon atoms. Represents an alkoxy group, an aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms or an acyl group having 2 to 20 carbon atoms, J ¹ represents an ionic functional group, and p and q are independent of each other. 1 or 2, and d is an integer of 2 or more. ]

  The ionic functional group possessed by these polymer compounds is preferably a sulfonic acid group. A polymer compound or block copolymer having a sulfonic acid group as an ionic functional group can constitute a polymer electrolyte membrane having particularly excellent proton conductivity.

［式中、Ａｒ^２２は、イオン性官能基を有しない２価の芳香族基を示し、Ｘ^２２は、直接結合、オキシ基、チオキシ基、カルボニル基又はスルホニル基を示す。ｅは２以上の整数である。］ On the other hand, it is preferable that the nonionic segment in said block copolymer has a structure represented by following General formula (5). Thereby, formation of a phase-separated structure with said ionic segment becomes advantageous.

[In the formula, Ar ²² represents a divalent aromatic group having no ionic functional group, and X ²² represents a direct bond, an oxy group, a thioxy group, a carbonyl group or a sulfonyl group. e is an integer of 2 or more. ]

［式中、ａ、ｂ及びｃはそれぞれ独立に０又は１であり、ｚは正の整数である。Ａｒ^２、Ａｒ^３、Ａｒ^４及びＡｒ^５はそれぞれ独立にそれぞれ独立にイオン性官能基を有しない２価の芳香族基を示し、Ｘ及びＸ´はそれぞれ独立に直接結合又は２価の基を示し、Ｙ及びＹ´はそれぞれ独立にオキシ基又はチオキシ基を示す。］ More specifically, as the nonionic segment, those having a structure represented by the following general formula (6) are preferable.

[Wherein, a, b and c are each independently 0 or 1, and z is a positive integer. Ar ² , Ar ³ , Ar ⁴ and Ar ⁵ each independently represent a divalent aromatic group having no ionic functional group, and X and X ′ each independently represent a direct bond or a divalent group. Y and Y ′ each independently represent an oxy group or a thioxy group. ]

  The method for producing a polymer electrolyte membrane according to the present invention is a method for suitably producing the polymer electrolyte membrane of the present invention. That is, the production method of the present invention comprises a polymer electrolyte membrane comprising a polymer electrolyte containing a polymer compound containing an ionic segment having an ionic functional group and a nonionic segment substantially having no ionic functional group. The method includes: a step of applying a solution containing a polymer electrolyte onto a substrate having a surface made of a metal or metal oxide, and an evaporation step of evaporating the solvent from the solution. In the evaporation step, the time from the start of the evaporation of the solvent to the completion thereof is set to 60 minutes or less.

  As described above, when the polymer electrolyte membrane has the distribution of the ionic segments as described above in its surface region, it can exhibit excellent proton conductivity particularly in the film thickness direction. Therefore, confirmation of the distribution of the ionic segments in the surface region can be applied as a method for evaluating proton conductivity in the film thickness direction of the polymer electrolyte membrane.

Based on such a viewpoint, the present invention is directed to proton conduction of a polymer electrolyte membrane containing a polymer compound containing an ionic segment having an ionic functional group and a nonionic segment having substantially no ionic functional group. In this method, sputtering using C ₆₀ ions is performed from the surface to the inside, and the XPS measurement of the surface at each time point during the elapsed time t is performed, whereby the ionicity at each time point t is measured. A step of obtaining an intensity A of a specific signal selected from signals derived from a segment and an intensity B of a specific signal selected from signals derived from a nonionic segment, and expressed by A / (A + B) with respect to t Determining whether the change in value is a substantially monotonic decrease.

  In the above evaluation method, when it is determined that the change in the value represented by A / (A + B) with respect to t in the surface region is a substantially monotonic decrease, the polymer electrolyte membrane is in the film thickness direction. It can be evaluated that it has sufficient proton conductivity.

In such an evaluation method, in the first step, A / (A + B) is measured every time a time of 0.1 nm to 0.5 nm in terms of SiO ₂ has elapsed from the start of sputtering, and the second step In the above, the correlation coefficient between t obtained by the first measurement to any nth measurement and the value represented by A / (A + B) is obtained, and all correlation coefficients obtained when n is 4 or more It is preferable to determine the positive / negative of. Thereby, it becomes possible to grasp the decreasing tendency of the ionic segment in the surface region more accurately, and the proton conductivity in the film thickness direction of the polymer electrolyte membrane can be evaluated well.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the polymer electrolyte membrane which has the proton conductivity excellent in the film thickness direction. It is also possible to provide a method for producing such a polymer electrolyte membrane of the present invention and a method for evaluating the proton conductivity of the polymer electrolyte membrane.

  Hereinafter, preferred embodiments of the present invention will be described.

(Polymer electrolyte)
First, the suitable polymer electrolyte which comprises the polymer electrolyte membrane of suitable embodiment is demonstrated. The polyelectrolyte contains a polymer compound containing an ionic segment having an ionic functional group and a nonionic segment having substantially no ionic functional group.

As such a polymer electrolyte, any polymer electrolyte can be used without particular limitation as long as it has the above structure. For example, the following (A)-(D) are mentioned as a typical example of the polymer electrolyte which has an ionic functional group as a proton conductive group.
(A) a polymer electrolyte in which an ionic functional group is introduced into a hydrocarbon polymer compound having a main chain composed of an aliphatic hydrocarbon;
(B) an aromatic polymer electrolyte in which an ionic functional group is introduced into an aromatic polymer compound having a main chain containing an aromatic ring,
(C) a hydrocarbon polymer electrolyte in which an ionic functional group is introduced into a polymer having a main chain composed of an inorganic unit structure such as an aliphatic hydrocarbon and a siloxane group or a phosphazene group
(D) A polymer electrolyte in which an ionic functional group is introduced into a copolymer in which the repeating units possessed by the polymer compound before the introduction of the ionic functional group in (A) to (C) are appropriately combined Is mentioned.

  Among these, from the viewpoint of heat resistance and ease of recycling, the polymer electrolyte is preferably an aromatic polymer electrolyte such as the above (B). Suitable aromatic polymer electrolytes include polymer compounds having an aromatic ring in the main chain of the polymer chain and an ionic functional group in the side chain and / or main chain. . This aromatic polymer electrolyte is preferably soluble in a solvent. These can be easily formed into a film by a known solution casting method.

  The ionic functional group in the aromatic polyelectrolyte may be directly substituted on the aromatic ring constituting the main chain of the polymer, and the linking group is connected to the aromatic ring constituting the main chain. Or may be both of them.

  Here, the aromatic polymer compound having a main chain containing an aromatic ring includes, for example, those having a main chain in which aromatic rings are linked, such as polyarylene, and the aromatic ring via a divalent group. Some have a main chain linked together. Examples of the divalent group in the latter main chain include an oxy group, a thioxy group, a carbonyl group, a sulfinyl group, a sulfonyl group, an amide group, an ester group, a carbonate group, an alkylene group having about 1 to 4 carbon atoms, and a carbon number of 2 An alkenyl group having about ˜4, an alkynyl group having about 2 to 4 carbon atoms and the like can be mentioned. Of these, an oxy group, a thioxy group, a sulfonyl group, or a carbonyl group is preferable.

  The aromatic ring contained in the main chain of the aromatic polymer compound includes divalent aromatic groups such as phenylene group, naphthylene group, anthracene diyl group, fluorenediyl group, biphenylylene group, pyridinediyl group, flange, etc. And divalent aromatic heterocyclic groups such as yl, thiophenylene, imidazolyl, indolediyl and quinoxalinediyl.

［式中、Ａｒ^１は、芳香環に直接結合したイオン性官能基を置換基として少なくとも有する２価の芳香族基を示し、Ｘ^１は、直接結合、オキシ基、チオキシ基、カルボニル基又はスルホニル基を示す。］ As such an aromatic polymer electrolyte, those containing a structural unit represented by the following general formula (1) are suitable.

[Wherein Ar ¹ represents a divalent aromatic group having at least an ionic functional group directly bonded to an aromatic ring as a substituent, and X ¹ represents a direct bond, an oxy group, a thioxy group, a carbonyl group or a sulfonyl group. Indicates a group. ]

As Ar ¹ in the general formula (1), the divalent aromatic groups exemplified above are preferable, and a phenylene group, a biphenylene group, and a naphthalenediyl group are particularly preferable. This divalent aromatic group may have a substituent in addition to the above ionic functional group. As a substituent, it may have a C1-C20 alkyl group which may have a substituent, a C1-C20 alkoxy group which may have a substituent, and a substituent. Examples thereof include an aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms which may have a substituent, an acyl group having 2 to 20 carbon atoms, a halogeno group, and a nitro group.

