KR102245897B1 - Selective oxygen permeable porous polymers functionalized grid-aligned monomer embedded nanomembranes and their fabrication method - Google Patents

Abstract

The present invention relates to a selective oxygen permeable membrane for selectively permeating oxygen and excluding impurities other than oxygen and a manufacturing method thereof. The nanofiber membrane includes: a plurality of nanofibers arranged by electrospinning an electrospinning solution containing a single molecule as a starting material of the porous polymer that has a function of selectively permeating oxygen in the atmosphere and suppressing the permeation of moisture and carbon dioxide gas; and the porous polymer formed by growing the monomolecules on the surfaces of the nanofibers.

Description

A single-molecule mixed-spinning nanofiber membrane in which a selective oxygen permeable porous polymer is arranged in a functionalized grid, and its manufacturing method {SELECTIVE OXYGEN PERMEABLE POROUS POLYMERS FUNCTIONALIZED GRID-ALIGNED MONOMER EMBEDDED NANOMEMBRANES AND THEIR FABRICATION METHOD}

Existing lithium-ion secondary batteries are an important technology used in the general industry, but they do not meet the energy density requirements required for high value-added technologies. Accordingly, new systems have been proposed as alternatives to compensate for the low energy density of lithium-ion secondary batteries, and among them, lithium-air battery systems with a theoretical energy density of 1000% or more higher than that of lithium-ion secondary batteries (gasoline energy It is in the spotlight as an alternative. In particular, lithium-air batteries are attracting attention in high value-added and eco-friendly energy technologies based on their high energy density. In electric vehicle technology, which is a representative eco-friendly energy technology, lithium-ion batteries for electric vehicles are currently commercialized, but due to their low capacity, long-distance driving is subject to great restrictions. In particular, for long-distance operation of 400km or more, energy density that is 2-3 times higher than that of the currently commercialized lithium-ion battery is required, and thus the lithium-air battery system is expected as a system capable of long-distance operation of 400km or more.

The lithium-air battery is one of the batteries with the highest energy density among the next-generation energy storage systems. When discharged, oxygen and lithium ions from the outside meet to generate lithium oxide (Li ₂ O ₂ /Li ₂ O). The reaction (Oxygen reduction reaction (ORR)) and the oxygen evolution reaction (OER) in which lithium oxide is decomposed during charging must be reversibly performed. However, the actual oxygen concentration in the atmosphere is about 20%, which not only lowers the solubility and diffusion of oxygen, but also generates reaction by-products that require high overvoltage due to the penetration of impurities such as moisture, resulting in a rapid decrease in battery life and rate characteristics. -There are difficulties in commercializing air batteries. In particular, the non-decomposed lithium oxide reacts with the carbon material in _{the cathode to generate irreversible side-reactants such as Li 2} CO ₃ and LiRCO _3, and forms solid insulating particles on the surface of the cathode, inhibiting the reversible reaction of the battery and life characteristics. It acts as a very lethal factor in reducing (50 cycles or less).

Therefore, there is a need to develop a selective oxygen permeable membrane capable of preventing impurities from penetrating and selectively permeating oxygen so that oxygen can effectively participate in ORR and OER.

The lithium-air battery is a new energy storage device to replace the secondary battery. It is a battery that uses lithium metal as an active metal for the negative electrode and oxygen in the atmosphere in the presence of carbon and non-carbon-based carriers for the positive electrode. However, the conventional lithium-air battery has a problem that the possibility of commercialization is very low because it is operated only in a limited environment (high purity oxygen, non-humidified environment). Therefore, it is urgent to introduce a selective oxygen permeable membrane capable of selectively introducing only oxygen even under an actual atmosphere.

Typical conventional selective oxygen permeable membranes use polyethylene-based membranes such as LDPE (low density polyethylene) and HDPE (high density polyethylene), which are non-polar, to increase the permeability of non-polar oxygen and to prevent the permeation of polar carbon dioxide and moisture. It is a suppressive technique. In addition, there is a technology for inhibiting moisture permeation by using polymers of the PVDF (Polyvinylidene fluoride) and PVDF-HFP (Polyvinylidene fluoride-co-hexafluoropropylene) series having hydrophobic properties. In the case of a lithium-air battery incorporating such a selective oxygen permeable membrane, improved electrochemical characteristics and charge/discharge reaction characteristics were shown in an environment similar to the atmosphere. However, the conventional polymers developed above have a limitation of inhibiting oxygen permeation kinetics in the atmosphere because they do not have intrinsic pores as linear polymers and are generally manufactured in the form of membranes that do not have porosity. In addition, driving in the actual atmosphere is still producing by-products requiring a high overvoltage due to the penetration of impurities in the atmosphere such as moisture and carbon dioxide, thus revealing a limitation of lowering the reversible charge/discharge reaction.

Therefore, in order to solve the above limitations, it is based on a porous polymer that can maximize oxygen permeation with intrinsic pores and a membrane structure that can have a porosity of up to 90%, and selectively permeates only oxygen having a non-polar property. At the same time, it is essential to develop a membrane functionalized with a porous polymer capable of selective oxygen permeation based on non-polarity that can inhibit the penetration _{of polar impurities (including moisture/CO 2) contained in the atmosphere.}

The porous polymer is a high-vapor heterogeneous material in which small pores are dispersed in a polymer matrix material, and has the advantages of high surface area, high porosity, and easy pore control. Porous polymers dealt with in the present invention are amorphous porous materials that do not have crystallinity, and these are excellent in thermal/chemical stability than crystalline porous materials, and are being actively studied for use in various fields of application. For the selective oxygen permeation and impurity prevention membrane design, it is necessary to synthesize a porous polymer with a non-polar skeleton to _{increase the affinity with non-polar oxygen and to reduce the permeation kinetic of polar gases (moisture, CO 2 ).} In order to suppress the inflow of gas, a structure having a porosity similar to that of oxygen is required. Therefore, it is required to design and synthesize a covalently bonded organic structure having a neutral structure or a porous polymer having non-polar carbon as a constituent element in the atmosphere.

Currently, lithium-ion secondary batteries are commercially available and do not satisfy the energy density required for useful technologies used in the entire industry or high value-added technologies. Accordingly, various alternatives have been proposed to solve the low energy density of the lithium-ion secondary battery, and among the alternatives, a lithium-air battery having a theoretical energy density of 10 times higher than that of a lithium-ion secondary battery is emerging as an alternative. In particular, lithium-air batteries are attracting attention as eco-friendly energy technologies because they are driven by receiving oxygen from the air introduced from the outside.

