A raft reagent for photo-controlled polymerization and preparation method and application thereof

Abstract

The application discloses a kind of for light-controlled polymerization RAFT reagent and its preparation method and application, belong to RAFT reagent synthesis technical field.The structure general formula of the RAFT reagent for light-controlled polymerization of the application is: R2, R3All be selected from hydrogen atom, R1It is selected from methyl.The structure of the RAFT reagent is stable, and simple in synthesis, can realize fast light-controlled polymerization under blue light.It is proved that when the RAFT reagent is used for polymerization, reaction time only needs a few minutes, and acrylic ester and acrylamide monomer can realize higher conversion rate.Moreover, when the RAFT reagent is used for polymerization, it is not necessary to introduce additional initiator or photocatalyst, and the RAFT reagent itself can carry out chain initiation and chain transfer process under blue light.Compared with other light-controlled polymerization, not only polymerization rate is faster, but also additional impurities are not introduced in final product, and it will not affect polymerization color and performance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of synthesis of RAFT reagents, and particularly relates to a RAFT reagent for light-controlled polymerization and a preparation method and application thereof. BACKGROUND

[0002] The information disclosed in this Background section is only for the purpose of increasing the understanding of the general background of the application and does not necessarily constitute an admission or any kind of suggestion that this information forms the prior art already known to a person of ordinary skill in the art.

[0003] RAFT polymerization is the abbreviation of Reversible Addition-Fragmentation Chain Transfer Polymerization. RAFT polymerization can precisely control the structure of polymers, including average molecular weight, polydispersity and specific functions. This control can synthesize polymers with customized properties and specific structures, such as block copolymers, star polymers, gradient copolymers, etc. RAFT polymerization is compatible with various monomers, including hydrophilic and hydrophobic monomers, as well as various functional monomers. In addition, RAFT polymerization has very good compatibility in various solvents. RAFT polymerization can be carried out in various solvents, whether polar or non-polar. In general, the advantages of RAFT polymerization make it a powerful tool for synthesizing polymers with specific functions and specific chain lengths, enabling enhanced control over polymer structure and function, and widely used in academic research and industrial production.

[0004] The combination of light-controlled polymerization and RAFT polymerization enables RAFT polymerization to control polymerization in time, thereby more conveniently obtaining polymers with target molecular weight and low dispersity. Light-controlled RAFT polymerization is a technology that uses light to initiate, regulate or terminate the polymerization process. Compared with traditional methods, it has the advantages of spatial and temporal control, low energy consumption and less by-products. In recent years, the field of light-controlled polymerization has developed rapidly and is widely used in the fields of materials science, biotechnology, nanotechnology, etc. However, current light-controlled RAFT polymerization still faces some challenges, such as slow polymerization rate, the need to add photo-initiators, etc. SUMMARY

[0005] In order to solve the problems of the prior art, the purpose of the present application is to provide a RAFT reagent for light-controlled polymerization and a preparation method and application thereof. The RAFT reagent provided by the present application has stable structure and chemical properties, is simple to synthesize, and can perform fast light-controlled polymerization.

[0006] In order to achieve the above-mentioned purpose, the technical scheme of the present application is as follows:

[0007] In a first aspect, the present invention provides a RAFT reagent for photopolymerization, wherein the general structural formula of the RAFT reagent for photopolymerization is:

[0008]

[0009] Among them, R1, R2, and R3 are all selected from hydrogen atoms;

[0010] Alternatively, R2 and R3 are both selected from hydrogen atoms, and R1 is selected from methyl groups;

[0011] Alternatively, R1 is selected from methyl, R2 is selected from bromine atom, and R3 is selected from hydrogen atom;

[0012] Alternatively, R1 is selected from methyl, R2 is selected from hydrogen atom, and R3 is selected from methoxy.

[0013] In some embodiments of the present invention, R2 and R3 are both selected from hydrogen atoms, and R1 is selected from methyl.

[0014] A second aspect of the present invention provides a method for preparing the above-described RAFT reagent for photopolymerization, comprising the following steps:

[0015] Will The metal hydroxide was dissolved in a solvent, and the reaction system was kept warm in an ice-water bath. Then, carbon disulfide was added dropwise while the reaction was continuously stirred in an ice-water bath to obtain intermediate product I.

[0016] Intermediate product I was dissolved in a solvent, an oxidizing agent was added, and the mixture was stirred to react, yielding intermediate product II.

[0017] Intermediate product II and azobisisovalerate were dissolved in a solvent, heated and stirred, and nitrogen gas was introduced. After the reaction was completed, the RAFT reagent for photocontrolled polymerization was obtained.

