JP2011190332A - Polymer electrolyte and utilization thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrocarbon-based polymer electrolyte efficiently retaining water even under a water-deficient condition and ensuring proton conductivity. <P>SOLUTION: The polymer electrolyte comprises a polyphenylene ether-based polymer containing a structure represented by formula (1) in a main chain of the polymer, wherein a and b represent 0-1, provided that a+b≠0; R represents alkyl, aryl, alkoxy, aryloxy, carbonyl, sulfonyl or halogen; c and d represent 0-6; and when a plurality of symbols R exist, they may be the same or different. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a polymer electrolyte, a polymer electrolyte membrane using the polymer electrolyte, a membrane / electrode assembly, and a fuel cell including these.

  In recent years, fuel cells have attracted attention as a highly efficient and clean energy source from the viewpoint of environmental problems such as global warming. In particular, the polymer electrolyte fuel cell can be operated at a low temperature and can be reduced in size and weight, and its application to a moving body such as an automobile and a home cogeneration system is being studied. Among the materials for polymer electrolyte fuel cells, one of the most important members is a polymer electrolyte. In particular, development of polymer electrolytes composed of polymer compounds containing a proton conductive functional group such as a sulfo group (sulfonic acid group) has been active.

  Since fuel cells are used in various environments, polymer electrolyte membranes are required to efficiently retain water and efficiently conduct protons even under conditions with little water. In order to conduct proton conduction under a condition with little water, it is necessary to increase the retention of water. Therefore, a structure containing many sulfo groups having high acidity is generally used. However, a polymer having many sulfo groups has a problem that the strength as a polymer electrolyte membrane is insufficient because it dissolves in water or swells severely. For example, Non-Patent Document 1 exemplifies a polyparaphenylene ether-based polymer having many sulfo groups, but it is described that this polymer is water-soluble.

  Various polymers have been developed to suppress solubility in water. Among them, for example, Patent Document 1 uses polyquinoline having a quinoline structure as a polymer having a rigid structure. Since this polymer does not have a sulfo group, it is necessary to form a complex with phosphoric acid or phosphoric acid esters for proton conduction, and such a polymer electrolyte membrane containing phosphoric acid is generally used. Performance degradation due to leakage of phosphoric acid is a problem. In addition, since such a polyquinoline is a basic polymer containing nitrogen, it has a disadvantageous structure for obtaining acidity advantageous for proton conduction even if a sulfo group is introduced.

JP 2000-273159 A

New Materials For Fuel Cell And Modern Battery Systems II 794-785

  An object of the present invention is to provide a hydrocarbon-based polymer electrolyte that can efficiently retain water even in a situation where water is low and can ensure proton conductivity.

  As a result of intensive studies to solve the above problems, the present inventors use a polymer electrolyte containing a polymer having a sulfo group advantageous for proton conductivity and having a rigid binaphthyl structure in the main chain. As a result, the present inventors have found that the proton conductivity in a situation where the membrane strength is increased and the moisture content is low, and the present invention has been completed.

  That is, the present invention is a polymer electrolyte containing a polyphenylene ether polymer having a structure represented by the following formula (1) in the main chain of the polymer.

(Wherein, a and b represent 0 to 1 and a + b is not 0. R represents an alkyl group, an aryl group, an alkoxy group, an aryloxy group, a carbonyl group, a sulfonyl group or a halogen group, and c, d Represents 0 to 6. When a plurality of R are present, they may be the same or different.
In the polymer electrolyte of the present invention, the polyphenylene ether polymer preferably has a structure selected from the group consisting of the following formulas (2) to (4) in the main chain.

(In the formula, a, b, c, d and R are the same as in the above formula (1). E and f represent 0 to 4.)

(In the formula, a, b, c, d and R are the same as in the above formula (1). E and f represent 0 to 4.)

