CN108503647B

CN108503647B - Benzocyclobutene-terminated imide monomer, and preparation method and curing method thereof

Info

Publication number: CN108503647B
Application number: CN201810311133.9A
Authority: CN
Inventors: 邱志明; 阙显沣; 严玉蓉
Original assignee: South China University of Technology SCUT
Current assignee: South China University of Technology SCUT
Priority date: 2018-04-09
Filing date: 2018-04-09
Publication date: 2021-09-21
Anticipated expiration: 2038-04-09
Also published as: CN108503647A

Abstract

The invention discloses a benzocyclobutene-terminated imide monomer and a preparation method and a curing method thereof, which comprises the steps of taking anthranilic acid as a starting material, diazotizing by isoamyl nitrite to obtain corresponding diazonium salt, heating the obtained diazonium salt in 1, 4-dioxane to 50 ℃, reacting with acrylonitrile to obtain 1-cyanobenzocyclobutene, reducing by a sodium borohydride/Raney nickel system to obtain 1-aminomethyl benzocyclobutene, and then carrying out imidization reaction on the 1-aminomethyl benzocyclobutene and aromatic dianhydride to obtain a target monomer. The monomer has excellent processing performance, can be dissolved in various organic solvents, has a lower melting point, can be directly heated to be molten or can be directly heated to be molten and then rotationally coated on a substrate or injected into a mold for curing, and only needs to be heated in the curing process without discharging by-products.

Description

Benzocyclobutene-terminated imide monomer, and preparation method and curing method thereof

Technical Field

The invention relates to the technical field of polymer dielectric materials, in particular to a benzocyclobutene-terminated imide monomer and a preparation method and a curing method thereof.

Background

Benzocyclobutene (BCB) is a high-performance material that has attracted much attention in the field of microelectronics in recent years, and its molecule contains benzene ring and cyclobutene structure. Under the heating condition, benzocyclobutene generates a four-membered ring opening reaction to form a high-activity o-diadenequinone intermediate, which is very easy to generate Diels-Alder reaction with dienophile and can also generate a cross-linking reaction among self molecules to finally form a high-degree cross-linked polymer. Benzocyclobutene thermosetting resins have the following advantages: 1. the curing performance is good, and the curing temperature of the resin can be adjusted within the range of 150-300 ℃. No additive is needed in the curing process, no micromolecule and by-product are generated, and the product is pure and has small shrinkage; 2. the thermal stability and the solvent resistance are good, the thermal decomposition temperature of most benzocyclobutene resins is higher than 400 ℃, the benzocyclobutene resins can be used for a long time below 300 ℃, and the benzocyclobutene resins are insoluble in organic solvents; 3. the dielectric property is excellent, the dielectric constant of the benzocyclobutene resin is usually less than 3, the dielectric loss is less than 0.01, and the benzocyclobutene resin has lower dielectric constant and dielectric loss in a wider temperature and frequency range; 4. the film forming property is good, the benzocyclobutene monomer has good film forming property, the thickness of a single-layer film can easily reach the micron level, and the flatness of the film is more than 95%; 5. the adhesive strength is high, the adhesive strength between the benzocyclobutene resin and the metal substrate is high, and the adhesive capacity can be further optimized by adjusting and controlling the curing process.

Polyimide (PI) is a high-performance polymer containing imide rings on a main chain, has excellent heat resistance and excellent mechanical and electrical properties, and has volume resistivity of more than 1015 omega-m and dielectric constant of 3-4. Polyimide materials have been widely used in the fields of composite materials, microelectronics, separation membranes, high temperature structural adhesives, and the like. However, most polyimides are not only structurally rigid and highly crystalline, but also have some charge transfer effect between molecules, and thus have poor solubility and high melting point (or lack thereof), which makes processing and molding of polyimide materials very difficult. Polyimide films are generally prepared by thermal imidization of polyamic acids. Firstly, dianhydride and diamine are reacted in an organic solvent (dimethyl acetamide or m-cresol is commonly used) to generate a polyamic acid solution, and then the solution is paved and heated to 150-300 ℃ to be dehydrated and imidized to obtain the polyimide film. This process is accompanied by the release of water vapor, which tends to leave pores or other defects in the film, which also reduces the flatness of the film.

Disclosure of Invention

In order to overcome the defects and shortcomings of the prior art, the invention provides a benzocyclobutene-terminated imide monomer with good solubility and low melting point, and a preparation method and a curing method thereof.

