Naphthalimide photoinitiator, synthetic method and application

Abstract

The invention relates to a naphthalimide photoinitiator as well as a synthesis method and application thereof. The method takes 4-bromo-1, 8-naphthenic anhydride as a starting raw material, and is efficiently synthesized through three steps of reaction: 1, under the catalysis of cuprous iodide and bis (triphenylphosphine) palladium dichloride, carrying out Sonogashira coupling on the compound and 1-octyne in tetrahydrofuran, and introducing an eight-carbon alkyne long chain to obtain a compound 3; secondly, the compound 3 and ethanolamine (0.37 g, 6 mmol) are subjected to aminolysis in ethyl alcohol, an intermediate compound 4 containing hydroxyl is generated, and the yield is as high as 92%; and 3, reacting the compound 4 with 2-chloroethyl isocyanate under the catalysis of dibutyltin dilaurate to generate a final product compound 1, and the yield reaches 95%. The process route is simple, the condition is mild, the total yield is high, and the obtained photoinitiator has excellent solubility, reaction activity and compatibility with high polymer materials and is suitable for a photocuring system.

Description

Technical Field

[0001] This invention belongs to the field of photoinitiator synthesis technology, and specifically relates to a naphthalimide photoinitiator, its synthesis method, and its application. Background Technology

[0002] The development of photoinitiators for polymerization is an active research field. Developing initiators that can be activated in the visible light range and under low light intensity has been a key focus of research in both academia and industry. Compared to traditional thermal polymerization, photopolymerization transforms liquid resin into a solid polymer film upon exposure to a light source, offering many significant advantages. For example, compared to the hours required for traditional thermal polymerization to produce the target polymer, photopolymerization can complete the polymerization process rapidly. Furthermore, photopolymerization can be carried out under solvent-free conditions, greatly limiting the release of volatile organic compounds (VOCs). Additionally, no post-polymerization processing is required. Thanks to these advantages, the application of photopolymerization was initially limited to coatings and adhesives, but has recently expanded into emerging research areas such as 3D and 4D printing.

[0003] In recent years, the polyaromatic compound families of 1,8-naphthoic anhydride and naphthalimide have been extensively studied due to their ease of synthesis and the ease of tuning their photophysical properties. In particular, full-color, crosslinked, or water-soluble photoinitiators have been developed using inexpensive 1,8-naphthoic anhydride as a starting material. However, 1,8-naphthoimide compounds exhibit poor solubility in organic materials and are prone to migration and precipitation within the material.

[0004] Specifically, current naphthalimide photoinitiators have the following drawbacks: (1) Poor compatibility and dispersibility in resin systems: The unmodified 1,8-naphthalimide core structure exhibits poor solubility in organic resins, making it difficult to disperse uniformly in polymerization precursors (monomers / oligomers). This poor compatibility can lead to uneven illumination, low curing efficiency, and affect the mechanical properties and appearance uniformity of the final polymer materials (such as coatings and 3D printed products). (2) Small molecule migration and precipitation are severe Traditional small-molecule naphthalimide photoinitiators only physically blend with polymer networks, lacking chemical bonding. After polymerization or during product use, initiator molecules and their degradation products migrate from the interior of the cured material to the surface and precipitate. This leads to yellowing and aging of the material, affecting the long-term stability and appearance of the product. The leached substances may pose biotoxicity or sensitization risks, making them unsuitable for applications in fields with high safety requirements, such as biomedicine and food packaging. This is a fundamental obstacle preventing their application in high-value-added fields, such as high-end electronic packaging and biocompatible devices. (3) Single molecular function: Traditional molecular structures lack functional groups for specific applications, such as those requiring high lipid solubility or copolymerization with resins. Their limited modifiability and adaptability restrict their performance in complex formulations and advanced manufacturing technologies, such as thick-section curing and 4D printing.

[0005] Therefore, it is necessary to improve upon the above-mentioned defects and invent a naphthalimide photoinitiator / photoinitiator compound that can increase its lipid solubility and solve the problem of easy precipitation and migration in application. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention uses naphthalimide as a substrate and introduces an alkynyl chain at position 6 of the naphthalic anhydride core to form a naphthalimide photoinitiator. This initiator is characterized by modifying the naphthalene ring structure with a long-chain structure, increasing its lipophilicity and simultaneously adjusting the light response wavelength range. The introduction of groups that readily covalently condense with resins in this structure solves the problem of easy precipitation and migration of naphthalimide photoinitiators during application.

