The purpose of this study is to correlate the nano-organization in water of coil-rod-coil amphiphilic block copolymers constituted of a conjugated segment to their optoelectronic properties. The ABA block copolymer structures, easily achieved via coupling reactions, are based on conjugated rod of dihexylfluorene and 3,4-ethylenedioxythiophene units linked to two flexible poly(ethylene oxide) or poly[(ethylene oxide)-ran-(propylene oxide)] chains. These well-defined copolymers exhibited a range of specific morphologies in water, a good solvent of coil blocks and a bad solvent of the conjugated rod. Particularly, vesicles and micelles with spherical, cylindrical, or elongated shape were noticed. Correlations were attempted to be established between the weight percent of the conjugated sequence contained in the copolymers, the morphology of the nanostructures obtained by self-assembly in solution and the resulting optical properties. (C) 2008 Wiley Periodicals, Inc.