A gradient-doped block copolymer functionalized polystyrene composite microsphere and a microflow control preparation method thereof

Abstract

The application discloses a gradient-doped block copolymer functionalized polystyrene composite microsphere and a microflow control preparation method thereof, and belongs to the field of polymer materials and microflow control technology. The gradient-doped block copolymer and polystyrene composite microsphere is prepared by using a microflow control buoyancy desolventization method. The blended polymer is dissolved in a solvent to form a dispersed phase, a salt solution is used as a continuous phase, the shearing emulsification is carried out through a T-shaped microflow control chip, the buoyancy desolventization solidification is carried out in a gradient salt column, and the composite microsphere with uniform particle size, stable functional groups and controllable bromine content is obtained. Through the gradient-doping design, the rigidity, elasticity and functional stability of the microsphere are considered, the problems of wide particle size distribution, complex functionalization steps and easy collapse of the high block copolymer doping in the traditional polymerization method are solved, a green, simple and scalable technical route is provided for the large-scale application in the field of waste acid adsorption, and the problems of complex preparation process, low functionalization degree and high price of the functionalized polystyrene microsphere are solved, which is beneficial to the subsequent popularization and application of the functionalized polystyrene composite microsphere.

Description

Technical Field

[0001] This invention belongs to the field of microfluidics and polymer materials technology, and relates to a copolymer-polystyrene functionalized composite microsphere and its preparation method, specifically to a gradient-doped block copolymer functionalized polystyrene composite microsphere and its microfluidic preparation method. Background Technology

[0002] Polystyrene microspheres possess advantages such as being non-toxic and odorless, inexpensive, chemically stable, and having high mechanical strength, and can be functionalized. They have wide applications in hydrometallurgy, food processing, biological detection, drug delivery, plant extraction, water treatment, analytical chemistry, chromatographic separation, and water and waste gas treatment. To adapt to different application areas, functionalization of polystyrene microspheres is a crucial prerequisite for their various applications. Therefore, researchers typically utilize the reactivity of the benzene ring in polystyrene microspheres to introduce functional groups such as chlorination, amination, carboxylation, sulfonation, and nitration onto the aromatic ring through substitution reactions, thereby endowing the microspheres with new functions such as adsorption and catalysis, and preparing solid-phase carriers with different applications.

[0003] Currently, functionalized polystyrene microspheres are typically prepared using two methods: chemical bonding and physical adsorption. Chemical bonding involves bonding functional groups, such as benzyl chloride or hexanoyl chloride (bromine), to the surface of polystyrene microspheres, making them active functional groups. Chinese invention patent (CN 115722159 A) discloses an adsorbent for treating hexavalent molybdenum in alkaline wastewater. This method first reacts tetramethylethylenediamine with bromoalkane to generate a monoquaternary ammonium salt intermediate, and then chemically bonds cross-linked polystyrene microspheres to the monoquaternary ammonium salt intermediate in a one-step reaction to obtain a bisquaternary ammonium salt chloride microsphere adsorbent. However, its functionalization process is complex and requires large amounts of organic solvents, which is detrimental to the green mass production and environmental protection of functionalized polystyrene microspheres. Physical adsorption involves directly adsorbing a layer of hydrophilic polymer onto the surface of the microspheres, and then cross-linking the adsorbent layer with a cross-linking agent to increase its stability. However, these physical coating methods all suffer from the problem of requiring a final cross-linking fixation of the adsorbent layer and the tendency for the adsorbent layer to detach.

[0004] In summary, there is an urgent need to find a simple, compatible, and stable method for preparing functionalized polystyrene composite microspheres. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned shortcomings of existing technologies by providing a microfluidic preparation method for functionalized polystyrene composite microspheres, thus solving the problems of complex preparation processes and poor compatibility of functionalized polystyrene microspheres. This invention, through gradient doping design, balances the rigidity, elasticity, and functionalization stability of the microspheres, solving the problems of wide particle size distribution, complex functionalization steps, and easy collapse of high-block copolymers in traditional polymerization methods. It provides a green, simple, and scalable technical route for large-scale applications in fields such as waste acid adsorption. Solving the problems of complex preparation processes, low functionalization levels, and high costs of functionalized polystyrene microspheres is beneficial for the subsequent promotion and application of functionalized polystyrene composite microspheres.