[0007] In the compounds synthesized in this invention, the structure modified at position 2 of the naphthenic anhydride core can be grafted and crosslinked with some organic resins, eliminating its migration from the interior of the resin material to the surface and precipitation; the long-chain structure modified at position 6 of the naphthenic anhydride core and the lipophilic group modified at position 2 both increase the compatibility of the compounds in organic resins.

[0008] The naphthalimide photoinitiator of the present invention has the following structural formula: .

[0009] The above-mentioned method for synthesizing naphthalimide photoinitiators is as follows: using naphthalimide as a substrate, an alkynyl chain is introduced at position 6 of the naphthalic anhydride core to form a naphthalimide photoinitiator.

[0010] Given that naphthalimide photoinitiators have the above-mentioned structure, they are applied in coatings, adhesives, 3D and 4D printing.

[0011] The synthetic route for the naphthalimide photoinitiator in this application is as follows: (1)

[0012] (2)

[0013] (3)

[0014] Naphthalimide photoinitiators have the following structural formula: .

[0015] Using naphthalimides as substrates, an alkynyl chain is introduced at position 6 of the naphthalic anhydride core to form a naphthalimide photoinitiator.

[0016] The synthesis method of naphthalimide photoinitiators includes the following steps: (1) Naphthalic anhydride is designated as compound II. Naphthalic anhydride, triphenylphosphine, triethylamine and tetrahydrofuran are taken and stirred under nitrogen protection. Cuprous iodide and bistriphenylphosphine palladium dichloride are then added, followed by tetrahydrofuran and 1-octyne. The mixture is heated to reflux and reacted. The mixture is then slowly cooled to room temperature. Deionized water is added and filtered to obtain a brown solid. The solid is dissolved in dichloromethane, washed with deionized water, and separated to obtain a dichloromethane solution. The dichloromethane solvent is removed by distillation to obtain a solid product, designated as compound III. (2) Add compound III to ethanol, heat to reflux, then add ethanolamine, reflux and stir. The resulting solution gradually changes from turbid to clear. After cooling to room temperature, a precipitate is formed. Filter to obtain a yellow solid. Wash with cold water and cold ethanol, and dry under vacuum. The product obtained is called: compound IV. (3) Compound IV and 2-chloroethyl isocyanate were added to dichloromethane and stirred thoroughly. Then, dibutyltin dilaurate was added to react, cooled, filtered, and the solvent was removed by vacuum distillation to obtain a naphthalimide photoinitiator, denoted as compound I.

[0017] Preferably, in (1) above, the naphthoic anhydride is 4-bromo-1,8-naphthoic anhydride; The molar ratio of naphthic anhydride to triphenylphosphine and triethylamine is (8~12):(0.2~1.2):(15~25). The volume-to-mass ratio of the first addition of tetrahydrofuran to naphthalic anhydride was (10~50) mL : (2~3) g; The molar ratios of cuprous iodide, palladium dichloride bis(triphenylphosphine) and naphthic anhydride are respectively: (0.1~0.5): (0.06~0.15) (6~15); The volume-to-mass ratio of the second addition of tetrahydrofuran to naphthalic anhydride was (5~15) mL : (2~3) g; The molar ratio of 1-octyne to naphthenic anhydride is (5~15):(6~16); The ratio of deionized water to total tetrahydrofuran is 1:1.8~2.4.

[0018] Preferably, in the above (1), the mixture is stirred for 0.8 to 1.2 hours under nitrogen protection; the mixture is heated for 2 to 3 hours; and refluxed for 8 to 16 hours.

[0019] Preferably, in (2) above, the mass-volume ratio of compound III to ethanol is (1.0~2.5) g : (20~50) mL; the molar ratio of compound III to added ethanolamine is (4~8) : (4~10).

[0020] Preferably, in step (2) above, the mixture is refluxed and stirred for 0.5 to 3 hours; and washed 1 to 5 times each with cold water and cold ethanol.

[0021] Preferably, in the above (3), the molar ratio of compound IV, 2-chloroethyl isocyanate and dibutyltin dilaurate is (3.0~8.0):(3.0~10.0):(0.03~0.12); the mass-volume ratio of compound IV to dichloromethane is (1.0~3.0) g:(10~30) mL.

