Diamine monomer and preparation method thereof, polyimide and preparation method and application thereof

Abstract

The invention discloses a diamine monomer and a preparation method thereof, polyimide and a preparation method and application thereof, and a novel TADF (thermally-induced delayed fluorescence) polyimide polymer material is prepared by adopting a polymer room-temperature polycondensation synthesis method based on a light-emitting structural unit. The polyimide has the advantages of excellent solubility, high glass transition temperature and high thermal stability. Furthermore, the organic light-emitting device with excellent device performance is prepared by taking the polymer as a light-emitting layer through a simple solution spin-coating mode. The method provided by the invention has the main characteristics of extremely high step economy and atom economy, simple experimental method operation, low design difficulty, diversified combination modes and good reaction region selectivity.

Description

Technical Field

[0001] The present invention relates to the technical field of organic optoelectronic polymers, and specifically to a diamine monomer, a preparation method thereof, a polyimide, a preparation method thereof and an application thereof. Background Art

[0002] In 2016, the Adachi research group (Adv. Mater., 2016, 28, 4019.) prepared a series of novel alternating D-A type TADF polymers by Suzuki reaction polymerization. Using this polymer as a luminescent material, the fabricated doped OLEDs devices emit green light, and the maximum external quantum efficiency (EQE) can reach 9.3%. The Huang research group (J. Mater. Chem. C, 2018, 6, 2690.) alternately copolymerized an electron-deficient diphenyl sulfone monomer and an electron-rich amino derivative to prepare PTSn series blue light polymers. The external quantum efficiency of the fabricated doped devices by solution spin coating is relatively low, only 5.3%, but the purity of its blue emission spectrum is extremely close to the National Television Standards Committee (NTSC) standard. The Nikolaenko research group (Adv. Mater., 2015, 27, 7236.) first synthesized a novel soluble non-conjugated polymer material with TADF luminescent units in the main chain, which is formed by condensation polymerization of a donor unit and an acceptor unit through Suzuki reaction, and the external quantum efficiency of its devices can reach 10.1%. Bryce et al. (Macromolecules, 2016, 49, 5452.) first copolymerized styrene and V-PTZ-DBTO2 monomers in different ratios to obtain a TADF luminescent polymer, and the device efficiency is good, and the maximum external quantum efficiency can reach 20.1%, but its efficiency roll-off is obvious, and the efficiencies at 100 cdm-2 and 1000 cdm-2 are 5.5% and 1.8% respectively. Although these TADF polymer materials are used as the electroluminescent layer to fabricate electroluminescent devices and achieve certain external quantum efficiencies, their limitations are relatively large.

[0003] First, the main chain structure of conjugated polymers is single, and the triplet energy levels of the conjugated main chain are often relatively low, which cannot effectively suppress energy dissipation and it is difficult to obtain blue light devices. In addition, although high external quantum efficiency light-emitting devices can be prepared, it is difficult to adjust the spectrum, and the emission color is relatively single. Secondly, the solubility of conjugated polymers is poor. In the process of designing conjugated polymers, flexible alkyl tail chains must be introduced to improve the solubility of the polymers. To a certain extent, the tail chains greatly reduce the solubility of conjugated polymers. Moreover, it is greatly affected by the degree of polymerization of the polymer main chain, and the spectra obtained with different degrees of polymerization are quite different, and the emission color purity is often difficult to control. Second, the non-conjugated polymers currently used in electroluminescent materials are usually flexible polymer polymers. Although they can greatly improve the triplet energy level, their transport performance is poor, the polymer preparation process is complex, and metal catalysts are required to participate in the reaction, and it is difficult to completely remove the metal catalysts later.

[0004] Whether it is inorganic materials or organic materials, foreign impurities have a great impact on the structural performance of the device. For polymer materials, not only the influence of foreign impurities exists, but the internal microstructural defects will also generate a large number of charge traps. The existence of traps is likely to cause local accumulation of space charge, which in turn induces partial discharge and electrical aging. Moreover, its heat resistance, polymer structure stability, and anti-aging properties are all difficult to compare with rigid polymers, and these indicators are particularly important for optoelectronic devices. Therefore, it is necessary to develop a new type of thermally activated delayed fluorescence (TADF) material with a simple preparation process and a wide range of applications. Summary of the Invention

[0005] The main object of the present invention is to provide a diamine monomer, its preparation method, polyimide, its preparation method and application. By adjusting and selecting a reasonable monomer molecular structure, different brightness and external quantum efficiency can be imparted to the polymer material. The target monomer can be homopolymerized with commercial diamines and dianhydrides, and the obtained polyimide material has good thermal properties and electroluminescent properties.

[0006] A diamine monomer, the general molecular structure formula is:

[0007]

[0008] In the formula, M is selected from one of an independent chemical bond single bond, -S-, -O, group, and R1 and R2 are each selected from one of H, methoxy, alkyl or dialkylamine.

