(LC). At much lower surface concentrations and at low enough temperatures, the monolayer undergoes a first-order transition into a gaseous phase. At very high lateral pressures, solidification occurs, as indicated by a discontinuity in the pressure-area isotherms. Subsequently, these systems were also studied using X-ray[@Mohwald2; @Dutta; @Rondelez; @Schlossmann] and neutron[@neutron] scattering techniques, indicating the existence of a large number of different condensed phases. In this paper we will be concerned only with the LE/LC transition. Therefore, we do not introduce appropriate order parameters needed to distinguish the different condensed phases[@Bibo].

The nature of the LE/LC transition has been the subject of much discussion[@Pallas]. It is analogous to the “main” transition in lipid bilayers[@Mohwald], where domains of the LE and the LC phase have been shown to coexist over a wide range of lipid surface concentrations (or area per molecule). In this coexistence region, the condensed domains show a large variety of different shapes[@McConnell] and grow as the area per molecule is decreased, whereas the number of domains depends on the initial conditions and typically stays fixed. The isotherms in the coexistence region, however, were found to be non-horizontal, which led to the postulation of a limited cooperativity of this transition[@Albrecht1]. 