Photo-crosslinked anion exchange membrane and preparation method thereof

Abstract

The present disclosure relates to a photo-crosslinked anion exchange membrane and a preparation method thereof, and relates to the technical field of anion exchange membranes. The method comprises: S10, obtaining a first polymer containing a vinyl imidazolium structure; the first polymer comprises a styrene repeating unit and a vinyl imidazolium modified styrene repeating unit in a molar ratio of (0.7~1.5):1; S20, dissolving the first polymer and a phenyl ether polymer in a mass ratio of (1~9):1 in a first organic solvent, adding a photo crosslinker and a photoinitiator, stirring for 0.5~3h, and obtaining an anion exchange membrane precursor; S30, spreading the anion exchange membrane precursor in a container for photo crosslinking reaction, and obtaining a photo crosslinked anion exchange membrane. The photo crosslinked anion exchange membrane obtained by the preparation method disclosed herein has a low swelling ratio at high temperature and has high dimensional stability.

Description

Technical Field

[0001] The present disclosure relates to the technical field of anion exchange membranes, and in particular to a photo-crosslinked anion exchange membrane and a preparation method thereof. Background Art

[0002] As a new type of power generation device, fuel cells directly convert chemical energy into electrical energy through electrochemical reactions, without being restricted by the Carnot cycle. Among them, polymer electrolyte membrane fuel cells have extremely high theoretical specific energy and can achieve zero emissions. They are one of the most important energy supply methods for future electric vehicles and portable power sources. As a key component in fuel cells, polymer electrolytes play the role of transmitting ions and isolating the anode and cathode, which directly affects the energy output and service life of the battery. Therefore, the development of polymer electrolytes with good mechanical properties and ion transmission capabilities is the focus of current research.

[0003] Polymer electrolytes are usually composed of a polymer backbone and ionic groups. Among them, proton exchange membrane fuel cells were the first to be studied and have been commercialized. Such proton exchange membranes must use precious metals as catalysts and are expensive. The anion exchange membrane electrode reaction rate is faster, and non-precious metals can be used as catalysts, which greatly reduces the cost of use. In order to ensure that the anion exchange membrane has good mechanical stability, polymers with good mechanical properties such as polystyrene (PS), polyphenylene ether (PPO), polyetheretherketone (PEEK), polyethylene glycol (PEG), and polyvinyl alcohol (PVA) are usually used as the backbone of the anion exchange membrane. Since the mobility of hydroxide in water is much lower than that of protons, it is crucial to study the ion transport mechanism and further improve the conductivity while ensuring the stability of the anion exchange membrane. The usual way to increase the conductivity of the anion exchange membrane is to increase the number of ions in the membrane, but too many ions will cause the membrane to swell excessively, resulting in a decrease in dimensional stability. In addition, different types of ionic groups will also affect the chemical stability of the anion exchange membrane. For example, traditional quaternary ammonium cations are easily degraded by Hofmann elimination or nucleophilic substitution under alkaline conditions, and the stability needs to be further improved.

[0004] Therefore, it is necessary to develop new anion exchange membranes.

[0005] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present disclosure, and therefore may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0006] The purpose of the present invention is to overcome the deficiencies of the above-mentioned prior art and provide a photo-crosslinked anion exchange membrane and a preparation method thereof, which can significantly reduce the swelling ratio of the photo-crosslinked anion exchange membrane without reducing the conductivity and improve the dimensional stability of the photo-crosslinked anion exchange membrane.

[0007] According to one aspect of the present disclosure, there is provided a method for preparing a photo-crosslinked anion exchange membrane, comprising the following steps:

[0008] S10, obtaining a first polymer containing a vinyl imidazolium structure; the first polymer comprises styrene repeating units and vinyl imidazolium-modified styrene repeating units;

[0009] The structural formula of the styrene repeating unit is:

[0010]

[0011] The structural formula of the vinyl imidazolium-modified styrene repeating unit is:

[0012]

[0013] Wherein, the molar ratio of the styrene repeating unit to the vinyl imidazolium-modified styrene repeating unit is (0.7-1.5):1;

[0014] S20, dissolving the first polymer and polyphenylene ether in a mass ratio of (1-9):1 in a first organic solvent, adding a photocrosslinking agent and a photoinitiator, and stirring for 0.5-3 hours to obtain an anion exchange membrane precursor; the structural formula of the photocrosslinking agent is:

[0015]

[0016] Wherein, R is a methylene group containing 3 to 15 carbon atoms;

[0017] S30, spread the anion exchange membrane precursor in a container and expose it to 365nm ultraviolet light for 10-30min, then o C for 12 to 48 hours to obtain a photo-crosslinked anion exchange membrane.

[0018] In an exemplary embodiment of the present disclosure, in step S20, the mass of the photocrosslinking agent is 0.5% to 20% of the mass of the first polymer.

[0019] In an exemplary embodiment of the present disclosure, in step S20, the mass of the photoinitiator is 0.1% to 10% of the mass of the first polymer.

[0020] In an exemplary embodiment of the present disclosure, in step S30, the photo-crosslinked anion exchange membrane obtained after the heat treatment is immersed in a 0.5-1 mol / L NaOH or KOH solution for 12-36 hours.

