侧链有序交联型咪唑功能化阴离子交换膜
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摘要
利用甲基氢醌和4,4′-二氟二苯基甲酮的缩聚反应,合成了含苯甲基的聚芳醚酮二元有序结构的聚合物.随后,利用N-溴代琥珀酰亚胺(NBS)溴代,溴代产物同时接枝1-甲基咪唑和1-乙烯基咪唑制备了一系列侧链有序交联型的阴离子交换膜(Im-PEEK-x).透射电子显微镜图显示Im-PEEK-0.7膜具有较好的微相分离结构.ImPEEK-0.7膜的离子传导率为6.68×10~(-2)S/cm,拉伸强度达到60.03MPa,并且在80℃的吸水率、溶胀率分别为16.56%, 18.2%.在耐碱稳定性测试中, Im-PEEK-0.7膜浸泡在80℃, 1 mol/L NaOH溶液中200 h后,其IEC值仍为泡碱前的81.5%,表现出优异的耐碱稳定性.说明侧链有序具有微相分离结构的交联型阴离子交换膜具有优异的离子传导率和稳定性.
In recent years, the development of alkaline anion exchange membrane fuel cells(AEMFCs) has received widespread attention. On the one hand, non-noble metals can be used as catalysts in alkaline anion exchange membrane fuel cells(AEMFCs), such as silver and nickel which reduced the cost of fuel cell devices. On the other hand, the hydroxide ions move in the opposite direction with the fuel, which reduce fuel permeability and the cost on other aspects. Therefore, the development prospect of alkaline fuel cells is good, while anion exchange membrane, as the core component of alkaline fuel cells, has problems such as the insufficient ion conductivity and alkaline stability, which hinder the successful realization of AEMFCs technology. Until now, many cationic groups have been widely investigated, such as quaternary ammonium, imidazolium, guanidinium and phosphonium. Quaternary ammonium group and imidazolium group are the most commonly used cationic group. The experimental results suggest that imidazole-type anion exchange membrane have better performance. Due to the existence of the conjugated π bond in the unique N-heterocyclic structure, imidazolium grafted membranes exhibit not only high ionic conductivity, but also excellent chemical and thermal stability. The formation of cross-linked network structure is advantageous in suppressing the swelling of the membrane, thereby improving the dimensional stability of the membrane. Meantime, we introduce 1-vinylimidazole to improve the performance of the 1-methylimidazole grafted membrane. This monomer contains not only imidazolium cation groups, but also double bonds can be cross-linked. The imidazole group can transfer OH~-ions. The dense network structure formed by double bonds cross-linking makes membranes have good mechanical properties and dimensional stability, and conducive to defense strong nucleophile OH~-attack. First, a benzylmethyl-containing poly ether(ether ether ketone)(PEEK) copolymer was synthesized through condensation polymerization of 4,4′-difluorobenzopheno and methylhydroquinone. Then, dissolved the PEEK by 1,1,2,2-tetra-chloroethane, the yellow precipitate bromination of polyether ether ketone(BPEEK) was synthesized by adding NBS and BPO into the solution and reacted at 80°C for 5 h under the nitrogen atmosphere. The BPEEK was chosen to react directly with the functional reagent, 1-methyl imidazole and 1-vinylimidazole and obtained poly(ether ether ketone) crosslinked anion exchange membranes. The structure was characterized by ~1H NMR spectroscopy. The morphology and microstructure of the resulting samples were characterized using transmission electron microscopy(TEM). The ion conductivity of the Im-PEEK-x membrane was measured by four-probe alternating current(AC) impedance technique. The thermal stability was tested by thermogravimetric analysis(TGA). The alkaline solution stability of the Im-PEEK-x membrane was evaluated by measuring the changes in IEC values after immersed in 1 mol/L NaOH for a certain time. Water uptake, swelling ratio and mechanical properties of the membranes were also measured. The results indicated that the Im-PEEK-x membrane had been synthesized. After grafting of 1-vinylimidazole, for the membrane of Im-PEEK-0.7, the maximum stress is 60.03 MPa, and the swelling rate is 18.2% at 80°C. After soaking in 1 mol L~(–1) NaOH solution for 200 h at 80°C, the IEC value was about 81.5% of the initial, which exhibited excellent alkaline stability.
