A photoinitiating system suitable for blue light, and a preparation method and application thereof
By using a blue light photoinitiation system combining boron-containing conjugated aromatic hydrocarbon fluorescent dyes and iodonium salts, the safety and energy consumption issues of ultraviolet lamps in photopolymerization have been solved, achieving a highly efficient and uniform polymerization reaction, which is suitable for fluorescence sensing, photopolymerization, and photocatalysis.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- GUANGDONG UNIV OF TECH
- Filing Date
- 2024-09-04
- Publication Date
- 2026-05-29
AI Technical Summary
In existing photopolymerization technologies, ultraviolet lamps pose safety hazards, consume a lot of energy, and have poor penetration, leading to uneven polymerization.
A blue light photoinitiation system was developed using a boron-containing conjugated aromatic hydrocarbon fluorescent dye as a photosensitizer and iodonium salt. Free radicals were generated under blue LED irradiation to initiate polymerization, thus avoiding the use of ultraviolet light.
It achieves safe and efficient polymerization reactions, improves polymerization uniformity and penetration, reduces energy consumption, and is suitable for fields such as fluorescence sensing, photopolymerization, and photocatalysis.
Smart Images
Figure CN119119329B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of organic photosensitizer materials technology, and more specifically, to a photoinitiating system suitable for blue light, its preparation method and application. Background Technology
[0002] Photopolymerization is a technology that uses light as an energy source to rapidly convert liquid resins into solid polymers. Compared to traditional thermal polymerization processes, photopolymerization offers extremely high efficiency, economic benefits, and environmental advantages, continuously expanding the market for photopolymer materials. These advantages and benefits can be attributed to the use of light energy, rather than heat energy, to induce the polymerization reaction. Photopolymerization requires significantly less energy; the energy used in polymerization is a fraction of that in traditional thermal systems, and the process can provide high production rates at low curing temperatures. Photopolymerization offers tremendous spatial and temporal control over the reaction; the initiating light can be directed to the location of interest within the system, and switching is easily controlled. As a highly efficient, low-cost, and green technology, photopolymerization is involved in industries such as general coatings, adhesives, composite materials, imaging science, circuit board manufacturing, and chip fabrication. It also has wide applications in the biomedical field, using stereolithography to create three-dimensional models. Advanced applications of photopolymerization have expanded photocuring from common thin-film applications to the curing of thick composite materials, and from deep ultraviolet (UV) or near-visible wavelengths to visible or infrared wavelengths in biological applications. Currently, photopolymerization has become a very attractive alternative, offering a wide range of advantages and benefits that make it highly promising.
[0003] Currently, photopolymerization processes in industrial production mostly use ultraviolet (UV) lamps as the light source. UV lamps emit relatively high light intensity, have a limited lifespan, consume a lot of energy, and can be harmful to human health. Furthermore, the shorter wavelength of UV light has poor penetration into polymers, making it easy for the degree of polymerization to be uneven in polymers of a certain thickness and in large quantities. With the development of LED technology, visible light LEDs are gradually becoming a potential light source for photopolymerization. Due to their advantages such as low operating temperature, energy saving, environmental friendliness, and long lifespan, they have been widely used in 3D printing and the food and pharmaceutical industries.
[0004] Therefore, developing a photoinitiation system that can undergo photopolymerization under blue light is a technical problem that urgently needs to be solved by those skilled in the art.
[0005] Application content
[0006] To overcome at least one of the problems existing in the prior art, this application provides a photoinitiating system suitable for blue light. This photoinitiating system consists of a photosensitizer and a co-initiator. The photosensitizer provided in this visible light initiator system is a boron-containing conjugated aromatic hydrocarbon fluorescent dye. This photosensitizer and iodonium salt can generate phenyl radicals under blue LED light irradiation, initiating the polymerization of acrylates. It exhibits strong absorption in the 460nm wavelength range, which can be well matched with blue LED light sources, thus solving the safety issues arising from the need for ultraviolet light for photoinitiators in the prior art.
[0007] Another objective of this application is to provide a method for preparing the aforementioned boron-containing conjugated aromatic hydrocarbon fluorescent dye.
