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Zhao, Y.; Yoshimura, Kimio; Shishitani, Hideyuki*; Yamaguchi, Susumu*; Tanaka, Hirohisa*; Koizumi, Satoshi*; Szekely, N.*; Radulescu, A.*; Richter, D.*; Maekawa, Yasunari
Soft Matter, 12(5), p.1567 - 1578, 2016/02
Times Cited Count:27 Percentile:80.24(Chemistry, Physical)Yoshimura, Kimio; Koshikawa, Hiroshi; Yamaki, Tetsuya; Shishitani, Hideyuki*; Yamamoto, Kazuya*; Yamaguchi, Susumu*; Tanaka, Hirohisa*; Maekawa, Yasunari
Journal of the Electrochemical Society, 161(9), p.F889 - F893, 2014/06
Times Cited Count:21 Percentile:61.31(Electrochemistry)Graft-type anion-conducting electrolyte membranes (AEMs) with imidazolium cations on graft polymers were synthesized through radiation-induced graft polymerization of -vinylimidazole (NVIm) on poly(ethylene-co-tetrafluoroethylene) (ETFE) films, followed by -propylation and ion-exchange reactions. The -propylation proceeded quantitatively, whereas the ion-exchange reactions in 1 M KOH at 60C were accompanied by partial -elimination of the imidazolium cations(AEM2), which exhibited an ion-exchange capacity (IEC) of 0.85 mmol g and ionic conductivity of 10 mS cm. AEM2 showed alkaline stability at 60C but it gradually degraded at 80C for ca. 150 h. The copolymer-type AEM (AEM3) with an IEC of 1.20 mmol g was prepared through the copolymerization of NVIm with styrene on ETFE films, followed by the same -propylation and ion-exchange reactions. AEM3 was shown higher alkaline durability in 1 M KOH at 80C. As a result, it exhibited higher conductivity (10 mS cm) for 250 h. Therefore, alkylimidazolium cations in copolymer grafts are a promising anion conducting group for alkaline-durable AEMs. A maximum power density of 75 mW cm is obtained for AEM3 in a direct hydrazine hydrate fuel cell.
Yoshimura, Kimio; Koshikawa, Hiroshi; Yamaki, Tetsuya; Maekawa, Yasunari; Yamamoto, Kazuya*; Shishitani, Hideyuki*; Asazawa, Koichiro*; Yamaguchi, Susumu*; Tanaka, Hirohisa*
ECS Transactions, 50(2), p.2075 - 2081, 2012/10
no abstracts in English
Koshikawa, Hiroshi; Yamaki, Tetsuya; Asano, Masaharu; Yoshimura, Kimio; Maekawa, Yasunari; Yamamoto, Kazuya*; Shishitani, Hideyuki*; Asazawa, Koichiro*; Yamaguchi, Susumu*; Tanaka, Hirohisa*
no journal, ,
We investigated the effect of the length of the linear chain on the structure of quaternary ammonium ions on the membrane properties such as durability of ion conductivity. Graft polymerization was performed by immersing the pre-irradiated ETFE film in the CMS solution. The ETFE-g-CMS film was then quaternized in four different tertiary amines, that is, trimethylamine (n = 1), dimethylethylamine (n = 2), n-butyldimethylamine (n = 4) and n-hexyldimethylamine (n = 6) solutions. The n dependence of the OH conductivity and chemical durability, which was represented by a residual percentage of the conductivity after treatment with a Fenton solution. When n increased from 1 to 6, the OH conductivity decreased slightly, but it still stayed 20 mS/cm for n = 6. The chemical durability seemed to increase eight-fold at the same time. The chemical attack by hydroxyl radicals on the quaternary ammonium ions would be controlled by hydrophobicity and steric hindrance of the alkyl group.
Yoshimura, Kimio; Sinnananchi, W.; Koshikawa, Hiroshi; Yamaki, Tetsuya; Maekawa, Yasunari; Yamamoto, Kazuya*; Shishitani, Hideyuki*; Asazawa, Koichiro*; Yamaguchi, Susumu*; Tanaka, Hirohisa*
no journal, ,
no abstracts in English
Asano, Masaharu; Koshikawa, Hiroshi; Yamaki, Tetsuya; Maekawa, Yasunari; Yamamoto, Kazuya*; Sampei, Fumihiro*; Shishitani, Hideyuki*; Asazawa, Koichiro*; Yamaguchi, Susumu*; Tanaka, Hirohisa*
no journal, ,
no abstracts in English
Asano, Masaharu; Koshikawa, Hiroshi; Yamaki, Tetsuya; Yoshimura, Kimio; Maekawa, Yasunari; Yamamoto, Kazuya*; Sampei, Fumihiro*; Shishitani, Hideyuki*; Asazawa, Koichiro*; Yamaguchi, Susumu*; et al.