[0022] Preferably, the method for synthesizing naphthalimide photoinitiators includes the following steps: (1) Take naphthic anhydride, triphenylphosphine, triethylamine and tetrahydrofuran, stir the above raw materials for 0.8~1.2h under nitrogen protection, then add cuprous iodide and bistriphenylphosphine palladium dichloride, then add tetrahydrofuran and 1-octyne, heat the mixture to reflux, react for 8~12h, slowly cool to room temperature, add deionized water, filter to obtain brown solid, dissolve it in dichloromethane, distill to remove dichloromethane solvent to obtain solid product, denoted as: compound III; The molar ratio of naphthic anhydride, triphenylphosphine, and triethylamine is (9.0~11.0):(0.5~1.1):(18~22). The volume-to-mass ratio of the first addition of tetrahydrofuran to naphthalic anhydride was (20~40) mL : (2.5~3.0) g; The molar ratios of cuprous iodide, palladium dichloride bis(triphenylphosphine) and naphthic anhydride are respectively: (0.1~0.5):(0.06~0.15):(6.0~15.0). The volume-to-mass ratio of the second addition of tetrahydrofuran to naphthalic anhydride was (8.0~12.0) mL : (2.5~3) g; The molar ratio of 1-octyne to naphthic anhydride is (8.0~12.0):(8.0~11.0); The ratio of deionized water to total tetrahydrofuran is 1:1.9~2.2.

[0023] (2) Compound III was added to ethanol and heated to reflux. Then ethanolamine was added and stirred under reflux. The resulting solution gradually changed from turbid to clear. After cooling to room temperature, a precipitate was formed. The precipitate was filtered to obtain a yellow solid. The solid was washed three times with cold water and three times with cold ethanol and dried under vacuum. The product was named: Compound IV. The mass-volume ratio of Compound III to ethanol was (1.0~2.0) g : (20.0~40.0) mL. The molar ratio of Compound III to added ethanolamine was (5.0~7.0) : (5.0~8.0). (3) Compound IV and 2-chloroethyl isocyanate were added to dichloromethane. After stirring thoroughly, dibutyltin dilaurate was added to react. After cooling, filtration, and removal of solvent by vacuum distillation, a naphthimide photoinitiator was obtained, denoted as compound I. The molar ratio of compound IV, 2-chloroethyl isocyanate and dibutyltin dilaurate was (4.0~6.0):(4.0~7.0):(0.05~0.09). The mass-volume ratio of compound IV to dichloromethane was (1.0~2.0) g:(15~30) mL.

[0024] The present invention also includes the use of naphthalimide photoinitiators in the preparation of coatings or adhesives, and in 3D or 4D printing.

[0025] The present invention has the following advantages and effects compared with the prior art: (1) In the compound synthesized in this invention, the structure modified at position 2 of the naphthalene anhydride core can be grafted and crosslinked with some organic resins, eliminating its migration from the interior of the resin material to the surface and precipitation; the long-chain structure modified at position 6 of the naphthalene anhydride core and the lipophilic group modified at position 2 both increase the compatibility of the compound in organic resins.

[0026] (2) This invention starts with the structure of naphthalimide and uses 4-bromo-1,8-naphthalic anhydride as raw material. Under the action of palladium catalyst, a long alkynyl chain is introduced at the 6 position of the naphthalene ring through a coupling reaction, which increases the solubility of the compound in organic matter. The resulting compound is condensed with aminoethanol and then with 2-chloroethyl isocyanate, which makes it easy to covalently bond with resin materials, prevent material migration and precipitation, and obtain a high-performance photoinitiator. (3) The entire synthesis process requires only three steps, and the operation process is clear; the yield of each step is high (92% in the second step and 95% in the third step), the emissions of waste are low, the total yield of the final product is high, and the raw materials and catalysts are common or commercial reagents that are easy to obtain, which provides a basis for the reproducibility and scale-up of the method and is conducive to industrial production. (4) The reaction is safe and reliable, the reaction conditions are mild, the post-processing is simple, and the product purity is high. The key steps are carried out at reflux temperature, avoiding extreme high temperature or high pressure conditions, reducing energy consumption and equipment requirements, and making the production process safer and more controllable. (5) This method successfully introduces long alkyne chains and active urethane structures into the naphthalimide skeleton through efficient coupling reaction and aminolysis / addition reaction. These groups are crucial for enhancing the solubility, reactivity and compatibility of the photoinitiator with polymer materials. (6) High-purity intermediates and final products can be obtained without complicated column chromatography separation, which simplifies the operation and reduces costs. Attached Figure Description

