Electrochromic properties of a soluble conducting polymer of 1-benzyl-2,5-di(thiophene-2-yl)-1H-pyrrole

In this study, synthesis of a thiophene functionalized monomer, 1-benzyl-2,5-di(thiophene-2-yl)-1H-pyrrole (SNBS) was achieved. A new polythiophene derivative was synthesized by both chemical and electrochemical polymerization. The polymer synthesized via chemical oxidative method was soluble in organic solvents and characterized by nuclear magnetic resonance (1H and 13C NMR) spectroscopy. The average molecular weight of the chemically synthesized polymer was determined by gel permeation chromatography (GPC) as Mn = 8.0 × 103. The electrochemical oxidative polymerization of SNBS was performed via potentiodynamic method using NaClO4/LiClO4 as the supporting electrolyte in acetonitrile (AN). Characterizations of the resulting polymer were performed by cyclic voltammetry (CV), Fourier transform infrared (FTIR), scanning electron microscopy (SEM) and UV–vis spectroscopy. Electrical conductivity of P(SNBS) was measured by the four-probe technique. Spectroelectrochemical analysis presents that the polymer has an electronic bandgap of 1.9 eV, with a light gray color in the fully reduced form and a dark gray color in the fully oxidized form. The switching ability of P(SNBS) was monitored and the percent transmittance (%T) was found as 12%. Dual-type complementary colored electrochromic device (ECD) using P(SNBS)/poly(3,4-ethylenedioxythiophene) (PEDOT) in sandwich configuration were constructed. Spectroelectrochemistry, switching ability and optical memory of the electrochromic devices were investigated.