S. Mafe et al., PHOSPHOLIPID MONOLAYERS AT WATER-VERTICAL-BAR-OIL INTERFACES - THEORETICAL MODELING OF SURFACE PRESSURE MOLECULAR AREA ISOTHERMS, Journal of electroanalytical chemistry [1992], 457(1-2), 1998, pp. 155-162
The phospholipid adsorption and surface pressure-molecular area isothe
rms at interfaces are interpreted theoretically from two-dimensional (
2D) lattice and real gas models that incorporate a minimum number of a
djustable parameters. The first model is based on the lattice statisti
cs of binary solutions and the molecular parameters introduced are the
energy changes involved in the mixing process of the phospholipid and
organic solvent molecules and the effective phospholipid head area. T
he surface pressure is interpreted in terms of the difference between
the two liquid surface tensions. The second model makes use of (i) a n
on-localised adsorption model with a square-well potential energy term
for the calculation of the surface concentration of the phospholipids
at the interface as a function of the volume concentration of the pho
spholipids in the organic solvent phase, and (ii) a 2D hard disc gas m
odel with a mean-field term accounting for the attractive interactions
between the tails of the adsorbed phospholipids. The molecular parame
ters introduced in this model are the interfacial phospholipid adsorpt
ion energy, the effective hard disc diameter of the phospholipid head
and the interaction energy between the phospholipid tails. The surface
pressure is interpreted in terms of a 2D gas pressure in this model.
The theoretical results obtained are compared with experimental data f
or the water / 1,2-dichloroethane and water / air interfaces. The two
models predict correctly the typical order of magnitude for surface co
ncentration and pressure values, as well as some qualitative features
of the experimental isotherms, for low phospholipid surface concentrat
ions. (C) 1998 Elsevier Science S.A. All rights reserved.