KR20190023249A - Anion-exchange membranes for fuel cells and preparation method thereof - Google Patents

Abstract

The present invention relates to an anion exchange membrane for a fuel cell and a method for manufacturing the same. More particularly, the present invention relates to a technology for manufacturing a thin film of a poly(phenylene oxide) polymer into which various conductive functional groups are introduced and applying the thin film to an anion exchange membrane for a fuel cell. The poly(phenylene oxide) polymer thin film manufactured according to the present invention, which have various functional groups introduced therein, can successfully control IEC by increasing interactions among conductive functional groups bonded to side chains and interaction with hydroxyl ions, and can obtain excellent ion conductivity at high and low temperatures. In addition, under conditions of low humidity and high humidity, a dimensional change is low and mechanical stability is remarkably improved, so that the film can be commercialized as an anion exchange membrane for a fuel cell.

Description

[0001] The present invention relates to an anion exchange membranes for fuel cells,

The present invention relates to an anion exchange membrane for a fuel cell and a method for producing the same, and more particularly, to a technique for manufacturing a thin film using a poly (phenylene oxide) polymer into which various conductive functional groups are introduced and applying the membrane to an anion exchange membrane for fuel cells.

Recently, many advantages of anion exchange membrane alkaline fuel cells (AEMFC) have been discovered, and much interest in the field of proton exchange membrane fuel cells (PEMFC) has been shifted to anion exchange membrane alkaline fuel cells (AEMFC). For example, AEMFCs can use relatively low cost metal catalysts due to fast reduction kinetics at the cathode, low corrosion and high pH of the process conditions, without using noble metal electrode catalysts.

Despite these advantages, it still has limitations in performance as a fuel cell. Therefore, it is necessary to improve the ionic conductivity, chemical stability, mechanical strength, expansion preventing property, durability and life stability of AEMFC.

In the AEMFC, anion exchange membrane (AEM) plays a major role as a major component. Recently, such anion exchange membranes have been actively studied and developed.

Many polymers including anionic complexes including poly (ether sulfone), poly (ether ketone), polyimide, poly (phenylene oxide) and inorganic materials have been developed as polymers for anion exchange membranes developed so far, Due to the low stability at high pH conditions, practical use in anion exchange membrane alkaline fuel cells (AEMFC) is limited. In addition, it is difficult to develop anion exchange membrane (AEM) because OH - ion conductivity can not be achieved due to low electrochemical mobility of OH - ion compared with the mobility of H + in water. The most straightforward and direct method to maximize OH-ion conductivity in AEM is to increase the ion exchange capacity (IEC), defined as the milliequivalents (meq) of the conductive groups per gram of polymer. However, a high ion exchange capacity (IEC) is accompanied by excessive water absorption which inevitably leads to a considerable swelling of the corresponding membrane, impairing the mechanical properties and causing the problem of decomposing the AEM, especially at high temperatures.

The stability of such a membrane can generally be increased by crosslinking the polymer, but crosslinking necessarily involves a decrease in the ionic conductivity of the polymer membrane. Therefore, development of a method that induces crosslinking but minimizes the reduction of conductivity is required.

Therefore, the inventors of the present invention have conducted extensive studies to expand application fields of poly (phenylene oxide) -based polymer thin films in order to improve thermal and chemical stability and mechanical properties. As a result, they have found that poly (phenylene oxide) The present invention has been completed based on the fact that the polymer membrane can be manufactured as an anion exchange membrane for a fuel cell based on improvement in stability and lifetime characteristics against decrease in ionic conductivity of a polymer membrane.

Patent Document 1: Korean Patent Laid-Open Publication No. 10-2012-0093298

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to provide a poly (phenylene oxide) polymer thin film having various ionic conductivity and ion conductivity, And a method for producing the same.

In order to accomplish the above object, the present invention provides an anion exchange membrane for a fuel cell comprising a poly (phenylene oxide) polymer having a repeating unit represented by the following general formula (1).

Wherein R ₁ is a quaternary ammonium group of -N (R ₂ R ₃ R ₄ ) ⁺ , or any one selected from the following structural formula 1, and n and m are mole ratios in the repeating unit, 0.9, 0.1? M? 0.9, n + m = 1,

[Structural formula 1]

,

,

,

,

In the R ₁ and the following structural formula 1 wherein R _2, R ₃ and R ₄ are each independently an alkoxy group of hydrogen, hydroxy, halogen, linear or branched alkyl group having 1 to 6 carbon atoms and having 1 to 6 carbon atoms and having 5 to 30 carbon atoms Lt; / RTI >

In the above formula (1), R ₁ may be any one selected from quaternary ammonium group, imidazolium group, piperidinium group and mopolinium group.

In the above Formula 1, n: m may be 0.2? N? 0.4, 0.6? M? 0.8, and n + m = 1.

The anion exchange membrane for a fuel cell may have a thickness of 40 to 50 占 퐉.

The anion exchange membrane for a fuel cell may have an ion exchange capacity of 1.8 to 2.0 meg / g.

Wherein the anion exchange membrane for fuel cells has a hydrogen ion conductivity of 0.01 to 0.04 S / cm at a relative humidity of 95 to 100% and a hydrogen ion conductivity of 20 to 50 ° C, a hydrogen ion conductivity of 0.06 to 0.09 S / cm at a relative humidity of 95 to 100% / Cm. ≪ / RTI >

The present invention relates to a method for preparing a poly (phenylene oxide) polymer, comprising the steps of: I) reacting a poly (phenylene oxide) polymer and N-bromosuccinimide to synthesize a brominated poly (phenylene oxide) polymer;

II) adding a compound having an anion-exchange group to a polymer solution obtained by dissolving the brominated poly (phenylene oxide) polymer of the step I) in an organic solvent and reacting the resultant to obtain a poly Phenylene oxide) polymer; And

III) forming a poly (phenylene oxide) polymer thin film having a repeating unit represented by the formula (1) obtained in the step (II).

The brominated poly (phenylene oxide) polymer in the step I) may be represented by the following general formula (7).

(Wherein n and m are as defined in formula (1)

The compound having an anion-exchange group in the step II) may be any one selected from the group consisting of quaternary ammonium, imidazolium, piperidinium and morpholinium.

The step II) may be carried out at 20 to 70 ° C for 40 to 50 hours using a solvent such as N-methylpyrrolidone (NMP).

