A metal-free molecular photocatalyst, a preparation method and application thereof

Abstract

The application discloses a metal-free molecular photocatalyst and a preparation method and application thereof. The metal-free molecular photocatalyst capable of realizing visible light photocatalytic monomer controllable polymerization reaction is a kind of donor-acceptor type organic molecule composed of an electron donor molecular fragment and an electron acceptor molecular fragment. The donor-acceptor type metal-free molecular photocatalyst can catalyze the polymerization reaction of acrylic monomer molecules under the irradiation of visible light. By adjusting the molar ratio of the acrylic monomer molecules and the photocatalyst in the photocatalytic polymerization reaction, a polymer product with a narrow polymerization degree distribution (a polymerization degree dispersion coefficient is less than 1.6, and under optimal conditions, the polymerization degree dispersion coefficient can be as low as 1.2) and adjustable polymerization degree can be obtained.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalyst development, and relates to a metal-free molecular photocatalyst and a preparation method and application thereof, in particular to a metal-free molecular photocatalyst capable of realizing controllable polymerization of acrylic monomers under visible light and a preparation method and application thereof. TECHNICAL BACKGROUND

[0002] Radical polymerization has a wide range of practical applications in the preparation of plastics, rubber, paint and adhesive, drug production, surface coating and modification, and photolithographic micro-nano processing. Among all the synthetic polymer products produced by human beings, more than one-third of them are produced by using the radical polymerization method. However, the traditional radical polymerization reaction cannot well control the molecular weight, molecular weight distribution and regularity of the polymer product because it cannot control the transfer and termination of active radicals in the reaction process. In order to solve the above technical problems and realize more precise structure control, the concept of controllable radical polymerization is developed. Controllable radical polymerization is a kind of radical polymerization reaction that controls the molecular weight, molecular weight distribution and terminal functionality of the polymer by using the balance between growing radicals and various dormant species. One of the key goals is to achieve a narrow molecular weight distribution to overcome the problem that the traditional radical polymerization often leads to a wide molecular weight distribution (polydispersity index greater than 1.6), and the polymers with different molecular weights have great differences in solubility, viscosity, elasticity, photoelectron band and other aspects, and the differences in polymer properties will produce many unpredictable effects in the production or application of biological medicines or optoelectronic materials. Through controllable radical polymerization, the conditions such as the concentration of initiator and reaction temperature can be adjusted to achieve a slower and controllable reaction rate, thereby reducing the occurrence of radical chain transfer side reactions, and finally achieving a narrow molecular weight distribution of the polymer product. In addition, controllable radical polymerization also provides greater flexibility for the controllable introduction of functional monomers at the molecular level and the preparation of complex structure copolymers.

[0003] Currently, there are mainly three methods to achieve controllable radical polymerization: (1) stable free radical mediated polymerization (SFRP), which refers to the process that stable free radicals are added to generate "dormant species" to deactivate active free radicals, and the "dormant species" can reversibly decompose into stable free radicals and active free radical to continue chain growth. Among them, nitroxyl radical has the best regulating effect. (2) Reversible addition-fragmentation chain transfer polymerization (RAFT), which usually adds a dithioester derivative as a chain transfer agent to reversibly form a dormant intermediate with growing chain radicals, limiting the irreversible bimolecular termination side reaction between growing chain radicals. (3) Atom transfer radical polymerization (ATRP), which usually forms a redox process between various transition metal complexes and chain radicals, thereby establishing a reversible balance between "dormant species" and "active species", keeping the "active species" at a low concentration level to effectively reduce the irreversible bimolecular termination side reaction.

[0004] Photocatalytic controllable radical reactions have attracted great interest from researchers in recent years due to their mild conditions, environmental friendliness, and easy control of space and time. In the past decade, photocatalytic atom transfer radical polymerization has become a research hotspot due to its low temperature operation, high response, and optical control. In the early research of atom transfer radical polymerization catalysts, most catalysts are metal complex catalysts centered on metal with variable valence, such as copper or iridium complexes. The products and polymers obtained by traditional atom transfer radical polymerization are inevitably contaminated by trace metal residues, which may cause problems in electronic and biomedical applications. In response to this problem, some pure organic non-metal molecular photocatalysts have been developed in recent years to achieve photocatalytic atom transfer radical polymerization. However, the currently available organic non-metal molecular photocatalysts are still in the high-throughput screening stage, and there is no specific molecular design strategy, so the molecules that can achieve photocatalytic controllable radical polymerization are limited to a few types such as polycyclic aromatic hydrocarbons and thienazoles. SUMMARY

[0005] To improve the above technical problems, the present application provides a photocatalyst, which is an electron donor-acceptor organic molecule. Preferably, the photocatalyst is composed of an electron donor molecule fragment and an electron acceptor molecule fragment.

[0006] According to an embodiment of the present application, the combination ratio of the electron donor molecule fragment and the electron acceptor molecule fragment is an integer between 1 and 4.

[0007] According to an embodiment of the present application, the electron donor molecule fragment can be selected from one of different alkyl chain substituted fluorene, bi-fluorene or benzene as a linker to connect benzimidazole modified fluorene; in bi-fluorene, fluorene can be used as a repeating unit, and the number of repeating units is an integer from 2 to 10.