However, the actual oxygen concentration in the atmosphere is only 20%, and when the lithium-air battery is operated under actual atmospheric conditions, a by-product that requires a high overvoltage is formed due to the limitation of the solubility and diffusion of oxygen and the introduction of impurities into the atmosphere. The reversible reaction of the battery is lowered, making it difficult to judge the possibility of commercialization of a lithium-air battery. In particular, the introduction of impurities (CO ₂ , moisture) into the atmosphere is a very big problem in driving a stable lithium-air battery by forming irreversible side reaction products such as _{Li 2} CO ₃ and LiRCO _{3 in driving the cathode.} In particular, since moisture (0.265 nm) and CO ₂ (0.330 nm) have a size smaller or similar to that of oxygen (0.346 nm), it selectively _{inhibits moisture and CO 2} transmission through physical and chemical methods, and oxygen transmission is possible. Research on air poles is urgent.

As a conventional technique for solving this problem, a membrane is made of a non-polar polyethylene-based polymer having a high affinity with oxygen, which is non-polar, and a PVDF-based hydrophobic polymer having a very low affinity with water due to its hydrophobic property, is used as a membrane. There is a technology that is manufactured and used by laminating it with an air electrode. However, the developed polymers are not only linear polymers without pores, but also have a problem in that the permeability of oxygen, which is a chemical reactant, is lowered because they are manufactured in the form of a membrane that does not have porosity.

Therefore, the development of an oxygen-friendly porous polymer that can increase oxygen permeability while preventing the penetration of impurities in the atmosphere, and the development of a membrane-based selective oxygen-permeable porous polymer nanofiber membrane that can effectively introduce oxygen to the anode of a lithium air battery. Silver can provide high oxygen permeability and low moisture permeability that conventional selective oxygen permeable membranes cannot provide. In particular, a nanofiber membrane formed by arranging nanofibers in a grid form provides a higher porosity per unit area than a membrane formed by randomly arranging nanofibers, thereby maximizing oxygen permeation kinetics.

The porous polymer nanofiber membrane, which is functionalized with oxygen-friendly porous polymers, uses a complex spinning solution containing single molecules in the electrospinning process, and is arranged in a grid form containing a large amount of single molecules inside and on the surface of the nanofibers. A nanofiber membrane and a method of manufacturing the same can be provided.

Through a solvent heat process in which a porous polymer is grown on a membrane in-situ, it is possible to functionalize a porous polymer with high density between individual nanofibers and on the nanofiber surface. A method of growing and binding on the fibers can be provided.

The electrospinning solution containing a single molecule, a starting material of a porous polymer that selectively permeates oxygen in the atmosphere and suppresses the permeation of moisture and carbon dioxide gas, is electrospinned to form a single axis or grid. A plurality of nanofibers formed in a structure; And the porous polymer formed by growing the single molecule on the surfaces of the plurality of nanofibers.

According to one side, the single molecule may be characterized in that molecules composed of carbon and hydrogen elements that do not have polarity are connected by covalent bonds.

According to another aspect, the porous polymer may be characterized in that it has a selective oxygen permeation function through a structure formed by crosslinking a benzene ring made of a carbon element.

According to another aspect, the porous polymer has intrinsic pores with a single molecule as a unit structure, the size of the pores is in the range of 0.5 nm to 10 nm, and a specific surface area of 1,000 cm ² /g It may be characterized by being included in the range of ~ 2,500 cm ^{2 /g.}

According to another aspect, the porous polymer is formed by growing single molecules included in each of the plurality of nanofibers in a state bound to the surface of the plurality of nanofibers through a solvent heat process. I can.

According to another aspect, the electrospinning solution contains the single molecule and the polymer, the weight ratio of the single molecule is included in the concentration range of 1 to 5% by weight relative to the total spinning solution, and the weight ratio of the polymer is a total It is included in a concentration range of 5 to 20% by weight relative to the spinning solution, and the coating density of a single molecule in the plurality of nanofibers can be adjusted according to the concentration ratio of the single molecule and the polymer.

According to another aspect, the plurality of nanofibers may be characterized in that they have hydrophobic properties in order to suppress the penetration of moisture in the atmosphere.

According to another aspect, the diameter of the plurality of nanofibers is included in the range of 50 nm to 5 μm, the diameter includes pores included in the range of 10 nm to 25 μm, and the porosity is in the range of 40 to 90%. It may be characterized by being included.

According to another aspect, the thickness of the nanofiber membrane is included in the range of 5 μm to 100 μm, and the area of the nanofiber membrane may be characterized in that it is included in the range of ^{1 cm 2} to 900 cm ^2.

A method of manufacturing a nanofiber membrane, comprising: (a) preparing an electrospinning solution in which a single molecule and a polymer are mixed; (b) synthesizing a plurality of nanofibers through alignment electrospinning with the electrospinning solution; (c) impregnating the plurality of nanofibers in a porous polymer synthesis solution to grow a single molecule contained in the plurality of nanofibers into a porous polymer through a solvent heat process; And (d) drying the plurality of nanofibers in which the porous polymer is grown to prepare a nanofiber membrane in which the porous polymer is functionalized.

According to one side, the step (b) includes: (b-1) synthesizing nanofibers aligned in one direction through alignment electrospinning combined with a double insulating block; (b-2) moving the current collector in which the nanofibers are aligned in a direction perpendicular to the alignment direction of the nanofibers; (b-3) rotating the current collector at a predetermined angle; And (b-4) repeating steps (b-2) and (b-3) a predetermined number of times.

According to another aspect, the high voltage generator for the alignment electrospinning applies a voltage included in the range of 1 to 30 kV, the discharge rate of the electrospinning solution is included in the range of 5 to 200 μl/min, and the The rotation speed of the current collector may be characterized in that it is controlled within a range of 0.5 mm/s to 40 mm/s in order to control the alignment direction and diameter of the nanofibers and the size of pores between the nanofibers.

According to another aspect, the single molecule is 1,3,5-Triphenylbenzene, 1,2,3-Triphenylbenzene, 1,3,5-Tris(4-bromophenyl)benzene, 1,3,5-Tris(4- It may be characterized in that it contains one or more single molecules selected from iodophenyl)benzene and 1,3,5-Tris(2-methylphenyl)benzene.