The poly (phenylene oxide) polymer thin films prepared according to the present invention, which have various functional groups introduced therein, can successfully control the IEC by increasing the interaction between the conductive functional groups bonded to the side chains and the hydroxyl ions, Excellent ion conductivity can be obtained at a low temperature. In addition, under the conditions of low humidity and high humidity, the dimensional change is low and the mechanical stability is remarkably improved, and it can be commercialized as an anion exchange membrane for a fuel cell.

1 is a ¹ H-NMR graph of a poly (phenylene oxide) polymer according to Synthesis Examples 2 to 5;
FIG. 2A is a graph showing an ion exchange capacity (IEC) change observed before and after drying of an anion exchange membrane for fuel cells according to Examples 1 to 4. FIG.
FIG. 2B is a graph showing changes in water absorption (%) at high temperature (80 ° C.) and low temperature (20 ° C.) of the anion exchange membrane for fuel cells according to Examples 1 to 4.
Fig. 2C is a graph showing the change in lambda at high temperature (80 DEG C) and low temperature (20 DEG C) of the anion exchange membrane for fuel cells according to Examples 1 to 4. Fig.
3 is a graph showing changes in conductivity of hydroxide ion depending on conditions of temperature in an anion exchange membrane for a fuel cell and an anion exchange membrane for a Tokuyama A201 fuel cell according to Examples 1 to 4.
4 is an Arrhenius plot showing conductivity changes of the anion exchange membrane for fuel cell and the anion exchange membrane for Tokuyama A201 fuel cell according to Examples 1 to 4 under 1000 / T (K ^-1 ) condition.
5 is a graph showing changes in hydroxide ion conductivity at 60 DEG C, 95%, or 100% relative humidity conditions of the anion exchange membrane for fuel cells according to Examples 1 to 4. Fig.
6 is an atomic force microscope (AFM) image of an anion exchange membrane for fuel cells according to Examples 1 to 4. Fig.
7 is a SAXS graph of an anion exchange membrane for fuel cells according to Examples 1 to 4;
8 is a graph showing changes in conductivity of a thin film after immersing the anion exchange membrane for fuel cells according to Examples 1 to 4 in a 1 M KOH solution at 60 DEG C for 500 hours.
9 is a graph showing changes in ion exchange capacity (IEC) of a thin film after immersing the anion exchange membrane for fuel cells according to Examples 1 to 4 in a 1 M KOH solution at 60 DEG C for 500 hours.
10 is a graph showing the performance of an anion exchange membrane for fuel cells according to Examples 1 to 4 in a unit cell at 95% relative humidity and 60 ° C.
11A is a DSC graph showing DSC characteristics of an anion exchange membrane for fuel cells manufactured according to Examples 1 to 4 according to heating conditions.
FIG. 11B is a graph showing a change in stress (MPa) according to the tensile rate (%) of the anion exchange membrane for a fuel cell manufactured according to Examples 1 to 4.

Hereinafter, an anion exchange membrane for a fuel cell and a method for producing the same according to the present invention will be described in detail with reference to examples and accompanying drawings.

The present invention provides an anion exchange membrane for a fuel cell comprising a poly (phenylene oxide) polymer having a repeating unit represented by the following formula (1).

≪ Formula 1 >

Wherein R ₁ is a quaternary ammonium group of -N (R ₂ R ₃ R ₄ ) ⁺ , or any one selected from the following structural formula 1, n and m are mole ratios in the repeating unit, 0.9, 0.1? M? 0.9, n + m = 1,

<Structure 1>

,

,

,

,

In the R ₁ and the following structural formula 1 wherein R _2, R ₃ and R ₄ are each independently an alkoxy group of hydrogen, hydroxy, halogen, linear or branched alkyl group having 1 to 6 carbon atoms and having 1 to 6 carbon atoms and having 5 to 30 carbon atoms Lt; / RTI &gt;

Also, in the above formula (1), the arrangement of each phenylene component having the subscript n, m may be arbitrary or one block.

The poly (phenylene oxide) polymer has a poly (phenylene oxide) repeating unit as a backbone and at least one conductive functional group (preferably an anion-exchange functional group) in its side chain. And has excellent chemical and thermal stability.

In particular, the poly (phenylene oxide) polymer, in the formula 1 R ₁ is a quaternary ammonium group, preferred that the imidazole ryumgi, any one selected from the group consisting of piperidinyl nyumgi and Mo Pollini umgi, which is a poly (phenylene oxide) Based polymer has been variously introduced into a polymer, and the properties of the anion-exchange membrane, including the shape and properties of the polymer, have been extensively investigated. From the results obtained by introducing other conductive functional groups other than the conductive functional groups, There is still a problem such that it has low stability under the conditions or the ionic conductivity is greatly lowered under high temperature and high humidity conditions.

Specifically, the poly (phenylene oxide) polymer represented by the formula (1) may be represented by any one of repeating units selected from the following formulas (2) to (5).

(2)

(3)

&Lt; Formula 4 >

&Lt; Formula 5 >

In the poly (phenylene oxide) polymer having a repeating unit represented by any one of Chemical Formulas 2 to 5, the ratio (n: m) of n and m is preferably in the range of 0.2? N? 0.4, 0.6? M? = 1, the interaction between the conductive functional group bonded to the side chain and the interaction with the hydroxide ion is increased, and the IEC can be successfully controlled, and excellent ionic conductivity can be obtained at high temperature and low temperature. It can be seen that the dimensional change is low and the mechanical stability is remarkably improved under low humidity and high humidity conditions. Most preferably, n in Formula 1 is 0.3.

The poly (phenylene oxide) polymer represented by the formula (1) of the present invention can be used for an anion exchange membrane of a fuel cell by improving the mechanical properties and chemical stability by crosslinking the polymer skeleton. The poly (phenylene oxide) Mu m.

Therefore, in the present invention, the thickness of an anion exchange membrane for a fuel cell obtained from a poly (phenylene oxide) polymer having repeating units represented by any one of Chemical Formulas 2 to 5 (where n is 0.3 and m is 0.7) is 40 to 50 占 퐉 By using a very thin material, an anion exchange membrane can be optimally formed when a fuel cell is applied, which is more preferable because the structural stability is extremely high. At this time, if the thickness of the anion exchange membrane is less than 40 탆, it is difficult to withstand a high operating pressure, and if the thickness exceeds 50 탆, resistance to hydroxide ion transfer may be problematic. Furthermore, since the degree of condensation between polymer chains can be controlled and the ion exchange capacity can be maximized, it can be applied to anion exchange membranes for fuel cells in addition to excellent chemical and thermal stability.

