4-pyridine oxide or morpholine tertiary amine oxide with high steric hindrance and application of 4-pyridine oxide or morpholine tertiary amine oxide in synthesis of low-PDI polymerization product

Abstract

The invention discloses a high-steric-hindrance 4-pyridine oxide or morpholine tertiary amine oxide and application thereof in synthesis of low-PDI polymerization products, secondary amine and aryl halide are subjected to catalytic oxidation and then refined and separated to obtain the tertiary amine oxide, and the tertiary amine oxide can be used for active free radical polymerization in a solvent system and can be used for preparing high-PDI polymerization products. And effective regulation and control of the polymerization process are realized through binding-dissociation balance with the growth chain segment in the polymerization process. The oxide of the 4-oxopiperidine / morpholine high-steric-hindrance tertiary amine derivative is more suitable for the polymerization reaction of acrylate monomers, the Mw of the polymerization product is distributed in a range of 8000-50000, and the PDI adjusting range is 1.21-1.40.

Description

Technical Field

[0001] The present invention belongs to the technical field of living radical polymerization, and particularly relates to the aryl capping and oxidation of secondary amine compounds and the application of the obtained products as regulators in controlled / living radical polymerization. Background Art

[0002] In the actual production process of general free radical polymerization, the obtained polymer products have a wide molecular weight distribution, and the mechanical strength, heat resistance and other properties of polymer products with different molecular weights have obvious differences in the application scenarios. Relevant researchers (Surf.Sci.2004,570(1-2):1-12; J.Polym.Res.2014,21:1-9; J.Am.Chem.Soc.2006,128(23):7622-7629.) systematically summarized the defects in the traditional free radical polymerization process due to the kinetic characteristics of "slow initiation, fast propagation, and rapid termination", resulting in irreversible termination of free radical chains, broad molecular weight distribution (PDI>2), and difficulty in accurately controlling the degree of polymerization.

[0003] Regarding nitroxide-mediated radical polymerization (NMP), there have been some reports on the structure of nitroxide stable radicals (Macromolecules 31.9(1998):2883-2888; J.Am.Chem.Soc.122.25(2000):5929-5939; US20130059964A1; US20170015762A1; US20230192962A1; CN115380054A). They are all based on the reaction products of secondary amine structures and peroxides, and can be accurately controlled during polymerization. However, the secondary amine precursors of such structures often require complex synthesis steps and are not common chemical raw materials. Some secondary amine oxides such as 2,2,6,6-tetramethylpiperidine oxide have been developed on a large scale and are commercially available, but the yields in the synthesis process are generally low, the synthesis cost is high, and generally a high temperature above 120°C is required to maintain its reaction activity during its application, resulting in high energy consumption, and the side reactions brought about by high temperature cannot be controlled.

[0004] Some researchers have used the reaction products of secondary amine structures and peroxides for precise control during polymerization. However, the synthesis steps of the secondary amine precursors of such structures are complex, the raw material sources are not common substances on the market, and the yields in the synthesis process are generally low, the synthesis cost is high. Generally, a high temperature above 120°C is required to maintain its reaction activity during its application, resulting in high energy consumption, and the side reactions brought about by high temperature cannot be controlled.

[0005] The regulation of the existing amine oxides on the polymerized free radical chain segments is that the oxygen atoms in a certain oxide carry partial positive charges, and through single electron transfer, they act on the free radical long chains obtained by polymerization, and then combine with them. The regulation of the molecular weight distribution is achieved through the dynamic equilibrium of binding-dissociation, as shown below:

[0006]

[0007] The dynamic equilibrium of the binding of polyether amine oxides to free radical chain segments. However, such structures are single in variety, and most of them use long-chain amine polyethoxy ethers as oxidation precursors, and can only be applied to emulsion polymerization systems, with relatively single reaction scenarios. Summary of the Invention

[0008] Object of the Invention: Aiming at the defects and technical problems existing in the background technology, the present invention provides a high steric hindrance 4-pyridine oxide or morpholine tertiary amine oxide and its application in the synthesis of low-PDI polymer products. The initiation system of the oxidation product of this high steric hindrance tertiary amine compound is applicable to solution polymerization occurring in common solvents such as toluene, xylene, butyl acetate, DMSO, DMF, etc., and the PDI range of the polymerized product is 1.21 - 1.40.

[0009] Technical Solution: To achieve the above object of the invention, the present invention adopts the following technical solution: A high steric hindrance 4-pyridine oxide or morpholine tertiary amine oxide has the following molecular structural formula,

[0010]

[0011] In the structural formula, R’ is mono- to octa-substituted, and the substituents are each independently selected from a hydrogen atom, C 1-4 alkyl, ester group; Y is selected from an oxygen atom or a carbonyl group; Ar is selected from an indenyl group, a fluorenyl group or a dimethylfluorenyl group, a naphthyl group, a substituted phenyl group, a phenanthryl group; there is at least 1 substituent on the substituted phenyl group, and it is independently selected from an ester group, an alkyl group, an alkoxy group.

[0012] The present invention also provides a synthesis method of the above high steric hindrance 4-pyridine oxide or morpholine tertiary amine oxide, including the following steps:

[0013] S1, Synthesis of the tertiary amine precursor: In a reaction vessel, add a solvent, a secondary amine, and a halogenated hydrocarbon. After fully dissolving and mixing evenly, continue to add a basic catalyst, and raise the temperature to 60 - 150 °C and react for 4 - 48 h to obtain a crude tertiary amine product; the halogenated hydrocarbon is a halogenated aromatic hydrocarbon or a halogenated cycloalkane;

[0014] S2, Refining of the tertiary amine: Column chromatography separation of the crude tertiary amine product with a petroleum ether / ethyl acetate eluent with a volume ratio of 50:1 - 1:1 to obtain a pure tertiary amine product;

[0015] S3, Synthesis of tertiary amine oxide: Add the pure tertiary amine product and an organic solvent into a container, heat up to 40 - 150 °C to fully dissolve them; then dropwise add hydrogen peroxide into it, react for 3 - 72 h to obtain a tertiary amine oxide solution;

[0016] S4, After removing the solvent from the tertiary amine oxide solution by vacuum distillation, tertiary amine oxide is obtained.

[0017] Further, in step S1, the molar ratio of the halogenated hydrocarbon to the secondary amine is 0.5 - 3:1.

[0018] Further, the secondary amine is selected from 3 - methylmorpholine, 2,2 - dimethylmorpholine, 3,3 - dimethylmorpholine, 2,6 - dimethylmorpholine, 2,2,3 - trimethylmorpholine, 2,2,5 - trimethylmorpholine, 2,2,6 - trimethylmorpholine, 2,5,5 - trimethylmorpholine, 3,3,5 - trimethylmorpholine, 2,2,6,6 - tetramethylmorpholine, 3,3,5,5 - tetramethylmorpholine, 2 - isopropylmorpholine, 3 - isopropylmorpholine, 2 - isobutylmorpholine, 3 - isobutylmorpholine, methyl 3 - morpholinecarboxylate, ethyl morpholine - 3 - carboxylate, methyl 4 - oxopiperidine - 2 - carboxylate, methyl 6 - methyl - 4 - oxopiperidine - 2 - carboxylate, 2,6 - dimethylpiperidin - 4 - one, 2,2,6,6 - tetramethyl - 4 - piperidone.

