A coumarin-based thioester photoinitiator suitable for photopolymerization and its preparation method

Abstract

The application discloses a coumarin-based thioester photoinitiator suitable for photopolymerization and a preparation method thereof, relates to the field of polymer photopolymerization, and solves the problems of a deep color of a cured film, relatively large cytotoxicity and incapability of initiating cationic photopolymerization of an existing photoinitiator under light source irradiation. The application has the beneficial effect that the initiator has good absorption capacity in the visible light region, can not only break bonds to initiate polymerization by itself under light source irradiation, but also can be compounded with a co-initiator tertiary amine to produce high initiation efficiency, and in addition, can sensitize cationic photoinitiators to realize effective polymerization of cationic monomers or resins. The initiator has good photobleaching performance and biocompatibility, and is helpful to the development of the photopolymerization industry.

Description

Technical Field

[0001] This invention relates to the field of photocuring (photopolymerization), and more specifically to a coumarin-based thioester photoinitiator suitable for photopolymerization and its preparation method. Background Technology

[0002] Currently available photoinitiators, in order to increase their absorption wavelength, often require highly stacked chromophore structures in their molecular structure. This complicates the synthetic routes of the initiator molecules and uses expensive metal catalysts as raw materials, increasing the biotoxicity of the initiator molecules and causing inconvenience to practical production applications. Furthermore, large conjugated structures can also deepen the color of the cured system. Therefore, the development of novel photoinitiators that can be used with long-wavelength light sources, have simple structures and synthetic routes, good biocompatibility, and photobleaching capabilities is urgently needed in the field of photocuring.

[0003] Meanwhile, most of the Norrish I-type photoinitiators reported so far cannot be compounded with tertiary amines and cannot sensitize cationic photoinitiators. Therefore, designing and synthesizing novel photoinitiators that can both act as Norrish I-type photoinitiators to initiate monomer polymerization and can be compounded with tertiary amines, and can also sensitize cationic photoinitiators, is one of the current research hotspots in the field of photocuring. Summary of the Invention

[0004] The technical problem solved by this invention is to provide a coumarin-based thioester photoinitiator suitable for photopolymerization and its preparation method. The initiator of this invention exhibits excellent absorption performance in the ultraviolet to visible light region, and is particularly well-matched to the emission wavelength of LED light sources, demonstrating good initiation performance under a 405nm LED light source. The initiator of this invention can effectively initiate the photopolymerization of acrylate monomers regardless of the presence or absence of a hydrogen donor. Furthermore, when the initiator is combined with iodonium salts, it can effectively initiate the cationic photopolymerization of epoxy resins. The initiator of this invention possesses good photobleaching properties and biocompatibility, and can be applied in the fields of colorless photopolymer materials and biomacromolecule materials. This type of photoinitiator is simple to synthesize, has low synthesis cost, and has extremely high practical value.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] 1. A coumarin-based thioester photoinitiator of general formula (I) suitable for photopolymerization, particularly for LED photopolymerization:

[0007]

[0008] in,

[0009] L represents: R1 is selected from O, S, and -NR. 14 -; R2, R3, R4, R5, R6, R7, R8, R9, R 10 R 11 R 12 and R 13 The electron-donating or electron-withdrawing groups, whether identical or different, are independently selected from those reported in the literature that have a good effect on improving the performance of the initiator, such as hydrogen, halogen, hydroxyl, amino, aryl, aralkyl, arylthio, aryloxy, ether chain, C1-C 20 Alkyl, C1-C 20 alkoxy groups, C1-C 20 alkyl mercapto, C1-C 20 hydroxyalkyl, C3-C 10 Cycloalkyl, mono(C1-C6 alkyl)amino, di(C1-C6 alkyl)amino, -OCF3, -OC6H5, -COOH, -CHO, -NO2, -CN, -CF3; R 14 Selected from hydrogen, C1-C 20 Alkyl groups. Preferably, R2, R3, R4, R5, R6, R7, R8, R9, R 10 R 11 R 12 and R 13 The same or different, and independently selected from aryl, hydrogen, fluorine, and methoxy groups. The wavy line in the structural formula represents a covalent bond connected to sulfur in structural formula (I).

[0010] 2. A coumarin-based thioester photoinitiator suitable for photopolymerization according to claim 1, characterized in that R 10 and R 13 The same and independent choices are H; R 11 R 12 The options were hydrogen, fluorine, and methoxy, but R... 11 and R 12 It cannot be both fluorine and both methoxy; if one is fluorine, the other cannot be methoxy.

[0011] 3. A coumarin-based thioester photoinitiator suitable for photopolymerization according to any one of claims 1 and 2, characterized in that L is... R2, R3, R5, R6, R7, R8, and R9 are selected as H; R4 is selected as fluorine or methoxy.

