Theoretical study on polyimide-Cu(100)/Ni(100) adhesion

The interfacial properties of polyimide (PI)/M(100) (M = Cu and Ni) were investigated using density functional theory (DFT). A PMDA-ODA monomer unit was used to represent the full PI and the surface was represented by periodically repeated slabs. PI prefers the bridge and top sites on a Cu(100) surface but only forms weak C=O-Cu interactions. PI favors the bridge site on a Ni(100) surface and can form strong C-Ni, N-Ni, and C=O-Ni bonds. The adsorption energies of PI on Cu(100) and Ni(100) surfaces are -0.58 and -4.7 eV, respectively. Compared to the adsorption energies of O and O-2 on a Cu(100) surface, the adsorption of PI on Cu(100) is not energetically favorable, which leads to the easy oxidation of Cu particles in a Cu/PI nanocomposite. The good adhesion at PI/Ni(100) suggests that Ni is a better candidate as a metal filler compared to Cu in the metal-polyimide composite.