Use of polybenzimidazoles as mechanochromic materials

Abstract

The application relates to the technical field of force-induced color-changing materials, and discloses application of polybenzimidazole as a force-induced color-changing material.

Description

Technical Field

[0001] This invention relates to the field of mesochromic materials, specifically to the application of polybenzimidazole as a mesochromic material. Background Technology

[0002] Mechanochromic materials are a class of materials whose color, luminescence, and other properties change when subjected to external forces, such as grinding, stretching, and pressing. Mechanochromic materials show broad application prospects in many fields, including mechanical sensing, secure communication, non-destructive testing of materials, and human motion monitoring.

[0003] Currently, small molecule types account for a large proportion of mechanochromic materials, while polymer types account for a smaller proportion. The processability and mechanical strength of polymers make them more widely applicable. Mechanochromic polymer materials typically incorporate chromochromic molecules into the polymer through blending or chemical bonding. Reported polymer materials with chromochromic groups incorporated through chemical bonding include polymers containing spiropyran, rhodamine, or diarylbenzofuranone structures. These typically have low melting points or glass transition temperatures and poor heat resistance, failing to meet the requirements for high-temperature applications. Summary of the Invention

[0004] The purpose of this invention is to provide a polymer material with mechanochromic properties, which has a high thermal decomposition temperature / thermal stability and high mechanical properties, thereby meeting the requirements for use under high temperature and / or high mechanical property conditions.

[0005] The inventors of this invention unexpectedly discovered that polybenzimidazole polymers inherently possess mechanochromic properties, without the need to dope mechanochromic small molecules into the polymer or to attach mechanochromic groups to the polymer molecular chain via chemical or non-chemical bonds. More specifically, the inventors of this invention unexpectedly discovered that the fluorescence emission peak of polybenzimidazole polymers undergoes a significant shift under external stimulation.

[0006] Therefore, the present invention provides the application of polybenzimidazole polymers as mechanochromic materials.

[0007] The polybenzimidazole polymer, as a mechanochromic material, can be used in applications such as mechanical sensing, communication, anti-counterfeiting, non-destructive testing of materials, motion detection, and micro-flow monitoring.

[0008] This invention provides the following beneficial effects:

[0009] (1) This invention has discovered that polybenzimidazole has mechanochromic properties, which broadens the application field of polybenzimidazole;

[0010] (2) Existing mechanochromic materials often exhibit a red shift in fluorescence emission peak after being stimulated by external force, while some embodiments of the present invention provide polybenzimidazole with a blue shift in fluorescence emission peak after being stimulated by external force.

[0011] (3) Polybenzimidazole materials have excellent thermal stability and high mechanical strength, which broadens the application scenarios of mechanochromic materials. Attached Figure Description

[0012] Figure 1 These are the 1H NMR spectra of polymer (PBI-1) from Example 1 and polymer (PBI-7) from Example 7;

[0013] Figure 2 This is the thermogravimetric analysis spectrum of the polymer (PBI-1) in Example 1;

[0014] Figure 3 These are the fluorescence spectra of the polymer (PBI-2) in Example 2 before and after grinding; and

[0015] Figure 4 The fluorescence spectra of the polymer film product (PBI-9) in Example 9 before and after stretching are shown. Detailed Implementation

[0016] 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.

[0017] The first aspect of this invention provides the application of polybenzimidazole as a mechanochromic material. This application discovers that polybenzimidazole possesses mechanochromic properties. In this invention, the polybenzimidazole can be any polybenzimidazole polymer known in the prior art.

[0018] According to some embodiments of the present invention, the polybenzimidazole contains structural unit A, which has the structure shown in formula (1):

[0019]

[0020] Wherein, the X1 group is a linking group provided by an aromatic hydrocarbon compound containing 1-10 benzene rings; and the Y group is an aromatic hydrocarbon containing 1-10 benzene rings, a heterocyclic aromatic hydrocarbon containing 1-10 heterocycles, an aromatic hydrocarbon containing 1-3 heterocycles and 1-8 benzene rings, or a C4-C4 aromatic hydrocarbon. 10The linking group is provided by at least one compound selected from cycloalkanes, C1-C8 alkanes, and C2-C8 alkenes; wherein at least one substituent selected from hydroxyl, amino, cyano, halogen, C1-C4 alkyl, and C1-C4 haloalkyl is independently present or absent on the X1 and Y groups. In some embodiments, the polybenzimidazole is composed of structural unit A.