[0012] 4. A method for preparing a coumarin-based thioester photoinitiator suitable for photopolymerization as described in any one of items 1-3, characterized in that the general synthesis process of the photoinitiator is as follows:

[0013] (a)

[0014] (b)

[0015] Where L, R 10 R 11 R 12 and R 13 As described in Requirement 1.

[0016] 5. A method for preparing a coumarin-based thioester photoinitiator suitable for photopolymerization according to claim 4, characterized in that the preparation method of the compound includes the following steps:

[0017] (1) In step (a), reactant A is added to the reaction vessel, then isopropyl malonate is added, and an appropriate amount of solvent is added to dissolve the reactant. After the reaction is completed, the solid is retained and the intermediate product B is obtained by separation and purification.

[0018] (2) In step (b), intermediate product B, L-SH and catalyst are dissolved in solvent and added to the reaction vessel. Then, dehydrating agent is dissolved in solvent and added to the reaction vessel. Stirring continues. The solvent is removed and the final product is obtained after separation and purification.

[0019] 6. A method for preparing a coumarin-based thioester photoinitiator suitable for photopolymerization according to item 5, characterized in that, in step (a), the solvent is selected from deionized water, dichloromethane, ethyl acetate, tetrahydrofuran, dimethyl sulfoxide, and N,N-dimethylformamide; the molar ratio of reactant A to isopropyl malonate is preferably 1:1.1-1:2; in step (b), the dehydrating agent is preferably dicyclohexylcarbodiimide, diisopropylcarbodiimide, and 1-(3-dimethylaminopropyl)3-ethylcarbodiimide; the catalyst is preferably 4-dimethylaminopyridine, piperidine, 3-methylpiperidine, or triethylamine; the molar amount of the catalyst is preferably 1%-20% of intermediate product B, the molar amount of the dehydrating agent is preferably 100%-150% of intermediate product B, and the molar ratio of intermediate product B to L-SH is preferably 2:1-4:1.

[0020] 7. A composition capable of free radical photopolymerization, characterized in that it comprises a coumarin-based thioester photoinitiator suitable for photopolymerization as described in items 1, 2 and 3; preferably, the composition comprises 0.1%-2% of the coumarin-based thioester photoinitiator and 98%-99.9% of a photocurable resin or monomer, based on the total weight of the composition.

[0021] 8. The composition according to item 7, characterized in that the photopolymerizing resin is selected from one or more of epoxy (meth)acrylate resin, polyurethane (meth)acrylate resin, polyester (meth)acrylate resin, polyether (meth)acrylate resin, and acrylated poly (meth)acrylate resin; and the monomer is one or more of monofunctional, difunctional, or polyfunctional (meth)acrylate esters.

[0022] 9. The application of the coumarin-based thioester compound described in item 1 in colorless photopolymerization.

[0023] 10. The application of a coumarin-based thioester compound as described in item 1 in biopolymer materials.

[0024] In the following description of the invention, unless otherwise expressly stated, all numerical values ​​in this application are to be regarded as being modified by the word "approximately". However, the inventors have reported the numerical values ​​in the embodiments as accurately as possible, although these numerical values ​​inevitably include a certain degree of error.

[0025] The beneficial effects of this invention are as follows: The photoinitiator prepared by this invention can be applied in the field of photocuring. Under irradiation with commonly used emission wavelengths such as 365nm, 385nm, 395nm, and 405nm, it can act as a Norrish Type I photoinitiator to initiate the polymerization of (meth)acrylate monomers such as tripropylene glycol diacrylate (TPGDA), trimethylolpropane triacrylate (TMPTA), 1,6-hexanediol diacrylate (HDDA), 1,4-butanediol diacrylate (BDDA), ethylene glycol diacrylate, propylene glycol diacrylate, dipropylene glycol diacrylate, neopentyl glycol diacrylate, hexamethylene glycol diacrylate, and bisphenol A diacrylate; trimethylolethane triacrylate, trimethylolpropane trimethacrylate, methacrylate, triethylene glycol dimethacrylate (TEGDMA), and trimethylolethane trimethacrylate, etc. In addition, it can also act as a Norrish... Type II photoinitiators, when combined with tertiary amines such as ethyl 4-dimethylaminobenzoate and triethanolamine, produce excellent initiation effects. Furthermore, they can sensitize cationic photoinitiators, such as triphenylthionium hexafluorophosphate, diphenyliodonium hexafluorophosphate, and bis(4-tert-butylphenyl)iodohexafluorophosphate, to initiate the cationic photopolymerization of epoxy resins such as bisphenol A diglycidyl ether, 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexylcarbamate (E4221), and epoxy resin E51. The photoinitiators of this invention possess excellent photobleaching properties and biocompatibility, contributing to the development of the photocuring field.

