Cation exchange graft polymer, preparation method thereof and proton exchange membrane

Abstract

The invention relates to a cation exchange graft polymer, a preparation method thereof and a proton exchange membrane, and belongs to the technical field of ion exchange polymers. The preparation method of the cation exchange graft polymer comprises the following steps: carrying out graft polymerization reaction on an indole monomer and a main chain polymer under the catalytic action of phosphorus pentoxide and methanesulfonic acid to obtain the cation exchange graft polymer, the indole monomer is a sulfonated indole monomer as shown in a formula 1 or consists of the sulfonated indole monomer as shown in the formula 1 and a non-sulfonated indole monomer as shown in a formula 2. The indole polymer is prepared by carrying out graft polymerization reaction on the indole monomer and the main chain polymer, so that the flexibility of the main chain polymer and the free radical oxidation resistance, high mechanical strength and swelling resistance of the chain segment of the side chain indole polymer can be considered at the same time; further, the cation exchange polymer with good oxidation resistance, mechanical property and conductivity is obtained.

Description

Technical Field

[0001] The invention relates to a cation exchange graft polymer and a preparation method thereof, and a proton exchange membrane, belonging to the technical field of ion exchange polymers. Background Art

[0002] Cation exchange membranes, especially proton exchange membranes (PEMs), have great application prospects in the fields of fuel cells, water electrolysis to produce hydrogen, flow batteries, etc. Although PEMs based on perfluorosulfonic acid polymers have high conductivity and ultra-high chemical stability, they are expensive and have average selectivity. PEMs based on aromatic polymers are widely considered to be a very promising alternative to perfluorosulfonic acid membranes. Existing research has made significant progress and many beneficial common conclusions in the relationship between the structural design of aromatic PEMs and membrane properties. For example, compared with general main chain PEMs, side branch PEMs have higher conductivity and lower swelling; reducing ether oxygen structures can improve oxidation resistance and stability; increasing nitrogen heteroaromatic rings can reduce swelling. Chinese patent document CN116253673A discloses an indole sulfonated polymer and a proton exchange membrane. The main chain of the indole sulfonated polymer disclosed in the patent document is completely connected by a rigid indole ring and a carbonyl group, so that the corresponding PEM can maintain low swelling at high ion exchange capacity and temperature. However, the main chain is too rigid, resulting in a lack of flexibility of the membrane, which is not conducive to the assembly of the membrane electrode.

[0003] Therefore, there is an urgent need to develop a cation exchange polymer that can be used in proton exchange membranes and has antioxidant properties, low swelling, high conductivity and high toughness. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing a cation exchange graft polymer to solve the problem of poor toughness of the currently prepared low swelling cation exchange polymer.

[0005] The second object of the present invention is to provide a cation exchange graft polymer to solve the problem of poor toughness of the current low swelling cation exchange polymer.

[0006] The third object of the present invention is to provide a proton exchange membrane to solve the problem that the current proton exchange membrane cannot take into account oxidation resistance, low swelling degree, high conductivity and high toughness.

[0007] In order to achieve the above purpose, the technical scheme adopted by the preparation method of the cation exchange graft polymer of the present invention is:

[0008] A method for preparing a cation exchange graft polymer comprises the following steps: subjecting an indole monomer and a main chain polymer to a graft polymerization reaction under the catalytic action of phosphorus pentoxide and methanesulfonic acid to obtain a cation exchange graft polymer; the indole monomer is a sulfonated indole monomer as shown in Formula 1 or is composed of a sulfonated indole monomer as shown in Formula 1 and a non-sulfonated indole monomer as shown in Formula 2;

[0009]

[0010] In Formula 1, G1 is -(CH2)n-, n is 3 or 4, and G2 is -SO3M; M in -SO3M and -OM in Formula 1 are both selected from any one of Li, Na, K or H; in Formula 2, G3 is selected from -H or a saturated straight-chain alkyl group of C1-C12;

[0011] The inherent viscosity of the main chain polymer is greater than 0.4 dL / g, and the structural formula is as follows:

[0012]

[0013] In the formula, Ar 1 ,Ar 2 ,Ar 3 with Ar 4 Represent the structural units of the main chain polymer, and x represents the structural unit Ar 1 with Ar 2 The mole fraction of the main chain structure of the entire polymer, 0 <x≤1;

[0014] Ar 1 It is a structural unit shown in Formula 3 to Formula 7:

[0015]

[0016] Ar 2 and Ar 4 Independently selected from the structural units represented by Formula 8 to Formula 12:

[0017]

[0018] Ar 3 It is a structural unit shown in Formula 13 to Formula 14:

[0019]

[0020] Wherein, R1 is -H or methyl; R2 and R3 are independently selected from -O- or -S-; R4 and R5 are independently selected from -O- or -S-; R6 and R7 are independently selected from -O- or -S-, R8 is methyl or phenyl; R9 and R 10 are independently selected from -O- or -S-; R11 and R 13 are independently selected from -O- or -S-, R 12 is a single bond, -S-, a sulfone group, a carbonyl group, an isopropyl group or a hexafluoroisopropyl group.

[0021] The preparation method of the cation exchange graft polymer of the present invention is prepared by graft polymerization reaction of indole monomer and main chain polymer, which can take into account the flexibility of the main chain polymer and the free radical oxidation resistance, high mechanical strength and swelling resistance of the side chain indole polymer segment, thereby obtaining a cation exchange polymer with good oxidation resistance, mechanical properties and conductivity. In the preparation method of the cation exchange graft polymer of the present invention, the main chain polymer contains electron-rich aromatic sites that can undergo acylation reaction with carboxyl groups, such as the para position of aromatic ether oxygen structure, the para position of alkyl substituted benzene ring, the 1-position or 4-position of biphenyl or fluorene structure, the para position of carbazole nitrogen structure, etc.