[0021] According to the present invention, in some embodiments, the polybenzimidazole contains structural unit A and structural unit C, contains structural unit A and structural unit D, or contains structural unit A, structural unit B, structural unit C and structural unit D; wherein structural unit A has the structure shown in formula (1), structural unit B has the structure shown in formula (2), structural unit C has the structure shown in formula (1-1), and structural unit D has the structure shown in formula (2-2):

[0022]

[0023] Wherein, X1 and X2 groups are each independently provided as linking groups for aromatic compounds containing 1-10 benzene rings; and Y and Z groups are each independently provided as aromatic compounds containing 1-10 benzene rings, heterocyclic aromatic compounds containing 1-10 heterocycles, aromatic compounds containing 1-3 heterocycles and 1-8 benzene rings, C4-C 10 The linking group is provided by at least one compound selected from cycloalkanes, C1-C8 alkanes, and C2-C8 alkenes; wherein at least one substituent selected from hydroxyl, amino, cyano, halogen, C1-C4 alkyl, and C1-C4 haloalkyl is independently present or absent on each of the X1, X2, Y, and Z groups. In some embodiments, the polybenzimidazole is composed of structural unit A and structural unit C. In some embodiments, the polybenzimidazole is composed of structural unit A and structural unit D. In some embodiments, the polybenzimidazole is composed of structural unit A, structural unit B, structural unit C, and structural unit D.

[0024] According to the present invention, in some embodiments, the polybenzimidazole contains structural unit A and optional structural unit B or is composed of structural unit A and optional structural unit B, wherein structural unit A has the structure shown in formula (1) and structural unit B has the structure shown in formula (2).

[0025]

[0026] Wherein, X1 and X2 groups are each independently provided as linking groups for aromatic compounds containing 1-10 benzene rings; Y and Z groups are each independently provided as aromatic compounds containing 1-10 benzene rings, heterocyclic aromatic compounds containing 1-10 heterocycles, aromatic compounds containing 1-3 heterocycles and 1-8 benzene rings, C4-C 10The linking group is provided by at least one compound selected from cycloalkanes, C1-C8 alkanes, and C2-C8 alkenes, and Y is different from Z when structural unit B is present; wherein, X1, X2, Y and / or Z groups are present independently or not present at least one substituent selected from hydroxyl, amino, cyano, halogen, C1-C4 alkyl, and C1-C4 haloalkyl.

[0027] In this invention, those skilled in the art know the connection method of the X1 and X2 groups in formulas (1) and (2).

[0028] For example, for formulas (1) and (2), when the X1 and X2 groups are each independently linked groups provided by benzene, the structural formulas of formulas (1) and (2) can be respectively... In other words, the benzene ring and the imidazole ring share two pairs of carbon atoms. Any two pairs of adjacent carbon atoms on the benzene ring in groups X1 and X2 participate in the formation of the imidazole ring. The two pairs of adjacent carbon atoms can come from the same benzene ring or from different benzene rings in multiple benzene rings. For example, when group X1 is a linking group provided by biphenyl, each benzene ring of biphenyl can provide one pair of carbon atoms to form an imidazole ring, or it can provide two pairs of adjacent carbon atoms to a benzene ring to form an imidazole ring.

[0029] In this invention, C4-C 10 Cycloalkanes can be, for example, cyclobutane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclononane, or cyclodecane.

[0030] In this invention, the C1-C8 alkanes may be, for example, methane, ethane, n-propane, isopropane, butane, pentane, hexane, heptane, or octane. In some embodiments, the C1-C8 alkanes may also be C1-C8 alkanes substituted with one or more halogen atoms, wherein the halogen atoms may be selected from fluorine, chlorine, and bromine atoms.

[0031] In this invention, the C2-C8 olefins may be, for example, ethylene, propylene, butene, pentene, hexene, hepten, or octene.

[0032] In this invention, halogens may be selected from fluorine, chlorine and bromine, for example.

[0033] In this invention, C1-C4 alkyl groups can be, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, or tert-butyl.

[0034] In this invention, the C1-C4 haloalkyl group can be, for example, halomethyl, haloethyl, halopropyl, haloisopropyl, halobutyl, halosec-butyl, haloisobutyl or halotert-butyl; the halogen atom in the C1-C4 haloalkyl group can be, for example, selected from fluorine atom, chlorine atom and bromine atom.

[0035] According to the present invention, preferably, in some embodiments, the X1 and X2 groups are each independently provided by a linking group of at least one compound selected from benzene, biphenyl, terphenyl, bridged benzene, pterene, and fused-ring aromatic hydrocarbons containing 1-10 benzene rings; more preferably, the X1 and X2 groups are each independently provided by a linking group of at least one compound selected from benzene, biphenyl, bridged benzene, pterene, and naphthalene; and even more preferably, the bridged benzene has the structure shown in formula (3), formula (4), or formula (5), wherein R1, R3, and R4 are each independently selected from an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, a methylene group, and a halogen-substituted methylene group; and R2 is selected from a heterocyclic aromatic ring.

[0036]

[0037] In this invention, the heterocyclic aromatic ring may be, for example, pyridine or pyrimidine.