[0018] The structure of intermediate product I is shown in Formula I, and the structure of intermediate product II is shown in Formula II.

[0019]

[0020] Among them, R1, R2, and R3 are all selected from hydrogen atoms;

[0021] Alternatively, R2 and R3 are both selected from hydrogen atoms, and R1 is selected from methyl groups;

[0022] Alternatively, R1 is selected from methyl, R2 is selected from bromine atom, and R3 is selected from hydrogen atom;

[0023] Alternatively, R1 is selected from methyl, R2 is selected from hydrogen atom, and R3 is selected from methoxy.

[0024] In some embodiments of the present invention, the metal hydroxide is selected from at least one of potassium hydroxide and sodium hydroxide.

[0025] In some embodiments of the present application, the solvent comprises tetrahydrofuran or acetone.

[0026] In some embodiments of the present application, after adding carbon disulfide and stirring until the reaction is completed, the product is extracted, washed with deionized water, dried, and the intermediate product I is obtained.

[0027] In some embodiments of the present application, after adding the oxidizing agent and stirring until the reaction is completed, the solvent and the oxidizing agent are removed, the product is extracted, dried, and the intermediate product II is obtained.

[0028] In some embodiments of the present application, the oxidizing agent comprises elemental iodine.

[0029] In some embodiments of the present application, the product is rotary evaporated to remove the solvent.

[0030] In some embodiments of the present application, a reducing agent is added to remove the oxidizing agent; preferably, the reducing agent comprises sodium thiosulfate.

[0031] In some embodiments of the present application, after the reaction is completed, the solvent is removed by passing nitrogen and heating, and the product is purified by column chromatography to obtain the RAFT agent for photo-controlled polymerization.

[0032] Preferably, when the product is purified by column chromatography, the mobile phase is a mixed solution of petroleum ether and ethyl acetate in a volume ratio of 10:1.

[0033] In a third aspect of the present application, the use of the above-mentioned RAFT agent in a RAFT polymerization reaction is provided, and the RAFT polymerization reaction is a photo-controlled polymerization reaction.

[0034] In some embodiments of the present application, the photo-controlled polymerization reaction is as follows: the monomer, the RAFT agent of claim 1, and the solvent are mixed uniformly, and the reaction is carried out under blue light of 420-430 nm to obtain a polymer.

[0035] The present application has the following beneficial effects:

[0036] The RAFT reagent provided by the application has stable structure and chemical properties, is simple to synthesize, and can realize rapid photo-controlled polymerization under blue light. It has been verified that when the RAFT reagent is used for polymerization, the reaction time is only a few minutes, and high conversion rates of acrylate and acrylamide monomers can be realized, which is much less than the reaction time of other photo-controlled polymerization (such as PET-RAFT polymerization, photo-ATRP polymerization, etc.). Moreover, when the RAFT reagent is used for polymerization, no additional initiator or photocatalyst needs to be introduced, and the RAFT reagent itself can perform chain initiation and chain transfer processes under blue light. Compared with other photo-controlled polymerization (such as PET-RAFT polymerization, photo-ATRP polymerization, etc.), the polymerization rate is faster, and no additional impurities are introduced into the final product, which does not affect the color and performance of the polymerization. BRIEF DESCRIPTION OF DRAWINGS

[0037] The accompanying drawings, which form a part of the present description, illustrate the present application and together with the description serve to explain the application. In the drawings that are included to provide a further understanding of the application and of its

[0038] Figure 1 HNMR chart of RAFT1 (Z1) prepared for Example 1 of the application 1 HNMR chart of RAFT1 (Z1) prepared for Example 1 of the application

[0039] Figure 2 HNMR chart of RAFT2 (Z2) prepared for Example 2 of the application 1 HNMR chart of RAFT2 (Z2) prepared for Example 2 of the application

[0040] Figure 3 HNMR chart of RAFT3 (Z3) prepared for Example 3 of the application 1 HNMR chart of RAFT3 (Z3) prepared for Example 3 of the application

[0041] Figure 4 HNMR chart of RAFT4 (Z4) prepared for Example 4 of the application 1 HNMR chart of RAFT4 (Z4) prepared for Example 4 of the application

[0042] Figure 5 UV-visible absorption spectrum of the RAFT reagent prepared for the application, which can be used as a basis for selecting a light source

[0043] Figure 6 HNMR chart of RAFT2 (Z2) 1 HNMR chart of RAFT2 (Z2)

[0044] Figure 7 Polymerization kinetics broken line chart of RAFT2 (Z2) under different wavelengths

