Four single-chain bolaamphiphiles, in which the hydrophobic chain was made of the flexible dodecamethylene unit and the bissalicylideneimine unit, were designed and synthesized. These bolaamphiphiles can form two types of stable ordered monolayer membranes in dilute aqueous solution, linear and curved monolayers (vesicles), which have been characterized by transmission electron microscopy and X-ray diffraction. The aggregate structure and thermal behavior of monolayer membranes from these bolaamphiphiles have been investigated by variable temperature H-1 NMR, Fourier transform infrared and UV-vis spectra, and differential scanning calorimetry. The results indicated that the large rigid segments (bissalicylideneimine unit) in the middle stacked densely to establish ordered packing backbones for these bolaamphiphiles to form monolayer membranes, and the alkyl chains packed loosely in dilute aqueous solutions. Also, the problem of these bolaamphiphile monolayers possessing no marked gel-to-liquid crystalline phase transition has been explained from the structural nature of them.