Polyaniline electrochromic devices

D. DeLongchamp and P. T. Hammond. 2001. Layer-by-layer assembly of PEDOT/polyaniline electrochromic devices. Adv Mater 13(19) 1455-1459. 

Sheng, K. Bai, H. Sun, Y. Li, C. Shi, G., Layer-by-layer assembly of graphene/polyaniline multilayer films and their application for electrochromic devices. Polymer 2011. 

Another interesting application that uses the dynamic properties of conducting polymers is electrochromic devices.44,45 46 47 An electrochromic device based on polypyrrole is shown in Figure 1.8. The polypyrrole changes from colorless to black when it is oxidized by the application of positive potentials. Similarly, polythiophene and polyaniline undergo distinct color changes when an electrical potential is applied. 

Shim, G.H., Han, M.G., Sharp-Norton, J.C., Creager, S.E., Foulger, S.H., 2008. Inkjet-printed electrochromic devices utilizing polyaniline-silica and poly(3,4-ethylenedioxythiophene)-silica colloidal composite particles. J. Mater. Chem. 18,594-601. 

Hu, H., L. Hechavarria, and J. Campos. 2003. Optical and electrical responses of polymeric electrochromic devices Effect of polyacid incorporation in polyaniline film. Solid State Ionics 161 165-172. 

Self-doped polyanilines are advantageous due to properties such as solubility, pH independence, redox activity and conductivity. These properties make them more promising in various applications such as energy conversion devices, sensors, electrochromic devices, etc. (see Chapter 1, section 1.6). Several studies have focused on the preparation of self-doped polyaniline nanostructures (i.e., nanoparticles, nanofibers, nanofilms, nanocomposites, etc.) and their applications. Buttry and Tor-resi et al. [51, 244, 245] prepared the nanocomposites from self-doped polyaniline, poly(N-propane sulfonic acid, aniline) and V2O5 for Li secondary battery cathodes. The self-doped polyaniline was used instead of conventional polyaniline to minimize the anion participation in the charge-discharge process and maximize the transport number of Li". In lithium batteries, it is desirable that only lithium cations intercalate into the cathode, because this leads to the use of small amounts of electrolyte... 

C. H. Yang, Y. K. Chih, W. C. Wu, C. H. Chen, Molecular assembly engineering of self-doped polyaniline film for application in electrochromic devices, Electrochemical and Solid State Letters 2006, 9, C5. 

Impedance Spectroscopy. Impedance spectroscopy has been carried out on devices with WO3 as the cathodic electrochromic layer, counter electrodes of iridium oxide, polyaniline or Prussian blue, and polymers as electrolytes (Katsube et al [1986], Friestad et al [1997]). The equivalent circuit for a whole device becomes very complicated. In the works quoted above simplified, Randles-type circuits were used for the two electrochromic layers, while the ion conductor was modeled by a pure resistance, or neglected. Extraction of device parameters from the data fitting was reported. However, it is clear that in many cases it will be difficult to distinguish the contributions from the different layers in a device, in particular if the migration impedances, ion diffusion impedances, etc. are of the same order of magnitude. When it comes to characterizing electrochromic devices, impedance spectroscopy is a very time-consuming process, since a spectrum down to low frequencies should be taken at a number of equilibrium potentials. Thus we believe that transient current measurements in many cases offer a faster alternative that sometimes allows a simple determination of diffusion coefficients. 

Other successful electrochromic devices have been realized by Kelly et al. using polyaniline-impregnated fibres [79]. In situ electrochemical polymerization of polyaniline is used to bind poly aniline to a PET or viscose spacer fabric. The fabric is then impregnated with an electrolyte and sandwiched between two electrodes. For the bottom electrode, carbon black or silver ink can be printed directly on the fabric. Polyaniline colour changes from green to blue through oxidation—reduction processes. However, the lifetime of this structure is also short and does not exceed dozens of oxidation—reduction cycles. 

Duck et al. [292] have reported that poly(ethylene oxide-co-epichlorohydrin containing LiC104 has a desirable transparency and ionic conductivity at room temperature to be used as a solid electrolyte in electrochromic devices. These authors have used polyaniline and Prussian blue as an electrochromic material and have characterized the device by doublestep spectrochronoamperometry using monochromatic light at 650 nm. 

