Diamine monomers containing pendant urea groups, polyimides, and methods of making and using the same

Abstract

The application provides a diamine monomer containing a side chain urea group, a polyimide and a preparation method and application thereof, and relates to the field of dielectric polymer materials. The structural formula of the diamine monomer is shown as formula 1, the structural formula of the polyimide is shown as formula 5, and the application further provides a preparation method of the polyimide. The polyimide containing a side chain urea group provided by the application has high dielectricity and low loss, and can be used as a high-dielectric material, and has a great application prospect in electronic equipment, especially in the fields of high-energy storage capacitors and organic thin film transistors.

Description

Technical Field

[0001] This invention relates to the field of dielectric polymer materials, and more particularly to a diamine monomer containing a side-chain urea group, a polyimide, its preparation method, and its application. Background Technology

[0002] With the rapid miniaturization and integration of electronic devices, higher standards have been set for the overall performance of electronic materials. Traditional high-dielectric materials, as crucial components of electronic devices, are increasingly failing to meet the high demands of advanced power electronic equipment. Therefore, it is urgent to develop novel high-dielectric materials with superior performance to address this current predicament.

[0003] Compared to traditional inorganic dielectric materials, polymers are more suitable for the development and application of dielectric materials due to their advantages such as light weight, flexibility, ease of processing, and breakdown resistance. However, the low dielectric constant of polymers limits their application in the field of high-dielectric materials. To improve the dielectric constant, researchers have carried out a series of modifications to polymer materials. High-dielectric-constant inorganic nanofillers are added to polymers to prepare polymer nanocomposites. However, host-guest incompatibility between inorganic fillers and polymers, dielectric mismatch, nanoparticle aggregation, and difficulty in controlling film thickness still need further solutions, making it very difficult for polymer nanocomposites to maintain excellent dielectric properties and achieve large-scale production. Based on the above analysis, intrinsically high-dielectric pure polymer materials have irreplaceable advantages. By incorporating high-dipole groups into the polymer backbone, the dielectric constant is further increased by utilizing dipole rotation to increase dipole polarization, while maintaining low dielectric loss through dipole-dipole interactions.

[0004] Polyimide is a special engineering polymer with an imide ring structure in its molecular backbone. It possesses excellent heat resistance, dimensional stability, electrical properties, mechanical properties, and good structural designability, and is widely used in microelectronics, materials packaging, aerospace, and other fields. Through molecular structure design, some progress has been made in the preparation of intrinsically high-dielectric-low-loss polyimides, as shown in CN 113480450A, CN 113754571A, and CN 114349670A. Introducing small-sized and high-dipole side-chain cyano and sulfone groups into the polyimide backbone yields relatively high dielectric constants, but inevitably comes with slightly higher dielectric losses. Structure determines performance; the rational design of monomer structures will optimize the performance of polymer materials. Therefore, the preparation of novel intrinsically high-dielectric-low-loss polyimides still requires further exploration. Summary of the Invention

[0005] This invention discloses a diamine monomer containing a side-chain urea group, a polyimide, its preparation method, and its application. A series of polyimides are prepared by polymerizing the diamine monomer containing the side-chain urea group provided by this invention with a dianhydride monomer, exhibiting high dielectric constant, low dielectric loss, good thermal stability, and film-forming properties.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a diamine monomer containing a side-chain urea group, with the structural formula shown in Formula 1:

[0008]

[0009] In Formula 1, R1 and R2 are substituents containing urea groups.

[0010] Preferably, R1 and R2 are one of the following structures:

[0011]

[0012] Where a, b ≥ 0.

[0013] This invention provides a method for preparing a diamine monomer containing a side-chain urea group, the specific steps of which include the following:

[0014] Step 1: Under an inert atmosphere of nitrogen or argon, a dibromoalkyldinitro compound having the structure of Formula 2 reacts with potassium phthalimide, and then the dialkyl primary aminedinitro compound having the structure of Formula 3 is obtained by the Gabriel reaction.

[0015]

[0016]

[0017] In equations 2 and 3, a ≥ 0;

[0018] Step 2: React the dialkyl primary amine dinitro compound of Formula 3 with isocyanate or thioisocyanate to obtain the diurea dinitro compound of Formula 4;

[0019]

[0020] In Formula 4, R1 and R2 are substituents containing a urea group structure;

[0021] Step 3: The diurea dinitro compound of Formula 4 is reduced to obtain the diamine monomer of Formula 1 containing a side-chain urea group;

[0022]

[0023] In Formula 1, R1 and R2 are substituents containing urea groups.

