WO2025227816A1 - Polybenzimidazole, polymer film, preparation method, and use - Google Patents

Abstract

The present invention relates to the technical field of polybenzimidazoles. Disclosed are a polybenzimidazole, a polymer film, a preparation method, and a use. The polybenzimidazole of the present invention comprises a structural unit A1 and a structural unit A2 and optionally comprises a structural unit B1 and a structural unit B2, wherein the structural unit A1 has a structure represented by formula (A1), the structural unit A2 has a structure represented by formula (A2), the structural unit B1 has a structure represented by formula (B1), and the structural unit B2 has a structure represented by formula (B2). The polybenzimidazole of the present invention has relatively high light transmittance and relatively low haze, and the film has relatively high elongation at break.

Description

Polybenzimidazole and polymer films, their preparation methods and applications Technical Field

This invention relates to the field of polybenzimidazole technology, specifically to polybenzimidazole and polymer films, their preparation methods, and applications.

Background Technology

Polybenzimidazole (PBI) is an aromatic heterocyclic polymer with repeating benzimidazole structural units in its main chain. PBI is a high-performance engineering plastic with excellent high-temperature resistance, chemical stability, and mechanical properties. It can withstand long-term use temperatures up to 375°C, exhibiting excellent heat resistance and good mechanical strength. PBI can be used in extreme high-temperature, harsh chemical, and plasma environments, or in applications requiring high durability and abrasion resistance.

Ultraviolet (UV) light has a short wavelength and high energy, which easily causes chemical bond breakage, leading to changes in material properties. Therefore, UV radiation is one of the main causes of photoaging in materials. Polybenzimidazole (PB) has good UV absorption and can be used as a UV absorbing film to absorb UV light and extend the lifespan of devices. However, PB film is usually yellowish-brown and dark in color, which results in poor light transmittance, greatly limiting its application in the optical field. PB film materials cannot be used in some fields with high transparency requirements, such as flexible displays and flexible backsheets for solar cells.

Polybenzimidazole materials typically have low solubility, and homopolymers of polybenzimidazole also suffer from excessive rigidity and overly regular molecular chain arrangement, resulting in materials with sufficient rigidity but insufficient toughness. Copolymerization can usually balance the properties of different structures, yielding materials with good overall performance. However, because copolymerization introduces molecular chain segments with different structures, the regular arrangement of the molecular chains is usually affected, leading to a decrease in the optical properties of the material, such as light transmittance and/or transparency.

Summary of the Invention

The purpose of this invention is to overcome the problems of existing polybenzimidazole materials, such as dark color, low light transmittance, and low toughness. This invention provides a polybenzimidazole, a polybenzimidazole film, its preparation method, and its applications. The polybenzimidazole film can maintain high light transmittance and good transparency while ensuring good mechanical properties, thus broadening the application fields of polybenzimidazole.

To achieve the above objectives, a first aspect of the present invention provides a polybenzimidazole comprising structural unit A1 and structural unit A2, and optionally structural unit B1 and structural unit B2, wherein structural unit A1 has the structure shown in formula (A1), structural unit A2 has the structure shown in formula (A2), structural unit B1 has the structure shown in formula (B1), and structural unit B2 has the structure shown in formula (B2).

Wherein, _R1 and _R2 are each independently any one of the following: a substituted or unsubstituted arylene, a substituted or unsubstituted cycloalkyl, a substituted or unsubstituted alkyl subchain, a substituted or unsubstituted alkenyl, a substituted or unsubstituted heterocyclic group, a divalent organic group consisting of _2-5 substituted or unsubstituted _monocyclic arylene groups spaced apart by at least one of single bonds, -O-, -C(=O ₎ -, -S(=O)-, -SO2-, substituted or unsubstituted _C2 - _C5 alkenyl, and substituted or unsubstituted _C1 -C5 alkenyl; and a divalent organic group consisting of 2-5 substituted or unsubstituted heterocyclic groups spaced apart by at least one of single bonds, -O-, -C(=O ₎ -, -S(=O)-, -SO2-, substituted or unsubstituted C2 _{- C5} alkenyl, and substituted or unsubstituted _C1 - _C5 alkenyl. ₂ are not the same; and _X1 and _X2 are each independently fluorinated hydrocarbon groups, and _X1 is different from _X2 when structural units B1 and B2 are present.

A second aspect of the present invention provides a method for preparing polybenzimidazole, the method comprising: polymerizing a monomer in a first solvent under polymerization reaction conditions;

The monomers include monomer a1, monomer b, monomer c and optional monomer a2, wherein monomer a1 and a2 each have the structure shown in formula (1-1), and monomer b and monomer c each have the structure shown in HOOC-R-COOH; monomer b is different from monomer c, and when monomer a2 is present, the X group in monomer a1 is different from the X group in monomer a2.

Wherein, R is selected from the group consisting of substituted or unsubstituted arylene, substituted or unsubstituted cycloalkyl, substituted or unsubstituted alkyl subchain, substituted or unsubstituted alkenyl, substituted or unsubstituted heterocyclic, a divalent organic group consisting of 2-5 substituted or unsubstituted monocyclic arylene groups spaced apart by at least one of single bond, -O-, -C(=O)-, -S(=O)-, _-SO2- , substituted or unsubstituted C2 _{- C5} alkenyl and substituted or unsubstituted _C1 - _C5 alkenyl, and a divalent organic group consisting of 2-5 substituted or unsubstituted heterocyclic groups spaced apart by at least one of single bond, -O-, -C(=O)-, -S(=O)-, _-SO2- , substituted or unsubstituted _C2 - _C5 alkenyl and substituted or unsubstituted _C1 - _C5 alkenyl; and X is selected from the group consisting of fluorinated alkylene groups.

A third aspect of the present invention provides polybenzimidazole prepared by the method described above.

A fourth aspect of the present invention provides a polymer membrane containing the polybenzimidazole described above.

The fifth aspect of the present invention provides a method for preparing a polymer membrane, the method comprising: contacting the polybenzimidazole of the present invention with a second solvent to obtain a solution A; preparing a liquid membrane from solution A with or without solid-liquid separation; and drying the liquid membrane to obtain a polymer membrane.

The sixth aspect of the present invention provides a polymer film prepared by the method described above.

The seventh aspect of the present invention provides the use of the above-described polybenzimidazole and/or the above-described polymer film as a light-transmitting or transparent material.

Through the above technical solution, the present invention can achieve the following beneficial effects:

(1) The polybenzimidazole of the present invention, after being made into a film, has a light color, is colorless and transparent or nearly colorless and transparent; under a standard C light source, it has high transmittance and low haze, and the film has high toughness (i.e., high elongation at break); the polybenzimidazole of the present invention can be used to prepare films with high transmittance, high transparency and high flexibility, thus expanding the application field of polybenzimidazole.

(2) The polybenzimidazole of the present invention, after being made into a film, has good absorption capacity for ultraviolet light and can delay the photoaging of the device.

(3) In some embodiments of the present invention, polybenzimidazole not only has a colorless and transparent or almost colorless and transparent appearance, high light transmittance, low haze and high toughness, but also has a high viscosity-average molecular weight and good solubility, which is beneficial for subsequent processing and application.

Attached Figure Description

Figure 1 is the 1H NMR spectrum of the polybenzimidazole prepared in Preparation Example 1;

Figure 2 shows the 1H NMR spectra of the polybenzimidazoles prepared in Preparation Example 2 and Preparation Example 4.

Figure 3 is the 1H NMR spectrum of the polybenzimidazole prepared in Preparation Example 5;

Figure 4 is the 1H NMR spectrum of the polybenzimidazole prepared in Preparation Example 6;

Figure 5 is the 1H NMR spectrum of the polybenzimidazole prepared in Preparation Example 7;

Figure 6 is the 1H NMR spectrum of the polybenzimidazole prepared in Preparation Examples 8-11;

Figure 7 shows the UV-Vis spectra of the polybenzimidazole films of Examples 1-3 and Comparative Examples 1 and 2.

Detailed Implementation

The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

A first aspect of the present invention provides a polybenzimidazole comprising (repeating) structural units A1 and A2, and optionally comprising (repeating) structural units B1 and B2, wherein structural unit A1 has the structure shown in formula (A1), structural unit A2 has the structure shown in formula (A2), structural unit B1 has the structure shown in formula (B1), and structural unit B2 has the structure shown in formula (B2).

