A high-performance large Stokes shift luminescent polyimide, preparation method, photoluminescent material, converter

Abstract

The present invention provides a high-performance large Stokes shift luminescent polyimide, a preparation method, a photoluminescent material, and a converter, belonging to the technical field of organic polymer materials. The polyimide of the present invention is obtained by reacting an aromatic diamine with excited state proton transfer characteristics and various dianhydrides as raw materials. The polyimide provided by the present invention not only has a large Stokes shift and high luminescence intensity, but also has a high glass transition temperature, thermal stability, and excellent mechanical properties, etc., and is suitable for preparing photoluminescent products and wavelength down-converters for solar cells.

Description

Technical Field

[0001] The present invention relates to the technical field of organic polymer materials, and particularly relates to a high-performance large Stokes shift luminescent polyimide, a preparation method, a photoluminescent material, and a converter. Background Art

[0002] Polymer luminescent materials have many characteristics such as diverse structures, easy functionalization, and easy processing, and are widely used in polymer optoelectronic devices, chemical sensors, stimulus-responsive intelligent materials, bioimaging and other fields. However, with the development of technology, traditional polymer luminescent materials are gradually difficult to meet the needs of modern applications. For most polymer luminescent materials, there are generally problems such as difficult purification, insufficient color purity, poor thermal stability, insufficient chemical stability, and low luminescence efficiency, which have severely restricted their development.

[0003] Polyimide is a class of high-performance polymers containing imide rings in the main chain, and has advantages such as high mechanical strength, resistance to high and low temperatures, chemical corrosion resistance, good dimensional stability, and dielectric properties, and has wide applications in aerospace, microelectronic devices, liquid crystal displays and other fields. More importantly, most of its syntheses are carried out through the highly reactive condensation polymerization reaction between diamine monomers and dianhydride monomers and subsequent dehydration cyclization reaction. Not only are the reaction conditions simple and the reaction time is short, but the by-product is water, and no purification or the purification process is simple. At the same time, the designability of the monomers is strong, which brings great convenience to the functionalization of polyimide. Among many luminescent bodies, molecules and polymers that undergo excited state intramolecular proton transfer (ESIPT) exhibit significant photoluminescence properties. The ESIPT photophysical process can achieve photoluminescence (PL) with a large difference between the excitation wavelength and the emission wavelength, that is, large Stokes shift fluorescence appears. Therefore, ESIPT molecules and polymers have broad application prospects in spectral conversion applications. At present, various types of organic ESIPT dyes have been reported, but many of these dyes have problems such as low photo-stability and insufficient thermal stability, which limit their long-term use in solar cells. In addition, most of them are small molecules and are not suitable for direct use in solar cells, which also limits their applications. Therefore, fluorescent polyimide (PI) with long-term durability and high thermal stability has great application potential in photoluminescent films.

[0004] In the development of highly fluorescent polymers, a useful design strategy is widely used, which is to introduce photophores into the main chain or side groups of the polymers. Some methods for improving the luminescence efficiency of polyimides are to synthesize semi-aromatic or non-aromatic polyimides using alicyclic monomers. Although the resulting highly fluorescent polyimides, such as ODPA / DCHM, exhibit high transparency in the visible region, under the excitation of ultraviolet light, they only show blue emission. The alicyclic polyimides synthesized from perfluoroaromatic dianhydrides exhibit strong blue-green and red emissions respectively. This indicates that fluorinated aromatic dihydrides can provide fluorescent polyimides with red-shifted emission. However, fluorinated polyimides show strong absorption at shorter wavelengths in the visible light region (400 - 600 nm), which reduces the optical transparency. Since colorless and highly transparent polyimide films are preferred for optical and photon applications, a new molecular design concept to control the fluorescence color (emission wavelength) while maintaining high optical transparency has been strongly demanded. Summary of the Invention

[0005] In view of this, the object of the present invention is to provide a high-performance large Stokes shift luminescent polyimide and its preparation method and application. The high-performance large Stokes shift luminescent polyimide provided by the present invention has high photoluminescence efficiency and large Stokes shift, the maximum transmittance in the visible light region is greater than 87.6%, the transmittance at 450 nm exceeds 82%, and it has high glass transition temperature, thermal stability and excellent mechanical properties.

