Preparation of heterogeneous photocatalyst and application of heterogeneous photocatalyst in controllable free radical polymerization

Abstract

The invention relates to the field of photocatalysis and high polymer material preparation, and discloses preparation of a heterogeneous photocatalyst and application of the heterogeneous photocatalyst in controllable free radical polymerization, and the preparation method comprises the following steps: step 1, the adopted photocatalyst has the following structure: a conjugated structure unit containing an electron-donating group and an electron-withdrawing group is connected; according to the efficient cross-linking conjugated catalyst, rapid and controllable free radical polymerization is achieved under the condition of low catalyst dosage, high production efficiency and low production cost are achieved, a deoxygenization device and deoxygenization operation can be omitted through the light-induced controllable free radical polymerization method, polymerization reaction can be accelerated in the presence of oxygen, and the polymerization efficiency is improved. According to the present invention, the heterogeneous photocatalyst is adopted as the catalyst, good polymerization controllability is maintained, the catalyst can be further recycled, the pollution problem of the traditional photocatalyst to the product is avoided, and the light-induced controllable free radical polymerization using the heterogeneous photocatalyst comprises atom transfer free radical polymerization (ATRP) and reversible addition-fragmentation chain transfer (RAFT) polymerization.

Description

Technical Field

[0001] The invention belongs to the field of photocatalysis and polymer material preparation, and in particular relates to the preparation of a heterogeneous photocatalyst and the application of the photocatalyst in controlled free radical polymerization. Background Art

[0002] Controlled radical polymerization can precisely control the molecular weight and molecular chain structure of polymers, and has important applications in the fields of functional polymer materials, elastomers, surface grafting modification, biomedicine, fine chemicals, etc. In recent years, controlled radical polymerization induced by ultraviolet, visible or near-infrared light has attracted widespread attention. Compared with traditional methods, light-induced controlled radical polymerization has the advantages of being green, efficient, simple, and time- and space-controllable. Photoinduced atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer (RAFT) polymerization are currently widely studied and used methods. Oxidative quenching is a common catalytic reaction pathway. The photocatalyst in the excited state transfers electrons to the dormant species of ATRP or RAFT polymers to generate free radical active species, thereby causing chain growth. After that, the catalytic cycle is completed by reverse electron transfer deactivation, achieving a reversible balance between free radical active species and dormant species. Reducing the excited state oxidation potential of the photocatalyst can achieve low reaction free energy, thereby increasing the electron transfer reaction rate constant. In addition, the triplet excited state has a long lifetime, which can effectively improve the activity of the photocatalyst.

[0003] Photoredox based on organic small molecules and organometallic complexes provides a new strategy for controlled free radical polymerization. However, a large amount of organic small molecules and organometallic complex photocatalysts remain in the product after the polymerization is completed, which makes it difficult to recycle and reuse, and adds cumbersome polymer purification steps (J. W. Kramer, C. J. Hawke, B. P. Foss, N. J. Tritt, Controlled radical polymerization of acrylates regulated by light, application publication number: CN106164109A, Geng Jin, Li Zhiying, Zhang Pengfei, Xu Youwei, Zhang Yichuan, Application of DCDPP-2TPA as a photocatalyst for controlled active polymerization of PET-RAFT, CN 116239715 B; Chen Xiangyu, Wang Zhixiang, Li Xiang, A method for atom transfer radical polymerization of methacrylate monomers, application publication number: CN117986418A).

