A diamine monomer containing adamantane structure, a preparation method thereof and a polyimide polymer

Abstract

The application provides a diamine monomer containing adamantane structure, a preparation method of the diamine monomer and a polyimide polymer. The diamine monomer containing adamantane structure has a structure shown in formula I. By introducing adamantane into the diamine monomer, the adamantane has a highly symmetrical and very stable alicyclic structure, and the unique cage structure of the adamantane enables the diamine containing the adamantane structure to effectively reduce the dielectric constant of the polymer when used as a polymerization monomer. It is tested that a semi-aromatic PI material obtained by polycondensation of the diamine monomer containing adamantane structure and a dianhydride monomer has a low dielectric constant.

Description

Technical Field

[0001] This invention belongs to the field of organic polymer materials technology, specifically relating to a diamine monomer containing an adamantane structure, its preparation method, and a polyimide polymer. Background Technology

[0002] Polyimide (PI) is a polymer containing stable imide ring structures in its molecular chain segments. Simultaneously, its molecular chain also contains stable aromatic ring structures, making it a semi-trapezoidal cyclic polymer. Therefore, it exhibits many unique properties and is widely studied and applied. As the primary insulating substrate for flexible printed circuits, PI's dielectric constant (3.4@1MHz) is too high at high frequencies, failing to meet the needs of 5G development. To meet the requirements of high-speed high-frequency signal transmission and minimizing signal delay, crosstalk, and loss, further improving PI performance by reducing its dielectric constant is urgently needed.

[0003] Adamantane is a highly symmetrical and very stable cage-like hydrocarbon. It can be used as a raw material to synthesize various mono- and poly-substituted adamantane derivatives. Based on the adamantane structure, disubstituted derivatives with bifunctional groups can easily synthesize a variety of different polymer materials. These materials exhibit good transparency, high hardness, excellent impact resistance, and superior thermal stability, showing broad application prospects in the field of organic new materials, especially in communications. However, a systematic study of the dielectric constant properties of polyimide film materials containing adamantane structures is currently lacking. Summary of the Invention

[0004] In view of this, the object of the present invention is to provide a diamine monomer containing an adamantane structure, a method for preparing the same, and a polyimide polymer. The polyimide material prepared from this diamine monomer has a low dielectric constant, which meets the application requirements.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a diamine monomer containing an adamantane structure, having the structure shown in Formula I:

[0007]

[0008] In Formula I, Ar is selected from phenyl or substituted phenyl.

[0009] Preferably, the Ar is selected from any one of the following formulas: Ar-1 to Ar-3:

[0010]

[0011] Secondly, the present invention provides a method for preparing the above-mentioned diamine monomer containing an adamantane structure, comprising:

[0012] S1: 1-Aminoadamantane and a nitro-containing haloalkanes are reacted in the presence of an alkaline catalyst to obtain a dinitro compound;

[0013] The structural formula of the nitro-containing halocarbon compound is shown in Formula II below:

[0014] X-Ar—N02 Type II,

[0015] In Formula II, Ar is selected from phenyl or substituted phenyl, and X is selected from -F, -Cl, -Br and -I;

[0016] S2: The dinitro compound is reacted under the action of a combination of reducing agent and catalyst to obtain a diamine monomer containing adamantane structure.

[0017] Preferably, the alkaline catalyst is selected from any one or more of sodium hydride, potassium hydride, potassium tert-butoxide, sodium tert-butoxide, cesium fluoride, potassium carbonate, sodium carbonate, or cesium carbonate.

[0018] Preferably, the combination of reducing agent and catalyst is selected from any one of the following combinations: hydrazine hydrate and palladium on carbon, hydrogen and palladium on carbon, hydrogen and nickel, stannous chloride and hydrochloric acid, zinc powder and hydrochloric acid, iron powder and hydrochloric acid, and zinc powder and acetic acid.

[0019] Preferably, the molar ratio of 1-aminoadamantane, the nitro-containing halocarbon compound, and the basic catalyst is 1:(2-2.5):(2-2.5).

