JANUS membrane as well as preparation method and application thereof

Abstract

The invention provides a JANUS membrane which comprises a hydrophobic layer, and the hydrophobic layer is made of a hydrophobic polymer; the hydrophilic layer is formed by modifying a hydrophobic polymer through a water-soluble pore-foaming agent, and the hydrophobic polymer of the hydrophilic layer is the same as the hydrophobic polymer of the hydrophobic layer. The liquid one-way permeability of the Janus membrane is effectively improved, reverse osmosis is avoided, the interlayer binding force of the membrane can be remarkably improved, device forming and processing of the Janus membrane are facilitated, and the one-way moisture guiding performance and integrity can be effectively maintained in the long-term matched use process of the Janus membrane device.

Description

Technical Field

[0001] The present invention relates to a membrane material and a preparation method thereof, and particularly to a Janus membrane, a preparation method and an application thereof, belonging to the technical field of materials science. Background Art

[0002] At present, the preparation methods of filter membranes for industrialization mainly include the phase inversion method, the nuclear track etching method and the mechanical stretching method. Among them, in the process of preparing membranes by the phase inversion method, there are many factors affecting the accuracy of the filter membrane, a large amount of scientific research work, and great difficulty in accuracy control; the filter membrane prepared by the nuclear track etching method has high accuracy and is easy to control, but there is an accidental phenomenon of connected pores, resulting in uneven pore size distribution and affecting the filtration effect. If you want to avoid this situation, you need to control the amount of bombarding particles, the porosity of the membrane is limited, the liquid unidirectional permeability is poor, and the nuclear pore membrane has certain radioactivity, which will endanger the health of patients; the filter membrane prepared by the mechanical stretching method also has great difficulty in accuracy control, uneven pore size distribution, unstable interception and filtration performance, poor integrity, and the raw material can only use high polymers with moderate molecular weight and medium number of long chains, and the industrialization is difficult.

[0003] CN101837247B prepared a filter membrane by combining the phase conversion method of a polyvinylidene fluoride membrane and the membrane material composite technology. This method has the advantages of large flow rate, good biocompatibility and chemical compatibility, and hydrophilicity. However, the pore size of the membrane is not sufficient to filter pathogenic microorganisms such as bacteria, so the prepared membrane material cannot meet the stringent requirements of medical or edible products for the microbial content. CN101766959B irradiated a thin film with high-energy sulfur ions, and after forming a columnar damage area, a small-pore nuclear pore filter membrane was prepared by means of ultraviolet irradiation, aging, ultrasonic etching, etc. This method is simple, low-cost, can be widely popularized and industrialized, but the preparation period is long, the parameters are difficult to directly migrate to other membrane substrate systems, and there are deficiencies in the performance such as the porosity of the prepared membrane is limited and the liquid unidirectional permeability is poor. CN107059251B describes a preparation method of a unidirectional moisture-conducting nanofiber multi-layer composite membrane with a wetting gradient. By using polymer macromolecules with different wettabilities, a nanofiber membrane composed of three layers, namely a hydrophilic layer, a diversion layer and a hydrophobic layer, is mainly prepared by layer-by-layer electrospinning. Although it has good unidirectional moisture-conducting ability, due to the poor bonding force between its layers, it is easy to delaminate, shed chips and has poor membrane integrity during the device forming process or long-term use, which are not conducive to the processing and use of the final device. Summary of the Invention

[0004] The purpose of the present invention is to provide a Janus membrane for the problems of safety, durability and device processing of existing fiber membranes. This membrane has a two-layer structure, which can not only improve the interfacial bonding force of the membrane but also improve the liquid permeation unidirectionality of the membrane. The present invention also discloses a method for preparing the Janus membrane of the present invention by an electrospinning process.

[0005] The first aspect of the present invention provides a Janus membrane, comprising a hydrophobic layer made of a hydrophobic polymer; and a hydrophilic layer formed by modifying the hydrophobic polymer with a water-soluble pore-forming agent, wherein the hydrophobic polymer of the hydrophilic layer is the same as that of the hydrophobic layer.

[0006] Among them, the Janus membrane of the present invention can not only significantly improve the bonding force between the membrane layers, thus significantly improving the forming and processing difficulty of the device and its long-term durability, but also significantly increase the hydrostatic breakthrough pressure difference on both sides of the membrane, which is beneficial to the unidirectional diffusion of liquids, further improving the unidirectional liquid permeability of the membrane and avoiding liquid backflow.

[0007] In some embodiments, the hydrophobic polymer is selected from any one or more of polycaprolactone (PCL), polyurethane (PU), or polyvinylidene fluoride (PVDF).

[0008] In some embodiments, the hydrophobic polymer is polyurethane (PU) or polyvinylidene fluoride (PVDF).

[0009] In some embodiments, the hydrophobic polymer is selected from any one or more of polycaprolactone (PCL), polyurethane (PU), polyvinylidene fluoride (PVDF), and polyimide (PI).

[0010] In a specific embodiment, the hydrophobic polymer is polycaprolactone (PCL), polyurethane (PU), or polyimide (PI).

[0011] In a specific embodiment, the hydrophobic polymer is polyurethane (PU).

[0012] In some embodiments, the water-soluble pore-forming agent is selected from water-soluble polymer pore-forming substances or water-soluble salt pore-forming substances.

[0013] In some embodiments, the water-soluble salt pore-forming substance is any one or more of sodium chloride, potassium chloride, or potassium sulfate.

[0014] In some embodiments, the water-soluble polymer pore-forming substance is any one or more of gelatin, polyvinylpyrrolidone, or polyethylene glycol, preferably polyvinylpyrrolidone.

[0015] In some embodiments, the thickness of the hydrophilic layer is 20 - 60 μm. In a specific embodiment, the thickness of the hydrophilic layer is 20 - 50 μm or 30 - 50 μm. In a preferred embodiment, the thickness of the hydrophilic layer is 20 μm, 30 μm, 40 μm, 50 μm, or 60 μm.

[0016] In some embodiments, the thickness of the hydrophobic layer is 10 - 40 μm. In certain embodiments, the thickness of the hydrophobic layer is 10 - 30 μm, 10 - 20 μm, 20 - 30 μm, or 20 - 40 μm. In preferred embodiments, the thickness of the hydrophobic layer is 10 μm, 20 μm, 30 μm, or 40 μm.

[0017] In some embodiments, the thickness of the hydrophilic layer is not less than the thickness of the hydrophobic layer. The thickness of the hydrophilic layer is 1 - 5 times, 1 - 4 times, 1 - 3 times, 1 - 2.5 times, 1 - 2 times, or 1 - 1.5 times the thickness of the hydrophobic layer. In preferred embodiments, the thickness of the hydrophilic layer is 1 time, 1.5 times, 2 times, 2.5 times, or 5 times the thickness of the hydrophobic layer.

[0018] In some embodiments, the thickness of the hydrophobic layer is not less than the thickness of the hydrophilic layer. In certain embodiments, the thickness ratio of the hydrophobic layer to the hydrophilic layer is 1:1 - 2:1 or 1:1 - 3:2. In preferred embodiments, the thickness ratio of the hydrophobic layer to the hydrophilic layer is 1:1, 4:2, or 3:2.

[0019] In some embodiments, the hydrostatic breakthrough pressure of the hydrophobic surface of the membrane is greater than the hydrostatic breakthrough pressure of the hydrophilic surface. In certain embodiments, the hydrostatic breakthrough pressure of the hydrophobic surface of the membrane is 5 cm - 30 cm, and the hydrostatic breakthrough pressure of the hydrophilic surface is 2 cm - 26 cm. In certain embodiments, the hydrostatic breakthrough pressure of the hydrophobic surface of the membrane is 5 cm - 23 cm, and the hydrostatic breakthrough pressure of the hydrophilic surface is 2 cm - 15 cm. In certain embodiments, the hydrostatic breakthrough pressure of the hydrophobic surface of the membrane is 5 cm - 20 cm, and the hydrostatic breakthrough pressure of the hydrophilic surface is 2 cm - 9 cm. In certain embodiments, the hydrostatic breakthrough pressure of the hydrophobic surface of the membrane is 7 cm - 13 cm, and the hydrostatic breakthrough pressure of the hydrophilic surface is 2 cm - 4 cm. In certain embodiments, the hydrostatic breakthrough pressure of the hydrophobic surface of the membrane is 7 cm - 9 cm, and the hydrostatic breakthrough pressure of the hydrophilic surface is 2 cm - 4 cm.

