In this work, the effects of various dendrimer shells on the intermolecular interactions of oligo(phenyleneethynylene) s (OPE) molecular wires in thin films have been studied. Electronic and fluorescence spectra showed that the dendrimer shells can effectively inhibit the aggregation of the molecular wires in both solutions and thin films. Tapping mode atomic force microscopy (TM-AFM) revealed that with the increase of dendrimer size, the film morphologies changed from fibrous to dendritic, indicating a strong shell-dependent molecular packing. This work demonstrated that such 'core-shell' molecular design strategy can be used to precisely tailor the molecular environment surrounding the molecular wires. (C) 2008 Elsevier B.V. All rights reserved.