A triazine polymer, its preparation method and application

Abstract

The present invention belongs to the technical field of thermally activated delayed fluorescence materials, and discloses a triazine-based polymer, a preparation method thereof, and an application as a thermally activated delayed fluorescence material. The triazine-based polymer provided by the present invention is a triazine series polymer with both thermal stability, long delayed lifetime, and high-efficiency fluorescence emission characteristics. Moreover, the preparation method of the triazine-based polymer provided by the present invention has a simple process and low cost; the triazine-based polymer provided by the present invention has good application prospects as a thermally activated delayed fluorescence emitting material in organic light-emitting diodes.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermally activated delayed fluorescence materials, and particularly relates to a triazine-based polymer, a preparation method thereof, and an application as a thermally activated delayed fluorescence material. Background Art

[0002] Organic light-emitting diodes (OLEDs) have been widely used in the field of electronic device displays due to their advantages such as simple structure, low turn-on voltage, simple structure, low driving voltage, flexibility, bendability, greenness, low cost, and high luminous efficiency. The selection of luminescent materials has a crucial impact on the luminescent performance of OLEDs. As people's requirements for device displays are getting higher and higher, the selection of luminescent materials that can be better applied to OLEDs has also been a research topic that people have been studying. Triazine-structured compounds are not only classic organic luminescent materials but also one of the luminescent materials with the broadest application prospects in OLEDs, namely thermally activated delayed fluorescence (TADF) materials. Adjusting the structure of triazine compounds, introducing different substituents, or synthesizing different types of fused-ring compounds to improve the luminous efficiency of devices has been a research hotspot in the field of flat panel displays in recent years.

[0003] By adjusting the substituents of the triazine compound structure, the luminescence efficiency of the material can be improved, and these derivatives have good luminescence efficiency and device performance. Lee et al. (Dong Ryun Lee, Mounggon Kim, Sang Kyu Jeon, Seok-Ho Hwang, Chil Won Lee, and Jun Yeob Lee. Design Strategy for 25% External Quantum Efficiency in Green and Blue Thermally Activated Delayed Fluorescent Devices, Adv Mater, 2015, 5861-5867) designed and synthesized three compounds. By introducing different aromatic groups onto the triazine structure and increasing the number of donor units, a molecular design for achieving high EQE in TADF devices was carried out, aiming for a high quantum fluorescence yield close to 100% and a high EQE exceeding 25% in green and blue OLEDs. However, due to the influence of the rigid planar structure of the molecule, the luminescence efficiency was low and the emission spectrum was impure. Sung et al. (Sung Moo Kim, Sung Yong Byeon, Seok-Ho Hwang and Jun Yeob Lee, Rational design of host materials for phosphorescent organic light-emitting diodes by modifying the 1-position of carbazole, Chem Commun, 2015, 10672-10677) synthesized four derivatives based on the carbazole and triazine series, and introduced a carbazole group with a methyl group, which has a torsional space, as a donor unit in the side chain. The coupling of this multi-carbazole modified structure enables the host material to achieve a quantum efficiency higher than 20% in the device and can provide an OLED device with a power of up to 104 lm / W. However, the result of not being able to effectively balance the current density is not satisfactory.Cui et al. (Lin-Song Cui, Alexander J. Gillett, Xian-Kai Chen, Ze-Sen Lin, Richard H. Friend, Shou-Feng Zhang, Hao Ye, Emrys W. Evans. Fast spin-flip enables efficient and stable organic electroluminescence from charge-transfer states, Nature Photonics, 2020, 636-642) designed and synthesized a number of high-efficiency OLED luminescent materials with carbazole donors and triazine structures. Their devices showed a maximum EQE of 29.3%, and the EQE decay at high brightness was only 2.3%, but there were still problems such as slow reverse intersystem crossing, device stability, and efficiency decay. Niu et al. (Rui Niu, Jiuyan Li, Di Liu, Ruizhi Dong, Wenkui Wei, Houru Tian, Chunlong Shi, A versatile carbazole donor design strategy for blue emission switching from normal fluorescence to thermally activated delayed fluorescence, DYES AND PIGMENTS, 2021, 1873-3743) designed a donor-acceptor type blue OLED with a triazine core and carbazole, and achieved spatial separation of molecular orbitals through a phenyl bridge structure and a twisted spatial structure. And a TADF luminescent material with or without methyl groups was designed, and the external quantum efficiency in the pure blue light-emitting device reached 13.07%. However, the effective radiation and delayed lifetime shown due to the limitations of its structural characteristics and processes are not very ideal, and there is still a large room for improvement.Zhou et al. (Tao Zhou, Kaizhi Zhang, Qingpeng Cao, Hui Xu, Xinxin Ban, Peng Zhu, Qile Li, Linxing Shi, Fengjie Ge and Wei Jiang, Benzonitrile-based AIE polymer host with a simple synthesis process for high-efficiency solution-processable green and blue TADF organic light emitting diodes, Journal of Materials Chemistry C, 2022, 2109-2120) designed four novel benzonitrile-based polymer OLED host materials. Their maximum external quantum efficiencies (EQEs) for green and blue TADF are as high as 20.9% and 13.4% respectively. The significant improvement in device efficiency indicates that TADF homopolymers with AIE properties can effectively suppress exciton self-quenching, suggesting good film-forming properties of this polymer. However, the synthesis process of this series of molecules is relatively long and has strict molecular polymerization ratios, which is not conducive to large-scale industrial production and practical application value. Summary of the Invention

[0004] Object of the Invention: Aiming at the above problems, the present invention provides a series of triazine polymers with thermal stability, long delayed fluorescence lifetime, and high-efficiency fluorescence emission characteristics. Another object of the present invention is to provide a method for synthesizing the monomer and polymer with simple process and low cost. Another object of the present invention is to provide the application of this polymer as a luminescent material in OLEDs.