[0021] In an exemplary embodiment of the present disclosure, in step S10, obtaining a first polymer containing a vinyl imidazolium structure comprises:

[0022] S101, adding styrene and p-chloromethylstyrene to a second organic solvent to obtain a first mixed solution; wherein the mass ratio of styrene to p-chloromethylstyrene is (0.5-1):1;

[0023] S102, adding a free radical polymerization initiator to the first mixed solution, reacting for 10 to 12 hours, and then adding the free radical polymerization initiator to the first precipitant in batches to obtain a copolymer; the mass of the free radical polymerization initiator is 0.1% to 10% of the mass of the first mixed solution;

[0024] S103, dissolving the copolymer in a third organic solvent, adding vinyl imidazole, reacting at 50-80°C for 24-48 hours, and then adding the mixture to a second precipitant in batches to obtain a first polymer containing a vinyl imidazolium structure; wherein the mass ratio of the vinyl imidazole to the copolymer is (1-7):10.

[0025] In an exemplary embodiment of the present disclosure, in step S102, the free radical polymerization initiator is one or more of dibenzoyl peroxide and azobisisobutyronitrile.

[0026] In an exemplary embodiment of the present disclosure, in step S20, the photoinitiator is one or more of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, 1-hydroxycyclohexylphenyl ketone, and 2-methyl-2-(4-morpholinyl)-1-[4-(methylthio)phenyl]-1-propanone.

[0027] According to another aspect of the present disclosure, there is provided a photo-crosslinked anion exchange membrane obtained by the above-mentioned preparation method;

[0028] The photo-crosslinked anion exchange membrane comprises a second polymer and polyphenylene ether; the second polymer comprises a styrene repeating unit and a crosslinking repeating unit;

[0029] The styrene repeating unit is shown in structural formula 1:

[0030] Structural formula 1

[0031] The cross-linked repeating unit is shown in structural formula 2:

[0032] Structural formula 2

[0033] The polyphenylene ether has a phenylene ether repeating unit shown in structural formula 3:

[0034] Structural formula 3

[0035] Among them, X - Cl - or OH - .

[0036] In an exemplary embodiment of the present disclosure, the mass ratio of the second polymer to the polyphenylene ether is (1-10):1.

[0037] In an exemplary embodiment of the present disclosure, the molar ratio of the styrene repeating unit to the cross-linking repeating unit is (1.4-3.0):1.

[0038] The present invention prepares a photo-crosslinked anion exchange membrane based on polystyrene / polyphenylene ether, wherein the polystyrene main chain (the polystyrene main chain formed by the styrene repeating units and the vinyl imidazolium-modified styrene repeating units in the first polymer) undergoes a photo-crosslinking reaction through "thiol-ene" click chemistry, and a polyphenylene ether main chain with excellent mechanical properties is introduced at the same time. This anion exchange membrane can combine the advantages of both polystyrene and polyphenylene ether polymers, and the formed cross-linked structure can effectively improve the mechanical properties and alkali resistance stability of the membrane while ensuring the conductivity. The anion exchange membrane prepared by the present invention has high ion conductivity, low swelling at high temperature, and stability tested at 80°C in a 1 mol / L NaOH solution, and the conductivity can maintain 71.3% of the initial value, and has good alkali resistance, and has broad application prospects in the field of fuel cells.

[0039] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The accompanying drawings herein are incorporated into the specification and constitute a part of the specification, illustrate embodiments consistent with the present disclosure, and together with the specification are used to explain the principles of the present disclosure. Obviously, the accompanying drawings described below are only some embodiments of the present disclosure, and for ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without creative work.

[0041] Figure 1 The present invention is a flow chart of a method for preparing a photo-crosslinked anion exchange membrane in one embodiment of the present invention.

[0042] Figure 2 This is a schematic diagram of the structure of a photo-crosslinked anion exchange membrane in one embodiment of the present disclosure.

[0043] Figure 3 This is a nuclear magnetic resonance spectrum characterization diagram of the first polymer and the copolymer in one embodiment of the present disclosure.

[0044] Figure 4 This is a schematic diagram of the mechanical properties test results of a photo-crosslinked anion exchange membrane in one embodiment of the present disclosure.

[0045] Figure 5 The figure is a swelling ratio curve diagram of the photo-crosslinked anion exchange membrane at different temperatures in some embodiments of the present disclosure.

[0046] Figure 6 The conductivity curves of the photo-crosslinked anion exchange membrane at different temperatures in some embodiments of the present disclosure are shown.

[0047] Figure 7 The present invention discloses a conductivity curve of a photo-crosslinked anion exchange membrane under different alkali immersion times in one embodiment. DETAILED DESCRIPTION

[0048] Example embodiments will now be described more fully with reference to the accompanying drawings. However, the example embodiments can be implemented in a variety of forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that the present disclosure will be comprehensive and complete and fully convey the concepts of the example embodiments to those skilled in the art. The same reference numerals in the figures represent the same or similar structures, and thus their detailed description will be omitted. In addition, the drawings are only schematic illustrations of the present disclosure and are not necessarily drawn to scale.

