Diamine monomer containing acrylonitrile structure and black polyimide synthesized by diamine monomer

Abstract

The invention belongs to the technical field of organic polymer materials, and discloses a diamine monomer containing an acrylonitrile structure and black polyimide synthesized by the diamine monomer. The black diamine monomer containing the acrylonitrile structure is synthesized by taking a monomer containing a benzyl cyanide structure and a monomer containing a benzaldehyde structure as raw materials. And carrying out polycondensation on the synthesized diamine monomer (added with other diamines) and a dianhydride monomer to obtain a polyamide acid solution, and preparing the black polyimide by a thermal method or a chemical imine method. The diamine monomer containing the acrylonitrile structure with the large-plane conjugated structure and the light absorption effect is used for preparing the intrinsic black polyimide, the method is simple and efficient, and the black polyimide can be prepared without adding or coating any black substance. The prepared black polyimide is excellent in shading performance and heat resistance and has wide application value in the fields of electronic industry, aerospace, instrument communication and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of organic polymer materials, and particularly relates to a diamine monomer containing an acrylonitrile structure and a black polyimide synthesized therefrom. Background Art

[0002] Polyimide (PI), a prominent representative of engineering plastics, is widely used in many high-tech fields due to its excellent comprehensive properties, including high and low temperature stability, excellent chemical resistance, excellent mechanical properties, and excellent electrical insulation. Driven by the rapid development of optoelectronic devices, black polyimide, a new type of polyimide, has seen a surge in demand in many fields due to its complete absorption of visible light. For example, it can be used as a light-absorbing film in optical fixed attenuators and optical terminals to eliminate and prevent various light interferences on imaging systems and sensors; as a masking layer on printed circuit boards to protect the intellectual property of circuit designs; and as an insulating protective film on the copper connectors of lithium-ion batteries to prevent copper oxidation under the influence of light and heat.

[0003] At present, the method for preparing black polyimide is to add various light-shielding materials, such as carbon black, graphene, carbon nanotubes, black BR (CI solvent black 34), metal oxides or other inorganic or organic black fillers, to a polyamic acid (PAA) matrix. For example, a method in which a prepared black slurry is added to a polyamic acid resin solution, stirred and heated to obtain a black polyamic acid solution, and finally a black polyimide film is prepared is disclosed in patent CN 105418948A. This method inevitably destroys its mechanical properties, heat resistance, etc. Due to the uneven distribution and pinholes caused by the introduction of carbon materials and metal oxides, the mechanical properties are inevitably destroyed, and the composite material of organic compounds also reduces the heat resistance of PI.

[0004] The present invention provides a method for preparing an intrinsically black polyimide film. The film produced by this method covers nearly the entire visible light range, exhibiting a significant shielding effect and good thermodynamic properties. This black polyimide film has broad application prospects in the electronics industry and aerospace fields. Summary of the Invention

[0005] The main purpose of the present invention is as follows:

[0006] 1.Synthesize a diamine monomer with an acrylonitrile structure.

[0007] 2. Provide a method for synthesizing the above-mentioned diamine monomer.

[0008] 3. Provide a black polyimide prepared only from the above diamine monomer without adding a black substance or coating a light-shielding substance.

[0009] 4. Provide a method for preparing the above-mentioned black polyimide.

[0010] In order to achieve the above objectives, the present invention provides the following technical solutions:

[0011] 1. Preparation method and main steps of diamine monomer containing acrylonitrile structure

[0012] (1) Using monomers containing a benzyl cyanide structure and a benzaldehyde structure as raw materials, ethanol as solvent, and sodium ethoxide or piperidine as catalyst, stirring and refluxing for about 36 hours, cooling to room temperature, and then filtering to obtain a solid, washing with water and ethanol, drying, and then purifying by silica gel chromatography to obtain product 1 (containing a dinitro group) and product 2 (not containing a nitro group);

[0013] (2) adding the product 2 (containing no nitro group) of step (1) to a mixed solution of concentrated nitric acid and dilute sulfuric acid, heating the mixture for 24 h, filtering the solid product, washing it with water and ethanol, drying it, and then purifying it by silica gel chromatography to obtain product 3;

[0014] (3) The product 1 (containing a nitro group) in step (1) or the product 3 in step (2) is used as a raw material to undergo reductive amination to obtain a diamine monomer containing an acrylonitrile structure.

[0015] 2. Preparation of a black polyimide:

[0016] The black polyimide prepared from the diamine monomer containing acrylonitrile structure of the present invention has the following structural formula: R1 = an aliphatic or aromatic group, and the position of R1 can be 2, 3, 4, 5, or 6 on the benzene ring. R2 = aliphatic or aromatic group, and the position of R1 can be 2, 3, 4, 5, or 6 on the benzene ring. R3= R4=

[0017] The preparation method of the black polyimide film involved in the present invention is as follows:

[0018] (1) The prepared dry diamine monomer containing an acrylonitrile structure (other diamines may be added) is dissolved in an anhydrous polar aprotic solvent, wherein the molar content of the diamine monomer containing an acrylonitrile structure is 5% to 25%. Then, the dianhydride monomer is added, and mechanical stirring is performed at low temperature for a period of time to obtain a uniform polyamic acid solution.

[0019] (2) The polyamic acid solution in step (1) is subjected to thermal imidization or chemical imidization to obtain a black polyimide containing an acrylonitrile structure.

[0020] Preferably, the other diamine monomers are one or more of the following diamines: 4,4'-diaminodiphenyl ether, m-phenylenediamine, p-phenylenediamine, p-phenylenediamine, benzyldiamine, 4,4'-diaminodiphenyl sulfide, benzidine, 3,3'-diaminobiphenyl, 1,3-bis(4-nitrophenoxy)benzene, 1,4-bis(4-nitrophenoxy)benzene; the dianhydride is pyromellitic dianhydride, 2,3,3',4-biphenyl dianhydride, 2,3,2',3 ' any one or more of the dianhydrides selected from the group consisting of biphenyl dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 2,3,3',4-benzophenone tetracarboxylic dianhydride, 2,2',3,3'-diphenyl ether tetracarboxylic dianhydride, 3,4,3',4'-diphenyl ether dianhydride, 2,3,2',3'-diphenyl ether dianhydride, 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride and 4,4'-oxydiphthalic dianhydride.

