On the Nature of The Liquid Expanded/Liquid Condensed Phase Transition in Monolayers of Polar Molecules

Abstract

During the liquid expanded/liquid condensed (LE/LC) phase transition, the long range repulsive interactions among fatty acid or phospholipid molecules induce the formation of a dispersion of LC islands (of almost the same size) as a superlattice in a continuous phase of LE molecules. Assuming that the transformation occurs at thermodynamic equilibrium, one demonstrates that, as the surface fraction of LC phase increases, the surface pressure π increases. Consequently, the LE/LC transition can have characteristics different from those of the conventional first order transitions.