Volume 14, Issue 13 p. 2694-2697
Communication

OH Conductive Properties and Water Uptake of Anion Exchange Thin Films

Fangfang Wang

Fangfang Wang

School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa, 923-1292 Japan

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Dongjin Wang

Dongjin Wang

School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa, 923-1292 Japan

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Dr. Yuki Nagao

Corresponding Author

Dr. Yuki Nagao

School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa, 923-1292 Japan

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First published: 29 April 2021
Citations: 11

Graphical Abstract

Anion exchange: Poly[(9,9-bis(6′-(N,N,N-trimethylammonium)-hexyl)-9H-fluorene)-alt-(1,4-benzene)] (PFB+) is used as a model ionomer to investigate the OH conductivity and water uptake in thin film form. Reduced OH conductivity is observed in the thinner film at 95 % relative humidity, which can be attributed to the decreased amount of water content. The OH conductivity is only slightly reduced under the same water uptake.

Abstract

Several investigations have indicated that proton conduction and hydration properties of acidic ionomers differ from those of membranes. However, relations between the OH conductivity and water uptake in thin film forms of anion exchange membranes have not been reported yet. For this study, new in situ measurements were established to elucidate the OH conductivity and water uptake without allowing any influence of CO2 from the air. Poly[(9,9-bis(6′-(N,N,N-trimethylammonium)-hexyl)-9H-fluorene)-alt-(1,4-benzene)], denoted as PFB+, was synthesized as a model ionomer. The highest OH conductivity of 273 nm-thick PFB+ film was 5.3×10−2 S cm−1 at 25 °C under 95 % relative humidity (RH), which is comparable to the reported OH conductivity of PFB+ membrane. Reduced OH conductivity was found in the thinner film at 95 % RH. The decreased OH conductivity is explainable by the reduced number of water molecules contained in the thinner film. The OH conductivity was reduced only slightly under the same water uptake.