Method for preparing star block copolymer by using microreactor and application thereof

Abstract

This invention proposes a method for preparing a polyacrylate block copolymer, comprising the following steps: a) dissolving monomer A, an initiator, and a ligand in a first organic solvent and pumping the mixture into a first microreactor to carry out a polymerization reaction, thereby obtaining a first reaction solution; b) dissolving monomer B in a second organic solvent and mixing the mixture with the first reaction solution output from step a) and pumping the mixture into a second microreactor to carry out a polymerization reaction, thereby obtaining a second reaction solution; c) precipitating the second reaction solution and separating the precipitate to obtain the polyacrylate block copolymer.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis, specifically to a method and application for preparing star-shaped block copolymers using microreactors, particularly as a lubricant additive. Background Technology

[0002] Lubricating oil additives are mainly used to formulate multi-grade oils, improve their viscosity-temperature properties, reduce machine wear, and effectively expand their application range. Commonly used lubricating oil additives are oil-soluble chain polymers that are soluble in hydrocarbon base oils. At low temperatures, the polymer chains shrink and coil, resulting in less internal friction and thus less impact on viscosity. At high temperatures, the polymer chains swell, increasing their hydrodynamic volume and surface area, significantly increasing internal friction and leading to a marked increase in viscosity. This compensates for some of the viscosity decrease in base oils as temperatures rise.

[0003] Currently, commonly used lubricant additives both domestically and internationally include polystyrene isoprene, polyethylene diene polymers, polybutene, polyethylene propylene copolymers, and polymethyl methacrylate polymers. Polymethyl methacrylate polymers are pale yellow viscous liquids that have both thickening and thinning functions, good thermal stability, shear resistance, and good stability.

[0004] In 1995, Matyjaszewski and Sawamoto's group first proposed the concept of atom transfer radical polymerization (ATRP), which establishes a reversible equilibrium between chain-growing free radicals and dormant species existing in the form of alkyl halides or macromolecular halides, thereby achieving living and controlled polymerization. In recent years, ATP has become one of the most powerful polymer synthesis techniques. However, the polymerization process faces problems such as slow polymerization rates and wide polymer molecular weight distributions. Microfluidic technology, with its enhanced mass and heat transfer capabilities and continuous flow with low backmixing, offers a promising technical solution to overcome these limitations. Summary of the Invention

[0005] The purpose of this invention is to provide a method and application for preparing star-shaped block copolymers using a microreactor. The method of this invention is a method for preparing star-shaped block copolymers by atom transfer radical polymerization at the microscale, which can solve the problems of slow reaction rate and insufficient controllability of polymerization process in the prior art.

[0006] To solve the above problems, the technical solution adopted by the present invention is as follows.

[0007] In a first aspect, the present invention provides a method for preparing a polyacrylate block copolymer.

[0008] As a specific embodiment of the present invention, the preparation method includes the following steps:

[0009] a) Dissolve monomer A, initiator and ligand in a first organic solvent and pump the solution into a first microreactor to carry out a polymerization reaction, thereby obtaining a first reaction solution;

[0010] b) Dissolve monomer B in a second organic solvent, mix it with the first reaction solution obtained in step a, and pump it into a second microreactor to carry out a polymerization reaction, thereby obtaining a second reaction solution;

[0011] c) The second reaction solution is precipitated and separated to obtain the polyacrylate block copolymer.

[0012] Preferably, the polyacrylate block copolymer has a three-armed star configuration, a molecular weight distribution index of 1.2 to 1.5, and a number-average molecular weight of 32,000 to 75,000 g / mol.

[0013] Preferably, the process of dissolving monomer A, initiator, and ligand in the first organic solvent in step a) and / or dissolving monomer B in the second organic solvent in step b) is carried out in an anhydrous environment under inert gas protection; and / or the pumping process in steps a) and / or b) uses a microsyringe; and / or the first microreactor and / or the second microreactor are copper tube microreactors, and the pumping flow rate in steps a) and / or b) is preferably 4.167 to 66.67 μL / min, more preferably 8.333 to 16.67 μL / min; and / or the first organic solvent and / or the second organic solvent are the same or different, and each independently consists of one or more of tetrahydrofuran, toluene, N,N-dimethylacetamide, N,N-dimethylformamide, and dimethyl sulfoxide; and / or the microsyringe is preferably an SEG syringe.

