Coumarin sulfonium salt photoinitiators, methods of making and using the same

Abstract

The present application relates to coumarin sulfonium salt photoinitiator and its application in photocuring, and belongs to the technical field of photoinitiator. Disclosed is a coumarin sulfonium salt photoinitiator, and a macromolecular coumarin sulfonium salt photoinitiator and its application developed based on the same; the single-component photoinitiator of the present application can generate active free radicals and cationic active species by photolysis, and can induce the curing of free radical type resin, cationic type resin and hybrid resin under the induction of ultraviolet and visible light sources. The coumarin sulfonium salt photoinitiator provided herein has absorption in multiple wave bands, and can induce polymerization by LED ultraviolet light and LED visible light, thereby avoiding the problems of large heat, low light energy utilization rate, generation of ozone and the like of traditional mercury lamps. The small molecule photoinitiator prepared herein has better solubility and presents good initiation efficiency, and the further developed macromolecular coumarin sulfonium salt photoinitiator has good migration stability, and has wide application prospect in the fields of food packaging, medical materials and the like.

Description

Technical Field

[0001] This invention relates to coumarin thionium salt photoinitiators and their application in photocuring, belonging to the field of photoinitiator technology. Background Technology

[0002] Photopolymerization technology, with its advantages of rapid reaction, low energy consumption, room temperature operation, and solvent-free or low-solvent formulations, has become a cutting-edge field in polymer synthesis and has been successfully applied in fields such as photocurable coatings, photocurable inks, photoresists, 3D printing, and microelectronics processing.

[0003] Photoinitiators are a crucial component of photocuring systems. Currently, based on the different active species they generate, they are classified into free radical photoinitiators and cationic photoinitiators. Typically, free radical photoinitiators in the ultraviolet region are mainly used in photocuring systems. Free radical and cationic photoinitiators each have their own characteristics in photocuring systems. Free radical photocuring systems have fast curing speeds but suffer from oxygen inhibition and significant volume shrinkage; cationic photocuring systems have moderate curing speeds, exhibit dark reactions, but suffer from severe corrosion of the substrate. Furthermore, residual photoinitiators or photodegradation debris can, under certain conditions, contaminate food packaging or various coating surfaces through chemical migration or physical contact, posing a potential health hazard.

[0004] Therefore, developing highly efficient dual-initiated radical / cation hybrid photoinitiators is of great practical significance. Summary of the Invention

[0005] This invention provides a single-component, dual-initiator radical / cationic hybrid coumarin thioonium salt photoinitiator and its preparation method. This type of single-component photoinitiator can simultaneously generate active radicals and cations through photolysis, initiating the curing of radical-type resins, cationic resins, and hybrid resins. This invention prepares a hybrid photoinitiator by salting coumarin with a thioglycolic acid derivative, which can induce the curing of radical-type resins, cationic resins, and hybrid resins in the ultraviolet region. This type of photoinitiator exhibits good initiation efficiency in experiments.

[0006] The first objective of this invention is to provide a coumarin thionium salt photoinitiator, characterized by having the following general structural formula:

[0007]

[0008] Where X is SbF6, BF4, PF6 or AsF6;

[0009] R1 is hydrogen, alkyl, alkoxy, aryl, arylalkoxy, alkenyl, hydroxyl, amino, cyano, acyl, halogen, acrylate, alkynyl, or amino.

[0010] R2 and R3 are alkyl, aryl, or aralkyl, and at least one of R2 and R3 is an alkyl group.

[0011] A second objective of this invention is to provide a method for preparing a coumarin thionium salt photoinitiator, characterized by comprising the following steps:

[0012] Step 1: R1-substituted salicylaldehyde is reacted with a thioglycolic acid derivative via a Knoevenagel condensation reaction to prepare a coumarin derivative, with the structure shown in Formula 1.

[0013]

[0014] Step 2: The compound with structure 1 obtained in Step 1 reacts with a haloalkane in the presence of a silver salt to undergo S... N1 The reaction yields a coumarin thionium salt photoinitiator, with the structural formula shown in Formula 2.

[0015]

[0016] Further, step 1 specifically includes: adding salicylaldehyde derivative, mercaptoacetic acid derivative, and 2-chloro-1-methylpyridine iodide to a triethylamine acetonitrile solution, refluxing, and removing the solvent under vacuum after the reaction is complete; extracting with dichloromethane and removing the solvent under vacuum again; dissolving the intermediate product in DMF with Cs2CO3 and reacting at room temperature in the dark; after the reaction is complete, extracting with ethyl acetate, and separating the crude product by silica gel column chromatography to obtain compound of formula 1.

[0017] Further, step 2 specifically includes: dissolving the compound of formula 1, the haloalkane and the silver salt in dichloroethane, reacting them at room temperature in a light-protected environment, and separating and purifying the compound of formula 2 after the reaction is completed.