no journal, ,
no abstracts in English
Yoshimura, Kimio; Koshikawa, Hiroshi; Yamaki, Tetsuya; Sampei, Fumihiro*; Shishitani, Hideyuki*; Asazawa, Koichiro*; Yamaguchi, Susumu*; Tanaka, Hirohisa*; Maekawa, Yasunari
no journal, ,
no abstracts in English
Yoshimura, Kimio; Sinananwanich, W.*; Koshikawa, Hiroshi; Asano, Masaharu; Yamaki, Tetsuya; Maekawa, Yasunari; Yamamoto, Kazuya*; Shishitani, Hideyuki*; Asazawa, Koichiro*; Yamaguchi, Susumu*; et al.
no journal, ,
no abstracts in English
Maekawa, Yasunari; Yoshimura, Kimio; Koshikawa, Hiroshi; Yamaki, Tetsuya; Yamamoto, Kazuya*; Shishitani, Hideyuki*; Asazawa, Koichiro*; Yamaguchi, Susumu*; Tanaka, Hirohisa*
no journal, ,
Anion-exchange membranes (AEM) for hydrazine fuel cells, in which non precious metals are used as an electrode catalyst, have been developing by radiation techniques. AEMs having polyvinylimidazolium grafts were synthesized by radiation-induced graft polymerization of N-vinylimidazole or the copolymerizaiton with styrene onto ETFE film, followed by N-alkylation and ion exchange reactions. The alkaline durability of the membranes was evaluated in 1M KOH at 80 C. The AEM consisting of the homopolymer grafts showed alkaline stability at 80 C for ca. 150 hours. In contrast, the copolymer (1:1 molar ratio) grafts type AEM kept its ion conductivity above 10 mS/cm in 1M KOH at 80 C for 250 h. The alkylimidazolium group in the copolymer grafts is a promising anion exchange group in AEMs for highly alkaline durable fuel cells.
Koshikawa, Hiroshi; Yamaki, Tetsuya; Asano, Masaharu; Yoshimura, Kimio; Maekawa, Yasunari; Yamamoto, Kazuya*; Shishitani, Hideyuki*; Asazawa, Koichiro*; Yamaguchi, Susumu*; Tanaka, Hirohisa*
no journal, ,
We prepared anion-exchange membranes based on an ethylene-tetrafluoroethylene copolymer by -ray-induced graft polymerization of chloromethylstyrene (CMS) and the subsequent quaternization reaction. The crosslinker effect was investigated in terms of membrane preparation and performance of a hydrazine fuel cell. The quaternization ratio appeared to decrease as the concentration of divinylbenzene (DVB) in the CMS grafting solution increased. Importantly, the crosslinker lowered the water uptake of the resulting membranes in the Cl and OH forms, possibly thereby restricting excessive swelling during the fuel-cell operation.
Koshikawa, Hiroshi; Asano, Masaharu; Yamaki, Tetsuya; Yoshimura, Kimio; Maekawa, Yasunari; Yamamoto, Kazuya*; Shishitani, Hideyuki*; Asazawa, Koichiro*; Yamaguchi, Susumu*; Tanaka, Hirohisa*
no journal, ,
We investigated the effect of a linear carbon chain length (n) in quaternary ammonium ions, on the durability of ion conductivity of anion exchange membrane. The poly(ethylene-co-tetrafluoroethylene) grafted chloromethylstyrene film was quaternized in four different tertiary amines, that is, trimethylamine (n=1), dimethylethylamine (n=2), n-butyldimethylamine (n=4) and n-hexyldimethylamine (n=6) solutions. The n dependence of ion conductivity and chemical durability, which was represented by a residual percentage of the conductivity after treatment with a Fenton solution (3% hydrogen peroxide+ 4 ppm iron sulfate) at 80 C for 2 h. When n increased from 1 to 6, the ion conductivity decreased slightly, but it still stayed 20 mS/cm for n = 6. Interestingly, the chemical durability seemed to increase eight-fold at the same time. The chemical attack by hydroxyl radicals on the quaternary ammonium ions would be controlled by hydrophobicity and steric hindrance of the alkyl group.