Polyaniline (PAn)/inorganic composites have been considered as new class of materials due to their improved properties compared with those of pure conducting polymers and inorganic materials [73-77]. For example, the combination of electrical conductivity of PAn and UV sensitivity of anatase Ti02 are expected to find applications in electrochromic devices, nonlinear optical system, and photochemical devises [73], From this point of view, it is in particular interest to prepare fluoroalkyl end-capped oligomers/PAn/titanium oxide nanocomposites. In fact, fluoroalkyl end-capped acrylic acid oligomer [Rp—(ACA) —Rp]/, 2-methacryloyloxyethane sulfonic acid oligomer [Rp—(MES) —Rp]/, 2-acrylamido-2-methylpropanesulfonic acid... 

The instability of PANI above 0.8 V aside, the redox behavior of the first couple of polyaniline, leucoemeraldine to emeraldine, is stable and has been exploited in EC systems (9,13,24). Thin layer electrochromic devices have been reported by a number of groups, however despite the seemingly good results derived it would be desirable to address the pemigraniline (blue) form as well. If it were possible to access this state reversibly, then PANI or related materials could find utility in glare reduction applications and in smart windows since the band associated with this form best matches the solar spectrum (25). 

Electrochemical applications of polyanilines comprise electrochromic devices, -> electrochemical sensors, and bio electro chemical devices biosensors, biofuel... 

Multicolor electrochromic devices consist of different electrochromic active conducting polymers showing specific colors at quite different operation potentials. Polyaniline-poly(sodium acrylate)-PT and polyaniline-poly(sodiimi acrylate)-3-methylPT films are constructed by combining polyaniline-poly(sodium acrylate) with its specific color in the oxidized state with PT and 3-methylPT films showing their specific color in the reduced state [168]. 

Duek, E. A. R., De Paoli, M.-A., and Mastragostino, M., A solid-state electrochromic device based on polyaniline, Prussian blue and an elastomeric electrolyte, Adv. Mater., 5, 650, 1993. 

Ferraris and colleagues studied laminate films of PEDOTT spin coated on electropolymerized N-methylpolypyrrole, polyaniline spin coated on PEDOT PSS, and polyaniline deposited on electropolymerized N-methylpolypyr-role. The films were analyzed using CIE (x, i/)-chromaticity coordinates. The observed colors in their fully doped and reduced states were found to be linearly dependent on the color coordinates of the two individual polymers of the laminate, which allows for adjusting the observed color by variation of layer thickness of an electrochromic device in a viable and predictable way. Inganas ° studied a laminate structure made from polypyrrole electro-chemically deposited on top of a PEDOTPSS layer formed by spin coating. In contrast to Ferraris et al. he found that the spectra of the laminate electrode matches well with spectra of pure polypyrrole. 

L.-M. Huang, C.-H. Chen, and T.-G. Wen. 2006. Development and characterization of flexible electrochromic devices based on polyaniline and poly(3,4-ethylenedioxythiophene)-poly(st5ume sulfonic acid). Electrochim Acta 51(26) 5858-5863. 

Electrochromic devices have also utilized LbL assembled films for immobilizing the active electrochromic material that changes color at an applied voltage. Polyviologen (PV) was the first active material that was used for such purposes within PV-PSS multilayers, while the first LbL-based solid-state electrochromic device utilized poly(3,4-ethylene-dioxythiophene) (PEDOT) colloid as the electrochromic material within multilayers of PEDOT/PSS and polyaniline. Other nanoparticles were used for the development of electrochromic devices with LbL films, such as Pmssian blue, polyoxometalate, and tungsten oxide. A recent example demonstrated the use of coordination chemistry-based LbL assembly to fabricate fast-switching electrochromic films of zinc polyiminofiuorene and terpyridine. ... 

Kobayashi T., Yoneyama H., Tamura H. Polyaniline film-coated electrodes as electrochromic display devices J.Electroanal.Chem., 1984 161 429-23... 

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