[0020] Preferably, the molar ratio of the dinitro compound, reducing agent, and catalyst is 1:(2-8):(0.01-8).

[0021] Preferably, the reaction temperature in steps S1 and S2 is independently 0–200°C, and the reaction time is independently 5–24 h.

[0022] Preferably, the reaction in step S1 is carried out in the presence of an inert atmosphere and an organic solvent.

[0023] Preferably, the organic solvent is selected from any one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, tetrahydrofuran, toluene, or xylene.

[0024] Preferably, the reaction in step S2 is carried out in an anaerobic environment and in the presence of an organic solvent.

[0025] Preferably, the organic solvent is selected from any one or more of ethanol, methanol, acetone, acetonitrile, acetic acid, tetrahydrofuran, or dioxane.

[0026] Thirdly, the present invention provides a polyimide polymer obtained by polycondensation reaction of a diamine monomer and a dianhydride monomer; wherein the diamine monomer includes the adamantane-containing diamine monomer involved in the above-mentioned technical solution.

[0027] Preferably, the dianhydride monomer includes, but is not limited to, any one or more of the following structural formulas:

[0028]

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] This invention provides a diamine monomer containing an adamantane structure, the structural formula of which is shown in Formula I. By introducing adamantane into the diamine monomer, this invention leverages the highly symmetrical and stable alicyclic structure of adamantane. Its unique cage-like structure results in a low dielectric constant for semi-aromatic polyimide materials containing the adamantane structure. Furthermore, the adamantane-containing polyimide resin prepared in this invention has an adamantane group located on the polymer side chain, and the diphenylamine structure in the main chain makes the polymer chain segments more twisted, effectively increasing the polymer free volume and further reducing the polymer's dielectric constant. Attached Figure Description

[0031] Figure 1 The infrared spectra of the dinitro compound and the diamine compound obtained in Example 1 are shown below.

[0032] Figure 2 The 1H NMR spectrum of the diamine compound obtained in Example 1;

[0033] Figure 3 The infrared spectra of the dinitro compound and the diamine compound obtained in Example 4 are shown below.

[0034] Figure 4 The 1H NMR spectrum of the diamine compound obtained in Example 4;

[0035] Figure 5 Comparison of infrared spectra of the diamine compounds obtained in Examples 1, 4, and 5;

[0036] Figure 6 The 1H NMR spectrum of the diamine compound obtained in Example 5;

[0037] Figure 7 A comparison curve of the dielectric constants of PI(ODA) and PI(ODA-Ad);

[0038] Figure 8 The graph shows a comparison of the dielectric constants of PI(ODA-CF3) and PI(ODA-Ad-CF3). Detailed Implementation

[0039] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0040] This invention provides a diamine monomer containing an adamantane structure, having the structure shown in Formula I:

[0041]

[0042] In Formula I, Ar is selected from phenyl or substituted phenyl.

[0043] In some embodiments of the present invention, the diamine monomer containing the adamantane structure has the structure shown in Formula I, wherein Ar is selected from any one of the following formulas Ar-1 to Ar-3:

[0044]

[0045] This invention introduces an adamantane structure into a diamine monomer, which results in a lower dielectric constant. Introducing this structure into the molecular chain of PI is expected to reduce the dielectric constant of PI, thereby meeting the application requirements.

[0046] The present invention also provides a method for preparing the above-mentioned diamine monomer containing an adamantane structure, comprising:

[0047] S1: 1-Aminoadamantane and a nitro-containing haloalkanes are reacted in the presence of an alkaline catalyst to obtain a dinitro compound;

[0048] S2: The dinitro compound is reacted under the action of a combination of reducing agent and catalyst to obtain a diamine monomer containing adamantane structure.

[0049] According to the present invention, 1-aminoadamantane and a nitro-containing haloalkanes are first reacted under the action of an alkaline catalyst to obtain a dinitro compound.

