Structure and Dynamics of PEO Grafted to Nanoparticles in Water

Polymer-grafted nanoparticles (PGNs) are highly promising for applications ranging from drug delivery to advanced electronic materials. The polymer coating enables tethering specific functionality and controls the interactions of the nanoparticles with their surroundings. Grafted polymer brushes have been well studied, demonstrating that the structure of the polymer at the nanoparticle interface depends on numerous factors including molecular parameters (inherent rigidity, molecular weights and polymer-solvent interaction) as well as grafting density and the nature of the interface. The current work aims to resolve the structure and dynamics of poly(ethylene oxide) (PEO) grafted silicon oxide nanoparticles at the nanoparticle-water interface, using fully atomistic molecular dynamics simulations. PEO is biocompatible thus suitable for drug delivery, tissue engineering scaffolds, and medical device coatings; all operated in aqueous environment where the ionic strength varies. In contrast to previous studies, the current work focuses on long PEO chains as the grafting topology is controlled. Here, the PEO is end-grafted to the nanoparticle either at one end or with both ends grafted to form a ring. The structure of the brush PEO layer as a function of the grafting density and polymer chain length will be discussed as the electrostatic characteristics of the water, mediated by salt water are varied.