[0008] According to an embodiment of the present application, the electron acceptor molecular fragment is one of benzothiadiazole (such as 4,7-dibromo-2,1,3-benzothiadiazole), benzoselenadiazole, naphthalene, benzopyrazine and fluorenone.

[0009] According to an embodiment of the present application, in the photocatalyst, the electron donor molecular fragment is an end-capping group and the electron acceptor molecular fragment is a linking group; or the electron donor molecular fragment is a linking group and the electron acceptor molecular fragment is an end-capping group. For example, the photocatalyst has an electron acceptor molecular fragment-electron donor molecular fragment-electron acceptor molecular fragment structure or an electron donor molecular fragment-electron acceptor molecular fragment-electron donor molecular fragment structure.

[0010] According to an exemplary embodiment of the present application, the electron donor molecular fragment has one of the following structures:

[0011]

[0012] wherein R is a linear alkane or a branched alkane, the number of carbons of the alkane substituent is 1-30; n is the number of repeating units, which is an integer of 2-10, and * is a connecting bond to the rest of the molecule.

[0013] It should be noted that the electron donor molecular fragment of the present application can be an end-capping group or an intermediate linking group. When it is an intermediate linking group, it has two connecting bonds *; when it is an end-capping group, it has only one connecting bond *.

[0014] According to an exemplary embodiment of the present application, the electron acceptor molecular fragment has one of the following structures:

[0015]

[0016] It should be noted that the electron acceptor molecular fragment of the present application can be an end-capping group or an intermediate linking group. When it is an intermediate linking group, it has two connecting bonds *; when it is an end-capping group, it has only one connecting bond *.

[0017] According to an exemplary embodiment of the present application, the photocatalyst has the following structure of Formula I or Formula II:

[0018]

[0019] According to an embodiment of the present application, the photocatalyst is a kind of metal-free molecular photocatalyst that can realize visible light catalyzed monomer controlled polymerization.

[0020] The present application also provides a preparation method of the above-mentioned photocatalyst, which comprises preparing the photocatalyst by coupling reaction of the electron donor molecular fragment and the electron acceptor molecular fragment.

[0021] According to an embodiment of the present application, the reaction mass ratio of the electron donor molecular fragment and the electron acceptor molecular fragment is (1-4):1, and an example is 3.6:1.

[0022] In an embodiment of the present application, the preparation method can be carried out in the presence of a solvent, such as an organic solvent. For example, the organic solvent can be selected from 1,4-dioxane.

[0023] In an embodiment of the present application, a base and / or a catalyst are preferably added in the coupling reaction.

[0024] Preferably, the base is selected from one, two or more of potassium acetate, potassium carbonate, sodium tert-butoxide, potassium tert-butoxide, potassium phosphate, and sodium acetate.

[0025] Preferably, the catalyst is selected from tetrakis(triphenylphosphine)palladium.

[0026] In an embodiment of the present application, the preparation method further comprises a step of separating the solid product from the reacted mixture after the reaction is completed. For example, after removing the solvent under vacuum, the organic phase is extracted and washed with dichloromethane and saturated brine respectively, and dried with sodium sulfate to obtain the solid product. Further, the preparation method further comprises a step of purifying the product. For example, the purification can be carried out by column chromatography.

[0027] According to an embodiment of the present application, the electron donor molecular fragment is prepared by coupling reaction of 9,9-dihexyl-2-bromofluorene and bis(pinacolato)diboron.

[0028] In an embodiment of the present application, the molar ratio of 9,9-dihexyl-2-bromofluorene to bis(pinacolato)diboron is 1:(1-2), and an example is 1:1, 1:1.5, or 1:2.

[0029] In an embodiment of the present application, the preparation method of the electron donor molecular fragment can be carried out in the presence of a solvent, such as an organic solvent. For example, the organic solvent can be selected from 1,4-dioxane.

[0030] In an embodiment of the present application, a base and / or a catalyst are preferably added in the reaction of 9,9-dihexyl-2-bromofluorene and bis(pinacolato)diboron.

[0031] Preferably, the molar ratio of the base to 9,9-dihexyl-2-bromofluorene is 1:(1-5), and an example is 1:1, 1:4, or 1:5.

[0032] Preferably, the molar ratio of the catalyst to 9,9-dihexyl-2-bromofluorene is 1:

[0033] (0.05-0.2), exemplarily 1:0.05, 1:0.1, 1:0.2.

[0034] Preferably, the base is selected from one, two or more of potassium acetate, potassium carbonate, sodium tert-butoxide, potassium tert-butoxide, potassium phosphate, sodium acetate.

[0035] Preferably, the catalyst is selected from [1,1'-bis(diphenylphosphino)ferrocene] dichloropalladium.

[0036] In one embodiment of the present application, the method for preparing the electron donor molecule fragment further comprises a step of separating the solid product from the reacted mixture after the reaction is completed. For example, after the solvent is removed under vacuum, the organic phase is extracted and washed with ethyl acetate and saturated brine respectively, and dried by adding sodium sulfate to obtain the solid product. Further, the method for preparing further comprises a step of purifying the product. For example, the purification can be performed by column chromatography.