Wherein, _R1 and _R2 are each independently any one of the following: a substituted or unsubstituted arylene, a substituted or unsubstituted cycloalkyl, a substituted or unsubstituted alkyl subchain, a substituted or unsubstituted alkenyl, a substituted or unsubstituted heterocyclic group, a divalent organic group consisting of _2-5 substituted or unsubstituted _monocyclic arylene groups spaced apart by at least one of single bonds, -O-, -C(=O)-, -S(=O)-, _-SO2- , substituted or unsubstituted _C2 - _C5 alkenyl, and substituted or unsubstituted _C1 -C5 alkenyl; and a divalent organic group consisting of 2-5 substituted or unsubstituted heterocyclic groups spaced apart by at least one of single bonds, -O-, -C(=O ₎ -, -S(=O)-, -SO2-, substituted or unsubstituted C2 _{- C5} alkenyl, and substituted or unsubstituted _C1 - _C5 alkenyl. ₂ are not the same; and _X1 and _X2 are each independently fluorinated hydrocarbon groups, and _X1 is different from _X2 when structural units B1 and B2 are present.

According to the present invention, preferably, _R1 and _R2 are each independently a substituted or unsubstituted _C6 - _C24 arylene, a substituted or unsubstituted _C5 - _C24 cycloalkylene, a substituted or unsubstituted _C2 -C20 alkylene, a substituted or unsubstituted _C2 - _C20 alkenylene, a substituted or unsubstituted _C3 - _C20 heterocyclic group, a divalent organic group consisting of 2-3 substituted or unsubstituted _monocyclic arylene groups spaced apart by at least one of single bonds, -O-, -C(=O)-, -S(=O)-, _-SO2- , substituted or unsubstituted _C2 - _C5 alkenylene, and substituted or unsubstituted _C1 - _C5 alkylene, and a divalent organic group consisting of single bonds, -O-, -C(=O)-, -S(=O)-, _-SO2- , substituted or unsubstituted _C2 -C Any one of the following: a divalent organic group consisting of at least one of a ₅ -olefinic group and at least two or three spaced-apart substituted or unsubstituted heterocyclic groups of _C1 - _C5 alkylene groups.

In this invention, the substituted or unsubstituted arylene group can be a substituted or unsubstituted _C6 - _C24 arylene group, such as a substituted or unsubstituted _C6 - _C14 arylene group; wherein the arylene group can be a monocyclic arylene group or a polycyclic arylene group. For example, the arylene group can be phenylene or naphthylene. When substituted, the substituent can be a hydroxyl group, a halogen (e.g., F, Cl, Br, and I), or a substituted or unsubstituted C1- _C5 alkyl group; wherein the substituent in the C1 _{-C5 alkyl group} can be a halogen (e.g., F, Cl, Br, and I), such as trifluoromethyl- _CF3 .

In this invention, the substituted or unsubstituted cycloalkylene group can be a substituted or unsubstituted _C5 - _C24 cycloalkylene group, such as a substituted or unsubstituted _C5 - _C10 cycloalkylene group. For example, the cycloalkylene group can include, but is not limited to, substituted or unsubstituted cyclopentylene, cyclohexylene, cycloheptylene, cyclooctylene, cyclononylene, etc. When substituted, the substituent of the cycloalkylene group can be a C1 _{- C5} alkylene group or a C1 _{-C5 alkylene} group substituted with a halogen (e.g., F, Cl, Br, and I), such as methyl, ethyl, trifluoromethyl- _CF3 , etc.

In this invention, the substituted or unsubstituted sub-alkyl group can be a substituted or unsubstituted _C2 - _C20 sub-alkyl group, such as a substituted or unsubstituted _C2 - _C12 sub-alkyl group. For example, the sub-alkyl group can include, but is not limited to, substituted or unsubstituted ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, etc. When substituted, the substituent of the sub-alkyl group can be a halogen (e.g., F, Cl, Br, and I) or a substituted or unsubstituted _C1 - _C5 alkyl group, wherein the substituent in the C1 _{- C5} alkyl group can be a halogen (e.g., F, Cl, Br, and I), such as trifluoromethyl- _CF3 . For example, the substituted sub-alkyl group can be a fluorinated alkylene, such as -C( _CF3 ) _2- .

In this invention, the substituted or unsubstituted alkenyl group can be a substituted or unsubstituted _C2 - _C20 alkenyl group, such as a substituted or unsubstituted _C2 - _C10 alkenyl group. For example, the alkenyl group can include, but is not limited to, substituted or unsubstituted vinylidene, propenylidene, butenylidene, etc. When substituted, the substituent of the alkenyl group can be a halogen (e.g., F, Cl, Br, and I), a substituted or unsubstituted C1- _C5 alkyl group, or _a substituted or unsubstituted phenyl group, wherein the substituent in the C1- _{C5 alkyl} group can be a halogen (e.g., F, Cl, Br, and I), such as trifluoromethyl- _CF3 , and wherein the substituent in the phenyl group can be a halogen (e.g., F, Cl, Br, and I) and the above substituted or unsubstituted _C1 - _C5 alkyl groups.

In this invention, the substituted or unsubstituted heterocyclic group can be a substituted or unsubstituted _C3 - _C20 heterocyclic group, such as a substituted or unsubstituted _C3 - _C10 heterocyclic group; wherein, the heteroatom in the heterocyclic group can be at least one of N, O, and S, preferably N. The number of heteroatoms in the substituted or unsubstituted heterocyclic group can be 1-4, preferably 1-3. The heterocyclic group can be a monocyclic heterocyclic group or a polycyclic heterocyclic group. The monocyclic heterocyclic group can be a _C3 - _C8 heterocyclic group. The polycyclic heterocyclic group can be composed of at least two monocyclic heterocyclic groups, or composed of at least one monocyclic heterocyclic group and at least one monocyclic arylene group, such as phenylene. The monocyclic heterocyclic group includes, but is not limited to, pyridinyl, pyrimidinyl, triazineyl, pyrroleyl, imidazolyl, etc. When substituted, the substituent can be a hydroxyl group, a halogen (e.g., F, Cl, Br and I), or a substituted or unsubstituted _C1 - _C5 alkyl group; wherein the substituent in the C1- _{C5 alkyl} group can be a halogen (e.g., F, Cl, Br and I), such as trifluoromethyl- _CF3 .

In this invention, _R1 and _R2 can each independently be a divalent organic group consisting of _2-5 substituted or unsubstituted monocyclic aryl groups spaced apart by at least one of a single bond, -O-, -C(=O)-, -S(=O)-, -SO2-, a substituted or unsubstituted _C2 - _C5 alkenyl group and a substituted or unsubstituted C1- _C5 alkyl group; wherein the substituent in the _{C1 - C5} alkyl group can be a halogen (e.g., F, Cl, Br and I), such as trifluoromethyl- _CF3 , and wherein the substituent in the _C2 - _C5 alkenyl group can be a phenyl group. In this case, the "substituted or unsubstituted monocyclic aryl group" can be a substituted or unsubstituted phenylene group; when substituted, the substituent can be a hydroxyl group, a halogen (e.g., F, Cl, Br, and I), or a substituted or unsubstituted C1- _C5 alkyl group; wherein the substituent in the C1 _{-C5 alkyl group} can be a halogen (e.g., F, Cl, Br, and I), such as trifluoromethyl- _CF3 . In this case, _R1 and _R2 can each independently be one of the following divalent organic groups:

In this invention, _R1 and _R2 can each independently be a divalent organic group consisting of 2-5 substituted or unsubstituted heterocyclic groups spaced apart by at least one of a single bond, -O-, -C(=O)-, -S(=O)-, _-SO2- , a substituted or unsubstituted _C2 - _C5 alkenyl group, and a substituted or unsubstituted C1- _{C5 alkyl group, wherein the substituent in the C1-C5 alkyl group can} be a halogen (e.g., F, Cl, Br, and I), such as trifluoromethyl- _CF3 , and wherein the substituent in the C2 _{- C5} alkenyl group can be a phenyl group. In this case, the "substituted or unsubstituted heterocyclic group" is the substituted or unsubstituted heterocyclic group described above. In this case, _R1 and _R2 can each independently be, for example, the following divalent organic groups:

In this invention, more preferably, the heterocyclic group can be selected from the group consisting of pyridyl, pyrroleyl, furanyl, quinolinyl, thiophenyl, pyranyl, and pyrazinyl.

