Atom transfer radical polymerization photocatalyst based on dipyridylthiadiazole quaternary ammonium salt derivatives and preparation method and application thereof

Abstract

The present invention provides 1. an atom transfer radical polymerization photocatalyst based on a dipyridylthiadiazole quaternary ammonium salt derivative, and a preparation method and application thereof. The catalyst is a dipyridylthiadiazole quaternary ammonium salt derivative, and the dipyridylthiadiazole derivative has a structure shown in formula (I): wherein R is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-hexyl, benzyl, p-methylbenzyl or p-tert-butylbenzyl. The catalyst is prepared by a simple organic synthesis reaction, and has a photocatalytic effect on the atom transfer radical polymerization reaction of various monomers. The preparation method provided by the present invention starts from a simple organic raw material, is simple and convenient to prepare, has a low catalytic loading, a high reaction conversion rate, and a wide range of trial monomers.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer synthesis and relates to an atom transfer free radical polymerization catalyst and a preparation method and application thereof. Background Art

[0002] As a new type of living polymerization method, atom transfer radical polymerization has the advantages of controllable reaction process, controllable product molecular weight, narrow molecular weight distribution, and modifiable polymer chain ends compared to traditional free radical polymerization. It has broad applications in the fine synthesis and structural control of polymer materials such as plastics, resins, and gels. Since the emergence of atom transfer radical polymerization technology, in order to overcome the shortcomings of traditional copper and iridium catalysts, which are highly biotoxic and difficult to remove, a variety of pure organic photocatalysts with good light control performance, low catalytic loading, and easy removal have been developed one after another.

[0003] In traditional free radical polymerization, the chain initiation process can produce a large number of free radicals, so the reaction rate is fast, and there is an automatic acceleration process and a large number of chain transfers and double radical terminations. Therefore, the reaction process is uncontrollable, the molecular weight of the resulting polymer cannot be customized, and the molecular weight distribution is wide. Atom transfer radical polymerization refers to the homolytic cleavage of the carbon-halogen bond of the initiator through the action of a catalyst, and the concentration of the active species is kept at a low level through the balance of active species and dormant species, thereby reducing the occurrence of chain transfer and double radical termination.

[0004] There are certain challenges in replacing precious metals with pure organic compounds as ATRP photocatalysts. As ATRP photocatalysts, molecules need to have a suitable redox potential to maintain the active species-dormant species balance; they need to have a large molar absorption coefficient to reduce the catalyst loading; they need to have good solubility to adapt to a variety of monomers and solvent systems; and they need to have a certain stability to maintain good polymerization control.

[0005] Recent research has focused on using phenothiazines, phenoxazines, dihydrophenazines and oxygen-doped aromatic ring molecules as photocatalysts for atom transfer radical polymerization. The raw material cost of such catalysts is relatively high and the preparation process is relatively complicated. Improving the molar absorption coefficient, increasing the wavelength of light required for the reaction, and improving the stability and universality of the catalyst are important directions for future catalyst research. Summary of the invention

[0006] The purpose of the present invention is to provide a highly efficient atom transfer radical polymerization photocatalyst and its application.

[0007] The atom transfer radical polymerization photocatalyst provided by the present invention is a dipyridylthiadiazole salt derivative, as shown in formula (I):

[0008]

[0009] Among them, R is methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-hexyl, benzyl, p-methylbenzyl, p-tert-butylbenzyl, etc.

[0010] The present invention also provides a method for preparing an atom transfer radical polymerization photocatalyst based on a dipyridylthiadiazole quaternary ammonium salt derivative, which comprises mixing a catalyst, an initiator, a monomer and a solvent, and irradiating the mixture with a wavelength of 360-480nm for a period of time to obtain a polymer.

[0011] Furthermore, the monomers used for catalyzing atom transfer radical polymerization are (II-1) to (II-

[0012] 13) One or more of the monomers described above are mixed:

[0013]

[0014] In a preferred embodiment, the initiator used to catalyze atom transfer radical polymerization is (III-

[0015] 1) One or more of the bromine initiators described in (III-5) are mixed:

[0016]

[0017] In a preferred embodiment, when used in atom transfer radical polymerization, the amount of catalyst used (relative to the monomer) is 10-1000 ppm.

