Electrosynthesis Of Poly(4,5-Ethylenedioxyindole)(PEDOI) And Investations Of The Electrochromic Properties

Polyindole is an important electrochromic material, which has become one of the focuses on the investigations of electrochromism for its obvious color change, fast response time, high coloration efficiency, low cost, easy processing and easy molecular design. 4,5-ethylenedioxyindole(EDOI) is a new polyindole derivative.Electrochemical polymerization has been proved to be one of the most useful methods for the preparation of poly(4,5-ethylenedioxyindole)(PEDOI). In this paper, the electrochemical polymerizations in different solvents and characterizations of PEDOI and graphene/poly(4,5-ethylenedioxyindole)(ERGO/PEDOI) were studied, and the electrochromic properties and its applications in electrochromic devices of the as-formed polymers were also investigated.1. A novel high-quality free-standing PEDOI films were successfully synthesized electrochemically by direct anodic oxidation of EDOI in which pure boron trifluoride diethyl etherate(BFEE) was selected as the ideal solvent. PEDOI films obtained from this medium showed good electrochemical activities, electrochemical stabilities and good thermal stability with a conductivity of 0.21 S cm-1. The polymerization mechanism were studied by FT-IR. The fluorescent propertities and scanning electron microscopy of the polymer were also studied. Solid fluorescent spectral studies indicate that solid PEDOI film is a good yellow emitter, which is different from the other indole derivatives.2. Spectroelectrochemical studies show that PEDOI prepared in BFEE can be changed from brown to green along with the change of potentials. Kinetic studies show that the coloration efficiency of PEDOI is calculated to be 126 cm2 C-1, higher than any other polyindole derivatives. ECD based on PEDOI andpoly(3,4-ethylenedioxythiophene)(PEDOT) was also fabricated and showed a good electrochromic performance, a gradual color change from dark green to dark blue.The ECD constructed by PEDOI and PEDOT has coloration efficiency(586 cm2 C-1),fast response time(1.9 s at 1320 nm), high optical contrast(35% at 616 nm), better optical memory and good long-term stability.3. A new conducting nanostructured composite, ERGO/PEDOI, was synthesized by electrochemical polymerization of EDOI monomer with ERGO modified electrode in dichloromethane(CH2Cl2). As the results of cyclic voltammetry(CV) studies,ERGO/PEDOI composite film showed low oxidation potential, high current density of peak and good electrochemical activity compared with pure poly(4,5-ethylenedioxyindole)(PEDOI). Scanning electron microscope(SEM)showed that graphene film was a tight layer of thin film, while the composite film presented as net-like structure.4. Spectroelectrochemical studies show that ERGO/PEDOI can be changed from yellow(-0.2 V) to green(1.0 V) along with the change of potentials. Kinetic studie shows that has a full optical contrast of 34% at 590 nm. The time required for coloring was calculated to be 0.7 s and ERGO/PEDOI exhibited a switch time to bleached state of 1.0 s. ERGO/PEDOI/PEDOT ECD based on ERGO/PEDOI was also fabricated and showed a good electrochromic performance, a gradual color change from light green(-0.3 V) to lake blue(1.3 V). The optical contrast of ERGO/PEDOI/PEDOT ECD is 41% and the coloration efficiency of it is 604 cm2 C-1.These properties may have great potential in applications and will help broaden the Gr/CPs composites in biosensing field.