Accordingly, the anion exchange membrane for a fuel cell manufactured by the combination of the above-described components has an ion exchange capacity of 1.8 to 2.0 meg / g calculated by the following formula 1, and the anion exchange membrane for a fuel cell has a relative humidity of 95 to 100% And has hydrogen ion conductivity of 0.01 to 0.04 S / cm at 50 DEG C, 95 to 100% relative humidity and hydrogen ion conductivity of 0.06 to 0.09 S / cm at 60 to 90 DEG C, and further characterized by chemical It has an advantage of being excellent in thermal stability, excellent in anion exchange performance, and capable of forming a thin film with low cost and high efficiency by a particularly simple and environmentally friendly heat treatment process. To satisfy these characteristics at the same time, it is preferable that the poly (phenylene oxide) polymer represented by the formula (4) or (5), wherein n is 0.3 and m is 0.7, in which a piperidinium group and a molesphenium group are introduced as a conductive functional group.

[Formula 1]

Wherein V _{0 NaOH} and V _{x NaOH} are the volumes of NaOH consumed in the titration under the absence of each thin film or thin film, C _NaOH is the molar concentration of NaOH titrated by standard oxalic acid solution, W _dry is the weight of the dried film. The concrete contents are described in an experimental example (FIG. 2 and Table 1) to be described later, and will not be described.

Specifically, in the case where room temperature, water or high humidity conditions or mechanical stability are required, the poly (phenylene oxide) polymer represented by Chemical Formula 5, in which the molsulinium group is introduced as a conductive functional group, (Phenylene oxide) polymer represented by the formula (4) in which a piperidinium group is introduced as a conductive functional group when a relative humidity of 100 to 95% and high temperature and chemical stability are required, And have favorable performance characteristics over a range of significance higher than that of one polymer.

In the present invention, the structure of the poly (phenylene oxide) polymer represented by the formula (1) is obtained by brominating a poly (phenylene oxide) to obtain a poly (phenylene oxide) polymer in which a benzyl position is selectively substituted with bromine , Which is then reacted with a compound having an anion-exchange group. In addition, it is synthesized by replacing the benzyl position of the poly (ethylene oxide) polymer with bromine to form a synthesized brominated poly (ethylene oxide) intermediate and then reacting with a compound having an anion-exchange group to be added. There is provided a process for producing an anion exchange membrane for a fuel cell comprising the following steps.

I) reacting a poly (phenylene oxide) polymer and N-bromosuccinimide to synthesize a brominated poly (phenylene oxide) polymer;

II) adding a compound having an anion-exchange group to a polymer solution obtained by dissolving the brominated poly (phenylene oxide) polymer in step I) in an organic solvent and reacting the solution to obtain a poly (phenylene oxide) polymer having a repeating unit represented by the formula (1) Obtaining a polymer; And

III) forming a poly (phenylene oxide) polymer thin film having a repeating unit represented by the formula (1) obtained in the step (II).

The poly (phenylene oxide) polymer according to the present invention is generally limited in its practical use in an anion-exchange membrane alkaline fuel cell (AEMFC) due to its low stability under alkaline (high pH) conditions, - ion conductivity can not be achieved due to the low electrochemical mobility of - ions. Accordingly, the present invention solves the problems of the above-mentioned poly (phenylene oxide) polymer, and at the same time has excellent mechanical properties and chemical stability, but also has excellent ionic conductivity at high temperature and high humidity, (Phenylene oxide) -based polymer.

The brominated poly (phenylene oxide) polymer in the step I) may be represented by the following general formula (7).

&Lt; Formula 7 >

(Wherein n and m are as defined in formula (1)

The compound having an anion-exchange group in step II) may be any one selected from the group consisting of quaternary ammonium, imidazolium, piperazinium, and morpholinium, (N-methylpiperidine) or 4-methylmorpholine (4-methylpiperidine) may be used in the embodiment of the present invention, considering that the thermal and chemical properties can be further improved. methylmorpholine) was used.

That is, in the step I), the poly (phenylene oxide) polymer and N-bromosuccinimide are dissolved in an organic solvent such as 2,2'-azobisisobutyronitrile (AIBN) And stirred to synthesize a brominated poly (phenylene oxide) polymer represented by the following formula (7).

&Lt; Formula 7 >

(Wherein n and m are as defined in formula (1)

At this time, the bromination reaction is performed at 100 ~ 150 ° C for 1 ~ 6 hours.

Next, II) a step of adding a compound having an anion-exchange group to a polymer solution obtained by dissolving the brominated poly (phenylene oxide) polymer of step I) in an organic solvent and reacting to obtain a poly (phenylene Oxide) polymer.

At this time, the step II) may be carried out at 20 to 70 ° C for 40 to 50 hours using a solvent such as N-methylpyrrolidone (NMP).

The poly (phenylene oxide) polymer having the repeating unit represented by the above formula (1) is exemplified by the following reaction formula, and the detailed synthesis method and analysis result thereof will be omitted because they are described in detail in the following embodiments.

<Reaction Scheme>

Finally, (III) a poly (phenylene oxide) polymer thin film having a repeating unit represented by the above formula (1) is formed to produce an anion exchange membrane for a fuel cell, which is an object of the present invention.

In the step (III), the poly (phenylene oxide) polymer having the repeating unit represented by the formula (1) is reacted with a solvent such as N-methylpyrrolidone (NMP) at 50 to 70 ° C for 10 to 30 hours Followed by a primary heat treatment and a secondary heat treatment at 60 to 100 ° C for 1 to 5 hours to form a thin film.

The method according to the present invention can reduce the amount of polymer used in comparison with a commonly used non-solvent induced phase separation (NIPS) or thermally induced phase separation (TIPS) Because the process itself is simple and short, it has advantages in its manufacturing cost.

Hereinafter, embodiments according to the present invention will be described in detail with reference to the accompanying drawings.

The materials used in the synthesis examples and examples according to the present invention are as follows.