[0038] In this invention, the connection positions (indicated by "dashed lines") of the structures shown in equations (3), (4), and (5) can be as follows:

[0039]

[0040] In this invention, the connection positions include, but are not limited to, the above representations; for example, any two adjacent connection positions on the same benzene ring are feasible.

[0041] According to the present invention, preferably, in some embodiments, the X1 and X2 groups are each independently selected from the following linking groups:

[0042]

[0043]

[0044] Wherein, G is selected from hydrogen atom, methyl and trifluoromethoxy; J is selected from oxygen atom, sulfur atom, carbonyl, sulfonyl, methylene and methyl or trifluoromethyl substituted methylene; L is selected from bromine atom, phenyl and trifluoromethyl substituted phenyl; and R is selected from hydrogen atom, carboxyl, hydroxyl and trifluoromethyl.

[0045] In some embodiments of the present invention, the connection positions of the X1 and X2 groups may include, but are not limited to, the following connection positions:

[0046]

[0047] According to the present invention, in some embodiments, the Y and Z groups are each independently benzene, a 5-6 member nitrogen-containing heterocyclic compound, an aromatic compound containing 2-7 benzene rings, an aromatic compound containing 1-2 nitrogen-containing heterocycles and 1-5 benzene rings, or a C4-C4 compound. 10The linking group is provided by a compound of at least one of cycloalkanes, C1-C8 alkanes, and C2-C8 alkenes.

[0048] According to the present invention, in some embodiments, the molar ratio of the X2 and X1 groups can be 0-9999, preferably 0-99; for example, it can be 0, 0.001, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 99, 100, and any range consisting of any two of the above points. In the present invention, unless otherwise specified, the content ratio of the X2 and X1 structural units or groups in polybenzimidazole is calculated based on the amount of feed.

[0049] According to the present invention, preferably, in some embodiments, the Y and Z groups can each independently be linking groups selected from the following:

[0050]

[0051] C1-C8 chain alkyl;

[0052] Wherein, M is selected from hydrogen atom, cyano, methyl, phenyl and methyl or trifluoromethyl substituted phenyl; P is selected from oxygen atom, sulfur atom, carbonyl, sulfonyl, cyclobutyl, halogen-substituted cyclobutyl, methylene and halogen-substituted methylene; Q is selected from bromine atom, phenyl and trifluoromethyl substituted phenyl; and T is selected from hydrogen atom and methyl.

[0053] In this invention, the connection positions of the Y and Z groups are not particularly limited and can be any position on the connecting group. For example, when the Y and Z groups contain a cyclic structure, the connection position can be a carbon atom on the cyclic structure; when the Y and Z groups are C1-C8 alkyl chains, the connection position can be any carbon atom in the alkyl chain. In this invention, the connection positions of the Y and Z groups can include, but are not limited to, the following connection positions:

[0054]

[0055] In some embodiments, the polybenzimidazole polymer of the present invention does not contain methanogenic groups commonly known in the art, including but not limited to methanogenic groups derived from tetraphenylethylene, triarylamine, spiropyran, rhodamine, coumarin, etc.

[0056] In this invention, the molecular weight of the polybenzimidazole is not particularly limited. For example, the molecular weight of the polybenzimidazole can be selected according to specific application requirements.

[0057] According to some embodiments of the present invention, the intrinsic viscosity of the polybenzimidazole can be 0.15-3.0 dLg. -1 For example, it could be 0.15 dL g. -1 0.2 dL g -1 0.3dL g -1 0.4 dL g -1 0.8 dL g -1 1.2 dL g -1 1.6dLg -1 1.7dL g -1 1.8dL g -1 1.9dL g -1 2dL g -1 2.1dL g -1 2.2dL g -1 2.3dL g -1 2.4 dL g -1 2.5 dL g -1 2.6 dL g -1 2.7 dL g -1 2.8 dL g -1 2.9dL g -1 3.0 dL g -1 And the range formed by any two of the above points.

[0058] According to the present invention, in some embodiments, the molar ratio of the Z and Y groups can be 0-9999, preferably 0-99; for example, it can be 0, 0.001, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 99, 100, and any range consisting of any two of the above points. In the present invention, unless otherwise specified, the content ratio of the Y and Z structural units or groups in polybenzimidazole is calculated based on the amount of feed.

[0059] In some embodiments of the present invention, a polybenzimidazole with a blue shift in fluorescence emission peak after being stimulated by external force is provided.

[0060] In some embodiments of the present invention, the polybenzimidazole is poly(2,5-benzimidazole). Polybenzimidazole is a polymer known in the art. The present invention may use polybenzimidazole polymers with various structures known in the art.

[0061] The preparation of polybenzimidazole is known in the art. Various preparation methods known in the art can be used to prepare polybenzimidazole.

[0062] In some embodiments, the present invention also provides a method for preparing the polybenzimidazole of the first aspect, the method comprising reacting at least one compound having the structure shown in formula (6) with HOOC-Y-COOH and optionally HOOC-Z-COOH;

[0063]

[0064] The X group in formula (6) is the same as the X1 and / or X2 groups in formula (1) and formula (2), and will not be repeated here.

