Asymmetric Thin Film of Poly(p-phenylene) Prepared by Vacuum Deposition

Abstract

The thin film, prepared by a vacuum deposition method from poly( p-phenylene) synthesized from benzene by a CuCl–AlCl3–O2 catalytic system, had an asymmetric property in its photo-luminescence spectra. Namely, the spectrum observed from the region near the surface had maximum emission peaks at 400–500 nm, while the spectrum observed from the region near the substrate had a maximum emission peak at wavelength above 600 nm. This asymmetric property was observed in the case of the film prepared with a low-temperature substrate. To the contrary, the thin film, prepared at high substrate temperature (150° C), or heat-treated (200° C, in N2, 1 h) after preparation, had no such asymmetric property. The asymmetric property was related to the surface crystallinity and probably the morphology of the film. The surface of the asymmetric film was almost structureless except for some structures resembling whiskers. The surface of the film without the asymmetric property, however, consisted of meshlike structure constructed by small round particles or a complicated meshlike structure.