[0022] Preferably, the Ar 1 is a structural unit shown in Formula 3, Formula 5 or Formula 7, R1 in Formula 3 is -H, and R4 and R5 in Formula 5 are both -S-; Ar 2 and Ar 4 independently selected from the structural units shown in Formula 8, Formula 9, Formula 10 or Formula 12; R9 and R in Formula 13 10 All are -O-; R in formula 13 11 and R 13 All are -O-, R 12 is a single bond, a sulfone group or a hexafluoroisopropyl group; the sulfonated indole monomer shown in Formula 1 is dipotassium 1-sulfopropanyl-6-indolecarboxylate, and the non-sulfonated indole monomer shown in Formula 2 is 6-indolecarboxylic acid.

[0023] Preferably, x is 0.1-1.

[0024] Preferably, the inherent viscosity of the cation exchange graft polymer is greater than 1.0 dL / g; and the mass ratio of phosphorus pentoxide to methanesulfonic acid is (7-10):100.

[0025] Preferably, the inherent viscosity of the cation exchange graft polymer is 1.1-6.3 dL / g; and the mass ratio of phosphorus pentoxide to methanesulfonic acid is (8.5-10):100.

[0026] Preferably, the ratio of the total mass of the main chain polymer and the indole monomer to the total mass of phosphorus pentoxide and methanesulfonic acid is (5-30):100.

[0027] Preferably, the indole monomer is a sulfonated indole monomer as shown in Formula 1, and the sulfonated indole monomer is 1The molar ratio of the units is (5-20):1; or the indole monomer is composed of a sulfonated indole monomer as shown in Formula 1 and a non-sulfonated indole monomer as shown in Formula 2, and the sulfonated indole monomer and the Ar in the main chain polymer 1 The molar ratio of the units is (10-15):1, the non-sulfonated indole monomer and the Ar in the main chain polymer 1 The molar ratio of the units is (5-10):1.

[0028] Preferably, the graft polymerization reaction is carried out at a temperature of 30 to 100° C. and for a time of 2 to 24 hours.

[0029] The technical solution adopted by the cation exchange graft polymer of the present invention is:

[0030] A cation exchange graft polymer prepared by the method for preparing a cation exchange graft polymer as described above.

[0031] The cation exchange graft polymer of the present invention comprises a main chain polymer and a rigid indole sulfonated polymer segment grafted on the side chain of the main chain polymer and completely free of ether bonds, and has the flexibility of the main chain polymer and the resistance to free radical oxidation, high mechanical strength and swelling resistance of the side chain polymer segment. Compared with the completely rigid indole sulfonated polymer, the cation exchange graft polymer of the present invention has better toughness. At the same time, compared with the main chain indole sulfonated polymer, the side chain indole sulfonated polymer segment has a reduced amount of indole sulfonated monomers and a lower cost. In addition, the hydrophobic main chain and the hydrophilic side branches are more conducive to forming a microphase separation structure and promoting the transfer of ions.

[0032] The technical solution adopted by the proton exchange membrane of the present invention is:

[0033] A proton exchange membrane using the cation exchange graft polymer described above.

[0034] The proton exchange membrane of the invention is made of cation exchange graft polymer and has high ion exchange capacity, proton conductivity, swelling rate, tensile strength, elongation at break and oxidation resistance.

[0035] Preferably, the preparation method of the proton exchange membrane is as follows: a cation exchange graft polymer solution is coated on the surface of a substrate, and after drying, a proton exchange membrane is obtained; the cation exchange graft polymer solution is composed of a cation exchange graft polymer and a solvent, the mass fraction of the cation exchange graft polymer is 5 to 15%, and the solvent is dimethyl sulfoxide, dimethylacetamide, and 1-methylpyrrolidone. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The hydrogen nuclear magnetic resonance spectrum of the main chain polymer Z1 used in the present invention (deuterated chloroform as solvent).

[0037] Figure 2 This is the hydrogen nuclear magnetic resonance spectrum of the graft polymer 4-1 prepared in Example 22 of the present invention (deuterated dimethyl sulfoxide is the solvent). DETAILED DESCRIPTION

[0038] The preparation method of the cation exchange graft polymer of the present invention is a pioneering invention. The present invention is prepared by graft polymerization reaction of indole monomer and main chain polymer, which can take into account the flexibility of the main chain polymer and the free radical oxidation resistance, high mechanical strength and swelling resistance of the side chain indole polymer segment, thereby obtaining a cation exchange polymer with good oxidation resistance, mechanical properties and conductivity.

[0039] In the present invention, when the indole monomer consists only of the sulfonated indole monomer shown in Formula 1, the grafted segment in the grafted polymer obtained by the graft polymerization reaction is a segment completely formed by the sulfonated indole monomer unit.