[0021] Preferably, the dianhydride monomer is: pyromellitic dianhydride, 2,3,3',4-biphenyl dianhydride, 2,3,2',3'biphenyl dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 2,3,3',4-benzophenone tetracarboxylic dianhydride, 2,2',3,3'-diphenyl ether tetracarboxylic dianhydride, 3,4,3',4'-diphenyl ether dianhydride, 2,3,2',3'-diphenyl ether dianhydride, 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride, 4,4'-oxydiphthalic dianhydride and the like.

[0022] Preferably, the polar aprotic solvent is any one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, and dimethyl sulfoxide.

[0023] Preferably, the feed ratio of the diamine monomer containing acrylonitrile structure to the aromatic dianhydride is 1:1.05 to 1:1.1.

[0024] Preferably, the condensation reaction between the amino group and the acid anhydride is carried out at low temperature, under nitrogen protection, and for a reaction time of 16 hours to 24 hours.

[0025] Preferably, the programmed temperature conditions of the thermal imidization method are: 75°C to 85°C / 30min to 60min, 120°C to 140°C / 30min to 60min, 150°C to 180°C / 30min to 60min, 210°C to 240°C / 1h to 2h, and 270°C to 300°C / 2h to 3h.

[0026] The diamine monomer and polyimide synthesis method involved in the present invention has the following advantages compared with the reported methods:

[0027] (1) The diamine monomer synthesized by this method has high yield and short reaction time, and the diamine monomer has good solubility in most aprotic solvents.

[0028] (2) This method utilizes the introduction of an acrylonitrile structure with a light-absorbing effect to prepare a diamine monomer with a black-red color.

[0029] (3) This method utilizes the above-mentioned diamine monomer to prepare an intrinsically black polyimide film.

[0030] (4) The black polyimide film prepared by this method has excellent absorption in the visible light region without the need to add any black material or coating. Compared with traditional polyimide films, it has superior light-shielding properties and also exhibits superior thermodynamic properties. This film has broad application prospects in the fields of electronics, aerospace, and other fields, and is particularly significant for the development of photothermal materials and core technology materials for electronic products. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the H-NMR spectrum of the diamine monomer containing acrylonitrile structure synthesized in Example 1.

[0032] Figure 2 This is the infrared absorption spectrum of the black polyimide prepared in Example 1.

[0033] Figure 3 This is the ultraviolet spectrum of the black polyimide prepared in Example 1.

[0034] Figure 4 This is a physical picture of the black polyimide prepared in Example 1. Specific implementation methods

[0035] The present invention will be further described below in conjunction with examples. These examples are intended to illustrate the present invention only and are not intended to limit the scope of the invention. The raw materials, reagents, etc. used in the following examples, unless otherwise specified, are all raw materials and reagents available from commercial sources such as conventional markets. Any insubstantial changes and replacements made by those skilled in the art based on the present invention all fall within the scope of protection claimed in the present invention.

[0036] Example 1

[0037] This example provides a method for synthesizing 3,3'-(1,4-phenylene)bis(2-(4-nitrophenyl)acrylonitrile) and its black polyimide (added in an amount of 10%):

[0038] (1) Synthesis of 3,3'-(1,4-phenylene)bis(2-(4-nitrophenyl)acrylonitrile)

[0039] In a 250 mL three-necked flask, 5.000 g (37.3 mmol) of terephthalaldehyde and 12.089 g (74.6 mmol) of 4-nitrophenylacetonitrile were weighed using an analytical balance and added to 125 mL of anhydrous ethanol. The mixture was heated and stirred until completely dissolved. Then, the catalyst sodium ethoxide (approximately 2 g) was added. After the reaction was completed, the mixture was filtered and washed with water, anhydrous ethanol, and tetrahydrofuran. After vacuum drying, a reddish-brown product 1 was obtained.

[0040] In a 100ml two-necked flask, weigh 3.000g (7.1mmol) of 3,3'-(1,4-phenylene)bis(2-(4-nitrophenyl)acrylonitrile) and 3.411g (14.2mmol) of sodium sulfide nonahydrate. Add the sodium sulfide nonahydrate (Na2S·9H2O) to 35.5mL of 1,4-dioxane and heat with stirring until dissolved. Then, add 3,3'-(1,4-phenylene)bis(2-(4-nitrophenyl)acrylonitrile) and heat to 80°C for 36 hours. After the reaction is complete, cool to room temperature and adjust the reaction mixture to pH 7-8 with saturated sodium bicarbonate solution. Filter, rinse with copious amounts of water, and dry in an oven at 80°C to obtain the desired dark red product.

[0041] product 1 HNMR, infrared spectra such as Figure 1 As shown in the figure, it can be seen that the product synthesized by the reaction is the 3,3'-(1,4-phenylene)bis(2-(4-nitrophenyl)acrylonitrile) of the present invention.

[0042] (2) Preparation method of black polyimide prepared from the above monomers: 0.2g of diamine containing acrylonitrile structure, 1.00g of para-aminodiphenyl ether (ODA), and 1.63g of biphenyltetracarboxylic dianhydride (BPDA), with a molar ratio of 1:9:10, of which the diamine containing acrylonitrile structure accounts for 10%, and 14.16g of N,N'-dimethylacetamide (DMAc). First, the diamine containing acrylonitrile structure and ODA are added to a two-necked flask. Under argon protection, DMAc is added and stirred to dissolve the diamine solid. Then, BPDA is added to the flask. After stirring in a cold water bath for 4 hours, stirring is continued at room temperature for 20 hours to obtain a PAA acid solution with a solid content of 20wt%.

