Polystyrene-vinylpyridine block copolymer composite membrane and preparation method thereof
By leveraging the synergistic effect of chain transfer agents and free radical initiators, combined with spin coating technology, the problems of process complexity and insufficient mechanical properties of polystyrene-vinylpyridine block copolymer films were solved, resulting in the preparation of a high-efficiency and stable composite film with excellent mechanical properties and nanostructure.
Patent Information
- Application Number
- CN202511850013.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-09
- Publication Date
- 2026-02-10
AI Technical Summary
Existing technologies for preparing polystyrene-vinylpyridine block copolymer films suffer from problems such as complex processes, high costs, insufficient mechanical properties, and weak composite film interfaces. In particular, it is difficult to achieve efficient, stable nanostructures and mechanical integrity in large-scale production.
By employing the synergistic effect of chain transfer agents and free radical initiators, monomer conversion and molecular weight distribution are controlled through two heating copolymerization reactions. Combined with spin coating technology, a block copolymer composite film is formed on the surface of a porous base film, ensuring high conversion and narrow molecular weight distribution, and providing mechanical support through the base film.
High monomer conversion rate and narrow molecular weight distribution were achieved, which improved polymerization efficiency and produced a composite membrane with porous surface, high tensile modulus and high tensile strength, which has good mechanical properties and efficient pollutant retention capacity.
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Figure CN121495166A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of block copolymer materials technology. Background Technology
[0002] Polystyrene-polyvinylpyridine block copolymers are widely used in separation membranes, interface control, catalyst supports, and smart response systems because they can form stable microphase separation structures at the nanoscale. However, there are two main requirements for the practical application of these materials: first, the block sequence and molecular weight must be controlled to obtain reproducible morphology and channel structure; second, sufficient mechanical integrity and long-term service stability are required after film formation.
[0003] Regarding the first point, the industry has long used living anionic polymerization to prepare polystyrene-polyvinylpyridine block copolymers. This route can obtain samples with extremely narrow molecular weight distribution, precise block length, and clear phase morphology under strict anhydrous and oxygen-free conditions and high-purity monomers. However, it has extremely high requirements for equipment and raw material purity, operating environment, and reaction conditions. The process window is narrow, and the scale-up cost and quality control cost are significant, making it difficult to meet the economic and manufacturability requirements for application.
[0004] In contrast, living radical polymerization has advantages such as higher solvent and impurity tolerance and simpler process, making it theoretically more suitable for engineering and large-scale production. However, in the styrene / vinylpyridine system, conventional radical controlled polymerization generally faces problems such as low monomer conversion, limited achievable molecular weight, and a widened molecular weight distribution: extending the reaction time can improve some conversion, but it also leads to the accumulation of termination / transfer side reactions, resulting in a wider molecular weight distribution of the finished product. Consequently, during subsequent film formation, this manifests as increased film defects, a narrower phase separation window, and decreased batch-to-batch reproducibility.
[0005] Regarding the second point, self-supporting copolymer films are prone to cracking and peeling due to the inherent brittleness of the material under swelling / drying cycles or external forces. As a countermeasure, block copolymers are composited with porous base films, with the base film providing mechanical support and dimensional stability, while the block thin layers assume selectivity and interfacial functions. However, the synthesized polymers have low conversion rates and broad distributions, making it difficult to obtain continuous, uniform, and reproducible nanostructures on the surface of the composite film. At the same time, the complex multi-step film formation / post-processing also amplifies batch variations and the risk of interfacial instability. Summary of the Invention
[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing polystyrene-vinylpyridine block copolymer composite films by synergistically optimizing the synthesis and film formation stages, thereby solving the problems of insufficient mechanical properties, weak composite film interface, and complex preparation process of traditional block copolymer films.
