Thioxanthone photoinitiator intermediates and methods for their preparation, aqueous polymerizable thioxanthone photoinitiators and methods for their preparation

Abstract

The application discloses a thioxanthone photoinitiator intermediate and a preparation method thereof, and a water-soluble polymerizable thioxanthone photoinitiator prepared from the thioxanthone photoinitiator intermediate. The molecular structure of the thioxanthone photoinitiator intermediate is shown in formula I-6. The water-soluble polymerizable thioxanthone photoinitiator has the molecular structure shown in formula S. The solubility, photoinitiation efficiency and safety of the photoinitiator in a water-based system are improved by designing the molecular structure of the photoinitiator. The water-soluble polymerizable thioxanthone photoinitiator prepared by the application has good water solubility and high photoinitiation efficiency. The molecular structure of the water-soluble polymerizable thioxanthone photoinitiator can be copolymerized with monomers in a photoinitiation polymerization reaction, and is covalently combined with a polymer main chain after solidification, so that the migration of the photoinitiator is effectively avoided. The application further discloses a preparation method of the water-soluble polymerizable thioxanthone photoinitiator.

Description

Technical Field

[0001] This invention belongs to the field of photoinitiator technology, specifically relating to a thioxanthone photoinitiator intermediate and its preparation method. This invention also relates to an aqueous polymerizable thioxanthone photoinitiator prepared from the thioxanthone photoinitiator intermediate and its preparation method. Background Technology

[0002] Photoinitiators are important compounds in the field of photochemistry. Under ultraviolet or visible light irradiation, they absorb photon energy and initiate polymerization reactions through free radical or cationic mechanisms, enabling the rapid curing of materials such as coatings, inks, and adhesives. Photocurable materials have advantages such as fast curing speed, low energy consumption, and minimal environmental pollution, and are widely used in industrial coatings, 3D printing, and biomedical materials.

[0003] With increasingly stringent environmental regulations and growing demand for sustainable development, the application of waterborne photocurable materials is receiving increasing attention. However, most traditional photoinitiators are oil-based systems, insoluble in water, and prone to migration, seriously affecting the environmental friendliness of the materials and the safety of their final application. Therefore, developing photoinitiators with good water solubility, polymerizability, and no migration is an important research direction in the field of photochemistry.

[0004] Thioxanthone compounds are widely used in the design of photoinitiators due to their high molar extinction coefficient, strong absorption capacity, and good photochemical activity. However, traditional thioxanthone photoinitiators still have the following shortcomings:

[0005] 1. Poor water solubility: Most existing thioxanthone photoinitiators lack water-soluble groups, resulting in poor solubility in aqueous systems, which limits their application in environmentally friendly waterborne photocuring systems.

[0006] II. Low initiation efficiency: Traditional thioxanthone photoinitiators have low photoinitiation efficiency in aqueous systems, resulting in slow polymerization rates that are difficult to meet the needs of industrial applications.

[0007] III. Environmental Unfriendliness and Migration: Traditional thioxanthone photoinitiators tend to migrate within the cured material after polymerization because their chemical structure is not covalently bonded to the polymer backbone. For example, patent document CN107400112B discloses a photoinitiator and its preparation method. The photoinitiator achieves long-wavelength absorption based on the thioxanthone core and has strong absorption for 395nm UV LED light sources. By introducing fluorocarbon chains, it imparts low surface tension to the photoinitiator, allowing it to float to the surface of the coating / ink layer in the formulation system. In other words, the photoinitiator can accumulate on the surface, generating a high concentration of free radicals after light absorption, which counteracts surface oxygen inhibition polymerization.

[0008] The photoinitiators in the prior art contain quaternary ammonium groups, which are linked to a thioxanthone aromatic ring via a methylene group. This structure has photosensitive degradation properties. However, the molecular structure of this photoinitiator has no polymerizable groups, so it cannot covalently bond with the backbone of other organic polymers in the formulation system. It is prone to migration in the cured material. Photoinitiator migration can lead to harmful residues in the cured material, making the final product unable to meet the requirements of environmental regulations or safety standards. It is not suitable for use in fields with high safety requirements such as food and medicine. Summary of the Invention

[0009] To address the problems in related technologies, this invention proposes a thioxanthone photoinitiator intermediate and its preparation method, and also discloses a water-based polymerizable thioxanthone photoinitiator and its preparation method. By introducing water-soluble groups and polymerizable chemical groups into the thioxanthone structure, the water solubility and reaction efficiency of the initiator are significantly improved, and the photoinitiator prepared by this invention can covalently bond with the polymer backbone after photopolymerization, thereby overcoming the aforementioned technical problems in existing related technologies, effectively solving the problem of photoinitiator migration, improving the safety and physical properties of cured materials containing photoinitiators, and enabling the photoinitiator prepared by this invention to be applied to environmentally friendly water-based photocurable materials.

[0010] The technical solution of this invention is implemented as follows:

[0011] A thioxanthone photoinitiator intermediate, the molecular structure of which is shown in Formula I-6:

[0012]

[0013] The preparation method of the above-mentioned thioxanthone photoinitiator intermediate includes the following steps:

[0014] 1) Thiosyl salicylic acid and thiophene are prepared at a molar ratio of 0.8–1.2:0.8–1.2 and react under the condition of concentrated sulfuric acid as a catalyst to generate intermediate I-3, the molecular structure of which is shown in formula I-3:

[0015]

[0016] 2) Intermediate I-3 and a bromine-containing alkoxy compound were prepared in a molar ratio of 0.8–1.2:0.8–1.2, mixed and dissolved in an organic solvent, and under alkaline catalysis, a nucleophilic substitution reaction was carried out to give intermediate I-5, the molecular structure of which is shown in Formula I-5:

[0017]

[0018] 3) Intermediate I-5 and imidazole compound are mixed in a molar ratio of 0.8-1.2:0.8-1.2 to undergo a substitution reaction, thereby obtaining the thioxanthone photoinitiator intermediate I-6.

[0019] Preferably, steps 1) to 3) are accompanied by heating and holding operations and stirring operations during the reaction process. The reaction system is heated to 80-90°C and held at that temperature. After the reaction is completed, stirring is stopped and an inorganic salt solution is added to quench the reaction. Then the temperature is lowered to equal to or below room temperature.

[0020] More preferably, the inorganic salt solution is one of a saturated sodium chloride solution, potassium chloride, or ammonium chloride.

[0021] Preferably, in step 2), the molecular structure of the bromine-containing alkoxy compound is as shown in Formula I-4:

[0022]

[0023] Preferably, in step 2), the alkaline catalyst is one of triethylamine, ethylenediamine, 4-dimethylaminopyridine, and potassium carbonate.

[0024] More preferably, step 1) includes the following steps:

[0025] 1.1) First, slowly add thiosalicylic acid to concentrated sulfuric acid and stir for at least 5 minutes. While stirring, slowly add thiophenol. The addition time of thiophenol should be controlled to be at least 30 minutes. After the addition is completed, stir at room temperature for at least 1 hour.

[0026] 1.2) Heat to 80-90℃, keep stirring, react for 1.5-2 hours, and then let stand for at least 10 hours;

[0027] 1.3) Turn on the stirring and keep stirring. Add the mixture obtained in step 1.2) to boiling water with a volume equal to or greater than 10 times its own volume, and boil for 5 to 8 minutes.

[0028] 1.4) After boiling, the solution is cooled to room temperature, filtered to remove solid residue, and recrystallized in a dioxane aqueous solution with a mass concentration of 20-80% to obtain intermediate I-3.

[0029] More preferably, step 2) includes the following steps:

[0030] 2.1) Dissolve intermediate I-3 obtained in step 1) in an organic solvent, add an alkaline catalyst, the molar ratio of the alkaline catalyst to intermediate I-3 is 2 to 4:9, and add an alkoxy compound containing a bromine group dropwise, with the total dropwise addition time controlled to be at least 30 min.

[0031] 2.2) After the addition is complete, raise the temperature to 80-90℃ and stir the reaction for 11-13 hours;

[0032] 2.3) After the reaction is complete, the liquid obtained in step 2.2) is cooled to room temperature, and then an inorganic salt solution is added to quench the reaction;

[0033] 2.4) Separate the organic phase from the feed solution in step 2.3), wash and dry the organic phase, remove the organic solvent, and obtain intermediate I-5 by chromatography.

[0034] More preferably, step 3) includes the following steps:

[0035] 3.1) Dissolve the intermediate I-5 obtained in step 2) in an organic solvent, and slowly add imidazole under stirring conditions;

[0036] 3.2) Keep stirring, raise the temperature to 80-90℃, and stir for 5-7 hours;

[0037] 3.3) After the reaction is complete, the solution is cooled to room temperature, and then an inorganic salt solution is added to quench the reaction;

[0038] 3.4) Separate the organic phase from the liquid obtained in step 3.3), wash and dry the organic phase, remove the organic solvent, and obtain the thioxanthone photoinitiator intermediate I-6 by chromatography.

[0039] Preferably, the organic solvent in steps 1) to 3) above is one or more of toluene, xylene, and chloroform in any proportion.