[0004] In addition, the free radical active species add oxygen molecules to form low-activity peroxy radical species, so oxygen has a high efficiency in inhibiting free radical polymerization. Controlled free radicals need to be carried out under strict deoxygenation conditions, which is cumbersome to operate and has harsh reaction conditions. Researchers have proposed many methods to consume oxygen in the reaction device by using oxidation reaction, photocatalytic oxidation reaction and enzyme-catalyzed oxidation reaction (Boyer, C. et al. Oxygen tolerance in living radical polymerization: investigation of mechanism and implementation in continuous flow polymerization. Macromolecules 2016, 49, 6779-6789; Boyer, C. et al. An oxygen paradox: catalytic use of oxygen in radical photopolymerization. Angew. Chem. Int. Ed. 2019, 131, 16967-16970; Matyjaszewski, K. et al. Fully oxygen-tolerant visible-light-induced ATRP of acrylates in water: towards synthesis of protein-polymer hybrids. Macromolecules 2023, 56, 2017-2026; An, Z. et al. Enzymatic cascade catalysis for the synthesis of multiblock and ultrahigh-molecular-weight polymers with oxygen tolerance.Angew.Chem.Int.Ed.2017,129,14040-14044; Pan Xiangcheng, Chen Zhe, A method for realizing controlled free radical polymerization in air atmosphere and its application, CN 114149527 B; Pan Xiangcheng, Lv Chunna, He Congze, A method for realizing "active" / controlled free radical polymerization under air conditions, CN108976367B). This type of method improves the tolerance of polymerization to oxygen, but requires the addition of a large amount of reducing agents or biological enzymes and other substances, and has many restrictions on reaction conditions such as reaction temperature, which increases the complexity of the reaction system and limits their scope of application.

[0005] Although the reported heterogeneous photocatalysts have achieved photocatalyst recovery and multiple recycling, they cannot effectively consume the oxygen in the reaction system. Therefore, the polymerization system is highly sensitive to oxygen. It is a problem that needs to be solved in the art to achieve oxygen tolerance and photocatalyst recovery in simultaneously controlled free radical polymerization through the design of photocatalysts. To this end, the present invention proposes a preparation method of a heterogeneous photocatalyst and its application in controlled free radical polymerization. Summary of the invention

[0006] The reported heterogeneous photocatalysts have achieved photocatalyst recovery and multiple recycling, avoiding catalyst residues in polymer products, but the reported controlled free radical polymerization based on heterogeneous photocatalysts is highly sensitive to oxygen.

[0007] The present invention proposes a conjugated cross-linked polymer containing electron-donating groups and electron-withdrawing groups as a photocatalyst. The groups with strong electron-donating effect in the photocatalyst improve the catalytic activity of the photocatalyst, thereby achieving the purpose of rapid polymerization at a low dosage of the photocatalyst.

[0008] The intramolecular electron donor-acceptor structure formed by the electron-donating group and the electron-withdrawing group makes the photocatalyst form a triplet excited state after light excitation, and further undergoes triplet-triplet annihilation with oxygen molecules to generate singlet oxygen. Singlet oxygen consumes oxygen in the air by oxidizing dimethyl sulfoxide or other solvents, achieving the purpose of oxygen tolerance of light-induced controllable free radical polymerization.

[0009] The photocatalyst proposed in the present invention is insoluble in water and organic solvents, achieving the purpose of recycling and reuse after polymerization and facilitating polymer purification. In short, the photocatalyst and light-induced controlled free radical polymerization method proposed in the present invention have important application value in large-scale synthesis of polymer materials.

[0010] To achieve the above object, the present invention provides a method for preparing a heterogeneous photocatalyst comprising the following steps:

[0011] Step 1: The photocatalyst used has the following structure: a conjugated structural unit containing an electron-donating group and an electron-withdrawing group, and its chemical structure is:

[0012]

[0013] Among them, dihydrophenazine, dihydrobenzophenazine, dihydrodibenzophenazine, 9,9-dimethyl-9,10-dihydroacridine, phenoxazine, phenothiazine, dihydroacridine and dimethyldihydroacridine are strong electron-donating groups, and the aromatic substituent group Ar' of the N atom is a phenyl group containing one or more electron-withdrawing substituents such as cyano, trifluoromethyl and fluorine atoms, or is an aromatic heterocyclic group with electron-withdrawing properties such as pyridine, quinoline and triazine;

[0014] Step 2: The photocatalyst is synthesized by the Friedel-Crafts reaction between the above structural unit and p-phenylenedimethyl ether in the presence of a solvent, an oxidant and a catalyst, and the crude product is washed and extracted with an organic solvent to obtain a high-purity product;

[0015] Step 3: The catalyst used in the Friedel-Crafts reaction is one or more of ferric chloride, aluminum chloride, titanium tetrachloride, and zinc chloride;

[0016] Step 4: the solvent is one or more of nitrobenzene, toluene and xylene;

[0017] Step 5: The solvent used for purifying the product is one or more of acetone, methanol, dichloromethane, tetrahydrofuran, dimethylformamide, and dimethyl sulfoxide.