2,2'-azobisisobutyronitrile (AIBN, 99%) and N-methyl-2-pyrrolidone (NMP, 99% N-bromosuccinimide (NBS), 98% was purchased from TCI, chlorobenzene (99.5%), 4-methylmorpholine, 99 %), Trimethyl amine (45 wt% aqueous solution), N-methylpiperidine (99%) and 2-methylimidazole (99%) were purchased from Aldrich .

All compounds used commercially available sources unless otherwise noted. All experiments were carried out using distilled water.

Synthesis Example 1 Bromination of poly (2,6-dimethyl-1,4-phenylene) oxide (Formula 7)

<Reaction Scheme 1-1>

  [Chemical Formula 6] (7)

Bromination of poly (2,6-dimethyl-1,4-phenylene) oxide (hereinafter also referred to as PPO) is carried out through the following procedure. First, a 500 ml two-necked flask equipped with a magnetic stirrer, a condenser and a nitrogen inlet was prepared. The prepared flask was charged with 6.0 g (50 mmol) of PPO (poly (2,6-dimethyl-1,4-phenylene) oxide) dissolved in 100 ml of chlorobenzene, and then N-bromosuccinic acid A mixture was prepared by adding 4.0 g (22.5 mmol) of N-bromosuccinimide (NBS) and 246 mg (1.5 mmol) of 2,2'azobisisobutyronitrile (AIBN). The mixture was heated at 135 DEG C for 3 hours, cooled to room temperature, and precipitated by adding methanol (1000 mL). The precipitate was washed three times, filtered to remove by-products, and then dried in vacuo at 80 ° C for 24 hours to synthesize and recover the brominated poly (phenylene oxide) polymer represented by Formula 7 of yellow solid powder (Yield: 96%, bromination rate: 30%). This was named Br-PPO.

&Lt; Formula 7 >

The synthesis of the brominated poly (phenylene oxide) polymer from Synthesis Examples 1 to 7 was confirmed by ¹ H-NMR data as follows.

_{δ H (400 MHz, CDCl 3} ) 6.74-6.60 (6H, brsignal, Ar H), 6.56-6.40 (14H, br signal, Ar H), 4.40-4.25 (6H, br signal, ArC H 2 Br), 2.20 -1.94 (51H, br signal, ArC H 3)

[Synthesis Example 2] Synthesis of poly (phenylene oxide) polymer containing quaternary ammonium group

Synthesis of quaternary ammonium group-containing poly (phenylene oxide) polymer is carried out through the following procedure. Br-PPO (DS = 30%) (1.44 g, 1 mmol) prepared in Example 1 was dissolved in 25 ml of N-methyl-2-pyrrolidone. Trimethylamine (TMA, 45 wt%) (1.97 g, 15 mmol) was added thereto to prepare a mixed solution. Ethyl acetate (250 mL) was added to the reaction solution prepared by stirring the mixture at room temperature for 48 hours. The resulting precipitate was washed with ethyl acetate three times, filtered to remove by-products, and then dried at 80 ^° C under vacuum for 24 hours to obtain a dark brown solid powder of a quaternary ammonium group-containing poly (phenylene Oxide) polymer was synthesized and recovered (yield: 89%). This was named QA-PPO.

(2)

The synthesis of the quaternary ammonium group-containing poly (phenylene oxide) polymer represented by the general formula (2) from the above-mentioned synthesis example 2 was confirmed by ¹ H-NMR data as follows.

_{δ H (400MHz, DMSO-d} 6) 7.10-6.82 (6H, brsignal, Ar H), 6.64-6.38 (14H, br signal, Ar H), 4.63-4.15 (6H, br signal, Ar-C H 2 _­­ -N), 3.41-2.82 (27H, br signal, CH 2 -NC H 3), 2.33-1.72 (51H, br signal, ArC H 3)

[Synthesis Example 3] Synthesis of imidazolium group-containing poly (phenylene oxide) polymer

The synthesis of the imidazolium group-containing poly (phenylene oxide) polymer is carried out through the following procedure. Br-PPO (DS = 30%) (1.44 g, 1 mmol) prepared in Example 1 was dissolved in 15 ml of N-methyl-2-pyrrolidone. 2-methylimidazole (0.58 g, 6 mmol) was added thereto to prepare a mixed solution. Ethyl acetate (250 ml) was added to the reaction solution prepared by stirring the mixture at 40 ° C for 48 hours. The resulting precipitate was washed with ethyl acetate three times, filtered to remove by-products, and then dried in vacuo at 80 캜 for 24 hours to obtain a dark brown solid powder of imidazolium group-containing poly (phenyl (Yield: 97%). &Lt; tb &gt; &lt; TABLE &gt; This was named IM-PPO.

(3)

It was confirmed by ¹ H-NMR data that the imidazolium group-containing poly (phenylene oxide) polymer represented by Formula 3 was synthesized from Synthesis Example 3 as follows.

_{δ H (400 MHz, DMSO-} d 6), 7.66-7.41 (6H, br signal, Ar H), 6.95-6.59 (6H, br signal, Ar H), 6.59-6.32 (14H, br signal, Ar H) , 5.43-5.11 (6H, br signal, Ar-C H 2 -N), 3.78-3.50 (9H, br signal, NC H 3), 2.58-2.37 (9H, br signal, CC H 3), 2.27-1.70 (51H, br signal, ArC H ₃ )

[Synthesis Example 4] Synthesis of poly (phenylene oxide) polymer containing piperidine group

The synthesis of piperidine-containing poly (phenylene oxide) polymer is carried out through the following procedure. (1.44 g, 1 mmol) prepared in Example 1 was dissolved in 15 ml of N-methyl-2-pyrrolidone. N-methylpiperidine (0.60 g, 6 mmol) was added thereto to prepare a mixed solution. Ethyl acetate (250 mL) was added to the reaction solution prepared by stirring the mixture at 40 DEG C for 48 hours. The resulting precipitate was washed with ethyl acetate three times, filtered to remove by-products, and then dried in vacuo at 80 ^° C for 24 hours to obtain a dark brown solid powder of a poly (phenylene Oxide) polymer was synthesized and recovered (yield: 95%). This was named PI-PPO.

&Lt; Formula 4 >

The synthesis of the piperidine group-containing poly (phenylene oxide) polymer represented by the formula (4) from the above-mentioned synthesis example 4 was confirmed by ¹ H-NMR data as follows.