[0040] This invention also discloses an aqueous polymerizable thioxanthone photoinitiator, the molecular structure of which is shown in Formula S:

[0041]

[0042] Among them, X ˉ It is at least one of fluoride ion, chloride ion, bromide ion, iodide ion, phosphate ion, sulfonate ion, carbonate ion, hexafluorophosphate ion or nitrate ion;

[0043] The structure of R is * indicates a link position, and R' represents an alkyl, cyano, aryl, substituted aryl, benzyl, substituted benzyl, or oligoether group.

[0044] Preferably, the alkyl group is C10. n H m , where n and m are independent natural numbers less than 30.

[0045] Preferably, the molecular structure of the oligoether group is as follows: Where m is a natural number less than 30.

[0046] Preferably, the water-based polymerizable thioxanthone photoinitiator is one of the following formulas S-1 to S-16:

[0047]

[0048] The water-based polymerizable thioxanthone photoinitiator has a maximum absorption wavelength range of 420–450 nm and an absorbance ≥1.0.

[0049] Specifically, when the polymerizable thioxanthone photoinitiator is of formula S-8 or S-13, and its concentration in deionized water reaches 1 mg / mL or above, its absorbance at a wavelength of 420 nm is 1.4 or above.

[0050] The preparation method of the above-mentioned water-based polymerizable thioxanthone photoinitiator includes at least the following steps:

[0051] 1) Prepare the above-mentioned thioxanthone photoinitiator intermediate I-6;

[0052] 2) Thioxanthone photoinitiator intermediate I-6 is alkylated with an acrylate-containing brominated compound at a molar ratio of 0.8–1.2:0.8–1.2 to obtain water-based polymerizable thioxanthone photoinitiator I-8, with the molecular structure shown in Formula I-8:

[0053]

[0054] Wherein, the structure of R is * indicates a link position, and R' represents an alkyl, cyano, aryl, substituted aryl, benzyl, substituted benzyl, or oligoether group.

[0055] Preferably, the alkyl group is C10. n H m Where n and m are both independent natural numbers less than 30; the molecular structure of the oligoether group is as follows: Where m is a natural number less than 30.

[0056] This invention also discloses another method for preparing the above-mentioned water-based polymerizable thioxanthone photoinitiator, comprising the following steps:

[0057] 1) Prepare the above-mentioned thioxanthone photoinitiator intermediate I-6;

[0058] 2) Thioxanthone photoinitiator intermediate I-6 is alkylated with an acrylate-containing brominated compound at a molar ratio of 0.8–1.2:0.8–1.2 to obtain intermediate I-8 containing an imidazole ionic liquid unit, with the molecular structure shown in formula I-8:

[0059]

[0060] Wherein, the structure of R is * indicates the link position, and R' represents alkyl, cyano, aryl, substituted aryl, benzyl, substituted benzyl, or oligoether groups;

[0061] 3) Intermediate I-8 and ammonium salt NH4X are mixed in a molar ratio of 0.8-1.2:0.8-1.2 to undergo an ion exchange reaction, thereby obtaining a water-based polymerizable thioxanthone photoinitiator;

[0062] Wherein, X is at least one of fluoride ion, chloride ion, iodide ion, phosphate ion, sulfonate ion, carbonate ion, hexafluorophosphate ion, or nitrate ion.

[0063] Preferably, the alkyl group is C10. n H m Where n and m are both independent natural numbers less than 30; the molecular structure of the oligoether group is as follows: Where m is a natural number less than 30.

[0064] Preferably, the ammonium salt is ammonium hexafluorophosphate.

[0065] Preferably, in step 2) of the above two preparation methods, the reaction process is accompanied by heating and holding operations and stirring operations. The reaction system is heated to 80-90°C and held at that temperature. After the reaction is completed, stirring is stopped and the temperature is lowered to equal to or below room temperature.

[0066] More preferably, step 2) of the above two preparation methods includes the following steps:

[0067] 2.1) Dissolve the thioxanthone photoinitiator intermediate I-6 and the acrylate-containing brominated compound in an organic solvent and stir until homogeneous;

[0068] 2.2) Heat to 80–90℃ and stir for 9–11 hours;

[0069] 2.3) After the reaction is complete, the liquid should be cooled to room temperature;

[0070] 2.4) Add water to the liquid in step 5.3) and mix. After separation of the layers, separate the aqueous phase. Extract the aqueous phase several times with an organic extractant to remove unreacted organic matter and byproducts.

[0071] 2.5) Remove moisture and dry to obtain water-based polymerizable thioxanthone photoinitiator I-8; if step 3) is included, intermediate I-8 is obtained.

[0072] Preferably, the organic solvent in step 2.1) is one or more of toluene, xylene, and chloroform in any proportion; the organic extract in step 5.4) is one of ethyl acetate, diethyl ether, and dichloromethane.

[0073] Preferably, in step 2) of the above two preparation methods, the preparation method of the bromine compound containing acrylate includes the following steps:

[0074] a) Acryloyl chloride or its derivatives and 2-bromoethanol are mixed and dissolved in an organic solvent at a molar ratio of 0.8–1.2:0.8–1.2;

[0075] b) Start stirring and maintain the temperature, raise the temperature to 80-90°C, and stir for 5-7 hours;

[0076] c) After the reaction is complete, the liquid is cooled to room temperature, and then an inorganic salt solution is added to quench the reaction.

[0077] d) Separate the organic phase from the liquid obtained in step 4.3), wash and dry the organic phase, remove the organic solvent, purify, and obtain a brominated compound containing acrylate.

[0078] Preferably, the organic solvent in step a) is one or more of toluene, xylene, and chloroform in any proportion; the inorganic salt solution in step c) is a saturated sodium chloride solution.

[0079] Preferably, in step 2) of the above two preparation methods, the bromine compound containing acrylate is one of the following formulas 1-3 to 8-3:

[0080]

[0081]

[0082] Preferably, in the preparation method of the above-mentioned water-based polymerizable thioxanthone photoinitiator, step 3) includes the following steps:

[0083] 3.1) Dissolve intermediate I-8 in water, and slowly add ammonium salt under stirring conditions. The total addition time of ammonium salt should be at least 18 minutes.

[0084] 3.2) Keep stirring and react at room temperature for 3–5 hours;

[0085] 3.3) Remove the water from the liquid obtained in step 3.2), recrystallize it, filter and dry it to obtain a water-based polymerizable thioxanthone photoinitiator.

[0086] The general formula for synthesizing the water-based polymerizable thioxanthone photoinitiator of the present invention is shown below:

[0087]

[0088] The beneficial effects of this invention are:

[0089] This invention provides a water-based polymerizable thioxanthone photoinitiator obtained through the above-mentioned thioxanthone photoinitiator intermediate. By further introducing water-soluble quaternary ammonium salt groups into the molecular structure, it achieves excellent water solubility, making it widely applicable to environmentally friendly water-based photocuring systems. Simultaneously, polymerizable functional groups are designed into the molecular structure, achieving:

[0090] I. Covalent Bonding with Polymers to Prevent Migration: By introducing polymerizable double bonds or other copolymerizable groups with monomers into the thioxanthone structure, the initiator can participate in polymerization along with the polymer matrix, thus covalently bonding to the polymer backbone. This effectively prevents the migration of the photoinitiator in the cured product after polymerization. Solving the migration problem not only significantly improves the physicochemical stability of the material but also reduces potential threats to human health and the environment, making this material particularly suitable for applications with high safety requirements, such as medical and food packaging.

[0091] II. Improve the overall performance of materials: By introducing polymerizable groups, photoinitiators are no longer simple additives, but become part of the polymer structure. This can improve the density of the entire polymer network and enhance the mechanical strength, scratch resistance and chemical corrosion resistance of the material.

[0092] Third, improve reaction efficiency: Polymerizable photoinitiators can significantly improve initiation efficiency because they can participate in the polymerization reaction, increase the concentration of free radicals and promote the reaction, thereby increasing the polymerization rate. They are especially suitable for some industrial applications that require rapid curing, such as high-speed coating curing and 3D printing, and are of great significance.

[0093] In summary, this invention significantly improves the solubility, photoinitiation efficiency, and safety of photoinitiators in aqueous systems through targeted design of their molecular structure. The water-based polymerizable thioxanthone photoinitiator prepared by this invention exhibits good water solubility and high photoinitiation efficiency. Furthermore, its molecular structure allows it to copolymerize with monomers during photoinitiated polymerization, achieving covalent bonding to the polymer backbone after curing. This effectively avoids the migration problem of the photoinitiator, improving the physical properties and long-term stability of materials containing the water-based polymerizable thioxanthone photoinitiator of this invention. It is particularly suitable for applications in various water-based photocuring and high-efficiency photocuring industries. Detailed Implementation

[0094] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the examples. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0095] Example 1

[0096] The synthesis route in this embodiment is shown below:

[0097]

[0098] 1) Preparation of intermediate I-3

[0099] 1.1) Slowly add 160g of thiosalicylic acid (1.0mol as shown in Formula I-1) to 1500mL of concentrated sulfuric acid and stir for 5min to ensure thorough mixing. Then, slowly add 600g of thiophenol (5.5mol as shown in Formula I-2) while stirring. The entire addition process takes 30min. After the addition is complete, continue stirring at room temperature for 1h.