[0005] Technical Solution: A triazine polymer according to the present invention has the following general structural formula:

[0006]

[0007] wherein, the degree of polymerization n ranges from 2 to 100,000;

[0008] wherein, the substituent R1 is independently selected from phenyl, carbazolyl, dimethylcarbazolyl, di-tert-butylcarbazolyl, phenoxazinyl, diphenylamino, phenothiazinyl, acridinyl;

[0009] Similarly, the substituent R2 is independently selected from phenyl, carbazolyl, dimethylcarbazolyl, di-tert-butylcarbazolyl, phenoxazinyl, diphenylamino, phenothiazinyl, acridinyl;

[0010] It should be noted that the substituents R1 and R2 may be the same or different.

[0011] The compounds represented by R1-H above: benzene, carbazole, dimethylcarbazole, ditert-butylcarbazole, phenoxazine, diphenylamine, phenothiazine, and acridine have chemical structural formulas as shown in the following formulas in sequence:

[0012]

[0013] Among them, the substituent R3 independently selects from hydrogen, methyl, or an alkyl chain with 1-10 carbon atoms; similarly, the substituent R4 independently selects from hydrogen, methyl, or an alkyl chain with 1-10 carbon atoms. It should be noted that R3 and R4 can be the same or different.

[0014] Preferably, the triazine polymer structure is selected from any one of the following compounds:

[0015]

[0016]

[0017] The preparation method of the triazine polymer of the present invention includes the following steps:

[0018] Prepare intermediate product c: Add compound a, 4-hydroxycarbazole, and potassium carbonate into a reaction vessel containing N,N-dimethylformamide (DMF) solvent, and then inject another raw material compound b, 4-chloromethylstyrene. Stir at 80 °C under reflux for 6 hours, while avoiding becoming double-substituted due to too long time. After stopping the reaction, extract with dichloromethane (DCM) by liquid separation, spin-dry the organic solvent with a rotary evaporator, and separate and purify through a silica gel chromatography column to obtain a white solid product, that is, compound c.

[0019]

[0020] The preparation process of intermediate triazine compound f: Dissolve compound d and compound d' in dried THF, and cool to 0 °C; under a nitrogen atmosphere, dropwise add n-butyllithium (n-BuLi) into it, and then stir for 2 hours; continue under a nitrogen atmosphere, slowly add a solution of compound e, cyanuric chloride, dissolved in tetrahydrofuran (THF), and stir and heat under reflux again. After the reaction ends, slowly add water dropwise to quench, and extract with dichloromethane by stirring. Take the organic phase and evaporate the solvent, and recrystallize with ethyl acetate to obtain a light yellow solid, and dry to obtain intermediate triazine compound f; when the substituent R1 = R2, compound d = compound d', and the compound f with the same substituent is directly obtained by mixing the molar mass ratio of compound d, compound d', and compound e as 1:1:1 in one step. When the substituent R1 is different from R2, compound d and compound e first react according to a molar mass ratio of 1:1, and then take compound d' equal to compound d to react to prepare compound f with different substituents.

[0021]

[0022] Preparation of triazine intermediate h: Dissolve triazine compound f, p-fluorophenylboronic acid compound g and the catalyst tetrakis(triphenylphosphine)palladium in tetrahydrofuran, then add an aqueous potassium carbonate solution and heat to 70 °C with stirring. After the reaction is completed, cool to room temperature. Add water and dichloromethane to extract the organic layer. Remove the solvent from the organic layer, and then dry to obtain the white solid triazine intermediate h.

[0023]

[0024] Preparation of compound monomer i: React intermediate compound h, compound c, potassium tert-butoxide and N,N-dimethylformamide (DMF) in a reaction vessel by heating and stirring under reflux. After the reaction is completed, add water and filter to obtain a solid, and separate and purify it by silica gel column chromatography to obtain compound monomer i.

[0025]

[0026] Preparation of the final triazine polymer: Add polymer monomer i and initiator azobisisobutyronitrile AIBN to a device containing chlorobenzene solution. Remove the oxygen in the solution by freezing with low-temperature techniques such as liquid nitrogen, thaw it under a nitrogen atmosphere and repeat several times, then heat to 80 °C and stir for 48 hours. After completion, add methanol solution and let it stand for sedimentation to obtain the final product, namely the triazine polymer.

[0027]

[0028] The present invention also provides the application of the above triazine polymer material as a thermally activated delayed fluorescence emitting material in an organic light emitting diode.

