PREPARATION AND PROPERTIES OF SULFONATED POLY (ARYL ETHER KETONE) BEARING PENDANT SULFONIC ACID GROUPS/PVA CROSSLINKED COMPOSITE MEMBRANES FOR DIRECT METHANOL FUEL CELLS

In order to meet the requirements of proton exchange membranes in direct methanol fuel cells (DMFCs), sulfonated poly(aryl ether ketone) bearing pendant sulfonic acid groups/PVA (S-SPAEK/PVA) crosslinked composite membranes with different contents of PVA are prepared by solution blend method. S-SPAEK/PVA crosslinked composite membranes are obtained by a heating reaction at 120 degrees C. FTIR spectra show that crosslinked structure is formed due to the bonds of C-O-S between the sulfonic acid groups on S-SPAEK and hydroxyl groups on PVA. The swelling ratio both at length and thickness, water retention capacity and methanol permeability of S-SPAEK/PVA cross-linked membranes are improved due to the introduction of PVA. The water diffusion coefficient of the S-SPAEK/PVA (85/15) cross-linked membrane reaches 2.9 x 10(-9) cm(2)/s which is lower than that of pure S-SPAEK membrane (3.1 x 10(-8) cm(2)/s). The methanol diffusion coefficient values of S-SPAEK/PVA (85/15) cross-linked membranes at 25 degrees C and 60 degrees C reach 2.6 x 10(-7) cm(2)/s and 3.9 x 10(-7) cm(2)/s, respectively, which are obviously lower than 8.1 x 10(-7) cm(2)/s and 14.5 x 10(-7) CM2/s of pure S-SPAEK membranes under the same test conditions. It can be obviously seen that the methanol diffusion coefficient of S-SPAEK/PVA cross-linked membranes decreases with increasing the content of PVA. Although the proton conductivities of S-SPAEK/PVA (85/15) cross-linked membranes are decreased, they still reach 0.055 S/cm at 25 degrees C and 0.083 S/cm at 80 degrees C, respectively. All the results indicate that the S-SPAEK/PVA (85/15) crosslinked composite membranes are promising as proton exchange membranes for DMFCs applications.