CN114479081B - Phosphonic acid functionalized polybenzimidazole and preparation method and application thereof - Google Patents

Abstract

The invention discloses a phosphonic acid functionalized polybenzimidazole, a preparation method and application thereof, and belongs to the technical field of high-temperature proton exchange membranes. The preparation method is to combine 2-((diethoxyphosphoryl)methyl)-[1,1'-biphenyl]-4,4'-dicarboxylic acid, aromatic dicarboxylic acid and 3,3'-diamino Add aniline to the mixture of polyphosphoric acid and phosphorus pentoxide to remove dissolved oxygen, react at 120-170°C for 5-20 hours, then raise the temperature to 190-210°C for reaction; pour the reaction solution into deionized water to precipitate solid , Soak the obtained solid in an aqueous solution of sodium bicarbonate and stir, wash; soak the product obtained by washing in concentrated hydrochloric acid, wash until neutral; dry. The introduction of the methylphosphonic acid side group in the present invention reduces the close packing degree of the polybenzimidazole main chain, increases the free volume of the polymer, and contributes to increasing the phosphoric acid doping amount. Phosphonic acid groups can form hydrogen bonds with phosphoric acid molecules, helping to improve proton conductivity.

Description

A kind of phosphonic acid functionalized polybenzimidazole and its preparation method and application

technical field

The invention relates to the technical field of high-temperature proton exchange membranes, in particular to a phosphonic acid functionalized polybenzimidazole, a preparation method thereof and an application in high-temperature proton exchange membranes.

Background technique

Proton exchange membrane fuel cell (PEMFC) is an efficient and clean electrochemical device that can realize the direct conversion of chemical energy to electrical energy. It has broad application prospects in the fields of electric vehicles and stationary power supplies. The proton exchange membrane is one of the key components in PEMFC, which determines the performance and life of the fuel cell to a certain extent. The Nafion proton exchange membrane invented by DuPont is now widely used in PEMFC. However, the proton conductivity of the membrane is heavily dependent on the ambient humidity, which requires low temperature and high humidity working conditions, which brings technical problems such as easy catalyst poisoning and high purity of raw materials to the fuel cell. Therefore, the development of high-temperature proton exchange membranes with excellent performance has become a hot research topic in recent years.

Polybenzimidazole (PBI) is a rigid polymer containing benzimidazole rings, which has excellent heat resistance, oxygen resistance, chemical corrosion resistance and good mechanical properties, and it also has proton donor and acceptor functions. structure, making it an excellent candidate material for high-temperature proton exchange membranes. However, the proton conductivity of PBI itself is extremely low, so it is difficult to be directly used as a proton exchange membrane. In 1995, Wainright et al. first proposed phosphoric acid-doped polybenzimidazole proton exchange membrane (PA/PBI), and found that it has excellent proton conductivity at high temperature, creating a PA/PBI high-temperature proton exchange membrane. Research findings in the past two decades have shown that the proton conductivity of PA/PBI is dependent on the doping content of phosphoric acid, which negatively affects the mechanical properties of the membrane. Therefore, it is particularly important for PA/PBI to increase the phosphoric acid doping level of PBI film under the premise of ensuring good mechanical properties.

Phosphonic acid functionalization is an effective way to improve the proton conductivity of PBI proton exchange membranes. The introduction of methylphosphonic acid groups can destroy the close-packed structure of molecular chains, increase the free volume of molecular chains, and increase the doping level of phosphoric acid. On the other hand, the phosphonic acid group has a hydrogen bond site that interacts with phosphoric acid, which not only improves the adsorption stability of phosphoric acid, but also serves as a proton conduction site to further improve the proton conductivity. At present, phosphonic acid-grafted polybenzimidazoles are mostly introduced into the main chain by post-modification methods, which are inefficient. For example, Chinese invention patent 201911265652.7 discloses phosphoric acid-modified polybenzimidazole proton exchange membrane and its preparation method. The main steps include: (1) preparation of polybenzimidazole solution; (2) preparation of polybenzimidazole membrane; (3) Acidic modification in phosphoric acid vapor atmosphere; (4) high temperature curing to obtain proton exchange membrane. In this technology, the method of modifying polybenzimidazole with phosphoric acid vapor in a closed environment is used to prepare phosphoric acid-modified polybenzimidazole proton exchange membranes. The anhydrous phosphoric acid vapor atmosphere used in step 2 is difficult to control. The equipment requirements are high, and at the same time, the grafting on the polymer main chain cannot be realized accurately and efficiently, and the proton conductivity of the obtained proton exchange membrane is not high.

Contents of the invention

The first object of the present invention is to provide a phosphonic acid functionalized polybenzimidazole with mild synthesis conditions and good mechanical properties and proton conductivity and its preparation method;

The second object of the present invention is to provide the application of the phosphonic acid functionalized polybenzimidazole in high temperature proton exchange membrane.

The present invention prepares phosphonic acid functionalized polybenzimidazole under mild polymerization conditions through the polymerization of functionalized monomers, realizes the grafting of phosphoric acid on the main chain of polybenzimidazole more simply and directly, and simplifies the process , and the introduction of phosphonic acid groups improved the proton conductivity of polybenzimidazole-based proton exchange membranes. The phosphonic acid functionalized polybenzimidazole proton exchange membrane prepared by the invention has good mechanical properties and proton conductivity.