[0006] To achieve the above object, the present invention provides the following technical solutions: A high-performance large Stokes shift luminescent polyimide having the structure shown in Formula Ι:

[0007]

[0008] Wherein, n and m represent the degree of polymerization, n / m = 1 / 99 - 100 / 0, X and W are each independently selected from a tetravalent aromatic hydrocarbon group or an aliphatic hydrocarbon group, Z is a divalent aromatic hydrocarbon group or an aliphatic hydrocarbon group, and Y is one or more of the groups shown in Structural Formula Ⅱ, Structural Formula Ⅲ and Structural Formula Ⅳ:

[0009]

[0010] Wherein, R1, R2, R3, and R4 are the same or different, and are each independently selected from one or more of -H, -OCH3, -Br, -CF3, -Cl, -F, -CH3, -CHO, -COOCH2CH3.

[0011] Preferably, the tetravalent aromatic hydrocarbon group or aliphatic hydrocarbon group has the following structural formula:

[0012]

[0013] Preferably, the divalent aromatic hydrocarbon group or aliphatic hydrocarbon group has the following structural formula:

[0014]

[0015] The present invention also provides a method for preparing the high-performance large Stokes shift luminescent polyimide described in the above technical solution, including the following steps: In a nitrogen or argon atmosphere, a diamine containing the Y structure described in the above technical solution or a diamine containing the Y and Z structures described in the above technical solution and a dianhydride containing the X structure described in the above technical solution or a dianhydride containing the X and W structures described in the above technical solution are dissolved in an aprotic organic solvent, and stirred at room temperature for 2 to 72 hours to obtain a polyamic acid solution, and then the polyamic acid is imidized to obtain a polyimide material.

[0016] Preferably, the molar ratio of the diamine containing the Y structure described in the above technical solution or the diamine containing the Y and Z structures described in the above technical solution to the dianhydride containing the X structure described in the above technical solution or the dianhydride containing the X and W structures described in the above technical solution is 1:(0.9 - 1.1).

[0017] Preferably, the aprotic organic solvent is selected from at least one of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, sulfolane, 1,4-dioxane, m-phenol, and tetrahydrofuran.

[0018] Preferably, the imidization method is a chemical imidization method or a thermal imidization method.

[0019] The present invention also provides a photoluminescent material comprising the high-performance large Stokes shift luminescent polyimide described in the above technical solution.

[0020] The present invention also provides a converter comprising the high-performance large Stokes shift luminescent polyimide described in the above technical solution.

[0021] Beneficial technical effects: The present invention provides a high-performance large Stokes shift luminescent polyimide and its preparation method and application. The present invention uses an aromatic diamine with excited-state proton transfer characteristics and various dianhydrides as raw materials to react to obtain a polyimide. The polyimide provided by the present invention not only has a large Stokes shift and high luminescence intensity, but also has a high glass transition temperature, thermal stability and excellent mechanical properties, etc., and is suitable for preparing photoluminescent products and wavelength down-converters for solar cells. Description of the Drawings

[0022] Figure 1 It is the infrared spectrum diagram of the polyimides obtained in Examples 1 - 4. Detailed Embodiments

[0023] The present invention provides a high-performance large Stokes shift luminescent polyimide having the structure shown in Formula Ι:

[0024]

[0025] Wherein, n and m represent the degree of polymerization, n / m = 1 / 99 to 100 / 0, X and W are each independently selected from a tetravalent aromatic hydrocarbon group or an aliphatic hydrocarbon group, Z is a divalent aromatic hydrocarbon group or an aliphatic hydrocarbon group, and Y is one or more of the groups shown in Structural Formula II, Structural Formula III, and Structural Formula IV:

[0026]

[0027] Wherein, R1, R2, R3, and R4 are the same or different, and are each independently selected from one or more of -H, -OCH3, -Br, -CF3, -Cl, -F, -CH3, -CHO, -COOCH2CH3.