[0049] The terms "a", "an", "the", "said" and "at least one" are used to indicate the presence of one or more elements / components / etc.; the terms "including" and "having" are used to express an open-ended inclusive meaning and mean that additional elements / components / etc. may exist in addition to the listed elements / components / etc.; the terms "first", "second" and "third" etc. are used merely as labels and are not intended to limit the quantity of their objects.

[0050] The present disclosure provides a method for preparing a photo-crosslinked anion exchange membrane. Figure 1 As shown, the following steps are included:

[0051] S10, obtaining a first polymer containing a vinyl imidazolium structure; the first polymer comprises styrene repeating units and vinyl imidazolium-modified styrene repeating units.

[0052] The structural formula of the styrene repeating unit is:

[0053]

[0054] The structural formula of the vinyl imidazolium-modified styrene repeating unit is:

[0055]

[0056] Wherein, the molar ratio of the styrene repeating unit to the vinyl imidazolium-modified styrene repeating unit is (0.7-1.5):1;

[0057] S20, dissolving the first polymer and polyphenylene ether in a mass ratio of (1-9):1 in a first organic solvent, adding a photocrosslinking agent and a photoinitiator, and stirring for 0.5-3 hours to obtain an anion exchange membrane precursor; the structural formula of the photocrosslinking agent is:

[0058]

[0059] Wherein, R is a methylene group containing 3 to 15 carbon atoms;

[0060] S30, spread the anion exchange membrane precursor in a container and expose it to 365nm ultraviolet light for 10-30min, then o C for 12 to 48 hours to obtain a photo-crosslinked anion exchange membrane.

[0061] In this embodiment, the first polymer includes a polystyrene main chain formed by styrene repeating units, and some styrene repeating units on the polystyrene main chain are modified with vinyl imidazolium to form vinyl imidazolium modified styrene repeating units. The first polymer is mixed with polyphenylene ether, and the two chain structure compounds are mixed to form a network structure. Then, a photocrosslinking reaction is carried out through "thiol-ene" click chemistry, and the photocrosslinking agent uses a dithiol compound, so that the vinyl imidazolium structure is connected through the photocrosslinking agent, thereby obtaining a more stable and dense network structure. Figure 2 As shown, along Figure 2 The lateral extension shown in the figure is polyphenylene ether A1; Figure 2 The longitudinal extension shown in the figure is the polystyrene main chain A2 of the first polymer, which can be connected by a photocrosslinking agent A3, and the polystyrene main chain A2 of the first polymer also has an imidazolium ion A4 on the styrene repeating unit. Among them, the chain structure formed by the polyphenylene ether A1 and the mesh structure formed by the polystyrene main chain A2. In this way, on the one hand, the photocrosslinking agent connects the polystyrene main chains of multiple first polymers, reduces the transitional swelling of the anion exchange membrane, and improves the dimensional stability of the anion exchange membrane. On the other hand, the polyphenylene ether has excellent mechanical properties, strong rigidity and no ions, which further reduces the swelling of the anion exchange membrane and improves the mechanical properties. In other words, the anion exchange membrane prepared by the preparation method provided in this embodiment reduces the swelling of the anion exchange membrane without affecting the conductivity, and at the same time improves the mechanical properties and alkali resistance stability of the anion exchange membrane.

[0062] In one example, the first organic solvent is an organic solvent that can dissolve the first polymer and the polyphenylene ether. The first organic solvent includes but is not limited to one or more of N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), and dimethyl sulfoxide (DMSO).

[0063] In one embodiment of the present disclosure, in step S20, the mass of the photocrosslinker is 0.5% to 20% of the mass of the first polymer. For example, the mass of the photocrosslinker is a, and the mass of the first polymer is M1, then a / M1 can be 0.5%, 1%, 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18% or 20%.

[0064] In one embodiment of the present disclosure, in step S20, the mass of the photoinitiator is 0.1% to 10% of the mass of the first polymer. For example, the mass of the photoinitiator is b, and the mass of the first polymer is M1, then b / M1 can be 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%.

[0065] In one example, in step S20, the photoinitiator is one or more of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, 1-hydroxycyclohexylphenyl ketone, and 2-methyl-2-(4-morpholinyl)-1-[4-(methylthio)phenyl]-1-propanone.

[0066] In one embodiment of the present disclosure, in step S30, the anions in the cross-linked anion exchange membrane obtained after the heat treatment are chloride ions, that is, the cross-linked anion exchange membrane obtained after the heat treatment is a chloride ion type cross-linked anion exchange membrane. As an example, the chloride ion type cross-linked anion exchange membrane obtained after the heat treatment can be used as the cross-linked anion exchange membrane prepared by the present invention.

[0067] In another embodiment of the present disclosure, in step S30, the cross-linked anion exchange membrane obtained after the heat treatment is soaked in a 0.5-1 mol / L NaOH or KOH solution for 12-36 hours. The cross-linked anion exchange membrane obtained after the heat treatment is a chloride ion cross-linked anion exchange membrane. After the chloride ion cross-linked anion exchange membrane is soaked in a solution containing hydroxide ions, part or all of the chloride ions are replaced by hydroxide ions, so that the chloride ion cross-linked anion exchange membrane is converted into a hydroxide cross-linked anion exchange membrane. In this way, in this embodiment, the cross-linked anion exchange membrane prepared by the present invention is a hydroxide cross-linked anion exchange membrane.

