Preparation of functional quaternized polycarbazolyl polymer electrolyte

Abstract

The invention firstly provides the preparation method of the functional quaternized polycarbazolyl polymer electrolyte. Starting from the design of a small molecular structure, the polycarbazolyl polymer electrolyte containing a functional quaternized cationic group is finally prepared through the experimental steps of synthesis, polymerization, quaternization and the like, a side chain and a fluorine-containing monomer are added to construct a more developed hydrophilic-hydrophobic phase separation structure, and the ionic conductivity is improved; and quaternization is carried out by using a cyclohexane structure with large steric hindrance and electron donating capability, so that the alkali-resistant stability is improved. Experimental results show that the ion conductivity of the anion exchange membrane prepared from the polymer electrolyte is 76.54 mS cm <-1 > at 80 DEG C (the thickness of the membrane is 35 microns).

Description

Technical Field

[0001] This invention belongs to the technical field of high molecular polymer electrolytes and relates to a method for preparing a functional quaternized polycarbazole-based polymer electrolyte. Background Art

[0002] Polymer electrolytes are generally composed of a polymer skeleton and functionalized molecular groups. They have the characteristics of high strength and plasticity that polymer materials possess. The functional groups make polymer electrolytes have rich application prospects and broad development space in alkaline fuel cells, water splitting to produce hydrogen, and interfacial chemistry.

[0003] The ion conductivity and functional group stability of polymer electrolytes are two important requirements for polymer electrolytes in the actual production and development of society. In the actual research process, quaternary ammonium salts and their derivatives are often used as functional groups due to their simple preparation and low cost. The piperidine group is a kind of quaternary ammonium salt derivative. It relies on the ring structure conformation to reduce the nucleophilic substitution activity of the piperidine group, so that the polymer electrolyte using piperidine as the cationic group has better stability. In the application scenario of polymer electrolytes, its ion conductivity has a very significant impact on the specific application performance of polymer electrolytes. The methods to improve the ion conductivity of polymer electrolytes can be roughly divided into two categories: improving the management of water absorption behavior and promoting the aggregation of ion groups to form ion clusters. Generally speaking, due to its strong electronegativity, fluorine is often used to construct the hydrophobic phase region of the material. Its application in polymer electrolytes can well promote the construction of the hydrophilic and hydrophobic phase separation structure of the polymer electrolyte. The hydrophilic and hydrophobic phase separation structure of the polymer electrolyte is conducive to promoting the construction of ion channels and further improving the ion conductivity. Another common method to improve ion conductivity (promoting the aggregation of ionic groups to form ion clusters) is to add flexible side chains to the main chain structure of the polymer skeleton. The swing of the flexible side chains can promote the formation of ion clusters and the improvement of ion conductivity. Summary of the invention

[0004] According to the above methods for improving the ionic conductivity of polymer electrolytes and the analysis of alkali resistance stability, the present invention aims to provide a structural design of a high molecular polymer electrolyte that takes into account both the ionic conductivity improvement strategy and high alkali resistance stability based on the design of the molecular structure. The present invention uses a fluorinated polymer as the main chain and utilizes long side chains and highly sterically hindered quaternary ammonium functional groups to improve the ionic conductivity and group stability of the polymer electrolyte.

[0005] The preparation of a functional quaternized polycarbazole-based polymer electrolyte disclosed herein comprises: (1) preparation of a molecule containing a piperidine group; (2) preparation of a fluorine-containing polymer; and (3) preparation of a highly sterically hindered quaternary ammonium salt. The preparation method, steps and conditions described in (1) are as follows

[0006] a. Preparation of carbazole monomers containing flexible side chains

[0007] Under the protection of nitrogen or inert gas, carbazole and double-terminal brominated straight-chain alkane are dissolved in toluene or ethyl acetate, tetrabutylammonium bromide is added, and after mixing evenly, a potassium hydroxide solution with a mass fraction of 25wt% to 50wt% is added, and the mixture is reacted at 25 to 70°C for 12 to 14 hours. After the reaction is completed, the mixture is poured into water to quench the reaction, and then the product is extracted with dichloromethane. The dichloromethane is removed by rotary evaporation, and the product is purified by silica gel column chromatography.

