Boric acid substituted polybenzimidazole polymer and preparation method thereof

Abstract

The invention discloses a boric acid polybenzimidazole polymer and a preparation method thereof, and particularly, under the protection of nitrogen flow, 3, 3 '-diaminobenzidine and boric acid substituted aromatic dicarboxylic acid react for 6-24 hours at 180-240 DEG C by taking polyphosphoric acid as a medium, and the boric acid substituted polybenzimidazole polymer is obtained through polycondensation. The boric acid substituted polybenzimidazole polymer disclosed by the invention has post-modification and self-repairing potentials and has a wide application prospect.

Description

Technical Field

[0001] The invention relates to the field of high-temperature fuel cell proton exchange membranes, and in particular to a boric acid-substituted polybenzimidazole polymer and a preparation method thereof. Background Art

[0002] At present, the proton exchange membrane widely used in high-temperature proton exchange membrane fuel cells is a PBI (polybenzimidazole) type proton exchange membrane. The PBI membrane was first introduced to the market by the American Hoechst Celanese Company. Since the membrane must be mixed with inorganic phosphoric acid and relies on inorganic phosphoric acid to conduct protons, its biggest disadvantage is the loss of inorganic phosphoric acid. Since water is generated when the fuel cell is working, and the generated water is discharged from the membrane, this will cause the inorganic phosphoric acid to be lost along with the removal of the generated water, thereby causing the proton conductivity of the membrane to decrease, and causing the battery performance to decay, and also shortening the stable service life of the fuel cell.

[0003] At present, in some self-repairing material research, the characteristics of boric acid that can be dehydrated and condensed to form boric acid esters or form coordination with nitrogen-containing heterocycles have emerged to self-repair mechanically damaged materials. PBI itself is a nitrogen-containing heterocyclic polymer. Therefore, introducing boric acid groups into the PBI molecular skeleton may improve the mechanical strength of the membrane under high temperature conditions, while developing the self-repair function of high-temperature proton exchange membranes and increasing the service life of fuel cells.

[0004] At present, there is no public technical report on the preparation of boric acid substituted polybenzimidazole polymers. Therefore, it is urgent to develop a preparation method of boric acid substituted polybenzimidazole polymers. Summary of the invention

[0005] The purpose of the present invention is to provide a boric acid substituted polybenzimidazole polymer and a preparation method thereof.

[0006] In a first aspect of the present invention, a method for preparing a boric acid-substituted polybenzimidazole polymer is provided, characterized in that the method comprises:

[0007] In an inert atmosphere, in the presence of an acid, the tetraamine compound represented by Formula I and the aromatic dicarboxylic acid substituted with boric acid represented by Formula II are polymerized to prepare a polybenzimidazole polymer represented by Formula III:

[0008]

[0009] in:

[0010] n=2-10000; preferably, n=50-2000;

[0011] Selected from the following group: C6-C 10 Aryl, bicyclic (C6-C 10 Aryl), or (C6-C 10 Aryl)-R-(C6-C 10 aryl); wherein, said R is selected from the following group: O, S, NH, C(O), S(O)2, substituted or unsubstituted C1-C6 alkylene, substituted or unsubstituted C2-C6 alkenylene;

[0012] Selected from the group consisting of: substituted or unsubstituted C6-C 10 aryl, substituted or unsubstituted 5-12 membered heteroaryl;

[0013] Furthermore, the substitution in the substituted or unsubstituted group refers to that one or more hydrogen atoms on the group are replaced by a substituent selected from the group consisting of halogen, phenyl, and 5-7 membered heteroaryl.

[0014] In some embodiments, the method includes one or more of the following features:

[0015] (1) The molar ratio of the compound of formula I to the compound of formula II is 1:0.6-1.5;

[0016] (2) The acid is selected from the group consisting of polyphosphoric acid;

[0017] (3) The acid is 5-100 times the total mass of the compound of formula I and the compound of formula II; preferably, 10-80 times; more preferably, 15-50 times;

[0018] (4) The polymerization is carried out at 150°C-300°C; preferably at 180-250°C.

[0019] In some embodiments, the compound of formula I is selected from the following group:

[0020]

[0021] In some embodiments, the compound of formula II is:

[0022]

[0023] In another preferred embodiment, the compound of formula II is

[0024] In some embodiments, the method comprises the steps of:

[0025] (1) adding acid into a reaction kettle and heating in an inert atmosphere;

[0026] (2) Adding the compound of formula I and the compound of formula II into a reaction kettle, and performing a polymerization reaction under an inert atmosphere to obtain a polybenzimidazole polymer.

[0027] In some embodiments,

[0028] The heating temperature in step (2) is 50-250°C, preferably 100-200°C

[0029] The reaction temperature of step (2) is 150°C-300°C, preferably 180-250°C.

[0030] In some embodiments, the steps are also included:

[0031] (3) washing the polybenzimidazole polymer obtained in step (2), crushing it, washing it again, filtering it, and drying it to obtain the polybenzimidazole polymer.

