Fully undoped and soluble oligo(3,4-ethylenedioxythiophene)s: spectroscopic study and electrochemical characterization

Fully undoped oligo(3,4-ethylenedioxythiophene)s have been synthesized from polycondensation of the corresponding dibromomonomer in the presence of a catalytic Ni(0)-based complex in N,N-dimethylacetamide (DMA). HPLC analysis indicated that the material is constituted of three main oligomers which have also been clearly detected by UV-Visible spectroscopy. Due to its partial solubility in DMA, processability is improved compared to the corresponding insoluble polymer and thin films of oligomers can be deposited by evaporation. Electrochemical and electrochromic properties of undoped film have been carried out. Deep purple in its undoped state, the material becomes sky blue in the oxidized form. The mixture of oligomers was characterized by means of Raman scattering, IR absorption and X-Ray dffraction (XRD), and compared to the poly(3,4-ethylenedioxythiophene) obtained by the oxidative route.