The invention adopts the following technical scheme:

the structure of a benzocyclobutene-terminated imide monomer is shown as the following formula:

wherein:

the invention relates to a preparation method of benzocyclobutene-terminated imide monomer, which is obtained by adopting a three-step method, and comprises the following steps of firstly, after diazotization of anthranilic acid, heating, refluxing and stirring diazonium salt and acrylonitrile in an organic solvent under nitrogen to obtain an intermediate compound II; reducing the intermediate compound II by sodium borohydride under the catalysis of Raney nickel to obtain an intermediate compound III; and carrying out imidization reaction on the intermediate compound III and aromatic dianhydride to obtain the benzocyclobutene-terminated imide monomer.

The method comprises the following specific steps:

(1) synthesis of intermediate compound II: mixing and dissolving anthranilic acid and trichloroacetic acid in an organic solvent, slowly dripping isoamyl nitrite at the temperature of-5-0 ℃, and stirring for reacting for 1-3 hours. Filtering and separating white precipitate generated in the reaction, adding acrylonitrile, mixing and stirring in an organic solvent, and reacting for 3-6 hours at 40-60 ℃ under the protection of nitrogen. Filtering the reaction mixture, distilling under reduced pressure to remove the solvent, and purifying by silica gel column chromatography to obtain a light yellow oily intermediate compound II with the yield of 40-50%.

(2) Synthesis of intermediate compound III: dissolving the intermediate compound II in an organic solvent, adding Raney nickel as a catalyst, and stirring at room temperature under nitrogen. And then slowly dropwise adding the aqueous solution of sodium hydroxide and sodium borohydride into the solution, and continuously reacting for 4-8 hours at room temperature. And then neutralizing the solution with dilute hydrochloric acid until the pH value is 10, filtering, extracting with an organic solvent, washing the organic phase with deionized water for 1-3 times, then removing the organic solvent by reduced pressure distillation, and purifying by a silica gel column chromatography to obtain a colorless oily intermediate compound III with the yield of 70-90%.

(3) Synthesizing benzocyclobutene-terminated imide monomers: mixing the intermediate compound III and the aromatic dianhydride in a molar ratio of 2:1, dissolving the mixture in a strong polar aprotic solvent, stirring the mixture at room temperature for 4 to 10 hours under the protection of nitrogen, then adding acetic anhydride and a catalyst, and heating the mixture to 80 to 120 ℃ for reaction for 2 to 6 hours. Pouring the solution into deionized water for precipitation, filtering and separating a large amount of generated white precipitates, washing with saturated sodium carbonate solution for 1-3 times, washing with deionized water for 2-4 times, and then heating and drying in a vacuum drying oven to obtain a white powdery product benzocyclobutene-terminated imide monomer with the yield of 80-95%.

In the step (1), the organic solvent is one or a mixture of diethyl ether, tetrahydrofuran, dichloromethane and 1, 2-dichloroethane; the mass fraction of the anthranilic acid dissolved in the organic solvent is 4-25%; the molar ratio of anthranilic acid to trichloroacetic acid is 5-20: 1, the molar ratio of anthranilic acid to isoamylnitrite is 1: 1.5-4, and the molar ratio of anthranilic acid to acrylonitrile is 1: 2-5; the eluent used for silica gel column chromatography is a mixture of petroleum ether and dichloromethane, and the volume ratio of the petroleum ether to the dichloromethane is 2-5: 1.

In the step (2), the organic solvent for dissolving the reactant is one or a mixture of methanol, ethanol, n-propanol and isopropanol, and the organic solvent for extracting the product is one or a mixture of dichloromethane, chloroform and carbon tetrachloride; the mass fraction of the intermediate compound II dissolved in the organic solvent is 10-25%, and the mass fraction of the sodium hydroxide dissolved in the water is 10-20%; the dosage of the Raney nickel catalyst is 1 to 5 percent of the mass of the intermediate compound II; the molar ratio of the intermediate compound II to the sodium borohydride is 1: 2-5, and the molar ratio of the sodium borohydride to the sodium hydroxide is 1: 2-5; the eluent used for silica gel column chromatography is a mixture of petroleum ether and dichloromethane, the volume ratio of the petroleum ether to the dichloromethane is 1: 1-5, and a small amount of triethylamine is added into the eluent, wherein the volume of the triethylamine is 0.1% -0.5% of the eluent.

