In situ observation of interfacial bonding of an organic monolayer confined between two solid surfaces

Silicon substrates coated with a long-chain hydrocarbon monolayer terminated by carboxylic acid ester groups were brought into molecular contact with different solid counter surfaces ranging from inert hydrocarbon surfaces to hydrophilic oxide surfaces. The interaction of the terminal ester groups with the counter surface was probed with infrared spectroscopy. Interfacial hydrogen bonds are reversibly formed upon contact formation, and the total degree of bonding can be adjusted by variation of the hydroxyl group density of the counter surface and quantified from the monolayer IR spectra.