_{δ H (400 MHz, DMSO-} d 6), 7.03-6.82 (6H, br signal, Ar H 1), 6.66-6.38 (14H, br signal, Ar H 2), 4.63-4.19 (6H, br signal, Ar _{CH 2), 3.11-2.83 (9H,} br signal, N CH 3), 2.32-1.85 (51H, br signal, Ar CH3), 1.85-1.64 (12H, br signal, CH 3 CH 2), 1.62-1.30 ( 9H, br signal, CH ₂ CH ₃ )

[Synthesis Example 5] Synthesis of poly (phenylene oxide) polymer containing molsulinium group

The synthesis of the poly (phenylene oxide) polymer containing mopulnium group is carried out through the following process. Br-PPO (DS = 30%) (1.44 g, 1 mmol) prepared in Example 1 was dissolved in 15 ml of N-methyl-2-pyrrolidone. 4-Methylmorpholine (0.60 g, 6 mmol) was added thereto to prepare a mixed solution. Ethyl acetate (250 ml) was added to the reaction solution prepared by stirring the mixture at 40 ° C for 48 hours. The resulting precipitate was washed three times with ethyl acetate, filtered to remove by-products, and then dried in vacuo at 80 DEG C for 24 hours to obtain a dark brown solid powder of a polyunsaturated poly (phenyl (Yield: 95%). &Lt; tb &gt; &lt; TABLE &gt; This was named MO-PPO.

&Lt; Formula 5 >

It was confirmed by ¹ H-NMR data that the poly (phenylene oxide) polymer containing a molsulinium group represented by the formula (5) was synthesized as described below.

_{δ H (400 MHz, DMSO-} d 6), 7.15-6.82 (6H, br signal, Ar H 1), 6.68-6.36 (14H, br signal, Ar H 2), 4.78-4.36 (6H, br signal, Ar _{CH 2), 4.15-3.78 (12H,} br signal, O CH 2), 3.74-3.22 (12H, br signal, N CH 2), 3.22-2.89 (9H, br signal, N CH 3), 2.34-1.66 ( _{51H, br signal, Ar CH 3} )

[Examples 1 to 4] Preparation of anion exchange membrane for fuel cell

A polymer solution obtained by dissolving various functional group-containing poly (phenylene oxide) polymers obtained in Synthesis Examples 2 to 5 in N-methyl-2-pyrrolidone (NMP) to a concentration of 5 wt% was filtered using a cotton plug, Diameter petri dish to form a thin film. The thin film was subjected to a primary heat treatment at 60 ° C. for 24 hours and a secondary heat treatment at 80 ° C. for 4 hours to have a crosslinked structure, thereby preparing various functional group-containing poly (phenylene oxide) polymer thin films having a crosslinked structure. The prepared thin film was immersed in deionized water and separated from the Petri dish. The separated thin films were stored in deionized water for 24 hours before analyzing properties such as mechanical properties.

Figure 1a is a ¹ H NMR spectrum of QA-PPO polymer, 1b is IM-PPO and ¹ H NMR spectrum of the polymer, Fig. 1c is a ¹ H NMR spectrum of PI-PPO polymer au, Figure 1d is a MO-PPO polymer &Lt; ¹ &gt; H NMR spectrum.

¹ H NMR spectra were obtained using an Agilent 400-MR (400 MHz) instrument using d ₆ -DMSO or CDCl ₃ as a reference.

As shown in FIG. 1, the structure of the anion exchange membrane according to each conductive agent was analyzed. First, in the Br-PPO prepared from Synthesis Example 1, the integral ratio of H ₁ , a benzylic hydrogen, and H ₂ , The conversion rate is 30%. The bromobenzyl groups of the thus synthesized polymer were all converted into poly (phenylene oxide) groups by using 4 kinds of conductive functional groups (4-gold ammonium group, imidazolium group, piperidinium group and mopolinium group) through Synthesis Examples 2, And introduced into the polymer.

Specifically, in FIG. 1A, a distinct peak was observed at around 3.1 ppm of H _{2, which} is the hydrogen of the methyl group of the ammonium group, indicating that the H ₂ position of the bromobenzyl hydrogen of Br-PPO was replaced with the ammonium benzyl hydrogen H ₃ .

In addition, the bromobenzyl hydrogen H ₂ -dipole peak appearing near 4.3 ppm in FIG. 1 b disappears, and a distinct peak appears near 5.3 ppm indicating imidazolium benzyl hydrogen H ₄ -direction, and a peak appearing near 2.5 ppm and 3.6 ppm The peak of hydrogen H ₇ of the imidazolium group due to the resonance structure was observed at around 7.5 ppm as well as a distinct peak attributed to the H ₂ and H ₃ positions of the methyl hydrogen of the dodolium was observed, It can be seen that the moiety of the benzylic hydrogen was replaced with the imidazolium group.

In addition, in Fig. 1 (c), peaks were observed in the vicinity of peaks similar to those observed in QA-PPO, and the typical piperidinium group-introduced methyl and hydrogen radicals in the vicinity of 1.6, 1.8, 3.0 _{, As the 5-} digit peak was observed, it was confirmed that the PI-PPO was also completely substituted with the piperidinium benzyl hydrogen H ₆ position of the bromobenzyl hydrogen H ₂ position.

In FIG. 1d, a distinct peak near 4.5 ppm indicating a mopolinium group at a position similar to that of bromobenzyl hydrogen H2 at 4.3 ppm was observed, and methyl peaks in the methyl group and cyclic methyl ether ) A new peak near 3.1, 3.5, 4.0 ppm due to _2,3,4- position of hydrogen H was observed, indicating that the bromobenzyl hydrogen was completely replaced by the modulonium group.

As described above, the thin films prepared in Examples 1 to 4 of the present invention tend to dissolve well in DMF, DMSO, NMP and DMAC, and a strong and tough thin film of 40-50 μm is formed by solvent-casting under NMP .