[0045] Figure 8The related graph of RAFT2(Z2) in oxygen and anaerobic environment; wherein, A is the kinetic broken line graph in anaerobic environment, B is M n and M w / M n The graph of change with conversion rate, C is the GPC molecular weight distribution graph in anaerobic environment; D is the kinetic broken line graph in oxygen environment, E is M n and M w / M n The graph of change with conversion rate, F is the GPC molecular weight distribution graph in oxygen environment;

[0046] Figure 9 The kinetic broken line graph of RAFT2(Z2) with different proportions;

[0047] Figure 10 The GPC graph of RAFT2(Z2) with different proportions. DETAILED DESCRIPTION

[0048] The embodiment of the present application provides a RAFT reagent, wherein, the indazole compound group is used as the Z group of the RAFT reagent, and the R group is a structure that has been reported, and the structural general formula of the RAFT reagent for light-controlled polymerization is as follows:

[0049]

[0050] Wherein, R1, R2, R3 are all selected from hydrogen atoms;

[0051] Or, R2 and R3 are both selected from hydrogen atoms, and R1 is selected from a methyl group;

[0052] Or, R1 is selected from a methyl group, R2 is selected from a bromine atom, and R3 is selected from a hydrogen atom;

[0053] Or, R1 is selected from a methyl group, R2 is selected from a hydrogen atom, and R3 is selected from a methoxy group.

[0054] In the embodiment, when R1, R2 and R3 are all selected from hydrogen atoms, that is, the Z group is an indazole group, in order to distinguish from other types of Z groups, the Z group is named as a Z1 group, and the structure of the Z1 group is as follows:

[0055]

[0056] In the embodiment, when R2 and R3 are both selected from hydrogen atoms, and R1 is selected from a methyl group, that is, the Z group is a methyl-substituted indazole group, the Z group is named as a Z2 group, and the structure of the Z2 group is as follows:

[0057]

[0058] In this embodiment, when R1 is selected from methyl, R2 is selected from bromine atoms, and R3 is selected from hydrogen atoms, that is, when the Z group is a disubstituted indazole group, this Z group is named the Z3 group, and the structure of the Z3 group is as follows:

[0059]

[0060] In this embodiment, when R1 is selected from methyl, R2 is selected from hydrogen atoms, and R3 is selected from methoxy, that is, when the Z group is a disubstituted indazole group, this Z group is named the Z4 group, and the structure of the Z4 group is as follows:

[0061]

[0062] This invention also provides a method for preparing the RAFT reagent described herein, comprising the following steps:

[0063] Will The metal hydroxide was dissolved in a solvent, and the reaction system was kept warm in an ice-water bath. Then, carbon disulfide was added dropwise while the reaction was continuously stirred in an ice-water bath to obtain intermediate product I.

[0064] Intermediate product I was dissolved in a solvent, an oxidizing agent was added, and the mixture was stirred to react, yielding intermediate product II.

[0065] Intermediate product II and azobisisovalerate were dissolved in a solvent, heated and stirred, and nitrogen gas was introduced. After the reaction was completed, the RAFT reagent for photocontrolled polymerization was obtained.

[0066] The structure of intermediate product I is shown in Formula I, and the structure of intermediate product II is shown in Formula II.

[0067]

[0068] Among them, R1, R2, and R3 are all selected from hydrogen atoms;

[0069] Alternatively, R2 and R3 are both selected from hydrogen atoms, and R1 is selected from methyl groups;

[0070] Alternatively, R1 is selected from methyl, R2 is selected from bromine atom, and R3 is selected from hydrogen atom;

[0071] Alternatively, R1 is selected from methyl, R2 is selected from hydrogen atom, and R3 is selected from methoxy.

[0072] In this embodiment, It can be selected from one of indazole, 3-methyl-1H-indazole, 5-bromo-3-methyl-1H-indazole or 6-methoxy-3-methyl-1H-indazole.

[0073] The preparation method is simple and efficient, the prepared RAFT reagent has stable structure and chemical property, can be used for fast photo-controlled polymerization, is suitable for various monomers, does not introduce additional groups into the final product, and does not have additional influence on the properties of the final product.

[0074] In the embodiment, a suitable solvent can be selected according to actual needs, such as tetrahydrofuran, acetone and the like.

[0075] In an embodiment, the metal hydroxide is at least one selected from potassium hydroxide and sodium hydroxide, but is not limited thereto.

[0076] In an embodiment, after the carbon disulfide is added and the stirring reaction is completed, the product is suction filtered, washed with deionized water, dried, and the intermediate product I is obtained.