[0008] b. Bromine site substitution of carbazole monomer

[0009] Under nitrogen or inert gas protection, the carbazole monomer and piperidine prepared in a are dissolved in dimethyl sulfoxide, 0.3 to 0.6 equivalents of sodium hydroxide are added as a catalyst, and the reaction is carried out at 45 to 65° C. for 14 to 24 hours. After the reaction is completed, the reaction is quenched with water, and then extracted with ethyl acetate three times, the organic phase is extracted with a saturated sodium chloride solution to remove dimethyl sulfoxide, and the water in the organic phase is removed with anhydrous magnesium sulfate.

[0010] The preparation method, steps and conditions described in (2) are as follows

[0011] The monomer prepared in (1)a and 1-(3,5-difluorophenyl)-2,2,2-trifluoroethanone are dissolved in dichloromethane, stirred at 0-3°C for 20-60 minutes using a mechanical stirrer, trifluoromethanesulfonic acid is added dropwise to the reaction system, and stirring is continued until the viscosity is acceptable, and the reaction is quenched using a 1-3M sodium hydroxide solution. The product is then washed with ethyl acetate.

[0012] The preparation method, steps and conditions described in (3) are as follows

[0013] The high molecular polymer prepared in (2) is dissolved in N-methylpyrrolidone, iodocyclohexane and tetrabutylammonium bromide (catalyst) are added, and the mixture is reacted for 48 to 72 hours at 40 to 70° C. in a dark environment. After the reaction is completed, the mixture solution is dropped into water to precipitate the polymer electrolyte, and the obtained crude product is washed with ethyl acetate, and then the washed product is boiled in water at 65 to 80° C. for 8 to 10 hours, and then dried.

[0014] Beneficial effects:

[0015] The present invention first provides a method for preparing a functional quaternized polycarbazole-based polymer electrolyte. Starting from the design of a small molecule structure, a polycarbazole-based polymer electrolyte containing a functional quaternized cationic group is finally prepared through experimental steps such as synthesis, polymerization, and quaternization. Not only are side chains and fluorinated monomers added to construct a more developed hydrophilic-hydrophobic phase separation structure and improve ion conductivity, but quaternization is also performed with a cyclohexane structure with large steric hindrance and electron-donating ability to improve alkali resistance and stability. Experimental results show that the ion conductivity of the present invention is 76.54 mS cm at 80°C. -1 (The thickness of the anion exchange membrane used for the test was 35 μm). BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The carbazole monomer containing piperidine and a flexible side chain synthesized in step (1) b of the present invention is 1 H NMR spectrum

[0017] Figure 2 The functional quaternized polycarbazolyl polymer electrolyte synthesized in step (3) of the present invention is 1 HNMR spectrum

[0018] Figure 3 The ion conductivity of the anion exchange membrane prepared by using the polymer electrolyte prepared in the present invention at different temperatures. DETAILED DESCRIPTION

[0019] Example 1

[0020] (1) 10.0324 g of carbazole and 73.1701 g of 1,6-dibromohexane were dissolved in 80 ml of toluene, and then 3.2660 g of tetrabutylammonium bromide was added. After stirring for 0.5 hours, a potassium hydroxide solution with a mass fraction of 50 wt% was added, and the mixture was reacted at 40° C. for 12 hours. After the reaction was completed, the mixture was poured into more than 1 L of deionized water to quench the reaction, and then the product aqueous phase was extracted with dichloromethane. The organic phase was collected and the dichloromethane was removed by rotary evaporation, and the product was purified by silica gel column chromatography (the developing solvent ratio was: V 二氯甲烷 :V 石油醚 =1:5). The obtained pure product was white needle-shaped crystals, which were dried in an oven at 30°C with a yield of 78.52%.