In the step (3) of the present invention, the aromatic dianhydride used is selected from the group consisting of pyromellitic dianhydride, 3,3 ', 4,4' -biphenyltetracarboxylic dianhydride, 2 ', 3, 3' -biphenyltetracarboxylic dianhydride, 2,3,3 ', 4' -biphenyltetracarboxylic dianhydride, 3,3 ', 4,4' -diphenylethertetracarboxylic dianhydride, 2 ', 3, 3' -diphenylethertetracarboxylic dianhydride, 2,3,3 ', 4' -diphenylethertetracarboxylic dianhydride, 3,3 ', 4,4' -benzophenonetetracarboxylic dianhydride, 2 ', 3, 3' -benzophenonetetracarboxylic dianhydride, 2,3,3 ', 4' -benzophenonetetracarboxylic dianhydride, 3,3 ', 4,4' -diphenylsulfonetetracarboxylic dianhydride, 2 ', 3, 3' -diphenylsulfonetetracarboxylic dianhydride, One of 2,3,3 ', 4' -diphenylsulfone tetracarboxylic dianhydride, 2-bis (3, 4-dicarboxyphenyl) hexafluoropropane dianhydride, 2-bis [4,4 '-bis (3, 4-dicarboxyphenoxy) phenyl ] propane dianhydride, 1, 4-bis (3, 4-dicarboxyphenoxy) benzene dianhydride, 2-bis [4,4' -bis (3, 4-dicarboxyphenoxy) phenyl ] hexafluoropropane dianhydride; the strong polar aprotic solvent is a mixture of more than one of N, N-dimethylformamide, N-dimethylacetamide and N-methyl-2-pyrrolidone;

the mass fraction of the intermediate compound III dissolved in the strong polar aprotic solvent is 2 to 10 percent; the catalyst is selected from one or a mixture of triethylamine, tripropylamine, tributylamine, pyridine, 2-methylpyridine, 3-methylpyridine and 4-methylpyridine; the molar ratio of the acetic anhydride to the aromatic dianhydride is 3-10: 1, and the molar ratio of the acetic anhydride to the catalyst is 1-5: 1.

The benzocyclobutene-terminated imide monomer synthesized by the method has excellent processing performance, can be dissolved in various organic solvents such as dichloromethane, chloroform, acetone, dimethylformamide, dimethylacetamide, methyl pyrrolidone, m-cresol and the like, has melting points lower than 165 ℃, and can be prepared into a solution or be coated on a substrate or molded by a mold after being heated to be molten. The curing process of the monomer only needs heating, no additive is needed, no low molecular by-product is discharged in the curing process, and the product is pure and has small shrinkage.

The invention also provides a curing method of the benzocyclobutene-terminated imide monomer, which comprises the following steps: dissolving a monomer in an organic solvent to prepare a solution with a certain concentration, coating a film on a glass or silicon substrate, and then heating and curing; or heating the monomer to be molten, coating a film on a hot glass or silicon substrate, and then heating and curing; or dissolving the monomer in an organic solvent to prepare a solution, injecting the solution into a mold, and then heating to volatilize and solidify the solvent; or heating the monomer to melt, injecting the monomer into a mold, and then further heating to solidify. The curing procedure is carried out in a nitrogen or argon atmosphere, and the curing temperature is 150-300 ℃.

The structural formulas of the intermediate compounds II and III are as follows:

the invention has the beneficial effects that:

the benzocyclobutene curing resin containing the imide structure has high heat resistance, high glass transition temperature, low dielectric constant and low dielectric loss, high hydrophobicity and excellent surface smoothness.

Can be applied to the fields of microelectronics, composite materials and the like, and can be used as a novel electronic packaging material, a dielectric material or a high-performance resin matrix.

Detailed Description

The present invention will be described in further detail with reference to examples, but the embodiments of the present invention are not limited thereto.

