Preparation method of high-density carboxyl magnetic polymer microspheres

Abstract

The invention discloses a preparation method of high-density carboxyl magnetic polymer microspheres, which comprises the following steps: preparation of polystyrene-silicon dioxide microspheres: coating silicon dioxide on the surfaces of polystyrene microspheres by adopting an in-situ polymerization method to obtain silicon-coated polystyrene microspheres; magnetizing the silicon-coated polystyrene microspheres, namely precipitating ferroferric oxide nano magnetic particles on the surfaces of the silicon-coated polystyrene microspheres by adopting a coprecipitation method to obtain magnetized polystyrene-silicon dioxide microspheres; surface modification: modifying the surfaces of the magnetized polystyrene-silicon dioxide microspheres by using oleic acid or ammonium oleate to obtain double-bond modified magnetized polystyrene-silicon dioxide microspheres; and preparing carboxyl magnetic polymer microspheres, namely copolymerizing carboxyl-containing small molecules on the surfaces of the double-bond modified magnetized polystyrene-silicon dioxide microspheres to obtain a finished product. The carboxyl magnetic polymer microspheres obtained in the invention are uniform and controllable in particle size and high in carboxyl density.

Description

Technical Field

[0001] This invention relates to the field of magnetic materials, and more particularly to a method for preparing high-density carboxyl magnetic polymer microspheres. Background Technology

[0002] Magnetic microspheres possess excellent superparamagnetism and can be magnetized under an applied magnetic field, enabling rapid separation. By modifying the surface of magnetic microspheres with different functional groups, they can be endowed with diverse application properties. Therefore, functionalized magnetic microspheres have broad application prospects in protein separation and purification, targeted drug therapy, and immunoassay.

[0003] Currently, most magnetic microspheres commonly used in immunoassay and nucleic acid extraction on the market are diffuse, sandwich, or core-shell structures. Among them, carboxyl magnetic beads used in nucleic acid extraction have a core-shell structure and are prepared by coating magnetic nanoparticles with silica, and then further modified with silanol groups on the surface to obtain carboxyl magnetic beads. These magnetic beads have several drawbacks in application: (1) The magnetic core density is high, and due to the small size effect and magnetic dipole attraction, the magnetic beads are prone to agglomeration and sedimentation during use; (2) The magnetic beads are usually synthesized by hydrothermal method, and the resulting carboxyl magnetic beads have uneven particle size, which will affect the nucleic acid extraction effect and lead to unstable extraction results.

[0004] For example, Chinese invention patent CN115069222A describes a method that first prepares Fe3O4 magnetic cores using a solvothermal method, then coats their surface with a silanizing agent, and finally modifies them with carboxylation. The carboxylated magnetic beads prepared by this method are typically small and non-uniform in size, making them prone to aggregation and non-specific adsorption during later use.

[0005] For example, Chinese invention patent CN111849022A first modifies magnetic Fe3O4 nanoparticles with oleic acid, and then uses swollen porous carboxylated polystyrene microspheres to adsorb the oleic acid-modified magnetic Fe3O4 nanoparticles, ultimately obtaining carboxylated magnetic polystyrene microspheres. However, this method suffers from low adsorption efficiency of magnetic Fe3O4 nanoparticles during preparation, uneven distribution of magnetic nanoparticles in the microspheres leading to slow magnetic response, and a tendency for magnetic leakage during use.

[0006] For example, Chinese invention patent CN114093586A describes a process for preparing carboxylated polystyrene microspheres that requires sulfonation to modify the surface of the microspheres to make them hydrophilic, followed by the introduction of ester groups using a distillation-precipitation polymerization method. This preparation of carboxylated magnetic microspheres involves the use of toxic acetonitrile and highly corrosive sulfuric acid, which can pollute the environment and is also hazardous. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing high-density carboxyl magnetic polymer microspheres.

[0008] The innovation of this invention lies in the fact that the carboxyl magnetic polymer microspheres obtained in this invention have uniform and controllable particle size and high carboxyl density.

[0009] To achieve the above-mentioned objectives, the technical solution of this invention is: a method for preparing high-density carboxyl magnetic polymer microspheres, comprising the following steps, characterized in that:

[0010] (1) Preparation of polystyrene@silica microspheres: Silicon-coated polystyrene microspheres were obtained by coating the surface of polystyrene microspheres with silica using an in-situ polymerization method;

[0011] (2) Magnetization of silica-coated polystyrene microspheres: Ferric oxide nanoparticles were deposited on the surface of silica-coated polystyrene microspheres by co-precipitation method to obtain magnetized polystyrene@silica microspheres.