[0014] Preferably, the mixing process in step b) is carried out in a microreactor mixer.

[0015] Preferably, the microreactor has a Y-shaped structure, and the solution formed by monomer B dissolved in the second organic solvent and the first reaction solution are converged and mixed through the Y-shaped structure of the microreactor.

[0016] Preferably, in step c), a precipitant is used to precipitate the second reaction solution, and the precipitant is preferably methanol.

[0017] Preferably, monomer A is one or more of methyl methacrylate, butyl acrylate, and methacrylate; the initiator is 1,1,1-tris(2-bromoisobutyryloxymethyl)ethane; and the ligand is tris(2-dimethylaminoethyl)amine and / or pentamethyldivinyltriamine.

[0018] Preferably, the molar ratio of monomer A to initiator is 10:1 to 500:1, more preferably 100 to 500:1; and / or the molar ratio of initiator to ligand is 1 to 0.2:1, more preferably 0.5 to 0.2:1; and / or the concentration of monomer A in the first organic solvent is 1 to 5 mol / L, more preferably 1 to 3 mol / L.

[0019] Preferably, in step a), the polymerization temperature is 40–80°C, more preferably 60–70°C, and the polymerization time is 0.5–6 h, more preferably 1–3 h.

[0020] Preferably, in step b),

[0021] The monomer B is one or more of dodecyl methacrylate, tetradecyl methacrylate, hexadecyl methacrylate, and octadecyl methacrylate.

[0022] Preferably, the molar ratio of monomer B to initiator is 10–500:1, more preferably 100–500:1; and / or the molar ratio of bromine atom to ligand in initiator is 5–1:1, more preferably 3–5:1; and / or the concentration of monomer B in the second organic solvent is 1–5 mol / L, more preferably 1–3 mol / L.

[0023] Preferably, in step b), the polymerization temperature is 40–80°C, and more preferably 60–70°C.

[0024] Preferably, in step a), the volume of the first microreactor is 1-4 mL, more preferably 1-2 mL; the inner diameter is 1-2 mm; and the length is 0.318-5.10 m, more preferably 0.318-1.27 m.

[0025] Preferably, in step b), the volume of the second microreactor is 1-8 mL, more preferably 2-4 mL; the inner diameter is 0.5-5 mm, more preferably 1-2 mm; and the length is 0.200-8.00 m, more preferably 0.637-5.10 m.

[0026] Preferably, the first microreactor and / or the second microreactor are spiral-shaped.

[0027] In a second aspect, the present invention provides a polyacrylate block copolymer prepared according to the preparation method described in the first aspect.

[0028] As a specific embodiment of the present invention, the polyacrylate block copolymer has a three-arm star configuration, a molecular weight distribution index of 1.2 to 1.5, and a number-average molecular weight of 32,000 to 75,000 g / mol.

[0029] Thirdly, the present invention provides the use of the polyacrylate block copolymer prepared according to the preparation method of the first aspect or the polyacrylate block copolymer of the second aspect as a lubricating oil additive.

[0030] All of the above-mentioned raw materials used in this invention can be prepared in-house or purchased commercially; this invention does not impose any particular limitations on them.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] (1) The method provided by the present invention uses a copper tube microreactor to synthesize a three-arm star-shaped block copolymer in a continuous flow, which improves the controllability of the polymerization reaction, reduces the reaction time, reduces the molecular weight distribution index of the polymer, eliminates the catalyst activation process, and realizes continuous production.

[0033] (2) The method provided by the present invention also has the advantages of mild reaction conditions, high efficiency, low energy consumption, fast reaction rate and simple operation. Attached Figure Description

[0034] Figure 1 This is a simplified reaction flow diagram for the continuous flow synthesis of three-armed star-shaped block copolymers at the microscale according to an embodiment of the present invention.