[0077] In an embodiment, after the oxidizing agent is added and the stirring reaction is completed, the solvent and the oxidizing agent are removed, extraction is performed, and drying is performed to obtain the intermediate product II.

[0078] The oxidizing agent includes, but is not limited to, oxygen, chlorine, bromine, iodine and the like.

[0079] The solvent can be removed by rotary evaporation of the product.

[0080] The oxidizing agent can be removed by adding a reducing agent.

[0081] The reducing agent includes, but is not limited to, sodium thiosulfate, ascorbic acid (Vitamin C), ferrous ammonium sulfate and the like.

[0082] In an embodiment, after nitrogen is introduced and the heating reaction is completed, the solvent is removed, the product is purified by column chromatography, and the RAFT reagent for photo-controlled polymerization is obtained.

[0083] When the product is purified by column chromatography, the mobile phase is a mixed solution of petroleum ether and ethyl acetate in a volume ratio of 10:1.

[0084] When the heating reaction is performed, the heating temperature is 70-80°C.

[0085] The embodiment of the present application also provides application of the RAFT reagent in the RAFT polymerization reaction, and the RAFT polymerization reaction is a photo-controlled polymerization reaction. In the embodiment, the RAFT reagent can be used for polymerization of various monomers and does not introduce additional groups into the final product, and does not have additional influence on the properties of the final product. Most importantly, when the RAFT reagent is used for the RAFT polymerization reaction, the polymerization rate of the monomer can be greatly improved. For the template monomer methyl acrylate, the conversion rate of the monomer can reach more than 77% under blue light illumination for 3 minutes.

[0086] In a further embodiment, the photo-controlled polymerization reaction is: mixing the monomer, the above-mentioned RAFT agent and the solvent uniformly, and irradiating under blue light of 420-430 nm to obtain the polymer. When the RAFT agent of the present application is used for the photo-controlled polymerization reaction, no photo-initiator needs to be added in the whole reaction system, no additional groups are introduced into the final product, and no additional influence is exerted on the properties of the final product.

[0087] In order to enable those skilled in the art to more clearly understand the technical solutions of the present application, the technical solutions of the present application will be described in detail below in combination with specific examples.

[0088] Example 1

[0089] Synthesis of RAFT1 (Z1):

[0090] The synthesis route is as follows:

[0091]

[0092] (1) Indazole (2 g) and potassium hydroxide (960 mg) were dissolved in 200 mL of tetrahydrofuran, and the reaction system was kept in an ice water bath for 15 min, then carbon disulfide (0.73 mL) was added dropwise and stirring was continued under the ice water bath for 4-6 h. The product was suction filtered and washed with deionized water for 3-5 times, and the solid product was dried to obtain the intermediate product I.

[0093] (2) The intermediate product I (2 g) was dissolved in tetrahydrofuran, then iodine (2.2 g) was added, and stirring was continued for 12 h; then the product was rotary evaporated to remove tetrahydrofuran, and an appropriate amount of aqueous sodium thiosulfate solution was added to remove excess iodine, and the product was extracted with diethyl ether and dried to obtain the intermediate product II.

[0094] (3) The intermediate product II (2 g) and azobisisovaleronitrile (1.85 g) were dissolved in 200 mL of ethyl acetate solution, and stirring was continued at 78°C for 16 h while nitrogen was continuously introduced; after heating was completed, the product was rotary evaporated to remove ethyl acetate, and the product was purified by column chromatography. The mobile phase was petroleum ether and ethyl acetate with a volume ratio of 10:1.

[0095] As shown in the following scheme, it has been verified that RAFT1 (Z1) is successfully synthesized. Figure 1

[0096] Example 2: Synthesis of RAFT2 (Z2):

[0097] The synthesis route of RAFT2 (Z2) is consistent with that of RAFT1 (Z1), except that the initial raw material is changed.

[0098] ​​​​​​​​​​​​​​​​​​​​​​​​​​​​(1), 3-methyl-1H-indazole (2 g), potassium hydroxide (850 mg) were dissolved in 200 mL of tetrahydrofuran, and the reaction system was kept in ice water bath for 20 min, then carbon disulfide (0.87 mL) was added dropwise and stirred under ice water bath for 10-12 h. The product was suction filtered, and washed with deionized water for 3-5 times, and the solid product was dried to obtain intermediate product I.

[0099] (2), intermediate product I (2 g) was dissolved in tetrahydrofuran, then iodine (2.06 g) was added, and stirred for 24 h; then the product was rotary evaporated to remove tetrahydrofuran, and an appropriate amount of aqueous sodium thiosulfate solution was added to remove excess iodine, and extracted with diethyl ether, dried to obtain intermediate product II.