[0018] The implementation of induced controlled radical polymerization, based on the preparation method of the heterogeneous photocatalyst, uses the photocatalyst proposed by the present invention, adds monomers, solvents, initiators and metal complexes, and carries out controlled radical polymerization under light induction, and can obtain a molecular weight of 500-5000000 g / mol, and the molecular weight polydispersity is low, that is, M w / M n =1.05-1.35 polymer, with a low photocatalyst dosage of <0.2g / L, and the reaction device does not need to be deoxygenated. After the polymerization is completed, the photocatalyst is recovered and recycled by filtration and centrifugation. The catalytic performance does not decrease after being recycled for more than five times.

[0019] Furthermore, the monomer is one or more of methyl methacrylate, benzyl methacrylate, perfluorobutylethyl methacrylate, polyethylene glycol monomethyl ether methacrylate, dimethylaminoethyl methacrylate, methyl acrylate, butyl acrylate, acrylamide, dimethylacrylamide, acrylic acid, sodium acrylate, styrene and vinylpyridine.

[0020] Furthermore, the initiator is one of ethyl α-bromophenylacetate, ethyl α-chlorophenylacetate, diethyl 2-bromo-2-methylmalonate, ethyl 2-bromoisobutyrate and hydroxyethanol 2-bromoisobutyrate.

[0021] Furthermore, the metal complex is a complex formed by ferric bromide, copper bromide, copper chloride, ruthenium chloride and a ligand, and the complex ligand is one or more of tetrabutylammonium bromide, tris(2-dimethylaminoethyl)amine, tris(2-pyridylmethyl)amine, and N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine.

[0022] Furthermore, the solvent is one or more of water or an organic solvent selected from the group consisting of dimethyl sulfoxide, dimethylformamide, dimethylacetamide and acetonitrile.

[0023] Furthermore, the light source is one of a monochromatic ultraviolet, visible, near-infrared light source and a white light source with a wavelength of 320nm to 850nm.

[0024] A heterogeneous photocatalyst is used in controlled radical polymerization. Based on the preparation method of the heterogeneous photocatalyst and the implementation of light-induced controlled radical polymerization, the heterogeneous photocatalyst is used in controlled radical polymerization of light-induced atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer (RAFT) polymerization, achieving oxygen-resistant polymerization with good controllability at a low photocatalyst dosage, and significantly accelerating polymerization in the presence of oxygen, which is beneficial to improving the production efficiency of the polymerization reaction. Based on the characteristics of the conjugated cross-linked photocatalyst being insoluble in organic solvents and water, the photocatalyst is recovered and recycled by filtration and centrifugation after the polymerization is completed.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The highly efficient cross-linking conjugated catalyst proposed in the present invention can realize rapid and controllable free radical polymerization under the condition of low catalyst dosage, and has high production efficiency and low production cost.

[0027] 2. The light-induced controlled free radical polymerization method proposed in the present invention can omit the deoxygenation device and deoxygenation operation, and can accelerate the polymerization reaction in the presence of oxygen and maintain good polymerization controllability.

[0028] 3. The catalyst can be further recycled and reused, avoiding the pollution problem of traditional photocatalysts on products, reducing production costs and being more environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The synthetic route diagram of the conjugated cross-linking catalyst is shown in FIG.

[0030] Figure 2 is the scanning electron microscope image of the cross-linking catalyst;

[0031] Figure 3 is the UV diffuse reflectance image of the cross-linking catalyst;

[0032] Figure 4 is the infrared absorption spectrum of the cross-linking catalyst;

[0033] Figure 5 It is the GPC spectrum and NMR hydrogen spectrum of polymethyl methacrylate;

[0034] Figure 6 It is the GPC spectrum and NMR hydrogen spectrum of polymethyl methacrylate and perfluorobutyl ethyl methacrylate block;

[0035] Figure 7The GPC spectrum and NMR hydrogen spectrum of polybutyl acrylate;

[0036] Figure 8 These are the GPC spectrum and NMR hydrogen spectrum of polymethacrylate polyethylene glycol monomethyl ether ester. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] The invention provides a preparation method of a heterogeneous photocatalyst and an application of the heterogeneous photocatalyst in controlled free radical polymerization.