[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a method for preparing a polystyrene-vinylpyridine block copolymer composite film, comprising the following steps: Step 1: Under an inert atmosphere, organic compounds containing thioester, trithiocarbonate, or dithiocarbamate structures are added to an organic solvent as chain transfer agents, vinylpyridine monomers, and free radical initiators. The reaction is heated at 50-80°C for 8-24 h. When the monomer conversion rate reaches more than 95%, the reaction is stopped by cooling with liquid nitrogen. The mixture is then poured into ethanol to settle and filtered. Finally, it is vacuum dried at 15-30°C for 8-24 h to obtain polyvinylpyridine macromolecular chain transfer agent. The volume ratio of vinylpyridine monomers to organic solvents is 1:5-1:15; the molar ratio of vinylpyridine monomers to free radical initiators is 100:1-400:1; and the molar ratio of vinylpyridine monomers to chain transfer agents is 30:1-100:1. Step 2: Under an inert atmosphere, add polyvinylpyridine macromolecular chain transfer agent, styrene monomer and free radical initiator to an organic solvent, and carry out the first heating copolymerization reaction at 70-100℃; In the first heating copolymerization reaction, the volume ratio of styrene to organic solvent is 1:1-1:3; the molar ratio of styrene to free radical initiator is 500:1-1000:1; and the molar ratio of polyvinylpyridine macromolecular chain transfer agent to styrene monomer is 1:100-1:400. When the styrene conversion reaches 30-60%, a free radical initiator is added, and a second heating copolymerization reaction is carried out at the original temperature. After the monomer conversion reaches more than 90%, the reaction is stopped by cooling with liquid nitrogen. The product is then poured into ethanol to settle and filtered. Next, it is vacuum dried at 15-30℃ for 8-24 h to obtain polystyrene-polyvinylpyridine block copolymer. In the second heating copolymerization reaction, the amount of free radical initiator is 50-120% of the amount of the initial free radical initiator; Step 3: Dissolve the obtained polystyrene-polyvinylpyridine block copolymer in an organic solvent to prepare a polymer solution with a weight percentage of 1-5 wt%. After filtering to remove impurities through a microporous membrane, add the solution dropwise onto the surface of a porous base membrane at a rate of 0.03-0.06 mL / cm². 2 ; Next, after spin coating at 1000-3000 rpm for 20-60 s, the film is annealed in organic solvent vapor for 20-60 s, then placed in a polar solvent and swollen at 40-60℃ for 1-4 h. Finally, it is vacuum dried at 30-50℃ for 8-24 h to obtain a polystyrene-polyvinylpyridine block copolymer composite film. The pore size of the microporous filter membrane is 0.1-0.45 μm.
[0008] Furthermore, the vinylpyridine monomer in step one is one or more of 2-vinylpyridine, 3-vinylpyridine, and 4-vinylpyridine.
[0009] Furthermore, the organic solvent is an amide, ketone, ester, or ether organic solvent.
[0010] Furthermore, the organic solvent is N , N -Dimethylformamide or dimethylacetamide.
[0011] Furthermore, the free radical initiator is an azo or peroxide compound.
[0012] Furthermore, in the polystyrene-polyvinylpyridine block copolymer described in step two, the conversion rate of all monomers is higher than 90%, and the molecular weight distribution is 1.1-1.3.
[0013] Furthermore, in the second heating copolymerization reaction in step two, the amount of the free radical initiator is 80-100% of the amount of the initial free radical initiator.
[0014] Furthermore, the porous base membrane in step three is a polyvinylidene fluoride, polysulfone, or polyethersulfone microfiltration membrane; the organic solvent vapor is chloroform or tetrahydrofuran; and the polar solvent is any one of anhydrous ethanol, acetone, or isopropanol.
[0015] The present invention also provides a polystyrene-vinylpyridine block copolymer composite membrane prepared by the method described above, characterized in that the surface of the composite membrane is porous, the tensile modulus is higher than 1000 MPa, the tensile strength is higher than 100 MPa, and the rejection rate of 30 nm-level pollutants is higher than 95%.