[0100] (3), intermediate product II (2 g) and azobisisovaleronitrile (1.85 g) were dissolved in 200 mL of ethyl acetate solution, and stirred under heating at 78°C for 24 h, and nitrogen was continuously introduced; after heating was completed, the product was rotary evaporated to remove ethyl acetate, and the product was purified by column chromatography. The mobile phase was petroleum ether and ethyl acetate with a volume ratio of 12:1.

[0101] As shown in Figure 2 , it is verified that RAFT2 (Z2) is successfully synthesized.

[0102] Example 3: Synthesis of RAFT3 (Z3) :

[0103] The synthesis route of RAFT3 (Z3) is consistent with that of RAFT1 (Z1), except that the initial raw material is changed.

[0104] (1), 5-bromo-3-methyl-1H-indazole (2 g), potassium hydroxide (532 mg) were dissolved in 200 mL of tetrahydrofuran, and the reaction system was kept in ice water bath for 15 min, then carbon disulfide (0.57 mL) was added dropwise and stirred under ice water bath for 6-8 h. The product was suction filtered, and washed with deionized water for 3-5 times, and the solid product was dried to obtain intermediate product I.

[0105] (2), intermediate product I (2 g) was dissolved in tetrahydrofuran, then iodine (1.56 g) was added, and stirred for 12 h; then the product was rotary evaporated to remove tetrahydrofuran, and an appropriate amount of aqueous sodium thiosulfate solution was added to remove excess iodine, and extracted with diethyl ether, dried to obtain intermediate product II.

[0106] (3), Intermediate product II (2g) and azobisisovaleronitrile (810mg) were dissolved in 200ml of ethyl acetate solution, heated and stirred at 78℃ for 16h, and nitrogen was continuously introduced; after heating was completed, the product was rotary evaporated, and the ethyl acetate was removed, and the product was purified by column chromatography. The mobile phase was petroleum ether and ethyl acetate, and the volume ratio was 15:1.

[0107] As shown in Figure 3 , it is verified that RAFT3(Z3) is successfully synthesized.

[0108] Example 4: Synthesis of RAFT4(Z4):

[0109] The synthesis route of RAFT4(Z4) is consistent with that of RAFT1(Z1), except that the initial raw material is changed.

[0110] (1), 6-methoxy-3-methyl-1H-indazole (2g), potassium hydroxide (692mg) were dissolved in 200ml of tetrahydrofuran, and the reaction system was incubated in an ice water bath for 15min, then carbon disulfide (0.742ml) was added dropwise and stirred in an ice water bath for 6-8h. The product was suction filtered, washed with deionized water for 3-5 times, and the solid product was dried to obtain intermediate product I.

[0111] (2), Intermediate product I (2g) was dissolved in tetrahydrofuran, then iodine (1.84g) was added, and stirred for 12h; then the product was rotary evaporated, and the tetrahydrofuran was removed, and an appropriate amount of sodium thiosulfate aqueous solution was added to remove excess iodine, and extracted with diethyl ether, dried to obtain intermediate product II.

[0112] (3), Intermediate product II (2g) and azobisisovaleronitrile (810mg) were dissolved in 200ml of ethyl acetate solution, heated and stirred at 78℃ for 16h, and nitrogen was continuously introduced; after heating was completed, the product was rotary evaporated, and the ethyl acetate was removed, and the product was purified by column chromatography. The mobile phase was petroleum ether and ethyl acetate, and the volume ratio was 15:1.

[0113] As shown in Figure 4 , it is verified that RAFT4(Z4) is successfully synthesized.

[0114] Figure 5 The ultraviolet-visible absorption spectrum of the RAFT reagent prepared in examples 1-4 can be used as a basis for selecting light sources for each RAFT reagent.

[0115] Example 5: Verification of polymerization rate of RAFT reagent prepared in examples 1-4

[0116] 1. Kinetics experiment of light-controlled RAFT polymerization under blue light:

[0117] 1.1 Kinetic solution preparation: monomer and RAFT agent were configured into solution according to the molar ratio of [monomer]: [RAFT agent] = 200:1, and dimethyl sulfoxide was added as a solvent, and the volume ratio of monomer and solvent was 1:1. Among them, the monomer is methyl acrylate MA, and the RAFT agent is the RAFT agent prepared in examples 1-4.

