Conjugated polymers electrochromic devices

Lu, W., B.R. Mattes, A.G. Fadeev, and B. Qi. 2003. Stable conjugated polymer electrochromic devices incorporating ionic liquids. United States Ratent 6, 667, 825. 

The apphcation of a high electric field across a thin conjugated polymer film has shown the materials to be electroluminescent (216—218). Until recentiy the development of electroluminescent displays has been confined to the use of inorganic semiconductors and a limited number of small molecule dyes as the emitter materials. Expansion to the broad array of conjugated polymers available gives advantages in control of emission frequency (color) and facihty in device fabrication as a result of the ease of processibiUty of soluble polymers (see Chromogenic materials,electrochromic). 

Rational Design of Conjugated Polymers for Electrochromic Devices... 

Another mechanism to realize electrochromism is electrothermal chromatic transition. Electricity is much easier to control compared to heat and most of the conductive materials, including many metals and conjugated polymers, can generate heat upon pass of electric current. Electrochromic device based on the electrothermal mechanism is generally composed of chromic and electrically conducting layers. 

PEDOT, one of the most popular jr-conjugated polymers, has been intensively studied for developing nanoscale materials as well as for application to various nanodevices such as biosensors and electrochromic devices, and for drug delivery [82-84]. However, studies on PEDOT nanomaterials and bulk films have mainly focused on their electrical and structural properties and on the various applications of the conducting form of the material (i.e., doped PEDOT systems). The light-emitting characteristics of doped and de-doped PEDOT nanomaterials were first reported by Park et al. in 2008 [43]. 

Among the conjugated polymers, polypyrrole (PPy) is the most representative one for its easy polymerization and wide application in gas sensors, electrochromic devices and batteries. Polypyrrole can be produced in the form of powders, coatings, or films. It is intrinsically conductive, stable and can be quite easily produced also continuously. The preparation of polypyrrole by oxidation of pyrrole dates back to 1888 and by electrochemical polymerization to 1957. However, this organic p>-system attracted general interest and was foimd to be electrically conductive in 1963. Polypyrrole has a high mechanical and chemical stability and can be produced continuously as flexible film (thickness 80 mm trade name Lutamer, BASF) by electrochemical techniques. Conductive polypyrrole films are obtained directly by anodic polymerization of pyrrole in aqueous or organic electrolytes. 

P. M. Beaujuge, J. R. Reynolds, Color Control in Il-Conjugated Organic Polymers for Use in Electrochromic Devices. Chem. Rev. 2010,110,268-320. 

Conjugated polymers demonstrate reasonable electrical conductivity which can be used in antistatic coatings, electronic devices, batteries, electromagnetic interference (EMI) shielding, electrochromic devices, optical switching devices, sensors, and textiles. ... 

Meng, H., et al. 2003. An unusual electrochromic device based on a new low-bandgap conjugated polymer. Adv Mater 15 146. 

While an invaluable tool in producing conjugated polymers on conducting substrates, electropolymerization has limitations that include a lack of primary structure verification and characterization along with the inability to synthesize large quantities of processable polymer. To overcome the insolubility of PEDOT, a water-soluble polyelectrolyte, poly(styrenesulfonate) (PSS) was incorporated as the counterion in the doped PEDOT to yield the commercially available PEDOT/PSS (Baytron P) (39), which forms a dispersion in aqueous solutions [140]. While this polymer finds most of its application as a conductor for antistatic films, solid state capacitors, and organic electronic devices, its electrochromism is distinct and should not be ignored. 

A number of conjugated heterocyclic polymers, viz., poly(pyrrole) [9], poly(p-phenylene) [10], poly(thiophene) [11], and poly(aniline) [12] are also electrically conducting and continue to be developed and studied for electrochromic devices [13-14 see also the companion chapter in this volume] and ion switching devices [15-16], among others. Polymer films with high electrical conductivity have been generated by electrochemical polymerization of benzenoid, nonbenzenoid and heterocyclic aromatics, in particular from the derivatives of pyrrole, thiophene, carbazole, azulene, pyrene, triphenylene and aniline. The electrochemical approach for making these films is very versatile and it provides a facile way to vary the properties of the films. The realization of the applications for each electroactive polymer depends on the control and particularly the enhancement of the... 

An electrochromic material is one that changes colour in a persistent but reversible manner by an electrochemical reaction. Accordingly, conjugated polymers that can be repeatedly driven from insulating to conductive states electrochemically with high contrast in colour are promising materials for electrochromic device technology [1]. 

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