Incorporation of nanoparticles (NPs) into polymers is an attractive approach for enhancing their thermomechanical properties and introducing new functions into the polymer. While traditional applications of polymer-nanoparticle composites (PNCs) have relied on well-dispersed NPs, newer applications of PNCs could benefit from higher-order organization of NPs in the polymer. Recently, we proposed an approach for assembling NPs into unique higher-order structures within polymers that involves trapping polymer-grafted NPs at the interface between two mutually immiscible polymers.<sup>1</sup> Using coarse-grained molecular dynamics simulations, we demonstrated how this approach could assemble NPs into unusual clusters, networks, and layered architectures. However, the full potential of this approach could not be explored due to the high computational costs of such simulations in predicting the globally stable assembly states of the NPs. Here, we present a new computational approach for rapidly determining the assembly configuration of binary systems of NPs trapped at fluid-fluid interfaces. The approach uses analytical models to describe pairwise interparticle interactions and NP interactions with the liquid layers and a tailored Monte Carlo global optimization method to locate the ground-state configuration of the NPs. By exploring binary NP systems of varying size ratios, interparticle interaction strengths, and interaction differences with the fluid layers, we uncover a spectrum of monolayer and bilayer superlattices exhibiting complex tessellation patterns that could have applications in optical metamaterials. Simultaneously, we are developing improved analytical models for interparticle interactions that account for multibody effects. As example, we present a three-body potential for interactions between polymer-grafted NPs in a polymer matrix that would allow us to explore anisotropic assembly of polymer-grafted NPs over large time and length scales.<sup>2,3</sup>

Interfacial assembly of binary nanoparticle superlattices

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.