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Updated: May 31, 2026

Self-assembling Morphologies Obtained from Helical Polycarbodiimide Copolymers and Their Triazole Derivatives
Published on: February 7, 2017
Low bandgap polymers by copolymerization of thiophene with benzothiadiazole
Youjun He1, Xiang Wang, Jing Zhang
1Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China; Graduate University of Chinese Academy of Sciences, Beijing 100039, P. R. China.
Abstract:
Three low bandgap copolymers of thiophene and benzothiadiazole with electron-donating and electron-withdrawing substituents, P1, P2, and P3, have been synthesized by Pd-catalyzed Stille-coupling. Electronic energy levels of the polymers are estimated by cyclic voltammetry. The polymer films show a broad absorption band in the wavelength range from 300 to 750 nm. Among the polymers, the polymer that contains the 5,6-dinitrobenzothiadiazole unit, P3, possesses the smallest bandgap of 1.55 eV calculated from its absorption band-edge at ≈800 nm. With the increase of the electron-withdrawing ability of the substituents on the benzothiadiazole unit, the energy bandgap of the polymers decreased in the order P1 > P2 > P3. The results indicate that stronger electron-withdrawing substituents on the acceptor unit can effectively decrease the bandgap of the polymers.
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