[0012] (3) Surface modification: The surface of magnetized polystyrene@silica microspheres was modified with oleic acid or ammonium oleate to obtain double bond modified magnetized polystyrene@silica microspheres;

[0013] (4) Preparation of carboxyl magnetic polymer microspheres: Copolymerization of carboxyl small molecules on the surface of double bond modified magnetized polystyrene@silica microspheres was carried out to obtain the finished product.

[0014] Furthermore, the polystyrene microspheres in step (1) are prepared by dispersion polymerization, and the preparation steps are as follows:

[0015] The dispersant polyvinylpyrrolidone was dissolved in an ethanol-water mixture at a mass ratio of 3:150-200 in an ethanol-water mixture at a mass ratio of 9-10:1. Under argon protection, after the dispersant polyvinylpyrrolidone was completely dissolved, the temperature was raised to 65-95°C. Then, styrene and an initiator that had been mixed evenly beforehand were added. The mass ratio of the initiator to styrene was 1-2:100, and the mass ratio of the ethanol-water mixture to styrene was 5:1-0.4. The mixture was then stirred continuously at 250-350 rpm for 12-18 hours. After the reaction was completed, the mixture was repeatedly washed with ethanol by centrifugation and dried in a vacuum oven at 40-60°C to obtain polystyrene microspheres.

[0016] Furthermore, the dispersion coefficient of the polystyrene microspheres is less than 0.05.

[0017] Furthermore, the dispersant polyvinylpyrrolidone is one or two of K-30, K-60 and K-88; when repeatedly centrifuged and washed with ethanol, the centrifugation speed is 1000-3000 rpm and the number of washing times is 3-5; the initiator is azobisisobutyronitrile or benzoyl peroxide.

[0018] Furthermore, the specific steps for preparing polystyrene@silica microspheres are as follows:

[0019] Dispersant No. 1 was dissolved in an ethanol-water mixture with a mass ratio of 4-6-5 at a mass ratio of 0.5-1:100. After the dispersant No. 1 was completely dissolved, polystyrene microspheres were added at a mass ratio of 100:1-3 (ethanol-water mixture to polystyrene microspheres). The temperature was raised to 35-45℃. Once the polystyrene microspheres were monodisperse, a silicon source was added at a mass ratio of 2:1-0.25 (polystyrene microspheres to silicon source). The mixture was stirred for 30-60 minutes, and then ammonia was added to adjust the pH to 8-10 for further reaction. The reaction was continued at 200-300 rpm for 3-6 hours. After the reaction was completed, the microspheres were washed alternately by centrifugation with ethanol and deionized water, and then dried in a vacuum oven at 40-60℃ to obtain polystyrene@silica microspheres.

[0020] Furthermore, the first dispersant is one or two of hexadecyltrimethylammonium bromide, dodecyltrimethylammonium bromide, sodium dodecyl sulfate, or sodium dodecylbenzene sulfonate; the first dispersant is dispersed in the ethanol-water mixed solution by mechanical stirring or ultrasonication.

[0021] Furthermore, the silicon source is tetraethyl orthosilicate, methyl orthosilicate, or 3-aminopropyltriethoxysilane, and the mass ratio of the silicon source to the polystyrene microspheres is 0.8 to 1.2:1.

[0022] Furthermore, the specific steps for magnetizing the silicon-coated polystyrene microspheres are as follows:

[0023] Silicon-coated polystyrene microspheres were dispersed in an ethanol-water mixture with a mass ratio of 4-6:5 at a mass ratio of 1.5-2.5:100. After the microspheres were evenly dispersed, ferric chloride hexahydrate and ferrous chloride tetrahydrate were added at a molar ratio of 2:1, and the mass ratio of the microspheres to ferric chloride hexahydrate was 1:1-0.5. After stirring for 20-30 minutes, ammonia was added to adjust the pH to 9-10 and the reaction was carried out. The temperature was then raised to 75-95℃ and the reaction was carried out for 3-5 hours under argon protection throughout the reaction. After the reaction was completed, the microspheres were washed alternately with ethanol and deionized water using magnetic adsorption, and dried in a vacuum oven at 50℃ to obtain magnetized polystyrene@silica microspheres.

[0024] Furthermore, the specific steps of the surface modification are as follows:

[0025] Magnetized polystyrene@silica microspheres were dispersed in ethanol at a mass ratio of 1.5–2.5:100. After the magnetic polystyrene@silica microspheres were evenly dispersed, oleic acid or ammonium oleate at a mass ratio of 1:1–1.2 was added. The mixture was stirred for 10–20 min and then heated to 75–95 °C for 2–4 h. Argon gas was used for protection throughout the reaction. After the reaction was completed, the microspheres were magnetically washed with ethanol to obtain double-bond modified magnetic polystyrene@silica microspheres, which were stored in ethanol or n-hexane for quantitative preparation and later use.

