Polystyrene microspheres for upic and methods of making and functionalizing

Abstract

The application discloses a polystyrene microsphere for UPIC, a preparation method and a functionalization method, and belongs to the technical field of polymer synthesis, and comprises the following steps: polystyrene seed is obtained by polymerization of styrene monomers in the presence of a molecular weight regulator; the seed is activated by swelling in a swelling agent to obtain a seed dispersion liquid; a monomer dispersion liquid is obtained by emulsifying a crosslinking monomer, a functional monomer and a second initiator in an aqueous solution; the monomer dispersion liquid is mixed with the seed dispersion liquid and is secondarily swelled, and then is mixed with an aqueous phase, and a crosslinking polymerization reaction is carried out to obtain the polystyrene microsphere; and the polystyrene microsphere is subjected to a functionalization treatment method such as epoxidation modification and / or amination modification to obtain grafted anion microspheres. The polystyrene microsphere obtained by the application has a highly uniform particle size, excellent monodispersity and regular morphology, and the comprehensive performance of the polystyrene microsphere can directly meet the requirements of UPIC fillers on particle size, pressure resistance and chemical stability.

Description

Technical Field

[0001] This invention belongs to the field of polymer synthesis technology, specifically relating to a polystyrene microsphere for UPIC and its preparation and functionalization methods. Background Technology

[0002] Polymer microspheres, especially cross-linked polystyrene-divinylbenzene (PS-DVB) microspheres, have become important matrix materials for high-pressure chromatography columns due to their excellent mechanical strength, chemical stability, wide acid and alkali resistance range, and ease of functionalization. As analytical science continues to demand higher separation efficiency, speed, and throughput, chromatographic technology is evolving towards ultra-performance. While mature ultra-high performance liquid chromatography (UHPLC) technology has been developed in the field of liquid chromatography, ultra-high performance ion chromatography (UPIC), which offers advantages in high resolution and rapid analysis, is still under development.

[0003] The core challenge in realizing UPIC lies in developing matching key components, among which the chromatographic packing material (stationary phase) is the most critical factor determining column efficiency, back pressure, and stability. UPIC systems require packing material to possess: 1) smaller particle size (typically ≤2.5 μm) to provide higher column efficiency; 2) extremely high mechanical strength to withstand continuous high pressures (typically exceeding 30 MPa); 3) highly uniform particle size and regular morphology to ensure low column back pressure and good packing reproducibility; and 4) abundant and robust functionalizable sites to meet diverse separation mode requirements.

[0004] Numerous technological explorations have been undertaken to prepare monodisperse polymer chromatographic packing materials, but each still has its limitations, making it difficult to simultaneously meet the aforementioned requirements. Regarding improving mechanical strength, CN102766305A discloses a method to enhance the mechanical strength and heat resistance of microspheres by introducing siloxane-containing monomers to form an organic-inorganic composite network. However, the suspension polymerization method used in this approach struggles to precisely control the particle size and monodispersity of the microspheres, while particle size uniformity is a primary prerequisite for high-performance chromatographic packing materials. In terms of particle size control, CN104017118A discloses a one-step process for preparing 2 μm polystyrene microspheres, emphasizing its simplicity. However, the one-step method has limited control over the uniformity of the internal cross-linking network, pore structure, and simultaneous functionalization capabilities of the microspheres, making it difficult to meet the demands of complex separation scenarios requiring precise packing structure. Furthermore, to achieve specific chromatographic functions, existing technologies generally employ a route of surface chemical modification of pre-prepared inert matrices. For example, polymers such as poly(amine-epoxychloropropane) are used to coat or graft onto the surface of microspheres to prepare anion exchange packing materials (see "Preparation and Application of Poly(amine-epoxychloropropane) Modified Anion Chromatography Packing Materials"). While such post-modification methods can introduce functional groups, they have inherent drawbacks: First, the functional layer adheres to the matrix surface only through physical adsorption or weak chemical bonds. Under the high pressure, high flow rate, and extreme pH conditions of long-term operation of ultra-high performance ion chromatography (UPIC), there is a risk of coating swelling, peeling, or loss of functional groups, leading to shortened column life and decreased reproducibility. Second, the surface modification layer may block some of the original pores of the matrix, increasing mass transfer resistance and limiting further improvements in separation rate and column efficiency. Third, the preparation process involves multiple complex surface chemical reactions, resulting in poor process controllability and difficulty in guaranteeing batch stability. These drawbacks make it difficult for traditional post-modification techniques to prepare high-performance, high-stability packing materials that meet the extreme requirements of UPIC.

[0005] Therefore, developing a polymer microsphere preparation method that can precisely control the matrix structure from the source of synthesis, take into account both high strength and suitable pore structure, and achieve in-situ uniform introduction of functional groups is an urgent need to break through the bottleneck of UPIC packing technology and promote ion chromatography into the era of ultra-high efficiency. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a polystyrene microsphere for UPIC, as well as a preparation method and a functionalization method. The polystyrene microsphere provided by the present invention has a high degree of crosslinking and a controllable structure, which can meet the stringent requirements of ultra-high performance ion chromatography (UPIC).

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing polystyrene microspheres, the method comprising:

[0009] S1. Styrene monomers are polymerized in a reaction system containing a dispersant, a molecular weight regulator and a first initiator to obtain monodisperse polystyrene seeds;

[0010] S2. Monodisperse polystyrene seeds are swollen and activated in the first aqueous solution to obtain a seed dispersion;

[0011] S3. A monomer mixture is obtained by mixing crosslinking monomers, functional monomers, optionally a porogen and a second initiator. The monomer mixture is emulsified with a second aqueous solution to obtain a monomer dispersion. The monomer dispersion is mixed with a seed dispersion and subjected to secondary swelling to obtain a reaction oil phase.

[0012] S4. The reaction oil phase and the aqueous phase containing the stabilizer are mixed and subjected to a cross-linking polymerization reaction to obtain a product dispersion;

[0013] S5. Separate and purify the product, removing the optional porogen, to obtain the polystyrene microspheres.

[0014] The preparation method provided by this invention has the following advantages:

[0015] i. Innovatively, in the two-step seed swelling process, a molecular weight regulator is introduced during the seed preparation stage to control the molecular weight of polystyrene seeds. At the same time, combined with the two-step seed swelling process, the cross-linking network and pore structure of polystyrene microspheres are controlled, so that the final polystyrene microspheres have a controllable hierarchical pore structure that is conducive to rapid mass transfer.

[0016] ii. At the same time, the preparation method provided by the present invention can avoid the problem of pore blockage caused by excessive crosslinking while introducing a high degree of crosslinking by introducing a high degree of crosslinking monomers, thus solving the contradiction between particle size, strength and mass transfer;

[0017] iii. The preparation method provided by this invention introduces functional monomers. The functional monomers with active functional groups are introduced into polystyrene microspheres through in-situ polymerization. That is, the active functional groups are uniformly and firmly distributed in the form of covalent bonds throughout the polymer skeleton. This overcomes the defects of uneven functional layer and weak binding force in the post-modification method. It provides an ideal matrix platform for preparing various derivatized stationary phases with high capacity and high stability. The chromatographic packing materials derived from this (such as strong anion exchange packing materials) are expected to achieve high column efficiency and excellent stability.

[0018] Therefore, the polystyrene microspheres prepared by the method provided by the present invention have a highly uniform particle size, preferably 2.0±0.2 μm, excellent monodispersity, and regular morphology. At the same time, their comprehensive performance can directly meet the full requirements of UPIC fillers for particle size, pressure resistance, chemical stability, and functionalizability.

[0019] Furthermore, the polystyrene microspheres prepared by the method provided by this invention can be derived into various stationary phases (such as ion exchange, hydrophobic, hydrophilic, and affinity stationary phases) through the introduction of functional monomers. They are not only specifically designed for UPIC, but also applicable to various separation and analysis scenarios such as conventional high-performance liquid chromatography and ion chromatography, achieving multiple uses with one method.

[0020] This invention fundamentally solves the technical bottleneck of traditional packing materials that cannot simultaneously achieve high strength, high column efficiency, and high stability, providing a key universal material platform for the realization and development of UPIC technology, and has significant value in the fields of high-end analytical instruments and separation science.

[0021] Preferably, in step S1, the molecular weight regulator includes any one or a combination of at least two of n-dodecyl mercaptan, tert-dodecyl mercaptan, α-methylstyrene dimer, n-butyritin or isopropanethiol, preferably n-dodecyl mercaptan and / or tert-dodecyl mercaptan.

[0022] Preferably, the mass of the molecular weight regulator is 0.4-2.2% of the mass of the styrene monomer, for example, 0.4%, 0.6%, 0.8%, 1.0%, 1.2%, 1.5%, 2.0%, 2.2% or any of the above values.

[0023] Preferably, the styrene monomers include styrene and / or vinylethylbenzene.

