Oxime ester photoinitiator with donor-acceptor structure, preparation method and application thereof

Abstract

The present invention discloses a preparation method and application of an oxime ester photoinitiator having a donor-acceptor structure. The preparation method constructs a large conjugated donor-acceptor structure oxime ester photoinitiator with triphenylamine as a donor, pyridinium salt as an acceptor, and oxime ester as a photoinitiator group through reactions such as Suzuki coupling, hydroxylation, oxime esterification, and salt formation. The photoinitiator can be used in photocuring systems such as coatings, inks, and 3D printing. It has high photoinitiation efficiency under both visible light and sunlight, and can meet the requirements of deep curing in different complex environments. The photoinitiator has the advantages of high initiation efficiency, ultra-low addition amount, and deep curing depth. The preparation process is simple, the raw materials are easily available, and large-scale industrial production can be achieved.

Description

Technical Field

[0001] The present invention belongs to the field of new chemical materials, and in particular relates to a preparation method and application of an oxime ester photoinitiator having a donor-acceptor structure. Background Art

[0002] In recent years, photopolymerization has garnered increasing attention for producing a variety of polymer materials. Photopolymerization utilizes light radiation in the presence of a photoinitiator (PI) to initiate the polymerization of monomers and oligomers. This technology offers advantages such as low VOC content, energy conservation, cost-effectiveness, and rapid monomer conversion. Consequently, it has been widely used in coatings, inks, photoresists, dental restorations, and 3D printing.

[0003] Photoinitiators are a type of key ingredient that can generate active free radicals to initiate monomer polymerization under light irradiation, either alone or in conjunction with other additives. The addition amount of photoinitiators for existing free radical polymerization is generally 1% to 3%, and high-efficiency systems can be as low as 0.5%. The addition amount of photoinitiators used for thick layer curing or 3D printing may require 2% to 5% to ensure deep reaction. However, excessive addition of photoinitiators can lead to changes in material properties, such as yellowing and embrittlement, decreased transparency; light shielding effects, such as surface over-curing and deep curing; the generation of bubbles and stratification, and the decomposition of some initiators will produce CO2, forming micropores or interface stratification. Therefore, there is an urgent need to develop high-performance photoinitiators with ultra-low addition amounts and high initiation efficiency.

[0004] The light source is an essential component of the photopolymerization system. Light sources can be divided into ultraviolet (UV) lamps, artificial visible light light-emitting diodes (LEDs), or sunlight. LEDs have the advantages of low cost, long service life, compact structure, durability, and easy availability. Compared with UV light sources, LED light sources have higher wavelength stability and are highly compatible with the absorption peak of photoinitiators, which can reduce energy waste and is suitable for precise control of polymerization reactions. Full-spectrum sunlight, as a natural light source, is not only easy to obtain but also low in cost. Depending on the application requirements, the use of full-spectrum sunlight is harmless to the environment and is particularly suitable for large-scale outdoor photocuring applications. Therefore, the development of visible light / sunlight-induced photoinitiators has important scientific research value and practical significance in the field of photopolymerization.

[0005] Oxime esters (OXEs), a class of cleavage-type photoinitiators, have been widely used in photopolymerization due to their high initiation efficiency, making them a promising system for developing visible light / solar photopolymerization. However, currently commercially available OXE-01 and OXE-02 still suffer from limitations such as UV absorption, high dosage requirements, and low cure depth. Therefore, the design of new, high-performance oxime ester photoinitiators with visible light absorption, ultra-low dosage requirements, high initiation efficiency, and deep cure is of great significance. Summary of the Invention

[0006] The purpose of the present invention is to overcome the problems existing in the prior art, propose a coupling strategy of large conjugated donor-acceptor structure to prolong absorption and dual-acceptor electron attraction to reduce oxime ester cracking energy, and develop ultra-low addition photoinitiators with high initiation efficiency for visible light / sunlight initiation. First, using triphenylamine as the donor and bispyridinium salt as the acceptor, a strong donor-acceptor type large conjugated structure is constructed to increase photosensitivity and red-shift the absorption wavelength of the photoinitiator to the visible light region; secondly, the strong electron-withdrawing effect of the bispyridinium salt is utilized to attract and migrate the electron cloud of the oxime ester to the triphenylamine region, reduce the dissociation energy of the oxime ester cracking bond, and enhance the photoinitiator activity. Based on the above strategy, its structural advantages are combined to exert the coupling effect, prolong absorption to the visible light absorption region, enhance the photoinitiator activity, and achieve deep curing with visible light / sunlight initiation, ultra-low addition, and high initiation activity.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] The preparation method and application of the oxime ester photoinitiator having a donor-acceptor structure have a general structural formula as shown in formula (I):

[0009] (I)

[0010] In formula (I):

[0011] R is independently selected from electron donating groups.