According to the present invention, preferably, _X1 and _X2 are each independently a C1 _{- C10} fluorinated alkylene group; more preferably, they are C1 _{- C5} fluorinated alkylene groups. In some embodiments, preferably, _X1 is -C( _CF3 ) _2- . In some embodiments, preferably, _X1 and _X2 are each -C( _CF3 ) _2- , i.e., structural unit B1 and structural unit B2 are not present in this case.

According to some embodiments of the present invention, the polybenzimidazole does not include structural units B1 and B2.

According to the present invention, when the polybenzimidazole includes structural unit B1 and structural unit B2, the ratio of the total number of moles of structural unit A1 and structural unit A2 to the total number of moles of structural unit B1 and structural unit B2 in the polymer can be any suitable ratio, for example, it can be 0.01:1-100:1.

According to the present invention, preferably, _R1 and _R2 are each independently selected from the groups shown in formulas (3)-(24):
Where n is an integer from 2 to 8, for example, n can be 2, 3, 4, 5, 6, 7 or 8.

According to the present invention, preferably, _R1 is a group shown in formula (3) and _R2 is any one of the groups shown in formulas (4) to (24).

In some preferred embodiments, _R1 is the group shown in formula (3) and _R2 is any one of the groups shown in formula (4), formula (13) and formula (24).

According to some preferred embodiments of the present invention, the structural unit A1 can be One of them; and the structural unit A2 can be one of them; One of them.

According to some preferred embodiments of the present invention, the structural unit A1 can be And the structural unit A2 can be One of them.

According to the present invention, preferably, the molar ratio of structural unit A1 to structural unit A2 can be 0.02:1-50:1, and more preferably 0.05:1-20:1. For example, the molar ratio of structural unit A1 to structural unit A2 can be 0.02:1, 0.03:1, 0.04:1, 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1, 0.1:1, 0.15:1, 0.2:1, 0.25:1, 0.3:1, 0.4:1, 0.5:1, 0.7:1, 1:1, 1.5:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 15:1, 20:1, 30:1, 40:1, 50:1, or any range of any two of the above values.

According to the present invention, preferably, the viscosity-average molecular weight of the polybenzimidazole can be 2000-500000 g/mol; more preferably 10000-400000 g/mol; even more preferably 30000-400000 g/mol; for example, it can be 40000-350000 g/mol or 100000-350000 g/mol. For example, the viscosity-average molecular weight of the polybenzimidazole can be 2000 g/mol, 4000 g/mol, 6000 g/mol, 7000 g/mol, 8000 g/mol, 9000 g/mol, 10000 g/mol, 11000 g/mol, 12000 g/mol, 13000 g/mol, 14000 g/mol, 15000 g/mol, 16000 g/mol, 18000 g/mol, 20000 g/mol, 25000 g/mol, 30000 g/mol, 40000 g/mol, 5 0000 g/mol, 60000 g/mol, 70000 g/mol, 80000 g/mol, 90000 g/mol, 100000 g/mol, 120000 g/mol, 140000 g/mol, 160000 g/mol, 180000 g/mol, 200000 g/mol, 250000 g/mol, 300000 g/mol, 350000 g/mol, 400000 g/mol, 450000 g/mol, 500000 g/mol, and any range of any two of the above values.

According to the present invention, preferably, the polybenzimidazole has good solubility in a good solvent; wherein the good solvent may be selected from any one or more of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

According to the present invention, preferably, at 80°C and a stirring linear speed of 0.5 m/s, the time required for 1.0 g of the polybenzimidazole of the present invention to completely dissolve in 30 mL of dimethyl sulfoxide is 0.3-8 h, more preferably 0.3-4 h, and more preferably 0.3-2 h. In the present invention, the stirring linear speed is the linear speed at the end of the stirring paddle or the end of the rotor.

According to the present invention, preferably, the intrinsic viscosity of the polybenzimidazole is 0.1-6.5 dL/g; more preferably, it is 0.5-6 dL/g; for example, it can be 2-5 dL/g. For example, the intrinsic viscosity of the polybenzimidazole can be 0.1 dL/g, 0.2 dL/g, 0.3 dL/g, 0.4 dL/g, 0.5 dL/g, 0.6 dL/g, 0.7 dL/g, 0.8 dL/g, 0.9 dL/g, 1 dL/g, 1.1 dL/g, 1.2 dL/g, 1.3 dL/g, 1.4 dL/g, 1.5 dL/g, 1.6 dL/g, 1.7 dL/g, 1.8 dL/g, 1.9 dL/g, 2.0 dL/g, 2.2 dL/g, 2.4 dL/g, or 2.6 dL/g. 2.8 dL/g, 3.0 dL/g, 3.2 dL/g, 3.4 dL/g, 3.6 dL/g, 3.8 dL/g, 4.0 dL/g, 4.1 dL/g, 4.2 dL/g, 4.3 dL/g, 4.4 dL/g, 4.5 dL/g, 4.6 dL/g, 4.7 dL/g, 4.8 dL/g, 4.9 dL/g, 5.0 dL/g, 5.2 dL/g, 5.4 dL/g, 5.6 dL/g, 5.8 dL/g, 6.0 dL/g, 6.5 dL/g, and any range of any two of the above values.

The polybenzimidazole of the present invention is a random copolymer in which structural units A1 and A2, and optionally included structural units B1 and B2, are randomly distributed in the polybenzimidazole polymer chain.

The polybenzimidazole of the present invention can be prepared by methods commonly known in the art for preparing polybenzimidazole. In some embodiments, preferably, the polybenzimidazole of the present invention can be prepared by the method for preparing polybenzimidazole provided in the second aspect of the present invention.

A second aspect of the present invention provides a method for preparing polybenzimidazole, the method comprising: polymerizing a monomer in a first solvent under polymerization reaction conditions;

The monomers include monomer a1, monomer b, monomer c and optional monomer a2, wherein monomer a1 and a2 each have the structure shown in formula (1-1), and monomer b and monomer c each have the structure shown in HOOC-R-COOH; monomer b is different from monomer c, and when monomer a2 is present, the X group in monomer a1 is different from the X group in monomer a2.

Wherein, R is selected from the group consisting of substituted or unsubstituted arylene, substituted or unsubstituted cycloalkyl, substituted or unsubstituted alkyl subchain, substituted or unsubstituted alkenyl, substituted or unsubstituted heterocyclic, a divalent organic group consisting of 2-5 substituted or unsubstituted monocyclic arylene groups spaced apart by at least one of single bond, -O-, -C(=O)-, -S(=O)-, _-SO2- , substituted or unsubstituted C2 _{- C5} alkenyl and substituted or unsubstituted _C1 - _C5 alkenyl, and a divalent organic group consisting of 2-5 substituted or unsubstituted heterocyclic groups spaced apart by at least one of single bond, -O-, -C(=O)-, -S(=O)-, _-SO2- , substituted or unsubstituted _C2 - _C5 alkenyl and substituted or unsubstituted _C1 - _C5 alkenyl; and X is a fluorinated alkylene group.

According to the present invention, preferably, X is a _C1 - _C10 fluorinated alkylene group; more preferably, it is a C1 _{- C5} fluorinated alkylene group; and even more preferably, X is -C( _CF3 ) _2- .

According to the present invention, preferably, R is selected from substituted or unsubstituted _C6 - _C24 arylene, substituted or unsubstituted _C5 - _C24 cycloalkylene, substituted or unsubstituted _C2 - _C20 alkylene, substituted or unsubstituted _C2 - _C20 alkenylene, substituted or unsubstituted _C3 - _C20 heterocyclic, a divalent organic group consisting of 2-3 substituted or unsubstituted monocyclic arylene groups spaced apart by at least one of single bond, -O-, -C(=O)-, -S(=O)-, _-SO2- , substituted or unsubstituted _C2 - _C5 alkenylene, and substituted or unsubstituted _C1 - _C5 alkylene, and a divalent organic group consisting of single bond, -O-, -C(=O)-, -S(=O)-, _-SO2- , substituted or unsubstituted C2- _C5 alkenylene, and substituted or unsubstituted _{C1-C5 alkylene} . The group consisting of at least one of the _five alkylene groups, consisting of two to three spaced-apart substituted or unsubstituted heterocyclic groups, forming a divalent organic group.

