The pathways to control assembly and integration of nanoparticles into polymeric matrices will be probed using multi-million atom molecular dynamics simulations. The potential of nanoparticles has been long realized; however, integrating them in different devices remains a challenge. Our study will probe ways to overcome the major barriers to integrating nanoparticles into a range of advances devices, controllably dispersing and organizing them within durable matrices while retaining their unique properties. By zooming into the interaction regions between the nanoparticles and the surrounding polymeric matrix, we will provide the needed molecular level understanding of the assembly process. Specifically, we seek to resolve the factors that control the assembly of multiple nanoparticles in the bulk and in thin films. As producing well-dispersed polymer nanocomposites is a major hurdle for making new materials, we will concentrate our studies on identifying the parameters that control nanoparticle dispersion. We will explore a recent new approach to disperse NPs in a polymer matrix is to separately optimize the enthalpic and entropic components by end-grafting a mixture of short and long chains to the nanoparticle. The short chains are to screen the enthalpic interaction between nanoparticles while the long chains mix with the polymeric matrix, producing enhanced mechanical and thermal stability. As many polymer films are made by first dissolving the nanoparticles and polymer in a solvent and evaporating the solvent, we model the effect of solvent vaporation rate on the dry polymer film. Rapid solvent evaporation can lead to long-lived metastable states in which the nanoparticles are trapped in the polymer film, providing a means to disperse nanoparticles when in equilibrium they would aggregate. We then determine the rheological response and mechanical properties of the resulting polymer nanocomposites and study molecular transport through polymer nanocomposite membranes for gas separation. Motivated by the numerous potential applications of polymer nanocomposites with unique new properties, we will use large-scale molecular dynamics simulations to define the interaction of nanoparticles and control their miscibility in polymer melts and their self-assembly that will serve as building blocks for new materials and devices. Access to petascale computational resources will enabled to capture the essential time and length scales that dominate the physics of nanoparticle assembly and integration into polymer matrices.
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