[0028] In the present invention, the tetravalent aromatic hydrocarbon group or aliphatic hydrocarbon group is preferably a structural formula as shown below:

[0029]

[0030] In the present invention, the divalent aromatic hydrocarbon group or aliphatic hydrocarbon group is preferably a structural formula as shown below:

[0031]

[0032] The present invention also provides a preparation method of the high-performance large Stokes shift luminescent polyimide described in the above technical solution, including the following steps: in a nitrogen or argon atmosphere, a diamine containing the Y structure described in the above technical solution or a diamine containing the Y and Z structures described in the above technical solution and a dianhydride containing the X structure described in the above technical solution or a dianhydride containing the X and W structures described in the above technical solution are dissolved in an aprotic organic solvent, stirred at room temperature for 2 to 72 hours to obtain a polyamic acid solution, and then the polyamic acid is imidized to obtain a polyimide material.

[0033] In the present invention, the molar ratio of the diamine containing the Y structure described in the above technical solution or the diamine containing the Y and Z structures described in the above technical solution to the dianhydride containing the X structure described in the above technical solution or the dianhydride containing the X and W structures described in the above technical solution is preferably 1:(0.9 - 1.1), and more preferably 1:1.

[0034] In the present invention, the aprotic organic solvent is preferably at least one of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, sulfolane, 1,4-dioxane, m-phenol, and tetrahydrofuran.

[0035] In the present invention, the imidization method is preferably a chemical imidization method or a thermal imidization method.

[0036] In the present invention, when the imidization method is a chemical imidization method, the present invention can prepare the polyamic acid into a polyimide powder or a polyimide film.

[0037] Preferably, the polyimide powder is prepared from the polyamic acid by adding a dehydrating agent to the polyamic acid solution, heating and stirring the solution at 30 to 200° C. for 2 to 72 hours, cooling the solution to room temperature, and then pouring the solution into methanol, ethanol or acetone to obtain a precipitate, which is then filtered to obtain the polyimide powder.

[0038] Further preferably, the dehydrating agent is selected from one of a mixed solution of pyridine and acetic anhydride, a mixed solution of triethylamine and acetic anhydride, and a mixed solution of sodium acetate and acetic anhydride.

[0039] Preferably, the method for preparing the polyimide film from the polyamic acid is as follows: dissolving the polyimide powder obtained above in an organic solvent, and after it is completely dissolved, applying the polyimide solution on a clean substrate by scraping, and then placing the substrate in an oven, heating it to 70-300°C to dry and remove the solvent, and obtaining a polyimide film after cooling.

[0040] More preferably, the organic solvent is N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, sulfolane, 1,4-dioxane, m-phenol or tetrahydrofuran.

[0041] Further preferably, the substrate is a glass plate, copper, aluminum, iron or silicon substrate.

[0042] In the present invention, when the imidization method is a thermal imidization method, the present invention can prepare the polyamic acid into a polyimide film.

[0043] Preferably, the method for preparing polyamic acid into polyimide film is: coating the polyamic acid solution on a clean substrate, placing the substrate in an oven, heating the oven to perform imidization, and obtaining the polyimide film after cooling.

[0044] Further preferably, the substrate is a glass plate, copper, aluminum, iron or silicon substrate.

[0045] Further preferably, the heating program is as follows: heating from room temperature to 50 - 180 °C and then maintaining a constant temperature for 10 - 240 minutes; then heating to 180 - 250 °C and maintaining a constant temperature for 10 - 240 minutes; finally heating to 250 - 380 °C for 10 - 360 minutes.

[0046] The present invention also provides a photoluminescent material comprising the high-performance large Stokes shift luminescent polyimide described in the above technical solution.