[0008] Another objective of this application is to provide the application of the above-mentioned photoinitiation system suitable for blue light in fluorescence sensing, photopolymerization or photocatalysis.
[0009] To solve the above-mentioned technical problems, the technical solution adopted in this application is:
[0010] A photoinitiation system suitable for blue light includes a photosensitizer and a co-initiator, wherein the photosensitizer is a boron-containing conjugated aromatic hydrocarbon fluorescent dye, and wherein the boron-containing conjugated aromatic hydrocarbon fluorescent dye has the chemical structure shown in formula (I):
[0011]
[0012] In the formula, R can be selected from one of the following structural formulas:
[0013]
[0014]
[0015] Preferably, the boron-containing conjugated aromatic hydrocarbon fluorescent dye is selected from any of the following structural formulas:
[0016]
[0017] More preferably, R is selected from the following structural formula:
[0018] Preferably, the iodonium is
[0019] Preferably, the method further includes a polymeric monomer, wherein the polymeric monomer is selected from:
[0020] This application also provides a method for preparing the above-mentioned boron-containing conjugated aromatic hydrocarbon fluorescent dye, the method comprising the following steps:
[0021] S1. Preparation of intermediate product 1:
[0022] 3,6-Di-tert-butylcarbazole and potassium carbonate were dissolved in DMF and stirred at room temperature. Then, 5-bromo-1,3-difluoro-2-iodobenzene was added, and the mixture was stirred at 140°C for 12 h. After the reaction was completed, the mixture was concentrated under reduced pressure and purified by column chromatography to obtain a white solid intermediate 1. The structural formula of intermediate 1 is shown below:
[0023]
[0024] S2. Preparation of intermediate product 2
[0025] Intermediate 1 from step S1 was subjected to argon purging in a dry o-xylene solution. At low temperature, n-butyllithium was slowly added to the solution, and the reaction was carried out at room temperature for 1 hour. Then, boron tribromide was slowly added at 0°C, and the mixture was stirred at room temperature for 1 hour. Next, N,N-diisopropylamine was added at 0°C, and the mixture was further stirred at 160°C for 24 hours. After the reaction was complete, the mixture was cooled to room temperature, quenched with water, concentrated under reduced pressure, and purified by column chromatography (neutral alumina, petroleum ether) to obtain a yellow solid intermediate 2. The structural formula of intermediate 2 is shown below:
[0026]
[0027] S3. Preparation of intermediate product 3:
[0028] Under an inert gas atmosphere, intermediate 2 from step 2, pinacol diborate, 1,1'-bis(diphenylphosphine)ferrocene palladium dichloride, and potassium acetate were dissolved in ultra-dry 1,4-dioxane. The mixture was stirred at 100°C. After the reaction was complete, it was cooled to room temperature, and the reaction mixture was added to a large amount of water. Extraction was performed with dichloromethane, and the organic layer was dried on anhydrous sodium sulfate. The crude product was filtered, evaporated, and purified by silica gel column chromatography. The purified product was eluted to obtain a yellow solid intermediate 3, the structural formula of which is shown below:
[0029]
[0030] S4. Preparation of the target product MR-MR
[0031] Under inert gas protection, intermediate product 2 obtained in step S2, intermediate product 3 obtained in step S3, tetrakis(triphenylphosphine)palladium, and potassium carbonate were dissolved in a mixed solution of toluene, ethanol, and water. The mixture was stirred at 85°C. After the reaction was completed, the mixture was cooled to room temperature, and the reaction mixture was added to a large amount of water and extracted with dichloromethane. The organic layer was dried on anhydrous sodium sulfate. The crude product was filtered, evaporated, and purified by silica gel column chromatography. After elution and purification, an orange-yellow solid MR-MR was obtained.
[0032] Preferably, in step S1, the molar ratio of 3,6-di-tert-butylcarbazole, potassium carbonate, and 5-bromo-1,3-difluoro-2-iodobenzene is 5:5:2.
[0033] Preferably, the molar ratio of intermediate product 1 to boron tribromide in step S2 is 2:3.