[0019] Further, the halogenated aromatic hydrocarbon is selected from 2 - bromoindene, 1 - bromo - 9H - fluorene, 2 - bromofluorene, 3 - bromo - 9H - fluorene, 4 - bromo - 9H - fluorene, 9,9 - dimethyl - 2 - bromofluorene, 3 - bromo - 9,9 - dimethylfluorene, 4 - bromo - 9,9 - dimethylfluorene, 1 - bromonaphthalene, 2 - bromonaphthalene, ethyl 2 - bromobenzoate, tert - butyl 2 - bromobenzoate, dimethyl 2 - bromoisophthalate, 1 - bromo - 4 - tert - butyl - 2 - ethylbenzene, 2,6 - di - tert - butylbromobenzene, 1 - bromo - 2,6 - dimethoxybenzene, 1 - bromo - 2,4,6 - trimethoxybenzene, 3 - bromophenanthrene, 9 - bromophenanthrene.

[0020] Further, the basic catalyst is selected from sodium bicarbonate, potassium bicarbonate, sodium carbonate, potassium carbonate, cesium carbonate, sodium hydroxide, potassium hydroxide, calcium hydroxide, cesium hydroxide, sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, sodium isopropoxide, trimethylamine, triethylamine, ethylenediamine, diethylamine, tert - butylamine, piperidine, pyridine, 4 - dimethylaminopyridine, sodium tert - butoxide, potassium tert - butoxide, lithium diisopropylamide, n - butyllithium, sodium triphenylmethyl.

[0021] Further, the organic solvent is selected from benzene, toluene, ethylbenzene, xylene, dichloromethane, chloroform, carbon tetrachloride, dichloroethane, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, acetone, butanone, cyclohexanone, ether, tetrahydrofuran, ethylene glycol dimethyl ether, ethyl acetate, butyl acetate, dimethyl carbonate, diethyl carbonate, N, N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, hexamethylphosphoric triamide, sulfolane.

[0022] Further, the molar ratio of the addition amount of the halogenated hydrocarbon to the addition amount of the secondary amine is 1-1.5:1, the molar ratio of the basic catalyst to the secondary amine is 1.2-1.8:1, and the molar ratio of hydrogen peroxide to the pure tertiary amine product is 8-20:1.

[0023] Further, the reaction temperature in step S1 is 80±10°C, and the reaction time is 8±1 h; the reaction temperature in step S3 is 85±5°C, and the reaction temperature is 8±1 h.

[0024] The present invention also provides an application of the above-mentioned high steric hindrance 4-oxidopyridine or morpholine tertiary amine oxide in a radical polymerization reaction to obtain a polymerization product with a lower PDI.

[0025] In the synthesis method of the low-PDI polymerization product of the present invention, in a reaction vessel, after adding a polymerization monomer, an azo initiator and an appropriate amount of solvent, add the high steric hindrance 4-oxidopyridine or morpholine tertiary amine oxide according to any one of claims 1-9 in a molar ratio of 0.1-3% relative to the polymerization monomer. After sealing and freeze-thaw degassing several times, heat the system to 60-140°C. After reacting for 3-12 hours, immediately place it in liquid nitrogen to terminate the reaction, and rotary evaporate to remove the solvent and the remaining monomer to obtain a low-PDI polymerization product.

[0026] Further, the polymerization monomer is selected from acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, 2-hydroxyethyl acrylate, methyl methacrylate, ethyl methacrylate, 2-hydroxyethyl methacrylate, N,N-dimethylaminoethyl acrylate, allyl polyether, allyl epoxy-terminated polyether, allyl methyl-terminated polyether, diallyl-terminated polyether.

[0027] Further, the azo initiator is azobisisobutyronitrile, azobisisoheptonitrile, dimethyl azobisisobutyrate, azobisisobutamidine hydrochloride, azobisisobutimidazoline hydrochloride, azoisopentanenitrile, azoisobutyronitrile carboxamide. Beneficial effects: Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The steric hindrance in the molecular structure of the tertiary amine is larger, and its oxidation product has a better regulation and stabilization effect on the chain growth radical, and can effectively adjust the molecular weight during the polymerization process. Especially when targeting polymerization monomers such as acrylic acid, acrylate or allyl polyether, it has an excellent PDI value.

[0029] (2) When this tertiary amine oxide is used as a regulator in solution polymerization, it exhibits the characteristics of living polymerization, and the resulting polymer has a narrow molecular weight distribution.

[0030] (3) Develop a high steric hindrance tertiary amine oxide regulator with a small molecular weight. Based on the previous tertiary amine oxide surfactants, the application scenario has been broadened to the solution polymerization system. Moreover, this type of tertiary amine oxide has a small molecular weight, moderate polarity, can dissolve in a variety of organic solvents, and has a certain universality.

[0031] (4) The temperature required to maintain the reaction activity of the tertiary amine oxide is lower, only 80 - 90 °C, and the energy consumption is less. Brief Description of the Drawings

[0032] Figure 1 It is the molecular structural formula of the high steric hindrance pyridine 4 - oxide or morpholine tertiary amine oxide described in the present invention. Detailed Embodiments

[0033] The following further clarifies the present invention in conjunction with the drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. After reading the present invention, various equivalent modifications made by those skilled in the art fall within the scope defined by the appended claims of this application.

[0034] Example 1

[0035]

[0036] Synthesis of tertiary amine compound a1: In a round - bottom flask, successively add 145 mg of methyl 3 - morpholinocarboxylate, 10 mL of DMF, and 234 mg of 2 - bromoindene. After stirring evenly to ensure complete dissolution of each component, add 106 mg of sodium carbonate. After stirring evenly to dissolve, heat up to 80 °C. After reacting for 8 hours, filter to obtain the filtrate. After rotary evaporation, the crude product is obtained, and column chromatography purification is carried out with an eluent ratio of petroleum ether / ethyl acetate of 10:1 to obtain the pure product.

[0037] Synthesis of tertiary amine oxide b1: Add 259 mg of tertiary amine compound a1 and 20 mL of ethanol to the flask, then heat up to 60 °C to fully dissolve the two. Slowly dropwise add 1.1 mL of 30% hydrogen peroxide, raise the temperature to 85 °C, and heat under reflux for 7 hours. After evaporating the solvent, the oxide is obtained.

[0038] Example 2

[0039]

[0040] Synthesis of tertiary amine compound a2: In a round-bottom flask, 145 mg of methyl 3-morpholinocarboxylate, 10 mL of DMF, and 260 mg of 3-bromo-9H-fluorene were added in sequence. After stirring evenly to ensure complete dissolution of each component, 106 mg of sodium carbonate was added. After stirring evenly to dissolve, the temperature was raised to 80 °C. After reacting for 9 hours, the filtrate was obtained by filtration. After rotary evaporation, the crude product was obtained, and column chromatography purification was carried out with a petroleum ether / ethyl acetate eluent ratio of 13:1 to obtain the pure product.