[0027] Figure 1 The 1H NMR spectrum of compound 3; Figure 2 The 1H NMR spectrum of compound 4; Figure 3 The carbon NMR spectrum of compound 4; Figure 4 The 1H NMR spectrum of compound 1; Figure 5 This is the carbon NMR spectrum of compound 1. Detailed Implementation

[0028] To enable those skilled in the art to better understand the present invention, specific embodiments will now be described in further detail. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0029] Example 1: 4-Bromo-1,8-naphthoic anhydride (compound 2, 2.6 g, 9.5 mmol), triphenylphosphine (0.2 g, 0.76 mmol), triethylamine (2 g, 19.9 mmol) and 30 mL of tetrahydrofuran were added to a 100 mL flask and stirred for 1 h under nitrogen protection. Cuprous iodide (0.054 g, 0.28 mmol) and bis(triphenylphosphine) palladium dichloride (0.067 g, 0.095 mmol) were then added. After heating the mixture for 2.5 h, 10 mL of a tetrahydrofuran solution containing 1-octyne (1.1 g, 10 mmol) was gradually added dropwise. After reflux for 12 h, the mixture was slowly cooled to room temperature, and 20 mL of deionized water was added. Filtering yielded a brown solid. The solid was dissolved in dichloromethane, washed three times with deionized water, dried the organic phase, and the solvent was evaporated under reduced pressure to give 2.50 g of compound 3, with a yield of 87%.

[0030] The proton NMR spectrum of compound 3 is as follows: Figure 1 As shown.

[0031] 1H NMR (500 MHz, CDCl3) δ 7.70 (1H, d, -ArH), 7.60 (1H, d, -ArH), 7.39(1H, d, -ArH), 7.25 (1H, d, -ArH),7.23 (1H, d, -ArH), 2.26-2.22 (2H, m, -CH2-), 2.04-1.97 (2H, m, -CH2-), 1.95-1.1.92 (2H, m, -CH2-), 0.98-0.96 (2H, m,-CH2-), 0.90-0.84 (2H, m, -CH2-), 0.80-0.76 (3H, m, -CH3) Example 2: 4-Bromo-1,8-naphthoic anhydride (compound 2, 2.6 g, 9.5 mmol), triphenylphosphine (0.125 g, 0.475 mmol), triethylamine (2 g, 19.9 mmol) and 30 mL of tetrahydrofuran were added to a 100 mL flask and stirred for 1 h under nitrogen protection. Cuprous iodide (0.054 g, 0.28 mmol) and bis(triphenylphosphine)palladium dichloride (0.067 g, 0.095 mmol) were then added. After heating the mixture for 2.5 h, 10 mL of a tetrahydrofuran solution containing 1-octyne (1.1 g, 10 mmol) was gradually added dropwise. After reflux for 12 h, the mixture was slowly cooled to room temperature, and 20 mL of deionized water was added. Filtering yielded a brown solid. The solid was dissolved in dichloromethane, washed three times with deionized water, dried the organic phase, and the solvent was evaporated under reduced pressure to give 2.09 g of compound 3, with a yield of 73%.

[0032] Example 3: 4-Bromo-1,8-naphthoic anhydride (compound 2, 2.6 g, 9.5 mmol), triphenylphosphine (0.2 g, 0.76 mmol), triethylamine (2 g, 19.9 mmol) and 30 mL of tetrahydrofuran were added to a 100 mL flask and stirred for 1 h under nitrogen protection. Cuprous iodide (0.054 g, 0.28 mmol) and bis(triphenylphosphine) palladium dichloride (0.034 g, 0.048 mmol) were then added. After heating the mixture for 2.5 h, 10 mL of a tetrahydrofuran solution containing 1-octyne (1.1 g, 10 mmol) was gradually added dropwise. After reflux for 12 h, the mixture was slowly cooled to room temperature, and 20 mL of deionized water was added. The resulting product was a brown solid, which was dissolved in dichloromethane and washed with deionized water. The solution was then separated and rotary evaporated to give 1.79 g of compound 3, with a yield of 62.4%.