[0037] The present application also provides the use of the above-mentioned photocatalyst in a radical polymerization reaction, preferably in a photocatalytic atom transfer radical polymerization reaction. For example, in the catalysis of the polymerization reaction of acrylic monomer molecules.

[0038] The present application also provides a polymerization method, comprising the use of the above-mentioned photocatalyst with monomers, in the presence of a polymerization initiator and an electron donor, to initiate the polymerization of the monomers by a visible light source.

[0039] According to an embodiment of the present application, the monomer can be an acrylic compound. Exemplarily, the monomer is methyl methacrylate, butyl methacrylate or methyl acrylate. The degree of polymerization of the polymerization product in the present application can be controlled by the ratio of the photocatalyst, the polymerization initiator, the electron donor and the monomer, and the degree of polymerization is between 10 and 1000; and the dispersion of the polymerization product is low (for example, the polydispersity index (PDI) of the polymerization product is controlled between 1.1 and 1.6).

[0040] In the present application, the implementation of the visible light photocatalytic controlled polymerization of monomers comprises six necessary conditions: a visible light excitation light source, a suitable solvent phase, a visible light catalyst, a polymerization initiator, an electron donor, and strict oxygen removal.

[0041] According to an embodiment of the present application, the polymerization reaction is carried out in a solvent system. For example, the solvent can be any one or a blend of several of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, tetrahydrofuran, and chloroform.

[0042] According to an embodiment of the present application, the concentration of the monomer is 10 mg / mL to 2 g / mL.

[0043] According to an embodiment of the present application, the polymerization initiator can be any one of 2-bromopropionic acid ethyl ester, ethyl α-bromophenylacetate, 2-bromoisobutyric acid ethyl ester, bromomalonate diethyl ester, (1-bromoethyl)benzene and 4-bromoacetophenone.

[0044] According to an embodiment of the present application, the molar ratio of the monomer to the polymerization initiator is 25:1 to 1000:1, preferably 50:1 to 800:1, and exemplarily 50:1, 100:1, 200:1, 400:1, 600:1, 800:1.

[0045] According to an embodiment of the present application, the molar ratio of the polymerization initiator to the photocatalyst is 1:0.1 to 1:0.00001, preferably 1:0.1 to 1:0.05, and exemplarily 1:0.02.

[0046] According to an embodiment of the present application, the electron donor can be any one of triethylamine, triethanolamine, N,N,N,N-tetramethyl-1,4-butanediamine, N,N,N',N",N"-pentamethyldiethylenetriamine.

[0047] According to an embodiment of the present application, the molar ratio of the polymerization initiator to the electron donor is 1:0.1 to 1:40, and exemplarily 1:20.

[0048] According to an embodiment of the present application, the reaction temperature of the polymerization reaction is 15°C to 30°C, and exemplarily 25°C.

[0049] In the present application, the polymerization reaction is carried out in a reaction vessel sealed after oxygen removal, and the reaction is controlled at 15°C to 30°C by water cooling. Further, the polymerization reaction is stirred in a visible light excitation light source light irradiation environment, and monomer controlled polymerization is achieved after a certain period of time.

[0050] According to an embodiment of the present application, the type of the visible light excitation light source can be any one of a xenon lamp, a halogen lamp, an LED, and a laser. Further, the wavelength of the excitation light source should be within the absorption wavelength range (400-700 nm) of the visible light catalyst that achieves monomer controlled polymerization, and the excitation light source intensity range is 20 mW / cm 2 to 500 mW / cm 2 .

[0051] According to an embodiment of the present application, the time of the polymerization reaction can be 10 minutes to 10 hours.

[0052] According to the embodiment of the present application, after the polymerization reaction, the reaction solution can also be dropped into methanol, stirred (for example, 0.5 to 6 hours), and the polymer can be precipitated. Further, the controllable polymerization product can be obtained by filtering with a polytetrafluoroethylene filter, washing with methanol, and drying.

[0053] In the present application, 3-5 mg of the polymerization product can be dissolved in 1 mL of N,N-dimethylformamide, and the molecular weight and the polydispersity index of the polymer can be measured by gel permeation chromatography.

[0054] The present application also provides a polymer prepared by the above polymerization reaction.

[0055] According to the embodiment of the present application, the polymerization degree of the polymer is 10-1000, for example, 10, 50, 100, 200, 500, or 1000.

[0056] According to the embodiment of the present application, the polydispersity index (PDI) of the polymer is less than 1.6, for example, 1.2-1.6, for example, 1.2, 1.3, 1.4, 1.5, or 1.6.

[0057] According to the embodiment of the present application, the number average molecular weight of the polymer is 5 k / mol-30 kg / mol, for example, 5 k / mol, 10 k / mol, 15 k / mol, 20 k / mol, or 30 k / mol.