FIG. 2A is a graph showing the change in ion exchange capacity (IEC) of a thin film before and after drying for the fuel cell anion exchange membrane according to Examples 1 to 4. FIG. 2C is a graph showing the change of water absorption (%) at high temperature (80 DEG C) and low temperature (20 DEG C) of an anion exchange membrane. FIG. (20 &lt; 0 &gt; C). Table 1 below summarizes the numerical values of Figs. 2a, b and c.

division
IEC (meq / g) IEC _v (meg / cm ³ ) Water absorption (%) Dimensional change (%) lambda value (#) The Exp dry wet 20 ℃ 80 ℃ 20 캜 (Δt) 80 ° C (Δt) 20 ℃ 80 ℃ Example 1
QA-PPO 2.10 1.86 2.14 1.30 55.6 95.4 18.2 26.8 16.6 28.5 Example 2
IM-PPO 2.03 1.91 2.63 1.63 45.1 73.8 15.5 23.7 13.1 21.5 Example 3
PI-PPO 2.04 1.95 2.30 1.35 59.7 106.1 19.6 30.6 17.0 30.2 Example 4
MO-PPO 2.03 1.83 2.21 1.38 49.7 75.8 9.3 20.5 15.1 23.0

At this time, the ion exchange capacity (IEC) was determined by a back titration method. First, a membrane of 20 mg hydroxy (OH ^- ) was immersed in a 0.01 M HCl standard solution for 48 hours. The acid solution was then titrated with 0.01 M NaOH solution until the solution reached neutral pH. Phenolphthalein was used as an indicator and the ion exchange capacity (IEC) was calculated from the titration record using the following formula.

[Formula 1]

In this formula,

V _{0 NaOH} and V _{x NaOH} are the volume of NaOH consumed in the absence of the respective thin film or thin film, C _NaOH is the molar concentration of NaOH titrated by the standard oxalic acid solution, and W _dry is the weight of the dried film, and the volume measurement IEC (IEC _V ) can be calculated from the following equation:

[Formula 2]

[Formula 3]

Total water uptake (%) and swelling ratios were measured at 20 ° C or 80 ° C as described below. The film was immersed in distilled water for 24 hours, wiped with filter paper and immediately weighed (W _wet , t _wet ). The film was then dried under vacuum at 80 캜 until a constant weight was obtained (W _dry , t _dry ). The water absorption and the dimensional change of the thin film were determined by the following equation.

Water absorption (WU _W ) (wt%) = [(W _wet - W _dry ) / W _dry ]

Dimensional change (Δt) = [(t _wet - t _dry ) / t _dry ] ㅧ 100

Where W _wet and W _dry are respectively the weight of the wet film and the weight of the dried film, and t _wet and t _dry are the thickness of the film and the thickness of the dried film, respectively.

Water absorption (WU _V ) due to volume was also determined by the following equation.

[Formula 4]

Where rho _w and rho _m are the density of the dried film and water, respectively. Three repetitive measurements were made from each film and the IEC, moisture absorption and dimensional changes were averaged over three measurements.

Moisture absorption is one of the most important properties for anion exchange membranes. If moisture absorption is high and the dimensional change is low, it can be said that the damage of the thin film due to the temperature change is minimized. Therefore, moisture absorption and dimensional change of the anion exchange membrane for a fuel cell according to the present invention are analyzed through FIG. 2 and Table 1.

As shown in FIG. 2, moisture absorption and dimensional changes of the thin films prepared in Examples 1 to 4 at 20 ° C or 80 ° C were examined. As a result, the anion exchange membrane for fuel cell of Example 3 exhibited the highest water absorption and dimensional change And it was confirmed that it was the anion exchange membrane for fuel cell of Example 1. This is because the anion exchange membrane for fuel cell of Example 3 contains a PI-PPO polymer, and since the PI-PPO polymer has a bulky side chain than the QA-PPO polymer, it has an additional free volume, Because it can absorb more. On the other hand, the anion exchange membrane for fuel cell of Example 4 having a side chain similar to PI-PPO polymer has low water absorption and dimensional change, which is considered to be due to the difference in hydrogen bonding.

In order to compare the ion conductivity and dimensional stability of each polymer contained in the thin films of Examples 1 to 4, the number of water molecules absorbed per half of the conductive functional group (? Value) was set at 20 占 폚 and 80 Lt; 0 &gt; C (Table 1 and Fig. 2c). It can be seen that the anion exchange membrane for fuel cell of Example 4, which had the lowest dimensional change before, shows a marked difference in dimensional change at high temperature and low temperature. That is, it was confirmed that the oxygen atom of the mopolinium group of the anion exchange membrane for fuel cells of Example 4 at the low temperature provides an additional hydrogen bonding site between the water and the hydroxide ion, thereby increasing the density of the polymer and thus obtaining better dimensional stability. However, as the temperature increases, the hydrogen bonds become slightly broken and the dimensional stability is lowered.

It can be confirmed that the anion exchange membrane for fuel cell of Example 2 has a low moisture absorption even at a high temperature because it interferes with the absorption of water by the interaction of π-π which is a hydrophobic interaction.

Figure 3 is an embodiment 1-4 in a graph showing a conductivity (hydroxide conductivity) changes in hydroxyl ion according to another fuel cell anion exchange membrane and Tokuyama A201-Temperature conditions of the fuel cell, the anion exchange membrane, Figure 4 is 1000 / T (K ^{- 1} is an Arrhenius plot showing the change in conductivity of the anion exchange membrane for a fuel cell and the anion exchange membrane for a Tokuyama A201 fuel cell according to Examples 1 to 4.

The ionic conductivity (σ) of the anion exchange membrane (size: 1 cm x 4 cm) was obtained by using the equation σ = l / RA (1: distance between reference electrodes and A: sectional area of membrane coupon). Here, the ohmic resistance (R) was measured by 4-point probe alternating current impedance spectroscopy, and the conductivity in the liquid state was measured for each temperature. To minimize unnecessary carbon formation, the cell was completely immersed in deaerated and dehydrated water and quickly obtained an impedance spectrum. Conductivity values were obtained from the mean values for at least three measurements over the same time interval.

As shown in FIGS. 3 and 4, the hydroxide conductivity was measured (20 ° C. to 80 ° C.) by temperature under 100% RH. At room temperature, the anion exchange membranes for fuel cells of Examples 1 to 4 exhibited similar conductivity. Among them, the anion exchange membrane for fuel cell of Example 4 exhibited the highest conductivity of 0.03 S / cm.

From the viewpoint of the activation energy, it was confirmed that the anion exchange membrane for fuel cell of Example 4 had the lowest value and the anion exchange membrane for fuel cell of Example 3 which had no oxygen atoms in the side chain had the highest value.