  The ionic functional group is a functional group that can cause ion conduction, particularly proton conduction, when a polymer electrolyte membrane is formed, and an ion exchange group is representative. The ion exchange group may be either a cation exchange group (acidic group) or an anion exchange group (basic group), but a cation exchange group is preferred from the viewpoint of obtaining high proton conductivity.

Examples of the cation exchange group include —SO ₃ H, —COOH, —PO (OH) ₂ , —POH (OH), —SO ₂ NHSO ₂ —, —Ph (OH) (Ph represents a phenyl group), and the like. it can. On the other hand, as the anion exchange group, —NH ₂ , —NHR, —NRR ′, —NRR′R ″ ⁺ , —NH ₃ ^{+ and the} like (R, R ′ and R ″ each independently represents an alkyl group, And a cycloalkyl group or an aryl group). Some or all of these ion exchange groups may form a salt with a counter ion.

  Representative examples of the aromatic polymer compound having the structure represented by the general formula (1) include polyether ketone, polyether ether ketone, polysulfone, polyether sulfone, polyether ether sulfone, poly (arylene ether), Polymers such as polyimide, polyphenylene, poly ((4-phenoxybenzoyl) -1,4-phenylene), polyphenylene sulfide, polyphenylquinoxalene, etc., each having an ionic functional group introduced, or sulfoarylated polybenz Imidazole, sulfoalkylated polybenzimidazole, phosphoalkylated polybenzimidazole (for example, JP-A-9-110882), phosphonated poly (phenylene ether) (for example, J. Appl. Polym. Sci., 18, 1969 ( 1974)).

  The polymer compound constituting the polyelectrolyte is composed of a segment having an ionic functional group (hereinafter abbreviated as “ionic segment”) and a segment having substantially no ionic functional group (nonionic segment). Have both. Here, the “segment” means a structural unit having a certain physicochemical property in the polymer compound. For example, the “segment” is a structural unit in which main components are composed of the same repeating unit. A block in a polymer compound called a block copolymer is a typical example of such a segment. In addition, one repeating unit in an alternating copolymer or a random copolymer (for example, JP-A-11-116679) can also be regarded as such a segment.

  Among them, when the polymer compound constituting the polymer electrolyte is the above block copolymer, that is, a block copolymer having an ionic segment and a nonionic segment, an ionic segment and a nonionic segment However, it is preferable to form a phase-separated film into a phase containing many ionic segments and a phase containing many nonionic segments by forming domains in the film. Such a block copolymer may have other structural units in addition to the ionic segment and the nonionic segment. Examples of the other structural unit include a structural unit that connects an ionic segment and a nonionic segment.

  Specific examples of the block copolymer include a block copolymer having a sulfonated aromatic polymer segment described in JP-A-2001-250567, JP-A-2003-32322, and JP-A-2004-359925. No. 2005-234439, JP-A No. 2003-113136, etc., a block having a polyether ketone and a polyether sulfone as a main chain structure and a segment containing a sulfonic acid group A copolymer is mentioned.

  Hereinafter, a suitable example of a block copolymer having an ionic segment and a nonionic segment suitable as a polymer electrolyte will be described in detail.

［式中、Ａｒ^１１は、芳香環に直接結合したイオン性官能基を置換基として少なくとも有する２価の芳香族基を示し、Ｘ^１１は、直接結合、オキシ基、チオキシ基、カルボニル基又はスルホニル基を示す。ｄは２以上の整数である。］ First, as the ionic segment, a segment including a structure in which a plurality of structural units represented by the general formula (1) is connected is preferable. In addition, in such a segment, there is a structural unit having no ionic functional group, for example, a structural unit having a divalent aromatic group not having an ionic functional group as Ar ¹ in the general formula (1). It may be included in a part. In this case, as a guideline corresponding to the ionic segment, there is an average of 0.5 or more ionic functional groups per structural unit. Examples of the ionic segment include a segment having a structure represented by the following general formula (2).

[In the formula, Ar ¹¹ represents a divalent aromatic group having at least an ionic functional group directly bonded to an aromatic ring as a substituent, and X ¹¹ represents a direct bond, an oxy group, a thioxy group, a carbonyl group or a sulfonyl group. Indicates a group. d is an integer of 2 or more. ]

Ar ¹¹ in the formula can be exemplified by the same as Ar ¹ described above. Specific examples of the substituent other than the ionic functional group of the divalent aromatic group in Ar ¹¹ include the following. That is, first, as the alkyl group having 1 to 20 carbon atoms which may have a substituent, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, C1-C20 alkyl groups such as isobutyl group, n-pentyl group, 2,2-dimethylpropyl group, cyclopentyl group, n-hexyl group, cyclohexyl group, 2-methylpentyl group, etc., and fluorine atoms in these groups , Hydroxyl groups, nitrile groups, amino groups, methoxy groups, ethoxy groups, isopropyloxy groups, phenyl groups, naphthyl groups, phenoxy groups, naphthyloxy groups and the like. These groups are preferably those having a total carbon number of 1 to 20.

  Examples of the alkoxy group having 1 to 20 carbon atoms which may have a substituent include a methoxy group, an ethoxy group, an n-propyloxy group, an isopropyloxy group, an n-butyloxy group, a sec-butyloxy group, and a tert- 1 to 20 carbon atoms such as butyloxy group, isobutyloxy group, n-pentyloxy group, 2,2-dimethylpropyloxy group, cyclopentyloxy group, n-hexyloxy group, cyclohexyloxy group, 2-methylpentyloxy group Alkoxy groups and groups in which these groups are substituted with fluorine atoms, hydroxyl groups, nitrile groups, amino groups, methoxy groups, ethoxy groups, isopropyloxy groups, phenyl groups, naphthyl groups, phenoxy groups, naphthyloxy groups, etc. . These groups preferably have 1 to 20 carbon atoms in total.

  Examples of the aryl group having 6 to 20 carbon atoms which may have a substituent include aryl groups such as a phenyl group, a naphthyl group, an anthracenyl group, and a biphenyl group, and these groups include a fluorine atom, a hydroxyl group, and a nitrile. And groups substituted by a group, amino group, methoxy group, ethoxy group, isopropyloxy group, phenyl group, naphthyl group, phenoxy group, naphthyloxy group, and the like. These groups preferably have a total carbon number of 6-20.

  Examples of the aryloxy group having 6 to 20 carbon atoms which may have a substituent include aryloxy groups such as a phenoxy group, a naphthyloxy group, an anthracenyloxy group, and a biphenyloxy group, and these groups. Examples include groups substituted by fluorine atoms, hydroxyl groups, nitrile groups, amino groups, methoxy groups, ethoxy groups, isopropyloxy groups, phenyl groups, naphthyl groups, phenoxy groups, naphthyloxy groups, and the like. These groups also preferably have a total carbon number of 6-20.

  Examples of the acyl group having 2 to 20 carbon atoms include acyl groups such as a benzoyl group, a naphthoyl group, an acetyl group, and a propionyl group, and may have a substituent. Examples of the substituent include a fluorine atom, a hydroxyl group, a nitrile group, an amino group, a methoxy group, an ethoxy group, an isopropyloxy group, a phenyl group, a naphthyl group, a phenoxy group, and a naphthyloxy group. These groups also preferably have a total carbon number of 2-20.

  D in the general formula (2) is an integer of 2 or more indicating the number of repeating units of the structure in parentheses, and is a number representing the degree of polymerization of this ionic segment. d is preferably an integer of 5 or more, more preferably an integer in the range of 5 to 1000, still more preferably an integer of 10 to 1000, and even more preferably an integer of 20 to 500. It is preferable that d is 5 or more because proton conductivity by the polymer electrolyte containing such an ionic segment is improved. On the other hand, it is preferable that the value of d is 1000 or less because the production of the segment can be facilitated while sufficiently ensuring proton conductivity.

［式中、Ｘ^１２は、直接結合、オキシ基、チオキシ基、カルボニル基又はスルホニル基を示し、Ｒ^１は、それぞれ独立に、水素原子、炭素数１〜２０のアルキル基、炭素数１〜２０のアルコキシ基、炭素数６〜２０のアリール基、炭素数６〜２０のアリールオキシ基又は炭素数２〜２０のアシル基を示し、Ｊ^１はイオン性官能基を示し、ｐ及びｑはそれぞれ独立に１又は２であり、ｄは２以上の整数である。］ Preferable specific examples of the segment represented by the general formula (2) include a segment represented by the following general formula (3a) or (3b).

[Wherein, X ¹² represents a direct bond, an oxy group, a thioxy group, a carbonyl group or a sulfonyl group, and each R ¹ independently represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or 1 to 20 carbon atoms. Represents an alkoxy group, an aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms or an acyl group having 2 to 20 carbon atoms, J ¹ represents an ionic functional group, and p and q are independent of each other. 1 or 2, and d is an integer of 2 or more. ]

A polymer electrolyte comprising a block copolymer containing such an ionic segment is a polymer electrolyte membrane that has a high proton conductivity, is also excellent in water absorption dimensional stability, and is particularly excellent in membrane strength. It can be formed. R ¹ in the formulas (3a) and (3b) represents the above substituent, and among them, a hydrogen atom is preferable. That is, as the aromatic groups in the formulas (3a) and (3b), those that are each a phenylene group or a naphthalenediyl group and have no substituent other than the ionic functional group are particularly suitable.

