Hindered amine modified imidazolyl-terminated hyperbranched polymer and preparation method thereof, proton exchange membrane and preparation method and application thereof

Abstract

According to the invention, a hindered amine modified imidazolyl-terminated hyperbranched polymer with a three-dimensional structure and rich alkalescent groups and perfluorosulfonic acid polymer molecules are subjected to chemical crosslinking and self-assembly to form the composite proton exchange membrane, so that the prepared composite membrane is ensured to have extremely low gas permeability and relatively high chemical stability. The cross-linking degree of the composite membrane can be controlled through the ratio of the imidazole group to the hindered amine group and the molecular weight and chemical degree of the hyperbranched polymer, and meanwhile, the hindered amine group of the hyperbranched polymer can realize charge transfer of active free radicals so as to ensure that the proton membrane has enough oxidation resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to a hindered amine-modified imidazole-terminated hyperbranched polymer and a preparation method thereof, a proton exchange membrane and a preparation method and application thereof. Background Art

[0002] As an efficient and clean hydrogen production technology, the performance of the electrolyzer, the core device of water electrolysis, directly depends on the design and material properties of the membrane electrode. The membrane electrode integrates the proton exchange membrane with the anode and cathode catalysts to achieve efficient proton conduction and effective gas separation. Among them, the proton exchange membrane (PEM) must have high proton conductivity, excellent gas barrier properties and long-term chemical stability to ensure the efficient operation and safety of the electrolyzer. Although the currently widely used perfluorosulfonic acid resin proton exchange membrane (such as Nafion membrane) has excellent proton conductivity, its low crystallinity leads to a loose microstructure and insufficient gas barrier performance. Especially under high pressure difference conditions, hydrogen can easily penetrate the membrane layer and mix with oxygen, resulting in a decrease in product purity, a decrease in Faraday efficiency and a potential explosion risk.

[0003] To improve gas barrier properties, existing technologies primarily employ two strategies: One is to introduce catalysts such as platinum or manganese oxide into perfluorosulfonic acid membranes to catalyze the reaction of permeated hydrogen with oxygen, but this approach sacrifices some hydrogen yield. The other is to enhance the physical-chemical crosslinking of the membrane structure by adding inorganic nanoparticles (such as graphene oxide and nanosilicon oxide) or linear coupling agents. However, the low proton conductivity of inorganic particles limits their addition, and excessive use significantly increases proton transport resistance. Linear coupling agents, on the other hand, only achieve single-dimensional crosslinking, making it difficult to form a dense three-dimensional network, resulting in limited gas barrier effectiveness and insufficient long-term stability.

[0004] In recent years, hyperbranched polymers have been considered as potential candidates for improving the performance of membrane materials due to their three-dimensional structure and rich terminal functional groups. For example, hyperbranched polyethyleneimine can construct a cross-linked network through multi-generation chain extension reactions, but its terminal group functionality is single and it is difficult to simultaneously meet the requirements of gas barrier, proton conduction and antioxidant properties. Existing studies have attempted to introduce sulfonic acid groups or hydrophilic groups into hyperbranched polymers to enhance proton conduction, but have ignored the synergistic improvement of gas barrier and free radical scavenging capabilities. In addition, traditional hyperbranched polymers have poor compatibility with perfluorosulfonic acid resins, which can easily lead to uneven dispersion and affect the structural uniformity and mechanical strength of the membrane. Summary of the Invention

[0005] Based on this, it is necessary to provide a hindered amine-modified imidazole-terminated hyperbranched polymer and a preparation method thereof, a proton exchange membrane and a preparation method and application thereof, so as to break through the technical bottleneck of the existing proton exchange membrane.

[0006] To achieve the above object, the present invention provides a technical solution:

[0007] A hindered amine-modified imidazole-terminated hyperbranched polymer, wherein the structural formula of the hindered amine-modified imidazole-terminated hyperbranched polymer is as follows, in parts by weight:

[0008]

[0009] Wherein, n is the number of imidazole groups in the hyperbranched polymer, which is a positive integer from 0 to 24; m is the number of hindered amine groups, which is a positive integer from 12 to 36; the sum of the values of n and m is 36. It is a hyperbranched polymer skeleton.