[0065] According to the preparation method of the present invention, preferably, in some embodiments, the compound having the structure shown in formula (6) is selected from at least one of the following compounds:

[0066]

[0067] Wherein, G is selected from hydrogen atom, methyl and trifluoromethoxy, namely -H, -CH3, -OCF3;

[0068] J is selected from oxygen atom, sulfur atom, carbonyl group, sulfonyl group, methylene group, and methylene group substituted with methyl or trifluoromethyl, for example, -O-, -S-.

[0069] L is selected from bromine atoms, phenyl groups, and trifluoromethyl-substituted phenyl groups, for example, -Br as well as

[0070] R is selected from hydrogen atom, carboxyl group, hydroxyl group and trifluoromethyl, namely -H, -COOH, -OH, -CF3.

[0071] According to the preparation method of the present invention, preferably, in some embodiments, HOOC-Y-COOH and optionally HOOC-Z-COOH are each independently selected from at least one of the following compounds:

[0072]

[0073]

[0074] Where n = 1 - 8;

[0075] M is selected from hydrogen atom, cyano, methyl, phenyl, and methyl or trifluoromethyl substituted phenyl groups, for example, -H, - C N,

[0076] P is selected from oxygen atom, sulfur atom, carbonyl group, sulfonyl group, cyclobutyl group, halogen-substituted cyclobutyl group, methylene group, and methyl or trifluoromethyl-substituted methylene group, for example, -O-. -S-,

[0077] Q is selected from phenyl groups substituted with bromine, phenyl, and trifluoromethyl groups, such as -Br. as well as

[0078] T is selected from hydrogen atoms and methyl groups, i.e., -H, -CH3.

[0079] According to the preparation method of the present invention, preferably, in some embodiments, the reaction is carried out in a solvent, more preferably, the solvent is a mixed solution of methanesulfonic acid / phosphorus pentoxide or polyphosphoric acid, and even more preferably a mixed solution of methanesulfonic acid / phosphorus pentoxide, wherein the mass of phosphorus pentoxide is 2-10% of the mass of methanesulfonic acid. The concentration of the mixed monomers in the reaction system can be 3wt%-20wt%. According to the preparation method of the present invention, preferably, in some embodiments, the molar ratio of the compound having the structure shown in formula (6) to the total molar ratio of HOOC-Y-COOH and optionally HOOC-Z-COOH is 1:0.6-2, preferably 1:0.8-1.2.

[0080] In some implementations, 3,4-diaminobenzoic acid is used as a monomer to prepare poly(2,5-benzimidazole).

[0081] According to the preparation method of the present invention, preferably, in some embodiments, the reaction time can be 1-8 hours, more preferably 3-5 hours. The reaction temperature can be 60-230°C, preferably 60-170°C, more preferably 100-150°C. The reaction pressure can be atmospheric pressure. According to the preparation method of the present invention, preferably, in some embodiments, the molar ratio of the compound having the structure shown in formula (6) to the total molar ratio of HOOC-Y-COOH and optionally HOOC-Z-COOH is 1:0.6-2; for example, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, and any two of the above ranges; preferably 1:0.8-1.2; wherein the molar ratio of X2 to X1 groups can be 0-9999, preferably 0-99, for example, 0, 0.001, 0.01, 0.02, 0.03, 0.0 4, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 99, 100, and any two of the above ranges; the molar ratio of Z to Y groups is 0-9999, preferably 0-99, for example, it can be 0, 0.001, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 1 0, 20, 30, 40, 50, 60, 70, 80, 90, 99, 100, and any two of the above.

[0082] In some embodiments, the polybenzimidazole of the present invention may have one of the following structures:

[0083]

[0084] In the structures shown above, for copolymers, the structures shown only indicate that the polymer chain segment contains the shown repeating structural units or that the polymer chain segment is composed of the shown repeating structural units, and do not indicate the distribution of the shown repeating structural units in the polymer chain.

[0085] This invention discovers that polybenzimidazole possesses mechanochromic properties, meaning that its fluorescence emission peak shifts significantly (red shift or blue shift) under external force stimulation. The external force stimulation includes, but is not limited to, mechanical actions such as grinding, stretching, pressing, and impact. This discovery is unexpected because existing polymers with mechanochromic properties either require doping with mechanochromic small molecules or require the mechanochromic groups to be attached to or on the polymer molecular chain via chemical or non-chemical bonds.