[0026] Further, the specific steps for preparing the carboxyl magnetic polymer microspheres are as follows: Dispersant polyvinylpyrrolidone is dissolved in an ethanol-water mixture at a mass ratio of 2:150-200 in an ethanol-water mixture at a mass ratio of 9-10:1. Under argon protection, after the dispersant polyvinylpyrrolidone is completely dissolved, double-bond modified magnetized polystyrene@silica microspheres are added. After dispersing for 40-60 minutes, styrene, methacrylic acid, and an initiator that have been mixed uniformly beforehand are added. The mass ratio of initiator to styrene is 1-2:100, the mass ratio of methacrylic acid to styrene is 1-2:0.5, and the mass ratio of double-bond modified magnetized polystyrene@silica microspheres to styrene is 1:1-0.4. The mixture is then continuously stirred at 250-350 rpm for 12-18 hours at a reaction temperature of 65-75°C. After the reaction is complete, the microspheres are repeatedly washed with ethanol using magnetic adsorption and stored in ethanol for quantitative preparation.

[0027] The beneficial effects of this invention are:

[0028] 1. This invention addresses the problem of polystyrene microspheres easily swelling and degrading in organic solvents by adding a protective silicon layer to the surface of the microspheres, thereby increasing their stability during later use.

[0029] 2. In this invention, the surface of polystyrene microspheres is coated with a silicon layer and contains a large number of silanol groups, which is more conducive to the hydrophilic modification of the surface and the uniform adhesion of the magnetic particles on the surface. At the same time, the silicon layer coating greatly increases the specific surface area of ​​the microspheres, which is beneficial to the subsequent functionalization modification and improves the density of functional groups.

[0030] 3. The modification with oleic acid or ammonium oleate in this invention can result in a large number of double bonds on the surface of the microspheres, which is beneficial for the next step of carboxyl copolymerization and allows the carboxyl groups to be evenly distributed on the surface of the microspheres.

[0031] 4. The carboxyl modification method using small carboxyl molecules and styrene copolymerization in this invention is beneficial for controlling the carboxyl density by adjusting the proportion of small carboxyl molecules in styrene; at the same time, the addition of styrene can form a polymer protective layer on the surface of the magnetic layer, which can effectively protect the magnetic particles and prevent the occurrence of magnetic leakage.

[0032] 5. Compared with traditional methods that use concentrated sulfuric acid sulfonation and other methods to modify the surface of polystyrene microspheres, the method of this invention has the advantages of safe and simple operation process and will not cause environmental pollution. Attached Figure Description

[0033] Figure 1 Scanning electron microscope image of polystyrene microspheres in Example 2.

[0034] Figure 2 Scanning electron microscope image of carboxyl magnetic polymer microspheres in Example 2. Detailed Implementation

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Example 1: A method for preparing high-density carboxyl-based magnetic polymer microspheres, comprising the following steps:

[0036] (1) Preparation of polystyrene@silica microspheres: Silicon-coated polystyrene microspheres were obtained by coating the surface of polystyrene microspheres with silica using an in-situ polymerization method;

[0037] Polystyrene microspheres were prepared by dispersion polymerization. The preparation steps are as follows: Polyvinylpyrrolidone (PVP) was dissolved in an ethanol-water mixture at a mass ratio of 3:150 in an ethanol-water mixture at a mass ratio of 9:1. Under argon protection, after the PPVP was completely dissolved, the temperature was increased to 65°C. Then, styrene and an initiator, which were pre-mixed evenly, were added. The mass ratio of initiator to styrene was 1:100, and the mass ratio of the ethanol-water mixture to styrene was 5:1. The mixture was then stirred continuously at 250 rpm for 12 hours. After the reaction was complete, the microspheres were repeatedly washed with ethanol by centrifugation and dried in a vacuum oven at 40°C to obtain polystyrene microspheres. The dispersion coefficient of the polystyrene microspheres was less than 0.05. The PPVP dispersant was K-30; the centrifugation speed was 1000 rpm, and the washing was performed three times; the initiator was azobisisobutyronitrile (AIB).