[0039] Example 1: Synthesis of PC1

[0040] Monomer synthesis: Benzophenazine (2.15mmol, 500mg) and 3-bromopyridine (4mmol, 632mg), tris(dibenzylideneacetone)dipalladium (0.1mmol, 92mg), 2-cyclohexylphosphine-2',6'-diisopropoxy-1,1'-biphenyl (RuPhOs) (0.16mmol, 75mg), sodium tert-butoxide (4mmol, 384mg) and 10mL dioxane were added to a 50mL two-necked bottle and stirred at 110°C for 32 hours. After the reaction, 520mg of yellow-brown powder was obtained by extraction and dichloromethane / petroleum ether (10:3) column chromatography, with a yield of 62.5%.

[0041] Cross-linking: The above yellow solid (0.3mmol, 116mg) and the raw materials of p-phenylenedimethyl ether (2.4mmol, 332mg), FeCl3 (7.2mmol, 1.17g), and nitrobenzene (10mL) were added to a 50mL reaction bottle, and reacted at 80°C for 4 hours and at 110°C for 20 hours. After the reaction, the mixture was washed and filtered with acetone, THF, dichloromethane, DMF, and DMSO solvents, washed and filtered with methanol, and finally further washed with methanol, DMF, and DMSO through a Soxhlet extractor, and dried in a vacuum oven to obtain a dark yellow solid with a yield of 293mg.

[0042] Example 2: Synthesis of PC2

[0043] Monomer synthesis: Add benzophenazine (1mmol, 232mg) and 4-bromobenzonitrile (4mmol, 728mg), tris(dibenzylideneacetone)dipalladium (0.1mmol, 92mg), 2-cyclohexylphosphine-2',6'-diisopropoxy-1,1'-biphenyl (RuPhOs) (0.16mmol, 75mg), sodium tert-butoxide (4mmol, 384mg) and 10mL dioxane to a 50mL two-necked bottle and stir at 110°C for 24 hours. After the reaction, extract and dichloromethane / petroleum ether (1:1) column chromatography were performed to obtain 220mg of yellow powder with a yield of 50%.

[0044] Cross-linking: The above yellow solid (0.3mmol, 132mg) and raw materials p-phenylenedimethyl ether (2.4mmol, 332mg), FeCl3 (7.2mmol, 1.17g), and nitrobenzene (10mL) were added to a 50mL reaction bottle, and reacted at 80°C for 4 hours and at 110°C for 20 hours. After the reaction, the mixture was washed and filtered with acetone, THF, dichloromethane, DMF, and DMSO solvents, washed and filtered with methanol, and finally further washed with methanol, DMF, and DMSO through a Soxhlet extractor, and dried in a vacuum oven to obtain a dark yellow solid with a yield of 270mg.

[0045] Example 3: Synthesis of PC-3

[0046] Monomer synthesis: Benzophenazine (1mmol, 232mg) and p-bromotrifluorotoluene (4mmol, 900mg), tris(dibenzylideneacetone)dipalladium (0.1mmol, 92mg), 2-cyclohexylphosphine-2',6'-diisopropoxy-1,1'-biphenyl (RuPhOs) (0.16mmol, 75mg), sodium tert-butoxide (4mmol, 384mg) and 10mL dioxane were added to a 50mL two-necked bottle and stirred at 110°C for 24 hours. After the reaction, 300mg of yellow powder was obtained by extraction and dichloromethane / petroleum ether (2:1) column chromatography to obtain a dark yellow solid with a yield of 53%.