[0016] The beneficial effects of this invention are as follows: This invention provides a polystyrene-vinylpyridine block copolymer composite membrane and its preparation method. First, a polyvinylpyridine macromolecular chain transfer agent is prepared. Then, a polystyrene-vinylpyridine block copolymer is prepared. The synthesized polystyrene-vinylpyridine block copolymer is dissolved and spin-coated onto the surface of a microfiltration membrane. The membrane formation and pore formation parameters are adjusted to form a continuous and uniform membrane layer on the base membrane surface, while maintaining a tight bond with the base membrane interface. This method achieves a high monomer conversion rate and a narrow molecular weight distribution through the synergistic effect of the chain transfer agent and the free radical initiator. Furthermore, by supplementing the initiator at different stages to maintain polymerization activity, the polymerization efficiency is effectively improved. Attached Figure Description
[0017] Figure 1This is a flowchart illustrating the preparation process of the present invention; Figure 2 GPC elution curves of block copolymers with different monomer ratios and molecular weights according to the present invention; Figure 3 The surface morphology of the composite film prepared in this invention; Figure 4 Characterization of the tensile properties of the composite film prepared in this invention; Figure 5 The performance curves of the composite membrane prepared according to the present invention are shown. Detailed Implementation
[0018] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.
[0019] To achieve the above objectives, the present invention provides the following specific embodiments: Example 1: As Figure 1 As shown, a method for preparing a polystyrene-vinylpyridine block copolymer composite film includes the following steps, the overall method steps as follows: Figure 1 As shown: Step 1: Under an inert atmosphere, organic compounds containing thioester, trithiocarbonate, or dithiocarbamate structures are added to an organic solvent as chain transfer agents, vinylpyridine monomers, and free radical initiators. The reaction is heated at 50-80°C for 8-24 h. When the monomer conversion rate reaches more than 95%, the reaction is stopped by cooling with liquid nitrogen. The mixture is then poured into ethanol to settle and filtered. Finally, it is vacuum dried at 15-30°C for 8-24 h to obtain polyvinylpyridine macromolecular chain transfer agent. The volume ratio of vinylpyridine monomers to organic solvents is 1:5-1:15; the molar ratio of vinylpyridine monomers to free radical initiators is 100:1-400:1; and the molar ratio of vinylpyridine monomers to chain transfer agents is 30:1-100:1. The free radical initiator is an azo or peroxide compound; the vinylpyridine monomer is one or more of 2-vinylpyridine, 3-vinylpyridine, and 4-vinylpyridine; and the organic solvent is an amide, ketone, ester, or ether organic solvent.
[0020] Step 2: Under an inert atmosphere, add polyvinylpyridine macromolecular chain transfer agent, styrene monomer and free radical initiator to an organic solvent, and carry out the first heating copolymerization reaction at 70-100℃; In the first heating copolymerization reaction, the volume ratio of styrene to organic solvent is 1:1-1:3; the molar ratio of styrene to free radical initiator is 500:1-1000:1; and the molar ratio of polyvinylpyridine macromolecular chain transfer agent to styrene monomer is 1:100-1:400. When the styrene conversion reaches 30-60%, a free radical initiator is added, and a second heating copolymerization reaction is carried out at the original temperature. After the monomer conversion reaches more than 90%, the reaction is stopped by cooling with liquid nitrogen. The product is then poured into ethanol to settle and filtered. Next, it is vacuum dried at 15-30℃ for 8-24 h to obtain polystyrene-polyvinylpyridine block copolymer. In the second heating copolymerization reaction, the amount of free radical initiator is 50-120% of the amount of the initial free radical initiator; Step 3: Dissolve the obtained polystyrene-polyvinylpyridine block copolymer in an organic solvent to prepare a polymer solution with a weight percentage of 1-5 wt%. After filtering to remove impurities through a microporous membrane, add the solution dropwise onto the surface of a porous base membrane at a rate of 0.03-0.06 mL / cm². 2 ; Next, after spin coating at 1000-3000 rpm for 20-60 s, the film is annealed in organic solvent vapor for 20-60 s, then placed in a polar solvent and swollen at 40-60℃ for 1-4 h. Finally, it is vacuum dried at 30-50℃ for 8-24 h to obtain a polystyrene-polyvinylpyridine block copolymer composite film. The microporous filter membrane has a pore size of 0.1-0.45 μm; The porous base membrane is a polyvinylidene fluoride, polysulfone, or polyethersulfone microfiltration membrane; the organic solvent vapor is chloroform or tetrahydrofuran; and the polar solvent is any one of anhydrous ethanol, acetone, or isopropanol.