  Examples of the segment represented by the general formula (3a) include a segment containing a structural unit selected from the following 3a-1 to 3a-12 when exemplified by those having a sulfonic acid group as an ionic functional group. It is done. These segments can be manufactured according to, for example, Japanese Patent Application Laid-Open No. 2004-190002.

In addition, specific examples of the segment represented by the general formula (3b) include structural units selected from the following 3b-1 to 3b-12 when exemplified by those having a sulfonic acid group as an ionic functional group. Segment.

  Further, the ionic segment may be a segment having a combination of the structural unit constituting the segment represented by the general formula (3a) and the structural unit constituting the segment represented by the general formula (3b). . Such segments are preferably formed by connecting a total of d segments.

As described above, the ionic functional group is preferably a cation exchange group, and in particular, a group represented by —COOH, —SO ₃ H, —PO (OH) _2, or —SO ₂ NHSO ₂ is preferable. The functional group which has these in the sex segment may be sufficient. Among these, it is particularly preferable that a sulfonic acid group (—SO ₃ H) which is a strong acid group is included as an ionic functional group.

  On the other hand, a nonionic segment is a segment which does not have an ionic functional group substantially. Here, the segment having substantially no ionic functional group means a segment that cannot exhibit ionic conductivity. Therefore, a structural unit containing an ion functional group may be included as long as the ion conductivity is not exhibited by the segment. The nonionic segment preferably has an average of 0.1 or less ionic functional groups per structural unit, more preferably 0.05 or less, and 0 (that is, Those having no ionic functional group are particularly preferred.

［式中、Ａｒ^２２は、イオン性官能基を有しない２価の芳香族基を示し、Ｘ^２２は、直接結合、オキシ基、チオキシ基、カルボニル基又はスルホニル基を示す。ｅは２以上の整数である。］ Specifically, the nonionic segment is preferably a segment having a structure represented by the following general formula (5).

[In the formula, Ar ²² represents a divalent aromatic group having no ionic functional group, and X ²² represents a direct bond, an oxy group, a thioxy group, a carbonyl group or a sulfonyl group. e is an integer of 2 or more. ]

Here, Ar ²² is an aromatic group in the general formula (5) may have a substituent other than ionic functional groups. Examples of such a substituent include an optionally substituted alkyl group having 1 to 20 carbon atoms, an optionally substituted alkoxy group having 1 to 20 carbon atoms, and a substituent. Examples thereof include an aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms which may have a substituent, and an acyl group having 2 to 20 carbon atoms. Specific examples of these groups include those similar to the substituent of Ar ¹¹ in the general formula (2). As long as the definition of the nonionic segment described above is satisfied, the structure represented by the general formula (5) includes a structural unit in which Ar ²² has an ionic functional group. It may be.

  E is an integer of 2 or more indicating the number of repeating units of the structure in parentheses, and is a number indicating the degree of polymerization of this ionic segment. This e is preferably an integer of 5 or more, more preferably an integer of 5 to 1000, still more preferably an integer of 10 to 1000, and even more preferably an integer of 20 to 500. When the value of e is 5 or more, a polymer electrolyte membrane for a fuel cell tends to be obtained having excellent membrane strength. On the other hand, if the value of e is 1000 or less, the production of the segment tends to be easier.

［式中、ａ、ｂ及びｃはそれぞれ独立に０又は１であり、ｚは正の整数である。Ａｒ^２、Ａｒ^３、Ａｒ^４及びＡｒ^５はそれぞれ独立に２価の芳香族基であり、炭素数１〜２０のアルキル基、炭素数１〜２０のアルコキシ基、炭素数６〜２０のアリール基、炭素数６〜２０のアリールオキシ基又は炭素数２〜２０のアシル基で置換されていてもよい。Ｘ及びＸ´はそれぞれ独立に直接結合又は２価の基を示し、Ｙ及びＹ´はそれぞれ独立にオキシ基又はチオキシ基を示す。］ Specifically, as the nonionic segment, a segment represented by the following general formula (6) is preferable.

[Wherein, a, b and c are each independently 0 or 1, and z is a positive integer. Ar ² , Ar ³ , Ar ⁴ and Ar ⁵ are each independently a divalent aromatic group, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, and an aryl group having 6 to 20 carbon atoms. The aryloxy group having 6 to 20 carbon atoms or the acyl group having 2 to 20 carbon atoms may be substituted. X and X ′ each independently represent a direct bond or a divalent group, and Y and Y ′ each independently represent an oxy group or a thioxy group. ]

Here, z is an integer of 2 or more indicating the number of repetitions of the structure in parentheses, and is a number indicating the degree of polymerization of the segment. This z is preferably an integer of 5 or more, more preferably an integer of 5 to 1000, still more preferably an integer of 10 to 1000, and still more preferably an integer of 20 to 500. When the value of z is 5 or more, a polymer electrolyte membrane for a fuel cell tends to be easily obtained with excellent membrane strength. On the other hand, if the value of z is 1000 or less, the production of the segment tends to be easier. In the structure represented by the general formula (6), as in the case of the general formula (5), Ar ² , Ar ³ , Ar ⁴ , Ar, and Ar as long as the definition of the nonionic segment described above is satisfied. A structural unit such that ⁵ has an ionic functional group may be contained.

  As a suitable representative example of the segment represented by the general formula (6), those having the following structure can be exemplified.

  In the above, preferred examples of the polymer compound constituting the polymer electrolyte have been described. From the viewpoint of expressing excellent ion conductivity, this polymer compound has its ion exchange capacity (per unit weight of the polymer compound). The number of equivalents of the ionic functional group is preferably 0.5 to 4 meq / g, and more preferably 1.0 to 3.0 meq / g.

(Production method of polymer electrolyte membrane)
Next, a method for producing a polymer electrolyte membrane according to a preferred embodiment will be described. The polymer electrolyte membrane is a solution containing a polymer electrolyte comprising a polymer compound having a segment having an ionic functional group and a nonionic segment substantially having no ionic functional group on a predetermined substrate. It can be manufactured through a step of applying (application step) and a step of evaporating the solvent from the applied solution (evaporation step). As the polymer electrolyte, those of the above-described embodiment can be applied without particular limitation, and a block copolymer having an ionic segment represented by the above formula (1) and a nonionic segment represented by the above formula (5). When a polymer compound containing a polymer is used, a suitable polymer electrolyte membrane as described later tends to be easily obtained by this method.

  Application of the solution containing the polymer electrolyte in the coating step onto the substrate can be performed by, for example, a casting method, a dip method, a grade coating method, a spin coating method, a gravure coating method, a flexographic printing method, an inkjet method, or the like. .

  The solvent used for the solution containing the polymer electrolyte is preferably a solvent that can dissolve the polymer electrolyte and that can be removed within the evaporation time in the evaporation step described later. A suitable solvent is appropriately selected depending on the structure of the polymer electrolyte and the like.

  Examples of such solvents include aprotic polar solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, dichloromethane, chloroform, 1,2-dichloroethane. Chlorinated solvents such as chlorobenzene and dichlorobenzene, alcohols such as methanol, ethanol and propanol, alkylene glycol monoalkyl ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether and propylene glycol monoethyl ether Is mentioned. These may be used singly or in combination of two or more solvents as necessary.

  As described above, the optimum solvent varies depending on the molecular structure of the polymer electrolyte. For example, the ionic segment represented by the above formula (3a) or (3b) and the non-ion represented by the above formula (6) In the case of a polymer electrolyte containing a block copolymer having a functional segment, the main component is aprotic polarity such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide A solvent containing a solvent is preferable, and dimethyl sulfoxide is particularly preferable. By using these solvents, it becomes easy to adjust the drying time of the solvent within a suitable range.

  The concentration of the polymer electrolyte in the solution is preferably 5 to 40% by weight, more preferably 5 to 30% by weight, although it depends on the molecular weight of the polymer electrolyte. When this concentration is 5% by weight or more, a polymer electrolyte membrane having a practical film thickness tends to be easily obtained. On the other hand, if it is 40% by weight or less, the solution viscosity of the polymer electrolyte solution becomes low, and a polymer electrolyte membrane having a smoother surface tends to be obtained.

  In the polyelectrolyte solution, additives such as plasticizers, stabilizers, and mold release agents used in ordinary polymer compounds may be further added within a range that does not contradict the purpose of the present invention. .

