Use of polybenzimidazole as mechanochromic material

Abstract

The use of polybenzimidazole as a mechanochromic material, relating to the technical field of mechanochromic materials.

Description

Application of polybenzimidazole as mechanochromic material Technical Field

[0001] The present invention relates to the field of mechanochromic materials, and in particular to the application of polybenzimidazole as a mechanochromic material. Background Art

[0002] Mechanochromic materials are materials that change color, luminescence, and other properties in response to external stimuli, such as abrasion, stretching, and compression. Mechanochromic materials hold great promise for applications in a wide range of fields, including mechanical sensing, secure communications, nondestructive testing of materials, and human motion monitoring.

[0003] Small molecules account for a large proportion of existing mechanochromic materials, while polymers account for a smaller proportion. The processability and mechanical strength of polymers broaden their application. Mechanochromic polymer materials typically incorporate color-changing molecules into polymers through blending or chemical bonding. Reported polymer materials incorporating color-changing groups through chemical bonds include polymers containing spiropyran, rhodamine, or diarylbenzofuranone structures. These typically have low melting points or glass transition temperatures, poor heat resistance, and cannot meet the requirements for use under high-temperature conditions.

[0004] Summary of the Invention

[0005] The object of the present invention is to provide a polymer material with mechanochromic properties, which has a high thermal decomposition temperature / thermal stability and high mechanical properties to meet the requirements of use under high temperature and / or high mechanical property conditions.

[0006] The inventors of the present invention unexpectedly discovered that polybenzimidazole polymers inherently possess mechanochromic properties, without the need to dope the polymer with mechanochromic small molecules or chemically or non-chemically link mechanochromic groups to or on the polymer chain. More specifically, the inventors unexpectedly discovered that the fluorescence emission peak of polybenzimidazole polymers undergoes a significant shift when stimulated by an external force.

[0007] Therefore, the present invention provides the use of polybenzimidazole polymer as a mechanochromic material.

[0008] The polybenzimidazole polymer can be used as a mechanochromic material in applications such as mechanical sensing, communication, anti-counterfeiting, non-destructive testing of materials, motion detection, and micro-flow monitoring.

[0009] The present invention provides the following beneficial effects:

[0010] (1) The present invention discovered that polybenzimidazole has mechanochromic properties, which broadens the application field of polybenzimidazole;

[0011] (2) The fluorescence emission peak of the existing mechanochromic materials often red-shifts after being stimulated by external force, while some embodiments of the present invention provide polybenzimidazoles whose fluorescence emission peak blue-shifts after being stimulated by external force;

[0012] (3) Polybenzimidazole materials have excellent thermal stability and high mechanical strength, which broadens the application scenarios of mechanochromic materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG1 is a hydrogen nuclear magnetic spectrum of the polymer of Example 1 (PBI-1) and the polymer of Example 7 (PBI-7);

[0014] FIG2 is a thermogravimetric analysis spectrum of the polymer (PBI-1) of Example 1;

[0015] FIG3 is a fluorescence spectrum of the polymer (PBI-2) of Example 2 before and after grinding; and

[0016] FIG4 is a fluorescence spectrum of the polymer film product (PBI-9) of Example 9 before and after stretching. DETAILED DESCRIPTION

[0017] The endpoints of the ranges and any values ​​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 endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0018] In a first aspect, the present invention provides the use of polybenzimidazole as a mechanochromic material. The present invention finds that polybenzimidazole has mechanochromic properties. In the present invention, the polybenzimidazole can be any polybenzimidazole polymer known in the prior art.

[0019] According to the present invention, in some embodiments, the polybenzimidazole contains a structural unit A, and the structural unit A has a structure shown in formula (1):

[0020] Wherein, the X1 group is a linking group provided by an aromatic compound containing 1-10 benzene rings; and the Y group is an aromatic compound containing 1-10 benzene rings, a heteroaromatic compound containing 1-10 heterocyclic rings, an aromatic compound containing 1-3 heterocyclic rings and 1-8 benzene rings, a C4-C 10The linking group is provided by at least one compound selected from the group consisting of a cycloalkane, a C1-C8 alkane, and a C2-C8 alkene; wherein the X1 and Y groups each independently contain or are not present at least one substituent selected from the group consisting of hydroxyl, amino, cyano, halogen, C1-C4 alkyl, and C1-C4 haloalkyl. 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, structural unit A and structural unit D, or structural unit A, structural unit B, structural unit C and structural unit D; wherein the structural unit A has a structure represented by formula (1), the structural unit B has a structure represented by formula (2), the structural unit C has a structure represented by formula (1-1), and the structural unit D has a structure represented by formula (2-2):