[0021] Example 2: Same as Example 1, except that the organic solvent is... N , N -Dimethylformamide or dimethylacetamide.
[0022] Example 3: Same as Example 1, except that in the polystyrene-polyvinylpyridine block copolymer in step two, the conversion rate of all monomers is higher than 90%, and the molecular weight distribution is 1.1-1.3.
[0023] Furthermore, in the second heating copolymerization reaction, the amount of the free radical initiator is 80-100% of the amount of the initial free radical initiator.
[0024] Example 4: The present invention also provides a polystyrene-vinylpyridine block copolymer composite membrane prepared by the method described in Examples 1-3. The composite membrane has a porous surface, a tensile modulus higher than 1000 MPa, a tensile strength higher than 100 MPa, and a rejection rate of 30 nm-level pollutants higher than 95%.
[0025] like Figures 2-5 As shown, to further illustrate the technical solution and effects of the present invention, preparation examples and comparative experiments are provided: Preparation Example 1: Under an inert atmosphere, 1.58 mmol of trithiocarbonate (CPABD), 10 mL (95.8 mmol) of 2-vinylpyridine (2VP), and 85.7 mg (0.52 mmol) of azobisisobutyronitrile (AIBN) were dissolved in 100 mL of dimethylformamide (DMF) and reacted at 60 °C. After 18 h of reaction, the monomer conversion reached 96.1%, and the reaction was terminated by cooling with liquid nitrogen. The product was dissolved in dichloromethane, precipitated twice with n-hexane, filtered, and dried under vacuum at 20 °C for 12 h. The number-average molecular weight of the product was determined by GPC (…). M n Approximately 7.0 kDa, molecular weight distribution index (MDI) The ratio of 1.12 yielded a poly(2-vinylpyridine) (P2VP) macromolecular chain transfer agent.
[0026] Under an inert atmosphere, the obtained P2VP (1 g, 0.14 mmol), 4.46 mL (38.6 mmol) of styrene (St), 7.7 mg (0.042 mmol) of AIBN, and 6 mL of 1,4-dioxane were sequentially added to a 100 mL reaction flask. After reacting at 90 °C for 24 h, 7.7 mg (0.042 mmol) of AIBN was added, and the reaction was continued for another 48 h. The final monomer conversion reached 80.3%. The product was dissolved in dichloromethane, precipitated in n-hexane, filtered, and dried under vacuum at 20 °C for 12 h. GPC analysis of the product... M n It is 32.6 kDa. The value was 1.22, resulting in a polystyrene-2-vinylpyridine block copolymer (PS- b -P2VP).
[0027] Weigh the above block copolymer and dissolve it in chloroform to prepare a 3wt% solution. Remove impurities by sonication for 10 min and filtration through a 0.22 μm needle filter membrane. Add the solution dropwise to the surface of a pre-wetted water-treated polyvinylidene fluoride (PVDF) microfiltration membrane at a rate of 0.045 mL / cm². 2 And spin-coated at 2000 rpm for 30 s to obtain PS- b-P2VP / PVDF composite membrane. The sample was then annealed in chloroform vapor for 35 s, removed, and dried for 10 min. The annealed sample was then immersed in anhydrous ethanol at 50°C for 3 h to swell, and then vacuum dried at 40°C for 12 h to obtain the porous composite membrane. (The text abruptly ends here.) Figure 3 SEM observations showed that the block copolymer formed a porous structure on the membrane surface.