In order to achieve the above-mentioned purpose of the invention, the present invention provides the following technical solutions:

A kind of phosphonic acid functionalized polybenzimidazole, its structural formula general formula is:

Wherein 0.01≤x≤0.25, 0.75≤y≤0.99, and x+y=1;

In the general structural formula, R is any one or both of the following structures:

The preparation method of the phosphonic acid functionalized polybenzimidazole: under the protection of protective gas, 2-((diethoxyphosphoryl)methyl)-[1,1'-biphenyl]-4,4'- Dicarboxylic acid, aromatic dicarboxylic acid and 3,3'-diaminobenzidine are added to the mixture of polyphosphoric acid and phosphorus pentoxide for deoxygenation, react at 120-170°C for 5-20 hours, and then heat up to React at 190-210°C for 6-24 hours; pour the reaction liquid into deionized water to precipitate solids, soak the obtained solids in aqueous sodium bicarbonate solution and stir for 24-36 hours, then wash; soak the washed products in concentrated hydrochloric acid at 60-90°C 12 to 48 hours, washed to neutral; dried to obtain phosphonic acid functionalized polybenzimidazole.

In order to further realize the purpose of the present invention, preferably, the molar ratio of the 3,3'-diaminobenzidine to the aromatic dicarboxylic acid is 1:1; The molar ratio of 1,1'-biphenyl]-4,4'-dicarboxylic acid to aromatic dicarboxylic acid is 1:3～1:99; 2-((diethoxyphosphoryl)methyl)-[1 ,1'-biphenyl]-4,4'-dicarboxylic acid, aromatic dicarboxylic acid and 3,3'-diaminobenzidine total dosage is 2-10% of the mass of polyphosphoric acid; phosphorus pentoxide and polyphosphoric acid The mass ratio of polyphosphoric acid is 1:20～1:10.

Preferably, the aromatic dicarboxylic acid is 4,4'-dicarboxydiphenyl ether, 2,6-pyridinedicarboxylic acid, [2,2'-bipyridyl]-5,5'-dicarboxylic acid and Any one or two of 2,2-bis(4-carboxyphenyl)hexafluoroisopropane.

Preferably, the protective gas is nitrogen or argon; the concentration of the sodium bicarbonate solution is 5-10wt%; the washing and washing to neutrality are all washed with deionized water; the drying is Vacuum dry at 80°C-110°C for 24-48h.

Preferably, the 2-((diethoxyphosphoryl)methyl)-[1,1'-biphenyl]-4,4'-dicarboxylic acid is synthesized through the following steps:

1) Dimethyl 2-methyl-[1,1'-biphenyl]-4,4'-dicarboxylate, N-bromosuccinimide and azobisisobutyronitrile were dissolved in tetrachloro In carbonization, react at 75-85°C for 2-12 hours; after the reaction is complete, remove the solvent, purify, and dry to obtain 2-(bromomethyl)-[1,1'-biphenyl]-4,4' - dimethyl dicarboxylate;

(2) Dissolve dimethyl 2-(bromomethyl)-[1,1'-biphenyl]-4,4'-dicarboxylate, triethyl phosphite and zinc bromide in 1,4-bis In oxyhexane, react at 100-110°C for 4-8 hours; after the reaction is complete, remove the solvent and separate to obtain 2-((diethoxyphosphoryl)methyl)-[1,1'-biphenyl] -Dimethyl 4,4'-dicarboxylate;

(3) Dissolve dimethyl 2-((diethoxyphosphoryl)methyl)-[1,1'-biphenyl]-4,4'-dicarboxylate and lithium hydroxide in a mixed solution of water and ethanol reaction at 35-55°C for 1.5-4 hours; after the reaction is complete, adjust the system to be neutral, remove ethanol, add concentrated hydrochloric acid dropwise until white powder precipitates, wash and dry to obtain 2-((diethoxyphosphoryl )methyl)-[1,1'-biphenyl]-4,4'-dicarboxylic acid.

Further preferably, in step 1), the moles of dimethyl 2-methyl-[1,1'-biphenyl]-4,4'-dicarboxylate and N-bromosuccinimide The ratio is 1:1～1:1.5; the molar ratio of azobisisobutyronitrile to 2-methyl-[1,1'-biphenyl]-4,4'-dicarboxylic acid dimethyl ester is 1:20～1:10; the concentration of dimethyl 2-methyl-[1,1'-biphenyl]-4,4'-dicarboxylate is 0.25～0.1mol/L;

In step 2), the molar ratio of dimethyl 2-(bromomethyl)-[1,1'-biphenyl]-4,4'-dicarboxylate to triethyl phosphite is 1:5 ~1:10; the molar ratio of zinc bromide to 2-(bromomethyl)-[1,1'-biphenyl]-4,4'-dicarboxylate dimethyl is 1:0.6~1 : 1; the concentration of the 2-(bromomethyl)-[1,1'-biphenyl]-4,4'-dicarboxylic acid dimethyl ester is 0.1～0.5mol/L;

In step 3), the molar ratio of dimethyl 2-((diethoxyphosphoryl)methyl)-[1,1'-biphenyl]-4,4'-dicarboxylate to lithium hydroxide is 1:8～1:12; the concentration of dimethyl 2-((diethoxyphosphoryl)methyl)-[1,1'-biphenyl]-4,4'-dicarboxylate is 0.05 ~0.1mol/L; the volume ratio of water and ethanol is 1:0.5~1:5.

Further preferably, step 1) removes the solvent by using a rotary evaporator at 40-55°C; the purification is achieved by recrystallizing the crude product with isopropanol for more than two times;

Step 2) The solvent removal is carried out by a rotary evaporator at 55-70° C. and the separation is carried out by silica gel column chromatography;

Step 3) Adjusting the system to be neutral is achieved by adding concentrated hydrochloric acid dropwise; removing ethanol is carried out at 40-55°C through a rotary evaporator, washing is repeated washing with deionized water; drying is vacuum drying at 55-65°C 24 to 48 hours.

The application of the phosphonic acid functionalized polybenzimidazole in the preparation of high-temperature proton exchange membranes.

