Photo-initiation system suitable for blue light as well as preparation method and application of photo-initiation system

Abstract

The invention provides a photo-initiation system suitable for blue light as well as a preparation method and application of the photo-initiation system, and relates to the field of photo-initiators. The visible light initiator system comprises a photosensitizer and a co-initiator, the photosensitizer is MR-TADF and is composed of a plurality of carbazole compounds with boron and nitrogen atoms as the core and the periphery, the photosensitizer and the co-initiator iodonium salt are combined to form a photo-initiation system, and the polymerization of acrylate monomers is efficiently initiated under the irradiation of a blue light LED. The photosensitizer provided by the invention has strong absorption in the wavelength range of 460mm, and can be well matched with a blue light LED light source. According to the photosensitizer, under the condition that iodonium salt is added, polymerization of acrylate monomers can be efficiently initiated by irradiation of a blue light LED, and the problem that a photosensitizer containing transition metal or heavy atoms is used is solved. When the monomer is compounded with iodonium salt, the double-bond conversion rate of the monomer can reach 90% or above under the condition that the dosage is small.

Description

Technical Field

[0001] The present application relates to the technical field of organic photosensitizer materials, and more specifically, to a photoinitiator system suitable for blue light and a preparation method and application thereof. Background Art

[0002] Photopolymerization technology is a technology that uses light as an energy source to quickly convert liquid resin into solid polymers. Compared with traditional thermal polymerization processes, photopolymerization technology has extremely efficient, economical process and environmental benefits, and has continuously expanded the market for photopolymer materials. These advantages and benefits can be attributed to the use of light energy rather than heat energy to induce polymerization reactions. Photopolymerization requires less energy, and the energy used for polymerization is a small fraction of that in traditional thermal systems. The process can provide efficient production rates at low curing temperatures. Photopolymerization provides great spatial and temporal control over the reaction. The starting light can be directed to the location of interest in the system and is easy to control on and off. As an efficient, low-cost, and green technology, photopolymerization reactions are involved in industries such as general coatings, adhesives, composites, image science, circuit board manufacturing, and chip production. It is also widely used in the biomedical field, where stereolithography methods are used to make three-dimensional models. Advanced applications of photopolymerization have expanded photocuring from general thin film applications to the field of thick composite material curing, and from applications in deep ultraviolet (UV) or near-visible wavelengths to biological applications in visible or infrared wavelengths. At present, photopolymerization has become an attractive alternative. This technology provides a variety of advantages and benefits that make them widely prospective.

[0003] At present, the photopolymerization process in industrial production mostly uses ultraviolet lamps (UV) as light sources. The light intensity emitted by UV lamps is relatively high, and its service life is limited, the energy consumption is large, and it can also cause harm to human health. In addition, the short-wavelength UV light has poor penetration in polymers, which makes it easy to cause uneven polymerization degree of products in polymerization reactions with a certain thickness and a large amount. With the development of LED technology, visible light LEDs have gradually become a potential light source for photocuring. Due to its advantages such as low operating temperature, energy saving and environmental protection, and long service life, it has been widely used in 3D printing and food and medicine fields.

[0004] Therefore, developing a photoinitiator system that can undergo photopolymerization under blue light is a technical problem that needs to be urgently solved by those skilled in the art.

[0005] Application Contents

[0006] In order to overcome at least one problem of the above-mentioned prior art, the present application provides a photoinitiator system suitable for blue light. The photoinitiator system is composed of a photosensitizer and a co-initiator. The photosensitizer provided by the visible light initiator system is a boron-containing conjugated aromatic hydrocarbon fluorescent dye. The photosensitizer and the iodonium salt can generate phenyl radicals under the irradiation of blue LED light, which can initiate the polymerization of acrylates, have strong absorption in the wavelength range of 460mm, and can be well matched with the blue LED light source, which can solve the safety problem caused by the need to use ultraviolet light for photoinitiators in the prior art.

[0007] Another object of the present application is to provide a method for preparing the above-mentioned boron-containing conjugated aromatic hydrocarbon fluorescent dye.

[0008] Another object of the present application is to provide the application of the above-mentioned photoinitiator system suitable for blue light in fluorescence sensing, photopolymerization or photocatalysis.