[0012] The substituent R includes any one of a phenyl group, a thienyl group, a furyl group, a C3-C6 cycloalkyl group, and a C1-C5 straight-chain alkyl group.

[0013] The structural formula of the oxime ester photoinitiator having a donor-acceptor structure is one of the following structures:

[0014]

[0015] The synthetic route of the oxime ester photoinitiator with a donor-acceptor structure is as follows:

[0016]

[0017] The synthesis process of the intermediate monomer S1 is to sequentially add 4-[N,N-bis(4-bromophenyl)amino]benzaldehyde, pyridine boronic acid, an acid-binding agent, a catalyst, and an organic solvent into a container equipped with a stirring device, and react in an oil bath at 65-85°C. After the reaction is completed, the liquids are separated and extracted, and the organic solvent is removed using a rotary evaporator. The pure product is purified by silica gel column chromatography to obtain the intermediate monomer S1.

[0018] Preferably, the acid binding agent is one or more of sodium carbonate, potassium carbonate, and cesium carbonate.

[0019] Preferably, the catalyst is one or more of a salt of zero-valent Pd(0) and Ni(0) and a phosphorus complex.

[0020] Preferably, the organic solvent for the Suzuki coupling reaction is one or more of toluene, tetrahydrofuran, and acetonitrile.

[0021] Preferably, the molar ratio of the pyridine boronic acid to 4-[N,N-bis(4-bromophenyl)amino]benzaldehyde is (2.1-2.8):1.

[0022] The synthesis of intermediate monomer S2 is carried out by reacting with hydroxylamine hydrochloride under the catalysis of base to produce oxime structure S2.

[0023] Preferably, the base for the hydroxylation reaction is one or more of sodium hydroxide, potassium hydroxide, sodium acetate, and potassium acetate.

[0024] Preferably, the solvent for the hydroxylation reaction is one or more of ethanol, methanol, isopropanol, and n-butanol.

[0025] The intermediate product S2 is further esterified with an acyl chloride under the action of a base acid-binding agent to prepare an oxime ester compound S3.

[0026] Preferably, the alkaline acid-binding agent for the esterification reaction is one or more of triethylamine, sodium carbonate, sodium bicarbonate, potassium carbonate, and sodium hydride.

[0027] Preferably, the solvent for the esterification reaction is one or more of dichloromethane, chloroform, and tetrahydrofuran.

[0028] The intermediate monomer S3 and n-butane iodide are refluxed in an organic solvent according to a measured molar ratio. After the reaction is completed, the solid is filtered and collected to obtain an oxime ester photoinitiator having a donor-acceptor structure in the general formula (I).

[0029] Preferably, the molar ratio of the intermediate monomer S3 to n-butane iodide is 1:(2.5-3.5).

[0030] Preferably, the solvent for the salt-forming reaction is one or more of acetonitrile, toluene, and N,N-dimethylformamide.

[0031] The invention discloses an oxime ester photoinitiator having a donor-acceptor structure, and is used as a photoinitiator in a free radical photopolymerization formulation system. The absorption wavelength of the photoinitiator is above 420 nm.

[0032] A photoinitiator for use in a free radical photopolymerization system comprises an oxime ester photoinitiator having a donor-acceptor structure and any one of tripropylene glycol diacrylate, polyethylene glycol diacrylate, trimethylolpropane triacrylate, and di(trimethylolpropane)tetraacrylate to prepare a resin composition, and further comprises any one of diphenyliodonium hexafluorophosphate and N-methyldiethanolamine as a co-initiator.

[0033] The diphenyliodonium hexafluorophosphate, N-methyldiethanolamine, polyethylene glycol diacrylate, trimethylolpropane triacrylate and di(trimethylolpropane) tetraacrylate can realize the functions and effects of co-initiator and polymerization monomer in the free radical photopolymerization system according to their respective properties.

