KR101293196B1 - Polybenzimidazolium based solid electrolytes - Google Patents

Abstract

In the present specification, a novel polybenzimidazolim, which is a stable and excellent polymer electrolyte material, is provided. By using the polybenzimidazolim, the polymer electrolyte having high stability and high performance is provided by compensating for the disadvantage of an unstable anion exchanger. There is an effect that can provide a membrane or a catalyst binder.

Description

Polybenzimidazolium-based solid electrolytes

The invention disclosed herein relates to the use of the novel polybenzimidazolium and its polybenzimidazolium.

Proton exchange membrane fuel cell systems have been developed a lot, but the path to large-scale commercialization is still far from high costs and the difficulty of obtaining platinum.

As an alternative, there is an alkaline anion exchange membrane (AAEMFC). Because of the high pH in the fuel cell, it is possible to use non-noble metal based catalysts such as silver or nickel. In addition, at high pH, the corrosion rate is slow, resulting in improved electrode kinetics at the cathode and the use of cheap metal anode plates.

However, the major drawbacks of hydroxide exchange membranes are that the hydroxide anions react with CO ₂ to form carbonates, and that the anion exchangers are very chemically unstable and above the fuel cell operating temperature of 60 ° C. It is difficult to use. Thus, a means is needed to overcome the unstable disadvantages of anion exchangers.

Polybenzimidazole (PBI) -based polymers are heterocyclic polymers, which are inexpensive and thermally and chemically stable in various environments. In addition, the main chain has a rigid structure and has a high glass transition temperature (Tg). In anion exchange resins or membranes made of polybenzimidazole, the counter ions can be easily exchanged by immersing the polymer in a salt or base solution. However, polybenzimidazole resins or membranes ion-exchanged with hydroxides can be very unstable, leading to brittleness and failure.

The technique disclosed herein is to provide a novel polybenzimidazolium.

One embodiment of the present invention aims to provide a stable polybenzimidazolium.

Another embodiment of the present invention aims to provide a stable and excellent polymer electrolyte membrane.

One embodiment of the present invention, a polybenzimidazolium having a structure of formula (1) or (2), wherein the polybenzimidazoli is 5 to 100% of the total benzimidazole monomer is an anion Polybenzimidazoli, an added benzimidazolium, is disclosed.

Where

A is a direct bond or oxygen,

B is a group of diacid having 1 to 5 heteroatoms or a group of diacid containing 9 or more carbon atoms,

R ₁ to R ₄ are the same as or different from each other, and each independently hydrogen, a C _1-6 alkyl group, or an aromatic substituent,

X- is an anion selected from the group consisting of halogen, OH-, carbonate, hydrogen carbonate, sulfate, acetate, formiate, methanolate and ethanolate,

n is an integer of 1 or more.

In another embodiment of the present invention, the diacid may include an aromatic ring.

In another embodiment of the invention, the divalent acid may have two separate phenyl rings.

In another embodiment of the invention, the aromatic ring is O-alkyl, O-phenyl, alkyl, nitrile, COOH, chloride, fluoride, nitro, sulfonate, phosphonate, S-alkyl, S-phenyl, It may be substituted by one or more substituents selected from the group consisting of sulfone-phenyl, acyl and benzoyl.

In another embodiment of the present invention, the divalent acid may be any one of the divalent acids of Formula 3 below.

In another embodiment of the present invention, the polybenzimidazole may be para-PBI.

In another embodiment of the invention, the polybenzimidazolium, as the monomer, polybenzoxazole (polybenzoxazole, PBO), polyphenylquinoxaline, polybenzothiazole (PBT), tetraamine and carboxyl It may be a copolymer further comprising one or more monomers selected from the group consisting of acids.

In another embodiment of the invention, R ₁ to R ₄ are the same or different from each other, each being unsubstituted, hydrogen, methyl, benzyl, functionalized benzyl, trityl, functionalized trityl, tert-butyl or May be a combination.

In another embodiment of the present invention, the polybenzimidazolium may be one having a structure of Formula 4 below.

In another embodiment of the present invention, the polybenzimidazolium may be one having a structure of Formula 5 below.

In another embodiment of the invention, X- may be OH-.

In another embodiment of the present invention, the aromatic ring may be substituted with O-alkyl.

In another embodiment of the present invention, when the divalent acid has a structure of the following formula, the OH group of the benzene ring may be O-methylated.

In another embodiment of the present invention, the polybenzimidazolium may be cross-linked.

In another embodiment of the present invention, the polybenzimidazolium may be cross-linked with α, α'-dihaloxylene (dihaloxylene).

