Sulfonated monomer and preparation method thereof, polymer and proton exchange membrane

Abstract

The invention discloses a sulfonated monomer, a preparation method thereof, a polymer and a proton exchange membrane, and belongs to the field of organic materials. The sulfonated monomer comprises a first phenyl group, an electron withdrawing group-containing chain segment and a second phenyl group, the electron withdrawing group-containing chain segments are respectively connected to a first carbon atom of the first phenyl group and a second carbon atom of the second phenyl group; each of the first phenyl group and the second phenyl group has a fluoro group and a sulfonated group, the fluoro group in the first phenyl group is in meta-position arrangement relative to a first carbon atom, the sulfonated group in the first phenyl group is in para-position arrangement relative to the first carbon atom, and the fluoro group in the second phenyl group is in meta-position arrangement relative to a second carbon atom; sulfonating groups in the second phenyl group are in para-position arrangement with respect to the second carbon atom. When the sulfonated monomer is polymerized to form a sulfonated polymer, the high-activity fluorine group enables the sulfonated monomer to be subjected to meta-position polymerization, so that the flexibility of the formed sulfonated polymer is improved.

Description

Technical Field

[0001] The present disclosure relates to the field of organic materials, and in particular to a sulfonated monomer and a preparation method thereof, a polymer, and a proton exchange membrane. Background Art

[0002] Sulfonated hydrocarbon polymers can be used to prepare proton exchange membranes (PEMs), which make the proton exchange membranes have the advantages of low hydrogen permeability and strong proton conductivity. The preparation methods of sulfonated hydrocarbon polymers generally include the following two methods: First, the polymer body is first prepared, and then the polymer body is sulfonated to prepare the sulfonated hydrocarbon polymer. However, this preparation method requires the use of a large amount of strong acid, which is not only easy to cause equipment corrosion, but also easy to cause the polymer body to degrade or cross-link. Second, the sulfonated monomer and other functional monomers are polymerized to prepare the sulfonated hydrocarbon polymer. This method avoids the use of a large amount of strong acid and has the advantage of strong controllability of the structure of the sulfonated hydrocarbon polymer.

[0003] Sulfonated polyphenylene sulfone, as a sulfonated hydrocarbon polymer, has high proton conductivity. The related technology uses 3,3′-sodium disulfonate-4,4′-dichlorodiphenyl sulfone as a sulfonation monomer to prepare sulfonated polyphenylene sulfone. However, the physical stability of sulfonated polyphenylene sulfone needs to be improved.

[0004] Public Content

[0005] In view of this, the present disclosure provides a sulfonated monomer and a preparation method thereof, a polymer, and a proton exchange membrane, which can solve the technical problems in the related art.

[0006] Specifically, the following technical solutions are included:

[0007] In one aspect, the embodiments of the present disclosure provide a sulfonated monomer, the sulfonated monomer comprising: a first phenyl group, a segment containing an electron-withdrawing group, and a second phenyl group;

[0008] The electron-withdrawing group-containing segments are respectively connected to the first carbon atom of the first phenyl group and the second carbon atom of the second phenyl group;

[0009] The first phenyl group and the second phenyl group both have a fluorine group and a sulfonated group, the fluorine group in the first phenyl group is arranged in the meta position relative to the first carbon atom, the sulfonated group in the first phenyl group is arranged in the para position relative to the first carbon atom, the fluorine group in the second phenyl group is arranged in the meta position relative to the second carbon atom, and the sulfonated group in the second phenyl group is arranged in the para position relative to the second carbon atom.

[0010] The sulfonated monomer provided by the present disclosure embodiment includes the first phenyl group, the electron-withdrawing group segment and the second phenyl group connected in sequence, based on the electron-withdrawing property of the electron-withdrawing group segment, so as to enhance the strong acidity of the sulfonated monomer. The first phenyl group and the second phenyl group are both replaced by fluoro groups and sulfonated groups, wherein the fluoro groups in the first phenyl group are arranged in meta position relative to the first carbon atom, and the fluoro groups in the second phenyl group are arranged in meta position relative to the second carbon atom. In this way, when the sulfonated monomer is polymerized to form a sulfonated polymer, the highly active fluoro groups make the sulfonated monomer meta-polymerized, which is conducive to improving the flexibility of the formed sulfonated polymer, and the flexibility enhancement of the sulfonated polymer is more advantageous for improving the durability of the polymer film. In addition, the sulfonated polymer is synthesized based on the sulfonated monomer, and the use of strong acid substances can also be avoided in the synthesis process, so that the preparation process of the sulfonated polymer has the advantages of safe and reliable, green and environmentally friendly, and easy to operate.

[0011] In some possible implementations, the electron-withdrawing group-containing segment includes a first electron-withdrawing group, and the number of the first electron-withdrawing group is 1 to 11. On the one hand, the first electron-withdrawing group can increase the acidity of the sulfonated group, which is beneficial to improving the proton conductivity of the polymer after the sulfonated monomer is polymerized to form a polymer; on the other hand, after the sulfonated monomer is polymerized to form a polymer, the first electron-withdrawing group has a higher antioxidant stability than the electron-donating group, which is beneficial to improving the physical stability of the polymer.

[0012] In some possible implementations, the number of the first electron-withdrawing groups is greater than or equal to 2, and the electron-withdrawing group-containing segment further comprises: an aromatic group or a heteroaromatic ring containing 5 to 18 carbon atoms, wherein the aromatic group or the heteroaromatic ring is connected between two of the first electron-withdrawing groups. When the sulfonated monomer is polymerized to form a polymer, such aromatic group or heteroaromatic ring is beneficial to improving the heat resistance and physical stability of the polymer, and is also beneficial to further improving the flexibility of the polymer.

[0013] In some possible implementations, the aromatic or heteroaromatic ring contains a second electron-withdrawing group, thereby further increasing the acidity of the sulfonated monomer.

[0014] In some possible implementations, the chemical structural formula of the sulfonated monomer is as follows:

[0015]

[0016] Wherein, X is the first electron-withdrawing group, Ar is an aromatic group or an aromatic heterocycle containing 5 to 18 carbon atoms, and M is a monovalent cation;

[0017] n is an integer from 0 to 10.

[0018] In some possible implementations, the first electron-withdrawing group is selected from at least one of a sulfone group, a ketone group, and an imide group.

[0019] On the other hand, the present disclosure also provides a method for preparing a sulfonated monomer, wherein the sulfonated monomer is as described above; the method for preparing the sulfonated monomer comprises:

[0020] A precursor compound is provided, wherein the precursor compound comprises a third phenyl group, a segment containing an electron-withdrawing group, and a fourth phenyl group, wherein the segment containing an electron-withdrawing group is respectively connected to the first carbon atom of the third phenyl group and the second carbon atom of the fourth phenyl group; the third phenyl group and the fourth phenyl group both have a fluorine group and a thiol group, the fluorine group in the third phenyl group is arranged in a meta position relative to the first carbon atom, the thiol group in the third phenyl group is arranged in a para position relative to the first carbon atom, the fluorine group in the fourth phenyl group is arranged in a meta position relative to the second carbon atom, and the thiol group in the fourth phenyl group is arranged in a para position relative to the second carbon atom;

[0021] The precursor compound is subjected to sulfonation treatment so that the thiol group is converted into a sulfonated group to obtain the sulfonated monomer.

[0022] In some possible implementations, providing a precursor compound includes:

[0023] A raw material compound is provided, wherein the raw material compound comprises a third phenyl group, a segment containing an electron-withdrawing group, and a fourth phenyl group; the segment containing an electron-withdrawing group is respectively connected to the first carbon atom of the third phenyl group and the second carbon atom of the fourth phenyl group; the third phenyl group and the fourth phenyl group each have two fluorine groups, the two fluorine groups in the third phenyl group are respectively arranged in the meta position and the para position relative to the first carbon atom, and the two fluorine groups in the fourth phenyl group are respectively arranged in the meta position and the para position relative to the second carbon atom;

[0024] The fluorine group at the para position of the raw material compound is selectively replaced by a sulfur-containing compound, so that the fluorine group at the para position is converted into a thiol group to obtain a precursor compound, wherein the sulfur-containing compound includes sodium hydrosulfide or sodium sulfide.