[0043] After allowing the polyamic acid solution to stand naturally to defoam, it was evenly coated onto a dry, clean glass plate and subjected to thermal imidization. The temperature was programmed as follows: 80°C for 3 hours to evaporate the solvent; then the temperature was increased to 110°C / hour, 150°C / hour, 200°C / hour, 250°C / hour, and 300°C / hour. After the imidization was complete, the film was cooled naturally and then demolded to produce a black polyimide film.

[0044] The infrared spectrum of polyimide is as follows ( Figure 2 ) It can be seen that there is an obvious characteristic peak of the imide group, 1778cm -1 C=O asymmetric stretching vibration peak, 1721cm -1 is the C=O symmetric stretching vibration peak, 1358cm -1 It is the CN stretching vibration peak. At 3500-3200cm -1 There is no characteristic absorption peak of amine group at 2900-3200cm -1 There are no characteristic absorption peaks of amide groups (COOH and NH2) (2871cm -1 These peaks indicate that the polyimide acid has been successfully imidized into polyimide. -1 Around 30 ℃, the latter showed an absorption peak, which was the absorption peak of -CN, indicating that the synthesized diamine monomer participated in the polymerization.

[0045] The UV spectrum of polyimide ( Figure 3 ), we can see from the figure that the product has low transmittance and large cutoff wavelength. The film thickness is about 40μm, and the cutoff wavelength λ cut-off The transmittance at 700nm is less than 10%, which can cover the entire visible light region. Figure 4 The results are consistent with the physical images of polyimide shown.

[0046] Example 2

[0047] This example provides a method for synthesizing 2,2'-(1,4-phenylene)bis(3-(4-aminophenyl)acrylonitrile) and its black polyimide:

[0048] (1) Synthesis of 2,2'-(1,4-phenylene)bis(3-(4-aminophenyl)acrylonitrile)

[0049] Take a 250mL three-necked flask, use an analytical balance to weigh 5.000g (47.1mmol) of benzaldehyde and 3.72g (23.55mmol) of 1,4-benzenediacetonitrile, add them to 125mL of anhydrous ethanol, heat and stir until completely dissolved, then add the catalyst sodium ethoxide (about 2g). After the reaction is completed, filter, wash with water, anhydrous ethanol, and tetrahydrofuran, and vacuum dry to obtain a reddish-brown product.

[0050] In a 100ml two-necked flask, weigh 3.000g (7.1mmol) of 2,2'-(1,4-phenylene)bis(3-(4-nitrophenyl)acrylonitrile) and 3.411g (14.2mmol) of sodium sulfide nonahydrate. Add the sodium sulfide nonahydrate (Na2S·9H2O) to 35.5mL of 1,4-dioxane and heat with stirring until dissolved. Then, add 3,3'-(1,4-phenylene)bis(2-(4-nitrophenyl)acrylonitrile) and heat to 80°C for 36 hours. After the reaction is complete, cool to room temperature and adjust the reaction mixture to pH 7-8 with saturated sodium bicarbonate solution. Filter, rinse with copious amounts of water, and dry in an oven at 80°C to obtain the desired dark red product.

[0051] (2) Preparation of a black polyimide from the above monomers: 0.2 g of acrylonitrile-containing diamine, 1.00 g of para-aminodiphenyl ether (ODA), 1.63 g of biphenyltetracarboxylic dianhydride (BPDA), in a molar ratio of 1:9:10, and 14.16 g of N,N'-dimethylacetamide (DMAc). The acrylonitrile-containing diamine and ODA were first added to a two-necked flask. Under argon protection, DMAc was added and stirred to dissolve the diamine solid. BPDA was then added to the flask. After stirring in a cold water bath for 4 h, stirring was continued at room temperature for 20 h to obtain a PAA acid solution with a solid content of 20 wt%.

[0052] After allowing the polyamic acid solution to stand naturally to defoam, it was evenly coated onto a dry, clean glass plate and subjected to thermal imidization. The temperature was programmed as follows: 80°C for 3 hours to evaporate the solvent; then the temperature was increased to 110°C / hour, 150°C / hour, 200°C / hour, 250°C / hour, and 300°C / hour. After the imidization was complete, the film was cooled naturally and then demolded to produce a black polyimide film.

[0053] Example 3

[0054] This example provides a method for synthesizing 2,3-bis(4-aminophenyl)acrylonitrile and its black polyimide (added in an amount of 10%):

[0055] (1) Synthesis of 2,3-bis(4-aminophenyl)acrylonitrile

[0056] Take a 250mL three-necked flask, use an analytical balance to weigh 5.000g (33.08mmol) of 4-nitrobenzaldehyde and 5.36g (33.08mmol) of 4-nitrophenylacetonitrile, add them to 125mL of anhydrous ethanol, heat and stir until completely dissolved, then add the catalyst sodium ethoxide (about 2g). After the reaction is completed, filter, wash with water, anhydrous ethanol, and tetrahydrofuran, and vacuum dry to obtain a reddish-brown product.

[0057] In a 100ml two-necked flask, weigh 5g (16.9mmol) of 2,3-bis(4-aminophenyl)acrylonitrile and 10g (41.6mmol) of sodium sulfide nonahydrate. Add the sodium sulfide nonahydrate (Na2S·9H2O) to 100mL of 1,4-dioxane and heat with stirring until dissolved. Then, add 2,3-bis(4-nitrophenyl)acrylonitrile and heat to 80°C for 36 hours. After the reaction is complete, cool to room temperature and adjust the pH of the reaction mixture to 7-8 with saturated sodium bicarbonate solution. Filter, rinse with copious amounts of water, and dry in an oven at 80°C to obtain the desired dark-red product.