[0041] Synthesis of tertiary amine oxide b2: 309 mg of tertiary amine compound a2 and 20 mL of ethanol were added to a flask, and then the temperature was raised to 60 °C to fully dissolve the two. 1.1 mL of 30% hydrogen peroxide was added dropwise at a constant speed, the temperature was raised to 85 °C, and reflux was carried out for 7 hours. After evaporating the solvent, the oxide was obtained.

[0042] Example 3

[0043]

[0044] Synthesis of tertiary amine compound a3: In a round-bottom flask, 145 mg of methyl 3-morpholinocarboxylate, 10 mL of DMF, and 285 mg of 3-bromo-9,9-dimethylfluorene were added in sequence. After stirring evenly to ensure complete dissolution of each component, 106 mg of sodium carbonate was added. After stirring evenly to dissolve, the temperature was raised to 80 °C. After reacting for 9 hours, the filtrate was obtained by filtration. After rotary evaporation, the crude product was obtained, and column chromatography purification was carried out with a petroleum ether / ethyl acetate eluent ratio of 15:1 to obtain the pure product.

[0045] Synthesis of tertiary amine oxide b3: 337 mg of tertiary amine compound a3 and 20 mL of ethanol were added to a flask, and then the temperature was raised to 60 °C to fully dissolve the two. 1.1 mL of 30% hydrogen peroxide was added dropwise at a constant speed, the temperature was raised to 85 °C, and reflux was carried out for 7 hours. After evaporating the solvent, the oxide was obtained.

[0046] Example 4

[0047]

[0048] Synthesis of tertiary amine compound a4: In a round-bottom flask, 145 mg of methyl 3-morpholinocarboxylate, 10 mL of DMF, and 228 mg of 1-bromonaphthalene were added in sequence. After stirring evenly to ensure complete dissolution of each component, 106 mg of sodium carbonate was added. After stirring evenly to dissolve, the temperature was raised to 80 °C. After reacting for 9 hours, the filtrate was obtained by filtration. After rotary evaporation, the crude product was obtained, and column chromatography purification was carried out with a petroleum ether / ethyl acetate eluent ratio of 8:1 to obtain the pure product.

[0049] Synthesis of tertiary amine oxide 4: Add 271 mg of tertiary amine compound a4 and 20 mL of ethanol into a flask, then heat up to 60 °C to fully dissolve the two. Slowly add 1.1 mL of 30% hydrogen peroxide dropwise, raise the temperature to 85 °C, and reflux for 7 hours. After evaporating the solvent, the oxide is obtained.

[0050] Example 5

[0051]

[0052] Synthesis of tertiary amine compound a5: Add 145 mg of methyl 3-morpholinecarboxylate, 10 mL of DMF, and 300 mg of dimethyl 2-bromoisophthalate into a round-bottom flask in sequence. After stirring evenly to ensure complete dissolution of each component, add 106 mg of sodium carbonate. After stirring evenly and dissolving, heat up to 80 °C and react for 9 hours. Then filter to obtain the filtrate, and after rotary evaporation, the crude product is obtained. Column chromatography purification is carried out with a petroleum ether / ethyl acetate eluent ratio of 6:1 to obtain the pure product.

[0053] Synthesis of tertiary amine oxide b5: Add 337 mg of tertiary amine compound a5 and 20 mL of ethanol into a flask, then heat up to 60 °C to fully dissolve the two. Slowly add 1.1 mL of 30% hydrogen peroxide dropwise, raise the temperature to 85 °C, and reflux for 7 hours. After evaporating the solvent, the oxide is obtained.

[0054] Example 6

[0055]

[0056] Synthesis of tertiary amine compound a6: Add 145 mg of methyl 3-morpholinecarboxylate, 10 mL of DMF, and 296 mg of 2,6-di-tert-butylbromobenzene into a round-bottom flask in sequence. After stirring evenly to ensure complete dissolution of each component, add 106 mg of sodium carbonate. After stirring evenly and dissolving, heat up to 80 °C and react for 9 hours. Then filter to obtain the filtrate, and after rotary evaporation, the crude product is obtained. Column chromatography purification is carried out with a petroleum ether / ethyl acetate eluent ratio of 6:1 to obtain the pure product.

[0057] Synthesis of tertiary amine oxide b6: Add 337 mg of tertiary amine compound a6 and 20 mL of ethanol into a flask, then heat up to 60 °C to fully dissolve the two. Slowly add 1.1 mL of 30% hydrogen peroxide dropwise, raise the temperature to 85 °C, and reflux for 7 hours. After evaporating the solvent, the oxide is obtained.

[0058] Example 7

[0059]

[0060] Synthesis of tertiary amine compound a7: 145 mg of methyl 3-morpholinecarboxylate, 10 mL of DMF, and 272 mg of 1-bromo-2,4,6-trimethoxybenzene were successively added to a round-bottom flask. After stirring evenly to ensure complete dissolution of each component, 106 mg of sodium carbonate was added. After stirring evenly to dissolve, the temperature was raised to 80 °C. After reacting for 9 hours, the filtrate was obtained by filtration. After rotary evaporation, the crude product was obtained and purified by column chromatography with a petroleum ether / ethyl acetate eluent ratio of 5:1 to obtain the pure product.

[0061] Synthesis of tertiary amine oxide b7: 311 mg of tertiary amine compound a7 and 20 mL of ethanol were added to a flask. Then the temperature was raised to 60 °C to fully dissolve the two. 1.1 mL of 30% hydrogen peroxide was added dropwise at a constant speed, and the temperature was raised to 85 °C. After heating under reflux for 7 hours, the solvent was evaporated to obtain the oxide.

[0062] Example 8

[0063]

[0064] Synthesis of tertiary amine compound a8: 145 mg of methyl 3-morpholinecarboxylate, 10 mL of DMF, and 349 mg of 9-bromophenanthrene were successively added to a round-bottom flask. After stirring evenly to ensure complete dissolution of each component, 106 mg of sodium carbonate was added. After stirring evenly to dissolve, the temperature was raised to 80 °C. After reacting for 9 hours, the filtrate was obtained by filtration. After rotary evaporation, the crude product was obtained and purified by column chromatography with a petroleum ether / ethyl acetate eluent ratio of 9:1 to obtain the pure product.

[0065] Synthesis of tertiary amine oxide b8: 311 mg of tertiary amine compound a8 and 20 mL of ethanol were added to a flask. Then the temperature was raised to 60 °C to fully dissolve the two. 1.1 mL of 30% hydrogen peroxide was added dropwise at a constant speed, and the temperature was raised to 85 °C. After heating under reflux for 7 hours, the solvent was evaporated to obtain the oxide.

[0066] Example 9

[0067]

[0068] Synthesis of tertiary amine compound a9: 129 mg of 3-isopropylmorpholine, 10 mL of DMF, and 213 mg of 2-bromoindene were successively added to a round-bottom flask. After stirring evenly to ensure complete dissolution of each component, 106 mg of sodium carbonate was added. After stirring evenly to dissolve, the temperature was raised to 80 °C. After reacting for 9 hours, the filtrate was obtained by filtration. After rotary evaporation, the crude product was obtained and purified by column chromatography with a petroleum ether / ethyl acetate eluent ratio of 13:1 to obtain the pure product.