According to another aspect, the polymer is poly-ε-(caprolactone) (Polycaprolactone, PCL), chitosan, polyamide, polylactic acid (PLLA), polylactic acid- Glycolic acid copolymer (poly(lactic-co-glycolic acid), PLGA), polyanhydrides, polyacrylic acid, poly-N-isopropyl acrylamide, poly Vinylidene fluoride (PVDF), poly(vinylidene fluoride-co-hexafluoropropylene) (Poly(vinylidene fluoride-co-hexa fluoropropylene), Perfluoropolymer, Polyvinylchloride chloride; PVC), polyvinylidene chloride (PVDC), polyethyleneglycol dialkylether, polyethyleneglycol dialkylester, poly(oxymethylene-oligo-oxyethylene) (Poly(oxymethylene) -oligo-oxyethylene), polypropylene oxide (PPO), polyvinylacetate, poly(vinylpyrrolidone-vinylacetate) (Poly(vinylpyrrolidone-vinylacetate)), polystyrene (PS), polyacrylic Lonitrile (PAN), polymethylmethacrylate, polyamide, polyimide, poly (meta-phenylene isophthalamide) (Poly (meta-phenylene isophthalamide), polysulfone ( Polysulfone), Polyetherk etone), Polyetherimide, Polyethylene terephthalate, Polyethylene naphthalate, Polyester, Poly(1,1,2,2-tetrafluoroethylene) ), polyphosphazene, polyurethane, cellulose acetate, copolymers thereof, and mixtures thereof.

According to another aspect, the solvent included in the electrospinning solution is formic acid, acetic acid, phosphoric acid, sulfuric acid, m-cresol, thifluoroacet and hydride/dichloromethane. Phosphorus, water, N-methylmorpholine N-oxide, chloroform, tetrahydrofuran and aliphatic ketone group methyl isobutyl ketone, methyl ethyl ketone, aliphatic hydroxyl group m-butyl alcohol, isobutyl alcohol, isopropyl alcohol, methyl Alcohol, ethanol, aliphatic compounds such as hexane, tetrachloroethylene, acetone, propylene glycol, diethylene glycol, ethylene glycol as a glycol group, trichloroethylene, dichloromethane as a halogen compound group, toluene and xylene as an aromatic compound group, As alicyclic compound group, cyclohexanone, cyclohexane and ester group as n-butyl acetate, ethyl acetate, aliphatic ether group as butyl cellosalb, acetate 2-ethoxyethanol, 2-ethoxyethanol, amide as dimethylformamide , Dimethylacetamide, and mixtures thereof.

According to another aspect, the method of manufacturing the nanofiber membrane includes controlling the thickness and porosity of the nanofiber membrane by adjusting the alignment electrospinning process time in the range of 10 minutes to 24 hours in the step (b). It can be characterized by that.

According to another aspect, the step (c) is performed by controlling the pressure and temperature in the reaction system in a solvent heat process conducted in a reaction system capable of withstanding the loss and pressure of gas by heating to the boiling point of the reaction solvent. It can be characterized.

According to another aspect, the porous polymer synthesis solution is 1,3,5-Triphenylbenzene, 1,2,3-Triphenylbenzene, 1,3,5-Tris(4-bromophenyl)benzene, 1,3,5-Tris (4-iodophenyl)benzene, 1,3,5-Tris (2-methylphenyl) benzene containing one or more monomolecules selected from, and containing a Lewis acid for accelerating the Diels alder reaction as a catalyst, It may be characterized in that it contains a complex synthetic solution containing dichloromethane and chloroform as a solvent.

According to another aspect, in the step (c), the molar ratio of the single molecule contained in the porous polymer synthesis solution is adjusted to a concentration range of 0.01M to 0.04M relative to the solvent, and the molar ratio of the catalyst for the polymer reaction is adjusted. By controlling the concentration range of 0.06M to 0.09M relative to the solvent, it may be characterized in that the coating density of the porous polymer grown on the surface of the plurality of nanofibers is adjusted according to the molar concentration ratio of the single molecule and the catalyst.

According to another aspect, in the step (c), the time of the solvent heating process is adjusted in the range of 10 minutes to 48 hours, and the temperature is adjusted in the range of 40 to 60°C, so that the surface of the plurality of nanofibers It may be characterized in that at least one of the chain length, thickness, and porosity of the porous polymer grown thereon is controlled.

According to another aspect, in the step (c), by weaving and connecting the plurality of nanofibers and a stainless steel (SUS) mesh as a support, the nanofiber membrane during the solvent heat process It may be characterized by controlling structural stability.

According to another aspect, the (c) step, (c-1) may be characterized in that it comprises the step of washing the plurality of nanofibers on which the porous polymer is grown with a solvent to wash off side-reactants and impurities. have.

According to another aspect, in the step (c-1), the number of washings is included in the range of 3 to 10 times, the volume of the solvent used for washing is included in the range of 10 to 500 mL, and the washing According to at least one of the number of times and the volume of the solvent, the residual amount of impurities and the residual amount of the catalyst and single molecule remaining without reaction may be controlled.

According to another aspect, the solvent used for washing is n-butanol, isopropanol, n-propanol, ethanol, methanol, and water. ) It may be characterized in that it contains at least two or more solvents selected from.

The porous polymer composite grid nanofiber membrane capable of selective oxygen permeation of the present invention has a grid-shaped nanofiber membrane containing a single molecule in a large amount inside and outside the nanofiber as a basic structure, and a porous polymer is placed on this structure. situ) to contain oxygen-friendly porous polymers with high density on the pores of the nanofibers and on the surface of the nanofibers, thereby selectively permeating only oxygen in the atmosphere and inhibiting the penetration of impurities such as moisture. Have. Furthermore, by growing a porous polymer on a nanofiber membrane containing a single molecule, it has the advantage that it can contain a higher amount of porous polymer at a higher density than a porous polymer grown on a general nanofiber membrane that does not contain a single molecule. You can give it an ability. In addition, the porous polymer having a very large specific surface area and a pore size of several nm can physically block impurities in the air to prevent penetration, and has a structure consisting of only carbon and hydrogen to increase the affinity with oxygen. And it has a chemical blocking ability to suppress the inflow of gases such as moisture, which are polar. In addition, the membrane in which the grid-shaped nanofibers obtained by the electrospinning method including the insulating block are aligned has excellent porosity, and thus oxygen permeability can be maximized. In addition, fabrication of a membrane according to an electrospinning technique capable of synthesizing a large area is very easy to use as a next-generation battery system. In particular, it will be a technology that solves the limitations of the conventional selective oxygen permeable membrane in the form of a linear polymer membrane without pores and enables a lithium-air battery to be driven even under an actual atmosphere.