[0033] Example 4: 4-Bromo-1,8-naphthoic anhydride (compound 2, 26 g, 95 mmol), triphenylphosphine (2 g, 7.6 mmol), triethylamine (20 g, 199 mmol) and 300 mL of tetrahydrofuran were added to a 500 mL flask and stirred for 1 h under nitrogen protection. Cuprous iodide (5.4 g, 28 mmol) and bis(triphenylphosphine)palladium dichloride (0.34 g, 0.48 mmol) were then added. After heating the mixture for 2.5 h, 50 mL of tetrahydrofuran solution containing 1-octyne (11 g, 100 mmol) was gradually added dropwise; after reflux for 18 h, the mixture was slowly cooled to room temperature, and 100 mL of deionized water was added; after filtration, a brown solid was obtained. The solid was dissolved in dichloromethane, washed three times with deionized water, dried the organic phase, and the solvent was evaporated under reduced pressure to give 24.5 g of compound 3, with a yield of 85%.

[0034] Example 5: Compound 3 (1.7 g, 5.5 mmol) was added to 30 mL of ethanol and heated to reflux. Then, ethanolamine (0.37 g, 6 mmol) was added and stirred under reflux for 1 h. The solution gradually changed from turbid to clear. After cooling to room temperature, a precipitate was formed. The precipitate was filtered to obtain a yellow solid. The solid was washed three times with cold water and three times with cold ethanol and dried under vacuum to obtain 1.78 g of compound 4, with a yield of 92%.

[0035] The proton NMR spectrum of compound 4 is as follows: Figure 2 As shown; the carbon NMR spectrum of compound 4 is as follows. Figure 3 As shown.

[0036] 1 H NMR (500 MHz, DMSO-d6) δ 8.57 (1H, d, J = 7.9 Hz, -ArH), 8.54 (1H, d, J = 7.9 Hz, -ArH), 8.33 (1H, d, J =7.8 Hz, -ArH), 8.22 (1H, d, J =7.8 Hz, -ArH), 8.00 (1H, d, J =7.3 Hz, -ArH), 4.14 (2H, t, J =6.5 Hz, -CH2OH), 3.63 (2H, t, J=5.7Hz, -NCH2-), 1.23-1.18 (2H, m, -CH2-), 1.16-1.08 (2H, m, -CH2-), 1.06-1.04(2H, m, -CH2-), 1.00-0.93 (2H, m, -CH2-), 0.92-0.87 (2H, m, -CH2-), 0.85-0.76(3H, m, -CH3); 13 C NMR (125 MHz, DMSO-d6) δ 163.4, 163.3, 132.9, 132.5, 132.4,132.0, 131.9, 131.7, 131.3, 130.1, 129.4, 129.2, 129.1, 123.2, 122.5, 58.2,42.4, 31.2, 28.6, 28.4, 22.5, 14.4.

[0037] Example 6: Compound 3 (1.7 g, 5.5 mmol) was added to 30 mL of ethanol and heated to reflux. Then, ethanolamine (0.34 g, 5.5 mmol) was added and stirred under reflux for 1 h. The solution gradually changed from turbid to clear. After cooling to room temperature, a precipitate was formed. The precipitate was filtered to obtain a yellow solid. The solid was washed three times with cold water and three times with cold ethanol and dried under vacuum to obtain 1.70 g of compound 4, with a yield of 88%.

[0038] Example 7: Compound 3 (17 g, 55 mmol) was added to 200 mL of ethanol and heated to reflux. Then, ethanolamine (3.7 g, 60 mmol) was added and stirred under reflux for 1 h. The solution gradually changed from turbid to clear. After cooling to room temperature, a precipitate was formed. The precipitate was filtered to obtain a yellow solid. The solid was washed three times with cold water and three times with cold ethanol and dried under vacuum to obtain 17.4 g of compound 4, with a yield of 90%.

[0039] Example 8: Compound 4 (1.7 g, 4.9 mmol) and 2-chloroethyl isocyanate (0.53 g, 5.0 mmol) were added to 20 mL of dichloromethane. After thorough stirring, dibutyltin dilaurate (0.05 g, 0.08 mmol) was added. The mixture was reacted at 100 °C for 2 h, cooled, filtered, and the solvent was removed by vacuum distillation to obtain 2.1 g of compound 1, with a yield of 95%.