[0010] The present invention also provides a method for preparing a hindered amine-modified imidazole-terminated hyperbranched polymer, which comprises the steps of:

[0011] Using polyamine as the starting molecule, a chain extension reaction is carried out with dicarbonyl imidazole in the presence of a basic catalyst to generate a third-generation imidazole-terminated hyperbranched polymer.

[0012] The polyamine includes at least one of polyethyleneimine, ethylenediamine, diethylenetriamine and triethylenepentamine.

[0013] The third generation imidazole-terminated hyperbranched polymer is reacted with a nitrogen oxide stable free radical compound to introduce a hindered amine or group to form a hindered amine or hindered phenol modified imidazole-terminated hyperbranched polymer.

[0014] In some embodiments, the specific steps of generating the third-generation imidazole-terminated hyperbranched polymer include:

[0015] S100. A polyamine reacts with dicarbonyl imidazole in the presence of an alkaline catalyst to generate a first-generation imidazole-terminated hyperbranched polymer; wherein the molar ratio of polyamine: dicarbonyl imidazole: triethylamine is 1: (1.2-1.5): (0.01-0.05).

[0016] S200. Adding polyamine and dicarbonyl imidazole to the first generation imidazole-based hyperbranched polymer again to react to generate a second generation imidazole-based hyperbranched polymer; the molar ratio of polyamine: dicarbonyl imidazole: triethylamine is: 1: (1.2-1.5): (0.01-0.05).

[0017] S300. Repeat step S200 once to obtain the third generation imidazole-terminated hyperbranched polymer. If the chain extension reaction is continued, the yield will be greatly reduced due to the polymer steric effect.

[0018] In some embodiments, the molecular weight of the third-generation imidazole-terminated hyperbranched polymer is 5000Da-20000Da; and / or

[0019] The branching degree of the third-generation imidazole-terminated hyperbranched polymer is 0.3-0.6.

[0020] In some embodiments, the basic catalyst includes at least one of triethylamine, pyridine and sodium carbonate.

[0021] In some embodiments, the nitroxide-stabilizing free radical compound includes a hindered amine or its derivatives, and / or a hindered phenol or its derivatives.

[0022] In some embodiments, the hindered amine includes 2,2,6,6-tetramethylpiperidine and its derivatives, and / or 4-amino-2,2,6,6-pentamethylpiperidine and its derivatives.

[0023] In some embodiments, the hindered phenol includes 2,6-di-tert-butyl-4-methylphenol and its derivatives and / or pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and its derivatives.

[0024] A proton exchange membrane, wherein the raw material for preparing the proton exchange membrane comprises the hindered amine-modified imidazole-terminated hyperbranched polymer according to claim 1 or the hindered amine-modified imidazole-terminated hyperbranched polymer prepared according to any one of claims 2 to 7.

[0025] The present invention also provides a method for preparing a proton exchange membrane, comprising the steps of:

[0026] S1. Dispersing the hindered amine-modified imidazole-terminated hyperbranched polymer in a first polar solvent to form a dispersion.

[0027] The first polar solvent includes at least one of N,N-dimethylformamide, dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide and acetone.

[0028] S2. dissolving the perfluorosulfonic acid resin in a second polar solvent to form a solution.

[0029] Wherein, the second polar solvent includes at least one of N,N-dimethylformamide, dimethylacetamide and dimethyl sulfoxide.

[0030] The perfluorosulfonic acid resin includes at least one of a perfluorosulfonic acid polymer, a sulfonated polyetheretherketone, and a sulfonated polyphenylene sulfide.

[0031] S3. The dispersion was mixed with the solution to form a slurry having a solid content of 8%-15% and a viscosity of 200mPa·s-2000mPa·s;

[0032] S4. The slurry is coated on the back membrane, and after the composite reinforcement layer is applied, the slurry is dried and heat-treated at 80° C.-150° C. for 1 h-5 h to obtain the proton exchange membrane.

