Electrochemical polymerization process and excellent electrochromic properties of ferrocene-functionalized polytriphenylamine derivative

Abstract

A novel triphenylamine (TPA) derivative (E)N-(4-(Diphenylamino)phenyl)- formimidoylferrocene) (TPAFc) containing ferrocene (Fc) unit was designed and synthesized successfully. Theoretical calculation and experimental data show TPAFc possesses higher HOMO energy level and the lower onset oxidative potential compared to TPA monomer. Cyclic voltammetry test demonstrates coupling reaction between TPA units and the formation of an electroactive polymer film during successive scans. This intriguing phenomenon may be ascribed to the multi-step oxidation process and Fc unit plays an important role as charge transport center for electrons moving from TPA units and the surface of the forming oligomer film to the electrode. SEM images indicate PTPAFc film shows the surface morphology of uniform tubular structures, which may largely increase the area of interface between the electrolyte solution and the polymer film. Interestingly, PTPAFc film exhibits reversible multicolor changes switched from neutral transparent color to light orange and blue in fully oxidized state, which are attributed to that the existence of Fc unit brings out multiple redox states. In addition, the polymer film presents excellent electrochromic performances in the aspect of high optical contrast (∼58%), good coloration efficiency (∼130 cm2 C−1) and fast switching time (∼2 s). In view of these excellent features, the developed PTPA derivative is very satisfactory for applications on high-performance electrochromic devices.