[0024] Preferably, the volume of the styrene monomer is 8-35% of the total volume of the reaction system, for example, 8%, 10%, 15%, 20%, 25%, 30%, 35% or any of the above values.

[0025] Preferably, the dispersant comprises any one or a combination of at least two of polyvinylpyrrolidone, polyvinyl alcohol, and polyethylene glycol.

[0026] Preferably, the mass of the dispersant is 6-10% of the mass of the styrene monomer, for example, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, or any of the above values.

[0027] Preferably, step S1 is as follows: styrene monomers, dispersants, and molecular weight regulators are mixed in a solvent, and under the initiation of a first initiator, a polymerization reaction is carried out at 65-75℃ (e.g., 65℃, 66℃, 67℃, 68℃, 69℃, 70℃, 71℃, 72℃, 73℃, 75℃ or any range between the above values) for 20-24 h (e.g., 20 h, 20.5 h, 21 h, 21.5 h, 22 h, 22.5 h, 23 h, 23.5 h, 24 h or any range between the above values). After the reaction is completed, the mixture is centrifuged, washed, and dried to obtain the monodisperse polystyrene seeds.

[0028] Preferably, the first initiator used in the polymerization reaction includes any one or a combination of at least two of azobisisobutyronitrile, azobisisoheptanenitrile, or azobiscyclohexylformitrile, with azobisisobutyronitrile being the most preferred.

[0029] Preferably, the amount of the first initiator used in the polymerization reaction is 0.8-3.2% of the mass of the styrene monomer, for example, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.2% or any of the above values.

[0030] Preferably, step S1 is:

[0031] S11. In a nitrogen atmosphere, using anhydrous ethanol or a mixture of anhydrous ethanol and deionized water as the reaction solvent, styrene monomers, dispersants, and molecular weight regulators are added to the reaction solvent and mixed. The volume ratio of anhydrous ethanol to deionized water in the mixed medium is 85:15 to 95:5, for example, 85:15, 86:14, 87:13, 88:12, 90:10, 92:8, 94:6, 95:5, or any range between the above values.

[0032] S12. Under a nitrogen atmosphere, the first initiator is added and the polymerization reaction is carried out at 65-75°C for 20-24 h with vigorous stirring at 200-300 r / min (e.g., 200 r / min, 220 r / min, 240 r / min, 250 r / min, 260 r / min, 280 r / min, 300 r / min or any of the above values).

[0033] S13. After the reaction is complete, cool to room temperature and centrifuge at 8000-10000 r / min (e.g., 8000 r / min, 8200 r / min, 8500 r / min, 8800 r / min, 9000 r / min, 9500 r / min, 10000 r / min or any of the above values) for 15-20 min (e.g., 15 min, 16 min, 17 min, 18 min, 19 min, 20 min or any of the above values). Wash the precipitate with anhydrous ethanol, preferably 2-4 times, e.g., 2 times, 3 times, 4 times or any of the above values. Vacuum dry at 30-50℃ (e.g., 30℃, 35℃, 40℃, 41℃, 42℃, 43℃, 44℃, 45℃, 46℃, 47℃, 48℃, 50℃ or any of the above values) for 8-12 h (e.g., 8 h, 8.5 h, 9 h, 9 h, 10000 r / min or any of the above values). The monodisperse polystyrene seed is obtained by taking h, 9.5h, 10h, 10.5h, 11h, 11.5h, 12h or any of the above values.

[0034] The method for preparing polystyrene seeds provided by this invention can precisely and controllably regulate the seed particle size by limiting the amount of molecular weight regulator. The resulting seed particle size is between 0.9 and 1.1 μm, and the molecular weight is between 30,000 and 90,000 Da. This ensures the monodispersity of the seeds and lays the foundation for the monodispersity of the polystyrene microspheres obtained subsequently, thus solving the technical pain point of wide particle size distribution in traditional seeds.

[0035] Preferably, step S2 is as follows: the monodisperse polystyrene seeds are dispersed in the first aqueous solution, a swelling agent is added and ultrasonically emulsified for 20-40 min, and finally swollen at 25-40℃ for 5-10 h to obtain the seed dispersion.

[0036] Preferably, step S2 includes:

[0037] S21. Disperse the monodisperse polystyrene seeds obtained in step S1 in an aqueous solution of sodium dodecyl sulfate (SDS aqueous solution) and stir for 15-20 min (e.g., 15 min, 16 min, 17 min, 18 min, 19 min, 20 min or any range between the above values) until uniformly dispersed. Preferably, the SDS concentration in the SDS aqueous solution is 0.2-0.3% (w / v), e.g., 0.2% (w / v), 0.22% (w / v), 0.24% (w / v), 0.25% (w / v), 0.26% (w / v), 0.28% (w / v), 0.3% (w / v) or any range between the above values.

[0038] S22. After adding the swelling agent, perform ultrasonic emulsification for 20-40 min (e.g., 20 min, 22 min, 24 min, 25 min, 26 min, 28 min, 30 min, 32 min, 35 min, 40 min or any range between the above values, preferably 30 min) to form uniform micro-droplets of the swelling agent. Preferably, the power of the ultrasonic emulsification is 100-300 W, e.g., 100 W, 150 W, 200 W, 250 W, 300 W or any range between the above values.

[0039] S23. The ultrasonically emulsified system is swollen for 5-10 h (e.g., 25℃, 26℃, 27℃, 28℃, 29℃, 30℃, 32℃, 35℃, 38℃, 40℃ or any of the above values, preferably 35℃) under stirring conditions of 25-40℃ and 100-150 r / min (e.g., 100 r / min, 110 r / min, 120 r / min, 130 r / min, 140 r / min, 150 r / min or any of the above values, preferably 6-8 h) to obtain the seed dispersion.

[0040] Preferably, the swelling agent comprises any one or a combination of at least two of dibutyl phthalate, dioctyl phthalate, dibutyl sebacate, dibutyl adipate, dodecyl chloride, toluene, or liquid paraffin, and more preferably a combination of any one or at least two of dibutyl phthalate, dodecyl chloride, or toluene.

[0041] Preferably, the mass ratio of the swelling agent to the monodisperse polystyrene seed is (0.5-2.5):1, for example, 0.5:1, 0.6:1, 0.8:1, 1.0:1, 1.2:1, 1.5:1, 1.8:1, 2.0:1, 2.5:1 or any range of the above values, preferably (1-1.8):1.

[0042] Preferably, the concentration of the monodisperse polystyrene seeds in the seed dispersion is 0.01-0.06 g / mL, for example, 0.01 g / mL, 0.02 g / mL, 0.03 g / mL, 0.04 g / mL, 0.05 g / mL, 0.06 g / mL, or any range between the above values.

[0043] Preferably, step S3 includes:

[0044] S31. A monomer mixture is obtained by mixing a crosslinking monomer, a functional monomer, a porogen, and a second initiator. The monomer mixture is then mixed with a second aqueous solution and emulsified in a homogenizer to form uniform micro-droplets, thereby obtaining a monomer dispersion.

[0045] S32. Slowly add the monomer dispersion to the seed dispersion for secondary swelling, allowing the monomers (crosslinking monomers and functional monomers) and pore-forming agents to fully penetrate into the seed interior.

[0046] Preferably, in step S3, the crosslinking monomer is selected from divinylbenzene.

[0047] Preferably, the functional monomer comprises any one or a combination of at least two of the following: ether or ester functional monomers, chloromethyl functional monomers, carboxylic acid functional monomers, hydroxyl-containing functional monomers, or tertiary amine / pyridine functional monomers. More preferably, allyl glycidyl ether, glycidyl methacrylate, glycidyl acrylate, p-chloromethylstyrene, acrylic acid, methacrylic acid, dimethylaminoethyl methacrylate, and hydroxyethyl acrylate. N Any one or a combination of at least two of hydroxymethylacrylamide or 4-vinylpyridine.

[0048] Preferably, based on the total mass of the monodisperse polystyrene seeds, crosslinking monomers, and functional monomers as 100%, the content of the monodisperse polystyrene seeds is 5-20%, for example, 5%, 6%, 8%, 10%, 12%, 15%, 18%, 20%, or any of the above values; the content of the functional monomers is 10-40%, for example, 10%, 12%, 15%, 18%, 20%, 25%, 28%, 30%, 32%, 35%, 38%, 40%, or any of the above values; and the content of the crosslinking monomers is ≥50%, for example, 50%, 52%, 55%, 58%, 60%, 62%, 65%, 68%, 70%, or any of the above values.

[0049] This invention introduces a large amount of crosslinking monomers, that is, through the design of high crosslinking degree, the polystyrene microspheres obtained can stably withstand 90-100 MPa pressure, which is fully compatible with the high pressure conditions of ultra-high performance ion chromatography (UPIC), and solves the problems of easy breakage and unstable column pressure of traditional microspheres under high pressure.