[0034] Preferably, in step S1, the column chromatography method uses basic alumina, and the eluent is dichloromethane and petroleum ether, with a volume ratio of dichloromethane to petroleum ether of 1:4.
[0035] Preferably, in step S2, the column chromatography method uses neutral alumina and the eluent is petroleum ether.
[0036] In the photoinitiating system suitable for blue light provided in this application, the photosensitizer is the above-mentioned bis(dipyrrole) zinc complex, and the co-initiator is iodonium salt.
[0037] More preferably, the iodonium salt is selected from...
[0038] This application also provides the application of the above-mentioned photoinitiation system suitable for blue light in fluorescence sensing, photopolymerization or photocatalysis.
[0039] Compared with the prior art, the beneficial effects of this application are:
[0040] The boron-containing conjugated aromatic hydrocarbon fluorescent dye photosensitizer provided in this application, suitable for blue light photoinitiation systems, is a photosensitizer with strong blue light absorption and free radical generation phenomena synthesized by introducing suitable electron donors or acceptors, with boron-nitrogen MR molecules as the core. It is combined with iodonium salts as co-initiators to form a photoinitiation system. In this blue light initiator system, under blue LED irradiation, the photosensitizer absorbs photon energy and undergoes an electronic transition to the excited singlet state, then jumps to the excited triplet state via intersystem crossing. The photosensitizer molecule in the excited triplet state has high reactivity and can generate free radicals through energy transfer, electron transfer, or proton transfer with iodonium salt co-initiators, initiating monomer polymerization. This solves the safety issues associated with the use of ultraviolet light for photoinitiators in existing technologies. Applications based on the dimer boron-nitrogen MR molecules in fluorescence sensing, photopolymerization, or photocatalysis have significant economic value. Attached Figure Description
[0041] Figure 1 For the monomeric DMA in the MR-MR / Iod system under LED@460nm irradiation 1 HNMR spectrum.
[0042] Figure 2 The conversion rate of monomeric DMA in the MR-MR / Iod system under LED@460nm irradiation.
[0043] Figure 3 The time-dependent absorption spectrum of the MR-MR / Iod system under LED illumination at 460 nm.
[0044] Figure 4 The time-dependent emission spectrum of the MR-MR / Iod system under LED illumination at 460 nm is shown.
[0045] Figure 5 The ESR spectrum of the MR-MR / Iod / phenyl-n-tert-butanol (PBN) system under LED @ 460 nm irradiation. Detailed Implementation
[0046] The embodiments of this application will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of this application. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.
[0047] It should be noted that:
[0048] Unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions.
[0049] In this application, unless otherwise stated, the various reactions or operation steps may be performed sequentially or in a particular order. Preferably, the reaction methods described herein are performed sequentially.
[0050] Unless otherwise stated, the technical and scientific terms used herein have the same meanings as those familiar to a person skilled in the art. Furthermore, any methods or materials similar to or equivalent to those described herein may also be used in this application.
[0051] This application provides a photoinitiating system suitable for blue light, comprising a photosensitizer and a co-initiator, wherein the photosensitizer is a boron-containing conjugated aromatic hydrocarbon fluorescent dye, and wherein the boron-containing conjugated aromatic hydrocarbon fluorescent dye has the chemical structure shown in formula (I):
[0052]
[0053] In the formula, R can be selected from one of the following structural formulas:
[0054]
[0055]
[0056] The boron-containing conjugated aromatic hydrocarbon fluorescent dye photosensitizer in the blue light photoinitiation system provided in this application is a photosensitizer with strong blue light absorption and free radical generation, synthesized by introducing suitable electron donors or acceptors, with boron-nitrogen MR molecules as the core. It is combined with the co-initiator iodonium salt to form a photoinitiation system. In the blue light initiator system of this application, under blue LED irradiation, the photosensitizer absorbs photon energy and undergoes an electronic transition to the excited singlet state, and then undergoes intersystem crossing to the excited triplet state. Photosensitizer molecules in the excited triplet state have high reactivity and can generate free radicals through energy transfer, electron transfer, or proton transfer with iodonium salt co-initiators, initiating monomer polymerization. This solves the safety issues caused by the need for ultraviolet light in existing photoinitiators. In other words, it solves the problem that photopolymerization processes often use ultraviolet lamps (UV) as the light source, but UV lamps emit relatively high light intensity, have limited lifespan, consume a lot of energy, and can be harmful to human health. In addition, the short wavelength of UV light has poor penetration in polymers, which can easily lead to uneven polymerization degree in polymerization reactions with a certain thickness and large dosage.