[0009] In order to solve the above technical problems, the technical solution adopted in this application is:

[0010] A blue light photoinitiator system includes a photosensitizer and a co-initiator, wherein the photosensitizer is a boron-containing conjugated aromatic hydrocarbon fluorescent dye, wherein the boron-containing conjugated aromatic hydrocarbon fluorescent dye has a 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 one of the following structural formulas:

[0016]

[0017] More preferably, the R is selected from the structural formula:

[0018] Preferably, the iodonium is

[0019] Preferably, the polymerizable monomer is also included, and the polymerizable monomer is selected from:

[0020] The present application also provides a method for preparing the above-mentioned boron-containing conjugated aromatic hydrocarbon fluorescent dye, which comprises the following steps:

[0021] S1. Preparation of intermediate 1:

[0022] 3,6-di-tert-butylcarbazole and potassium carbonate were dissolved in DMF, stirred at room temperature, and then 5-bromo-1,3-difluoro-2-iodobenzene was added. The mixture was stirred at 140°C for 12 hours. After the reaction was completed, the mixture was concentrated under reduced pressure and purified by column chromatography to obtain a white solid intermediate product 1. The structural formula of the intermediate product 1 is shown below:

[0023]

[0024] S2. Preparation of Intermediate 2

[0025] The intermediate 1 of step S1 was subjected to argon replacement in a dry o-xylene solution, and n-butyl lithium was slowly added to the solution at low temperature. After reacting at room temperature for 1 hour, boron tribromide was slowly added at 0°C, stirred at room temperature for 1 hour, and N, N-diisopropylamine was added at 0°C, and further stirred at 160°C for 24 hours. After the reaction was completed, it 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 which is shown below:

[0026]

[0027] S3. Preparation of intermediate product 3:

[0028] Under the protection of inert gas, the intermediate product 2 of step 2, biboric acid pinacol ester, 1,1'-bis(diphenylphosphino)ferrocene palladium dichloride and potassium acetate are dissolved in ultra-dry 1,4-dioxane, stirred at 100°C, and after the reaction is completed, the reaction mixture is cooled to room temperature, and then added into a large amount of water, extracted with dichloromethane, and the organic layer is dried over anhydrous sodium sulfate. The crude product is filtered and evaporated, and then purified by silica gel column chromatography, and purified by elution to obtain a yellow solid intermediate product 3, wherein the structural formula of the intermediate product 3 is as follows:

[0029]

[0030] S4. Preparation of target product MR-MR

[0031] Under the protection of inert gas, the intermediate product 2 obtained in step S2, the intermediate product 3 obtained in step S3, tetrakis(triphenylphosphine)palladium and potassium carbonate are dissolved in a mixed solution of toluene, ethanol and water, and stirred at 85°C. After the reaction is completed, the reaction mixture is cooled to room temperature, and then added to a large amount of water and extracted with dichloromethane. The organic layer is dried over anhydrous sodium sulfate, and the crude product is filtered and evaporated, and then purified by silica gel column chromatography, and eluted and purified to obtain an orange-yellow solid MR-MR.

[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, in step S2, the molar ratio of the intermediate product 1 to boron tribromide is 2:3.

[0034] Preferably, in step S1, the column chromatography method uses alkaline alumina, the eluent is dichloromethane and petroleum ether, and the volume ratio of dichloromethane to petroleum ether is 1:4.

[0035] Preferably, in step S2, the column chromatography method uses neutral alumina and the eluent is petroleum ether.

[0036] The present application also provides a blue light photoinitiator system, wherein the photosensitizer is the above-mentioned bis(bis(pyrrole) zinc complex, and the co-initiator is an iodonium salt.