In another embodiment of the present invention, the α, α'-dihaloxylene may be α, α'-dibromoxylene.

One embodiment of the present invention discloses an electrolyte membrane comprising the polybenzimidazolium mentioned above.

Another embodiment of the present invention discloses a catalyst binder comprising the polybenzimidazolium mentioned above.

Another embodiment of the present invention discloses a fuel cell, an electrolyzer or a battery comprising the electrolyte membrane.

Another embodiment of the present invention discloses a fuel cell or an electrolytic cell comprising the catalyst binder.

By using the present invention, it is possible to provide a polymer electrolyte membrane or a catalyst binder having high stability and high performance by supplementing the disadvantages of the unstable anion exchanger.

1 is an NMR spectrum in DMSO-d6 of 1,3-dimethyl-meta-polybenzimidazolilium iodide. On the right is an aromatic signal for PBI with 91% methylation degree (84% imidazolium).
2 is an NMR spectrum of PBI-dicarboxyl acid-diphenylether (PBI-DCDPE) Me 2 73 I. FIG.
FIG. 3A shows NMR of I-polybenzimidazoli of m-PBI, and FIG. 3B shows NMR results of I-imidazolium of 1,3-dimethyl-2-phenyl-benzimidazole.
Figure 4 compares the hydrolytic stability of K- of 1- (benzyl) -2-phenyl-benzimidazole with 1- (4-methoxybenzyl) -2- (4-methoxyphenyl) -benzimidazole Schematic diagram shown.
5 is an experimental result confirming that benzoic acid was formed by the benzoic acid addition experiment.

As used herein, the term "polybenzimidazolium" refers to a polymer in the form of a salt formed by the addition of anions to polybenzimidazole. The polybenzimidazolium includes not only anions added to all benzimidazole monomers but also anions added to only some benzimidazole monomers. For example, only 50%, 60%, and 70% of monomers, such as 50% imidazolium, 60% imidazolium, and 70% imidazolium, are in the form of imidazolium to which anions are added. In the description herein in the form of "PBI-XX_number_anion", "XX" refers to the main features of the PBI, in particular the type and number of substituents that substitute for the nitrogen of the imidazole, and "number" refers to the imidazolium The ratio "anion" refers to the kind of anion added.

The "nitrogen, N" of imidazole in the structure of Formula 1 or Formula 2 may each independently be unsubstituted or substituted with R ₁ to R ₄ . When N is substituted, stability may be enhanced. When substituted, R ₁ to R ₄ may be an alkyl group or an aromatic substituent. The alkyl group may be a C _1-6 lower alkyl group such as methyl group, ethyl group, propyl group and butyl group. In particular, a methyl group, benzyl group, functionalized benzyl group, trityl, functionalized trityl, tert-butyl or a combination thereof is preferable.

In Formula 1, A may be a direct bond or oxygen.

For example, when A is oxygen, PBI-OO (poly-[(1- (4,4_-diphenylether) -5-oxybenzimidazole) -benzimidazole]) as follows:

The PBI-OO can be purchased from FUMA-Tech, Germany.

Examples of the case where A is a direct bond include PBI-DCDPE (PBI-dicarboxylic acid-diphenylether) as described below.

B may be a group of diacids having 1 to 5 heteroatoms. Here, the term "heteroatom" may be any atom other than carbon and hydrogen. For example, it may be nitrogen, oxygen, sulfur, phosphorus, boron, chlorine, bromine or iodine and the like. Meanwhile, B may be a group of divalent acid containing 9 or more carbon atoms. Divalent acids containing more than 9 carbon atoms significantly increase the stability of the polybenzimidazolium structure. B may be a group comprising an aromatic ring, in particular having two separate phenyl rings. The two phenyl rings may be separated by hetero atoms. Two phenyl rings contribute to the structural stability of the compound. The reason for this is that the positive charge of the imidazole moves around the imidazole ring and the phenyl ring to stabilize the structure. If there is only one phenyl ring, two positive charges are concentrated on one phenyl ring, and thus the structure stabilization effect is weak. If more than one phenyl ring is present, the two positive charges can be dispersed in two or more phenyl rings, so that the structure is stabilized. On the other hand, the phenyl ring may be further substituted with O-alkyl and the like. Such substitution further stabilizes the structure of the compound. In other words, when the 2-position phenyl group is substituted with an electron donation group (+ M-effect) such as methoxy, the stability of the compound is significantly improved.