[0006] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows: A microfluidic preparation method for gradient-doped block copolymer functionalized polystyrene composite microspheres includes the following steps: Step 1: At room temperature, block copolymers and polystyrene in different proportions are dissolved in a solvent to prepare polymer solutions, and stirred until completely dissolved; at the same time, salt solutions are prepared as the dispersed phase and the desolventizing solution, respectively, wherein the salt solution as the dispersed phase has a high concentration and the salt solution as the desolventizing solution has a low concentration.

[0007] Furthermore, in the polymer solution, the mass ratio of the block copolymer to polystyrene is 1:5 to 5:1, the total solid content of the polymer solution is 1–5 wt%, and the solvent is one of tetrahydrofuran, 2-methyltetrahydrofuran, or γ-valerolactone; the mass ratio of the block copolymer to polystyrene is preferably 1:1, the total solid content of the polymer solution is preferably 3 wt%, and the solvent is preferably tetrahydrofuran.

[0008] Furthermore, the salt solution as the dispersed phase is one of NaCl, KCl, or MgCl2, with a concentration of 20-25 wt%. The salt solution is preferably a NaCl solution.

[0009] Furthermore, the salt solution used as the desolvent is one of NaCl, KCl, or MgCl2, with a concentration of 4-6 wt%.

[0010] Furthermore, the polymer in the polymer solution is one or more of polystyrene-butadiene-styrene copolymer, derivatives of polystyrene-butadiene-styrene copolymer (e.g., CMSBS), polystyrene-isoprene-styrene copolymer, derivatives of polystyrene-isoprene-styrene copolymer, and polystyrene-methyl acrylate copolymer, with CMSBS being the preferred polymer.

[0011] Step 2: Assemble the microfluidic device; The microfluidic device includes a first injection pump P1, a second injection pump P2, and a T-shaped microfluidic chip. Each injection pump is equipped with a syringe and a first control valve V1 and a second control valve V2, respectively. The first injection pump P1 is used to deliver polymer solutions, and the second injection pump P2 is used to deliver high-concentration saline solutions.

[0012] The T-shaped microfluidic chip includes a polymer solution delivery pipeline, a high-concentration saline solution delivery pipeline, and a segmented solution delivery pipeline, i.e., two inlets and one outlet. The two inlets are respectively connected to a first injection pump P1 and a second injection pump P2 via polytetrafluoroethylene (PTFE) tubing, and the outlet is connected to a desolvation glass column 1, with a rubber stopper 2 at the connection point. The desolvation glass column 1 is injected with a saline solution for desolvation.

[0013] Furthermore, the T-shaped microfluidic chip and polytetrafluoroethylene tubing are hydrophilically treated, and their internal surfaces are pretreated with a 0.1 M H2SO4 solution containing 1% KMnO4.

[0014] Step 3: The polymer solution and saline solution are loaded into syringes, serving as the dispersed and continuous phases respectively, and then installed on the first and second injection pumps. The injection pumps are connected to the desolvated glass column 1 containing the desolvated solvent through the microfluidic chip channel of the microfluidic device. Inside the T-shaped microfluidic chip, the polymer solution flow delivered by the first injection pump P1 is segmented and sheared by the saline solution flow delivered by the second injection pump P2, forming polymer solution droplets. The microfluidic chip outlet is connected to delivery line c, used to deliver the mixed flow of the generated polymer solution droplets and the high-concentration saline solution to the desolvated glass column 1. The flow rate of the injection pumps is adjusted to begin droplet formation; the flow rates of the two injection pumps are adjusted to obtain stable and uniformly sized droplets within the glass column.

[0015] Furthermore, the microfluidic chip channel size is 100-200µm; the continuous phase is a 20-25wt% saline solution, the flow rate ratio of the continuous phase to the dispersed phase is 7:1 to 2:1, and the flow rate of the dispersed phase is 30-90µL / min; the continuous phase is preferably a 20wt% NaCl aqueous solution, the flow rate ratio of the continuous phase to the dispersed phase is preferably 4:1, and the flow rate of the dispersed phase is preferably 60µL / min.