[0047] Cross-linking: The above yellow solid (0.3mmol, 156mg) and the raw materials of p-phenylenedimethyl ether (2.4mmol, 332mg), FeCl3 (7.2mmol, 1.17g), and nitrobenzene (10mL) were added to a 50mL reaction bottle, and reacted at 80°C for 4 hours and at 110°C for 20 hours. After the reaction, the mixture was washed and filtered with acetone, THF, dichloromethane, DMF, and DMSO solvents, washed and filtered with methanol, and finally further washed with methanol, DMF, and DMSO through a Soxhlet extractor, and dried in a vacuum oven to obtain a dark yellow solid with a yield of 300mg.

[0048] Example 4: Synthesis of PC-4

[0049] Monomer synthesis: Dihydrobenzophenazine (2mmol, 568mg) and 3-bromopyridine (8mmol, 1.26g), tris(dibenzylideneacetone)dipalladium (0.1mmol, 92mg), 2-cyclohexylphosphine-2',6'-diisopropoxy-1,1'-biphenyl (RuPhOs) (0.32mmol, 148mg), sodium tert-butoxide (4mmol, 384mg) and 10mL dioxane were added to a 50mL two-necked bottle and stirred at 110°C for 24 hours. After the reaction, 512mg of yellow powder was obtained by extraction and dichloromethane / ethyl acetate (40:1) column chromatography with a yield of 60%.

[0050] Cross-linking: The above yellow solid (0.2mmol, 87mg) and raw materials p-phenylenedimethyl ether (1.6mmol, 221mg), FeCl3 (4.8mmol, 779g), and nitrobenzene (10mL) were added to a 50mL reaction bottle, and reacted at 80°C for 4 hours and at 110°C for 20 hours. After the reaction, the mixture was washed and filtered with acetone, THF, dichloromethane, DMF, and DMSO solvents, washed and filtered with methanol, and finally further washed with methanol, DMF, and DMSO through a Soxhlet extractor, and dried in a vacuum oven to obtain a dark yellow solid with a yield of 230mg.

[0051] Example 5: Synthesis of PC-5

[0052] Monomer synthesis: Dihydrobenzophenazine (1mmol, 284mg) and 4-bromobenzonitrile (4mmol, 728mg), tris(dibenzylideneacetone)dipalladium (0.1mmol, 92mg), 2-cyclohexylphosphine-2',6'-diisopropoxy-1,1'-biphenyl (RuPhOs) (0.16mmol, 75mg), sodium tert-butoxide (4mmol, 384mg) and 10mL dioxane were added to a 50mL two-necked bottle and stirred at 110°C for 24 hours. After the reaction, 252mg of yellow powder was obtained by extraction and dichloromethane / petroleum ether (1.5:1) column chromatography with a yield of 52%.

[0053] Cross-linking: The above yellow solid (0.25mmol, 123mg) and raw materials p-phenylenedimethyl ether (2mmol, 280mg), FeCl3 (6mmol, 987g), and nitrobenzene (10mL) were added to a 50mL reaction bottle, and reacted at 80°C for 4 hours and at 110°C for 20 hours. After the reaction, the mixture was washed and filtered with acetone, THF, dichloromethane, DMF, and DMSO solvents, washed and filtered with methanol, and finally further washed with methanol, DMF, and DMSO through a Soxhlet extractor, and dried in a vacuum oven to obtain a dark yellow solid with a yield of 261mg.

[0054] Example 6: Synthesis of PC-6

[0055] Monomer synthesis: Dihydrobenzophenazine (1mmol, 284mg) and p-bromotrifluorotoluene (4mmol, 900mg), tris(dibenzylideneacetone)dipalladium (0.1mmol, 92mg), 2-cyclohexylphosphine-2',6'-diisopropoxy-1,1'-biphenyl (RuPhOs) (0.16mmol, 75mg), sodium tert-butoxide (4mmol, 384mg) and 10mL dioxane were added to a 50mL two-necked bottle and stirred at 110°C for 24 hours. After the reaction, 290mg of yellow powder was obtained by extraction and dichloromethane / petroleum ether (2.5:1) column chromatography to obtain a dark yellow solid with a yield of 51%.

[0056] Figure 2 Scanning electron microscope images of the cross-linked conjugated catalysts PC1 to PC6 are shown:

[0057] The morphology of the cross-linked catalyst was observed from the scanning electron microscope image, and it was found that it had a pore structure with disordered pore size and a lamellar structure.