[0050] Preferably, the pore-forming agent comprises any one or a combination of at least two of toluene, chlorobenzene, ethylbenzene, anisole, phenyl acetate, n-heptane, cyclohexanol, n-hexane, isooctane, or tert-butanol.

[0051] Preferably, the mass ratio of the porogen to the total mass of the monodisperse polystyrene seed, crosslinking monomer, and functional monomer is (0.01-1.5):1, for example, 0.01:1, 0.05:1, 0.1:1, 0.2:1, 0.3:1, 0.5:1, 0.6:1, 0.8:1, 1:1, 1.2:1, 1.5:1, or any range of the above values.

[0052] Preferably, the second initiator comprises benzoyl peroxide (BPO).

[0053] Preferably, the amount of the second initiator added is 1.5-7.5% of the total mass of the styrene monomer and the crosslinking monomer, for example, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5% or any of the above values, preferably 1.5-5%.

[0054] Preferably, the mass ratio of the monomer mixture and the second aqueous solution is 1:(0.1-15), for example, 1:0.1, 1:1, 1:2, 1:3, 1:4, 1:5, 1:8, 1:10, 1:15 or any range of the above values.

[0055] Preferably, the emulsification time in the homogenizer is 10-40 min, for example 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min or any range between the above values, preferably 20 min.

[0056] Preferably, the temperature of the secondary swelling is 25-40℃, for example, 25℃, 26℃, 27℃, 28℃, 29℃, 30℃, 32℃, 35℃, 38℃, 40℃ or any of the above values; the stirring rate is 100-150 r / min, for example, 100 r / min, 110 r / min, 120 r / min, 130 r / min, 140 r / min, 150 r / min or any of the above values; and the time is 8-12 h, for example, 8 h, 9 h, 10 h, 10.5 h, 11 h, 11.5 h, 12 h or any of the above values.

[0057] This invention innovatively employs a specific swelling agent and introduces a large amount of crosslinking monomers and functionalized monomers. By matching the amount of swelling agent with the seed type, and the amount of DVB with the amount of pore-forming agent, it ensures both the high degree of crosslinking of microspheres (withstanding high pressure of 90-100MPa) and the avoidance of pore structure collapse, thus guaranteeing mass transfer efficiency.

[0058] Preferably, step S4 includes:

[0059] S41. Add the aqueous phase to the reaction oil phase, stir for 10-30 min, for example 10 min, 15 min, 20 min, 25 min, 30 min or any range between the above values, and purge with nitrogen for 10-30 min, for example 10 min, 15 min, 20 min, 25 min, 30 min or any range between the above values, to remove oxygen from the system.

[0060] S42. The reaction system obtained in step S41 is heated to carry out cross-linking polymerization. During the reaction, the system temperature is kept constant to avoid local overheating that could lead to uneven particle size.

[0061] Preferably, in step S4, the volume ratio of the reaction oil phase to the water phase is 1:(0.1-1), for example, 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.8, 1:1 or any range between the above values.

[0062] Preferably, in step S4, the aqueous phase is an aqueous solution containing a stabilizer. The stabilizer preferably includes any one or a combination of at least two of polyvinyl alcohol, hydroxyethyl cellulose, polyethylene glycol, polyacrylic acid, polymethyl methacrylate oligomers, or modified chitosan, preferably polyvinyl alcohol and / or hydroxyethyl cellulose. The amount of stabilizer used is preferably 0.1-1.5% of the mass of the aqueous phase, for example, 0.1%, 0.2%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, or any range of the above values.

[0063] Preferably, in step S4, the temperature of the crosslinking polymerization reaction is 65-80℃, for example, 65℃, 66℃, 68℃, 70℃, 72℃, 75℃, 78℃, 80℃ or any of the above values; the stirring rate is 200-500 r / min, for example, 200 r / min, 300 r / min, 400 r / min, 500 r / min or any of the above values; and the time is 20-24h, for example, 20 h, 20.5 h, 21 h, 21.5 h, 22 h, 22.5 h, 23 h, 23.5 h, 24 h or any of the above values.

[0064] Preferably, in step S4, the heating rate of the crosslinking polymerization reaction is 2-3℃ / min, for example, 2℃ / min, 2.2℃ / min, 2.5℃ / min, 2.8℃ / min, 3℃ / min or any of the above values, to avoid local overheating.

[0065] Preferably, in step S5, the method for removing the pore-forming agent is an extraction method.

[0066] Preferably, step S5 includes:

[0067] S51. Cool the product dispersion to room temperature, collect the solid product by suction filtration, and wash it 2-3 times each with deionized water and ethanol to remove unreacted monomers, dispersants and emulsifiers to obtain the primary product.

[0068] S52. The primary product is extracted with an extractant in a Soxhlet extractor to remove the porogen in the system and form a porous structure.

[0069] S53. After extraction, the product is washed 1-2 times with ethanol and dried in a vacuum drying oven at 40-60℃ (e.g., 40℃, 42℃, 45℃, 48℃, 50℃, 52℃, 55℃, 58℃, 60℃ or any range between the above values) for 12-24 h (e.g., 12 h, 15 h, 16 h, 18 h, 20 h, 22 h, 24 h or any range between the above values) to obtain the polystyrene microspheres.

[0070] Preferably, the extractant comprises any one or a combination of at least two of dichloromethane, trichloromethane, carbon tetrachloride, 1,2-dichloroethane, chloroethane, toluene, xylene, ethylbenzene, benzene, chlorobenzene, methanol, ethanol, isopropanol, n-propanol, or ethyl acetate, and more preferably any one or a combination of at least two of dichloromethane, xylene, or ethanol.

[0071] Preferably, the extraction time is 8-24 h, for example 8 h, 10 h, 12 h, 15 h, 18 h, 20 h, 22 h, 24 h or any of the above values, preferably 12-18 h.

[0072] The preparation method provided by this invention has the advantage of parameter standardization. By clearly defining the core process parameters of each step (stirring speed, temperature, time, reagent dosage, etc.), the preparation process can be repeated, the product performance is stable, and it is suitable for industrial scale-up production.

[0073] Secondly, the present invention provides polystyrene microspheres prepared by the preparation method described in the first aspect, wherein the particle size variation coefficient of the polystyrene microspheres is ≤2.9%. The polystyrene microspheres provided by the present invention have good monodispersity and sphericity, and after packing the chromatographic column, they have high column efficiency and good separation repeatability, and can achieve rapid and efficient separation of seven anions within 3 minutes, meeting the high-efficiency separation requirements of UPIC.

[0074] The polystyrene microspheres provided by this invention achieve a breakthrough unification of key performance characteristics of chromatographic packing matrix, providing a reliable material basis for ultra-high performance ion chromatography (UPIC). The average particle size of the polystyrene microspheres in this invention is 2.0±0.2 μm, exhibiting excellent monodispersity and the ability to stably withstand 100 MPa pressure. Compared to existing polystyrene microspheres that struggle to achieve high mechanical strength at smaller particle sizes, this invention introduces a molecular weight regulator during the seed polymerization stage to actively control the chain length of the seed polymer. This results in a more uniform, dense, and elastic cross-linked network when subsequently copolymerized with a high proportion of divinylbenzene (DVB≥30%), simultaneously overcoming the technical contradiction between high column efficiency (small particle size) and high pressure resistance at the microscale.

[0075] Meanwhile, the polystyrene microspheres provided by this invention solve the industry problem of unstable functional layers in post-modified fillers, ensuring exceptional chromatographic stability and reproducibility. Compared to existing post-modification methods where functional layers are easily lost under high pressure, this invention directly covalently bonds the active groups (such as epoxy groups) of functional monomers (such as GMA) to the polymer backbone through in-situ copolymerization, achieving a uniform and robust distribution of functional sites within the microsphere phase. Therefore, the functional groups (such as quaternary ammonium groups) obtained after derivatization have extremely strong binding forces, capable of withstanding the long-term high pressure and high flow rate impact of the UPIC system, resulting in a longer service life and better data analysis reproducibility.

[0076] The polystyrene microspheres provided by this invention are "general-purpose high-performance matrices," rather than single-function end-fillers. The polystyrene microspheres provided by this invention can be rapidly developed into a variety of specialized fillers (such as anion / cation exchange, hydrophilic interaction, etc.) through mature chemical reactions (such as one-step amination, epoxy ring-opening-amination, etc.), which greatly shortens the research and development cycle and reduces process development costs. It can promote the progress of high-end chromatographic fillers and reduce the analysis costs in fields such as environmental monitoring, biomedicine, and food safety, and has high efficiency and flexibility.

[0077] Meanwhile, the polystyrene microspheres provided by this invention, after functionalization, undergo multi-step washing, extraction and purification, leaving no residual porogens and unreacted monomers. They do not swell or break during long-term use, and the column efficiency decays by ≤8% after 300 consecutive injections. They have a long service life and excellent stability.