[0034] Preferably, in the photopolymerization system, the amount of the oxime ester photoinitiator having a donor-acceptor structure is 0.001 wt% to 0.1 wt% of the photopolymerization system.

[0035] Compared with the prior art, the preparation method and application of the oxime ester photoinitiator with a donor-acceptor structure of the present invention have the following advantages and beneficial effects:

[0036] (1) A coupling strategy of large conjugated donor-acceptor structures to extend absorption and dual-acceptor electron attraction to reduce the oxime ester cleavage energy was proposed to develop ultra-low-dosage photoinitiators with high initiation efficiency that can be initiated by visible light / sunlight.

[0037] (2) Using triphenylamine as a donor and bispyridinium salt as an acceptor, a strong donor-acceptor type large conjugated structure is constructed to increase photosensitivity and at the same time red-shift the absorption wavelength of the photoinitiator to the visible light region, wherein the visible light region is 420nm and above.

[0038] (3) By utilizing the strong electron-withdrawing effect of the bipyridinium salt, the electron cloud of the oxime ester is attracted and migrated to the triphenylamine region, thereby reducing the dissociation energy of the oxime ester bond cleavage and improving the photoinitiator activity.

[0039] (4) The photoinitiator has high photoinitiation efficiency under both visible light and sunlight, and can meet the requirements of deep curing in different complex environments.

[0040] (5) This photoinitiator has the advantages of high initiation efficiency, ultra-low addition amount, and deep curing depth; its preparation process is simple, and the raw materials are easily available, which can be realized in large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is the H NMR spectrum of the intermediate monomer S1 of Example 1.

[0042] Figure 2 This is the high-resolution mass spectrum of the intermediate monomer S1 in Example 1.

[0043] Figure 3 This is the H NMR spectrum of the intermediate monomer S2 in Example 1.

[0044] Figure 4 This is the high-resolution mass spectrum of the intermediate monomer S2 in Example 1.

[0045] Figure 5 This is the H NMR spectrum of the intermediate monomer S3 in Example 1.

[0046] Figure 6 This is the high-resolution mass spectrum of the intermediate monomer S3 in Example 1.

[0047] Figure 7 This is the H NMR spectrum of the photoinitiator of Example 1.

[0048] Figure 8 This is the high-resolution mass spectrum of the photoinitiator of Example 1.

[0049] Figure 9 This is the H NMR spectrum of the intermediate monomer S3 of Example 2.

[0050] Figure 10 This is the high-resolution mass spectrum of the intermediate monomer S3 in Example 2.

[0051] Figure 11 This is the H NMR spectrum of the photoinitiator of Example 2.

[0052] Figure 12 This is the high-resolution mass spectrum of the photoinitiator of Example 2.

[0053] Figure 13 This is the photopolymerization effect data of Example 1.

[0054] Figure 14 This is the photopolymerization effect data of Example 4.

[0055] Figure 15 This is the photopolymerization effect of Example 11.

[0056] Figure 16 This is the photopolymerization effect of Example 12.

[0057] Figure 17 This is the photopolymerization effect of Example 13. DETAILED DESCRIPTION

[0058] The present invention is further described below with reference to the following examples, but the scope of protection claimed in the present invention is not limited to the scope described in the examples.

[0059] Example 1:

[0060] The synthesis route of the photoinitiator of Example 1 is as follows:

[0061]

[0062] (1) Under N2 protection, 4-[N,N-bis(4-bromophenyl)amino]benzaldehyde (10 mmol), pyridine boronic acid (22 mmol), potassium carbonate (25 mmol), Pd(PPh3)4 (0.5 mmol), toluene (50 mL), and ethanol (25 mL) were added in sequence to a container equipped with a stirring device. The mixture was reacted in an oil bath at 85°C. After the reaction was completed, the mixture was separated and extracted, and the organic solvent was removed by a rotary evaporator. The pure product was purified by silica gel column chromatography to obtain the intermediate monomer S1 with a yield of 97.9%.

