We solve in mean-field approximation a model describing the lamellar phases of lyotropic liquid crystals as stacks of interacting bilayer membranes. The model is a synthesis of a Landau-Ginzburg theory of membrane-melting transitions and a continuum treatment of the molecular forces acting between bilayers. The resulting phase diagrams include both planar and modulated phases and are in semiquantitative agreement with experimental observation on neutral lipids. The approach highlights the role of interactions in the thermodynamic behavior of membrane systems.

• Received 2 June 1988

DOI:https://doi.org/10.1103/PhysRevLett.61.2213