In this invention, the substituted or unsubstituted arylene group, substituted or unsubstituted cycloalkyl group, substituted or unsubstituted sub-alkyl group, substituted or unsubstituted alkenyl group, substituted or unsubstituted heterocyclic group and the divalent organic group mentioned in the above method are as described in the first aspect, and will not be repeated here.

According to the present invention, preferably, R is selected from the groups shown in formulas (3)-(24):
Where n is an integer from 2 to 8, for example, n can be 2, 3, 4, 5, 6, 7 or 8.

According to the present invention, preferably, R in monomer b is a group shown in formula (3) and R in monomer c is any one of the groups shown in formula (4) to formula (24).

According to the present invention, more preferably, R in monomer b is a group shown in formula (3) and R in monomer c is any one of the groups shown in formula (4), formula (13) and formula (24).

According to the present invention, preferably, HOOC-R-COOH is selected from compounds of formula (3-1) to formula (24-1);

Where n is an integer from 2 to 8, for example, n can be 2, 3, 4, 5, 6, 7 or 8.

According to the present invention, preferably, monomer b is a compound of formula (3-1) and monomer c is at least one of compounds of formula (4-1) to formula (24-1).

According to the present invention, more preferably, monomer b is a compound of formula (3-1) and monomer c is a compound of formula (4-1), formula (13-1) or formula (24-1).

According to the present invention, preferably, the molar ratio of the total amount of monomers b and c to the amount of monomers a1 and a2 is 0.9:1-1.1:1, for example, 0.9:1, 0.95:1, 1:1, 1.05:1, 1.1:1, and any two of the above ranges.

According to the present invention, preferably, the molar ratio of monomer b to monomer c is 0.02:1-50:1, more preferably 0.05-20:1; for example, the molar ratio of monomer b to monomer c can be 0.02:1, 0.03:1, 0.04:1, 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1, 0.1:1, 0.15:1, 0.2:1, 0.25:1, 0.3:1, 0.4:1, 0.5:1, 0.7:1, 1:1, 1.5:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 15:1, 20:1, 30:1, 40:1, 50:1, and any two of the above ranges.

According to the present invention, the conditions for the polymerization reaction can be conventional polymerization conditions in the art. Preferably, the conditions for the polymerization reaction may include: a polymerization temperature of 100-220°C (e.g., 100°C, 110°C, 120°C, 140°C, 160°C, 180°C, 200°C, 220°C, and any range of any two of the above points), and a polymerization time of 1-24 hours (e.g., 1 hour, 2 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 10 hours, 15 hours, 20 hours, 24 hours, and any range of any two of the above points). Preferably, the polymerization reaction is carried out under stirring.

According to the present invention, preferably, the polymerization reaction is carried out under a non-reactive atmosphere. For example, the non-reactive atmosphere may be provided by at least one of nitrogen, argon, helium and neon, preferably nitrogen.

According to the present invention, preferably, the first solvent may include at least one of polyphosphoric acid, methanesulfonic acid, phosphorus pentoxide and phosphoric acid.

According to the present invention, preferably, the amount of the first solvent used is 2-20 kg relative to each 1 mol of monomers a1 and a2, for example, it can be 2 kg, 4 kg, 6 kg, 8 kg, 10 kg, 15 kg, 20 kg, and any two of the above ranges.

In the method of the present invention, a polymer solution is obtained after polymerization. According to the present invention, the method may further include a step of extracting the polymer from the polymer solution obtained after polymerization. The polymer extraction method may be a polymer extraction method commonly used in the art. For example, the method may further include contacting the polymer-containing polybenzimidazole solution obtained after polymerization with a precipitant to obtain polybenzimidazole as a precipitate. The precipitant may be water and/or an alkaline solution. The alkaline solution may be at least one of an aqueous solution of an alkali metal hydroxide, an aqueous solution of an alkaline earth metal hydroxide, an aqueous solution of an alkali metal salt, an aqueous solution of an alkaline earth metal salt, and ammonia; more preferably at least one of ammonia, a saturated aqueous solution of sodium carbonate, an aqueous solution of potassium carbonate, an aqueous solution of sodium bicarbonate, an aqueous solution of potassium bicarbonate, an aqueous solution of magnesium carbonate, an aqueous solution of sodium hydroxide, and an aqueous solution of potassium hydroxide. The obtained polybenzimidazole may then be washed with the alkaline solution and/or water, for example, until neutral. The obtained polybenzimidazole may then be dried, for example, by heating in a vacuum oven. For example, polybenzimidazole can be placed in a vacuum oven at 40-120℃ for 2-48 hours, or in a vacuum oven at 80℃ for 24 hours.

A third aspect of the present invention provides a polybenzimidazole prepared by the method described above. In some preferred embodiments, the polybenzimidazole of the first aspect of the present invention was prepared by the method described above.

A fourth aspect of the present invention provides a polymer membrane containing polybenzimidazole, wherein the polybenzimidazole is the polybenzimidazole described above herein. In this invention, the polymer membrane may be in the form of a planar membrane. Those skilled in the art can suitably select the membrane thickness, for example, the membrane thickness may be from several nanometers to several millimeters. In some embodiments, the thickness of the polymer membrane of the present invention may be, for example, from 0.02 micrometers to 0.5 millimeters.

According to the present invention, preferably, the elongation at break of the polymer film can be 5-100%, more preferably 6-80%. In some embodiments, more preferably, the elongation at break of the polymer film can be 8-60%, more preferably 20-50%. For example, the elongation at break of the polymer film can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 14%, 16%, 18%, 20%, 22%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 70%, 80%, 90%, 100%, and any range consisting of two of the above values.

According to the present invention, the transmittance of the polymer film can be 70-95%, preferably 75-95%, more preferably 80-95%, and even more preferably 83-90%, for example, 84-90%. For example, the transmittance of the polymer film can be 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, and any range of two of the above values. According to the present invention, the haze of the polymer film can be 0.05-20%, preferably 0.1-16%, more preferably 0.2-8% or 0.3-6%. For example, the haze of the polymer film can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, or any range of two of the above values. In this invention, the transmittance and haze values are obtained using a transmittance-haze meter according to GB/T 2410-2008 standard, using a standard C light source and a 25-micron thick film.

In this invention, the thickness of the membrane is obtained by measuring the thickness at 5 points on the membrane using a thickness gauge and taking the arithmetic average.

According to the present invention, the polymer film may further include inorganic additives and/or polymer additives. Preferably, the inorganic additives may include at least one selected from nano-silica, nano-titanium dioxide, graphene, nano-tin oxide, carbon nanotubes, fullerenes, and nano-zirconia. Preferably, the polymer additives may include at least one selected from polyimide, polysulfone, polyetheretherketone, polybenzoxazole, polyethylene terephthalate, ethylene-vinyl alcohol copolymer, polyolefin elastomer, polyethylene glycol, and polyethylene oxide.

According to the present invention, preferably, the content of the inorganic additive can be 0-10 parts by weight and the content of the polymer additive can be 0-100 parts by weight relative to 100 parts by weight of polybenzimidazole.

The polymer membrane of the present invention can be prepared by methods commonly known in the art for preparing membranes. In some embodiments, the polymer membrane can be prepared by: preparing a solution of polybenzimidazole; preparing a liquid membrane from the solution A; and drying the liquid membrane to obtain the polymer membrane.

The fifth aspect of the present invention provides a method for preparing a polymer membrane, the method comprising: contacting the polybenzimidazole described above with a second solvent to obtain a solution A; preparing a liquid membrane from solution A with or without solid-liquid separation; and drying the liquid membrane to obtain a polymer membrane.

In this invention, solution A can be prepared into a liquid membrane by solid-liquid separation and then using the filtrate, or it can be directly prepared into a liquid membrane without solid-liquid separation. Those skilled in the art can reasonably choose whether to perform solid-liquid separation based on the solid content and solubility in solution A.

According to the present invention, preferably, the second solvent may include at least one selected from dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, methanesulfonic acid, formic acid, phosphoric acid, polyphosphoric acid, sulfuric acid, and trichlorotoluene.