  Moreover, as a base material that supports the coating film of the solution in the coating step, a substrate that is not swelled or dissolved by the polymer electrolyte solution and that can peel off the film obtained after the film formation is preferable. For example, a metal, a metal oxide, a resin film etc. are mentioned as a base material. However, considering the influence of the substrate on the composition distribution of the outermost surface of the polymer electrolyte membrane, a substrate having a surface made of a metal or metal oxide is suitable.

  Examples of the metal constituting the surface of the substrate or the whole include aluminum, chromium, nickel, iron, gold, silver, copper, platinum, tin, palladium, tantalum, zinc, titanium, silicon, or an alloy containing these as a main component. It is done. Among these, aluminum is preferable from the viewpoints of versatility and cost. Examples of the metal oxide include aluminum oxide, titanium oxide, tin oxide, zinc oxide, and glass. Of these, aluminum oxide or glass is preferable from the viewpoints of cost, versatility, and the like.

  Further, if the surface of the base material used in the coating process is contaminated, it is difficult to obtain a good polymer electrolyte membrane, and the effects of the present invention may not be sufficiently obtained. Therefore, in order to avoid such contamination of the surface, it is preferable that the surface of the substrate is washed as necessary. The method for cleaning the substrate surface can be appropriately selected according to the material of the substrate. Moreover, the base material which has the surface in which the thin film of the metal or metal oxide mentioned above was formed by vapor deposition is also preferable from having a clean surface. In this case, the vapor deposition method is appropriately selected from known methods.

  In the evaporation step, the time from the start to the completion of solvent evaporation (hereinafter referred to as “evaporation time”) is set to 60 minutes or less. This evaporation time is from the start of evaporation of the solvent in the solution applied to the substrate or the polymer electrolyte membrane formed from this solution until the concentration change of the polymer electrolyte does not substantially occur. It's time. The concentration change of the polymer electrolyte can be measured by, for example, periodically extracting a part of the solution or formed polymer electrolyte membrane during the evaporation step and measuring the concentration.

  More specifically, this evaporation time is, for example, the time during which the mass change has substantially occurred in a portion of a certain area in the solution applied to the substrate or the polymer electrolyte membrane formed therefrom during the evaporation step. It can be. In this case, whether or not a mass change has occurred can be confirmed by periodically extracting a portion of a certain area of the solution or the polymer electrolyte membrane during the evaporation step and measuring the mass.

  Actually, the evaporation time is, for example, the time when the solvent evaporation starts when the solution is applied and formed on the substrate, and the time when the concentration change or mass change of the polymer electrolyte does not substantially occur. The earlier of the time when the evaporation step is completed may be regarded as the time from the start to the completion of the evaporation as the time when the evaporation of the solvent is completed. “The concentration change of the polymer electrolyte does not substantially occur” means that the difference (change amount) in the concentration of the polymer electrolyte cannot be detected before and after the predetermined time (less than 0.1% by mass). . Similarly, “the mass change of the polymer electrolyte does not substantially occur” means that the difference (change amount) in the mass of the polymer electrolyte before and after the predetermined time cannot be detected (less than 0.1% by mass). To do.

  The evaporation time in the evaporation step is preferably 55 minutes or less, and more preferably 40 minutes or less. The lower limit of the evaporation time is preferably 10 seconds. By setting it as such evaporation time, the manufacturing time of a polymer electrolyte membrane can be shortened, and a polymer electrolyte membrane having a suitable configuration as described later tends to be easily obtained. The evaporation time can be adjusted by appropriately setting conditions such as temperature, pressure, and ventilation conditions in the evaporation step.

  In addition, the temperature in the evaporation step is preferably a temperature not lower than the temperature of the freezing point of the solvent and not higher than 50 ° C. higher than the boiling point of the solvent. If the temperature condition of the evaporation step is less than this, evaporation of the solvent is extremely difficult to occur. On the other hand, when this temperature is exceeded, it tends to be difficult to form a uniform film. Therefore, the temperature is preferably set so that the evaporation time described above can be obtained from such a suitable temperature range.

  From the viewpoint of more reliably obtaining a polymer electrolyte membrane having a good structure, the upper limit of the temperature in the evaporation step is preferably 10 ° C. lower than the boiling point of the solvent, and 30 ° C. lower than the boiling point of the solvent. More preferably. Moreover, it is preferable that a minimum shall be 20 degreeC. For example, when the solvent is dimethyl sulfoxide, the temperature in the evaporation step is preferably 30 to 150 ° C, more preferably 40 to 120 ° C, still more preferably 40 to 110 ° C, and 50 It is especially preferable to set it to -100 degreeC.

(Polymer electrolyte membrane)
The polymer electrolyte membrane of this embodiment can be suitably obtained by the manufacturing method of the above-described embodiment. Such a polymer electrolyte membrane is a membrane composed of a polymer electrolyte, and includes a microphase including a phase containing many ionic segments (microdomain) and a phase containing many nonionic segments (microdomain). It has a separation structure.

  The thickness of the polymer electrolyte membrane is not particularly limited, but is preferably 5 to 200 μm, more preferably 8 to 60 μm, and still more preferably 15 to 50 μm. When it is thicker than 5 μm, it tends to be a polymer electrolyte membrane having a strength that can withstand practical use. Moreover, when it is thinner than 200 μm, the membrane resistance is sufficiently reduced, and the output is easily improved when applied to a fuel cell or the like. The film thickness of the polymer electrolyte membrane can be controlled by changing the concentration of the polymer electrolyte solution used at the time of manufacture and the coating thickness on the substrate.

  In the polymer electrolyte membrane of a preferred embodiment, the ionic segments have the following specific distribution state in the surface region. That is, in the polymer electrolyte membrane, in the surface region, the change in the amount of ionic segments from the surface side toward the inner side is substantially monotonously reduced. Hereinafter, a suitable measurement method for the change in the amount of the ionic segment will be specifically described.

  The amount of the ionic segment in the polymer electrolyte membrane is suitably represented by the intensity of the signal derived from the ionic segment obtained by measuring the composition of the membrane by X-ray photoelectron spectroscopy (XPS). Here, the signal derived from the ionic segment is a signal derived from a chemical structure characterizing the ionic segment, and for example, a signal derived from an ionic functional group in the ionic segment is preferable.

  The change in the amount of ionic segments from the surface side to the inner side is preferably grasped by the relative change between the amount of ionic segments and the amount of nonionic segments in the polymer electrolyte membrane. Specifically, by XPS measurement, a signal derived from a nonionic segment is measured together with a signal derived from an ionic segment, and their intensities are compared. The signal derived from the nonionic segment is a signal derived from a chemical structure characteristic of the nonionic segment as in the case of the ionic segment.

  Here, a plurality of signals derived from each segment are usually observed corresponding to the chemical structure in the segment. For the measurement of the relative change described above, a specific signal is selected from the plurality of signals. It can be arbitrarily selected and used. From the viewpoint of accurately grasping the change in the amount of ionic segments, the same signal is used for each segment in a series of measurements on the same surface of one polymer electrolyte membrane. From the same viewpoint, it is preferable to select only one signal as the specific signal.

  The change in the amount of the ionic segment is a value represented by A / (A + B) where A is the intensity of the signal derived from the ionic segment by XPS and B is the intensity of the signal derived from the nonionic segment. Can be suitably tracked. If this value is substantially monotonically decreasing from the surface side toward the inner side, it can be determined that the amount of the ionic segment is substantially monotonically decreasing from the surface side toward the inner side. .

  As the signal intensity, the signal intensity obtained by measurement (the total number of photoelectrons or the number of counts per unit time) may be used as it is, and this is multiplied by a constant such as a sensitivity coefficient attached to the device, analysis software, etc. May be used. From the viewpoint of obtaining the change in the value of A / (A + B) accurately by minimizing the influence of the error, a specific signal derived from each segment is used so that the difference in signal strength between A and B does not become extremely large. Is preferably selected.

  From the viewpoint of more accurately grasping the change in the amount of ionic segments, it is particularly preferable to select the following as specific signals derived from ionic or nonionic segments. That is, it is preferable to select a signal that is not observed from the main nonionic segment as the specific signal selected from the signals derived from the ionic segment. On the other hand, as the specific signal selected from the signals derived from the nonionic segments, it is preferable to select signals that are not observed from the main ionic segments. As a result, at least one of the signals derived from the ionic segment and the non-ionic segment becomes a signal not derived from the other main segment, and thus the intensity of the one signal is substantially equal to the signal. Only the amount of segments represented will be reflected.

The measurement of the signal intensity from the surface side toward the inner side described above is performed by measuring the surface at each time point in the removal process by XPS while removing the polymer electrolyte membrane little by little from the surface in the inner direction. be able to. In this case, the polymer electrolyte is preferably removed by sputtering using C ₆₀ ions. By repeatedly performing the step of performing sputtering with C ₆₀ ions for a predetermined time and the step of performing XPS measurement of the surface after the sputtering, it becomes possible to measure the intensity of each signal from the surface side to the inner side. .

