Preparation And Properties Of Fluorinated Poly(Aryl Ether)s Anion Exchange Membranes

Energy and environmental issues have led to the introduction of renewable energy research,and fuel cells with high efficiency and low pollution have attracted the attention of many countries.Anion exchange membrane fuel cell(AEMFC)has attracted wide attention due to its various outstanding advantages.The anion exchange membrane(AEM),as one of the important components,plays a double role of blocking fuel and conducting hydroxide ions,and its performance has great influence on the performance of fuel cells.In this dissertation,several kinds of anion exchange membranes based on quaternized poly(aryl ether)s were successfully prepared,and the fundamental properties of water uptake,swelling ratio,ion conductivity,physic-chemical stability were investigated.Firstly,a series of uniform and transparent fluorinated poly(aryl ether)s type anion exchange membrane(QPFAE)were successfully synthesized from 9,9'-dihydroxyfluorene,decafluorobiphenyl and 4,4'-bisphenol via random polymerization,Friedel-Crafts chloromethylation,quaternization and alkalization.The influence of fluorene and fluorine on the AEM performance was discussed.The results indicated that the introduction of fluorene and fluorine could effectively reduce the water uptake and improve the physic-chemical stability of the membranes.For the QPFAE membranes with ion exchange capacity(IEC)of 0.95-1.94 mmol/g,they displayed low water uptake and methanol permeability(4.59-26.1×10-8 cm2/s at 25?),fairly good dimensional stability,high mechanical toughness,as well as fine thermal-oxidative-hydrolytic stability and ion conductivity at least 10 mS/cm,which could meet the practical requirements of fuel cells.Furthermore,the QPFAE membranes had outstanding alkaline stability,which can maintain good mechanical strength and ion conductivity after immersed in 1-2 mol/L NaOH solution at 60 ? for 10 days.Secondly,using QPFAE as matrix,a series of crosslinked fluorinated poly(aryl ether)s AEMs were successfully prepared from bisphenol A(BPA),4,4'-(hexafluoroisopropylidene)diphenol(HFBPA)and crosslinked polyacrylamide(CPAM)as crosslinking agent,with crosslinking degree of 5%and 10%.The results indicated that the AEMs of QPFAE-BPA and QPFAE-HFBPA with BPA and HFBPA as crosslinking agent,respectively,had lower water uptake,swelling ratio and methanol permeability,better solvent resistance and chemical stability compared with QPFAE membranes,and the higher crosslinking degree,the more improvement of the performance.However,the ion conductivity decreased after the crosslinking.The QPFAE-CPAM membranes containing semi-interpenetrating polymer network with CPAM as crosslinking agent showed some differences compared with the BPA and HFBPA crosslinked membranes.At 30 ?,the water uptake of QPFAE-BPA-5 was 29.8%,while the water uptake of QPFAE-CPAM-5 was 35.5%,and the higher water uptake also resulted in the larger swelling ratio.The QPFAE-CPAM membranes showed slightly worse hydrolytic stability than the QPFAE membranes due to the easy hydrolyse of polyacrylamide.