Polybenzimidazoles herein include meta-PBI, para-PBI, AB-PBI [poly (2,5-benzimidazole)], or other derivatives. Meta-PBI means PBI in which No. 1 and 3 of the aromatic ring are bonded to benzimidazole when “B” of Formula 1 or 2 is an aromatic ring. For example, poly (2,2 '-(1,3-phenylene) 5,5'-bibenzimidazole) can be mentioned. Para-PBI means PBI in which No. 1 and 4 of the aromatic ring of “B” of Formula 1 or 2 are bonded with benzimidazole. For example, poly (2,2 '-(1,4-phenylene) 5,5'-bibenzimidazole) is mentioned. In addition, pyridine-PBI (PPBI) or 2OH-PBI [poly- (2,2 '-(2,5-dihydroxy-1,4-phenylene) 5,5'-bibenzimidazole)] and the like Included. The PBI may be substituted with a substituent such that the structure of Formula 1 or 2, that is, "B" is a hetero atom or a bond by divalent acid having 9 or more carbon atoms. For example, in 2OH-PBI [poly- (2,2 '-(2,5-dihydroxy-1,4-phenylene) 5,5'-bibenzimidazole)] "OH" is an "O-methyl group May be substituted with ". 2OH-PBI [poly- (2,2 '-(2,5-dihydroxy-1,4-phenylene) 5,5'-bibenzimidazole)] was published in Seonghan Yu, et al., Macromolecules 2009, 42, 8640-8648.

The "X-" anion in Formula 1 or 2 is selected from the group consisting of halogen, OH-, carbonate, hydrogen carbonate, sulphate, acetate, formiate, methanolate and ethanolate It may be an anion. When X- is OH-, there is an advantage that the ion conductivity is very high. However, polybenzimidazolium electrolyte membranes, wherein X- is OH-, are easily decomposed or broken because the structure is very unstable. The present invention solves this problem through various means. First, a method of adding a substituent to the nitrogen of benzimidazole, second, a method of changing the "B" of the formula (1) or 2, and third, a method of stabilizing through crosslinking (crosslinking). Through such means, the ion exchange membrane or resin ion-exchanged with the OH- group can maintain a very stable state.

Hydroxide exchanged anion exchange membranes can usually be readily obtained by dipping a halide containing membrane in potassium hydroxide (KOH) solution.

 In another embodiment of the invention, the polybenzimidazolium, as the monomer, polybenzoxazole (polybenzoxazole, PBO), polyphenylquinoxaline, polybenzothiazole (PBT), tetraamine and carboxyl It may be a copolymer further comprising one or more monomers selected from the group consisting of acids. Specific examples of the PBO include poly (2,2 '-[acid monomer] -5,5'-bibenzoxazole) [acid monomer] (for example, 4,4'-diphenyl ether). Specific examples of the PBT include poly (2,2 '-[acid monomer] -5,5'-bibenzothiazole). In addition, 3,3 ', 4,4'-tetraaminobiphenyl, 2,3,5,6-tetraaminopyridine, 1,2,4,5-tetraaminobenzene, bis (3,4-diamino Phenyl) sulfone, bis (3,4-diaminophenyl) ether, 3,3 ', 4,4'-tetraaminobenzophenone, 3,3'4,4'-tetraaminodiphenylmethane and 3,3' It may further comprise a tetraamino compound monomer, such as 4,4'-tetraaminodiphenyldimethylmethane. 5-hydroxyisophthalic acid, 4-hydroxyisophthalic acid, 2-hydroxyisophthalic acid, 2,5-dihydroxyterephthalic acid, 2,6-dihydroxyisophthalic acid, 4,6-dihydroxyiso Phthalic acid, 2,3-dihydroxyphthalic acid, 2,4-dihydroxyphthalic acid, 3,4-dihydroxyphthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2 , 6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, diphenic acid, 1,8-dihydroxynaphthalene-3,6-dicarboxylic acid, bis (4-carboxyphenyl) ether, It may further include a carboxylic acid monomer such as biphenyl-4,4'-dicarboxylic acid, 4,4'-steelbendicarboxylic acid.

In Formula 1 or 2 n may be an integer of 1 or more. In other embodiments n can be an integer from 20 to 500. In another embodiment n can be from 80 to 200. In another embodiment n can be 96 to 175. The molecular weight (Mn) of the polybenzimidazolium polymer described herein may be 40,000 to 70,000.

In the present specification, the term "battery" is a broad concept that includes a flow battery. In particular, it includes a redox flow cell.

Hereinafter, the present invention will be described with reference to Examples, but this is only for illustrative purposes and is not intended to limit the scope of the present invention.