(In the formula, a, b, c, d and R are the same as the above formula (1). E represents 0 to 4)
The polymer electrolyte of the present invention is a block copolymer in which the polyphenylene ether polymer is composed of a unit having a sulfonic acid group and a unit not having a sulfonic acid group, and the unit having a sulfonic acid group is represented by the formula It is preferable to have the structure represented by (1) in the main chain.

  The polymer electrolyte membrane of the present invention includes the polymer electrolyte membrane of the present invention.

  The membrane / electrode assembly of the present invention includes the polymer electrolyte membrane of the present invention.

  The polymer electrolyte fuel cell of the present invention includes the polymer electrolyte membrane or the membrane / electrode assembly of the present invention.

  The polymer electrolyte of the present invention has high membrane strength when it is used as a polymer electrolyte membrane, and can have excellent proton conductivity in a situation where moisture is low.

  An embodiment of the present invention will be described as follows. The present invention is not limited to the following description.

<Polymer electrolyte>
The polymer electrolyte of the present invention is characterized by comprising a polyphenylene ether-based polymer having a binaphthyl structure having a sulfo group represented by the following formula (1) in the main chain.

(Wherein, a and b represent 0 to 1 and a + b is not 0. R represents an alkyl group, an aryl group, an alkoxy group, an aryloxy group, a carbonyl group, a sulfonyl group or a halogen group, and c, d Represents 0 to 6. When a plurality of R are present, they may be the same or different.
In the present invention, R represents an alkyl group, an aryl group, an alkoxy group, an aryloxy group, a carbonyl group, a sulfonyl group, or a halogen group. An alkyl group having 1 to 10 carbon atoms, an aryl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an aryloxy group having 1 to 12 carbon atoms and a partially fluorinated one thereof, or the above alkyl group , An aryl group, an alkoxy group, an aryloxy group-containing carbonyl group or a sulfonyl group, or a halogen group such as fluorine, chlorine, bromine or iodine.

  The polyphenylene ether-based polymer in the present invention preferably has at least one structure selected from the group consisting of the following formulas (2) to (4) in the main chain for ease of polymer synthesis.

(In the formula, a, b, c, d and R are the same as in the above formula (1). E and f represent 0 to 4.)

(In the formula, a, b, c, d and R are the same as in the above formula (1). E and f represent 0 to 4.)

(In the formula, a, b, c, d and R are the same as the above formula (1). E represents 0 to 4)
The polyphenylene ether polymer in the present invention may be a random copolymer, a graft copolymer or a block copolymer as long as it has a binaphthyl structure having the sulfo group in the main chain. Good.

  Under low humidification conditions, the water inside the polymer electrolyte membrane is reduced, but in order to increase proton conduction, it is necessary to effectively use the water that serves as the proton conduction medium. More preferably, it is a block copolymer capable of producing a water-rich phase.

  Furthermore, in the block copolymer that forms microphase separation, it is possible to collect more water in the hydrophilic phase by separating the hydrophilic phase and the hydrophobic phase. The block copolymer is preferably composed of a hydrophilic unit having a hydrophobic unit and a hydrophobic unit having no sulfonic acid group.

  When the polyphenylene ether polymer in the present invention is a block copolymer composed of a hydrophilic unit having a sulfonic acid group and a hydrophobic unit having no sulfonic acid group, the hydrophilic unit having a sulfonic acid group The main chain may have a binaphthyl structure having the sulfo group as described above, but those containing the structures (2) to (4) as a repeating structure are preferable from the viewpoint of ease of synthesis.

  The hydrophobic unit having no sulfonic acid group preferably has a structure having a large number of aromatic rings having an electron-withdrawing group in which the sulfonic acid group is difficult to be introduced by sulfonation reaction, and among them, the following formulas (5) to ( Those having the structure represented by 7) are preferred because they are not easily sulfonated by chlorosulfonic acid in a halogen-based organic solvent.

