A microwave irradiation method for preparing room temperature phosphorescent polymer films based on polyacrylamide

Abstract

This invention relates to a microwave radiation method for preparing room-temperature phosphorescent polymer films based on polyacrylamide, belonging to the field of organic light-emitting materials. The method involves dissolving acrylamide monomer, ammonium persulfate initiator, and β-diketone ligand in a mixed solvent of water and acetonitrile, placing the solution in a microwave reactor, and polymerizing it under microwave radiation to obtain the polymer. The resulting colloidal solution, dissolved in deionized water, is uniformly coated onto a polytetrafluoroethylene (PTFE) or silicone plate, and dried to obtain the room-temperature phosphorescent polymer film based on polyacrylamide. The prepared polymer film exhibits blue or blue-green fluorescence and a green afterglow. The polymer film containing 4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedione has an afterglow time of up to 7.5 seconds. The raw materials of this invention are readily available, the preparation method is simple, convenient, and rapid, requiring no inert gas protection, the solvent does not require treatment, polymerization can be completed in minutes, and the obtained material is non-toxic, non-polluting, free of heavy metals and halogens, has good water solubility, and has broad application prospects.

Description

TECHNICAL FIELD

[0001] The application relates to a microwave radiation method for preparing a polyacrylamide-based room-temperature phosphorescent polymer film and belongs to the field of organic luminescent materials. BACKGROUND

[0002] The amide groups in the polyacrylamide structure can easily construct intermolecular and intramolecular hydrogen bonds, effectively limit the molecular chain movement and inhibit non-radiative transition. * The sensitivity of room-temperature phosphorescent materials to temperature, oxygen and humidity requires strict control of oxygen and humidity in the realization of room-temperature phosphorescence. In order to inhibit the quenching effect of oxygen and humidity on room-temperature phosphorescent materials, the preparation of a polyacrylamide-based room-temperature phosphorescent polymer film is mostly realized through solution polymerization by a traditional heating method under the conditions of water-free organic solvents and inert gas. The long reaction period, strictly required organic solvents, synthesis conditions and atmosphere increase the synthesis difficulty, reduce the reaction rate and make the yield decrease. Meanwhile, the generation of linear polymers in the polymerization process increases the viscosity of the reaction system or generates net structure polymers to hinder the continuous polymerization of monomers, resulting in the decrease of the conversion rate and the continuous improvement of the polymerization degree of the polymers.

[0003] Compared with infrared rays, far infrared rays and other radiation heating electromagnetic waves, the penetration, selective heating and non-ionization characteristics of microwaves rapidly catalyze the application of microwave technology in the field of organic synthesis. Microwave is a special high-frequency energy. In a polar solvent system, microwave energy has strong penetration and can accelerate the vigorous movement of solvent and solute molecules and also can have a deep heating effect on the molecules in the system, i.e. a "thermal effect", so that the reaction can be completed in a short time. In solution polymerization, the use of the microwave method can make the polymerization completed in a short time and obtain polymers with a large molecular weight, which can overcome the defects of the traditional heating method.

[0004] The application rapidly prepares a polyacrylamide-based room-temperature phosphorescent polymer film by a microwave radiation method. The solvent does not need to be water-free and the polymerization can be completed in an air atmosphere. The groups (beta-diketone, fluorine atom, etc.) in the beta-diketone ligand (4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedione or trifluoro-1-(2-furyl)-1,3-butanedione) in the system interact with the polymer, so that the polymer chains are better aggregated, the molecular chain movement is more effectively limited and non-radiative transition is inhibited, thereby realizing phosphorescent emission. SUMMARY

[0005] The application aims to provide a microwave radiation method for preparing a polyacrylamide-based room-temperature phosphorescent polymer film.

[0006] The technical solution adopted to achieve the purpose of this invention is as follows:

[0007] Acrylamide monomer, ammonium persulfate initiator, and β-diketone ligand were added to a round-bottom flask and dissolved in a mixed solvent of deionized water and acetonitrile. The mass ratio of monomer, initiator, ligand, and solvent in the system was 100:0.5~1.2:0.5~1:800~1500. The flask was placed in a microwave chemical reactor and microwave refluxed at a certain microwave power for 3~15 min. After cooling to room temperature, the flask was precipitated with methanol, filtered, and the filter cake was thoroughly washed with methanol. The resulting colloidal solution was dissolved in deionized water and uniformly coated onto a polytetrafluoroethylene plate or a silicone plate. The solution was dried at 40~50℃ to obtain a room temperature phosphorescent polymer film based on polyacrylamide.

[0008] The β-diketone ligand is 4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedione or trifluoro-1-(2-furanyl)-1,3-butanedione.

[0009] The volume ratio of the deionized water and acetonitrile mixed solvent is 10:1~1.5.

[0010] The microwave output power of the microwave reactor is 50W~750W.

[0011] Compared with existing technologies, the present invention has the following significant advantages:

[0012] The polymer films prepared according to this invention emit blue or blue-green fluorescence under 254nm or 365nm ultraviolet light irradiation. After the ultraviolet light is extinguished, they exhibit a strong green afterglow and a long afterglow time at room temperature. The polymer phosphorescent material containing 4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedione has an afterglow time of up to 7.5 seconds. Furthermore, the preparation method is simple and convenient, the preparation conditions are mild, the condenser is directly connected to the atmosphere during the reaction process, no inert gas protection is required, the solvent and raw materials do not require special treatment, the raw materials are readily available, and the preparation is rapid using a microwave chemical reactor, with polymerization completed in just a few minutes. The phosphorescent material prepared by this invention is non-toxic, non-polluting, free of heavy metals and halogens, has good water solubility, and has broad application prospects. Attached Figure Description

[0013] Figure 1 The fluorescence excitation and emission spectra of the room-temperature phosphorescent polymer film based on polyacrylamide prepared in Example 1 are shown.