[0022] Wherein, the X1 and X2 groups are each independently a linking group provided by an aromatic compound containing 1-10 benzene rings; and the Y and Z groups are each independently an aromatic hydrocarbon containing 1-10 benzene rings, a heteroaromatic hydrocarbon containing 1-10 heterocyclic rings, an aromatic hydrocarbon containing 1-3 heterocyclic rings and 1-8 benzene rings, a C4-C 10 A linking group is provided by at least one compound selected from the group consisting of a cycloalkane, a C1-C8 alkane, or a C2-C8 alkene; wherein each of the X1, X2, Y, and Z groups independently contains or does not contain at least one substituent selected from the group consisting of hydroxyl, amino, cyano, halogen, C1-C4 alkyl, and C1-C4 haloalkyl. In some embodiments, the polybenzimidazole is composed of structural units A and C. In some embodiments, the polybenzimidazole is composed of structural units A and D. In some embodiments, the polybenzimidazole is composed of structural units A, B, C, and D.

[0023] According to the present invention, in some embodiments, the polybenzimidazole contains or consists of a structural unit A and an optional structural unit B, wherein the structural unit A has a structure represented by formula (1), and the structural unit B has a structure represented by formula (2);

[0024] Wherein, the X1 and X2 groups are each independently a linking group provided by an aromatic compound containing 1-10 benzene rings; the Y and Z groups are each independently an aromatic compound containing 1-10 benzene rings, a heteroaromatic compound containing 1-10 heterocyclic rings, an aromatic compound containing 1-3 heterocyclic rings and 1-8 benzene rings, a C4-C 10The connecting group is provided by at least one compound selected from cycloalkanes, C1-C8 alkanes, and C2-C8 olefins, and when the structural unit B is present, Y and Z are different; wherein the X1, X2, Y and / or Z groups are each independently present or absent at least one substituent selected from hydroxyl, amino, cyano, halogen, C1-C4 alkyl, and C1-C4 haloalkyl.

[0025] In the present invention, those skilled in the art know how to connect the X1 and X2 groups in formula (1) and formula (2).

[0026] For example, for formula (1) and formula (2), when the X1 and X2 groups are each independently a linking group provided by benzene, the structural formulas of formula (1) and formula (2) can be That is, the benzene ring and the imidazole ring share two pairs of carbon atoms. Any two pairs of ortho-positioned carbon atoms on the benzene rings in the X1 and X2 groups participate in forming the imidazole ring. The two pairs of ortho-positioned carbon atoms can be from the same benzene ring or from different benzene rings. For example, when the X1 group is a linking group provided by biphenyl, each benzene ring of the biphenyl can provide a pair of carbon atoms to form the imidazole ring, or a single benzene ring can provide two pairs of ortho-positioned carbon atoms to form the imidazole ring.

[0027] In the present invention, C4-C 10 The cycloalkane may be, for example, cyclobutane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclononane or cyclodecane.

[0028] In the present invention, the C1-C8 alkane can be, for example, methane, ethane, n-propane, isopropane, butane, pentane, hexane, heptane or octane. In some embodiments, the C1-C8 alkane can also be a C1-C8 alkane substituted with one or more halogen atoms, wherein the halogen atoms can be selected from fluorine atoms, chlorine atoms and bromine atoms.

[0029] In the present invention, the C2-C8 olefin may be, for example, ethylene, propylene, butene, pentene, hexene, heptene or octene.

[0030] In the present invention, the halogen can be selected from, for example, fluorine, chlorine and bromine.

[0031] In the present invention, the C1-C4 alkyl group may be, for example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group or a tert-butyl group.

[0032] In the present invention, the C1-C4 haloalkyl group can be, for example, a halomethyl group, a haloethyl group, a halopropyl group, a haloisopropyl group, a halobutyl group, a halosec-butyl group, a haloisobutyl group or a halotert-butyl group; the halogen atom in the C1-C4 haloalkyl group can be, for example, selected from a fluorine atom, a chlorine atom and a bromine atom.

