Abstract Five homologous series of α-and α, ω-substituted oligothiophenes up to an undecamer with branched and linear alkyl chains, respectively, are presented. These series are compared with respect to self-organisation in solution and in solid state. UV/Vis absorption data for the long disubstituted branched oligothiophenes indicate the formation of aggregates in solution, expressed by a bathochromic shift of the absorption maximum and ...