[0040] The proton NMR spectrum of compound 1 is as follows: Figure 4 As shown; the carbon NMR spectrum of compound 1 is as follows. Figure 5 As shown.

[0041] 1 H NMR (500 MHz, DMSO-d6) δ 8.55 (1H, d, J =7.9 Hz, -ArH), 8.52 (1H, d, J =7.9 Hz, -ArH), 8.31 (1H, d, J =7.8 Hz, -ArH), 8.20 (1H, d, J =7.9 Hz, -ArH), 7.99 (1H, d, J =7.3 Hz, -ArH), 4.28 (2H, t, J =5.8 Hz, -CH2O-), 4.29 (2H, t, J =5.7Hz, -NCH2-), 3.45 (2H, t, J =6.3Hz, -NCH2-), 3.18 (2H, t, J =6.1Hz, -CH2Cl),1.49-1.48 (2H, m, -CH2-), 1.37-1.33 (2H, m, -CH2-), 1.27-1.23 (2H, m, -CH2-),1.18-1.14 (2H, m, -CH2-), 1.06-0.88 (2H, m, -CH2-), 0.87-0.77 (3H, m, -CH3); 13 CNMR (125 MHz, DMSO-d6) δ 163.3, 163.3, 156.5, 133.1, 132.1, 131.8, 131.5,130.2, 129.7, 129.2, 128.7, 123.1, 122.3,61.3, 43.6, 42.7, 31.8, 31.2, 29.8,29.5, 29.2, 28.6, 22.6, 22.5, 14.4.

[0042] Example 9: Compound 4 (17 g, 49 mmol) and 2-chloroethyl isocyanate (5.3 g, 50 mmol) were added to 150 mL of dichloromethane. After thorough stirring, dibutyltin dilaurate (0.5 g, 0.8 mmol) was added. The mixture was reacted at 100 °C for 5 h, cooled, filtered, and the solvent was removed by vacuum distillation to obtain 19.6 g of compound 1, with a yield of 89%.

[0043] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. All equivalent changes and modifications made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. A naphthalimide-based photoinitiator, characterized in that: The initiator has the following structural formula: 。 2. The method for synthesizing naphthalimide photoinitiators as described in claim 1, characterized in that, Using naphthalimides as substrates, an alkynyl chain is introduced at position 6 of the naphthalic anhydride core to form a naphthalimide photoinitiator.

3. The method for synthesizing naphthalimide photoinitiators as described in claim 1, characterized in that, The steps include the following: (1) Naphthalic anhydride is designated as compound II. Naphthalic anhydride, triphenylphosphine, triethylamine and tetrahydrofuran are taken and stirred under nitrogen protection. Cuprous iodide and bistriphenylphosphine palladium dichloride are then added, followed by tetrahydrofuran and 1-octyne. The mixture is heated to reflux and reacted. The mixture is then slowly cooled to room temperature. Deionized water is added and filtered to obtain a brown solid. The solid is dissolved in dichloromethane, washed with deionized water, and separated to obtain a dichloromethane solution. The dichloromethane solvent is removed by distillation to obtain a solid product, designated as compound III. (2) Add compound III to ethanol, heat to reflux, then add ethanolamine, reflux and stir. The resulting solution gradually changes from turbid to clear. After cooling to room temperature, a precipitate is formed. Filter to obtain a yellow solid. Wash with cold water and cold ethanol, and dry under vacuum. The product obtained is called: compound IV. (3) Compound IV and 2-chloroethyl isocyanate were added to dichloromethane and stirred thoroughly. Then, dibutyltin dilaurate was added to react, cooled, filtered, and the solvent was removed by vacuum distillation to obtain a naphthalimide photoinitiator, denoted as compound I.

