A bifunctional photoinitiator for diblock copolymers and its preparation method and application

Abstract

The present invention relates to a bifunctional photoinitiator for diblock copolymers, a preparation method, and applications thereof, belonging to the technical field of diblock copolymer preparation. The bifunctional photoinitiator disclosed in the present invention has the structural formula: wherein HR is any one of , and has good application prospects in catalyzing the preparation of diblock copolymers.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of diblock copolymer initiators, and relates to a bifunctional photoinitiator for a diblock copolymer, a preparation method and an application thereof. Background Art

[0002] Inspired by nature's natural polymers, the efficient artificial synthesis of sequence-controlled polymers, including diblock copolymers, multiblock copolymers, and star-shaped polymers, has always been a research hotspot in the polymer field, with broad application prospects in the fields of photolithography, catalysis, new energy, drug release, and self-assembly. Photopolymerization is a green and environmentally friendly technology that uses photoinitiators to generate free radicals, cations, and other active species to initiate the cross-linking of monomers or oligomers, ultimately forming a three-dimensional network polymer. It has attracted much attention due to its advantages such as high efficiency, energy saving, and time-space controllability, and has been maturely applied in high-value-added fields such as microelectronics, bioengineering, and additive manufacturing. Photopolymerization technology can usually only produce random copolymers, with polymer chains randomly distributed. How to use photopolymerization technology to prepare ordered polymerization and endow polymer materials with excellent properties is a key issue to be solved in the field of photopolymerization.

[0003] Therefore, further research is needed to investigate the initiators that can catalyze the preparation of diblock copolymers. Summary of the Invention

[0004] In view of this, one of the objects of the present invention is to provide a bifunctional photoinitiator for a diblock copolymer; a second object of the present invention is to provide a method for preparing the bifunctional photoinitiator for a diblock copolymer; and a third object of the present invention is to provide an application of the bifunctional photoinitiator for a diblock copolymer in the catalytic preparation of a diblock copolymer.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] 1. A bifunctional photoinitiator for a diblock copolymer, wherein the bifunctional photoinitiator has the structural formula: HR is Any one of .

[0007] Preferably, the structural formula of the bifunctional photoinitiator includes but is not limited to:

[0008] 2. A method for preparing the above-mentioned bifunctional photoinitiator, comprising the following steps:

[0009] (1) Dissolve triethyl phosphoacetate in tetrahydrofuran, add lithium amide dropwise at -10 to 0°C, stir and mix thoroughly, then add conjugated tertiary amine dropwise and react. After TLC detection, purify by column chromatography to obtain vinyl ester intermediate I containing conjugated tertiary amine;

[0010] (2) dissolving the vinyl ester intermediate I containing a conjugated tertiary amine in a methanol aqueous solution, adding NaOH as a catalyst to react, and performing recrystallization purification after TLC detection to obtain an ethylene acid intermediate II containing a conjugated tertiary amine;

[0011] (3) The vinyl acid intermediate II containing a conjugated tertiary amine is dissolved in dichloromethane, and 2-hydroxy-4-(2-hydroxyethoxy)-2-methylpropiophenone (Irgacure 2959) as an initiator, 4-dimethylaminopyridine as a catalyst, and carbodiimide hydrochloride are added in sequence. The reaction is carried out at room temperature. After TLC detection shows that the reaction is complete, column chromatography is performed for purification to prepare a bifunctional photoinitiator.

[0012] Preferably, in step (1), the structural formula of the aldehyde containing conjugated tertiary amine is

[0013] In step (1), the molar ratio of the aldehyde of the conjugated tertiary amine to triethyl phosphoacetate is 1:1 to 1:3;

[0014] In step (1), the molar ratio of the aldehyde of the conjugated tertiary amine to the catalyst is 1:1 to 1:2;

[0015] In step (1), the reaction conditions are: -10 to 0°C;

[0016] In step (1), the eluent used in the column chromatography purification is a mixed solution formed by mixing petroleum ether and ethyl acetate in a volume ratio of 10:1 to 20:1.

