The thermal ageing of poly(3,4-ethylenedioxythiophene). An investigation by X-ray absorption and X-ray photoelectron spectroscopy Original Research Article

Oxidatively prepared poly(3,4-ethylenedioxythiophene tetrachloroferrate) (PEDT) has been characterized by X-ray absorption spectroscopy and XPS to study the thermal degradation of the polymer. XANES spectra were measured at the Electron Stretcher Accelerator ELSA in Bonn and compared with measurements made with the conventional XPS technique. These investigations show that after 48 h at 150°C due to baking and moisture irreversible structural changes in the polymer main chain occur. They were identified as a partial oxidation of the sulfur of the polymer backbone to the sulfate anion and the decomposition of the counter ion resulting in loss of conductivity. A possible degradation mechanism is presented.