[0068] In one example, the photo-crosslinked anion exchange membrane provided by the present disclosure may be in the form of a chloride-type anion exchange membrane, and an alkalization treatment is performed before being used in a hydrogen fuel cell to obtain a hydroxide-type photo-crosslinked anion exchange membrane.

[0069] In one embodiment of the present disclosure, in step S10, the step of obtaining the first polymer containing a vinyl imidazolium structure comprises the following steps S101 to S103.

[0070] S101, adding styrene and p-chloromethylstyrene to a second organic solvent to obtain a first mixed solution, wherein the mass ratio of styrene to p-chloromethylstyrene is (0.5-1): 1. For example, the mass ratio of styrene to p-chloromethylstyrene may be 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1 or 1:1.

[0071] S102, adding a free radical polymerization initiator to the first mixed solution and reacting for 10 to 12 hours, and then adding the free radical polymerization initiator to the first precipitant in batches to obtain a copolymer; the mass of the free radical polymerization initiator is 0.1% to 10% of the mass of the first mixed solution. For example, the mass of the free radical polymerization initiator can be 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10% of the mass of the first mixed solution.

[0072] In this example, the copolymer includes styrene repeating units and p-chloromethylstyrene repeating units. The structural formula of the p-chloromethylstyrene repeating unit is shown below:

[0073] .

[0074] S103, dissolving the copolymer in a third organic solvent, adding vinyl imidazole, reacting at 50-80°C for 24-48 hours, and then adding the second precipitant in batches to obtain a first polymer containing a vinyl imidazole structure. The mass ratio of the vinyl imidazole to the copolymer is (1-7):10. For example, the mass ratio of the vinyl imidazole to the copolymer can be 1:10, 2:10, 3:10, 4:10, 5:10, 6:10 or 7:10.

[0075] In one example, the second organic solvent may be one or more of benzene, toluene, chlorobenzene, and xylene. The second organic solvent is used to dissolve styrene, p-chloromethylstyrene, and a free radical initiator.

[0076] In one example, the third organic solvent may be one or more of N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), and dimethyl sulfoxide (DMSO). The third organic solvent is used to dissolve the copolymer.

[0077] In one example, the first precipitant and the second precipitant may be a mixture of one or more of anhydrous methanol, anhydrous ethanol, and anhydrous ether. The first precipitant is used to precipitate the copolymer; the second precipitant is used to precipitate the first polymer.

[0078] In one embodiment of the present disclosure, in step S102, the free radical polymerization initiator is one or more of dibenzoyl peroxide and azobisisobutyronitrile.

[0079] The embodiment of the present disclosure also provides a photo-crosslinked anion exchange membrane, which is obtained by the above preparation method. The photo-crosslinked anion exchange membrane comprises a second polymer and polyphenylene ether; the second polymer comprises styrene repeating units and crosslinking repeating units.

[0080] The styrene repeating unit is shown in structural formula 1:

[0081] Structural formula 1

[0082] The cross-linked repeating unit is shown in structural formula 2:

[0083] Structural formula 2

[0084] The polyphenylene ether has a phenylene ether repeating unit shown in structural formula 3:

[0085] Structural formula 3

[0086] Among them, X - Cl - (chloride ion) or OH - (hydroxide ion), R is a methylene group containing 3 to 15 carbon atoms.

[0087] In step S10, two vinyl imidazolium modified styrene repeating units can react with a photocrosslinker to generate crosslinking repeating units whose anions are chloride ions. After the chloride ion type photocrosslinking anion exchange membrane is soaked in alkali solution, the crosslinking repeating units whose anions are chloride ions are at least partially converted into crosslinking repeating units whose anions are hydroxide ions, or crosslinking repeating units containing both chloride ions and hydroxide ions. In the click chemistry reaction process of step S10, the two vinyl imidazolium modified styrene repeating units reacting with the photocrosslinker can be located on the same polystyrene main chain or on different polystyrene main chains.

[0088] Wherein, at least part of the styrene units of the cross-linked repeating units are located on different polystyrene main chains, so that different polystyrene main chains are interconnected through the photo-crosslinking agent, thereby limiting the swelling of the photo-crosslinked anion exchange membrane.

[0089] In one embodiment of the present disclosure, the mass ratio of the second polymer to the polyphenylene ether is (1-10):1.

[0090] In one embodiment of the present disclosure, the molar ratio of the styrene repeating unit to the cross-linking repeating unit is (1.4-3.0):1.

[0091] The photo-crosslinked anion exchange membrane and the preparation method thereof provided by the present disclosure are further described below in conjunction with specific embodiments.

[0092] Example 1

[0093] Step 1, adding styrene and p-chloromethylstyrene into toluene, heating to 70° C. to dissolve, and obtaining a first mixed solution; wherein the mass ratio of styrene to p-chloromethylstyrene is 0.5:1.

[0094] Step 2: Add 2,2'-azobisisobutyronitrile to the first mixed solution and react for 10 hours. After cooling to room temperature, slowly or in batches, add the reacted solution to anhydrous ethanol, wash the precipitate several times and dry it to obtain a copolymer. The mass of 2,2'-azobisisobutyronitrile is 3% of the mass of the first mixed solution. The copolymer is characterized by nuclear magnetic resonance spectroscopy. The results are as follows: Figure 3 shown.

