CN113025024A - Comb type polyarylether ion exchange membrane containing double cations and preparation method thereof - Google Patents

Abstract

The invention discloses a double cation comb-containing polyarylether ion exchange membrane and a preparation method thereof, wherein the preparation method comprises the following steps: (1) preparing a bisphenol monomer; (2) the method comprises the following steps of (1) preparing a polyoxadiazole aryl ether derivative by taking fluorobenzene oxadiazole, a bisphenol monomer and biphenyl diphenol as monomers through polycondensation, and preparing a dication comb type polyarylether ion exchange membrane through bromination and quaternization; the AEMs have pendant quaternary ammonium salts separated from the main chain by phenoxy groups, which can reduce OH^‑Hydrolysis of the main chain, increasing AEMsAlkali resistance; in addition, the side group structure of the dication structure improves the IEC of the membrane, is beneficial to self-assembly of quaternary ammonium salt into an effective ion channel, combines the advantages of long-side chain type and dense functional anion exchange membranes, and has good potential application prospect.

Description

Comb type polyarylether ion exchange membrane containing double cations and preparation method thereof

Technical Field

The invention belongs to the technical field of fuel cell materials, and particularly relates to a comb type polyarylether ion exchange membrane containing double cations and a preparation method thereof.

Background

Anion Exchange Membranes (AEMs) are important components of alkaline fuel cells, and conductivity and alkali resistance are two main indicators for evaluating the performance of the alkaline fuel cells, and the performance of the alkaline fuel cells is composed of two indicators. Under alkaline working conditions, the ionic groups and backbone structures of AEMs are susceptible to degradation damage, and therefore a strong, rigid polymer backbone is required to maintain the thermal and chemical stability of the material. In addition, the construction of efficient ion transmission channels is an important way for improving the conductivity of membrane materials, on one hand, the Ion Exchange Capacity (IEC) of AEMs can be improved, and on the other hand, the microphase extinct structure is regulated and controlled through molecular structure design. However, too much amount of ionic groups can affect the water content of the membrane, thereby causing the membrane to swell and affecting the structural stability of the AEMs.

Polyoxadiazole Aryl Ether (PAEO) is a high performance engineering material that has received much attention due to its excellent solvent and thermal properties and high glass transition temperature. Oxaoxadiazoles and fluorobenzenes give materials with excellent mechanical properties, thermal stability, chemical stability and good solubility and hydrophobicity. The Huquhui takes decafluoro oxadiazole and 3,3,5, 5-tetramethyl bisphenol A as monomers to synthesize polyoxadiazole aryl ether, benzyl bromide is obtained through bromination, and quaternary amination reaction is carried out on the benzyl bromide and a tertiary amine compound to prepare AEMs (preparation and characterization of polyfluoro polyoxadiazole aryl ether anion exchange membrane for Huquhui alkaline fuel cells [ D ]. Hunan Tan university, 2012.). The fluorine atom is introduced into the polymer, so that the polymer has more excellent thermal stability, solubility, flame retardance, transparency and hydrophobicity. Although the excellent hydrophobicity of the polymer and the excellent chemical stability of the oxadiazole ring reduce the degree of hydrolysis of AEMs by alkali, the problems that an ionic group is close to the main chain of the polymer, a strong electron induction effect is generated on a main chain benzene ring, and the alkali-resistant stability of the main chain structure is reduced still exist.

Disclosure of Invention

The invention aims to provide a double-cation comb type polyarylether ion exchange membrane, PAEO is used as a polymer framework, the AEMs combine the advantages of long side chain type and dense functional anion exchange membranes, and the membrane has good alkali resistance and ion transfer efficiency, and has the structure shown in the formula (I):

wherein x and y are integers, and x/y is 0.5-2.

The reaction process and the preparation method of the comb-type polyarylether ion exchange membrane containing the dications are as follows:

1. preparation of bisphenol monomers

With K₂CO₃Taking N, N-dimethylformamide as a solvent, and nucleophilic substitution of 4-fluoro-2, 2, 2-trifluoro acetophenone and 3, 5-dimethylphenol to prepare an intermediate a;

the intermediate a and phenol react under the catalysis of trifluoromethanesulfonic acid to obtain bisphenol monomer.