The reason why these differences arise even though they have the same poly (phenylene oxide) as a backbone is that since the conductive functional groups of the polymers used in Examples 1 to 4 are different from each other, the conduction mechanisms of the functional groups and the It is believed to be due to the diffusion rate.

In summary, it was observed that the anion exchange membranes for fuel cells of Examples 1 to 4 according to the present invention had hydroxyl ion conductivities equal to or superior to those of Tokuyama A201 at low temperature and high temperature as a whole, The battery anion exchange membrane means that it can be used as an excellent hydroxide conductor for AEM fuel cells. It is most preferable to use the anion exchange membrane for fuel cell of Example 3, which is 0.03 S / cm at the low temperature and 0.07 to 0.08 S / cm at the high temperature, most preferably the fuel cell anion exchange membrane of Example 4. This is a 20% increase over the conductivity of poly (phenylene oxide) polymers with other functional groups in general, and the increase in this range is a significant improvement over a significant range in the field.

5 is a graph showing changes in hydroxide ion conductivity at 60 DEG C, 95%, or 100% relative humidity conditions of the anion exchange membranes for fuel cells according to Examples 1 to 4. FIG.

5 is a graph showing the results of measurement in an actual humidification state, unlike FIGS. 3 and 4, and can be more accurately analyzed when applied to a fuel cell. Specifically, the fuel cell anion exchange membrane of Example 3 exhibited the highest conductivity at 100% relative humidity (100% RH), and the anion exchange membrane for fuel cell of Example 1 had the highest conductivity at 95% relative humidity (95% RH) Respectively. Hydrophilic ions can dissociate and diffuse due to the presence of a large amount of water in the air under high humidity conditions. However, in a relatively low humidity (RH 95%) condition, dissociation of hydroxide ions is difficult because of less water in the air than at 100% , The Grotthuss mechanism and the surface diffusion mechanism, which are different from the mechanism in high humidity conditions. Therefore, the types of thin films having excellent effects in high humidity conditions and low humidity conditions are different. It can be confirmed that the anion exchange membranes for fuel cells of Examples 3 and 4 which exhibit balanced performance under the conditions of high humidity and low humidity are most preferable.

FIG. 6 is an atomic force microscope (AFM) image of an anion exchange membrane for fuel cells according to Examples 1 to 4. As shown in FIG. 6, the anion exchange membranes for fuel cells according to Examples 1 to 4 are all hydrophobic bright portions and hydrophilic dark Partial phase separation was observed. In addition, the anion exchange membrane for fuel cell of Example 1 has a small cluster shape and is regularly dispersed. On the contrary, the anion exchange membrane for fuel cell of Example 3 does not have a distinct cluster shape, but confirms that well- Respectively. The anion exchange membranes for fuel cells of Examples 2 and 4 were relatively large in cluster or domain size and the anion exchange membranes for fuel cells of Example 4 were larger than those of the anion exchange membranes for fuel cells of Example 3, Cluster.

FIG. 7 is a SAXS graph of an anion exchange membrane for fuel cells prepared according to Examples 1 to 4, wherein anion exchange membranes for fuel cells prepared according to Examples 1 to 4 all have ionomer peaks at 0.02 A and d = 2 & / q, the d-spacing was observed to be about 30 nm. However, in the anion exchange membranes for fuel cells of Examples 4 and 2, an additional peak appeared at about 0.2 A, indicating that it was due to the hydrogen bonding in the π-π interaction or the mopolinium period between the imidazolium groups.

8 is a graph showing changes in ionic conductivity of a thin film after immersing the anion exchange membrane for fuel cells according to Examples 1 to 4 in a 1 M KOH solution at 60 DEG C for 500 hours, (IEC) of the thin film after immersing the anion exchange membrane for fuel cell according to the present invention in a 1 M KOH solution at 60 ° C for 500 hours. At this time, the change of ionic conductivity was measured by immersing OH-type thin film in stirred 1M KOH solution at 60 ° C to change the appearance and ionic conductivity.

As shown in FIGS. 8 and 9, the anion exchange membranes for fuel cells prepared according to Examples 1 to 4 were observed for conductivity and IEC change over 500 hours, and as a result, they were found to maintain excellent conductivity and IEC until 200 hours, It can be seen that the chemical stability is high under the hydroxide condition. However, the anion exchange membrane for fuel cell of Example 3 maintained 80% conductivity even after 500 hours, and it was confirmed that it is the most stable in the alkali condition. This is believed to be due to the bulky side chains interfering with the attack of hydroxides. On the contrary, the anion exchange membrane for fuel cell of Example 4 maintained 57% conductivity after 500 hours, and relatively low chemical stability was confirmed, and the anion exchange membrane for fuel cell of Example 1 had 20% It was confirmed that only conductivity was maintained. Therefore, it can be seen that the stability of the anion exchange membrane for fuel cell of Example 3 is more than twice as long as the chemical stability.

FIG. 10 is a graph showing a single cell prepared using the anion exchange membranes for fuel cells according to Examples 1 to 4, and measuring the performance thereof. Specifically, FIG. 10 is an IV curve of a single cell. The experiment was carried out at 95% RH and 60 ° C.

10, it was observed that the conductivity of the anion exchange membrane for fuel cell of Example 3 was the highest at 64.2 ms / cm at the condition of 95% RH in a single cell. In Example 4, Example 1, Example 2 Of the anion exchange membrane for fuel cell.

In the case of the 100% RH condition, the anion exchange membrane for fuel cell of Example 1 was found to have the highest conductivity at 4.28 ms / cm, which is consistent with the tendency of the ion conductivity measured in the foregoing FIG. 5. It was confirmed that the anion exchange membrane for fuel cell of the present invention had the best cell performance when it was practically applied to a battery. This is because the effect of surface diffusion of the quaternary ammonium group causes another bulky side chain This is because hopping is more advantageous than the anion exchange membranes for fuel cells of Examples 3 and 4.

Subsequently, it was confirmed that the anion exchange membrane for fuel cell of Example 4 also exhibits excellent cell performance because the Grotthuss mechanism due to hydrogen bonding dominates rather than the diffusion effect, so that the conductivity is higher than the lambda value. In addition, the anion exchange membrane for fuel cell of Example 3 showed similar or superior cell performance to that of the anion exchange membrane for fuel cell of Example 4, and showed the most balanced performance in high humidity and low humidity conditions.