[0100] 1.2) Heat the reaction mixture to 80°C and maintain the reaction for 2 hours, then let it stand overnight (more than 10 hours) at room temperature.

[0101] 1.3) The next day, carefully pour the reaction mixture into boiling water that is 10 times the original volume, stirring constantly while continuing to boil for 5 minutes.

[0102] 1.3) Cool the solution to room temperature and filter to remove solid residue. Recrystallize from a 60% dioxane-water mixed solvent to obtain 195 g of intermediate I-3, i.e., 2-mercaptothioanthrone. The 1H NMR data are as follows:

[0103] 1 H NMR (500MHz, Chloroform) δ7.59–6.87 (m, 7H), 3.45 (s, 1H).

[0104] 2) Preparation of intermediate I-5

[0105] 2.1) Weigh 183g of intermediate I-3 (0.75mol) obtained in step 1) and dissolve it in 500mL of toluene, and add 227.7g of triethylamine (2.25mol) as an alkaline catalyst; then weigh 206.25g of alkoxy compound (as shown in formula I-4, 0.75mol) and slowly add it dropwise to the solution with stirring for 30min.

[0106] 2.2) After the addition is complete, heat the reaction mixture to 80°C and stir for 12 h, during which thin-layer chromatography (TLC) is used to monitor the progress of the reaction.

[0107] 2.3) After the reaction is complete, cool the mixture to room temperature and add 500 mL of saturated sodium chloride solution to quench the reaction.

[0108] 2.4) Separate the organic phase using a separatory funnel, wash the organic phase three times with 300 mL of water, dry it with anhydrous sodium sulfate for 1 h, and then filter to remove the desiccant.

[0109] 2.5) Finally, the organic phase was evaporated under reduced pressure to remove toluene, yielding a crude product. This crude product was then purified by column chromatography using petroleum ether / ethyl acetate as eluent to obtain 260 g of intermediate I-5. The 1H NMR data are as follows:

[0110] 1 H NMR (500MHz, Chloroform) δ7.68–6.80 (m, 7H), 3.99–3.66 (m, 4H), 3.60–3.36 (m, 6H), 3.25 (dd, J = 21.4, 7.4Hz, 2H).

[0111] 3) Preparation of thioxanthone photoinitiator intermediate I-6

[0112] 3.1) Weigh 219.5g of intermediate I-5 (0.5mol) obtained in step 2) and dissolve it in 400mL of toluene. Under stirring conditions, slowly add 38g of imidazole (0.5mol) and continue stirring the mixture.

[0113] 3.2) Heat to 80℃ and react for 6 hours.

[0114] 3.3) After the reaction is complete, cool the reaction system to room temperature and add 400 mL of saturated sodium chloride solution to quench the reaction.

[0115] 3.4) Separate the organic phase using a separatory funnel, wash the organic phase three times with 300 mL of water, dry it with anhydrous sodium sulfate for 1 h, and then filter to remove the desiccant.

[0116] 3.5) Toluene was removed by vacuum distillation to obtain the crude product. The crude product was purified by column chromatography using petroleum ether / ethyl acetate as eluent to obtain 170 g of thioxanthone photoinitiator intermediate I-6. The 1H NMR data are as follows:

[0117] 1 H NMR(500MHz,Chloroform)δ7.92(s,1H),7.58–7.25(m,5H),7.28–6.97(m,3H),6.78(d,J= 15.0Hz, 1H), 4.33 (t, J = 8.1Hz, 2H), 3.94–3.69 (m, 4H), 3.52 (s, 4H), 3.27 (t, J = 9.4Hz, 2H).

[0118] Example 2

[0119] The synthesis route in this embodiment is shown below:

[0120]

[0121] 4) Preparation of brominated compounds containing acrylates 1-3

[0122] 4.1) Weigh 104 g of the compound shown in Formula 1-1 (1.0 mol) and 125 g of the compound shown in Formula 1-2 (1.0 mol), dissolve them in 300 mL of anhydrous toluene, and place them in a three-necked flask and attach it to a reflux condenser.

[0123] 4.2) The mixture was slowly heated to 80°C under stirring and the reaction was maintained for 6 hours to ensure that the reaction was complete. During the reaction, the reaction progress was detected by thin-layer chromatography (TLC).

[0124] 4.3) After the reaction is complete, stop heating and cool the reaction mixture to room temperature. Add 200 mL of saturated sodium chloride solution to the reaction mixture to quench the reaction.

[0125] 4.4) Use a separatory funnel to separate the organic phase. Wash the organic phase three times with 200 mL of water, then dry it with anhydrous sodium sulfate for 1 hour and filter to remove the desiccant.

[0126] 4.5) Toluene was then removed by vacuum evaporation in a rotary evaporator to obtain the crude product; the crude product was purified by column chromatography using petroleum ether / ethyl acetate as eluent to obtain 156 g of purified acrylate-containing brominated compounds 1-3. The 1H NMR data are as follows:

[0127] 1 H NMR (500MHz, Chloroform) δ6.73–6.06 (m, 2H), 4.64 (t, J = 7.9 Hz, 2H), 3.65 (t, J = 8.0 Hz, 2H), 2.01 (t, J = 2.0 Hz, 3H).

[0128] 5) Preparation of water-based polymerizable thioxanthone photoinitiator S-1

[0129] 5.1) Weigh 106.5g of the thioxanthone photoinitiator intermediate I-6 (0.25mol) prepared in Example 1, dissolve it in 200mL of anhydrous toluene, and prepare it in a three-necked flask; then weigh 68.75g of the acrylate-containing brominated compound 1-3 (0.25mol) prepared in step 4), slowly add it to the solution, and stir until homogeneous.

[0130] 5.2) Heat the reaction mixture to 85°C and maintain the reaction for 10 h, monitoring the reaction by thin-layer chromatography (TLC).

[0131] 5.3) After the reaction is complete, stop heating and cool to room temperature.

[0132] 5.4) Add 200 mL of deionized water and separate the layers through a separatory funnel. Collect the aqueous phase and extract it three times with ethyl acetate (50 mL each time) to remove unreacted organic matter and byproducts.

[0133] 5.5) The aqueous phase was then concentrated under reduced pressure to obtain the crude ionic liquid product; further purification was performed by vacuum evaporation to remove residual water, followed by freeze-drying, finally yielding 121g of purified aqueous polymerizable thioxanthone photoinitiator S-1. The 1H NMR spectral data are as follows:

[0134] 1 H NMR(500MHz,Chloroform)δ8.92(s,1H),7.62–7.22(m,5H),7.16(td,J=7.5,1.5 Hz,1H),7.09(d,J=1.3Hz,1H),6.59–6.25(m,2H),5.04(d,J=7.5Hz,1H),4.94(d, J=7.5Hz,1H),4.79(t,J=4.0Hz,2H),4.47(t,J=4.0Hz,2H),4.33(t,J=4.2Hz,2H ), 3.81 (dt, J = 15.7, 4.3Hz, 4H), 3.52 (s, 4H), 3.27 (t, J = 4.5Hz, 2H), 2.01 (s, 3H).

[0135] Example 3

[0136] The synthesis route in this embodiment is shown below:

[0137]

[0138] 4) Preparation of brominated compounds containing acrylates 2-3

[0139] 4.1) Weigh 118 g of the compound shown in Formula 2-1 (1.0 mol), dissolve it in 200 mL of anhydrous toluene, and prepare it in a three-necked flask; then weigh 125 g of the compound shown in Formula 2-2 (1.0 mol), slowly add it to the solution with stirring, stir until homogeneous, and continue stirring at room temperature for 30 min to ensure that the reactants are fully mixed.

[0140] 4.2) The reaction mixture was then heated to 90°C and maintained at this temperature for 6 h to promote the reaction, during which the reaction progress was monitored by thin-layer chromatography (TLC).

[0141] 4.3) After the reaction is complete, stop heating and cool the reaction mixture to room temperature. Add 300 mL of saturated sodium chloride solution to quench the reaction.

[0142] 4.4) Use a separatory funnel to separate the organic phase. Wash the organic phase three times with 200 mL of deionized water to remove water-soluble byproducts. Then dry it with anhydrous sodium sulfate for 1 hour and filter to remove the desiccant.

[0143] 4.5) The organic phase was placed on a rotary evaporator and toluene was removed under reduced pressure to obtain a crude product. The crude product was purified by recrystallization to obtain 134 g of purified brominated compound 2-3 containing acrylate. The 1H NMR data are as follows:

[0144] 1 H NMR(500MHz,Chloroform)δ6.29(dt,J=4.1,2.0Hz,1H),5.46(dt,J=4.1,2.0Hz,1H),4.64(t, J=15.0Hz, 2H), 3.65 (t, J=15.0Hz, 2H), 2.44 (qd, J=13.4, 11.5Hz, 2H), 1.07 (t, J=13.4Hz, 3H).

