An active initiator solution, its preparation method and application

Abstract

The present invention belongs to the technical field of controlled radical polymerization, and particularly relates to an active initiator solution, a preparation method thereof and an application. The metal-free controlled radical polymerization realized by activating a sulfonyl chloride initiator provided by the present invention is as follows: first, a sulfonyl chloride and an activator react in an organic solvent to obtain an active initiator solution; then, a bromide salt, an organic catalyst and a monomer are added to the active initiator solution; under the condition of light, a metal-free controlled radical polymerization reaction is carried out to prepare a polymer with a controllable molecular weight, a narrow molecular weight distribution and a high chain-end fidelity, and block polymers can be directly prepared through post-modification after chain extension. The polymerization method in the present invention uses a variety of commercially available sulfonyl chlorides as initiators, has a high initiation efficiency, simple reaction conditions and equipment, can avoid the toxic effects of metals on electronic devices and organisms, and expands the application scope of controllable synthesis of polymers.

Description

Technical Field

[0001] The present invention belongs to the technical field of controlled radical polymerization, and particularly relates to an active initiator solution, a preparation method thereof, and an application thereof. Background Art

[0002] Controlled radical polymerization methods can achieve the controlled synthesis of polymers, and can prepare polymers with adjustable molecular weights and narrow molecular weight distributions, providing important means for the preparation of high-end organic dielectric materials, light-emitting waterproof polymer coatings, biomedical materials, etc. Therefore, it is of great significance to develop controlled radical polymerization methods.

[0003] Atom transfer radical polymerization (ATRP) is a widely used controlled radical polymerization method, which realizes the "living" growth of polymer molecular chains by using transition metal catalysts (such as Cu, Ru, Fe). However, it is difficult to completely remove the metal catalysts in the polymers, which limits the application of related methods in many frontier fields (such as the microelectronics field and biomedicine).

[0004] For a long time, researchers have proposed many strategies to reduce the transition metal residues in polymers, such as reducing the catalyst dosage, and performing purification in the later stage of polymerization (such as precipitation, adsorption), etc. However, these methods are still difficult to completely eliminate the possibility of metal residues. In this regard, Professor Hawker and Professor Fors reported a metal-free ATRP reaction using ethyl α-bromophenylacetate as an initiator and phenothiazine as an organic catalyst, realizing the photo-regulated radical polymerization of methyl methacrylate. Professor Miyake reported a metal-free ATRP reaction using ethyl α-bromophenylacetate as an initiator and diaryldihydrophenazine, etc. as organic catalysts, realizing the photo-regulated radical polymerization of methyl methacrylate. However, so far, the above metal-free ATRP reactions all require the use of alkyl bromides as initiators, which limits the application scope of the controlled synthesis of high polymers.

[0005] Therefore, finding a kind of initiator that is rich in variety and can be commercialized, in order to directly generate polymers with different terminal substituents, which is convenient for subsequent derivatization, has become a technical problem to be solved urgently. Summary of the Invention

[0006] In view of this, the first object of the present invention is to provide a preparation method of an initiator system with a rich variety and commercialization for the problems existing in the prior art.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A preparation method of an active initiator solution, wherein the sulfonyl chloride and an activator are mixed and reacted in an organic solvent to obtain the active initiator solution.

[0009] Preferably, the chemical formula of the sulfonyl chloride is shown in Formula (1) to Formula (5):

[0010]

[0011] Among them, R 1 to R 7 are selected from hydrogen, methyl, methoxy, halogen atom, nitro, trifluoromethyl, straight-chain or branched-chain alkane with 2 - 8 carbon atoms, cycloalkyl with 3 - 8 carbon atoms or phenyl group; X is selected from O, S or N atom.

[0012] Preferably, the chemical formula of the activator is shown in Formula (6) to Formula (16):

[0013]

[0014] Among them, R 8 to R 14 are selected from hydrogen, methyl, methoxy, dimethylamino or phenyl group.

[0015] It should be noted that pyridine as an activator is introduced into the active initiator solution disclosed in the present invention, so that the single activator sulfonyl chloride is changed into an active initiator solution containing a sulfonylpyridine intermediate. The reduction potential of this intermediate is more positive than that of pure sulfonyl chloride. That is, compared with pure sulfonyl chloride, in a photoinduced redox-mediated polymerization system, this intermediate is more easily reduced by the excited-state photocatalyst to generate carbon radicals. Therefore, the active initiator solution containing the effective component of the sulfonylpyridine intermediate has a higher controlled radical polymerization initiation efficiency, can more effectively regulate the molecular weight distribution of the polymer, and improve the fidelity of the chain end compared with single sulfonyl chloride.