[0009] A preparation method of a diamine monomer, comprising the following steps:

[0010] (1) React a monoamine monomer containing the structures of M, R1 and R2 with difluorobenzophenone in an alkaline environment to obtain a monosubstituted fluorinated benzophenone compound;

[0011] (2) The monosubstituted fluorinated benzophenone derivative prepared in step (1) is further reacted with 3,6-dibromocarbazole or 2,7-dibromocarbazole in a DMF dispersion containing an equivalent amount of base to obtain a disubstituted brominated benzophenone compound;

[0012] (3) The disubstituted brominated benzophenone compound prepared in step (2) and aminophenylboronic acid hydrochloride are subjected to a Suzuki reaction to catalyze the phenylboronic acid coupling reaction in a mixed solvent of an organic solvent and an alkaline aqueous solution, thereby preparing the diamine monomer.

[0013] A polyimide polymer having thermally activated delayed fluorescence properties, with a general molecular structure formula as follows:

[0014] In the formula, n and m represent the degree of polymerization, n / m = 1 / 99 - 100 / 0, X and W are tetravalent aromatic hydrocarbon groups or aliphatic hydrocarbon groups, Z is a divalent aromatic hydrocarbon group or aliphatic hydrocarbon group, and Y is the diamine monomer.

[0015]

[0016] A method for preparing a polyimide polymer, comprising the following steps:

[0017] In an atmosphere of nitrogen or argon, a diamine monomer containing a Y structure or a mixed diamine monomer containing both Y and Z structures and a dianhydride monomer containing an X structure or a mixed dianhydride monomer containing both X and W structures are dissolved in a polar aprotic solvent in a molar ratio of 1:(1 - 1.2), and continuously stirred and reacted at -10°C to 30°C for 24 - 48 h to obtain a polyamic acid viscous liquid. Through chemical imidization or thermal imidization methods, a polyimide polymer with the general formula (I) can be obtained.

[0018] Application of polyimide in organic optoelectronic diodes or optical information storage device materials.

[0019] Preferably, an organic light-emitting device of polyimide includes: a first electrode, a second electrode, and a light-emitting layer sandwiched between the first electrode and the second electrode, and the light-emitting layer includes a polyimide with a general molecular structure formula (I).

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] The polyimide including Y structural units according to the present invention exhibits high PL quantum efficiency. Compared with traditional polymer organic light-emitting devices, the organic light-emitting devices prepared from the polyimide according to the present invention have improved luminescence characteristics in terms of efficiency and brightness. The glass transition temperature of the polyimide can be as high as 300 °C to 350 °C. Generally speaking, when the glass transition temperature is lower than 120 °C, the heat resistance of the device is low. Compared with most other polymers, such as polyethylene polymers, when the glass transition temperature is higher than 200 °C, the monomers are prone to breakage during polymerization. The polymer obtained in the present invention has obvious advantages. Description of the Drawings

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the present invention will be described in detail below with reference to the drawings and specific embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts. Among them:

[0023] Figure 1 It is the infrared spectrum diagram of the polyimide prepared in Example 1 of the present invention;

[0024] Figure 2 It is the thermogravimetric curve diagram of the polyimide prepared in Example 1 of the present invention;

[0025] Figure 3 It is the variable-temperature lifetime spectrum diagram of the polyimide prepared in Example 1 of the present invention;

[0026] Figure 4 It is the interface diagram of the organic optoelectronic device structure in Example 1 of the present invention;

[0027] Figure 5 It is the ultraviolet-visible light projection performance diagram of the transparent film prepared in Example 2 of the present invention. Detailed Embodiments

[0028] In order to make the above-mentioned objects, features, and advantages of the present invention more obvious and understandable, the specific embodiments of the present invention will be described in detail below with reference to the drawings.

[0029] Example 1

[0030] 4-Fluoro-4'-phenothiazine benzophenone compound was obtained by nucleophilic substitution reaction of phenothiazine and 4,4'-difluorobenzophenone, and further reacted with 3,6-dibromocarbazole to obtain a disubstituted benzophenone compound. Finally, the target diamine monomer containing Y structure was obtained by suzuki reaction with 4-aminophenylboronic acid hydrochloride, as follows:

[0031] At room temperature, 5 g (25.1 mmol) of phenothiazine and 1.2 g (30.1 mmol, 60 wt.%

[0032] inkerosene) of sodium hydride were dissolved in anhydrous tetrahydrofuran. After reacting for 30 min under a nitrogen atmosphere, 5.47 g (25.1 mmol) of 4,4'-difluorobenzophenone was quickly added. After continuing the reaction for 24 h, 5 mL of dilute hydrochloric acid was added to terminate the reaction. The target product, 4-fluoro-4'-phenothiazine benzophenone compound, was separated by column chromatography. 1H NMR (400 MHz, DMSO-d6, δ): 7.89–7.75 (m, 4H), 7.46–7.33 (m, 4H), 7.33–7.22 (m, 4H), 7.22–7.14 (td, J 7.6, 1.2, 2H), 7.12–7.04 (dd, J = 8.0, 1.2, 2H).