[0057] Applications based on dimer boron nitrogen MR molecules in fluorescence sensing, photopolymerization, or photocatalysis have significant economic value.
[0058] The blue light used in the photoinitiator system of this application is a lower-energy wavelength light, which is safer than UV light, the main light source currently represented in photocuring literature. Secondly, blue light penetrates deeper than UV light, thus enabling more complete curing, especially for polymerization reactions involving fillers.
[0059] In some preferred embodiments, the boron-containing conjugated aromatic hydrocarbon fluorescent dye is selected from any of the following structural formulas:
[0060]
[0061] In some preferred embodiments, R is selected from the following structural formula:
[0062] In some preferred embodiments, the method further includes a polymeric monomer, wherein the polymeric monomer is selected from:
[0063] This application also provides a method for preparing the above-mentioned boron-containing conjugated aromatic hydrocarbon fluorescent dye, the method comprising the following steps:
[0064] S1. Preparation of intermediate product 1:
[0065] 3,6-Di-tert-butylcarbazole and potassium carbonate were dissolved in DMF and stirred at room temperature. Then, 5-bromo-1,3-difluoro-2-iodobenzene was added, and the mixture was stirred at 140°C for 12 h. After the reaction was completed, the mixture was concentrated under reduced pressure and purified by column chromatography to obtain a white solid intermediate 1. The structural formula of intermediate 1 is shown below:
[0066]
[0067] S2. Preparation of intermediate product 2
[0068] Intermediate 1 from step S1 was subjected to argon purging in a dry o-xylene solution. At low temperature, n-butyllithium was slowly added to the solution, and the reaction was carried out at room temperature for 1 hour. Then, boron tribromide was slowly added at 0°C, and the mixture was stirred at room temperature for 1 hour. Next, N,N-diisopropylamine was added at 0°C, and the mixture was further stirred at 160°C for 24 hours. After the reaction was complete, the mixture was cooled to room temperature, quenched with water, concentrated under reduced pressure, and purified by column chromatography (neutral alumina, petroleum ether) to obtain a yellow solid intermediate 2. The structural formula of intermediate 2 is shown below:
[0069]
[0070] S3. Preparation of intermediate product 3:
[0071] Under an inert gas atmosphere, intermediate 2 from step 2, pinacol diborate, 1,1'-bis(diphenylphosphine)ferrocene palladium dichloride, and potassium acetate were dissolved in ultra-dry 1,4-dioxane. The mixture was stirred at 100°C. After the reaction was complete, it was cooled to room temperature, and the reaction mixture was added to a large amount of water. Extraction was performed with dichloromethane, and the organic layer was dried on anhydrous sodium sulfate. The crude product was filtered, evaporated, and purified by silica gel column chromatography. The purified product was eluted to obtain a yellow solid intermediate 3, the structural formula of which is shown below:
[0072]
[0073]
[0074] S4. Preparation of the target product MR-MR
[0075] Under inert gas protection, intermediate product 2 obtained in step S2, intermediate product 3 obtained in step S3, tetrakis(triphenylphosphine)palladium, and potassium carbonate were dissolved in a mixed solution of toluene, ethanol, and water. The mixture was stirred at 85°C. After the reaction was completed, the mixture was cooled to room temperature, and the reaction mixture was added to a large amount of water and extracted with dichloromethane. The organic layer was dried on anhydrous sodium sulfate. The crude product was filtered, evaporated, and purified by silica gel column chromatography. After elution and purification, an orange-yellow solid MR-MR was obtained.
[0076] In some preferred embodiments, the molar ratio of 3,6-di-tert-butylcarbazole, potassium carbonate, and 5-bromo-1,3-difluoro-2-iodobenzene in step S1 is 5:5:2.
