Phase separation in bulk mixtures commonly leads to an isotropic, diso
rdered morphology of the coexisting phases(1). The presence of a surfa
ce can significantly alter the phase-separation process, however(2,3).
Here we show that the domains of a phase-separating mixture of polyme
rs in a thin film can be guided into arbitrary structures by a surface
with a prepatterned variation of surface energies. Such a pattern can
be imposed on a surface by using printing methods for depositing micr
ostructured molecular films(4), thereby allowing for such patterns to
be readily transferred to a two-component polymer film. This approach
might provide a simple means for fabricating polymer-based microelectr
onic circuits(5) or polymer resists for lithographic semiconductor pro
cessing.