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Synthesis and electrochromic properties of a multichromic, conducting, soluble polythiophene derivative and its copolymer

Özyurt, Funda
A new polythiophene derivative, poly-2,3-bis(4-tert-butylphenyl)-5,8-bis(4-hexylthiophen-2-yl)quinoxaline PHTQ was synthesized by both chemical and electrochemical polymerization and its electrochemical properties were reported. The monomer was electrochemically polymerized in the presence of tetrabutylammonium hexafluorophosphate(TBAPF6) as the supporting electrolyte in dichloromethane-acetonitrile (5:95, v:v). Nuclear magnetic resonance spectroscopy (1H-NMR, 13C-NMR) was utilized for the characterization of the monomer and the soluble polymer. The polymer was further characterized by Gel Permeation Chromatography (GPC). Spectroelectrochemistry and switching ability of the polymer were investigated by UV–vis spectrophotometer and cyclic voltammetry. The polymer revealed three distinctive colors upon doping which indicated that the polymer is multichromic. Tert-butyl group on the pendant phenyl rings and hexyl groups on thiophene enhanced the solution processability of the electrochromic polymer. The electrochemical and spectral properties of the chemically synthesized polymer were investigated via spray coating on ITO glass slides. Electrochemical copolymerization of 2,3-bis(4-tert-butylphenyl)-5,8-bis(4-hexylthiophen-2-yl) quinoxaline (HTQ) with 3,4-ethylenedioxythiophene(EDOT) was performed to fulfill a strategy in achieving fine-tuned electrochromic properties. The copolymer, P(HTQ-co-EDOT) was characterized via detailed studies of cyclic voltammetry and spectroelectrochemistry. Band gap (Eg) of the copolymer was calculated as 1.4 eV and showed 34 % optical contrast with switching times less than 1 second.