[0077] In some preferred embodiments, the molar ratio of intermediate product 1 to boron tribromide in step S2 is 2:3.
[0078] In some preferred embodiments, in step S1, the column chromatography method uses basic alumina, and the eluent is dichloromethane and petroleum ether, with a volume ratio of dichloromethane to petroleum ether of 1:4.
[0079] In some preferred embodiments, in step S2, the column chromatography method uses neutral alumina and the eluent is petroleum ether.
[0080] In the photoinitiating system suitable for blue light provided in this application, the photosensitizer is the above-mentioned bis(dipyrrole) zinc complex, and the co-initiator is iodonium salt.
[0081] In some preferred embodiments, the iodonium salt is selected from...
[0082] This application also provides the application of the above-mentioned photoinitiating system suitable for blue light in fluorescence sensing, photopolymerization, or photocatalysis.
[0083] The applicant also provides a method for preparing the above-mentioned boron-containing conjugated aromatic hydrocarbon fluorescent dye.
[0084] The preparation method of the boron-containing conjugated aromatic hydrocarbon fluorescent dye in this application will be described in detail below with specific embodiments.
[0085] Example 1
[0086] A boron-containing conjugated aromatic hydrocarbon fluorescent dye has the molecular structure described in the following formula and is named MR-MR.
[0087]
[0088] The preparation method of the boron-containing conjugated aromatic hydrocarbon fluorescent dye MR-MR includes the following steps:
[0089] Step S1: Preparation of intermediate product 1
[0090] 3,6-Di-tert-butylcarbazole (13.97 g, 50.0 mmol) and potassium carbonate (6.90 g, 50.0 mmol) were dissolved in DMF (200 mL). After stirring at room temperature for 30 minutes, 5-bromo-1,3-difluoro-2-iodobenzene (6.38 g, 20.0 mmol) was added, and the mixture was stirred at 140 °C for 12 h. After the reaction was complete, the mixture was concentrated under reduced pressure and purified by column chromatography (silica gel, dichloromethane / petroleum ether, 1 / 4, v / v) to give 12.57 g of white solid. (Yield: 75%) The reaction equation is as follows:
[0091]
[0092] Step S2: Preparation of intermediate product 2
[0093] Intermediate product 1 (5.03 g, 6.0 mmol) from step S11 was purged with argon in a dry o-xylene (120 mL) solution. At -30 °C, n-butyllithium (4.1 mL, 6.6 mmol) was slowly added to the solution, and the reaction was allowed to proceed at room temperature for 1 h. Then, boron tribromide (2.25 g, 9.0 mmol) was slowly added at 0 °C, and the mixture was stirred at room temperature for 1 h. Next, N,N-diisopropylamine (2.4 mL, 13.5 mmol) was added at 0 °C, and the mixture was further stirred at 160 °C for 24 h. After the reaction was complete, the mixture was cooled to room temperature, quenched with water, concentrated under reduced pressure, and purified by column chromatography (neutral alumina, petroleum ether) to obtain 1.32 g of a yellow solid (yield: 31%).
[0094] The reaction equation is as follows:
[0095]
[0096] Step S3: Preparation of intermediate product 3
[0097] Under nitrogen protection, the target product from step 2 (0.72 g, 1.0 mmol), pinacol diborate (0.38 g, 1.5 mmol), 1,1'-bis(diphenylphosphine)ferrocene palladium dichloride (0.04 g, 0.05 mmol), and potassium acetate (0.29 g, 3.0 mmol) were dissolved in ultra-dry 1,4-dioxane (15 mL). The mixture was stirred at 100 °C for 24 h. After the reaction was complete, the mixture was cooled to room temperature, and the reaction mixture was added to a large volume of water and extracted with dichloromethane. The organic layer was dried over anhydrous sodium sulfate. The crude product was filtered, evaporated, and purified by silica gel column chromatography (petroleum ether / dichloromethane, 4 / 1, v / v), yielding 0.51 g of a yellow solid (yield: 67%).