[0037] More preferably, the iodonium salt is selected from

[0038] The present application also provides the application of the above-mentioned photoinitiator 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 suitable for the blue light photoinitiator system provided in the present application is a photosensitizer with a boron nitrogen MR molecule as the core, and a blue light absorption ability is synthesized by introducing a suitable electron donor or acceptor to produce free radicals and other phenomena, and is combined with a co-initiator iodonium salt to form a photoinitiator system. In the blue light initiator system of the present application, when the photosensitizer absorbs photon energy under the irradiation of a blue light LED, an electron transition occurs to an excited singlet state, and then jumps to an excited triplet state through intersystem crossing. The photosensitizer molecules in the excited triplet state have a high reactivity, and can undergo energy transfer, electron transfer or proton transfer with iodonium salt co-initiators to produce free radicals, initiating polymerization of monomers, thereby solving the safety problem caused by the need to use ultraviolet light for photoinitiators in the prior art. The application of fluorescence sensing, photopolymerization or photocatalysis based on dimer boron nitrogen MR molecules has significant economic value. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 The DMA monomer in the MR-MR / Iod system under LED@460nm irradiation 1 HNMR spectrum.

[0042] Figure 2 is the conversion rate of monomer DMA in the MR-MR / Iod system under LED@460nm irradiation.

[0043] Figure 3 Time-dependent absorption spectrum of the MR-MR / Iod system under LED@460nm irradiation

[0044] Figure 4 This is the time-dependent emission spectrum of the MR-MR / Iod system under LED@460nm irradiation.

[0045] Figure 5 This is the ESR spectrum of the MR-MR / Iod / phenyl-n-tert-butylnitrone (PBN) system under LED@460nm irradiation. DETAILED DESCRIPTION

[0046] The embodiments of the present application will be described in detail below in conjunction with the examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present application and should not be considered as limiting the scope of the present application. In the examples, if specific conditions are not specified, they are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0047] It should be noted that:

[0048] In this application, unless otherwise specified, all the embodiments and preferred implementation methods mentioned herein can be combined with each other to form a new technical solution.

[0049] In the present application, unless otherwise specified, each reaction or operation step can be carried out sequentially or in a sequential manner. Preferably, the reaction method herein is carried out sequentially.

[0050] Unless otherwise specified, the professional and scientific terms used herein are the same as those familiar to those skilled in the art. In addition, any method or material similar or equivalent to the described content may also be applied to the present application.

[0051] The present application provides a blue light photoinitiator system, comprising a photosensitizer and a co-initiator, wherein the photosensitizer is a boron-containing conjugated aromatic hydrocarbon fluorescent dye, wherein the boron-containing conjugated aromatic hydrocarbon fluorescent dye has a 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 fluorescent dye photosensitizer suitable for the blue light photoinitiator system provided in the present application is a photosensitizer with strong blue light absorption ability and free radical generation by introducing a suitable electron donor or acceptor, and is combined with an iodonium salt as a co-initiator to form a photoinitiator system. In the blue light initiator system of the present application, when the photosensitizer absorbs photon energy under the irradiation of a blue light LED, an electronic transition occurs to an excited singlet state, and then an intersystem crossing occurs to an excited triplet state. The photosensitizer molecules in the excited triplet state have high reactivity, can transfer energy, electrons or protons with iodonium salt co-initiators to generate free radicals, and initiate polymerization of monomers, thereby solving the safety problem caused by the need for ultraviolet light to be used as a photoinitiator in the prior art, that is, solving the problem that the photopolymerization process mostly uses ultraviolet lamps (UV) as light sources, while the light intensity emitted by UV lamps is relatively high, and its service life is limited, the energy consumption is large, and it can also cause harm to human health. In addition, the penetration of UV light with a shorter wavelength in polymers is poor, which makes it easy to cause the problem of uneven polymerization degree of the product in a polymerization reaction with a certain thickness and a large amount.

[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 the present application is a relatively low-energy wavelength light, which is safer than UV light, the main light source currently represented in the photocuring literature. Secondly, blue light penetrates deeper than UV, so more complete curing can be achieved, especially for polymerization reactions with fillers.