[0033] According to the present invention, preferably, in some embodiments, the X1 and X2 groups are each independently a linking group provided by at least one compound selected from benzene, biphenyl, terphenyl, bridged phenyl, pterygene, and a condensed aromatic hydrocarbon containing 1 to 10 benzene rings; more preferably, the X1 and X2 groups are each independently a linking group provided by at least one compound selected from benzene, biphenyl, bridged phenyl, pterygene, and naphthalene; further preferably, the bridged phenyl has a 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 heteroaromatic ring;

[0034] In the present invention, the heteroaromatic ring-containing compound may be, for example, pyridine or pyrimidine.

[0035] In the present invention, the connection positions (indicated by "dashed lines") of the structures represented by formula (3), formula (4) and formula (5) can be as follows:

[0036] In the present invention, the connection positions include but are not limited to the above-mentioned representations; for example, any two adjacent connection positions on the same benzene ring are feasible.

[0037] According to the present invention, preferably, in some embodiments, the X1 and X2 groups are each independently selected from the following linking groups:

[0038] wherein G is selected from a hydrogen atom, a methyl group, and a trifluoromethoxy group; J is selected from an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, a methylene group, and a methylene group substituted with a methyl group or a trifluoromethyl group; L is selected from a bromine atom, a phenyl group, and a phenyl group substituted with a trifluoromethyl group; and R is selected from a hydrogen atom, a carboxyl group, a hydroxyl group, and a trifluoromethyl group.

[0039] 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:

[0040] According to the present invention, in some embodiments, the Y and Z groups are each independently benzene, a 5-6 membered nitrogen-containing heterocyclic compound, an aromatic compound containing 2-7 benzene rings, an aromatic compound containing 1-2 nitrogen-containing heterocyclic rings and 1-5 benzene rings, a C4-C 10 The linking group is provided by a compound of at least one of cycloalkanes, C1-C8 alkanes, and C2-C8 alkenes.

[0041] According to the present invention, in some embodiments, the molar content 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 ranges 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 the polybenzimidazole is calculated based on the feed amount.

[0042] According to the present invention, preferably, in some embodiments, the Y and Z groups may each independently be a linking group selected from the following: C1-C8 chain alkyl;

[0043] wherein M is selected from a hydrogen atom, a cyano group, a methyl group, a phenyl group, and a phenyl group substituted with a methyl group or a trifluoromethyl group; P is selected from an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, a cyclobutyl group, a halogen-substituted cyclobutyl group, a methylene group, and a halogen-substituted methylene group; Q is selected from a bromine atom, a phenyl group, and a trifluoromethyl-substituted phenyl group; and T is selected from a hydrogen atom and a methyl group.

[0044] In the present invention, the connection position of the Y and Z groups is 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 groups, the connection position can be any carbon atom in the alkyl group. In the present invention, the connection position of the Y and Z groups can include, but is not limited to, the following connection positions:

[0045] In some embodiments, the polybenzimidazole polymers of the present invention do not contain mechanochromic groups generally known in the art, including but not limited to mechanochromic groups derived from tetraphenylethylene, triarylamines, spiropyrans, rhodamines, coumarins, and the like.

[0046] In the present invention, there is no particular limitation on the molecular weight of the polybenzimidazole. For example, the molecular weight of the polybenzimidazole can be selected according to specific application requirements.

[0047] According to the present invention, in some embodiments, the intrinsic viscosity of the polybenzimidazole can be 0.15-3.0 dL g -1 ; For example, it can be 0.15dL g -1 , 0.2dL g -1 , 0.3dL g-1 、0.4dL g -1 、0.8dL g -1 、1.2dL g -1 、1.6dL g -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 、2.4dL g -1 、2.5dL g -1 、2.6dL g - 1 、2.7dL g -1 、2.8dL g -1 、2.9dL g -1 、3.0dL g -1 and the range consisting of any two of the above points.

[0048] According to the present invention, in some embodiments, the molar content 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 ranges 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 the polybenzimidazole is calculated based on the feed amount.

[0049] In some embodiments of the present invention, a polybenzimidazole is provided whose fluorescence emission peak blue-shifts after being stimulated by an external force.

[0050] 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 can use polybenzimidazole polymers of various structures known in the art.