Example 1

A preparation method of benzocyclobutene-terminated imide monomers comprises the following steps:

a mixture of 13.71g (100mmol) of anthranilic acid and 1.63g (10mmol) of trichloroacetic acid was dissolved in 150mL of tetrahydrofuran, the temperature of the solution was lowered to-5 ℃ and 23.43g (200mmol) of isoamyl nitrite was slowly added dropwise with stirring for reaction for 2 hours. The reaction produced a large amount of white precipitate which was isolated by filtration, then 200mL of 1, 4-dioxane and 15.92g (300mmol) of acrylonitrile were added, mixed and stirred under nitrogen to form a suspension, and the temperature was raised to 50 ℃ for 5 hours. The reaction mixture was filtered, and the solvent was distilled off under reduced pressure to give a brown viscous liquid. Purifying by silica gel column chromatography, eluting with mixed solvent of petroleum ether and dichloromethane (volume ratio of 5:1) to obtain yellowish oily intermediate compound II with yield of 50%.

6.45g (50mmol) of intermediate compound II were weighed out and dissolved in 30mL of methanol, 0.08g of Raney nickel was added, and the mixture was stirred at room temperature under nitrogen. Then, 20g (500mmol) of sodium hydroxide and 5.67g (150mmol) of sodium borohydride were dissolved in 100mL of water to prepare a solution, which was slowly added dropwise to the reaction mixture, and the reaction was continued at room temperature for 6 hours after the addition. The solution was then neutralized to pH 10 with dilute hydrochloric acid, filtered, extracted with dichloromethane (4 × 100mL), and the combined organic phases were washed 3 times with deionized water, and the organic solvent was then distilled off under reduced pressure to give a light brown oily liquid. Purification by silica gel column chromatography using a mixed solvent of petroleum ether and dichloromethane (volume ratio 1:2) as the eluent and 0.3% by volume of triethylamine was added to the eluent to give intermediate compound III as a colorless oil in 87% yield.

3.99g (30mmol) of intermediate compound III and 6.66g (15mmol) of 2, 2-bis (3, 4-dicarboxyphenyl) hexafluoropropane dianhydride were dissolved in 100ml N-methyl-2-pyrrolidone, stirred at room temperature for 8 hours under nitrogen protection, then 6.13g (60mmol) of acetic anhydride and 4.75g (60mmol) of pyridine were added, and the mixture was heated to 90 ℃ to react for 4 hours. And pouring the solution into deionized water for precipitation, filtering and separating a large amount of generated white precipitate, washing with saturated sodium carbonate solution for 2 times, then washing with deionized water for 3 times, and then drying in a vacuum drying oven at 120 ℃ for 24 hours to obtain white benzocyclobutene-terminated imide monomer powder with the yield of 87%.

The curing method comprises the following steps: dissolving benzocyclobutene-terminated imide monomer into dichloromethane to prepare a solution with the mass fraction of 20%, then dripping the solution on a glass substrate with a clean surface, spin-coating for 20 seconds at the rotating speed of 2000 rpm, and then volatilizing dichloromethane solvent at 50 ℃ to obtain a colorless transparent film. And (3) putting the glass substrate carrying the film into an oven to be heated and cured under nitrogen atmosphere, wherein the temperature rise procedure comprises heating at 200 ℃ for 1.5 hours, heating at 250 ℃ for 1 hour and finally heating at 300 ℃ for 30 minutes to obtain a light yellow transparent cured film with a smooth surface. The detection result of the atomic force microscope on the surface appearance of the cured film shows that the film has excellent surface smoothness, the average surface roughness is 0.30nm, the root mean square roughness is 0.41nm, and the maximum height difference of the surface is 5.37 nm. The films had low dielectric constants and dielectric losses of 2.81 and 0.0019, respectively, at a frequency of 1 MHz.

Example 2

13.71g (100mmol) of anthranilic acid and 1.31g (8mmol) of trichloroacetic acid are weighed out and dissolved in 150mL of dichloromethane, the temperature of the solution is lowered to-5 ℃ and 35.15g of benzoic acid are slowly added dropwise

(300mmol) isoamyl nitrite and stirring the reaction for 2.5 hours. A large amount of white precipitate generated in the reaction was separated by filtration, and the resulting solution was stirred in 250mL of methylene chloride to form a suspension, 21.22g (400mmol) of acrylonitrile was added, nitrogen gas was introduced into the reaction flask, and the reaction was refluxed at 50 ℃ for 6 hours. The reacted liquid was filtered, and the solvent was distilled off under reduced pressure to obtain a brown viscous liquid. Purifying by silica gel column chromatography, eluting with mixed solvent of petroleum ether and dichloromethane (volume ratio of 4:1) to obtain yellowish oily intermediate compound II with yield of 46%.