Preferably, the phosphonic acid functionalized polybenzimidazole is dissolved in an organic solvent and formulated into a polymer solution with a solid content of 1 to 10 wt %; the polymer solution is evenly cast onto flat glass and then dried; cooled to After room temperature, immerse in deionized water to peel off the film, and then dry the wet film in vacuum to obtain a phosphonic acid functionalized polybenzimidazole film;

The obtained phosphonic acid functionalized polybenzimidazole membrane is soaked in an aqueous phosphoric acid solution with a mass fraction of 60-85 wt%, and dried after removing surface phosphoric acid to obtain a phosphonic acid functionalized polybenzimidazole high-temperature proton exchange membrane.

Further preferably, the solvent is one or both of N-methylpyrrolidone and dimethyl sulfoxide; the dissolution temperature is 60-120°C; the polymer solution is evenly cast onto flat glass The way of drying after coating is to put the flat glass coated with polymer solution into an oven, set it to dry at 60-80°C for 12-24 hours, and then set it at 100-120°C for 12-24 hours; The wet film is vacuum-dried at 90-110°C for 24-48 hours; the method of removing surface phosphoric acid and then drying is vacuum-drying at 90-110°C for 8-24 hours; the surface phosphoric acid is removed by wiping with filter paper.

Compared with the prior art, the advantages and beneficial effects of the present invention are:

(1) The present invention prepares the phosphonic acid functionalized polybenzimidazole polymer by the method of monomer polymerization, compared with the method of post-grafting to introduce phosphoric acid, the process steps are simple, and the introduction of no impurities is convenient for post-treatment;

(2) The introduction of the phosphonic acid group of the present invention destroys the close-packed structure between the polybenzimidazole molecular chains, so that the phosphonic acid functionalized polybenzimidazole has good dissolution and film-forming properties;

(3) The rigid main chain structure and dense conjugated structure of the polybenzimidazole of the present invention make the ion exchange membrane have good thermal stability and mechanical properties;

(4) The introduction of phosphonic acid groups enriches the hydrogen bonding between molecular chains and phosphoric acid molecules and provides additional proton transfer sites. Therefore, the proton exchange membrane has excellent proton conductivity and has applications in the field of high-temperature fuel cells. prospect.

Description of drawings

Figure 1 is a schematic diagram of the synthesis of 2-((diethoxyphosphoryl)methyl)-[1,1'-biphenyl]-4,4'-dicarboxylic acid in Example 1-3.

Fig. 2 is a schematic diagram of ¹ HNMR of 2-((diethoxyphosphoryl)methyl)-[1,1'-biphenyl]-4,4'-dicarboxylic acid in Example 1.

Fig. 3 is a schematic diagram of ¹ HNMR of 2-((diethoxyphosphoryl)methyl)-[1,1'-biphenyl]-4,4'-dicarboxylic acid in Example 2.

Fig. 4 is a schematic ¹ H NMR diagram of 2-((diethoxyphosphoryl)methyl)-[1,1'-biphenyl]-4,4'-dicarboxylic acid in Example 3.

Fig. 5 is a schematic diagram of the infrared spectrum characterization of the phosphonic acid functionalized polybenzimidazole in Examples 4-8 and the polybenzimidazole in the comparative example.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention more clear, the present invention will be further described below in conjunction with the accompanying drawings and embodiments. It should be noted that the embodiments of the present invention are not limited to this.

Example 1

As shown in Figure 1, in a dry 1000ml three-necked flask, 28.4g (0.1mol) 2-methyl-[1,1'-biphenyl]-4,4'-dicarboxylic acid dimethyl ester, 17.8g (0.1mol) N-bromosuccinimide and 0.82g (0.05mol) azobisisobutyronitrile were dissolved in 400mL carbon tetrachloride, and heated to 83°C under nitrogen protection for 3h under reflux. After the reaction was complete, the solvent was removed by a rotary evaporator at 45°C, the yellow crude product was recrystallized twice with isopropanol, and dried under vacuum at 45°C to obtain a white powder, which was 2-(bromomethyl)-[1, Dimethyl 1'-biphenyl]-4,4'-dicarboxylate. Yield: 63%.

In a dry 500ml three-necked flask, 20.1g (0.055mol) 2-(bromomethyl)-[1,1'-biphenyl]-4,4'-dicarboxylic acid dimethyl ester, 6.6g (0.03mol ) zinc bromide and 30 g (0.181 mol) of triethyl phosphite were dissolved in 240 ml of 1,4-dioxane, and the temperature was raised to 103° C. for 8 hours under nitrogen protection. When the reaction was complete, the solvent was removed by a rotary evaporator at 65°C, and a light yellow oil was obtained by silica gel column chromatography, which was 2-((diethoxyphosphoryl)methyl)-[1,1'-bis Dimethyl phenyl]-4,4'-dicarboxylate. Wherein the eluent is petroleum ether/ethyl acetate=1:1. Yield: 86%.

In a dry 500ml three-necked flask, 12.2g (0.031mol) 2-((diethoxyphosphoryl)methyl)-[1,1'-biphenyl]-4,4'-dicarboxylic acid dimethyl , 6.8g (0.121mol) of lithium hydroxide was dissolved in a mixed solvent of 160ml of deionized water and 160ml of ethanol, and the temperature was raised to 40°C for 2h. Until the reaction is complete, add concentrated hydrochloric acid dropwise until the system is neutral, remove ethanol at 50°C with a rotary evaporator, then add concentrated hydrochloric acid dropwise until white powder precipitates, collect the white powder by filtration, and then wash it repeatedly with water and ethyl acetate. Vacuum drying at 50°C for 24 hours gave 2-((diethoxyphosphoryl)methyl)-[1,1'-biphenyl]-4,4'-dicarboxylic acid. Yield: 89%. The structure of 2-((diethoxyphosphoryl)methyl)-[1,1'-biphenyl]-4,4'-dicarboxylic acid is characterized by ¹ H NMR, as shown in Figure 2, its specific peak position The assignments are as follows: 13.06 (s, 2H, -COOH), 8.11 (s, 1H, ArH), 8.07-8.01 (d, 2H, ArH), 7.90 (d, 1H, ArH), 7.57 (d, 2H, ArH) , 7.39 (d, 1H, ArH), 3.88 (p, 4H, -OCH2-), 3.23 (d, 2H, Ar-CH2-), 1.13 (t, 6H, -CH3).