Preparation Example 1 Preparation of Permethyl m-PBI Iodide (Permethylation of meta-PBI (PBI-Me2 XX I ))

Meta from isophthalic acid and 3,3 ', 4,4'-tetraaminobiphenyl (TAB) according to PPA process (L. Xiao et al., Fuel Cells, 2005, 5 (2), 287-295) ) -PBI was prepared. All reagents were obtained from Sigma. 509.1 mg meta-PBI was dissolved in a mixture of 400 mg of lithium chloride in 15 ml of dry NMP at 160 ° C. under argon atmosphere. The resulting solution was cooled to room temperature and 170 mg of sodium hydride (suspension in 60% hexane) and 1 ml of iodomethane were added and reacted overnight. 1 ml of iodomethane was further added and the temperature was raised to 80 ° C. A bright colored precipitate could be observed. After one day the mixture was cooled to room temperature and poured into 200 ml of acetone. Alternatively, excess iodomethane can be decomposed by reacting with ammonia water before the precipitation step. The precipitate obtained by filtration was washed with acetone, dried and soaked in 450 ml of deionized water overnight. After filtration, the polymer was dried in a vacuum at 40 ° C. to give 702.7 mg of a slightly brownish polymer.

The results are shown in Fig. The DMSO solution was heated to about 160 ° C. to cause methylation. As a result, materials having a low degree of methylation were obtained. Methyl-PBI iodide with 45% imidazolium is referred to as "PBI-Me2 45 I" and 65% imidazolium methyl-PBI iodide is referred to as "PBI-Me2 65 I".

The NMR spectrum of FIG. 1 is permethylated PBI, with only four broad signals appearing in the aromatic region between 8.21 and 8.78. In contrast, polymers with lower degrees of substitution showed many more signals between 7.7 and 8.9 ppm.

Production Example 2: Preparation of monobenzyl-PBI bromide 1 (Monobenzylation of meta-PBI, (PBI-Bn1 XX Br)>

500 mg of lithium chloride was dissolved in 10 ml of dry NMP under inert atmosphere. 558 mg of meta-PBI was added and stirred at 165 ° C. overnight. The dark colored solution was cooled to room temperature and 170 mg sodium hydride (60% in hexane) and 1.3 ml benzyl bromide were then added. After 5 hours the temperature was raised to 80 ° C. for one day. In addition, 0.6 ml of benzyl bromide was added and the temperature was set to 100 ° C. After 24 hours the solution (no precipitate was observed) was cooled to room temperature and 5 ml of ammonia water was added and allowed to react for 2.5 hours. The polymer precipitated in 150 ml acetone was filtered, washed with acetone, dried and dispersed in water to remove the remaining salts. The polymer was recovered again by filtration and dried at 60 ° C. under reduced pressure. The dry weight was about 886 mg of the light colored material. NMR data were as follows:

NMR (DMSO-d 6): δ = 5.29-6.28 (3.9H, BnCH ₂ ), 6.90-9.16 (22.0H, aromatic signals).

According to the NMR data, the polymer is monobenzylated.

Preparation Example 3 Preparation of Benzyl-PBI Bromide 2 (Benzylation of meta-PBI (PBI-Bn 2 XX Br))

Under 160 ° C. and argon atmosphere, 548.4 mg of meta-PBI was dissolved in a mixture of 500 mg of lithium chloride and 10 ml of dry NMP. At room temperature, 170 mg sodium hydride (60% suspension in hexane) and 1 ml benzyl bromide were added and the resulting mixture was stirred at 80 ° C. for 15 hours. After further adding 1 ml of benzyl bromide, the temperature was raised to 160 ° C. and stirred for 9 hours. After further addition of 1 ml of benzyl bromide, the temperature was lowered back to room temperature. After 15 hours 0.5 ml was collected for NMR analysis. The polymer was found to contain three benzyl groups per repeat unit (75% substitution, 50% imidazolium bromide). 1 ml of benzyl bromide was further added and the temperature was raised to 80 ° C. and stirred for 1 day. The resulting high viscosity product was diluted with 10 ml of NMP, precipitated in 200 ml of acetone, filtered, washed and dried in vacuo at 40 ° C. The polymer powder obtained was immersed in 400 ml of distilled water overnight, then filtered, washed and vacuum dried at 40 ° C. As a result, 937 mg of polymer powder was obtained. NMR analysis showed that the final product had 3.3 benzyl groups per repeat unit, corresponding to 63% of all imidazole moieties converted to imidazolium bromide.

