Preparation of radiation-grafted ion exchange membranes for application to fuel cells; New strategies emerging with recent developments

放射線グラフト法による燃料電池用イオン交換膜の作製; 最近の進展と新しい戦略

八巻 徹也; 浅野 雅春; 吉田 勝*

Yamaki, Tetsuya; Asano, Masaharu; Yoshida, Masaru*

放射線グラフト法による燃料電池用イオン交換膜の作製と評価について、最近の研究をレビューする。特に、燃料電池用途に向けた、グラフト重合のベースポリマーの選択とグラフトモノマー又はモノマー/架橋剤の組合せとについて最初に記述する。このような既存の研究の流れに加え、(1)放射線グラフト重合に放射線架橋を組合せた新規架橋フッ素電解質膜の作製,(2)イオンビームで厚さ方向に形成された穿孔によるナノ構造制御イオン交換膜の実現について、著者らの研究を詳細に報告する。最後に、これらに関連して、イオン交換膜におけるプロトン伝導経路の構造などに関する基礎研究の重要性、さらには当該分野への中性子ビームの応用可能性に言及する。

We reviewed many recent publications on radiation-grafted ion exchange membranes for fuel cells in terms of their preparation and characterization. At first, primary attention was paid to how to select the base polymer films and the monomers or monomer/crosslinker combinations in order to meet many fuel-cell requirements at the same time. Next, as a main subject, novel synthetic strategies emerging recently were highlighted: (1) a combination of radiation grafting with radiation crosslinking of the base polymer, giving a crosslinking structure of the fluorocarbon main chain, which is absent in the Nafion-like membranes; (2) the use of swift heavy ions as a radiation source to introduce the graft chains into only the very narrow cylindrical region along ion tracks, leading to the preparation of what is called "nano-structure controlled membranes." Finally, there remains an increasing necessity to pursue more basic research of the membrane regarding its structure and the behavior of the chemical species diffusing therein, i.e., protons, water, methanol, etc.