[0040] In the present invention, when the indole monomer is composed of the sulfonated indole monomer shown in Formula 1 and the non-sulfonated indole monomer shown in Formula 2, the sulfonated indole monomer and the non-sulfonated indole monomer can be added at the same time, or the non-sulfonated indole monomer can be added first for graft polymerization reaction for a period of time and then the sulfonated indole monomer can be added to continue the graft polymerization reaction, or the sulfonated indole monomer can be added first for graft polymerization reaction for a period of time and then the non-sulfonated indole monomer can be added to continue the graft polymerization reaction, preferably, the non-sulfonated indole monomer is added first for graft polymerization reaction for a period of time and then the sulfonated indole monomer is added to continue the graft polymerization reaction. The order of adding the two monomers determines the arrangement order of the sulfonated indole monomer unit and the non-sulfonated indole monomer unit in the graft segment. When the sulfonated indole monomer and the non-sulfonated indole monomer are added at the same time, the grafted segments in the grafted polymer obtained by the graft polymerization reaction are random copolymer segments, that is, the two units are randomly arranged in the grafted segments; when the sulfonated indole monomer is added first for a period of graft polymerization and then the non-sulfonated indole monomer is added to continue the graft polymerization reaction, the grafted segments in the grafted polymer obtained by the graft polymerization reaction are diblock copolymer segments formed by the segments formed by the sulfonated indole monomer units and the segments formed by the non-sulfonated indole monomer units, wherein the sulfonated indole monomer is The two ends of the chain segment formed by the body unit are respectively connected to the main chain and the chain segment formed by the non-sulfonated indole monomer unit; when the non-sulfonated indole monomer is first added for graft polymerization reaction for a period of time and then the sulfonated indole monomer is added to continue the graft polymerization reaction, the grafted chain segment in the grafted polymer obtained by the graft polymerization reaction is a diblock copolymer chain segment formed by combining the chain segment formed by the non-sulfonated indole monomer unit and the chain segment formed by the sulfonated indole monomer unit, wherein the two ends of the chain segment formed by the non-sulfonated indole monomer unit are respectively connected to the main chain and the chain segment formed by the sulfonated indole monomer unit.

[0041] It is understandable that in order to avoid the reaction of phosphorus pentoxide with water during the reaction process, which may cause the graft polymerization reaction to fail, the graft polymerization reaction is carried out under anhydrous conditions.

[0042] It is understood that the cations corresponding to the sulfonate anions in the cation exchange graft polymer can be converted by conventional ion exchange methods to obtain cations using other cations (such as H + 、Na + , K + Cation exchange graft polymers (eg,

[0043] In the present invention, drying includes atmospheric pressure drying and vacuum drying performed sequentially, the atmospheric pressure drying temperature is 60° C., the time is 24 hours, and the vacuum drying temperature is 80° C., the time is 12 hours.

[0044] The technical solution of the present invention is further described below in conjunction with specific implementation methods.

[0045] The inherent viscosity of the polymers in Examples 1-27 and Comparative Examples was measured by the following method: using 99% pure methanesulfonic acid as solvent, the polymer was prepared into a solution with a concentration of 0.3 g / 100 mL, and the inherent viscosity was measured using an Ubbelohde viscometer at a temperature of 30°C. The purity of the monomers and solvents used in the present invention is greater than 99%. Nuclear magnetic resonance hydrogen spectrum ( 1 H NMR) was recorded on a Bruker AVANCE AV400 nuclear magnetic resonance spectrometer using deuterated chloroform or deuterated dimethyl sulfoxide (DMSO-d6, tetramethylsilane as internal standard) as solvent.

[0046] The main chain polymers in Examples 1-27 can be prepared according to the methods of the prior art, for example, according to Reference 1: Attwood TE, Dawson PC, Freeman JL, et al. Synthesis and properties of polyaryletherketones [J]. Polymer, 1981, 22 (8): 1096-1103.; Reference 2: Shin DW, Lee SY, Kang NR, et al. Durable Sulfonated Poly (arylene sulfide sulfone nitrile) s Containing Naphthalene Units for Direct Methanol Fuel Cells (DMFCs) [J]. Macromolecules, 2013, 46 (9): 3452-3460.; Reference 3: Gao Y, Hlil A, Wang J, et al. Synthesis of Homo- and Copoly (arylene bicarbazole) s via Nucleophilic Substitution Polycondensation Reactions of NH Groups with Activated Dihalides[J].Macromolecules, 2007, 40(14):4744-4746. In general, the main chain polymers in Examples 1-27 are prepared by polymerization of a certain proportion of bisphenol or bisthiophenol or bisamino aromatic monomers and activated halogenated aromatic monomers in a high boiling point polar aprotic solvent (such as N-methyl-2-pyrrolidone, cyclopentane sulfone, etc.) under the action of a base; the main chain polymers in the present invention can be dissolved in methanesulfonic acid, and the inherent logarithmic viscosity of the main chain polymer is 0.82-2.03 dL / g.

[0047] The preparation method of the main chain polymer Z1 is as follows: 8.4239 g of 4,4′-difluorobenzophenone, 0.4248 g of resorcinol, 11.6767 g of hexafluorobisphenol A, and 6.38 g of anhydrous potassium carbonate powder are weighed in sequence and added into a 250 mL three-necked flask equipped with a magnetic stirrer, a nitrogen inlet / outlet, a Dean-Stark water separator, and a reflux condenser; 40 mL of toluene and 38 mL of N-methyl-2-pyrrolidone are measured and poured into a three-necked flask, and then the mixture is gradually heated to 145° C. under a nitrogen atmosphere, and stirred and refluxed for 3 hours to remove water by azeotropic distillation; then the temperature is raised to 180° C. and the reaction is continued for 5 hours; the reaction is stopped, 15 mL of N-methyl-2-pyrrolidone is added to dilute the reaction solution, and then slowly poured into 500 mL of distilled water, the resulting precipitate is fully extracted and washed with a 95% ethanol solution, and finally dried at 105° C. for 48 hours to obtain the main chain polymer Z1. The H NMR spectrum of the main chain polymer Z1 is as follows Figure 1 As shown, the nuclear magnetic resonance hydrogen spectrum shows that the structure of the polymer is consistent with expectations. The chemical reaction equation occurring during the reaction is expressed as follows:

[0048]

[0049] The preparation method of the main chain polymer Z2 is the same as that of the main chain polymer Z1, except that the molar ratio of the monomers resorcinol to 4,4′-difluorobenzophenone is changed from 0.1 to 0.2, and the molar ratio of hexafluorobisphenol A to 4,4′-difluorobenzophenone is changed from 0.9 to 0.8, while other conditions remain unchanged.