Preparation Example 4 Preparation of Methyl, Benzyl-PBI Iodide (Methylation of monobenzylated meta-PBI (PBI-BnMe XX I))

521.9 mg of 1-benzyl-meth-polybenzimidazole was dissolved in 20 ml of DMSO at room temperature. 1 ml of iodomethane was added and the resulting solution was stirred at 80 ° C. for 17 hours. More 0.5 ml of iodomethane was added and the reaction proceeded for another 24 hours. After cooling to ambient temperature, 3 ml of ammonia water was added and reacted for about 1 hour. The polymer obtained was precipitated in 200 ml of acetone, filtered, dried for 3 hours at 40 ° C. in vacuum, dispersed in 400 ml overnight, filtered, washed with water, and dried again at 40 ° C. in vacuum. As a result, 603 mg of dried polymer was obtained. As a result of rapid dissolution of the yellow polymer in DMSO, NMR showed that the average repeating unit contained about 2.2 benzyl groups and 1.25 methyl groups (corresponding to 72% imidazolium and 28% imidazole groups).

¹ H NMR (300 MHz, DMSO- d ₆ , δ: 7.95-8.99 (4.5H, aromatic signals),

6.96-7.66 (7.4H, aromatic signals), 5.33-6.24 (2.3H, BnCH ₂ ), 3.76-4.24 (2.0H, Me).

Preparation Example 5 Preparation of PBI-DCDPE and PBI-DCDPE Me 2 I

First, PBI-DCDPE (PBI-dicarboxylic acid-diphenylether) was prepared, and then an anion I- was added.

5 g of P ₂ O ₅ was dissolved in ₂₇ ml of methanesulfonic acid under an argon atmosphere. 1.2911 g (5 mmol) of 4,4'-dicarboxylic acid-diphenyl ether and 1.0708 g (5 mmol) of diaminobenzidine were mixed and added to the solution at 80 ° C. The temperature was raised to 145-155 ° C. and the solution stirred at that temperature for 45 minutes. Pour into 1 L of ice water to precipitate the polymer, stir overnight, wash with 5% sodium carbonate solution at 60 ° C. for 1 day and again with water at 60 ° C. for 1 day. It dried at 60 degreeC under vacuum and obtained 2.0854g (104% of theory) of a polymer which has a following formula.

NMR (300 MHz, DSMSO): 8.30 (d, 4H, 5.37), 7.87 (s, 2H), 7.70 (d, 2H, 6.34 Hz), 7.58 (d, 2H, 7.33 Hz), 7.32 (d, 4H, 5.37 Hz)

(Formula of PBI-DCDPE)

504.9 mg of PBI-DCDPE obtained above was dissolved in dry NMP and 400 mg LiCl. 170 mg sodium hydride (60% in hexane) and 1 ml iodomethane were added sequentially. The resulting mixture was stirred overnight at 40 ° C. 1 ml of iodomethane was added and the temperature raised to 80 ° C. After 24 hours, the polymer precipitated in 200 ml acetone. After standing in acetone for one day, the polymer was washed with 200 ml of water. The polymer was obtained by filtration and drying at 70-80 ° C. under vacuum. The resulting polymer was dissolved in 15 ml of DMSO, some solvent was removed and the solution was cast on a glass plate and dried at 40 ° C. As a result, polybenzimidazolium, PBI-DCDPE Me 2 73 I (73% imidazolium, 27% imidazole unit) having the following formula was obtained. The NMR spectrum is as shown in FIG.

(Formula of PBI-DCDPE Me 2 I)

Production Example 6: Preparation of Membrane

The polymer batch obtained above was dissolved in 20 ml dimethyl sulfoxide at room temperature (or 160 ° C. for demethylation). If the solution still contained visible precipitate, it was centrifuged and decanted at 12000 rpm. Once a clear solution was obtained it was filtered through a 0.45 μm PTFE filter. The filtered solution was evaporated under reduced pressure from a flat bottom petri dish. The dried membrane was easily delaminated from the glass after swelling with water.

Preparation Example 7 Preparation of Crosslinked Membrane 1

45 mg of 65% imidazolium iodide-modified meta-PBI was dissolved in DMSO at room temperature. The resulting solution was filtered and 3 mg of α, α′-dibromo- p- xylene was added and the clear solution was evaporated under 40 ° C. vacuum. The dried polymer was then maintained at 80 ° C. vacuum for 8 hours. 34.6 mg of the resulting crosslinked polymer was immersed in 9 ml of DMSO and the mixture was vigorously stirred at room temperature for 4.5 days. The dispersion was filtered through a 0.45 μm PTFE filter and the filtrate was concentrated to dryness in 60 ° C. vacuum. 4.9 mg of polymer was obtained, corresponding to a gel content of 86%.