[0017] Preferably, in step (2), the volume ratio of methanol to water in the methanol aqueous solution is 1:1 to 1:2;

[0018] In step (2), the reaction temperature is 50-70°C;

[0019] In step (2), the mass ratio of the vinyl ester intermediate I containing conjugated tertiary amine to NaOH is 2:1.

[0020] Preferably, in step (3), the molar ratio of the ethylene acid intermediate II containing a conjugated tertiary amine, 2-hydroxy-4-(2-hydroxyethoxy)-2-methylpropiophenone (Irgacure 2959), 4-dimethylaminopyridine and carbodiimide hydrochloride is 1:1:2:2;

[0021] In step (3), the eluent used in the column chromatography purification is a mixed solution formed by mixing petroleum ether and ethyl acetate in a volume ratio of 10:1.

[0022] 3. Application of the above-mentioned bifunctional photoinitiator in the catalytic preparation of diblock copolymers.

[0023] The beneficial effects of the present invention are as follows: the present invention discloses a bifunctional photoinitiator of a diblock copolymer, the structural formula of which is The invention has the following effects: (1) the bifunctional photoinitiator of the present invention can be used in conjunction with visible light initiators such as camphorquinone and thioxanthone. The bifunctional initiator can be hydrogenated under visible light excitation to generate highly active α-aminoalkyl radicals, which trigger monomer I (monomer I is a monofunctional monomer that undergoes the first cross-linking reaction, which can be acrylamide, methyl methacrylate, phenyl methacrylate, hydroxyethyl methacrylate, etc.) to undergo a cross-linking reaction to form an α-hydroxyketone macromolecular photoinitiator; (2) further, the macromolecular photoinitiator (the product of the first photocrosslinking, which requires a second photocrosslinking to form the final diblock copolymer, and the specific reaction logic is bifunctional initiator-macromolecular photoinitiator-diblock copolymer) is photolyzed under ultraviolet light excitation to generate highly active benzoyl radicals, which trigger monomer II (a monofunctional monomer that undergoes the second cross-linking reaction) to undergo a cross-linking reaction, and finally form a diblock copolymer. It can be seen that the bifunctional photoinitiator of the diblock copolymer of the present invention can efficiently prepare diblock copolymers and can make a significant contribution to enriching the structure and performance of traditional photocurable materials.

[0024] Other advantages, objects, and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art upon examination of the following description or may be learned from practice of the present invention. The objects and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below with reference to the accompanying drawings, in which:

[0026] Figure 1 This is the H-NMR spectrum of the bifunctional photoinitiator (PAA-2959) for the diblock copolymer prepared in Example 1;

[0027] Figure 2 Liquid chromatography of the bifunctional photoinitiator (PAA-2959) for preparing the diblock copolymer in Example 1;

[0028] Figure 3The photolysis curve of the mixture of the bifunctional photoinitiator (PAA-2959) and camphorquinone (CQ) (PAA-2959 / CQ) of the diblock copolymer prepared in Example 1 under visible light excitation at 465 nm;

[0029] Figure 4 This is the polymerization kinetic curve of PAA-2959 / CQ under 465 nm visible light excitation;

[0030] Figure 5 This is the electron paramagnetic resonance (EPR) detection result of PAA-2959 / CQ under 465nm visible light excitation;

[0031] Figure 6 This is the photolysis curve of PAA-2959 / CQ after being excited by visible light at 465 nm and then irradiated by ultraviolet light at 275 nm.