  The polymer electrolyte of the present invention preferably has an ion exchange capacity of 0.5 to 4.0, more preferably 0.8 to 3.0, and even more preferably 1.1 to 2.5. This is preferable because both proton conductivity and the strength of the polymer electrolyte membrane are excellent.

<Synthesis of polyphenylene ether polymer of the present invention>
For the synthesis of the polyphenylene ether-based polymer of the present invention, a general polymerization reaction (“New Polymer Experimental Science 3 Polymer Synthesis Method / Reaction (2) Synthesis of Condensed Polymer” p. 7-213, (1996) Kyoritsu Publishing Co., Ltd.) can be applied.

  As the monomer used for polymerization, a bisphenol compound having two hydroxyl groups and a halogen compound having two halogen groups are preferably used. Among these, binaphthol having a binaphthyl structure is preferably used as the bisphenol compound because a rigid structure can be easily introduced. Binaphthol may have a sulfo group in advance. Among the binaphthols, 1,1′-bi-2-naphthol is preferable because it is relatively easy to synthesize. Since 1,1′-bi-2-naphthol has axial asymmetry, it is known that there are two optical isomers. However, either optical isomer may be present in the same amount. May be.

  In the present invention, another bisphenol compound may be used together with binaphthol. Examples of bisphenol compounds that can be mixed include hydroquinone, 4,4′-dihydroxybenzophenone, 4,4′-dihydroxydiphenyl sulfone, 4,4′-dihydroxybiphenyl, 4,4′-dihydroxydiphenyl ether, 4,4 Examples include '-dihydroxydiphenyl sulfide, 9,9-bis (4-hydroxyphenyl) fluorene, and structural isomers thereof.

  Examples of the halogen compound include 4,4′-dichlorobenzophenone, 4,4′-difluorobenzophenone, 4,4′-dichlorodiphenyl sulfone, 4,4′-difluorodiphenyl sulfone, 2,6-dichlorobenzonitrile, 2 , 6-difluorobenzonitrile, and structural isomers thereof. Among these, 4,4′-difluorobenzophenone, 4,4′-difluorodiphenyl sulfone, and 2,6-difluorobenzonitrile are preferable because of high reactivity.

  The polymerization reaction is performed in an air atmosphere, a nitrogen gas atmosphere, or an argon atmosphere, preferably in a nitrogen atmosphere.

  The solvent in the polymerization reaction step is not particularly limited as long as polymerization is not prohibited, and carbonate compounds (ethylene carbonate, propylene carbonate, etc.), heterocyclic compounds (N, N-dimethylacetamide (hereinafter referred to as DMAc), N, N— Dimethylformamide (hereinafter DMF), 3-methyl-2-oxazolidinone, 1-methyl-2-pyrrolidone (hereinafter NMP), N, N-dimethylimidazolidinone (hereinafter DMI), cyclic ethers (dioxane, tetrahydrofuran, etc.) ), Chain ethers (diethyl ether, ethylene glycol dialkyl ether, etc.), nitrile compounds (acetonitrile, glutarodinitrile, methoxyacetonitrile, etc.), aprotic polar substances (dimethyl sulfoxide (hereinafter DMSO), sulfolane, etc.), nonpolar Medium (toluene, xylene) chlorinated solvent (dichloromethane, dichloroethane, etc.), water and the like can be enumerated, among others DMAc or DMF from solubility, NMP, DMI, DMSO and the like bases, has high solubility of the polymer preferred. Of these, DMAc is preferred because of its high polymer solubility. These may be used alone or in combination of two or more. In addition, in order to remove water generated in the polymerization process, it is effective to remove water by azeotropy by adding an azeotropic solvent such as benzene, toluene, xylene and cyclohexane.

  What is necessary is just to set the reaction temperature of a polymerization reaction process suitably according to a polymerization reaction. Specifically, it may be set to 20 ° C to 330 ° C, more preferably 40 ° C to 280 ° C, and still more preferably 60 ° C to 240 ° C. If the temperature is lower than this range, the reaction rate is slow, and if the temperature is higher, there is a concern that the polymer may be greatly affected by a small amount of impurities and coloring of the polymer or unwanted side reactions may occur.

