Utilizing Polymer-Grafted, Anisotropic Nanoparticles for the Design of Novel Materials

Abstract

The range of available design elements to synthesize and functionalize nanoparticle building blocks that self-assemble into superlattice structures has increased drastically over the last 30 years. From the introduction of patch interactions driven by grafting polymers to nanoparticle surfaces, to the proliferation of techniques that allow for the synthesis of a plethora of different nanoparticle shapes, we now have the experimental capability to leverage a vast toolbox of nanoscale components. For example, the shape, size, and composition of the nanoparticle core, the architecture, size, and interactions of the grafted polymers, as well as the choice of solvent, temperature, and external fields can all now be tuned experimentally. Rather than continuing to increase the variety of available nanoscale components, future work in our field will largely be focused on how to effectively utilize the nanoscale components to design building blocks that yield crystal structures with desired material properties. This work explores new ways to conceptualize and organize existing nanoscale components to advance our understanding of building block interactions for the purpose of designing novel materials.

We begin by applying polymer scaling theory to explore a new way to conceptualize polymer-grafted, anisotropic nanoparticles in the intermediate length regime. Previously, the cores of these polymer-grafted particles have been deemed entirely hard whereas the polymer shell had been considered entirely soft, creating a conceptual picture of nanoparticle assembly where the nanoparticle cores arrange themselves according to the packing properties of their shapes and the polymer shells deform such that they are purely space filling. Utilizing the scaling theory, we explore the proposition that in the interior of the polymer shell, the polymers are rigid such that the shape of the hard core is effectively modified, altering the nanoparticle hard-core packing properties.

We next explore the use of iodine for the synthesis of polymer-grafted, gold core nanoparticles in collaboration with the Chen group at the University of Illinois at Urbana-Champaign. In their experiments, specific regions of the nanoparticle surface become occupied by iodine and are no longer accessible for polymer grafting. Using simulation models and scaling theory, we demonstrate that this synthesis technique can create building blocks with novel patch morphologies, which we then utilize for the simulated assembly of nanoparticle crystal structures.

Finally, I enumerate my scientific software contributions, which aid in finding solutions to significant problems in our field today. I begin with a set of plugins to HOOMD-blue enabling inverse design across a wider building block parameter space. Then, I discuss textit{agrippa}: a python package enabling end-to-end workflows for high-throughout screening of nanoparticle building block design spaces. Lastly, I discuss a new neighbor finding algorithm which may give more physically intuitive neighborhoods for systems of shaped particles.