Example 2

In a dry 1000ml three-necked flask, 28.4g (0.1mol) dimethyl-[1,1'-biphenyl]-4,4'-dicarboxylate, 17.8g (0.1mol) N- Bromosuccinimide and 0.82g (0.05mol) of azobisisobutyronitrile were dissolved in 300mL of carbon tetrachloride, and the temperature was raised to 75°C under nitrogen protection and refluxed for 2h. After the reaction was complete, the solvent was removed by a rotary evaporator at 45°C, the yellow crude product was recrystallized twice with isopropanol, and dried under vacuum at 45°C to obtain a white powder, which was 2-(bromomethyl)-[1, Dimethyl 1'-biphenyl]-4,4'-dicarboxylate. Yield: 59%.

In a dry 500ml three-necked flask, 20.1g (0.055mol) 2-(bromomethyl)-[1,1'-biphenyl]-4,4'-dicarboxylic acid dimethyl ester and 30g (0.181mol) Triethyl phosphite was dissolved in 240ml of 1,4-dioxane, and the temperature was raised to 103°C for 8 hours under the protection of nitrogen. When the reaction was complete, the solvent was removed by a rotary evaporator at 65°C, and a light yellow oil was obtained by silica gel column chromatography, which was 2-((diethoxyphosphoryl)methyl)-[1,1'-bis Dimethyl phenyl]-4,4'-dicarboxylate. Wherein the eluent is petroleum ether/ethyl acetate=1:1. Yield: 69%.

In a dry 500ml three-necked flask, 12.2g (0.031mol) 2-((diethoxyphosphoryl)methyl)-[1,1'-biphenyl]-4,4'-dicarboxylic acid dimethyl , 8.5g (0.151mol) of lithium hydroxide was dissolved in a mixed solvent of 160ml of deionized water and 160ml of ethanol, and the temperature was raised to 60°C for 2h. Until the reaction is complete, add concentrated hydrochloric acid dropwise until the system is neutral, remove ethanol at 50°C with a rotary evaporator, then add concentrated hydrochloric acid dropwise until white powder precipitates, collect the white powder by filtration, and then wash it repeatedly with water and ethyl acetate. Vacuum drying at 50°C for 24 hours gave 2-((diethoxyphosphoryl)methyl)-[1,1'-biphenyl]-4,4'-dicarboxylic acid. Yield: 82%. The structure of 2-((diethoxyphosphoryl)methyl)-[1,1'-biphenyl]-4,4'-dicarboxylic acid is characterized by ¹ H NMR, as shown in Figure 3, the specific peak position The assignments are as follows: 13.1 (s, 2H, -COOH), 8.10 (s, 1H, ArH), 8.07-8.01 (d, 2H, ArH), 7.92 (d, 1H, ArH), 7.58 (d, 2H, ArH) , 7.40 (d, 1H, ArH), 3.87 (p, 4H, -OCH2-), 3.21 (d, 2H, Ar-CH2-), 1.10 (t, 6H, -CH3).

Example 3

In a dry 250ml three-necked flask, 14.2g (0.05mol) of 2-methyl-[1,1'-biphenyl]-4,4'-dicarboxylic acid dimethyl ester, 13.4g (0.075mol) of N-bromo Substituted succinimide and 0.49g (0.03mol) of azobisisobutyronitrile were dissolved in 180mL of carbon tetrachloride, and the temperature was raised to 75°C under nitrogen protection and refluxed for 6h. After the reaction was complete, the solvent was removed by a rotary evaporator at 50°C, the yellow crude product was recrystallized twice with isopropanol, and dried under vacuum at 45°C to obtain a white powder, which was 2-(bromomethyl)-[1, Dimethyl 1'-biphenyl]-4,4'-dicarboxylate. Yield: 55%.

In a dry 500ml three-necked flask, 9.08 (0.025mol) 2-(bromomethyl)-[1,1'-biphenyl]-4,4'-dicarboxylic acid dimethyl ester and 10g (0.06mol) Triethyl phosphate was dissolved in 150ml of 1,4-dioxane, and heated to 103°C under nitrogen protection to reflux for 12h. When the reaction was complete, the solvent was removed by a rotary evaporator at 65°C, and a light yellow oil was obtained by silica gel column chromatography, which was 2-((diethoxyphosphoryl)methyl)-[1,1'-bis Dimethyl phenyl]-4,4'-dicarboxylate. Wherein the eluent is petroleum ether/ethyl acetate=1:1. Yield: 56%.

