Cyclization strategy-induced intrinsic long-life room-temperature phosphorescent material and preparation method thereof

Abstract

The present invention discloses a cyclization strategy to induce an intrinsic long-life room temperature phosphorescent material, and further discloses a preparation method of the phosphorescent material, wherein the method prepares a functionalized phosphor by reacting a fluorene series derivative with 4-chloromethylstyrene; the functionalized phosphor is then subjected to free radical polymerization with methacrylic acid and acrylonitrile to graft the phosphor small molecules onto the polymer chain in the form of a covalent bond to prepare a PMI series intrinsic room temperature phosphorescent material; secondly, a rearrangement isomerization reaction of carboxyl and cyano groups occurs at high temperature to generate a six-membered imide ring, and the continuous cyclic structure on the polymer chain further enhances the rigid environment of the polymer matrix, thereby obtaining a polymer room temperature phosphorescent material with excellent luminous performance. The present invention adopts a convenient one-pot reaction, the preparation method is simple and controllable, and the cost is low and the raw materials are easily obtained, providing a new approach for designing new pure organic phosphorescent materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic room temperature phosphorescent luminescent materials, and in particular relates to a cyclization strategy-induced intrinsic long-life room temperature phosphorescent material and a preparation method thereof. Background Art

[0002] Room temperature phosphorescence is a unique photoluminescence phenomenon. In recent years, with the unremitting efforts of researchers, the excellent luminescence properties of room temperature phosphorescent materials have given them good application prospects in light-emitting devices, multi-level information encryption, sensing, bioimaging and other fields. According to the luminescence mechanism of phosphorescence, there are two key factors in the construction of efficient room temperature phosphorescent materials. The first is to promote the intersystem crossing of excitons from the singlet state to the triplet state, which is a spin-forbidden process. The second is to reduce the non-radiative deactivation rate of triplet excitons to ensure that they can survive long enough to slowly emit phosphorescence. However, molecular motion and the presence of quenchers such as water and oxygen can easily deactivate triplet excitons. Therefore, it is difficult to construct effective organic room temperature phosphorescent materials.

[0003] In recent years, structurally controllable, pure organic room-temperature phosphorescent materials have emerged as a rising star in the field of long-lasting luminescence materials. Due to the spin-forbidden intersystem crossing process, their large nonradiative vibrational relaxation, and the susceptibility of triplet excitons to quenching by quenchers such as water and oxygen, most organic phosphorescent materials can only be realized under conditions such as 77K and inert environments, and are not suitable for room temperature. Although fluorene derivatives are considered promising luminescent materials, their large molecular conjugation and rigid structure, which are beneficial for suppressing molecular motion and compressing nonradiative transitions to achieve high phosphorescence efficiency, have led to their widespread application in blue light and organic light-emitting diodes (OLEDs), their singlet exciton efficiency is low, and the spin-forbidden intersystem crossing process also presents significant difficulties in improving triplet excitons. Therefore, their use as room-temperature phosphorescent materials is rare. Summary of the Invention

[0004] In view of the above-mentioned deficiencies in the prior art, the present invention aims to provide a phosphorescent material to solve the problems of poor luminescence stability of current polymer-based room temperature phosphorescent materials and limited application of fluorene series phosphors in the field of room temperature phosphorescence.

[0005] Furthermore, the present invention also provides a method for preparing an intrinsic long-life room temperature phosphorescent material induced by the cyclization strategy, which solves the problems of complex preparation and high cost of existing polymer room temperature phosphorescent materials.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] A cyclization strategy-induced intrinsic long-life room-temperature phosphorescent material, characterized by having the following structure:

[0008]

[0009] Further, its synthetic route comprises the steps:

[0010] S1. Synthesis of functionalized phosphor SFDM:

[0011]

[0012] S2. Synthesis of a copolymer of functionalized phosphor, methacrylic acid and acrylonitrile, P-SFDM:

[0013]

[0014] S3. Synthesis of a cyclic copolymer of functionalized phosphor, methacrylic acid and acrylonitrile, Cy-P-SFDM:

[0015]

[0016] Furthermore, the specific preparation steps also include:

[0017] S1. Synthesis of functionalized phosphor SFDM:

[0018] 9,9-bis(4-hydroxy-3-methylphenyl)fluorene, potassium hydroxide and N,N-dimethylformamide were added to a reaction vessel and stirred at 50°C under reflux for 20 minutes; then, 4-chloromethylstyrene was quickly added to the reaction vessel and stirred at 50°C for 48 hours; finally, the obtained product was reprecipitated in methanol, and the precipitate was washed and dried to obtain a functionalized phosphor SFDM;

[0019] S2. Synthesis of a copolymer of functionalized phosphor, methacrylic acid and acrylonitrile, P-SFDM:

[0020] The functionalized phosphor obtained in step 1, methacrylic acid, acrylonitrile, and dimethyl sulfoxide are added to a reaction vessel. After dissolving, azobisisobutyronitrile is added and mixed evenly. The mixture is reacted under an inert atmosphere at 65°C for 72 hours. Finally, the resulting product is precipitated in deionized water, the solid is removed, dissolved in dimethyl sulfoxide, and then precipitated again. The solid is removed and dried to obtain the polymer P-SFDM. The drying step is performed at 60°C under vacuum for 12 hours. The dimethyl sulfoxide provides a reaction environment for the reaction.

[0021] S3. Synthesis of a cyclic copolymer of functionalized phosphor, methacrylic acid and acrylonitrile, Cy-P-SFDM:

[0022] The polymer P-SFDM obtained in step 2 is placed in a forced air oven for heating treatment to obtain the corresponding cyclic copolymer Cy-P-SFDM.

[0023] Furthermore, the molar ratio of the 9,9-bis(4-hydroxy-3-methylphenyl)fluorene, potassium hydroxide and 4-chloromethylstyrene is 2:5:8.

[0024] Furthermore, the molar ratio of the functionalized phosphor to the total amount of comonomers is 1:1000-4000.

[0025] Furthermore, the molar ratio of the comonomers methacrylic acid and acrylonitrile is 1:1.

[0026] Furthermore, the added amount of azobisisobutyronitrile is 1% of the total mass of the functionalized phosphor, methacrylic acid and acrylonitrile.

[0027] Furthermore, the heating treatment temperature is 170° C., and the time is 10 min, 14 min, 18 min, and 22 min.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The cyclization strategy of the present invention induces an intrinsic long-life room-temperature phosphorescent material containing a cyclic polymer Cy-P-SFDM, which exhibits blue fluorescence under ultraviolet light. The polymer afterglow lasts for up to 14 seconds after cyclization for 18 minutes, indicating good luminescence stability. It is suitable for the field of pure organic room-temperature phosphorescence and provides a new material and method for constructing long-life polymer room-temperature phosphorescent materials by enhancing intersystem crossing and rigid environment; and solves the problem of limited application of fluorene series phosphors in the field of room-temperature phosphorescence.

[0030] 2. The cyclization strategy of the present invention induces an intrinsic long-lifetime room-temperature phosphorescent material. By adjusting the cyclization time, the obtained intrinsic long-lifetime room-temperature phosphorescent material achieves significantly improved photophysical properties. Its phosphorescence lifetime and phosphorescence quantum yield are increased by 17 times and 9 times respectively compared with those before cyclization.

[0031] 3. The present invention proposes a new method for preparing room-temperature phosphorescent materials, which can effectively promote the intersystem crossing process and reduce the non-radiative transition of triplet excitons. First, a fluorene derivative with excellent luminescence performance is functionalized, and then the functionalized phosphor is free radical copolymerized with methacrylic acid and acrylonitrile to graft the phosphor small molecules onto the polymer chain in the form of covalent bonds. At the same time, the abundant carbonyl and carboxyl groups on the polymer chain can effectively promote spin-orbit coupling, which is conducive to the intersystem crossing from singlet to triplet state to produce a large number of triplet excitons; then the obtained polymer is placed in a 170°C forced air oven for heating treatment. The carboxyl and cyano groups on the polymer chain will undergo rearrangement isomerization to form a six-membered ring at high temperature. The continuous ring structure further improves the rigid environment of the polymer, which not only increases the intersystem crossing channel between singlet and triplet states and has excellent intersystem crossing efficiency, but also suppresses molecular vibration, thereby reducing non-radiative transitions and significantly improving the phosphorescence performance.

