Abstract
A series of crosslinked sulfonated polystyrene (SPS) membranes with different degree of sulfonation (DS) were prepared in the presence of phosphorous pentoxide-methanesulfonic acid (PPMA) in the ratio of 1:10 by weight via the condensation reaction between the sulfonic acid groups and the activated hydrogen atoms of SPS. The crosslinking reaction was confirmed by 1H-NMR and Fourier transform infrared spectrometry. In comparison with uncrosslinked SPS membrane, the crosslinked one showed much higher thermal stability as the degradation temperature increased from about 200 to 300 °C, lower but enough ion exchange capacity (IEC), lower water uptake, and lower swelling ratio. Moreover, the crosslinked SPS membranes still maintained high proton conductivity (3.3—6.1 × 10-2 S cm-1) and keep good shape at room temperature in 100% relative humidity. The relationships among crosslinking time, crosslinking ratio, DS and membrane properties are discussed.
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