Study of the Electrochemical, Mechanical and Solvation Properties of Poly(ethylenedioxy)thiophene (PEDOT) Films Using the QCM, Crystal Admittance and Neutron Reflectivity

Poly(ethylenedioxy)thiophene, PEDOT, is a conducting polymer material that has been the subject of an intensive research effort in recent years primarily because of its applications in both electroluminescent and electrochromic display technology [1]. The monomer (EDOT) is also unusual amongst substituted thiophenes because it has a very low oxidation potential that facilitates electrochemical deposition of high quality thinfilm coatings. In addition, the monomer has C2 symmetry about the central sulfur atom that is a consequence of the substitution pattern of the thiophene ring. This means that polymers derived from this monomer are necessarily regioregular. It has been shown previously that the electrochemical and mechanical properties (parameterized by the orthogonal components of the shear modulus) of mono-substituted polyalkylthiophenes are greatly influenced by the substitution patterns [2]. For example the electrochemical voltammetric response of regioregular films is characterized by a series of features that are attributed to redox processes of crystalline and amorphous regions. Corresponding voltammograms for regiorandom materials show only an “averaged” response with no fine detail.