Synthesis and characterization of monodisperse oligo(fluorene-co-bithiophene)s

被引:41
作者
Zhang, Xiaojie
Qu, Yao
Bu, Laju
Tian, Hongkun
Zhang, Jingping
Wang, Lixiang
Geng, Yanhou
Wang, Fosong
机构
[1] Chinese Acad Sci, Grad Sch, Changchun Inst Appl Chem, State Key Lab Polymer Phys & Chem, Changchun 130022, Peoples R China
[2] NE Normal Univ, Fac Chem, Changchun 130024, Peoples R China
关键词
conjugation; cross-coupling; liquid crystals; oligomers;
D O I
10.1002/chem.200700007
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
A series of monodisperse oligo(9,9-di-n-octylfluorene-co-bithiophene)s (OFbTs) with molecular lengths of up to 19.5 nm and molecular weights up to 7025 g mol(-1) has been synthesized by a divergent/convergent approach involving Stille coupling reactions. Stille coupling is quite efficient in preparing this class of oligomers, and even the molecule with nine fluorene units and eight bithiophene units (F9Th16) can be synthesized in a yield as high as 70%. Because of easy functionalization of the thiophene ring at its alpha position, no additional protecting group allowing activation for further reaction is necessary. However, the synthetic routes must be optimized to eliminate contamination of the targeting compounds with the homocoupling product of the organotin reagents. Synthesis of the longest oligomer F13Th24 in a relative large quantity is limited by its low yield due to the pronounced ligand-exchange side reactions of the starting materials and reaction intermediates. All oligomers longer than F4Th6 are nematic mesomorphs and exhibit enhanced glass transition temperature and clearing point with increasing molecular length, as revealed by differential scanning calorimetry and polarizing optical microscopy. Absorption and photoluminescence (PL) measurements reveal that OFbTs are well-conjugated systems with an effective conjugation length longer than the length of F13Th24.
引用
收藏
页码:6238 / 6248
页数:11
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