This paper presents a straightforward method for patterning thin films of polymers, i.e. a prepatterned mask is used to induce self-assembly of polymers and the resulting pattern is the same as the lateral structures in the mask on a submicrometre length scale, The patterns can be formed at above T-g + 30 degreesC in a short time and the external electric field is not crucial. Electrostatic force is assumed to be the driving force for the pattern transfer. Viscous fingering and novel stress-relief lateral morphology induced under the featureless mask are also observed and the formation mechanisms are discussed. (C) 2003 Elsevier Science Ltd. All rights reserved.