[0029] As a preferred embodiment, the triazine polymer is doped into a host material and used as a light-emitting layer material to be coated into a film as the light-emitting layer in an organic light emitting diode. The host material is 2,6-bis[3-(9H-carbazol-9-yl)phenyl]pyridine, namely 26DCzPPy or bis[2-((oxo)diphenylphosphino)phenyl]ether, namely DPEPO.

[0030] As a preferred embodiment, the doping concentration range of the triazine polymer is 10-100 wt%;

[0031] As a preferred embodiment, the organic light emitting diode is fabricated by spin-coating PEDOT:PSS as an injection layer on the surface of a conductive ITO substrate, then spin-coating the light-emitting layer material, and then depositing an electron transport layer and a Ca / Ag electrode.

[0032] Principle of invention: First, compound intermediates are prepared by C-N coupling reaction under the condition of inorganic salt potassium carbonate, C-N coupling under the condition of organic strong base n-butyllithium, and Suzuki coupling reaction respectively. Then, the intermediate is prepared by C-N coupling reaction under the condition of organic salt potassium tert-butoxide. Finally, the organic monomers are polymerized under the condition of a radical initiator to complete. The designed molecular structure contains strong electron-donating groups such as benzene, carbazole, dimethylcarbazole, di-tert-butylcarbazole, phenoxazine, diphenylamine, phenothiazine, and acridine, and a strong electron-withdrawing structure triazine. A benzene or a benzene connection method with an alkyl torsion space form is used between the two structural units described above, ensuring a relatively low molecular orbital energy level difference. These methods and measures are used to design this type of molecule as a thermally activated delayed fluorescence molecule, ensuring a relatively high quantum yield and the property of delayed fluorescence. In addition, to solve the problem of poor film-forming property of this type of molecule during device fabrication, a styrene cross-linking group is introduced to enable this type of molecule to form polymer macromolecules, so as to improve the film-forming property and device efficiency in the fabrication of devices by solution method.

[0033] Advantageous effects: In view of the prior art, for the device preparation of organic light-emitting diode (OLED), if the small molecule evaporation coating method of thermally activated delayed fluorescence (TADF) is adopted, it is not conducive to the large-area preparation of flexible devices, and the film-forming property of small molecule materials is poor; while the existing TADF polymers have good film-forming properties, but the preparation process of the existing TADF polymer materials is complex and the controllability is relatively low. To solve the problem of poor film-forming property of small molecule materials, the triazine-based styrene polymer provided by the present invention is used as the light-emitting layer material of the device. Under better preparation conditions, it has both the fluorescence quantum efficiency of 90% of the thermally activated delayed fluorescence molecular material and the photophysical data of a delayed fluorescence lifetime of up to 9.4 μs, and has a current efficiency of 6 cd / A and a luminance of 1000 cd / m 2 under the condition of good film-forming property of the polymer, indicating that this polymer is beneficial to the application value and commercial industrialization of OLED. Description of the drawings

[0034] Figure 1 is the relative proportion diagram of the weight-average number distribution of polymers A and B;

[0035] Figure 2 is the thermogravimetric analysis (TGA) diagram of the thermal stability of polymers A and B;

[0036] Figure 3 is the differential scanning calorimetry (DSC) diagram of the thermal stability of polymers A and B;

[0037] Figure 4 is the current-voltage curve of the electrochemical oxidation and reduction of polymers A and B;

[0038] Figure 5It is the ultraviolet absorption and infrared emission spectrograms of polymers A and B in dichloromethane solution;

[0039] Figure 6a It is the photoluminescence spectrograms of polymer A in four different solutions: toluene, dichloromethane, tetrahydrofuran, and N,N-dimethylformamide;

[0040] Figure 6b It is the photoluminescence spectrograms of polymer B in four different solutions: toluene, dichloromethane, tetrahydrofuran, and N,N-dimethylformamide;

[0041] Figure 7 It is the fluorescence and phosphorescence spectrograms of polymers A and B at low temperature;

[0042] Figure 8 and Figure 9 It is the absorption and emission spectrograms of the thin films made by doping polymers A and B in DPEPO;

[0043] Figure 10 It is the delayed fluorescence lifetime diagrams of the thin films made by doping polymers A and B in DPEPO;

[0044] Figure 11 It is the luminescence intensity-voltage curve diagram of polymer A doped in the host material 26DCzPPy.

[0045] Figure 12 It is the current density-voltage curve diagram of polymer A doped in the host material 26DCzPPy.

[0046] Figure 13 It is the luminance-voltage curve diagram of polymer A doped in the host material 26DCzPPy.

[0047] Figure 14 It is the current efficiency-luminance curve diagram of polymer A doped in the host material 26DCzPPy. Detailed implementation manners

[0048] The present invention will be further described below with reference to the accompanying drawings and embodiments. The 1 1H NMR, 13 13C NMR nuclear magnetic data involved in the compound characterization in the following embodiments were tested using a 400 MHz superconducting nuclear magnetic spectrometer produced by Bruker Corporation, with deuterated chloroform as the solvent. The mass spectrometry was measured on an Autoflex Speed MALDI-TOF produced by Bruker Daltonics.