[0024] This invention provides a polyimide containing the above-mentioned diamine monomer, with the structural formula shown in Formula 5:

[0025]

[0026] In Equation 5, m and n are the degree of polymerization, m:n = 0.1 / 0.9-1 / 0, where n = 0 when Y1 is homopolymer; X1 and X2 can be aromatic or aliphatic groups, Y1 is the above-mentioned diamine monomer, and Y2 is a diamine residue.

[0027] Preferably, X1 and X2 can be the same or different, and are selected from the following structures:

[0028]

[0029] Preferably, Y2 is a diamine residue selected from the following structures:

[0030]

[0031] Preferably, the polyimide has the following structure:

[0032]

[0033] The present invention also provides a method for preparing the above-mentioned polyimide, the method comprising the following steps:

[0034] Under an inert atmosphere of nitrogen or argon, a diamine monomer with a Y1 structure containing a side-chain urea group or a mixed diamine monomer with Y1 and Y2 structures is dissolved in an aprotic polar solvent and subjected to a polycondensation reaction to obtain a uniform and transparent precursor polyamic acid solution, which is then dehydrated to obtain polyimide.

[0035] Preferably, the diamine monomer with a side-chain urea group having the Y1 structure or the mixed diamine monomer having the Y1 and Y2 structures is in a molar ratio of 1:1 to 1.02 with the dianhydride monomer having the X1 structure or the mixed dianhydride monomer having the X1 and X2 structures.

[0036] The present invention also provides the application of the above-mentioned polyimide as a high dielectric material in the fields of high energy storage capacitors and organic thin film transistors.

[0037] Beneficial effects of the present invention

[0038] This invention discloses a diamine monomer containing a side-chain urea group, a polyimide, its preparation method, and its applications. This invention introduces the polar urea group into the side chain of the polyimide, utilizing the high dipole moment of the urea group to obtain an intrinsically high-dielectric polyimide material. Under the action of an electric field, the small-sized, high-dipole side-chain urea groups can orient and rotate along the direction of the electric field, increasing the dielectric constant of the polymer material. The mutual coupling between urea groups and the hydrogen bonding interactions between urea groups result in low dielectric loss in the polyimide containing the side-chain urea group. Simultaneously, the biphenyl structure in the diamine monomer ensures that the synthesized polyimide containing the side-chain urea group exhibits good thermal properties.

[0039] The preparation process of this invention is simple, the reaction conditions are mild, it has broad applicability, and it can be applied to large-scale production.

[0040] The high-dielectric-low-loss polyimide containing side-chain urea provided by this invention can be used as a high-dielectric material and has great application prospects in electronic devices, especially in the fields of high-energy storage capacitors and organic thin-film transistors. Attached Figure Description

[0041] To more clearly illustrate the embodiments of the present invention or existing technical solutions, the drawings used in the embodiments will be briefly introduced below. The drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 The (4,4'-dinitro-[1-1'-biphenyl]-2,2'-dimethyl]dimethylamine in Example 1 of this invention 1 HNMR.

[0043] Figure 2 The 1,1'-((4,4'-dinitro-[1,1'-biphenyl]-2,2'-diyl)bis(methylene))bis-(3-benzylurea) in Example 1 of this invention 1 HNMR.

[0044] Figure 3 The 1,1'-((4,4'-diamino-[1,1'-biphenyl]-2,2'-diyl)bis(methylene))bis-(3-benzylurea) in Example 1 of this invention 1 HNMR.

[0045] Figure 4 The infrared spectra of the three urea-containing polyimides prepared in Examples 2-4 of this invention are shown.

[0046] Figure 5 The NMR spectra are those of the three polyimides containing side-chain urea groups prepared in Examples 2-4 of this invention.

[0047] Figure 6 The thermogravimetric curves of the three types of urea-containing polyimides prepared in Examples 2-4 of this invention are shown.

[0048] Figure 7 The images show the room temperature spectra of the three urea-containing polyimides prepared in Examples 2-4 of this invention. Detailed Implementation

[0049] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0050] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0051] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0052] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0053] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0054] This invention provides a diamine monomer containing a side-chain urea group, with the structural formula shown in Formula 1:

[0055]

[0056] In Formula 1, R1 and R2 are substituents containing a urea group, and R1 and R2 are preferably one of the following structures:

[0057]

[0058] Where a, b ≥ 0.