[0018]

[0019] The third objective of this invention is to provide a macromolecular coumarin thionium salt photoinitiator, characterized in that it is prepared by copolymerization of the coumarin thionium salt photoinitiator described above and acrylic acid monomer, or by copolymerization of the coumarin thionium salt photoinitiator prepared by the method described above and acrylic acid monomer, wherein R1 is an acrylate group.

[0020] The structural formula of the macromolecular coumarin thionium salt photoinitiator is Formula 3.

[0021]

[0022] Since this application provides two coumarin-based photoinitiators, in order to better distinguish them from the macromolecular coumarin thionium salt photoinitiator, the other one is also referred to as a small molecule photoinitiator (i.e., the coumarin thionium salt photoinitiator provided in the first object of this invention).

[0023] Furthermore, the preparation method of the macromolecular coumarin thiamium salt photoinitiator includes the following steps: An acrylate-substituted thiamium salt, methyl methacrylate, and azobisisobutyronitrile are added to a Schlenk reaction tube containing tetrahydrofuran. The mixture is deoxygenated through a freeze-vacuum-thaw procedure, followed by stirring and heating. After the reaction is complete, the mixture is cooled to room temperature, and the polymer is precipitated in stirred ice-cold methanol. The macromolecular coumarin thiamium salt photoinitiator is obtained by centrifugation.

[0024] Furthermore, the application of the coumarin thionium salt photoinitiator or the macromolecular coumarin thionium salt photoinitiator described above is characterized by its application in the curing of free radical resin systems, cationic resin systems, or free radical / cationic hybrid resin systems.

[0025] Furthermore, the free radical resin system includes one or more of the following: dipropylene glycol diacrylate, trimethylolpropane triacrylate, tripropylene glycol diacrylate, pentaerythritol triacrylate, neopentyl glycol diacrylate, 1,6-hexanediol acrylate, dipentaerythritol hexaacrylate, and ditrimethylolpropane tetraacrylate.

[0026] Furthermore, the cationic resin system includes one or more of the following: cyclohexane oxide, vinyl ether, 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexylcarboxylate, bisphenol A diglycidyl ether, and neopentyl glycol diglycidyl ether.

[0027] Furthermore, the hybrid resin system includes 3,4-epoxycyclohexylmethyl methacrylate.

[0028] A fourth objective of this invention is to provide applications of the macromolecular coumarin thioonium salt compounds described above, characterized in that they are used as photoinitiators in the fields of food packaging, medical materials, coatings, and inks.

[0029] The fifth object of the present invention is to provide applications of the macromolecular coumarin thioonium salt compound described above, characterized in that it is used as a photoacid generator in photolithography processes, UV-curable adhesives, photosensitive resins, nanomaterial preparation, coatings and inks, and the pharmaceutical field.

[0030] The sixth object of the present invention is to provide a method for using the coumarin thiamium salt photoinitiator described above or the macromolecular coumarin thiamium salt compound, characterized in that...

[0031] In one embodiment, during the curing of the free radical resin system, the amount added is 0.05wt%-2wt% of the monomer mass;

[0032] In one embodiment, the amount added to the cationic resin system is 0.5 wt% to 10 wt% of the monomer mass;

[0033] In one embodiment, the amount added to the radical / cation hybrid system is 0.5 wt% to 10 wt% of the monomer mass.

[0034] In one embodiment, when R1 is 7-hydroxyl, the specific preparation steps of the macromolecular coumarin thionium salt photoinitiator are as follows:

[0035] (1-1) 2,4-Dihydroxybenzaldehyde, its mercaptoacetic acid derivative, and 2-chloro-1-methylpyridine iodide were added to an acetonitrile solution of triethylamine. The mixture was refluxed until complete, and the solvent was removed under vacuum. After extraction with dichloromethane and further solvent removal under vacuum, the product was dissolved in DMF with Cs₂CO₃ and reacted at room temperature in the dark. After the reaction was complete, the product was extracted with ethyl acetate and purified to obtain the first-step product.

[0036] (1-2) The product of step 1, the halohydrocarbon and the silver salt were dissolved in dichloroethane and reacted at room temperature in a dark environment. After the reaction was completed, the thioonium salt photoinitiator was separated and purified.

[0037] In one embodiment, the preparation method of the macromolecular coumarin thionium salt photoinitiator includes the following specific steps:

[0038] (2-1) 2,4-Dihydroxybenzaldehyde, its mercaptoacetic acid derivative, and 2-chloro-1-methylpyridine iodide were added to an acetonitrile solution of triethylamine. The mixture was refluxed until complete, and the solvent was removed under vacuum. After extraction with dichloromethane and further solvent removal under vacuum, the product was dissolved in DMF with Cs₂CO₃ and reacted at room temperature in the dark. After the reaction was complete, the product was extracted with ethyl acetate and purified to obtain the first-step product.