[0020] In a second aspect, the present invention also provides a preparation process for a Janus membrane. The hydrophobic layer spinning solution and the hydrophilic layer spinning solution are sequentially electrospun and stacked into a membrane by the layer-by-layer spinning method, which specifically includes the following steps:

[0021] S1: A homogeneous solution formed by dissolving a hydrophobic polymer in an organic solvent is obtained to get the hydrophobic layer spinning solution;

[0022] S2: A homogeneous solution formed by blending a hydrophobic polymer and a water-soluble pore-forming agent and dissolving them in an organic solvent is obtained to get the hydrophilic layer spinning solution;

[0023] S3: The hydrophobic layer spinning solution and the hydrophilic layer spinning solution are sequentially electrospun and stacked into a membrane by the layer-by-layer spinning method;

[0024] S4: Immerse the membrane in water to remove the water-soluble pore-forming agent in the hydrophilic layer, rinse and dry it to obtain the Janus membrane.

[0025] In the present invention, the hydrophilic layer formed by electrospinning the homogeneous solution formed by blending a hydrophobic polymer and a water-soluble pore-forming agent and dissolving them in an organic solvent on the hydrophobic layer not only has a large specific surface area, but also the formed holes are all open pores, with a high porosity, a small mass transfer resistance, a concentrated pore size, increased hydrophilicity, and better unidirectional water permeability. Moreover, the inventors also found that due to the common organic solvent between the hydrophilic layer spinning solution and the hydrophobic layer spinning solution, the compatibility between the two layers is effectively improved, and the polymer molecular chains of the spinning entangle at the interface layer during the electrospinning process, enhancing their binding force.

[0026] In each embodiment, the concentration of the hydrophobic material in the hydrophobic spinning solution is 5% - 15%. In a specific embodiment, the mass concentration of the hydrophobic material is 5% - 12% or 5 - 10%. In a preferred embodiment, the mass concentration of the hydrophobic material is 5%, 7%, 8%, 10%, 12% or 15%.

[0027] In each embodiment, in the homogeneous solution formed by blending the hydrophobic polymer and the water-soluble pore-forming agent and dissolving them in an organic solvent, the mass ratio of the hydrophobic polymer to the water-soluble pore-forming agent is 1:0.1 - 9. In a specific embodiment, the mass ratio of the hydrophobic polymer to the water-soluble pore-forming agent is 1:0.1 - 5, 1:0.5 - 3, 1:0.5 - 2 or 1:0.1 - 1. In a preferred embodiment, the mass ratio of the hydrophobic polymer to the water-soluble pore-forming agent is 1:0.1, 1:0.3, 1:0.5, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8 or 1:9.

[0028] In some embodiments, the mass ratio of the hydrophobic polymer to the water-soluble pore-forming agent is 1:0.1 - 1. In a specific embodiment, the mass ratio of the hydrophobic polymer to the water-soluble pore-forming agent is 1:0.3 - 1 or 0.5 - 1. In a preferred embodiment, the mass ratio of the hydrophobic polymer to the water-soluble pore-forming agent is 1:0.1, 1:0.3, 1:0.5 or 1:1.

[0029] In each embodiment, in the homogeneous solution formed by blending the hydrophobic polymer and the water-soluble pore-forming agent and dissolving them in an organic solvent, the solid content of the homogeneous solution is 5% - 20%. In a specific embodiment, the solid content of the homogeneous solution is 5% - 10%, 8% - 20%, 8% - 10%, 10% - 20%, 10% - 15%, or 12% - 20%. In a preferred embodiment, the solid content of the homogeneous solution is 5%, 8%, 10%, 12%, 14%, 16%, 18% or 20%.

[0030] In some embodiments, the organic solvent is selected from any one or more of N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), dichloromethane (DCM), dimethyl sulfoxide (DMSO), hexafluoroisopropanol, or tetrahydrofuran. In some embodiments, the organic solvent is N,N-dimethylformamide (DMF) or N,N-dimethylacetamide (DMAc). In some embodiments, the organic solvent is N,N-dimethylformamide (DMF).

[0031] By carefully examining conventional organic solvents such as dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), dichloromethane (DCM), hexafluoroisopropanol, or tetrahydrofuran that are suitable for the electrospinning process, it is found that when N,N-dimethylformamide (DMF) or N,N-dimethylacetamide (DMAc) is used to prepare a homogeneous spinning solution, a continuous jet can be formed, the operation is more convenient, there is no beaded structure between the fibers, and the electrospinning effect is better.

[0032] In some embodiments, the organic solvent further contains a volatile promoting substance, and the boiling point of the volatile promoting substance is lower than that of the organic solvent. In some embodiments, the volatile promoting substance is selected from any one or more of acetone, tetrahydrofuran, ethyl acetate, or dichloromethane.

[0033] In each embodiment, during the electrospinning process of the hydrophobic spinning solution, the parameters of the electrospinning are as follows: positive voltage 10 - 20 kV, negative voltage -2 kV to -0.5 kV, working distance between the needle tip and the collector 5 cm - 30 cm, spinning solution extrusion speed 0.5 mL / h - 2.0 mL / h, room temperature, and spinning time 0.5 h - 6 h.

[0034] In each embodiment, during the electrospinning process of the hydrophobic spinning solution, the parameters of the electrospinning are as follows: positive voltage 10 - 20 kV, negative voltage -0.5 kV to 2 kV, working distance between the needle tip and the collector 5 cm - 30 cm, spinning solution extrusion speed 0.5 mL / h - 2.0 mL / h, room temperature, and spinning time 0.5 h - 6 h.

[0035] Among them, in a specific embodiment, the positive voltage is 10 kV - 18 kV, 10 kV - 16 kV, 10 kV - 14 kV or 10 kV - 12 kV. In a preferred embodiment, the positive voltage is 10 kV, 11 kV, 12 kV, 13 kV, 14 kV, 15 kV, 16 kV, 17 kV, 18 kV, 19 kV or 20 kV. In a specific embodiment, the negative voltage is -2 kV to -1 kV, -1.5 kV to -0.5 kV or -1 kV to 0.5 kV. In a preferred embodiment, the negative voltage is -2 kV, -1 kV, -1.5 kV or 0.5 kV. In a specific embodiment, the negative voltage is 0.5 kV to 2 kV, 0.5 kV to 1.5 kV or 0.5 kV to 1 kV. In a preferred embodiment, the negative voltage is 2 kV, 1.5 kV, 1 kV or 0.5 kV.

[0036] In a specific embodiment, the working distance between the tip and the collector is 5 cm - 25 cm, 5 cm - 20 cm, 10 cm - 20 cm or 10 cm - 15 cm. In a preferred embodiment, the working distance between the tip and the collector is 5 cm, 8 cm, 10 cm, 12 cm, 15 cm, 18 cm, 20 cm, 23 cm, 25 cm, 28 cm or 30 cm.

[0037] In a specific embodiment, the extrusion speed of the spinning solution is 0.5 mL / h - 1.5 mL / h, 1.0 mL / h - 1.5 mL / h or 1.5 mL / h - 2.0 mL / h. In a preferred embodiment, the extrusion speed of the spinning solution is 0.5 mL / h, 1.0 mL / h, 1.5 mL / h or 2.0 mL / h. In a specific embodiment, the spinning time is 0.5 h - 5.5 h, 1.0 h - 5.5 h, 1.5 h - 5.0 h or 2.0 h - 4.0 h. In a preferred embodiment, the spinning time is 0.5 h, 1.0 h, 1.5 h, 2.0 h, 2.5 h, 3.0 h, 3.5 h, 4.0 h, 4.5 h, 5.0 h, 5.5 h or 6.0 h.

[0038] In each embodiment, during the electrospinning process of the homogeneous solution of the hydrophobic polymer and the water-soluble hydrophilic material, the parameters of the electrospinning are: positive voltage 10 kV - 20 kV, negative voltage -2 kV to -0.5 kV, the working distance between the tip and the collector is 5 cm - 30 cm, the extrusion speed of the spinning solution is 0.5 mL / h - 2.0 mL / h, room temperature, and the spinning time is 0.5 h - 6 h.