[0018] In a preferred embodiment, the solvent system of the reaction is one or a mixture of water, dichloromethane, acetonitrile, ethanol, methanol, tetrahydrofuran, and dimethyl sulfoxide.

[0019] In a preferred embodiment, it is used to prepare other polymer materials such as plastics, resins, gels, adhesives, etc.

[0020] In a preferred embodiment, the organic solvent is one or a mixture of dichloromethane, ethanol, methanol, tetrahydrofuran, ethyl acetate, and water.

[0021] The invention also proposes an application of an atom transfer radical polymerization photocatalyst based on a dipyridylthiadiazole quaternary ammonium salt derivative, which is applied in the preparation of plastic, resin, gel and adhesive polymer materials.

[0022] The raw materials described in the present invention are all pure organic compounds, with a wide range of sources, easy to obtain, low price, simple synthesis and convenient preparation. The photocatalyst prepared in the present invention has low loading, good polymerization control and is easy to remove after the reaction.

[0023] Example 1

[0024] This Example 1 provides a general preparation method for the dipyridylthiadiazole quaternary ammonium salt derivatives mentioned herein. The specific steps are:

[0025]

[0026] (1) Add 640 mg (5.3 mmol) of dithiooxamide, 880 mg (10.6 mmol) of pyridine-4-carboxaldehyde and 50 mL of anhydrous DMF in a 100 mL three-necked flask. Stir well and heat under reflux overnight under the protection of argon. After the reaction is completed, cool to room temperature and a large amount of brown-yellow precipitate will precipitate out of the system. Collect the filter cake by vacuum filtration, and then repeatedly wash the collected filter cake with acetone and water. Finally, filter and dry to obtain 785 mg of yellow powder with a yield of 52%.

[0027] (2) 250 mg (0.84 mmol) of the yellow powder obtained in the previous step and 7.5 mL of methyl p-toluenesulfonate were added to a 20 mL round-bottom flask in sequence. The mixture was stirred at room temperature for 2 days to obtain a yellow-green turbid solution. The turbid solution was then poured into 100 mL of ethyl acetate and the precipitated yellow precipitate was collected.

[0028] (3) The yellow precipitate was dissolved in 10 mL of deionized water and then gradually added dropwise to 100 mL of acetone to reprecipitate a yellow-green precipitate. Finally, the product was vacuum dried after the above reprecipitation operation to obtain 363 mg of light yellow powder with a yield of 60%. 1H NMR (400MHz, DMSO-d6): δ9.15(d,J=6.7Hz,4H),8.75(d,J=6.7Hz,4H),7.47(d,8.0Hz,4H),7.10(d,8.0Hz,4H),4.40(s,6H),and 2.28(s,6H)ppm; 13C NMR(101MHz, DMSO-d6): δ165.1,154.9,146.6,145.5,145.0,138.0,128.1,125.4,123.7,47.9,and 20.7ppm; HRMS(ESI+)calcd for C16H14N4S22+m / z 163.0324; found m / z 163.0329.

[0029] For other types of substituents of bipyridylthiadiazole quaternary ammonium salts, this method can also be used to prepare. Based on the yellow precipitate prepared in step (1), the following method is used to prepare:

[0030]

[0031] Example 2

[0032] This embodiment 2 provides a method and application of atom transfer radical polymerization of acrylic acid ester monomers using such a catalyst.

[0033] The atom transfer radical polymerization method provided in this embodiment uses methyl dipyridylthiadiazole quaternary ammonium salt as a catalyst and methyl methacrylate as a monomer. The specific steps for preparing the polymer are as follows:

[0034] (1) Add 13.2 mg (0.02 mmol) of methyldipyridinium thiadiazole quaternary ammonium salt and 48.6 mg (0.2 mmol) of ethyl α-bromophenylacetate to 4 ml of DMSO, keep it away from light, shake or sonicate it to dissolve, and then add 2 ml (2.0 g, 20 mmol) of methyl methacrylate to the solution. Transfer the solution to a 20 ml quartz Shrek tube, seal it and perform three freeze-thaw cycles to remove oxygen from the reaction system. Use a purple LED light to continuously irradiate for 12 hours. After the reaction is completed, dilute the resulting polymer solution with 4 ml of dichloromethane, and then add the solution dropwise to 100 ml of methanol under stirring to precipitate the polymer. After stirring for 2 hours, filter it, and then dry the resulting polymer at 40°C for 24 hours to obtain 1.78 g (89%) of polymethyl methacrylate.

