The self-assembling ability of block copolymers offers an attractive strategy for the organization of pi-conjugated polymers. This article reports the synthesis of a coil-rod-coil triblock copolymer consisting of oligo(p-phenyleneethynylene) as the rodlike segment and polystyrene as the coil-like segment. The chemical structure of the afforded triblock copolymer has been fully characterized by various spectroscopic techniques such as NMR, Raman, gel permeation chromatography, differential scanning calorimetry, ultraviolet-visible, and fluorescence spectroscopy. The small-angle neutron scattering and photophysical measurements indicate that this triblock copolymer exhibits unique solvatochromatic behaviors through the interplay of aggregation-induced pi-pi stacking and planarization of the conjugated backbone. Supramolecular gel nanostructures have been produced via the controlled assembly of the polymer into H-aggregates. It has been demonstrated that the use of the solvent composition to influence chain conformations and thus to manipulate the packing of the conjugated polymer blocks is important for achieving control in the assembly of conducting polymers and associated optical characteristics. (c) 2005 Wiley Periodicals, Inc.