Photoluminescences from Aromatic Polyimides in Thin Films: Effects of Precursor Origin and Imidization History

Poly(p-phenylene biphenyltetracarboximide) and poly(4,4'-oxydiphenylene pyromellitimide) in thin films were prepared from their poly(amic acid)s (PAA's) and poly(amic diethyl ester) s (PAE's), respectively, through thermal imidizations over 300-415 degrees C. The photoluminescence characteristic, molecular orientation, and density of these polyimides were dependent strongly on the precursor origin as well as the imidization history. Higher temperature imidization produced higher density and molecular in-plane orientation in the resultant polyimide film, regardless of the precursor origin. However, as the imidization temperature increased, the fluorescence intensity in the films from the PAA's increased, whereas that in the films from the PAE's decreased. These indicate that PAE's lead quite different morphologies and molecular conformations in the resultant polyimide films, compared to the PAA's