Preparation Example 8 Preparation of Crosslinked Membrane 2

PBI-DCDPE Me 2 36 I (36% imidazolium) was dissolved in DMSO and filtered, then 10% by weight of α, α'-dibromo- p- xylene was added and the solution was poured into Petri dishes to cover And maintained at 80 ° C. for 8 hours. The membrane was obtained by evaporation of the solvent under 40 ° C. vacuum. The membrane was not dissolved in DMAc. The gel content was about 100%.

Preparation Example 9 Preparation of Polybenzimidazolium Having OH—

A polybenzimidazolium having OH- as an anion was prepared by immersing the membrane prepared with PBI iodide obtained above in KOH solution for several days and then washing.

The membrane prepared according to Preparation Example 6 with the permethyl m-PBI iodide prepared in Preparation Example 1 was immersed in 0.5 M ethanol KOH and 10% water for 2 days, and then washed with water for 5 hours to prepare PBI-Me2 84 OH membranes were prepared.

In addition, PBI-DCDPE Me 2 I prepared in Preparation Example 5 was immersed in 1M KOH solution for 3 days to prepare a PBI-DCDPE Me2 73 OH membrane.

Experimental Example 1: Stabilization Effect of 2-phenyl Substituter

The positive charge of the imidazolium may continue to be repositioned while wandering the phenyl ring in the 2-position, as shown in the formula below.

In order to examine the stabilizing effect of the 2-position phenyl ring, I-imides of I-polybenzimidazoli and 1,3-dimethyl-2-phenyl-benzimidazole of m-PBI having the following two formulas NMR was measured for dazolium. The results are shown in Figures 3a and 3b. FIG. 3A shows NMR of I-polybenzimidazoli of m-PBI, and FIG. 3B shows NMR results of I-imidazolium of 1,3-dimethyl-2-phenyl-benzimidazole.

(Formula of I-polybenzimidazoli of m-PBI)

(Formula of I-imidazolium of 1,3-dimethyl-2-phenyl-benzimidazole)

As shown in FIGS. 3A and 3B, the I-imidazolium of 1,3-dimethyl-2-phenyl-benzimidazole compared to the methyl and aromatic signals of I-polybenzimidazolium of m-PBI It can be seen that the methyl group signal and the aromatic signal ppm are lowered. The methyl group signal was lowered from 4.14 / 4.22 to 3.90 / 3.90 and the aromatic signal lowered from 8.90-8.31 to 8.13-7.73. In the I-polybenzimidazolium of m-PBI, the phenyl ring should stabilize two positive charges, whereas in the I-imidazolium of 1,3-dimethyl-2-phenyl-benzimidazole, the phenyl ring has only one positive charge. Since it is necessary to stabilize, the latter compound is more stable. Normally, "naked protons" in the NMR spectrum have high ppm values (ie, peaks are on the left), but higher electron density shields the protons, causing the peaks to shift to the right. I-imidazolium of 1,3-dimethyl-2-phenyl-benzimidazole is a proton shield due to higher electron density, causing the peak to shift to the right. Thus, it can be seen that more stable. This means that the larger the number of phenyl rings bonded at position 2, the more stable the structure is.

Experimental Example 2: Stabilization Effect by Methoxy Group

This experiment was conducted to demonstrate that the stability of the compound is further improved when the 2-phenyl group is substituted by methoxy. To this end, 1- (benzyl) -2-phenyl-benzimidazole and 1- (4-methoxybenzyl) -2- (4-methoxyphenyl) -benzimidazole were synthesized as follows.

1- (benzyl) -2- Phenyl - Of benzimidazole  synthesis

5.407 g ortho-phenylenediamine (50 mmol) was dissolved in 100 ml ethanol and 3 ml concentrated hydrochloric acid. 10.2 ml of benzaldehyde was added in two portions over 10 minutes. After stirring at room temperature for 3.5 hours the mixture was filtered. The solid was 3.0982 g of 1,3-di-benzyl-2-phenyl-benzimidazole and the filtrate was 7.3 g of crude product. The two batches of crude product were combined and then dissolved in chloroform and washed with potassium hydroxide solution and water. After evaporation of the solvent, the residue was recrystallized from ethanol. A slightly yellowish colorless solid was obtained with a yield of 16.95 g.

Nmr (300 MHz, DMSO-d 6): 6.99-7.74 (m, 14H, aromatic signals), 5.59 (d, 2H CH 2).

