Polymer electrochromic materials color change mechanism

Electrochromism is a phenomenon displayed by some materials reversibly changing colors. Various materials can be used to construct electrochromic devices, such as transition metal oxides, liquid crystals, photonic crystals, and polymers (Booth and Casey, 2009 Nicoletta et al., 2005 Arsenault et al., 2007 Gamier et al., 1983). Here, we will focus on the electrochromic materials based on polymers. There are several mechanisms to explain the color changes of polymer electrochromic materials like electro-induced oxidation-reduction and electrothermal chromatic transition and so on. 

Electrochromism describes a color change as a result of an applied potential, typically via an electrochemical mechanism. Many electrochemically switchable materials such as polythiophenes and polyaniline have this capability. Table 4.1 shows a very few of the materials and colors available today. Other nonpolymeric materials such as viologens [10] offer a higher contrast, but are not themselves conducting and therefore must be combined with a conducting polymer or another conducting... 

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