A soluble conducting polymer of 4-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)benzenamine and its multichromic copolymer with EDOT

Here we report the synthesis of a monomer, 4-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)benzenamine (SNS-NH2) produced by the reaction of 1,4-di(2-thienyl)-1,4-butanedione and benzene-1,4-diamine. This monomer was electrochemically polymerized in the presence of LiClO4, NaClO4 (1:1) as the supporting electrolyte in acetonitrile. Copolymerization in the presence of 3,4-ethylenedioxythiophene (EDOT) was achieved in acetonitrile NaClO4/LiClO4 (0.1 M:0.1 M) solvent–electrolyte couple. Resulting homopolymer and copolymer were characterized by means of cyclic voltammetry, Fourier transform infrared spectroscopy, nuclear magnetic resonance, scanning electron microscopy and ultraviolet–visible spectroscopy. Spectroelectrochemistry analysis of homopolymer, P(SNS-NH2), reflected electronic transitions at 376 and 650 nm indicating π–π∗ transition and polaron band formation, respectively. The polymer has an electronic bandgap of 2.12 eV with a yellow color in the fully reduced form and a blue color in the fully oxidized form. Switching ability of the homopolymer was evaluated by kinetic studies upon measuring the %T as 20.7% at the maximum contrast point. Copolymer revealed multichromic property with five different colors at different applied potentials. Colorimetry studies for P(SNS-NH2-co-EDOT) proved that it is possible to provide fine tuning of these colors by varying applied potential during synthesis. Dual-type complementary colored electrochromic devices (ECD) using P(SNS-NH2-co-EDOT)/poly(3,4-ethylenedioxythiophene) (PEDOT) in sandwich configuration were constructed. Spectroelectrochemistry, switching ability and optical memory of the electrochromic devices were investigated.