[0021] (2) Under nitrogen protection, 4.9541 g of the monomer prepared in (1) and 1.9159 g of piperidine were dissolved in 20 ml of dimethyl sulfoxide, 1.2 g of sodium hydroxide was added as a catalyst, and the mixture was reacted at 65° C. for 14 hours. After the reaction was completed, the reaction was quenched with 500 ml of deionized water, and then extracted three times with ethyl acetate. The organic phase was collected and extracted with a saturated sodium chloride solution to remove dimethyl sulfoxide. The water in the organic phase was removed with anhydrous magnesium sulfate, and then the product was rotary evaporated to obtain a yellow oily product. The product was dried at 40° C. with a yield of 85.33%.

[0022] (3) 0.5018 g of the monomer (BHC-Pip) prepared in (2) and 0.3782 g of 1-(3,5-difluorophenyl)-2,2,2-trifluoroacetone were dissolved in 1 ml of dichloromethane. After stirring at 3°C ​​for 30 minutes using a mechanical stirrer, 1.5757 g of trifluoromethanesulfonic acid was added dropwise to the reaction system. Stirring was continued until the polymer viscosity met the requirements. The reaction was quenched with a 1 M sodium hydroxide solution. The product was then washed with ethyl acetate to obtain a light grey fibrous solid. The product was dried at 70°C with a yield of 65.29%.

[0023] (3) 0.7900 g of the polymer prepared in (3) was dissolved in 5 ml of N-methylpyrrolidone, and 0.4727 g of iodocyclohexane and 0.0806 g of tetrabutylammonium bromide were added, and the mixture was reacted for 72 hours at 40° C. in a dark environment. After the reaction, the mixture solution was dropped into 250 ml of water to precipitate the polymer electrolyte, and the obtained crude product was washed with ethyl acetate, and then the washed product was boiled in water at 80° C. for 8 hours, and then dried to obtain a light yellow fibrous solid.

[0024] Figure 1 The carbazole monomer containing piperidine and a flexible side chain synthesized in Example 1 (2) of the present invention is 1 H NMR spectrum

[0025] Figure 2 The functional quaternized polycarbazolyl polymer electrolyte synthesized in Example 1 (4) of the present invention 1 HNMR spectrum

[0026] Figure 3 is the ion conductivity of the anion exchange membrane prepared from the polymer electrolyte synthesized in Example 1 of the present invention. The ion conductivity of the anion exchange membrane increases with increasing temperature.

[0027] Example 2

[0028] (1) 10.0324 g of carbazole and 38.8638 g of 1,4-dibromobutane were dissolved in 80 ml of toluene, and then 3.2660 g of tetrabutylammonium bromide was added. After stirring for half an hour, a potassium hydroxide solution with a mass fraction of 50 wt% was added, and the mixture was reacted at 25° C. for 14 hours. After the reaction was completed, the mixture was poured into more than 1 L of deionized water to quench the reaction, and then the product aqueous phase was extracted with dichloromethane. The organic phase was collected and the dichloromethane was removed by rotary evaporation, and the product was purified by silica gel column chromatography (the developing solvent ratio was: V 二氯甲烷 :V 石油醚 =1:3). The obtained pure product was light yellow needle-shaped crystals, which were dried in an oven at 50°C with a yield of 51.36%.

[0029] (2) Under nitrogen protection, 4.4546 g of the monomer (BHC-4) prepared in (1) and 1.9159 g of piperidine were dissolved in 20 ml of dimethyl sulfoxide, 1.8 g of sodium hydroxide was added as a catalyst, and the mixture was reacted at 65° C. for 24 hours. After the reaction was completed, the reaction was quenched with 500 ml of deionized water, and then extracted three times with ethyl acetate. The organic phase was collected and extracted with a saturated sodium chloride solution to remove dimethyl sulfoxide. The water in the organic phase was removed with anhydrous magnesium sulfate. After the solvent was removed, a yellow oily product was obtained by rotary evaporation. The product was dried at 50° C. with a yield of 73.56%.

