A polymer isotropic membrane, its preparation method and use

Abstract

The application discloses a kind of polymer uniform pore membrane and its preparation method and application.The top of the polymer uniform pore membrane is honeycomb type porous membrane structure, bottom is smooth and flat, has one of reentrant, a little small hole and top porous structure communication and a large number of large hole and top porous structure communication;Top aperture is 1-20 microns;Standard deviation is 0.09-0.11 microns;Coefficient of variation is 1.0-3.0%.By controlling the high humidity air injection time of substrate surface and the condensation time of polymer solution surface droplet, the hierarchical structure of the membrane can be controlled, and the bottom large hole is connected with the top small hole.The method is simple, not only reduces the contact area of the bottom layer and the substrate, but also significantly widens the self-supporting strength of the porous membrane under the condition of ensuring the uniformity of the top small aperture, making it more widely adaptable.

Description

Technical Field

[0001] This application relates to a polymer uniformly porous membrane, its preparation method and application, belonging to the field of membrane materials. Background Technology

[0002] The Breath Figure method is a widely used approach for preparing porous polymer membranes. Its key feature is the condensation of water droplets on the surface of a polymer solution, which, as the solvent evaporates, form a regular honeycomb-like pore structure. This method is important in fields such as filtration and tissue engineering because it can produce porous membranes with uniform and controllable pore sizes.

[0003] Shimomura et al. (Polymer Journal, Vol. 41, No. 8, pp. 667-671, 2009) significantly improved the stability and ordered arrangement of water droplets by adding amphiphilic copolymers (such as amphiphilic polyacrylamide copolymers) to polymer solutions, thus enabling the fabrication of porous membranes with uniform pore sizes over large areas. However, when using the Breath Figure method to prepare uniformly porous membranes with through-holes, a common practice is to prepare the membrane on ice, which usually requires additional mesh support structures to prevent membrane collapse (J. Am. Chem. Soc. 2012, 134, 95-98). Another method is to prepare the membrane on a hydrophilic low-temperature glass substrate, but the membrane peeling process is difficult, limiting its practicality and large-scale application. Summary of the Invention

[0004] This application proposes an innovative "secondary Breath Figure method" to address these issues and achieve a simple preparation of a bilayer porous membrane with interconnected layers. The method first involves condensing micron-sized water droplets (10-100 micrometers) on a cooled substrate, then casting a polymer solution onto it, and finally blowing high-humidity air onto the solution surface to perform a second breath figure. The membrane prepared by this method has an interconnected structure, with a macroporous support layer at the bottom and a microporous filter layer at the top. The two layers are tightly connected, significantly improving mechanical strength.

[0005] Compared to traditional methods, this "secondary breath figure method" simplifies the fabrication process of interconnected structures. Due to the significantly reduced contact area of ​​the bottom layer, the membrane is easier to peel off, yet its self-support is enhanced, and its tensile strength is significantly improved. This innovation provides a new solution for porous membranes requiring high strength and multilayer structures, and expands their application potential in filtration, separation, and other fields.

[0006] According to one aspect of this application, a polymer uniformly porous membrane is provided, characterized in that...

[0007] The top of the polymer uniformly porous membrane is a honeycomb porous membrane structure, and the bottom is one of the following: smooth and flat, with depressions, a few small pores connected to the top porous structure, or a large number of large pores connected to the top porous structure.

[0008] The top pore size of the polymer uniformly porous membrane is 1 to 20 micrometers;

[0009] The standard deviation of the top pore size of the polymer uniformly porous membrane is 0.09–0.11 micrometers;

[0010] The coefficient of variation of the top pore size of the polymer uniformly porous membrane is 1.0 to 3.0%.

[0011] According to another aspect of this application, a method for preparing the above-mentioned polymer uniformly porous membrane is provided, comprising the following steps:

[0012] In an environment with a relative humidity of 50-80%, high-humidity air generated by water bubbling is sprayed onto the substrate surface, causing small droplets to condense on the substrate surface. Then, casting liquid is coated onto the substrate surface with condensed droplets, and high-humidity air generated by water bubbling is sprayed again. Under the action of lateral capillary force, the polymer uniformly porous membrane is obtained.