[0069] Synthesis of tertiary amine oxide b9: Add 243 mg of tertiary amine compound a9 and 20 mL of ethanol into a flask, then heat up to 60 °C to fully dissolve the two. Slowly add 1.1 mL of 30% hydrogen peroxide dropwise, raise the temperature to 85 °C, and reflux for 7 hours. After evaporating the solvent, the oxide is obtained.

[0070] Example 10

[0071]

[0072] Synthesis of tertiary amine compound a10: Add 129 mg of 3 - isopropylmorpholine, 10 mL of DMF, and 270 mg of 3 - bromo - 9H - fluorene into a round - bottom flask in sequence. After stirring evenly to ensure complete dissolution of each component, add 106 mg of sodium carbonate. After stirring evenly and dissolving, heat up to 80 °C and react for 9 hours. Then filter to obtain the filtrate, and after rotary evaporation, the crude product is obtained. Purify it by column chromatography with an eluent ratio of petroleum ether / ethyl acetate of 11:1 to obtain the pure product.

[0073] Synthesis of tertiary amine oxide b10: Add 293 mg of tertiary amine compound a10 and 20 mL of ethanol into a flask, then heat up to 60 °C to fully dissolve the two. Slowly add 1.1 mL of 30% hydrogen peroxide dropwise, raise the temperature to 85 °C, and reflux for 7 hours. After evaporating the solvent, the oxide is obtained.

[0074] Example 11

[0075]

[0076] Synthesis of tertiary amine compound a11: Add 129 mg of 3 - isopropylmorpholine, 10 mL of DMF, and 285 mg of 3 - bromo - 9,9 - dimethylfluorene into a round - bottom flask in sequence. After stirring evenly to ensure complete dissolution of each component, add 106 mg of sodium carbonate. After stirring evenly and dissolving, heat up to 80 °C and react for 9 hours. Then filter to obtain the filtrate, and after rotary evaporation, the crude product is obtained. Purify it by column chromatography with an eluent ratio of petroleum ether / ethyl acetate of 12:1 to obtain the pure product.

[0077] Synthesis of tertiary amine oxide b11: Add 321 mg of tertiary amine compound a11 and 20 mL of ethanol into a flask, then heat up to 60 °C to fully dissolve the two. Slowly add 1.1 mL of 30% hydrogen peroxide dropwise, raise the temperature to 85 °C, and reflux for 7 hours. After evaporating the solvent, the oxide is obtained.

[0078] Example 12

[0079]

[0080] Synthesis of tertiary amine compound a12: Add 129 mg of 3-isopropylmorpholine, 10 mL of DMF, and 228 mg of 1-bromonaphthalene into a round-bottom flask in sequence. After stirring evenly to ensure complete dissolution of each component, add 106 mg of sodium carbonate. After stirring evenly to dissolve, heat up to 80 °C. After reacting for 9 hours, filter to obtain the filtrate. After rotary evaporation, obtain the crude product, and perform column chromatography purification with a petroleum ether / ethyl acetate eluent ratio of 10:1 to obtain the pure product.

[0081] Synthesis of tertiary amine oxide b12: Add 255 mg of tertiary amine compound a12 and 20 mL of ethanol into a flask, then heat up to 60 °C to fully dissolve the two. Slowly add 1.1 mL of 30% hydrogen peroxide dropwise, raise the temperature to 85 °C, and heat under reflux for 7 hours. After evaporating the solvent, the oxide is obtained.

[0082] Example 13

[0083]

[0084] Synthesis of tertiary amine compound a13: Add 129 mg of 3-isopropylmorpholine, 10 mL of DMF, and 301 mg of dimethyl 2-bromoisophthalate into a round-bottom flask in sequence. After stirring evenly to ensure complete dissolution of each component, add 106 mg of sodium carbonate. After stirring evenly to dissolve, heat up to 80 °C. After reacting for 9 hours, filter to obtain the filtrate. After rotary evaporation, obtain the crude product, and perform column chromatography purification with a petroleum ether / ethyl acetate eluent ratio of 10:1 to obtain the pure product.

[0085] Synthesis of tertiary amine oxide b13: Add 321 mg of tertiary amine compound a13 and 20 mL of ethanol into a flask, then heat up to 60 °C to fully dissolve the two. Slowly add 1.1 mL of 30% hydrogen peroxide dropwise, raise the temperature to 85 °C, and heat under reflux for 7 hours. After evaporating the solvent, the oxide is obtained.

[0086] Example 14

[0087]

[0088] Synthesis of tertiary amine compound a14: Add 129 mg of 3-isopropylmorpholine, 10 mL of DMF, and 300 mg of 1,3-di-tert-butyl-2-bromobenzene into a round-bottom flask in sequence. After stirring evenly to ensure complete dissolution of each component, add 106 mg of sodium carbonate. After stirring evenly to dissolve, heat up to 80 °C. After reacting for 9 hours, filter to obtain the filtrate. After rotary evaporation, obtain the crude product, and perform column chromatography purification with a petroleum ether / ethyl acetate eluent ratio of 17:1 to obtain the pure product.

[0089] Synthesis of tertiary amine oxide b14: Add 317 mg of tertiary amine compound a14 and 20 mL of ethanol into a flask, then heat up to 60 °C to fully dissolve the two. Slowly add 1.1 mL of 30% hydrogen peroxide drop by drop, raise the temperature to 85 °C, and reflux for 7 hours. After evaporating the solvent, the oxide is obtained.

[0090] Example 15

[0091]

[0092] Synthesis of tertiary amine compound a15: Add 129 mg of 3 - isopropylmorpholine, 10 mL of DMF, and 271 mg of 2 - bromo - 1,3,5 - trimethoxybenzene into a round - bottom flask in sequence. After stirring evenly to ensure complete dissolution of each component, add 106 mg of sodium carbonate. After stirring evenly and dissolving, heat up to 80 °C and react for 9 hours. Then filter to obtain the filtrate. After rotary evaporation, the crude product is obtained and purified by column chromatography with a petroleum ether / ethyl acetate eluent ratio of 9:1 to obtain the pure product.

[0093] Synthesis of tertiary amine oxide b15: Add 295 mg of tertiary amine compound a15 and 20 mL of ethanol into a flask, then heat up to 60 °C to fully dissolve the two. Slowly add 1.1 mL of 30% hydrogen peroxide drop by drop, raise the temperature to 85 °C, and reflux for 7 hours. After evaporating the solvent, the oxide is obtained.

[0094] Example 16

[0095]

[0096] Synthesis of tertiary amine compound a16: Add 129 mg of 3 - isopropylmorpholine, 10 mL of DMF, and 283 mg of 9 - bromophenanthrene into a round - bottom flask in sequence. After stirring evenly to ensure complete dissolution of each component, add 106 mg of sodium carbonate. After stirring evenly and dissolving, heat up to 80 °C and react for 9 hours. Then filter to obtain the filtrate. After rotary evaporation, the crude product is obtained and purified by column chromatography with a petroleum ether / ethyl acetate eluent ratio of 9:1 to obtain the pure product.