[0033] In some implementations, the mass ratio of the hindered amine-modified imidazole-terminated hyperbranched polymer to the perfluorosulfonic acid resin is (1:9) to (2:8).

[0034] Another aspect of the present invention provides an application of a proton exchange membrane in an electrolytic cell for producing hydrogen by electrolyzing water.

[0035] Beneficial effects of the present invention:

[0036] 1. The present invention uses a hindered amine-modified imidazole-terminated hyperbranched polymer with a three-dimensional structure and abundant weakly basic groups to achieve chemical crosslinking and self-assembly of a composite proton exchange membrane with perfluorosulfonic acid polymer molecules, ensuring that the prepared composite membrane has extremely low gas permeability and high chemical stability.

[0037] 2. The degree of cross-linking of the composite membrane can be controlled by adjusting the ratio of imidazole groups to hindered amine groups, the molecular weight of the hyperbranched polymer, and the degree of polymerization. At the same time, the hindered amine groups of the hyperbranched polymer can realize the charge transfer of active free radicals to ensure that the proton membrane has sufficient antioxidant capacity.

[0038] 3. The obtained cross-linked polymer contains a large number of imidazole and amino hydrophilic groups, which have better compatibility with the PFSA polymer matrix. The weak alkaline properties of imidazole can be directly mixed with the PFSA dispersion without forming a gel. The acid-base cross-linked structure will improve the mechanical properties and dimensional stability of the proton exchange membrane.

[0039] 4. The basic groups on the hindered amine form hydrogen bonds with the sulfonic acid groups of the PFSA polymer. At the same time, the PFSA molecular chains are entangled with each other, so that the carbon quanta can be better fixed inside the proton membrane, avoiding the migration of hyperbranched polymers and the reduction of gas barrier and free radical scavenging capabilities.

[0040] 5. The weakly basic groups and sulfonic acid groups form a continuous acid-base pair structure, which is conducive to the jumping of protons between different groups, making the prepared proton exchange membrane have higher proton conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 Schematic diagram of the synthesis of hindered amine-modified imidazole-terminated hyperbranched polymers in one embodiment;

[0042] Figure 2 Schematic diagram of the synthesis of hindered amine-modified imidazole-terminated hyperbranched polymer in another embodiment;

[0043] Figure 3 This is the tensile performance test result diagram;

[0044] Figure 4 This is the test result diagram of electrolysis performance;

[0045] Figure 5 This is the test result diagram of electrolysis performance;

[0046] Figure 6 This is a diagram showing the results of the durability test. DETAILED DESCRIPTION

[0047] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below with reference to specific embodiments.

[0048] In the examples, the test methods used are conventional methods unless otherwise specified, and the materials, reagents, etc. used are all commercially available unless otherwise specified.

[0049] 1. Preparation of Hindered Amine-Modified Imidazole-Terminated Hyperbranched Polymers

[0050] S100. Add 30 mL of N,N-dimethylformamide (DMP) to a three-necked flask and dissolve 0.81 g (0.005 mol) of N,N-carbonyldiimidazole (CDI).

[0051] Take 20mL DMF in a small beaker, add 0.43g (0.01mol) polyethyleneimine, dissolve under heating (or ultrasound) conditions, and slowly add it in batches to a three-necked flask. The reaction temperature is 60℃, and the reaction is stirred for 6 hours to obtain a first-generation imidazole-terminated macromolecule.

[0052] S200. Take a small beaker, add 20mL DM, add 0.22g (0.005mol) polyethyleneimine, dissolve it and add it to the three-necked flask in step 2. Reaction temperature 50℃, stir for 6h. 4. Take another small beaker, take 20mL DMF, add 4.86g (0.03mol) CDI, and slowly add it to the flask in step 3 to obtain a second-generation imidazole-terminated macromolecule.

[0053] Take 20 mL of DMF in a small beaker, add 0.86 g (0.02 mol) of polyethyleneimine and 0.1 g of triethylamine, dissolve under heating (or ultrasound), and slowly add to the three-necked flask in batches. The reaction temperature is 60°C and stirred for 6 hours to obtain a second-generation amine-terminated macromolecule.