[0039] (2-2) Under ice bath conditions, the product of the first step, triethylamine, and anhydrous calcium chloride were added to anhydrous dichloromethane in solution, followed by the addition of acryloyl chloride to the mixed solution, and the reaction was carried out at room temperature. After the reaction was completed, the reaction was quenched with water, and then extracted with dichloromethane. The crude product was separated by silica gel column chromatography to obtain the product of the second step.

[0040] (2-3) Dissolve the product of step 2, the haloalkane and silver hexafluoroantimonate in dichloroethane and react at room temperature in the dark. After the reaction is completed, separate and purify to obtain the product of step 3.

[0041] (2-4) The product of step 3, the acrylic acid derivative, and AIBN were added to THF and deoxygenated through a freeze-vacuum-thaw process until 70°C. After the reaction was complete, the mixture was cooled to room temperature, and the polymer was precipitated in stirred ice-cold methanol. The macromolecular thionium salt was obtained by centrifugation.

[0042] In one embodiment, the coumarin thionium salt photoinitiator exhibits absorption at both 365 nm and 405 nm.

[0043] In one embodiment, the macromolecular coumarin thionium salt photoinitiator exhibits absorption at 365 nm, 405 nm, and 980 nm.

[0044] The macromolecular coumarin thionium salt photoinitiator exhibits good migration stability and has potential applications in food packaging, medical materials, and other fields.

[0045] The beneficial effects of this invention are:

[0046] The coumarin thioonium salt photoinitiator provided by this invention combines the advantages of both free radical and cationic initiation systems, exhibiting excellent initiation efficiency in the photocuring of alkenyl monomers / epoxy monomers / alkenylepoxy hybrid monomers. The prepared small-molecule photoinitiator has good solubility; when using the small-molecule photoinitiator-coumarin thioonium salt photoinitiator to initiate the hybrid system, the double bond conversion rate can reach 80%.

[0047] When the prepared macromolecular coumarin thionium salt photoinitiator is used, the epoxy conversion rate can reach 88% and the double bond conversion rate can reach 81%; it also has good migration stability and has broad application prospects in food packaging, medical materials and other fields.

[0048] The coumarin thionium salt photoinitiator provided by this invention has absorption in multiple wavelengths and can be polymerized by LED ultraviolet light and LED visible light, avoiding the problems of traditional mercury lamps such as high heat, low light energy utilization, and ozone generation.

[0049] The coumarin thionium salt photoinitiator provided by this invention can be widely used in coatings, adhesives, inks, electronic packaging, 3D printing, food packaging and biomedicine. Attached Figure Description

[0050] Figure 1 The synthetic route of the photoinitiator in Example 1 of this invention is shown below;

[0051] Figure 2 This is the synthetic route for the macromolecular photoinitiator in Example 2 of the present invention;

[0052] Figure 3 The above is the 1H NMR spectrum of the photoinitiator H-PI in Example 1 of this invention;

[0053] Figure 4 The above is the 1H NMR spectrum of the photoinitiator OMe-PI in Example 1 of this invention;

[0054] Figure 5The above is the 1H NMR spectrum of the photoinitiator OH-PI in Example 1 of this invention;

[0055] Figure 6 The above is the 1H NMR spectrum of the photoinitiator Ph-PI in Example 1 of this invention;

[0056] Figure 7 The above are the 1H NMR spectra of photoinitiator P (Acrylate-PI) and Acrylate-PI in Example 2 of this invention.

[0057] Figure 8 The above is the 1H NMR spectrum of the photoinitiator P (Acrylate-PI) in Example 2 of this invention;

[0058] Figure 9 The UV-Vis absorption spectra of photoinitiator P (Acrylate-PI) and Acrylate-PI prepared in Example 2 of this invention are shown.

[0059] Figure 10 The photoinitiator P (Acrylate-PI) prepared in Example 2 of this invention is shown in the photodispersive spectra under LED illumination at 365 nm (a) and 405 nm (b).

[0060] Figure 11 Steady-state photolysis curve of photoinitiator P (Acrylate-PI) prepared in Example 2 of the present invention under 365nm LED illumination;

[0061] Figure 12 The concentration of the photoinitiator was reduced using acetone for the polymer prepared by photopolymerization of TMPTA and EPOX in Example 3 of this invention;

[0062] Figure 13 The UV-Vis absorption spectra of the four photoinitiators prepared in Example 1 of this invention;

[0063] Figure 14 Steady-state photolysis curves of four thionium salts prepared in Example 1 of this invention under LED@365nm irradiation (a: H-PI; b: OMe-PI; c: OH-PI; d: Ph-PI);

[0064] Figure 15 Steady-state photolysis curves of four thionium salts prepared in Example 1 of this invention under LED @ 405nm irradiation (a: H-PI; b: OMe-PI; c: OH-PI; d: Ph-PI);

[0065] Figure 16 Steady-state photolysis curve of the photoinitiator Ph-PI prepared in Example 1 of the present invention under 365nm LED illumination;

[0066] Figure 17 Hybrid polymerization kinetics of four thionium salts and commercial photoinitiators prepared in Example 1 of this invention under 365nm LED illumination; (a): epoxy conversion of EPOX, (b) double bond conversion of TMPTA. Detailed Implementation

[0067] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0068] Example 1: Synthesis of coumarin thionium salt photoinitiator, the specific synthetic route is as follows: Figure 7 As shown.

