In situ spectroelectrochemical Raman studies of poly(3,4-ethylenedioxythiophene) (PEDT)

The vibrational properties of poly(3,4-ethylenedioxythiophene) (PEDT) have been studied by means of UV-vis-NIR optical absorption spectroscopy and res onance Raman scattering (RRS) spectroscopy with two excitation lines: green (514 nm) and infrared (1064 nm). The two-step oxidative doping process doe s not induce a drastic change for the Raman bands, but the changes that occ ur are clearly evidenced. During doping, new bands appear, indicating a mod ification of the electronic structure of the polymer. Vibrational calculati ons were carried out using a symmetrized dynamical matrix model and the res ults were compared with experimental data, especially in the 1200-1600 cm(- 1) range, where the C-alpha=C-beta and C-beta-C-beta Stretching vibrations are active. It appears that PEDT seems to have an intermediate electronic s tructure, between the quinoid and benzoid structures.