In a dry 500ml three-necked flask, 12.2g (0.031mol) 2-((diethoxyphosphoryl)methyl)-[1,1'-biphenyl]-4,4'-dicarboxylic acid dimethyl , 6.8g (0.121mol) of lithium hydroxide was dissolved in a mixed solvent of 240ml of deionized water and 160ml of ethanol, and the temperature was raised to 80°C for 2h. Until the reaction is complete, add concentrated hydrochloric acid dropwise until the system is neutral, remove ethanol at 50°C with a rotary evaporator, then add concentrated hydrochloric acid dropwise until white powder precipitates, collect the white powder by filtration, and elute with methanol/dichloromethane The solvent was separated by column chromatography, and the solvent was removed by a rotary evaporator at 40°C, and dried in vacuum at 50°C for 24h to obtain 2-((diethoxyphosphoryl)methyl)-[1,1'-biphenyl]- 4,4'-dicarboxylic acid. Yield: 32%. The structure of 2-((diethoxyphosphoryl)methyl)-[1,1'-biphenyl]-4,4'-dicarboxylic acid is characterized by ¹ H NMR, as shown in Figure 4, the specific peak position The assignments are as follows: 13.13 (s, 2H, -COOH), 8.10 (s, 1H, ArH), 8.05-7.98 (d, 2H, ArH), 7.89 (d, 1H, ArH), 7.58 (d, 2H, ArH) , 7.35 (d, 1H, ArH), 3.85 (p, 4H, -OCH2-), 3.20 (d, 2H, Ar-CH2-), 1.16 (t, 6H, -CH3).

Example 4

Under nitrogen protection, add 38g of polyphosphoric acid and 4g of phosphorus pentoxide into a dry 100ml three-neck flask, raise the temperature to 120°C and stir for 2 hours until the phosphorus pentoxide dissolves. After cooling to room temperature, add 0.8657g (4mmol) 3,3'-diaminobenzidine, 0.8537g (3.24mmol) 4,4'-dicarboxydiphenyl ether and 0.3034g (0.76mmol) 2-((diethyl Oxyphosphoryl)methyl)-[1,1'-biphenyl]-4,4'-dicarboxylic acid (prepared in Example 1), reacted at 120°C for 2h, 140°C for 11h, and 170°C for 3h , 200 ° C reaction 6h. After fully reacting, the reaction solution was poured into 500ml of deionized water while it was hot, and a reddish-brown filamentous solid was precipitated. Then, the polymer was soaked in 10wt% sodium bicarbonate aqueous solution, stirred for 24 hours, and then washed repeatedly with deionized water until neutral. Then the polymer was soaked in concentrated hydrochloric acid at 60° C. for 24 hours, washed with deionized water until neutral, and finally vacuum-dried at 90° C. for 48 hours to obtain phosphonic acid functionalized polybenzimidazole. Figure 5 carried out infrared characterization of the phosphonic acid functionalized polybenzimidazole in the above example 4, and the characteristic peaks of imidazole structure and benzene ring can be observed at 1623, 1601 cm ^-1 , which confirms the successful synthesis of polybenzimidazole; Compared with the ratio infrared spectrum, the characteristic peak of phosphonic acid group can be observed at 1050cm ^-1 , indicating the introduction of phosphonic acid group in the main chain structure of the polymer, and confirming the successful synthesis of phosphonic acid functionalized polybenzimidazole.

Dissolve the above phosphonic acid functionalized polybenzimidazole in NMP to prepare a 2wt% solution, cast the solution in an ultra-flat glass container, dry at 80°C for 12 hours, then dry at 100°C for 12h, cool and soak in water The polymer film was peeled off, and the polymer film was vacuum-dried at 100°C to constant weight to obtain a phosphonic acid functionalized polybenzimidazole film with a thickness of about 40±10 μm; it was soaked in 85% phosphoric acid solution at 80°C for treatment After 24 hours, the phosphoric acid on the surface was wiped clean with filter paper, and vacuum-dried at 100°C for 8 hours to obtain a phosphonic acid-functionalized polybenzimidazole high-temperature proton exchange membrane.

Example 5

Under nitrogen protection, add 38g of polyphosphoric acid and 3.5g of phosphorus pentoxide into a dry 100ml three-neck flask, raise the temperature to 120°C and stir for 2 hours until the phosphorus pentoxide dissolves. After cooling to room temperature, add 0.8657g (4mmol) 3,3'-diaminobenzidine, 0.8854g (3.24mmol) 4,4'-dicarboxydiphenyl ether and 0.2565g (0.76mmol) 2-((diethyl Oxyphosphoryl)methyl)-[1,1'-biphenyl]-4,4'-dicarboxylic acid (prepared in Example 1), reacted at 120°C for 2h, 140°C for 11h, and 170°C for 3h , 200 ° C reaction 6h. After fully reacting, the reaction solution was poured into 500ml of deionized water while it was hot, and a reddish-brown filamentous solid was precipitated. Then, the polymer was soaked in 10wt% sodium bicarbonate aqueous solution, stirred for 24 hours, and then washed repeatedly with deionized water until neutral. Then the polymer was soaked in concentrated hydrochloric acid at 60° C. for 24 hours, washed with deionized water until neutral, and finally vacuum-dried at 90° C. for 48 hours to obtain phosphonic acid functionalized polybenzimidazole. Figure 5 carries out the infrared characterization of the phosphonic acid-functionalized polybenzimidazole in the above example 5, and the characteristic peaks of the imidazole structure and the benzene ring can be observed at 1625 and 1601 cm ^-1 , which confirms the successful synthesis of polybenzimidazole; Compared with the ratio infrared spectrum, the characteristic peak of phosphonic acid group can be observed at 1049cm ^-1 , indicating the introduction of phosphonic acid group in the main chain structure of the polymer, and confirming the successful synthesis of phosphonic acid functionalized polybenzimidazole.

Dissolve the above-mentioned phosphonic acid-functionalized polybenzimidazole in NMP to prepare a 2% solution, cast the solution in an ultra-flat glass container, dry at 80°C for 12 hours, then dry at 100°C for 12 hours, cool and soak in water The polymer film was peeled off, and the polymer film was vacuum-dried at 100°C to constant weight to obtain a phosphonic acid functionalized polybenzimidazole film with a thickness of about 40±10 μm; it was soaked in 85% phosphoric acid solution at 80°C for treatment After 24 hours, the phosphoric acid on the surface was wiped clean with filter paper, and vacuum-dried at 100°C for 8 hours to obtain a phosphonic acid-functionalized polybenzimidazole high-temperature proton exchange membrane.

