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 resonance Raman scattering (RRS) spectroscopy with two excitation lines: green (514 nm) and infrared (1064 nm). The two-step oxidative doping process does not induce a drastic change for the Raman bands, but the changes that occur are clearly evidenced. During doping, new bands appear, indicating a modification of the electronic structure of the polymer. Vibrational calculations were carried out using a symmetrized dynamical matrix model and the results were compared with experimental data, especially in the 1200−1600 cm-1 range, where the CαCβ and Cβ−Cβ stretching vibrations are active. It appears that PEDT seems to have an intermediate electronic structure, between the quinoid and benzoid structures.