[0049] Example 1: Synthesis of triazine-based polymer A

[0050] Preparation of intermediate c, i.e., carbazole-styrene cross-linked compound: Under a nitrogen atmosphere, 4-hydroxycarbazole (6 g, 32.7 mmol), 4-chloromethylstyrene (6 g, 40 mmol), and potassium carbonate (13.87 g, 100.5 mmol) were added to a 250 mL three-necked flask, and then N,N-dimethylformamide (80 mL) was injected as a solvent. The temperature was raised to 80 °C and stirred for six hours. After the reaction was stopped, liquid-liquid extraction was carried out with 100 mL of water and 100 mL × 3 of dichloromethane. The organic solvent was evaporated to dryness using a rotary evaporator and separated and purified by a silica gel chromatography column (eluent: PE / DCM = 2 / 1, V / V). After rotary evaporation, 6.4 g of a white solid was obtained, and the yield was 53.5%.

[0051] 1H NMR spectrum: 1 H NMR(400MHz,Chloroform-d)δ8.35(d,J=7.7Hz,1H),8.04(s,1H),7.57(d,J=8.0Hz,2H),7.51(d,J=8.0Hz,2H),7.41(d,J=4.0Hz,2H),7.35(t,J=8.0Hz,1H),7.29~7.22(m,1H),7.06(d,J=8.0Hz,1H),6.87~6.77(m,1H),6.77~6.72(m,1H),5.83(d,J=17.6Hz,1H),5.35(s,2H),5.31(d,J=10.8Hz,1H).

[0052]

[0053] Preparation of triazine bis-carbazole substituted compound f-1, i.e.,

[0054] 9,9'-(6-chloro-1,3,5-triazine-2,4-diyl)bis(9H-carbazole): Dissolve carbazole (3.64 g, 22 mmol) in 44 mL of dried tetrahydrofuran solution and cool it to 0 °C. Under a nitrogen atmosphere, add n-butyllithium (8.8 mL, 22 mmol) with a content of 2.5 mmol / mL dropwise thereto, and then stir for 2 hours. Continue under a nitrogen atmosphere, and dropwise add a solution of cyanuric chloride (1.84 g, 10 mmol) dissolved in 20 mL of the same dried and cooled-to-0 °C tetrahydrofuran. After stirring for 2 hours, heat the reaction to 80 °C and reflux for 6 h. After the reaction is completed, slowly add water dropwise to quench it, and add 100 mL of dichloromethane, stir and extract. Take the organic phase, evaporate the solvent, add a small amount of ethyl acetate to dissolve, filter to obtain a solid, and recrystallize with ethyl acetate to obtain a light yellow solid. After drying, 2.64 g of the target product is obtained with a yield of 55%.

[0055] 1H NMR spectrum: 1 H NMR (400 MHz, Chloroform-d) δ 8.96–8.87 (m, 4H), 8.10–8.02 (m, 4H), 7.48 (m, J = 27.5, 7.3, 1.2 Hz, 8H).

[0056]

[0057] Preparation of triazine intermediate compound h-1, namely

[0058] 9,9'-(6-(4-fluoro-3-methylphenyl)-1,3,5-triazine-2,4-diyl)bis(9H-carbazole), 9,9'-(6-(4-fluoro-3-methyl)-1,3,5-triazine-2,4-diyl)bis(9H-carbazole): Add 9,9'-(6-chloro-1,3,5-triazine-2,4-diyl)bis(9H-carbazole) (1.35 g, 3 mmol) and 4-fluorophenylboronic acid (0.448 g, 3.2 mmol) into a 100 mL three-necked flask. Evacuate and refill with nitrogen three times using a double-tube system to create a nitrogen atmosphere inside the flask. Then, inject 15 mL of tetrahydrofuran and 8 mL of 2 mol / L aqueous potassium carbonate solution through a syringe. After stirring at 30 °C for 30 min, add tetrakis(triphenylphosphine)palladium (0.1 g, 0.08 mmol). Heat the reaction mixture to 80 °C and react for 6 h before ending the reaction. After cooling, remove the organic solvent, perform liquid-liquid extraction with water and dichloromethane, and then separate and purify by silica gel column chromatography (eluent: PE / DCM = 1 / 1, V / V) to obtain 1.25 g of a light yellow solid with a yield of 75%.

[0059] 1H NMR spectrum: 1 H NMR (400 MHz, Chloroform-d) δ 8.94 (d, J = 8.3 Hz, 4H), 8.50 (t, J = 6.5 Hz, 2H), 8.03 (d, J = 7.5 Hz, 4H), 7.46 (t, J = 7.7 Hz, 4H), 7.37 (t, J = 7.2 Hz, 4H), 7.17 (t, J = 2.5 Hz, 1H), 2.45–2.35 (s, 3H).

[0060] Mass spectrum: MS (MADLI-TOF): m / z (M+H) + calcd. For C 34 H 22 FN 5 , 519; found, 519.000.

[0061]

[0062] Preparation of monomeric triazine compound i-1, i.e., 9,9'-(6-(3-methyl-4-(4-((4-methoxy)phenyl)-9H-carbazol-9-yl)styryl)-1,3,5-triazine-2,4-diyl)bis(carbazole): Under a nitrogen atmosphere, triazine intermediate compound h-1 (1.04 g, 2 mmol), styrene cross-linking group compound c (0.66 g, 2.2 mmol), and potassium tert-butoxide (0.24 g, 2.2 mmol) were dissolved in 10 mL of DMF. After stirring well for 2 hours, the mixture was heated to 140 °C and reacted for 2 h before ending. After the reaction cooled down, 100 mL of water at 0 °C was added. The solid was filtered and dried, and finally, 0.08 g of monomeric triazine compound d as a light yellow solid was obtained through purification by a silica gel chromatography column (eluent: PE / DCM = 2 / 1, V / V), with a yield of 5%.

