Synthesis And Properties Of Containing Different N Heterocyclic Ring Proton Exchange Membrane

As the energy depletion and environmental pollution getting worse and worse, to develop alternative clean-energy has become an effective method to improve the dilemma. The proton exchange membrane fuel cell (PEMFC) which is using hydrogen as fuel gradually causes the attention of many scientists for its character, friendly and efficiency. It has been considered the most potential fuel cell using in the field of transportation and power stations. And the performance of proton exchange membrane (PEM) will directly affect the use of the fuel cell.At present, the commercialized PEM is Nafion which is made by DuPont. But it has high cost and the low proton conductivity at high temperatures, its widely application is limited. Combined with proton conduction mechanism, the influence of different proton-containing heterocyclic structure to the performance of proton exchange membrane materials was studied in this paper. Sulfonated poly (aryl ether ketone sulfone) copolymers have good mechanical properties and thermal stability characteristics. Thus a series of sulfonated poly (aryl ether ketone sulfone) copolymers containing different types of heterocyclic were synthesis. In this way, sulfonic acid groups and heterocyclic were all fixed on the polymer backbone. The heterocyclic can be preventing doping from the polymer, and the sulfonation degree can be control easily."Different proton-containing heterocyclic structure" mainly refers to triazole and oxadiazole in this paper. So oxadiazole and triazole monomers with double fluoride terminal groups were prepared at first, and the structures of them were proved by FT-IR and 1H NMR. Then, the sulfonated copolymers containing different nitrogen heterocyclic were synthesized using these two monomers, respectively. The proton conduction of membranes exhibited a low dependence on relative humidity. At 100℃, the proton conductivity of SPAEKST-30% reached to 1.1 mScm-1 under 20%. By comparing and testing the properties of these two copolymers, they both have good water absorption and proton conductive, even in a relatively high temperature. The water retention capacity of polymer containing triazole is better than the polymer containing oxadiazole, but the dimensional stability is weaker than that. Relatively speaking, these two copolymers with different nitrogen heterocyclic have their own advantage and disadvantage.In order to improve the mechanical properties and the structure density of the membrane, the composite membrane of sulfonated poly (aryl ether ketone sulfone) copolymers and poly (aryl ether sulfone) oxadiazole copolymers is prepared by co-solvent method. The sulfonate acid group and heterocyclic group are fixed on different polymer backbones to reduce chain steric hindrance. The test results show that the composite film has good dimensional stability. The methanol permeability of S/P is 3.9×10-7～6.6×10-7cm2/ s, all smaller than SPAEKS. At a relatively high temperature or low humidity condition, the introduction of oxadiazole group enhanced the proton conductivity. At 100℃, the proton conductivity of S/P reached to 0.074Scm-1. So the composite films have the potential to be applied to the field of proton exchange membrane material.