Modulating the Properties of Azulene‐containing Polymers Through Functionalization at the 2‐Position of Azulene

Poly(2‐arylazulene‐alt‐fluorene) and poly(2‐arylazulene‐alt‐thiophene) are synthesized via Suzuki and Stille cross‐coupling polymerization, respectively, using 1,3‐dibromo‐2‐arylazulenes as monomers, which are prepared by a novel directed C−H activation method of 2‐carboxylic azulene and subsequent...

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Published in:Chemistry, an Asian journal an Asian journal, 2020-08, Vol.15 (16), p.2505-2512
Main Authors: Mao Png, Zhuang, Xu, Jianwei
Format: Article
Language:English
Subjects:
2-arylazulene
Absorption spectra
Acid-responsive
Aromatic compounds
Azulene
Azulene-containing Conjugated Polymers
Bromination
Chemistry
Cross coupling
C−H Activation
Electrochromic
Electrochromic cells
Electrochromism
Monomers
Polymers
Properties (attributes)
Protonation
Sensitivity enhancement
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Summary:Poly(2‐arylazulene‐alt‐fluorene) and poly(2‐arylazulene‐alt‐thiophene) are synthesized via Suzuki and Stille cross‐coupling polymerization, respectively, using 1,3‐dibromo‐2‐arylazulenes as monomers, which are prepared by a novel directed C−H activation method of 2‐carboxylic azulene and subsequent bromination reaction. Our study shows that functionalization at the 2‐position of azulene monomers influences polymer properties. For instance, different from electron‐withdrawing groups that discourage the protonation of azulene, electron‐donating aryl groups, however, enhances the sensitivity of response to acid. Protonation of the polymers leads to significant shifts in absorption spectra accompanying with obvious color changes from green to brown in majority cases because of the formation of poly(azulenium cation). The electrochromic properties of polymers are examined, exhibiting that nature of aryl group at the 2‐position of azulene influences the stability of their electrochromic devices. Functionalization at the 2‐position of azulene molecules through directed C−H activation, followed by bromination, affords 1,3‐dibromo‐2‐arylazulenes, which undergo cross‐coupling polymerization with another suitable monomer to give azulene‐containing polymers. The polymer properties such as acid response and electrochromism are regulated by substitution of azulene at its 2‐position.
ISSN:1861-4728
1861-471X
DOI:10.1002/asia.202000627