Nmr (300 MHz, CDCl 3): 7.92 (d, 1H, aromatic, 8.3 Hz), 7.72-7.75 (m, 2H, aromatic), 7.24-7.53 (m, 9H, aromatic), 7.14-7.17 (m, 2H, aromatic), 5.50 (s, 2H, CH 2).

1- (4-methoxybenzyl) -2- (4- Methoxyphenyl ) - Of benzimidazole  synthesis

5.407 g of ortho-phenylenediamine (50 mmol) was dissolved in 75 ml of EtOH and 3 ml concentrated hydrochloric acid. Within 15 minutes, 100 mmol (13.6 g) para-methoxybenzaldehyde in 20 ml ethanol was added. When the color of the reaction mixture turned rosy color, stirring was continued for 2 hours 20 minutes. The mixture was filtered and the filtrate was evaporated to dryness. The residue was again dissolved in chloroform and washed with sodium hydroxide solution. The solvent was evaporated again and the viscous residue was poured into ethanol. After 2 hours of storage in the refrigerator, a precipitate formed and a white solid was obtained in a yield of 7.2796 g) 21.1 mmol) = 42.2% by filtration and drying at 60 ° C vacuum.

Nmr (300 MHz, CDCl3): 6.87-7.88 (m, 12H, aromatic signals), 5.42 (s, 2H, CH2), 3.88 (s, 3H, Me), 3.82 (s, 3H, Me)

The two compounds obtained were methylated and treated with KOH at room temperature. The result is shown in FIG. As shown in FIG. 4, both compounds changed color from brown to yellow immediately after treatment. In addition, it shifted to low ppm in the NMR spectrum. However, when the two compounds were treated at 85 ° C. for 22 hours, the reactions of the two compounds were completely different. Compounds not substituted with methoxy turned brown again, and NMR confirmed the formation of benzoic acid. The formation of benzoic acid means that the compound has been degraded. In contrast, methoxy substituted compounds showed no change in color or NMR spectrum. When sulfuric acid was added, the color returned to brown, the original color, and a spectrum very similar to the original spectrum was obtained. Some changes in the spectrum are mainly due to changes in solvent composition.

It was confirmed by the benzoic acid addition experiment that benzoic acid was formed. If the addition of benzoic acid increases the specific peak intensity by a factor of two and no other secondary signal is changed, the specific peak means benzoic acid, which can be seen to be benzoic acid formed by decomposition of the compound. In order to confirm that the compound which was not substituted with methoxy was decomposed to form benzoic acid, the compound was treated in a 1.1M KOH solution at 85 ° C. to completely hydrolyze the diamine and benzoic acid, and then NMR was measured and again benzoic acid was added. After the NMR was measured again, the two results were compared and shown in FIG. 5. As shown in FIG. 5, it was confirmed that the benzoic acid did not change twice in strength at the 7.8 ppm position and at other positions.

In short, the compound not substituted with methoxy was hydrolyzed by KOH treatment, but the compound substituted with methoxy was found to be stable despite KOH treatment. In other words, it can be seen that the stability of the compound is remarkably improved when the 2-position phenyl group is substituted with an electron donation group (+ M-effect) such as methoxy.

Experimental Example 3: Stability of PBI-DCDPE Me 2 73 OH

Stability experiments were performed on PBI-Me 2 45 I prepared in Preparation Example 1 and PBI-DCDPE Me 2 73 I prepared in Preparation Example 5. After forming the polymer membranes according to Preparation Example 6, each polymer membrane was immersed in 1M KOH solution at room temperature for 3 days, and then, I- was exchanged with OH-, respectively, PBI-Me 2 45 OH and PBI-DCDPE Me. 2 73 OH was prepared. The PBI-Me 2 45 OH polymer membrane was broken upon contact, but the PBI-DCDPE Me 2 73 OH polymer membrane was flexible. The PBI-DCDPE Me 2 73 OH polymer membrane was still flexible after treatment with 1M KOH for two more days.

Experimental Example 4: OH- Conductivity of PBI-DCDPE Me 2 73 OH>

Ion conductivity was measured using impedance spectroscopy. Samples were assembled into four-electrode cells and then immersed in water or measured in a climate controlled chamber. The ion conductivity of the polymer membrane prepared according to Preparation Example 6 with PBI-DCDPE Me 2 73 I prepared in Preparation Example 5 was measured at 18 ° C., and an OH- conductivity of 17.3 mS / cm was obtained.