[0032] In a second aspect of the present invention, a polybenzimidazole polymer is provided, wherein the polybenzimidazole polymer has a structure selected from the following group:

[0033]

[0034] Wherein, n=2-10000; preferably, n=50-2000;

[0035] R is selected from the group consisting of O, S, NH, C(O), S(O)2, substituted or unsubstituted C1-C6 alkylene, substituted or unsubstituted C2-C6 alkenylene;

[0036] R 1 for

[0037] It should be understood that within the scope of the present invention, the above-mentioned technical features of the present invention and the technical features specifically described below (such as embodiments) can be combined with each other to form a new or preferred technical solution. Due to space limitations, they will not be described one by one here. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is the hydrogen spectrum of 3,5-dicarboxyphenylboronic acid (deuterated DMSO).

[0039] Figure 2 This is the hydrogen spectrum (deuterated DMSO) of the polybenzimidazole polymer substituted with boronic acid.

[0040] Figure 3 The morphology of the boric acid-substituted polybenzimidazole polymer after drying (after crushing) is shown.

[0041] Figure 4 This is the TGA diagram of boric acid substituted polybenzimidazole polymer.

[0042] The boric acid-substituted polybenzimidazole polymer of the present invention is mainly characterized in that:

[0043] (1) The introduction of boric acid groups strengthens the hydrogen bonds between polymer molecular chains, increasing the mechanical strength of the material. In addition, under high temperature conditions, boric acid can be dehydrated to form boric acid esters (intermolecular crosslinking), further improving the mechanical strength of the material, especially the mechanical strength of the proton exchange membrane under high temperature conditions.

[0044] (2) The introduction of boronic acid groups enables the nitrogen-containing heterocycles in polybenzimidazole polymers to form coordination with boric acid or boric acid esters, giving the material the potential for self-healing.

[0045] (3) The introduction of boronic acid groups. Due to the activity of boronic acid groups, they can undergo a series of reactions such as coupling, which greatly increases the ability of polybenzimidazole polymers to be post-modified and modified. DETAILED DESCRIPTION

[0046] After long-term and in-depth research, the inventors found that a polybenzimidazole polymer with high proton conductivity can be prepared by high-temperature polymerization of a tetraamine compound and a boric acid-substituted aromatic dicarboxylic acid. The boric acid-substituted polybenzimidazole polymer of the present invention has the potential for post-modification and self-repair, and has a wide range of application prospects. Based on the above findings, the inventors have completed the present invention.

[0047] Preparation of polybenzimidazole polymers by solution polymerization

[0048] The present invention provides a method for preparing a polybenzimidazole polymer by solution polymerization, the method comprising:

[0049] In an inert atmosphere, in the presence of an acid, a tetraamine compound and an aromatic dicarboxylic acid substituted with boric acid are polymerized to prepare a polybenzimidazole polymer.

[0050] The tetraamine compound is selected from the following group:

[0051]

[0052] The boric acid-substituted aromatic dicarboxylic acid is:

[0053] The acid is polyphosphoric acid.

[0054] The specific operation method of the polymerization is:

[0055] The first step is to add acid into the reactor, heat it to about 100°C, start mechanical stirring, and increase the nitrogen flow to deoxygenate.

[0056] In the second step, when the acid is heated to 150°C, the tetraamine compound is added. After it is completely dissolved, the aromatic dicarboxylic acid substituted with boric acid is added at a molar ratio of 1:1, and the temperature is started to rise to above 150°C. The reaction is carried out at this temperature for 14 hours. At this time, the stirring speed drops significantly, stirring becomes difficult, and the reaction is stopped.

[0057] Preferably, the nitrogen flow rate is 1%-800% of the volume of the reactor per minute, more preferably 100%-500%.

[0058] Preferably, the amount of the acid is 5-100 times the total mass of the tetraamine compound and the boric acid-substituted aromatic dicarboxylic acid; more preferably, 10-80 times; more preferably, 15-50 times.

[0059] Preferably, the reaction temperature of the second step is 150-300°C, more preferably 160-280°C, more preferably 180-250°C.

[0060] Preferably, the reaction time of the second step is 6-30 hours, more preferably 12-28 hours, and more preferably 15-25 hours.

[0061] Example 1

[0062] Preparation of Boronic Acid Substituted Polybenzimidazole Polymers:

[0063]

[0064] Under nitrogen protection, polyphosphoric acid (160g) was first added to a three-necked reaction bottle equipped with mechanical stirring. When heated to about 100°C, mechanical stirring was started and nitrogen flow was increased for deoxygenation. When heated to 150°C, 3,3'-diaminobenzidine (3.2141g, 15mmol) was added. After it was completely dissolved, 3,5-dicarboxylic acid phenylboronic acid (3.1492g, 15mmol) was added and the temperature was raised to 220°C. The reaction was carried out at this temperature for 12 hours. At this time, the stirring speed dropped seriously and stirring was difficult, so the reaction was stopped. The reaction solution was poured into deionized water to precipitate filamentous solids. When the filamentous solids were soaked and washed in deionized water until the water was weakly acidic, the filamentous product was crushed into powder with a pulverizer, and continued to be soaked and washed with deionized water and NaOH was added for neutralization. After soaking for 24 hours, the water was changed and soaked and washed until the water was neutral, and then filtered and dried to obtain a polybenzimidazole polymer substituted with boric acid. Intrinsic viscosity test (30°C) [η] = 2.15 (dL / g) [Test conditions: dissolve the polymer in 98% concentrated sulfuric acid to make a solution with a concentration of 0.5g / mL]. Solubility test: 150mg of polymer is dissolved in 5mL DMSO and heated to 80°C. After half an hour, the polymer is completely dissolved. Stop heating and cool to room temperature. The solution has moderate fluidity.