4. The method for synthesizing naphthalimide photoinitiators as described in claim 3, characterized in that, In (1), the naphthoic anhydride is 4-bromo-1,8-naphthoic anhydride; The molar ratio of naphthic anhydride to triphenylphosphine and triethylamine is (8~12):(0.2~1.2):(15~25). The volume-to-mass ratio of the first addition of tetrahydrofuran to naphthalic anhydride was (10~50) mL : (2~3) g; The molar ratios of cuprous iodide, palladium dichloride bis(triphenylphosphine) and naphthic anhydride are respectively: (0.1~0.5): (0.06~0.15) (6~15); The volume-to-mass ratio of the second addition of tetrahydrofuran to naphthalic anhydride was (5~15) mL : (2~3) g; The molar ratio of 1-octyne to naphthenic anhydride is (5~15):(6~16); The ratio of deionized water to total tetrahydrofuran is 1:1.8~2.

4.

5. The method for synthesizing the naphthalimide photoinitiator according to any one of claims 3-4, characterized in that, (1) Stir under nitrogen protection for 0.8~1.2h; heat the mixture for 2~3h; reflux for 8~16h.

6. The method for synthesizing naphthalimide photoinitiators as described in claim 5, characterized in that, In (2), the mass-volume ratio of compound III to ethanol is (1.0~2.5) g : (20~50) mL; the molar ratio of compound III to added ethanolamine is (4~8) : (4~10).

7. The method for synthesizing the naphthalimide photoinitiator as described in claim 6, characterized in that, (2) Reflux and stir for 0.5 to 3 hours; wash with cold water and cold ethanol 1 to 5 times each.

8. The method for synthesizing the naphthalimide photoinitiator as described in claim 7, characterized in that, In (3), the molar ratio of compound IV, 2-chloroethyl isocyanate and dibutyltin dilaurate is (3.0~8.0): (3.0~10.0): (0.03~0.12); the mass-volume ratio of compound IV to dichloromethane is (1.0~3.0) g: (10~30) mL.

9. The method for synthesizing the naphthalimide photoinitiator as described in claim 3, comprising the following steps: (1) Take naphthic anhydride, triphenylphosphine, triethylamine and tetrahydrofuran, stir the above raw materials for 0.8~1.2h under nitrogen protection, then add cuprous iodide and bistriphenylphosphine palladium dichloride, then add tetrahydrofuran and 1-octyne, heat the mixture to reflux, react for 8~12h, slowly cool to room temperature, add deionized water, filter to obtain brown solid, dissolve it in dichloromethane, distill to remove dichloromethane solvent to obtain solid product, denoted as: compound III; in, The molar ratio of naphthic anhydride, triphenylphosphine, and triethylamine is (9.0~11.0):(0.5~1.1):(18~22). The volume-to-mass ratio of the first addition of tetrahydrofuran to naphthalic anhydride was (20~40) mL : (2.5~3.0) g; The molar ratios of cuprous iodide, palladium dichloride bis(triphenylphosphine) and naphthic anhydride are respectively: (0.1~0.5):(0.06~0.15):(6.0~15.0). The volume-to-mass ratio of the second addition of tetrahydrofuran to naphthalic anhydride was (8.0~12.0) mL : (2.5~3) g; The molar ratio of 1-octyne to naphthic anhydride is (8.0~12.0):(8.0~11.0); The ratio of deionized water to total tetrahydrofuran used is 1:1.9~2.2; (2) Compound III was added to ethanol and heated to reflux. Then ethanolamine was added and stirred under reflux. The resulting solution gradually changed from turbid to clear. After cooling to room temperature, a precipitate was formed. The precipitate was filtered to obtain a yellow solid. The solid was washed three times with cold water and three times with cold ethanol and dried under vacuum. The product was named: Compound IV. The mass-volume ratio of Compound III to ethanol was (1.0~2.0) g : (20.0~40.0) mL. The molar ratio of Compound III to added ethanolamine was (5.0~7.0) : (5.0~8.0). (3) Compound IV and 2-chloroethyl isocyanate were added to dichloromethane. After stirring thoroughly, dibutyltin dilaurate was added to react. After cooling, filtration, and removal of solvent by vacuum distillation, a naphthimide photoinitiator was obtained, denoted as compound I. The molar ratio of compound IV, 2-chloroethyl isocyanate and dibutyltin dilaurate was (4.0~6.0):(4.0~7.0):(0.05~0.09). The mass-volume ratio of compound IV to dichloromethane was (1.0~2.0) g:(15~30) mL.

10. Application of naphthalimide photoinitiators in the preparation of coatings or adhesives, and in 3D or 4D printing.

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