There are several applications for the use of lithium-air batteries, but among them, by far the field of electric vehicles is being discussed. Therefore, the technology of the present invention will act as a core technology to overcome the low energy density, which is a limitation of lithium ion batteries currently applied to electric vehicles, and will become an important technology that can be used as a system for electric vehicles to go beyond gasoline vehicles. .

Furthermore, since the lithium-air battery is a system that uses air as an energy source, it is eco-friendly and can contribute to reducing environmental pollution. Through the development of technology that contributes to the commercialization of the eco-friendly lithium-air battery, it will be able to contribute to environmental protection such as prevention of global warming by reducing the generation of environmental pollution and carbon dioxide.

The accompanying drawings, which are included as part of the detailed description to aid in understanding of the present invention, provide embodiments for the present invention, and describe the technical spirit of the present invention together with the detailed description.
1 is a diagram of a selective oxygen-permeable nanofiber membrane in which a single molecule, which is a starting material of a porous polymer having a selective oxygen permeability, is mixed and spun with a polymer, and then a porous polymer is grown in situ from the single molecule in an embodiment of the present invention. It is a schematic diagram.
2 is a flow chart showing an example of a method of manufacturing a nanofiber membrane according to an embodiment of the present invention.
3 is a flow chart showing an example of a method for synthesizing nanofibers arranged in a grid in an embodiment of the present invention.
4 is a diagram showing a digital image and a scanning electron microscope image of a nanofiber membrane in which a single molecule and a polymer are mixed and spun according to an embodiment of the present invention.
5 is a diagram showing the molecular structural formula of a porous polymer according to an embodiment of the present invention.
6 is a view showing a BET specific surface area analysis result for a porous polymer according to an embodiment of the present invention.
7 is a diagram showing a pore size distribution diagram for a porous polymer according to an embodiment of the present invention.
8 is a diagram showing a digital image and a scanning electron microscope image of a nanofiber membrane in which a porous polymer is grown in situ according to an embodiment of the present invention.
9 is a view showing the oxygen permeability evaluation results of the nanofiber membrane according to an embodiment of the present invention.
10 is a view showing the result of evaluating the moisture permeability of the nanofiber membrane according to an embodiment of the present invention.

The present invention may apply various transformations and may have various embodiments. Hereinafter, specific embodiments will be described in detail based on the accompanying drawings.

In describing the present invention, when it is determined that a detailed description of a related known technology may obscure the subject matter of the present invention, a detailed description thereof will be omitted.

Terms such as first and second may be used to describe various components, but the components are not limited by the terms, and the terms are only for the purpose of distinguishing one component from other components. Is used.

Hereinafter, a selective oxygen-permeable porous polymer single-axis/grid-aligned nanofiber membrane in which a porous polymer having a selective oxygen permeability is functionalized and a method of manufacturing the same will be described in detail with reference to the accompanying drawings.

Embodiments of the present invention include a vertical woven nanofiber membrane and a porous polymer synthesis technique. At this time, the vertical woven nanofiber membrane according to an embodiment may be synthesized using electrospinning equipment including an insulating block and a rotatable conductive current collector. It is a method of uni-axially limiting the motion of the electrospinning jet by placing an insulating block-shaped material near the electrospinning nozzle and applying an electric field.The substrate is repeatedly rotated 90 degrees to form a grid of nanofibers. Can be sorted. At this time, it is possible to manufacture an orthogonal nanofiber-based membrane having a desired characteristic by controlling variables such as the type, thickness, and density of the nanofiber.

In a more specific embodiment, a plurality of one-dimensional nanofibers are arranged in a single axis/grid form using an alignment electrospinning method capable of dissolving a polymer and a single molecule in a completely soluble solvent, and adjusting the rotation speed and direction of the substrate. Having a network and growing an oxygen-friendly porous polymer in-situ through a Solvothermal process on the prepared single-axis/grid-shaped membrane, the porous polymer is contained in high density between nanofibers and on the surface of nanofibers. , It is possible to prepare a selective oxygen-permeable porous polymer uniaxial/grid aligned nanofiber membrane having a function of inhibiting the penetration of high oxygen permeability and impurities (materials other than oxygen, such as CO _{2 and moisture).} Porous polymers grown on single-molecule mixed-spinning membranes prepared by electrospinning a complex spinning solution containing a high amount of single molecules are differentiated from the conventional method of coating and growing a porous polymer on the fiber surface. High amounts of porous polymers can be incorporated between individual fibers and on the surface of the fibers. In addition, a membrane having a network in which nanofibers are aligned in a uniaxial/grid form contains more developed porosity and porosity than a membrane having a conventional disordered nanofiber network, thereby maximizing oxygen permeability. In addition, the method of growing a porous polymer on a uniaxial/grid-type nanofiber membrane has a high specific surface area and porosity, unlike a method of forming a conventional polymer membrane, and thus can have excellent oxygen permeability capability. In addition, the polymeric nanofiber membrane made of a plurality of nanofibers is a matrix having a hydrophobic property, and has a very low affinity with moisture in the atmosphere, and thus may have the ability to prevent the penetration of moisture. Furthermore, the porous polymer that forms a network through the connection between the benzene ring consisting of carbon and hydrogen atoms has a non-polar property and has excellent affinity with oxygen, while its affinity with polar gases such as moisture and carbon dioxide is very low. It may have a selective oxygen permeation capability. In addition, the non-polar porous polymer is very different from the conventional non-polar linear polymer and can have a myriad of pores per unit weight and excellent specific surface area than conventional polymers.

The nanofiber membrane in which the selective oxygen-permeable porous polymer having the above characteristics is functionalized and arranged in a uniaxial/grid form provided excellent oxygen permeability and low water permeability compared to the conventionally reported selective oxygen permeable membrane. Nanofibers arranged in a single-axis/grid form in which a selective oxygen-permeable porous polymer is functionalized through an efficient and easy electrospinning process and SOLVOTHERMAL process that can be synthesized over a large area to manufacture a selective oxygen-permeable nanofiber membrane having the above characteristics. It is characterized by implementing a membrane and a method of manufacturing the same.

