Electrochemical synthesis, optical, electrochemical and electrochromic characterizations of indene and 1,2,5-thiadiazole-based poly(2,5-dithienylpyrrole) derivatives

Abstract

Indene and benzothiadiazole units were incorporated to the central pyrrole ring of the poly(thienylpyrrole) backbone, and they are denoted PDIT and PBDTA, respectively. PDIT, PBDTA and their corresponding copolymers (P(DIT-co-DTP) and P(BDTA-co-DTP)) were electrochemically synthesized and their electrochromic properties are reported. The PDIT and PBDTA films were not only reversibly oxidized and reduced but also accompanied by obvious color change (yellow, green, and blue). Their corresponding P(DIT-co-DTP) and P(BDTA-co-DTP) copolymer films present multicolor electrochromism. ΔT_max of the P(DIT-co-DTP) and P(BDTA-co-DTP) films were measured as 45.3% at 1314 nm and 43.5% at 930 nm, respectively, in an ionic liquid solution, and the η of PBDTA and P(DIT-co-DTP) films were calculated to be 167.8 cm² C⁻¹ at 1070 nm and 177.4 cm² C⁻¹ at 1314 nm, respectively, in an ionic liquid solution. ECDs based on PDIT, PBDTA, P(DIT-co-DTP), and P(BDTA-co-DTP) as anodic polymers and poly(3,4-(2,2-diethylpropylenedioxy)thiophene) (PProDOT-Et₂) as a cathodic polymer were constructed. PBDTA/PProDOT-Et₂ ECD showed a high ΔT_max (43.8%) at 590 nm and satisfactory cyclic voltammetry stability, whereas P(BDTA-co-DTP)/PProDOT-Et₂ ECD showed high ΔT_max (44.0%) and coloration efficiency (504.6 cm² C⁻¹) at 594 nm.