[0016] Furthermore, the desolventizing column height is 25–40 cm, the salt concentration is 4–6 wt%, and the operating temperature is 25 °C.

[0017] Furthermore, the post-treatment includes water washing, alcohol washing, filtration, and drying.

[0018] A gradient-doped block copolymer functionalized polystyrene composite microsphere is prepared by a microfluidic buoyancy desolventizing method: the blended polymer is dissolved in a solvent to form a dispersed phase and mixed uniformly. A salt solution is used as the continuous phase. After shearing by a T-type microfluidic chip, the microspheres are buoyant desolventized and solidified in a salt column to obtain composite microspheres with uniform particle size, stable functional groups, and controllable bromine content.

[0019] The functionalized polystyrene composite microspheres are formed by microfluidic processing of a polystyrene mixture system. The functional components are blended during the dissolution of polystyrene and are integrated into the microspheres. The particle size of the functionalized polystyrene composite microspheres is 80–130 µm, with a CV of <8%. The functional groups in the microspheres are C–Br bonds, which are uniformly distributed and have a uniform particle size. They can be used in the field of waste acid adsorption or separation.

[0020] In the preparation method of this invention, droplets enter a glass column containing desolvated solvent. The density of the droplets is lower than that of the NaCl solution in the column. After entering the column, they move upward by buoyancy. During the upward movement, the solvent diffuses from the droplets into the surrounding NaCl aqueous solution, and the droplets gradually desolvate, forming solid polymer microspheres. As the solvent is continuously removed, the density of the microspheres gradually increases. When its density exceeds that of the surrounding solution, the microspheres sink to the bottom of the column. The height of the glass column and the amount of salt solution are changed to ensure that the droplets are completely desolvated and form solid microspheres during the upward movement. The microspheres at the bottom of the desolvated glass column are collected, and the microspheres are separated using an appropriate method to remove residual salt.

[0021] The present invention has the following beneficial effects: (1) The copolymer and polystyrene raw materials selected for the gradient doped copolymer-polystyrene composite microspheres prepared by this invention are inexpensive, non-toxic and harmless and easy to obtain. Functionalization can be completed by microfluidic method, which significantly reduces the preparation cost and improves the content and distribution uniformity of functional groups, which is conducive to subsequent large-scale promotion.

[0022] (2) This invention requires only one set of microfluidic chip and buoyancy desolvation column equipment to synthesize composite microspheres with uniform particle size, adjustable gradient and excellent dispersibility in one go. It simplifies the multi-step post-modification process of traditional suspension polymerization, and the process is simple, energy consumption is low and it is easy to scale up to industrial scale.

[0023] (3) The functional groups of the microspheres prepared by the present invention are stably anchored by C–Br covalent bonds, which are resistant to solvents, acids and alkalis and do not fall off during repeated use; at the same time, the gradient doping design takes into account both elasticity and rigidity, avoids the risk of sphere collapse under high block copolymer content, and ensures the integrity and long-term stability of the functional layer. Attached Figure Description

[0024] Figure 1 This is a diagram of the experimental setup.

[0025] Figure 2 This is a scanning electron microscope image of the functionalized polystyrene composite microspheres prepared in Example 2.

[0026] Figure 3 This is the energy spectrum of the functionalized polystyrene composite microspheres prepared in Example 2. Figure 3 (a) is a scanning electron microscope image of functionalized polystyrene composite microspheres; Figure 3 (b) in Figure (a) is the C element distribution diagram corresponding to the microspheres in Figure (a); Figure 3 (c) in the figure is the Br element distribution diagram corresponding to the microspheres in Figure (a).

[0027] In the diagram: P1 is the first injection pump; P2 is the second injection pump; V1 is the first control valve; V2 is the second control valve; 1 is the desolvated glass column; 2 is the rubber stopper; 3 is the T-type microfluidic chip; a is the polymer solution delivery line; b is the 20-25% saline solution delivery line; c is the segmented solution delivery line. Detailed Implementation

[0028] The technical solution of the present invention will be further explained and described below with reference to specific embodiments and accompanying drawings.

