Switchable Self-Assembly Of Aromatic Amphiphile For Accelerating Reaction And Helical Polymerization

Switchable supramolecular chemistry plays an important role in the enzyme catalysis of biological organisms in nature.In recent years,many switchable functional supramolecular materials have been explored to mimic chemical reaction and information transfer behavior in vivo.How to design reasonable amphiphilic molecular structure and functionalize the building block to construct responsive supramolecular assemblies have always been an important research direction in the emerging field of supramolecular chemistry.This thesis focuses on the assembly and recognition of the aromatic amphiphilic molecules to mimic the chemical reaction of the enzyme catalysis in vivo.Switchable supramolecular assemblies are also constructed through the addition of substrates or the stimulation of external environment,to achieve efficient catalysis for chemical reaction.1)The thermal responsive behavior of aromatic amphiphilic molecules is explored.2)The concept of substrate-directed transient selfassembly for accelerating a chemical reaction and spontaneous disassembly with releasing the products is carried out.3)the chiral cyclization of substrate is realized by the chiral recognition between the substrate and supramolecular nanocage formed by amphiphilic molecule.In the first part,in order to construct a transient nanoreactor for the substrate recognition,the U-shape aromatic amphiphile is functionalized by pyridine,to induce hydrogen bonding with substrate,and then construct a nanoreactor with confined space.TEM shows that amphiphilic molecules and hydrophobic thiol co-assemble to form vesicle structure based on the curvation of the bilayer structure.The reaction undergoes in the confined space formed by bilayer structure,which significantly increases the local concentration of the substrate and promotes the rate of substitution reaction.The chemical reaction triggers disassembly of the aggregation because of the protonation of the pyridine amphiphile with simultaneous release of the product that can be spontaneously separated out of the solution by precipitation.Neutralization of the amphiphilic molecule leads to a new cycle of self-assembly entrapping substrates and disassembly with releasing the product,which improves conversion times of the nanoreactor.In the second part,in order to construct the asymmetric single-molecular nanocage for chemical reaction,amphiphilic molecule is further modified to synthesis aromatic amphiphilic molecule with chiral oligo ether dendron,and achieve the asymmetric cyclization of the linear substrate.The formation of the nanocage by amphiphilic molecules produce the cavity with space confinement enforce the single-molecular cyclization by the linear hydrophobic substrate,as well as the free rotation of the linear chain to result the preferred conformation and finally achieve the Suzuki coupling reaction for the asymmetric planner chiral product.CD spectra shows the negative Cotton effect of the self-assembly,indicates the supramolecular nanocage induce the preferred asymmetric conformation of the linear substrate and catalyze the chemical reaction to form the planner chiral product,which provides a feasible way for the cyclic planner chiral drug synthesis.In the third part,in order to construct the supramolecular asymmetric nanoreactor,the thermal switchable behavior of the tubular chiral nanocarrier is further discussed.Based on the research of U-shaped aromatic amphiphilic molecule,both ends of the Ushaped aromatic block is connected by chiral ethylene glycol to result cyclic amphiphilie molecule.Because of the linkage of the aromatic segment,the degree of freedom in the aromatic segment is confined,which induce the assembly of the amphiphilic molecule to form toroid structure and finally stacking to the tubular structure.In room temperature,the hydrophilic segment of the aromatic amphiphilic molecule shows the high flexibility to prevent the ordered assembly of the aromatic segement in the tubular structure,which results the random packing of the amphiphilic molecule.But after heat treatment,the flexibility of the hydrophilic segment decreases a lot because of the dehydration of the oligo ether dendron,which induce the strong interaction between the aromatic segment,resulting highly ordered supramolecular helical polymer.Such a unique tubular wall will offer an opportunity to explore temperature-responsive nanoreactors for chemical transformations due to different spatial confinements.