Preparation And Study Of A Kind Of Anion Exchange Membrane With Ether Bond

Compared with PEMFC, AAEMFC are better performing due to the facile kinetics at the cathode as well as at the anode; possibility that cheaper non-noble metal catalysts and cheaper material can be used. Using AAEMFC also helps to reduce the methanol crossover and simplify the water management. Yet, the ion exchange membrane fuel cells always need to work at high temperature. However, quaternary ammonium, which is used as ion exchange group in the strong alkaline anion exchange membranes (AAEM), will be easily suffered from Hoffman elimination reaction in alkaline condition at high temperature, coursing degradation of quaternary ammonium as well as decline of IEC of membrane. Therefore, it will bring us significant impact to develop a kind of membrane with high thermal stability.In this paper, we choose Poly(2,6-dimethyl-1,4-phenylene oxide)(PPO) which can be easily to make membrane as the base membrane, and synthesize a kind of homogeneous anion exchange membrane. According to the mechanism of Hoffman elimination reaction, we tried to make the AAEM more thermal stable by electro-effect, which is inducing the ether bond next to theβcarbon of quaternary ammonium, so as to increase the density of electronic cloud of theβcarbon and decrease the acidity ofβhydrogen. First, by radical substitution brominating, a certain proportion of benzyl hydrogen is replaced with bromine. Then, through the Williamson ether reaction, the ether bond is induced to the PPO chains, and tertiary PPO is synthesized, which is following made to get dense membranes. In the last step, the membrane is reacted with iodomethane to get quaternary ammonium in the PPO chains, which is anion exchange membrane.Compared with DF-120 commercial anion exchange membrane, our membrane is much more thermal stable. At the same time, the ion conductivity of our membrane is significantly higher than the commercial membrane. The ion conductivity of our membrane can reach 0.025 S·cm-1 at room temperature and 0.055 S·cm-1 at 70℃. Yet, the swelling degree of our membrane is very high, and the mechanical strength becomes seriously lower if the membrane is immersed into hot water (above 80℃) for a long time. Therefore, if properly modified, our membrane will have hope in alkaline anion exchange membrane fuel cell application.