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

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

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.