[0025] The preparation method of the sulfonated monomer provided in the embodiment of the present disclosure selectively replaces the fluorine group in the para position of the raw material compound by a sulfur-containing compound, and the fluorine group in the raw material compound is more active when it is in the para position than when it is in the meta position, so that the fluorine group in the para position of the raw material compound can be selectively replaced, and the fluorine group in the para position is converted into a thiol group to obtain a precursor compound. By sulfonation treatment, the thiol group in the precursor compound is converted into a sulfonated group, so that a sulfonated monomer can be prepared.

[0026] In some possible implementations, the selective substitution of the fluorine group at the para position with the sulfur-containing compound comprises: reacting the sulfur-containing compound with the raw material compound at a reaction temperature of 0° C. to 40° C. to achieve the selective substitution.

[0027] The disclosed embodiment allows the sulfur-containing compound to react with the raw material compound for a longer time at a lower reaction temperature, with mild reaction conditions and extended reaction time, thereby ensuring that the two fluorine groups in the more active para positions in the raw material compound can be replaced by thiol groups.

[0028] In some possible implementations, providing a precursor compound includes:

[0029] A raw material compound is provided, wherein the raw material compound comprises a third phenyl group, a segment containing an electron-withdrawing group, and a fourth phenyl group; the segment containing an electron-withdrawing group is respectively connected to the first carbon atom of the third phenyl group and the second carbon atom of the fourth phenyl group; the third phenyl group and the fourth phenyl group each have two fluorine groups, the two fluorine groups in the third phenyl group are respectively arranged in the meta position and the para position relative to the first carbon atom, and the two fluorine groups in the fourth phenyl group are respectively arranged in the meta position and the para position relative to the second carbon atom;

[0030] Allowing benzyl mercaptan to undergo a selective substitution reaction with the raw material compound to obtain an intermediate compound;

[0031] The intermediate compound is reacted with boron tribromide or aluminum trichloride to obtain the precursor compound.

[0032] The preparation method of the sulfonated monomer provided by the embodiment of the present disclosure is to selectively replace the raw material compound by benzyl mercaptan, and the fluorine group in the raw material compound is more active when it is located in the para position than in the meta position, so that the fluorine group in the para position of the raw material compound can be selectively replaced, so that the fluorine group in the para position is converted into a benzylthio group. Boron tribromide or aluminum chloride is reacted with the intermediate compound to convert the benzylthio group into a sulfhydryl group to obtain a precursor compound. By sulfonation, the sulfhydryl group in the precursor compound is converted into a sulfonated group, so that a sulfonated monomer can be prepared.

[0033] In some possible implementations, the subjecting the benzyl mercaptan to a selective substitution reaction with the raw material compound comprises: subjecting the benzyl mercaptan to a reaction with the raw material compound at a reaction temperature of 0° C. to 40° C. to achieve the selective substitution reaction.

[0034] In some possible implementations, the precursor compound is subjected to a sulfonation treatment so that the thiol group is converted into a sulfonated group to obtain the sulfonated monomer, comprising:

[0035] Performing the sulfonation treatment on the precursor compound by using an oxidant, so that the thiol group is converted into a sulfonic acid group, thereby obtaining a precursor of the sulfonated monomer;

[0036] The precursor of the sulfonated monomer is treated with a saturated salt to convert the sulfonic acid group into a sulfonate group, thereby obtaining the sulfonated monomer.

[0037] On the other hand, an embodiment of the present disclosure further provides a polymer, which includes a first structural unit, wherein the first structural unit is derived from a first monomer compound, and the first monomer compound is any of the sulfonated monomers described above.

[0038] When the sulfonated monomer provided by the embodiment of the present disclosure is polymerized to form a polymer, the polymerization site occurs at the meta position where the fluorine group is located, that is, at the 3 position and the 3' position, so that the benzene rings are arranged nonlinearly, but present a certain angle, which is beneficial to enhancing the interaction between the molecular chains and allowing the molecular chains to be twisted, thereby improving the flexibility of the formed polymer. The enhanced flexibility of the polymer correspondingly improves the flexibility of the polymer film, so that its tensile strength and elongation at break and other properties are improved, thereby effectively improving the durability of the polymer film.

[0039] In some possible implementations, the polymer further includes a second structural unit, the second structural unit is derived from a second monomer compound, the second monomer compound includes at least two functional groups for condensation polymerization, and the functional groups for condensation polymerization include at least one of a thiol group and a hydroxyl group.

[0040] On the other hand, the embodiments of the present disclosure further provide a proton exchange membrane, which is prepared from any of the above-mentioned polymers. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 The hydrogen NMR spectrum of the relevant compound provided in Example 1 of the present disclosure;

[0042] Figure 2 The hydrogen NMR spectrum of the sulfonated polymer provided in Example 5 of the present disclosure;

[0043] Figure 3 This is the hydrogen NMR spectrum of the sulfonated polymer provided in Comparative Example 2 of the present disclosure. DETAILED DESCRIPTION

[0044] The related technology uses 3,3′-sodium disulfonate-4,4′-dichlorodiphenyl sulfone as a sulfonation monomer to prepare sulfonated polyphenylsulfone. Sulfonated polyphenylsulfone, as a sulfonated hydrocarbon polymer, has high proton conductivity. However, the physical stability of sulfonated polyphenylsulfone needs to be improved.

[0045] The disclosed embodiment provides a sulfonated monomer, which includes: a first phenyl group, a segment containing an electron-withdrawing group, and a second phenyl group; the segment containing an electron-withdrawing group is respectively connected to the first carbon atom of the first phenyl group and the second carbon atom of the second phenyl group. The first phenyl group and the second phenyl group both have a fluorine group and a sulfonated group, the fluorine group in the first phenyl group is arranged in the meta position relative to the first carbon atom, the sulfonated group in the first phenyl group is arranged in the para position relative to the first carbon atom, the fluorine group in the second phenyl group is arranged in the meta position relative to the second carbon atom, and the sulfonated group in the second phenyl group is arranged in the para position relative to the second carbon atom.

[0046] The sulfonated monomer provided by the present disclosure embodiment includes the first phenyl group, the electron-withdrawing group segment and the second phenyl group connected in sequence, based on the electron-withdrawing property of the electron-withdrawing group segment, so as to enhance the strong acidity of the sulfonated monomer. The first phenyl group and the second phenyl group are both replaced by fluoro groups and sulfonated groups, wherein the fluoro groups in the first phenyl group are arranged in meta position relative to the first carbon atom, and the fluoro groups in the second phenyl group are arranged in meta position relative to the second carbon atom. In this way, when the sulfonated monomer is polymerized to form a sulfonated polymer, the highly active fluoro groups make the sulfonated monomer meta-polymerized, which is conducive to improving the flexibility of the formed sulfonated polymer, and the flexibility of the sulfonated polymer is enhanced for improving the physical stability and durability of the polymer film. In addition, the sulfonated polymer is synthesized based on the sulfonated monomer, and the use of strong acid substances can also be avoided in the synthesis process, so that the preparation process of the sulfonated polymer has the advantages of safe and reliable, green and environmentally friendly, and easy to operate.

[0047] In some embodiments, the electron-withdrawing group-containing segment includes a first electron-withdrawing group, and the number of the first electron-withdrawing groups is 1-11, including: the number of electron-withdrawing groups can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11.

[0048] By setting the above number of first electron-withdrawing groups, on the one hand, the first electron-withdrawing group can increase the acidity of the sulfonated group, which is beneficial to improving the proton conductivity of the polymer after the sulfonated monomer is polymerized to form a polymer; on the other hand, after the sulfonated monomer is polymerized to form a polymer, the first electron-withdrawing group has a higher antioxidant stability than the electron-donating group, which is beneficial to improving the physical stability of the polymer. On the other hand, the above number of first electron-withdrawing groups also reduces the difficulty of preparing the sulfonated monomer.