[0032] 4. The cyclization strategy of the present invention induces intrinsic long-life room-temperature phosphorescent materials with simple components, easily available raw materials, low cost, convenient preparation, and simple and controllable process, providing new theoretical guidance and technical support for the efficient production of room-temperature phosphorescent materials with excellent photophysical properties.

[0033] 5. The purely organic, intrinsic, long-lifetime room-temperature phosphorescent material prepared by this invention overcomes the shortcomings of traditional inorganic phosphorescent materials, such as high cost and scarce rare earth element resources. Furthermore, compared with other organic phosphorescent materials, this invention overcomes the difficulties in preparing crystalline materials, their brittleness, the proneness to phase separation and poor compatibility of small-molecule host-guest doped long-lasting glow materials, and the lack of effective methods to promote intersystem crossing and inhibit non-radiative deactivation. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is the hydrogen nuclear magnetic resonance spectrum of the functionalized phosphor SFDM in Example 1 of the present invention;

[0035] Figure 2 1H NMR spectra of the polymer P-SFDM before and after cyclization in Example 1 of the present invention;

[0036] Figure 3 The phosphorescence spectrum of the polymer P-SFDM in Examples 1-6 of the present invention when excited at 310 nm;

[0037] Figure 4 This is a photo of the phosphorescence of the polymer P-SFDM with a copolymerization ratio of 2500:2500:1 under a 310nm ultraviolet lamp in Example 7 of the present invention;

[0038] Figure 5 The phosphorescence spectrum of the polymer P-SFDM with a copolymerization ratio of 2500:2500:1 in Example 7 of the present invention excited at 310 nm is shown;

[0039] Figure 6 This is the phosphorescence lifetime decay curve of the polymer P-SFDM with a copolymerization ratio of 2500:2500:1 excited by 310 nm in Example 7 of the present invention. DETAILED DESCRIPTION

[0040] The present invention will be further described in detail below with reference to the embodiments.

[0041] The numerical ranges herein are understood to specifically disclose every intervening value between the upper and lower limits of the range. Each smaller range between any stated value or intervening value in a stated range and any other stated value or intervening value in that stated range is also encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

[0042] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art. Although the present invention has only described preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail. As used herein, "comprising", "including", "having", "containing", etc. are all open-ended terms, meaning including but not limited to.

[0043] Unless otherwise specified, the experimental methods used in the present invention are all conventional methods.

[0044] Unless otherwise specified, the materials, reagents, etc. used in the present invention can be purchased or synthesized by known methods.

[0045] The quantitative tests in the present invention were repeated three times and the results were averaged.

[0046] 1. The present invention provides a cyclization strategy to induce an intrinsic long-life room-temperature phosphorescent material, comprising a cyclic polymer Cy-P-SFDM with the following structure:

[0047]

[0048] Second, the present invention also provides a method for preparing the intrinsic long-life room temperature phosphorescent material induced by the cyclization strategy, the process of which includes:

[0049] S1. Synthesis of functionalized phosphor SFDM:

[0050]

[0051] S2. Synthesis of a copolymer of functionalized phosphor, methacrylic acid and acrylonitrile, P-SFDM:

[0052]

[0053] S3. Synthesis of a cyclic copolymer of functionalized phosphor, methacrylic acid and acrylonitrile, Cy-P-SFDM:

[0054]

[0055] 3. Examples

[0056] Example 1

[0057] A method for preparing an intrinsic long-life room-temperature phosphorescent material induced by a cyclization strategy comprises the following steps:

[0058] (1) Synthesis of functionalized phosphor SFDM:

[0059] 9,9-bis(4-hydroxy-3-methylphenyl)fluorene (10 mmol, 3.86 g), potassium hydroxide (40 mmol, 2.24 g) and N,N-dimethylformamide (60 mL) were added to a 150 mL three-necked flask and stirred at 50 ° C for 20 minutes under reflux conditions. Then, 4-chloromethylstyrene (30 mmol, 4.3 mL) was quickly added to the above solution and stirred under the same conditions for 48 hours. When the reaction was completed, the solution was light brown. The obtained product was poured into methanol (600 mL) for precipitation and then filtered to obtain a white powder. The white powder was washed again with water. Repeat the above two-step washing operation three times. Finally, the product was dried in a vacuum oven at 65 ° C for 24 hours to obtain the functionalized phosphor SFDM.