[0086] In some embodiments, this application provides the use of polybenzimidazole as a mechanochromic material, which may include the step of measuring the fluorescence emission spectrum of polybenzimidazole after it has been subjected to an external force. Further, the application may also include the step of comparing the position of the fluorescence emission peak in the fluorescence emission spectrum of polybenzimidazole measured after the external force is applied with the position of the fluorescence emission peak in the fluorescence emission spectrum of polybenzimidazole before the external force is applied. The application may also issue a warning signal based on the comparison result. For example, if the shift of the fluorescence emission peak in the fluorescence emission spectrum before and after the external force exceeds a set threshold (e.g., 3 nm, 5 nm, or 10 nm), a warning signal may be issued.

[0087] This invention also provides applications of polybenzimidazole polymers as mechanochromic materials in mechanical sensing, communication, anti-counterfeiting, non-destructive testing of materials, motion detection, and micro-flow monitoring. Preferably, these applications include at least one of stress sensors, anti-counterfeiting paper, color-changing textiles, pressure sensors for compression therapy bandages, and micro-flow monitors. In these applications, polybenzimidazole, for example, can change color in response to mechanical forces, thereby providing useful information.

[0088] For example, polybenzimidazole can be coated or encapsulated on the inner surface of a microchannel. When the fluid flow rate inside the microchannel changes, the polybenzimidazole experiences a change in stress, causing a change in the fluorescence emission peak. This change can be captured by a detector connected to the microchannel, thus enabling flow monitoring. As another example, a polybenzimidazole membrane can be placed on the outside of a pipe. When the pipe deforms, the polybenzimidazole membrane deforms, causing a change in the fluorescence emission peak. This change can be captured by an external detector, thus enabling early warning of pipe aging.

[0089] The present invention will be described in detail below through embodiments.

[0090] In the following embodiments,

[0091] Polymer yield is calculated using the following formula:

[0092] Yield = Actual polymer yield ÷ Theoretical polymer yield × 100%;

[0093] Wherein, the theoretical yield of the polymer = the number of moles of the compound shown in equation (6) × the molar mass of the repeating unit in the polymer structure.

[0094] 3,3′,4,4′-Tetraaminobiphenyl: Sigma-Aldrich; purity 98%;

[0095] 4,4′-Diphenyl ether dicarboxylic acid: Bailingwei Technology; purity 98%;

[0096] Isophthalic acid: Bailingwei Technology, purity 98%;

[0097] Terephthalic acid: Bailingwei Technology, purity 98%;

[0098] 4,6-Pyrimidinedicarboxylic acid: Bailingwei Technology, purity 98%;

[0099] 2,5-Dihydroxyterephthalic acid: Bailingwei Technology, purity 98%;

[0100] 3,5-Pyridinedicarboxylic acid: Bailingwei Technology, purity 98%;

[0101] 5-Aminophthalic acid: Bailingwei Technology, purity 98%;

[0102] 1-Methylbenzimidazole: Inokai Technology, purity 98%;

[0103] 2-Hydroxybenzimidazole: Inokai Technology, purity 98%.

[0104] Example 1

[0105] A mixture of monomers, 3,3′,4,4′-tetraaminobiphenyl (2.14 g) and 4,4′-diphenyl ether dicarboxylic acid (2.79 g), in a molar ratio of 1:1.08, was added to a methanesulfonic acid / phosphorus pentoxide solution (solvent 44 g) to form a reaction system. The reaction was carried out at 150 °C for 3 h to obtain a reaction solution. The reaction solution was then introduced into water to precipitate the polymer, followed by neutralization (sodium bicarbonate) and filtration to obtain polymer PBI-1. The weight ratio of methanesulfonic acid to phosphorus pentoxide in the methanesulfonic acid / phosphorus pentoxide solution was 20:1, and the concentration of the mixed monomers in the reaction system was 10 wt%. The yield of polymer PBI-1 was 99%. The 1H NMR spectrum of PBI-1 was measured in Test Example 6. Figure 1 The structure is shown in the figure. Its structure was confirmed by 1H NMR spectroscopy.

[0106] Example 2

[0107] The procedure was carried out according to Example 1, except that 4,4′-diphenyl ether dicarboxylic acid was replaced with an equimolar amount of terephthalic acid, and the reaction time was 4 h. The yield of polymer PBI-2 was 99%. Its structure was confirmed by 1H NMR spectroscopy.

[0108] Example 3

[0109] A mixture of monomers in a molar ratio of 1:0.945:0.105, consisting of 2.14 g of 3,3′,4,4′-tetraaminobiphenyl, 1.57 g of isophthalic acid, and 0.18 g of 4,6-pyrimidinedicarboxylic acid, was added to a methanesulfonic acid / phosphorus pentoxide solution (solvent 35 g) to form a reaction system. The reaction was carried out at 150 °C for 3 h to obtain a reaction solution. The reaction solution was then introduced into water to precipitate the polymer, followed by neutralization (with sodium bicarbonate) and filtration to obtain polymer PBI-3. The weight ratio of methanesulfonic acid to phosphorus pentoxide in the methanesulfonic acid / phosphorus pentoxide solution was 20:1, and the concentration of the mixed monomers in the reaction system was 10 wt%. The yield of polymer PBI-3 was 99%. Its structure was confirmed by 1H NMR spectroscopy.