Here, sputtering using C ₆₀ ions is a technique capable of reducing damage caused by sputtering as compared with sputtering using rare gas ions such as argon, which are usually used for surface analysis. Therefore, sputtering using C ₆₀ ions is suitable for a sample that is easily damaged by an organic material such as a polymer electrolyte membrane in this embodiment (Surface and Interface Analysis, 2004, 36, p. 280). -282, Journal of Surface Analysis, 2005, 12, p.178 etc.).

  The measurement area when performing XPS measurement is preferably a measurement area that is sufficiently large relative to the size of microphase separation in the polymer electrolyte membrane. By doing so, it becomes possible to more accurately measure the amount of chemical structure in the ionic segment and nonionic segment in the polymer electrolyte membrane subjected to microphase separation. For example, when the size of microphase separation is about several nanometers to several tens of nanometers, the diameter of the measurement region is preferably 1 μm or more and 10 mm or less, and more preferably 10 μm or more and 1 mm or less. In this case, if the diameter of the measurement region exceeds 10 mm, the measurement result is likely to be affected by unevenness of the polymer electrolyte membrane or unevenness of the sputtering depth, or the ionic or nonionic segment in the measurement region. In some cases, the concentration distribution of the chemical structure to which it belongs is averaged, making it impossible to measure the exact distribution. On the other hand, if the diameter of the measurement region is smaller than 1 μm, the measurement result is greatly influenced by a part of the microphase separation shape in the measurement region, and the distribution of the entire phase may not be measured appropriately.

When sputtering using C ₆₀ ions, the change in the value of A / (A + B) from the surface side to the inner side is obtained by the elapsed time t from the start of sputtering and the XPS measurement of the surface at each time t. It is shown by the relationship with the value of A / (A + B). The XPS measurement is performed every time a predetermined time has elapsed from the start of sputtering, but the XPS measurement interval Δt is not necessarily constant throughout the measurement.

Here, as a unit of t and Δt, in addition to hours, minutes, seconds, etc., which are normal units indicating time,
It can also be expressed as SiO ₂ equivalent Xnm. This means the time required to remove the X nm thickness when the same method is used to remove SiO ₂ . In addition, when noting the distance (depth) from the initial surface of the surface at each time point, it can be expressed as SiO ₂ equivalent Xnm. This means the depth from the initial surface of the surface obtained when sputtering is performed for a time of X nm in terms of SiO ₂ . The depth in terms of SiO ₂ is generally proportional to the actual depth. The proportionality constant in this case varies depending on the type of polymer electrolyte membrane, but the actual depth is usually about 2 to 20 times the SiO ₂ equivalent depth Xnm.

It is preferable to set Δt, which is the interval of XPS measurement, to an appropriate time depending on the magnitude of microphase separation of the polymer electrolyte membrane. This Δt is preferably small from the viewpoint of measuring the distribution of chemical structures belonging to ionic and nonionic segments in the polymer electrolyte membrane in detail. However, if it is too small, the number of times sputtering is stopped increases. The speed tends to be unstable. From these viewpoints, Δt is preferably 0.1 nm or more and 0.5 nm or less in terms of SiO ₂ .

In the polymer electrolyte membrane, the distribution of ionic segments and nonionic segments near the outermost surface is particularly important. Therefore, it is preferable to set a smaller Δt particularly in the region close to the surface. For example, in the depth range of up to terms of SiO ₂ 2 nm, Delta] t is preferable to be in terms of SiO ₂ 0.1nm or 0.3nm or less. From the viewpoint of ensuring a sufficiently stable sputtering rate, Δt is desirably set to at least 10 seconds or more.

When sputtering time t is too long, and damage of the polymer electrolyte membrane surface, may influence by carbon component derived from the C ₆₀ increases, it may become difficult to accurately XPS measurements. Therefore, in order to avoid such an inconvenience, it is desirable to set the upper limit of t appropriately according to the polymer electrolyte membrane.

Sputtering with C ₆₀ ions is preferably performed at such a rate that removal of 0.5 nm or more and 2 nm or less in terms of SiO ₂ occurs per minute, and at a rate of removal of about 1 nm in terms of SiO ₂ per minute. More preferably. In this way, a sufficiently stable sputtering rate can be obtained, and damage to the sample can be sufficiently reduced.

As described above, the signal derived from the ionic segment and the signal derived from the nonionic segment can be obtained by selecting an arbitrary signal for each segment from the spectrum of XPS. Further, the intensity of these signals can be obtained by performing peak separation by waveform analysis as appropriate using the integrated value of each spectrum. In the case of performing C ₆₀ sputtering as described above, since there is an increase in the carbon composition is seen to be derived therefrom with the irradiation of the C ₆₀ ion, of C1s C-C and C-H bonds It is preferable to exclude peaks.

  The relationship between the sputtering time t measured as described above and the value of A / (A + B) at each t represents a change in the amount of ionic segments from the surface to the inner side in the polymer electrolyte membrane. In the polymer electrolyte of the preferred embodiment, A / (A + B) is substantially monotonously decreased with respect to t in the surface region.

  Here, the monotonic decrease is generally defined as follows. That is, if x1 <x2, the case where f (x1) ≧ f (x2) is satisfied corresponds to a monotonic decrease (for example, see Iwanami Mathematics Dictionary 3rd Edition (edited by the Mathematical Society of Japan, Iwanami Shoten)). However, in the polymer electrolyte membrane of the present embodiment, f (t) = A / (A + B) only needs to be substantially monotonously decreased, and a case in which such a definition is not satisfied is included. Good.

The “substantially monotonous decrease” in the present invention corresponds to a case where the following conditions are satisfied. That is, first, the value of A / (A + B) in the sputtering time t, f (t) = A / (A + B) and when expressed, sputtering time _{t 1,} t 2 for performing XPS measurement, ..., the _{t n,} In this case, f (t ₁ ), f (t ₂ ),..., F (t _n ) are obtained. Here, t ₁ means the start time of sputtering. Therefore, f (t ₁ ) is A / (A + B) on the outermost surface of the polymer electrolyte membrane (surface at the start of sputtering).

If the measurement is performed m times (more than 4 times) from the start of sputtering, t ₁ , t ₂ ,..., T _n and f (t (t) obtained from the first measurement to any n-th measurement are obtained. ₁ ), f (t ₂ ),..., F (t _n ), all of the correlation coefficients obtained between n = 2 to m are all obtained when n is 4 or more. When the correlation coefficient is negative, it is recognized that A / (A + B) is “substantially monotonically decreasing” with respect to t. That is, in other words, the “substantially monotonic decrease” in the value of A / (A + B) includes t and A / (A + B) obtained by the measurement from the first time at the start of sputtering to any nth time. This corresponds to the case where all the correlation coefficients obtained when n is 4 or more are negative.

The above-mentioned correlation coefficient is a statistical numerical value, and generally, the more the number of data points, the higher the reliability. This correlation coefficient is defined by the following mathematical formula (1), which means that the relationship with the linear relationship between x and y is good (for example, see Introduction to Statistics (Department of Statistics, Faculty of Liberal Arts, the University of Tokyo, Tokyo University Press)) ). The sign of the correlation coefficient matches the slope of the regression line by x and y.

When obtaining this correlation coefficient, it is preferable that Δt which is the measurement interval by XPS is constant. However, in the polymer electrolyte membrane of the present embodiment, since the distribution of the region close to the surface is particularly important, Δt is The region close to the surface and the inner region may be changed. For example, Δt at a depth position of 2 nm or more in terms of SiO ₂ may be 1 to 3 times as large as Δt at a depth position of 2 nm or less in terms of SiO ₂ . In this way, the distribution of the region close to the surface can be confirmed in detail, and the measurement time can be shortened appropriately.

  As described above, in the polymer electrolyte membrane of the present embodiment, the change in the amount of ionic segments from the surface side toward the inner side is substantially monotonously reduced in the surface region. And by having such a distribution of ionic segments in the surface region, it is possible to exhibit excellent proton conductivity in the film thickness direction.

Note that the surface area, as described above, preferable to be a region at a depth from the surface of the polymer electrolyte to 4nm expressed in depth in terms of SiO _2, more preferable to be a region at a depth of up to 6 nm, 10 nm It is more preferable that the depth region is up to. In addition, the polymer electrolyte membrane only needs to have the above-described ionic segment distribution on at least one surface, but when both surfaces have such a distribution, a particularly excellent proton in the film thickness direction is obtained. Since conductivity is obtained, it is preferable.

  Further, as described above, the polymer electrolyte membrane of the present invention is phase-separated into a phase containing many ionic segments and a phase containing many nonionic segments, and has a nonionic property in its surface region. It is preferred that the segment concentration does not have a layered portion substantially higher than the overall average.