[0029] The microfluidic devices assembled in each embodiment have the same structure, specifically: the microfluidic device includes a first injection pump P1, a second injection pump P2, and a T-shaped microfluidic chip. Each injection pump is equipped with a syringe and a first control valve V1 and a second control valve V2, respectively. The first injection pump P1 is used to deliver the polymer solution, and the second injection pump P2 is used to deliver the high-concentration saline solution. The T-shaped microfluidic chip includes a polymer solution delivery line, a high-concentration saline solution delivery line, and a segmented solution delivery line, i.e., two inlets and one outlet. The two inlets are connected to the first injection pump P1 and the second injection pump P2 respectively via polytetrafluoroethylene (PTFE) tubing, and the outlet is connected to the desolvation glass column 1, with a rubber stopper 2 at the connection point. The desolvation glass column 1 is injected with a saline solution for desolvation.

[0030] Example 1 (1) At room temperature, dissolve 1g SIS and 4g polystyrene in 100mL tetrahydrofuran to prepare a 5wt% polymer solution and stir until completely dissolved; prepare 6wt% and 25wt% NaCl aqueous solutions.

[0031] (2) At room temperature, hydrophilically pretreat the microfluidic pipeline and connect the microfluidic device; put the polymer solution and 25wt% NaCl solution into the syringes respectively and install them on the injection pump; adjust the flow rate of the injection pump, the flow rate ratio of the continuous phase to the dispersed phase is 7:1, the flow rate of the dispersed phase is 60µL / min, and obtain stable and uniform droplets.

[0032] (3) The droplets enter a 30cm desolvation glass column, rise in a 6wt% NaCl solution, and fall after the solvent is completely removed to form solid microspheres. Collect the microspheres at the bottom of the desolvation glass column, filter, wash with water, filter, wash with alcohol, filter and dry the sample to obtain functionalized polystyrene composite microspheres.

[0033] Product characterization: The average particle size was 108 μm as determined by laser particle size analyzer, with a CV of 7.2%, and the microspheres had regular shapes.

[0034] Example 2 (1) At room temperature, dissolve 0.5g CMSBS and 1.5g polystyrene in 100mL tetrahydrofuran to prepare a 2wt% mixed solution and stir until completely dissolved; prepare 5wt% and 20wt% NaCl aqueous solutions.

[0035] (2) At room temperature, hydrophilically pretreat the microfluidic pipeline and connect the microfluidic device; put the polymer solution and 20wt% NaCl solution into the syringes and install them on the injection pump; adjust the flow rate of the injection pump, the flow rate ratio of the continuous phase to the dispersed phase is 3:1, the flow rate of the dispersed phase is 60µL / min, and obtain stable and uniformly sized droplets.

[0036] (3) The droplets enter a 35cm desolvation glass column, rise in a 5wt% NaCl solution, and fall after the solvent is completely removed, forming solid microspheres. Collect the microspheres at the bottom of the desolvation glass column, filter, wash with water, filter, wash with alcohol, filter and dry the sample to obtain functionalized polystyrene composite microspheres.

[0037] Product characterization: The average particle size was 104 μm as determined by laser particle size analyzer, with a CV of 6.3%, and the microspheres had regular shapes.

[0038] Example 3 (1) At room temperature, dissolve 1.5g SEBS and 1.5g polystyrene in 100mL tetrahydrofuran to prepare a 3wt% mixed solution and stir until completely dissolved; prepare 5wt% and 22wt% NaCl aqueous solutions.

[0039] (2) At room temperature, hydrophilically pretreat the microfluidic pipes and connect the microfluidic device; put the polymer solution and 22wt%KCl solution into syringes and install them on the injection pump; adjust the flow rate of the injection pump, the flow rate ratio of the continuous phase to the dispersed phase is 5:1, the flow rate of the dispersed phase is 60µL / min, and obtain stable and uniform droplets.

[0040] (3) The droplets enter a 35cm desolvation glass column, rise in a 5wt% NaCl solution, and fall after the solvent is completely removed, forming solid microspheres. Collect the microspheres at the bottom of the desolvation glass column, filter, wash with water, filter, wash with alcohol, filter and dry the sample to obtain functionalized polystyrene composite microspheres.

[0041] Product characterization: The average particle size was 111 μm as determined by laser particle size analyzer, with a CV of 6.6%, and the microspheres had regular shapes.

