The Self-assembly Of Amphiphilic Calixarene And The Application Of Their Nanohybrids

Research in this thesis is based on the previous work from our laboratory. The group initiated a"block-copolymer free" self-assembly strategy, i.e. constructing of "Non-covalently connected micelles (NCCM)"by hydrogen bonds and other specific interactions. In recent years, host-guest interactions of cyclodextrins (CD) have been firstly introduced to this strategy by us too, resulting in new self-assembly routes and functional materials driven by host-guest interactions. However, we noticed that in supramolecular chemistry, research on the third generation host molecule calixarene mainly focused on design and synthesis of structures, as well as related metal complexation abilities. Report on its self-assembly behavior is limited. In this thesis, we focus on the self-assembly behavior of amphiphilic calixarene in the mixture of water and ethanol, as well as related preparation of functional hybrid materials made of silica and gold nanoparticles. The content of this thesis is as follows:(1) Impact of structural factors of amphiphilic calix [6] bis crowns on their self-assembly behaviorsIn our previous study, we found that amphiphilic calix[6]biscrowns can undergo micelle-to-vesicle transition when the polarity of the solvent increases. In this chapter, we studied the relationship between the morphology transitions of the self-assembled structures and chemical structures of the building blocks. Thus five different calix[6]biscrowns have been synthesized, followed by their self-assembly behaviors in the mixture of water and ethanol.It was found that the crown ether chain could restrain conformation exchange of the calixarene, resulting regular self-assembled structures. And the amide bond promoted the inter-molecular hydrogen bonds, resulting1D nanotube structure in medium with high polarity. Packing mode from X-ray crystallography exhibited "shoulder-to-shoulder" molecular pattern. Besides, Langmuir-Blodgett film experiment indicated that the calixarene with amide linkage has different self-assembly behavior compared to its derivatives. Meanwhile, increase of alkyl chains and hydrophilicity can effectively increase the molecular curvature of calixarenes, resulting in self-assembled structures with smaller diamters.(2) A one-pot approach to coaxial hybrid nanotubes of calixarene/silica with applications of ion exchangeThe1D nanotube obtained by self-assembly of calix[6]biscrowns is covered by amine groups, resulting in a high pH value of the tube surface. Thus we utilized the ID nanotube as template to prepare silica by hydrolysis of TEOS. In this one-pot approach, amphiphilic terminal amino calix[6]-biscrowns (TAC) self-assembled quickly into nanotubes, on the surface of which, tetraethoxysilane (TEOS) was absorbed and hydrolyzed under the catalysis by the amino groups of TAC leading to the formation of the outer layer of silica. The thickness of silica coating layer in the resultant coaxial nanotubes is controlled by changing either the reaction time or the dosage of TEOS. The hybrid nanotubes exhibit a capability of selective complexation with metal ions as evidenced by the substitution of K+by Cs+. In addition, more functionalities could be introduced on the nanotube surface with potential applications in biological research.(3) Study of hybrid structure of calix[6]biscrown and gold nanoparticles and its catalytic properties in hydrogenation reactionsRecently, metal nanoparticles with small diamters attract great interest because of their outstanding properties in catalysis. In this chapter, UV irradiation was adopted to prepare hybrid nanoparticles, in which gold nanoparticles (AuNPs) with a diameter of2nm were incorporated and dispersed well in self-assembled organic spheres of calix[6]b is crowns with a diameter around60nm (denoted as NPAs). We further applied these hybrid nanoparticles as catalysts in the hydrogenation reaction of crotonaldehyde. Merits of this method include:1) Self-assembly of the organic component (calix[6]biscrownTAC) into spheres and the reduction of chloroauric acid (HAuCL) take place simultaneously.2) Combining UV irradiation and formaldehyde addition reduces the size and homogenizes the distribution of the resultant AuNPs within the TAC spheres.3) Obtained material NPA gives attractive catalytic property to hydrogenation reaction of crotonaldehyde.4) This method could be also extended to other noble metals leading to the hybrid nanoparticles with a fine structure, such as Ag and Pt.(4) Preliminary Study of construction of supramolecular polymer using calixarene and poly ethylene glycol (PEG) through dynamic covalent bondsOur goal in this chapter is to construct supramolecular polymer using TAC and PEG driven by dynamic covalent bonds. For this purpose, amino-terminal calixarene and aldehyde-terminal PEG were selected, which may form linear supramolecular polymer in acid condition at room temperature. Since this imine bond is sensitive to pH variations, the resultant polymer could be pH-sensitive too. In our research, we choose two different building blocks with different molecular weights to form supramolecular polymers with TAC. The completed work included synthesis and modification of related building blocks (TAC, triethylene glycol, PEG114), preliminary study of condensation polymerization conditions and characterization of obtained product. This part of work is in progress.