[0118] 1.2 Kinetic experiment steps: 0.4 mL of the kinetic solution was transferred to a cuvette and sealed with a rubber plug and sealing film. Under the 420-430 nm 10 mW / cm 2 LED light, light irradiation was carried out, and the monomer vinyl C-H bond vibration absorption peak near 6200 cm -1 was integrated by Fourier infrared spectroscopy (FTIR), and the monomer residual amount was monitored by peak area, so as to track the conversion rate of the monomer, and the apparent polymerization rate (k p app ) was calculated by using the kinetic equation. When the monomer conversion rates were 40%, 50%, 60%, and 70% respectively, samples were taken, and gel permeation chromatography (GPC) was used to detect samples with different conversion rates to observe whether the molecular weight was controllable during polymerization, and the dispersity of the polymer was monitored. The test results are shown in Table 1.

[0119] Table 1 Polymerization rates of different RAFT agents

[0120]

[0121]

[0122] From Table 1, the polymerization rate ranking is: RAFT4>RAFT2>RAFT3>RAFT1. Based on the polymerization rate of each RAFT agent, and the synthesis cost of RAFT4 is relatively high, the RAFT agent used in the following examples is RAFT2 synthesized in Example 2.

[0123] Example 6: Performance verification of the RAFT agent prepared in the example

[0124] 1. Kinetic experiment of light-controlled RAFT polymerization under blue light:

[0125] 1.1 Kinetic solution preparation: monomer and RAFT agent were configured into solution according to the molar ratio of [monomer]: [RAFT agent] = 200:1, and dimethyl sulfoxide was added as a solvent, and the volume ratio of monomer and solvent was 1:1. Among them, the monomer is methyl acrylate MA, and the RAFT agent is the RAFT agent prepared in examples 1-4.

[0126] 1.2 Kinetic Experiment Procedure: Transfer 0.4 mL of the kinetic solution to a cuvette and seal it with a rubber stopper and sealing film. At 10 mW / cm²... 2 Illumination was performed under LED lights, and Fourier transform infrared spectroscopy (FTIR) was used to analyze the image at a depth of 6200 cm⁻¹. -1 The absorption peaks of the vinyl CH bond vibrations of the nearby monomers were integrated, and the remaining monomer amount was monitored at regular intervals and quantitatively by analyzing the peak area, thereby tracking the monomer conversion rate. The apparent polymerization rate (k) was then calculated using kinetic equations. p app Samples were taken at monomer conversion rates of approximately 40%, 50%, 60%, and 70%, respectively. Gel permeation chromatography (GPC) was used to analyze the samples at different conversion rates to observe whether the molecular weight was controllable during the polymerization process and to monitor the polymer dispersion. After the conversion rate reached approximately 70% (after the fourth sampling), the polymer was purified, and then nuclear magnetic resonance spectroscopy (NMR) was used to verify the retention of polymer molecular chain end groups.

[0127] Magnetic resonance spectroscopy (NMR) detection results are as follows Figure 6 As shown, the polymer molecular chain end groups retain the Z-terminal and R-terminal groups of RAFT2(Z2).

[0128] 2. Polymerization kinetics data of RAFT reagent (RAFT2 prepared in Example 2) under different wavelengths of LED light in an anaerobic environment:

[0129] As a renewable and clean energy source, how to fully utilize light energy has always been a hot research topic. To better utilize light energy, we measured the UV-Vis absorption of different RAFT reagents. We found that RAFT1-4 reagents all had absorption peaks in the 400-460 nm wavelength range. To utilize light energy more efficiently and fully, we screened the absorption wavelengths of RAFT reagents with the fastest polymerization rate through kinetic experiments at different wavelengths. We used RAFT2 reagent and methyl acrylate monomer as examples and conducted kinetic experiments at different wavelengths. The specific experimental data are shown in Table 2.

[0130] Table 2 Polymerization rates of RAFT reagents at different wavelengths

[0131]

[0132] Through Table 2 and Figure 7 It is known that the polymerization rate of RAFT reagent is highest at a wavelength of 420-430 nm. Therefore, the following experiments were conducted at a wavelength of 420-430 nm, comparing aerobic and anaerobic environments, different ratios of RAFT reagent, different solvents, and different monomers.

[0133] 3. Comparison of RAFT agent (RAFT2 prepared in Example 2) under the presence and absence of oxygen under 420-430 nm LED light:

[0134] In practical applications, the polymerization process is usually carried out in an open environment, and it is difficult to achieve an oxygen-free environment, which limits the application of RAFT agents. In order to better apply RAFT agents to various fields, it is necessary to solve the problem of oxygen tolerance of light-controlled RAFT polymerization. Since the polymerization mechanism itself belongs to free radical polymerization, it is easily affected by oxygen. Therefore, we carried out kinetic experiments on RAFT agents under the presence and absence of oxygen to study the oxygen tolerance of RAFT agents.