Example 6

Under the protection of nitrogen, add 38g of polyphosphoric acid and 3.0g of phosphorus pentoxide into a dry 100ml three-neck flask, raise the temperature to 120°C and stir for 2h until the phosphorus pentoxide dissolves. After cooling to room temperature, add 0.8657g (4mmol) 3,3'-diaminobenzidine, 0.9170g (3.24mmol) 4,4'-dicarboxydiphenyl ether and 0.2082g (0.76mmol) 2-((diethyl Oxyphosphoryl)methyl)-[1,1'-biphenyl]-4,4'-dicarboxylic acid (prepared in Example 1), reacted at 120°C for 2h, 140°C for 11h, and 170°C for 3h , 200 ° C reaction 6h. After fully reacting, the reaction solution was poured into 500ml of deionized water while it was hot, and a reddish-brown filamentous solid was precipitated. Then, the polymer was soaked in 10wt% sodium bicarbonate aqueous solution, stirred for 24 hours, and then washed repeatedly with deionized water until neutral. Then the polymer was soaked in concentrated hydrochloric acid at 60° C. for 24 hours, washed with deionized water until neutral, and finally vacuum-dried at 90° C. for 48 hours to obtain phosphonic acid functionalized polybenzimidazole. Figure 5 carries out the infrared characterization of the phosphonic acid-functionalized polybenzimidazole in the above example 6, and the characteristic peaks of the imidazole structure and the benzene ring can be observed at 1624, 1599 cm ^-1 , which confirms the successful synthesis of polybenzimidazole; Compared with the ratio infrared spectrum, the characteristic peak of phosphonic acid group can be observed at 1048cm ^-1 , indicating the introduction of phosphonic acid group in the main chain structure of the polymer, and confirming the successful synthesis of phosphonic acid functionalized polybenzimidazole.

Dissolve the above phosphonic acid-functionalized polybenzimidazole in DMSO to prepare a 2% solution, cast the solution in an ultra-flat glass container, dry at 80°C for 12 hours, then dry at 100°C for 12 hours, cool and soak in water The polymer film was peeled off, and the polymer film was vacuum-dried at 100°C to constant weight to obtain a phosphonic acid functionalized polybenzimidazole film with a thickness of about 40±10 μm; it was soaked in 85% phosphoric acid solution at 80°C for treatment After 24 hours, the phosphoric acid on the surface was wiped clean with filter paper, and vacuum-dried at 100°C for 8 hours to obtain a phosphonic acid-functionalized polybenzimidazole high-temperature proton exchange membrane.

Example 7

Under the protection of nitrogen, add 72g of polyphosphoric acid and 7.3g of phosphorus pentoxide into a dry 100ml three-neck flask, raise the temperature to 120°C and stir for 2 hours until the phosphorus pentoxide dissolves. After cooling to room temperature, add 1.0713g (5mmol) 3,3'-diaminobenzidine, 0.5165g (2mmol) 4,4'-dicarboxydiphenyl ether, 0.4178 (2.5mmol) 2,6-pyridinedicarboxylic acid 0.1962g (0.5mmol) 2-((diethoxyphosphoryl)methyl)-[1,1'-biphenyl]-4,4'-dicarboxylic acid (prepared in Example 1), respectively at 120°C Reacted for 2h, 140°C for 11h, 170°C for 3h, 210°C for 12h. After fully reacting, the reaction solution was poured into 500ml of deionized water while it was hot, and a reddish-brown filamentous solid was precipitated. Then, the polymer was soaked in 10wt% sodium bicarbonate aqueous solution, stirred for 24 hours, and then washed repeatedly with deionized water until neutral. Then the polymer was soaked in concentrated hydrochloric acid at 60° C. for 24 hours, washed with deionized water until neutral, and finally vacuum-dried at 90° C. for 48 hours to obtain phosphonic acid functionalized polybenzimidazole. Figure 5 carries out the infrared characterization of the phosphonic acid functionalized polybenzimidazole in the above example 7, and the characteristic peaks of the imidazole structure, benzene ring and pyridine ring can be observed at 1623, 1600 and 1573 cm ^-1 , which confirms the polybenzimidazole Successfully synthesized; compared with the infrared spectrum of the comparative example, the characteristic peak of the phosphonic acid group can be observed at 1048cm ^-1 , indicating the introduction of the phosphonic acid group on the main chain structure of the polymer, confirming that the phosphonic acid functionalized polybenzimidazole successful synthesis.

Dissolve the above phosphonic acid-functionalized polybenzimidazole in DMSO to prepare a 2% solution, cast the solution in an ultra-flat glass container, dry at 80°C for 12 hours, then dry at 100°C for 12 hours, cool and soak in water The polymer film was peeled off, and the polymer film was vacuum-dried at 100°C to constant weight to obtain a phosphonic acid functionalized polybenzimidazole film with a thickness of about 40±10 μm; it was soaked in 85% phosphoric acid solution at 80°C for treatment After 24 hours, the phosphoric acid on the surface was wiped clean with filter paper, and vacuum-dried at 100°C for 8 hours to obtain a phosphonic acid-functionalized polybenzimidazole high-temperature proton exchange membrane.

