含双阳离子梳型聚芳醚砜阴离子交换膜的合成与性能

Synthesis and properties of dications-containing poly(aryl ether sulfone) anion exchange membranes

为了提高聚合物阴离子交换膜的电导率、碱稳定性和尺寸稳定性,本研究通过分子结构设计,利用4-氟-2,2,2-三氟苯乙酮、3,5-二甲基苯酚、苯酚为起始原料,经两步有机反应合成了含二甲基苯氧基苯侧基的新型活性双酚单体:1,1-二(4-羟基苯基)-1-(4-(3,5-二甲基苯氧基)苯基)苯基-2,2,2-三氟乙烷(2),并将其与联苯二酚、4,4’-二氟二苯砜经芳香亲核共缩聚、溴代、季铵化反应制备了两类具有梳型结构的聚芳醚砜阴离子交换膜材料(2-PAES-QA-xx和2-PAES-Im-xx).利用核磁共振光谱对制备的活性双酚单体、含甲基结构初始聚芳醚砜、澳化聚芳醚砜及离子化聚合物的结构进行了表征和分析;详细研究了2-PAES-QA-xx和2-PAES-Im-xx膜的吸水率、尺寸稳定性、离子电导率、热稳定性、机械性能、耐碱稳定性等,并进一步比较了不同类型阴离子交换膜(AEM)的结构与性能之间的关系.得到的AEM表现出了较好的综合性能,60℃时膜的OIT电导率分别为35.9~51.6和32.6~44.9 mS/cm.代表性的2-PAES-QA-60和2-PAES-Im-60的OH^-电导率在80℃的4 mol/L NaOH中浸泡336 h后分别保持初始值的79.7%和88.5%.本研究为梳型AEM材料的设计制备提供了新策略.

Since the 21st century,energy and environmental issues have become the focus of global attention.Traditional fossil energy resources such as oil and natural gas are drying up.Meanwhile,a large number of harmful gases and other Pollutants would be produced in the use of traditional energy,which has a serious damage to the environment and climate.With the rapid increase of energy consumption and the need of environmental Protection,the demand for clean and efficient energy is growing.Fuel cell(FC)is considered as one of the most promising energy conversion technologies that can replace conventional fossil fuels,and it is also an important choice in the use of hydrogen,methanol,ethanol and other renewable energy.As a new energy with great potential,FC can reduce the energy crisis and environmental pollution effectively by directly converting the chemical energy of the exterlal input fuel into electrical energy and continuously supplying power to the outside.Ion exchange membrane(IEM)is an important component of FC,which is responsible for transferring ions and forming a complete FC circuit.According to the types of conducting ions,IEM can be divided into proton exchange membrane(PEM)and anion exchange membrane(AEM),which are applied to proton exchange membrane fuel cell(PEMFC)and alkaline anion exchange membrane fuel cell(AAEMFC),respectively.Compared with PEMFC,AAEMFC has the advantages of using non noble metal catalyst,high electrode reaction reactivity,and low fuel purity requirements and so on.However,the commercial AEM with organic cations often has low ionic conductivity and poor alkali and dimensional stability,which seriously hinders its development and application in AAEMFC.Therefore,it is urgent to design and develop new high-performance AEM materials.In order to improve the conductivity,alkali stability and dimensional stability of AEMs,a novel reactive bisphenol monomer with pendant dimethylphenoxybenzene group,1,1-bis(4-hydroxyphenyl)-1-(4-(3,5-dimethylphenoxy)phenyl)phenyl-2,2,2-trifluoroethane(2),was synthesized based on molecular design using 4-fluoro-2,2,2-trifluoroacetophenone,3,5-dimethylphenoh and phenol as starting materials by a two-step organic reaction.Then,two series of poly(aryl ether sulfone)anion exchange membranes(2-PAES-QA-xx and 2-PAES-Im-xx)with comb structure were prepared through aromatic nucleophilic copoly condensation,bromination and quaternization reaction based on monomer 2.The structures of the active bisphenol monomer,the poly(aryl sulfone)containing methyl groups,the brominated poly(aryl ether sulfone)s and the ionized polymers were characterized systematically by nuclear magnetic resonance spectroscopy,respectively.The water uptake,swelling ratio,ionic conductivity,thermal stability,mechanical properties,and alkaline resistance stability of the prepared 2-PAES-QA-xx and 2-PAES-Im-xx membranes were studied in detail.The relationship between the structure and properties of different types of AEMs is further compared.The obtained AEMs showed good overall performance,and the OH^-conductivity of these membranes at 60℃is 35.9-51.6 and 32.6-44.9 mS/cm,respectively.The IEC values of the representative 2-PAES-QA-60 and 2-PAES-Im-60 maintained at 79.7%and 88.5%of the initial values after immersion in 4 mollL NaOH at 80℃for 336 h,respectively.This work provides a new strategy for the design and preparation of combtype AEM materials.