FIG. 11A is a graph showing the results observed by differential scanning calorimetry (DSC) according to heating conditions of an anion exchange membrane for fuel cells manufactured according to Examples 1 to 4. FIG.

As shown in FIG. 11A, the glass transition temperature (Tg) and the phase behavior of the anion exchange membranes for fuel cells prepared according to Examples 1 to 4 were examined. The anion exchange membranes for fuel cells of Example 1 exhibited an observation It is expected that the temperature will be higher because the attraction between the main chains is stronger than that of other anion-exchange membranes for fuel cells. The anion exchange membranes for fuel cells of Examples 2, 3 and 4 were observed to have lower glass transition temperatures (T _g ) than the anion exchange membranes for fuel cells of the Examples (endothermic peaks observed at temperatures below 250 ° C) . However, the anion exchange membranes for fuel cells of Example 3 and Example 4 were observed to have a difference in glass transition temperature (T _g ) despite their similar structures, It is believed that this is due to the formation of additional mutual bonds by hydrogen bonding of atoms and OH ^- .

FIG. 11B is a graph showing changes in tensile strength (MPa) according to elongation (strain,%) of an anion exchange membrane for a fuel cell manufactured according to Examples 1 to 4.

As shown in FIG. 11B, it was confirmed that the anion exchange membranes for fuel cells prepared according to Examples 1 to 4 exhibited a maximum elongation at 20% and an appropriate tensile strength (MPa) of 50 MPa. However, even if the polymer has the same main chain, the tensile strength and the elongation of the membrane slightly differ depending on the kind of the introduced functional group and the molar fraction. For example, the anion for fuel cell of Examples 3 and 4 The exchange membrane had the highest tensile strength, but it was confirmed that the anion exchange membrane for fuel cell of Example 4 had better elongation than the anion exchange membrane for fuel cell of Example 3. Among these, the anion exchange membrane for fuel cell of Example 4 having the highest elongation and tensile strength showed the most favorable mechanical characteristics, and this tendency can be confirmed also in the SAXS of FIG.

In the present invention, poly (phenylene oxide) to which various conductive functional groups have been introduced for an anion exchange membrane for a fuel cell are presented. As a result, the PI-PPO polymer of Synthesis Example 4 has the highest ionic conductivity (76.5 ms cm ^-1 ) And chemical stability (23% loss over 500 hours). Also, the QA-PPO polymer of Synthesis Example 2 showed the highest performance (250 mA cm ^-2 ) in the single cell test, but no excellent performance was observed in terms of chemical stability and the like.

The MO-PPO polymer of Synthesis Example 5 was found to have the highest ionic conductivity (36.1 ms cm ^-1 ) and dimensional stability at room temperature, and the ion channel is formed well by AFM, Respectively. Furthermore, the single cell evaluation showed higher performance than the PI-PPO polymer of Synthesis Example 3 having a similar structure. Based on these results, it has been confirmed that the four conductive functional groups mentioned in the present invention can be used as an anion exchange membrane through bonding with poly (phenylene oxide) in the field of anion exchange membranes of fuel cells, A poly (phenylene oxide) polymer represented by Chemical Formula 4 or 5, into which a mordenium group is introduced as a conductive functional group, is excellent in chemical and thermal stability to an alkali compound and has excellent anion exchange performance, It is confirmed that the thin film can be formed at low cost and high efficiency by the heat treatment process.

Claims (10)

1. An anion exchange membrane for fuel cells comprising a poly (phenylene oxide) polymer having a repeating unit represented by the following formula (1).
&Lt; Formula 1 >

Wherein R ₁ is a quaternary ammonium group of -N (R ₂ R ₃ R ₄ ) ⁺ , or any one selected from the following structural formula 1, and n and m are mole ratios in the repeating unit, 0.9, 0.1? M? 0.9, n + m = 1,
<Structure 1>

,

,

In the R ₁ and the following structural formula 1 wherein R _2, R ₃ and R ₄ are each independently an alkoxy group of hydrogen, hydroxy, halogen, linear or branched alkyl group having 1 to 6 carbon atoms and having 1 to 6 carbon atoms and having 5 to 30 carbon atoms Lt; / RTI &gt; The method according to claim 1,
Wherein R ₁ is any one selected from the group consisting of a quaternary ammonium group, an imidazolium group, a piperidinium group, and a mullulanium group. The method according to claim 1,
Wherein n: m is in the range of 0.2? N? 0.4, 0.6? M? 0.8, and n + m = 1. The method according to claim 1,
Wherein the anion exchange membrane for fuel cells has a thickness of 40 to 50 占 퐉. The method according to claim 1,
Wherein the anion exchange membrane for a fuel cell has an ion exchange capacity of 1.8 to 2.0 meg / g. The method according to claim 1,
Wherein the anion exchange membrane for fuel cells has a hydrogen ion conductivity of 0.01 to 0.04 S / cm at a relative humidity of 95 to 100% and a hydrogen ion conductivity of 20 to 50 ° C, a hydrogen ion conductivity of 0.06 to 0.09 S / cm at a relative humidity of 95 to 100% / Cm &lt; / RTI &gt; for an anion exchange membrane for a fuel cell. I) reacting a poly (phenylene oxide) polymer and N-bromosuccinimide to synthesize a brominated poly (phenylene oxide) polymer;
II) adding a compound having an anion-exchange group to a polymer solution obtained by dissolving the brominated poly (phenylene oxide) polymer of the step I) in an organic solvent and reacting the resultant to obtain a poly Phenylene oxide) polymer; And
III) forming a poly (phenylene oxide) polymer thin film having a repeating unit represented by the formula (1) obtained in the step (II). 8. The method of claim 7,
Wherein the brominated poly (phenylene oxide) polymer of step I) is represented by the following general formula (7).
&Lt; Formula 7 >

(Wherein n and m are as defined in formula (1) 8. The method of claim 7,
Wherein the compound having an anion-exchange group in step II) is any one selected from the group consisting of quaternary ammonium, imidazolium, piperidinium, and morpholinium. 8. The method of claim 7,
Wherein the step II) is carried out at 20 to 70 ° C for 40 to 50 hours using a solvent such as N-methylpyrrolidone (NMP).

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