Electrochromism conducting polymers

Sotzing, G.A., J.R. Reynolds, and P.J. Steel. 1996. Electrochromic conducting polymers via electrochemical polymerization of bis(2-(3,4-ethylendioxy)thienyl) monomers. Chem Mater 8 882. 

Metal Oxide Electrochromism Viologen Electrochromism Prussian Blue Electrochromism Conducting Polymer Electrochromism... 

Otero, T.F., and I. Boyano. 2003. Nucleation and nonstoichiometry in electrochromic conducting polymers. ChemPhysChem 4 868. 

Figure 20.3 Electrochromic device based on electrospun conducting polymer nanofibers. The neutral state (a) and oxidized state (b) are shown. The precursor polymer becomes conjugated and electrochromic by the scheme shown in (c). From S. Jang, V. Seshadri, M. Khil, A. Kumar, M. Marquez, P. T. Mather, G. A. Sotzing, Welded electrochromic conductive polymer nanofibers by electrostatic spinning, Adv. Mater. 17, 2177 (2005). Copyright Wiley-VCH Verlag GmbH Co. KGaA. Reproduced with permission...

Most recently Beaupre et al. developed a flexible electrochromic device using textile in 2006 [71]. The structure is made with a transparent electrode, covered with spray-coated electrochromic polymer, a gel electrolyte and finally with a conductive textile. The textile electrode is made with a textile fabric coated with copper and nickel. The other electrode is made of glass or polyester (PET) coated with ITO. Two electrochromic conductive polymers have been tested. Similar colours and colour changes are obtained for structures using two PET-ITO electrodes, or two glass-ITO electrodes, or one textile electrode with one PET-ITO electrode. The colour change is visible but slow. When a plastic electrode and a textile electrode are used, the structure is flexible. A similar structure, using a copper-coated textile cathode, was described by Zhan et al. in 2013 [72]. 

An early reported example of an electrochromic conducting polymer is polypyrrole (56), which in the imdoped (reduced) insulating state is yellow/green, with a peak maximum characteristic of a jt-jt interband transition. The interband transition energy decreases upon doping to yield the blue/violet doped (oxidized) conductive state (Fig. 7). 

The electrochromism of polyp5UTole is unlikely to be exploited, because of the degradation of the film on repetitive color switching. Electrochromic conducting polymers based on thiophene and aniline have received greater attention. 

Both kinds of advanced materials - electrochromic conducting polymers and SPLs - have been intensively investigated in recent years. These materials can be used in several major electrochromic applications, namely display devices, reflective mirrors and smart windows, since their optical... 

The use of small electrochromic points allows the construction of monochromic or multichromic flat screens. Using different conducting polymers with complementary colors on ITO-coated flexible plastics (now available commercially), camouflage cloths can be envisaged which, once connected to a video camera and a system of image treatment, would be able to mimic any surrounding, as chameleons or cuttlefish do. 

Conducting polymers have found applications in a wide variety of areas,44 45 and many more have been proposed. From an electrochemical perspective, the most important applications46 appear to be in batteries and supercapacitors 47,48 electroanalysis and sensors49-51 electrocatalysis,12,1, 52 display and electrochromic devices,46 and electromechanical actuators.53... 

The enormous efforts put into the basic research and development of conducting polymers are naturally related to hopes of feasible technical apphcations The starting point of this development was the discovery that PA can fimction as an active electrode in a rechargeable polymer battery. Since then, the prospects of technical application have grown considerably Apart from the battery electrode, conducting polymers are discussed as potential electrochromic displays... 

Numerous workers126-132 have combined PB with the conducting polymer polyaniline in complementary ECDs that exhibit deep blue-to-light green electrochromism. Electrochromic compatibility is obtained by combining the colored oxidized state of the polymer1 with the blue PB, and the bleached reduced state of the polymer with PG (Equation (17)) ... 

Doped silicon, conductivity in, 23 35 Doped/undoped electrochromic organic films, 6 580-582 Dope-dyeing, 9 197 Dope-making process, in acrylic fiber solution spinning, 11 204 Dope solids, in air gap spinning, 11 209 Doping, 23 838—839 calcium, 23 842-844 conducting polymers, 7 528-529... 

The development of conducting polymers is naturally related to hopes of feasible technical applications. Thus, conducting polymers are discussed as active battery electrodes [10], electrochromic displays (BCD) [11], anticorrosives [12], sensors [13], electrocatalysts [14], antistatic materials [15], or light-emitting materials (OLED) [16],... 

Since the band structure which develops upon doping induces changes not only in the conductivity but also in the optical absorption (see Fig. 9.8), conducting polymers may be exploited for electrochromic displays, which are optical devices with marked colour transitions. An example is illustrated diagramatically in Fig. 9.18. 

Electronically conducting polymers also have an important role to play as electrodes in electrochromic devices. This is described in Chapter 9. 

There is a large potential for conducting polymers as corrosion-inhibiting coatings. For instance, the corrosion protection ability of polyaniline is pH-dependent. At lower pH polyaniline-coated steel corrodes about 100 times more slowly than noncoated steel. By comparison, at a pH of about 7 the corrosion protection time is only twice for polyaniline-coated steel. Another area of application involves creation of solid state rechargeable batteries and electrochromic cells. Polyheterocycles have been cycled thousands of times with retention of over 50% of the electrochromic activity for some materials after 10,000 cycles. IR polarizers based on polyaniline have been shown to be as good as metal wire polarizers. 

All inorganic electrochromes exist in the solid state in both the colourless and coloured states, e.g. Prussian Blue and tungsten trioxide. Conducting polymers such as polyanilines, polypyrroles and polythiophenes also fall into this class of electrochromes (see 1.5.3.5). 

One of the big drawbacks associated with the use of many conducting polymers as electrochromic materials is their low cycle life stability. To overcome this, and other electrochromic properties, many composite materials have been studied. These composites include mixtures with other optically complementary, conducting polymers and inorganic electrochromes, such as tungsten trioxide and Prussian Blue, and colour enhancing agents or redox indicators, exemplified by the inherently electrochromic indigo carmine (1.96). °... 

Further research on the substitution of the thiophene 3-position with phenyl groups containing electron-withdrawing or electron-donating groups (such as methyl, methoxy, fluoro, chloro, bromo, trifluoromethyl, sulfoxy) in the para position have lead to polymers with unique features [57]. The electron-withdraw-ing groups allow the formation of a radical anion and thus stabilize the n-doped state. As a result, such conducting polymers can be reversibly oxidized and reduced and electrochromic devices can be built with identical anode and cathode materials [58]. 

Examples of electrochromic materials other than conducting polymers W03 (transparent - blue), Ir02 (transparentdark gray),... 

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