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Yamaki, Tetsuya; Motokawa, Ryuhei; Iwase, Hiroki*; Sawada, Shinichi; Asano, Masaharu; Koizumi, Satoshi; Maekawa, Yasunari
no journal, ,
The nanometer-to-micrometer hierarchical structure was investigated by small-angle neutron/X-ray scattering (SANS/SAXS) analysis, a dissipative particle dynamics (DPD) simulation, and transmission electron microscopy (TEM) observation and then discussed in relation to proton conductivity. In a macroscopic scale, the grafting reaction was found to occur in a PTFE amorphous layer between rigid lamellar crystals and, however, a main reaction field was the outside of the lamellae, which would determine proton conductivity of the membranes. The microscopically-aggregated ionic clusters basically appeared smaller than that of Nafion, and the phase-separated domain including them grew large by connecting with each other toward high ion exchange capacities. This morphological change was accompanied by an increase in the self-diffusion coefficient of protons mainly representing proton conductivity.
Yamaki, Tetsuya; Kobayashi, Misaki*; Asano, Masaharu; Nomura, Kumiko*; Takagi, Shigeharu*; Maekawa, Yasunari; Yoshida, Masaru*
no journal, ,
Our presentation deals with the application of high-energy heavy ion beams to the preparation of nano-structure controlled electrolyte membranes. The membrane preparation involves (1) irradiation of commercially-available base polymer films with 100 MeV 
O, 400 MeV 
Fe, or 450 MeV 
Xe, (2) graft polymerization of vinyl monomers into latent tracks, and (3) sulfonation of the graft polymers. The resulting membranes exhibited anisotropic proton transport, i.e., higher conductivity in the through-plane direction. According to microscopic observations, this is probably because the nearly columnar electrolyte phase with a width of tens-to-hundreds nanometers extended through the membrane. Interestingly, our ion irradiation technique would be able to control the nano-structure of proton-conducting pathways in the membranes. Other excellent membrane properties should also be due to such a controlled structure.