According to the present invention, preferably, the content of polybenzimidazole can be 0.1-20% by weight, based on the total weight of solution A. In some embodiments, the content of polybenzimidazole in solution A can be 0.1% by weight, 0.2% by weight, 0.4% by weight, 0.6% by weight, 1% by weight, 2% by weight, 3% by weight, 4% by weight, 5% by weight, 6% by weight, 8% by weight, 10% by weight, 12% by weight, 14% by weight, 16% by weight, 18% by weight, 20% by weight, or any range of two of the above values.

According to the present invention, preferably, the contact conditions may include: a contact temperature of 30-160°C (e.g., 30°C, 50°C, 60°C, 80°C, 100°C, 140°C, 160°C, and any two of the above ranges), and a contact time of 10 min-24 h (10 min, 30 min, 1 h, 2 h, 3 h, 4 h, 10 h, 20 h, 24 h, and any two of the above ranges). The contact may be carried out under stirring, preferably with a stirring linear velocity of 0.05-1 m/s, more preferably 0.1-0.8 m/s.

In this invention, the solid-liquid separation method can be a commonly used solid-liquid separation method in the art, such as filtration. Preferably, the solid-liquid separation method is sand core funnel filtration; more preferably, the pore size of the sand core funnel is 30-50 μm.

In this invention, the liquid film can be prepared using any method commonly known in the art, including but not limited to blade coating, spray coating, slot coating, and natural flow coating. For example, a solution, whether or not it has undergone solid-liquid separation, can be poured onto a substrate and then a liquid film can be formed using a blade coating method. The substrate can be a rigid substrate such as a glass plate, stainless steel plate, or polytetrafluoroethylene plate; or a flexible substrate such as a polyimide membrane, polyethylene terephthalate membrane, polysulfone membrane, cellulose membrane, or nonwoven fabric.

In this invention, after obtaining the liquid film, the liquid film can be dried. Those skilled in the art can appropriately select the drying conditions for the liquid film. According to the invention, preferably, the drying conditions may include: a drying temperature of 60-160°C and a drying time of 0.5-24 hours. In some embodiments, the drying can be carried out in air.

According to the present invention, preferably, the method further includes: contacting an inorganic additive and/or a polymeric additive with a second solvent to obtain a solution B; mixing solution B with solution A to obtain a solution C; then performing solid-liquid separation on solution C to form a liquid membrane; and drying the liquid membrane to obtain a polymer membrane. The inorganic additive and/or polymeric additive may be the inorganic additive and/or polymeric additive mentioned in the fourth aspect of the present invention, and will not be elaborated further here. In this manner, a polymer membrane further comprising the inorganic additive and/or polymeric additive can be prepared.

According to the present invention, preferably, the conditions for contacting the inorganic additive and/or polymer additive with the second solvent may include: a temperature of 30-160°C and a time of 0.5-24 h. The contact method may include stirring and/or ultrasonic treatment.

According to the present invention, optionally, in some embodiments, a co-solvent may be added during the preparation of solution A to promote the dissolution of polybenzimidazole. The co-solvent may be selected from any one or more of lithium chloride, sodium chloride, and lithium trifluoromethanesulfonylimide, for example.

The sixth aspect of the present invention provides a polymer film prepared by the method described above.

The polybenzimidazole and polymer film of the present invention have good light transmittance and transparency, and can also have good mechanical properties (including tensile strength and/or elongation at break). Therefore, the seventh aspect of the present invention provides the application of the above-described polybenzimidazole and/or the above-described polymer film as light-transmitting or transparent materials.

According to the present invention, preferably, the light-transmitting or transparent material includes, but is not limited to, flexible backsheets for solar cells, flexible display substrates, anti-counterfeiting packaging, high-temperature resistant transparent components for electronic devices/sensors, high-temperature resistant optical lenses, high-temperature protective masks, flexible printed circuits, and aircraft cockpit protective covers.

Example

The present invention will be described in detail below through examples. In the following examples, all raw materials are commercially available products.

3,3'-Diaminobenzidine (Sigma-Aldrich, 99%); 2,2-bis(3,4-diaminophenyl)hexafluoropropane (CAS No.: 61005-79-6, Puyang Runtu New Materials Co., Ltd., Henan, China, 98%); 4,4-dicarboxylic acid diphenyl ether (J&K Technology Co., Ltd., 98%); isophthalic acid (J&K Technology Co., Ltd., 98%); cyclohexanedicarboxylic acid (Beijing Inokai Technology Co., Ltd., 98%); azelaic acid (Beijing Inokai Technology Co., Ltd., 98%); 3,5-pyridinedicarboxylic acid (J&K Technology Co., Ltd., 98%). Limited Company, 97%); 4,4'-methylenebisbenzoic acid (J&K Technology Co., Ltd., 98%); 4,4'-(2,2-diphenylethylene-1,1-diyl)dibenzoic acid (Annegi Chemical, 98%); methanesulfonic acid (J&K Technology Co., Ltd., 98%); phosphorus pentoxide (J&K Technology Co., Ltd., 98%); sodium carbonate (J&K Technology Co., Ltd., 98%); N,N-dimethylacetamide (Beijing Inokai Technology Co., Ltd., 99.5%); dimethyl sulfoxide (J&K Technology Co., Ltd., 98%).

All reagents were used directly without secondary purification.

The molar ratio of structural unit A1 to structural unit A2 in polybenzimidazole was determined by quantitative analysis using 1H NMR spectroscopy. The specific testing method involved performing the test on a Bruke DMX400 NMR spectrometer (using deuterated reagent ^d⁴ - _CH₃OH and tetramethylsilane (TMS) as an internal standard) and determining the molar ratio of structural unit A1 to structural unit A2 based on the ratio of their respective characteristic peak areas.

Preparation Example 1

This preparation example illustrates the preparation process of polybenzimidazole.

Under a nitrogen atmosphere, polyphosphoric acid (60 g), 2,2-bis(3,4-diaminophenyl)hexafluoropropane (10 mmol), 4,4-dicarboxylic acid (8 mmol), and isophthalic acid (2 mmol) were added to a reactor, and the mixture was heated to 200 °C for 4 h under stirring. After the reaction, the resulting solution was poured into a saturated sodium bicarbonate aqueous solution to precipitate the polymer. The polymer was then repeatedly washed with water and sodium bicarbonate solution until neutral. Finally, the polymer was placed in a vacuum oven at 80 °C for 24 h to obtain polybenzimidazole.

The structural formula of structural unit A1 in the prepared polybenzimidazole is as follows: The structural formula of structural unit A2 is as follows

The 1H NMR spectrum of polybenzimidazole is shown in Figure 1. The molar ratio of structural unit A1 to structural unit A2 is calculated to be 4.465:1 from the 1H NMR spectrum of polybenzimidazole.

Preparation Example 2

This preparation example illustrates the preparation process of polybenzimidazole.

Under a nitrogen atmosphere, methanesulfonic acid (54 g), phosphorus pentoxide (5 g), 2,2-bis(3,4-diaminophenyl)hexafluoropropane (10 mmol), cyclohexanedicarboxylic acid (2 mmol), and 4,4-dicarboxylic acid diphenyl ether (8 mmol) were added to a reactor. The mixture was stirred and heated to 140 °C for 6 h. After the reaction, the resulting solution was poured into a saturated sodium bicarbonate aqueous solution to precipitate the polymer. The polymer was then repeatedly washed with water and sodium bicarbonate solution until neutral. Finally, the polymer was placed in a vacuum oven at 80 °C for 24 h.

The structural formula of structural unit A1 in the prepared polybenzimidazole is as follows: The structural formula of structural unit A2 is as follows

The 1H NMR spectrum of polybenzimidazole is shown in Figure 2. The molar ratio of structural unit A1 to structural unit A2 was calculated to be 2.817:1 from the 1H NMR spectrum of polybenzimidazole.

Preparation Example 3

Polybenzimidazole was prepared according to the method of Preparation Example 2, except that the amount of cyclohexanedicarboxylic acid used was 1 mmol and the amount of 4,4-dicarboxylic diphenyl ether used was 9 mmol.

The 1H NMR spectrum of polybenzimidazole is similar to that of Preparation Example 2 and will not be shown again. The molar ratio of structural unit A1 to structural unit A2 was calculated to be 3.657:1 from the 1H NMR spectrum of polybenzimidazole.