[0110] Example 4

[0111] The reaction was carried out according to the method of Example 3, except that 4,6-pyrimidinedicarboxylic acid was replaced with an equimolar amount of 2,5-dihydroxyterephthalic acid, and the reaction time was 4 h. The yield of polymer PBI-4 was 99%. Its structure was confirmed by 1H NMR spectroscopy.

[0112] Example 5

[0113] The reaction was carried out according to the method of Example 3, except that 4,6-pyrimidinedicarboxylic acid was replaced with an equimolar amount of 3,5-pyridinedicarboxylic acid, and the reaction time was 5 h. The yield of polymer PBI-5 was 99%. Its structure was confirmed by 1H NMR spectroscopy.

[0114] Example 6

[0115] The reaction was carried out according to the method of Example 3, except that 4,6-pyrimidinedicarboxylic acid was replaced with an equimolar amount of 5-aminoisophthalic acid, and the reaction time was 4 h. The yield of polymer PBI-6 was 99%. Its structure was confirmed by 1H NMR spectroscopy.

[0116] Example 7

[0117] A mixture of monomers in a molar ratio of 1:0.945:0.105, consisting of 2.14 g of 3,3′,4,4′-tetraaminobiphenyl, 2.44 g of 4,4′-diphenyl ether dicarboxylic acid, and 0.19 g of 5-aminoisophthalic acid, was added to a methanesulfonic acid / phosphorus pentoxide solution (solvent 43 g) to form a reaction system. The reaction was carried out at 150 °C for 3 h to obtain a reaction solution. The reaction solution was then introduced into water to precipitate the polymer, followed by neutralization (with sodium bicarbonate) and filtration to obtain polymer PBI-7. The weight ratio of methanesulfonic acid to phosphorus pentoxide in the methanesulfonic acid / phosphorus pentoxide solution was 20:1, and the concentration of the mixed monomers in the reaction system was 10 wt%. The yield of polymer PBI-7 was 99%. The 1H NMR spectrum of PBI-7 was measured in Test Example 6. Figure 1 The structure is shown in the figure. Its structure was confirmed by 1H NMR spectroscopy.

[0118] Example 8

[0119] The procedure was carried out according to Example 7, except that the molar ratio was changed to 1:0.714:0.306, and the reaction time was 8 h. The yield of polymer PBI-8 was 99%. Its structure was confirmed by 1H NMR spectroscopy.

[0120] Example 9

[0121] The procedure was carried out according to Example 1, except that 4,4′-diphenyl ether dicarboxylic acid was replaced with an equimolar amount of isophthalic acid, and the reaction time was 5 h. The yield of polymer PBI-9 was 99%. Its structure was confirmed by 1H NMR spectroscopy.

[0122] PBI-9 was dissolved in DMSO solvent (concentration 4wt%), cast onto a flat glass plate, and placed in an 80℃ oven for 10 hours to obtain a PBI-9 film product, which was labeled as PBI-9.

[0123] Example 10

[0124] We purchased PBI membrane products from FuMA-Tech in Germany, labeled as PBI-10.

[0125] Example 11

[0126] The membrane products were purchased from BASF in Germany and are labeled as PBI-11.

[0127] Test Example 1

[0128] The mechanochromic properties of the polymers (powders) prepared in Examples 1-8 above were tested.

[0129] Test method: The polymer powder was placed in a solid fixture (two transparent quartz plates, one of which had a groove for placing the sample) and then placed in a fluorescence spectrometer (Edinburgh-FLS1000 steady-state / transient fluorescence spectrometer) to obtain the fluorescence emission spectrum. Then, the polymer powder was manually ground in a mortar for 30 seconds and placed back in the solid fixture, and the fluorescence emission spectrum was detected again. The shifts of the strongest fluorescence emission peak before and after grinding are shown in Table 1.

[0130] Test Example 2

[0131] The mechanochromic properties of the polymer films in Examples 9-11 were tested.

[0132] Mechanism-induced colorimetric properties of polymer films were tested as follows: The film was placed in a solid fixture and analyzed using a fluorescence spectrometer (Edinburgh-FLS1000 steady-state / transient fluorescence spectrometer). The film was then stretched for 30 seconds with tweezers holding both ends to prevent breakage, and then placed back in the solid fixture. The fluorescence emission spectrum was analyzed again using the fluorescence spectrometer. The film thickness was 40 ± 5 μm. The shifts of the strongest fluorescence emission peak before and after stretching are shown in Table 1.

[0133] Table 1

[0134]

[0135] Note: "#" indicates a blue shift of the emission peak; "*" indicates a red shift of the emission peak.

[0136] Test Example 3

[0137] The thermal stability of the polymers prepared in the above examples was tested.