[0035] Figure 2 The NMR spectrum is shown for the three-armed star-shaped polymethyl methacrylate-polylaurate block copolymer synthesized according to an embodiment of the present invention. Detailed Implementation

[0036] The present invention will be further described below with reference to specific embodiments, but this does not constitute any limitation on the present invention.

[0037] The present invention can be better understood from the following embodiments. However, those skilled in the art will readily understand that the descriptions in the embodiments are for illustrative purposes only and should not, and will not, limit the invention as described in detail in the claims.

[0038] The reaction apparatus used in the following embodiments is as follows: Figure 1 As shown, it includes a first syringe 1, a first microreactor 2, a second syringe 4, a microreactor 3, a second microreactor 5, and a material receiving device 6.

[0039] The first syringe 1 and the second syringe 4 are SEG syringes, i.e., micro-injectors, and the first microreactor 2 and the second microreactor 5 are copper tube microreactors. The microreactor 3 has a Y-shaped structure, through which the solution of monomer B dissolved in the second organic solvent and the first reaction solution converge and mix.

[0040] In the following examples and comparative examples, the number-average molecular weight (Mn) and molecular weight distribution index (PDI) of the polymers were determined by gel permeation chromatography (GPC). Specifically, a Shimadzu LC-20AD gel permeation chromatograph was used, with tetrahydrofuran as the mobile phase, narrow-distribution polystyrene as the standard, and the mobile phase flow rate was 1.0 mL / min.

[0041] Examples 1-6 are used to specifically describe the preparation method of the diblock copolymer of the present invention, namely, the preparation of star-shaped polymethyl methacrylate-polylauryl methacrylate block copolymer by atom transfer radical polymerization at the microscale.

[0042] Example 1

[0043] A copper tube microreactor with an inner diameter of 1 mm, a length of 2.54 m, and a retention volume of 2 mL was used as the first microreactor. A copper tube microreactor with an inner diameter of 1 mm, a length of 5.09 m, and a retention volume of 4 mL was used as the second microreactor. The apparatus was connected, and the reaction tubes were rinsed with tetrahydrofuran solvent. In a reaction flask after high-temperature dehydration, under nitrogen protection, methyl methacrylate (0.05 mol, 5.006 g), 1,1,1-tris(2-bromoisobutyryloxymethyl)ethane (0.0002 mol, 0.1134 g), and tris(2-dimethylaminoethyl)amine (0.00012 mol, 0.0276 g) were dissolved in 14.7 mL of tetrahydrofuran, stirred thoroughly, and transferred to the first syringe. Lauryl methacrylate (0.02 mol, 5.0082 g) was dissolved in 14.2 mL of tetrahydrofuran solution, stirred thoroughly, and transferred to the second syringe. The oil bath temperature of the first and second microreactors was adjusted to 60°C. In this embodiment, the flow rate of the syringe pump was 16.67 μL / min. The solution in the first syringe was continuously pumped into the first microreactor. The outflowing reaction solution was mixed with the solution in the second syringe and then continuously pumped into the second microreactor. After 5 hours, the reaction solution was collected, 100 mL of methanol was added, precipitation was carried out, and the mixture was filtered and vacuum dried to obtain polymethyl methacrylate-polylauryl methacrylate block copolymer. The number average molecular weight of the polymer was 48370 g / mol and the molecular weight distribution index was 1.32, as determined by GPC.

[0044] Example 2

[0045] When all other conditions are the same as in Example 1, and 6.4085g of butyl acrylate is used instead of methyl methacrylate, the number-average molecular weight of the polymer measured by GPC is 50210g / mol, and the molecular weight distribution index is 1.35.

[0046] Example 3

[0047] When all other conditions are the same as in Example 1, and 4.2035g of methacrylate is used instead of methyl methacrylate, the number-average molecular weight of the polymer, as measured by GPC, is 23200g / mol, and the molecular weight distribution index is 1.38.