[0145] 5) Preparation of water-based polymerizable thioxanthone photoinitiator S-2

[0146] 5.1) Weigh 106.5g of the thioxanthone photoinitiator intermediate I-6 (0.25mol) prepared in Example 1, dissolve it in 200mL of anhydrous toluene, and prepare it in a three-necked flask; then weigh 51.25g of the acrylate-containing brominated compound 2-3 (0.25mol) prepared in step 4), slowly add it to the solution, and stir until homogeneous.

[0147] 5.2) Heat the reaction mixture to 85°C and maintain the reaction for 10 h, monitoring the reaction by thin-layer chromatography (TLC).

[0148] 5.3) After the reaction is complete, stop heating and cool to room temperature.

[0149] 5.4) Add 200 mL of deionized water to separate the layers, collect the aqueous phase to retain the ionic liquid, and extract the aqueous phase three times with ethyl acetate (50 mL each time) to remove unreacted organic matter and byproducts.

[0150] 5.5) The aqueous phase was then concentrated under reduced pressure to obtain the crude ionic liquid product; further purification was performed by vacuum evaporation to remove residual water, followed by freeze-drying, ultimately yielding 98g of purified aqueous polymerizable thioxanthone photoinitiator S-2. The 1H NMR spectral data are as follows:

[0151] 1 H NMR (500MHz, Chloroform) δ8.92 (s, 1H), 7.56–7.24 (m, 2H), 7.14 (ddd, J = 22.5, 16.8, 3. 1Hz,1H),6.29(dt,J=4.1,2.0Hz,1H),5.46(dt,J=4.1,2.0Hz,1H),4.96(d,J=7.5Hz,1H) ,4.85–4.70(m,1H),4.47(t,J=9.6Hz,1H),4.33(t,J=8.0Hz,1H),3.79(dt,J=17.1,9.0 Hz,1H),3.52(s,1H),3.27(t,J=10.0Hz,1H),2.67–2.23(m,1H),1.07(t,J=13.4Hz,1H).

[0152] Example 4

[0153] The synthesis route in this embodiment is shown below:

[0154]

[0155] 4) Preparation of brominated compounds containing acrylates 3-3

[0156] 4.1) Weigh 146 g of the compound shown in Formula 3-1 (1.0 mol), dissolve it in 300 mL of anhydrous toluene, and place it in a three-necked flask and attach it to a reflux condenser; then weigh 125 g of the compound shown in Formula 3-2 (1.0 mol), and slowly add it to the solution under stirring. The entire addition process should last for 30 min to ensure that the two are thoroughly mixed.

[0157] 4.2) After the addition is complete, heat the reaction mixture to 90°C and maintain the reaction for 8 hours to promote the reaction. During this period, monitor the reaction progress by thin-layer chromatography (TLC).

[0158] 4.3) After the reaction is complete, cool the reaction mixture to room temperature and add 300 mL of saturated sodium chloride solution to quench the reaction.

[0159] 4.4) Use a separatory funnel to separate the organic phase. Wash the organic phase three times with 200 mL of deionized water to remove water-soluble impurities. Dry the organic phase with anhydrous sodium sulfate for 1 hour and filter to remove the desiccant.

[0160] 4.5) The organic phase was placed in a rotary evaporator, and toluene was removed by vacuum distillation to obtain a crude product. The crude product was further purified by recrystallization using ethanol to obtain 134 g of bromoacrylate-containing compound 3-3. The 1H NMR data are as follows:

[0161] 1 H NMR(500MHz,Chloroform)δ6.29(dt,J=4.1,2.0Hz,1H),5.46(dt,J=4.1,2.0Hz,1H),4.64(t,J=8.0Hz ,2H),3.65(t,J=8.0Hz,2H),2.41(tt,J=11.2,1.8Hz,2H),1.62–1.09(m,4H),0.93(t,J=12.6Hz,3H).

[0162] 5) Preparation of water-based polymerizable thioxanthone photoinitiator S-3

[0163] 5.1) Weigh 58.75g of the acrylate-containing brominated compound 3-3 (0.25mol) obtained in step 4), dissolve it in 200mL of anhydrous toluene, and prepare it in a three-necked flask. Then weigh 106.5g of the thioxanthone photoinitiator intermediate I-6 (0.25mol) obtained in Example 1, slowly add it to the solution, and stir until homogeneous.

[0164] 5.2) Heat the reaction mixture to 85°C and maintain the reaction for 10 h to ensure that the reaction proceeds fully; monitor the reaction by thin-layer chromatography (TLC) during the process.

[0165] 5.3) After the reaction is complete, stop heating and cool to room temperature.

[0166] 5.4) Add 200 mL of deionized water to the reaction mixture, separate the layers using a separatory funnel, collect the aqueous phase, and extract the aqueous phase three times with ethyl acetate (50 mL each time) to remove unreacted organic matter and byproducts.

[0167] 5.5) The aqueous phase was then concentrated under reduced pressure to remove most of the water, followed by freeze-drying to obtain 94g of purified aqueous polymerizable thioxanthone photoinitiator S-3. The 1H NMR spectral data are as follows:

[0168] 1 H NMR(500MHz,Chloroform)δ8.92(s,1H),7.61–6.91(m,7H),6.29(dt,J=4.1,1.9Hz,1H),5.46(dt,J=4.1,2.0Hz,1H),5.24(d,J=7.5Hz,1H),4.93–4.60(m ,3H),4.56–4.19(m,4H),3.85(dt,J=12.9,8.4Hz,4H),3.52(s,4H),3.27(t, J=9.2Hz,2H),2.48–2.23(m,2H),1.62–1.07(m,4H),0.93(t,J=12.7Hz,3H).

[0169] Example 5

[0170] The synthesis route in this embodiment is shown below:

[0171]

[0172] 4) Preparation of brominated compounds containing acrylates 4-3

[0173] 4.1) Weigh 160g of the compound shown in Formula 4-1 (1.0 mol), dissolve it in 300mL of anhydrous toluene, and place it in a three-necked flask and attach it to a reflux condenser; then weigh 125g of the compound shown in Formula 4-2 (1.0 mol), and slowly add it to the solution under stirring. The entire addition process should last for 30min to ensure that the two are thoroughly mixed.

[0174] 4.2) After the addition is complete, heat the reaction mixture to 90°C and maintain the reaction for 8 hours to promote the reaction. During this period, monitor the reaction progress by thin-layer chromatography (TLC).

[0175] 4.3) After the reaction is complete, cool the reaction mixture to room temperature and add 300 mL of saturated sodium chloride solution to quench the reaction.

[0176] 4.4) Use a separatory funnel to separate the organic phase. Wash the organic phase three times with 200 mL of deionized water to remove water-soluble impurities. Dry the organic phase with anhydrous sodium sulfate for 1 hour and filter to remove the desiccant.

[0177] 4.5) The organic phase was placed in a rotary evaporator, and toluene was removed under reduced pressure to obtain a crude product. The crude product was then purified by column chromatography using petroleum ether / ethyl acetate as eluent to obtain 213 g of acrylate-containing brominated compound 4-3. The 1H NMR data are as follows:

[0178] 1 H NMR(500MHz,Chloroform)δ6.29(dt,J=4.1,2.0Hz,1H),5.46(dt,J=4.0,1.9Hz,1H),4.64(t,J=7.7Hz,2H),3.6 5(t,J=7.6Hz,2H),2.41(tt,J=11.6,1.9Hz,2H),1.77–1.42(m,1H),1.40–1.22(m,2H),0.91(d,J=12.5Hz,6H).

[0179] 5) Preparation of water-based polymerizable thioxanthone photoinitiator S-4

[0180] 5.1) Weigh 62.25g of the acrylate-containing brominated compound 4-3 (0.25mol) obtained in step 4), dissolve it in 200mL of anhydrous toluene, and prepare it in a three-necked flask. Then weigh 106.5g of the thioxanthone photoinitiator intermediate I-6 (0.25mol) obtained in Example 1, slowly add it to the solution, and stir until homogeneous.

[0181] 5.2) Heat the reaction mixture to 85°C and maintain the reaction for 10 h to ensure that the reaction proceeds fully; monitor the reaction by thin-layer chromatography (TLC) during the process.

[0182] 5.3) After the reaction is complete, stop heating and cool to room temperature.

[0183] 5.4) Add 200 mL of deionized water to the reaction mixture, separate the layers using a separatory funnel, collect the aqueous phase, and extract the aqueous phase three times with ethyl acetate (50 mL each time) to remove unreacted organic matter and byproducts.

[0184] 5.5) The aqueous phase was then concentrated under reduced pressure to remove most of the water, followed by freeze-drying to obtain 108g of purified aqueous polymerizable thioxanthone photoinitiator S-4. The 1H NMR spectral data are as follows:

[0185] 1 H NMR(500MHz,Chloroform)δ8.92(s,1H),7.64–6.94(m,7H),6.29(dt,J=4.1,2.0Hz,1H ),5.46(dt,J=3.9,1.9Hz,1H),5.05–4.69(m,4H),4.40(dt,J=15.9,9.0Hz,4H),3.80(d t,J=23.2,8.0Hz,4H),3.52(s,4H),3.27(t,J=8.1Hz,2H),2.41(tt,J=11.4,1.9Hz,2H ), 1.59 (ddd, J = 23.3, 11.9, 5.9 Hz, 1H), 1.31 ( q, J = 11.2 Hz, 2H), 0.91 ( d, J = 12.5 Hz, 6H).