According to an embodiment, a grid-shaped monomolecular mixed-spinning nanofiber membrane is synthesized through an electrospinning process having an insulating block using a composite spinning solution containing a single molecule having a non-polar property. The mixed-spinning nanofiber membrane may contain a single molecule in a high amount inside and outside the nanofiber. Such a nanofiber membrane can functionalize a porous polymer capable of selectively permeating oxygen at high density between individual nanofibers and on the surface by growing an oxygen-friendly porous polymer through an in-situ solvothermal process. In driving the air cell, it is possible to prevent impurities from penetrating and to effectively penetrate oxygen into the cathode.

The porous polymer that selectively permeates oxygen can effectively receive oxygen through control through physical/chemical methods and have the ability to exclude _{moisture and CO 2, which are impurities.} Oxygen, carbon dioxide, and moisture can be controlled through a chemical blocking method (polarity control), and other gases can be blocked by controlling pores because they have a larger physical size than these gases. The chemical blocking method may include a method of forming a membrane composed of non-polar molecules in order to increase the membrane permeation kinetics of non-polar oxygen. Contrary to non-polar oxygen, moisture and carbon dioxide are polar molecules, and when they pass through a membrane made of non-polar molecules, it becomes difficult to penetrate the membrane due to low affinity, resulting in lower moisture permeability and carbon dioxide permeability. As such, the nanofiber membrane according to the present embodiment may have a porous polymer capable of selectively permeating only oxygen, which is a chemical reactant, through a chemical/physical method.

At this time, the nanofiber membrane is synthesized through the electrospinning process of a composite spinning solution containing a single molecule consisting only of carbon and hydrogen having a non-polar property, which is the starting material of the porous polymer, so that a large amount of single molecules are transferred to the inside and outside of the nanofiber. It can be included uniformly. Here, the weight ratio of the single molecule in the nanofiber membrane may be included in the concentration range of 1 to 5% by weight relative to the total solvent, and the weight ratio of the polymer may be included in the concentration range of 5 to 20% by weight relative to the total solvent.

A single molecule including a plurality of nanofibers can be grown in-situ on the surface of a plurality of nanofibers included in the nanofiber membrane, and thus, a large amount of porous polymer between the nanofibers, In addition, it is coated on the surface of the nanofibers at high density, so that it can be stably bonded without detachment from the nanofibers. Here, the porous polymer may have a single molecule having a rigid orientation as a unit structure, and may contain pores having a size in the range of 0.5 nm to 10 nm. Pore intrinsic to such a porous polymer may act as a physical barrier. In addition, the specific surface area of the porous polymer may be included in the range of ^{1,000 cm 2} /g to 2,500 cm ^{2 /g.}

The nanofiber membrane has a shape formed by arranging a plurality of nanofibers having a one-dimensional structure in a grid form, thereby maximizing air permeability. At this time, the thickness of the nanofiber membrane may be included in the range of 5 μm to 100 μm, and the area may be included in the range of 1 cm ² to 900 cm ² . The diameter of each of the plurality of nanofibers may be included in the range of 50 nm to 5 μm, and the average diameter may include pores included in the range of 10 nm to 25 μm. At this time, the porosity of the nanofiber membrane may be included in the range of 40 to 90%.

1 is a schematic diagram of a selective oxygen-permeable nanofiber membrane in which a porous polymer is grown in situ after spinning a composite spinning solution containing a single molecule, which is a starting material of a porous polymer capable of selective oxygen permeation, according to an embodiment of the present invention. to be.

The first nanofiber membrane 101 shows the result of synthesizing a mixed solution obtained by mixing a single molecule as a starting material of a porous polymer capable of selective oxygen permeation and a polymer as a raw material for the membrane through alignment electrospinning. At this time, the single molecule is a molecule composed of carbon and hydrogen elements that do not have polarity, and includes four benzene rings, and a single molecule connected by a covalent bond may be applied. The second nanofiber membrane 102 shows the result of growing in situ a porous polymer capable of selective oxygen permeation through a solvent heat (solvothermal) process on a membrane synthesized through alignment electrospinning. At this time, the porous polymer may have a network bond in which a benzene ring having a non-polar property is crosslinked, made of a non-polar carbon element, and has excellent affinity with oxygen. Among gases, it may be a selective oxygen-permeable porous polymer having the ability to selectively transmit only oxygen. The third nanofiber membrane 103 represents a membrane in which water permeation is effectively suppressed by bonding a polyethylene (PE) film to the second nanofiber membrane.

At this time, the diameter of the polymer nanofibers is preferably included in the range of 50 nm to 5 μm. The diameter of the nanofibers can be controlled through the viscosity and boiling point of the single molecule and polymer composite solution, the size of the voltage applied to the electrospinning device, the discharge speed, and the radius of the nozzle. When the diameter of individual nanofibers is 5 μm or more, not only the pores between the fibers are significantly lowered, but also the specific surface area is small, so that the flow of external oxygen is not smooth, and the oxygen permeability may be lowered. In other words, as nanofibers having a diameter range of 50 nm ~ 5 μm are stacked in a single-axis aligned structure or a grid structure aligned structure, manufacturing a selective oxygen-permeable nanofiber membrane having structural stability while maintaining high oxygen permeability. It can be beneficial to Additionally, by adjusting the rotation speed and angle of the substrate on the conductive current collector, the discharge speed of the spinning solution, and the radius of the nozzle, the spacing between the nanofibers can be adjusted, and the pore size distribution can be adjusted in the range of 50 nm to 10 μm. have.

In addition, the amount and distribution of single molecules contained in the polymer nanofibers are very important factors. In order to grow the porous polymer in situ on the membrane at high density without uniformly and strongly desorbing, it is important to contain a high amount of single molecules evenly inside and outside the nanofibers.

2 is a flow chart showing an example of a method of manufacturing a nanofiber membrane according to an embodiment of the present invention. The manufacturing method of the nanofiber membrane according to the present embodiment includes the steps of preparing an electrospinning solution in which a single molecule and a polymer are mixed (210), and synthesizing a plurality of nanofibers through alignment electrospinning of the electrospinning solution ( 220), by impregnating a plurality of nanofibers in a porous polymer synthesis solution to grow a single molecule containing a plurality of nanofibers into a porous polymer through a solvent heat (solvothermal) process (230), and a plurality of porous polymers grown It may include a step 240 of drying the nanofibers to prepare a nanofiber membrane in which the porous polymer is functionalized.

