荧光猝灭研究芳醚树枝形聚合物构象

Study on the Conformation of Poly(aryl ether)Dendrimers by Fluorescence Quenching

本工作分别合成了外围修饰一个芘基团和核心修饰一个芘基团两个系列的芳醚树枝形聚合物Py-Gn-OH和Gn-CH2-Py（n=1-4）。Py-Gn-OH和Gn-CH2-Py的发光随代数增加而增强,荧光寿命增加。荧光猝灭实验结果表明,树枝形聚合物Py-Gn-OH和Gn-CH2-Py的双分子猝灭速率常数均随代数增加而减小,表明树枝形聚合物发生了构象折叠,位于核心和外围的芘基团均被树枝形聚合物骨架包裹,随代数增加树枝形聚合物骨架增大,对芘基团包裹作用增强,导致猝灭剂接近芘基团的位阻增大。Gn-CH2-Py体系的双分子猝灭速率常数均比相应代数Py-Gn-OH体系略小,说明树枝形聚合物骨架对连接在核心的芘基团的包裹程度比对连接在外围的芘基团略强。本工作为新型功能芳醚树枝形聚合物设计和应用提供了参考。

Two series of poly （aryl ether） dendrimers with only one pyrene chromophore attached to the periphery （Py-Cm-OH） orto the focal point （Gn-CH2-Py）were synthesized. Fluorescence emission and fluorescence lifetime of Py-Gn-OH and Gn-CH2-Py increase with increasing the generation. Fluorescence quenching experiments demonstrate that the bimolecular quenching rate constant kq of Py-Gn-OH and Gn-CH2- Py decreases as the generation increases, indicating that the poly（aryl ether） dendrimers possess a folding back conformation. The pyrene chromophore located either at the periphery or at the core is encapsulated by the dendritic backbone. The extent of encapsulation increases with the generation, giving an increased shield effect from the encounter with solvent and quencher molecules. The kq value of Gn-CHz-Py is slightly smaller than those of the corresponding generation of Py-Gn-OH, indicating that the dendritic backbone exhibits a better extent of encapsulation for the chromophore at core than that at the periphery. This study provides a reference for designand application of novel functional dendrimers.