[0032] Figure 7 The polymerization kinetics curve of the bifunctional photoinitiator (PAA-2959) for the diblock copolymer prepared in Example 1 under 275 nm excitation;

[0033] Figure 8 The electron paramagnetic resonance (EPR) test results of the bifunctional photoinitiator (PAA-2959) for the diblock copolymer prepared in Example 1 under ultraviolet light excitation at 275 nm are shown;

[0034] Figure 9 This is the GPC spectrum of the polymer prepared by the bifunctional photoinitiator (PAA-2959) for the diblock copolymer prepared in Example 1 under 465nm excitation and dual-color excitation;

[0035] Figure 10 H NMR spectrum of the block copolymer prepared using the bifunctional photoinitiator (PAA-2959) for preparing the diblock copolymer in Example 1;

[0036] Figure 11 This is the preparation process of the block copolymer PPMA-b-PBMA in Example 2;

[0037] Figure 12 The diagram shows the mechanism of preparing diblock copolymers catalyzed by the bifunctional photoinitiator of the diblock copolymers disclosed in the present invention. DETAILED DESCRIPTION

[0038] The following describes the embodiments of the present invention by means of specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0039] The reaction formula of the bifunctional photoinitiator of the diblock copolymer of the present invention is , where HR is Any one of .

[0040] Example 1

[0041] A bifunctional photoinitiator (PAA-2959) of a diblock copolymer has the structural formula: The preparation method is as follows:

[0042] (1) 8.9 mmol of triethyl phosphinoacetate (1.78 mL) was added dropwise to 10 mL of THF. 8.9 mL of lithium amide solution (8.9 mmol of lithium amide (LiHMDS) was dissolved in 8.9 mL to form a 1 M lithium amide solution) was added dropwise at 0°C. After stirring for 30 min, 7.0 mmol of N-methyl-2-pyrrolaldehyde (0.75 mL) was added dropwise. After stirring at 0°C for 20 min, the mixture was reacted at room temperature for 4 h (TLC detection showed that the reaction was complete). 10 mL of saturated NH4Cl solution was added to quench the reaction. 10 mL of water was added and the mixture was extracted with dichloromethane (2×40 mL). The organic phases were combined, washed with saturated brine, dried over anhydrous sodium sulfate, concentrated, and purified by column chromatography (the eluent used was a mixed solution of petroleum ether and ethyl acetate in a volume ratio of 20:1). 1.14 g of colorless oily substance was obtained, which was vinyl ester intermediate I containing conjugated tertiary amine (yield: 91%).

[0043] (2) Dissolve the vinyl ester intermediate I containing a conjugated tertiary amine (2.5 g, 13.9 mmol) in 15 mL of methanol, add 10 mL of water, and continue to add 69.5 mmol of NaOH (2.78 g) and react at 50°C for 4 h. After the reaction is complete by TLC, add a 1 M dilute hydrochloric acid solution dropwise and adjust the pH to a weakly acidic state to precipitate a white powder. Filter and dry to obtain 1.90 g of white powder, which is the vinyl acid intermediate II containing a conjugated tertiary amine (yield: 90%).

[0044] (3) 3.31 mmol of vinyl acid intermediate II containing conjugated tertiary amine (500 mg) was dissolved in 15 mL of dichloromethane, and an initiator (4.9 mmol of 2-hydroxy-4-(2-hydroxyethoxy)-2-methylpropiophenone) (1.11 g), a catalyst (1.65 mmol of 4-dimethylaminopyridine (DMAP 201 mg), and a carbodiimide hydrochloride (EDCI 315 mg)) were added in sequence. The mixture was reacted at room temperature for 6 h (TLC detection showed that the reaction was complete). After that, 10 ml of water was added and the mixture was extracted with dichloromethane (2×30 mL). The organic phases were combined and washed with saturated brine, dried over anhydrous sodium sulfate, concentrated, and purified by column chromatography (the eluent used was a mixed solution of petroleum ether and ethyl acetate in a volume ratio of 10:1). 968 mg of white powder was obtained, which was the bifunctional photoinitiator (PAA-2959) for the diblock copolymer (yield: 82%).