[0059] The diamine monomer containing a side-chain urea group is preferably 1,1'-((4,4'-diamino-[1,1'-biphenyl]-2,2'-diyl)bis(methylene))bis-(3-benzylurea), with the following structure:

[0060]

[0061] This invention provides a method for preparing a diamine monomer containing a side-chain urea group, the specific steps of which include the following:

[0062] Step 1: Under an inert nitrogen or argon atmosphere, a dibromoalkyldinitro compound having the structure of Formula 2 reacts with potassium phthalimide. The reaction temperature is preferably room temperature, and the reaction time is preferably 12-24 h. Then, a Gabriel reaction is performed, preferably at 80-100 °C, for 2-4 h, to obtain a dialkyl primary amine dinitro compound having the structure of Formula 3. The organic solvent used in the reaction of the dibromoalkyldinitro compound having the structure of Formula 2 with potassium phthalimide is preferably one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, or dimethyl sulfoxide. The organic solvent used in the Gabriel reaction is preferably hydrazine hydrate or methanol / ethanol. The molar ratio of the dibromoalkyldinitro compound of Formula 2 to potassium phthalimide is preferably 1:2.4.

[0063]

[0064] In equations 2 and 3, a ≥ 0;

[0065] Step 2: Reaction of the dialkyl primary amine dinitro compound of Formula 3 with isocyanate or thioisocyanate, preferably at room temperature and for 6-12 h, to obtain the diurea dinitro compound of Formula 4; wherein the organic solvent used in the reaction is preferably one of ethyl acetate, dichloromethane, acetonitrile, 1,4-dioxane, or tetrahydrofuran, and the isocyanate or thioisocyanate is alkyl-substituted or aromatic-substituted, and the molar ratio of the dialkyl primary amine dinitro compound of Formula 3 to the isocyanate or thioisocyanate is preferably 1:2.4;

[0066]

[0067] In Formula 4, R1 and R2 are substituents containing a urea group structure;

[0068] Step 3: The diurea dinitro compound of Formula 4 is subjected to a reduction reaction. The reduction reaction is preferably carried out at a temperature of 105-110℃ and for a time of 24-36 hours to obtain a diamine monomer containing a side-chain urea group of Formula 1. The catalyst used in the reduction reaction is preferably palladium on carbon, the reducing agent is preferably hydrazine hydrate, and the solvent is preferably one or more of 1,4-dioxane, ethanol, or ethyl acetate. The mass ratio of the catalyst to the diurea dinitro compound of Formula 4 is preferably 10%-20%, and the molar ratio of the diurea dinitro compound of Formula 4 to the reducing agent is preferably 1:10-30.

[0069]

[0070] In Formula 1, R1 and R2 are substituents containing urea groups.

[0071] This invention provides a polyimide containing the above-mentioned diamine monomer, with the structural formula shown in Formula 5:

[0072]

[0073] In Equation 5, m and n are the degree of polymerization, m:n = 0.1 / 0.9-1 / 0, where n = 0 when Y1 is homopolymer; X1 and X2 can be aromatic or aliphatic groups, Y1 is the above-mentioned diamine monomer, and Y2 is a diamine residue.

[0074] According to the present invention, X1 and X2 may be the same or different, and are selected from the following structures:

[0075]

[0076] According to the present invention, Y1 is the above-mentioned diamine monomer, and Y2 is a diamine residue selected from the following structures:

[0077]

[0078] Preferably, the polyimide has the following structure:

[0079]

[0080] The present invention also provides a method for preparing the above-mentioned polyimide, the method comprising the following steps:

[0081] Under an inert atmosphere of nitrogen or argon, a diamine monomer with a Y1 structure containing a side-chain urea group or a mixed diamine monomer with Y1 and Y2 structures is dissolved in an aprotic polar solvent to carry out a polycondensation reaction. The polycondensation reaction is preferably carried out at room temperature and for a time of 12-24 hours to obtain a uniform and transparent precursor polyamic acid solution, which is then dehydrated to obtain polyimide.