[0013] The casting solution is an organic solvent solution containing polymer compounds and surfactants;

[0014] The polymer compound is selected from at least one of polysulfone, polylactic acid, and polymethyl methacrylate;

[0015] The surfactant is selected from amphiphilic polyacrylamide copolymers;

[0016] The organic solvent is selected from at least one of chloroform, dichloromethane, dichloroethane, and benzene.

[0017] The surfactant is selected from amphiphilic polyacrylamide copolymers.

[0018] The concentration of the polymer compound in the casting solution is 1–10 g / L;

[0019] The surfactant is present in a mass of 5 to 20 wt% of the polymer compound.

[0020] The bubbling rate is 0.01–5 L / min;

[0021] The spraying time is 1 to 10 minutes.

[0022] The temperature of the substrate is 0–30°C;

[0023] The substrate is selected from at least one of glass, polypropylene film, and aerospace mirror aluminum.

[0024] According to another aspect of this application, an application of the above-described polymer homogeneous porous membrane is provided for microsphere separation, blood cell separation, or oil-water separation.

[0025] The beneficial effects that this application can produce include:

[0026] 1) It significantly broadens the application range of the adaptability of the vertically connected membrane. Under the same conditions, the original single-sided open porous membrane can be transformed into a vertically connected porous membrane by a simple method of condensing droplets on the substrate.

[0027] 2) Significantly increased the tensile strength of the membrane.

[0028] 3) The reduced contact area with the substrate makes the film easier to peel off.

[0029] 4) The prepared uniformly porous membrane has a uniform pore size and exhibits excellent performance in applications such as microsphere and blood cell separation. Attached Figure Description

[0030] Figure 1 The image shows an electron microscope (EM) image of the top layer of the uniformly porous membrane obtained in Example 1, at a scale of 1 μm.

[0031] Figure 2 The image shows an electron microscope (EM) image of the bottom layer of the uniformly porous membrane obtained in Example 1, at a scale of 10 μm.

[0032] Figure 3 The image shows an electron microscope (EM) image of the bottom layer of the uniformly porous membrane obtained in Example 2, at a scale of 10 μm.

[0033] Figure 4 The image shows an electron microscope (EM) image of the top layer of the uniformly porous membrane obtained in Example 3, at a scale of 10 μm.

[0034] Figure 5 The image shows an electron microscope (EM) image of the top layer of the uniformly porous membrane obtained in Example 3, at a scale of 10 μm.

[0035] Figure 6 The image shows an electron microscope (EM) image of the bottom layer of the uniformly porous membrane obtained in Comparative Example 1, at a scale of 5 μm.

[0036] Figure 7 The image shows a cross-section of the uniformly porous membrane obtained in Comparative Example 1 with the bottom layer on top, at a scale of 10 μm. Detailed Implementation

[0037] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0038] Unless otherwise specified, the raw materials and catalysts used in the embodiments of this application were all purchased commercially.

[0039] Example 1:

[0040] 0.909 g of polymethyl methacrylate and 0.091 g of the surfactant amphiphilic polyacrylamide copolymer were added to 100 mL of chloroform and mechanically stirred for 24 hours to completely dissolve the polymer. The mixture was then degassed by ultrasonic oscillation. 100 mL of the aqueous solution was used as the bubbling solution and added to a 250 mL Mendel's gas washing bottle, and bubbling was performed at a flow rate of 5 L / min. A 10 cm x 10 cm glass substrate was used and placed on a tissue cryostat, with the temperature adjusted to 7°C. The ambient humidity was 60%. After standing for 120 seconds, 2 mL of the polymer solution was coated onto the substrate. Subsequently, air treated by the Mendel's gas washing bottle was guided by a glass funnel and blown onto the surface of the polymer solution. After the chloroform and droplets evaporated, a homogeneous porous membrane was formed.