[0039] In some embodiments, during the electrospinning process of a homogeneous solution of a hydrophobic polymer and a water-soluble hydrophilic material, the parameters of the electrospinning are as follows: a positive voltage of 10 kV - 20 kV, a negative voltage of 0.5 kV to 2 kV, a working distance between the tip of the needle and the collector of 5 cm - 30 cm, an extrusion speed of the spinning solution of 0.5 mL / h - 2.0 mL / h, at room temperature, and a spinning time of 0.5 h - 6 h.

[0040] In certain embodiments, the positive voltage is 10 kV - 18 kV, 10 kV - 16 kV, 10 kV - 14 kV, or 10 kV - 12 kV. In preferred embodiments, the positive voltage is 10 kV, 11 kV, 12 kV, 13 kV, 14 kV, 15 kV, 16 kV, 17 kV, 18 kV, 19 kV, or 20 kV. In certain embodiments, the negative voltage is -0.5 - 1.5 kV, 0 - 2 kV, 0.5 - 1.5 kV, or 1 - 1.5 kV. In preferred embodiments, the negative voltage is -2 kV to -1 kV, -1.5 kV to -0.5 kV, or -1 kV to 0.5 kV. In preferred embodiments, the negative voltage is -2 kV, -1 kV, -1.5 kV, or 0.5 kV.

[0041] In certain embodiments, the negative voltage is 0 - 2 kV, 0.5 kV - 2 kV, 0.5 - 1.5 kV, 0.5 - 1.5 kV, or 1 - 1.5 kV. In preferred embodiments, the negative voltage is 1 kV to 2 kV, 0.5 kV to 1.5 kV, or 0.5 kV to 1 kV. In preferred embodiments, the negative voltage is 2 kV, 1.5 kV, 1 kV, or 0.5 kV. In certain embodiments, the working distance between the tip of the needle and the collector is 5 - 25 cm, 5 - 20 cm, 10 - 20 cm, or 10 - 15 cm. In preferred embodiments, the working distance between the tip of the needle and the collector is 5 cm, 8 cm, 10 cm, 12 cm, 15 cm, 18 cm, 20 cm, 23 cm, 25 cm, 28 cm, or 30 cm. In certain embodiments, the extrusion speed of the spinning solution is 0.5 mL / h - 1.5 mL / h, 1.0 mL / h - 1.5 mL / h, or 1.5 mL / h - 2.0 mL / h. In preferred embodiments, the extrusion speed of the spinning solution is 0.5 mL / h, 1.0 mL / h, 1.5 mL / h, or 2.0 mL / h. In certain embodiments, the spinning time is 0.5 h - 5.5 h, 1.0 h - 5.5 h, 1.5 h - 5.0 h, or 2.0 h - 4.0 h. In preferred embodiments, the spinning time is 0.5 h, 1.0 h, 1.5 h, 2.0 h, 2.5 h, 3.0 h, 3.5 h, 4.0 h, 4.5 h, 5.0 h, 5.5 h, or 6.0 h.

[0042] The third aspect of the present invention provides an antibacterial Janus membrane, which includes a hydrophobic layer made of a hydrophobic polymer, and a hydrophilic layer formed by blending the hydrophobic polymer used in the hydrophobic layer and an antibacterial hydrophobic polymer and modifying it with a water-soluble pore-forming agent.

[0043] Among them, the antibacterial hydrophobic polymer is an antibacterial polymer obtained by antibacterial modification of the same type of polymer as the hydrophobic polymer of the hydrophobic layer.

[0044] The "same type of polymer" in the present invention refers to polymers formed by the polymerization of the same or similar monomers. For example, polyurethanes prepared by the polymerization of different diols (diamines) and diisocyanates belong to the same type of polymers with a polyurethane matrix.

[0045] The antibacterial modification in the present invention is a conventional process, which can be selected from any one or more of in-situ polymerization modification process, blending antibacterial modification process, antibacterial layer coating process or graft modification process.

[0046] In some embodiments, the antibacterial modification process is an in-situ polymerization modification reaction process. In a specific embodiment, the in-situ polymerization modification reaction process is to uniformly disperse antibacterial monomers in the polymerization system during the polymerization of the hydrophobic polymer, and obtain an antibacterial hydrophobic polymer through polymerization reaction.

[0047] The antibacterial substances in the present invention are selected from at least one of quaternary ammonium salt antibacterial monomers, haloamine antibacterial monomers, guanidine antibacterial monomers, imidazole antibacterial monomers, and bronopol antibacterial monomers. In a preferred embodiment, the antibacterial substance is a bronopol antibacterial monomer.

[0048] In each embodiment, the mass ratio of the hydrophobic polymer to the antibacterial-modified hydrophobic polymer in the hydrophilic layer is 1:0.1-2. In a specific embodiment, the mass ratio is 1:0.1-1, 1:0.1-0.5, 1:0.25-1, 1:0.25-0.5, 1:0.5-2, 1:1:0.5-1.5, 1:0.5-0.1, 1:1-2 or 1:1-1.5. In a preferred embodiment, the mass ratio is 1:0.25, 1:0.5, 1:1, 1:1.5 or 1:2.

[0049] The fourth aspect of the present invention provides the application of the Janus membrane in unidirectional drainage products, and the unidirectional drainage products are selected from dressings, drainage implants, drug delivery carriers, filter materials or medical packaging materials.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] The Janus membrane provided by the present invention comprises a hydrophobic layer made of a hydrophobic polymer; and a hydrophilic layer formed from the same hydrophobic polymer modified with a water-soluble porogen. The hydrophilic layer modified with the water-soluble porogen not only has uniform pore size but also significantly greater porosity than the hydrophobic layer, facilitating water conduction. Furthermore, the significant difference in hydrostatic breakthrough pressure between the hydrophobic and hydrophilic layers facilitates unidirectional water diffusion, further enhancing the membrane's unidirectional liquid permeability and preventing reverse osmosis.

[0052] At the same time, the hydrophilic layer is made of the same hydrophobic polymer as the hydrophobic layer but modified with a water-soluble hydrophilic material. This allows the membrane to have unidirectional moisture conduction capabilities while effectively improving its compatibility with the interface of the hydrophobic layer, making the two membranes more firmly bonded and enhancing interfacial compatibility, thus preventing the hydrophilic layer from easily falling off. This not only helps in the molding and processing of the Janus membrane, but also helps in maintaining the unidirectional moisture conduction performance during long-term use with the device after molding, thereby reducing the growth of insoluble particles, which is particularly important for the safety of unidirectional drainage products.

[0053] The present invention forms a hydrophilic layer by electrostatically spinning a homogeneous solution formed by blending a hydrophobic polymer with a water-soluble porogen and dissolving it in an organic solvent on a hydrophobic layer. The hydrophilic layer not only has a large specific surface area, but also has open holes formed by overlapping, high porosity, low mass transfer resistance, and concentrated pore size, which significantly increases its hydrophilicity. In addition, after the water-soluble porogen is removed by soaking, the water-soluble porogen in the membrane is effectively prevented from falling off or dissolving into liquid products during subsequent use, causing compatibility problems with liquid products. This is particularly important for sterile products such as medicines.

[0054] During the electrospinning process, when the hydrophilic layer is deposited on the hydrophobic layer, the inventors found that the shared organic solvent of the hydrophobic polymer and the hydrophobic polymer / water-soluble porogen is conducive to more complete bonding between the hydrophilic layer and the hydrophobic layer, which is conducive to improving compatibility. This may be because the shared organic solvent can make the spinning polymer miscible in the interface layer, and after spinning, the polymer molecules are entangled with each other, thereby enhancing the binding force of the polymer at the interface.

[0055] The Janus membrane of the present invention has been subjected to tests such as bonding strength test, hydrostatic breakthrough pressure test, ink droplet diffusion test, dynamic water contact angle test, antibacterial test, and in vitro compatibility test. It was found that the Janus membrane of the present invention not only has good bonding strength and unidirectional liquid permeability to meet the requirements of unidirectional drainage product assembly, but also has the characteristics of antibacterial, antibacterial, biocompatibility and leachate, which can meet the safety requirements of unidirectional drainage products such as dressings, drainage implants, drug delivery carriers, filter materials or medical packaging materials.