[0030] (3) 0.4763 g of the monomer prepared in (2) and 0.3782 g of 1-(3,5-difluorophenyl)-2,2,2-trifluoroacetone were dissolved in 1 ml of dichloromethane. After stirring at 3°C ​​for 30 minutes using a mechanical stirrer, 1.5757 g of trifluoromethanesulfonic acid was added dropwise to the reaction system. Stirring was continued until the polymer viscosity met the requirements. The reaction was quenched with a 1 M sodium hydroxide solution. The product was washed with ethyl acetate to obtain a light gray fibrous solid. The product was dried at 70°C with a yield of 82.36%.

[0031] (4) 0.7900 g of the polymer prepared in (3) was dissolved in 5 ml of N-methylpyrrolidone, and 0.4727 g of iodocyclohexane and 0.0806 g of tetrabutylammonium bromide were added, and the mixture was reacted for 48 hours at 40° C. in a dark environment. After the reaction, the mixture solution was dropped into 250 ml of water to precipitate the polymer electrolyte, and the obtained crude product was washed with ethyl acetate, and then the washed product was boiled in water at 80° C. for 8 hours, and then dried to obtain a light yellow fibrous solid.

Claims

1. A method for preparing a functional quaternized polycarbazole-based polymer electrolyte, wherein the polymer electrolyte is mainly composed of a fluorinated polycarbazole-based main chain skeleton, a highly sterically hindered piperidinium cation, and a flexible side chain; wherein: The designed monomer molecular structure is prepared through phase transfer catalysis and nucleophilic substitution reaction, and then the prepared monomer is polymerized into a high molecular polymer using superacid catalysis reaction, and finally iodocyclohexane is used for quaternization to achieve the introduction of high steric hindrance quaternary ammonium cations.

2. In the method for preparing a functional quaternized polycarbazole-based polymer electrolyte according to claim 1, the reaction step of the phase transfer catalytic reaction is: under the protection of nitrogen or inert gas, dissolve carbazole and double-terminal brominated straight-chain alkane in toluene or ethyl acetate, add tetrabutylammonium bromide, mix well, add 25wt% to 50wt% potassium hydroxide solution, and react at 25 to 70°C for 12 to 14 hours. After the reaction is completed, pour the mixture into water to quench the reaction, and then extract the product with dichloromethane. After removing dichloromethane by rotary evaporation, purify the product by silica gel column chromatography.

3. In the method for preparing a functional quaternized polycarbazole-based polymer electrolyte according to claim 1, the reaction step of the nucleophilic substitution reaction is: under the protection of nitrogen or inert gas, the carbazole-based monomer and piperidine prepared in claim 2 are dissolved in dimethyl sulfoxide, 0.3 to 0.6 equivalents of sodium hydroxide are added as a catalyst, and the reaction is carried out at 45 to 65° C. for 14 to 24 hours. After the reaction is completed, the reaction is quenched with water, and then extracted with ethyl acetate three times, the organic phase is extracted with a saturated sodium chloride solution to remove dimethyl sulfoxide, and the water in the organic phase is removed with anhydrous magnesium sulfate.

4. In the method for preparing a functional quaternized polycarbazole-based polymer electrolyte according to claim 1, the reaction step of the superacid catalytic reaction is: dissolving the monomer prepared in claim 3 and 1-(3,5-difluorophenyl)-2,2,2-trifluoroacetone or 1,1,1-trifluoroacetone in dichloromethane, stirring at 0-3°C for 20-60 minutes with mechanical stirring, then dripping trifluoromethanesulfonic acid into the reaction system, continuing to stir until the viscosity is qualified, and quenching the reaction with 1-3M sodium hydroxide solution. Then, washing the product with ethyl acetate.

5. In the method for preparing a functional quaternized polycarbazole-based polymer electrolyte according to claim 1, the quaternization reaction step of the polymer is: dissolving the high molecular weight polymer prepared in claim 4 in N-methylpyrrolidone, adding iodocyclohexane and tetrabutylammonium bromide (catalyst), and reacting for 48 to 72 hours under the conditions of 40 to 70° C. in the dark. After the reaction is completed, the mixture solution is dripped into water to precipitate the polymer electrolyte, the obtained crude product is washed with ethyl acetate, and then the washed product is boiled in water at 65 to 80° C. for 8 to 10 hours, and then dried.

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