[0016] In some embodiments, the molar ratio of the sulfonyl chloride to the activator is 1:(1.0 - 6.0).

[0017] Preferably, the organic solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, diethyl carbonate, dimethyl carbonate, toluene, acetone or acetonitrile.

[0018] Considering the complete implementation of the technical solution of the present invention, the mixing method includes stirring at room temperature, ultrasonic stirring or heating and stirring.

[0019] The second object proposed by the present invention is to provide an active initiator solution prepared by the above preparation method.

[0020] An active initiator solution obtained by the above preparation method, comprising an organic solvent, sulfonyl chloride, an activator and an intermediate obtained by mixing and reacting the sulfonyl chloride and the activator.

[0021] It should be noted that the intermediates of the reaction of the sulfonyl chloride with the activator include the intermediate obtained by the reaction of the sulfonyl chloride with the activator, the intermediate obtained by mixing the sulfonyl chloride with the organic solvent, the intermediate obtained by mixing the activator with the organic solvent, and the intermediate obtained by the co-reaction of the sulfonyl chloride, the activator and the organic solvent.

[0022] The third object of the present invention is to provide an application of the active initiator solution as described above.

[0023] In order to achieve the above object, the present invention adopts the following technical solutions:

[0024] For an application of the active initiator solution as described above, a bromide salt, an organic catalyst and a monomer are added to the active initiator solution as described above. After deoxygenating the system, a metal-free controlled radical polymerization reaction is carried out under light irradiation.

[0025] After the polymerization reaction is completed, a polymer with metal-free controlled molecular weight, narrow molecular weight distribution and high chain-end fidelity is obtained by purification.

[0026] It should be noted that in the controlled radical polymerization reaction of the present invention, the molecular weight of the polymer increases linearly with the increase of the monomer conversion rate, and the molecular weight distribution is narrow. If the monomer is consumed completely, the chain end of the polymer still remains active, and new monomers can be added to continue the polymerization to prepare block polymers.

[0027] Considering the reaction rate and time, the metal-free controlled radical polymerization reaction can be heated.

[0028] Preferably, the bromide salt is one or more of sodium bromide, potassium bromide, lithium bromide, and tetrabutylammonium bromide.

[0029] Preferably, the organic catalyst is a phenothiazine derivative, a phenoxazine derivative, a 2,4,5,6-tetra(diphenylamino)-isophthalonitrile derivative, a dihydro-phenazine derivative or a bis(phenothiazine)biphenyl compound.

[0030] It should be noted that the structural formula of the organic catalyst is shown as (17) to (20):

[0031]

[0032] Among them, R 15 to R 30 are selected from hydrogen, methyl, methoxy, dimethylamino or phenyl groups; X is selected from S or O atoms.

[0033] Preferably, the monomer is one or more of methyl acrylate, ethyl acrylate, n-butyl acrylate, tert-butyl acrylate, ethylene glycol methyl ether acetate, trifluoroethyl acrylate, hexafluorobutyl acrylate, acrylamide, methyl methacrylate, ethyl methacrylate, trifluoroethyl methacrylate, hexafluorobutyl methacrylate, perfluorobutylethyl methacrylate, styrene, and vinyl acetate.

[0034] Preferably, the light source used for the light irradiation is a white light lamp within the wavelength range of 400 - 700 nm, a purple light lamp within the wavelength range of 380 - 450 nm, or a blue light lamp within the wavelength range of 400 - 480 nm.

[0035] It should be noted that compared with the existing photoinduced radical polymerization reaction initiated by sulfonyl chloride, the present invention uses an activation strategy of sulfonyl chloride, that is, an active initiator solution prepared by reacting an activating reagent with sulfonyl chloride, which improves the initiation efficiency of controlled radical polymerization, enabling the reactions of the activator, bromide salt, and organic catalyst to effectively regulate the molecular weight distribution of the polymer and improve the fidelity of the chain end. When adding a new monomer, it can be used for chain extension polymerization to prepare block polymers, expanding the application of the controlled radical polymerization method in fields such as surface-initiated polymerization and graft polymerization.

[0036] The present invention discloses a metal-free controlled radical polymerization achieved by activating a sulfonyl chloride initiator. This method uses a variety of commercially available sulfonyl chlorides as initiators, and after the reaction, polymers with different end substituents can be directly generated, which is convenient for subsequent derivatization; through a one-step sulfonyl chlorination synthesis reaction, the sulfonyl chloride initiation site can be efficiently introduced into the (hetero)aromatic ring, facilitating the post-chain extension modification of aryl-containing polymers to prepare functional polymer materials.