[0041] When water is used as the bubbling liquid, such as Figure 1 As shown, the microporous membrane has uniformly sized honeycomb-shaped pores in both the connected and non-connected regions, with pore sizes of 2.58 and 2.15 micrometers, respectively. The membrane was peeled off the glass surface with the bottom layer facing upwards for observation. Figure 2 As shown, the bottom layer of the membrane is also a planar and porous membrane, with openings connected to the top layer.

[0042] Example 2:

[0043] Similar to Example 1, the difference is that the substrate is made of aerospace-grade mirror aluminum and left to stand for 120 seconds.

[0044] When made from aerospace mirror aluminum, such as Figure 3 As shown, the bottom layer of the microporous membrane has macropores surrounded by micropores.

[0045] Example 3:

[0046] Similar to Example 1, the difference is that polysulfone is used as the polymer, and aerospace mirror aluminum is used as the substrate, and the mixture is left to stand for 60 seconds.

[0047] When using polysulfone to form a film, such as Figure 4 As shown, the microporous membrane has uniformly sized honeycomb-shaped pores, with a pore size of 5 micrometers. The membrane was peeled off the glass surface, with the bottom layer facing upwards, for observation. Figure 5 As shown, the bottom layer of the membrane is a porous membrane, and the openings are connected to the top layer.

[0048] Comparative Example 1:

[0049] Similar to Example 1, the difference is that after standing for 30 seconds, 2 mL of polymer solution is then uniformly coated onto the glass surface.

[0050] After allowing the film to stand for 30 seconds, peel the film off the glass surface with the bottom layer facing upwards for observation. Figure 6 As shown, holes were observed in the bottom layer, but they were not penetrated.

[0051] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A polymer uniformly porous membrane, characterized in that, The top of the polymer uniformly porous membrane is a honeycomb porous membrane structure, and the bottom is one of the following: smooth and flat, with depressions, a few small pores connected to the top porous structure, or a large number of large pores connected to the top porous structure. The top pore size of the polymer uniformly porous membrane is 1 to 20 micrometers; The standard deviation of the top pore size of the polymer uniformly porous membrane is 0.09–0.11 micrometers; The coefficient of variation of the top pore size of the polymer uniformly porous membrane is 1.0 to 3.0%.

2. A method for preparing the polymer uniformly porous membrane according to claim 1, characterized in that, Includes the following steps: In an environment with a relative humidity of 50-80%, high-humidity air generated by water bubbling is sprayed onto the substrate surface, causing small droplets to condense on the substrate surface. Then, casting liquid is coated onto the substrate surface with condensed droplets, and high-humidity air generated by water bubbling is sprayed again. Under the action of lateral capillary force, the polymer uniformly porous membrane is obtained.

3. The preparation method according to claim 1, characterized in that, The casting solution is an organic solvent solution containing polymer compounds and surfactants; The polymer compound is selected from at least one of polysulfone, polylactic acid, and polymethyl methacrylate; The surfactant is selected from amphiphilic polyacrylamide copolymers; The organic solvent is selected from at least one of chloroform, dichloromethane, dichloroethane, and benzene.

4. The preparation method according to claim 2, characterized in that, The surfactant is selected from amphiphilic polyacrylamide copolymers.

5. The preparation method according to claim 2, characterized in that, The concentration of the polymer compound in the casting solution is 1–10 g / L; The surfactant is present in a mass of 5 to 20 wt% of the polymer compound.

6. The preparation method according to claim 2, characterized in that, The bubbling rate is 0.01–5 L / min; The spraying time is 1 to 10 minutes.

7. The preparation method according to claim 2, characterized in that, The temperature of the substrate is 0–30°C; The substrate is selected from at least one of glass, polypropylene film, and aerospace mirror aluminum.

8. An application of the polymer uniformly porous membrane according to claim 1, characterized in that, Used for microsphere separation, blood cell separation, or oil-water separation.

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