[0058] Figure 3 The UV-visible diffuse reflectance image of the benzophenazine or dihydrobenzophenazine cross-linked conjugated catalyst is shown:

[0059] From the UV-visible diffuse reflectance image, we can see that all six catalysts have absorption in the range of 300-800nm, which further illustrates that the polymerization system has a wide selection range of light sources.

[0060] Figure 4 The infrared spectrum results of the benzophenazine or dihydrobenzophenazine cross-linked conjugated catalysts shown are:

[0061] From the infrared spectrum, we can see that the main C=C and C=N absorption peaks and the weakened stretching vibration amplitude further illustrate its cross-linked structure. The cross-linking leads to a decrease in double bond properties, which further reduces its stretching frequency.

[0062] Example 7: Oxygen-resistant light-induced controlled free radical polymerization

[0063] 0.1 mg of catalyst, methyl methacrylate (1 mL), ethyl α-bromophenylacetate (8.2 μL), copper bromide (0.021 mg), tris(2-picolylamine) (0.194 mg), and DMSO (780 μL) were added to a 5 mL vial, mixed evenly, stirred with a magnetic stirrer, and irradiated with 420 nm blue light for 6 h of polymerization. A small amount of sample was taken for NMR. 1H NMR and GPC tests, using PC1, PC2, PC3, PC4, PC5, PC6 as photocatalysts, the corresponding monomer conversion rates were 85%, 91%, 90%, 87%, 92%, 93%, respectively, corresponding to the number average molecular weight of the polymer M n =17800, 21400, 21000, 19800, 21800, 22100, corresponding to the molecular weight distribution M of the polymer respectively. w / M n =1.30, 1.28, 1.32, 1.31, 1.29, 1.32, 1.33.

[0064] Example 8: Controlled Radical Polymerization after Deoxygenation

[0065] 0.1 mg of catalyst, methyl methacrylate (1 mL), ethyl α-bromophenylacetate (8.2 μL), copper bromide (0.021 mg), tris(2-picolylamine) (0.194 mg), and DMSO (780 μL) were added to a 5 mL vial, mixed evenly, stirred with a magnetic stirrer, purged with argon gas in the solution and the headspace in the reaction bottle for 10 minutes, illuminated with 420 nm blue light, and polymerized for 6 hours. A small amount of sample was taken for NMR. 1 The H NMR and GPC tests showed that the conversion rates of the monomers were 33%, 35%, 32%, 36%, 38%, and 39%, respectively, corresponding to the number average molecular weight of the polymers. n =7800, 8400, 7600, 8800, 9000, 9600, corresponding to the molecular weight distribution M of the polymer respectively. w / M n =1.25, 1.29, 1.30, 1.28, 1.27, 1.31, 1.25.

[0066] Comparison of Example 7 and Example 8 shows that, under the same reaction conditions and reaction time, the polymerization rate under the condition of no deoxygenation is significantly increased by using the photocatalyst proposed in the present invention compared with the polymerization under the condition of deoxygenation. Comparison of molecular weight and molecular weight distribution shows that omitting the deoxygenation step has no significant effect on the controllability of polymerization.

[0067] Example 9: Oxygen-resistant polymerization of other methacrylate monomers:

[0068] 1. Add catalyst PC2 (1 mg), benzyl methacrylate (1 mL), ethyl α-bromophenylacetate (5.2 μL), copper bromide (0.013 mg), tris(2-picolylamine) (0.12 mg), and DMSO to a 5 mL vial, mix well, stir with a magnetic stirrer, illuminate with 420 nm blue light, and polymerize for 6 h. Take a small amount of sample for 1H NMR and GPC tests showed a conversion rate of 90%, and a number average molecular weight of M n =21600, molecular weight distribution is M w / M n =1.29.