[0038] The specific steps for preparing polystyrene@silica microspheres are as follows: Dispersant No. 1 is dissolved in an ethanol-water mixture with a mass ratio of 4:5 at a mass ratio of 0.5:100. After the dispersant No. 1 is completely dissolved, polystyrene microspheres are added, with a mass ratio of 100:1 between the ethanol-water mixture and the polystyrene microspheres. The temperature is raised to 35℃, and once the polystyrene microspheres are monodisperse, a silicon source is added at a mass ratio of 2:1 between the polystyrene microspheres and the silicon source. After stirring for 30 minutes, ammonia is added to adjust the pH to 8, and the reaction is continued at 200 rpm for 3 hours. After the reaction is complete, the microspheres are washed alternately by centrifugation with ethanol and deionized water, and then dried in a vacuum oven at 40℃ to obtain polystyrene@silica microspheres. Dispersant No. 1 is hexadecyltrimethylammonium bromide; it is dispersed in the ethanol-water mixture using mechanical stirring. The silicon source is tetraethyl orthosilicate, with a mass ratio of 0.8:1 between the silicon source and the polystyrene microspheres.

[0039] (2) Magnetization of silica-coated polystyrene microspheres: Ferric oxide nanoparticles were deposited on the surface of silica-coated polystyrene microspheres by co-precipitation method to obtain magnetized polystyrene@silica microspheres.

[0040] Silicon-coated polystyrene microspheres were dispersed in an ethanol-water mixture with a mass ratio of 1.5:100 at a mass ratio of 4:5. After the silicon-coated polystyrene microspheres were evenly dispersed, ferric chloride hexahydrate and ferrous chloride tetrahydrate were added at a molar ratio of 2:1, and the mass ratio of silicon-coated polystyrene microspheres to ferric chloride hexahydrate was 1:1. After stirring for 20 min, ammonia water was added to adjust the pH to 9 and the reaction was carried out. The temperature was then raised to 75℃ and the reaction was carried out for 3 h under argon protection throughout the reaction. After the reaction was completed, the microspheres were washed alternately with ethanol and deionized water using magnetic adsorption, and dried in a vacuum oven at 50℃ to obtain magnetized polystyrene@silica microspheres.

[0041] (3) Surface modification: Ammonium oleate was used to modify the surface of magnetized polystyrene@silica microspheres to obtain double bond modified magnetized polystyrene@silica microspheres;

[0042] Magnetized polystyrene@silica microspheres were dispersed in ethanol at a mass ratio of 1.5:100. After the magnetic polystyrene@silica microspheres were evenly dispersed, oleic acid at a mass ratio of 1:1 was added. The mixture was stirred for 10 min and then heated to 75 °C for 2 h. Argon gas was used for protection throughout the reaction. After the reaction was completed, the microspheres were magnetically washed with ethanol to obtain double-bond modified magnetic polystyrene@silica microspheres, which were stored in ethanol or n-hexane for quantitative preparation and later use.

[0043] (4) Preparation of carboxyl magnetic polymer microspheres: Copolymerization of carboxyl small molecules on the surface of double bond modified magnetized polystyrene@silica microspheres was carried out to obtain the finished product.

[0044] The dispersant polyvinylpyrrolidone was dissolved in an ethanol-water mixture at a mass ratio of 2:150 in a mass ratio of 9:1. Under argon protection, after the dispersant polyvinylpyrrolidone was completely dissolved, double-bond modified magnetized polystyrene@silica microspheres were added. After dispersing for 40 min, styrene, methacrylic acid, and an initiator that had been mixed uniformly beforehand were added. The mass ratio of initiator to styrene was 1:100, the mass ratio of methacrylic acid to styrene was 1:0.5, and the mass ratio of double-bond modified magnetized polystyrene@silica microspheres to styrene was 1:1. The reaction was then continuously stirred at 250 rpm for 12 h at a reaction temperature of 65 °C. After the reaction was completed, the mixture was repeatedly washed with ethanol using magnetic adsorption and stored in ethanol for quantitative preparation for later use.

[0045] Example 2: A method for preparing high-density carboxyl magnetic polymer microspheres, comprising the following steps:

[0046] (1) Preparation of polystyrene@silica microspheres: Silicon-coated polystyrene microspheres were obtained by coating the surface of polystyrene microspheres with silica using an in-situ polymerization method;

[0047] Polystyrene microspheres were prepared by dispersion polymerization. The preparation steps are as follows: Polyvinylpyrrolidone (PVP) was dissolved in an ethanol-water mixture at a mass ratio of 3:160 in an ethanol-water mixture at a mass ratio of 9.3:1. Under argon protection, after the PPVP was completely dissolved, the temperature was increased to 75°C. Then, styrene and an initiator, which were pre-mixed evenly, were added. The mass ratio of initiator to styrene was 1.3:100, and the mass ratio of the ethanol-water mixture to styrene was 5:0.8. The mixture was then stirred continuously at 280 rpm for 15 hours. After the reaction was complete, the microspheres were repeatedly washed by centrifugation with ethanol and dried in a vacuum oven at 45°C to obtain polystyrene microspheres. The dispersion coefficient of the polystyrene microspheres was less than 0.05. The PPVP dispersant was K-88; the centrifugation speed was 1500 rpm, and the washing was performed four times; the initiator was benzoyl peroxide.

