Study of Metal/Epoxy Interfaces between Epoxy Precursors and Metal Surfaces Using a Newly Developed Reactive Force Field for Alumina-Amine Adhesion

In this work, we study the adhesion between various alumina surfaces and precursors of amine-containing epoxies. To accomplish this we have developed a reactive force field (ReaxFF) parametrization for the aluminum-nitrogen interaction and combined this with the aluminum-water and glycine force fields reported in earlier work. Molecular clusters and reaction paths selected to model interfacial phenomena of amine-containing epoxy precursors on alumina were used in the fitting of the ReaxFF parameters. It is shown how this new force field satisfactorily reproduces equilibrium bond lengths and angles as well as binding energies for the proposed structures. Reaction profiles are also fitted in agreement with ab initio calculations performed making use of the nudge elastic band method. To substantiate the parametrization, room temperature molecular dynamics results of ammonia adsorption on alumina are compared using ab initio and ReaxFF methods. Using this new interaction scheme, adsorption energies of dimethylamine and DETA on differently terminated alumina surfaces are determined for 10 different moleculesurface approach conditions each. We find that the mean and rms adsorption energy values vary considerably with the particular molecule/surface combination. It is also shown that the adhesion of the studied epoxy precursors decreases linearly with the hydroxyl coverage on alumina surfaces.