[0048] Example 4

[0049] A copper tube microreactor with an inner diameter of 1 mm, a length of 2.54 m, and a retention volume of 2 mL was used as the first microreactor. A copper tube microreactor with an inner diameter of 1 mm, a length of 5.09 m, and a retention volume of 4 mL was used as the second microreactor. The apparatus was connected, and the tubes were rinsed with tetrahydrofuran solvent. In a reaction flask after high-temperature dehydration, under nitrogen protection, methyl methacrylate (0.05 mol, 5.006 g), 1,1,1-tris(2-bromoisobutyryloxymethyl)ethane (0.0005 mol, 0.2835 g), and tris(2-dimethylaminoethyl)amine (0.00012 mol, 0.0276 g) were dissolved in 14.7 mL of tetrahydrofuran, stirred thoroughly, and transferred to the first syringe. Lauryl methacrylate (0.02 mol, 5.0082 g) was dissolved in 14.2 mL of tetrahydrofuran solution, stirred thoroughly, and transferred to the second syringe. The oil bath temperature of the two microreactors was adjusted to 60℃. In this embodiment, the flow rate of the syringe pump was 16.67 μL / min. The solution in the first syringe was continuously pumped into the first microreactor. The outflowing reaction solution was mixed with the solution in the second syringe and then continuously pumped into the second microreactor. After 5 hours, the reaction solution was collected, 100 mL of methanol was added, precipitation was carried out, and the mixture was filtered and vacuum dried to obtain polymethyl methacrylate-polylauryl methacrylate block copolymer. The number average molecular weight of the polymer was 32100 g / mol and the molecular weight distribution index was 1.29, as determined by GPC.

[0050] Example 5

[0051] When other conditions are the same as in Example 4, and the amount of 1,1,1-tris(2-bromoisobutyryloxymethyl)ethane is 0.0001 mol and 0.0567 g, the number-average molecular weight of the polymer was 74600 g / mol and the molecular weight distribution index was 1.33 as determined by GPC.

[0052] Example 6

[0053] A copper tube microreactor with an inner diameter of 1 mm, a length of 2.54 m, and a retention volume of 2 mL was used as the first microreactor. A copper tube microreactor with an inner diameter of 1 mm, a length of 5.09 m, and a retention volume of 4 mL was used as the second microreactor. The apparatus was connected, and the tubes were rinsed with tetrahydrofuran solvent. In a reaction flask after high-temperature dehydration, under nitrogen protection, methyl methacrylate (0.05 mol, 5.006 g), 1,1,1-tris(2-bromoisobutyryloxymethyl)ethane (0.0002 mol, 0.1134 g), and tris(2-dimethylaminoethyl)amine (0.00012 mol, 0.0276 g) were dissolved in 14.7 mL of tetrahydrofuran, stirred evenly, and transferred to the first syringe. Lauryl methacrylate (0.02 mol, 5.0082 g) was dissolved in 14.2 mL of tetrahydrofuran solution, stirred evenly, and transferred to the second syringe. The oil bath temperature of the two microreactors was adjusted to 60℃. In this embodiment, the flow rate of the syringe pump was 16.67 μL / min. The solution in the first syringe was continuously pumped into the first microreactor. The outflowing reaction solution was mixed with the solution in the second syringe and then continuously pumped into the second microreactor. After 5 hours, the reaction solution was collected, 100 mL of methanol was added, precipitation was carried out, and the mixture was filtered and vacuum dried to obtain polymethyl methacrylate-polylauryl methacrylate block copolymer. The number average molecular weight of the polymer was 48370 g / mol and the molecular weight distribution index was 1.32, as determined by GPC.

[0054] Example 7

[0055] When other conditions are the same as in Example 6, and the amount of tris(2-dimethylaminoethyl)amine is 0.0002 mol and 0.0461 g, the number-average molecular weight of the polymer was 43250 g / mol and the molecular weight distribution index was 1.39 as measured by GPC.