[0056] Through the investigation of the hydrostatic breakthrough pressure on both sides of the membrane, it is found that although the existence of a pressure difference on both sides of the membrane is a necessary condition for the membrane to have the function of unidirectional moisture conduction, and the greater the pressure difference on both sides of the membrane, the easier it is for the membrane to have the function of unidirectional moisture conduction. However, if the hydrostatic breakthrough pressure on both sides of the membrane is too large or too small, it is likely to damage the unidirectional moisture conduction function of the membrane during normal use. For example, if the hydrostatic breakthrough pressure on both sides of the membrane is too large, the liquid cannot penetrate into the membrane whether on the hydrophobic surface or the hydrophilic surface, and the liquid moisture conduction cannot be realized; while if the hydrostatic breakthrough pressure on both sides of the membrane is too small, the liquid will completely penetrate through the membrane whether on the hydrophobic surface or the hydrophilic surface, and the unidirectionality of the membrane cannot be realized.

[0057] Through the investigation of the long-term use scenario of simulating the unidirectional drainage product on the layer bonding strength, hydrostatic breakthrough pressure, and liquid unidirectional permeability of the Janus membrane of the present invention, it is found that during the long-term use of the Janus membrane of the present invention, the performance stability such as the integrity and liquid unidirectional permeability of the membrane is significantly better than that of the existing Janus membranes with two-layer or multi-layer structures, and it is more suitable for the long-term use and safety requirements of the unidirectional drainage product. Detailed implementation manners

[0058] The following embodiments further elaborate on the technical solutions of the present invention and shall not be construed as a further limitation to the protection scope of the present invention. Based on the embodiments of the present invention, all other technical solutions obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0059] 1. Test method for the layer bonding strength of the Janus membrane

[0060] Place the Janus membrane in liquid nitrogen at -196 °C, quickly cut it short with scissors, then perform gold spraying on the cross-section, and observe the cross-section condition with SEM. If the cross-section of the membrane is a whole, it indicates good layer bonding strength.

[0061] 2. Test method for the layer strength of the Janus membrane by cyclic tensile test

[0062] Perform 20 manual cyclic tensile tests on the Janus membrane to observe the separation of each layer. If the Janus membrane still maintains a complete single-layer structure without delamination, with a clean surface and no obvious burrs, it indicates good layer bonding force.

[0063] 3. Test of the hydrostatic breakthrough pressure

[0064] Use a 70 cm long and 16 mm inner diameter tube to measure the breakthrough pressure on both sides of the fiber membrane by the height of water that can be withstood on both sides of the membrane, so as to investigate the pressure difference on both sides of the fiber membrane. The greater the pressure difference on both sides of the fiber membrane, the better the liquid unidirectional permeability of the membrane.

[0065] Among them, for the static water breakthrough pressure test of the hydrophobic surface, with the hydrophilic surface of the membrane facing upwards, water is injected using a tube with a length of 70 cm and an inner diameter of 16 mm, and the water level inside the tube that breaks through the hydrophobic surface of the membrane is measured; for the static water breakthrough pressure test of the hydrophilic surface, with the hydrophobic surface of the membrane facing upwards, water is injected using a tube with a length of 70 cm and an inner diameter of 16 mm, and the water level inside the tube that breaks through the hydrophilic surface of the membrane is measured.

[0066] 4. Bacterial retention test

[0067] Staphylococcus aureus was activated in liquid medium for 12 h, then diluted 10-fold with PBS, and the bacterial concentration was 2.87×10 7 CFU / mL. The Janus membrane was placed in a sintered glass funnel with a diameter of 20 mm (filter element G2, average pore diameter: 40 - 80 μm). The sintered glass funnel without any fabric was used as a control. 20 mL of the bacterial solution was added to each group, and then filtration was carried out. Then, the filtered bacterial solution was taken for dilution and plating, and cultured in an incubator for 18 h. The retention of bacteria was observed using a microscope.

[0068] 5. Sterilization test

[0069] Staphylococcus aureus was cultured to the logarithmic growth phase, and then diluted to 10 4 CFU / mL with sterile PBS buffer. Then, 50 mg of the Janus membrane was mixed with 1 mL of the diluted bacterial solution. The bacterial solution without the Janus membrane was used as a blank control. It was cultured in a constant temperature shaker at 37 °C for 12 h. 100 μL of the co-cultured bacterial suspension was evenly spread on an agar plate and incubated at 37 °C for 18 h. The growth of bacterial colonies on the agar plate was observed using a microscope.

[0070] 6. Cytotoxicity test

[0071] The cytotoxicity of the Janus membrane was detected by the CCK-8 method. The Janus membrane was immersed in cell culture medium, and the concentration was controlled at 2 cm 2 / mL. It was incubated in an incubator at 37 °C for 24 h, and then the extract was diluted to different ratios (0.5 cm 2 / mL, 1 cm 2 / mL, 2 cm 2 / mL) with cell culture medium. At the same time, L929 cells were seeded in a 96-well plate at a density of 0.5×10 4 cells / well and cultured for 24 h, and then incubated with the extract of the Janus membrane at different concentrations in a humidified incubator. After culturing for 24 h, the extract was aspirated, 200 μL of CCK-8 solution was added to each well, and incubated for 2 h. Finally, the cell viability was measured at an absorbance mode of 450 nm on an enzyme-linked immunosorbent assay (ELISA) reader, and the optical density was tested.

[0072] 7. Dynamic water contact angle test

[0073] The droplet method was adopted, and the water contact angle (WCA) on the surface of the nanofiber membrane was measured by a contact angle tester (Harke-SPCAX1, China), and the change of the contact angle of water droplets on the surface of different nanofiber membranes with time was observed.

[0074] 8. Ink Droplet Diffusion Experiment

[0075] 50 μL of methylene blue dye solution was respectively dropped on the hydrophilic surface and the hydrophobic surface of the Janus membrane, and the diffusion process of the ink droplets within 300 s was observed. Description of the Drawings

[0076] Figure 1 SEM images of the interlayer of the Janus membranes described in Comparative Examples 1 and 2 and Examples 1 and 2 of the present invention

[0077] Figure 2 Cyclic tensile separation diagrams of the interlayer of the Janus membranes described in Comparative Examples 1 and 2 and Examples 1 and 2 of the present invention

[0078] Figure 3 Ink droplet diffusion diagrams of the Janus membranes described in Examples 1 and 2 of the present invention

[0079] Figure 4 Dynamic water contact angle change diagrams of the Janus membranes described in Examples 1 and 2 of the present invention Detailed Description of the Invention

[0081] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. For those not specified in the following embodiments, they shall be carried out according to conventional conditions or conditions recommended by the manufacturer.

[0082]

[0083] Reagents or instruments without indicating the manufacturer are all conventional products that can be obtained through commercial purchase.

[0084] The features and properties of the present invention will be further described in detail below in conjunction with the embodiments.

[0085] Comparative Example 1:

[0086] A Janus membrane with a double-layer structure of a hydrophobic polymer polyurethane (PU) - hydrophilic material polyacrylonitrile (PAN) was selected, where the hydrophobic layer was polyurethane (PU) and the hydrophilic layer was polyacrylonitrile (PAN). The specific preparation process was as follows:

[0087] (1) Preparation of the hydrophobic layer spinning solution: 7 g of polyurethane (PU) was dissolved in 93 g of N,N-dimethylformamide (DMF) solution to prepare a homogeneous solution with a mass fraction of 7%.

[0088] (2) Preparation of the hydrophilic layer spinning solution: 10 g of polyacrylonitrile (PAN) was dissolved in 90 g of N,N-dimethylformamide (DMF) solution to prepare a homogeneous solution with a mass fraction of 10%.

[0089] (3) Preparation of the Janus membrane: Electrospinning was carried out successively with the hydrophobic layer spinning solution and the hydrophilic layer spinning solution at room temperature to obtain the Janus membrane. The positive and negative voltages were set at 13 kV and 1 kV respectively, the working distance between the needle tip and the collector was 15 cm, the extrusion speed of the spinning solution was 2.0 mL / h, and the spinning time was 3 h for both.