6.45g (50mmol) of intermediate compound II were weighed out and dissolved in 40mL of ethanol, 0.10g of Raney nickel was added, and the mixture was stirred at room temperature under nitrogen. Then, 24g (600mmol) of sodium hydroxide and 7.57g (200mmol) of sodium borohydride were dissolved in 150mL of water to prepare a solution, which was slowly added dropwise to the reaction mixture, and the reaction was continued at room temperature for 5 hours after the completion of the addition. The solution was then neutralized to pH 10 with dilute hydrochloric acid, filtered, extracted with chloroform (4 × 100mL), and the combined organic phases were washed 3 times with deionized water, and then the organic solvent was distilled off under reduced pressure to give a light brown oily liquid. Purification by silica gel column chromatography using a mixed solvent of petroleum ether and dichloromethane (volume ratio 1:3) as the eluent and 0.2% by volume of triethylamine was added to the eluent to give intermediate compound III as a colorless oil in 74% yield.

3.99g (30mmol) of intermediate compound III and 4.65g (15mmol) of 3,3 ', 4,4' -diphenylether tetracarboxylic dianhydride were dissolved in 100mL of N, N-dimethylacetamide, stirred at room temperature for 5 hours under nitrogen protection, then 9.19g (90mmol) of acetic anhydride and 4.05g (40mmol) of triethylamine were added, and the mixture was heated to 100 ℃ to react for 4 hours. And pouring the solution into deionized water for precipitation, filtering and separating a large amount of generated white precipitate, washing with saturated sodium carbonate solution for 2 times, then washing with the deionized water for 3 times, and then drying in a vacuum drying oven at 120 ℃ for 24 hours to obtain white benzocyclobutene-terminated imide monomer powder with the yield of 85%.

Taking benzocyclobutene-terminated imide monomer powder with a certain mass, heating to 140 ℃ to melt the powder into light yellow low-viscosity liquid, injecting the liquid into a specific mold, then placing the mold into an oven, heating and curing under the argon atmosphere, wherein the temperature rise procedure is heating at 200 ℃ for 1.5 hours, at 250 ℃ for 1 hour, and at last at 300 ℃ for 30 minutes to obtain yellow transparent cured resin with a certain shape. The tensile strength of the cured resin is 73MPa, the 5% weight loss temperature is 452 ℃, the glass transition temperature is 278 ℃, and the water absorption is about 0.81 percent after the cured resin is soaked in distilled water at the temperature of 23 ℃ for 24 hours.

Example 3

a mixture of 13.71g (100mmol) of anthranilic acid and 1.96g (12mmol) of trichloroacetic acid was dissolved in 200mL of tetrahydrofuran, the temperature of the solution was lowered to-5 ℃ and 17.57g (150mmol) of isoamyl nitrite was slowly added dropwise with stirring for reaction for 1.5 hours. The reaction yielded a large amount of white precipitate which was isolated by filtration, then 300mL of 1, 2-dichloroethane and 13.27g (250mmol) of acrylonitrile were added, mixed and stirred under nitrogen to form a suspension, and the temperature was raised to 55 ℃ for 4 hours under reflux. The reaction mixture was filtered, and the solvent was distilled off under reduced pressure to give a brown viscous liquid. Purifying by silica gel column chromatography, eluting with mixed solvent of petroleum ether and dichloromethane (volume ratio of 3:1) to obtain yellowish oily intermediate compound II with a yield of 42%.

6.45g (50mmol) of intermediate compound II are weighed out and dissolved in 25mL of isopropanol, 0.15g of Raney nickel are added and stirring is carried out at room temperature under nitrogen. Then 20g (500mmol) of sodium hydroxide and 4.73g (125mmol) of sodium borohydride were dissolved in 90mL of water to prepare a solution, which was slowly added dropwise to the reaction mixture, and the reaction was continued at room temperature for 5 hours after the addition. The solution was then neutralized to pH 10 with dilute hydrochloric acid, filtered, extracted with carbon tetrachloride (4 × 100mL), and the combined organic phases were washed 3 times with deionized water, and then the organic solvent was distilled off under reduced pressure to give a light brown oily liquid. Purification by silica gel column chromatography using a mixed solvent of petroleum ether and dichloromethane (volume ratio 1:4) as the eluent and 0.15% by volume of triethylamine was added to the eluent to give intermediate compound III as a colorless oil in 71% yield.