[0060] (2) Synthesis of functionalized phosphor, methacrylic acid, and acrylonitrile copolymer P-SFDM:

[0061] The successfully synthesized phosphor SFDM (20.6 mg), methacrylic acid (3 mL), acrylonitrile (2.33 mL), and dimethyl sulfoxide (25 mL) were added to a 100 mL polymerization tube. After dissolution, the initiator azobisisobutyronitrile (0.0494 mg) was added and mixed thoroughly. The tube was repeatedly evacuated and filled with argon five times to expel the gas, and stirred at 65°C for 72 hours. The solution was initially clear and transparent. As the reaction time increased, the solution viscosity increased and the color gradually turned light yellow. After the reaction was completed, the resulting product was placed in a beaker filled with 1000 mL of deionized water for precipitation. The solid was then removed and dissolved in dimethyl sulfoxide (10 mL) for reprecipitation. The solid was removed and the product was dried in a vacuum oven at 60°C for 12 hours to obtain the polymer P-SFDM.

[0062] (3) Synthesis of Cyclic Copolymer Cy-P-SFDM of Functionalized Phosphor, Methacrylic Acid and Acrylonitrile:

[0063] The polymer obtained in step 2 is placed in a forced air oven at 170° C. for heating treatment to obtain the corresponding cyclic polymer Cy-P-SFDM.

[0064] Examples 2-6

[0065] Examples 2-6 provide a method for preparing an intrinsic long-lifetime room-temperature phosphorescent material induced by a cyclization strategy. The preparation method is similar to that of Example 1, except that the ratio of the functionalized phosphor to methacrylic acid and acrylonitrile is different. Specific examples are shown in Table 1:

[0066] Table 1 Raw material addition amount of Examples 1-6

[0067]

[0068] Example 7

[0069] The phosphorescent materials obtained in Examples 1-6 were placed in a forced air oven at 170° C. for heating treatment, thereby obtaining the corresponding cyclic polymer materials in Examples 1-6.

[0070] 4. Result detection and analysis

[0071] In order to verify whether the phosphor SFDM in Example 1 is successfully synthesized, the nuclear magnetic resonance hydrogen spectrum of the product SFDM in Example 1 is as follows Figure 1 As shown, the H signal on the raw material hydroxyl group has disappeared, while the H signal at 5.03ppm comes from -CH2, the H signal at 5.24-5.85ppm comes from -CH=CH2, and the H signal at 6.69-7.90ppm comes from the aromatic ring, indicating that the phosphor SFDM has been successfully synthesized and has the following structure:

[0072]

[0073] The polymer P-SFDM in Example 1 was tested by nuclear magnetic resonance hydrogen spectrum before and after cyclization, and the test results are as follows: Figure 2 As shown, the H signal at 12.73 ppm comes from -COOH on the polymer chain. After cyclization, the H signal of -COOH disappears, and the H signal of -NH on the cyclized imide ring appears at 10.50 ppm, indicating that the polymer P-SFDM is successfully cyclized and has the following structure:

[0074]

[0075] At room temperature and atmospheric conditions, the photophysical properties of the polymers obtained in Examples 1-6 were tested using a spectrometer, and the phosphorescence emission spectra were obtained as follows: Figure 3 As shown in the figure, the phosphorescence intensity of the polymer shows a trend of first increasing and then decreasing, and reaches the optimal value when the molar ratio is 2500:2500:1.

[0076] like Figure 4 As shown, under atmospheric conditions, the intrinsic polymer room temperature phosphorescent materials of different degrees of cyclization obtained in Example 7 at a copolymerization ratio of 2500:2500:1 were irradiated with a 310 nm UV lamp. All exhibited blue fluorescence. After the excitation source was removed, a blue afterglow of varying durations could be observed with the naked eye. The afterglow of the polymer after cyclization for 18 minutes lasted as long as 14 seconds.

[0077] Figure 5 The phosphorescence emission spectra of the intrinsic long-life room temperature phosphorescent material with different cyclization times and a copolymerization ratio of 2500:2500:1 in Example 7 are shown. The phosphorescence intensity of the cyclized polymer also shows a trend of first increasing and then decreasing, reaching the best when the cyclization time is 18 minutes, which is consistent with the visual observation effect. In addition, Figure 6 The phosphorescence decay lifetime also further confirmed that this cyclization time was the optimal cyclization time for the polymer, and the highest phosphorescence lifetime reached 914.0ms, which was about 17 times higher than that before cyclization.