[0049] Other functional groups can be arranged between the two electron-withdrawing groups. In some examples, the number of electron-withdrawing groups is greater than or equal to 2, and the electron-withdrawing group-containing segment further includes: an aromatic group or a heteroaromatic ring containing 5-18 carbon atoms, and the aromatic group or the heteroaromatic ring is connected between the two first electron-withdrawing groups.

[0050] The number of carbon atoms contained in the aryl group may be 5-18, and the aryl group includes but is not limited to phenyl, naphthyl, anthracenyl, phenanthryl, benzyl, tolyl, xylyl and the like.

[0051] The number of carbon atoms contained in the heteroaromatic ring can be 5-18, and the heteroaromatic ring includes but is not limited to pyridyl, pyrrolyl, pyrazolyl, furanyl, benzofuranyl, isobenzofuranyl, pyrrolyl, indolyl, isoindolyl, thienyl, benzo[b]thienyl, benzo[c]thienyl, imidazolyl, quinolyl, etc.

[0052] By connecting an aromatic group or heteroaromatic ring containing 5 to 18 carbon atoms between two electron-withdrawing groups, when the sulfonated monomer is polymerized to form a polymer, the aromatic group or heteroaromatic ring is beneficial to improving the heat resistance and physical stability of the polymer, and is also beneficial to further improving the flexibility of the polymer.

[0053] In some examples, the aromatic group or heteroaromatic ring contains a second electron withdrawing group, and the second electron withdrawing group is selected from at least one of a sulfone group, a ketone group, and an imide group, thereby further increasing the acidity of the sulfonated monomer.

[0054] In some possible implementations, the chemical structural formula of the sulfonated monomer involved above is as follows:

[0055]

[0056] Wherein, X is the first electron-withdrawing group, Ar is an aromatic group or a heteroaromatic ring containing 5 to 18 carbon atoms, M is a monovalent cation; and n is an integer of 0 to 10.

[0057] The carbon atom connected to the electron-withdrawing group X in the first phenyl group is defined as the 1 position, and the carbon atom connected to the electron-withdrawing group X in the second phenyl group is defined as the 1' position. Then, the two fluorine groups in the sulfonated monomer are located at the 3 position and the 3' position, respectively, and the two sulfonated groups are located at the 4 position and the 4' position, respectively. When the sulfonated monomer is polymerized to form a sulfonated polymer, the highly active fluorine group causes the sulfonated monomer to polymerize in the meta position, which is conducive to improving the flexibility of the formed sulfonated polymer. The enhanced flexibility of the sulfonated polymer is more beneficial to improving the durability of the polymer film.

[0058] For the first electron withdrawing group represented by X, the first electron withdrawing group is selected from at least one of a sulfone group, a ketone group, and an imide group.

[0059] When the number of the first electron withdrawing groups is greater than or equal to 2, the numbers of these electron withdrawing groups may be the same or different. For example, one of the first electron withdrawing groups may be a sulfone group, and the other first electron withdrawing group may be a ketone group.

[0060] The monovalent cation represented by M may be a sodium ion, a potassium ion, an ammonium ion, a lithium ion, a hydrogen ion, or the like.

[0061] On the other hand, the present disclosure also provides a method for preparing a sulfonated monomer, wherein the sulfonated monomer is as described above. The method for preparing the sulfonated monomer comprises:

[0062] Step S001, providing a precursor compound, the precursor compound comprising a third phenyl group, an electron-withdrawing group-containing segment and a fourth phenyl group; the electron-withdrawing group-containing segment is respectively connected to the first carbon atom of the third phenyl group and the second carbon atom of the fourth phenyl group; the third phenyl group and the fourth phenyl group both have a fluorine group and a thiol group, the fluorine group in the third phenyl group is arranged in the meta position relative to the first carbon atom, the thiol group in the third phenyl group is arranged in the para position relative to the first carbon atom, the fluorine group in the fourth phenyl group is arranged in the meta position relative to the second carbon atom, and the thiol group in the fourth phenyl group is arranged in the para position relative to the second carbon atom.

[0063] The chemical structure of the precursor compound is shown below:

[0064]

[0065] Wherein, X is the first electron withdrawing group, Ar is an aromatic group or heteroaromatic ring containing 5-18 carbon atoms, and n is an integer of 0-10.

[0066] Step S002: sulfonating the precursor compound using an oxidant to convert the thiol group into a sulfonated group to obtain a sulfonated monomer.

[0067] Depending on the specific type of the precursor compound, it can be obtained by using an existing compound product or synthesized using specific chemical raw materials. The following is an exemplary description of the preparation method of the precursor compound, which includes but is not limited to the following:

[0068] In some examples (1), the precursor compound is prepared by the following method:

[0069] Step S11, providing a raw material compound, wherein the raw material compound includes a third phenyl group, an electron-withdrawing group-containing segment and a fourth phenyl group; the electron-withdrawing group-containing segment is respectively connected to the first carbon atom of the third phenyl group and the second carbon atom of the fourth phenyl group; the third phenyl group and the fourth phenyl group both have two fluorine groups, the two fluorine groups in the third phenyl group are respectively arranged in the meta position and the para position relative to the first carbon atom, and the two fluorine groups in the fourth phenyl group are respectively arranged in the meta position and the para position relative to the second carbon atom.

[0070] Step S12, selectively replacing the fluorine group at the para position of the raw material compound with a sulfur-containing compound, so that the fluorine group at the para position is converted into a thiol group to obtain a precursor compound, wherein the sulfur-containing compound includes sodium hydrosulfide or sodium sulfide.

[0071] The method for preparing a sulfonated monomer provided in the above example (1) selectively replaces the fluorine group in the para position of the raw material compound by a sulfur-containing compound. The fluorine group in the raw material compound is more active when it is in the para position than when it is in the meta position, so that the fluorine group in the para position of the raw material compound can be selectively replaced, and the fluorine group in the para position is converted into a thiol group to obtain a precursor compound. By sulfonation treatment, the thiol group in the precursor compound is converted into a sulfonated group, so that a sulfonated monomer can be prepared.

[0072] For step S11, the chemical structural formula of the raw material compound involved is as follows:

[0073]

[0074] Wherein, X is the first electron withdrawing group, Ar is an aromatic group or heteroaromatic ring containing 5-18 carbon atoms, and n is an integer of 0-10.

[0075] According to the specific type of the raw material compound, it can be obtained by using existing compound products or synthesized using specific chemical raw materials.

[0076] In some examples, the method for preparing the raw material compound includes: determining multiple chemical raw materials for synthesizing the raw material compound according to the chemical structural formula of the raw material compound, and preparing the raw material compound by subjecting the multiple chemical raw materials to an acylation reaction.

[0077] Taking 3,3′,4,4′-tetrafluorodiphenyl sulfone as a raw material compound as an example, the preparation method thereof is exemplified. The chemical structure of 3,3′,4,4′-tetrafluorodiphenyl sulfone is shown below:

[0078]

[0079] At least two chemical raw materials are provided, including 3,4-difluorobenzenesulfonyl chloride and o-difluorobenzene, and 3,4-difluorobenzenesulfonyl chloride and o-difluorobenzene are subjected to acylation reaction to synthesize 3,3′,4,4′-tetrafluorodiphenyl sulfone.