[0082] According to the present invention, the molar ratio of the diamine monomer containing a side-chain urea group with the Y1 structure or the mixed diamine monomer with the Y1 and Y2 structures to the dianhydride monomer with the X1 structure or the mixed dianhydride monomer with the X1 and X2 structures is preferably 1:1-1.02, and the mass ratio of the diamine monomer containing a side-chain urea group with the Y1 structure or the mixed diamine monomer with the Y1 and Y2 structures to the dianhydride monomer with the X1 structure or the mixed dianhydride monomer with the X1 and X2 structures to the aprotic polar solvent used is 10%-20%.

[0083] According to the present invention, the aprotic polar solvent used is preferably one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone or dimethyl sulfoxide.

[0084] According to the present invention, the method for dehydrating the precursor polyamic acid solution to form polyimide is chemical imidization or thermal imidization.

[0085] According to the present invention, the preferred steps of the chemical imide method are as follows: a dehydrating agent is added to a polyamic acid precursor solution, and the mixture is stirred for 12-24 hours. The reacted solution is then poured into ethanol, and the resulting polyimide product is in strip or powder form. The product is filtered, pulverized, washed with deionized water and ethanol, and dried to obtain polyimide powder. The dried polyimide powder is dissolved in one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, or dimethyl sulfoxide. The resulting homogeneous and transparent polyimide solution is uniformly cast onto a clean glass plate, heated to 150°C to remove the solvent, cooled, and peeled off with deionized water to obtain a polyimide film. The dehydrating agent is preferably acetic anhydride or pyridine / triethylamine.

[0086] According to the present invention, the preferred steps of the thermal imidization method are: uniformly casting a precursor polyamic acid solution onto a clean glass plate, and preparing a polyimide film by programmed temperature increase. The temperature increase program for thermal imidization is as follows: heating from room temperature to 60-70°C and holding for 1-3 hours; then heating to 100-110°C and holding for 1-2 hours; then heating to 150-160°C and holding for 1-2 hours; then heating to 200-210°C and holding for 1-2 hours; then heating to 250-260°C and holding for 1-2 hours; and finally heating to 280°C and holding for 1-2 hours.

[0087] The present invention also provides the application of the above-mentioned polyimide as a high dielectric material in the fields of high energy storage capacitors and organic thin film transistors.

[0088] The present invention will be further described in detail below with reference to specific embodiments. All raw materials involved in the embodiments are commercially available.

[0089] Example 1

[0090] (a) 4.30 g (10 mmol) of 2,2'-di(bromomethyl)-4,4'-dinitro-1,1'-biphenyl and 4.44 g (24 mmol) of potassium phthalimide were dissolved in 50 mL of N,N-dimethylformamide and stirred for 12 h at room temperature under an argon atmosphere. The reaction solution was then poured into 300 mL of deionized water, precipitating a white solid, which was filtered, washed, and dried. The resulting white solid was added to 200 mL of ethanol, followed by the addition of 1.5 g (30 mmol) of hydrazine hydrate, and refluxed under an argon atmosphere with stirring for 2 h. Ethyl acetate / ethanol column chromatography yielded the target product (4,4'-dinitro-[1,1'-biphenyl]-2,2'-diyl]dimethylamine, in 80% yield. Figure 1 As shown, 1 H NMR (400MHz, DMSO-d6, δ, ppm): 8.55 (d, J = 2.4Hz, 2H), 8.16 (dd, J = 8.3, 2.5Hz, 2H), 7.41 (d, J = 8.4Hz, 2H), 3.43 (q, J = 15.7Hz, 4H), 1.92 (s, 4H).

[0091] The structure is as follows:

[0092]

[0093] (b) 3.02 g (10 mmol) of (4,4'-dinitro-[1,1'-biphenyl]-2,2'-diyl]dimethylamine was dissolved in 50 mL of acetonitrile, and then 3.2 g (24 mmol) of benzyl isocyanate was added dropwise. The mixture was stirred at room temperature under an argon atmosphere for 6 h. A white solid precipitated, which was filtered, washed, and dried to give the target product 1,1'-((4,4'-dinitro-[1,1'-biphenyl]-2,2'-diyl)bis(methylene))bis-(3-benzylurea), in 85% yield. Figure 2 As shown, 1H NMR (400MHz, DMSO-d6, δ, ppm): 8.30 (s, 2H), 8.20 (d, J = 8.3Hz, 2H), 7.46 (d, J = 8.2Hz, 2H), 7.26 (t, J = 7.3Hz, 4H), 7.19 (t ,J=8.4Hz,6H),6.66(d,J=5.1Hz,4H),4.15(d,J=5.7Hz,4H),4.05(dd,J=16.2,6.1Hz,2H),3.95(dd,J=16.2,5.7Hz,2H).

