Polythiophenes electrochromic devices

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. 

Polythiophenes for Electrochemical and Optical Sensors Metal-containing Polythiophenes Polythiophenes for Electrochromic Devices Polythiophenes for Electronic Devices... 

Gazotti, Jr., W.A., M.-A. De Paoli, G. Casalbore-Miceli, A. Geri, and G. Zotti. 1999. A soKd-state electrochromic device based on complementary polypyrrole/polythiophene derivatives and an elastomeric electrolyte, f Appl Electrochem 20-153-131. 

Poly (thiophene)s are of particular interest as electfochromic materials owing to their chemical stability, ease of synthesis and processability. For the most part, current research has been focused on composites, blends and copolymer formations of several conjugated polyheterocyclics, polythiophene and its derivatives, especially PEIX)T. In one example, poly(3,4-ethylenedioxythiophene) (PEDOT)/poly(2-acrylamido-2-methyl-l-propanesulfonate) (PAMPS) composite films were prepared by Sonmez et al. for alternative electrochromic applications [50]. Thin composite films comprised of PEDOT/PAMPS were reported to switch rapidly between oxidized and neufial states, in less than 0.4 s, with an initial optical contrast of 76% at A.max. 615 nm. Nanostructured blends of electrochromic polymers such as polypyrrole and poly(3,4-ethylenedioxythiophene) were developed via self-assembly by Inganas etal. for application as an electrochromic window [26]. Uniir etal. developed a graft-type electrochromic copolymer of polythiophene and polytetrahydrofuran for use in elecfiochromic devices [51]. Two EDOT-based copolymers, poly[(3,4-ethylenedioxythiophene)-aZ/-(2,5-dioctyloxyphenylene)] and poly[(3,4-ethylenedioxythiophene)-aft-(9,9 -dioctylfluorene)] were developed by Aubert et al. as other candidates for electrochromic device development [52],... 

Polythiophenes and their derivatives have been intensely studied due to their interesting electronic properties. Owing to the combination of their electronic properties, environmental stability, stmctural versatility, low bandgap, low cost and ease of preparation, polythiophene and its derivatives have been utilized in the development of many new electrochromic devices. Here, we focus on the use of polythiophenes for electrochromic applications in terms of their basic properties bandgap and its relation to stability, chain length of substituted functional groups and optical properties such as electrochromic contrast (with some examples from the literature). 

In this section, the constmction of electrochromic devices whose principle electrochromic materials are polythiophenes is discussed. 3-Substituted polythiophenes are the most popular electrochromic materials for such devices. A solid-state electrochromic device was assembled by using poly[3-[12-(p-methoxyphenoxy)dodecyl]thiophene] and poly(3,4-ethylenedioxythiophene) doped with poly(styrene-sulfonate), which showed a color variation from red in the reduced state to blue in the oxidized state during ca. 500 charge-discharge cycles [80]. 

An electrochromic display (BCD) is a thin solid state device that changes color reversibly when subjected to a small electrical potential. Since the doping processes of certain conducting polymers are accompanied by changes in the color, this effect has been conveniently exploited in the realization of BCD devices. Thin films of a conducting polymer polythiophene, for example, are red in the doped state and deep blue in the undoped state. 

MAJOR APPLICATIONS Polythiophenes and the substituted polythiophenes are utilized in a variety of applications where their conducting properties pose an advantage. They are presently used as antistatic coatings and films. Research is being done to explore their use in electrochromic and electroluminescent devices. They have also shown some promise as material for biosensors and storage batteries. Used in making Schottky barrier diodes and field effect transistors. 

K-Conjugated polymers and oligomers are organic materials with many interesting and useful properties [1, 2], Examples of this class of materials include polyacetylene, polythiophene, polypyrrole, poly(phenylenevinylene) and their derivatives. Electronic conductivity, luminescence and nonlinear optical behavior are all observed in these materials and these properties have been exploited in applications such as electroluminescent devices (polymer light-emitting devices or PLEDs), electrostatic coatings, electrochromic windows, chemical sensors and memory devices [3-9]. 

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