[0051] The preparation of polybenzimidazole is known in the art. Polybenzimidazole can be prepared using various preparation methods known in the art.

[0052] 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 a structure represented by formula (6) with HOOC-Y-COOH and optionally HOOC-Z-COOH;

[0053] The X group in formula (6) is the same as the X1 and / or X2 group in formula (1) and formula (2), and will not be described in detail here.

[0054] 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:

[0055] Wherein, G is selected from hydrogen atom, methyl and trifluoromethoxy, i.e. -H, -CH3, -OCF3;

[0056] J is selected from oxygen atoms, sulfur atoms, carbonyl groups, sulfonyl groups, methylene groups and methylene groups substituted with methyl or trifluoromethyl groups, for example,

[0057] L is selected from bromine atoms, phenyl groups and trifluoromethyl-substituted phenyl groups, for example, as well as

[0058] R is selected from hydrogen, carboxyl, hydroxyl and trifluoromethyl, i.e., -H, -COOH, -OH, -CF3.

[0059] According to the preparation method of the present invention, preferably, in some embodiments, HOOC-Y-COOH and the optional HOOC-Z-COOH are each independently selected from at least one of the following compounds:

[0060] Wherein, n=1-8;

[0061] M is selected from hydrogen, cyano, methyl, phenyl and phenyl substituted with methyl or trifluoromethyl, for example,

[0062] P is selected from oxygen atoms, sulfur atoms, carbonyl groups, sulfonyl groups, cyclobutyl groups, halogen-substituted cyclobutyl groups, methylene groups and methyl or trifluoromethyl-substituted methylene groups, for example,

[0063] Q is selected from bromine atoms, phenyl groups and trifluoromethyl-substituted phenyl groups, for example: as well as

[0064] T is selected from a hydrogen atom and a methyl group, ie, -H, -CH3.

[0065] 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, further preferably a mixed solution of methanesulfonic acid / phosphorus pentoxide, the mass of phosphorus pentoxide being 2-10% of the mass of methanesulfonic acid. The concentration of the mixed monomers in the reaction system may be 3wt%-20wt%. According to the preparation method of the present invention, preferably, in some embodiments, the ratio of the molar amount of the compound having the structure represented by formula (6) to the total molar amount of HOOC-Y-COOH and the optional HOOC-Z-COOH is 1:0.6-2, preferably 1:0.8-1.2.

[0066] In some embodiments, poly(2,5-benzimidazole) is prepared using 3,4-diaminobenzoic acid as a monomer.

[0067] According to the preparation method of the present invention, preferably, in some embodiments, the reaction time can be 1-8 hours, 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 normal pressure. According to the preparation method of the present invention, preferably, in some embodiments, the ratio of the molar amount of the compound having the structure shown in formula (6) to the total molar amount of HOOC-Y-COOH and the optional 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 the range consisting of any two of the above points; preferably 1:0.8-1.2; wherein the molar content ratio of the X2 to X1 group can be 0-9999, preferably 0-99, for example, 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 ranges consisting of any two of the above; the molar ratio of the Z to Y groups is 0-9999, preferably 0-99, for example, The amount may 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, or a range consisting of any two of the above.

[0068] In some embodiments, the polybenzimidazole of the present invention may have one of the following structures:

[0069] In the structures shown above, for copolymers, the structures shown only indicate that the polymer segments contain the repeating structural units shown or the polymer segments consist of the repeating structural units shown, and do not indicate the distribution of the repeating structural units shown in the polymer chain.

[0070] The present invention discovers that polybenzimidazole exhibits mechanochromic properties, i.e., its fluorescence emission peak undergoes a significant shift (red or blue shift) under external force stimulation. The external force stimulation includes, but is not limited to, mechanical effects such as grinding, stretching, pressing, and impact. This discovery is surprising because prior art polymers exhibiting mechanochromic properties either require doping with mechanochromic small molecules or the mechanochromic groups to be chemically or non-chemically bonded to or attached to the polymer molecular chain.

