2006 年 19 巻 2 号 p. 297-304
The thermal and optical properties of four kinds of aromatic polyimides (PIs) having a common skeletal structure have been investigated using thermogravimetric analysis and UV/Vis absorption and fluorescence spectroscopy. Pyromellitic dianhydride (PMDA) and 1,4-difluoropyromellitic dianhydride (P2FDA) were used as the dianhydrides for model compounds and PIs to examine the charge transfer (CT) nature of the nPIs. In addition, methosy (-OCH3) group was chosen as the side group to introduce atrong electron donating property to the diamines. The PIs derived from P2FDA exhibit an intense and characteristic absorption band at -550 nm and two independent pairs of the excitation and emission peaks. The spectral data from the modelcompounds demonstrate that the characteristic absorption/emission at 550nm is attributable to the local π-π* transition with P2FDA moiety. In contrast, the emissions appearing at the longer wavelengths for the P2FDA-based PIs (720-730 nm) and those for the PMDA-based PIs (540 and 620 nm) are closely reatedd to the charge transfer (CT) interactions between the dianhydride and diamine moieties, and their behaviors accord with the calculated molecular orbital energies using the density functional theory.
