Partially Sulfonated Poly(1,4-phenylene ether-ether-sulfone) and Poly(vinylidene fluoride) Blend Membranes for Fuel Cells
Blend membranes based on high conductive sulfonated poly(1,4-phenylene ether-ether-sulfone) (SPEES) and poly(vinylidene fluoride) (PVDF) having excellent chemical stability were prepared and characterized for direct methanol fuel cells. The effects of PVDF content on the proton conductivity, water uptake, and chemical stability of SPEES/PVDF blend membranes were investigated. The morphology, miscibility, thermal, and mechanical properties of blend membranes were also studied by means of scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA) measurements. The blend membrane containing 90wt.% SPEES (degree of sulfonation -DS=72%) and 10wt.% PVDF (M-w=180,000) exhibits optimum properties among various SPEES72/PVDF membranes. Addition of PVDF enhanced resistance of the SPEES membrane against peroxide radicals and methanol significantly without deterioration of its proton conductivity. It's proton conductivity at 80 degrees C and 100% relative humidity is higher than Nafion 115 while it's methanol permeability is only half of that of Nafion 115 at 80 degrees C. The direct methanol fuel cell performance of the SPEES membranes was better than that of Nafion 115 membrane at 80 degrees C.