[0063] 1H NMR spectrum: 1 H NMR (400 MHz, Chloroform-d) δ 9.11 (d, J = 5.8 Hz, 1H), 9.09 (d, J = 5.8 Hz, 2H), 8.84 (s, 1H), 8.76 (d, J = 8.2 Hz, 1H), 8.44 (dd, J = 7.6, 2.9 Hz, 1H), 8.22 (d, J = 7.8 Hz, 1H), 8.13 (d, J = 7.6 Hz, 3H), 7.69 (d, J = 8.2 Hz, 1H), 7.62–7.50 (m, 8H), 7.44 (m, J = 15.5, 6.4 Hz, 7H), 7.37–7.30 (m, 2H), 7.20 (d, J = 8.1 Hz, 1H), 6.83 (m, J = 10.4, 8.0 Hz, 1H), 6.80–6.72 (m, 1H), 5.83 (m, J = 17.6, 2.9 Hz, 1H), 5.40 (d, J = 5.6 Hz, 2H), 5.31 (d, J = 10.9 Hz, 1H), 2.22 (s, 3H).

[0064] 13C NMR spectrum: 1313C NMR (101 MHz, Chloroform-d) δ 172.36, 164.82, 164.75, 155.40, 154.77, 142.37, 140.90, 140.54, 140.29, 140.20, 138.91, 137.95, 137.88, 137.45, 136.91, 136.55, 136.48, 136.37, 132.49, 132.44, 129.95, 129.87, 128.19, 128.15, 127.82, 127.78, 127.54, 127.05, 126.92, 126.63, 126.58, 126.55, 126.15, 126.10, 125.90, 125.30, 123.63, 123.49, 123.38, 123.31, 122.71, 120.51, 120.30, 119.99, 119.80, 119.77, 117.69, 117.59, 116.76, 114.25, 114.14, 112.75, 110.31, 109.95, 109.34, 105.87, 103.12, 102.18, 77.26, 76.89, 70.15, 70.02, 31.97, 29.75, 29.71, 29.41, 22.74, 18.31, 14.17.

[0065] Mass spectrometry: MS (MALDI-TOF): m / z (M + H) + calcd. C 55 H 38 N 6 O, 789; found, 789.986.

[0066]

[0067] Preparation of triazine polymer A, i.e., triazine polymer 5 described in the invention content: Triazine compound monomer i-1 (112 mg, 0.14 mmol) and initiator AIBN (1 mg, 0.006 mmol) were added to a device containing chlorobenzene solution. Oxygen was removed by freezing with liquid nitrogen or other low-temperature techniques and thawed repeatedly. Then, it was heated to 80 °C and stirred for 48 hours. After completion, a methanol solution was added and allowed to stand for sedimentation to obtain 88 mg of yellow solid, i.e., product triazine polymer A, with a yield of 78.5%, Mw = 18608, Mn = 12850, and PDI (Mw / Mn) = 1.40.

[0068]

[0069] Synthesis of triazine polymer B in Example 2

[0070] The preparation process of Polymer B in Example 2 includes the following operations:

[0071] Preparation of triazine intermediate compound h-2: Add 2-chloro-4,6-diphenyl-1,3,5-triazine (1.06 g, 4 mmol) and 4-fluorophenylboronic acid (0.58 g, 4.2 mmol) into a 100 mL three-necked flask. Evacuate and refill with nitrogen three times through a double-row tube to create a nitrogen atmosphere inside the flask. Then, inject 10 mL of K2CO3 solution (2 M) and 20 mL of tetrahydrofuran (THF) through a syringe. Stir at room temperature (25 °C) for 30 min, add 0.12 g of tetrakis(triphenylphosphine)palladium, and then heat to 75 °C and react for 6 h. After the reaction is completed, cool to room temperature. First, rotary evaporate the organic solvent, then add water and dichloromethane to extract the organic layer. Remove the solvent from the organic layer and dry it. Put the dried solid into a sublimation device and sublime it under a reduced pressure of 0.1 times the standard atmospheric pressure at a temperature of 280 °C to obtain 1.2 g of a white solid. The yield is 92%.

[0072] 1H NMR spectrum: 1 H NMR(400MHz,Chloroform-d)δ8.73(d,J=6.2Hz,2H),8.69(m,J=8.1Hz,4H),7.56–7.47(m,6H),7.18(t,J=8.7Hz,2H).

[0073]

[0074] Preparation of monomer triazine compound i-2: Add compound h-2 (1.0 g, 3.05 mmol) and compound c (0.92 g, 3.07 mmol) into a dried 100 mL three-necked flask. Evacuate and refill with nitrogen three times through a double-row tube, and then quickly add 0.34 g (3.07 mmol) of potassium tert-butoxide under a nitrogen atmosphere. Inject 10 mL of DMSO and stir for half an hour, then raise the temperature to 140 °C and continue the reaction for about 6 hours. After the reaction is completed, cool to room temperature, extract three times with water and dichloromethane, and then separate and purify by silica gel column chromatography (eluent: PE / DCM = 2 / 1, V / V) to obtain 1.3 g of a light yellow solid. The yield is 70%.