[0050] The structural formulas of the 1-aminoadamantane and the nitro-containing halocarbon compound are shown in Formula 1 and Formula II below:

[0051]

[0052] In Formula II, Ar is selected from phenyl or substituted phenyl, and X is selected from -F, -Cl, -Br and -I;

[0053] In some embodiments of the present invention, the structural formula of the nitro-containing halocarbon compound is selected from any one of the following formulas II-1 to II-3:

[0054]

[0055] Wherein, X is selected from one of -F, -Cl, -Br or -I, preferably -F and -Cl.

[0056] In some preferred embodiments of the present invention, 1-aminoadamantane and a nitro-containing haloalkane compound undergo a nucleophilic substitution reaction under an inert atmosphere in the presence of a basic catalyst and an organic solvent to yield a dinitro compound. The present invention does not impose any particular limitation on the inert atmosphere; any atmosphere well known to those skilled in the art is acceptable, with nitrogen being preferred. In the present invention, the basic catalyst includes, but is not limited to, any one or more of sodium hydride, potassium hydride, potassium tert-butoxide, sodium tert-butoxide, cesium fluoride, potassium carbonate, sodium carbonate, or cesium carbonate, preferably cesium fluoride and / or cesium carbonate; the organic solvent is selected from any one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, tetrahydrofuran, toluene, or xylene, preferably any one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, or N-methylpyrrolidone.

[0057] In some embodiments of the present invention, preferably under an inert atmosphere, the molar ratio of 1-aminoadamantane, the nitro-containing haloalkane compound, and the basic catalyst is 1:(2-2.5):(2-2.5), more preferably 1:(2.1-2.4):(2.1-2.4), and even more preferably 1:(2.2-2.3):(2.2-2.3), and the three reactants are reacted in an organic solvent at 0-200°C for 5-24 hours, preferably at 50-150°C for 8-15 hours. The reaction is preferably carried out under stirring. The amount of the organic solvent is 3-10 times the mass of the reactants, preferably 4-6 times. The reactants refer to 1-aminoadamantane and the nitro-containing haloalkane compound. After the reaction is completed, some embodiments of the present invention further include precipitation, washing, filtration and purification of the obtained mixture. The washing can be water washing and / or alcohol washing. Preferably, the mixture is precipitated in water and purified by recrystallization. After drying, the dinitro compound can be obtained.

[0058] After obtaining the dinitro compound, the present invention characterized it with infrared radiation and found that it had two corresponding nitro characteristic peaks, indicating that the dinitro compound was successfully prepared.

[0059] After obtaining the nitro compound, according to the present invention, the dinitro compound is reacted under the action of a combination of a reducing agent and a catalyst to obtain a diamine monomer containing an adamantane structure. The combination of the reducing agent and catalyst includes, but is not limited to, any one of the following: a combination of hydrazine hydrate and palladium on carbon; a combination of hydrogen and palladium on carbon; a combination of hydrogen and nickel; a combination of stannous chloride and hydrochloric acid; a combination of zinc powder and hydrochloric acid; a combination of iron powder and hydrochloric acid; and a combination of zinc powder and acetic acid, preferably hydrazine hydrate and palladium on carbon.

[0060] In some preferred embodiments of the present invention, under an inert atmosphere, the dinitro compound, reducing agent, and catalyst are fed in a molar ratio of 1:(2-8):(0.01-8), preferably 1:(3-6):(0.5-6), more preferably 1:(4-5):(1-5), and reacted at 0-200°C for 5-24 hours, preferably at 50-150°C for 8-15 hours, in the presence of an organic solvent, to undergo a hydrogenation reduction reaction. The organic solvent is selected from any one or more of ethanol, methanol, acetone, acetonitrile, acetic acid, tetrahydrofuran, or dioxane, preferably any one or more of ethanol, methanol, or tetrahydrofuran. The reaction is preferably carried out under stirring. After the reaction is completed, in some embodiments of the present invention, the obtained mixture is further subjected to filtration, crystallization, and purification. Preferably, the obtained mixture is filtered to obtain a solution of the diamine compound, which is then crystallized under an inert atmosphere to obtain a crude product, purified by recrystallization, and dried to obtain the diamine compound.

