Stability of poly(3-dodecylthiophene) upon doping and thermal de-doping

Poly(3-dodecylthiophene) (p3ddt) was prepared by oxidative polymerisation, doped with iodine, and characterised by surface resistivity, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), to study its stability and structural changes upon repeated doping and de-doping. The surface resistivity of p3ddt was greatly affected by the thermal de-doping temperature; at lower de-doping temperatures (<200 °C), its conductivity gradually recovered with doping time; it would partially or completely lose conductivity above the de-doping temperature at 200 °C. Both the pristine and doped p3ddt decomposed at around 350 °C; the iodine uptake ability decreased while re-doping with the increase in heating temperature. XPS results revealed that doping and heating was accompanied by oxidation with the participation of oxygen. These structural distortions and chemical transformations may contribute to the increase in surface resistivity upon heating.