Example 8

Under the protection of nitrogen, add 72g of polyphosphoric acid and 7.3g of phosphorus pentoxide into a dry 100ml three-neck flask, raise the temperature to 120°C and stir for 2 hours until the phosphorus pentoxide dissolves. After cooling to room temperature, add 1.0713g (5mmol) 3,3'-diaminobenzidine, 0.3873g (1.5mmol) 4,4'-dicarboxydiphenyl ether, 0.5014 (3mmol) 2,6-pyridinedicarboxylic acid 0.1962g (0.5mmol) 2-((diethoxyphosphoryl)methyl)-[1,1'-biphenyl]-4,4'-dicarboxylic acid (prepared in Example 1), respectively at 120°C Reacted for 2h, 140°C for 11h, 170°C for 3h, 210°C for 12h. After fully reacting, the reaction solution was poured into 500ml of deionized water while it was hot, and a reddish-brown filamentous solid was precipitated. Then, the polymer was soaked in 10wt% sodium bicarbonate aqueous solution, stirred for 24 hours, and then washed repeatedly with deionized water until neutral. Then the polymer was soaked in concentrated hydrochloric acid at 60° C. for 24 hours, washed with deionized water until neutral, and finally vacuum-dried at 90° C. for 48 hours to obtain phosphonic acid functionalized polybenzimidazole. Figure 5 carries out the infrared characterization of the phosphonic acid functionalized polybenzimidazole in the above example 8, and the characteristic peaks of the imidazole structure, benzene ring and pyridine ring can be observed at 1623, 1601 and 1575 cm ^-1 , which confirms the polybenzimidazole Successfully synthesized; compared with the infrared spectrum of the comparative example, the characteristic peak of the phosphonic acid group can be observed at 1048cm ^-1 , indicating the introduction of the phosphonic acid group on the main chain structure of the polymer, confirming that the phosphonic acid functionalized polybenzimidazole successful synthesis.

Dissolve the above phosphonic acid-functionalized polybenzimidazole in DMSO to prepare a 2% solution, cast the solution in an ultra-flat glass container, dry at 80°C for 12 hours, then dry at 100°C for 12 hours, cool and soak in water The polymer film was peeled off, and the polymer film was vacuum-dried at 100°C to constant weight to obtain a phosphonic acid functionalized polybenzimidazole film with a thickness of about 40±10 μm; it was soaked in 85% phosphoric acid solution at 80°C for treatment After 24 hours, the phosphoric acid on the surface was wiped clean with filter paper, and vacuum-dried at 100°C for 8 hours to obtain a phosphonic acid-functionalized polybenzimidazole high-temperature proton exchange membrane.

comparative example

Under nitrogen protection, add 38g of polyphosphoric acid and 4g of phosphorus pentoxide into a dry 100ml three-neck flask, raise the temperature to 120°C and stir for 2 hours until the phosphorus pentoxide dissolves. After cooling to room temperature, add 0.8657g (4mmol) 3,3'-diaminobenzidine, 1.0329g (4mmol) 4,4'-dicarboxydiphenyl ether, react at 120°C for 2h, 140°C for 11h, 170°C ℃ reaction 3h, 200 ℃ reaction 6h. After fully reacting, the reaction solution was poured into 500ml of deionized water while it was hot, and a reddish-brown filamentous solid was precipitated. Then, the polymer was soaked in 10wt% sodium bicarbonate aqueous solution, stirred for 24 hours, and then washed repeatedly with deionized water until neutral. Then the polymer was soaked in concentrated hydrochloric acid at 60°C for 24 hours, washed with deionized water until neutral, and finally dried in vacuum at 90°C for 48 hours to obtain polybenzimidazole.

Dissolve the above polybenzimidazole in DMSO to prepare a 2% solution, cast the solution in an ultra-flat glass container, dry at 80°C for 12 hours, then dry at 100°C for 12 hours, soak in water after cooling to peel off the polymer film , the polymer film was vacuum-dried at 100°C to constant weight to obtain a polybenzimidazole film with a thickness of about 35 μm; soak it in 85% phosphoric acid solution at 80°C for 24 hours, take it out and wipe its surface with filter paper Phosphoric acid was dried under vacuum at 100°C for 8 hours to obtain a polybenzimidazole high temperature proton exchange membrane.

Cut the polybenzimidazole membranes prepared in Examples 4-9 and Comparative Examples into 20mm×20mm sample membranes, soak them in 85wt% phosphoric acid aqueous solution at 80°C for doping, take out the membranes after 24h, and filter them with filter paper Wipe off the phosphoric acid solution on the surface, then dry it in vacuum at 100°C for 8 hours, then weigh it, and calculate the phosphoric acid doping level according to the weight of the sample film before and after doping with acid; the proton conductivity of the sample film is tested by a two-electrode AC impedance method The polybenzimidazole film prepared in the embodiment and the comparative example is cut into 5 dumbbell bar samples of 50mm * 4mm, and its effective test area is 20mm * 4mm, is tested with tensile rate 1mm/min by universal stretching machine Tensile strength and elongation at break of different sample films.

The test results are shown in Table 1 below:

Table 1

By comparing the test results in Table 1, it can be found that the phosphonic acid functionalized polybenzimidazole proton exchange membrane has good mechanical properties and shows a higher phosphoric acid doping level and proton conductivity performance. Compared with the Chinese invention patent 201911265652.7, the present invention effectively realizes the introduction of phosphonic acid groups into the main chain structure of polybenzimidazole, which enriches the effective sites for proton transfer, so the phosphonic acid functionalized polybenzimidazole proton exchange membrane has a higher proton conductivity.