[0069] 2. Add catalyst PC2 (1 mg), perfluorobutyl ethyl methacrylate (1 mL), ethyl α-bromophenylacetate (3.7 μL), copper bromide (0.009 mg), tris(2-picolylamine) (0.086 mg), and DMSO to a 5 mL vial, mix well, stir with a magnetic stirrer, illuminate with 420 nm blue light, and polymerize for 6 h. Take a small amount of sample for 1 H NMR and GPC tests showed a conversion rate of 93%, and a number average molecular weight of M n =22100, molecular weight distribution is M w / M n =1.29.

[0070] Example 10: Oxygen-resistant polymerization of acrylic acid ester monomers:

[0071] Catalyst PC2 (1 mg), butyl acrylate (1 mL), ethyl α-bromophenylacetate (8.2 μL), copper bromide (0.016 mg), tris(2-picolylamine) (0.14 mg), and DMSO were added to a 5 mL vial, mixed evenly, stirred with a magnetic stirrer, and irradiated with 420 nm blue light for 6 h of polymerization. A small amount of sample was taken for 1 H NMR and GPC tests, the results are as follows Figure 7 As shown, the conversion rate of butyl propiobutyrate is 90%, and the number average molecular weight M n =21000, molecular weight distribution is M w / M n =1.27.

[0072] Example 11: Catalyst polymerization in water phase:

[0073] Catalyst PC2, polyethylene glycol monomethyl ether methacrylate OEOMA475 (0.52 mL), 2-bromoisobutyric acid hydroxyethanol ester (1.7 μL), copper bromide (0.079 mg), tris(2-picolylamine) (0.46 mg), and PBS buffer (2.87 mL) were added to a 5 mL vial, mixed evenly, stirred with a magnetic stirrer, and irradiated with 420 nm blue light for 6 h. Take a small amount of sample for 1 H NMR and GPC tests, the results are as follows Figure 8 As shown, the conversion rate of OEOMA475 is 93%, and the number average molecular weight M n =36700, molecular weight distribution is M w / M n =1.16.

[0074] Example 12: Preparation of block copolymer

[0075] We used photoinduced ATRP to synthesize PMMA-Br(M n =19.7 kDa, M w / M n =1.21) as a macromolecular initiator, perfluorobutylethyl methacrylate (NFHMA) as a monomer, PC-3 (0.5 mg / mL), 10 ppm CuBr2 / TPMA for chain extension, and M n =30100 and M w / M n =1.33 block copolymer PMMA-b-PNFHMA-Br was taken with a small amount of sample 1 H NMR and GPC tests, the results are as follows Figure 6 As shown, the conversion rate of PNFHMA is 94%, and the number average molecular weight M n =30100, molecular weight distribution is M w / M n =1.33.

[0076] Example 13: Photocatalytic RAFT organic phase polymerization:

[0077] Catalyst PC2 (1 mg), methyl methacrylate (1 mL), 2-cyanopropyl-2-ylbenzene disulfate (10.4 mg), and DMSO (989 μL) were added to a 5 mL vial, mixed evenly, stirred with a magnetic stirrer, and irradiated with 420 nm blue light for 6 h of polymerization. 1 HNMR and GPC tests showed a conversion rate of 98%, and a number average molecular weight of M n =22300, molecular weight distribution is M w / M n =1.26.

[0078] Example 14: Photocatalytic RAFT polymerization:

[0079] Catalyst PC2 (1 mg), polyethylene glycol monomethyl ether methacrylate OEOMA475 (1 mL), 2-cyanopropyl-2-ylbenzene disulfate (6.03 mg), and water (993 uL) were added to a 5 mL vial, mixed evenly, stirred with a magnetic stirrer, and irradiated with 420 nm blue light for 6 hours of polymerization. A small amount of sample was taken for 1H NMR and GPC testing, and the conversion rate was 99%, and the number average molecular weight M n =44100, molecular weight distribution is M w / M n =1.25.

[0080] Example 15: Recovery and recycling of photocatalyst:

[0081] The PMMA product containing PC2 catalyst in Example 7 was recovered by centrifugation, washing, filtering and drying with dichloromethane, ethyl acetate and acetonitrile solvents. The recovered PC2 was used to perform polymerization again according to the conditions of Example 7. After 6 hours of polymerization, a small amount of sample was taken for NMR. 1 H NMR and GPC test results are as follows:

[0082]

[0083] From the above results, it can be seen that the photocatalyst is insoluble in water and organic solvents, thus achieving the purpose of recycling and reusing after polymerization and facilitating polymer purification.