In recent years, the development of alkaline anion exchange membrane fuel cells(AEMFCs) has received widespread attention. On the one hand, non-noble metals can be used as catalysts in alkaline anion exchange membrane fuel cells(AEMFCs), such as silver and nickel which reduced the cost of fuel cell devices. On the other hand, the hydroxide ions move in the opposite direction with the fuel, which reduce fuel permeability and the cost on other aspects. Therefore, the development prospect of alkaline fuel cells is good, while anion exchange membrane, as the core component of alkaline fuel cells, has problems such as the insufficient ion conductivity and alkaline stability, which hinder the successful realization of AEMFCs technology. Until now, many cationic groups have been widely investigated, such as quaternary ammonium, imidazolium, guanidinium and phosphonium. Quaternary ammonium group and imidazolium group are the most commonly used cationic group. The experimental results suggest that imidazole-type anion exchange membrane have better performance. Due to the existence of the conjugated π bond in the unique N-heterocyclic structure, imidazolium grafted membranes exhibit not only high ionic conductivity, but also excellent chemical and thermal stability. The formation of cross-linked network structure is advantageous in suppressing the swelling of the membrane, thereby improving the dimensional stability of the membrane. Meantime, we introduce 1-vinylimidazole to improve the performance of the 1-methylimidazole grafted membrane. This monomer contains not only imidazolium cation groups, but also double bonds can be cross-linked. The imidazole group can transfer OH~-ions. The dense network structure formed by double bonds cross-linking makes membranes have good mechanical properties and dimensional stability, and conducive to defense strong nucleophile OH~-attack. First, a benzylmethyl-containing poly ether(ether ether ketone)(PEEK) copolymer was synthesized through condensation polymerization of 4,4′-difluorobenzopheno and methylhydroquinone. Then, dissolved the PEEK by 1,1,2,2-tetra-chloroethane, the yellow precipitate bromination of polyether ether ketone(BPEEK) was synthesized by adding NBS and BPO into the solution and reacted at 80°C for 5 h under the nitrogen atmosphere. The BPEEK was chosen to react directly with the functional reagent, 1-methyl imidazole and 1-vinylimidazole and obtained poly(ether ether ketone) crosslinked anion exchange membranes. The structure was characterized by ~1H NMR spectroscopy. The morphology and microstructure of the resulting samples were characterized using transmission electron microscopy(TEM). The ion conductivity of the Im-PEEK-x membrane was measured by four-probe alternating current(AC) impedance technique. The thermal stability was tested by thermogravimetric analysis(TGA). The alkaline solution stability of the Im-PEEK-x membrane was evaluated by measuring the changes in IEC values after immersed in 1 mol/L NaOH for a certain time. Water uptake, swelling ratio and mechanical properties of the membranes were also measured. The results indicated that the Im-PEEK-x membrane had been synthesized. After grafting of 1-vinylimidazole, for the membrane of Im-PEEK-0.7, the maximum stress is 60.03 MPa, and the swelling rate is 18.2% at 80°C. After soaking in 1 mol L~(–1) NaOH solution for 200 h at 80°C, the IEC value was about 81.5% of the initial, which exhibited excellent alkaline stability.
引文
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5 Dang H S,Jannasch P.Anion-exchange membranes with polycationic alkyl side chains attached via spacer units.J Mater Chem A,2016,4:17138-17153
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7 Gong X,Yan X M,Li T T,et al.Design of pendent imidazolium side chain with flexible ether-containing spacer for alkaline anion exchange membrane.J Membr Sci,2017,523:216-224
8 Zhuo Y Z,Lai A L,Zhang Q G,et al.Enhancement of hydroxide conductivity by grafting flexible pendant imidazolium groups into poly(arylene ether sulfone)as anion exchange membranes.J Mater Chem A,2015,3:18105-18114
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12 Zhao J,Feng Y,Chen Z,et al.Microemulsion polymerization of cationic pyrroles bearing an imidazolum-ionic liquid moiety.J Polym Sci Part A Polym Chem,2010,47:746-753
13 Liu L S,Ahlfield J,Tricker A,et al.Anion conducting multiblock copolymer membranes with partial fluorination and long head-group tethers.J Mater Chem A,2016,4:16233-16244
14 Agel E,Bouet J,Fauvarque J F.Characterization and use of anionic membranes for alkaline fuel cells.J Power Sources,2001,101:267-274.