[0058] (2) Preparation of a black polyimide from the above monomers: 1 g of acrylonitrile-containing diamine, 6.10 g of para-aminodiphenyl ether (ODA), 9.96 g of biphenyltetracarboxylic dianhydride (BPDA), in a molar ratio of 1:9:10, and 85 g of N,N'-dimethylacetamide (DMAc). The acrylonitrile-containing diamine and ODA were first added to a two-necked flask. Under argon protection, DMAc was added and stirred to dissolve the diamine solid. BPDA was then added to the flask. After stirring in a cold water bath for 4 h, stirring was continued at room temperature for 20 h to obtain a PAA acid solution with a solid content of 20 wt%.

[0059] After allowing the polyamic acid solution to stand naturally to defoam, it was evenly coated onto a dry, clean glass plate and subjected to thermal imidization. The temperature was programmed as follows: 80°C for 3 hours to evaporate the solvent; then the temperature was increased to 110°C / hour, 150°C / hour, 200°C / hour, 250°C / hour, and 300°C / hour. After the imidization was complete, the film was cooled naturally and then demolded to produce a black polyimide film.

[0060] Example 4

[0061] This example provides a method for synthesizing (2Z,2'Z)-2,2'-(6,6'-dihydroxy-5,5'-dimethoxy-[1,1'-biphenyl]-3,3'-diyl)bis(3-(4-aminophenyl)acrylonitrile) and the intrinsic black polyimide prepared therefrom (addition amount is 10%):

[0062] (1) Synthesis method of (2Z, 2'Z)-2,2'-(6,6'-dihydroxy-5,5'-dimethoxy-[1,1'-biphenyl]-3,3'-diyl)bis(3-(4-nitrophenyl)acrylonitrile

[0063] Take a 250mL three-necked flask, use an analytical balance to weigh 5.000g (33.08mmol) of 4-nitrobenzaldehyde and 5.36g (33.08mmol) of 4-nitrophenylacetonitrile, add them to 125mL of anhydrous ethanol, heat and stir until completely dissolved, then add the catalyst sodium ethoxide (about 2g). After the reaction is completed, filter, wash with water, anhydrous ethanol, and tetrahydrofuran, and vacuum dry to obtain a reddish-brown product.

[0064] In a 100ml two-necked flask, weigh 5g (16.9mmol) of the above product and 10g (41.6mmol) of sodium sulfide nonahydrate. Add the sodium sulfide nonahydrate (Na2S·9H2O) to 100mL of 1,4-dioxane and heat with stirring until dissolved. Then add the above product and heat to 80°C for 36h. After the reaction is complete, cool to room temperature and adjust the pH of the reaction mixture to 7-8 with saturated sodium bicarbonate solution. Filter, rinse with copious amounts of water, and dry in an 80°C oven to obtain the desired dark red product.

[0065] (2) Preparation of a black polyimide from the above monomers: 0.5 g of acrylonitrile-containing diamine, 6.10 g of para-aminodiphenyl ether (ODA), 9.96 g of biphenyltetracarboxylic dianhydride (BPDA), in a molar ratio of 1:9:10, and 85 g of N,N'-dimethylacetamide (DMAc). The acrylonitrile-containing diamine and ODA were first added to a two-necked flask. Under argon protection, DMAc was added and stirred to dissolve the diamine solid. BPDA was then added to the flask. After stirring in a cold water bath for 4 h, stirring was continued at room temperature for 20 h to obtain a PAA acid solution with a solid content of 20 wt%.

[0066] After allowing the polyamic acid solution to stand naturally to defoam, it was evenly coated onto a dry, clean glass plate and subjected to thermal imidization. The temperature was programmed as follows: 80°C for 3 hours to evaporate the solvent; then the temperature was increased to 110°C / hour, 150°C / hour, 200°C / hour, 250°C / hour, and 300°C / hour. After the imidization was complete, the film was cooled naturally and then demolded to produce a black polyimide film.

[0067] Example 5

[0068] This example provides a method for synthesizing 3,3'-(1,4-phenylene)bis(2-(4-nitrophenyl)acrylonitrile) and its black polyimide (added in an amount of 5%):

[0069] (1) Synthesis of 3,3'-(1,4-phenylene)bis(2-(4-nitrophenyl)acrylonitrile)

[0070] In a 250 mL three-necked flask, 5.000 g (37.3 mmol) of terephthalaldehyde and 12.089 g (74.6 mmol) of 4-nitrophenylacetonitrile were weighed using an analytical balance and added to 125 mL of anhydrous ethanol. The mixture was heated and stirred until completely dissolved. Then, the catalyst sodium ethoxide (approximately 2 g) was added. After the reaction was completed, the mixture was filtered and washed with water, anhydrous ethanol, and tetrahydrofuran. After vacuum drying, a reddish-brown product 1 was obtained.

[0071] In a 100ml two-necked flask, weigh 3.000g (7.1mmol) of 3,3'-(1,4-phenylene)bis(2-(4-nitrophenyl)acrylonitrile) and 3.411g (14.2mmol) of sodium sulfide nonahydrate. Add the sodium sulfide nonahydrate (Na2S·9H2O) to 35.5mL of 1,4-dioxane and heat with stirring until dissolved. Then, add 3,3'-(1,4-phenylene)bis(2-(4-nitrophenyl)acrylonitrile) and heat to 80°C for 36 hours. After the reaction is complete, cool to room temperature and adjust the reaction mixture to pH 7-8 with saturated sodium bicarbonate solution. Filter, rinse with copious amounts of water, and dry in an oven at 80°C to obtain the desired dark red product.

[0072] (2) Preparation method of black polyimide prepared from the above monomers: diamine containing acrylonitrile structure, para-aminodiphenyl ether (ODA), and biphenyltetracarboxylic dianhydride (BPDA), the molar ratio of the three is 1:19:20, of which the diamine containing acrylonitrile structure accounts for 5%, and a certain amount of N,N'-dimethylacetamide (DMAc). First, the diamine containing acrylonitrile structure and ODA are added to a two-necked flask. Under argon protection, DMAc is added and stirred to dissolve the diamine solid. Then, BPDA is added to the flask. After stirring in a cold water bath for 4 hours, stirring is continued at room temperature for 20 hours to obtain a PAA acid solution with a solid content of 20wt%.

