Pillararene-Based Responsive Supramolecular Self-Assembly

Molecular self-assembly refers to the process by which molecules spontaneously self-assembled to a stable state with special structures driven by weak forces such as hydrogen bondings,electrostatic interactions,hydrophobic effects,van der Waals forces,etc.In chemical science,supramolecular chemistry provides novel ideas and approaches to the design and preparation of self-assembly building blocks and to explore unique molecular self-assembly means,so that molecules with specific structures and groups could spontaneously assembled into the supramolecular materials with desired properties in a certain way.Host-guest interaction is a very important driving force for constructing supramolecular self-assembly systems because of its inherent reversibility and adaptability and the particularity of the macrocycilc hosts themselves.Macrocyclic host-based supramolecular self-assembly is a hot spot in recent years and various macrocyclic host-based supramolecular self-assembly systems have been widely studied,such as supramolecular amphiphiles,supramolecular polymer,supramolecular organic and inorganic hybrid materials,and further applied in different areas,such as biomedicine,materials science,analytical chemistry.In this thesis,we mainly focuse on the construction of a variety of functional self-assembly systems based on an emerging macrocyclic host-pillararene.The paper mainly includes these following five parts:In the first part,we prepared a novel linear supramolecular polymer and a supramolecular network based on the pillar[5]arene/secondary ammonium salt molecular recognition motif in CDCI3/CH3CN.The presence of an azobenzene moity acting as a molecular bridge and the pH-controlled reversible host-guest complexation played essential roles for the supramolecular polymer to show UV and pH-responsiveness,making it possible to achieve reversible polymer-oligomer and polymer-monomer transitions,respectively.More interestingly,the crosslinked supramolecular network exhibited liquid crystal property,and could be easily controlled by photo irradiation,bringing about lots of potential photonics applications.In the second part,we have developed an effective strategy to fabricate a linear supramolecular pseudopolyrotaxane with control and studied the mechanism behind the supramolecular polymerization,which can enrich the general self-sorting methodology to realize controllable supramolecular polymerization.This process prefers to accomplish selective recognition with larger numerical differences in the binding affinities among each interaction.We can foresee that our method has a tremendous potential in fabricating supramolecular polymers by different interactions with a variety of possible topologies.In the third part,we reported the first synthesis of water-soluble pillar[10]arene and the host-guest chemistry was fully investigated by kinds of methods.Furthermore,supramolecular amphiphiles based on these new host-guest systems were constructed,and their pH-responsive self-assembly in water were studied.These novel recognition motifs based on the water soluble pillar[10]arene in aqueous media will be helpful for the fabrication of functional architectures and definitely bring about many promising applications,such as supramolecular polymers,nanoelestronics,drug-delivery and controlled release.In the fourth part,we have successfully constructed a UV-responsive supra-amphiphile based on the host-guest complexation of a water-soluble pillar[6]arene.In contrast to the nanosheets formed by the amphiphilic guest itself,the supra-amphiphile self-assembled into nanorods.Upon irradiation with UV light,the transformation from nanorods to nanosheets was obtained.Furthermore,we applied this supramolecualr system in the photo-responsive dispersion of MWNTs into water.This new kind of supramolecular organic/inorganic hybrid material has numerous potential applications in many fields,including nanoelectronics,sensors and organic-inorganic hybrid materials.In the last part,a gas and photo dual-responsive host-guest recognition motif was established based on a water-soluble pillar[6]arene and an azobenzene derivative in an aqueous medium.This smart inclusion complex was further applied in the construction of a supra-amphiphile that could reversibly self-assemble into vesicles as a smart carrier for stimuli-responsive controlled release upon UV/vis irradiation or bubbling with N2/CO2.It is anticipated that utilizing green stimuli methods to realize unique self-assembly behavior in aqueous solution may offer new possibilities in "on demand" release or absorption of chemicals such as drugs.As both CO2 and light are crucial for living organisms,the system also provides inspiration for biomimicry by using synthetic supramolecular systems.