A well-defined triblock copolymer is synthesized by using a strategy in which the a-coupling of 11 thiophene rings of the middle block and the monodispersity (d.p. = 30 and 1.1) of the two polystyrene outer blocks is ensured. Monofunctional polystyrene is modified with an a-terthiophene unit and two of these units are coupled in a double Stetter reaction with a difunctional a-terthiophene to yield a tetraketone as the precursor of the triblock copolymer, which was formed with excess Lawesson's reagent. The triblock copolymer is fully characterized with IR and NMR spectroscopy and MALDI-TOF mass spectrometry. Size exclusion chromatog., transmission electron microscopy, and scanning force microscopy show that the copolymer is self-assembled into spherical, micellar structures with av. diams. of 12 nm, which corresponds to about 60 block copolymer mols. per aggregate. The optical properties are in full agreement with an assocd. unsubstituted oligothiophene. Electrochem. doping is hampered by the polystyrene shell; however, chem. doping afforded small nanoscopic charged aggregates that are sol. in org. solvents