Preparation And Characterization Of Novel Anion Exchange Membranes

Anion exchange membrane fuel cells(AEMFCs), operating at medium and low temperatures, have broad application prospects due to its inexpensive price, low methanol permeability, fast oxidation reaction and so on. As the key material of the AEMFCs, the anion exchange membrane(AEMs) play an important role in the performance of the fuel cells. Therefore, development of the AEMs with high ionic conductivity, good chemical and mechanical stability is of the requirement.In this work, casting of the membranes with chloromethylated or bromomethylated different polymers including polyphenylene oxide, poly(ether ether ketone), poly(ether sulfones), and poly(ether ether sulfones) were investigated. The polyphenylene oxide(PPO) was chosen as the raw material to prepare the AEMs. The bromomethylated PPO(BPPO) with a bromination degree of 132%,58%and 40% were synthesized, respectively. The bromination degree was determined according to the NMR spectra. The membrane casted from BPPO with a bromination degree of 132% exhibited poor mechanical properties. Therefore, it is not suitable to be used as the material of AEMs.The BPPO with a bromination degree of 40% was used to prepare AEMs with functional groups of one kind of imidazolium, two types of quaternary ammoniums, and three types of quaternary phosphoniums. Comprehensive characterizations and comparisons of these membranes were made. The obtained polyphenylene oxide -imidazolium(ImPPO) membranes, which displayed higher tolerance towards alkali, showed a conductivity of 39 mS cm-1 at 60?, and the conductivity of 13 mS cm-1 at 60? was maintained after immersing the membrane in 3 M KOH solution at 60? for 132h. A highest tensile strength at break of 42.52 MPa at room temperature was reached by the quaternary ammonium membrane with the functional group of triethylamine(QAPPO-TEA), which presented a conductivity of 21 mS cm-1 at 60?.