We investigate the surface ordering and orientation of a synthetic rigid-flexible block molecule containing a rigid penta-p-phenylene and poly(propylene oxide) flexible chains at the air-water interface. This supramolecular amphiphile self-organizes into a honeycomb-like structure in the bulk, but it behaves differently with the conventional amphiphilies at the air-water interface. Surface press it re-a rea isotherms, TEM and AFM results show that the rod-coil molecule forms a stable monolayer at the air-water surface. After monolayer collapses, the molecule exhibits island morphology with the (10) layer spacing of similar to 18 nm. From these results, we discuss the self-assembling mechanism of microphase separation between the rigid moiety and the flexible segments on the water subphase. (C) 2007 Elsevier B.V. All rights reserved.