[0090] Comparative Example 2:

[0091] A Janus membrane with a three-layer structure was prepared using the hydrophobic polymer polyurethane (PU) and the hydrophilic material polyacrylonitrile (PAN). The hydrophobic layer was a mixture of polyurethane (PU) and polyacrylonitrile (PAN) with a mass ratio of 9:1, the middle layer was a mixture of polyurethane (PU) and polyacrylonitrile (PAN) with a mass ratio of 5:5, and the hydrophilic layer was polyacrylonitrile (PAN). The specific preparation process was as follows:

[0092] (1) Preparation of the hydrophobic layer spinning solution: 6.3 g of polyurethane (PU) and 0.7 g of polyacrylonitrile (PAN) were dissolved in 93 g of N,N-dimethylformamide (DMF) solution according to a mass ratio of 9:1 to prepare a homogeneous solution with a mass fraction of 7%.

[0093] (2) Preparation of the middle layer spinning solution: 3.5 g of polyurethane (PU) and 3.5 g of polyacrylonitrile (PAN) were dissolved in 93 g of N,N-dimethylformamide (DMF) solution according to a mass ratio of 5:5 to prepare a homogeneous solution with a mass fraction of 7%.

[0094] (3) Preparation of the hydrophilic layer spinning solution: 10 g of polyacrylonitrile (PAN) was dissolved in 90 g of N,N-dimethylformamide (DMF) solution to prepare a homogeneous solution with a mass fraction of 10%.

[0095] (4) Preparation of the Janus membrane: Electrospinning was carried out successively with the hydrophobic layer spinning solution, the middle layer spinning solution and the hydrophilic layer spinning solution at room temperature to obtain the Janus membrane. The positive and negative voltages were set at 13 kV and 1 kV respectively, the working distance between the needle tip and the collector was 15 cm, the extrusion speed of the spinning solution was 2.0 mL / h, and the spinning times were 3 h, 1 h and 2 h respectively.

[0096] Example 1

[0097] A Janus membrane with a bilayer structure is prepared from a hydrophobic polymer polyurethane (PU). It includes a hydrophobic layer made of polyurethane (PU), and a hydrophilic layer formed by modifying the polyurethane (PU) used in the hydrophobic layer with polyvinylpyrrolidone (PVP). The specific preparation process is as follows:

[0098] (1) Preparation of the hydrophobic layer spinning solution: Dissolve 7 g of polyurethane (PU) in 93 g of N,N-dimethylformamide (DMF) solution to prepare a homogeneous solution with a mass fraction of 7%.

[0099] (2) Preparation of the hydrophilic fiber layer spinning solution: Dissolve 7 g of polyurethane (PU) in 93 g of N,N-dimethylformamide (DMF) solution to prepare a homogeneous solution with a mass fraction of 7%, and then add 7 g of polyvinylpyrrolidone (PVP-K30) to form a homogeneous solution with a solid content of 13.08%.

[0100] (3) Preparation of the bilayer structure Janus membrane: Electrospinning is carried out successively with the hydrophobic layer spinning solution and the hydrophilic fiber layer spinning solution at room temperature to obtain a bilayer structure Janus membrane containing polyvinylpyrrolidone (PVP-K30) in its hydrophilic layer. Among them, the positive and negative voltages are set to 13 kV and 1 kV respectively, the working distance between the needle tip and the collector is 15 cm, the extrusion speed of the spinning solution is 2.0 mL / h, and the spinning time is 3 h.

[0101] (4) Removal of the pore-forming agent: Immerse the bilayer structure Janus membrane containing polyvinylpyrrolidone (PVP-K30) in water for 24 - 48 h, then wash off the polyvinylpyrrolidone (PVP-K30), and then rinse with deionized water and hang to dry naturally to obtain a bilayer structure Janus membrane without polyvinylpyrrolidone (PVP-K30).

[0102] Example 2

[0103] [ A Janus membrane with antibacterial function and a bilayer structure is prepared from a hydrophobic polymer polyurethane (PU, BASF polyurethane 2280A). The Janus membrane includes a hydrophobic layer made of PU, and a hydrophilic layer formed by blending the PU used in the hydrophobic layer with antibacterial PU and modifying it with polyvinylpyrrolidone (PVP-K30). The specific preparation process is as follows:

[0104] (1) Preparation of the hydrophobic layer spinning solution: Dissolve 7 g of PU in 93 g of DMF solution to prepare a homogeneous solution with a mass fraction of 7%.

[0105] (2) Preparation of the spinning solution for the hydrophilic fiber layer: 1.4 g of antibacterial PU and 5.6 g of PU were dissolved in 93 g of DMF solution to prepare a homogeneous solution with a mass fraction of 7%, and then 7 g of polyvinylpyrrolidone (PVP-K30) was added to form a homogeneous solution.

[0106] (3) Preparation of the antibacterial Janus membrane: Electrospinning was carried out successively with the hydrophobic layer spinning solution and the hydrophilic fiber layer spinning solution at room temperature to obtain an antibacterial Janus membrane containing polyvinylpyrrolidone (PVP-K30). The positive and negative voltages were set at 13 kV and 1 kV respectively, the working distance between the needle tip and the collector was 15 cm, the extrusion speed of the spinning solution was 2.0 mL / h, and the spinning time was 3 h.

[0107] (4) Removal of the pore-forming agent: The double-layer structured antibacterial Janus membrane containing polyvinylpyrrolidone (PVP-K30) was immersed in flowing water for 24 h, then polyvinylpyrrolidone (PVP-K30) was washed off, and then rinsed with deionized water and hung to dry naturally to obtain a Janus membrane without polyvinylpyrrolidone (PVP-K30).

[0108] Among them, the antibacterial polyurethane (PBU) was prepared by an in-situ polymerization modification reaction process, specifically prepared according to the antibacterial polyurethane (PBU) preparation process disclosed in the patent CN115961383A:

[0109] S1: The vacuum-dried polycaprolactone (PCL) was added to a three-necked flask, and then dehydrated under vacuum at 100 °C for 2 h. After that, 4,4'-diphenyl diisocyanate (MDI) was added and mixed for the first prepolymerization reaction for 1.5 h. After the reaction ended, an organic solution of the antibacterial substance bronopol was added at 85 °C for the second prepolymerization reaction for 0.5 h to obtain a prepolymer; in the prepolymerization reaction, the molar ratio of the two groups of OH and NCO was 1:1.05;

[0110] S2: 141.2 g of the prepolymer and 9.3 g of 1,4-butanediol (BDO) were stirred at high speed for chain extension, then poured into a tetrafluoroethylene mold, and cured at 80 °C for 12 h to carry out a curing crosslinking reaction to obtain a polyurethane material (PBU) with bulk antibacterial performance.

[0111] Example 3: Investigation of the interfacial bonding strength of the Janus membrane

[0112] In this experiment, the Janus membranes described in Comparative Example 1, Comparative Example 2, Example 1, and Example 2 were respectively placed in liquid nitrogen at -196 °C, quickly cut short with scissors, then the cross-section was sputter-coated with gold, and the cross-section condition was observed using SEM. It was found through SEM observation of the cross-section condition that as Figure 1As shown: The cross-section of the Janus membranes described in Example 1 and Example 2 is an integral whole, while the fiber density at the interface of the Janus membranes described in Comparative Example 1 and Comparative Example 2 is significantly lower than that in other places, and obvious gaps even appear at local positions.

[0113] At the same time, after the Janus membranes described in Comparative Example 1, Comparative Example 2, Example 1, and Example 2 were manually stretched in a cyclic reciprocating manner 20 times respectively, the separation situation between the membrane layers was observed. It was found that as Figure 2 shown: The Janus membranes described in Example 1 and Example 2 still remained intact, with a clean surface and no obvious burrs, while obvious delamination occurred in each layer of the Janus membranes described in Comparative Example 1 and Comparative Example 2, and obvious burrs existed on both the front and back sides of the membranes.

[0114] Through the investigation of the interfacial bonding force of the Janus membrane in this experiment, it is known that the interfacial bonding force of the Janus membrane provided by the present invention is significantly better than that of the Janus membranes described in Comparative Example 1 and Comparative Example 2, and it is more suitable for the forming process of Janus membrane appliances.

[0115] Example 4: Investigate the hydrostatic breakthrough pressure on both sides of the Janus membrane.

