Polythiophene regular copolymers bearing amino or nitro moieties directly linked to the conjugated backbone are produced by anodic coupling of 3',4'-diamino- or 3,4'-dinitro-terthiophenes. The polymers are characterized by cyclic voltammetry, FTIR reflection-absorption and UV-vis spectroscopy and in situ conductivity. Post-polymerization functionalization of polymer films leads to the quantitative transformation of the diamine to pyrazine and of the dinitro to diamine and subsequently pyrazine moieties. Conjugation of starting and ending functionalizations with the polythiophene backbone produces dramatic changes in electronic (electrochemical and optical) properties. (C) 2004 Elsevier Ltd. All rights reserved.