3.99g (30mmol) of intermediate compound III and 4.41g (15mmol) of 3,3 ', 4,4' -biphenyltetracarboxylic dianhydride were dissolved in 100ml of N, N-dimethylformamide, stirred at room temperature for 6 hours under nitrogen protection, then added with 8.17g (80mmol) of acetic anhydride and 2.87g (20mmol) of tripropylamine, and reacted at 110 ℃ for 3 hours. And pouring the solution into deionized water for precipitation, filtering and separating a large amount of generated white precipitate, washing with saturated sodium carbonate solution for 2 times, then washing with the deionized water for 3 times, and then drying in a vacuum drying oven at 120 ℃ for 24 hours to obtain white benzocyclobutene-terminated imide monomer powder with the yield of 92%.

Dissolving benzocyclobutene-terminated imide monomer in m-cresol to prepare a solution with the mass fraction of 20%, then dripping the solution on a silicon substrate with a clean surface, spin-coating at the rotating speed of 1500 rpm for 20 seconds, then putting the silicon substrate into an oven to heat and solidify under nitrogen atmosphere, and heating up at 150 ℃ for 1 hour, 200 ℃ for 1 hour, 250 ℃ for 1 hour and finally 300 ℃ for 30 minutes to obtain a light yellow transparent solidified film with a smooth surface. The detection result of the atomic force microscope on the surface appearance of the cured film shows that the film has excellent surface smoothness, the average surface roughness is 0.63nm, the root mean square roughness is 0.87nm, and the maximum height difference of the surface is 8.76 nm. The films had lower dielectric constants and dielectric losses, 2.92 and 0.0032 at a frequency of 1MHz, respectively.

Example 4

a mixture of 13.71g (100mmol) of anthranilic acid and 3.27g (20mmol) of trichloroacetic acid was dissolved in 200mL of diethyl ether, the temperature of the solution was lowered to-5 ℃ and 41.00g (350mmol) of isoamyl nitrite was slowly added dropwise with stirring for 1 hour. A large amount of white precipitate generated by the reaction was separated by filtration, mixed with 250mL of 1, 4-dioxane and 18.58g (350mmol) of acrylonitrile under nitrogen and stirred to form a suspension, and heated to 50 ℃ for reflux reaction for 6 hours. The reaction mixture was filtered, and the solvent was distilled off under reduced pressure to give a brown viscous liquid. Purifying by silica gel column chromatography, eluting with mixed solvent of petroleum ether and dichloromethane (volume ratio of 2:1) to obtain yellowish oily intermediate compound II with yield of 49%.

6.45g (50mmol) of intermediate compound II are weighed out and dissolved in 30mL of n-propanol, 0.20g of Raney nickel are added and stirring is carried out at room temperature under nitrogen. Then, 30g (750mmol) of sodium hydroxide and 9.46g (250mmol) of sodium borohydride were dissolved in 180mL of water to prepare a solution, which was slowly added dropwise to the reaction mixture, and the reaction was continued at room temperature for 8 hours after the addition. The solution was then neutralized to pH 10 with dilute hydrochloric acid, filtered, extracted with dichloromethane (4 × 100mL), and the combined organic phases were washed 3 times with deionized water, and the organic solvent was then distilled off under reduced pressure to give a light brown oily liquid. Purification by silica gel column chromatography using a mixed solvent of petroleum ether and dichloromethane (volume ratio 1:5) as the eluent and 0.4% by volume of triethylamine was added to the eluent to give intermediate compound III as a colorless oil in 81% yield.

3.99g (30mmol) of intermediate compound III and 4.83g (15mmol) of 3,3 ', 4,4' -benzophenone tetracarboxylic dianhydride were dissolved in 100mL of N, N-dimethylformamide, stirred at room temperature for 6 hours under nitrogen protection, then 15.31g (150mmol) of acetic anhydride and 9.27g (50mmol) of tributylamine were added, and the mixture was heated to 100 ℃ to react for 4 hours. And pouring the solution into deionized water for precipitation, filtering and separating a large amount of generated white precipitate, washing with saturated sodium carbonate solution for 2 times, then washing with the deionized water for 3 times, and then drying in a vacuum drying oven at 120 ℃ for 24 hours to obtain white benzocyclobutene-terminated imide monomer powder with the yield of 89%.