Preparation Example 4

Polybenzimidazole was prepared according to the method of Preparation Example 2, except that "2 mmol cyclohexanedicarboxylic acid" was replaced with "7 mmol azelaic acid", and the amount of 4,4-dicarboxylic diphenyl ether was 3 mmol.

The structural formula of structural unit A1 in the prepared polybenzimidazole is as follows: The structural formula of structural unit A2 is as follows

The 1H NMR spectrum of polybenzimidazole is shown in Figure 2. The molar ratio of structural unit A1 to structural unit A2 was calculated to be 0.524:1 from the 1H NMR spectrum of polybenzimidazole.

Preparation Example 5

Polybenzimidazole was prepared according to the method of Preparation Example 2, except that "2 mmol cyclohexanedicarboxylic acid" was replaced with "5 mmol 4,4'-(2,2-diphenylethylene-1,1-diyl)dibenzoic acid", and the amount of 4,4-dicarboxylic acid diphenyl ether was 5 mmol. The reaction temperature was 120 °C, and the reaction time was 4 hours.

The structural formula of structural unit A1 in the prepared polybenzimidazole is as follows: The structural formula of structural unit A2 is as follows

The 1H NMR spectrum of polybenzimidazole is shown in Figure 3. The molar ratio of structural unit A1 to structural unit A2 is calculated to be 1.028:1 from the 1H NMR spectrum of polybenzimidazole.

Preparation Example 6

Polybenzimidazole was prepared according to the method of Preparation Example 1, except that "8 mmol 4,4-dicarboxylic acid diphenyl ether" was replaced with "1 mmol 3,5-pyridinedicarboxylic acid", and the amount of isophthalic acid was 9 mmol; the reaction time was 6 h.

The structural formula of structural unit A1 in the prepared polybenzimidazole is as follows: The structural formula of structural unit A2 is as follows

The 1H NMR spectrum of polybenzimidazole is shown in Figure 4. The molar ratio of structural unit A1 to structural unit A2 is calculated to be 0.09:1 based on the 1H NMR spectrum of polybenzimidazole.

Preparation Example 7

Polybenzimidazole was prepared according to the method of Preparation Example 1, except that "2 mmol isophthalic acid" was replaced with "5 mmol 4,4'-methylenebisbenzoic acid", and the amount of 4,4-dicarboxylic acid diphenyl ether was 5 mmol; the reaction time was 6 h.

The structural formula of structural unit A1 in the prepared polybenzimidazole is as follows: The structural formula of structural unit A2 is as follows

The 1H NMR spectrum of polybenzimidazole is shown in Figure 5. The molar ratio of structural unit A1 to structural unit A2 is calculated to be 1.08:1 based on the 1H NMR spectrum of polybenzimidazole.

Preparation Example 8

Polybenzimidazole was prepared according to the method of Preparation Example 1, except that "8 mmol 4,4-dicarboxylic acid diphenyl ether" was replaced with "1 mmol 2,2'-bipyridine-4,4'-dicarboxylic acid", and the amount of isophthalic acid was 9 mmol; the reaction time was 8 h.

The structural formula of structural unit A1 in the prepared polybenzimidazole is as follows: The structural formula of structural unit A2 is as follows

The 1H NMR spectrum of polybenzimidazole is shown in Figure 6. The molar ratio of structural unit A1 to structural unit A2 is calculated to be 0.05:1 based on the 1H NMR spectrum of polybenzimidazole.

Preparation Example 9

Polybenzimidazole was prepared according to the method of Preparation Example 2, except that "8 mmol 4,4-dicarboxylic acid diphenyl ether" was replaced with "8 mmol azelaic acid", and the reaction temperature was 120°C and the reaction was carried out for 6 h.

The structural formula of structural unit A1 in the prepared polybenzimidazole is as follows: The structural formula of structural unit A2 is as follows

The 1H NMR spectrum of polybenzimidazole is shown in Figure 6.

Preparation Example 10

Polybenzimidazole was prepared according to the method of Preparation Example 2, except that "2 mmol cyclohexanediol" was replaced with "2 mmol perfluorooctanoic acid"; and the reaction temperature was 120°C and the reaction was carried out for 6 hours.

The structural formula of structural unit A1 in the prepared polybenzimidazole is as follows: The structural formula of structural unit A2 is as follows

The 1H NMR spectrum of polybenzimidazole is shown in Figure 6.

Preparation Example 11

Polybenzimidazole was prepared according to the method of Preparation Example 1, except that "8 mmol 4,4-dicarboxylic diphenyl ether" was replaced with "3 mmol 2,2'-bis(4-carboxyphenyl)hexafluoropropane", and the amount of isophthalic acid was 7 mmol; the reaction time was 8 h.

The structural formula of structural unit A1 in the prepared polybenzimidazole is as follows: The structural formula of structural unit A2 is as follows

The 1H NMR spectrum of polybenzimidazole is shown in Figure 6.

Comparative Preparation Example 1

Polybenzimidazole was prepared according to the method of Preparation Example 1, except that "2,2-bis(3,4-diaminophenyl)hexafluoropropane" was replaced with an equimolar amount of "3,3'-diaminobenzidine".

Comparative Preparation Example 2

Polybenzimidazole was prepared according to the method of Preparation Example 2, except that "2,2-bis(3,4-diaminophenyl)hexafluoropropane" was replaced with an equimolar amount of "3,3'-diaminobenzidine".

Comparative preparation example 3

Polybenzimidazole was prepared according to the method of Preparation Example 2, except that the amount of cyclohexanedicarboxylic acid used was 10 mmol, and 4,4-dicarboxylic diphenyl ether was not added.

Comparative preparation example 4

Polybenzimidazole was prepared according to the method of Preparation Example 2, except that the amount of 4,4-dicarboxylic acid diphenyl ether was 10 mmol and isophthalic acid was not added.

Comparative preparation example 5

Polybenzimidazole was prepared according to the method of Preparation Example 1, except that the amount of isophthalic acid used was 10 mmol and 4,4-dicarboxylic acid was not added.

Comparative preparation example 6

Polybenzimidazole was prepared according to the method of Comparative Preparation Example 4, except that "2,2-bis(3,4-diaminophenyl)hexafluoropropane" was replaced with an equimolar amount of "3,3'-diaminobenzidine".

Comparative preparation example 7

Polybenzimidazole was prepared according to the method of Comparative Preparation Example 5, except that "2,2-bis(3,4-diaminophenyl)hexafluoropropane" was replaced with an equimolar amount of "3,3'-diaminobenzidine".

Comparative Preparation Example 8

Polybenzimidazole was prepared according to the method of Comparative Preparation Example 3, except that "2,2-bis(3,4-diaminophenyl)hexafluoropropane" was replaced with an equimolar amount of "3,3'-diaminobenzidine".

Comparative preparation example 9

Polybenzimidazole was prepared according to the method of Comparative Preparation Example 3, except that "2,2-bis(3,4-diaminophenyl)hexafluoropropane" was replaced with an equimolar amount of "3,3'-diaminobenzidine" and "cyclohexanedicarboxylic acid" was replaced with an equimolar amount of "2,2'-bis(4-carboxyphenyl)hexafluoropropane".

Test Example 1

The intrinsic viscosity and viscosity-average molecular weight of polybenzimidazole (PBI) prepared in the test preparation example and the comparative preparation example are shown in Table 1.

(1) Test method for intrinsic viscosity: PBI powder was dissolved in concentrated sulfuric acid (98wt%) to prepare a sulfuric acid solution with a concentration of 0.6 g/dL. The sulfuric acid solution was added to an Ubbelohde viscometer with a capillary inner diameter of 1.0-1.1 mm and stabilized in a constant temperature water bath at 25℃ for 30 min. The outflow time of the solution was recorded as _t1 , the outflow time of the concentrated sulfuric acid was recorded as _t0 , and the concentration of the polymer solution was recorded as C. The intrinsic viscosity of PBI was calculated according to Formula 1 and Formula 2.

Increased specific viscosity

Intrinsic viscosity

The viscosity-average molecular weight M of the polymer is obtained by conversion from the Mark–Houwink–Sakurada equation (Equation 3), where the constant K = 1.94 × ^10⁻⁴ and α = 0.791.
[η]＝KM ^α Formula 3

(2) Test method for initial decomposition temperature: The sample was tested using a Netzsch STA409PC thermal analyzer; the test atmosphere was _N2 atmosphere, the flow rate was 50 mL/min; the heating rate was 10 K/min, and the scanning range was 298–1273 K.

