TY  - JOUR
AU  - Yoshimura, Kimio
AU  - Zhao, Yue
AU  - Hasegawa, Shin
AU  - Hiroki, Akihiro
AU  - Kishiyama, Yoshihiro
AU  - Shishitani, Hideyuki
AU  - Yamaguchi, Susumu
AU  - Tanaka, Hirohisa
AU  - Koizumi, Satoshi
AU  - Appavou, Marie-Sousai
AU  - Radulescu, Aurel
AU  - Richter, Dieter
AU  - Maekawa, Yasunari
TI  - Imidazolium-based anion exchange membranes for alkaline anion fuel cells: (2) elucidation of the ionic structure and its impact on conducting propertiesu
JO  - Soft matter
VL  - 13
SN  - 1744-6848
CY  - London
PB  - Royal Soc. of Chemistry
M1  - FZJ-2017-07370
SP  - 8463-8473
PY  - 2017
AB  - In our previous study (Soft Matter, 2016, 12, 1567), the relationship between the morphology and properties of graft-type imidazolium-based anion exchange membranes (AEMs) was revealed, in that the semi-crystalline features of the polymer matrix maintain its mechanical properties and the formation of interconnected hydrophilic domains promotes the membrane conductivity. Here, we report a novel ionic structure of the same graft-type AEMs with different grafting degrees, analyzed using a small-angle X-ray scattering method under different relative humidity (RH) conditions. The characteristic “ionomer peak” with a corresponding correlation distance of approximately 1.0 nm was observed at RH < 80%. This distance is much smaller than the literature-reported mean distance between two ionic clusters, but close to the Bjerrum length of water. Since the representative number of water molecules per cation, nw, was small, we proposed that dissociated ion-pairs are distributed in the hydrophilic domains (ion-channels). At RH < 80%, ion-channels are disconnected, however in liquid water, they are well-connected as evidenced by the sharp increase in nw. The disconnected ion-channels even under relatively high RH conditions should be a substantial factor for the low power generation efficiency of AEM-type fuel cells.
LB  - PUB:(DE-HGF)16
C6  - pmid:29090306
UR  - <Go to ISI:>//WOS:000416066400014
DO  - DOI:10.1039/C7SM01774J
UR  - https://juser.fz-juelich.de/record/838860
ER  -