[0095] See also Figure 3The H NMR spectrum of the copolymer shows that the peak with a chemical shift of about 7.26 ppm is the solvent peak of deuterated chloroform; the peak with a chemical shift of about 1.55 ppm is the water peak in deuterated chloroform; the chemical shifts of peaks 1 and 2 are approximately between 6.3 and 7.1 ppm, which are the peaks of hydrogen on the benzene ring in the copolymer; the chemical shift of peak 3 is about 4.5 ppm, which is the peak of the methylene connected to chlorine in the repeating unit of p-chloromethylstyrene; the chemical shift of peak 4 is approximately between 1.6 and 1.8 ppm, which is the methylene peak after the polymerization of vinyl groups; the chemical shift of peak 5 is approximately between 1.2 and 1.5 ppm, which is the peak of hydrogen on the tertiary carbon connected to the benzene ring.

[0096] according to Figure 3 It can be seen that step 2 yields a high-purity copolymer.

[0097] Step 3, dissolving the copolymer in N-methylpyrrolidone, adding vinyl imidazole dropwise, reacting at 80°C for 24h, adding the solution after the reaction dropwise into anhydrous ethanol, washing the precipitated precipitate several times and drying it to obtain a first polymer containing a vinyl imidazole structure; wherein the mass ratio of the vinyl imidazole to the copolymer is 7:10. The first polymer containing a vinyl imidazole structure is characterized by a nuclear magnetic resonance spectrometer, and the results are as follows: Figure 3 shown.

[0098] See also Figure 3 H NMR spectrum of the first polymer.

[0099] The peak with a chemical shift of about 2.50 ppm is the solvent peak of deuterated DMSO; the peak with a chemical shift of about 3.33 ppm is the water peak in deuterated DMSO; and the peak with a chemical shift of about 2.1 ppm is the peak of acetone that has not been completely removed from the copolymer.

[0100] See also Figure 3 , peaks 7, 8, and 10 are peaks of hydrogen on imidazole; peaks 9, 11, and 12 are peaks of hydrogen on vinyl; peaks 1 and 2 are peaks on the benzene ring; peaks 3 and 6 are peaks formed by the methylene between the benzene ring and imidazole in different resonance states; peaks 4 and 5 are peaks formed by the alkyl chain on the main chain of polystyrene. This indicates that vinyl imidazole reacts with the chloromethylstyrene repeating unit in the copolymer; the first polymer has a vinyl imidazolium structure.

[0101] Step 4: After dissolving the first polymer and polyphenylene ether in a mass ratio of 9:1, add 1,8-octanedithiol and 2,4,6-trimethylbenzoylphenylphosphonic acid ethyl ester, and stir for 3 hours to obtain an anion exchange membrane precursor. The mass of 1,8-octanedithiol is 20% of the mass of the first polymer; the mass of 2,4,6-trimethylbenzoylphenylphosphonic acid ethyl ester is 10% of the mass of the first polymer.

[0102] Step 5: pour the anion exchange membrane precursor into a glass culture dish and expose it to 365 nm ultraviolet light for 10 min to perform a "thiol-ene" photocrosslinking reaction. After the photocrosslinking reaction, the glass culture dish is placed in a vacuum oven, dried at 120° C. for 12 h, and then immersed in 1 mol / L NaOH solution for 12 h. The obtained photocrosslinked anion exchange membrane is defined as anion exchange membrane 1.

[0103] The water absorption swelling ratio and conductivity of the anion exchange membrane 1 were tested, and the results were as follows: Figure 5 As shown in the figure, at 20°C, the water swelling ratio of anion exchange membrane 1 is less than 10%; at 80°C, the water swelling ratio of anion exchange membrane 1 is 26%. This indicates that anion exchange membrane 1 has low water swelling properties and good dimensional stability, thus avoiding the reduction of mechanical properties caused by swelling of the photo-crosslinked anion exchange membrane. Figure 6 As shown, at 20°C, the conductivity of anion exchange membrane 1 is close to 25 mS / cm; in an aqueous solution at 80°C, the conductivity of anion exchange membrane 1 is 71.5 mS / cm, and the conductivity is positively correlated with temperature.

[0104] Thus, at room temperature, when the conductivity of the anion exchange membrane 1 is close to 25 mS / cm, the swelling ratio is less than 10%; at 80°C, the conductivity is as high as 71.5 mS / cm, while the swelling ratio is only 26%. This indicates that the photo-crosslinked anion exchange membrane provided by the present disclosure significantly reduces the swelling property without affecting the conductivity, thereby improving the dimensional stability of the photo-crosslinked anion exchange membrane.

[0105] Mechanical properties test of anion exchange membrane 1: Take a 3×1 cm dumbbell-shaped anion exchange membrane 1 sample and test it at a clamp pulling rate of 5 mm / min. After three parallel experiments, calculate the average values ​​of tensile strength (TS) and elongation at break (Eb). The mechanical properties test results of anion exchange membrane 1 are shown in Figure 1. Figure 4 As shown, the tensile strength exceeds 34 MPa and the elongation at break exceeds 15%, indicating that the anion exchange membrane 1 has good mechanical strength.