[0026] The photoinitiator of this invention is applicable to commonly used light sources in the field of photopolymerization, including ultraviolet (UV) light sources, UV-LED light sources, visible light LED light sources, etc. Attached Figure Description

[0027] Figure 1 This is a possible initiation mechanism diagram of the photoinitiator of the present invention;

[0028] Figure 2 and Figure 3 The images show the UV absorption spectra of the coumarin-based thioester photoinitiators prepared in Examples 1-9.

[0029] Figure 4 This is a photopolymerization kinetic diagram of the polymerization of monomer tripropylene glycol diacrylate (TPGDA) initiated by the coumarin-based thioester photoinitiator prepared in Examples 1-9 under a 405nm LED light source;

[0030] Figure 5 This is a photopolymerization kinetic diagram of the polymerization of the monomer triethylene glycol dimethacrylate (TEGDMA) initiated by the coumarin-based thioester photoinitiator prepared in Synthesis Example 1 under a 405nm LED light source;

[0031] Figure 6 This is a photopolymerization kinetic diagram of the polymerization of monomer tripropylene glycol diacrylate initiated by the combination of coumarin-based thioester photoinitiator prepared in Examples 1-9 and hydrogen donor tertiary amine ethyl 4-dimethylaminobenzoate (EDB) under a 405nm LED light source.

[0032] Figure 7 This is a photopolymerization kinetic diagram of the polymerization of bisphenol A diglycidyl ether monomers initiated by the coumarin thioester photoinitiator prepared in Examples 1, 2, 5, 6, and 8 and diphenyliodonium hexafluorophosphate under a 405nm LED light source.

[0033] Figure 8 This is a color comparison image before and after the polymerization of the monomer dipropylene glycol diacrylate initiated by the coumarin-based thioester photoinitiator 6O-CTE prepared in Synthesis Example 1.

[0034] Figure 9 This is a graph showing the cell viability of human cervical cancer cells cultured with the coumarin-based thioester photoinitiator 6O-CTE prepared in Example 1. Detailed Implementation

[0035] To make the technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below through embodiments and in conjunction with the accompanying drawings. The following embodiments describe the present invention in detail, but do not limit the scope of the present invention.

[0036] The aforementioned photoinitiators can initiate polymerization under irradiation by commonly used LED light sources (emission wavelengths of 365nm, 385nm, 395nm, and 405nm), and their initiation mechanism is shown in the attached figure. Figure 1 As shown.

[0037] Example 1:

[0038] The synthesis of the photoinitiator 6O-CTE is as follows:

[0039] (a)

[0040] (b)

[0041] (a) 2-Hydroxy-5-methoxybenzaldehyde (1.52 g, 10 mmol) and isopropyl malonate (1.72 g, 12 mmol) were added to a 100 mL single-necked flask, along with 10 mL of deionized water. The resulting suspension was placed in an oil bath at 90 °C and stirred for 4 h. After the reaction was complete, the solvent was removed by filtration, and the solid was retained. The solid product was washed three times with 10 mL of deionized water to obtain a white solid product, 6-methylcoumarin-3-carboxylic acid.

[0042] (b) 2-Naphthiophenol (1.92 g, 12 mmol), 6-methoxycoumarin-3-carboxylic acid (2.20 g, 10 mmol) synthesized in (a) and 4-dimethylaminopyridine (DMAP, 0.12 g, 1 mmol) were added to a 100 mL single-necked flask, and 30 mL of dichloromethane was added to completely dissolve all three. Dicyclohexylcarbodiimide (DCC, 2.47 g, 12 mmol) was dissolved in 20 mL of dichloromethane and transferred to a dropping funnel. The DCC solution was added dropwise to the single-necked flask at a rate of 2-3 drops per second. After the addition was complete, the mixture was stirred at 25 °C for 1 h. After the reaction was complete, the white precipitate in the system was filtered off, and the resulting liquid was purified by vacuum distillation to remove the solvent, followed by purification by silica gel column chromatography to obtain the yellow solid product 6O-CTE.

[0043] The proton NMR data for photoinitiator 6O-CTE are as follows: 1 H NMR (400MHz, DMSO-d6) δ8.79 (s, 1H), 8.15 (d, J = 1.7Hz, 1H), 8.10–7.95 (m, 3H), 7.71–7.36 (m, 6H), 3.83 (s, 3H).

[0044] The carbon spectral data of the photoinitiator 6O-CTE are as follows: 13C NMR(100MHz,DMSO-d6)δ186.57,158.36,156.43,149.54,147.74,134.96,133.64,133.43,131.76, 129.16,128.39,128.18,127.94,127.25,125.77,123.79,122.66,118.91,117.95,112.99,56.35.

[0045] Example 2:

[0046] The synthesis of the photoinitiator 6F-CTE is as follows:

[0047] (a)

[0048] (b)

[0049] (a) 5-Fluoro-2-hydroxybenzaldehyde (1.40 g, 10 mmol) and isopropyl malonate (1.72 g, 12 mmol) were added to a 100 mL single-necked flask, along with 10 mL of deionized water. The resulting suspension was placed in an oil bath at 90 °C and stirred for 4 h. After the reaction was complete, the solvent was removed by filtration, and the solid was retained. The solid product was washed three times with 10 mL of deionized water to obtain a white solid product, 6-fluorocoumarin-3-carboxylic acid.