[0078] Thirdly, the present invention provides a method for functionalizing polystyrene microspheres as described in the second aspect, as follows:

[0079] a. When the functional monomer is an ether or ester compound, such as allyl glycidyl ether (AGE), glycidyl methacrylate (GMA), or glycidyl acrylate (GA), the functionalization method includes: reacting a polystyrene microsphere dispersion with an epoxy compound and / or an amine compound to obtain grafted anionic microspheres.

[0080] Preferably, the functionalization method includes:

[0081] Polystyrene microspheres were dispersed in water to obtain a polystyrene microsphere dispersion.

[0082] An aqueous solution of amine compounds was mixed with a dispersion of polystyrene microspheres to react, and the mixture was then filtered and washed.

[0083] Following the method described above, the aqueous solution of amine compounds was replaced with an aqueous solution of epoxide compounds for the reaction. After the reaction was completed, the mixture was filtered and washed.

[0084] Preferably, the functionalization method includes:

[0085] Polystyrene microspheres were dispersed in deionized water at a concentration of 0.1-0.5 g / mL (e.g., 0.1 g / mL, 0.2 g / mL, 0.3 g / mL, 0.4 g / mL, 0.5 g / mL, or any range thereof). The mixture was then reacted with an aqueous methylamine solution at 50-70°C (e.g., 50°C, 55°C, 60°C, 65°C, 70°C, or any range thereof). The amount of methylamine added was 0.1-1 times the mass of the polystyrene microspheres (e.g., 0.1 times, 0.2 times, 0.5 times, 0.6 times, 0.8 times, 1 times, or any range thereof). The reaction was carried out for 20-40 min (e.g., 20 min, 25 min, 30 min, 35 min, 40 min, or any range thereof). After the reaction, the mixture was filtered and washed with deionized water. Then, following the same procedure, an aqueous epichlorohydrin solution (already ultrasonically dispersed) was added and reacted for 20-40 min (e.g., 20 min, 25 min, 30 min, 40 min, or any range thereof). The amount of epichlorohydrin added is 0.5-1 times the mass of the polystyrene microspheres (e.g., 0.5, 0.6, 0.7, 0.8, 0.9, 1 times, or any of the above values), after the reaction is completed, the mixture is filtered and washed. Alternating these two steps is called a single grafting reaction. The final product is dried to obtain grafted anion exchange microspheres. In this invention, the alternating single reaction of the polystyrene microspheres with epoxy compounds and amine compounds is called a single grafting reaction. By controlling different grafting reaction times, this invention prepares quaternized packing materials with different numbers of functional groups, i.e., grafted anion exchange microspheres for ion chromatography, suitable for the separation and detection of different concentrations of anions in complex samples, with a wide range of applications.

[0086] Preferably, the reaction temperature with epichlorohydrin is 60°C and the time is 30 min; more preferably, the reaction temperature with the amine compound is 60°C and the time is 30 min.

[0087] This invention employs a post-functionalization method of "alternating grafting of methylamine and epichlorohydrin". By adjusting the number of grafting reactions, the number of quaternary ammonium functional groups can be flexibly controlled to meet different anion separation requirements. Moreover, the reaction conditions are mild (60℃, 30 min / time), and the operation is simple and reproducible.

[0088] The functionalized polystyrene microspheres obtained by this invention have an average particle size of 2.0-2.5 μm, CV≤2.9%, high pressure resistance of 90-100 MPa, and can separate seven anions within 3 min.

[0089] The grafted anion microspheres provided by this invention can be used as packing materials for ultra-high performance ion chromatography (UPIC), and are particularly suitable for F - Cl - NO2 - ,Br - NO3 - SO4 2- PO4 2- Rapid separation of seven anions.

[0090] b. The functional monomer is a chloromethyl functional monomer, such as p-chloromethylstyrene (CMSt), and the functionalization method includes: reacting an amine compound with polystyrene microspheres using a nucleophilic substitution reaction of chloromethyl to obtain quaternized anionic microspheres.

[0091] Preferably, the functionalization method includes:

[0092] Polystyrene microspheres were dispersed in anhydrous ethanol to obtain a polystyrene microsphere dispersion.

[0093] An aqueous solution of an amine compound (e.g., trimethylamine) is mixed with a dispersion of polystyrene microspheres to react, followed by filtration and washing.

[0094] Preferably, the functionalization method includes:

[0095] Polystyrene microspheres were dispersed in anhydrous ethanol at a concentration of 0.1-0.5 g / mL (e.g., 0.1 g / mL, 0.2 g / mL, 0.3 g / mL, 0.4 g / mL, 0.5 g / mL, or any range thereof). The mixture was then reacted with an aqueous trimethylamine solution at 30-50°C (e.g., 30°C, 35°C, 40°C, 45°C, 50°C, or any range thereof). The amount of trimethylamine added was 1-5 times the mass of the polystyrene microspheres (e.g., 1, 2, 3, 4, 5 times, or any range thereof). The reaction was carried out for 24-48 h (e.g., 24 h, 30 h, 35 h, 40 h, 45 h, 48 h, or any range thereof). After the reaction was complete, the mixture was filtered and washed with deionized water to obtain quaternized anionic microspheres.

[0096] Examples are listed below:

[0097] 3 g of polystyrene microspheres were dispersed in 30 mL of anhydrous ethanol solvent. Taking advantage of the nucleophilic substitution reaction of chloromethyl groups, 30 mL of 30% trimethylamine ethanol solution was added, and the reaction was carried out at 40 °C for 24-48 h to obtain quaternized anionic microspheres.

[0098] c. The functional monomer is a carboxyl functional monomer, such as acrylic acid (AA) or methacrylic acid (MAA), and the functionalization method includes: reacting a polystyrene microsphere dispersion with an epoxy compound and / or an amine compound to obtain grafted anionic microspheres.

[0099] Preferably, the functionalization method includes:

[0100] Polystyrene microspheres were dispersed in water to obtain a polystyrene microsphere dispersion.

[0101] An epoxy compound (preferably epichlorohydrin or ethylene glycol diglycidyl ether) is mixed with a polystyrene microsphere dispersion and reacted, where the carboxyl group and epoxy group undergo a ring-opening esterification reaction, introducing hydroxyl groups and active halogen sites.

[0102] After the reaction, an amine compound (preferably ethylenediamine or triethanolamine) is added, and the temperature is increased to achieve amination and quaternization.

[0103] Alternatively, the functionalization method includes: dispersing polystyrene microspheres in water to obtain a polystyrene microsphere dispersion; subjecting the dispersion to an amidation reaction with ethylenediamine under the action of a condensing agent to introduce amine groups on the surface of the microspheres; after protonation of the amine groups, stable anion exchange sites are formed; after post-treatment, weakly basic anion exchange microspheres are obtained; after the reaction is completed, the microspheres are filtered, washed until neutral, and dried to finally obtain anion microspheres.

[0104] Preferably, the functionalization method includes:

[0105] Polystyrene microspheres are dispersed in deionized water at a concentration of 0.1-0.5 g / mL (e.g., 0.1 g / mL, 0.2 g / mL, 0.3 g / mL, 0.4 g / mL, 0.5 g / mL or any range of the above values, preferably 0.1 g / mL). The mixture is then reacted with an epoxy compound (preferably epichlorohydrin or ethylene glycol diglycidyl ether) at 40-50°C (e.g., 40°C, 42°C, 45°C, 48°C, 50°C or any range of the above values) for 5-7 h (e.g., 5 h, 5.2 h, 5.5 h, 5.8 h, 6 h, 6.2 h, 6.5 h, 6.8 h, 7 h or any range of the above values). This causes a ring-opening esterification reaction between the carboxyl and epoxy groups, introducing hydroxyl groups and active halogen sites.

[0106] After the reaction is complete, an amine compound (preferably ethylenediamine or triethanolamine) is added, and the temperature is raised to 60-70℃ (e.g., 60℃, 62℃, 65℃, 68℃, 70℃ or any range between the above values) and reacted for 4-6 h (e.g., 4 h, 4.5 h, 5 h, 5.5 h, 6 h or any range between the above values) to achieve amination and quaternization.

[0107] d. The functional monomer is a hydroxyl-based functional monomer, such as hydroxyethyl acrylate (HEA) or N-hydroxymethylacrylamide (NMA). The functionalization method includes reacting a polystyrene microsphere dispersion with an epoxy compound and / or an amine compound to obtain grafted anionic microspheres.

[0108] Preferably, the functionalization method includes:

[0109] Polystyrene microspheres were dispersed in water to obtain a polystyrene microsphere dispersion.

[0110] An epoxy compound (preferably epichlorohydrin or ethylene glycol diglycidyl ether) is mixed with a polystyrene microsphere dispersion and reacted, where the hydroxyl groups and epoxy groups undergo a ring-opening reaction, introducing epoxy groups or active halogen sites.