[0106] The anion exchange membrane 1 was immersed in a 1 mol / L NaOH solution at 80°C, and the conductivity of the hydroxide-type anion exchange membrane at room temperature was measured after the membrane was taken out at different time intervals. Figure 7 As shown in the figure, after 264 h of alkaline treatment, the hydroxide conductivity can still maintain 71.3% of the initial value, indicating that the anion exchange membrane 1 has good alkaline stability.

[0107] Example 2

[0108] Step 1, adding styrene and p-chloromethylstyrene into benzene, heating to 80° C. to dissolve, and obtaining a first mixed solution; wherein the mass ratio of styrene to p-chloromethylstyrene is 0.6:1.

[0109] Step 2: Add dibenzoyl peroxide to the first mixed solution and react for 11 hours. After cooling to room temperature, slowly or in batches, add the reacted solution to anhydrous methanol, wash the precipitated precipitate several times, and dry it to obtain a copolymer. The mass of dibenzoyl peroxide is 4% of the mass of the first mixed solution.

[0110] Step 3, dissolving the copolymer in N,N-dimethylformamide, adding vinyl imidazole dropwise, reacting at 50°C for 48 hours, adding the solution after the reaction dropwise into anhydrous methanol, washing the precipitated precipitate several times and drying it to obtain a first polymer containing a vinyl imidazole structure; wherein the mass ratio of the vinyl imidazole to the copolymer is 5:10.

[0111] Step 4: After dissolving the first polymer and polyphenylene ether in a mass ratio of 8:2, add 1,3-propanedithiol and 1-hydroxycyclohexyl phenyl ketone, and stir for 2 hours to obtain an anion exchange membrane precursor. The mass of 1,3-propanedithiol is 15% of the mass of the first polymer; the mass of 1-hydroxycyclohexyl phenyl ketone is 5% of the mass of the first polymer.

[0112] Step 5: Pour the anion exchange membrane precursor into a glass culture dish and expose it to 365 nm ultraviolet light for 15 min to perform a "thiol-ene" photocrosslinking reaction. After the photocrosslinking reaction, the glass culture dish is placed in a vacuum oven, dried at 100° C. for 24 h, and then immersed in a 1 mol / L NaOH solution for 24 h. The obtained photocrosslinked anion exchange membrane is defined as anion exchange membrane 2.

[0113] See also Figure 5 and Figure 6The water absorption and swelling ratio of anion exchange membrane 2 at 80°C is 23.1%, and the hydroxyl conductivity in aqueous solution at 80°C is 65.2 mS / cm, and the conductivity change trend is positively correlated with temperature. This shows that anion exchange membrane 2 improves the dimensional stability of the photo-crosslinked anion exchange membrane without affecting the conductivity.

[0114] Example 3

[0115] Step 1, adding styrene and p-chloromethylstyrene into chlorobenzene, heating to 90° C. to dissolve, and obtaining a first mixed solution; wherein the mass ratio of styrene to p-chloromethylstyrene is 0.7:1.

[0116] Step 2: Add 2,2'-azobisisobutyronitrile to the first mixed solution and react for 12 hours. After cooling to room temperature, slowly or in batches, add the reacted solution to anhydrous ether, wash the precipitated precipitate several times, and dry it to obtain a copolymer. The mass of 2,2'-azobisisobutyronitrile is 6% of the mass of the first mixed solution.

[0117] Step 3, dissolving the copolymer in N-methylpyrrolidone, adding vinyl imidazole dropwise, reacting at 60°C for 36 hours, adding the solution after the reaction dropwise into anhydrous ether, washing the precipitated precipitate several times and drying it to obtain a first polymer containing a vinyl imidazolium structure; wherein the mass ratio of the vinyl imidazole to the copolymer is 4.5:10.

[0118] Step 4: After dissolving the first polymer and polyphenylene ether in a mass ratio of 7:3, add N, N-dimethylacetamide, add 1,4-butanedithiol and 2-methyl-2-(4-morpholinyl)-1-[4-(methylthio)phenyl]-1-propanone, and stir for 1.5 hours to obtain an anion exchange membrane precursor. The mass of 1,4-butanedithiol is 10% of the mass of the first polymer; the mass of 2-methyl-2-(4-morpholinyl)-1-[4-(methylthio)phenyl]-1-propanone is 7% of the mass of the first polymer.

[0119] Step 5: pour the anion exchange membrane precursor into a glass culture dish and expose it to 365 nm ultraviolet light for 10 min to perform a "thiol-ene" photocrosslinking reaction. After the photocrosslinking reaction, the glass culture dish is placed in a vacuum oven, dried at 70° C. for 48 h, and then immersed in 1 mol / L NaOH solution for 24 h. The obtained photocrosslinked anion exchange membrane is defined as anion exchange membrane 3.

[0120] See also Figure 5 and Figure 6The water absorption swelling ratio of anion exchange membrane 3 at 80°C is 17.3%, the hydroxyl conductivity in 80°C aqueous solution is 60.8 mS / cm, and the conductivity change trend is positively correlated with temperature. Similarly, it shows that anion exchange membrane 3 improves the dimensional stability of the photo-crosslinked anion exchange membrane without affecting the conductivity.