[0078] In summary, the cyclization strategy provided by the present invention induces an intrinsic long-life room-temperature phosphorescent material with excellent luminescence stability and is suitable for use in the field of pure organic room-temperature phosphorescence. The present invention provides a new material and method for achieving long-life polymer room-temperature phosphorescent materials by enhancing intersystem crossing and a rigid environment. This not only addresses the poor luminescence stability of existing polymer-based room-temperature phosphorescent materials, but also solves the problem of the limited application of fluorene-based phosphors in the field of room-temperature phosphorescence. Furthermore, the preparation method of the long-life room-temperature phosphorescent material solves the problems of complex preparation and high cost of existing polymer room-temperature phosphorescent materials.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the technical solutions. Those skilled in the art should understand that modifications or equivalent replacements of the technical solutions of the present invention that do not depart from the purpose and scope of the technical solutions of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A cyclization strategy induced intrinsic long-life polymer room temperature phosphorescent material, characterized in that: It is prepared by the following method: S1. Synthesis of functionalized phosphor SFDM: S2. Synthesis of a copolymer of functionalized phosphor, methacrylic acid and acrylonitrile, P-SFDM: S3. The copolymer P-SFDM obtained in step S2 is subjected to heat treatment, so that the carboxyl and cyano groups on the polymer chain undergo rearrangement isomerization at high temperature to form a six-membered ring, and finally the cyclization strategy is used to induce the intrinsic long-life polymer room temperature phosphorescent material to be a cyclic copolymer Cy-P-SFDM.

2. The method of claim 1, wherein the cyclization strategy induces an intrinsic long-lifetime room temperature phosphorescent material, The specific preparation steps include: S1. Synthesis of functionalized phosphor SFDM: 9,9-bis(4-hydroxy-3-methylphenyl)fluorene, potassium hydroxide and N,N-dimethylformamide were added to a reaction vessel and stirred at 50°C under reflux for 20 minutes; then, 4-chloromethylstyrene was quickly added to the reaction vessel and stirred at 50°C for 48 hours; finally, the obtained product was reprecipitated in methanol, and the precipitate was washed and dried to obtain a functionalized phosphor SFDM; S2. Synthesis of a copolymer of functionalized phosphor, methacrylic acid and acrylonitrile, P-SFDM: The functionalized phosphor obtained in S1, methacrylic acid, acrylonitrile, and dimethyl sulfoxide were added to a reaction vessel, dissolved, and then azobisisobutyronitrile was added and mixed evenly. The mixture was reacted under an inert atmosphere at 65°C for 72 hours. Finally, the obtained product was precipitated in deionized water, the solid was removed, dissolved in dimethyl sulfoxide, and then precipitated again. The solid was removed and dried to obtain the polymer P-SFDM. S3. Synthesis of a cyclic copolymer of functionalized phosphor, methacrylic acid and acrylonitrile, Cy-P-SFDM: The polymer P-SFDM obtained in S2 is placed in a forced air oven for heating treatment to obtain the corresponding cyclic copolymer Cy-P-SFDM.

3. The method of claim 2, wherein the cyclization strategy induces an intrinsic long-lifetime room temperature phosphorescent material, The molar ratio of the 9,9-bis(4-hydroxy-3-methylphenyl)fluorene, potassium hydroxide and 4-chloromethylstyrene is 2:5:

8.

4. The method of claim 2, wherein the cyclization strategy induces an intrinsic long-lifetime room temperature phosphorescent material, The molar ratio of the functionalized phosphor to the total amount of the comonomers is 1:1000-4000.

5. The method of claim 2, wherein the cyclization strategy induces an intrinsic long-lifetime room temperature phosphorescent material, The molar ratio of the comonomers methacrylic acid and acrylonitrile is 1:

1.

6. The cyclization strategy-induced intrinsic long-lifetime room-temperature phosphorescent material according to claim 2, characterized in that: The added amount of the azobisisobutyronitrile is 1% of the total mass of the functionalized phosphor, methacrylic acid and acrylonitrile.

7. The cyclization strategy-induced intrinsic long-life room temperature phosphorescent material according to claim 2, characterized in that: The heating treatment temperature is 170° C., and the heating treatment time is 10 min, 14 min, 18 min or 22 min.

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