[0080] The synthetic route of 3,3′,4,4′-tetrafluorodiphenyl sulfone is as follows:

[0081]

[0082] Of course, similar to the above-mentioned synthesis route of 3,3′,4,4′-tetrafluorodiphenyl sulfone, when the raw material compound is 3,3′,4,4′-tetrafluorobenzophenone, 3,4-difluorobenzoyl chloride and o-difluorobenzene are subjected to acylation reaction to synthesize 3,3′,4,4′-tetrafluorobenzophenone. When 3,3′,4,4′-tetrafluorobenzophenone is used to synthesize a sulfonated monomer, it can be named 4,4′-sodium disulfonate-3,3′-difluorobenzophenone. The synthesis route and preparation method of 4,4′-sodium disulfonate-3,3′-difluorobenzophenone can refer to the synthesis route and preparation method of 4,4′-sodium disulfonate-3,3′-difluorodiphenyl sulfone in Example 1 below.

[0083] In step S12, the fluorine group at the para position of the raw material compound is selectively substituted with a sulfur-containing compound, so that the fluorine group at the para position is converted into a thiol group, thereby obtaining a precursor compound.

[0084] According to the difference in the reactivity of the fluorine groups at different substitution positions of the benzene ring, the sulfur-containing compound can selectively replace the fluorine group at the para position as a nucleophilic agent. Some suitable sulfur-containing compounds can be sodium hydrosulfide, sodium sulfide, etc.

[0085] In some implementations, the fluorine group in the para position is selectively replaced by a sulfur-containing compound, including: reacting the sulfur-containing compound with the raw material compound at a reaction temperature of 0°C-40°C, for example, the reaction time is 2 hours to 48 hours, and further can be 10 hours to 48 hours, to achieve selective replacement.

[0086] The reaction temperature of the selective substitution includes but is not limited to: 5°C, 7°C, 15°C, 17°C, 18°C, 19°C, 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, 30°C, 31°C, 32°C, 33°C, 34°C, 35°C, 38°C and the like.

[0087] The reaction time for the selective substitution includes, but is not limited to, 10 hours, 15 hours, 20 hours, 22 hours, 24 hours, 26 hours, 28 hours, 30 hours, 32 hours, 35 hours, 40 hours, 48 ​​hours, etc.

[0088] The disclosed embodiments react the sulfur-containing compound with the raw material compound at a relatively low reaction temperature, and the reaction conditions are mild, so as to ensure that the two fluorine groups in the more active para positions of the raw material compound can be replaced by thiol groups, while the fluorine groups in the meta positions do not react and are retained.

[0089] Furthermore, by extending the reaction time, for example, the reaction time is 10 hours to 48 hours, it is ensured that the two fluorine groups in the more active para position in the raw material compound can be replaced by thiol groups.

[0090] The reaction system in which the sulfur-containing compound and the raw material compound are located also includes a solvent so that the two are fully dispersed therein. The solvent can be a polar organic solvent. Some suitable polar organic solvents include but are not limited to: N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, etc.

[0091] The content of the polar organic solvent is such that the solid content of the reaction system is 10 wt % to 90 wt %, for example, 20 wt % to 60 wt %.

[0092] In some examples, the molar ratio of the raw material compound to the sulfur-containing compound, such as sodium hydrosulfide, is 1:2-1:20, thereby ensuring that the fluorine group at the para position in the raw material compound can be completely replaced.

[0093] After the sulfur-containing compound and the raw material compound have reacted, the generated precursor compound can be separated from the product system by the following method: by adding an acidic solution to the product system, the pH value of the product system is adjusted to 4-6, so that the precursor compound is precipitated in an acidic environment. The precipitated precursor compound is acid-washed, and then filtered to separate the precursor compound.

[0094] In some examples, an acidic solution is added to the product system to adjust the pH value of the product system to 4-6, so that the precursor compound is precipitated in an acidic environment, including: adding deionized water to the product system, and then continuing to add acid solution to adjust the pH value of the product system to 4-6, thereby precipitating the precursor compound.

[0095] Exemplarily, the acid solution can be a single acid or a mixture of several acids to provide a more excellent acid catalysis. For example, a mixture of dilute sulfuric acid and acetic acid (e.g., equal volumes of both) can be used to make the regulation of the pH value of the product system more controllable.

[0096] The volume of the deionized water can be 0.1 to 10 times, and further 2 to 10 times, of the volume of the polar organic solvent. The volume of the acid solution is sufficient to adjust the pH value of the product system to 4-6.

[0097] In some examples, the precipitated precursor compound is acid-washed and then filtered to separate the precursor compound, including: washing the precursor compound with at least one of a sulfuric acid solution, a hydrochloric acid solution, and a nitric acid solution, the washing times can be 1-5 times, for example, 3 times, and then filtering to separate the precursor compound, and ensuring that the precursor compound has a high purity. For example, a 0.1 mol / L-5 mol / L sulfuric acid solution can be used for the above washing.

[0098] In some examples (2), the precursor compound is prepared by the following method:

[0099] Step S21, providing a raw material compound, wherein the raw material compound includes a third phenyl group, an electron-withdrawing group-containing segment and a fourth phenyl group; the electron-withdrawing group-containing segment is respectively connected to the first carbon atom of the third phenyl group and the second carbon atom of the fourth phenyl group; the third phenyl group and the fourth phenyl group both have two fluorine groups, the two fluorine groups in the third phenyl group are respectively arranged in the meta position and the para position relative to the first carbon atom, and the two fluorine groups in the fourth phenyl group are respectively arranged in the meta position and the para position relative to the second carbon atom.

[0100] Step S22, subjecting benzyl mercaptan to a selective substitution reaction (ie, a nucleophilic substitution reaction) with the raw material compound to obtain an intermediate compound.

[0101] Step S23: react the intermediate compound with boron tribromide or aluminum trichloride to obtain a precursor compound.

[0102] The method for preparing a sulfonated monomer provided in the above example (2) is to selectively replace the raw material compound by benzyl mercaptan. The fluorine group in the raw material compound is more active when it is located in the para position than in the meta position, so that the fluorine group in the para position of the raw material compound can be selectively replaced, so that the fluorine group in the para position is converted into a benzylthio group. Boron tribromide or aluminum trichloride is reacted with the intermediate compound to convert the benzylthio group into a sulfhydryl group to obtain a precursor compound. The sulfhydryl group in the precursor compound is converted into a sulfonated group by sulfonation treatment, so that a sulfonated monomer can be prepared.

[0103] For step S21, the raw material compound involved therein has the same chemical structural formula as the raw material compound involved in step S11, and will not be described in detail here.

[0104] For step S22, the chemical structural formula of the intermediate compound obtained is as follows:

[0105]

[0106] Wherein, X is the first electron withdrawing group, Ar is an aromatic group or heteroaromatic ring containing 5-18 carbon atoms, and n is an integer of 0-10.

[0107] For step S22, the reaction is carried out in the presence of an alkaline reagent to promote the reaction. Some suitable alkaline reagents include but are not limited to: triethylamine, potassium carbonate, potassium hydroxide, sodium hydroxide and the like.

[0108] In some examples, the selective substitution reaction described in step S22 can be performed under an inert atmosphere to improve the reaction effect.

[0109] In some examples, the benzyl mercaptan is reacted with the raw material compound for a selective substitution reaction, including: reacting the benzyl mercaptan with the raw material compound at a reaction temperature of 0°C-40°C, for example, the reaction time is 2 hours-48 hours, and further can be 10 hours-48 hours, to achieve selective substitution.

[0110] The reaction temperature of the selective substitution includes but is not limited to: 5°C, 7°C, 15°C, 17°C, 18°C, 19°C, 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C, 30°C, 31°C, 32°C, 33°C, 34°C, 35°C, 38°C and the like.

[0111] The reaction time for the selective substitution includes, but is not limited to, 10 hours, 15 hours, 20 hours, 22 hours, 24 hours, 26 hours, 28 hours, 30 hours, 32 hours, 35 hours, 40 hours, etc.

[0112] The disclosed embodiments react the sulfur-containing compound with the raw material compound at a relatively low reaction temperature, and the reaction conditions are mild, so as to ensure that the two fluorine groups in the more active para positions of the raw material compound can be replaced by thiol groups, while the fluorine groups in the meta positions do not react and are retained.