[0050] (b) 2-Naphthiophenol (1.92 g, 12 mmol), 6-fluorocoumarin-3-carboxylic acid (2.08 g, 10 mmol) synthesized in (a) and DMAP (0.12 g, 1 mmol) were dissolved in 30 mL of dichloromethane. DCC (2.47 g, 12 mmol) was dissolved in 20 mL of dichloromethane and transferred to a dropping funnel. The DCC solution was added dropwise to a single-necked flask at a rate of 2-3 drops per second. After the addition was complete, the mixture was stirred at 25 °C for 1 h. After the reaction was complete, the white precipitate was filtered off. The resulting liquid was purified by vacuum distillation to remove the solvent, followed by silica gel column chromatography to obtain the yellow solid product 6F-CTE.

[0051] The proton NMR data for photoinitiator 6F-CTE are as follows: 1 H NMR (400MHz, Chloroform-d) δ8.53 (s, 1H), 7.58 (d, J = 8.7Hz, 1H), 7.48–7.39 (m, 2H), 7.06–6.83 (m, 4H), 3.95 (s, 3H), 3.87 (s, 3H).

[0052] The carbon spectral data of the photoinitiator 6F-CTE are as follows:13 C NMR(100MHz,Chloroform-d)δ187.71,165.62,160.78,158.93,157.47,146.82, 136.40,131.64,119.15,118.87,114.90,114.18,111.90,100.43,56.13,55.38.

[0053] Example 3:

[0054] The synthesis of the photoinitiator 7F-CTE is as follows:

[0055] (a)

[0056] (b)

[0057] (a) 4-fluoro-2-hydroxybenzaldehyde (1.40 g, 10 mmol) and isopropyl malonate (1.72 g, 12 mmol) were added to a 100 mL single-necked flask, along with 10 mL of deionized water. The resulting suspension was placed in an oil bath at 90 °C and stirred for 4 h. After the reaction was complete, the solvent was removed by filtration, and the solid was retained. The solid product was washed three times with 10 mL of deionized water to obtain a white solid, 7-fluorocoumarin-3-carboxylic acid.

[0058] (b) 2-Naphthiophenol (1.92 g, 12 mmol), 7-fluorocoumarin-3-carboxylic acid (2.08 g, 10 mmol) synthesized in (a) and DMAP (0.12 g, 1 mmol) were added to a 100 mL single-necked flask, and 30 mL of dichloromethane was added to completely dissolve all three. DCC (2.47 g, 12 mmol) was dissolved in 20 mL of dichloromethane and transferred to a dropping funnel. The DCC solution was added dropwise to the single-necked flask at a rate of 2-3 drops per second. After the addition was complete, the mixture was stirred at 25 °C for 1 h. After the reaction was complete, the white precipitate in the system was filtered off. The resulting liquid was purified by vacuum distillation to remove the solvent, and then purified by silica gel column chromatography to obtain the yellow solid product 7F-CTE.

[0059] The proton NMR data for photoinitiator 7F-CTE are as follows: 1 H NMR (400MHz, Chloroform-d) δ8.58(s,1H),8.07(s,1H),7.99–7.84(m,3H),7.69(dd,J=8.7,5.9Hz,1H),7.63–7.51(m,3H),7.21–7.04(m,2H).

[0060] The carbon spectral data of the photoinitiator 7F-CTE are as follows:13 C NMR(100MHz,Chloroform-d)δ186.83,146.16,134.79,133.56,132.32,131.12,128.8 6,128.11,127.86,127.34,126.62,125.10,114.89,113.97,113.74,104.74,104.48.

[0061] Example 4:

[0062] The synthesis of the photoinitiator 7OBO-CTE is as follows:

[0063] (a)

[0064] (b)

[0065] (a) 2-Hydroxy-4-methoxybenzaldehyde (1.52 g, 10 mmol) and isopropyl malonate (1.72 g, 12 mmol) were added to a 100 mL single-necked flask, along with 10 mL of deionized water. The resulting suspension was placed in an oil bath at 90 °C and stirred for 4 h. After the reaction was complete, the solvent was removed by filtration, and the solid was retained. The solid product was washed three times with 10 mL of deionized water to obtain the pink solid product 7-methoxycoumarin-3-carboxylic acid.

