CN115626990A

CN115626990A - Synthesis and polymerization method of AB type polybenzoxazole monomer containing benzimidazole structure

Info

Publication number: CN115626990A
Application number: CN202211141557.8A
Authority: CN
Inventors: 张青龙; 吕汪洋; 陈文兴
Original assignee: Zhejiang Sci Tech University ZSTU
Current assignee: Zhejiang Sci Tech University ZSTU
Priority date: 2022-09-20
Filing date: 2022-09-20
Publication date: 2023-01-20
Anticipated expiration: 2042-09-20
Also published as: CN115626990B

Abstract

The invention relates to a benzoxazole polymer, in particular to a method for synthesizing and polymerizing an AB type polybenzoxazole monomer containing a benzimidazole structure and a precursor thereof, wherein the synthesizing steps comprise: (1) imidazole ring forming reaction; (2) reducing nitro; and (3) dehydrating, cyclizing and polymerizing. The method has the advantages of mild reaction, easy control, less three wastes and considerable yield.

Description

Synthesis and polymerization method of AB type polybenzoxazole monomer containing benzimidazole structure

Technical Field

The invention relates to a synthesis and polymerization method of 2-amino-4- (5 or 6-carboxyl benzimidazole-2-yl) phenol.

Background

A high-performance polymer poly (P-phenylene benzobisoxazole) (PBO for short) with high-temperature and corrosion resistance is prepared from AA type 4,6-diaminoresorcinol hydrochloride (DAR.2 HCl) and BB type terephthalic acid (TPA) ₂ O ₅ A polycondensation in polyphosphoric acid in the presence of a catalyst. DAR.2 HCl is easily oxidized at high temperature, TPA has low solubility in polyphosphoric acid, and the high-temperature sublimation causes that the equivalent ratio of two monomers is difficult to accurately control during polycondensation, and finally the polymerization degree of PBO is further improved. The AB type monomer of polybenzoxazole contains equivalent reactive groups, so that end-capped oligomer caused by feeding metering error is avoided in polymerization reaction, and high molecular weight polymerization is easier to obtainThe compound (I) is prepared. As shown in formula 1, the reaction formula for preparing poly (p-phenylene-2,6-benzobisoxazole) has been studied in many ways around semi-rigid poly (p-phenylene-2,6-benzobisoxazole) obtained by auto-polycondensation of AB type monomer 3-amino-4-hydroxybenzoic acid and its hydrochloride (Han Zhewen, liu Zhibao, dan Xiaoyang, wu Pingping. Synthesis and structure and performance of lyotropic liquid crystal polymer polybenzoxazole [ J36, liu Zhibao, dan Xiaoyang, wu Pingping ]]The journal of macromolecules 1997 (02): 14-19), but the preparation of such polymers with high molecular weights still faces difficulties in removing the corrosive gases hydrogen chloride, poor monomer storage stability, etc.

As shown in formula 2, although the random Polymer poly (benzimidazole-co-benzoxazole) is obtained by pre-polycondensation and high-temperature ring closure of 3,4-diaminobenzoic acid hydrochloride and 3-amino-4-hydroxybenzoic acid hydrochloride, the preparation process is complicated and time-consuming, and a random block polycondensate (Nag A, ali M A, watanabase, M, singh, M, amorwachirabole, K, & Kato, S, et al. High-performance poly (benzoxazole/benzoquinone) is obtained, which has a more difficult molecular interaction and more difficult intermolecular force formation between the Polymer and the Polymer Degradation and Degradation, 2019, 201162). Through experimental verification of the scheme, the monomer used by the method is very easy to absorb water and oxidize, and meanwhile, the polymerization time is long, the energy consumption is high, and corrosive gas hydrogen chloride is removed. In order to form regular and ordered intermolecular hydrogen bonds and reduce dehydration load in a cyclization process, a novel AB type monomer 2-amino-4- (5 or 6-carboxyl benzimidazole-2-yl) phenol containing a benzimidazole structure is designed and synthesized, and a preparation and polymerization method of the AB type PBO novel monomer with easily available raw materials, considerable yield and mild conditions is provided.