[0098] The reaction equation is as follows:
[0099]
[0100] S4. Preparation of the target product MR-MR
[0101] Under nitrogen protection, the target product of step 2 (0.36 g, 0.5 mmol), the target product of step 3 (0.38 g, 0.5 mmol), tetrakis(triphenylphosphine)palladium (0.008 g, 0.005 mmol), and potassium carbonate (0.27 g, 2.0 mmol) were dissolved in a mixed solution of toluene (14 mL), ethanol (4 mL), and water (2 mL), and stirred at 85 °C for 48 hours. After the reaction was completed, the mixture was cooled to room temperature, and the reaction mixture was added to a large amount of water and extracted with dichloromethane. The organic layer was dried over anhydrous sodium sulfate. The crude product was filtered, evaporated, and purified by silica gel column chromatography (petroleum ether / dichloromethane, 4 / 1, v / v), eluting to obtain 0.25 g of orange-yellow solid (yield: 40%). The reaction equation is as follows:
[0102]
[0103] Photopolymerization Experiment
[0104] A photoinitiator system consisting of 0.6 wt% MR-MR and 0.4 wt% Iod was used. 3 mL of DMA monomer was added, and the mixture was ultrasonically mixed in the dark to remove oxygen. Under a nitrogen atmosphere, the mixture was evenly distributed into five small sample vials, and the irradiation time was controlled. The vials were irradiated for 0 s, 10 s, 20 s, 30 s, and 40 s under a 460 nm blue LED. After irradiation, the monomer showed varying degrees of solidification. Each irradiated sample was dissolved in trimethylbenzene and deuterated chloroform as an internal standard. 1 The monomer conversion rate was obtained by comparison with HNMR nuclear magnetic resonance.
[0105] Monomer conversion test method: using trimethylbenzene as an internal standard (integral signal (6.76–6.82 ppm) set to 1). Specific hydrogen atoms (H+) in the DMA monomer were selected. A This was used to monitor the changes in monomers under red light irradiation. The integral value of HA at the beginning (0s) was H0, and H0 was calculated after t seconds of blue light treatment. A The integral value is H t .
[0106] The conversion formula is:
[0107] Figure 1 For the monomeric DMA in the MR-MR / Iod system under LED@460nm irradiation 1 HNMR spectrum.
[0108] from Figure 1It can be seen that the viscosity of the sample gradually increases with increasing irradiation time of the blue LED. After adding the MR-MR / Iod system, the viscosity increases within 40 seconds. 1 The conversion rate monitored by HNMR is almost 100%, and the curing time is significantly shortened and the degree of curing is improved compared with commercial UV lamps of the same power.
[0109] Figure 2 The conversion rate of monomeric DMA in the MR-MR / Iod system under LED@460nm irradiation.
[0110] Table 1: Equivalent conversion rate of DMA in the MR-MR / Iod system under LED@460nm irradiation
[0111]
[0112] from Figure 2 It can be seen that the polymerization reaction begins immediately after 460nm red light radiation, and the curing rate accelerates after 10s and the polymerization is basically completed within 40s.
[0113] Photochemical reactivity
[0114] The photosensitizer molecule MR-MR and the co-initiator Iod were respectively formulated to a concentration of 1*10. -5 M and 5*10 -5 A DCM solution of M was injected into a cuvette with an optical path length of 1 cm and irradiated with a 460 nm LED light source for a certain period of time. The UV-Vis absorption spectra and emission spectra after irradiation for 0 s, 10 s, 20 s, 30 s, 40 s, and 50 s were measured to observe the decomposition of the photosensitizer molecules with increasing irradiation time. The test results are as follows: Figure 3 and 4 As shown, the photosensitizer molecules exhibit rapid degradation under light irradiation, indicating that in the red light curing system, the photosensitizer molecules can generate free radicals through energy transfer and electron transfer with iodonium salt co-initiators, thereby initiating monomer polymerization.
[0115] Figure 3 and Figure 4 The time-dependent absorption and emission spectra of the MR-MR / Iod system under LED @460nm illumination from 0-40s are shown. Figure 3 and Figure 4 It can be seen that the photosensitizer molecules exhibit rapid degradation under light irradiation, which indicates that the photosensitizer molecules can generate free radicals through energy transfer and electron transfer with iodonium salt co-initiators in the blue light curing system, thereby initiating monomer polymerization.