[0063] The structure of the intermediate monomer S1 was confirmed by H NMR and mass spectrometry data:

[0064] 1 H NMR (CDCl3, 500 MHz), (ppm): 9.86 (1H), 8.65-8.64 (4H), 7.75-7.77(2H), 7.64-7.62 (4H), 7.50-7.49 (4H), 7.29-7.72 (4H), 7.19-7.17 (2H), ( Figure 1 ).

[0065] HRMS: C 29 H 21 N3O cal. 427.1785, Measured [M+H] + : 428.1767, ( Figure 2 ).

[0066] (2) Under N2 protection, the intermediate monomer S1 (20 mmol), hydroxylamine hydrochloride (30 mmol), sodium acetate (40 mmol), ethanol (50 mL), water (10 mL), and tetrahydrofuran (10 mL) were added sequentially to a container equipped with a stirring device and reacted at room temperature for 24 h. The reaction progress was monitored by TLC. After the reaction was completed, the liquid was separated and extracted, and the organic solvent was removed by a rotary evaporator. The pure product was purified by silica gel column chromatography to obtain the intermediate monomer S2 with a yield of 89.2%;

[0067] The structure of the intermediate monomer S2 was confirmed by H NMR and mass spectrometry data:

[0068] 1 H NMR (CDCl3, 500 MHz), (ppm): 9.86 (1H), 8.66-8.64 (4H), 8.15 (1H), 7.59-7.57 (4H), 7.55 (2H), 7.51-7.50 (4H), 7.24-7.22 (4H), 7.16-7.14 (2H), ( Figure 3 ).

[0069] HRMS: C 29 H 22 N4O cal. 442.1867, Measured [M+H] + : 443.1873, ( Figure 4 ).

[0070] (3) Under N2 protection, the intermediate monomer S2 (10 mmol), 2-thiophenecarbonyl chloride (15 mmol), triethylamine (60 mmol), and dichloromethane (50 mL) were added sequentially to a container equipped with a stirring device and reacted at room temperature for 24 h. The reaction progress was monitored by TLC. After the reaction was completed, the liquids were separated and extracted, and the organic solvent was removed by a rotary evaporator. The pure product was purified by silica gel column chromatography to obtain the intermediate monomer S3 with a yield of 72.8%;

[0071] The structure of the intermediate monomer S3 was confirmed by H NMR and mass spectrometry data:

[0072] 1 H NMR (CDCl3, 500 MHz), (ppm): 8.66-8.63 (5H), 7.64-7.60 (6H), 7.52-7.48(6H), 7.27-7.25 (5H), 7.14-7.12 (2H), ( Figure 5 ).

[0073] HRMS: C 34 H 24 N4O2S cal. 552.1622, Measured [M+H] + : 553.1699, ( Figure 6 ).

[0074] (4) Under N2 protection, the intermediate monomer S3 (12 mmol), n-butyl iodide (36 mmol) and 20 mL of acetonitrile were added sequentially to a container equipped with a stirring device. The reaction was refluxed overnight and the reaction progress was monitored by TLC. After the reaction was completed, the solid phase was collected by filtration and rinsed with acetonitrile three times to obtain a red solid photoinitiator with a yield of 82.9%.

[0075] The structure of photoinitiator 1 was confirmed by H NMR and mass spectrometry data:

[0076] 1 H NMR (CDCl3, 500 MHz), (ppm): 9.10-9.08 (4H), 8.52-8.50 (4H), 8.18-8.15(4H), 7.84-7.82 (2H), 7.35-7.33 (4H), 7.26-7.23 (2H), 4.61-4.57 (4H), 1.96-1.89 (4H), 1.35-1.30 (4H), 0.95-0.91 (6H), ( Figure 7 ).

[0077] HRMS: C 42 H 42 I2N4O2S cal. 920.0101, Measured [M+Na] + : 943.0107, ( Figure 8 ).

[0078] Example 2:

[0079] The only difference from Example 1 is that 2-thiophenecarbonyl chloride in step (3) is replaced by benzoyl chloride.

[0080] The structure of the intermediate monomer S3 was confirmed by H NMR and mass spectrometry data:

[0081] 1 H NMR (CDCl3, 500 MHz), (ppm): 8.66-8.65 (4H), 8.51 (1H), 8.13-8.11(2H), 7.73-7.71 (2H), 7.62-7.60 (4H), 7.52-7.46 (7H), 7.27-7.25 (4H), 7.19-7.17 (2H), ( Figure 9 ).