[0069] (1) 8.8 mmol of 2-(phenylthio)acetic acid, 8.0 mmol of 2-hydroxy-1-naphthaldehyde, 20.0 mmol of triethylamine, and 16.0 mmol of 2-chloro-N-methylpyridinium iodide were sequentially added to 80 mL of acetonitrile solution. The mixture was reacted at 90 °C for 2 h, and then the solvent was removed. Dilute hydrochloric acid was added to the concentrated reaction solution, and the aqueous layer was extracted with CH2Cl2 (3 × 40 mL). The combined organic layers were washed with brine (50 mL) and dried over Na2SO4. The solvent was removed by vacuum distillation, and the brown oily intermediate was dissolved in DMF (80 mL). 40.0 mmol of Cs2CO3 was added, and the reaction mixture was stirred at 23 °C for 16 h. The reaction was quenched by adding saturated NH4Cl solution (100 mL), the aqueous layer was extracted with EtOAc (3 × 50 mL), the combined organic layers were washed successively with saturated brine, dried with Na2SO4, and finally the solvent was removed. The crude product was separated by silica gel column chromatography to obtain a yellow solid product.

[0070]

[0071] (2) The products from the first step, 1.2 mmol C, 2.4 mmol iodoethane, and 1.2 mmol silver hexafluoroantimonate, were sequentially added to 20 mL of dichloroethane solution and stirred at room temperature for 48 hours in the dark. After the reaction was complete (detected by TLC), the crude product was obtained by diatomaceous earth filtration and vacuum distillation. The crude product was purified by silica gel column chromatography to obtain a pale yellow solid, which was the photoinitiator Ph-PI.

[0072]

[0073] The synthesis method for PI with R1 substituted with hydrogen, hydroxyl, or methoxy groups is the same as the synthesis method for the benzene ring of R1. The resulting photoinitiators are designated as H-PI, OH-PI, and OMe-PI, respectively.

[0074] The NMR spectra of H-PI, OMe-PI, OH-PI, and Ph-PI are as follows: Figure 3 , Figure 4 , Figure 5 , Figure 6 As shown:

[0075] 1H NMR spectrum of H-PI: 1 H NMR (400MHz, Acetonitrile-d3) Figure 3 As shown. 1H NMR data: 1 HNMRδ8.71(s,1H),7.98(dd,J=7.8,1.7Hz,2H),7.91–7.83(m,3H),7.74(t,J=7.8Hz,2H), 7.56–7.47(m,2H),4.26–4.14(m,1H),4.03(dq,J=12.5,7.3Hz,1H),1.47(t,J=7.3Hz,3H).

[0076] OMe-PI 1H NMR spectrum: 1 H NMR (400MHz, Acetonitrile-d3) Figure 4 As shown. 1H NMR data: 1 HNMRδ8.68(s,1H),8.03–7.94(m,2H),7.91–7.83(m,1H),7.80(d,J=8.9Hz,1H),7.78–7.71(m,2H),7.11(dd,J=8.8,2.4Hz, 1H), 7.04 (d, J=2.4Hz, 1H), 4.22 (dq, J=12.5, 7.3Hz, 1H), 4.05 (dq, J=12.5, 7.4Hz, 1H), 3.97 (s, 3H), 1.49 (t, J=7.4Hz, 3H).

[0077] 1H NMR spectrum of OH-PI: 1 H NMR (400MHz, Acetonitrile-d3) Figure 5 As shown. 1H NMR data: 1HNMR δ8.69 (s, 1H), 8.03–7.96 (m, 2H), 7.89–7.82 (m, 1H), 7.79–7.71 (m, 3H), 7.01 (dd, J=8.7, 2.3Hz, 1H ),6.91–6.86(m,1H),4.21(dq,J=12.5,7.4Hz,1H),4.05(dq,J=12.5,7.4Hz,1H),1.48(t,J=7.4Hz,3H).

[0078] Ph-PI 1H NMR spectrum: 1 H NMR (400MHz, Acetonitrile-d3) Figure 6 As shown. 1H NMR data: 1 ¹H NMR δ 9.42 (s, ¹H), 8.41 (dd, J = 8.7, 1.0 Hz, ¹H), 8.28 (d, J = 9.0 Hz, ¹H), 8.03–7.96 (m, ¹H), 7.98–7.91 (m, 2H), 7.79 (ddd, J = 8.4, 7.0, 1.4 Hz, ¹H), 7.77–7.68 (m, ¹H), 7.68–7.58 (m, 3H), 7.47 (d, J = 9.1 Hz, ¹H), 4.28 (dq, J = 12.5, 7.3 Hz, ¹H), 4.07 (dq, J = 12.5, 7.4 Hz, ¹H), 1.42 (t, J = 7.4 Hz, 3H). Example 2: Synthesis of macromolecular coumarin thionium salt photoinitiator P (Acrylate-PI);