[0061] The preparation method provided by this invention is simple, convenient, and easy to implement, which is conducive to industrialization or production.

[0062] This invention also provides a polyimide polymer, which is obtained by a polycondensation reaction between a diamine monomer and a dianhydride monomer; the diamine monomer is the adamantane-containing diamine monomer involved in the above-mentioned technical solution. This invention does not impose any particular limitation on the dianhydride monomer; any commercially available dianhydride monomer is acceptable.

[0063] In some embodiments of the present invention, the dianhydride monomer may specifically include, but is not limited to, any one or more of the following structural formulas:

[0064]

[0065] The structural formula of the polyimide polymer provided by this invention can be selected from any of the following (where n is the proportion of repeating units containing adamantane structure, m represents the degree of polymerization, which can be set as needed; generally, the range of n is 0 < n ≤ 1, and the range of m is m ≥ 20):

[0066]

[0067] Ar is selected from phenyl or substituted phenyl; C includes, but is not limited to, one or more of the following structures:

[0068]

[0069] D includes, but is not limited to, one or more of the following structures:

[0070]

[0071] To further illustrate the present invention, the following embodiments provide a detailed description. The experimental materials used in the following embodiments of the present invention are all commercially available products.

[0072] Example 1

[0073] (1) 15.125 g of 1-aminoadamantane (0.1 mol), 33.864 g of p-fluoronitrobenzene (0.24 mol), 36.456 g of cesium fluoride (0.24 mol), 20 mL of toluene, and 195 mL of N,N-dimethylformamide were added to a 500 mL three-necked flask. The mixture was heated to reflux under continuous high-purity nitrogen gas and mechanical stirring. The reaction system was dehydrated using an oil-water separator for 2 hours. Excess toluene was then discharged, and the temperature was raised to 150 °C and the reaction continued for 12 hours. After cooling, the product was discharged into distilled water. The crude product was washed with water and ethanol, and then purified by recrystallization using toluene as a solvent. After drying, 28.0 g of a dinitro compound, denoted as Ad-diNO2, was obtained. Infrared characterization was performed as follows: Figure 1 As shown, 1535cm -1 and 1376cm -1 Characteristic peaks corresponding to nitro groups.

[0074] (2) Transfer the dried dinitro compound Ad-diNO2 to a 500mL three-necked flask, add 0.5g palladium on carbon (10%) and 200mL ethanol, and heat to a gentle boiling state under continuous high-purity nitrogen gas and mechanical stirring. Then, use a constant-pressure dropping funnel to add 50mL of hydrazine hydrate for reduction reaction. After the addition is complete, continue heating and stirring for 2h. Then, filter while hot to obtain an ethanol solution of the diamine compound. Crystallize under nitrogen protection to obtain the crude product, which is purified by recrystallization from ethanol, dried, and the diamine compound is obtained, denoted as Ad-diNH2. Infrared characterization is as follows. Figure 1 and Figure 5 As shown, Figure 1 In Ad-diNH2, 1535cm -1 and 1376cm -1 The characteristic peak corresponding to the nitro group disappears, and the peak value is between 3300-3500 cm⁻¹. -1 The presence of characteristic peaks for amino groups indicates that the nitro group has been completely reduced to an amino group; the 1H NMR spectrum is as follows: Figure 2 As shown, the three signal peaks between chemical shifts of 1.50 and 2.25 ppm correspond to the three hydrogen atoms in adamantane, the signal peak at chemical shift of 3.5 ppm corresponds to the hydrogen atom in amino groups, and the two signal peaks between chemical shifts of 6.5 and 7.0 ppm correspond to the two hydrogen atoms on the benzene ring.