[0094] The structure is as follows:

[0095]

[0096] (c) 5.68 g (10 mmol) of 1,1'-((4,4'-dinitro-[1,1'-biphenyl]-2,2'-diyl)bis(methylene))bis-(3-benzylurea), 0.56 g palladium / carbon, and 1.5 g (30 mmol) hydrazine hydrate were added to 50 mL of 1,4-dioxane and stirred under argon atmosphere for 24 h under reflux. The mixture was filtered and recrystallized from 1,4-dioxane to give the pale yellow target product 1,1'-((4,4'-diamino-[1,1'-biphenyl]-2,2'-diyl)bis(methylene))bis-(3-benzylurea), abbreviated as BUBPA, with a yield of 78%. Figure 3 As shown, 1 H NMR (400MHz, DMSO-d6, δ, ppm): 7.25 (t, J=7.3Hz, 4H), 7.16 (dd, J=19.8, 7.1Hz, 6H), 6.68 (d, J=8.1Hz, 2H), 6.59 (d, J=2.4Hz ,2H),6.44(dt,J=10.0,4.4Hz,4H),6.25(t,J=5.8Hz,2H),5.16(s,4H),4.08(d,J=6.0Hz,4H),3.82(dd,J=15.0,5.7Hz,4H).

[0097] The structure is as follows:

[0098]

[0099] Example 2

[0100] At room temperature, 0.5086 g (1 mmol) of 1,1'-((4,4'-diamino-[1,1'-biphenyl]-2,2'-diyl)bis(methylene))bis-(3-benzylurea) was dissolved in 7.87 ml of N,N-dimethylacetamide. Then, 0.3102 g (1 mmol) of 4,4-oxophthalic anhydride (ODPA) was added to the system, and the reaction was carried out for 12 h under an argon atmosphere to generate a homogeneous, transparent, viscous precursor polyamic acid solution (PAA). The obtained PAA solution was cast onto a clean glass plate and dried under vacuum at 70 °C for 4 h. The temperature was then programmed to rise to 100 °C, 150 °C, 200 °C, 250 °C, and 280 °C for 1 h each for thermal imidization treatment. After cooling to room temperature, the film was peeled off by immersion in deionized water and then dried in a vacuum oven for 6 h to remove moisture, yielding polyimide ODPA-BUBPA containing side-chain urea groups.

[0101]

[0102] Where n≥100.

[0103] Example 3

[0104] At room temperature, 0.5086 g (1 mmol) of 1,1'-((4,4'-diamino-[1,1'-biphenyl]-2,2'-diyl)bis(methylene))bis-(3-benzylurea) was dissolved in 9.16 ml of N,N-dimethylacetamide. Then, 0.4442 g (1 mmol) of 4,4'-(hexafluoroisopropene)phthalic anhydride (6FDA) was added to the system, and the reaction was carried out for 12 h under an argon atmosphere to generate a homogeneous, transparent, viscous precursor polyamic acid solution (PAA). The obtained PAA solution was cast onto a clean glass plate and dried under vacuum at 70 °C for 4 h. The temperature was then programmed to rise to 100 °C, 150 °C, 200 °C, 250 °C, and 280 °C for 1 h each for thermal imidization treatment. After cooling to room temperature, the film was peeled off by immersion in deionized water and then dried in a vacuum oven for 6 h to remove moisture, yielding polyimide 6FDA-BUBPA containing a side-chain urea group structure.

[0105]

[0106] Where n≥100.

[0107] Example 4

[0108] At room temperature, 0.5086 g (1 mmol) of 1,1'-((4,4'-diamino-[1,1'-biphenyl]-2,2'-diyl)bis(methylene))bis-(3-benzylurea) was dissolved in 8.33 ml of N,N-dimethylacetamide, and then 0.3582 g (1 mmol) of 3,3',4,4'-diphenylsulfone tetracarboxylic acid dianhydride (DSDA) was added to the system. The reaction was carried out under an argon atmosphere for 12 h to generate a homogeneous, transparent, viscous precursor polyamic acid solution (PAA). The obtained PAA solution was cast onto a clean glass plate and vacuum dried at 70°C for 4 hours. The temperature was then programmed to rise to 100°C, 150°C, 200°C, 250°C, and 280°C for 1 hour each for thermal imidization. After cooling to room temperature, the film was peeled off by immersion in deionized water and then dried in a vacuum oven for 6 hours to remove moisture, thus obtaining polyimide DSDA-BUBPA containing side-chain urea groups.

