聚集诱导发光分子聚集态结构的精确调控及其发光特性

The core of aggregation-induced emission (AIE) is that aggregation of AIE luminogens activates their emission decay process. It is apparent that tuning aggregation of AIE molecules is the only way to optimize their emission and to understand mechanism of AIE. Unfortunately, it is difficult to regulate efficiently the aggregation of luminogens by employing traditional chemistry approaches. To address this issue, this project aims to develop new strategies to tune the aggregation structure of AIE luminogens by utilizing crystallization of polymers. This project will begin with controlled synthesis of a series of crystalline polymers modified with AIE luminogens. These fluorescent crystallizable polymers will be allowed to crystallize under optimized conditions to form regular lamellae. AIE molecules are excluded out of polymer lamellae during crystallization of polymers, consequently "grafting" onto polymer lamellae due to being covalently attached to polymers. The grafting density of AIE luminogens on polymer lamellae surface will be optimized via varying the fractions of AIE luminogens in polymers. Contrasting to the traditional chemistry method, this approach possesses overwhelming advantages: (1) Tuning aggregation of AIE luminogens is achieved through a physical approach, avoiding the effects of chemical structure factor on emission. Consequently, effect of aggregation structure on emission can be identified in a definite way. More importantly, this approach is applicable to tune aggregation structure of amorphous AIE molecules, which is impossible for traditional chemistry methods; (2) The distance between adjacent AIE molecules and thickness of AIE layer are able to be tuned in a continuous manner, allowing precisely regulating aggregation structure of AIE luminogens; (3) AIE luminogens are exposed on the surface of polymer lamellae, which is helpful for the achievement of explosive sensors with high sensitivity. In summary, carrying out this project is helpful for deeply understanding mechanism of AIE, and for the fabrication of fluorescent materials with high performance.

为克服传统化学方法难以有效调控聚集诱导发光分子聚集态结构的缺陷，本项目设计了一种优化发光分子聚集态结构的新途径，即利用聚合物的结晶来调控发光分子的聚集。首先合成发光分子改性的结晶性聚合物，诱导聚合物主链结晶形成片晶，发光分子在聚合物结晶过程中被排除出片晶，由于通过共价键和聚合物链连接，发光分子在聚合物结晶过程中被规整地"接枝"在片晶表面，改变聚合物中发光分子含量调控其在聚合物片晶表面的接枝密度。所设计方法具有如下优点：①通过物理方法实现了发光分子聚集态结构的调控，可确定聚集态结构对发光特性的影响规律；此外，该方法也适用于无定形发光分子，这是传统化学方法无法比拟的；②可连续调控发光分子间距和发光分子层厚度，实现发光分子聚集态结构的精确调控；③发光分子被暴露在聚合物片晶表面，这为制备高灵敏易爆物检测器提供了良好平台。本项目有助于深入理解聚集诱导发光机理，有利于实现有机发光材料的高性能化。

荧光材料的性能在很大程度上取决于荧光基团在材料中的空间分布，然而在纳米尺度上调控功能基团的分布仍面临诸多挑战。我们开发了一种结晶辅助制备结构可控的聚合物纳米材料的新方法，首先采用开环聚合和后功能化方法合成了四苯乙烯（TPE）改性的结晶性聚合物，诱导聚合物结晶，在聚合物结晶过程中，TPE荧光分子被排除出聚合物片晶，由于和聚合物链通过共价键相连，TPE分子被排列在聚合物片晶表面。由于TPE分子暴露在表面，纳米材料对易爆物和水污染物表现出灵敏的响应特性，检出限远低于文献报道的同类材料。此外，此类结晶性荧光聚合物的荧光强度表现出显著的温度依赖性。有趣的是，荧光强度在升温和降温扫描过程中出现了明显的滞后效应，这赋予聚合物材料热刺激记录功能，可实现off-on 和on-off双向记录功能，聚合物薄膜上记录的文字可重复擦写。此外，可通过检测荧光强度跟踪聚合物的热历史。此类聚合物材料具有合成简便、高的响应灵敏度、显著的温敏响应特性、优异的柔性和生物兼容性，有望应用于生物探针、记忆材料及智能器件等领域，研究成果在ACS Macro Lett., Macromolecules, ACS Sensors, J. Mater. Chem. A, Carbon, Chem. Comm., Polym. Chem., Langmuir, J. Phys. Chem. B等期刊发表SCI论文15篇，中国发明专利授权2项，撰写英文专著章节1部。