[0050] The preparation method of the main chain polymer Z3 is as follows: 3.2231 g of 1,4-bis(4-fluorobenzoyl)benzene, 3.8254 g of 9,9'-bis(4-mercaptophenyl)fluorene, and 1.52 g of anhydrous potassium carbonate powder were weighed in sequence and added into a 150 mL three-necked flask equipped with a magnetic stirrer, nitrogen inlet / outlet, Dean-Stark water separator, and reflux condenser; 30 mL of toluene and 30 mL of N-methyl-2-pyrrolidone were weighed and poured into the three-necked flask. The mixture was gradually heated to 145°C in a nitrogen atmosphere, and stirred and refluxed for 3 hours, and water was removed by azeotropic distillation; the temperature was then raised to 170°C, and the reaction was continued for 6 hours; the reaction was stopped, 15 mL of N-methyl-2-pyrrolidone was added to dilute the reaction solution, and then slowly poured into 500 mL of distilled water; the obtained precipitate was fully extracted and washed with 95% ethanol solution, and finally vacuum dried at 105°C for 48 hours to obtain the main chain polymer Z3. The chemical reaction equation occurring during the reaction is expressed as follows:

[0051]

[0052] The preparation method of the main chain polymer Z4 is as follows: 3.2231 g of 1,4-bis(4-fluorobenzoyl)benzene, 1.9127 g of 9,9'-bis(4-mercaptophenyl)fluorene, 1.0113 g of 4,4'-biphenylphenol, and 1.52 g of anhydrous potassium carbonate powder are weighed in sequence and added into a 150 mL three-necked flask equipped with a magnetic stirrer, nitrogen inlet / outlet, Dean-Stark water separator, and reflux condenser; 30 mL of toluene and 26 mL of N-methyl-2-nitropropene are weighed ...; 30 mL of toluene and 26 mL of N-methyl-2-nitropropene are weighed and added into a 150 mL three-necked flask; 30 mL of toluene and 26 mL of N-methyl-2-nitropropene are weighed and added into a 150 mL three-necked flask; 30 mL of toluene and -Pour pyrrolidone into a three-necked flask, then gradually heat the mixture to 145°C under a nitrogen atmosphere, stir and reflux for 3h, remove water by azeotropic distillation; then raise the temperature to 180°C, continue stirring and react for 6h; stop the reaction, add 15mL of N-methyl-2-pyrrolidone to dilute the reaction solution, then slowly pour into 500mL of distilled water, the resulting precipitate is fully extracted and washed with 95% ethanol solution, and finally vacuum dried at 105°C for 48h to obtain the main chain polymer Z4. The chemical reaction equation occurring during the reaction is expressed as follows:

[0053]

[0054] The preparation method of the main chain polymer Z5 is as follows: 3.2231g of 1,4-bis(4-fluorobenzoyl)benzene, 3.3241g of 3,3′-bicarbazole, and 2.07g of anhydrous potassium carbonate powder are weighed in sequence and added into a 150mL three-necked flask equipped with a magnetic stirrer, a nitrogen inlet / outlet, a Dean-Stark water separator, and a reflux condenser; 30mL of toluene and 26mL of cyclopentane are measured and poured into a three-necked flask, and then the mixture is gradually heated to 145°C under a nitrogen atmosphere, and stirred and refluxed for 3h, and water is removed by azeotropic distillation; then the temperature is raised to 190°C, and the stirring reaction is continued for 6h; the reaction is stopped, 15mL of cyclopentane is added to dilute the reaction solution, and then slowly poured into 500mL of distilled water, and the resulting precipitate is fully extracted and washed with a 95% ethanol solution, and finally vacuum dried at 105°C for 48h to obtain the main chain polymer Z5. The chemical reaction equation occurring during the reaction is expressed as follows:

[0055]

[0056] The preparation method of the main chain polymer Z6 is as follows: 2.5425 g of 4,4′-difluorodiphenyl sulfone, 3.3241 g of 3,3′-bicarbazole, 1.1011 g of hydroquinone, 3.1427 g of bis(4-fluorophenyl)phenylphosphine oxide, and 6.61 g of anhydrous potassium carbonate powder are weighed in sequence and added into a 250 mL three-necked flask equipped with a magnetic stirrer, a nitrogen inlet / outlet, a Dean-Stark water separator, and a reflux condenser; 45 mL of methanol is measured. Benzene and 38 mL of sulfolane were poured into a three-necked flask, and then the mixture was gradually heated to 145°C under a nitrogen atmosphere, and stirred and refluxed for 3 hours, and water was removed by azeotropic distillation; then the temperature was raised to 190°C, and the reaction was continued for 6 hours with stirring, and the reaction was stopped, 15 mL of sulfolane was added to dilute the reaction solution, and then slowly poured into 500 mL of distilled water, and the resulting precipitate was fully extracted and washed with 95% ethanol solution, and finally vacuum dried at 105°C for 48 hours to obtain the main chain polymer Z6. The chemical reaction equation occurring during the reaction is expressed as follows:

[0057]

[0058] The preparation method of the main chain polymer Z7 is as follows: 1.8606g of hexafluorobenzene, 1.6621g of 3,3′-bicarbazole, 1.2514g of 4,4′-dihydroxydiphenyl sulfone, and 1.65g of anhydrous potassium carbonate powder are weighed in sequence and added into a 150mL three-necked flask equipped with a magnetic stirrer, nitrogen inlet / outlet, Dean-Stark water separator, and reflux condenser; 25mL of N-methyl-2-pyrrolidone is measured and poured into a three-necked flask, and then the mixture is gradually heated to 80°C under a nitrogen atmosphere, stirred for 12h, the reaction is stopped, and the reaction solution is slowly poured into 500mL of distilled water, and the resulting precipitate is fully extracted and washed with a 95% ethanol solution, and finally vacuum dried at 105°C for 48h to obtain the main chain polymer Z7. The chemical reaction equation occurring during the reaction is expressed as follows:

[0059]

[0060] The chemical structure of the main chain polymer is shown below:

[0061]

[0062] In the formula, Ar 1 ,Ar 2 ,Ar 3 with Ar 4 Represent the structural units of the main chain polymer, and x represents the structural unit Ar 1 with Ar 2The molar fraction in the main chain structure of the entire polymer, where 0 < x ≤ 1. Table 1 summarizes the structures and inherent viscosity η1 of the representative main chain polymers Z1 to Z7 used.

