Construction And Properties Of Supramolecular Liquid-crystalline Metal-organic Cages

Coordination-driven self-assembly is an efficient strategy for the construction of discrete supramolecular assemblies of well-defined size and shape.Through the rational design and selection of building blocks,the numbers,locations and relative orientations of functional groups in the assemblies could be precisely controlled,laying a solid foundation for the bottom-up construction of functional supramolecular assemblies and materials.With their tunable three-dimensional structure,unique domain-limited cavities and easily to be modified,metal-organic cages have a wide range of applications in separation,catalysis,sensing and so on.In the meanwhile,metal-organic cages could be further used as modular “building blocks” for constructing higher-order supramolecular assemblies.Liquid crystals,as classical supramolecular self-assembled materials,have been widely used in daily life.While liquid crystal systems based on metal-organic cages are still rarely reported and their functional applications need to be further developed.On account of this,this thesis will focus on the construction of liquid crystal functionalized metal-organic cages through coordination-driven self-assembly strategy,and further explore their functional applications.This thesis is divided into the following parts:Chapter one.The design and construction strategies of metal-organic cages,the functions and applications of metal-organic cages and the research progress of liquid crystal functionalized metal-organic cages were reviewed.On account of this,the topic was proposed.Chapter two.Liquid crystal functionalized metal-organic cages were efficiently constructed by coordination-driven self-assembly and their application in holographic imaging was successfully realized.Two types of liquid-crystalline metal-organic cages with different three-dimensional structures were constructed by different aniline ligands,mental ions and novel pyridine-formaldehyde ligands containing coumarin moieties modified by alkyl chains with different chain lengths via coordination-driven selfassembly.Furthermore,the effects of the length of the side chains and the threedimensional skeleton on the liquid crystal properties of the metal-organic cages were investigated.Due to the liquid crystal properties of the constructed metal-organic cages and their good compatibility with holographic polymer dispersion liquid crystal systems,holographic gratings were successfully prepared using specific metal-organic cages,and holographic image storage and multiple encryption of information based on the metal-organic cages were achieved.Chapter three.Stimuli-responsive liquid-crystalline metal-organic cage was successfully constructed via coordination-driven self-assembly and their photostimulated phase transition properties and applications in the preparation of deformation composite film materials were further explored.Stimuli-responsive pyridine-formaldehyde ligand containing azobenzene moieties was designed and synthesized,and stimuli-responsive liquid-crystalline metal-organic cage was further constructed through coordination-driven self-assembly strategy.Furthermore,the stimuli-responsive properties of the metal-organic cage were investigated in the solution,liquid crystal phase,and the isothermal phase transition from liquid crystal phase to liquid phase under ultraviolet light irradiation was achieved based on the good photoresponsiveness of the metal-organic cage.In addition,composite film materials containing metal-organic cage was prepared by doping with polymers to achieve macroscopic deformation in response to ultraviolet light stimulation.