Synthesis and properties of poly(aryl ether benzimidazole) copolymers for high-temperature fuel cell membranes |
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Authors: | Tae-Ho Kim Sung-Kon KimTae-Wook Lim Jong-Chan Lee |
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Institution: | Department of Chemical and Biological Engineering, Seoul National University, 599 Gwanak-ro, Gwanak-Gu, Seoul 151-744, Republic of Korea |
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Abstract: | A series of poly(aryl ether benzimidazole) copolymers bearing different aryl ether linkage contents were synthesized by condensation polymerization in polyphosphoric acid (PPA) by varying the feed ratio of 4,4′-dicarboxydiphenyl ether (DCPE) to terephthalic acid (TA). As the ether unit content in the copolymer increased, the solubility of the copolymer in PPA and N,N′-dimethylacetamide/LiCl improved. For example 3–7 wt.% DMAc solution containing 2 wt.% of LiCl could be prepared from the copolymers. XRD studies revealed that the incorporation of flexible aryl ether linkages increased the chain d-spacings of the polymer backbones and decreased the crystallinity of the copolymers. Still, these copolymers having ether linkages showed reasonably good thermal/mechanical stability and high proton conductivity. For example, the copolymer with 30 mol% ether linkage had a tensile strength of 43 MPa (at 26 °C and 40% relative humidity) at an acid doping level of 7.5 mol H3PO4 and a proton conductivity of 0.098 S cm−1 (at 180 °C and 0% relative humidity) at an acid doping level of 6.6 mol H3PO4. |
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Keywords: | Fuel cells Copolymer Ionomers Polybenzimidazole Proton conductivity |
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