[0135] Table 3 Influence of oxygen on polymerization of RAFT agent under 420-430 nm LED light

[0136]

[0137] From Table 3 and Figure 8 It can be seen that the monomer polymerization rate under the presence of oxygen is lower than that under the absence of oxygen. RAFT polymerization follows the mechanism of free radical polymerization, and the free radicals generated by light are affected by oxygen and are easily quenched, so the polymerization rate under the absence of oxygen is higher than that under the presence of oxygen.

[0138] From A in Figure 8 , D in Figure 8 , it can be seen that when the light is stopped, the polymerization stops immediately, and when the light continues, the polymerization continues, and the light has very good control over the polymerization.

[0139] From B in Figure 8 , E in Figure 8 , it can be seen that even in the presence of oxygen, the polymerization is still controllable, and are all less than 1.2, which shows that even in the presence of oxygen, the control is very good.

[0140] 4. Polymerization of RAFT agent (RAFT2 prepared in Example 2) under different ratios in the absence of oxygen:

[0141] In the previous experiments, the ratio of monomer to RAFT agent was controlled at 200:1. For higher monomer ratios (such as 500:1, 1000:1), or lower monomer ratios (such as 100:1), in order to find the controllable range of RAFT agents, we carried out kinetic experiments under different ratios of RAFT agent and monomer, and studied different monomer and RAFT agent ratios.

[0142] Table 4 Kinetic data of RAFT agent at different ratios

[0143]

[0144] From Table 4, Figure 9 and Figure 10 it can be seen that the higher the amount of RAFT agent, the faster the polymerization rate, but the longer the induction period. For higher monomer ratios (such as 1000:1) and lower monomer ratios (such as 100:1), the RAFT agent has very good control, the molecular weight measured by GPC is close to the theoretical value, and the dispersity is good, less than 1.3, which belongs to the category of controlled polymerization.

[0145] 5. In an oxygen-free environment, the polymerization of RAFT agent (RAFT2 prepared in Example 2) in different solvents:

[0146] Table 5 Compatibility of RAFT agent with different polar solvents

[0147]

[0148]

[0149] From Table 5, it can be seen that in solvents of different polarity, the RAFT agent can complete polymerization, which shows that the RAFT agent has good compatibility with solvents of different polarity. When the solvent is dimethyl sulfoxide, the polymerization rate is the fastest, and the monomer conversion rate can reach 77.7% after 3 minutes of irradiation.

[0150] 6. In an oxygen-free environment, the compatibility of RAFT agent (RAFT2 prepared in Example 2) with different monomers:

[0151] Table 6 Compatibility of RAFT agent with different monomers

[0152]

[0153]

[0154] The structures of the above monomers are as follows:

[0155]

[0156] From Table 6, it can be seen that the polymerization rate of acrylic acid or acrylate monomers is fast, while the polymerization rate of acrylamide monomers is slow. Whether it is acrylic acid or acrylate monomers, or acrylamide monomers, the polymerization rate is much higher than the conventional light-controlled RAFT polymerization rate.

[0157] Comparative Example 1

[0158] 1.1 Kinetic solution preparation: monomer and RAFT agent were configured into solution according to the molar ratio of [monomer]:[RAFT agent]=200:1, and dimethyl sulfoxide was added as solvent, the volume ratio of monomer and solvent was 1:1. Among them, the monomer was methyl acrylate MA, and the RAFT agent was CDTPA. The structure of CDTPA is as follows:

[0159]

[0160] 1.2 Kinetic experiment steps: 0.4 mL of kinetic solution was transferred to a cuvette and sealed with a rubber plug and sealing film. Under anaerobic conditions, the sample was irradiated under a 10 mW / cm 2 LED lamp, and the monomer vinyl C-H bond vibration absorption peak near 6200 cm -1 was integrated by Fourier infrared spectroscopy (FTIR), and the monomer remaining amount was quantitatively monitored by peak area, so as to track the monomer conversion rate, and the apparent polymerization rate (k p app ) was calculated by using the kinetic equation. When the monomer conversion rates were 40%, 50%, 60%, and 70% respectively, samples were taken, and gel permeation chromatography (GPC) was used to detect samples with different conversion rates to observe whether the molecular weight was controllable during polymerization, and the polydispersity of the polymer was monitored; after the conversion rate was about 70% (after the fourth sampling was completed), the polymer was purified. The test results are shown in Table 7.

[0161] Comparative Example 2

[0162] The difference from Comparative Example 1 is that the RAFT agent is DTPA, and ZnTPP is also added as a photocatalyst, wherein the molar ratio of [monomer]:[RAFT agent]:[ZnTPP] is 200:1:0.01. The structures of DTPA and ZnTPP are as follows:

[0163]

[0164] The experimental results are shown in Table 7.