[0075] 1H NMR spectrum: 11H NMR (400 MHz, Chloroform-d) δ 9.05–8.98 (m, 2H), 8.87–8.80 (m, 4H), 7.82 (d, J = 8.1 Hz, 2H), 7.63 (m, J = 9.6, 6.9 Hz, 6H), 7.60–7.57 (m, 2H), 7.54–7.49 (m, 3H), 7.45–7.40 (m, 1H), 7.36 (t, J = 8.0 Hz, 1H), 7.31 (t, J = 7.4 Hz, 1H), 6.84 (d, J = 7.9 Hz, 1H), 6.78 (m, J = 17.6, 10.9 Hz, 1H), 5.81 (d, J = 17.6 Hz, 1H), 5.39 (s, 2H), 5.32–5.28 (m, 1H).

[0076] 13C NMR: 13 13C NMR (101 MHz, Chloroform-d) δ 171.62, 155.15, 141.80, 141.54, 137.14, 136.66, 136.33, 135.97, 134.82, 132.48, 130.41, 128.84, 128.82, 128.53, 127.53, 126.69, 126.34, 125.11, 123.25, 122.95, 120.50, 113.93, 109.14, 102.92, 102.46, 69.83.

[0077] Mass spectrum: MS (MADLI-TOF): m / z (M + H) + calcd. C 42 H 30 N 4 O, 606; found, 606.478.

[0078]

[0079] To prepare triazine polymer B, namely triazine polymer 1 described in the invention content: Monomer i-2 (248 mg, 0.41 mmol), initiator AIBN (2 mg, 0.012 mmol). After the polymerization process, 183 mg of yellow solid, namely the final triazine polymer B, was obtained with a yield of 73.7%, Mw = 18116, Mn = 12159, PDI (Mw / Mn) = 1.48.

[0080]

[0081] Figure 1The polymer data obtained by testing polymers A and B using a gas chromatography column method are given, which represents the relative proportion of the polymer weight (MW) in each test unit volume, indicating that the polymer method is feasible and can obtain better polymer macromolecular effects.

[0082] Test Example 1: Thermal stability test of materials A and B

[0083] Figure 2 , Figure 3 The thermogravimetric analysis and scanning calorimetry analysis of compounds A and B are shown. The 5% decomposition temperatures of compounds A and B are 442°C and 427°C, and the glass transition temperatures are 209°C and 207°C, respectively. This indicates that the compounds have good thermal stability, which is beneficial to the stability of the device and the life of the device.

[0084] Test Example 2: Electrochemical Performance of Compounds A and B

[0085] Figure 4 The electrochemical properties of compounds A and B are given; dichloromethane is used as the solvent in the oxidation process, tetrahydrofuran is used as the solvent in the reduction process, all solvents are treated with dehydration and deoxygenation, tetrabutylammonium hexafluorophosphate is used as the electrolyte, glassy carbon electrode / platinum wire counter electrode / Ag / AgCl reference electrode is used, and the current-voltage curve is tested on an electrochemical workstation. It can be seen from the figure that the reduction process is obviously reversible. By calculating the electrochemical onset peak position, the HOMO energy level and LUMO energy level of A and B are -1.85eV and -5.21eV, 1.94eV and -5.24eV, respectively.

[0086] Test Example 3: Photophysical properties of materials

[0087] Figure 5 The UV absorption and emission spectra of compound A in dichloromethane solution are given, and its UV absorption spectrum is tested in a fluorescence cuvette. As can be seen from the figure, the UV absorption peaks of compound A are at 290nm and 340nm, and the emission peak is 490nm, and the UV absorption peaks of compound B are at 290nm and 320nm, and the emission peak is 490nm. These data show that it is suitable for TADF luminescent materials.

[0088] Figure 6a and Figure 6b The photoluminescence spectra of compound A and compound B in four different solutions of toluene, N,N-dimethylformamide, tetrahydrofuran and dichloromethane are given respectively. These data show that the emission spectrum is blue-shifted in toluene solution and also has an obvious red-shift in N,N-dimethylformamide solvent.

[0089] Figure 7 The fluorescence and phosphorescence emission spectra of compounds A and B in dimethyltetrahydrofuran solutions at low temperature are given.-5 In a mol / L solution, the infrared spectrophotometer was tested using a liquid nitrogen cryogenic device. It can be seen that the main peaks of phosphorescence and fluorescence emission of Polymer A at low temperature of 77 K are at 420 nm and 410 nm, respectively, and the triplet energy level and singlet energy level are 2.95 eV and 3.02 eV, respectively. For Polymer B at low temperature of 77 K, the main peaks of phosphorescence and fluorescence emission are at 465 nm and 409 nm, respectively, and the triplet energy level and singlet energy level are 2.67 eV and 3.03 eV, respectively.