[0048] The specific steps for preparing polystyrene@silica microspheres are as follows: Dispersant No. 1 is dissolved in an ethanol-water mixture with a mass ratio of 4.5:5 at a mass ratio of 0.6:100. After the dispersant No. 1 is completely dissolved, polystyrene microspheres are added, with a mass ratio of 100:2 between the ethanol-water mixture and the polystyrene microspheres. The temperature is raised to 38℃, and once the polystyrene microspheres are monodisperse, a silicon source is added, with a mass ratio of 2:0.75 between the polystyrene microspheres and the silicon source. After stirring for 40 minutes, ammonia is added to adjust the pH to 8.5, and the reaction is continued at 230 rpm for 4 hours. After the reaction is complete, the microspheres are washed alternately by centrifugation with ethanol and deionized water, and dried in a vacuum oven at 45℃ to obtain polystyrene@silica microspheres. Dispersant No. 1 is dodecyltrimethylammonium bromide; it is dispersed in the ethanol-water mixture using ultrasound. The silicon source is methyl orthosilicate, with a mass ratio of 0.9:1 between the silicon source and the polystyrene microspheres.

[0049] (2) Magnetization of silica-coated polystyrene microspheres: Ferric oxide nanoparticles were deposited on the surface of silica-coated polystyrene microspheres by co-precipitation method to obtain magnetized polystyrene@silica microspheres.

[0050] Silicone-coated polystyrene microspheres were dispersed at a mass ratio of 1.8:100 in a substrate with a mass ratio of 4.5:

[0051] In a 5% ethanol-water mixed solution, after the silica-coated polystyrene microspheres were evenly dispersed, ferric chloride hexahydrate and ferrous chloride tetrahydrate were added in a molar ratio of 2:1 and a mass ratio of silica-coated polystyrene microspheres to ferric chloride hexahydrate of 1:0.8. After stirring for 22 min, ammonia water was added to adjust the pH to 9.3 and the reaction was carried out. Then the temperature was raised to 80℃ and the reaction was carried out for 3.5 h. Argon gas was used for protection throughout the reaction. After the reaction was completed, the microspheres were washed alternately with ethanol and deionized water using magnetic adsorption, and dried in a vacuum oven at 50℃ to obtain magnetized polystyrene@silica microspheres.

[0052] (3) Surface modification: Ammonium oleate was used to modify the surface of magnetized polystyrene@silica microspheres to obtain double bond modified magnetized polystyrene@silica microspheres;

[0053] Magnetized polystyrene@silica microspheres were dispersed in ethanol at a mass ratio of 1.8:100. After the microspheres were evenly dispersed, ammonium oleate at a mass ratio of 1:1.1 was added. The mixture was stirred for 13 min and then heated to 80 °C for 2.5 h. Argon gas was used for protection throughout the reaction. After the reaction was completed, the microspheres were magnetically washed with ethanol to obtain double-bond modified magnetized polystyrene@silica microspheres, which were stored in ethanol or n-hexane for quantitative preparation and later use.

[0054] (4) Preparation of carboxyl magnetic polymer microspheres: Copolymerization of carboxyl small molecules on the surface of double bond modified magnetized polystyrene@silica microspheres was carried out to obtain the finished product.

[0055] The dispersant polyvinylpyrrolidone was dissolved in an ethanol-water mixture at a mass ratio of 2:160 in an ethanol-water mixture at a mass ratio of 9.3:1. Under argon protection, after the dispersant polyvinylpyrrolidone was completely dissolved, double-bond modified magnetized polystyrene@silica microspheres were added. After dispersing for 45 min, styrene, methacrylic acid, and an initiator that had been mixed uniformly beforehand were added. The mass ratio of initiator to styrene was 1.2:100, the mass ratio of methacrylic acid to styrene was 1.3:0.5, and the mass ratio of double-bond modified magnetized polystyrene@silica microspheres to styrene was 1:0.8. The reaction was then continuously stirred at 280 rpm for 13 h at a reaction temperature of 68 °C. After the reaction was completed, the mixture was repeatedly washed with ethanol using magnetic adsorption and stored in ethanol for quantitative preparation for later use.