[0014] Figure 2 The delayed emission spectrum of the room-temperature phosphorescent polymer film based on polyacrylamide prepared in Example 1 is shown.

[0015] Figure 3 The fluorescence excitation and emission spectra of the room-temperature phosphorescent polymer film based on polyacrylamide prepared in Example 2 are shown.

[0016] Figure 4 The image shows the delayed emission spectrum of the room-temperature phosphorescent polymer film based on polyacrylamide prepared in Example 2. Detailed Implementation

[0017] The present invention will be further described below through specific embodiments, but these specific embodiments do not limit the scope of protection of the present invention in any way. Example 1

[0018] 1 g of acrylamide, 0.009 g of ammonium persulfate, and 0.007 g of 4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedione were added to a round-bottom flask and dissolved in a mixture of 9 mL of deionized water and 1 mL of acetonitrile. The mixture was placed in a microwave chemical reactor and microwaved under reflux at 600 W for 8 min. After cooling to room temperature, the polymer was precipitated with methanol and filtered to obtain the polymer. The polymer was then washed several times with methanol to remove unreacted small molecules. The resulting colloidal solution was dissolved in 15 mL of deionized water and uniformly coated onto a polytetrafluoroethylene plate or a silicone plate. The solution was dried at 40-50 °C to obtain a room-temperature phosphorescent polymer film based on polyacrylamide.

[0019] The prepared polymer film exhibited blue luminescence under 254nm and 365nm ultraviolet light irradiation. Figure 1 The images show the fluorescence excitation and emission spectra of the prepared polymer. Blue light emission at 440 nm was observed under excitation at wavelengths of 267 nm and 365 nm.

[0020] After irradiation with 254nm and 365nm ultraviolet lamps and then the light source was turned off, both exhibited a bright green afterglow, with afterglow times of 7 seconds and 7.5 seconds, respectively.

[0021] Figure 2 This is the delayed emission spectrum of the polymer film, with the delayed emission wavelength at 545 nm, which is green light. Example 2

[0022] Add 1g acrylamide, 0.01g ammonium persulfate, and 0.0065g trifluoro-1-(2-furanyl)-1,3-butanedione to a round-bottom flask, dissolve them in a mixture of 8mL deionized water and 2mL acetonitrile, place the flask in a microwave chemical reactor, and microwave reflux at 375W for 11min. After cooling to room temperature, precipitate the polymer with methanol, filter to obtain the polymer, wash the polymer several times with methanol to remove unreacted small molecules, dissolve the resulting colloidal solution in 15mL deionized water, and uniformly coat it onto a polytetrafluoroethylene plate or silicone plate. Dry at 40~50℃ to obtain a room temperature phosphorescent polymer film based on polyacrylamide.

[0023] The prepared polymer film exhibited blue-green light and blue light under 254nm and 365nm ultraviolet light, respectively. Figure 3 The images show the fluorescence excitation and emission spectra of the prepared polymer. Under 254 nm excitation, the emission wavelength is 493 nm, and under 365 nm excitation, the emission wavelengths are 436 nm and 493 nm.

[0024] After irradiation with 254nm and 365nm ultraviolet lamps, the afterglow time was 2 seconds and 3.5 seconds, respectively, when the light source was turned off.

[0025] Figure 4 The image shows the delayed emission spectrum of the polymer film. In the emission spectrum with a delay time of 1 ms, the emission wavelength at 254 nm is 493 nm, with a blue-green afterglow, and the emission wavelength at 365 nm is 519 nm, with a green afterglow.

Claims

1. A method for preparing a room temperature phosphorescent polymeric film based on polyacrylamide, characterized by In a round bottom flask, acrylamide monomer, ammonium persulfate initiator and β-diketone ligand are added, and a mixed solvent of deionized water and acetonitrile is added for dissolution, the mass ratio of monomer, initiator, ligand and solvent in the round bottom flask system is 100:0.5~1.2:0.5~1:800~1500, placed in a microwave chemical reactor, microwave refluxed at a certain microwave power for 3~15min, cooled to room temperature, precipitated with methanol, filtered, the filter cake is washed with methanol, then dissolved in deionized water to obtain a colloidal solution, uniformly coated on a polytetrafluoroethylene plate or a silica gel plate, dried at 40~50℃ to obtain a room temperature phosphorescent polymer film based on polyacrylamide; The β-diketone ligand is 4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedione or trifluoro-1-(2-furyl)-1,3-butanedione; The microwave output power of the microwave reactor is 50W~750W.

2. The method of claim 1, wherein the polyacrylamide-based room temperature phosphorescent polymer film is prepared by the following steps: (1) dissolving the polyacrylamide-based room temperature phosphorescent polymer in a solvent to prepare a solution; (2) coating the solution on a substrate to form a film; and (3) drying the film. The volume ratio of the mixed solvent of deionized water and acetonitrile is 10:1~1.5.

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