[0063] Table 1 Composition structural units Ar of the main chain polymer 1 , Ar 2 , Ar 3 , Ar 4 , x and inherent viscosity η1

[0064]

[0065]

[0066] I. Specific examples of the cation exchange graft polymer and its preparation method of the present invention are as follows:

[0067] For the preparation method of the cation exchange graft polymer in Examples 1 - 9, it specifically includes the following steps: Add the main chain polymer and a mixture composed of phosphorus pentoxide and methanesulfonic acid (the mass ratio of phosphorus pentoxide to methanesulfonic acid is 8.5:100) into a glass reaction kettle filled with nitrogen, stir and dissolve at 100 °C, then add dipotassium 1-sulfopropyl-6-indolecarboxylate, continue to stir and react at temperature T for t hours. After the reaction, slowly add the obtained viscous reaction solution into water, let it stand, the insoluble substances in the viscous reaction solution precipitate in water, filter, extract the obtained precipitate with water through a Soxhlet extractor for 24 hours, and finally vacuum dry at 100 °C for 24 hours to obtain the graft polymer, which is the cation exchange graft polymer. The chemical structure of the main chain polymer is shown as the following formula:

[0068]

[0069] In the formula, Ar 1 , Ar 2 , Ar 3 and Ar 4 respectively represent the composition structural units of the main chain polymer, x represents the molar fraction of the composition structural unit Ar 1 and Ar 2 in the main chain structure of the entire polymer, where 0 < x ≤ 1.

[0070] Denote the ratio of the total mass of the main chain polymer and the reaction monomer (dipotassium 1-sulfopropyl-6-indolecarboxylate) to the total mass of phosphorus pentoxide and methanesulfonic acid as w, and the ratio of dipotassium 1-sulfopropyl-6-indolecarboxylate to Ar in the main chain polymer 1The ratio of the amount of substance of the unit is recorded as r, the reaction temperature is T, and the reaction time is t. The codes of the graft polymers prepared in Examples 1-9 are 1-1, 1-2, 1-3, 1-4, 1-5, 1-6, 1-7, 1-8 and 1-9, respectively. The inherent viscosity η2 of the obtained graft polymers is shown in Table 2.

[0071] Table 2 Relevant parameters in the preparation method of Examples 1-9

[0072]

[0073]

[0074] The chemical reaction equation for preparing the graft polymer 1-1 in Example 1 is as follows:

[0075]

[0076] The para position of the ether oxygen structure in the resorcinol structural unit of the main chain polymer can undergo an acylation reaction with the carboxyl group of 1-sulfopropanyl-6-indolecarboxylic acid dipotassium and continue to polymerize, thereby forming a side chain composed of a sulfonated indole structure, and the average length of the side chain is determined by the ratio r of the amount of substance of 1-sulfopropanyl-6-indolecarboxylic acid dipotassium to the resorcinol structural unit in the main chain polymer.

[0077] The preparation method of the cation exchange graft polymer of Examples 10-15 specifically includes the following steps: adding a main chain polymer and a mixture consisting of phosphorus pentoxide and methanesulfonic acid (the mass ratio of phosphorus pentoxide to methanesulfonic acid is 8.5:100) into a glass reactor filled with nitrogen and stirring and dissolving at 80°C, then adding 1-sulfopropane-6-indolecarboxylic acid dipotassium and 6-indolecarboxylic acid, and continuing to stir and react at 80°C for 24 hours. After the reaction is completed, slowly adding the obtained viscous reaction liquid into water, letting it stand, and the insoluble matter in the viscous reaction liquid precipitates in water, filtering, and extracting the obtained precipitate with water through an extractor for 24 hours, and finally vacuum drying at a temperature of 100°C for 24 hours to obtain a grafted polymer, that is, a cation exchange graft polymer.

[0078] The ratio of the total mass of the main chain polymer and the reaction monomers (1-sulfopropane-6-indolecarboxylic acid dipotassium and 6-indolecarboxylic acid) to the total mass of phosphorus pentoxide and methanesulfonic acid was controlled to be 15:100. 1 The ratio of the amount of substance in the unit is denoted by r 1 , 6-indolecarboxylic acid and Ar in the main chain polymer 1 The ratio of the amount of substance in the unit is denoted by r 2The codes of the grafted polymers prepared in Examples 10-15 are 2-1, 2-2, 2-3, 2-4, 2-5 and 2-6, respectively. The inherent logarithmic viscosity η2 of the grafted polymers is shown in Table 3.

[0079] Table 3 Relevant parameters in the preparation method of Examples 10-15

[0080]

[0081]

[0082] The chemical reaction equation for preparing the graft polymer 2-1 in Example 10 is as follows:

[0083]

[0084] The para position of the ether oxygen structure in the resorcinol structural unit of the main chain polymer can undergo an acylation reaction with the carboxyl group of 1-sulfopropanyl-6-indolecarboxylic acid dipotassium or 6-indolecarboxylic acid and continue to polymerize, thereby forming a side chain composed of a sulfonated indole structure and a non-sulfonated indole structure. Since 1-sulfopropanyl-6-indolecarboxylic acid dipotassium and 6-indolecarboxylic acid are added simultaneously, the sulfonated indole structure and the non-sulfonated indole structure in the side chain are randomly distributed, and the ratio of the sulfonated indole structure to the non-sulfonated indole structure is determined by r 1 With r 2 The average length of the side chain is determined by the ratio of 1 With r 2 of and determine.