Experimental Example 5: Measurement of Ionic Conductivity

Ion conductivity was measured by impedance spectroscopy on the membranes prepared according to the above examples. Samples were assembled into four-electrode cells and then immersed in water or measured in a climate controlled chamber. The results are shown in Table 1 below.

PBI-x Theoretical  IEC a) [mmol / g (mmol / ml)] Water uptake [%] Hydratio n number Wet density [g / ml] Conductivity in water at 26 ℃ Conductivity in water at 60 ℃ E _akt  [kJ / mol] Me2 45 I 1.94 (1.38) 53 15 1.09 5.7 mS / cm 11.6 mS / cm 20.7 Me2 65 I 2.50 (1.74) 65 15 1.15 6.9 mS / cm 16.0 mS / cm 17.1 Me2 84 I 2.92 (2.66) 29 6 1.19 4.5 mS / cm 6.9 mS / cm 11.8 Me2 65 OH 3.44 41 7 29.3 mS / cm b) 57.8 mS / cm 16.6 Bn2 63 Br 1.78 (1.38) 33 10 1.03 3.1 mS / cm 7.7 mS / cm b) 21.6 BnMe 72 I 2.03 (2.03) 17 5 1.17 9.9 mS / cm b) 22.6 mS / cm b) 20.1

As shown in the table, PBI-Me2 65 OH had the best conductivity.

Claims (20)

As polybenzimidazolium having the structure of Formula 1 or Formula 2,
The polybenzimidazolium is polybenzimidazolium, in which 5-100 mol% of the monomers of the total benzimidazole monomers are benzimidazolium to which an anion is added:
(Formula 1)

(2)

In this formula,
A is a direct bond or oxygen,
B is a group of diacid having 1 to 5 heteroatoms or a group of diacid containing 9 or more carbon atoms,
R ₁ to R ₄ are the same as or different from each other, and each independently hydrogen, a C _1-6 alkyl group, or an aromatic substituent,
X- is an anion selected from the group consisting of halogen, OH-, carbonate, hydrogen carbonate, sulfate, acetate, formiate, methanolate and ethanolate,
n is an integer of 1 or more. The method of claim 1,
The diacid is a polybenzimidazolium containing an aromatic ring. 3. The method of claim 2,
The divalent acid has two separate phenyl rings, polybenzimidazolium. 3. The method of claim 2,
The aromatic ring consists of O-alkyl, O-phenyl, alkyl, nitrile, COOH, chloride, fluoride, nitro, sulfonate, phosphonate, S-alkyl, S-phenyl, sulfone-phenyl, acyl and benzoyl Polybenzimidazolium, substituted by one or more substituents selected from the group. 3. The method of claim 2,
The divalent acid is any one of the divalent acids of the formula (3), polybenzimidazolium.
(Formula 3)

The method of claim 1,
The polybenzimidazolium is polybenzimidazoli, which is a salt of para-PBI. The method of claim 1,
The polybenzimidazoli, as a monomer, at least one monomer selected from the group consisting of polybenzoxazole (PBO), polyphenylquinoxaline, polybenzothiazol (PBT), tetraamine and carboxylic acid Polybenzimidazoli which is a copolymer further comprising. The method of claim 1,
R ₁ to R ₄ are the same or different from one another and each is hydrogen, methyl, benzyl, functionalized benzyl, trityl, functionalized trityl, tert-butyl or combinations thereof. The method of claim 1,
The polybenzimidazolium, polybenzimidazolium having the structure of formula (4).
(Formula 4)

The method of claim 1,
The polybenzimidazolium, polybenzimidazolium having a structure of the formula (5).
(Formula 5)

The method of claim 1,
X- is OH-, polybenzimidazolium. The method of claim 4, wherein
Wherein said aromatic ring is substituted with O-alkyl. The polybenzimidazolium of claim 5, wherein when the divalent acid has a structure of the following formula, the OH group of the benzene ring is O-methylated.

The polybenzimidazoli of claim 1, wherein the polybenzimidazoli is crosslinked. The polybenzimidazoli of claim 14, wherein the polybenzimidazolium is cross-linked with α, α'-dihaloxylene. The polybenzimidazolium of claim 15, wherein the α, α'-dihaloxylene is α, α'-dibromoxylene. An electrolyte membrane comprising the polybenzimidazolium according to any one of claims 1 to 16. Catalyst bindner comprising the polybenzimidazolium according to any one of claims 1 to 16. A fuel cell, electrolyzer or battery comprising the electrolyte membrane according to claim 17. A fuel cell or electrolytic cell comprising the catalyst binder according to claim 18.

Images