  In the polymerization reaction step, it is preferable to perform a stopping operation, which can be performed by cooling, diluting, or adding a polymerization inhibitor. You may take out the polymer | macromolecule produced | generated after the polymerization reaction process. Further purification steps may be added.

  When the polyphenylene ether-based polymer of the present invention is synthesized as a block copolymer, the polymer having the binaphthyl structure in the main chain can be used as a unit component having a sulfonic acid group. The other unit component constituting the block copolymer may be any unit component that can perform a polycondensation reaction with a polymer having the binaphthyl structure in the main chain. For example, polyether ketone, polyether sulfone, polyether ketone ether sulfone, In addition, these derivatives, those in which these ether bonds are replaced with thioether bonds, and derivatives thereof can be mentioned.

  In order to perform block copolymerization, it is only necessary that the ends of the polymer as a raw material react with each other, and it is preferable that one polymer end is a halogen group and the other polymer end is a hydroxyl group. Among them, it is more preferable that the halogen group at the polymer terminal is a fluoro group because of high reactivity. Moreover, even if the polymer terminal of the raw material which performs block copolymerization is all a hydroxyl group or a halogen group, a block copolymer can be manufactured by using a coupling agent. For example, when the terminal is a hydroxyl group, a linking agent such as decafluorobiphenyl, hexafluorobenzene, difluorobenzonitrile, 4,4′-difluorodiphenylsulfone, 4,4′-difluorobenzophenone, which is a fluorine polysubstituted aromatic compound, is used. be able to. For example, when the terminal is a halogen group, a compound having two hydroxyl groups can be used as a linking agent.

  The number average molecular weight of the polymer used for sulfonation in the polyphenylene ether-based polymer in the present invention is preferably 3,000 to 2,000,000. More preferably, it is 8,000 to 1,800,000, more preferably 12,000 to 1,600,000, the workability for producing the polymer electrolyte membrane and the strength of the polymer electrolyte membrane are Since both are excellent, it is preferable.

<Method of sulfonation>
Sulfonation is a reaction for introducing a sulfo group. Examples of the sulfonating agent include sulfuric acid, chlorosulfonic acid, fuming sulfuric acid and the like, and among them, chlorosulfonic acid is preferable because it has an appropriate reactivity.

  The solvent in the sulfonation is not particularly limited as long as it does not inhibit the reaction, and cyclic ethers (dioxane, tetrahydrofuran, etc.), chain ethers (diethyl ether, ethylene glycol dialkyl ether, etc.), nonpolar solvents (toluene, Xylene and the like) chlorinated solvents (dichloromethane, dichloroethane and the like) can be listed, and among them, chlorinated solvents such as dichloromethane and 1,2-dichloroethane are preferred in terms of solubility. These may be used alone or in combination of two or more.

  The reaction temperature of the sulfonation may be appropriately set according to the reaction, specifically, it may be set to −80 ° C. to 200 ° C. which is the optimum use range of the sulfonating agent, more preferably −50 ° C. to 120 ° C. More preferably, it is −20 ° C. to 80 ° C. If the temperature is lower than this range, the reaction is slow, and if the temperature is high, a rapid reaction occurs and the intended sulfonation does not proceed to 100%.

  The polymer electrolyte of the present invention can be used in various industries, and its use (use) is not particularly limited, but is suitable for a polymer electrolyte membrane, a membrane / electrode assembly, and a fuel cell. It is.

