Preparation And Properties Of Crosslinking And Sulfonated Poly(Arylene Ether)S With N Heterocyclic Ring For Proton Exchange Membrane Material

Proton exchange membrane fuel cell (PEMFC) possesses the advantages of simple operation, fast start, high fuel efficiency and non-pollution. As a core component of PEMFC, proton exchange membrane (PEM) directly affects the performance of PEMFC pratical application. Perfluorinated polymers such as Nafion(?) are the most widely commercially available PEM materials for PEMFC. However, the high cost, high methanol crossover and decreased conductivity under low humidity or high temperature have limited the extent of their applications. Therefore, a high performance and cheap cost PEM material is imminent.Sulfonated poly(arylene ether)s have good thermal stability, excellent chemical stability and relatively low cost. However, a high sulfonated degree (Ds) leads to poor dimensional stability, mechanical property and methanol crossover, which limit the final application in fuel cells. Therefore, to modify the membrane material and improve their overall performance will be very important.We synthesized S-SPAEK/PVA and C-SPAEKS/Am-SPAEKS crosslinked membranes. After the test, we found that the thermal stability and chemical stability of the crosslinked membranes are improved. The methanol permeability coefficients of S-SPAEK/PVA-30and C-SPAEKS/Am-SPAEKS-40at60℃were2×10-7cm2s-1and2.35×10-7cm2s-1. respectively. In addition, the proton conductivity of C-SPAEKS/Am-SPAEKS-40was0.089S/cm, which was higher than that of C-SPAEKS (0.085S/cm) and Am-SPAEKS membranes (0.065S/cm) at80℃.In order to solve the formation of microphase-separated structures, we also synthesized Am-SPAEKS membrane. The internal ionic interaction in the membrane led to a dense membrane structure. For comparison, we prepared C-Am-SPAEKS crosslinked membranes through heat treatment. The proton conductivity of both Am-SPAEKS-3and C-Am-SPAEKS membranes were above0.08S/cm, which were higher than0.063S/cm of Nafion.In addition, we also synthesized2,5-bis(4-fluorophenyl)-1,3,4-oxadiazole (BFO) monomer and a series of sulfonated poly(arylene ether sulfone) containing1,3,4-oxadiazole copolymers (SPAESO) with different Ds. The heterocyclic structure (C=N) in the membranes may interact with the sulfonic acid groups, which make the membrane structure more compact and decrease the methanol permeability of the membranes. The nitrogen atom in the heterocyclic structure acts as a proton donor and acceptor. Thus be able to form a good transport channel and improve the proton conductivity of the membranes. The results indicate that the proton conductivity of SPAESO increase with the introduction of oxadiazole ring. The proton conductivity of SPAESO-3reach0.075Scm-1, which is higher than0.063Scm-1of Nafion. Consequently, the copolymer membranes are proved to be promising proton exchange membranes materials for PEMFC applications.