[0138] Thermogravimetric analysis (TGA) test method: A TA Q500 thermogravimetric analyzer (USA) was used, and the test was conducted in a nitrogen atmosphere. The heating rate was 10℃ / min, and the temperature range was 25-700℃. The thermal decomposition temperature T of the polymer was determined. d5 The percentage (temperature at which 5% of mass is lost) is shown in Table 2.

[0139] Table 2

[0140]

[0141] Test Example 4

[0142] The intrinsic viscosity of the polymer prepared in the above examples was tested.

[0143] Intrinsic viscosity test method: PBI is dissolved in concentrated sulfuric acid to prepare a sulfuric acid solution with a concentration of 0.6 g dL⁻¹. The sulfuric acid solution is added to an Ubbelohde viscometer and placed in a constant temperature water bath at 25°C for 30 min. The outflow time of the solution is measured. Each sample is measured three times, with a time difference not exceeding 1 s. The average value is recorded as t1, and the outflow time of the concentrated sulfuric acid is recorded as t0. The intrinsic viscosity [η] of PBI is calculated as follows: (Specific viscosity...) Intrinsic viscosity Where C represents the concentration of the PBI sulfuric acid solution. The test results are shown in Table 3.

[0144] Table 3

[0145]

[0146] Test Example 5

[0147] The mechanical strength of the membrane prepared in Example 9 was tested.

[0148] Mechanical testing method: The Instron 5965 universal tensile testing machine was used, with a tensile rate of 1 mm / min and a test temperature of 25℃.

[0149] The PBI-9 membrane has a modulus of 2.5 GPa, and the nominal modulus of the purchased PBI-10 is 4.5 GPa, both exhibiting excellent mechanical properties.

[0150] Test Example 6

[0151] The 1H NMR spectrum of the polymer in the test example.

[0152] The method for proton nuclear magnetic resonance (NMR) spectroscopy was as follows: an Agilent 400-MR DD2 NMR spectrometer was used at a frequency of 400 MHz, tetramethylsilane (TMS) was used as an internal standard, DMSO-d6 was used as the solvent, and the test temperature was 40 ℃.

[0153] The 1H NMR spectra of the polymers in Examples 1 and 7 are as follows: Figure 1 As shown, the proton signal at chemical shift 13.0 ppm in the spectrum can be attributed to the characteristic peak of active hydrogen in the PBI structural unit; the proton signals at 7.30 ppm and 8.28 ppm can be attributed to the characteristic peaks of the corresponding structural units after the polymerization of 4,4′-diphenyl ether dicarboxylic acid monomer; and the proton signals at 7.55-8.02 ppm can be attributed to the characteristic peaks of the corresponding structural units after the polymerization of tetraamine monomer and 5-aminoisophthalic acid monomer.

[0154] The results of the proton NMR spectrum indicate that polymers PBI-1 to PBI-9 were successfully obtained.

[0155] Comparative Example

[0156] Following the method in Test Example 1, the mechanochromic properties of 1-methylbenzimidazole and 2-hydroxybenzimidazole were tested respectively. The test results showed that after grinding, the strongest fluorescence emission peaks of both remained unchanged, indicating that they did not exhibit mechanochromic properties.

[0157] 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

1. Applications of polybenzimidazole as a mesochromic material, among which, The polybenzimidazole contains structural unit A or the polybenzimidazole is poly(2,5-benzimidazole), wherein structural unit A has the structure shown in formula (1): Equation (1) Wherein, the X1 group is a linking group provided by an aromatic hydrocarbon compound containing 1-10 benzene rings; and the Y group is an aromatic hydrocarbon containing 1-10 benzene rings, a heterocyclic aromatic hydrocarbon containing 1-10 heterocycles, an aromatic hydrocarbon containing 1-3 heterocycles and 1-8 benzene rings, or a C4-C4 aromatic hydrocarbon. 10 The linking group is provided by at least one compound selected from cycloalkanes, C1-C8 alkanes, and C2-C8 alkenes; wherein at least one substituent selected from hydroxyl, amino, cyano, halogen, C1-C4 alkyl, and C1-C4 haloalkyl is independently present or absent on the X1 and Y groups.

2. The application according to claim 1, wherein, The polybenzimidazole contains structural unit A and structural unit C, contains structural unit A and structural unit D, or contains structural unit A, structural unit B, structural unit C and structural unit D; Wherein structural unit A has the structure shown in equation (1), structural unit B has the structure shown in equation (2), structural unit C has the structure shown in equation (1-1), and structural unit D has the structure shown in equation (2-2): Equation (1) Equation (2) Equation (1-1) Equation (2-2) Wherein, X1 and X2 groups are each independently provided as linking groups for aromatic compounds containing 1-10 benzene rings; Y and Z groups are each independently provided as aromatic compounds containing 1-10 benzene rings, heterocyclic aromatic compounds containing 1-10 heterocycles, aromatic compounds containing 1-3 heterocycles and 1-8 benzene rings, C4-C 10 The linking group is provided by at least one compound selected from cycloalkanes, C1-C8 alkanes, and C2-C8 alkenes; wherein each of the X1, X2, Y, and Z groups has or does not have at least one substituent selected from hydroxyl, amino, cyano, halogen, C1-C4 alkyl, and C1-C4 haloalkyl.