Claims (6)

1. A preparation method of phosphonic acid functionalized polybenzimidazole, characterized in that: under the protection of protective gas, 2-((diethoxyphosphoryl) methyl)-[1,1'-biphenyl]- Add 4,4'-dicarboxylic acid, aromatic dicarboxylic acid and 3,3'-diaminobenzidine to the mixture of polyphosphoric acid and phosphorus pentoxide for deoxygenation, and react at 120～170℃ for 5～ After 20 hours, heat up to 190-210°C and react for 6-24 hours; pour the reaction liquid into deionized water to precipitate solids, soak the obtained solids in sodium bicarbonate aqueous solution and stir for 24-36 hours, and wash; soak the washed products in 60- In concentrated hydrochloric acid at 90°C for 12 to 48 hours, wash until neutral; dry to obtain phosphonic acid functionalized polybenzimidazole; The structural formula general formula of described phosphonic acid functionalized polybenzimidazole is: Wherein 0.01≤x≤0.25, 0.75≤y≤0.99, and x+y=1; In the general structural formula, R is any one or both of the following structures: 2. The preparation method of the phosphonic acid functionalized polybenzimidazole according to claim 1, characterized in that: the molar ratio of the 3,3'-diaminobenzidine to the aromatic dicarboxylic acid is 1:1; The molar ratio of 2-((diethoxyphosphoryl)methyl)-[1,1'-biphenyl]-4,4'-dicarboxylic acid to aromatic dicarboxylic acid is 1:3～1:99; 2 The total amount of -((diethoxyphosphoryl)methyl)-[1,1'-biphenyl]-4,4'-dicarboxylic acid, aromatic dicarboxylic acid and 3,3'-diaminobenzidine is more than 2-10% of the mass of polyphosphoric acid; the mass ratio of phosphorus pentoxide to polyphosphoric acid is 1:20-1:10. 3. The preparation method of phosphonic acid functionalized polybenzimidazole according to claim 1, characterized in that: the aromatic dicarboxylic acid is 4,4'-dicarboxydiphenyl ether, 2,6-pyridine diphenyl ether, Any one or both of carboxylic acid, [2,2'-bipyridine]-5,5'-dicarboxylic acid and 2,2-bis(4-carboxyphenyl)hexafluoroisopropane; The protective gas is nitrogen or argon; the concentration of the sodium bicarbonate solution is 5-10wt%; the washing and washing to neutrality are all washed with deionized water; the drying is at 80°C Vacuum dry at ~110°C for 24-48 hours. 4. the preparation method of phosphonic acid functionalized polybenzimidazole according to claim 1, is characterized in that, described 2-((diethoxyphosphoryl) methyl)-[1,1'-biphenyl ]-4,4'-dicarboxylic acid is synthesized by the following steps: 1) Dimethyl 2-methyl-[1,1'-biphenyl]-4,4'-dicarboxylate, N-bromosuccinimide and azobisisobutyronitrile were dissolved in tetrachloro In carbonization, react at 75-85°C for 2-12 hours; after the reaction is complete, remove the solvent, purify, and dry to obtain 2-(bromomethyl)-[1,1'-biphenyl]-4,4' - dimethyl dicarboxylate; 2) Dimethyl 2-(bromomethyl)-[1,1'-biphenyl]-4,4'-dicarboxylate, triethyl phosphite and zinc bromide were dissolved in 1,4-diox In the hexacyclic ring, react at 100-110°C for 4-8 hours; after the reaction is complete, remove the solvent and separate to obtain 2-((diethoxyphosphoryl)methyl)-[1,1'-biphenyl]- Dimethyl 4,4'-dicarboxylate; 3) Dissolve dimethyl 2-((diethoxyphosphoryl)methyl)-[1,1'-biphenyl]-4,4'-dicarboxylate and lithium hydroxide in a mixed solution of water and ethanol , react at 35-55°C for 1.5-4 hours; after the reaction is complete, adjust the system to be neutral, remove ethanol, add concentrated hydrochloric acid dropwise until white powder precipitates, wash and dry to obtain 2-((diethoxyphosphoryl) Methyl)-[1,1'-biphenyl]-4,4'-dicarboxylic acid. 5. The preparation method of the phosphonic acid functionalized polybenzimidazole according to claim 4, characterized in that, in step 1), the 2-methyl-[1,1'-biphenyl]-4, The molar ratio of dimethyl 4'-dicarboxylate to N-bromosuccinimide is 1:1～1:1.5; the azobisisobutyronitrile and 2-methyl-[1,1 The molar ratio of '-biphenyl]-4,4'-dicarboxylate is 1:20～1:10; the 2-methyl-[1,1'-biphenyl]-4,4' -The concentration of dimethyl dicarboxylate is 0.25～0.1mol/L; In step 2), the molar ratio of dimethyl 2-(bromomethyl)-[1,1'-biphenyl]-4,4'-dicarboxylate to triethyl phosphite is 1:5 ~1:10; the molar ratio of zinc bromide to 2-(bromomethyl)-[1,1'-biphenyl]-4,4'-dicarboxylate dimethyl is 1:0.6~1 : 1; the concentration of the 2-(bromomethyl)-[1,1'-biphenyl]-4,4'-dicarboxylic acid dimethyl ester is 0.1～0.5mol/L; In step 3), the molar ratio of dimethyl 2-((diethoxyphosphoryl)methyl)-[1,1'-biphenyl]-4,4'-dicarboxylate to lithium hydroxide is 1:8～1:12; the concentration of dimethyl 2-((diethoxyphosphoryl)methyl)-[1,1'-biphenyl]-4,4'-dicarboxylate is 0.05 ～0.1mol/L; the volume ratio of the water and ethanol is 1:0.5～1:5; 6. The preparation method of the phosphonic acid functionalized polybenzimidazole according to claim 4, is characterized in that, step 1) solvent removal is carried out at 40～55 ℃ by rotary evaporator; Purification is to use crude product Isopropanol recrystallization is achieved more than twice; Step 2) The solvent removal is carried out by a rotary evaporator at 55-70° C. and the separation is carried out by silica gel column chromatography; Step 3) Adjusting the system to be neutral is achieved by adding concentrated hydrochloric acid dropwise; removing ethanol is carried out at 40-55°C through a rotary evaporator, washing is repeated washing with deionized water; drying is vacuum drying at 55-65°C 24 to 48 hours.

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