[0082] HRMS: C 36 H 26 N4O2cal. 546.2141, Measured [M+H] + : 547.2135, ( Figure 10 ).

[0083] The structure of photoinitiator 2 was confirmed by H NMR and mass spectrometry data:

[0084] 1 H NMR (CDCl3, 500 MHz), (ppm): 9.10-9.08 (4H), 8.51-8.50 (4H), 8.17-8.15(4H), 7.94-7.86 (1H), 7.84-7.82 (1H), 7.35-7.33 (4H), 7.26-7.24 (2H), 4.61-4.57 (4H), 1.96-1.89 (4H), 1.36-1.30 (4H), 0.95-0.91 (6H), ( Figure 11 ).

[0085] HRMS: C 44 H 44 I2N4O2cal. 914.1435, Measured [M+Na] + : 937.1453, ( Figure 12 ).

[0086] Example 3:

[0087] The only difference from Example 1 is that 2-thiophenecarbonyl chloride in step (3) is replaced by 2-furocarbonyl chloride.

[0088] Example 4:

[0089] The only difference from Example 1 is that 2-thenoyl chloride in step (3) is replaced by cyclopropylcarbonyl chloride.

[0090] Example 5:

[0091] The only difference from Example 1 is that 2-thenoyl chloride in step (3) is replaced by cyclobutylcarbonyl chloride.

[0092] Example 6:

[0093] The only difference from Example 1 is that 2-thenoylcarbonyl chloride in step (3) is replaced by cyclopentylcarbonyl chloride.

[0094] Example 7:

[0095] The only difference from Example 1 is that 2-thenoyl chloride in step (3) is replaced by cyclohexylcarbonyl chloride.

[0096] Example 8:

[0097] The only difference from Example 1 is that 2-thenoyl chloride in step (3) is replaced by acetyl chloride.

[0098] Example 9:

[0099] The only difference from Example 1 is that 2-thenoyl chloride in step (3) is replaced by propionyl chloride.

[0100] Example 10:

[0101] The only difference from Example 1 is that 2-thenoyl chloride in step (3) is replaced by butyryl chloride.

[0102] Example 11:

[0103] The only difference from Example 1 is that 2-thenoyl chloride in step (3) is replaced by valeryl chloride.

[0104] Example 12:

[0105] The only difference from Example 1 is that 2-thenoyl chloride in step (3) is replaced by hexanoyl chloride.

[0106] Preparation of a photocuring system: The photoinitiators in Examples 1 to 12 were respectively mixed with an acrylic free radical photocuring system to prepare resin compositions.

[0107] Application Example 1:

[0108] The photoinitiator in Example 1 was combined with tripropylene glycol diacrylate to prepare a resin composition. The amount of photoinitiator used was 0.01 wt % of the total weight of the photopolymerization system. The photopolymerization process was monitored using a Bruker ALPHA II Fourier transform infrared spectrometer with a spectral scanning range of 7000-4000 cm -1 The main absorption of the free radical resin was measured by infrared spectroscopy as a function of illumination time. The sample thickness was 1.5 mm, a xenon lamp was used as the light source, and each sample was tested three times in parallel. Figure 13 is the photopolymerization effect of the photoinitiator.

[0109] Application Example 2:

[0110] The only difference from Application Example 1 is that the photoinitiator is the photoinitiator prepared in Example 2.

[0111] Application Example 3:

[0112] The only difference from Application Example 1 is that the photoinitiator is the photoinitiator prepared in Example 3.

[0113] Application Example 4:

[0114] The only difference from Application Example 1 is that the photoinitiator is the photoinitiator prepared in Example 4.

[0115] Application Example 5:

[0116] The only difference from Application Example 1 is that the photoinitiator is the photoinitiator prepared in Example 5.

[0117] Application Example 6:

[0118] The only difference from Application Example 1 is that the photoinitiator is the photoinitiator prepared in Example 6.

[0119] Application Example 7:

[0120] The only difference from Application Example 1 is that the photoinitiator is the photoinitiator prepared in Example 7.

[0121] Application Example 8:

[0122] The only difference from Application Example 1 is that the photoinitiator is the photoinitiator prepared in Example 8.