[0075] The synthetic route of Example 1 is shown below:

[0076]

[0077] Example 2

[0078] (1) In step (1) of Example 1, p-fluoronitrobenzene was replaced with p-chloronitrobenzene (39.39 g, 0.25 mol), cesium fluoride was replaced with calcium hydride (8.4 g, 0.2 mol) and cesium fluoride (3.04 g, 0.02 mol), and N,N-dimethylformamide was replaced with N,N-dimethylacetamide (200 mL). The reaction temperature was changed to 160 °C, and the other reaction conditions remained unchanged. After reacting for 10 h, the product was discharged into distilled water after cooling. The crude product was washed with water and ethanol, and then purified by recrystallization with toluene as solvent. After drying, 31.8 g of dinitro compound was obtained, which was denoted as Ad-diNO2.

[0079] (2) Transfer the dried dinitro compound Ad-diNO2 to a 500mL three-necked flask, add 10.5g of zinc powder and 200mL of methanol, and heat to a slight boiling state under continuous high-purity nitrogen gas and mechanical stirring. Then, use a constant pressure dropping funnel to add 32.4mL of concentrated hydrochloric acid (concentration 36%) dropwise to carry out the reduction reaction. After the addition is completed, continue heating and stirring for 2h. Then filter while hot to obtain a methanol solution of diamine compound. Crystallize under nitrogen protection to obtain crude product, purify by recrystallization with ethanol, and dry to obtain diamine compound, denoted as Ad-diNH2.

[0080] The synthetic route of Example 2 is shown below:

[0081]

[0082] Example 3

[0083] (1) In step (1) of Example 1, cesium fluoride was replaced with potassium tert-butoxide (22.44 g, 0.2 mol), N,N-dimethylformamide was replaced with tetrahydrofuran (200 mL), the reaction temperature was changed from 0 °C to room temperature, and the other reaction conditions remained unchanged. After reacting for 10 h, the product was discharged into distilled water after cooling. The crude product was washed with water and ethanol, and then purified by recrystallization with toluene as solvent. After drying, 25.2 g of dinitro compound was obtained, which was denoted as Ad-diNO2.

[0084] (2) Transfer the dried dinitro compound Ad-diNO2 to a 500mL three-necked flask, add 10.5g of zinc powder and 200mL of acetic acid, and react at room temperature for 8h under continuous high-purity nitrogen gas and mechanical stirring. Then filter to obtain an acetic acid solution of the diamine compound, pour it into distilled water, precipitate the solid, filter it, and then purify it by recrystallization with ethanol. After drying, the diamine compound is obtained and denoted as Ad-diNH2.

[0085] The synthetic route of Example 2 is shown below:

[0086]

[0087] Example 4

[0088] (1) 15.125 g of 1-aminoadamantane (0.1 mol), 41.18 g of 2-chloro-5-nitrotoluene (0.24 mol), 65.16 g of cesium carbonate (0.2 mol), 20 mL of xylene, and 280 mL of N-methylpyrrolidone were added to a 500 mL three-necked flask. The mixture was heated to reflux under continuous high-purity nitrogen gas and mechanical stirring. The reaction system was dehydrated using an oil-water separator for 2 hours. Excess xylene was then discharged, and the temperature was raised to 180 °C and the reaction continued for 8 hours. After cooling, the product was discharged into distilled water. The crude product was washed with water and ethanol, and then purified by recrystallization using toluene as a solvent. After drying, 35.0 g of a dinitro compound, denoted as Ad-CH3-diNO2, was obtained. Infrared characterization was performed as follows: Figure 3 and Figure 5 As shown.