[0066] (b) 1.68 g (12 mmol) of p-methoxybenzylthiophenol, 2.20 g (10 mmol) of 7-methoxycoumarin-3-carboxylic acid synthesized in (a), and 0.12 g (1 mmol) of DMAP were added to a 100 mL single-necked flask, and 30 mL of dichloromethane was added to completely dissolve all three. 2.47 g (12 mmol) of DCC was dissolved in 20 mL of dichloromethane and transferred to a dropping funnel. The DCC solution was added dropwise to the single-necked flask at a rate of 2-3 drops per second. After the addition was complete, the mixture was stirred at 25 °C for 1 h. After the reaction was complete, the white precipitate in the system was filtered off. The resulting liquid was purified by vacuum distillation to remove the solvent and then purified by silica gel column chromatography to obtain the reddish-brown solid product 7OBO-CTE.

[0067] The proton NMR data for the photoinitiator 7OBO-CTE are as follows: 1 H NMR (400MHz, Chloroform-d) δ8.53 (s, 1H), 7.58 (d, J = 8.7Hz, 1H), 7.48–7.39 (m, 2H), 7.06–6.83 (m, 4H), 3.95 (s, 3H), 3.87 (s, 3H).

[0068] The carbon spectral data for the photoinitiator 7OBO-CTE are as follows: 13 C NMR(100MHz,Chloroform-d)δ187.71,165.62,160.78,158.93,157.47,146.82, 136.40,131.64,119.15,118.87,114.90,114.18,111.90,100.43,56.13,55.38.

[0069] Example 5:

[0070] Synthesis of photoinitiator 6OBO-CTE; the structural formula of 6OBO-CTE is as follows:

[0071] (a)

[0072] (b)

[0073] (a) 2-Hydroxy-5-methoxybenzaldehyde (1.52 g, 10 mmol) and isopropyl malonate (1.72 g, 12 mmol) were added to a 100 mL single-necked flask, and 10 mL of deionized water was added. The resulting suspension was placed in an oil bath at 90 °C and stirred for 4 h. After the reaction was complete, the solvent was removed by filtration, and the solid was retained. The solid product was washed three times with 10 mL of deionized water to obtain a yellow solid product, 6-methylcoumarin-3-carboxylic acid.

[0074] (b) In a 100 mL single-necked flask, 2.20 g (10 mmol) of 6-methoxycoumarin-3-carboxylic acid, 1.68 g (12 mmol) of p-methoxythiophenol, and 0.12 g (1 mmol) of DMAP synthesized in (a) were added, followed by 30 mL of dichloromethane to dissolve them completely. 2.47 g (12 mmol) of DCC was dissolved in 20 mL of dichloromethane and transferred to a dropping funnel. The DCC solution was added dropwise to the single-necked flask at a rate of 2-3 drops per second. After the addition was complete, the mixture was stirred at 25 °C for 1 h. After the reaction was complete, the white precipitate was removed by filtration. The resulting liquid was purified by vacuum distillation to remove the solvent, followed by purification using a silica gel column chromatography to obtain the yellow solid product 6OBO-CTE.

[0075] The proton NMR data for the photoinitiator 6OBO-CTE are as follows: 1 H NMR (400MHz, Chloroform-d) δ8.49 (s, 1H), 7.46–7.23 (m, 4H), 7.06 (d, J = 2.9Hz, 1H), 7.03–6.94 (m, 2H), 3.87 (d, J = 8.4Hz, 6H).

[0076] The carbon spectral data for the photoinitiator 6OBO-CTE are as follows: 13 C NMR(100MHz,Chloroform-d)δ187.72,160.86,158.57,156.52,149.57,146.38, 136.32,123.41,123.04,118.56,118.37,117.93,114.95,111.14,55.97,55.39.

[0077] Example 6:

[0078] Synthesis of photoinitiator BO-CTE, the structural formula of BO-CTE is as follows:

[0079] (a)

[0080] (b)

[0081] (a) Salicylaldehyde (1.52 g, 10 mmol) and isopropyl malonate (1.72 g, 12 mmol) were added to a 100 mL single-necked flask, along with 10 mL of deionized water. The resulting suspension was placed in an oil bath at 90 °C and stirred for 4 h. After the reaction was complete, the solvent was removed by filtration, and the solid was retained. The solid product was washed three times with 10 mL of deionized water to obtain a white solid product, coumarin-3-carboxylic acid (1.34 g, 88% yield).

[0082] (b) 1.68 g (12 mmol) of p-methoxythiophenol, 1.90 g (10 mmol) of coumarin-3-carboxylic acid synthesized in (a), and 0.12 g (1 mmol) of DMAP were added to a 100 mL single-necked flask, and 30 mL of dichloromethane was added to completely dissolve them. 2.47 g (12 mmol) of DCC was dissolved in 20 mL of dichloromethane and transferred to a dropping funnel. The DCC solution was added dropwise to the single-necked flask at a rate of 2-3 drops per second. After the addition was complete, the mixture was stirred at 25 °C for 1 h. After the reaction was complete, the white precipitate in the system was removed by filtration. The obtained liquid was purified by vacuum distillation to remove the solvent, and then purified by silica gel column chromatography to obtain the white solid product BO-CTE.

