Preparation and Characterization of Conducting Polymer Materials for Electrochromic Devices

An attempt has been made to improve the physical-chemical properties of conducting polymers by switching from aqueous solutions towards ionic liquids as novel electrolytic media in order to fabricate novel electrochromic materials. Formation and electrochemical characterization of Poly (2,3,5,6- Tetrafluoroaniline) (PTFA) was performed in aqueous solutions. The optical response was observed in order to establish the electrochromic properties of this material. Electrochromic activity of PTFA conducting polymer in aqueous conditions was investigated. Results indicated a slow colour change of 40 seconds, from delicate orange to a much intense orange colour. Electrochemical copolymerization of two monomers pyrrole (Py) and 3,4- ethylenedioxythiophene (EDOT) was performed in an ionic liquid employing a novel ‘micro-cell’ in order to use the materials efficaciously. Characterization of the copolymers electrochemical features was performed for different Py : EDOT ratios (1:2, 1:1, 2:1) in both aqueous and ionic liquid electrolytes. A series of spectroscopic and microscopic studies were also carried out in order to prove the copolymer formation. All three copolymers presented different absorbance spectra, while the FTIR were not very clear. However, the morphology investigation highlighted the different features of copolymers which showed various distributions of globules, pores and holes. Ionic movement between aqueous phase and ionic liquid was studied, and a model was developed to describe the interfacial processes occurring between two immiscible liquid phases. In the present work the Ferrocene ion transport across the ionic liquid / water interface was studied experimentally and in comparison to a model for a thin film of ionic liquid. Results obtained from experimental and modelling data had similar trends of increase in the peak to peak separation with increased scan rate, but the peak to peak separation in the experimental was larger. A new, cost-effective prototype of ‘micro-sandwich electrochromic cell’ was fabricated, based on an ‘ion jelly’ electrolyte. The ‘ion jelly’ solid state electrolyte was a successful replacement for the costly ionic liquids. This prototype of electrochromic cell showed dark-bluish and light-blue colours upon redox switch, but optimization is needed in order to reach the desirable features of a high-performance electrochromic device

Characterization and Electrochromic Properties of Poly(2,3,5,6-Tetrafluoroaniline): Progress Towards a Transparent Conducting Polymer

Electrochromic films of poly(2,3,5,6-tetrafluoroaniline) (PTFA) were formed on ITO substrates from aqueous solutions utilising perchloric acid (HClO4) as dopant. Electrochemical and spectroscopic characterization of PTFA films was performed in background electrolyte and in solutions with the addition of tetrahydrofuran. When the PTFA film was removed from its growth medium, a significant decrease in the faradaic current was observed. The faradaic response increased on addition of tetrahydrofuran which facilitates ion movement through the polymer matrix. PTFA films deposited on ITO substrate were orange and light orange in the oxidized and reduced forms, respectively. The films were ca. 25 nm in thickness. In aqueous solution the films showed a porous structure with a non-uniform distribution of pore diameters. In the presence of tetrahydrofuran a less porous structure was observed

Electrodeposition and Characterisation of Copolymers Based on Pyrrole and 3,4-Ethylenedioxythiophene in BMIM BF4 Using a Microcell Configuration

Electrochemical copolymerization of pyrrole (Py) and 3,4-ethylenedioxythiophene (EDOT) was performed in an ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate, (BMIM BF4) employing a ‘micro-cell’ in order to use the materials efficiently. Characterization of the copolymers formed on an ITO substrate was performed for different Py: EDOT ratios (1:2, 1:1, 2:1) in both aqueous and ionic liquid electrolytes. Electrochemical and spectroelectrochemical analysis revealed that the properties of the copolymer depend upon the Py/EDOT monomer ratio used. The copolymer PPy-co-PEDOT (2:1) displayed good stability, a switching time of 20 s and a colouration efficiency of 101.3 C-1cm2. The presence of Py in the copolymer stabilised the polaron state of the copolymer and allowed greater ion mobility compared to the PEDOT alone

Electrodeposition and characterisation of copolymers based on pyrrole and 3,4-ethylenedioxythiophene in BMIM BF4 using a microcell configuration

Electrochemical copolymerization of pyrrole (Py) and 3,4-ethylenedioxythiophene (EDOT) was performed in an ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate, (BMIM BF4) employing a 'micro-cell' in order to use the materials efficiently. Characterization of the copolymers formed on an ITO substrate was performed for different Py: EDOT ratios (1:2, 1:1, 2:1) in both aqueous and ionic liquid electrolytes. The three copolymers displayed different absorbance spectra with lambda max of the polaron species at 507,540 and 580 nm for PPy-co-PEDOT ratios of 1:2, 1:1, 2:1, respectively. Electrochemical and spectroelectrochemical analysis revealed that the properties of the copolymer depend upon the Py/EDOT monomer ratio used. The copolymer PPy-co-PEDOT (2:1) displayed good stability, a switching time of 20 s and a colouration efficiency of 101.3 C-1cm2. The presence of Py in the copolymer stabilised the polaron state of the copolymer and allowed greater ion mobility compared to the PEDOT alone. (C) 2013 Elsevier Ltd. All rights reserved