| 초록 |
The sulfonated polyimides (SPI) were successfully synthesized with 3,3',4,4'-Benzophenonetetracarboxylic dianhydride (BTDA), 2,2'-Benzidinedisulfonic acid (BDSA), 4,4'-Oxydianiline (ODA) by classical two-step method via sulfonated poly(amic acid)s and prepared with different sulfonation level by controlling the ratio of BDSA to ODA. The structure of SPI was characterized by FT-IR as increasing temperature and the sulfonic acid concentration (i.e. sulfonation level or ion exchange capacity) was determined by elemental analysis. The water uptake experiment was carried out as sulfonation degree and small angle X-ray scattering experiment was performed in order to investigate the microphase-separated structure between hydrophobic polymer matrix and hydrophilic ionic site when SPI fully hydrated. It could be observed that the water clusters into SPI membrane increased in the number but it has regular size as increasing sulfonation level. The proton conductivity and the methanol permeability of SPI membrane were measured, as a result, a sudden jump at around 35mol% was observed as percolation phenomenon. In the meanwhile, SPI membrane featured relatively high proton conductivity and extremely low methanol permeability, as showing the feasibility as suitable electrolyte for direct methanol fuel cells. |