[0111] After the reaction, an amine compound (preferably diethylenetriamine or 3-aminopropyltriethoxysilane) is added to react and achieve amino grafting and quaternization.

[0112] Alternatively, the functionalization method includes: first extending the chain with ethylene glycol diglycidyl ether, then reacting it with diethylenetriamine to construct a multilayer grafted anion exchange structure; after the reaction is completed, cooling, filtering, washing, and drying are performed to obtain grafted anion microspheres.

[0113] Preferably, the functionalization method includes:

[0114] Polystyrene microspheres are dispersed in deionized water at a concentration of 0.1-0.5 g / mL (e.g., 0.1 g / mL, 0.2 g / mL, 0.3 g / mL, 0.4 g / mL, 0.5 g / mL or any range of the above values, preferably 0.1 g / mL). The mixture is then reacted with an epoxy compound (preferably epichlorohydrin or ethylene glycol diglycidyl ether) at 50-60°C (e.g., 50°C, 52°C, 55°C, 58°C, 60°C or any range of the above values) for 4-6 h (e.g., 4 h, 4.2 h, 4.5 h, 4.8 h, 5 h, 5.2 h, 5.5 h, 5.8 h, 6 h or any range of the above values). The hydroxyl groups undergo a ring-opening reaction with the epoxy groups, introducing epoxy groups or active halogen sites.

[0115] After the reaction is complete, an amine compound (preferably diethylenetriamine or 3-aminopropyltriethoxysilane) is added, and the reaction continues for 5-7 h (e.g., 5 h, 5.5 h, 6 h, 6.5 h, 7 h or any range between the above values) to achieve amino grafting and quaternization.

[0116] e. The functional monomer is a tertiary amine / pyridyl functional monomer, such as dimethylaminoethyl methacrylate (DMAEMA) or 4-vinylpyridine (4-VP). The functionalization method includes reacting a polystyrene microsphere dispersion with an epoxy compound and / or an amine compound to obtain grafted anionic microspheres.

[0117] Preferably, the functionalization method includes:

[0118] Polystyrene microspheres and an acid-binding agent were dispersed in ethanol to obtain a polystyrene microsphere dispersion;

[0119] The epoxy compound (preferably brominated propylene oxide or epichlorohydrin) is mixed with a polystyrene microsphere dispersion and reacted. The tertiary amine or pyridinium group directly undergoes nucleophilic attack with the epoxy compound, achieving quaternization in one step and generating a strongly basic quaternary ammonium salt site.

[0120] After the reaction, an amine compound (preferably trimethylamine) is added to further quaternize the compound, thereby increasing the site density and stability.

[0121] Alternatively, the functionalization method includes: firstly, grafting and extending the chain with ethylene glycol diglycidyl ether, then reacting it with trimethylamine to construct a multilayer grafted anion exchange structure; after the reaction is completed, cooling, filtering, washing, and drying are performed to obtain grafted anion microspheres.

[0122] Preferably, the functionalization method includes:

[0123] Polystyrene microspheres are dispersed in anhydrous ethanol solvent at a concentration of 0.1-0.5 g / mL (e.g., 0.1 g / mL, 0.2 g / mL, 0.3 g / mL, 0.4 g / mL, 0.5 g / mL or any range between the above values, preferably 0.1 g / mL). Anhydrous sodium carbonate is added as an acid-binding agent, and the mixture is reacted with an epoxy compound (preferably brominated propylene oxide or epichlorohydrin) at 40-60°C (e.g., 4 h, 5 h, 6 h, 7 h, 8 h or any range between the above values) for 4-8 h (e.g., 4 h, 5 h, 6 h, 7 h, 8 h or any range between the above values). The tertiary amine or pyridinium group directly undergoes nucleophilic attack with the epoxy compound, realizing the quaternization reaction in one step and generating a strongly basic quaternary ammonium salt site.

[0124] Alternatively, the chain can be extended by grafting with ethylene glycol diglycidyl ether, followed by the addition of trimethylamine for further quaternization to improve site density and stability. After the reaction is complete, the mixture is cooled, filtered, washed until neutral, and dried to finally obtain grafted anionic microspheres.

[0125] The epoxy compound includes any one or a combination of at least two of epichlorohydrin, brominated epichlorohydrin, epichlorohydrin (ECH), ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene oxide, or ethylene oxide; and the amine compound is methylamine, dimethylamine, trimethylamine, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, ethylamine, diethylamine, triethylamine, ethanolamine, diethanolamine, triethanolamine, etc. N,N -Methyldiethanolamine, N,N - Any one or a combination of at least two of the following: dimethylethanolamine, 3-aminopropyltriethoxysilane, and 3-aminopropyltrimethoxysilane.

[0126] Fourthly, the present invention provides an application of the preparation method described in the first aspect, the polystyrene microspheres described in the second aspect, or the functionalization method described in the third aspect in ultra-high performance ion chromatography.

[0127] Compared with the prior art, the present invention has the following beneficial effects:

[0128] (1) Solving the contradiction between mechanical strength and mass transfer efficiency: The preparation method provided by this invention introduces an innovative means of controlling the seed molecular weight by introducing a molecular weight regulator to precisely design the cross-linking network and pore structure of the final polystyrene microspheres. This allows the prepared microspheres to have a high degree of cross-linking (≥30% cross-linking monomer) to ensure ultra-high mechanical strength (withstanding the high pressure of the UPIC system), while also forming a controllable multi-level pore structure that is conducive to rapid mass transfer. This avoids the problem of pore blockage caused by excessive cross-linking, thus solving the contradiction between particle size, strength and mass transfer in one fell swoop.

[0129] (2) Overcoming the defects of the functional layer in the post-modification method and realizing the integration of functionalization and matrix synthesis: The preparation method provided by the present invention directly involves functional monomers (such as epoxy-containing GMA, AGE, etc.) in copolymerization, so that the active functional groups are uniformly and firmly bonded in the entire polymer skeleton (including the interior and surface) during the formation of polystyrene microspheres, overcoming the defects of uneven functional layer and weak bonding force in the post-modification method, and providing an ideal matrix platform for the preparation of various derivatized stationary phases with high capacity and high stability;

[0130] (3) Provides a key filler matrix suitable for UPIC: The polystyrene microspheres prepared by the method provided in this invention have uniform particle size (2 μm level), excellent monodispersity, and regular morphology. Their comprehensive performance can directly meet the comprehensive requirements of UPIC fillers for particle size, pressure resistance, chemical stability and functionalizability.

[0131] (4) Expanding application scenarios: The polystyrene microspheres obtained by the preparation method provided by this invention can be used to generate a variety of stationary phases (such as ion exchange, hydrophobic, hydrophilic, and affinity stationary phases) through different functionalizations. They are not only used exclusively for UPIC, but also applicable to various separation and analysis scenarios such as conventional high-performance liquid chromatography and ion chromatography, realizing multiple uses of one method. Attached Figure Description

[0132] Figure 1 Scanning electron microscope image of functionalized polystyrene microspheres obtained by functionalizing the polystyrene microspheres provided in Example 1;

[0133] Figure 2 Infrared spectrum of functionalized polystyrene microspheres obtained by functionalizing the polystyrene microspheres provided in Example 1;

[0134] Figure 3 The functionalized polystyrene microspheres obtained by functionalizing the polystyrene microspheres provided in Example 1 are used for anion separation. Detailed Implementation

[0135] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0136] In this invention, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0137] In this invention, "at least one" refers to one or more items, and "more than one" refers to two or more items. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of a single item or multiple items. For example, "at least one of a, b, or c," or "at least one of a, b, and c," can both represent: a, b, a+b, a+c, b+c, or a+b+c, where a, b, and c can be single or multiple. It should be understood that in the various embodiments of this application, the sequence number of the above processes does not imply the order of execution. Some or all steps can be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this invention.

[0138] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0139] The weights of the relevant components mentioned in the embodiments of this invention can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this invention is within the scope disclosed in the embodiments of this invention. Specifically, the mass described in the embodiments of this invention can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0140] The terms "first" and "second" are used for descriptive purposes only, to distinguish objects, such as substances, from one another, and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. For example, without departing from the scope of the embodiments of this application, "first XX" may also be referred to as "second XX," and similarly, "second XX" may also be referred to as "first XX." Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0141] The term "St" is an abbreviation for "Styrene," meaning styrene.

[0142] The term "DVB" is an abbreviation for "Divinylbenzene," which stands for divinylbenzene.

[0143] The term "SDS" is an abbreviation for "Sodium Lauryl Sulfate," which stands for sodium lauryl sulfate.

[0144] The term "BPO" is an abbreviation for "Dibenzoyl peroxide," which stands for benzoyl peroxide.

[0145] The term "HEC" is an abbreviation for "Hydroxyethyl cellulose," which stands for hydroxyethyl cellulose.

