Characterization of the interface between pyromellitic dianhydride/oxydianiline polyimide and silver using surface-enhanced Raman scattering

SERS spectra of the polyimide obtained after curing the polyamic acid against rough silver substrates were more similar to SERS spectra of the polyamic acid than to normal Raman spectra of the polyimide, indicating that curing of the polymer was inhibited by interaction with the substrate. The results led to the conclusion that the pyromellitic dianhydride moieties were adsorbed onto the silver surface edge-on with the carbonyl bonds perpendicular to the surface. Some evidence for formation of isoimide or degradation products containing C=N bonds in the interface was obtained.