[0116] In this experiment, the Janus membranes described in Comparative Example 1, Comparative Example 2, Example 1, and Example 2 were subjected to hydrostatic breakthrough pressure tests. The results are shown in Table 1 below:

[0117] Table 1 Hydrostatic breakthrough pressure test results of Janus membranes

[0118] Height of water that can be withstood Comparative Example 1 Comparative Example 2 Example 1 Example 2 Hydrophobic surface (cm) 6.47 5.58 7.86 7.83 Hydrophilic surface (cm) 2.28 2.02 2.76 2.78 Difference in hydrostatic breakthrough pressure across the membrane 4.19 3.56 5.10 5.05

[0119] Through the hydrostatic breakthrough pressure test of the Janus membrane in this experiment, it is shown that the hydrostatic breakthrough pressures on both sides of the Janus membranes described in Example 1 and Example 2 are equivalent, and the difference between the two sides is significantly higher than that of the Janus membranes described in Comparative Example 1 and Comparative Example 2. Thus, it can be seen that the Janus membranes described in Example 1 and Example 2 have obvious liquid unidirectional permeability.

[0120] Example 5: Conductivity performance test of nanofiber membranes

[0121] In this experiment, through the ink droplet diffusion experiment on the Janus membranes described in Example 1 and Example 2 respectively, it was found that as Figure 3As shown: When the ink droplet lands on the hydrophilic surface of the Janus membranes described in Example 1 and Example 2, the ink droplet first spreads along the hydrophilic surface and slightly penetrates into the hydrophilic layer to form a light blue water layer. However, the overall spreading area of the ink droplet within the membrane is not large, and no ink droplet penetrates the hydrophobic surface. When the ink droplet lands on the hydrophobic surface of the Janus membranes described in Example 1 and Example 2, the ink droplet first accumulates on the hydrophobic surface and then quickly transitions to the hydrophilic layer, continuously spreading within the hydrophilic layer, leaving a trace of the ink droplet passing through on the hydrophilic surface, and no ink droplet residue remains on the hydrophobic surface.

[0122] In this experiment, the dynamic water contact angle of the Janus membranes described in Example 1 and Example 2 was also tested and it was found that the droplets showed different behaviors on the hydrophilic side and the hydrophobic side of the Janus membranes described in Example 1 and Example 2, such as Figure 4 shown: When the droplet lands on the hydrophilic surface, the contact angle of the droplet rapidly decreases, quickly adheres to the surface of the pore structure and spreads rapidly to form a liquid film, and the contact angle of the hydrophilic surface shows almost no change; while when the droplet lands on the hydrophobic surface, the droplet is quickly sucked to the surface of the hydrophilic fiber layer under the capillary action of the hydrophilic fiber layer, and the contact angle of the hydrophobic side rapidly decreases to 0 and oozes out from the surface of the hydrophilic fiber layer.

[0123] Through the test of the moisture conduction performance of the Janus membrane in this experiment, it was found that the Janus membranes described in Example 1 and Example 2 both have good one-way moisture conduction effects.

[0124] Example 6: Bacteria retention experiment

[0125] In this experiment, through the bacteria retention tests using the Janus membranes described in Example 1 and Example 2 respectively, it was found that for the bacteria solution with a concentration of 2.83×10 7 CFU / mL filtered by the sand core funnel, only 1.39% of the bacteria were retained, while for the bacteria solutions filtered by the Janus membranes described in Example 1 and Example 2 with concentrations of 35CFU / mL and 33CFU / mL respectively, the bacteria retention rates of the two exceeded 99.9999%. Thus, it can be seen that the Janus membranes described in Example 1 and Example 2 have obvious bacteria removal and filtration effects.

[0126] Example 7: Antibacterial experiment

[0127] In this experiment, the antibacterial test was carried out on the Janus membrane provided in Example 2 and it was found that after culturing the Janus membrane described in Example 2 in contact with bacteria for 12h, no bacterial colonies were observed on the plate, indicating that the antibacterial rate of the Janus membrane described in Example 2 reached more than 99.99%. Thus, it can be seen that the Janus membrane described in Example 2 has good antibacterial effects.

[0128] Example 8: Cytotoxicity test

[0129] In this experiment, the Janus membranes described in Example 1 and Example 2 were respectively subjected to cytotoxicity tests and found that the cytotoxicities of the Janus membranes described in Example 1 and Example 2 were both relatively low. At an extraction concentration of 2 cm 2 / mL, the cell viabilities were 85.42% and 83.76% respectively. The results showed that the cytotoxicities of the Janus membranes described in Example 1 and Example 2 met the requirements of the national standard "Biological Evaluation of Medical Devices - In Vitro Cytotoxicity Test" (GB / T 16886.5-2017) and the "Method for Testing the Cytotoxicity of Pharmaceutical Packaging Materials" in the 2020 Edition of the "Chinese Pharmacopoeia" - 4014.

[0130] Example 9: Influence of long-term use on the hydrostatic breakthrough pressure and one-way moisture conduction function on both sides of the membrane

[0131] In this example, the "manual cyclic stretching 20 times" method was used to simulate the long-term use scenario. After the Janus membrane described in Example 2 was manually cyclically stretched 20 times, the hydrostatic breakthrough pressure test and the ink drop diffusion test were respectively carried out to investigate the unidirectionality of the membrane and the stability of the one-way moisture conduction after 20 times of manual cyclic stretching.

[0132] Among them, the results of the hydrostatic breakthrough pressure test are shown in Table 2 below:

[0133] Table 2 Results of the hydrostatic breakthrough pressure test of the Janus membrane after repeated manual cyclic stretching

[0134]

[0135] The results of the ink drop diffusion test are as follows:

[0136] When the ink drop was dropped on the hydrophilic surface of the membrane, the ink drop first diffused along the hydrophilic surface and penetrated into the hydrophilic layer to form a light blue water layer. The overall spreading area of the ink drop in the membrane was not large, and no ink drop penetrated through the hydrophobic surface. When the ink drop was dropped on the hydrophobic surface of the membrane, the ink drop first accumulated on the hydrophobic surface, then quickly transitioned to the hydrophilic layer, and continuously diffused in the hydrophilic layer, leaving a trace of the ink drop passing through on the hydrophilic surface, and no ink drop remained on the hydrophobic surface.

[0137] The above tests showed that the long-term use of the Janus membrane described in Example 2 had no obvious influence on the hydrostatic breakthrough pressure on both sides of the membrane and the one-way moisture conduction function.

[0138] Example 10: Porosity test on both sides of the membrane

[0139] The porosity of the Janus membranes described in Example 1 and Example 2 was measured by the drainage method. First, different fiber membranes were placed in an 80 °C oven for drying and weighed regularly until the weight remained constant, which was recorded as m1. Then, the fiber membranes were immersed in ultrapure water for 24 h to allow the water to fully soak into the internal pores of the fiber membranes. After that, the fiber membranes were taken out, the surface water droplets were wiped off, and the weight was recorded as m2. Then, the fiber membranes were placed in a graduated cylinder, and a certain volume (V1) of water was added, and the liquid level height (V2) was recorded. The porosity of the fiber membrane = (m2 - m1) / (V2 - V1).

[0140] The test results are as follows:

[0141] Porosity of the hydrophobic layer Porosity of the hydrophilic layer Example 1 55.45％ 63.81％ Example 2 56.70％ 64.05％

[0142] The Janus membranes described in Example 1 and Example 2 form a wettability gradient between the layers and have a unidirectional moisture conduction effect.

[0143] Example 11:

[0144] The difference between the double-layer Janus membrane described in this example and the double-layer Janus membrane described in Example 2 is that the spinning time of the hydrophobic layer spinning solution is 1 h, and the spinning time of the hydrophilic fiber layer spinning solution is 5 h. Among them, the thickness ratio of the hydrophobic layer to the hydrophilic fiber layer of the double-layer Janus membrane described in this example is 1:5.

[0145] Example 12:

[0146] The difference between the double-layer Janus membrane described in this example and the double-layer Janus membrane described in Example 2 is that the spinning time of the hydrophobic layer spinning solution is 5 h, and the spinning time of the hydrophilic fiber layer spinning solution is 1 h. Among them, the thickness ratio of the hydrophobic layer to the hydrophilic fiber layer of the double-layer Janus membrane described in this example is 5:1.

