| 초록 |
The structure effects on optical anisotropy and relative permittivity of the thin films of PMDA-4,4’ODA (pyromellitic dianhydride-4,4’-oxydianiline), PMDA-3,4’ODA (pyromellitic dianhydride-3,4’-oxydianiline), 6FDA-4,4’ODA (4,4’-hexafluoroisopropylidene bis(phthalic anhydride)) and 6FDA-3,4’ODA has been examined by using a prism coupling method. Their morphological structure was investigated by wide-angle X-ray diffraction (WAXD). The trends of mean intermolecular distances in X-ray study are consistent with the fractional free volume results were calculated in the optical and dielectric studies. The birefringence of the polyimides thin films decreased as the film thickness increased. But PMDA-3,4’ODA film increased as the film thickness increased. The polyimides with the 6FDA exhibited relatively low dielectric constants and refractive indices. It is due to a simultaneous increased in the fractional free volume. The PMDA-4,4’ODA showed relatively lower dielectric constant and refractive index than the PMDA-3,4’ODA, whereas the 6FDA-4,4’ODA showed higher than the 6FDA-3,4’ODA. It might result from optical anisotropy by chemical structure. |