[0058] Advantages of the present application:

[0059] The present application discloses a molecular design of an organic metal-free molecular photocatalyst based on an electron donor-acceptor organic molecule and a controllable photocatalytic polymerization effect. The metal-free molecular photocatalyst of the present application can realize a visible light catalytic controllable polymerization of monomer molecules, especially acrylic monomer molecules. By adjusting the feeding ratio of the photocatalyst, the polymerization initiator, and the monomer, the polymerization degree of the polymerization product can be controlled to obtain a high molecular polymerization product with a number average molecular weight in the range of 5 k / mol-30 kg / mol and a very narrow polymerization degree distribution (polydispersity index less than 1.6, and under the optimal conditions, the polydispersity index can be as low as 1.2). BRIEF DESCRIPTION OF DRAWINGS

[0060] Figure 1 A one-dimensional nuclear magnetic resonance spectrum of the metal-free molecular photocatalyst of Example 1, which can realize a visible light photocatalytic controllable polymerization of monomers.

[0061] Figure 2 A mass spectrum data spectrum of the metal-free molecular photocatalyst of Example 1, which can realize a visible light photocatalytic controllable polymerization of monomers.

[0062] Figure 3 The graph of the relationship between the conversion rate of the visible light photocatalytic controlled polymerization reaction of methyl methacrylate monomers and the polydispersity index of the polymerization degree of the product poly(methyl methacrylate) of Example 2.

[0063] Figure 4 The graph of the relationship between the molar ratio of the polymerization initiator 2-bromopropionic acid ethyl ester and the monomer methyl methacrylate in the visible light photocatalytic controlled polymerization reaction of methyl methacrylate monomers and the number average molecular weight of the product poly(methyl methacrylate) of Examples 3-7.

[0064] Figure 5 The graph of the relationship between the reaction conversion rate caused by the alternately turning on and off of the visible light source during the visible light photocatalytic controlled polymerization reaction of methyl methacrylate monomers of Example 8 and the reaction time.

[0065] Figure 6 The one-dimensional nuclear magnetic resonance spectrum of the metal-free molecular photocatalyst capable of realizing visible light photocatalytic controlled polymerization reaction of monomers of Example 9.

[0066] Figure 7 The mass spectrum data spectrum of the metal-free molecular photocatalyst capable of realizing visible light photocatalytic controlled polymerization reaction of monomers of Example 9.

[0067] Figure 8 The gel permeation chromatogram of the product of the visible light photocatalytic controlled polymerization reaction of methyl methacrylate monomers of Example 10.

[0068] Figure 9 The gel permeation chromatogram of the product of the visible light photocatalytic controlled polymerization reaction of butyl methacrylate and methyl acrylate monomers of Examples 11 and 12. DETAILED DESCRIPTION

[0069] The technical solutions of the present application will be further described in detail below in combination with specific examples. It should be understood that the following examples are only illustratively described and explained, and should not be interpreted as limiting the scope of protection of the present application. Any technology realized based on the above description of the present application is covered within the scope of protection intended by the present application.

[0070] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0071] Example 1

[0072] A metal-free molecular photocatalyst capable of realizing visible light photocatalytic controlled polymerization reaction of monomers was prepared, in which fluorene was the electron donor fragment and benzothiadiazole was the electron acceptor fragment, and the molecular formula was as follows:

[0073]

[0074] The preparation method of the metal-free molecular photocatalyst comprises the following steps:

[0075] (1) The synthesis step of the molecule 1: 580 mg of 9,9-dihexyl-2-bromofluorene, 540 mg of bis(pinacolato)diboron, 410 mg of potassium acetate, and 100 mg of [1,1'-bis(diphenylphosphino)ferrocene] dichloropalladium are weighed and added into 50 mL of 1,4-dioxane solution, argon is introduced for 30 minutes, and the reaction is carriedied out at 85°C for 20 hours. After the solvent is removed under vacuum, the organic phase is extracted and washed with 3*40 mL of ethyl acetate and 80 mL of saturated brine respectively, dried by adding sodium sulfate, and purified by column chromatography (using dichloromethane as an eluent) to obtain 540 mg of the product molecule 1.

[0076] (2) The synthesis step of the metal-free molecular photocatalyst capable of realizing visible light catalytic monomer controlled polymerization reaction: 320 mg of the product molecule 1 obtained in step (1), 89 mg of 4,7-dibromo-2,1,3-benzothiadiazole, 125 mg of potassium carbonate, and 35 mg of tetrakis(triphenylphosphine)palladium are taken and added into 40 mL of a mixed solution of 1,4-dioxane and 8 mL of water, argon is introduced for 30 minutes, and the reaction is carriedied out at 85°C for 8 hours. After the solvent is removed under vacuum, the organic phase is extracted and washed with 3*40 mL of dichloromethane and 80 mL of saturated brine respectively, dried by adding sodium sulfate, and purified by column chromatography (using dichloromethane as an eluent) to obtain 220 mg of the target metal-free molecular photocatalyst capable of realizing visible light catalytic monomer controlled polymerization reaction. The organic synthesis preparation route is as shown in the following:

[0077]

[0078] The nuclear magnetic resonance data graph of the metal-free molecular photocatalyst capable of realizing visible light catalytic monomer controlled polymerization reaction prepared in this embodiment is as shown in Figure 1 The mass spectrum data graph is as shown in Figure 2 From the graph, it can be seen that the metal-free molecular photocatalyst capable of realizing visible light catalytic monomer controlled polymerization reaction is successfully prepared, and the relative molecular mass is 800.510 g / mol.