Dissolving benzocyclobutene-terminated imide monomer in dimethylacetamide to prepare a solution with the mass fraction of 30%, injecting the solution into a specific mold, then putting the mold into an oven, heating and curing under argon atmosphere, wherein the temperature rise procedure comprises the steps of heating at 150 ℃ for 1 hour, heating at 200 ℃ for 1 hour, heating at 250 ℃ for 1 hour, and finally heating at 300 ℃ for 30 minutes to obtain yellow transparent curing resin with a certain shape. The tensile strength of the cured resin is 79MPa, the 5 percent weight loss temperature is 447 ℃, the glass transition temperature is 301 ℃, and the water absorption rate is about 0.88 percent after the cured resin is soaked in distilled water at the temperature of 23 ℃ for 24 hours.

Example 5

a mixture of 13.71g (100mmol) of anthranilic acid and 2.45g (15mmol) of trichloroacetic acid was weighed out and dissolved in 250mL of tetrahydrofuran, the temperature of the solution was lowered to-5 ℃ and 29.29g (250mmol) of isoamyl nitrite was slowly added dropwise and the reaction was stirred for 2 hours. A large amount of white precipitate generated in the reaction is filtered and separated, and put into 200mL of 1, 4-dioxane to be stirred to form a suspension, 13.26g (250mmol) of acrylonitrile is added, nitrogen is introduced into a reaction bottle, and the reaction is refluxed at 50 ℃ for 6 hours. The reacted liquid was filtered, and the solvent was distilled off under reduced pressure to obtain a brown viscous liquid. Purifying by silica gel column chromatography, eluting with mixed solvent of petroleum ether and dichloromethane (volume ratio of 4:1) to obtain yellowish oily intermediate compound II with yield of 48%.

6.45g (50mmol) of intermediate compound II were weighed out and dissolved in 35mL of methanol, 0.12g of Raney nickel was added, and the mixture was stirred at room temperature under nitrogen. Then, 24g (600mmol) of sodium hydroxide and 5.67g (150mmol) of sodium borohydride were dissolved in 100mL of water to prepare a solution, which was slowly added dropwise to the reaction mixture, and the reaction was continued at room temperature for 5 hours after the completion of the addition. The solution was then neutralized to pH 10 with dilute hydrochloric acid, filtered, extracted with chloroform (4 × 100mL), and the combined organic phases were washed 3 times with deionized water, and then the organic solvent was distilled off under reduced pressure to give a light brown oily liquid. Purification by silica gel column chromatography using a mixed solvent of petroleum ether and dichloromethane (volume ratio 1:3) as the eluent and 0.5% by volume of triethylamine was added to the eluent to give intermediate compound III as a colorless oil in 88% yield.

3.99g (30mmol) of intermediate compound III and 8.17g (15mmol) of 2, 2-bis [4,4' -bis (3, 4-dicarboxyphenoxy) phenyl ] hexafluoropropane dianhydride were dissolved in 100mL of N, N-dimethylacetamide, stirred at room temperature for 7 hours under nitrogen protection, and then 15.31g (150mmol) of acetic anhydride and 2.79g (30mmol) of 4-methylpyridine were added, and the mixture was heated to 120 ℃ and reacted for 2 hours. And pouring the solution into deionized water for precipitation, filtering and separating a large amount of generated white precipitate, washing with saturated sodium carbonate solution for 2 times, then washing with the deionized water for 3 times, and then drying in a vacuum drying oven at 120 ℃ for 24 hours to obtain white benzocyclobutene-terminated imide monomer powder with the yield of 90%.

Taking a certain mass of benzocyclobutene-terminated imide monomer powder, and heating to 130 ℃ to melt the powder into light yellow low-viscosity liquid. A glass substrate with a clean surface is taken and preheated in an oven at 160 ℃ for 30 minutes, then a melt is dripped on the glass substrate, spin-coated for 20 seconds at the rotating speed of 2000 r/min, then the glass substrate is placed in an oven to be heated and solidified under nitrogen atmosphere, the temperature rise procedure is heating for 1.5 hours at 200 ℃, 1 hour at 250 ℃ and finally 30 minutes at 300 ℃, and a light yellow transparent solidified film with a smooth surface is obtained. The detection result of the atomic force microscope on the surface appearance of the cured film shows that the film has excellent surface smoothness, the average surface roughness is 0.27nm, the root mean square roughness is 0.38nm, and the maximum height difference of the surface is 4.56 nm. The films had low dielectric constants and dielectric losses of 2.85 and 0.0022 at 1MHz, respectively.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.