First, in the step 210 of preparing an electrospinning solution in which a single molecule and a polymer are mixed, when preparing the spinning solution, the polymer is first dissolved in a selected solvent, and then the single molecule is added to the final electrospinning solution. It can be prepared to be evenly mixed. The weight ratio of a single molecule for forming such an electrospinning solution may be included in the concentration range of 1 to 5% by weight of the total spinning solution, and the weight ratio of the polymer is included in the concentration range of 5 to 20% by weight of the total spinning solution. I can. At this time, the coating density of the single molecule and the polymer on the membrane can be adjusted according to the ratio of the single molecule and the polymer. Here, the stirring is performed at room temperature, and sufficiently stirred within the range of 50 to 200 rpm (preferably 100 to 200 rpm) between 3 to 24 hours so that the polymer and single molecule are completely dissolved in the solvent.

Next, in the step 220 of synthesizing a plurality of nanofibers through alignment electrospinning for the electrospinning solution, the electrospinning solution prepared in step 210 is transferred to a syringe (Syringe) of an appropriate capacity, and then the syringe By applying pressure to the syringe at a constant speed using a pump, a certain amount of solution is discharged at a certain time. The nanofiber membrane manufactured through this may have a shape formed by randomly intertwining a plurality of nanofibers having a one-dimensional shape, or a shape arranged in a specific direction and stacked. Solvents used for electrospinning are volatilized after electrospinning and are not included in the membrane. The thickness of the prepared nanofiber membrane may be included in the range of 5 μm to 100 μm, and the area may be included in the range of 1 cm ² to 900 cm ² . More specifically, a voltage in the range of 1 to 30 kV is applied through a high voltage application device, the discharge rate of the electrospinning solution is adjusted in the range of 5 to 200 μl/min, and the rotation speed of the current collector is 0.5 mm/s to By adjusting within the range of 40 mm/s, the alignment direction and diameter of the nanofibers and the pore size between the fibers can be controlled. In addition, the thickness and porosity of the membrane may be controlled by adjusting the electrospinning process time in the range of 10 minutes to 24 hours. A specific method for making the nanofibers aligned in a specific direction to have a stacked shape will be described in more detail later with reference to FIG. 3.

Next, in step 230, the process of increasing the structural stability of the membrane by weaving the nanofiber membrane and the support, SUS (stainless steel) mesh, and heating to the boiling point of the reaction solvent to reduce the loss of gas and pressure. It may include a solvent heat process that proceeds within a durable reaction system that can withstand. The reaction time of the solvate process may be adjusted within the range of 10 minutes to 48 hours, and the temperature of the solvate process may be adjusted within the range of 40 to 60°C. According to the control of the reaction time and temperature, at least one of the chain length, thickness, and porosity of the porous polymer grown on the surface of the nanofiber may be adjusted.

In addition, in step 230, the nanofiber membrane in which the porous polymer has been grown in situ may be washed. The number of washings may be adjusted within the range of 3 to 10 times, and the volume of the solvent used for washing may be adjusted within the range of 10 to 500 mL. At this time, it is possible to adjust the residual amounts of impurities and catalysts and single molecules remaining without reaction according to the volume of the solvent and the number of washings. The solvent used for washing is at least two of n-butanol, isopropanol, n-propanol, ethanol, methanol, and water. Can include.

Next, step 240 may be a process of drying the washed nanofiber membrane. At this time, the washing solvent is evaporated and dried for about 2 hours at a boiling point of disappearance, and the solvent used for washing is completely evaporated to prepare a nanofiber membrane functionalized with a porous polymer.

A PE film may be bonded to the prepared nanofiber membrane through thermocompression. For example, it is preferable to perform thermocompression bonding in a temperature range between 100° C. and 300° C.

3 is a flow chart showing an example of a method for synthesizing nanofibers arranged in a grid in an embodiment of the present invention. The method for synthesizing the nanofibers arranged in a grid according to the present embodiment includes the step of synthesizing the nanofibers 310 aligned in one direction through alignment electrospinning combined with a double insulating block (310), a current collector in which the nanofibers are aligned. Step 320 of moving the nanofibers in a direction perpendicular to the alignment direction of each other, repeating the steps 330 and 320 and 330 of rotating the current collector at a predetermined angle a predetermined number of times. Step 340 may be included.

In step 310, the double insulating block may transform the electric field so that the nanofibers are aligned in a specific direction. For example, the double insulating block may be formed of a material having a relative dielectric constant of 50 or less. As a more specific example, the double insulation block may be formed of one or more materials selected from the group consisting of a styrofoam material, a Teflon material, a wood material, a plastic material, a glass material, a quartz material, a silicon oxide material, and a metal material. At this time, if the current collector is moved in a direction perpendicular to the alignment direction of the nanofibers in step 320, the nanofibers may be aligned parallel to each other and parallel to the current collector. In addition, as the current collector is rotated at a predetermined angle (eg, 90 degrees) in step 330, the nanofibers formed thereafter may be stacked orthogonally to the previously formed nanofibers. Accordingly, like the first nanofiber membrane 101 of FIG. 1, a grid-shaped nanofiber membrane may be formed.

Hereinafter, the present invention will be described in detail through examples. The examples are for illustrative purposes only, and the present invention is not limited to the following examples, and it is obvious to those skilled in the art that various changes and modifications can be made within the scope and spirit of the present invention. It is natural to fall within the scope of this appended claim.

Example 1: Synthesis of a single-axis/grid-aligned nanofiber membrane functionalized with a porous polymer capable of selective oxygen permeation

In order to synthesize a uniaxial/grid-aligned nanofiber membrane in which a porous polymer capable of selective oxygen permeation is bonded, a method of manufacturing a nanofiber membrane described below and above with reference to FIG. 2 may be performed.

4 is a diagram showing a digital image and a scanning electron microscope image of a nanofiber membrane in which a single molecule and a polymer are mixed and spun according to an embodiment of the present invention. 4 shows a digital image showing a nanofiber membrane formed by mixing and spinning a single molecule and a polymer, and a scanning electron microscope image showing the appearance of a nanofiber embedded with a single molecule. The monomolecule that becomes the starting material of the porous polymer is a molecule composed of non-polar carbon and hydrogen elements and contains four benzene rings, and the monomolecule that is connected by covalent bonds is mixed with the polymer and radiated through a scanning electron microscope image. As shown, single molecules can be contained in high amounts inside and outside the nanofibers.