[0079] (1) 8.8 mmol of 2-(phenylthio)acetic acid, 8.0 mmol of 2,4-dihydroxybenzaldehyde, 20.0 mmol of triethylamine and 16.0 mmol of 2-chloro-N-methylpyridinium iodide were added to 80 mL of acetonitrile solution and reacted at 90 °C for 2 hours. The solvent was then removed. Dilute hydrochloric acid was added to the concentrated reaction solution, and the aqueous layer was extracted with CH2Cl2 (3 × 40 mL). The combined organic layers were washed with brine (50 mL) and dried over Na2SO4. The solvent was removed by vacuum distillation, and the brown oily intermediate was dissolved in DMF (80 mL). 40.0 mmol of Cs2CO3 was added, and the reaction mixture was stirred at 23 °C for 16 hours. The reaction was quenched by adding saturated NH4Cl solution (100 mL). The aqueous layer was extracted three times with EtOAc (3 × 50 mL). The combined organic layers were washed successively with saturated brine, dried with Na2SO4, and finally the solvent was removed. The crude product was separated by silica gel column chromatography to obtain a yellow solid product A.

[0080]

[0081] (2) Weigh 1.8 mmol of product A. Under ice bath conditions, add 1.8 mmol of 4a, 3.6 mmol of triethylamine, and 0.18 mmol of anhydrous calcium chloride to 30 mL of anhydrous dichloromethane solution. Then, slowly add 1.8 mmol of acryloyl chloride dropwise to the mixed solution and stir at room temperature for 3 hours. After the reaction is complete, quench the reaction with 10 mL of water, then neutralize with dilute hydrochloric acid (1 M), extract with dichloromethane (3 × 30 mL), and dry on Na2SO4. Separate the crude product by silica gel column chromatography to obtain a yellow solid product B.

[0082]

[0083] (3) 1.2 mmol of the product B from the second step, 2.4 mmol of iodoethane, and 1.2 mmol of silver hexafluoroantimonate were added sequentially to 20 mL of dichloroethane solution, and stirred at room temperature for 48 hours in the dark. After the reaction was complete (detected by TLC), the crude product was obtained by diatomaceous earth filtration and vacuum distillation. The crude product was purified by silica gel column chromatography to obtain the target product, a pale yellow solid thionium salt photoinitiator, Acrylate-PI.

[0084]

[0085] 1H NMR spectrum: 1 H NMR (400MHz, Acetonitrile-d3) Figure 7 As shown. 1H NMR data: 1 H NMR(400MHz,Chloroform-d)δ8.92(s,1H),7.98(dd,J=7.8,1.7Hz,2H),7.89(d,J=8.6Hz,1H),7.76–7.69(m,1H),7.64(dd,J=8.5,7.0Hz,2H),7.28 –7.17(m,2H),6.59(dd,J=17.2,1.1Hz,1H),6.24(dd,J=17.3,10.5Hz,1H),6.05(dd,J=10.5,1.0Hz,1H),4.25–4.14(m,2H),1.48(t,J=7.3Hz,3H).

[0086] (4) The products of the third step reaction, 0.77 mmol Acrylate-PI, 2.26 mmol MMA, and 0.06 mmol AIBN, were added to a Schlenk reaction tube containing 4 mL THF. After deoxygenation, the mixture was heated to 70 °C and stirred for 3.5 h. After the reaction was completed, the mixture was cooled to room temperature, and the polymer was precipitated in ice-cold methanol under stirring. P(Acrylate-PI) was obtained by centrifugation.

[0087]

[0088] The 1H NMR spectrum of P(Acrylate-PI) is as follows: Figure 8 As shown, the broad peak at chemical shift 8.81 ppm (a) is attributed to the hydrogen on the double bond in the macromolecular side chain thioonium salt, and the broad peak at chemical shift 4.18 ppm (b) is attributed to the hydrogen on the methylene group connected to the sulfur active center in the macromolecular thioonium salt. Compared with Acrylate-PI, the 1H NMR of the macromolecularized thioonium salt shows broad peaks near 8.81 ppm and 4.18 ppm. This is due to the different chemical environments of the repeating units of each thioonium salt after macromolecularization. This also confirms the successful preparation of the macromolecular coumarin thioonium salt photoinitiator P (Acrylate-PI).

[0089] Example 3: Performance Testing of P (Acrylate-PI)

[0090] (1) Ultraviolet-Visible Absorption Test: The concentration was prepared at 2.2 × 10⁻⁶. -5 The acetonitrile solution of P(Acrylate-PI) prepared in Example 2 with a concentration of mol / L was used to measure the UV-Vis absorption using a TU1901 UV-Vis spectrophotometer from Lambda Corporation, Japan.