[0056] Example 3: A method for preparing high-density carboxyl magnetic polymer microspheres, comprising the following steps:

[0057] (1) Preparation of polystyrene@silica microspheres: Silicon-coated polystyrene microspheres were obtained by coating the surface of polystyrene microspheres with silica using an in-situ polymerization method;

[0058] Polystyrene microspheres were prepared by dispersion polymerization. The preparation steps are as follows: Polyvinylpyrrolidone (PVP) was dissolved in an ethanol-water mixture at a mass ratio of 3:200 in an ethanol-water mixture at a mass ratio of 10:1. Under argon protection, after the PPVP was completely dissolved, the temperature was increased to 95°C. Then, styrene and an initiator, which were pre-mixed evenly, were added. The mass ratio of initiator to styrene was 2:100, and the mass ratio of the ethanol-water mixture to styrene was 5:1. The mixture was then stirred continuously at 350 rpm for 18 hours. After the reaction was complete, the microspheres were repeatedly washed with ethanol by centrifugation and dried in a vacuum oven at 60°C to obtain polystyrene microspheres. The dispersion coefficient of the polystyrene microspheres was less than 0.05. The PPVP dispersant was K-88; the centrifugation speed was 3000 rpm, and the washing frequency was 5 times; the initiator was azobisisobutyronitrile (AIB).

[0059] The specific steps for preparing polystyrene@silica microspheres are as follows: Dispersant No. 1 is dissolved in an ethanol-water mixture with a mass ratio of 6:5 at a mass ratio of 1:100. After the dispersant No. 1 is completely dissolved, polystyrene microspheres are added, with a mass ratio of 100:3 between the ethanol-water mixture and the polystyrene microspheres. The temperature is raised to 45℃, and once the polystyrene microspheres are monodisperse, a silicon source is added, with a mass ratio of 2:0.25 between the polystyrene microspheres and the silicon source. After stirring for 60 minutes, ammonia is added to adjust the pH to 10, and the reaction is continued at 300 rpm for 6 hours. After the reaction is complete, the microspheres are washed alternately by centrifugation with ethanol and deionized water, and dried in a vacuum oven at 60℃ to obtain polystyrene@silica microspheres. Dispersant No. 1 is sodium dodecyl sulfate; it is dispersed in the ethanol-water mixture using mechanical stirring. The silicon source is 3-aminopropyltriethoxysilane, with a mass ratio of 1.2:1 between the silicon source and the polystyrene microspheres.

[0060] (2) Magnetization of silica-coated polystyrene microspheres: Ferric oxide nanoparticles were deposited on the surface of silica-coated polystyrene microspheres by co-precipitation method to obtain magnetized polystyrene@silica microspheres.

[0061] Silicon-coated polystyrene microspheres were dispersed in an ethanol-water mixture with a mass ratio of 6:5 at a mass ratio of 2.5:100. After the silicon-coated polystyrene microspheres were evenly dispersed, ferric chloride hexahydrate and ferrous chloride tetrahydrate were added at a molar ratio of 2:1, and the mass ratio of silicon-coated polystyrene microspheres to ferric chloride hexahydrate was 1:0.5. After stirring for 30 min, ammonia water was added to adjust the pH to 10 and the reaction was carried out. The temperature was then raised to 95℃ and the reaction was carried out for 5 h under argon protection throughout the reaction. After the reaction was completed, the microspheres were washed alternately with ethanol and deionized water using magnetic adsorption, and dried in a vacuum oven at 50℃ to obtain magnetized polystyrene@silica microspheres.

[0062] (3) Surface modification: Oleic acid was used to modify the surface of magnetized polystyrene@silica microspheres to obtain double bond modified magnetized polystyrene@silica microspheres;

[0063] Magnetized polystyrene@silica microspheres were dispersed in ethanol at a mass ratio of 2.5:100. After the microspheres were evenly dispersed, oleic acid at a mass ratio of 1:1.2 was added. The mixture was stirred for 20 min and then heated to 95 °C for 4 h. Argon gas was used for protection throughout the reaction. After the reaction was completed, the microspheres were magnetically washed with ethanol to obtain double-bond modified magnetized polystyrene@silica microspheres, which were stored in ethanol or n-hexane for quantitative preparation and later use.

[0064] (4) Preparation of carboxyl magnetic polymer microspheres: Copolymerization of carboxyl small molecules on the surface of double bond modified magnetized polystyrene@silica microspheres was carried out to obtain the finished product.