[0083] The proton NMR data for the photoinitiator BO-CTE are as follows: 1 H NMR (400MHz, Chloroform-d) δ8.56(s,1H),7.76–7.66(m,2H),7.48–7.34(m,4H),7.05–6.97(m,2H),3.89(s,1H).

[0084] The carbon spectral data of the photoinitiator BO-CTE are as follows:13 C NMR(100MHz,Chloroform-d)δ187.69,160.89,158.40,154.97,146.56,136. 34,134.79,130.36,125.19,123.01,118.47,118.09,116.88,114.97,55.39.

[0085] Example 7:

[0086] Synthesis of photoinitiator BF-CTE; the structural formula of BF-CTE is as follows:

[0087] (a)

[0088] (b)

[0089] (a) Salicylaldehyde (1.52 g, 10 mmol) and isopropyl malonate (1.72 g, 12 mmol) were added to a 100 mL single-necked flask, along with 10 mL of deionized water. The resulting suspension was placed in an oil bath at 90 °C and stirred for 4 h. After the reaction was complete, the solvent was removed by filtration, and the solid was retained. The solid product was washed three times with 10 mL of deionized water to obtain a white solid product, coumarin-3-carboxylic acid.

[0090] (b) 1.52 g (12 mmol) of p-fluorothiophenol, 1.90 g (10 mmol) of coumarin-3-carboxylic acid synthesized in (a), and 0.12 g (1 mmol) of DMAP were added to a 100 mL single-necked flask, and 30 mL of dichloromethane was added to completely dissolve them. 2.47 g (12 mmol) of DCC was dissolved in 20 mL of dichloromethane and transferred to a dropping funnel. The DCC solution was added dropwise to the single-necked flask at a rate of 2-3 drops per second. After the addition was complete, the mixture was stirred at 25 °C for 1 h. After the reaction was complete, the white precipitate in the system was removed by filtration. The obtained liquid was purified by vacuum distillation to remove the solvent, and then purified by silica gel column chromatography to obtain the white solid product BF-CTE.

[0091] The proton NMR data for the photoinitiator BF-CTE are as follows: 1 H NMR (400MHz, DMSO-d6) δ8.83(s,1H),8.02(dd,J=7.8,1.6Hz,1H),7.82(ddd,J=8.7,7.3,1.6Hz,1H),7.63–7.27(m,6H).

[0092] The carbon spectral data of the photoinitiator BF-CTE are as follows: 13C NMR(100MHz,DMSO-d6)δ186.29,158.24,154.95,148.06,137.73,137.64, 135.78,131.71,125.71,124.02,122.42,118.48,117.12,116.90,116.81.

[0093] Example 8:

[0094] Synthesis of the photoinitiator Ph-BO-CTE; the structural formula of Ph-BO-CTE is as follows:

[0095] (a)

[0096] (b)

[0097] (a) 1.72 g (10 mmol) of 2-hydroxy-1-naphthaldehyde and 1.72 g (12 mmol) of isopropyl malonate were added to a 100 mL single-necked flask, and 10 mL of deionized water was added. The resulting suspension was placed in an oil bath at 80 °C and stirred for 6 h. After the reaction was complete, the solvent was removed by filtration, and the solid was retained. The solid product was washed three times with 10 mL of deionized water to obtain a yellow solid, 5,6-benzocoumarin-3-carboxylic acid.

[0098] (b) In a 100 mL single-necked flask, 3.62 g (10 mmol) of 5,6-benzocoumarin-3-carboxylic acid, 1.68 g (12 mmol) of p-methoxythiophenol, and 0.12 g (1 mmol) of DMAP synthesized in (a) were added, followed by 30 mL of dichloromethane to completely dissolve the compounds. 2.47 g (12 mmol) of DCC was dissolved in 20 mL of CH2Cl2 and transferred to a dropping funnel. The DCC solution was added dropwise to the single-necked flask at a rate of 2–3 drops per second. After the addition was complete, the mixture was stirred at 25 °C for 1 h. After the reaction was complete, the white precipitate was removed by filtration. The resulting liquid was purified by vacuum distillation to remove the solvent, followed by purification using a silica gel column chromatography to obtain the yellow solid product Ph-BO-CTE.

[0099] The proton NMR data for the photoinitiator Ph-BO-CTE are as follows: 1H NMR(400MHz,Chloroform-d)δ9.36(s,1H),8.32(d,J=8.4Hz,1H),8.16(d,J=9.0Hz,1H),8.01–7.92(m,1H),7.78( ddd,J=8.4,7.0,1.3Hz,1H),7.65(ddd,J=8.1,7.0,1.1Hz,1H),7.58–7.45(m,3H),7.07–7.00(m,2H),3.89(s,3H).

