Phase separation of carboxylic acids on graphite surface at submonolayer regime
Instituto Ciencia Materiales de Sevilla-Departamento Química Inorgánica, CSIC-Universidad de Sevilla, Avenida Américo Vespucio s/n, 41092 Sevilla, Spain
2 Department of Chemistry and BP Institute, University of Cambridge, Cambridge, CB3 0HZ, UK
3 Dpt. Ingeniería Química y Química Inorgánica, Universidad de Cantabria, Avda. de los Castros s/n, 39005 Santander, Spain
Mixing behaviour of solid crystalline monolayers adsorbed onto graphite from different mixtures of undecanoic and dodecanoic acids at submonolayer coverage has been investigated. X-ray diffraction measurements have been collected from a variety of compositions as a function of temperature. An extensive phase separation is found for all the compositions – the scattering patterns characteristic of the pure material crystalline structures being preserved across the entire composition range. The temperature dependence of the monolayer melting points and their depression is also clearly indicative of separation of the two surface components, in clear contrast to that expected if the two carboxylic acids mixed ideally in the monolayer.
© EDP Sciences, Springer-Verlag, 2009