[0065] The dispersant polyvinylpyrrolidone was dissolved in an ethanol-water mixture at a mass ratio of 2:200 in an ethanol-water mixture at a mass ratio of 10:1. Under argon protection, after the dispersant polyvinylpyrrolidone was completely dissolved, double-bond modified magnetized polystyrene@silica microspheres were added. After dispersing for 60 min, styrene, methacrylic acid, and an initiator that had been mixed uniformly beforehand were added. The mass ratio of initiator to styrene was 2:100, the mass ratio of methacrylic acid to styrene was 2:0.5, and the mass ratio of double-bond modified magnetized polystyrene@silica microspheres to styrene was 1:0.4. The reaction was then continuously stirred at 350 rpm for 18 h at a reaction temperature of 75 °C. After the reaction was completed, the mixture was repeatedly washed with ethanol using magnetic adsorption and stored in ethanol for quantitative preparation for later use.

[0066] Example 4: Referring to Example 3, the mass ratio of methacrylic acid to styrene was adjusted to 1.4:0.5.

[0067] Example 5: Referring to Example 3, the mass ratio of methacrylic acid to styrene was adjusted to 1:0.5.

[0068] Example 6: Referring to Example 1, the dispersant polyvinylpyrrolidone is one or two of the following: K-30, K-60 and K-88.

[0069] Dispersant No. 1 is one or two of hexadecyltrimethylammonium bromide, dodecyltrimethylammonium bromide, sodium dodecyl sulfate, or sodium dodecylbenzene sulfonate.

[0070] Comparative Example 1: Referring to Example 3, step (4) is omitted.

[0071] The specific performance testing methods are as follows:

[0072] (1) Particle size testing of high-density carboxyl magnetic polymer microspheres:

[0073] SEM characterization was used, followed by particle size statistics to calculate the average particle size. Each statistical measurement of microspheres required more than 500 microspheres.

[0074] (2) Carboxyl density test of high-density carboxyl magnetic polymer microspheres:

[0075] Potentiometric titration was used, referring to the national standard GB / T 23840-2009.

[0076] Table 1 Comparison of performance parameters between Comparative Example 1 and Examples 1-6

[0077]

[0078]

[0079] The described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for preparing high-density carboxyl magnetic polymer microspheres, comprising the following steps, characterized in that: (1) Preparation of polystyrene@silica microspheres: Silicon-coated polystyrene microspheres were obtained by coating the surface of polystyrene microspheres with silica using an in-situ polymerization method; (2) Magnetization of silica-coated polystyrene microspheres: Ferric oxide nanoparticles were deposited on the surface of silica-coated polystyrene microspheres by co-precipitation method to obtain magnetized polystyrene@silica microspheres. (3) Surface modification: The surface of magnetized polystyrene@silica microspheres was modified with oleic acid or ammonium oleate to obtain double bond modified magnetized polystyrene@silica microspheres; (4) Preparation of carboxyl magnetic polymer microspheres: Copolymerization of carboxyl small molecules on the surface of double bond modified magnetized polystyrene@silica microspheres was carried out to obtain the finished product.

2. The method for preparing high-density carboxyl magnetic polymer microspheres according to claim 1, characterized in that, The polystyrene microspheres in step (1) are prepared by dispersion polymerization, and the preparation steps are as follows: The dispersant polyvinylpyrrolidone was dissolved in an ethanol-water mixture at a mass ratio of 3:150-200 in an ethanol-water mixture at a mass ratio of 9-10:

1. Under argon protection, after the dispersant polyvinylpyrrolidone was completely dissolved, the temperature was raised to 65-95°C. Then, styrene and an initiator that had been mixed evenly beforehand were added. The mass ratio of the initiator to styrene was 1-2:100, and the mass ratio of the ethanol-water mixture to styrene was 5:1-0.

4. The mixture was then stirred continuously at 250-350 rpm for 12-18 hours. After the reaction was completed, the mixture was repeatedly washed with ethanol by centrifugation and dried in a vacuum oven at 40-60°C to obtain polystyrene microspheres.

3. The method for preparing high-density carboxyl magnetic polymer microspheres according to claim 1, characterized in that, The polystyrene microspheres have a dispersion coefficient of less than 0.

05.

4. The method for preparing high-density carboxyl magnetic polymer microspheres according to claim 2, characterized in that, The dispersant, polyvinylpyrrolidone, is one or two of K-30, K-60, and K-88; when repeatedly centrifuged and washed with ethanol, the centrifugation speed is 1000-3000 rpm, and the number of washes is 3-5; the initiator is azobisisobutyronitrile or benzoyl peroxide.