[0045] The bifunctional photoinitiator (PAA-2959) of the diblock copolymer prepared above was subjected to nuclear magnetic resonance and mass spectrometry tests, and the nuclear magnetic hydrogen spectrum and liquid chromatography obtained were as follows: Figure 1 and Figure 2 As shown, the result is: 1 H NMR (400MHz, DMSO-d6) δ8.21 (d, J = 8.9 Hz, 2H), 7.56 (d, J = 15.6 Hz, 1H), 7.04 (d, J = 8.9 Hz, 1H), 7.00 (d, J = 2.1 Hz, 1H), 6.85–6.77 (m, 1H), 6.24 (d, J = 15.7 Hz, 1H), 6.10 (m, 1H), 5.67 (s, 1H), 4.51–4.41 (m, 2H), 4.37–4.27 (m, 2H), 3.69 (s, 3H), 1.38 (s, 6H). ESI-MS (m / z): 380.6 [M+Na]+. This indicates that Example 1 indeed prepared the product having the structural formula Bifunctional photoinitiator for diblock copolymers.

[0046] Example 2

[0047] The bifunctional photoinitiator (PAA-2959) of the diblock copolymer prepared in Example 1 was used in the preparation process of the diblock copolymer PPMA-b-PBMA, as shown below:

[0048] (1) 10 mg of camphorquinone (CQ) and 20 mg of the bifunctional photoinitiator (PAA-2959) of the diblock copolymer prepared in Example 1 were dispersed in 0.8 ml of phenyl methacrylate (PMA), irradiated under 465 nm LED light for 5 min, separated by precipitation in cyclohexane, and purified and removed from the residual photoinitiator (PAA-2959 / CQ) by multiple reprecipitations in tetrahydrofuran (THF) to obtain the compound PPMA-2959.

[0049] (2) 50 mg of the compound PPMA-2959 prepared above was dissolved in 0.6 ml of butyl methacrylate (BMA), irradiated under 275 nm LED light for 5 min, and precipitated in methanol to obtain a diblock copolymer PPMA-b-PBMA (maximum thermal decomposition temperature of 285°C, Shore hardness of 160DA).

[0050] Comparative Example 1

[0051] Preparation of random copolymer PPMA-PBMA by photopolymerization:

[0052] 10 mg of 2-hydroxy-4-(2-hydroxyethoxy)-2-methylpropiophenone (Irgacure 2959) was dissolved in a mixed solution of 0.8 ml of phenyl methacrylate (PMA) and 0.6 ml of n-butyl methacrylate (BMA), irradiated under ultraviolet light for 5 minutes, and precipitated and washed in methanol to obtain a random copolymer PPMA-PBMA (maximum thermal decomposition temperature of 215°C and Shore hardness of 100DA).

[0053] Example 3

[0054] The bifunctional photoinitiator (PAA-2959) of the diblock copolymer prepared in Example 1 was used in the preparation process of the diblock copolymer PAM-b-PHMA, as shown below:

[0055] (1) 10 mg of 2-isopropylthioxanthone (ITX) and 20 mg of the bifunctional photoinitiator (PAA-2959) of the diblock copolymer prepared in Example 1 were dispersed in 1 ml of acrylamide (AM), irradiated with 405 nm LED light for 5 min, and separated by precipitation in n-hexane. The compound PAM-2959 was purified and the residual photoinitiator was removed by multiple reprecipitations in tetrahydrofuran (THF) to obtain the compound.

[0056] (2) 50 mg of the compound PAM-2959 prepared above was dissolved in 0.9 ml of hydroxyethyl methacrylate (HMA) and irradiated under 275 nm LED light for 5 min. The diblock copolymer PAM-b-PHMA (maximum thermal decomposition temperature of 238 ° C and Shore hardness of 200 DA) was obtained by precipitation in methanol.

[0057] Comparative Example 2

[0058] Preparation of random copolymer PAM-PHMA by photopolymerization:

[0059] 10 mg of 2-hydroxy-4-(2-hydroxyethoxy)-2-methylpropiophenone (Irgacure 2959) was dissolved in a mixed solution of 1 ml of monomer acrylamide (AM) and 0.9 ml of hydroxyethyl methacrylate, irradiated under ultraviolet light for 5 minutes, and precipitated and washed in methanol to obtain PAM-PHMA (maximum thermal decomposition temperature of 238°C and Shore hardness of 200DA).