[0054] S300. Take another small beaker, take 50 mL of DMF, add 13 g (0.16 mol) of CDI, and slowly add it to the flask in step 5 to obtain a 3rd generation imidazole-terminated macromolecule.

[0055] Take 1.0 g of the imidazole-terminated product and dissolve it in 20 mL of DMF to form a solution. Add 0.1 g of triethylamine and 5.0 g of NH2-TEMP (excess). The reaction temperature is 80° C. and the reaction is carried out for 12 h.

[0056] The product was dialyzed in ultrapure water or pure water for 24 hours and dried to obtain three products, namely, an amino-terminated hyperbranched polymer, an imidazole-terminated hyperbranched polymer, and a hindered amine-terminated hyperbranched polymer.

[0057] 2. Preparation of Proton Exchange Membrane

[0058] 1.0 g of imidazole-terminated hyperbranched polymer was first uniformly dispersed in 20 mL of N,N-dimethylformamide solvent, and then 9.0 g of perfluorosulfonic acid resin was dissolved in 50 mL of N,N-dimethylformamide solvent, and 0.1 g of dispersant was added and mixed to prepare a polymer mixed slurry with a solid content of 15% and a viscosity of 1500 mPa.s. The slurry was evenly coated on the back film, and a composite reinforcement layer was completely infiltrated. Then, another layer of the slurry was coated. After drying and heat treatment, a proton exchange membrane doped with imidazole-modified imidazole-terminated hyperbranched polymer (HBP-MZ / PFSA) was obtained.

[0059] The imidazole-terminated hyperbranched polymer was replaced by a hindered amine-terminated hyperbranched polymer. The other steps, experimental conditions and dosages were the same as those for preparing HBP-MZ / PFSA above, and a proton exchange membrane doped with an imidazole-modified imidazole-terminated hyperbranched polymer (HBP-HA / PFSA) was prepared.

[0060] Without adding the two hyperbranched polymers, PFSA resin was directly used instead of the mixed slurry. The other steps, experimental conditions and dosages were the same as those for preparing HBP-MZ / PFSA to prepare a PFSA membrane.

[0061] Test Example 1

[0062] Tensile properties test

[0063] The test was conducted using GB / T20042.3-2022 Proton Exchange Membrane Fuel Cell Part 3: Proton Exchange Membrane Test Method. Figure 3 shown.

[0064] Depend on Figure 3 The tensile properties test results show that the mechanical properties of the proton exchange membranes HBP-MZ / PFSA and HBP-HA / PFSA with the addition of hindered amine-modified imidazole-terminated hyperbranched polymers are greatly improved, which are 4.5MPa and 7.2MPa higher than those without the addition.

[0065] Test Example 2

[0066] Electrolytic performance test

[0067] The electrolytic cell performance test method in GB / T45541-2025PEM was used for testing. The test results are as follows: Figure 4 and Figure 5 As shown by Figure 4 and Figure 5 It can be seen that by introducing the acid-base cross-linking structure, the prepared proton exchange membrane exhibits a lower high-frequency impedance value and excellent electrolytic performance. The ohmic impedance of HBP-MZ / PFSA and HBP-HA / PFSA is reduced by 22 mΩ cm respectively compared with the PFSA membrane. 2 and 12 mΩ cm 2 , the electrolytic performance was improved by 11mV and 5mV respectively.

[0068] Test Example 3

[0069] Durability test

[0070] The electrolytic cell performance test method in GB / T45541-2025PEM was used for testing. The test results are as follows: Figure 6 As shown by Figure 6 It can be seen that by introducing nitrogen-oxygen stable free radicals and acid-base cross-linking to reduce permeability, the proton exchange membrane has better durability and stability. In the constant current accelerated test, the voltage decay rates of HBP-MZ / PFSA and HBP-HA / PFSA membranes were only 4.0μV / h and 8.4μV / h, respectively, which are much lower than the 12.5μV / h of the PFSA membrane, effectively improving the durability and stability of the proton exchange membrane.

