Electrochromic behavior of poly(pyridinium triflates) films: Electrolyte ions influence

Electrochromic properties of two poly(pyridinium) salts (PV1 and PV2 with additional methyl substituent) in different supporting electrolytes were investigated. KCl, NaCl, LiCl and KBr supporting electrolytes were used to analyze the ions transfer due to ions size variation. The electrochromic properties of polymer films were examined by electrochemical and spectroelectrochemical methods. Both polymers demonstrate reversible redox process in all studied supporting electrolytes. In general, replacement of K+ ions by Li+ or Na+ ions leads to deterioration in the optical contrast and coloring time in contrast to bleaching time which is improved for both studied polymers. The reason behind this is thought to be an increasing cation size obstructing the cation transport in redox reactions. Comparing the relative changes in polymer electrochromic characteristics by the electrolyte replacement is less significant for PV2 films. The replacement of supporting electrolyte anions has practically no effect on the electrochromic properties of both polymers.