[0089] (2) Transfer the dried dinitro compound Ad-CH3-diNO2 to a 500mL three-necked flask, add 0.5g palladium on carbon (10%) and 200mL ethanol, and heat to a gentle boiling state under continuous high-purity nitrogen gas and mechanical stirring. Then, use a constant pressure dropping funnel to add 50mL of hydrazine hydrate for reduction reaction. After the addition is complete, continue heating and stirring for 2h. Then, filter while hot to obtain an ethanol solution of the diamine compound. Crystallize under nitrogen protection to obtain the crude product. Purify by recrystallization from ethanol, and dry to obtain the diamine compound, denoted as Ad-CH3-diNH2. Infrared characterization is as follows. Figure 3 As shown, Figure 3 In Ad-CH3-diNH2, 1530cm -1 and 1376cm -1 The characteristic peak corresponding to the nitro group disappears, and the peak value is between 3300-3500 cm⁻¹. -1 The presence of characteristic peaks for amino groups indicates that the nitro group has been completely reduced to an amino group; the 1H NMR spectrum is as follows: Figure 4As shown, the chemical shifts of each hydrogen atom have good assignments. Specifically, the three signal peaks between chemical shifts of 1.50 and 2.25 ppm correspond to the three hydrogen atoms in adamantane, the signal peak at 2.75 ppm corresponds to the hydrogen atom in methyl, the signal peak at 3.25 ppm corresponds to the hydrogen atom in amino, and the three signal peaks between chemical shifts of 6.5 and 7.0 ppm correspond to the three hydrogen atoms on the benzene ring.

[0090] The synthetic route of Example 4 is shown below:

[0091]

[0092] Example 5

[0093] (1) 15.125g of 1-aminoadamantane (0.1mol), 54.13g of 2-chloro-5-nitrotrifluorotoluene (0.24mol), 34.5g of potassium carbonate (0.25mol), 20mL of xylene and 280mL of N-methylpyrrolidone were added to a 500mL three-necked flask. The mixture was heated to reflux under continuous high-purity nitrogen gas and mechanical stirring. The reaction system was dehydrated using an oil-water separator. After 2 hours of continuous water removal, excess xylene was discharged. The temperature was raised to 180℃ and the reaction was continued for 8 hours. After cooling, the product was discharged into distilled water. The crude product was washed with water and ethanol, and then purified by recrystallization using toluene as a solvent. After drying, 35.0g of dinitro compound was obtained, denoted as Ad-CF3-diNO2.

[0094] (2) Transfer the dried dinitro compound Ad-CF3-diNO2 to a 500mL three-necked flask, add 0.5g palladium on carbon (10%) and 200mL ethanol, and heat to a gentle boiling state under continuous high-purity nitrogen gas and mechanical stirring. Then, use a constant pressure dropping funnel to add 50mL of hydrazine hydrate for reduction reaction. After the addition is complete, continue heating and stirring for 2h. Then, filter while hot to obtain an ethanol solution of the diamine compound. Crystallize under nitrogen protection to obtain the crude product. After recrystallization and purification with ethanol, dry to obtain the diamine compound, denoted as Ad-CF3-diNH2. Infrared characterization is as follows. Figure 5 As shown, in Ad-CF3-diNH2, the characteristic peak of the nitro group disappears, and the peak value is between 3300-3500 cm⁻¹. -1 The presence of characteristic peaks for amino groups indicates that the nitro group has been completely reduced to an amino group; the 1H NMR spectrum is as follows: Figure 6 As shown, the chemical shifts of each hydrogen atom have good assignments. Specifically, the three signal peaks between chemical shifts of 1.50 and 2.25 ppm correspond to the three hydrogen atoms in adamantane, the signal peak at 3.75 ppm corresponds to the hydrogen atom in amino groups, and the three signal peaks between chemical shifts of 6.75 and 7.25 ppm correspond to the three hydrogen atoms on the benzene ring.

[0095] The synthetic route of Example 5 is shown below:

[0096]

[0097] Example 6

[0098] Accurately weigh 1.6019 g of 4,4-diaminodiphenyl ether (0.008 mol) and 0.6670 g of Ad-diNH2 (0.002 mol) prepared in Example 1 into a 50 mL three-necked flask. Add 28 mL of N,N-dimethylacetamide (DMAc), purge with high-purity nitrogen, and dissolve using magnetic stirring. After the solid dissolves, weigh 4.4424 g of 4,4'-(hexafluoroisopropene)phthalic anhydride (abbreviated as 6FDA) (0.01 mol) and add it to the solution in three batches. Rinse the weighing paper and the inner wall of the container with 3 mL of DMAc. After stirring the reaction system continuously for 12 h, pour the solution onto a clean glass plate and use a film scraper to smooth the solution into a film. Transfer the glass plate to an oxygen-free high-temperature oven and heat it to 350 °C at a rate of 1 °C / min, then turn off the heating and allow it to cool naturally. The thin film is removed from the glass plate and denoted as PI (ODA-Ad). Its structural formula is shown below:

[0099]

[0100] The dielectric constant of the PI (ODA-Ad) thin film was measured (instrument model: Novocontrol Technologies, Concept 41) at a scan frequency of 1-1 MHz. The results are as follows: Figure 7 As shown.

[0101] Comparative experiment

[0102] Accurately weigh 2.0024 g of 4,4-diaminodiphenyl ether (0.01 mol) into a 50 mL three-necked flask, add 20 mL of N,N-dimethylacetamide (DMAc), purge with high-purity nitrogen and dissolve using magnetic stirring. After the solid dissolves, weigh 4.4424 g of 6FDA (0.01 mol) and add it to the solution in three batches. Rinse the weighing paper and the inner wall of the container with 4 mL of DMAc. After stirring the reaction system for 12 hours, pour the solution onto a clean glass plate and use a film scraper to smooth the solution into a film. Transfer the glass plate to an oxygen-free high-temperature oven and heat it to 350 °C at a rate of 1 °C / min, then turn off the heating and allow it to cool naturally. Remove the film from the glass plate and denote it as PI (ODA). The structural formula is shown below:

[0103]

[0104] The dielectric constant of the PI(ODA) thin film was measured (instrument model: Novocontrol Technologies, Concept 41) at a scan frequency of 1-1 MHz. The results are as follows: Figure 7 As shown.

[0105] from Figure 7 In the polymerization process, the dielectric constant of PI(ODA) is 2.97 at 1 MHz. When the Ad-diNH2 monomer partially replaces the 4,4'-diaminophenyl ether during polymerization, introducing the adamantane structure into the polymer structure, the dielectric constant of PI(ODA-Ad) at 1 MHz decreases to 2.92. This demonstrates that the introduction of the adamantane structure can effectively reduce the dielectric constant of PI.

[0106] Example 7

[0107] Accurately weigh 1.0012 g of 4,4-diaminodiphenyl ether (0.005 mol) and 2.3474 g of Ad-CF3-diNH2 (0.005 mol) prepared in Example 5 into a 50 mL three-necked flask. Add 28 mL of N,N-dimethylacetamide (DMAc), purge with high-purity nitrogen, and dissolve using magnetic stirring. After the solid dissolves, weigh 4.4424 g of 6FDA (0.01 mol) and add it to the solution in three batches. Rinse the weighing paper and the inner wall of the container with 3 mL of DMAc. After stirring the reaction system for 12 h, pour the solution onto a clean glass plate and use a film scraper to smooth the solution into a film. Transfer the glass plate to an oxygen-free high-temperature oven and heat it to 350 °C at a rate of 1 °C / min, then turn off the heating and allow it to cool naturally. Remove the film from the glass plate and label it PI (ODA-Ad-CF3). The structural formula is shown below:

[0108]

[0109] The dielectric constant of PI (ODA-Ad-CF3) thin films was measured (instrument model: Novocontrol Technologies, Concept 41), with a scan frequency of 1-1 MHz. The results are as follows: Figure 8 As shown.

