Competitive adsorption of simple linear alkane mixtures onto graphite

The combination of differential scanning calorimetry and incoherent elastic neutron scattering has been used to demonstrate the formation of solid layers adsorbed onto graphite from pure alkanes and binary alkane mixtures. We report enthalpies and temperatures of the monolayer transitions for pure alkanes and mixtures and note that the solid monolayers melt at approximately 1.1 times the melting point of the bulk liquid or solution. In the mixtures the longer alkane is found to be preferentially adsorbed with the formation of a solid monolayer even when it is present as the minor component in the solution and when the carbon chain lengths differ by only a single CH2 group.