[0097] Synthesis of tertiary amine oxide b16: Add 305 mg of tertiary amine compound a16 and 20 mL of ethanol into a flask, then heat up to 60 °C to fully dissolve the two. Slowly add 1.1 mL of 30% hydrogen peroxide drop by drop, raise the temperature to 85 °C, and reflux for 7 hours. After evaporating the solvent, the oxide is obtained.

[0098] Example 17

[0099]

[0100] Synthesis of tertiary amine compound a17: Add 155 mg of 2,2,6,6-tetramethyl-4-piperidone, 10 mL of DMF, and 213 mg of 2-bromoindene into a round-bottom flask in sequence. After stirring evenly to ensure complete dissolution of each component, add 106 mg of sodium carbonate. After stirring evenly and dissolving, heat up to 80 °C. After reacting for 9 hours, filter to obtain the filtrate. After rotary evaporation, the crude product is obtained, and column chromatography purification is carried out with a petroleum ether / ethyl acetate eluent ratio of 10:1 to obtain the pure product.

[0101] Synthesis of tertiary amine oxide b17: Add 269 mg of tertiary amine compound a17 and 20 mL of ethanol into a flask, then heat up to 60 °C to fully dissolve the two. Slowly add 1.1 mL of 30% hydrogen peroxide dropwise, raise the temperature to 85 °C, and heat under reflux for 7 hours. After evaporating the solvent, the oxide is obtained.

[0102] Example 18

[0103]

[0104] Synthesis of tertiary amine compound a18: Add 155 mg of 2,2,6,6-tetramethyl-4-piperidone, 10 mL of DMF, and 270 mg of 3-bromo-9H-fluorene into a round-bottom flask in sequence. After stirring evenly to ensure complete dissolution of each component, add 106 mg of sodium carbonate. After stirring evenly and dissolving, heat up to 80 °C. After reacting for 9 hours, filter to obtain the filtrate. After rotary evaporation, the crude product is obtained, and column chromatography purification is carried out with a petroleum ether / ethyl acetate eluent ratio of 13:1 to obtain the pure product.

[0105] Synthesis of tertiary amine oxide b18: Add 319 mg of tertiary amine compound a18 and 20 mL of ethanol into a flask, then heat up to 60 °C to fully dissolve the two. Slowly add 1.1 mL of 30% hydrogen peroxide dropwise, raise the temperature to 85 °C, and heat under reflux for 7 hours. After evaporating the solvent, the oxide is obtained.

[0106] Example 19

[0107]

[0108] Synthesis of tertiary amine compound a19: Add 155 mg of 2,2,6,6-tetramethyl-4-piperidone, 10 mL of DMF, and 285 mg of 3-bromo-9,9-dimethylfluorene into a round-bottom flask in sequence. After stirring evenly to ensure complete dissolution of each component, add 106 mg of sodium carbonate. After stirring evenly and dissolving, heat up to 80 °C. After reacting for 9 hours, filter to obtain the filtrate. After rotary evaporation, the crude product is obtained, and column chromatography purification is carried out with a petroleum ether / ethyl acetate eluent ratio of 15:1 to obtain the pure product.

[0109] Synthesis of tertiary amine oxide b19: Add 347 mg of tertiary amine compound a19 and 20 mL of ethanol to a flask, then heat to 60 °C to fully dissolve the two. Slowly add 1.1 mL of 30% hydrogen peroxide dropwise, raise the temperature to 85 °C, and reflux for 7 hours. After evaporating the solvent, the oxide is obtained.

[0110] Example 20

[0111]

[0112] Synthesis of tertiary amine compound a20: Add 155 mg of 2,2,6,6-tetramethyl-4-piperidone, 10 mL of DMF, and 228 mg of 1-bromonaphthalene to a round-bottom flask in sequence. After stirring evenly to ensure complete dissolution of each component, add 106 mg of sodium carbonate, stir evenly to dissolve, heat to 80 °C, react for 9 hours, filter to obtain the filtrate, and obtain the crude product after rotary evaporation. Purify by column chromatography with an eluent ratio of petroleum ether / ethyl acetate of 13:1 to obtain the pure product.

[0113] Synthesis of tertiary amine oxide b20: Add 281 mg of tertiary amine compound a20 and 20 mL of ethanol to a flask, then heat to 60 °C to fully dissolve the two. Slowly add 1.1 mL of 30% hydrogen peroxide dropwise, raise the temperature to 85 °C, and reflux for 7 hours. After evaporating the solvent, the oxide is obtained.

[0114] Example 21

[0115]

[0116] Synthesis of tertiary amine compound a21: Add 155 mg of 2,2,6,6-tetramethyl-4-piperidone, 10 mL of DMF, and 301 mg of dimethyl 2-bromoisophthalate to a round-bottom flask in sequence. After stirring evenly to ensure complete dissolution of each component, add 106 mg of sodium carbonate, stir evenly to dissolve, heat to 80 °C, react for 9 hours, filter to obtain the filtrate, and obtain the crude product after rotary evaporation. Purify by column chromatography with an eluent ratio of petroleum ether / ethyl acetate of 10:1 to obtain the pure product.

[0117] Synthesis of tertiary amine oxide b21: Add 347 mg of tertiary amine compound a21 and 20 mL of ethanol to a flask, then heat to 60 °C to fully dissolve the two. Slowly add 1.1 mL of 30% hydrogen peroxide dropwise, raise the temperature to 85 °C, and reflux for 7 hours. After evaporating the solvent, the oxide is obtained.

[0118] Example 22

[0119]

[0120] Synthesis of tertiary amine compound a22: Add 155 mg of 2,2,6,6-tetramethyl-4-piperidone, 10 mL of DMF, and 300 mg of 1,3-di-tert-butyl-2-bromobenzene into a round-bottom flask in sequence. After stirring evenly to ensure complete dissolution of each component, add 106 mg of sodium carbonate. After stirring evenly to dissolve, heat up to 80 °C. After reacting for 9 hours, filter to obtain the filtrate. After rotary evaporation, a crude product is obtained, and column chromatography purification is carried out with a petroleum ether / ethyl acetate eluent ratio of 19:1 to obtain the pure product.

[0121] Synthesis of tertiary amine oxide b22: Add 343 mg of tertiary amine compound a22 and 20 mL of ethanol into a flask, then heat up to 60 °C to fully dissolve the two. Slowly dropwise add 1.1 mL of 30% hydrogen peroxide, raise the temperature to 85 °C, and heat under reflux for 7 hours. After evaporating the solvent, the oxide is obtained.

[0122] Example 23

[0123]

[0124] Synthesis of tertiary amine compound a23: Add 155 mg of 2,2,6,6-tetramethyl-4-piperidone, 10 mL of DMF, and 271 mg of 2-bromo-1,3,5-trimethoxybenzene into a round-bottom flask in sequence. After stirring evenly to ensure complete dissolution of each component, add 106 mg of sodium carbonate. After stirring evenly to dissolve, heat up to 80 °C. After reacting for 9 hours, filter to obtain the filtrate. After rotary evaporation, a crude product is obtained, and column chromatography purification is carried out with a petroleum ether / ethyl acetate eluent ratio of 9:1 to obtain the pure product.

