Swollen lamellar phases confined in capillarylike pores

Structure and mechanical properties of swollen lamellar phases confined in square-base pipes are studied in a mesoscopic lattice model for oil-water-surfactant mixtures. Structure depends crucially on a thermodynamic state and is quite different far and close to the coexistence with a uniform phase. Lamellar domains with different orientations of lamellas are formed in most cases, and the mechanics is determined mainly by domain-wall energies. Shift of phase equilibria in square-base pipes compared to the bulk is just opposite to the shift in slits. We find capillary delamellarization for short-period and for swollen phases, for hydrophilic and for neutral external surfaces.