[0059] In some preferred embodiments, the boron-containing conjugated aromatic hydrocarbon fluorescent dye is selected from any one of the following structural formulas:

[0060]

[0061] In some more preferred embodiments, the R is selected from the structural formula:

[0062] In some preferred embodiments, the polymerizable monomer is selected from:

[0063] The present application also provides a method for preparing the above-mentioned boron-containing conjugated aromatic hydrocarbon fluorescent dye, which comprises the following steps:

[0064] S1. Preparation of intermediate 1:

[0065] 3,6-di-tert-butylcarbazole and potassium carbonate were dissolved in DMF, stirred at room temperature, and then 5-bromo-1,3-difluoro-2-iodobenzene was added. The mixture was stirred at 140°C for 12 hours. After the reaction was completed, the mixture was concentrated under reduced pressure and purified by column chromatography to obtain a white solid intermediate product 1. The structural formula of the intermediate product 1 is shown below:

[0066]

[0067] S2. Preparation of Intermediate 2

[0068] The intermediate 1 of step S1 was subjected to argon replacement in a dry o-xylene solution, and n-butyl lithium was slowly added to the solution at low temperature. After reacting at room temperature for 1 hour, boron tribromide was slowly added at 0°C, stirred at room temperature for 1 hour, and N, N-diisopropylamine was added at 0°C, and further stirred at 160°C for 24 hours. After the reaction was completed, it 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 which is shown below:

[0069]

[0070] S3. Preparation of intermediate product 3:

[0071] Under the protection of inert gas, the intermediate product 2 of step 2, biboric acid pinacol ester, 1,1'-bis(diphenylphosphino)ferrocene palladium dichloride and potassium acetate are dissolved in ultra-dry 1,4-dioxane, stirred at 100°C, and after the reaction is completed, the reaction mixture is cooled to room temperature, and then added into a large amount of water, extracted with dichloromethane, and the organic layer is dried over anhydrous sodium sulfate. The crude product is filtered and evaporated, and then purified by silica gel column chromatography, and purified by elution to obtain a yellow solid intermediate product 3, wherein the structural formula of the intermediate product 3 is as follows:

[0072]

[0074] S4. Preparation of target product MR-MR

[0075] Under the protection of inert gas, the intermediate product 2 obtained in step S2, the intermediate product 3 obtained in step S3, tetrakis(triphenylphosphine)palladium and potassium carbonate are dissolved in a mixed solution of toluene, ethanol and water, and stirred at 85°C. After the reaction is completed, the reaction mixture is cooled to room temperature, and then added to a large amount of water and extracted with dichloromethane. The organic layer is dried over anhydrous sodium sulfate, and the crude product is filtered and evaporated, and then purified by silica gel column chromatography, and eluted and purified to obtain an orange-yellow solid MR-MR.

[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 the 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, the eluent is dichloromethane and petroleum ether, and the volume ratio of dichloromethane to petroleum ether is 1:4.

[0079] In some preferred embodiments, in step S2, the column chromatography method uses neutral alumina and the eluent is petroleum ether.

[0080] The present application also provides a blue light photoinitiator system, wherein the photosensitizer is the above-mentioned bis(bis(pyrrole) zinc complex, and the co-initiator is an iodonium salt.

[0081] In some preferred embodiments, the iodonium salt is selected from

[0082] The present application also provides the application of the above-mentioned blue light photoinitiator system 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] Next, the preparation method of the boron-containing conjugated aromatic hydrocarbon fluorescent dye in the present application is described in detail with specific examples.

[0085] Example 1

[0086] A boron-containing conjugated aromatic hydrocarbon fluorescent dye has a molecular structure as shown 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 comprises the following steps:

[0089] Step S1: Preparation of Intermediate 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), stirred at room temperature for 30 minutes, and then 5-bromo-1,3-difluoro-2-iodobenzene (6.38 g, 20.0 mmol) was added and stirred at 140°C for 12 hours. After the reaction was completed, the mixture was concentrated under reduced pressure and purified by column chromatography (silica gel, dichloromethane / petroleum ether, 1 / 4, v / v) to obtain 12.57 g of a white solid. (Yield: 75%) The reaction equation is as follows:

[0091]

[0092] Step S2: Preparation of intermediate 2

[0093] The intermediate product 1 (5.03 g, 6.0 mmol) of step S11 was replaced with argon in dry o-xylene (120 mL). At -30 ° C, n-butyl lithium (4.1 mL, 6.6 mmol) was slowly added to the solution. After reacting at room temperature for 1 h, boron tribromide (2.25 g, 9.0 mmol) was slowly added at 0 ° C and stirred at room temperature for 1 h. N, N-diisopropylamine (2.4 mL, 13.5 mmol) was added at 0 ° C and further stirred at 160 ° C for 24 h. After the reaction was completed, it 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 yellow solid (yield: 31%).