[0073] After allowing the polyamic acid solution to stand naturally to defoam, it was evenly coated onto a dry, clean glass plate and subjected to thermal imidization. The temperature was programmed as follows: 80°C for 3 hours to evaporate the solvent; then the temperature was increased to 110°C / hour, 150°C / hour, 200°C / hour, 250°C / hour, and 300°C / hour. After the imidization was complete, the film was cooled naturally and then demolded to produce a black polyimide film.

[0074] Example 6

[0075] This example provides a method for synthesizing 3,3'-(1,4-phenylene)bis(2-(4-nitrophenyl)acrylonitrile) and its black polyimide (addition amount is 15%):

[0076] (1) Synthesis of 3,3'-(1,4-phenylene)bis(2-(4-nitrophenyl)acrylonitrile)

[0077] In a 250 mL three-necked flask, 5.000 g (37.3 mmol) of terephthalaldehyde and 12.089 g (74.6 mmol) of 4-nitrophenylacetonitrile were weighed using an analytical balance and added to 125 mL of anhydrous ethanol. The mixture was heated and stirred until completely dissolved. Then, the catalyst sodium ethoxide (approximately 2 g) was added. After the reaction was completed, the mixture was filtered and washed with water, anhydrous ethanol, and tetrahydrofuran. After vacuum drying, a reddish-brown product 1 was obtained.

[0078] In a 100ml two-necked flask, weigh 3.000g (7.1mmol) of 3,3'-(1,4-phenylene)bis(2-(4-nitrophenyl)acrylonitrile) and 3.411g (14.2mmol) of sodium sulfide nonahydrate. Add the sodium sulfide nonahydrate (Na2S·9H2O) to 35.5mL of 1,4-dioxane and heat with stirring until dissolved. Then, add 3,3'-(1,4-phenylene)bis(2-(4-nitrophenyl)acrylonitrile) and heat to 80°C for 36 hours. After the reaction is complete, cool to room temperature and adjust the reaction mixture to pH 7-8 with saturated sodium bicarbonate solution. Filter, rinse with copious amounts of water, and dry in an oven at 80°C to obtain the desired dark red product.

[0079] (2) Preparation method of black polyimide prepared from the above monomers: diamine containing acrylonitrile structure, para-aminodiphenyl ether (ODA), and biphenyltetracarboxylic dianhydride (BPDA), the molar ratio of the three being 3:17:20, wherein the diamine containing acrylonitrile structure accounts for 15%, and N,N'-dimethylacetamide (DMAc). First, the diamine containing acrylonitrile structure and ODA are added to a two-necked flask. Under argon protection, a certain amount of DMAc is added and stirred to dissolve the diamine solid. Then, BPDA is added to the flask. After stirring in a cold water bath for 4 hours, stirring is continued at room temperature for 20 hours to obtain a PAA acid solution with a solid content of 20wt%.

[0080] After allowing the polyamic acid solution to stand naturally to defoam, it was evenly coated onto a dry, clean glass plate and subjected to thermal imidization. The temperature was programmed as follows: 80°C for 3 hours to evaporate the solvent; then the temperature was increased to 110°C / hour, 150°C / hour, 200°C / hour, 250°C / hour, and 300°C / hour. After the imidization was complete, the film was cooled naturally and then demolded to produce a black polyimide film. Example 7

[0081] This example provides a method for synthesizing 3,3'-(1,4-phenylene)bis(2-(4-nitrophenyl)acrylonitrile) and its black polyimide (added in an amount of 20%):

[0082] (1) Synthesis of 3,3'-(1,4-phenylene)bis(2-(4-nitrophenyl)acrylonitrile)

[0083] In a 250 mL three-necked flask, 5.000 g (37.3 mmol) of terephthalaldehyde and 12.089 g (74.6 mmol) of 4-nitrophenylacetonitrile were weighed using an analytical balance and added to 125 mL of anhydrous ethanol. The mixture was heated and stirred until completely dissolved. Then, the catalyst sodium ethoxide (approximately 2 g) was added. After the reaction was completed, the mixture was filtered and washed with water, anhydrous ethanol, and tetrahydrofuran. After vacuum drying, a reddish-brown product 1 was obtained.

[0084] In a 100ml two-necked flask, weigh 3.000g (7.1mmol) of 3,3'-(1,4-phenylene)bis(2-(4-nitrophenyl)acrylonitrile) and 3.411g (14.2mmol) of sodium sulfide nonahydrate. Add the sodium sulfide nonahydrate (Na2S·9H2O) to 35.5mL of 1,4-dioxane and heat with stirring until dissolved. Then, add 3,3'-(1,4-phenylene)bis(2-(4-nitrophenyl)acrylonitrile) and heat to 80°C for 36 hours. After the reaction is complete, cool to room temperature and adjust the reaction mixture to pH 7-8 with saturated sodium bicarbonate solution. Filter, rinse with copious amounts of water, and dry in an oven at 80°C to obtain the desired dark red product.

[0085] (2) Preparation method of black polyimide prepared from the above monomers: diamine containing acrylonitrile structure, para-aminodiphenyl ether (ODA), and biphenyltetracarboxylic dianhydride (BPDA), the molar ratio of the three being 4:16:20, wherein the diamine containing acrylonitrile structure accounts for 20%, and N,N'-dimethylacetamide (DMAc). First, the diamine containing acrylonitrile structure and ODA are added to a two-necked flask. Under argon protection, a certain amount of DMAc is added and stirred to dissolve the diamine solid. Then, BPDA is added to the flask. After stirring in a cold water bath for 4 hours, stirring is continued at room temperature for 20 hours to obtain a PAA acid solution with a solid content of 20wt%.