[0079] Example 2

[0080] The specific experimental method of the visible light catalytic monomer controlled polymerization reaction comprises the following steps:

[0081] (1) Add 800 μL of N,N-dimethylformamide as a solvent, 213 μL of methyl methacrylate as a monomer, 0.64 mg of the metal-free molecular photocatalyst prepared in Example 1, 5.2 μL of ethyl 2-bromopropionate as a polymerization initiator, and 112 μL of triethylamine as an electron donor to the sample vial. The molar ratio of monomer to initiator, electron donor, and catalyst is 50:1:20:0.02. Seal the vial after thoroughly purging oxygen from the system.

[0082] (2) Place the deoxygenated and sealed sample vial from step (1) in water, and use water cooling to control the reaction at 25°C. At 470 nm and 100 mW / cm², 2 The reaction was carried out under LED light source illumination and magnetic stirring for 6 hours.

[0083] (3) Take 200 μL of the solution after the reaction in step (2) and add it to deuterated chloroform. Measure the conversion rate of the visible light photocatalytic controlled polymerization reaction of methyl methacrylate monomer by nuclear magnetic resonance hydrogen spectroscopy. Drop the remaining reaction solution from step (2) into 200 mL of methanol and stir for 1 hour to allow polymethyl methacrylate to be fully extracted. Then filter the product through a polytetrafluoroethylene filter, wash it three times with methanol, and dry it to obtain the polymethyl methacrylate product.

[0084] 3 mg of polymethyl methacrylate (PMMA) product was dissolved in 1 mL of N,N-dimethylformamide. The molecular weight and degree of polymerization (DOP) of the PMMA polymer were determined by gel permeation chromatography. The relationship between the conversion rate of the visible light photocatalyzed controlled polymerization of PMMA monomer and the DOP of the product PMMA is as follows: Figure 3 As shown in the figure, it can be seen that as the reaction time of the visible light photocatalytic monomer controllable polymerization reaction is extended (1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours), the monomer conversion rate gradually increases, but the degree of polymerization dispersion coefficient of the product remains at about 1.3, thus achieving controllability of the degree of polymerization dispersion coefficient of the polymerization product.

[0085] Example 3

[0086] The specific experimental method for the visible light photocatalytic monomer controllable polymerization reaction is basically the same as that in Example 2, except that: step (1) is as follows: 800 μL of N,N-dimethylformamide as solvent and 213 μL of methyl methacrylate as monomer are added to the sample bottle, along with 0.32 mg of the metal-free molecular photocatalyst prepared in Example 1, 2.6 μL of ethyl 2-bromopropionate as polymerization initiator, and 56 μL of triethylamine as electron donor; wherein the molar ratio of monomer to initiator, electron donor, and photocatalyst is 100:1:20:0.02, respectively; after fully purging the oxygen in the system, it is sealed.

[0087] Example 4

[0088] The specific experimental method of the visible light photocatalytic monomer controllable polymerization reaction is basically the same as that of Example 2, except that in step (1), 800 μL of N,N-dimethylformamide is added as a solvent, 213 μL of methyl methacrylate is added as a monomer, 0.16 mg of the metal-free molecular photocatalyst prepared in Example 1 is added, 1.3 μL of 2-bromopropionic acid ethyl ester is added as a polymerization initiator, and 28 μL of triethylamine is added as an electron donor; wherein the molar ratio of the monomer to the initiator, the electron donor and the photocatalyst is 200:1:20:0.02 respectively; and the system is sealed after the oxygen in the system is sufficiently exhausted.

[0089] Example 5

[0090] The specific experimental method of the visible light photocatalytic monomer controllable polymerization reaction is basically the same as that of Example 2, except that in step (1), 800 μL of N,N-dimethylformamide is added as a solvent, 213 μL of methyl methacrylate is added as a monomer, 0.08 mg of the metal-free molecular photocatalyst prepared in Example 1 is added, 0.65 μL of 2-bromopropionic acid ethyl ester is added as a polymerization initiator, and 14 μL of triethylamine is added as an electron donor; wherein the molar ratio of the monomer to the initiator, the electron donor and the photocatalyst is 400:1:20:0.02 respectively; and the system is sealed after the oxygen in the system is sufficiently exhausted.

[0091] Example 6

[0092] The specific experimental method of the visible light photocatalytic monomer controllable polymerization reaction is basically the same as that of Example 2, except that in step (1), 800 μL of N,N-dimethylformamide is added as a solvent, 213 μL of methyl methacrylate is added as a monomer, 0.06 mg of the metal-free molecular photocatalyst prepared in Example 1 is added, 0.43 μL of 2-bromopropionic acid ethyl ester is added as a polymerization initiator, and 9.3 μL of triethylamine is added as an electron donor; wherein the molar ratio of the monomer to the initiator, the electron donor and the photocatalyst is 600:1:20:0.02 respectively; and the system is sealed after the oxygen in the system is sufficiently exhausted.