[0110] Comparative experiment

[0111] Accurately weigh 1.0012 g of 4,4-diaminodiphenyl ether (0.005 mol) and 1.6812 g of 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether (0.005 mol) into a 50 mL three-necked flask. Add 20 mL of N,N-dimethylacetamide (DMAc), purge with high-purity nitrogen, and dissolve using magnetic stirring. After the solid dissolves, weigh 4.4424 g of 6FDA (0.01 mol) and add it to the solution in three batches. Rinse the weighing paper and the inner wall of the container with 4 mL of DMAc. After stirring the reaction system for 12 h, pour the solution onto a clean glass plate and use a film scraper to smooth the solution into a film. Transfer the glass plate to an oxygen-free high-temperature oven and heat it to 350 °C at a rate of 1 °C / min. Then, turn off the heating and allow it to cool naturally. Remove the film from the glass plate and denote it as PI (ODA-CF3). The structural formula is shown below:

[0112]

[0113] The dielectric constant of the PI(ODA-CF3) thin film was measured (instrument model: Novocontrol Technologies, Concept 41), with a scan frequency of 1-1 MHz. The results are as follows: Figure 8 As shown.

[0114] from Figure 8 In the polymerization process, the dielectric constant of PI(ODA-CF3) is 2.91 at 1 MHz. When the 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether monomer is replaced with Ad-CF3-diNH2 during polymerization, introducing the adamantane structure into the polymer structure, the dielectric constant of PI(ODA-Ad-CF3) at 1 MHz decreases to 2.84. This demonstrates that the introduction of the adamantane structure can effectively reduce the dielectric constant of PI.

[0115] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A diamine monomer represented by Formula I: Formula I; in, In formula I, Ar is selected from any one of the following formulas Ar-1 to Ar-3: Formula Ar-1; Formula Ar-2; Formula Ar-3.

2. A method for preparing a diamine monomer as described in claim 1, characterized in that, include: S1: 1-Aminoadamantane and a nitro-containing haloalkanes are reacted in the presence of an alkaline catalyst to obtain a dinitro compound; The structural formula of the nitro-containing halocarbon compound is shown in Formula II below: Formula II, In Formula II, Ar is selected from phenyl or substituted phenyl, and X is selected from -F, -Cl, -Br and -I; S2: The dinitro compound is reacted under the action of a combination of reducing agent and catalyst to obtain a diamine monomer.

3. The preparation method according to claim 2, characterized in that, The alkaline catalyst is selected from any one or more of sodium hydride, potassium hydride, potassium tert-butoxide, sodium tert-butoxide, cesium fluoride, potassium carbonate, sodium carbonate, or cesium carbonate. The reducing agent and catalyst combination is selected from any one of the following combinations: hydrazine hydrate and palladium on carbon, hydrogen and palladium on carbon, hydrogen and nickel, stannous chloride and hydrochloric acid, zinc powder and hydrochloric acid, iron powder and hydrochloric acid, and zinc powder and acetic acid.

4. The preparation method according to claim 2 or 3, characterized in that, The molar ratio of 1-aminoadamantane, the nitro-containing halocarbon compound, and the basic catalyst is 1:(2~2.5):(2~2.5); The molar ratio of the dinitro compound, reducing agent, and catalyst is 1:(2~8):(0.01~8).

5. The preparation method according to any one of claims 2 to 4, characterized in that, The reaction temperatures in steps S1 and S2 are each independently 0~200℃, and the reaction times are each independently 5~24 h.

6. The preparation method according to any one of claims 2 to 5, characterized in that, The reaction described in step S1 is also carried out in the presence of an inert atmosphere and an organic solvent; The organic solvent is selected from any one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, tetrahydrofuran, toluene, or xylene.

7. The preparation method according to any one of claims 2 to 6, characterized in that, The reaction described in step S2 is also carried out in the presence of an inert atmosphere and an organic solvent; The organic solvent is selected from any one or more of ethanol, methanol, acetone, acetonitrile, acetic acid, tetrahydrofuran, or dioxane.

8. A polyimide polymer, characterized in that, It is obtained by polycondensation of diamine monomer and dianhydride monomer, followed by imidization reaction; The diamine monomer includes the diamine monomer of claim 1 or the diamine monomer prepared by the preparation method according to any one of claims 2 to 7.

9. The polyimide polymer according to claim 8, characterized in that, The dianhydride monomer includes, but is not limited to, any one or more of the following structural formulas: , , , , , , , , , and .

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