[0042] Example 4 (1) At room temperature, 0.5g of polystyrene-methyl acrylate copolymer and 0.5g of polystyrene were dissolved in 100mL of 2-methyltetrahydrofuran to prepare a 1wt% mixed solution, and stirred until completely dissolved; 4wt% and 20wt% MgCl2 aqueous solutions were prepared.

[0043] (2) At room temperature, hydrophilically pretreat the microfluidic pipeline and connect the microfluidic device; put the polymer solution and 20wt% NaCl solution into the syringes and install them on the injection pump; adjust the flow rate of the injection pump, the flow rate ratio of the continuous phase to the dispersed phase is 3:1, the flow rate of the dispersed phase is 60µL / min, and obtain stable and uniformly sized droplets.

[0044] (3) The droplets enter a 40cm desolvation glass column, rise in a 4wt% NaCl solution, and fall after the solvent is completely removed to form solid microspheres. Collect the microspheres at the bottom of the desolvation glass column, filter, wash with water, filter, wash with alcohol, filter and dry the sample to obtain functionalized polystyrene composite microspheres.

[0045] Product characterization: The average particle size was 114 μm as determined by laser particle size analyzer, with a CV of 7.5%, and the microspheres had regular shapes.

[0046] The CV value reflects the monodispersity of the microspheres; a smaller value indicates higher microsphere size regularity. The functional polystyrene composite microspheres prepared in Examples 1-4 above showed good monodispersity, with CV values ​​less than 8%, as determined by laser particle size diffraction. Testing of the functional group content of the microspheres demonstrated that this polymerization method can increase the content of functional groups in the microspheres, and that the elements are evenly distributed within the microspheres. Immersion experiments demonstrated the strong stability of the functional groups within the microspheres.

[0047] This invention employs a microfluidic buoyancy desolvation method, which allows for the one-time synthesis of gradient-doped copolymer-polystyrene composite microspheres with varying copolymer contents, particle sizes, and excellent dispersibility using only a microfluidic chip and gradient salt column equipment. The selected copolymers and polystyrene raw materials are inexpensive, non-toxic, harmless, and readily available. The functional groups are stable through C–Br covalent bonds, resulting in a simple and stable composite principle that does not detach during recycling. Solubility tests revealed that the functional groups successfully adhere to the microsphere surface, reducing the preparation cost of functionalized composite microspheres and simplifying the molding and functionalization process of high-block copolymer content microspheres. This is beneficial for subsequent applications in fields such as waste acid adsorption, enabling large-scale industrial production.

[0048] The above-described embodiments are merely illustrative of the implementation methods of the present invention, but should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the protection scope of the present invention.

Claims

1. A microfluidic preparation method for graded-doped block copolymer functionalized polystyrene composite microspheres, characterized in that, The microfluidic preparation method includes the following steps: Step 1: At room temperature, block copolymers and polystyrene in different proportions are dissolved in a solvent to prepare polymer solutions, and stirred until completely dissolved; at the same time, salt solutions are prepared as the dispersed phase and the desolventizing solution, respectively, wherein the salt solution as the dispersed phase has a high concentration and the salt solution as the desolventizing solution has a low concentration. Step 2: Assemble the microfluidic device; The microfluidic device includes a first injection pump, a second injection pump, and a T-shaped microfluidic chip. Each injection pump is equipped with a syringe, and the flow rate is controlled by a control valve. The first injection pump is used to deliver the polymer solution, and the second injection pump is used to deliver the high-concentration saline solution. The T-shaped microfluidic chip includes a polymer solution delivery line, a high-concentration saline solution delivery line, and a segmented solution delivery line, i.e., two inlets and one outlet. The two inlets are connected to the first injection pump and the second injection pump respectively through polytetrafluoroethylene (PTFE) tubing, and the outlet is connected to a desolvation glass column. The desolvation glass column is filled with a saline solution for desolvation. Step 3: The polymer solution and the salt solution are loaded into two syringes, which serve as the dispersed phase and the continuous phase, respectively. The injection pump is connected to the desolvated glass column 1 containing the desolvated solvent through the microfluidic chip channel of the microfluidic device. Inside the T-shaped microfluidic chip, the polymer solution flow delivered by the first injection pump P1 is segmented and sheared by the brine solution flow delivered by the second injection pump P2 to form a polymer solution. The polymer solution droplets and the high-concentration brine solution are mixed and transported to the desolvated glass column 1, and then post-processed to obtain gradient-doped block copolymer functionalized polystyrene composite microspheres.