[0093] Example 7

[0094] The specific experimental method of the visible light photocatalytic monomer controllable polymerization reaction is basically the same as that of Example 2, except that in step (1), 800 μL of N,N-dimethylformamide is added as a solvent, 213 μL of methyl methacrylate is added as a monomer, 0.04 mg of the metal-free molecular photocatalyst prepared in Example 1 is added, 0.32 μL of 2-bromoethyl propionate is added as a polymerization initiator, and 7.0 μL of triethylamine is added as an electron donor. The molar ratio of the monomer to the initiator, the electron donor, and the photocatalyst is 800:1:20:0.02. After the oxygen in the system is sufficiently exhausted, the system is sealed.

[0095] The relationship between the molar ratio of the polymerization initiator 2-bromoethyl propionate and the monomer methyl methacrylate in the visible light photocatalytic methyl methacrylate monomer controllable polymerization reaction in Examples 3-7 and the number average molecular weight of the product polymethyl methacrylate is shown in FIG. 1. As can be seen from the figure, by controlling the ratio of the photocatalyst, the polymerization initiator, the electron donor, and the monomer, the number average molecular weight of the product polymethyl methacrylate can be controllably changed from 13.6 kg / mol to 25.1 kg / mol. Figure 4

[0096] Example 8

[0097] The visible light excitation light source is one of the necessary conditions for realizing the visible light photocatalytic monomer controllable polymerization reaction. By controlling the presence or absence of the visible light source, the present application can very sensitively control the progress and termination of the controllable polymerization reaction. The specific experimental method is as follows:

[0098] (1) 800 μL of N,N-dimethylformamide is added as a solvent, 213 μL of methyl methacrylate is added as a monomer, 0.64 mg of the metal-free molecular photocatalyst prepared in Example 1 is added, 5.2 μL of 2-bromoethyl propionate is added as a polymerization initiator, and 112 μL of triethylamine is added as an electron donor. The molar ratio of the monomer to the initiator, the electron donor, and the photocatalyst is 50:1:20:0.02. After the oxygen in the system is sufficiently exhausted, the system is sealed.

[0099] (2) The sample bottle sealed after oxygen removal in step (1) is placed in water, and the reaction is controlled at 25°C under water cooling. The 470 nm, 100 mW / cm 2 LED light source is alternately turned on and off every half hour, and the conversion rate of the visible light photocatalytic methyl methacrylate monomer controllable polymerization reaction changes with time as shown in FIG. 2. Figure 5 ​As can be seen from the figure: when the light source is turned on, the conversion rate of the controlled polymerization reaction of methyl methacrylate monomer continues to rise. When the light source is turned off, the conversion rate of the controlled polymerization reaction of methyl methacrylate monomer hardly changes, and when the light source is turned on again, the polymerization reaction of methyl methacrylate monomer can continue. Therefore, by controlling the on-off of the LED light source, the occurrence and stop of the controlled polymerization reaction can be very sensitive.

[0100] Example 9

[0101] The metal-free molecular photocatalyst for visible light photocatalytic controlled polymerization of monomers has the following molecular formula:

[0102]

[0103] The preparation method of the metal-free molecular photocatalyst comprises the following steps:

[0104] (1) Synthesis of molecule 2: 1.00 g of 9,9-dihexyl-2-bromofluorene, 2.06 g of bisbinaphthylboron, 1.58 g of potassium acetate and 385 mg of [1,1'-bis(diphenylphosphino)ferrocene] dichloropalladium are weighed and added to 50 mL of 1,4-dioxane solution, argon is introduced for 30 minutes, and the reaction is carried out at 85°C for 20 hours. After removing the solvent under vacuum, the organic phase is extracted and washed with 3×40 mL of ethyl acetate and 80 mL of saturated brine, respectively, and dried with sodium sulfate, and purified by column chromatography (using a mixture of petroleum ether: dichloromethane with a volume ratio of 20:1 as eluent) to obtain 1.03 g of product molecule 2.

[0105] (2) Synthesis of molecule 3: 700 mg of product molecule 2 obtained in step (1), 2.23 g of 9,9-dihexyl-2,7-dibromofluorene, 8 mL of 4.0M potassium carbonate aqueous solution and 175 mg of tetrakis(triphenylphosphine)palladium are weighed and added to 40 mL of 1,4-dioxane, argon is introduced for 30 minutes, and the reaction is carried out at 85°C for 8 hours. After removing the solvent under vacuum, the organic phase is extracted and washed with 3×40 mL of dichloromethane and 80 mL of saturated brine, respectively, and dried with sodium sulfate, and purified by column chromatography (using a mixture of petroleum ether: dichloromethane with a volume ratio of 15:1 as eluent) to obtain 820 mg of product molecule 3.

[0106] (3) Synthesis of molecule 4: 800 mg of product molecule 3 obtained in step (2), 589 mg of bis(pinacolato)diboron, 456 mg of potassium acetate and 57 mg of [1,1'-bis(diphenylphosphino)ferrocene] palladium dichloride were added into 50 mL of 1,4-dioxane solution, argon was introduced for 30 minutes, and then the mixture was reacted at 85°C for 20 hours. After removing the solvent under vacuum, the organic phase was extracted and washed with 3*40 mL of ethyl acetate and 80 mL of saturated brine respectively, dried by adding sodium sulfate, and then purified by column chromatography (using a mixture of petroleum ether: dichloromethane with a volume ratio of 10:1 as eluent) to obtain 510 mg of product molecule 4.

