Electrochromic properties of 'Trimeric' thiophene-pyrrole-thiophene derivative grown from electrodeposited 6-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)hexan-1-amine and its copolymer

A centrosymmetric polymer precursor, namely 6-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)hexan-1-amine (TPHA), was synthesized via a Knorr-Paal reaction using 1,4-di(2-thienyl)-1,4-butanedione and hexane-1,6-diamine. The resultant monomer was characterized by Nuclear Magnetic Resonance (H-1-NMR). Electroactivity of TPHA was investigated via cyclic voltammetry. The electronic structure and the nature of electrochromism in P(TPHA) and its copolymer with EDOT, (P(TPHA-co-EDOT)), were examined via spectroelectrochemistry studies. P(TPHA) switches between claret red neutral state and blue oxidized state. Optical response times for coloring and bleaching processes of the P(TPHA) and P(TPHA-co-EDOT) were found as 2.1 s and 1.6s, respectively. The copolymer of TPHA was used to construct dual type polymer electrochromic devices (ECDs) against poly(3,4-ethylenedioxythiophene) (PEDOT). Spectroelectrochemistry and electrochromic switching out of the devices were investigated.