[0116] Electron spin trapping experiment
[0117] The interaction between MR-MR molecules and Iod involves an electron transfer process, generating aryl radicals. The formed radicals can be verified using ESR spin trapping (ESR-ST). Irradiation of the MR-MR / Iod / phenyl-n-tert-butanilide (PBN) system with an LED at 460 nm yielded a strong signal, such as... Figure 5 As shown. In the MR-MR / Iod / phenyl-n-tert-butanol (PBN) system, nitrogen (α N ) and hydrogen (α) H The ultrafine pyrolysis constants of PBN and Iod are 15 and 2.7 G, respectively, which can be attributed to PBN and phenyl adducts. Therefore, MR-MR and Iod undergo electron transfer upon photoexcitation to form phenyl radicals, initiating polymerization.
[0118] This application discloses a photoinitiating system suitable for blue light, comprising a photosensitizer and a co-initiator, wherein the photosensitizer is a boron-containing conjugated aromatic hydrocarbon fluorescent dye, and wherein the boron-containing conjugated aromatic hydrocarbon fluorescent dye has the chemical structure shown in formula (I):
[0119]
[0120] In the formula, R can be selected from one of the following structural formulas:
[0121]
[0122] In summary, the photoinitiating system suitable for blue light provided in this application comprises a photosensitizer and a co-initiator. The photosensitizer is MR-TADF, composed of boron and nitrogen atoms as the core and multiple carbazole compounds on the periphery. Combined with the co-initiator iodonium salt, it forms a photoinitiating system that efficiently initiates the polymerization of acrylate monomers under blue LED irradiation. The photosensitizer provided in this application exhibits strong absorption in the 460nm wavelength range, which is well-matched with blue LED light sources. This photosensitizer, even with the addition of iodonium salt, can efficiently initiate the polymerization of acrylate monomers under blue LED irradiation, solving the problem of avoiding the use of photosensitizers containing transition metals or heavy atoms. When combined with iodonium salt, even with a small dosage, the double bond conversion rate of the monomer can reach over 90%.
[0123] The boron-containing conjugated aromatic hydrocarbon fluorescent dye photosensitizer in the blue light photoinitiation system provided in this application is a photosensitizer with strong blue light absorption and free radical generation, synthesized by introducing suitable electron donors or acceptors, with boron-nitrogen MR molecules as the core. It is combined with the co-initiator iodonium salt to form a photoinitiation system. In the blue light initiator system of this application, under blue LED irradiation, the photosensitizer absorbs photon energy and undergoes an electronic transition to the excited singlet state, and then undergoes intersystem crossing to the excited triplet state. Photosensitizer molecules in the excited triplet state have high reactivity and can generate free radicals through energy transfer, electron transfer, or proton transfer with iodonium salt co-initiators, initiating monomer polymerization. This solves the safety issues caused by the need for ultraviolet light in existing photoinitiators. In other words, it solves the problem that photopolymerization processes often use ultraviolet lamps (UV) as the light source, but UV lamps emit relatively high light intensity, have limited lifespan, consume a lot of energy, and can be harmful to human health. In addition, the short wavelength of UV light has poor penetration in polymers, which can easily lead to uneven polymerization degree in polymerization reactions with a certain thickness and large dosage.
[0124] Applications based on dimer boron nitrogen MR molecules in fluorescence sensing, photopolymerization, or photocatalysis have significant economic value.
[0125] The blue light used in the photoinitiator system of this application is a lower-energy wavelength light, which is safer than UV light, the main light source currently represented in photocuring literature. Secondly, blue light penetrates deeper than UV light, thus enabling more complete curing, especially for polymerization reactions involving fillers.
[0126] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.
[0127] Although several embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.