[0123] Application Example 9:

[0124] The only difference from Application Example 1 is that the photoinitiator is the photoinitiator prepared in Example 9.

[0125] Application Example 10:

[0126] The only difference from Application Example 1 is that the photoinitiator is the photoinitiator prepared in Example 10.

[0127] Application Example 11:

[0128] The only difference from Application Example 1 is that the photoinitiator is the photoinitiator prepared in Example 11.

[0129] Application Example 12:

[0130] The only difference from Application Example 1 is that the photoinitiator is the photoinitiator prepared in Example 12.

[0131] Application Example 13:

[0132] The only difference from Application Example 1 is that diphenyliodonium hexafluorophosphate co-initiator is added. Figure 14 This is the photopolymerization effect of the two-component photoinitiator system.

[0133] Application Example 14:

[0134] The only difference from Application Example 1 is that N-methyldiethanolamine co-initiator is added.

[0135] Application Example 15:

[0136] The only difference from Application Example 1 is that diphenyliodonium hexafluorophosphate is added as a co-initiator and the polymerization monomer is polyethylene glycol diacrylate.

[0137] Application Example 16:

[0138] The only difference from Application Example 1 is that diphenyliodonium hexafluorophosphate is added as a co-initiator and the polymerization monomer is trimethylolpropane triacrylate.

[0139] Application Example 17:

[0140] The only difference from Application Example 1 is that diphenyliodonium hexafluorophosphate is added as a co-initiator and the polymerization monomer is di(trimethylolpropane)tetraacrylate.

[0141] Application Example 18:

[0142] The only difference from Application Example 1 is that diphenyliodonium hexafluorophosphate co-initiator is added and the mold thickness is 3 mm.

[0143] Application Example 19:

[0144] The only difference from Application Example 1 is that diphenyliodonium hexafluorophosphate co-initiator is added and the mold thickness is 6 mm.

[0145] Application Example 20:

[0146] The only difference from Application Example 1 is that diphenyliodonium hexafluorophosphate co-initiator is added and the light source is an LED lamp (450 nm). Figure 15 This is the photopolymerization effect of the two-component photoinitiator system.

[0147] Application Example 21:

[0148] The only difference from Application Example 1 is that the light source is outdoor natural sunlight. Figure 16 is the photopolymerization effect of the initiator.

[0149] Application Example 22:

[0150] The only difference from Application Example 1 is that diphenyliodonium hexafluorophosphate co-initiator is added and the light source is outdoor natural sunlight. Figure 17 This is the photopolymerization effect of the two-component photoinitiator system.

[0151] Application Example 23:

[0152] The only difference from Application Example 1 is that the amount of photoinitiator used in Example 1 is 0.001 wt % of the photopolymerization system.

[0153] Application Example 24:

[0154] The only difference from Application Example 1 is that the amount of photoinitiator used in Example 1 is 0.1 wt % of the photopolymerization system.

[0155] The effects of photoinitiators are shown in Table 1 below.

[0156] Application Comparative Example 1:

[0157] The only difference from Application Example 1 is that the photoinitiator is commercial OXE-01.

[0158] The effects of photoinitiators are shown in Table 1 below.

[0159] Application Comparative Example 2:

[0160] The only difference from Application Example 1 is that the photoinitiator is commercial OXE-02.

[0161] The effects of photoinitiators are shown in Table 1 below.

[0162] Application Comparative Example 3:

[0163] The only difference from Application Example 1 is that the photoinitiator is commercial OXE-01 and the light source is an LED lamp (450 nm).

[0164] Application Comparative Example 4:

[0165] The only difference from Application Example 1 is that the photoinitiator is commercial OXE-01 and the light source is outdoor natural sunlight.

[0166] The effects of photoinitiators are shown in Table 1 below.

[0167] Table 1 Photoinitiator test results

[0168]

[0169] Table 1 shows the free radical polymerization results. Under irradiation with light sources such as LED @ 450nm, xenon lamp (simulated sunlight), and outdoor sunlight, the final double bond conversion rates of tripropylene glycol diacrylate initiated by these 12 donor-acceptor oxime ester photoinitiators were highly correlated with the substituent groups, showing a trend of aromatic groups > cycloalkyl groups > linear alkyl groups. Specifically, under irradiation with light sources such as LED @ 450nm, xenon lamp (simulated sunlight), and outdoor sunlight, the final monomer conversion rate of tripropylene glycol diacrylate induced by aromatic groups reached over 90% (cured thickness of 1.5mm). Addition of co-initiators such as diphenyliodonium hexafluorophosphate and N-methyldiethanolamine shortened the curing time to 120 seconds. These results demonstrate that these donor-acceptor oxime ester photoinitiators possess excellent free radical photoinitiating activity.

