Adsorption of Unsaturated Amides on a Graphite Surface: trans-Unsaturated Amides

The adsorption of three unsaturated amides on graphite is investigated using a combination of synchrotron X-ray diffraction and differential scanning calorimetry (DSC). In this work unsaturated amides with chain lengths of six and nine carbons have been studied with one trans double bond in the alkyl chain at different positions. The structure of each unsaturated amide has been separately determined using synchrotron X-ray diffraction at submonolayer coverages. These monolayer structures are compared with the structure of the saturated amide of the same chain length. The hydrogen bond geometries in these structures are discussed, and these indicate that the position of the double bond relative to the amide headgroup has an important influence on the stability of the monolayer, a finding also supported by the DSC results. Binary mixtures of saturated and trans-unsaturated amides have also been studied using DSC and the behavior discussed using the monolayer structures of the individual species.