[0113] Furthermore, by extending the reaction time, for example, the reaction time is 10 hours to 48 hours, it is ensured that the two fluorine groups in the more active para position in the raw material compound can be replaced by thiol groups.

[0114] For step S23, boron tribromide or aluminum trichloride can be added to the reaction system in the form of a solution by dropwise addition, and the reaction temperature can be 20°C-80°C.

[0115] For step S002, the precursor compound is subjected to sulfonation treatment so that the sulfhydryl group is converted into a sulfonated group to obtain a sulfonated monomer, which may include: using an oxidant to sulfonate the precursor compound so that the sulfhydryl group is converted into a sulfonic acid group to obtain a precursor of the sulfonated monomer. Using a saturated salt to treat the precursor of the sulfonated monomer so that the sulfonic acid group is converted into a sulfonate group to obtain a sulfonated monomer.

[0116] First, an oxidant is used to convert the mercapto group in the precursor compound into a sulfonic acid group, and then a saturated salt is used to convert the sulfonic acid group into a sulfonate group, thereby facilitating separation of the sulfonated monomer from the product system.

[0117] In some examples, the precursor compound is sulfonated with an oxidant to convert the thiol group into a sulfonic acid group to obtain a precursor of a sulfonated monomer, including: dissolving the precursor compound in an acidic solvent, adding the oxidant to the reaction system under low temperature conditions and in the presence of an acid catalyst, and reacting for 1 to 2 hours under low temperature conditions. Then, the reaction system is heated to a high temperature condition, and the precursor compound and the oxidant are reacted under high temperature conditions for at least 20 hours to obtain a precursor of a sulfonated monomer.

[0118] The acidic solvent used in the above sulfonation treatment includes, but is not limited to, concentrated sulfuric acid, dilute sulfuric acid, glacial acetic acid, citric acid, formic acid, trifluoroacetic acid, etc. For example, 20 ml to 250 ml of the acidic solvent is used for every 10 g of the precursor compound.

[0119] The low temperature condition involved in the above sulfonation treatment refers to a temperature condition below 5° C., for example, the temperature range corresponding to the low temperature condition is −5° C. to 5° C. In some examples, the low temperature condition can be provided by an ice water bath.

[0120] The high temperature conditions involved in the above-mentioned sulfonation treatment refer to temperature conditions in the temperature range of 0°C-50°C, that is, the temperature range corresponding to the high temperature conditions is 0°C-50°C.

[0121] The oxidation reaction can be carried out under low temperature conditions. By further raising the temperature to high temperature conditions, it is possible to ensure that the residual oxidant reacts further and the reaction is fully and thoroughly ensured.

[0122] The acid catalyst involved in the sulfonation treatment can be at least one of concentrated sulfuric acid, dilute sulfuric acid, glacial acetic acid, citric acid, formic acid, and trifluoroacetic acid, so that the pH value of the acidic catalytic environment is 5 to 6. For example, the acid can be dilute sulfuric acid.

[0123] The oxidants involved in the above sulfonation treatment include but are not limited to hydrogen peroxide, m-chloroperbenzoic acid, peracetic acid, etc. For example, a hydrogen peroxide solution with a mass concentration of 25%-50% can be used as the oxidant, which has the advantage of no by-products.

[0124] As an example, the acid catalyst can be mixed with an oxidant for use. For example, the acid catalyst, such as dilute sulfuric acid, and a hydrogen peroxide solution with a mass concentration of 25%-50% can be mixed in a volume ratio of 3:5-8.

[0125] As another example, the acid catalyst and the oxidant are added to the reaction system in sequence.

[0126] At least one of the acid catalyst and the oxidant can be added to the reaction system in a dropwise manner.

[0127] The oxidant is usually added in excess to ensure that the thiol groups are completely converted into sulfonic acid groups. After the reaction is completed, the oxidant can be removed. For example, when the oxidant is hydrogen peroxide, the excess hydrogen peroxide can be volatilized by heating (e.g., heating to 100°C-120°C).

[0128] When the precursor of the sulfonated monomer is treated with a saturated salt, the saturated salt used includes but is not limited to sodium chloride, lithium chloride, potassium chloride, ammonium chloride, etc. By adding an excess of salt to the product system, the sulfonic acid group is converted into a sulfonate group, and the sulfonated monomer is precipitated.

[0129] In some examples, for the preparation method described in example (1), the synthesis route of the sulfonated monomer provided in the embodiments of the present disclosure can be found below.

[0130] In the first stage, the fluorine group at the para position of the raw material compound is selectively replaced by a sulfur-containing compound, so that the fluorine group at the para position is converted into a thiol group to obtain a precursor compound.

[0131]

[0132] In the second stage, the precursor compound is sulfonated using an oxidant to convert the thiol group into a sulfonic acid group to obtain a precursor of a sulfonated monomer.

[0133]

[0134] In the third stage, the precursor of the sulfonated monomer is treated with a saturated salt to convert the sulfonic acid group into a sulfonate group to obtain a sulfonated monomer.

[0135]

[0136] In summary, although acid solution is used in the preparation of sulfonated monomers in the embodiments of the present disclosure, the concentration of the acid solution is relatively low and will not cause corrosion, thus avoiding the use of highly corrosive reagents, making the preparation process safer and gentler, and the preparation process is simple and easy to operate.

[0137] On the other hand, the embodiment of the present disclosure further provides a polymer, the polymer includes a first structural unit, the first structural unit is derived from a first monomer compound, the first monomer compound is any one of the above-mentioned sulfonated monomers provided in the embodiment of the present disclosure. The polymer is a sulfonated polymer.

[0138] The chemical structural formula of the first structural unit contained in the polymer is shown below, wherein the * represents other structural units.

[0139]

[0140] When the sulfonated monomer provided by the embodiment of the present disclosure is polymerized to form a polymer, the polymerization site occurs at the meta position where the fluorine group is located, that is, at the 3 position and the 3' position, so that the benzene rings are arranged nonlinearly, but present a certain angle, which is beneficial to enhancing the interaction between the molecular chains and allowing the molecular chains to be twisted, thereby improving the flexibility of the formed polymer. The enhanced flexibility of the polymer correspondingly improves the flexibility of the polymer film, so that its tensile strength and elongation at break and other properties are improved, thereby effectively improving the durability of the polymer film.

[0141] In some examples, the polymer provided by the embodiments of the present disclosure further includes a second structural unit, the second structural unit is derived from a second monomer compound, the second monomer compound includes at least two functional groups for polycondensation reaction, and the functional groups for polycondensation reaction include at least one of thiol and hydroxyl. The second monomer compound also includes a main chain, which may include one or a combination of substituted or unsubstituted chain alkyl, substituted or unsubstituted aromatic ring structure, substituted or unsubstituted heteroaromatic ring structure, and at least two functional groups for polycondensation reaction are connected to the main chain of the second monomer compound.

[0142] In other examples, the polymer provided by the embodiments of the present disclosure also includes other structural units (corresponding to other monomer compounds), which are different from the first structural unit and the second structural unit, and the types of the other structural units can be one, two, three, four, five or more.

[0143] For example, the polymer provided in the embodiment of the present disclosure also includes a third structural unit, and the third structural unit comes from a third monomer compound, and the third monomer compound is a fluorine-containing monomer. For example, the third monomer compound includes a fifth phenyl group, an electron-withdrawing group-containing segment and a sixth phenyl group, and the electron-withdrawing group-containing segment is respectively connected to the first carbon atom of the fifth phenyl group and the second carbon atom of the sixth phenyl group. The fifth phenyl group and the sixth phenyl group both have a fluoro group. The fluoro group in the fifth phenyl group can be arranged in the meta position relative to the first carbon atom, or in the para position; the fluoro group in the sixth phenyl group can be arranged in the meta position relative to the second carbon atom, or in the para position. The electron-withdrawing group-containing segment in the third monomer compound can refer to the electron-withdrawing group-containing segment in the sulfonated monomer in the embodiment of the present disclosure, and will not be repeated here.

