Conducting polymer-based electrochromics

Somani, R, A.B. Mandale, and S. Radhakrishnan. 2000. Study and development of conducting polymer-based electrochromic display devices. Acta Materialia 48 2859-2871. 

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. 

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. 

Although some electrochromic displays offer some advantages over LED and LCD displays (e.g. lower power consumption than LEDs, multiple colours and wider viewing angles than LCDs), they have been hampered by a number of disadvantages. In particular, they have tended to suffer from shorter lifetimes and lower numbers of operational cycles, and it remains to be seen whether the newly emerging conductive-polymer-based devices are able to improve upon this limitation. 

Chandraseldiar, P., "Conducting Polymer Based Actively IR Modulating Electrochromics", Monthly Report Numbers 1-7 towards Contract No. F29601-98-C-0142 for Kirtland Airforce Base, New Mexico (1998). 

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. 

High-resolution circuitry and active devices employing Langmuir-Blodgett film techniques or polymer-based transistors are being considered for the sophisticated electronics required in future vehicles. Temperature or energy balance in the vehicle could be controlled through conductive polymers or semiconductor deposits on electrochromic windows. Electroluminescent liquid crystals and fluorescent and electrochromic materials used for visual displays show promise for future development. 

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