[0033] 4 g (10.1 mmol) of 4-fluoro-4'-phenothiazine benzophenone compound and 3.27 g (10.1 mmol) of 3,6-dibromocarbazole were dissolved in 20 mL of anhydrous N,N'-dimethylformamide. 4.92 g of cesium carbonate was added, and the reaction was carried out at 150 °C under a nitrogen atmosphere for 24 h. It was settled with water, and the filter cake was collected by filtration and washed with ethanol and ethyl acetate to obtain the target product, the disubstituted benzophenone compound.

[0034] 1 1H NMR (400 MHz, DMSO-d6, δ): 8.67–8.56 (s, 2H), 8.06–7.97 (m, 2H), 7.95–7.85 (d, J = 8.3, 2H), 7.86–7.77 (m, 2H), 7.67–7.56 (dt, J = 8.8, 1.6, 2H), 7.53–7.38 (dd, J = 15.0, 8.1, 4H), 7.39–7.24 (dt, J = 12.2, 8.0, 4H), 7.24–7.10 (m, 4H).

[0035] 4 g (5.7 mmol) of the disubstituted benzophenone compound was dissolved in 100 mL of tetrahydrofuran. Under a nitrogen atmosphere, a catalytic equivalent of tetrakis(triphenylphosphine)palladium (5 wt.%) was added, and the mixture was stirred at room temperature for 10 min. 30 mL of 2 M potassium carbonate solution was added, and stirring was continued for 10 min. Finally, 2.46 g of 4-aminophenylboronic acid hydrochloride was added, and the reaction was carried out at 85 °C for 24 h. The target product, the target diamine monomer containing the Y structure, was separated by column chromatography.

[0036] 1H NMR (400 MHz, DMSO-d6, δ): 8.58–8.53 (d, J = 1.8, 2H), 8.09–8.02 (m, 2H), 7.96–7.90 (m, 2H), 7.91–7.85 (m, 2H), 7.69–7.64 (dd, J = 8.7, 1.9, 2H), 7.60–7.55 (d, J = 8.6, 2H), 7.55–7.49 (m, 4H), 7.47–7.42 (dd, J = 7.7, 1.5, 2H), 7.35–7.27 (m, 4H), 7.22–7.16 (td, J = 7.6, 1.3, 2H), 7.15–7.10 (dd, J = 8.1, 1.3, 2H), 6.73–6.67 (m, 4H), 5.23–5.12 (s, 4H).

[0037] At -10 °C under argon protection, 4.0 g (5.5 mmol) of the target diamine monomer containing the Y structure and 4.9 g (22.0 mmol) of 4,4'-diaminodiphenyl ether were dissolved in 48 mL of anhydrous N,N'-dimethylformamide. After complete dissolution, 5.6 g (28.0 mmol) of hydrogenated pyromellitic dianhydride was added, and the mixture was continuously stirred at low temperature for 30 h to obtain a homogeneous, transparent, and viscous polyimide acid solution. 18.78 mL of acetic anhydride and 7.51 mL of pyridine were added to the obtained viscous liquid, and after continued stirring for 30 h, the obtained polyimide solution was slowly poured into 1 L of ethanol to obtain a bulk precipitate, which was extracted with tetrahydrofuran in a Soxhlet apparatus for 24 h and then dried to obtain the final target polymer PI-1.

[0038] The 5% thermal weight loss temperature of this polymer is 520 °C, and the glass transition temperature is 328 °C. PI-1 has good solubility in strong polar organic solvents such as N,N'-dimethylformamide, N,N'-dimethylacetamide, and dimethyl sulfoxide. Its infrared spectrum is as Figure 1 shown, and the thermogravimetric curve is as Figure 2 shown.

[0039] Figure 3 Further characterization confirmed that PI-1 has obvious TADF characteristics and can be used for the preparation of optoelectronic devices. Therefore, the above-prepared PI-1 was formulated into a 10 mg / mL DMF solution, and then 10 mg of 9,9

[0040] '-(1,3-phenyl)di-9H-carbazole was dissolved thoroughly and stored at low temperature. The ITO glass substrates were washed successively with deionized water, isopropanol, and acetone, and then dried for use. The PEDOT:PSS aqueous solution was spin-coated on the ITO glass at a speed of 2000 r / s for 60 s, and then heated at 120 °C for 30 min to remove the residual solvent. After cooling to room temperature, the above PI-1 DMF solution was spin-coated thereon at a speed of 2000 r / s for 60 s, and then heated at 150 °C for 30 min. After cooling, it was transferred to an evaporation chamber, and DPEPO, TPBi, LiF, and Al were evaporated successively to fabricate the second type of device, and its specific structure was

[0041] ITO / PEDOT:PSS / PI:mCP / DPEPO / TPBi / LiF / Al, and its cross-sectional structure was as Figure 4 shown.

