Synthesis And Properties Of Branched Sulfonated Poly (Aryl Ether Ketone) Copolymers As Proton Exchange Membrane

Most recently, since the issues of energy shortages and environmental pollutionhave become the two global problems that all mankind concerned, looking for a greenand clean energy instead of fossil fuels is necessary. As a novel energy conversiondevice, fuel cells have drawn extensive attention on spaceflight, military affairs,vehicles and portable devices, because of the high efficiency and low emission ofpollutants. Polymer electrolyte membrane fuel cells （PEMFCs） have been recognizedas promising energy devices in automotive, stationary and portable electronicapplications. Proton exchange membranes, which are the proton conducting corecomponent of PEMFC, have a great influence on the performance of fuel cells.At present, the membranes traditionally used in PEMFCs are perfluorosulfonicpolymers such as Dupont Nafion. However, sufferring from poor conductivity atrelative low humidity and high temperature, high methanol permeability and the highcost of materials, have limited their usages. Therefore, it is necessary to prepare a newkind of membrane with better performance.Among the potential alternatives, sulfonated poly（aryl ether ketone） is a promisingmaterial due to its high thermal stability, excellent mechanical strength, costcompetitiveness, and strong resistance to fuel crossover for fuel cells. Throughdecades of research, study on SPAEKs for proton exchange membranes has achievedfruitful results. Then, in our research work, we tried a new method for modifying thetraditional linear sulfonated polymer by introduction of branched structure.In order to gain highly branched polymers and study theirs properties as PEMs,two parts of research have been carried on. In the first part, we choose two differentkinds of branch monomer, and prepared a series of branched sulfonated polymermembranes with the same IEC and different DB, via the polycondensation of A₂+ BB’₂method. Then, comparing with linear SPAEKs, we found that branchedmembranes had higher water uptake and proton conductivity with the same IEC. Inaddition, we identified that the branch monomer of TFBP-1had the best performanceunder the content of20%.Next, in the second part, choosing TFBP-1branch monomer and content of20%,we obtained a series of branched sulfonated membranes with a high IEC by enhancingthe feeding ratio of sulfonated monomer. Compared with Nafion-117, branchedsulfonated membranes （Br1-20-SPAEK-40） had very close proton conductivity.Moreover, the swelling ratio of Br1-20-SPAEK-40membranes was lower than that ofNafion-117. Based on the above results, we indicated that Br1-20-SPAEK-40had thebest selectivity and integrated performance.