[0125] Synthesis of tertiary amine oxide b23: Add 321 mg of tertiary amine compound a23 and 20 mL of ethanol into a flask, then heat up to 60 °C to fully dissolve the two. Slowly dropwise add 1.1 mL of 30% hydrogen peroxide, raise the temperature to 85 °C, and heat under reflux for 7 hours. After evaporating the solvent, the oxide is obtained.

[0126] Example 24

[0127]

[0128] Synthesis of tertiary amine compound a24: Add 155 mg of 2,2,6,6-tetramethyl-4-piperidone, 10 mL of DMF, and 283 mg of 9-bromophenanthrene into a round-bottom flask in sequence. After stirring evenly to ensure complete dissolution of each component, add 106 mg of sodium carbonate. After stirring evenly to dissolve, heat up to 80 °C. After reacting for 9 hours, filter to obtain the filtrate. After rotary evaporation, a crude product is obtained, and column chromatography purification is carried out with a petroleum ether / ethyl acetate eluent ratio of 9:1 to obtain the pure product.

[0129] Synthesis of tertiary amine oxide b24: Add 331 mg of tertiary amine compound a24 and 20 mL of ethanol into a flask, then heat up to 60 °C to fully dissolve the two. Slowly add 1.1 mL of 30% hydrogen peroxide dropwise, raise the temperature to 85 °C, and reflux for 7 hours. After evaporating the solvent, the oxide is obtained.

[0130] Example 25

[0131]

[0132] Synthesis of tertiary amine compound a25: Add 172 mg of methyl 6-methyl-4-oxopiperidine-2-carboxylate, 10 mL of DMF, and 213 mg of 2-bromoindene into a round-bottom flask in sequence. After stirring evenly to ensure complete dissolution of each component, add 106 mg of sodium carbonate, stir evenly to dissolve, then heat up to 80 °C, react for 9 hours, filter to obtain the filtrate, and obtain the crude product after rotary evaporation. Purify by column chromatography with an eluent ratio of petroleum ether / ethyl acetate of 14:1 to obtain the pure product.

[0133] Synthesis of tertiary amine oxide b25: Add 286 mg of tertiary amine compound a25 and 20 mL of ethanol into a flask, then heat up to 60 °C to fully dissolve the two. Slowly add 1.1 mL of 30% hydrogen peroxide dropwise, raise the temperature to 85 °C, and reflux for 7 hours. After evaporating the solvent, the oxide is obtained.

[0134] Example 26

[0135]

[0136] Synthesis of tertiary amine compound a26: Add 172 mg of methyl 6-methyl-4-oxopiperidine-2-carboxylate, 10 mL of DMF, and 270 mg of 3-bromo-9H-fluorene into a round-bottom flask in sequence. After stirring evenly to ensure complete dissolution of each component, add 106 mg of sodium carbonate, stir evenly to dissolve, then heat up to 80 °C, react for 9 hours, filter to obtain the filtrate, and obtain the crude product after rotary evaporation. Purify by column chromatography with an eluent ratio of petroleum ether / ethyl acetate of 13:1 to obtain the pure product.

[0137] Synthesis of tertiary amine oxide b26: Add 335 mg of tertiary amine compound a26 and 20 mL of ethanol into a flask, then heat up to 60 °C to fully dissolve the two. Slowly add 1.1 mL of 30% hydrogen peroxide dropwise, raise the temperature to 85 °C, and reflux for 7 hours. After evaporating the solvent, the oxide is obtained.

[0138] Example 27

[0139]

[0140] Synthesis of tertiary amine compound a27: 172 mg of methyl 6-methyl-4-oxopiperidine-2-carboxylate, 10 mL of DMF, and 285 mg of 3-bromo-9,9-dimethylfluorene were successively added to a round-bottom flask. After stirring evenly to ensure complete dissolution of each component, 106 mg of sodium carbonate was added. After stirring evenly and dissolving, the temperature was raised to 80 °C. After reacting for 9 hours, the filtrate was obtained by filtration. After rotary evaporation, the crude product was obtained and purified by column chromatography with a petroleum ether / ethyl acetate eluent ratio of 15:1 to obtain the pure product.

[0141] Synthesis of tertiary amine oxide b27: 363 mg of tertiary amine compound a27 and 20 mL of ethanol were added to a flask, and then the temperature was raised to 60 °C to fully dissolve the two. 1.1 mL of 30% hydrogen peroxide was added dropwise at a constant rate, the temperature was raised to 85 °C, and the mixture was heated under reflux for 7 hours. After evaporating the solvent, the oxide was obtained.

[0142] Example 28

[0143]

[0144] Synthesis of tertiary amine compound a28: 172 mg of methyl 6-methyl-4-oxopiperidine-2-carboxylate, 10 mL of DMF, and 228 mg of 1-bromonaphthalene were successively added to a round-bottom flask. After stirring evenly to ensure complete dissolution of each component, 106 mg of sodium carbonate was added. After stirring evenly and dissolving, the temperature was raised to 80 °C. After reacting for 9 hours, the filtrate was obtained by filtration. After rotary evaporation, the crude product was obtained and purified by column chromatography with a petroleum ether / ethyl acetate eluent ratio of 13:1 to obtain the pure product.

[0145] Synthesis of tertiary amine oxide b28: 297 mg of tertiary amine compound a28 and 20 mL of ethanol were added to a flask, and then the temperature was raised to 60 °C to fully dissolve the two. 1.1 mL of 30% hydrogen peroxide was added dropwise at a constant rate, the temperature was raised to 85 °C, and the mixture was heated under reflux for 7 hours. After evaporating the solvent, the oxide was obtained.

[0146] Example 29

[0147]

[0148] Synthesis of tertiary amine compound a29: 172 mg of methyl 6-methyl-4-oxopiperidine-2-carboxylate, 10 mL of DMF, and 301 mg of dimethyl 2-bromoisophthalate were successively added to a round-bottom flask. After stirring evenly to ensure complete dissolution of each component, 106 mg of sodium carbonate was added. After stirring evenly and dissolving, the temperature was raised to 80 °C. After reacting for 9 hours, the filtrate was obtained by filtration. After rotary evaporation, the crude product was obtained and purified by column chromatography with a petroleum ether / ethyl acetate eluent ratio of 10:1 to obtain the pure product.

[0149] Synthesis of tertiary amine oxide b29: Add 363 mg of tertiary amine compound a29 and 20 mL of ethanol to a flask, then heat to 60 °C to fully dissolve the two. Slowly add 1.1 mL of 30% hydrogen peroxide dropwise, raise the temperature to 85 °C, and reflux for 7 hours. After evaporating the solvent, the oxide is obtained.

[0150] Example 30

[0151]

[0152] Synthesis of tertiary amine compound a30: Add 172 mg of methyl 6-methyl-4-oxopiperidine-2-carboxylate, 10 mL of DMF, and 297 mg of 1,3-di-tert-butyl-2-bromobenzene to a round-bottom flask in sequence. After stirring evenly to ensure complete dissolution of each component, add 106 mg of sodium carbonate. After stirring evenly and dissolving, heat to 80 °C and react for 9 hours. Then filter to obtain the filtrate, and after rotary evaporation, the crude product is obtained. Column chromatography purification is carried out with a petroleum ether / ethyl acetate eluent ratio of 13:1 to obtain the pure product.