[0084] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0085] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a heterogeneous photocatalyst, characterized in that: The method comprises the following steps: Step 1: The photocatalyst used has the following structure: a conjugated structural unit containing an electron-donating group and an electron-withdrawing group, and its chemical structure is: Among them, dihydrophenazine, dihydrobenzophenazine, dihydrodibenzophenazine, 9,9-dimethyl-9,10-dihydroacridine, phenoxazine, phenothiazine, dihydroacridine and dimethyldihydroacridine are strong electron-donating groups, and the aromatic substituent group Ar' of the N atom is a phenyl group containing one or more electron-withdrawing substituents such as cyano, trifluoromethyl and fluorine atoms, or is an aromatic heterocyclic group with electron-withdrawing properties such as pyridine, quinoline and triazine; Step 2: The photocatalyst is synthesized by the Friedel-Crafts reaction between the above structural unit and p-phenylenedimethyl ether in the presence of a solvent, an oxidant and a catalyst, and the crude product is washed and extracted with an organic solvent to obtain a high-purity product; Step 3: The catalyst used in the Friedel-Crafts reaction is one or more of ferric chloride, aluminum chloride, titanium tetrachloride, and zinc chloride; Step 4: the solvent is one or more of nitrobenzene, toluene and xylene; Step 5: The solvent used for purifying the product is one or more of acetone, methanol, dichloromethane, tetrahydrofuran, dimethylformamide, and dimethyl sulfoxide.

2. The implementation of light-induced controlled free radical polymerization is based on the preparation method of the heterogeneous photocatalyst according to claim 1, characterized in that: Using the photocatalyst proposed in the present invention, under the conditions of adding monomers, solvents, initiators and metal complexes, atom transfer radical polymerization, i.e. ATRP, can be carried out under light induction to obtain a molecular weight of 500-5000000 g / mol with low molecular weight polydispersity, i.e. M w / M n =1.05-1.35 polymer, with a low photocatalyst dosage of <0.2g / L, and the reaction device does not need to be deoxygenated. After the polymerization is completed, the photocatalyst is recovered and recycled by filtration and centrifugation. The catalytic performance does not decrease after being recycled for more than five times.

3. The method of claim 2, wherein: The monomer is one or more of methyl methacrylate, benzyl methacrylate, perfluorobutyl ethyl methacrylate, polyethylene glycol monomethyl ether methacrylate, dimethylaminoethyl methacrylate, methyl acrylate, butyl acrylate, acrylamide, dimethylacrylamide, acrylic acid, sodium acrylate, styrene and vinyl pyridine.

4. The method of claim 2, wherein: The initiator is one of ethyl α-bromophenylacetate, ethyl α-chlorophenylacetate, diethyl 2-bromo-2-methylmalonate, ethyl 2-bromoisobutyrate and hydroxyethanol 2-bromoisobutyrate.

5. The method of claim 2, wherein: The metal complex is a complex formed by ferric bromide, copper bromide, copper chloride, ruthenium chloride and a ligand, and the ligand of the complex is one or more of tetrabutylammonium bromide, tris(2-dimethylaminoethyl)amine, tris(2-pyridylmethyl)amine and N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine.

6. The method of claim 2, wherein: The solvent is one or more of water or an organic solvent selected from the group consisting of dimethyl sulfoxide, dimethylformamide, dimethylacetamide and acetonitrile.

7. The method of claim 2, wherein: The light source is one of a monochromatic ultraviolet, visible, near-infrared light source and a white light source with a wavelength of 320nm to 850nm.

8. An application of a heterogeneous photocatalyst in controlled free radical polymerization, based on the preparation method of the heterogeneous photocatalyst according to any one of claims 1 to 9 and the implementation of light-induced controlled free radical polymerization, characterized in that: The heterogeneous photocatalyst is applied to light-induced atom transfer radical polymerization, i.e. ATRP, and reversible addition-fragmentation chain transfer, i.e. RAFT polymerization.

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