A Monte Carlo technique was applied to simulate a mixture of water with three-segment or with bolaform six-segment amphiphilic molecules in a coarse-grained lattice model. The molecular interactions between hydrophobic and hydrophilic segments, and between hydrophobic segments and water are purely repulsive; no additional attractive interactions are included. With a constant water content of 90% in both systems, we obtained the formation of layer structures at low temperatures and a sharp phase transition to high-temperature phases. The heat capacity has a significant peak at the phase transition in both systems. Structural and thermodynamic properties of the layers as a function of temperature were studied. Typical snapshots and statistically averaged density profiles illustrate the bilayer structure.