[0056] Example 8

[0057] A copper tube microreactor with an inner diameter of 1 mm, a length of 2.54 m, and a retention volume of 2 mL was used as the first microreactor. A copper tube microreactor with an inner diameter of 1 mm, a length of 5.09 m, and a retention volume of 4 mL was used as the second microreactor. The apparatus was connected, and the tubes were rinsed with tetrahydrofuran solvent. In a reaction flask after high-temperature dehydration, under nitrogen protection, methyl methacrylate (0.05 mol, 5.006 g), 1,1,1-tris(2-bromoisobutyryloxymethyl)ethane (0.0002 mol, 0.1134 g), and tris(2-dimethylaminoethyl)amine (0.00012 mol, 0.0276 g) were dissolved in 44.7 mL of tetrahydrofuran, stirred thoroughly, and transferred to the first syringe. Lauryl methacrylate (0.02 mol, 5.0082 g) was dissolved in 44.4 mL of tetrahydrofuran solution, stirred thoroughly, and transferred to the second syringe. The oil bath temperature of the two microreactors was adjusted to 60℃. In this embodiment, the flow rate of the syringe pump was 16.67 μL / min. The solution in the first syringe was continuously pumped into the first microreactor. The outflowing reaction solution was mixed with the solution in the second syringe and then continuously pumped into the second microreactor. After 5 hours, the reaction solution was collected, 100 mL of methanol was added, precipitation was carried out, and the mixture was filtered and vacuum dried to obtain pure polymethyl methacrylate-polylauryl methacrylate block copolymer. The number average molecular weight of the polymer was 46520 g / mol and the molecular weight distribution index was 1.37, as determined by GPC.

[0058] Example 9

[0059] When all other conditions were the same as in Example 8, but methyl methacrylate, 1,1,1-tris(2-bromoisobutyryloxymethyl)ethane, and tris(2-dimethylaminoethyl)amine were dissolved in 11.36 mL of tetrahydrofuran, and lauryl methacrylate was dissolved in 10.80 mL of tetrahydrofuran solution, the number-average molecular weight of the polymer was 53460 g / mol and the molecular weight distribution index was 1.39, as determined by GPC.

[0060] Example 10

[0061] A copper tube microreactor with an inner diameter of 1 mm, a length of 2.54 m, and a retention volume of 2 mL was used as the first microreactor. A copper tube microreactor with an inner diameter of 1 mm, a length of 5.09 m, and a retention volume of 4 mL was used as the second microreactor. The apparatus was connected, and the tubes were rinsed with tetrahydrofuran solvent. In a reaction flask after high-temperature dehydration, under nitrogen protection, methyl methacrylate (0.05 mol, 5.006 g), 1,1,1-tris(2-bromoisobutyryloxymethyl)ethane (0.0002 mol, 0.1134 g), and tris(2-dimethylaminoethyl)amine (0.00012 mol, 0.0276 g) were dissolved in 14.7 mL of tetrahydrofuran, stirred evenly, and transferred to the first syringe. Lauryl methacrylate (0.02 mol, 5.0082 g) was dissolved in 14.2 mL of tetrahydrofuran solution, stirred evenly, and transferred to the second syringe. The oil bath temperature of the two microreactors was adjusted to 70℃. In this embodiment, the flow rate of the syringe pump was 16.67 μL / min. The solution in the first syringe was continuously pumped into the first microreactor. The outflowing reaction solution was mixed with the solution in the second syringe and then continuously pumped into the second microreactor. After 5 hours, the reaction solution was collected, 100 mL of methanol was added, precipitation was carried out, and the mixture was filtered and vacuum dried to obtain pure polymethyl methacrylate-polylauryl methacrylate block copolymer. The number average molecular weight of the polymer was 49830 g and the molecular weight distribution index was 1.42, as determined by GPC.