[0037] Compared with the prior art, the present invention overcomes the above-mentioned defects of the existing ATRP method through the activation strategy of the sulfonyl chloride initiator and has the following advantages:

[0038] (1) The reaction conditions are mild (room temperature, atmospheric pressure), and the polymerization equipment is simple;

[0039] (2) The polymerization start and stop can be controlled by light switch, and the polymerization reaction rate can be adjusted by changing the wavelength and intensity of the light source;

[0040] (3) There is no residual transition metal in the polymer, and it is expected to be applied in fields such as microelectronics, biomedicine, and energy chemistry;

[0041] (4) The initiation efficiency of the polymerization reaction is high (>90%), the molecular weight of the polymer can be adjusted, the molecular weight distribution is narrow (1.18 - 1.35), the chain end fidelity is high, and block polymers can be prepared by chain extension reaction of the polymer;

[0042] (5) Sulfonyl chloride initiators and activators are rich in variety and low in price, suitable for large-scale synthesis.

[0043] (6) After sulfonyl chlorination of polymers with aryl groups in the side chain or main chain (such as polystyrene, polyethylene terephthalate, polysulfone), functional polymer materials can be directly prepared by post-modification of chain extension using the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0045] Figure 1 Chemical reaction schematic diagram of the active initiator solution in Example 1.

[0046] Figure 2 13C NMR spectrum of the main body of the active initiator solution in Example 1.

[0047] Figure 3 1H NMR spectrum of the main body of the active initiator solution in Example 2.

[0048] Figure 4 Schematic diagram of the metal-free controlled radical polymerization reaction in Example 3.

[0049] Figure 5 1H NMR spectrum of the reaction product in Example 3

[0050] Figure 6 SEC chart of the polymer in Example 3.

[0051] Figure 7 NMR spectrum of the polymer in Example 4.

[0052] Figure 8 NMR spectrum of the polymer in Example 5.

[0053] Figure 9 SEC chart of the polymer in Example 5.

[0054] Figure 10 SEC charts of the polymer before and after the chain extension reaction in Example 6

[0055] Figure 11 Monomer conversion rate in the metal-free controlled radical polymerization reaction controlled by the light source as a switch in Example 7.

[0056] Figure 121H NMR spectrum of polystyrene after sulfonyl chloride treatment in Example 8.

[0057] Figure 13 1H NMR spectrum of the branched polymer in Example 8.

[0058] Figure 14 CV diagram of the active initiator in Example 2.

[0059] Figure 15 Schematic diagram of metal-free controlled radical polymerization activated by sulfonyl chloride initiator disclosed in the present invention. Detailed implementation manners

[0060] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0061] The special term "embodiment" here, any embodiment described as "exemplary" does not have to be construed as superior or better than other embodiments. For the performance index tests in the embodiments of this application, unless otherwise specified, conventional test methods in the art are adopted. It should be understood that the terms described in this application are only used to describe specific embodiments and are not used to limit the content disclosed in this application.

[0062] Unless otherwise specified, the technical and scientific terms used herein have the same meanings as commonly understood by those of ordinary skill in the technical field to which this application belongs; the test methods and technical means not specifically noted in other parts of this application refer to the experimental methods and technical means commonly adopted by those of ordinary skill in the art.

[0063] To better illustrate the content of this application, numerous specific details are given in the following specific embodiments. Those skilled in the art should understand that this application can still be implemented without some specific details. In the embodiments, some methods, means, instruments, equipment, etc. well-known to those skilled in the art are not described in detail in order to highlight the gist of this application.

[0064] On the premise of no conflict, the technical features disclosed in the embodiments of this application can be combined arbitrarily, and the obtained technical solutions belong to the content disclosed in the embodiments of this application.

[0065] The present invention provides a metal-free controlled radical polymerization activated by a sulfonyl chloride initiator. First, an organic solvent, a sulfonyl chloride initiator, an activator, and a magnetic stir bar are added to a reaction flask, and stirred for several hours to prepare an active initiator solution. Then, a bromide salt, an organic catalyst, and a monomer are added to the reaction flask. After deoxygenation, the reaction flask is sealed, and a metal-free controlled radical polymerization reaction is carried out under light (heating can accelerate the polymerization reaction). After the polymerization reaction is completed, a polymer with metal-free controlled molecular weight, narrow molecular weight distribution, and high chain-end fidelity is obtained by purification.