[0186] Example 6

[0187] The synthesis route in this embodiment is shown below:

[0188]

[0189] 4) Preparation of brominated compounds containing acrylates 5-3

[0190] 4.1) Weigh 166g of the compound shown in Formula 5-1 (1.0 mol), dissolve it in 300mL of anhydrous toluene, and place it in a three-necked flask and attach it to a reflux condenser; then weigh 125g of the compound shown in Formula 5-2 (1.0 mol), and slowly add it to the solution under stirring. The entire addition process should last for 30min to ensure that the two are thoroughly mixed.

[0191] 4.2) After the addition is complete, heat the reaction mixture to 90°C and maintain the reaction for 8 hours to promote the reaction. During this period, monitor the reaction progress by thin-layer chromatography (TLC).

[0192] 4.3) After the reaction is complete, cool the reaction mixture to room temperature and add 300 mL of saturated sodium chloride solution to quench the reaction.

[0193] 4.4) Use a separatory funnel to separate the organic phase. Wash the organic phase three times with 200 mL of deionized water to remove water-soluble impurities. Dry the organic phase with anhydrous sodium sulfate for 1 hour and filter to remove the desiccant.

[0194] 4.5) The organic phase was placed in a rotary evaporator, and toluene was removed under reduced pressure to obtain a crude product. The crude product was then purified by column chromatography using petroleum ether / ethyl acetate as eluent to obtain 225 g of bromoacrylate-containing compound 5-3. The 1H NMR data are as follows:

[0195] 1 H NMR (500MHz, Chloroform) δ 7.59–7.26 (m, 3H), 7.29–6.89 (m, 2H), 6.28 (dd, J = 51.1, 4.2Hz, 2H), 4.64 (t, J = 8.0Hz, 2H), 3.65 (t, J = 8.0Hz, 2H).

[0196] 5) Preparation of water-based polymerizable thioxanthone photoinitiator S-5

[0197] 5.1) Weigh 63.5g of the acrylate-containing brominated compound 5-3 (0.25mol) obtained in step 4), dissolve it in 200mL of anhydrous toluene, and prepare it in a three-necked flask. Then weigh 106.5g of the thioxanthone photoinitiator intermediate I-6 (0.25mol) obtained in Example 1, slowly add it to the solution, and stir until homogeneous.

[0198] 5.2) Heat the reaction mixture to 85°C and maintain the reaction for 10 h to ensure that the reaction proceeds fully; monitor the reaction by thin-layer chromatography (TLC) during the process.

[0199] 5.3) After the reaction is complete, stop heating and cool to room temperature.

[0200] 5.4) Add 200 mL of deionized water to the reaction mixture, separate the layers using a separatory funnel, collect the aqueous phase, and extract the aqueous phase three times with ethyl acetate (50 mL each time) to remove unreacted organic matter and byproducts.

[0201] 5.5) The aqueous phase was then concentrated under reduced pressure to remove most of the water, followed by freeze-drying to obtain 113g of purified aqueous polymerizable thioxanthone photoinitiator S-5. The 1H NMR spectral data are as follows:

[0202] 1 H NMR(500MHz,Chloroform)δ8.92(s,1H),7.57–7.26(m,8H),7.22–7.00(m,4H),6.20(d,J=4.2Hz,1H),5.90(d,J=4.2Hz,1H),4. 91(q,J=7.5Hz,2H),4.77(t,J=8.4Hz,2H),4.40(dt,J=22.3,9.8Hz,4H),3.89–3.69(m,4H),3.52(s,4H),3.27(t,J=8.9Hz,2H).

[0203] Example 7

[0204] The synthesis route in this embodiment is shown below:

[0205]

[0206] 4) Preparation of brominated compounds containing acrylates 6-3

[0207] 4.1) Weigh 180g of the compound shown in Formula 6-1 (1.0 mol), dissolve it in 300mL of anhydrous toluene, and place it in a three-necked flask and attach it to a reflux condenser; then weigh 125g of the compound shown in Formula 6-2 (1.0 mol), and slowly add it to the solution under stirring. The entire addition process should last for 30min to ensure that the two are thoroughly mixed.

[0208] 4.2) After the addition is complete, heat the reaction mixture to 90°C and maintain the reaction for 8 hours to promote the reaction. During this period, monitor the reaction progress by thin-layer chromatography (TLC).

[0209] 4.3) After the reaction is complete, cool the reaction mixture to room temperature and add 300 mL of saturated sodium chloride solution to quench the reaction.

[0210] 4.4) Use a separatory funnel to separate the organic phase. Wash the organic phase three times with 200 mL of deionized water to remove water-soluble impurities. Dry the organic phase with anhydrous sodium sulfate for 1 hour and filter to remove the desiccant.

[0211] 4.5) The organic phase was placed in a rotary evaporator, and toluene was removed under reduced pressure to obtain a crude product. The crude product was then purified by column chromatography using petroleum ether / ethyl acetate as eluent to obtain 215 g of acrylate-containing brominated compound 6-3. The 1H NMR data are as follows:

[0212] 1 H NMR (500MHz, Chloroform) δ7.39–6.91 (m, 4H), 6.26 (dd, J = 74.5, 4.2Hz, 2H), 4.64 (t, J = 13.6Hz, 2H), 3.65 (t, J = 13.6Hz, 2H), 2.41 (s, 3H).

[0213] 5) Preparation of water-based polymerizable thioxanthone photoinitiator S-6

[0214] 5.1) Weigh 67g of the acrylate-containing brominated compound 6-3 (0.25mol) obtained in step 4), dissolve it in 200mL of anhydrous toluene, and prepare it in a three-necked flask. Then weigh 106.5g of the thioxanthone photoinitiator intermediate I-6 (0.25mol) obtained in Example 1, slowly add it to the solution, and stir until homogeneous.

[0215] 5.2) Heat the reaction mixture to 85°C and maintain the reaction for 10 h to ensure that the reaction proceeds fully; monitor the reaction by thin-layer chromatography (TLC) during the process.

[0216] 5.3) After the reaction is complete, stop heating and cool to room temperature.

[0217] 5.4) Add 200 mL of deionized water to the reaction mixture, separate the layers using a separatory funnel, collect the aqueous phase, and extract the aqueous phase three times with ethyl acetate (50 mL each time) to remove unreacted organic matter and byproducts.

[0218] 5.5) The aqueous phase was then concentrated under reduced pressure to remove most of the water, followed by freeze-drying to obtain 93g of purified aqueous polymerizable thioxanthone photoinitiator S-6. The 1H NMR spectral data are as follows:

[0219] 1H NMR(500MHz,Chloroform)δ8.92(s,1H),7.57–6.98(m,11H),6.39(d,J=4.0Hz,1H),6.11(d,J=4.2Hz,1H),4.80(ddd,J=53.9, 26.8, 4.0Hz, 4H), 4.40 (dt, J = 70.1, 8.4Hz, 4H), 3.80 (dt, J = 52.2, 8.5Hz, 4H), 3.52 (s, 4H), 3.27 (t, J = 8.4Hz, 2H), 2.41 (s, 3H).

[0220] Example 8

[0221] The synthesis route in this embodiment is shown below:

[0222]

[0223] 4) Preparation of brominated compounds containing acrylates 7-3

[0224] 4.1) Weigh 180g of the compound shown in Formula 7-1 (1.0 mol), dissolve it in 300mL of anhydrous toluene, and place it in a three-necked flask and attach it to a reflux condenser; then weigh 125g of the compound shown in Formula 7-2 (1.0 mol), and slowly add it to the solution under stirring for 30 minutes to ensure that the two are thoroughly mixed.

[0225] 4.2) After the addition is complete, heat the reaction mixture to 90°C and maintain the reaction for 8 hours to promote the reaction. During this period, monitor the reaction progress by thin-layer chromatography (TLC).

[0226] 4.3) After the reaction is complete, cool the reaction mixture to room temperature and add 300 mL of saturated sodium chloride solution to quench the reaction.

[0227] 4.4) Use a separatory funnel to separate the organic phase. Wash the organic phase three times with 200 mL of deionized water to remove water-soluble impurities. Dry the organic phase with anhydrous sodium sulfate for 1 hour and filter to remove the desiccant.

[0228] 4.5) The organic phase was placed in a rotary evaporator, and toluene was removed under reduced pressure to obtain a crude product. The crude product was then purified by column chromatography using petroleum ether / ethyl acetate as eluent to obtain 241 g of acrylate-containing brominated compound 7-3. The 1H NMR data are as follows:

[0229] 1H NMR (500MHz, Chloroform) δ7.57–6.84(m,5H),6.12(dt,J=4.1,1.9Hz,1H),5.40(dt,J=4.1,2.0Hz,1H),4.64(t,J=15.0Hz,2H),3.83–3.33(m,4H).