Yoshimura, Kimio; Koshikawa, Hiroshi; Yamaki, Tetsuya; Shishitani, Hideyuki*; Asazawa, Koichiro*; Yamaguchi, Susumu*; Tanaka, Hirohisa*; Maekawa, Yasunari
no journal, ,
no abstracts in English
Yoshimura, Kimio; Koshikawa, Hiroshi; Yamaki, Tetsuya; Shishitani, Hideyuki*; Yamaguchi, Susumu*; Tanaka, Hirohisa*; Maekawa, Yasunari
no journal, ,
no abstracts in English
Yoshimura, Kimio; Koshikawa, Hiroshi; Yamaki, Tetsuya; Shishitani, Hideyuki*; Yamaguchi, Susumu*; Tanaka, Hirohisa*; Maekawa, Yasunari
no journal, ,
no abstracts in English
Yoshimura, Kimio; Koshikawa, Hiroshi; Yamaki, Tetsuya; Shishitani, Hideyuki*; Yamaguchi, Susumu*; Tanaka, Hirohisa*; Maekawa, Yasunari
no journal, ,
Anion-conducting electrolyte membrane fuel cells (AEMFCs) especially in direct hydrazine fuel cells have recently received considerable attention. Due to high temperature and highly basic operating condition, it is required to develop alkaline durable AEMs. In this work, we synthesized the AEM based on a 4(5)-vinylimidazole (4VIm) monomer by radiation-induced grafting and subsequent -alkylation and ion exchange reactions () because 4VIm does not possess -protons, leading to a Hoffman elimination reaction, which is the main degradation route in 1-vinylimidazolium-grafted AEM (). The alkaline stability of AEMs was estimated by monitoring the change in conductivity of AEMs in 1 M KOH at 60C. As a result, the conductivity of suddenly decreased within few hours, while the initial decrement of conductivity of was clearly suppressed. It clearly showed that the prevention of a Hoffman elimination reaction enhanced the alkaline durability of the imidazolium-type AEM.
Yoshimura, Kimio; Zhao, Y.; Koshikawa, Hiroshi; Yamaki, Tetsuya; Shishitani, Hideyuki*; Yamaguchi, Susumu*; Tanaka, Hirohisa*; Koizumi, Satoshi*; Maekawa, Yasunari
no journal, ,
Anion conducting polymer electrolyte membranes (AEMs) having poly 2-methyl-1-vinylimidazolium grafts were synthesized by radiation-induced graft coplymerizaiton of 2-methyl-1-vinylimidazole with styrene onto an ETFE film, followed by N-alkylation and ion exchange reactions. The excellent long-term stability of the prepared AEMs was confirmed in 1M KOH at 80C. The graft-type AEM with an ion exchange capacity of 1.80 mmol/g showed a maximum power density of 210 mW cm in a direct hydrazine hydrate fuel cell test. The contrast variation experiment in small-angle neutron scattering measurement displayed the advantageous three-phase structures, consisting of crystalline, amorphous hydrophobic, and amorphous hydrophilic domains.
Yoshimura, Kimio; Koshikawa, Hiroshi; Yamaki, Tetsuya; Shishitani, Hideyuki*; Yamaguchi, Susumu*; Tanaka, Hirohisa*; Maekawa, Yasunari
no journal, ,
Since anion-conducting electrolyte membrane fuel cells (AEMFCs) such as direct hydrazine fuel cells operated under high temperature and highly basic condition, it is required to develop alkaline durable AEMs. In this work, we synthesized AEM with poly 2-methyl-1-vinylimidazolium grafts by radiation-induced graft coplymerizaiton to protect 2-position of imidazolium ring from alkaline hydroxide ion attack. The AEM with an ion-exchange capacity (IEC) of 1.80 mmol g exhibited ionic conductivity of 123 mS cm at 60C. The durability of the membrane was evaluated. The excellent long-term alkaline stability of the prepared AEM was confirmed in 1M KOH at 80C. Therefore, the protection of 2-position by methyl group suppresses ring opening degradation reactions, resulting in the improvement of the alkaline durability of imidazolium-type AEMs.
Maekawa, Yasunari; Zhao, Y.; Yoshimura, Kimio; Shishitani, Hideyuki*; Yamaguchi, Susumu*; Tanaka, Hirohisa*; Koizumi, Satoshi*
no journal, ,
no abstracts in English
Yoshimura, Kimio; Shishitani, Hideyuki*; Yamaguchi, Susumu*; Tanaka, Hirohisa*; Maekawa, Yasunari
no journal, ,
no abstracts in English