[0109]

[0110] Where n≥100.

[0111] The infrared spectra of the three side-chain urea-containing polyimides in Examples 2-4 are as follows: Figure 4 As shown in the infrared spectrum, it can be observed that in the 3500-3200 cm⁻¹ range... -1 The characteristic peak of the stretching vibration of the NH bond in the urea group appeared at 1780 cm⁻¹. -1 1710cm -1 and 1360cm -1 The characteristic vibrational peaks of the imide ring in polyimide are shown, namely the asymmetric and symmetric stretching vibrations of the C=O bond and the CN stretching vibration peaks in the imide ring.

[0112] The NMR spectra of the three side-chain urea-containing polyimides in Examples 2-4 are as follows: Figure 5 As shown in the NMR spectra, the hydrogen chemical shifts of the urea groups in the three polyimides containing side-chain urea groups appear at approximately 6.50 ppm and 6.60 ppm, respectively.

[0113] The thermogravimetric curves of the three side-chain urea-containing polyimides in Examples 2-4 are as follows: Figure 6 As shown in the thermogravimetric curves, the 5% thermogravimetric temperature of ODPA-BUBPA is 340℃, that of 6FDA-BUBPA is 321℃, and that of DSDA-BUBPA is 315℃.

[0114] The room temperature spectra of the three side-chain urea-containing polyimides in Examples 2-4 are as follows: Figure 7As shown in the dielectric constant-frequency diagram, at 1 kHz, the dielectric constant of ODPA-BUBPA is 6.14, that of 6FDA-BUBPA is 5.66, and that of DSDA-BUBPA is 7.7. Meanwhile, the dielectric loss-frequency diagram shows that the dielectric loss of ODPA-BUBPA is 0.0098, that of 6FDA-BUBPA is 0.0095, and that of DSDA-BUBPA is 0.0114.

Claims

1. A diamine monomer containing a side-chain urea group, characterized in that, The structural formula is shown in Equation 1:

2. The method for preparing a diamine monomer containing a side-chain urea group according to claim 1, characterized in that, The specific steps include the following: Step 1: Under an inert atmosphere of nitrogen or argon, a dibromoalkyldinitro compound having the structure of Formula 2 reacts with potassium phthalimide, and then the dialkyl primary aminedinitro compound having the structure of Formula 3 is obtained by the Gabriel reaction. Step 2: React the dialkyl primary amine dinitro compound of formula 3 with isocyanate to obtain the diurea dinitro compound of formula 4; Step 3: The diurea dinitro compound of Formula 4 is reduced to obtain the diamine monomer of Formula 1 containing a side-chain urea group; 3. A polyimide containing the diamine monomer of claim 1, characterized in that, The structural formula is shown in Equation 5: In Formula 5, m and n are the degree of polymerization, m:n = 0.1 / 0.9-1 / 0, where n = 0 in the case of homopolymerization of Y1; X1 and X2 can be aromatic or aliphatic groups, Y1 is a residue of the diamine monomer according to claim 1, and Y2 is a diamine residue.

4. The polyimide according to claim 3, characterized in that, X1 and X2 can be the same or different, and can be selected from the following structures:

5. The polyimide according to claim 3, characterized in that, Y2 is a diamine residue selected from the following structures:

6. The polyimide according to claim 3, characterized in that, The polyimide described above has the following structure:

7. A method for preparing the polyimide according to claim 4, characterized in that, The preparation method includes the following steps: Under an inert atmosphere of nitrogen or argon, a diamine monomer with a Y1 structure containing a side-chain urea group or a mixed diamine monomer with Y1 and Y2 structures is dissolved in an aprotic polar solvent and subjected to a polycondensation reaction to obtain a uniform and transparent precursor polyamic acid solution, which is then dehydrated to obtain polyimide.

8. The method for preparing polyimide according to claim 7, characterized in that, The diamine monomer with a Y1 structure containing a side-chain urea group or a mixed diamine monomer with Y1 and Y2 structures is in a molar ratio of 1:1-1.02 to a dianhydride monomer with an X1 structure or a mixed dianhydride monomer with X1 and X2 structures.

9. The application of the polyimide of claim 4 as a high dielectric material in the fields of high-energy-storage capacitors and organic thin-film transistors.

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