[0071] In some embodiments, the present application provides the application of polybenzimidazole as a force-induced chromic material, which may include the step of measuring the fluorescence emission spectrum of polybenzimidazole after the polybenzimidazole is subjected to an external force. Further, the application may also include the step of comparing the position of the fluorescence emission peak of the fluorescence emission spectrum of the polybenzimidazole measured after the external force is applied with the position of the fluorescence emission peak of the fluorescence emission spectrum of the polybenzimidazole before the external force is applied. The application may also send a warning signal based on the comparison result. For example, if the offset of the fluorescence emission peak of the fluorescence emission spectrum before and after the external force is applied exceeds a set threshold value (for example, 3nm, 5nm or 10nm, etc.), a warning signal may be issued.

[0072] The present invention also provides applications of polybenzimidazole polymers as mechanochromic materials in mechanical sensing, communications, anti-counterfeiting, non-destructive material testing, motion detection, and microflow monitoring. Preferably, these applications include at least one of stress sensors, anti-counterfeiting paper, color-changing textiles, pressure sensors for compression therapy bandages, and microflow monitors. In these applications, polybenzimidazole can, for example, change color in response to mechanical forces, thereby providing useful information.

[0073] 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 force on the polybenzimidazole changes, causing a change in the fluorescence emission peak. This change can be captured by a detector external to the microchannel, thus enabling flow monitoring. Another example is a polybenzimidazole membrane placed on the outside of a pipe. When the pipe deforms, the polybenzimidazole membrane also deforms, causing a change in the fluorescence emission peak. This change can be captured by an external detector, thus providing an early warning of pipe aging.

[0074] The present invention will be described in detail below through examples.

[0075] In the following examples,

[0076] The polymer yield was calculated according to the following formula:

[0077] Yield = actual polymer yield ÷ theoretical polymer yield × 100%;

[0078] The theoretical yield of the polymer = the number of moles of the compound represented by formula (6) × the molar mass of the repeating units in the polymer structure.

[0079] 3,3′,4,4′-Tetraaminobiphenyl: Sigma-Aldrich; purity: 98%;

[0080] 4,4′-Diphenylether dicarboxylic acid: J&K Technology; purity 98%;

[0081] Isophthalic acid: J&K Technology, purity 98%;

[0082] Terephthalic acid: J&K Technology, purity 98%;

[0083] 4,6-pyrimidinedicarboxylic acid: J&K Technology, purity 98%;

[0084] 2,5-Dihydroxyterephthalic acid: J&K Technologies, purity 98%;

[0085] 3,5-Pyridinedicarboxylic acid: J&K Technology, purity 98%;

[0086] 5-aminoisophthalic acid: J&K Technology, purity 98%;

[0087] 1-Methylbenzimidazole: Inokai Technology, purity 98%;

[0088] 2-Hydroxybenzimidazole: Inotech Technology, purity 98%.

[0089] Example 1

[0090] A mixture of 3,3',4,4'-tetraaminobiphenyl (2.14 g) and 4,4'-diphenylether dicarboxylic acid (2.79 g) in a molar ratio of 1:1.08 was added to a methanesulfonic acid / phosphorus pentoxide solution (44 g solvent) to form a reaction system. The mixture was reacted at 150°C for 3 hours to obtain a reaction solution. The reaction solution was then introduced into water to precipitate the polymer, which was then neutralized (with sodium bicarbonate) and filtered 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 H NMR spectrum of PBI-1 was measured in Test Example 6 and is shown in Figure 1. Its structure was confirmed by H NMR spectrum.

[0091] Example 2

[0092] The reaction was carried out according to the method of Example 1, except that 4,4′-diphenyl ether dicarboxylic acid was replaced with an equal molar amount of terephthalic acid. The reaction time was 4 h. The yield of polymer PBI-2 was 99%. Its structure was confirmed by H NMR spectroscopy.

[0093] Example 3

[0094] A mixture of 3,3',4,4'-tetraaminobiphenyl (2.14 g), isophthalic acid (1.57 g), and 4,6-pyrimidinedicarboxylic acid (0.18 g) in a molar ratio of 1:0.945:0.105 was added to a methanesulfonic acid / phosphorus pentoxide solution (35 g solvent) to form a reaction system. The mixture was reacted at 150°C for 3 hours to obtain a reaction solution. The reaction solution was then poured into water to precipitate the polymer, which was then neutralized (with sodium bicarbonate) and filtered 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 mixture in the reaction system was 10 wt%. The yield of polymer PBI-3 was 99%. Its structure was confirmed by H NMR spectroscopy.

