Light stability of 3,4-ethylenedioxythiophene-based derivatives

The light stability of two 3,4-ethylenedioxythiophene-based derivatives, i.e. the oligomeric compound 5,5″-diphenyl-2,2′-5′,2″-ter(3,4-ethylenedioxythiophene) (1, 3-EDT) and the corresponding polymer of 2-tetradecyl-2,3-dihydro-thieno[3,4-b][1,4]dioxine (2, PEDT-C14), was investigated. Their stability upon irradiation with a xenon lamp was studied by means of UV-Vis spectroscopy. These measurements lead to the proposal of a photooxidation mechanism that seems to be operative in chlorinated solvents, followed by H-abstraction. Furthermore, the experiments point out that it is mainly UV light that causes the instability of the oxidatively doped compounds.