[0147] Example 13:

[0148] The difference between the double-layer Janus membrane described in this example and the double-layer Janus membrane described in Example 2 is that the spinning time of the hydrophobic layer spinning solution is 2 h, and the spinning time of the hydrophilic fiber layer spinning solution is 4 h. Among them, the thickness ratio of the hydrophobic layer to the hydrophilic fiber layer of the double-layer Janus membrane described in this example is 2:4.

[0149] Example 14:

[0150] The difference between the double-layer Janus membrane described in this example and the double-layer Janus membrane described in Example 2 is that the spinning time of the hydrophobic layer spinning solution is 4 h, and the spinning time of the hydrophilic fiber layer spinning solution is 2 h. Among them, the thickness ratio of the hydrophobic layer to the hydrophilic fiber layer of the double-layer Janus membrane described in this example is 4:2.

[0151] Example 15:

[0152] The difference between the Janus membrane with a bilayer structure in this example and that in Example 2 lies in that the spinning time of the hydrophobic layer spinning solution is 2 h, and the spinning time of the hydrophilic fiber layer spinning solution is 3 h. Among them, the thickness ratio of the hydrophobic layer to the hydrophilic fiber layer of the Janus membrane with a bilayer structure in this example is 2:3.

[0153] Example 16:

[0154] The difference between the Janus membrane with a bilayer structure in this example and that in Example 2 lies in that the spinning time of the hydrophobic layer spinning solution is 3 h, and the spinning time of the hydrophilic fiber layer spinning solution is 2 h. Among them, the thickness ratio of the hydrophobic layer to the hydrophilic fiber layer of the Janus membrane with a bilayer structure in this example is 3:2.

[0155] Example 17:

[0156] The difference between the Janus membrane with a bilayer structure in this example and that in Example 2 lies in the preparation of the hydrophilic fiber layer spinning solution: 1.4 g of antibacterial PBU and 5.6 g of PU (BASF) are dissolved in 93 g of DMF, and then 0.7 g of PVP-K30 is added and stirred to dissolve at 60 °C to form a homogeneous solution. The dosage ratio of the hydrophobic material to the water-soluble pore-forming agent is 10:1.

[0157] Example 18:

[0158] The difference between the Janus membrane with a bilayer structure in this example and that in Example 2 lies in the preparation of the hydrophilic fiber layer spinning solution: 1.4 g of antibacterial PBU and 5.6 g of PU (BASF) are dissolved in 93 g of DMF, and then 2.1 g of PVP-K30 is added and stirred to dissolve at 60 °C to form a homogeneous solution. The dosage ratio of the hydrophobic material to the water-soluble pore-forming agent is 10:3.

[0159] Example 19:

[0160] The difference between the Janus membrane with a bilayer structure in this example and that in Example 2 lies in the preparation of the hydrophilic fiber layer spinning solution: 1.4 g of antibacterial PBU and 5.6 g of PU (BASF) are dissolved in 93 g of DMF, and then 3.5 g of PVP-K30 is added and stirred to dissolve at 60 °C to form a homogeneous solution. The dosage ratio of the hydrophobic material to the water-soluble pore-forming agent is 10:5.

[0161] Example 20:

[0162] The difference between the Janus membrane with a bilayer structure in this example and that in Example 2 lies in the preparation of the hydrophilic fiber layer spinning solution: 1.4 g of antibacterial PBU and 5.6 g of PU (BASF) are dissolved in 93 g of DMF, and then 14 g of PVP-K30 is added and stirred to dissolve at 60 °C to form a homogeneous solution. The dosage ratio of the hydrophobic material to the water-soluble pore-forming agent is 1:2.

[0163] Example 21:

[0164] The difference between this example and the double-layer Janus membrane in Example 2 lies in the preparation of the hydrophilic fiber layer spinning solution: 1.4 g of antibacterial PBU and 5.6 g of PU (BASF) are dissolved in 93 g of DMF, and then 21 g of PVP-K30 is added and stirred to dissolve at 60 °C to form a homogeneous solution. The dosage ratio of the hydrophobic material to the water-soluble pore-forming agent is 1:3.

[0165] Example 22:

[0166] A double-layer Janus membrane is prepared from a hydrophobic polymer polyvinylidene fluoride (PVDF). The Janus membrane includes a hydrophobic layer made of PVDF; and a hydrophilic layer formed by modifying the PVDF used in the hydrophobic layer with polyvinylpyrrolidone (PVP-K30). The specific preparation process is as follows:

[0167] (1) Preparation of the hydrophobic layer spinning solution: Weigh 10 g of PVDF powder into 90 g of DMF solution, stir to dissolve to form a homogeneous solution, and prepare a homogeneous solution with a mass fraction of 10%.

[0168] (2) Preparation of the hydrophilic fiber layer spinning solution: Weigh 10 g of PVDF powder into 90 g of DMF solution, and then add 10 g of PVP-K30, stir to dissolve to form a homogeneous solution.

[0169] (3) Preparation of the double-layer Janus membrane: Electrospinning is carried out successively with spinning solution A and spinning solution B at room temperature to obtain a PVDF / PVDF-PVP Janus membrane. The positive and negative voltages are set to 16 kV and 1 kV respectively, the working distance between the needle tip and the collector is 17 cm, the extrusion speed of the spinning solution is 2.0 mL / h, and the spinning time is 3 h.

[0170] (4) Removal of the pore-forming agent: The PVDF / PVDF-PVP Janus membrane is soaked in flowing water for 24 h to wash away PVP, and then rinsed with deionized water and hung to dry naturally for standby.

[0171] Example 23:

[0172] A double-layer Janus membrane is prepared from polycaprolactone (PCL). The Janus membrane includes a hydrophobic layer made of polycaprolactone; and a hydrophilic layer formed by modifying the polycaprolactone used in the hydrophobic layer with polyvinylpyrrolidone (PVP-K30). The specific preparation process is as follows:

[0173] (1) Preparation of the hydrophobic layer spinning solution: Weigh 8 g of polycaprolactone (PCL) powder into 92 g of DMF solution, stir and dissolve to form a homogeneous solution, and prepare a homogeneous solution with a mass fraction of 8%.

[0174] (2) Preparation of the hydrophilic fiber layer spinning solution: Weigh 8 g of polycaprolactone (PCL) powder into 92 g of DMF solution, and then add 8 g of PVP-K30, stir and dissolve to form a homogeneous solution.

[0175] (3) Preparation of the double-layer structure Janus membrane: Electrospinning was carried out successively with spinning solution A and spinning solution B at room temperature to obtain the PCL / PCL-PVP Janus membrane. The positive and negative voltages were set at 18 kV and 2 kV respectively, the working distance between the needle tip and the collector was 10 cm, the extrusion speed of the spinning solution was 2.0 mL / h, and the spinning time was 3 h.

[0176] (4) Removal of the pore-forming agent: Immerse the PCL / PCL-PVP Janus membrane in flowing water for 24 h to wash away PVP, then rinse with deionized water and hang to dry naturally for standby.

[0177] Example 24:

[0178] Prepare a double-layer structure Janus membrane with polyimide (PI). The Janus membrane includes a hydrophobic layer made of polycaprolactone; and a hydrophilic layer formed by modifying the polycaprolactone used in the hydrophobic layer with polyvinylpyrrolidone (PVP-K30). The specific preparation process is as follows:

[0179] (1) Preparation of the hydrophobic layer spinning solution: Weigh 8 g of polyimide (PI) powder into 92 g of DMF solution, stir and dissolve to form a homogeneous solution, and prepare a homogeneous solution with a mass fraction of 8%.

[0180] (2) Preparation of the hydrophilic fiber layer spinning solution: Weigh 8 g of polyimide (PI) powder into 92 g of DMF solution, and then add 8 g of PVP-K30, stir and dissolve to form a homogeneous solution.

[0181] (3) Preparation of the double-layer structure Janus membrane: Electrospinning was carried out successively with spinning solution A and spinning solution B at room temperature to obtain the PI / PI-PVP Janus membrane. The positive and negative voltages were set at 18 kV and 2 kV respectively, the working distance between the needle tip and the collector was 10 cm, the extrusion speed of the spinning solution was 2.0 mL / h, and the spinning time was 3 h.

[0182] (4) Removal of the pore-forming agent: Immerse the PI / PI-PVP Janus membrane in flowing water for 24 h to wash away PVP, then rinse with deionized water and hang to dry naturally for standby.