[0230] 5) Preparation of water-based polymerizable thioxanthrone photoinitiator S-7

[0231] 5.1) Weigh 67g of the acrylate-containing brominated compound 7-3 (0.25mol) obtained in step 4), dissolve it in 200mL of anhydrous toluene, and prepare it in a three-necked flask. Then weigh 106.5g of the thioxanthone photoinitiator intermediate I-6 (0.25mol) obtained in Example 1, slowly add it to the solution, and stir until homogeneous.

[0232] 5.2) Heat the reaction mixture to 85°C and maintain the reaction for 10 h to ensure that the reaction proceeds fully; monitor the reaction by thin-layer chromatography (TLC) during the process.

[0233] 5.3) After the reaction is complete, stop heating and cool to room temperature.

[0234] 5.4) Add 200 mL of deionized water to the reaction mixture, separate the layers using a separatory funnel, collect the aqueous phase, and extract the aqueous phase three times with ethyl acetate (50 mL each time) to remove unreacted organic matter and byproducts.

[0235] 5.5) The aqueous phase was then concentrated under reduced pressure to remove most of the water, followed by freeze-drying to obtain 109g of purified aqueous polymerizable thioxanthone photoinitiator S-7. The 1H NMR spectral data are as follows:

[0236] 1 H NMR(500MHz,Chloroform)δ8.92(s,1H),7.54–6.97(m,12H),6.12(dt,J=4.1,1.9Hz,1H),5.40(dt,J=4.1,2.0Hz,1H),4.86(t,J=8.1Hz,2H ), 4.68(dd,J=7.5,0.6Hz,1H), 4.40(dt,J=69.5,8.1Hz,4H), 3.83(ddd,J=28.7,15.9,8.6Hz,5H), 3.60–3.43(m,6H), 3.27(t,J=9.2Hz,2H).

[0237] Example 9

[0238] The synthesis route in this embodiment is shown below:

[0239]

[0240] 4) Preparation of brominated compounds containing acrylates 8-3

[0241] 4.1) Weigh 114 g of the compound shown in Formula 8-1 (1.0 mol), dissolve it in 300 mL of anhydrous toluene, and place it in a three-necked flask and attach it to a reflux condenser; then weigh 125 g of the compound shown in Formula 8-2 (1.0 mol), and slowly add it to the solution under stirring conditions. The entire addition process should last for 30 min to ensure that the two are thoroughly mixed.

[0242] 4.2) After the addition is complete, heat the reaction mixture to 90°C and maintain the reaction for 8 hours to promote the reaction. During this period, monitor the reaction progress by thin-layer chromatography (TLC).

[0243] 4.3) After the reaction is complete, cool the reaction mixture to room temperature and add 300 mL of saturated sodium chloride solution to quench the reaction.

[0244] 4.4) Use a separatory funnel to separate the organic phase. Wash the organic phase three times with 200 mL of deionized water to remove water-soluble impurities. Dry the organic phase with anhydrous sodium sulfate for 1 hour and filter to remove the desiccant.

[0245] 4.5) The organic phase was placed in a rotary evaporator, and toluene was removed under reduced pressure to obtain a crude product. The crude product was then purified by column chromatography using petroleum ether / ethyl acetate as eluent to obtain 174 g of bromoacrylate-containing compound 8-3. The 1H NMR data are as follows:

[0246] 1 H NMR (500MHz, Chloroform) δ6.99 (d, J = 4.2 Hz, 1H), 6.56 (d, J = 4.0 Hz, 1H), 4.65 (t, J = 15.0 Hz, 2H), 3.65 (t, J = 15.0 Hz, 2H).

[0247] 5) Preparation of water-based polymerizable thioxanthrone photoinitiator S-8

[0248] 5.1) Weigh 50.5g of the acrylate-containing brominated compound 8-3 (0.25mol) obtained in step 4), dissolve it in 200mL of anhydrous toluene, and prepare it in a three-necked flask. Then weigh 165.5g of the thioxanthone photoinitiator intermediate I-6 (0.25mol) obtained in Example 1, slowly add it to the solution, and stir until homogeneous.

[0249] 5.2) Heat the reaction mixture to 85°C and maintain the reaction for 10 h to ensure that the reaction proceeds fully; monitor the reaction by thin-layer chromatography (TLC) during the process.

[0250] 5.3) After the reaction is complete, stop heating and cool to room temperature.

[0251] 5.4) Add 200 mL of deionized water to the reaction mixture, separate the layers using a separatory funnel, collect the aqueous phase, and extract the aqueous phase three times with ethyl acetate (50 mL each time) to remove unreacted organic matter and byproducts.

[0252] 5.5) The aqueous phase was then concentrated under reduced pressure to remove most of the water, followed by freeze-drying to obtain 86g of purified aqueous polymerizable thioxanthone photoinitiator S-8. The 1H NMR spectral data are as follows:

[0253] 1 H NMR(500MHz,Chloroform)δ8.92(s,1H),7.58–7.25(m,5H),7.14(ddd,J=22.5,16.8,3.1Hz,2H),6.67(d,J=4.2Hz,1H),6. 46(d,J=4.2Hz,1H),4.97–4.63(m,4H),4.56–4.21(m,4H),3.83(td,J=8.5,2.5Hz,4H),3.52(s,4H),3.27(t,J=8.6Hz,2H).

[0254] Example 10

[0255] The synthesis route in this embodiment is shown below:

[0256]

[0257] 6.1) Weigh 61.8g of S-1 prepared in Example 2, dissolve it in 150mL of deionized water, place it in a three-necked flask, and install a stirring device. Then weigh 16.3g of ammonium hexafluorophosphate and slowly add it to the aqueous solution of S-1 while maintaining the stirring of the solution to ensure that the two are fully mixed and carry out the ion exchange reaction. The entire addition process takes about 20 minutes.

[0258] 6.2) After the addition is complete, continue stirring the reaction at room temperature for 4 hours to ensure the reaction is complete.

[0259] 6.3) After the reaction was complete, the mixture was evaporated under reduced pressure to remove most of the water, yielding a crude product. The crude product was then dissolved in 100 mL of anhydrous ethanol for recrystallization. The filter cake was collected after filtration and dried to constant weight in a vacuum drying oven to obtain 59.4 g of purified aqueous polymerizable thioxanthone photoinitiator S-9. The 1H NMR data are as follows:

[0260] 1H NMR(500MHz,Chloroform)δ8.86(s,1H),7.54–7.22(m,5H),7.09(ddd,J=22.4,16.7,3.1Hz,2H),6.39(ddq,J=39.9,4.0,2.0Hz,2H),5.05(d,J=7.5H z,1H),4.85–4.62(m,3H),4.44(t,J=7.8Hz,2H),4.30(t,J=7.6Hz,2H),3. 92–3.69(m,4H),3.49(s,4H),3.25(t,J=8.2Hz,2H),2.00(t,J=1.9Hz,3H).

[0261] Example 11

[0262] The synthesis route in this embodiment is shown below:

[0263]

[0264] 6.1) Weigh 63.3g of S-2 prepared in Example 3, dissolve it in 150mL of deionized water, and place the solution in a three-necked flask. Install a stirrer. Then weigh 16.3g of ammonium hexafluorophosphate and slowly add it to the aqueous solution of S-2 while stirring to ensure thorough mixing and ion exchange reaction. The entire addition process takes about 20 minutes.

[0265] 6.2) After the addition is complete, continue stirring at room temperature for 4 hours to ensure that the reaction is complete.

[0266] 6.3) After the reaction was complete, most of the water in the mixture was removed by vacuum evaporation to obtain the crude product. The crude product was then dissolved in 100 mL of anhydrous ethanol for recrystallization. The filter cake was collected after filtration and dried to constant weight in a vacuum drying oven to obtain 53.6 g of purified aqueous polymerizable thioxanthone photoinitiator S-10. The 1H NMR data are as follows:

[0267] 1H NMR(500MHz,Chloroform)δ8.90(s,1H),7.66–7.29(m,5H),7.22–6.94(m,2H),6.28(dt,J=4.1,1 .9Hz,1H),5.45(dt,J=4.0,2.0Hz,1H),5.04(d,J=7.5Hz,1H),4.89(dd,J=7.5,0.6Hz,1H),4.78(t d,J=14.3,1.0Hz,2H),4.46(td,J=14.3,1.0Hz,2H),4.32(t,J=7.8Hz,2H),3.80(dt,J=14.2,8.1 Hz, 4H), 3.51 (s, 4H), 3.26 (t, J = 8.4Hz, 2H), 2.44 (qt, J = 13.2, 1.8Hz, 2H), 1.07 (t, J = 13.4Hz, 3H).

[0268] Example 12

[0269] The synthesis route in this embodiment is shown below:

[0270]

[0271] 6.1) Weigh 66.1g of S-3 prepared in Example 4, dissolve it in 150mL of deionized water, and place it in a three-necked flask with a stirrer installed. Then weigh 16.3g of ammonium hexafluorophosphate and slowly add it to the aqueous solution of S-3 while stirring to ensure thorough mixing and ion exchange reaction. The entire addition process takes about 20 minutes.