[0094] The reaction equation is as follows:

[0095]

[0096] Step S3: Preparation of intermediate 3

[0097] Under nitrogen protection, the target product of step 2 (0.72g, 1.0mmol), biboronic acid pinacol ester (0.38g, 1.5mmol), 1,1'-bis(diphenylphosphino)ferrocene palladium dichloride (0.04g, 0.05mmol) and potassium acetate (0.29g, 3.0mmol) were dissolved in ultra-dry 1,4-dioxane (15ml). Stir at 100°C for 24h. After the reaction was completed, the reaction mixture was cooled to room temperature, 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 and evaporated, and then purified by silica gel column chromatography (petroleum ether / dichloromethane, 4 / 1, v / v), and 0.51g of yellow solid was obtained (yield: 67%).

[0098] The reaction equation is as follows:

[0099]

[0100] S4. Preparation of target product MR-MR

[0101] Under nitrogen protection, the target product of step 2 (0.36g, 0.5mmol), the target product of step 3 (0.38g, 0.5mmol), tetrakis(triphenylphosphine)palladium (0.008g, 0.005mmol) and potassium carbonate (0.27g, 2.0mmol) were dissolved in a mixed solution of toluene (14mL), ethanol (4mL) and water (2ml) and stirred at 85°C for 48 hours. After the reaction was completed, the reaction mixture was cooled to room temperature, 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 and evaporated, and then purified by silica gel column chromatography (petroleum ether / dichloromethane, 4 / 1, v / v), eluted and purified to obtain 0.25g of orange-yellow solid (yield: 40%). The reaction equation is as follows:

[0102]

[0103] Photopolymerization experiments

[0104] A photoinitiator system consisting of 0.6wt% MR-MR and 0.4wt% Iod was used, 3mL DMA monomer was added, deoxygenated in dark, and ultrasonically mixed. The mixture was evenly distributed into 5 small sample bottles under a nitrogen atmosphere, and the irradiation time was controlled, and irradiated under a 460nm blue light LED for 0s, 10s, 20s, 30s, and 40s respectively. After irradiation, the monomers were cured to varying degrees. Each irradiated sample was dissolved with internal standard trimethylbenzene and deuterated chloroform. 1 The monomer conversion rate was obtained by HNMR nuclear magnetic resonance comparison.

[0105] The test method of monomer conversion rate is as follows: mesitylene is used as the internal standard (the integral signal (6.76-6.82 ppm) is set to 1). Select the specific hydrogen (H A ) to monitor the changes of the monomer under red light irradiation. The integral value of HA at the beginning (0s) is H0, and the integral value of HA at t seconds after the blue light treatment is H A The integral value is H t .

[0106] The conversion formula is:

[0107] Figure 1 The DMA monomer in the MR-MR / Iod system under LED@460nm irradiation 1 HNMR spectrum.

[0108] from Figure 1It can be seen that with the increase of blue LED irradiation time, the viscosity of the sample gradually increased. After adding the MR-MR / Iod system, the viscosity of the sample increased within 40 seconds. 1 The conversion rate monitored by HNMR is almost 100%. Compared with commercial UV lamps of the same power, the curing time is greatly shortened and the degree of curing is improved.

[0109] Figure 2 is the conversion rate of monomer DMA in the MR-MR / Iod system under LED@460nm irradiation.

[0110] Table 1: Calculated conversion rate of DMA in MR-MR / Iod system under LED@460nm irradiation

[0111]

[0112] from Figure 2 It can be seen that after irradiation with 460 nm red light, the polymerization reaction starts immediately, and the curing rate accelerates after 10 s and is basically polymerized within 40 s.

