Department of Chemistry Education, Kongju National University, Gongju-si 32588, Korea.
Department of Chemistry and Biotechnology, Graduate School of Engineering, Tottori University, Tottori 680-8552, Japan.
Molecules. 2021 Jul 15;26(14):4294. doi: 10.3390/molecules26144294.
The creation of fluorescent micro- and macrostructures with the desired morphologies and sizes is of considerable importance due to their intrinsic functions and performance. However, it is still challenging to modulate the morphology of fluorescent organic materials and to obtain insight into the factors governing the morphological evolution. We present a facile bottom-up approach to constructing diverse micro- and macrostructures by connecting fluorescent spherical particles (SPs), which are generated via the spherical assembly of photoisomerizable azobenzene-based propeller-shaped chromophores, only with the help of commercially available polyethylene glycol (PEG) derivatives. Without any extra additives, solvent evaporation created a slow morphological evolution of the SPs from short linear chains (with a length of a few micrometers) to larger, interconnected networks and sheet structures (ranging from tens to >100 µm) at the air-liquid interface. Their morphologies and sizes were significantly dependent on the fraction and length of the PEG. Our experimental results suggest that noncovalent interactions (such as hydrophobic forces and hydrogen bonding) between the amphiphilic PEG chains and the relatively hydrophobic SPs were weak in aqueous solutions, but play a crucial role in creating the morphologically diverse micro- and macrostructures. Moreover, short-term irradiation with visible light caused fast morphological crumpling and fluorescence switching of the obtained structures.
由于荧光微结构和宏观结构具有内在的功能和性能，因此它们的形态和尺寸的理想设计具有重要意义。然而，调节荧光有机材料的形态仍然具有挑战性，并且难以深入了解控制形态演变的因素。我们提出了一种简便的自下而上的方法，通过连接荧光球形颗粒（SPs）来构建各种微观和宏观结构，这些 SPs 是通过光致异构化的偶氮苯基螺旋状生色团的球形组装仅在商业上可获得的聚乙二醇（PEG）衍生物的帮助下产生的。在没有任何额外添加剂的情况下，溶剂蒸发会导致 SPs 从短线性链（长度为数微米）缓慢地演变为更大的互连网络和片状结构（从数十到> 100μm），在气液界面处形成。它们的形态和尺寸与 PEG 的分数和长度密切相关。我们的实验结果表明，在水溶液中，两亲性 PEG 链与相对疏水性 SPs 之间的非共价相互作用（例如疏水作用力和氢键）较弱，但在创建形态多样的微观和宏观结构中起着关键作用。此外，用可见光进行短期照射会导致所获得结构的快速形态褶皱和荧光转换。
