Surface chemistry of polyimide formation on Cu(111)

We have investigated the adsorption and reaction of the monomers pyromellitic dianhydride (PMDA) and oxydianiline (ODA) to form the intermediate amic acid and then polyimide adsorbed on Cu(111) using solventless vapor deposition in ultrahigh vacuum. Unenhanced surface Raman spectroscopy was used to identify the adsorbed species. The initial reaction of PMDA and ODA at 383 K created an amic acid ion that was bound to the surface via carboxylate and surface amide linkages. Upon heating the intermediate acid to 473 K, polyimide was formed; it was bound to the surface only via a surface carboxylate. The interfacial polymerization produced only relatively short polyimide chains. The surface Raman spectrum of the amic acid was resonantly enhanced.