[0113] Photochemical reactivity

[0114] The photosensitizer molecule MR-MR and the co-initiator Iod were prepared to a concentration of 1*10 -5 M and 5*10 -5 The DCM solution of 100 M was injected into a cuvette with a light path of 1 cm, and irradiated with a 460 nm LED light source for a certain period of time. The UV-visible absorption spectra after 0s, 10s, 20s, 30s, 40s, and 50s of illumination and the emission spectra after 0s, 10s, 20s, and 30s of illumination were tested to observe the decomposition of the photosensitizer molecules as the illumination time increases. The test results are shown in Figure 3 and 4 As shown, the photosensitizer molecules degrade rapidly under light, which indicates that the photosensitizer molecules can generate free radicals through energy transfer and electron transfer with iodonium salt co-initiators in the red light curing system, thereby initiating polymerization of the monomers.

[0115] Figure 3 and Figure 4 The time-dependent absorption and emission spectra of the MR-MR / Iod system under LED@460nm irradiation for 0-40s. Figure 3 and Figure 4 It can be seen that the photosensitizer molecules degrade rapidly under light, 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 polymerization of the monomers.

[0116] Electron spin trapping experiment

[0117] Based on the interaction between MR-MR molecules and Iod, an electron transfer process is involved to generate aromatic free radicals. The formed free radicals can be verified by ESR spin trapping (ESR-ST). The MR-MR / Iod / phenyl-n-tert-butylnitrone (PBN) system is irradiated with LED @ 460nm, and a strong signal is obtained, such as Figure 5 In the MR-MR / Iod / phenyl-n-tert-butylnitrone (PBN) system, nitrogen (α N ) and hydrogen (α H ) have ultrafine fragmentation constants of 15 and 2.7 G, respectively, which can be attributed to PBN and phenyl adducts. Therefore, MR-MR and Iod, after being excited by light, undergo electron transfer to form phenyl radicals, initiating polymerization.

[0118] The present application discloses a blue light photoinitiator system, comprising a photosensitizer and a co-initiator, wherein the photosensitizer is a boron-containing conjugated aromatic hydrocarbon fluorescent dye, wherein the boron-containing conjugated aromatic hydrocarbon fluorescent dye has a 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 photoinitiator system suitable for blue light provided in the present application, the visible light initiator system includes a photosensitizer and a co-initiator, wherein the photosensitizer is MR-TADF, which is composed of a boron nitrogen atom as the core and a plurality of carbazole compounds on the periphery, and is combined with the co-initiator iodonium salt to form a photoinitiator system, which efficiently initiates the polymerization of acrylate monomers under the irradiation of a blue light LED. The photosensitizer provided in the present application has strong absorption at a wavelength in the range of 460 mm, and can be well matched with a blue light LED light source. The photosensitizer can efficiently initiate the polymerization of acrylate monomers by irradiation with a blue light LED when an iodonium salt is added, thereby solving the problem of avoiding the use of photosensitizers containing transition metals or heavy atoms. When compounded with an iodonium salt, the double bond conversion rate of the monomer can reach more than 90% when the dosage is small.

[0123] The boron-containing conjugated aromatic fluorescent dye photosensitizer suitable for the blue light photoinitiator system provided in the present application is a photosensitizer with strong blue light absorption ability and free radical generation by introducing a suitable electron donor or acceptor, and is combined with an iodonium salt as a co-initiator to form a photoinitiator system. In the blue light initiator system of the present application, when the photosensitizer absorbs photon energy under the irradiation of a blue light LED, an electronic transition occurs to an excited singlet state, and then an intersystem crossing occurs to an excited triplet state. The photosensitizer molecules in the excited triplet state have high reactivity, can transfer energy, electrons or protons with iodonium salt co-initiators to generate free radicals, and initiate polymerization of monomers, thereby solving the safety problem caused by the need for ultraviolet light to be used as a photoinitiator in the prior art, that is, solving the problem that the photopolymerization process mostly uses ultraviolet lamps (UV) as light sources, while the light intensity emitted by UV lamps is relatively high, and its service life is limited, the energy consumption is large, and it can also cause harm to human health. In addition, the penetration of UV light with a shorter wavelength in polymers is poor, which makes it easy to cause the problem of uneven polymerization degree of the product in a polymerization reaction with a certain thickness and a large amount.

[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 the present application is a relatively low-energy wavelength light, which is safer than UV light, the main light source currently represented in the photocuring literature. Secondly, blue light penetrates deeper than UV, so more complete curing can be achieved, especially for polymerization reactions with fillers.

