Optical and electrochemical properties of soluble N-hexylcarbazole-co-3,4-ethylenedioxythiophene copolymers

We synthesised soluble N-hexylcarbazoie-co-3,4-ethylenedioxythiophene (HCz- co-EDOT) copolymers from mixtures in various ratio of the two corresponding dihalogenated monomers. From EDOT-HCz starting molar ratio: 0.25, 1,4, we obtained random copolymers named, respectively, C1, C2 and C3 and we compar ed their properties to the two homopolymers synthesised in the same way. Th e Infra red studies clearly indicated, as expected, that an increase in the amount of ethylenedioxythiophene in the feed composition leads to an incre ase of the proportion of the corresponding comonomer in the final materials . Elemental analysis point out that the reactivity of dibrominated EDOT see ms slightly lower than that of dibrominated HCz. Thin films of copolymer ha ve been prepared and their electrochemical response have been investigated. Absorption and luminescence of these materials have been also studied in C HCl3. Copolymers mainly composed of one monomer (C1 and C3) behaves like th e corresponding homopolymers. On an other hand, copolymer (C2) obtained fro m an equimolar amount of each monomer in the feed composition clearly exhib its distinct signals in optical spectra and in electrochemical behaviour, p robably due to the presence of each monomer unit short segments. So, the use of C2 has been explored for possible application in light emitt ing devices indicating that the p-doping of the material would be facilitat ed leading to an improved hole injecting when compared to carbazoles homopo lymer. It could be particularly interesting as a hole transporting layer in multilayer organic light emitting devices. (C) 2001 Elsevier Science B.V. All rights reserved.