The Adhesion of Maleic Anhydride on Native Aluminum Oxide: An Approach by Infrared Spectroscopy and Quantum Mechanical Modeling

The bonding between maleic anhydride, a curing agent for epoxy resins, and natively oxidized aluminum is studied by a combination of infrared spectroscopy and quantum mechanical modeling. On native aluminum oxide, maleic anhydride is hydrolyzed to maleic acid in the early stages of adhesion. The acid prefers a bridged chelate bond of one of its acid groups to two Al atoms of the metal oxide. Furthermore, a monodentate bond between a carbonyl oxygen of an acid group and an Al atom is identified. The anhydride itself shows no tendency to adhere on the native aluminum oxide. Since maleic acid is less reactive in the polymerization than the anhydride, the results imply that the chemical curing reaction could be hampered in the vicinity of the Al substrate.