Electrochromic materials based on PAni, chitosan and clay show distinct colour variation depending on the compound present in the hybrid material.

Hybrid materials based on polyaniline (PAni) were obtained by in situ polymerization of aniline with chitosan and/or organically modified clay (nanomer I-24) in HCl. The samples were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and direct current (DC) electrical conductivity. Thin films of PAni, PAni-clay, PAni-chitosan and PAni-chitosan-clay were prepared by casting a solution of each sample in N-methyl-2-pyrrolidone (NMP) onto indium tin oxide (ITO)/glass electrodes and their electrochromic properties were investigated. It was observed color variation from transparent yellow in the reduced state (E = −0.2 V vs. Ag/AgCl), green in the intermediate state (E = 0.5 V) and dark blue in the oxidized state (E = 0.8 V) for all samples. The color changes of each material in function of the applied potential were tracked using the Commission Internationale de l'Eclairage (CIE) system of colorimetry, in which the color change was much more significant for PAni-clay film.Keywords: conjugated polymer, hybrid material, polyaniline, chitosan, organophilic clay IntroductionConjugated polymers have attracted the attention of academia and industries mainly because of their electrical, magnetic, and optical properties, which make them useful for applications in organic optoelectronic devices. Currently, the development of new hybrid materials based on conjugated polymers have afforded materials with excellent characteristics for application in organic light emitting diodes (OLEDs), 1,2 organic field effect transistors (OFETs), 3 organic solar cells (OSCs), 4 and electrochromic devices (ECDs). [5][6][7] Electrochromic materials based on conjugated polymers show many interesting properties such as multicolor, fast switching speed, flexibility and easy to optimize their properties through molecular tailoring. 8,9 Among the organic polymeric electrochromic materials, polyaniline (PAni) has been widely studied due to many advantageous properties including high optical contrast (∆%T), environmental stability, easy synthesis, as well as comparatively low cost.8 Furthermore, the high pseudocapacitance arising from the versatile redox reactions and its corresponding color changes make PAni promising candidate for electrochemical capacitors 10,11 and ECDs. 12,13 However, the difficulties in processing of PAni into films due to its very low solubility in most of the available solvents and the relatively poor mechanical properties decrease its performances and utilities in such applications.Despite PAni can be synthesized by chemical 14 or electrochemical 15 polymerization methods described in the literature, PAni films with good mechanical properties and adherence to a surface are not usually achieved from the conventional chemical methods of synthesis, which yield PAni as an insoluble and infusible bulky powder. 16 In order to increase the processability and mechanical properties of PAni, significant efforts have been done in preparation of blends based on PA...