[0272] 6.2) After the addition is complete, continue stirring at room temperature for 4 hours to ensure that the reaction is complete.

[0273] 6.3) After the reaction was complete, most of the water in the mixture was removed by vacuum evaporation to obtain the crude product. The crude product was then dissolved in 100 mL of anhydrous ethanol for recrystallization. The filter cake was collected after filtration and dried to constant weight in a vacuum drying oven to obtain 61.4 g of purified aqueous polymerizable thioxanthone photoinitiator S-11. The 1H NMR data are as follows:

[0274] 1H NMR(500MHz,Chloroform)δ8.92(s,1H),7.57–7.29(m,5H),7.14(ddd,J=22.5,16.7,3.1Hz,2H),6.29 (dt,J=4.1,2.0Hz,1H),5.46(dt,J=4.1,2.0Hz,1H),5.25(d,J=7.5Hz,1H),4.78(dd,J=16.6,5.6Hz,2H ),4.62(d,J=7.5Hz,1H),4.46(dd,J=16.5,5.7Hz,2H),4.33(t,J=7.6Hz,2H),3.85(dt,J=12.9,8.4Hz, 4H), 3.52 (s, 4H), 3.27 (t, J = 9.2Hz, 2H), 2.54–2.32 (m, 2H), 1.56–1.07 (m, 4H), 0.93 (t, J = 12.7Hz, 3H).

[0275] Example 13

[0276] The synthesis route in this embodiment is shown below:

[0277]

[0278] 6.1) Weigh 67.5g of S-4 prepared in Example 5, dissolve it in 150mL of deionized water, and place it in a three-necked flask with a stirrer attached. Then weigh 16.3g of ammonium hexafluorophosphate and slowly add it to the aqueous solution of S-4 while stirring to ensure thorough mixing and ion exchange reaction. The entire addition process takes about 20 minutes.

[0279] 6.2) After the addition is complete, continue stirring at room temperature for 4 hours to ensure that the reaction is complete.

[0280] 6.3) After the reaction was complete, most of the water in the mixture was removed by vacuum evaporation to obtain the crude product. The crude product was then dissolved in 100 mL of anhydrous ethanol for recrystallization. The filter cake was collected after filtration and dried to constant weight in a vacuum drying oven to obtain 55.9 g of purified aqueous polymerizable thioxanthone photoinitiator S-12. The 1H NMR data are as follows:

[0281] 1H NMR(500MHz,Chloroform)δ8.92(s,1H),7.53–7.28(m,5H),7.14(ddd,J=22.5,16.7,3.1Hz,2H),6.29(d t,J=4.1,2.0Hz,1H),5.46(dt,J=4.1,2.0Hz,1H),5.25(d,J=7.5Hz,1H),4.78(dd,J=16.6,5.6Hz,2H),4 .62(d,J=7.5Hz,1H),4.46(dd,J=16.5,5.7Hz,2H),4.33(t,J=7.6Hz,2H),3.85(dt,J=12.9,8.4Hz,4H), 3.52(s,4H),3.27(t,J=9.2Hz,2H),2.56–2.26(m,2H),1.49–1.11(m,4H),0.93(dd,J=15.0,10.5Hz,3H).

[0282] Example 14

[0283] The synthesis route in this embodiment is shown below:

[0284]

[0285] 6.1) Weigh 68.1g of S-5 prepared in Example 6, dissolve it in 150mL of deionized water, and place it in a three-necked flask with a stirrer installed. Then weigh 16.3g of ammonium hexafluorophosphate and slowly add it to the S-5 aqueous solution while stirring to ensure thorough mixing and ion exchange reaction. The entire addition process takes about 20 minutes.

[0286] 6.2) After the addition is complete, continue stirring at room temperature for 4 hours to ensure that the reaction is complete.

[0287] 6.3) After the reaction was complete, most of the water in the mixture was removed by vacuum evaporation to obtain the crude product. The crude product was then dissolved in 100 mL of anhydrous ethanol for recrystallization. The filter cake was collected after filtration and dried to constant weight in a vacuum drying oven to obtain 73.5 g of purified aqueous polymerizable thioxanthone photoinitiator S-13. The 1H NMR data are as follows:

[0288] 1H NMR(500MHz,Chloroform)δ8.92(s,1H),7.58–7.29(m,8H),7.20–7.01(m,4H),6.18(dd,J=35.5,4.2Hz,2H),4.97(d,J=7.5Hz,1H) ,4.87–4.70(m,3H),4.47(t,J=7.8Hz,2H),4.33(t,J=8.0Hz,2H),3.81(dt,J=14.7,8.7Hz,4H),3.52(s,4H),3.27(t,J=9.4Hz,2H).

[0289] Example 15

[0290] The synthesis route in this embodiment is shown below:

[0291]

[0292] 6.1) Weigh 69.4g of S-6 prepared in Example 7, dissolve it in 150mL of deionized water, and place the solution in a three-necked flask with a stirrer attached. Then weigh 16.3g of ammonium hexafluorophosphate and slowly add it to the S-6 aqueous solution while stirring to ensure thorough mixing and ion exchange reaction. The entire addition process takes about 20 minutes.

[0293] 6.2) After the addition is complete, continue stirring at room temperature for 4 hours to ensure that the reaction is complete.

[0294] 6.3) After the reaction was complete, most of the water in the mixture was removed by vacuum evaporation to obtain the crude product. The crude product was then dissolved in 100 mL of anhydrous ethanol for recrystallization. The filter cake was collected after filtration and dried to constant weight in a vacuum drying oven to obtain 61.5 g of purified aqueous polymerizable thioxanthone photoinitiator S-14. The 1H NMR data are as follows:

[0295] 1 H NMR(500MHz,Chloroform)δ8.92(s,1H),7.57–7.30(m,5H),7.26–6.98(m,6H),6.30(d,J=4.2Hz,1H),6.08(d,J=4.2Hz,1H),5.26(dd,J=7.5,0 .6Hz,1H),4.83(t,J=8.8Hz,2H),4.47(t,J=8.8Hz,2H),4.36–4.12(m,3 H), 3.92–3.63 (m, 4H), 3.52 (s, 4H), 3.27 (t, J = 9.6Hz, 2H), 2.41 (s, 3H).

[0296] Example 16

[0297] The synthesis route in this embodiment is shown below:

[0298]

[0299] 6.1) Weigh 69.5g of S-7 prepared in Example 8, dissolve it in 150mL of deionized water, and place it in a three-necked flask with a stirrer installed. Then weigh 16.3g of ammonium hexafluorophosphate and slowly add it to the aqueous solution of S-7 while stirring to ensure thorough mixing and ion exchange reaction. The entire addition process takes about 20 minutes.

[0300] 6.2) After the addition is complete, continue stirring at room temperature for 4 hours to ensure that the reaction is complete.

[0301] 6.3) After the reaction was complete, most of the water in the mixture was removed by vacuum evaporation to obtain the crude product. The crude product was then dissolved in 100 mL of anhydrous ethanol for recrystallization. The filter cake was collected after filtration and dried to constant weight in a vacuum drying oven to obtain 65.3 g of purified aqueous polymerizable thioxanthone photoinitiator S-15. The 1H NMR data are as follows:

[0302] 1 H NMR (500MHz, Chloroform) δ8.92 (s, 1H), 7.54–7.01 (m, 12H), 6.12 (dt, J = 4.1, 1.9Hz,1H),5.40(dt,J=4.1,2.0Hz,1H),5.23(d,J=7.5Hz,1H),5.09(d,J=7.5 Hz,1H),4.75(dd,J=16.0,5.5Hz,2H),4.46(dd,J=15.9,5.6Hz,2H),4.33(t,J =8.4Hz, 2H), 3.79 (q, J = 8.7Hz, 4H), 3.62–3.40 (m, 6H), 3.27 (t, J = 9.0Hz, 2H).

[0303] Example 17

[0304]

[0305] 6.1) Weigh 62.9g of S-8 prepared in Example 9, dissolve it in 150mL of deionized water, and place it in a three-necked flask with a stirrer installed. Then weigh 16.3g of ammonium hexafluorophosphate and slowly add it to the aqueous solution of S-8 while stirring to ensure thorough mixing and ion exchange reaction. The entire addition process takes about 20 minutes.

[0306] 6.2) After the addition is complete, continue stirring at room temperature for 4 hours to ensure that the reaction is complete.

[0307] 6.3) After the reaction was complete, most of the water in the mixture was removed by vacuum evaporation to obtain the crude product. The crude product was then dissolved in 100 mL of anhydrous ethanol for recrystallization. The filter cake was collected after filtration and dried to constant weight in a vacuum drying oven to obtain 57.4 g of purified aqueous polymerizable thioxanthone photoinitiator S-16. The 1H NMR data are as follows:

[0308] 1 H NMR(500MHz,Chloroform)δ8.92(s,1H),7.55–7.24(m,5H),7.22–7.11(m,1H),7.09(d,J=2.5Hz,1H),6.82(d,J=4.2Hz,1H),6.57(d,J=4.2Hz,1H), 4.89(s,2H),4.78(t,J=9.2Hz,2H),4.47(t,J=9.2Hz,2H),4.33(t,J=8.4 Hz, 2H), 3.79 (dd, J = 13.3, 5.1 Hz, 4H), 3.52 (s, 4H), 3.27 (t, J = 9.2 Hz, 2H).