[0085] The preparation method of the cation exchange graft polymer of Examples 16-21 specifically includes the following steps: adding the main chain polymer and a mixture consisting of phosphorus pentoxide and methanesulfonic acid (the mass ratio of phosphorus pentoxide to methanesulfonic acid is 8.5:100) into a glass reactor filled with nitrogen and stirring and dissolving at 80°C, then adding 1-sulfopropane-6-indolecarboxylic acid dipotassium, continuing to stir and react at 80°C for 12 hours, and then adding 6-indolecarboxylic acid, continuing to stir and react at 80°C for 12 hours. After the reaction is completed, slowly adding the obtained viscous reaction liquid into water, letting it stand, the insoluble matter in the viscous reaction liquid precipitates in water, filtering, extracting the obtained precipitate with water through an extractor for 24 hours, and finally vacuum drying at 100°C for 24 hours to obtain a grafted polymer, i.e., a cation exchange graft polymer.

[0086] The ratio of the total mass of the main chain polymer and the reaction monomers (1-sulfopropane-6-indolecarboxylic acid dipotassium and 6-indolecarboxylic acid) to the total mass of phosphorus pentoxide and methanesulfonic acid was controlled to be 15:100. 1 The ratio of the amount of substance in the unit is denoted by r1 , 6-indolecarboxylic acid and Ar in the main chain polymer 1 The ratio of the amount of substance in the unit is denoted by r 2 The codes of the graft polymers prepared in Examples 16 to 21 are 3-1, 3-2, 3-3, 3-4, 3-5 and 3-6 respectively. The inherent viscosity η2 of the graft polymers is shown in Table 4.

[0087] Table 4 Relevant parameters in the preparation method of Examples 16-21

[0088]

[0089]

[0090] The chemical reaction equation for preparing the graft polymer 3-1 in Example 16 is as follows:

[0091]

[0092] In Example 16, since the 1-sulfopropane-6-indolecarboxylic acid dipotassium monomer is first added to carry out polymerization for a period of time, the para position of the ether oxygen structure in the resorcinol structural unit of the main chain polymer first undergoes an acylation reaction with the 1-sulfopropane-6-indolecarboxylic acid dipotassium and continues to undergo polymerization, thereby forming a side chain composed of a sulfonated indole structure; then the 6-indolecarboxylic acid monomer is continued to be added for polymerization, and the acylation polymerization reaction continues to occur at the end of the existing side chain, thereby forming a chain segment composed of a non-sulfonated indole structure. In the side chain finally formed, the sulfonated indole structure and the non-sulfonated indole structure are distributed in blocks, and the average lengths of the sulfonated indole structure and the non-sulfonated indole structure segments are respectively r 1 With r 2 It was determined that the non-sulfonated indole segment was at the end of the side chain.

[0093] The preparation method of the cation exchange graft polymer of Examples 22-27 specifically includes the following steps: adding the main chain polymer and a mixture consisting of phosphorus pentoxide and methanesulfonic acid (the mass ratio of phosphorus pentoxide to methanesulfonic acid is 8.5:100) into a glass reactor filled with nitrogen and stirring and dissolving at 80°C, then adding 6-indolecarboxylic acid, continuing to stir and react at 80°C for 12 hours, and then adding 1-sulfopropane-6-indolecarboxylic acid dipotassium, continuing to stir and react at 80°C for 12 hours. After the reaction is completed, slowly adding the obtained viscous reaction liquid into water and letting it stand. The insoluble matter in the viscous reaction liquid is precipitated in water, filtered, and the obtained precipitate is extracted with water through an extractor for 24 hours. Finally, it is vacuum dried at 100°C for 24 hours to obtain a grafted polymer, which is a cation exchange graft polymer.

[0094] The ratio of the total mass of the main chain polymer and the reaction monomers (1-sulfopropane-6-indolecarboxylic acid dipotassium and 6-indolecarboxylic acid) to the total mass of phosphorus pentoxide and methanesulfonic acid was controlled to be 15:100. 1 The ratio of the amount of substance in the unit is denoted by r 1 , 6-indolecarboxylic acid and Ar in the main chain polymer 1 The ratio of the amount of substance in the unit is denoted by r 2 The codes of the graft polymers prepared in Examples 22-27 are 4-1, 4-2, 4-3, 4-4, 4-5 and 4-6 respectively. The inherent viscosity η2 of the graft polymers is shown in Table 5.

[0095] Table 5 Relevant parameters in the preparation method of Examples 22-27

[0096]

[0097] The chemical reaction equation for preparing the graft polymer 4-1 in Example 22 is as follows:

[0098]

[0099] In Example 22, since the 6-indolecarboxylic acid monomer is first added and polymerized for a period of time, the para position of the ether oxygen structure in the resorcinol structural unit of the main chain polymer first undergoes an acylation reaction with the 6-indolecarboxylic acid and continues to polymerize, thereby forming a side chain composed of a non-sulfonated indole structure; then, the 1-sulfopropane-6-indolecarboxylic acid dipotassium monomer is continuously added for polymerization, and the acylation polymerization reaction continues to occur at the end of the existing side chain, thereby forming a chain segment composed of a sulfonated indole structure. In the side chain finally formed, the non-sulfonated indole structure and the sulfonated indole structure are distributed in blocks, and the average lengths of the sulfonated indole structure and the non-sulfonated indole structure chain segments are respectively r 1 With r 2 It was determined that the sulfonated indole segment was at the end of the side chain. The H NMR spectrum of the graft polymer 4-1 prepared in Example 22 is as follows: Figure 2 As shown, Figure 2 In addition to the peak of aromatic hydrogen of the main chain polymer (8.0-7.0 ppm), there are also peaks of aromatic hydrogen on the side chain indole structure (8.6-8.0 ppm) and peaks of aliphatic hydrogen on the side chain indole structure (4.66 ppm, 2.57 ppm, 2.22 ppm), indicating that grafting polymerization has occurred on the side chain of the main chain polymer.