[0047] The present invention also provides a converter comprising the high-performance large Stokes shift luminescent polyimide described in the above technical solution. Materials for solar cells tend to absorb light from green to near-infrared, while sunlight contains ultraviolet and blue light with low utilization efficiency by solar cell materials. The large Stokes shift luminescent material provided by the present invention can absorb ultraviolet or blue light and emit green to near-infrared light. A converter with this material can convert ultraviolet and blue light to green to near-infrared light for use by solar cells.

[0048] To better understand the present invention, the content of the present invention will be further illustrated below in conjunction with embodiments. However, the content of the present invention is not limited to the following embodiments.

[0049] Example 1

[0050] The molecular structural formula of the high-performance large Stokes shift luminescent polyimide in this example is as follows:

[0051]

[0052] At room temperature, 4.09 g (0.01 mol) of 4,4”-diamino-5'-(benzo[d]thiazol-2-yl)-[1,1':3',1''-terphenyl]-4'-ol and 15 ml of N,N-dimethylacetamide were added to a three-necked flask. Argon was introduced. After complete dissolution by stirring, 2.2417 g (0.01 mol) of hydrogenated pyromellitic dianhydride was added, and the reaction was stirred at room temperature for 24 h to obtain a homogeneous, transparent, viscous polyimide solution; then 0.01 mol of acetic anhydride and 0.01 mol of pyridine were added for chemical imidization. After reacting at room temperature for 72 hours, it was precipitated in ethanol, filtered and dried to obtain polyimide powder. The polyimide powder was dissolved in N,N-dimethylformamide. After complete dissolution, the polyimide solution was spin-coated on a clean glass plate, and then the above substrate was placed in an oven, heated to 200 °C to dry off the solvent, and cooled to obtain a polyimide film. The infrared spectrum of this polyimide film is as Figure 1 shown in PI1.

[0053] Example 2

[0054] The molecular structural formula of the high-performance large Stokes shift luminescent polyimide in this example is as follows:

[0055]

[0056] At room temperature, 0.409 g (0.001 mol) of 4,4”-diamino-5'-(benzo[d]thiazol-2-yl)-[1,1':3',1”-terphenyl]-4'-ol, 1.81 g (0.009 mol) of 4,4'-diaminodiphenyl ether and 10 ml of N,N-dimethylacetamide were added to a three-necked flask, and argon was introduced. After complete dissolution by stirring, 2.2417 g (0.01 mol) of hydrogenated pyromellitic dianhydride was added, and the reaction was stirred at room temperature for 24 h to obtain a homogeneous, transparent and viscous polyimide solution; then 0.01 mol of acetic anhydride and 0.01 mol of pyridine were added for chemical imidization. After reacting at room temperature for 72 hours, it was precipitated in ethanol, filtered and dried to obtain polyimide powder. The polyimide powder was dissolved in N,N-dimethylformamide. After complete dissolution, the polyimide solution was spin-coated on a clean glass plate, and then the above substrate was placed in an oven and heated to 200 °C to dry off the solvent. After cooling, a polyimide film was obtained. The infrared spectrum of this polyimide film is as Figure 1 shown in PI2 of

[0057] Example 3

[0058] The molecular structural formula of the high-performance large Stokes shift luminescent polyimide in this example is as follows:

[0059]

[0060] At room temperature, 0.409 g (0.001 mol) of 4,4”-diamino-5'-(benzo[d]thiazol-2-yl)-[1,1':3',1”-terphenyl]-4'-ol, 1.81 g (0.009 mol) of 4,4'-diaminodiphenyl ether and 12 ml of N,N-dimethylacetamide were added to a 50 three-necked flask. Argon was introduced. After complete dissolution by stirring, 3.0631 g (0.01 mol) of hydrobiphenyltetracarboxylic dianhydride was added. The reaction was stirred at room temperature for 24 h to obtain a homogeneous, transparent and viscous polyimide solution; then 0.01 mol of acetic anhydride and 0.01 mol of pyridine were added for chemical imidization. After reacting at room temperature for 72 hours, it was precipitated in ethanol, filtered and dried to obtain polyimide powder. The polyimide powder was dissolved in N,N-dimethylformamide. After complete dissolution, the polyimide solution was spin-coated on a clean glass plate. Then the above substrate was placed in an oven and heated to 200 °C to dry off the solvent. After cooling, a polyimide film was obtained. The infrared spectrum of this polyimide film is as shown in Figure 1 PI3 shown in