(3) Test method for dissolution time: Take 1g of polybenzimidazole sample and disperse it in 30mL of dimethyl sulfoxide. Dissolve it under stirring conditions of 80℃ and stirring speed of 0.5m/s, and test the time for complete dissolution.

Table 1

Example 1

This embodiment illustrates the preparation process of polybenzimidazole membrane.

(1) 1g of polybenzimidazole prepared in Preparation Example 1 was added to 30mL of dimethyl sulfoxide and stirred at 80°C for 2h to dissolve the polybenzimidazole and obtain a solution. The linear speed of stirring was 0.31m/s.

(2) The solution is filtered using a G2 pore size sand core funnel (pore size is 30-50μm) to obtain filtrate. Then the filtrate is poured onto a glass plate and scraped with a scraper to form a uniform liquid film on the glass plate.

(3) Dry the glass plate with the liquid film at 80°C for 12 hours to obtain a polybenzimidazole film.

Example 2

Polybenzimidazole membranes were prepared according to the method of Example 1, except that the polybenzimidazole in Preparation Example 1 was replaced with an equal weight of polybenzimidazole in Preparation Example 2.

Example 3

Polybenzimidazole membranes were prepared according to the method of Example 2, except that the polybenzimidazole in Preparation Example 2 was replaced with an equal weight of polybenzimidazole in Preparation Example 3.

Example 4

Polybenzimidazole membranes were prepared according to the method of Example 2, except that the polybenzimidazole in Preparation Example 2 was replaced with an equal weight of polybenzimidazole in Preparation Example 4.

Example 5

Polybenzimidazole membranes were prepared according to the method of Example 2, except that the polybenzimidazole in Preparation Example 2 was replaced with an equal weight of the polybenzimidazole in Preparation Example 5.

Example 6

The polybenzimidazole membrane was prepared according to the method of Example 2, except that the polybenzimidazole in Preparation Example 2 was replaced with an equal weight of the polybenzimidazole in Preparation Example 6.

Example 7

The polybenzimidazole membrane was prepared according to the method of Example 2, except that the polybenzimidazole in Preparation Example 2 was replaced with an equal weight of the polybenzimidazole in Preparation Example 7.

Example 8

Polybenzimidazole membranes were prepared according to the method of Example 1, except that the polybenzimidazole in Preparation Example 1 was replaced with an equal weight of the polybenzimidazole in Preparation Example 8.

Example 9

Polybenzimidazole membranes were prepared according to the method of Example 1, except that the polybenzimidazole in Preparation Example 1 was replaced with an equal weight of polybenzimidazole in Preparation Example 9.

Example 10

Polybenzimidazole membranes were prepared according to the method of Example 1, except that the polybenzimidazole in Preparation Example 1 was replaced with an equal weight of polybenzimidazole in Preparation Example 10.

Example 11

Polybenzimidazole membranes were prepared according to the method of Example 1, except that the polybenzimidazole in Preparation Example 1 was replaced with an equal weight of polybenzimidazole in Preparation Example 10.

Comparative Example 1

The polybenzimidazole membrane was prepared according to the method of Example 1, except that the polybenzimidazole in Preparation Example 1 was replaced with an equal weight of the polybenzimidazole in Comparative Preparation Example 1, and lithium chloride (mass fraction of 5% of the polybenzimidazole material) was added as a co-solvent when preparing the polybenzimidazole solution in step (1), and the dissolution time was 3h.

When no co-solvent was added during the preparation of the polybenzimidazole solution in Comparative Example 1, a large number of powdery particles remained unswelled after 8 hours of dissolution; after adding the co-solvent, the solution became a semi-gel state after 1 hour of dissolution.

Comparative Example 2

The polybenzimidazole membrane was prepared according to the method of Example 2, except that the polybenzimidazole in Preparation Example 2 was replaced with an equal weight of the polybenzimidazole in Comparative Preparation Example 2, and lithium chloride (mass fraction of 8% of the polybenzimidazole material) was added as a co-solvent when preparing the polybenzimidazole solution in step (1), and the dissolution time was 5h.

When Comparative Example 2 did not add a co-solvent during the preparation of the polybenzimidazole solution, the polybenzimidazole was difficult to dissolve; after adding a co-solvent, the dissolution time was longer.

Comparative Example 3

Polybenzimidazole membranes were prepared according to the method of Example 2, except that the polybenzimidazole in Preparation Example 2 was replaced with an equal weight of the polybenzimidazole in Comparative Preparation Example 3.

However, compared to the polybenzimidazole prepared in Example 3, the polybenzimidazole film-forming properties were poor, and it was unable to form a large-area self-supporting film. Moreover, the film was extremely fragile and could not be tested for mechanical properties.

Comparative Examples 4-7

Polybenzimidazole membranes were prepared according to the method of Example 1, except that the polybenzimidazole in Preparation Example 1 was replaced with equal weights of the polybenzimidazole in Comparative Preparation Examples 4-7.

Comparative Example 8

Polybenzimidazole membranes were prepared according to the method of Example 1, except that the polybenzimidazole in Preparation Example 1 was replaced with an equal weight of the polybenzimidazole in Comparative Preparation Example 8.

However, compared to the polybenzimidazole in Preparation Example 8, the molecular weight is small, making it impossible to form a large-area self-supporting film, and the film is easily broken, making it impossible to test its mechanical properties.

Comparative Example 9

Polybenzimidazole membranes were prepared according to the method of Example 1, except that the polybenzimidazole in Preparation Example 1 was replaced with an equal weight of the polybenzimidazole in Comparative Preparation Example 9.

The membrane prepared from polybenzimidazole in Comparative Preparation Example 9 was easily broken, and its mechanical properties were not tested.

Test Example 2

The transmittance, haze, elongation at break, tensile strength, and tensile modulus of the polybenzimidazole film were tested, and the test results are shown in Table 2.

(1) Transmittance and haze testing: The transmittance and haze were tested according to GB/T 2410-2008 standard using a WGT-S transmittance/haze tester (Shanghai Shenguang Instrument Co., Ltd.) and a standard C light source. The transmittance and haze values of a polybenzimidazole sample film with a thickness of about 25 micrometers were tested and are shown in Table 2.

(2) Mechanical property testing: The membrane was cut into rectangular strips of 4*1cm for testing mechanical properties. Under the conditions of room temperature (25±2)℃ and humidity (50±10)%, the initial distance between the upper and lower clamps was 15mm. The mechanical properties (elongation at break, tensile strength, and tensile modulus) of the membrane strips were tested using an Instron 5965 universal tensile tester at a tensile rate of 1mm/min.

(3) Test of the ultraviolet-visible spectrum of polybenzimidazole film: The spectrum was obtained using an ultraviolet-visible-near-infrared spectrometer (Shimadzu UV3600 spectrophotometer).

Table 2

The UV-Vis absorption of the polybenzimidazole films of Examples 1-3 and Comparative Examples 1 and 2 is shown in Figure 7. As can be seen from Figure 7, almost all UV light is absorbed in the UV band. Compared to the polybenzimidazole films of Comparative Examples 1 and 2, the polybenzimidazole films of Examples 1-3 maintain high transmittance in the visible light band >400 nm; while Comparative Examples 1 and 2 exhibit low transmittance in the visible light band.