[0086] After allowing the polyamic acid solution to stand naturally to defoam, it was evenly coated onto a dry, clean glass plate and subjected to thermal imidization. The temperature was programmed as follows: 80°C for 3 hours to evaporate the solvent; then the temperature was increased to 110°C / hour, 150°C / hour, 200°C / hour, 250°C / hour, and 300°C / hour. After the imidization was complete, the film was cooled naturally and then demolded to produce a black polyimide film.

[0087] Example 8

[0088] This example provides a method for synthesizing 2,3-bis(4-aminophenyl)acrylonitrile and its black polyimide (added in an amount of 5%):

[0089] (1) Synthesis of 2,3-bis(4-aminophenyl)acrylonitrile

[0090] Take a 250mL three-necked flask, use an analytical balance to weigh 5.000g (33.08mmol) of 4-nitrobenzaldehyde and 5.36g (33.08mmol) of 4-nitrophenylacetonitrile, add them to 125mL of anhydrous ethanol, heat and stir until completely dissolved, then add the catalyst sodium ethoxide (about 2g). After the reaction is completed, filter, wash with water, anhydrous ethanol, and tetrahydrofuran, and vacuum dry to obtain a reddish-brown product.

[0091] In a 100ml two-necked flask, weigh 5g (16.9mmol) of 2,3-bis(4-aminophenyl)acrylonitrile and 10g (41.6mmol) of sodium sulfide nonahydrate. Add the sodium sulfide nonahydrate (Na2S·9H2O) to 100mL of 1,4-dioxane and heat with stirring until dissolved. Then, add 2,3-bis(4-nitrophenyl)acrylonitrile and heat to 80°C for 36 hours. After the reaction is complete, cool to room temperature and adjust the pH of the reaction mixture to 7-8 with saturated sodium bicarbonate solution. Filter, rinse with copious amounts of water, and dry in an oven at 80°C to obtain the desired dark-red product.

[0092] (2) Preparation of a black polyimide from the above-mentioned monomers: a diamine containing an acrylonitrile structure, para-aminodiphenyl ether (ODA), biphenyltetracarboxylic dianhydride (BPDA), the molar ratio of the three being 1:19:20, and a certain amount of N,N'-dimethylacetamide (DMAc). The diamine containing an acrylonitrile structure and ODA were first added to a two-necked flask. Under argon protection, DMAc was added and stirred to dissolve the diamine solid. BPDA was then added to the flask. After stirring in a cold water bath for 4 hours, stirring was continued at room temperature for 20 hours to obtain a PAA acid solution with a solid content of 20 wt%.

[0093] After allowing the polyamic acid solution to stand naturally to defoam, it was evenly coated onto a dry, clean glass plate and subjected to thermal imidization. The temperature was programmed as follows: 80°C for 3 hours to evaporate the solvent; then the temperature was increased to 110°C / hour, 150°C / hour, 200°C / hour, 250°C / hour, and 300°C / hour. After the imidization was complete, the film was cooled naturally and then demolded to produce a black polyimide film.

[0094] Example 9

[0095] This example provides a method for synthesizing 2,3-bis(4-aminophenyl)acrylonitrile and its black polyimide (added in an amount of 15%):

[0096] (1) Synthesis of 2,3-bis(4-aminophenyl)acrylonitrile

[0097] Take a 250mL three-necked flask, use an analytical balance to weigh 5.000g (33.08mmol) of 4-nitrobenzaldehyde and 5.36g (33.08mmol) of 4-nitrophenylacetonitrile, add them to 125mL of anhydrous ethanol, heat and stir until completely dissolved, then add the catalyst sodium ethoxide (about 2g). After the reaction is completed, filter, wash with water, anhydrous ethanol, and tetrahydrofuran, and vacuum dry to obtain a reddish-brown product.

[0098] In a 100ml two-necked flask, weigh 5g (16.9mmol) of 2,3-bis(4-aminophenyl)acrylonitrile and 10g (41.6mmol) of sodium sulfide nonahydrate. Add the sodium sulfide nonahydrate (Na2S·9H2O) to 100mL of 1,4-dioxane and heat with stirring until dissolved. Then, add 2,3-bis(4-nitrophenyl)acrylonitrile and heat to 80°C for 36 hours. After the reaction is complete, cool to room temperature and adjust the pH of the reaction mixture to 7-8 with saturated sodium bicarbonate solution. Filter, rinse with copious amounts of water, and dry in an oven at 80°C to obtain the desired dark-red product.

[0099] (2) Preparation of a black polyimide from the above-mentioned monomers: a diamine containing an acrylonitrile structure, para-aminodiphenyl ether (ODA), and biphenyltetracarboxylic dianhydride (BPDA), in a molar ratio of 3:17:20, and 85 g of N,N'-dimethylacetamide (DMAc). The diamine containing an acrylonitrile structure and ODA were first added to a two-necked flask. Under argon protection, DMAc was added and stirred to dissolve the diamine solid. BPDA was then added to the flask. After stirring in a cold water bath for 4 h, stirring was continued at room temperature for 20 h to obtain a PAA acid solution with a solid content of 20 wt%.

[0100] After allowing the polyamic acid solution to stand naturally to defoam, it was evenly coated onto a dry, clean glass plate and subjected to thermal imidization. The temperature was programmed as follows: 80°C for 3 hours to evaporate the solvent; then the temperature was increased to 110°C / hour, 150°C / hour, 200°C / hour, 250°C / hour, and 300°C / hour. After the imidization was complete, the film was cooled naturally and then demolded to produce a black polyimide film.

[0101] Example 10

[0102] This example provides a method for synthesizing 2,3-bis(4-aminophenyl)acrylonitrile and its black polyimide (added in an amount of 20%):

[0103] (1) Synthesis of 2,3-bis(4-aminophenyl)acrylonitrile

[0104] Take a 250mL three-necked flask, use an analytical balance to weigh 5.000g (33.08mmol) of 4-nitrobenzaldehyde and 5.36g (33.08mmol) of 4-nitrophenylacetonitrile, add them to 125mL of anhydrous ethanol, heat and stir until completely dissolved, then add the catalyst sodium ethoxide (about 2g). After the reaction is completed, filter, wash with water, anhydrous ethanol, and tetrahydrofuran, and vacuum dry to obtain a reddish-brown product.

