Wh. Mulder, THERMODYNAMIC ANALYSIS OF PHASE COEXISTENCE AND STABILITY IN TEXTUREDAMPHIPHILIC MONOLAYERS AT THE AIR WATER INTERFACE/, JOURNAL OF PHYSICAL CHEMISTRY B, 102(28), 1998, pp. 5460-5467
Starting from an expression for the Gibbs energy derived previously fo
r a monolayer consisting of a single amphiphilic component present in
the (LE/LC) coexistence region, the general thermodynamic criteria for
internal equilibrium are derived. It is assumed that the solid phase
is present as a dispersion of equally sized circular islands. The assu
mption of isodispersity is justified by the results of an earlier stud
y. The necessary and sufficient conditions for stability of the equili
bria are formulated within the constraints imposed by the model. All o
f these are stated in a general form, independent of the specific anal
ytical expressions for the various thermodynamic quantities. It is poi
nted out that a more or less complete analysis will only be possible o
nce an explicit expression for the line tension and an equation of sta
te for a 2D fluid of rigid disks with smeared-out dipole moment become
available. The latter would allow the calculation of the free energy
of mixing, G(mix),, as well as the formulation of a 2D equation of sta
te for the film within the coexistence region of the phase diagram. A
generic functional form of these functions is given that is consistent
with the requirements set by dimensional analysis. Finally, generaliz
ations of the thermodynamic formalism to mixed monolayers and noncircu
lar domain shapes are suggested.