Disclosure of Invention

The invention aims to provide a method for synthesizing and polymerizing 2-amino-4- (5 or 6-carboxyl benzimidazole-2-yl) phenol serving as an AB type polybenzoxazole monomer containing a benzimidazole structure, which has low cost, high yield and mild conditions, and is characterized in that the reaction route is as shown in formula (3):

further, the synthesis and polymerization of 2-amino-4- (5 or 6-carboxybenzimidazol-2-yl) phenol comprises the following steps:

step (1) imidazole ring formation reaction: adding raw materials of 3-nitro-4-hydroxybenzaldehyde and a reaction solvent into a reaction container at normal temperature, stirring, dropwise adding inorganic salt sodium bisulfite or sodium metabisulfite and a water blend, adding 3,4-diaminobenzoic acid again after dropwise adding, heating to 50-120 ℃ for cyclization reaction for 3-48 h, and then carrying out solvent recovery, suction filtration and washing treatment on reaction liquid to obtain an intermediate 2-nitro-4- (5 or 6-carboxybenzimidazole-2-yl) phenol;

step (2), reduction of nitro group: adding 2-amino-4- (5 or 6-carboxyl benzimidazole-2-yl) phenol, a solvent and a reducing agent into a reaction kettle, carrying out reduction reaction for 0.5-8 h, and then carrying out post-treatment on reaction liquid to obtain a product 2-amino-4- (5 or 6-carboxyl benzimidazole-2-yl) phenol;

step (3), dehydration, cyclization and polymerization reaction: in a dehydrating agent polyphosphoric acid or Eaton reagent system, carrying out polymerization reaction for 3-30 hours at 120-180 ℃, and cooling, washing and drying a polymerization solution to obtain the polymer.

The structural formula of the prepared polymer is shown as the formula (4)

Preferably, in the step (1), the solvent is one or a mixture of tetrahydrofuran, methyltetrahydrofuran, dioxane, dimethylformamide, dimethyl sulfoxide, dimethyl pyrrolidone, ethylene glycol methyl ether and diethylene glycol methyl ether, aliphatic alcohol containing 1-6 carbon atoms and aliphatic ketone containing 3-6 carbon atoms; the molar ratio of the raw materials of 3-nitro-4-hydroxybenzaldehyde, inorganic salt and 3,4-diaminobenzoic acid is 1:1.05 to 3:1.0 to 3. More preferably, the molar ratio of the raw material 3-nitro-4-hydroxybenzaldehyde, the inorganic salt and the 3,4-diaminobenzoic acid is 1:1.05 to 1.2:1.0 to 1.2

Preferably, in the step (1), the temperature of the inorganic salt added dropwise is controlled to be within. + -. 20 ℃ at room temperature, and the reaction temperature for the imidazole ring-forming reaction is 55 to 100 ℃.

Preferably, in the step (1), the inorganic salt and the water are added dropwise in a mass ratio of 1:2 to 1:15. more preferably, the mass ratio of the inorganic salt to water added dropwise is 1:2 to 1:3.5.

preferably, in the step (2), the reduction system for the nitro group reduction reaction comprises: a. an activated iron powder, water and a fatty alcohol system containing 1 to 5 carbon atoms; b. zinc powder in an organic acid system containing 1-3 carbon atoms; c. a sulfur-containing reducing salt and alkaline aqueous solution system; d. hydrogen, palladium on carbon and tetrahydrofuran, methyltetrahydrofuran, dioxane, fatty alcohol systems containing 1-6 carbons. The corresponding reaction temperature is 60-110 ℃, 20-120 ℃, 55-100 ℃ and 20-60 ℃ respectively; the corresponding reaction time is 0.5 to 3 hours, 5 to 15 hours, 1 to 5 hours and 2 to 25 hours respectively; more preferably, the reaction temperatures are 75 to 90 ℃,60 to 100 ℃, 75 to 100 ℃ and 40 to 50 ℃ respectively; the corresponding reaction time is 1 to 3 hours, 6 to 8 hours, 1 to 5 hours and 8 to 20 hours respectively

Preferably, in the step (2), the organic alcohol solvent is one or a mixture of methanol, ethanol, n-propanol, isopropanol, n-butanol, ethylene glycol monomethyl ether and diethylene glycol methyl ether.