[0309] Performance testing

[0310] (I) Solubility and dispersibility test: Evaluate the solubility or dispersibility of S1 to S16 in water to determine their application potential in waterborne photocuring systems.

[0311] Experimental steps:

[0312] 1. Sample preparation: Weigh S1 to S16 and prepare solutions with a concentration of 1 mg / mL.

[0313] 2. Stirring and dissolving: Add samples S1 to S16 to deionized water and stir with a magnetic stirrer for 30 minutes.

[0314] 3. Solubility assessment: Visually observe the state of each solution and record the solubility of T1 to T16 in water.

[0315] 4. Ultraviolet-Visible Spectroscopy: The absorbance of each sample at the maximum absorption wavelength was measured using an ultraviolet-visible spectrometer.

[0316] The experimental results are shown in the table below.

[0317]

[0318] S1 to S16 all exhibit good water solubility, indicating that by introducing water-soluble groups, the polymerizable thioxanthone photoinitiators prepared in this invention have good water solubility, making them suitable for waterborne photocuring systems. This meets the needs of environmental protection and sustainable development, overcoming the shortcomings of traditional oil-based photoinitiators that are difficult to apply to waterborne systems. On the other hand, the maximum absorption wavelength range of the waterborne polymerizable thioxanthone photoinitiators S1 to S16 is 420 to 450 nm, and the absorbance range is 1.0 to 1.4.

[0319] (II) Photoinitiation efficiency experiment: The initiation efficiency of S1 to S16 under ultraviolet light was measured, and their performance under different light exposure time and concentration was evaluated.

[0320] Experimental steps:

[0321] 1. Sample preparation: Prepare a solution containing acrylate monomer (PEGDA), and add S1 to S16 to make a mixed solution with a concentration of 1wt%.

[0322] 2. UV Curing: Place the above samples in a quartz vial and use a UV curing system (wavelength 365nm, light intensity 500mW / cm²). 2 The sample was irradiated with ultraviolet light, and the light response was recorded at different time periods (10 seconds, 30 seconds, 1 min, 5 min).

[0323] 3. Viscosity measurement: The viscosity change of the solution is measured after different light exposure times.

[0324] 4. FT-IR monitoring: The polymerization reaction was monitored in real time using a Fourier transform infrared spectrometer to detect the intensity change of the characteristic peak of the C=C double bond of acrylate (approximately 1630 cm⁻¹) and to calculate the initiation efficiency.

[0325] 5. DSC exothermic determination: Differential scanning calorimetry (DSC) is used to measure the exothermic properties of the polymerization reaction and to evaluate the reaction rate.

[0326] The experimental results are shown in the table below.

[0327]

[0328]

[0329] Samples containing S1 to S16 exhibited high initiation efficiency under ultraviolet light irradiation, especially under long-term light irradiation, the efficiency of the polymerization reaction increased significantly. S-8 and S-13 showed the highest initiation efficiency, achieving rapid curing and high polymerization rate, making them suitable for industrial applications requiring rapid photocuring, such as high-speed coating curing and 3D printing.

[0330] (III) Initiator migration experiment: Based on the material synthesis, evaluate whether S1 to S16 migrate after the polymer is cured, verify their initiation efficiency and judge their stability.

[0331] Experimental steps:

[0332] 1. Thin film preparation: The mixture of S1 to S16 and acrylate monomers at a concentration of 1 wt% above is cured by a UV curing system to prepare a polymer film.

[0333] 2. Immersion test: The prepared polymer film was immersed in water for 24h, 48h and 72h.

[0334] 3. Absorption peak detection: The solution sample was taken out every 24 hours and the presence of photoinitiator in the soaking solution was detected by ultraviolet-visible spectroscopy. The migration was evaluated by detecting the changes in characteristic absorption peaks.

[0335] 4. HPLC detection: The concentration of photoinitiator in the soaking solution was quantitatively analyzed using high performance liquid chromatography (HPLC).

[0336] The experimental results are shown in the table below.

[0337]

[0338]

[0339] S1 to S16 all exhibited low migration after polymer curing, with almost no migration in aqueous media, indicating good long-term stability. This demonstrates that by introducing polymerizable groups into the thioxanthone structure, the photoinitiator prepared in this invention can covalently bond with the polymer matrix, avoiding the migration problem of traditional photoinitiators in polymers. This significantly improves the physicochemical stability of the cured material, reduces potential threats to human health and the environment, and ensures the environmental friendliness and safety of the final product. It is particularly suitable for fields with high safety requirements, such as medical and food packaging.

[0340] Based on the disclosure and teachings of the foregoing specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A thioxanthone-based photoinitiator intermediate, characterized in that, Its molecular structure is shown in Formula I-6:

2. The method for preparing the thioxanthone photoinitiator intermediate according to claim 1, characterized in that, It should include at least the following steps: 1) Thiosyl salicylic acid and thiophene are prepared at a molar ratio of 0.8–1.2:0.8–1.2 and react under the condition of concentrated sulfuric acid as a catalyst to generate intermediate I-3, the molecular structure of which is shown in formula I-3: 2) Intermediate I-3 and a bromine-containing alkoxy compound were prepared in a molar ratio of 0.8–1.2:0.8–1.2, mixed and dissolved in an organic solvent, and under alkaline catalysis, a nucleophilic substitution reaction was carried out to give intermediate I-5, the molecular structure of which is shown in Formula I-5: 3) Intermediate I-5 and imidazole compound are mixed in a molar ratio of 0.8-1.2:0.8-1.2 to undergo a substitution reaction, thereby obtaining the thioxanthone photoinitiator intermediate I-6.

3. The method for preparing the thioxanthone photoinitiator intermediate according to claim 2, characterized in that, Steps 1) to 3) are accompanied by heating and holding operations and stirring operations during the reaction. The reaction system is heated to 80-90℃ and held at that temperature. After the reaction is completed, stirring is stopped and an inorganic salt solution is added to quench the reaction. Then the temperature is lowered to equal to or below room temperature.

4. A water-based polymerizable thioxanthone photoinitiator, characterized in that, Its molecular structure is shown in formula S: Wherein, Xˉ is at least one of fluoride ion, chloride ion, bromide ion, iodide ion, phosphate ion, sulfonate ion, carbonate ion, hexafluorophosphate ion or nitrate ion. The structure of R is * indicates a link position, R' represents alkyl, cyano, phenyl, tolyl, or benzyl, and the alkyl group is C. n H m , where n and m are independent natural numbers less than 30.

5. The water-based polymerizable thioxanthone photoinitiator according to claim 4, characterized in that, It is one of formulas S-1 to S-16:

6. The water-based polymerizable thioxanthone photoinitiator according to claim 5, characterized in that, Maximum absorption wavelength range: 420–450 nm, absorbance ≥1.

0.

7. A method for preparing an aqueous polymerizable thioxanthone photoinitiator, characterized in that, At least the following steps are included: 1) Prepare the thioxanthone photoinitiator intermediate I-6 as described in claim 1; 2) Thioxanthone photoinitiator intermediate I-6 is alkylated with an acrylate-containing brominated compound at a molar ratio of 0.8–1.2:0.8–1.2 to obtain water-based polymerizable thioxanthone photoinitiator I-8, with the molecular structure shown in Formula I-8: Wherein, the structure of R is * indicates a link position, R' represents alkyl, cyano, methyl, tolyl, or benzyl, and the alkyl group is C. n H m , where n and m are independent natural numbers less than 30.

8. The method for preparing the waterborne polymerizable thioxanthone photoinitiator according to claim 7, characterized in that, In step 2), the bromine compound containing the acrylate is one of the following formulas 1-3 to 8-3:

9. A method for preparing an aqueous polymerizable thioxanthone photoinitiator, characterized in that, Includes the following steps: 1) Prepare the thioxanthone photoinitiator intermediate I-6 as described in claim 1; 2) Thioxanthone photoinitiator intermediate I-6 is alkylated with an acrylate-containing brominated compound at a molar ratio of 0.8–1.2:0.8–1.2 to obtain intermediate I-8, the molecular structure of which is shown in formula I-8: Wherein, the structure of R is * indicates a link position, R' represents alkyl, cyano, phenyl, tolyl, or benzyl, and the alkyl group is C. n H m Where n and m are independent natural numbers less than 30; 3) Intermediate I-8 and ammonium salt NH4X are mixed in a molar ratio of 0.8-1.2:0.8-1.2 to undergo an ion exchange reaction, thereby obtaining a water-based polymerizable thioxanthone photoinitiator; Wherein, X is at least one of fluoride ion, chloride ion, iodide ion, phosphate ion, sulfonate ion, carbonate ion, hexafluorophosphate ion, or nitrate ion.

10. The method for preparing the waterborne polymerizable thioxanthone photoinitiator according to claim 9, characterized in that, In step 2), the bromine compound containing the acrylate is one of the following formulas 1-3 to 8-3:

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