Exploring the electrochromic properties of poly(thieno[3, 2-b]thiophene)s decorated with electron-deficient side groups. Issue 4 (21st December 2016)

• Record Type: Journal Article
• Authors: Shao, Shan; Shi, Jingjing; Murtaza, Imran; Xu, Panpan; He, Yaowu; Ghosh, Sanjay; Zhu, Xiaosi; Perepichka, Igor F.; Meng, Hong
• Is Part Of: Polymer chemistry. Volume 8:Issue 4(2017)
• Page Start: 769
• Page End: 784
• Publication Date: 2016-12-21
• Subjects: Polymers -- Periodicals; Macromolecules -- Periodicals; Polymerization -- Periodicals; 547.705
• DOI: 10.1039/c6py01847e
• Languages: English
• ISSNs: 1759-9954

Abstract

Abstract : Electron-deficient cyanophenyl side groups decrease the response time and drastically improve the stability of electrochromic polymers. Abstract : Two novel thieno[3, 2- b ]thiophene (TT)/3, 4-ethylenedioxythiophene (EDOT)-based compounds of 2, 5-(EDOT–TT–EDOT) type bearing electron-withdrawing side groups (4-cyanophenyl or 4-pyridyl) at 3, 6-positions of the TT moiety have been synthesized. Their electropolymerization leads to electroactive conjugated polymers, P(CNPh-ETTE) andP(Py-ETTE), which possess electrochromic properties changing the color from purple to pale grey-blue or from sand brown to pale grey-green, respectively. Cyclic voltammetry and spectroelectrochemical experiments reveal that functionalization with electron-withdrawing side groups decreases the HOMO and LUMO energy levels and contracts the band gap of materials. Both new polymers demonstrated extremely short response times of 0.9–1.1 s for bleaching and 0.34–0.35 s for coloring.P(CNPh-ETTE) andP(Py-ETTE) polymers showed reasonably good contrast (16–23%) and coloration efficiency (120–190 cm 2 C −1 ) in the visible region (at the maxima of their π–π* transitions, 540/570 nm), and high contrast and coloration efficiency in the near-infrared region (50–62% and 324–440 cm 2 C −1 at 1500 nm, respectively). While the stability of the pyridine-functionalized polymer, P(Py-ETTE), was shown to be low (with unstable charge–discharge characteristics, presumably due to the protonation of the pyridine ring during the redox process), P(CNPh-ETTE) demonstrated superior electrochromic performance retaining 91–96% of its electroactivity after 2000 cycles between −0.5 and +1.0 V. DFT calculations on these and related EDOT–TT–EDOT polymers reported by us early have been presented and analyzed to understand the structure–property relationships in this class of electrochromic polymers.