Synthesis of Functional Nanostructured Materials by Covalent Self-assembly and Their Applications

Abstract

This thesis describes advances in the field of nanostructured materials synthesis by covalent self-assembly. In a set of chapters, studies on development of novel technique to introduce metal nanoparticles on the surface of polymer nanocapsules made of cucurbit[6]uril, catalytic applications of the metal nanoparticle-decorated polymer nanocapsules in aqueous media, and the construction of helical tubular structures by flow-induced covalent self-assembly are described. Chapter 1 is a brief summary of the recent developments in construction of nanostructured materials by covalent self-assembly. Recently, we have achieved novel synthetic methods for constructing robust nanospheres, 2D polymers, and microrings from carefully designed flat and rigid-core building blocks and linkers through covalent bond formations and demonstrated some of their applications including drug delivery, diagnosis, and imaging. This chapter describes the introductory aspects of covalent self-assembly and their applications. Chapter 2 describes a facile method to prepare highly stable, water-dispersible metal-nanoparticle-decorated polymer nanocapsules (M@CB-PNs: M = Pd, Au, and Pt) with a narrow size distribution of NPs. The hollow polymer nanocapsule made of CB[6] provides unique properties as a versatile platform to introduce various NPs on the surface, prevent self-aggregation, and provide high stability and dispersibility in water. The M@CB-PNs are potentially useful for catalysis, imaging, and nanomedicine. Chapter 3 demonstrates the application of palladium nanoparticle-decorated polymer nanocapsule (Pd@CB-PN) in heterogeneous catalysis for carbon−carbon and carbon−nitrogen bond-forming reactions in aqueous media. Pd@CB-PN shows outstanding properties as green and sustainable heterogeneous catalyst with excellent recycling and reusability. With such exciting properties, this material may bring new possibilities to the field of the green and sustainable chemistry. Chapter 4 presents a new and facile method to construct helical tubular structures by flow-induced covalent self-assembly. In our experimental set up, we observed the emergence of one-handed helical tubular structures from allyloxyCB[6], a highly symmetric flat and rigid core building block with multiple polymerizable groups isotropically predisposed in all direction. The key to success of this approach is the presence of vorticity with only one-handedness in micro-flow system. We envisage that the diversity of superstructures by covalent self-assembly could be further extended by choosing a building block having different shapes and solubility properties and controlling dynamic flow condition during self-assembly process.