[0107] (4) Synthesis of molecule 5: 510 mg of product molecule 4 obtained in step (3), 233 mg of 4-bromo-2,1,3-benzothiadiazole, 8 mL of 4.0 M potassium carbonate aqueous solution and 104 mg of tetrakis(triphenylphosphine)palladium were added into 40 mL of 1,4-dioxane, argon was introduced for 30 minutes, and then the mixture was reacted at 85°C for 8 hours. After removing the solvent under vacuum, the organic phase was extracted and washed with 3*40 mL of dichloromethane and 80 mL of saturated brine respectively, dried by adding sodium sulfate, and then purified by column chromatography (using a mixture of petroleum ether: dichloromethane with a volume ratio of 2:1 as eluent) to obtain 239 mg of product molecule 5.

[0108] (5) Synthesis of metal-free molecular photocatalyst for visible light photocatalytic monomer controlled polymerization: 230 mg of product molecule 5 obtained in step (4), 56 mg of o-phenylenediamine and 182 mg of sodium metabisulfite were added into 50 mL of N,N-dimethylformamide solution, argon was introduced for 30 minutes, and then the mixture was reacted at 95°C for 6 hours. After removing the solvent under vacuum, the organic phase was extracted and washed with 3*40 mL of chloroform and 80 mL of saturated brine respectively, dried by adding sodium sulfate, and then purified by column chromatography (using a mixture of petroleum ether: dichloromethane with a volume ratio of 1:1 as eluent) to obtain 120 mg of metal-free molecular photocatalyst for visible light photocatalytic monomer controlled polymerization. The organic synthesis preparation route is shown in the following:

[0109]

[0110] The nuclear magnetic resonance data of the metal-free molecular photocatalyst for visible light photocatalytic monomer controlled polymerization prepared in the example is shown in Figure 6 The mass spectrum data is shown in Figure 7 From the figures, it can be seen that the metal-free molecular photocatalyst for visible light photocatalytic monomer controlled polymerization is successfully prepared, and the relative molecular mass is 661.282 g / mol.

[0111] Example 10

[0112] The specific experimental method of the visible light photocatalytic monomer controllable polymerization reaction comprises the following steps:

[0113] (1) 800 μL of N,N-dimethylformamide as a solvent, 213 μL of methyl methacrylate as a monomer, 0.80 mg of the metal-free molecular photocatalyst prepared in Example 9, 5.2 μL of 2-bromopropionic acid ethyl ester as a polymerization initiator, and 112 μL of triethylamine as an electron donor were added to a sample bottle. The molar ratio of the monomer to the initiator, the electron donor, and the catalyst was 50:1:20:0.02. After the oxygen in the system was sufficiently exhausted, the sample bottle was sealed.

[0114] (2) The sample bottle sealed after oxygen removal in step (1) was placed in water, and the reaction was controlled at 25°C under water cooling. Under the irradiation of a 470 nm, 100 mW / cm 2 LED light source, the reaction was magnetically stirred for 6 hours.

[0115] (3) The solution after the reaction in step (2) was dropped into 200 mL of methanol, stirred for 1 hour to allow the polymethyl methacrylate to be eluted, then filtered with a polytetrafluoroethylene filter, washed with methanol three times, and dried to obtain the polymethyl methacrylate product.

[0116] 3 mg of the polymethyl methacrylate product was taken out and dissolved in 1 mL of N,N-dimethylformamide, and the molecular weight and the polydispersity index of the polymethyl methacrylate polymer were determined by gel permeation chromatography. The gel permeation chromatography curve is shown in Figure 8 . The number average molecular weight of the product was 13.8 kg / mol, and the polydispersity index was 1.29. This indicates that the controllable preparation of the polydispersity index of the polymethyl methacrylate is achieved.

[0117] Example 11

[0118] The specific experimental method of the visible light photocatalytic monomer controllable polymerization reaction comprises the following steps:

[0119] (1) 800 μL of N,N-dimethylformamide as a solvent, 213 μL of methyl methacrylate as a monomer, 0.80 mg of the metal-free molecular photocatalyst prepared in Example 9, 5.2 μL of 2-bromopropionic acid ethyl ester as a polymerization initiator, and 112 μL of triethylamine as an electron donor were added to a sample bottle. The molar ratio of the monomer to the initiator, the electron donor, and the catalyst was 50:1:20:0.02. After the oxygen in the system was sufficiently exhausted, the sample bottle was sealed.

[0120] (2) The sample bottle sealed after oxygen removal in step (1) was placed in water, and the reaction was controlled at 25°C under water cooling. Under the irradiation of a 470 nm, 100 mW / cm 2under the irradiation of the LED light source, the reaction was carried out under magnetic stirring for 6 hours.

[0121] (3) The solution after the reaction of step (2) was dropped into 200 mL of methanol, stirred for 1 hour to make the polybutyl methacrylate precipitate, then filtered with a polytetrafluoroethylene filter screen, washed with methanol for three times, and dried to obtain the polybutyl methacrylate product.

