Lattice model results for lamellar phases in slits

A mixture of oil, water, and surfactant confined between parallel hydrophil ic walls is studied close to phase boundaries between lamellar and uniform phases within a vector lattice model in a mean-held approximation. Relation s between energy and force-distance profiles, and the structure of the conf ined fluid (given by density profiles) are found and discussed. For large w all separations L elastic response to compression or decompression, accompa nied by shrinking or swelling of the period lambda of the lamellar phase, i s found for lamellar and induced (by capillary condensation) lamellar phase s. Very good agreement with recent experiments is obtained. For L<4 lambda the system responds to decompression by swelling of the central, either oil - or water-rich layer, with the layers adsorbed at the surfaces remaining u naffected. The solvation force is very weak and independent of L when the c entral layer is swollen, and jumps to much larger values when new layers ar e introduced into the slit. [S1063-651X(99)02212-6].