树枝化对聚芴类分子发光行为的影响

Effect of Dendronization on the Luminescence Behavior of Fluorene-based Polymers

运用稳态吸收、稳态荧光光谱及皮秒时间分辨荧光光谱等手段,研究了树枝化对聚芴分子的光谱动力学行为的影响.在1×10-5mol/L四氢呋喃溶液中,非树枝化聚芴和不同代数的树枝化聚芴的稳态吸收和稳态荧光光谱基本一致,表明树枝化不影响聚芴基团的本征电子性质;在薄膜状态下,紧密排列的聚芴分子表现出明显的链间聚集行为.不同代数树枝化聚芴的时间分辨荧光动力学研究结果表明,溶液状态下的发光为单指数衰减行为,而薄膜状态下的发光为多指数衰减行为,且其发光寿命随树枝化代数增加而增长,表明树枝化基团抑制了邻近的聚芴分子之间能量传递所致的激发态能量耗散.

Steady-state absorption and fluorescence together with picosecond time-resolved photoluminescence （PL） spectroscopies were used to investigate the effect of dendronization on the luminescence character of fluorene-based polymers. For dilute tetrahydrofuran solution at 1 × 10^-5 tool/L, non-dendronized 9,9-dioctyl- polyfluorene（ PF）, the first-generation dendronized PF（ PFgl ）, the second-generation dendronized PF（PFg2） and third-generation dendronized PF（PFg3） show identical spectra in their steady-sate absorption and fluorescence measurement, indicating that the conjugated core is not affected by dendronization. However, highlypacking PF chains appear to form aggregate in film form. Further picosecond PL studies on dendronized PFs show that the fluorene-based emission in dilute solution follows a single exponential decay, whereas those in thin film decayed in a muhi-phase manner and the lifetime prolongs with the generation of dendronization. These observations are discussed in terms of dispersive transport happening between adjacent chains in film. The dispersive relaxation can be controlled by site isolation of bulky dendrons. Our results prove that dendronization is highly effective in controlling the inter-chain interactions of fluorene-based polymers.