[0042] The turn-on voltage of the obtained device was 5.0 V, the maximum current brightness could reach 5000 cd / m2, and the maximum external quantum efficiency was as high as 7.3%.

[0043] The molecular structural formula of the electroluminescent polyimide (PI-1) in this example was as follows:

[0044]

[0045] Example 2

[0046] At 5 °C under argon protection, 4.0 g (17.8 mmol) of 4,4'-diaminodiphenyl ether was dissolved in 48 mL of anhydrous N,N'-dimethylformamide. After complete dissolution, 3.7 g (20.2 mmol) of hydrogenated pyromellitic dianhydride was added, and the mixture was continuously stirred at low temperature for 30 h to obtain a homogeneous, transparent, and viscous polyimide acid solution. 18.78 mL of acetic anhydride and 7.51 mL of pyridine were added to the obtained viscous solution, and stirring was continued for 30 h. Then, the obtained polyimide solution was slowly poured into 1 L of ethanol to obtain a fibrous precipitate, which was extracted by Soxhlet extraction with ethanol for 24 h and then dried to obtain the final target polymer PI-5.

[0047]

[0048] The 5% thermal weight loss temperature of this polymer was 452 °C, and the glass transition temperature was 340 °C. PI-5 had good solubility in strongly polar organic solvents such as dichloromethane, tetrahydrofuran, N,N'-dimethylformamide, N,N'-dimethylacetamide, and dimethyl sulfoxide.

[0049] The polymer obtained from the above structure was a white fiber, which was dissolved in DMF solvent and then coated on a glass plate again. After annealing at 250 °C, a colorless and transparent film could be obtained. The ultraviolet-visible light transmittance experiment of the film was asFigure 5 As shown, the light transmittance at 400 nm can reach 75%, which is beneficial to the transmission of electroluminescent photons. However, since it does not contain the PTCN luminescent center, the obtained polymer has no fluorescence property, further proving that the luminescent center is the PTCN unit, and the ODA unit is an illegal light center and only serves as a linking group.

Claims

1. A diamine monomer, characterized in that The general molecular structure is: In the formula, M is selected from an independent chemical bond, single bond, -S-, -O, One of the groups, R1 and R2 are each selected from one of H, methoxy, alkyl or dialkylamine.

2. A method for preparing a diamine monomer according to claim 1, characterized in that: The following steps are involved: (1) reacting a monoamine monomer containing the structures of M, R1 and R2 with difluorobenzophenone in an alkaline environment to obtain a monosubstituted fluorinated benzophenone compound; (2) the monosubstituted fluorinated benzophenone derivative prepared in step (1) is further reacted with 3,6-dibromocarbazole or 2,7-dibromocarbazole in a DMF dispersion containing an equivalent amount of a base to obtain a disubstituted brominated benzophenone compound; (3) The disubstituted brominated benzophenone compound prepared in step (2) and aminophenylborate hydrochloride are subjected to a Suzuki reaction to catalyze a phenylboronic acid coupling reaction in a mixed solvent of an organic solvent and an alkaline aqueous solution to prepare the diamine monomer.

3. A polyimide polymer having thermally delayed fluorescence properties containing the diamine monomer according to claim 1, characterized in that: The general molecular structure is: In the formula, n and m represent the degree of polymerization, n / m=1 / 99-100 / 0, X and W are tetravalent aromatic hydrocarbon groups or aliphatic hydrocarbon groups, Z is a divalent aromatic hydrocarbon group or aliphatic hydrocarbon group, and Y is the diamine monomer.

4. A method for preparing a polyimide polymer according to claim 3, characterized in that: The following steps are involved: In a nitrogen or argon atmosphere, a diamine monomer containing a Y structure or a mixed diamine monomer containing both Y and Z structures and a dianhydride containing an X structure or a mixed dianhydride monomer containing both X and W structures are dissolved in a polar aprotic solvent at a molar ratio of 1:(1-1.2), and the reaction is continuously stirred at -10°C to 30°C for 24-48h to obtain a polyamic acid viscous liquid, which is then subjected to a chemical imidization method or a thermal imidization method to obtain a polyimide polymer of the general formula (I).

5. Use of the polyimide according to claim 3 in organic photodiodes or optical information storage device materials.

6. An organic light-emitting device of polyimide according to claim 3, characterized in that: include: A first electrode, a second electrode and a light-emitting layer sandwiched between the first electrode and the second electrode, wherein the light-emitting layer comprises polyimide with a molecular structure of general formula (I).

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