5 is a view showing the molecular structural formula of a porous polymer according to an embodiment of the present invention, Figure 6 is a view showing the BET specific surface area analysis result of the porous polymer according to an embodiment of the present invention, Figure 7 Is a diagram showing a pore size distribution for a porous polymer according to an embodiment of the present invention. FIG. 5 shows the molecular structural formula of a porous polymer having a high affinity with oxygen because it exhibits a nonpolar property in which four benzene rings made of porous carbon and hydrogen elements are connected. In addition, FIG. 6 shows the high specific surface area of the porous polymer, and FIG. 7 shows that the porous polymer has ultra-fine pores corresponding to a size of 1.25 nm. This means that it is possible to provide a porous polymer having a high selective oxygen permeability through a myriad of pores and ultrafine pores.

8 is a diagram showing a digital image and a scanning electron microscope image of a nanofiber membrane in which a porous polymer is grown in situ according to an embodiment of the present invention. The scanning electron microscope image of FIG. 8 shows a state in which the porous polymer is uniformly bound between individual nanofibers and on the surface of the nanofibers at high density. In the porous polymer synthesis solution, the molar ratio of the single molecule is adjusted within the concentration range of 0.01M to 0.04M relative to the solvent, and the ratio of the catalyst for the polymer reaction is adjusted within the concentration range of 0.06M to 0.09M relative to the solvent. It can be synthesized, and the coating density of the porous polymer in the nanofiber membrane can be adjusted according to the ratio of the single molecule and the polymer. In particular, when comparing the digital image of FIG. 4 with the digital image of FIG. 8, the surface color of the nanofiber membrane shown in the digital image of FIG. 4 is white, whereas the surface color of the nanofiber membrane shown in the digital image of FIG. 8 is yellow. You can see that it stands out. This may mean that a porous polymer is grown at a high density on the nanofiber membrane.

Experimental Example 1: Evaluation of oxygen permeability characteristics of a single-axis/grid aligned nanofiber membrane functionalized with a porous polymer capable of selective oxygen permeation

9 is a view showing the oxygen permeability evaluation results of the nanofiber membrane according to an embodiment of the present invention. The oxygen permeability for about 20 hours for the nanofiber membrane prepared according to the embodiment of the present invention was measured using an OX-TRAN Model 2/21 device, and as a result, it corresponds to ^{about 2,968 cm 3} /(m ^{2 day)} The oxygen permeability value was derived.

Experimental Example 2: Evaluation of water permeability characteristics of a single-axis/grid aligned nanofiber membrane functionalized with a porous polymer capable of selective oxygen permeation

10 is a view showing the result of evaluating the moisture permeability of the nanofiber membrane according to an embodiment of the present invention. The moisture permeability for about 24 hours for the nanofiber membrane prepared according to the embodiment of the present invention was measured using a Permatran-W 3/33 MA instrument, and as a result, a moisture permeability corresponding to ^{about 7 g/(m 2 day)} Values were derived.

The above description is merely illustrative of the technical idea of the present invention, and those of ordinary skill in the art to which the present invention pertains will be able to make various modifications and variations without departing from the essential characteristics of the present invention. Therefore, the embodiments described in the present invention are not intended to limit the technical idea of the present invention, but to explain it, and are not limited to these embodiments. The scope of protection of the present invention should be interpreted by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

Claims (23)