[0066] To better understand the present invention, the following examples are used to further specifically illustrate the present invention, but it should not be construed as a limitation of the present invention. For those skilled in the art, some non-essential improvements and adjustments made according to the above invention content are also considered to fall within the protection scope of the present invention.

[0067] Example 1

[0068] An active initiator solution and its preparation method:

[0069] p-Toluenesulfonyl chloride (4 mmol), activator pyridine (6 mmol), and ultra-dry acetonitrile (1 mL) are added to a 10 mL reaction flask with a stir bar, and stirred for several hours at room temperature to prepare an active initiator solution ( Figure 1 ). After the reaction is completed, the solution is concentrated under reduced pressure to obtain a white solid product. The solid product is characterized by 13 13C NMR ( Figure 2 ).

[0070] Example 2

[0071] An active initiator solution and its preparation method:

[0072] p-Toluenesulfonyl chloride (4 mmol), activator pyridine (6 mmol), and ultra-dry acetonitrile (1 mL) are added to a 10 mL reaction flask, and the mixture is placed in an ultrasonic bath and ultrasonically stirred for several hours to prepare an active initiator solution. After the reaction is completed, the solution is concentrated under reduced pressure to obtain a white solid product. The solid product is characterized by 1 1H NMR ( Figure 3 ).

[0073] Example 3

[0074] An active initiator solution and its application:

[0075] 2-Thiophenesulfonyl chloride (0.02 mmol), quinoline (0.08 mmol) and ultradry DMF (1 mL) were added to a 4 mL reaction flask equipped with a magnetic stir bar, and the mixture was stirred under heating at 50 °C to prepare an active initiator solution. 10-Phenylphenothiazine (2 μmol), KBr (0.02 mmol), n-butyl acrylate (2 mmol) and ethyl benzoate (1 mmol) as an internal standard were added to the reaction flask. After degassing the system, the reaction flask was sealed and reacted overnight under white light irradiation in the wavelength range of 400 - 700 nm( Figure 4 ). After the reaction was completed, a small amount of the sample was taken out to 1 determine the monomer conversion rate to be 83% by 1H NMR( Figure 5 ), and the M n，SEC and of the polymer were analyzed by SEC( Figure 6 ).

[0076] Example 4

[0077] An active initiator solution and its application:

[0078] 3-Chlorobenzenesulfonyl chloride (0.04 mmol), pyridine (0.08 mmol) and ultradry acetonitrile (1 mL) were added to a 4 mL reaction flask, and the mixture was sonicated and stirred to prepare an active initiator solution. 10-Phenylphenothiazine (2 μmol), NaBr (0.12 mmol) and methyl acrylate (172.1 mg, 2 mmol) were added to the reaction flask. After degassing, the reaction flask was sealed and reacted overnight under irradiation with a 400 nm ultraviolet lamp. After the reaction was completed, the polymer was purified and then characterized by 1 1H NMR for the structure of the polymer( Figure 7 ).

[0079] Example 5

[0080] An active initiator solution and its application:

[0081] Trifluoromethylbenzenesulfonyl chloride (0.02 mmol), pyridine (0.08 mmol) and ultradry DEC (1 mL) were added to a 4 mL reaction flask equipped with a magnetic stir bar, and the mixture was stirred at room temperature for several hours to prepare an active initiator solution. 5,10-Dihydro-5,10-diphenylphenazine (4 μmol), LiBr (0.06 mmol), 2,2,2-trifluoroethyl acrylate (2 mmol) and ethyl benzoate (1 mmol) as an internal standard were added to the reaction flask. After degassing the system, the reaction flask was sealed and reacted overnight under irradiation with a 400 nm ultraviolet lamp. After the reaction was completed, a small amount of the sample was taken out to 1 determine the monomer conversion rate to be 96% by 1H NMR( Figure 8 ), and the M n，SECand ( Figure 9 )。

[0082] Example 6

[0083] An active initiator solution and its application:

[0084] First, prepare the macromolecular initiator PMA: Add p-toluenesulfonyl chloride (0.04 mmol), pyridine (0.16 mmol), and ultradry DEC (1 mL) into a 4 mL reaction flask equipped with a magnetic stirrer. Stir and react under an argon atmosphere at 25 °C to prepare the active initiator solution. Add the organic catalyst 10-phenylphenothiazine (2 μmol), NaBr (0.12 mmol), and methyl acrylate (172.1 mg, 2 mmol) into the reaction flask. After deoxygenation, seal the reaction flask and irradiate it with a UV lamp at a wavelength of 400 nm overnight. The monomer conversion rate is 95%. Then, add methyl methacrylate (2 mmol) to the reaction mixture for chain extension. After deoxygenation, seal the reaction flask and initiate the polymerization reaction again under UV lamp irradiation. The reaction ends after 8 h. Analyze the M of the polymer by SEC n，SEC and ( Figure 10 )。

