HOW FORMALDEHYDE INTERACTS AND REACTS WITH CHROMIUM AND CHROMIUM-OXIDE SURFACES - A MODEL FOR CHROMIUM-POLYIMIDE BINDING

Chemical interactions of chromium and chromium oxide with carbonyl functional groups of a polyimide chain were investigated theoretically. Band calculations of the extended Hückel type were performed on model systems. The chromium (chromium oxide) surface was represented by a three-layered slab of material, and for computational economy, the polyimide carbonyls were represented by the formaldehyde molecule. Results suggested that while formaldehyde binds to Cr2O3 via its oxygen lone pair electrons, it binds to metallic Cr in a π or η2 (dihapto) fashion. Further, the calculations indicated that formaldehyde was susceptible to decomposition when bound to clean Cr, but was not susceptible to decomposition when bound to Cr2O3. These differences were attributed to the relatively lower Fermi energy of Cr2O3. By analogy, the imide groups in polyimide may be substantially decomposed at the polyimide/Cr interface, with strong covalent bonding between the metal and the fragmented polymer. © 1990.