The bisphenol monomer has a molecular structure of formula (II):

2. preparation of decafluorobenzene oxadiazole monomers

Synthesized according to the method of the literature "preparation and characterization of polyfluoro polyoxadiazole aryl ether anion exchange membrane for alkaline fuel cell" (huquhui, the university of Huntan Master thesis, 2012), the specific reaction process is as follows:

polyphosphoric acid is used as a solvent, pentafluorobenzoic acid and hydrazine sulfate are subjected to polymerization reaction for 2 hours at 150 ℃ under the protection of nitrogen, the temperature is increased to 200 ℃ for cyclization reaction for 3 hours, reaction liquid is poured into deionized water, and after precipitation, washing and drying of a product, recrystallization is carried out by using a mixed solvent of isopropanol/toluene (V/V-3/1) to obtain the decafluorobenzene oxadiazole monomer.

3. Polycondensation preparation of polyoxadiazole aryl ether derivatives (PAEO-DM)

Using decafluorobenzene oxadiazole, bisphenol monomer and biphenyl diphenol as monomers, K₂CO₃The polyarylether derivative (PAEO-DM) is prepared by performing polycondensation reaction at 80-100 ℃ by using a mixed solvent (V/V is 2/1) of N, N-dimethylacetamide and toluene as a reaction solvent.

The molar ratio of the decafluorobenzene oxadiazole to the bisphenol monomer to the biphenyl diphenol is 1: 0.3-0.7.

The PAEO-DM has a molecular structure of formula (III):

4. preparation of brominated Polyoxadiazole aryl Ether derivatives (PAEO-DMX)

The preparation method comprises the following steps of carrying out bromination reaction on 1, 2-dichloroethane as a solvent, Benzoyl Peroxide (BPO) as an initiator, N-bromosuccinimide (NBS) as a bromination agent and PAEO-DM to prepare the PAEO-DMX.

5. Preparation of a Dicationic comb polyarylether ion exchange Membrane (PAEO-g-DMQAs)

Using N, N-dimethylformamide as a solvent, reacting the PAEO-DMX with a trimethylamine aqueous solution to prepare PAEO-g-DMQAs, filtering the reaction solution, pouring the reaction solution into a glass plate, drying the glass plate in a vacuum drying oven, finally soaking the obtained membrane in NaOH solution for ion exchange, and storing the membrane in deionized water.

The invention has the following advantages and beneficial effects:

the prepared double-cation comb-type polyarylether ion exchange membrane takes the PAEO as a polymer framework, and has good alkali resistance and mechanical strength; the pendant quaternary ammonium salt is separated from the main chain by phenoxy group, which can reduce OH^-The hydrolysis of the main chain further improves the alkali resistance of the AEMs. The side group of the dication structure improves IEC and is beneficial to self-assembly of quaternary ammonium salt into an effective ion channel. In combination with the above, the AEMs combine the advantages of long-side chain type and dense functional anion exchange membranes, and have good potential application prospects.

Drawings

FIG. 1 is a graph of conductivity as a function of time for AEMs prepared in example 4 in 2mol/L KOH solutions at 60 ℃.

Figure 2 is a plot of ionic conductivity versus temperature for AEMs prepared in example 4.

Fig. 3 is a graph of cell performance for the B1 sample film prepared in example 4.

Detailed Description

The present invention will be described in further detail with reference to specific examples, which are not intended to limit the present invention in any manner. Reagents, methods and apparatus used in the present invention are conventional in the art unless otherwise indicated.

The test of the invention comprises the following steps:

water content (WU) and Swelling Ratio (SR) test: cutting 1cm × 4cm film, soaking in 80 deg.C deionized water for 24 hr, and measuring wet film mass m_wAnd length l_wDrying the film at 60 ℃ in vacuum to constant weight, and measuring the mass m of the dry film_dAnd length l_dCalculating the value of WU or SR according to:

ion Exchange Capacity (IEC) test: completely dry sample film, measured by Mohr titration, is weighed W_dryImmersing in 1mol/L NaCl solution at room temperature for 24h for ion exchange, taking out the membrane, and washing with deionized water to remove free Cl^-Then the film was immersed in 0.5mol/L Na₂SO₄Ion exchange is carried out in the aqueous solution for 24h to completely release Cl^-. Then with K₂CrO₄For the indicator, the solution was titrated with 0.01mol/L AgNO3 aqueous solution. The IEC value is calculated according to the following formula:

and (3) ion conductivity test: and measuring the impedance of the anion exchange membrane by using a Princeton Versa STAT 4 electrochemical comprehensive test system, wherein the frequency range is 1 MHz-1 Hz. The ionic conductivity (σ, mS/cm) of the membrane at 80 ℃ was calculated according to the following formula

Wherein L is the distance between two copper electrodes, cm; a denotes the cross-sectional area of the membrane between the two electrodes, cm²(ii) a R is the resistance value of the film, K omega.