[0060] The maximum thermal decomposition temperatures of PAM-PHMA and PAM-b-PHMA are 198℃ and 238℃, respectively, and the Shore hardnesses are 178DA and 200DA, respectively.

[0061] Example 4

[0062] The bifunctional photoinitiator (PAA-2959) of the diblock copolymer prepared in Example 1 was used in the preparation process of the diblock copolymer PPE-b-PLMA, as shown below:

[0063] (1) 10 mg of 2-isopropylthioxanthone (ITX) and 20 mg of the bifunctional photoinitiator (PAA-2959) of the diblock copolymer prepared in Example 1 were dispersed in 1 ml of propyl acrylate (PE), irradiated with 405 nm LED light for 5 min, and separated by precipitation in n-hexane. The compound PPE-2959 was purified and the residual photoinitiator was removed by multiple reprecipitations in tetrahydrofuran (THF) to obtain the compound.

[0064] (2) Dissolve 50 mg of the above-mentioned compound PPE-2959 in 1 ml of lauryl methacrylate (LMA), irradiate under 275 nm LED light for 5 min, and precipitate in methanol to obtain the diblock copolymer PPE-b-PLMA (maximum thermal decomposition temperature of 238 ° C, Shore hardness of 250 DA).

[0065] Comparative Example 3

[0066] Preparation of random copolymer PPE-PLMA by photopolymerization:

[0067] 10 mg of 2-hydroxy-4-(2-hydroxyethoxy)-2-methylpropiophenone (Irgacure 2959) was dissolved in a mixed solution of 1 ml of monomer acrylamide and 1 ml of lauryl methacrylate, irradiated under ultraviolet light for 1 min, and then precipitated and washed in methanol to obtain PPE-PLMA (maximum thermal decomposition temperature of 198°C and Shore hardness of 177DA).

[0068] Performance Testing

[0069] Figure 3 This is the photolysis curve of a mixture of the bifunctional photoinitiator (PAA-2959) and camphorquinone (CQ) (PAA-2959 / CQ) of the diblock copolymer prepared in Example 1, excited by 465 nm visible light. This curve demonstrates that camphorquinone (CQ) can theoretically abstract hydrogen from the conjugated tertiary amines of PAA-2959, generating aminoalkyl radicals.

[0070] Figure 4 The polymerization kinetics curve of PAA-2959 / CQ under 465 nm visible light excitation indicates that the aminoalkyl radicals generated by hydrogen abstraction from the bifunctional photoinitiator (PAA-2959) of the diblock copolymer prepared in Example 1 mixed with camphorquinone (CQ) can rapidly initiate monomer polymerization.

[0071] Figure 5 The electron paramagnetic resonance (EPR) results of PAA-2959 / CQ under 465nm visible light excitation indicate that the initiator system undergoes a hydrogen abstraction reaction to generate aminoalkyl radicals.

[0072] Figure 6 Figure 3 shows the photolysis curve of PAA-2959 / CQ after excitation with 465nm visible light and subsequent irradiation with 275nm UV light. This demonstrates that the initiation system formed by mixing the bifunctional photoinitiator (PAA-2959) and camphorquinone (CQ) of the diblock copolymer prepared in Example 1 can continue to photolyze under a second beam of UV light after the initial photolysis.

[0073] Figure 7 The following is a polymerization kinetics curve of the bifunctional photoinitiator (PAA-2959) used to prepare the diblock copolymer in Example 1 under 275 nm excitation. It can be seen that the bifunctional photoinitiator (PAA-2959) used to prepare the diblock copolymer in Example 1 decomposes upon 275 nm excitation to produce benzoyl radicals, which can rapidly initiate monomer polymerization.

