| 초록 |
Many important properties required for fuel cell application including hydrolytic stability, depend on various factors like flexibility of the polymer backbone, ring structure and phase separation. This paper primarily focused on studying the effect of the chemical backbone structure on the hydrolytic stability and other properties. To study the difference in the hydrolytic stability with change in the chemical backbone structure of sulfonated polyimides we synthesized phthalic sulfonated polyimides and naphthalenic sulfonated polyimides. Two series of phthalic sulfonated polyimides were prepared using 4,4’-oxydiphthalic anhydride (ODPA) and 4,4’-methylene dianiline (MDA) and 4,4’-(hexafluoroisopropylidine) diphthalic anhydride (6FDA) and oxydianiline (ODA). 4,4’-Diaminobiphenyl 2,2’-disulfonic acid (BDSA) was used to introduce sulfonic acid group in both the series. Naphthalenic polyimides were synthesized from 1,4,5,8-naphthalenetetra-carboxylic dianhydride, BDSA, MDA and ODA. Also to observe other properties according to variation of sulfonic acid content, the degree of functionalization was effectively controlled by altering the mole ratio between the sulfonated and non-sulfonated diamine monomers in phthalic sulfonated polyimides. The hydrolytic stabililty of the polyimides were followed by FT-IR spectroscopy on regular intervals. Polyimides prepared using naphthalenic dianhydride, NTDA, exhibited higher hydrolytic stability than the phthalic dianhydrides. The proton conductivity, ion exchange capacity (IEC) and water uptake measurements revealed the dependence on the molecular weight of the repeating unit. The proton conductivity of the sulfonated polyimides was found to vary with chemical backbone structure. |