Alkali resistance test: immersing the membrane in 2mol/L KOH solution at 60 ℃, sampling at intervals, and measuring the ionic conductivity of the membrane;

example 1

Preparation of bisphenol monomers

55.32g (0.29mol) of 4-fluoro-2, 2, 2-trifluoroacetophenone, 35.18g (0.29mol) of 3, 5-dimethylphenol, 39.77g (0.28mol) of K are placed in a three-necked flask with reflux condenser, mechanical stirrer and nitrogen protection₂CO₃And 300mL of N, N-Dimethylformamide (DMF). Stirring until the raw materials are completely dissolved, heating to 110 ℃ to react for 4h, gradually changing the orange transparent liquid into milky turbid liquid, continuously reacting for 5h, and pouring the milky turbid liquid into water to precipitate to obtain a milky oily product. Washing with deionized water for 5 times to remove K₂CO₃And the solvent DMF to afford intermediate a.

Adding 23.62g (0.08mol) of intermediate a and 45.32g (0.48mol) of phenol into a three-neck flask provided with a reflux condenser tube, a mechanical stirrer and nitrogen protection, stirring until the intermediate a and the phenol are completely dissolved, dropwise adding 9.64g (64mmol) of trifluoromethanesulfonic acid, heating to 60 ℃ after the dropwise adding, reacting for 8 hours, pouring the reaction liquid into deionized water, settling to obtain a light yellow powdery solid, drying, and recrystallizing with toluene to obtain a white crystalline product bisphenol monomer.

¹H-NMR(400MHz,DMSO,δ):9.60(s,2H,OH),7.01(d,2H,ArH),6.94(d,2H,ArH),6.83(d,1H,ArH),6.80(s,4H,ArH),6.74(d,4H,ArH),6.67(s,2H,ArH),2.24(s,6H,-CH3).

Example 2

Preparation of decafluorobenzene oxadiazole monomers

Synthesized according to the method of the literature "preparation and characterization of polyfluoro polyoxadiazole aryl ether anion exchange membrane for alkaline fuel cell" (huquhui, the university of Huntan Master thesis, 2012), the specific reaction process is as follows:

30.22g (0.14mol) of pentafluorobenzoic acid, 11.12g (0.08mol) of hydrazine sulfate and 200mL of polyphosphoric acid are added into a three-neck flask provided with a reflux condenser tube, a mechanical stirrer and a nitrogen protection device, the mixture is slowly heated to 150 ℃ to carry out condensation reaction for 2h, and then the temperature is continuously increased to 200 ℃ to carry out cyclization reaction for 3 h. When no significant bubble generation was observed at the liquid level, heating was stopped. When the reaction mixture is cooled to 70 ℃, the reaction solution is poured into 800mL of ionized water for precipitation, and the solid precipitate is washed by hot water until the filtrate is neutral. Suction filtering, drying, and recrystallizing with mixed solvent of isopropanol/toluene (3:1) to obtain colorless needle crystal as decafluorobenzene oxadiazole monomer.

Example 3

Preparation of brominated Polyoxadiazole aryl Ether derivatives (PAEO-DMX)

Adding decafluorobenzene oxadiazole, bisphenol monomer, biphenyl diphenol and K into a flask provided with a reflux condenser, a water separator, a mechanical stirrer and nitrogen atmosphere protection₂CO₃Adding a mixed solvent (V/V is 2/1) of N, N-dimethylacetamide and toluene, fully stirring and dissolving, heating to 80 ℃ for polycondensation reaction, pouring methanol after 12h of reaction to separate out flocculent polymer, washing for 3 times, and carrying out vacuum drying treatment to obtain the PAEO-DM.