[0085] Example 7

[0086] An active initiator solution and its application:

[0087] Add p-toluenesulfonyl chloride (0.04 mmol), pyridine (0.16 mmol), and ultradry DEC (2 mL) into a 10 mL reaction flask equipped with a magnetic stirrer. Stir at room temperature for several hours to prepare the intermediate solution. Add the organic catalyst 10-phenylphenothiazine (2 μmol), NaBr (0.12 mmol), and methyl acrylate (4 mmol) into the reaction flask. After deoxygenation, seal the reaction flask and transfer the sealed reaction flask to a glove box. Irradiate it with a UV lamp by "turning on" or "turning off" at the corresponding time. Take aliquots with a microsyringe at each time point and immediately take them out of the glove box for characterization: Use 1 1H NMR to calculate the monomer conversion rate.

[0088] Example 8

[0089] An active initiator solution and its application:

[0090] Add polystyrene (0.2 mmol, M n,SEC = 5.4 kDa, ) and ultradry DCM (20 mL) into a 100 mL flask equipped with a magnetic stirrer. At 0 °C, add ClSO 3H was slowly added to the flask. The system was stirred at room temperature for several hours. After the reaction was complete, it was concentrated under reduced pressure to obtain sulfonyl chloride-modified polystyrene ( Figure 12 ). Sulfonyl chloride-modified polystyrene (4×10 -3 mmol) was used as the initiator, pyridine (0.01 mmol) and ultra-dry DEC (1 mL) were added to a 4 mL reaction flask equipped with a magnetic stirrer, and the mixture was stirred at room temperature for several hours to prepare an active initiator solution. Perfluorobutylethyl methacrylate monomer (2 mmol), NaBr (0.03 mmol), and organic catalyst 10-phenylphenothiazine (2 μmol) were added to the reaction flask. After deoxygenation, the reaction flask was sealed and reacted overnight under irradiation with a UV lamp at a wavelength of 400 nm. After the reaction was completed, the polymer was purified, and 1 1H NMR was used to analyze the composition of the polymer ( Figure 13 ).

[0091] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. Application of an active initiator solution Characterized in that A bromide salt, an organic catalyst and a monomer are added to the active initiator solution. After deoxygenating the system, a metal-free controlled radical polymerization reaction is carried out under light irradiation; The structural formula of the organic catalyst is shown as (17) to (20): wherein, R 15 to R 30 is selected from a hydrogen, methyl, methoxy, dimethylamino or phenyl group; X is selected from an S or O atom; The active initiator solution is obtained by mixing and reacting sulfonyl chloride with an activator in an organic solvent; The chemical formula of the sulfonyl chloride is shown as formula (1) to formula (5): Among them, R 1 to R 7 is selected from hydrogen, methyl, methoxy, halogen atom, nitro, trifluoromethyl, a straight-chain or branched-chain alkane having 2 to 8 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms or a phenyl group; X is selected from an O, S or N atom; The chemical formula of the activator is shown as formula (6) to formula (16): wherein, R 8 to R 14 is selected from a hydrogen, methyl, methoxy, dimethylamino or phenyl group.

2. The application according to claim 1 Characterized in that The organic solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, diethyl carbonate, dimethyl carbonate, toluene, acetone or acetonitrile.

3. The application according to claim 1 Characterized in that The bromide salt is one or more of sodium bromide, potassium bromide, lithium bromide, tetrabutylammonium bromide.

4. The application according to claim 1 Characterized in that The monomer is one or more of methyl acrylate, ethyl acrylate, n-butyl acrylate, tert-butyl acrylate, trifluoroethyl acrylate, hexafluorobutyl acrylate, acrylamide, methyl methacrylate, ethyl methacrylate, trifluoroethyl methacrylate, hexafluorobutyl methacrylate, perfluorobutylethyl methacrylate, styrene, vinyl acetate.

5. The application according to claim 1 Characterized in that The light source used for the light irradiation is a white light lamp in the wavelength range of 400 - 700 nm, a purple light lamp in the wavelength range of 380 - 450 nm or a blue light lamp in the wavelength range of 400 - 480 nm.

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