  This is because, when it is considered that the surface region of the polymer electrolyte membrane is composed of an arbitrary plurality of layers in the thickness direction of the membrane, all of these layers are non-layered in the entire polymer electrolyte membrane. It means that the concentration of the nonionic segment is lower than the average value of the concentration of the ionic segment. In a polymer electrolyte membrane having a surface region that satisfies such conditions, ionic conduction in the thickness direction is less significantly inhibited by nonionic segments in the surface region. Therefore, according to this polymer electrolyte membrane, it is possible to obtain excellent ion conductivity in the thickness direction.

(Method for evaluating proton conductivity of polymer electrolyte membrane)
The polymer electrolyte membrane has excellent proton conductivity in the film thickness direction by having the distribution state of the ionic segments as described above in the surface region. Therefore, if the distribution state of such ionic segments in the surface region is confirmed, the proton conductivity in the film thickness direction of the unknown polymer electrolyte membrane can be evaluated.

In particular, it performs C ₆₀ sputtering, how to determine the distribution of the ionic segment by the relationship between the value represented by the / sputtering time t and the A (A + B) may be able to accurately evaluate the proton conductivity To preferred.

In such an evaluation, first, sputtering using C ₆₀ ions is performed in the depth direction from the surface, and the XPS measurement of the surface at that point in the elapsed time t of this sputtering is performed. Then, based on this result, the intensity A of the signal derived from the ionic segment at each time point t at which XPS measurement was performed and the intensity B of the signal derived from the nonionic segment were obtained, and A / (A + B ) Is calculated (step 1).

  Subsequently, it is determined whether or not the change in the value represented by A / (A + B) with respect to the elapsed time t of sputtering is a substantially monotonous decrease (step 2).

  In Step 2, when the change in the value represented by A / (A + B) with respect to t is monotonously decreased, the polymer electrolyte membrane is evaluated as having excellent proton conductivity in the film thickness direction. be able to. On the other hand, if it is not monotonically decreasing but increases or a large change including both increases and decreases, it can be evaluated that proton conductivity in the film thickness direction is insufficient.

Here, as described above, whether or not the monotonous decrease can be determined based on the correlation coefficient between t and A / (A + B). That is, first, in the first step, A / (A + B) is measured every time a time of 0.1 nm to 0.5 nm in terms of SiO ₂ elapses from the start of sputtering.

  Next, in the second step, a correlation coefficient between t obtained by arbitrary n-th measurement and a value represented by A / (A + B) is obtained, and all obtained when n is 4 or more. Determine whether the correlation coefficient is positive or negative. As a result of such determination, when all correlation coefficients obtained in the fourth and subsequent measurements are negative, it can be recognized that A / (A + B) is substantially monotonically decreasing with respect to t. And it can be evaluated that the polymer electrolyte membrane which shows such a tendency has the proton conductivity excellent in the film thickness direction. On the other hand, when all the correlation coefficients obtained in the fourth and subsequent measurements are not negative, it can be evaluated that the proton conductivity in the film thickness direction is insufficient.

  As conditions for XPS measurement area, sputtering rate, t, Δt, etc. in these evaluations, the same conditions as those described in the above-mentioned “polymer electrolyte membrane” embodiment can be adopted.

EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to these Examples.
[Manufacture of polymer electrolytes]

(Synthesis Example 1)
In an argon atmosphere, a flask equipped with an azeotropic distillation apparatus was charged with 600 ml of dimethyl sulfoxide (DMSO), 200 ml of toluene, 26.5 g (106.3 mmol) of sodium 2,5-dichlorobenzenesulfonate, 7) polyethersulfone (Sumitomo Chemical Sumika Excel PES5200P) 10.0 g and 2,2′-bipyridyl 43.8 g (280.2 mmol) were added and stirred.

Next, the temperature of the solution was raised to 150 ° C., toluene was distilled off by heating to azeotropically dehydrate water in the system, and then cooled to 60 ° C. Next, 73.4 g (266.9 mmol) of bis (1,5-cyclooctadiene) nickel (0) was added thereto, and then the mixture was heated to 80 ° C. and stirred at the same temperature for 5 hours. After allowing this solution to cool, the resulting reaction solution was poured into a large amount of 6 mol / L hydrochloric acid to precipitate a polymer compound, which was filtered off. Thereafter, the obtained polymer compound was repeatedly washed with 6 mol / L hydrochloric acid and filtered several times, and then washed with water until the filtrate became neutral. Then, the polymer compound was dried under reduced pressure to obtain 16.3 g of a polyarylene block copolymer represented by the following chemical formula (8), which is a target polymer electrolyte. The ion exchange capacity of this block copolymer was 2.3 [meq / g].

In the formulas (7) and (8), d and z are numbers indicating the degree of polymerization of each segment as described above, and the expression “block” is a structure (segment) connected by this notation. ) Means that they are block copolymerized (the same applies hereinafter).
[Manufacture of polymer electrolyte membranes]

(Example 1)
The polyarylene block copolymer obtained in Synthesis Example 1 was dissolved in DMSO to a concentration of 10 wt% to prepare a polymer electrolyte solution. After casting this polymer electrolyte solution onto an aluminum-deposited polyethylene terephthalate (PET) substrate, the solvent is removed from the coating film by evaporating the solvent in a temperature range of 60 to 100 ° C. for 20 minutes under normal pressure. This allowed the membrane to dry. Then, the polymer electrolyte membrane containing a polyarylene-type block copolymer was produced through hydrochloric acid treatment and washing with ion exchange water. Hereinafter, the surface that is not in contact with the base material in the polymer electrolyte membrane is defined as the first surface, and the surface that is in contact with the base material is defined as the second surface.

(Comparative Example 1)
A polymer electrolyte membrane was produced in the same manner as in Example 1 except that the polymer electrolyte solution was directly cast on a PET substrate.
[Confirmation of phase separation structure of polymer electrolyte membrane]

The polymer electrolyte membranes of Example 1 and Comparative Example 1 were immersed in an aqueous dyeing solution containing 15% potassium iodide and 5% iodine for 30 minutes at room temperature, and then preliminarily cured with an epoxy resin. After embedding, a section having a thickness of 60 nm was cut out by a microtome. The slices thus obtained were collected on a Cu mesh and observed with a transmission electron microscope (H9000NAR, manufactured by Hitachi, Ltd.). According to potassium iodide, the phase containing many ionic functional groups is dyed and darkened. From this result, both of the polymer electrolyte membranes of Example 1 and Comparative Example 1 are phases containing many ionic segments. And phase separation into a phase containing many nonionic segments.
[Evaluation of the structure of the surface region of the polymer electrolyte membrane]

The structure of the surface region of the polymer electrolyte membrane of Example 1 and Comparative Example 1 was evaluated by the following method. That is, first, C ₆₀ sputtering is performed inward from the surface of the polymer electrolyte membrane, and each time a certain time has elapsed from the start of sputtering, the Quantera SXM (ULVAC-PHI Imaging XPS) is applied to the surface at that time. The XPS measurement using was performed.

  Thereby, the S2p spectrum at each sputtering time t, which is the elapsed time from the start of sputtering, was obtained. Then, waveform analysis of these spectra is performed, and the waveform is separated into a sulfonic acid-derived signal and a sulfone-derived signal, and based on this, the former signal intensity (A) and the latter signal intensity (B) are obtained. Obtained. And the value of A / (A + B) in each sputtering time t was obtained. Such measurement was performed on both the first surface and the second surface of the polymer electrolyte membrane.

  Here, in XPS, a monochromatic AlKα ray (1486.6 eV, X-ray spot 100 μm) is used as the X-ray, and a neutralizing electron gun 1 eV and an argon ion gun 7 eV are used for charging correction during measurement. did. Furthermore, the measurement was performed by entering X-rays from a direction of 25 ° from the sample normal direction and detecting photoelectrons in a direction of 20 ° from the sample normal direction. The peak position used in the waveform analysis was a value obtained by measuring a polymer film containing only one of an ionic segment and a nonionic segment as a standard sample and analyzing the waveform.

C ₆₀ sputtering was performed from a direction of 70 ° with respect to the normal direction of the sample using a C ₆₀ ion gun (PHI06-C60, ULVAC-PHI). The acceleration voltage was 10 kV, and the sputtering rate was 1 nm / min when sputtering SiO ₂ . Further, XPS measurement was performed every 0.2 minutes for the first 2 minutes of sputtering, and measurement was performed every 0.4 minutes for 2 to 6 minutes. Sputtering time t when XPS measurement is performed is defined as t ₁ , t ₂ ... T _n .