<2. Polymer Electrolyte Membrane According to the Present Invention>
The polymer electrolyte membrane according to the present invention is obtained by molding the polymer electrolyte into a membrane by an arbitrary method. As such a film forming method, a known method can be appropriately used. Examples of the leaving method include a film forming method from a solution such as a hot extrusion method, an inflation method, a melt extrusion molding method such as a T-die method, a casting method, and an emulsion method. For example, a casting method is exemplified as a method for forming a film from a solution. This is a method in which a polymer electrolyte solution with adjusted viscosity is applied onto a flat plate such as a glass plate using a bar coater, a blade coater or the like, and the solvent is evaporated to obtain a film. Industrially, it is also common to apply a solution continuously from a coating die onto a belt and vaporize the solvent to obtain a long product.

  Furthermore, in order to control the molecular orientation of the polymer electrolyte membrane, the obtained polymer electrolyte membrane is subjected to a treatment such as biaxial stretching or a heat treatment for controlling the crystallinity. Also good. In addition, it is also within the scope of the present invention to add various fillers in order to improve the mechanical strength of the polymer electrolyte membrane or to combine a reinforcing agent such as a glass nonwoven fabric with the polymer electrolyte membrane by pressing. is there.

  The thickness of the manufactured polymer electrolyte membrane can be selected arbitrarily depending on the application. For example, in consideration of reducing the internal resistance of the obtained polymer electrolyte membrane, the polymer film is preferably as thin as possible. On the other hand, in consideration of gas barrier properties and handling properties of the obtained polymer electrolyte membrane, it may not be preferable if the thickness of the polymer electrolyte membrane is too thin. Considering these, the thickness of the polymer electrolyte membrane is preferably 1.2 μm or more and 350 μm or less. When the thickness of the polymer electrolyte membrane is within the range of the above numerical values, handling is improved such that handling is easy and damage is unlikely to occur. In addition, the proton conductivity of the obtained polymer electrolyte membrane can be expressed within a desired range.

  It is also possible to introduce a sulfonic acid group after forming a polymer electrolyte membrane. In that case, the method for forming the polymer electrolyte membrane can be read as the method for forming the polymer electrolyte membrane precursor film. That is, a method for producing a film from a polymer that introduces a sulfonic acid group or a complex that includes a polymer that introduces a sulfonic acid group is exemplified. In this case, the polymer electrolyte membrane is finally obtained by sulfonating the film.

  In order to further improve the characteristics of the polymer electrolyte membrane of the present invention, it is possible to irradiate radiation such as electron beam, γ-ray, ion beam and the like. As a result, a crosslinked structure or the like can be introduced into the polymer electrolyte membrane, and the performance may be further improved. In addition, various surface treatments such as plasma treatment and corona treatment can improve properties such as improving adhesion to the catalyst layer on the surface of the polymer electrolyte membrane.

<3. Membrane / electrode assembly and fuel cell according to the present invention>
The membrane / electrode assembly (hereinafter referred to as “MEA”) according to the present invention uses the polymer electrolyte or polymer electrolyte membrane of the present invention.
Such an MEA can be used, for example, in a fuel cell, in particular, a polymer electrolyte fuel cell.

  Methods for producing MEA are conventionally studied polymer electrolyte membranes made of perfluorocarbon sulfonic acid and other hydrocarbon polymer electrolyte membranes (for example, sulfonated polyetheretherketone, sulfonated polyethersulfone, sulfone). A known method performed with a sulfonated polysulfone, a sulfonated polyimide, a sulfonated polyphenylene sulfide, or the like is applicable.

  In addition to the examples described above, the polymer electrolyte according to the present invention can be used as an electrolyte of a polymer electrolyte fuel cell known in, for example, Japanese Patent Application Laid-Open No. 2006-179298. Based on these known patent documents, those skilled in the art can easily construct a solid polymer fuel cell using the polymer electrolyte of the present invention.

  Hereinafter, examples will be shown and the embodiment of the present invention will be described in more detail. Of course, the present invention is not limited to the following examples.