[0100] 2. The specific embodiments of the proton exchange membrane of the present invention are as follows:

[0101] 1.0 g of the cation exchange graft polymer prepared in Examples 1-27 was dissolved in 15 mL of dimethyl sulfoxide to obtain a cation exchange graft polymer solution. The cation exchange graft polymer solution was then poured onto a clean horizontal glass plate and placed at 60° C. for 24 hours to allow the dimethyl sulfoxide to evaporate completely. The polymer film formed on the glass plate was then peeled off the glass plate and placed in a vacuum drying oven at 80° C. for 12 hours to remove the residual dimethyl sulfoxide solvent, thereby obtaining a proton exchange membrane. The proton exchange membranes prepared from the cation exchange graft polymers prepared in Examples 1-27 are named proton exchange membrane 1-1, proton exchange membrane 1-2, proton exchange membrane 1-3, proton exchange membrane 1-4, proton exchange membrane 1-5, proton exchange membrane 1-6, proton exchange membrane 1-7, proton exchange membrane 2-1, proton exchange membrane 2-2, proton exchange membrane 2-3, proton exchange membrane 2-4, proton exchange membrane 2-5, proton exchange membrane 2-6, proton exchange membrane 3-1, proton exchange membrane 3-2, proton exchange membrane 3-3, proton exchange membrane 3-4, proton exchange membrane 3-5, proton exchange membrane 3-6, proton exchange membrane 4-1, proton exchange membrane 4-2, proton exchange membrane 4-3, proton exchange membrane 4-4, proton exchange membrane 4-5, and proton exchange membrane 4-6.

[0102] Comparative Example

[0103] The proton exchange membrane of this comparative example is made of random polymer, and the preparation method is the same as the preparation method of proton exchange membrane 1-1, specifically, 1.0g of random polymer is dissolved in 15mL of dimethyl sulfoxide to obtain a polymer solution, and then the obtained polymer solution is poured on a clean horizontal glass plate, and placed at 60°C for 24h to completely volatilize the dimethyl sulfoxide, and then the polymer film formed on the glass plate is peeled off from the glass plate, and placed in a vacuum drying oven at a temperature of 80°C for 12h to remove the residual dimethyl sulfoxide solvent, so as to obtain a proton exchange membrane. The proton exchange membrane prepared in this comparative example is named random polymer membrane; wherein, the preparation method of the random polymer is as follows: nitrogen is introduced into a glass reactor to The air is replaced, and then 359.5g (1mol) of 1-sulfopropane-6-indolecarboxylic acid dipotassium, 161.2g (1mol) of 6-indolecarboxylic acid, and 5207g of a mixture of phosphorus pentoxide and methanesulfonic acid (the mass ratio of phosphorus pentoxide to methanesulfonic acid is 8.5:100) are added to a glass reactor passed with nitrogen, and the reaction is carried out by mechanical stirring at a temperature of 80°C for 12h, and then the obtained viscous reaction liquid is slowly added to water, allowed to stand, and the obtained precipitate is extracted with water through an extractor for 24h, and finally vacuum dried at a temperature of 100°C for 24h to obtain an indole sulfonated polymer, that is, a random polymer, and the logarithmic viscosity of the random polymer is 4.3dL / g.

[0104] Experimental Example 1

[0105] In order to evaluate the performance of the proton exchange membranes of the cation exchange grafted polymers prepared using Examples 1-27 and the performance differences with the random polymer membranes of the comparative examples, the ion exchange capacity, proton conductivity, swelling ratio, tensile strength, elongation at break and oxidation resistance of each proton exchange membrane were tested respectively. Among them, the ion exchange capacity, proton conductivity and swelling rate are measured at 80°C according to the method in the standard GB / T20042.3-2009; the tensile strength and elongation at break are measured at room temperature according to the method in the national standard GB / T 1040.3-2006; the test method for oxidation resistance is as follows: a proton exchange membrane sample with a size of 2cm×2cm is immersed in a screw-mouth glass sample bottle containing 20mL of a newly prepared Fenton reagent (Fenton reagent is a 3% H2O2 aqueous solution containing 2ppm of FeSO4), the bottle cap is tightly closed, and the bottle is placed in an oven at 80°C for 3h to observe whether the proton exchange membrane sample remains intact, and the oxidation resistance is evaluated by whether the proton exchange membrane sample is intact after aging in the Fenton reagent.

[0106] The test results of ion exchange capacity, proton conductivity, swelling ratio, tensile strength, elongation at break and oxidation resistance of the random polymer membrane and the proton exchange membrane prepared from the cation exchange graft polymer prepared in Examples 1-27 are shown in Table 6.