[0074] Figure 8The following are the electron paramagnetic resonance (EPR) results of the bifunctional photoinitiator (PAA-2959) for the diblock copolymer prepared in Example 1 under UV excitation at 275 nm. This indicates that the bifunctional photoinitiator (PAA-2959) for the diblock copolymer prepared in Example 1 can cleave to produce benzoyl radicals and ketyl radicals upon UV excitation at 275 nm.

[0075] Figure 9 This is the GPC spectrum of the diblock copolymer prepared in Example 1 using the bifunctional photoinitiator (PAA-2959) under 465nm excitation and dual-color excitation. It can be seen that the photoinitiator system formed by the bifunctional photoinitiator (PAA-2959) and camphorquinone (CQ) used in the diblock copolymer prepared in Example 1 produced a diblock copolymer (PPMA-b-PBMA) under dual-color excitation.

[0076] Figure 10 This is the H NMR spectrum of a block copolymer prepared using the bifunctional photoinitiator (PAA-2959) used to prepare the diblock copolymer in Example 1. This spectrum indicates that the photoinitiator system formed by the bifunctional photoinitiator (PAA-2959) used to prepare the diblock copolymer in Example 1 and camphorquinone (CQ) produced a diblock copolymer (PPMA-b-PBMA) under dual-color excitation.

[0077] Figure 11 The preparation process of the block copolymer PPMA-b-PBMA in Example 2 is as follows: 10 mg of camphorquinone (CQ) and 20 mg of the bifunctional photoinitiator (PAA-2959) of the diblock copolymer prepared in Example 1 were dispersed in 0.8 ml of phenyl methacrylate (PMA), irradiated with 465 nm LED light for 5 minutes, separated by precipitation in cyclohexane, and purified and removed by multiple reprecipitations in tetrahydrofuran (THF) to obtain the compound PPMA-2959. 50 mg of the prepared compound PPMA-2959 was dissolved in 0.6 ml of butyl methacrylate (BMA), irradiated with 275 nm LED light for 5 minutes, and precipitated in methanol to obtain the diblock copolymer PPMA-b-PBMA.

[0078] By replacing "N-methyl-2-pyrrolecarboxaldehyde" in Example 1 with other conjugated tertiary amines (such as "1-methylimidazole-5-carboxaldehyde", "2-(dimethylamino)benzaldehyde" and "N-ethylcarbazole-2-carboxaldehyde"), the structural formulas of Bifunctional photoinitiator for diblock copolymers.

[0079] The bifunctional photoinitiators of the diblock copolymer disclosed in the present invention are composed of conjugated tertiary amine and α-hydroxyketone groups and have the function of preparing diblock copolymers. The principle is as follows Figure 12 Specifically, the bifunctional initiator of the diblock copolymer, in combination with visible light initiators such as camphorquinone (CQ) and thioxanthone, can be excited by visible light to abstract hydrogen, thereby generating highly active α-aminoalkyl radicals on the conjugated tertiary amine group, initiating a cross-linking reaction of the monomer to form an α-hydroxyketone macromolecular photoinitiator containing polymer 1; further, under ultraviolet light excitation, photolysis produces highly active benzoyl radicals, ultimately forming a diblock copolymer containing polymer 1 and polymer 2 segments. Therefore, the PAA-2959 embodiment can represent other compounds. Therefore, the bifunctional photoinitiator of the diblock copolymer disclosed in the present invention has good application prospects in catalyzing the preparation of diblock copolymers.