Preferably, in the step (2), the organic acid used for the reduction of the nitro group is formic acid, acetic acid or propionic acid, the reaction temperature is 60-100 ℃, and the reaction time is 5-15 h.

Preferably, in the step (2), the sulfur-containing reducing salt used in the reduction nitro reaction is one or more of sodium sulfide, sodium polysulfide and sodium hydrosulfite.

Preferably, in the step (2), the alkaline aqueous solution used for the reduction of the nitro group is one or more of alkaline earth metal hydroxide and alkaline earth metal carbonate

Preferably, in the step (2), the reaction pressure of the hydrogen reduction reaction is from normal pressure to 4MPa.

Preferably, in the step (3), the mass ratio of the dehydrating solvent to the monomer is 5:1.0 to 35:1.0.

preferably, in the step (3), the temperature is raised in a stepwise manner, the polymerization reaction is stabilized at 140 ℃ or higher, and the viscosity of the polymerization system increases rapidly with the reaction time.

The method has the advantages of easily obtained raw materials, simple and convenient product post-treatment, small pollution and high atom economy, and the prepared 2-amino-4- (5 or 6-carboxyl benzimidazole-2-yl) phenol has high quality and good stability, and the prepared product can be directly polymerized into polybenzoxazole containing a benzimidazole structure.

Drawings

FIG. 1 shows the NMR spectrum of 2-nitro-4- (5-or 6-carboxybenzoimidazol-2-yl) phenol prepared in example 2.

FIG. 2 is a nuclear magnetic spectrum of 2-amino-4- (5 or 6-carboxybenzimidazol-2-yl) phenol prepared in example 6.

FIG. 3 is a nuclear magnetic hydrogen spectrum of a solid of poly (benzimidazole-benzoxazole) prepared in example 11.

Detailed Description

The invention is further illustrated by the following examples, without limiting the scope of the invention.

Example 1

A500 mL flask was charged with 200 g of ethanol and 16.5 g of 3-nitro-4-hydroxybenzaldehyde and ultrasonically dispersed uniformly. And (3) dropwise adding 40 g of a freshly prepared 30% sodium bisulfite aqueous solution at the temperature of 20 ℃ of the reaction system, and continuing to perform heat preservation reaction for half an hour after the addition is finished. 15.6 g of 3,4-diaminobenzoic acid is added into the yellow slurry reaction system, after heating reflux reaction is carried out for 12 hours, most of solvent is recovered, and the obtained solid is sequentially washed by ethanol and water, and dried in vacuum at 80 ℃ to obtain yellow solid 2-nitro-4- (5 or 6-carboxyl benzimidazole-2-yl) phenol, the HPLC purity of the product is 98.3 percent, and the yield is 89.2 percent.

Example 2

A500 mL flask was charged with 100 grams of dioxane and 80 grams of tetrahydrofuran and 16.5 grams of 3-nitro-4-hydroxybenzaldehyde and ultrasonically dispersed to homogeneity. Maintaining the reaction system at 10 ℃, dropwise adding 73 g of a freshly prepared 15% sodium metabisulfite aqueous solution, adding 16.6 g of 3,4-diaminobenzoic acid, reacting for 12 hours at 60 ℃, recovering most of the solvent, pulping and purifying the obtained solid by 95 ethanol to obtain a yellow solid, namely 2-nitro-4- (5 or 6-carboxybenzimidazole-2-yl) phenol, wherein the HPLC purity of the product is 99.1%, and the yield is 83.7%.

