Construction Of Switchable Supramolecular Architectures Based On Macrocyclic Amphiphiles

Construction of supramolecular architectures in nanoscale has been attracted many interests due to their novel features in the case of functional materials and biological functions.The self-assemblies of macrocyclic amphiphiles which consisting of the hydrophobic cyclic aromatic segments with specific molecular conformation and the hydrophilic flexible chains in aqueous solution provide the unique topic in this field.This thesis discuss the recent progress regarding the construction of switchable supramolecular architectures based on macrocyclic amphiphiles,which have stimuliresponsive behavior under thermodynamic or out-of-equilibrium control.The important factors affecting the self-assembly morphologies are discussed and summarized.In the second chapter,a switchable nanoribbon show zipping motion and spontaneous encapsulation in the presence of carbohydrate guests is discussed.We will focus on the swtichable morphology of the supramolecular ribbon under external stimuli via rearrangement of the intermolecular interactions.We designed and synthesized the more hydrophobic macrocyclic amphiphiles based on our previous experience which self-assembled into 2D flatten nano-ribbon in methanol solution.The width of ribbons is 28 nm with the thickness of 3.5 nm,which provided from morphology investigation of TEM and AFM experiments.The experiment results demonstrate that the ribbon consist of 8 laterally-associated elementary fibrils in which disc-shaped macrocyclic amphiphiles are stacked along their axis.Upon addition of fructose,these flat structures spontaneously fold into closed tubules,with an outer diameter of ~8 nm,through zipping of the two sides of the ribbons.Notably,the folding and then zipping of the flat ribbons is accompanied by spontaneous capture of the fructose molecules inside the tubular cavities.In the third chapter,we continuously extend the self-assembly architectures based on macrocyclic amphiphiles,which provide an autonomous helical propagation of active toroids with mechanical action.Self-assembly in nature is fundamentally dynamic,existing in out-of-equilibrium state in which the systems have the ability to autonomously respond to environmental changes.However,artificial systems exist in a global minimum state,which are incapable of conducting such complex functions.Here we report that input of thermal energy can trigger fixed artificial toroids to spontaneously nucleate helical growth.The helical polymerization undergoes reversible and repeatable cycles with subsequent energy input.The excellent match between experimental results and theoretical simulations provide the insight to understand the mechanism of polymerization,and the mathematic approach through Dynamic Monte-Carlo simulation gives modeling study of the polymerizationdepolymerization cycles.When the toroids are located inside of lipid vesicles,the polymerization-depolymerization cycle is accompanied by reversible elongation of spherical vesicles.Such liberation from a global minimum state will pave the way to create emergent structures with functions as complex as those of living systems.In the fourth chapter,we will introduce the supramolecular helical polymerization with rapid response rate through optimizing the molecular conformation,and the helicity of supramolecular polymer chains can be tuned by addition of chiral regulators.In chapter 3 we summarized helical polymerization under out-of-equilibrium control,however,the process of cycle with long hysteresis effect have clear limitation for the practical applications.We speed up the rate of polymerization-depolymerization cycle via modification of the conformation of oligoether chains which decreasing the steric effect in folded molecular conformation.The rapid hierarchical polymerization mimic the propagation of TMV protein in the presence of RNA.Notably,the helicity of the polymer can be tuned when addition of chiral regulator,such as 2-butanol.The chiral induction mechanism is explained by NMR experiments.The results may give a good example to design helical supramolecular polymers and an opportunity to explain the symmetry breaking of racemic mixture.