[0065] Example 2

[0066] Preparation of Boronic Acid Substituted Polybenzimidazole Polymers:

[0067]

[0068] Under nitrogen protection, polyphosphoric acid (160g) was first added to a three-necked reaction bottle equipped with mechanical stirring. When heated to about 100°C, mechanical stirring was started and nitrogen flow was increased for deoxygenation. When heated to 150°C, 3,3'-diaminobenzidine (3.2141g, 15mmol) was added. After it was completely dissolved, 3,5-dicarboxylic acid phenylboronic acid (4.8914g, 15mmol) was added and the temperature was raised to 210°C. The reaction was carried out at this temperature for 12 hours. At this time, the stirring speed dropped significantly and the reaction was stopped. The reaction solution was poured into deionized water to precipitate a filamentous solid. When the solid was soaked and washed in deionized water until the water was weakly acidic, the filamentous product was crushed into powder with a pulverizer, and the filamentous product was continued to be soaked and washed in deionized water until the water was neutral, and then filtered and dried to obtain a polybenzimidazole polymer substituted with boric acid. Intrinsic viscosity test (30°C) [η] = 1.85 (dL / g) [Test conditions: dissolve the polymer in 98% concentrated sulfuric acid to make a solution with a concentration of 0.5 g / mL]. Solubility test: 150 mg of polymer is dissolved in 5 mL of DMSO and heated to 80°C. After half an hour, the polymer is completely dissolved. Stop heating and cool to room temperature. The solution has good fluidity.

[0069] All documents mentioned in the present invention are cited as references in this application, just as each document is cited as reference individually. In addition, it should be understood that after reading the above teachings of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A method for preparing a boric acid-substituted polybenzimidazole polymer, characterized in that: The method includes: In an inert atmosphere, in the presence of an acid, the tetraamine compound represented by Formula I and the aromatic dicarboxylic acid substituted with boric acid represented by Formula II are polymerized to prepare a polybenzimidazole polymer represented by Formula III: in: n=2-10000; preferably, n=50-2000; Selected from the following group: C6-C 10 Aryl, bicyclic (C6-C 10 Aryl), or (C6-C 10 Aryl)-R-(C6-C 10 aryl); wherein, said R is selected from the following group: O, S, NH, C(O), S(O)2, substituted or unsubstituted C1-C6 alkylene, substituted or unsubstituted C2-C6 alkenylene; Selected from the group consisting of: substituted or unsubstituted C6-C 10 aryl, substituted or unsubstituted 5-12 membered heteroaryl; Furthermore, the substitution in the substituted or unsubstituted group refers to that one or more hydrogen atoms on the group are replaced by a substituent selected from the group consisting of halogen, phenyl, and 5-7 membered heteroaryl.

2. The preparation method according to claim 1, characterized in that The method includes one or more of the following features: (1) The molar ratio of the compound of formula I to the compound of formula II is 1:0.6-1.5; (2) The acid is selected from the group consisting of polyphosphoric acid; (3) The acid is 5-100 times the total mass of the compound of formula I and the compound of formula II; preferably, 10-80 times; more preferably, 15-50 times; (4) The polymerization is carried out at 150°C-300°C; preferably at 180-250°C.

3. The preparation method according to claim 1, characterized in that: The compound of formula I is selected from the following group:

4. The preparation method according to claim 1, characterized in that: The compound of formula II is: In another preferred embodiment, the compound of formula II is 5. The preparation method according to claim 1, characterized in that: The method comprises the steps of: (1) adding acid into a reaction kettle and heating in an inert atmosphere; (2) Adding the compound of formula I and the compound of formula II into a reaction kettle, and performing a polymerization reaction under an inert atmosphere to obtain a polybenzimidazole polymer.

6. The preparation method according to claim 5, characterized in that: The heating temperature in step (2) is 50-250°C, preferably 100-200°C The reaction temperature of step (2) is 150°C-300°C, preferably 180-250°C.

7. The preparation method according to claim 5, characterized in that: Also includes the steps: (3) washing the polybenzimidazole polymer obtained in step (2), crushing it, washing it again, filtering it, and drying it to obtain the polybenzimidazole polymer.

8. A polybenzimidazole polymer, characterized in that: The polybenzimidazole polymer has a structure selected from the following group: Wherein, n=2-10000; preferably, n=50-2000; R is selected from the group consisting of O, S, NH, C(O), S(O)2, substituted or unsubstituted C1-C6 alkylene, substituted or unsubstituted C2-C6 alkenylene; R 1 for

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