[0095] Example 4

[0096] The reaction was carried out according to the method of Example 3, except that 4,6-pyrimidinedicarboxylic acid was replaced with an equal molar amount of 2,5-dihydroxyterephthalic acid. The reaction time was 4 h. The yield of polymer PBI-4 was 99%. Its structure was confirmed by H NMR spectroscopy.

[0097] Example 5

[0098] The reaction was carried out according to the method of Example 3, except that 4,6-pyrimidinedicarboxylic acid was replaced with an equal molar amount of 3,5-pyridinedicarboxylic acid. The reaction time was 5 h. The yield of polymer PBI-5 was 99%. Its structure was confirmed by H NMR spectroscopy.

[0099] Example 6

[0100] The reaction was carried out according to the method of Example 3, except that 4,6-pyrimidinedicarboxylic acid was replaced with an equal molar amount of 5-aminoisophthalic acid. The reaction time was 4 h. The yield of polymer PBI-6 was 99%. Its structure was confirmed by H NMR spectroscopy.

[0101] Example 7

[0102] A mixture of 3,3',4,4'-tetraaminobiphenyl (2.14 g), 4,4'-diphenylether dicarboxylic acid (2.44 g), and 5-aminoisophthalic acid (0.19 g) in a molar ratio of 1:0.945:0.105 was added to a methanesulfonic acid / phosphorus pentoxide solution (43 g solvent) to form a reaction system. The mixture was reacted at 150°C for 3 hours to obtain a reaction solution. The reaction solution was then introduced into water to precipitate the polymer, which was then neutralized (with sodium bicarbonate) and filtered 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 H NMR spectrum of PBI-7 was measured in Test Example 6 and is shown in Figure 1. Its structure was confirmed by H NMR spectrum.

[0103] Example 8

[0104] The procedure of Example 7 was followed, 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 H-NMR spectroscopy.

[0105] Example 9

[0106] The reaction was carried out according to the method of Example 1, except that 4,4′-diphenyl ether dicarboxylic acid was replaced with an equal molar amount of isophthalic acid. The reaction time was 5 h. The yield of polymer PBI-9 was 99%. Its structure was confirmed by H NMR spectroscopy.

[0107] PBI-9 was dissolved in DMSO solvent (concentration of 4 wt%), cast on a flat glass, placed in an 80° C. oven for 10 h, and then taken out to obtain a PBI-9 membrane product, which was labeled as PBI-9.

[0108] Example 10

[0109] The PBI membrane products were purchased from FuMA-Tech in Germany and were labeled as PBI-10.

[0110] Example 11

[0111] The PBI membrane products purchased were from BASF in Germany and were labeled as PBI-11.

[0112] Test Example 1

[0113] The polymers (powders) prepared in Examples 1-8 above were tested for their mechanochromic properties.

[0114] Testing method: Polymer powder was placed in a solid fixture (two transparent quartz plates, one with a sample recess) and placed in a fluorimeter (Edinburgh Steady-State / Transient Fluorescence Spectrometer FLS1000) to measure the fluorescence emission spectrum. The polymer powder was then manually ground in a mortar for 30 seconds, placed in the solid fixture, and again placed in the fluorimeter to measure the fluorescence emission spectrum. The shifts in the strongest fluorescence emission peaks before and after grinding of the polymer powder are shown in Table 1.

[0115] Test Example 2

[0116] The polymer films of Examples 9-11 were tested for their mechanochromic properties.

[0117] Mechanochromic properties of polymer films were tested by placing the film in a solid fixture and measuring the fluorescence emission spectrum using a fluorimeter (Edinburgh Steady-State / Transient Fluorescence Spectrometer FLS1000). The film was clamped at both ends with tweezers and stretched for 30 seconds without breaking. The film was then placed in the solid fixture and placed back in the fluorimeter to measure the fluorescence emission spectrum. The film thickness was 40 ± 5 μm. The shifts in the peak fluorescence emission before and after stretching are shown in Table 1.

[0118] Table 1

[0119] Note: “#” indicates the emission peak is blue-shifted; “*” indicates the emission peak is red-shifted.

[0120] Test Example 3

[0121] The thermal stability of the polymers prepared in the above examples was tested.