[0071] It should be noted that the specific parameters or some reagents in the above embodiments are specific embodiments or preferred embodiments under the concept of the present invention, and are not intended to limit the present invention; those skilled in the art can make adaptive adjustments within the concept and protection scope of the present invention.

Claims

1. A hindered amine-modified imidazole-terminated hyperbranched polymer, characterized in that: The structural formula of the hindered amine-modified imidazole-terminated hyperbranched polymer is as follows, in parts by weight: Where n is a positive integer between 0 and 24, m is a positive integer between 12 and 36, and the sum of the values of n and m is 36. It is a hyperbranched polymer skeleton.

2. A method for preparing a hindered amine-modified imidazole-terminated hyperbranched polymer as claimed in claim 1, characterized in that: Including steps: Using polyamine as the starting molecule, a chain extension reaction is carried out with dicarbonyl imidazole in the presence of a basic catalyst to generate three generations of hyperbranched polymers with terminal imidazole groups of different generations. The third generation imidazole-terminated hyperbranched polymer is reacted with a nitrogen oxide stable free radical compound to introduce a hindered amine group to form a hindered amine-modified imidazole-terminated hyperbranched polymer.

3. The method for preparing a hindered amine-modified imidazole-terminated hyperbranched polymer according to claim 2, wherein: The specific steps of generating three generations of imidazole-terminated hyperbranched polymers of different generations include: S100. A polyamine reacts with dicarbonyl imidazole in the presence of a basic catalyst to produce a first-generation imidazole-terminated hyperbranched polymer; S200. Adding a polyamine and dicarbonyl imidazole to the first generation of imidazole-based hyperbranched polymer again to react to generate a second generation of imidazole-based hyperbranched polymer; S300. Repeat step S200 to obtain a third-generation imidazole-terminated hyperbranched polymer.

4. The method for preparing a hindered amine-modified imidazole-terminated hyperbranched polymer according to claim 2, wherein: The molecular weight of the third generation imidazole-terminated hyperbranched polymer is 5000Da-20000Da; and / or The branching degree of the third-generation imidazole-terminated hyperbranched polymer is 0.3-0.

6.

5. The method for preparing a hindered amine-modified imidazole-terminated hyperbranched polymer according to claim 2, wherein: The alkaline catalyst includes at least one of triethylamine, pyridine and sodium carbonate.

6. The method for preparing a hindered amine-modified imidazole-terminated hyperbranched polymer according to claim 2, wherein: The nitrogen oxide stable free radical compound includes hindered amine or its derivatives, and / or hindered phenol or its derivatives.

7. The method for preparing a hindered amine-modified imidazole-terminated hyperbranched polymer according to claim 6, wherein: The hindered amines include 2,2,6,6-tetramethylpiperidine and its derivatives, and / or 4-amino-2,2,6,6-pentamethylpiperidine and its derivatives.

8. A proton exchange membrane, characterized in that The raw material for preparing the proton exchange membrane includes the hindered amine-modified imidazole-terminated hyperbranched polymer according to claim 1 or the hindered amine-modified imidazole-terminated hyperbranched polymer prepared according to any one of claims 2 to 7.

9. A method for preparing a proton exchange membrane according to claim 8, characterized in that: Including steps: dispersing the hindered amine-modified imidazole-terminated hyperbranched polymer in a first polar solvent to form a dispersion; dissolving a perfluorosulfonic acid resin in a second polar solvent to form a solution; The dispersion and the solution are mixed to prepare a slurry having a solid content of 8% to 15% and a viscosity of 200 mPa·s to 2000 mPa·s; The slurry is coated on a back membrane, and after compounding a reinforcement layer, the slurry is dried and heat-treated at 80° C. to 150° C. for 1 h to 5 h to obtain the proton exchange membrane.

10. Use of the proton exchange membrane according to claim 8 or the proton exchange membrane produced by the method according to claim 9 in an electrolytic cell for producing hydrogen by electrolysis of water.

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