[0028] Preparation Example 2: Under an inert atmosphere, 1.58 mmol CPADB, 10 mL (95.8 mmol) 4-vinylpyridine (4VP), and 85.7 mg (0.52 mmol) AIBN were added to 100 mL DMF and heated to 60 °C. After 18 h, the monomer conversion reached over 95%, and the reaction was terminated by cooling with liquid nitrogen. The resulting polymer was dissolved in dichloromethane, precipitated twice with n-hexane, filtered, and vacuum dried at 20 °C for 12 h. GPC analysis showed... M n It is 7.2 kDa. The value was 1.13, thus obtaining a poly(4-vinylpyridine) (P4VP) macromolecular chain transfer agent.
[0029] 1 g (0.14 mmol) of the prepared P4VP, 4.46 mL (38.6 mmol) of St, 7.7 mg (0.042 mmol) of AIBN, and 6 mL of 1,4-dioxane were weighed and added to a 100 mL reaction flask. The mixture was heated at 90 °C for 24 h, and then 7.7 mg of AIBN in a 1,4-dioxane solution was added, and the reaction was continued for another 48 h. The final monomer conversion rate reached 92%. The product was settled, dried, and measured by GPC. M n It is 31.5 kDa. The value was 1.20, resulting in a polystyrene-4-vinylpyridine block copolymer (PS- b -P4VP).
[0030] The obtained PS- b -P4VP was dissolved in chloroform to prepare a 3wt% solution, which was then ultrasonicated and filtered before being dropped onto the surface of the PVDF substrate membrane (0.045 mL / cm²). 2 A composite film was formed by spin coating at 2000 rpm for 30 s. The sample was annealed in chloroform vapor for 40 s, swollen in ethanol at 50℃ for 3 h, and then vacuum dried at 40℃ for 12 h to obtain PS- b -P4VP porous composite membrane.
[0031] Preparation Example 3: Based on Preparation Example 1, the monomer feeding ratio of St to P2VP macromolecular chain transfer agent was adjusted to 77.2 mmol : 0.14 mmol, and other steps were the same as in Example 1. The obtained polymer monomer conversion rate was approximately 91%. M n It is 58.0 kDa. It is 1.25.
[0032] Comparative Experiment 1: Under the conditions of Preparation Experiment 1, without adding AIBN midway, only a one-time initiation was performed. The reaction was terminated after 48 h at 90℃, and the monomer conversion rate was only 48.5%. The polymer obtained after sedimentation and drying... M n It is 21.0 kDa. The value was 1.35. The results showed that the conversion rate was significantly insufficient and the polymerization efficiency was significantly reduced.
[0033] Comparative Experiment 2: Under the conditions of Preparation Experiment 1, PS- b The P2VP solution was directly spin-coated onto the glass substrate without being combined with the PVDF base film. The self-supporting film obtained after chloroform vapor annealing and ethanol swelling developed large-area cracks during the drying process. The film was extremely brittle and easily broken, making it unsuitable for routine mechanical testing and application.
[0034] Figure 2 The GPC effluent curves of block copolymers with different monomer ratios and molecular weights were obtained during the experimental verification of this invention. As can be seen from the figure, they are all monodisperse and have a narrow distribution. Figure 3 The surface morphology of the composite membrane prepared in this invention is shown in the figure. As can be seen from the figure, the surface is porous. Figure 4 The tensile properties of the composite film prepared in this invention are characterized, and it can be seen from the figure that it has certain elasticity and good strength. Figure 5 The left side shows the rejection rate of the composite membrane (for bovine serum albumin with a particle size of 36 nm), and the right side shows the water flux of the composite membrane as a function of the number of uses. It can be seen from the figure that the composite membrane has a certain degree of durability.