[0146] The term "UPIC" is an abbreviation for "Ultra Performance Ion Chromatography," which refers to ultra-high performance ion chromatography.

[0147] Unless otherwise specified, the raw materials involved in the following specific embodiments of the present invention are all conventional materials in the art and can be purchased from commercially available products.

[0148] Example 1

[0149] This embodiment provides a polystyrene microsphere and its preparation method, as follows:

[0150] (1) Preparation of monodisperse polystyrene seeds

[0151] In a 500 mL four-necked polymerization reactor purged with nitrogen, 90 mL of anhydrous ethanol, 10 g of styrene, 0.9 g of polyvinylpyrrolidone (PVP K22-K27, purchased from Anaiji, amounting to 9.0% of the mass of styrene) and 0.05 g of n-dodecyl mercaptan (molecular weight regulator, amounting to 0.5% of the mass of styrene) were added sequentially.

[0152] Under a stable nitrogen atmosphere and with stirring at 250 r / min, 0.2 g of azobisisobutyronitrile (AIBN, amounting to 2.0% of the mass of styrene) was added, and the reactor was placed in an oil bath at 70℃ for polymerization reaction for 22 h.

[0153] After the reaction was completed, the product was cooled to room temperature and centrifuged at 10,000 r / min for 15 min. The precipitate was washed three times with anhydrous ethanol and dried under vacuum at 45℃ for 10 hours to obtain monodisperse polystyrene seeds with an average particle size of 0.9 μm, a number average molecular weight of 90,000 Da, and a molecular weight distribution of 2.8.

[0154] (2) Preparation of polystyrene microspheres

[0155] Seed swelling and activation: 1.0 g of monodisperse polystyrene seeds were dispersed in 100 mL of 0.25% (w / v) sodium dodecyl sulfate (SDS) aqueous solution and magnetically stirred for 20 min. 0.5 g of chlorododecane was added as a swelling agent, and the mixture was ultrasonically emulsified in an ultrasonic cleaner (power 200 W) for 30 min. Subsequently, the system was transferred to a three-necked flask and activated and swollen for 6 h under stirring conditions of 35 °C and 120 r / min to obtain the seed dispersion.

[0156] Pre-emulsification: 6.0 g divinylbenzene (DVB, purity 80%, addition amount calculated based on the amount of DVB), 3.0 g glycidyl methacrylate (GMA) and 0.2 g benzoyl peroxide (BPO) were mixed evenly. The mixed oil phase was added to 50 mL of 0.25% SDS aqueous solution and emulsified at 10000 r / min for 20 min using a homogenizer to form a homogeneous monomer emulsion. The homogeneous monomer emulsion was slowly added to the seed dispersion and stirred at 30℃ and 120 r / min for a second swelling for 10 h to obtain a pre-emulsified solution.

[0157] Polymerization: 15 mL of 2% (w / v) hydroxyethyl cellulose (HEC) aqueous solution was added to the pre-emulsified solution as a stabilizer. The mixture was stirred for 15 min, and after purging with nitrogen for 20 min to remove oxygen, the temperature was increased to 75℃ at a rate of 2.5℃ / min. The stirring speed was increased to 300 r / min, and the polymerization reaction was carried out for 22 h.

[0158] Post-processing: After the reaction was completed, the product was cooled, collected by vacuum filtration, washed three times with deionized water and ethanol, and then placed in a Soxhlet extractor for extraction with acetone for 24 h. Finally, the product was washed once with ethanol and dried in a vacuum drying oven at 40 °C for 12 h to obtain the polystyrene microspheres.

[0159] Example 2

[0160] This embodiment provides a polystyrene microsphere and its preparation method.

[0161] The difference from Example 1 is that in this example, in the pre-emulsification of step (2), toluene, a pore-forming agent, is added, with a mass of 0.1 times the total mass of the seeds, glycidyl methacrylate and divinylbenzene.

[0162] Example 3

[0163] This embodiment provides a polystyrene microsphere and its preparation method.

[0164] The difference from Example 2 is that in this example, the molecular weight regulator in step (1) is replaced with tert-dodecyl mercaptan, and the resulting monodisperse polystyrene seeds have an average particle size of 0.9 μm, a number-average molecular weight of 80104 Da, and a molecular weight distribution of 2.2.

[0165] Example 4

[0166] This embodiment provides a polystyrene microsphere and its preparation method.

[0167] The difference from Example 3 is that in this example, the amount of molecular weight regulator added in step (1) is 0.2g, which is 2% of the mass of styrene monomer. The average particle size of the monodisperse polystyrene seeds is 0.9 μm, the number average molecular weight is 57854 Da, and the molecular weight distribution is 2.5.

[0168] Example 5

[0169] This embodiment provides a polystyrene microsphere and its preparation method.

[0170] The difference from Example 4 is that in this example, the styrene polymer monomer in step (1) is replaced with the same mass of vinyl ethylbenzene, and the resulting monodisperse polystyrene seeds have an average particle size of 1.1 μm, a number average molecular weight of 70564 Da, and a molecular weight distribution of 2.6.

[0171] Example 6

[0172] This embodiment provides a polystyrene microsphere and its preparation method.

[0173] The difference from Example 4 is that in this example, the functional monomer GMA in step (2) is replaced with an equal mass of glycidyl acrylate (GA).

[0174] Example 7

[0175] This embodiment provides a polystyrene microsphere and its preparation method.

[0176] The difference from Example 4 is that in this example, the swelling agent chlorododecane in step (2) is replaced with dibutyl phthalate.

[0177] Example 8

[0178] This embodiment provides a polystyrene microsphere and its preparation method.

[0179] The difference from Example 4 is that in this example, the mass ratio of swelling agent to seed in step (2) is 2.5:1.

[0180] Example 9

[0181] This embodiment provides a polystyrene microsphere and its preparation method.

[0182] The difference from Example 4 is that in this example, the amount of DVB added in step (2) is 5 g, and the amount of GMA added is 4 g.

[0183] Example 10

[0184] This embodiment provides a polystyrene microsphere and its preparation method.

[0185] The difference from Example 4 is that in this example, the amount of seed added in step (2) is 2 g, the amount of DVB added is 6 g, and the amount of GMA added is 1 g.

[0186] Example 11

[0187] This embodiment provides a polystyrene microsphere and its preparation method.

[0188] The difference from Example 4 is that in this example, the mass of the pore-forming agent is 0.8 times the total mass of the seeds, glycidyl methacrylate, and divinylbenzene.

[0189] Example 12

[0190] This embodiment provides a polystyrene microsphere and its preparation method, as follows:

[0191] (1) Preparation of monodisperse polystyrene seeds

[0192] Add 90 mL of anhydrous ethanol, 10 g of styrene, 0.6 g of polyvinylpyrrolidone (PVP K22-K27, amounting to 6% of the mass of styrene) and 0.20 g of tert-dodecyl mercaptan (molecular weight regulator, amounting to 2% of the mass of styrene) sequentially to a 500 mL four-necked polymerization reactor purged with nitrogen.

[0193] Under a stable nitrogen atmosphere and with stirring at 200 r / min, 0.32 g of azobisisobutyronitrile (AIBN, amounting to 3.2% of the mass of styrene) was added, and the reactor was placed in an oil bath at 75℃ for polymerization reaction for 20 h.

[0194] After the reaction was completed, the product was cooled to room temperature and centrifuged at 10,000 r / min for 15 min. The precipitate was washed twice with anhydrous ethanol and dried under vacuum at 50 °C for 8 hours to obtain monodisperse polystyrene seeds with an average particle size of 1.0 μm, a number average molecular weight of 30,694 Da, and a molecular weight distribution of 2.4.

[0195] (2) Preparation of polystyrene microspheres

[0196] Seed swelling and activation: 1.0 g of monodisperse polystyrene seeds were dispersed in 100 mL of 0.2% (w / v) sodium dodecyl sulfate (SDS) aqueous solution and magnetically stirred for 20 min. 2.5 g of liquid paraffin was added as a swelling agent, and the mixture was ultrasonically emulsified in an ultrasonic cleaner (300 W) for 20 min. Subsequently, the system was transferred to a three-necked flask and activated and swollen for 5 h under stirring conditions of 40 °C and 100 r / min to obtain the seed dispersion.

[0197] Pre-emulsification: 7.0 g divinylbenzene (DVB, 80% purity), 3.0 g glycidyl acrylate (GA), 2.0 g toluene (porogen) and 0.11 g benzoyl peroxide (BPO) were mixed evenly. The mixed oil phase was added to 100 mL of 0.3% SDS aqueous solution and emulsified at 10000 r / min for 10 min using a homogenizer to form a homogeneous monomer emulsion. The homogeneous monomer emulsion was slowly added to the seed dispersion and stirred at 25°C and 100 r / min for a second swelling for 12 h to obtain a pre-emulsified solution.

