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Low Bandgap Polymers by Copolymerization of Thiophene with Benzothiadiazole
Author(s) -
He Youjun,
Wang Xiang,
Zhang Jing,
Li Yongfang
Publication year - 2009
Publication title -
macromolecular rapid communications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.348
H-Index - 154
eISSN - 1521-3927
pISSN - 1022-1336
DOI - 10.1002/marc.200800507
Subject(s) - band gap , thiophene , materials science , polymer , stille reaction , copolymer , polymer chemistry , photochemistry , electron acceptor , optoelectronics , chemistry , organic chemistry , composite material
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.