[0080] In summary, the present invention discloses a bifunctional photoinitiator of a diblock copolymer, the structural formula of which is The invention has the following effects: (1) the bifunctional photoinitiator of the present invention can be used in conjunction with visible light initiators such as camphorquinone and thioxanthone. The bifunctional initiator can be hydrogenated under visible light excitation to generate highly active α-aminoalkyl radicals, which trigger monomer I (monomer I is a monofunctional monomer that undergoes the first cross-linking reaction, which can be acrylamide, methyl methacrylate, phenyl methacrylate, hydroxyethyl methacrylate, etc.) to undergo a cross-linking reaction to form an α-hydroxyketone macromolecular photoinitiator; (2) further, the macromolecular photoinitiator (the product of the first photocrosslinking, which requires a second photocrosslinking to form the final diblock copolymer, and the specific reaction logic is bifunctional initiator-macromolecular photoinitiator-diblock copolymer) is photolyzed under ultraviolet light excitation to generate highly active benzoyl radicals, which trigger monomer II (a monofunctional monomer that undergoes the second cross-linking reaction) to undergo a cross-linking reaction, and finally form a diblock copolymer. It can be seen that the bifunctional photoinitiator of the diblock copolymer of the present invention can efficiently prepare diblock copolymers and can make a significant contribution to enriching the structure and performance of traditional photocurable materials.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. A bifunctional photoinitiator for a diblock copolymer, characterized in that: The structural formula of the bifunctional photoinitiator is: , where HR is 、 、 or Any one of .

2. The bifunctional photoinitiator according to claim 1, characterized in that The structural formula of the bifunctional photoinitiator is as follows: 、 、 or .

3. The method for preparing the bifunctional photoinitiator according to any one of claims 1 to 2, characterized in that: The preparation method comprises the following steps: (1) Dissolve triethyl phosphoacetate in tetrahydrofuran, add lithium amide dropwise at -10~0℃, stir and mix evenly, then add conjugated tertiary amine dropwise and react. After TLC detection, purify by column chromatography to obtain vinyl ester intermediate I containing conjugated tertiary amine. The chemical reaction formula is as follows: ; (2) The vinyl ester intermediate I containing conjugated tertiary amine is dissolved in a methanol aqueous solution, and NaOH is added as a catalyst to react. After TLC detection shows that the reaction is complete, the vinyl acid intermediate II containing conjugated tertiary amine is purified by recrystallization to obtain the vinyl acid intermediate II. The chemical reaction formula is as follows: ; (3) The vinyl acid intermediate II containing conjugated tertiary amine is dissolved in dichloromethane, and 2-hydroxy-4-(2-hydroxyethoxy)-2-methylpropiophenone as an initiator, 4-dimethylaminopyridine as a catalyst, and carbodiimide hydrochloride are added in sequence. The reaction is carried out at room temperature. After the reaction is complete by TLC detection, column chromatography is performed for purification to prepare a bifunctional photoinitiator. The chemical reaction formula is as follows: .

4. The preparation method according to claim 3, characterized in that In step (1), the structural formula of the aldehyde containing conjugated tertiary amine is 、 、 or ; In step (1), the molar ratio of the aldehyde of the conjugated tertiary amine to triethyl phosphoacetate is 1:1 to 1:3; In step (1), the molar ratio of the aldehyde of the conjugated tertiary amine to the catalyst is 1:1 to 1:2; In step (1), the reaction conditions are: -10~0°C; In step (1), the eluent used in the column chromatography purification is a mixed solution formed by mixing petroleum ether and ethyl acetate in a volume ratio of 10:1 to 20:

1.

5. The preparation method according to claim 3, characterized in that In step (2), the volume ratio of methanol to water in the methanol aqueous solution is 1:1 to 1:2; In step (2), the reaction temperature is 50-70°C; In step (2), the mass ratio of the vinyl ester intermediate I containing conjugated tertiary amine to NaOH is 2:

1.

6. The preparation method according to claim 3, characterized in that In step (3), the molar ratio of the ethylene acid intermediate II containing a conjugated tertiary amine, 2-hydroxy-4-(2-hydroxyethoxy)-2-methylpropiophenone, 4-dimethylaminopyridine and carbodiimide hydrochloride is 1:1:2:2; In step (3), the eluent used in the column chromatography purification is a mixed solution formed by mixing petroleum ether and ethyl acetate in a volume ratio of 10:

1.

7. Use of the bifunctional photoinitiator according to any one of claims 1 to 2 in the catalytic preparation of diblock copolymers.

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