  Furthermore, the spectrum analysis was performed using MultiPakV6.1A (ULVAC-PHI). The binding energy of the spectrum was calibrated with C1s C—C and C—H bonds as 284.6 eV. And it measured using the polymer film containing only one of an ionic segment and a nonionic segment as a standard sample, and performed waveform analysis of S2p spectrum using the obtained peak position. In addition, although the sulfur component reduced to 163.6 eV was observed by sputtering, this was separated and excluded at the time of waveform analysis.

  As a result of such XPS measurement, for each of the polymer electrolyte membranes of Example 1 and Comparative Example 1, the results shown in the graph showing the change in the value of A / (A + B) with respect to the sputtering time t as shown in FIG. Got. In FIG. 1, black and white square plots indicate the first and second surfaces of the polymer electrolyte membrane of Example 1, respectively, and black and white triangle plots indicate those of Comparative Example 1. The 1st surface and 2nd surface of a polymer electrolyte membrane are each shown.

From FIG. 1, in the polymer electrolyte membrane of Example 1, it was confirmed that the value of A / (A + B) decreased substantially monotonously in the surface region (0 to ₆ nm in terms of SiO ₂ from the surface). .

  On the other hand, in the polymer electrolyte membrane of Comparative Example 1, an increase in A / (A + B) was observed on the second surface when the sputtering time t was in the range up to 0.6 minutes. In addition, a non-monotonic change of A / (A + B) was observed when t was in the range of 0 to 2 minutes.

Also, based on the results obtained above, for each of the polymer electrolyte membranes of Example 1 and Comparative Example 1, f (t) = A / (A + B) and t at the sputtering time t _n (n ≧ 4). ₁ , t ₂ ,... T _n and all correlation coefficients between f (t ₁ ), f (t ₂ ),... F (t _n ) were calculated. As a result, the result shown in the graph showing the change of the correlation coefficient with respect to the sputtering time t as shown in FIG. 2 was obtained. In FIG. 2, black and white square plots indicate the first and second surfaces of the polymer electrolyte membrane of Example 1, respectively, and black and white triangle plots indicate those of Comparative Example 1. The 1st surface and 2nd surface of a polymer electrolyte membrane are each shown.

As shown in FIG. 2, according to the polymer electrolyte membrane of Example 1, it was confirmed that the correlation coefficient was negative in the entire measured range. On the other hand, in the polymer electrolyte membrane of Comparative Example 2, the correlation coefficient was positive in the range where the sputtering time was 1.4 minutes or less on the second surface. Further, on the first surface, there was a range in which the correlation coefficient was positive after about 4 minutes of sputtering time.
[Measurement of membrane resistance]

  The membrane resistance in the film thickness direction of the polymer electrolyte membranes of Example 1 and Comparative Example 1 was measured according to the following method. The obtained results are shown in Table 1 together with the film thickness and ion exchange capacity of each polymer electrolyte membrane.

That is, first, ^two measurement cells each having a carbon electrode pasted on one side of a silicon rubber (thickness: 200 μm) having an opening of 1 cm ² were prepared and arranged so that the carbon electrodes face each other. Then, the terminal of the impedance measuring device was directly connected to the measuring cell.

  Next, a polymer electrolyte membrane was sandwiched between the two measurement cells, and the resistance value between the two measurement cells was measured at a measurement temperature of 23 ° C. Subsequently, the resistance value was measured again with the polymer electrolyte membrane removed.

Then, the resistance value obtained in the state having the polymer electrolyte membrane is compared with the resistance value obtained in the state without the polymer electrolyte membrane, and based on the difference between these resistance values, The film resistance in the film thickness direction was calculated. The measurement was performed in a state where 1 mol / L dilute sulfuric acid was in contact with both sides of the polymer electrolyte membrane.

From Table 1, it was confirmed that the polymer electrolyte membrane of Example 1 had a smaller membrane resistance in the film thickness direction than that of Comparative Example 1, and had excellent proton conductivity in the film thickness direction.
[Manufacture of polymer electrolytes]

(Synthesis Example 2)
1.62 g of anhydrous nickel chloride and 15 mL of dimethyl sulfoxide were mixed and adjusted to an internal temperature of 70 ° C. To this, 2.15 g of 2,2′-bipyridine was added and stirred at the same temperature for 10 minutes to prepare a nickel-containing solution.

  In addition, in a solution obtained by dissolving 1.49 g of 2,5-dichlorobenzenesulfonic acid (2,2-dimethylpropyl) and 0.50 g of polyethersulfone (Sumitomo Chemical Sumika Excel PES5200P) in 5 mL of dimethyl sulfoxide. Then, 1.23 g of zinc powder was added and adjusted to 70 ° C. Next, the above nickel-containing solution was poured into this, and a polymerization reaction was performed at 70 ° C. for 4 hours. The reaction mixture was added to 60 mL of methanol, and then 60 mL of 6 mol / L hydrochloric acid was added, and this was stirred for 1 hour. And the depositing solid was isolate | separated by filtration and it dried and obtained 1.62g of grayish white polyarylene.

［高分子電解質膜の製造］ 0.23 g of the obtained polyarylene was added to a mixed solution of 0.16 g of lithium bromide monohydrate and 8 mL of N-methyl-2-pyrrolidone, and reacted at 120 ° C. for 24 hours. Furthermore, the reaction mixture was poured into 80 mL of 6 mol / L hydrochloric acid and stirred for 1 hour. The precipitated solid was separated by filtration. The separated solid was dried to obtain 0.06 g of a polyarylene block copolymer represented by the following general formula (9). The ion exchange capacity of this block copolymer was 2.4 meq / g.

[Manufacture of polymer electrolyte membranes]

(Example 2)
The polyarylene block copolymer obtained in Synthesis Example 2 was dissolved in DMSO to a concentration of 10 wt% to prepare a polymer electrolyte solution. This polymer electrolyte solution was cast-coated on a silicon substrate. Then, the solvent was removed by evaporation from the coating film at 80 ° C. for 60 minutes under normal pressure, thereby drying the film. Then, the polymer electrolyte membrane containing a polyarylene-type block copolymer was produced through hydrochloric acid treatment and washing with ion exchange water.

(Comparative Example 2)
A polymer electrolyte membrane was produced in the same manner as in Example 2 except that the polymer electrolyte solution was directly cast on a PET substrate.

(Comparative Example 3)
A polymer electrolyte membrane was produced in the same manner as in Comparative Example 2 except that the time for evaporating the solvent was 90 minutes.
[Confirmation of phase separation structure of polymer electrolyte membrane]

The polymer electrolyte membranes of Example 2, Comparative Example 2 and Comparative Example 3 were observed with a transmission electron microscope (H9000NAR, manufactured by Hitachi, Ltd.) in the same procedure as described above, and the phase separation of the polymer electrolyte membrane was performed. The structure was confirmed. As a result, it was confirmed that the polymer electrolyte membranes of Example 2, Comparative Example 2 and Comparative Example 3 were all phase-separated into a phase containing many ionic segments and a phase containing many nonionic segments. It was done.
[Evaluation of the structure of the surface region of the polymer electrolyte membrane]

About the structure of the surface region of the polymer electrolyte membrane of Example 2, Comparative Example 2 and Comparative Example 3, the neutralization electron gun 4 eV and the argon ion gun 3 eV were used, and the sputtering time was 6 minutes every 0.2 minutes. Evaluation was performed in the same manner as in Example 1 except that XPS measurement was performed. The sputtering rate at this time was 1.3 nm / min when SiO ₂ was sputtered. Similarly to the above, the peak around 163.6 eV was separated and excluded by waveform analysis.

  As a result of such XPS measurement, for each of the polymer electrolyte membranes of Example 2, Comparative Example 2 and Comparative Example 3, the change in the value of A / (A + B) with respect to the sputtering time t as shown in FIGS. The results shown in the representing graph were obtained. In FIG. 3, black and white square plots show the first and second surfaces of the polymer electrolyte membrane of Example 2, respectively, and black and white triangle plots show the comparative example 2 plots. The first surface and the second surface of the polymer electrolyte membrane are shown, respectively. In FIG. 4, black and white circle plots show the first surface and the second surface of the polymer electrolyte membrane of Comparative Example 3, respectively. ing.

From FIG. 3, in the polymer electrolyte membrane of Example 2, the value of A / (A + B) substantially monotonously decreases in the surface region of the second surface (0 to 7.8 nm in terms of SiO ₂ from the surface). It was confirmed.

  On the other hand, in the polymer electrolyte membrane of Comparative Example 3, an increase in A / (A + B) was clearly confirmed on the second surface in the range where the sputtering time t was up to about 1 minute.

Further, based on the results obtained above, for each of the polymer electrolyte membranes of Example 2, Comparative Example 2 and Comparative Example 3, f (t) = A / (A + B) and sputtering time t _n (n ≧ All the correlation coefficients between t ₁ , t ₂ ,... T _n and f (t ₁ ), f (t ₂ ),... F (t _n ) in 4) were calculated. As a result, the result shown in the graph showing the change of the correlation coefficient with respect to the sputtering time t as shown in FIG. 5 was obtained. In FIG. 5, black and white square plots indicate the first and second surfaces of the polymer electrolyte membrane of Example 2, respectively, and black and white triangle plots indicate those of Comparative Example 2. The first and second surfaces of the polymer electrolyte membrane are shown, respectively, and the black and white circle plots show the first and second surfaces of the polymer electrolyte membrane of Comparative Example 3, respectively.