Claims

1. An oxime ester photoinitiator having a donor-acceptor structure, the general chemical structure of which is shown in the following formula (I): In formula (I): The substituent R is selected from any one of a phenyl group, a thienyl group, a furyl group, a C3-C6 cycloalkyl group, and a C1-C5 straight-chain alkyl group.

2. The oxime ester photoinitiator having a donor-acceptor structure according to claim 1, characterized in that: The structural formula of the photoinitiator is selected from any one of the following structures: 。 3. The method for preparing the oxime ester photoinitiator having a donor-acceptor structure according to claim 1, wherein: The steps include: (1) 4-[N,N-bis(4-bromophenyl)amino]benzaldehyde, pyridine boronic acid, acid binding agent, catalyst, and organic solvent are reacted in an oil bath at 65-85°C. After the reaction is completed, the liquid is separated and extracted, the organic solvent is removed, and the reaction is purified to obtain the intermediate monomer S1; (2) The intermediate monomer S1 reacts with hydroxylamine hydrochloride under the catalysis of a base to produce the oxime structure S2; (3) The intermediate product S2 continues to undergo esterification reaction with acyl chloride under the action of a base acid-binding agent to prepare an oxime ester intermediate monomer S3; (4) reflux reaction of the oxime ester intermediate monomer S3 and iodinated n-butane in an organic solvent, and after completion of the reaction, filter and collect the solid to obtain the oxime ester photoinitiator having a donor-acceptor structure in the general formula (I); The synthetic route is as follows: 。 4. The preparation method according to claim 3, characterized in that The acid binding agent in step (1) includes one or more of sodium carbonate, potassium carbonate, and cesium carbonate; The catalyst is one or more of a salt of zero-valent Pd(0) and Ni(0) and a phosphorus complex; The organic solvent is one or more of toluene, tetrahydrofuran, and acetonitrile; The molar ratio of the pyridine boronic acid to 4-[N,N-bis(4-bromophenyl)amino]benzaldehyde is (2.1-2.8):

1.

5. The preparation method according to claim 3, characterized in that The base in step (2) is one or more of sodium hydroxide, potassium hydroxide, sodium acetate, and potassium acetate; The reaction process also contains a solvent, which is one or more of ethanol, methanol, isopropanol, and n-butanol.

6. The preparation method according to claim 3, characterized in that The alkaline acid-binding agent in step (3) is one or more of triethylamine, sodium carbonate, sodium bicarbonate, potassium carbonate, and sodium hydride; The reaction process also contains a solvent, which is one or more of dichloromethane, chloroform, and tetrahydrofuran.

7. The preparation method according to claim 3, characterized in that The molar ratio of the intermediate monomer S3 and n-butane iodide in step (4) is 1:(2.5-3.5); The organic solvent is one or more of acetonitrile, toluene and N,N-dimethylformamide.

8. A visible light photoinitiator, characterized in that The oxime ester photoinitiator having a donor-acceptor structure according to claim 1 or 2.

9. A photoinitiator for use in a free radical photopolymerization system, characterized in that: The resin composition is prepared by comprising the oxime ester photoinitiator with a donor-acceptor structure according to claim 1 or 2 and any one of tripropylene glycol diacrylate, polyethylene glycol diacrylate, trimethylolpropane triacrylate and di(trimethylolpropane) tetraacrylate.

10. The photoinitiator for use in a free radical photopolymerization system according to claim 9, characterized in that: The photoinitiator used in the free radical photopolymerization system further contains a co-initiator, wherein the co-initiator is any one of diphenyliodonium hexafluorophosphate and N-methyldiethanolamine; In the photopolymerization system, the amount of the oxime ester photoinitiator having a donor-acceptor structure is 0.001 wt% to 0.1 wt% of the photopolymerization system.

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