[0122] 3 mg of the polybutyl methacrylate product was taken out and dissolved in 1 mL of N,N-dimethylformamide, and the molecular weight and the polydispersity index of the polybutyl methacrylate polymer were determined by gel permeation chromatography, and the gel permeation chromatography curve is shown in Figure 9 The number average molecular weight of the product was 5.99 kg / mol, and the polydispersity index was 1.32. It is shown that the polybutyl methacrylate polymer with controllable polydispersity index is realized.

[0123] Example 12

[0124] The specific experimental method of the visible light photocatalytic monomer controllable polymerization reaction comprises the following steps:

[0125] (1) 800 μL of N,N-dimethylformamide was added to a sample bottle as a solvent, 179 μL of methyl acrylate was added as a monomer, 0.64 mg of the metal-free molecular photocatalyst prepared in Example 1 was added, 5.2 μL of 2-bromopropyl ethyl ester was added as a polymerization initiator, and 112 μL of triethylamine was added as an electron donor. The molar ratio of the monomer to the initiator, the electron donor and the catalyst is 50:1:20:0.02. After the oxygen in the system is fully exhausted, it is sealed.

[0126] (2) The sample bottle sealed after oxygen removal in step (1) was placed in water, and the reaction was carried out at 25℃ under water cooling. Under the irradiation of the LED light source with a wavelength of 470 nm and a power of 100 mW / cm 2 , the reaction was carried out under magnetic stirring for 6 hours.

[0127] (3) The solution after the reaction of step (2) was dropped into 200 mL of methanol, stirred for 1 hour to make the polybutyl methacrylate precipitate, then filtered with a polytetrafluoroethylene filter screen, washed with methanol for three times, and dried to obtain the polybutyl methacrylate product.

[0128] 3 mg of the polybutyl methacrylate product was taken out and dissolved in 1 mL of N,N-dimethylformamide, and the molecular weight and the polydispersity index of the polybutyl methacrylate polymer were determined by gel permeation chromatography, and the gel permeation chromatography curve is shown in Figure 9 . The number average molecular weight of the product was 5.99 kg / mol, and the polydispersity index was 1.32. It is shown that the polybutyl methacrylate polymer with controllable polydispersity index is realized.

[0129] The above describes the embodiments of the present application. However, the present application is not limited to the above-described embodiments. Any modification, equivalent replacement, improvement, and the like made within the spirit and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A photocatalyst characterized by comprising: The photocatalyst has the structure shown in the following formula I: Formula I.

2. Application of a photocatalyst in catalyzing a polymerization reaction of an acrylic monomer molecule, comprising exciting the monomer to occur polymerization reaction by a visible light source in the presence of a polymerization initiator and an electron donor with the photocatalyst and the monomer; The photocatalyst has the structure shown in the following formula I or formula II: Formula I Formula II The monomer is an acrylic compound. The polymerization initiator is any one of 2-bromopropionic acid ethyl ester, alpha-bromophenylacetic acid ethyl ester, 2-bromoisobutyric acid ethyl ester, bromo-malonic acid diethyl ester, (1-bromoethyl)benzene and 4-bromoacetophenone. The electron donor is any one of triethylamine, triethanolamine, N,N,N,N-tetramethyl-1,4-butanediamine and N,N,N',N'',N''-pentamethyldiethylenetriamine.

3. A polymerization process characterized by, The photocatalyst has the structure shown in the following formula I or formula II: Formula I Formula II The monomer is an acrylic compound. The polymerization initiator is any one of 2-bromopropionic acid ethyl ester, alpha-bromophenylacetic acid ethyl ester, 2-bromoisobutyric acid ethyl ester, bromo-malonic acid diethyl ester, (1-bromoethyl)benzene and 4-bromoacetophenone. The electron donor is any one of triethylamine, triethanolamine, N,N,N,N-tetramethyl-1,4-butanediamine and N,N,N',N'',N''-pentamethyldiethylenetriamine. The monomer is methyl methacrylate, butyl methacrylate or methyl acrylate.

4. The polymerization process of claim 3 wherein, The polymerization reaction is carried out in a solvent system, and the solvent is any one or a blend of several of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, tetrahydrofuran and chloroform.

5. The polymerization process of claim 3 wherein, The concentration of the monomer is 10 mg / mL to 2 g / mL.

6. The polymerization process of claim 3 wherein, The molar ratio of the monomer to the polymerization initiator is 25:1 to 1000:

1.

7. The polymerization process of claim 3 wherein, The molar ratio of the monomer to the polymerization initiator is 50:1 to 800:

1.

8. The polymerization process of claim 7 wherein, The molar ratio of the polymerization initiator to the photocatalyst is 1:0.1 to 1:0.00001.

9. The polymerization process of claim 3 wherein, The molar ratio of the polymerization initiator to the photocatalyst is 1:0.1 to 1:0.

05.

10. The polymerization process of claim 9, wherein, The molar ratio of the polymerization initiator to the electron donor is 1:0.1 to 1:

40.

11. The polymerization process of claim 3 wherein, The reaction temperature of the polymerization reaction is 15°C to 30°C, and the time of the polymerization reaction is 10 minutes to 10 hours.

12. The polymerization process according to any one of claims 3 to 11, characterized in that, ​

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