  The molecular weight of the polymer obtained in the synthesis example, the ion exchange capacity of the polymer electrolyte obtained in the example, and the proton conductivity of the polymer electrolyte membrane were measured as follows.

[Measurement method of molecular weight]
The molecular weight was measured by GPC method. The conditions are as follows.

GPC measuring device HLC-8220 manufactured by TOSOH
Two columns, Super AW 4000 and Super AW 2500, manufactured by SHOWA DENKO, are connected in series. Column temperature 40 ° C
Mobile phase solvent NMP (LiBr added to 10 mmol / dm ³ )
Solvent flow rate 0.3 mL / min
[Measurement method of ion exchange capacity (hereinafter abbreviated as IEC)]
A target electrolyte membrane (about 100 mg: sufficiently dried) was immersed in 20 mL of a saturated aqueous solution of sodium chloride at 25 ° C., and subjected to an ion exchange reaction in a water bath at 60 ° C. for 3 hours. After cooling to 25 ° C., the membrane was thoroughly washed with ion exchanged water, and all of the saturated aqueous sodium chloride solution and the washing water were collected. To this collected solution, a phenolphthalein solution was added as an indicator, and neutralization titration was performed with a 0.01N sodium hydroxide aqueous solution to calculate IEC.

[Measurement method of proton conductivity]
Proton conductivity measurement is performed using a constant temperature and humidity chamber (manufactured by ESPEC, SH-221), keeping the temperature and humidity constant (about 3 hours), and using an impedance analyzer (manufactured by Hioki, 3532-50) The resistance of was measured. Specifically, the frequency response from 50 kHz to 5 MHz was measured with an impedance analyzer, and the proton conductivity was calculated from the following equation.
Proton conductivity (S / cm) = D / (W × T × R)
Here, D is a distance between electrodes (cm), W is a film width (cm), T is a film thickness (cm), and R is a measured resistance value (Ω). In this measurement, D = 1 cm and W = 1 cm, and the film thickness was a value measured using a micrometer for each sample. The temperature was 85 ° C., and the humidity was 30% RH, which is a low humidification condition.

(Synthesis Example 1)
To a 100 mL three-necked flask equipped with a nitrogen inlet and a reflux tube, (+/−)-1,1′-bi-2-naphthol (5.3 g, 18.5 mmol, manufactured by Tokyo Chemical Industry Co., Ltd.) and 2 , 6-difluorobenzonitrile (2.83 g, 20.3 mmol, manufactured by Tokyo Chemical Industry Co., Ltd.), potassium carbonate (3.65 g, 26.43 mmol, manufactured by Kanto Chemical Co., Inc.), N, N-dimethylimidazolidinone ( DMI, 5 mL, manufactured by Kanto Chemical Co., Ltd.) and toluene (10 mL, manufactured by Kanto Chemical Co., Inc.) were added. A three-necked flask was equipped with a Dean-Stark trap and the mixture was heated at 200 ° C. for 2 hours. After completion of the reaction, DMI (20 mL) was added, the mixture was cooled to room temperature, and the reaction solution was slowly dropped into 500 mL of pure water. The resulting precipitate was collected by suction filtration, washed with pure water at 80 ° C. for 3 hours, washed with methanol, and vacuum dried at 60 ° C. for 15 hours to obtain white polymer A.

(Synthesis Example 2)
In a 100 mL three-necked flask equipped with a nitrogen inlet and a reflux tube, 4,4′-dihydroxydiphenylsulfone (5.1 g, 20.4 mmol, manufactured by Tokyo Chemical Industry Co., Ltd.) and 4,4′-difluorodiphenylsulfone ( 4.8 g, 18.9 mmol, manufactured by Tokyo Chemical Industry Co., Ltd.), potassium carbonate (4.2 g, 30.6 mmol, manufactured by Kanto Chemical Co., Inc.), DMI (25 mL, manufactured by Kanto Chemical Co., Inc.), and toluene (5 mL, Kanto Chemical Co., Ltd.) Chemical Co., Ltd.) was added. A three-necked flask was equipped with a Dean-Stark trap and the mixture was heated at 180 ° C. for 2 hours. After completion of the reaction, the reaction solution was cooled to room temperature, and the reaction solution was slowly dropped into 500 mL of pure water. The resulting precipitate was collected by suction filtration, washed with pure water at 80 ° C. for 3 hours, washed with methanol, and vacuum dried at 60 ° C. for 15 hours to obtain white polymer B.

