On the origin of green emission in polyfluorene polymers: The roles of thermal oxidation degradation and crosslinking

被引:151
作者
Zhao, W [1 ]
Cao, T
White, JM
机构
[1] Univ Texas, Dept Chem & Biochem, Austin, TX 78712 USA
[2] Univ Texas, Ctr Mat Chem, Austin, TX 78712 USA
关键词
D O I
10.1002/adfm.200305173
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
The green emission of poly(9,9"-dioctylfluorenyl-2,7"-diyl), end-capped by polyhedral oligomeric silsequioxanes, (PFOPOSS) has been investigated by photoluminescence (PL) and photoexcitation (PE), gel permeation chromatography (GPC), and transmission Fourier transform infrared (FTIR) spectroscopy. The green emission is closely correlated with thermal oxidation degradation and crosslinking of the polymer and is enhanced by annealing at elevated temperatures. The green-to-blue emission intensity ratio, used to assess the emission properties of thin (90 nm) films, was 3.70, 4.35, and 1.54 for an air-annealed film, its insoluble residue (crosslinked), and a film cast from its soluble portion, respectively. For thick (5-6 mum) film, the ratios are 13.33, 13.33, and 0.79, respectively. However, FTIR spectroscopy of thick films leads to the conclusion that the carbonyl-to-aromatic ring concentration ratio are 0.018, 0.015, and 0.032, respectively. Focusing on the recast films, the green emission is relatively low while the carbonyl concentration is relatively high. This suggests that the energy traps at crosslinked chains play an important role in green emission. It is likely that the crosslinking enhances the excitation energy migration and energy transfer to the defects by hindering chain segment twisting.
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页码:783 / 790
页数:8
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