[0122] Thermogravimetric analysis test method: The test was conducted using a Q500 thermogravimetric analyzer from TA (USA) in a nitrogen atmosphere. The heating rate was 10°C / min and the temperature range was 25-700°C. The thermal decomposition temperature of the polymer was T d5％ (Temperature at 5% mass loss) is shown in Table 2.

[0123] Table 2

[0124] Test Example 4

[0125] The intrinsic viscosity of the polymers prepared in the above examples was tested.

[0126] Intrinsic viscosity test method: PBI was dissolved in concentrated sulfuric acid to a concentration of 0.6 g dL - 1Sulfuric acid solution. Add the sulfuric acid solution to the Ubbelohde viscometer and place it in a 25°C constant temperature water bath to stabilize for 30 minutes. Measure the outflow time of the solution. Each sample is measured three times, and the time difference is no more than 1 second. The average value is recorded as t1, and the outflow time of concentrated sulfuric acid is recorded as t0. The formula for calculating the intrinsic viscosity [η] of PBI is as follows: Intrinsic viscosity Wherein, C is the concentration of PBI sulfuric acid solution. The test results are shown in Table 3.

[0127] Table 3

[0128] Test Example 5

[0129] The mechanical strength of the film prepared in Example 9 was tested.

[0130] Mechanical testing method: The 5965 universal tensile testing machine from Instron (USA) was used, with a tensile rate of 1 mm / min and a test temperature of 25°C.

[0131] The modulus of the PBI-9 membrane is 2.5 GPa, and the nominal modulus of the purchased PBI-10 is 4.5 GPa, both of which exhibit excellent mechanical properties.

[0132] Test Example 6

[0133] The polymers of the examples were tested by hydrogen nuclear magnetic spectra.

[0134] H NMR test method: Agilent 400-MR DD2 NMR spectrometer was used with a frequency of 400 MHz, tetramethylsilane (TMS) as the internal standard, DMSO-d6 as the solvent, and a test temperature of 40°C.

[0135] The H NMR spectra of the polymers of Example 1 and Example 7 are shown in Figure 1. The proton signal at the chemical shift of 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.

[0136] The results of H-NMR spectra showed that polymers PBI-1 to PBI-9 were successfully obtained.

[0137] Comparative Example

[0138] The mechanochromic properties of 1-methylbenzimidazole and 2-hydroxybenzimidazole were tested according to the method of Test Example 1. The test results showed that after grinding, the strongest fluorescence emission peaks of the two materials did not change, indicating that they did not exhibit mechanochromic properties.

[0139] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. Application of polybenzimidazole as mechanochromic material.

2. The use according to claim 1, wherein: The polybenzimidazole contains a structural unit A, and the structural unit A has a structure shown in formula (1): wherein the X1 group is a connecting group provided by an aromatic compound containing 1 to 10 benzene rings; and the Y group is an aromatic compound containing 1 to 10 benzene rings, a heteroaromatic compound containing 1 to 10 heterocyclic rings, an aromatic compound containing 1 to 3 heterocyclic rings and 1 to 8 benzene rings, a C4-C 10 A connecting group is provided by at least one compound selected from cycloalkanes, C1-C8 alkanes, and C2-C8 olefins; wherein the X1 and Y groups each independently contain or do not contain at least one substituent selected from hydroxyl, amino, cyano, halogen, C1-C4 alkyl, and C1-C4 haloalkyl.

3. The use according to claim 1 or 2, wherein: The polybenzimidazole contains structural unit A and structural unit C, structural unit A and structural unit D, or structural unit A, structural unit B, structural unit C and structural unit D; The structural unit A has a structure shown in formula (1), the structural unit B has a structure shown in formula (2), the structural unit C has a structure shown in formula (1-1), and the structural unit D has a structure shown in formula (2-2): Wherein, the X1 and X2 groups are each independently a connecting group provided by an aromatic compound containing 1 to 10 benzene rings; the Y and Z groups are each independently an aromatic compound containing 1 to 10 benzene rings, a heteroaromatic compound containing 1 to 10 heterocyclic rings, an aromatic compound containing 1 to 3 heterocyclic rings and 1 to 8 benzene rings, a C4-C 10 A connecting group provided by at least one compound selected from cycloalkane, C1-C8 alkane, C2-C8 olefin; wherein X1, X2, Y and Z groups independently contain or do not contain at least one selected from hydroxyl, amino, cyano, halogen, C1-C4 alkyl, C1-C4 haloalkyl Substituent.

