Strategies to Enhance the Electrochromic Properties of Conjugated Polymers Bearing Pyromellitic Diimide Acceptors

• Published in: Chemistry, an Asian journal an Asian journal, 2024-06, Vol.19 (12), p.e202400236-n/a
• Main Authors: Hui, Bryan Yat Kit, Chin, Kang Le Osmund, Lim, Jovan Jun Long, Soo, Xiang Yun Debbie, Lu, Xuehong, Zhu, Qiang, Liu, Xiaogang, Xu, Jianwei, Chua, Ming Hui
• Format: Article
• Language: English
• Subjects: Color; Colour Tuning; Conjugated Polymers; Diimide; Electrochromic; Electrochromism; Industrial parks; Organic Optoelectronics; Polymers; Pyromellitic Diimide; Switching; Thin films
• ISSN: 1861-4728; 1861-471X; 1861-471X
• DOI: 10.1002/asia.202400236

A series of conjugated polymers bearing thiophene‐based donors and pyromellitic diimide (PMDI) acceptor were prepared, and their electrochromic (EC) properties were studied via using fabricated thin‐film EC devices. It was observed that structurally regular alternating polymers with fewer (1 and 2) thiophene donors do not exhibit any EC properties while increasing the number of donors eventually led to the emergence of orange‐red‐to‐green colour switching. On this basis, two more random co‐polymers containing higher donor‐to‐acceptor ratios were synthesized to further improve EC switching properties. The two polymers, which bear a PMDI‐to‐thiophene ratio of ca. 1 : 7 and 1 : 8, revealed orange red‐to‐blue colour switching and generally improved optical contrasts and switching speeds in both the visible and near infra‐red (NIR) region. In addition, the subtle modulation of polymer colour and hue via variation of the number of thiophene donors was evident through colorimetric study. This work therefore demonstrates the potential and possibility of using the PMDI acceptor unit to construct EC‐active conjugated polymers, and considerations for future tuning of colour and switching performances. The use of pyromellitic diimide to construct electrochromic‐active conjugated polymers were studied, and it was found that increasing the number and proportion of thiophene donors in the polymers, electrochromic properties (e. g., optical contrasts, switching speed and switching stability) can emerge and be enhanced, while switching colours (in both neutral and oxidized states) can be modulated.