Example 3

A250 mL flask was charged with 90 grams of methyltetrahydrofuran, 0.1 grams of palladium on carbon, and 10.5 grams of 2-nitro-4- (5 or 6-carboxybenzimidazol-2-yl) phenol. The reaction flask is heated to 45 ℃ after three times of nitrogen replacement and is introduced with hydrogen to react for 23 hours. After the palladium-carbon is recovered by heat filtration, the solvent is recovered, the obtained light yellow solid is 2-amino-4- (5 or 6-carboxyl benzimidazole-2-yl) phenol, the HPLC purity of the product is 98.5 percent, and the yield is 97.3 percent.

Example 4

Adding 8.00g of 2-nitro-4- (5 or 6-carboxyl benzimidazole-2-yl) phenol and 42mL of acetic acid into a 250mL three-neck flask with a mechanical stirrer and a spherical condenser in sequence, heating a reaction system to 105 ℃, adding 3.1 g of zinc powder in batches, reacting for 2 hours, stopping heating, cooling to room temperature, adding 30mL of distilled water, performing suction filtration, drying a filter cake, analyzing the purity of a product by HPLC (high performance liquid chromatography) to be 96.1%, and obtaining the yield of 85.9%.

Example 5

5.00g 2-nitro-4- (5 or 6-carboxyl benzimidazole-2-yl) phenol and 70mL propionic acid are sequentially added into a 250mL three-neck flask provided with a mechanical stirring and spherical condenser, a reaction system is heated to 100 ℃, zinc powder is added in batches for 4.1g, after 5 hours of reaction, heating is stopped, most of propionic acid is removed and cooled to room temperature, 100mL of distilled water is added into the flask, suction filtration is carried out, a filter cake is dried, the purity of a product is 96.1% by HPLC analysis, and the yield is 91.4%.

Example 6

Adding 4.1g of 2-nitro-4- (5 or 6-carboxyl benzimidazole-2-yl) phenol, 60mL of isopropanol and 0.5g of Pd/C (5%) into a 100mL magnetic stirring autoclave as catalysts, sequentially replacing gas in the autoclave with nitrogen and hydrogen for three times, then opening a hydrogen valve, controlling the reaction temperature to be 28 ℃ and carrying out hydrogenation reaction for 8 hours, releasing pressure after the reaction is finished, discharging after the hydrogen is exhausted by using the nitrogen, heating reaction liquid, filtering out the catalyst, cooling filtrate to separate out beige solid product 2-amino-4- (5 or 6-carboxyl benzimidazole-2-yl) phenol, and analyzing the purity of the product by HPLC to be 99.39% and the yield to be 90.5%.

Example 7

47 g of polyphosphoric acid (PPA) is put into a three-neck flask provided with a mechanical stirrer and a nitrogen inlet, 5.2 g of monomer 2-amino-4- (5 or 6-carboxyl benzimidazole-2-yl) phenol is added and mixed evenly, the temperature is raised to 120 ℃ under the protection of nitrogen, the reaction is kept for 1 hour, and the color of the reaction system is changed from light yellow to grass yellow. And then heating to 160 ℃, preserving the heat for 2 hours, stopping heating after the reaction is finished, naturally cooling, and continuously stirring. The resultant viscous solution was soaked in 200 ml of deionized water, washed, and dried to obtain a polymer. The yield thereof was found to be 99.2%.

Example 8

Adding 18g of 2-nitro-4- (5 or 6-carboxyl benzimidazole-2-yl) phenol, 100mL of distilled water and 6.8 g of lithium hydroxide into a 500mL three-mouth reaction flask with a stirring and condensing tube, heating to 90 ℃, adding a mixture of 26.3 g of sodium hydrosulfite and 120 g of water in batches, carrying out heat preservation reaction for 1 hour, cooling to room temperature, adding hydrochloric acid to adjust the pH to about 7, carrying out suction filtration, and carrying out vacuum drying on a filter cake to obtain a light yellow solid product, namely 2-amino-4- (5 or 6-carboxyl benzimidazole-2-yl) phenol, wherein the purity of an HPLC product is 98.8%, and the yield is 96.3%.