[0107] Table 6 Ion exchange capacity, proton conductivity, swelling ratio, tensile strength, elongation at break and oxidation resistance of random polymer membranes and proton exchange membranes prepared from cation exchange grafted polymers prepared in Examples 1-27

[0108]

[0109]

[0110] As shown in Table 6, compared with the random polymer membrane, the tensile strength and elongation at break of the proton exchange membrane prepared by the grafted polymer prepared in Example 1-27 of the present invention are generally improved, indicating that the grafting modification can improve the strength and toughness of the polymer membrane; compared with the random polymer membrane, the proton exchange membranes with smaller ion exchange capacity, such as 1-2, 1-4, 2-2, 2-5, 3-2, 2-5, 4-2, 4-5, etc., show higher proton conductivity, which should be because when the sulfonated units are concentrated on the side chains of the polymer, it is more conducive to the sulfonated units. The elements form a microphase separation structure in the membrane, i.e., a more continuous proton transmission channel; compared with random polymer membranes, proton exchange membranes such as 1-5, 1-7, 2-2, 2-5, 3-2, 4-2, 4-5, etc. have considerable oxidation resistance; by comparing the performance of proton exchange membranes formed by grafted polymers with different grafting sequences, it is found that the grafted polymer formed by first adding non-sulfonated indole monomers and then adding sulfonated indole monomers, i.e., the grafted polymer in which the sulfonated indole segment in the side chain is at the end of the side chain rather than the sulfonated indole segment in the middle of the side chain, has better oxidation resistance and conductivity. These results show that the proton exchange membrane prepared by the grafted polymer prepared by Example 1-27 of the present invention can improve mechanical properties and conductivity without sacrificing oxidation resistance, and has good comprehensive performance.

Claims

1. A method for preparing a cation exchange graft polymer, characterized in that: The following steps are involved: The indole monomer and the main chain polymer are subjected to a graft polymerization reaction under the catalysis of phosphorus pentoxide and methanesulfonic acid to obtain a cation exchange graft polymer; the indole monomer is a sulfonated indole monomer as shown in Formula 1 or is composed of a sulfonated indole monomer as shown in Formula 1 and a non-sulfonated indole monomer as shown in Formula 2; In Formula 1, G1 is -(CH2)n-, n is 3 or 4, and G2 is -SO3M; M in -SO3M and -OM in Formula 1 are both selected from any one of Li, Na, K or H; in Formula 2, G3 is selected from -H or a saturated straight-chain alkyl group of C1-C12; The inherent viscosity of the main chain polymer is greater than 0.4 dL / g, and the structural formula is as follows: In the formula, Ar 1 ,Ar 2 ,Ar 3 with Ar 4 Represent the structural units of the main chain polymer, and x represents the structural unit Ar 1 with Ar 2 The mole fraction of the main chain structure of the entire polymer, 0 <x≤1; Ar 1 It is a structural unit shown in Formula 3 to Formula 7: Ar 2 and Ar 4 Independently selected from the structural units represented by Formula 8 to Formula 12: Ar 3 It is a structural unit shown in Formula 13 to Formula 14: Wherein, R1 is -H or methyl; R2 and R3 are independently selected from -O- or -S-; R4 and R5 are independently selected from -O- or -S-; R6 and R7 are independently selected from -O- or -S-, R8 is methyl or phenyl; R9 and R 10 are independently selected from -O- or -S-; R 11 and R 13 are independently selected from -O- or -S-, R 12 is a single bond, -S-, a sulfone group, a carbonyl group, an isopropyl group or a hexafluoroisopropyl group.

2. The method for preparing a cation exchange graft polymer according to claim 1, characterized in that: The Ar 1 is a structural unit shown in Formula 3, Formula 5 or Formula 7, R1 in Formula 3 is -H, and R4 and R5 in Formula 5 are both -S-; Ar 2 and Ar 4 independently selected from the structural units shown in Formula 8, Formula 9, Formula 10 or Formula 12; R9 and R in Formula 13 10 All are -O-; R in formula 13 11 and R 13 All are -O-, R 12 is a single bond, a sulfone group or a hexafluoroisopropyl group; the sulfonated indole monomer shown in Formula 1 is dipotassium 1-sulfopropanyl-6-indolecarboxylate, and the non-sulfonated indole monomer shown in Formula 2 is 6-indolecarboxylic acid.

3. The method for preparing a cation exchange graft polymer according to claim 1 or 2, characterized in that: x is 0.1~1.

4. The method for preparing a cation exchange graft polymer according to claim 1 or 2, characterized in that: The inherent logarithmic viscosity of the cation exchange graft polymer is greater than 1.0 dL / g; the mass ratio of phosphorus pentoxide to methanesulfonic acid is (7-10):

100.

5. The method for preparing a cation exchange graft polymer according to claim 4, characterized in that: The inherent logarithmic viscosity of the cation exchange graft polymer is 1.1-6.3 dL / g; the mass ratio of phosphorus pentoxide to methanesulfonic acid is (8.5-10):

100.

6. The method for preparing a cation exchange graft polymer according to claim 1, characterized in that: The ratio of the total mass of the main chain polymer and the indole monomer to the total mass of phosphorus pentoxide and methanesulfonic acid is (5-30):

100.

7. The method for preparing a cation exchange graft polymer according to claim 1 or 2, characterized in that: The indole monomer is a sulfonated indole monomer as shown in Formula 1. 1 The molar ratio of the units is (5-20):1; or the indole monomer is composed of a sulfonated indole monomer as shown in Formula 1 and a non-sulfonated indole monomer as shown in Formula 2, and the sulfonated indole monomer and the Ar in the main chain polymer 1 The molar ratio of the units is (10-15):1, the non-sulfonated indole monomer and the Ar in the main chain polymer 1 The molar ratio of the units is (5-10):

1.

8. The method for preparing a cation exchange graft polymer according to claim 1, characterized in that: The graft polymerization reaction is carried out at a temperature of 30 to 100° C. and for a time of 2 to 24 hours.

9. A cation exchange graft polymer prepared by the method for preparing a cation exchange graft polymer according to any one of claims 1 to 8.

10. A proton exchange membrane using the cation exchange graft polymer according to claim 9.

Images