Self-assembly Of Rod-coil Molecular Aggregates Through Dynamic Covalent Bonds

Stimuli-responsive shape transformation plays an important role in organisms at various scales from molecular,cellular to macroscopic ranges,and during the process biological entities maintain normal functions or respond to stress.In recent years,stimuli-triggered self-assembly has been developed to provide elaborate control over structural transformation in supramolecular entities.Various kinds of stimuli-responsiveness have been achieved by incorporating stimuli-sensitive groups into the building blocks in the supramolecular systems,such as pH,light,temperature,redox and CO2 responsiveness.Therein,the facilely available and tractable pH,light,CO2 and enzyme triggers have attracted increasing attention.They usually cause changes in chemical structures of the corresponding responsive groups in the selfassembly building block molecules,leading to large and robust alternations in hydrophobicity/hydrophilicity,polarity and charge.Therefore,the morphology and property transformations of self-assembled nanostructures can be modulated effectively and efficiently.The stimuli-triggered morphology transformation of supramolecular assemblies provides a powerful approach to prepare functional organic nanomaterials with well-defined structures in water.Through this method,nanomaterials with complex and unique morphologies(e.g.,micro-/nanostructures and hierarchical sac structure)can be obtained,which are inaccessible via conventional self-assembly processes.The dynamic nature of these in situ supramolecular transformations enables applications of the strategy in photo-electrical devices,sensing,hierarchical cargo release,and construction of metastable materials,etc.Avoidance of using organic solvents,simplified in situ fabrication process as well as in combination with relatively“green”triggers-pH,light,CO2 and enzyme promises it an environmentally friendly and economic strategy for the development of "green materials".Intelligent or stimuli-responsive materials have been persisted over many decades,and a great deal of work has been dedicated to developing sensitive self-assembled systems that can be crafted into novel smart materials.Dynamic covalent bonds are protruding for its advantages and gain much attention in the field of supramolecular science,as they are similar to noncovalent interactions due to the dynamic nature.Stimuli-responsive self-assemblies exhibit diverse controllable aggregates with different morphologies such as vesicles,micelles,fibers.The morphological modulation and evolution could be realized facilely through dynamic covalent bond chemistry.The control over morphology is important in the design of intelligent materials due to the relationship between the assembled nanostructures and molecular chemical structure.In this paper,a propeller-type molecule was designed and synthesized,and their self-assembly behavior of target molecules in aqueous solution was investigated by UV-Vis spectroscopy,fluorescence spectroscopy,circular dichroism(CD),atomic force microscopy(AFM),transmission electron microscopy(TEM).