Polymers containing thiophene systems have been a subject of research for more than twenty five years. One of the first examples was the polymer with thiophene units and conjugated double bonds |{poly(2.5-thiophenediylvinylene)]. It has been studied intensively because of its good electrical conductivity, being a member of the family of synthetic metals or organic metals.Polythiophene has been synthesized chemically by polycondensation reactions of difunctionalized (hio-phene derivatives (starting from 2.5-dihalothiophene) as well as by electropolymerization of thiophene itself. One may also start with bithiophene, lerlhiophene or higher oligomers of thiophene in order to prepare polymers with thiophene systems, but with differing properties, especially with regard to (he electrochemical behaviour.Polythiophenes are not only interesting because of their electrical properties. On oxidation (p-doping), the electrical conductivity can be enhanced from about 10*7 S.cm-1 (pristine material) up to several thousand S.cnv1 in the oxidized form. This layers of polythiophenes are also of interest due to their large number of special electrophysical properties: Thermochromism, electrochromism, solvatochromism, ionochromism, color changes under pressure and effected by electricity.