[0198] Polymerization: Add 50 mL of 2% (w / v) hydroxyethyl cellulose (HEC) aqueous solution as a stabilizer to the above pre-emulsified solution, stir for 15 min, purge with nitrogen for 10 min to remove oxygen, then raise the temperature to 65℃ at 3℃ / min, increase the stirring speed to 500 r / min, and polymerize for 24 h.

[0199] Post-processing: After the reaction was completed, the product was cooled, filtered to collect the solid product, washed three times with deionized water and ethanol in sequence, placed in a Soxhlet extractor and extracted with acetone for 24 h to completely remove the pore-forming agent, and finally washed once with ethanol and dried in a vacuum drying oven at 60 °C for 12 h to obtain the polystyrene microspheres.

[0200] Example 13

[0201] This embodiment provides a polystyrene microsphere and its preparation method, as follows:

[0202] (1) Preparation of monodisperse polystyrene seeds

[0203] To a 500 mL four-necked polymerization reactor purged with nitrogen, add sequentially 90 mL of a mixture of anhydrous ethanol and deionized water (volume ratio 95:5), 10 g of styrene, 1 g of PVP (PVP K22-K27, purchased from Anaiji, amounting to 10.0% of the styrene mass), and 0.05 g of tert-dodecyl mercaptan (molecular weight regulator, amounting to 0.5% of the styrene mass).

[0204] Under a stable nitrogen atmosphere and with stirring at 300 r / min, 0.08 g of azobisisobutyronitrile (AIBN, amounting to 0.8% of the mass of styrene) was added, and the reactor was placed in an oil bath at 65℃ for polymerization reaction for 24 h.

[0205] After the reaction was completed, the product was cooled to room temperature and centrifuged at 8000 r / min for 20 min. The precipitate was washed three times with anhydrous ethanol and dried under vacuum at 40℃ for 12 hours to obtain monodisperse polystyrene seeds with an average particle size of 0.9 μm, a number average molecular weight of 87460 Da, and a molecular weight distribution of 2.8.

[0206] (2) Preparation of polystyrene microspheres

[0207] Seed swelling and activation: 1.0 g of monodisperse polystyrene seeds were dispersed in 20 mL of 0.3% (w / v) sodium dodecyl sulfate (SDS) aqueous solution and magnetically stirred for 15 min. 0.5 g of chlorododecane was added as a swelling agent. The mixture was ultrasonically emulsified in an ultrasonic cleaner (100 W power) for 40 min. Subsequently, the system was transferred to a three-necked flask and activated and swollen for 10 h under stirring conditions of 25 °C and 150 r / min to obtain the seed dispersion.

[0208] Pre-emulsification: 6.0 g divinylbenzene (DVB, 80% purity), 2.0 g glycidyl methacrylate (GMA), 2.0 g chlorobenzene (porogen) and 0.5 g benzoyl peroxide (BPO) were mixed evenly. The mixed oil phase was added to 80 mL of 0.2% SDS aqueous solution and emulsified at 8000 r / min for 40 min using a homogenizer to form a homogeneous monomer emulsion. The homogeneous monomer emulsion was slowly added to the seed dispersion and stirred at 40℃ and 150 r / min for a second swelling for 8 h to obtain a pre-emulsified solution.

[0209] Polymerization: 15 mL of 2% (w / v) hydroxyethyl cellulose (HEC) aqueous solution was added to the pre-emulsified solution as a stabilizer. The mixture was stirred for 10 min, and after purging with nitrogen for 30 min to remove oxygen, the temperature was increased to 80℃ at a rate of 2℃ / min. The stirring speed was increased to 200 r / min, and the polymerization reaction was carried out for 20 h.

[0210] Post-processing: After the reaction was completed, the product was cooled, filtered to collect the solid product, washed three times with deionized water and ethanol in sequence, placed in a Soxhlet extractor, and extracted with acetone for 8 h to completely remove the pore-forming agent. Finally, the product was washed once with ethanol and dried in a vacuum drying oven at 40 °C for 24 h to obtain the polystyrene microspheres.

[0211] Comparative Example 1

[0212] This comparative example provides a polystyrene microsphere and its preparation method.

[0213] The difference from Example 4 is that in this comparative example, the mass ratio of swelling agent to seed in step (2) is 3:1.

[0214] Comparative Example 2

[0215] This comparative example provides a polystyrene microsphere and its preparation method.

[0216] The difference from Example 4 is that in this comparative example, the mass ratio of swelling agent to seed in step (2) is 0.3:1.

[0217] Comparative Example 3

[0218] This comparative example provides a polystyrene microsphere and its preparation method.

[0219] The difference from Example 4 is that in this comparative example, the amount of DVB added in step (2) is 4 g and the amount of GMA added is 5 g.

[0220] Comparative Example 4

[0221] This comparative example provides a polystyrene microsphere and its preparation method.

[0222] The difference from Example 4 is that in this comparative example, the amount of DVB added in step (2) is 8.5 g and the amount of GMA added is 0.5 g.

[0223] Comparative Example 5

[0224] This comparative example provides a polystyrene microsphere and its preparation method.

[0225] The difference from Example 4 is that, in this comparative example, the mass of the pore-forming agent is twice the total mass of the seeds, divinylbenzene, and glycidyl methacrylate.

[0226] Comparative Example 6

[0227] This comparative example provides a polystyrene microsphere and its preparation method.

[0228] The difference from Example 1 is that in this comparative example, no molecular weight regulator is added in step (1).

[0229] Comparative Example 7

[0230] This comparative example provides a polystyrene microsphere and its preparation method.

[0231] The difference from Example 1 is that in this comparative example, no functional monomer is introduced in step (2).

[0232] After functionalization, the polystyrene microspheres provided in Comparative Example 7 were found to be essentially unable to undergo graft polymerization modification, and grafted anion exchange microspheres could not be obtained. Therefore, performance testing was not conducted on this comparative example.

[0233] Application examples

[0234] This application example provides a method for functionalizing polystyrene microspheres, as follows:

[0235] 3 g of polystyrene microspheres provided in the examples or comparative examples were dispersed in 30 mL of deionized water, heated to 60°C, and 20 mL of 4% methylamine aqueous solution was added and reacted for 30 min. After the reaction was completed, the mixture was filtered and washed with deionized water. Then, following the same steps, 20 mL of 10% epichlorohydrin aqueous solution (already ultrasonically dispersed) was added and reacted for 30 min. After the reaction was completed, the mixture was filtered and washed. Alternating between these two steps is called a grafting reaction. The final product was dried to obtain grafted anion exchange microspheres.

[0236] Performance testing

[0237] The performance of the monodisperse polystyrene seeds and polystyrene microspheres provided in the examples and comparative examples was tested using the following methods:

[0238] (1) Average particle size, number-average molecular weight, and molecular weight distribution of monodisperse polystyrene seeds:

[0239] The surface morphology of the microspheres was observed using a scanning electron microscope (JSM-IT800). After the samples were sputter-coated with gold, the accelerating voltage was 5-15 kV. The diameter of at least 100 microspheres was randomly measured using image analysis software, and their average particle size was calculated.

[0240] The molecular weight and molecular weight distribution were determined by gel permeation chromatography (GPC, Waters-201) with tetrahydrofuran as the mobile phase, a flow rate of 1.0 mL / min, and a column temperature of 30 °C. Polystyrene was used as the standard for calibration.

[0241] (2) Average particle size and coefficient of variation of polystyrene microspheres:

[0242] The surface morphology of the microspheres was observed using a scanning electron microscope (JSM-IT800). After the samples were sputter-coated with gold, the accelerating voltage was 5-15 kV. The diameter of at least 100 microspheres was randomly measured using image analysis software, and their average particle size and particle size variation coefficient were calculated.

[0243] The polystyrene microspheres provided in the examples and comparative examples were functionalized according to the application examples, and the performance of the resulting grafted anionic microspheres was tested as follows:

[0244] (3) Functional group verification: Fourier transform infrared spectroscopy (Bruker VERTEX 70V) was used for determination. The sample was mixed with potassium bromide and pressed into a pellet. The scanning range was 400-4000 cm⁻¹. -1 Verify the characteristic absorption peaks of epoxy groups, ion exchange groups, etc.

[0245] (4) High pressure resistance stability: The microspheres were packed into a 100 mm × 2 mm chromatographic column using the slurry packing method. Deionized water was used as the mobile phase. A high pressure resistance test was performed using a high-pressure pump. A high-performance liquid pump was connected, and deionized water was used as the mobile phase. The flow rate of the mobile phase was gradually increased, and the column pressure change was recorded. The column was run continuously for one week at the target operating pressure. During the operation, the column pressure stability and whether the column bed collapsed were monitored. If the column pressure was stable and the column bed did not collapse, the surface morphology of the microspheres was observed by SEM after the operation. At least 100 microspheres were randomly selected to observe whether the microspheres were broken. The maximum test pressure that the microspheres could withstand (i.e., the microspheres did not break after the test) was recorded as the high pressure resistance stability test result.