[0121] Example 4

[0122] Step 1, adding styrene and p-chloromethylstyrene into xylene, heating to 80° C. to dissolve, and obtaining a first mixed solution; wherein the mass ratio of styrene to p-chloromethylstyrene is 0.8:1.

[0123] Step 2: Add dibenzoyl peroxide to the first mixed solution and react for 11 hours. After cooling to room temperature, slowly or in batches, add the reacted solution to anhydrous methanol, wash the precipitated precipitate several times, and dry it to obtain a copolymer. The mass of dibenzoyl peroxide is 3% of the mass of the first mixed solution.

[0124] Step 3, dissolving the copolymer in dimethyl sulfoxide, adding vinyl imidazole dropwise, reacting at 80°C for 24 hours, adding the solution after the reaction dropwise into anhydrous ethanol, washing the precipitated precipitate several times and drying it to obtain a first polymer containing a vinyl imidazole structure; wherein the mass ratio of the vinyl imidazole to the copolymer is 2:10.

[0125] Step 4: After dissolving the first polymer and polyphenylene ether in a mass ratio of 6:4, add 1,5-pentanedithiol and 2,4,6-trimethylbenzoylphenylphosphonic acid ethyl ester, and stir for 1 hour to obtain an anion exchange membrane precursor. The mass of 1,5-pentanedithiol is 8% of the mass of the first polymer; the mass of 2,4,6-trimethylbenzoylphenylphosphonic acid ethyl ester is 3% of the mass of the first polymer.

[0126] Step 5: pour the anion exchange membrane precursor into a glass culture dish and expose it to 365 nm ultraviolet light for 15 min to perform a "thiol-ene" photocrosslinking reaction. After the photocrosslinking reaction, the glass culture dish is placed in a vacuum oven, dried at 120° C. for 12 h, and then immersed in 1 mol / L NaOH solution for 36 h. The obtained photocrosslinked anion exchange membrane is defined as anion exchange membrane 4.

[0127] See also Figure 5 and Figure 6The water absorption swelling ratio of anion exchange membrane 4 at 80°C is 13.2%, the hydroxyl conductivity in aqueous solution at 80°C is 55.3 mS / cm, and the conductivity change trend is positively correlated with temperature. This shows that anion exchange membrane 4 can improve the dimensional stability of photo-crosslinked anion exchange membrane without affecting the conductivity.

[0128] Example 5

[0129] Step 1, adding styrene and p-chloromethylstyrene into chlorobenzene, heating to 75° C. to dissolve, and obtaining a first mixed solution; wherein the mass ratio of styrene to p-chloromethylstyrene is 1:1.

[0130] Step 2: Add 2,2'-azobisisobutyronitrile to the first mixed solution and react for 12 hours. After cooling to room temperature, slowly or in batches, add the reacted solution to anhydrous ether, wash the precipitated precipitate several times, and dry it to obtain a copolymer. The mass of 2,2'-azobisisobutyronitrile is 1.5% of the mass of the first mixed solution.

[0131] Step 3, dissolving the copolymer in dimethyl sulfoxide, adding vinyl imidazole dropwise, reacting at 50°C for 48 hours, adding the solution after the reaction dropwise into anhydrous ether, washing the precipitated precipitate several times and drying it to obtain a first polymer containing a vinyl imidazole structure; wherein the mass ratio of the vinyl imidazole to the copolymer is 1:10.

[0132] Step 4: After dissolving the first polymer and polyphenylene ether in a mass ratio of 5:5, add 1,6-hexanedithiol and 1-hydroxycyclohexyl phenyl ketone, and stir for 1 hour to obtain an anion exchange membrane precursor. The mass of 1,6-hexanedithiol is 0.5% of the mass of the first polymer; the mass of 1-hydroxycyclohexyl phenyl ketone is 0.1% of the mass of the first polymer.

[0133] Step 5, pour the anion exchange membrane precursor into a glass culture dish and expose it to 365nm ultraviolet light for 30 minutes to perform a "thiol-ene" photocrosslinking reaction. After the photocrosslinking reaction, the glass culture dish is placed in a vacuum oven, dried at 100°C for 24 hours, and then immersed in 1 mol / L NaOH solution for 24 hours. The obtained photocrosslinked anion exchange membrane is defined as anion exchange membrane 5.

[0134] See also Figure 5 and Figure 6, the water absorption swelling ratio of the anion exchange membrane 5 at 80°C is 11.4%, the hydroxyl conductivity in the 80°C aqueous solution is 50.5 mS / cm, and the conductivity change trend is positively correlated with the temperature. In this embodiment, when the conductivity of the anion exchange membrane 5 is 50.5 mS / cm, the swelling ratio is only 11.4%. This shows that the anion exchange membrane 5 improves the dimensional stability of the photo-crosslinked anion exchange membrane without affecting the conductivity.