[0061] Example 4

[0062] The molecular structural formula of the high-performance large Stokes shift luminescent polyimide in this example is as follows:

[0063]

[0064] At room temperature, 3.91 g (0.01 mol) of 4,4”-diamino-5'-(benzo[d]oxazol-2-yl)-[1,1':3',1”-terphenyl]-4'-ol and 12 ml of N,N-dimethylacetamide were added to a 50 three-necked flask. Argon was introduced. After complete dissolution by stirring, 3.0631 g (0.01 mol) of hydrobiphenyltetracarboxylic dianhydride was added. The reaction was stirred at room temperature for 24 h to obtain a homogeneous, transparent and viscous polyimide solution; then 0.01 mol of acetic anhydride and 0.01 mol of pyridine were added for chemical imidization. After reacting at room temperature for 72 hours, it was precipitated in ethanol, filtered and dried to obtain polyimide powder. The polyimide powder was dissolved in N,N-dimethylformamide. After complete dissolution, the polyimide solution was spin-coated on a clean glass plate. Then the above substrate was placed in an oven and heated to 200 °C to dry off the solvent. After cooling, a polyimide film was obtained. The infrared spectrum of this polyimide film is as shown in Figure 1 PI4 shown in

[0065] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. High-performance large Stokes shift luminescent polyimide with the structure shown in Formula Ι: Among them, n and m represent the degree of polymerization, n / m = 1 / 99 - 100 / 0, X and W are each independently selected from tetravalent aromatic hydrocarbon groups or aliphatic hydrocarbon groups, Z is a divalent aromatic hydrocarbon group or aliphatic hydrocarbon group, and Y is one or more of the groups shown in Structural Formula Ⅱ, Structural Formula Ⅲ, and Structural Formula Ⅳ: Wherein, R1, R2, R3, and R4 are the same or different, and are each independently selected from one or more of -H, -OCH3, -Br, -CF3, -Cl, -F, -CH3, -CHO, -COOCH2CH3; The tetravalent aromatic hydrocarbon group or aliphatic hydrocarbon group has the structural formula shown below: The divalent aromatic hydrocarbon group or aliphatic hydrocarbon group has the structural formula shown below:

2. The preparation method of the high-performance large Stokes shift luminescent polyimide according to claim 1, characterized in that, In a nitrogen or argon atmosphere, a diamine containing the Y structure described in Claim 1 or a diamine containing the Y and Z structures described in Claim 1 and a dianhydride containing the X structure described in Claim 1 or a dianhydride containing the X and W structures described in Claim 1 are dissolved in an aprotic organic solvent, and stirred at room temperature for 2 - 72 hours to obtain a polyamic acid solution, and then the polyamic acid is imidized to obtain a polyimide material.

3. The preparation method according to claim 2, characterized in that, The molar ratio of the diamine containing the Y structure described in Claim 1 or the diamine containing the Y and Z structures described in Claim 1 to the dianhydride containing the X structure described in Claim 1 or the dianhydride containing the X and W structures described in Claim 1 is 1:(0.9 - 1.1).

4. The preparation method according to claim 2, characterized in that, The aprotic organic solvent is selected from at least one of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, sulfolane, 1,4-dioxane, m-phenol, and tetrahydrofuran.

5. The preparation method according to claim 2, characterized in that, The imidization method is a chemical imidization method or a thermal imidization method.

6. A photoluminescent material, characterized in that, Comprising the high-performance large Stokes shift luminescent polyimide described in Claim 1.

7. A converter, characterized in that, Comprising the high-performance large Stokes shift luminescent polyimide described in Claim 1.

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