[0091] like Figure 9 The UV-Vis absorption spectrum shows that the macromolecular photoinitiator P (Acrylate-PI) has absorption at 365 nm and 405 nm, indicating that it can be used as a photoinitiator in the UV-Vis region.

[0092] (2) Photolysis test: The concentration was prepared at 2.2 × 10⁻⁶. -5 A 3 mL solution of P(Acrylate-PI) in acetonitrile prepared in Example 1 (mol / L) was added to a quartz cuvette, and a magnetic flux was added. The cuvette was irradiated with a RUNLED-UVP60 visible light point source, with the distance between the fiber optic source and the cuvette fixed. The irradiation power at the cuvette was measured to be 100 mW / cm² using a UV radiometer. 2 The ultraviolet-visible absorption was measured using a TU1901 UV-Vis spectrophotometer from Lambda, Japan.

[0093] like Figure 10 As shown, P(Acrylate-PI) undergoes photolysis under light irradiation; this indicates that the photoinitiator synthesized in this invention can be decomposed under ultraviolet radiation, and can initiate monomer polymerization or cross-linking reactions.

[0094] (3) Photoinitiator photoacid production test: The concentration of photoinitiator P (Acrylate-PI) was prepared to be 1.3 × 10⁻⁶.-5 mol L -1 Prepare a Rhodamine B solution by mixing acetonitrile solution with potassium tert-butoxide to neutralize the solution. Irradiate the solution with 3 mL of initiator solution for 0 s, 30 s, 60 s, 90 s, and 120 s, respectively. After irradiation, add 25 μL of Rhodamine B solution and measure the UV spectra.

[0095] like Figure 11 As shown, with increasing irradiation time, the absorption peak of P(Acrylate-PI) at 335 nm gradually decreases, while the absorption peak at 555 nm continuously increases. This indicates that the photoinitiator can generate Bronsted acid during photolysis, thus possessing the potential to initiate the ring-opening polymerization of epoxy compounds.

[0096] (4) Migration stability test: Test samples were prepared by photopolymerization. Photoinitiators of the same molar concentration were dissolved in 1g of EPOX and TMPTA monomers, respectively, and tested under LED at 365nm (60mW / cm²). 2 The sample was cured into a thin film under irradiation, ground into small particles, and then soaked in 10.0 mL of acetone at room temperature for 4 days. The leaching amount of the photoinitiator was investigated by measuring the fluorescence emission spectrum of the sample supernatant.

[0097] Test results are as follows Figure 12 As shown, the migration concentrations of P(Acrylate-PI) in the TMPTA and EPOX polymers were 0.01 μM and 1.01 μM, respectively, while the migration concentrations of Acrylate-PI were 0.26 μM and 24.7 μM, respectively. The migration concentrations of P(Acrylate-PI) in the polymers were only 1.0% and 1.05% of those of Acrylate-PI. This indicates that P(Acrylate-PI), as a macromolecular photoinitiator, significantly reduced the migration rate of photoinitiator molecules during polymerization, exhibiting good migration stability.

[0098] Example 4: P(Acrylate-PI) polymerization kinetics test

[0099] P(Acrylate-PI)(5.75mg, 2×10) -3 0.4 g of UCNPs (10 w.t.%) (irradiated at 980 nm) was added to a Schlenk reaction tube containing 2 mL of dichloromethane. With stirring, 1 mL of monomers (CHO, MMA, NVC, BE, and St) were added to the mixture. The solution was degassed by purging with dry nitrogen before irradiation, and the entire photopolymerization process was carried out under a nitrogen atmosphere. Subsequently, 365 nm and 405 nm (60 mW / cm²) were used. 2 ) and 980nm (16W / cm 2The polymer was precipitated in an ice-cold methanol solution after being exposed to a light source for different durations. The polymer was collected by centrifugation and dried under vacuum at 60°C for 24 hours. The conversion rate of all samples was determined by gravimetric method.

[0100] Table 1 shows the polymerization kinetics of the photoinitiator in Example 2 of this invention under irradiation with 365nm, 405nm LED, and 980nm light sources. As shown in Table 1, the epoxy conversion rate of cyclohexane oxide (CHO) cured with 365nm LED is 88%; the epoxy conversion rate of cyclohexane oxide (CHO) cured with 405nm LED is 82%; the double bond conversion rate of n-butyl vinyl ether (BVE) cured with 365nm LED is 81%; the epoxy conversion rate of N-vinylcarbazole (NVC) cured with 365nm LED is 84%; the double bond conversion rate of styrene (St) cured with 365nm LED can reach 72%; the double bond conversion rate of methyl acrylate (MMA) cured with 365nm LED is 78%; and the double bond conversion rate of methyl acrylate (MMA) cured with 405nm LED is 71%.

[0101] Table 1. Results of P (Acrylate-PI)-initiated polymerization of various cationic / radical monomers under different reaction conditions.