[0144] Of course, the polymer provided by the embodiment of the present disclosure may further include a fourth structural unit, a fifth structural unit, etc. The type of each structural unit may be selected according to the actual use of the polymer.

[0145] The types of the second monomer compound and other optional monomer compounds are determined according to the actual use of the polymer, and the chemical structures of the second structural unit and other optional structural units are further determined.

[0146] For example, when the polymer is used to prepare a proton exchange membrane, the second monomer compound can be 4,4'-thiobisthiophenol, so that the second structural unit is a thiobisphenyl group, so that the prepared polymer meets the performance requirements of the proton exchange membrane and has higher proton conductivity and stronger durability.

[0147] When preparing the polymer provided in the embodiments of the present disclosure, the sulfonated monomer and the monomer corresponding to the second structural unit are polymerized under the action of an alkaline catalyst to synthesize the polymer. The alkaline catalyst may be, for example, potassium carbonate, sodium carbonate, potassium hydroxide, anhydrous potassium phosphate, etc.

[0148] In order to improve the reaction efficiency of the polymer, a water-carrying agent may be added to the reaction system. The water-carrying agent may be toluene, for example.

[0149] In some examples, the polymerization reaction includes a first polymerization stage and a second polymerization stage, wherein the reaction temperature corresponding to the first polymerization stage is lower than the reaction temperature corresponding to the second polymerization stage, for example, the reaction temperature corresponding to the first polymerization stage is 140° C.-160° C., and the reaction temperature corresponding to the second polymerization stage is 180° C.-220° C. The reaction time corresponding to the first polymerization stage is lower than the reaction time corresponding to the second polymerization stage, for example, the reaction time corresponding to the first polymerization stage is 2h-5h, and the reaction time corresponding to the second polymerization stage is 5h-10h.

[0150] By carrying out the above arrangement for the polymerization reaction process, it has the advantages of simple operation (such as one-step feeding, etc.), complete water separation, and efficient polymerization reaction.

[0151] After the polymerization reaction is completed, the synthesized polymer is separated from the product system by separation treatment. Exemplarily, the separation treatment includes extraction, and the extractant used can be isopropanol.

[0152] In summary, the synthesis of sulfonated polymers based on sulfonated monomers can avoid the use of strong acid substances during the synthesis process, making the polymer preparation process safe, reliable, green, environmentally friendly, and easy to operate.

[0153] On the other hand, the embodiments of the present disclosure further provide a proton exchange membrane, which is prepared from any one of the polymers mentioned above.

[0154] For example, the polymer corresponding to the proton exchange membrane includes a first structural unit and a second structural unit, wherein the first structural unit is derived from the sulfonated monomer provided by the embodiment of the present disclosure, and the second structural unit is derived from 4,4′-thiobisbenzenethiol (also known as 4,4′-thiobisbenzenethiol).

[0155] The proton exchange membrane based on the above-mentioned structural unit provided in the embodiments of the present disclosure has the advantages of low hydrogen permeability, strong proton conductivity, strong flexibility, strong durability, long cycle life, etc.

[0156] The membrane electrode (MEA) prepared using the proton exchange membrane provided by the embodiment of the present disclosure has lower high-frequency impedance, so that the current density at a specific voltage is stronger.

[0157] The specific implementation of the disclosed embodiment will be described in more detail below. Although the specific implementation of the disclosed embodiment is described below, it should be understood that the disclosed embodiment can be implemented in various forms and should not be limited by the implementation methods set forth herein. If specific techniques or conditions are not specified in the embodiment, they are carried out according to the techniques or conditions described in the literature in this area or according to the product specification. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0158] Example 1

[0159] This embodiment 1 provides a sulfonated monomer named 4,4′-sodium disulfonate-3,3′-difluorodiphenyl sulfone. The synthetic route and preparation method of the sulfonated monomer are as follows:

[0160]

[0161] 10.0 g (34.5 mmol) of 3,3′,4,4′-tetrafluorodiphenyl sulfone, 22.0 g of sodium hydrosulfide (mass concentration of 70%, 275 mmol) and 120 mL of N,N-dimethylacetamide (DMAc) solvent were added to a 500 mL single-necked flask, and the mixture was reacted at room temperature (maintained at 23° C.-28° C.) for 24 hours to prepare a precursor compound named 4,4′-dimercapto-3,3′-difluorodiphenyl sulfone.

[0162] 100 mL of deionized water was added to the product system containing 4,4′-dimercapto-3,3′-difluorodiphenyl sulfone, and then 50 mL of dilute sulfuric acid and 50 mL of glacial acetic acid were slowly added dropwise to make the pH value of the product system 5, thereby acidifying the product system so that a white solid precipitated therein, which was 4,4′-dimercapto-3,3′-difluorodiphenyl sulfone. The white solid was washed three times with a 1 mol / L sulfuric acid solution, and then filtered to separate 4,4′-dimercapto-3,3′-difluorodiphenyl sulfone.

[0163] Add 4,4′-dimercapto-3,3′-difluorodiphenyl sulfone to a 500 mL single-necked flask, continue to add 100 mL of glacial acetic acid to the single-necked flask, place the single-necked flask in an ice-water bath, and slowly drop 30 mL of concentrated sulfuric acid and 70 mL of a 30% mass concentration hydrogen peroxide solution into the single-necked flask. Allow the reaction system to react in an ice-water bath for 1 hour, then heat to 45°C and continue to react for 24 hours until the product system is colorless and transparent. Heat the product system to 110°C and maintain for 2 hours, remove excess hydrogen peroxide, and then add excess sodium chloride to precipitate a white solid in the solution, dry the white solid, and obtain 4,4′-sodium disulfonate-3,3′-difluorodiphenyl sulfone.

[0164] Example 1 also tested the H NMR spectra of 3,3′,4,4′-tetrafluorodiphenyl sulfone and 4,4′-sodium disulfonate-3,3′-difluorodiphenyl sulfone. The test results are shown in Figure 1 .Depend on Figure 1 The comparison of the H NMR spectrum shows that the characteristic peaks of the H NMR spectrum of 4,4′-sodium disulfonate-3,3′-difluorodiphenyl sulfone are clear and free of impurities, indicating that its purity is as high as 99% or more. The characteristic peaks on the benzene ring of 4,4′-sodium disulfonate-3,3′-difluorodiphenyl sulfone are significantly shifted to the low field region relative to the characteristic peaks of 3,3′,4,4′-tetrafluorodiphenyl sulfone, which is related to the electron-withdrawing effect of the sulfonate group.

[0165] Example 2

[0166] This Example 2 still provides 4,4′-sodium disulfonate-3,3′-difluorodiphenyl sulfone. The preparation method of the 4,4′-sodium disulfonate-3,3′-difluorodiphenyl sulfone is the same as that of Example 1, except that 30 mL of glacial acetic acid and 70 mL of a 30% hydrogen peroxide solution are slowly added dropwise to a single-necked flask.

[0167] It can be seen that Example 2 can also synthesize 4,4′-sodium disulfonate-3,3′-difluorodiphenyl sulfone with a purity of 91.4%.

[0168] Example 3

[0169] This Example 3 still provides 4,4'-sodium disulfonate-3,3'-difluorodiphenyl sulfone. In the process of preparing 4,4'-sodium disulfonate-3,3'-difluorodiphenyl sulfone, the sulfur-containing compound used is benzyl mercaptan.

[0170] The synthetic route and preparation method of the sulfonated monomer are respectively as follows:

[0171]

[0172] Using 3,3′,4,4′-tetrafluorodiphenyl sulfone (14.5 g, 0.05 mol) and benzyl mercaptan (12.4 g, 0.10 mol) as raw materials and dichloromethane solution as solvent, the reaction system was reacted at room temperature (23°C-28°C) for 24 hours under the catalytic condition of triethylamine (abbreviated as Et3N), and then water was added to quench the reaction, and the reaction was terminated.

