物理学报2017，Vol.66Issue(24)：266-275,10.DOI:10.7498/aps.66.248201
共轭聚合物单分子构象和能量转移特性研究
The role of chain conformation in energy transfer prop erties of single conjugated p olymer molecule
摘要
Abstract
Study of the relationship between conformation and photophysics of individual π-conjugated polymer chain is one of the most important problems in polymer nanoscience and nanotechnology, which will facilitate the application of conjugated polymer in a range of electronic devices such as organic field-effect transistors, light-emitting diodes, and solar cells. Single-molecule spectroscopy has emerged as a powerful tool to unravel structure and dynamic heterogeneities that are hidden in ensemble average. Identification of the emitting segments through fluorescence of single conjugated polymer molecules and their dependence on the conformation can help reveal the mechanism and the extent of energy transfer process in a single polymer chain. In this paper, the photophysical properties of individual poly[2, 7-(9, 9-dioctylfluorene)-alt-4, 7-bis(thiophen-2-yl) benzo-2, 1, 3-thiadiazole] (PFO-DBT) conjugated polymer molecules are measured based on the defocused wide-field microscopy of single molecules. The single PFO-DBT molecules are prepared on cleaned glass coverslips by spin-coating solution of poly[methyl methacrylate] (PMMA) containing 1×10-9 mol/L PFO-DBT molecules in chloroform and toluene, respectively. Defocused imaging of single conjugated polymer molecule is performed based on a wide-field fluorescence microscope system. The change of defocused patterns of individual polymer chain maps the angular distribution of emitted chromophore and thus the emitting dipole orientation. Fluorescence trajectory and corresponding emission dipole moments of single conjugated polymer molecules are analyzed to identify the emitting conjugated segments. It is found that single PFO-DBT conjugated polymer molecules prepared by chloroform solvent show extended conformation. The intrachain energy transfer is dominant in the single conjugated polymer molecules that take extended conformation, which leads to photophysical properties of multiple chromophores. In contrast, singlePFO-DBT conjugated polymer molecules prepared by toluene solvent hold folded conformation, which exhibit emission from single chromophore due to efficient interchain energy transfer. The emitting chromophore is not constant in a single PFO-DBT conjugated polymer molecule with folded conformation. About 35％of the single conjugated molecules prepared with toluene show only one constant emitting chromophore before photobleaching. However, about 65％ of single conjugated polymer molecules prepared with toluene show two or more sequencely emitting chromophores. It can be concluded that the energy transfer properties of single PFO-DBT conjugated polymer molecule is greatly dependent on the conformation, which can be reflected in its photophysical properties. The study on the influence of single conjugated polymer conformation on energy transfer efficiency can provide the reference for the preparation and performance of optoelectronic devices and molecular devices based on conjugated polymer.关键词
共轭聚合物/能量转移/构象/散焦成像Key words
conjugated polymer/energy transfer/conformation/defocused imaging引用本文复制引用
秦亚强,陈瑞云,石莹,周海涛,张国峰,秦成兵,高岩,肖连团,贾锁堂..共轭聚合物单分子构象和能量转移特性研究[J].物理学报,2017,66(24):266-275,10.基金项目
国家重点研发计划(批准号:2017YFA0304203)、国家自然科学基金(批准号:61527824,11504216,11374196,61675119,11404200,61605104,U1510133)、长江学者和创新团队发展计划(批准号:IRT13076)和山西省应用基础研究计划(批准号:201601D021016)资助的课题.Project supported by the National Key Research and Development Program of China (Grant No.2017YFA0304203),the National Natural Science Foundation of China (Grant Nos.61527824,11504216,11374196,61675119,11404200,61605104,U1510133),the Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China (Grant No.IRT13076),and the Applied Basic Research Program of Shanxi Province,China (Grant No.201601D021016). （批准号:2017YFA0304203）