Respectively adding PAEO-DM and dichloroethane into a three-neck flask provided with a reflux condenser tube, a mechanical stirrer and nitrogen atmosphere protection, heating to 60 ℃, stirring to completely dissolve a polymer, cooling to room temperature, respectively adding BPO and NBS into the three-neck flask, heating to 80 ℃, reacting for 5 hours, pouring a reaction solution into ethanol, precipitating to obtain white floccule, washing for 5 times by using the ethanol, and then placing in a 100 ℃ vacuum oven for drying for 12 hours to obtain the PAEO-DMX.

Said K₂CO₃Is 2 times of the molar amount of the decafluorobenzene oxadiazole.

The reactant feed molar ratios and numbers for each sample are shown in table 1.

TABLE 1

a. Intrinsic viscosity [ η ]: the polymer was dissolved in N-methylpyrrolidone to prepare a 0.5g/L solution, and the intrinsic viscosity of the PAEO-DMX was measured at 30 ℃ using a Ubbelohde viscometer.

b. Gel Permeation Chromatography (GPC): the molecular weight of the PAEO-DMX is tested by a WATERS 515 type gel permeation chromatograph at normal temperature by taking N, N-dimethylformamide as a solvent and narrow distribution linear polystyrene as a standard sample.

Example 4

Preparation of a Dicationic comb polyarylether ion exchange Membrane (PAEO-g-DMQAs)

Adding PAEO-DMX and N, N-dimethylformamide into a flask provided with a constant pressure dropping funnel and mechanical stirring, stirring and dissolving fully, then starting to slowly drop trimethylamine aqueous solution (33 wt%), stirring at room temperature for 24h to finish the reaction, filtering the reaction solution by a PTFE filter tip with the aperture of 0.45 mu m, pouring the filtered reaction solution on a glass plate, placing the glass plate on a vacuum drying oven at 60 ℃ for drying for 24h, finally soaking the obtained membrane in 1mol/L NaOH solution for ion exchange for 24h, and storing the membrane in deionized water to obtain the dicationic comb-type polyarylether ion exchange membrane.

The feed ratio of each reactant and the results of the performance test are shown in Table 2.

TABLE 2

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.

Claims (3)

1. A dication-containing comb type polyarylether ion exchange membrane is characterized in that the dication-containing comb type polyarylether ion exchange membrane has a structure of a formula (I):

wherein x and y are integers, and x/y is 0.5-2.

2. A preparation method of a comb-type polyarylether ion exchange membrane containing dications is characterized by comprising the following steps:

(1) preparation of bisphenol monomers

With K₂CO₃Taking N, N-dimethylformamide as a solvent, and nucleophilic substitution of 4-fluoro-2, 2, 2-trifluoro acetophenone and 3, 5-dimethylphenol to prepare an intermediate a;

reacting the intermediate a with phenol under the catalytic action of trifluoromethanesulfonic acid to obtain a bisphenol monomer;

the bisphenol monomer has a molecular structure of formula (II):

(2) polycondensation preparation of polyoxadiazole aryl ether derivatives (PAEO-DM)

Using decafluorobenzene oxadiazole, bisphenol monomer and biphenyl diphenol as monomers, K₂CO₃Performing polycondensation reaction at 80-100 ℃ by taking a mixed solvent (V/V-2/1) of N, N-dimethylacetamide and toluene as a catalyst to prepare polyarylether derivatives (PAEO-DM);

the PAEO-DM has a molecular structure of formula (III):

(3) preparation of brominated Polyoxadiazole aryl Ether derivatives (PAEO-DMX)

Carrying out bromination reaction on 1, 2-dichloroethane as a solvent, Benzoyl Peroxide (BPO) as an initiator and N-bromosuccinimide (NBS) as a brominating agent to prepare the PAEO-DMX;

(4) preparation of a Dicationic comb polyarylether ion exchange Membrane (PAEO-g-DMQAs)

Using N, N-dimethylformamide as a solvent, reacting the PAEO-DMX with a trimethylamine aqueous solution to prepare PAEO-g-DMQAs, filtering the reaction solution, pouring the reaction solution into a glass plate, drying the glass plate in a vacuum drying oven, finally soaking the obtained membrane in NaOH solution for ion exchange, and storing the membrane in deionized water.

3. The method for preparing the dication comb type polyarylether ion exchange membrane according to claim 2, wherein the molar ratio of the decafluorobenzene oxadiazole, the bisphenol monomer and the diphenol in the step (2) is 1: 0.3-0.7.

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