Example 9

5.00g of 2-nitro-4- (5 or 6-carboxyl benzimidazole-2-yl) phenol, 2.8 g of potassium carbonate and 56 g of water are sequentially added into a 250mL four-neck flask provided with a thermometer and a spherical condenser, stirred and heated to 65 ℃, 98 g of 28% sodium sulfide aqueous solution is dropwise added after the temperature is raised, the heating is stopped after the reaction is carried out for 5 hours, the mixture is cooled to the room temperature, a 3M hydrochloric acid is used for regulating the system to be neutral, the mixture is subjected to suction filtration, a filter cake is dried, 70mL of absolute ethyl alcohol is used for pulping and refining to obtain a light yellow product 2-amino-4- (5 or 6-carboxyl benzimidazole-2-yl) phenol, the purity of an HPLC product is 97.6%, and the yield is 82.3%.

Example 10

83 grams of Eaton reagent is put into a three-neck flask provided with a mechanical stirrer and a nitrogen inlet, 8 grams of monomer 2-amino-4- (5 or 6-carboxyl benzimidazole-2-yl) phenol is added and mixed evenly, the temperature is raised to 160 ℃ under the protection of nitrogen, the reaction is kept for 1 hour, and the color of the reaction system is changed from light yellow to dark brown. After the reaction is finished, heating is stopped, part of solvent is recovered, and the viscous solution after natural cooling is soaked in 180 ml of deionized water, washed and dried to obtain the polymer. The yield thereof was found to be 89.4%.

Example 11

107 g of polyphosphoric acid is put into a three-neck flask provided with a mechanical stirrer and a nitrogen inlet, 10.8 g of monomer 2-amino-4- (5 or 6-carboxyl benzimidazole-2-yl) phenol is added and mixed evenly, the temperature is raised to 120 ℃ under the protection of nitrogen, the reaction is kept for 3 hours, and the color of the reaction system is changed from light yellow to dark brown. And after the reaction is finished, stopping heating, and naturally cooling the viscous solution, soaking in deionized water, cleaning and drying to obtain the polymer. The yield thereof was found to be 89.4%.

Although the above embodiments have been described in detail, they are only a part of the embodiments of the present invention, and not all of them.

Claims

1. A synthesis and polymerization method of AB type polybenzoxazole monomer 2-amino-4- (5 or 6-carboxyl benzimidazole-2-group) phenol containing benzimidazole structure is characterized in that the reaction route is as formula (3):

2. the method for synthesizing and polymerizing the polybenzoxazole monomer 2-amino-4- (5 or 6-carboxybenzimidazole-2-yl) phenol containing the benzimidazole structure AB as in claim 1, wherein the method comprises the following steps: (1) imidazole ring forming reaction: adding raw materials of 3-nitro-4-hydroxybenzaldehyde and a reaction solvent into a reaction container at normal temperature, stirring, dropwise adding an inorganic salt sodium bisulfite or sodium metabisulfite aqueous solution, adding 3,4-diaminobenzoic acid again after dropwise adding, heating to 50-120 ℃ for carrying out cyclization reaction for 3-48 h, and then carrying out solvent recovery, suction filtration and washing treatment on a reaction solution to obtain an intermediate 2-nitro-4- (5 or 6-carboxyl benzimidazole-2-yl) phenol; and (2) reduction of nitro: adding 2-nitro-4- (5 or 6-carboxyl benzimidazole-2-yl) phenol, a solvent and a reducing agent into a reaction kettle, carrying out reduction reaction for 0.5-25 h at the temperature of 20-120 ℃, and then carrying out post-treatment on reaction liquid to obtain a product 2-amino-4- (5-or 6-carboxyl benzimidazole-2-yl) phenol; (3) dehydration and cyclization polymerization: in a dehydrating agent polyphosphoric acid or Eaton reagent system, carrying out polymerization reaction for 3-30 hours at 120-180 ℃, and cooling, washing and drying a polymerization solution to obtain a polymer, namely poly (benzimidazole-benzoxazole) for short.

