Electrochemical synthesis and spectroelectrochemical characterization of triazole/thiophene conjugated polymers

Abstract

Novel electropolymerizable monomers based on triazole–thiophene units were characterized by both spectroscopic and electrochemical methods. It was found that those monomers which were enriched with additional thiophene units in their chemical structure showed red-shifted electronic transitions and lower oxidation potentials when compared with the short-chain disubstituted triazole monomer. The monomers studied were electropolymerized in organic medium giving rise to their corresponding electroactive polymers. These materials can be p-doped at potentials values which can be properly correlated with the thiophene conjugation length of the parent precursor. As a general rule, it was observed that the longer the conjugation length, the lower the HOMO level. Only the alternating bisthiophene–triazole polymer, poly-TTT, can be both p- and n-doped within the electrochemical window of the solvent employed. The doping processes are characterized by the formation of charge traps that avoid the reversible recovery of the injected charge. In addition, polaronic species formed upon electrochemical doping seem to be at the origin of the electronic transition bands observed for all the materials in the visible low-frequency to near-infrared optical range.