Synthesis of ion-exchange membranes for polyelectrolyte fuel cells on the basis of fluoropolymers bombarded with swift heavy ions, 2; Effect of nano-scale structuring of proton conducting pathways

Hiroki, Akihiro; Yamaki, Tetsuya; Asano, Masaharu; Yoshida, Masaru

Films of various fluoropolymers such as ETFE and PTFE were bombarded with swift heavy ions to produce a cylindrical damage zone along the incident axis. The active species generated in this so-called ion track were used to initiate the grafting of styrene, and subsequently the graft chains were sulfonated to produce nano-scaled electrolyte regions. According to a theoretical calculation, the diameter of the ion track in a PTFE film irradiated with Ar (3.8 MeV/n) and Xe (3.5 MeV/n) ions was estimated to be about 120 and 215 nm, respectively. As the ion track was small, the proton conductivity of the resulting polyelectrolyte membranes became large.