3. The method for synthesizing and polymerizing 2-amino-4- (5 or 6-carboxybenzimidazol-2-yl) phenol, which is a polybenzoxazole monomer containing an AB type with a benzimidazole structure, according to claim 2, wherein in the step (1), the solvent is one or more of tetrahydrofuran, methyltetrahydrofuran, dioxane, dimethylformamide, dimethyl sulfoxide, dimethyl pyrrolidone, ethylene glycol methyl ether and diethylene glycol methyl ether, aliphatic alcohols containing 1 to 6 carbons, and aliphatic ketones containing 3 to 6 carbons; the mol ratio of the raw materials of 3-nitro-4-hydroxybenzaldehyde, inorganic salt and 3,4-diaminobenzoic acid is 1:1.05 to 3:1.0 to 3.

4. The method for synthesizing and polymerizing 2-amino-4- (5 or 6-carboxybenzimidazole-2-yl) phenol as a polybenzoxazole monomer containing an AB type benzimidazole structure according to claim 2, wherein in the step (1), the temperature of inorganic salt is controlled to be within the range of +/-20 ℃ at room temperature, and the reaction temperature of imidazole ring formation reaction is 55-100 ℃; dropwise adding inorganic salt and water in a mass ratio of 1:2 to 1:15.

5. the method for synthesizing and polymerizing 2-amino-4- (5 or 6-carboxybenzimidazol-2-yl) phenol, which is a polybenzoxazole monomer containing an AB type with a benzimidazole structure, according to claim 2, wherein in the step (2), the reduction system used for the reduction of the nitro group comprises: a. an activated iron powder, water and a fatty alcohol system containing 1 to 5 carbon atoms; b. zinc powder in an organic acid system containing 1-3 carbon atoms; c. a sulfur-containing reducing salt and alkaline aqueous solution system; d. hydrogen, palladium on carbon and tetrahydrofuran, methyltetrahydrofuran, dioxane, fatty alcohol systems containing 1-6 carbons.

6. The method for synthesizing and polymerizing the AB type polybenzoxazole monomer containing the benzimidazole structure 2-amino-4- (5 or 6-carboxybenzimidazole-2-yl) phenol according to claim 5, wherein the reaction temperature of the reduction system a is 60 to 120 ℃, and the reaction time is 0.5 to 3 hours; the reaction temperature of the reduction system b is 20-120 ℃, and the reaction time is 5-15 h; the reaction temperature of the reduction system c is 55-100 ℃, and the reaction time is 1-12 h; the reaction temperature of the reduction system d is 20-60 ℃, and the reaction time is 2-25 h.

7. The method for synthesizing and polymerizing the polybenzoxazole monomer 2-amino-4- (5 or 6-carboxybenzimidazole-2-yl) phenol containing the benzimidazole structure AB as the monomer according to claim 5 or 6, wherein in the step (2), the organic alcohol solvent of the reduction system a is one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, ethylene glycol monomethyl ether and diethylene glycol methyl ether.

8. The method for synthesizing and polymerizing the polybenzoxazole monomer 2-amino-4- (5 or 6-carboxybenzimidazole-2-yl) phenol containing the benzimidazole structure AB according to claim 5 or 6, wherein in the step (2), the organic acid used in the nitro reduction reaction of the reduction system b is formic acid, acetic acid or propionic acid, the reaction temperature is 20 to 120 ℃, and the reaction time is 1 to 15 hours.

9. The method for synthesizing and polymerizing 2-amino-4- (5 or 6-carboxybenzimidazol-2-yl) phenol as a polybenzoxazole monomer containing an AB type with a benzimidazole structure according to claim 5 or 6, wherein in the step (2), the reducing salt containing sulfur used in the reduction nitro group reaction of the reducing system c is one or more of sodium sulfide, sodium polysulfide and sodium hydrosulfite; the alkaline aqueous solution used in the reduction nitro reaction is one or more of alkaline earth metal hydroxide and alkaline earth metal carbonate.

10. The method for synthesizing and polymerizing the polybenzoxazole monomer 2-amino-4- (5 or 6-carboxybenzimidazole-2-yl) phenol containing the benzimidazole structure AB according to claim 5 or 6, wherein the reaction pressure of the hydrogen reduction reaction in the reduction system d is normal pressure to 4MPa in the step (2).