5. The method for preparing high-density carboxyl magnetic polymer microspheres according to claim 1, characterized in that, The specific steps for preparing polystyrene@silica microspheres are as follows: Dispersant No. 1 was dissolved in an ethanol-water mixture with a mass ratio of 4-6-5 at a mass ratio of 0.5-1:

100. After the dispersant No. 1 was completely dissolved, polystyrene microspheres were added at a mass ratio of 100:1-3 (ethanol-water mixture to polystyrene microspheres). The temperature was raised to 35-45℃. Once the polystyrene microspheres were monodisperse, a silicon source was added at a mass ratio of 2:1-0.25 (polystyrene microspheres to silicon source). The mixture was stirred for 30-60 minutes, and then ammonia was added to adjust the pH to 8-10 for further reaction. The reaction was continued at 200-300 rpm for 3-6 hours. After the reaction was completed, the microspheres were washed alternately by centrifugation with ethanol and deionized water, and then dried in a vacuum oven at 40-60℃ to obtain polystyrene@silica microspheres.

6. The method for preparing high-density carboxyl magnetic polymer microspheres according to claim 5, characterized in that, The first dispersant is one or two of hexadecyltrimethylammonium bromide, dodecyltrimethylammonium bromide, sodium dodecyl sulfate, or sodium dodecylbenzene sulfonate; the first dispersant is dispersed in an ethanol-water mixed solution by mechanical stirring or ultrasonication.

7. The method for preparing high-density carboxyl magnetic polymer microspheres according to claim 5, characterized in that, The silicon source is tetraethyl orthosilicate, methyl orthosilicate, or 3-aminopropyltriethoxysilane, and the mass ratio of the silicon source to the polystyrene microspheres is 0.8 to 1.2:

1.

8. The method for preparing high-density carboxyl magnetic polymer microspheres according to claim 1, characterized in that, The specific steps for magnetizing the silicon-coated polystyrene microspheres are as follows: Silicon-coated polystyrene microspheres were dispersed in an ethanol-water mixture with a mass ratio of 4-6:5 at a mass ratio of 1.5-2.5:

100. After the microspheres were evenly dispersed, ferric chloride hexahydrate and ferrous chloride tetrahydrate were added at a molar ratio of 2:1, and the mass ratio of the microspheres to ferric chloride hexahydrate was 1:1-0.

5. After stirring for 20-30 minutes, ammonia was added to adjust the pH to 9-10 and the reaction was carried out. The temperature was then raised to 75-95℃ and the reaction was carried out for 3-5 hours under argon protection throughout the reaction. After the reaction was completed, the microspheres were washed alternately with ethanol and deionized water using magnetic adsorption, and dried in a vacuum oven at 50℃ to obtain magnetized polystyrene@silica microspheres.

9. The method for preparing high-density carboxyl magnetic polymer microspheres according to claim 1, characterized in that, The specific steps of the surface modification are as follows: Magnetized polystyrene@silica microspheres were dispersed in ethanol at a mass ratio of 1.5–2.5:

100. After the magnetic polystyrene@silica microspheres were evenly dispersed, oleic acid or ammonium oleate at a mass ratio of 1:1–1.2 was added. The mixture was stirred for 10–20 min and then heated to 75–95 °C for 2–4 h. Argon gas was used for protection throughout the reaction. After the reaction was completed, the microspheres were magnetically washed with ethanol to obtain double-bond modified magnetic polystyrene@silica microspheres, which were stored in ethanol or n-hexane for quantitative preparation and later use.

10. The method for preparing high-density carboxyl magnetic polymer microspheres according to claim 1, characterized in that, The specific steps for preparing the carboxyl magnetic polymer microspheres are as follows: Dispersant polyvinylpyrrolidone is dissolved in an ethanol-water mixture with a mass ratio of 9-10:1 at a mass ratio of 2:150-200. Under argon protection, after the dispersant polyvinylpyrrolidone is completely dissolved, double-bond modified magnetized polystyrene@silica microspheres are added. After dispersing for 40-60 minutes, styrene, methacrylic acid, and an initiator that have been mixed uniformly beforehand are added. The mass ratio of initiator to styrene is 1-2:100, the mass ratio of methacrylic acid to styrene is 1-2:0.5, and the mass ratio of double-bond modified magnetized polystyrene@silica microspheres to styrene is 1:1-0.

4. The mixture is then continuously stirred at 250-350 rpm for 12-18 hours at a reaction temperature of 65-75℃. After the reaction is complete, the microspheres are repeatedly washed with ethanol using magnetic adsorption and stored in ethanol for quantitative preparation.

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