[0062] Example 11

[0063] A copper tube microreactor with an inner diameter of 1 mm, a length of 2.54 m, and a retention volume of 2 mL was used as the first microreactor. A copper tube microreactor with an inner diameter of 1 mm, a length of 5.09 m, and a retention volume of 4 mL was used as the second microreactor. The apparatus was connected, and the tubes were rinsed with toluene solvent. In a reaction flask after high-temperature dehydration, under nitrogen protection, methyl methacrylate (0.05 mol, 5.006 g), 1,1,1-tris(2-bromoisobutyryloxymethyl)ethane (0.0002 mol, 0.1134 g), and tris(2-dimethylaminoethyl)amine (0.00012 mol, 0.0276 g) were dissolved in 14.7 mL of toluene, stirred evenly, and transferred to the first syringe. Lauryl methacrylate (0.02 mol, 5.0082 g) was dissolved in 14.2 mL of toluene, stirred evenly, and transferred to the second syringe. The oil bath temperature of the two microreactors was adjusted to 60℃. In this embodiment, the flow rate of the syringe pump was 16.67 μL / min. The solution in the first syringe was continuously pumped into the first microreactor. The outflowing reaction solution was mixed with the solution in the second syringe and then continuously pumped into the second microreactor. After 5 hours, the reaction solution was collected, 100 mL of methanol was added, precipitation was carried out, and the mixture was filtered and vacuum dried to obtain pure polymethyl methacrylate-polylauryl methacrylate block copolymer. The number average molecular weight of the polymer was 40100 g / mol and the molecular weight distribution index was 1.41, as determined by GPC.

[0064] Example 12

[0065] When all other conditions were the same as in Example 12, but the pipeline was rinsed with N,N-dimethylacetamide solvent, and methyl methacrylate, 1,1,1-tris(2-bromoisobutyryloxymethyl)ethane, and tris(2-dimethylaminoethyl)amine were dissolved in 14.7 mL of N,N-dimethylacetamide, and lauryl methacrylate was dissolved in 14.2 mL of N,N-dimethylacetamide, the number-average molecular weight of the polymer was 43540 g / mol and the molecular weight distribution index was 1.48, as determined by GPC.

[0066] Example 13

[0067] When all other conditions were the same as in Example 12, but the pipeline was rinsed with N,N-dimethylformamide solvent, methyl methacrylate, 1,1,1-tris(2-bromoisobutyryloxymethyl)ethane, and tris(2-dimethylaminoethyl)amine were dissolved in 14.7 mL of N,N-dimethylformamide, and lauryl methacrylate was dissolved in 14.2 mL of N,N-dimethylformamide, the number-average molecular weight of the polymer was 46940 g / mol and the molecular weight distribution index was 1.51 as determined by GPC.

[0068] Example 14

[0069] When all other conditions were the same as in Example 12, but the pipeline was rinsed with dimethyl sulfoxide solvent, and methyl methacrylate, 1,1,1-tris(2-bromoisobutyryloxymethyl)ethane, and tris(2-dimethylaminoethyl)amine were dissolved in 14.7 mL of dimethyl sulfoxide, and lauryl methacrylate was dissolved in 14.2 mL of dimethyl sulfoxide, the number average molecular weight of the polymer was 42570 g / mol and the molecular weight distribution index was 1.42 as determined by GPC.

[0070] Any numerical value mentioned in this invention, if there is only a two-unit interval between any minimum and any maximum value, includes all values ​​that increase by one unit each time from the minimum to the maximum value. For example, if the amount of a component, or the value of a process variable such as temperature, pressure, or time, is stated as 50-90, in this specification it means specifically listing values ​​such as 51-89, 52-88… and 69-71 and 70-71, etc. For non-integer values, it may be appropriately considered that a unit is 0.1, 0.01, 0.001, or 0.0001. These are merely some specifically specified examples. In this application, in a similar manner, all possible combinations of numerical values ​​between the listed minimum and maximum values ​​are considered to have been disclosed.

[0071] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A method for preparing polyacrylate block copolymers, characterized in that, Includes the following steps: a) Monomer A, initiator and ligand are dissolved in a first organic solvent and pumped into a first microreactor to carry out a polymerization reaction to obtain a first reaction solution; b) Dissolve monomer B in a second organic solvent, mix it with the first reaction solution obtained in step a, and pump it into a second microreactor to carry out a polymerization reaction, thereby obtaining a second reaction solution; c) The second reaction solution is precipitated and separated to obtain the polyacrylate block copolymer; Wherein, monomer A is one or more of methyl methacrylate and butyl acrylate; The initiator is 1,1,1-tris(2-bromoisobutyryloxymethyl)ethane; The ligand is tris(2-dimethylaminoethyl)amine and / or pentamethyldivinyltriamine; The monomer B is one or more of dodecyl methacrylate, tetradecyl methacrylate, hexadecyl methacrylate, and octadecyl methacrylate.

