In this thesis, a joint experimental and theoretical study of heteroaromatic oligomers has been carried out. Chapter 1 covers the basic concepts and principles about the conjugated polymers and oligomers. A number of issues related to some potential applications of these materials in electronic devices and recent developments are also discussed. Described in Chapter 2 is the progress of chemical approaches to conjugated oligothiophenes and thienylene-vinylenes. After the analyses of various strategies used to control the molecular properties and to modulate the device characteristics, the aims and scope of this work are then outlined. Chapter 3 details the synthesis and characterization of a series of new heteroaromatic oligomers. The combined application of the Wittig reaction, the Knoevenagel condensation reaction and coupling reactions resulted in the introduction of different organic groups such as thienyl, ethylene, benzene and cyano into the oligomers. A combination of semi-empirical calculations (MNDO, AM1, PM3, ZINDO/S) and oligothiophenes has been carried out in Chapter 4 to evaluate their conformations and the lowest singlet-singlet electronic transition energies. The results show the computed transition energies are in good agreement with the experimental values, both in the solid state, where the oligomers might be expected to be planar, and in solution where twisted conformers are expected. Chapter 5 deals with the electronic properties of target compounds. PM3 and ZINDO/S approaches for the HOMO and LUMO levels and the absorption energies gave satisfactory results. The successive oxidation of all target oligomers with FeCl₃ was carried out. The UV-Vis-NIR spectra of doped species including cation radicals and dications were recorded. The correlations of stability of doped species with their structure variation show that the introduction of electron-withdrawing groups tends to destabilise the positively charged species and electron-donating groups have an opposite effect.