[0153] Synthesis of tertiary amine oxide b30: Add 359 mg of tertiary amine compound a30 and 20 mL of ethanol to a flask, then heat to 60 °C to fully dissolve the two. Slowly add 1.1 mL of 30% hydrogen peroxide dropwise, raise the temperature to 85 °C, and reflux for 7 hours. After evaporating the solvent, the oxide is obtained.

[0154] Example 31

[0155]

[0156] Synthesis of tertiary amine compound a31: Add 172 mg of methyl 6-methyl-4-oxopiperidine-2-carboxylate, 10 mL of DMF, and 271 mg of 2-bromo-1,3,5-trimethoxybenzene to a round-bottom flask in sequence. After stirring evenly to ensure complete dissolution of each component, add 106 mg of sodium carbonate. After stirring evenly and dissolving, heat to 80 °C and react for 9 hours. Then filter to obtain the filtrate, and after rotary evaporation, the crude product is obtained. Column chromatography purification is carried out with a petroleum ether / ethyl acetate eluent ratio of 9:1 to obtain the pure product.

[0157] Synthesis of tertiary amine oxide b31: Add 337 mg of tertiary amine compound a31 and 20 mL of ethanol to a flask, then heat to 60 °C to fully dissolve the two. Slowly add 1.1 mL of 30% hydrogen peroxide dropwise, raise the temperature to 85 °C, and reflux for 7 hours. After evaporating the solvent, the oxide is obtained.

[0158] Example 32

[0159]

[0160] Synthesis of tertiary amine compound a32: 172 mg of methyl 6-methyl-4-oxopiperidine-2-carboxylate, 10 mL of DMF, and 283 mg of 9-bromophenanthrene were successively added to a round-bottom flask. After stirring evenly to ensure complete dissolution of each component, 106 mg of sodium carbonate was added. After stirring evenly to dissolve, the temperature was raised to 80 °C. After reacting for 9 hours, the filtrate was obtained by filtration. After rotary evaporation, the crude product was obtained, and column chromatography purification was carried out with a petroleum ether / ethyl acetate eluent ratio of 9:1 to obtain the pure product.

[0161] Synthesis of tertiary amine oxide b32: 347 mg of tertiary amine compound a32 and 20 mL of ethanol were added to a flask, and then the temperature was raised to 60 °C to fully dissolve the two. 1.1 mL of 30% hydrogen peroxide was added dropwise at a constant speed, the temperature was raised to 85 °C, and the mixture was heated under reflux for 7 hours. After evaporating the solvent, the oxide was obtained.

[0162] Comparative Example 1

[0163] Synthesis of tertiary amine oxide c1: 155 mg of 1,2,2,6,6-pentamethylpiperidine and 20 mL of toluene were added to a flask, and then the temperature was raised to 70 °C to fully dissolve the two. 2.5 mL of 30% hydrogen peroxide was added dropwise at a constant speed, the temperature was raised to 90 °C, and the reaction was carried out for 6 hours. After evaporating the solvent, the oxide c1 was obtained, and its structure is shown below.

[0164]

[0165] Comparative Example 2

[0166] Synthesis of tertiary amine oxide c2: 145 mg of 3-(4-morpholino)-1-propanol and 20 mL of xylene were added to a flask, and then the temperature was raised to 75 °C to fully dissolve the two. 2.5 mL of 30% hydrogen peroxide was added dropwise at a constant speed, the temperature was raised to 100 °C, and the reaction was carried out for 8 hours. After evaporating the solvent, the oxide c2 was obtained, and its structure is shown below.

[0167]

[0168] Application test

[0169] To systematically explore the effects of different tertiary amine oxide regulators in various monomer copolymerization systems, we applied all the even-numbered tertiary amine oxide regulators in the examples and the two molecular weight regulators in the comparative examples to the polymerization reactions of different monomers, compared their performances in specific polymerization reactions, and systematically discussed the effects of the addition of different tertiary amine oxides on the final monomer conversion rate, weight-average molecular weight M w 、number-average molecular weight M n 、PDI and other indicators.

[0170] In the following table, unless otherwise specified, the reaction conditions and feedstocks are as follows: 1 mol of tertiary amine oxide, 246 mg of azobisisobutyronitrile, 0.4 mol of a specific monomer, and 40 mL of dioxane were successively added to a 100 mL Schlenk tube. After sealing, the tube was degassed by freezing and thawing with liquid nitrogen three times. After returning to room temperature, it was placed at a specific temperature for a specific time, and the reaction was terminated by freezing with liquid nitrogen. The solvent and unreacted monomer were removed by rotary evaporation under reduced pressure, and then dried in a vacuum oven to a constant weight. The conversion rate, weight-average molecular weight, number-average molecular weight, and PDI were measured and calculated.

[0171] Table 1

[0172]

[0173]

[0174] It can be seen from the results in Table 1 that after adding the oxide of 4-oxopiperidine / morpholine high steric hindrance tertiary amine derivative to the methyl methacrylate reaction system, the molecular weight distribution with a maximum of 1.40 and a minimum of 1.21 can be obtained. Among them, tertiary amine oxide b30 corresponds to the lowest PDI of 1.21, which proves that the strategy of preparing a molecular weight regulator based on the oxidation of high steric hindrance piperidine tertiary amine derivatives is feasible, and regulators of this structure can indeed effectively control the free radical polymerization process. Subsequently, the performance of tertiary amine oxide b30 in the polymerization of three monomers, styrene, vinyl acetate, and acrylonitrile, was discussed. The PDI obtained under the same reaction conditions was slightly higher, indicating that tertiary amine oxides represented by b30 are more suitable in the acrylate polymerization system, which may be related to the compatibility between the tertiary amine oxide and the monomer structure. The PDI adjustment range of the oxide of the 4-oxopiperidine / morpholine high steric hindrance tertiary amine derivative of the present invention in the polymerization of acrylate monomers is 1.21 - 1.40.

[0175] To explore the performance of the structures obtained by oxidizing common tertiary amines in the same polymerization system, c1 and c2 were added, and the obtained PDI values were all above 2.0, which were relatively close to the PDI of the blank group without adding tertiary amine oxide. Therefore, it is impossible to effectively regulate the polymerization process by oxidizing the existing tertiary amine structure. The effects of reaction temperature and reaction time were discussed, and it was found that the reaction rate of vinyl acetate was relatively slow at 60 °C in this system. When the reaction time was extended to 12 h, both the PDI and M w increased.

[0176] The above embodiments are only illustrative of the principles and effects of this application, and are not intended to limit this application. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of this application. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed in this application should still be covered by the claims of this application.

Claims

1. A high steric hindrance 4 - pyridine oxide or morpholine tertiary amine oxide, having the following molecular structural formula, ， In the structural formula, R' is mono- to octa-substituted, and the substituents are each independently selected from a hydrogen atom, a C 1-4 alkyl group, an ester group; Y is selected from an oxygen atom or a carbonyl group; Ar is selected from an indenyl group, a fluorenyl group, a dimethylfluorenyl group, a naphthyl group, a substituted phenyl group, a phenanthryl group; there is at least one substituent on the substituted phenyl group, and the substituents are independently selected from an ester group, an alkyl group, an alkoxy group.