[0090] Test Example 4: Absorption and Emission Spectra of Films Prepared by Doping Materials in DPEPO

[0091] Figure 8 The infrared fluorescence emission spectra of the film-like samples prepared by doping Compounds A and B in DPEPO are given. Compounds A and B were doped into DPEPO at a mass concentration of 6% wt to form a film, and then their fluorescence spectra were measured. From Figure 7 it can be seen that the main peaks of fluorescence emission of A and B are near 450 nm, showing good fluorescence. Compared with the fluorescence photoluminescence spectrum of the solution, all fluorescence wavelengths have undergone a blue shift, which is due to the influence of DPEPO.

[0092] Figure 9 The ultraviolet absorption spectra of the film-like samples prepared by doping Compounds A and B in DPEPO are given. Compounds A and B were doped into DPEPO at a mass concentration of 6% wt to form a film, and then their ultraviolet absorption spectra were measured. From Figure 8 it can be seen that there are absorption peaks at 290 nm and 340 nm, respectively.

[0093] Test Example 5: Delayed Fluorescence Lifetime and Fluorescence Quantum Efficiency of Films Prepared by Doping Materials in DPEPO

[0094] Figure 10 The delayed fluorescence lifetime diagrams of Compounds A and B are given. They were also doped into the films prepared by DPEPO at a ratio of 6% wt using a transient spectrometer, and relevant lifetime tests were carried out by exciting with a xenon lamp at a wavelength of 340 nm. As shown in the figure, the instrument gave relevant fitting data, and the delayed fluorescence lifetimes τ 1 / τ 2 = 9.4 (75.96%) / 53.8 (24.04%) μs, 2.5 (17.34%) / 9.7 (82.66%) μs. These data indicate that the polymers made of this D-A type monomer have excellent delayed fluorescence lifetimes and are expected to be used as high-efficiency TADF devices. Also on this test instrument, in the form of an integrating sphere, the fluorescence quantum efficiencies were measured respectively, and the fluorescence quantum efficiencies of A and B were 38% and 90%, respectively.

[0095] Example 3 Preparation of OLED Device Using Polymer Material A

[0096] In this embodiment, the compound 26DCzPPy is used as the host material, and the guest polymer material A is doped into the host material at different doping ratios to prepare a series of devices.

[0097] The device structure is ITO / PEDOT:PSS / (26DCzPPy:Xwt%) / TPBI / Ca:Ag, that is, the light-emitting layer is doped with Xwt% and the host material, where X = 10, 20, 30, 50, 100. TPBI is used as the electron injection layer and Ca:Ag is used as the cathode.

[0098] In the specific implementation process, the solution process is used to prepare the OLED device, and PEDOT:PSS is spin-coated on the surface of the conductive ITO substrate as an injection layer, followed by spin-coating the light-emitting layer. The light-emitting layer material uses polymer A doped with compound 26DCzPPy, and then deposits the electron transport layer and Ca / Ag electrodes to complete the preparation of a multilayer device with a structure of ITO / PEDOT:PSS (30nm) / (26DCzPPy:Xwt%) (30nm) / TPBI (35nm) / Ca:Ag (15:100nm). The specific operation steps are as follows:

[0099] Etch the ITO glass so that the width of each ITO glass light strip is 2.3mm, place the ITO glass on a special polytetrafluoroethylene-based sheet frame, soak it in dichloromethane and ultrasonicate it to remove organic stains on the substrate, then use ultrapure water to ultrasonicate three times, each time for 15 minutes, then use acetone and ethanol to ultrasonicate for 20 minutes each, and finally dry it at 120℃ for 20 minutes; irradiate the dried substrate with ultraviolet light for 20-30 minutes to increase the affinity of the surface to PEDOT:PSS and enhance the hole injection ability. Spin coat PEDOT:PSS at 3000r / s to obtain a film thickness of about 30nm, and then anneal at 120℃ for 20 minutes; configure the guest polymer material A and 26DCzPPy at a ratio of Xwt% to a chloroform solution of 4mg / mL (X=10, 20, 30, 50, 100), stir for more than 10 hours, so that the material can be fully dissolved. In a glove box with a nitrogen atmosphere, the solution was spin-coated on the upper layer at a speed of 3000 r / min for 30 s and annealed at 120 °C for 20 min to obtain a luminescent layer film with a thickness of 30 nm. -5 Pa, per second 35nm of TPBi was evaporated as the electron transport layer, and then a 2mm wide electrode was scraped out. Next, 15nm of calcium was vacuum evaporated as the electron injection layer and 100nm of silver was vacuum evaporated as the cathode to complete the device preparation.

[0100] Figure 11It shows the electroluminescence spectrum diagram of the device when polymer A is doped in the host material 26DCzPPy at a content of 10 wt% under the starting voltage. In the figure, the abscissa is the wavelength range and the ordinate is the electroluminescence intensity. It can be seen from the figure that with the change of the working voltage, the wavelength of the maximum electroluminescence emission peak remains at 450 nm, which is a typical blue light material.

[0101] Figure 12 It shows the current density-voltage curve of polymer A doped into the host material 26DCzPPy at different concentrations. In the figure, the abscissa is the voltage and the ordinate is the current density. When the working voltage is 9 V and the doping concentration is 10% wt, the current density reaches 1200 mA / cm 2 , and its color coordinates are CIE(0.17, 0.12).

