SOLVENT EFFECTS ON THE MONOLAYER STRUCTURE OF LONG N-ALKANE MOLECULESADSORBED ON GRAPHITE

Neutron diffraction patterns of dotriacontane (n-C32D66) monolayers ad sorbed on an exfoliated graphite substrate from a heptane (n-C7D16) so lution reveal striking differences in the molecular orientation, latti ce constant, and coherence length from those of the same monolayer ads orbed from the gas phase. Neither n-C32D66 monolayer phase appears to be fully consistent with Groszek's model of n-alkane registry on the g raphite (0001) surface. A reversible transformation between the two mo nolayer phases can be induced by adding as little as a monolayer of th e heptane solvent.