[0105] In a 100ml two-necked flask, weigh 5g (16.9mmol) of 2,3-bis(4-aminophenyl)acrylonitrile and 10g (41.6mmol) of sodium sulfide nonahydrate. Add the sodium sulfide nonahydrate (Na2S·9H2O) to 100mL of 1,4-dioxane and heat with stirring until dissolved. Then, add 2,3-bis(4-nitrophenyl)acrylonitrile and heat to 80°C for 36 hours. After the reaction is complete, cool to room temperature and adjust the pH of the reaction mixture to 7-8 with saturated sodium bicarbonate solution. Filter, rinse with copious amounts of water, and dry in an oven at 80°C to obtain the desired dark-red product.

[0106] (2) Preparation method of black polyimide prepared from the above monomers: diamine containing acrylonitrile structure, para-aminodiphenyl ether (ODA, biphenyltetracarboxylic dianhydride (BPDA), the molar ratio of the three is 4:16:20, and a certain amount of N,N'-dimethylacetamide (DMAc). First, the diamine containing acrylonitrile structure and ODA are added to a two-necked flask, and under argon protection, DMAc is added. Stir to dissolve the diamine solid, and then add BPDA to the flask. After stirring in a cold water bath for 4 hours, stirring is continued at room temperature for 20 hours to obtain a PAA acid solution with a solid content of 20wt%.

[0107] After allowing the polyamic acid solution to stand naturally to defoam, it was evenly coated onto a dry, clean glass plate and subjected to thermal imidization. The temperature was programmed as follows: 80°C for 3 hours to evaporate the solvent; then the temperature was increased to 110°C / hour, 150°C / hour, 200°C / hour, 250°C / hour, and 300°C / hour. After the imidization was complete, the film was cooled naturally and then demolded to produce a black polyimide film.

[0108] Example 11

[0109] This example provides a method for synthesizing (2Z,2'Z)-2,2'-(6,6'-dihydroxy-5,5'-dimethoxy-[1,1'-biphenyl]-3,3'-diyl)bis(3-(4-aminophenyl)acrylonitrile) and the intrinsic black polyimide prepared therefrom (addition amount is 5%):

[0110] (1) Synthesis method of (2Z, 2'Z)-2,2'-(6,6'-dihydroxy-5,5'-dimethoxy-[1,1'-biphenyl]-3,3'-diyl)bis(3-(4-nitrophenyl)acrylonitrile

[0111] Take a 250mL three-necked flask, weigh 5.000g of coupled vanillin and 10g of 4-nitrophenylacetonitrile using an analytical balance, add them to 125mL of anhydrous ethanol, heat and stir until completely dissolved, then add the catalyst sodium ethoxide (about 2g). After the reaction is completed, filter, wash with water, anhydrous ethanol, and tetrahydrofuran, and vacuum dry to obtain a reddish-brown product.

[0112] In a 100ml two-necked flask, weigh 5g of the above product and 15g of sodium sulfide nonahydrate. Add the sodium sulfide nonahydrate (Na2S·9H2O) to 100mL of 1,4-dioxane and heat with stirring until dissolved. Then add the above product and heat to 80°C for 36 hours. After the reaction is complete, cool to room temperature and adjust the pH of the reaction mixture to 7-8 with saturated sodium bicarbonate solution. Filter, rinse with copious amounts of water, and dry in an oven at 80°C to obtain the dark red target product.

[0113] (2) Preparation of a black polyimide from the above-mentioned monomers: a diamine containing an acrylonitrile structure, para-aminodiphenyl ether, biphenyltetracarboxylic dianhydride, the molar ratio of the three being 1:19:20, and a certain amount of N,N'-dimethylacetamide (DMAc). The diamine containing an acrylonitrile structure and ODA were first added to a two-necked flask. Under argon protection, DMAc was added and stirred to dissolve the diamine solid. BPDA was then added to the flask. After stirring in a cold water bath for 4 hours, stirring was continued at room temperature for 20 hours to obtain a PAA acid solution with a solid content of 20 wt%.

[0114] After allowing the polyamic acid solution to stand naturally to defoam, it was evenly coated onto a dry, clean glass plate and subjected to thermal imidization. The temperature was programmed as follows: 80°C for 3 hours to evaporate the solvent; then the temperature was increased to 110°C / hour, 150°C / hour, 200°C / hour, 250°C / hour, and 300°C / hour. After the imidization was complete, the film was cooled naturally and then demolded to produce a black polyimide film.

[0115] Example 12

[0116] This example provides a method for synthesizing (2Z,2'Z)-2,2'-(6,6'-dihydroxy-5,5'-dimethoxy-[1,1'-biphenyl]-3,3'-diyl)bis(3-(4-aminophenyl)acrylonitrile) and the intrinsic black polyimide prepared therefrom (addition amount is 15%):

[0117] (1) Synthesis method of (2Z, 2'Z)-2,2'-(6,6'-dihydroxy-5,5'-dimethoxy-[1,1'-biphenyl]-3,3'-diyl)bis(3-(4-nitrophenyl)acrylonitrile

[0118] Take a 250mL three-necked flask, weigh 5.000g of coupled vanillin and 10g of 4-nitrophenylacetonitrile using an analytical balance, add them to 125mL of anhydrous ethanol, heat and stir until completely dissolved, then add the catalyst sodium ethoxide (about 2g). After the reaction is completed, filter, wash with water, anhydrous ethanol, and tetrahydrofuran, and vacuum dry to obtain a reddish-brown product.