[0126] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiments or examples are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0127] Although several embodiments of the present application have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present application, and that the scope of the present application is defined by the claims and their equivalents.

Claims

1. A blue light photoinitiator system, comprising a photosensitizer and a co-initiator, characterized in that: The photosensitizer is a boron-containing conjugated aromatic hydrocarbon fluorescent dye, wherein the boron-containing conjugated aromatic hydrocarbon fluorescent dye has a chemical structure shown in formula (I): In the formula, R can be selected from one of the following structural formulas:

2. The blue light photoinitiator system according to claim 1, characterized in that: The boron-containing conjugated aromatic hydrocarbon fluorescent dye is selected from any one of the following structural formulas:

3. The blue light photoinitiator system according to claim 1, characterized in that: The R is selected from the structural formula:

4. The method for preparing the boron-containing conjugated aromatic hydrocarbon fluorescent dye according to claim 1, characterized in that: The steps include: S1. Preparation of intermediate 1: 3,6-di-tert-butylcarbazole and potassium carbonate were dissolved in DMF, stirred at room temperature, and then 5-bromo-1,3-difluoro-2-iodobenzene was added. The mixture was stirred at 140°C for 12 hours. After the reaction was completed, the mixture was concentrated under reduced pressure and purified by column chromatography to obtain a white solid intermediate product 1. The structural formula of the intermediate product 1 is shown below: S2. Preparation of Intermediate 2 The intermediate 1 of step S1 was subjected to argon replacement in a dry o-xylene solution, and n-butyl lithium was slowly added to the solution at low temperature. After reacting at room temperature for 1 hour, boron tribromide was slowly added at 0°C, stirred at room temperature for 1 hour, and N, N-diisopropylamine was added at 0°C, and further stirred at 160°C for 24 hours. After the reaction was completed, it 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 which is shown below: S3. Preparation of intermediate product 3: Under the protection of inert gas, the intermediate product 2 of step 2, biboric acid pinacol ester, 1,1'-bis(diphenylphosphino)ferrocene palladium dichloride and potassium acetate are dissolved in ultra-dry 1,4-dioxane, stirred at 100°C, and after the reaction is completed, the reaction mixture is cooled to room temperature, and then added into a large amount of water, extracted with dichloromethane, and the organic layer is dried over anhydrous sodium sulfate. The crude product is filtered and evaporated, and then purified by silica gel column chromatography, and purified by elution to obtain a yellow solid intermediate product 3, wherein the structural formula of the intermediate product 3 is as follows: S4. Preparation of target product MR-MR Under the protection of inert gas, the intermediate product 2 obtained in step S2, the intermediate product 3 obtained in step S3, tetrakis(triphenylphosphine)palladium and potassium carbonate are dissolved in a mixed solution of toluene, ethanol and water, and stirred at 85°C. After the reaction is completed, the reaction mixture is cooled to room temperature, and then added to a large amount of water and extracted with dichloromethane. The organic layer is dried over anhydrous sodium sulfate, and the crude product is filtered and evaporated, and then purified by silica gel column chromatography, and eluted and purified to obtain an orange-yellow solid MR-MR.

5. The method for preparing the bis(bis(dipyrrole) zinc complex according to claim 4, characterized in that: 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.

6. The method for preparing the bis(bis(dipyrrole) zinc complex according to claim 4, characterized in that: The molar ratio of the intermediate product 1 to boron tribromide in step S2 is 2:

3.

7. The method for preparing the bis(bis(dipyrrole) zinc complex according to claim 4, characterized in that: In step S1, the column chromatography method uses alkaline alumina, the eluent is dichloromethane and petroleum ether, and the volume ratio of dichloromethane to petroleum ether is 1:

4.

8. The method for preparing the bis(bis(dipyrrole) zinc complex according to claim 4, characterized in that: In step S2, the column chromatography method uses neutral alumina and the eluent is petroleum ether.

9. The blue light photoinitiator system according to claim 1, characterized in that: The auxiliary initiator is an iodonium salt, and the iodonium salt is 10. Use of the blue light photoinitiator system according to claim 1, 2 or 3 in fluorescence sensing, photopolymerization or photocatalysis.

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