[0100] The carbon spectral data of the photoinitiator Ph-BO-CTE are as follows: 13 C NMR(100MHz,Chloroform-d)δ188.02,160.89,158.62,155.90,142.29,136.74,136.37,130. 33,129.84,129.42,129.35,126.82,121.59,121.14,118.70,116.60,114.97,112.75,55.40.

[0101] Example 9:

[0102] Synthesis of the photoinitiator Nap-CTE; the structural formula of Nap-CTE is as follows:

[0103] (a)

[0104] (b)

[0105] (a) Salicylaldehyde (1.52 g, 10 mmol) and isopropyl malonate (1.72 g, 12 mmol) were added to a 100 mL single-necked flask, along with 10 mL of deionized water. The resulting suspension was placed in an oil bath at 90 °C and stirred for 4 h. After the reaction was complete, the solvent was removed by filtration, and the solid was retained. The solid product was washed three times with 10 mL of deionized water to obtain a white solid product, coumarin-3-carboxylic acid (1.34 g, 88% yield).

[0106] (b) 2-Naphthiophenol (1.92 g, 12 mmol), coumarin-3-carboxylic acid (1.90 g, 10 mmol) synthesized in (a) and DMAP (0.12 g, 1 mmol) were added to a 100 mL single-necked flask, and 30 mL of dichloromethane was added to completely dissolve them. DCC (2.47 g, 12 mmol) was dissolved in 20 mL of dichloromethane and transferred to a dropping funnel. The DCC solution was added dropwise to the single-necked flask at a rate of 2-3 drops per second. After the addition was complete, the mixture was stirred at 25 °C for 1 h. After the reaction was complete, the white precipitate in the system was removed by filtration. The solvent in the resulting liquid was removed by vacuum distillation, and then purified by silica gel column chromatography. The washings yielded the yellow solid product Nap-CTE.

[0107] The proton NMR data for the photoinitiator Nap-CTE are as follows: 1 H NMR (400MHz, DMSO-d6) δ8.86(s,1H),8.16(d,J=1.7Hz,1H),8.10–7.96(m,4H),7.82(ddd,J=8.7,7.3,1.6Hz,1H),7.70–7.42(m,5H).

[0108] The carbon spectral data of the photoinitiator Nap-CTE are as follows: 13 C NMR(100MHz,DMSO-d6)δ186.50,158.24,154.96,147.96,135.74,134.96,133.64,133.43, 131.75,131.70,129.17,128.40,128.19,127.95,127.26,125.70,122.61,118.50,116.80.

[0109] Example 10:

[0110] The purpose of Example 10 is to illustrate the light absorption properties of the coumarin-based thioester photoinitiators prepared in Examples 1-9.

[0111] The photoinitiators prepared in Examples 1-9 were respectively formulated to a concentration of 1×10⁻⁶. 4 mol L- 1 Anhydrous acetonitrile solutions were used. The absorption curves of these nine photoinitiator solutions in the wavelength range of 200-500 nm were measured using a UV spectrophotometer, i.e., the UV-Vis absorption spectra.

[0112] The UV-Vis absorption spectra of 9 photoinitiators are as follows: Figure 2 as well as Figure 3 As shown; from Figure 2 and Figure 3It can be observed that the nine photoinitiators exhibit good absorption capacity in the region above 200-400 nm. They are compatible with mercury lamps and LED light sources commonly used in photoemission polymerization.

[0113] Examples 11-14

[0114] The purpose of Examples 11-14 is to demonstrate that the coumarin-based thioester photoinitiators prepared in Examples 1-9 can effectively initiate the polymerization of (meth)acrylate monomers and sensitize cationic initiators to initiate the polymerization of epoxy monomers under LED light source irradiation.

[0115] 1. Preparation of photosensitive resin for light curing

[0116] Photosensitive solutions were prepared using three monomers—tripropylene glycol diacrylate (TPGDA), triethylene glycol dimethacrylate (TEGDMA), and bisphenol A diglycidyl ether (BADGE)—and a prepared coumarin-based thioester photoinitiator, respectively, in the following proportions:

[0117] Example 11: Weigh appropriate amounts of the monomer tripropylene glycol diacrylate (TPGDA) and the photoinitiator prepared in Examples 1-9 to prepare a homogeneous photosensitive liquid. The mass ratio of photoinitiator to monomer is: photoinitiator: TPGDA = 0.2:100.

[0118] Example 12: Weigh appropriate amounts of the monomer triethylene glycol dimethacrylate (TEGDMA) and the photoinitiator prepared in Example 1 to prepare a uniform photosensitive liquid. The mass ratio of photoinitiator to monomer is: photoinitiator: TEGDMA = 0.2:100.

[0119] Example 13: Appropriate amounts of the monomers tripropylene glycol diacrylate (TPGDA), ethyl 4-dimethylaminobenzoate (EDB), and the photoinitiator prepared in Examples 1-9 were weighed and prepared into a homogeneous photosensitive solution. The mass ratio of photoinitiator, monomer, and hydrogen donor was: photoinitiator: TPGDA: EDB = 0.2:100:1.