2. The preparation method according to claim 1, characterized in that, The polyacrylate block copolymer has a three-armed star configuration, a molecular weight distribution index of 1.2 to 1.5, and a number-average molecular weight of 32,000 to 75,000 g / mol.

3. The preparation method according to claim 1, characterized in that, The process of dissolving monomer A, initiator and ligand in the first organic solvent in step a) and / or dissolving monomer B in the second organic solvent in step b) is carried out in an anhydrous and inert gas protected environment; And / or, the pumping process in step a) and / or step b) uses a microsyringe; And / or, the first microreactor and / or the second microreactor are copper tube microreactors, and the pumping flow rate in step a) and / or step b) is 4.167~66.67 μL / min; And / or, the first organic solvent and / or the second organic solvent are the same or different, and each independently is one or more of tetrahydrofuran, toluene, N,N-dimethylacetamide, N,N-dimethylformamide and dimethyl sulfoxide; And / or, the microsyringe is a SEG injector.

4. The preparation method according to claim 3, characterized in that, The pumping flow rate for steps a) and / or b) is 8.333~16.67 μL / min.

5. The preparation method according to claim 1, characterized in that, The mixing process in step b) is carried out in a microreactor mixer; The microreactor has a Y-shaped structure, and the solution formed by monomer B dissolved in the second organic solvent and the first reaction solution are converged and mixed through the Y-shaped structure of the microreactor.

6. The preparation method according to claim 1, characterized in that, In step c), the second reaction solution is precipitated using a precipitant, wherein the precipitant is methanol.

7. The preparation method according to any one of claims 1-6, characterized in that, The molar ratio of monomer A to initiator is 10:1 to 500:1; And / or, the molar ratio of the initiator to the ligand is 1 to 0.2:1; And / or, the concentration of monomer A in the first organic solvent is 1~5 mol / L; And / or, in step a), the polymerization temperature is 40~80℃ and the polymerization time is 0.5~6h.

8. The preparation method according to claim 7, characterized in that, The molar ratio of monomer A to initiator is 100~500:1; And / or, the molar ratio of the initiator to the ligand is 0.5 to 0.2:1; And / or, the concentration of monomer A in the first organic solvent is 1~3 mol / L; And / or, in step a), the polymerization temperature is 60~70℃ and the polymerization time is 1~3h.

9. The preparation method according to any one of claims 1-6, characterized in that, In step b), The molar ratio of monomer B to initiator is 10~500:1; and / or, the molar ratio of bromine atom to ligand in initiator is 5~1:1; and / or, the concentration of monomer B in the second organic solvent is 1~5 mol / L; And / or, in step b), the polymerization temperature is 40~80℃.

10. The preparation method according to claim 9, characterized in that, In step b), The molar ratio of monomer B to initiator is 100-500:1; and / or, the molar ratio of bromine atoms to ligands in initiator is 3-5:1; and / or, the concentration of monomer B in the second organic solvent is 1-3 mol / L. And / or, in step b), the polymerization temperature is 60~70℃.

11. The preparation method according to any one of claims 1-6, characterized in that, In step a), the first microreactor has a volume of 2 mL, an inner diameter of 1 mm, a length of 2.54 m, and / or In step b), the volume of the second microreactor is 4 mL; the inner diameter is 1 mm; and the length is 5.09 m.

12. The preparation method according to claim 11, characterized in that, The first microreactor and / or the second microreactor are spiral-shaped.

13. The polyacrylate block copolymer prepared by any one of claims 1-12, characterized in that, The polyacrylate block copolymer has a three-armed star configuration, a molecular weight distribution index of 1.2 to 1.5, and a number-average molecular weight of 32,000 to 75,000 g / mol.

14. The use of the polyacrylate block copolymer prepared by any one of claims 1-12 or the polyacrylate block copolymer of claim 13 as a lubricating oil additive.

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