[0165] Table 7 Polymerization rate of RAFT agent under anaerobic conditions

[0166]

[0167] By comparing the data in Table 3 and Table 7, it can be seen that the currently reported light-controlled RAFT polymerization without catalyst addition, taking CDTPA as an example (Comparative Example 1), the apparent polymerization rate is only 0.008 min -1The RAFT agent of the present application can reach a polymerization rate of 0.704 min -1 , which is 80 times of the polymerization rate of CDTPA. Compared with PET-RAFT polymerization, the apparent polymerization rate can reach 35 times or more with DTPA / ZnTPP (0.019 min -1 ) as a contrast (Comparative Example 2). The polymerization time is shortened from several hundred or tens of minutes to within ten minutes.

[0168] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. The present application can be variously changed and modified by those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A RAFT reagent for photocontrolled polymerization, wherein the general structural formula of the RAFT reagent for photocontrolled polymerization is: ； in, R1, R2, and R3 are all selected from hydrogen atoms; Alternatively, R2 and R3 are both selected from hydrogen atoms, and R1 is selected from methyl groups; Alternatively, R1 is selected from methyl, R2 is selected from bromine atom, and R3 is selected from hydrogen atom; Alternatively, R1 is selected from methyl, R2 is selected from hydrogen atom, and R3 is selected from methoxy.

2. The RAFT reagent for photopolymerization as described in claim 1, characterized in that, R2 and R3 are both selected from hydrogen atoms, and R1 is selected from methyl groups.

3. A method for preparing the RAFT reagent for photocontrolled polymerization as described in claim 1 or 2, characterized in that, Includes the following steps: Will The metal hydroxide was dissolved in a solvent, and the reaction system was kept warm in an ice-water bath. Then, carbon disulfide was added dropwise while the reaction was continuously stirred in an ice-water bath to obtain intermediate product I. Intermediate product I was dissolved in a solvent, an oxidizing agent was added, and the mixture was stirred to react, yielding intermediate product II. Intermediate product II and azobisisovalerate were dissolved in a solvent, heated and stirred, and nitrogen gas was introduced. After the reaction was completed, the RAFT reagent for photocontrolled polymerization was obtained. The structure of intermediate product I is shown in Formula I, and the structure of intermediate product II is shown in Formula II. Formula I Formula II Among them, R1, R2, and R3 are all selected from hydrogen atoms; Alternatively, R2 and R3 are both selected from hydrogen atoms, and R1 is selected from methyl groups; Alternatively, R1 is selected from methyl, R2 is selected from bromine atom, and R3 is selected from hydrogen atom; Alternatively, R1 is selected from methyl, R2 is selected from hydrogen atom, and R3 is selected from methoxy.

4. The preparation method according to claim 3, characterized in that, The metal hydroxide is potassium hydroxide; Alternatively, the solvent may be selected from at least one of tetrahydrofuran or acetone.

5. The preparation method according to claim 3, characterized in that, After the reaction with carbon disulfide was completed, the product was filtered, washed with deionized water, and dried to obtain intermediate product I.

6. The preparation method according to claim 3, characterized in that, After the oxidant was added and the reaction was stirred to completion, the solvent and oxidant were removed, and the product was extracted and dried to obtain intermediate product II.

7. The preparation method according to claim 6, characterized in that, The oxidizing agent is elemental iodine.

8. The preparation method according to claim 6, characterized in that, The product was rotary evaporated to remove the solvent; Alternatively, a reducing agent can be added to remove the oxidizing agent.

9. The preparation method according to claim 8, characterized in that, The reducing agent is sodium thiosulfate.

10. The preparation method according to claim 3, characterized in that, Nitrogen gas was introduced, and after the reaction was completed by heating, the solvent was removed, and the product was purified by column chromatography to obtain the RAFT reagent for photocontrolled polymerization.

11. The preparation method according to claim 10, characterized in that, When purifying the product by column chromatography, the mobile phase is a mixed solution of petroleum ether and ethyl acetate with a volume ratio of 10:

1.

12. The application of the RAFT reagent according to claim 1 or 2 in a RAFT polymerization reaction, wherein the RAFT polymerization reaction is a photocontrolled polymerization reaction.

13. The application as described in claim 12, characterized in that, The photocontrolled polymerization reaction is as follows: the monomer, the RAFT reagent as described in claim 1 or 2, and the solvent are mixed evenly, and the reaction is carried out under blue light at 420-430 nm to obtain the polymer.

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