科研之友
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摘要
Proton exchange membranes based on partially sulfonated poly(styrene-block-methyl methacrylate) (SPS-b-PMMA) which was obtained via postsulfonation of poly(styrene-block-methyl methacrylate) (PS-b-PMMA) synthesized via sequential atom transfer radical polymerization were performed. Two block copolymers were synthesized having 7 and 12 wt.% poly(methyl methacrylate) (PMMA) block, respectively. The block copolymers were successfully converted to their ionomers by sulfonation using acetyl sulfate as sulfonating agent. The sulfonation reaction was performed at 30 degrees C. The structures and molecular characteristics of the sulfonated block copolymers were studied by FTIR and (1)H NMR spectroscopy. Both the membranes from synthesized SPS-b-PMMA and its polyvinylidene fluoride (PVDF) blends were prepared by solution casting method. The obtained membranes were characterized in terms of proton conductivity, ion exchange capacity (IEC), water uptake and thermal properties. SPS-b-PMMA membrane with 1.95 mmol/g IEC exhibited conductivity (151.0 mS/cm) higher than that of Nafion 117 (133.3 mS/cm) measured at 80 degrees C and relative humidity of 100%. Oxidative stabilities of the membranes were also investigated by Fenton test. The effect of block copolymer composition and ion exchange capacity on membrane flexibility as well as chemical stability was investigated. The microstructures of dry membranes examined by scanning electron microscopy showed microphase-separated structure that induced efficient proton conductivity and chemical stability. More homogeneous dispersion of PVDF domain into SPS-b-PMMA matrix was observed in SPS-b-PMMA/PVDF blend membranes than in partially sulfonated PS/PVDF blend membrane.
- 出版日期2009-11-15