[0102] Serial Number Monomer types Light source (nm) Time (min) Yield (%) <![CDATA[Mn(×10 3 )]]> 1 CHO 365 30 88 12.4 2 CHO 405 30 82 11.2 3 CHO 980 30 31 5.0 4 BVE 365 30 81 59.7 5 NVC 365 30 84 122.0 6 St 365 30 72 20.3 7 MMA 365 120 78 10.5 8 MMA 405 120 71 11.8 9 MMA 980 120 33 5.8

[0103] Example 5: Performance testing of different thionium photoinitiators

[0104] (1) Ultraviolet-Visible Absorption Test: The concentration was prepared at 3.7 × 10⁻⁶. -5 Acetonitrile solutions of different thionium photoinitiators prepared in Example 3 (mol / L) were analyzed for UV-Vis absorption using a Lambda TU1901 UV-Vis spectrophotometer (Japan). The UV-Vis absorption spectra are shown below. Figure 13 As shown,

[0105] Depend on Figure 13 As can be seen, the absorption spectra of these four thionium salts are mainly located in the 350–450 nm range, with HPI exhibiting an absorption peak at 331 nm and a molar extinction coefficient of 6630 μmol. -1 cm -1 Its absorption band has poor matching with the emission band of LED; when a methoxy or hydroxyl group is introduced at position 7, the unshared electron pair on the O atom forms p-π conjugation with the aromatic ring, causing the photoinitiator λ max A redshift occurs, and the λ of OMe-PI and OH-PI... max The wavelengths are 353 nm and 352 nm, with molar extinction coefficients of 22537 L mol, respectively. -1 cm -1 16767 Lmol-1 cm -1 When a benzene substituent is introduced into the aromatic ring of coumarin, the absorption spectrum of Ph-PI extends to 430 nm due to the increased degree of conjugation. These results indicate that OMe-PI, OH-PI, and Ph-PI possess good absorption characteristics in the near-ultraviolet and visible light range, demonstrating that the photoinitiator of this invention can be used as a photoinitiator in the ultraviolet-visible region.

[0106] (2) Photolysis test: The concentration was prepared at 3.7 × 10⁻⁶. -5 An acetonitrile solution of different thionium photoinitiators prepared in Example 3 (mol / L) was added to a quartz cuvette in 3 mL, and a magnetic magnet was added. The cuvette was irradiated with a RUNLED-UVP60 visible light point source, with the distance between the optical fiber of the point source and the cuvette fixed. The irradiation power at the cuvette was measured to be 60 mW / cm² using a UV radiometer. 2 The ultraviolet-visible absorption was measured using a TU1901 UV-Vis spectrophotometer from Lambda, Japan.

[0107] The change curve of ultraviolet absorption of photolysis is as follows: Figure 14 , 15 As shown, this type of photoinitiator undergoes photolysis under light irradiation. This indicates that the photoinitiator we synthesized can be degraded under ultraviolet radiation.

[0108] (3) Photoinitiator photoacid production test: The concentration was 5.0 × 10⁻⁶. -5 Prepare a Rhodamine B solution using an acetonitrile solution of mol / L Ph-PI, adjust the pH to neutral with potassium tert-butoxide, and irradiate 3 mL of initiator solution for 0 s, 30 s, 60 s, 90 s, and 120 s respectively. After irradiation, add 25 μL of Rhodamine B solution and measure the UV spectra.

[0109] Test results are as follows Figure 16 As shown, when RhB is added to the acetonitrile solution of Ph-PI as a steady-state photolysis sample, rapid photolysis of the initiator can be observed. This indicates that the photoinitiator can generate Bronsted acid during the photolysis process, which means it has the potential to initiate the ring-opening polymerization of epoxy compounds.

[0110] Example 6: Polymerization kinetics tests of different thionium photoinitiators

[0111] Under light-protected conditions, a single-component photoinitiator with a concentration of 5.6 × 10⁻⁶ was prepared. -5 The concentration of the multi-component photoinitiating system is 5.6 × 10 mol / g. -5 mol / g (ITX: 2-isopropylthioxanthone and 1.12×10) -4A photopolymerization formulation of mol / g (Iod: iodine salt) was uniformly mixed using ultrasound and physical vibration. A certain amount of the photopolymerization formulation was coated onto a potassium bromide sheet, and then covered with another potassium bromide sheet. The irradiation power for the photopolymerization kinetics experiment was 70 mW / cm². 2 Real-time Fourier Total Reflectance Infrared Spectrometer (Spectral range: 600–4000 cm⁻¹) -1 ) was used to monitor polymerization reactions. By monitoring double bonds (1650 cm⁻¹) -1 ) or epoxy resin (790cm) -1 The reduction in the absorption peak area of ​​functional groups was used to study polymerization kinetics. The conversion rate was calculated using the following formula. (A) t (A0 represents the characteristic peak area of ​​the double bond or epoxy at time t, and A0 represents the characteristic peak area before illumination.)