  1 g of the obtained polymer B was dissolved in 20 mL of dichloromethane, 3 g of chlorosulfonic acid was added, and the mixture was stirred at room temperature for 16 hours. Thereafter, the reaction solution was added to a large amount of water to precipitate a solid. Suction filtration was performed, and washing was performed with water until the filtrate became neutral. The washed solid was vacuum dried at 70 ° C. for 15 hours to obtain a white solid. When the ion exchange capacity of the obtained solid was measured, it was 0.04 meq / g. From this, it was found that in the polymer B, sulfo groups were hardly introduced under the sulfonation conditions.

(Synthesis Example 3)
Polymer A (1.2 g) synthesized in Synthesis Example 1, Polymer B (1.4 g) synthesized in Synthesis Example 2, and potassium carbonate (51 mg) in a 100 mL three-necked flask equipped with a nitrogen inlet and a reflux tube 0.4 mmol, manufactured by Kanto Chemical Co., Ltd.) and DMI (5 mL, manufactured by Kanto Chemical Co., Inc.) were added. The mixture was heated at 200 ° C. for 2 hours and then heated at 180 ° C. for 2 hours. After completion of the reaction, DMI (10 mL) was added and then cooled to room temperature, and the reaction solution was slowly added dropwise into an aqueous hydrochloric acid solution (500 mL, 5 mL concentrated hydrochloric acid / 500 mL pure water). This operation was repeated once again, washed with methanol, and then vacuum-dried at 60 ° C. for 15 hours to obtain a polymer compound having a sulfonateable structure. The number average molecular weight of the obtained polymer was 64,000. When calculated from the charged amount, it is calculated that a block copolymer consisting of units of m = 13 and n = 10 on average is obtained.

(Synthesis Example 4)
In a 100 mL three-necked flask equipped with a nitrogen inlet and a reflux tube, 4,4′-dihydroxydiphenylsulfone (1.58 g, 6.3 mmol, manufactured by Tokyo Chemical Industry Co., Ltd.) and hydroquinone (1.39 g, 12.6 mmol) , Manufactured by Tokyo Chemical Industry Co., Ltd.), 4,4'-difluorodiphenylsulfone (4.81 g, 18.9 mmol, manufactured by Tokyo Chemical Industry Co., Ltd.) and potassium carbonate (3.40 g, 24.6 mmol, manufactured by Kanto Chemical Co., Inc.) DMAc (20 mL, manufactured by Kanto Chemical Co., Inc.) and toluene (5 mL, manufactured by Kanto Chemical Co., Inc.) were added. A three-necked flask was equipped with a Dean-Stark trap, and the mixture was heated at 180 ° C. for 2 hours, followed by heating at 160 ° C. for 4 hours. After completion of the reaction, the reaction solution was cooled to room temperature, and the reaction solution was slowly dropped into 500 mL of pure water. The resulting precipitate was collected by suction filtration, washed with pure water at 80 ° C. for 3 hours, washed with methanol, and vacuum dried at 60 ° C. for 15 hours to obtain a white polymer. The number average molecular weight of the polymer was 47000. When calculated from the charged amount, it is calculated that a random copolymer of m: n = 2: 1 is obtained on average.

  1.6 g of the polymer obtained in Synthesis Example 3 was dissolved in 50 ml of dichloromethane, and 6 g of chlorosulfonic acid was added for sulfonation. The reaction solution was added to a large amount of water to precipitate a sulfonated polymer. Suction filtration was performed, and washing was performed with water until the filtrate became neutral. The washed solid was vacuum dried at 70 ° C. for 15 hours to obtain a sulfonated polymer.