[0173] The product system was extracted three times with dichloromethane, the solvent was spin-dried, and the product was dried to obtain an intermediate product, 4,4′-dibenzylthio-3,3′-difluorodiphenyl sulfone.

[0174] The intermediate product 4,4′-dibenzylthio-3,3′-difluorodiphenyl sulfone was directly dissolved in dichloromethane without purification, and anhydrous boron tribromide solution was added dropwise to the reaction system. After 3 hours of reaction, water was added to quench. The product system was extracted three times with dichloromethane, the solvent was dried, and 4,4′-dimercapto-3,3′-difluorodiphenyl sulfone was prepared by drying.

[0175] Add 4,4′-dimercapto-3,3′-difluorodiphenyl sulfone to a 500mL single-necked flask, continue to add 100mL of glacial acetic acid to the single-necked flask, place the single-necked flask in an ice-water bath, and slowly drop 30mL of concentrated sulfuric acid and 70mL of a 30% mass concentration of hydrogen peroxide solution into the single-necked flask. Allow the reaction system to react in an ice-water bath for 1 hour, then heat to 45°C and continue to react for 24 hours until the product system is colorless and transparent. Heat the product system to 110°C and maintain for 2h, remove excess hydrogen peroxide, then add excess sodium chloride to precipitate a white solid in the solution, dry the white solid, and obtain 4,4′-sodium disulfonate-3,3′-difluorodiphenyl sulfone. According to the hydrogen nuclear magnetic resonance spectrum test, the chemical structure of the 4,4′-sodium disulfonate-3,3′-difluorodiphenyl sulfone conforms to its theoretical chemical structure formula.

[0176] Example 4

[0177] This embodiment 4 provides a sulfonated monomer and a preparation method thereof. The sulfonated monomer provided in embodiment 4 is named 1,4-bis(3-fluoro-4-sulfonate lithium phenylsulfone)benzene, and its synthesis route and preparation method are as follows:

[0178]

[0179] Add 1,4-benzenedisulfonyl chloride (13.8 g, 0.05 mol) and 1,2-difluorobenzene (45.6 g, 0.4 mol) to a 500 mL single-mouth flask and mix them evenly. Then slowly add aluminum chloride (14.5 g) to the reaction system in batches, react at room temperature (25°C-30°C) for 1 hour, then slowly heat up to 80°C and react at this reaction temperature for 8 hours. Cool the reaction system to room temperature, slowly pour the mixed solution into ice water, and precipitate. After filtering the product precipitate, recrystallize it with isopropanol and vacuum dry it at 80°C to obtain 17.6 g of white solid 1,4-bis(3,4-difluorophenylsulfone)benzene.

[0180] 35 mmol of 1,4-bis(3,4-difluorophenylsulfone)benzene and 276 mmol of sodium hydrosulfide with a mass concentration of 70% were dissolved in 150 mL of N-methylpyrrolidone solvent, and reacted at room temperature (maintained at 25° C.-30° C.) for 20 hours to prepare a precursor compound.

[0181] 100 mL of deionized water was added to the product system containing the precursor compound, and then 50 mL of dilute sulfuric acid and 50 mL of glacial acetic acid were slowly added dropwise to make the pH value of the product system 4, thereby acidifying the product system so that a white solid precipitated therein, and the white solid was named 1,4-bis(3-fluoro-4-mercaptophenylsulfone)benzene. The white solid was washed three times with a 1 mol / L sulfuric acid solution and then filtered to obtain purified 1,4-bis(3-fluoro-4-mercaptophenylsulfone)benzene.

[0182] Add 1,4-bis(3-fluoro-4-mercaptophenylsulfone)benzene to a 500mL single-necked flask, continue to add 100mL of glacial acetic acid to the single-necked flask, place the single-necked flask in an ice-water bath, and slowly drop 50mL of dilute sulfuric acid and 70mL of a 30% mass concentration of hydrogen peroxide solution into the single-necked flask. The reaction system was allowed to react in an ice-water bath for 1.5 hours, then heated to 35°C and continued to react for 36 hours. The product system was heated to 110°C and maintained for 2h, excess hydrogen peroxide was removed, and then excess lithium chloride was added thereto to precipitate a white solid in the solution, which was dried to obtain 1,4-bis(3-fluoro-4-sulfonate lithium phenylsulfone)benzene. According to the hydrogen nuclear magnetic resonance spectrum test, the chemical structure of the 1,4-bis(3-fluoro-4-sulfonate lithium phenylsulfone)benzene conforms to its theoretical chemical structure formula.

[0183] Comparative Example 1

[0184] Comparative Example 1 adopts the same preparation method as Example 1 to synthesize 4,4′-sodium disulfonate-3,3′-difluorodiphenyl sulfone. The difference between Comparative Example 1 and Example 1 is that when preparing the precursor compound 4,4′-dimercapto-3,3′-difluorodiphenyl sulfone, the reaction temperature is increased from room temperature to 60°C.

[0185] The product of Example 1 was tested by thin layer liquid chromatography analysis, which showed that it contained a large amount of tri-substituted products and tetra-substituted products. This shows that when the reaction temperature is increased to 60°C, the substitution effect of the fluorine element at the 3 and 3' positions is poor, and the desired selective substitution effect cannot be achieved.

[0186] Example 5

[0187] This embodiment 5 provides a sulfonated polymer, which uses the 4,4′-sodium disulfonate-3,3′-difluorodiphenyl sulfone provided in embodiment 1 as the first monomer compound, and also uses 4,4′-thiobisthiophenol as the second monomer compound.

[0188] The preparation method of the sulfonated polymer is as follows:

[0189] In a 250ml four-necked bottle, 10.80g of 4,4′-disulfonic acid sodium-3,3′-difluorodiphenyl sulfone, 5.50g of 4,4′-thiobisthiophenol, 3.32g of potassium carbonate, 30ml of toluene and 48ml of nitrogen methyl pyrrolidone were added. The reaction system was heated, and water was brought to the water separator connected to the four-necked bottle based on toluene, and the excess toluene was refluxed from the water separator to the four-necked bottle. Under continuous stirring, the reaction was carried out at a reaction temperature of 150°C for 3h. Subsequently, toluene and water were separated from the water separator, and the reaction temperature was raised to 200°C, and the reaction was continued for 8h. Subsequently, the product system in the four-necked bottle was poured into isopropanol to precipitate a solid. The solid was dissolved with a 0.5mol / L hydrochloric acid aqueous solution, and precipitated again with isopropanol, and the operation process was repeated 3 times. Then, the separated product is placed in a dialysis bag and soaked in deionized water for more than 2 hours, and the sulfonated polymer is obtained after suction filtration and drying.

[0190] The chemical structure and H NMR spectrum of the sulfonated polymer are as follows Figure 2 As shown, it can be seen that the sulfonated polymer has a characteristic signal peak (corresponding to hydrogen No. 1) at 7.15ppm-7.25ppm in the low field region of the nuclear magnetic hydrogen spectrum, and the signal peak is a single peak.

[0191] Comparative Example 2

[0192] This comparative example 2 provides a sulfonated polymer, which is prepared in the same manner as in Example 5, except that in Comparative Example 2, 3,3′-sodium disulfonate-4,4′-dichlorodiphenyl sulfone is used to replace the 4,4′-sodium disulfonate-3,3′-difluorodiphenyl sulfone provided in Example 1 as the sulfonated monomer, and 4,4′-thiobisthiophenol is also used as another monomer, and other operating conditions are the same.

[0193] The chemical structure and H NMR spectrum of the prepared sulfonated polymer are as follows: Figure 3 As shown, it can be seen that there is a great difference in the chemical structure between the sulfonated polymer prepared in Comparative Example 2 and the polymer prepared in Example 5. The different chemical structures of the two make the properties of the two different.

[0194] Test Example 1

[0195] With respect to the sulfonated polymers provided in Example 5 and Comparative Example 2, polymer membranes were prepared respectively using the solution casting method using the two sulfonated polymers, and the thickness of the polymer membranes was 50±3 μm.