Claims
1. A photoinitiating system suitable for blue light, comprising a photosensitizer and a co-initiator, characterized in that: The photosensitizer is a boron-containing conjugated aromatic hydrocarbon fluorescent dye, wherein the co-initiator is an iodonium salt, and the iodonium salt is... The boron-containing conjugated aromatic hydrocarbon fluorescent dye has the following structural formula: 。 2. The photoinitiating system suitable for blue light as described in claim 1, characterized in that, A method for preparing boron-containing conjugated aromatic hydrocarbon fluorescent dyes includes the following steps: S1. Preparation of intermediate product 1: 3,6-Di-tert-butylcarbazole and potassium carbonate were dissolved in DMF and stirred at room temperature. Then, 5-bromo-1,3-difluoro-2-iodobenzene was added, and the mixture was stirred at 140°C for 12 h. After the reaction was completed, the mixture was concentrated under reduced pressure and purified by column chromatography to obtain a white solid intermediate 1. The structural formula of intermediate 1 is shown below: ； S2. Preparation of intermediate product 2 Intermediate 1 from step S1 was subjected to argon purging in a dry o-xylene solution. At low temperature, n-butyllithium was slowly added to the solution, and the reaction was carried out at room temperature for 1 hour. Then, boron tribromide was slowly added at 0°C, and the mixture was stirred at room temperature for 1 hour. Next, N,N-diisopropylamine was added at 0°C, and the mixture was further stirred at 160°C for 24 hours. After the reaction was completed, the mixture was cooled to room temperature, quenched with water, concentrated under reduced pressure, and purified by column chromatography to obtain a yellow solid intermediate 2. The structural formula of intermediate 2 is shown below: ； ； S3. Preparation of intermediate product 3: Under an inert gas atmosphere, intermediate 2 from step 2, pinacol diborate, 1,1'-bis(diphenylphosphine)ferrocene palladium dichloride, and potassium acetate were dissolved in ultra-dry 1,4-dioxane. The mixture was stirred at 100°C. After the reaction was complete, it was cooled to room temperature, and the reaction mixture was added to a large amount of water. Extraction was performed with dichloromethane, and the organic layer was dried on anhydrous sodium sulfate. The crude product was filtered, evaporated, and purified by silica gel column chromatography. The purified product was eluted to obtain a yellow solid intermediate 3, the structural formula of which is shown below: ； ； S4. Preparation of the target product MR-MR Under inert gas protection, intermediate product 2 obtained in step S2, intermediate product 3 obtained in step S3, tetrakis(triphenylphosphine)palladium, and potassium carbonate were dissolved in a mixed solution of toluene, ethanol, and water. The mixture was stirred at 85°C. After the reaction was completed, the mixture was cooled to room temperature, and the reaction mixture was added to a large amount of water. The mixture was extracted with dichloromethane, and the organic layer was dried on anhydrous sodium sulfate. The crude product was filtered, evaporated, and purified by silica gel column chromatography. After elution and purification, an orange-yellow solid MR-MR was obtained.
3. The photoinitiating system suitable for blue light according to claim 2, characterized in that: In step S1 of the method for preparing boron-containing conjugated aromatic hydrocarbon fluorescent dyes, the molar ratio of 3,6-di-tert-butylcarbazole, potassium carbonate, and 5-bromo-1,3-difluoro-2-iodobenzene is 5:5:
2.
4. The photoinitiating system suitable for blue light according to claim 2, characterized in that: In step S2 of the method for preparing boron-containing conjugated aromatic hydrocarbon fluorescent dyes, the molar ratio of intermediate product 1 to boron tribromide is 2:
3.
5. The photoinitiating system suitable for blue light according to claim 2, characterized in that: In step S1 of the method for preparing boron-containing conjugated aromatic hydrocarbon fluorescent dyes, the column chromatography method uses basic alumina, and the eluent is dichloromethane and petroleum ether, with a volume ratio of dichloromethane to petroleum ether of 1:
4.
6. The photoinitiating system suitable for blue light according to claim 2, characterized in that: In step S2 of the method for preparing boron-containing conjugated aromatic hydrocarbon fluorescent dyes, the column chromatography method uses neutral alumina and the eluent is petroleum ether.
7. The application of the photoinitiating system suitable for blue light as described in claim 1 in fluorescence sensing, photopolymerization or photocatalysis.