Linear and branched electroactive polymers based on ethylenedioxythiophene–triarylamine conjugates

Abstract

Triphenylamines with one, two, or three 3,4-ethylenedioxythiophene (EDOT) substituents attached to the para-phenyl carbons have been prepared via metal-catalyzed cross-coupling reactions. The amines with two or three EDOTs (compounds 4 and 3, respectively) can be oxidatively electropolymerized (via intermolecular coupling between two EDOT groups at their respective α-carbon atoms) to afford stable, linear and cross-linked polymers, respectively. The linear polymer (poly-4) exhibits two resolved, reversible oxidation waves corresponding to the oxidation of the amine and EDOT centers. These two oxidation processes occur at the same potential in cross-linked poly-3 giving rise to one broad, reversible oxidation wave. The observation of redox processes associated with the EDOT-based chromophores contrasts the properties of related (non-EDOT-containing) polymers for which the thiophene backbone serves only as a conjugated ‘linker’. These polymers are highly stable to electrochemical oxidation and can be electrochemically cycled hundreds of times with no detectable decomposition; color changes accompany the redox processes, interconverting between reduced (yellow) and oxidized (green–blue) forms.