15 Li C P,Wang S B,Wang W P,et al.A cross-linked fluorinated poly(aryl ether oxadiazole)s using a thermal cross-linking for anion exchange membranes.Int J Hydrog Energy,2013,38:11038-11044
16 Lai A N,Wang L S,Lin C X,et al.Phenolphthalein-based poly(arylene ether sulfone nitrile)s multiblock copolymers as anion exchange membranes for alkaline fuel cells.ACS Appl Mater Interfaces,2015,7:8284
17 Han K W,Ko K H,Abu-Hakmeh K,et al.Molecular dynamics simulation study of a polysulfone-based anion exchange membrane in comparison with the proton exchange membrane.J Phys Chem C,2014,118:12577-12587
18 Zhu L,Pan J,Wang Y,et al.Multication side chain anion exchange membranes.Macromolecules,2016,49:815-824
19 Fang J,Lyu M,Wang X,et al.Synthesis and performance of novel anion exchange membranes based on imidazolium ionic liquids for alkaline fuel cell applications.J Power Sources,2015,284:517-523
20 Ngo H L,LeCompte K,Hargens L,et al.Thermal properties of imidazolium ionic liquids.Thermochim Acta,2000,357:97-102
21 Merle G,Wessling M,Nijmeijer K.Anion exchange membranes for alkaline fuel cells:A review.J Membr Sci,2011,377:1-35
22 Meek K M,Elabd Y A.Alkaline chemical stability of polymerized ionic liquids with various cations.Macromolecules,2015,48:7071-7084
23 Meek K M,Nykaza J R,Elabd Y A.Alkaline chemical stability and ion transport in polymerized ionic liquids with various backbones and cations.Macromolecules,2016,49:3382-3394
24 Guo D,Zhuo Y Z,Lai A N,et al.Interpenetrating anion exchange membranes using poly(1-vinylimidazole)as bifunctional crosslinker for fuel cells.J Membr Sci,2016,518:295-304
2 Varcoe J R,Slade R C,Wright G L,et al.Steady-state dc and impedance investigations of H2/O2 alkaline membrane fuel cells with commercial Pt/C,Ag/C,and Au/C cathodes.J Phys Chem B,2006,110:21041-21049
3 Tang D,Pan J,Lu S,et al.Alkaline polymer electrolyte fuel cells:Principle,challenges,and recent progress.Sci China Chem,2010,53:357-364
4 Spendelow J S,Goodpaster J D,Kenis P J,et al.Mechanism of CO Oxidation on Pt(111)in alkaline media.J Phys Chem B,2006,110:9545-9555
5 Dang H S,Jannasch P.Anion-exchange membranes with polycationic alkyl side chains attached via spacer units.J Mater Chem A,2016,4:17138-17153
6 He S Q,Liu L,Wang X C,et al.Azide-assisted self-crosslinking of highly ion conductive anion exchange membranes.J Membr Sci,2016,509:48-56
7 Gong X,Yan X M,Li T T,et al.Design of pendent imidazolium side chain with flexible ether-containing spacer for alkaline anion exchange membrane.J Membr Sci,2017,523:216-224
8 Zhuo Y Z,Lai A L,Zhang Q G,et al.Enhancement of hydroxide conductivity by grafting flexible pendant imidazolium groups into poly(arylene ether sulfone)as anion exchange membranes.J Mater Chem A,2015,3:18105-18114
9 Lee K H,Cho D H,Kim Y M,et al.Highly conductive and durable poly(arylene ether sulfone)anion exchange membrane with end-group cross-linking.Energy Environ Sci,2017,10:275-285
10 Sajjad S D,Liu D,Wei Z,et al.Guanidinium based blend anion exchange membranes for direct methanol alkaline fuel cells(DMAFCs).J Power Sources,2015,300:95-103
11 Lin B,Qiu L,Qiu B,et al.Correction to a soluble and conductive polyfluorene ionomer with pendant imidazolium groups for alkaline fuel cell applications.Macromolecules,2011,44:9642-9649
12 Zhao J,Feng Y,Chen Z,et al.Microemulsion polymerization of cationic pyrroles bearing an imidazolum-ionic liquid moiety.J Polym Sci Part A Polym Chem,2010,47:746-753
13 Liu L S,Ahlfield J,Tricker A,et al.Anion conducting multiblock copolymer membranes with partial fluorination and long head-group tethers.J Mater Chem A,2016,4:16233-16244
14 Agel E,Bouet J,Fauvarque J F.Characterization and use of anionic membranes for alkaline fuel cells.J Power Sources,2001,101:267-274.
15 Li C P,Wang S B,Wang W P,et al.A cross-linked fluorinated poly(aryl ether oxadiazole)s using a thermal cross-linking for anion exchange membranes.Int J Hydrog Energy,2013,38:11038-11044
16 Lai A N,Wang L S,Lin C X,et al.Phenolphthalein-based poly(arylene ether sulfone nitrile)s multiblock copolymers as anion exchange membranes for alkaline fuel cells.ACS Appl Mater Interfaces,2015,7:8284
17 Han K W,Ko K H,Abu-Hakmeh K,et al.Molecular dynamics simulation study of a polysulfone-based anion exchange membrane in comparison with the proton exchange membrane.J Phys Chem C,2014,118:12577-12587
18 Zhu L,Pan J,Wang Y,et al.Multication side chain anion exchange membranes.Macromolecules,2016,49:815-824
19 Fang J,Lyu M,Wang X,et al.Synthesis and performance of novel anion exchange membranes based on imidazolium ionic liquids for alkaline fuel cell applications.J Power Sources,2015,284:517-523
20 Ngo H L,LeCompte K,Hargens L,et al.Thermal properties of imidazolium ionic liquids.Thermochim Acta,2000,357:97-102
21 Merle G,Wessling M,Nijmeijer K.Anion exchange membranes for alkaline fuel cells:A review.J Membr Sci,2011,377:1-35
22 Meek K M,Elabd Y A.Alkaline chemical stability of polymerized ionic liquids with various cations.Macromolecules,2015,48:7071-7084
23 Meek K M,Nykaza J R,Elabd Y A.Alkaline chemical stability and ion transport in polymerized ionic liquids with various backbones and cations.Macromolecules,2016,49:3382-3394
24 Guo D,Zhuo Y Z,Lai A N,et al.Interpenetrating anion exchange membranes using poly(1-vinylimidazole)as bifunctional crosslinker for fuel cells.J Membr Sci,2016,518:295-304