THEORETICAL MONOMER CLUSTER MODEL OF A POLYMER-METAL INTERFACE - POLY(METHACRYLONITRILE) ON A NICKEL SURFACE

A low-energy contribution at 283.6 eV noted in the C 1s region of the XPS spectrum of thin films of poly(methacrylonitrile) obtained via cathodic electropolymerization of 2-methyl-2-propenenitrile on nickel surfaces and recent electrochemical impedance measurements are strongly indicative of a chemical bond formed between the first monomer and metallic atoms during the grafting step of the reaction. A model of a carbon/nickel surface bond comprising a saturated monomer of 2-methyl-2-propenenitrile bound to nickel clusters (Ni3 and Ni7) is designed to mimic the final state of the reaction of cathodic electropolymerization. Hartree-Fock calculations are performed to obtain optimized geometry parameters. An evaluation of the chemical shift obtained on the XPS spectrum is made by computing the C 1s ionization potentials via Koopmans' theorem. In addition, the analysis of the electronic redistribution upon chemisorption brings valuable insights on the precise nature of chemisorption sites as well as on the validity of a cluster/monomer approach to render the present polymer/metal interface.