[0183] Example 25:

[0184] In this example, the "interlayer bonding force investigation method" described in Example 3, the "hydrostatic breakthrough pressure test of Janus membrane" described in Example 4, and the ink drop test described in Example 5 were carried out to test the interlayer bonding force, the hydrostatic breakthrough pressure on both sides of the membrane, and the unidirectional water vapor permeability effect of the double-layer Janus membranes prepared in Examples 12-24. The specific results are shown in the following table:

[0185] Table 3 Investigation results of the interlayer bonding force and the hydrostatic breakthrough pressure on both sides of the Janus membrane

[0186]

[0187] Table 4 Test results of the ink drop test of the Janus membrane

[0188]

[0189]

[0190] Example 26

[0191] By investigating the bacteriostatic effect of the double-layer Janus membranes prepared in Examples 12-24 through the bacteriostatic test described in the present invention, it was found that the double-layer Janus membranes prepared in Examples 12-24 all had obvious bactericidal and filtration effects.

Claims

1. A Janus membrane is composed of a hydrophobic layer and a hydrophilic layer. Among them, the hydrophobic layer is made of a hydrophobic polymer; the hydrophilic layer is made of a hydrophobic polymer modified by a water-soluble porogen, and the hydrophobic polymer in the hydrophilic layer is the same as the hydrophobic polymer in the hydrophobic layer.

2. The Janus membrane according to claim 1, characterized in that, The hydrophobic polymer is preferably any one or more of polycaprolactone (PCL), polyurethane (PU), polyvinylidene fluoride (PVDF), or polyimide (PI), more preferably polyurethane (PU), polycaprolactone (PCL), or polyimide (PI), and most preferably polyurethane (PU); the water-soluble porogen is a water-soluble polymer-based porogenic substance or a water-soluble salt-based porogenic substance. Among them, the water-soluble polymer-based porogenic substance is selected from any one or more of gelatin, polyvinylpyrrolidone, or polyethylene glycol; the water-soluble salt-based porogenic substance is selected from any one or more of sodium chloride, potassium chloride, or potassium sulfate.

3. The Janus membrane according to claim 1, characterized in that, The thickness of the hydrophobic layer is not less than the thickness of the hydrophilic layer. Among them, the thickness ratio of the hydrophobic layer to the hydrophilic layer is preferably 1:1 - 2:1, more preferably 1:1 - 3:2, and most preferably 1:

1.

4. The Janus membrane according to claim 1, wherein The hydrostatic breakthrough pressure of the hydrophobic surface of the membrane is 5 cm - 30 cm, and the hydrostatic breakthrough pressure of the hydrophilic surface is 2 cm - 26 cm; Furthermore, the hydrostatic breakthrough pressure of the hydrophobic surface of the membrane is 5 cm - 23 cm, and the hydrostatic breakthrough pressure of the hydrophilic surface is 2 cm - 15 cm; Still further, the hydrostatic breakthrough pressure of the hydrophobic surface of the membrane is 5 cm - 20 cm, and the hydrostatic breakthrough pressure of the hydrophilic surface is 2 cm - 9 cm; Still further, the hydrostatic breakthrough pressure of the hydrophobic surface of the membrane is 7 cm - 13 cm, and the hydrostatic breakthrough pressure of the hydrophilic surface is 2 cm - 4 cm; Still further, the hydrostatic breakthrough pressure of the hydrophobic surface of the membrane is 7 cm - 9 cm, and the hydrostatic breakthrough pressure of the hydrophilic surface is 2 cm - 4 cm.

5. An antibacterial Janus membrane, characterized in that, In the hydrophilic layer of the Janus membrane according to any one of claims 1 - 4, there is an antibacterial hydrophobic polymer, and the antibacterial hydrophobic polymer is a hydrophobic polymer obtained by antibacterial modification of the same type of polymer as the hydrophobic polymer in the hydrophobic layer.

6. The Janus membrane according to claim 5, wherein, The antibacterial modification is selected from any one or more of in-situ polymerization modification process, blending antibacterial modification process, antibacterial layer coating process, or graft modification process, and is preferably the in-situ polymerization modification process.

7. The Janus membrane according to claim 6, characterized in that, The in-situ polymerization modification process is to uniformly disperse an antibacterial monomer in a polymerization system during the polymerization of a hydrophobic polymer, and an antibacterial hydrophobic polymer is obtained through a polymerization reaction. Among them, the antibacterial substance is selected from at least one of quaternary ammonium salt-based antibacterial monomers, haloamine-based antibacterial monomers, guanidine-based antibacterial monomers, imidazole-based antibacterial monomers, and bronopol-based antibacterial monomers, and is preferably bronopol-based antibacterial monomers.

8. The Janus membrane according to claim 7, characterized in that, The dosage ratio of the hydrophobic polymer to the antibacterial hydrophobic polymer in the hydrophilic layer is preferably 1:0.1 - 2.

9. The Janus membrane according to any one of claims 1-8, characterized in that, The preparation method of the Janus membrane is to use the layer-by-layer electrospinning method to sequentially electrospin and stack the hydrophobic layer spinning solution and the hydrophilic layer spinning solution to form a membrane.

10. The Janus membrane according to claim 9, wherein, The hydrophobic layer spinning solution is a homogeneous solution formed by dissolving a hydrophobic polymer in an organic solvent, and the hydrophilic layer spinning solution is a homogeneous solution formed by blending a hydrophobic polymer with a water-soluble pore-forming agent and dissolving it in an organic solvent.

11. The Janus membrane according to claim 10, characterized in that, The organic solvent of the hydrophobic layer spinning solution is the same as that of the hydrophilic layer spinning solution, and the organic solvent is selected from any one or more of N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), dichloromethane (DCM), dimethyl sulfoxide (DMSO), hexafluoroisopropanol or tetrahydrofuran, and more preferably N,N-dimethylformamide (DMF) or N,N-dimethylacetamide (DMAc); Furthermore, the organic solvent further contains a volatilization-promoting substance, and the boiling point of the volatilization-promoting substance is lower than that of the organic solvent, and the volatilization-promoting substance is selected from any one or more of acetone, tetrahydrofuran, ethyl acetate or dichloromethane.

12. The Janus membrane according to claim 10, wherein The dosage ratio of the hydrophobic polymer to the water-soluble pore-forming agent in the hydrophilic layer spinning solution is 1:0.1-9, preferably 1:0.1-1, more preferably 1:0.3-1, more preferably 1:0.5-1, and most preferably 1:

1.

13. The Janus membrane according to claim 9, characterized in that, The preparation method specifically includes the following steps: (1) A homogeneous solution formed by dissolving a hydrophobic polymer in an organic solvent is obtained to obtain a hydrophobic spinning solution; (2) A homogeneous solution formed by blending a hydrophobic polymer with a water-soluble pore-forming agent and dissolving it in an organic solvent is obtained to obtain a hydrophilic layer spinning solution; (3) The hydrophobic layer spinning solution and the hydrophilic layer spinning solution are sequentially electrospun and laminated into a film by the layer-by-layer spinning method; (4) The film is immersed in water to remove the water-soluble pore-forming agent in the hydrophilic layer, rinsed and dried to obtain a Janus film; Among them, the concentration of the hydrophobic polymer in the hydrophobic layer spinning solution in step (1) can be 5%-15%, preferably 5-10%, more preferably 5-8%; The solid content of the hydrophilic layer spinning solution in step (2) can be 5%-20%, preferably 10%-20%, more preferably 10%-15%; the specific parameters of the electrospinning in step (3) are preferably: positive voltage 10-20 kV, negative voltage 0.5-2 kV, the working distance between the needle tip and the collector is 5 cm-30 cm, the extrusion speed of the spinning solution is 0.5 mL / h-2.0 mL / h, room temperature, and the spinning time is 0.5 h-6 h; more preferably, the positive and negative voltages are set to 13 kV and 1 kV respectively, the working distance between the needle tip and the collector is 15 cm, the extrusion speed of the spinning solution is 2.0 mL / h, room temperature, and the spinning time is 3 h.

14. Use of the Janus membrane according to any one of claims 1-13, characterized in that, The application of the Janus film in a one-way drainage product.

15. The application of the Janus membrane according to claim 14, wherein The one-way drainage product is selected from dressings, drainage implants, drug delivery carriers, filter materials or medical packaging materials.

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