in situ FTIR study of adhesive interactions of 4,4′-methylene diphenyl diisocyanate and native metals

Native surfaces of Al, Cu and Au are exposed to diluted solutions of 4,4′-methylene diphenyl diisocyanate (4,4′-MDI). The resulting 4,4′-MDI adsorption state is characterised by in situ infrared external reflection absorption spectroscopy. On Au, the adsorbate state differs from bulk but the interactions are weak. On Al and Cu, rich spectral features and resistance against desorption indicate strong adhesion which is most likely chemical by nature. However, further quantum mechanical modelling is needed for final conclusions on the adhesion mechanism.