[0246] (5) Separation performance and column efficiency test: The packed column was washed with K2CO3 solution at a flow rate of 0.5 mL / min for at least 12 h, and then installed in an ion chromatography system equipped with a conductivity detector for column efficiency test; Chromatographic test conditions: the eluent was a mixture of 4.0 mmol / L K2CO3 + 4.5 mmol / L KHCO3, the flow rate was 1.0 mL / min, the injection volume was 30 μL, the suppressor current was 17 mA, and the column temperature was 30 °C; the column containing F was injected. - Cl - NO2 - ,Br - NO3 - SO4 2- PO4 2- Mixed standard solutions were used to record chromatograms and calculate theoretical plate numbers to evaluate the separation performance and column efficiency of the chromatographic column.

[0247] The evaluation criteria are as follows:

[0248] Excellent: All 7 anions achieved complete baseline separation within 3 minutes, with symmetrical peak shapes;

[0249] Good: All 7 anions achieved complete baseline separation within 3 minutes or more, with excellent peak shape;

[0250] Generally: All 7 anions achieve complete baseline separation within 3 minutes or more, but the peak shape has a large tail.

[0251] Poor: Complete baseline separation was not achieved for the seven anions;

[0252] (6) Column exchange capacity: The breakthrough curve method was used for determination. The column was first washed with 50 mmol / L NaCl aqueous solution at a flow rate of 0.5 mL / min for 4 h, then washed with deionized water at a flow rate of 0.5 mL / min for 2 h, and finally washed with 5 mmol / L NaNO3 aqueous solution. The effluent was monitored by a UV detector at a wavelength of 210 nm. The column was washed at a flow rate of 1 mL / min until breakthrough. The ion exchange capacity Q (μmol / column) was calculated using the following formula:

[0253] ;

[0254] in:

[0255] C represents the concentration of NaNO3 (mmol / L).

[0256] F is the flow rate of the NaNO3 solution (mL / min).

[0257] t b Breakthrough time (min);

[0258] t0 is the dead time (min).

[0259] The test results are as follows:

[0260] Figure 1 Scanning electron microscope (SEM) image of functionalized polystyrene microspheres obtained after functionalizing the polystyrene microspheres provided in Example 1. Figure 1 It can be seen that the polystyrene microspheres and functional polystyrene microspheres provided by the present invention have high particle size uniformity and good monodispersity.

[0261] Figure 2 The infrared spectrum of functionalized polystyrene microspheres obtained by functionalizing the polystyrene microspheres provided in Example 1 is shown below. Figure 2 It can be seen that after quaternization modification, the infrared spectrum of the polymer microspheres is at 3450 cm⁻¹. -1 A broad absorption peak appears at 1050-1300 cm⁻¹, which is a characteristic peak of the stretching vibration of OH or NH bonds. This indicates that the absorption peaks are due to the superposition of hydroxyl groups generated after the ring-opening reaction of epoxy groups during the microsphere modification process and the residual amine groups from the quaternization process. This also shows that the polymer microspheres contain abundant hydroxyl groups on their surface, which is an important factor in their good hydrophilicity; meanwhile, at 1050-1300 cm⁻¹... -1 There are two absorption peaks, which are the result of the superposition of the stretching vibrations of CN and CO bonds. This can be attributed to the nitrogen-containing branched layer structure generated by the reaction of epichlorohydrin and methylamine. Based on the above infrared spectral characterization results, it can be concluded that the microspheres prepared by the method of this invention have been successfully grafted with quaternary ammonium groups.

[0262] Figure 3 The image shows the effect of functionalized polystyrene microspheres obtained by functionalizing the polystyrene microspheres provided in Example 1 on anion separation. Figure 3 It is known that the functional polystyrene microspheres provided by the present invention can achieve complete baseline separation of seven common anions within 3 minutes, and the peaks are symmetrical.

[0263] The specific test results are shown in Table 1:

[0264] Table 1

[0265]

[0266] As can be seen from the examples and performance tests, the polystyrene microspheres provided by the present invention have a uniform particle size of 2.0±0.2 μm, excellent monodispersity, and regular morphology. At the same time, the comprehensive performance of the grafted anionic microspheres obtained by functionalizing polystyrene microspheres can directly meet the comprehensive requirements of UPIC fillers for particle size, pressure resistance, and chemical stability.

[0267] The present invention has been illustrated through the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing polystyrene microspheres for UPIC, characterized in that, The polystyrene microspheres have a particle size of 2.0 ± 0.2 μm and a particle size variation coefficient ≤ 2.9%. The preparation method includes: S1. Styrene monomers are polymerized in a reaction system containing a dispersant and a molecular weight regulator to obtain monodisperse polystyrene seeds with a particle size of 0.9-1.1 μm and a molecular weight of 30,000-90,000 Da. The mass of the molecular weight regulator is 0.4-2.2% of the mass of the styrene monomers, and the mass of the dispersant is 6-9% of the mass of the styrene monomers. S2. Monodisperse polystyrene seeds are swollen and activated in a first aqueous solution containing a swelling agent to obtain a seed dispersion. In the seed dispersion, the concentration of monodisperse polystyrene seeds is 0.01-0.06 g / mL, and the mass ratio of the swelling agent to the monodisperse polystyrene seeds is (0.5-2.5):

1. The swelling agent is dodecyl chloride. S3. A monomer mixture is obtained by mixing crosslinking monomer, functional monomer, porogen, and second initiator. The monomer mixture is emulsified with a second aqueous solution to obtain a monomer dispersion. The monomer dispersion is mixed with a seed dispersion and subjected to secondary swelling to obtain a reaction oil phase. Based on the total mass of the monodisperse polystyrene seed, crosslinking monomer, and functional monomer as 100%, the content of the monodisperse polystyrene seed is 5-15%, the content of the functional monomer is 10-40%, the content of the crosslinking monomer is ≥55%, and the ratio of the mass of the porogen to the total mass of the monodisperse polystyrene seed, crosslinking monomer, and functional monomer is (0.1-0.8):

1. The functional monomer is selected from any one or a combination of at least two of allyl glycidyl ether, glycidyl methacrylate, or glycidyl acrylate. S4. The reaction oil phase and the aqueous phase containing the stabilizer are mixed at a volume ratio of 1:(0.1-1) and crosslinked polymerization is carried out at 65-80℃ for 20-24 h to obtain the product dispersion; S5. Separate the product and react it alternately with amine compounds and epoxy compounds to obtain the polystyrene microspheres; The amine compound is selected from any one or a combination of at least two of methylamine, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, ethylamine, or ethanolamine; The epoxy compound is selected from any one or a combination of at least two of epichlorohydrin, brominated epichlorohydrin, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, and 1,4-butanediol diglycidyl ether.

2. The preparation method according to claim 1, characterized in that, In step S1, the molecular weight regulator is selected from any one or a combination of at least two of n-dodecyl mercaptan, tert-dodecyl mercaptan, α-methylstyrene dimer, n-butanethiol or isopropanethiol; And / or, the styrene monomers are selected from styrene and / or vinylethylbenzene; And / or, the volume of the styrene monomer is 8-35% of the total volume of the reaction system.

3. The preparation method according to claim 1, characterized in that, Step S1 is as follows: styrene monomers, dispersants, and molecular weight regulators are mixed in a solvent and polymerized at 65-75°C for 20-24 h under the initiation of an initiator. After the reaction is completed, the mixture is centrifuged, washed, and dried to obtain the monodisperse polystyrene seeds. The solvent is selected from anhydrous ethanol or a mixture of anhydrous ethanol and deionized water.

4. The preparation method according to claim 1, characterized in that, Step S2 is as follows: Monodisperse polystyrene seeds are dispersed in a first aqueous solution, a swelling agent is added and ultrasonically emulsified for 20-40 min, and finally swollen at 25-40℃ for 5-10 h to obtain the seed dispersion.

5. The preparation method according to claim 1, characterized in that, In step S3, the crosslinking monomer is selected from divinylbenzene; And / or, the pore-forming agent is selected from any one or a combination of at least two of toluene, chlorobenzene, ethylbenzene, anisole, phenyl acetate, n-heptane, cyclohexanol, n-hexane, isooctane or tert-butanol; And / or, the secondary swelling temperature is 25-40℃, and the time is 8-12 h.

6. The preparation method according to claim 1, characterized in that, Step S5 further includes removing the porogen, wherein the method for removing the porogen is an extraction method.

7. A polystyrene microsphere prepared by any one of claims 1-6, wherein the particle size variation coefficient of the polystyrene microsphere is ≤2.9%.

8. The preparation method according to any one of claims 1-6 or the application of the polystyrene microspheres according to claim 7 in ultra-high performance ion chromatography.

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