Electrical properties polythiophene conductivity

On the basis of the dependence of the adhesion force versus applied bias and the current-voltage characteristics of polythiophene, it can be concluded that characterization of electrical properties of conducting polymers using CP-AFM at a desired force requires knowledge of the adhesion force. 

AppHcations of polythiophenes being considered utilize either the electrical properties of the doped conducting state with either anionic or cationic... 

Another interesting application that uses the dynamic properties of conducting polymers is electrochromic devices.44,45 46 47 An electrochromic device based on polypyrrole is shown in Figure 1.8. The polypyrrole changes from colorless to black when it is oxidized by the application of positive potentials. Similarly, polythiophene and polyaniline undergo distinct color changes when an electrical potential is applied. 

Poly(3,4-ethylenedioxythiophene) (PEDOT) is one of the most important conducting polymers industrially due to its superior electrical properties and high thermal stability [3,186-196]. PEDOT is also one of the few polythiophenes that can be synthesized through simple oxidative chemical polymerization without using any catalyst. 

Polythiophenes are not only interesting because of their electrical properties. On oxidation (p-doping), the electrical conductivity can be enhanced from about 10 S.cm (pristine material) up to several thousand S.cm 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. 

Yumoto, Y., and S. Yoshimura Synthesis and Electrical Properties of a New Conducting Polythiophene Prepared by Electrochemical Polymerization of a-Ter-thienyl. Synth. Met. 13, 185 (1986). 

As pointed out by Lomas et al., MDOT was expected to be an extraordinarily useful monomer for conductive polythiophenes. Logically, by simple linear continuation of the behavior known from EDOT, 3,4-propylenedioxy-thiophene (ProDOT), and 3,4-butylenedioxythiophene (BuDOT), the polymer from MDOT should exhibit better electric properties than FEDOT. In other words, "EDOT is situated on a continuum between 3,4-methyIenedioxythio-phene and other 3,4-aIkylenedioxy-, 3-aIkoxy- and 3,4-diaIkoxythiophenes. " ... 

Regioregular poly(3-alkylthiophene)s have received a lot of attention, especially because of their high electrical conductivities in the doped state, and because of their unusual solvatochromic and thermochromic behavior . Hence, a lot of research has been focused on clarifying the structure of these materials, both in the solid state and in solution. Today, it is agreed that supramolecular aggregation of polythiophene chains plays an important role in their physical properties. 

Toward an understanding of the conduction properties of polythiophenes (26) and polypyrroles (25) a large number of soluble oligomers has been prepared. Oligothiophenes, indeed, represent the most common model compounds for electrically conducting polymers [149]. Thereby, lower oligomers... 

Intercalation of electroactive polymers such as polyaniline and polypyrrole in mica-type layered silicates leads to metal-insulator nanocomposites. The conductivity of these nanocomposites in the form of films is highly anisotropic, with the in-plane conductivity 10 to 10 times higher than the conductivity in the direction perpendicular to the film. Conductive polymer/oxide bronze nanocomposites have been prepared by intercalating polythiophene in V2O5 layered phase, which is analogous to clays. °° Studies of these composites are expected not only to provide a fundamental understanding of the conduction mechanism in the polymers, but also to lead to diverse electrical and optical properties. 

---