Claims

1. The benzocyclobutene-terminated imide monomer is characterized by having the following monomer structure:

2. a method for preparing the imide monomer of claim 1 comprising the steps of:

s1, dissolving anthranilic acid and trichloroacetic acid in an organic solvent, dropwise adding isoamyl nitrite at the temperature of-5-0 ℃, stirring to react for 1-3 hours, filtering and separating white precipitate generated in the reaction, then adding acrylonitrile, mixing and stirring in the organic solvent, reacting for 3-6 hours at the temperature of 40-60 ℃ under the protection of nitrogen, filtering the reaction mixture, distilling under reduced pressure to remove the organic solvent, and purifying by a silica gel column chromatography to obtain an intermediate compound II;

s2, dissolving an intermediate compound II in an organic solvent, adding raney nickel as a catalyst, stirring at room temperature under nitrogen, slowly dropwise adding an aqueous solution of sodium hydroxide and sodium borohydride into the solution, continuously reacting at room temperature for 4-8 hours, neutralizing the reacted solution with dilute hydrochloric acid until the pH value is 10, filtering, extracting with the organic solvent, washing with deionized water for 1-3 times, distilling under reduced pressure to remove the organic solvent, and purifying with a silica gel column chromatography to obtain an intermediate compound III;

s3, mixing and dissolving an intermediate compound III and aromatic dianhydride in a molar ratio of 2:1 in a strong-polarity aprotic solvent, stirring at room temperature for 4-10 hours under the protection of nitrogen, adding acetic anhydride and a catalyst, heating to 80-120 ℃, reacting for 2-6 hours, pouring a reaction solution into deionized water for precipitation, filtering and separating a large amount of generated white precipitates, washing with a saturated sodium carbonate solution for 1-3 times, washing with deionized water for 2-4 times, and heating and drying to obtain a benzocyclobutene-terminated imide monomer;

the aromatic dianhydride is 3,3 ', 4,4' -diphenyl ether tetracarboxylic dianhydride, 3 ', 4,4' -biphenyl tetracarboxylic dianhydride, 3 ', 4,4' -benzophenone tetracarboxylic dianhydride, 2-bis (3, 4-dicarboxyphenyl) hexafluoropropane dianhydride or 2, 2-bis [4,4' -bis (3, 4-dicarboxyphenoxy) phenyl ] hexafluoropropane dianhydride;

the catalyst in the S3 is more than one of triethylamine, tripropylamine, tributylamine, pyridine, 2-methylpyridine, 3-methylpyridine and 4-methylpyridine.

3. The method according to claim 2, wherein the organic solvent in S1 is a mixture of one or more of diethyl ether, tetrahydrofuran, dichloromethane, and 1, 2-dichloroethane.

4. The method according to claim 2, wherein the molar ratio of anthranilic acid to trichloroacetic acid in S1 is 5 to 20:1, the molar ratio of anthranilic acid to isoamyl nitrite is 1:1.5 to 4, and the molar ratio of anthranilic acid to acrylonitrile is 1:2 to 5.

5. The preparation method according to claim 2, wherein in S2, the mass fraction of intermediate compound II dissolved in the organic solvent is 10% to 25%; the mass fraction of the sodium hydroxide dissolved in the water is 10-20%.

6. The preparation method according to claim 2, wherein in S2, the eluent for silica gel column chromatography is a mixture of petroleum ether and dichloromethane, the volume ratio of the petroleum ether to the dichloromethane is 1: 1-5, and a small amount of triethylamine is added into the eluent, and the volume of the triethylamine is 0.1-0.5% of the eluent.

7. The method according to claim 2, wherein the strongly polar aprotic solvent in S3 is a mixture of one or more selected from N, N-dimethylformamide, N-dimethylacetamide and N-methyl-2-pyrrolidone.

8. The method for curing an imide monomer as claimed in claim 1, wherein the imide monomer is dissolved in an organic solvent, and then coated on a glass or silicon substrate, followed by heat curing; or heating the monomer to be molten, coating a film on a hot glass or silicon substrate, and then heating and curing; or dissolving the monomer in an organic solvent to prepare a solution, injecting the solution into a mold, and then heating to volatilize and solidify the solvent; or heating the monomer to be molten, injecting the monomer into a mold, and further heating and curing, wherein the curing process is carried out in a nitrogen or argon atmosphere, and the curing temperature is 150-300 ℃.