Nanopatterns of hydrophobic triblock copolymer SEBS thin films formed on a water surface by using drop spreading casting and dilute solution casting methods have been studied. It is found that the surface morphologies of thin films, as well as the spreading behavior of polymer solutions on water, depend strongly on the selectivity of the solvent and the functional group which interacts with the water subphase. The resulting nanopatterns were examined in terms of the relative interaction parameter (Delta chi) and the copolymer volume fraction (phi) in the solution, based on the physics of solvent annealing and evaporation. (C) 2011 Elsevier B.V. All rights reserved.