The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims (15)

A polybenzimidazole, characterized in that the polybenzimidazole comprises structural unit A1 and structural unit A2, and optionally includes structural unit B1 and structural unit B2, wherein structural unit A1 has the structure shown in formula (A1), structural unit A2 has the structure shown in formula (A2), structural unit B1 has the structure shown in formula (B1), and structural unit B2 has the structure shown in formula (B2):
Wherein, _R1 and _R2 are each independently one of the following: a substituted or unsubstituted arylene, a substituted or unsubstituted cycloalkyl, a substituted or unsubstituted alkyl subchain, a substituted or unsubstituted alkenyl, a substituted or unsubstituted heterocyclic group, a divalent organic group consisting of _2-5 substituted or unsubstituted _monocyclic arylene groups spaced apart by at least one of a single bond, -O-, -C(=O ₎ -, -S(=O)-, -SO2-, a substituted or unsubstituted C2 _{- C5} alkenyl, and a substituted or unsubstituted C1-C5 alkenyl; and a divalent organic group consisting of 2-5 substituted or unsubstituted heterocyclic groups spaced apart by at least one of a single bond, -O-, -C(=O)-, -S(=O)-, _-SO2- , a substituted or unsubstituted C2 _{- C5} alkenyl, and a substituted or unsubstituted _C1 - _C5 alkenyl, and _R1 and _R2 are not the same; and _X1 and _X2 are each independently a fluorinated hydrocarbon group, and _X1 is different from _X2 when structural units B1 and B2 are present. According to claim 1, the polybenzimidazole, wherein _R1 and _R2 are each independently a substituted or unsubstituted _C6 - _C24 arylene, a substituted or unsubstituted _C5 - _C24 cycloalkylene, a substituted or unsubstituted C2- _C20 alkylene, a substituted or unsubstituted _C2 - _C20 alkenylene, a substituted or unsubstituted _C3 - _C20 heterocyclic, a divalent organic group consisting of 2-3 substituted or unsubstituted _monocyclic arylene groups spaced apart by at least one of single bond, -O-, -C(=O)-, -S(=O)-, _-SO2- , substituted or unsubstituted _C2 - _C5 alkenylene, and substituted or unsubstituted _C1 - _C5 alkylene, and a divalent organic group consisting of a single bond, -O-, -C(=O)-, -S(=O)-, _-SO2- , substituted or unsubstituted _C2 -C5 alkylene. Any one of the following: a divalent organic group consisting of at least one of a ₅ -eneyl group and at least two or three substituted or unsubstituted heterocyclic groups spaced apart from each other in a _C1 - _C5 alkylene group; and _X1 and _X2 are each independently a _C1 - _C10 fluorinated alkylene group; Preferably, the heterocyclic group is selected from the group consisting of pyridylene, pyrroleylene, furanylene, quinolinylene, thiophenylene, pyranylene, and pyrazinylene. The polybenzimidazole according to any one of claims 1-2, wherein _R1 and _R2 are each independently selected from the groups shown in formulas (3)-(24):
Where n is an integer from 2 to 8; Preferably, _R1 is a group shown in formula (3) and _R2 is any one of the groups shown in formulas (4) to (24); More preferably, _R1 is the group shown in formula (3) and _R2 is any one of the groups shown in formula (4), formula (13) and formula (24). The polybenzimidazole according to any one of claims 1-3, wherein the molar ratio of structural unit A1 to structural unit A2 is 0.02:1-50:1, preferably 0.05:1-20:1; and/or The polybenzimidazole has a viscosity-average molecular weight of 2000-500000 g/mol; preferably 10000-400000 g/mol; more preferably 30000-400000 g/mol; and/or The intrinsic viscosity of the polybenzimidazole is 0.1-6.5 dL/g; preferably 0.5-6 dL/g. A method for preparing polybenzimidazole, characterized in that the method comprises: polymerizing the monomer in a first solvent under polymerization reaction conditions; The monomers include monomer a1, monomer b, monomer c and optional monomer a2; The monomers a1 and a2 each independently have the structure shown in formula (1-1); the monomers b and c each independently have the structure shown in HOOC-R-COOH; monomer b is different from monomer c, and when monomer a2 is present, the X group in monomer a1 is different from the X group in monomer a2;
Wherein, R is selected from the group consisting of substituted or unsubstituted arylene, substituted or unsubstituted cycloalkyl, substituted or unsubstituted alkylene, substituted or unsubstituted alkenyl, substituted or unsubstituted heterocyclic, a divalent organic group consisting of 2-5 substituted or unsubstituted monocyclic arylene groups spaced apart by at least one of single bond, -O-, -C(=O)-, -S(=O)-, _-SO2- , substituted or unsubstituted _C2 - _C5 alkenyl and substituted or unsubstituted _C1 - _C5 alkenyl, and a divalent organic group consisting of 2-5 substituted or unsubstituted heterocyclic groups spaced apart by at least one of single bond, -O-, -C(=O)-, -S(=O)-, _-SO2- , substituted or unsubstituted _C2 - _C5 alkenyl and substituted or unsubstituted _C1 - _C5 alkenyl; and X is a fluorinated hydrocarbon group; Preferably, R is selected from substituted or unsubstituted _C6 - _C24 arylene, substituted or unsubstituted _C5 - _C24 cycloalkylene, substituted or unsubstituted _C2 - _C20 alkylene, _substituted or unsubstituted C2- _C20 alkenylene, substituted or unsubstituted _C3 - _C20 heterocyclic, a divalent organic group consisting of 2-3 substituted or unsubstituted monocyclic arylene groups spaced apart by at least one of single bond, -O-, -C(=O)-, -S(=O)-, _-SO2- , substituted or unsubstituted _C2 - _C5 alkenylene, and substituted or unsubstituted _C1 - _C5 alkylene, and a divalent organic group consisting of single bond, -O-, -C(=O)-, -S(=O)-, _-SO2- , substituted or unsubstituted C2- _{C5 alkenylene} , and substituted or unsubstituted C1- _C5 alkylene. The group consisting of at least one of ₅ alkylene groups, comprising 2-3 spaced-apart substituted or unsubstituted heterocyclic groups, and X being a _C1 - _C10 fluorinated alkylene group. According to the method of claim 5, wherein R is selected from the groups shown in formulas (3)-(24):
Where n is an integer from 2 to 8; Preferably, R in monomer b is a group shown in formula (3) and R in monomer c is any one of the groups shown in formula (4) to formula (24); More preferably, R in monomer b is a group shown in formula (3) and R in monomer c is any one of the groups shown in formula (4), formula (13) and formula (24). According to the method of claim 5 or 6, the molar ratio of the total amount of monomers b and c to the total amount of monomers a1 and a2 is 0.9:1-1.1:1; and/or The molar ratio of monomer b to monomer c is 0.02:1-50:1, preferably 0.05:1-20:1; and/or The conditions for the polymerization reaction include: a polymerization temperature of 100-220℃ and a polymerization time of 1-24h; and/or The polymerization reaction is carried out under an inert atmosphere; and/or The first solvent includes at least one of polyphosphoric acid, methanesulfonic acid, phosphorus pentoxide, and phosphoric acid; and/or The amount of the first solvent used is 2-20 kg relative to 1 mol of monomers a1 and a2. Polybenzimidazole prepared by the method according to any one of claims 5-7. A polymer membrane, characterized in that the polymer membrane contains polybenzimidazole as described in any one of claims 1-4 and 8. According to claim 9, the polymer film has an elongation at break of 5-100%, preferably 6-80%, more preferably 8-60%, and even more preferably 20-50%; and/or The transmittance of the polymer film is 70-95%, preferably 75-95%, more preferably 80-95%, and even more preferably 84-90%; and/or The haze of the polymer film is 0.05-20%, preferably 0.1-16%, and more preferably 0.2-8%. A method for preparing a polymer film, characterized in that the method comprises: Solution A is obtained by contacting the polybenzimidazole according to any one of claims 1-4 and 8 with a second solvent; Liquid membranes are prepared from solution A with or without solid-liquid separation; and The liquid film is dried to obtain a polymer film. According to the method of claim 11, wherein the second solvent comprises at least one selected from dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, methanesulfonic acid, formic acid, phosphoric acid, polyphosphoric acid, sulfuric acid, and trichlorotoluene; and/or Based on the total weight of solution A, the content of the polybenzimidazole is 0.1-20% by weight; and/or The contact conditions include: a contact temperature of 30-160℃ and a contact time of 10 min-24 h; preferably, the contact is carried out under stirring, preferably the linear velocity of the stirring is 0.05-1 m/s, more preferably 0.1-0.8 m/s; and/or The drying conditions include a drying temperature of 60-160℃ and a drying time of 0.5-24h. The polymer film prepared by the method of claim 11 or 12. The use of the polybenzimidazole as described in any one of claims 1-4 and 8 and/or the polymer film as described in any one of claims 9, 10 and 13 as a light-transmitting or transparent material. According to the application of claim 14, the light-transmitting or transparent material is selected from flexible backsheets of solar cells, flexible display substrates, anti-counterfeiting packaging, high-temperature resistant transparent components of electronic devices/sensors, high-temperature resistant optical lenses, high-temperature protective masks, flexible printed circuits, and aircraft cockpit protective covers.