2. A method for synthesizing the high steric hindrance 4 - pyridine oxide or morpholine tertiary amine oxide according to claim 1, comprising the following steps: S1, Synthesis of the tertiary amine precursor: In a reaction vessel, add a solvent, a secondary amine, and a halogenated hydrocarbon. After fully dissolving and mixing evenly, continue to add a basic catalyst, and heat to 60 - 150 °C for reaction for 4 - 48 h to obtain a crude tertiary amine product; the halogenated hydrocarbon is a halogenated aromatic hydrocarbon or a halogenated cycloalkane; S2, Purification of the tertiary amine: Column chromatography separate the crude tertiary amine product with a petroleum ether / ethyl acetate eluent with a volume ratio of 50:1 - 1:1 to obtain a pure tertiary amine product; S3, Synthesis of the tertiary amine oxide: Add the pure tertiary amine product and an organic solvent into a container, heat to 40 - 150 °C to fully dissolve it; then dropwise add hydrogen peroxide thereto, and react for 3 - 72 h to obtain a tertiary amine oxide solution; S4, After the tertiary amine oxide solution is distilled under reduced pressure to remove the solvent, a tertiary amine oxide is obtained.

3. The synthesis method of the high steric hindrance 4-oxidopyridine or morpholine tertiary amine oxide according to claim 2, characterized in that, In step S1, the molar ratio of the halogenated hydrocarbon to the secondary amine is 0.5 - 3:

1.

4. The synthesis method of the high steric hindrance 4-oxidopyridine or morpholine tertiary amine oxide according to claim 2, characterized in that, The secondary amine is selected from 3 - methylmorpholine, 2,2 - dimethylmorpholine, 3,3 - dimethylmorpholine, 2,6 - dimethylmorpholine, 2,2,3 - trimethylmorpholine, 2,2,5 - trimethylmorpholine, 2,2,6 - trimethylmorpholine, 2,5,5 - trimethylmorpholine, 3,3,5 - trimethylmorpholine, 2,2,6,6 - tetramethylmorpholine, 3,3,5,5 - tetramethylmorpholine, 2 - isopropylmorpholine, 3 - isopropylmorpholine, 2 - isobutylmorpholine, 3 - isobutylmorpholine, methyl 3 - morpholinecarboxylate, ethyl morpholine - 3 - carboxylate, methyl 4 - oxopiperidine - 2 - carboxylate, methyl 6 - methyl - 4 - oxopiperidine - 2 - carboxylate, 2,6 - dimethylpiperidin - 4 - one, 2,2,6,6 - tetramethyl - 4 - piperidone.

5. The synthesis method of the high steric hindrance 4-oxidopyridine or morpholine tertiary amine oxide according to claim 2, characterized in that, The halogenated aromatic hydrocarbon is selected from 2 - bromoindene, 1 - bromo - 9H - fluorene, 2 - bromofluorene, 3 - bromo - 9H - fluorene, 4 - bromo - 9H - fluorene, 9,9 - dimethyl - 2 - bromofluorene, 3 - bromo - 9,9 - dimethylfluorene, 4 - bromo - 9,9 - dimethylfluorene, 1 - bromonaphthalene, 2 - bromonaphthalene, ethyl 2 - bromobenzoate, tert - butyl 2 - bromobenzoate, dimethyl 2 - bromoisophthalate, 1 - bromo - 4 - tert - butyl - 2 - ethylbenzene, 2,6 - di - tert - butylbromobenzene, 1 - bromo - 2,6 - dimethoxybenzene, 1 - bromo - 2,4,6 - trimethoxybenzene, 3 - bromophenanthrene, 9 - bromophenanthrene.

6. The synthesis method of the high steric hindrance 4-oxidopyridine or morpholine tertiary amine oxide according to claim 2, wherein, The basic catalyst is selected from sodium bicarbonate, potassium bicarbonate, sodium carbonate, potassium carbonate, cesium carbonate, sodium hydroxide, potassium hydroxide, calcium hydroxide, cesium hydroxide, sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, sodium isopropoxide, trimethylamine, triethylamine, ethylenediamine, diethylamine, tert - butylamine, piperidine, pyridine, 4 - dimethylaminopyridine, sodium tert - butoxide, potassium tert - butoxide, lithium diisopropylamide, n - butyllithium, sodium triphenylmethyl.

7. The synthesis method of the high steric hindrance 4-oxidopyridine or morpholine tertiary amine oxide according to claim 2, wherein The organic solvent is selected from benzene, toluene, ethylbenzene, xylene, dichloromethane, chloroform, carbon tetrachloride, dichloroethane, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, acetone, butanone, cyclohexanone, ether, tetrahydrofuran, ethylene glycol dimethyl ether, ethyl acetate, butyl acetate, dimethyl carbonate, diethyl carbonate, N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, hexamethylphosphoric triamide, sulfolane.

8. The synthesis method of the high steric hindrance 4-oxidopyridine or morpholine tertiary amine oxide according to claim 2, characterized in that, The molar ratio of the addition amount of the halogenated hydrocarbon to the addition amount of the secondary amine is 1-1.5:1, the molar ratio of the basic catalyst to the secondary amine is 1.2-1.8:1, and the molar ratio of hydrogen peroxide to the pure tertiary amine product is 8-20:

1.

9. The synthesis method of the high steric hindrance 4-oxidopyridine or morpholine tertiary amine oxide according to claim 9, characterized in that, The reaction temperature of step S1 is 80±10°C and the reaction time is 8±1 h; the reaction temperature of step S3 is 85±5°C and the reaction time is 8±1 h.

10. Use of any one of the high steric hindrance 4-oxidopyridine or morpholine tertiary amine oxide described in claims 1-9 in a radical polymerization reaction to obtain a polymerization product with a lower PDI.

11. A method for synthesizing a polymer product with low PDI, characterized in that, In a reaction vessel, after adding a polymerization monomer, an azo initiator and an appropriate amount of solvent, add any one of the high steric hindrance 4-oxidopyridine or morpholine tertiary amine oxide described in claims 1-9 in a molar ratio of 0.1-3% relative to the polymerization monomer. After sealing and freeze-thaw degassing several times, heat the system to 60-140°C. After reacting for 3-12 hours, immediately place it in liquid nitrogen to terminate the reaction, and rotary evaporate to remove the solvent and the remaining monomer to obtain a low PDI polymerization product.

12. The method for synthesizing a low-PDI polymerization product according to claim 12, wherein The polymerization monomer is selected from acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, 2-hydroxyethyl acrylate, methyl methacrylate, ethyl methacrylate, 2-hydroxyethyl methacrylate, N,N-dimethylaminoethyl acrylate, allyl polyether, allyl epoxy-capped polyether, allyl methyl-capped polyether, diallyl-capped polyether.

13. The method for synthesizing a low PDI polymer product according to claim 12, wherein, The azo initiator is azobisisobutyronitrile, azobisisoheptonitrile, dimethyl 2,2'-azobis(2-methylpropionate), 2,2'-azobis(2-methylpropionamidine) dihydrochloride, 2,2'-azobis(2-methyl-N-(2-hydroxyethyl)propionamide), azobisisovaleronitrile, 2-cyano-2-propylazoformamide.

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