Kinetic Manipulation of Self-Assembling Systems for Scalable Nanomaterials Synthesis

Abstract

Nanoparticle assembly is an approach to materials development in which macroscopic materials are constructed through the autonomous self-organization of nanoparticle-based building blocks. Since individual nanoparticles can be synthesized with tailored size, shape, composition, and chemical functionality, this synthetic strategy offers extremely fine control over material structure at the nanometer length scale. However, because an enormous quantity of these building blocks is typically required to produce macroscopic materials, the scalability of this approach has remained a significant obstacle to large scale production. In this dissertation, I demonstrate that polymer-grafted nanoparticles (PGNPs) can be used to not only address these scalability challenges, but also generate novel microscale and nanoscale architectures that are otherwise difficult to realize through bulk processing. First, I show that in concentrated colloidal dispersions of PGNPs, adjusting the solvent quality enables sufficiently precise control over polymer-polymer interactions to yield ordered nanoparticle arrays on much shorter timescales than previously reported assembly techniques. This facile and rapid assembly methodology is highly desirable because it uses generic polymer ligands that are amenable to large scale production, can be performed without specialized equipment, and is easily adapted to particles of arbitrary composition. Second, I show that by using polymer ligands end-modified with supramolecular binding moieties, nanoparticles can be assembled into previously unobserved nonequilibrium crystal habits. Interestingly, the prevalence of these kinetically-driven morphologies follow exactly the opposite trend of what would be expected in conventional crystal growth, revealing new mechanistic pathways in the morphogenesis of crystals derived from colloidal constituents. Finally, I show that ordered PGNP arrays can be thermally processed to induce interparticle sintering, resulting in interconnected porous networks. This allows nanoparticle assembly to serve as a versatile route to mesoporous metals, ceramics, and even heterostructures with multiple components, thus providing a powerful platform for generating catalytic materials with tunable surface area and activity. Collectively, these findings reveal that kinetic control underpins the practical scalability and structural diversity of PGNP-based materials and establishes nanoparticle assembly as a kinetically tunable platform for engineering complex nanoscale architectures.