[0112]

[0113] like Figure 17 As shown, except for OH-PI, the other three thionium salt photoinitiators exhibit good initiation activity for hybrid monomers, with TMPTA achieving a double bond conversion rate of 80% within 15 seconds. TMPTA's rapid polymerization rate results in a hybrid polymerization system with high viscosity in the early stages of polymerization, allowing for rapid curing. This limits the... The migration of acid-active species resulted in a lower final epoxy conversion rate compared to the pure EPOX system. Specifically, the epoxy conversion rates of the hybrid systems induced by OMe-PI and Ph-PI at 365 nm reached 50% and 51%, respectively, significantly higher than the 37% of the ITX / Iod photoinitiated system. The photopolymerization kinetics of TMPTA / EPOX (1:1) (light intensity: 60 mW / cm²) are also described.

[0114] Those skilled in the art should understand that the above description is merely a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A coumarin thionium salt photoinitiator, characterized in that, It has the following general structural formula: The general formula for the structure is selected from the following structures: 。 2. The method for preparing the coumarin thionium salt photoinitiator according to claim 1, characterized in that, Includes the following steps: Step 1: R1-substituted salicylaldehyde is reacted with a thioglycolic acid derivative via a Knoevenagel condensation reaction to prepare a coumarin derivative, with the structure shown in Formula 1. ； Step 2, the compound of Formula 1 reacts with the haloalkane in the presence of silver salt to undergo S... N1 The reaction yields a coumarin thionium salt photoinitiator, with the structural formula shown in Formula 2. ； R1, R2, and R3 are the corresponding groups in the general formula of claim 1.

3. The method for preparing the coumarin thionium salt photoinitiator according to claim 2, characterized in that, Step 1 specifically includes: adding salicylaldehyde derivative, mercaptoacetic acid derivative, and 2-chloro-1-methylpyridine iodide to an acetonitrile solution of triethylamine, refluxing, and removing the solvent under vacuum after the reaction is complete; extracting with dichloromethane and removing the solvent under vacuum again; dissolving the intermediate product in DMF with Cs2CO3 and reacting at room temperature in the dark; after the reaction is complete, extracting with ethyl acetate, and separating the crude product by silica gel column chromatography to obtain compound of formula 1.

4. The method for preparing the coumarin thionium salt photoinitiator according to claim 2 or 3, characterized in that, Step 2 specifically includes: dissolving the compound of formula 1, the haloalkane, and the silver salt in dichloroethane, reacting them at room temperature in a light-protected environment, and separating and purifying them after the reaction is complete to obtain the compound of formula 2.

5. A macromolecular coumarin thionium salt photoinitiator, characterized in that, The coumarin thionium salt photoinitiator prepared by the method described in claim 1 or any one of claims 2-4 is copolymerized with an acrylic acid monomer, wherein R1 is an acrylate group; The structural formula of the macromolecular coumarin thionium salt photoinitiator is Formula 3. 。 6. The macromolecular coumarin thionium salt photoinitiator according to claim 5, characterized in that, The preparation method includes the following steps: The coumarin thionium salt photoinitiator, methyl methacrylate, and azobisisobutyronitrile were added to a Schlenk reaction tube containing tetrahydrofuran. After deoxygenation through a freeze-vacuum-thaw procedure, the mixture was stirred and heated. After the reaction was complete, the mixture was cooled to room temperature, and the polymer was precipitated in stirred ice-cold methanol. The macromolecular coumarin thionium salt photoinitiator was obtained by centrifugation.

7. The application of the coumarin thionium salt photoinitiator according to claim 1 or the macromolecular coumarin thionium salt photoinitiator according to claim 5, characterized in that, It can be applied to free radical resin systems, cationic resin systems, or free radical / cationic hybrid resin systems.

8. The application according to claim 7, characterized in that, The free radical resin system includes one or more of the following: dipropylene glycol diacrylate, trimethylolpropane triacrylate, tripropylene glycol diacrylate, pentaerythritol triacrylate, neopentyl glycol diacrylate, 1,6-hexanediol acrylate, dipentaerythritol hexaacrylate, and ditrimethylolpropane tetraacrylate. The cationic resin system includes one or more of the following: cyclohexane oxide, vinyl ether, 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexyl carboxylate, bisphenol A diglycidyl ether, and neopentyl glycol diglycidyl ether. The hybrid resin system includes 3,4-epoxycyclohexylmethyl methacrylate.

9. The application according to claim 7 or 8, characterized in that, In the curing of free radical resin systems, the addition amount is 0.05 wt%-2 wt% of the monomer mass; In cationic resin systems, the addition amount is 0.5 wt%-10 wt% of the monomer mass; The amount added to the radical / cationic hybrid system is 0.5 wt%-10 wt% of the monomer mass.

10. The application according to claim 7, characterized in that, It is used in food packaging, medical materials, coatings and inks.

11. The application according to claim 7, characterized in that, As a photoacid generator, it is used in photolithography processes, UV-curable adhesives, photosensitive resins, nanomaterial preparation, coatings and inks, and the pharmaceutical industry.

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