0.5 g of a sulfonated polymer was dissolved in 30 mL of DMSO, cast into a glass petri dish, and vacuum dried at 70 ° C. for 15 hours to obtain an electrolyte membrane. The IEC of the membrane was 1.57 (meq / g), and the proton conductivity measured under low humidity conditions was 1.6 × 10 ⁻⁴ S / cm.

(Comparative Example 1)
2.0 g of the polymer obtained in Synthesis Example 4 was dissolved in 50 ml of dichloromethane and sulfonated by adding 6 g of chlorosulfonic acid. The reaction solution was added to a large amount of water to precipitate a sulfonated polymer. Suction filtration was performed, and washing was performed with water until the filtrate became neutral. The washed solid was vacuum dried at 70 ° C. for 15 hours to obtain a sulfonated polymer.

  0.5 g of a sulfonated polymer was dissolved in 30 mL of DMSO, cast into a glass petri dish, and vacuum dried at 70 ° C. for 15 hours to obtain an electrolyte membrane. The IEC of the membrane was 1.54 (meq / g). However, under low humidification conditions, the flexibility of the membrane was lost and it became brittle, and proton conductivity could not be measured.

  From a comparison between Example 1 and Comparative Example 1, it can be seen that the polymer electrolyte of the present invention is strong even under low humidification conditions and exhibits excellent proton conductivity.

  Therefore, it is clear that the polymer electrolyte of the present invention is useful as a material for a solid polymer fuel cell, and particularly useful as a polymer electrolyte membrane.

Claims (7)

A polymer electrolyte comprising a polyphenylene ether polymer having a structure represented by the following formula (1) in the main chain of the polymer.

(Wherein, a and b represent 0 to 1 and a + b is not 0. R represents an alkyl group, an aryl group, an alkoxy group, an aryloxy group, a carbonyl group, a sulfonyl group or a halogen group, and c, d Represents 0 to 6. When a plurality of R are present, they may be the same or different. The polymer electrolyte according to claim 1, wherein the polyphenylene ether-based polymer has a structure selected from the group consisting of the following formulas (2) to (4) in the main chain.

(Wherein, a and b represent 0 to 1 and a + b is not 0. R represents an alkyl group, an aryl group, an alkoxy group, an aryloxy group, a carbonyl group, a sulfonyl group or a halogen group, and c, d Represents 0 to 6. When a plurality of Rs are present, they may be the same or different, and e and f represent 0 to 4.)

(Wherein, a and b represent 0 to 1 and a + b is not 0. R represents an alkyl group, an aryl group, an alkoxy group, an aryloxy group, a carbonyl group, a sulfonyl group or a halogen group, and c, d Represents 0 to 6. When a plurality of Rs are present, they may be the same or different, and e and f represent 0 to 4.)

(Wherein, a and b represent 0 to 1 and a + b is not 0. R represents an alkyl group, an aryl group, an alkoxy group, an aryloxy group, a carbonyl group, a sulfonyl group or a halogen group, and c, d Represents 0 to 6. When a plurality of R exist, they may be the same or different from each other.   The polyphenylene ether polymer is a block copolymer comprising a unit having a sulfonic acid group and a unit having no sulfonic acid group, and the unit having a sulfonic acid group has a structure represented by the formula (1). The polymer electrolyte according to claim 1 or 2, which is present in the main chain.   A polymer electrolyte membrane comprising the polymer electrolyte according to claim 3.   A membrane / electrode assembly comprising the polymer electrolyte membrane according to claim 4.   A solid polymer fuel cell comprising the polymer electrolyte membrane according to claim 4.   A polymer electrolyte fuel cell comprising the membrane electrode assembly according to claim 5.