  As shown in FIG. 5, in the polymer electrolyte membrane of Example 2, the correlation coefficient became negative over the entire range measured on the second surface. On the other hand, on the first surface, the correlation coefficient was positive when the sputtering time was 1.2 minutes or less.

  On the other hand, in the polymer electrolyte membrane of Comparative Example 2, there is a range in which the correlation coefficient is positive when the sputtering time is about 1.2 minutes on the first surface, and the sputtering time is 2 minutes or less on the second surface. The correlation coefficient became positive.

Furthermore, in the polymer electrolyte membrane of Comparative Example 3, there is a range where the correlation coefficient is positive when the sputtering time is about 2.4 minutes on the first surface, and the correlation coefficient is the entire measured range on the second surface. It became positive.
[Measurement of membrane resistance]

The membrane resistance in the film thickness direction of the polymer electrolyte membranes of Example 2, Comparative Example 2 and Comparative Example 3 was measured in the same manner as Example 1. The obtained results are shown in Table 2 together with the film thickness and ion exchange capacity of each polymer electrolyte membrane.

  From Table 2, it is confirmed that the polymer electrolyte membrane of Example 2 has smaller membrane resistance in the film thickness direction and superior proton conductivity in the film thickness direction as compared with Comparative Example 2 and Comparative Example 3. It was.

6 is a graph showing changes in the value of A / (A + B) with respect to sputtering time t in the polymer electrolyte membranes of Example 1 and Comparative Example 1. 6 is a graph showing a change in correlation coefficient with respect to sputtering time t in the polymer electrolyte membranes of Example 1 and Comparative Example 1. 6 is a graph showing a change in A / (A + B) value with respect to sputtering time t in the polymer electrolyte membranes of Example 2 and Comparative Example 2. 10 is a graph showing a change in A / (A + B) value with respect to sputtering time t in the polymer electrolyte membrane of Comparative Example 3. 4 is a graph showing a change in correlation coefficient with respect to sputtering time t in polymer electrolyte membranes of Example 2, Comparative Example 2, and Comparative Example 3.

Claims (18)

A polymer electrolyte membrane comprising a polymer compound comprising an ionic segment having an ionic functional group and a nonionic segment substantially free of ionic functional groups,
Phase-separated into a phase containing many ionic segments and a phase containing many non-ionic segments,
In at least one surface region, the change in the amount of the ionic segment from the surface side to the inner side is a substantially monotonic decrease.
A polymer electrolyte membrane characterized by that. A polymer electrolyte membrane comprising a polymer compound comprising an ionic segment having an ionic functional group and a nonionic segment substantially free of ionic functional groups,
Phase-separated into a phase containing many ionic segments and a phase containing many non-ionic segments,
When the intensity of a specific signal selected from signals derived from the ionic segment by X-ray photoelectron spectroscopy is A and the intensity of a specific signal selected from signals derived from the non-ionic segment is B,
In at least one surface region, the change in the value represented by A / (A + B) from the surface side to the inner side is a substantially monotonous decrease.
A polymer electrolyte membrane characterized by that. The change in the value represented by A / (A + B) is A / (A + B) with respect to the sputtering time t when sputtering using C ₆₀ ions and measurement of the value represented by A / (A + B) are repeated. The polymer electrolyte membrane according to claim 2, wherein In the surface region,
The value of A / (A + B) is measured every time a time of 0.1 nm or more and 0.5 nm or less in terms of SiO ₂ has elapsed since the start of the sputtering, and t obtained by the measurement from the first time to any nth time. And the correlation coefficient between the value represented by A / (A + B),
All the correlation coefficients obtained when n is 4 or more are negative;
The polymer electrolyte membrane according to claim 3.   The high signal according to claim 2, wherein the specific signal selected from signals derived from the ionic segments is a signal that is not observed from the main nonionic segments. Molecular electrolyte membrane.   The high signal according to any one of claims 2 to 5, wherein the specific signal selected from signals derived from the non-ionic segment is a signal that is not observed from the main ionic segment. Molecular electrolyte membrane. A polymer electrolyte membrane comprising a polymer compound comprising an ionic segment having an ionic functional group and a nonionic segment substantially free of ionic functional groups,
Phase-separated into a phase containing many ionic segments and a phase containing many non-ionic segments,
In its surface region, the non-ionic segment has no layered portion whose concentration is substantially higher than the overall average,
A polymer electrolyte membrane characterized by   The polymer electrolyte membrane according to claim 1, wherein the polymer compound is an aromatic polymer compound. The polymer electrolyte membrane according to any one of claims 1 to 8, wherein the polymer compound includes a structural unit represented by the following general formula (1).

[Wherein Ar ¹ represents a divalent aromatic group having at least an ionic functional group directly bonded to an aromatic ring as a substituent, and X ¹ represents a direct bond, an oxy group, a thioxy group, a carbonyl group or a sulfonyl group. Indicates a group. ]   The polymer electrolyte membrane according to any one of claims 1 to 8, wherein the polymer compound is a block copolymer having the ionic segment and the nonionic segment. The polymer electrolyte membrane according to claim 10, wherein the ionic segment has a structure represented by the following general formula (2).

[In the formula, Ar ¹¹ represents a divalent aromatic group having at least an ionic functional group directly bonded to an aromatic ring as a substituent, and X ¹¹ represents a direct bond, an oxy group, a thioxy group, a carbonyl group or a sulfonyl group. Indicates a group. d is an integer of 2 or more. ] The polymer electrolyte membrane according to claim 10 or 11, wherein the ionic segment has a structure represented by the following general formula (3a) or the following general formula (3b).

[Wherein, X ¹² represents a direct bond, an oxy group, a thioxy group, a carbonyl group or a sulfonyl group, and each R ¹ independently represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or 1 to 20 carbon atoms. Represents an alkoxy group, an aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms or an acyl group having 2 to 20 carbon atoms, J ¹ represents an ionic functional group, and p and q are independent of each other. 1 or 2, and d is an integer of 2 or more. ]   The polymer electrolyte membrane according to any one of claims 1 to 12, wherein the ionic functional group is a sulfonic acid group. The polymer electrolyte membrane according to any one of claims 10 to 13, wherein the nonionic segment has a structure represented by the following general formula (5).

[In the formula, Ar ²² represents a divalent aromatic group having no ionic functional group, and X ²² represents a direct bond, an oxy group, a thioxy group, a carbonyl group or a sulfonyl group. e is an integer of 2 or more. ] The polymer electrolyte membrane according to any one of claims 10 to 14, wherein the nonionic segment has a structure represented by the following general formula (6).

[Wherein, a, b and c are each independently 0 or 1, and z is a positive integer. Ar ² , Ar ³ , Ar ⁴ and Ar ⁵ each independently represent a divalent aromatic group having no ionic functional group, X and X ′ each independently represent a direct bond or a divalent group, Y And Y ′ each independently represents an oxy group or a thioxy group. ] A method for producing a polymer electrolyte membrane comprising a polymer electrolyte containing a polymer compound containing an ionic segment having an ionic functional group and a nonionic segment substantially having no ionic functional group,
Applying a solution containing the polymer electrolyte onto a substrate having a surface made of metal or metal oxide;
Evaporating the solvent from the solution, and
In the evaporation step, the time from the start of evaporation of the solvent to the completion is 60 minutes or less,
A method for producing a polymer electrolyte membrane. A method for evaluating proton conductivity of a polymer electrolyte membrane comprising a polymer compound comprising an ionic segment having an ionic functional group and a nonionic segment substantially having no ionic functional group,
Sputtering using C ₆₀ ions is performed from the surface side to the inner side, and X-ray photoelectron spectroscopic measurement of the surface at the time of the elapsed time t of the sputtering is performed, whereby the ionic segment at each time t A first step of determining an intensity A of a specific signal selected from a signal derived from and an intensity B of a specific signal selected from a signal derived from the nonionic segment;
a second step of determining whether the change in value represented by A / (A + B) with respect to t is a substantially monotonic decrease;
The evaluation method characterized by having. In the first step, A / (A + B) is measured each time a time of 0.1 nm to 0.5 nm in terms of SiO ₂ has elapsed from the start of the sputtering,
In the second step, a correlation coefficient between t obtained by measurement from the first time to an arbitrary n-th time and a value represented by A / (A + B) is obtained, and obtained when n is 4 or more. Determining the sign of all the correlation coefficients;
The evaluation method according to claim 17, wherein:

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