Correlation of interface chemistry and growth mode of Ce on polyimide (pyromellitic dianhydride–oxydianiline)

Abstract

Interface properties such as chemical bonding and structure play an important role in adhesion of metals in polymers. Ce, a highly reactive metal, was chosen for these experiments in order to promote enhanced chemistry at the interface to polyimide [pyromellitic dianhydride–oxydianiline (PMDA–ODA)] and to distinguish anticipated reaction products on the basis of their valency. We have studied the progression of interface formation upon metal deposition over a wide coverage range, in situ, by high-resolution x-ray photoelectron spectroscopy, monitoring the polyimide- and Ce-related core levels and changes in the valence-band regime. The interaction is completely dominated by compound formation which differentiates this metal–polymer (MP) system from others studied thus far. The results suggest less selectivity towards the PMDA moiety, indicative of parallel reaction pathways. One can therefore conclude that charge transfer is not a necessary prerequisite of subsequent compound formation for this MP interface. The termination of this spontaneous reaction process at room temperature is evidenced by the peculiar nucleation of unreacted metal at surface defects and the growth of huge planar islands. No other MP system has exhibited such distinct behavior.