[0035] Example 3

[0036] This embodiment 3 provides a method and application of atom transfer radical polymerization of styrene monomers using such a catalyst.

[0037] The atom transfer radical polymerization method provided in this embodiment uses methyldipyridylthiadiazole quaternary ammonium salt as a catalyst and styrene as a monomer. The specific steps for preparing the polymer are as follows:

[0038] (1) Add 14.9 mg (0.02 mmol) of dihexyldipyridiniumthiadiazole quaternary ammonium salt and 48.6 mg (0.2 mmol) of ethyl α-bromophenylacetate to 4 ml of dichloromethane, keep it away from light, shake or sonicate it to dissolve, and then add 2 ml (2.0 g, 20 mmol) of styrene to the solution. Transfer the solution to a 20 ml quartz Shrek tube, seal it and perform three freeze-thaw cycles to remove oxygen from the reaction system. Use a purple LED light to continuously irradiate for 12 hours. After the reaction is completed, dilute the resulting polymer solution with 4 ml of dichloromethane, and then add the solution dropwise to 100 ml of methanol under stirring to precipitate the polymer. After stirring for 2 hours, filter it, and then dry the resulting polymer at 40°C for 24 hours to obtain 1.44 g (72%) of polystyrene.

[0039] Example 4

[0040] This embodiment 4 provides a method and application of carrying out atom transfer radical polymerization in water phase using such a catalyst.

[0041] The atom transfer radical polymerization method provided in this embodiment uses methyldipyridylthiadiazole quaternary ammonium salt as a catalyst and PEGA480 as a monomer. The specific steps for preparing the polymer are as follows:

[0042] (1) Add 13.2 mg (0.02 mmol) of dimethyldipyridinium thiadiazole quaternary ammonium salt and 42.2 mg (0.2 mmol) of ethylene glycol bromoisobutyrate to 5 ml of water, keep it away from light, and then add 5 ml (5.0 g, 10.2 mmol) of PEGA480 to the solution. Transfer the solution to a 20 ml quartz Shrek tube, seal it and perform three freeze-thaw cycles to remove oxygen from the reaction system. Use a purple LED light to continuously irradiate for 12 hours. After the reaction is completed, dilute the resulting polymer solution with 10 ml of deionized water, extract it three times with 10 ml of dichloromethane, combine the resulting dichloromethane, remove the dichloromethane by rotary evaporation, and then dry the resulting polymer at 40°C for 24 hours to obtain 3.68 g (73%) of polyPEGA480.

[0043] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An atom transfer radical polymerization photocatalyst based on a dipyridylthiadiazole quaternary ammonium salt derivative, characterized in that: The catalyst is a dipyridylthiadiazole quaternary ammonium salt derivative, and the dipyridylthiadiazole derivative has a structure shown in formula (I): Among them, R is n-butyl, isobutyl, tert-butyl, or n-hexyl.

2. A method for performing atom transfer radical polymerization based on the atom transfer radical polymerization photocatalyst of the dipyridylthiadiazole quaternary ammonium salt derivative according to claim 1, characterized in that: The atom transfer radical polymerization photocatalyst, initiator, monomer and solvent are mixed, and irradiated with light at a wavelength of 360-480 nm for a period of time to obtain a polymer; Wherein, the catalyst is a dipyridylthiadiazole quaternary ammonium salt derivative; Wherein, for catalyzing atom transfer radical polymerization, the monomer is one or a mixture of the following (II-1) to (II-13): Among them, for catalyzing atom transfer radical polymerization reaction, the initiator is one or a mixture of (III-1) to (III-5): Wherein, the solvent is one or a mixture of water, dichloromethane, acetonitrile, ethanol, methanol, tetrahydrofuran, and dimethyl sulfoxide.

3. The method according to claim 2, characterized in that When used in atom transfer radical polymerization, the amount of catalyst used relative to the monomer is 10-1000ppm.

4. An application of an atom transfer radical polymerization photocatalyst based on a dipyridylthiadiazole quaternary ammonium salt derivative according to claim 1, characterized in that: It is used in the preparation of plastics, resins, gels, adhesives and polymer materials.

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