2. The microfluidic preparation method of gradient-doped block copolymer functionalized polystyrene composite microspheres according to claim 1, characterized in that, In step 1: The mass ratio of block copolymer to polystyrene in the polymer solution is 1:5 to 5:1, the total solid content of the polymer solution is 1–5 wt%, and the solvent is one of tetrahydrofuran, 2-methyltetrahydrofuran or γ-valerol. The polymer in the polymer solution is one or more of the following: polystyrene-butadiene-styrene copolymer, derivatives of polystyrene-butadiene-styrene copolymer, polystyrene-isoprene-styrene copolymer, derivatives of polystyrene-isoprene-styrene copolymer, and polystyrene-methyl acrylate copolymer. The salt solution used as the dispersed phase is one of NaCl, KCl, or MgCl2, with a concentration of 20-25 wt%; The salt solution used as a desolvent is one of NaCl, KCl or MgCl2, with a concentration of 4-6 wt%.

3. The microfluidic preparation method of gradient-doped block copolymer functionalized polystyrene composite microspheres according to claim 1, characterized in that, In step 1: The preferred mass ratio of block copolymer to polystyrene in the polymer solution is 1:1, the total solid content of the polymer solution is 3 wt%, and the solvent is tetrahydrofuran. The salt solution is a NaCl solution; The polymer in the polymer solution is CMSBS, a derivative of polystyrene-butadiene-styrene copolymer.

4. The microfluidic preparation method of gradient-doped block copolymer functionalized polystyrene composite microspheres according to claim 1, characterized in that, In step 2, the T-shaped microfluidic chip and polytetrafluoroethylene tubing are hydrophilically treated, and their internal surfaces are pretreated with a 0.1 M H2SO4 solution with a mass concentration of 1% KMnO4.

5. The microfluidic preparation method of gradient-doped block copolymer functionalized polystyrene composite microspheres according to claim 1, characterized in that, The microfluidic chip channel size is 100-200µm; the flow rate ratio of the continuous phase to the dispersed phase is 7:1 to 2:1, and the flow rate of the dispersed phase is 30-90µL / min.

6. The microfluidic preparation method of gradient-doped block copolymer functionalized polystyrene composite microspheres according to claim 1, characterized in that, The continuous phase was a 20 wt% NaCl aqueous solution, the flow rate ratio of the continuous phase to the dispersed phase was 4:1, and the flow rate of the dispersed phase was 60 µL / min.

7. The microfluidic preparation method of gradient-doped block copolymer functionalized polystyrene composite microspheres according to claim 1, characterized in that, The height of the desolvation column injected into the solvation glass column is 25–40 cm, and the temperature is 25℃.

8. The microfluidic preparation method of gradient-doped block copolymer functionalized polystyrene composite microspheres according to claim 1, characterized in that, In step 3, the flow rate of the syringe pump is adjusted to begin forming droplets, and the flow rates of the two syringe pumps are adjusted to obtain stable and uniformly sized droplets within the glass column; the post-treatment consists of water washing, alcohol washing, filtration, and drying.

9. A gradient-doped block copolymer functionalized polystyrene composite microsphere, characterized in that, The composite microspheres prepared by the microfluidic buoyancy desolvation method according to any one of claims 1-8 are characterized by uniform particle size, stable functional groups, and controllable bromine content.

10. The graded-doped block copolymer functionalized polystyrene composite microspheres according to claim 9, characterized in that, The composite microspheres are formed by microfluidic processing of a polystyrene mixture system. The functional components are blended during the dissolution of polystyrene and are integrated into the microspheres. The particle size of the functionalized polystyrene composite microspheres is 80–130 µm, with a CV of <8%. The functional groups in the microspheres are C–Br bonds, which are uniformly distributed and have a uniform particle size. They can be applied to the field of waste acid adsorption or separation.

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