Exploiting polymer single crystals to assemble and functionalize nanomaterials

Abstract

Nanomaterials are fundamental building blocks for nanoscience and nanotechnology. They can generally be categorized into three classes: zero-dimensional (0D) (e.g. nanoparticles), onedimensional (1D) (e.g. carbon nanotubes) and two-dimensional (2D) (e.g. thin films) nanomaterials.Assembly of nanomaterials is the key step to transfer their fascinating mechanical, electronic and optical properties from nano- to micro- or macro- scale. Among all types of assemblies,assembling across different nanomaterial classes is of particular interest. For example, assembling 0D nanoparticles with 1D nanotubes or 2D thin films. These assembled structures have the advantage of possessing properties from both classes of nanomaterials.Functionalization of nanomaterials is important from both scientific and technological points of view. A newly developed field of functionalization is called “patchy particles”. Multiple types of functional molecules form different domains on particle surface. Each domain contains only one type of functional molecules. These domains are called patches. These patchy particles are advanced building blocks, which may assemble into useful complex structures.In this thesis, polymer single crystals are exploited to assemble and functionalize nanomaterials. Polymer single crystals have a lamellar structure. Since the thickness of these lamellae is ~10 nm, polymer single crystals are introduced as a new type of 2D nanomaterials. Different from the traditional 2D nanomaterials such as Langmuir-Blodgett films, self-assembledmonolayers and thin films made by Layer-by-Layer technique, these polymer single crystals are free-standing, which means no substrate is needed. Furthermore, the surface of these polymer single crystals can be readily functionalized by crystallizing end-functionalized polymers.Based on the studied polymers, this thesis is divided into two parts. The first part is focused on single crystals of poly(ethylene oxide) (PEO). Thiol-terminated PEO is used to makefunctional lamellar single crystals. Assembling 0D nanoparticles with these 2D lamellae leads to nanoparticles sheets with three different structures: monolayer, bilayer and sandwich.Furthermore, by assembling nanoparticles during crystallization of PEO, nanoparticle sheets with frame-like patterns are obtained. The morphology of these frames can be readily controlled by tuning experimental parameters. Finally, as nanoparticles sheets form, patchy nanoparticles are produced as well. Structures like “bilines” and nanowires are formed by self-assembly of these patchy nanoparticles.The second part deals with single crystals of polyethylene-block-poly(ethylene oxide) (PE-b-PEO). Single crystals of PE-b-PEO are used to functionalize carbon nanotubes and assemblenanoparticles with these nanotubes. Alternating patterns are formed on carbon nanotube surface by thin film crystallization of PE-b-PEO. As a result, the surface of a carbon nanotube isuniformly divided into many sub-10 nm pieces along the tube axis. This functionalization opens the door to…