[0035] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for preparing a polystyrene-vinylpyridine block copolymer composite film, characterized in that, Includes the following steps: Step 1: Under an inert atmosphere, organic compounds containing thioester, trithiocarbonate, or dithiocarbamate structures are added to an organic solvent as chain transfer agents, vinylpyridine monomers, and free radical initiators. The reaction is heated at 50-80°C for 8-24 h. When the monomer conversion rate reaches more than 95%, the reaction is stopped by cooling with liquid nitrogen. The mixture is then poured into ethanol to settle and filtered. Finally, it is vacuum dried at 15-30°C for 8-24 h to obtain polyvinylpyridine macromolecular chain transfer agent. The volume ratio of vinylpyridine monomers to organic solvents is 1:5-1:15; the molar ratio of vinylpyridine monomers to free radical initiators is 100:1-400:1; and the molar ratio of vinylpyridine monomers to chain transfer agents is 30:1-100:
1. Step 2: Under an inert atmosphere, add polyvinylpyridine macromolecular chain transfer agent, styrene monomer and free radical initiator to an organic solvent, and carry out the first heating copolymerization reaction at 70-100℃; In the first heating copolymerization reaction, the volume ratio of styrene to organic solvent is 1:1-1:3; the molar ratio of styrene to free radical initiator is 500:1-1000:1; and the molar ratio of polyvinylpyridine macromolecular chain transfer agent to styrene monomer is 1:100-1:
400. When the styrene conversion reaches 30-60%, a free radical initiator is added, and a second heating copolymerization reaction is carried out at the original temperature. After the monomer conversion reaches more than 90%, the reaction is stopped by cooling with liquid nitrogen. The product is then poured into ethanol to settle and filtered. Next, it is vacuum dried at 15-30℃ for 8-24 h to obtain polystyrene-polyvinylpyridine block copolymer. In the second heating copolymerization reaction, the amount of free radical initiator is 50-120% of the amount of the initial free radical initiator; Step 3: Dissolve the obtained polystyrene-polyvinylpyridine block copolymer in an organic solvent to prepare a polymer solution with a weight percentage of 1-5 wt%. After filtering to remove impurities through a microporous membrane, add the solution dropwise onto the surface of a porous base membrane at a rate of 0.03-0.06 mL / cm². 2 ; Next, after spin coating at 1000-3000 rpm for 20-60 s, the film is annealed in organic solvent vapor for 20-60 s, then placed in a polar solvent and swollen at 40-60℃ for 1-4 h. Finally, it is vacuum dried at 30-50℃ for 8-24 h to obtain a polystyrene-polyvinylpyridine block copolymer composite film. The pore size of the microporous filter membrane is 0.1-0.45 μm.
2. The method for preparing the polystyrene-vinylpyridine block copolymer composite film as described in claim 1, characterized in that, The vinylpyridine monomer in step one is one or more of 2-vinylpyridine, 3-vinylpyridine, and 4-vinylpyridine.
3. The method for preparing the polystyrene-vinylpyridine block copolymer composite film as described in claim 1, characterized in that, The organic solvent is an amide, ketone, ester, or ether organic solvent.
4. The method for preparing the polystyrene-vinylpyridine block copolymer composite film as described in claim 3, characterized in that, The organic solvent is N , N -Dimethylformamide or dimethylacetamide.
5. The method for preparing the polystyrene-vinylpyridine block copolymer composite film according to claim 1, characterized in that, The free radical initiator is an azo or peroxide compound.
6. The method for preparing the polystyrene-vinylpyridine block copolymer composite film according to claim 1, characterized in that, In the polystyrene-polyvinylpyridine block copolymer described in step two, the conversion rate of all monomers is higher than 90%, and the molecular weight distribution is 1.1-1.
3.
7. The method for preparing the polystyrene-vinylpyridine block copolymer composite film according to claim 1, characterized in that, In the second heating copolymerization reaction in step two, the amount of the free radical initiator is 80-100% of the amount of the initial free radical initiator.
8. The method for preparing the polystyrene-vinylpyridine block copolymer composite film according to claim 1, characterized in that, The porous base membrane mentioned in step three is a polyvinylidene fluoride, polysulfone, or polyethersulfone microfiltration membrane; the organic solvent vapor is chloroform or tetrahydrofuran; and the polar solvent is any one of anhydrous ethanol, acetone, or isopropanol.
9. A polystyrene-vinylpyridine block copolymer composite film obtained by the preparation method according to any one of claims 1-8, characterized in that, The composite membrane has a porous surface, a tensile modulus higher than 1000 MPa, a tensile strength higher than 100 MPa, and a rejection rate of more than 95% for 30 nm-level pollutants.