[0102] Figure 13 It shows the luminance-voltage curve of polymer A doped into the host material 26DCzPPy at different concentrations. In the figure, the abscissa is the voltage and the ordinate is the device luminance. When the working voltage is 8 V, the luminance of the devices doped at different ratios reaches 5000 cd / m 2 , and the color coordinates of the device fabricated with a 20% wt concentration doping are CIE(0.16, 0.11).

[0103] Figure 14 It shows the efficiency-luminance curve of polymer A doped into the host material 26DCzPPy at different concentrations. In the figure, the abscissa is the luminance and the ordinate is the device current efficiency. Among them, the device with a doping content of 10% wt has the best current efficiency at a luminance of 1000 cd / m 2 , reaching 6 cd / A.

Claims

1. A triazine polymer, characterized in that, the chemical structural formula of the triazine polymer is as follows: wherein, the degree of polymerization n ranges from 2 to 100,000; both the substituent R1 and the substituent R2 are independently selected from any one of phenyl, carbazolyl, dimethylcarbazolyl, di-tert-butylcarbazolyl, phenoxazinyl, diphenylamino, phenothiazinyl or acridinyl; both the substituent R3 and the substituent R4 are independently selected from any one of hydrogen, methyl or an alkyl chain having 1 to 10 carbon atoms.

2. A triazine polymer according to claim 1, characterized in that, the structure of the triazine polymer is selected from any one of the following compounds:

3. A preparation method of a triazine polymer, characterized in that, the preparation method comprises the following steps: Adding compound a, namely 4-hydroxycarbazole and potassium carbonate into a reaction vessel containing N,N-dimethylformamide (DMF) solvent, then injecting another raw material compound b, namely 4-chloromethylstyrene, and stirring at 80 °C under reflux for 6 hours, while avoiding double substitution due to too long reaction time; after stopping the reaction, separating and extracting with dichloromethane (DCM) by liquid separation, drying the organic solvent by rotary evaporator, and separating and purifying through a silica gel chromatography column to obtain a white solid intermediate, namely compound c; Dissolving compound d and compound d’ in dried THF and cooling to 0 °C; under a nitrogen atmosphere, dropwise adding n-butyllithium (n-BuLi) thereto, and then stirring for 2 hours; continuing under a nitrogen atmosphere, slowly adding compound e, namely cyanuric chloride dissolved in a tetrahydrofuran (THF) solution, and stirring and heating under reflux again; after the reaction is completed, slowly dropwise adding water to quench, stirring and extracting with dichloromethane; taking the organic phase, evaporating the solvent and recrystallizing with ethyl acetate to obtain a light yellow solid, and drying to obtain an intermediate triazine compound f; when the substituent R1 = R2, compound d = compound d’, and compound d, compound d’ and the compound e are directly mixed in a molar mass ratio of 1:1:1 to obtain an intermediate triazine compound f with the same substituent; when the substituent R1 is different from R2, compound d and compound e are first reacted in a molar mass ratio of 1:1, and then an amount of compound d’ equal to that of compound d is taken for reaction to prepare an intermediate triazine compound f with different substituents; Dissolving the triazine compound f, the p-fluorophenylboronic acid compound g and the catalyst tetrakis(triphenylphosphine)palladium in tetrahydrofuran, adding an aqueous potassium carbonate solution and heating to 70 °C for stirring, and cooling to room temperature after the reaction is completed; adding water and dichloromethane to extract the organic layer, removing the solvent from the organic layer, and then drying to obtain a white solid, namely an intermediate triazine intermediate h; Heating the intermediate compound h, compound c, potassium tert-butoxide and N,N-dimethylformamide (DMF) in a reaction vessel, stirring and refluxing; after the reaction is completed, adding water and filtering to obtain a solid, separating and purifying through a silica gel chromatography column to obtain a compound monomer i; Polymer monomer class i and initiator azobisisobutyronitrile AIBN were added to a device containing a chlorobenzene solution. Oxygen in the solution was removed by freezing with cryogenic techniques such as liquid nitrogen, and after thawing under a nitrogen atmosphere, this process was repeated multiple times. Then, it was heated to 80 °C and stirred for 48 hours. After that, a methanol solution was added and allowed to stand for sedimentation to obtain the final product, namely the triazine polymer.

4. Application of the triazine polymer according to claim 1 as a thermally activated delayed fluorescence emitting material in an organic light emitting diode.

5. Application of the triazine polymer according to claim 4 as a thermally activated delayed fluorescence emitting material in an organic light emitting diode, characterized in that, the triazine polymer is doped into a host material and used as a light emitting layer material to be coated into a film as the light emitting layer in an organic light emitting diode, and the host material is 26DCzPPy or DPEPO.

6. Application of the triazine polymer according to claim 5 as a thermally activated delayed fluorescence emitting material in an organic light emitting diode, characterized in that, the organic light emitting diode is fabricated by spin-coating PEDOT:PSS as an injection layer on the surface of a conductive ITO substrate, then spin-coating the light emitting layer material, and then depositing an electron transport layer and a Ca / Ag electrode.

7. Application of the triazine polymer according to claim 5 as a thermally activated delayed fluorescence emitting material in an organic light emitting diode, characterized in that, the doping concentration range of the triazine polymer is 10 - 100 wt%.

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