판상형 단량체의 공유 자기조립으로 형성된 고분자 구조체의 합성과 그 응용

Abstract

This thesis describes the construction of hollow toroidal polymer microrings by irreversible covalent self-assembly, and the synthesis of iron oxide nanoparticle decorated polymer nanocapsules and their potential applications as a theranostic contrast agent.Irreversible covalent self-assembly is equivalent to performing a one-pot reaction that results in complex structures, which provides an easy method for constructing robust frameworks while avoiding unnecessary multistep procedures. However, there are only a few examples of polymeric architectures using this covalent self-assembly

even so, some additives including template and pre-organized structure are necessary to limit polymerization in a certain direction and to construct polymeric materials with desirable structure.Recently, the synthesis of nanometer–sized polymer hollow spheres involving shape–directed covalent self–assembly or self–organization without using a template or preorganized structure has been achieved in our laboratory. In this work, highly symmetric flat and rigid–core tectons with multiple functional groups isotropically predisposed in all lateral directions were cross–linked with linear linkers. This new strategy can be extended to the synthesis of a wide variety of polymer nanocapsules that may be useful in many nanotechnological applications such as targeted drug/gene delivery, encapsulation, catalysis, and imaging. Such self-assembly is driven by intrinsic factors presented in the molecular tecton such as size, shape and directionality of bond formation as well as external factors such as the polarity of the reaction medium. Thus careful control of self-assembly conditions and design of organic molecules with specific size, shape and directionality can be used to produce interesting polymeric architectures. This thesis describes the construction of hollow ring architectures by adjusting the intrinsic factor, directionality of bond formation in covalent self-assembly. Also, the synthesis of iron oxide nanoparticle decorated polymer nanocapsules and their potential application as a theranostic contrast agent is presented.Chapter 2 describes a facile synthesis of the polymer microrings with a hollow nanotubular wall. It was achieved with ready control over size in mesoscale through a bottom-up self-organization approach. The synthesis of the hollow toroidal polymer microrings relies on rectangular, flat and rigid core monomers with anisotropically predisposed alkene groups, dithiol linkers and thiol–ene photopolymerization. The microrings are thoroughly characterized by spectroscopic and microscopic techniques in solution and surface. The resulting superstructures are shape–persistent and mechanically robust in solution. In addition, their size can be tuned by controlling the initial monomer concentrations, an observation which is supported by a theoretical analysis. The hollow microrings can encapsulate guest molecules in the intratoroidal nanospace, as shown with C60 inclusion. Also, the microrings can act as templates for circular arrays of metal nanoparticles on their peripheries. Chapter 3 presents that the hollow polymer nanocapsules can be used as a scaffold to display multiple nanoparticles for magnetic resonance imaging. The complexation of the polymer nanocapsules and iron oxide nanoparticles was achieved by host-guest chemistry between cucurbit[6]urils on the shell of the polymer nanocapsules, and amine-functionalized iron oxide nanoparticles. Increasing the number of nanoparticles (~ 12) delivered by each targeting molecule would lead to higher signal-to-noise ratios and would improve image contrast. After incorporation of targeting molecules on the surface of these magnetic nanocomposites and encapsulation of dye molecules inside of the polymer nanocapsules, their receptor-mediated endocytosis into human oral cancer KB cells was monitored by fluorescence and confocal microscopy. These results demonstrated the potential applications of magnetic nanocomposites as a theranostic smart contrast agent.