Low dielectric (low-kappa) materials are of key importance for the performance of microchips. In this study, we show that nanosized cowpea mosaic virus (CPMV) particles can be assembled with poly(amic acid) (PM) in aqueous solutions via the layer-by-layer technique. Then, upon thermal treatment CPMV particles are removed and PM is converted into polyimide in one step, resulting in a porous low-kappa polyimide film. The multilayer self-assembly process was monitored by quartz crystal microbalance and UV-Vis spectroscopy. Imidization and the removal of the CPMV template was confirmed by Fourier transform infrared spectroscopy and atomic force microscopy respectively. The dielectric constant of the nanoporous polyimide film thus prepared was 2.32 compared to 3.40 for the corresponding neat polyimide. This work affords a facile approach to fabrication of low-kappa polyimide ultrathin films with tunable thickness and dielectric constant. (C) 2011 Elsevier B.V. All rights reserved.