Effect of dopant on thermal properties of polythiophene

Polythiophene (PT) was chemically synthesized, undoped using aqueous ammonia and then re-doped using FeCl 3 as well as iodine. Doping concentration was changed by changing the duration of doping process. FTIR results indicate the complex formation between PT and each of the dopants. Elemental analysis of FeCl 3 doped samples show that as the duration increases concentration of Fe + ions increases. In case of iodine doped samples atom equivalent of iodine per thiophene unit increases with doping duration. XRD analysis has been used to calculate crystallinity. It is observed that for FeCl 3 and iodine (except 120 min) doped samples there is increase in crystallinity due to doping and crystallinity increases with increase in dopant concentration. TGA analysis shows that FeCl 3 doped samples are thermally stable compared to iodine doped samples. Results of DTA as well as DSC indicate that Tg values vary with dopant as well as with dopant concentrations. Reduction in Tg values for all FeCl 3 doped samples indicate that FeCl 3 acts as plasticizer in PT. In iodine doped samples for low values of dopant concentrations Tg increases indicating anti-plasticizer effect whereas for high concentration of iodine, there is decrease in Tg value indicating plasticizer effect of iodine in PT.