[0135] like Figure 5 and Figure 6 As shown, as the mass ratio of polyphenylene ether increases when the first polymer is mixed with polyphenylene ether, the swelling ratio of the prepared photo-crosslinked anion exchange membrane becomes lower. This is because polyphenylene ether has high rigidity and does not carry ions, thereby reducing the swelling ratio of the anion exchange membrane. At the same time, as the mass ratio of polyphenylene ether increases, the mass ratio of the corresponding first polymer decreases. For example, the conductivity of the photo-crosslinked anion exchange membrane in Example 2-Example 4 is reduced relative to Example 1. Within the mass ratio range of the first polymer to polyphenylene ether provided in the embodiment of the present disclosure, at 80°C, when the swelling ratio is 11.4%, the conductivity of the anion exchange membrane is still as high as 50.5 mS / cm. In other words, the anion exchange membrane with a mesh structure formed by the first polymer and polyphenylene ether provided in the present disclosure has both high conductivity and high dimensional stability.

[0136] It should be noted that, although the steps of the method for preparing a photo-crosslinked anion exchange membrane in the present disclosure are described in a specific order in the accompanying drawings, this does not require or imply that the steps must be performed in this specific order, or that all the steps shown must be performed to achieve the desired results. Additionally or alternatively, some steps may be omitted, multiple steps may be combined into one step, and / or one step may be decomposed into multiple steps, etc.

[0137] Those skilled in the art will readily appreciate other embodiments of the present disclosure after considering the specification and practicing the invention disclosed herein. This application is intended to cover any modifications, uses or adaptations of the present disclosure, which follow the general principles of the present disclosure and include common knowledge or customary technical means in the art that are not disclosed in the present disclosure.

Claims

1. A method for preparing a photo-crosslinked anion exchange membrane, characterized in that: The following steps are involved: S10, obtaining a first polymer containing a vinyl imidazolium structure; the first polymer comprises styrene repeating units and vinyl imidazolium-modified styrene repeating units; The structural formula of the styrene repeating unit is: ； The structural formula of the vinyl imidazolium-modified styrene repeating unit is: ； Wherein, the molar ratio of the styrene repeating unit to the vinyl imidazolium-modified styrene repeating unit is (0.7-1.5):1; S20, dissolving the first polymer and polyphenylene ether in a mass ratio of (1-9):1 in a first organic solvent, adding a photocrosslinking agent and a photoinitiator, and stirring for 0.5-3 hours to obtain an anion exchange membrane precursor; the structural formula of the photocrosslinking agent is: ； Wherein, R is a methylene group containing 3 to 15 carbon atoms; S30, spread the anion exchange membrane precursor in a container and expose it to 365nm ultraviolet light for 10-30min, then o C for 12 to 48 hours to obtain a photo-crosslinked anion exchange membrane; Wherein, in step S10, obtaining the first polymer containing a vinyl imidazolium structure comprises: S101, adding styrene and p-chloromethylstyrene to a second organic solvent to obtain a first mixed solution; wherein the mass ratio of styrene to p-chloromethylstyrene is (0.5-1):1; S102, adding a free radical polymerization initiator to the first mixed solution, reacting for 10 to 12 hours, and then adding the free radical polymerization initiator to the first precipitant in batches to obtain a copolymer; the mass of the free radical polymerization initiator is 0.1% to 10% of the mass of the first mixed solution; S103, dissolving the copolymer in a third organic solvent, adding vinyl imidazole, reacting at 50-80°C for 24-48 hours, and then adding the mixture to a second precipitant in batches to obtain a first polymer containing a vinyl imidazolium structure; wherein the mass ratio of the vinyl imidazole to the copolymer is (1-7):

10.

2. The method for preparing a photo-crosslinked anion exchange membrane according to claim 1, characterized in that: In step S20, the mass of the photocrosslinking agent is 0.5% to 20% of the mass of the first polymer.

3. The method for preparing a photo-crosslinked anion exchange membrane according to claim 1, characterized in that: In step S20, the mass of the photoinitiator is 0.1% to 10% of the mass of the first polymer.

4. The method for preparing a photo-crosslinked anion exchange membrane according to claim 1, characterized in that: In step S30, the photo-crosslinked anion exchange membrane obtained after the heat treatment is immersed in a 0.5-1 mol / L NaOH or KOH solution for 12-36 hours.

5. The method for preparing a photo-crosslinked anion exchange membrane according to claim 1, characterized in that: In step S102, the free radical polymerization initiator is one or more of dibenzoyl peroxide and azobisisobutyronitrile.

6. The method for preparing a photo-crosslinked anion exchange membrane according to claim 1, characterized in that: In step S20, the photoinitiator is one or more of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, 1-hydroxycyclohexylphenyl ketone, and 2-methyl-2-(4-morpholinyl)-1-[4-(methylthio)phenyl]-1-propanone.

7. A photo-crosslinked anion exchange membrane, characterized in that: Obtained by the preparation method according to any one of claims 1 to 6; The photo-crosslinked anion exchange membrane comprises a second polymer and polyphenylene ether; the second polymer comprises a styrene repeating unit and a crosslinking repeating unit; The styrene repeating unit is shown in structural formula 1: Structural formula 1 The cross-linked repeating unit is shown in structural formula 2: Structural formula 2 The polyphenylene ether has a phenylene ether repeating unit shown in structural formula 3: Structural formula 3 Among them, X - Cl - or OH - ; The mass ratio of the second polymer to the polyphenylene ether is (1-10): 1; The molar ratio of the styrene repeating unit to the cross-linking repeating unit is (1.4-3.0):1.

Images