3. The application according to claim 1, wherein, The polybenzimidazole contains structural unit A and optional structural unit B, wherein structural unit A has the structure shown in formula (1) and structural unit B has the structure shown in formula (2); Equation (1) Equation (2) Wherein, X1 and X2 groups are each independently provided as linking groups for aromatic compounds containing 1-10 benzene rings; Y and Z groups are each independently provided as aromatic compounds containing 1-10 benzene rings, heterocyclic aromatic compounds containing 1-10 heterocycles, aromatic compounds containing 1-3 heterocycles and 1-8 benzene rings, C4-C 10 The linking group is provided by at least one compound selected from cycloalkanes, C1-C8 alkanes, and C2-C8 alkenes, and Y and Z are different when structural unit B is present; wherein, each of the X1, X2, Y and / or Z groups has or does not have at least one substituent selected from hydroxyl, amino, cyano, halogen, C1-C4 alkyl, and C1-C4 haloalkyl.

4. The application according to any one of claims 1-3, wherein, The X1 and X2 groups are each independently provided by a linking group from at least one of benzene, diphenyl, terphenyl, bridged benzene, pterene, and fused-ring aromatic hydrocarbons containing 1 to 10 benzene rings.

5. The application according to claim 4, wherein, The X1 and X2 groups are each independently provided by a linking group from at least one compound selected from benzene, biphenyl, bridged benzene, pterene, and naphthalene.

6. The application according to claim 5, wherein, Bridged benzene has the structure shown in formula (3), formula (4) or formula (5), wherein R1, R3, and R4 are each independently selected from oxygen atom, sulfur atom, carbonyl group, sulfonyl group, methylene group and halogen-substituted methylene group; and R2 is selected from heteroaromatic rings; Equation (3) Equation (4) Equation (5).

7. The application according to claim 5, wherein, The X1 and X2 groups are each independently selected from the following linking groups: ； Wherein, G is selected from hydrogen atom, methyl and trifluoromethoxy; J is selected from oxygen atom, sulfur atom, carbonyl, sulfonyl, methylene and methyl or trifluoromethyl substituted methylene; L is selected from bromine atom, phenyl and trifluoromethyl substituted phenyl; and R is selected from hydrogen atom, carboxyl, hydroxyl and trifluoromethyl.

8. The application according to any one of claims 2-3, wherein, The Y and Z groups are each independently benzene, a 5-6 member nitrogen-containing heterocyclic compound, an aromatic compound containing 2-7 benzene rings, an aromatic compound containing 1-2 nitrogen-containing heterocycles and 1-5 benzene rings, or C4-C4 compounds. 10 The linking group is provided by a compound of at least one of cycloalkanes, C1-C8 alkanes, and C2-C8 alkenes.

9. The application according to claim 8, wherein, The Y and Z groups are each independently selected from the following linking groups: , C1-C8 alkyl groups; Wherein, M is selected from hydrogen atom, cyano, methyl, phenyl and methyl or trifluoromethyl substituted phenyl; P is selected from oxygen atom, sulfur atom, carbonyl, sulfonyl, cyclobutyl, halogen-substituted cyclobutyl, methylene and halogen-substituted methylene; Q is selected from bromine atom, phenyl and trifluoromethyl substituted phenyl; and T is selected from hydrogen atom and methyl.

10. The application according to any one of claims 1-3, wherein, The intrinsic viscosity of the polybenzimidazole is 0.15-3.0 dL / g. -1 ; and / or, The molar ratio of X2 to X1 groups in the polybenzimidazole is 0-9999; and / or, The molar ratio of Z to Y groups in the polybenzimidazole is 0-9999.

11. The application according to claim 10, wherein, The molar ratio of X2 to X1 groups in the polybenzimidazole is 0-99; and / or, The molar ratio of Z to Y groups in the polybenzimidazole is 0-99.

12. The application according to any one of claims 1-3, wherein the polybenzimidazole is used as a mechanochromic material in mechanical sensing, communication, anti-counterfeiting, non-destructive testing of materials, motion detection, and micro-flow monitoring.

13. The application according to claim 12, wherein the polybenzimidazole is used as a mechanochromic material in stress sensors, anti-counterfeiting paper, color-changing textiles, pressure sensors for bandages used in compression therapy, and microflow monitors.

14. The application according to any one of claims 1-3, wherein the fluorescence emission peak of the polybenzimidazole undergoes a blue shift after being stimulated by an external force.

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