[0196] The two polymer membranes were subjected to strength tests. Specifically, the tensile strength and elongation at break of the polymer membranes were tested using the proton exchange membrane test method specified in GB / T 20042.3-2009.

[0197] The test results show that the tensile strength of the polymer membrane obtained based on the sulfonated polymer provided in Example 5 is 22 MPa, and the elongation at break is 20%. The tensile strength of the polymer membrane obtained based on the sulfonated polymer provided in Comparative Example 2 is 23 MPa, and the elongation at break is 9%.

[0198] It can be seen that the flexibility of the sulfonated polymer provided in Example 5 is significantly improved compared with the flexibility of the sulfonated polymer provided in Comparative Example 2.

[0199] In addition, based on the sulfonated monomer provided in Example 3 and Example 4 as the first monomer compound, 4,4'-thiobisthiophenol as the second monomer compound, the corresponding sulfonated polymers were synthesized in the same manner as in Example 5, and the two sulfonated polymers were used to prepare polymer membranes using the solution casting method, and the thickness of the polymer membranes was 50±3μm. After testing, the polymer membrane obtained from the sulfonated monomer corresponding to Example 3 had an elongation at break of 20%, and the polymer membrane obtained from the sulfonated monomer corresponding to Example 4 had an elongation at break of 18%.

[0200] The above description is only for the purpose of facilitating those skilled in the art to understand the technical solution of the present disclosure and is not intended to limit the present disclosure. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. A sulfonated monomer, characterized in that: The sulfonated monomer comprises: a first phenyl group, a segment containing an electron-withdrawing group, and a second phenyl group; The electron-withdrawing group-containing segments are respectively connected to the first carbon atom of the first phenyl group and the second carbon atom of the second phenyl group; The first phenyl group and the second phenyl group both have a fluorine group and a sulfonated group, the fluorine group in the first phenyl group is arranged in the meta position relative to the first carbon atom, the sulfonated group in the first phenyl group is arranged in the para position relative to the first carbon atom, the fluorine group in the second phenyl group is arranged in the meta position relative to the second carbon atom, and the sulfonated group in the second phenyl group is arranged in the para position relative to the second carbon atom.

2. The sulfonated monomer according to claim 1, characterized in that The electron-withdrawing group-containing segment includes a first electron-withdrawing group, and the number of the first electron-withdrawing group is 1-11.

3. The sulfonated monomer according to claim 2, characterized in that The number of the first electron-withdrawing groups is greater than or equal to 2, and the electron-withdrawing group-containing segment further includes: an aromatic group or a heteroaromatic ring containing 5 to 18 carbon atoms, and the aromatic group or the heteroaromatic ring is connected between two of the first electron-withdrawing groups.

4. The sulfonated monomer according to claim 3, characterized in that The aryl or heteroaryl ring contains a second electron withdrawing group.

5. The sulfonated monomer according to any one of claims 1 to 4, characterized in that The chemical structural formula of the sulfonated monomer is as follows: Wherein, X is the first electron-withdrawing group, Ar is an aromatic group or an aromatic heterocycle containing 5-18 carbon atoms, M is a monovalent cation; and n is an integer of 0-10.

6. The sulfonated monomer according to any one of claims 2 to 5, characterized in that The first electron-withdrawing group is selected from at least one of a sulfone group, a ketone group, and an imide group.

7. A method for preparing a sulfonated monomer, characterized in that: The sulfonated monomer is as described in any one of claims 1 to 6; the preparation method of the sulfonated monomer comprises: A precursor compound is provided, wherein the precursor compound comprises a third phenyl group, a segment containing an electron-withdrawing group, and a fourth phenyl group, wherein the segment containing an electron-withdrawing group is respectively connected to the first carbon atom of the third phenyl group and the second carbon atom of the fourth phenyl group; the third phenyl group and the fourth phenyl group both have a fluorine group and a thiol group, the fluorine group in the third phenyl group is arranged in a meta position relative to the first carbon atom, the thiol group in the third phenyl group is arranged in a para position relative to the first carbon atom, the fluorine group in the fourth phenyl group is arranged in a meta position relative to the second carbon atom, and the thiol group in the fourth phenyl group is arranged in a para position relative to the second carbon atom; The precursor compound is subjected to sulfonation treatment so that the thiol group is converted into a sulfonated group to obtain the sulfonated monomer.

8. The method for preparing a sulfonated monomer according to claim 7, characterized in that: The precursor compound provided comprises: A raw material compound is provided, wherein the raw material compound comprises a third phenyl group, a segment containing an electron-withdrawing group, and a fourth phenyl group; the segment containing an electron-withdrawing group is respectively connected to the first carbon atom of the third phenyl group and the second carbon atom of the fourth phenyl group; the third phenyl group and the fourth phenyl group each have two fluorine groups, the two fluorine groups in the third phenyl group are respectively arranged in the meta position and the para position relative to the first carbon atom, and the two fluorine groups in the fourth phenyl group are respectively arranged in the meta position and the para position relative to the second carbon atom; The fluorine group at the para position of the raw material compound is selectively replaced by a sulfur-containing compound, so that the fluorine group at the para position is converted into a thiol group to obtain a precursor compound, wherein the sulfur-containing compound includes sodium hydrosulfide or sodium sulfide.

9. The method for preparing a sulfonated monomer according to claim 8, characterized in that: The selective substitution of the fluorine group at the para position by using the sulfur-containing compound comprises: reacting the sulfur-containing compound with the raw material compound at a reaction temperature of 0° C. to 40° C. to achieve the selective substitution.

10. The method for preparing a sulfonated monomer according to claim 7, characterized in that: The precursor compound provided comprises: A raw material compound is provided, wherein the raw material compound comprises a third phenyl group, a segment containing an electron-withdrawing group, and a fourth phenyl group; the segment containing an electron-withdrawing group is respectively connected to the first carbon atom of the third phenyl group and the second carbon atom of the fourth phenyl group; the third phenyl group and the fourth phenyl group each have two fluorine groups, the two fluorine groups in the third phenyl group are respectively arranged in the meta position and the para position relative to the first carbon atom, and the two fluorine groups in the fourth phenyl group are respectively arranged in the meta position and the para position relative to the second carbon atom; Allowing benzyl mercaptan to undergo a selective substitution reaction with the raw material compound to obtain an intermediate compound; The intermediate compound is reacted with boron tribromide or aluminum trichloride to obtain the precursor compound.

11. The method for preparing a sulfonated monomer according to claim 10, characterized in that: The selective substitution reaction of benzyl mercaptan and the raw material compound comprises: reacting the benzyl mercaptan and the raw material compound at a reaction temperature of 0° C. to 40° C. to achieve the selective substitution reaction.

12. The method for preparing a sulfonated monomer according to claim 7, characterized in that: The step of subjecting the precursor compound to sulfonation so that the thiol group is converted into a sulfonated group to obtain the sulfonated monomer comprises: Performing the sulfonation treatment on the precursor compound by using an oxidant, so that the thiol group is converted into a sulfonic acid group, thereby obtaining a precursor of the sulfonated monomer; The precursor of the sulfonated monomer is treated with a saturated salt to convert the sulfonic acid group into a sulfonate group, thereby obtaining the sulfonated monomer.

13. A polymer, characterized in that The polymer comprises a first structural unit, wherein the first structural unit is derived from a first monomer compound, and the first monomer compound is the sulfonated monomer according to any one of claims 1 to 6.

14. The polymer according to claim 13, characterized in that The polymer further includes a second structural unit, the second structural unit is derived from a second monomer compound, the second monomer compound includes at least two functional groups for polycondensation reaction, and the functional groups for polycondensation reaction include at least one of a thiol group and a hydroxyl group.

15. A proton exchange membrane, characterized in that: The proton exchange membrane is prepared from the polymer according to claim 13 or 14.

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