[0119] In a 100ml two-necked flask, weigh 5g of the above product and 15g of sodium sulfide nonahydrate. Add the sodium sulfide nonahydrate (Na2S·9H2O) to 100mL of 1,4-dioxane and heat with stirring until dissolved. Then add the above product and heat to 80°C for 36 hours. After the reaction is complete, cool to room temperature and adjust the pH of the reaction mixture to 7-8 with saturated sodium bicarbonate solution. Filter, rinse with copious amounts of water, and dry in an oven at 80°C to obtain the dark red target product.

[0120] (2) Preparation of a black polyimide from the above-mentioned monomers: a diamine containing an acrylonitrile structure, para-aminodiphenyl ether, and biphenyltetracarboxylic dianhydride, in a molar ratio of 3:17:20, and a certain amount of N,N'-dimethylacetamide (DMAc). The diamine containing an acrylonitrile structure and ODA were first added to a two-necked flask. Under argon protection, DMAc was added and stirred to dissolve the diamine solid. BPDA was then added to the flask. After stirring in a cold water bath for 4 hours, stirring was continued at room temperature for 20 hours to obtain a PAA acid solution with a solid content of 20 wt%.

[0121] After allowing the polyamic acid solution to stand naturally to defoam, it was evenly coated onto a dry, clean glass plate and subjected to thermal imidization. The temperature was programmed as follows: 80°C for 3 hours to evaporate the solvent; then the temperature was increased to 110°C / hour, 150°C / hour, 200°C / hour, 250°C / hour, and 300°C / hour. After the imidization was complete, the film was cooled naturally and then demolded to produce a black polyimide film.

[0122] The above description is merely an example of the embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the scope of protection of the present invention.

Claims

1. A diamine monomer containing an acrylonitrile structure and a black polyimide synthesized therefrom, characterized in that: The chemical structure of the acrylonitrile-containing monomer is shown in formula (1):

2. The diamine monomer containing an acrylonitrile structure and the black polyimide synthesized therefrom according to claim 1, characterized in that: The steps for synthesizing the diamine monomer containing acrylonitrile structure are as follows: (1) Using monomers containing a benzyl cyanide structure and a benzaldehyde structure as raw materials, ethanol as solvent, and sodium ethoxide or piperidine as catalyst, stirring and refluxing for about 36 hours, cooling to room temperature, and then filtering to obtain a solid, washing with water and ethanol, drying, and then purifying by silica gel chromatography to obtain product 1 (containing a dinitro group) and product 2 (not containing a nitro group); (2) adding the product 2 (containing no nitro group) of step (1) to a mixed solution of concentrated nitric acid and dilute sulfuric acid, heating the mixture for 24 h, filtering the solid product, washing it with water and ethanol, drying it, and then purifying it by silica gel chromatography to obtain product 3; (3) The product 1 (containing a nitro group) in step (1) or the product 3 in step (2) is used as a raw material to undergo reductive amination to obtain a diamine monomer containing an acrylonitrile structure.

3. The diamine monomer containing an acrylonitrile structure and the black polyimide synthesized therefrom according to claim 2, characterized in that: The raw materials containing benzyl cyanide structure in the step (1) are: 1,4-benzenediacetonitrile and 4-nitrophenylacetonitrile.

4. The diamine monomer containing an acrylonitrile structure and the black polyimide synthesized therefrom as claimed in claim 2, characterized in that: The raw materials containing benzaldehyde structure in step (1) are: 5-hydroxy-4-nitrobenzaldehyde, 5-nitrosalicylicaldehyde, 5-nitrobenzylamine, terephthalaldehyde, coupled vanillin, and 4-nitrobenzaldehyde.

5. The diamine monomer containing an acrylonitrile structure and the black polyimide synthesized therefrom as claimed in claim 2, characterized in that: The raw material of the product 2 (not containing nitro group) in the step (2).

6. The diamine monomer containing an acrylonitrile structure and the black polyimide synthesized therefrom as claimed in claim 2, characterized in that: The raw material of the product 3 in step (2).

7. The diamine monomer containing acrylonitrile structure and the black polyimide synthesized therefrom according to claim 1, characterized in that: The structure of the polyimide is shown in formula (2):

8. The diamine monomer containing acrylonitrile structure and the black polyimide synthesized therefrom as claimed in claim 2, characterized in that: The synthesis method of the polyimide comprises the following steps: (1) Dissolve the prepared dry diamine monomer containing acrylonitrile structure (other diamines may be added) in an anhydrous polar aprotic solvent, wherein the molar content of the diamine monomer containing acrylonitrile structure is 5%-25%. Then add the dianhydride monomer and stir in an ice bath or at elevated temperature for 24 hours; (2) The polyamic acid solution in step (1) is subjected to thermal imide to obtain a black polyimide containing an acrylonitrile structure.

9. The diamine monomer containing an acrylonitrile structure and the black polyimide synthesized therefrom as claimed in claim 8, characterized in that: In the step (1), the other diamine monomers are one of diamines such as 4,4'-diaminodiphenyl ether, m-phenylenediamine, p-phenylenediamine, p-phenylenediamine, benzyl diamine, 4,4'-diaminodiphenyl sulfide, benzidine, 3,3'-diaminobiphenyl, 1,3-bis(4-nitrophenoxy)benzene, and 1,4-bis(4-nitrophenoxy)benzene, or the dianhydride is any one or more of dianhydrides such as pyromellitic dianhydride, 2,3,3',4-benzophenone tetracarboxylic dianhydride, 2,2',3,3'-diphenyl ether tetracarboxylic dianhydride, 3,4,3',4'-diphenyl ether dianhydride, 2,3,2',3'-diphenyl ether dianhydride, 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride, and 4,4'-oxydiphthalic dianhydride.

10. The diamine monomer containing an acrylonitrile structure and the black polyimide synthesized therefrom as claimed in claim 8, characterized in that: The polar aprotic solvent in step (1) is any one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, and dimethyl sulfoxide.

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