The electrospinning solution containing a single molecule, a starting material of a porous polymer that selectively permeates oxygen in the atmosphere and suppresses the permeation of moisture and carbon dioxide gas, is electrospinned to form a single axis or grid. A plurality of nanofibers formed in a structure; And
The porous polymer formed by growing the single molecule on the surfaces of the plurality of nanofibers
Nanofiber membrane comprising a. The method of claim 1,
The single molecule is a nanofiber membrane, characterized in that molecules composed of non-polar carbon and hydrogen elements are covalently linked, and thus have a selective oxygen permeation function through a structure formed by crosslinking benzene rings. . The method of claim 1,
The porous polymer has intrinsic pores with a single molecule as a unit structure,
The pore size is included in the range of 0.5 nm to 10 nm,
Those with a specific surface area in the range of 1,000 cm ² /g to 2,500 cm ² /g
Nanofiber membrane, characterized in that. The method of claim 1,
The porous polymer is formed by growing single molecules included in each of the plurality of nanofibers in a state bound to the surface of the plurality of nanofibers through a solvent heat process. The method of claim 1,
The electrospinning solution contains the single molecule and the polymer,
The weight ratio of the single molecule is included in the concentration range of 1 to 5% by weight relative to the total spinning solution,
The weight ratio of the polymer is included in the concentration range of 5 to 20% by weight relative to the total spinning solution,
Nanofiber membrane, characterized in that it is possible to adjust the coating density of the single molecule in the plurality of nanofibers according to the concentration ratio of the single molecule and the polymer. The method of claim 1,
The nanofiber membrane, characterized in that the plurality of nanofibers have hydrophobic properties in order to suppress the penetration of moisture in the atmosphere. The method of claim 1,
The diameter of the plurality of nanofibers is included in the range of 50 nm to 5 μm,
It contains pores whose diameter is in the range of 10 nm to 25 μm,
Porosity is included in the range of 40 to 90%
Nanofiber membrane, characterized in that. The method of claim 1,
The thickness of the nanofiber membrane is included in the range of 5 μm to 100 μm,
The area of the nanofiber membrane is included in the range of ^{1 cm 2} ~ 900 cm ²
Nanofiber membrane, characterized in that. In the manufacturing method of the nanofiber membrane,
(a) preparing an electrospinning solution in which a single molecule and a polymer are mixed;
(b) synthesizing a plurality of nanofibers through alignment electrospinning with the electrospinning solution;
(c) impregnating the plurality of nanofibers in a porous polymer synthesis solution to grow a single molecule contained in the plurality of nanofibers into a porous polymer through a solvent heat process; And
(d) drying the plurality of nanofibers on which the porous polymer is grown to prepare a nanofiber membrane functionalized with the porous polymer
Method for producing a nanofiber membrane comprising a. The method of claim 9,
The step (b),
(b-1) synthesizing nanofibers aligned in one direction through alignment electrospinning combined with a double insulating block;
(b-2) moving the current collector in which the nanofibers are aligned in a direction perpendicular to the alignment direction of the nanofibers;
(b-3) rotating the current collector at a predetermined angle; And
(b-4) repeating steps (b-2) and (b-3) a predetermined number of times
Method for producing a nanofiber membrane comprising a. The method of claim 10,
The high voltage generator for the alignment electrospinning applies a voltage included in the range of 1 to 30 kV,
The discharge rate of the electrospinning solution is included in the range of 5 to 200 μl/min,
The rotation speed of the current collector is controlled within the range of 0.5 mm/s to 40 mm/s in order to control the alignment direction and diameter of the nanofibers and the size of pores between the nanofibers.
Method for producing a nanofiber membrane, characterized in that. The method of claim 10,
The single molecule is 1,3,5-Triphenylbenzene, 1,2,3-Triphenylbenzene, 1,3,5-Tris(4-bromophenyl)benzene, 1,3,5-Tris(4-iodophenyl)benzene, 1, 3,5-Tris (2-methylphenyl) benzene method of manufacturing a nanofiber membrane, characterized in that it contains at least one single molecule selected from. The method of claim 9,
The polymer is poly-ε-(caprolactone) (Polycaprolactone, PCL), chitosan, polyamide, polylactic acid (PLLA), polylactic acid-glycolic acid copolymer (poly( lactic-co-glycolic acid), PLGA), polyanhydrides, polyacrylic acid, poly-N-isopropyl acrylamide, polyvinylidene fluoride; PVDF), poly(vinylidene fluoride-co-hexafluoropropylene), perfluoropolymer, polyvinyl chloride (PVC), poly Vinylidene chloride (PVDC), polyethyleneglycol dialkylether, polyethyleneglycol dialkylester, poly(oxymethylene-oligo-oxyethylene) (Poly(oxymethylene-oligo-oxyethylene), Polypropylene oxide (PPO), polyvinylacetate, poly(vinylpyrrolidone-vinylacetate) (Poly(vinylpyrrolidone-vinylacetate)), polystyrene (PS), polyacrylonitrile (PAN), Polymethylmethacrylate, Polyamide, Polyimide, Poly(meta-phenylene isophthalamide) (Poly(meta-phenylene isophthalamide), Polysulfone, Polyetherketone) (Polyetherketone), polyether Polyetherimide, polyethylene terephthalate, polyethylene naphthalate, polyester, polytetrafluoroethylene (Poly(1,1,2,2-tetrafluoroethylene)), polyphosphazene (Polyphosphazene), polyurethane (Polyurethane), cellulose acetate (Cellulose acetate), copolymers thereof, including one or more polymers selected from the group consisting of mixtures thereof
Method for producing a nanofiber membrane, characterized in that. The method of claim 9,
The solvent contained in the electrospinning solution is formic acid, acetic acid, phosphoric acid, sulfuric acid, m-cresol, thifluoroacet and hydride/dichloromethane, water, N- Methylmorpholine N-oxide, chloroform, tetrahydrofuran and aliphatic ketone group methyl isobutyl ketone, methyl ethyl ketone, aliphatic hydroxyl group m-butyl alcohol, isobutyl alcohol, isopropyl alcohol, methyl alcohol, ethanol, aliphatic compounds Phosphorus hexane, tetrachloroethylene, acetone, propylene glycol as a glycol group, diethylene glycol, ethylene glycol, trichloroethylene as a halogen compound group, dichloromethane, toluene as an aromatic compound group, xylene, cyclone as an alicyclic compound group Hexanone, cyclohexane and ester group as n-butyl acetate, ethyl acetate, aliphatic ether group as butyl cellosalb, acetic acid 2-ethoxyethanol, 2-ethoxy ethanol, amide as dimethylformamide, dimethylacetamide and these Containing one or more solvents selected from the group consisting of mixtures of
Method for producing a nanofiber membrane, characterized in that. The method of claim 9,
The method of manufacturing a nanofiber membrane, characterized in that the thickness and porosity of the nanofiber membrane are controlled by adjusting the process time of the alignment electrospinning in the range of 10 minutes to 24 hours in the step (b). The method of claim 9,
The step (c),
A method of manufacturing a nanofiber membrane, characterized in that in a solvent heat process conducted in a reaction system capable of withstanding the loss of gas and pressure by heating to the boiling point of the reaction solvent, by controlling the pressure and temperature in the reaction system. The method of claim 9,
The porous polymer synthesis solution,
1,3,5-Triphenylbenzene, 1,2,3-Triphenylbenzene, 1,3,5-Tris(4-bromophenyl)benzene, 1,3,5-Tris(4-iodophenyl)benzene, 1,3,5- Contains one or more monomolecules selected from Tris(2-methylphenyl)benzene,
A Lewis acid for accelerating the Diels alder reaction is included as a catalyst,
Containing a complex synthetic solution containing dichloromethane and chloroform as a solvent
Method for producing a nanofiber membrane, characterized in that. The method of claim 9,
The step (c),
The molar ratio of the single molecule contained in the porous polymer synthesis solution was adjusted to a concentration range of 0.01M to 0.04M relative to the solvent, and the molar ratio of the catalyst for the polymer reaction was adjusted to a concentration range of 0.06M to 0.09M relative to the solvent. , The method of manufacturing a nanofiber membrane, characterized in that controlling the coating density of the porous polymer grown on the surface of the plurality of nanofibers according to the ratio of the molar concentration of the single molecule and the catalyst. The method of claim 9,
The step (c),
The length, thickness, and pores of the porous polymer grown on the surface of the plurality of nanofibers by controlling the time of the solvent heat process in the range of 10 minutes to 48 hours and the temperature in the range of 40 to 60°C A method of manufacturing a nanofiber membrane, characterized in that at least one of the drawings is controlled. The method of claim 9,
The step (c),
The method of manufacturing a nanofiber membrane, wherein structural stability of the nanofiber membrane is controlled during the solvent heat process by weaving and connecting the plurality of nanofibers and the SUS mesh as a support. The method of claim 9,
The step (c),
(c-1) washing the plurality of nanofibers on which the porous polymer is grown with a solvent to wash off side reactants and impurities
Method for producing a nanofiber membrane comprising a. The method of claim 21,
In step (c-1),
The number of washings is included in the range of 3 to 10 times,
The volume of the solvent used for washing is included in the range of 10 to 500 mL,
The method of manufacturing a nanofiber membrane, wherein the residual amount of impurities and the residual amount of the catalyst and single molecule remaining without reaction are controlled according to at least one of the number of washings and the volume of the solvent. The method of claim 21,
The solvent used for the washing is at least two selected from n-butanol, isopropanol, n-propanol, ethanol, methanol, and water. Method for producing a nanofiber membrane, characterized in that it contains more than one kind of solvent.

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