4. The use according to claim 1 or 2, wherein: The polybenzimidazole contains a structural unit A and an optional structural unit B, wherein the structural unit A has a structure represented by formula (1), and the structural unit B has a structure represented by formula (2); Wherein, the X1 and X2 groups are each independently a connecting group provided by an aromatic compound containing 1 to 10 benzene rings; the Y and Z groups are each independently an aromatic compound containing 1 to 10 benzene rings, a heteroaromatic compound containing 1 to 10 heterocyclic rings, an aromatic compound containing 1 to 3 heterocyclic rings and 1 to 8 benzene rings, a C4-C 10 A connecting group is provided by at least one compound selected from cycloalkanes, C1-C8 alkanes, and C2-C8 olefins, and when the structural unit B is present, Y and Z are different; wherein, at least one substituent selected from hydroxyl, amino, cyano, halogen, C1-C4 alkyl, C1-C4 haloalkyl is present or absent on the X1, X2, Y and / or Z groups independently.

5. The use according to any one of claims 2 to 4, wherein: The X1 and X2 groups are each independently a linking group provided by at least one compound selected from benzene, biphenyl, terphenyl, bridged benzene, pterygene and condensed aromatic hydrocarbons containing 1 to 10 benzene rings; preferably, the X1 and X2 groups are each independently a linking group provided by at least one compound selected from benzene, biphenyl, bridged benzene, pterygene and naphthalene; more preferably, the bridged benzene has a structure shown in formula (3), formula (4) or formula (5), wherein R1, R3 and R4 are each independently selected from oxygen atoms, sulfur atoms, carbonyl groups, sulfonyl groups, methylene groups and halogen-substituted methylene groups; and R2 is selected from heteroaromatic rings; Further preferably, the X1 and X2 groups are each independently selected from the following linking groups: wherein G is selected from a hydrogen atom, a methyl group and a trifluoromethoxy group; J is selected from an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, a methylene group and a methylene group substituted with a methyl group or a trifluoromethyl group; L is selected from a bromine atom, a phenyl group and a phenyl group substituted with a trifluoromethyl group; and R is selected from a hydrogen atom, a carboxyl group, a hydroxyl group and a trifluoromethyl group.

6. The use according to any one of claims 2 to 5, wherein: The Y and Z groups are each independently benzene, a 5-6 membered nitrogen-containing heterocyclic compound, an aromatic compound containing 2-7 benzene rings, an aromatic compound containing 1-2 nitrogen-containing heterocyclic rings and 1-5 benzene rings, a C4-C 10 A linking group provided by a compound of at least one of cycloalkane, C1-C8 alkane and C2-C8 alkene; Preferably, the Y and Z groups are each independently a linking group selected from the following: C1-C8 alkyl; wherein M is selected from a hydrogen atom, a cyano group, a methyl group, a phenyl group, and a phenyl group substituted with a methyl group or a trifluoromethyl group; P is selected from an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, a cyclobutyl group, a cyclobutyl group substituted with a halogen group, a methylene group, and a methylene group substituted with a halogen group; Q is selected from a bromine atom, a phenyl group, and a phenyl group substituted with a trifluoromethyl group; and T is selected from a hydrogen atom and a methyl group.

7. The use according to claim 1, wherein the polybenzimidazole is poly(2,5-benzimidazole).

8. The use according to any one of claims 1 to 7, wherein: The intrinsic viscosity of the polybenzimidazole is 0.15-3.0 dL g -1 and / or, The molar content ratio of X2 to X1 groups in the polybenzimidazole is 0-9999, preferably 0-99; and / or, The molar content ratio of the Z and Y groups in the polybenzimidazole is 0-9999, preferably 0-99.

9. The use according to any one of claims 1-8, wherein the polybenzimidazole is used as a mechanochromic material in mechanical sensing, communication, anti-counterfeiting, non-destructive material testing, motion detection, and micro-flow monitoring; preferably, it is used in stress sensors, anti-counterfeiting paper, color-changing textiles, pressure sensors for bandages during compression therapy, and micro-flow monitors.

10. The use according to any one of claims 1 to 9, wherein the fluorescence emission peak of the polybenzimidazole blue-shifts after being stimulated by external force.

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