Substituent Effect on the Optoelectronic Properties of Alternating Fluorene-Cyclopentadithiophene Copolymers
Resource
Macromolecules 41: 6664-6671
Journal
Macromolecules
Pages
6664-6671
Date Issued
2008
Date
2008
Author(s)
Pal, Bikash
Yen, Wei-Che
Hung, Ying-Chieh
Chuang, Chia-Hao
Abstract
A novel series of soluble alternating conjugated copolymers, comprised of 9,9-dihexylfluorene and cyclopentadithiophenes (P1−P5), were synthesized via Pd-catalyzed Suzuki coupling reaction in good yields. The UV−vis absorption spectra, fluorescence spectra, fluorescence quantum yields, and cyclic voltammograms of P1−P5 are also reported. The P2 and P3 with electron-donating non-π-substituents (ethylenedioxy and propylenedioxy bridges the 3,3-positions of the thiophene groups) display high fluorescence quantum yields and red-shifted absorption as compared with nonsubstituted P1. However, the P4 and P5 are weakly fluorescent and exhibit blue-shifted absorption which are due to the presence of electron-withdrawing π-substituents (carbonyl and dicyanoethenyl). The behavior of P4 and P5 can be attributed to the significant electronic coupling between the π-substituents and the conjugated polymer backbone that leads to a less allowed optical transition between the ground and the lowest excited state, resembling the meta conjugation effect in phenylene-derived conjugated π-systems. This argument is supported by molecular orbital distribution calculations.
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Type
journal article
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