[0120] Example 14: Appropriate amounts of monomer bisphenol A diglycidyl ether (BADGE), diphenyl iodonium hexafluorophosphate (810), and the photoinitiator prepared in Examples 1, 2, 5, 6, and 8 were weighed and prepared into a homogeneous photosensitive solution. The mass ratio of photoinitiator, monomer, and iodonium salt was: photoinitiator: TPGDA: 810 = 0.2:100:1.

[0121] 2. Photopolymerization performance test

[0122] A certain amount of the prepared photosensitive solution was drawn up using a capillary tube and evenly coated onto a salt plate made of KBr. The thickness of the photosensitive solution layer was approximately 30 μm. Then, another salt plate was placed on top of the first layer. Photopolymerization kinetics were tested using a real-time infrared spectrometer (Thermo Fisher Scientific, Nicolet 5700). The emission wavelength of the light source was 405 nm (the light intensity reaching the photosensitive solution was set to 60 mW cm⁻¹). -2 ).

[0123] The photopolymerization test results of Examples 11, 12, 13, and 14 are as follows: Figure 4 , Figure 5 , Figure 6 and Figure 7 As shown, the coumarin-based thioester photoinitiator prepared in this invention can effectively initiate the photopolymerization reaction between (meth)acrylate monomers and epoxy resin under irradiation with a 405nm LED light source. Furthermore, Figure 5 The results show that, compared with the commercially available photoinitiator diphenyl-(2,4,6-trimethylbenzoyl)phosphorus oxychloride (TPO), the invented photoinitiator 6O-CTE exhibits a higher conversion rate when initiating the polymerization of methyl-containing acrylate monomers. This indicates that the photoinitiator of the present invention has better initiation performance and applicability in LED photopolymerization systems.

[0124] Example 15

[0125] The purpose of Example 15 is to demonstrate that the coumarin-based thioester photoinitiator 6O-CTE prepared in Example 1 has good photobleaching properties under LED light source irradiation.

[0126] 1. Preparation of photopolymerizable photosensitive resin

[0127] A photosensitive solution was prepared using tripropylene glycol diacrylate monomer (TPGDA) and the coumarin-based thioester photoinitiator 6O-CTE prepared in Example 1, according to the following mass ratio:

[0128] Tripropylene glycol diacrylate (TPGDA): Photoinitiator (6O-CTE) = 100:0.2.

[0129] 2. Photobleaching performance test

[0130] The photosensitive liquid prepared above was added to a silicone mold, and then covered with a coverslip to isolate oxygen. The mold was then irradiated with a 405nm LED light source for 10s and 15s respectively.

[0131] The results of the photobleaching test of the photosensitive solution prepared in Example 15 are as follows: Figure 8As shown, the photoinitiator 6O-CTE prepared in this invention becomes colorless after 15 seconds of irradiation with a 405nm LED light source, indicating that the prepared photoinitiator 6O-CTE exhibits good photobleaching performance under LED light source irradiation.

[0132] Example 16

[0133] The purpose of Example 16 is to demonstrate that the coumarin-based thioester photoinitiator 6O-CTE prepared in Example 1 has good biocompatibility.

[0134] 1. Cytotoxicity test

[0135] 6O-CTE was dissolved in a certain amount of dimethyl sulfoxide and added to the culture medium of cervical cancer cells (HeLa) at different concentrations. The cells were cultured at 25°C for 24 hours, and the absorbance at a specific wavelength was measured using an ELISA reader to detect cell viability.

[0136] Test results are as follows Figure 9 As shown, L represents the illumination of the 6O-CTE dimethyl sulfoxide solution with a 405nm LED lamp before cell culture. Figure 9 The results indicate that HeLa cells maintain high activity in cell culture media containing different concentrations of 6O-CTE, suggesting that the prepared photoinitiator 6O-CTE has good biocompatibility.

Claims

1. A free-radical photopolymerisable composition characterised in that, The composition comprises 0.1-2% of a coumarin-based thioester photoinitiator of general formula (I) and 98-99.9% of a photocuring resin or monomer, based on the total weight of the composition; wherein: L represents: ; wherein R2, R3, R5, R6, R7, R8, R9 are hydrogen, and R4 is fluorine or methoxy; R 10 and R 13 are H; R 11 , R 12 is hydrogen, fluorine or methoxy, but R 11 and R 12 cannot both be fluorine or both be methoxy, wherein if one is fluorine the other cannot also be methoxy; The photocuring resin is selected from one or more of an epoxy (meth)acrylic resin, a polyurethane (meth)acrylic resin, a polyester (meth)acrylic resin, a polyether (meth)acrylic resin, an acrylated poly(meth)acrylic resin; and the monomer is one or more of a monofunctional, difunctional or polyfunctional (meth)acrylate.

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